1,543 research outputs found
Morphological variation of the newly confirmed population of the javelin sand boa, Eryx jaculus (Linnaeus, 1758) (Serpentes, erycidae) in Sicily, Italy
The presence of the Javelin sand boa in Sicily has recently been confirmed. Here the morphological characters and sexual dimorphism of the Sicilian population of Eryx jaculus are presented. Seven meristic and six metric characters in 96 specimens from Sicily were examined. The results show that tail length, snout-vent length, the distance between nostrils and the number of ventral and subcaudal scales are different between sexes. The characters found in the Sicilian population of the Javelin sand boa resemble those of the African population (ssp. jaculus) rather than the Eurasian population (ssp. turcicus), but biomolecular studies are necessary to understand its taxonomic identity
Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water
At low temperatures proteins exist in a glassy state, a state which has no
conformational flexibility and shows no biological functions. In a hydrated
protein, at and above 220 K, this flexibility is restored and the protein is
able to sample more conformational sub-states, thus becomes biologically
functional. This 'dynamical' transition of protein is believed to be triggered
by its strong coupling with the hydration water, which also shows a similar
dynamic transition. Here we demonstrate experimentally that this sudden switch
in dynamic behavior of the hydration water on lysozyme occurs precisely at 220
K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC,
the structure of hydration water makes a transition from predominantly
high-density (more fluid state) to low-density (less fluid state) forms derived
from existence of the second critical point at an elevated pressure.Comment: 6 pages (Latex), 4 figures (Postscript
Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water
By confining water in nano-pores of silica glass, we can bypass the
crystallization and study the pressure effect on the dynamical behavior in
deeply supercooled state using neutron scattering. We observe a clear evidence
of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that
the transition temperature decreases steadily with an increasing pressure,
until it intersects the homogenous nucleation temperature line of bulk water at
a pressure of 1600 bar. Above this pressure, it is no longer possible to
discern the characteristic feature of the F-S transition. Identification of
this end point with the possible second critical point is discussed.Comment: 4 pages, 3 figure
Diversity and Distribution of the Inland Water Decapods of Sicily (Crustacea, Malacostraca)
The current knowledge of Sicilian inland water decapod malacostracans is scarce and an updated synopsis on species distribution is lacking. Therefore, we reviewed the checklist and recent distribution of Sicilian inland water decapods based on published and unpublished records and novel observations with the aim of providing an exhaustive repository, also to be used as a sound baseline for future surveys. Overall, five native decapod species occur in the study area, i.e., the atyid shrimp Atyaephyra desmarestii, the palaemonid shrimps Palaemon adspersus, P. antennarius, and P. elegans, and the freshwater crab Potamon fluviatile, and their current local distributions are described. In addition, three alien species were recorded: the common yabby Cherax destructor and the red swamp crayfish Procambarus clarkii, strictly linked to inland waters, and the Atlantic blue crab Callinectes sapidus, a mainly marine species that can also colonise the lower stretches of rivers and coastal brackish waters. The collected data suggest the existence of a partial segregation of native versus non-native species, with the latter currently confined to coastal water bodies and the lower stretches of rivers. Moreover, the exclusively freshwater caridean A. desmarestii and P. antennarius show a parapatric distribution in the study area, which may suggest the existence of mutual exclusion phenomena. The results obtained raise some concerns about the effects of alien species on the native biota, and dedicated monitoring and management strategies should be implemented in order to better understand and mitigate their impact
Relation Between the Widom line and the Strong-Fragile Dynamic Crossover in Systems with a Liquid-Liquid Phase Transition
We investigate, for two water models displaying a liquid-liquid critical
point, the relation between changes in dynamic and thermodynamic anomalies
arising from the presence of the liquid-liquid critical point. We find a
correlation between the dynamic fragility transition and the locus of specific
heat maxima (``Widom line'') emanating from the critical point.
