22,988 research outputs found
Corrigendum to "Knot Floer homology detects fibred knots"
We correct a mistake on the citation of JSJ theory in \cite{Ni}. Some
arguments in \cite{Ni} are also slightly modified accordingly.Comment: 3 page
Lorentz invariance violation and charge (non--)conservation: A general theoretical frame for extensions of the Maxwell equations
All quantum gravity approaches lead to small modifications in the standard
laws of physics which lead to violations of Lorentz invariance. One particular
example is the extended standard model (SME). Here, a general phenomenological
approach for extensions of the Maxwell equations is presented which turns out
to be more general than the SME and which covers charge non--conservation
(CNC), too. The new Lorentz invariance violating terms cannot be probed by
optical experiments but need, instead, the exploration of the electromagnetic
field created by a point charge or a magnetic dipole. Some scalar--tensor
theories and higher dimensional brane theories predict CNC in four dimensions
and some models violating Special Relativity have been shown to be connected
with CNC and its relation to the Einstein Equivalence Principle has been
discussed. Due to this upcoming interest, the experimental status of electric
charge conservation is reviewed. Up to now there seem to exist no unique tests
of charge conservation. CNC is related to the precession of polarization, to a
modification of the --Coulomb potential, and to a time-dependence of the
fine structure constant. This gives the opportunity to describe a dedicated
search for CNC.Comment: To appear in Physical Review
Q & A Experiment to Search for Vacuum Dichroism, Pseudoscalar-Photon Interaction and Millicharged Fermions
A number of experiments are underway to detect vacuum birefringence and
dichroism -- PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed
optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical
interpretations of this result include a possible pseudoscalar-photon
interaction and the existence of millicharged fermions. Here, we report the
progress and first results of Q & A (QED [quantum electrodynamics] and Axion)
experiment proposed and started in 1994. A 3.5-m high-finesse (around 30,000)
Fabry-Perot prototype detector extendable to 7-m has been built and tested. We
use X-pendulums and automatic control schemes developed by the
gravitational-wave detection community for mirror suspension and cavity
control. To polarize the vacuum, we use a 2.3-T dipole permanent magnet, with
27-mm-diameter clear borehole and 0.6-m field length,. In the experiment, the
magnet is rotated at 5-10 rev/s to generate time-dependent polarization signal
with twice the rotation frequency. Our
ellipsometer/polarization-rotation-detection-system is formed by a pair of
Glan-Taylor type polarizing prisms with extinction ratio lower than 10-8
together with a polarization modulating Faraday Cell with/without a quarter
wave plate. We made an independent calibration of our apparatus by performing a
measurement of gaseous Cotton-Mouton effect of nitrogen. We present our first
experimental results and give a brief discussion of our experimental limit on
pseudo-scalar-photon interaction and millicharged fermions.Comment: 21 pages, 13 figures, submitted to Modern Physics Letter
Loosely Synchronised Spreading Code Aided Network Performance of Quasi-Synchronous UTRA-like TDD and FDD CDMA Systems
It is demonstrated that loosely synchronised (LS) spreading codes exhibit a so-called interference-free window, where both the autocorrelation and cross-correlation of the codes become zero. Therefore LS codes have the promise of mitigating the effects of both inter-symbolinterference and multiple-access-interference in time dispersive channels. Hence, LS codes have the potential of increasing the capacity of CDMA networks. The work reported has studied the achievable network performance and compared it to that of a UTRA-like time division duplex (TDD) and frequency division duplex (FDD) CDMA system using orthogonal variable rate spreading factor codes
Loosely synchronized spreading code aided network performance of quasi-synchronous UTRA-like TDD/CDMA systems
In this paper we investigate the achievable capacity of a UTRA-like Time Division Duplex (TDD) Code Division Multiple Access (CDMA) system employing Loosely Synchronized (LS) spreading codes. The family of operational CDMA systems is interference limited, suffering from Inter-Symbol-Interference (ISI), since the orthogonality of the spreading sequences is destroyed by the frequency selective channel. They also suffer from Multiple-Access-Interference (MAI) owing to the non-zero cross-correlations of the spreading codes. By contrast, the family of LS codes exhibits a so-called Interference Free Window (IFW), where both the auto-correlation and cross-correlation of the codes become zero. Therefore LS codes have the promise of mitigating the effects of both ISI and MAI in time dispersive channels. Hence, LS codes have the potential of increasing the capacity of CDMA networks. This contribution studies the achievable network performance in comparison to that of a UTRA-like TDD/CDMA system using Orthogonal Vari- MSO able Rate Spreading Factor (OVSF) codes
An extensible product structure model for product lifecycle management in the make-to-order environment
