27,722 research outputs found
Assessment of density functional methods with correct asymptotic behavior
Long-range corrected (LC) hybrid functionals and asymptotically corrected
(AC) model potentials are two distinct density functional methods with correct
asymptotic behavior. They are known to be accurate for properties that are
sensitive to the asymptote of the exchange-correlation potential, such as the
highest occupied molecular orbital energies and Rydberg excitation energies of
molecules. To provide a comprehensive comparison, we investigate the
performance of the two schemes and others on a very wide range of applications,
including the asymptote problems, self-interaction-error problems, energy-gap
problems, charge-transfer problems, and many others. The LC hybrid scheme is
shown to consistently outperform the AC model potential scheme. In addition, to
be consistent with the molecules collected in the IP131 database [Y.-S. Lin,
C.-W. Tsai, G.-D. Li, and J.-D. Chai, J. Chem. Phys., 2012, 136, 154109], we
expand the EA115 and FG115 databases to include, respectively, the vertical
electron affinities and fundamental gaps of the additional 16 molecules, and
develop a new database AE113 (113 atomization energies), consisting of accurate
reference values for the atomization energies of the 113 molecules in IP131.
These databases will be useful for assessing the accuracy of density functional
methods.Comment: accepted for publication in Phys. Chem. Chem. Phys., 46 pages, 4
figures, supplementary material include
Differential Good Arm Identification
This paper targets a variant of the stochastic multi-armed bandit problem
called good arm identification (GAI). GAI is a pure-exploration bandit problem
with the goal to output as many good arms using as few samples as possible,
where a good arm is defined as an arm whose expected reward is greater than a
given threshold. In this work, we propose DGAI - a differentiable good arm
identification algorithm to improve the sample complexity of the
state-of-the-art HDoC algorithm in a data-driven fashion. We also showed that
the DGAI can further boost the performance of a general multi-arm bandit (MAB)
problem given a threshold as a prior knowledge to the arm set. Extensive
experiments confirm that our algorithm outperform the baseline algorithms
significantly in both synthetic and real world datasets for both GAI and MAB
tasks
COLOR III: a multicentre randomised clinical trial comparing transanal TME versus laparoscopic TME for mid and low rectal cancer
Total mesorectal excision (TME) is an essential component of surgical management of rectal cancer. Both open and laparoscopic TME have been proven to be oncologically safe. However, it remains a challenge to achieve complete TME with clear circumferential resections margin (CRM) with the conventional transabdominal approach, particularly in mid and low rectal tumours. Transanal TME (TaTME) was developed to improve oncological and functional outcomes of patients with mid and low rectal cancer.An international, multicentre, superiority, randomised trial was designed to compare TaTME and conventional laparoscopic TME as the surgical treatment of mid and low rectal carcinomas. The primary endpoint is involved CRM. Secondary endpoints include completeness of mesorectum, residual mesorectum, morbidity and mortality, local recurrence, disease-free and overall survival, percentage of sphincter-saving procedures, functional outcome and quality of life. A Quality Assurance Protocol including centralised MRI review, histopathology re-evaluation, standardisation of surgical techniques, and monitoring and assessment of surgical quality will be conducted.The difference in involvement of CRM between the two treatment strategies is thought to be in favour of the TaTME. TaTME is therefore expected to be superior to laparoscopic TME in terms of oncological outcomes in case of mid and low rectal carcinomas
How micropatterns and air pressure affect splashing on surfaces
We experimentally investigate the splashing mechanism of a millimeter-sized
ethanol drop impinging on a structured solid surface, comprised of
micro-pillars, through side-view and top-view high speed imaging. By increasing
the impact velocity we can tune the impact outcome from a gentle deposition to
a violent splash, at which tiny droplets are emitted as the liquid sheet
spreads laterally. We measure the splashing threshold for different
micropatterns and find that the arrangement of the pillars significantly
affects the splashing outcome. In particular, directional splashing in
direction in which air flow through pattern is possible. Our top-view
observations of impact dynamics reveal that an trapped air is responsible for
the splashing. Indeed by lowering the pressure of the surrounding air we show
that we can suppress the splashing in the explored parameter regime.Comment: 7 pages, 9 figure
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Comparing the rates of absorption and weight loss during a desorption test using near infrared spectroscopy
The importance of determining skin hydration has over the years prompt the development of many instruments and methods, specifically designed to assess this parameter or water contents especially in the stratum corneum, and have greatly matured to suit different anatomical sites and measure multiple attributes. Of those, Near Infrared Spectroscopy (NIRS) has gained wide interest as a precise, safe, fast and noninvasive technique for determining skin hydration due to its high sensitivity to hydrogen bonding and ability to measure the amount of water in skin directly using the intensities of overtone and combination bands of OH and HOH water bonds occurring in the NIR region, that are good indicators of the state of skin hydration. This paper reports near infrared spectrophotometric measurements using a highly sophisticated spectrophotometer in the region of 1000-2500 nm to study the water uptake and dehydration properties of skin in vitro using samples of porcine skin. Initial results of pure liquid water and skin samples have clearly displayed the prominent bands associated with water content, and desorption tests have been able to verify changes in these bands associated with water content, although a clear correlation between the rates of weight loss and absorbance loss at various hydration periods has not yet been established. These preliminary results are expected to further explain the relationship between water and skin, and its role within, in hope to aid the future development of a portable instrument based on near infrared spectroscopy that would be capable of directly measuring skin hydration and/or water content in a fast and noninvasive manner
A Model for High Temperature Superconductors using the Extended Hubbard Model
We derive a method to study the phase diagram for high temperature
superconductors (HTCS). Our starting point is the Hubbard Hamiltonian with a
weak attractive interaction to obtain the formation of bound pairs. We consider
this attractive potential at different positions for different compounds
accordingly to the experimental results of the coherence length. We then
construct a wave function of the BCS type by a variational method using the
Fourier transform of this extended Hubbard potential and then derive an energy
gap equation. This approach allows us to obtain the critical temperature as
function of the doping concentration which gives very good agreement with the
experimental phase diagrams of YBaCuO and La(Sr,Ba)CuO compounds.Comment: 9 pages, RevTex preprint style, 2 figs. packed with uufile
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