The high energy spectrum of alpha particles emitted from a single isotope uniformly contaminating a bulk solid has a flat energy spectrum with a high end cutoff energy equal to the maximal alpha ...kinetic energy (T sub(alpha)) of the decay. In this flat region of the spectrum, we show the surface rate r sub(b)(Bq keV super(-1) cm super(-2)) arising from a bulk alpha contamination rho sub(b)(Bq cm super(-3)) from a single isotope is given by r sub(b)=rho sub(b)Delta R/ 4 Delta E, where Delta E= E sub(1)-E sub(2>0) is the energy interval considered (keV) in the flat region of the spectrum and Delta R= R sub(2)-R sub(1), where R sub(2)(R sub(1)) is the amount of the bulk material (cm) necessary to degrade the energy of the alpha from T sub(alpha) to E sub(2)(E sub(1)). We compare our calculation to a rate measurement of alphas from super(147) Sm, (15.32 + or - 0.03% of Sm(nat) and half life of (1.06 + or - 0.01)x 10 super(11) yr 1), and find good agreement, with the ratio between prediction to measurement of 100.2%+ or - 1.6% (stat)+ or - 2.1% (sys). We derive the condition for the flat spectrum, and also calculate the relationship between the decay rate measured at the surface for a near surface contamination with an exponential dependence on depth and a second case of an alpha source with a thin overcoat. While there is excellent agreement between our implementation of the sophisticated Monte Carlo program SRIM 2 and our intuitive model in all cases, both fail to describe the measured energy distribution of a super(148) Gd alpha source with a thin (~200mug cm super(-2)) Au overcoat. We discuss possible origins of the disagreement and suggest avenues for future study.
CUORE—the Cryogenic Underground Observatory for Rare Events—is an experiment searching for the neutrinoless double-beta (0νββ) decay of 130Te with an array of 988 TeO2 crystals operated as bolometers ...at ∼10 mK in a large dilution refrigerator. With this detector, we aim for a 130Te 0νββ decay half-life sensitivity of 9×1025 y with 5 y of live time, and a background index of ≲10−2 counts/keV/kg/y. Making an effort to maintain radiopurity by minimizing the bolometers' exposure to radon gas during their installation in the cryostat, we perform all operations inside a dedicated cleanroom environment with a controlled radon-reduced atmosphere. In this paper, we discuss the design and performance of the CUORE Radon Abatement System and cleanroom, as well as a system to monitor the radon level in real time.
Summary Background First-line chemotherapy for patients with cisplatin-ineligible locally advanced or metastatic urothelial carcinoma is associated with short response duration, poor survival, and ...high toxicity. This study assessed atezolizumab (anti-programmed death-ligand 1 PD-L1) as treatment for metastatic urothelial cancer in cisplatin-ineligible patients. Methods For this single-arm, multicentre, phase 2 study, in 47 academic medical centres and community oncology practices in seven countries in North America and Europe, we recruited previously untreated patients with locally advanced or metastatic urothelial cancer who were cisplatin ineligible. Patients were given 1200 mg intravenous atezolizumab every 21 days until progression. The primary endpoint was independently confirmed objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 (central review), assessed in prespecified subgroups based on PD-L1 expression and in all patients. All participants who received one or more doses of atezolizumab were included in the primary and safety analyses. This study was registered with ClinicalTrials.gov , number NCT02108652. Findings Between June 9, 2014, and March 30, 2015, we enrolled 123 patients, of whom 119 received one or more doses of atezolizumab. At 17·2 months' median follow-up, the objective response rate was 23% (95% CI 16 to 31), the complete response rate was 9% (n=11), and 19 of 27 responses were ongoing. Median response duration was not reached. Responses occurred across all PD-L1 and poor prognostic factor subgroups. Median progression-free survival was 2·7 months (2·1 to 4·2). Median overall survival was 15·9 months (10·4 to not estimable). Tumour mutation load was associated with response. Treatment-related adverse events that occurred in 10% or more of patients were fatigue (36 30% patients), diarrhoea (14 12% patients), and pruritus (13 11% patients). One treatment-related death (sepsis) occurred. Nine (8%) patients had an adverse event leading to treatment discontinuation. Immune-mediated events occurred in 14 (12%) patients. Interpretation Atezolizumab showed encouraging durable response rates, survival, and tolerability, supporting its therapeutic use in untreated metastatic urothelial cancer. Funding F Hoffmann-La Roche, Genentech.
