An arrangement for activation of a thermotransfer print head has a unit to determine a transport delay and a unit to generate supplementary heating pulses to maintain a temperature required for printing at the thermo-printing heating elements. The unit to determine a transport delay is connected with the thermotransfer print head via the unit to generate supplementary heating pulses. A method for activation of a thermotransfer print head includes the steps of determining a transport delay and generating supplementary heating pulses for maintenance of a temperature necessary for printing at the thermo-printing heating elements for which a printing requirement is present.

1. Field of the Invention
The present invention concerns an arrangement for activation of a thermotransfer print head as well as a method for activation of a thermotransfer print head. The invention is particularly suited for use in franking machines, address machines and similar accounting or mail processing apparatuses.
2. Description of the Prior Art
The thermotransfer franking machine T1000 manufactured by Francotyp-Postalia has a thermotransfer print head, mounted fixed in a housing, for printing a franking imprint and a tray, externally attached to the housing, to accept an exchangeable thermotransfer ink ribbon cartridge. The tray encloses a non-secure region. A mail piece is moved through the printing station synchronized with the thermotransfer ink ribbon, the movement being monitored by a detector that generates an output signal representing a parameter proportional to the ribbon movement (European Application 18 92 69 equivalent to U.S. Pat. No. 4,705,417).
Although a door leading to the tray can be opened at any time, access to the secure region of the printing device is prevented by a security housing. Due to the security housing, no special security measures must be taken to protect the activation and data signals for the print head that allows a printing of fixed, semi-permanent and variable information (U.S. Pat. No. 4,746,234).
For the thermotransfer print head, it is known from German OS 05 38 33 746 to integrate an internal switching unit, charged via an external activation unit, into the print head that contains the thermo-printing heating elements in a single row, which enables a selective activation with pre-heating of the thermo-printing heating elements to reduce the heat output upon printing. The resistance heating elements are directly pre-heated to a pre-heating temperature with a clock frequency adapted (in terms of pulse amplitude and pulse width) to the necessary heat energy. At the end of the printing time, the pre-heating temperature is maintained with such a clock frequency.
A method for control of the feed of a thermo-printing heating element is disclosed in European patent 536 526 B1. A print requirement is determined in advance at the respective raster points in time of a predetermined print raster. An output of current pulses to the respective thermo-printing heating elements ensues both for the raster points in time without a print requirement and for the raster points in time with a print requirement. The current pulses (pre-heating pulses) (which are output according to a specific algorithm before a raster point in time with a print requirement) effect a pre-heating of the respective thermo-printing heating element up to a temperature just below a limit temperature at which a print point is delivered by a thermotransfer ink ribbon and is visible on a carrier material (mail piece). Pre-heating pulses cannot be output in a sequence that is too fast nor at intervals that are too large for the respective thermo-printing heating element, because otherwise the aforementioned limit temperature would be exceeded or undershot. In the first case, the print image appears too heavy and smeared. In the second case the print image is too thin and pale because by itself the main printing pulse effects only a short-term exceeding of the limit temperature at the raster point in time with a print requirement.
A method is also known wherein a predetermined pre-heating temperature is maintained in the printing pauses at the respective heating element by means of pre-heating and post-heating pulses (German OS 38 33 746).
A controller that, dependent on the print head temperature, influences the pulse width or amplitude of the heating pulses in order to achieve overheating protection is known from U.S. Pat. No. 4,510,507 and German OS 33 27 904.
A print head thermo-controller is disclosed in European Patent 730 972 wherein the power electronic associated with the print control unit regulates the amplitude of the print head voltage, corresponding to the environment temperature and is combined with a control unit that operates according to an anticipatory control algorithm for feeding individual thermo-printing heating elements with pre-heating pulses and printing pulses of variable pulse duration.
For such a franking machine, a method and arrangement for fast generation of a security imprint are disclosed in the European Patent EP 576 113. The method enables embedding of variable data during the printing of the security imprint, but this then allows only a brief projection to determine a print requirement.
Very high requirements are placed on a security imprint by some postal authorities, in particular with regard to its machine-readability and communications about auxiliary services of the postal carrier that can change from letter to letter. Since April 2004, Deutsche Post AG has promoted the launch of the first franking machines in Germany with a digital indicium "FRANKIT": (/www.deutschepost.de/download/broschueren/20403000_Frankit_Folder.pdf). The following are encrypted in a matrix code:                a) all specifications readable in plain text, such as date, postage value etc.,        b) information regarding the franking type, product code, current shipment number, machine identification and serial number,        c) copy protection information.
Such a security imprint contains previously entered and stored postal information including the postal rate data for transport of the letter and, if applicable, a marking with security information. In modern franking machines, the accounting and storage of postal rate data (European Application 789 333) and internal security measures (U.S. Pat. No. 6,351,220, and German Utility Models 299 05 219, and 201 12 350) are implemented and the aforementioned security information are generated (German OS 199 28 058, U.S. Pat. No. 6,041,704) by a postal security module arranged inside the meter housing. The prior calculation of security information requires a majority of the time in the postal security module, and thus the security information is available for embedding into the print image only relatively late. Even a partial prior calculation of security information well before a franking by the franking machine can not prevent that the matrix code in the marking field from changing from mail piece to mail piece. This makes it more difficult to still determine a print requirement in advance in a timely manner. The printout of a machine-readable matrix code requires a higher number of raster points in time, corresponding to the higher print resolution, which is associated with a higher computing capacity. A requirement for a 25-50% faster mail piece transport also has a detrimental effect. The raster points in time follow one another in shorter intervals the higher the selected mail piece transport speed. If the thermo-printing heating elements are pre-heated by means of pre-heating pulses up to a preheating temperature up to relatively close to the aforementioned limit temperature without exceeding the latter, the maximum possible duration of the pre-heating pulses is limited by the reduced intervals between the successive main heating pulses. The (in practice controllable) maximum possible pre-heating pulse height is likewise limited. Conventional methods for thermotransfer printing control the temperature at the individual thermo-printing heating elements of the print head via the most varied methods. Given a high print image resolution and transport speed, the print image of the first print columns appears to be printed more faintly at the beginning of the printing than in the remaining print columns of a stamp imprint. Moreover, a wave-shaped repeating attenuation in the print pattern (Ratter effect) acts in an interfering manner in the remaining print columns the higher and more non-uniform the mail piece transport speed is during the printing. If a transport delay occurs for any reason, the resistance heating elements that generate the print image points (dots) cool, and given further printing a section of the print pattern is printed that appears somewhat fainter since the temperature is no longer reached. This can only then be adjusted again after more than one further print column has been printed.

Arrangement and method for activation of a thermotransfer print head


An assembly for packaging a catheter having a flexible distal shaft and a proximal fitting coupled thereto comprises a flexible tube capable of being coiled and having a proximal end. A tubular retainer having a passageway extending therethrough has a substantially oval proximal section and a substantially circular distal section, the distal section for fittingly receiving the proximal end of the flexible tube. A resilient member is coupled to a wall of the retainer and projects into the passageway for controllably impeding movement through the passageway.

