Disclosed is a low-power data transfer circuit having a high data transfer rate. This data transfer circuit of the invention includes a first selection circuit for selecting two signal lines out of three signal lines and precharging the remaining signal line to a first potential; and a second selection circuit for selecting and connecting the two data signal lines selected by the first selection circuit to a reception side circuit. With the configuration, a period of precharging a signal line is included in a data transfer period. Thus, there is no need to provide a specific precharge period after data transfer, and data can be transferred effectively.

1. Field of the Invention
The present invention relates to a data transfer circuit and, more particularly, a data transfer circuit for transferring data synchronously with a clock signal.
2. Description of the Background Art
Conventionally, as a method of transferring data between semiconductor integrated circuit devices or in a semiconductor integrated circuit device, a method of precharging two data transfer lines disposed between a transmission side circuit and a reception side circuit once to the same potential (for example, xe2x80x9cHxe2x80x9d level) and setting one of the two data transfer lines selected according to transfer data to the xe2x80x9cLxe2x80x9d level, thereby transferring data xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d is known.
According to the data transfer method, each time data is transferred, the two data transfer lines have to be precharged once to the xe2x80x9cHxe2x80x9d level.
Consequently, when the data transfer lines become longer and wiring capacity and wiring resistance accordingly increase, time necessary for precharging becomes long, and it causes a problem such that the data transfer rate deteriorates.
Japanese Patent Laying-Open No. 2000-132970 discloses a method in which three data transfer lines are disposed between a transmission side circuit and a reception side circuit, while data is transferred by using two data transfer lines, the remaining data transfer line is precharged to the xe2x80x9cHxe2x80x9d level and, then, data is transferred by using the two data transfer lines of the xe2x80x9cHxe2x80x9d level including the precharged data transfer line among the three data transfer lines, thereby preventing deterioration in data transfer rate.
Since precharging is performed during data transfer, the data transfer system has, however, a problem that the power consumption is high as compared with the conventional technique of performing precharging after data transfer.
Japanese Patent Laying-Open No. 2000-339968 discloses a method of transferring charges between a data transfer line to be precharged and a data transfer line changed from the xe2x80x9cHxe2x80x9d level to the xe2x80x9cLxe2x80x9d level for data transfer, thereby reducing power consumption.
This method, however, has a problem of a low transfer rate due to a circuit operation of electrically connecting the data transfer lines at the time of data transfer to transfer charges, interrupting the electrical connection and, after that, further changing the potential of the data transfer line by a driver.
An object of the invention is to provide a low-power data transfer circuit having a high data transfer rate.
A data transfer circuit, includes: three data signal lines; a first selection circuit for selecting two data signal lines having first and second potentials which are complementary to each other for transmitting data, out of the three data signal lines and for precharging a non-selected data signal line to the first potential; and a second selection circuit for selectively and electrically connecting the two data signal lines selected by the first selection circuit out of the three data signal lines to a reception side circuit, and the first selection circuit includes a driver circuit provided corresponding to each of the three data signal lines and connected between the first and third potentials and the second potential is set to a level between the first and third potentials.
By using two out of three data transfer lines to transfer data and precharging the remaining one data transfer line while data is transferred, data transfer can be performed efficiently and maintaining one of potentials of the selected two data transfer lines at a first potential as a potential for precharging and setting the other potential to a second potential between a third potential (for example, ground potential GND) and the first potential, power consumption to precharge the data transfer line to the first potential can be reduced.
Preferably, the first selection circuit selects two data signal lines of same potential levels out of the three data signal lines, on the basis of the potentials of predetermined two data signal lines out of the three data signal lines.
A data transfer line to be selected next can be selected based on the potentials of two data transfer lines out of the three data transfer lines. Consequently, it is unnecessary to supply a selection signal from the outside, and the number of components can be reduced.
Preferably, the second selection circuit includes an amplifying circuit for amplifying a potential difference between the two data signal lines selected by the first selection circuit out of the three data signal lines, and
on the basis of the potential difference amplified by the amplifying circuit, selectively and electrically connects the two data signal lines selected by the first selection circuit to the reception side circuit.
The data transfer lines used for data transfer out of the three data transfer lines can be selected by a potential difference of the two data transfer lines. Thus, it is unnecessary to supply a selection signal from the outside, and the number of components can be reduced.
Preferably, the data transfer circuit further includes a latching circuit for holding the potentials of predetermined two data signal lines out of the three data signal lines as binary data; and the first selection circuit selects two data signal lines out of the three data signal lines on the basis of the binary data held by the latching circuit.
Particularly the first selection circuit includes a logic control section for selecting two data signal lines out of the three data signal lines and selecting one of the first potential and third potential supplied by the potential supply source to each of the three data signal lines.
Particularly the driver circuit is activated in response to a driver enable signal, and the second potential is set in accordance with an active period of the driver enable signal.
The semiconductor integrated circuit includes: a memory cell array having a plurality of memory cells arranged in a matrix; an input/output control circuit for outputting data held in a selected memory cell designated on the basis of an address signal out of the memory cell; a data buffer circuit for outputting a reading data read from the input/output control circuit to an external output-terminal a data transfer circuit placed between the input/output control circuit and the data buffer circuit and for transmitting the reading data to the data buffer circuit a first input/output line for transmitting the reading data from the input/output control circuit to the data transfer circuit and a second input/output line for transmitting the reading data from the data transfer circuit to the data buffer circuit, and the data transfer circuit includes; three data signal lines are longer than the first and second input/output line; a first selection circuit for selecting two data signal lines whose potentials change to first and second potentials which are complementary to each other in accordance with the data to be transmitted out of the three data signal lines and for precharging a non-selected data signal line to the first potential; a second selection circuit for selectively and electrically connecting the two data signal lines selected by the first selection circuit out of the three data signal lines to a reception side circuit; and the first selection circuit having a driver circuit provided corresponding to each of the three data signal lines and connected between the first potential and third potential and the logic control section for selecting two data signal lines out of the three data signal lines in conjunction with selecting one of the first potential and third potential supplied by the potential supply source to each of the three data signal lines and the driver circuit activates on the basis of a driver enable signal, and the second potential is set by a period of time during supplying the driver enable signal the second selection circuit having an amplifying circuit for amplifying a potential difference between the two data signal lines selected by the first selection circuit out of the three data signal lines, and on the basis of the potential difference amplified by the amplifying circuit, selectively and electrically connects the two data signal lines having selected by the first selection circuit to the second input/output line.
The semiconductor integrated circuit of the invention uses two out of three data transfer lines to transfer data and precharges the remaining one data transfer line while data is transferred, thereby enabling data transfer to be performed efficiently and by maintaining one of potentials of the selected two data transfer lines at a first potential as a potential for precharging and setting the other potential to a second potential between a third potential (for example, ground potential GND) and the first potential, power consumption to precharge the data transfer line to the first potential can be reduced.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Data transfer circuit and semiconductor integrated circuit having the same


Disclosed is a process which comprises reacting a polyimide precursor with borane. Also disclosed is a thermal ink jet printhead containing a layer comprising the product of this reaction.

