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Notes: Using real-time in situ laser light scattering we study, in this work, the influence of growth kinetics on the initial development of the crosshatched morphology and its subsequent evolution. The crosshatched morphology is characteristic of relaxed low strained layers (cursive-epsilon〈 2%) and has been traditionally related to the plastic relaxation process driven by generation and multiplication of dislocations. However we have observed that, if the growth rate is slow enough, the onset of crosshatch formation takes place at a layer thickness in which the dislocation formation and multiplication processes have not appeared yet. This reveals that the stress field generated by the small density of misfit dislocations formed by bending of the dislocations preexisting in the substrate is strong enough to affect the evolution of the growth front morphology. Our results also show that the starting point and evolution of this characteristic morphology depend on the growth rate in such a way that when the growth rate is lower the crosshatched morphology starts to develop at a smaller thickness and shows a faster evolution rate. © 2001 American Institute of Physics.

Notes: The localization of the L-like conduction states is found to change from the islands to the substrate in InAs quantum dots grown on GaAs as the island-size decreases. This is due to a size-induced modification of the strain state of the islands. The critical size should correspond to dislocation formation. As a result, small InAs islands coherently strained to GaAs exhibit optical properties markedly different from those of bulk InAs. © 2000 American Institute of Physics.

Notes: We have studied the influence of InP buffer-layer morphology in the formation of InAs nanostructures grown on InP(001) substrates by solid-source molecular-beam epitaxy. Our results demonstrate that when InP buffer layers are grown by atomic-layer molecular-beam epitaxy, InAs quantum dot-like structures are formed, whereas InP buffer layers grown by MBE produce quantum-wire-like structures. The optical properties of these corrugated structures make them potential candidates for their use in light-emitting devices at 1.55 μm. © 2000 American Institute of Physics.

Notes: In-plane optical anisotropies of (001)-oriented InAs/InP self-assembled quantum wires and dots structures are studied by means of photoreflectance in the spectral region of the E1 transition of bulk InAs. The energy position of the transition observed in the quantum wires depends on the light polarization; quantum dots do not exhibit, in contrast, such an optical anisotropy. This anisotropy is attributed to the splitting of the four-fold degenerate E1 transition produced by the strong triaxial behavior of the strain that appears in wires and not in dots. © 2000 American Institute of Physics.

Notes: Starting from optimal control, various series of infrared, ultrashort laser pulses with analytical shapes are designed in order to drive a preoriented molecule from its ground torsional state, which represents the coherent superposition of left and right atropisomers, towards a single enantiomer. Close analysis of the population dynamics, together with the underlying symmetry selection rules for the laser induced transitions, yields the mechanism. Namely, the molecule is driven from its ground vibrational state towards the coherent superposition of the lowest doublet of states via a doublet of excited torsional states with opposite symmetries. This pump-and-dump mechanism can be achieved by simpler series of analytical laser pulses. This decomposition of the optimal pulse into analytical subpulses allows us to design different scenarios for the selective preparation of left or right enantiomers. Exemplary this is demonstrated by quantum simulations of representative wave packets for the torsional motions of the model system, H2POSH, in the electronic ground state, based on the ab initio potential energy surface, and with ab initio dipole couplings. © 2000 American Institute of Physics.

Notes: The orbital free ab initio molecular dynamics method is applied to study the static and dynamic structure of liquid Al near the triple point. The method uses a new kinetic energy functional, along with a local pseudopotential constructed within the same kinetic energy functional. The results obtained for the dynamic structure factor are compared with recent experimental data. © 2001 American Institute of Physics.

Notes: Highly filled composites, Ormocers (organically modified ceramics) and ‘smart’ materials have been developed to overcome the polymerization shrinkage problems of conventional composite materials. The purpose of the current study was to investigate the effect of longer-term (up to 8 weeks) ageing of these resin-based dental restorative materials and determine the effect of post-curing on cytotoxicity. Twelve discs of each material (Colombus/IDR, Definite/Degussa, Ariston pHc/Vivadent) were either light-cured (Lc) or light-cured and post-cured (Pc). For cytotoxicity testing, the discs were placed in contact with cell culture medium (DMEM) and incubated at 37 °C. Extracts from composite materials were collected after 24 h and weekly over a time period of 8 weeks. Cytotoxicity of the eluates to cultured fibroblasts (Balb/c3T3) were measured by the succinic dehydrogenase (SDH) activity (MTT assay) and the results expressed in percentage of negative controls (Teflon discs). The results showed that ageing significantly influenced the cytotoxicity of the materials. Except for Ariston pHc, materials were less cytotoxic after 8 weeks of ageing than they were in early intervals and post-curing was not generally useful in reducing cytotoxicity. The Ariston pHc was initially moderately toxic, but then become highly cytotoxic for 5 weeks before returning to initial levels. The current study demonstrated the importance of assessing the cytotoxicity of resin composite materials at multiple times.

