Acoustically-induced slip in sheared granular layers: application to dynamic earthquake triggering

A fundamental mystery in earthquake physics is ``how can an earthquake be triggered by distant seismic sources?'' Here, we use discrete element method simulations of a granular layer, during stick-slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. Using Coulomb friction law for grains interaction, we observe delayed triggering of slip in the granular gouge. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance, {\it i.e.}, transient vibration and triggered slip are simultaneous. The critical strain is order of $10^{-6}$, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses

How to cluster in parallel with neural networks

Partitioning a set of N patterns in a d-dimensional metric space into K clusters - in a way that those in a given cluster are more similar to each other than the rest - is a problem of interest in astrophysics, image analysis and other fields. As there are approximately K(N)/K (factorial) possible ways of partitioning the patterns among K clusters, finding the best solution is beyond exhaustive search when N is large. Researchers show that this problem can be formulated as an optimization problem for which very good, but not necessarily optimal solutions can be found by using a neural network. To do this the network must start from many randomly selected initial states. The network is simulated on the MPP (a 128 x 128 SIMD array machine), where researchers use the massive parallelism not only in solving the differential equations that govern the evolution of the network, but also by starting the network from many initial states at once, thus obtaining many solutions in one run. Researchers obtain speedups of two to three orders of magnitude over serial implementations and the promise through Analog VLSI implementations of speedups comensurate with human perceptual abilities

Klinička prosudba sedativnih svojstava acepromazin-ksilazina u kombinaciji s atropinom i njihov učinak na fiziološke vrijednosti temperature, bila i disanja u pasa.

The purpose of this study was to clinically evaluate the sedative effects of different doses of acepromazinexylazine combinations with or without atropine in dogs. One hundred and twenty dogs of various breeds and both sexes were used in a prospective randomized, blinded clinical study. Dogs, presented to the Veterinary Clinic for various diagnostic and surgical procedures, were randomly divided into four groups (n=30/group) and received the following drug combinations intramuscularly: Group AX: acepromazine (0.05 mg kg-1) + Xylazine (0.5 mg kg-1), Group AXA: Acepromazine (0.05 mg kg 1) + Xylazine (0.5 mg kg-1) + Atropine (0.04 mg kg-1) Group LA HX: Acepromazine (Low dose: 0.03 mg kg-1) + Xylazine (High dose: 0.8 mg kg-1), Group HA-LX: Acepromazine (High dose: 0.08 mg kg-1) + Xylazine (Low dose: 0.3 mg kg-1). Heart and respiratory rates, electrocardiogram and rectal temperature were recorded before drug injection (baseline) and during maximum sedation. Sedation was scored using descriptive categories. Heart rate significantly decreased from the baseline following sedation in the AX, LA-HX and HA-LX groups. A significant reduction in respiratory rate was observed in all treatment groups. The median sedation score did not differ significantly between the groups; however, the quality of sedation was enhanced when atropine was added to the acepromazine-xylazine combination and a higher number of dogs were assigned score 3 in AXA group. No adverse effects were recorded during the study. The acepromazine-xylazine combination, particularly with atropine, can be used effectively for sedation and premedication before general anaesthesia in healthy dogs.Svrha ovog rada bila je klinički procijeniti sedativne učinke različitih doza acepromazin-ksilazina u kombinaciji s atropinom u pasa. Istraživanje je bilo provedeno na 120 nasumce odabranih pasa različitih pasmina obaju spolova s dvostruko slijepim probama. Psi su bili klinički obrađivani na jednoj veterinarskoj klinici zbog potrebe za različitim dijagnostičkim i kirurškim pregledima. Za potrebe istraživanja bili su podijeljeni u četiri skupine (30 pasa po skupini), a po skupinama su intramuskularno dobivali sljedeće kombinacije lijekova: skupina AX dobivala je acepromazin (0,05 mg kg-1) i ksilazin (0,5 mg kg-1), skupina AXA dobivala je acepromazin (0,05 mg kg-1), ksilazin (0,5 mg kg-1) i atropin (0,04 mg kg-1), skupina LA-HX dobivala je acepromazin (malu dozu od 0,03 mg kg-1) i ksilazin (veliku dozu od 0,8 mg kg-1), a skupina HA-LX acepromazin (veliku dozu od 0,08 mg kg-1) i ksilazin (malu dozu od 0,3 mg kg-1). Vrijednosti bila, frekvencije disanja, elektrokardiograma i rektalne temperature bile su izmjerene prije davanja sedativa te za vrijeme maksimalne sedacije. Sedacija je bila bodovana opisno. Vrijednosti bila značajno su se smanjile nakon sedacije u pasa skupina AX, LA HX i HALX. Značajno smanjena frekvencija disanja bila je zabilježena u svim skupinama. Srednji broj bodova sedacije nije se značajno razlikovao među skupinama, ali je kvaliteta sedacije bila bolja kada je atropin bio dodan kombinaciji acepromazin-ksilazin te su tri boda bila dodijeljena većem broju pasa u skupini AXA. Nuspojave nisu bile zabilježene. Kombinacija acepromazin-ksilazin, osobito s atropinom, može se rabiti za učinkovitu sedaciju i premedikaciju prije opće anestezije u zdravih pasa

