Distribution Of Vertices Research Articles

Observation of Two-Proton Radioactivity ofMg19by Tracking the Decay Products

We have observed the two-proton radioactivity of the previously unknown (19)Mg ground state by tracking the decay products in-flight. For the first time, the trajectories of the 2p-decay products, (17)Ne+p+p, have been measured by using tracking microstrip detectors which allowed us to reconstruct the 2p-decay vertices and fragment correlations. The half-life of (19)Mg deduced from the measured vertex distribution is 4.0(15) ps in the system of (19)Mg. The Q value of the 2p decay of the (19)Mg ground state inferred from the measured p-p-(17)Ne correlations is 0.75(5) MeV.

BACKGROUND STUDIES FOR SINGLE MUON MEASUREMENTS IN Au+Au COLLISIONS AT $\sqrt{^SNN} = 200 GeV$ IN THE PHENIX EXPERIMENT AT RHIC

We present background studies for single muon measurements in Au + Au collisions at [Formula: see text]. To estimate the background coming from the high multiplicity, we applied the half octant swapping method. The swapped data was compared with the real data, and we know that the background ratio doesn't depend on the vertex distribution as already expected.

Growing networks under geographical constraints

Inspired by the structure of technological weblike systems, we discuss network evolution mechanisms which give rise to topological properties found in real spatial networks. Thus, we suggest that the peculiar structure of transport and distribution networks is fundamentally determined by two factors. These are the dependence of the spatial interaction range of vertices on the vertex attractiveness (or importance within the network) and on the inhomogeneous distribution of vertices in space. We propose and analyze numerically a simple model based on these generating mechanisms which seems, for instance, to be able to reproduce known structural features of the Internet.

Ultra-small scale-free geometric networks

We consider a family of long-range percolation models (Gp)p>0on ℤdthat allow dependence between edges and have the following connectivity properties forp∈ (1/d, ∞): (i) the degree distribution of vertices inGphas a power-law distribution; (ii) the graph distance between pointsxandyis bounded by a multiple of logpdlogpd|x-y| with probability 1 -o(1); and (iii) an adversary can delete a relatively small number of nodes fromGp(ℤd∩ [0,n]d), resulting in two large, disconnected subgraphs.

Ultra-small scale-free geometric networks

We consider a family of long-range percolation models (G p ) p>0 on ℤ d that allow dependence between edges and have the following connectivity properties for p ∈ (1/d, ∞): (i) the degree distribution of vertices in G p has a power-law distribution; (ii) the graph distance between points x and y is bounded by a multiple of log pd log pd | x - y | with probability 1 - o(1); and (iii) an adversary can delete a relatively small number of nodes from G p (ℤ d ∩ [0, n] d ), resulting in two large, disconnected subgraphs.

Evidence for a neurophysiologic auditory deficit in children with benign epilepsy with centro-temporal spikes

Benign focal epilepsy in childhood with centro-temporal spikes (BECTS) is one of the most common forms of epilepsy. Recent studies have questioned the benign nature of BECTS, as they have revealed neuropsychological deficits in many domains including language. The aim of this study was to investigate whether the epileptic discharges during the night have long-term effects on auditory processing, as reflected on electrophysiological measures, during the day, which could underline the language deficits. In order to address these questions we recorded base line electroencephalograms (EEG), sleep EEG and auditory event related potentials in 12 children with BECTS and in age- and gender-matched controls. In the children with BECTS, 5 had unilateral and 3 had bilateral spikes. In the 5 patients with unilateral spikes present during sleep, an asymmetry of the auditory event related component (P85-120) was observed contralateral to the side of epileptiform activity compared to the normal symmetrical vertex distribution that was noted in all controls and in 3 the children with bilateral spikes. In all patients the peak to peak amplitude of this event related potential component was statistically greater compared to the controls. Analysis of subtraction waveforms (deviant - standard) revealed no evidence of a mismatch negativity component in any of the children with BECTS. We propose that the abnormality of P85-120 and the absence of mismatch negativity during wake recordings in this group may arise in response to the long-term effects of spikes occurring during sleep, resulting in disruption of the evolution and maintenance of echoic memory traces. These results may indicate that patients with BECTS have abnormal processing of auditory information at a sensory level ipsilateral to the hemisphere evoking spikes during sleep.

