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PubMed2003

Molecular clocks and explosive radiations.

Molecular data are ideal for exploring evolutionary history because of its universality, stochasticity, and abundance. These features provide a means of exploring the evolutionary history of all organisms (including those that do not tend to leave fossils), potentially within a statistical framework that allows testing of evolutionary hypotheses. However, the discrepancy between molecular and paleontological dates for three key "explosive" radiations inferred from the fossil record--the Cambrian explosion of animal phyla and the post-KT radiations of modern orders of mammals and birds--have led to a reexamination of the assumptions on which molecular dates are based. Could variation in the rate of molecular evolution, perhaps associated with "explosive" radiations, cause overestimation of diversification dates? Here I examine four hypothetical causes of fast molecular rates in explosive radiations--body size, morphological rate, speciation rate, and ecological diversification--using available empirical evidence on patterns of variation in rate of molecular evolution.

Animals↗
PubMed1998

Metabolism of explosive compounds by sulfate-reducing bacteria.

The metabolism of various explosive compounds-1,3,5-trinitrobenzene (TNB), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX)-by a sulfate-reducing bacterial consortium, Desulfovibrio spp., was studied. The results indicated that the Desulfovibrio spp. used all of the explosive compounds studied as their sole source of nitrogen for growth. The concentrations of TNB, RDX, and HMX in the culture media dropped to below the detection limit (<0.5 ppm) within 18 days of incubation. We also observed the production of ammonia from the nitro groups of the explosive compounds in the culture media. This ammonia served as a nitrogen source for the bacterial growth, and the concentration of ammonia later dropped to <0.5 mg/L. The sulfate-reducing bacteria may be useful in the anaerobic treatment of explosives-contaminated soil.

Ammonia↗
PubMed1993

Post Gulf war explosive injuries in liberated Kuwait.

We collected the statistics of the victims affected by explosive injuries in liberated Kuwait during the period March to December 1991. Included were 1679 patients treated at nine different hospitals in Kuwait. As members of a trauma team, we, the plastic surgeons, were involved in the care of 152 victims of explosive injuries admitted at Al-Razi Orthopaedic Hospital. The records of these patients were reviewed in detail and the results were analysed. Of the patients, 58 had penetrating wounds and 94 explosive blast wounds. In all, 69 patients (45.3 per cent) were found to have associated fractures, 8 (5.3 per cent) had vascular injuries and in 10 (6.5 per cent) a nerve was also involved. There were 41 patients (26.9 per cent) who required amputations. The mainstay of surgical treatment was adequate wound excision, skeletal fixation and soft tissue coverage. Split-skin grafts were used in 34 patients, local flaps in seven and free flaps in four. Most patients healed within 2-3 weeks. There were 10 patients with explosive blast wounds who developed infection and needed staged wound excision before providing final coverage.

Adolescent↗
PubMed2004

Damage caused to fibres by vapour cloud explosions.

Research on the very specific damage to single textile fibres caused by vapour cloud explosions is presented. Vapour cloud explosion experiments were carried out using a selection of 41 garments differing in colour, fibre composition and textile construction. Fibres subjected to a vapour cloud explosion become wider at the end, often taking the form of a ball, bulb or shovel, while the morphological structure of the remaining part of the fibre remains almost unchanged. The presented results can clearly indicate that an explosion took place at the scene of the crime. The authors would like to be able to provide investigators with specific information on how to link clothes (and thus people) to a specific type of crime.

Journal Article↗
PubMed2006

Using molecular recognition of beta-cyclodextrin to determine molecular weights of low-molecular-weight explosives by MALDI-TOF mass spectrometry.

This study presents a novel method for determining the molecular weights of low molecular weight (MW) energetic compounds through their complexes of beta-cyclodextrin (beta-CD) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in a mass range of 500 to 1700 Da, avoiding matrix interference. The MWs of one composite explosive composed of 2,6-DNT, TNT, and RDX, one propellant with unknown components, and 14 single-compound explosives (RDX, HMX, 3,4-DNT, 2,6-DNT, 2,5-DNT, 2,4,6-TNT, TNAZ, DNI, BTTN, NG, TO, NTO, NP, and 662) were measured. The molecular recognition and inclusion behavior of beta-CD to energetic materials (EMs) were investigated. The results show that (1) the established method is sensitive, simple, accurate, and suitable for determining the MWs of low-MW single-compound explosives and energetic components in composite explosives and propellants; and (2) beta-CD has good inclusion and modular recognition abilities to the above EMs.

Journal Article↗
PubMed2001

Steam-explosion of olive stones: hemicellulose solubilization and enhancement of enzymatic hydrolysis of cellulose.