Catheters may be inserted into a patient's vasculature and deployed at various locations within the patient for a wide variety of purposes and medical procedures. For example, one type of catheter is used in percutaneous catheter intervention (PCI) for the treatment of a vascular constriction generally known as a stenosis. In this instance, the catheter has a distally mounted balloon that can be placed, in a deflated or collapsed condition, within the stenosis, and then inflated or expanded to dilate the narrowed lumen of a blood vessel. This type of balloon dilation therapy is generally referred to as percutaneous transluminal angioplasty (PTA). When the treatment is more specifically intended for vessels of the heart, the process is known as percutaneous transluminal coronary angioplasty (PTCA). PTCA is utilized to open coronary arteries that have been occluded by a build up of cholesterol fats and atherosclerotic plaque. The balloon at the distal end of the catheter is inflated causing a widening at the site of the stenosis.
Dilation of an occlusion, however, can form flaps, fissures, and dissections, that may result in reclosure of the dilated vessel or even perforations in the vessel wall. Implantation of a stent can provide support for such flaps and dissections and thereby prevent reclosure of the vessel or provide a patch repair for a perforated vessel wall until corrective surgery can be performed. The stent is typically a cylindrically shaped device formed from wire(s) or a metal tube and is intended to act as a permanent prosthesis. The stent is deployed in a body lumen in a radially compressed configuration and is subsequently radially expanded to contact and support a body lumen. The stent can be implanted during an angioplasty procedure by using a balloon catheter having deployed thereon a compressed stent that has been loaded onto the balloon. The stent radially expands as the balloon is inflated thus forcing the stent into contact with the body lumen and forming a supporting relationship with the lumen walls. Alternatively, self expanding stents may be deployed with a sheath-based delivery catheter. Deployment is effected after the stent has been introduced percutaneously, transported transluminally, and positioned at a desired location by the delivery catheter. In addition to angioplasty and stenting procedures, other therapeutic procedures require the use of a delivery catheter; e.g. drug delivery devices, filters, occlusion devices, diagnostic devices, and radiation treatment.
Typically, the placement of such therapeutic delivery catheters involves the use of a guide wire that may be inserted into a patient's vasculature through the skin and advanced to the location of the treatment site. The delivery catheter, which has a lumen adapted to receive the guide wire, is then advanced over the guide wire. Alternatively, the guide wire and delivery catheter may be advanced together with the guide wire protruding from the distal end of the delivery catheter. In either case, the guide wire serves to guide the delivery catheter to the location to be treated.
There are four general types of catheters; i.e. Over The Wire (OTW) catheters, Multi-Exchange (MX) catheters of the type, for example, disclosed in U.S. Pat. No. 4,988,356 issued Jan. 29, 1991 and entitled "CATHETER AND GUIDE WIRE EXCHANGE SYSTEM" and U.S. Published Patent Application No. 2003/0191491A1 published Oct. 9, 2003 and entitled "CATHETER AND GUIDE WIRE EXCHANGE SYSTEM"; rapid exchange catheters, and fixed wire or a balloon on a wire catheters.
OTW and rapid exchange catheters require use of a guide wire separate from the catheter while a fixed wire or balloon on a wire catheter has an integral guide wire. An OTW catheter comprises a guide wire lumen that extends the entire length of the catheter. The guide wire extends through the catheter guide wire lumen, and the distal and proximal portions of the guide wire extend beyond the distal and proximal ends of the catheter respectively. An MX catheter has an over-the-wire configuration while the catheter is within a patient's body. Thus, the guide wire is disposed entirely within the catheter wire lumen except for the distal and proximal portions of the guide wire that extend beyond the distal and proximal ends of the catheter respectively when the catheter is fully inserted into the patient.
OTW and MX catheters have many advantages traceable to the presence of the full length guide wire lumen, such as sufficient stiffness and pushability for readily advancing the catheter through the torturous vasculature and across tight stenosis. The full-length guide wire lumen permits removal and replacement of the guide wire in an indwelling catheter, as may be required to alter the shape of the guide wire tip. It is also sometimes desirable to exchange one guide wire for another guide wire having a different stiffness. For example, a relatively soft or flexible guide wire may prove to be suitable for guiding a PTCA catheter through a particularly tortuous anatomy, whereas following up with a stent delivery catheter through the same vasculature region may require a guide wire that is relatively stiffer.
Traditional over-the-wire catheters do have some shortcomings, however. For example, it often becomes necessary, in the performance of a PCI, to exchange one indwelling catheter for another. In order to maintain a guide wire in position while withdrawing the catheter, the guide wire must be gripped at its proximal end to prevent it from being pulled out of the blood vessel with the catheter. For example, a PTCA catheter that may typically be in the order of 135 centimeters long is longer than the proximal portion of the standard guide wire that protrudes out of a patient. Therefore, exchanging an over-the-wire PTCA catheter requires an exchange guide wire of about 300 centimeters long, whereas a standard guide wire is approximately 175 centimeters long.
In one type of over-the-wire catheter exchange, the standard length guide wire is first removed from the lumen of the indwelling catheter. Then, a longer exchange guide wire is passed through the catheter to replace the original wire. While holding the exchange guide wire by its proximal end to control its position in the patient, the catheter is withdrawn proximally from the blood vessel over the exchange guide wire. After the first catheter has been removed, the next OTW catheter is threaded onto the proximal end of the exchange guide wire and is advanced along the exchange guide wire, through the guiding catheter and into the patient's blood vessel until the distal end of the catheter is at the desired location. The exchange guide wire may be left in place or it may be exchanged for a shorter, conventional length guide wire. In an alternative type of catheter exchange procedure, the length of the initial guide wire may be extended by way of a guide wire extension apparatus. Regardless of which exchange process is used, the very long exchange guide wire is awkward to handle, thus requiring at least two operators to perform the procedure.
A balloon catheter capable of both very fast exchange and simple guide wire and catheter exchange is particularly advantageous, and catheters designed to address these needs are sold by Medtronic Vascular of Santa Rosa, Calif. under the trademarks MULTI-EXCHANGE, ZIPPER MX, ZIPPER AND/OR MX. Such a catheter is shown and described in the above referenced U.S. Pat. No. 4,988,356 which is incorporated herein by reference in its entirety. An MX catheter includes the catheter shaft having a cut that extends longitudinally between the proximal end and the distal end of the catheter and extends radially from the catheter shaft outer surface to the guide wire lumen. A guide member coupled to the catheter shaft functions to temporarily open the cut such that the guide wire may extend transversly into or out of the cut at any location along its path. By moving the proximal shaft through the guide member, the effect of the over-the-wire length of the MX catheter is adjustable.
When using the MX catheter, the guide wire is maneuvered through the patient's vascular system such that the distal end of a guide wire is positioned across the treatment site. With the guide member positioned near the distal end of the catheter, the proximal end of the guide wire is threaded into the guide wire lumen opening at the distal end of the catheter and through the guide member such that the proximal end of the guide wire protrudes out the proximal end of the guide member. By securing the guide member and the proximal end of the guide wire in a fixed position, the catheter may then be delivered over the guide wire by advancing the catheter toward the guide member. In so doing, the catheter advances through the guide member such that the guide wire lumen envelopes the guide wire as the catheter is advanced in to the patient's vasculature. In a PTCA embodiment, the MX catheter may be advanced over the guide wire until the distal end of the catheter having the dilation balloon thereon if positioned within the stenosis and essentially the entire length of the guide wire is encompassed within the guide wire lumen. Furthermore, the indwelling MX catheter may be exchanged with another catheter by reversing the operation described above. To this end, the indwelling catheter may be removed by withdrawing the proximal end of the catheter from the patient while holding the proximal end of guide wire and the guide member in a fixed position. When the catheter has been withdrawn to the point where the distal end of the cut has reached the guide member, the distal portion of the catheter over the guide wire is of a sufficiently short length that the catheter may be drawn over the proximal end of the guide wire without releasing control of the guide wire or disturbing it's position within the patient. After the catheter has been removed, another MX catheter may be threaded onto the guide wire and advanced over the guide wire in the same manner described above with respect to the MX catheter. The MX catheter not only permits a catheter exchange without the use of a very long exchange guide wire and without requiring withdrawal of the initial placed guide wire, but it also overcomes many other difficulties discussed in association with rapid exchange catheters described below.
Rapid exchange catheters were developed in an attempt to eliminate the need of a guide wire extension or exchange wires. Catheters of this type are formed so that the guide wire is located outside of the catheter except for a short guide wire lumen that extends within only a comparatively short, distal segment of the catheter. The rapid exchange catheter's proximal exit port is typically located about 5 centimeters to 30 centimeters proximal to the catheter's distal end. In use, the guide wire is typically placed in the patient's vascular system. The distal segment of the rapid exchange catheter is then threaded onto the wire. The catheter can be advanced alongside the guide wire with its distal segment being attached to and guided along the guide wire. The rapid exchange catheter can be removed and exchanged for another rapid exchange catheter without the use of a very long exchange guide wire and without required withdrawal of the initially placed guide wire.
A difficulty associated with rapid exchange catheters is that it is not possible to exchange guide wires in an indwelling rapid exchange catheter, as can be done advantageously with OTW catheters. A guide wire can be withdrawn, sometimes unintentionally, from the proximal guide wire port, thus derailing an indwelling rapid exchange catheter. However, neither the first guide wire, nor the replacement guide wire, can be directed back into the catheters proximal guide wire port that is hidden remotely in the guiding catheter within the patient.
Guide wires are commonly back loaded into the delivery catheter. In this operation, the guide wire proximal end is inserted into the distal tip of the catheter. It is pushed through the catheter until it extends out of the proximal guide wire exit. In a traditional over-the-wire catheter, the proximal guide wire exit is in the proximal end of the catheter through its inflation luer. The rapid exchange proximal guide wire exit is the termination of the short guide wire tube a few centimeters (typically 25 centimeters) beyond the distal tip of the catheter. In the MX catheter, the proximal guide wire exits through the guide member position on the proximal shaft of the catheter. As an alternative to back loading a guide wire into the delivery system, a guide wire may also be front-loaded. In a front-loading operation, the distal tip of the guide wire is inserted into the guide wire lumen on the proximal shaft and pushed through until it exits the distal tip of the delivery catheter. A front-loading operation is possible with OTW and MX catheters if the guide wire will be exchanged during procedures. A front-loading operation is not used with a rapid exchange catheter since the guide wire cannot be exchanged while the catheter is inserted into the patient. With a rapid exchange catheter, the insertion of the distal tip into the proximal end of an indwelling catheter guide wire lumen is pure chance due to the fact that the proximal end is typically 125 centimeters from the exit location of the catheter from the patient at the femoral artery in the patient's groin.
Over-the-wire and rapid exchange catheters are commonly packaged and stored in a packaging hoop that consists of coiled tubing into which the catheter is inserted. A fitting located at the proximal end of the catheter is provided with a distal hub that fits into an opening in the tubing thus securing the catheter in the hoop. However, the guide member of an OTW/SW catheter may have a diameter greater than the diameter of the tubing used in the standard catheter hoop and, as a result, the guide member will not fit into the tubing opening and the distal hub will be unable to secure the catheter.
In an attempt to overcome this problem, a packaging component has been developed that may be secured to an open end of a coiled tube and is configured to receive the guide member therein. The packaging component comprises a tubular body having a passageway extending therethrough comprised of a first cavity and a second cavity. The first cavity is sized to receive the guide member therein, and the second cavity has at least one resilient arm projecting into the passageway. The resilient arm prevents movement of the guide member through the second cavity unless sufficient force is supplied to overcome the force of the resilient arm. A device of this type is shown and described in U.S. patent application Ser. No. 10/251,575 filed on Sep. 20, 2002 and assigned to the assignee of the present invention.
This packaging component has an opening therethrough which is generally tubular having a longitudinal axis, and the cross section of this opening is substantially circular. Thus, the fitting may be inserted into the packaging component along its longitudinal axis and at any angle of rotation with respect to the longitudinal access. That is, the fitting may be freely rotated within the packaging component or retainer about its longitudinal axis. This, however presents certain problems. For example, when an operator is loading a catheter into the hoop through the retainer, the fitting can be inserted into the retainer at any angle with respect to the periphery of the retainer (i.e. 360 degrees of freedom). Any rotation of the fitting with respect to the catheter shaft could result in a twisting of the catheter shaft resulting in a damaged catheter. Furthermore, an operator may couple the catheter fitting to an inflation device before removing the catheter from its packaging possibly causing unwanted twisting of the catheter and likewise resulting in catheter damage.
Accordingly, it would be desirable to provide an improved packaging assembly for an OTW/SW catheter which not only provides a relatively stable guide member traction force over time, but one that also prevents unwanted twisting of the catheter fitting with respect to the catheter shaft. Other desirable features and characteristics of the present invention will become apparent from the following detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.


