Biomedical subjects

E Müller

Publications and source records attributed to E Müller.

At least 55 records · Page 3Linked to original sources

PubMed2001

[Congenital diaphragmatic hernia in a polytrauma patient].

A case of congenital, bilateral, diaphragmatic hernia in a patient with multiple trauma after a motor accident is presented. No anamnestic information was available because of the need for intubation at the accident site. After the insertion of bilateral chest tubes because of left sided pneumothorax and right sided haematopneumothorax a mediastinal mass became apparent. A CT scan revealed a bilateral diaphragmatic hernia. Problems and therapy of this condition as well as differentiation between congenital and traumatic hernias are discussed in this case report. A mediastinal mass of unknown origin in multiple trauma patients suggests the presence of traumatic diaphragmatic hernia. Diagnostic signs suggesting congenital hernia as compared to acute traumatic hernia are: unilateral or bilateral localisation in the dorsal muscular part of the diaphragm and non-suspicious appearance of parenchymal abdominal organs in relation to the size of the hernia. Diaphragmatic hernias reduce the vital and functional residual capacity of the lungs, possibly leading to respiratory complications and infections.

Aged↗

PubMed2001

Landscape metrics for assessment of landscape destruction and rehabilitation.

This investigation tested the usefulness of geometry-based landscape metrics for monitoring landscapes in a heavily disturbed environment. Research was carried out in a 75 sq km study area in Saxony, eastern Germany, where the landscape has been affected by surface mining and agricultural intensification. Landscape metrics were calculated from digital maps (1912, 1944, 1973, 1989) for the entire study area and for subregions (river valleys, plains), which were defined using the original geology and topography of the region. Correlation and factor analyses were used to select a set of landscape metrics suitable for landscape monitoring. Little land-use change occurred in the first half of the century, but political decisions and technological developments led to considerable change later. Metrics showed a similar pattern with almost no change between 1912 and 1944, but dramatic changes after 1944. Nonparametric statistical methods were used to test whether metrics differed between river valleys and plains. Significant differences in the metrics for these regions were found in the early maps (1912, 1944), but these differences were not significant in 1973 or 1989. These findings indicate that anthropogenic influences created a more home geneous landscape.

Animals↗

PubMed2001

Toxicity of waters from two streams to early life stages of brown trout (Salmo trutta f. fario L.), tested under semi-field conditions.

The development of brown trout (Salmo trutta f. fario L.) in water of two differently polluted streams and in a control situation was monitored in order to get insights into the impact of anthropogenic chemical stressors on the reproductive success of this fish species indigenous to both streams. The test streams, situated in the south of Stuttgart, Germany, were the complexly polluted Körsch stream and the less polluted Krähenbach stream. Bypass systems connected to the streams and a laboratory control system were used for continuous exposure of early brown trout stages shortly after fertilisation up to the end of the embryonic development. Temperature and oxygen conditions were standardised in all test series in order to minimise unspecific effects. The examined endpoints were: (1) mortality, (2) developmental rate, (3) time course of hatching, (4) malformations, and (5) growth. A retarded development, reduced growth rates and higher mortality rates of Körsch stream water exposed embryos indicated an embryotoxic potential for the more polluted stream. High infection-related mortality rates of embryos suggested the presence of confounding factors also in the less polluted Krähenbach stream. In parallel to the exposure experiment, physicochemical and limnochemical parameters as well as concentrations of organic contaminants and heavy metals were monitored. Analytical data confirm the different degrees of pollution of both streams.

Animals↗

PubMed2001

New allo-cedrane type sesquiterpene hemiketals and further sesquiterpene lactones from fruits of Illicium floridanum.

