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PubMedDate not supplied

Influence of familiarization on a backward, overhead medicine ball explosive power test.

This study examined the influence of familiarization with the backward, overhead medicine ball throw test of explosive power. Male rugby players (N = 28) aged 15 to 16 (M +/- SD = 15.1 +/- 0.5) years completed the medicine ball throw six times. Repeated measures ANOVA indicated that the distance thrown differed across trials (F5,135 = 12.83, p < 0.01). Least significant differences post hoc multiple comparisons revealed significant differences between a number of trials; however, no significant difference was evident between the fifth and sixth trials (Mdiff = .005, p > 0.05). Typical error of measurement became less as trials progressed, with the typical error of measurement being 0.10 m between the fifth and sixth trials indicating little within subject variation between medicine ball throws following a familiarization period. The backward, overhead medicine ball throw may be a practical, reliable method to assess total body, explosive power of male teen-aged rugby players; however, completion of at least 5 to 6 practice trials is suggested for participants to obtain a stable score.

Adolescent↗
PubMed1990

Explosive onset of continuous wave laser tissue ablation.

The phenomena at the onset of and during tissue ablation using continuous wave lasers were studied. Aortic and myocardial bovine tissues were exposed in air and in water to Nd-YAG (10 to 60 W) and argon (3.5 W) laser light. The transmitted light was measured, the surface of the tissue was filmed and the tissue was processed for histology. Three distinct phases were observed. Phase A was tissue denaturation. Phase B started with explosive vaporisation ('popcorn') in conjunction with a drop of about 50% in light transmission due to enhanced reflection and scattering. The 'popcorn' is possibly associated with a layered structure of the tissue. Phase C started with carbonisation of the tissue beginning in the centre and expanding in a cyclic fashion while the tissue was vaporised leaving a crater. Forward light transmission did not decrease. Thin layers of carbon (20 microns) and vacuoles (30 microns) suggested a large temperature gradient along the tissue ablation front. The ablation velocity was constant (r greater than 0.92) and tissue dependent. Reported models on laser tissue ablation need to be extended to include explosive vaporisation ('popcorn') at the onset and cyclic carbonisation during steady-state crater formation.

Animals↗
PubMed2002

Treatment of mood lability and explosive rage with minerals and vitamins: two case studies in children.

A micronutrient supplement containing a broad range of dietary minerals and vitamins is being examined for the treatment of mood lability in both adults and children (Kaplan et al. 2001; Popper 2001). During pilot work, two medication-free boys with mood lability and explosive rage were studied in an open-label treatment followed by reversal and retreatment. One child was an 8-year-old with atypical obsessive-compulsive disorder, and the other was a 12-year-old with pervasive developmental delay. Both boys were monitored using the mood and temper items from the Conners Parent Rating Scale, as well as the Child Behavior Checklist. In addition, the boy with atypical obsessive-compulsive disorder was monitored with the child version of the Yale-Brown Obsessive Compulsive Scale. Both boys benefited from the micronutrient supplement when examined in ABAB designs: mood, angry outbursts, and obsessional symptoms improved when initially treated, returned when not taking the supplement, and remitted when the micronutrient supplement was reintroduced. Both boys have been followed and are stable on the nutritional supplement for over 2 years. These cases suggest that mood lability and explosive rage can, in some cases, be managed with a mixture of biologically active minerals and vitamins, without using lithium or other traditional psychopharmacologic agents.

Child↗
PubMed2005

Optimal load for increasing muscle power during explosive resistance training in older adults.

