3,952 research outputs found
Commitment and Oblivious Transfer in the Bounded Storage Model with Errors
The bounded storage model restricts the memory of an adversary in a
cryptographic protocol, rather than restricting its computational power, making
information theoretically secure protocols feasible. We present the first
protocols for commitment and oblivious transfer in the bounded storage model
with errors, i.e., the model where the public random sources available to the
two parties are not exactly the same, but instead are only required to have a
small Hamming distance between themselves. Commitment and oblivious transfer
protocols were known previously only for the error-free variant of the bounded
storage model, which is harder to realize
The self-consistent quantum-electrostatic problem in strongly non-linear regime
The self-consistent quantum-electrostatic (also known as
Poisson-Schr\"odinger) problem is notoriously difficult in situations where the
density of states varies rapidly with energy. At low temperatures, these
fluctuations make the problem highly non-linear which renders iterative schemes
deeply unstable. We present a stable algorithm that provides a solution to this
problem with controlled accuracy. The technique is intrinsically convergent
including in highly non-linear regimes. We illustrate our approach with (i) a
calculation of the compressible and incompressible stripes in the integer
quantum Hall regime and (ii) a calculation of the differential conductance of a
quantum point contact geometry. Our technique provides a viable route for the
predictive modeling of the transport properties of quantum nanoelectronics
devices.Comment: 28 pages. 14 figures. Added solution to a potential failure mode of
the algorith
Detection of Contact Binaries Using Sparse High Phase Angle Lightcurves
We show that candidate contact binary asteroids can be efficiently identified
from sparsely sampled photometry taken at phase angles >60deg. At high phase
angle, close/contact binary systems produce distinctive lightcurves that spend
most of the time at maximum or minimum (typically >1mag apart) brightness with
relatively fast transitions between the two. This means that a few (~5) sparse
observations will suffice to measure the large range of variation and identify
candidate contact binary systems. This finding can be used in the context of
all-sky surveys to constrain the fraction of contact binary near-Earth objects.
High phase angle lightcurve data can also reveal the absolute sense of the
spin.Comment: 4 pages, 4 figures, 1 table. Accepted for publication in ApJ
Characterisation of candidate members of (136108) Haumea's family: II. Follow-up observations
From a dynamical analysis of the orbital elements of transneptunian objects
(TNOs), Ragozzine & Brown reported a list of candidate members of the first
collisional family found among this population, associated with (136108) Haumea
(a.k.a. 2003 EL61). We aim to distinguish the true members of the Haumea
collisional family from interlopers. We search for water ice on their surfaces,
which is a common characteristic of the known family members. The properties of
the confirmed family are used to constrain the formation mechanism of Haumea,
its satellites, and its family. Optical and near-infrared photometry is used to
identify water ice. We use in particular the CH4 filter of the Hawk-I
instrument at the European Southern Observatory Very Large Telescope as a short
H-band (Hs), the (J-Hs) colour being a sensitive measure of the water ice
absorption band at 1.6 {\mu}m. Continuing our previous study headed by
Snodgrass, we report colours for 8 candidate family members, including
near-infrared colours for 5. We confirm one object as a genuine member of the
collisional family (2003 UZ117), and reject 5 others. The lack of infrared data
for the two remaining objects prevent any conclusion from being drawn. The
total number of rejected members is therefore 17. The 11 confirmed members
represent only a third of the 36 candidates. The origin of Haumea's family is
likely to be related to an impact event. However, a scenario explaining all the
peculiarities of Haumea itself and its family remains elusive.Comment: 8 pages, 4 figures, accepted for publication in A&
Sputtering of Oxygen Ice by Low Energy Ions
Naturally occurring ices lie on both interstellar dust grains and on
celestial objects, such as those in the outer solar system. These ices are
continu- ously subjected to irradiation by ions from the solar wind and/or
cosmic rays, which modify their surfaces. As a result, new molecular species
may form which can be sputtered off into space or planetary atmospheres. We
determined the experimental values of sputtering yields for irradiation of
oxygen ice at 10 K by singly (He+, C+, N+, O+ and Ar+) and doubly (C2+, N2+ and
O2+) charged ions with 4 keV kinetic energy. In these laboratory experiments,
oxygen ice was deposited and irradiated by ions in an ultra high vacuum chamber
at low temperature to simulate the environment of space. The number of
molecules removed by sputtering was observed by measurement of the ice
thickness using laser interferometry. Preliminary mass spectra were taken of
sputtered species and of molecules formed in the ice by temperature programmed
desorption (TPD). We find that the experimental sputtering yields increase
approximately linearly with the projectile ion mass (or momentum squared) for
all ions studied. No difference was found between the sputtering yield for
singly and doubly charged ions of the same atom within the experimental
uncertainty, as expected for a process dominated by momentum transfer. The
experimental sputter yields are in good agreement with values calculated using
a theoretical model except in the case of oxygen ions. Preliminary studies have
shown molecular oxygen as the dominant species sputtered and TPD measurements
indicate ozone formation.Comment: to be published in Surface Science (2015