The present invention is directed to processes for curing polyimides and to thermal ink jet printheads containing polyimide components prepared by this process. More specifically, the present invention is directed to processes for curing polyimides by reacting polyimide precursors with borane. One embodiment of the present invention is directed to a process which comprises reacting a polyimide precursor with borane. Another embodiment of the present invention is directed to an ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, and (iii) a thick film layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, said thick film layer comprising the reaction product of a polyimide precursor with borane, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles. Yet another embodiment of the present invention is directed to a process for preparing an ink jet printhead which comprises the steps of:
(a) providing a photopatternable polyimide precursor polymer; PA1 (b) depositing a thick film layer comprising the photopatternable polymer onto a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, said photopatternable polymer being deposited onto the surface having the heating elements and addressing electrodes thereon; PA1 (c) exposing the thick film layer to actinic radiation in an imagewise pattern, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes; PA1 (d) removing the photopatternable polymer from the unexposed areas, thereby forming recesses in the thick film layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; PA1 (e) reacting the photopatternable polymer in the exposed areas with borane; PA1 (f) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, and PA1 (g) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles. PA1 (a) providing a photopatternable polyimide precursor polymer; PA1 (b) depositing a thick film layer comprising the photopatternable polymer onto a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, said photopatternable polymer being deposited onto the surface having the heating elements and addressing electrodes thereon; PA1 (c) exposing the thick film layer to actinic radiation in an imagewise pattern, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes; PA1 (d) removing the photopatternable polymer from the unexposed areas, thereby forming recesses in the thick film layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes; PA1 (e) reacting the photopatternable polymer in the exposed areas with borane; PA1 (f) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and PA1 (g) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are different types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system's ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
The other type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the "bubble jet" system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280.degree. C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The surface of the printhead encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet equipment and processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, U.S. Pat. No. 4,532,530, and U.S. Pat. No. 4,774,530, the disclosures of each of which are totally incorporated herein by reference.
In ink jet printing, a printhead is usually provided having one or more ink-filled channels communicating with an ink supply chamber at one end and having an opening at the opposite end, referred to as a nozzle. These printheads form images on a recording medium such as paper by expelling droplets of ink from the nozzles onto the recording medium. The ink forms a meniscus at each nozzle prior to being expelled in the form of a droplet. After a droplet is expelled, additional ink surges to the nozzle to reform the meniscus.
In thermal ink jet printing, a thermal energy generator, usually a resistor, is located in the channels near the nozzles a predetermined distance therefrom. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble which expels an ink droplet. As the bubble grows, the ink bulges from the nozzle and is contained by the surface tension of the ink as a meniscus. The rapidly expanding vapor bubble pushes the column of ink filling the channel towards the nozzle. At the end of the current pulse the heater rapidly cools and the vapor bubble begins to collapse. However, because of inertia, most of the column of ink that received an impulse from the exploding bubble continues its forward motion and is ejected from the nozzle as an ink drop. As the bubble begins to collapse, the ink still in the channel between the nozzle and bubble starts to move towards the collapsing bubble, causing a volumetric contraction of the ink at the nozzle and resulting in the separation of the bulging ink as a droplet. The acceleration of the ink out of the nozzle while the bubble is growing provides the momentum and velocity of the droplet in a substantially straight line direction towards a recording medium, such as paper.
Ink jet printheads include an array of nozzles and may, for example, be formed of silicon wafers using orientation dependent etching (ODE) techniques. The use of silicon wafers is advantageous because ODE techniques can form structures, such as nozzles, on silicon wafers in a highly precise manner. Moreover, these structures can be fabricated efficiently at low cost. The resulting nozzles are generally triangular in cross-section. Thermal ink jet printheads made by using the above-mentioned ODE techniques typically comprise a channel plate which contains a plurality of nozzle-defining channels located on a lower surface thereof bonded to a heater plate having a plurality of resistive heater elements formed on an upper surface thereof and arranged so that a heater element is located in each channel. The upper surface of the heater plate typically includes an insulative layer which is patterned to form recesses exposing the individual heating elements. This insulative layer is referred to as a "pit layer" and is sandwiched between the channel plate and heater plate. For examples of printheads employing this construction, see U.S. Pat. No. 4,774,530 and U.S. Pat. No. 4,829,324, the disclosures of each of which are totally incorporated herein by reference. Additional examples of thermal ink jet printheads are disclosed in, for example, U.S. Pat. No. 4,835,553, U.S. Pat. No. 5,057,853, and U.S. Pat. No. 4,678,529, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 4,601,777 (Hawkins et al.), the disclosure of which is totally incorporated herein by reference, discloses fabricating processes for ink jet printheads, each printhead being composed of two parts aligned and bonded together. One part is a substantially flat substrate which contains on the surface thereof a lineal array of heating elements and addressing electrodes, and the second part is a substrate having at least one recess anisotropically etched therein to serve as an ink supply manifold when the two parts are bonded together. A lineal array of parallel grooves are formed in the second part, so that one end of the grooves communicates with the manifold recess and the other ends are open for use as ink droplet expelling nozzles. Many printheads can be made simultaneously by producing a plurality of sets of heating elements array with their addressing electrodes on a silicon wafer and by placing alignment marks thereon at predetermined locations. A corresponding plurality of sets of channels and associated manifolds are produced in a second silicon wafer and, in one embodiment, alignment openings are etched thereon at predetermined locations. The two wafers are aligned via the alignment openings and alignment marks, then bonded together and diced into many separate printheads.
U.S. Pat. No. 4,678,529 (Drake et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of bonding ink jet printhead components together by coating a flexible substrate with a relatively thin, uniform layer of an adhesive having an intermediate non-tacky curing stage with a shelf life with around one month for ease of alignment of the parts and ease of storage of the components having the adhesive thereon. Transferring about half of the adhesive layer on the flexible substrate to the high points or lands of one of the printhead components within a predetermined time of the coating of the flexible substrate is achieved by placing it in contact therewith and applying a predetermined temperature and pressure to the flexible substrate prior to peeling it from the printhead component. This process causes the adhesive to fail cohesively in the liquid state, assuring that about half of the thickness of the adhesive layer stays with the flexible substrate and is discarded therewith, leaving a very thin uniform layer of adhesive on the printhead component lands. The transferred adhesive layer remaining on the printhead component enters an intermediate non-tacky curing stage to assist in subsequent alignment of the printhead components. The printhead components are aligned and the adhesive layer cured to complete fabrication of the printhead.
Known thermal ink jet printheads frequently include a barrier layer or pit layer of a polyimide material. Many polyimide barrier layers are unable to withstand prolonged contact with the materials commonly employed in thermal ink jet inks. Aqueous inks having a pH of 8 or more are particularly likely to cause hydrolysis and delamination of the polyimide barrier layer in a thermal ink jet printhead. While not being limited to any particular theory, it is believed that the partially cured polyimide layer is subject to hydrolytic attack when contacted with basic inks.
Accordingly, while known compositions and processes are suitable for their intended purposes, a need remains for improved thermal ink jet printheads. In addition, a need remains for thermal ink jet printheads in which the barrier layer exhibits reduced lamination upon exposure to inks. Further, there is a need for thermal ink jet printheads with barrier layers having increased resistance to hydrolysis. Additionally, there is a need for thermal ink jet printheads which exhibit improved adhesion of the heater wafer to the channel wafer subsequent to prolonged exposure to inks. There is also a need for processes for preparing improved thermal ink jet printheads with these advantages. A further need exists for processes for curing polyimide components without the need for application of heat. Additionally, a need remains for processes for curing polyimide components wherein shrinkage of the material during curing is reduced or eliminated. A further need exists for processes for curing polyimide films without reduced stresses induced by heat cure during the imidization step.

Polyimide curing process and improved thermal ink jet printhead prepared thereby


This invention relates to novel substituted 1,4-benzodioxine compounds having antidiabetic, antihyperglycemic, and antiobesity properties represented by the formula ##STR1## wherein R.sup.1 and R.sup.6 are independently hydrogen, C.sub.1 to C.sub.6 alkyl, trifluoromethyl, cyano, C.sub.1 to C.sub.6 alkoxy, or halogen;. R.sup.2 is hydrogen or C.sub.1 to C.sub.6 trialkylsilyl; R.sup.3 is hydrogen or C.sub.1 to C.sub.6 alkoxycarbonyl; PA1 or R.sub.2 and R.sup.3 are joined to form the oxazolidinone ring ##STR2## R.sup.4 and R.sup.5 are independently hydrogen or C.sub.1 to C.sub.6 alkyl; PA1 R.sup.7 and R.sup.8 are independently OR.sup.9 or NR.sup.10 R.sup.11 ; PA1 R.sup.9 is hydrogen, C.sub.1 to C.sub.12 alkyl, C.sub.1 to C.sub.12 cycloalkyl, C.sub.1 to C.sub.12 silylalkyl, phenyl, naphthyl phenyl C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy C.sub.1 to C.sub.6 alkyl, pyridyl, thiophenyl, furanyl, imidazolyl, oxazolyl, --CHR.sup.12 COOR.sup.13 --CHR.sup.12 C(O)R.sup.13, --CHR.sup.12 CONR.sup.10 R.sup.11, --CHR.sup.12 OCOOR.sup.13, or --CHR.sup.12 OC(O)R.sup.13 ; PA1 R.sup.10 and R.sup.11 are independently hydrogen, C.sub.1 to C.sub.12 alkyl, phenyl, naphthyl, phenyl-C.sub.1 to C.sub.6 alkyl, furanylalkyl, or alkoxycarbonylalkyl; PA1 R.sup.12 and R.sup.13 are independently hydrogen, C.sub.1 to C.sub.12 alkyl, phenyl, naphthyl, or phenyl-C.sub.1 to C.sub.6 alkyl; and the pharmaceutically acceptable salts thereof, a salt thereof;. an enantiomer thereof, the racemic mixtures thereof, and the diastereomeric mixtures thereof. The present invention also relates to a pharmaceutical composition, and methods for treating diabetes and/or hyperglycemia and/or obesity in mammals and producing lean meat in edible domestic animals.

