Triggered high-purity telecom-wavelength single-photon generation from p-shell-driven InGaAs/GaAs quantum dot.

We report on the experimental demonstration of triggered single-photon emission at the telecom O-band from In(Ga)As/GaAs quantum dots (QDs) grown by metal-organic vapor-phase epitaxy. Micro-photoluminescence excitation experiments allowed us to identify the p-shell excitonic states in agreement with high excitation photoluminescence on the ensemble of QDs. Hereby we drive an O-band-emitting GaAs-based QD into the p-shell states to get a triggered single photon source of high purity. Applying pulsed p-shell resonant excitation results in strong suppression of multiphoton events evidenced by the as measured value of the second-order correlation function at zero delay of 0.03 (and ~0.005 after background correction).

Green light emission from terbium doped silicon rich silicon oxide films obtained by plasma enhanced chemical vapor deposition.

The effect of silicon concentration and annealing temperature on terbium luminescence was investigated for thin silicon rich silicon oxide films. The structures were deposited by means of plasma enhanced chemical vapor deposition. The structural properties of these films were investigated by Rutherford backscattering spectrometry, transmission electron microscopy and Raman scattering. The optical properties were investigated by means of photoluminescence and photoluminescence decay spectroscopy. It was found that both the silicon concentration in the film and the annealing temperature have a strong impact on the terbium emission intensity. In this paper, we present a detailed discussion of these issues and determine the optimal silicon concentration and annealing temperature.

Correlation between stress and carrier nonradiative recombination for silicon nanocrystals in an oxide matrix.

Silicon nanocrystals embedded in an oxide matrix formed in a multilayer architecture were deposited by the magnetron sputtering method. By means of Raman spectroscopy we have found that compressive stress is exerted on the silicon nanocrystal core. The stress varies as a function of silicon concentration (O/Si ratio) in the silicon-rich oxide (SRO) layers, which can be attributed to the changing nanocrystal environment. By conducting the time-resolved spectroscopy experiment, we demonstrate that, depending on the nanocrystal surroundings, a different amount of nonradiative recombination sites participates in the excited carrier relaxation process, leading to changes of the relative quantum yield of photoluminescence.

Quantitative evaluation of boron-induced disorder in multilayers containing silicon nanocrystals in an oxide matrix designed for photovoltaic applications.

The effect of doping by boron on optical properties of multilayers containing Si-NCs were studied by means of photoluminescence (PL), time-resolved PL, photoluminescence excitation (PLE), transmission and reflection measurements. It was found that PL decay is strongly non-single exponential and can be described by means of Laplace transform of log-normal decay rates distribution. It was also proposed that changes observed in the distribution central moments reflect the disorder induced by boron-doping.

Temperature dependent emission quenching for silicon nanoclusters.

Silicon reach-silicon-oxide (SRSO) film containing silicon nanoclusters was obtained by the reactive magnetron sputtering. Photoluminescence (PL) spectra were measured as a function of temperature at different excitation wavelengths and additionally at different excitation power densities. Obtained PL spectra characterize by two emission bands centered at 1.6 and 2.4 eV. For these bands, temperature behaviour of PL intensities strongly differs but clearly correlate each other. Moreover, it has been observed that obtained PL intensities versus temperature exhibit a strong dependence on the excitation power density in the low temperature range.

Effects of Si-rich oxide layer stoichiometry on the structural and optical properties of Si QD/SiO2 multilayer films.

The effects of the stoichiometry of the Si-rich oxide (SRO) layer, O/Si ratio, on the structural and optical properties of SRO/SiO2 multilayer films were investigated in this work. SRO/SiO2 multilayer films with different O/Si ratios were grown by a co-sputtering technique, and Si quantum dots (QDs) were formed with post-deposition annealing. By transmission electron microscopy (TEM) and glancing incidence x-ray diffraction (GIXRD), it was found that the Si QD size decreases with increases in O/Si ratio. The photoluminescence (PL) spectrum varies with the O/Si ratio in band position, shape and intensity. In addition, it was observed that the absorption edge blue-shifts with increases in the O/Si ratio. The change in the absorption edge is consistent with strengthening quantum confinement effects in Si QDs, as indicated by TEM and GIXRD. The optical properties were also investigated by 2D photoluminescence excitation (2D-PLE) and lifetime measurements. The origin of emission and absorption is discussed based on the absorption, PL, 2D-PLE and decay time measurements.

Enhanced photoluminescence stability of CdS nanocrystals through a zinc acetate reagent.

