Distillation of Liquid Xenon to Remove Krypton

A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = $\sim 3 \times 10^{-12}$ was achieved. This development is crucial in facilitating high sensitivity low background experiments such as the search for dark matter in the universe.Comment: 15 pages, 11 figure

TeV Gamma Ray Emission from Southern Sky Objects and CANGAROO Project

We report recent results of the CANGAROO Collaboration on very high energy gamma ray emission from pulsars, their nebulae, SNR and AGN in the southern sky. Observations are made in South Australia using the imaging technique of detecting atmospheric Cerenkov light from gamma rays higher than about 1 TeV. The detected gamma rays are most likely produced by the inverse Compton process by electrons which also radiate synchrotron X-rays. Together with information from longer wavelengths, our results can be used to infer the strength of magnetic field in the emission region of gamma rays as well as the energy of the progenitor electrons. A description of the CANGAROO project is also given, as well as details of the new telescope of 7 m diameter which is scheduled to be in operation within two years.Comment: 5 pages, 1 figure, LaTeX 2.09 with aipproc.sty & epsfig.sty, to appear in proceedings of the 4th Compton Symposium, Williamsburg, 199

A phase II study of cisplatin and 5-fluorouracil with concurrent hyperfractionated thoracic radiation for locally advanced non-small-cell lung cancer: a preliminary report from the Okayama Lung Cancer Study Group

A recent meta-analysis and randomized studies have demonstrated that combined chemoradiotherapy is associated with a survival advantage for selected patients with locally advanced unresectable non-small-cell lung cancer (NSCLC). We conducted a phase II study of combined chemoradiotherapy to find a more effective combination of drugs and radiation than those previously reported for such patients. Between January 1994 and November 1996, 50 previously untreated patients with locally advanced unresectable NSCLC (stage IIIA with N2 or IIIB disease) were entered in this study. Patients were required to have Eastern Cooperative Oncology Group performance status ≤ 2, age ≤ 75 years and adequate organ function. Treatment consisted of three cycles of cisplatin (20 mg m−2, days 1–5) and 5-fluorouracil (5-FU) (500 mg m−2, days 1–5) every 4 weeks, and concurrent hyperfractionated thoracic radiation (1.25 Gy twice daily, with a 6-h interfraction interval; total radiation dose, 62.5–70 Gy). Of the 50 patients entered, 37 (74%) responded to this chemoradiotherapy, including two (4%) with complete response. By a median follow-up time of 41.0 months, 35 patiennts had died and 15 were stil alive. The median time to progression for responding patients was 14.1 months (range, 2.6–51.3+ months). The median survival time was 18.7 months, with a survival rate of 66.0% at 1 year, 46.0% at 2 years and 27.6% at 3 years. Survival outcome was strongly affected by the extent of nodal involvement (median survival time, 27.4 months for N0–2 disease (n = 37) vs 10.7 months for N3 disease (n = 13);P = 0.007). The major toxicities of treatment were leukopenia and neutropenia (≥ Grade 3, 58% and 60% respectively). Other toxicities of ≥ Grade 3 included thrombocytopenia (26%), anaemia (26%), nausea/vomiting (16%) and radiation oesophagitis (6%). Treatment-related death occurred for one patient. Our findings suggest that cisplatin and 5-FU in combination with concurrent hyperfractionated thoracic radiation is effective and feasible for the treatment of locally advanced unresectable NSCLC. The short-term survival in this study appeared to be more encouraging than those of similar chemoradiation trials. A randomized trial will be needed to compare the combination of cisplatin and 5-FU with other platinum-based regimens together with concurrent hyperfractionated thoracic radiation. In addition, in future studies, inclusion criteria for N3 disease with or without supraclavicular involvement should be reconsidered to correctly evaluate the effect of combined chemoradiotherapy for locally advanced unresectable NSCLC. © 2000 Cancer Research Campaig

Very High-Energy Gamma-Ray Observations of PSR B1509-58 with the CANGAROO 3.8m Telescope

