Optically active aziridine esters by nucleophilic addition of nitrogen heterocycles to a chiral 2H-azirine-2-carboxylic ester

Chiral enriched ethyl 3-methyl-2H-azirine-2-carboxylate acts as an efficient alkylating agent for a variety of five membered aromatic nitrogen heterocycles.Fundação para a Ciência e Tecnologia - POCTI/32723/QUI/2000. FEDER

Harmonically Trapped Quantum Gases

We solve the problem of a Bose or Fermi gas in $d$-dimensions trapped by $\delta \leq d$ mutually perpendicular harmonic oscillator potentials. From the grand potential we derive their thermodynamic functions (internal energy, specific heat, etc.) as well as a generalized density of states. The Bose gas exhibits Bose-Einstein condensation at a nonzero critical temperature $T_{c}$ if and only if $d+\delta >2$, and a jump in the specific heat at $T_{c}$ if and only if $d+\delta >4$. Specific heats for both gas types precisely coincide as functions of temperature when $d+\delta =2$. The trapped system behaves like an ideal free quantum gas in $d+\delta$ dimensions. For $\delta =0$ we recover all known thermodynamic properties of ideal quantum gases in $d$ dimensions, while in 3D for $\delta =$ 1, 2 and 3 one simulates behavior reminiscent of quantum {\it wells, wires}and{\it dots}, respectively.Comment: 14 pages including 3 figures and 3 table

Results of Endovascular Procedures Performed in Dysfunctional Arteriovenous Accesses for Haemodialysis

Aim. Percutaneous endovascular procedures have become the standard treatment of arteriovenous fistulae and graft stenosis. This study evaluates the immediate results of angiographic procedures performed by nephrologists in patients with dysfunctional arteriovenous fistulae and arteriovenous graft stenosis. Patients and Methods. A retrospective analysis was performed on patients referred to the three Interventional Nephrology units between April and June, 2010. Clinical data were recorded. Results. A total of 113 procedures were performed: 59 in arteriovenous fistulae and 54 in arteriovenous graft stenosis. The main reasons for referral were increased venous pressure (21%), limb oedema (21%) and decreased intra-access flow (20%). Stenoses were detected in 85% of the procedures, mostly in patients with arteriovenous graft stenosis (56%). The main locations of stenosis were the outflow vein (cephalic/basilic) in arteriovenous fistulae (34%) and venous anastomosis in arteriovenous graft stenosis(48%). Angioplasty was performed in 73% of procedures where stenoses were detected. The immediate success rate was 91% for arteriovenous fistulae and 83% for arteriovenous graft stenosis. Partial success was obtained in 11% of angiographies. The complication rate was 7%. Conclusions. Physical examination findings led, in at least half the cases, to angiography referral and enabled the diagnosis and treatment of stenoses. For this reason, we advocate that this tool should be included in any vascular access monitoring programme. Our results support the safety of these procedures performed by nephrologists and their efficacy in the recovery of dysfunctional arteriovenous fistulae and arteriovenous graft stenosis

Cooper pairs as bosons

Although BCS pairs of fermions are known not to obey Bose-Einstein (BE) commutation relations nor BE statistics, we show how Cooper pairs (CPs), whether the simple original ones or the CPs recently generalized in a many-body Bethe-Salpeter approach, being clearly distinct from BCS pairs at least obey BE statistics. Hence, contrary to widespread popular belief, CPs can undergo BE condensation to account for superconductivity if charged, as well as for neutral-atom fermion superfluidity where CPs, but uncharged, are also expected to form.Comment: 8 pages, 2 figures, full biblio info adde

Eficiência do reforço de CFRP em estruturas de concreto sob efeito térmico

Uma das questões que merece atenção quando da utilização de reforço de estruturas de concreto por intermédio da aplicação de materiais compósitos a base de matriz epóxi é a redução de resistência do material com o aumento de temperatura. A temperatura máxima de utilização dos adesivos epoxídicos, normalmente empregados na construção civil, é de aproximadamente 70o C. Este fato tem sido relatado por diversos pesquisadores como uma das desvantagens da aplicação das técnicas que utilizam este material como ponte de aderência entre o reforço e o substrato de concreto. Dados sobre a eficiência do reforço por meio da utilização de mantas e laminados de fibras de carbono (Carbon Fiber Reinforced Polymer – CFRP) em estruturas de concreto, quando submetidas a temperaturas acima da ambiente, são necessários para qualificar a segurança da estrutura reforçada e apreciar a técnica de reforço com CFRP mais eficaz para o efeito de temperatura, dados estes pouco explorados na literatura sobre o tema. Este fato nos motivou a desenvolver um estudo experimental em peças de concreto reforçadas com 03 (três) técnicas: manta colada sobre a superfície do concreto, laminado também colado sobre a superfície do concreto e laminado colado em entalhes executados no concreto. As peças de concreto reforçadas foram submetidas a 03 (três) temperaturas acima da temperatura ambiente, sendo posteriormente ensaiadas à flexão. Os resultados experimentais são apresentados e a partir da sua discussão pode-se avaliar o comportamento de cada técnica de reforço, sob efeito da temperatura, indicando a técnica mais eficaz

Detecting Discontinuities Over Triangular Meshes Using Multiwavelets

It is well known that solutions to nonlinear hyperbolic PDEs develop discontinuities in time. The generation of spurious oscillations in such regions can be prevented by applying a limiter in the troubled zones. In earlier work, we constructed a multiwavelet troubled-cell indicator for one and (tensor-product) two dimensions (SIAM J. Sci. Comput. 38(1):A84–A104, 2016). In this paper, we investigate multiwavelet troubled-cell indicators on structured triangular meshes. One indicator uses a problem-dependent parameter; the other indicator is combined with outlier detection