It is well known that medicinal agents are employed in the treatment of persons suffering from diabetes, hyperglycemia, and obesity. The compounds of the present invention achieve their antidiabetic, antihyperglycemic, and antiobesity effects by acting as selective agonists at .beta..sub.3 adrenergic receptors. The stimulation of these receptors on white and brown adipocytes promotes both lipolysis (breakdown of fat) and energy expenditure. Selective stimulation of .beta..sub.3 adrenergic receptors is important for chronic treatment. Stimulation of other, .beta.-receptors could cause side effects such as increased heart rate (.beta..sub.1 effect) and/or muscle tremor (.beta..sub.2 effect). The compounds of the present invention show high selectivity for .beta..sub.3 adrenergic receptors.
Bloom, et al., U.S. Pat. No. 5,061,727, disclose substituted 5-(2-((2-aryl-2-hydroxyethyl)amino)propyl)-1,3-benzodioxoles of general formula (I) ##STR3## wherein R.sup.1 and R.sup.4 may be one or more groups which may be the same or different and are selected from the group consisting of hydrogen, C.sub.1 to C.sub.4 alkyl, C.sub.1 to C.sub.4 alkoxy, hydroxy, halogen, trifluoromethyl, carboxy, hydroxyalkyl, alkoxycarbonyl, C.sub.1 to C.sub.4 thioalkyl, sulfonyl and sulfinyl; X is a divalent radical consisting of ##STR4## wherein R' is selected from the group consisting of hydrogen, C.sub.1 to C.sub.4 alkyl and C.sub.1 to C.sub.4 acyl and Y is selected from the group consisting of carbonyl and thiocarbonyl; R.sup.2 and R.sup.3 may be the same or different and are selected from the group consisting of hydrogen and C.sub.1 to C.sub.4 alkyl; R.sup.5 and R.sup.6 are selected from the group consisting of hydrogen, carboxy, alkoxycarbonyl, hydroxymethyl, --CH.sub.2 OCH.sub.2 COOR.sub.7 and --CH.sub.2 OCH.sub.2 CH,.sub.2 OR.sub.7, where R.sup.7 is hydrogen or C.sub.1 to C.sub.4 alkyl; with the provision that R.sup.5 and R.sup.6 may not both be hydrogen; which have antihyperglycemic and antiobesity activity.
The synthesis, antidiabetic effects, and antiobesity effects of (R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1,3-benzodiox ole-2,2-dicarboxylate, disclosed by Bloom, et al. in U.S. Pat. No. 5,061,727, are detailed in Bloom, et al. J. Med. Chem., 1992,35, 3081, Largis, et al. Drug Dev. Res., 1994, 32, 69, and Bloom, et al. Drugs of the Future, 1994,19, 23.
The compounds of the present invention contain a 1,4-benzodioxane ring, whereas the compounds in Bloom, et al., U.S. Pat. No. 5,061,727 contain a 1,3-benzodioxole. They retain high selectivity for the .beta..sub.3 receptor and show much higher antiobesity and antihyperglycemic activity in animal models. Therefore, the compounds of this invention are useful in treating diabetes, hyperglycemia, and obesity, exhibiting minimal side effects such as heart rate increase and/or muscle tremor in humans and animals, when formulated into pharmaceutical compositions. Health-conscious individuals today are making an effort to reduce body fat through exercise and low fat diet. An invention compound can help a human reduce body fat and through treatment of domestic edible animals such as cattle, swine, sheep, goats, turkeys and chickens can provide leaner meats for human consumption.

Substituted Benzo[1,4]dioxines as antiobesity agents


Described is a gene and its encoded secreted tumor antigen, termed 36P6D5, and to diagnostic and therapeutic methods and compositions useful in the management of various cancers which express 36P6D5, particularly including cancers of the bladder, kidney, prostate, breast, colon, ovary and pancreas.

Cancer is the second leading cause of human death next to coronary disease. Worldwide, millions of people die from cancer every year. In the United States alone, cancer causes the death of well over a half-million people each year, with some 1.4 million new cases diagnosed per year. While deaths from heart disease have been declining significantly, those resulting from cancer generally are on the rise. In the early part of the next century, cancer is predicted to become the leading cause of death.
Worldwide, several cancers stand out as the leading killers. In particular, carcinomas of the lung, prostate, breast, colon, pancreas, and ovary represent the primary causes of cancer death. These and virtually all other carcinomas share a common lethal feature. With very few exceptions, metastatic disease from a carcinoma is fatal. Moreover, even for those cancer patients who initially survive their primary cancers, common experience has shown that their lives are dramatically altered. Many cancer patients experience strong anxieties driven by the awareness of the potential for recurrence or treatment failure. Many cancer patients experience physical debilitations following treatment. Many cancer patients experience a recurrence.
Generally speaking, the fundamental problem in the management of the deadliest cancers is the lack of effective and non-toxic systemic therapies. Molecular medicine, still very much in its infancy, promises to redefine the ways in which these cancers are managed. Unquestionably, there is an intensive worldwide effort aimed at the development of novel molecular approaches to cancer diagnosis and treatment. For example, there is a great interest in identifying truly tumor-specific genes and proteins that could be used as diagnostic and prognostic markers and/or therapeutic targets or agents. Research efforts in these areas are encouraging, and the increasing availability of useful molecular technologies has accelerated the acquisition of meaningful knowledge about cancer. Nevertheless, progress is slow and generally uneven.
As discussed below, the management of prostate cancer serves as a good example of the limited extent to which molecular biology has translated into real progress in the clinic. With limited exceptions, the situation is more or less the same for the other major carcinomas mentioned above.
Worldwide, prostate cancer is the fourth most prevalent cancer in men. In North America and Northern Europe, it is by far the most common male cancer and is the second leading cause of cancer death in men. In the United States alone, well over 40,000 men die annually of this disease—second only to lung cancer. Despite the magnitude of these figures, there is still no effective treatment for metastatic prostate cancer. Surgical prostatectomy, radiation therapy, hormone ablation therapy, and chemotherapy remain fixed as the main treatment modalities. Unfortunately, these treatments are ineffective for many and are often associated with significant undesirable consequences.
On the diagnostic front, the lack of a prostate tumor marker that can accurately detect early-stage, localized tumors remains a significant limitation in the management of this disease. Although the serum PSA assay has been a very useful tool, its specificity and general utility is widely regarded as lacking in several important respects, as further discussed below. Most prostate cancers initially occur in the peripheral zone of the prostate gland, away from the urethra. Tumors within this zone may not produce any symptoms and, as a result, most men with early-stage prostate cancer will not present clinical symptoms of the disease until significant progression has occurred. Tumor progression into the transition zone of the prostate may lead to urethral obstruction, thus producing the first symptoms of the disease. However, these clinical symptoms are indistinguishable from the common non-malignant condition of benign prostatic hyperplasia (BPH). Early detection and diagnosis of prostate cancer currently relies on digital rectal examinations (DRE), prostate specific antigen (PSA) measurements, transrectal ultrasonography (TRUS), and transrectal needle biopsy (TRNB). At present, serum PSA measurement in combination with DRE represent the leading tool used to detect and diagnose prostate cancer. Both have major limitations which have fueled intensive research into finding better diagnostic markers of this disease.
Similarly, there is no available marker that can predict the emergence of the typically fatal metastatic stage of prostate cancer. Diagnosis of metastatic stage is presently achieved by open surgical or laparoscopic pelvic lymphadenectomy, whole body radionuclide scans, skeletal radiography, and/or bone lesion biopsy analysis. Clearly, better imaging and other less invasive diagnostic methods offer the promise of easing the difficulty those procedures, place on a patient, as well as improving diagnostic accuracy and opening therapeutic options. A similar problem is the lack of an effective prognostic marker for determining which cancers are indolent and which ones are or will be aggressive. PSA, for example, fails to discriminate accurately between indolent and aggressive cancers. Until there are prostate tumor markers capable of reliably identifying early-stage disease, predicting susceptibility to metastasis, and precisely imaging tumors, the management of prostate cancer will continue to be extremely difficult.
PSA is the most widely used tumor marker for screening, diagnosis, and monitoring prostate cancer today. In particular, several immunoassays for the detection of serum PSA are in widespread clinical use. Recently, a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for PSA mRNA in serum has been developed. However, PSA is not a disease-specific marker, as elevated levels of PSA are detectable in a large percentage of patients with BPH and prostatitis (25–86%)(Gao et al., 1997, Prostate 31: 264–281), as well as in other nonmalignant disorders and in some normal men, a factor which significantly limits the diagnostic specificity of this marker. For example, elevations in serum PSA of between 4 to 10 ng/ml are observed in BPH, and even higher values are observed in prostatitis, particularly acute prostatitis. BPH is an extremely common condition in men. Further confusing the situation is the fact that serum PSA elevations may be observed without any indication of disease from DRE, and visa-versa. Moreover, it is now recognized that PSA is not prostate-specific (Gao et al., supra, for review).
Various methods designed to improve the specificity of PSA-based detection have been described, such as measuring PSA density and the ratio of free vs. complexed PSA. However, none of these methodologies have been able to reproducibly distinguish benign from malignant prostate disease. In addition, PSA diagnostics have sensitivities of between 57–79% (Cupp & Osterling, 1993, Mayo Clin Proc 68:297–306), and thus miss identifying prostate cancer in a significant population of men with the disease.
There are some known markers which are expressed predominantly in prostate, such as prostate specific membrane antigen (PSM), a hydrolase with 85% identity to a rat neuropeptidase (Carter et al., 1996, Proc. Natl. Acad. Sci. USA 93: 749; Bzdega et al., 1997, J. Neurochem. 69: 2270). However, the expression of PSM in small intestine and brain (Israeli et al., 1994, Cancer Res. 54: 1807), as well its potential role in neuropeptide catabolism in brain, raises concern of potential neurotoxicity with anti-PSM therapies. Preliminary results using an Indium-111 labeled, anti-PSM monoclonal antibody to image recurrent prostate cancer show some promise (Sodee et al., 1996, Clin Nuc Med 21: 759–766). More recently identified prostate cancer markers include PCTA-1 (Su et al., 1996, Proc. Natl. Acad. Sci. USA 93: 7252) and prostate stem cell antigen (PSCA) (Reiter et al., 1998, Proc. Nad. Acad. Sci. USA 95: 1735). PCTA-1, a novel galectin, is largely secreted into the media of expressing cells and may hold promise as a diagnostic serum marker for prostate cancer (Su et al., 1996). PSCA, a GPI-linked cell surface molecule, was cloned from LAPC-4 cDNA and is unique in that it is expressed primarily in basal cells of normal prostate tissue and in cancer epithelia (Reiter et al., 1998). Vaccines for prostate cancer are also being actively explored with a variety of antigens, including PSM and PSA.
While previously identified markers such as PSA, PSM, PCTA and PSCA have facilitated efforts to diagnose and treat prostate cancer, there is need for the identification of additional markers and therapeutic targets for prostate and related cancers in order to further improve diagnosis and therapy.