Complexity Analysis of Yeast Proteome Network

Topological and compositional complexity of protein-protein networks is assessed in a variety of ways making use of graph theory and information theory. The methodology used is borrowed from mathematical chemistry and includes complexity descriptors such as substructure count, overall connectivity, walk count, and information on various vertex distributions. The approach is applied to the (incomplete) proteome of Saccharomyces cerevisiae containing 232 protein complexes of a total of 1,440 proteins. The proteome network and each of its nine functional subsets of protein complexes are disconnected graphs, containing a number of noninteracting species and a major component. A weighted edge between two vertices in these graphs stands for the number of shared proteins between the respective complexes. The major component is a highly connected, 'small-world' network, in which the average vertex distance between protein complexes does not exceed 2.2 (2.4 for the entire proteome), whereas the maximum distance does not exceed 4 (or 5 for the proteome). The vertex degree distribution in the major proteome component with 199 complexes follows the power law P(k) approximately k(-gamma), with gamma approximately = 1.7. The analysis of the functional organization of the yeast proteome has shown that, for any pair of biological functions, there always exist many proteins that can perform both functions. The potential application of the quantitative proteome descriptors discussed includes quantitative relationships between the structure and biological action of dynamic protein complexes in changing environment, identification of targets for markers/drugs, as well as system analysis and comparative studies of proteomes.

A Tabular Approach Memory-Based Learning

One type of machine learning, called memory-based learning, which is characterized by memorization of observed events, has been investigated. Given an input vector, some data are retrieved from a memory and fed to an output computational function. Existing memory-based schemes were usually introduced, discussed, and treated as different, unrelated techniques. In this paper, we unify them into one category. A Memory-Based Learning Structure (MBLS) receives training samples and stores data at memory locations associated with selected (fired) vertices, which are assigned points in the input domain. Memory-based learning that uses a structured vertex distribution is categorized as a tabular approach. One merit of a tabular MBLS is that the size of allocated memory can be pre-determined and much smaller than the number of available observations. Another advantage is that the training process filters out noise automatically and makes the MBLS less sensitive. Since data are stored in memory directly addressable by queries, data retrieving is fast and memorization of vertex locations is unnecessary.

A first level trigger subsystem CIP2k for the H1 experiment at HERA

The ep-collider HERA at DESY and the high energy physics experiment H1 were upgraded in the years 2000–2002. A specific luminosity three times higher than before has recently been observed. To cope with the higher luminosity and the more complex background situation a set of five new cylindrical multiwire proportional chambers (CIP2k) were built providing information to distinguish between beam-gas induced background events and true ep-interactions within 2.3 microseconds on a first level trigger stage using all channels of the chambers. The five cylindrical chambers with a cathode pad readout have each a 16 fold segmentation of the azimuth angle and a segmentation of about 120 in z along the beam axis. The total number of readout channels amounts to 9600. Groups of 60 cathode pads are read out via striplines by a custom designed readout chip (CIPix). The on-chamber electronics digitizes and multiplexes the data and sends it via optical links to the trigger and data acquisition system at a rate of about 10 GBit/s per optical link. A histogram of the vertex distribution along the beam axis of the tracks crossing the chamber is calculated by the trigger system. From this histogram trigger informations are derived dividing the histogram in regions of background and physics events. The tracking algorithm is based on bit pattern comparison of pad data. Field-programmable gate arrays (FPGA) were chosen to accomplish this complex and highly parallelized task. In addition the FPGAs contain pipelines to store the chamber data making it possible to read out the information if a trigger occurs. The trigger, data acquisition and high voltage system are controlled and monitored by the experiment control system (ECS) based on commercial software called PVSSII.

