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Search Results: 1 - 10 of 437895 matches for " P. J. Dortmans "
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pp <-> pi+ d process at low energy: Interplay between s-- and p-wave mechanisms
L. Canton,A. Davini,P. J. Dortmans
Physics , 1998, DOI: 10.1103/PhysRevC.58.1929
Abstract: The large variety of experimental data around the pion-production threshold are compared with a meson-exchange isobar model which includes the pion-nucleon interaction in s-- and p-waves. Theoretical results obtained with two different NN potentials (Bonn and Paris) indicate that the behavior of the excitation function at threshold is sensitive to the details of the NN correlations. The complete model presented, while developed originally to reproduce the reaction around the Delta resonance, is shown to describe well the integral (Coulomb-corrected) cross-section at threshold along with its angular distribution. At low energies the angular dependence of the analyzing power Ay0 is well reproduced also. Finally, the energy dependence of the analyzing power for theta=90 from threshold up to the Delta resonance is considered and discussed.
Microscopic model analyses of the elastic scattering of 65 MeV protons from targets of diverse mass
P. J. Dortmans,K. Amos,S. Karataglidis,J. Raynal
Physics , 1998, DOI: 10.1103/PhysRevC.58.2249
Abstract: Nonlocal coordinate space optical potentials for the scattering of 65 MeV protons from nuclei ranging in mass from 6Li to 238U have been defined by folding a complex, medium dependent effective interaction with the density matrix elements of each target. The effective interaction is based upon solutions of the Lippmann--Schwinger and Brueckner--Bethe--Goldstone equations having the Paris potential as input. The nuclear structure information required in our folding model are the one body density matrix elements for the target and the single nucleon bound state wave functions that they weight. For light mass nuclei, very large basis shell model calculations have been made to obtain the one body density matrix elements. For medium and heavy mass nuclei, a very simple shell model prescription has been used. The bound state single particle wave functions that complete the nuclear density matrices are either Woods--Saxon or harmonic oscillator functions. The former are employed in most cases when large basis structure is available. For light nuclei (A < 16) Woods--Saxon potential parameters and harmonic oscillator lengths are determined from fits to electron scattering form factors. For all other nuclei, we use harmonic oscillator functions with the oscillator lengths set from an A^{1/6} mass law. Using this microscopic model, optical potentials result from which differential cross sections, analyzing powers and spin rotations are found. In general the calculated results compare very well with data when the effective interactions are determined from a mapping of nucleon--nucleon g matrices. This is not the case when effective interactions built from a mapping of (free) t matrices are used.
Complex Conjugate Pairs in Stationary Sturmians
P. J. Dortmans,L. Canton,G. Pisent,K. Amos
Physics , 1993, DOI: 10.1103/PhysRevC.49.2828
Abstract: Sturmian eigenstates specified by stationary scattering boundary conditions are particularly useful in contexts such as forming simple separable two nucleon t matrices, and are determined via solution of generalised eigenvalue equation using real and symmetric matrices. In general, the spectrum of such an equation may contain complex eigenvalues. But to each complex eigenvalue there is a corresponding conjugate partner. In studies using realistic nucleon--nucleon potentials, and in certain positive energy intervals, these complex conjugated pairs indeed appear in the Sturmian spectrum. However, as we demonstrate herein, it is possible to recombine the complex conjugate pairs and corresponding states into a new, sign--definite pair of real quantities with which to effect separable expansions of the (real) nucleon--nucleon reactance matrices.
Alternative evaluations of halos in nuclei
S. Karataglidis,P. J. Dortmans,K. Amos,C. Bennhold
Physics , 1998, DOI: 10.1103/PhysRevC.61.024319
Abstract: Data for the scattering of 6He, 8He, 9Li, and 11Li from hydrogen are analyzed within a fully microscopic folding model of proton-nucleus scattering. Current data suggest that of these only 11Li has a noticeable halo. For 6He, we have also analysed the complementary reaction 6Li(gamma,pi)6He(gs). The available data for that reaction support the hypothesis that 6He may not be a halo nucleus. However, those data are scarce and there is clearly a need for more to elicit the microscopic structure of 6He.
Virulence of newcastle disease virus: what is known so far?
