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At least 721 records · Page 40Linked to original sources
PubMed1979

A theory of light-induced explosion.

This paper presents a theoretical analysis, based on a simplified one-dimensional model, of the response of an explosive to a wide range of light intensities. A primary result has been the identification and development of a relationship among the important critical parameters. Numerical results illustrating the relationship among the critical light intensity, sample dimension, and ambient temperature have been obtained, with lead azide as the example.

Journal Article↗
PubMed1996

Mass extinctions and supernova explosions.

In a recent contribution to this journal Ellis and Schramm [Ellis, J. & Schramm, D. N. (1995) Proc. Natl. Acad. Sci. USA 92, 235-238] claim that supernova explosions can cause massive biological extinctions as a result of strongly enhanced stratospheric NOx (NO + NO2) production by accompanying galactic cosmic rays. They suggested that these NOx productions which would last over several centuries and occur once every few hundred million years would result in ozone depletions of about 95%, leading to vastly increased levels of biologically damaging solar ultraviolet radiation. Our detailed model calculations show, however, substantially smaller ozone depletions ranging from at most 60% at high latitudes to below 20% at the equator.

Journal Article↗
PubMed1998

Testing the Cambrian explosion hypothesis by using a molecular dating technique.

Molecular studies have the potential to shed light on the origin of the animal phyla by providing independent estimates of the divergence times, but have been criticized for failing to account adequately for variation in rate of evolution. A method of dating divergence times from molecular data addresses the criticisms of earlier studies and provides more realistic, but wider, confidence intervals. The data are not compatible with the Cambrian explosion hypothesis as an explanation for the origin of metazoan phyla, and provide additional support for an extended period of Precambrian metazoan diversification.

Animals↗
PubMed1998

The thermal explosion revisited.

The classical problem of the thermal explosion in a long cylindrical vessel is modified so that only a fraction alpha of its wall is ideally thermally conducting while the remaining fraction 1-alpha is thermally isolated. Partial isolation of the wall naturally reduces the critical radius of the vessel. Most interesting is the case when the structure of the boundary is a periodic one, so that the alternating conductive alpha and isolated 1-alpha parts of the boundary occupy together the segments 2pi/N (N is the number of segments) of the boundary. A numerical investigation is performed. It is shown that at small alpha and large N, the critical radius obeys a scaling law with the coefficients depending on N. For large N, the result is obtained that in the central core of the vessel the temperature distribution is axisymmetric. In the boundary layer near the wall having the thickness approximately 2pir0/N (r0 is the radius of the vessel), the temperature distribution varies sharply in the peripheral direction. The temperature distribution in the axisymmetric core at the critical value of the vessel radius is subcritical.

Journal Article↗
PubMed1999

Afterglows from the largest explosions in the universe.

The distinction of "largest explosions in the universe" has been bestowed on cosmic gamma-ray bursts. Their afterglows are brighter than supernovae and therefore are called hypernovae. Photometry and spectroscopy of these afterglows have provided major breakthroughs in our understanding of this mysterious phenomenon.

Journal Article↗
PubMed2004

Atomic resolution structures and solution behavior of enzyme-substrate complexes of Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase. Multiple conformational states and implications for the mechanism of nitroaromatic explosive degradation.

The structure of pentaerythritol tetranitrate (PETN) reductase in complex with the nitroaromatic substrate picric acid determined previously at 1.55 A resolution indicated additional electron density between the indole ring of residue Trp-102 and the nitro group at C-6 of picrate. The data suggested the presence of an unusual bond between substrate and the tryptophan side chain. Herein, we have extended the resolution of the PETN reductase-picric acid complex to 0.9 A. This high-resolution analysis indicates that the active site is partially occupied with picric acid and that the anomalous density seen in the original study is attributed to the population of multiple conformational states of Trp-102 and not a formal covalent bond between the indole ring of Trp-102 and picric acid. The significance of any interaction between Trp-102 and nitroaromatic substrates was probed further in solution and crystal complexes with wild-type and mutant (W102Y and W102F) enzymes. Unlike with wild-type enzyme, in the crystalline form picric acid was bound at full occupancy in the mutant enzymes, and there was no evidence for multiple conformations of active site residues. Solution studies indicate tighter binding of picric acid in the active sites of the W102Y and W102F enzymes. Mutation of Trp-102 does not impair significantly enzyme reduction by NADPH, but the kinetics of decay of the hydride-Meisenheimer complex are accelerated in the mutant enzymes. The data reveal that decay of the hydride-Meisenheimer complex is enzyme catalyzed and that the final distribution of reaction products for the mutant enzymes is substantially different from wild-type enzyme. Implications for the mechanism of high explosive degradation by PETN reductase are discussed.