In this study, the role of a zinc acetate precursor in improving the luminescence stability of purple-emitting CdS nanocrystals is investigated. The oleate-capped core of CdS nanocrystals exhibits intense photodarkening under prolonged UV excitation. From the results of photoluminescence experiments, we can observe that photobleaching is responsible for the degradation of temporal stability, i.e., decline in photoluminescence intensity. Herein, we demonstrate that by adding zinc acetate to the synthesis solution, one can enhance the photoluminescence stability by the complete suppression of the bleaching processes of nanocrystals. We can distinguish between the effects caused by zinc ions and those caused by acetate ligands. Acetate ligands improve the photoluminescence stability of the core of CdS nanocrystals. However, only when zinc acetate is used, the PL stability can be conserved at high excitation power. Simultaneously, we have studied the influence of zinc cations and acetate ligands on the kinetics of nanocrystal growth. The presented results underline the importance of short surface capping ligands and zinc cations in CdS nanocrystal synthesis. This study exhibits a new advantage of exploiting zinc acetate reagents in one-pot nanocrystal synthesis.

Scope and specificity of acarbose in slowing carbohydrate absorption in man.

Fifty-gram carbohydrate tolerance tests were performed on healthy volunteers to test the activity and specificity of an alpha-glucoside hydrolase inhibitor, acarbose (BAY g 5421). Two hundred milligrams acarbose reduced the area under the blood glucose response curve by 89% (P less than 0.001) after sucrose by 80% (P less than 0.002) after starch, by 19% (N.S.) after maltose, with no effect on glucose. Breath hydrogen measurements indicated an almost complete malabsorption of the sucrose. At 50 mg acarbose, some reduction in blood glucose and insulin response to sucrose was still seen, but no significant hydrogen production. It is suggested that at lower doses, acarbose may prolong the time course over which carbohydrate is absorbed as does dietary fiber; as with fiber, it may be a useful adjunct to diabetic therapy.

Effect of acarbose on the 24-hour blood glucose profile and pattern of carbohydrate absorption.

Acarbose (Bay g 5421) is a powerful alpha-glucoside hydrolase inhibitor of potential value in the treatment of diabetes and hypoglycemic dumping syndrome after gastric surgery. The extent of its use may be limited by symptoms produced by carbohydrate malabsorption. To minimize these, the action of low doses of acarbose on 24-h blood glucose profiles and hydrogen evolution have been studied on four ambulant volunteers on control diets, after exclusion of sucrose and also after addition of guar in an attempt to enhance the therapeutic effect. Replacement of dietary sucrose by starch abolished significant hydrogen evolution in the morning after low doses of acarbose but did not reduce its effectiveness in decreasing the mean three-meal blood glucose area by 41% (P less than 0.002). Addition of hydrated guar to this diet reduced the mean three-meal glucose area after acarbose further by 72% (P less than 0.001) but increased hydrogen evolution. The results suggest that acarbose will be both effective and acceptable given at low dose when the dietary carbohydrate is starch.

Ion-ion interactions in ß-NaGdF4:Yb(3+),Er(3+) nanocrystals--the effect of ion concentration and their clustering.

In this work we report co-thermolysis as a suitable method for nanomaterial synthesis which allows the creation of hexagonal upconverting nanocrystals, NaGdF4:Yb(3+),Er(3+), in a wide range of sizes (20-120 nm). Only a very high Yb(3+) concentration (above 70%) results in pure cubic-phase nanocrystals with irregular shape. Additionally, we showed that the impact of Yb(3+), Er(3+) and Gd(3+) ions on the size and optical properties of nanocrystals is significant. We found that the main changes in optical properties do not depend on the nanocrystal size mostly, but are determined by the ion-ion interactions which include both Er(3+)-Er(3+) and Er(3+)-Yb(3+) cross relaxation.

Human papillomavirus (HPV) types specific of epidermodysplasia verruciformis detected in warts induced by HPV3 or HPV3-related types in immunosuppressed patients.

Epidermodysplasia verruciformis (EV) is characterized by an abnormal genetic predisposition to infection with specific types of human papillomavirus (HPV). Specific defects of the cell-mediated immunity and/or of the control of HPV infection in keratinocytes are assumed to be involved in the development of the disease. As a model to test this hypothesis, we have studied the prevalence of EV-specific HPV in skin warts of 56 immunosuppressed patients. All main types of cutaneous HPV (HPV1, 2, 3, 4, 10, and 28) responsible for skin warts in the general population were detected by blot hybridization. EV-specific HPV (HPV5, 20, and 23) were detected in three patients. Four additional patients were found infected with HPV49, first characterized in the course of this study, and found to be related to EV HPV. A most important finding was that HPV5, 20, 23, and 49 were always codetected with HPV3 or the related types HPV10 and 28. None of the specimens showed the typical clinical morphology of EV lesions. In none of these specimens was the specific cytopathic effect of EV recognized; instead that of HPV3 and related types was seen. No evidence for productive EV HPV DNA replication was obtained for the three specimens that could be further analyzed by in situ hybridization. Our data suggest that HPV3 infection favors infection with EV HPV in immunosuppressed patients but that the full expression of EV HPV is usually restricted as in the general population.

