Biaxial tests of flat graphite/epoxy laminates

The influence of biaxially applied loads on the strength of composite materials containing holes was analyzed. The analysis was performed through the development of a three dimensional, finite element computer program that is capable of evaluating fiber breakage, delamination, and matrix failure. Realistic failure criteria were established for each of the failure modes, and the influence of biaxial loading on damage accumulation under monotonically increasing loading was examined in detail. Both static and fatigue testing of specially designed biaxial specimens containing central holes were performed. Static tests were performed to obtain an understanding of the influence of biaxial loads on the fracture strength of composite materials and to provide correlation with the analytical predictions. The predicted distributions and types of damage are in reasonable agreement with the experimental results. A number of fatigue tests were performed to determine the influence of cyclic biaxial loads on the fatigue life and residual strength of several composite laminates

Darwin-Lagrangian Analysis for the Interaction of a Point Charge and a Magnet: Considerations Related to the Controversy Regarding the Aharonov-Bohm and Aharonov-Casher Phase Shifts

The classical electromagnetic interaction of a point charge and a magnet is discussed by first calculating the interaction of point charge with a simple model magnetic moment and then suggesting a multiparticle limit. The Darwin Lagrangian is used to analyze the electromagnetic behavior of the model magnetic moment (composed of two oppositely charged particles of different mass in an initially circular orbit) interacting with a passing point charge. The changing mangetic moment is found to put a force back on a passing charge; this force is of order 1/c^2 and depends upon the magnitude of the magnetic moment. It is suggested that in the limit of a multiparticle magnetic toroid, the electric fields of the passing charge are screened out of the body of the magnet while the magnetic fields penetrate into the magnet. This is consistent with our understanding of the penetration of electromagnetic velocity fields into ohmic conductors. Conservation laws are discussed. The work corresponds to a classical electromagnetic analysis of the interaction which is basic to understanding the controversy over the Aharonov-Bohm and Aharonov-Casher phase shifts and represents a refutation of the suggestions of Aharonov, Pearle, and Vaidman.Comment: 33 page

Comparative in vitro activity of piperacillinl tazobactam against Gramnegative bacilli

Objective. To describe the in vitro activity of piperacillinl tazobactam against clinical isolates of Gram-negative bacteria, compared with other antibacterial agents.Design. Survey of susceptibility of clinical isolates of Gram-negative bacilli.Setting. Academic hospitals of the University of the Witwatersrand teaching complex. Bacterial strains_ 180 selected clinical isolates of Gramnegative bacilli.Main outcome measures. Minimum inhibitory concentrations (MICs) determined by agar dilution using techniques according to the recommendations of the National Committee for Clinical Laboratory Standards.Results. Ciprofloxacin, biapenem, imipenem, cefepime and cefpirome were all highly active against most of the Enterobacteriaceae. All the ampicillin-resistant strains of Enterobacteriaceae were susceptible to piperacillinl tazobactam, MICSll values being 4/4 mgll for Klebsiella and Proteus/Providencia spp., 8/4 mg/l for Citrobacter and Serratia spp_, and 16/4 mg/l for Escherichia coli. All the agents, with the exception of ampicillin (MIC90 4 mg/l) and chloramphenicol (MIC90 4 mg/l), were highly active against the Haemophilus influenzae isolates tested. All Bacteroides fragilis strains were susceptible to piperacillinllazobaclam (MIC90 8/4 mgll), as well as 10 co-amoxiclav (MIC90 4/2 mg/I), biapenem and imipenem (MIC90 0.5 mg/l). The Pseudomonas spp. lested included strains resistant to piperacillinltazobactam, ceftazidime, biapenem, gentamicin, tobramycin and ciprofloxacin. Cefepime was the most active agent against Pseudomonas isolates, with 90% of the strains being susceptible to this agent, while biapenem was the mast active agent against the Acinetobacter isolates investigated.Conclusions. The in vitro spectrum of activity of piperacillin!tazobactam against the majority of isolates was comparable to those of the other new agents tested

Ingestion of a Nutritional Supplement Pre-Workout Will Increase Exercise Time-to-Fatigue

Everyone fatigues at the end of an intense exercise bout. However, previous research has indicated that ingestion of a mixed nutrient supplement one hour pre-exercise will increase exercise time-to-fatigue¹. For this experiment, four females between the ages 20-50 participated in a controlled pilot study. Exercise was performed using a row machine, where time- to-fatigue was measured from a baseline of 80% max HR (220 minus age). The nutrient supplement was ingested 1 hour pre-rowing and contained 30g of protein, 5g carbohydrate, and 3g of fat. Results showed that pre-exercise ingestion of a mixed protein supplement did increase row time-to-fatigue

The Paradoxical Forces for the Classical Electromagnetic Lag Associated with the Aharonov-Bohm Phase Shift

The classical electromagnetic lag assocated with the Aharonov-Bohm phase shift is obtained by using a Darwin-Lagrangian analysis similar to that given by Coleman and Van Vleck to identify the puzzling forces of the Shockley-James paradox. The classical forces cause changes in particle velocities and so produce a relative lag leading to the same phase shift as predicted by Aharonov and Bohm and observed in experiments. An experiment is proposed to test for this lag aspect implied by the classical analysis but not present in the currently-accepted quantum topological description of the phase shift.Comment: 8 pages, 3 figure

