A driving circuit of a display device like liquid crystal display, which is small in circuit size, ensures good quality images, and can freely change the display gradation, is configured to execute digital-analog conversion by reallocating charges between a primary-side capacitor and a secondary-side capacitor and includes a plurality of such capacitors in the primary side or the secondary side to enable both quick conversion and reliable potential output to signal lines. Also in an output circuit, output of signal potentials not affected by fluctuation of properties of TFT and inverters can be realized.

This invention relates to a driving circuit of a display device and a liquid crystal display device. More particularly, the invention relates to those having a simple structure, ensuring representation of good-quality images, and very easy to change the gradation of display.
As one type of flat displays used in personal computers, thin-type television receivers, etc., there is a display using a plurality of pixels having a capacitive load. An example thereof is liquid crystal displays.
So-called xe2x80x9cactive matrix type liquid crystal displaysxe2x80x9d using a pixel switching element like thin-film transistor (TFT) or thin film diode (TFD) for each pixel provide clear images, and have a high-density display ability equivalent to or higher than that of CRT. In particular, TFT liquid crystal displays (TFT-LCD) using thin film transistors as pixel switching elements are under active developments toward their practical use.
TFT typically uses amorphous silicon or polycrystalline silicon as its semiconductor active layer (channel, source and drain regions). For years, vigorous energy is being paid toward development of TFT-LCD of a driving circuit built-in type, in which scanning line driving circuits and video signal line driving circuits are formed together with pixel TFT on a transparent insulating substrate. This structure enables extending the effective display area of the transparent insulating substrate of a liquid crystal display and reducing the manufacturing cost.
TFT-LCD of this driving circuit built-in type includes on its pixel substrate a digital-analog converter circuit (hereinafter abbreviated DAC) for converting digital signals input as video signals from outside into analog signals.
However, conventional driving circuit built-in TFT-LCDs involved the problem that when the bit number of digital input signals was increased for the purpose of attaining higher definition of display images, DAC was enlarged in size and hence narrowed the effective display area of the screen. This problem is discussed below with reference to the drawings.
FIG. 56 is a conceptional diagram showing the structure of a capacitor-arrayed DAC used in conventional liquid displays. DAC shown here is of a parallel input type and includes a switch control circuit 41, reference voltage source 42, switch array 43, capacitor array 44, reset switch 45 and buffer amplifier 46.
In the example shown here, digital data of 6 bits such as (B6, B5, . . . B1) are input in parallel as video signals.
The capacitor array 44 includes capacitors more by one than the number of bits of the digital data. Capacitance values of these capacitors are weighted in six different values from C through C/32 depending upon the binary coding. These capacitors are commonly connected at one end of each thereof, and connected to a vides signal line via the amplifier 46. The capacitors are connected at the other end of each thereof selectively to a reference voltage Vs or the ground potential by MOS switches of the switch array 43.
Each switch of the switch array 43 is directly controlled by binary data of an input which coincides with the capacitance weighting order of the capacitors.
In the example shown in FIG. 56, 6-bit conversion is possible. That is, when the parallel data (B6, B5, . . . B1) are input, the output voltage Vout is expressed by the following equation.                               V          out                =                              ∑                          i              =              1                        6                                          xe2x80x83                                                        B              i                        ·                          2                              (                                  i                  -                  7                                )                                      ·            Vs                                              (        1        )
This DAC, however, needs (n+1) capacitors for converting digital data of n bits. Therefore, in order to ensure high definition image display with a high display gradation by increasing the number of bits, the problem of a dimensional increase of the circuit inevitably occurs. In case of liquid crystal displays having a built-in driving circuit, dimensional increase of the DAC circuit makes it difficult to keep a sufficient effective pixel area, and causes the problem that the size of the display need be increased, and the weight becomes heavy.
On the other hand, in DAC of FIG. 56, since the capacitors in the capacitor array 44 must be weighted in capacitance so as to correspond to the binary coding, more and more accurate control of their capacitance values must be guaranteed as the number of bits increases. Therefore, the design and manufacturing margins are strict, and the production yield is liable to decrease.
Another problem with conventional DAC as shown in FIG. 56 lies in that digital data it can convert is fixed in number of bit. That is, the gradation of video signals it can handle is fixed to a predetermined value according to the circuit arrangement of DAC, and it cannot be changed later. This means, in a personal computer, for example, that users cannot readily change the display mode depending on the content to be displayed.
Under the circumstances, Japanese Patent Laid-Open Publication No. H7-72822 includes description about the use of serial DAC made up of two capacitor elements. This structure, however, was limited in increasing the data processing speed because it required different periods for digital-analog conversion and input of analog signals into capacitor elements or output of digital signal from the capacitor elements.
The invention has been made starting with the recognition of the above-explained problems. It is therefore an object of the invention to provide a display device driving circuit and a liquid crystal display device enabling the use of a small-scaled circuit, ensuring good-quality images and enabling free changes of the display gradations.
To attain the object, the basic structure of the invention is made up of a reference voltage selecting circuit for exclusively selecting and outputting one of a plurality of reference voltages in response to individual bit signals of serial data of a plurality of bits which are time-serially input, a first capacitor element connected to the reference voltage selecting circuit to hold a reference voltage output from the reference voltage selecting circuit, a second capacitor element connected to the first capacitor element through a connection circuit to hold an electric charged distributed from the first capacitor element due to a short-circuit of the connection circuit at a timing prior to the input of individual signals into the reference voltage selecting circuit, and an output line which outputs the voltage held in the second capacitor element as a display signal.
That is, the display device driving circuit according to the invention is one configured to input digital data and output it after convert it into an analog video signal, which comprises a first capacitor, a selecting circuit introducing one of bits of the digital data to determine the charge voltage of the first capacitor as a first voltage when the value of the bit is xe2x80x9c1xe2x80x9d but determine the charge voltage of the first capacitor as a second voltage different from the first voltage when the value of the bit is xe2x80x9c0xe2x80x9d, a second capacitor, and a connection circuit which connects the first capacitor and the second capacitor to reallocate their charging electric charges so as to equalize their charging voltage, such that the charging voltage of the first capacitor or the second capacitor obtained by activating the selecting circuit and the connection circuit in this sequence for each of the bits of the digital data from its most significant bit to the least significant bit be output as the analog video signal.
Based on the basic structure shown above, the first display device driving circuit according to the invention is a driving circuit of a display device including a digital-analog converter circuit which introduces a digital data and outputs an analog video signal, in which the digital-analog converter circuit has an input capacitor parallel type structure including: a reference voltage selecting circuit which is responsive to each of bit signals of time-serially input data of a plurality of bits to exclusively select and output one of a plurality of reference voltages; a group of input-side capacitor elements connected to the reference voltage selecting circuit and including a plurality of capacitor elements which hold the reference voltage output from the reference voltage selecting circuit; an output-side capacitor element connected to each capacitor element in the group of input-side capacitor elements via a connection circuit to short-circuit the connection circuit at a predetermined timing, thereby selectively connected to individual capacitor elements in the group of input-side capacitors sequentially and holding charges distributed from individual capacitor elements in the group of input-side capacitor elements, thereby outputting the voltage held in the output-side capacitor element as an analog video signal.
The second display device driving circuit according to the invention is a driving circuit of a display device including a digital-analog converter circuit which introduces digital data and outputs an analog video signal, in which the digital-analog converter circuit has an output capacitor parallel type structure including: a reference voltage selecting circuit which is responsive to each of bit signals of time-serially input data of a plurality of bits to exclusively select and output one of a plurality of reference voltages; an input-side capacitor element connected to the reference voltage selecting circuit to hold the reference voltage output from the reference voltage selecting circuit; a group of output-side capacitor elements connected to the input-side capacitor element via a connection circuit to short-circuit the connection circuit at a predetermined timing, thereby connected to the input-side capacitor element and holding charges distributed from the input-side capacitor element, thereby selectively outputting a voltage held in a capacitor element in the group of output-side capacitor elements as an analog video signal.
The third display device driving circuit according to the invention is a driving circuit of a display device including a digital-analog converter circuit which introduces digital data and outputs an analog video signal, in which the digital-analog converter circuit has an input-output capacitor parallel type structure including: a reference voltage selecting circuit which is responsive to each of bit signals of time-serially input data of a plurality of bits to exclusively select and output one of a plurality of reference voltages; a group of input-side capacitor elements connected to the reference voltage selecting circuit and including a plurality of capacitor elements which hold the reference voltage output from the reference voltage selecting circuit; a group of output-side capacitor elements connected to respective capacitor elements in the group of input-side capacitor elements via a connection circuit to short-circuit the connection circuit at a predetermined timing, thereby selectively sequentially connected to individual capacitor elements in the group of input-side capacitor elements and holding charges distributed from individual capacitor elements in the group of input-side capacitor elements, thereby selectively outputting a voltage held in-a capacitor element in the group of output-side capacitor elements as an analog video signal.
The first to third driving circuits may further comprise a shutoff circuit connected between the reference voltage selecting circuit and the input-side capacitor to cut the connection between the reference voltage selecting circuit and the input-side capacitor element before short-circuiting the input-side capacitor element and the output-side capacitor element. Thereby, a back flow of the electric charge from the input-side capacitor element to the reference voltage selecting circuit can be prevented.
The input-side capacitor element and the output-side capacitor element may be substantially same in capacitance value to ensure even reallocation of the electric charge.
On the other hand, the fourth display device driving circuit according to the invention is a display device driving circuit having a plurality of signal lines and scanning lines arranged to intersect at right angles with each other and pixel switching elements provided at crossing points of the signal lines and the scanning lines to display gradient representation of 2m on the basis of data of m bits (m is a plural number), comprising: a data distributing circuit supplied with the data of m bits; a data latch circuit sequentially storing the data of n bits and outputting them at a predetermined timing; a gamma correction circuit which stores the output from the data latch circuit and outputs it at a predetermined timing; one of the digital-analog converter circuits recited in claims 1 through 9 which stores the output from the gamma correction circuit and outputs it at a predetermined timing; and an amplifier circuit for amplifying the output from the digital-analog converter circuit.
On the other hand, a liquid crystal display device according to the invention comprises one of the above-summarized display device driving circuits, and a liquid crystal controlled by the pixel switching elements, and it is characterized in that the threshold value of the liquid crystal is about 2.5 Volts.
Another liquid crystal display device according to the invention comprises one of the above-summarized display device driving circuits, and a liquid crystal controlled by the pixel switching elements, and it is characterized in that the threshold value of the liquid crystal is about 1.5 Volts.
Another liquid crystal display device according to the invention is a transmission type liquid crystal display device comprising one of the above-summarized display device driving circuits, and a light source provided behind when viewed from the direction of the image watching surface.
Another liquid crystal display device according to the invention is a reflection type liquid crystal display device comprising one of the above-summarized display device driving circuits, and a reflector provided behind when viewed from the direction of the image watching surface to display images by reflecting external light entering from the direction of the image watching surface with the reflector.
Another liquid crystal display device according to the invention comprises one of the above-summarized display device driving circuits, a light source provided behind when viewed from the direction of the image watching surface and a reflector provided behind when viewed from the direction of the image watching surface, and it is characterized in representing images by letting light released from the light source to pass through or by reflecting external light entering from the direction of the image watching surface with the reflector.
Another liquid crystal display device according to the invention comprises one of the above-summarized display device driving circuits, and a pixel switching element provided for each display pixel, and it is characterized in that the driving circuit and the pixel switching elements are provided on a common substrate and share a common semiconductor layer stacked on the substrate.
The invention is used in the above-summarized modes, and gives the effects explained below.
First of all, according to the invention, serially input digital video signals are reliably and easily converted into analog signals. Additionally, according to the invention, the circuit arrangement of DAC is very simple, and the circuit area can be reduced more largely than conventional ones. The dimensional reduction of the circuit becomes more effective with the number of bits of digital data. Namely, as the quality of the displayed images becomes higher, this effect becomes larger.
That is, as compared with typical n-bit parallel input type DAC, the circuit scale of DAC in the present invention is about 1/n, and as the number of bits increases, the effect of dimensional reduction of the circuit becomes larger. This is especially advantageous in polysilicon TFT liquid crystal display devicees integrating the driving circuit into the panel. Although an increase in display gradation, i.e. number of bits of video signals, is necessary for higher quality of displayed images, the invention need not increase the circuit scale, and simultaneously reconciles miniaturization of the panel and improvement of the image quality.
Further, the invention also enables conversion of digital data different in number of bits into analog video signals without changing the circuit. That is, according to the invention, by repeating the above-explained operations for individual bits of serially input digital data, it is possible to convert the digital data into an analog form without relying on the number of bits.
This effect of the invention is especially advantageous when it is applied to display devicees of computers. That is, in computers, it is often required to switch the image display mode depending upon its use or software. In that case, it is desirable to change the display gradation, i.e. number of gradation bits, together with its display resolution. According to the invention, even in that case, analog conversion is possible by using the same DAC.
Furthermore, according to the invention, digital data can be input in parallel at a high speed by providing a plurality of primary-side capacitors of DAC. In addition, by providing a plurality of secondary-side capacitors of DAC, it is possible to execute in parallel the DA conversion for the next signal line and writing of the analog potential to the preceding signal line. This results in increasing the operation speed and enabling reliable writing of a predetermined analog potential even when the parasitic capacitance of the signal line is large in a high-definition display device.
Moreover, according to the invention, as the output circuit controls to increase the voltage of a signal line when the voltage of the signal line is lower than the voltage of the input signal and decrease the voltage of the signal line when the voltage of the signal line is higher than the voltage of the input signal, the voltage of the signal line can be equalized to the voltage of the input signal.
Furthermore, by setting the voltage of the input terminal of each inverter forming the output circuit at the threshold voltage of its own before the output circuit controls the voltage of the signal line, adverse affection to the voltage of the signal line can be prevented even when the inverters fluctuate in threshold voltage.
As explained above, according to the invention, it is possible to reliably write digital data different in number of bits onto signal lines after converting them into analog video signals by using a much simpler circuit arrangement than conventional ones, and its industrial advantages are great.

