Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110<m(H)<600 GeV. The analysis uses data corresponding to an integrated luminosity of 4.7 fb(-1) recorded by the CMS detector in pp collisions at √s=7 TeV from the LHC. Seventy-two events are observed with four-lepton invariant mass m(4ℓ)>100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.

Search for signatures of extra dimensions in the diphoton mass spectrum at the large hadron collider

A search for signatures of extra spatial dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s=7 TeV corresponding to an integrated luminosity of 2.2 fb(-1). In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.

Study of Z Boson Production in PbPb Collisions at √S(NN)=2.76 TeV

A search for Z bosons in the μ(+)μ(-) decay channel has been performed in PbPb collisions at √S(NN)=2.76  TeV with the CMS detector at the LHC, in a 7.2 μb(-1) data sample. The number of opposite-sign muon pairs observed in the 60-120 GeV/c(2) invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of [33.8±5.5(stat)±4.4(syst)]×10(-8), in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.

Measurement of dijet angular distributions and search for quark compositeness in pp collisions at √s = 7 TeV

Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at √s = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 pb⁻¹. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of Λ⁺ = 5.6 TeV (Λ⁻ = 6.7 TeV) for destructive (constructive) interference is obtained at the 95% confidence level.

Search for pair production of second-generation scalar leptoquarks in pp collisions at √s = 7 TeV

A search for pair production of second-generation scalar leptoquarks in the final state with two muons and two jets is performed using proton-proton collision data at √s = 7 TeV collected by the CMS detector at the LHC. The data sample used corresponds to an integrated luminosity of 34 pb⁻¹. The number of observed events is in good agreement with the predictions from the standard model processes. An upper limit is set on the second-generation leptoquark cross section times β² as a function of the leptoquark mass, and leptoquarks with masses below 394 GeV are excluded at a 95% confidence level for β = 1, where β is the leptoquark branching fraction into a muon and a quark. These limits are the most stringent to date.

Search for pair production of first-generation scalar leptoquarks in pp collisions at √s = 7 TeV

A search for pair production of first-generation scalar leptoquarks is performed in the final state containing two electrons and two jets using proton-proton collision data at √s = 7 TeV. The data sample used corresponds to an integrated luminosity of 33 pb⁻¹ collected with the CMS detector at the CERN LHC. The number of observed events is in good agreement with the predictions for the standard model background processes, and an upper limit is set on the leptoquark pair production cross section times β² as a function of the leptoquark mass, where β is the branching fraction of the leptoquark decay to an electron and a quark. A 95% confidence level lower limit is set on the mass of a first-generation scalar leptoquark at 384 GeV for β = 1, which is the most stringent direct limit to date.

Dijet azimuthal decorrelations in pp collisions at √s=7 TeV

Measurements of dijet azimuthal decorrelations in pp collisions at √s=7 TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9 pb⁻¹. The results are compared to predictions from perturbative QCD calculations and various Monte Carlo event generators. The dijet azimuthal distributions are found to be sensitive to initial-state gluon radiation.

Measurement of the B(+) production cross section in pp collisions at sqrt[s]=7 TeV

Measurements of the total and differential cross sections dσ/dp(T)(B) and dσ/dy(B) for B(+) mesons produced in pp collisions at sqrt[s]=7  TeV are presented. The data correspond to an integrated luminosity of 5.8  pb(-1) collected by the CMS experiment operating at the LHC. The exclusive decay B(+)→J/ψK(+), with J/ψ→μ(+)μ(-), is used to detect B(+) mesons and to measure the production cross section as a function of p(T)(B) and y(B). The total cross section for p(T)(B)>5  GeV and |y(B)|<2.4 is measured to be 28.1±2.4±2.0±3.1  μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement.

Measurement of the isolated prompt photon production cross section in pp collisions at √s=7 TeV

The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E(T)(γ) in pp collisions at √s=7  TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9  pb(-1). Photons are required to have a pseudorapidity |η(γ)|<1.45 and E(T)(γ)>21  GeV, covering the kinematic region 0.006<x(T)<0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations.

