783 research outputs found
Checklist of lizards and amphisbaenians of Argentina: an update
We update the list of lizards of Argentina, reporting a total of 261 species from the country, arranged in 27 genera and 10 families. Introduced species and dubious or erroneous records are discussed. Taxonomic, nomenclatural and distributional comments are provided when required. Considering species of probable occurrence in the country (known to occur in Bolivia, Brazil, Chile and Paraguay at localities very close to the Argentinean border) and still undescribed taxa, we estimate that the total number of species in Argentina could exceed 300 in the next few years.Fil: Avila, Luciano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Martinez, L.e.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Morando, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin
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Comparison of Microstructures and Mechanical Properties for Solid Cobalt-Base Alloy Components and Biomedical Implant Prototypes Fabricated by Electron Beam Melting
The microstructures and mechanical behavior of simple, as-fabricated, solid
geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed
femoral (knee) prototypes all produced by additive manufacturing (AM) using electron
beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this
study. Microstructures and microstructural issues are examined by optical metallography,
SEM, TEM, EDS, and XRD while mechanical properties included selective specimen
tensile testing and Vickers microindentation (HV) and Rockwell C-scale (HRC) hardness
measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM
produced unique, orthogonal and related Cr23C6 carbide (precipitate) cellular arrays with
dimensions of ~2μm in the build plane perpendicular to the build direction, while
connected carbide columns were formed in the vertical plane, parallel to the build
direction.Mechanical Engineerin
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Microstructure Architecture Development in Metals and Alloys By Additive Manufacturing Using Electron Beam Melting
The concept of materials with controlled microstructural architecture (MCMA) to
develop and fabricate structural materials with novel and possibly superior properties and
performance characteristics is a new paradigm or paradigm extension for materials science and
engineering. In the conventional materials science and engineering paradigm, structure
(microstructure), properties, processing, and performance features are linked in the development
of desirable materials properties and performance through processing methodologies which
manipulate microstructures. For many metal or alloy systems, thermomechanical treatment
combining controlled amounts of plastic deformation with heat treatment or aging cycles can
achieve improved mechanical properties beyond those attainable by conventional processing
alone (such as rolling or forging for example) through controlled microstructure development. In
this paper we illustrate a new concept involving the fabrication of microstructural architectures
by the process development and selective manipulation of these microstructures ideally defining
material design space. This allows for the additional or independent manipulation of material
properties by additive manufacturing (AM) using electron beam melting (EBM). Specifically we
demonstrate the novel development of a carbide (M23C6) architecture in the AM of a Co-base
alloy and an oxide (Cu2O) precipitate-dislocation architecture in the AM of an oxygen-containing Cu. While more conventional processing can produce various precipitate
microstructures in these materials, EBM produces spatial arrays of precipitate columns or
columnar-like features often oriented in the build direction. These microstructural architectures
are observed by optical microscopy and scanning and transmission electron microscopy.