Transplante alogénico de células estaminais em doentes com síndrome mielodisplásica: análise de acordo com o Índice de Prognóstico Internacional
© Ordem dos MédicosWe determined the outcome of patients with myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (sAML) after allogeneic stem cell transplantation according to their international prognostic scoring system (IPSS) risk categories at diagnosis. A total of 11 females and 7 males, with a median age of 45 years, were transplanted. With a median follow-up of 60 months, the 6-year actuarial event-free survival (EFS) for Less Advanced (Low and Intermediate-1 risk IPSS) and Advanced (Intermediate-2 and High risk IPSS) MDS was 71.4% and 43.6%, respectively (p=0.002). We did not observe a difference in EFS depending on cytogenetics at diagnosis (good risk 53.8% Vs intermediate and high risk 53.3%, p=ns), neither on the type of conditioning regimen used (myeloablative 50% Vs reduced intensity 52.2%, p=ns). Our results support that IPSS score at diagnosis may be used to predict EFS in patients with MDS undergoing allogeneic SCT.Neste estudo avaliámos o valor preditivo do índice prognóstico internacional (IPSS) na altura do diagnóstico em doentes com síndrome mielodisplásica (SMD) e leucemia mielóide aguda secundária submetidos a transplante alogénico de células estaminais. Foram transplantados um total de 11 mulheres e sete homens, com uma mediana de idades de 45 anos. Com um seguimento mediano de 60 meses, a sobrevivência livre de eventos aos 6 anos nos doentes com doença menos avançada (IPSS Risco Baixo e Intermédio 1) e com doença avançada (IPSS Intermédio 2 e Alto Risco) foi de 71.4% e 43.6%, respectivamente (p=0.002). Não observámos diferenças significativas na sobrevivência livre de eventos de acordo com a análise citogenética na altura do diagnóstico (risco bom 53,8% VS risco intermédio e alto 53,3%, p=ns) nem com o tipo de regime de condicionamento utilizado (mieloablativo 50% VS intensidade reduzida 52,2%, p=ns). Os nossos resultados demonstram que o IPSS na altura do diagnóstico pode ser utilizado para predizer a sobrevivência livre de eventos em doentes com SMD submetidos a transplante alogénico de células estaminaisinfo:eu-repo/semantics/publishedVersio
Quantum critical 5f-electrons avoid singularities in U(Ru,Rh)2Si2
We present specific heat measurements of 4% Rh-doped U(Ru,Rh)2Si2 at magnetic
fields above the proposed metamagnetic transition field Hm~34 T, revealing
striking similarities to the isotructural Ce analog CeRu2Si2, suggesting that
strongly renormalized hybridized band models apply equally well to both
systems. The vanishing bandwidths as H --> Hm are consistent with a putative
quantum critical point close to Hm. The existence of a phase transition into an
ordered phase in the vicinity of Hm for 4% Rh-doped U(Ru,Rh)2Si2, but not for
CeRu2Si2, is consistent with a stronger super-exchange in the case of the U 5-f
system, with irreversible processes at the transition revealing a strong
coupling of the 5f orbitals to the lattice, most suggestive of orbital or
electric quadrupolar order.Comment: 4 pages, 4 figure
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: Accepted for publication in A&
A recuperação das fachadas do edifício do IRB, monumento da arquitetura modernista brasileira, no Rio de Janeiro
O edifício do IRB- Instituto Brasileiro de Resseguros, foi projetado pelo escritório MMM Roberto em 1941, e nele os arquitetos colocaram em prática as pesquisas que já vinham desenvolvendo sobre o uso do brise no controle da luz intensa do Rio de Janeiro. O projeto do IRB, não só incorporou esse elemento, já sedimentado no repertório modernista, como inovou ao trazer para o partido duas novas experiências, que tornaram o edifício um símbolo na evolução do estilo que iria seria conhecido como arquitetura modernista brasileira: a inserção de movimento na geometria rígida estabelecida pelos princípios do modernismo; e o uso de modulação que permitiu criar um dos primeiros edifícios, do Brasil, a utilizar elementos construtivos pré-fabricados.
O edifício tem as fachadas totalmente revestidas por um tipo de mármore de estrutura laminar, um material de que não há mais jazidas conhecidas no país, e que se encontrava alterado pelo intemperismo a ponto de se destacarem placas da fachada.
Procedeu-se então ao estudo dos materiais e das condições do ambiente, para que fosse possível detectar as causas das patologias e erradicá-las ou minorá-las sensívelmente.
Foram testados e propostos métodos de limpeza e consolidação do mármore da fachada e de sustentação das placas que ameaçavam desprendimento.Tópico 3: Construcciones en piedra. Durabilidad y preservación de las rocas
A recuperação das cantarias da Capela de N.Sra da Glória do Outeiro, no Rio de Janeiro
A Capela de Nossa Senhora da Glória do Outeiro, localizada sobre um morro beirando o mar da baía de Guanabara é uma jóia do século XVIII. Sua planta poligonal é formada por dois octógonos irregulares, alongados e interligados, antecedidos pela base quadrada da única torre sineira, cujo pé forma a galilé de acesso à capela Cada uma das arestas dos octógonos é marcada (interna e externamente, por pilastras de cantaria, coroadas por pináculos. São também de cantaria os emolduramentos de janelas, portas e óculos, as cimalhas e a galilé, os elementos de composição do arco cruzeiro e a cobertura plana da edificação. Foram esses elementos de cantaria, atacados pela umidade e pelo intemperismo, que foram objeto do estudo para determinar os processos de limpeza e consolidação adequados.
As principais patologias identificadas foram o descolamento de placas da cantaria, a presença de crostas negras, o ataque por fungos e vegetação superior e as manchas de grafitti e de matérias graxas. Cada uma destas patologias foi estudada e testados processos e materiais de limpeza e consolidação e integração das lacunas existentes.Tópico 3: Construcciones en piedra. Durabilidad y preservación de las rocas
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