7,625 research outputs found
Reassessing the Numerous Proposed and Existing U-values for Lebanon
Since 2005 a number of publications have proposed different U-values to be used in Lebanon in order to reduce the buildings’ energy demand for cooling and heating. This research considers those different values from the two editions of the Thermal Standard for Buildings in Lebanon (2005 & 2010) and Lebanon Center for Energy Conservation LCEC guidelines (2014), in addition to recommended U-values from similar worldwide climates. In the second part of the paper, dynamic thermal simulation software (EDSL TAS) is used to test the proposed U-values in conjunction with typical local construction materials and using Bayrouth weather files (Meteonorm 7). The tridimensional model used for the simulations is based on a typical existing building with characteristics kept constant throughout the comparative study. Furthermore the same internal heat gains and patterns for occupancy and appliances, as well as window opening areas and schedules are also kept the same in all the simulations. For each case, the four main cardinal orientations are tested. The research compares the overall yearly energy demand for mechanically heated and cooled buildings, in order to assess which U-values will give the lowest energy demand under varying levels of internal heat gains
Locked nucleic acid oligomers as handles for single molecule manipulation.
Single-molecule manipulation (SMM) techniques use applied force, and measured elastic response, to reveal microscopic physical parameters of individual biomolecules and details of biomolecular interactions. A major hurdle in the application of these techniques is the labeling method needed to immobilize biomolecules on solid supports. A simple, minimally-perturbative labeling strategy would significantly broaden the possible applications of SMM experiments, perhaps even allowing the study of native biomolecular structures. To accomplish this, we investigate the use of functionalized locked nucleic acid (LNA) oligomers as biomolecular handles that permit sequence-specific binding and immobilization of DNA. We find these probes form bonds with DNA with high specificity but with varied stability in response to the direction of applied mechanical force: when loaded in a shear orientation, the bound LNA oligomers were measured to be two orders of magnitude more stable than when loaded in a peeling, or unzipping, orientation. Our results show that LNA provides a simple, stable means to functionalize dsDNA for manipulation. We provide design rules that will facilitate their use in future experiments
Constraining Non-thermal and Thermal properties of Dark Matter
We describe the evolution of Dark Matter (DM) abundance from the very onset
of its creation from inflaton decay under the assumption of an instantaneous
reheating. Based on the initial conditions such as the inflaton mass and its
decay branching ratio to DM, reheating temperature, and the DM mass and
interaction rate with the thermal bath, the DM particles can either thermalize
(fully/partially) with the primordial bath or remain non-thermal throughout
their evolution history. In the thermal case, the final abundance is set by the
standard freeze-out mechanism for large annihilation rates, irrespective of the
initial conditions. For smaller annihilation rates, it can be set by the
freeze-in mechanism, also independent of the initial abundance, provided it is
small to begin with. For even smaller interaction rates, the DM decouples while
being non-thermal, and the relic abundance will be essentially set by the
initial conditions. We put model-independent constraints on the DM mass and
annihilation rate from over-abundance by exactly solving the relevant Boltzmann
equations, and identify the thermal freeze-out, freeze-in and non-thermal
regions of the allowed parameter space. We highlight a generic fact that
inflaton decay to DM inevitably leads to an overclosure of the Universe for a
large range of DM parameter space, and thus poses a stringent constraint that
must be taken into account while constructing models of DM. For the thermal DM
region, we also show the complementary constraints from indirect DM search
experiments, Big Bang Nucleosynthesis, Cosmic Microwave Background, Planck
measurements, and theoretical limits due to the unitarity of S-matrix. For the
non-thermal DM scenario, we show the allowed parameter space in terms of the
inflaton and DM masses for a given reheating temperature, and compute the
comoving free-streaming length to identify the hot, warm and cold DM regimes.Comment: 29 pages, 8 figures; some clarifications and references added;
published versio
What can quantum optics say about computational complexity theory?
