An Experimental Study of Individual Air Bubble Entrainment at a Planar Plunging Jet

At the impact of a plunging liquid jet with a receiving pool, air bubbles may be entrained if the impact velocity exceeds a critical velocity. New experiments were performed in a two-dimensional plunging jet. The flow conditions near the inception of air entrainment were investigated. Two mechanisms of air entrainment were visualized at low jet velocities: by elongated air cavity and by foam bubble s. The breakage of entrained air bubbles was studied also. The results highlight that the bubble breakage process depends critically upon the initial bubble size

Note on the hydrodynamic description of thin nematic films: strong anchoring model

We discuss the long-wave hydrodynamic model for a thin film of nematic liquid crystal in the limit of strong anchoring at the free surface and at the substrate. We rigorously clarify how the elastic energy enters the evolution equation for the film thickness in order to provide a solid basis for further investigation: several conflicting models exist in the literature that predict qualitatively different behaviour. We consolidate the various approaches and show that the long-wave model derived through an asymptotic expansion of the full nemato-hydrodynamic equations with consistent boundary conditions agrees with the model one obtains by employing a thermodynamically motivated gradient dynamics formulation based on an underlying free energy functional. As a result, we find that in the case of strong anchoring the elastic distortion energy is always stabilising. To support the discussion in the main part of the paper, an appendix gives the full derivation of the evolution equation for the film thickness via asymptotic expansion

AER Auditory Filtering and CPG for Robot Control

Address-Event-Representation (AER) is a communication protocol for transferring asynchronous events between VLSI chips, originally developed for bio-inspired processing systems (for example, image processing). The event information in an AER system is transferred using a highspeed digital parallel bus. This paper presents an experiment using AER for sensing, processing and finally actuating a Robot. The AER output of a silicon cochlea is processed by an AER filter implemented on a FPGA to produce rhythmic walking in a humanoid robot (Redbot). We have implemented both the AER rhythm detector and the Central Pattern Generator (CPG) on a Spartan II FPGA which is part of a USB-AER platform developed by some of the authors.Commission of the European Communities IST-2001-34124 (CAVIAR)Comisión Interministerial de Ciencia y Tecnología TIC-2003-08164-C03-0

The early X-ray afterglows of optically bright and dark Gamma-Ray Bursts

A systematical study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift has been presented. Our sample includes 25 GRBs. Among them 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes ($F_{X}$), the gamma-ray fluxes ($S_{\gamma}$), and the ratio ($R_{\gamma, X}$) for both the D-GRBs and B-GRBs are similar. The differences of these distributions for the two kinds of GRBs should be statistical fluctuation. These results indicate that the progenitors of the two kinds of GRBs are the same population. Their total energy explosions are comparable. The suppression of the optical emissions from D-GRBs should results from circumburst but not their central engine.Comment: 10 pages, 3 figures, 1 table; accepted by ChJA

Drinking in social groups. Does 'groupdrink' provide safety in numbers when deciding about risk?

AimsTo investigate the impact of alcohol consumption on risk decisions taken both individually and while part of a four- to six-person ad-hoc group.DesignA 2 (alcohol: consuming versus not consuming alcohol) x 2 (decision: individual, group) mixed-model design; decision was a repeated measure. The dependent variable was risk preference, measured using choice dilemmas.SettingOpportunity sampling in campus bars and a music event at a campus-based university in the United Kingdom.ParticipantsA total of 101 individuals were recruited from groups of four to six people who either were or were not consuming alcohol.MeasurementsParticipants privately opted for a level of risk in response to a choice dilemma and then, as a group, responded to a second choice dilemma. The choice dilemmas asked participants the level of accident risk at which they would recommend someone could drive while intoxicated.FindingsFive three-level multi-level models were specified in the software program HLM 7. Decisions made in groups were less risky than those made individually (B = -0.73, P < 0.001). Individual alcohol consumers opted for higher risk than non-consumers (B = 1.27, P = 0.025). A significant alcohol?×?decision interaction (B = -2.79, P = 0.001) showed that individual consumers privately opted for higher risk than non-consumers, whereas risk judgements made in groups of either consumers or non-consumers were lower. Decisions made by groups of consumers were less risky than those made by groups of non-consumers (B = 1.23, P < 0.001).ConclusionsModerate alcohol consumption appears to produce a propensity among individuals towards increased risk-taking in deciding to drive while intoxicated, which can be mitigated by group monitoring processes within small (four- to six-person) groups

Extensional flow of nematic liquid crystal under electric field gradient

Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fi bers), albeit with a modi fied "Trouton ratio". However, with a symmetry-breaking electric field gradient applied, behavior deviates from the Newtonian case, and the sheet can undergo fi nite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations

Heme iron from meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved

Red meat and processed meat intake is associated with a risk of colorectal cancer, a major cause of death in affluent countries. Epidemiological and experimental evidence supports the hypothesis that heme iron present in meat promotes colorectal cancer. This meta-analysis of prospective cohort studies of colon cancer reporting heme intake included 566,607 individuals and 4,734 cases of colon cancer. The summary relative risk of colon cancer was 1.18 [95%C.I.: 1.06-1.32] for subjects in the highest category of heme iron intake compared with those in the lowest category. Epidemiological data thus show a suggestive association between dietary heme and risk of colon cancer. The analysis of experimental studies in rats with chemically-induced colon cancer showed that dietary hemoglobin and red meat consistently promote aberrant crypt foci, a putative pre-cancer lesion. The mechanism is not known, but heme iron has a catalytic effect on (i) the endogenous formation of carcinogenic N-nitroso compounds and (ii) the formation of cytotoxic and genotoxic aldehydes by lipoperoxidation. A review of evidence supporting these hypotheses suggests that both pathways are involved in heme iron toxicit

The Spin-down of Swift J1822.3-1606: A New Galactic Magnetar

On 2011 July 14, a new magnetar candidate, Swift J1822.3-1606, was identified via a rate trigger on the Swift/Burst Alert Telescope. Here we present an initial analysis of the X-ray properties of the source, using data from the Rossi X-ray Timing Explorer, Swift, and the Chandra X-ray Observatory, spanning 2011 July 16--September 22. We measure a precise spin period of P=8.43771963(5) s and a spin-down rate of 2.97(28)E-13, at MJD 55761.0, corresponding to an inferred surface dipole magnetic field strength of B=5.1E13 G, the second lowest thus far measured for a magnetar, though similar to 1E~2259+586 as well as to several high-magnetic field radio pulsars. We show that the pulsed X-ray flux decay in the 2--10 keV band is best fit by an exponential with a time constant of 16.4+/-0.3 days. After increasing from ~35% during the first week after the onset of the outburst, the pulsed fraction in the 2--10 keV band remained constant at ~45. We argue that these properties confirm this source to be a new member of the class of objects known as magnetars.Comment: 7 pages, 3 figures. Submitted to the Astrophysical Journal Letter

The influence of mothers' and fathers' parenting stress and depressive symptoms on own and partner's parent-child communication

This study examines how parenting stress and depressive symptoms experienced by mothers and fathers influence their own (actor effects) and the partner's (partner effects) parent–child communication. Based on the Actor-Partner Interdependence Model, data from 196 families were analyzed, with both parents rating their parenting stress and depressive feelings, and parents as well as children rating the open parent–child communication. Actor effects were found between parenting stress and open parent–child communication, whereas partner effects were prominent between depressive symptoms and open parent–child communication. The results provide no evidence for gender differences in the strength of the pathways to open parent–child communication. Our findings demonstrate the need to include both parents in studies on parent–child communication to enhance our understanding of the mutual influence among family members