What is new in the epidemiology and pathogenesis of peptic ulcer?

The old dictum 'no acid--no ulcer' is no longer a sufficient explanation of the pathogenesis of ulcer disease. The real question is 'if acid--why ulcer?' Although acid remains predominant, some of the other factors influencing ulcerogenesis are nocturnal acid secretion, pepsin enzyme subspecies, the mucus layer, bicarbonate levels, prostaglandins, Campylobacter pylori infection, consumption of non-steroidal anti-inflammatory drugs, and smoking habits. Although the ulcer burden has been greatly reduced by the introduction of H2-receptor antagonists, complications such as bleeding and perforation remain a problem, especially in the elderly. Medical treatment, in the form of H2-receptor antagonists, is effective for many patients.

Is oropharyngeal anaesthesia with topical lignocaine useful in upper gastrointestinal endoscopy?

The aim of this study was to determine whether patients' tolerance of upper gastrointestinal endoscopy is related to the dose of lignocaine spray used for oropharyngeal anaesthesia and to measure plasma concentrations at these doses. Sixty consecutive patients undergoing routine upper gastrointestinal endoscopy with sedation were randomized to receive lignocaine spray 50 mg (Group A), 100 mg (Group B) or 200 mg (Group C). Patient, endoscopist and endoscopy nurse were unaware of the variation in dose used. Each patient's tolerance of the intubation and of the remainder of the gastroscopy was assessed independently by the patient, endoscopy nurse, and endoscopist using a visual analogue scale. Plasma lignocaine concentration was measured at 20, 40, 60 and 80 min after administration of the spray. Fifty (83%) patients were unable to recall either the intubation, or the procedure. On the endoscopy nurse's assessment, the patients in Group B tolerated the intubation better than those in Group A, and Groups B and C tolerated the remainder of the gastroscopy better than those in Group A. On the endoscopist's assessment, Groups B and C tolerated the remainder of the gastroscopy better than Group A. There were fewer gags per min in Groups B and C compared to Group A. Mean plasma lignocaine concentrations showed a dose-dependent absorption of the spray, but none exceeded the potentially toxic level of 5 mg/L.

Oral or intravenous erythromycin has no effect on human distal colonic motility.

Erythromycin is a prokinetic agent for the lower oesophageal sphincter, the stomach, the gallbladder and the small bowel, acting directly on motilin receptors. Its effect on pressure activity of the human colon has not been investigated. Eight healthy volunteers were studied on 2 occasions and given intravenous or oral erythromycin, or placebo in a single-blind, randomized crossover study. Sigmoid pressure activity was measured using a 4-lumen water perfused system placed sigmoidoscopically at 50, 45, 30 and 15 cm from the anal verge. The pressures were analysed for activity index (mmHg.min) for the 35 cm colonic study segment using dedicated software. No significant difference was found in the activity index following oral erythromycin (500 mg) or placebo, or following intravenous erythromycin 1.8 mg/kg or placebo. A further 8 subjects were studied in a single-blind crossover study to determine the effect of oral erythromycin (500 mg) b.d. on colonic transit, measured with radio-opaque markers and a single abdominal X-ray. Mean or segmental colonic transit times were not statistically significantly different (Student's paired t-test) in the subjects on placebo or erythromycin. This lack of effect of erythromycin on the distal large intestine may indicate the absence of receptors for motilin in that part of the gut.

Two-week eradication regimen for metronidazole-resistant Helicobacter pylori.