Three new tetracyclic sesquiterpene hemiketals possessing the very rare allo-cedrane carbon skeleton, debenzoyl-7-deoxo-1 alpha,7 alpha-dihydroxytashironin, debenzoyl-7-deoxo-7 alpha-hydroxytashironin, and debenzoyl-7-deoxo-7 alpha-hydroxy-3-oxotashironin (1--3), were isolated from the fruits of Illicium floridanum ELLIS (American Star Anise, Star bush). Their structures were elucidated by mass and NMR spectroscopic analyses. The molecular structure of 1, including absolute stereochemistry, was determined by single-crystal X-ray diffraction of its monohydrate. Only one compound of this type, tashironin, has previously been isolated from Illicium tashiroi. Furthermore, a new sesquiterpene lactone of the seco-prezizaane type, 3,4-anhydro-13,14-dihydroxyfloridanolide (4), and the known anislactone B (5) were isolated. The occurrence of further allo-cedrane sesquiterpenes in another Illicium species confirms the hypothesis of previous authors that this type of compound is a biogenetic precursor of the typical seco-prezizaane sesquiterpene lactones found in this genus. Moreover, regarding their co-occurrence with anislactone B as reported here, they may also be considered precursors for the anislactone skeletal type.

Crystallography, X-Ray↗

PubMed2001

[Treatment for acute renal failure--concepts and controversies. 1. Pharmacologic treatment and experimental strategies].

Acute renal failure is the common result of various damaging mechanisms. Prophylaxis and differentiated therapy of acute renal failure are of outmost importance in anaesthesiology and intensive care medicine. The efficiency of pharmacotherapy is narrowly limited. Diuretics increase the urine output, but they do neither ameliorate the clinical course of the patient nor the prognosis of established acute renal failure. Dopamine and natriuretic peptides have no use in prevention and treatment of acute renal failure. Calcium-channel-blockers are valuable in cadaveric kidney transplantation. Osmodiuretics prevent intratubular precipitation of hemoglobin and myoglobin crystals; they also have some value in cadaveric kidney transplantation. Experimental studies investigated the possibility to enhance the regeneration of the tubular epithelial cell. Whereas in vitro studies and studies in animal models using various growth factors yielded promising results, these could not be reproduced in patients with acute renal failure. The physiology of NO in the kidney is incompletely understood. Actual progress is made in the understanding of lipid peroxidation and potential pharmacological implications. The mainstay for the assurance of high-quality patient care remain a vigilant identification of the patient at risk and an arduous search to avoid nephrotoxic substances and situations implicating potential renal damage.

Acute Kidney Injury↗

PubMed2001

[Treatment of acute renal failure--concepts and controversies. 2. Extracorporeal renal replacement and peritoneal dialysis].

Therapy of prolonged acute renal failure regularly requires a renal replacement therapy. This can be achieved by different extracorporal renal replacement therapies (ERRT) or by peritoneal dialysis. ERRT are classified according to the physical principle underlying toxin elimination as hemodialysis (diffusion) and hemofiltration (convection). Another classification refers to intermittent or continuous application modes. Biocompatibility of membranes is judged according to their activation of the complement system. Prospective randomized studies did not consolidate the assumptions about the benefit of particular modalities proposed on theoretical foundations. Mortality, duration and complication rates of acute renal failure are not significantly decreased by use of biocompatible membranes. Continuous modalities are not generally preferable but optimize treatment in hemodynamically unstable patients, in whom they endorse fluid balancing and maintenance of sufficient arterial blood pressure. The use of demanding hemofiltration techniques for cytokine removal should be limited to clinical studies. The effects of ERRT-"intensity" and the best timing for initiation of ERRT have not been evaluated sufficiently. The choice of the ERRT modality is subject to clinical judgement (criterion: hemodynamic situation), practical aspects (criteria: availability of equipment and handling experience), and costs. Prior to their general use new and expensive technical modalities and membrane types should be thoroughly evaluated in studies with regard to outcome-related aspects such as patient survival and preservation of renal function.

Acute Kidney Injury↗

PubMed2001

Creatine kinase, myosin heavy chains and magnetic resonance imaging after eccentric exercise.

