Evolution of Beryllium and Boron in the Inhomogeneous Early Galaxy

A model of supernova-driven chemical evolution of the Galactic halo, recently proposed by Tsujimoto, Shigeyama, & Yoshii (1999, ApJL, 519, 64), is extended in order to investigate the evolution of light elements such as Be and B (BeB), which are produced mainly through spallative reactions with Galactic cosmic rays. In this model each supernova sweeps up the surrounding interstellar gas into a dense shell and directly enriches it with ejecta which consist of heavy elements produced in each Type II supernova with different progenitor masses. We propose a two-component source for GCRs such that both interstellar gas and fresh SN ejecta engulfed in the shell are accelerated by the shock wave. Our model results include: (1) a prediction of the intrinsic scatter in BeB and [Fe/H] abundances within the model, (2) a successful prediction of the observed linear trend between BeB and [Fe/H], (3) a proposal for using BeB as a cosmic clock, as an alternative to [Fe/H], and (4) a method for possibly constraining the BBN model from future observations of metal-poor stars.Comment: 3 color figures in 7 pages, accepted by ApJ Letter

Saccades and smooth pursuit eye movements in central vertigo

In order to analyze the diagnostic efficiency of saccadic and pursuit eye movements compared to findings from brain magnetic resonance imaging in patients with central vertigo, 108 patients were selected from 580 dizzy patients as cases of suspected central origin; the saccadic and pursuit eye movements were evaluated by electronystagmography and findings were compared to information from magnetic resonance imaging. The study of oculomotor movements in patients suspected of having a central lesion revealed a 83.3% sensitivity and 21.2% specificity. Restricting consideration to severe alterations in eye movements as indicative of a central origin, this test gives a 71.4% sensitivity and 50.0% specificity. In conclusion, the study of alterations in oculomotor movements, in patients with suspected central lesions, proved to be a test with good sensitivity also compared with results of magnetic resonance imaging

Roles of Supernova Ejecta in Nucleosynthesis of Light Elements, Li, Be, and B

Explosions of type Ic supernovae (SNe Ic) are investigated using a relativistic hydrodynamic code to study roles of their outermost layers of the ejecta in light element nucleosynthesis through spallation reactions as a possible mechanism of the "primary" process. We have confirmed that the energy distribution of the outermost layers with a mass fraction of only 0.001 % follows the empirical formula proposed by previous work when the explosion is furious. In such explosions, a significant fraction of the ejecta ($>$0.1 % in mass) have the energy greater than the threshold energy for spallation reactions. On the other hand, it is found that the outermost layers of ejecta become more energetic than the empirical formula would predict when the explosion energy per unit ejecta mass is smaller than \sim 1.3\times 10^{51}{ergs/}\Msun. As a consequence, it is necessary to numerically calculate explosions to estimate light element yields from SNe Ic. The usage of the empirical formula would overestimate the yields by a factor of \gtsim 3 for energetic explosions such as SN 1998bw and underestimate the yields by a similar factor for less energetic explosions like SN 1994I. The yields of light elements Li, Be, and B (LiBeB) from SNe Ic are estimated by solving the transfer equation of cosmic rays originated from ejecta of SNe Ic and compared with observations.Comment: 10 pages, 6 figures, 2 tables, to appear in The Astrophysical Journa

Cosmic Ray production of Beryllium and Boron at high redshift

Recently, new observations of Li6 in Pop II stars of the galactic halo have shown a surprisingly high abundance of this isotope, about a thousand times higher than its predicted primordial value. In previous papers, a cosmological model for the cosmic ray-induced production of this isotope in the IGM has been developed to explain the observed abundance at low metallicity. In this paper, given this constraint on the Li6, we calculate the non-thermal evolution with redshift of D, Be, and B in the IGM. In addition to cosmological cosmic ray interactions in the IGM, we include additional processes driven by SN explosions: neutrino spallation and a low energy component in the structures ejected by outflows to the IGM. We take into account CNO CRs impinging on the intergalactic gas. Although subdominant in the galactic disk, this process is shown to produce the bulk of Be and B in the IGM, due to the differential metal enrichment between structures (where CRs originate) and the IGM. We also consider the resulting extragalactic gamma-ray background which we find to be well below existing data. The computation is performed in the framework of hierarchical structure formation considering several star formation histories including Pop III stars. We find that D production is negligible and that a potentially detectable Be and B plateau is produced by these processes at the time of the formation of the Galaxy (z ~ 3).Comment: 9 pages, 7 figure

