835 research outputs found

    Giant spin-orbit splitting of point defect states in monolayer WS2_2

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    The spin-orbit coupling (SOC) effect has been known to be profound in monolayer pristine transition metal dichalcogenides (TMDs). Here we show that point defects, which are omnipresent in the TMD membranes, exhibit even stronger SOC effects and change the physics of the host materials drastically. In this Article we chose the representative monolayer WS\sub{2} slabs from the TMD family together with seven typical types of point defects including monovacancies, interstitials, and antisites. We calculated the formation energies of these defects, and studied the effect of spin-orbit coupling (SOC) on the corresponding defect states. We found that the S monovacancy (V\sub{S} ) and S interstitial (adatom) have the lowest formation energies. In the case of V\sub{S} and both of the W\sub{S and W\sub{S2} antisites, the defect states exhibit giant splitting up to 296 meV when SOC is considered. Depending on the relative position of the defect state with respect to the conduction band minimum (CBM), the hybrid functional HSE will either increase the splitting by up to 60 meV (far from CBM), or decrease the splitting by up to 57 meV (close to CBM). Furthermore, we found that both the W\sub{S} and W\sub{S2} antisites possess a magnetic moment of 2 Ī¼B\mu_{B} localized at the antisite W atom and the neighboring W atoms. All these findings provide new insights in the defect behavior under SOC point to new possibilities for spintronics applications for TMDs.Comment: 8 pages, 6 figure

    SafeWeb: A Middleware for Securing Ruby-Based Web Applications

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    Web applications in many domains such as healthcare and finance must process sensitive data, while complying with legal policies regarding the release of different classes of data to different parties. Currently, software bugs may lead to irreversible disclosure of confidential data in multi-tier web applications. An open challenge is how developers can guarantee these web applications only ever release sensitive data to authorised users without costly, recurring security audits. Our solution is to provide a trusted middleware that acts as a ā€œsafety netā€ to event-based enterprise web applications by preventing harmful data disclosure before it happens. We describe the design and implementation of SafeWeb, a Ruby-based middleware that associates data with security labels and transparently tracks their propagation at different granularities across a multi-tier web architecture with storage and complex event processing. For efficiency, maintainability and ease-of-use, SafeWeb exploits the dynamic features of the Ruby programming language to achieve label propagation and data flow enforcement. We evaluate SafeWeb by reporting our experience of implementing a web-based cancer treatment application and deploying it as part of the UK National Health Service (NHS)

    Recovery from Developmental Nonylphenol Exposure is Possible I. Male

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    Nonylphenol (NP) is an environmental endocrine-disrupting chemical (EDC) that has been detected in human cord blood and milk. It is unavoidable that human fetus and infant exposure to this environmental contaminant. According to ā€œfetal origins adult diseaseā€ hypothesis, the biological impact and healthcare will encounter unavoidable impact. We previously observed that developmental NP exposure led to increased body weight, elevated plasma ACTH, higher production and concentrations of corticosterone and aldosterone, and more 11?-hydroxysteroid dehydrogenase I (11?-HSD1) expression/activity during the first generation at the adult stage. With these phenomena, is human going to evolution to a heavier with metabolic syndrome state or back to ā€œdefault stateā€ after generation(s) of hygienic up. This study addressed the possibility of recovering from NP exposure. Female rats were timed-mated in this experiment. Throughout gestation and lactation, one group of pregnant females was given a 2? Āµg/ml NP drinking solution and another group was given water. The litters were marked as first-generation F1 NP or F1 Veh offspring. At approximately 13 weeks of age, the F1 females were timed-mated with non-sibling F1 males from identical prenatal and neonatal treatment groups. The females were not manipulated in any way. The resulting litters were designated as the second-generation F2 NP or F2 Veh offspring. At 13 weeks of age, the male offspring from each F1 and F2 group were decapitated. The experimental results showed that NP exposure resulted in F1 offspring hyperadrenalism and weight increases. These effects were not observed in the F2 offspring. The F2 generation status was set back to the ā€˜defaultā€™ stage, which shows the elevated body weight and hyperadrenalism returned to normal. This study indicates developmental exposure to NP results in life long impact. The recovery to ā€œdefault stateā€ is possible only after generation(s) suffer with expensive healthcare burden. Keywords: NP, developmental exposure, 11?-HSD1, body weight, hyperadrenalis