A delay locked loop includes a variable delay line circuit configured to delay a pulse selection circuit output to generate an output signal, a delay model circuit to delay the output signal to generate a first feedback signal, a first phase comparator circuit to control the variable delay line circuit according to the input signal and the first feedback signal, a pulse generation circuit to generate a pulse signal according to the input signal and the first feedback signal, a pulse retainer circuit to delay the output signal to generate a second feedback signal, a pulse selection circuit to select the pulse signal generated by the pulse generation circuit or the second feedback signal as the pulse selection circuit output during the tracking operation, and a second phase comparator circuit to control the variable delay line circuit according to the pulse selection circuit output and the output signal.

1. Technical Field
Various embodiments generally relate to a delay locked loop, and more particularly, to a delay locked loop with a shorter tracking time.
2. Related Art
FIG. 1 is a block diagram showing a conventional delay locked loop (DLL). The conventional delay locked loop 10 includes a variable delay line circuit 11 for adjusting a delay time of an input signal iCLK in response to a control signal code and generating an output signal rCLK, a delay model circuit 12 for delaying the output signal rCLK and outputting a feedback signal fbCLK, and a phase comparator circuit 13 for generating the control signal code based on a phase difference between the feedback signal fbCLK from the delay model circuit 12 and the input signal iCLK.
The conventional delay locked loop 10 executes a tracking operation to determine a delay amount of the variable delay line circuit 11 by initially performing several feedback operations. In the conventional delay locked loop 10, the signal rCLK outputted from the variable delay line circuit 11 is delayed by a given time, which is determined by the delay model circuit 12, before being transmitted to the phase comparator circuit 13. Several feedback operations are performed to complete the tracking operation, and the delay of the delay model circuit 12 accumulates as the several feedback operations are performed. As a result, the tracking time increases.

Industry-Academic Cooperation Foundation, Yonsei University


A routing device for forwarding data packets in a communication system includes a set of routing processors at least one interface that receives and transmits data packets and a routing table manager that maintains a forwarding table of routes provided by the set of routing processors. Each routing processor is associated with a routing protocol that determines a set of routes. The routing device may also include a set of fast forward engines that forward a data packet based on the forwarding table. The routing table manager may be implemented on a separate processor than each routing processor.

In today's information age it is typical for computers to be internetworked over a communication network. Communication networks utilize many data forwarding devices (e.g., routers and switches) to forward data messages (also referred to herein as packets) within the communication network. A router acts as a gateway between two or more network segments, and processes packets according to addressing information contained in the packets. Among other things, such forwarding devices include both routing software and a corresponding routing hardware platform that cooperate to forward packets to their appropriate destinations.
FIG. 1 shows a communication system including a number of routers. The communication system includes edge routers (ER1 (102), ER2 (106), ER3 (108), ER4 (110)) and routers R1 (104) and R2 (104) within Network A (112) and routers R3 (104) and R4 (104) within Network B (114). An edge router, such as ER1 (102), routes data between local networks, such as Network A (112) and Network B (114) and to the routers within particular networks. Typically, data packets are routed through a communication network using a networking protocol such as the Internet Protocol (IP).
When a router (e.g., router ER1 (102)) receives a packet from a particular network segment, the router determines whether to drop the packet, process the packet, or forward the packet. Specifically, the router may drop the packet if the packet is destined for the same network segment from which it was received. The router may forward the packet if the packet is destined for a different network segment. The router may process the packet if the packet is destined for the router itself. In order to forward packets, a router uses a routing protocol, such as Open Shortest Path First (OSPF) or Roufing Information Protocol (RIP), to determine network routes and uses the network routes to build and maintain a forwarding table. The forwarding table includes forwarding entries mapping each destination address to a corresponding router interface based upon the network routes. Alternatively, packets of information may be routed using a label switching protocol such as multiprotocol label switching (MPLS). Label switching allows a packet to be transported across a network domain using labels rather than the network layer address.
Often when processing routes in a communication network, bottlenecks may occur at a router or routers within the network due to limited resources. For example, when only one processor in a device is used for multiple routing tasks, the processor spends a significant portion of time waiting on other tasks. The exponential growth of today's communication networks (e.g., the Internet) demands scalability beyond what current architectures are able to sustain. Routers often become obsolete prematurely because they are unable to handle the growth of the Internet. Network management complexity is holding up mass deployment of networking products. The tolerance for downtime due to hardware and software upgrades may be very expensive. Software solutions can become very complicated and are difficult to manage as the performance needs of the routing device grow.


Disclosed herein are pharmaceutical compositions and methods for inhibiting oxidative stress in a subject having atrial or ventricular arrhythmias, ventricular failure or heart failure. The methods include administering an effective amount of a NOX2 inhibitor agent to the subject, wherein said administering is under conditions such that a level of oxidative stress in myocardial tissue is reduced or eliminated. The pharmaceutical compositions include a NOX2 inhibitor agent.

