The accuracy of dynamic wedge dose computation in the ADAC Pinnacle RTP system

The nonphysical wedge is a modality that uses computer‐controlled jaw motion to generate wedge‐shaped dose distributions. There are Varian enhanced dynamic wedges (EDWs) and Siemens virtual wedges (VWs). We recently commissioned dynamic wedges on both Varian and Siemens LINACs. The beam data, acquired with a Wellhöfer chamber array and a Sun Nuclear profiler, are used for modeling in the ADAC Pinnacle system. As recommended by ADAC, only a limited number of beam data is measured and used for beam modeling. Therefore, the dose distributions of dynamic wedges generated by Pinnacle must be examined. Following the commissioning of the dynamic wedges, we used Pinnacle to generate a number of dose distributions with different energies, wedge angles, field sizes, and depths. The computed data from Pinnacle are then compared with the measured data.

The deviations of the output factor in all square and rectangular fields are mostly within 2.0% for both EDW and VW. For asymmetric fields, the deviations are within 3%. However, exceptions of differences more than 3% have been found in a larger field and large wedge combinations. The precision of the beam profiles generated by Pinnacle is also evaluated. As a result of this investigation, we present a scope of quality assurance tests that are necessary to ensure acceptable consistency between the delivered dose and the associated treatment plan when dynamic wedges are applied.

PACS numbers: 8753 Dq, 87.53.Xd

Recovery of hippocampal cell proliferation and BDNF levels, both of which are reduced by repeated restraint stress, is accelerated by chronic venlafaxine

The present study investigated the poststress (PS) cellular and molecular changes in the hippocampus of rats subjected to repeated restraint stress (RS) and the effects of chronic administration of an antidepressant drug, venlafaxine, on these changes. It was found that RS suppressed hippocampal cell proliferation, decreased brain-derived neurotrophic factor (BDNF) levels, and increased both the levels of copper/zinc superoxide dismutase (Cu/Zn-SOD) and the number of Cu/Zn-SOD immunostained hippocampal interneurons. In venlafaxine-treated rats, the changes in cell proliferation, BDNF levels, and the number of Cu/Zn-SOD interneurons returned to control levels on PS Days 21, 14, 7, respectively. In vehicle-injected rats, BDNF and the number of Cu/Zn-SOD interneurons returned to control levels on PS Days 21 and 14, respectively, but cell proliferation was still suppressed on PS Day 21. The stress-induced elevation of Cu/Zn-SOD protein remained during the 3-week PS period, and it was further increased by about 20% after 3 weeks of venlafaxine administration.

Search for supersymmetry with gauge-mediated breaking in diphoton events at D0

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.

Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

Effect of resonator dimensions on nonlinear standing waves

An investigation of the effect of resonator dimensions on nonlinear standing waves in shaped resonators is conducted. Simple forms of the shear viscosity term in the momentum equations are developed for an axisymmetric (2D) resonator and a low aspect ratio rectangular (3D) resonator. The cross sections of the resonators are exponentially expanded and the one-dimensional wave equations are solved by using the Galerkin's method. The quality factors, pressure waveforms, compression ratios, and resonance frequencies are calculated for different dimensionless cross sections and lengths of the resonators. The results show that, apart from the resonator length, the ratio of the cross-section dimension to the length of the resonator is an important parameter. If the ratio is greater than 0.04, the characteristics of the shaped resonator are not affected significantly. However, when the ratio is less than 0.01, the resonance becomes weak, the compression ratio drops substantially, and the frequency response changes as well.

Observation and properties of the X(3872) decaying to J/psipi(+)pi(-) in pp collisions at sqrt[s]=1.96 TeV

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

Search for doubly charged higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in pp collisions at sqrt[s]=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

A precision measurement of the mass of the top quark

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Search for narrow tt resonances in pp collisions at square root of (s)=1.8 TeV

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

Anomalous dispersion relations by symmetry breaking in axially uniform waveguides

We show that modes of axially uniform waveguides of arbitrary cross section can be made to have anomalous dispersion relations resulting from strong repulsion between two modes. When the axial wave vector k is 0, the two modes have different TE/TM symmetry and thus can be brought arbitrarily close to an accidental frequency degeneracy. For nonzero k, the symmetry is broken causing the modes to repel. When the modes are sufficiently close together this repulsion leads to unusual features such as extremely flattened dispersion relations, backward waves, zero group velocity for nonzero k, atypical divergence of the density of states, and nonzero group velocity at k=0.

