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21.
Arthur J. Bush 《Experimental Mechanics》1976,16(7):249-257
Dimensionless stress-intensity factors were determined for single-edge-crack solid and hollow round bars loaded in bending. These factors were calculated from experimental compliance (inverse slope of load-displacement curve) measurements made on round bars loaded in three-point bending. The compliance specimens had span to diameter ratios of 6.67 and 3.33, and measurements were made over a range of dimensionless crack lengths from 0.002 to 0.70. The tests were made using 3-in. (76-mm) and 6-in. (152-mm) solid and hollow round bars notched on one side; the hollow bars had an inner to outer diameter ratio of 0.33. A comparison was made with data in the literature for rectangular bars; for ana/D of 0.0001, the dimensionless stress-intensity factor for a solid round bar is 1.3 vs. 2.0 for a rectangular bar. 相似文献
22.
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
23.
Kenneth J. Laszlo John H. Buckner Eleanor B. Munger Matthew F. Bush 《Journal of the American Society for Mass Spectrometry》2017,28(7):1382-1391
The relationship between structures of protein ions, their charge states, and their original structures prior to ionization remains challenging to decouple. Here, we use cation-to-anion proton transfer reactions (CAPTR) to reduce the charge states of cytochrome c ions in the gas phase, and ion mobility to probe their structures. Ions were formed using a new temperature-controlled nanoelectrospray ionization source at 25 °C. Characterization of this source demonstrates that the temperature of the liquid sample is decoupled from that of the atmospheric pressure interface, which is heated during CAPTR experiments. Ionization from denaturing conditions yields 18+ to 8+ ions, which were each isolated and reacted with monoanions to generate all CAPTR products with charge states of at least 3+. The highest, intermediate, and lowest charge-state products exhibit collision cross-section distributions that are unimodal, multimodal, and unimodal, respectively. These distributions depend strongly on the charge state of the product, although those for the intermediate charge-state products also depend on that of the precursor. The distributions of the 3+ products are all similar, with averages that are less than half that of the 18+ precursor ions. Ionization of cytochrome c from native-like conditions yields 7+ and 6+ ions. The 3+ CAPTR products from these precursors have slightly more compact collision cross-section distributions that are indistinguishable from those for the 3+ CAPTR products from denaturing conditions. More broadly, these results indicate that the collision cross-sections of ions of this single domain protein depend strongly on charge state for charge states greater than ~4. 相似文献
24.
Several of the physical properties of α-Bi2O3 have been studied in the temperature region above room temperature: the thermal expansion, the thermally stimulated current,
the permittivity, the electrical resistance, and the specific heat. X-ray diffraction measurements and a thermogravimetric
analysis have also been carried out. Several unusual properties in the physical properties of bismuth oxide have been detected
in the temperature interval 450–570 K: exothermic maxima on the DTA and DSC curves, a small maximum and a sharp increase of
the permittivity of the single crystal, a jump and a change of sign in the thermally stimulated current, and a sharp falloff
of the electrical resistance of ceramic samples. At the same time, no appreciable changes in the monoclinic structure of α-Bi2O3 have been recorded in the indicated temperature interval.
Fiz. Tverd. Tela (St. Petersburg) 39, 865–870 (May 1997) 相似文献
25.
Magnetoelectric and pyroelectric properties have been investigated in heterostructures of nickel zinc ferrite (NZFO)-lead zirconate titanate (PZT) and lanthanum calcium manganite (LCMO)-PZT. The magnetoelectric (ME) coupling, mediated by mechanical strain, is found to be two orders of magnitude stronger in NZFO-PZT than in LCMO-PZT. The pyroelectric effect is investigated by measuring the current through the sample as the temperature is varied at 0.1 K/s. For NZFO-PZT the pyroelectric coefficient is in the range 0.2-15 nC/cm2 K, depending on the temperature. A much weaker current is observed in LCMO-PZT. A reversal in the current direction is detected when the thermal cycle is switched from heating to cooling. The pyroelectric coefficient is found to scale with the strength of ME interactions. A clear correlation between pyroelectric current and ME interactions is evident from the results. 相似文献
26.
The structures of lithiated and sodiated alpha-methyl-proline (alpha-Me-Pro) and structural isomers, both with and without a water molecule, are investigated using blackbody infrared radiative dissociation (BIRD) and density functional theory. From the BIRD kinetic data measured as a function of temperature, combined with master equation modeling of these data, threshold dissociation energies for the loss of a water molecule from these clusters are obtained. These energies are 77.5 +/- 0.5 and 53 +/- 1 kJ/mol for lithiated and sodiated alpha-Me-Pro, respectively. For the nonzwitterionic isomer, proline methyl ester, these values are 3.0-4.5 kJ/mol higher. These results provide compelling experimental evidence that alpha-Me-Pro is zwitterionic in these clusters. Theory at the temperature corrected B3LYP/6-311++G**//B3LYP/6-31++G** level indicates that the salt-bridge or zwitterionic forms of lithiated and sodiated alpha-Me-Pro are between 17 and 23 kJ/mol lower in energy than the nonzwitterionic or charge-solvated forms and that attachment of a single water molecule does not significantly change the structure or the relative energies of these clusters. The proton affinity of proline is 8 kJ/mol higher than that of alpha-Me-Pro, indicating that lithiated and sodiated singly hydrated proline should also be zwitterionic. 相似文献
27.
