Influence of atomic mixing and preferential sputtering on depth profiles and interfaces

Atomic mixing and preferential sputtering impose a depth resolution limit on the use of sputter sectioning to measure the composition of metal–semiconductor interfaces. Experimental evidence obtained with the Pt–Si system is used to demonstrate ion‐induced atomic mixing and then its effect on sputter etching and depth profiling. Starting with discrete layer structures, a relatively low ion dose (≳3×10^(15) cm^(−2)) first produced a mixed surface layer with thickness comparable to the ion range. Higher ion doses then result in successive sputter etching and continual atomic mixing over a constant surface layer thickness. A model is developed that is based on a sputter removal (including preferential sputtering) of atoms at the surface and a uniform mixing of atoms over a constant thickness. The model predicts the influences of atomic mixing and preferential sputtering on the depth profiling of thin‐film structures and interfaces

Depth dependence of atomic mixing by ion beams

Ion backscattering spectrometry has been used to investigate the depth dependence of atomic mixing induced by ion beams. Samples consisting of a thin Pt (or Si) marker a few tens of angstroms thick buried at different depths in a deposited Si (or Pt) layer were bombarded with Xe+ of 300 keV at 2×10^16 cm^–2 dose and Ar+ of 150 keV at 5×10^15cm^–2 dose. Significant spreading of the marker was observed as a result of ion irradiation. The amount of spreading was measured as a function of depth of the marker, which was then compared with the deposited energy distribution. Measurements of this kind promise new insight into the nature of the interaction between ion beams and solids

Contrasting controls on seasonal and spatial distribution of marine cable bacteria (Candidatus Electrothrix) and Beggiatoaceae in seasonally hypoxic Chesapeake Bay

Marine cable bacteria (Candidatus Electrothrix) and large colorless sulfur-oxidizing bacteria (e.g., Beggiatoaceae) are widespread thiotrophs in coastal environments but may exert different influences on biogeochemical cycling. Yet, the factors governing their niche partitioning remain poorly understood. To map their distribution and evaluate their growth constraints in a natural setting, we examined surface sediments across seasons at two sites with contrasting levels of seasonal oxygen depletion in Chesapeake Bay using microscopy coupled with 16S rRNA gene amplicon sequencing and biogeochemical characterization. We found that cable bacteria, dominated by a single phylotype closely affiliated to Candidatus Electrothrix communis, flourished during winter and spring at a central channel site which experiences summer anoxia. Here, cable bacteria density was positively correlated with surface sediment chlorophyll, a proxy of phytodetritus sedimentation. Cable bacteria were also present with a lower areal density at an adjacent shoal site which supports bioturbating macrofauna. Beggiatoaceae were more abundant at this site, where their biomass was positively correlated with sediment respiration, but additionally potentially inhibited by sulfide accumulation which was evident during one summer. A springtime phytodetritus sedimentation event was associated with a proliferation of Beggiatoaceae and multiple Candidatus Electrothrix phylotypes, with cable bacteria reaching 1000 m length cm−2. These observations indicate the potential impact of a spring bloom in driving a hot moment of cryptic sulfur cycling. Our results suggest complex interactions between benthic thiotroph populations, with bioturbation and seasonal oscillations in bottom water dissolved oxygen, sediment sulfide, and organic matter influx as important drivers of their distribution

Calibration and Irradiation Study of the BGO Background Monitor for the BEAST II Experiment

Beam commissioning of the SuperKEKB collider began in 2016. The Beam Exorcism for A STable experiment II (BEAST II) project is particularly designed to measure the beam backgrounds around the interaction point of the SuperKEKB collider for the Belle II experiment. We develop a system using bismuth germanium oxide (BGO) crystals with optical fibers connecting to a multianode photomultiplier tube (MAPMT) and a field-programmable gate array (FPGA) embedded readout board for monitoring the real-time beam backgrounds in BEAST II. The overall radiation sensitivity of this system is estimated to be $(2.20\pm0.26)\times10^{-12}$ Gy/ADU (analog-to-digital unit) with the standard 10 m fibers for transmission and the MAPMT operating at 700 V. Our $\gamma$-ray irradiation study of the BGO system shows that the exposure of BGO crystals to $^{60}$Co $\gamma$-ray doses of 1 krad has led to immediate light output reductions of 25--40%, and the light outputs further drop by 30--45% after the crystals receive doses of 2--4 krad. Our findings agree with those of the previous studies on the radiation hard (RH) BGO crystals grown by the low thermal gradient Czochralski (LTG Cz) technology. The absolute dose from the BGO system is also consistent with the simulation, and is estimated to be about 1.18 times the equivalent dose. These results prove that the BGO system is able to monitor the background dose rate in real time under extreme high radiation conditions. This study concludes that the BGO system is reliable for the beam background study in BEAST II

Cardioplastic Approach to Omental Flap Coverage for Severe Aortic Root Infections in the Opioid Era

Aortic root abscesses are severe sequelae of endocarditis that clinically manifest as life-threatening infection. As the opioid epidemic continues to yield a national crisis, the incidence and severity of this disease process have increased. Reconstruction of the aortic root is a challenging undertaking and carries the risk of recurrent infection. The omentum has an established reputation as a reliable flap in thoracic reconstruction, given its amorphous form and immunogenic properties, but it has not been utilized for aortic root infections. We present a novel indication for the omental flap using a cardioplastic approach in coverage of aortic root reconstruction. Four patients were treated with pedicled omental flap coverage after aortic root reconstruction. All patients had successful flap healing with no evidence of recurrent infection. This series demonstrates the technical feasibility and clinical utility for providing soft tissue coverage and antimicrobial protection when used in aortic root reconstruction

Utility of Parental Mediation Model on Youth’s Problematic Online Gaming

The Parental Mediation Model PMM) was initially designed to regulate children’s attitudes towards the traditional media. In the present era, because of prevalent online media there is a need for similar regulative measures. Spending long hours on social media and playing online games increase the risks of exposure to the negative outcomes of online gaming. This paper initially applied the PMM developed by European Kids Online to (i) test the reliability and validity of this model and (ii) identify the effectiveness of this model in controlling problematic online gaming (POG). The data were collected from 592 participants comprising 296 parents and 296 students of four foreign universities, aged 16 to 22 years in Kuala Lumpur (Malaysia). The study found that the modified model of the five-factor PMM (Technical mediation, Monitoring mediation, Restrictive mediation, Active Mediation of Internet Safety, and Active mediation of Internet Use) functions as a predictor for mitigating POG. The findings suggest the existence of a positive relation between ‘monitoring’ and ‘restrictive’ mediation strategies and exposure to POG while Active Mediation of Internet Safety and Active mediation of Internet use were insignificant predictors. Results showed a higher utility of ‘technical’ strategies by the parents led to less POG. The findings of this study do not support the literature suggesting active mediation is more effective for reducing youth’s risky behaviour. Instead, parents need to apply more technical mediations with their children and adolescents’ Internet use to minimize the negative effects of online gaming

Information theoretical analysis of two-party secret computation

Abstract. Privacy protection has become one of the most important issues in the information era. Consequently, many protocols have been developed to achieve the goal of accomplishing a computational task cooperatively without revealing the participants' private data. Practical protocols, however, do not guarantee perfect privacy protection, as some degree of privacy leakage is allowed so that resources can be used efficiently, e.g., the number of random bits required and the computation time. A metric for measuring the degree of information leakage based on an information theoretical framework was proposed i