843 research outputs found
Electronic and optical properties of lead iodide
ABSTRACT: Lead iodide (PbI2) is a very important material with a technological applicability as a room-temperature radiation detector. It is a wide-band-gap semiconductor (Eg.2 eV) with high environmental stability efficiency. The performance of the detector cannot be fully understood unless its electronic and optical properties are determined. Recently, its band-gap energy and thermal properties were determined by photoacoustic spectroscopy. A single crystal of PbI2 was grown by the Bridgman method with the c-axis oriented perpendicular to the growth axis. The purpose of this work is to obtain the electronic structure of PbI2, its dielectric functions e 1 and e 2 by ellipsometry and theoretically by full-potential linear muffin-tinorbital ~FPLMTO! method, and the temperature dependence of the measured band-gap energy by optica absorption. The obtained Eg(T) can be fitted by two different methods, leading to Eg ~0 K! and Eg ~300 K!
TiO2 nanorods doped with g-C3N4 â Polyethylene composite coating for self-cleaning applications
Visible-light-absorbing graphitic carbon nitrideâTiO2 nanorod nanomaterials (g-C3N4@TiO2NR) were successfully immobilized using a one-step UVA-induced photocatalytic procedure on commercially obtained flexible low-density polyethylene (LDPE) films. Self-cleaning properties were evaluated in solidâliquid and solidâgas phases using malachite green as a model molecule under UV-A and visible light irradiation. For comparison purpose, LDPE films containing P25 TiO2 nanoparticles was prepared using the same synthetic strategy (P25/LDPE). Among the fabricated films, the g-C3N4@TiO2NR/LDPE films exhibited the highest photocatalytic activity both in solidâliquid and solidâgas phases after 120 min of visible light irradiation (Îť > 455 nm) removing efficiently malachite green stains probably due to the attack of photoinduced reactive oxygen species (ROS) such as singlet oxygen (1O2), hydroxyl radical (â˘OH) and superoxide anion radical (O2ââ˘). Furthermore, the g-C3N4@TiO2NR/LDPE films retained their visible-light-photoinduced photocatalytic properties after four reuse cycles. The g-C3N4@TiO2NR/LDPE films also exhibited significant visible-light-photoinduced hydrophilicity. The high visible-light-photoinduced photocatalytic capacity of g-C3N4@TiO2NR/LDPE films was found to be related to the textural and electronic properties, superior visible-light absorption, and surface roughness of the films.Fil: Osorio Vargas, Paula Alejandra. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas; Argentina. Universidad del Bio Bio; ChileFil: Pais Ospina, Daniel Humberto. Universidad Nacional de TucumĂĄn. Instituto de FĂsica del Noroeste Argentino. - Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet Noa Sur. Instituto de FĂsica del Noroeste Argentino; Argentina. Universidad TecnolĂłgica de Pereira; ColombiaFil: MarĂn Silva, Diego Alejandro. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos; ArgentinaFil: Pinotti, Adriana Noemi. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de InvestigaciĂłn y Desarrollo en CriotecnologĂa de Alimentos; Argentina. Universidad Nacional de La Plata. Facultad de IngenierĂa; ArgentinaFil: Damonte, Laura Cristina. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; ArgentinaFil: Canneva, Antonela. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas; Argentina. YPF - TecnologĂa; ArgentinaFil: Donadelli, Jorge AndrĂŠs. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas; Argentina. YPF - TecnologĂa; ArgentinaFil: Pereira da Costa, Luiz. Universidad Federal del Amazonas.; BrasilFil: Pizzio, Luis Rene. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Torres, Cecilia C.. Universidad AndrĂŠs Bello; ChileFil: Campos, Cristian H.. Universidad de ConcepciĂłn; ChileFil: Rengifo Herrera, Julian Andres. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de InvestigaciĂłn y Desarrollo en Ciencias Aplicadas; Argentin
Search for associations containing young stars. III- Ages and Li abundances
Our study is a follow-up of the SACY project, an extended survey in the
Southern Hemisphere targeted to search for young nearby associations. Nine
associations have either been newly identified, or had their member list better
defined. These associations, with ages between about 6 Myr and 70 Myr, form an
excellent sample to study the Li depletion in the pre-main sequence (PMS)
evolution. We investigate the use of Li abundances as an independent clock to
constrain the PMS evolution. We have calculated the LTE Li abundances for 376
members of different young associations. In addition we considered the effects