Web crawlers crawl websites to access documents of the website for purposes of indexing the documents for search engines. The web crawlers crawl a specified website at a crawl rate that is based on multiple factors. One of the factors is a pre-set crawl rate limit. According to certain embodiments, an owner for a specified website is enabled to modify the crawl rate limit for the specified website when one or more pre-set criteria are met.

A search engine is a tool that identifies documents, typically stored on hosts distributed over a network, which satisfy search queries specified by users. Web search engines work by storing information about a large number of documents (such as web pages) which they retrieve from the World Wide Web (WWW) via a web crawler. Crawling a website during high traffic periods and/or excessive load during crawling can deplete network resources from the website, rendering the website less accessible to others. On the other hand, it may be that not enough crawling is performed for the website. Thus, it may be advantageous to enable a website owner to control the rate at which the website is crawled.
Like reference numerals refer to corresponding parts throughout the drawings.

This patent is subject to a terminal disclaimer.

System and method for enabling website owners to manage crawl rate in a website indexing system


The present invention relates to a use of mutant haptoglobin having angiogenesis-promoting activity and, more particularly, to a mutant haptoglobin polypeptide, a recombinant vector containing a polynucleotide encoding the polypeptide, or a composition for promoting angiogenesis containing, as an active ingredient, a transformant transformed with the recombinant vector. The mutant haptoglobin according to the present invention includes an amino acid sequence of SEQ ID NO: 1 in which the 143rd amino acid is substituted with an amino acid other than Arg. The mutant haptoglobin according to the present invention has excellent angiogenesis-promoting activity and excellent capillary-like tube formation capability as compared with wild-type haptoglobin, and promotes cell migration, and thus is useful as a therapeutic agent for treating diseases caused by non-angiogenesis.

Ischemic tissue damage needs angiogenesis in the damaged area for the tissue recovery. After birth, new vessels are generated by angiogenesis, arteriogenesis, and vasculogenesis. Angiogenesis is related to the proliferation and migration of endothelial cells that are developed from the mature endothelial cells, while arteriogenesis is the process of remodeling of arteriolar connection as collateral vessels (Carmeliet, P. (2000) Mechanisms of angiogenesis and arteriogenesis. Nat. Med. 6, 389.395). In the meantime, vasculogenesis is progressed through the course wherein endothelial progenitor cells (EPC) are developed into the mature endothelial cells (Asahara, T. and Kawamoto, A. (2004) Endothelial progenitor cells for postnatal vasculogenesis. Am. J. Physiol. Cell Physiol. 287, 572.579.). EPCs that are developed from the bone marrow and circulated thereafter to migrate to the area of injury of blood vessels and are involved in angiogenesis by being inserted directly in the newly generated blood vessels or by inducing the secretion of various angiogenesis factors and nutritional factors (Jujo, K., Ii, M. and Losordo, D. W. (2008) Endothelial progenitor cells in neovascularization of infracted myocardium. J. Mol. Cell. Cardiol. 45, 530.544., Urbich, C., Aicher, A., Heeschen, C., Dernbach, E., Hofmann, W. K., Zeiher, A. M. and Dimmeler, S. (2005) Soluble factors released by endothelial progenitor cells promote migration of endothelial cells and cardiac resident progenitor cells. J. Mol. Cell. Cardiol. 39, 733.742.). Therefore, EPCs are the potential target of concern for the treatment by revascularization (Jujo, K., Ii, M. and Losordo, D. W. (2008) Endothelial progenitor cells in neovascularization of infracted myocardium. J. Mol. Cell. Cardiol. 45, 530.544.).
Recent studies on EPCs are mainly focused on the EPCs that are genetically modified ex vivo in order to increase the functions of cells. For that purpose, vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1a have been used because they displayed the activity of increasing the pro-angiogenic capacity of EPCs (Iwaguro, H., Yamaguchi, J., Kalka, C., Murasawa, S., Masuda, H., Hayashi, S., Silver, M., Li, T., Isner, J. M. and Asahara, T. (2002) Endothelial progenitor cell vascular endothelial growth factor gene transfer for vascular regeneration. Circulation 105, 732.738., Jiang, M., Wang, B., Wang, C., He, B., Fan, H., Guo, T. B., Shao, Q., Gao, L. and Liu, Y. (2008) Angiogenesis by transplantation of HIF-1a modified EPCs into ischemic limbs. J. Cell. Biochem. 103, 321.334.).
Haptoglobin (Hp) is an acute-phase glycoprotein existing in blood circulation system, and the well known biological function of Hp is capturing hemoglobin. Hp forms HP-hemoglobin complex which is known to be functioning to prevent hemoglobin-stimulated oxidative tissue damage (Lim, Y. K., Jenner, A., Ali, A. B., Wang, Y., Hsu, S. I., Chong, S. M., Baumman, H., Halliwell, B. and Lim, S. K. (2000) Haptoglobin reduces renal oxidative DNA and tissue damage during phenylhydrazine-induced hemolysis. Kidney Int. 58, 1033.1044., Buehler, P. W., Abraham, B., Vallelian, F., Linnemayr, C., Pereira, C. P., Cipollo, J. F., Jia, Y., Mikolajczyk, M., Boretti, F. S., Schoedon, G., Alayash, A. I. and Schaer, D. J. (2009) Haptoglobin preserves the CD163 hemoglobin scavenger pathway by shielding hemoglobin from peroxidative modification. Blood 113, 2578.2586).
Hp can be expressed in artery (Smeets, M. B., Pasterkamp, G., Lim, S. K., Velema, E., van Middelaar, B. and de Kleijn, D. P. V. (2002) Nitric oxide synthesis is involved in arterial haptoglobin expression after sustained flow changes. FEBS Lett. 529, 221.224.) and thus can be functioning as a cell migration factor that is particularly involved in arterial restructuring (de Kleijn, D. P. V., Smeets, M. B., Kemmeren, P. P. C. W., Lim, S. K., van Middelaar, B. J., Velema, E., Schoneveld, A., Pasterkamp, G. and Borst, C. (2002) Acutephase protein haptoglobin is a cell migration factor involved in arterial restructuring. FASEB J. 16, 1123.1125., Lohr, N. L., Warltier, D. C., Chilian, W. M. and Weihrauch, D. (2005) Haptoglobin expression and activity during coronary collateralization. Am. J. Physiol. Heart Circ. Physiol. 288, H1389.H1395).
However, there are no reports so far that suggest the mutant haptoglobin can induce angiogenesis.
Therefore, the present inventors studied and confirmed that the mutant haptoglobin had the higher activity of promoting angiogenesis than that of the wild type haptoglobin, leading to the completion of this invention.

Use of mutant haptoglobin having angiogenesis promoting activity

CATHOLIC UNIVERISTY INDUSTRY ACADEMIC COOPERATION FOUNDATION


Soot formation in the partial oxidation of carbonaceous feed is controlled by controlling the momentum of the oxidant stream relative to the momentum of the carbonaceous feed stream.

Partial oxidation and similar operations involve contacting hydrocarbons with oxygen under conditions that form a gaseous product stream having a desired composition of gaseous components. However, past experience has shown that the gaseous product stream often contains solid particulate byproducts such as soot, especially when the gaseous product stream is produced under conditions that are intended to retain a significant component of one or more hydrocarbon components by not fully reacting or combusting them. These solid particulate byproducts may also be present when the partial oxidation reactions take place at low temperatures. That is, if the reaction conditions do not achieve complete oxidation of all oxidizable components that are present, or if the reactor temperature is low, then some unoxidized matter that is present in the product stream would be expected to be in the solid phase. Alternately the reaction conditions could be such that the cracking temperature of the feed is exceeded without adequate conversion of the feed to a gaseous product stream. The solid particulate byproduct is referred to generally as "soot" and may comprise elemental carbon, and/or carbon-containing hydrocarbons. The presence of this material in the product stream from the partial oxidation operation is often undesirable. However, previous efforts to lower the amount of this material that is in the product stream have required sacrificing yield, or increasing the usage of reactants such as oxygen, which are approaches that have drawbacks.


