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At least 73 records · Page 4Linked to original sources
PubMed2003

Impact of ozone mini-holes on the heterogeneous destruction of stratospheric ozone.

A comprehensive study of ozone mini-holes over the mid-latitudes of both hemispheres is presented, based on model simulations with the coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM representing atmospheric conditions in 1960, 1980, 1990 and 2015. Ozone mini-holes are synoptic-scale regions of strongly reduced total ozone, directly associated with tropospheric weather systems. Mini-holes are supposed to have chemical and dynamical impacts on ozone levels. Since ozone levels over northern mid-latitudes show a negative trend of approximately -4%/decade and since it exists a negative correlation between total column ozone and erythemally active solar UV-radiation reaching the surface it is important to understand and assess the processes leading to the observed ozone decline. The simulated mini-hole events are validated with a mini-hole climatology based on daily ozone measurements with the TOMS (total ozone mapping spectrometer) instrument on the satellite Nimbus-7 between 1979 and 1993. Furthermore, possible trends in the event frequency and intensity over the simulation period are assessed. In the northern hemisphere the number of mini-hole events in early winter decreases between 1960 and 1990 and increases towards 2015. In the southern hemisphere a positive trend in mini-hole event frequency is detected between 1960 and 2015 in spring associated with the increasing Antarctic Ozone Hole. Finally, the impact of mini-holes on the stratospheric heterogeneous ozone chemistry is investigated. For this purpose, a computer-based detection routine for mini-holes was developed for the use in ECHAM4.L39(DLR)/CHEM. This method prevents polar stratospheric cloud formation and therefore heterogeneous ozone depletion inside mini-holes. Heterogeneous processes inside mini-holes amount to one third of heterogeneous ozone destruction in general over northern mid- and high-latitudes during winter (January-April) in the simulation.

Atmosphere↗
PubMed1989

New high-flow "cloud" catheter for safer delivery of contrast material.

The authors describe a new angiographic catheter, which delivers equal flow rates through the side holes and reduced flow through the end hole compared with conventional catheters. Computer analysis of catheter-flow models revealed that placement of larger side holes proximally and smaller side holes distally produces more uniform flow rates out of the holes. This decreases the risk of potentially hazardous delivery of high-pressure jets of contrast material from the end hole. The flow pattern is so uniform that it resembles a cloud of contrast material on injection. This catheter design is particularly applicable for 3-5-F catheters, which require high-pressure injections. Clinical testing in 50 cases revealed no extravasations or unintentional selective injections with use of this catheter.

Angiography↗
PubMed2003

Rationalization of membrane protein crystallization with polyethylene glycol using a simple depletion model.

Based on the importance of crystallizing membrane proteins in a rational way, cytochrome bc(1) complex (BC1) was crystallized using polyethylene glycol (PEG) as a sole crystallization agent. Interaction between protein-detergent complexes of BC1 was estimated by dynamic light scattering, and was compared with the numerical calculation using the Derjaguin-Landau-Verwey-Overbeek potential plus a depletion potential, without considering specific surface properties of the protein-detergent complexes. The experiments and calculation were found to be consistent and we obtained a relation between PEG molecular weight M and the range of depletion zone delta as delta approximately M(0.48+/-0.02). The stability of liquid phase of BC1 solutions was controlled by a ratio of (the range of depletion zone)/(the radius of a BC1 particle), which was consistent with recent theoretical predictions. The crystallization was most successful under a condition where the stability of the liquid phase changed from stable to unstable. The PEG molecular weight that fulfilled this condition coincided with the one used empirically to crystallize BC1 in the past by a number of groups. These results are compared to the fact that membrane proteins were often successfully crystallized close to the detergent cloud point.

Animals↗
PubMed1992

[Bilateral epidural hematomas].

Bilateral epidural haematomata are rare and comprise only approximately 2% of all the intracranial haematomata. The symptomatology frequently differs from that of unilateral haematomata in that lateralisation is frequently absent. Most commonly, protracted or secondary development of clouding of consciousness is encountered. In cases of head injury, the above mentioned symptoms are indications for emergency computed tomographic (CT) scanning. When operation is performed early, the prognosis is good.

