10,090 research outputs found
Core-periphery analysis: a tale of two nations
Bias, unreliability and omission have been documented in traditional sources of trade
data; the lack of service data in trade statistics is the most frequently cited
shortcoming. Current trade liberalization is likely to exacerbate these deficiencies.
This paper develops and applies a location quotient based methodology for
analysing core-periphery dualism, thus obviating the use of trade data. Our
application to the European Union shows agglomeration in core areas of high
technology, large scale manufacturing, and producer service industries. Peripheral
countries are shown to specialize in agriculture, extractives, low technology
manufacturing, and standardized production. Detailed examination of two peripheral
economies, Ireland and Denmark, finds that each departs from the mean of
peripheral nations. A comparison of proxied trade data to actual trade data indicates
that the location quotient method is a statistically viable means of proxying trade
patterns
The president's proposed corporate tax reforms: a move toward tax neutrality
Tax reform ; Investments
Short distance potential and the thick center vortex model
The short distance potentials between heavy SU(3) and SU(4) sources are
calculated by increasing the role of vortex fluxes piercing Wilson loops with
contributions close to the trivial center element and by fluctuating the vortex
core size in the model of thick center vortices. By this method, a Coulombic
potential consistent with Casimir scaling is obtained. In addition, all other
features of the potential including a linear intermediate potential in
agreement with Casimir scaling and a large distance potential proportional to
the -ality of the representation are restored. Therefore, the model of thick
center vortices may be used as a phenomenological model, which is able to
describe the potential for all regimes.Comment: 9 pages and 6 figure
Quality assurance in stereotactic radiosurgery/radiotherapy according to DIN 6875-1
The new DIN (' Deutsche Industrie- Norm') 6875- 1, which is currently being finalised, deals with quality assurance ( QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/ radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4- mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in- house, the use of commercially available tools facilitated the QA according to the DIN 6875- 1 with which our results complied. Copyright (C) 2004 S. Karger AG, Basel
In-Situ Particle Acceleration in Extragalactic Radio Hot Spots: Observations Meet Expectations
We discuss, in terms of particle acceleration, the results from optical VLT
observations of hot spots associated with radio galaxies. On the basis of
observational and theoretical grounds, it is shown that:
1. relatively low radio-radio power hot spots are the optimum candidates for
being detected at optical waves. This is supported by an unprecedented optical
detection rate of 70% out of a sample of low radio power hot spots.
2. the shape of the synchrotron spectrum of hot spots is mainly determined by
the strength of the magnetic field in the region. In particular, the break
frequency, related to the age of the oldest electrons in the hot spots, is
found to increase with decreasing synchrotron power and magnetic field
strength.
Both observational results are in agreement with an in-situ particle
acceleration scenario.Comment: 5 pages, TeX (or Latex, etc), 4 figures, to appear in MNRAS Letter,
Updated reference
Factorizing Numbers with the Gauss Sum Technique: NMR Implementations
Several physics-based algorithms for factorizing large number were recently
published. A notable recent one by Schleich et al. uses Gauss sums for
distinguishing between factors and non-factors. We demonstrate two NMR
techniques that evaluate Gauss sums and thus implement their algorithm. The
first one is based on differential excitation of a single spin magnetization by
a cascade of RF pulses. The second method is based on spatial averaging and
selective refocusing of magnetization for Gauss sums corresponding to factors.
All factors of 16637 and 52882363 are successfully obtained.Comment: 4 pages, 4 figures; Abstract and Conclusion are slightly modified.
References added and formatted with Bibte
The Study of the Influence of Formulation and Process Variables on the properties of Simvastatin-Phospholipid Complex
Objectives: The aim of the present study was to examine the influence of the formulation and process variables on the entrapment efficiency of simvastatin-phospholipid complex (SPC), prepared with a goal of improving the solubility and permeability of simvastatin.
Method: The SPC was prepared using a solvent evaporation method. The influence of formulation and process variables on simvastatin entrapment was assessed using a central composite design. An additional SPC was prepared using the optimized variables from the developed quadratic model. This formulation was characterized for its physical-chemical properties. The functional attributes of the optimized SPC formulation were analyzed by apparent aqueous solubility analysis, in-vitro dissolution studies, dissolution efficiency analysis, and ex-vivo permeability studies.
Results: The factors studied were found to significantly influence on the entrapment efficiency. The developed model was validated using the optimized levels of formulation and process variables. The physical-chemical characterization confirmed a formation of the complex. The optimized SPC demonstrated over 25-fold higher aqueous solubility of simvastatin, compared to that of pure simvastatin. The optimized SPC exhibited a significantly higher rate and extent of simvastatin dissolution (\u3e98%), compared to that of pure simvastatin (∼16%). The calculated dissolution efficiency was also found to be significantly higher for the SPC (∼54 %), compared to that of pure simvastatin (∼8%). Finally, the optimized SPC exhibited a significantly higher simvastatin permeability (\u3e78%), compared to that of pure simvastatin (∼11%).
Implications: The present study shows that simvastatin-phospholipid complex can be a promising strategy for improving the delivery of simvastatin, and similar drugs with low aqueous solubility
Upper Bound on the Dark Matter Total Annihilation Cross Section
We consider dark matter annihilation into Standard Model particles and show
that the least detectable final states, namely neutrinos, define an upper bound
on the total cross section. Calculating the cosmic diffuse neutrino signal, and
comparing it to the measured terrestrial atmospheric neutrino background, we
derive a strong and general bound. This can be evaded if the annihilation
products are dominantly new and truly invisible particles. Our bound is much
stronger than the unitarity bound at the most interesting masses, shows that
dark matter halos cannot be significantly modified by annihilations, and can be
improved by a factor of 10--100 with existing neutrino experiments.Comment: 4 pages, 3 figures; version accepted for publication in PR
- …