Olive stones (whole stones and seed husks in fragments) were processed by steam-explosion under different experimental conditions of temperature and time, 200-236 degrees C for 2-4 min, with or without previous acid impregnation with 0.1%, H2SO4 (w/w). This paper examines the solubilization of hemicelluloses and their molecular weight distribution. The subsequent enzymatic hydrolysis of the solid residue, using a preparation of cellulase, was also studied. The maximum yield of the pentosan recovered in the water solution was 63% pentose in the starting material for seed husk treated at 200 degrees C for 2 min (log R0 3.24) prior to acid-impregnation, or at 215 degrees C for 2 min (log R0 3.69) without acid, compared to 39% of the potential yield for whole stones pre-impregnated with acid under more severe conditions (at log R0 = 4.07). This indicates that the autohydrolysis of hemicellulose in seed husks when compared to whole stones is enhanced. The molecular weight distribution of profile sugars showed that the depolymerization of hemicelluloses is a function of the severity of the treatment. Steam-explosion improved the accessibility of the cellulose and increased the enzymatic hydrolysis yield after steam-explosion with respect to material without steam explosion (ball-milled material), although little increase in the extent of saccharification occurred when the alkali-soluble lignin was removed. Only when the substrate was post-treated with Na-chlorite was the enzymatic hydrolysis improved, the water-insoluble residue being almost completely hydrolyzed in 8 h of incubation.

Atmospheric Pressure↗
PubMed2000

Neuromuscular responses to explosive and heavy resistance loading.

The EMG power spectrum may shift towards higher frequencies with higher movement velocities. Fatigue, on the other hand, can cause a decrease in the frequency components. The purpose of this study was to examine acute effects of explosive (EE) and heavy resistance (HRE) concentric leg press exercise on muscle force, EMG and blood lactate. The EE included five sets of ten repetitions with 40+/-6% of the isometric maximum at a 100 degrees knee angle performed as explosively as possible. The same number of repetitions was performed in HRE but with a heavier load (67+/-7% of the isometric maximum at a 100 degrees knee angle). Maximal isometric and single concentric actions of different loads, and an isometric fatigue test were measured before and after both exercises. Surface EMG was recorded from the vastus medialis muscles for analyses of average EMG (aEMG) and EMG power spectrum. Muscle fiber composition of the vastus lateralis was determined and blood lactate measured throughout the exercises. Mean power frequency and median frequency were higher during EE than during HRE (P<0.05). They increased during EE (P<0.05) as the exercise progressed, whereas during HRE no change or even slight decreases were observed. Signs of fatigue after pure concentric work were not observed after EE, and even after HRE, possibly due to the relatively small range of motion and short duration of action time, the fatigue was not that extensive. The relative number of fast twitch fibers was correlated (r=0.87, P<0.05) with the change in blood lactate in HRE. It was concluded that there may be a greater use of fast twitch motor units in explosive movements and that instead of fatigue, the present number of concentric actions in explosive exercise seems to have facilitated the neuromuscular system.

Adult↗
PubMed2002

Composition of explosives by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

Commercial explosives are complex mixtures that contain not only the active explosive agent(s) but also a host of other organic and inorganic compounds. The ultrahigh mass resolving power (m/delta m50% >200,000) and mass accuracy (<1 ppm) of electrospray ionization Fourier transform ion cyclotron resonance (ESI FTICR) mass spectrometry allow for definitive identification of various species in TNT, RDX, and HMX. We are thereby able to correct prior misassignments of the elemental compositions of the most abundant negative ions from electrospray of RDX and HMX. Although the (known) active agents of many explosives may be identified by low-resolution MS or MS/MS, it is the other characteristic components (indigenous or artificial additives) whose presence and elemental composition can potentially identify the source of the product. ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue. In contrast, the residue recovered from an explosion of military C4 yielded several species derived from RDX but virtually none from other ingredients.

Journal Article↗
PubMed2005

Archiving and absolute quantitation of solutes separated by single charged droplet coulomb explosion.

The electrospray (ES) ion source relies on the transfer of low-volatility solutes to the gas phase as an outcome of coulomb explosion events of charged droplets generated by electrical atomization. Introduced here are two methods for archiving compounds separated by coulomb explosion of single droplets having net charge that had been levitated in an electrodynamic balance. We categorized compounds separated by the explosion as either material ejected, including progeny droplets, or the material retained in the main residue. The potential for this methodology is illustrated by (i) qualitative characterization of solute states, aqueous versus precipitated in the separated material, and (ii) absolute quantitation of solutes separated by such an event. For a droplet containing 5 x 10(7) 20-nm-diameter fluospheres, its first encountered coulomb explosion event resulted in the ejection of 1.70% of them. The capability to acquire such detailed information regarding the individual steps in the process of transferring low-volatility solutes to the gas phase in an ES ion source is essential to develop strategies for absolute quantitation in applications of ES mass spectrometry.

