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Notes: We report the improvement of quantum cascade lasers emitting at λ∼5 μm by introducing AlAs blocking barriers together with strain-compensating InAs layers into the active regions. The blocking barriers are designed to selectively prevent electrons in the initial laser state from tunneling out of the active region, while maintaining the high tunneling probabilities of the electrons in the final laser states. Adopting blocking barriers, the maximum peak power per facet at 77 K (300 K) is increased from 285 (30 mW) to 900 mW (240 mW), and the maximum operation temperature in pulsed mode has been improved from 320 to 350 K with respect to a reference sample without blocking barriers. © 2002 American Institute of Physics.

Notes: A microscopic laser theory is used to investigate gain and threshold properties in a GaAsSb quantum-well laser. Depending on the geometry of the type-II quantum-well gain region, there may be appreciable band distortions due to electron–hole charge separation. The charge separation and accompanying band distortions lead to interesting optical behaviors, such as excitation-dependent oscillator strength and band edge energies. Implications to laser operation include significant blueshift of the gain peak with increasing injection current, and inhibition of spontaneous emission, which may result in threshold current reduction. © 2001 American Institute of Physics.

Notes: We present theoretical and experimental results for the temperature dependence of threshold current in an InGaAsN/GaAs vertical-cavity surface-emitting laser (VCSEL) operating at 1.3 μm under continuous-wave current injection. Using a microscopic many-body laser theory, good agreement with experimental data is obtained. The influence of radiative and nonradiative recombination processes on the threshold current–density is investigated theoretically. Also, comparison to a GaAs/AlGaAs VCSEL emitting at 850 nm is made. © 2001 American Institute of Physics.

Notes: Microscopic calculations of laser gain spectra are presented for AlGaInN wurtzite quantum-well structures that are under compressive, zero and tensile strain. It is found that the optical nonlinearities induced by the combination of strain, quantum-confined Stark effect and many-body Coulomb interactions give rise to optical behavior that can differ significantly from that in conventional semiconductor lasers. © 2002 American Institute of Physics.

Notes: Thromboxanes are produced in excess and platelets are activated in active Crohn’s disease. Preliminary reports have suggested that ridogrel, a dual thromboxane synthase inhibitor and receptor antagonist, may have therapeutic benefit in patients with inflammatory bowel disease.〈section xml:id="abs1-2"〉〈title type="main"〉Aims:To investigate the efficacy of ridogrel in patients with active Crohn’s disease.〈section xml:id="abs1-3"〉〈title type="main"〉Patients and methods:This was an international, multicentre, randomized, double-blind, placebo-controlled trial of 5 mg/day oral ridogrel for 12 weeks in 85 patients with moderately active Crohn’s disease. Sixty patients were randomized to receive ridogrel, and 25 to placebo. The Crohn’s disease activity index (CDAI) was used to assess disease activity: remission was defined as a CDAI 〈 150. Changes in clinical condition, as assessed by the Harvey–Bradshaw index, global evaluation by the investigator and the patient, and blood measures of inflammation, were used as secondary outcomes.〈section xml:id="abs1-4"〉〈title type="main"〉Results:The patients’ mean (s.d.) CDAI at recruitment was 277 (68) in the ridogrel treated group and 265 (70) in the placebo group. At their final assessment, 20 out of 60 (35%) patients who had been given ridogrel in an intention-to-treat analysis and seven out of 25 (28%) patients given placebo were in remission (no significant difference). No significant differences in Harvey– Bradshaw index or global evaluation were noted between patients given ridogrel and those given placebo. Adverse events were similar in both groups.〈section xml:id="abs1-5"〉〈title type="main"〉Conclusion:A 5-mg dose of oral ridogrel was not more effective than placebo in inducing remission in patients with moderately active Crohn’s disease. If thromboxane synthesis and platelet function are to be targeted for the treatment of Crohn’s disease, more potent agents require development and assessment.