Methods and apparatus for triggering roaming in a mobile network device are disclosed. A speed of the network device is detected. One or more maximum/minimum trigger values corresponding to one or more trigger events are ascertained at the speed of the network device. One or more trigger counters associated with the one or more trigger events are maintained. Roaming of the network device is triggered when one of the trigger counters associated with one of the trigger events is equal to or exceeds (or is less than or equal to) one of the trigger values corresponding to the trigger event at the speed of the network device.

1. Field of the Invention
The present invention relates to network technology. More particularly, the present invention relates to reducing roaming latency in a network device.
2. Description of the Related Art
Over recent years, the market for wireless communications has enjoyed tremendous growth. Hundreds of millions of people exchange information every day using pagers, cellular telephones, and other wireless communication products. With tremendous success of wireless telephony and messaging services, it is hardly surprising that wireless communication is beginning to be applied to the realm of personal and business computing. No longer bound by the harnesses of wired networks, people will be able to access and share information on a global scale nearly anywhere they venture.
Many network users, especially mobile users in businesses, the medical profession, factories, and universities, to name a few, find benefit from the added capabilities of wireless Local Area Networks (LANs). The major motivation and benefit from wireless LANs is increased mobility. Untethered by conventional network connections, network users can move about almost without restriction and access LANs from nearly anywhere. In addition to increased mobility, wireless LANs offer increased flexibility. Moreover, sometimes it is more economical to use a wireless LAN. Thus, wireless LANs offer the connectivity and the convenience of wired LANs without the need for expensive wiring or rewiring.
Various protocols have been developed to support wireless networks. As one example, IEEE 802.11 refers to a family of specifications developed by the IEEE for wireless LAN technology. IEEE 802.11 specifies an over-the-air interface between a wireless client (e.g., Mobile Node) and a base station (e.g., Access Point) or between two wireless clients.
Mobile IP is another protocol which allows laptop computers or other mobile computer units (referred to as "Mobile Nodes" herein) to roam between various sub-networks at various locations—while maintaining internet and/or WAN connectivity. Without Mobile IP or a related protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks. This is because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. If a user desires to take a computer which is normally attached to one node and roam with it so that it passes through different sub-networks, it cannot use its home base IP address. As a result, a business person traveling across the country cannot merely roam with his or her computer across geographically disparate network segments or wireless nodes while remaining connected over the internet. This is not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 2002 of the Network Working Group, C. Perkins, Ed., October 1996. Mobile IP is also described in the text "Mobile IP Unplugged" by J. Solomon, Prentice Hall. Both of these references are incorporated herein by reference in their entireties and for all purposes.
The Mobile IP process and environment are illustrated in FIG. 1. As shown there, a Mobile IP environment 2 includes the internet (or a WAN) 4 over which a Mobile Node 6 can communicate remotely via mediation by a Home Agent 8 and a Foreign Agent 10. Typically, the Home Agent and Foreign Agent are routers or other network connection devices performing appropriate Mobile IP functions as implemented by software, hardware, and/or firmware. A particular Mobile Node (e.g., a laptop computer) plugged into its home network segment connects with the internet through its designated Home Agent. When the Mobile Node roams, it communicates via the internet through an available Foreign Agent. Presumably, there are many Foreign Agents available at geographically disparate locations to allow wide spread internet connection via the Mobile IP protocol. Note that it is also possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1, Mobile Node 6 normally resides on (or is "based at") a network segment 12 which allows its network entities to communicate over the internet 4 through Home Agent 8 (an appropriately configured router denoted R2). Note that Home Agent 8 need not directly connect to the internet. For example, as shown in FIG. 1, it may be connected through another router (a router R1 in this case). Router R1 may, in turn, connect one or more other routers (e.g., a router R3) with the internet.
Now, suppose that Mobile Node 6 is removed from its home base network segment 12 and roams to a remote network segment 14. Network segment 14 may include various other nodes such as a PC 16. The nodes on network segment 14 communicate with the internet through a router which doubles as Foreign Agent 10. Mobile Node 6 may identify Foreign Agent 10 through various solicitations and advertisements which form part of the Mobile IP protocol. When Mobile Node 6 engages with network segment 14, Foreign Agent 10 relays a registration request to Home Agent 8 (as indicated by the dotted line "Registration"). The Home and Foreign Agents may then negotiate the conditions of the Mobile Node's attachment to Foreign Agent 10. For example, the attachment may be limited to a period of time, such as two hours. When the negotiation is successfully completed, Home Agent 8 updates an internal "mobility binding table" which specifies the care-of address (e.g., a collocated care-of address or the Foreign Agent's IP address) in association with the identity of Mobile Node 6. Further, the Foreign Agent 10 updates an internal "visitor table" which specifies the Mobile Node address, Home Agent address, etc. In effect, the Mobile Node's home base IP address (associated with segment 12) has been shifted to the Foreign Agent's IP address (associated with segment 14).
Now, suppose that Mobile Node 6 wishes to send a message to a corresponding node 18 from its new location. A message from the Mobile Node is then packetized and forwarded through Foreign Agent 10 over the internet 4 and to corresponding node 18 (as indicated by the dotted line "packet from MN") according to a standard internet protocol. If corresponding node 18 wishes to send a message to Mobile Node—whether in reply to a message from the Mobile Node or for any other reason—it addresses that message to the IP address of Mobile Node 6 on sub-network 12. The packets of that message are then forwarded over the internet 4 and to router R1 and ultimately to Home Agent 8 as indicated by the dotted line ("packet to MN(1)"). From its mobility binding table, Home Agent 8 recognizes that Mobile Node 6 is no longer attached to network segment 12. It then encapsulates the packets from corresponding node 18 (which are addressed to Mobile Node 6 on network segment 12) according to a Mobile IP protocol and forwards these encapsulated packets to a "care of" address for Mobile Node 6 as shown by the dotted line ("packet to MN(2)"). The care-of address may be, for example, the IP address of Foreign Agent 10. Foreign Agent 10 then strips the encapsulation and forwards the message to Mobile Node 6 on sub-network 14. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as "tunneling."
As described above, a Mobile Node may roam from one Foreign Agent to another Foreign Agent. Similarly, the Mobile Node may roam from one Access Point to another Access Point. An Access Point may be defined as a point of connectivity in a wireless or non-wireless network. During roaming, the Mobile Node registers with its Home Agent to notify the Home Agent of its new location.
Specific events trigger the roaming of the mobile node to one Foreign Agent or Access Point to another Foreign Agent or Access Point when the mobile node is traveling at relatively low speed (e.g., walking speed). However, at a higher speed, these events do not trigger the roaming process quickly enough. As a result, the Foreign Agent or Access Point via which communications are received by the Mobile Node may be outside the coverage area of the Foreign Agent or Access Point. Accordingly, communications may be disrupted.
In view of the above, it would be beneficial if the roaming process could be improved to support travel of Mobile Nodes at higher speeds.

Methods and apparatus for reducing roaming latency in a mobile node


An aroma diffuser includes an air pump including an air inlet port and an air outlet port, an aromatherapy nebulizer including a fragrance bottle, an air accumulator, a dip tube, an air outlet tube in communication with the fragrance bottle and an air outlet tube in communication with the air accumulator. When a compressed flow of air is induced by the air pump into the accumulation chamber of the air accumulator, a Venturi effect is created in the outlet of the accumulation chamber, causing the liquid fragrance to be sucked out of the fragrance bottle toward and mixed with the compressed flow of air for diffusion through a spray chamber in the air accumulator and the air outlet tube.

1. Field of the Invention
The present invention relates to nebulizers and more particularly, to an aroma diffuser, which automatically sprays a predetermined amount of fine mist of liquefied aromatic substance at a predetermined time interval.dfd
2. Description of the Related Art
In certain spaces where people live or work, air-conditioners and air purifiers are commonly used to alter the properties of air or to remove dust from air, improving thermal comfort and indoor air quality. Aroma diffusers and aroma sprayers may also be used in buildings for diffusing fragrance. However, conventional aroma diffusers and sprayers are not practical for large space application. Further, after each use, the cleaning of conventional aroma diffusers and sprayers is not an easy job.
An aroma sprayer generally comprises a pressure can and a liquefied aromatic substance contained in the pressure can. The user can apply a pressure to the pressure can directly or through a mechanical device, driving the pressure can to spray a fine mist of liquefied aromatic substance through a spray nozzle. This design of aroma sprayer is still not satisfactory in function. Because the pressure accumulated in the pressure can is very limited, this design of aroma sprayer can simply be used in a limited indoor space area. Therefore, it is desirable to provide an aroma diffuser, which is practical for large space application.


Methods and systems for processing semiconductor materials with a focused laser beam. Laser light may be focused on a sample to alter material properties at the sample surface. The laser beam has a peak power, a pulse width and is modulated to a selected duty cycle to provide a selected energy per pulse and average power to the sample surface. The focused laser beam is scanned over the sample surface to provide controlled process effects limited to the area of the beam diameter and along the scanning path. For example, process effects such as curing, annealing, implant activation, selective melting, deposition and chemical reaction may be achieved at dimensions limited by the focused beam diameter. The wavelength may be selected to be appropriate for the process effect chosen.

