The Boson peak in supercooled water

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line TW. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.We thank S. V. Buldyrev and S. Sastry for helpful discussions. The simulations were in part performed using resources provided by the Swedish National Infrastructure for Computing (SNIC) at the NSC and HPC2N centers. LGMP, KTW and DS were supported by the Swedish Research Council. KTW is also supported by the Icelandic Research Fund through the START programme. PK acknowledges the support of National Academies Keck Future Initiatives award. HES thanks NSF Grants No. CHE0911389, No. CHE0908218, and No. CHE-1213217. (Swedish Research Council; Icelandic Research Fund through the START programme; National Academies Keck Future Initiatives award; CHE0911389 - NSF; CHE0908218 - NSF; CHE-1213217 - NSF)Published versio

The Boson peak in supercooled water

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line $T_W$. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.Comment: 25 pages, 9 figure

Característica de la mano de obra en la construcción

Debido al énfasis dado al sector construcción en el Plan de Desarrollo 1970-1973, es importante tener información sobre indicadores tales como nivel y tipos de ocupación, ingreso, edad, lugar de origen y educación de la mano de obra en el sector, insumo que representa cerca de un 30% del valor final de las edificaciones. En consecuencia, el objeto de este trabajo es analizar algunas de las principales características de la fuerza de trabajo en el sector construcción

HAPTIC: Haptic Anatomical Positioning to Improve Clinical Monitoring

Hospitals are inundated by the sounds of patient monitoring devices and alarms. These are meant to help, yet also create a stressful environment for physicians and patients. To address this issue, we consider the possibility of delivering complementary haptic alarm stimuli via a wearable tactile display. This may reduce the necessity for the plethora of audible alarms in the Intensive Care Unit and Operating Room, potentially decreasing fatigue among clinicians, and improving sleep quality for patients. The study described here sought to determine a suitable anatomical location where such a tactile display could be worn. Although the wrist is an obvious default, based on the success of smartwatches and fitness monitors, wearable devices below the elbow are disallowed in aseptic procedural environments. We hypothesized that haptic perception would be approximately equivalent at the wrist and ankle, and confirmed this experimentally. Thus, for a healthcare setting, we suggest that the ankle is a suitable alternative for the placement of a tactile display

Isomonodromic deformations of connections with singularities of parahoric formal type

In previous work, the authors have developed a geometric theory of fundamental strata to study connections on the projective line with irregular singularities of parahoric formal type. In this paper, the moduli space of connections that contain regular fundamental strata with fixed combinatorics at each singular point is constructed as a smooth Poisson reduction. The authors then explicitly compute the isomonodromy equations as an integrable system. This result generalizes work of Jimbo, Miwa, and Ueno to connections whose singularities have parahoric formal type.Comment: 32 pages. One of the main theorems (Theorem 5.1) has been significantly strengthened. It now states that the isomonodromy equations give rise to an integrable system on the moduli space of framed connections with fixed combinatorics instead of only on a principal GL_n bundle over this space. Sections 5 and 6 have been substantially rewritte

Joint astrometric solution of Hipparcos and Gaia: A recipe for the Hundred Thousand Proper Motions project

The first release of astrometric data from Gaia is expected in 2016. It will contain the mean stellar positions and magnitudes from the first year of observations. For more than 100 000 stars in common with the Hipparcos Catalogue it will be possible to compute very accurate proper motions due to the time difference of about 24 years between the two missions. This Hundred Thousand Proper Motions (HTPM) project will be part of the first release. Our aim is to investigate how early Gaia data can be optimally combined with information from the Hipparcos Catalogue in order to provide the most accurate and reliable results for HTPM. The Astrometric Global Iterative Solution (AGIS) was developed to compute the astrometric core solution based on the Gaia observations and will be used for all releases of astrometric data from Gaia. We adapt AGIS to process Hipparcos data in addition to Gaia observations, and use simulations to verify and study the joint solution method. For the HTPM stars we predict proper motion accuracies between 14 and 134 muas/yr, depending on stellar magnitude and amount of Gaia data available. Perspective effects will be important for a significant number of HTPM stars, and in order to treat these effects accurately we introduce a scaled model of kinematics. We define a goodness-of-fit statistic which is sensitive to deviations from uniform space motion, caused for example by binaries with periods of 10-50 years. HTPM will significantly improve the proper motions of the Hipparcos Catalogue well before highly accurate Gaia- only results become available. Also, HTPM will allow us to detect long period binary and exoplanetary candidates which would be impossible to detect from Gaia data alone. The full sensitivity will not be reached with the first Gaia release but with subsequent data releases. Therefore HTPM should be repeated when more Gaia data become available.Comment: Revised manuscript following referee report. Accepted for publication in A&

