Thermosensitivity control of polyethlyenimine by simple acylation

Branched polyethylenimine (b-PEI), an amine-rich polymer, can obtain thermosensitivity by a simple acylation reaction. The resulting N-acylated b-PEI derivatives showed a similar lower critical solution temperature (LCST) transition as their linear correspondent, poly(N-alkyloxazoline). Three acyl groups (propionyl, and isobutyryl, and n-butyryl) were introduced and resulted in LCSTs ranging from 10 °C to 90 °C depending on the structure and environment. The hydrophobicity of N-acylated b-PEI can be controlled by varying the acyl group and degree of acylation. Because the LCST transition is determined by the delicate balance between the hydrophobicity and hydrophilicity of the polymers, an increase of the hydrophobicity in N-acylated b-PEI lowers the transition temperature. Also, N-acylated b-PEI contains tertiary amines as well as unacylated primary or secondary amines which can be protonated during acidification from a pH of 7.4 to a pH of 5.5. The LCST transition was observed at elevated temperatures due to the increase of hydrophilicity by the protonation in the acidic environment. The LCST was also influenced by the salt concentration. A decrease of the LCST was observed as the NaCl concentration increased, probably due to the dominance of the salting-out effect. The very simple introduction of thermosensitivity into pre-existing polymers can be easily applied for the development of various dual or multiple signal-sensitive polymer systems.     

Hybrid stepping motor vibration

This article presents a simple method to calculate the stator surface vibration of a unipolar four-phase hybrid stepping motor. The approximate radial magnetic force per pole is calculated by using a permeance model and its equivalent magnetic circuit. Based on the calculated radial magnetic forces and the measured stator mobility values, the radial vibration spectrum on top of a stator pole is estimated. The results have shown that there is a reasonable agreement between the calculated and measured radial vibration levels. This verifies the analytical approach which, due to the special structure and excitation of the motor, is significantly different from the technique commonly employed for vibration study for induction machines     

A TEM study on melt-crystallized poly(butylene terephthalate)

A study was made to investigate an optimum condition for ruthenium tetraoxide staining of poly(butylene terephthalate) (PBT) with glass transition temperature as low as ca. 23 degrees C for TEM observation of melt-grown PBT crystals. The morphological study of ultrathin sections prepared based on optimum staining at 25 degrees C for 8 h revealed formation of fringed-micellar crystal nuclei in the early stage and folded-chain fringed-micellar crystals in the later stage of isothermal crystallization at 40 degrees C from melt. The fraction of chain-folded crystals increased with increasing crystallization temperature from the quantitative analysis of crystal thickness in comparison with the reported morphology using the replica method.     

Holographic optical elements recorded in silver halide sensitized gelatin emulsions. Part 2. Reflection holographic optical elements

Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOEs). The drawback of DCG is its low energetic sensitivity and limited spectral response. Silver halide materials can be processed in such away that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-fine-grain silver halide (AgHal) emulsions. In particular, high spatial-frequency fringes associated with HOEs of the reflection type are difficult to construct when SHSG processing methods are employed. Therefore an optimized processing technique for reflection HOEs recorded in the new AgHal materials is introduced. Diffraction efficiencies over 90% can be obtained repeatably for reflection diffraction gratings. Understanding the importance of a selective hardening process has made it possible to obtain results similar to conventional DCG processing. The main advantage of the SHSG process is that high-sensitivity recording can be performed with laser wavelengths anywhere within the visible spectrum. This simplifies the manufacturing of high-quality, large-format HOEs, also including high-quality display holograms of the reflection type in both monochrome and full color.     

Combined and interacting effects of hand and head movement delays on discrete manual performance in a virtual environment

Transmission delays occur when a virtual environment responds to the hand and head movements of an operator. The effects of hand and head-related delays on discrete manual performance was investigated experimentally and compared. Imposed hand and head-related pure delays equal to or greater than 110 ms and 220 ms, respectively, significantly increased hand Movement Time (MT). The effect of hand-related delays was greater than that of head-related delays of the same magnitude. A regression model describing the combined effects of both delays on MT is reported (R(2) = 0.95). Analyses of the interactions among delays, target width, and distances have shown the need to adopt the traditional classification of delays into (1) control delay, and (2) display delay. The use of this taxonomy and the regression analyses to describe and explain the effects of individual and combined effects of delays on discrete target-reaching task performance in virtual environments are discussed.     

An approach to modelling DC-DC converter circuits using graph theoretic concepts

An approach to modelling DC-DC converter circuits based on graph theoretic concepts is discussed in this paper. the DC-DC converter circuits are treated as networks containing switches, with the magnitudes of their associated eigenvalues much smaller than the switching frequency. the procedure for modelling this class of networks essentially involves separating the original network into two N-port networks, one containing those branches responsible for all phenomena peculiar to the switching action and the other containing the remaining branches of the network. the two N-port networks thus formed lead to a systematic and convenient way of developing low-frequency circuit models for DC-DC converter circuits.     

Clinical studies on renal trauma

A total of 18 kidneys in 17 patients with renal trauma were treated at the Department of Urology, Mitoyo General Hospital between April 1991 and August 1997. Patients were between 10 and 88 years old (median; 52). Eleven of them were male and 6 were female. The main cause of injury was a traffic accident in 11 cases (64.7%), which was similar in tendency to previous reports in this country. According to the Classification of Renal Injury by the Japanese Association for the Surgery of Trauma in Japan, there were 8 cases (47.1%) of Type I (sub-capsular injury) and Type II (superficial injury) that was classified a minor injury, and there were 9 cases (52.9%) of Type III (deep injury), Type IV (pedicle injury) and open injury that was classified as a major injury. Surgical treatment was performed in 8 cases (47.1%), which were all classified as a major injury. Posttraumatic plasma lactate dehydrogenase (LDH) was elevated immediately in case of major injury in comparison with a case of minor injury. Serum LDH may be useful as a parameter of the degree of renal trauma.     

Immunohistochemical quantitation for extracellular matrix proteins in rats with glomerulonephritis induced by monoclonal anti-Thy-1.1 antibody

During clot retraction, platelets interact with fibrin resulting in marked reduction of clot volume. Altered fibrin structure has been reported to affect clot retraction as measured by serum expression. This study was performed to test whether such altered retraction was the result of increased resistance to network collapse or due to decreased force development by platelets. Altered fibrin structure was documented as variation of fibre mass/length ratios (mu) and shifts in clot elastic modulus. The force developed by platelets during clotting was measured directly. Increasing the fibrinogen concentration led to thinner fibre formation (decreased mu), and a linear increase in gel elastic modulus. Over a fibrinogen concentration range of 100 to 400 mg/dl, force development was minimally affected. Force development and clot elastic modulus increased in a linear fashion with increasing platelet concentration. Increasing the calcium concentration from 5 to 20 mM caused a 160% increase in fibrin fibre size (mu), and a 52% decline in clot modulus. Force developed at 1200 s declined by 17%. At 15 mg/ml, dextran and hydroxyethyl starch (HES) also increased mu, and decreased clot modulus; however, both agents markedly reduced force development. Increasing ionic strength or the addition of IgG decreased mu and increased gel elastic modulus. Force development increased modestly with increased ionic strength, did not change with addition of IgG in saline and declined with addition of IgG in maltose. This study indicates that force development is primarily dependent on platelet function while clot modulus depends on both fibrin structure and platelet function.(ABSTRACT TRUNCATED AT 250 WORDS)