Prospects for EBM architecture development in precipitation-hardenable Al alloys is also
discussed. In the EBM build process using precursor powders, the electron beam parameters
(including beam focus, scan speed and sequencing) produce localized, requisite thermodynamic
regimes which create or organize the precipitate-related spatial arrays. This feature demonstrates
the utility of AM not only in the fabrication of complex components, but also prospects for
selective property design using CAD for MCMA development: a new or extended processing-microstructure-property-performance paradigm for materials science and engineering in
advanced manufacturing involving solid free-form fabrication (SFF).Mechanical Engineerin
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Effect of Build Parameters and Build Geometries on Residual Microstructures and Mechanical Properties of Ti-6Al-4V Components Built by Electron Beam Melting (EBM)
In this study, involving additive manufacturing (AM) using electron beam melting (EBM), we
have examined build defects which result from beam tripping, porosities (including unmelted or
unsintered zones) due to excursions from optimal build parameters (especially variations in melt
scan beam current and scan speed), and gas bubbles trapped in atomized Ti-6Al-4V starting
powder as well as recycled powder, and retained in the build. At optimized build conditions we
have also examined microstructure-mechanical property (hardness, tensile strength, and
elongation) variations for multiple rake building and multiple melt scans using optical
metallography and scanning and transmission electron microscopy (SEM and TEM). These
build variances cause cooling rate variances which promote α-phase growth and variations in
dislocation density, as well as α-to-α' (martensite) phase changes, all of which produce some
degree of mechanical property variations. These features (especially α-to-α' phase changes) are
notable on comparing solid builds in comparison with a variety of mesh arrays where strut
dimension and build-element complexities alter the cooling rates in a significant way. We
illustrate these microstructure variations with corresponding variations in microindentation
hardness measurements made directly on fine mesh (strut) structures. Finally, we have examined
Ti-6Al-4V powder chemistries and solid build chemistries which for single-pass melt scans at
optimized build conditions are shown to be relatively constant up to 40 cycles of powder reuse
with the exception of Al content which was reduced by 10 to 15% in solid builds at optimized
conditions. However, Al loss in solid builds approached 25% for multiple (2 and 3) melt scans,
while no changes in Ar gas-bubble density were observed with changes in α-phase (grain) width
which increased from 3 µm for a single melt scan to 4.5 and 6 µm for 2 and 3 melt scans,
respectively. Corresponding Rockwell C-scale (HRC) hardness varied from 37, 36, and 35,
respectively; with ultimate tensile strengths exceeding 1.2 GPa at elongations of 12% or higher
for this melt scan sequence.Mechanical Engineerin
The impact of the COVID-19 pandemic on grocery shopper behaviour: Analysis of shopper behaviour change using store transaction data
The systemic shock of coronavirus (COVID-19) and its impact on the global economy has been unprecedented with grocery shopper behaviour changing dramatically through various stages of the pandemic. COVID-19 has caused unusual market conditions, with significant changes to grocery shopper behaviour that need to be understood to allow for appreciation of shopperbehaviour change and retail planning implications during future systemic shocks. The aim of this study was therefore to understand grocery shopping behaviour during COVID19. Specific objectives were to investigate changes to grocery sale patterns by basket size, composition and category, as well as during specific time periods of the pandemic. The use of transaction data using a range of market basket indicators (e.g. value, size, product mix), revealed profound changes that indicate the challenge shoppers faced navigating a new ‘normal grocery shop’ and the pressure on retailers to analyse consumption changes inorder to prioritise demand planning. While the use of this data and analysis approach is an important contribution to consumer behaviour research, our focus was on the bigger patterns observed through the data pertaining to changes in shopper behaviour during systemic shocks.A key contribution of this paper is how the use of transaction data from grocery retail provides a nuanced understanding of how grocery shoppers responded leading up to and during the pandemic. For example, we found that grocery shoppers purchased more than just ‘daily staples’ to stock up during the pandemic, with increased awareness of health and wellbeing an important aspect
