Step bunching with both directions of the current: Vicinal W(110) surfaces versus atomistic scale model

We report for the first time the observation of bunching of monoatomic steps on vicinal W(110) surfaces induced by step up or step down currents across the steps. Measurements reveal that the size scaling exponent {\gamma}, connecting the maximal slope of a bunch with its height, differs depending on the current direction. We provide a numerical perspective by using an atomistic scale model with a conserved surface flux to mimic experimental conditions, and also for the first time show that there is an interval of parameters in which the vicinal surface is unstable against step bunching for both directions of the adatom drift.Comment: 17 pages, 10 figure

Alignment of the CMS tracker with LHC and cosmic ray data

© CERN 2014 for the benefit of the CMS collaboration, published under the terms of the Creative Commons Attribution 3.0 License by IOP Publishing Ltd and Sissa Medialab srl. Any further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation and DOI.The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multi-processor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10μm

The Effects of Low-Frequency Noise on Rats: Evidence of Chromosomal Aberrations in the Bone Marrow Cells and the Release of Low-Molecular-Weight DNA in the Blood Plasma

Objectives: Evaluation of the effect of low-frequency noise (LFN) on the frequency of chromosomal aberrations in the bone marrow cells and on the content of low-molecular-weight DNA (lmwDNA) in the blood plasma of rats. Materials and Methods: A total of 96 male Wistar rats were exposed to either single (17 min session) or multiple (17 min session repeated five times a week for 13 weeks) LFN, with the maximum range below 250 Hz and the sound pressure levels (SPLs) at 120 and 150 dB, respectively. The rats in the control groups were not subjected to any impact. The frequency of chromosomal aberrations in the bone marrow cells and the levels of lmwDNA in the blood plasma were measured afterwards. Results: It has been detected that a single LFN exposure with either corresponding SPLs had a significant increase in the frequency of chromosomal aberrations (more than 10-fold) compared to the controls (0.9 ± 0.3%) and resulted in the appearance of dicentric chromosomes in the aberration spectrum, both of which are evident for the occurrence of deoxyribonucleic acid double strand breaks triggered by the exposure. Furthermore, the lmwDNA levels in the blood plasma measured the following day after a single LFN exposure were significantly higher (7.7- and 7.6-fold, respectively) than that in the control group (11.0 ± 5.4 ng/ml), and such levels were maintained higher (4.8- and 2.1-fold, respectively) in the week after a single LFN exposure for the SPL of 120 and 150 dB, respectively, compared to the control group (18.8 ± 1.6 ng/ml). Similar results were obtained from the group with multiple LFN exposures (36.4- and 22.4-fold, respectively) compared to the control (17.7 ± 1.7 ng/ml) and suggest the enhancement of cellular apoptosis as a result of the LFN impact. Conclusion: Presumably, the LFN may have possible mutagenic effects and cause massive cell death

Modeling the coherence of the financial system and economy of Russia

The article assesses the coherence of the financial system and economy of Russia, and also reveals the uncertainties in interrelation between the flow of finance and economic activity. The work reveals the possibilities of ensuring preservation of the form and content of economic system in the process of creating and using monetary funds. An analysis of the actual change of pace in the growth rate of finances and economic activity was carried out to eliminate the uncertainty of interrelation between the flow of finance and economic activity. In the result of the analysis, it was revealed that financial and economic measures are resorted to in order to eliminate uncertainty, and thereby, to ensure the preservation of coherence of the financial system of the modern Russian economy. Financial measures include an increase in gold reserves and monetary base; economic measures include an increase in the production of crude oil and natural gas and petroleum (associated) gas, extraction and dressing of iron ores. As a result of modeling the dynamics of the financial and economic systems with application of the modified Cobb-Douglas formula it is revealed that the financial system actively follows the dynamics of the economic system and there is sufficient compensating reaction of the former.Coherence of the Russian financial system and economy determines the capability and ability to maintain the form and content of the Russian economy with the help of finance. Elimination of the uncertainty of interrelation between the flow of finance and economic activity is confirmed by active following of the Russian financial system in path of the economic system dynamics and compensating reaction of the financial system