The aim of this study was to examine the relationship between myosin heavy chain (MHC) release as a specific marker of slow-twitch muscle fibre breakdown and magnetic resonance imaging (MRI) of skeletal muscle injury after eccentric exercise. The effects of a single series of 70 high-intensity eccentric contractions of the quadriceps femoris muscle group (single leg) on plasma concentrations of creatine kinase and MHC fragments were assessed in 10 young male sport education trainees before and 1 and 4 days after exercise. To visualize muscle injury, MRI of the loaded thigh was performed before and 4 days after the eccentric exercise. All participants recorded an increase (P < 0.05) in creatine kinase after exercise. In five participants, T2 signal intensity was unchanged post-exercise compared with pre-exercise and MHC plasma concentration was normal; however, they showed an increase (P < 0.05) in creatine kinase after exercise. For the remaining five participants, there was an increase in T2 signal intensity of the loaded vastus intermedius and vastus lateralis. These changes in MRI were accompanied by an increase in MHC plasma concentration (P< 0.01) as well as an increase in creatine kinase (P < 0.01). We suggest that changes in MRI T, signal intensity after muscle damage induced by eccentric exercise are closely related to damage to structurally bound contractile filaments of some muscle fibres. Additionally, MHC plasma release indicates that this damage affects not only fast-twitch fibres but also some slow-twitch fibres.

Adult↗

PubMed2001

Alcohol intake and high density lipoprotein-cholesterol: comparison of food frequency questionnaire and diet record in a general population sample.

BACKGROUND: Moderate alcohol consumption is known to affect several cardiovascular risk factors, including high density lipoprotein-cholesterol (HDL-C). Accurate measurement of alcohol intake in epidemiological studies is crucial for valid estimation of alcohol-related effects. METHODS: We compared two widely used alcohol-intake assessment methods, a food frequency questionnaire (FFQ) and a 7-day diet record (DR) regarding the association between alcohol intake and HDL-C in the general population. RESULTS: In a representative sample (842 men, 1103 women) of the population of former West Germany (VERA study), 75.6% of the participants reported drinking alcoholic beverages in the FFQ, whereas the percentage was 84.9% according to the DR. The median daily alcohol intake of consumers was 10.3 and 12.1 g, as assessed by the FFQ and the DR, respectively. There was moderate agreement between reported consumption levels ranked by quintiles according to FFQ and DR (kappa = 0.49). With both approaches alcohol intake showed a strong positive association with HDL-C in linear regression models. The estimated increases in HDL-C (mg dL(-1)) per gram alcohol per day from the FFQ and DR were 0.15 [95% confidence interval (CI): 0.12-0.18] and 0.14 (95% CI: 0.11-0.17), respectively. When participants with different classification of the amount of alcohol consumed by FFQ and DR were excluded from the analysis, the association between alcohol intake and HDL-C was more pronounced. DISCUSSION: Our analyses suggest that both FFQ and DR lead to similar results regarding the alcohol-HDL-C association in the general population, despite major differences in the recorded prevalence of drinking and amount of alcohol consumed. Both methods may tend to under-estimate the true alcohol-HDL-C association.

Adult↗

PubMed2001

Economic evaluation of collagenase-containing ointment and hydrocolloid dressing in the treatment of pressure ulcers.

OBJECTIVE: To evaluate the efficacy and cost effectiveness of two treatments of pressure sores on the heel: a collagenase-containing ointment and a hydrocolloid dressing. DESIGN: Study and cost data were collected prospectively in a randomised clinical trial in The Netherlands by counting the resource use for each patient until wound healing occurred. STUDY PARTICIPANTS: All 24 female study participants were inpatients from the same hospital with grade IV pressure sores on the heel following orthopaedic surgery. INTERVENTIONS: Two different treatment strategies were analysed: a collagenase-containing ointment (Novuxol) and a hydrocolloid dressing (Duoderm). PERSPECTIVE: Hospital perspective. MAIN OUTCOME MEASURES AND RESULTS: The average costs per patient for treatment with the hydrocolloid dressing were about 5% higher than those with the collagenase-containing ointment. The treatment costs were similarly distributed within both groups, with 34% for materials and 66% for personnel. The cost-effectiveness analysis revealed that cost savings of 899 Dutch guilders (1998 values) per successfully treated patient could be expected using the collagenase-containing ointment instead of the hydrocolloid dressing. In addition, wound healing was achieved, on average, within a shorter time period with the collagenase treatment (10 weeks) compared with the hydrocolloid treatment (14 weeks). The robustness of the results were also tested using sensitivity analyses. These analyses served to confirm that collagenase treatment provides a better cost-effectiveness ratio than hydrocolloid treatment. CONCLUSIONS: With regard to overall costs and costs per successfully treated patient, this study showed collagenase treatment to be more cost effective than the hydrocolloid treatment in patients with grade IV pressure sores on the heel and that the amount of time needed for wound healing was shorter.