Search for stopped Gluinos in pp collisions at square root s=7 TeV

The results of the first search for long-lived gluinos produced in 7 TeV pp collisions at the CERN Large Hadron Collider are presented. The search looks for evidence of long-lived particles that stop in the CMS detector and decay in the quiescent periods between beam crossings. In a dataset with a peak instantaneous luminosity of 1×10(32) cm-2 s-1, an integrated luminosity of 10 pb-1, and a search interval corresponding to 62 hours of LHC operation, no significant excess above background was observed. Limits at the 95% confidence level on gluino pair production over 13 orders of magnitude of gluino lifetime are set. For a mass difference mg - mχ1(0) >100 GeV/c2, and assuming BR(g→gχ1(0))=100%, mg < 370 GeV/c2 are excluded for lifetimes from 10 μs to 1000 s.

Search for quark compositeness with the dijet centrality ratio in pp collisions at √s=7 TeV

A search for quark compositeness in the form of quark contact interactions, based on hadronic jet pairs (dijets) produced in proton-proton collisions at √s=7 TeV, is described. The data sample of the study corresponds to an integrated luminosity of 2.9 pb(-1) collected with the CMS detector at the LHC. The dijet centrality ratio, which quantifies the angular distribution of the dijets, is measured as a function of the invariant mass of the dijet system and is found to agree with the predictions of the standard model. A statistical analysis of the data provides a lower limit on the energy scale of quark contact interactions. The sensitivity of the analysis is such that the expected limit is 2.9 TeV; because the observed value of the centrality ratio at high invariant mass is below the expectation, the observed limit is 4.0 TeV at the 95% confidence level.

Search for dijet resonances in 7 TeV pp collisions at CMS

A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9 pb⁻¹ collected by the CMS experiment at the Large Hadron Collider. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E6 diquarks, in specific mass intervals. This extends previously published limits on these models.

First measurement of Bose-Einstein correlations in proton-proton collisions at √s=0.9 and 2.36 TeV at the LHC

Bose-Einstein correlations have been measured using samples of proton-proton collisions at 0.9 and 2.36 TeV center-of-mass energies, recorded by the CMS experiment at the CERN Large Hadron Collider. The signal is observed in the form of an enhancement of pairs of same-sign charged particles with small relative four-momentum. The size of the correlated particle emission region is seen to increase significantly with the particle multiplicity of the event.

Cortical Cell Assemblies: A Possible Mechanism for Motor Programs

The concept of a motor program has been used to interpret a diverse range of empirical findings related to preparation and initiation of voluntary movement. In the absence of an underlying mechanism, its exploratory power has been limited to that of an analogy with running a stored computer program. We argue that the theory of cortical cell assemblies suggests a possible neural mechanism for motor programming. According to this view, a motor program may be conceptualized as a cell assembly, which is stored in the form of strengthened synaptic connections between cortical pyramidal neurons. These connections determine which combinations of corticospinal neurons are activated when the cell assembly is ignited. The dynamics of cell assembly ignition are considered in relation to the problem of serial order. These considerations lead to a plausible neural mechanism for the programming of movements and movement sequences that is compatible with the effects of precue information and sequence length on reaction times. Anatomical and physiological guidelines for future quantitative models of cortical cell assemblies are suggested. By taking into account the parallel re-entrant loops between the cerebral cortex and basal ganglia, the theory of cortical cell assemblies suggests a mechanism for motor plans that involve longer sequences. The suggested model is compared with other existing neural network models for motor programming.

Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at square root of s = 7 TeV

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at square root of s = 7  TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dN(ch)/dη|(|η|<0.5) = 5.78 ± 0.01(stat) ± 0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from square root of s = 0.9 to 7 TeV is [66.1 ± 1.0(stat) ± 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 ± 0.005(stat) ± 0.015(syst)  GeV/c. The results are compared with similar measurements at lower energies.

Ocular photodynamic therapy with verteporfin for choroidal neovascularization secondary to ocular histoplasmosis syndrome

PURPOSE

To evaluate the use of ocular photodynamic therapy (OPT) with verteporfin in patients with choroidal neovascularization (CNV) from ocular histoplasmosis syndrome (OHS) and to compare these results with those for a natural history group.

