11,039 research outputs found
Comparative studies of lunar, Martian, and Mercurian craters and plains
The spatial distribution of lunar smooth plains is not consistent with experimental simulations of melt rock emplacement during cratering in layered materials. Nor is it consistent with the location of melt rocks (suevite) near the Ries basin. Lunar smooth plains surrounding Imbrium are most extensive in areas where pre-existing craters are most degraded. This observation suggests that plains form by impact of basin and local primary crater ejecta, together with deposition of debris excavated by the resultant secondary cratering events. Craters within the belt of smooth plains surrounding the Caloris basin on Mercury are most degraded nearest the basin; this suggests that Mercurian smooth plains must, at least in part, be emplaced in a manner similar to plains surrounding the Imbrium basin. Mercurian uplands have a primary crater population deficient in small crater diameters (less than approximately 30 km). Lunar uplands far from major basins also have a crater population deficient in small crater sizes. Martian cratered terrain exhibits a similar crater deficiency, which was previously interpreted as due to obliteration of small craters (less than approximately 30 km) by some surface process. A crater size distribution deficient in small sizes (less than approximately 30 km) on the Mercurian, lunar, and Martian uplands has implications for the origin of debris bombarding the inner solar system during the period recorded by these surfaces. It is proposed that during late heavy bombardment, the inner solar system was inundated with bodies that broke up under tidal fission as they approached the planets. Such a mechanism would lend to production of a crater population deficient in small crater sizes, and it would also explain the large degree of spatial clustering of primary craters on Mercury, the moon, and Mars
Quantum computing on long-lived donor states of Li in Si
We predict a gigantically long lifetime of the first excited state of an
interstitial lithium donor in silicon. The nature of this effect roots in the
anomalous level structure of the {\em 1s} Li manifold under external stress.
Namely, the coupling between the lowest two states of the opposite parity is
very weak and occurs via intervalley phonon transitions only. We propose to use
these states under the controlled ac and dc stress to process quantum
information. We find an unusual form of the elastic-dipole interaction between
%the electronic transitions in different donors. This interaction scales with
the inter-donor distance as or for the transitions
between the states of the same or opposite parity, respectively. The long-range
interaction provides a high fidelity mechanism for 2-qubit operations
Energy levels and radiative rates for transitions in Cr-like Co IV and Ni V
We report calculations of energy levels and radiative rates (-values) for
transitions in Cr-like Co IV and Ni V. The quasi-relativistic Hartree-Fock
(QRHF) code is adopted for calculating the data although GRASP (general-purpose
relativistic atomic structure package) and flexible atomic code (FAC) have also
been employed for comparison purposes. No radiative rates are available in the
literature to compare with our results, but our calculated energies are in
close agreement with those compiled by NIST for a majority of the levels.
However, there are discrepancies for a few levels of up to 3\%. The -values
are listed for all significantly contributing E1, E2 and M1 transitions, and
the corresponding lifetimes reported, although unfortunately no previous
theoretical or experimental results exist to compare with our data.Comment: The paper will appear in ADNDT (2016) and in October 2015 on the we
Methotrexate induced accelerated nodulosis
Methotrexate induced accelerated nodulosis (MIAN) is a rare but unique side effect of methotrexate therapy. There is paucity of data from our country about this entity. We analyzed 14 cases of MIAN and studied its association with gender, rheumatoid factor positivity and dose and duration of methotrexate. Fourteen patients (8 females), 12 with rheumatoid arthritis (8 seropositive), one each with juvenile idiopathic (JIA) and psoriatic arthritis (PsA) were detected to have MIAN during study period. All the patients presented with acute onset of multiple nodules. Radial border of fingers was the most commonly involved site. Disease was inactive in all but two patients at the time of appearance of MIAN. There was no association of MIAN with gender, rheumatoid factor positivity, disease duration, cumulative dose and duration of methotrexate therapy. Two patients each were treated with colchicine, D-penicillamine or hydroxy-chloroquine for 3-6 months without any response. We conclude that MIAN is a benign side effect of methotrexate treatment
Electron Impact Excitation Cross Sections for Hydrogen-Like Ions
We present cross sections for electron-impact-induced transitions n --> n' in
hydrogen-like ions C 5+, Ne 9+, Al 12+, and Ar 17+. The cross sections are
computed by Coulomb-Born with exchange and normalization (CBE) method for all
transitions with n < n' < 7 and by convergent close-coupling (CCC) method for
transitions with n 2s and 1s
--> 2p are presented as well. The CCC and CBE cross sections agree to better
than 10% with each other and with earlier close-coupling results (available for
transition 1 --> 2 only). Analytical expression for n --> n' cross sections and
semiempirical formulae are discussed.Comment: RevTeX, 5 pages, 13 PostScript figures, submitted to Phys. Rev.