Aged↗

PubMed2001

Identification of novel polymorphisms in intron 7 of the human p53 gene in acute myeloid leukemia and healthy donors.

Screening for mutations by PCR-SSCP in exons 5 to 9 of the p53 gene in 38 bone marrow or peripheral blood specimens of patients with acute myeloid leukemia (AML) showed abnormal shifts in 9 cases. One reflected a mutation in exon 8, whereas in the other cases there were no exonic mutations identified by sequencing. As PCR primers were chosen annealing in the introns flanking the exon region, following sequencing of the encompassing introns identified 5 base substitutions at various sites in intron 7. Two of them have been described previously [1] and 3 novel polymorphisms could be identified. To determine whether these polymorphisms are linked to the pathogenesis of AML, we screened peripheral blood specimens of 26 healthy controls. We found identical base substitutions in 6 out of 26 controls. Our data suggest that these polymorphisms are not related to the pathogenesis of AML.

Acute Disease↗

PubMed2001

[Laparoscopic Toupet partial fundoplication as general surgical therapy of gastroesophageal reflux. 1-year results of a 5-year prospective long-term study].

INTRODUCTION: A variety of laparoscopic antireflux operations exist for patients with gastroesophageal reflux diseases (GERD). Most surgeons operate using the concept of "tailored approach", which depends on esophageal motility. We have abandoned this concept because of the relatively high incidence of wrap-related complications in patients treated with laparoscopic Nissen fundoplication compared with patients treated with partial fundoplication. It is our policy to perform laparoscopic Toupet partial fundoplication in all patients suffering from GERD, independent of their esophageal motility. METHODS: In a prospective trial we have assessed and evaluated our 1-year results of the first 100 consecutive patients treated with Toupet partial fundoplication. All patients underwent esophagogastroscopy and 24-h pH manometry before operation. One third of patients (n = 34) underwent control manometry 8 weeks postoperatively. The patients were followed up clinically 1, 2, 6 and 12 months postoperatively. RESULTS: In this study group we achieved a healing rate in GERD of 97%. In 3% of patients GERD recurred. The median clinical DeMeester score decreased from 4.27 +/- 1.5 points preoperatively to 0.25 +/- 0.5 points 1 year postoperatively (P < 0.0005). The median fractional time with pH < 4 decreased from 17.8% +/- 12.5% preoperatively to 0.9% +/- 1.2% 8 weeks postoperatively (P < 0.0005). Because of persistent dysphagia 5% of our patients required postoperative dilatation therapy. The rate of reoperation and mortality was 0%. The total morbidity rate was 18%. In 50% of patients with preoperatively recorded esophageal motility disorder, an improvement of esophageal motility was found postoperatively. CONCLUSIONS: Our 1-year results encourage us to continue to perform laparoscopic Toupet partial fundoplication as the primary repair in all GERD patients, independent of their esophageal motility. Laparoscopic Toupet partial fundoplication has proven to be a safe and highly successful therapeutic option in these patients.

Adult↗

PubMed2001

[Comparison study of the HUMFGA and HTPO STR system in the Saxon and Czech population].