Atrial Fibrillation (AF) is the most common heart rhythm disorder (Benjamin E J, Levy D, Vaziri S M, D'Agostino R B, Belanger A J, Wolf P A. "Independent risk factors for atrial fibrillation in a population-based cohort. The Framingham Heart Study," JAMA 1994; 271:840-4), and is a major risk factor for stroke and HF (Balasubramaniam R, Kistler P M. AF and "Heart failure: the chicken or the egg?" Heart 2009; 95:535-9; Lakshminarayan K, Anderson D C, Herzog C A, Qureshi A I. "Clinical epidemiology of atrial fibrillation and related cerebrovascular events in the United States," Neurologist 2008; 14:143-50; Lip G Y, Kakar P, Watson T. "Atrial fibrillation—the growing epidemic" [comment], Heart 2007; 93:542-3). Since a majority of AF triggers arise in the pulmonary veins (PVs) and the adjoining adjoining posterior left atrium (PLA), ablation procedures that electrically isolate the PVs have emerged in recent years as a viable therapy for focal AF. Nonetheless, moderately high ablation success rates have only been achieved in selected patients (Nademanee K, McKenzie J, Kosar E et al. "A new approach for catheter ablation of atrial fibrillation: mapping of the electrophysiologic substrate" [see comment], J. Am. Coll. Cardiol. 2004; 43:2044-53; Nademanee K, Schwab M C, Kosar E M et al. "Clinical outcomes of catheter substrate ablation for high-risk patients with atrial fibrillation," J. Am. Coll. Cardiol. 2008; 51:843-9; Taylor G W, Kay G N, Zheng Bishop S, Ideker R E. "Pathological effects of extensive radiofrequency energy applications in the pulmonary veins in dogs," Circulation 2000; 101:1736-42). Indeed, in patients with structural heart disease e.g. heart failure (HF), success rates do not exceed 50-60% (Estner H L, Hessling G, Ndrepepa G et al. "Electrogram-guided substrate ablation with or without pulmonary vein isolation in patients with persistent atrial fibrillation," Europace 2008; 10:1281-7; Weerasooriya R, Khairy P, Litalien J et al. "Catheter ablation for atrial fibrillation: are results maintained at 5 years of follow-up?" J. Am. Coll. Cardiol. 2011; 57:160-6). One reason for this low efficacy is that current ablation strategies primarily employ an anatomical, 'one-size fits all' strategy (with some minor variations) that does not address the specific mechanisms underlying AF (Ben Morrison T, Jared Bunch T, Gersh B J. "Pathophysiology of concomitant atrial fibrillation and heart failure: implications for management," Nat. Clin. Pract. Cardiovasc. Med 2009; 6:46-56). Recent research has therefore attempted to better define the mechanisms underlying AF, in order to improve upon the success of ablation and to develop new biological therapies for AF.
In the setting of structural heart disease—specifically HF—a variety of mechanisms e.g. stretch, oxidative stress (OS), autonomic imbalance and structural changes such as fibrosis are thought to contribute to a vulnerable AF substrate (Nattel S. "From guidelines to bench: implications of unresolved clinical issues for basic investigations of atrial fibrillation mechanisms," Can. J. Cardiol. 2011; 27:19-26; Nattel S, Burstein B, Dobrev D. "Atrial remodeling and atrial fibrillation: mechanisms and implications," Circ. Arrhythm. Electrophysiol. 2008; 1:62-73). OS is known to be elevated in the atria in AF (Youn J Y, Zhang J, Zhang Y et al. "Oxidative stress in atrial fibrillation: an emerging role of NADPH oxidase," J. Mol. Cell. Cardiol. 2013; 62:72-9) and reactive oxygen species (ROS) have effects on the atrial action potential and Ca2+ cycling. However, the precise effects of ROS on atrial electrophysiology in the intact atria—and how these electrophysiological changes contribute to formation of AF substrate—are not known.
Oxygen derivatives with instabilities and increased reactivity, e.g. O2, H2O2, and OH, are generically termed ROS (Maejima Y, Kuroda J, Matsushima S, Ago T, Sadoshima J. "Regulation of myocardial growth and death by NADPH oxidase," J. Mol. Cell. Cardiol. 2011; 50:408-16). While ROS at low doses mediates physiological functions such as growth, differentiation, metabolism (id.), excess ROS damages DNA, protein and lipids, and causes cell death (id.). A wealth of research points to increased OS as a key driver of cardiac remodeling caused by chronic pressure overload, loss of functional myocardium or AF (Kohlhaas M, Maack C. "Interplay of defective excitation-contraction coupling, energy starvation, and oxidative stress in heart failure," Trends Cardiovasc. Med 2011; 21:69-73; Maulik S K, Kumar S. "Oxidative stress and cardiac hypertrophy: a review," Toxicol. Mech. Methods 2012; 22:359-66). In addition, chronic ROS elevation activates signaling pathways such as TGF-1, MAP kinase subfamilies (Hori M, Nishida K. "Oxidative stress and left ventricular remodelling after myocardial infarction," Cardiovas. Res. 2009; 81:457-64; Tsai K H, Wang W J, Lin C W et al. "NADPH oxidase-derived superoxide anion-induced apoptosis is mediated via the JNK-dependent activation of NF-kappaB in cardiomyocytes exposed to high glucose," J. Cell. Physiol. 2012; 227:1347-57) that result in structural changes e.g. fibrosis. Moreover, ROS generation (e.g. by Ang II mediated NOX activation) has been shown to lead to modifications of CaMKII (Erickson J R, He B J, Grumbach I M, Anderson M E. "CaMKII in the cardiovascular system: sensing redox states," Physiol. Rev. 2011; 91:889-915), an important serine-threonine kinase involved in a variety of E-C coupling related processes in cardiac myocytes.
ROS are generated by the mitochondrial electron transport chain, the xanthine oxidase/dehydrogenase system, 'uncoupled' NOS, cytochrome P450 and NADPH oxidases. The NADPH oxidase enzyme family are a major source of cardiovascular ROS (Murdoch C E, Zhang M, Cave A C, Shah A M. "NADPH oxidase-dependent redox signalling in cardiac hypertrophy, remodelling and failure," Cardiovasc. Res. 2006; 71:208-15; Cave A C, Brewer A C, Narayanapanicker A et al "NADPH oxidases in cardiovascular health and disease," Antioxid Redox. Signal 2006; 8:691-728) with NOX2 being the dominant ROS-generating NADPH isoform in HF (Nabeebaccus A, Zhang M, Shah A M. "NADPH oxidases and cardiac remodeling," Heart Fail. Rev. 2011; 16:5-12; Maejima Y, Kuroda J, Matsushima S, Ago T, Sadoshima J. "Regulation of myocardial growth and death by NADPH oxidase," J Mol. Cell. Cardiol. 2011; Cave A C, Brewer A C, Narayanapanicker A et al. "NADPH oxidases in cardiovascular health and disease," Antioxid Redox. Signal. 2006; 8:691-728; Zhang P, Hou M, Li Y et al "NADPH oxidase contributes to coronary endothelial dysfunction in the failing heart," Am. J. Physiol Heart. Circ. Physiol 2009; 296:H840-6; Dworakowski R, Alom-Ruiz S P, Shah A M. "NADPH oxidase-derived reactive oxygen species in the regulation of endothelial phenotype," Pharmacol. Rep. 2008; 60:21-8). However, more recent studies indicate that NOX4 in mitochondria plays an essential role in mediating OS during pressure overload-induced cardiac hypertrophy (Nabeebaccus A, Zhang M, Shah A M. "NADPH oxidases and cardiac remodeling," Heart Fail Rev. 2011; 16:5-12; Kuroda J, Ago T, Matsushima S, Zhai P, Schneider M D, Sadoshima J. "NADPH oxidase 4 (Nox4) is a major source of oxidative stress in the failing heart," Proc. Natl. Acad Sci. U.S.A. 2010; 107:15565-70; Zhang M, Brewer A C, Schroder K et al. "NADPH oxidase-4 mediates protection against chronic load-induced stress in mouse hearts by enhancing angiogenesis," Proc. Natl. Acad Sci. U.S.A. 2010; 107:18121-6) NOX4 also appears to contribute significantly to the formation of fibrosis; in addition, it appears to be activated by pro-fibrotic signaling pathways e.g. TGF-β (Yeh Y H, Kuo C T, Chang G J, Qi X Y, Nattel S, Chen W J. "Nicotinamide adenine dinucleotide phosphate oxidase 4 mediates the differential responsiveness of atrial versus ventricular fibroblasts to transforming growth factor-beta," Circ. Arrhythm. Electrophysiol. 2013; 6:790-8; Zhang M, Perino A, Ghigo A, Hirsch E, Shah A M. "NADPH oxidases in heart failure: poachers or gamekeepers?" Antioxid Redox. Signal. 2013; 18:1024-41).
Recent evidence indicates that OS also contributes to structural and electrical remodeling in AF. Mihm et al. demonstrated significant oxidative damage in atrial appendages of AF patients undergoing the Maze procedure (Huang C X, Liu Y, Xia W F, Tang Y H, Huang H. Oxidative stress: a possible pathogenesis of atrial fibrillation. Med Hypotheses 2009; 72:466-7). Carnes et al showed that dogs with sustained AF had an increase in protein nitration, suggesting enhanced OS (Carnes C A, Janssen P M, Ruehr M L et al. "Atrial glutathione content, calcium current, and contractility," J. Biol. Chem. 2007; 282:28063-73; Carnes C A, Chung M K, Nakayama T et al. "Ascorbate attenuates atrial pacing-induced peroxynitrite formation and electrical remodeling and decreases the incidence of postoperative atrial fibrillation," Circ. Res. 2001; 89:E32-8). Kim et al showed that NADPH oxidase (NOX2) was a major source of atrial ROS in patients with AF (Kim Y M, Guzik T J, Zhang Y H et al "A myocardial Nox2 containing NAD(P)H oxidase contributes to oxidative stress in human atrial fibrillation," Circ. Res. 2005; 97:629-36). More recently, Reilly et al. have shown that atrial sources of ROS vary with the duration and substrate of AF, with NADPH oxidase being elevated early in AF (e.g. with post-operative AF) and with mitochondrial oxidases and uncoupled NOS being noted in long standing AF (Reilly S N, Jayaram R, Nahar K et al "Atrial sources of reactive oxygen species vary with the duration and substrate of atrial fibrillation: implications for the antiarrhythmic effect of statins," Circulation 2011; 124:1107-17). More recent data demonstrates that NOX4—which, as mentioned above, appears to contribute to the generation of mitochondrial ROS, specifically H2O2 (which more explicitly promotes fibrosis (Cucoranu I, Clempus R, Dikalova A et al. "NAD(P)H Oxidase 4 Mediates Transforming Growth Factor-1-Induced Differentiation of Cardiac Fibroblasts Into Myofibroblasts," Circ. Res. 2005; 97:900-7))—is also elevated in AF (Joun et al. (2013) supra; Zhang J, Youn J Y, Kim A et al. "NOX4-dependent Hydrogen Peroxide Overproduction in Human Atrial Fibrillation and HL-1 Atrial Cells: Relationship to Hypertension," Front. Physiol. 2012; 3)
The detrimental electrical effects of an enhanced, pathological late INa include the following: (i) diastolic depolarization during phase 4 of the AP that may lead to spontaneous AP firing and abnormal automaticity, (ii) an increase of AP duration, which may lead to EADs and triggered activity, as well as increased spatiotemporal differences of repolarization time, which promote reentrant electrical activity; and (iii) the indirect effects of a late INa-induced increase of Na+ entry to alter Ca2+ homeostasis in myocytes, which may lead to Ca2+ alternans and DADs. Acquired conditions and drugs that enhance late INa are associated with atrial tachyarrhythmias, ventricular tachyarrhythmias including torsades de pointes (TdP), afterpotentials (EADs, DADs), and triggered activity (Shryock J C, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. "The arrhythmogenic consequences of increasing late INa in the cardiomyocyte," Cardiovasc. Res. 2013; 99:600-11). Recent investigations implicate a role for abnormal Ca2+ handling in the genesis of ventricular and atrial arrhythmias (Aistrup G L, Balke C W, Wasserstrom J A. Arrhythmia triggers in heart failure: the smoking gun of [Ca2+]i dysregulation," Heart Rhythm. 2011; 8:1804-8; Antoons G, Sipido K R. "Targeting calcium handling in arrhythmias," Europace 2008; 10:1364-9; Laurita K R, Rosenbaum D S. "Mechanisms and potential therapeutic targets for ventricular arrhythmias associated with impaired cardiac calcium cycling," J. Mol. Cell. Cardiol. 2008; 44:31-43). Abnormal Ca2+ handling can contribute to arrhythmogenesis directly by triggering abnormal depolarizations and indirectly by modulating action potential time course and duration. DADs are typically result from cellular Ca2+ overload, with SCR increasing forward NCX and producing an inward current resulting in DADs (Antoons et al. (2008) supra; Volders P G, Vos M A, Szabo B et al "Progress in the understanding of cardiac early afterdepolarizations and torsades de pointes: time to revise current concepts," Cardiovasc. Res. 2000; 46:376-92). More recent evidence has accumulated for Ca2+-mediated EADs (Volders et al. (2000) supra), which could contribute to triggered activity or at least prolong action potential duration. Indeed, abnormal Ca2+ cycling and resulting Ca2+ transient alternans predisposes to changes in the action potential that set up conditions for reentry (Laurita et al. (2008) supra). Abnormal SR Ca2+ release has also been suggested to contribute to reentry in the intact atria, including the PVs (Chou C C, Nihei M, Zhou S et al. "Intracellular calcium dynamics and anisotropic reentry in isolated canine pulmonary veins and left atrium," Circulation 2005; 111:2889-97). In HF, a number of atrial ion-channel and E-C coupling proteins (Li D, Melnyk P, Feng J et al. "Effects of Experimental Heart Failure on Atrial Cellular and Ionic Electrophysiology," Circulation 2000; 101:2631-8. 61. Yeh Y-H, Wakili R, Qi X-Y et al. "Calcium-Handling Abnormalities Underlying Atrial Arrhythmogenesis and Contractile Dysfunction in Dogs With Congestive Heart Failure," Circ. Arrhythm. Electrophysiol. 2008; 1:93-102) can be modulated by ROS (Hool L C. "Reactive Oxygen Species in Cardiac Signalling: From Mitochondria to Plasma Membrane Ion Channels," Clin. Exp. Pharm. Phys. 2006; 33:146-51; Zima A V, Blatter L A. "Redox regulation of cardiac calcium channels and transporters," Cardiovasc. Res. 2006; 71:310-21; Nediani C, Raimondi L, Borchi E, Cerbai E. "Nitric Oxide/Reactive Oxygen Species Generation and Nitroso/Redox Imbalance in Heart Failure: From Molecular Mechanisms to Therapeutic Implications," Antioxidants & Redox Signaling 2011; 14:289-331) at least in part via ROS activation of kinases and inactivation of phosphatases, resulting in aberrant phosphorylation (e.g. of RyR2 and phospholamban). Also, ROS directly decrease SERCA function, but increase NCX function (Kuster G M, Lancel S, Zhang J et al. "Redox-mediated reciprocal regulation of SERCA and Na+-Ca2+ exchanger contributes to sarcoplasmic reticulum Ca2+ depletion in cardiac myocytes," Free Rad Biol. Med. 2010; 48:1182-7) which parallels the changes in SERCA and NCX in HF. Additionally, ROS increases late/persistent INa (INa_late) (Luo A, Ma J, Zhang P, Zhou H, Wang W. "Sodium Channel Gating Modes During Redox Reaction," Cell. Phys. Bioch. 2007; 19:9-20), which again parallels that in HF (Valdivia C R, Chu W W, Pu J et al. "Increased late sodium current in myocytes from a canine heart failure model and from failing human heart," J. Mol. Cell. Cardiol. 2005; 38:475-83) and INa, late can significantly contribute to the induction of EADs and DADs (Li D, Melnyk P, Feng J et al. "Effects of Experimental Heart Failure on Atrial Cellular and Ionic Electrophysiology," Circulation 2000; 101:2631-8; Song Y, Shryock J C, Belardinelli L. "An increase of late sodium current induces delayed afterdepolarizations and sustained triggered activity in atrial myocytes," Am. J. Physiol-Heart and Circ. Physiol. 2008; 294:H2031-H9; Wasserstrom J A, Sharma R, O'Toole M J et al. "Ranolazine Antagonizes the Effects of Increased Late Sodium Current on Intracellular Calcium Cycling in Rat Isolated Intact Heart," J. Pharm. Exp. Ther. 2009; Undrovinas N, Maltsev V, Belardinelli L, Sabbah H, Undrovinas A. "Late sodium current contributes to diastolic cell Ca2+ accumulation in chronic heart failure," J. Physiol. Sci. 2010; 60:245-57) both in ventricles and atria. Additional promotion of triggered activity could come from the increased Ca2+ sensitivity of hyperphosphorylated RyR2s in HF (Terentyev D, Gyorke I, Belevych A E et al. "Redox Modification of Ryanodine Receptors Contributes to Sarcoplasmic Reticulum Ca2+ Leak in Chronic Heart Failure," Circ. Res. 2008; 103:1466-72), which together with OS modifications of RyR2 (nitrosylation, oxidation) (Valdivia C R, Chu W W, Pu J et al "Increased late sodium current in myocytes from a canine heart failure model and from failing human heart," J. Mol. Cell. Card 2005; 38:475-83. 65. Song Y, Shryock J C, Belardinelli L. "An increase of late sodium current induces delayed after depolarizations and sustained triggered activity in atrial myocytes," Am. J. Physiol. Heart Circ. Physiol. 2008; 294:H2031-H9) in HF lead to leaky ventricular RyR2s (Gonzalez D R, Beigi F, Treuer A V, Hare J M. "Deficient ryanodine receptor S-nitrosylation increases sarcoplasmic reticulum calcium leak and arrhythmogenesis in cardiomyocytes," Proc. Natl. Acad. Sci. U.S.A. 2007; 104:20612-7; Marx S O, Marks A R. "Dysfunctional ryanodine receptors in the heart: new insights into complex cardiovascular diseases," J. Mol. Cell. Cardiol. 2013; 58:225-31). The oxidation/nitrosylation state of atrial RyR2s in HF has not been fully scrutinized; however, there appear to be significant differences in atrial versus ventricular E-C coupling, as has previously been suggested by others (Bootman M D, Smyrnias I, Thul R, Coombes S, Roderick H L. "Atrial cardiomyocyte calcium signaling," Biochim. Biophys. Acta 2011; 1813:922-34). The majority of the studies mentioned above have been performed in isolated myocytes; the specific contribution oxidized INa, RyR2 to the electrophysiological characteristics of the intact atrium—and how this contributes to arrhythmogenesis—is not known.
Excessively activated CaMKII is implicated in the genesis of HF and arrhythmias. Recent evidence suggests that both CaMKII and H2O2 increase RyR2 (Marx S O, Marks A R. "Dysfunctional ryanodine receptors in the heart: new insights into complex cardiovascular diseases," J. Mol. Cell. Cardiol. 2013; 58:225-31; Niggli E, Ullrich N D, Gutierrez D, Kyrychenko S, Polakova E, Shirokova N. "Posttranslational modifications of cardiac ryanodine receptors: Ca(2+) signaling and EC-coupling," Biochim. Biophys. Acta 2013; 1833:866-75) PO (Undrovinas N, Maltsev V, Belardinelli L, Sabbah H, Undrovinas A. "Late sodium current contributes to diastolic cell Ca2+ accumulation in chronic heart failure," J. Physiol. Sci 2010; 60:245-57; Gonzalez D R, Beigi F, Treuer A V, Hare J M. "Deficient ryanodine receptor S-nitrosylation increases sarcoplasmic reticulum calcium leak and arrhythmogenesis in cardiomyocytes," Proc. Natl. Acad Sci. U.S.A. 2007; 104:20612-7; Donoso P, Sanchez G, Bull R, Hidalgo C. "Modulation of cardiac ryanodine receptor activity by ROS and RNS," Front. Biosci. (Landmark Ed) 2011; 16:553-67; Terentyev D, Gyorke I, Belevych A E, et al. "Redox modification of ryanodine receptors contributes to sarcoplasmic reticulum Ca2+ leak in chronic heart failure," Circ. Res. 2008; 103:1466-72), thereby promoting SR Ca2+ leak and arrhythmias (Belevych A E, Terentyev D, Terentyeva R et al. "Shortened Ca2+ signaling refractoriness underlies cellular arrhythmogenesis in a postinfarction model of sudden cardiac death," Circ. Res. 2012; 110:569-77). Since OS-mediated oxidation of Met 281/282 residues in the regulatory domain of CaMKII transforms CaMKII into a constitutively active form (ox-CaMKII), leading to aberrant phosphorylation of multiple E-C coupling proteins (Swaminathan P D, Purohit A, Hund T J, Anderson M E. "Calmodulin-dependent protein kinase II: linking heart failure and arrhythmias," Circ. Res. 2012; 110:1661-77; Erickson J R, He B J, Grumbach I M, Anderson M E. "CaMKII in the cardiovascular system: sensing redox states," Physiol. Rev. 2011; 91:889-915), OS may affect RyR2PO both directly (via ROS) and indirectly (via ox-CaMKII) Indeed, expression of ox-CaMKII has been found to be increased in atria of AF patients, indicating a potential role of ROS induced CaMKII activation in AF (Purohit A, Rokita A G, Guan X et al. "Oxidized Ca2+/Calmodulin-Dependent Protein Kinase II Triggers Atrial Fibrillation," Circulation 2013; 128:1748-57). CaMKII has also been shown to modulate the gating of NaV1.5, at least in part by phosphorylation of NaV1.5 at multiple sites (Ashpole N M, Herren A W, Ginsburg K S et al. "Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates cardiac sodium channel NaV1.5 gating by multiple phosphorylation sites," J. Biol. Chem. 2012; 287:19856-69). A recent study demonstrates a fundamental requirement for targeting of CaMKII to a controlling phosphorylation site, S571, on NaV1.5 (Hund T J, Koval O M, Li J et al. "A beta(IV)-spectrin/CaMKII signaling complex is essential for membrane excitability in mice," J. Clin. Invest. 2010; 120:3508-19).
CaMKII phosphorylation of NaV1.5 is thought to decrease transient INa, but increase INa,late, again thereby contributing to the genesis of triggered activity (Hashambhoy Y L, Winslow R L, Greenstein J L. "CaMKII-dependent activation of late INa contributes to cellular arrhythmia in a model of the cardiac myocyte," Conf Proc. IEEE Eng Med Biol. Soc. 2011; 2011:4665-8). Modeling studies also suggest that ox-CaMKII may create substrate for reentry by regulating conduction characteristics of the myocardium (Hashambhoy et al. (2011) supra; Christensen M D, Dun W, Boyden P A, Anderson M E, Mohler P J, Hund T J. "Oxidized calmodulin kinase II regulates conduction following myocardial infarction: a computational analysis," PLoS Comput. Biol. 2009; 5:e1000583), with this substrate thought to be at least partially mediated by modulation of INa.
A summary of the various mechanisms for reactive oxygen species production, oxidative stress generation, and development of fibrosis and atrial fibrillation is illustrated in FIG. 1.

