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PubMed2000

Proper orthogonal decomposition and galerkin projection for a three-dimensional plasma dynamical system

A general method by which to investigate nonlinear dynamical systems close to a stability threshold is presented. This method combines a proper orthogonal decomposition and a subsequent Galerkin projection. This technique is applied to three-dimensional resistive ballooning plasma fluctuations in a tokamak. The corresponding dynamical system belongs to a large family of convective fluid systems including Rayleigh-Benard convection. A proper orthogonal decomposition of the fluctuating signal obtained by numerical simulation shows that the relevant modes are close to the linear (global) modes. The Galerkin projection provides a low-dimensional system that allows the study of shear flow generation, its subsequent fluctuation reduction, and the evolution to oscillating states.

Journal Article↗
PubMed2004

Self-organization of a plasma due to 3D evolution of the Weibel instability.

The nonlinear evolution of the thermal Weibel instability is studied by using three-dimensional particle-in-cell simulations. After a fast saturation due to a reduction in the temperature anisotropy, the instability evolves to a quasistationary state which includes a single mode long wavelength helical magnetic field and a finite degree of temperature anisotropy. The nonlinear stability of this state is explained by periodic variations of the temperature anisotropy axis. At long time scales the magnetic field, wave number, and temperature anisotropy slowly evolve to the decreasing magnitudes.

Journal Article↗
PubMed1995

Structure and epitope characterisation of the O-specific polysaccharide of Proteus mirabilis O28 containing amides of D-galacturonic acid with L-serine and L-lysine.

The O-specific polysaccharide of Proteus mirabilis O28 was found to contain D-galactose, D-galacturonic acid (GalA), 2-acetamido-2-deoxy-D-glucose, L-serine, L-lysine, and O-acetyl groups in molar ratios 1:2:1:1:1:1, the amino acids being linked via their alpha-amino group to the carboxyl group of GalA. The polysaccharide was studied using 1H- and 13C-NMR spectroscopy, including selective spin-decoupling, one-dimensional total correlation spectroscopy, two-dimensional homonuclear correlation spectroscopy (COSY), heteronuclear 13C,1H COSY, one-dimensional NOE, and two-dimensional rotating-frame NOE spectroscopy and partial acid hydrolysis followed by borohydride reduction, methylation, and GLC/MS analysis of the derived glycosyl alditols. The following structure of the repeating unit was established: [formula: see text] Epitope specificity of the P. mirabilis O28 polysaccharide was analysed using a homologous rabbit polyclonal antiserum in quantitative precipitation, passive immunohemolysis, and inhibition of passive immunohemolysis. Study with related synthetic glycopolymers (2-acrylamidoethyl glycosides of amides of alpha-D-GalA with amino acids copolymerised with acrylamide) showed the importance of D-GalA(L-Lys) for manifesting serological specificity of the O-antigen. Serological cross-reactions between P. mirabilis O28, S1959, and R14/S1959 (a transient-like form) are discussed.

Amides↗
PubMed1983

A three-dimensional treatment programme for chronic pain.

The treatment of chronic pain contains several problems such as ineffectiveness, side effects and drug dependence. The concepts of respondent and operant pain are introduced, together with a general operant learning model for analysis and treatment of psychological problems. To make a psychological analysis of pain, evidence for learned pain behaviour must be assessed, reinforcers for treatment revealed, goal behaviours set up, and support in the environment secured. In the further analysis, account must be taken to a) time pattern of pain, b) pain behaviour, c) reactions from the environment, d) pain activators, e) pain reducers, f) the effect of tension versus relaxation on pain, and g) changes in the family structure necessary because of the pain problem. A three-dimensional operant treatment programme for chronic pain is presented. It consists of 1) reduction of medication, 2) increase of activity, and 3) reduction of pain behaviour. Results, supporting the efficacy of the model, are presented.

Analgesics↗
PubMedDate not supplied

Comparative study of cryogen spray cooling with R-134a and R-404a: implications for laser treatment of dark human skin.

