2,021 research outputs found
Beam Loss in Linacs
Beam loss is a critical issue in high-intensity accelerators, and much effort
is expended during both the design and operation phases to minimize the loss
and to keep it to manageable levels. As new accelerators become ever more
powerful, beam loss becomes even more critical. Linacs for H- ion beams, such
as the one at the Oak Ridge Spallation Neutron Source, have many more loss
mechanisms compared to H+ (proton) linacs, such as the one being designed for
the European Spallation Neutron Source. Interesting H- beam loss mechanisms
include residual gas stripping, H+ capture and acceleration, field stripping,
black-body radiation and the recently discovered intra-beam stripping
mechanism. Beam halo formation, and ion source or RF turn on/off transients,
are examples of beam loss mechanisms that are common for both H+ and H-
accelerators. Machine protection systems play an important role in limiting the
beam loss.Comment: 24 pages, contribution to the 2014 Joint International Accelerator
School: Beam Loss and Accelerator Protection, Newport Beach, CA, USA , 5-14
Nov 201
Simulation and reconstruction study of a future surface scintillator array at the IceCube Neutrino Observatory
A Computer-Assisted Uniqueness Proof for a Semilinear Elliptic Boundary Value Problem
A wide variety of articles, starting with the famous paper (Gidas, Ni and
Nirenberg in Commun. Math. Phys. 68, 209-243 (1979)) is devoted to the
uniqueness question for the semilinear elliptic boundary value problem
-{\Delta}u={\lambda}u+u^p in {\Omega}, u>0 in {\Omega}, u=0 on the boundary of
{\Omega}, where {\lambda} ranges between 0 and the first Dirichlet Laplacian
eigenvalue. So far, this question was settled in the case of {\Omega} being a
ball and, for more general domains, in the case {\lambda}=0. In (McKenna et al.
in J. Differ. Equ. 247, 2140-2162 (2009)), we proposed a computer-assisted
approach to this uniqueness question, which indeed provided a proof in the case
{\Omega}=(0,1)x(0,1), and p=2. Due to the high numerical complexity, we were
not able in (McKenna et al. in J. Differ. Equ. 247, 2140-2162 (2009)) to treat
higher values of p. Here, by a significant reduction of the complexity, we will
prove uniqueness for the case p=3
Metamaterials proposed as perfect magnetoelectrics
Magnetoelectric susceptibility of a metamaterial built from split ring
resonators have been investigated both experimentally and within an equivalent
circuit model. The absolute values have been shown to exceed by two orders of
magnitude that of classical magnetoelectric materials. The metamaterial
investigated reaches the theoretically predicted value of the magnetoelectric
susceptibility which is equal to the geometric average of the electric and
magnetic susceptibilities.Comment: 5 pages, 3 figure
2-methylene-(20S,25S)-19,27-dinor-(22E)-vitamin D analogs
This invention discloses 2-methylene-(20S,25S)-19,27-dinor-(22E)-vitamin D analogs, and specifically 2-methylene-(20S,25S)-19,27-dinor-(22E)-1.alpha.,25-dihydroxyvitamin D.sub.3, and pharmaceutical uses therefor. This compound exhibits pronounced activity in arresting the proliferation of undifferentiated cells and inducing their differentiation to the monocyte thus evidencing use as an anti-cancer agent and for the treatment of skin diseases such as psoriasis as well as skin conditions such as wrinkles, slack skin, dry skin and insufficient sebum secretion. This compound also has little, if any, calcemic activity and therefore may be used to treat autoimmune disorders or inflammatory diseases in humans as well as renal osteodystrophy. This compound may also be used for the treatment or prevention of obesity
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Rationale and Development of a Security Assurance Index with Application toward the Development of a World Risk Index
Assurance categories were previously developed to support the Department of Homeland Security’s efforts in the mitigation of Cyber Control System events. Defined according to the risk of life and economic loss, the minimum range is designated by policy, whereas the maximum limit seems to be constrained only by limits and interdependencies of the event. Use of this life / assets scale has proven to be helpful in managing risk due to the scale's ease of use, communication, and understanding. Suggestions have been made that this scale could be applied to all events of terror, disaster, and calamity of an international scale, with equally good results. This paper presents the history of some existing scales of disaster and assurance, the rationale behind the development of the original Security Assurance Index, and our proposed scale of disaster and calamity as a World Risk Index
Visual Physics Analysis (VISPA) - Concepts and First Applications
VISPA is a novel development environment for high energy physics analyses,
based on a combination of graphical and textual steering. The primary aim of
VISPA is to support physicists in prototyping, performing, and verifying a data
analysis of any complexity. We present example screenshots, and describe the
underlying software concepts.Comment: Parallel talk at ICHEP08, Philadelphia, USA, July 2008. 4 pages, 2
figure
Reversible Cortical Blindness Following Successful Surgical Repair Of Two Stab Wounds In The Heart
This report describes a case of cortical blindness that followed successful surgical repair of two stab wounds in the heart in a 29-year old Libyan man. The patient presented in a state of pre cardiac arrest (shock and low cardiac output status), following multiple chest stab wounds. Chest tube was immediately inserted. Surgery was urgently performed suturing the two wounds; in the root of the aorta and in the left ventricle, and haemostasis was secured. Cardiac arrest was successfully prevented. The patient recovered smoothly, but 24 hours later he declared total blindness. Ophtalmic and neurological examinations and investigations that included fundoscopy, Electroencephalograms (EEGs) and Computed Tomography Scans revealed no abnormalities, apart from absence of alpha waves in the EEGs. We diagnosed the case as cortical blindness and continued caring for the patient conservatively. Three days later, the patient regained his vision gradually and was discharged on the 7th postoperative day without any remarks
Surface Gap Soliton Ground States for the Nonlinear Schr\"{o}dinger Equation
We consider the nonlinear Schr\"{o}dinger equation , with and and with periodic in each coordinate direction. This problem
describes the interface of two periodic media, e.g. photonic crystals. We study
the existence of ground state solutions (surface gap soliton ground
states) for . Using a concentration compactness
argument, we provide an abstract criterion for the existence based on ground
state energies of each periodic problem (with and ) as well as a more practical
criterion based on ground states themselves. Examples of interfaces satisfying
these criteria are provided. In 1D it is shown that, surprisingly, the criteria
can be reduced to conditions on the linear Bloch waves of the operators
and .Comment: definition of ground and bound states added, assumption (H2) weakened
(sign changing nonlinearity is now allowed); 33 pages, 4 figure
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