Adult↗
PubMed1997

Neutron RBEs for cytopenia and repopulation of stroma and hematopoietic stem cells: mathematical models of marrow cell kinetics.

The objectives of this study were to (a) extend previous bone-marrow cell kinetics models that have been published for ionizing photons to include neutron radiations, and (b) provide Relative Biological Effectiveness (RBE) values for time-specific cell killing (cytopenia) and compensatory cellular proliferation (repopulation in response to toxic injury) for neutron doses ranging from 0.01 to 4.5 Gy delivered uniformly over one minute, hour, day, week, and month. RBEs for cytopenia of a cell lineage were based on ratios of protocol-specific doses that determined the same cell population nadir, whereas the RBEs for repopulation of a lineage were based on the ratios of protocol-specific doses that corresponded to the same total number of cells killed over the radiation treatments, and which should be replaced for long-term survival of the animal. Time-dependent RBEs were computed for neutron exposures relative to the effect of 60Co gamma rays given as a prompt dose. By the use of these RBE factors, low or variable dose rates, dose fractionations given over long periods of time, and different protocols involving several radiation qualities can be converted realistically, and by standard convention, into an equivalent dose of a reference radiation comprised of x or gamma rays given either as a pulse or at any other reference dose rate for which risk information based on epidemiological or animal dose-response data are available. For stromal tissues irradiated by fission neutrons, time-dependent RBEs for cytopenia were computed to range from 4.24 to 0.70 and RBEs for repopulation varied from a high of 6.88 to a low of 2.24. For hematopoietic stem cells irradiated by fission neutrons, time-dependent RBEs for cytopenia were computed to range from 5.02 to 0.22 and RBEs for repopulation varied from a high of 5.02 to a low of 1.98. RBEs based on tissue-kerma-free-in-air would be about twofold lower for isotropic cloud or rotational exposure geometries because marrow dose from isotropic neutron fields suffer factor-of-two greater attenuation than the gamma doses from gamma photons. For certain doses and dose rates, the RBE values computed for compensatory cellular proliferation clearly demonstrate the behavior that is commonly referred to as an inverse dose-rate effect, i.e., protraction of exposure may-under certain conditions-increase the magnitude of the dose response. Furthermore, because of non-linear rates for repair and repopulation, the highest RBEs are not necessarily found for the lowest doses nor the lowest RBEs always found at the highest doses.

Animals↗
PubMed1989

The thermal structure of Titan's atmosphere.

We have developed a radiative-convective model of the thermal structure of Titan's atmosphere. The model computes the solar and infrared radiation in a series of spectral intervals with vertical resolution. Sources of opacity in the visible and near infrared include stratospheric haze particles, methane cloud particles, and gaseous methane; sources of opacity in the thermal infrared include the pressure-induced opacity of N2, CH4, and H2, the permitted transitions of C2H2 and C2H6, and particulate opacity. The haze properties are determined with a simple microphysics model. The model contains a minimum of free parameters and we try to determine these by fits to independent data sets. We find that gas and haze opacity alone, with the temperatures fixed by Voyager observations, produces a model that is within a few percent of radiative convective balance everywhere in the atmosphere. In a self-consistent computation of temperatures, we find that our model calculation for the surface temperature is, in general, colder than the observed value by 5-10 degrees K. The presence or absence of methane condensation clouds only slightly alters the results. Good agreement can be obtained by adjusting the parameters in the model. The model parameters in these optimized cases are typically within 15% of the baseline values and within the limits allowed by observations. We conclude that the most important factors controlling Titan's thermal structure are absorption of sunlight by the stratospheric haze and the pressure-induced gas opacity in the infrared. Within the uncertainties of the model, these effects can explain the observed temperature profile. Condensation clouds play a minor role, if any.

Atmosphere↗
PubMed1997

Analysis of the role of the Spitzenkörper in fungal morphogenesis by computer simulation of apical branching in Aspergillus niger.

