Improving the characteristics of InAlAs/InGaAs heterojunction bipolar transistors by employing thin base and collector layers

InAlAs/InGaAs heterojunction bipolar transistors with thin base and collector layers are fabricated. The maximum value of current gain cutoff frequency is as high as 96 GHz. It is shown that thinning of the base and collector is very effective not only for reducing the base and collector transit times but also for suppressing the space charge effect in the collector.<>     

Hepatic Expression of Long-Chain Acyl-CoA Synthetase 3 is Upregulated in Hyperlipidemic Hamsters

Members of the mammalian long-chain acyl-CoA synthetase (ACSL) family are key enzymes for cellular fatty acid metabolism that catalyze the initial step in activation of long-chain fatty acids. However, the specificity of individual isoforms of ACSL to the lipid metabolic process is not well studied. In addition, the regulation of expression of individual ACSL isoforms under hyperlipidemic conditions is largely unknown. We cloned the hamster ACSL3 cDNA coding region and generated specific antibodies recognizing the ACSL3 protein. We next observed the changes in ACSL3 mRNA and protein expression in hamsters fed a standard chow diet or a high fat and high cholesterol (HFHC) diet. HFHC feeding significantly increased ACSL3 mRNA and protein expression in liver and to a lesser extent in muscle but not in adipose, brain, heart, or testis. Additionally, ACSL3 mRNA abundance was differentially regulated by the nutritional status in different tissues with liver, muscle, and adipose being the most sensitive tissues. Importantly, the hepatic ACSL3 mRNA expression pattern in response to fasting and refeeding in hyperlipidemic hamsters differed from that observed in normal chow-fed hamsters. Together, these results provide the first in vivo evidence of altered regulation of hepatic ACSL3 expression under hyperlipidemic conditions and suggest important regulatory roles for this enzyme in lipid metabolism.     

Assessment of Swallowing Ability Scale for oral and oropharyngeal cancer patients

The Swallowing Ability Scale (SAS) has been recently reported by us. This scale is a new method to assess dysphagia after therapy for oral and oropharyngeal cancer. The preliminary results on 23 patients showed that the scale was reliable and sensitive to functional differences across a broad spectrum of oropharyngeal dysphagia after therapy. This paper confirmed the above facts in 73 oral and oropharyngeal cancer patients who were treated in two hospitals between 1995 and 1996. As stated in the previous paper, SAS consists of a 2-step questionnaire: the MTF score and the Dysphagia score. The MTF score is a simple and practical assessment tool consisting of three subscales: 1) Method of intake, 2) Time of intake, and 3) Food. The Dysphagia score is a relevant assessment tool for defining patients' anatomic or physiologic swallowing disorders. In 40 patients with wide resection of the tongue, the Dysphagia score (p < 0.05) and the MTF score (p < 0.01) were significantly decreased. And we found a correlation between the MTF score and the Dysphagia score (r = 0.78, p < 0.001) in 73 patients. The usefulness of the SAS will be further studied for the assessment of rehabilitation to improve postoperative dysphagia.     

ARTS: Accelerated Ray-Tracing System

In this article we propose algorithms that address the two basic problems encountered in generating continuous-tone images by ray tracing: speed and aliasing. We examine previous approaches to the problem and then propose a scheme based on the coherency of an auxiliary data structure imposed on the original object domain. After investigating both simple spatial enumeration and a hybrid octree approach, we developed 3DDDA, a 3D line generator for efficient traversing of both structures. 3DDDA provides an order of magnitude improvement in processing speed compared to other known ray-tracing methods. Processing time is found to be virtually independent of the number of objects involved in the scene. For large numbers of objects, this method actully becomes faster than scan-line methods. To remove jags from edges, a scheme for identifying edge orientation and distance from pixel center to true edge has been implemented. The time required for antialiasing depends on the total length of the edges encountered, but it is normally only a fractional addition to the time needed to produce the scene without antialiasing.     

