The localization spread and polarizability of rings and periodic chains

The localization spread gives a criterion to decide between metallic and insulating behavior of a material. It is defined as the second moment cumulant of the many-body position operator, divided by the number of electrons. Different operators are used for systems treated with open or periodic boundary conditions. In particular, in the case of periodic systems, we use the complex position definition, which was already used in similar contexts for the treatment of both classical and quantum situations. In this study, we show that the localization spread evaluated on a finite ring system of radius R with open boundary conditions leads, in the large R limit, to the same formula derived by Resta and co-workers [C. Sgiarovello, M. Peressi, and R. Resta, Phys. Rev. B 64, 115202 (2001)] for 1D systems with periodic Born-von Kármán boundary conditions. A second formula, alternative to Resta’s, is also given based on the sum-over-state formalism, allowing for an interesting generalization to polarizability and other similar quantities

COMPARAÇÃO ENTRE DOIS MÉTODOS DE ARTRODESE INTERFALANGEANA PROXIMAL EM EQÜINOS

The aim of this study was thecomparison between the cerclage associatedto articular cartilage curettage with the injectionof monoiodoacetate to induce ankylosis of theproximal interphalangeal joint (PIJ) in horses.Twelve horses were randomly allotted in two groups(n=6): surgical arthrodesis (CerG) and chemicalarthrodesis (MiaG), observed during seven months.After each treatment, animals were evaluated forlameness on days 7, 14 and 30, and also every30 days until the end of follow up. They were alsoevaluated for radiographic signs of osteoarthritis on days 30, 90, 120, 150, 180 e 210. During thefirst 24 hours (M0), MiaG showed more discomfortwhen compared to CerG, with lameness grade 5 inall animals. But, at M210, there was no differenceon lameness between groups. Radiographic signsfor osteoarthritis were observed on both groups,but they indicated greater tendency to ankylosis inCerG. Therefore, fusion was not observed in anygroup. It was concluded that both techniques werenot efficient for the induction of ankylosis in the PIJin horses.O objetivo da presente pesquisa foi acomparação entre a cerclagem óssea associada aoestímulo osteogênico e a injeção intraarticular demonoiodoacetato de sódio para indução de artrodeseda articulação interfalangeana proximal (AIP) emeqüinos. Foram utilizados 12 eqüinos dispostos aleatoriamenteem dois grupos (n=6): artrodese cirúrgica(CerG) e artrodese química (MiaG), acompanhadospor um período de sete meses. Após cada procedimento,os indivíduos foram avaliados quanto ao graude claudicação nos dias 7, 14 e 30 e a cada 30 diasaté o final do período de acompanhamento e, também,quanto aos sinais radiográficos de osteoartritenos dias 30, 90, 120, 150, 180 e 210. Nas primeiras24 horas (M0), o MiaG apresentou maior desconfortoem relação ao CerG, com grau 5 de claudicaçãopara todos os animais. Porém, em M210, não houvediferença no grau de claudicação entre os grupos.Os sinais radiográficios indicativos de osteoartriteforam evidentes para ambos os grupos e indicaramuma tendência maior à anquilose no CerG. Entretanto,a fusão não foi observada em nenhum animal tratado.Conclui-se que ambas as técnicas estudadasmostraram ser métodos ineficientes de indução de artrodese na AIP em equinos