Considering the problem of sampling from the output photon-counting
probability distribution of a linear-optical network for input Gaussian states,
we obtain results that are of interest from both quantum theory and the
computational complexity theory point of view. We derive a general formula for
calculating the output probabilities, and by considering input thermal states,
we show that the output probabilities are proportional to permanents of
positive-semidefinite Hermitian matrices. It is believed that approximating
permanents of complex matrices in general is a #P-hard problem. However, we
show that these permanents can be approximated with an algorithm in BPP^NP
complexity class, as there exists an efficient classical algorithm for sampling
from the output probability distribution. We further consider input
squeezed-vacuum states and discuss the complexity of sampling from the
probability distribution at the output.Comment: 5 pages, 1 figur
Impact-ionization and noise characteristics of thin III-V avalanche photodiodes
It is, by now, well known that McIntyre\u27s localized carrier-multiplication theory cannot explain the suppression of excess noise factor observed in avalanche photodiodes (APDs) that make use of thin multiplication regions. We demonstrate that a carrier multiplication model that incorporates the effects of dead space, as developed earlier by Hayat et al. provides excellent agreement with the impact-ionization and noise characteristics of thin InP, In/sub 0.52/Al/sub 0.48/As, GaAs, and Al/sub 0.2/Ga/sub 0.8/As APDs, with multiplication regions of different widths. We outline a general technique that facilitates the calculation of ionization coefficients for carriers that have traveled a distance exceeding the dead space (enabled carriers), directly from experimental excess-noise-factor data. These coefficients depend on the electric field in exponential fashion and are independent of multiplication width, as expected on physical grounds. The procedure for obtaining the ionization coefficients is used in conjunction with the dead-space-multiplication theory (DSMT) to predict excess noise factor versus mean-gain curves that are in excellent accord with experimental data for thin III-V APDs, for all multiplication-region widths
Philosophical Arguments for Bodily Resurrection: Reconsidering Mullâ Shadrâ's Eschatological Thought
: Apart from investigating the meaning of death, reality of soul, proof of life after death, eschatology also studies the sole bodily resurrection. With regard to soul, almost all Muslim philosophers agree on soul resurrection, but they differ however, as far as the body is concerned. Different to the previous essensialists philosophers, Mullâ Shadrâ who adhered to existentialist school argued that as the case of soul, man's body itsel would be similarly resurrected in the hereafter. Shadrâ supported his argument by existensialist philosophy approach leaned on the principle of trans-substantial motion. Through this approach, Shadrâ succeeded philosophically in proofing the necessity ofsouland bodily resurrection simultaneously in the hereafter
Finite Mirror Effects in Advanced Interferometric Gravitational Wave Detectors
Thermal noise is expected to be the dominant source of noise in the most
sensitive frequency band of second generation ground based gravitational wave
detectors. Reshaping the beam to a flatter wider profile which probes more of
the mirror surface reduces this noise. The "Mesa" beam shape has been proposed
for this purpose and was subsequently generalized to a family of hyperboloidal
beams with two parameters: twist angle alpha and beam width D. Varying alpha
allows a continuous transition from the nearly-flat to the nearly-concentric
Mesa beam configurations. We analytically prove that in the limit of infinite D
hyperboloidal beams become Gaussians. The Advanced LIGO diffraction loss design
constraint is 1 ppm per bounce. In the past the diffraction loss has often been
calculated using the clipping approximation that, in general, underestimates
the diffraction loss. We develop a code using pseudo-spectral methods to
compute the diffraction loss directly from the propagator. We find that the
diffraction loss is not a strictly monotonic function of beam width, but has
local minima that occur due to finite mirror effects and leads to natural
choices of D. For the Mesa beam a local minimum occurs at D = 10.67 cm and
leads to a diffraction loss of 1.4 ppm. We find that if one requires a
diffraction loss of strictly 1 ppm, the alpha = 0.91 pi hyperboloidal beam is
optimal, leading to the coating thermal noise being lower by about 10% than for
a Mesa beam while other types of thermal noise decrease as well. We then
develop an iterative process that reconstructs the mirror to specifically
account for finite mirror effects. This allows us to increase the D parameter
and lower the coating noise by about 30% compared to the original Mesa
configuration.Comment: 13 pages, 12 figures, 4 tables. Referee input included and typos
fixed. Accepted by Phys. Rev.
Electronic and optical properties in non-uniformly shaped QDashes
We theoretically study the optical properties and the electronic structure of
highly elongated quantum dots (quantum dashes) and show how carrier trapping
due to geometrical fluctuations of the confining potential affects the
excitonic spectrum of the system. We focus on the study of the optical
properties of a single exciton confined in the structure. The dependence of the
absorption and emission intensities on the geometrical properties (depth and
position) of the trapping center of a quantum dash is analyzed and the
dependence of the degree of linear polarization on these geometrical parameters
is studied in detail.Comment: 17 pages, 9 figure
- …