Cutaneous laser treatment in dark skin patients is challenging due to significant light absorption by the melanin at the basal layer of epidermis, which can result in irreversible nonspecific thermal injury to the epidermis. Cryogen spray cooling (CSC) with R-134a (boiling point approximately -26.2 degrees C at 1 atm), which is currently used during cutaneous laser treatment, has shown poor efficacy in protecting dark human skin. We investigated the potential of CSC with R-404a (boiling point approximately -46.5 degrees C at 1 atm), which has a lower boiling point than R-134a, for improved therapeutic outcome in dark human skin at three levels: in vitro (epoxy resin skin phantom), ex vivo (normal dark human skin sample), and in vivo (skin of the rabbit external ear). The skin phantom was used to acquire the surface and internal temperature profiles in response to CSC with R-134a or R-404a at various spurt durations, based upon which CSC-induced heat removal from the skin phantom was estimated using an algorithm that solved a one-dimensional inverse heat conduction problem. CSC with R-404a increased the temperature reductions within the phantom and subsequently the amount of heat removal from the phantom in comparison to that with R-134a. Normal ex vivo Fitzpatrick types V-VI human skin samples were used to investigate the thermal response of dark human skin epidermis to CSC (R-134a or R-404a) at various spurt durations in conjunction with 595-nm pulsed dye laser irradiation at various radiant exposures. Cryogen R-404a increased the threshold radiant exposures for irreversible thermal injury to the epidermis in dark pigmentation skin. No obvious CSC-induced morphological changes to human skin was observed when sprayed with R404-a spurts using durations up to 300 ms. In vivo rabbit ear vasculature was used as a model of cutaneous anomalies to assess the influences of CSC (with R-134a or R-404a) on the photothermolysis of dermal blood vessels. CSC (R-134a or R-404a) with the spurt durations of 100 to 300 ms increased the most superficial depth of thermally damaged dermal blood vessel compared with the sites without CSC, implying possible nonspecific cooling of superficial dermal blood vessels by the cryogen spurts with the settings applied.

Aerosol Propellants↗
PubMed2003

Automatic detection of small lung nodules on CT utilizing a local density maximum algorithm.

Increasingly, computed tomography (CT) offers higher resolution and faster acquisition times. This has resulted in the opportunity to detect small lung nodules, which may represent lung cancers at earlier and potentially more curable stages. However, in the current clinical practice, hundreds of such thin-sectional CT images are generated for each patient and are evaluated by a radiologist in the traditional sense of looking at each image in the axial mode. This results in the potential to miss small nodules and thus potentially miss a cancer. In this paper, we present a computerized method for automated identification of small lung nodules on multislice CT (MSCT) images. The method consists of three steps: (i) separation of the lungs from the other anatomic structures, (ii) detection of nodule candidates in the extracted lungs, and (iii) reduction of false-positives among the detected nodule candidates. A three-dimensional lung mask can be extracted by analyzing density histogram of volumetric chest images followed by a morphological operation. Higher density structures including nodules scattered throughout the lungs can be identified by using a local density maximum algorithm. Information about nodules such as size and compact shape are then incorporated into the algorithm to reduce the detected nodule candidates which are not likely to be nodules. The method was applied to the detection of computer simulated small lung nodules (2 to 7 mm in diameter) and achieved a sensitivity of 84.2% with, on average, five false-positive results per scan. The preliminary results demonstrate the potential of this technique for assisting the detection of small nodules from chest MSCT images.

Algorithms↗
PubMed2004

Neuraminidase inhibitor-rimantadine combinations exert additive and synergistic anti-influenza virus effects in MDCK cells.

