A theory of pseudo cross-link

Summary A theory of pseudo cross-link model suggests the existence of multiple links of various size composed of 116 segmental units. They possesses the heat and entropy of various magnitude giving various transition temperature, T_A for the cross-link composed of 4 segments and T_B for that of 16 segments. The glass-transition point T_g and the melting point T_m are defined by the different size of lateral multiple links. Relationships, T_m = 2 T_A and T_g = (2/3)T_m = (4/3)T_A, are derived. A wedge-type relaxation spectrum is obtained as a distribution of size of cross-links. For temperature dependence the WLF-equation is obtained.     

Measurement of heat of mixing for ammonium chloride + ammonia system at 25 °c

Heat of mixing for ammonium chloride in liquid ammonia at 25°C was determined in the concentration range 0-50 wt% NH₄Cl. It was calculated from the differential heat of solution observed in this work and the differential heat of dilution estimated from activities of solvent. A twin isoperibol calorimeter consisting of two stainless Dewar vessels was used at a relatively high pressure (up to 1.5 MPa). The accuracy of this calorimetry was examined by measuring the heat of solution for tris-(hydroxymethyl)aminomethane(THAM) in 0.1 kmol/m³ HCl at 25°C, and satisfactory agreement within 1.1% between experimental and literature value was obtained. The reproducibility for the experiment was within 2.8%.     

X-ray spectroscopy of highly ionised atoms of Ti through Zn in a dense plasma

X-ray spectra for several elements have been observed from a high-temperature plasma produced in a vacuum spark using a curved-crystal spectrometer. The transition wavelengths of the He-like resonance lines for Ti through Zn are determined for the first time under careful experimental treatments. The result is compared with theoretical predictions. The transition wavelengths of the Fe He-like resonance series lines up to 1s6p–1s² and the Kβ transition energies of Ti partially M-shell-ionised ions (Ti VI–XIII) are also determined. As a result, several satellite lines are found.     

Estimation method of frequency bias using normal operating data

A technique of calculating the frequency bias of an electric power system from frequency fluctuation data and total output power is described. An evaluation method for testing the calculations by the new method is developed. The results are in good agreement with estimates based on generator speed regulation but the method gives an excessively high figure for the load frequency bias.     

The role of malonyl-coa in the coordination of fatty acid synthesis and oxidation in isolated rat hepatocytes

Fatty acid synthesis and fatty acid oxidation were examined in rat hepatocytes under a variety of experimental conditions. In cells from fed animals, glucagon acutely switched the direction of fatty acid metabolism from synthesis to oxidation. Addition of lactate plus pyruvate had the opposite effect. The inhibitory action of glucagon on fatty acid synthesis and its stimulatory effect on fatty acid oxidation were largely, but not completely, offset by the simultaneous addition of lactate plus pyruvate. Changes in cellular citrate and malonyl-CoA levels indicated that glucagon exerted its inhibitory effect on fatty acid synthesis at two levels: (i) blockade of glycolysis; and (ii) partial inhibition of a more distal step, probably acetyl-CoA carboxylase. Under all conditions, fatty acid oxidation was related in a linear and reciprocal fashion to the rate of fatty acid synthesis and the tissue malonyl-CoA content. The latter fluctuated through a range of 1 to 6 nmol per g wet weight of cells. Since malonyl-CoA inhibits carnitine acyltransferase I of liver mitochondria with a Ki in the region of 1 to 2 micron, the present studies support the concept that this compound plays a pivotal role in the coordination of hepatic fatty acid synthesis and oxidation. The ketogenic effect of glucagon on liver appears to be manifested in large part through the ability of the hormone to reduce the tissue malonyl-CoA concentration.     

In vivo pressure estimation using subharmonic contrast microbubble signals: proof of concept

Changes in ambient pressure affects the reflectivity of ultrasound contrast microbubbles leading to an excellent correlation between subharmonic signals and hydrostatic pressure. The aortas of two dogs were scanned with an experimental pulse-echo system to validate in vivo pressure estimation based on subharmonic microbubble signals. Results matched well with instantaneous pressure measurements (from 20-60 mmHg) obtained simultaneously with a pressure catheter (root mean square errors <27%).     

Anisotropy of styrene–butadiene rubber

Anisotropy of styrene–butadiene rubber (SBR) was investigated. The anisotropy of the copolymer varies linearly with the styrene content and the ultimate value coincides with that of polystyrene at elevated temperature. From these facts, the transverse configuration of the pendant phenyl group is estimated irrespective of the styrene content of SBR.     

Monitoring biofilm development in a microfluidic device using modified confocal reflection microscopy

The feasibility of a method to monitor biofilm development non-destructively in a microfluidic device was addressed. Here, we report that biofilm growth could be non-destructively monitored by an image analysis technique based on modification of confocal reflection microscopy.     

Synthesis of proton conductive membranes based on inorganic–organic hybrid structure bound with phosphonic acid

Proton conductive inorganic–organic hybrid membranes were synthesized from styrene derivatives of alkoxysilane and ethyl 2-[3-(dihydroxyphosphonyl)-2-oxopropyl] acrylate (EPA) through copolymerization followed by sol–gel reaction. Self-standing, homogeneous and transparent hybrid membranes with chemically bound phosphonic acid groups were synthesized. FT-IR analysis exhibited the hybrid membranes included phosphonic acid groups. ¹³C and ²⁹Si NMR studies indicated that alkoxysilyl functionalized styrene derivatives were not only copolymerized with EPA but also condensed yielding Si–O–Si linkages by sol–gel reaction. TG–DTA analysis revealed that these membranes were thermally stable up to 200 °C in dry O₂. The proton conductivities of the hybrid membranes increased with phosphonic acid content and temperature. The P/Si ratio of the membrane was dependent on the number of alkoxy group in the starting alkoxysilane. The hybrid membrane from (dimethylmethoxysilylmethyl)styrene (DMMSMS(M))/EPA = 1/6 revealed proton conductivities of 6.3 × 10⁻³ and 2.4 × 10⁻⁴ S cm⁻¹ at 68.0% relative humidity and 18.8% relative humidity, respectively, at 140 °C.     

BP神经网络权值初始值与收敛性问题研究

BP神经网络的收敛性问题是一直受到广泛关注的问题。本文针对BP网络在运算过程中陷入局部最小区，收敛速度慢的问题，从BP算法的原理出发，讨论了权值初始值对网络训练速度的强烈影响（仿真结果证明了这一点），并提出了解决方法。