Our findings are consistent with a possible relation between the previously
hypothesized liquid-liquid phase transition and the transition in the dynamics
recently observed in neutron scattering experiments on confined water. More
generally, we argue that this connection between and dynamic
crossover is not limited to the case of water, a hydrogen bond network forming
liquid, but is a more general feature of crossing the Widom line. Specifically,
we also study the Jagla potential, a spherically-symmetric two-scale potential
known to possess a liquid-liquid critical point, in which the competition
between two liquid structures is generated by repulsive and attractive ramp
interactions.Comment: 6 pages and 5 figure
Catalytic asymmetric C–C cross-couplings enabled by photoexcitation
Enantioselective catalytic processes are promoted by chiral catalysts that can execute a specific mode of catalytic reactivity, channeling the chemical reaction through a certain mechanistic pathway. Here, we show how by simply using visible light we can divert the established ionic reactivity of a chiral allyl–iridium(iii) complex to switch on completely new catalytic functions, enabling mechanistically unrelated radical-based enantioselective pathways. Photoexcitation provides the chiral organometallic intermediate with the ability to activate substrates via an electron-transfer manifold. This redox event unlocks an otherwise inaccessible cross-coupling mechanism, since the resulting iridium(ii) centre can intercept the generated radicals and undergo a reductive elimination to forge a stereogenic centre with high stereoselectivity. This photochemical strategy enables difficult-to-realize enantioselective alkyl–alkyl cross-coupling reactions between allylic alcohols and readily available radical precursors, which are not achievable under thermal activation. [Figure not available: see fulltext.
Enantioselective Biocascade Catalysis with a Single Multifunctional Enzyme
Asymmetric catalytic cascade processes offer direct access to complex chiral molecules from simple substrates and in a single step. In biocatalysis, cascades are generally designed by combining multiple enzymes, each catalyzing individual steps of a sequence. Herein, we report a different strategy for biocascades based on a single multifunctional enzyme that can promote multiple stereoselective steps of a domino process by mastering distinct catalytic mechanisms of substrate activation in a sequential way. Specifically, we have used an engineered 4-oxalocrotonate tautomerase (4-OT) enzyme with the ability to form both enamines and iminium ions and combine their mechanisms of catalysis in a complex sequence. This approach allowed us to activate aldehydes and enals toward the synthesis of enantiopure cyclohexene carbaldehydes. The multifunctional 4-OT enzymes could promote both a two-component reaction and a triple cascade characterized by different mechanisms and activation sequences
Experimental and numerical analysis of continuous RC slab strips strengthened with CFRP laminates by using the NSM technique
Os programas experimentais para o reforço à flexão de estruturas de concreto armado (CA) segundo a técnica
NSM (Near Surface Mounted, em lÃngua inglesa) com laminados de fibras de carbono (CFRP) são, em geral,
realizados com vigas simplesmente apoiadas. Deste modo, há uma carência de estudos experimentais e teóricos
sobre a redistribuição de momentos em elementos estruturais estaticamente indeterminados reforçados segundo a
técnica NSM. Assim, de forma a avaliar a influência da técnica de reforço NSM no incremento de capacidade de
carga e na redistribuição de momentos em elementos contÃnuos de CA, um programa experimental composto por
dezessete faixas de laje foi realizado, onde seis faixas de lajes foram ensaiadas sem qualquer tipo de reforço
compósito (SL15-H/HS, SL30-H/HS e SL45-H/HS), formando o conjunto de lajes de referência, e onze faixas de laje
(SL15s25-H/HS, SL15s50-H, SL30s25-H/HS, SL30s50-H/HS, SL45s25-H/HS e SL45s50-H/HS) foram reforçadas
com laminados de CFRP inseridos no concreto de recobrimento segundo a técnica NSM. Para fins de validação, os
resultados experimentais são comparados com os valores previstos pela análise efetuada com um programa de
cálculo automático baseado no método dos elementos finitos (MEF). Por fim, um estudo paramétrico composto por
288 modelos numéricos foi realizado para investigar a influência da configuração de reforço e da percentagem de
CFRP no incremento da capacidade de carga e da redistribuição de momentos em faixas de lajes reforçadas
segundo a técnica NSM. Os programas experimental e numérico referentes às faixas de laje das séries SL15-H/HS
são descritos e os resultados obtidos são apresentados e analisados neste trabalho.The experimental programs for the flexural strengthening of reinforced concrete (RC) structures using the Near
Surface Mounted (NSM) technique with Carbon Fiber Reinforced Polymer (CFRP) laminates were, in general,
conducted with simply supported beams. Therefore, there is a lack of experimental and theoretical studies on the
moment redistribution of statically indeterminate RC elements strengthened with NSM technique. Thus, in order to
assess the influence of the NSM CFRP flexural strengthening technique on the increase of the load carrying capacity
and the moment redistribution capacity of continuous RC elements, an experimental composed of seventeen RC
slab strips was carried out, in which six of the RC slabs were unstrengthened, forming a control set (SL15-H/HS,
SL30-H/HS and SL45-H/HS), and eleven slabs (SL15s25-H/HS, SL15s50-H, SL30s25-H/HS, SL30s50-H/HS,
SL45s25-H/HS and SL45s50-H/HS) were strengthened with CFRP laminates according to the NSM technique.