There is insufficient information about combination therapy with approved anti-influenza agents. We tested combinations that paired a neuraminidase (NA) inhibitor (zanamivir, oseltamivir carboxylate, or peramivir) with rimantadine against infection of MDCK cells with H1N1 and H3N2 subtypes of influenza A virus and characterized their mode of interaction. When reduction of extracellular virus was analyzed by individual regression models and three-dimensional representations of the data, all three combinations showed additive and synergistic effects with no cytotoxicity. Maximum synergy against A/New Caledonia/20/99 (H1N1) virus infection was observed with <2.5 microM rimantadine paired with low concentrations of NA inhibitors. All combinations reduced the extracellular yield of A/Panama/2007/99 (H3N2) influenza virus synergistically. However, our findings were different for the cell-associated virus yield. At some drug concentrations, the yield of cell-associated virus was inhibited antagonistically. Therefore, the method of analysis can be a crucial factor in evaluating the interactions of drugs with different mechanisms. We hypothesize that assays based on cell-associated virus yield may underestimate the efficacies of drug combinations that include an NA inhibitor. Taken together, our results suggest that regimens that combine NA inhibitors and rimantadine exert synergistic anti-influenza effects in vitro. These findings provide baseline information for therapeutic testing of the drug combinations in vivo.

Acetamides↗
PubMed1997

A lesion in the DNA replication initiation factor Mcm10 induces pausing of elongation forks through chromosomal replication origins in Saccharomyces cerevisiae.

We describe a new minichromosome maintenance factor, Mcm10, and show that this essential protein is involved in the initiation of DNA replication in Saccharomyces cerevisiae. The mcm10 mutant has an autonomously replicating sequence-specific minichromosome maintenance defect and arrests at the nonpermissive temperature with dumbbell morphology and 2C DNA content. Mcm10 is a nuclear protein that physically interacts with several members of the MCM2-7 family of DNA replication initiation factors. Cloning and sequencing of the MCM10 gene show that it is identical to DNA43, a gene identified independently for its putative role in replicating DNA. Two-dimensional DNA gel analysis reveals that the mcm10-1 lesion causes a dramatic reduction in DNA replication initiation at chromosomal origins, including ORI1 and ORI121. Interestingly, the mcm10-1 lesion also causes replication forks to pause during elongation through these same loci. This novel phenotype suggests a unique role for the Mcm10 protein in the initiation of DNA synthesis at replication origins.

Alleles↗
PubMed1994

Ultrasonic B-mode image enhancement based on level-dependent spread functions.

The concept of level-dependent spatial summation is applied to the 2-dimensional amplitude distribution comprising an ultrasonic brightness image. The distribution is convolved with a level-dependent kernel. The size (i.e., extent) of the kernel is inversely proportional to the local signal level. The result is a 2-dimensional distribution of Mach bands, accentuating edges and providing useful information for the reduction of speckle. In addition, a small but powerful extension of the processing scheme is presented that supports global edge enhancement and contrast enhancement. The level of improvement has been quantified in terms of an increase in the lesion signal-to-noise ratio on the order of 60 percent. Only two system-dependent parameters have to be supplied for adjustment. The algorithm is rather insensitive to the exact choice of the parameters, making it quite robust. Since only a limited number of simple operations is required for the processing of a frame, the algorithm is expected to be suitable for real time application.

Image Enhancement↗
PubMed1996

Type I Glanzmann's thrombasthenia in a Great Pyrenees dog.

An 8-month-old female Great Pyrenees dog with chronic epistaxis and a history of gingival bleeding during shedding of deciduous teeth was evaluated for platelet function. Platelet morphology was normal at both the light and electron microscopic level. Platelet number and mean platelet volume were also normal. Platelet aggregation responses to adenosine diphosphate, collagen, platelet activating factor, and thrombin were markedly reduced, although shape change responses were normal. Clot retraction was markedly impaired. Monoclonal antibody (MoAb) Y2/51, a murine anti-human platelet beta 3 antibody that cross-reacts with canine platelet beta 3, and MoAb 5G11, a murine anti-dog platelet alpha IIb beta 3 antibody, bound minimally to affected dog platelets, as demonstrated by flow cytometry. Binding of MoAb Y2/51 was not detectable by immunoblot. MoAb CAP1, a murine anti-dog fibrinogen receptor-induced binding site antibody, failed to bind to affected dog platelets, as demonstrated by flow cytometry. A reduction in glycoproteins alpha IIb and beta 3 was demonstrated by two-dimensional protein electrophoresis. This is the first reported case of type I Glanzmann's thrombasthenia in the dog that closely resembles the clinical syndrome and the platelet morphology described in type I Glanzmann's thrombasthenia of human beings.