At present there is no generally accepted treatment regimen for eradicating metronidazole-resistant Helicobacter pylori. This study determines the eradication rate after treatment with 40 mg omeprazole o.m. and 500 mg amoxycillin q.d.s. for 14 days, with 120 mg tripotassium dicitrato bismuthate q.d.s. for the first week (Days 1-7) and 750 mg ciprofloxacin b.d. for the second week (Days 8-14). Thirty patients (16 male, mean age 45 years, range 16-80 years) with duodenal ulcers (n = 18) or non-ulcer dyspepsia (n = 2) and metronidazole-resistant H. pylori detected by histology, culture, in vitro sensitivity tests and a positive 13C-urea breath test entered the study. Follow-up was by 13C-urea breath test at the end of treatment and at 1, 3, 6, and 12 months. Eradication was defined as a negative 13C-urea breath test at least 1 month after finishing treatment. H. pylori was successfully eradicated in 21/30 (71%) patients (median follow-up 10.2 months, range 4-12 months). A pre-treatment ciprofloxacin-resistant strain was isolated in 1/9 patients in whom eradication failed. Of 30 patients 29 completed the 2-week regimen; one patient experienced dizziness after 3 days of treatment. The most common side-effect was increased stool frequency (n = 6). This 2-week treatment regimen for metronidazole-resistant H. pylori is well tolerated and achieves an eradication rate of 70%.

Eradication of Helicobacter pylori and prevention of recurrence of duodenal ulcer: a randomized, double-blind, multi-centre trial of omeprazole with or without clarithromycin.

BACKGROUND: Antimicrobial treatment for Helicobacter pylori eradication is currently recommended for all patients with duodenal ulcer disease, but consensus on the best treatment is lacking. METHODS: Patients with active duodenal ulcer and H. pylori were enrolled in a double-blind, randomized, placebo-controlled multi-centre study. Patients received omeprazole 40 mg daily for 28 days and either clarithromycin 500 mg t.d.s. or placebo t.d.s. for the first 14 days. Patients underwent endoscopy before starting treatment, at 2 weeks, immediately after stopping treatment if unhealed at 2 weeks, and at 1, 6 and 12 months after the end of treatment, or at the recurrence of symptoms. Eradication of H. pylori, duodenal ulcer healing and ulcer recurrence were measured. RESULTS: One-hundred and fifty-four patients were recruited and randomized to omeprazole plus clarithromycin (n = 74) or to omeprazole plus placebo (n = 80). One month after treatment, H. pylori was eradicated in 57 of 69 (83%; 95% CI: 72-91%) patients receiving omeprazole plus clarithromycin, compared with 1 of 75 (1%; 95% CI: 0-7%) receiving omeprazole alone (P < 0.001). In patients receiving omeprazole plus clarithromycin the ulcer healed at 2 weeks in 83% (95% CI: 71-91%) and at 4 weeks in 100% (95% CI: 95-100%), compared with 77% (95% CI: 66-86%) and 97% (95% CI: 91-100%) in those given omeprazole plus placebo (N.S.). Ulcers recurred at 12 months in 6% (95% CI: 1-16%) of patients given omeprazole plus clarithromycin, compared with 76% (95% CI: 63-86%) of patients given omeprazole plus placebo (P < 0.001). The incidence of side-effects was similar in both treatment groups (38% with clarithromycin dual therapy and 29% with omeprazole plus placebo; P = 0.304). Ninety per cent of patients took at least 90% of their prescribed medication. CONCLUSIONS: Omeprazole plus clarithromycin dual therapy eradicated H. pylori in 83% of patients with duodenal ulcer and significantly decreased 12-month recurrence from 76% to 6%.

Eradication of Helicobacter pylori with lansoprazole and clarithromycin.

BACKGROUND: Helicobacter pylori eradication with omeprazole and clarithromycin varies between 40 and 80%. The dose, frequency and duration of treatment may account for these differences. Lansoprazole, a recently introduced proton pump inhibitor, is a more potent H. pylori bacteriostat in vitro than omeprazole. The aim of this open, comparative, randomized study was to investigate the efficacy and safety of lansoprazole 30 mg once or twice a day (and for 2 vs. 4 weeks) plus clarithromycin 500 mg t.d.s. for 2 weeks. in the eradication of H. pylori. METHODS: Sixty-six patients with H. pylori infection received clarithromycin 500 mg t.d.s. for 2 weeks and one of four lansoprazole regimens: 30 mg once a day for 2 (Group 1, n = 16) or 4 (Group 2, n = 16) weeks, or 30 mg b.d. for 2 (Group 3, n = 18) or 4 (Group 4, n = 16) weeks. H. pylori eradication was determined by the 13C-urea breath test 4 weeks after finishing treatment. RESULTS: Per protocol analysis (53 patients) shows that H. pylori was eradicated in 6/13 (46%) in Group 1, 7/13 (54%) in Group 2, 9/14 (64%) in Group 3 and 9/13 (69%) in Group 4. Thirty-one of 68 patients experienced side effects. Analysis on an intention-to-treat basis gave similar results. CONCLUSION: The dose of lansoprazole appears to be more important than the duration of therapy. Dual therapy with lansoprazole and clarithromycin should be investigated further as a possible treatment regimen for H. pylori infection.

