An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses optical plethysmography responsive to variations in arterial pulse amplitude to detect the hemodynamic status of a patient. A light source and light detector are positioned for a reflected-light configuration on a device housing and coupled to electronic circuitry in the housing via a hermetic feedthrough. In one embodiment, the light source and detector are positioned in a recess in a wall of the device housing and surrounded by an encapsulant. The source and detector are positioned for a reflected-light configuration and are preferably an infrared (IR) LED and photodiode, respectively. The source and detector may be placed in a single recess that is created when the device housing is manufactured. An opaque optical barrier is place between the source and detector, which ensures that no light passes between them without first interacting with the overlying tissue. Light reflected from the source to the detector is modulated by pulsation of blood from vasculature in the surrounding body tissue thus enabling sensing of the strength of a heartbeat.

I. Field of the Invention
This invention relates generally to cardiac devices, and more particularly to the assessment of hemodynamic status by a cardiac device.
II. Description of the Related Art
A critical function of implantable cardioverter defibrillators (ICDs) is to identify and terminate hemodynamically unstable arrhythmias such as ventricular fibrillation (VF) and ventricular tachycardia (VT). A technical challenge is to achieve high sensitivity, so that the occurrence of such arrhythmias does not go undetected, while maximizing specificity, so that relatively benign rhythms such as atrial fibrillation (AF) and sinus tachycardia (ST) are not treated.
Conventional implantable cardioverter defibrillators (ICDs) perform discrimination through analysis of the intracardiac electrogram, where features such as rate, interval regularity, and QRS morphology are analyzed in order to identify the underlying rhythm. This approach is convenient because electrical sensing can be easily performed using the same leads that the device requires to deliver therapy. Furthermore, electrogram features provide reasonable accuracy in rhythm identification. However, the accuracy of this approach is ultimately limited because there are inherent ambiguities in cardiac electrical activity that prevent perfect identification. For example, VT, which typically generates a wide QRS complex morphology and regular intervals, may exhibit narrow complexes, particularly if bipolar sensing is used, and irregular intervals. On the other hand, AF, which typically generates narrow QRS complexes and irregular intervals, may exhibit a wide QRS complex, due to a fixed- or rate-related bundle branch block or interventricular conduction defect. In addition AF may produce extended sequences of regular intervals. Thus, there is a theoretical limit to the accuracy with which electrogram analysis can identify cardiac rhythms. The problem is compounded by the fact that practical considerations, such as power consumption and manufacturing costs, impose compromises in the algorithms and sensing configurations that are implemented.
The conventional approach to the detection of pathological arrhythmias using electrogram analysis rests on the premise that the type of therapy is appropriately determined by the underlying cardiac rhythm. In fact, from a clinical perspective, a more important criterion for determining therapy than the identification of the underlying rhythm is whether the rhythm is hemodynamically stable, that is, whether the heart is pumping blood sufficiently to ensure adequate perfusion of vital organs. For example, there are forms of VT that are hemodynamically stable which do not require immediate cardioversion. For these rhythms, low energy methods of termination such as anti-tachycardia pacing can be attempted without sacrificing safety. Such an approach improves device longevity, and avoids subjecting the conscious patient to painful and distressing electrical shocks. Conversely, there are cases of AF and supraventricular tachycardias that are hemodynamically unstable because of high rate or poor ventricular function, and therefore require rapid termination. Thus, the most relevant question clinically is not the identification of the underlying cardiac rhythm but rather whether the rhythm is hemodynamically stable. This point is well illustrated by the Universal Algorithm for emergency cardiac care, advocated by the American Heart Association, and described in the book Advanced Cardiac Life Support, R. O. Cummins, Ed., 1997. The major branch point, which occurs early in the algorithm, is the test for the presence of an arterial pulse, a rapid and robust method of assessing hemodynamic status. Subsequent evaluation and treatment along the two branches of the algorithm varies significantly depending on the outcome of this test. Only later in the algorithm is identification of the origin, ventricular vs. supraventricular, of the cardiac rhythm attempted.
Because of the inherent limitation in the accuracy that can be achieved in identifying cardiac rhythms using electrogram analysis, and more importantly, because what is of ultimate clinical relevance is the hemodynamic status of the patient, what is needed is a method and apparatus for rapidly assessing hemodynamic status that can be used by implantable cardiac devices.
Another application of rapid hemodynamic status assessment is in capture verification, a technique that verifies that a pacemaker-delivered stimulus has electrically captured the myocardium and initiated the propagation of a depolarization. The technique is useful because it allows continuous or periodic adjustment of the pacing energy to accommodate a changing threshold. It allows the pacemaker to deliver the minimum energy necessary to consistently capture the heart, which both maximizes the pacemaker longevity and enhances patient safety. A method of capture verification that is known in the art analyzes the electrical evoked response that is generated after a pace stimulus is delivered by the pacemaker. While this approach, disclosed in U.S. Pat. Nos. 5,165,404 and 5,165,405, has proven to be commercially viable, it requires sophisticated circuitry and low-polarization leads, and is potentially susceptible to electrical noise. It would be advantageous to have a capture verification technique based on hemodynamic status assessment.
One of the challenges of electrically detecting cardiac depolarizations is ensuring that the system is sufficiently sensitive so that myocardial depolarizations are recognized by the device, while at the same time not excessively sensitive so that repolarization waves or noise, such as that induced by diaphragmatic myopotentials, is incorrectly interpreted as a depolarization. Beat-to-beat hemodynamic sensing would allow oversensing of electrical noise to be recognized and distinguished from ventricular fibrillation (VF) or tachycardia. In oversensing of electrical noise, regular and robust mechanical cardiac contractions would occur along with higher-rate ventricular sensed events. In this case the sensitivity could be decreased until the ventricular sensed events occurred in concert with cardiac contractions. On the other hand, the detection of robust mechanical cardiac contractions during the absence of ventricular sensed events would indicate that the sense amplifier sensitivity is set too low and should be increased. Finally, the presence of rapid ventricular sensed events without detected cardiac contractions would indicate the presence of VF, hemodynamically unstable VT, or another hemodynamically unstable rhythm. It would thus be advantageous to provide an improved system for verification of sensed events and optimization of sensing thresholds.
Yet another application of hemodynamic sensing is in pace-parameter optimization, in which any of a number of parameters that define pacing characteristics is optimized. Pace-parameter optimization is particularly applicable to multi-site pacing. For example, in dual-chamber (atrial and ventricular) pacemakers the atrio-ventricular (AV) delay is optimized, so that the ventricular contraction is timed such that the contribution of the atrial contraction is maximally exploited. Another example is biventricular pacing for heart failure, in which ventricular synchrony is optimized by adjusting the timing that pace pulses are delivered to various sites. Currently, these parameters are set to default nominal values, or labor-intensive methods are used to assess hemodynamics in order to optimize the parameters at time of device implant. Examples of these methods include ultrasound to measure ejection fraction and left heart catheterization to measure the rate of change of left ventricular pressure during systole, which is a measure of contractility and mechanical efficiency. In addition to the substantial time and effort these approaches impose, the invasive techniques increase the perioperative risk to the patient. Furthermore, these approaches are possible only during device implant or follow-up examinations. A hemodynamic sensor incorporated into the device would allow frequent and dynamic optimization of pacing parameters.
In pace-parameter optimization, some measure of cardiac function is needed to serve as the feedback which determines how the pace parameters are adjusted. The measure of cardiac function provides the basis of optimization; it allows one set of parameter values to be deemed superior to another. To be filly general the measure must operate over short time scales, ideally on a beat-to-beat basis. While a slower response may be adequate for adjusting, for example, the overall pacing rate, a rapid response is necessary to dynamically adjust multi-site timing to changes in body posture, which is particularly important for certain diseases such as hypertrophic obstructive cardiomyopathy and dilated cardiomyopathy. Furthermore, a sensor capable of detecting changes in hemodynamic parameters on a beat-to-beat basis would allow the optimization algorithm to achieve the ideal parameter values quickly.
Still another application that would benefit from hemodynamic sensing is in the monitoring of disease status in heart failure patients. Hemodynamic sensing would allow the optimization of medical management of the heart failure patient. It would also allow the early recognition of a developing acute exacerbation. With early recognition the exacerbation could be relatively easily terminated, before it becomes fully developed and requires hospitalization and intensive intervention to terminate.
A further application of hemodynamic sensing is in the assessment of autonomic status. For example, the development of diabetic neuropathy is known to adversely affect the sympathetic/parasympathetic balance and the body""s response to autonomic perturbations. Since the control of cardiovascular system is in large part the responsibility of the autonomic nervous system, sensitive hemodynamic measurements can detect changes in autonomic tone, such as parasympathetic decline associated with the development of diabetic neuropathy or the sympathetic enhancement provoked by a CHF exacerbation.
Techniques for hemodynamic assessment are known in the art. In the context of arrhythmia discrimination Cohen and Liem (Circ., 1990, 82:394-406) systematically studied the use of a pressure transducer placed in the right ventricle, a configuration described in U.S. Pat. No. 4,774,950, and demonstrated that this approach effectively discriminated hemodynamically stable from hemodynamically unstable cardiac rhythms. The approach of Cohen and Liem is advantageous in that it directly characterizes important hemodynamic variables, namely central venous pressure and the pressure differentials that the heart is able to generate. However, incorporation of a hemodynamic sensor into an intracardiac lead is undesirable for several reasons. First, it increases the cost of the lead, which because of the significant engineering challenges associated with providing chronic intracardiac placement, already represents a sizable fraction of the overall cost of the system. More importantly, incorporation of a special sensor in an otherwise general-purpose lead imposes expensive compatibility constraints: any device that would make use of the sensor must have the special-purpose lead implanted with it, and once the lead has been implanted, any subsequent device changes, such as for upgrade or battery depletion, must have hardware capable of interfacing with the special-purpose sensor. Finally, a special class of patients, such as some pediatric patients and patients with congenital cardiovascular malformations, require epicardial placement of leads; intracardiac placement is not possible for them. These patients would not benefit from a hemodynamic sensing method that requires intracardiac placement. It is therefore desirable to provide a method and apparatus for hemodynamic sensing that does not require special intracardiac or intravascular leads. Such an invention would avoid expensive, special purpose leads. Furthermore, it would avoid imposing expensive lead-device compatibility constraints.
Erickson and Bennett, in U.S. Pat. No. 5,176,137, propose placing a two-wavelength oxygen saturation sensor in the right ventricle of the heart. Their disclosure assumes that during hemodynamically stable rhythms the oxygen saturation in blood returning to the right ventricle is pulsatile, and that the pulsatile character of the saturation decreases during hemodynamically unstable rhythms. Their disclosure further assumes that the average saturation level of the blood returning to the right ventricle decreases during hemodynamically stable sinus and ventricular tachycardias but remains approximately constant during unstable rhythms. The intracardiac placement of their sensor carries the disadvantages described above. More importantly, while slow changes in venous oxygen saturation can be expected with certain rhythms, the amount of time required for blood to return to the right ventricle from the periphery is substantial, on the order of tens of seconds. This delay is even longer for hemodynamically unstable rhythms. Delaying ICD therapy by this amount of time would compromise patient safety. What is needed is a method of assessing hemodynamic status that is robust and rapid. Ideally the method operates on the time scale of a single cardiac cycle, i.e., on a beat-to-beat basis.
Other examples of oxygen sensors exist in the art. U.S. Pat. Nos. 4,399,820, 4,467,807, 4,815,469, and 5,040,538 all present oxygen saturation or partial pressure sensors placed in the right ventricle for rate responsive pacing, in which the pacing rate of the pacemaker is controlled based on the metabolic demand of the body, which is a form of hemodynamic assessment and pace-parameter optimization. Assuming arterial O2 is constant, a fall in venous O2 below a critical level implies that the cardiac output is not sufficient to meet metabolic demand. In this case, a pacing parameter, the pacing rate, is increased. The time scale of this process is on the order of tens of seconds, much greater than the beat-to-beat assessment that is necessary to perform arrhythmia discrimination, capture verification, sensing gain and threshold optimization, and rapid pace-parameter optimization. Furthermore, the intravascular placement carries the disadvantages discussed above.
In U.S. Pat. No. 5,540,727, Tockman et al. disclose an algorithm for optimizing pacing parameters, including pacing mode. They mention a number of examples of a variety of measures of hemodynamic status, including both implantable embodiments (cardiac output measured using impedance plethysmography of the right ventricular volume, and right ventricular pressure) and external embodiments (cardiac output measured using Doppler ultrasound, heart sounds, blood pressure, respiratory gas analysis, and pulse oximetry). External measurements of hemodynamic status are labor-intensive and can only be used during periodic follow-up examination. They are therefore not suitable for arrhythmia discrimination, dynamic pace-parameter optimization, sensitivity optimization, or capture verification. The measures they present for implantable embodiments all require right ventricular placement, and thus carry with them the disadvantages described above.
