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Critical Nature (critical + nature)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Prosthetic Valve Thrombosis Presenting as an Acute Embolic Myocardial Infarction in a Pregnant Patient: Issues on Anticoagulation Regimens and Thrombolytic Therapy

ECHOCARDIOGRAPHY, Issue 9 2006
Padmini Varadarajan M.D.
Mechanical valves are inherently thrombogenic and require meticulous anticoagulation. Pregnancy produces a hypercoagulable state and achieving adequate anticoagulation is difficult. We present a pregnant patient who had a nonobstructive thrombus of mechanical mitral valve causing embolic acute myocardial infarction. Issues surrounding management of anticoagulation and use of thrombolytic therapy during pregnancy are discussed. Education regarding the critical nature of adequate anticoagulation in these patients is important. [source]

Structure,activity analysis of the potentiation by aminothiols of the chromosome-damaging effect of bleomycin in G0 human lymphocytes

ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2001
George R. Hoffmann
Abstract The radioprotective aminothiols 2-[(aminopropyl)amino] ethanethiol (WR-1065) and cysteamine (CSM) potentiate the induction of chromosomal damage by the radiomimetic compound bleomycin (BLM) in G0 human lymphocytes. To investigate the mechanism of potentiation, we measured the clastogenic activity of BLM in the cytokinesis-block micronucleus assay in the presence and absence of amines, thiols, and aminothiols. The hydroxy analog of WR-1065, 2-(3-aminopropylamino) ethanol (WR-OH), potentiates BLM only slightly, indicating the critical nature of the thiol group. As thiols, WR-1065 and CSM may donate electrons for the activation of Fe+2 -BLM or for the regeneration of Fe+2 -BLM from inactive Fe+3 -BLM. The amines putrescine, spermidine, and spermine all potentiate BLM, but they are weaker potentiators than the aminothiols, and they are effective only at high concentrations. Their activity, like that of WR-OH, is probably a consequence of conformational alteration of DNA. Dithioerythritol (DTE) and 2-mercaptoethanol (2-ME), thiols lacking an amino group, are less effective potentiators of BLM than are the aminothiols. The thiol group of WR-1065 and CSM is therefore essential, but insufficient, for explaining the strong enhancement of BLM activity. The cationic nature of CSM and WR-1065, conferred by the amino groups, evidently concentrates the active thiol function at the site of BLM action on DNA. As expected on this basis, the diamine WR-1065 is a more effective potentiator of BLM than is the monoamine CSM, whereas cysteine and N -acetylcysteine (NAC), which lack a net positive charge, potentiate BLM only weakly. These studies suggest that potentiation of the clastogenic action of BLM by aminothiols can be explained by the combination of a thiol-mediated redox mechanism and an amine-mediated targeting of the thiol function to DNA. Environ. Mol. Mutagen. 37:117,127, 2001 © 2001 Wiley-Liss, Inc. [source]

Processing, modelling and predicting time-lapse effects of overpressured fluid-injection in a fractured reservoir

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2002
Erika Angerer
Summary Time-lapse seismology is important for monitoring subsurface pressure changes and fluid movements in producing hydrocarbon reservoirs. We analyse two 4-D, 3C onshore surveys from Vacuum Field, New Mexico, USA, where the reservoir of interest is a fractured dolomite. In Phase VI, a time-lapse survey was acquired before and after a pilot tertiary-recovery programme of overpressured CO2 injection, which altered the fluid composition and the pore-fluid pressure. Phase VII was a similar time-lapse survey in the same location but with a different lower-pressure injection regime. Applying a processing sequence to the Phase VI data preserving normal-incidence shear-wave anisotropy (time-delays and polarization) and maximizing repeatability, interval-time analysis of the reservoir interval shows a significant 10 per cent change in shear-wave velocity anisotropy and 3 per cent decrease in the P -wave interval velocities. A 1-D model incorporating both saturation and pressure changes is matched to the data. The saturation changes have little effect on the seismic velocities. There are two main causes of the time-lapse changes. Any change in pore-fluid pressures modifies crack aspect ratios. Additionally, when there are overpressures, as there are in Phase VI, there is a 90° change in maximum impedance directions, and the leading faster split shear wave, instead of being parallel to the crack face as it is for low pore-fluid pressures, becomes orthogonal to the crack face. The anisotropic poro-elasticity (APE) model of the evolution of microcracked rock, calculates the evolution of cracked rock to changing conditions. APE modelling shows that at high overburden pressures only nearly vertical cracks, to which normal incidence P waves are less sensitive than S waves, remain open as the pore-fluid pressure increases. APE modelling matches the observed time-lapse effects almost exactly demonstrating that shear-wave anisotropy is a highly sensitive diagnostic of pore-fluid pressure changes in fractured reservoirs. In this comparatively limited analysis, APE modelling of fluid-injection at known pressure correctly predicted the changes in seismic response, particularly the shear-wave splitting, induced by the high-pressure CO2 injection. In the Phase VII survey, APE modelling also successfully predicted the response to the lower-pressure injection using the same Phase VI model of the cracked reservoir. The underlying reason for this remarkable predictability of fluid-saturated reservoir rocks is the critical nature and high crack density of the fluid-saturated cracks and microcracks in the reservoir rock, which makes cracked reservoirs critical systems. [source]

A NEW NEW ORLEANS?

JOURNAL OF URBAN AFFAIRS, Issue 3 2008
LOCAL RELATIONSHIP IN THE RECOVERY PROCESS, UNDERSTANDING THE ROLE OF HISTORY AND THE STATE
ABSTRACT:,Two years after Hurricane Katrina struck New Orleans, the city still struggles to rebuild and recover. In this article, we examine how deeply rooted historical patterns of state,local conflict reasserted themselves even after the terrible destruction of Katrina and the redemptive promise of a new beginning. We also explain how state government, some city leaders, and most New Orleanians took advantage of the opportunities presented by Hurricane Katrina to change certain aspects of governance in New Orleans. This research highlights the importance of the state,local relationship in understanding urban affairs and the critical nature of historical patterns and their persistence. State,local conflicts over finances, control of local politics, and cultural differences have plagued New Orleans for decades, and they continue to do so in the post-Katrina era. [source]

Performance of an Autonomous Telemonitoring System in Children and Young Adults with Congenital Heart Diseases

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2008
PETER ZARTNER M.D.
Background:Integrated telemonitoring systems controlling circulatory and electrical parameters in adults with an implanted pacemaker have shown to be advantageous during follow-up of this patient group. In children and young adults with a congenital heart disease (CHD), these systems have to cope with a diversity of varying arrhythmias and a broad range of intrinsic cardiac parameters. Additional problems arise from the patients' growth and anatomic anomalies. Methods:Since 2005, eight young patients (age 4.1, 37 years, mean 15.5 years) with a CHD received a pacemaker or implantable cardioverter defibrillator with an autonomous telemonitoring system at our clinic. The mean follow-up time was 395 days (range 106,834 days, 8.7 patient years). Results:In seven of eight patients the system transmitted information, which led to beneficial modifications of the current antiarrhythmic therapy. In three patients the reported events were of a critical nature. One patient remained event-free for 192 days after implantation. During follow-up, 96% of the days were covered. The system also transferred additional information on the effectiveness of antiarrhythmic medication and the impact of physical activity. Conclusions:Young patients with an insufficient intrinsic heart rate or progressing arrhythmia, in addition to the conventional indications for pacemaker or defibrillator implantation, seem to profit to a high percentage from a telemetric surveillance system. The fully automated procedure of device interrogation and information transmission gives a daily overview on system function and specific arrhythmic events, especially in children who are unaware of any symptoms. [source]