ICA-based denoising for ASL perfusion imaging

Arterial Spin Labelling (ASL) imaging derives a perfusion image by tracing the accumulation of magnetically labeled blood water in the brain. As the image generated has an intrinsically low signal to noise ratio (SNR), multiple measurements are routinely acquired and averaged, at a penalty of increased scan duration and opportunity for motion artefact. However, this strategy alone might be ineffective in clinical settings where the time available for acquisition is limited and patient motion are increased. This study investigates the use of an Independent Component Analysis (ICA) approach for denoising ASL data, and its potential for automation.72 ASL datasets (pseudo-continuous ASL; 5 different post-labeling delays: 400, 800, 1200, 1600, 2000 m s; total volumes = 60) were collected from thirty consecutive acute stroke patients. The effects of ICA-based denoising (manual and automated) where compared to two different denoising approaches, aCompCor, a Principal Component-based method, and Enhancement of Automated Blood Flow Estimates (ENABLE), an algorithm based on the removal of corrupted volumes. Multiple metrics were used to assess the changes in the quality of the data following denoising, including changes in cerebral blood flow (CBF) and arterial transit time (ATT), SNR, and repeatability. Additionally, the relationship between SNR and number of repetitions acquired was estimated before and after denoising the data.The use of an ICA-based denoising approach resulted in significantly higher mean CBF and ATT values (p [less than] 0.001), lower CBF and ATT variance (p [less than] 0.001), increased SNR (p [less than] 0.001), and improved repeatability (p [less than] 0.05) when compared to the raw data. The performance of manual and automated ICA-based denoising was comparable. These results went beyond the effects of aCompCor or ENABLE. Following ICA-based denoising, the SNR was higher using only 50% of the ASL-dataset collected than when using the whole raw data.The results show that ICA can be used to separate signal from noise in ASL data, improving the quality of the data collected. In fact, this study suggests that the acquisition time could be reduced by 50% without penalty to data quality, something that merits further study. Independent component classification and regression can be carried out either manually, following simple criteria, or automatically

Evidence for Blue Straggler Stars Rejuvenating the Integrated Spectra of Globular Clusters

Integrated spectroscopy is the method of choice for deriving the ages of unresolved stellar systems. However, hot stellar evolutionary stages, such as hot horizontal branch stars and blue straggler stars (BSSs), can affect the integrated ages measured using Balmer lines. Such hot, "non-canonical" stars may lead to overestimations of the temperature of the main sequence turn-off, and therefore underestimations of the integrated age of a stellar population. Using an optimized Hbeta index in conjunction with HST/WFPC2 color-magnitude diagrams (CMDs), we show that Galactic globular clusters exhibit a large scatter in their apparent "spectroscopic" ages, which does not correspond to that in their CMD-derived ages. We find for the first time that the specific frequency of BSSs, defined within the same aperture as the integrated spectra, shows a clear correspondence with Hbeta in the sense that, at fixed metallicity, higher BSS ratios lead to younger "apparent" spectroscopic ages. Thus, the specific frequency of BSSs in globular clusters sets a fundamental limit on the accuracy for which spectroscopic ages can be determined for globular clusters, and maybe for other stellar systems like galaxies. The observational implications of this result are discussed.Comment: 5 pages, 2 figures, 1 table. Accepted for publication in ApJ

Effect of surfactants during drop formation in a microfluidic channel: a combined experimental and computational fluid dynamics approach

The effect of surfactants on the flow characteristics during rapid drop formation in a microchannel is investigated using high-speed imaging, micro-particle image velocimetry and numerical simulations; the latter are performed using a three- dimensional multiphase solver that accounts for the transport of soluble surfactants in the bulk and at the interface. Drops are generated in a flow-focusing microchannel, using silicone oil ( 4.6 mPa s) as the continuous phase and a 52 % w/w glycerol solution as the dispersed phase. A non-ionic surfactant (Triton X-100) is dissolved in the dispersed phase at concentrations below and above the critical micelle concentration. Good agreement is found between experimental and numerical data for the drop size, drop formation time and circulation patterns. The results reveal strong circulation patterns in the forming drop in the absence of surfactants, whose intensity decreases with increasing surfactant concentration. The surfactant concentration profiles in the bulk and at the interface are shown for all stages of drop formation. The surfactant interfacial concentration is large at the front and the back of the forming drop, while the neck region is almost surfactant free. Marangoni stresses develop away from the neck, contributing to changes in the velocity profile inside the drop

Computational Complexity of Atomic Chemical Reaction Networks

Informally, a chemical reaction network is "atomic" if each reaction may be interpreted as the rearrangement of indivisible units of matter. There are several reasonable definitions formalizing this idea. We investigate the computational complexity of deciding whether a given network is atomic according to each of these definitions. Our first definition, primitive atomic, which requires each reaction to preserve the total number of atoms, is to shown to be equivalent to mass conservation. Since it is known that it can be decided in polynomial time whether a given chemical reaction network is mass-conserving, the equivalence gives an efficient algorithm to decide primitive atomicity. Another definition, subset atomic, further requires that all atoms are species. We show that deciding whether a given network is subset atomic is in $\textsf{NP}$, and the problem "is a network subset atomic with respect to a given atom set" is strongly $\textsf{NP}$-$\textsf{Complete}$. A third definition, reachably atomic, studied by Adleman, Gopalkrishnan et al., further requires that each species has a sequence of reactions splitting it into its constituent atoms. We show that there is a $\textbf{polynomial-time algorithm}$ to decide whether a given network is reachably atomic, improving upon the result of Adleman et al. that the problem is $\textbf{decidable}$. We show that the reachability problem for reachably atomic networks is $\textsf{Pspace}$-$\textsf{Complete}$. Finally, we demonstrate equivalence relationships between our definitions and some special cases of another existing definition of atomicity due to Gnacadja