BACKGROUND: Muscle power (force x velocity) recedes at a faster rate than strength with age and may also be a stronger predictor of fall risk and functional decline. The optimal training paradigm for improving muscle power in older adults is not known, although some literature suggests high velocity, low load training is optimal in young adults. METHODS: One hundred twelve healthy older adults (69 +/- 6 years) were randomly assigned to either explosive resistance training at 20% (G20), 50% (G50), or 80% (G80) one repetition maximum (1RM) for 8-12 weeks or to a nontraining control group (CON). Participants trained twice per week (five exercises; three sets of eight rapidly concentric and slow eccentric repetitions) using pneumatic resistance machines. Repeated-measures analysis of variance and covariance (ANOVA and ANCOVA) were used to determine the effects of training. RESULTS: Average peak power increased significantly and similarly in G80 (14 +/- 8%), G50 (15 +/- 9%), and G20 (14 +/- 6%) compared to CON (3 +/- 6%) (p < .0001). By contrast, a positive dose-response relationship with training intensity was observed for relative changes in average strength (r = .40, p = .0009) and endurance (r = .43, p = .0005). Average strength increased in G80 (20 +/- 7%), G50 (16 +/- 7%), and G20 (13 +/- 7%) compared to CON (4 +/- 4%) (p < .0001). Average muscle endurance increased in G80 (185 +/- 126%, p < .0001), G50 (103 +/- 75%, p = .0004), and G20 (82 +/- 57%, p = .0078) compared to CON (28 +/- 29%). CONCLUSION: Peak muscle power may be improved similarly using light, moderate, or heavy resistances, whereas there is a dose-response relationship between training intensity and muscle strength and endurance changes. Therefore, using heavy loads during explosive resistance training may be the most effective strategy to achieve simultaneous improvements in muscle strength, power, and endurance in older adults.

Age Factors↗
PubMed2004

Molecular clocks do not support the Cambrian explosion.

The fossil record has long supported the view that most animal phyla originated during a brief period approximately 520 MYA known as the Cambrian explosion. However, molecular data analyses over the past 3 decades have found deeper divergences among animals (approximately 800 to 1,200 MYA), with and without the assumption of a global molecular clock. Recently, two studies have instead reported time estimates apparently consistent with the fossil record. Here, we demonstrate that methodological problems in these studies cast doubt on the accuracy and interpretations of the results obtained. In the study by Peterson et al., young time estimates were obtained because fossil calibrations were used as maximum limits rather than as minimum limits, and not because invertebrate calibrations were used. In the study by Aris-Brosou and Yang, young time estimates were obtained because of problems with rate models and other methods specific to the study, and not because Bayesian methods were used. This also led to many anomalous findings in their study, including a primate-rodent divergence at 320 MYA. With these results aside, molecular clocks continue to support a long period of animal evolution before the Cambrian explosion of fossils.

Animals↗
PubMed2006

Mitochondrial genomes and avian phylogeny: complex characters and resolvability without explosive radiations.

We improve the taxon sampling for avian phylogeny by analyzing 7 new mitochondrial genomes (a toucan, woodpecker, osprey, forest falcon, American kestrel, heron, and a pelican). This improves inference of the avian tree, and it supports 3 major conclusions. The first is that some birds (including a parrot, a toucan, and an osprey) exhibit a complete duplication of the control region (CR) meaning that there are at least 4 distinct gene orders within birds. However, it appears that there are regions of continued gene conversion between the duplicate CRs, resulting in duplications that can be stable for long evolutionary periods. Because of this stable duplicated state, gene order can eventually either revert to the original order or change to the new gene order. The existence of this stable duplicate state explains how an apparently unlikely event (finding the same novel gene order) can arise multiple times. Although rare genomic changes have theoretical advantages for tree reconstruction, they can be compromised if these apparently rare events have a stable intermediate state. Secondly, the toucan and woodpecker improve the resolution of the 6-way split within Neoaves that has been called an "explosive radiation." An explosive radiation implies that normal microevolutionary events are insufficient to explain the observed macroevolution. By showing the avian tree is, in principle, resolvable, we demonstrate that the radiation of birds is amenable to standard evolutionary analysis. Thirdly, and as expected from theory, additional taxa breaking up long branches stabilize the position of some problematic taxa (like the falcon). In addition, we report that within the birds of prey and allies, we did not find evidence pairing New World vultures with storks or accipitrids (hawks, eagles, and osprey) with Falconids.

Animals↗
PubMed2002

Explosive spread and high prevalence of HIV infection among injecting drug users in Togliatti City, Russia.

