305 research outputs found
Dynamics of airflow in a short inhalation
During a rapid inhalation, such as a sniff, the flow in the airways
accelerates and decays quickly. The consequences for flow development and
convective trans- port of an inhaled gas were investigated in a subject
geometry extending from the nose to the bronchi. The progress of flow
transition and the advance of an inhaled non-absorbed gas were determined using
highly resolved simulations of a sniff 0.5 s long, 1 litre per second peak
flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved
through three phases: (i) an initial transient of about 50 ms, roughly the
filling time for a nasal volume, (ii) quasi-equilibrium over the majority of
the inhalation, and (iii) a terminating phase. Flow transition commenced in the
supraglottic region within 20ms, resulting in large- amplitude fluctuations
persisting throughout the inhalation; in the nose, fluctuations that arose
nearer peak flow were of much reduced intensity and diminished in the flow
decay phase. Measures of gas concentration showed non-uniform build-up and
wash-out of the inhaled gas in the nose. At the carina, the form of the
temporal concentration profile reflected both shear dispersion and airway
filling defects owing to recirculation regions.Comment: 15 page
Long-term results of cyclosporine-steroid therapy in 131 non-matched cadaveric renal transplants.
One-hundred-and-twenty-eight recipients of 131 consecutive, non-matched cadaver renal allografts were treated with cyclosporine and steroids. They have been followed for 4 to 6 yr. Cumulative patient survival at 1-yr was 92.2% and at 6yr it is 77.8%. Cumulative graft survival at 1-yr was 79.4% and at 6 yr it is 50.0%. After the high-risk 1st yr, the rate of graft loss was even and similar to that reported after the 1st yr for grafts treated with azathioprine and steroids. This indicates that cyclosporine nephrotoxicity has not had an obvious adverse effect on the survival of chronically functioning grafts. The results were better with primary grafting versus retransplantation, but were not significantly influenced by age, diabetes mellitus, or a delayed switch in patients from cyclosporine to azathioprine. We have concluded that cyclosporine-steroid therapy is safe and effective for long-term use after cadaveric renal transplantation
Velocity Map Imaging with No Spherical Aberrations
Velocity map imaging (VMI) is a powerful technique that allows to infer the
kinetic energy of ions or electrons that are produced from a large volume in
space with good resolution. The size of the acceptance volume is determined by
the spherical aberrations of the ion optical system. Here we present an
analytical derivation for velocity map imaging with no spherical aberrations.
We will discuss a particular example for the implementation of the technique
that allows using the reaction microscope recently installed in the Cryogenic
storage ring (CSR) in a VMI mode. SIMION simulations confirm that a beam of
electrons produced almost over the entire volume of the source region, with
width of 8 cm, can be focused to a spot of 0.1 mm on the detector. The use of
the same formalism for position imaging, as well as an option of position
imaging in one axis and velocity map imaging in a different axis, are also
discussed
Sefer Tesubot Dunas ben Labrat : Kritik des Dunasch ben Labrat über einzelne Stellen aus Saadia's arabischer Uebersetzung des A.T. und aus dessen grammatischen Schriften
Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 201
Projectile-Charge Sign Dependence of Four-Particle Dynamics in Helium Double Ionization
Double ionization of helium by 6 MeV proton impact has been explored in a kinematically complete experiment using a “reaction microscope.” For the first time, fully differential cross sections for positively charged projectiles have been obtained and compared with data from 2 keV electron impact. The significant differences observed in the angular distribution of the ejected electrons are attributed to the charge sign of the projectile, resulting in different dynamics of the four-particle Coulomb system, which is not considered in the first Born approximation
Separation of Recollision Mechanisms in Nonsequential Strong Field Double Ionization of Ar: The Role of Excitation Tunneling
Vector momentum distributions of two electrons created in double ionization of Ar by 25 fs, 0.25PW/cm2 laser pulses at 795 nm have been measured using a “reaction microscope.” At this intensity, where nonsequential ionization dominates, distinct correlation patterns are observed in the two-electron momentum distributions. A kinematical analysis of these spectra within the classical “recollision model” revealed an (e,2e)-like process and excitation with subsequent tunneling of the second electron as two different ionization mechanisms. This allows a qualitative separation of the two mechanisms demonstrating that excitation-tunneling is the dominant contribution to the total double ionization yield
Non-Sequential Double Ionization of Ne in Intense Laser Pulses: A Coincidence Experiment
The dynamics of Neon double ionization by 25 fs, 1.0 PW/cm2 laser pulses at 795 nm has been studied in a many particle coincidence experiment. The momentum vectors of all ejected atomic fragments (electrons and ions) have been measured using combined electron and recoil-ion momentum spectroscopy. Electron emission spectra for double and single ionization will be discussed. In both processes the mean electron energies differ considerably and high energetic electrons with energies of more than 120 eV have been observed for double ionization. The experimental results are in qualitative agreement with the rescattering model
Sequential and Direct Two-Photon Double Ionization of D₂ at Flash
Sequential and direct two-photon double ionization (DI) of D2 molecule is studied experimentally and theoretically at a photon energy of 38.8 eV. Experimental and theoretical kinetic energy releases of D++D+fragments, consisting of the contributions of sequential DI via the D2+(1sσg) state and direct DI via a virtual state, agree well with each other
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