Investigation on the biomimetic influence of biopolymers on calcium phosphate precipitation-part 2: Chitosan

A better understanding of how macromolecules act in the precipitation of inorganic phases is the key to designing biomimetic routes for producing self-organized materials with remarkable properties. The role of small amounts of biopolymers (ppm) in the precipitation of calcium phosphate was studied: chitosan and alginate were chosen to be explored in our group studies since they are polysaccharides that present, respectively, amino and carboxyl groups, the most common functions in biopolymers. The effect of chitosan was found to be more intense than that of alginate in terms of influence (compared to blank samples) and also in orientation of the inorganic phase that was obtained. These results may indicate that polymers have interactions, but just enough to conduct ions for molecular recognition and correct epitaxy to orient crystals. Strong interactions would lead to the binding of the species, making them unavailable for further oriented growth.     

Design concept of antennas for small mobile terminals and the future perspective

With the progress and rapid increase in mobile terminals, the design of antennas for small mobile terminals is acquiring great importance. In view of this situation, the design concept of antenna systems for small mobile terminals and its future perspective are discussed, referring to the trends in modern mobile communications and the demands for the antenna system. The design concept of antenna systems has changed along with the progress of mobile systems. In the conventional design, the conducting material of the equipment case, existing near the antenna element, is included as a part of the radiator in the antenna system, without regard to whether or not it has been considered. In the latest mobile phones, the design concept has been advanced to aim at improving the antenna's performance, and the treatment of the case, etc., has become a part of this. Some particular considerations for the design are to relieve the degradation of the antenna's performance due to the human-body effect, to overcome the SAR problems, and yet to make the size small. Furthermore, it is now time to proceed to the more-advanced concept, in which implementation of adaptive control and software is considered, even in small mobile terminals. Typical trends in modern communications systems are discussed, and the demands of these trends-which are summarized as down-sizing, function, and intelligence-are taken up for future antenna structures. Small-antenna technology and the application of the integration technology to antenna systems are essential for realizing such future structures.     

Overproduction of Mpd2p suppresses the lethality of protein disulfide isomerase depletion in a CXXC sequence dependent manner

The third multicopy suppressor gene of the PDI1 deletion from Saccharomyces cerevisiae, MPD2, was isolated and characterized. The MPD2 gene encodes a protein with a putative signal sequence, ER retention signal, and a disulfide isomerase active site like sequence. The amino acid sequence around the active site like sequence is similar to the thioredoxin-like domains of PDI and PDI related proteins, although the similarity is comparatively low. A delta-pdi1 strain over-producing Mpd2p showed slow growth and was sensitive to 1 mM dithiothreitol. Mpd2p can be detected in wild type cells and is a glycoprotein. Although the MPD2 gene was not essential for growth, overexpression of the gene partially restored the maturation defect of carboxypeptidase Y caused by the PDI1 deletion. Mutagenesis analysis revealed that Mpd2p can compensate for the loss of PDI with its CXXC sequence.     

Low energy elastic scattering of positrons by CO: An application of continued fractions and Schwinger variational iterative methods

Iterative Schwinger variational methods and the method of continued fractions, widely used for electron-molecule scattering, are applied for the first time to investigate positron-molecule interactions. Specifically, integral and differential cross sections for elastic positron scattering by CO in the (0.5-20) eV energy range are calculated and reported. In our calculation, a static plus correlation-polarization potential is used to represent the collisional dynamics. Our calculated results are in general agreement with the theoretical and experimental data available in the literature.     

Control System With High-Speed and Real-Time Communication Links

Recent technological advances have enabled distributed control systems to be implemented via networks. This allows feedback control loops to be closed over communication channels. This paper develops a control system with high-speed and real-time communication links. Two-degrees-of-freedom control is utilized in this servo control system, and sigma-delta modulation is employed to compress data and to transmit the signal over the transmission channels between the controller and the controlled plant. Simulation results show that the controller can compensate the possible existing noise in the transmission channels. In addition, the developed system is implemented in field-programmable gate arrays. We developed a real-time closed-loop control system that has a communication channel whose control-sampling period is 600 ns and can reduce the sampling period of the controller module to hundreds of nanoseconds.     

Coherent optical communication with injection-locked high-power semiconductor laser array

Heterodyne FSK communication at 110 Mbit/s is demonstrated with an injection-locked high-power 20-stripe semiconductor laser array. It is shown that a high-power (>300 mW) coherent optical transmitter can be constructed without penalty in bit error rate performance.<>