669 research outputs found
Magnetic pair breaking in disordered superconducting films
A theory for the effects of nonmagnetic disorder on the magnetic pair
breaking rate induced by paramagnetic impurities in quasi
two-dimensional superconductors is presented. Within the framework of a
strong-coupling theory for disordered superconductors, we find that the
disorder dependence of is determined by the disorder enhancements of
both the electron-phonon coupling and the spin-flip scattering rate. These two
effects have a tendency to cancel each other. With parameter values appropriate
for Pb_{0.9} Bi_{0.1}, we find a pair breaking rate that is very weakly
dependent on disorder for sheet resistances 0 < R < 2.5 kOhm, in agreement with
a recent experiment by Chervenak and Valles.Comment: 6 pp., REVTeX, epsf, 2 eps figs, final version as publishe
Stress corrosion cracking in Al-Zn-Mg-Cu aluminum alloys in saline environments
Copyright 2013 ASM International. This paper was published in Metallurgical and Materials Transactions A, 44A(3), 1230 - 1253, and is made
available as an electronic reprint with the permission of ASM International. One print or electronic copy may
be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via
electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or
modification of the content of this paper are prohibited.Stress corrosion cracking of Al-Zn-Mg-Cu (AA7xxx) aluminum alloys exposed to saline environments at temperatures ranging from 293 K to 353 K (20 °C to 80 °C) has been reviewed with particular attention to the influences of alloy composition and temper, and bulk and local environmental conditions. Stress corrosion crack (SCC) growth rates at room temperature for peak- and over-aged tempers in saline environments are minimized for Al-Zn-Mg-Cu alloys containing less than ~8 wt pct Zn when Zn/Mg ratios are ranging from 2 to 3, excess magnesium levels are less than 1 wt pct, and copper content is either less than ~0.2 wt pct or ranging from 1.3 to 2 wt pct. A minimum chloride ion concentration of ~0.01 M is required for crack growth rates to exceed those in distilled water, which insures that the local solution pH in crack-tip regions can be maintained at less than 4. Crack growth rates in saline solution without other additions gradually increase with bulk chloride ion concentrations up to around 0.6 M NaCl, whereas in solutions with sufficiently low dichromate (or chromate), inhibitor additions are insensitive to the bulk chloride concentration and are typically at least double those observed without the additions. DCB specimens, fatigue pre-cracked in air before immersion in a saline environment, show an initial period with no detectible crack growth, followed by crack growth at the distilled water rate, and then transition to a higher crack growth rate typical of region 2 crack growth in the saline environment. Time spent in each stage depends on the type of pre-crack (“pop-in” vs fatigue), applied stress intensity factor, alloy chemistry, bulk environment, and, if applied, the external polarization. Apparent activation energies (E a) for SCC growth in Al-Zn-Mg-Cu alloys exposed to 0.6 M NaCl over the temperatures ranging from 293 K to 353 K (20 °C to 80 °C) for under-, peak-, and over-aged low-copper-containing alloys (~0.8 wt pct), they are typically ranging from 20 to 40 kJ/mol for under- and peak-aged alloys, and based on limited data, around 85 kJ/mol for over-aged tempers. This means that crack propagation in saline environments is most likely to occur by a hydrogen-related process for low-copper-containing Al-Zn-Mg-Cu alloys in under-, peak- and over-aged tempers, and for high-copper alloys in under- and peak-aged tempers. For over-aged high-copper-containing alloys, cracking is most probably under anodic dissolution control. Future stress corrosion studies should focus on understanding the factors that control crack initiation, and insuring that the next generation of higher performance Al-Zn-Mg-Cu alloys has similar longer crack initiation times and crack propagation rates to those of the incumbent alloys in an over-aged condition where crack rates are less than 1 mm/month at a high stress intensity factor
Stability of gold nanowires at large Au-Au separations
The unusual structural stability of gold nanowires at large separations of
gold atoms is explained from first-principles quantum mechanical calculations.
We show that undetected light atoms, in particular hydrogen, stabilize the
experimentally observed structures, which would be unstable in pure gold wires.