Two-proton radioactivity search

Two-proton radioactivity, a spontaneous breakup of elements with emission of two protons, was predicted to exist near the proton drip line by V.I. Goldansky long time ago. The recent theoretical and experimental progress in a search for such an exotic nuclear decay is reviewed. In theory, the new three-body model which treats two-proton radioactivity as a genuine three-particle nuclear decay is considered. In experiment, the first evidence for two-proton decay of 45Fe is described. Four atoms of 45Fe, produced at the fragment separator of GSI, decayed via particle emission with a total energy of 1.1(1) MeV and a half-life of 3.2 −1.0 +2.6 ms. A possible experiment for a direct observation of two-proton emission from the ground state of 19Mg is considered for its decay in-flight. The half-life of 19Mg, as well as proton-proton correlations, might be derived from the distribution of the 19Mg decay vertices extrapolated from the measured trajectories of all fragments.

Relationship between Penrose vertices and decagonal covering configurations

Two-dimensional quasicrystals are generally described by the Penrose tiling model. An alternative is the cluster covering approach developed recently. There exists a correspondence between the two schemes. The distributions of rhombus vertices in Penrose tilings and the nearest neighbor configurations in the decagonal covering structures are studied. Their occurrence probabilities are expressed in terms of the powers of the golden mean τ and their relationship is obtained.

Performance of the NOMAD-STAR detector

The NOMAD-STAR detector is a silicon vertex detector installed in the NOMAD spectrometer at the CERN SPS neutrino beam. It consists of four layers of a passive boron carbide target with a total mass of 45 kg and five layers of 600 single-sided silicon microstrip detectors covering a total area of 1.14 m 2 . About 11,500ν μ charged current interactions were reconstructed in the fiducial volume of NOMAD-STAR from the neutrino run in 1998. The potential use of silicon detectors for ν μ(ν e)↔ν τ oscillations depends on the observation of the τ candidates by the experimental signature of a large impact parameter, in the case of the one prong decay of the τ, or a double vertex, in the case of the three prong decay. The main aim of NOMAD-STAR is to measure the impact parameter and vertex distributions of charged current interactions, which constitute the main backgrounds for the oscillation signals, to understand the significance of a potential signal in a future experiment. The present paper describes the experience gained in the operation of this silicon vertex detector, and the performance achieved with it.

Vertex counting: Statistical distribution of vertices in large sets of tree diagrams

We study the problem of determining the distribution of vertices of a particular given type in the set of all Feynman tree graphs in quantum field theories. We show that in almost all cases a Gaussian distribution arises asymptotically, and we compute the mean and variance of this distribution for several theories. We show that the distribution's ”fine structure”, arising from topological sum rules, can be obtained.

Magnetic interaction among particles in Co–Cr–Ta media and Co/Pt multilayered media evaluated by anomalous Hall effect

A new method for evaluating magnetic interaction among the particles in perpendicular magnetic recording layers under canted magnetic field has been proposed using anomalous Hall effect (AHE) measurement and vibrating sample magnetometer (VSM) measurement. Initial curves and magnetic hysteresis loops were measured to determine ΔM, an evaluation index to estimate interaction using the relation as ΔM=Minit−0.5×(Mup+Mdown). The degree of interaction ΔM can be determined as a vector by combining the results obtained by VSM and AHE measurements. Distribution of vertices (DOV) of ΔM can be regarded as a degree of interaction in a particular direction. The DOV of ΔM in Co–Cr–Ta thin film extended along the in-plane direction and showed gradual convergence as the applied field direction canted toward the film plane. This can be an indication that the magnetic particles in the Co–Cr–Ta thin film tend to incline to the applied field direction individually. On the other hand, the DOV of ΔM in Co/Pt multilayered thin film extended along the perpendicular direction and the shape of the trajectory of ΔM remained unchanged though the applied field direction deviated widely from the normal direction. This may be due to the strong perpendicular anisotropy in the Co/Pt multilayered thin film.

Array of Cherenkov radiators for PHOBOS at RHIC

An array of Cherenkov radiators (“the Cherenkov counters”) for the measurement of the vertex position of heavy-ion gold–gold collisions for the PHOBOS experiment at relativistic heavy ion collider is described. These simple, versatile, and highly efficient detectors provide a low bias and easily understood hardware (on-line) vertex trigger. This trigger is ready for the data-acquisition system in about 650 ns . The position resolution of the vertex distribution found by the Cherenkov counters is approx. 4 cm and is very stable as function of the centrality of the collisions. The general characteristics of the Cherenkov counters, their design parameters, and performance are presented, along with the implementation of the hardware vertex trigger used for PHOBOS during the 2001 run.