Surgeon practices regarding infection prevention for growth friendly spinal procedures

Purpose The rate of infection in patients having growth sparing surgery for early onset scoliosis has been reported up to 25 % during the course of treatment. A recent study demonstrated significant variability in the approach to infection prevention in adolescent and neuromuscular scoliosis. The purpose of this study is to conduct a similar survey in order to understand approaches used by experienced pediatric spinal surgeons with regard to infection prevention in growth friendly spinal procedures. Materials and methods After preliminary internal testing of a survey by the authors, a final 21-question survey was created and approved by the authors and electronically distributed to all members of the Chest Wall Spinal Deformity Study Group and the Growing Spine Study Group (n = 57). A total of 40 responses were obtained (70 %). Results: Significant variability in practice was demonstrated across the majority of the questions answered. Several of the questions demonstrated relative equipoise between practices, including preoperative MRSA screening, preoperative chlorhexidine baths, postoperative antibiotic duration after insertion, use of topical antibiotics, use of drains, use of IV gram negative coverage or vancomycin, and skin preparation. Conclusion: Other studies have demonstrated that variability in practice may have a negative impact on clinical outcomes, so one could postulate that steps that can reduce variability in the current population may help improve outcomes in this population. Areas of clinical equipoise can be used to help design and direct multicenter studies with an ultimate goal of reducing infections in this population. Level of evidence Level V. Electronic supplementary material The online version of this article (doi:10.1007/s11832-014-0584-1) contains supplementary material, which is available to authorized users

About Gravitomagnetism

The gravitomagnetic field is the force exerted by a moving body on the basis of the intriguing interplay between geometry and dynamics which is the analog to the magnetic field of a moving charged body in electromagnetism. The existence of such a field has been demonstrated based on special relativity approach and also by special relativity plus the gravitational time dilation for two different cases, a moving infinite line and a uniformly moving point mass, respectively. We treat these two approaches when the applied cases are switched while appropriate key points are employed. Thus, we demonstrate that the strength of the resulted gravitomagnetic field in the latter approach is twice the former. Then, we also discuss the full linearized general relativity and show that it should give the same strength for gravitomagnetic field as the latter approach. Hence, through an exact analogy with the electrodynamic equations, we present an argument in order to indicate the best definition amongst those considered in this issue in the literature. Finally, we investigate the gravitomagnetic effects and consequences of different definitions on the geodesic equation including the second order approximation terms.Comment: 16 pages, a few amendments have been performed and a new section has been adde

Enabling emergency flow prioritization in SDN networks

Emergency services must be able to transfer data with high priority over different networks. With 5G, slicing concepts at mobile network connections are introduced, allowing operators to divide portions of their network for specific use cases. In addition, Software-Defined Networking (SDN) principles allow to assign different Quality-of-Service (QoS) levels to different network slices.This paper proposes an SDN-based solution, executable both offline and online, that guarantees the required bandwidth for the emergency flows and maximizes the best-effort flows over the remaining bandwidth based on their priority. The offline model allows to optimize the problem for a batch of flow requests, but is computationally expensive, especially the variant where flows can be split up over parallel paths. For practical, dynamic situations, an online approach is proposed that periodically recalculates the optimal solution for all requested flows, while using shortest path routing and a greedy heuristic for bandwidth allocation for the intermediate flows.Afterwards, the offline approaches are evaluated through simulations while the online approach is validated through physical experiments with SDN switches, both in a scenario with 500 best-effort and 50 emergency flows. The results show that the offline algorithm is able to guarantee the resource allocation for the emergency flows while optimizing the best-effort flows with a sub-second execution time. As a proof-of-concept, a physical setup with Zodiac switches effectively validates the feasibility of the online approach in a realistic setup

Early and Late Reoperation Rates With Various MIS Techniques for Adult Spinal Deformity Correction.

