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Search Results: 1 - 10 of 325241 matches for " B. L. Berman "
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Beam-Helicity Asymmetries in Double-Charged-Pion Photoproduction on the Proton
CLAS Collaboration,S. Strauch,B. L. Berman
Physics , 2005, DOI: 10.1103/PhysRevLett.95.162003
Abstract: Beam-helicity asymmetries for the two-pion-photoproduction reaction gamma + p --> p pi+ pi- have been studied for the first time in the resonance region for center-of-mass energies between 1.35 GeV and 2.30 GeV. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized tagged photons incident on an unpolarized hydrogen target. Beam-helicity-dependent angular distributions of the final-state particles were measured. The large cross-section asymmetries exhibit strong sensitivity to the kinematics and dynamics of the reaction. The data are compared with the results of various phenomenological model calculations, and show that these models currently do not provide an adequate description for the behavior of this new observable.
Quasiperiodic Atom Optics, Focusing, and Wave packet Rephasing
J. L. Cohen,B. Dubetsky,P. R. Berman
Physics , 1998,
Abstract: We propose a laser field configuration which acts as a quasiperiodic atom optical diffraction grating. Analytical and computational results for the atomic center-of-mass wavefunction after the grating reveal a quasiperiodic density pattern, a semiclassical focusing effect, and a quasiperiodic self-imaging of the atomic wavefunction analogous to a Talbot effect.
Filtered Talbot lens: Producing $λ/2n$-periodic atomic patterns with standing wave fields having period $λ$
J. L. Cohen,B. Dubetsky,P. R. Berman,J. Schmiedmayer
Physics , 1999, DOI: 10.1103/PhysRevA.61.033610
Abstract: We propose a scheme to create high-contrast, periodic atom density distributions having period $\lambda /2n$ using the Talbot effect, where $% \lambda $ is the wave length of the optical fields that scatter the atoms and $n$ is a positive integer. This {\em filtered Talbot lens} is comprised of two standing-wave optical fields. An atomic beam propagates perpendicular to the fields. The first field, which is far-detuned from the atomic transition frequency, acts as an array of lenses that focuses the atoms. The second field, positioned at the atom optical focus of the first, is resonant with the atomic transition frequency and acts as an amplitude mask, leaving unperturbed only those atoms that pass through its nodes. At distances following the interaction with the second field that are equal to an integral fraction of the Talbot length, atomic density gratings having period $\lambda /2n$ are formed.
Atom focusing by far-detuned and resonant standing wave fields: Thin lens regime
J. L. Cohen,B. Dubetsky,P. R. Berman
Physics , 1999, DOI: 10.1103/PhysRevA.60.4886
Abstract: The focusing of atoms interacting with both far-detuned and resonant standing wave fields in the thin lens regime is considered. The thin lens approximation is discussed quantitatively from a quantum perspective. Exact quantum expressions for the Fourier components of the density (that include all spherical aberration) are used to study the focusing numerically. The following lens parameters and density profiles are calculated as functions of the pulsed field area $\theta $: the position of the focal plane, peak atomic density, atomic density pattern at the focus, focal spot size, depth of focus, and background density. The lens parameters are compared to asymptotic, analytical results derived from a scalar diffraction theory for which spherical aberration is small but non-negligible ($\theta \gg 1$). Within the diffraction theory analytical expressions show that the focused atoms in the far detuned case have an approximately constant background density $0.5(1-0.635\theta ^{- 1/2})$ while the peak density behaves as $% 3.83\theta ^{1/2}$, the focal distance or time as $\theta ^{-1}(1+1.27\theta ^{- 1/2})$, the focal spot size as $0.744\theta ^{-3/4}$, and the depth of focus as $1.91\theta ^{- 3/2}$. Focusing by the resonant standing wave field leads to a new effect, a Rabi- like oscillation of the atom density. For the far-detuned lens, chromatic aberration is studied with the exact Fourier results. Similarly, the degradation of the focus that results from angular divergence in beams or thermal velocity distributions in traps is studied quantitatively with the exact Fourier method and understood analytically using the asymptotic results. Overall, we show that strong thin lens focusing is possible with modest laser powers and with currently achievable atomic beam characteristics.
High resolution amplitude and phase gratings in atom optics
P. R. Berman,B. Dubetsky,J. L. Cohen
Physics , 1998, DOI: 10.1103/PhysRevA.58.4801
Abstract: An atom-field geometry is chosen in which an atomic beam traverses a field interaction zone consisting of three fields, one having frequency $\Omega =c/\lambda $ propagating in the $\hat{z}$ direction and the other two having frequencies $\Omega +\delta_{1}$ and $\Omega +\delta_{2}$ propagating in the -$\hat{z}$ direction. For $n_{1}\delta_{1}+n_{2}\delta_{2}=0$ and $|\delta_{1}| T,|\delta_{2}| T\gg 1$, where $n_{1}$ and $n_{2}$ are positive integers and $T$ is the pulse duration in the atomic rest frame, the atom-field interaction results in the creation of atom amplitude and phase gratings having period $% \lambda /[2(n_{1}+n_{2})]$. In this manner, one can use optical fields having wavelength $\lambda $ to produce atom gratings having periodicity much less than $\lambda $.