This patent is subject to a terminal disclaimer.

Inhibition of oxidative stress in atrial fibrillation


A foam support for use between a mobile electronic device display and a mobile electronic device frame having side edges for housing the display is provided. The foam support comprises a base and side tabs located around a perimeter of the base and configured to be folded into a position substantially perpendicular to the base and affixed to the side edges of the frame.

In recent years, mobile electronic devices have become a popular communication tool. Providing businesspeople the capability to transmit and receive messages when they are not in the office, for example, has been very advantageous in allowing them to communicate with others on a more immediate basis. Moreover, many businesspeople also use such devices as organizers, notebooks and even address books.
In order for the user to review the information stored in their mobile electronic device, the user looks at a display, generally a liquid crystal display (LCD), located within the mobile electronic device. The display provides an area for the user to review what is stored in the memory of the device, such as a monitor provides for a computer.
Presently, most mobile electronic devices include a foam support which is placed between the back of the mobile electronic device display and the mobile electronic device frame. This foam support provides cushioning between the display and the frame. Some of these devices also include individual foam tabs which are placed on the sides of the frame. However, it tends to be difficult to affix individual foam tabs to the frame since they are very small and cumbersome for a person to handle. It is also quite time consuming to individually affix a multiple number of foam tabs to the frame of a mobile electronic device. Furthermore, due to the size of the foam tabs, it is quite difficult to align the tabs with the side of the frame, and such an operation may require several attempts.