1. Field of Invention
This disclosure generally relates to processing of semiconductor substrates with a focused laser beam.
2. Related Art
Focused laser beams have found applications in drilling, scribing, and cutting of semiconductor wafers, such as silicon. Marking and scribing of non-semiconductor materials, such as printed circuit boards and product labels are additional common applications of focused laser beams. Micro-electromechanical systems (MEMS) devices are laser machined to provide channels, pockets, and through features (holes) with laser spot sizes down to 5 μm and positioning resolution of 1 μm. Channels and pockets allow the device to flex. All such processes rely on a significant rise in the temperature of the material in a region highly localized at the laser beam point of focus.
The foregoing applications, however, are all, to some degree, destructive, and relate generally to focused laser beams at power densities intended to ablate material. In silicon and related semiconductor and electronic materials, such applications are generally for mechanical results (e.g., dicing, drilling, marking, etc.). Thus, there is a need to provide and control laser beams to achieve processing effects for electronic and or optical device fabrication on semiconductor wafers.


A method of accessing information from a wireless device including processing a query and a wireless identifier received from the wireless device, searching a collection of data for a set of results matching the query, selectively reducing the set of results to generate a subset of results and outputting the subset of results on the wireless device according to a style sheet.

This invention relates to wireless information retrieval.
A search engine is a software program used for search and retrieval in database systems. The search engine often determines the searching capabilities available to a user. A web search engine is often an interactive tool to help people locate information available over the so-called World Wide Web (WWW). Web search engines are actually databases that contain references to thousands of resources. There are many search engines available on the web, from companies such as Alta Vista, Yahoo, Northern Light and Lycos.
The searching capabilities are also dependent upon the type of input/output device available to the user. For example, coupling search engines to handheld wireless input/output devices introduces an array of challenges due to, for example, small output display screens, cumbersome input methods prone to generating input errors, limited bandwidth connections, and so forth.


An improved socket for use in ball-and-socket joints, the socket including an outer shell and an inner low-friction bearing insert for mateable engagement with the head or ball-end of an associated component. The socket is suitable for prosthetic as well as non-prosthetic applications. The bearing insert is retained within the outer shell by a split, insert-retaining ring. The head of the associated component is retained within a spherical chamber within the bearing insert by a split annular bearing ring carried by and mated with annularly spaced apertures in the insert. Assembly of the device by inserting the head of the associated component causes expansion of the bearing ring to receive the head and the subsequent insertion of the bearing insert into the outer shell locks the head in place. Radially outwardly extending arcuate tabs on the bearing ring bear against the inner surface of the outer shell to thereby oppose expansion of the bearing ring after the device is assembled. The ends of the insert-retaining ring are accessible through an aperture in the outer shell to enable disassembly of the components.

1. Field of the Invention
This invention relates generally to ball-and-socket joints and, in particular, to implantable prostheses. More particularly, the invention relates to an implantable prosthetic socket having a bearing insert interposed between the spherical head of an associated prosthetic component and the socket component of the prosthesis.
2. Description of the Prior Art
Joint replacements--total and partial--have in recent years become reliable orthopedic procedures for the correction of disorders of natural joints. These procedures when applied to a hip joint, for example, involve the surgical implantation of a femoral stem prosthesis into the femur and an acetabular endoprosthesis into the acetabulum for receiving the femoral head. Similar procedures and components may be used with other ball-and-socket type joints such as, for example, a shoulder joint, although the preferred embodiment disclosed herein is described in terms of a hip joint. Additionally, while the preferred embodiment is described in terms of an implantable prosthetic socket, those skilled in the art will understand that the invention may be applied to ball-and-socket joints in general, whether intended to be implantable or not and indeed may be applied to other than "spherical" ball-and-socket joints.
Numerous devices have been developed in an effort to produce a prosthetic hip implant which is not only easy to implant or remove, if necessary, but which also approximates as closely as possible the performance of the natural joint. While all known devices have a femoral and an acetabular component, the design of the latter varies widely depending upon the dysfunction being corrected. The acetabular socket component is generally a biocompatible metallic member that may, for example, be either movably or immovably secured into the acetabulum. In either case, the acetabular socket has a low-friction biocompatible bearing insert (generally polyethylene) with a seat or socket chamber for receiving the spherical head or ball-end of the femoral component.
Those devices which have a fixed acetabular component have a rigid, cup-shaped socket component intended to be retained within the natural acetabular socket. They have a single articulating surface--that is, the head of the femoral component is movable within the bearing insert. Another class of devices is known wherein the acetabular socket component is movable within the natural socket. These, devices have a rigid, cup-shaped outer shell with a highly polished outer spherical surface designed to move within the natural socket. These devices have two articulating surfaces--the head and the outer surface of the socket--and are generally known as "bipolar", including both concentric and non-concentric designs, the latter having varying degrees of eccentricity or polar offset.
An important consideration in the design of bipolar hip endoprostheses is enhancement of the prosthesis to resist the tendency of the acetabular cup of these implants to rotate toward varus. Producing bipolar endoprostheses with an antivarus property (i.e. polar offset) is desirable in order to advantageously distribute the inherent forces which tend to deform the implant's components and, in the extreme, result in dislocation. The general manner in which an antivarus property is effected is by providing a polar offset. Ball-and-socket type joints are subject to dislocation under a certain types or amounts of stress and producing these joints (for hip applications) with a polar offset between the inner and outer articulating components tends to decrease these stresses, thereby decreasing the tendency of these components to come apart. It is a goal of all ball-and-socket type prostheses to overcome this tendency by more securely capturing the femoral head within the bearing insert. It is a particular object of this invention to provide a socket which strongly captures the femoral head over a wide range of polar offsets (to accomodate prostheses of various sizes).
The importance of securely capturing the head in a socket must be considered in the light of other desirable factors such as ease of assembly and installation and ease of disassembly. Occasionally, due to subsequent injury or disease, the replacement of all or part of the prosthesis becomes necessary. Consequently, while such devices are often designed with the intention of separating the various components if necessary, simultaneous consideration must be given to making sure the assembled components do not easily become separated during normal use. Numerous prior art devices are known which disclose many ways of accomodating ease of assembly, resistance to dislocation and ease of disassembly in prosthetic ball-and-socket joints.
U.S. Pat. No. 3,813,699 (Giliberty) discloses an outer shell with a bearing insert immovably secured to the shell. The insert has a constricted opening and is of a resilient silicone material capable of yielding sufficiently to enable the head of the femoral stem prosthesis to be inserted into the socket of the insert while thereafter capable of retaining the head in an articulating manner.
U.S. Pat. No. 3,818,512 (Shersher) discloses a prosthesis having a conventional, fixed acetabular component. The device includes an outer metal shell and a bearing insert having a plurality of fingers or leaves intended to be compressed inwardly to retain the head of the femoral component. The compression is achieved by a self-locking nut which threads into the outer metal shell, the inner surface of the nut being shaped to conform to the fingers of the bearing insert. The nut has several lugs to facilitate the threading of the nut into the acetabular component and is locked to the outer shell by a partial circumferential slot splitting the nut into two parallel parts which are then compressed together by a screw. While the Shersher device includes a locking element to more positively secure the head of the femoral prosthesis to the acetabular shell, this locking mechanism--even if it were adapted for use in a bipolar prosthesis--is difficult to use in practice because of the required threaded motion.