The enhanced cohesion is due to the partial charge transfer from gold to the
light atoms. This finding should resolve a long-standing controversy between
theoretical predictions and experimental observations.Comment: 7 pages, 3 figure
Quasiparticle Inelastic Lifetime from Paramagnons in Disordered Superconductors
The paramagnon contribution to the quasiparticle inelastic scattering rate in
disordered superconductors is presented. Using Anderson's exact eigenstate
formalism, it is shown that the scattering rate is Stoner enhanced and is
further enhanced by the disorder relative to the clean case in a manner similar
to the disorder enhancement of the long-range Coulomb contribution. The results
are discussed in connection with the possibility of conventional or
unconventional superconductivity in the borocarbides. The results are compared
to recent tunneling experiments on LuNiBC.Comment: 5 pages, no figure
A pathogenic PSEN1 Trp165Cys mutation associated with early-onset Alzheimers disease
Background
Presenilin-1 (PSEN1) is one of the causative genes for early onset Alzheimers disease (EOAD). Recently, emerging studies reported several novel PSEN1 mutations among Asian. We describe a male with EOAD had a pathogenic PSEN1 mutation.
Case presentation
A 53-year-old male presented with memory decline, followed by difficulty in finding ways. Patient had positive family history, since his mother and one of his brother was also affected with dementia. Brain magnetic resonance imaging (MRI) scan showed mild degree of atrophy of bilateral hippocampus and parietal lobe. 18F-Florbetaben-PET (FBB-PET) revealed increased amyloid deposition in bilateral frontal, parietal, temporal lobe and precuneus. Whole exome analysis revealed a heterozygous, probably pathogenic PSEN1 (c.695G > T, p.W165C) mutation. Interestingly, Trp165Cys mutation is located in trans membrane (TM)-III region, which is conserved between PSEN1/PSEN2. In vitro studies revealed that PSEN1 Trp165Cys could result in disturbances in amyloid metabolism. This prediction was confirmed by structure predictions and previous in vitro studies that the p.Trp165Cys could result in decreased Aβ42/Aβ40 ratios.
Conclusion
We report a case of EOAD having a pathogenic PSEN1 (Trp165Cys) confirmed with in silico and in vitro predictions.This work was supported by a National Research Foundation of Korea (NRF) Grants, awarded by the Korean government (MEST, No. 2017R1A2B4012636 & 2017R1C1B5017807). Dr. An SS receives the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST, No. 2017R1A2B4012636). Dr. Eva Bagyinszky receives the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST, No. 2017R1C1B5017807). Dr. Giau VV reports no disclosure. Dr. Pyun JM reports no disclosure. Dr. Suh J reports no disclosure. Dr. Kim SY reports no disclosure
In Situ Measurements of Stress Evolution in Silicon Thin Films During Electrochemical Lithiation and Delithiation
We report in situ measurements of stress evolution in a silicon thin-film
electrode during electrochemical lithiation and delithiation by using the
Multi-beam Optical Sensor (MOS) technique. Upon lithiation, due to substrate
constraint, the silicon electrode initially undergoes elastic deformation,
resulting in rapid rise of compressive stress. The electrode begins to deform
plastically at a compressive stress of ca. -1.75 GPa; subsequent lithiation
results in continued plastic strain, dissipating mechanical energy. Upon
delithiation, the electrode first undergoes elastic straining in the opposite
direction, leading to a tensile stress of ca. 1 GPa; subsequently, it deforms
plastically during the rest of delithiation. The plastic flow stress evolves
continuously with lithium concentration. Thus, mechanical energy is dissipated
in plastic deformation during both lithiation and delithiation, and it can be
calculated from the stress measurements; we show that it is comparable to the
polarization loss. Upon current interrupt, both the film stress and the
electrode potential relax with similar time-constants, suggesting that stress
contributes significantly to the chemical potential of lithiated-silicon.Comment: 12 pages, 3 figure
The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) family
The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that have diverse roles in tissue morphogenesis and patho-physiological remodeling, in inflammation and in vascular biology. The human family includes 19 members that can be sub-grouped on the basis of their known substrates, namely the aggrecanases or proteoglycanases (ADAMTS1, 4, 5, 8, 9, 15 and 20), the procollagen N-propeptidases (ADAMTS2, 3 and 14), the cartilage oligomeric matrix protein-cleaving enzymes (ADAMTS7 and 12), the von-Willebrand Factor proteinase (ADAMTS13) and a group of orphan enzymes (ADAMTS6, 10, 16, 17, 18 and 19). Control of the structure and function of the extracellular matrix (ECM) is a central theme of the biology of the ADAMTS, as exemplified by the actions of the procollagen-N-propeptidases in collagen fibril assembly and of the aggrecanases in the cleavage or modification of ECM proteoglycans. Defects in certain family members give rise to inherited genetic disorders, while the aberrant expression or function of others is associated with arthritis, cancer and cardiovascular disease. In particular, ADAMTS4 and 5 have emerged as therapeutic targets in arthritis. Multiple ADAMTSs from different sub-groupings exert either positive or negative effects on tumorigenesis and metastasis, with both metalloproteinase-dependent and -independent actions known to occur. The basic ADAMTS structure comprises a metalloproteinase catalytic domain and a carboxy-terminal ancillary domain, the latter determining substrate specificity and the localization of the protease and its interaction partners; ancillary domains probably also have independent biological functions. Focusing primarily on the aggrecanases and proteoglycanases, this review provides a perspective on the evolution of the ADAMTS family, their links with developmental and disease mechanisms, and key questions for the future
