Intrinsic scattering and absorption losses of Ge- and F-doped optical fibres prepared by PCVD

The scattering absorption and profile losses of PCVD fibres are analysed. The Rayleigh scattering increases proportionally to the sum of the F- and Ge-dopant concentrations, the UV absorption is proportional to the Ge concentration, and profiling losses are negligible.<>     

Effect of progressive systemic sclerosis on antral myoelectrical activity and gastric emptying

In patients with progressive systemic sclerosis (PSS) suffering from chronic dyspepsia the stomach may be affected by this disease. The objective of this study was to investigate both antral myoelectrical activity and gastric emptying in PSS patients. Electrogastrography (EGG) was performed in 17 PSS patients (16 female, one male, median age 58 years, range 32-74 years) with chronic dyspepsia. After an overnight fast during one hour in the fasting and one hour in the fed state after ingestion of a liquid-solid test meal (370 kcal; liquid phase labeled with 0.5 mCi 99mTc-colloid) antral electrical activity was measured by one pair of electrodes sonographically placed on the skin overlying the gastric antrum. Several EGG parameters including dominant frequency (DF), percentages of DF in the normal range (2-4 cycles per minute [cpm]), bradygastria (< 2 cpm) and tachygastria (4-10 cpm), dominant frequency instability coefficient (DFIC), and postprandial to preprandial power ratio (PR) were calculated. The data were correlated to results obtained in 20 age- and gender-matched healthy subjects. In addition, the data were compared to gastric retention of the radionuclide at 60 min measured by simultaneous scintigraphy. The PSS patients did not reveal electrical disturbances. They even exhibited a significant postprandial decrease in DFIC, bradygastria, and tachygastria (ns) compared to healthy subjects. Over 50% of the PSS patients showed a delayed gastric emptying. However, EGG did not correlate to radioscintigraphy significantly. Our results reflect an absent relationship between antral myoelectrical activity in EGG and gastric emptying. Therefore, electrogastrography is unsuitable to assess gastric involvement in PSS.     

The performance of depressed-cladding single-mode fibers withdifferent b/a ratios

Depressed-cladding single-mode fibers with a first cladding-to-core ratio (b/a) ranging from seven to one and relative refractive-index differences of the core from 0.25 to 0.35% and of the cladding from 0 to -0.2% are investigated experimentally with respect to the LP₁₁ mode cutoff properties, the mode-field diameter, the dispersion, and the bending attenuation. Numerical calculations based on actual profile parameters of the bend loss and the mode-field diameter agree well with experiment. It is demonstrated that low attenuation and bend losses independent of b/a can be obtained if the cutoff wavelength is kept constant by adjusting the core radius, the core index or the index of the first cladding     

Transitions of saturated monoacid triglycerides: Modeling conformational change at glycerol during α→β′→β transformation

The glycerol region geometry of modeled saturated monoacid triglycerides was altered by bond rotations and minor angle distortions to convert theoretical α-forms into bent β′- and β-forms. Direct α to β conversion involves lateral disruption of fatty chain packing to generate side-chain character typical of the β-form. Such disruption, which could contribute to fat bloom, allows additional molecular movement and shifts in molecular mechanics energy (MME) that may approximate thermal changes observed by differential scanning calorimetry during α to β transformations. Energy calculations at 100 points throughout each transformation identified plausible conversion routes. A two-stage conversion, α to either of two stereospecific β′-forms bent at glycerol followed by subsequent conversion to β, showed less chain movement and more favorable MME than direct α to β conversion. The preferred path, based on energy profiles of each conversion, involves a β′-D form and rotation of carbonyl to α-carbon bonds in chain #2 and a side chain (chain #3).     

An alternative approach to the synthesis of NaB3H8 and Na2B12H12 for solid electrolyte applications

Alkaline or alkaline earth octahydrotriborate M(B₃H₈)_x and dodecahydro-closo-dodecaborate M_xB₁₂H₁₂ (M = Li, Na, Mg or Ca with x = 1 or 2) have recently attracted a lot of interest for hydrogen storage and solid electrolyte applications. Nevertheless, their syntheses are still a roadblock for large scale applications. In this paper we propose a novel approach for their syntheses starting from the cheapest borohydride NaBH₄. The process involves first the solvothermal synthesis of tetrabutylammonium octahydrotriborate (C₄H₉)₄NB₃H₈ (TBAB₃H₈) being the basis for the syntheses of the others boranes. Starting from TBAB₃H₈, we have synthesized pure and unsolvated NaB₃H₈ by salt metathesis reaction with sodium tetraphenylborate. Then, we have successfully obtained Na₂B₁₂H₁₂ by solvothermal decomposition of NaB₃H₈. This approach has shown to be quantitative and reproducible, which could lead to the development of these boranes in real life applications.     