ON THE FORMULATION OF TIME-SPACE PRISMS TO MODEL CONSTRAINTS ON PERSONAL ACTIVITY-TRAVEL ENGAGEMENT

The notion of time-space prisms has often been used in the context of describing activity-travel patterns of individuals. This paper presents a methodology for estimating the temporal vertices of time-space prisms using the stochastic frontier modeling technique. Observed trip starting and ending times are used as dependent variables and socio-economic characteristics and commute characteristics serve as independent variables. The models are found to offer plausible results indicating that temporal vertices of time-space prisms, though unobservable, can be estimated based on temporal characteristics of observed activity-travel patterns. Comparisons of stochastic frontier models of prism vertices and the distributions of prism vertices are presented using two activity data sets collected in the United States – San Francisco and Miami. Differences and similarities in temporal vertex locations are highlighted in the paper.

Anomalous percolation properties of growing networks.

We describe the anomalous phase transition of the emergence of the giant connected component in scale-free networks growing under mechanism of preferential linking. We obtain exact results for the size of the giant connected component and the distribution of vertices among connected components. We show that all the derivatives of the giant connected component size S over the rate b of the emergence of new edges are zero at the percolation threshold b(c), and S infinity exp[-d(gamma)(b-b(c))(-1/2)], where the coefficient d is a function of the degree distribution exponent gamma. In the entire phase without the giant component, these networks are in a "critical state." The probability P(k) that a vertex belongs to a connected component of a size k is of a power-law form. At the phase transition point, P(k) approximately 1/(k ln k)(2). In the phase with the giant component, P(k) has an exponential cutoff at k(c) approximately 1/S. In the simplest particular case, we present exact results for growing exponential networks.

An efficient shape-based approach to image retrieval

We consider the problem of finding the best match for a given query shape among candidate shapes stored in a shape base. This is central to a wide range of applications, such as, digital libraries, digital film databases, environmental sciences, and satellite image repositories. We present an efficient matching algorithm built around a novel similarity criterion and based on shape normalization about the shape's diameter, which reduces the effects of noise or limited accuracy during the shape extraction procedure. Our matching algorithm works by gradually “fattening” the query shape until the best match is discovered. The algorithm exhibits poly-logarithmic time behavior assuming uniform distribution of the shape vertices in the locus of their normalized positions.

Extracting the flavour structure of a baryon-number R-parity violating coupling at the LHC

The detection of the flavour content of jets produced from R-parity violating neutralino decays is investigated in the case where one baryon-number violating coupling dominates. Simulations are performed of the ATLAS experiment at the LHC for all couplings, other than lambda"_tjk since neutralino decays through these couplings are very suppressed. Secondary vertex distributions and muons produced by heavy-quark (b- and c-) jets allow discrimination between LSP decay modes. The dominant coupling can be identified at better than 3.5 sigma in almost all cases, with the only remaining ambiguity caused by the inability to distinguish strange from down quarks.

Crumpled triangulations and critical points in 4D simplicial quantum gravity

We estimate analytically the critical coupling separating the weak and the strong coupling regime in 4D simplicial quantum gravity to be located at k 2 crit ⋍ 1.3093 . By carrying out a detailed geometrical analysis of the strong coupling phase we argue that the distribution of dynamical triangulations with singular vertices and singular edges, dominating in such a regime, is characterized by distinct subdominating peaks. The presence of such peaks generates volume-dependent pseudo-critical points: k 2 crit (N 4 = 32 000) ⋍ 1.25795,k 2 crit (N 4 = 48 000) ⋍ 1.26752 , k 2 crit (N 4 = 64 000) ⋍ 1.27466 , etc., which appear in good agreement with available Monte Carlo data. Under a certain scaling hypothesis we analytically characterize the (canonical) average value, c 1 ( N 4; k 2) = 〈 N 0〉/ N 4, and the susceptibility, c 2( N 4; k 2) = (〈 N 0 2〉 − 〈 N 0〉 2)/ N 4, associated with the vertex distribution of the 4D triangulations considered. Again, the resulting analytical expressions are found in quite a good agreement with their Monte Carlo counterparts.