High variability of repetitive DNA in a non-coding region of human genome affords possibilities for vestige identification and determination of their origin. For analysis of DNA many a time obtained from decomposed material, usually in a very small amount and sometimes partially degraded, polymerase chain reaction is considered as optimal technique. For identification of individuals is used an Amplified Fragment Length Polymorphisms (AmpFLP), which present repetitions 10 to 70 base pairs long in an amplification products of 170 to 1200 bp. In legal medicine PCR systems using tetrameric repetition polymorphism are widely used. These systems are highly sensitive, but in comparison to AmpFLP systems, imperceptibly influenced by nucleic acid degradation in cases of old or partially degraded samples. Aim of our study was to compare frequency data for 2 STR-systems, FGA and HTPO, both after PCR amplification, on 200 samples of Czech and 228 of German population. In FGA system of Czech population 14 different alleles and 44 genotypes were determined, while German population provided 13 different alleles and 47 genotypes. Furthermore, frequency of alleles and heterozygosity rate were determined. Heterozygosity rate for Czech samples was 85%, for German ones 87.1%. Alleles 21 and 22 were most frequent (approx. 20%) between both Czech and German population, followed by alleles 20, 23 and 24 (14-12%). Besides these data, three different transient alleles were detected. In HTPO systems of both population groups 12 different genotypes, consisting of 5 alleles, were determined. Genotypes 8/8 and 8/11 observed in 30% were the most frequent ones in both population groups. Heterozygosity rate for Czech samples was 62.5%, for German ones 65%. Results were statistically analyzed. In both population groups, no significant difference from Hardy-Weinberg's balance was found. Additionally, statistic parameters for forensic effectivity evaluation were constructed. Comparison of both populations using homogeneity tests provided non-significant difference. FGA system provides extraordinary high forensic exploitativeness and therefore is fully acceptable for vestige identification and determining of their origin. For significant determination of transient alleles analysis of fluorescein-labelled fragments in denaturing gel system should follow, using automated laser detection of fluorescence. Polymorphism of HTPO-system is significantly lower compared to FGA-system, but relatively small PCR product required as well as simple detection and imperceptible influence of nucleic acid degradation allow the use of HTPO for analysis of highly degraded DNA.

Czech Republic↗

PubMed2000

Expression of adhesion molecules in skin wounds: diagnostic value in legal medicine.

The adhesion molecules identified in recent years can help improve the diagnosis of the wound age, especially of injuries with a short survival time. This is also indicative of the vitality of the wounds. The material investigated in the study originated from 465 skin wounds. The samples were taken from human autopsy material, during the surgical treatment of wounds (excision) of patients and from experimental incised wounds of mice. To judge the age of skin wounds the endothelial adhesion molecules were detected in paraffin sections after autoclaving and using the ABC technique. Human skin wounds: strong positive staining was observed of ICAM-1 1.5 h at the earliest and 3.5 days at the latest, for the P-selectin 3 min at the earliest and 7 h at the latest, for the E-selectin 1 h at the earliest and 17 days at the latest and for VCAM-1 3 h at the earliest and 3.5 days at the latest after the time of injury. The L-selectin was expressed constitutively. Mice skin wounds: strong positive immunohistochemical reactions were found as a rule earlier than in human skin wounds. The detection of an increased expression of ICAM-1, VCAM-1 and P- and E-selectins can improve the wound age assessment in injuries with short survival times.

Animals↗

PubMed2000

Profilin I attached to the Golgi is required for the formation of constitutive transport vesicles at the trans-Golgi network.

Profilin I was identified, by mass spectrometric sequencing and immunoblotting, as a component of purified Golgi cisternae from HepG2 cells. Binding to the Golgi was verified by indirect immunofluorescence in MT-1 cells showing that a fraction of profilin I colocalizes with TGN38, a marker of the trans-Golgi network (TGN). Studying the formation of constitutive exocytic vesicles at the TGN in a cell-free system demonstrated that cytosolic profilin I has no effect, while incubation of Golgi cisternae with a profilin I-specific antibody reduced vesicle formation by about 50%. Notably, the antibody displaces a fraction of the Golgi-bound dynamin II indicating that profilin I may indirectly promote vesicle formation by supporting the binding of dynamin II to the Golgi membrane. The impact of dynamin II on vesicle formation is demonstrated by incubating the Golgi with the proline-rich domain of dynamin II which concomitantly displaces dynamin II and inhibits vesicle formation. The data provide evidence that profilin I attaches to the Golgi apparatus and is required for the formation of constitutive transport vesicles.