Driving circuit for display device and liquid crystal display device


A patient support apparatus includes a base having a first side, a second side, a head end, and a foot end, a head end caster and a foot end caster coupled to the base on the first side near the respective head and foot ends, and a head end link and a foot end link located on the first side and operably associated with the respective head and foot end casters on the first side. The head and foot end links on the first side move longitudinally in opposite directions to brake the respective head and foot end casters on the first side.

The present disclosure relates generally to a patient support apparatus, such as a hospital bed, having casters. More particularly, the present disclosure relates to an apparatus for controlling the brakes which engage the caster wheels supporting the patient support apparatus.
Hospital beds are provided with casters mounted around the base for rolling the bed from place to place. At least one of the casters, and usually two, have at least two operating modes, namely, neutral and brake modes. Also, one of the casters has all three operating modes, namely, neutral, brake and steer modes. In the neutral mode, the caster wheel is free to swivel and rotate. In the brake mode, a brake pad is pressed against the surface of the caster wheel to prevent it from rotating and swiveling. In the steer mode, the caster wheel is locked against swiveling movement, but is free to rotate. In addition, in the steer mode, the caster wheel is aligned parallel to a longitudinal dimension of the bed so that the bed can be pushed straight down a hallway without the bed drifting to one side or the other. An illustrative caster braking system is disclosed in U.S. Pat. No. 5,377,372, which is hereby incorporated by reference herein.


Provided is a light emitting material in which: a light emitting layer comprising a columnar part of which a cross-sectional shape is column such as cylindrical column, and a light emitting part of which a cross-sectional shape is cone or pyramid; and light generated in the light emitting part is extracted outside through the columnar part. The light emitting material allows light to be efficiently extracted to the outside to improve luminance.

1. Field of the Invention
The present invention relates to a light emitting structure and a light emitting device, which allow light to be extracted to the outside with efficiency to attain an improved luminance.
2. Description of the Related Art
Displays such as an electroluminescent (EL) display and a field emission display (FED) have been attracting attention as a flat panel display (FPD) using fine particles and a thin film both having a light-emitting function. The features of the EL display reside in that the EL display is self-luminous and is a perfect solid type, which is conducive to an excellent environmental tolerance.
Examples of the EL device include: an inorganic EL using electroluminescence produced by an inorganic material; and an organic EL using current injection luminescence produced by an organic material. In general, light generated in those EL devices is all reflected unless being made incident on an interface at an angle smaller than a critical angle, which makes it difficult to extract all the light to the outside. The light-extracting efficiency is typically around 20%, though depending on the material constituting the device. Examples of a method to improve the light-extracting efficiency include: a method disclosed in Japanese Patent Application Laid-Open No. 2002-278477, in which a low-refractive layer is provided between a transparent electrode layer and a transparent substrate; and a method disclosed in Japanese Patent Application Laid-Open No. 2004-296438, in which a transparent electrode is provided with an irregular surface.
According to the above-mentioned methods, however, it is necessary to provide the low-refractive layer or a light scattering layer in addition to the constituent elements such as the substrate and a light emitting layer, which makes the structure of the device and also a manufacturing process therefor complicated, leading to a difficulty in quality control of the light emitting device and to an increase in cost of manufacturing.
It is also possible to use a monocrystalline thin film for a light emitting part (thin-film type) (see FIG. 9A). In the case of using the monocrystalline thin film, excellent quantum efficiency can be assumed in general, whereas the light-extracting efficiency is limited to about 20%. Also, it is difficult to produce monocrystal in a large size, leading to an increase in cost.
Meanwhile, according to a conventional structure in which microcrystal or fine particles is used for a light emitting part (light emitting particle scattering type) (see FIG. 9B), the light-extracting efficiency is increased due to a scattering of light caused at the interface. At the same time, however, the surface area is increased, leading to an increase in the number of nonluminous centers, thereby decreasing the quantum efficiency. The quantum efficiency may be increased by adopting microcrystal in a relatively large size (0.1 μm or more), while adversely making the surface rough in general, which becomes an impediment in making the device thinner. In FIGS. 9A and 9B, reference numeral 91 denotes an electrode; 92, an insulating layer; 93, a dielectric film; 94, a light emitting layer; 95, a transparent electrode; and 96, a glass substrate. The above-mentioned problems can be solved by the following structure and manufacturing method according to the present invention.

Tapered light emitting structure and light emitting device having a columnar light extraction layer


The present invention relates to an improved faceplate used in a connector assembly for electrical, electronic and optical applications. The faceplate has a staggered profile from the leading end to the trailing end, thereby providing a row of mating surfaces. Each successive mating surface being lower than the preceding one. At least one internal connector is disposed on each mating surface. The rear of each internal connector is connected to electrical, electronic or optical equipment. Respective external mating connectors mate with the front of each respective internal connector in a mating direction towards the faceplate. A cable is secured to each external mating connector and extends generally perpendicular with respect to the mating direction and towards the trailing end of the faceplate. The staggered profile accommodates or at least partly accommodates the cables secured to the external mating connectors.

