Imperfect bonding between constituents is studied where displacements, electric and magnetic static potentials are considered to have a jump proportional to the normal component of the mechanical traction, electric displacement and magnetic flux. This condition may model various interface damages or the thin glue layer between two adjacent phases. They are termed as the mechanically compliant, dielectrically weakly capacitance and magnetically weakly inductance at the interface. It is shown that while the more imperfect the interface is, the overall properties become weaker, such as longitudinal shear stiffness, out-of-plane piezoelectric coupling, and magnetoelectric coupling. Out-of-plane piezomagnetic coupling, transverse dielectric permittivity and transverse dielectric permeability exhibit no influence by imperfect bonding. The imperfect interface proposed is mimicked by the springs, capacitors and inductances for the mechanical, electric and magnetic interaction between the phases and are highly sensitive to the interphase properties. The results are compared mainly with the self consistent model reported in the literature and good agreements are shown. 相似文献
Triton-emission cross sections were measured for Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ag, Ta, Tl, Pb and Bi with a 30 MeV d(Be) break-up neutron spectrum characterized by a multiple-foil activation technique. The accumulated tritium was separated by vacuum extraction and measured by low-level gas-phase β? counting. The systematic trend in the cross sections is somewhat similar to that in the 53 MeV d(Be) break-up neutron spectrum; apart from some initial decrease as a function of Z, the cross section is almost constant over the entire range of Z = 22 to 83. The magnitudes of the cross sections lie between those with 14 MeV neutrons and 53 MeV d(Be) break-up neutrons. Hauser-Feshbach calculations show that the statistical model describes the triton-emission cross sections for nuclei in the (2s, ld) shell within a factor of 2; for the heavier nuclei, however, the calculated cross sections are much smaller than the experimental values. 相似文献
The catalytic and structural properties of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were investigated. On the basis of kinetic and ITC (isothermal titration calorimetry) data, Zn(II) binds to ArgE with Kd values that differ by approximately 20 times. Moreover, ArgE exhibits approximately 90% of its full catalytic activity upon addition of one metal ion. Therefore, ArgE behaves similarly to the aminopeptidase from Aeromonas proteolytica (AAP) in that one metal ion is the catalytic metal ion while the second likely plays a structural role. The N-acetyl-L-ornithine (NAO) deacetylase activity of ArgE showed a linear temperature dependence from 20 to 45 degrees C, indicating that the rate-limiting step does not change over this temperature range. The activation energy for NAO hydrolysis by ArgE was 25.6 kJ/mol when loaded with Zn(II) and 34.3 kJ/mol when loaded with Co(II). Electronic absorption and EPR (electron paramagnetic resonance) spectra of [Co x (ArgE)] and [CoCo(ArgE)] indicate that both divalent metal binding sites are five coordinate. In addition, EPR data show clear evidence of spin-spin coupling between the Co(II) ions in the active site but only after addition of a second equivalent of Co(II). Combination of these data provides the first physical evidence that the ArgE from E. coli contains a dinuclear Zn(II) active site, similar to AAP and the carboxypeptidase G2 from Pseudomonas sp. strain RS-16 (CPG2). 相似文献
Reaction of hexa-N-Boc neomycin B with TPP and DIAD in toluene results in the formation of an epoxide in ring IV, not an aziridine or azetidine as previously reported. 相似文献
The magnetic layer structure of TlCo2Se2−xSx has been thoroughly re-investigated with neutron powder diffraction. The cobalt magnetic moments are ferromagnetically arranged within the layers, but the interlayer coupling differs profoundly with varying composition (x): the spins in TlCo2Se2 form a helix along the c-axis with a turning-angle of ∼119° at 1.4 K. This kind of helical structure prevails for 0≤x≤1.5 with a gradual decrease of the angle with increasing sulphur content, down to 34°, showing an almost linear relationship with the interlayer distance of Co-Co. For x≥1.75 the interlayer coupling changes to ferromagnetic. Unexpectedly, two helices were found to coexist at x=0.5 and x=1.0. The interaction between adjacent cobalt layers is there characterized by an incommensurate angle (106°, resp., 73°) together with a commensurate angle of 90°. The magnetic structures have been refined as two magnetic phases, each having a characteristic wave vector. A tentative model where the symmetry of the structure and the interlayer distance compete is considered for explaining the simultaneous occurrence of the two kinds of diffraction profile satellites. 相似文献
Inoculation of sourdough allows the fermentation medium to be dominated by desired microorganisms, which enables determining the kinetics of the conversion of chemical compounds by individual microorganisms. This knowledge may allow the design of functional food products with health features dedicated to consumers with special needs. The aim of the study was to assess the dynamics of transformations of fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) compounds from wheat flour as well as their antioxidant activity during inoculated and spontaneous sourdough fermentation. The FODMAP content in grain products was determined by the fructan content with negligible amounts of sugars and polyols. To produce a low-FODMAP cereal product, the fermentation time is essential. The 72 h fermentation time of L. plantarum-inoculated sourdough reduced the FODMAP content by 91%. The sourdough fermentation time of at least 72 h also positively influenced the content of polyphenols and antioxidant activity, regardless of the type of fermentation. The inoculation of both L. plantarum and L. casei contributed to a similar degree to the reduction in FODMAP in sourdough compared to spontaneous fermentation. 相似文献
Two ligand‐protected nanoscale silver moieties, [Ag46(SPhMe2)24(PPh3)8](NO3)2 and [Ag40(SPhMe2)24(PPh3)8](NO3)2 (abbreviated as Ag46 and Ag40, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag32S24P8, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag14 and a completely new core, Ag8, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT). 相似文献
Metal–organic frameworks (MOFs) enable the design of host–guest systems with specific properties. In this work, we show how the confinement of anthracene in a well‐chosen MOF host leads to reversible yellow‐to‐purple photoswitching of the fluorescence emission. This behavior has not been observed before for anthracene, either in pure form or adsorbed in other porous hosts. The photoresponse of the host–guest system is caused by the photodimerization of anthracene, which is greatly facilitated by the pore geometry, connectivity, and volume as well as the structural flexibility of the MOF host. The photoswitching behavior was used to fabricate photopatternable and erasable surfaces that, in combination with data encryption and decryption, hold promise in product authentication and secure communication applications. 相似文献
The eggshell of the hen is an important structure which provides protection for the developing chick, and also a container for the egg in the food industry. Egg breakage can reach up to 10% of total egg production, causing considerable economic losses. The eggshell consists of membranes, composed mainly of proteins, and the mineral shell composed mainly of the calcite polymorph of CaCO3. The average CaCO3 content of a chicken eggshell is between 93 and 97%, depending on animal genotype, age, housing system of laying hens and mineral nutrition. In the present study, eggs of the same breed and approximately same age were collected from four different production systems: organic farming, free-range production, deep litter system and battery cage system. The CaCO3 content was determined by the standard titration method and by atomic absorption spectroscopy. Thermal properties of dried eggshell powder were measured by thermogravimetric measurements between 30 and 900 °C in air, showing a significant mass loss of?≈?43% between 600 and 850 °C corresponding to the decomposition of CaCO3 to CaO and CO2. The relations between the thermal mass loss and CaCO3 content determined by the titration method/atomic absorption spectroscopy were studied using predictive models fitted by the linear regression method. A good prediction ability with an average prediction error of 0.01% was obtained between CaCO3 determined by titration and the thermal mass loss, indicating that TG could provide a reliable method for evaluation of CaCO3 content in eggshells.