Tuning the local temperature during feedback controlled electromigration in gold nanowires

Feedback controlled electromigration (FCE) in metallic nanowires has been widely used for various purposes. However, the control of the local temperature during FCE remains a challenge. Here, we report that the environment temperature can be used as a knob to tune the local temperature during FCE in gold nanowires. FCE was performed in gold nanowires at various environment temperatures ranging from 4.2 K to 300 K. We find that the dissipated power normalized by the cross section area of the nano constriction is linearly proportional to the environment temperature. Interestingly, the estimated local maximum temperature parabolically depends on the environment temperature. A minimum in the local temperature can be reached if an appropriate environment temperature is chosen. Our findings are well supported by the finite element simulation. Moreover, the data indicates the coupling between FCE triggering current density and local temperature. (C) 2014 AIP Publishing LLC.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000337161700073&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, AppliedSCI(E)[email protected]; [email protected]

Rotary Cutting Model and Experimental Study of Wax Deposits

Intelligent wax removal pig can strip wax deposition layer inside oil pipeline using its front rotary tool bit， and can improve pigging efficiency and avoid pigging wax plugging by cooperating with jet and governor mechanisms. To solve the problem of wax removal resistance calculation in rotary cutting of wax deposition layer， a rotary cutting model of wax deposits was built. Then， rotary cutting tests were conducted to measure the main cutting force under different cutting depths， feed rates， tool speeds and tool rake angles， and the test results were used to conduct regression analysis on the shear angle and friction angle of wax layer. Finally， a rotary cutting semi-empirical model of wax deposition layer was built to optimize the tool rake angle， and the wax removal resistance of rotary cutting mode was compared with the wax removal resistance test data of straight plate pig and cup pig in the literatures. The study results show that in the course of rotary wax removal， the main cutting force for wax removal of tool increases with the increase of cutting depth and feed rate， and has a linear relationship with cutting depth. The main cutting force decreases with the increase of cutting speed； when the cutting speed reaches more than 3 m/s， the main cutting force of wax removal is basically unchanged. The error between the established rotary cutting theoretical model and the test is about 10%， exhibiting good calculation accuracy. The optimal tool rake angle in the process of rotary wax removal is 46.6°. Under the rotary cutting condition of wax layer， the axial wax removal resistance is 30%-50% smaller than that of the traditional pig， effectively reducing the influence of the wax removal process on the running speed of the pig. The study results provide references for wax removal of oilfield pipelines

Geometric Distribution and Earthquake Rupture Characteristics of the Northern Anqiu–Juxian Fault in the Tan–Lu Fault Zone, Eastern China

The Northern Anqiu–Juxian Fault (NAJF) is one of the most active faults in the Tan-Lu Fault Zone (TLFZ), which produced the Anqiu M 7 earthquake in 70 BC. However, there is no clear understanding of the surface rupture caused by this historical earthquake. In this study, we determined the earthquake rupture characteristics of the NAJF based on high-precision surveying, geophysical exploration and drilling profiles. Based on an analysis of 87 horizontal offsets of gullies, we estimated a characteristic offset of ∼ 5 m along the NAJF for a rupture length about 130 km. Geophysical exploration results revealed a shallow geometric distribution of stepovers in the NAJF. We concluded that the ∼ 5 m offset and the rupture length of about 130 km are both in agreement with an empirical relationship among the magnitude, offset, and rupture length and imply that the ∼ 1 km wide stepover could not have terminated ruptures in the Anqiu M 7 earthquake. The relationship among the coseismic offset, magnitude, and surface rupture length of a strike-slip fault show that the 70 BC Anqiu earthquake was more likely to have had a magnitude of M ∼ 7.5.</jats:p

The origin of the transition voltage of gold–alkanedithiol–gold molecular junctions

We studied the origin of the transition voltage of octanedithiol (C8DT) molecules sandwiched between two gold electrodes. Au-C8DT-Au molecular junctions were fabricated using the feedback controlled electromigration technique. The conductance measurement and the inelastic electron tunneling spectrum validate that the observed current-voltage characteristics indeed originate from the C8DT molecule in the junction. The transition voltage of Au-C8DT-Au junctions is determined to be about 0.95 V, which cannot be interpreted using the energy difference between the highest occupied molecular orbital or lowest unoccupied molecular orbital of the alkyl chain and the Fermi level of electrodes. Instead, we relate the measured transition voltage to the Au-S bonds, which are about 1.4 eV below the gold Fermi level. Our interpretation is supported by the ultraviolet photoelectron spectroscopy measurements and first-principles quantum transport simulations. These findings provide convincing evidence that the Au-S occupied states play a significant role in the charge transport of Au-alkanedithiol-Au molecular devices. (C) 2015 Elsevier B.V. All rights reserved.National Natural Science Foundation of China [61321001, 21573014]; MOST of China [2011CB933001, 2013CB933404]SCI(E)[email protected]; [email protected]

Detection of sperm DNA damage in male infertility patients and evaluation of Levocarnitine efficacy using sperm chromatin diffusion (SCD) and AI-DFI methods: a cross-sectional study

Abstract The objective of this study was to elucidate the relationship between sperm DNA damage and sperm parameters in male infertility patients and to assess the changes in sperm DNA fragmentation index before and after treatment with Levocarnitine in patients with asthenozoospermia and oligozoospermia. The results of 508 patients’ semen samples tested between August 2021 and December 2022 in our Department of Urology and Reproductive Medicine were retrospectively analyzed. The 508 patients were divided into 3 groups: normal semen group (n = 181), asthenozoospermia group (n = 170), and oligozoospermia group (n = 157). Their sperm DNA integrity was evaluated using the sperm chromatin diffusion (SCD) method and an artificial Intelligence-based DNA fragmentation index (AI-DFI). The patients were divided into two groups based on the assessment of sperm DNA integrity: a sperm DNA damage group and a sperm DNA integrity group. The two groups were then compared in terms of sperm concentration, motility, viability, and the proportion of normal sperm morphology. Pearson’s correlation coefficient analysis was employed to examine the relationship between sperm DNA damage and semen parameters. The results showed that sperm concentration, progressive motility, viability, and normal morphology rate were significantly lower in the DNA damaged group, and correlation analysis showed that the results of sperm DNA damage detection was negatively correlated with these semen parameters. And the DNA fragmentation index (DFI) was highest in the asthenozoospermia group, followed by the oligospermia group and the normal group, with significant differences between the groups (20.30 ± 2.85; 18.62 ± 2.42; 12.83 ± 2.13, P = 0.01). Treatment of patients in the group with sperm DNA damage with Levocarnitine oral solution was found to significantly improve sperm concentration, progressive motility, viability, normal morphology rate, and DFI results after its use (t = 7.265, 5.823, 7.750, 8.737, 8.355; P = 0.03, 0.02, 0.02, 0.03, 0.01). This study concludes that men with asthenozoospermia and oligozoospermia have a high DFI, and Levocarnitine is effective in reducing DNA damage and improving sperm quality, suggesting that Levocarnitine has potential for clinical use