Indications of proton-dominated cosmic-ray composition above 1.6 EeV.

We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d/d[log(E)] of 47.9+/-6.0(stat)+/-3.2(syst) g/cm2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4x10(18) eV.

First observation of the Greisen-Zatsepin-Kuzmin suppression.

The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment.

We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

Chemotherapy with an every-2-week regimen of gemcitabine and paclitaxel in patients with transitional cell carcinoma who have received prior cisplatin-based therapy.

BACKGROUND: An every-2-week regimen of gemcitabine and paclitaxel was adapted for patients with advanced transitional cell carcinoma (TCC) who had received prior cisplatin-based chemotherapy. METHODS: Forty-one patients with advanced or metastatic TCC who had received prior cisplatin-based systemic chemotherapy were treated with an outpatient regimen of gemcitabine 2500-3000 mg/m(2) and paclitaxel 150 mg/m(2) every 2 weeks. RESULTS: Forty of 41 patients had measurable disease. Response was observed in 24 patients (60%; 95% confidence interval [CI], 45-75%). Eleven (28%) achieved complete response, and 13 (33%) obtained partial response. Twenty of 25 patients (80%; 95% CI, 64-96%) who had been previously treated in the neoadjuvant or adjuvant setting responded versus 4 of 15 (27%; 95% CI, 5-49%) in patients who received prior methotrexate, vinblastine, doxorubicin, cisplatin (M-VAC) for metastatic disease. The median duration of survival for patients given gemcitabine and paclitaxel after failing neoadjuvant or adjuvant M-VAC was 12 months (range, 2-43+), as compared with only 8 months (range, 2-28) for patients who had been treated after failure of prior therapy for metastatic disease. For all patients, the median duration of response was 6.4 months (range, 2-43.3+ months), and the median survival was 14.4 months (range, 2-43+). Thirteen patients (32%) developed World Health Organization Grade 3-4 neutropenia, with febrile neutropenia in 3 (7%) patients. Granulocyte colony-stimulating factor was given to 10 (24%) patients. There was no Grade 3-4 anemia or thrombocytopenia. CONCLUSIONS: The combination of gemcitabine and taxol in previously treated patients with recurrent TCC is highly effective and produces objective durable responses. This every-2-week schedule is a well tolerated outpatient regimen with minimal toxicity.