2,4-Dinitrophenol↗
PubMed1991

Rates for repair of pBR 322 DNA radicals by thiols as measured by the gas explosion technique: evidence that counter-ion condensation and co-ion depletion are significant at physiological ionic strength.

Rates of repair of pBR 322 plasmid DNA radicals by thiols of varying net charge (Z) at pH 7 and physiological ionic strength were measured using the oxygen explosion technique. The extent of conversion of supercoiled to relaxed circular plasmid was measured by HPLC as a function of the time of oxygen exposure before or after irradiation, the time-courses being fitted by a pseudo-first-order kinetic expression with k1 = k2[RSH]. Values of k2 (M-1 S-1) were: 2.1 x 10(5) (GSH, Z = -1), 1.4 x 10(6) (2-mercaptoethanol, Z = 0), 1.2 x 10(7) (cysteamine, Z = +1), 6.6 x 10(7) (WR-1065 or N-(2-mercaptoethyl)-1,3-diaminopropane, Z = +2). The approximately 6-fold increase in rate with each unit increase in Z is attributed to concentration of cationic thiols near DNA as a consequence of counter-ion condensation and reduced levels of anionic thiols near DNA owing to co-ion depletion. The results are quantitatively consistent with chemical repair as a significant mechanism for radioprotection of cells by neutral and cationic thiols under aerobic conditions, but indicate that repair by GSH will compete effectively with oxygen only at low oxygen tension.

Chromatography, High Pressure Liquid↗
PubMed1993

Predicting the impact sensitivity of explosive molecules using neuromimetic networks.

A new method for predicting the impact sensitivity of explosive molecules is presented. This method makes use of a network of formal neurons. The experiment uses 124 molecules belonging to different families. The molecular descriptors taken into account are the molecule's oxygen balance and the enumeration of certain groups. The results obtained are satisfactory: 80% of the molecules are correctly classed on a scale of four sensitivities. Comparison with a multivariate linear regression analysis gives a slight advantage to the neural network method.

Computer Simulation↗
PubMed2004

The off-label use of clozapine in adolescents with bipolar disorder, intermittent explosive disorder, or posttraumatic stress disorder.

OBJECTIVE: There are limited data in the literature regarding clozapine use in adolescents with diagnoses other than schizophrenia. This report describes the use of clozapine in adolescents with diagnoses of bipolar disorder, intermittent explosive disorder (IED), and posttraumatic stress disorder (PTSD). METHODS: A chart review of 39 adolescents treated with clozapine at two residential facilities was undertaken. Data extraction included demography, illness variables, medication information, and clinical outcomes. Categorical outcomes were analyzed using contingency statistics, and continuous variables were analyzed using a paired t test. RESULTS: The cohort included 26 females and 13 males with a mean age of 14 years. Clozapine was titrated slowly, and the mean daily dose was 102 mg. The diagnoses included bipolar disorder (n = 7), IED (n = 9), and PTSD (n = 19). There were significant reductions in polypharmacy once the clozapine dosage was stabilized. Prior to clozapine treatment, nearly 70% of the subjects were receiving either mood-stabilizing or antidepressant agents in combination with the previous antipsychotic drug. Once the clozapine dosage was stabilized, only 24% of the subjects required concomitant mood stabilizers (p < 0.001), and only 21% of the subjects required concomitant antidepressants (p < 0.001). Anxiolytic medication use was also significantly reduced during clozapine treatment. Most patients were discharged to a less restrictive setting. Eight subjects discontinued clozapine due to agranulocytosis (n = 1), neutropenia (n = 2), excessive weight gain (n = 2), or not requiring it long term (n = 1), and data were unavailable in 2 subjects. Significant weight gain (5% or greater change from baseline) was noted in 20 subjects. CONCLUSIONS: Clozapine, in relatively modest doses, appears to have clinical benefits for adolescent with bipolar disorder, IED, and PTSD. There is no labeled indication for clozapine use in these disorders. Clozapine is also associated with serious side effects in subsets of individuals. Therefore, a very careful evaluation of the risk-to-benefit ratio in each individual subject being considered for clozapine is highly recommended.

