3,143 research outputs found
Gauging hadronic systems
We present a general method for incorporating the electromagnetic interaction
into descriptions of hadronic processes based on four-dimensional scattering
integral equations. The method involves the idea of gauging the scattering
equations themselves, and results in electromagnetic amplitudes where an
external photon is effectively coupled to every part of every strong
interaction diagram in the model. Current conservation is therefore implemented
in the theoretically correct fashion. To illustrate our gauging procedure we
apply it to the three-nucleon problem whose strong interactions are described
by standard three-body integral equations. In this way we obtain the
expressions needed to calculate all possible electromagnetic processes of the
three-nucleon system: the electromagnetic form factors of the three-body bound
state, pd->pd gamma, gamma 3He-> pd, gamma 3He-> ppn, etc. As the photon is
coupled everywhere in the strong interaction model, a unified description of
the NNN-gamma NNN system is obtained. An interesting aspect of our results is
the natural appearance of a subtraction term needed to avoid the overcounting
of diagrams.Comment: 6 pages, revtex, epsf, 1 postscript figure, talk at the 15th Int.
Conf. on Few-Body Problems in Physics, Groningen, Netherlands, 22-26 July
1997. To be published in Nucl. Phys.
Report of Resolutions Committee
Your Committee on Resolutions begs to report as follows: Four matters had been submitted up to noon of this day to the Committee for its consideration
Jesu li humusne kiseline prirodne tvorevine?
Alkaline cleavage of soil organic matter was studied by following the changes in absorbance at 250–270 nm, but particularly using differential pulse polarography. The measurement of peak currents obtained by the latter technique allowed to follow changes in concentration of CH3Oand HO-substituted benzaldehydes as well as of α,β-unsaturated ketones with time directly in the suspension of soil. Kinetics of the cleavage of the organic materials from soil and in particular its pH-dependence, were similar to that of cleavage of lignin, but different from those obtained with samples of humic acids. Based on this comparison and on discussion of chemical processes taking place during procedures used for isolation of humic acids from soils and waters, it is strongly indicated that humic acids are man-made macromolecular species rather than natural products.Praćenjem promjena apsorpcije zračenja od 250 do 270 nm i diferencijalnom pulsnom polarografijom proučavano je u alkalnoj otopini cijepanje organske tvari izolirane iz tla. Mjerenje polarografskih vršnih struja omogućuje praćenje promjena koncentracija benzaldehida supstituiranih na CH3O- i HO- skupinama i α,β-nezasićenih ketona u suspenziji zemlje. Kinetika cijepanja organskih tvari izoliranih iz tla, a posebno njena zavisnost o pH, slična je kinetici cijepanja lignina, ali se razlikuje od kinetike cijepanja humusnih kiselina. Na osnovu razlike u kinetici cijepanja, a uzimajući u obzir kemijske procese koji se odvijaju tijekom izolacije humusnih kiselina iz tla i vode, zaključuje se da postoje indikacije da su humusne kiseline umjetno stvoreni polimeri, a ne prirodne tvari
Resonances Observed at BES
In last 10 years, resonances have been observed and studied at BES
in many processes, such as ,
, , , ,
, , , ,
, , ,
etc.. The results on resonances observed at BES
are reviewed.Comment: Plenary talk at SCADRON70, Lisbon, Feb. 200
Facies analysis and Reservoir Characterization of the Cambrian Mount Simon Formation in the Illinois Basin: Implications for CO Sequestration and Storage
This poster was presented at the American Association of Petroleum Geologists (AAPG) Annual Meeting, from June 7-10, 2009, in Denver, Colorado.Deep saline reservoirs have become a target of increased study with the development of carbon sequestration technologies. In the Illinois Basin, The Upper Cambrian Mt. Simon Formation has been proposed as a potential reservoir for CO2 sequestration. Depth and limited economic interest in the Mt. Simon have left it minimally explored with previous detailed depositional facies analysis only performed at localities outside of the Illinois Basin, where the Mt. Simon is much thinner and closer to the surface. From the analysis of recently acquired and preexisting relatively complete cores and composite cores of the Mt. Simon Formation in addition to basin wide correlation with geophysical well logs, we present a revised model for the deposition of the Mt. Simon Formation in the Illinois Basin region and the resulting implications for a CO2 reservoir. The Mt. Simon Formation is a sub-quartz to quartz arenite that unconformably overlies the crystalline basement of the interior North American craton. Thickness of the Mt. Simon ranges from a few hundred to over 2000 feet thick and structually from 2000 to over 14000 feet below sea level. The upper contact of the Mt. Simon Formation is gradational with the overlying Eau Clair Formation while the lower contact unconformably bounds the crystalline basement. Core analysis has led to the identification of several distinct facies within the Mt. Simon. The lowermost facies is dominated by medium grain to granular eolian sands with distinct interdunal red mudstone. Gradationally above the lowermost facies, tidal indicators become increasingly present with mud drapes and flaser bedding located in isolated units. This transgressive sequence from nonmarine to marine depositional environments correlates with sea level curves for the Upper Cambrian. By increasing our understanding of the Mt. Simon, we can better understand its CO2 reservoir potential
Machine Learning for Quantum Mechanical Properties of Atoms in Molecules
We introduce machine learning models of quantum mechanical observables of
atoms in molecules. Instant out-of-sample predictions for proton and carbon
nuclear chemical shifts, atomic core level excitations, and forces on atoms
reach accuracies on par with density functional theory reference. Locality is
exploited within non-linear regression via local atom-centered coordinate
systems. The approach is validated on a diverse set of 9k small organic
molecules. Linear scaling of computational cost in system size is demonstrated
for saturated polymers with up to sub-mesoscale lengths
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Automated High Throughput Drug Target Crystallography
The molecular structures of drug target proteins and receptors form the basis for 'rational' or structure guided drug design. The majority of target structures are experimentally determined by protein X-ray crystallography, which as evolved into a highly automated, high throughput drug discovery and screening tool. Process automation has accelerated tasks from parallel protein expression, fully automated crystallization, and rapid data collection to highly efficient structure determination methods. A thoroughly designed automation technology platform supported by a powerful informatics infrastructure forms the basis for optimal workflow implementation and the data mining and analysis tools to generate new leads from experimental protein drug target structures
NJL with eight quark interactions: Chiral phases at finite T
The thermodynamic potential and thermal dependence of low lying mass spectra
of scalars and pseudoscalars are evaluated in a generalized Nambu --
Jona-Lasinio model, which incorporates eight-quark interactions. These are
necessary to stabilize the scalar effective potential for the light and strange
quark flavors, which would be otherwise unbounded from below. In addition it
turns out that they are also crucial to i) lower the temperature of the chiral
transition, in conformity with lattice calculations, ii) sharpen the
temperature interval in which the crossover occurs, iii) or even allow for
first order transitions to occur with realistic quark mass values, from certain
critical values of the parameters. These are unprecedented results which cannot
be obtained within the NJL approaches restricted to quartic and six-quark
interactions.Comment: 6 pages, 3 figures, Talk presented at SCADRON 70 Workshop on Scalar
Mesons and Related Topics, Lisbon, 11-16 February 200
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