Foam support for mobile electronic device display


An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

Electrodes are necessary elements in devices or applications that employ electric fields or currents to act on liquids. Microanalytical devices that employ electrophoresis, electroosmosis, electrokinetic pumping, and various electrochemical detection schemes pose demanding requirements for electrodes, in particular because these electrodes are required to function in miniaturized reservoirs and/or microchannels.
Electric fields and currents are employed in microseparation systems employing electrophoresis for separation and sample concentration. These include capillary electrophoresis (CE), capillary zone electrophoresis (CZE), capillary electrochromatography (CEC), micellar electrokinetic chromatography (MEKC), and electrokinetically-driven high pressure liquid chromatography (EK-HPLC).
Sample pre-concentration schemes employed prior to separation in microfluidic separation devices have been accomplished by a variety of means employing electric fields. Examples include sample stacking by electrophoresis across a region of non-uniform analyte mobility, isoelectric focusing employing electric fields along pH gradients, and electrophoretic concentration against an analyte impermeable barrier such as a salt bridge or solid-polymer electrolyte. Many miniaturized and conventional-scale analytical systems employ electrochemical detection of analyte species by measurement of the conductivity of the analyte fluid stream.
Moreover, in many of the applications discussed above pressures in excess of 1000 psi can be generated. By way of example, by applying voltage across a porous bed having a charged-solid-liquid interface, electrokinetic pumps are capable of developing pressures in excess of 10,000 psi.
All the applications described above require electrodes to provide the necessary electric fields and currents. The most common electrode in use is simply a metal wire, principally because of both the ease of insertion into the small dimensions of a microfluidic channel and sealing against high pressure. These wires are generally made of nickel, steel, platinum, gold, or other passive or noble metal. The disadvantage attached to the use of these metal wire electrodes in microscale devices, i.e., devices having fluid flow channels ≈1 to 1000 μm, is the formation of gas bubbles, generally arising from the electrolysis of the solvent, e.g., water or formaldehyde. Because of the small dimensions of flow channels in microfluidic devices, these gas bubbles can occlude the current path to the electrodes and introduce electrical noise. In the worst case, the bubbles can block the entire flow channel and thereby open the electrical circuit. In flowing separation or detection systems, electrochemically produced hydrogen or oxygen can react with species of interest and bias or vitiate the analysis. Besides electrolytic gas bubble generation, electroactive species in the fluid being analyzed can be electrochemically reduced or oxidized on the exposed electrodes degrading the analysis and/or upsetting the separation or detection chemistry. In open or low-pressure systems and devices, conducting polymer or salt bridge devices have been used to separate electrodes away from sensitive areas in the device. However, in high pressure systems liquid permeation or loss of mechanical integrity precludes these conventional solutions. What is required is an electrode or electrode device that can be used in high pressure devices to provide the electric fields and currents necessary in the applications described above.

Electrodes for microfluidic applications


An echo removing apparatus for reducing the echo caused by sound returning from a speaker to a microphone of a small-sized communication terminal, such as a portable telephone. The echo removing apparatus includes a filter unit for outputting a pseudo echo signal estimating an echo component returning to the microphone based upon a generated sound signal supplied to the speaker, a subtractor for subtracting the pseudo echo signal supplied from the filter unit from the sound generated collection signal supplied from the microphone and a first characteristics conversion unit for converting frequency characteristics of sound generated collection signals from the microphone on the frequency axis. The characteristics of the filter unit are controlled for minimizing an error component between an output signal of the first characteristics conversion unit and an output signal of the filter unit.

This invention relates to an echo removing apparatus and, more particularly, to an echo removing apparatus for reducing the echo caused by the sound generated returning from a speaker to a microphone of a small-sized communication terminal, such as a portable telephone.
In keeping up with reduction in size of the sound generated communication terminal, such as a portable telephone, the effect as of the echo produced by the sound generated returning from the sound generated-receiving speaker to the sound generated-sending microphone becomes hardly negligible. For removing the echo caused by the sound generated returning round on the transmitter/receiver, an echo removing apparatus or an echo canceler shown for example in FIG. 1 is employed.
Referring to FIG. 1, a terminal 11 receives a speaker output signal x(k) transmitted from a communication partner to a speaker 12, where k denotes a sample number or a time position of discrete signals. A microphone input signal y(k), collected by a microphone 13 and thereby converted into an electrical signal, is supplied along with a pseudo echo signal supplied from a filter circuit 15 to a subtractor 14. The subtractor subtracts the pseudo echo signal supplied from the microphone input signal to form a resultant echo-reduced signal or a residual echo signal e(k) which is supplied to an input terminal 16. In a portable telephone, the speaker 12 and the microphone 13 are usually arranged close to each other as a telephone handset.
For the adaptive filter 15, a so-called finite response (FIR) filter is employed. The filter coefficients or tap coefficients are set for minimizing the error signal(k). The adaptive filter 15 filters the input signal, that is the speaker output signal x(k), for estimating the echo signal for generating the pseudo echo signal. This pseudo echo signal is provided to the subtractor 14 where the pseudo echo signal is subtracted from the microphone input signal y(k) to derive the residual echo signal or error signal e(k).
That is, if the input signal supplied from the terminal 11, that is the speaker output signal x(k), is the tap input to the N-tap FIR filter, operating as the adaptive filter 15, and the tap coefficients of the adaptive filter 15 are bk(i), where i=0, 1, . , N−1, the pseudo echo signal outputted by the adaptive filter 15 is given by
                                          y            ^                                          (            k            )                          =                              ∑                          i              =              0                                      N              -              1                                                                                b                k                                                          (                i                )                                                                x                                            (                                  k                  -                  1                                )                                                                        (        1        )
The subtractor 14 subtracts the pseudo echo signal of the equation (1) from the microphone input signal y(k) to derive the residual echo signal or error signal e(k) by:e(k)=y(k)−ŷ(k)  (2)
The tap coefficient {bk(i)} of the adaptive filter 15, where i=1, 2, . . . , N−1, is updated, by a suitable algorithm, such as a least mean square (LMS) algorithm, learning identification method or a recursive least square (RLS) algorithm, for minimizing the time average of the power of the error signal e(k) of the equation (2), that is,E[∥e(k)∥2]where E[ ] is an expected value or a mean value of the value within the brackets [ ] and ∥e(k)∥2 is the square sum of e(k). The tap coefficients of N taps of the adaptive filter 15 are equivalent to estimated values of the echo characteristics between the speaker 12 and the microphone 13.
Meanwhile, if desired to reduce the number of tapes N to the smallest possible value for simplifying the structure, the frequency characteristics of the residual echo are left in the low frequency range, even though the echo characteristics can be estimated partially with high accuracy by the adaptive filter 15, thus raising difficulties in effectively canceling the echo from sound generated input signals containing strong low-frequency components.
FIG. 2A shows the impulse response of the echo signals in association with the respective taps of the FIR filter. FIG. 2B, on the other hand, shows the impulse response of the residual echo signal obtained on subtracting the pseudo echo signal estimated by 20-tap FIR adaptive filter. It is seen from FIGS. 2A and 2B that the impulse response of the residual echo signal corresponding to 20 taps has been removed.
FIG. 3 shows, in association with FIGS. 2A and 2B, a spectral curve a of the echo signal and a spectral curve b of the residual echo signal produced on subtracting the estimated echo signal supplied from the 20-tap FIR adaptive filter.
Thus, even if it may appear that the echo characteristics can be substantially estimated by the 20-tap FIR adaptive filter, the frequency characteristics of the residual echo characteristics (curve b) are left in a region from 500 Hz to 1 kHz where the energy of sound generated signal would be concentrated to a larger extent.


An air supported play structure that may be configured into a large variety of forms and shapes. An expanse of air-permeable fabric is weighted around its edges, and the fabric is supported above a surface by a stream of air supplied by a fan. A plurality of connectors are attached to the fabric, and those connectors are arranged to allow any one connector to be secured to another connector. The geometric configuration of the play structure is altered by changing the position of the edge weights, and by selecting the connectors to be secured one to another.

1. Technical Field
This invention relates to a play structure that can be formed at will into an almost infinite number of geometric configurations. More specifically, this invention relates to a play structure that is formed of a generally planar expanse of air permeable fabric anchored about its perimeter to a surface, and supported by air pressure supplied by a fan.
2. Background Art
As every parent knows, children take delight in playing with and in playhouse structures, and a variety of such structures have been marketed over the years. Many of those play structures are patterned after conventional residential houses, usually including four walls, a roof and an entrance doorway. Often such play structures are of modular construction, allowing easy assembly for play and easy disassembly for storage. The collapsible playhouse that is described in U.S. Pat. No. 5,313,747 is an example of such play structures. Another similar playhouse is illustrated in the Drake, Jr. et al patent, U.S. Pat. No. 5,706,613. That patent describes a walk-in playhouse that is constructed of molded plastic wall panels and a roof. The playhouse also has a pair of pivotal, swing-out seats that are attached to a wall of the playhouse.
While many playhouses are patterned after conventional dwellings, other structural models are used as well. For example, U.S. Pat. No. 5,715,854 is directed to an igloo-like domed structure that is formed from a series of interlocking side panels of trapezoidal shape. The patent suggests that the structure is especially appropriate for winter play and may be used for other purposes, such as a hunting hut, as well.
Inflatable tubular passages have been used instead of conventional rod-like frame members to support a tent, and an example of such tent construction is set out in U.S. Pat. No. 5,636,478 Inflatable elements have also been used to construct childrens' play houses. An example of that approach is described in the patent to Boris et al, U.S. Pat. No. 5,145,440. That patent discloses a life size knockdown toy structure modeled after a log cabin. The cabin is formed from self interlocking, inflatable simulated logs. When not in use, the logs are deflated and stored in a relatively small container. Another play structure that uses inflatable elements is shown in U.S. Pat. No. 5,273,477 to Adams. Each inflatable element comprises a block having interlocking tongue and groove edge connections.
In spite of the elaborate play structures that are available, many parents have found that children will forego those fancy toys in favor of playing with empty packing cartons and the like. One reason for that preference is likely the freedom for imaginative play that is afforded by the cartons as contrasted to the relatively rigid and organized play patterns imposed by formal play structures.
In contrast to the rigidity of structure and use of previous play houses this invention provides a simple play structure that children can configure at will into an essentially endless variety of forms, thus reinforcing the imaginative elements of play.