Revealing electromigration on dielectrics and metals through the step-bunching instability

Electromigration, due to its technological and scientific significance, has been a subject of extensive studies for many years. We present evidence of electromigration in dielectric materials, namely C-plane sapphire, obtained from direct experimental observation of an atomic step-bunching instability driven by electromigration. We further expand upon our previously reported findings of electromigration induced step-bunching transformation of a metal surface. The only system where electromigration driven step bunching has been observed and comprehensively investigated is the low index surfaces of silicon. In this study we show that electromigration driven SB can be induced on a variety of crystallographic surfaces, including metals and insulating oxides, and may be more prevalent than previously thought. Electric fields were applied at high temperature to W(110) and Al2O3(0001) crystals whereupon their surface reordered to a morphology closely resembling that of Si(111) with atomic steps bunched by electromigration. This suggests that the mechanism of step bunching on the W(110), Al2O3(0001), and Si(111) can be fundamentally the same. Annealing W(110) offcut in the [001] direction with an up-step current produced a morphology with the bunch edges composed of zigzag segments meeting at a right angle

REVEALING ELECTROMIGRATION ON DIELECTRICS AND METALS THROUGH THE STEP-BUNCHING INSTABILITY

Electromigration, due to its technological and scientific significance, has been a subject of extensive studies for many years. We present evidence of electromigration in dielectric materials, namely C -plane sapphire, obtained from direct experimental observation of an atomic step-bunching instability driven by electromigration. We further expand upon our previously reported findings of electromigration induced step-bunching transformation of a metal surface. The only system where electromigration driven step bunching has been observed and comprehensively investigated is the low index surfaces of silicon. In this study we show that electromigration driven SB can be induced on a variety of crystallographic surfaces, including metals and insulating oxides, and may be more prevalent than previously thought. Electric fields were applied at high temperature to W(110) and A l 2 O 3 ( 0001 ) crystals whereupon their surface reordered to a morphology closely resembling that of Si(111) with atomic steps bunched by electromigration. This suggests that the mechanism of step bunching on the W(110), A l 2 O 3 ( 0001 ) , and Si(111) can be fundamentally the same. Annealing W(110) offcut in the [001] direction with an up-step current produced a morphology with the bunch edges composed of zigzag segments meeting at a right angle

Deformation and fracture of crystalline tungsten and fabrication of composite STM probes

Fracturing microscale constrictions in metallic wires, such as tungsten, platinum, or platinum-iridium, is a common fabrication method used to produce atomically sharp tips for scanning tunneling microscopy (STM), field-emission microscopy and field ion microscopy. Typically, a commercial polycrystalline drawn wire is locally thinned and then fractured by means of a dislocation slip inside the constriction. We examine a special case where a dislocation-free microscale constriction is created and fractured in a single crystal tungsten rod with a long side parallel to the [100] direction. In the absence of dislocations, vacancies become the main defects in the constriction which breaks under the tensile stress of approximately 10 GPa, which is close to the theoretical fracture strength for an ideal monocrystalline tungsten. We propose that the vacancies are removed early in the tensile test by means of deformation annealing, creating a defect-free tungsten constriction which cleaves along the W(100) plane. This approach enables fabrication of new composite STM probes which demonstrate excellent stability, atomic resolution and magnetic contrast that cannot be attained using conventional methods

Step bunching with both directions of the current: Vicinal W(110) surfaces versus atomistic-scale model

We report the observation of bunching of monoatomic steps on vicinal W(110) surfaces induced by step-up or step-down currents across the steps. Measurements reveal that the size-scaling exponent γ , connecting the maximal slope of a bunch with its height, differs depending on the current direction. We provide a numerical perspective by using an atomistic-scale model with a conserved surface flux to mimic experimental conditions, and also show that there is an interval of parameters in which the vicinal surface is unstable against step bunching for both directions of the adatom drif