OBJECTIVE: To establish the prevalence of antibodies to HIV (anti-HIV) and associated risk factors among injecting drug users (IDU) in Togliatti City, Samara Oblast, Russian Federation. DESIGN: An unlinked anonymous cross-sectional community recruited survey with oral fluid sample collection. METHODS: Between September and October 2001, 426 IDU were recruited by trained fieldworkers. Participants completed an interviewer administered questionnaire, and oral fluid samples were tested for anti-HIV. Univariate and multivariate analyses compared potential risk factors for anti-HIV. RESULTS: Anti-HIV prevalence was 56% (234/418). Three-quarters of anti-HIV-positive IDU (74%) were unaware of their positive status. In an adjusted model, the odds of HIV infection were higher among IDU who had ever injected home-produced drugs, who reported injecting with used needles and syringes in the past 4 weeks, and who were living in one particular district of the city (Komsomolksii). CONCLUSION: The high prevalence of HIV, and a recent increase in HIV detected through routine screening tests since 2000, suggests that an explosive epidemic has occurred among IDU in Togliatti City. In the face of currently inadequate HIV prevention coverage among IDU, this has urgent implications for maximizing the distribution of sterile injecting equipment as well as for enhancing sexual risk reduction. Recognizing that it is likely that similar explosive epidemics are taking place in other Russian cities, we recommend community-wide HIV prevention coverage supported by city and state policies oriented to harm reduction.

AIDS Serodiagnosis↗
PubMed1990

Additional calculations of radionuclide production following nuclear explosions and Pu isotopic ratios for Nevada Test Site events.

A method is reviewed for calculating dry ground deposition of any radionuclide in off-site fallout from a nuclear explosion. Calculations are in agreement with measurements. A list of all calculations to date is presented, along with how to obtain copies. In addition, a table of ratios of 240Pu:239Pu and 241Pu:239Pu for NTS explosions is included.

Environmental Exposure↗
PubMed1998

Effects of explosive brain death on cytokine activation of peripheral organs in the rat.

BACKGROUND: The success rate of transplanted organs from brain-dead cadaver donors is consistently inferior to that of living sources. As cadaver and living unrelated donors are equally genetically disparate with a given recipient, the difference must lie within the donor himself and/or the effects of organ preservation and storage. We have hypothesized that irreversible central nervous system injury may up-regulate proinflammatory mediators and cell surface molecules in peripheral organs to be engrafted, making them more prone to host inflammatory and immunological responses. METHODS: Rats undergoing surgically induced acutely increased intracranial pressure (explosive brain death) were followed for 6 hr. Their peripheral tissues were examined by reverse transcriptase polymerase chain reaction and immunohistology, serum factors were assessed by enzyme-linked immunosorbent assay, and the influence of inflammatory molecules in the blood stream was determined by cross-circulation experiments with normal animals. RESULTS: mRNA expression of both lymphocyte- and macrophage-associated products increased dramatically in all tissues. Similar factors in serum were coincidentally increased; these were shown to be active in vivo by cross-circulation with normal animals. The organs of all control groups, including animals with important ischemic injury and with hemorrhagic shock, were negative. Up-regulation of MHC class I and II antigens and the co-stimulatory molecule B7 suggests increased immunogenicity of the peripheral organs. These changes could be inhibited by: (i) administration of a recombinant soluble P-selectin glycoprotein ligand-Ig, a P- and E-selectin antagonist; and (ii) a fusion protein, cytotoxic T lymphocyte antigen 4-Ig, which blocks B7-mediated T-cell co-stimulation. CONCLUSIONS: Activation of peripheral organs following explosive brain death may be caused by various interrelated events, including the effects of massive acute central injury, hypotension, and circulating factors. Almost complete suppression of these changes could be produced by biological agents. Such interventions, if reproducible in humans, could improve the quality of organs from "marginal" donors, broadening the criteria for donor acceptance.

Animals↗
PubMed2000

Can fast early rates reconcile molecular dates with the Cambrian explosion?