Gaia data release 1: Principles of the photometric calibration of the G band

Context. Gaia is an ESA cornerstone mission launched on 19 December 2013 aiming to obtain the most complete and precise 3D map of our Galaxy by observing more than one billion sources. This paper is part of a series of documents explaining the data processing and its results for Gaia Data Release 1, focussing on the G band photometry. Aims. This paper describes the calibration model of the Gaia photometric passband for Gaia Data Release 1. Methods. The overall principle of splitting the process into internal and external calibrations is outlined. In the internal calibration, a self-consistent photometric system is generated. Then, the external calibration provides the link to the absolute photometric flux scales. Results. The Gaia photometric calibration pipeline explained here was applied to the first data release with good results. Details are given of the various calibration elements including the mathematical formulation of the models used and of the extraction and preparation of the required input parameters (e.g. colour terms). The external calibration in this first release provides the absolute zero point and photometric transformations from the Gaia G passband to other common photometric systems. Conclusions. This paper describes the photometric calibration implemented for the first Gaia data release and the instrumental effects taken into account. For this first release no aperture losses, radiation damage, and other second-order effects have not yet been implemented in the calibration.Comment: 15 pages, 16 figures, Gaia data release 1 documentation special volum

Cytokine Combination Therapy with Erythropoietin and Granulocyte Colony Stimulating Factor in a Porcine Model of Acute Myocardial Infarction

PurposeErythropoietin (EPO) and granulocyte colony stimulating factor (GCSF) have generated interest as novel therapies after myocardial infarction (MI), but the effect of combination therapy has not been studied in the large animal model. We investigated the impact of prolonged combination therapy with EPO and GCSF on cardiac function, infarct size, and vascular density after MI in a porcine model.MethodsMI was induced in pigs by a 90 min balloon occlusion of the left anterior descending coronary artery. 16 animals were treated with EPO+GCSF, or saline (control group). Cardiac function was assessed by echocardiography and pressure-volume measurements at baseline, 1 and 6 weeks post-MI. Histopathology was performed 6 weeks post-MI.ResultsAt week 6, EPO+GCSF therapy stabilized left ventricular ejection fraction, (41 ± 1% vs. 33 ± 1%, p < 0.01) and improved diastolic function compared to the control group. Histopathology revealed increased areas of viable myocardium and vascular density in the EPO+GCSF therapy, compared to the control. Despite these encouraging results, in a historical analysis comparing combination therapy with monotherapy with EPO or GCSF, there were no significant additive benefits in the LVEF and volumes overtime using the combination therapy.ConclusionOur findings indicate that EPO+GCSF combination therapy promotes stabilization of cardiac function after acute MI. However, combination therapy does not seem to be superior to monotherapy with either EPO or GCSF

A new species of Bungona in Turkey (Ephemeroptera, Baetidae): an unexpected biogeographic pattern within a pantropical complex of mayflies

By using an integrative approach, we describe a new species of mayfly, Bungona (Chopralla) pontica sp. n., from Turkey. The discovery of a representative of the tropical mayfly genus Bungona in the Middle East is rather unexpected. The new species shows all the main morphological characters of the subgenus Chopralla, which has its closest related species occurring in southeastern Asia. Barcoding clearly indicated that the new species represents an independent lineage isolated for a very long time from other members of the complex. The claw is equipped with two rows of three or four flattened denticles. This condition is a unique feature of Bungona (Chopralla) pontica sp. n. among West Palaearctic mayfly species. Within the subgenus Chopralla, the species can be identified by the presence of a simple, not bifid right prostheca (also present only in Bungona (Chopralla) liebenauae (Soldan, Braasch & Muu, 1987)), the shape of the labial palp, and the absence of protuberances on pronotum