It is common to house electronic, electrical and/or optical devices in a module with a faceplate. The faceplate has a leading end and a trailing end. One or more internal connectors are disposed on the faceplate for interconnecting with external mating connectors. Cables are attached to these external mating connectors. For instance, the telecommunications industry uses modules of this nature for switching and PBX applications. Copper lines or fibre optic lines from the phone company are connected to the cabinet. Copper cables or fibre optic cables attached to external mating connectors mate with the internal connectors in a mating direction which is generally perpendicular to the faceplate. The cables generally run at right angles to the mating direction and generally run towards the trailing end of the faceplate such that the cables extend over other internal connectors disposed on the faceplate towards the trailing end of the faceplate. The other end of the copper cables or fibre optic cables are typically attached to phones or data equipment.
Typically, inside each cable are numerous smaller cables. Depending on the number of these smaller cables and the thickness of the smaller cables, the cable can be quite thick. If the internal connectors are placed too close to each other on the faceplate, the cables connected to the external complementary connectors can interfere with each other. In addition, more stress can be placed on the connection point or points where the cables are connected to the connectors. The stress may become so high that the cables may break or the connection point or points may break. These problems may even be greater if a number of modules, each with a faceplate are placed closely together in a cabinet.
Typically, modules, each with a faceplate, are placed in a cabinet if one wants the modules to be interconnected to each other. At the other end of the module, opposite the faceplate, there is typically a connector disposed that interconnects with a mating connector inside the cabinet. The mating connectors inside the cabinet are typically connected to each other by means of cables or by means of a common circuit board.
To solve these problems mentioned above, persons skilled in the art have used larger faceplates with sufficient spacing in between the internal connectors. Consequently, the module can become quite large. If a number of these modules are placed in a cabinet, the size of the cabinet can become excessive.


A method for removing a surfactant from a palladium nanoparticle includes exposing the palladium nanoparticle to hydrogen and removing the surfactant from the palladium nanoparticle. A method includes synthesizing a palladium nanoparticle using a surfactant. The surfactant influences a geometric property of the palladium nanoparticle and bonds to the palladium nanoparticle. The method also includes exposing the palladium nanoparticle to hydrogen to remove the surfactant from the palladium nanoparticle.

Palladium and palladium alloy nanoparticles can be used as catalysts, particularly in fuel cells used to produce electrical energy. For example, in a hydrogen fuel cell, a palladium catalyst can be used to oxidize hydrogen gas into protons and electrons at the anode of the fuel cell. At the cathode of the fuel cell, the palladium catalyst triggers the oxygen reduction reaction (ORR), leading to formation of water.
Fuel cell performance depends in part on the available surface area of the palladium nanoparticles. Fuel cell performance generally increases when the surface area of the palladium nanoparticles is increased. In addition to size, the shape of the palladium nanoparticles can also be selected in order to further increase the oxygen reduction reaction (ORR) activity. Surfactants are commonly used during nanoparticle formation to control the particle size and shape. The surfactants bind to the nanoparticles as they are shaped and sized.
Once the nanoparticles have been formed, the surfactants used for shaping and sizing the particles need to be removed. Some surfactants can be removed by washing and low temperature heat treatment. Other surfactants, however, require long washing times (as long as weeks in special solvents) or high temperature treatment at temperatures above 300° C. For some catalyst nanoparticles, high temperature treatment presents problems. For example, at 300° C., cubic palladium nanoparticles may lose their shape and increase in particle size. As a result, using high temperature treatment to remove surfactants from the nanoparticles removes benefits the surfactants were intended to provide.

Surfactant removal from palladium nanoparticles


A process for rapid typing of yeast, parasites and bacteria is provided. It comprises the following steps: a) Preparing immobilized intact DNA in 5 to 60 minutes aided by a method involving a reagent kit that only contains buffer solution, a detergent, a metal chelating agent and an agent to disrupt the hydrogen bonds. b) Separating intact DNA molecules or their restriction fragments in miniequipments for Pulsed Field Gel Electrophoresis of the CHEF (Contour Clamped Homogeneous Electric Field) and TAFE (Transversal Alternating Field Electrophoresis) systems in times comprised between 2.5 and 7 hours. c) Selecting the optimal conditions that should be set in miniCHEF with the aid of a method to simulate the electrophoresis patterns d) Providing reorientation times, migration velocities and sizes of the molecules calculated with the aid of a method to analyze the migrated distances without the use of size markers.

