Photoluminescence studies on InGaAlP layers grown by low-pressure metalorganic chemical vapor deposition

The optical properties for In_0.5(Ga_1-x Al _x )_0.5P (0 <x < 0.4) layers, grown by low-pressure Metalorganic Chemical Vapor Deposition, have been studied with photolominescence (PL) measurement. The PL intensity decreases with the increase of the Al composition (0 <x < 0.4). This dependence could not be accounted for only by the electron overflow from theΓ band to the X band. And the PL intensity is directly proportional to the excitation power at low temperature, below 50 K. On the other hand, the PL intensity is proportional to the second power of the excitation power at a high temperature range (>200 K). These results indicate that non-radiative recombination centers bound to theΓ band in In_0.5(Ga_1-x Al _x )_0.5P play a very important role in the radiation mechanism. PL dependence also shows these non-radiative recombination centers are thought to have strong relation to the aluminum substitution for In_0.5(Ga_1-x Al _x )_0.5P.     

Design of an adaptive observer for sensorless vector control of induction machines under regenerating conditions

The objective of this investigation is to stabilize a sensorless vector control system of induction motors by means of an adaptive observer in regenerating mode at very low speed. The adaptive observer gain is designed by means of the Routh–Hurwitz criterion. It is verified by simulation and experiment that the proposed system is stable. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 78–87, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10202     

Cloning and sequencing of the Sphingomonas (Pseudomonas) paucimobilis gene essential for the O demethylation of vanillate and syringate

A growing body of evidence supports the existence of a tissue-based renin-angiotensin system (RAS) in the vasculature, but the functional capacity of vascular RAS was not investigated in humans. In 28 normotensive healthy control subjects, the metabolism of angiotensins through vascular tissue was investigated in normal, low, and high sodium diets by the measurement of arterial-venous gradient of endogenous angiotensin (Ang) I and Ang II in two different vascular beds (forearm and leg), combined with the study of 125I-Ang I and 125I-Ang II kinetics. In normal sodium diet subjects, forearm vascular tissue extracted 36+/-6% of 125I-Ang I and 30+/-5% of 125I-Ang II and added 14.9+/-5.1 fmol x 100 mL(-1) x min(-1) of de novo formed Ang I and 6.2+/-2.8 fmol x 100 mL(-1) x min(-1) of Ang II to antecubital venous blood. Fractional conversion of 125I-Ang I through forearm vascular tissue was about 12%. Low sodium diet increased (P<.01) plasma renin activity, whereas de novo Ang I and Ang II formation by forearm vascular tissue became undetectable. Angiotensin degradation (33+/-7% for Ang I and 30+/-7% for Ang II) was unchanged, and vascular fractional conversion of 125I-Ang I decreased from 12% to 6% (P<.01). In high sodium diet subjects, plasma renin activity decreased, and de novo Ang I and Ang II formation by forearm vascular tissue increased to 22 and 14 fmol x 100 mL(-1) x min(-1), respectively (P<.01). Angiotensin degradation did not significantly change, whereas fractional conversion of 125I-Ang I increased from 12% to 20% (P<.01). Leg vascular tissue functional activities of RAS paralleled those of forearm vascular tissue both at baseline and during different sodium intake. These results provide consistent evidence for the existence of a functional tissue-based RAS in vascular tissue of humans. The opposite changes of plasma renin activity and vascular angiotensin formation indicate that vascular RAS is independent from but related to circulating RAS.     

Stepwise analysis of cerebral blood flow SPECT imaging on standard brain atlas in patients with dementia of Alzheimer''s type

In 1994 the first human parvovirus B19 (B19) epidemic to be documented in Denmark was recorded from February 2 to September 30. In total, 10,333 serum samples were tested for specific B19 IgM and IgG antibodies, using IDEIA Parvovirus B19 IgM and IgG kits. The prevalence of B19 IgM positivity was 11% for the whole period and 29% at the peak of the epidemic in week 14, declining from week 39 and onwards to 1-3%. The prevalence of B19 IgG (IgM-negative samples) was 60%, indicating an earlier infection, and the same for men and women. The gender distribution of tested patients was the same at the beginning of the epidemic as at the end of the epidemic and a year after its peak, i.e. 86% of samples were from women and only 14% from men. Age distribution for women was the same for the three periods (median age 34 years). For men the median age was 32 years, 39 years and 31 years, respectively. Only a few samples from children were tested. No change in test pattern was observed during the three periods. Approximately 75% of all samples tested were from women of childbearing age (18-45 years old), suggesting a fear of fetal complications in an actual or future pregnancy, rather than a serological verification of clinical symptoms. From the sparse clinical information that accompanied the serum sample we were not able to demonstrate that women were more likely than men to have a symptomatic B19 infection. With reservations we estimate that 14% of adverse pregnancy outcome is correlated with a B19 infection.     

Steep Impulse Voltage Characteristics of Suspension Insulators

Transmission and distribution lines are sometimes struck by lightning and there is some risk of electrical puncture of suspension insulators due to high and steep lightning surge voltage. When the insulators suffer from steep lightning surge voltages, the solid insulating body of the insulators sometimes is punctured before external flashover in the air occurs. These characteristics were investigated on the insulators in the laboratory by using different steep impulse voltages. From the investigation results, both V-t characteristics of external flashover and internal puncture were obtained on the insulators. It was found that the puncture of the insulators is a matter of probability, depending on the dimensions of the insulators, steep impulse voltages and number of impulse voltage applications. Especially, the effect of number of voltage applications on puncture probability was clarified and partial damage by a small number of voltage applications was verified before complete puncture occurred. Based on the study results, an empirical equation relating to probability of puncture (P), impulse voltage (V) and number of voltage applications (N) was established.     