Contractile Proteins↗

PubMed2000

Immunological surrogate parameters in a prognostic model for multi-organ failure and death.

OBJECTIVE: To assess the ability of clinical or biochemical parameters to predict outcome (survival or non-survival; severe or moderate/no complication) using multiple regression analyses. DESIGN: Prospective, descriptive cohort study with no interventions SETTING: 12 surgical intensive care units of university hospitals and large community hospitals; four medical school research laboratories in eight European countries PATIENTS: 128 surgical patients with major intra-abdominal surgery admitted for at least two days to an intensive care unit MAIN OUTCOME MEASURES: Prediction of complications or survival based on analysis of clinical (Multiple Organ Dysfunction Score, Multi-Organ-Failure Score, Acute Physiology and Chronic Health Evaluation II scores) and immunological (plasma levels of endotoxin, endotoxin neutralizing capacity, IL-6, IL-8, cell associated IL-8, Fc-receptor polymorphism, soluble CD-14) parameters, with comparison of predicted and actual outcomes. RESULTS: APACHE II, MODS score, MOF score, platelets, IL-6, IL-8, ENC, cell ass. IL-8 were significantly different between survivors and non-survivors and patients with/without severe complications by univariate analysis. By multivariate analysis only MOF, MODS score, IL-6, platelets, comorbidity predicted complications with a sensitivity of 82% and a specificity of 87%. Multivariate analysis demonstrated that only APACHE II score, plasma IL-8 and complications predicted death (sensitivity 84%; specificity 90%). CONCLUSION: Immunological surrogate parameters may predict complications and death of surgical ICU patients. The use of several parameters may add to increase sensitivity and specificity in a prognostic model.

APACHE↗

PubMed2000

Trinuclear N,N-bridged copper(II) complexes involving a Cu3OH core: [Cu3(mu 3-OH)L3A(H2O)2]A.(H2O)x (L = 3-acetylamino-1,2,4-triazolate; a = CF3SO3, NO3, ClO4; x = 0, 2) synthesis, X-ray structures, spectroscopy, and magnetic properties.