During the past years, infectious diseases have increased and multi-drug resistance microorganisms have arisen (Acar J and Courvalein P pp 50-53; Aubry-Damon H and Andremot A, pp 54-55; Trieu-Cout P and Poyart C, pp 62-66, in 'La Recherche', vol 314, 1998).
Outbreaks of infectious diseases have generated the necessity of typing the causative microorganisms. Typing is the process by which different species of microorganisms of a given genus are classified in different subgroups or subtypes (Busch U and Nitschko H, J Chromatogr B, 1999, 722:263-278). Typing is important, from the epidemiological point of view, for recognizing outbreaks of infection, determining the way of transmission of nosocomial pathogens in the health centers and detecting the sources of the infections. It is also useful for identifying new virulent strains and monitoring vaccination programs. A typing process is been considered adequate if it fulfill the following criteria (Maslow J N et al., Clin Infect Dis, 1993, 17:153-164):                1. To give unambiguous results for each isolate analyzed.        2. To give reproducible results.        3. To differentiate unrelated strains within specie.
There are several microorganism typing methods. Some of them are based on the analysis of phenotypic features (phenotypic methods) and others on the analysis of genotypic features (genotypic methods). Phenotypic methods detect features expressed by microorganisms, whereas the genotypic ones evidence the differences among the DNA of microorganisms. Thus, phenotypic methods have the disadvantage of giving an indirect measure of the changes in the genetic background. Said disadvantage does not occur with the use of genotypic methods.
One of the genotypic typing methods most widely used is Pulsed Field Gel Electrophoresis (PFGE). This method is considered the gold standard for the molecular typing of microorganisms. PFGE typing is performed by separating in gels DNA molecules that are subjected to the action of electric pulses in two different directions. After electrophoresis, the band patterns given by DNA molecules of an isolate of microorganism are highly reproducible and discriminatory and characterize unequivocally its DNA (Oliver D M and Bean P, J Clin Microbiol, 1999, 37(6):1661-1669). Additionally, the whole genomes of numerous isolates can be compared in a single gel. Thus, PFGE has been proposed as the optimal typing method (Maslow J N, Mulligan M E and Arbeit R D, Clin Infect Dis, 1993(17):153-164; Busch U and Nitschko H, J Chromatogr B, 1999(722):263-278). The results obtained by PFGE depend on the experimental conditions applied in DNA separation and on the genus and specie of the microorganism subjected to study. Thus,    a) If the microorganism has several lineal chromosomes of sizes lower than 10 Mb (1 megabase=1 000 000 base pairs) the band pattern given by its chromosomes is obtained. Said band pattern is called 'the electrophoretic karyotype'. For instances, the microorganism can be yeast, unicellular parasites, etc.    b) If the microorganism has a single large circular chromosome the band pattern given by the macrorestriction fragments of said circular DNA is obtained. These patterns are called pulsetypes, since they are obtained in specific experimental conditions. For instances, the microorganism can be bacteria such as Escherichia coli, Staphylococcus aureus, etc.
The comparison of the electrophoretic karyotypes of different strains permits their characterization and differentiation. The same occurs with the restriction fragments of the bacterial DNA. Thus, both, the molecular karyotypes and the pulsotypes are used in the comparative study of fungi, bacteria and parasites. The routinely use of PFGE in medical microbiology has generated the necessity of improving the methods of sample preparation.
It also generated the need of designing a priori the running conditions to adequately separate the molecules and for analyzing the resulting electrophoresis patterns.
In general, the process of microorganism typing by PFGE comprises the following steps and procedures:    1) Preparing the samples: growing the microorganisms in nutrient broth, embedding the cells in gel and obtaining immobilized and deproteinized intact DNA molecules.    2) Designing the electrophoresis run: selecting the experimental conditions that should be set in PFGE equipments to obtain the optimal separation between the molecules.    3) Loading the samples in the gels and performing pulsed field gel electrophoresis to separate the DNA molecules.    4) Analyzing the band patterns obtained after the electrophoresis and comparing the results given by different isolates of microorganisms.
The equipments and procedures currently used in microorganism typing by PFGE are analyzed.
Pulsed Field Gel Electrophoresis
Pulsed field gel electrophoresis (PFGE) dates from 1984, when Schwartz and Cantor (Cell, 37, 67-75, 1984; U.S. Pat. No. 4,473,452) observed that applying electric pulses that periodically switched their orientation by a certain angle in relation to the agarose gel, large intact DNA molecules were resolved as band patterns.
The authors also determined that the separations of the molecules essentially depend on the duration of the electric pulses. Later, the angle formed by the field force lines, the electric field strength, the experimental temperature, the ionic strength of the buffer solution, the concentration of the agarose gel and the thickness of the agarose plugs, where the samples are embedded, were determined as the most important factors that influenced the resolution of DNA molecules. (Birren B. and Lai E. Pulsed Field Gel Electrophoresis: a practical guide. Academic Press. New York, 1993, p 107, 111, 129, 131, 135; López-Cánovas L. et al., J. of Chromatogr. A, 1998, 806, 123-139; López-Cánovas L. et al., J. of Chromatogr. A, 1998, 806, 187-197).
Different systems to perform PFGE have been developed. They have characteristic chambers with electrodes placed in different arrangements. Among these chambers are the OFAGE (Orthogonal Fi Id Alternating Gel Electrophor sis, Carle C. F. and Olson M. V. Nucleic Acids Res. 1984, 12, 5647-5664) CHEF ('Contour Clamped Homogeneous Electric Field', Chu G. Science 234, 1986, 1582-1585), TAFE ('Transversal Alternating Field Electrophoresis', U.S. Pat. No. 4,740,283), FIGE ('Field Inversion Gel Electrophor sis', U.S. Pat. No. 4,737,251 of Carle G. F. and Olson M. V) arrangements of electrodes, and the minichambers MiniTAFE and MiniCHEF (Riverón, A. M. et al., Anal. Lett, 1995, 28, 1973-1991; European Patent Application EP 0 745 844, Bula. 1996/49; U.S. patent application Ser. No. 08/688,607, 1995; Cuban patent RPI Nro. 02/95, 1995).
Commonly Used Systems for Microorganism Typing by PFGE
The most used systems for microorganism typing based on DNA analysis by PFGE are CHEF and TAFE. They provide straight band patterns in every lane of the gel, and thus, allow the comparison of the results obtained in a single run or in different electrophoresis runs.
The electrodes of CHEF system are placed in a hexagonal array around the gel and the voltages are clamped in them to guarantee homogenous electric field throughout the gel. The generation of homogeneous electric field throughout the chamber permits to obtain straight bands and reproducible migrations in the lanes of the gel. The electrodes of opposed polarities are 33.5 cm separated in CHEF chambers. It uses submarine gels that can be up to 21×14 cm in width and length. The gels are placed horizontally (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide. Catalog Numbers 170-3670 to 170-3673, BioRad, pp 11, 1995). As mentioned, CHEF systems have been extensively used for microorganism typing. For instances, bacteria (Beverly, S, Anal Biochem, 1989, 177:110-114; Dingwall A and Shapiro L, Proc Natl Acad Sci USA, 1989, 86:119-123; Ferdows M S and Barbour A G, Proc Natl Acad Sci USA, 1989, 86:5960-5973; Kohara Y, Akiyma K and Isono K, Cell, 1987, 50:495-508; Ohki M and Smith Cl, Nucleic Acids Res, 1989, 17:3479-3490; Schoenline P V, Gallman L M and Ely B, Gene, 1989, 70:321-329; Ventra L and Weiss A S, Gene, 1989, 78:29-36), Pseudomonas (Bautsch W, Grothues D and Tummler B, FEMS Microbiol Lett, 1988, 52:255-258; Romling U and Tummler B, J Clin Microbiol, 2000, 38(1):464-465), S. cerevisiae (Albig W and Entian K D, Gene, 1988, 73:141-152; Zerva L et al., J Clin Microbiol, 1996, 34(12):3031-3034), E. histolytica (Petter R et al., Infect Immun, 1993, 61(8):3574-3577), S. pneumoniae (McEllistrem M C et al., J Clin Microbiol, 2000, 38(1):351-353), S. aureus (Wichelhaus T A et al., J Clin Microbiol, 1999, 37(3):690-693), M. tuberculosis (Singh S P t al., J Clin Microbiol, 1999, 37(6):1927-1931), P. haemolytica (Kodjo A et al., J Clin Microbiol, 1999, 37(2):380-385), etc.
Due to the large dimensions of the CHEF chamber, it requires large amount of buffer solution to cover its electrode platform. Thus, the current intensity in the chamber can reach high values, even when low electric fields intensities are applied. Therefore, CHEF experiments demand power supplies of high rated power output. Besides it, large amount of heat is generated in the chambers, avoiding the reduction of run duration by increasing the electric field. CHEF chambers need at least 20 hours of electrophoresis to separate Saccharomyces cerevisiae chromosomes (molecules smaller than 1.6 Mb. 1 Mb=106 base pairs) in the characteristic pattern of 11 bands, and to type different strains of this yeast (Zerva L, et al., J Clin Microbiol, 1996, 34(12): 3031-3034). The CHEF chamber takes long time for separating the macrorestriction fragments of bacterial DNA molecules, since 20 hours, or more, are needed (van Belkum A et al., J Clin Microbiol 1998, 36(6):1653-1659; Marchadin H et al., Antimicrob Agents Chemother, 2000, 44(1):213-216; Romling U and Tummler B, J Clin Microbiol, 2000, 38(1):464-465). Similarly, long running times are needed to study parasites such as Entamoeba histolytica. To separate its chromosomes 24 hours are needed, at least (Petter R et al., Infect Immun, 1993, 61(8):3574-3577).
