Light Reflectance Characteristics and Remote Sensing of Waterlettuce

Waterlettuce ( Pistia stratiotes L.) is a free-floating exotic aquatic weed that often invades and clogs waterways in the southeastern United States. A study was conducted to evaluate the potential of using remote sensing technology to distinguish infestations of waterlettuce in Texas waterways. Field reflectance measurements showed that waterlettuce had higher visible green reflectance than associated plant species. Waterlettuce could be detected in both aerial color- infrared (CIR) photography and videography where it had light pink to pinkish-white image tonal responses. Computer analysis of CIR photographic and videographic images had overall accuracy assessments of 86% and 84%, respectively. (PDF contains 6 pages.

The growth and evolution of thin oxide films on δ-plutonium surfaces

The common oxides of plutonium are the dioxide (PuO2) and the sesquioxide (Pu2O3). The nature of an oxide on plutonium metal under air at room temperature is typically described as a thick PuO2 film at the gas-oxide interface with a thinner Pu2O3 film near the oxide-metal substrate interface. In a reducing environment, such as ultra high vacuum, the dioxide (Pu4+; O/Pu=2.0) readily converts to the sesquioxide (Pu3+; O/Pu=1.5) with time. In this work, the growth and evolution of thin plutonium oxide films is studied with x-ray photoelectron spectroscopy (XPS) under varying conditions. The results indicate that, like the dioxide, the sesquioxide is not stable on a clean metal substrate under reducing conditions, resulting in substoichiometric films (Pu2O3-y). The Pu2O3-y films prepared exhibit a variety of stoichiometries (y~0.2-1) as a function of preparation conditions, highlighting the fact that caution must be exercised when studying plutonium oxide surfaces under these conditions and interpreting resulting data

The growth and evolution of thin oxide films on δ-plutonium surfaces

The common oxides of plutonium are the dioxide (PuO2) and the sesquioxide (Pu2O3). The nature of an oxide on plutonium metal under air at room temperature is typically described as a thick PuO2 film at the gas-oxide interface with a thinner Pu2O3 film near the oxide-metal substrate interface. In a reducing environment, such as ultra high vacuum, the dioxide (Pu4+; O/Pu=2.0) readily converts to the sesquioxide (Pu3+; O/Pu=1.5) with time. In this work, the growth and evolution of thin plutonium oxide films is studied with x-ray photoelectron spectroscopy (XPS) under varying conditions. The results indicate that, like the dioxide, the sesquioxide is not stable on a clean metal substrate under reducing conditions, resulting in substoichiometric films (Pu2O3-y). The Pu2O3-y films prepared exhibit a variety of stoichiometries (y~0.2-1) as a function of preparation conditions, highlighting the fact that caution must be exercised when studying plutonium oxide surfaces under these conditions and interpreting resulting data

Newlywed Women’s Marital Expectations: Lifelong Monogamy?

Over time, perceptions of marriage in the United States have shifted from a social obligation to a decision based on personal fulfillment. This shift has been most pronounced for women who no longer rely upon marriage for financial security. Marriages based on personal fulfillment are more fragile so when love declines and constraints do not exist, infidelity and divorce are considered viable options. This study investigated newlywed women’s marital expectations along with their experiences of infidelity and expectations of divorce. Newlywed women (N=197) married 2 years or less completed an online survey. As expected, these women primarily conceptualized marriage in terms of love and personal fulfillment. They reported a variety of extramarital thoughts and behaviors, and 74% indicated some expectation of divorce

Reionization and the abundance of galactic satellites

One of the main challenges facing standard hierarchical structure formation models is that the predicted abundance of galactic subhalos with circular velocities of 10-30 km/s is an order of magnitude higher than the number of satellites actually observed within the Local Group. Using a simple model for the formation and evolution of dark halos, based on the extended Press-Schechter formalism and tested against N-body results, we show that the theoretical predictions can be reconciled with observations if gas accretion in low-mass halos is suppressed after the epoch of reionization. In this picture, the observed dwarf satellites correspond to the small fraction of halos that accreted substantial amounts of gas before reionization. The photoionization mechanism naturally explains why the discrepancy between predicted halos and observed satellites sets in at about 30 km/s, and for reasonable choices of the reionization redshift (z_re = 5-12) the model can reproduce both the amplitude and shape of the observed velocity function of galactic satellites. If this explanation is correct, then typical bright galaxy halos contain many low-mass dark matter subhalos. These might be detectable through their gravitational lensing effects, through their influence on stellar disks, or as dwarf satellites with very high mass-to-light ratios. This model also predicts a diffuse stellar component produced by large numbers of tidally disrupted dwarfs, perhaps sufficient to account for most of the Milky Way's stellar halo.Comment: 5 pages, 2 figures, Submitted to Ap

Redox and pH gradients drive amino acid synthesis in iron oxyhydroxide mineral systems

