Transport Through Andreev Bound States in a Graphene Quantum Dot

Andreev reflection-where an electron in a normal metal backscatters off a superconductor into a hole-forms the basis of low energy transport through superconducting junctions. Andreev reflection in confined regions gives rise to discrete Andreev bound states (ABS), which can carry a supercurrent and have recently been proposed as the basis of qubits [1-3]. Although signatures of Andreev reflection and bound states in conductance have been widely reported [4], it has been difficult to directly probe individual ABS. Here, we report transport measurements of sharp, gate-tunable ABS formed in a superconductor-quantum dot (QD)-normal system, which incorporates graphene. The QD exists in the graphene under the superconducting contact, due to a work-function mismatch [5, 6]. The ABS form when the discrete QD levels are proximity coupled to the superconducting contact. Due to the low density of states of graphene and the sensitivity of the QD levels to an applied gate voltage, the ABS spectra are narrow, can be tuned to zero energy via gate voltage, and show a striking pattern in transport measurements.Comment: 25 Pages, included SO

Trypsin inhibitor from tamarindus indica L. seeds reduces weight gain and food consumption and increases plasmatic cholecystokinin levels

OBJECTIVES: Seeds are excellent sources of proteinase inhibitors, some of which may have satietogenic and slimming actions. We evaluated the effect of a trypsin inhibitor from Tamarindus indica L. seeds on weight gain, food consumption and cholecystokinin levels in Wistar rats. METHODS: A trypsin inhibitor from Tamarindus was isolated using ammonium sulfate (30-60%) following precipitation with acetone and was further isolated with Trypsin-Sepharose affinity chromatography. Analyses were conducted to assess the in vivo digestibility, food intake, body weight evolution and cholecystokinin levels in Wistar rats. Histological analyses of organs and biochemical analyses of sera were performed. RESULTS: The trypsin inhibitor from Tamarindus reduced food consumption, thereby reducing weight gain. The in vivo true digestibility was not significantly different between the control and Tamarindus trypsin inhibitor-treated groups. The trypsin inhibitor from Tamarindus did not cause alterations in biochemical parameters or liver, stomach, intestine or pancreas histology. Rats treated with the trypsin inhibitor showed significantly elevated cholecystokinin levels compared with animals receiving casein or water. CONCLUSION: The results indicate that the isolated trypsin inhibitor from Tamarindus reduces weight gain by reducing food consumption, an effect that may be mediated by increased cholecystokinin. Thus, the potential use of this trypsin inhibitor in obesity prevention and/or treatment should be evaluated

Characterization of a methionine-rich protein from the seeds of Cereus jamacaru Mill. (Cactaceae) <A NAME="Home"></A>

We describe here the isolation and characterization of a major albumin from the seeds of Cereus jamacaru (Cactaceae), to which we gave the trivial name of cactin. This protein has a molecular mass of 11.3 kDa and is formed by a light chain (3.67 kDa) and a heavy chain (7.63 kDa). This protein was isolated using a combination of gel filtration chromatography and reverse-phase HPLC. The amino acid composition of cactin was determined and found to resemble that of the 2S seed reserve protein from the Brazil nut, a protein remarkable for its high methionine content. The usefulness of cactin as a molecular marker in the taxonomy of the Cactaceae is discussed

Magnitude e tendência da Leishmaniose Tegumentar Americana no Estado de São Paulo, Brasil, 1975 a 2008 Magnitude and trend of American Tegumentary Leishmaniasis in the State of São Paulo, Brazil, 1975 to 2008

O objetivo deste estudo foi analisar a magnitude e tendência da Leishmaniose Tegumentar Americana (LTA) no Estado de São Paulo entre 1975 e 2008. Foi conduzido um estudo ecológico que categorizou os municípios segundo a magnitude da transmissão. No período de 1975 a 1985, 45 municípios foram responsáveis pelo registro de 1.281 casos de LTA, passando a 258 municípios e 4.093 casos entre 1986 e 1995, e a 385 municípios e 7.604 casos entre 1996 a 2008. O vetor Lutzomyia intermedia s.l. foi coletado na maioria das pesquisas entomológicas. Na classificação dos municípios segundo a magnitude pode-se verificar que 67,5% possuíam "pequena magnitude", 19,2% "média magnitude" e 13,3% "grande magnitude". As maiores incidências de LTA permanecem restritas a algumas áreas carentes e próximas à Mata Atlântica. Houve aumento no número de municípios com pequena ocorrência de casos e ampliação da área de risco.<br>The aim of this study was to analyze the magnitude and trend of American Tegumentary Leishmaniasis (ATL) in the State of São Paulo from 1975 to 2008. An ecological study that classified municipalities according to the magnitude of transmission was performed. From 1975 to 1985, 1,281 cases of ATL were registered in 45 municipalities, rising to 258 municipalities and 4,093 cases from 1986 to 1995; and reaching 385 municipalities and 7,604 cases from 1996 to 2008. Lutzomyia intermedia s.l. was collected in most of the entomological surveys. In the classification of municipalities according to magnitude, 67.5% were observed to have a "small magnitude," 19.2% "moderate magnitude" and 13.3% "high magnitude." The highest incidences of ATL have been restricted to underserved areas close to the Atlantic fo-rest. There was an increase in the number of municipalities with small occurrence of cases and expansion in the area of risk

Bacteriopheophytin triplet state in Rhodobacter sphaeroides reaction centers

It is well established that photoexcitation of Rhodobacter sphaeroides reaction centers (RC) with reduced quinone acceptors results in the formation of a triplet state localized on the primary electron donor P with a significant yield. The energy of this long-lived and therefore potentially damaging excited state is then efficiently quenched by energy transfer to the RC spheroidenone carotenoid, with its subsequent decay to the ground state by intersystem crossing. In this contribution, we present a detailed transient absorption study of triplet states in a set of mutated RCs characterized by different efficiencies of triplet formation that correlate with lifetimes of the initial charge-separated state P+HA- . On a microsecond time scale, two types of triplet state were detected: in addition to the well-known spheroidenone triplet state with a lifetime of ~4 μs, in some RCs we discovered a bacteriopheophytin triplet state with a lifetime of ~40 μs. As expected, the yield of the carotenoid triplet increased approximately linearly with the lifetime of P+HA-, reaching the value of 42 % for one of the mutants. However, surprisingly, the yield of the bacteriopheophytin triplet was the highest in RCs with the shortest P+HA- lifetime and the smallest yield of carotenoid triplet. For these the estimated yield of bacteriopheophytin triplet was comparable with the yield of the carotenoid triplet, reaching a value of ~7 %. Possible mechanisms of formation of the bacteriopheophytin triplet state are discussed.</p