Weighted-density approximation for general nonuniform fluid mixtures

In order to construct a general density-functional theory for nonuniform fluid mixtures, we propose an extension to multicomponent systems of the weighted-density approximation (WDA) of Curtin and Ashcroft [Phys. Rev. A 32, 2909 (1985)]. This extension corrects a deficiency in a similar extension proposed earlier by Denton and Ashcroft [Phys. Rev. A 42, 7312 (1990)], in that that functional cannot be applied to the multi-component nonuniform fluid systems with spatially varying composition, such as solid-fluid interfaces. As a test of the accuracy of our new functional, we apply it to the calculation of the freezing phase diagram of a binary hard-sphere fluid, and compare the results to simulation and the Denton-Ashcroft extension.Comment: 4 pages, 4 figures, to appear in Phys. Rev. E as Brief Repor

Can filesharers be triggered by economic incentives? Results of an experiment

Illegal filesharing on the internet leads to considerable financial losses for artists and copyright owners as well as producers and sellers of music. Thus far, measures to contain this phenomenon have been rather restrictive. However, there are still a considerable number of illegal systems, and users are able to decide quite freely between legal and illegal downloads because the latter are still difficult to sanction. Recent economic approaches account for the improved bargaining position of users. They are based on the idea of revenue-splitting between professional sellers and peers. In order to test such an innovative business model, the study reported in this article carried out an experiment with 100 undergraduate students, forming five small peer-to-peer networks.The networks were confronted with different economic conditions.The results indicate that even experienced filesharers hold favourable attitudes towards revenue-splitting.They seem to be willing to adjust their behaviour to different economic conditions

Co-production in distributed generation:Renewable energy and creating space for fitting infrastructure within landscapes

This review describes the infrastructural elements of the socio-technical system of power supply based on renewables and the role of landscape concerns in decision-making about emerging ‘intelligent grids’. The considerable land areas required for energy infrastructure call for sizable ‘distributed generation’ close to energy consumption. Securing community acceptance of renewables’ infrastructure, perceived impacts on the community, and ‘landscape justice’ requires two types of co-production: in power supply and in making space available. With co-production, landscape issues are prominent, for some options dominant. However, ‘objectification’ of landscape, such as the use of ‘visibility’ as proxy for ‘visual impact’, is part of lingering centralised and hierarchical approaches to the deployment of renewables. Institutional tendencies of centralisation and hierarchy, in power supply management as well as in siting, should be replaced by co-production, as follows from common pool resources theory. Co-production is the key to respecting landscape values, furthering justice, and achieving community acceptance

Distorted maternal mental representations and atypical behavior in a clinical sample of violence-exposed mothers and their toddlers

Objective: To determine whether maternal violence-related posttraumatic stress disorder (PTSD), reflective functioning (RF), and/or quality of mental representations of her child predicts maternal behavior within a referred sample of mothers exposed to interpersonal violence and their children (aged 8–50 months). Method: A total of 41 dyads completed 2 videotaped visits including measures of maternal mentalrepresentations and behavior. Results: Negative and distorted maternal mental representations predicted atypical behavior (Cohen’s d \u3e 1.0). Although maternal PTSD and RF impacted mental representations, no significant relationships were found between PTSD, RF, and overall atypical caregiving behavior. Severity of maternal PTSD was, however, positively correlated with the avoidant caregiving behaviorsubscale. Conclusions: Maternal mental representations of her child are useful risk indicators that mark dysregulation of trauma-associated emotions in the caregiver

Kinematics and hydrodynamics of spinning particles

In the first part (Sections 1 and 2) of this paper --starting from the Pauli current, in the ordinary tensorial language-- we obtain the decomposition of the non-relativistic field velocity into two orthogonal parts: (i) the "classical part, that is, the 3-velocity w = p/m OF the center-of-mass (CM), and (ii) the so-called "quantum" part, that is, the 3-velocity V of the motion IN the CM frame (namely, the internal "spin motion" or zitterbewegung). By inserting such a complete, composite expression of the velocity into the kinetic energy term of the non-relativistic classical (i.e., newtonian) lagrangian, we straightforwardly get the appearance of the so-called "quantum potential" associated, as it is known, with the Madelung fluid. This result carries further evidence that the quantum behaviour of micro-systems can be adirect consequence of the fundamental existence of spin. In the second part (Sections 3 and 4), we fix our attention on the total 3-velocity v = w + V, it being now necessary to pass to relativistic (classical) physics; and we show that the proper time entering the definition of the four-velocity v^mu for spinning particles has to be the proper time tau of the CM frame. Inserting the correct Lorentz factor into the definition of v^mu leads to completely new kinematical properties for v_mu v^mu. The important constraint p_mu v^mu = m, identically true for scalar particles, but just assumed a priori in all previous spinning particle theories, is herein derived in a self-consistent way.Comment: LaTeX file; needs kapproc.st