Furthermore, for validation purposes, the experimental results are compared with values predicted by the analysis
carried out using a FEM-based computer program. Finally, a parametric study composed of 288 numerical models is
carried out to investigate the influence of the strengthening arrangement and CFRP percentage in terms of load
carrying capacity and moment redistribution capacity of continuous RC slab strips flexurally strengthened by the
NSM technique. The experimental and numerical programs concerns to the SL15-H/HS Series are described and
the obtained results are presented and analyzed in this paper
Kidney tubular function and serum phosphate levels in HIV-1-infected patients treated with tenofovir: preliminary results
Purpose of the study
There is concern that human immunodeficiency virus (HIV) infection and the use of highly active antiretro- viral therapy lead to cumulative toxicity. Tenofovir (TDF) is the first choice for most subjects. Even if it has a safe metabolic profile, much attention has been fixed on kidney tubular function and regulation of phosphate metabolism. We performed this study to evaluate the role of a TDF based regimen has on renal tubular over time.
Methods
Prospective, cross-sectional, single centre study was car- ried out. 121 HIV-1-infected patients were consecutively enrolled in six groups based on duration of TDF exposi- tion: G0, from 6 to 12 months; G1 from 13 to 24 months; G2 from 25 to 36 months; G3 from 37 to 48 months; G4 more than 48 months and G5 under HAART but never exposed to TDF. Glomerular func- tion was assessed using creatinine clearance (CrCL) cal- culated by MDRD. Tubular function was assessed using fractional excretion ratio of phosphate and normalized renal threshold phosphate concentration. Demographic, CD4, serum phosphate levels, viral load were collected.
Summary of results
A total of 121 consecutive HIV-1-infected patients were analyzed: 15 in G0, 11 in G1, 14 in G2, 32 in G3, 35 in G4 and 14 in G5. Mean of TDF exposure was 10.26, 21.4, 36.2, 47.3 and 67.4 months in G0, G1, G2, G3 and G4 respectively. There was no statistically significant dif- ference of mean values of FEP(11.2, 10.3, 8.4, 9.8, 11.1 and 10% in G0, G1, G2, G3, G4 and G5 respectively), TmPO4/GFR (3.5, 3.5, 3.6, 3.6, 3.4 and 3.4 mg/dl in G0, G1, G2, G3, G4 and G5 respectively ), CrCL (102.2, 94.3, 92.9, 106.5, 103.1 and 101.6 ml/min/1.73m2 in G0, G1, G2, G3, G4 and G5 respectively) and serum phos- phate levels (3.4, 3.3, 3.1, 3.5, 3.3 and 3.4 in G0, G1, G2, G3, G4 and G5 respectively) between groups. Moreover, we did not find correlation of FEP (r:0.04, p:0.6) and TmPO4/GFR (r:0.05, p:0.5) with duration of TDF therapy.
Conclusions
Treatment with TDF is not associated with altered kid- ney tubular function and serum phosphate levels over time
A systematic review of the safety of lisdexamfetamine dimesylate
BACKGROUND: Here we review the safety and tolerability profile of lisdexamfetamine dimesylate (LDX), the first long-acting prodrug stimulant for the treatment of attention-deficit/hyperactivity disorder (ADHD). METHODS: A PubMed search was conducted for English-language articles published up to 16 September 2013 using the following search terms: (lisdexamfetamine OR lisdexamphetamine OR SPD489 OR Vyvanse OR Venvanse OR NRP104 NOT review [publication type]). RESULTS: In short-term, parallel-group, placebo-controlled, phase III trials, treatment-emergent adverse events (TEAEs) in children, adolescents, and adults receiving LDX were typical for those reported for stimulants in general. Decreased appetite was reported by 25-39 % of patients and insomnia by 11-19 %. The most frequently reported TEAEs in long-term studies were similar to those reported in the short-term trials. Most TEAEs were mild or moderate in severity. Literature relating to four specific safety concerns associated with stimulant medications was evaluated in detail in patients receiving LDX. Gains in weight, height, and body mass index were smaller in children and adolescents receiving LDX than in placebo controls or untreated norms. Insomnia was a frequently reported TEAE in patients with ADHD of all ages receiving LDX, although the available data indicated no overall worsening of sleep quality in adults. Post-marketing survey data suggest that the rate of non-medical use of LDX was lower than that for short-acting stimulants and lower than or equivalent to long-acting stimulant formulations. Small mean increases were seen in blood pressure and pulse rate in patients receiving LDX. CONCLUSIONS: The safety and tolerability profile of LDX in individuals with ADHD is similar to that of other stimulants
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