Study designA multicenter retrospective review of an adult spinal deformity database.ObjectiveWe aimed to characterize reoperation rates and etiologies of adult spinal deformity surgery with circumferential minimally invasive surgery (cMIS) and hybrid (HYB) techniques.MethodsInclusion criteria were age ≥18 years, and one of the following: coronal Cobb >20°, sagittal vertical axis >5 cm, pelvic tilt >20°, and pelvic incidence-lumbar lordosis >10°. Patients with either cMIS or HYB surgery, ≥3 spinal levels treated with 2-year minimum follow-up were included.ResultsA total of 133 patients met inclusion for this study (65 HYB and 68 cMIS). Junctional failure (13.8%) was the most common reason for reoperation in the HYB group, while fixation failure was the most common reason in the cMIS group (14.7%). There was a higher incidence of proximal junctional failure (PJF) than distal junctional failure (DJF) within HYB (12.3% vs 3.1%), but no significant differences in PJF or DJF rates when compared to cMIS. Early (<30 days) reoperations were less common (cMIS = 1.5%; HYB = 6.1%) than late (>30 days) reoperations (cMIS = 26.5%; HYB = 27.7%), but early reoperations were more common in the HYB group after propensity matching, largely due to infection rates (10.8% vs 0%, P = .04).ConclusionsAdult spinal deformity correction with cMIS and HYB techniques result in overall reoperation rates of 27.9% and 33.8%, respectively, at minimum 2-year follow-up. Junctional failures are more common after HYB approaches, while pseudarthrosis/fixation failures happen more often with cMIS techniques. Early reoperations were less common than later returns to the operating room in both groups, but cMIS demonstrated less risk of infection and early reoperation when compared with the HYB group

Post Irradiation Evaluation of Thermal Control Coatings and Solid Lubricants to Support Fission Surface Power Systems

The development of a nuclear power system for space missions, such as the Jupiter Icy Moons Orbiter or a lunar outpost, requires substantially more compact reactor design than conventional terrestrial systems. In order to minimize shielding requirements and hence system weight, the radiation tolerance of component materials within the power conversion and heat rejection systems must be defined. Two classes of coatings, thermal control paints and solid lubricants, were identified as material systems for which limited radiation hardness information was available. Screening studies were designed to explore candidate coatings under a predominately fast neutron spectrum. The Ohio State Research Reactor Facility staff performed irradiation in a well characterized, mixed energy spectrum and performed post irradiation analysis of representative coatings for thermal control and solid lubricant applications. Thermal control paints were evaluated for 1 MeV equivalent fluences from 10(exp 13) to 10(exp 15) n per square centimeters. No optical degradation was noted although some adhesive degradation was found at higher fluence levels. Solid lubricant coatings were evaluated for 1 MeV equivalent fluences from 10(exp 15) to 10(exp 16) n per square centimeters with coating adhesion and flexibility used for post irradiation evaluation screening. The exposures studied did not lead to obvious property degradation indicating the coatings would have survived the radiation environment for the previously proposed Jupiter mission. The results are also applicable to space power development programs such as fission surface power for future lunar and Mars missions

The Character as subjective interface

This paper re-frames virtual interactive characters as " subjective interfaces " with the purpose of highlighting original affordances for interactive story-telling through conversation. This notion is theoretically unpacked in the perspectives of narratology, interaction design and game design. Existing and imagined scenarios are presented in which subjective interfaces are elevated as core interaction mechanics. Finally, technical challenges posed by this approach are reviewed alongside relevant existing research leads.Fonds de Recherche du Québec - Société et Cultur

Is There a Patient Profile That Characterizes a Patient With Adult Spinal Deformity as a Candidate for Minimally Invasive Surgery?

Study designRetrospective review.ObjectivesThe goal of this study was to evaluate the baseline characteristics of patients chosen to undergo traditional open versus minimally invasive surgery (MIS) for adult spinal deformity (ASD).MethodsA multicenter review of 2 databases including ASD patients treated with surgery. Inclusion criteria were age >45 years, Cobb angle minimum of 20°, and minimum 2-year follow-up. Preoperative radiographic parameters and disability outcome measures were reviewed.ResultsA total of 350 patients were identified: 173 OPEN patients and 177 MIS. OPEN patients were significantly younger than MIS patients (61.5 years vs 63.74 years, P = .013). The OPEN group had significantly more females (87% vs 76%, P = .006), but both groups had similar body mass index. Preoperative lumbar Cobb was significantly higher for the OPEN group (34.2°) than for the MIS group (26.0°, P < .001). The mean preoperative Oswestry Disability Index was significantly higher in the MIS group (44.8 in OPEN patients and 49.8 in MIS patients, P < .011). The preoperative Numerical Rating Scale value for back pain was 7.2 in the OPEN group and 6.8 in the MIS group preoperatively, P = .100.ConclusionsPatients chosen for MIS for ASD are slightly older and have smaller coronal deformities than those chosen for open techniques, but they did not have a substantially lesser degree of sagittal malalignment. MIS surgery was most frequently utilized for patients with an sagittal vertical axis under 6 cm and a baseline pelvic incidence and lumbar lordosis mismatch under 30°