Animals↗
PubMed1985

Brain metabolism as measured with positron emission tomography: serial assessment in a patient with familial Alzheimer's disease.

This paper presents, for the first time, repeated assessments of cerebral metabolism and neuropsychological competence in early Alzheimer's disease. Regional cerebral metabolic rates for glucose were measured with positron emission tomography and 18F-fluoro-2-deoxy-D-glucose on three occasions at 8-month intervals, in a 57-year-old man with Alzheimer's disease of 2 1/2 years' duration and with a family history of neuropathologically confirmed Alzheimer's disease. Data were compared with mean cerebral metabolic rates from 12 healthy men. No differences in regional cerebral metabolic rates for glucose were found on the initial patient scan, whereas metabolism on the second and third scans was reduced significantly in the parietal lobes and bilaterally in some parietal lobe regions. Memory loss was demonstrable at the first scan, but then and at later scans, other aspects of cognitive performance remained within normal limits (Wechsler Adult Intelligence Scale, Boston Naming Test, Two-dimensional Block Construction). The results show that memory loss can precede a measurable reduction of cerebral metabolism in early Alzheimer's disease, but that later reductions in parietal lobe metabolism may not be accompanied by additional measurable neuropsychological deficits.

Aged↗
PubMed1993

Reduced basal ganglia volumes in Tourette's syndrome using three-dimensional reconstruction techniques from magnetic resonance images.

Using a 1.5-tesla GE Signa MR scanner, we imaged the brains of 14 right-handed Tourette's syndrome (TS) patients (11 men, three women), aged 18 to 49 years, who had minimal lifetime neuroleptic exposure. We also studied an equal number of normal controls individually matched for age, sex, and handedness and group-matched for socioeconomic status. We circumscribed basal ganglia on sequential axial images from spin-echo proton density-weighted acquisitions (TR 1,700, TE 20; slice thickness, 3 mm with 1.5-mm skip) and submitted the images for three-dimensional processing at a computer graphics workstation. Our hypothesis of lenticular nucleus volume reduction in TS was confirmed for the left- but not the right-sided nucleus. Post hoc analyses revealed smaller mean volumes of the caudate, lenticular, and globus pallidus nuclei compared with controls on both the right and left. Further analyses of basal ganglia asymmetry indices suggest that TS basal ganglia do not have the volumetric asymmetry (left greater than right) seen in normal controls. These findings confirm and extend prior phenomenologic, neuropathologic, and neuroradiologic studies that implicate the basal ganglia in the pathogenesis of TS.

Adult↗
PubMed1995

Alteration of collagen-dependent adhesion, motility, and morphogenesis by the expression of antisense alpha 2 integrin mRNA in mammary cells.

