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

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

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

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°

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

Nutritional improvement following growing rod surgery in children with early onset scoliosis

Purpose We aimed to evaluate the nutritional status of children with early onset scoliosis (EOS) and to determine if treatment with growing rod instrumentation improves weight percentile. Methods: Data was retrospectively collected on 88 EOS patients treated with growing rods at six institutions. Mean age at surgery was 5.8 years, and mean Cobb angle was 75°. All patients were followed for at least 2 years (mean 4 years). Weights were converted to normative percentiles based on the patients’ age and gender. Results: Preoperatively, 47 % (41/88) of patients were 0.05). Children with neuromuscular and syndromic diagnoses do not appear to improve their mean nutritional status after surgery when compared to patients with idiopathic or congenital/structural scoliosis (p = 0.006). Conclusion: Following growing rod treatment, there was significant improvement in nutritional status in approximately 50 % of patients, similar to that reported with VEPTR. Neuromuscular and syndromic patients did not experience nutritional improvement post-operatively. These findings support the theory that growing rods improve the clinical status of EOS patients, as nutritional improvement is one outcome of improved clinical status. The relationship between age at initial surgery and nutritional improvement is intriguing