Adolescent↗
PubMed2004

Two viral strains and a possible novel recombinant are responsible for the explosive injecting drug use-associated HIV type 1 epidemic in Estonia.

HIV-1 infection has been rare in Estonia. In 2000, an explosive epidemic among injecting drug users was detected in the Eastern border region, resulting in 3603 newly reported cases by the end of 2003. The molecular epidemiology of the outbreak was studied to establish whether the Estonian epidemic is linked to the epidemics in Eastern Europe. Over 200 newly infected individuals were prospectively sampled from June 2000 to March 2002 in a geographically representative way, with known dates of diagnosis and information of probable route of transmission. Viral regions coding for two viral gene regions were directly sequenced from plasma viral RNA and phylogenetically analyzed. In addition, a larger region coding for the entire env gene was sequenced from one sample and studied for indications of possible recombinant structure. The Estonian HIV outbreak was found to be caused by simultaneous introduction of two strains: a minor subtype A strain very similar to the Eastern European subtype A strain (approximately 8% of cases), and a second major strain (77%) found to be most closely related to the CRF06-cpx strain, previously described only from African countries. The variability in the two clusters was very low, suggesting point source introductions. Ten percent of cases seemed to be newly generated recombinants of the A and CRF06-cpx strains. Analysis of viral diversification over time revealed a rate of change within the V3 region of 0.83%/year for the CRF06-cpx strain, consistent with findings from other subtypes. Due to the relatively frequently found novel recombinant forms, the Estonian HIV-1 epidemic may allow studies of coinfection and intersubtype recombination in detail.

Disease Outbreaks↗
PubMed1998

Explosive school-based measles outbreak: intense exposure may have resulted in high risk, even among revaccinees.

Even high levels of measles vaccination coverage have not always prevented outbreaks of measles spread by airborne transmission. It has been suggested that a large inoculum might increase vaccine failure risk. Airbome transmission might occasionally entail a large measles inoculum. The epidemiologic relevance of measles among properly vaccinated persons (i.e., those vaccinated after 15 months of age and with live attenuated virus) is increased when they become contagious. The authors studied inoculum intensities as measured by proxy variables and the contagiousness of properly vaccinated persons who contracted measles among 51 measles patients infected in one school, at home, or elsewhere, utilizing preexisting records of measles cases and 214 healthy controls from an explosive school outbreak that occurred in a rural Finnish municipality in 1989. One "super-spreader" infected 22 others in one day, including eight once-vaccinated students and one twice-vaccinated student, probably during an assembly of 144 students in a poorly ventilated hallway with no sunlight. Those infected later at home had high measles risk, even if they were revaccinees. When siblings shared a bedroom with a measles case, a 78 percent risk (seven out of nine children) was observed among vaccinees. Vaccinees had approximately 2 days' shorter incubation time than unvaccinated persons. Vaccinated and unvaccinated students were equally able to infect their siblings. Total protection against measles might not be achievable, even among revaccinees, when children are confronted with intense exposure to measles virus.

Adolescent↗
PubMed1989

An explosive point-source measles outbreak in a highly vaccinated population. Modes of transmission and risk factors for disease.

In 1985, 69 secondary cases, all in one generation, occurred in an Illinois high school after exposure to a vigorously coughing index case. The school's 1,873 students had a pre-outbreak vaccination level of 99.7% by school records. The authors studied the mode of transmission and the risk factors for disease in this unusual outbreak. There were no school assemblies and little or no air recirculation during the schooldays that exposure occurred. Contact interviews were completed with 58 secondary cases (84%); only 11 secondary cases (19%) of these may have had exposure to the index case in the classrooms, buses, or out of school. With the use of the Reed-Frost epidemic model, only 22-65% of the secondary cases were likely to have had at least one person-to-person contact with the index case during class exchanges, suggesting that this mode of transmission alone could not explain this outbreak. A comparison of the first 45 cases and 90 matched controls suggested that cases were less likely than controls to have provider-verifiable school vaccination records (odds ratio (OR) = 8.1) and more likely to have been vaccinated at less than age 12 months (OR = 8.6) or at age 12-14 months (OR = 7.0). Despite high vaccination levels, explosive measles outbreaks may occur in secondary schools due to 1) airborne measles transmission, 2) high contact rates, 3) inaccurate school vaccination records, or 4) inadequate immunity from vaccinations at younger ages.

Adolescent↗
PubMed1993

Laparoscopy explosion hazards with nitrous oxide.