Increased oxidative stress is associated with chronic intermittent hypoxia-mediated brain cortical neuronal cell apoptosis in a mouse model of sleep apnea

Chronic intermittent hypoxia (CIH), as occurs in obstructive sleep apnea (SA), is associated with substantial cortico-hippocampal damage leading to impairments of neurocognitive, respiratory and cardiovascular functions. Previous studies in a rat model have shown that CIH increases brain cortical neuronal cell death. However, the molecular events leading to CIH-mediated neuronal cell death remain largely undefined. The oscillation of O2 concentrations during CIH remarkably mimics the processes of ischemia/re-oxygenation and could therefore increase cellular production of reactive oxygen species (ROS). We extended the CIH paradigm to a mouse model of SA to identify the molecular mechanisms underlying cortical neuronal cell death. A significant increase of ROS production in mouse brain cortex and cortical neuronal cells was detected by fluorescent oxidation assays upon exposure of mice to CIH, followed by increased expression of oxidative stress response markers, c-Fos, c-Jun and NF-kappaB in mouse brain cortex, as revealed by immunohistochemical and LacZ reporter assays respectively. Long-term exposure of mice to CIH increased the levels of protein oxidation, lipid peroxidation and nucleic acid oxidation in mouse brain cortex. Furthermore, exposure of mice to CIH induced caspase-3 activation and increased some cortical neuronal cell apoptosis. On the other hand, transgenic mice overexpressing Cu,Zn-superoxide dismutase exposed to CIH conditions had a lower level of steady-state ROS production and reduced neuronal apoptosis in brain cortex compared with that of normal control mice. Taken together, these findings suggest that the increased ROS production and oxidative stress propagation contribute, at least partially, to CIH-mediated cortical neuronal apoptosis and neurocognitive dysfunction.

A novel applicator for low-dose-rate brachytherapy of gynecological cancers

The standard low-dose-rate (LDR) delivery system utilized in the definitive management of patients with cervical carcinoma involves an intrauterine tandem and a pair of vaginal colpostats (ovoids). This well-known application system may deliver inadequate dosage if the tumor extends to the lower vaginal mucosa. During the gauze packing of the ovoids, either operator error or narrowing of the vaginal apex can result in mal-alignment of the colpostats and subsequent inadequate dosing to the ecto-cervix. A novel vaginal cylinder has been designed to address these concerns. Beginning January 1, 2001, patients with cancer of the cervix, endometrium, or vagina requiring LDR brachytherapy have been enrolled into an institutionally sanctioned clinical trial. As of May 31, 2001, a total of 11 patients have been entered but only 10 were successfully implanted with the test device. Patient follow-up has ranged from 0.81 years to 1.2 years (median: 0.96 years). Using our study applicator, all patients received within 10% of the preimplant prescribed dose to tumor. Also, no one had cumulative dosage that exceeded 10% of the maximum allowed dose to the critical normal tissues. Thus far, all study patients have had no clinical evidence of persistence/recurrence of disease or complications from treatment. The preliminary results presented herein clearly demonstrate the feasibility of this novel LDR vaginal cylinder in the treatment of a variety of clinical situations involving gynecological cancers. Our institutional trial is continuing.

Search for large extra dimensions in the monojet+E(T) channel with the DØ detector

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

Diploid-dependent regulation of gene expression: a genetic cause of abnormal development in fish haploid embryos

A diploid-dependent regulatory mechanism of gene expression for spatial patterning of the eye in vertebrates has been determined by analyzing the phenotypes of haploid goldfish embryos. There are two gene loci in charge of eye spatial patterning during embryonic morphogenesis. The expressional probability for each copy of the two genes in a set of chromosomes is 50%. A pair of genes in two sets of homologous or heterologous chromosomes is 100% and essential for normal gene expression. The haploid condition itself would result in the obstruction of gene expression and abnormal development because the diploid-dependent regulatory apparatus will regulate gene expression in a haploid embryo according to the same rule as in the diploid embryo.

A novel applicator for low-dose-rate brachytherapy of gynecological cancers

The standard low-dose-rate (LDR) delivery system utilized in the definitive management of patients with cervical carcinoma involves an intrauterine tandem and a pair of vaginal colpostats (ovoids). This well-known application system may deliver inadequate dosage if the tumor extends to the lower vaginal mucosa. During the gauze packing of the ovoids, either operator error or narrowing of the vaginal apex can result in mal-alignment of the colpostats and subsequent inadequate dosing to the ecto-cervix. A novel vaginal cylinder has been designed to address these concerns. Beginning January 1, 2001, patients with cancer of the cervix, endometrium, or vagina requiring LDR brachytherapy have been enrolled into an institutionally sanctioned clinical trial. As of May 31, 2001, a total of 11 patients have been entered but only 10 were successfully implanted with the test device. Patient follow-up has ranged from 0.81 years to 1.2 years (median: 0.96 years). Using our study applicator, all patients received within 10% of the preimplant prescribed dose to tumor. Also, no one had cumulative dosage that exceeded 10% of the maximum allowed dose to the critical normal tissues. Thus far, all study patients have had no clinical evidence of persistence/recurrence of disease or complications from treatment. The preliminary results presented herein clearly demonstrate the feasibility of this novel LDR vaginal cylinder in the treatment of a variety of clinical situations involving gynecological cancers. Our institutional trial is continuing.

