392 research outputs found
A Problem of Relative, Constrained Motion
We develop a new method to determine the acceleration of a block sliding down
along the face of a moving wedge. We have been able to link the solution of
this problem to that of the inclined plane problem of elementary physics, thus
providing a simpler solution to it.Comment: 4 pages, 3 figure
Critical phenomena and quantum phase transition in long range Heisenberg antiferromagnetic chains
Antiferromagnetic Hamiltonians with short-range, non-frustrating interactions
are well-known to exhibit long range magnetic order in dimensions,
but exhibit only quasi long range order, with power law decay of correlations,
in d=1 (for half-integer spin). On the other hand, non-frustrating long range
interactions can induce long range order in d=1. We study Hamiltonians in which
the long range interactions have an adjustable amplitude lambda, as well as an
adjustable power-law , using a combination of quantum Monte Carlo
and analytic methods: spin-wave, large-N non-linear sigma model, and
renormalization group methods. We map out the phase diagram in the lambda-alpha
plane and study the nature of the critical line separating the phases with long
range and quasi long range order. We find that this corresponds to a novel line
of critical points with continuously varying critical exponents and a dynamical
exponent, z<1.Comment: 27 pages, 12 figures. RG flow added. Final version to appear in JSTA
Natural polymorphisms of HIV type 2 pol sequences from drug-naive individuals
Until today, the susceptibility of human immunodeficiency virus type 2 (HIV-2) to protease and nucleosidic reverse-transcriptase inhibitors (PI and NRTI, respectively) has not been clearly documented. In this report we studied HIV-2 proviral sequences (n = 30) from drug-naive patients. Our results revealed that several amino acid positions in the protease and reverse transcriptase coding sequence harbored residues that have been associated with drug resistance in HIV-1-infected patients. In particular, the M46I substitution in the protease was detected in 90% of the sequences analyzed, which, together with the other substitutions identified, may indicate a reduced susceptibility of HIV-2-infected drug-naive patients to PI. Furthermore, interpretation of genotypic data with four available algorithms, developed for interpretation of HIV-1 sequence data, suggested nonoverlapping profiles of drug resistance
Whole exome sequencing of patients with diffuse idiopathic skeletal hyperostosis and calcium pyrophosphate crystal chondrocalcinosis
Objectives: DISH/CC is a poorly understood phenotype
characterised by peripheral and axial enthesopathic
calcifications, frequently fulfilling the radiological
criteria for Diffuse Idiopathic Skeletal Hyperostosis
(DISH, MIM 106400), and in some cases associated
with Calcium Pyrophosphate Dihydrate (CPPD) Chondrocalcinosis
(CC). The concurrence of DISH and CC
suggests a shared pathogenic mechanism. In order to
identify genetic variants for susceptibility we performed
whole exome sequencing in four patients showing this
phenotype.
Materials and methods: Exome data were filtered in
order to find a variant or a group of variants that could
be associated with the DISH/CC phenotype. Variants
of interest were subsequently confirmed by Sanger sequencing.
Selected variants were screened in a cohort
of 65 DISH/CC patients vs 118 controls from Azores.
The statistical analysis was performed using PLINK
V1.07.
Results:We identified 21 genetic variants in 17 genes
that were directly or indirectly related to mineralization,
several are predicted to have a strong effect at a
protein level. Phylogenetic analysis of altered amino
acids indicates that these are either highly conserved
in vertebrates or conserved in mammals. In case-control
analyses, variant rs34473884 in PPP2R2D was significantly
associated with the DISH/CC phenotype
(p=0.028; OR=1.789, 95% CI= 1.060 - 3.021)).
Conclusion: The results of the present and preceding
studies with the DISH/CC families suggests that the
phenotype has a polygenic basis. The PPP2R2D gene could be involved in this phenotype in an as yet unknown way.FRCT: M3.1.2/F/023/2011info:eu-repo/semantics/publishedVersio
LINFOMA DE CÉLULAS B LOCALIZADO NA CAVIDADE ORAL NUM FELÍDEO – CASO CLÍNICO
Um felídeo de 14 anos europeu comum foi apresentado à consulta com história clínica de 1 mês de diminuição de apetite, halitose e deformação facial. O seu estado imunitário foi negativo para FIV e FELV. Os resultados hematológicos e bioquímicos revelaram apenas um aumento de globulinas séricas e a punção aspirativa de agulha fina revelou linfoma localizado sem sinais de envolvimento sistémico nos exames complementares. A cirurgia foi recomendada e consistiu em maxilectomia rostral unilateral, excisão labial, enxerto labial de avanço e colocação de tubo esofágico. O resultado histopatológico revelou linfoma de baixo índice mitótico e os exames imunohistoquímicos revelaram positividade ao marcador CD79a, um marcador de células B. O tumor foi classificado em Estádio I pelo sistema de estadiamento de linfoma felino. Apesar dos resultados histopatológicos sugerirem uma resposta pobre à quimioterapia, iniciou-se um protocolo terapêutico com ciclofosfamida, vincristina e prednisolona. Dois meses após o diagnóstico e seis semanas após início de quimioterapia o animal revelou anorexia e no exame ecográfico de controlo foram detectadas metástases. O gato foi hospitalizado e morreu uma semana depois. O prognóstico de linfoma localizado no gato é desconhecido devido à sua rara ocorrência. Está recomendado o controlo local do tumor com cirurgia ou radioterapia combinadas ou não com quimioterapia. Apesar da sobrevivência do animal ter sido breve após o tratamento cirúrgico os proprietários ficaram satisfeitos com o aumento de qualidade de vida após cirurgia
Peripherally Inserted Central Catheter Placement in a Cardiology Ward: A Focus Group Study of Nurses’ Perspectives
info:eu-repo/semantics/publishedVersio
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