634 research outputs found
A local field emission study of partially aligned carbon-nanotubes by AFM probe
We report on the application of Atomic Force Microscopy (AFM) for studying
the Field Emission (FE) properties of a dense array of long and vertically
quasi-aligned multi-walled carbon nanotubes grown by catalytic Chemical Vapor
Deposition on a silicon substrate. The use of nanometric probes enables local
field emission measurements allowing investigation of effects non detectable
with a conventional parallel plate setup, where the emission current is
averaged on a large sample area. The micrometric inter-electrode distance let
achieve high electric fields with a modest voltage source. Those features
allowed us to characterize field emission for macroscopic electric fields up to
250 V/m and attain current densities larger than 10 A/cm. FE
behaviour is analyzed in the framework of the Fowler-Nordheim theory. A field
enhancement factor 40-50 and a turn-on field 15 V/m at an inter-electrode distance of 1 m are estimated.
Current saturation observed at high voltages in the I-V characteristics is
explained in terms of a series resistance of the order of M. Additional
effects as electrical conditioning, CNT degradation, response to laser
irradiation and time stability are investigated and discussed
Myeloperoxidase: A New Biomarker of Inflammation in Ischemic Heart Disease and Acute Coronary Syndromes
Myeloperoxidase (MPO) is an enzyme stored in azurophilic granules of polymorphonuclear neutrophils and macrophages and released into extracellular fluid in the setting of inflammatory process. The observation that myeloperoxidase is involved in oxidative stress and inflammation has been a leading factor to study myeloperoxidase as a possible marker of plaque instability and a useful clinical tool in the evaluation of patients with coronary heart disease. The purpose of this review is to provide an overview of the pathophysiological, analytical, and clinical characteristics of MPO and to summarize the state of art about the possible clinical use of MPO as a marker for diagnosis and risk stratification of patients with acute coronary syndrome (ACS)
Immune system activation follows inflammation in unstable angina: pathogenetic implications
AbstractObjectives. The aim of this study was to assess the relations between inflammation, specific immune response and clinical course in unstable angina (UA).Background. Several studies suggest that either inflammation and/or T-cell activation might have a pathogenetic role in UA, but neither their potential reciprocal connection nor their relation to the clinical course is known.Methods. Serum levels of C-reactive protein (CRP) (inflammation), IgG, IgA, IgM, C3, C4 (humoral immunity), IL-2 and the percentage of CD4+, CD8+ and CD3+/DR+ T-cells (cell-mediated immunity) were measured in 35 patients with UA and 35 patients with chronic stable angina (CSA) during a period of 6 months.Results. The CRP levels and the main specific immune markers (CD4+ and CD3+/DR+ cells, IL-2 and IgM) were higher in unstable than in stable angina. In UA, the serum levels of IgM and IL-2 and the percentage of double positive CD3+/DR+ significantly increased at 7 to 15 days, and returned to baseline at 6 months. The increment of circulating activated T cells (CD3+/DR+) in UA was inversely related to the admission levels of CRP (r = −0.63, p = 0.003) and associated with a better outcome.Conclusions. Our data suggest that the inflammatory component systemically detectable in UA may be antigen-related and that the magnitude of the immune response correlates with the clinical outcome of instability
Biomarkers in Acute Coronary Syndrome
Background: Evaluation of patients who present to the hospital with acute undifferentiated chest pain or other symptoms and signs suggestive of Acute Coronary Syndrome (ACS) is often a clinical challenge. The initial assessment, requiring a focused history (including risk factors analysis), a physical examination, an electrocardiogram (EKG) and serum cardiac marker determination, is time-consuming and troublesome. Recent investigations have indicated that increases in biomarkers of necrosis, inflammation, ischemia and myocardial stretch may provide earlier assessment of overall patient risk, help in identifying the adequate diagnostic and therapeutic management for each patient and allow for prevention of substantial numbers of new events. Approach and Content: The purpose of this review is to provide an overview of the characteristics of several biomarkers that may have potential clinical utility to identify ACS patients. Patho-physiology, analytical and clinical characteristics have been evaluated for each marker, underlying the properties for potential routine clinical use. Summary: The biomarkers discussed in this review are promising and might lead to improved diagnosis and risk stratification of patients with ACS, however their clinical application requires further studies. It is important to define their clinical role as diagnostic markers, their predictive value and the specificity, standardization and detection limits of the assays
Clinical experience with power-injectable PICCs in intensive care patients
Introduction: In the ICU, peripherally inserted central catheters (PICCs) may be an alternative option to standard central venous catheters, particularly in patients with coagulation disorders or at high risk for infection. Some limits of PICCs (such as low flow rates) may be overcome with the use of power-injectable catheters.Methods: We retrospectively reviewed all of the power-injectable PICCs inserted in adult and pediatric patients in the ICU during a 12-month period, focusing on the rate of complications at insertion and during maintenance.Results: We collected 89 power-injectable PICCs (in adults and in children), both multiple and single lumen. All insertions were successful. There were no major complications at insertion and no episodes of catheter-related bloodstream infection. Non-infective complications during management were not clinically significant. There was one episode of symptomatic thrombosis during the stay in the ICU and one episode after transfer of a patient to a non-intensive ward.Conclusion: Power-injectable PICCs have many advantages in the ICU: they can be used as multipurpose central lines for any type of infusion including high-flow infusion, for hemodynamic monitoring, and for high-pressure injection of contrast media during radiological procedures. Their insertion is successful in 100% of cases and is not associated with significant risks, even in patients with coagulation disorders. Their maintenance is associated with an extremely low rate of infective and non-infective complications. © 2012 Pittiruti et al.; licensee BioMed Central Ltd
Early versus late tracheostomy in pediatric intensive care unit: does it matter? A 6-year experience
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