Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes

Employing spectra obtained with the new Keck I HIRES near-UV sensitive detector, we have performed a comprehensive chemical composition analysis of the binary blue metal-poor star CS29497-030. Abundances for 29 elements and upper limits for an additional seven have been derived, concentrating on elements largely produced via neutron-capture nucleosynthesis. Included in our analysis are the two elements that define the termination point of the slow neutron-capture process, lead and bismuth. We determine an extremely high value of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the single-feature result obtained in previous studies. We also detect Bi for the first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with those predicted from the most recent FRANEC calculations of the slow neutron-capture process in low-mass AGB stars. We find that the neutron-capture elemental abundances of CS29497-030 are best explained by an AGB model that also includes very significant amounts of pre-enrichment of rapid neutron-capture process material in the protostellar cloud out of which the CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and ``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can be further constrained by the abundance of the light odd-element [Na/Fe] which is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to appear in ApJ Letters; additional jpeg figure available at ftp://www.astro.caltech.edu/users/iii/cs2949703

Point-contact Andreev-reflection spectroscopy in segregation-free Mg_{1-x}Al_{x}B_2 single crystals up to x=0.32

We present new results of point-contact Andreev-reflection (PCAR) spectroscopy in single-phase Mg_{1-x}Al_{x}B_{2} single crystals with x up to 0.32. Fitting the conductance curves of our point contacts with the two-band Blonder-Tinkham-Klapwijk model allowed us to extract the gap amplitudes Delta_{sigma} and Delta_{pi}. The gap values agree rather well with other PCAR results in Al-doped crystals and polycrystals up to x=0.2 reported in literature, and extend them to higher Al contents. In the low-doping regime, however, we observed an increase in the small gap Delta_{pi} on increasing x (or decreasing the local critical temperature of the junctions, T_{c}^{A}) which is not as clearly found in other samples. On further decreasing T_{c}^{A} below 30 K, both the gaps decrease and, up to the highest doping level x=0.32 and down to T_{c}^{A}= 12 K, no gap merging is observed. A detailed analysis of the data within the two-band Eliashberg theory shows that this gap trend can be explained as being mainly due to the band filling and to an increase in the interband scattering which is necessary to account for the increase in Delta_{pi} at low Al contents (x < 0.1). We suggest to interpret the following decrease of Delta_{pi} for T_{c}^{A} < 30 K as being governed by the onset of inhomogeneity and disorder in the Al distribution that partly mask the intrinsic effects of doping and is not taken into account in standard theoretical approaches.Comment: 22 pages, 9 eps figures, Elsevier style. Theoretical details added in appendix. Characterization of crystals include

Predictions for low-metallicity s-process Lead stars showing peculiar r-process enhancements

n/

Intra- and inter-observer variability of computed tomographic measurements of the prostate gland in neutered dogs

The purpose of this study was to evaluate the intra- and inter-observer variability of computed tomographic measurements of linear prostate dimensions in neutered dogs without signs of prostatic disease, to determine potential associations between prostatic parameters and body weight or age and to provide reference ranges. Length, width and height of the prostate gland were measured in 62 neutered dogs with no signs of prostatic disease by three observers with different levels of training. Statistically significant positive associations were found between all prostatic parameters and body weight and between all prostatic parameters and age at castration, but not with age. Formulae allowing the calculation of the expected values for prostatic parameters based on body weight are provided [length = 15.3 + body weight (BW) × 0.3; height = 9.7 + BW × 0.16; width = 9.5 + BW × 0.2]. These may represent a useful tool for computed tomographic evaluation of the size of the prostate in neutered dogs. Subjective evaluations of the morphological appearance of the prostate gland are also provided

Investigation for the enrichment pattern of the element abundances in r+s star HE 0338-3945: a special r-II star?

The very metal-poor star HE 0338-3945 shows a double-enhanced pattern of the neutron-capture elements. The study to this sample could make people gain a better understanding of s- and r-process nucleosynthesis at low metallicity. Using a parametric model,we find that the abundance pattern of the neutron-capture elements could be best explained by a binary system formed in a molecular cloud, which had been polluted by r-process material. The observed abundance pattern of C and N can be explained by an AGB model(Karakas & Lattanzio 2007), . Combing with the parameters obtained from Cui & Zhang (2006), we suggest that the initial mass of the AGB companion is most likely to be about 2.5Msun, which excludes the possibility of forming a type-1.5 supernova. By comparing with the observational abundance pattern of CS 22892-052, we find that the dominating production of O should accompany with the production of the heavy r-process elements of r+s stars. Similar to r-II stars, the heavy r-process elements are not produced in conjunction with all the light elements from Na to Fe group. The abundance pattern of the light and r-process elements for HE 0338-3945 is very close to the pattern of the r-II star CS 22892-052. So, we suggest that this star HE 0338-3945 should be a special r-II star.Comment: 18 pages, 6 figures, published by Ap

