Advanced Studies on RPCs

The purpose of the present work is to to investigate the properties of the RPCs detectors with particular reference to the high rate operation that is more and more required by the experiments at present and future hadron colliders. This purpose brings in a natural way to investigate on RPC detector physics and to develop a more complete working model including the avalanche saturation phenomenon that was not accounted for in previous simulations. After a short presentation of the ATLAS experiment, with particular emphasis on the muon physics (chapter 1), RPCs are presented in their historical development. The behaviour of RPCs high rate is studied in chapter 3, where a working model based on global parameters as applied voltage, working current, incident particle flux and counting rate, and electrode plate resistivity. The results of this analysis are the basis of the Logistic Saturated Avalanche Model that is developed in chapter 4. This model explains the previous experimental results, and correctly predicts measurable physical quantities as the total charge to prompt charge ratio. This permits to implement an accurate detector simulation and can be the base for a deeper comprehension of the discharge process in a uniform field. The last chapter is dedicated to the systematic study of the detector ageing problems that are analyzed both on fully assembled detectors and on some of the individual components. One of the principa l contributions to the measured detector performance loss is evidenced and a possible solution is tested,with encouraging results

First results from an aging test of a prototype RPC for the LHCb Muon System

Recent results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge of about 0.45 C/cm$^2$, corresponding to about 4 years of LHCb running at the highest background rate. The performance of the chamber has been studied under several photon flux values exploiting a muon beam. A degradation of the rate capability above 1 kHz/cm$^2$ is observed, which can be correlated to a sizeable increase of resistivity of the chamber plates. An increase of the chamber dark current is also observed. The chamber performance is found to fulfill the LHCb operation requirements.Comment: 6 pages, 9 figures, presented at the International Workshop on Aging Phenomena in Gaseous Detectors'', DESY-Hamburg (Germany), October 200

Performances of linseed oil-free bakelite RPC prototypes with cosmic ray muons

A comparative study has been performed on Resistive Plate Chambers (RPC) made of two different grades of bakelite paper laminates, produced and commercially available in India. The chambers, operated in the streamer mode using argon, tetrafluroethane and isobutane in 34:59:7 mixing ratio, are tested for the efficiency and the stability with cosmic rays. A particular grade of bakelite (P-120, NEMA LI-1989 Grade XXX), used for high voltage insulation in humid conditions, was found to give satisfactory performance with stable efficiency of > 96% continuously for more than 130 days. A thin coating of silicone fluid on the inner surfaces of the bakelite RPC is found to be necessary for operation of the detector.Comment: 6 figures, Presented in IX International Workshop on Resistive Plate Chamber and related Detectors-2007, TIFR, Mumbai, India, February 13-16, 200

Palliative sedation in patients with advanced cancer followed at home: a prospective study.

Abstract CONTEXT: Home care programs in Italy. OBJECTIVES: The aim of this study was to assess a protocol for palliative sedation (PS) performed at home. METHODS: A total of 219 patients were prospectively assessed to evaluate a PS protocol in patients with advanced cancer followed at home by two home care programs with different territorial facilities. The protocol was based on stepwise administration of midazolam. RESULTS: A total of 176 of the patients died at home, and PS was performed in 24 of these patients (13.6%). Younger patients received the procedure more frequently than older patients (P=0.012). The principal reasons to start PS were agitated delirium (n=20) and dyspnea (n=4). Mean duration of PS was 42.2±30.4 hours, and the mean doses of midazolam were 23-58 mg/day. Both the home care team and the patients' relatives expressed optimal or good levels of satisfaction with the procedure in all but one case, respectively. CONCLUSION: This protocol for PS was feasible and effective in minimizing distress for a subgroup of patients who died at home. The characteristics of patients who may be effectively sedated at home should be better explored in future studies

Ageing test of the ATLAS RPCs at X5-GIF

An ageing test of three ATLAS production RPC stations is in course at X5-GIF, the CERN irradiation facility. The chamber efficiencies are monitored using cosmic rays triggered by a scintillator hodoscope. Higher statistics measurements are made when the X5 muon beam is available. We report here the measurements of the efficiency versus operating voltage at different source intensities, up to a maximum counting rate of about 700Hz/cm^2. We describe the performance of the chambers during the test up to an overall ageing of 4 ATLAS equivalent years corresponding to an integrated charge of 0.12C/cm^2, including a safety factor of 5.Comment: 4 pages. Presented at the VII Workshop on Resistive Plate Chambers and Related Detectors; Clermont-Ferrand October 20th-22nd, 200

Ten Things You Should Know About the Dynamic Conditional Correlation Representation

The purpose of the paper is to discuss ten things potential users should know about the limits of the Dynamic Conditional Correlation (DCC) representation for estimating and forecasting time-varying conditional correlations. The reasons given for caution about the use of DCC include the following: DCC represents the dynamic conditional covariances of the standardized residuals, and hence does not yield dynamic conditional correlations; DCC is stated rather than derived; DCC has no moments; DCC does not have testable regularity conditions; DCC yields inconsistent two step estimators; DCC has no asymptotic properties; DCC is not a special case of GARCC, which has testable regularity conditions and standard asymptotic properties; DCC is not dynamic empirically as the effect of news is typically extremely small; DCC cannot be distinguished empirically from diagonal BEKK in small systems; and DCC may be a useful filter or a diagnostic check, but it is not a model

The use of fentanyl buccal tablets for breakthrough pain by using doses proportional to opioid basal regimen in a home care setting.