This paper presents a product structure model with a semantic representation technique that make the product structure extensible for developing product lifecycle management (PLM) systems that is flexible for make-to-order environment. In the make-to-order business context, each product could have a number of variants with slightly different constitutions to fulfill different customer requirements. All the variants of a family have common characteristics and each variant has its specific features. A master-variant pattern is proposed for building the product structure model to explicitly represent common characteristics and specific features of individual variants. The model is capable of enforcing the consistency of a family structure and its variant structure, supporting multiple product views, and facilitating the business processes. A semantic representation technique is developed that enables entity attributes to be defined and entities to be categorized in a neutral and semantic format. As a result, entity attributes and entity categorization can be redefined easily with its configurable capability for different requirements of the PLM systems. An XML-based language is developed for semantically representing entities and entity categories. A prototype as a proof-of-concept system is presented to illustrate the capability of the proposed extensible product structure model
Constraint on intermediate-range gravity from earth-satellite and lunar orbiter measurements, and lunar laser ranging
In the experimental tests of gravity, there have been considerable interests
in the possibility of intermediate-range gravity. In this paper, we use the
earth-satellite measurement of earth gravity, the lunar orbiter measurement of
lunar gravity, and lunar laser ranging measurement to constrain the
intermediate-range gravity from lambda=1.2*10^{7}m - 3.8*10^{8}m. The limits
for this range are alpha=10^{-8}-5*10^{-8}, which improve previous limits by
about one order of magnitude in the range lambda=1.2*10^{7}m-3.8*10^{8}m.Comment: 8 pages, International Journal of Modern Physics D, in press (World
Scientific, 2005
Nausea, Vomiting and Retching of Patients with Cervical Cancer Undergoing Chemotherapy in Bali, Indonesia
Background: Nausea, vomiting and retching (NVR) was the frequently reported and troublesome adverse effect for patients receiving chemotherapy. Purpose: This study is a part of a larger study which aims to describe the NVR symptom experience in cervical cancer patients undergoing chemotherapy in Bali, Indonesia, and examine relationships with individual's risk factors. Method: Sixty-six patients with stage II and III cervical cancer receiving Paxus (Paclitaxel)-Cisplatin at the second or the third cycle were enrolled. NVR was measured by the Index of Nausea, Vomiting and Retching (INVR) at the second day of their chemotherapy. This current study included only patients with age ranged between 32 to 65 years (M = 47.15, SD = 9.64, min-max age 35 – 65 years). Result: The result showed that the NVR score was at a moderate level. Younger subjects (age 32-50 years old) reported significantly higher NVR scores than that of older subjects (age 51-65 years old) (t = 2.76, p = .007). The subjects with higher anxiety scores reported significantly higher NVR scores than those with lower anxiety scores (t = -2.41, p = .019). Subjects who had experience in motion sickness had significantly higher NVR scores (M = 12.69, SD = 2.60) than those who did not (M = 9.23, SD = 2.86) and the difference was statistically significant (t = 4.98, p <.01). Meanwhile, no significant difference was found between subjects who reported their expectation to have nausea and those who did not (t = 0.08, p = .94). Conclusion: The findings provide valuable information regarding NVR and the individual risk factors among patients with cervical cancer undergoing chemotherapy. Nurses should assess the anxiety level and a history of motion sickness of patients planned for chemotherapy and offer preventive interventions to prevent and control NVR occurrence and its distress
The effect of the motion of the Sun on the light-time in interplanetary relativistic experiments
In 2002 a measurement of the effect of solar gravity upon the phase of
coherent microwave beams passing near the Sun has been carried out with the
Cassini mission, allowing a very accurate measurement of the PPN parameter
. The data have been analyzed with NASA's Orbit Determination Program
(ODP) in the Barycentric Celestial Reference System, in which the Sun moves
around the centre of mass of the solar system with a velocity of
about 10 m/sec; the question arises, what correction this implies for the
predicted phase shift. After a review of the way the ODP works, we set the
problem in the framework of Lorentz (and Galilean) transformations and evaluate
the correction; it is several orders of magnitude below our experimental
accuracy. We also discuss a recent paper \cite{kopeikin07}, which claims wrong
and much larger corrections, and clarify the reasons for the discrepancy.Comment: Final version accepted by Classical and Quantum Gravity (8 Jan. 2008
Multicast broadcast services support in OFDMA-based WiMAX systems [Advances in mobile multimedia]
Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide'differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency
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