In U.S. Pat. No. 5,334,222, Salo et al. present a system tailored to heart failure patients that includes dual chamber (atrial and ventricular) pacing with defibrillation capability. An algorithm for optimizing AV delay is disclosed which uses information generated by a generic sensor of cardiac function. Particular embodiments of the sensor that are described include intracardiac impedance plethysmography to assess stroke volume and cardiac output, an intracardiac pressure transducer, and Doppler ultrasound to assess blood flow velocity. An additional modality that is described is heart sounds, though neither a physical embodiment of a heart sound sensor nor a method of using heart sound to obtain a measure of cardiac function are disclosed.
Methods of pace-parameter optimization have been proposed using non-hemodynamic surrogates, such as QRS width. In U.S. Pat. No. 5,527,347 Shelton and Warkentin adjust the AV delay such that QRS width is maximized. Their invention is tailored to patients with hypertrophic obstructive cardiomyopathy, in whom a thickened intraventricular septum obstructs the ejection of blood from the left ventricle during systole. Delivering a pre-excitation pulse to the right ventricular apex is thought to pull the septum toward the right side of the heart, thereby reducing the degree of obstruction. In the patent, maximizing the QRS width is claimed to provide the optimal AV delay.
In contrast to maximizing QRS width, minimizing the QRS width has been proposed in biventricular pacing for patients with dilated cardiomyopathy. In these patients, improving the synchrony of ventricular contractions is thought to improve cardiac function to a clinically significant degree. QRS width serves as a marker for the degree of synchrony. However, recent results of Kass et al. (Circ. 1999; 99:1567-1573) showed that in heart failure patients QRS width tends to increase in VDD pacing, regardless of the pacing site and despite the significantly improved hemodynamic performance in some of the pacing configurations they tested. Thus the suitability of QRS width as a hemodynamic surrogate is suspect in this patient population.
Use of the QRS width as a feedback variable in pace-parameter optimization schemes such as those just described is convenient because the intracardiac or far-field electrogram is readily available. However, while the rationale for using QRS width in special settings of pace-parameter optimization is intuitively appealing, QRS width is not itself a measure of hemodynamic function, which is what would ideally be optimized in pace-parameter adjustment. Furthermore, while QRS width can provide useful information in the special cases just described, it is not generally applicable. For example, for pacemaker-dependent patients with complete heart block, adjusting the AV delay does not affect the QRS width in any meaningful way. Assessment of hemodynamic performance on a beat-to-beat basis would be a direct and general way to provide for the optimization of pace parameters. It would be operable both in the common applications of sinus node dysfunction and heart block, as well as the special cases of biventricular pacing in heart failure and dual chamber pacing in hypertrophic obstructive cardiomyopathy. Indeed, the information it provides would be interpreted the same way whether the goal of therapy is to improve ventricular synchrony, as is the case with dilated cardiomyopathy, or to decrease synchrony, as with hypertrophic obstructive cardiomyopathy.
In U.S. Pat. No. 5,554,177, Kieval and Soykan present a pace-parameter optimization system that uses heart sounds as the feedback variable. They note that an acoustic sensor does not necessarily require intracardiac placement, but instead can be placed in the housing of the implanted device. As discussed above, this is advantageous because it does not require costly lead modifications, nor does it impose restrictive device/lead compatibility constraints. In their disclosure, pace-parameter optimization is performed using as feedback a particular heart sound which is xe2x80x9can artifact indication of a less than optimal heart condition.xe2x80x9d Their disclosure isolates the sound in time and adjusts the pacing parameters in order to xe2x80x9clower the volumexe2x80x9d of the sound. In the preferred embodiment the volume of the sound of mitral regurgitation is minimized. The generality of this approach is limited in several ways. Conditions that lack an artifact indication can not support this approach to parameter optimization. Furthermore, not all patients with a given disease, such as the example of dilated cardiomyopathy used by the authors to illustrate the invention, will have a given artifact indication, such as mitral regurgitation. More importantly, this approach, in which a particular abnormal heart sound is minimized, would fail dramatically in some applications of hemodynamic assessment, such as arrhythmia discrimination. Indeed, because it seeks to minimize heart sounds, the measure proposed in the ""177 Patent would falsely classify a hemodynamically unstable rhythm, such as ventricular fibrillation, as hemodynamically stable. Even in application to the examples presented in the ""177 Patent, hypertrophic and dilated cardiomyopathy, one is struck by the technical challenge of determining whether the minimization of the artifact heart sound results from, on the one hand, desirable parameter settings that increase cardiac hemodynamic performance, or, on the other hand, undesirable parameter settings that significantly compromise cardiac synchrony and therefore reduce the degree of regurgitation. The fundamental drawback of the approach the authors describe is that it does not provide hemodynamic sensing. What is reflected in the intensity of the sound of mitral regurgitation is the backward jet of blood into the left atrium from the left ventricle, not the forward output of blood from the heart. What is needed is a measure that is directly related to the hemodynamic function of the heart.
In U.S. Pat. No. 4,356,827, Uemura et al. describe the use of Korotkoff sounds in the detection of cardiac arrhythmias. Korotkoff sounds are the sounds generated when blood is pumped through an artery subjected to an external pressure which lies between the systolic and diastolic pressures. The invention clearly provides a measure of hemodynamic status in that it identifies the systolic and diastolic pressures as being respectively above and below the externally applied pressure. As a measure of hemodynamic status it is generally applicable to the problems presented above. However, the external pressure cuff precludes the use of the invention in an implanted device. A modified embodiment configured for internal use can be imagined, but such an approach would require surgical dissection of an artery and attachment of a pressure cuff, or similar element. The pressure applied by the cuff could be dynamically changed when the arterial pressure is checked, for example, as when tachycardia is detected. However, this approach would clearly increase both the device cost and the difficulty and duration of the implant procedure. These considerations make the practicality of such an approach questionable.
Lekholm, in U.S. Pat. No. 4,763,646, describes identifying various portions of the cardiac cycle using heart sounds to provide timing information for a pacemaker. For example, heart sounds are used to provide detection of ventricular contraction in order to inhibit the delivery of a ventricular pace pulse in a DDD pacer. In addition, an application to arrhythmia discrimination is presented. Specifically, heart sounds are used to determine the heart rate, from which tachycardia is detected. In contrast, changes in amplitude and the frequency spectrum of the heart sounds are used for the detection of fibrillation. This approach in effect detects the reduced hemodynamic performance of the heart that results from ventricular fibrillation (VF). However, because of its rapidly lethal character, it is necessary to quickly terminate VF, regardless of the hemodynamic status of the patient early in the arrhythmia. In contrast to VF, it is in the region of rate overlap between ventricular and supraventricular tachycardias that a transducer which is sensitive to diminished hemodynamic status would be most useful. In this region, however, the invention presented in the ""646 Patent uses heart sounds only to calculate rate, not to assess the hemodynamic performance of the heart. A final application of heart sounds in the ""646 Patent is to capture verification. Other systems using heart sounds are described in U.S. Pat. Nos. 3,985,121, 5,685,317, and 5,687,738, though none of these make use of sounds in hemodynamic assessment.
Plethysmography of vasculature is known in the art. It provides the basis of the conventional pulse oximeter, which by using two wavelengths of light, calculates the percent of arterial hemoglobin that is saturated with oxygen. The light is typically directed through the fingertip using a temporarily applied finger tab. It can also be directed through other fleshy appendages such as the ear and, in infants, the foot. Optical vascular plethysmography also provides the basis for a non-invasive, continuous blood pressure monitor. A cuff containing an optical source and detector is placed over the finger. The pressure in the cuff is continuously varied so that the amount of light measured at the detector remains constant, which indicates that the volume of the vasculature is constant. In this way the arterial pressure can be inferred from the cuff pressure that is necessary to maintain constant light detection. A final application of external plethysmography of the vasculature is described in U.S. Pat. No. 5,544,661, in which an external, temporary monitor provides continuous monitoring of a patient at risk for cardiac arrhythmias. Thus, while optical plethysmography of the vasculature is known in the art, it has to date been configured for temporary, external use. An implementation suitable for chronic, implanted use is necessary for useful hemodynamic measurements in the context of implantable cardiac devices.
Regarding the physical location of a sensor used by an implantable device, as described above in the context of pressure sensing in the right ventricle, it is desirable to place the sensor outside the bloodstream. Incorporation of the sensor inside or on the device would be most convenient. Prutchi and Paul, in U.S. Pat. No. 5,556,421 propose placement of a sensor within the header of a cardiac device. A disadvantage of this approach is that it does not necessarily provide for the optimal signal transduction of a particular sensor. For example, the performance of the optical sensor described in the Prutchi and Paul Patent would be so severely degraded by direct transmission of light from source to detector that one skilled in the art would question the functionality of the proposed solution. In addition, placement in a rigid epoxy header is simply not an option for some sensors, such as sound sensors, because of the dramatic degradation in the signal-to-noise ratio that the rigid header would impose. What is needed is a method of incorporating a hemodynamic sensor into a implantable device, providing it optimal access to the external milieu so that the signal of interest is optimally transduced, maintaining the hermetic enclosure provided by the device housing, and minimizing the added volume that the sensor imposes.
Fearnot in U.S. Pat. No. 5,040,533 teaches placement of a generalized window in the housing of the cardiac device. The window might be transparent to facilitate the transmission of light or flexible to facilitate pressure transduction. While the convenience, from the clinician""s perspective, of incorporating the sensors into the housing of the cardiac device is an obvious advantage, the technical difficulty in maintaining a hermetic seal between two different materials, particularly in a chronically implanted device, is equally obvious to one skilled in the art. The technical challenge is made more difficult by the greatly increased circumference, relative to that of standard feed-through connections known in the art, of the boundary between the window and the device housing. What is needed, therefore, is a method of placing a hemodynamic sensor in or on the device without compromising the integrity of the hermetic enclosure.
Because of the considerations described above, the principal object of the present invention is to provide an extravascular sensor that monitors a patient""s hemodynamic status.
An additional goal of the present invention is to provide hemodynamic sensing over short time scales, i.e., on the time scale of a single cardiac beat.
Another object of the invention is to provide a means of determining whether electrical therapy is needed based on the hemodynamic status of the cardiac rhythm.
A further object is to provide a means of capture verification for cardiac pacemakers.
Still another object is to allow the optimization of the sensitivity of sensing circuitry.
Yet another object is to provide immunity from electrical noise in the sensing of cardiac activity.
An additional object of the invention is to provide hemodynamic sensing for the optimization of pacing parameters.
Still another object of the invention is to provide for extravascular placement of the device and sensors, which minimizes the perioperative and long-term risk of complications.
Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
The present invention is directed to an implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses optical plethysmography responsive to variations in arterial pulse amplitude to detect the hemodynamic status of a patient. A light source and light detector are positioned for a reflected-light configuration on a device housing and coupled to electronic circuitry in the housing via a hermetic feedthrough. In one embodiment of the invention, the light source and detector are positioned in a recess in a wall of the device housing and surrounded by an encapsulant. The source and detector are positioned for a reflected-light configuration. The light source and detector are preferably an infrared (IR) LED and photodiode, respectively. They are placed on the side of the device that, following implantation, faces the interior of the body rather than the surface, and are configured such that light cannot pass directly from the source to the detector. In the preferred embodiment the source and detector are placed in a single recess that is created when the monitor housing is formed, or, alternatively, machined or cast. An opaque optical barrier is place between the source and detector, which ensures that no light passes between them without first interacting with the overlying tissue. Light reflected from the source to the detector is modulated by pulsation of blood from vasculature in the surrounding body tissue thus enabling sensing of the strength of a heartbeat.
In an alternative embodiment, the implantable medical device includes first and second recesses with the sensor including a light source positioned in the first recess and the light detector positioned in the second recess. When the light detector receives reflected light originating from the light source, it generates a signal which is indicative of variations in the reflected light and thus the expansion and contraction of arteries with each heartbeat. A biocompatible, optically transparent encapsulant may be used with either embodiment filling the recess(es) and surrounding both the light source and light detector.
Other embodiments of the invention include various placements of the light source and light detector relative to each other to prevent direct transmission of light from said source to said detector.
In another embodiment of the invention the light source and detector are placed on a substantially planar face of the device housing and covered with a biocompatible encapsulant.
The sensed plethysmography signals may be used to discriminate among possible cardiac arrhythmias, particularly hemodynamically stable and unstable arrhythmias such as may be the case between an atrial tachycardia and a ventricular tachycardia.
The medical device of the invention may further include an accelerometer for detecting motion artifacts that could interfere with the sensed plethysmography signals. Alternatively, the plethysmography signals themselves may be analyzed for motion artifacts.
In another embodiment the medical device of the invention is implemented in an implantable pulse generator that provides pacing therapy to a patient""s heart. The electronic circuitry uses the sensed plethysmography signals to optimize the timing of pacing pulses provided to said patient""s heart. This may include a posture sensor that triggers optimization of the timing of pacing pulses upon sensing of a change of the patient""s posture. The voltage level of pacing pulses provided to said patient""s heart may also be optimized or pacing capture may be verified. In addition, the sensed plethysmography signals may be used to optimize electrical sensing of cardiac signals.