The reaction of Haat [Haat = (3-acetylamino-1,2,4-triazole)] with aquated Cu(CF3SO3)2, Cu(NO3)2, and Cu(ClO4)2, respectively, in water results in the trinuclear complexes [Cu3(OH)(aat)3(CF3SO3)(H2O)2](CF3SO3) (1), [Cu3(OH)(aat)3(NO3)(H2O)2](NO3).(H2O)2 (2), and [Cu3(OH)(aat)3(ClO4)(H2O)2](ClO4) (3). The synthesis, X-ray structure, and magnetic and spectroscopic properties of the three title complexes are described. The cation of the three complexes is trinuclear with a Cu3OH skeleton which has the N-N diazine grouping of a triazole ring as bridge between each pair of copper atoms. The Cu3OH units have an average Cu-O distance of 1.991(6) (1), 2.000(6) (2), and 2.007(6) (3) A, an average Cu-Cu' distance of 3.355(2) (1), 3.341(1) (2), and 3.371(3) (3) A, and an average Cu-O-Cu' angle of 114.6(3) degrees (1), 112.4(2) degrees (2), and 115.4(3) degrees (3). The existence of the Cu3OH fragment is confirmed by a pseudotetrahedral oxygen environment, by detection of the OH hydrogen atom, and by stoichiometry. In the trinuclear unit the metal ions show, in the first approximation, a pseudo-square-planar pyramidal environment forming a CuN2O3 chromophore; three of the basal positions are occupied by N,N,O aat ligand atoms, the fourth one is occupied by the oxygen of the central OH group, and the apical site is occupied by an oxygen atom from a water molecule in the case of two of the copper(II) atoms and by an oxygen atom from the coordinating anion in the case of the third metal ion. The three compounds exhibit strong antiferromagnetic interaction, with similar J constants [J = -197.7 (1), J = -190.9 (2), J = -198.2 (3) cm-1], reaching complete spin coupling at ca. 75 K (1)/55 K (2)/95 K (3). At very low temperature the magnetic moment (magnetic susceptibility) falls below that expected for one unpaired electron. Magnetic parameters are discussed on the basis of the structural results and compared with those reported in the literature for related trimeric Cu(II) compounds with N-O or N-N peripheral bridges. Solid state EPR spectra of the three complexes recorded at liquid N temperature show axial signals. Crystal data: C14H20Cu3F6N12O12S2 (1) (Mw = 917.16) crystallizes in the monoclinic space group, P2(1)/c, Z = 4, with cell dimensions a = 13.080(2) A, b = 17.202(2) A, c = 13.840(2) A, beta = 92.40(1) degrees, and V = 3111.3(7) A3, Dcalcd = 1.958 Mg m-3; the final agreement values were R1 = 0.0582 and wR2 = 0.1462 for 7107 unique reflections. C12H24Cu3N14O14 (2) (Mw = 779.07) crystallizes in the triclinic space group, P1, Z = 2, with cell dimensions a = 9.647(2) A, b = 9.985(2) A, c = 15.314(2) A, alpha = 84.080(10), beta = 87.694(10), gamma = 65.030(10) degrees, and V = 1330.1(4) A3, Dcalcd = 1.945 Mg m-3; the final agreement values were R1 = 0.0397 and wR2 = 0.0950 for 7728 unique reflections. C12H20Cl2Cu3N12O14 (3) (Mw = 817.92) crystallizes in the monoclinic space group, P2(1)/a, Z = 4, with cell dimensions a = 14.238(5) A, b = 16.387(6) A, c = 11.678(4) A, gamma = 90.45(2) degrees, and V = 2724.6(18) A3, Dcalcd = 1.994 Mg m-3; the final agreement values were R1 = 0.0616 and wR2 = 0.1279 for 4038 unique reflections.

Journal Article↗

PubMed2000

Relativistic Jets from Collapsars.

Using a collapsar progenitor model of MacFadyen & Woosley, we have simulated the propagation of an axisymmetric jet through a collapsing rotating massive star with the GENESIS multidimensional relativistic hydrodynamic code. The jet forms as a consequence of an assumed (constant or variable) energy deposition in the range of 1050-1051 ergs s-1 within a 30 degrees cone around the rotation axis. The jet flow is strongly beamed (approximately less than a few degrees), spatially inhomogeneous, and time dependent. The jet reaches the surface of the stellar progenitor (R*=2.98x1010 cm) intact. At breakout, the maximum Lorentz factor of the jet flow is 33. After breakout, the jet accelerates into the circumstellar medium, whose density is assumed to decrease exponentially and then become constant, rhoext=10-5 g cm-3. Outside the star, the flow begins to expand laterally also (v approximately c), but the beam remains very well collimated. At a distance of 2.54 R*, where the simulation ends, the Lorentz factor has increased to 44.

Journal Article↗

PubMed2000

Nucleosynthesis and Clump Formation in a Core-Collapse Supernova.

High-resolution two-dimensional simulations were performed for the first 5 minutes of the evolution of a core-collapse supernova explosion in a 15 M middle dot in circle blue supergiant progenitor. The computations start shortly after bounce and include neutrino-matter interactions by using a lightbulb approximation for the neutrinos and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout the inner half of the helium core by Rayleigh-Taylor instabilities at the (Ni + Si)/O and (C + O)/He interfaces, seeded by convective overturn during the early stages of the explosion. Fast-moving nickel mushrooms with velocities up to approximately 4000 km s-1 are observed. This offers a natural explanation for the mixing required in light-curve and spectral synthesis studies of Type Ib explosions. A continuation of the calculations to later times, however, indicates that the iron velocities observed in SN 1987A cannot be reproduced because of a strong deceleration of the clumps in the dense shell left behind by the shock at the He/H interface.

Journal Article↗