Molecular dates consistently place the divergence of major metazoan lineages in the Precambrian, leading to the suggestion that the 'Cambrian explosion' is an artefact of preservation which left earlier forms unrecorded in the fossil record. While criticisms of molecular analyses for failing to deal with variation in the rate of molecular evolution adequately have been countered by analyses which allow both site-to-site and lineage-specific rate variation, no analysis to date has allowed the rates to vary temporally. If the rates of molecular evolution were much higher early in the metazoan radiation, molecular dates could consistently overestimate the divergence times of lineages. Here, we use a new method which uses multiple calibration dates and an empirically determined range of possible substitution rates to place bounds on the basal date of divergence of lineages in order to ask whether faster rates of molecular evolution early in the metazoan radiation could possibly account for the discrepancy between molecular and palaeontological date estimates. We find that allowing basal (interphylum) lineages the fastest observed substitution rate brings the minimum possible divergence date (586 million years ago) to the Vendian period, just before the first multicellular animal fossils, but excludes divergence of the major metazoan lineages in a Cambrian explosion.

Animals↗
PubMed2006

The effects and consequences of very large explosive volcanic eruptions.

Every now and again Earth experiences tremendous explosive volcanic eruptions, considerably bigger than the largest witnessed in historic times. Those yielding more than 450km3 of magma have been called super-eruptions. The record of such eruptions is incomplete; the most recent known example occurred 26000 years ago. It is more likely that the Earth will next experience a super-eruption than an impact from a large meteorite greater than 1km in diameter. Depending on where the volcano is located, the effects will be felt globally or at least by a whole hemisphere. Large areas will be devastated by pyroclastic flow deposits, and the more widely dispersed ash falls will be laid down over continent-sized areas. The most widespread effects will be derived from volcanic gases, sulphur gases being particularly important. This gas is converted into sulphuric acid aerosols in the stratosphere and layers of aerosol can cover the global atmosphere within a few weeks to months. These remain for several years and affect atmospheric circulation causing surface temperature to fall in many regions. Effects include temporary reductions in light levels and severe and unseasonable weather (including cool summers and colder-than-normal winters). Some aspects of the understanding and prediction of super-eruptions are problematic because they are well outside modern experience. Our global society is now very different to that affected by past, modest-sized volcanic activity and is highly vulnerable to catastrophic damage of infrastructure by natural disasters. Major disruption of services that society depends upon can be expected for periods of months to, perhaps, years after the next very large explosive eruption and the cost to global financial markets will be high and sustained.

Disaster Planning↗
PubMed2006

Darwin's dilemma: the realities of the Cambrian 'explosion'.

The Cambrian 'explosion' is widely regarded as one of the fulcrum points in the history of life, yet its origins and causes remain deeply controversial. New data from the fossil record, especially of Burgess Shale-type Lagerstätten, indicate, however, that the assembly of bodyplans is not only largely a Cambrian phenomenon, but can already be documented in fair detail. This speaks against a much more ancient origin of the metazoans, and current work is doing much to reconcile the apparent discrepancies between the fossil record, including the Ediacaran assemblages of latest Neoproterozoic age and molecular 'clocks'. Hypotheses to explain the Cambrian 'explosion' continue to be generated, but the recurrent confusion of cause and effect suggests that the wrong sort of question is being asked. Here I propose that despite its step-like function this evolutionary event is the inevitable consequence of Earth and biospheric change.

Animals↗
PubMed2000

Scaling behavior in explosive fragmentation

We investigate the explosive fragmentation process in two dimensions using molecular-dynamics simulations. We show that the mass distribution of fragments follows a power law, with a scaling exponent that is strongly dependent on the macroscopic characteristics of the system prior to the explosion process. In particular, for thermalized initial configurations at low temperatures, we observe that the exponent is close to -1. We suggest that this result can be interpreted in terms of a multiplicative fracture process.

Journal Article↗
PubMed2001

Explosion of limit cycles and chaotic waves in a simple nonlinear chemical system.