The advantage of currently used CHEF equipments is the possibility of analyzing 40 samples in a single run. This high throughput sample format facilitates the comparative analysis of the electrophoresis patterns given by samples of numerous isolates.
The TAFE system was proposed by K J Gardiner, W Laas and D Patterson in the paper published in Somatic Cell Mol Genet, 1986(12): 185. They called initially the system as "Vertical Pulsed Field Electrophoresis" (VPFE) and developed the equipment that was protected by the U.S. Pat. No. 4,740,283 of Apr. 26, 1988.
In TAFE system, two electrode pairs are placed parallel to both faces of the submarine gel (10×7.6×0.64 cm, length×width×thick), that is placed vertically in the chamber. Said electrode disposition generates electric field force lines that cross transversally the gel and compels the molecules to migrate through the gel thickness during each pulse. In TAFE, homogeneously sized molecules travel similar distances and migrate up to the same height in the gel leaving straight tracks, regardless the positions of the wells (into which the samples were loaded) in the gel. Thus, this system is useful for microorganism typing, since it facilitates the comparative analysis of the electrophoresis patterns given by samples of numerous isolates.
Based on these principles, Beckman Instruments manufactured the equipment called "Geneline I, or Transverse Alternating Field Electrophoresis System" (Beckman, The Geneline System Instruction Manual, ed. Spinco Division of Beckman Instruments Inc., 1988), which is also known as TAFE. This system uses a gel (11×7.2×0.6 cm, length×width×thickness) into which 20 samples can be loaded. Nevertheless, TAFE also requires large amount of buffer solution (3.5 liters) and biological sample. The equipment demands, at least, 20 hours to resolve the E. histolytica chromosomes (Báez-Camargo M et al., Mol Gen Genet 1996, 253:289-296). So, TAFE share the drawbacks with CHEF in microorganism typing.
As a conclusion, the commercially available equipments most frequently used to characterize the genome of microorganisms and parasites require long running time, and large amount of reagents and biological samples to resolve large DNA molecules in their band pattern.
FIGE system has been used for rapid typing of bacteria (Goering R V and Winters M A, J Clin Microbiol, 30(3):577-580, 1992; Grothues D et al., J Clin Microbiol, 26(10):1973-19771988). However, electrophoretic mobility inversion of DNA has been documented in FIGE experiments. Mobility inversion of DNA prevents correct size estimations and makes difficult the interpretation and comparison of the patterns given by numerous samples. The impossibility of predicting the moment of occurrence of DNA mobility inversion is one of the problems associated with said phenomenon (Birren B and Lai E. Pulsed Field Gel Electrophoresis: a practical guide, pp 10, Academic Press, Inc. San Diego, Calif. 1993). The main disadvantage of mobility inversion is the impossibility of identifying unambiguously the molecules present in a given band. To do it, the bands should be transferred and hybridized with specific probes. Hybridization notably increases the prices of the assay and is time demanding, thus the typing process will be more expensive and time consuming.
The attempts to reduce the electrophoresis time in current CHEF equipments, such as GeneNavigator (Amersham-Pharmacia-LKB, Pharmacia Molecular and Cell Biology Catalogue, Pulsed Field Gel Electrophoresis, Nucleic Acids Electrophoresis. 1998, pp 77-79), CHEF DRII and CHEF Mapper (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide. Catalog Numbers 170-3670 to 170-3673. Bio-Rad, pp 11, 1995) by increasing the voltage applied to the electrodes is nearly impossible. It is due to the limit of power supply output and the cooling system. Consequently, manufacturers recommend 9 V/cm as maximum electric field to apply in said equipments (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide. Catalog Numbers 170-3670 to 170-3673. Bio-Rad, pp 2, 1995). Therefore, the reduction of the electrophoresis duration by increasing the electric field intensity is prevented in CHEF system. Current TAFE equipments have similar problems.
PFGE Miniequipments
MiniPFGE equipments, miniCHEF and miniTAFE versions, were reported in 1995 (Riverón A M et al., Anal. Lett., 1995, vol. 28, pp 1973-1991; European Patent Application EP 0 745 844, Bull. 1996/49; U.S. patent application Ser. No. 08/688,607, 1995; Cuban Patent RPI 02/95, 1995). Miniequipments overcome most of the mentioned drawbacks of the PFGE equipments. Pulsed field electrophoresis experiments are performed in a minigel (4×4×0.5 cm; length×width×thickness) loaded with 7 samples in 4 to 6 hours. Electric field strength reaching 16 V/cm can be applied in MiniCHEF, providing good resolution of the electrophoresis band patterns in 2.7 hours. The short distance between the electrodes of opposed polarities permits to construct small chambers and to use small amount of buffer volumes to cover the electrodes. By applying a given voltage to a miniCHEF and CHEF chambers (certain electric field strength value 'E') the heat generated in the minichamber is always lesser than the heat generated in the commercially available CHEF (Riverón A M et al., Anal. Lett., 1995 vol. 28, pp. 1973-1991).
MiniTAFE equipments admit 22 V/cm, achieving resolution among the bands (Riverón A M et al., Anal. Lett., 1995 vol. 28, pp. 1973-1991). MiniTAFE permits to obtain the S. cerevisiae electrophoretic karyotype in 5 hours. MiniTAFE chambers with short separation (7.8 cm) between opposite electrodes are small and use small amount of buffer solution. However, if samples thicker than 0.1 cm are loaded in the minigels, longer running times are needed to achieve good resolution of the electrophoresis patterns. According to previous reports, sample thickness influences electrophoresis running time (López-Cánovas et al., J. Chromatogr. A, 1998, 806, pp. 187-197). As the samples are thicker, longer gels are needed to obtain the same band patterns. However, the reported miniCHEF minigels admit only 7 samples, whereas the miniTAFE supports 13 samples. They are low throughput sample formats for typing isolates of microorganisms in clinical laboratories.
Despite miniPFGE equipments have advantages over currently used systems, neither miniCHEF nor MiniTAFE were used for microorganism typing. Maybe, it obeys to the attempting of using samples as thick as the ones used in conventional gels. In addition, simple procedures to select miniequipment running parameters are not available.
Preparation of Immobilized DNA
A method to prepare intact DNA molecules is essential for microorganism typing by PFGE in current equipments or miniequipments. Previously reported methods of DNA isolation and purification in solution provoke shearing of said molecules (Schwartz D C and Cantor C R, Cell, 1984, 37, pp. 66-75). Schwartz and Cantor proposed a methodology to prepare samples for PFGE and only excluded the molecules with sizes smaller than 1 Mb (106 base pairs). The methodology consists in harvesting the cultured cells, washing the cells and embedding them in agarose plugs. In ulterior steps, spheroplasts (if cellular wall exists) are formed 'in situ' and further lysed in said plugs. Finally, the immobilized DNA molecules are deproteinized using proteinase K. The method has been effective to prepare samples from microorganisms of different genus, species and origins. However, spheroplasts need to be formed if said microorganisms possess cell wall, and the enzymes needed to form spheroplasts, as well as the proteases, are expensive. The reported procedure requires that samples were incubated overnight twice, which is 32 hours for sample preparation (U.S. Pat. No. 4,473,452, Sep. 25, 1984).
More recently, Gardner (Gardner D C J et al., Yeast, 1993, 9, 1053-1055) obtained band patterns of S. cerevisiae chromosomes from cells that did not form spheroplasts. In parallel, Higginson et al (Higginson D. et al., Anal. Lett., 1994, 27:7, 1255-1264) showed that S. cerevisiae DNA can be deproteinized using 8 M urea instead of proteinase K. However, the method described by Gardner is still expensive, because he used proteases to deproteinize the DNA, whereas, the method described by Higginson is cheap, but consumes 72 hours of incubation, which is a long time. Later, S. cerevisiae samples were prepared, and enzymes were not used: The plugs were sequentially incubated with LETK (10 mM Tris, 500 mM EDTA, 600 mM KCl, pH 7.5) for 4 hours, NDS (10 mM Tris, 500 mM EDTA, 1% sarcosyl, pH 9.5) for 2 hours, and NDS plus 4 M urea (NDSU) for 2 hours. This method needed 10 hours for sample preparation (López-Cánovas L, et al., Anal. Lett, 1996, 29:12, 2079-2084). Rapid methods for the preparation of immobilized DNA were described also, but they use enzymes (for instance, in Guidet F and Langridge P, Biotech, 1992, 12:2, 222-223).
As general rule, immobilized DNA for PFGE experiments requires the formation of spheroplasts and DNA deproteinization using proteases. These requirements are independent from the cell type studied (bacteria, yeast, etc) (Maule J, Mol. Biotech. 1998, 9: 107-126; Olive D M and Bean P, J. Clin. Microbiol, 1996, 37:6, 1661-1669). For instances, immobilized Staphilococcus aureus DNA were reported to be prepared in 2 hours by immobilizing cells with lysostaphin and incubating the plugs with detergents, whereas Streptococcus fecalis cells needed to be incubated with lysozyme and mutanolysin prior to the immobilization (Goering R V. and Winter M A., J. Clin. Microbiol, 1992, 30:3, 577-580). In the mentioned work, authors did not incubate the samples with proteinase K. However, Matushek et al. (Matushek M G et al., J. Clin. Microbiol, 1996, 34:10, 2598-2600) reported that they were unable to obtain the band patterns if the samples were not incubated with proteinase k. As alternative, they proposed a rapid method to prepare immobilized DNA samples using proteinase K. Recently, McEllistrem et al. (McEllistrem M C et al., J. Clin. Microbiol, 2000, 38:1, 351-353) reported a complete non-enzymatic method to prepare immobilized DNA of Streptococcus pneumoniae. However, it consumes 6 hours and the authors attributed the protocol success to the activation of an autolysin of the Streptococcus. At present, the spheroplast formation enzymes and the proteases have been deleted only from the protocols of preparation of intact DNA molecules of S. cerevisiae and Streptococcus pneumoniae, but the times required to complete these preparations are 10 and 6 hours, respectively, which are long times. Consensus does not exist about the feasibility of deleting the protoplast formation enzymes and proteinase K in sample preparation of microorganisms. Therefore, current methods are expensive and consume long times.