METHODS

A retrospective chart review was performed to identify cases of CNV secondary to OHS treated with OPT. Complete data were available for 38 of 41 eligible eyes. Data regarding the following variables were abstracted from the patient charts: demographic characteristics, previous surgery, angiographic features, number and timing of treatments with OPT, follow-up time, and visual acuity. The visual acuity results of eyes receiving photodynamic therapy were compared with those for a natural history cohort.

RESULTS

On average, OHS patients who received treatment developed 0.88 line of visual improvement. Visual acuity improved or stayed the same in 69% (22 of 32) of eyes, improved by > or = 2 lines in 44% (14 of 32), and improved by > or = 4 lines in 22% (7 of 32). Patients who received OPT were 2.07 times more likely to have improved or constant vision than were those in the natural history group as described in one retrospective series (odds ratio = 2.07; 95% confidence interval, 0.78-5.56; P = 0.162). Thirty-eight percent (12 of 32) of eyes had undergone submacular surgery for CNV before any OPT.

CONCLUSIONS

Ocular photodynamic therapy with verteporfin may be beneficial in patients with CNV secondary to OHS, even in the setting of previous submacular surgery.

Long-term survival characteristics of 832 resin-retained bridges and splints provided in a post-graduate teaching hospital between 1978 and 1993

The clinical performance of 832 resin-retained bridges and splints provided in the adult fixed prosthodontic clinic of a post-graduate teaching hospital was reviewed. Recall data was available for 58.4% of cases and the median survival was 7 years and 10 months. Analysis of clinical variables influencing survival revealed that the design and retainer coverage were significant factors. The experience of the operator carrying out treatment also had a pronounced effect which was not readily explained in terms of the distribution of other significant factors. Resin-retained restorations made with minimal tooth preparation are shown to be capable of extended clinical service and their failure rarely resulted in adverse consequences for the patient. Patient satisfaction with their treatment was reportedly high.

Striatal mechanisms in Parkinson's disease: new insights from computer modeling

We review data and hypotheses concerning the functional anatomy of the striatum and the role of its corticostriatal and nigrostriatal afferents in Parkinson's disease (PD). Starting from molecular mechanisms of glutamatergic and dopaminergic actions in the striatum we have developed a compartmental model of striatal principal neurons that displays a significant degree of biological realism. Simulations of a network of striatal projection neurons under conditions likely to be found in healthy subjects as well as untreated and therapeutic situations of advanced PD provide clues concerning the dynamics of neuronal interactions and their possible effects on downstream motor structures in the generation of positive and negative motor symptoms. We present tentative biological explanations of the symptoms of rigidity and akinesia in PD leading to predictions concerning the origin of abnormal movements and the beneficial effects of dopaminergic treatment. Although these attempts are not yet sufficient to account for the complexity of clinical symptoms found in PD they can guide further empirical research and foster fruitful interactions between experimentalists, theoreticians, and clinicians in unraveling the functional anatomy of the basal ganglia.

Does having to remember the position of a target improve reaction time?

In the monkey, reaction time in a precued delayed response task was found to be faster when the animals had to remember the precue than when it was continually available (Smyrnis, Taira, Ashe, & Georgopoulos, 1992). We investigated whether this reflects a general principle that applies to all types of precued tasks. However, we found the opposite result in a simpler task in humans. Our findings suggest that the beneficial effect of a memory requirement on reaction time in the monkey may reflect an effect of task difficulty, rather than a fundamental process involved in all precued movement tasks.

Surface treatment of gold alloys for resin adhesion

This in vitro study compared three methods of surface treating gold alloys to improve resin adhesion. The tensile bond strengths and modes of failure between specimen pairs cemented with a chemically adhesive resin were recorded. Heat-treated gold alloy specimens were significantly more resistant to bond failure under tensile loading than were either alumina-blasted or tin-plated gold specimens. There was no statistically significant difference in bond failure between alumina-blasted and tin-plated gold specimens. The surface treatment altered the mode of failure from adhesive and/or adhesive-cohesive for alumina-blasted and tinplated gold specimens to cohesive (within the resin) for heat-treated gold specimens. Three case reports are presented to illustrate clinical applications of heat-treated gold alloys.