High-resolution video microscopy, image analysis, and computer simulation were used to study the role of the Spitzenkörper (Spk) in apical branching of ramosa-1, a temperature-sensitive mutant of Aspergillus niger. A shift to the restrictive temperature led to a cytoplasmic contraction that destabilized the Spk, causing its disappearance. After a short transition period, new Spk appeared where the two incipient apical branches emerged. Changes in cell shape, growth rate, and Spk position were recorded and transferred to the FUNGUS SIMULATOR program to test the hypothesis that the Spk functions as a vesicle supply center (VSC). The simulation faithfully duplicated the elongation of the main hypha and the two apical branches. Elongating hyphae exhibited the growth pattern described by the hyphoid equation. During the transition phase, when no Spk was visible, the growth pattern was nonhyphoid, with consecutive periods of isometric and asymmetric expansion; the apex became enlarged and blunt before the apical branches emerged. Video microscopy images suggested that the branch Spk were formed anew by gradual condensation of vesicle clouds. Simulation exercises where the VSC was split into two new VSCs failed to produce realistic shapes, thus supporting the notion that the branch Spk did not originate by division of the original Spk. The best computer simulation of apical branching morphogenesis included simulations of the ontogeny of branch Spk via condensation of vesicle clouds. This study supports the hypothesis that the Spk plays a major role in hyphal morphogenesis by operating as a VSC-i.e., by regulating the traffic of wall-building vesicles in the manner predicted by the hyphoid model.

Aspergillus niger↗
PubMed1998

[A preventable case who died of miliary tuberculosis after receiving contact examination].

A 30-year-old-man was admitted to our hospital because of headache and fever. His consciousness on admission was clouding. Sputum examination was positive for acid fast bacilli which later identified as Mycobacterium tuberculosis. Chest-X-ray and computed tomogram on admission showed multiple cavitary lesions on bilateral upper lung fields and bilateral diffuse nodular shadow. He was diagnosed as miliary tuberculosis with tuberculous meningitis. His mother admitted because of pulmonary tuberculosis four months ago, and her sputum examination was smear positive for acid fast bacilli, Gaffky 4, and she complained of cough for 6 months before admission. Because of this situation, he rapidly underwent the contact examination with chest X-ray, but not examined by tuberculin skin test because he was 30-year-old. As then chest X-ray was normal, he was not indicated of chemoprophylaxis, and he died of miliary tuberculosis and tuberculous meningitis 4 months after the contact examination.

Adult↗
PubMed1992

Brain tumors manifesting as intracranial hemorrhage.

The clinical course and computed tomographic (CT) findings of 23 patients with brain tumors manifesting as tumoral hemorrhage were reviewed. The most common symptoms were headache and clouding of consciousness. A CT finding of a lesion located next to a solid or irregular clot indicated intratumoral hemorrhage. Precontrast CT demonstrating an indent on the hematoma surface was a valuable indicator of tumoral hemorrhage. A CT finding of accumulated levels of blood/fluid or a hyperdense mass containing small hematoma indicated intratumoral hemorrhage, and obscure hyperdensity indicated intratumoral hemorrhagic infarction. Such findings were often difficult to distinguish from spontaneous intracerebral hemorrhage due to other factors. The incidence of rebleeding from residual tumors was high, carrying a very poor prognosis, so radical removal of brain tumors with hemorrhage is very important.

Adolescent↗
PubMed2002

Laser transmission-backscattering through inhomogeneous cirrus clouds.