Jos CFM Dortmans, Guus Koch, Peter JM Rottier, Ben PH Peeters
Veterinary Research , 2011, DOI: 10.1186/1297-9716-42-122
Abstract: 1 Introduction2 Determination of NDV virulence3 Newcastle disease virus4 Viral entry proteins: major virulence determinants5 Immune evasion and virulence6 Replication and virulence7 Non-coding regions8 Concluding remarks9 Acknowledgements10 Competing interests11 Authors' contributions12 ReferencesThe virulence of a virus is determined by multiple genetic factors. These may involve its tissue or organ tropism, its ability to deal with the host's immune system and/or its efficacy of replication. In the literature the definition of a virulence factor or virulence determinant is not always clear-cut. Thus, many studies concluded that if a genetic mutation in a gene or a complete knock out of the gene function results in an attenuated phenotype, this particular gene or amino acid sequence is a virulence determinant. However, some proteins or protein domains are involved in basic replication processes, making them essential for virus reproduction. Hence, the terms "virulence factor" and "virulence determinant" should be used with care. Our definition of a virulence determinant is: a naturally occurring genetic difference between strains of the same species that is responsible for their difference in virulence. However, nowadays reverse genetics allows the genetic modification of viral genomes almost at will and as a consequence the effects of genetic modifications that have not been encountered in nature can also be studied. Indeed, these techniques have resulted in much more detailed information on the involvement of viral genes and proteins in the virus life cycle and consequently on their contribution to virulence. Therefore, it is arguable whether a particular "artificial" genetic difference still meets the above mentioned definition of a virulence determinant. Similar effects may occur in nature but may be countered by other factors or may be too subtle to be determined by the particular test used to measure differences in virulence.Newcastle disease (ND) is one of t
Cumulant Structure Factors of Jellium  [PDF]
P. Ziesche, J. Cioslowski
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.59083

For the ground state of the homogeneous electron gas (jellium), it is shown how the cumulant decomposition of the 2-matrix leads to the cumulant decomposition of the structure factors Sa,p(q) for the antiparallel (a) and parallel (p) spin pairs and how it simultaneously allows one to derive the momentum distribution n(k), which is a one-body quantity [Phys. Rev. A 86, 012508 (2012)]. The small-q and large-q behavior of Sa,p(q), and their normalizations are derived and compared with the results of P. Gori-Giorgi et al. [Physica A 280, 199 (2000) and Phys. Rev. B 61, 7353 (2000)].

In-vitro Studies of Biologically Important Barium Strontium Chromium Magnesium Hydrogen Phosphate (BaSrCrMgHPO4) Mixed Crystal Growth in SMS Gel Medium at Ambient Temperature and Its Characterization Studies  [PDF]
J. Kishore Kumar, P. Ramesh, P. Suresh, P. Sundaramoorthi
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.92010
Abstract: Kidney stone consists of various compounds. Mineral oxalate monohydrate and di-hydrate are the main constituent of kidney stones. However, the formation of calcium oxalate kidney stones is still not clearly understood. In this field of studies, several new hypotheses are created, which includes nucleation, reduction of nucleation, crystal growth and or aggregation of formation of different crystals such as oxalate monohydrate and oxalate di-hydrate. The effect of some urinary species such as ammonium oxalate, calcium, citrate, proteins and trace elements were reported by the author. The kidney stone constituents along with trace minerals are grown in silica gel medium (SMS) which provides the necessary growth simulation (in-vivo). In the artificial urinary stone growth process, growth parameters within the different chemical environments were carried out and reported for several urinary crystals such as CaHP, SrHP, SrMHP, BaHP, BaMHP and MgHP. In the present investigation, BaSrCrMHP (Barium Strontium Chromium Magnesium Hydrogen Phosphate) crystals are grown in different growth faces to attain the total nucleation reduction. Extension of this investigation, many characterization studies have been carried out and compared with reported results.
Defense Mechanism of Renal Functions and Calcium Mixed Mineral Formation in Agar-Agar Gel Medium at Laboratory Environment  [PDF]
J. Kishore Kumar, P. Sundaramoorthi
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2009, DOI: 10.4236/jmmce.2009.88057
Abstract: Calcium phosphates and oxalates are the most frequently observed bio-mineral phases. Many kinetics studies have been carried out on their crystal formation and dissolution in supersaturated and under saturated solutions, respectively. Major parameters include supernatant solution concentration, ionic strength, pH, temperature and solid surface behaviors. The growth of the calcium phosphate phases such as di-calcium phosphate di-hydrate (DCPD), octa-calcium phosphate (OCP), hydroxyapatite (HAP), and fluorapatite (FAP) crystals are observed. The ability of a surface to nucleate mineral phases is closely related to the magnitude of the interfacial energies. CaSeHPO4 crystals are grown in laboratory growth environments by the author in agar gel medium. Many characterization studies are done using grown crystals, such as FTIR, TGA/DTA, etching, SEM and XRD of the grown crystals are carried out and the results are reported.
Stability of Large Flocks: an Example
J. J. P. Veerman
Physics , 2010,
Abstract: The movement of a flock with a single leader (and a directed path from it to every agent) can be stabilized. Nonetheless for large flocks perturbations in the movement of the leader may grow to a considerable size as they propagate throughout the flock and before they die out over time. As an example we consider a string of N+1 oscillators moving in the line. Each one `observes' the relative velocity and position of only its nearest neighbors. This information is then used to determine its own acceleration. Now we fix all parameters except the number of oscillators. We then show (within a certain class of systems) that a perturbation in the leader's orbit is almost always amplified exponentially in N as it propagates towards the outlying members of the flock. The only exception is when there is a symmetry present in the interaction: in that case the growth of the perturbation is linear in N.
The Spectrum of the MSSM with Non-Standard Supersymmetry Breaking
J. P. J. Hetherington
Physics , 2001, DOI: 10.1088/1126-6708/2001/10/024
Abstract: The Minimal Supersymmetric Standard Model (MSSM) can include two soft breaking terms which are often neglected: a non-analytic scalar trilinear coupling and a Higgsino bilinear term. A set of high-scale boundary conditions consistent with the reparameterisation invariance which the model possesses is obtained. The three-family renormalisation group equations for the MSSM with these terms are presented. The ranges of the universal high-scale values of these couplings which lead to an acceptable TeV-scale theory are obtained, as is the supersymmetric particle spectrum at this scale. The effect of the new terms on fine-tuning is presented. SOFTSUSY, an existing program for calculating SUSY particle spectra, has been used, with as few modifications as possible.
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