Transport in the metallic regime of Mn doped III-V Semiconductors

The standard model of Mn doping in GaAs is subjected to a coherent potential approximation (CPA) treatment. Transport coefficients are evaluated within the linear response Kubo formalism. Both normal (NHE) and anomalous contributions (AHE) to the Hall effect are examined. We use a simple model density of states to describe the undoped valence band. The CPA bandstructure evolves into a spin split band caused by the $p-d$ exchange scattering with Mn dopants. This gives rise to a strong magnetoresistance, which decreases sharply with temperature. The temperature ($T$) dependence of the resistance is due to spin disorder scattering (increasing with $T$), CPA bandstructure renormalization and charged impurity scattering (decreasing with $T$). The calculated transport coefficients are discussed in relation to experiment, with a view of assessing the overall trends and deciding whether the model describes the right physics. This does indeed appear to be case, bearing in mind that the hopping limit needs to be treated separately, as it cannot be described within the band CPA.Comment: submitted to Phys. Rev.

A bibliography on formal methods for system specification, design and validation

Literature on the specification, design, verification, testing, and evaluation of avionics systems was surveyed, providing 655 citations. Journal papers, conference papers, and technical reports are included. Manual and computer-based methods were employed. Keywords used in the online search are listed

Clinical application of ceramics in anterior cervical discectomy and fusion: A review and update

Study Design: Narrative review. Objectives: Anterior cervical discectomy and fusion (ACDF) is a reliable procedure, commonly used for cervical degenerative disc disease. For interbody fusions, autograft was the gold standard for decades; however, limited availability and donor site morbidities have led to a constant search for new materials. Clinically, it has been shown that calcium phosphate ceramics, including hydroxyapatite (HA) and tricalcium phosphate (TCP), are effective as osteoconductive materials and bone grafts. In this review, we present the current findings regarding the use of ceramics in ACDF. Methods: A review of the relevant literature examining the clinical use of ceramics in anterior cervical discectomy and fusion procedures was conducted using PubMed, OVID and Cochrane. Result: HA, coralline HA, sandwiched HA, TCP, and biphasic calcium phosphate ceramics were used in combination with osteoinductive materials such as bone marrow aspirate and various cages composed of poly-ether-ether-ketone (PEEK), fiber carbon, and titanium. Stand-alone ceramic spacers have been associated with fracture and cracks. Metallic cages such as titanium endure the risk of subsidence and migration. PEEK cages in combination with ceramics were shown to be a suitable substitute for autograft. Conclusion: None of the discussed options has demonstrated clear superiority over others, although direct comparisons are often difficult due to discrepancies in data collection and study methodologies. Future randomized clinical trials are warranted before definitive conclusions can be drawn. © The Author(s) 2017

Evaluating the Application of International Laws on Navigation and Collision to Operating Autonomous Ships

The advent of maritime autonomous surface ships (MASS) and the trend towards autonomous shipping mark a significant evolution in the seaborne trade and have generated much debate on the requirements and prospect of MASS operations. Research indicates that MASS have the potential to bring about significant safety, economic and environmental benefits. The question, therefore, is not whether international operation of such vessels should be banned, but how their design, construction and operation should be regulated. However, given that the current international maritime law framework was developed on the presumption that merchant vessels are operated by on-board crew members, operation of MASS presents a full range of legal challenges. Since the United Nations Convention on the Law of the Sea (UNCLOS) confers certain navigational rights on ‘ships’ or ‘vessels’, the first obvious challenge is whether a MASS may constitute a ‘ship’ or a ‘vessel’ for the purposes of UNCLOS. A further uncertainty is whether the existing maritime law conventions are capable of accommodating such innovative vessels and regulating their operation merely through amendments to the conventions, or whether completely new legal instruments should be developed to ensure safe MASS operations. From a safety perspective, one of the most important maritime conventions is the International Regulations for Preventing Collisions at Sea (COLREGs) as MASS vessels may collide with conventional vessels or with various marine structures and cause casualties and/or damage to the marine environment. This thesis uses safety and instrumentalism as normative frameworks and the original contributions of the thesis to knowledge are as follows. First, it establishes that MASS enjoy the same navigational rights conferred on ‘ships’ or ‘vessels’ under UNCLOS. Second, it demonstrates that the existing dual framework and qualitative nature of COLREGs should be retained. Third, it shows that COLREGs need certain crucial amendments to enhance the safety of navigation. Finally, it argues that a suggested three-stage process should be adopted and followed for certification of MASS navigated by remote operators or by AI

Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking

The ordinary magnetoresistance (MR) of doped semiconductors is positive and quadratic in a low magnetic field, B, as it should be in the framework of the Boltzmann kinetic theory or in the conventional hopping regime. We observe an unusual highly-anisotropic in-plane MR in graphite, which is neither quadratic nor always positive. In a certain current direction MR is negative and linear in B in fields below a few tens of mT with a crossover to a positive MR at higher fields, while in a perpendicular current direction we observe a giant super-linear and positive MR. These extraordinary MRs are respectively explained by a hopping magneto-conductance via non-zero angular momentum orbitals, and by the magneto-conductance of inhomogeneous media. The linear orbital NMR is a unique signature of the broken time-reversal symmetry (TRS) in graphite. While some local paramagnetic centers could be responsible for the broken TRS, the observed large diamagnetism suggests a more intriguing mechanism of this breaking, involving superconducting clusters with unconventional (chiral) order parameters and spontaneously generated normal-state current loops in graphite.Comment: 4 pages, 5 figure