Lansoprazole, clarithromycin and metronidazole for seven days in Helicobacter pylori infection.

BACKGROUND: This study determines the efficacy and safety of a 1-week triple therapy regimen of lansoprazole, clarithromycin and metronidazole in an area with a high prevalence of pre-treatment metronidazole-resistant strains of Helicobacter pylori. METHODS: Seventy-five H. pylori positive patients with gastritis or duodenal ulcer were entered into an open study of lansoprazole 30 mg o.m., clarithromycin 250 mg b.d. and metronidazole 400 mg b.d. H. pylori status was determined by CLOtest, histology, culture and by 13C-urea breath test (repeated > or = 28 days after treatment). RESULTS: Seventy-one patients completed the treatment and returned for follow-up. H. pylori was eradicated in 61 of 71 (86%) patients by per-protocol analysis, and in 61 of 75 (81%) patients by intention-to-treat analysis. H. pylori was eradicated in 12 of 16 (75%) patients with metronidazole-resistant strains compared with 22 of 24 (92%) in patients with metronidazole-sensitive strains of H. pylori (P = 0.14). Fourty-five patients reported at least one adverse event, and three patients stopped treatment due to them (two with headaches and one with diarrhoea). CONCLUSIONS: A 1-week course of lansoprazole 30 mg o.m., clarithromycin 250 mg b.d. and metronidazole 400 mg b.d. eradicates H. pylori in up to 86% of patients. It is of proven benefit in patients with pre-treatment metronidazole-resistant strains of H. pylori.

Recurrence of duodenal ulcer after Helicobacter pylori eradication is related to high acid output.

BACKGROUND: Helicobacter pylori eradication reduces the recurrence of duodenal ulcers. It is unclear why duodenal ulcers rarely recur in the absence of reinfection with H. pylori or NSAID treatment. METHODS: Basal, gastrin-releasing peptide- and pentagastrin-stimulated peak acid outputs in patients with ulcer relapse after H. pylori eradication were measured, and compared with patients without ulcer relapse after H. pylori eradication. RESULTS: Pentagastrin-stimulated peak acid output was significantly higher in H. pylori-positive patients with duodenal ulcers than in H. pylori-negative controls, and fell significantly after H. pylori eradication. In H. pylori-negative patients with recurrent duodenal ulcers, pentagastrin-stimulated peak acid output was significantly higher than in controls and similar to H. pylori-positive patients with duodenal ulcers. CONCLUSIONS: These findings suggest that duodenal ulcer relapse after eradication of H. pylori may be related to high pentagastrin-stimulated peak acid output. In this subset of patients with duodenal ulcers, maintenance anti-secretory treatment may be necessary to prevent relapse.

Incidence of duodenal ulcer healing after 1 week of proton pump inhibitor triple therapy for eradication of Helicobacter pylori. The Lansoprazole Helicobacter Study Group.

BACKGROUND: A number of clinical studies have assessed the efficacy of short-term twice-daily Helicobacter pylori eradication regimens but few have investigated the proportion of patients in whom duodenal ulcer disease was healed with these regimens. AIM: To compare the safety and efficacy of four 1-week H. pylori eradication regimens in the healing of H. pylori associated duodenal ulcer disease. METHODS: Following endoscopic confirmation of duodenal ulcer disease and a positive CLO test, patients underwent a 13C-urea breath test to confirm H. pylori status. Treatment with one of four regimens: LAC, LAM, LCM or OAM, where L is lansoprazole 30 mg b.d., A is amoxycillin 1 g b.d., M is metronidazole 400 mg b.d., C is clarithromycin 250 mg b.d., and O is omeprazole 20 mg b.d., was assigned randomly to those patients who were H. pylori positive, with 62 (LAC), 64 (LAM), 61 (LCM) and 75 (OAM) patients in each treatment group. Follow-up breath tests and endoscopies were performed at least 28 days after the end of treatment. RESULTS: Duodenal ulcer disease was healed 28 days after treatment in 53/62 (85.5%) patients who were treated with LAC, 52/64 (81.3%) of patients treated with LAM, 49/61 (80.3%) of patients treated with LCM and 60/75 (80.0%) of patients treated with OAM (intention-to-treat analysis, n = 262, assumed unhealed if no follow-up endoscopy was performed). All the treatments were of similar efficacy (P = 0.85, chi-squared test) with regard to the healing of duodenal ulcer disease. CONCLUSIONS: The four 1-week treatment regimens were equally effective in healing H. pylori associated duodenal ulcer disease.