We consider a simple model of an autocatalytic chemical reaction where a limit cycle rapidly increases to infinite period and amplitude, and disappears under variation of a parameter. We show that this bifurcation can be understood from seeing the system as a singular perturbation problem, and we find the bifurcation point by an asymptotic analysis. Scaling laws for period and amplitude are derived. The unphysical bifurcation to infinity disappears under generic modifications of the model, and for a simple example we show is replaced by a canard explosion, that is, a narrow parameter interval with an explosive growth of the amplitude. The bifurcation to infinity introduces a strong sensitivity that may result in chaotic dynamics if diffusion is added. We show that this behavior persists even if the kinetics is modified to preclude the bifurcation to infinity.

Journal Article↗
PubMed2003

Front explosions in three-dimensional resonantly-forced oscillatory systems.

Interface dynamics in a three-dimensional coupled map lattice with a period-3 local map is studied. The system possesses a parameter regime where one typically finds three-phase patterns consisting of spatially uniform domains which follow the period-3 cycle and oscillate among the three different phases. The interfaces where these domains meet may exhibit complex irregular dynamics. The system also has a parameter regime of "turbulent" dynamics, which is a chaotic transient with a superexponentially long lifetime. The transition from the three-phase pattern regime to the turbulent regime is studied. As a control parameter is tuned, the interfaces between domains develop turbulent structure. The thickness of the turbulent zone remains finite up to a critical parameter value after which it is infinite. We characterize this "front explosion" transition in three-dimensional systems and compare it with the analogous transition in two-dimensional systems where the critical properties are markedly different. The front explosion in the three-dimensional resonantly-forced complex Ginzburg-Landau equation is also investigated briefly and its character differs from that in the three-dimensional coupled map lattice.

Journal Article↗
PubMed2003

Sensitivity of explosion to departure from partial equilibrium.

We study a thermochemical gaseous system in the vicinity of the bifurcation related to the emergence of bistability. Corrections to the standard deterministic dynamics induced by the perturbation of the particle velocity distribution are obtained from the solution of the Boltzmann equation. Using these results, analytical expressions including the nonequilibrium effects are derived for the ignition time in the explosive regime and mean first passage time in the bistable regime. It is demonstrated that a departure from partial equilibrium can shift the bifurcation point. The system which was bistable according to the standard deterministic approach, can become monostable and explosive in the presence of nonequilibrium effects. Even when the system remains in the bistable regime, the mean first passage time can be changed by several orders of magnitude. In the monostable domain, the ignition time can be about ten times smaller than the unperturbed value. These analytical predictions agree well with the results of the microscopic simulations of the dilute gas system.

Journal Article↗
PubMed2003

Coulomb explosions and energy loss of molecular ions in plasmas.

Interactions of swift molecular ions with high-density plasma targets are studied by means of the linearized Vlasov-Poisson theory, allowing the dynamically screened interaction potential among the constituent ions to be expressed in terms of the classical plasma dielectric function. Coulomb explosions and the energy losses of a molecular ion are simulated by solving the equations of motion for the constituent ions. It is found that, due to the wakelike asymmetry of the interaction potential, the molecular axis tends to align itself along the beam direction. In addition, a strong enhancement of the energy loss of the molecular ion has been found in the initial stages of Coulomb explosions due to proximity of the constituent ions, but this effect diminishes at latter stages when the ions are sufficiently far apart.

Journal Article↗
PubMed2005

Breakup of shells under explosion and impact.

A theoretical and experimental study of the fragmentation of closed thin shells made of a disordered brittle material is presented. Experiments were performed on eggshells under two different loading conditions: fragmentation due to an impact with a hard wall and explosion by a combustion mixture giving rise to power law fragment size distributions. For the theoretical investigations a three-dimensional discrete element model of shells is constructed. Molecular dynamics simulations of the two loading cases resulted in power law fragment mass distributions in satisfactory agreement with experiments. Based on large scale simulations we give evidence that power law distributions arise due to an underlying phase transition which proved to be abrupt and continuous for explosion and impact, respectively. Our results demonstrate that the fragmentation of closed shells defines a universality class, different from that of two- and three-dimensional bulk systems.

Journal Article↗