A virtual image display system for displaying a relatively large virtual image to a user derived from a relatively small image source. A lens group is provided for amplifying an image provided by the image source. A plurality of reflecting elements are provided for magnifying the image provided by the lens group and for displaying the relatively large virtual image. Several embodiments are provided that include on-axis and off-axis reflecting versions, and a holographic virtual image version. Conventional lenses and reflecting optics are used to provide the on- and off-axis versions of the system, while a holographic reflecting element is used to provide a holographic virtual image. A window element may also be employed to minimize ambient reflection viewed by the user and eliminates ambient reflection to reduce the user's eye fatigue. The display system improves a user's viewing comfort by positioning the image at a distance matching the visual requirements of the user's eye. The large image size also improves the legibility and readability of the display. The present system is especially useful for computer monitor or TV applications and the color version is useful in applications where selected colors are to be highlighted.

The present invention relates generally to virtual image display optical systems, and more particularly, to a wide spectral bandwidth virtual image display optical system as a display monitor for computer applications.
Conventional display systems such as CRT monitors or LCD panels are direct-view systems in which the users view a display image on the monitor surface. For a large screen size, the display is correspondingly larger in size. As a result, the conventional CRT monitors are not only costly, but are also bulky and heavy.
Prior art related to the present invention include U.S. Pat. No. 4,294,515 issued to Kaufman and U.S. Pat. No. 3,940,104 issued to Withrington. The Kaufman patent teaches a virtual image system using spherical mirrors. This approach is typically useful for a display system with small field-of-view (small display screen size). The Withrington patent teaches an optical system that is used in a transmissive configuration for head-up display applications with image distance at infinity. The system typically includes one aspherical optical mirror surface for displaying a monochrome image.


