Forty-Four Pass Fibre Optic Loop for Improving the Sensitivity of Surface Plasmon Resonance Sensors

A forty-four pass fibre optic surface plasmon resonance sensor that enhances detection sensitivity according to the number of passes is demonstrated for the first time. The technique employs a fibre optic recirculation loop that passes the detection spot forty- four times, thus enhancing sensitivity by a factor of forty-four. Presently, the total number of passes is limited by the onset of lasing action of the recirculation loop. This technique offers a significant sensitivity improvement for various types of plasmon resonance sensors that may be used in chemical and biomolecule detections.Comment: Submitted for publication; patent disclosure submitte

Exclusive Measurement of the Nonmesonic Weak Decay of ^{5}_{\Lambda}He Hypernucleus

We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of ^{5}_{\Lambda}He formed via the ^{6}Li(\pi^+,K^+) reaction. The energies of two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body decay of \Lambda p --> n p and \Lambda n --> n n, respectively. The ratio of the nucleon pair numbers was N_{nn}/N_{np}=0.45 \pm 0.11(stat)\pm 0.03(syst) in the kinematic region of cos(theta_{NN}) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of \Gamma(\Lambda p --> np)/\Gamma(\Lambda n --> nn). The ratio is consistent with recent theoretical calculations based on the heavy meson/direct quark exchange picture.Comment: Submitted to Phys. Rev. lett., 4 pages, 3 figure

Proton asymmetry in non-mesonic weak decay of light hypernuclei

We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward angles. Preliminary analysis shows that the decay asymmetry parameters are very small for these s-shell and p-shell hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and Strange Particle Physics (HYP2003

Measurement of the π−\pi^- decay width of Λ5^5_\LambdaHe

We have precisely measured $\Lambda \to p\pi^-$ decay width of \5LHe and demonstrated significantly larger $\alpha$ -$\Lambda$ overlap than expected from the central repulsion $\alpha$-$\Lambda$ potential, which is derived from YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure

pi^0 decay branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei

We precisely measured pi^0 branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei produced via (pi^+,k^+) reaction. Using these pi^0 branching ratios with the pi^- branching ratios and the lifetimes, we obtained the pi^0 decay widths and the non-mesonic weak decay widths at high statistics with the accuracy of ~5 % (stat) for both hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and Strange Particle Physics (HYP2003

Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C hypernuclei

We have measured both yields of neutron-proton and neutron-neutron pairs emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,K^+) reaction for the first time. We observed clean back-to-back correlation of the np- and nn-pairs in the coincidence spectra for both hypernuclei. The ratio of those back-to-back pair yields, Nnn / Nnp, must be close to the ratio of neutron- and proton-induced decay widths of the decay, Gn(Lambda n -> nn)/Gp(Lambda p -> np). The obtained ratios for each hypernuclei support recent calculations based on short-range interactions.Comment: 4 pages, 1 figure, International Nuclear Physics Conference (INPC 2004), Goteborg, Sweden, June 27 - July 2, 2004, to appear in Nuclear Physics

Prostatic stromal tumor with fatal outcome in a young man: histopathological and immunohistochemical case presentation

Stromal tumors of the prostate are rare and only a few cases have been described in the literature, including exceptional cases of stromal tumors with unknown malignant potential (STUMP) and a fatal outcome in young patients. Morphologically distinguishing a STUMP from a stromal sarcoma of the prostate (PSS) is still a challenge. We describe the histopathological and immunohistochemical findings in a 34-year-old man with a malignant specialized cell stromal tumor of the prostate that was diagnosed initially as STUMP, and he developed lung metastases within a few months. The patient attended our hospital because of lower urinary tract symptoms, after having excreted tissue through the urethra a few months before. Ultrasonography and urethrocystoscopy examinations showed a mass arising from the verumontanum, and a transurethral resection (TUR) revealed a highgrade spindle cell sarcoma reminiscent of a phyllode tumor of the breast. The tumor cells were immunoreactive for vimentin, progesterone receptor and, focally, CD34. The preliminary histological findings were subsequently confirmed after radical prostatectomy. The patient developed bilateral lung metastases and died 25 months after the initial diagnosis. Although rare in young patients, the challenging differential diagnosis of STUMP and PSS means that a prostate STUMP diagnosis made on the basis of biopsy or TUR specimens also requires urethrocystoscopic monitoring for the early detection of any progression to PSS. Radical prostatectomy should also be carefully considered

Neutron and proton energy spectra from the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C

We have simultaneously measured the energy spectra of neutrons and protons emitted in the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,k^+) reaction with much higher statistics over those of previous experiments. The neutron-to-proton yield ratios for both hypernuclei at a high energy threshold (60 MeV) were approximately equal to two, which suggests that the ratio of the neutron- and proton-induced decay channels, Gn(Lambda n -> nn)/Gp(Lambda p -> np), is about 0.5. In the neutron energy spectra, we found that the yield of the low-energy component is unexpectedly large, even for 5_Lambda-He.Comment: 13pages, 4figures, submitted to Physics Letters