Gastric emptying and antral myoelectrical activity in chronic alcoholics with dyspepsia

BACKGROUND/AIMS: Chronic alcoholism is known to effect gastric motor activity. An association between gastric motility disorders and abnormal myoelectrical activity has been observed in various gastrointestinal and extra-intestinal diseases. The aim of this study was to investigate the effect of chronic alcoholism on gastric emptying and antral myoelectrical activity. METHODOLOGY: Electrogastrography (EGG) was performed on 20 chronic alcoholics with chronic dyspepsia using a pair of electrodes sonographically placed on the skin overlying the gastric antrum. After an overnight fast, patients were tested over a period of one hour in the a) fasting and b) fed state, after ingestion of a 370 kcal liquid-solid test meal. The following EGG parameters were determined: dominant frequency (DF (cpm); DF (%) in the normal range (2-4 cpm); bradygastria (<2 cpm); tachygastria (4-10 cpm); dominant frequency instability coefficient (DFIC), and postprandial to fasting power ratio (PR). The data were correlated with results obtained from 20 controls matched for age and sex. In 18 alcoholics, the EGG data were compared to the percentage of radionuclides (liquid phase labeled with 99m Tc colloid) remaining in the stomach after 60 minutes (%) (gamma camera system). Moreover, for the alcoholics, various parameters such as ethanol consumption, and gastrointestinal symptoms were determined and related to EGG values and scintigraphy. RESULTS: About 50% of the alcoholics showed delayed gastric emptying compared to normal values previously reported (t 60 values: >68%). In opposite to scintigraphy, the alcoholics did not exhibit abnormalities in antral myoelectrical activity. They had significantly decreased bradygastria measures compared to controls (p<0.05). The scintigraphic t 60 values did not correlate either with EGG values or with dyspepsia and clinical parameters. EGG values did not correlate with dyspepsia. However, increased preprandial DF was significantly correlated with ethanol consumption. CONCLUSIONS: Chronic alcoholism induces a disturbance of gastric emptying, probably resulting from toxic damage of the gastrointestinal smooth muscles. Disturbances in antral myoelectrical activity were not found.     

Comparison of Rat Hepatic Cholesterol Biosynthesis During Skim Milk Versus Whey Permeate Ingestion

Whey permeate is an ultrafiltrate of whey that is devoid of protein but contains lactose, salts, and other soluble low molecular weight compounds. These experiments compared cholesterol concentrations of blood plasma, hepatic lipids, and hepatic cholesterol biosynthesis of rats ingesting skim milk powder versus whey permeate powder. Groups of young male rats weighing 90 to 92 g were fed a casein-based diet into which skim milk powder or whey permeate powder was incorporated isocalorically. No effects of skim milk or whey permeate on plasma cholesterol concentrations were observed at any time during 5-wk of feeding. However, 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was increased by either skim milk or whey permeate feeding. Hepatic cholesterol, triglyceride, and phospholipid concentrations at wk 5 were unchanged. Plasma and hepatic cholesterol responses of rats to whey permeate ingestion are similar to those that occur with skim milk consumption, and plasma and hepatic cholesterol concentrations do not reflect necessarily an increase in hepatic cholesterol biosynthesis.     

Influence of nutrition level on digestibility in high yielding cows and effects on energy evaluation systems

The objective of the study was to determine the effect of nutrition level (NL, multiples of maintenance energy requirement) on the digestibility of nutrients for dairy cows regarding the energy supply of the animal. The digestion of nutrients and energy was investigated in two trials using lactating dairy cows. The NL varied from 2.7 to 5.0 using diets similar composition. In addition, sheep were given the same feed with a NL of 1.4. Digestibility of dry matter (DM) and all specific measures of dietary components declined significantly as NL increased. Digestibility of energy decreased by 4.1% for each increase in NL. The metabolizable energy, the ability to metabolize energy (metabolizable energy/gross energy), and the content of net energy for lactation (NE(L)) per kilogram of DM intake were calculated for NL from 1 to 6 on the basis of these relationships and as well as the gross energy, methane energy, and urine energy. Accordingly the NEL content declined by 0.11 MJ/kg of DM intake or 1.6% as the NL increased by one unit. It means that the NE(L) requirement above the maintenance requirement increased by 0.07 MJ of NE(L) per kilogram of fat-corrected milk, if the NL increased by one unit.