Locks, lock mechanisms, lock assemblies, retro fit kits, and methods of using locks with cables and chains inside of strengthened flexible sleeves can conform to shape surfaces to which they are mounted, for preventing thefts of bicycles, motorcycles and other applications, such as but not limited to securing gates and doors, and other objects together. The flexible sleeve can include a series of ball and socket segments arranged next to one another, having a hollow conduit through which the cable or chain can pass through.

Cables and chains have been popular for locking bicycles and the like, to posts, etc. However, cables and chains have inherent problems. For example, when not being used as a lock the loose cables and chains can bang against the bike frame and cause scratches and damage to the bike. The loose cables and chains can also get tangled with the rider's legs, and can interfere with the wheels and pedals. Wrapping the chain can also be difficult since the wrapped chain can also move causing undesirable sound effects while it bangs about while the bicycle is being ridden.
Many cables and chains can also be cut open which defeats their purpose of securing the bicycle. Having thicker and larger cables and chains may be less prone to being cut, but their added weight can make them undesirable since riders do not want to add unnecessary weight on the bike,
Other types of bicycle locks have become popular such as U-shaped locks, which includes the KRYPTONITE® lock. However, these locks can also tend to bang around if attached to seat post or about a bike frame when not being used. To keep the U shaped lock stationary, special brackets must be attached to the bicycle frame, which adds extra undesirable weight. Additionally, the U shaped locks have a fixed position U shape which makes then difficult for attaching the lock to both a bicycle and a support member that is not closely located to the bicycle.
Thus, the need exists for solutions to the above problems with the prior art.


A cushion for a patient interface includes an outer membrane providing a sealing structure adapted to form a seal with the patient's face in use and an underlying membrane generally spaced away from the outer membrane. The underlying membrane provides a support structure for the outer membrane. The outer membrane and the underlying membrane each have an inner edge which defines an aperture to receive the patient's nose in use. The underlying membrane is segmented along its inner edge.

The use of nasal Continuous Positive Airway Pressure (nasal CPAP) to treat Sleep Disordered Breathing (SDB), for example Obstructive Sleep Apnea (OSA), was invented by Sullivan (See U.S. Pat. No. 4,944,310). Such treatment is typically accomplished using a source of air at positive pressure (e.g., a blower or flow generator) connected to a patient interface (e.g., a mask) via an air delivery conduit. To maintain a suitable pressure at the entrance to the patient's airways, it is necessary to provide a suitable seal between the patient interface and the patient's face. Early masks were glued to a patient's face every night. Today, however, the patient interface is usually held in position with headgear. Treatment is very successful in reducing SDB. However, gas pressurized in the range of 4-20 cmH2O can be noisy and uncomfortable. Poorly fitting masks can provide an inadequate seal against leak. After wearing a mask all night, some patients can have pressure sores on their faces, especially in such sensitive regions as the nasal bridge. Thus, mask designers and manufacturers are constantly striving to provide patient interfaces which provide a comfortable seal.
A variety of masks are available, such as nasal, full-face, and nose and mouth masks.
ResMed's MIRAGE® mask provided a significant improvement in masks for CPAP treatment. FIGS. 1-3 illustrate an embodiment of ResMed's MIRAGE® mask. It is available in both nasal and full-face versions. In the illustrated embodiment, the mask 2 includes (i) a rigid shell or frame 3 that defines a nose-receiving chamber, and (ii) a face-contacting cushion 4. The cushion 4 plays a role in improving the comfort and seal of the mask. For example, see U.S. Pat. Nos. 6,112,746; 6,357,441; 6,581,602 and 6,634,358. Other aspects of the mask, such as a forehead support and vent also play a role in the fit, comfort, and noise of a mask.
As shown in FIGS. 4-6, the cushion 4 of the MIRAGE® mask includes a dual membrane structure. As illustrated, the cushion 4 includes a thinner outer membrane 6 that is spaced away from a thicker inner or underlying membrane 8 at their inner edges.
The present invention is particularly directed towards a cushion with an improved inner or underlying membrane.


The present invention is directed to multi-element antennas that include, for each adjacent pair of antenna elements, at least one switch arranged to selectively connect that pair to thereby selectively alter an antenna dimension. Accordingly, a multi-element antenna can be configured to enhance its gain at different operational frequencies while a corresponding impedance matching network can enhance the impedance match (i.e., reduce reflected signal energy) between the antenna and a corresponding system (e.g., a transceiver system). The antenna and system can thus be effectively tuned across a wide operational band. The antenna and impedance matching network are configured with switch command signals and match command signals that are provided in response to each of a plurality of frequency codes.

1. Field of the invention
The present invention relates generally to antenna and transceiver systems and, more particularly, to systems that are directed to aircraft installations.
2. Description of the Related Art
There exists a substantial demand for antenna and transceiver systems that can rapidly hop between channels that are distributed over wide frequency bands for the purpose of communicating a variety of communication signals (e.g., voice, data, imagery and video). Although some conventional transceiver systems have operated across restricted frequency ranges, they do not generally satisfy the need for systems that have an extended range (e.g., from 30 MHz to upper limits in the 1 to 2 GHz range). Such extended frequency ranges have been difficult to achieve with a single system, especially when the antenna form factor must also satisfy the aerodynamic and radiative restraints of high speed aircraft.

Broadband tunable antenna and transceiver systems


Polyolefin substrates, for example polypropylene, polyethylene or thermoplastic olefin molded parts, are made scratch resistant by the incorporation therein of an additive combination of a maleated alpha-olefin functionalized with a long chain alcohol or long chain amine and a primary or secondary fatty acid amide. The present polyolefins exhibit good weatherability, scratch resistance, good processability, good mechanical strength, good gloss retention and are non-sticky. The functionalized maleated alpha-olefin is for example the ester or half ester of maleated C18-C26 alpha-olefin with tallow fatty alcohol. The fatty acid amide is for example oleyl palmitamide or stearyl erucamide.

Long chain alcohol functionalized maleic anhydride grafted polypropylene is disclosed in Polyolefins 2003, The International Conference of Polyolefins, Feb. 24-Feb. 26, Houston, Tex., as a processing aid for polyolefins.
U.S. Pat. No. 6,048,942 discloses thermoplastic olefin compositions comprising mar resistance additives selected from polysiloxanes, metal stearates, saturated fatty acid amides and unsaturated fatty acid amides.
JP2002338778 teaches a graft copolymer compositions comprising fatty acid amides.
U.S. Pat. No. 5,731,376 discloses polypropylene block copolymer with improved scratch resistance by inclusion of a polyorganosiloxane. The compositions may further include a fatty acid amide.
U.S. Pat. No. 5,585,420 teaches scratch resistant polyolefin compositions comprising a plate like inorganic filler. The compositions may further comprise high rubber ethylene-propylene copolymers, fatty acid amides, polyorganosiloxanes or epoxy resins.
JP2002003692 discloses polypropylene resin comprising fatty acid amides.
JP62072739 is aimed at molded articles for automobile parts made by compounding a specific polyolefin with a rubbery substance and a specific amount of mica of a specific particle size. The polyolefin consists of a certain polypropylene and a polyolefin modified with an unsaturated carboxylic acid (anhydride), for example maleic anhydride.
JP 63017947 is aimed at scratch resistant propylene polymer compositions.
JP 2001261902 is aimed at polypropylene resin compositions useful as molding material for preparation of interior trims.
U.S. published app. No. 2003/0004245 teaches blends of polyolefin and a reaction product of polyolefin and an alpha, beta unsaturated carboxylic ester, acid or anhydride.
Polyanhydride resins are described in a CPChem Specialty Chemicals data sheet of 2004.


An accelerator pedal apparatus of a vehicle is attached with a pedal plate at one end of one side and includes, at another end of the other side a pedal link member having an insertion recess. A weight member is detachable from and attachable to the insertion recess of the pedal link member such that a vibration of the accelerator pedal can be minimized.

Typically, an accelerator pedal apparatus of a vehicle controls the fuel injection volume delivered to an engine as a throttle body is operated by a cable when a driver presses the accelerator pedal. However, during depression of the accelerator pedal apparatus a vibration from engine is often transferred to the pedal through the cable. Therefore, the driver can feel discomfort through the pedal.

Accelerator pedal apparatus for a vehicle


A driver circuit employs an N-channel pull-down transistor of relatively small size, directly connecting an output node to ground, and another path consisting of a pair of series-connected N-channel transistors connecting the node to ground; the lower of these is driven by the logic voltage which is applied to the gate of the pull-down, and the other has its gate connected to the output node. Two parallel discharge paths are thus provided for the output node, one through the small pull-down transistor, and a second through the (larger) series transistors. When a returning wave from the output node (due to transmission line effects) hits the driver circuit, the series transistors turn off, but the pull-down transistor is still on keeping the driver output node at a valid "low." In cases of mismatch or noise, the pull-down transistor will help absorb refections or ringing. This output driver is especially adapted for small transistor sizes, producing transmission line effects at the chip-to-bus interface, because the circuitry controls overshoot and undershoot, but yet does not use on-chip series source terminations or external (off-chip) terminations). The driver circuit is less sensitive to process and temperature variations, and also less sensitive to variations in etched-conductor impedance, so is capable of driving from either the middle or end of the etched-conductor with no degradation in performance.

