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An agar dilution assay was used to assess the effect of inoculum size and culture period on the susceptibility of 15 clinical isolates of Helicobacter pylori to ampicillin, erythromycin, tetracycline, chloramphenicol, metronidazole and tinidazole. The mean MIC of the isolates increased 2.2- to 21.2-fold as the inoculum size progressed from 10(3) to 10(7) cfu/spot. Identical results were noted when isolates were maintained for two or four days prior to testing. Inoculum size should be carefully controlled when assessing the in vitro susceptibility of Helicobacter pylori. 相似文献
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Gal Tuvia Yiftach Frenkel Prasanna K. Rout Itai Silber Beena Kalisky Yoram Dagan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):2000216
In polar oxide interfaces phenomena such as superconductivity, magnetism, 1D conductivity, and quantum Hall states can emerge at the polar discontinuity. Combining controllable ferroelectricity at such interfaces can affect the superconducting properties and sheds light on the mutual effects between the polar oxide and the ferroelectric oxide. Here, the interface between the polar oxide LaAlO3 and the ferroelectric Ca-doped SrTiO3 is studied by means of electrical transport combined with local imaging of the current flow with the use of scanning a superconducting quantum interference device (SQUID). Anomalous behavior of the interface resistivity is observed at low temperatures. The scanning SQUID maps of the current flow suggest that this behavior originates from an intrinsic bias induced by the polar LaAlO3 layer. Such intrinsic bias combined with ferroelectricity can constrain the possible structural domain tiling near the interface. The use of this intrinsic bias is recommended as a method of controlling and tuning the initial state of ferroelectric materials by the design of the polar structure. The hysteretic dependence of the normal and the superconducting state properties on gate voltage can be utilized in multifaceted controllable memory devices. 相似文献
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An essential aspect of the development of organic-based electronics is the synthetic chemistry devised for the preparation of the semiconductor materials responsible for the activity of organic field-effect transistors. Access to organic semiconductors in sufficient purity and variety has led to breakthroughs in solid-state physics and circuit realization. In this Account, we review the synthetic methods that have been most useful for preparing a range of semiconductors, including thiophene-based oligomers, several kinds of fused rings, and polymers. The tradeoff between process efficiency and target purity is emphasized. 相似文献
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G Charach PD Rabinovich FM Konikoff I Grosskopf MS Weintraub T Gilat 《Canadian Metallurgical Quarterly》1998,29(3-4):125-136
In most patients with atherosclerosis, the underlying metabolic derangement remains undefined. Animal experiments have suggested that the ability to produce and excrete large amounts of bile acids may be an adaptation mechanism to cholesterol overload protecting against the atherogenic effects of cholesterol. However, there are very few data on bile acid excretion in human atherosclerosis. In the present study, we have investigated fecal bile acid secretion in subjects with and without coronary artery disease. The target group consisted of 30 patients with proven coronary artery disease and the control group consisted of 27 matched subjects without clinical or laboratory evidence of coronary atherosclerosis. Fecal bile acids were measured by gas-liquid chromatography from 24-hr stool collections under a controlled diet. The patients excreted significantly less bile acids than the controls (325+/-135 vs. 592+/-223 mg/day, respectively, p < 0.0001). The difference was primarily due to a reduced excretion of secondary bile acids. Less than 50% of deoxycholate was excreted by patients (180+/-81 mg/day) as compared to controls (367+/-168 mg/day, p < 0.0002), while lithocholic acid excretion was 111+/-62 mg/day in patients vs. 190 +/-70 mg/day in controls (p < 0.005). The fecal output of the two primary bile acids, cholic and chenodeoxycholic acid, did not differ significantly between patients and controls. The fecal output of total bile acids correlated with that of both secondary bile acids in patients as well as in controls. These findings suggest that patients with coronary heart disease are unable to excrete adequate amounts of bile acids to rid themselves of excess cholesterol, even if they are able to maintain a plasma cholesterol level comparable to that of healthy controls. 相似文献
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S Tuvia A Almagor A Bitler S Levin R Korenstein S Yedgar 《Canadian Metallurgical Quarterly》1997,94(10):5045-5049
Extracellular fluid macroviscosity (EFM), modified by macromolecular cosolvents as occurs in body fluids, has been shown to affect cell membrane protein activities but not isolated proteins. In search for the mechanism of this phenomenon, we examined the effect of EFM on mechanical fluctuations of the cell membrane of human erythrocytes. The macroviscosity of the external medium was varied by adding to it various macromolecules [dextrans (70, 500, and 2,000 kDa), polyethylene glycol (20 kDa), and carboxymethyl-cellulose (100 kDa)], which differ in size, chemical nature, and in their capacity to increase fluid viscosity. The parameters of cell membrane fluctuations (maximal amplitude and half-width of amplitude distribution) were diminished with the elevation of solvent macroviscosity, regardless of the cosolvent used to increase EFM. Because thermally driven membrane fluctuations cannot be damped by elevation of EFM, the existence of a metabolic driving force is suggested. This is supported by the finding that in ATP-depleted red blood cells elevation of EMF did not affect cell membrane fluctuations. This study demonstrates that (i) EFM is a regulator of membrane dynamics, providing a possible mechanism by which EFM affects cell membrane activities; and (ii) cell membrane fluctuations are driven by a metabolic driving force in addition to the thermal one. 相似文献
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The present paper reports the results of experiments to develop environmentally and economically friendly structural lightweight concretes utilizing coal ashes and other waste materials. The product complies with national and international regulations setting limits on the activity concentration of natural radioisotopes in building products. The utilization of coal ashes in the building industry carries (in addition to its economic advantages) a fringe environmental benefit. This utilization reduces the potential damage to the environment caused by the radioactivity in the combustion by-products (the ashes) stored in piles and ponds near the power stations prior to their disposal. The study deals with the radiological characteristics of coal ashes and lightweight concretes based on these ashes. The ashes are generated at Israel’s power stations from coal supplied from different sources in South Africa, Columbia and Indonesia. 相似文献
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Ronit Pakula Fred M. Konikoff Moshe Rubin Yehuda Ringel Yochanan Peled Aliza Tietz Tuvia Gilat 《Lipids》1996,31(3):295-303
The role of phospholipids in biliary cholesterol solubilization and crystallization has only recently begun to be appreciated.
