76 research outputs found
Model Independent Form Factors for Spin Independent Neutralino-Nucleon Scattering from Elastic Electron Scattering Data
Theoretical calculations of neutralino-nucleon interaction rates with various
nuclei are of great interest to direct dark matter searches such as CDMS,
EDELWEISS, ZEPLIN, and other experiments since they are used to establish upper
bounds on the WIMP-proton cross section. These interaction rates and cross
sections are generally computed with standard, one or two parameter
model-dependent nuclear form factors, which may not exactly mirror the actual
form factor for the particular nucleus in question. As is well known, elastic
electron scattering can allow for very precise determinations of nuclear form
factors and hence nuclear charge densities for spherical or near-spherical
nuclei. We use charge densities derived from elastic electron scattering data
to calculate model independent, analytic form factors for various target nuclei
important in dark matter searches, such as Si, Ge, S, Ca and others. We have
found that for nuclear recoils in the range of 1-100 keV significant
differences in cross sections and rates exist when the model independent form
factors are used: at 30 keV nuclear recoil the form factors squared differ by a
factor of 1.06 for Si, 1.11 for Ca, 1.27 for Ge, and 1.92
for Xe. We show the effect of different form factors on the upper limit
on the WIMP-proton cross section obtained with a hypothetical Ge
detector during a 100 kg-day effective exposure. Helm form factors with various
parameter choices differ at most by 10--20% from the best (Fourier Bessel) form
factor, and can approach it to better than 1% if the parameters are chosen to
mimic the actual nuclear density.Comment: 20 pages, 8 figure
An integrative clustering approach combining particle swarm optimization and formal concept analysis
Dynamics of viscous amphiphilic films supported by elastic solid substrates
The dynamics of amphiphilic films deposited on a solid surface is analyzed
for the case when shear oscillations of the solid surface are excited. The two
cases of surface- and bulk shear waves are studied with film exposed to gas or
to a liquid. By solving the corresponding dispersion equation and the wave
equation while maintaining the energy balance we are able to connect the
surface density and the shear viscocity of a fluid amphiphilic overlayer with
experimentally accessible damping coefficients, phase velocity, dissipation
factor and resonant frequency shifts of shear waves.Comment: 19 pages, latex, 3 figures in eps-forma
Muon capture by 3He nuclei followed by proton and deuteron production
The paper describes an experiment aimed at studying muon capture by
nuclei in pure and mixtures at various densities. Energy distributions of
protons and deuterons produced via and are measured for the
energy intervals MeV and MeV, respectively. Muon capture
rates, and are obtained using two different analysis methods. The
least--squares methods gives , . The Bayes theorem
gives ,
. The experimental
differential capture rates, and , are compared with theoretical
calculations performed using the plane--wave impulse approximation (PWIA) with
the realistic NN interaction Bonn B potential. Extrapolation to the full energy
range yields total proton and deuteron capture rates in good agreement with
former results.Comment: 17 pages, 13 figures, accepted for publication in PR
[Pertussis--an illness with typical clinical symptoms?]
There has been a noticeable increase in the incidence of pertussis in West Germany over the last decade. Since the availability of adequate bacteriological diagnosis a much broader clinical spectrum can be attributed to infections with B. pertussis. Three patients with an unusual clinical presentation of pertussis are presented. A three month old infant presented with severe apneic spells without cough as the sole clinical symptoms of the infection. B. pertussis was isolated in the nasopharyngeal swab. A nine month old premature infant with bronchopulmonary dysplasia after long time intubation and artificial ventilation presented with apneic spells, pulmonary and cardiac decompensation and required ventilatory support. The diagnosis was suggested by a massive leucocytosis with lymphocytosis. The diagnosis on the patient was established by serologic methods. Adult contacts of this patient developed longstanding cough and clinical signs of pertussis. The diagnosis of pertussis in these persons was established by nasopharyngeal culture. The third patient with trisomy 21 and a corrected AV canal suffered from nonspecific cough and gradually developed signs of congestive heart failure with pneumonia. B. pertussis was isolated from the nasopharynx. This patient showed neither the typical paroxysmal coughing spells nor disclosed the typical lymphocytosis in his white blood count. Microbiological investigations of patients with symptoms of respiratory tract infections should include the isolation of B. pertussis. Thus, additional cases of pertussis not suspected on the basis of their initial clinical presentation will be detecte
Papillenödem und akute bilaterale Amaurose bei akuter Sinusitis