U.S. Pat. No. 3,863,273 (Averill) discloses a similar type of locking or capture mechanism to secure the head of the femoral component into the bearing insert. The bearing insert of Averill is secured within the outer shell by a radially outwardly extending tab on the insert snapping into a corresponding annular groove on the inner wall of the outer shell. The open end of the bearing insert is a greatly constricted opening having longitudinal slots defining fingers which are radially expanded to enlarge the opening when the head is pushed in. The Averill device relies only on the tension of the fingers to hold the femoral head, the fingers being supported by the surrounding inner surface of the outer shell, and does not disclose any other positive locking mechanism to secure the head of the femoral component within the bearing insert. As will be understood by those skilled in the art, this structure and other similar types of structures described below necessarily require a large amount of plastic bearing insert material between the head and the opening of the metal shell. This contributes to deformation of the bearing insert and subsequent dislocation under high loads. The Averill device does not disclose any specific means for dissassembling the femoral head from the bearing insert.
U.S. Pat. No. 4,784,663 (Kenna) discloses a structure similar to Averill except that the resilient fingers or leaves of the bearing insert are prevented from expanding radially outwardly by a polyethylene locking ring interposed between the open end of the bearing insert and the open end of the outer shell and retained in place by the cooperative action of an annular rib and groove attaching mechanism. The Kenna device facilitates disassembly by having an annular gap between the lip of the locking ring and the adjacent periphery of the metal shell. The locking ring may be pulled apart from the bearing insert by prying the lip away from the shell periphery using a suitable tool inserted in the annular gap.
U.S. Pat. No. 4,770,658 (Geremakis) discloses another type of locking ring in a joint prosthesis. In this device a bearing insert is provided with a plurality of axially extending fingers designed to be pressed radially inwardly by a lock ring interposed between the fingers and the outer metal shell. The lock ring is carried by the outer shell in a first position enabling the insertion of the head of an associated component and a second position in which the lock ring tightly engages the bearing insert and the outer shell to maintain the bearing insert in overlapping relation to the head. Unlocking is achieved by pulling the lock ring axially away from the outer shell (a part of the rim of the shell is cut-out for this purpose).
U.S. Pat. No. 4,241,463 (Khovaylo) discloses a prosthetic hip implant wherein the femoral head is captured within the spherical cavity of a bearing insert by a split polyethylene retaining ring as opposed to a solid ring, the ring being interposed between the head and the inside of the insert (rather than the inside of the outer shell). The insert is keyed to prevent its rotation relative to the outer shell and the split ring is adapted to move within a cavity of the bearing insert within a limited axial range. Upon insertion of the femoral head into the bearing insert, the split ring is forced axially to one extreme end of its axial range of motion where the cavity is larger so the ring may expand radially to enable it to open up sufficiently to permit the head to enter the spherical seat of the insert. When the head is properly seated, it clears the split ring sufficiently to enable the ring to return to its normal size underneath the femoral head. The interior cavity of the bearing insert and the split ring are so angled that attempted removal of the femoral head tends to wedge the split ring against the interior of the bearing insert thereby preventing removal of the femoral head under normal circumstances. A slot is provided adjacent the opening of the bearing insert to enable a tool to be inserted in order to push the split ring inwardly to its expanded position in order to enable the femoral head to be removed.
U.S. Pat. No. 4,380,090 (Ramos) discloses a hip prosthesis with a split annular polyethylene bearing similar to Khovaylo, but adjacent the open end of a bearing insert between the head and the outer shell. The split bearing is retained by split metal locking ring held within an inner annular groove on the outer shell. Removal of the bearing insert is accomplished by compressing the metal locking ring to remove it, the bearing insert and the split annular bearing.
U.S. Pat. No. 4,619,658 (Pappas et al.) discloses various prosthetic hip implants, some having solid bearing rings and some having split bearing rings. In one embodiment, the body of the bearing insert is formed from a plurality of segments (split in a plane passing through and parallel to the axis) which are held together by a circular retaining ring and which are held within an outer metal shell by the cooperative action of the retaining ring with a groove on the inner surface of the outer shell. In another embodiment, the bearing insert is formed of two pieces split along a transverse plane: a primary bearing insert forming the major part of the spherical head of the insert and a split collar (i.e. bearing ring) for being attached to the open end of the primary bearing insert. The collar and the primary bearing insert are held together by the interaction of cooperative annular ribs and grooves and the assembly is then inserted into an outer metal shell. A substantially circular release tool may be inserted into the open end of the outer shell between it and the bearing insert to compress the ring of the first embodiment to remove the bearing insert from the outer metal shell. In the second embodiment the collar may be provided with holes or slots into which the ends of conventional clamps may be inserted to squeeze the collar together thereby reducing its circumference at the radial split in order to enable the bearing insert to be removed from the outer shell.
U.S. Pat. No. 4,714,477 (Fichera et al.) discloses another version of a split bearing ring in a single-piece bearing insert having an upper circumferential portion and a lower portion integrally connected to the upper portion but separated from it by a circumferential split (extending less than 360.degree.). The lower portion itself is split along a vertical line and is retained within the outer shell by an annular rib engaged within an annular groove of the shell.
All known ball-and-socket devices appear to suffer from the inherent limitation that, under extreme ranges of motion where the loads may be expected to be greatest, plastic flow may occur in the bearing insert (and other plastic components). This is especially true of those implantable devices subject to rotate toward varus so that the forces tend to be directed against the rim of the cup and insert. Even in embodiments which may not be subject to rotation toward varus (as in, for example, non-implanted joints) the forces causing dislocation of the head from the spherical cavity are, in many prior art designs, directed primarily against that portion of the bearing insert and/or bearing ring adjacent the open end of the outer cup. That is, the forces are directed against a portion of the bearing insert which is not supported by much more than the plastic mass of the bearing insert itself. Increasing the mass of bearing insert material has not been of any particular advantage in increasing the resistance of the prior art sockets to dislocation.
It is accordingly an object of this invention to produce an improved socket for use in ball-and-socket joints to provide increased resistance to dislocation.
It is another object of this invention to produce an implantable prosthetic socket wherein the head of an associated femoral stem prosthesis is captured within the socket of a bearing insert by a substantially annular bearing ring.
It is a further object of this invention to produce an implantable prosthetic socket joint capable of being easily assembled and disassembled. It is in part an object of this invention to facilitate the assembly and disassembly operations by minimizing the number of components and subassemblies required to produce an operational prosthetic joint.
It is yet another object of this invention to produce an implantable prosthetic socket having an outer shell and an inner bearing insert and utilizing a split bearing ring to form part of the socket chamber within the bearing insert, the prosthetic socket adapted to have the split bearing ring being directly in contact with both the head of an associated prosthetic component and the inner surface of the outer shell along an interior portion thereof distal from the opening.
It is also an object of this invention to produce a unique bipolar endoprosthesis adaptable to a range of eccentricities while also maximizing the ability of the assembled components to resist dislocation.


