25,696 research outputs found
Optimized cross-slot flow geometry for microfluidic extension rheometry
A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation of a strong and uniform birefringent strand when the dimensionless flow strength exceeds a critical Weissenberg number Wicrit 0:5. Birefringence and bulk pressure drop measurements provide self consistent estimates of the planar extensional viscosity of the fluid over a wide range of deformation rates (26 s1 "_ 435 s1) and are also in close agreement with numerical simulations performed by using a finitely extensible nonlinear elastic dumbbell model
NGC 2362: a Template for Early Stellar Evolution
We present UBVRI photometry for the young open cluster NGC 2362. From
analysis of the appropriate color-color and color-magnitude diagrams we derive
the fundamental parameters of the NGC 2362 cluster to be: age = 5 (+1-2) Myr,
distance = 1480 pc, E(B-V)=0.10 mag. The cluster age was independently
determined for both high mass (2.1 - 36Msun) and low mass (0.7 - 1.2Msun) stars
with excellent agreement between the ages derived using post-main sequence and
pre-main sequence evolutionary tracks for the high and low mass stars
respectively. Analysis of this cluster's color-magnitude diagram reveals a well
defined pre-main sequence (covering DeltaV ~ 9 magnitudes in V and extending
from early A stars to near the hydrogen burning limit) which makes this cluster
an ideal laboratory for pre-main sequence evolution studies.Comment: 9 pages, 3 figures, to be published in ApJ
Avaliação da gestão das UC do Sistema Estadual de Áreas Protegidas de Minas Gerais.
As Unidades de Conservação (UC) são espaços territoriais especialmente protegidos para a conservação dos recursos naturais. O estado de Minas Gerais abriga diversas UC federais, estaduais e municipais. Objetiva-se neste trabalho levantar, caracterizar e analisar como vem sendo implantado o Sistema Estadual de Unidades de Conservação em Minas Gerais. Especificamente, os objetivos foram: levantar as UC estaduais e sua distribuição por bioma e regionais do IEF, sua infra-estrutura básica, regularização fundiária, recursos humanos, existência de planos de manejo, conselhos consultivos, relação com a comunidade do entorno, existência de fluxo turístico, atividade de pesquisa e caracterizar os parceiros e voluntários que atuam na gestão das mesmas. A metodologia utilizada foi a de entrevistas semi-estruturadas e questionários sobre as UC aplicados a todos os gerentes, avaliando a situação espacial, fundiária, humana, estrutural entre outras. Os principais resultados encontrados foram: existem 74 UC estaduais que ocupam áreas significativas e representativas de todos os biomas presentes no estado; inexistem planos de manejo na maioria das UC; há carência de recursos humanos na gestão das UC, principalmente de gerentes; há sobreposição de funções, quantidade insuficiente de funcionários com capacitação para funções específicas; as UC com maior representatividade de área são as “Áreas de Proteção Ambiental” (APA) que enfrentam maiores carências em recursos humanos, materiais e financeiros, além da dificuldade de gerir o território em conjunto com os proprietários; as UC de proteção integral são as que possuem maiores problemas de regularização fundiári
Perfil e percepção dos chefes de unidades de conservação do sistema estadual de áreas protegidas em Minas Gerais.
As Unidades de Conservação (UC) são espaços territoriais especialmente protegidos para a proteção dos recursos naturais. Minas Gerais abriga diversas UC criadas pelos vários níveis de governo. Destes, o estadual vem se destacando, tanto pela criação como pelas medidas para implantação das UC. Os gerentes destas UC são importantes atores deste processo e estabelecem a interface entre governo e a realidade de campo. Objetivou-se com este trabalho definir o perfil profissional dos chefes de UC estaduais mineiras, seu nível de capacitação formal, sua distribuição pelo Sistema Estadual de Áreas Protegidas (SEAP), o tempo na função e no cargo e a satisfação e perspectivas de trabalho dos mesmos. A metodologia utilizada foi a de entrevistas semi-estruturadas e questionários aplicados a todos os gerentes. As principais conclusões foram: o quadro de gerentes cresceu ao longo do tempo, mas continua deficitário; a idade média dos gerentes diminuiu e a proporção de mulheres aumentou; há grande rotatividade na gerência das UC, impossibilitando a continuidade de muitos trabalhos; a formação acadêmica dos gerentes é considerada adequada; há apoio para o treinamento de funcionários, principalmente relacionados a cursos de caráter operacional, contudo, quase não ocorrem capacitações gerenciais; a remuneração é baixa e não estimula a maioria dos profissionais a fazer carreira na função; as condições desfavoráveis de atuação, por falta de recursos, desmotivam os gerentes; os gerentes lotados em sua região de origem apresentaram maior grau de satisfação, tendendo a se envolver mais em trabalhos de longo prazo e a se relacionar melhor com as comunidades; há acúmulo e desvio de função, comprometendo o desempenho gerencial
The Solar Twin Planet Search II. A Jupiter twin around a solar twin
Through our HARPS radial velocity survey for planets around solar twin stars,
we have identified a promising Jupiter twin candidate around the star HIP11915.