Search for the production of single sleptons through R-parity violation in pp; collisions at square root (s) =1.8 TeV

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94+/-5 pb(-1). Assuming that R parity is violated via the single coupling lambda'211, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m(0),m(1/2)) and (m(x),m(v)) planes for lambda(')(211)=0.09, 0.08, and 0.07.

Motor performance and motor learning in Lurcher mice

In adult Lurcher mice virtually all cerebellar Purkinje cells have degenerated as a direct consequence of mutant gene action, providing a natural model for studying the effect of cerebellar cortical lesions on the generation of compensatory eye movements. Lurcher mice possess both optokinetic (OKR) and vestibular (VOR) compensatory reflexes. However, clear differences were observed in control of the OKR consisting of a large reduction in gain and a moderate increase in phase lag. Minor differences were also observed in the VOR in that gain and phase lead of the reflex were both increased in Lurcher animals. Subjecting Lurcher animals to eight days of visuovestibular training tested the assumption that increased VOR gain reflected an adaptive mechanism within remaining brainstem oculomotor pathways to compensate for the reduced OKR. Contrary to control animals, Lurcher animals were unable to modify either VOR or OKR in the course of training and therefore confirmed that an intact cerebellum is indispensable for the implementation of adaptive modifications to the oculomotor system.

Analysis of Cx36 knockout does not support tenet that olivary gap junctions are required for complex spike synchronization and normal motor performance

Electrotonic coupling by gap junctions between neurons in the inferior olive has been claimed to underly complex spike (CS) synchrony of Purkinje cells in the cerebellar cortex and thereby to play a role in the coordination of movements. Here, we investigated the motor performance of mice that lack connexin36 (Cx36), which appears necessary for functional olivary gap junctions. Cx36 null-mutants are not ataxic, they show a normal performance on the accelerating rotorod, and they have a regular walking pattern. In addition, they show normal compensatory eye movements during sinusoidal visual and/or vestibular stimulation. To find out whether the normal motor performance in mutants reflects normal CS activity or some compensatory mechanism downstream of the cerebellar cortex, we determined the CS firing rate, climbing-fiber pause, and degree of CS synchrony. None of these parameters in the mutants differed from those in wildtype littermates. Finally, we investigated whether the role of coupling becomes apparent under challenging conditions, such as during application of the tremorgenic drug harmaline, which specifically turns olivary neurons into an oscillatory state at a high frequency. In both the mutants and wildtypes this application induced tremors of a similar duration with similar peak frequencies and amplitudes. Thus surprisingly, the present data does not support the notion that electrotonic coupling by gap junctions underlies synchronization of olivary spike activity and that these gap junctions are essential for normal motor performance.

Search for R-parity violating supersymmetry in two-muon and four-jet topologies

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Analysis of the desialidation process of the haemagglutinin protein of influenza B virus: the host-dependent desialidation step

It was reported previously that haemadsorption by the haemagglutinin (HA) protein of influenza B virus required that the protein must undergo desialidation. When MDCK and COS cells were infected with influenza B/Kanagawa/73 virus in the presence of a neuraminidase (NA) inhibitor, Zanamivir, haemadsorption on MDCK cells was inhibited but that on COS cells was not. The activity of the NA protein of the two types of infected cells was similar and both were inhibited by Zanamivir in a dose-dependent manner. A comparison of the desialidation of the HA protein was made on MDCK and COS cells in the presence of bacterial NA and both cells were found to have similar sensitivity. On the accumulation of the HA and NA proteins in the trans-Golgi network of MDCK cells by means of low-temperature treatment, desialidation of the HA protein in the presence of Zanamivir was detected by two-dimensional gel electrophoresis. Because this agent was reported to be unable to penetrate cells, these data suggest that, in MDCK cells, desialidation of the HA protein occurs on the cell surface but, in COS cells, the HA and NA proteins might accumulate in the trans-Golgi network, thus allowing NA desialidation before their migration to the cell surface.