Leo H. Sommer Carlo M. Golino David N. Roark Rodney D. Bush 《Journal of organometallic chemistry》1973,49(1):C3-C5
Stereochemistry-rate law correlations are given for the reduction of R3Si*X compounds with i-Bu2 AlH in either and n-hexane. 相似文献
28.
Bence Paul Kai Kysenius James B. Hilton Michael W. M. Jones Robert W. Hutchinson Daniel D. Buchanan Christophe Rosty Fred Fryer Ashley I. Bush Janet M. Hergt Jon D. Woodhead David P. Bishop Philip A. Doble Michelle M. Hill Peter J. Crouch Dominic J. Hare 《Chemical science》2021,12(30):10321
Tumours are abnormal growths of cells that reproduce by redirecting essential nutrients and resources from surrounding tissue. Changes to cell metabolism that trigger the growth of tumours are reflected in subtle differences between the chemical composition of healthy and malignant cells. We used LA-ICP-MS imaging to investigate whether these chemical differences can be used to spatially identify tumours and support detection of primary colorectal tumours in anatomical pathology. First, we generated quantitative LA-ICP-MS images of three colorectal surgical resections with case-matched normal intestinal wall tissue and used this data in a Monte Carlo optimisation experiment to develop an algorithm that can classify pixels as tumour positive or negative. Blinded testing and interrogation of LA-ICP-MS images with micrographs of haematoxylin and eosin stained and Ki67 immunolabelled sections revealed Monte Carlo optimisation accurately identified primary tumour cells, as well as returning false positive pixels in areas of high cell proliferation. We analysed an additional 11 surgical resections of primary colorectal tumours and re-developed our image processing method to include a random forest regression machine learning model to correctly identify heterogenous tumours and exclude false positive pixels in images of non-malignant tissue. Our final model used over 1.6 billion calculations to correctly discern healthy cells from various types and stages of invasive colorectal tumours. The imaging mass spectrometry and data analysis methods described, developed in partnership with clinical cancer researchers, have the potential to further support cancer detection as part of a comprehensive digital pathology approach to cancer care through validation of a new chemical biomarker of tumour cells.Digital pathology and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging reveals a unique elemental signature of colorectal cancer. 相似文献
29.
Neuroimaging methodology predominantly relies on the blood oxygenation level dependent (BOLD) signal. While the BOLD signal is a valid measure of neuronal activity, variances in fluctuations of the BOLD signal are not only due to fluctuations in neural activity. Thus, a remaining problem in neuroimaging analyses is developing methods that ensure specific inferences about neural activity that are not confounded by unrelated sources of noise in the BOLD signal. Here, we develop and test a new algorithm for performing semiblind (i.e., no knowledge of stimulus timings) deconvolution of the BOLD signal that treats the neural event as an observable, but intermediate, probabilistic representation of the system's state. We test and compare this new algorithm against three other recent deconvolution algorithms under varied levels of autocorrelated and Gaussian noise, hemodynamic response function (HRF) misspecification and observation sampling rate. Further, we compare the algorithms' performance using two models to simulate BOLD data: a convolution of neural events with a known (or misspecified) HRF versus a biophysically accurate balloon model of hemodynamics. We also examine the algorithms' performance on real task data. The results demonstrated good performance of all algorithms, though the new algorithm generally outperformed the others (3.0% improvement) under simulated resting-state experimental conditions exhibiting multiple, realistic confounding factors (as well as 10.3% improvement on a real Stroop task). The simulations also demonstrate that the greatest negative influence on deconvolution accuracy is observation sampling rate. Practical and theoretical implications of these results for improving inferences about neural activity from fMRI BOLD signal are discussed. 相似文献
30.
ABSTRACTBayfol (PC-PBT blend ?lm) is a class of polymeric solid-state nuclear track detector which has a lot of applications in several radiation detection ?elds. It is a bisphenol-A polycarbonate PC blended with polybutylene terephthalate PBT. Bayfol/Palladium (PC-PBT/Pd) nanocomposite films have been deposited using the molding technique. It is worth mentioning that this report is almost the first one dealing with the topic of the changes of physical properties of Bayfol/Pd nanocomposite due to laser exposure. Samples from PC-PBT/Pd (5?wt%) nanocomposite were exposed to IR-pulsed laser of 5-W power, capable of producing 2000 pulses per second with pulse duration of 200?ns at 904?nm. The laser fluences were in the range 2–25?J/cm2. The resultant modi?cations in the exposed nanocomposite samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction (XRD), UV spectroscopy and color difference studies. The results indicate the proper dispersion of Pd nanoparticles in the PC-PBT matrix that causes a strong intermolecular interaction between Pd and PC-PBT, resulted in an increase in refractive index and the amorphous phase. Also, it is found that the laser exposure reduces the optical energy gap that could be attributed to the increase in structural disorder of the exposed PC-PBT/Pd nanocomposites due to crosslinking. Further, the color intensity ΔE, which is the color difference between the exposed samples and the non-exposed one, was increased with increasing the laser fluence, convoyed by a significant increase in the green and yellow color components. 相似文献