Algunos aspectos específicos del mercado de capitales colombiano: tasas de interés y exenciones impositivas

Se justifica buscar que sea cada vez mayor la parte del ahorro doméstico representado en activos financieros, porque de este modo es posible llegar a una mejor asignación de recursos, (que son escasos por naturaleza) a un incremento en el rendimiento del capital, y a facilitar el más adecuado logro de un financiamiento de las inversiones, especialmente de las realizadas por el sector público

Host Cell Poly(ADP-ribose) glycohydrolase Is Crucial for Trypanosoma cruzi Infection Cycle

Trypanosoma cruzi, etiological agent of Chagas´ disease, has a complex life cycle which involves the invasion of mammalian host cells, differentiation and intracellular replication. Here we report the first insights into the biological role of a poly(ADPribose) glycohydrolase in a trypanosomatid (TcPARG). In silico analysis of the TcPARG gene pointed out the conservation of key residues involved in the catalytic process and, by Western blot, we demonstrated that it is expressed in a life stagedependant manner. Indirect immunofluorescense assays and electron microscopy using an anti-TcPARG antibody showed that this enzyme is localized in the nucleus independently of the presence of DNA damage or cell cycle stage. The addition of poly(ADP-ribose) glycohydrolase inhibitors ADP-HPD (adenosine diphosphate (hydroxymethyl)pyrrolidinediol) or DEA (6,9-diamino-2-ethoxyacridine lactate monohydrate) to the culture media, both at a 1 μM concentration, reduced in vitro epimastigote growth by 35% and 37% respectively, when compared to control cultures. We also showed that ADP-HPD 1 μM can lead to an alteration in the progression of the cell cycle in hydroxyurea synchronized cultures of T. cruzi epimastigotes. Outstandingly, here we demonstrate that the lack of poly(ADP-ribose) glycohydrolase activity in Vero and A549 host cells, achieved by chemical inhibition or iRNA, produces the reduction of the percentage of infected cells as well as the number of amastigotes per cell and trypomastigotes released, leading to a nearly complete abrogation of the infection process. We conclude that both, T. cruzi and the host, poly(ADP-ribose) glycohydrolase activities are important players in the life cycle of Trypanosoma cruzi, emerging as a promising therapeutic target for the treatment of Chagas´ disease.Fil: Vilchez Larrea, Salomé Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; ArgentinaFil: Schlesinger, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; ArgentinaFil: Kevorkian, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; ArgentinaFil: Flawia, Mirtha Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; ArgentinaFil: Alonso, Guillermo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; ArgentinaFil: Fernandez Villamil, Silvia Hebe. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentin

Climatic and Biogeochemical Effects of a Galactic Gamma-Ray Burst

It is likely that one or more gamma-ray bursts within our galaxy have strongly irradiated the Earth in the last Gy. This produces significant atmospheric ionization and dissociation, resulting in ozone depletion and DNA-damaging ultraviolet solar flux reaching the surface for up to a decade. Here we show the first detailed computation of two other significant effects. Visible opacity of NO2 is sufficient to reduce solar energy at the surface up to a few percent, with the greatest effect at the poles, which may be sufficient to initiate glaciation. Rainout of dilute nitric acid is could have been important for a burst nearer than our conservative nearest burst. These results support the hypothesis that the characteristics of the late Ordovician mass extinction are consistent with GRB initiation.Comment: 12 pages, 2 figures, in press at Geophysical Research Letters. Minor revisions, including details on falsifying the hypothesi