This invention relates to semiconductor integrated circuit devices, and more particularly to output drivers for CMOS integrated circuits.
In my U.S. Pat. No. 4,963,766, assigned to Digital Equipment Corporation, a CMOS driver circuit is shown which is of the type used as an output buffer in a single-chip microprocessor or memory circuit. A driver of this type is used to convert a logic voltage within the chip to a higher-level signal for driving a bus on a printed circuit board or other connection between chips. The circuit of Pat. No. 4,963,766 is adapted to be powered by a low-voltage supply, e.g., 3.3 v., but yet is able to withstand higher voltages imposed on its output node. A P-channel pull-up transistor is employed, and the N-well of this pull-up transistor is connected to a higher-level voltage supply, 5.0-volts.
As CMOS feature sizes continue to shrink, the resulting device speed has continually improved. Faster rise and fall times incident to these faster device speeds results in the etched-circuit conductors of a module changing from an RC-dominated environment to an LC or transmission line environment. An etch-conductor with its grounded plane, usually found in a circuit board, forms a transmission line at the frequencies present in logic voltages having fast rise and fall times. A transmission line environment requires that the driver, etched-conductor, and loading be carefully analyzed to ensure that transmission line effects such as overshoot, undershoot, and ringing do not impact data transfers.
One prior solution to the problems of the transmission line environment is to use series-source terminations on the chip. That is, a resistor is placed in series with the signal source, so the resistor appears in series between the output pad and the driver transistor. The resistor should match the impedance Z.sub.O of the transmission line appearing at the chip output. However, a series source termination is usually optimized for etched-conductor impedance, loading, and driver position on the etch (end or middle). Both the resistor (a diffusion) and the NMOS pull-down transistor are subject to process variations in manufacture and temperature variations in operation. It is thus desirable to find a solution that is more independent of these parameters.

High-speed, low-noise, CMOS output driver


A memory managing method for video data decoding process is provided. The memory managing method includes the following steps. A first frame having a first definition is stored, wherein the first frame is a first type or a second type. A second frame having the first definition is stored, wherein the second frame is the first type or the second type. A first frame having a second definition is stored in the memory space where the first frame having the first definition was originally stored, and the remaining memory space left after the original first frame having the first definition had been stored is released, wherein the memory space for storing the first frame having the first definition is greater than the memory space for storing the first frame having the second definition. A third frame having the second definition is stored, wherein the third frame is a third type.

1. Field of the Invention
The present invention relates to a decoding method and a memory managing method, and more particularly, to a video data decoding method and a memory managing method for video data decoding process.
2. Description of the Related Art
Generally speaking, the amount of the video data is usually enormous. In order to save the space for storing the video data, and to save the transmission bandwidth for transmitting the video data, the video data have to be compressed before it is transmitted. The object of the data compression is achieved by removing the superfluous information from the video data. For example, if a subsequent frame is similar to the previous frame, the previous frame is preserved and the same content in the subsequent frames are removed (that is, only the information with different content is preserved), such that the amount of the digital video data is significantly reduced.
For the MPEG (Motion Picture Experts Group) standard, the video decoding process usually produces three types of frames, which are intra-coding frame (I frame), prediction frame (P frame), and Bi-directional frame (B frame). It should be noted that P frame is decoded with reference to information of I frame stored in the memory. In addition, B frame is decoded with reference to information of both I frame and P frame stored in the memory.
When the High Definition Television (HDTV) or Digital Video Disc (DVD) data are being decoded, the memory size for storing I frame, P frame, and B frame are increased according to the big size of the video data. For example, in the specification defined by the Advanced Television Systems Committee (ATSC), the memory size and bandwidth for 1920×1080 interleaved displaying is about 6 times the memory size of the specification defined by the National Television System Committee (NTSC).
In a system having a limited memory size, if the data amount of the reference frame is directly reduced without considering other factors, the quality of the frame decoded based on the reference frame would deteriorate, which causes significant degradation of the group of picture quality. In addition, in order to avoid the significant degradation of the group of picture quality, the memory size has to be increased, which inevitably increases the manufacturing cost.

Memory managing method and video data decoding method


A first aspect addresses a method and device for making a media file accessible via a web page. First, a web design tool receives a media file to be made accessible via a web page. Then, said media file is sent to a streaming service provider. Subsequently, a key generated by said streaming service provider allowing to unambiguously identifying said sent media file is received and an identifier derived from said key is placed into the web page through which the media file should be accessed. A second aspect addresses a method and device installed at the streaming service provider's side for serving a user's request for hosting a media file to be streamed to a visitor's computer on its request.

1. Field of the Invention
The present invention generally relates to an environment for automated generation of web pages interfacing rich media. Particularly, the present invention relates to a method and a device is provided for making a media file accessible via a web page and, correspondingly, to a method and device installed at the streaming service provider's side for serving a user's request for hosting a media file to be streamed to a visitor's computer on its request.
2. Description of the Related Art
Rich media data extends traditional computer data formats into more natural data formats for the interaction of humans and computers by incorporating images, motion pictures, voice, audio, and video. Leading market, business, social, and technical indicators point to the growing importance of such digitally recorded content.
Furthermore, rich media data is getting more and more pervasive in Internet applications. All those Internet applications have different requirements and use cases, but they are all working with alike content data. Due to this fact, Internet applications are getting really complex and not easily customizable to individual requirements.
One of the key issues with rich media data is, however, transferring the huge amount of data through a network. In the past, data is transferred using the store & forward paradigm, i.e., the complete content is transferred before the data is presented. A prominent implementation of this paradigm is the File Transfer Protocol (FTP), one of the standard ways to transfer files throughout the World Wide Web. For conventional data this works fine, as the amounts of data to be transferred are comparably small. For audio and video clips, though, the latency time that passes between a request for rendering and the start of the rendering gets impractically long.
A couple of years ago another paradigm called streaming has emerged. Streaming allows the rendering of media to take place in parallel with the transfer of its content, which reduces latency times to a minimum. Streaming software always comes in pairs, a stream server pumping data continuously through the network and a player receiving the data and rendering it.
The player is always the part requesting a streaming data connection. While establishing such a data connection, the client sends so called meta data to the stream server, which identifies the requested rich media data object. In general, the meta data is used by the stream server to find the rich media object within its cache, but the meta data can also contain further information like access tickets, bandwidth information, offsets within the media etc.
In order to ensure the quality of the data stream, which in general means that the required bandwidth could be written to the network throughout the entire stream duration, current stream server require the rich media data object to reside on the local file system. So, every stream server, which likes to stream a rich media data object has to keep a copy within its local disk cache. Furthermore, a stream server has to be aware of the available system resources like CPU, memory, disk I/O capabilities, network connectivity, etc. If a new streaming request exceeds one of its resources the request has to be rejected in order to ensure the quality of established data streams.
In a distributed scenario like the Internet there could be a long distance between the stream server and the player. The data has to be transferred over an unknown number of nodes with an unpredictable overall bandwidth. So-called edge-servers are established to solve such kind of problems.
As described above, the creation and configuration requirements become more and more complex by using rich media content data applied with the services required or offered combining rich media data within today's Internet applications. Moreover, the time to market for these rich media Internet applications becomes shorter and shorter which forces requirements to handle these infrastructure and administration requests in very short time periods to be accessed from all over the world.
What can be seen from the above descriptions is that rich media services require a very complex infrastructure. In order to get acceptable media streaming services, a huge amount of distributed servers (edge-servers), hosting proxies services, distribution and caching services, streaming services, billing services, advertising services and metering services—to enable short access latency time—are required.
Building up, operating and maintaining this infrastructure with 24/7 QOS is very complex and expensive and needs high skilled operation personal. The entire infrastructure needed to present rich media in the Internet is quite expensive. In some of the business models this leads to unacceptable expenses for the users using these media offerings.
Therefore systems are currently appearing which offer Media Services to companies wanting to stream rich media to their end users without having the necessity to install and maintain all the infrastructure for streaming like stream servers, edge servers etc. The company who wants to include rich media into their Web Site can upload the media by simply invoking a standardized Web Service preferably with the help of a SOAP/XML like interface. A key is returned referring to that media and the company has as a subsequent step to include a CGI script or servlet into their Web Site which interacts with a second Web Service to get the so called Meta Media which the CGI script or servlet has to send to the browser of the end user requesting the rich media, so that the browser can finally contact the Media Service in order to get the requested content streamed to his system.
What can be seen from the above said is, that it is rather complex for a Web Designer to include rich media, even if a Media Service is used. Specific servlets or CGI scripts have to be programmed and included in the HTML pages and the designer of the Web Page has to know about streaming technologies, Meta Media and their proprietary formats, SOAP and other media related areas.

Method and a device for making a media file accessible via a web page

International Business Machines Corporation


An antenna module is disclosed, including an electronic element, an antenna and a connecting element. The antenna includes a hole. The connecting element includes a first connecting portion, a propping portion and a second connecting portion. The first connecting portion passes through the hole and is fixed to the antenna by the propping portion. The second connecting portion is electrically connected to the electronic element.

1. Field of the Invention
The invention relates to an antenna module and a manufacturing method thereof, and more particularly to an antenna module fixed via mechanical coupling and a manufacturing method thereof.
2. Description of the Related Art
A conventional antenna module comprises an antenna, an electronic element, and a plastic assembly. The electronic element may be a printed circuit board, a cable or another antenna. The antenna is electrically connected to the electronic element by soldering or adhesive. Then, the antenna and the electronic element are covered by a plastic assembly via injection molding for protecting the inner elements thereof. The above-mentioned steps form the antenna module.
During injection molding, high temperature and high pressure are generated. The soldering and adhesive areas on the antenna, which can not bear the high temperatures and high pressures are melted and then sealed off, resulting in an imperfect contact or no signal. Thus, the conventional antenna has low manufacturing yields.