Preliminary Evaluation of the Sural Nerve Using 22-MHz Ultrasound: A New Approach for Evaluation of Diabetic Cutaneous Neuropathy
Background: The application of 22-MHz high-frequency ultrasound allows for visualization of the inner part of the sural nerve. The aim of this study was to evaluate the morphological changes of sural nerves in patients with type 2 diabetes mellitus using ultrasound. Materials and Methods: The thickness/width (T/W) ratio, the cross-sectional area (CSA) of the sural nerves and the maximum thickness (MT) of the nerve fascicles were measured in 100 patients with type 2 diabetes mellitus and 50 healthy volunteers using 22-MHz ultrasound. Receiver operating characteristic (ROC) curves were plotted to determine the optimal cut-off values as well as the sensitivities and specificities. All parameters were significantly different between the subject and control groups. The ROC curves demonstrated that the MT was the most predictive of diabetic cutaneous neuropathy, with an optimal cut-off value of 0.365 mm that yielded a sensitivity of 90.3 % and a specificity of 87.7%. Conclusions: The results of this study suggest that 22-MHz ultrasound may be a valuable tool for evaluating diabeti
Shaping gold nanocomposites with tunable optical properties
We report the synthesis of morphological uniform composites using miniemulsions of poly(tert-butyl acrylate) or
poly(styrene) containing organically capped gold nanocrystals (NCs). The optical features of such hybrid structures are
dominated by plasmonic effects and depend critically on the morphology of the resulting nanocomposite. In particular,
we demonstrate the ability to tune the overall optical response in the visible spectral region by varying the Au NCs
arrangement within the polymer matrix, and therefore the interparticle plasmon coupling, using Au NCs resulting from
the same batch of synthesis. This is a consequence of two well-known effects on the optical properties of Au particles: the
variation of the surrounding dielectric refractive index and interparticle plasmonic coupling. The research reported here
shows a general strategy to produce optical responsive nanocomposites via control of the morphology of submicrometric
polymer particles containing metal nanocrystals and thus is an alternative to the more common strategy of size
tuning metal nanoparticles used as nanofillers
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High fat diet modifies the association of lipoprotein lipase gene polymorphism with high density lipoprotein cholesterol in an Asian Indian population
Background
Single nucleotide polymorphisms (SNPs) in lipoprotein lipase gene (LPL) have been shown to influence metabolism related to lipid phenotypes. Dietary factors have been shown to modify the association between LPL SNPs and lipids; however, to date, there are no studies in South Asians. Hence, we tested for the association of four common LPL SNPs with plasma lipids and examined the interactions between the SNPs and dietary factors on lipids in 1,845 Asian Indians.
Methods
The analysis was performed in 788 Type 2 diabetes cases and 1,057 controls randomly chosen from the cross-sectional Chennai Urban Rural Epidemiological Study. Serum triacylglycerol (TAG), serum total cholesterol, and high-density lipoprotein cholesterol (HDL-C) were measured using a Hitachi-912 autoanalyzer (Roche Diagnostics GmbH, Mannheim, Germany). Dietary intake was assessed using a semi-quantitative food frequency questionnaire. The SNPs (rs1121923, rs328, rs4922115 and rs285) were genotyped by polymerase chain reaction followed by restriction enzyme digestion and 20% of samples were sequenced to validate the genotypes obtained. Statistical Package for Social Sciences for Windows version 22.0 (SPSS, Chicago, IL) was used for statistical analysis.
Results
After correction for multiple testing and adjusting for potential confounders, SNPs rs328 and rs285 showed association with HDL-C (P = 0.0004) and serum TAG (P = 1×10−5), respectively. The interaction between SNP rs1121923 and fat intake (energy %) on HDL-C (P = 0.003) was also significant, where, among those who consumed a high fat diet (28.4 ± 2.5%), the T allele carriers (TT + XT) had significantly higher HDL-C concentrations (P = 0.0002) and 30% reduced risk of low HDL-C levels compared to the CC homozygotes. None of the interactions on other lipid traits were statistically significant.
Conclusion
Our findings suggest that individuals carrying T allele of the SNP rs1121923 have increased HDL-C levels when consuming a high fat diet compared to CC homozygotes. Our finding warrants confirmation in prospective studies and randomized controlled trials
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