BACKGROUND: Acute sinusitis can lead to severe complications. This includes involvement of the optical nerve with visual loss and brain abscess as a life-threatening complication. PATIENTS: Empyema of the chiasma opticum region with neuritis nervi optici and bilateral acute amaurosis was observed in a 13 year old boy with sinusitis sphenoidalis and ethmoidalis. In a 11 year old girl, pronounced papilledema was found to be closely associated with sinusitis sphenoidalis. While she recovered completely on appropriate antibiotic therapy, visual loss in the boy was irreversible despite surgical intervention. CONCLUSIONS: Sinusitis should always be considered in patients with impaired vision, neuritis nervi optici or unexplained papilledema, especially if occurring in association with an upper respiratory infection. In addition to physical examination, cranial computer tomography or magnetic resonance imaging of the brain including sinuses and chiasma opticum should be applied early. If empyema is found, immediate surgical intervention is of prognostic importance
Resonances and Surface Waves in Elastic Wave Scattering from Cavities and Inclusions
Elastic-wave scattering from various types of cavities and inclusions has been studied theoretically with special emphasis on surface wave effects that appear during the scattering process. Resonances in the scattering amplitudes are caused by the phase matching of circumnavigating surface waves, and manifest themselves as poles in the complex frequency plane that correspond to the (complex) eigenfrequencies of the cavity of inclusion. These results are most easily obtained for scatterers of separable geometry, such as spheres, where theoretical amplitudes are well-known. Here, the formalism for a complete treatment of elastic-wave scattering from infinite cylindrical cavities and solid inclusions has been worked out for general oblique incidence. Poles of scattering amplitudes have been found for evacuated and for fluid-filled cylinders, and have been physically interpreted in terms of helical surface waves propagating both interior and exterior to the cylinder. Dispersion, attenuation, and refraction of these surface waves have been obtained. Progressing to more generally-shaped obstacles, we have studied surface waves and complex-frequency poles for finite- length cylindrical cavities with flat ends. In this fashion, the resonance features(particularly the cavity eigenfrequencies) that appear prominently in the scattering amplitude can be understood as to their physical origin and their dependence on the type of cavity, and may be exploited for purposes of classification and identification of flaws by their ultrasonic resonances (ultrasonic “resonance spectroscopy”).</p
Surface Wave Modes on Spherical Cavities Excited by Incident Ultrasound
It has been shown both experimentally and theoretically1 that ultrasonic waves propagate circumferentially around the surface of cavities in an elastic medium, besides being reflected from its “flash points”. Surface wave returns were seen to decisively influence the time structure of the echo return from incident ultrasonic pulses. Nagase2 has solved a characteristic equation applicable to the spherical cavity problem, from which it could be shown3 that the surface of a spherical cavity supports a Rayleigh-type and two (P and S) Franz-type surface waves, of known speeds and dispersions. On the other hand, the complex eigenfrequencies of cavities were recently obtained numerically4. We have used these numerical results in order to satisfy Nagase’s solutions, presented in the form of propagation constants of the surface waves as series of fractional powers of the frequency, and have obtained in this way a mode number assignment for all the complex eigenfrequencies. Using this, we calculate dispersion curves for the Rayleigh, P and S- type surface wave phase velocities; their knowledge will permit an accurate interpretation of ultrasonic scattering experiments1, which previously could be analyzed in a qualitative way only.</p
Clinical characteristics of illness caused by Bordetella parapertussis compared with illness caused by Bordetella pertussis
In conjunction with a pertussis vaccine efficacy trial in Germany, nasopharyngeal specimens were collected from May, 1992, to March, 1993, from patients with cough illnesses. Clinical data were obtained by initial and follow-up questionnaires. Bordetella parapertussis was isolated from 38 patients (mean age, 3.5 years; 68% girls). Clinical characteristics in these cases were compared with those of 76 patients (matched by age and sex) with illness caused by Bordetella pertussis during the same period. Findings were: (B. pertussis/B. parapertussis): cough 0.0001) and 7800/mm3 and 3500/mm3 (P > 0.0001), respectively. Illness caused by B. parapertussis was typical of pertussis but less severe than that caused by B. pertussis. In contrast with B. pertussis infection, lymphocytosis is not a characteristic of B. parapertussis infection. This is most likely a result of the lack of production of lymphocytosis-promoting factor toxin by B. parapertussis
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