Antenna module and manufacturing method thereof


Stabilized particle reagents suitable for use in turbidimetric immunoassays are disclosed. The stabilized particle reagents contain functionalized polymer particles in which the surface of the particle has been modified with a molecular surface modifier having the structure: EQU R(OCH.sub.2 CH.sub.2).sub.n NH.sub.2. in which: R is --H, --CH.sub.3 or --CH.sub.2 CH.sub.3, and n is an integer between 2 and 10, inclusive. The stabilized particle reagents are resistant to premature or spontaneous aggregation during preparation or storage.

Agglutination, the reaction of bivalent antibodies with multivalent antigens to produce aggregates that can be detected and measured in various ways, has long been used to detect and quantify a wide variety of materials present in biological fluids. These materials, known generally as analytes, include drugs, drug metabolites, serum proteins, enzymes, and other materials of interest or clinical significance. With appropriate variations of the procedure either specific antigens or specific antibodies can be detected.
Increased sensitivity can be achieved by the use of particle reagents. A particle reagent typically consists of a latex particle containing an analyte, analyte derivative, or analyte analog on its surface. Although the analyte can be absorbed onto the surface of the latex particle, desorption during storage or use can produce variations in reagent properties that affect the sensitivity and reproducibility of the assay. Desorption problems can be overcome by covalently attaching an analyte, analyte derivative, or analyte analog to the surface of the particle. However, particle reagents in which the analyte, analyte derivative, or analyte analog is covalently attached to the surface of the particle can preaggregate during manufacture or not perform well in the intended assay. Preaggregation is an especially severe problem for particle reagents in which the covalently attached group is derived from a hydrophobic analyte.
To overcome the problem of preaggregation, functionalized polymer particles, in which the analyte, analyte derivative, or analyte analog is covalently attached to the surface of the particle by a hydrophilic linking agent, have been prepared. Hydrophilic diamines or polyamines have been used to attach groups that are either inherently amine-reactive or can be made amine-reactive by activation to epoxide-functionalized latex particles. Frey and Simons, U.S. Pat. No. 4,581,337, for example, disclose attachment of a theophylline derivative to epoxide-functionalized latex particles with hydrophilic diamine or polyamine linking agents.
The stability of the reagent is generally affected by several factors, including the amount of negative charge on the particle and the relative balance between hydrophilic and hydrophobic regions on the particle surface. Inclusion of excess hydrophilic diamine or polyamine during preparation of the functionalized polymer particle produces particles whose surface has been modified by reaction with the excess amine. Particle reagents containing these particles perform well in immunoassays, showing, for example, a rapid and precise agglutination rate when combined with an appropriate antibody.
In some cases, however, it is desirable to synthesize functionalized polymer particles from hydrophobic analytes that lack the amine-reactive functionality required for attachment by a hydrophilic diamine or polyamine linking agent. Particle reagents prepared with certain drugs or drug derivatives, particularly hydrophobic ones such as lidocaine, quinidine, procainamide, and derivatives of procainamide such as formyl procainamide, tend to aggregate during synthesis in the presence of excess hydrophilic diamine or polyamine, making them unusable in turbidimetric immunoassays. Thus, a need exists for stabilized polymer particles suitable for use in immunoassays that are not susceptible to premature aggregation.


A light source and method for fabricating the same are disclosed. The light source includes a die, a light conversion component, and a scattering ring. The die emits light of a first wavelength through a top surface of the die and one or more side surfaces of the die, and is bonded to a mounting substrate. The light conversion component converts light of the first wavelength to light of a second wavelength, the light conversion component having a bottom surface bonded to the top surface of the die. The light conversion component has lateral dimensions such that a space exists around the die, the space being bounded by the substrate and the light conversion component. The scattering ring is positioned in the space such that a portion of the light emitted from the side surfaces of the die is scattered into the light conversion component.

Light emitting diodes (LEDs) are attractive candidates for replacing conventional light sources such as incandescent lamps and fluorescent light sources. LEDs have substantially higher light conversion efficiencies than incandescent lamps and longer lifetimes than both types of conventional light sources. In addition, some types of LEDs now have higher conversion efficiencies than fluorescent light sources and still higher conversion efficiencies have been demonstrated in the laboratory. Finally, LEDs require lower voltages than fluorescent lamps, and hence, are better suited for applications in which the light source must be powered from a low-voltage source such as a battery or an internal computer DC power source.
Unfortunately, LEDs produce light in a relatively narrow spectral band. To replace conventional lighting systems, LED-based sources that generate light that appears to be "white" to a human observer are required. A light source that appears to be white and that has a conversion efficiency comparable to that of fluorescent light sources can be constructed from a blue LED that is covered with a layer of phosphor that converts a portion of the blue light to yellow light. Such light sources will be referred to as "phosphor converted" light sources in the following discussion. If the ratio of blue to yellow light is chosen correctly, the resultant light source appears white to a human observer. To provide the correct ratio, the thickness of the phosphor layer must be controlled. In addition, the uniformity of the phosphor layer over the die on which the LED is fabricated must be maintained to prevent variations in the color of the light over the light-emitting surface of the light source.
Cost, measured in terms of lumens of light produced per dollar, is an important concern in any light source that is directed to replacing conventional light sources. The cost of packaging the dies represents a significant fraction of the cost of the final light source. The packaging cost is increased by the need to capture light leaving the sides of the die. A significant fraction of the light produced in the blue LEDs used in phosphor converted light sources is trapped between the top and bottom surfaces of the die by internal reflection due to the difference in the index of refraction between the materials from which the dies are constructed and the surrounding medium. A significant fraction of this trapped light leaves the die through the sides of the die. To improve the light output of the die, a reflector is typically included in the light source to redirect the light leaving the side surfaces of the die such that the light leaves the die in the same direction as the light leaving the top surface of the die.
The packaging costs associated with providing a constant thickness of phosphor and a reflector are substantial. For example, in one design, the reflector is provided in the form of a cup that has reflective walls. The cup is mounted on a substrate that includes electrical traces for powering the die. A portion of the substrate is exposed through an opening in the bottom of the cup. The die is mounted on the portion of the substrate that is exposed through the bottom of the cup, and connected to the electrical traces. The cup is then filled with a suspension of phosphor particles in a material that can be cured to provide a solid layer of material in which the phosphor particles will remain suspended. Processes based on epoxy or silicone based materials for suspending the phosphor particles are known to the art.
These processes are difficult to automate in a manner that guarantees uniformity of the light emitted across the die. In particular, the fraction of the light that leaves the top surface of the die and is converted by the phosphor layer must be the same as the fraction of the light leaving the side surfaces of the die and is converted by the phosphor layer. In these processes, the phosphor layer is formed in the cup during the final assembly of the light sources on the light source assembly line by curing a carrier material that contains the phosphor particles. The phosphor particles tend to settle in the carrier material during the dispensing phase. To prevent the settling, the suspension must be augmented with various materials that slow the settling. In addition, the carrier must be formulated to provide a short curing time to prevent the particles from settling around the die in the cup. If the particles settle in the bottom of the cup, the amount of phosphor through which light leaving the sides of the die must pass is significantly different than the amount of phosphor through which the light leaving the top of the die must pass. As a result, the light that is redirected by the reflector has a different color than the light that leaves the top surface of the die. Hence, the light source exhibits a variation in color across the surface of the light source.
In addition, the process of providing individual cups for each die typically involves a number of additional fabrication steps. In the simplest designs, the cups are individually attached to the underlying substrate after the cups are fabricated. While designs in which the cups are created in a layer of material that is positioned over a number of dies have been suggested, the generation of the "cup layer" still represents a significant fraction of the cost of the final light source.

Method for fabricating a light source that includes phosphor-converted LED


A device for guiding a civil engineering/earthmoving machine using laser beams having a laser emitter and two laser receivers each mounted on a displacement unit mobile with two degrees of freedom. Two receiver position sensors are associated with each unit to measure its position with reference to two degrees of freedom and to generate signals representative of this position. A machine position sensor measures the position of the machine with reference to a fifth degree of freedom and generates a signal representing this position. A computer responsive to these signals stores the geometrical features of the surface over which the machine is guided and controls each receiver in two dimensions to maintain it centered on the beam from the laser emitter. The computer also generates in real time command instructions applied to actuators controlling the machine, on the basis of these geometrical features.