Cosmic Ray Production of Lithium-6 by Structure Formation Shocks in the Early Milky Way: A Fossil Record of Dissipative Processes during Galaxy Formation

While the abundances of Be and B observed in metal-poor halo stars are well explained as resulting from spallation of CNO-enriched cosmic rays (CRs) accelerated by supernova shocks, accounting for the observed $^6$Li in such stars with supernova CRs is more problematic. Here we propose that gravitational shocks induced by infalling and merging sub-Galactic clumps during hierarchical structure formation of the Galaxy should dissipate enough energy at early epochs, and CRs accelerated by such shocks can provide a natural explanation of the observed $^6$Li. In clear constrast to supernovae, structure formation shocks do not eject freshly synthesized CNO nor Fe, so that the only effective production channel at low metallicity is $\alpha-\alpha$ fusion, capable of generating sufficient $^6$Li with no accompanying Be or B and no direct correspondence with Fe. Correlations between the $^6$Li abundance and the kinematic properties of the halo stars may also be expected in this scenario. Further, more extensive observations of $^6$Li in metal-poor halo stars, e.g. by the Subaru HDS or VLT/UVES, may offer us an invaluable fossil record of dissipative dynamical processes which occurred during the formation of our Galaxy.Comment: Ap.J. in press; 6 pages, 1 figur

Occurrence of Anastrepha fraterculus (Diptera: Tephritidae) on raspberry (Rubus idaeus) and blackberry (Rubus fructicosus) fruit cultivated in a semiarid-temperate highland valley of Tucumán, Argentina

The Mediterranean fruit fly (CC), Ceratitis capitata, and the South American fruit fly (AF), Anastrepha fraterculus, are serious polyphagous insects considered pests of several plant families. Both species are widely distributed in Argentina, including the province of Tucumán, where their occurrence was reported in high-elevation valleys, affecting several cultivated and wild fruit species. Provided that raspberry (Rubus idaeus) and blackberry (Rubus fructicosus) are minor (but in expansion) crops in Tucumán, and the spectrum of pests affecting these crops is not very well known, the aim of this study was to determine the occurrence of AF and CF on these crops. During 2016, ripe fruit from plants of the blackberry cultivar ?878? and the raspberry cultivar ?Heritage? were collected from an organic orchard in Tafí del Valle (26°52′S, 65°41′W, 2014 m altitude). Sampling dates were Feb-5, 19 and 24, and Mar-10 and 23. Fruit sample was divided into 2 replicates of 20-30 fruits each, and placed into clamshells (20×20×30 cm) with sand at the bottom for larvae pupation. Clamshell lids were removed and replaced by voile fabric to allow air exchange and to prevent insects from escaping. They were kept at about 25°C and 60-70% RH for 20 days. Tephritid adults and pupae from each clamshell were recovered weekly, identified and counted. The reported fruit infestation level was based on the number of adults per fruit number and fruit weight obtained from each sample. Means and standard deviations (SD) were calculated. This is the first report of the occurrence of the South American fruit fly on blackberry and raspberry in Tucumán (Argentina).Fil: Meneguzzi, Natalia G.. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estacion Experimental.agropecuaria Famailla. Agencia de Extension Rural S M de Tucuman.; ArgentinaFil: Escobar, Lorena Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estacion Experimental.agropecuaria Famailla. Agencia de Extension Rural S M de Tucuman.; ArgentinaFil: Funes, Claudia Fernanda. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estacion Experimental.agropecuaria Famailla. Agencia de Extension Rural S M de Tucuman.; ArgentinaFil: Ovruski Alderete, Sergio Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Kirschbaum, Daniel Santiago. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estacion Experimental.agropecuaria Famailla. Agencia de Extension Rural S M de Tucuman.; Argentina9ª Reunión del Grupo de Trabajo en Moscas de la Fruta del Hemisferio OccidentalCiudad Autónoma de Buenos AiresArgentinaMinisterio de Agricultura, Ganadería y Pesca. Servicio Nacional de Sanidad y Calidad Agroalimentari