of their projected stellar rotation. We present the Li depletion as function of
age in the first hundred million years for the first time for the most extended
sample of Li abundances in young stellar associations. A clear Li depletion can
be measured in the temperature range from 5000K to 3500K for the age span
covered by these nine associations. The age sequence based on the Li-clock
agrees well with the isochronal ages, Cha association being the only
possible exception. The lithium depletion patterns for those associations
resemble those of the young open clusters, strengthening the notion that the
members proposed for these loose young associations have indeed a common
physical origin. The observed scatter in the Li abundances hampers the use of
Li to determine reliable ages for individual stars. Rotation velocities above
20 km s seem to inhibit the Li depletion.Comment: 16 pgs., 7 figs To be published by Astronomy and Astrophysics
(accepted
Phylogenetic Analysis of Bolivian Bat Trypanosomes of the Subgenus Schizotrypanum Based on Cytochrome b Sequence and Minicircle Analyses
The aim of this study was to establish the phylogenetic relationships of trypanosomes present in blood samples of Bolivian Carollia bats. Eighteen cloned stocks were isolated from 115 bats belonging to Carollia perspicillata (Phyllostomidae) from three Amazonian areas of the Chapare Province of Bolivia and studied by xenodiagnosis using the vectors Rhodnius robustus and Triatoma infestans (Trypanosoma cruzi marenkellei) or haemoculture (Trypanosoma dionisii). The PCR DNA amplified was analyzed by nucleotide sequences of maxicircles encoding cytochrome b and by means of the molecular size of hyper variable regions of minicircles. Ten samples were classified as Trypanosoma cruzi marinkellei and 8 samples as Trypanosoma dionisii. The two species have a different molecular size profile with respect to the amplified regions of minicircles and also with respect to Trypanosoma cruzi and Trypanosoma rangeli used for comparative purpose. We conclude the presence of two species of bat trypanosomes in these samples, which can clearly be identified by the methods used in this study. The presence of these trypanosomes in Amazonian bats is discussed
Neurodevelopment Genes in Lampreys Reveal Trends for Forebrain Evolution in Craniates
The forebrain is the brain region which has undergone the most dramatic changes through vertebrate evolution. Analyses conducted in lampreys are essential to gain insight into the broad ancestral characteristics of the forebrain at the dawn of vertebrates, and to understand the molecular basis for the diversifications that have taken place in cyclostomes and gnathostomes following their splitting. Here, we report the embryonic expression patterns of 43 lamprey genes, coding for transcription factors or signaling molecules known to be involved in cell proliferation, stemcellness, neurogenesis, patterning and regionalization in the developing forebrain. Systematic expression patterns comparisons with model organisms highlight conservations likely to reflect shared features present in the vertebrate ancestors. They also point to changes in signaling systems âpathways which control the growth and patterning of the neuroepithelium-, which may have been crucial in the evolution of forebrain anatomy at the origin of vertebrates
A draft genome sequence of the elusive giant squid, Architeuthis dux
Background: The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea-dwelling species will allow several pending evolutionary questions to be unlocked. Findings: We present a draft genome assembly that includes 200 Gb of Illumina reads, 4 Gb of Moleculo synthetic long reads, and 108 Gb of Chicago libraries, with a final size matching the estimated genome size of 2.7 Gb, and a scaffold N50 of 4.8 Mb. We also present an alternative assembly including 27 Gb raw reads generated using the Pacific Biosciences platform. In addition, we sequenced the proteome of the same individual and RNA from 3 different tissue types from 3 other species of squid (Onychoteuthis banksii, Dosidicus gigas, and Sthenoteuthis oualaniensis) to assist genome annotation. We annotated 33,406 protein-coding genes supported by evidence, and the genome completeness estimated by BUSCO reached 92%. Repetitive regions cover 49.17% of the genome. Conclusions: This annotated draft genome of A. dux provides a critical resource to investigate the unique traits of this species, including its gigantism and key adaptations to deep-sea environments
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
- âŚ