Phospholipid vesicles are believed to be the metastable carrier from which cholesterol nucleates. Cholesterol crystallization
is influenced by the phospholipid species in bile. Feeding rats and hamsters with diets enriched in phospholipids or their
precursors, especially ethanolamine, resulted in reduced cholesterol saturation of bile. Although whole phospholipids are
normal dietary constituents, the effects and safety of phospholipid components have not been tested in humans. In the present
study, we have evaluated the effects of a dietary phospholipid mixture, enriched with phosphatidylethanolamine, on human bile
and red blood cell membrane lipid composition. Five ambulatory volunteers having a chronic indwelling T-tube, with an intact
enterohepatic circulation, were investigated. Thirty-six grams of phospholipids (54% phosphatidylethanolamine, 54% linoleyl
acyl chains) were added to their daily diet for fourteen days. Biliary nucleation time, cholesterol carriers, as well as plasma,
red blood cell membrane, and bile lipid compositions, were monitored. Following phospholipid supplementation, the proportion
of linoleyl chains (18:2) in biliary phospholipids increased significantly from 31.1±1.2 to 37.7±5.3%, while that of oleyl
chains (18:1) decreased from 11.4±1.6 to 9.6±1.1%. These changes were accompanied by an increase of linoleate and its metabolite,
arachidonate, in red cell membranes. Phospholipid feeding did not cause any side effects, and no significant changes in biliary
nucleation time, cholesterol, phospholipid, or bile salt concentrations, or in the distribution of cholesterol within micelles
or vesicles. We conclude that phospholipid feeding is safe, and can be effective as a vehicle for lecithin fatty acyl chain
modulation of bile and lipid membranes. These findings may provide a basis for a controlled modulation of biliary phospholipids
to increase cholesterol solubility in bile. 相似文献
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A previously developed analytical formulation has been modified in order to more accurately account for the effects of hydrostatic stresses on the nonlinear, strain rate dependent deformation of polymer matrix composites. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical J2 plasticity theory definitions of effective stress and effective inelastic strain, along with the equations used to compute the components of the inelastic strain rate tensor, are appropriately modified. To verify the revised formulation, the shear and tensile deformation of a representative polymer are computed across a wide range of strain rates. Results computed using the developed constitutive equations correlate well with experimental data. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite for several fiber orientation angles across a variety of strain rates. The computed values compare well to experimentally obtained results. 相似文献
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Orr Scott P.; Metzger Linda J.; Lasko Natasha B.; Macklin Michael L.; Peri Tuvia; Pitman Roger K. 《Canadian Metallurgical Quarterly》2000,109(2):290
Differential conditioning was assessed in 15 medication-free individuals meeting Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) criteria for chronic posttraumatic stress disorder (PTSD) and 18 trauma-exposed individuals who never developed PTSD (non-PTSD). Conditioned stimuli (CSs) were colored circles, and the unconditioned stimulus was a "highly annoying" electrical stimulus. Individuals with PTSD had higher resting heart rate (HR) and skin conductance (SC) levels and produced larger SC orienting responses. During conditioning, the PTSD group showed larger differential SC, HR, and electromyogrant responses to the reinforced vs. nonreinforced stimuli (CS+ vs. CS-) compared with the non-PTSD group. Only PTSD participants continued to show differential SC responses to CS+ vs. CS- during extinction trials. Results suggest that individuals with PTSD have higher sympathetic nervous system arousal at the time of conditioning and are more conditionable than trauma-exposed individuals without PTSD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献