Most of the above methods rest on the assumption that microorganisms with cell walls must be immobilized previously to the enzymatic treatment. An exception is presented in the paper published by Goering and Winter (Goering R V and Winter M A, J. Clin. Microbiol, 1992, 30:3, 577-580). The authors suspended cells in a solution containing lysozyme and mutanolysin (two enzymes to form spheroplast) prior to their immobilization. However, a general non-enzymatic method to treat microorganisms with cell walls prior to their embedding in agarose gels has not been presented yet. Such method would be cheaper and simpler that current protocols in the preparation of samples.
Methods to isolate nuclei acids in solution, starting from cells heated in the presence of agents that provoke the permeability of the microorganism cell wall, were reported (European Patent 0,657,530, 1994, bulletin 95/24; U.S. Pat. No. 158,940, 1993). The method releases large fragments of undegraded nucleic acids from microorganisms without physically disrupting the entire cell wall. This method does not require lytic enzymes. However, intact DNA molecules are not obtained, because DNA is isolated in solution; and the authors did not propose the method to obtain the molecular karyotypes or the pulsetypes of the mentioned microorganisms. Authors reported that the obtained DNA is suitable for hybridization, but they did not address the possibility of DNA restriction with endonucleases. In conclusion, said method does not guarantee the obtaining of intact DNA molecules, whereas the possibility of digesting them with restriction enzymes remains unknown.
Therefore, a general procedure has not been proposed yet for the preparation of immobilized intact DNA from yeast, gram-positive and gram-negative bacteria and parasites by non-enzymatic methods in short times.
The preparation of immobilized DNA samples needs molds to form said samples. These molds can be reusable or disposable. The reusable molds should allow the sterilization. This is important for handling samples from pathogenic microorganism. The use of disposable molds requires continuous supply, which can be a limiting factor in laboratories with low budget.
Known molds are the following:    a) Molds that form independent and similar plugs (U.S. Pat. No. 4,473,452, Sep. 25, 1984);    b) Molds that form long ribbons, which are cut to form independent plugs;    c) Molds that form long square 'noodle' or long agarose rods, which are cut to form independent plugs (Birren B and Lai E. Pulsed Field Gel Electrophoresis: a practical guide, Academic Press, Inc. San Diego, Calif., 1993, pp 29-30).
In general, samples of dimensions larger than the gel slot are generated in said molds. For this reason, to obtain plugs with dimensions similar to the ones of slots, the ribbons, noodle, etc, need to be cut with a razor blade or another device. (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide pp 40, Section 7. Catalog Numbers 170-3670 to 170-3673. Bio-Rad. 1995). However, cutting the ribbons or noodles provokes plugs of non-homogeneous sizes and dimensions, which influence the quality of the electrophoresis patterns. DNA molecule resolutions in the gel depend on the sample thickness. Consequently, the comparison of the patterns obtained in different lanes of the gel is difficult. Difficulties in the comparisons of band patterns represent a disadvantage in microorganism typing.
A mold for embedding cells in agarose gels and treat plugs was disclosed in the U.S. Pat. No. 5,457,050, Oct. 10, 1995. The mold could be disposable or reusable, depending on the material used to make it. It is claimed that the facility of the mold is that samples are formed and treated inside said mold. However, it is a disadvantage: if the plugs are kept inside the mold during the incubations, the time needed to obtain the samples suitable for PFGE analysis is notably lengthened. The effector molecules of the lysis and deproteinization solutions can poorly reach the target molecules inside the cells, because the contact area between the plugs and the incubation solutions is at least reduced to half.
Selection of the PFGE Experimental Conditions
The selection of the experimental conditions is complex. Methods to select the running PFGE conditions have been reported.
For example, the CHEF Mapper from Bio-Rad has an option of auto-algorithm and another one of interactive algorithm (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide. pp 31-40 Catalog Numbers 170-3670 to 170-3673. Bio-Rad. 1995). Both options permit to calculate the pulse times, pulse ramp durations, reorientation angle, electric field and optimal running time to separate DNA molecules of a given sample. In contrast to the auto-algorithm, in which fixed experimental conditions are assumed, the buffer type, temperature and concentration, and the agarose type and concentration are permitted to vary as inputs in the interactive algorithm. Both algorithms work based on empirical and theoretical data collected during 5 years of experience (Bio-Rad Catalogue. Life Science Research Products. Bio-Rad Laboratories, pp185. 1998/99). However, the manufacturers recommend feed the auto-algorithm with DNA sizes smaller and larger than the expected sizes of the sample molecules. In addition, if extremely wide size ranges are entered to the auto-algorithm, as well as to the interactive program, erroneous results, such as band inversion in the mid range of the gel, can be generated.
Another empirical expression was proposed to give the electric pulse duration that separates the group of molecules of sizes falling between a given value and a higher one called RSL (Resolution Size Limit) (Smith D R. Methods I, 1990, 195-203). However, said expression is valid on specific experimental conditions alone, and it does not predict the resolution between two any molecules. Another function was proposed. It provides the approximate conditions of electric field and pulse time needed to separate a given group of molecules (Gunderson K and Chu G, Mol. Cell. Biol., 1991, 11:3348-3354). However, said function only permits to obtain rough estimates of the two mentioned variables, and does not provide the molecule migrations at any experimental condition.
Despite various theoretical studies were performed about DNA molecular reorientation during PFGE (Noolandi J, Adv. Electrophoresis, 1992, 5: 1-57; Maule J, Mol. Biotech. 1998, 9:107-126), said studies have not given a practical and useful result in the laboratories yet. They did not generate methods allowing the PFGE user to select and set the experimental conditions needed to separate the molecules under analysis.
The equations proposed by López-Cánovas et al. (López-Cánovas L et al., J. Chromatogr. A, 1998, 806:123-139) to describe DNA migration in PFGE, have not been used to predict the band patterns that should be obtained when varying the pulse time ramps, the electric field, temperature and running time. These variables are usually modified in microorganism typing.
PFGE Band Pattern Analysis
Computerized systems for image acquisition data from PFGE gels are available for band pattern analysis (Gerner-Smidt P et al., J. Clin. Microbiol, 1998, 37(3):876-877; Tenover F et al., J. Clin. Microbiol, 1995, 33(9):2233-2239; van Belkum A et al., J. Clin. Microbiol, 1998, 36(6):1653-1659). However, the comparison of the restriction patterns remains a subjective process, and it cannot be totally reduced to rigid algorithms (Tenover F et al., J. Clin. Microbiol, 1995, 33(9):2233-2239). Although computer based analyses were performed, the final interpretation of the patterns must be subordinated to previous visual inspection.
Automatic and non-automatic band pattern analysis give as result the number of bands and the sizes of the molecules in the bands. It is usually done by comparing unknown DNA migrations with the migrations of molecular weight markers. However, PFGE is relatively new, and size markers for wide DNA size range are not always available. Consequently, the criteria used for bacterial typing, based on the interpretation of PFGE band patterns, consist in the determination of the number of different restriction fragments found when digesting the DNA of the microorganisms under comparison.
Equations to describe DNA molecule migrations under a single pulse ramp, different electric field strength and distinct temperature were proposed from electrophoresis data collected in experiments done in 1.5% agarose, Lachema and 0.5×TBE, 1×TBE: 89 mM Tris, 89 mM Boric Acid, 2 mM EDTA (López-Cánovas L et al., J. Chromatogr. A, 1998, 806:123-139). However, a method to extend and apply said equations to the analysis of band patterns after the application of pulse time ramps does not exist. The application of pulse time ramps is usually done in the comparative study of microorganisms.
Current Process for Microorganism Typing by PFGE
Total process for microorganism typing needs long time and many resources. Electrophoresis demands around 20 hours, methods of sample preparation, recommended by manufacturers or reported in the literature, require to use large amounts of enzymes (For instances, 80 mg/ml proteinase k) and long incubation times (CHEF Mapper XA Pulsed Field Electrophoresis System. Instruction Manual and Application Guide. pp 40-43 Catalog Numbers 170-3670 to 170-3673. Bio-Rad. 1995). A factor limiting the use of PFGE for microorganism typing is the time needed to complete the analysis of isolates, It is from 2 to 3 days, thus reducing the capacity of the laboratories to analyze many samples (Olive D M and Bean P, J. Clin. Microbiol, 1999, 37:6, 1661-1669).