A communication apparatus which realizes communication flow control which is capable of preventing decrease in reception performance without causing disappearance of communication data. A first storage unit stores data transmitted from an external apparatus. A second storage unit stores data transferred from the first storage unit. A determination unit determines, in a case of executing communication with the external apparatus, determine a notification size to be notified to the external apparatus as a size of data that can be received by the communication apparatus on a basis of a size of a free space of the first storage unit and a size of a free space of the second storage unit. A notification unit notifies the notification size determined by the determination unit to the external apparatus.

1. Field of the Invention
The present invention relates to a communication apparatus, a communication control method and a storage medium, and more particularly, to a method for controlling a process for changing communication speed.
2. Description of the Related Art
There is known a communication method of performing communication flow control using a window size (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2004-064665). In this communication method, since a transmitting side (for example, a host computer (client computer)) can transmit data corresponding to a window size shown by a receiving side (for example, a printing apparatus) without an acknowledgement packet from the receiving side, the number of acknowledgements required can be suppressed. Therefore, communication efficiency can be improved by increasing the window size.
However, for example, in some connection-type communication methods using TCP (Transmission Control Protocol), when connection with a receiving side is established, a transmitting side starts transmission of print data immediately after the establishment, and the process normally ends as soon as the transmission of the print data ends. In this case, if the receiving side is in a state of not being able to receive the print data, the received print data is discarded on the receiving side. As a result, it seems to the user that the print data has disappeared because a sheet on which the print data is printed is not discharged from the receiving side though the process of transmitting the print data is successful.
As an example, FIG. 6A shows an example of a communication flow in a case where disappearance of print data may occur. Here, it is assumed that a window size of a printing apparatus, which is a receiving side, is 8 Kbytes, and that a host computer, which is a transmitting side, transmits print data with a size of 5 Kbytes to the printing apparatus. When the window size is larger than the print data size as described above, the host computer transmits the whole print data to the printing apparatus without waiting for an acknowledgement from the printing apparatus. Therefore, when the printing apparatus is in a printing-disabled state, disappearance of the print data occurs. It should be noted that, in FIG. 6A, "SYN", "ACK" and "FIN" represent synchronization (a connection request), a reception acknowledgement and end of transmission, respectively.
In order to cope with this problem, there is proposed a data disappearance preventing function of, by uniformly reducing an initial window size with which a receiving side responds so that a transmitting side cannot transmit all print data at a time, preventing occurrence of disappearance of the print data (for example, see Japanese Patent No. 4324048). FIG. 6B shows an example of a communication flow in a case where an initial window size of a receiving side is set small. Here, it is assumed that, when the initial window size of a printing apparatus, which is the receiving side, is set to 1 Kbyte, a transmitting-side host computer transmits print data with a total size of 5 Kbytes to the printing apparatus.
In this case, when the printing apparatus is in a printing-disabled state, the host computer cannot transmit subsequent print data after the first 1 Kbyte to the printing apparatus and, therefore, enters in a state of waiting for a response from the printing apparatus. When the host computer receives a negative acknowledgement from the printing apparatus, a print data transmission error occurs, and the user can confirm that a transmission error has occurred. It should be noted that, in FIG. 6B, "SYN" and "ACK" represent the same as in FIG. 6A, and "RST" represents reset but has the same meaning as "negative acknowledgement" here.
There is also proposed a protocol stack equipped with an automatic receive-window tuning function in order to improve communication performance (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 05-232058). FIG. 7A shows an example of a communication flow of performing automatic tuning of a receive window. The automatic receive-window tuning function is a function of a receiving-side printing apparatus dynamically changing a window size according to a data transmission speed of a transmitting-side printing apparatus. Thus, as the host computer transmits data without delay, the receiving side gradually increases the window size, and, thereby, high-speed communication can be realized.
However, when the data disappearance preventing function described before is realized in a printing apparatus which adopts the automatic receive-window tuning function, there may be a case where print data reception performance in the printing apparatus decreases. FIG. 7B shows an example of a communication flow in the case where the reception performance decreases.
For example, in an environment with a lot of network traffic or a network environment where a transmitting side and a receiving side are physically far away from each other, the data transmission speed of the transmitting side seems to be slow when seen from the receiving side. Therefore, the receiving side judges that it is not necessary to further increase the window size and continues data reception without increasing the size from the initial window size. That is, because the initial window size is 1 Kbyte, and the window size is not changed, it is necessary to perform a total of one hundred times of transmission/reception when the transmitting side wants to transmit print data with a total of 100 Kbytes, and a lot of time is required for transmission/reception of the print data. In comparison, for example, if the automatic receive-window tuning function works, and the second and third window sizes are changed to 50 Kbytes and 500 Kbytes, respectively, transmission of the print data is completed by a total of three times of transmission/reception.
As described above, a conventional communication flow has a problem that decrease in reception performance may become remarkable when it is attempted to solve the data disappearance problem, and, on the other hand, the data disappearance problem becomes remarkable when the initial window size is increased in order to improve the reception performance.

Communication apparatus performing communication speed changing process, communication control method and storage medium


A cricothyrotomy forceps for inserting an endotracheal tube through an incision in the crico-thyroid membrane particularly designed for use by a paramedic in the field and having a pair of coupling plates extending perpendicular to the jaws of the forceps on only to one side of the plane defined by the handles and having a wound introduction margin designed to facilitate the entry of an endotracheal tube through the incision into the trachea. The forceps may be packaged in a kit with a tube of a length designed for a cricothyrotomy.

The present invention relates to a forceps specially designed for inserting an endotracheal tube into the trachea of a patient through the crico-thyroid membrane.
It is important during emergency care to keep the patient's airway open. In fact, emergency care providers are trained to place attention on the Airway first, before Breathing and Circulation (the so-called ABC's of emergency care). The airway is easily obstructed. Anything from the patient's own tongue, blood, vomitus or small bits of food can occlude the airway, interrupting the flow of air into and out of the lungs. Failure to provide adequate oxygen to the lungs, and ultimately to the brain, can result in hypoxia, which can rapidly progress to anoxia and death. The most common technique in the emergency setting for securing the airway is to place an endotracheal tube into the trachea of the patient through the mouth. In some instances, the endotracheal tube can be inserted into the trachea through the nasal passages via the nasal-tracheal route. Sometimes oral or nasal introduction of the endotracheal tube is either not possible or is contra-indicated. For example, if the patient's jaw is clenched shut, one cannot use the oral-tracheal route. Blood flowing from the nose could be an indication of a basilar skull fracture, thus contra-indicating the nasal-tracheal route. At the scene of an accident, paramedics sometimes find patients with clenched jaws from a closed head injury or with blood flowing from the nose from a skull fracture. Inadequate respiration must be resolved in those instances by a surgical intervention through the crico-thyroid membrane.
As shown in FIG. 1, the crico-thyroid membrane (16) is a transverse oval-shaped membrane located below the thyroid cartilage (12) and above the cricoid cartilage (14) in the throat just below the prominence commonly known as the Adam's Apple (15).
The thyroid (derived from the Greek word for "shield") is the largest cartilage in the larynx and is shown in FIG. 2. It consists of two lateral walls (17, 19) united at an acute angle in front forming a vertical projection in the middle line which is prominence above and called the Adam's Apple (15). Each side is quadrilateral in form. The upper border (21) of the thyroid cartilage (12) is sinuously curved and is concave on the posterior part (23). The lower border of the thyroid cartilage (12) is nearly straight in front. This lower border of the thyroid cartilage (12) is connected to the cricoid cartilage (14) in and near the median line by the middle portion of the crico-thyroid membrane (16) and, on each side, by the crico-thyroid muscle (not shown). The cricoid cartilage (14) (derived from the Greek work for "ring" because it resembles a signet ring) is smaller, but thicker and stronger than thyroid cartilage (12) and forms the lower and back part of the cavity of the larynx. It consists of two parts: a quadrate portion (24) situated to the rear and a narrow ring anterior portion (23) or arch about 1/4 or 1/5 the depth of the posterior part, situated in front, thus, the appearance of a signet ring. The quadrate portion (24) rapidly narrows at the sides of the cartilage into the anterior portion (23). The anterior portion (23) is narrow and convex and affords attachment externally in front and at the sides of the crico-thyroid muscle (not shown). The lower border of the cricoid cartilage (14) is horizontal and connected to the upper ring of the trachea (18) by fibrous membrane. The upper border of cricoid cartilage (14) is directed obliquely upward and backward owing to the greater depth of the posterior surface. It gives attachment in front through the middle portion of the crico-thyroid membrane (16), at the sides to the lateral portion of the same membrane. The crico-thyroid membrane (16), thus, extends between the lower margin of the thyroid cartilage (12) and the upper margin of the cricoid cartilage (14). It is convex, concealed on each side by the crico-thyroid muscle, but subcutaneous in the middle line. It can accommodate endotracheal access through the tough cartilage below the vocal cords and at the entry way to the trachea (18).
In the hospital setting, surgeons use advanced tools to perform a surgical cricothyrotomy or they use the more difficult and technically advanced tracheotomy procedure. At the scene of an emergency, like a motor vehicle accident, paramedics do not have at their disposal the equipment that is available in the hospital setting. The only tool available to the paramedic is a scalpel to make the incision laterally across the crico-thyroid membrane. The fifth digit is used for blunt dissection prior to inspection of the endotracheal tube (22).
An endotracheal tube (22) is a curved, bendable plastic tube of a prescribed internal diameter varying usually from 3 to 9.5 mm and with a bias cut distal end (25). The tube (22) is introduced into the trachea (18) through a 10 mm incision (67) in the crico-thyroid membrane (16). The incision is made across the crico-thyroid membrane (16) transverse to the long axis of the neck of the patient. It can be very difficult to advance the tube (22) down trachea (18) since it is being introduced at a 90-degree angle through the incision with only a millimeter or two to spare. Paramedics frequently find that they have to make a larger incision in order to turn the endotracheal tube down the longitudinal axis of the trachea (18) or the paramedic must slowly advance the tube (22) into the trachea (18) by using the fifth digit to bend the distal end of the tube (22) in order to navigate the 90-degree angle, thus, wasting valuable time and executing an extremely difficult digital maneuver. When one considers the confusion that can exist at an emergency scene, one can easily see that it would be extremely helpful to have a device specially designed for use in the field to perform a surgical crico-thyrotomy more easily without resorting to the surgeon's tray full of instruments.
Standard endotracheal tubes designed for oral entry are longer than is necessary for a crico-thyroid membrane entry. When they are used in a crico-thyrotomy, the proximal end of the tube sticks out too far from the incision and can get in the way or even be hit by the attending personnel causing additional damage to adjacent structures.
The description of the anatomy was taken from Gray's Anatomy 1977, Crown Publishers, Inc., Library of Congress Catalog No. 76-52804, pp. 955-965.