We have developed a two-dimensional (2D) model for inhomogeneous cirrus clouds in plane-parallel and spherical geometries for the analysis of the transmission and backscattering of high-energy laser beams. The 2D extinction-coefficient and mean effective ice-crystal size fields for cirrus clouds can be determined from a combination of the remote sensing of cirrus clouds by use of the Advanced Very High Resolution Radiometer on board National Oceanic and Atmospheric Administration satellites and the vertical profiling of ice-crystal size distributions available from limited measurements. We demonstrate that satellite remote sensing of the position and the composition of high cirrus can be incorporated directly in the computer model developed for the transmission and backscattering of high-energy laser beams in realistic atmospheres. The results of laser direct transmission, forward scattering, and backscattering are analyzed carefully with respect to aircraft height, cirrus cloud optical depth, and ice-crystal size and orientation. Uncertainty in laser transmission that is due to errors in the retrieved ice-crystal size is negligible. But uncertainty of the order of 2% can be produced if the retrieved optical depth has errors of +/-0.05. With both the aircraft and the target near the cloud top, the direct transmission decreases, owing to the propagation of the laser beam through the curved portion of the cloud top. This effect becomes more pronounced as the horizontal distance between the aircraft and the target increases.

Journal Article↗
PubMed1989

[Lympho-renal fistula in lymphatic imaging].

On the case of 10 years old boy with chyluria the authors emphasize the importance of lymphographic examination for proving the pyelolymphatic connection. The lymphographic examination was applied after the complete examination including computer tomography and ultrasound, since these examinations did not prove changes of the urinary and lymphatic systems which could explain the milky clouding of the urine lasting for several months. Changes in the biochemical profile were significant as well as non-constant ejaculation of milky cloudy urine from the opening of the right ureter. The lymphographic examination proved the link between the lymphatic urinary systems with changes on the lymphatic vessels and nodes.

Child↗
PubMed1999

Absorbed dose from traversing spherically symmetric, Gaussian radioactive clouds.

If a large radioactive cloud is produced, sampling may require that an airplane traverse the cloud. A method to predict the absorbed dose to the aircrew from penetrating the radioactive cloud is needed. Dose rates throughout spherically symmetric Gaussian clouds of various sizes, and the absorbed doses from traversing the clouds, were calculated. Cloud size is a dominant parameter causing dose to vary by orders of magnitude for a given dose rate measured at some distance. A method to determine cloud size, based on dose rate readings at two or more distances from the cloud center, was developed. This method, however, failed to resolve the smallest cloud sizes from measurements made at 1,000 m to 2,000 m from the cloud center.

Absorption↗
PubMed2003

Detection, identification, and estimation of biological aerosols and vapors with a Fourier-transform infrared spectrometer.

Two experiments were conducted with a Fourier-transform infrared (FTIR) spectrometer. The purpose of the first experiment was to detect and identify Bacillus subtilis subsp. niger (BG) bioaerosol spores and kaolin dust in an open-air release for which the thermal contrast between the aerosol temperature and background brightness temperature is small. The second experiment estimated the concentration of a small amount of triethyl phosphate (TEP) vapor in a closed chamber in which an external blackbody radiation source was used and where the thermal contrast was large. The deduced BG (TEP) extinction spectrum (identification) showed an excellent match to the library BG (TEP) extinction spectrum. Analysis of the time sequence of the measurements coincided well with the presence (detection) of the BG during the measurements, and the estimated concentration of time-dependent TEP vapor was excellent. The data were analyzed with hyperspectral detection, identification, and estimation algorithms. The algorithms were based on radiative transfer theory and statistical signal-processing methods. A subspace orthogonal projection operator was used to statistically subtract the large thermal background contribution to the measurements, and a robust maximum-likelihood solution was used to deduce the target (aerosol or vapor cloud) spectrum and estimate its mass-column concentration. A Gaussian-mixture probability model for the deduced mass-column concentration was computed with an expectation-maximization algorithm to produce the detection threshold, the probability of detection, and the probability of false alarm. The results of this study are encouraging, as they suggest for the first time to the authors' knowledge the feasibility of detecting biological aerosols with passive FTIR sensors.

Journal Article↗
PubMedDate not supplied

Facile macrocyclizations to beta-turn mimics with diverse structural, physical, and conformational properties.