A fuel cell system is provided, the system comprising: a fuel cell (1) configured to generate electric power by use of a fuel gas; a reformer (2) configured to generate the fuel gas by reforming a raw material; a combustion burner (2a) configured to supply heat for reforming; a raw material feeder (10) configured to control the feed rate of combustion fuel to the combustion burner; a combustion fan (2b) configured to supply air to the combustion burner; a fuel gas passage (R1, R4); an off gas passage (R3, R5); a bypass passage (R2); a switching valve (8); and a controller (101), wherein the inside of the fuel cell is filled with the raw material before the fuel gas is supplied, and wherein the controller controls the raw material feeder so as to reduce the feed rate of the combustion fuel to the combustion burner when controlling the switching valve so as to shut off the bypass passage to supply the fuel gas generated in the reformer to the fuel cell. This fuel cell system is environmentally-friendly and capable of suppressing the emission of carbon monoxide at the start of a power generating operation to mitigate the adverse effect upon the ecosystem.

In fuel cell systems capable of high-efficiency, small-scale power generation, it is easy to construct a system for utilizing heat energy generated during power generation. Thanks to this, fuel cell systems have heretofore been developed as a dispersed power generation system capable of achievement of high energy utilization efficiency.
Fuel cell systems have fuel cell as the main body of the power generation section. The fuel cell directly converts the chemical energy of fuel gas and oxidizing gas into electric energy through a predetermined electrochemical reaction. Therefore, in the fuel cell systems, the fuel gas and oxidizing gas are respectively supplied to the fuel cell during power generating operation. Then, in the fuel cell, the specified electrochemical reaction which uses the supplied fuel gas and oxidizing gas proceeds, thereby generating electric energy. The electric energy generated in the fuel cell is fed to loads from the fuel cell system. The fuel cell systems discussed herein generally include a reformer and a blower. In the reformer, the hydrogen-rich fuel gas is generated by the steam reforming reaction which uses water and a raw material containing an organic compound composed of at least carbon and hydrogen, which is a natural gas. This fuel gas is supplied to the fuel cell as a fuel for power generation. It should be noted that the steam reforming reaction proceeds with the reforming catalyst of the reformer being heated by, for example, a combustion burner. The blower suctions air from the atmosphere. This air is fed to the fuel cell as the oxidizing gas used for power generation.
In a heretofore known fuel cell system, when stopping a power generating operation, the supply of the raw material to the reformer is cut off. This stops the supply of the fuel gas from the reformer to the fuel cell, stopping the progress of the electrochemical reaction in the fuel cell. As a result, the supply of electric power from the fuel cell system to the loads is stopped. If the supply of the raw material to the reformer is cut off, the fuel gas, which has been generated before the cutoff of the raw material, will stagnate in the fuel cell and its surrounding area throughout the period during which the power generating operation is stopped. In this case, if the stagnant fuel gas is mixed with air coming from the combustion burner opened to the atmosphere owing to natural convection, hydrogen contained in the fuel gas will be rapidly oxidized by oxygen contained in the air, which gives rise to a risk that the fuel cell system may be damaged by the reaction heat generated by the oxidation reaction.
To prevent the stagnation of the fuel gas within the fuel cell system, the known fuel cell system is configured to feed inert gas such as nitrogen gas to the passage where the fuel gas is stagnant during a power generation stop period and to burn the fuel gas forced out of the passage in a combustion burner. According to this configuration, the stagnation of the fuel gas within the fuel cell etc. during a power generation stop period can be prevented and therefore the rapid oxidation of hydrogen contained in the fuel gas can be prevented so that the fuel cell system ensures high security.
This known fuel system, however, requires an inert gas feeding means such as a nitrogen cylinder installed within or near the fuel cell system in order to replace the stagnant fuel gas with the inert gas such as nitrogen gas. This makes the fuel cell system large-sized and therefore makes it difficult to use the fuel cell system as a stationary dispersed power generation system for household use or an electrical vehicular power plant. Furthermore, the use of the feeing means of the inert gas such as nitrogen gas in addition to the existing components increases the initial cost of the fuel cell system. In addition, the known fuel cell system needs periodical replacement or replenishment of the inert gas feeding means such as a nitrogen cylinder, which leads to an increase in the running cost of the fuel cell system.
In this known fuel cell system, just after the start of a power generating operation, the fuel gas containing a high concentration of carbon monoxide is supplied from the reformer to the fuel cell. The reason for this is that the operating temperature of the reformer has not reached a specified value at the start of a power generating operation and therefore a sufficient amount of carbon monoxide cannot be removed from the fuel gas. If a solid polymer electrolyte fuel cell, for example, is supplied with the fuel gas containing a high concentration of carbon monoxide, the catalyst of the fuel electrode of the solid polymer electrolyte fuel cell will be poisoned by the carbon monoxide supplied. The poisoning of the catalyst of the fuel electrode significantly hinders the progress of the electrochemical reaction in the fuel cell. Therefore, the known fuel cell system suffers from the problem that the power generating performance of the fuel cell deteriorates, depending upon the number of stops and starts of power generating operation.
As a fuel cell system that can be easily used in the home and electric cars and is unlikely to cause progressive poisoning of the catalyst, there has been proposed a fuel system that is configured to cut off the supply of the fuel gas to the fuel cell just after the start of a power generating operation and to introduce, as a substitution gas, the raw material of the fuel gas into the fuel cell after stopping the power generating operation (e.g., Patent Document 1).
The proposed fuel cell system is comprised of: a reformer for generating a hydrogen-rich fuel gas from a raw material containing as a chief component an organic compound that contains carbon and hydrogen; a fuel gas feed passage for feeding a fuel gas from the reformer to a fuel cell; an off gas feed passage for feeding the fuel gas, which has been discharged from the fuel cell without being used in power generation (hereinafter referred to as "off gas"), to a combustion burner of the reformer; and a first bypass route provided between the fuel gas feed passage and the off gas feed passage, for switching the destination of the fuel gas from the fuel cell to the combustion burner of the reformer. This fuel cell system also comprises a raw material feeder for feeding the raw material of the fuel gas to the reformer and a second bypass route for feeding the raw material directly from the raw material feeder to the fuel cell, so as to bypass the reformer.
In the proposed fuel cell system, just after the start of a power generating operation, the fuel gas containing a high concentration of carbon monoxide and generated in the reformer is supplied to the combustion burner of the reformer by way of the first bypass route. In the combustion burner, the fuel gas is combusted to heat the reforming catalyst. After the temperature of the reforming catalyst in the reformer has reached a specified value after the start of a power generating operation, the fuel gas generated in the reformer is supplied to the fuel cell by way of the fuel gas feed passage. Then, the fuel gas is used as a fuel for power generation in the fuel cell. The off gas discharged from the fuel cell is supplied to the combustion burner of the reformer by way of the off gas feed passage. Then, the off gas is combusted for heating the reforming catalyst in the combustion burner.
In the proposed fuel cell system, after stopping the power generating operation, the raw material serving as a substitution gas is introduced from the raw material feeder to a fuel gas flow path of the fuel cell by way of the second bypass route. Thereby, the inside of the fuel cell and its surrounding area are sealed up by the raw material instead of the inert gas such as nitrogen gas throughout the period during which the power generating operation of the fuel cell system is stopped.
According to this fuel cell system, the raw material serving as a substitution gas is introduced into the fuel cell from the conventionally-used raw material feeder after stopping the power generation, which eliminates the need for provision of an inert gas feeding means such as a nitrogen cylinder within or in the proximity of the fuel cell system. The fuel cell system can avoid growing in size and therefore can be used as a stationary dispersed power generation system for household use or an electrical vehicular power plant. In addition, since there is no need to provide an inert gas (nitrogen gas) feeding means in addition to existing components, the initial cost of the fuel cell system can be kept low. Furthermore, periodical replacement of an inert gas (nitrogen gas) feeding means is unnecessary, which makes it possible to keep the running cost of the fuel cell system low.
The material introduced from the raw material feeder into the fuel cell is chemically stable compared to hydrogen contained in the fuel gas. Therefore, even if the raw material, stagnating in the fuel cell throughout a power generating operation stop period, is mixed with air penetrating thereinto, no rapid oxidizing reaction will occur. Accordingly, damage to the fuel cell system caused by reaction heat generated in the oxidizing reaction can be effectively prevented, by introducing the raw material into the fuel cell. In this way, the fuel cell system can ensure security in the power generating operation stop period.
In the proposed fuel cell system, the fuel gas containing a high concentration of carbon monoxide is not supplied to the fuel cell just after the start of a power generating operation. After the temperature of the reforming catalyst in the reformer has reached the specified temperature and the fuel gas whose carbon monoxide concentration has been sufficiently reduced is generated, the fuel gas is supplied from the reformer to the fuel gas. This prevents the poisoning of the catalyst of the fuel electrode in the solid polymer electrolyte fuel cell. Thus, the factors that interrupt the progress of the electrochemical reaction in the fuel cell are swept away and therefore the problem that the power generating performance of the fuel cell deteriorates depending on the number of stops and starts of power generating operation can be solved.    Patent Document 1: Japanese Laid-Open Patent Application Publication No. 2003-229149


A nitride semiconductor light emitting device has high internal quantum efficiency but low operating voltage. The nitride semiconductor light emitting device includes an n-nitride semiconductor layer; an active layer of multi-quantum well structure formed on the n-nitride semiconductor layer, and having a plurality of quantum well layers and a plurality of quantum barrier layers; and a p-nitride semiconductor layer formed on the active layer. One of the quantum well layers adjacent to the n-nitride semiconductor layer has an energy band gap greater than that of another one of the quantum well layers adjacent to the p-nitride semiconductor layer.

1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a high quality nitride semiconductor light emitting device having high internal quantum efficiency but low operating voltage.
2. Description of the Related Art
To date, Light Emitting Diodes (LEDs) or Laser Diodes (LDs) based on group III-V nitride semiconductor (hereinafter will be referred to as "nitride semiconductor" in short) are often used in light emitting devices for generating a blue or green wavelength of light, and applied as light sources of various products such as an electronic display board and lighting equipment. Such nitride semiconductor is made of a GaN based material having a composition of InxAlyGa(1-x-y)N, where 0≦x≦1, 0≦y≦1 and 0≦x+y≦1. To manufacture such a nitride semiconductor light emitting device, a nitride semiconductor light emitting structure is produced by sequentially forming an n-nitride semiconductor layer, an active layer and a p-nitride semiconductor layer on a growth substrate of for example sapphire.
An active layer in the light emitting structure may have a multi-quantum well structure. The active layer is composed of a plurality of quantum well and quantum barrier layers are stacked alternately on each other to form and thus a plurality of quantum wells exist at a small width in the active layer. With charge carriers (e.g., electrons and holes) easily captured in the quantum well structure, electron-hole recombination is more likely to take place in the active layer.
FIG. 1 is a diagram schematically illustrating an energy band structure of a conventional nitride semiconductor light emitting device. Particularly, FIG. 1 illustrates an energy band diagram about an active layer in a light emitting structure. Referring to FIG. 1, an active layer having a multi-quantum well structure is formed on an n-nitride semiconductor layer, and a p-nitride semiconductor layer is formed on the active layer. The active layer includes first to fifth quantum well layers 1st QW to 5th QW, which are arranged sequentially from the side adjacent to the n-nitride semiconductor layer, and quantum barrier layers of a relatively greater band gap alternating with the quantum well layers. The number of quantum well layers may be adjusted if necessary. Typically, a quantum well layer has In density set higher than that of a quantum barrier layer and thus its band gap is lower than that of the quantum barrier layer. The band gap (or the In density) of the quantum well layer is varied according to the wavelength of emitted light.
In a light emitting device having an active layer of such a quantum well structure, the band gaps of the quantum well layers are set to be substantially uniform. Then, the lattice constant of the active layer (particularly, the quantum well layer) shows a great difference from that of the n-nitride semiconductor layer. Such lattice mismatch causes a considerable amount of strain in the active layer. The strain in turn generates a piezoelectric field in the active layer, which increases the distance between electron wave function and hole wave function but lowers internal quantum efficiency. As a result, the overall brightness of the semiconductor light emitting device is lowered.
In addition, the strain in the active layer acts to degrade the uniformity of energy level in each quantum well. Accordingly, in application of high supply voltage, charge carriers are more likely to occupy higher energy level in the quantum well. Such band-filling phenomenon is a factor that creates blue shift, in which the wavelength of emitted light is shortened in application of high supply voltage, thereby causing the emitted light to have a wavelength beyond a designed range.

Nitride semiconductor light emitting device