Single-photon tunneling

Strong evidence of a single-photon tunneling effect, a direct analog of single-electron tunneling, has been obtained in the measurements of light tunneling through individual subwavelength pinholes in a thick gold film covered with a layer of polydiacetylene. The transmission of some pinholes reached saturation because of the optical nonlinearity of polydiacetylene at a very low light intensity of a few thousands photons per second. This result is explained theoretically in terms of "photon blockade", similar to the Coulomb blockade phenomenon observed in single-electron tunneling experiments. The single-photon tunneling effect may find many applications in the emerging fields of quantum communication and information processing.Comment: 4 pages, 4figure

Chiral perturbation theory calculation for pn -> dpipi at threshold

We investigate the reaction pn -> dpipi in the framework of Chiral Perturbation Theory. For the first time a complete calculation of the leading order contributions is presented. We identify various diagrams that are of equal importance as compared to those recognized in earlier works. The diagrams at leading order behave as expected by the power counting. Also for the first time the nucleon-nucleon interaction in the initial, intermediate and final state is included consistently and found to be very important. This study provides a theoretical basis for a controlled evaluation of the non-resonant contributions in two-pion production reactions in nucleon-nucleon collisions.Comment: 24 pages, 3 figures, 3 table

Risk factors for delay in symptomatic presentation: a survey of cancer patients

Background: Delay in symptomatic presentation leading to advanced stage at diagnosis may contribute to poor cancer survival. To inform public health approaches to promoting early symptomatic presentation, we aimed to identify risk factors for delay in presentation across several cancers. Methods: We surveyed 2371 patients with 15 cancers about nature and duration of symptoms using a postal questionnaire. We calculated relative risks for delay in presentation (time from symptom onset to first presentation >3 months) by cancer, symptoms leading to diagnosis and reasons for putting off going to the doctor, controlling for age, sex and deprivation group. Results: Among 1999 cancer patients reporting symptoms, 21% delayed presentation for >3 months. Delay was associated with greater socioeconomic deprivation but not age or sex. Patients with prostate (44%) and rectal cancer (37%) were most likely to delay and patients with breast cancer least likely to delay (8%). Urinary difficulties, change of bowel habit, systemic symptoms (fatigue, weight loss and loss of appetite) and skin symptoms were all common and associated with delay. Overall, patients with bleeding symptoms were no more likely to delay presentation than patients who did not have bleeding symptoms. However, within the group of patients with bleeding symptoms, there were significant differences in risk of delay by source of bleeding: 35% of patients with rectal bleeding delayed presentation, but only 9% of patients with urinary bleeding. A lump was a common symptom but not associated with delay in presentation. Twenty-eight percent had not recognised their symptoms as serious and this was associated with a doubling in risk of delay. Embarrassment, worry about what the doctor might find, being too busy to go to the doctor and worry about wasting the doctor’s time were also strong risk factors for delay, but were much less commonly reported (<6%). Interpretation: Approaches to promote early presentation should aim to increase awareness of the significance of cancer symptoms and should be designed to work for people of the lowest socioeconomic status. In particular, awareness that rectal bleeding is a possible symptom of cancer should be raised

Higher Partial Waves in p+p->p+p+eta near Threshold

Exclusive measurements of the production of eta mesons in the p+p->p+p+eta reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The deviations from phase space are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the eta meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the eta meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the eta angular anisotropy suggests that rho-exchange is important for this reaction.Comment: 16 pages, LaTeX2e, 3 EPS Figures, Updated version, Accepted for publication in Phys. Lett.

Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon

We present a microscopic theory of the low-frequency voltage noise (known as "1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This theory traces the noise back to the long-range fluctuations of the Coulomb potential produced by deep defects, thereby predicting the absolute noise intensity as a function of the distribution of defect activation energies. The predictions of this theory are in very good agreement with our own experiments in terms of both the absolute intensity and the temperature dependence of the noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added, but no conceptual revision