New developments in the treatment of actinic keratosis: focus on ingenol mebutate gel
Berman B
Clinical, Cosmetic and Investigational Dermatology , 2012, DOI: http://dx.doi.org/10.2147/CCID.S28905
Abstract: evelopments in the treatment of actinic keratosis: focus on ingenol mebutate gel Review (2171) Total Article Views Authors: Berman B Published Date August 2012 Volume 2012:5 Pages 111 - 122 DOI: http://dx.doi.org/10.2147/CCID.S28905 Received: 07 June 2012 Accepted: 18 July 2012 Published: 24 August 2012 Brian Berman University of Miami Miller School of Medicine, Miami, and Center for Clinical and Cosmetic Research, Aventura, FL, USA Abstract: Actinic keratosis is a common disease in older, fair-skinned people, and is a consequence of cumulative ultraviolet exposure. It is part of a disease continuum in photodamaged skin that may lead to invasive squamous cell carcinoma. Treatment options frequently used include cryosurgery and topical pharmacologic agents, which are examples of lesion-directed and field-directed strategies. Ingenol mebutate gel was recently approved by the US Food and Drug Administration for topical treatment of actinic keratosis. While the mechanism of action of ingenol mebutate is not fully understood, in vitro and in vivo studies using tumor models indicate it has multiple mechanisms. Ingenol mebutate directly induces cell death by mitochondrial swelling and loss of cell membrane integrity preferentially in transformed keratinocytes. It promotes an inflammatory response characterized by infiltration of neutrophils and other immunocompetent cells that kills remaining tumor cells. The ability of ingenol mebutate to eliminate mutant p53 patches in ultraviolet-irradiated mouse skin suggests that it may have the potential to treat chronically ultraviolet-damaged skin. In human studies, ingenol mebutate achieved high clearance of actinic keratosis on the head and body after 2–3 consecutive daily treatments when measured by complete or partial clearance of lesions. Localized inflammatory skin responses were generally mild to moderate and resolved in less than a month.
New developments in the treatment of actinic keratosis: focus on ingenol mebutate gel
Berman B
Clinical, Cosmetic and Investigational Dermatology , 2012,
Abstract: Brian BermanUniversity of Miami Miller School of Medicine, Miami, and Center for Clinical and Cosmetic Research, Aventura, FL, USAAbstract: Actinic keratosis is a common disease in older, fair-skinned people, and is a consequence of cumulative ultraviolet exposure. It is part of a disease continuum in photodamaged skin that may lead to invasive squamous cell carcinoma. Treatment options frequently used include cryosurgery and topical pharmacologic agents, which are examples of lesion-directed and field-directed strategies. Ingenol mebutate gel was recently approved by the US Food and Drug Administration for topical treatment of actinic keratosis. While the mechanism of action of ingenol mebutate is not fully understood, in vitro and in vivo studies using tumor models indicate it has multiple mechanisms. Ingenol mebutate directly induces cell death by mitochondrial swelling and loss of cell membrane integrity preferentially in transformed keratinocytes. It promotes an inflammatory response characterized by infiltration of neutrophils and other immunocompetent cells that kills remaining tumor cells. The ability of ingenol mebutate to eliminate mutant p53 patches in ultraviolet-irradiated mouse skin suggests that it may have the potential to treat chronically ultraviolet-damaged skin. In human studies, ingenol mebutate achieved high clearance of actinic keratosis on the head and body after 2–3 consecutive daily treatments when measured by complete or partial clearance of lesions. Localized inflammatory skin responses were generally mild to moderate and resolved in less than a month.Keywords: ingenol mebutate gel, actinic keratosis, field therapy, nonmelanoma skin cancer, protein kinase C delta
Photodisintegration of $^4$He into p+t
R. Nasseripour,B. L. Berman,N. Benmouna,Y. Ilieva,J. -M. Laget
Physics , 2009, DOI: 10.1103/PhysRevC.80.044603
Abstract: The two-body photodisintegration of $^4$He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid $^4$He target. This is the first measurement of the photodisintegration of $^4$He above 0.4 GeV. The differential cross sections for the $\gamma$$^4$He$\to pt$ reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of $^3$He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV .
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
CLAS Collaboration,S. Niccolai,G. Audit,B. L. Berman,J. M. Laget,S. Strauch
Physics , 2004, DOI: 10.1103/PhysRevC.70.064003
Abstract: The three-body photodisintegration of 3He has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.
Evidence for a backward peak in the gamma+d->pi^0+d cross section near the eta threshold
Y. Ilieva,B. L. Berman,A. E. Kudryavtsev,I. I. Strakovsky,V. E. Tarasov,for the CLAS Collaboration
Physics , 2007, DOI: 10.1140/epja/i2010-10918-x
Abstract: High-quality cross sections for the reaction gamma+d->pi^0+d have been measured using the CLAS at Jefferson Lab over a wide energy range near and above the eta-meson photoproduction threshold. At backward c.m. angles for the outgoing pions, we observe a resonance-like structure near E_gamma=700 MeV. Our model analysis shows that it can be explained by eta excitation in the intermediate state. The effect is the result of the contribution of the N(1535)S_11 resonance to the amplitudes of the subprocesses occurring between the two nucleons and of a two-step process in which the excitation of an intermediate eta meson dominates.
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