On-resin S(N)Ar reactions were performed to prepare the macrocyclic beta-turn mimics 1a-n (Scheme 1 and Table 1). These reactions occurred more efficiently than completely analogous macrocyclization reactions that do not involve an iodinated aromatic electrophile. The synthesis was also modified to allow introduction of an alkyne via a solid-phase Sonogashira reaction (giving compound 2, Scheme 2) and an aryne via a solid-phase Suzuki reaction (giving compound 3, Scheme 2). Conformational analyses of three illustrative compounds, i.e., 1i, 2, and 3, were performed using a combination of NMR, circular dichroism, and computer-aided molecular simulation methods. Overall, the preferred conformations of all three molecules tended to be type-I-like beta-turns, but for compound 3 interaction of the electron cloud of the aryl substituent with the oxygen lone pairs seems to cause differences in the preferred orientation of the turn frameworks. This study illustrates how iodinated electrophiles can be used in solid-phase S(N)Ar reactions to increase the molecular and conformational diversity in a library.

Alkynes↗
PubMed1990

[Studies on the crystallization tendency of calcium oxalate in urine--a study of experimental and computer-assisted determination of the risk of urinary calculi formation].

In this study a method o the semiquantitative determination of the crystallization tendency for calcium oxalate in urine is described. It is based on the addition of a well-defined amount of ammonium oxalate (31.3 nmol) to a urine sample (30 ml). The so caused clouding of the urine is measured by a photometer 20 min later. The method guarantees an acceptable reproducibility and is simple to be performed in each clinical laboratory. The results of mathematical correlation and discriminant analysis show that the calcium concentration influences the crystallization of calcium oxalate as most of all urinary constituents. Furthermore, evidence of a high specificity of the method is given by a reclassification rate of about 80% in the discriminant analytical computation.

Adolescent↗
PubMed2002

Universal behavior of entrainment due to coherent structures in turbulent shear flow.

A solution is suggested for a persistent mystery in the physics of turbulent flows: cumulus clouds rise to towering heights, practically without entraining the ambient medium, while apparently similar turbulent jets quickly lose their identity through entrainment and mixing. Dynamical system computations on a model vortical flow show that entrainment due to coherent structures depends sensitively on relative speeds of fluid parcels. Local heating, for example, can alter drastically the sizes of Kolmogorov-Arnol'd-Moser tori and chaotic mixing regions. The entrainment rate and, hence, the lifetime of a turbulent shear flow show a universal, nonmonotone dependence on the heating.

Journal Article↗
PubMed2002

Clinical proteomics for cancer biomarker discovery and therapeutic targeting.

As we emerge into the post-genome era, proteomics finds itself as the driving force field as we translate the nucleic acid information archive into understanding how the cell actually works and how disease processes operate. Even so, the traditionally held view of proteomics as simply cataloging and developing lists of the cellular protein repertoire of a cell are now changing, especially in the sub-discipline of clinical proteomics. The most relevant information archive to clinical applications and drug development involves the elucidation of the information flow of the cell; the "software" of protein pathway networks and circuitry. The deranged circuitry of the cell as the drug target itself as well as the effect of the drug on not just the target, but also the entire network, is what we now are striving towards. Clinical proteomics, as a new and most exciting sub-discipline of proteomics, involves the bench-to-bedside clinical application of proteomic tools. Unlike the genome, there are potentially thousands of proteomes: each cell type has its own unique proteome. Moreover, each cell type can alter its proteome depending on the unique tissue microenvironment in which it resides, giving rise to multiple permutations of a single proteome. Since there is no polymerase chain reaction equivalent to proteomics- identifying and discovering the "wiring diagram" of a human diseased cell in a biopsy specimen remains a daunting challenge. New micro-proteomic technologies are being and still need to be developed to drill down into the proteomes of clinically relevant material. Cancer, as a model disease, provides a fertile environment to study the application of proteomics at the bedside. The promise of clinical proteomics and the new technologies that are developed is that we will detect cancer earlier through discovery of biomarkers, we will discover the next generation of targets and imaging biomarkers, and we can then apply this knowledge to patient-tailored therapy.

Algorithms↗