We characterize this Keplerian signal and investigate its potential origins in
stellar activity. Our analysis indicates that HIP11915 hosts a Jupiter-mass
planet with a 3800-day orbital period and low eccentricity. Although we cannot
definitively rule out an activity cycle interpretation, we find that a planet
interpretation is more likely based on a joint analysis of RV and activity
index data. The challenges of long-period radial velocity signals addressed in
this paper are critical for the ongoing discovery of Jupiter-like exoplanets.
If planetary in nature, the signal investigated here represents a very close
analog to the solar system in terms of both Sun-like host star and Jupiter-like
planet.Comment: 8 pages, 5 figures; A&A accepted; typos corrected in this versio
Knowledge and attitude towards the gradual reduction of salt in bread – an online survey
Aim: Assess knowledge and attitude towards the gradual reduction of salt
in bread and the potential impact on eating habits of children (6-18 years)
and their families, as part as a Health Impact Assessment pilot study.N/
Exact solution for the energy density inside a one-dimensional non-static cavity with an arbitrary initial field state
We study the exact solution for the energy density of a real massless scalar
field in a two-dimensional spacetime, inside a non-static cavity with an
arbitrary initial field state, taking into account the Neumann and Dirichlet
boundary conditions. This work generalizes the exact solution proposed by Cole
and Schieve in the context of the Dirichlet boundary condition and vacuum as
the initial state. We investigate diagonal states, examining the vacuum and
thermal field as particular cases. We also study non-diagonal initial field
states, taking as examples the coherent and Schrodinger cat states.Comment: 10 pages, 8 figure
Top-down pathways to devices with few and single atoms placed to high precision
Solid-state devices that employ few and single atoms are emerging as a consequence of technological advances in classical microelectronics and proposals for quantum computers based on spin or charge. The fabrication of devices in both these areas requires the development of techniques for deterministic doping of silicon where few or single dopant atoms must be placed to, typically, nanometre precision. Here we discuss a top-down approach, based on deterministic ion implantation, which can potentially be used to fabricate devices intended to explore the novel challenges of designing, building and measuring solid-state devices at the single atom limit. In particular, we address the potential of fabricating more complex devices that exploit quantum coherence. We propose a prototype triple-donor device that transports electron spin qubits via the coherent tunnelling by adiabatic passage (CTAP) protocol for a scalable quantum computer. We examine theoretically the statistics of dopant placement using ion implantation by employing an analytical treatment of CTAP transport properties under hydrogenic assumptions. We evaluate the probability of fabricating proof of concept devices subject to the limitations of ion implantation. We find that the results are promising with a yield of one in six for 14keV phosphorus implanted into silicon with a target atom site spacing of 30 nm with even higher yields possible for lower-energy implants. This suggests that deterministic doping is an important tool to fabricate and test near-term practical quantum coherent device
Resolving the Diplodia complex on apple and other Rosaceae hosts
Diplodia species are known as pathogens on many woody hosts, including fruit trees, worldwide. In this study a collection of Diplodia isolates obtained mostly from apple and other Rosaceae hosts were identified based on morphological characters and DNA sequence data from ITS and EF1-α loci. The results show that the diversity of species associated with twig and branch cankers and fruit rot of apples is larger than previously recognised. Four species were identified, namely D. seriata and D. malorum (which is here reinstated for isolates with D. mutila-like conidia). Diplodia intermedia sp. nov. is closely related to D. seriata, and D. bulgarica sp. nov. is morphologically and phylogenetically distinct from all Diplodia species reported from apples.publishe
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