A survey of abnormalities in the colon and rectum in patients with haemorrhoids

Abstract Background Haemorrhoids are a common problem in daily practice. However, symptoms may also be caused by other abnormalities in the rectum or colon. Data on the presence of these abnormalities in patients with haemorrhoids is sparse. To examine the prevalence of abnormalities of the colon or rectum in patients with and without haemorrhoids, stratified for age. Methods In a 17-year period 1910 consecutive patients with haemorrhoids and 7936 patients without haemorrhoids were analysed retrospectively. All of these patients had an endoscopic examination for different clinical reasons. All significant endoscopic co-findings (diverticuli, polyps, cancer, angiodysplasia and varices, or colitis) were recorded. Results The patients were divided in 2 groups. Group 1 (n = 861 (45.1%)) consisted of patients with only haemorrhoids, group 2 (n = 1049 (54.9%)) consisted of patients with haemorrhoids and another endoscopic diagnosis. Patients in group 1 were significantly younger, mean age 55.3 ± 14.1 years versus 67.4 ± 12.1 years (p Conclusion In patients with haemorrhoids other abnormalities can be present. Especially in older patients the clinician must be cautious to attribute complaints solely to haemorrhoids.</p

The pp -> pp pi pi pi reaction channels in the threshold region

The cross section for prompt neutral and charged three pion production in pp interactions was measured at excess energies in the range 160 - 217 MeV. That comprises the first measurement of the pp->pp pi0pi0pi0 reaction and the comparison with the pp->pp pi+pi-pi0 reaction, in a very direct way. The experiment was performed above the eta meson production threshold and the cross section normalization was obtained from a concurrent measurement of the reaction pp->pp eta with the eta decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio sigma(pp->pp pi+pi-pi0)/sigma(pp->pp pi0\pi0\pi0) is compared to predictions of dominance of different isobars in the intermediate state.Comment: 12 pages, 4 figures New discussion on the pp->pp3pi reaction mechanis

INTERLAYER COUPLING AND THE METAL-INSULATOR TRANSITION IN Pr-SUBSTITUTED Bi(2)Sr(2)CaCu(2)O(8+y)

Substitution of rare-earth ions for Ca in Bi2Sr2CaCu2O8+y is known to cause a metal-insulator transition. Using resonant photoemission we study how this chemical substitution affects the electronic structure of the material. For the partial Cu-density of states at E_F and in the region of the valence band we observe no significant difference between a pure superconducting sample and an insulating sample with 60% Pr for Ca. This suggests that the states responsible for superconductivity are predomi- nately O-states. The partial Pr-4f density of states was extracted utilizing the Super- Koster-Kronig Pr 4d-4f resonance. It consists of a single peak at 1.36eV binding energy. The peak shows a strongly assymetric Doniach-Sunjic line- shape indicating the presence of a continuum of electronic states with sharp cut off at E_F even in this insulating sample. This finding excludes a bandgap in the insulating sample and supports the existance of a mobility gap caused by spatial localization of the carriers. The presence of such carriers at the Pr-site, between the CuO_2 planes shows that the electronic structure is not purely 2-dimensional but that there is a finite interlayer coupling. The resonance enhancement of the photoemission cross section, at the Pr-4d threshold, was studied for the Pr-4f and for Cu-states. Both the Pr-4f and the Cu-states show a Fano-like resonance. This resonance of Cu-states with Pr-states is another indication of coupling between the the Pr-states and those in the CuO_2 plane. Because of the statistical distribution of the Pr-ions this coupling leads to a non-periodic potential for the states in the CuO_2 plane which can lead to localization and thus to the observed metal-insulator transition.Comment: Gziped uuencoded postscript file including 7 figures Scheduled for publication in Physical Review B, May 1, 1995

Escherichia coli-mediated impairment of ureteric contractility is uropathogenic E. coli specific.

BACKGROUND: Ureters are fundamental for keeping kidneys free from uropathogenic Escherichia coli (UPEC), but we have shown that 2 strains (J96 and 536) can subvert this role and reduce ureteric contractility. To determine whether this is (1) a widespread feature of UPEC, (2) exhibited only by UPEC, and (3) dependent upon type 1 fimbriae, we analyzed strains representing epidemiologically important multilocus sequence types ST131, ST73, and ST95 and non-UPEC E. coli. METHODS: Contractility and calcium transients in intact rat ureters were compared between strains. Mannose and fim mutants were used to investigate the role of type 1 fimbriae. RESULTS: Non-UPEC had no significant effect on contractility, with a mean decrease after 8 hours of 8.8%, compared with 8.8% in controls. UPEC effects on contractility were strain specific, with decreases from 9.47% to 96.7%. Mannose inhibited the effects of the most potent strains (CFT073 and UTI89) but had variable effects among other UPEC strains. Mutation and complementation studies showed that the effects of the UTI89 cystitis isolate were fimH dependent. CONCLUSIONS: We find that (1) non-UPEC do not affect ureteric contractility, (2) impairment of contractility is a common feature of UPEC, and (3) the mechanism varies between strains, but for the most potent UPEC type 1 fimbriae are involved