Extending Rebeca with synchronous messages and reusable components

In this paper, we propose extended Rebeca as a tool-supported actor-based language for modeling and verifying of concurrent and distributed systems. We enrich Rebeca with a formal concept of components which integrates the message-driven computational model of actor-based languages with synchronous message passing. Components are used to encapsulate a set of internal active objects which react asynchronously to messages by means of methods and which additionally interact via a synchronous message passing mechanism. Components themselves interact only via asynchronous and anonymous messages. We present our compositional verification approach and abstraction techniques, and the theory corresponding to it, based on formal semantics of Rebeca. These techniques are exploited to overcome state explosion problem in model checkin

Temperature dependence of the charge carrier mobility in gated quasi-one-dimensional systems

The many-body Monte Carlo method is used to evaluate the frequency dependent conductivity and the average mobility of a system of hopping charges, electronic or ionic on a one-dimensional chain or channel of finite length. Two cases are considered: the chain is connected to electrodes and in the other case the chain is confined giving zero dc conduction. The concentration of charge is varied using a gate electrode. At low temperatures and with the presence of an injection barrier, the mobility is an oscillatory function of density. This is due to the phenomenon of charge density pinning. Mobility changes occur due to the co-operative pinning and unpinning of the distribution. At high temperatures, we find that the electron-electron interaction reduces the mobility monotonically with density, but perhaps not as much as one might intuitively expect because the path summation favour the in-phase contributions to the mobility, i.e. the sequential paths in which the carriers have to wait for the one in front to exit and so on. The carrier interactions produce a frequency dependent mobility which is of the same order as the change in the dc mobility with density, i.e. it is a comparably weak effect. However, when combined with an injection barrier or intrinsic disorder, the interactions reduce the free volume and amplify disorder by making it non-local and this can explain the too early onset of frequency dependence in the conductivity of some high mobility quasi-one-dimensional organic materials.Comment: 9 pages, 8 figures, to be published in Physical Review

Principles of primary survey and resuscitation in cases of pediatric trauma

Trauma is a common cause of death and disability in children. Proper approach to pediatric trauma involves adherence to ABCDE sequence in the primary survey and resuscitation in order to promptly recognize and manage life-threatening conditions immediately. This readily reviewed sequence includes A: establishment and maintenance of a patent airway while maintaining cervical spine immobilization; B: evaluation of breathing, ventilation and oxygenation, immediate treatment of tension pneumothorax, open pneumothorax and massive hemothorax; C: evaluation and treatment of circulatory compromise and shock; D: Disability and Neurologic Status, assessment of signs of increased intracranial pressure and impending cerebral herniation; and E: Exposure while preventing hypothermia. Implementing these assessment and management priorities can result in more favorable outcomes. © 2015 Tehran University of Medical Sciences. All rights reserve

Incidence of self-reported interpersonal violence related physical injury in Iran

Background: Violence is the cause of death for 1.5 million people in a year. Objectives: Our study aimed to estimate the incidence rate of self-reported interpersonal violence related physical injury (VRPI) and its associated factors in Iran. Patients and Methods: The sample included people ranged from 15 to 64 years old who were residing in Iran. A total of 1525 clusters were selected from the whole country. Six families were selected from each cluster via a systematic random sampling method. Then, the residential units were identified and the interviewers contacted the inhabitants. In the next step, one of the family members was selected by using Kish grid method. The instrument was a researcher-made questionnaire and consisted of two sections; demographics and project related data. Face validity and content validity of our questionnaire were investigated based on expert opinions and the reliability was confirmed by a pilot study, as well. The inclusion criteria were considered for choosing the interviewers. An interviewer was assigned for each 42 participants (7 clusters). An educational seminar was held for the administrative managers (54 persons) and interviewers (230 persons) for a week. The field work was distributed among all 46 Medical Sciences universities in Iran. In each university, administrative issues were related to an executive director. Mann-Whitney U test and odds ratio were used to analyze the data with 95 confidence interval. α value was considered less than 5. Results: The frequency of VRPI among 7886 participants was 24 during the last three months. The incidence rate of interpersonal VRPI was estimated at 3.04 per 1000 population (95 CI: 2.66-3.42) during a three-month interval in Iran. The incidence was 4.72 per 1000 population (95 CI: 4.01-5.43) for males and 1.78 per 1000 population (95 CI: 1.39-2.17) for females during a three-month interval. The mean (SD) of age of the participants with and without a history of VRPI were 26.5 (7.21) and 33.05 (12.05) years, respectively (P = 0.008). Considering the participants� gender, 66.7 were males (OR = 2.66, 95 CI: 1.14-6.23). Khuzestan Province had the most VRPIs (25 of all VRPIs). Streets and roads were the places with the highest frequency of injury (50). The most frequent injured organ was the upper limb (54.17). The most prevalent type of injury was a superficial wound (50). Finally, the most common place of treatment was home (45.83). Conclusions: We determined the incidence rate of self-reported interpersonal VRPI for the first time in Iran based on a national survey. The injuries were more common among young men. We suggest consecutive national surveys with different data gathering methods and more sample sizes. © 2015, Iranian Red Crescent Medical Journal