Notes: Studies assessing the efficacy of triple therapy containing clarithromycin and amoxicillin for the eradication of Helicobacter pylori infection and healing of duodenal ulcers in Asian and African countries are limited.〈section xml:id="abs1-2"〉〈title type="main"〉Aim:To determine the efficacy and safety of 1-week triple therapy with omeprazole, amoxicillin and clarithromycin for eradicating H. pylori infection in patients with active duodenal ulcer living in Asian and African regions.〈section xml:id="abs1-3"〉〈title type="main"〉Methods:This was an open-label, multicentre study in 11 centres in Asia and Africa. Patients with endoscopy-proven duodenal ulcer and who were H. pylori-positive were treated with clarithromycin 500 mg, omeprazole 20 mg, and amoxicillin 1000 mg, all given twice daily for 7 days. Upper endoscopy was repeated at week 6 to check for ulcer healing and H. pylori status.〈section xml:id="abs1-4"〉〈title type="main"〉Results:A total of 117 patients were recruited. H. pylori eradication rates were 85% by per protocol analysis and 80% by intention-to-treat analysis. Ulcer healing was found in 94% of subjects (per protocol analysis). Clinical success, measured by change of pre-treatment ulcer symptoms, was strongly supported by complete resolution or improvement in 100% of the evaluable patients (per protocol analysis). Since treatment-related adverse events, when present, were largely mild or moderate, the triple therapy regimen was considered safe.〈section xml:id="abs1-5"〉〈title type="main"〉Conclusion:Seven-day triple therapy with omeprazole, amoxicillin, and clarithromycin was efficacious for treating Asian and African patients with duodenal ulcer disease associated with H. pylori infection, and the treatment regimen was well-tolerated.

Notes: Introduction : Esomeprazole, the first proton pump inhibitor to be developed as an optical isomer, has demonstrated more effective healing vs. omeprazole and lansoprazole in patients with reflux oesophagitis (RO). However, RO recurs in a high proportion (∼80%) of these patients within 12 months of initial therapy, highlighting the importance of maintenance treatment. Previous studies have shown esomeprazole to be effective as maintenance therapy in healed RO patients.Aim:  This study was conducted to compare esomeprazole 20 mg once daily (o.d.) with lansoprazole 15 mg o.d. for the prevention of recurrence of RO.Methods:  1391 patients with endoscopically verified RO (LA classification) were enrolled in this randomized, double-blind, parallel-group, multicentre trial. During the initial healing phase of the study, all patients received 4–8 weeks' open treatment with esomeprazole 40 mg: 1236 healed (identified by endoscopy at 4 and 8 weeks) and symptom-free (i.e. no heartburn or acid regurgitation) patients were randomized to 6 months' maintenance treatment with esomeprazole 20 mg o.d. or lansoprazole 15 mg o.d.. Time to relapse (relapse of RO and/or discontinuation due to symptom recurrence) was analysed using a log-rank test.Results:  Esomeprazole maintained a significantly higher proportion of patients in remission than lansoprazole over the 6-month course of treatment (P 〈 0.0001, intention-to-treat analysis). After 6 months' treatment, 83% of esomeprazole recipients were in remission compared with 74% of lansoprazole recipients (life-table estimates). Esomeprazole gave a longer time to relapse than lansoprazole irrespective of baseline LA Grade, significantly so for baseline LA Grades B, C and D (P 〈 0.05 for each comparison). Significantly more patients were free from heartburn in the esomeprazole group compared with the lansoprazole group at 1, 3 and 6 months (P 〈 0.05). Significant differences at 6 months between esomeprazole 20 mg o.d. and lansoprazole 15 mg o.d. were also observed for control of epigastric pain and acid regurgitation (P 〈 0.05 and P 〈 0.001, respectively). Both treatment regimens were well tolerated.Conclusion:  Esomeprazole 20 mg o.d. is a more effective maintenance treatment than lansoprazole 15 mg o.d. for symptom-free patients with healed RO.

Notes: Aim : To compare the efficacy of esomeprazole, 20 mg once daily, vs. lansoprazole, 15 mg once daily, for the maintenance treatment of patients with healed reflux oesophagitis.Methods : During the initial open healing phase, 1391 patients with endoscopically verified reflux oesophagitis and a history of heartburn, with or without acid regurgitation, received esomeprazole 40 mg for 4–8 weeks. Patients who were healed (identified by endoscopy at 4 or 8 weeks) and symptom free were then randomized to receive 6 months of treatment with esomeprazole, 20 mg once daily, or lansoprazole, 15 mg once daily.Results : Esomeprazole, 20 mg once daily, maintained a significantly higher proportion of patients in remission than lansoprazole, 15 mg once daily, over 6 months [83% (95% CI, 80–86%) of esomeprazole recipients compared with 74% (95% CI, 70–78%) of lansoprazole recipients; P 〈 0.0001; life table estimates]. When data were analysed according to baseline Los Angeles grade classification, esomeprazole, 20 mg once daily, achieved consistently higher remission rates across all grades of disease severity, whereas the efficacy of lansoprazole decreased to a greater extent with increasing severity of reflux oesophagitis.Conclusion : Esomeprazole, 20 mg once daily, is more effective than lansoprazole, 15 mg once daily, in maintaining remission in patients with healed reflux oesophagitis.