Journal Article↗
PubMed2005

Multidimensional detection of nitroorganic explosives by gas chromatography-pyrolysis-ultraviolet detection.

We describe a new methodology for the trace detection of organic explosives containing nitro functionalities. Conventional gas chromatography separates the components of an explosive mixture. Effluent from the gas chromatograph is pyrolyzed by passage over a heated Nichrome wire. Nitric oxide produced on pyrolysis of a nitroorganic compound is then detected by ultraviolet absorption spectroscopy between 180 and 240 nm, using a deuterium lamp as the light source. Nitric oxide exhibits a sharply banded, characteristic spectrum in this region, enabling detection of nitroorganics. The system is tested using the explosive simulants nitrobenzene and 2,4-dinitrotoluene, and with the nitramine explosive tetryl. Detection limits are 25 ng for nitrobenzene and 50 ng for 2,4-dinitrotoluene. Tetryl is detected with a detection limit of 50 ng. The system is both easy to implement and could be built as a compact, low-power device.

Journal Article↗
PubMed2005

Application of photoassisted electrochemical detection to explosive-containing environmental samples.

High-performance liquid chromatography (HPLC) with ultraviolet (UV) absorbance and photoassisted electrochemical detection (PAED) is applied to the determination of explosives in groundwater and soil samples. On-line, solid-phase extraction minimizes sample pretreatment, enabling direct analysis of groundwater samples and soil extracts. Soils are extracted using pressurized fluid extraction, which is compared to the Environmental Protection Agency (EPA) sonication method. Limits of detection for explosives in the matrixes of interest are equivalent or superior (i.e., <10 parts-per-trillion for HMX) to those achieved using the EPA method 8330. HPLC-UV-PAED is also shown here to be more broadly applicable, as it is capable of determining nitro compounds of interest (e.g., nitroglycerin) that have poor UV chromophores. Additional selectivity of amine-substituted nitroaromatic explosives is achieved by using a photochemical reactor with a 366-nm wavelength lamp. By coupling reversed-phase columns of different selectivities together, baseline resolution of all 14 standard explosives is demonstrated.

Chromatography, High Pressure Liquid↗
PubMed2003

The explosion of knowledge, references, and citations. Psychology's unique response to a crisis.

The knowledge explosion has created enormous difficulties for researchers to be aware of, access, and process the volume of new literature. Electronic literature retrieval systems and specialization on narrow topics have been strategies used to cope with these problems. In this study, the authors examined the additional effects of the knowledge explosion on researchers' writing, referencing, and citing. Counts of references within sampled empirical journal articles in sociology, physics, biology, and experimental and social psychology revealed impacts of the knowledge explosion in all disciplines but the greatest effects within psychology. Detailed analyses indicated that substantial changes in the numbers of references and citations and in their format and use within the research article are psychology's unique response to the knowledge explosion.

Humans↗
PubMed2002

A chip-based capillary electrophoresis-contactless conductivity microsystem for fast measurements of low-explosive ionic components.

A miniaturized analytical system for separating and detecting inorganic explosive residues, based on the coupling of a micromachined capillary electrophoresis (CE) chip with a contactless conductivity detector is described. The low electroosmotic flow (EOF) of the poly(methylmethacrylate) (PMMA) chip material facilitates the rapid switching between analyses of cations and anions using the same microchannel and run buffer (and without an EOF modifier), and hence offers rapid (< 1 min) measurement of seven explosive-related cations and anions. Experimental parameters relevant to the separation and detection processes have been optimized. Addition of a 18-crown-6 ether modifier has been used for separating the peaks of co-migrating potassium and ammonium ions. The ionic-explosive microchip system combines the distinct advantages of contactless conductivity detection with the attractive features of plastic CE microchips. The new microsystem offers great promise for monitoring explosive-related ions at the sample source, with significant advantages of speed/warning, efficiency, cost, or sample size.

Electrophoresis, Capillary↗
PubMed1986

Yields of Soviet underground nuclear explosions at Novaya Zemlya, 1964-1976, from seismic body and surface waves.