Although integrins are known to mediate adhesive binding of cells to the extracellular matrix, their role in mediating cellular growth, morphology, and differentiation is less clear. To determine more directly the role of the alpha 2 beta 1 integrin, a collagen and laminin receptor, in mediating the collagen-dependent differentiation of mammary cells, we reduced expression of the integrin by the well differentiated human breast carcinoma cell line, T47D, by stably expressing alpha 2 integrin antisense mRNA. Flow cytometry demonstrated that the antisense-expressing clones had levels of alpha 2 beta 1 integrin on their surfaces that were decreased by 30-70%. Adhesion of antisense-expressing clones to both collagens I and IV was decreased relative to controls in a manner that correlated with the level of cell surface alpha 2 beta 1 integrin expression. Adhesion to fibronectin and laminin were not affected. Motility across collagen-coated filters in haptotaxis assays was increased for only those clones that exhibited intermediate levels of adhesion to collagen, suggesting that an intermediate density of cell-surface alpha 2 beta 1 integrin optimally supports cell motility. When cultured in three-dimensional collagen gels, T47D cells organized in a manner suggestive of a glandular epithelium. In contrast, antisense-expressing clones with decreased alpha 2 beta 1 integrin were not able to organize in three-dimensional collagen gels. The growth rate of T47D cells was reduced when the cells were cultured in three-dimensional collagen gels. Unlike adhesion, motility, and morphogenesis, growth rates were unaffected by reduction of alpha 2 beta 1 integrin expression. Our results suggest that adhesive interactions mediated by a critical level of surface alpha 2 beta 1 integrin expression are key determinants of the collagen-dependent morphogenetic capacity of mammary epithelial cells.

Animals↗
PubMed1999

Indications for treatment of subcondylar mandibular fractures.

BACKGROUND AND OBJECTIVES: The purpose of this study was to establish a reliable criteria for implementation of either an open surgical or a closed conservative treatment of subcondylar fractures, based on clinical data and analytical mathematical model. METHODS AND MATERIALS: A total of 512 subcondylar fractures were treated during a 3-year period. Of these, 256 were fractures characterized by either displacement or dislocation of the proximal (condylar) segment. Patients were treated with open reduction and internal fixation (ORIF) or closed reduction (CR) techniques. Patients were evaluated pre- and postoperatively by clinical examination, 3-dimensional axiography, radiographic imaging, and ultrasonography. A mathematical model was developed for estimating the loss of vertical ramus height. RESULTS AND/OR CONCLUSIONS: When the displacements were less than 37 degrees from the sagittal axis of the ascending ramus, the ensuing loss of vertical height was negligible when fractures were treated by conservative techniques. When the displacements exceeded 37 degrees, the fractures resulted in a significant decrease of vertical ramus height. Based on these data, 37 degrees appears to be the point for decision of whether to use closed or open treatment.

Adolescent↗
PubMed1999

Low-Molecular Collagen Peptides Have Different Effects on Peritoneal Macrophages and Neutrophils.

Two types of phagocytes - neutrophils and macrophages, are very important participants in inflammation. However, the roles played by these cells in the regulation of an inflammation are radically different. Neutrophils initiate and ensure the alteration phase. Macrophages, to the contrary, regulate the transition of an inflammation from alternative processes to reparative. During the early stages of an inflammation, under the effect of proteases and free radicals, destruction of collagen proteins occurs and a large number of low-molecular peptides are formed, the concentration of which changes as the inflammatory reaction develops. The object of this work was to study the effect of the total fraction of low-molecular type I collagen peptides on the key functions of neutrophils and macrophages. Under the action of the wide range of concentrations of the collagen peptides (1-1000 &mgr;g/ml), activation of the neutrophil migration into the three-dimensional collagen matrix, amplification of PMA-induced production of free radicals and reduction of apoptosis of those cells were observed. The action of collagen peptides on the functions of macrophages had the opposite effect, i.e. they caused inhibition of the macrophage migration and reduction of PMA-induced production of free radicals. Furthermore, at a concentration of 100 &mgr;g/ml the collagen peptides reliably reduced the apoptosis of macrophages. Thus, collagen peptides are potent regulators of an inflammation, promoting the successive development of its phases through regulation of the functional state of phagocytes.

Journal Article↗
PubMed1998

In vivo electron paramagnetic resonance imaging of tumor heterogeneity and oxygenation in a murine model.