Electron avalanches in liquid argon mixtures Kim, J.G.; Dardin, S.M.; Kadel, R.W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
534, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We have observed stable avalanche gain in liquid argon when mixed with small amounts of xenon (xe) in the high electric field (
>
7
MV/cm) near the point of a chemically etched needle in a ...point–plane geometry. We identify two gain mechanisms, one pressure dependent, and the other independent of the applied pressure. We conclude that the pressure-dependent signals are from avalanche gain in gas bubbles at the tip of the needle, while the pressure-independent pulses are from avalanche gain in liquid. We measure the decay time spectra of photons from both types of avalanches. The decay times from the pressure-dependent pulses decrease (increase) with the applied pressure (high voltage), while the decay times from the pressure-independent pulses are approximately independent of pressure or high voltage. For our operating conditions, the collected charge distribution from avalanches is similar for 60 or 122
keV photon sources. With krypton additives, instead of Xe, we measure behavior consistent with only the pressure-dependent pulses. Neon and TMS were also investigated as additives, and designs for practical detectors were tested.
Atezolizumab anti-programmed death-ligand 1 (anti-PD-L1) is well tolerated and efficacious in multiple cancers, but has not been previously evaluated in metastatic castration-resistant prostate ...cancer (mCRPC). This study examined the safety, efficacy, and biomarkers of atezolizumab monotherapy for mCRPC.
This phase Ia, open-label, dose-escalation and dose-expansion study (PCD4989g) enrolled patients with mCRPC who had progressed on sipuleucel-T or enzalutamide. Atezolizumab was given intravenously every 3 weeks until confirmed disease progression or loss of clinical benefit. Prespecified endpoints included safety, efficacy, biomarker analyses, and radiographic assessments.
All 35 evaluable patients median age, 68 years (range, 45-83 years) received atezolizumab after ≥1 prior line of therapy; 62.9% of patients had received ≥3 prior lines. Treatment-related adverse events occurred in 21 patients (60.0%), with no deaths. One patient had a confirmed partial response (PR) per RECIST 1.1, and 1 patient had a PR per immune-related response criteria. The confirmed 50% PSA response rate was 8.6% (3 patients). Median overall survival (OS) was 14.7 months 95% confidence interval (CI): 5.9-not evaluable, with a 1-year OS rate of 52.3% (95% CI: 34-70); 2-year OS was 35.9% (95% CI: 13-59). Median follow-up was 13.0 months (range, 1.2-28.1 months). Biomarker analyses showed that atezolizumab activated immune responses; however, a composite biomarker failed to reveal consistent correlations with efficacy.
Atezolizumab was generally well tolerated in patients with mCRPC, with a safety profile consistent with other tumor types. In heavily pretreated patients, atezolizumab monotherapy demonstrated evidence of disease control; however, its limited efficacy suggests a combination approach may be needed.
Electron avalanching in liquid argon is being studied as a function of voltage, pressure, radiation intensity, and the concentrations of certain additives, especially xenon. The avalanches produced ...in an intense electric field at the tip of a tungsten needle are initiated by ionization from a movable americium (/sup 241/Am) gamma-ray source. Photons from xenon excimers are detected as photomultiplier signals in coincidence with the current pulse from the needle. In pure liquid argon, the avalanche behavior is erratic, but the addition of even a small amount of xenon (/spl les/100 ppm) stabilizes the performance. Similar attempts with neon (30%) as an additive to argon have been unsuccessful. Tests with higher energy gamma-rays (/sup 57/Co) yield spectra and other performance characteristics quite similar to those using the /sup 241/Am source. Two types of signal pulses are commonly observed: a set of pulses that are sensitive to ambient pressure and a set of somewhat smaller pulses that are not pressure dependent.
Previously, we showed how small admixtures of xenon (Xe) stabilize electron avalanches in liquid Argon (LAr). In the present work, we have measured the positive charge carrier mobility in LAr with ...small admixtures of Xe to be 6.4/spl times/10/sup -3/ cm/sup 2//Vs, in approximate agreement with the mobility measured in pure LAr and consistent with holes as charge carriers. We have measured the concentration of Xe actually dissolved in the liquid and compared the results with expectations based on the amount of Xe gas added to the LAr. We also have tested LAr doped with krypton to investigate the mechanism of avalanche stabilization.
Measurement of the W boson mass Abe, F; Albrow, MG; Amidei, D ...
Physical review. D, Particles and fields,
11/1995, Letnik:
52, Številka:
9
Journal Article
The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this ...technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number-violating process: ^{130}Te neutrinoless double-beta decay. Examining a total TeO_{2} exposure of 86.3 kg yr, characterized by an effective energy resolution of (7.7±0.5) keV FWHM and a background in the region of interest of (0.014±0.002) counts/(keV kg yr), we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life of T_{1/2}^{0ν}(^{130}Te)>1.3×10^{25} yr (90% C.L.); the median statistical sensitivity of this search is 7.0×10^{24} yr. Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T_{1/2}^{0ν}(^{130}Te)>1.5×10^{25} yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find m_{ββ}<(110-520) meV, where the range reflects the nuclear matrix element estimates employed.
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