3,898 research outputs found
TORCH: A Cherenkov Based Time-of-Flight Detector
TORCH is a novel high-precision time-of-flight detector suitable for large area applications and
covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced
in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors.
For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners.
The development is divided into three phases. Phase 1 addresses the lifetime requirements for
TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes
that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial
tests show stable gain performance for integrated anode current >5 C/cm2
and a single photon
time resolution of †30 ps. Initial simulations indicate the single photon timing resolution of the
TORCH detector will be âŒ70 ps
Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb
The Ring Imaging Cherenkov detectors of the LHCb experiment at the Large
Hadron Collider at CERN are equipped with Hybrid Photo-Detectors. These vacuum
photo-detectors are affected by the stray magnetic field of the LHCb magnet,
which degrades their imaging properties. This effect increases the error on the
Cherenkov angle measurement and would reduce the particle identification
capabilities of LHCb. A system has been developed for the RICH2 Ring Imaging
Cherenkov detector to perform a detailed characterisation of the magnetic
distortion effects. It is described, along with the methods implemented to
correct for these effects, restoring the optimal resolution.Comment: 16 pages, 11 figure
Medical student attitudes to mental health and psychiatry: the use of a patient-experience short film
Background: Medical student attitudes to mental illness are significantly influenced by their undergraduate educational experience. Medical education therefore has a key role to play in challenging the stigma associated with mental illness. We developed a short educational film aimed at challenging stigmatising attitudes to mental illness and explored its effects on undergraduate medical student attitudes. We hypothesised that levels of stigmatising attitudes in medical students would reduce after students viewed the educational film. Method: We used a validated scale (Mental Illness: Clinician Attitudes, MICA) to examine undergraduate medical student attitudes to mental illness at two time points - prior to (T1) and following (T2) viewing the short film. The film focused on patient experiences and was designed to highlight personal experiences of mental illness. Results: 92 students completed the MICA before the film and 73 students at both time points. Having a personal history of mental illness was associated with less stigmatising attitudes (t=2.4, df=87, p=0.019). Stigma scores were reduced following the film viewing (t=7.101, df=72, p<0.001). Discussion: This study suggests that patient experience films, used as educational tools, can challenge student perceptions of mental illness and lead to a reduction in stigmatising attitudes, at least in the short term. Future studies are required to examine the longer-term effects of such educational interventions in terms of student perceptions and attitudes towards mental health and psychiatry
Adverse Childhood Life Events and Postpartum Mood Episodes in Bipolar Disorder
Background:
The early postpartum has been established as a period of increased vulnerability for psychiatric mood illness. Women with bipolar disorder (BD) in particular are at elevated risk of postnatal depression (PND) and of postpartum psychosis (PP). Though adverse childhood life events (ACLEs) have been implicated in the aetiology of PND, this has rarely been studied in relation to PP. Furthermore, despite being at high risk of relapse following childbirth, little research has assessed the relationship between ACLEs and postnatal mood episodes (PNEs) exclusively in women with BD. Therefore, our aim was to explore associations between ACLEs and occurrence of both PND and PP in a large sample of women with BD.
Methods:
Participants were 665 parous women with BD who had been recruited into the Bipolar Disorder Research Network study. Diagnoses and lifetime psychopathology were obtained via a semi-structured interview (SCAN). Postnatal psychiatric history and experience of 7 ACLEs were also assessed. Where available, all information obtained at interview was confirmed from psychiatric case notes. Women were classified into three groups according to postnatal psychiatric history: 1) those who had experienced no postnatal mood episode (no PNE, n=224), 2) women with a history of PND (n=223) and 3) women who had experienced PP (n=208). A Pearsonâs chi-square test was used to compare the prevalence of each type of ACLE between women in the no PNE group and those with a history of PND or PP.
Results:
Women with PND were significantly more likely to have experienced emotional, sexual or physical abuse in childhood compared with women who had no history of a PNE (p<0.05). In particular, childhood sexual abuse was reported significantly more in the PND than the no PNE group (P<0.05). In contrast, there were no significant differences in the frequency of reporting of any ACLEs between women who had no PNE and those with PP.
Conclusions:
Our findings indicate that childhood abuse, sexual abuse in particular, is associated with PND among women with BD. In contrast, we found no evidence for an association between any ACLE and PP, suggesting that biological factors are likely to play a more important role in the aetiology of psychosis in the early postpartum
Averaging lifetimes for B hadron species
The measurement of the lifetimes of the individual B species are of great interest. Many of these measurements are well below the 10 level of precision. However, in order to reach the precision necessary to test the current theoretical predictions, the results from different experiments need to be averaged. Therefore, the relevant systematic uncertainties of each measurement need to be well defined in order to understand the correlations between the results from different experiments. \par In this paper we discuss the dominant sources of systematic errors which lead to correlations between the different measurements. We point out problems connected with the conventional approach of combining lifetime data and discuss methods which overcome these problems
TORCH: A Cherenkov Based Time-of-Flight Detector
TORCH is a novel high-precision time-of-flight detector suitable for large area applications and
covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced
in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors.
For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners.