1. Field of the Invention
The present invention concerns a laser beam guidance device for a civil engineering/earthmoving plant controlled by means of actuators and required to move along a predetermined path having a three-dimensional surface, the device being of the kind using a laser emitter and two laser receivers.
2. Description of the Prior Art
A preferred but by no means exclusive application of the present invention is to guiding machines for surfacing roads or paths in three dimensions. These are wide machines (approximately 10 m wide) which at present are guided by means of wires stretched along either side of the road or path to be surfaced. These surfacing machines are well known and include, for example, the GP-2500 machine manufactured and marketed by the company Gomaco Corporation of Ida Grove, Iowa.
Using a guidance device of this kind is in practice somewhat complicated and time-consuming given the large number of operations required to lay the wires. Also, if the road or path is curved, the curve is approximated by a series of straight line segments along which the guide wires must be stretched, which increases the number of operations required to install and adjust the guidance device, especially when the machine reaches junctions between the segments.
One objective of the present invention is, therefore, to simplify the guidance device without requiring significant modification to the machine.
British Patent No. 2,228,507 discloses a surfacing machine embodying a tool adapted to be positioned heightwise relative to the machine and to the surface worked on, two laser receivers disposed on actuators mounted above the tool so that they move the laser receivers in a vertical direction, a device for measuring the distance travelled and logic responsive to signals from the receivers and the distance measuring device adapted to control the actuators. The laser receivers cooperate with a laser emitter mounted a predetermined height above the surface to be worked on and adapted to scan a laser beam in a reference plane.
The logic stores the required surface profile in memory. In response to logic signals transmitted by the laser receivers and the distance measuring device, the logic controls the actuators to maintain the receivers in the reference plane and positions the tool to shape the surface according to the stored profile.
Note that this machine can only position the tool relative to the reference plane along an axis perpendicular to the latter. It is, therefore, unable to guide the machine along a path or road with a three-dimensional surface. In particular, it is unable to guide the machine around a curve.
What is more, because the laser beam scans a large surface area and impinges on the receivers at two points only therein, much laser light energy is dissipated into the atmosphere. As the beam is not collimated at the receiver a high energy input is required to obtain a long range.
The present invention is directed to a guidance device implementing some of the teachings of British Patent No. 2,228,507 but adapted to guide a machine for shaping a three-dimensional surface, in particular for surfacing roads or paths, where the latter are curved, while being more efficient than the prior art machine described above.

Laser beam guidance device for civil engineering/earthmoving plant


The present disclosure discloses a method for preparing lenalidomide. The present disclosure provides a method for preparing lenalidomide I, which comprises the following steps: in a solvent, the lenalidomide intermediate II is reduced with a metal in the presence of an organic acid to obtain the lenalidomide I, wherein the metal is one or more selected from zinc, iron, aluminum and manganese. The preparation method of the disclosure has simple and safe operation, simple post-processing steps, environmental friendliness, high total yield. Moreover, the product obtained in the method has a purity of more than 99.90%, maximum single impurity of less than 0.10%, total heavy metal residue of less than 10 ppm and meet the heavy metal residue standard and API standard. Furthermore, the method has a low production cost and is suitable for industrial production.

Lenalidomide (Lenalidomide, I) is a new generation of anti-tumor drug developed by Celgene Biopharmaceutical Corporation in the United States, it is mainly used to treat myelodysplastic syndrome and multiple myeloma. On Dec. 27, 2005, FDA approved the lenalidomide capsules developed by Celgene to market through a rapid approval process. On Jun. 29, 2006, FDA approved lenalidomide combined with dexamethasone for the treatment of multiple myeloma patients who had previously received at least one treatment. As a first-line treatment of multiple myeloma, lenalidomide has been widely recognized by doctors and patients worldwide.

lenalidomide I was generally obtained as follows: lenalidomide intermediate II is synthesized by condensation of methyl 2-bromomethyl-3-nitrobenzoate and 3-amino-2,6-piperidinedione hydrochloride, and then reduced to lenalidomide I. The synthesis methods that have been reported under the existing technical conditions include patent literature WO2011050962 and so on.

In the above method, mental palladium catalyst was used for reduction hydrogenation, so that the residue defects of the metal palladium in the final product obtained in this process were relatively serious (39 ppm). Accordingly, additional steps to remove the metal palladium were necessary, accompany with low yield (total yield 55%) and increased production costs. In addition, the catalytic hydrogenation of the metal palladium requires a special equipment, which also limits the industrial production of lenalidomide. Therefore, it is necessary to find a method with simple operation, low cost and high yield for the preparation of lenalidomide I with high-purity and adapt to the needs of industrial production.

SHANGHAI BOCIMED PHARMACEUTICAL CO., LTD.


Methods and systems of ejecting ink drops from an inkjet printer are disclosed. The methods and systems can include a printhead with one or more tapered nozzles each with an associated taper angle and exit diameter. Ink can be received into the printhead and formed into ink drops in the tapered nozzles. The ink drops can each have an associated drop mass and drop speed. The tapered nozzles can be provided such that the exit diameter can independently dictate the drop mass and the taper angle can independently dictate the drop speed. As such, the complexity of jet design optimization is reduced.

In a conventional inkjet printer, a printhead has a series of droplet apertures or nozzles out of which the printing fluid or ink ejects to an image receiving substrate. Each nozzle can have a corresponding actuator for ejecting the ink through the nozzle. The ink drop mass, or size, and drop speed, or velocity, can influence the quality of the printing. For example, the drop mass and speed can affect drop placement and satellite formation. In inkjet printers with a constant diameter (cylindrical) nozzle, both the ejected ink drop mass and drop speed are dependent on the nozzle diameter. For example, an increase in nozzle diameter increases both the drop mass and drop speed of the ejected ink. As such, complicated design optimizations are undertaken to attempt to obtain an acceptable drop speed in conjunction with a desired drop mass.
As are known in the art, conventional tapered, or conical, nozzles can be used instead of cylindrical nozzles. The exit diameter of the conventional tapered nozzle, or the point at which the ink drop exits the nozzle, can be used to adjust drop mass. Further, the conventional tapered nozzle can increase drop speed and improve alignment tolerances. However, conventional tapered nozzle designs cannot maintain independent control of both the drop mass and the drop speed.
Thus, there is a need for a tapered nozzle design which can control the ink drop mass independently of the drop speed and reduce the need for complicated design optimizations.

Independent adjustment of drop mass and drop speed using nozzle diameter and taper angle


A dc-offset canceler circuit is provided, which cancels a dc offset more effectively. This circuit includes a first differential pair of emitter-coupled first and second bipolar transistors driven by a first constant current source/sink, and a second differential pair of emitter-coupled third and fourth bipolar transistors driven by a second constant current source/sink. The first and second differential pairs are coupled by a coupling capacitor. An emitter of a fifth bipolar transistor is connected to the emitters of the first and second transistors. An emitter of a sixth bipolar transistor is connected to the emitters of the third and fourth transistors. Bases of the first and fifth transistors are connected to a first input terminal. A base of the second transistor is connected to the first input terminal through a first resistor. Bases of the fourth and sixth transistors are connected to a second input terminal. A base of the third transistor is connected to the second input terminal through a second resistor. Collectors of the first, third, and sixth transistors are connected to a first output terminal, and those of the second, fourth, and fifth transistors are connected to a second output terminal.