Nitroxides are redox-sensitive probes, which are useful in noninvasively delineating tissue heterogeneity especially with respect to metabolic activity and tissue oxygenation. Recent studies have shown that nitroxides are in vitro and in vivo radioprotectors and selectively protect normal tissue compared to tumor tissue. It has been postulated that the basis for selective radioprotection of normal tissues is greater bioreduction of nitroxides in tumor tissue compared to normal tissue. The aim of the present study was to investigate the distribution and lifetime of nitroxides in tumor and normal tissues. Mice were implanted with tumor cells (RIF-1) in the thigh, and the tumor was allowed to grow to about 10-15 mm in diameter. After i.v. infusion of nitroxides, in vivo electron paramagnetic resonance spectroscopy and imaging of the tumor were performed using a specially built bridged-loop surface resonator. The pharmacokinetic and spatial distribution of the nitroxides in tumor tissue were followed and compared with those in normal tissue. Three-dimensional spatial images showed significant heterogeneity in the nitroxide distribution as well as reduction rates. The nitroxide reduction rates were significantly higher in tumors than in the normal tissue. Measurements using spin label oximetry showed a substantial difference in the level of oxygenation between normal tissue (muscle) and tumor tissue. Average pO2 levels in tumor tissue were found to be 3-fold lower than in a corresponding volume of normal tissue. The lower pO2 levels in tumor compared to normal tissue may explain the more rapid reduction of nitroxides in these tissues. This study demonstrates that electron paramagnetic resonance imaging can perform noninvasive anatomical as well as functional imaging and provide in vivo physiological information regarding cellular metabolism in tumor and normal tissues.

Animals↗
PubMed2004

Electrochemical reduction of hexahydro-1,3,5-trinitro-1,3,5-triazine in aqueous solutions.

Electrochemical reduction of RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine, a commercial and military explosive, was examined as a possible remediation technology for treating RDX-contaminated groundwater. A cascade of divided flow-through cells was used, with reticulated vitreous carbon cathodes and IrO2/Ti dimensionally stable anodes, initially using acetonitrile/water solutions to increase the solubility of RDX. The major degradation pathway involved reduction of RDX to the corresponding mononitroso compound, followed by ring cleavage to yield formaldehyde and methylenedinitramine. The reaction intermediates underwent further reduction and/or hydrolysis, the net result being the complete transformation of RDX to small molecules. The rate of degradation increased with current density, but the current efficiency was highest at low current densities. The technique was extended successfully both to 100% aqueous solutions of RDX and to an undivided electrochemical cell.

Electrochemistry↗
PubMed2006

Cardiac CINE MR imaging with a 32-channel cardiac coil and parallel imaging: impact of acceleration factors on image quality and volumetric accuracy.

PURPOSE: To assess the impact of parallel imaging algorithms on image quality and volumetric accuracy of CINE magnetic resonance imaging (MRI) with high temporal and spatial resolution using a new 32-channel dedicated cardiac phased array coil. MATERIALS AND METHODS: Fourteen individuals underwent steady-state free precession (SSFP) CINE MRI using a 32-element phased-array coil and parallel imaging acceleration using spatiotemporal sensitivity encoding (TSENSE). Acquisition acceleration ranged from R = 2 to 7. In conjunction with data extracted from phantom measurements, contrast-to-noise ratio (CNR) performance was evaluated for each acceleration factor and subjective image quality was evaluated by two independent readers. In addition, volumetric assessment was performed for each acceleration factor based on a single breath-hold multi-slice data acquisition. Results were compared to nonTSENSE measurements. RESULTS: CNR for non-accelerated CINE (R = 1) was 45.7 +/- 12.8 and showed a constant decrease with increase in acceleration of 51% at R = 4 and 86% at R = 7. CNR losses accompanied reductions in subjective image quality. Volumetric evaluation was accurate for R <or= 4, with significant underestimation of ejection fraction (EF) at higher accelerations. CONCLUSION: This study shows that one-dimensional acceleration factors up to R = 4 allow accurate SSFP CINE MRI even though CNR is significantly reduced. This allows for a marked reduction in scan time and allows for multi-slice CINE imaging with high spatial and temporal resolution.

Adult↗