The development is divided into three phases. Phase 1 addresses the lifetime requirements for
TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes
that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial
tests show stable gain performance for integrated anode current >5 C/cm2
and a single photon
time resolution of †30 ps. Initial simulations indicate the single photon timing resolution of the
TORCH detector will be âŒ70 ps
Stratification of the Risk of Bipolar Disorder Recurrences in Pregnancy and Postpartum
Background
Pregnancy and childbirth are a period of high risk for women with bipolar disorder and involve difficult decisions particularly about continuing or stopping medications.
Aims
To explore what clinical predictors may help to individualise the risk of perinatal recurrence in women with bipolar disorder.
Method
Information was gathered retrospectively by semi-structured interview, questionnaires and case-note review from 887 women with bipolar disorder who have had children. Clinical predictors were selected using backwards stepwise logistic regression, conditional permutation random forests and reinforcement
learning trees.
Results
Previous perinatal history of affective psychosis or depression was the most significant predictor of a perinatal recurrence (odds ratio (OR) = 8.5, 95% CI 5.04â14.82 and OR = 3.6, 95% CI 2.55â5.07 respectively) but even parous women with bipolar disorder without a previous perinatal mood episode were at risk
following a subsequent pregnancy, with 7% developing postpartum psychosis.
Conclusions
Previous perinatal history of affective psychosis or depression is the most important predictor of perinatal recurrence in women with bipola
Heavy Quark Spectroscopy and Matrix Elements: A Lattice Study using the Static Approximation
We present results of a lattice analysis of the parameter, , the
decay constant , and several mass splittings using the static
approximation. Results were obtained for 60 quenched gauge configurations
computed at on a lattice size of . Light quark
propagators were calculated using the -improved Sheikholeslami-Wohlert
action. We find \Bbstat(m_b) = 0.69\er{3}{4} {\rm(stat)}\er{2}{1}
{\rm(syst)}, corresponding to \Bbstat = 1.02\er{5}{6}\er{3}{2}, and \fbstat
= 266\err{18}{20}\err{28}{27} \mev, f_{B_s}^2 B_{B_s}/f_B^2 B_B =
1.34\er{9}{8}\er{5}{3}, where a variational fitting technique was used to
extract \fbstat. For the mass splittings we obtain M_{B_s}-M_{B_d} =
87\err{15}{12}\err{6}{12} \mev, M_{\Lambda_b}-M_{B_d} =
420\errr{100}{90}\err{30}{30} \mev and M_{B^*}^2-M_B^2 =
0.281\err{15}{16}\err{40}{37} \gev^2. We compare different smearing techniques
intended to improve the signal/noise ratio. From a detailed assessment of
systematic effects we conclude that the main systematic uncertainties are
associated with the renormalisation constants relating a lattice matrix element
to its continuum counterpart. The dependence of our findings on lattice
artefacts is to be investigated in the future.Comment: 40 pages, uuencoded compressed tar file, containing one LaTeX file
and 14 postscript files (to be included with epsf). Minor change in the value
of the B parameter. Contains corrected value for the B*-B mass splitting.
Version accepted for publication in Phys. Rev.
Monochromatic Propagation-Based Phase-Contrast Microscale Computed-Tomography System with a Rotating-Anode Source
We present an experimental setup for monochromatic propagation-based x-ray phase-contrast imaging based on a conventional rotating-copper-anode source, capable of an integrated flux up to 108 photons/s at 8 keV. In our study, the system is characterized in terms of spatial coherence, resolution, contrast sensitivity, and stability. Its quantitativeness is demonstrated by comparing theoretical predictions with experimental data on simple wire phantoms both in planar and computerized-tomography-scan geometries. Application to two biological samples of medical interest shows the potential for bioimaging on the millimeter scale with spatial resolution of the order of 10 \u3bcm and contrast resolution below 1%. All the scans are performed within laboratory-compatible exposure times, from 10 min to a few hours, and trade-offs between scan time and image quality are discussed
History of Premenstrual Mood Change and Postpartum Episodes are Associated with Perimenopausal Episodes in Women with Bipolar Disorder
Background and Aims: Reproductive life events are potential triggers of mood episodes in women with bipolar disorder. We aimed to establish whether a history of premenstrual mood change and postpartum episodes are associated with perimenopausal episodes in women who have bipolar disorder.
Methods: Participants were 339 post-menopausal women with DSM-IV bipolar disorder recruited into the Bipolar Disorder Research Network (www.bdrn.org). Women self-reported presence (N = 200) or absence (N = 139) of an illness episode during the perimenopausal period. History of premenstrual mood change was measured using the self-report Premenstrual Symptoms Screening Tool (PSST), and history of postpartum episodes was measured via semi-structured interview (Schedules for Clinical Assessment in Neuropsychiatry, SCAN) and inspection of case-notes.
Results: History of a postpartum episode within 6 months of delivery (OR = 2.13, p = 0.03) and history of moderate/severe premenstrual syndrome (OR = 6.33, p < 0.001) were significant predictors of the presence of a perimenopausal episode, even after controlling for demographic factors. When we narrowed the definition of premenstrual mood change to premenstrual dysphoric disorder, it remained significant (OR = 2.68, p = 0.007).
Conclusions: Some women who have bipolar disorder may be particularly sensitive to reproductive life events. Previous mood episodes in relation to the female reproductive lifecycle may help clinicians predict individual risk for women with bipolar disorder approaching the menopause. There is a need for prospective longitudinal studies of women with bipolar disorder providing frequent contemporaneous ratings of their mood to overcome the limitations of retrospective self-report data
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