1. Field of the Invention
The present invention relates to a dc-offset canceler circuit and a differential amplifier circuit and more particularly, to a dc-offset canceler circuit which is preferably used for an amplifier circuit amplifying a signal in a low-frequency region such as 1 kHz to 10 kHz (e.g., the baseband frequency region) in a portable telecommunication system such as a pager system, and a differential amplifier circuit equipped with the dc-offset canceler circuit.
2. Description of the Prior Art
In recent years, a direct conversion receiver has been popularly used as a portable radio receiver such as a pager instead of a conventional superheterodyne receiver.
A limiting amplifier circuit designed for a direct conversion receiver of a pager amplifies a signal in the baseband frequency region (typically, 1 kHz to 10 kHz). This limiting amplifier circuit has a configuration that a plurality of differential amplifier subcircuits are cascade-connected at a plurality of stages, in which the differential amplifier subcircuits located at two adjoining ones of the stages are directly coupled without coupling capacitors. This is due to the following reason.
The coupling capacitor needs to have a large capacitance for the signal in the baseband frequency region and as a result, this capacitor occupies a large area on an Integrated Circuit (IC) chip. Accordingly, the coupling configuration with the coupling capacitor having such the large capacitance is not suitable to ICs. On the other hand, the directly coupling configuration requires no coupling capacitor and therefore, no problem relating to the chip area will occur.
With the limiting amplifier circuit having the direct-coupling configuration, the "dc offset" generated in the differential amplifier subcircuits at the respective stages tends to cause some known problems. To solve the problems, various techniques have been studied and developed for a long time, an example of which is shown in FIG. 1.
FIG. 1 shows a conventional dc blocking amplifier circuit having a dc-offset canceling function, which is disclosed in the Japanese Non-Examined Patent Publication No. 2-305205 published in 1990.
As shown in FIG. 1, the conventional dc blocking amplifier circuit S300 includes a first differential amplifier subcircuit S100 and a second differential amplifier subcircuit S200, which are coupled together by an ac-coupling capacitor 113.
The first differential amplifier subcircuit S100 is comprised of an emitter-coupled pair of npn-type bipolar transistors 101 and 102. The coupled emitters of the transistors 101 and 102 are connected to one end of a constant current sink 111 sinking a constant current I.sub.101. The other end of the constant current sink 111 is connected to the ground.
A resistor 109 is connected to the bases of the transistors 101 and 102. The base of the transistor 101 is further connected to a first input terminal 114. The base of the transistor 102 is further connected to one end of the coupling capacitor 113.
The second differential amplifier subcircuit S200 is comprised of an emitter-coupled pair of npn-type bipolar transistors 103 and 104. The coupled emitters of the transistors 103 and 104 are connected to one end of a constant current sink 112 sinking a constant current I.sub.102. The other end of the constant current sink 112 is connected to the ground.
A resistor 110 is connected to the bases of the transistors 103 and 104. The base of the transistor 103 is further connected to the other end of the coupling capacitor 113. The base of the transistor 104 is further connected to a second input terminal 115.
First and second input voltages are differentially applied across the first and second input terminals 114 and 115, respectively.
Collectors of the transistors 101 and 103 are coupled together to be connected to an end of a load resistor 107. The other end of the load resistor 107 is applied with a power supply voltage V.sub.CC. The coupled collectors of the transistors 101 and 103 are further connected to a first output terminal 116.
Collectors of the transistors 102 and 104 are coupled together to be connected to one end of another load resistor 108. The other end of the load resistor 108 is applied with the power supply voltage V.sub.CC. The coupled collectors of the transistors 102 and 104 are further connected to a second output terminal 117.
First and second output voltages are differentially derived from the first and second output terminals 116 and 117, respectively.
The transistors 101, 102, 103, and 104 have a same emitter area.
Next, the operation of the conventional dc blocking amplifier circuit S300 in FIG. 1 is explained below.
First, base voltages of the transistors 101, 102, 103, and 104 with respect to a specific reference point (e.g. the ground) are defined as V.sub.B101, V.sub.B102, V.sub.B103, and V.sub.B104, respectively. Collector currents of the transistors 101, 102, 103, and 104 are defined as I.sub.C101, I.sub.C102, I.sub.C103, and I.sub.C104, respectively. First and second output currents flowing through the load resistor 107 and 108 are defined as I.sub.C113 and I.sub.C124, respectively.
Then, the following equations (1) and (2) are established. EQU I.sub.C113 =I.sub.C101 +I.sub.C103 ( 1) EQU I.sub.C124 =I.sub.C102 +I.sub.C104 ( 2)
The collector currents I.sub.C101, I.sub.C102, I.sub.C103, and I.sub.C104 of the transistors 101, 102, 103, and 104 are expressed as the following equations (3), (4), (5), and (6), respectively. ##EQU1##
In the equations (3), (4), (5), and (6), .alpha. is the dc common-base current gain factor of each transistor, k is the Boltzmann's constant, T is absolute temperature in degrees Kelvin, and q is the charge of an electron. Typically, the gain factor a is approximately equal to 1.
When the constant current I.sub.102 of the constant current sink 112 is equal to the constant current I.sub.101 of the constant current sink 111 (i.e., I.sub.101 =I.sub.102), and the difference between the base voltages V.sub.B104 and V.sub.B103 of the transistors 104 and 103 are equal to the difference between the base voltages V.sub.B101 and V.sub.B102 of the transistors 101 and 102 (i.e., V.sub.B101 -V.sub.B102 =V.sub.B104 -V.sub.B103), the first and second output currents I.sub.C113 and IC.sub.124 become equal to each other. If the load resistors 107 and 108 have a same resistance, the first and second output voltages will have a same dc level at the first and second output terminals 116 and 117.
If the dc voltage level of the first input voltage at the first input terminal 114 is higher than that of the second input voltage at the second input terminal 115 due to a dc offset, the base voltages V.sub.B101, V.sub.B102, V.sub.B104, and V.sub.B103 satisfy the relationships of
V.sub.B101 >V.sub.B102 and PA1 V.sub.B104 <V.sub.B103.
In this case, the collector current I.sub.C101 increases by an increment and the collector current I.sub.C102 decreases by the same increment in the first differential amplifier subcircuit S100. At the same time, the collector current I.sub.C103 increases by an increment and the collector current I.sub.C104 decreases by the same increment in the second differential amplifier subcircuit S200. Therefore, the first output current I.sub.C113 is increased and the second output current I.sub.C124 is decreased.
Thus, the dc voltage level at the first output terminal 116 is lowered and that at the second output terminal 117 is raised, thereby canceling the dc-voltage level difference (i.e., the dc offset) at the first and second input terminals 114 and 115. This means that no dc offset is generated between the first and second output terminals 116 and 117 even if the dc offset exists between the first and second input terminals 114 and 115.
The dc voltage levels at the first and second output terminals 116 and 117 are determined by a specific dc bias voltage applied to the conventional dc blocking amplifier circuit S300.
The same explanation as above is applied to the case where the dc voltage level at the first input terminal 114 is lower than that at the second input terminal 115.
However, the conventional dc blocking amplifier S300 in FIG. 1 has the following problem.
If any difference is generated between the constant currents I.sub.101 and I.sub.102 of the constant current sinks 111 and 112 (i.e., I.sub.101 .noteq.I.sub.102) due to the dc-voltage level difference greater than a specific value at the first and second input terminals 114 and 115, there arises a problem that a dc offset tends to occur between the first and second output terminals 116 and 117. It was found by the inventor that this problem is caused by the fact that the transistors forming one of the constant current sinks 111 and 112 operate in the saturation region while those forming another one of the constant current sinks 111 and 112 operate in the active region, resulting in some difference between the constant currents I.sub.102 and I.sub.102.
The dc bias offset thus generated at the first and second output terminals 116 and 117 is amplified by a differential amplifier located at a next stage. Therefore, there arises a disadvantage that the gain of the amplifier at the next stage needs to be set as sufficiently low.
Because of this problem, the conventional dc blocking amplifier S300 in FIG. 1 is not suitable to a dc-offset canceler for the limiting amplifier of the above sort.
Additionally, the difference between the constant currents I.sub.101 and I.sub.102 of the constant current sinks 111 and 112 may occur due to any other cause such as the unbalance in device layout of the current sinks 111 and 112.

DC-offset canceler circuit and differential amplifier circuit equipped therewith


A media server having at least one of a stride-based storage device space allocation scheme, stride-based method of striping data across multiple storage devices for continuous media streaming, server-based smoothing of variable bit-rate streams, distributed architecture, and fault tolerance.

Spatial and temporal compression have made practical the storage and transfer of digital video streams with acceptable quality. Standardization (for example, through the MPEG specifications) has facilitated widespread distribution and use of compressed video content in a range of applications from studio post-production editing to home entertainment (e.g. Digital Versatile Disks). Although media streams can optionally be encoded at a constant bit rate, it has been shown that equally acceptable quality can be achieved using variable bit-rate encoding with average bit rates reduced by 40%.
As the installed network bandwidth increases, scalable network servers are becoming the dominating bottleneck in the wide deployment of broadband services. Therefore, the potential scalability of network servers that support variable bit-rate media streams is becoming a fundamental problem.
System design complications coupled with excessive expectations from technological progress previously discouraged the development of media servers efficiently supporting video streams with variable bit rates. Several media server designs either i) support only constant bit-rate streams, ii) make resource reservations assuming a fixed bit rate for each stream, or iii) have only been demonstrated to work with constant bit rate streams.
It is therefore an aspect of an object of the present invention for providing a distributed continuous-media server architecture, called Exedra, that efficiently supports variable bit-rate streams and reduces the requirements for storage device space, storage device bandwidth, buffer space, and network bandwidth with respect to servers that support only constant bit-rate streams.
Vast storage and bandwidth capacity requirements of even compressed video streams make it necessary to stripe video files across multiple storage devices. Assuming that a media storage server serves requests for several different stream files, appropriate striping makes it possible to scale the number of supported streams to the limit of the server resources, independent of the particular stream file being requested by clients. This is possible by retrieving different parts of each stream file from different storage devices, thus restricting the degree of imbalance in utilization among the storage devices.
However, it has been previously shown that both load imbalance across disks and disk overhead is causing disk striping of variable bit-rate streams to be efficient only on disk arrays of limited size. Therefore, the scalability of network servers that stripe variable bit-rate streams across multiple storage devices is a fundamental problem.
It is an aspect of an object of the present invention for providing a new storage device space allocation technique and striping policies for variable bit-rate streams that increase system throughput and improve scalability.
The Internet and online services introduce increasing requirements for quality-of-service guarantees in order to ensure that a failure does not result in denial of service for clients. Hard drives or storage devices continue to be a major source of failure. This is not surprising since disks are essentially the only moving mechanical parts of computers.
It is therefore an aspect of an object of the present invention for providing fault tolerance in storage device arrays and clusters of computer nodes that support variable bit-rate streams.
Variable bit-rate encoding of video streams can achieve quality equivalent to constant bit-rate encoding while requiring average bit rate that is lower by 40%. However, variable bit-rate streams have high variability in their resource requirements, which can lead to low utilization of storage device and network bandwidth in the common case. This occurs because the aggregate bandwidth requirements of concurrently served streams can be significantly higher than on average at particular time instances, and the admission control process bases its decisions on peak aggregate demand when considering new stream requests.
In order to improve resource utilization and the throughput of the system, a number of smoothing techniques have been proposed that can remove peaks in the required transfer bandwidth of individual streams by appropriately prefetching stream data at times of lower bandwidth demand. To date smoothing schemes always prefetched data into the client buffers. Although such an approach can improve the utilization of both storage device and network bandwidth, it is dependent on the amount of buffer space available at the client. However, emergence of client devices with widely different hardware configurations make it necessary to reconsider such assumptions.
It is therefore an aspect of an object of the present invention a smoothing method that uses buffer space available in the server and provides efficient striping of variable bit-rate streams across either homogeneous or heterogeneous storage devices.