Graft preservation in heart transplantation: current approaches

Heart transplantation (HTx) represents the current best surgical treatment for patients affected by end-stage heart failure. However, with the improvement of medical and interventional therapies, the population of HTx candidates is increasingly old and at high-risk for mortality and complications. Moreover, the use of “extended donor criteria” to deal with the shortage of donors could increase the risk of worse outcomes after HTx. In this setting, the strategy of donor organ preservation could significantly affect HTx results. The most widely used technique for donor organ preservation is static cold storage in ice. New techniques that are clinically being used for donor heart preservation include static controlled hypothermia and machine perfusion (MP) systems. Controlled hypothermia allows for a monitored cold storage between 4°C and 8°C. This simple technique seems to better preserve the donor heart when compared to ice, probably avoiding tissue injury due to sub-zero °C temperatures. MP platforms are divided in normothermic and hypothermic, and continuously perfuse the donor heart, reducing ischemic time, a well-known independent risk factor for mortality after HTx. Also, normothermic MP permits to evaluate marginal donor grafts, and could represent a safe and effective technique to expand the available donor pool. However, despite the increasing number of donor hearts preserved with these new approaches, whether these techniques could be considered superior to traditional CS still represents a matter of debate. The aim of this review is to summarize and critically assess the available clinical data on donor heart preservation strategies employed for HTx

Compartmentalization of integrin α6β4 signaling in lipid rafts

Integrin α6β4 signaling proceeds through Src family kinase (SFK)–mediated phosphorylation of the cytoplasmic tail of β4, recruitment of Shc, and activation of Ras and phosphoinositide-3 kinase. Upon cessation of signaling, α6β4 mediates assembly of hemidesmosomes. Here, we report that part of α6β4 is incorporated in lipid rafts. Metabolic labeling in combination with mutagenesis indicates that one or more cysteine in the membrane-proximal segment of β4 tail is palmitoylated. Mutation of these cysteines suppresses incorporation of α6β4 in lipid rafts, but does not affect α6β4-mediated adhesion or assembly of hemidesmosomes. The fraction of α6β4 localized to rafts associates with a palmitoylated SFK, whereas the remainder does not. Ligation of palmitoylation-defective α6β4 does not activate SFK signaling to extracellular signal–regulated kinase and fails to promote keratinocyte proliferation in response to EGF. Thus, compartmentalization in lipid rafts is necessary to couple the α6β4 integrin to a palmitoylated SFK and promote EGF-dependent mitogenesis

Testing two nuclear physics approximations used in the standard leaky box model for the spallogenic production of LiBeB

The spallative production rates of Lithium, Beryllium and Boron (LiBeB) are a necessary component in any calculation of the evolution of these nuclei in the Galaxy. Previous calculations of these rates relied on two assumptions relating to the nuclear physics aspects: the straight-ahead approximation that describes the distribution of fragment energies and the assumption that the major contributor to the production rate arises from single-step reactions between primary cosmic ray projectiles and interstellar medium targets. We examine both assumptions by using a semi-empirical description for the spall's energy distribution and by including the reactions that proceed via intermediary fragments. After relaxing the straight-ahead approximation we find the changes in the production rates and emerging fluxes are small and do not warrant rejection of this approximation. In contrast we discover that two-step reactions can alter the production rate considerably leading to noticeable increases in the efficiency of producing the LiBeB nuclei. Motivated by this result we introduce a cascade technique to compute the production rates exactly and find that the results differ only slightly from those of our two-step calculations. We thus conclude that terminating the reaction network at the two-step order is sufficiently accurate for current studies of spallation.Comment: accepted in Ap

Magnetohydrodynamics of the Early Universe and the Evolution of Primordial Magnetic Fields

We show that the decaying magnetohydrodynamic turbulence leads to a more rapid growth of the correlation length of a primordial magnetic field than that caused by the expansion of the Universe. As an example, we consider the magnetic fields created during the electroweak phase transition. The expansion of the universe alone would yield a correlation length at the present epoch of 1 AU, whereas we find that the correlation length is likely of order 100 AU, and cannot possibly be longer than $10^4$ AU for non-helical fields. If the primordial field is strongly helical, the correlation length can be much larger, but we show that even in this case it cannot exceed 100 pc. All these estimates make it hard to believe that the observed galactic magnetic fields can result from the amplification of seed fields generated at the electroweak phase transition by the standard galactic dynamo.Comment: 15 pages, REVTeX. Added results of numerical simulation, enlarged and revise