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes.

peer reviewedThe synthesis of zwitterionic dithiocarboxylate adducts was achieved by deprotonating various aldiminium or 1,2,3-triazolium salts with a strong base, followed by the nucleophilic addition of the in situ-generated cyclic (alkyl)(amino) or mesoionic carbenes (CAACs or MICs) onto carbon disulfide. Nine novel compounds were isolated and fully characterized by 1H and 13C NMR, FTIR, and HRMS techniques. Moreover, the molecular structures of two CAAC·CS2 and two MIC·CS2 betaines were determined by X-ray diffraction analysis. The analytical data recorded for all these adducts were compared with those reported previously for related NHC·CS2 betaines derived from imidazolinium or (benz)imidazolium salts. Due to the absence of electronic communication between the CS2 unit and the orthogonal heterocycle, all the CAAC·CS2, MIC·CS2, and NHC·CS2 zwitterions displayed similar electronic properties and featured the same bite angle. Yet, their steric properties are liable to ample modifications by varying the exact nature of their cationic heterocycle and its substituents

Diseño e implementación del telegrama de datos actuales con interfaz gráfica para el Torpedo Antisuperficie SST-4

El torpedo SST-4, es un arma submarina guiado remotamente desde el sistema de control de tiro de las unidades submarinas por medio de un cable de comunicación. El proyecto de investigación trata de la Modernización del telegrama de datos actuales con interfaz gráfica para el torpedo SST-4, la finalidad es mantener la información actualizada del torpedo durante su desplazamiento bajo el agua, el contar con la información permite al sistema de control de tiro la mejora del sistema táctico de operación y control. Actualmente el sistema de comunicación del telegrama de retorno de datos actuales del torpedo SST-4 es limitado, debido a su tecnología proveniente de la década del 70, el cual solo transmite las señales de “pulso de control y detección de blanco”, limitando la operación táctica en el sistema de disparo y control de las unidades submarinas. La presente tesis de Maestría trata del diseño e implementación del telegrama de datos actuales con interfaz gráfica para el torpedo anti superficie SST-4, aplicado al sector militar de Defensa Nacional, el cual permitirá contribuir al sistema de disparo y control de las unidades submarinas pertenecientes a la Marina de Guerra del Perú, orientado a mejorar sus operaciones tácticas de combate, al tener la ubicación real del torpedo durante su corrida efectiva mediante el telegrama de datos actuales el torpedo podrá transmitir su performance acústica y dinámica de esta manera los datos serán visualizados en una interfaz gráfica instalado en las unidades submarinas. La investigación es de tipo experimental y aplicativo (enfoque cuantitativo), el propósito de esta investigación es aplicar el conocimiento científico para transmitir el telegrama de datos actuales, mediante la investigación experimental podemos manipular las variables relacionadas con las señales acústicas y dinámicas, por último la investigación aplicada nos permite asignar el resultado obtenido de una investigación experimental con la necesidad de buscar nuevas herramientas tecnológicas que permitan solucionar el problema del uso de tecnologías descontinuadas.Tesi

(S)-4-(2-Chloro­propan-2-yl)-1-(2,2,2-trichloro­eth­yl)cyclo­hexene

The title compound, C11H16Cl4, was synthesized by the reaction of (1S)-β-pinene with triethyl­amine in the presence of ZnCl2. The cyclo­hexene ring assumes a half-boat conformation. The crystal packing is governed only by van der Waals inter­actions. The structure, which has been refined in P21, presents a striking P21/m pseudosymmetry

Triterpenoid saponins from the stem bark of pentaclethra eetveldeana

Two previously undescribed triterpenoid saponins together with 4 known ones were isolated from the stem bark of Pentaclethra eetveldeana De Wild. & Th. Dur. Their structures were elucidated by spectroscopic methods including 1D and 2D NMR experiments in combination with mass spectrometry as 3- O-β- d -glucopyranosyl- (1→2)- [β- d -glucopyranosyl- (1→3)]-β- d -glucopyranosyl- (1→4)- β- d -glucopyranosyl- (1→3)-α- l -rhamnopyranosyl- (1→2)-[β- d-glucopyranosyl- (1→4)]-α- l -arabinopyranosyloleanolic acid and 3- O -β- d -glucopyranosyl- (1→2)-[β- d -glucopyranosyl- (1→3)]-β- d -glucopyranosyl- (1→4)-β- d -glucopyranosyl- (1→3)- α -l -rhamnopyranosyl- (1→2)-[β- d -glucopyranosyl- (1→4)]-α- l -arabinopyranosylhederagenin. © The Author(s) 2019