BACKGROUND: During laparoscopic surgery utilizing carbon dioxide as the insufflating agent, nitrous oxide will diffuse into the peritoneal cavity if it is used as part of the anesthetic. Bowel perforation and the subsequent release of volatile bowel gas could create a explosion hazard. METHODS: Two related studies were undertaken. The first quantified the transfer of nitrous oxide, over time, in 19 female patients undergoing laparoscopy. The second established the lower limits of flammability of a range of concentrations of methane and hydrogen diluted with nitrogen (simulated bowel gas) in a range of concentrations of nitrous oxide diluted with carbon dioxide (simulated peritoneal gas). RESULTS: The mean concentrations of N2O at 10, 20, and 30 min from the time of insufflation were 19.9 +/- 4.8%, 30.3 +/- 6.8%, and 36.1 +/- 6.9%, respectively. The maximum reported concentrations of methane and hydrogen in bowel gas are 56% and 69%, respectively. The concentration of nitrous oxide necessary to support combustion of 56% methane is approximately 47%. By contrast, the concentration of nitrous oxide needed to support combustion of 69% hydrogen is approximately 29%. CONCLUSIONS: The authors have shown that it is possible for nitrous oxide to reach concentrations in the peritoneal cavity that can support combustion of bowel gas.

Adult↗
PubMed1992

Mandibular joint dysfunction otalgia caused by a bomb explosion wave.

Four hundred ninety-five patients were exposed to bomb explosion waves in civilian and war areas during the Iraq/Iran conflict. These patients were referred to the Oral and Maxillofacial Surgery Clinic after complaining of temporomandibular joint dysfunction with otalgia. Treatment ranged from conservative measurement to active surgery. Generally, response was good.

Adolescent↗
PubMed1993

Measurement of an explosive behavior in the mouse, induced by MK-801, a PCP analogue.

MK-801, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor complex that binds with high-affinity to the phencyclidine (PCP) binding site, stimulated an outbred strain of NIH Swiss mice to display discrete episodes of explosive jumping behavior, designated as "popping." The episodes of this behavior were characterized with respect to their dose dependency, latency, and duration. The number of mice displaying this behavior increased with increasing doses of MK-801. The intensity of the popping behavior was sensitive to dose-dependent inhibition by haloperidol, a conventional antipsychotic medication, and clozapine, an atypical antipsychotic medication. In view of PCP's ability to precipitate a schizophreniform psychosis in humans, the behavior may serve as a useful preclinical paradigm for the screening of potentially novel antipsychotic medications.

Analysis of Variance↗
PubMed1979

Fractures of the distal tibial metaphysis with intra-articular extension--the distal tibial explosion fracture.

In a study of 26 distal tibial explosion fractures in 24 patients two fracture patterns were identified: Type A, a rotational pattern; and Type B, a compressive fracture pattern. The rotational pattern was found to be less common than the compressive fracture and to have a substantially better prognosis. Operative treatment of the Type A pattern led to an overall acceptable result of 84%, while the Type B patients had 53% acceptable results. The results of operative treatment were however, superior to the results of nonoperative treatment in both fracture groups. Adequate treatment consists of anatomic reconstruction of the distal tibia, rigid internal fixation, early active motion, and nonweight bearing in 3 to 5 months.

Ankle↗
PubMed1996

Pattern and mechanism of traumatic amputation by explosive blast.

The mechanism of traumatic amputation of limbs by explosion is presented. A survey of blast casualties from Northern Ireland revealed that amputations through joints were very uncommon--the principal site was through the shaft of the long bones. Computer modelling of a bone exposed to blast forces reinforced the hypothesis developed from the casualty survey, that the primary mechanism of the bone injury was the direct coupling of the blast wave into the tissues. The fracture occurs from the resulting axial stresses in the bone, prior to limb flailing from the gas flow over the limb. The gas flow completes the amputation. Field trials employing a goat hind limb model have confirmed the hypothesis. Having identified the mechanism, concepts to develop protective clothing may now be proposed.

Amputation, Traumatic↗
PubMed1997

The explosion of morbidity and mortality trials in hypertension.

The highlights of each generation of hypertension trials have been varied, but interrelated. The initial hypertension trials focused on middle-aged hypertensive individuals and later on the elderly, with emphasis on diastolic blood pressure and subsequently on systolic blood pressure. Past generations of trials elucidated whether and whom to treat. The current explosion of morbidity and mortality trials in hypertension largely seeks to learn what drugs should be used and to delineate what blood pressure goals should be targeted.

Aged↗