Transmission Properties of the oscillating delta-function potential
We derive an exact expression for the transmission amplitude of a particle
moving through a harmonically driven delta-function potential by using the
method of continued-fractions within the framework of Floquet theory. We prove
that the transmission through this potential as a function of the incident
energy presents at most two real zeros, that its poles occur at energies
(), and that the
poles and zeros in the transmission amplitude come in pairs with the distance
between the zeros and the poles (and their residue) decreasing with increasing
energy of the incident particle. We also show the existence of non-resonant
"bands" in the transmission amplitude as a function of the strength of the
potential and the driving frequency.Comment: 21 pages, 12 figures, 1 tabl
Indirect Dark Matter Detection from Dwarf Satellites: Joint Expectations from Astrophysics and Supersymmetry
We present a general methodology for determining the gamma-ray flux from
annihilation of dark matter particles in Milky Way satellite galaxies, focusing
on two promising satellites as examples: Segue 1 and Draco. We use the
SuperBayeS code to explore the best-fitting regions of the Constrained Minimal
Supersymmetric Standard Model (CMSSM) parameter space, and an independent MCMC
analysis of the dark matter halo properties of the satellites using published
radial velocities. We present a formalism for determining the boost from halo
substructure in these galaxies and show that its value depends strongly on the
extrapolation of the concentration-mass (c(M)) relation for CDM subhalos down
to the minimum possible mass. We show that the preferred region for this
minimum halo mass within the CMSSM with neutralino dark matter is ~10^-9-10^-6
solar masses. For the boost model where the observed power-law c(M) relation is
extrapolated down to the minimum halo mass we find average boosts of about 20,
while the Bullock et al (2001) c(M) model results in boosts of order unity. We
estimate that for the power-law c(M) boost model and photon energies greater
than a GeV, the Fermi space-telescope has about 20% chance of detecting a dark
matter annihilation signal from Draco with signal-to-noise greater than 3 after
about 5 years of observation
SUPEROVULAÇÃO OVARIANA E PRODUÇÃO DE EMBRIÕES EM Bubalus bubalis
The aim of the present research work
was to optimize ovarian superovulation rate and the
embryo production in Murrah and Mediterranean
buffaloes around the 60th day after parturition. Fourteen
animals were divided in two groups of 7 animals each,
G1 (treated animals) and G2 (untreated animals). All
animals were subjected to a step of oestrus
synchronization by receiving at the 0 day (OD) a vaginal
pressary with progestagen (CIDR-B, Intervet), followed
by the administration, in the morning of the day 1 (D1),
of 3 mg stradiol benzoate IM (Estrogin, Farmavet, SP).
The ovarian superovulation (SO) was carried out daily,
at intervals of 12 hours in the morning and the afternoon
by means of the administration of follicule stimulant
hormone (FSH) (Pluset, Serono, Italy) in both groups of
experimental animals, during four days according to the
following protocol: at the 6th day, 75 IU; at the 7th day, 40
IU; at the 8th day, 30 IU; and at the 9th day, 20 IU. At the
afternoon of the 8th day, administration of 500 µg of
cloprostenol IM (Closin-Schering-Plough) was performed
followed by the withdraw of the vaginal pessaries from
all animals. Then, observations on the estrus of the
experimental animals has been carried out. For this
purpose the animals were inseminated twice at intervals
of 12 hours. Additionaly, all animals from the G1, together
with the first artificial insemination (AI) received a dose
of 3000 UI of gonadotrophic chorionic hormone (GCH)
(Vetecor, Calier, IV) while the G2 animals received 1 ml
of saline as placebo. All animals from both G1 and G2
groups had their ovaries monitored by ultrasonography
from the first day of the AI up to the day when they had
their embryos collected. Ultrasography has been carried
out by means of an Aloka SSD-550 (Japan) instrument
aiming to evaluate the follicles, the ovulation, and the
corpora lutea. At the 5.5th after the estrus observation a
washing of the uterine cornus has been carried out for
the embryos harvesting and evaluation. According to the
present experiment, it was possible to conclude that the protocol used to promote superovulation (SO) in
buffaloes by means of FSH showed to be efficient
resulting in the production of significant number of antral