Interactions of glutamate and dopamine in a computational model of the striatum

A network model of simplified striatal principal neurons with mutual inhibition was used to investigate possible interactions between cortical glutamatergic and nigral dopaminergic afferents in the neostriatum. Glutamatergic and dopaminergic inputs were represented by an excitatory synaptic conductance and a slow membrane potassium conductance, respectively. Neuronal activity in the model was characterized by episodes of increased action potential firing rates of variable duration and frequency. Autocorrelation histograms constructed from the action potential activity of striatal model neurons showed that reducing peak excitatory conductance had the effect of increasing interspike intervals. On the other hand, the maximum value of the dopamine-sensitive potassium conductance was inversely related to the duration of firing episodes and the maximal firing rates. A smaller potassium conductance restored normal firing rates in the most active neurons at the expense of a larger proportion of neurons showing reduced activity. Thus, a homogeneous network with mutual inhibition can produce equally complex dynamics as have been proposed to occur in a striatal network with two neuron populations that are oppositely regulated by dopamine. Even without mutual inhibition it appears that increased dopamine concentrations could partially compensate for the effects of reduced glutamatergic input in individual neurons.

Striatal dopamine in motor activation and reward-mediated learning: steps towards a unifying model

On the basis of behavioural evidence, dopamine is found to be involved in two higher-level functions of the brain: reward-mediated learning and motor activation. In these functions dopamine appears to mediate synaptic enhancement in the corticostriatal pathway. However, in electrophysiological studies, dopamine is often reported to inhibit corticostriatal transmission. These two effects of dopamine seem incompatible. The existence of separate populations of dopamine receptors, differentially modulating cholinergic and glutamatergic synapses, suggests a possible resolution to this paradox. The synaptic enhancement which occurs in reward-mediated learning may also be involved in dopamine-mediated motor activation. The logical form of reward-mediated learning imposes constraints on which mechanisms can be considered possible. Dopamine D1 receptors may mediate enhancement of corticostriatal synapses. On the other hand, dopamine D2 receptors on cholinergic terminals may mediate indirect, inhibitory effects of dopamine on striatal neurons.

Electrically coupled but chemically isolated synapses: dendritic spines and calcium in a rule for synaptic modification

An influential model of learning assumes synaptic enhancement occurs when there is pre- and post-synaptic conjunction of neuronal activity, as proposed by Hebb (1949) and studied in the form of long-term potentiation (LTP). There is evidence that LTP has a post-synaptic locus of control and is triggered by an elevation of intracellular calcium ion concentration, [Ca2+]i. Since synapses which undergo LTP are usually situated on dendritic spines, three effects of spine morphology on this system should be considered: (i) synapses on spines are chemically isolated by the barrier to Ca2+ diffusion due to the spine neck dimensions; (ii) the resistance of the spine neck permits a given synaptic current to bring about greater depolarization (of the spine head membrane) than the same current into a dendrite; while (iii) the spine neck resistance does not significantly attenuate current flow (in the dendrite to spine direction) because of the relatively high impedance of the spine head, and this permits electrical coupling via the dendritic tree. The specificity of LTP to activated synapses on depolarized cells has recently been attributed to special properties of the receptor-linked channel specifically activated by N-methyl-D-aspartate (NMDA). This admits calcium and other ions only when there is both depolarization and receptor activation. However, consideration of point (ii) suggests that, for spines with high resistance necks, the current through a synapse on the spine head will cause sufficient depolarization to unblock the NMDA channel. Thus, the properties of the NMDA channel do not account for the requirement for conjunction of pre- and post-synaptic activity, if these channels are located on the spine head. This suggests that additional mechanisms are required to explain why it is necessary to depolarize the post-synaptic cell in order to induce LTP. As an alternative, it is postulated that there exist voltage-sensitive calcium channels (VSCCs) on the spine head membrane, of a type which require greater membrane depolarization for activation. To generate the greater depolarization required, both pre- and post-synaptic activation would be necessary. If so, the role of dendritic or somatically located NMDA channels may be to "prime" neurons for LTP by enchancing voltage-dependent responses. A corollary is that spine resistance may regulate the threshold number of synapses required to produce LTP. It is predicted that, on spines with very high neck resistance (say, greater than 600 M omega), synaptic current alone may produce sufficient depolarization to activate VSCCs.(ABSTRACT TRUNCATED AT 400 WORDS)