Degradation kinetics of metronidazole and its mutual prodrug with ciprofloxacin: a calorimetric analysis
Calorimetric technique has aroused considerable interest as a versatile tool in pharmaceutical industry and academia to provide useful information about thermodynamic and kinetic aspects of drug molecules. The present paper utilizes this technique to monitor the hydrolytic degradation of metronidazole and its prodrug with ciprofloxacin, i.e. 2-(2-methyl-5-nitroimidazol-1-yl)ethyl-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-quinoline-3-carboxylate. The synthesis of the present mutual prodrug was envisaged to combine the antiprotozoal and anaerobic antibacterial effects of metronidazole with antibacterial effects of ciprofloxacin. Heat flux microcalorimeter was used to determine the rate of heat evolved during the degradation of the drug and prodrug as a function of concentration, pH and temperature. In terms of enthalpy of hydrolysis the response is exothermic both for drug and prodrug. However, the absolute value of the enthalpy of reaction (ΔrH0) is low for the prodrug. The degradation followed pseudo first order kinetics, showed marked stability at pH 3-7 followed by accelerated hydrolysis at higher pH, characteristic of general acid-base catalysis. The catalytic rate constant for hydrogen ion (kH) and hydroxyl ion (kOH) were found to be 0.413 and 526.1 M-1h-1, respectively, at 318.15 K. The hydrolysis of the prodrug was found to be approximately 50-60 times faster than that of the drug. This may be attributed to the fact that hydrolysis of ester group in prodrug is assisted by keto group on the ciprofloxacin. However, there is no effect of protonation of nitrogen in piperazine ring in ciprofloxacin on the hydrolysis due to the distance from the ester moiety. Keywords: Calorimetry, stability studies, degradation kinetics, ciprofloxacin, metronidazole. International Journal of Biological and Chemical Sciences Vol. 1 (3) 2007: pp.197-21
Exploring the Impact of Evolutionary Computing based Feature Selection in Suicidal Ideation Detection
© 2019 IEEE. The ubiquitous availability of smartphones and the increasing popularity of social media provide a platform for users to express their feelings, including suicidal ideation. Suicide prevention by suicidal ideation detection on social media lights the path to controlling the rapidly increasing suicide rates amongst youth. This paper proposes a diverse set of features and investigates into feature selection using the Firefly algorithm to build an efficient and robust supervised approach to classifying tweets with suicidal ideation. The development of a suicidal language to create three diverse, manually annotated datasets leads to the validation of the proposed model. An in-depth result and error analysis lead to an accurate system for monitoring suicidal ideation on social media along with the discovery of optimal feature subsets and selection methods using a penalty based Firefly algorithm
Comparative Evaluation of Action Recognition Methods via Riemannian Manifolds, Fisher Vectors and GMMs: Ideal and Challenging Conditions
We present a comparative evaluation of various techniques for action
recognition while keeping as many variables as possible controlled. We employ
two categories of Riemannian manifolds: symmetric positive definite matrices
and linear subspaces. For both categories we use their corresponding nearest
neighbour classifiers, kernels, and recent kernelised sparse representations.
We compare against traditional action recognition techniques based on Gaussian
mixture models and Fisher vectors (FVs). We evaluate these action recognition
techniques under ideal conditions, as well as their sensitivity in more
challenging conditions (variations in scale and translation). Despite recent
advancements for handling manifolds, manifold based techniques obtain the
lowest performance and their kernel representations are more unstable in the
presence of challenging conditions. The FV approach obtains the highest
accuracy under ideal conditions. Moreover, FV best deals with moderate scale
and translation changes
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