follicles larger than 8.0 mm diameter at the estrus day
and that the gonadotropohic corionic hormone showed
significant efficiency by displaying larger percentual
ovulations in the treated group (pO presente estudo objetivou otimizar a
superovulação ovariana, a taxa de ovulação e a
produção de embriões em búfalas. Os animais eram
da raça Murrah e Mediterrâneo e estavam em torno do
60º dia pós parto. Quatorze animais foram divididos em
dois grupos, sendo um grupo tratado (G1=7 animais) e
outro não-tratado (G2=7 animais). Todos os animais
foram submetidos à sincronização do estro, recebendo
no dia 0 (D0) um pessário vaginal com progestágeno
(CIDR-B, Intervet); no dia 1 (D1) pela manhã foi aplicado
3 mg de benzoato de estradiol IM (Estrogin Farmavet,
SP). A superovulação ovariana (SO) foi executada pela
manhã e à tarde com hormônio folículo estimulante
(FSH)(Pluset, Serono, Itália)), administrado diariamente
a intervalo de 12 horas entre cada aplicação, durante
quatro dias seguidos nos dois grupos, conforme o
protocolo: dia 6, 75 UI; dia 7, 40 UI; dia 8, 30 UI; dia 9,
20 UI. No dia 8 à tarde administrou-se 500 microgramas
de cloprostenol IM (Ciosin - Schering-Plough) e em
seguida houve a retirada dos pessários vaginais de todos
os animais. Na sequência, foram feitas as observações
de cio; os animais foram inseminados duas vezes a
intervalos de 12 horas um do outro. Adicionalmente, o
G1 recebeu junto com a 1ª inseminação artificial (IA),
uma dose de 3000 UI de hormônio coriônico
gonadotrófico (hCG) (Vetecor, Calier, IV) e o G2 recebeu
1 ml de solução fisiológica, como placebo. Todos os
animais tiveram os ovários monitorados mediante
ultrassonografia, desde o dia da 1ª IA até o dia da coleta
dos embriões, mediante aparelho Aloka SSD-550
(Japão), visando a avaliação de folículos, ovulação e
corpos lúteos. No 5,5º dia pós a observação de cio,
procedeu-se às lavagens dos cornos uterinos para a
colheita dos embriões e avaliação. Concluiu-se que o
protocolo utilizado para SO em bubalinos com FSH, foi
eficiente, ao promover significativo numero de folículos
antrais maiores que 8,0 mm de diâmetro no dia do cio
e que o hCG mostrou-se significativamente eficiente,
pois proporcionou maior % de ovulações no grupo
tratado (
Influence of chronic ocular hypertension on emmetropia: Refractive, structural and functional study in two rat models
Chronic ocular hypertension (OHT) influences on refraction in youth and causes glaucoma in adulthood. However, the origin of the responsible mechanism is unclear. This study analyzes the effect of mild-moderate chronic OHT on refraction and neuroretina (structure and function) in young-adult Long-Evans rats using optical coherence tomography and electroretinography over 24 weeks. Data from 260 eyes were retrospectively analyzed in two cohorts: an ocular normotension (ONT) cohort (20 mmHg), in which OHT was induced either by sclerosing the episcleral veins (ES group) or by injecting microspheres into the anterior chamber. A trend toward emmetropia was found in both cohorts over time, though it was more pronounced in the OHT cohort (p < 0.001), especially in the ES group (p = 0.001) and males. IOP and refraction were negatively correlated at week 24 (p = 0.010). The OHT cohort showed early thickening in outer retinal sectors (p < 0.050) and the retinal nerve fiber layer, which later thinned. Electroretinography demonstrated early supranormal amplitudes and faster latencies that later declined. Chronic OHT accelerates emmetropia in Long–Evans rat eyes towards slowly progressive myopia, with an initial increase in structure and function that reversed over time. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
On the Exact Evaluation of Certain Instances of the Potts Partition Function by Quantum Computers
We present an efficient quantum algorithm for the exact evaluation of either
the fully ferromagnetic or anti-ferromagnetic q-state Potts partition function
Z for a family of graphs related to irreducible cyclic codes. This problem is
related to the evaluation of the Jones and Tutte polynomials. We consider the
connection between the weight enumerator polynomial from coding theory and Z
and exploit the fact that there exists a quantum algorithm for efficiently
estimating Gauss sums in order to obtain the weight enumerator for a certain
class of linear codes. In this way we demonstrate that for a certain class of
sparse graphs, which we call Irreducible Cyclic Cocycle Code (ICCC_\epsilon)
graphs, quantum computers provide a polynomial speed up in the difference
between the number of edges and vertices of the graph, and an exponential speed
up in q, over the best classical algorithms known to date
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