Abstract The dose of rapid onset opioids to be given for breakthrough cancer pain (BTcP) is controversial. Dose proportional to the basal opioid regimen seem to be safe and effective in hospital units. However, data in other less protected settings, like home care, are lacking. The aim of this open-label study was to assess the efficacy and safety in a group of patients with BTcP followed at home, after giving a dose of fentanyl buccal tablets (FBT) proportional to the opioid basal regimen, skipping the steps for dose titration. Consecutive patients admitted to a home care program presenting BTcP episodes and receiving stable doses of opioids for background pain were selected. Data from four consecutive episodes of BTcP were collected. For each episode, patients were instructed to routinely collect changes in pain intensity and severe adverse effects when pain got severe (T0) and to reassess the same items 15 min after FBT, given as a rescue medication in doses proportional to the daily opioid doses used for background pain (T15). One hundred twenty episodes of BTcP were recorded in 30 patients. One hundred eight episodes were defined as successfully treated, while 12 episodes required a further administration of opioids. Pain intensity significantly decreased at T15 (p < 0.001). In 95.5 and 90.8 % of episodes treated, there was a reduction in pain intensity of more than 33 and 50 %, respectively. No relevant adverse effects were recorded, even in older patients. This study suggests that FBT given in doses proportional to the basal opioid regimen for the management of BTcP is very effective and safe in clinical practice in the home care setting

The frequency of alcoholism in patients with advanced cancer admitted to an acute palliative care unit and a home care program

Context Cancer patients with a history of alcoholism may be problematic. The frequency of alcoholism among patients with advanced cancer has never been reported in Italy or other European countries. Objectives The aim of this prospective study was to determine the frequency of alcoholism, assessed with a simple and validated instrument, among patients with advanced cancer who were referred to two different palliative care settings: an acute inpatient palliative care unit (PCU) of a comprehensive cancer center in a metropolitan area and a home care program (HCP) in a territorial district, localized in the mountains of Italy. Methods A consecutive sample of patients admitted to an inpatient PCU and to an HCP was assessed for a period of eight months. Each patient who agreed to be interviewed completed the Cut down, Annoyed, Guilty, Eye-opener (CAGE) questionnaire. Patients were then interviewed informally to gather information about their history with alcohol. Results In total, 443 consecutive patients were surveyed; data from 249 to 194 patients were collected in the PCU and HCP, respectively, in the eight-month period. The mean age was 66.4 (SD 12.7) years, and 207 were males. The mean Karnofsky level was 54.2 (SD 14.6). Eighteen patients were CAGE positive (4.06%). Males (Pearson Chi-squared, P = 0.027) and younger patients (analysis of variance test, P = 0.009) were more likely to be CAGE positive. Informal interviews revealed that 17 patients (3.83%) were alcoholics or had a history of alcoholism, and that alcoholism was strongly correlated with CAGE (Pearson Chi-squared, P < 0.0001). Conclusion Only a minority of patients were CAGE positive, with a similar frequency in the PCU and HCP settings. CAGE-positive patients were more likely to be male and younger, independent of diagnosis and performance status. CAGE was positively correlated with informal interviews for detecting alcoholism. As CAGE patients express more symptom distress, it is important to detect this problem with a simple tool that has a high sensitivity and specificity and is easy to use even in patients with advanced disease

Pain intensity as prognostic factor in cancer pain management

Aim: The aim of this study was to prospectively assess the prognostic value of initial pain intensity and its duration in advanced cancer patients. Methods: A prospective study was conducted in a sample of patients with cancer requiring pain control. Patients underwent standard analgesic strategies used in our palliative care units. Pain intensity was measured at admission (T0) and after successful dose titration or opioid/route switching within a week (Ts). Patients were also asked about their pain intensity reported 15 days before admission (T-15). Doses of opioids and duration of opioid use were recorded. Patients were also assessed for the presence of incident pain, neuropathic pain, alcoholism, delirium, and symptom intensity, including items representing psychological distress. One week after or at time of stabilization (Ts), the opioid response was clinically graded as follows: (1) good pain control; (2) adequate pain control requiring more aggressive opioid escalation; (3) adequate pain control associated with the occurrence of adverse effects; (4) incapacity to achieve pain control within a week. Opioid escalation indexes and days for dose finding were also recorded. Results: Pain intensity at T0 and at T-15, opioid doses, duration of opioid therapy, and age were associated with more complex analgesic therapies, which were effective in almost all patients within a week. Conclusion: High levels of pain intensity, often due to previous undertreatment, are predictive of more complex analgesic treatment. Opioid tolerance, as well as younger age, may also play a role

Preliminary results of an aging test of RPC chambers for the LHCb Muon System

The preliminary results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge density of 0.42 C/cm^2, corresponding to about 4 years of LHCb running at the highest background rate. We observe a rise in the dark current and noise measured with source off. The current drawn with source on steadily decreased, possibly indicating an increase of resistivity of the chamber plates. The performance of the chamber, studied with a muon beam under several photon flux values, is found to still fulfill the LHCb operation requirements.Comment: 4 pages, 6 figures, presented at RPC2001, VIth Workshop on Resistive Plate Chambers and Related Detectors, November 26-27 2001, Coimbra, Portuga