Surface and body wave magnitudes are determined for 15 U.S.S.R. underground nuclear weapons tests conducted at Novaya Zemlya between 1964 and 1976 and are used to estimate yields. These events include the largest underground explosions detonated by the Soviet Union. A histogram of body wave magnitude (m(b)) values indicates a clustering of explosions at a few specific yields. The most pronounced cluster consists of six explosions of yield near 500 kilotons. Several of these seem to be tests of warheads for major strategic systems that became operational in the late 1970s. The largest Soviet underground explosion is estimated to have a yield of 3500 +/- 600 kilotons, somewhat smaller than the yield of the largest U.S. underground test. A preliminary estimation of the significance of tectonic release is made by measuring the amplitude of Love waves. The bias in m(b) for Novaya Zemlya relative to the Nevada test site is about 0.35, nearly identical to that of the eastern Kazakhstan test site relative to Nevada.

Journal Article↗
PubMed2002

Explosive power and asymmetry in leg muscle function in frequent fallers and non-fallers aged over 65.

BACKGROUND: although low strength is a risk factor for falls, lower limb explosive power is more predictive of functional difficulties than strength. Power may be more predictive of a future fall than strength per se. OBJECTIVE: to compare leg muscle strength and explosive power and asymmetry of leg strength and power of women aged 65 or over living at home, with and without a history of falls. DESIGN: a case controlled study of self-reported 'fallers' versus 'non-fallers'. SUBJECTS: twenty women, aged 65 or over, with a history of at least three falls in the previous year were age matched with 15 women with no history of falls in the previous year. METHODS: lower limb explosive power, isometric strength of the quadriceps and hamstrings, isokinetic concentric strength (100 degrees/sec) of the quadriceps, hamstrings, ankle plantar- and dorsi-flexors and quadriceps eccentric strength (100 degrees/sec). Habitual physical activity was assessed using the self-completed Habitual Activity Profile Questionnaire. RESULTS: the women with a history of falls were less active but were not significantly weaker in any of the strength measurements, apart from ankle dorsiflexion adjusted for body weight. Both groups had significant asymmetry in all the leg muscles for both strength and power. Although both groups were asymmetrical in their lower limb power, the fallers demonstrated a significantly greater asymmetry. When the least powerful legs were compared, the women with a history of falls were 24% less powerful for their weight than those who did not fall (P=0.04). CONCLUSIONS: weakness and asymmetry is prevalent in women aged 65 and over, with and without a history of falls. Poor lower limb explosive power combined with asymmetry between limbs may be more predictive of future falls than more traditional measurements of strength in older women who live independently.

Accidental Falls↗
PubMed2003

Thermodynamic evolution of phase explosion during high-power nanosecond laser ablation.

It is argued that phase explosion plays an important role during high-power laser ablation. A theoretical model which includes the effect of an expanding mass plasma has been developed to describe the process of phase explosion during the interactions of a high-power nanosecond laser pulse on an aluminum target. For a laser with a 3-ns pulse duration, if the laser intensity is high enough (>or=5 x 10(10) W/cm(2)), phase explosion was found to occur after the completion of the laser pulse, but not during the process of laser energy deposition. This result is consistent with recent experiments. It is also found that the pressure of the induced ablation plasma plays a crucial role in the process of phase explosion.

Journal Article↗
PubMed2003

Collapses and explosions in self-gravitating systems.

Collapse and explosion (reverse to collapse) transitions in self-gravitating systems are studied by molecular dynamics simulations. A microcanonical ensemble of point particles confined to a spherical box is considered. The particles interact via an attractive soft Coulomb potential. It is observed that a collapse indeed takes place when the energy of the uniform state is set near or below the metastability-instability threshold (collapse energy) as predicted by the mean-field theory. Similarly, an explosion occurs when the energy of the core-halo state is increased above the explosion energy, where according to the mean-field predictions the core-halo state becomes unstable. For systems consisting of 125-500 particles, the collapse takes about 10(5) single-particle crossing times to complete, while a typical explosion is by an order of magnitude faster. A finite lifetime of metastable states is observed. It is also found that the mean-field description of the uniform and core-halo states is exact within the statistical uncertainty of the molecular dynamics data.

Journal Article↗
PubMed2004

Routes to control of H2 Coulomb explosion in few-cycle laser pulses.

We have measured coincident ion pairs produced in the Coulomb explosion of H2 by 8-30 fs laser pulses at different laser intensities. We show how the Coulomb explosion of H2 can be experimentally controlled by tuning the appropriate pulse duration and laser intensity. For laser pulses less than 15 fs, we found that the rescattering-induced Coulomb explosion is dominated by first-return recollisions, while for longer pulses and at the proper laser intensity, the third return can be made to be the major one. Additionally, by choosing suitable pulse duration and laser intensity, we show H2 Coulomb explosion proceeding through three distinct processes that are simultaneously observable, each exhibiting different characteristics and revealing distinctive time information about the H2 evolution in the laser pulse.

Journal Article↗