Method for rapid typification of microorganisms and set of reagents used

Centro Nacional de Investigaciones Cientificas (CNIC)


In control apparatus for an internal combustion engine which includes a plurality of sensors for detecting parameters representing operation state of the engine to thereby output respective sensor signals, a crank angle sensor for generating a reference period signal in synchronism with rotation of the engine, a fuel injector for injecting fuel in the engine and an air-fuel ratio controller for determining a driving time of the fuel injector on the basis of one of the sensor signals and the reference period signal includes a filter for filtering the one sensor signal, a decision means for making decision as to normality or abnormality of the one sensor signal, and a means responsive to the decision of abnormality of the one sensor signal for thereby determining the driving time on the basis of another sensor signal and a means responsive to restoration of the one sensor signal to the normal state to thereby enable the determination of the injector driving time based on the one sensor signal to be resumed only after lapse of a first delay time from the restoration of the one sensor signal to the normal state. The driving time can be corrected by taking into account the temperature of the engine cooling water.

1. Field of the Invention
The present invention generally relates to a control apparatus for an internal combustion engine (hereinafter also referred to as the engine) of a motor vehicle for controlling optimally the air-fuel ratio of a fuel mixture supplied to the engine in dependence on engine operation state indicated by at least one sensor signal which undergoes filter processing. More particularly, the invention is concerned with an engine control apparatus capable of preventing output torque of the engine from lowering due to erroneous detection of the engine operation state which may occur upon restoration of the sensor signal to a normal level from abnormality suffering state.
2. Description of the Related Art
For a better understanding of the present invention, description will first be made in some detail of the background techniques.
FIG. 3 is a diagram showing schematically a structure of a conventional engine control apparatus together with an engine body. Referring to the figure, an internal combustion engine 1 including a plurality of cylinders (four cylinders in the case of the illustrated example) is equipped with an intake pipe 2 for supplying a fuel-containing mixture gas to the engine 1 and an exhaust pipe 3 for discharging an exhaust gas resulting from combustion of the fuel mixture within the engine cylinders.
An air flow sensor 4 is installed in the intake pipe 2 at an upstream side thereof. This sensor 4 may be constituted by a Karman vortex type sensor which generates a pulse-like signal Q indicative of an intake air flow rate. A throttle valve 5 is mounted in the pipe 2 at a position downstream of the air flow sensor 4 for controlling the intake air flow in dependence on depression of an accelerator pedal (not shown). A throttle sensor 6 is provided in association with the throttle valve 5 for detecting the opening degree thereof. Fuel injectors 7 are also mounted in an intake manifold in the vicinity of the engine cylinders for injecting fuel into the individual cylinders. A water temperature sensor 8 is provided for detecting the temperature K of a cooling water of the engine 1.
A signal representing the opening degree .phi. of the throttle valve 5 which corresponds to a torque command issued by the driver is generated by the throttle sensor 6 and used in the processing for determining the accelerating state of the engine. Further, the throttle sensor signal can be utilized for determining the fuel injection quantity in place of the intake air flow signal Q when a fault occurs in the air flow sensor 4, as will be described hereinafter, because the throttle opening degree .phi. bears a certain correlation to the intake air flow Q.
At this juncture, it should be mentioned that in addition to the above sensors 4, 6 and 8 destined for detecting the engine operation state parameters Q, .phi. and K mentioned above, there are provided other various sensors for detecting other parameters indicative of the engine operation state. Accordingly, it should be understood that the phrase "sensor means" as used herein covers the other various sensors as well although they are omitted from illustration for simplification.
A crank angle sensor 9 is provided in association with a crank shaft of the engine 1 for generating a pulselike reference period signal .theta. in synchronism with rotation (rpm) of the crank shaft and hence that of the engine 1. The reference period signal .theta. represents crank angular positions which serve as references for the various engine controls inclusive of the fuel injection control, ignition timing control and others of the engine 1. Besides, a signal Ne representing the engine speed (rpm) can be derived from the reference period signal .theta..
An air-fuel ratio controller 10 is incorporated in an engine control unit (ECU) which may be constituted by a microcomputer and serves for determining a fuel injection amount, i.e., a driving time or duration Ti of the fuel injectors 7 on the basis of the various sensor signals and the reference period signal .theta. to thereby generate a command signal J corresponding to the driving time Ti for controlling the fuel injector 7.
The air-fuel ratio controller 10 includes a decision means for making decision as to normality or abnormality of the sensor signals and a filter means for filtering at least one of the sensor signals indicative of the engine operation state (e.g. the intake air flow signal Q and/or the water temperature signal K) and serves to decide whether or not the one sensor signal (e.g. the intake air flow signal Q) is normal to thereby determine the driving duration or time Ti of the fuel injectors on the basis of other engine operation state signal (e.g. the throttle opening degree signal .phi.) when the one sensor signal is abnormal while determining the driving time Ti on the basis of the above-mentioned one sensor signal (i.e., the intake air flow signal Q) upon restoration thereof to the normal state or level.
The signals produced by the various sensors and representing the engine operation state are ordinarily subjected to the filtering or filter processing in the air-fuel ratio controller 10 for the purpose of eliminating noise components superposed on the sensor signals due to turn-on/off of various switches. In this conjunction, it is noted that the intake air flow signal Q outputted from the air flow sensor 4 mounted in the intake pipe 2 takes a relatively long time for rising up to the normal level which reflects the amount of intake air supplied actually to the engine 1. For this reason, the air intake flow signal Q undergoes the filter processing with a large time constant, whereby an intake air flow data signal A which can be used for determining the injector driving time Ti is ultimately derived. Similarly, the output signal of the water temperature sensor 8 undergoes the filter processing with a large time constant since the water temperature K is usually controlled to be constant at 80.degree. C. and less susceptible to abrupt change.
As mentioned previously, the air-fuel ratio controller 10 is incorporated in the computer-based engine control unit which is in charge of overall engine control and serves for the control of the air-fuel ratio on the basis of the sensor signal(s) and the reference period signal .theta..
FIG. 4 is a timing chart of the reference period signal .theta. and the command signal J. As can be seen in the figure, the reference period signal .theta. is of a pulse-like waveform and has a period of 180.degree. in terms of the crank angle, wherein the trailing or falling edge of the pulse is used as a reference for the fuel injection timing. In the case of the illustrated engine system, the fuel injectors 7 for all the cylinders are simultaneously driven at every crank angle of 360.degree. (upon every complete rotation of the crank shaft 1). The individual sensor signals are fetched at the falling timing t.sub.11 ; t.sub.12 of the reference period pulse signal .theta., whereby the fuel injectors 7 are actuated for the driving time or period T.sub.i (1); T.sub.i (2).
FIGS. 5 and 6 are views illustrating maps which are incorporated in the air-fuel ratio controller to be referenced in determining the amount to fuel to be injected. To this end, desired or target air-fuel ratios (e.g. 14.7, etc.) are contained in these maps as the data representing corresponding fuel amounts or quantities.
More specifically, FIG. 5 shows a fuel quantity map containing the air fuel ratios. This map is previously prepared on the basis of the engine speed Ne (rpm) derived from the reference period signal .theta. and the intake air flow data A derived from the intake air flow sensor signal Q, wherein the fuel quantities corresponding to the air-fuel ratios in two-dimensionally arrayed areas of the map are selectively determined in accordance with a function given generally in the form of f(Ne, A).
The fuel mixture having the density represented by the air-fuel ratio and injected through the injectors 7 during the driving time Ti is so controlled as to become lean as the engine speed Ne (rpm) increases and become rich as the intake air flow A increases, as can be seen from FIG. 5.
On the other hand, FIG. 6 shows a fuel map which is prepared on the basis of the engine speed Ne (rpm) and the throttle opening degree .phi. which can represent indirectly the intake air flow A. This map is used when the intake air flow signal Q suffers abnormality, wherein the fuel quantity corresponding to each of the air-fuel ratios stored in the two-dimensionally arrayed areas of the map is selectively determined in accordance with a function generally given in the form of f(Ne, .phi.).
Next, description will turn to the air-fuel ratio control operation of the conventional engine control apparatus by referring to FIGS. 3 to 6 together with a timing chart shown in FIG. 7.
Usually, the pulse-like intake air flow signal Q indicative of the intake air flow rate is outputted from the air flow sensor 4 so far as it operates normally. This intake air flow signal Q undergoes the filter processing in the fuel-air ratio controller 10, whereby the intake air flow data signal A is generated. On the basis of this intake air flow data A and the engine rotation speed Ne, a reference fuel quantity corresponding to a desired or target air-fuel ratio is determined in accordance with the function f(Ne, A) by referencing the map shown in FIG. 5. A command signal J is then generated on the basis of the reference fuel quantity by the air-fuel ratio controller 10 and applied to the fuel injectors 7. In this manner, the fuel injection can be controlled in dependence on the operation state of the engine.
More specifically, the operation state of the engine 1 is detected at a time point corresponding to the falling edge of the reference period pulse signal .theta. at every complete rotation of the crank shaft. A the same time, it is decided whether the intake air flow signal Q of the air flow sensor 4 and the water temperature signal K of the water temperature sensor 8 are normal. When these signals Q and K are normal, the injector driving time Ti is calculated in the manner described above, whereby the command pulse signal J having the pulse width or duration corresponding to the injector driving time T is generated.
At that time, the injector driving time Ti, i.e., the pulse width of the command signal J, is determined in accordance with the following expression (1): EQU Ti=f(Ne, A).times.Gi.times.Kw+Td (1)
where f(Ne, A) represents the reference fuel quantity for realizing the desired air-fuel ratio as a function of the rotation speed Ne of the engine and the intake air flow data A. Assuming, by way of example, that the engine speed Ne is 3000 rpm, the intake air flow data A is 2 g/cylinder, and that the target air-fuel ration is 15.0, the reference fuel amount of 2/15 (.times.0.133 g) is set as the map data shown in FIG. 5. Further, in the above-mentioned expression (1), Gi represents a gain for the driving time of fuel injector 7, which gain Gi is used for calculating the injector driving time Ti required for injecting the reference fuel quantity determined from the map data f(Ne, A). Furthermore, Kw represents a correcting coefficient for the water temperature signal K. This correcting coefficient Kw is set at a large value when the water temperature K is low. This is because carburetion susceptibility of the fuel is poor when the water temperature K is low, as in the case of the engine warming operation, and thus it is required to increase the fuel supply to ensure a sufficient amount of the fuel which contributes to combustion within the engine cylinders even in the engine operation state where the water temperature K is low. Finally, Td represents a dead time intervening between the reception of the command signal J and the actual start of the fuel injection. The dead time T depends on the battery voltage.
As will be apparent from the above description, the fuel injector driving time Ti is calculated in accordance with the expression (1) so long as the air flow sensor is normal.
On the other hand, when the intake air flow signal Q is at an abnormal level or unavailable from the air flow sensor 4 due to a fault (such as contact failure), the air-fuel ratio controller 10 decides abnormality of the intake air flow signal Q and calculates the injector driving time Ti in accordance with the undermentioned expression (2) by referencing the map data f(Ne, .phi.) which is prepared on the basis of the throttle opening degree .phi. as shown in FIG. 6. EQU Ti=f(Ne, .phi.).times.Gi.times.Kw+Td (2)
At this juncture, it should be mentioned that although the throttle opening degree .phi. can not represent the intake air flow rate with a high fidelity when compared with the output signal of the air flow sensor 4, the throttle opening degree can adequately be utilized as the back-up data replacing the intake air flow data A. Further, since the throttle opening degree signal .phi. is not subjected to the filter processing with a large time constant, there arises practically no problem when the input data to the air-fuel ratio controller 10 is changed over to the throttle opening degree signal .phi. from the intake air flow data A immediately upon detection of occurrence of abnormality in the latter.
In this conjunction, it is further to be noted that when the intake air flow signal Q resumes the normal level due to, for example, restoration of the contact from the disconnected state in the air flow sensor 4 at a time point t.sub.1 shown in FIG. 7, the air-fuel ratio controller 10 decides that the intake air flow signal Q is normal and calculates the fuel injector driving time Ti on the basis of the intake air flow data A in accordance with the expression (1).
However, it is at a time point t.sub.2 that the intake air flow data signal A resulting from the filter processing reaches a normal value or level A.sub.o corresponding to the actual intake air flow signal Q, as shown in FIG. 7. Consequently, during a period extending from the time point t.sub.1 to t.sub.2 after restoration of the air-flow sensor to the normal state, the driving time T.sub.1 is calculated in accordance with the expression (1) by referencing the map data shown in FIG. 5 on the basis of the intake air flow data A which assumes a lower value than the normal level A.sub.o indicating the actual intake air flow rate. As a result of this, the target air-fuel ratio is set to a value corresponding to a lean fuel gas mixture, which means that the fuel injector driving time Ti becomes shorter as shown in FIG. 7, lowering the engine rotation speed Ne and the output torque, giving rise to a problem. In this case, if the engine is in the idling state with an inherently low output torque, the engine stoppage may take place in the worst case.
On the other hand, unless the water temperature signal K is obtained from the water temperature sensor 8, the air-fuel ratio controller 10 decides abnormality of the water temperature sensor 8 and corrects the fuel injector driving time Ti in accordance with the undermentioned expression (3) by using a predetermined correction coefficient Kw(80) for a predetermined water temperature of 80.degree. C. in place of the correcting coefficient Kw corresponding to the actual water temperature K. EQU Ti.times.f(Ne, A).times.Gi.times.Kw(80)+Td (3)
In the above expression, the predetermined correcting coefficient Kw(80) is employed in place of the coefficient Kw in the expression (1). It goes however without saying that the coefficient Kw(80) may equally be used in the expression (2) as well. In this manner, when the water temperature sensor 8 is decided as suffering from a fault, the fuel injector driving time Ti is calculated in accordance with the expression (3). However, when the water temperature sensor signal is restored to the normal level, the fuel injector driving time Ti is then calculated in accordance with the expression (1) by using the correcting coefficient Kw. In that case, however, a time lag is involved in the restoration of the water temperature signal K to the normal level due to the filter processing, as mentioned hereinbefore, which results in intervention of a time lag in optimizing the fuel injector driving time Ti, to a disadvantage.
As is apparent from the foregoing description, in the case of the conventional fuel injection control system described above, the sensor signals are used as the control information by the air-fuel ratio controller 10 immediately when they are restored to the normal level, incurring a time lag in realizing the optimal driving time Ti for the fuel injectors due to incorrect detection of the engine operation state, giving rise to a problem that the engine output torque is undesirably lowered.

Control apparatus for internal combustion engine


A low cost drip irrigation line is made by molding a drip emitter having an elongated labyrinthine channel formed in the depth of the emitter body. A plastic film is extruded and passed through a film die with an air injection tube at one end forming a plastic film bubble. A feed tube sequentially feeds the emitters in series through the plastic film bubble and to the nip of laminating rolls for laminating the emitter to the plastic film bubble so that opposite wall portions of the plastic film are bonded to the opposite outer faces of the emitter. This encloses the labyrinthine channel and thereby forms a sealed labyrinthine passage. Inlet and outlet openings are formed at opposite ends of the labyrinth and the film bubble, following the laminating step, is formed into an elongated flexible drip irrigation conduit with the emitter on the inside of the conduit so the inlet receives water under pressure travelling in the conduit, passes it through the labyrinthine passage, and discharges the water to the exterior of the conduit at a drip rate. The emitter body can be made from an injection-molded polymer, such as polyethylene, which can contain trifluralin, for inhibiting root growth near the emitters during use of the drip irrigation line.

