28 research outputs found
Modelling Techniques for the Quantification of Some Electron Beam Induced Phenomena
This paper presents simulation models for quantifying the voltage contrast, cathodoluminescence and indirect specimen charging phenomena in the scanning electron microscope (SEM). The voltage contrast model comprises an electric field computation program using the finite-element approach, and a secondary electron trajectory tracking algorithm employing a linear electric field assumption. This trajectory tracking algorithm is more accurate than the conventional electron trajectory tracking algorithms which make use of a constant electric field assumption within each computation step. Using this model, results of qualitative voltage contrast effects on secondary electron trajectories in the specimen chamber of the SEM are shown. This model can also be used for quantitative voltage studies for designing low error voltage energy analysers. The cathodoluminescence (CL) model consists of programs for simulating the electron beam-specimen interaction via Monte Carlo analysis, excess carrier generation and distribution, and optical losses of the CL emission. This model has been used to simulate the CL intensity as a function of surface recombination velocity, diffusion length, and absorption coefficient. A model has also been developed to simulate indirect charging of specimens in the SEM. This model uses the finite-element method to solve for the self-consistent electric field due to the imposed boundary conditions, trapped and moving charges. Secondary electrons are tracked using the trajectory tracking scheme developed
A simple and rapid approach for screening of SARS-coronavirus genotypes: an evaluation study
BACKGROUND: The Severe Acute Respiratory Syndrome (SARS) was a newly emerged infectious disease which caused a global epidemic in 2002–2003. Sequence analysis of SARS-coronavirus isolates revealed that specific genotypes predominated at different periods of the epidemic. This information can be used as a footprint for tracing the epidemiology of infections and monitor viral evolution. However, direct sequencing analysis of a large number of clinical samples is cumbersome and time consuming. We present here a simple and rapid assay for the screening of SARS-coronavirus genotypes based on the use of fluorogenic oligonucleotide probes for allelic discrimination. METHODS: Thirty SARS patients were recruited. Allelic discrimination assays were developed based on the use of fluorogenic oligonucleotide probes (TaqMan). Genotyping of the SARS-coronavirus isolates obtained from these patients were carried out by the allelic discrimination assays and confirmed by direct sequencing. RESULTS: Genotyping based on the allelic discrimination assays were fully concordant with direct sequencing. All of the 30 SARS-coronavirus genotypes studied were characteristic of genotypes previously documented to be associated with the latter part of the epidemic. Seven of the isolates contained a previously reported major deletion but in patients not epidemiologically related to the previously studied cohort. CONCLUSION: We have developed a simple and accurate method for the characterization and screening of SARS-coronavirus genotypes. It is a promising tool for the study of epidemiological relationships between documented cases during an outbreak
Absence of association between angiotensin converting enzyme polymorphism and development of adult respiratory distress syndrome in patients with severe acute respiratory syndrome: a case control study
BACKGROUND: It has been postulated that genetic predisposition may influence the susceptibility to SARS-coronavirus infection and disease outcomes. A recent study has suggested that the deletion allele (D allele) of the angiotensin converting enzyme (ACE) gene is associated with hypoxemia in SARS patients. Moreover, the ACE D allele has been shown to be more prevalent in patients suffering from adult respiratory distress syndrome (ARDS) in a previous study. Thus, we have investigated the association between ACE insertion/deletion (I/D) polymorphism and the progression to ARDS or requirement of intensive care in SARS patients. METHOD: One hundred and forty genetically unrelated Chinese SARS patients and 326 healthy volunteers were recruited. The ACE I/D genotypes were determined by polymerase chain reaction and agarose gel electrophoresis. RESULTS: There is no significant difference in the genotypic distributions and the allelic frequencies of the ACE I/D polymorphism between the SARS patients and the healthy control subjects. Moreover, there is also no evidence that ACE I/D polymorphism is associated with the progression to ARDS or the requirement of intensive care in the SARS patients. In multivariate logistic analysis, age is the only factor associated with the development of ARDS while age and male sex are independent factors associated with the requirement of intensive care. CONCLUSION: The ACE I/D polymorphism is not directly related to increased susceptibility to SARS-coronavirus infection and is not associated with poor outcomes after SARS-coronavirus infection
Elective amputation and bionic substitution restore functional hand use after critical soft tissue injuries
Critical soft tissue injuries may lead to a non-functional and insensate limb. In these cases standard reconstructive techniques will not suffice to provide a useful outcome, and solutions outside the biological arena must be considered and offered to these patients. We propose a concept which, after all reconstructive options have been exhausted, involves an elective amputation along with a bionic substitution, implementing an actuated prosthetic hand via a structured tech-neuro-rehabilitation program. Here, three patients are presented in whom this concept has been successfully applied after mutilating hand injuries. Clinical tests conducted before, during and after the procedure, evaluating both functional and psychometric parameters, document the benefits of this approach. Additionally, in one of the patients, we show the possibility of implementing a highly functional and natural control of an advanced prosthesis providing both proportional and simultaneous movements of the wrist and hand for completing tasks of daily living with substantially less compensatory movements compared to the traditional systems. It is concluded that the proposed procedure is a viable solution for re-gaining highly functional hand use following critical soft tissue injuries when existing surgical measures fail. Our results are clinically applicable and can be extended to institutions with similar resources
Trichostrongylus infestation masquerading as conditioning toxicity of the gut in bone marrow transplantation [1]
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Use of fludarabine-containing chemotherapeutic regimen results in durable complete remission of subcutaneous panniculitis-like T-cell lymphoma
Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare lymphoma. The optimal therapy for SPTCL is undefined and the results of treatment with anthracycline-containing chemotherapy for aggressive cases have remained poor. A 27-year-old woman with multifocal and aggressive CD8+ SPTCL was treated with the purine analog fludarabine in combination with mitoxantrone and dexamethasone (FND). The patient achieved complete remission after one course of treatment. After completion of six courses of FND, the patient has remained in remission for more than 3 years. FND may be an effective treatment for aggressive SPTCL. © 2008 Adis Data Information BV. All rights reserved.link_to_subscribed_fulltex
Dopant extraction from scanning capacitance microscopy measurements of p-n junctions using combined inverse modeling and forward simulation
This article proposes a more accurate approach to dopant extraction using combined inverse modeling and forward simulation of scanning capacitance microscopy (SCM) measurements on p-n junctions. The approach takes into account the essential physics of minority carrier response to the SCM probe tip in the presence of lateral electric fields due to a p-n junction. The effects of oxide fixed charge and interface state densities in the grown oxide layer on the p-n junction samples were considered in the proposed method. The extracted metallurgical and electrical junctions were compared to the apparent electrical junction obtained from SCM measurements. (C) 2002 American Institute of Physics
Primary large B-cell lymphoma of the ampulla of Vater.
Primary lymphoma of the ampulla of Vater is rare. The clinico-pathological and interesting endoscopic and radiological features of a patient with this disorder is presented.link_to_subscribed_fulltex