Iron oxyhydroxide minerals, known to be chemically reactive and significant for elemental cycling, are thought to have been abundant in early-Earth seawater, sediments, and hydrothermal systems. In the anoxic Fe^(2+)-rich early oceans, these minerals would have been only partially oxidized and thus redox-active, perhaps able to promote prebiotic chemical reactions. We show that pyruvate, a simple organic molecule that can form in hydrothermal systems, can undergo reductive amination in the presence of mixed-valence iron oxyhydroxides to form the amino acid alanine, as well as the reduced product lactate. Furthermore, geochemical gradients of pH, redox, and temperature in iron oxyhydroxide systems affect product selectivity. The maximum yield of alanine was observed when the iron oxyhydroxide mineral contained 1:1 Fe(II):Fe(III), under alkaline conditions, and at moderately warm temperatures. These represent conditions that may be found, for example, in iron-containing sediments near an alkaline hydrothermal vent system. The partially oxidized state of the precipitate was significant in promoting amino acid formation: Purely ferrous hydroxides did not drive reductive amination but instead promoted pyruvate reduction to lactate, and ferric hydroxides did not result in any reaction. Prebiotic chemistry driven by redox-active iron hydroxide minerals on the early Earth would therefore be strongly affected by geochemical gradients of E_h, pH, and temperature, and liquid-phase products would be able to diffuse to other conditions within the sediment column to participate in further reactions

A genetic interaction between RAP1 and telomerase reveals an unanticipated role for RAP1 in telomere maintenance

RAP1 is one of the components of shelterin, the capping complex at chromosome ends or telomeres, although its role in telomere length maintenance and protection has remained elusive. RAP1 also binds subtelomeric repeats and along chromosome arms, where it regulates gene expression and has been shown to function in metabolism control. Telomerase is the enzyme that elongates telomeres, and its deficiency causes a premature aging in humans and mice. We describe an unanticipated genetic interaction between RAP1 and telomerase. While RAP1 deficiency alone does not impact on mouse survival, mice lacking both RAP1 and telomerase show a progressively decreased survival with increasing mouse generations compared to telomerase single mutants. Telomere shortening is more pronounced in Rap1-/- Terc-/- doubly deficient mice than in the single-mutant Terc-/- counterparts, leading to an earlier onset of telomere-induced DNA damage and degenerative pathologies. Telomerase deficiency abolishes obesity and liver steatohepatitis provoked by RAP1 deficiency. Using genomewide ChIP sequencing, we find that progressive telomere shortening owing to telomerase deficiency leads to re-localization of RAP1 from telomeres and subtelomeric regions to extratelomeric sites in a genomewide manner. These findings suggest that although in the presence of sufficient telomere reserve RAP1 is not a key factor for telomere maintenance and protection, it plays a crucial role in the context of telomerase deficiency, thus in agreement with its evolutionary conservation as a telomere component from yeast to humans.Research in the Blasco laboratory is funded by Spanish Ministry of Economy and Competitiveness (MINECO and FEDER) Project RETOS (SAF2013-45111-R), the European Research Council (ERC) Project TEL STEM CELL (ERC-2008-AdG/232854), and Fundacion Botin.S

Molecular determinants of chaperone interactions on MHC-I for folding and antigen repertoire selection.

The interplay between a highly polymorphic set of MHC-I alleles and molecular chaperones shapes the repertoire of peptide antigens displayed on the cell surface for T cell surveillance. Here, we demonstrate that the molecular chaperone TAP-binding protein related (TAPBPR) associates with a broad range of partially folded MHC-I species inside the cell. Bimolecular fluorescence complementation and deep mutational scanning reveal that TAPBPR recognition is polarized toward the α2 domain of the peptide-binding groove, and depends on the formation of a conserved MHC-I disulfide epitope in the α2 domain. Conversely, thermodynamic measurements of TAPBPR binding for a representative set of properly conformed, peptide-loaded molecules suggest a narrower MHC-I specificity range. Using solution NMR, we find that the extent of dynamics at "hotspot" surfaces confers TAPBPR recognition of a sparsely populated MHC-I state attained through a global conformational change. Consistently, restriction of MHC-I groove plasticity through the introduction of a disulfide bond between the α1/α2 helices abrogates TAPBPR binding, both in solution and on a cellular membrane, while intracellular binding is tolerant of many destabilizing MHC-I substitutions. Our data support parallel TAPBPR functions of 1) chaperoning unstable MHC-I molecules with broad allele-specificity at early stages of their folding process, and 2) editing the peptide cargo of properly conformed MHC-I molecules en route to the surface, which demonstrates a narrower specificity. Our results suggest that TAPBPR exploits localized structural adaptations, both near and distant to the peptide-binding groove, to selectively recognize discrete conformational states sampled by MHC-I alleles, toward editing the repertoire of displayed antigens

Low gain avalanche detectors for high energy physics experiments

Trabajo presentado a la 10th Spanish Conference on Electron Devices, celebrada en Aranjuez (Madrid, España) del 11 al 13 de febrero de 2015.This paper describes a new concept of Silicon radiation detector with internal multiplication of the charge generated by the incident particle, known as Low Gain Avalanche Detector (LGAD), with a gain in the range of 10-20. The LGAD is addressed to tracking applications for high energy physics with enhanced performances compared to the conventional detectors based on the PiN diode structure. The physical behavior, the critical design challenges and the first experimental data on the fabricated LGAD prototypes is described in the paper.Peer Reviewe