Drip irrigation systems usually include a continuous irrigation water supply line with emitter-type drippers installed along the line, usually at regular intervals. Irrigation water flows through the supply line under pressure, and a small amount of water continuously drips out at the intervals where the drippers are located. Drip irrigation has proved to be highly successful in producing greater growth of vegetation with the same amount of water, when compared with conventional irrigation techniques.
A number of different drip irrigation systems have been used in the past. They vary from the cheapest and simplest systems, namely, a hole in the wall of a water supply line, to expensive and complex multi-component dripper units.
Perhaps the most practical of the prior drip irrigation systems involves use of separate drip emitters or drippers installed in or on the supply line. The dripper taps off a portion of the water flowing in the water supply line and passes the water through a labyrinth or other meandering or circuitous path that produces a large pressure drop in the water and discharges it at a uniform drip rate. Generally, such pressure-reducing labyrinthine drippers are successful because they use a large enough hole in the supply pipe and a wide enough passage through the labyrinth to avoid clogging in most cases, while they also operate at reasonably high line pressures.
The U.S.D.A. and other research groups have recognized that drip irrigation can provide savings benefits for water, agricultural chemicals, energy and labor; and that these benefits particularly apply to low value field crops, such as alfalfa, sugar cane, corn and cotton. Furthermore, they have shown that use of drip irrigation can result in a meaningful reduction in the pollution of aquifers by salts and agricultural chemicals.
The present invention is directed to the problem of developing an economic drip irrigation system for low value crops where it is essential to reduce the capital costs for a precise system to a level lower than that achieved by drip irrigation systems presently available.
There are low cost drip irrigation systems made from thin plastic film, as thin as 0.004 inch in wall thickness. These products are not easy to use because of the low strength of the film, and they are used for one growing season only and then thrown away. There are similar drip irrigation systems with wall thicknesses up to about 0.02 inch, and if buried, they will last for many crops, but these systems have problems with root intrusion. In addition, the management to operate these systems for several crops is very difficult, and thus excludes most growers. Drip irrigation systems presently on the market also do not effectively combine with the technology to use herbicides, such as trifluralin, to keep roots out of drip systems. U.S. Pat. No. 5,116,414 to Burton et al. describes a method for preventing roots of plants from intruding into a zone of soil below the surface of the soil without killing the plants. The patent describes a method for incorporating the herbicide trifluralin into a polymer to form a controlled release of trifluralin, which is EPA-registered for this application. Because of the low vapor pressure of trifluralin and its resultant volatility, it is very difficult to extrusion mold drip irrigation products containing trifluralin, because the heat of extrusion dissipates the trifluralin. Furthermore, due to the high cost of trifluralin, it is essential in its application to drip irrigation to maintain the trifluralin in the area to be protected, i.e., the exit holes from the drip system. For instance, it can be prohibitively expensive to uniformly disperse trifluralin in the wall of a drip irrigation conduit for the length of the supply line. There are heavy walled products with a wall thickness of 0.045 inch, for example, such as taught by Ruskin in U.S. Pat. No. 5,052,625, which are combined with trifluralin. However, these products are much too expensive for low value field crops.
Hence, there is a need for a low cost drip irrigation system having low manufacturing costs, including the costs of materials, capital and labor, and high production speeds. There is also a need for a low cost dripper system suitable to carry trifluralin so that it is effective during use, and so that the end product will deliver precise amounts at each orifice. Such low cost dripper systems should be resistant to clogging by impurities in the water. There is also a need for a low cost drip irrigation system that will have an extended life beyond the growing season of one crop and can, in fact, be used for multiple growing seasons or multiple crops in sequence over an extended period of time, while the trifluralin also remains effective over such an extended period of time.

Process for making low cost drip irrigation lines using plastic extrusion and film blowing techniques


The present disclosure relates to oligodeoxynucleotides that suppress an immune response. Methods are disclosed for inhibiting or treating inflammatory lung disease by administering a therapeutically effective amount of a suppressive oligodeoxynucleotide.

Lung disease is the number three killer in America, responsible for one in seven deaths, and lung disease and other breathing problems are the number one killer of babies younger than one year old. Today, more than 30 million Americans are living with chronic inflammatory lung diseases such as emphysema and chronic bronchitis. In addition, approximately 150,000 Americans are affected by acute respiratory distress syndrome (ARDS) each year.
Many lung diseases are associated with lung inflammation. For example, ARDS involves the rapid onset of progressive malfunction of the lungs, and is usually associated with the malfunction of other organs due to the inability to take up oxygen. The condition is associated with extensive lung inflammation and small blood vessel injury in all affected organs. ARDS is commonly precipitated by trauma, sepsis (systemic infection), diffuse pneumonia, and shock. It also may be associated with extensive surgery, and certain blood abnormalities. In many cases of ARDS and other inflammatory lung diseases, the inflammatory response that accompanies the underlying disease state is much more dangerous than the underlying infection or trauma.
Many approaches to the prevention and management of ARDS have been unsuccessful or inconclusive. Treatments that have not improved outcome or prevented ARDS include monoclonal antibody to endotoxin, monoclonal antibody to tumor necrosis factor, interleukin-1 receptor antagonist, prophylactic (early) positive end-expiratory pressure (PEEP), extracorporeal membrane oxygenation and extracorporeal CO2 removal, IV albumin, volume expansion and cardiotonic drugs to increase systemic O2 delivery, corticosteroids in early ARDS, parenteral ibuprofen to inhibit cyclooxygenase, prostaglandin E1, and pentoxifylline.
Other common treatments for ARDS are also problematic. For example, there are safety and toxicity concerns regarding the use of inhaled NO. Inhaling very high levels of NO (5,000 to 20,000 ppm) can be lethal, causing a severe and acute accumulation of fluid in the lungs (pulmonary edema) and methomoglobinemia. Although OSHA has set the safety limit for NO2 at 5 ppm, some investigators have found that prolonged exposure to even 2 ppm of NO2 can be injurious to the lungs. Corticosteroids are of no proven benefit in acute ARDS, although anecdotal reports suggest benefit in some subjects with ARDS in the late fibroproliferative phase, which may develop after 7 to 10 days of mechanical ventilation. Mechanical ventilation, itself, carries risks, as well. For instance, tension pneumothorax is associated with the use of positive pressure ventilation (PPV) and PEEP, and may occur suddenly.
In view of the above, there exists a need for new therapies to treat inflammatory lung disease, particularly agents that suppress the inflammation associated with pneumonia, ARDS, respiratory distress of prematurity, chronic bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, pulmonary fibrosis, and pulmonary sarcoidosis.

Method of treating inflammatory lung disease with suppressors of CpG oligonucleotides

The United States of America as represented by the Secretary of the Department of Health and Human Services


A stent delivery and apposition detecting system includes at least one electrode pair of dissimilar metals mounted on a balloon of a balloon catheter. The electrode pair forms part of an electrochemical cell, and voltage and current generated from the electrochemical cell enables the system to detect when a stent mounted on the balloon achieves proper wall apposition. As the balloon is exposed to different environments, i.e., blood or tissue having different resistances, the electric potential of the electrochemical cell changes and an alert is generated by a feedback circuit to notify a user that the electrodes are in contact with tissue of the vessel wall. In one embodiment, the feedback circuit may be powered by the electrochemical cell. Multiple sets of electrode pairs may be mounted along the circumference and length of the balloon to detect differential contact between the deployed stent and the vessel wall.

Stent prostheses are known for implantation within body lumens to provide artificial radial support to a collapsing, weakened, and/or occluded passageway, such as blood vessels of the body. Stent prostheses are typically constructed of a metal or polymer and are generally a hollow cylindrical shape. When a balloon-expandable stent is to be implanted, a balloon catheter carrying the stent mounted on its balloon is advanced to the target site, such as a stenosis. The balloon and accompanying stent are positioned at the location of the stenosis, and the balloon is inflated to circumferentially expand and thereby implant the stent. As the balloon expands, it physically forces the stent to radially expand such that the outside surface of the stent comes into contact with the vessel wall. Thereafter, the balloon is deflated and the balloon catheter is withdrawn from the patient, leaving the stent in the expanded or deployed configuration.
One criterion for successful stent deployment is apposition of the stent against the vessel wall, since any regions of the stent that protrude into the lumen may cause blood turbulence, which in turn may lead to acute thrombosis and arterial blockage. By "apposition" or "wall apposition" herein it is meant that at least the outer surface of the deployed stent is fully positioned against, i.e., makes contact with, the vessel wall. The desire to prevent incomplete apposition leads to the common practice of dilating the stent after it is initially expanded with a second high-pressure balloon. This procedure intentionally overexpands the stent to ensure full apposition but may cause unnecessary injury to the vessel, which may lead to the primary failure mode of stents: the chronic hyperproliferative growth of smooth muscle cells called neointimal hyperplasia. This growth impinges on the lumen and reduces blood flow, which in approximately 30% of all stented patients is severe enough to require further intervention within three months of stent implantation.
In addition, the geometry or shape of many vessel lesions compounds the problem of incomplete vessel apposition. A so-called focal lesion is one that has a generally thicker midsection with one or more tapered ends, with the thicker midsection resulting in a constricted or occluded body lumen. When a stent is expanded over a focal lesion, the proximal and distal ends of the stent may not be apposed to the vessel wall although the middle of the stent has expanded sufficiently to restore patency. In order to achieve full apposition, the proximal and distal ends of the stent may require further expansion relative to the middle of the stent.
There exists a need in the art to ensure that a balloon expandable stent achieves complete or full apposition against the vessel wall during deployment. It is an object hereof to provide a stent delivery system that enables a physician the ability to adequately deploy a stent such that the implant will have complete apposition against the vessel wall.

Stent delivery system for detecting wall apposition of the stent during deployment