680 research outputs found
Downlink scheduling in CDMA data networks
We identify optimality properties for scheduling downlink transmissions to data users in CDMA networks. For arbitrary-topology networks, we show that under certain idealizing assumptions it is optimal for a base station to transmit to only one data user at a time. Moreover, for data-only networks, we prove that a base station, when on, should transmit at maximum power for optimality. We use these two properties to obtain a mathematical programming formulation for determining the optimal transmission schedule in linear data-only networks, with time allocations playing the role of decision variables. The optimality conditions imply that there exist (i) subsets of outer users on either side of the cell that should be served when only the neighboring base station on the opposite side is on; (ii) a subset of inner users in the center of the cell that should be served when both neighbors are on; (iii) a subset of users in the intermediate regions that should receive transmissions when both neighbors are off. Exploiting these structural properties, we derive a simple search algorithm for finding the optimal transmission schedule in symmetric scenarios. Numerical experiments illustrate that scheduling achieves significant capacity gains over conventional CDMA
The rDNA is biomolecular condensate formed by polymer-polymer phase separation and is sequestered in the nucleolus by transcription and R-loops
The nucleolus is the site of ribosome biosynthesis encompassing the ribosomal DNA (rDNA) locus in a phase separated state within the nucleus. In budding yeast, we find the rDNA locus and Cdc14, a protein phosphatase that co-localizes with the rDNA, behave like a condensate formed by polymer-polymer phase separation, while ribonucleoproteins behave like a condensate formed by liquid-liquid phase separation. The compaction of the rDNA and Cdc14's nucleolar distribution are dependent on the concentration of DNA cross-linkers. In contrast, ribonucleoprotein nucleolar distribution is independent of the concentration of DNA cross-linkers and resembles droplets in vivo upon replacement of the endogenous rDNA locus with high-copy plasmids. When ribosomal RNA is transcribed from the plasmids by Pol II, the rDNA-binding proteins and ribonucleoprotein signals are weakly correlated, but upon repression of transcription, ribonucleoproteins form a single, stable droplet that excludes rDNA-binding proteins from its center. Degradation of RNA-DNA hybrid structures, known as R-loops, by overexpression of RNase H1 results in the physical exclusion of the rDNA locus from the nucleolar center. Thus, the rDNA locus is a polymer-polymer phase separated condensate that relies on transcription and physical contact with RNA transcripts to remain encapsulated within the nucleolus
A CsI(Tl) Scintillating Crystal Detector for the Studies of Low Energy Neutrino Interactions
Scintillating crystal detector may offer some potential advantages in the
low-energy, low-background experiments. A 500 kg CsI(Tl) detector to be placed
near the core of Nuclear Power Station II in Taiwan is being constructed for
the studies of electron-neutrino scatterings and other keV-MeV range neutrino
interactions. The motivations of this detector approach, the physics to be
addressed, the basic experimental design, and the characteristic performance of
prototype modules are described. The expected background channels and their
experimental handles are discussed.Comment: 34 pages, 11 figures, submitted to Nucl. Instrum. Method
Refined Interfaces for Compositional Verification
The compositional verification approach of Graf & Steffen aims at avoiding state space explosion for individual processes of a concurrent system. It relies on interfaces that express the behavioural constraints imposed on each process by synchronization with the other processes, thus preventing the exploration of states and transitions that would not be reachable in the global state space. Krimm & Mounier, and Cheung & Kramer proposed two techniques to generate such interfaces automatically. In this report, we propose a refined interface generation technique that derives the interface of a process automatically from the examination of (a subset of) concurrent processes. This technique is applicable to formalisms where concurrent processes are composed either using synchronization vectors or process algebra parallel composition operators (including those of CCS, CSP, muCRL, LOTOS, and E-LOTOS). We implemented this approach in the EXP.OPEN 2.0 tool of the CADP toolbox. Several experiments indicate state space reductions by more than two orders of magnitude for the largest processes
Measurement of Cosmic-ray Muon-induced Spallation Neutrons in the Aberdeen Tunnel Underground Laboratory
AbstractMuon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
Measurement of the Probability of Gluon Splitting into Charmed Quarks in Hadronic Z Decays
We have measured the probability, n(g->cc~), of a gluon splitting into a
charm-quark pair using 1.7 million hadronic Z decays collected by the L3
detector. Two independent methods have been applied to events with a three-jet
topology. One method relies on tagging charmed hadrons by identifying a lepton
in the lowest energy jet. The other method uses a neural network based on
global event shape parameters. Combining both methods, we measure n(g->cc~)=
[2.45 +/- 0.29 +/- 0.53]%
Search for Extra Dimensions in Boson and Fermion Pair Production in e+e- Interactions at LEP
Extra spatial dimensions are proposed by recent theories that postulate the
scale of gravity to be of the same order as the electroweak scale. A sizeable
interaction between gravitons and Standard Model particles is then predicted.
Effects of these new interactions in boson and fermion pair production are
searched for in the data sample collected at centre-of-mass energies above the
Z pole by the L3 detector at LEP. In addition, the direct production of a
graviton associated with a Z boson is investigated. No statistically
significant hints for the existence of these effects are found and lower limits
in excess of 1 TeV are derived on the scale of this new theory of gravity
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP
We report on measurements of the triple-gauge-boson couplings of the W boson
in e+e- collisions with the L3 detector at LEP. W-pair, single-W and
single-photon events are analysed in a data sample corresponding to a total
luminosity of 76.7 pb^{-1} collected at centre-of-mass energies between 161 GeV
and 183 GeV. CP-conserving as well as both C- and P-conserving
triple-gauge-boson couplings are determined. The results, in good agreement
with the Standard-Model expectations, confirm the existence of the self
coupling among the electroweak gauge bosons and constrain its structure
- âŠ