Characteristics of the readback signal in digital magnetic recording

A theoretical treatment for the readback process in digital magnetic recording is presented. Three major factors, namely, the medium constantswhich defines the extent of the surface charge density, the head-to-medium spacingd, and the read head gap2 g,are taken into consideration. A general solution giving the characteristics of pulse readback signal is shown as a function ofs,dandg. Both amplitude and pulse width of the readback signal are arranged as a product of the medium loss, spacing loss, and gap loss, making it easy to describe the influence of each factor separately. The final value of the amplitude and the pulse width is proportional to that of the recorded surface charge density. Spacing loss simply depends on the ratio ofd/s; gap loss depends on the ratio ofg/(s + d). Theoretical results are compared with experiments which show good agreement for a wide combination ofs,d, andg.     

Optimally weighted wavelet transform based on supervised training for detection of microcalcifications in digital mammograms

We are developing a computer-aided diagnosis (CAD) scheme for detection of clustered microcalcifications in digital mammograms. The use of an empirically chosen wavelet and scale combination for detection of microcalcifications as an initial step of the CAD scheme has been reported by us previously. In this study, we developed a technique for optimizing the weights at individual scales in the wavelet transform to improve the performance of our CAD scheme based on the supervised learning method. In the learning process, an error function was formulated to represent the difference between a desired output and the reconstructed image obtained from weighted wavelet coefficients for a given mammogram. The error function was then minimized by modifying the weights for wavelet coefficients by means of a conjugate gradient algorithm. The Least Asymmetric Daubechies' wavelets were optimized with 297 regions of interest (ROIs) as a training set by a jackknife method. The performance of the optimally weighted wavelets was evaluated by means of receiver-operating characteristic (ROC) analysis by use of the above set of ROIs. The analysis yielded an average area under the ROC curve of 0.92, which outperforms the difference-image technique used in our existing CAD scheme, as well as the partial reconstruction method used in our previous study.     

Protein structural similarities predicted by a sequence-structure compatibility method

A method for protein structure prediction has been developed, which evaluates the compatibility of an amino acid sequence with known 3-dimensional structures and identifies the most likely structure. The method was applied to a large number of sequences in a database, and the structures of the following proteins were predicted: (1) shikimate kinase (SKase), (2) the hydrophilic subunit of mannose permease (IIABMan), (3) rat tyrosine aminotransferase (Tyr AT), and (4) threonine dehydratase (TDH). The functional and evolutionary implications of the predictions are discussed. (1) The structural similarity between SKase and adenylate kinase was predicted. Alignment of their sequences reveals that the ATP-binding type A sequence motif and 2 ATP-binding arginine residues are conserved. The prediction suggests a similarity in their functional mechanisms as well as an evolutionary relationship. (2) The structural similarity between IIABMan and galactose/glucose-binding protein (GGBP) was predicted. The IIA and IIB domains are aligned with the N- and C-terminal domains of GGBP, respectively. The 2 phosphorylated residues, His 10 and His 175, of IIABMan are threaded onto loops located in the substrate-binding cleft of GGBP. The prediction accounts for the phosphoryl transfer from His 10 to His 175, and to the sugar substrate. (3) The structural similarity between rat Tyr AT and Escherichia coli aspartate AT was predicted, as well as (4) the structural similarity between TDH and the tryptophan synthase beta subunit. Predictions (3) and (4) support the previous predictions based on observations of the functional similarities between the proteins.     

The full expression of the ity phenotype in ityr mice requires C3 activation by Salmonella lipopolysaccharide

Our previous study has shown that the rapid and sufficient activation of complement by Salmonella lipopolysaccharide occurs in genetically resistant (Ityr) A/J mice. To assess whether the level of complement activation by a virulent strain of Salmonella typhimurium regulates the level of murine natural resistance, we compared levels of serum complement activation by S. typhimurium and kinetics of serum-opsonized S. typhimurium grown in macrophages using several strains of resistant (Ityr) and susceptible (Itys) mice. Itys macrophages killed intracellular S. typhimurium to the same extent as did Ityr macrophages when the pathogen was opsonized with Ityr serum. Opsonization of S. typhimurium with Itys serum reduced intracellular killing activity in Ityr macrophages to the same level as seen with Itys macrophages. Incubation of S. typhimurium with 25% Mg2+ EGTA (5 mm MgCl2-3 mm ethylene glycol-bis (beta-aminotheyl either)-N,N,N',N'-tetraacetic acid)-chelated Ityr serum resulted in higher levels of C3 deposition onto the surface of this bacteria, C3b generation and also C3 consumption, compared with that with Mg2+ EGTA-chelated Itys serum. Opsonization of S. typhimurium with A/J serum prior to infection increased early resistance in Itys mice. Infection with a virulent strain of S. typhimurium induced the expression of interleukin-10 (IL-10) mRNA at higher levels in C57BL/6 mice than in A/J mice. However, opsonization of S. typhimurium with A/J serum decreased bacterial growth in the spleen of C57BL/6 mice to the same level as observed for A/J mice in association with decreased expression levels of IL-10 mRNA. Moreover, administration of anti-C3 antibodies reduced the resistance of A/J mice in association with a decrease in serum levels of C3. These results indicate that the high level of complement activation via the alternative pathway in Ityr serum by a virulent strain of S. typhimurium reduces the virulence of this pathogen, which may contribute to the full expression of Ity phenotype in Ityr mice.