The gamma-ray pulsar PSR B1509-58 and its surrounding nebulae have been observed with the CANGAROO 3.8m imaging atmospheric Cherenkov telescope. The observations were performed from 1996 to 1998 in Woomera, South Australia, under different instrumental conditions with estimated threshold energies of 4.5 TeV (1996), 1.9 TeV (1997) and 2.5 TeV (1998) at zenith angles of ~30 deg. Although no strong evidence of the gamma-ray emission was found, the lowest energy threshold data of 1997 showed a marginal excess of gamma-ray--like events at the 4.1 sigma significance level. The corresponding gamma-ray flux is calculated to be (2.9 +/- 0.7) * 10^{-12}cm^{-2}s^{-1} above 1.9 TeV. The observations of 1996 and 1998 yielded only upper limits (99.5% confidence level) of 1.9 * 10^{-12}cm^{-2}s^{-1} above 4.5 TeV and 2.0 * 10^{-12}cm^{-2}s^{-1} above 2.5 TeV, respectively. Assuming that the 1997 excess is due to Very High-Energy (VHE) gamma-ray emission from the pulsar nebula, our result, when combined with the X-ray observations, leads to a value of the magnetic field strength ~5 micro G. This is consistent with the equipartition value previously estimated in the X-ray nebula surrounding the pulsar. No significant periodicity at the 150ms pulsar period has been found in any of the three years' data. The flux upper limits set from our observations are one order of magnitude below previously reported detections of pulsed TeV emission.Comment: Accepted to publication in Astrophys. Journal, 25 pages, 2 figure

Detection of Gamma Rays of Up to 50 TeV From the Crab Nebula

Gamma rays with energies greater than 7 TeV from the Crab pulsar/nebula have been observed at large zenith angles, using the Imaging Atmospheric Technique from Woomera, South Australia. CANGAROO data taken in 1992, 1993 and 1995 indicate that the energy spectrum extends up to at least 50 TeV, without a change of the index of the power law spectrum. The observed differential spectrum is \noindent $(2.01\pm 0.36)\times 10^{-13}(E/{7 TeV})^{-2.53 \pm 0.18} TeV^{-1}cm^{-2}s^{-1}$ between 7 TeV and 50 TeV. There is no apparent cut-off. The spectrum for photon energies above $\sim$10 TeV allows the maximum particle acceleration energy to be inferred, and implies that this unpulsed emission does not originate near the light cylinder of the pulsar, but in the nebula where the magnetic field is not strong enough to allow pair creation from the TeV photons. The hard gamma-ray energy spectrum above 10 TeV also provides information about the varying role of seed photons for the inverse Compton process at these high energies, as well as a possible contribution of $\pi ^{\circ}$-gamma rays from proton collisions.Comment: 19 pages, 4 figures, LaTeX2.09 with AASTeX 4.0 maros, to appear in Astrophys. J. Let

Dual mechanism of brain injury and novel treatment strategy in maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited disorder of branched-chain amino acid metabolism presenting with lifethreatening cerebral oedema and dysmyelination in affected individuals. Treatment requires life-long dietary restriction and monitoring of branched-chain amino acids to avoid brain injury. Despite careful management, children commonly suffer metabolic decompensation in the context of catabolic stress associated with non-specific illness. The mechanisms underlying this decompensation and brain injury are poorly understood. Using recently developed mouse models of classic and intermediate maple syrup urine disease, we assessed biochemical, behavioural and neuropathological changes that occurred during encephalopathy in these mice. Here, we show that rapid brain leucine accumulation displaces other essential amino acids resulting in neurotransmitter depletion and disruption of normal brain growth and development. A novel approach of administering norleucine to heterozygous mothers of classic maple syrup urine disease pups reduced branched-chain amino acid accumulation in milk as well as blood and brain of these pups to enhance survival. Similarly, norleucine substantially delayed encephalopathy in intermediate maple syrup urine disease mice placed on a high protein diet that mimics the catabolic stress shown to cause encephalopathy in human maple syrup urine disease. Current findings suggest two converging mechanisms of brain injury in maple syrup urine disease including: (i) neurotransmitter deficiencies and growth restriction associated with branchedchain amino acid accumulation and (ii) energy deprivation through Krebs cycle disruption associated with branched-chain ketoacid accumulation. Both classic and intermediate models appear to be useful to study the mechanism of brain injury and potential treatment strategies for maple syrup urine disease. Norleucine should be further tested as a potential treatment to prevent encephalopathy in children with maple syrup urine disease during catabolic stress