    Magnetostriction and elasticity of body centered cubic Fe100āˆ’xBex alloys

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    Magnetostriction measurements from 77 K to room temperature on oriented (100) and (110) disk samples of Fe93.9Be6.1 and Fe88.7Be11.3 reveal substantial increases in Ī»100compared to iron. For the 11.3% alloy, Ī»100=110ā€‰ppm, a sixfold increase above that of Ī±-Fe. For the 6.1% alloy, Ī»100=81ā€‰ppm, āˆ¼40% and āˆ¼170% greater than Ī»100 of comparable Feā€“Ga and Feā€“Al alloys, respectively, for H=15ā€‰kOe. Large differences exist between the values of Ī»100 and Ī»111 (Ī»100\u3e0,ā€‰Ī»111\u3c0) and their temperature dependencies. Elastic constants, c11, c12, and c44, from 4 to 300 K were obtained on the same Feā€“Be alloys. From these measurements, the magnetoelastic energy coefficients b1 and b2 were calculated. While the magnitudes of the magnetostrictions Ī»100 and Ī»111 are widely different, the magnitudes of b1 and b2 are within a factor of 2. The Feā€“Be alloys are highly anisotropic magnetostrictively, elastically, and magnetoelastically. For Fe88.7Be11.3 at room temperature Ī»100/Ī»111, 2c44/(c11āˆ’c12), and b1/b2 are āˆ’6.6, 3.55, and āˆ’1.86, respectively

    Temperature dependence of the magnetostriction and magnetoelastic coupling in Fe100āˆ’xAlx (x = 14.1,16.6,21.5,26.3) and Fe50Co50

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    In this paper, we report magnetostriction measurements, (Ī»100) on Fe-rich Feā€“Al alloys and Fe50Co50 as functions of temperature from 77ā€„K to room temperature (RT). From these measurements and elastic constant (cā€²) measurements, the tetragonal magnetoelastic coupling constants (b1ā€™s) were calculated. Significant differences were found between our RT measurements and earlier magnetostriction measurements for the higher Al concentration alloys (16.6%, 21.5%, 26.3% Al) and the Fe50Co50 alloy. Reminiscent of the temperature dependence of Ī»100 for pure Fe, magnetostriction changes with temperature are minimal for Feā€“Al alloys having the disordered bcc (A2)structure (x\u3c19% Al). In contrast, the alloy possessing the ordered (D03) structure shows an anomalous decrease in magnetostriction in Ī»100 with decreasing temperature. For the Feā€“Al alloy system, the magnetoelastic coupling constant, āˆ£b1āˆ£, exhibits a peak at room temperature maximizing at 16.6% Al with a value of 12.3ā€„MJ/m3. For Fe50Co50, āˆ£b1āˆ£ was calculated to be āˆ¼ 34ā€„MJ/m3 at room temperature

    Effect of interstitial additions on magnetostriction in Feā€“Ga alloys

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    The additions of trace amounts of small interstitial atoms (carbon, boron, and nitrogen) to Feā€“Ga (Galfenol) alloys have a small but beneficial effect on the magnetostriction of Feā€“Ga alloys especially at high Ga compositions. The saturated magnetostrictions [(3/2)Ī»100ā€™s] of both slow cooled and quenched single crystal Feā€“Gaā€“C alloys with Ga contents \u3e18ā€„at.ā€‰% are about 10%ā€“30% higher than those of the comparable binary Feā€“Ga alloys. For boron and nitrogen additions, the magnetostrictions of slow cooled alloys with Ga content \u3e18ā€„at.ā€‰% were approximately 20% higher than those of the binary Feā€“Ga alloys. We assume that these small atoms enter interstitially into the octahedral site as in pure Ī±-Fe and inhibit chemical ordering, resulting in increased Ī»100. Thermal analysis of the Feā€“Ga binary alloys and Feā€“Gaā€“C ternary alloys indicates that the addition of C into the Feā€“Ga system decreases the formation kinetics of D03 and extends the disordered region beyond the maximum for slow cooled binary samples
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