An electric hydraulic excavator (1) includes an automotive lower traveling structure (2) and

A hydraulic excavator representative of a construction machine is provided with an automotive lower travelling structure, an upper revolving structure mounted on the lower travelling structure to be capable of revolving thereto. A vehicle body of the hydraulic excavator is configured with the lower traveling structure and the upper revolving structure. A working mechanism thereof is mounted on a front side of the upper revolving structure to be capable of lifting and tilting thereto and performs an excavating operation and the like. Here, there is known an electric hydraulic excavator that operates the vehicle body and the working mechanism by driving a hydraulic pump by an electric motor.
Among the electric hydraulic excavators, there is an electric hydraulic excavator that is provided with an electric motor and a motor control unit as an electric power source and drives the electric motor by electric power supplied from an external electric current source. On the other hand, there is an electric hydraulic excavator that is provided with an electric motor, a motor control unit, a battery and a battery charger as an electric power source and drives the electric motor by electric power from the battery. In this case, in the electric hydraulic excavator provided with the electric motor and the motor control unit as the electric power source, the external electric current source and the motor control unit are all the time connected by a power feeding cable. On the other hand, in the electric hydraulic excavator provided with the electric motor, the motor control unit, the battery and the battery charger as the electric power source, the external electric current source and the battery charger are all the time connected by a power feeding cable. In this way, in the electric hydraulic excavator the electric power source mounted on the vehicle body and the external electric current source are all the time connected by the power feeding cable.
Here, there is proposed an electric hydraulic excavator provided with a cable arm for holding the power feeding cable, as the electric hydraulic excavator connecting the electric power source and the external electric current source. In this electric hydraulic excavator, the cable arm is attached at its base end portion to a housing cover disposed on a front side of a counterweight to be rotatable through a bearing thereto. The power feeding cable passes above the counterweight in a state of being held by the cable arm. Then, the power feeding cable is inserted through a cable insertion hole formed in the housing cover into the housing cover and is connected to the electric power source accommodated in the housing cover (Patent Document 1).

Abstract: an upper revolving structure (3) mounted on the lower traveling structure (2) to be capable of revolving thereto. The upper revolving structure (3) includes a revolving frame (5) as a base, a counterweight (13) disposed on a rear side of the revolving frame (5), and an electric power source (9) that is positioned on a front side of the counterweight (13) to be mounted on the revolving frame (5) and is power-fed from an external electric current source. The counterweight (13) is provided with a cable insertion hole (16) as disposed therein. A power feeding cable (12) is inserted in the cable insertion hole (16) for connection between the external electric current source and the electric power source (9).

Hitachi Construction Machinery Tierra Co., Ltd.


An arc fault detector of the type which generates a trip signal when a time attenuated accumulation of pulses produced each time an arc is struck reaches a selected value, includes a pulse conditioner which discriminates against false trips induced by phenomena such as tungsten bulb burn out and turn on of a cold tungsten bulb controlled by a dimmer. The pulse conditioner includes a zener diode which limits the amplitude of the pulses applied to the integrator, and stretches all of the pulses to reduce the variation in pulse duration. The latter can be accomplished by a peak detector which stretches pulses which reach the zener limit to a duration of at least about a half cycle.

1. Field of the Invention
This invention relates to detection and interruption of currents and circuits experiencing arc faults. More particularly, it relates to an arc fault detector and a circuit breaker incorporating such an arc fault detector which minimize the effects of other phenomena such as the burnout of tungsten bulbs, which can falsely provide an indication of an arc fault.
2. Background Information
Arc faults can occur in electrical systems for instance between adjacent bared conductors, between exposed ends of broken conductors, at a faulty connection, and in other situations where conducting elements are in close proximity. Arc faults in ac systems can be intermittent as the magnetic repulsion forces generated by the arc current force the conductors apart to extinguish the arc. Mechanical forces then bring the conductors together again so that another arc is struck.
Arc faults typically have high resistance so that the arc current is below the instantaneous or magnetic trip thresholds of conventional circuit breakers. Also, the intermittent nature of an arc fault can create an average RMS current value which is below the thermal threshold for such circuit breakers. Even so, the arcs can cause damage or start a fire if they occur near combustible material. It is not practical to simply lower the pickup currents on conventional circuit breakers as there are many typical loads which draw similar currents, and would therefore, cause nuisance trips.
Much attention has been directed toward trying to distinguish arc currents from other intermittent currents. It has been recognized that arc currents generate a step increase in current when the arc is struck. However, many typical loads generate a similar step increase, such as for instance when the device is turned on. In many instances, the step increases generated by these loads are singular events while an arc fault generates a series of step increases. The arc fault detector described in U.S. Pat. No. 5,224,006 counts the step increases in current and generates a trip signal if a selected number of step increases occur within a given interval. However, there are loads, such as a solid state dimmer switch with the firing angle phased back substantially, which also generate repetitive step increases in current. This problem is addressed by the arc fault detector in U.S. Pat. No. 5,691,869 in which the arc current is passed through a bandwidth limited filter which generates pulses having an amplitude proportional to the step increases. An arc indication is generated when a time attenuated accumulation of these pulses reaches a predetermined value. Thus, a few very large magnitude step increases within a period of time, or a larger number of more modest step increases within a similar time period, generate a trip signal. The trip level can be set so that the cyclic pulses generated by a dimmer do not generate the time attenuated accumulation which reaches the trip level.
There is at least one arc condition which can occur in a protected circuit to which it is desired that the arc fault circuit not respond. This is an arc created by the burnout of a tungsten filament such as in a light bulb. When the filament burns through, a small gap is created between the burned out ends of the filament. An arc is struck across this gap and can quickly envelop the entire filament so that it extends between the two conductors thereby drawing a very large arc current. In order to terminate this arc, tungsten bulbs are provided with a small fuse in the base. Even so, burnout of the filament and blowing of the fuse results typically in a pair of current pulses of opposite polarity. This pair of pulses can be of sufficient magnitude that the threshold value of the time attenuated accumulation of pulses in the circuit breaker described in U.S. Pat. No. 5,691,869 is exceeded and the circuit breaker is tripped. This is considered a nuisance trip as the fuse has interrupted the arc.
Tungsten filament bulbs can also generate false trips when used with a dimmer. As mentioned, a dimmer which is phased back can generate repetitive step increases in current on each half cycle. As also discussed, the circuit breaker can be set so that the threshold of the time attenuated accumulation of pulses generated by the dimmer do not reach the trip level with normal loads. However, when a tungsten filament lamp is first turned on, the cold filament has a very low resistance and can draw up to fifteen times normal current. This can result in a nuisance trip when a tungsten lamp controlled by a dimmer switch is first turned on.
Commonly owned U.S. patent application Ser. No. 08/939,976 filed on Sep. 29, 1997, addresses the problems created by a tungsten filament bulb by disclosing an arc fault detector in which a zener diode places amplitude limits on pulses having an amplitude proportional to the magnitude of step increases in current in the protected circuit so that the time attenuated accumulation of these pulses does not reach the trip level based upon a few very large pulses which can be generated by burnout of a tungsten lamp or turn on of a tungsten lamp controlled by a dimmer switch. In particular, the zener diode clips the pulses generated in response to the step increases in current in the protected circuit before the time attenuated accumulation of the pulses. As true arc faults will continue to strike at a random rate, and therefore raise the time attenuated accumulation of pulses to the trip threshold, false trips due to burnout of a tungsten lamp or turn on of a cold tungsten bulb are avoided. While the arc detector described in the cited patent application reduces false trips due to tungsten lamp burnout and turn on of dimmer controlled tungsten bulbs, there is room for improvement.
There is a need for an arc fault detector and circuit breaker incorporating such a detector which can respond faster to true arc faults, yet not falsely trip on other phenomena such as burnout of a tungsten bulb or turn on of a tungsten bulb controlled by a dimmer.
There is a need for achieving such a result with a simple, reliable and low cost detector.
In particular there is a need for such apparatus which can respond sooner to step increases in current in a protected circuit, whether small or large and yet discriminate against current discontinuities caused by tungsten bulbs.

Arc fault detector with protection against nuisance trips and circuit breaker incorporating same