Notes: To perform a meta-analysis of studies comparing twice daily, one-week triple therapy with a proton pump inhibitor, clarithromycin (C) and amoxycillin (A) (PCA) vs. those using proton pump inhibitor, clarithromycin and a nitroimidazole (N) (PCN) for H. pylori eradication.〈section xml:id="abs1-2"〉〈title type="main"〉Review methods:Selection criteria: Comparative randomized trials of PCA vs. PCN were included. Data sources: PubMed database and abstracts from congresses until September 1999. Statistics: Meta-analysis was performed combining the Odds Ratios (OR) of the individual studies in a global OR (Peto method) both on an intention-to-treat (ITT) and on a per protocol (PP) basis.〈section xml:id="abs1-3"〉〈title type="main"〉Results:Twenty-two studies fulfilled the inclusion criteria. Eighteen studies reported ITT and 20 PP analysis. Mean H. pylori eradication rates were 81% (95% CI: 79–83%) ITT, and 84% (82–86%) PP with PCA, and 81% (78–83%) ITT and 84% (82–86%) PP with PCN; the odds ratio for the effect of PCA vs. PCN was 1 (0.83–1.22) on an ITT, and 0.98 (0.8–1.2) on a PP basis. Subanalysis showed that mean H. pylori eradication efficacy with PC(250 b.d.)A was 81% (78–85%) ITT, vs. 86% (83–89%) with PC(250 b.d.)N. The odds ratio for this comparison was 0.68 (0.48–0.98). Finally, when comparing PC(500 b.d.)A against PC(250 b.d.)N ITT cure rates were 77% (74–80%), and 75% (72–78%) with an odds ratio of 1.18 (0.93–1.5).〈section xml:id="abs1-4"〉〈title type="main"〉Conclusion:Overall, one-week combination regimens of PCA and PCN present similar H. pylori eradication efficacy. Nevertheless, the PCN regimen obtains significantly better results when using low doses of C (250 mg b.d.).

Notes: To evaluate whether proton pump inhibitors are more effective than H2-antagonists (H2-A) for the treatment of bleeding peptic ulcer.〈section xml:id="abs1-2"〉〈title type="main"〉Data sources:PubMed database until January 2000.〈section xml:id="abs1-3"〉〈title type="main"〉Study selection:Comparative randomized trials of proton pump inhibitors (omeprazole, lansoprazole, or pantoprazole) vs. H2-A (cimetidine, ranitidine or famotidine).〈section xml:id="abs1-4"〉〈title type="main"〉Data extraction:Meta-analysis combining the odds ratios (OR) of the individual studies in a global OR (Peto method).〈section xml:id="abs1-5"〉〈title type="main"〉Outcomes evaluated:Persistent or recurrent bleeding, need for surgery, or mortality.〈section xml:id="abs1-6"〉〈title type="main"〉Data synthesis:Eleven studies fulfilled the inclusion criteria and contained data for at least one of the planned comparisons. Persistent or recurrent bleeding was reported in 6.7% (95% CI: 4.9–8.6%) of the patients treated with proton pump inhibitors, and in 13.4% (95% CI: 10.8–16%) of those treated with H2-A (OR 0.4; 95% CI: 0.27–0.59) (χ2-homogeneity test, 18; P=0.09). Surgery was needed in 5.2% (95% CI: 3.4–6.9%) of the patients treated with proton pump inhibitors, and in 6.9% (95% CI: 4.9–8.9%) of the patients treated with H2-A (OR 0.7; 95% CI: 0.43–1.13). Respective percentages for mortality were 1.6% (95% CI: 0.9–2.9%) and 2.2% (95% CI: 1.3–3.7%) (OR 0.69; 95% CI: 0.31–1.57).〈section xml:id="abs1-7"〉〈title type="main"〉Sub-analysis:Five studies evaluated the effect of both therapies given in bolus injections on persistent or recurrent bleeding rate, which was 6% (95% CI: 3.6–8.3%) and 8.1% (95% CI: 5.3–10.9%), respectively (OR, 0.57; 95% CI: 0.31–1.05). Persistent or recurrent bleeding in high risk patients (Forrest Ia, Ib and IIa) occurred in 13.2% (95% CI: 7.9–8%) of the patients treated with proton pump inhibitors and in 34.5% (27–42%) of those treated with H2-A (OR 0.28; 95% CI: 0.16–0.48). In patients not having endoscopic therapy, persistent or recurrent bleeding was reported, respectively, in 4.3% (95% CI: 2.7–6.7%) and in 12% (95% CI: 8.7–15%) (OR 0.24; 95% CI: 0.13–0.43). Less marked differences were observed in patients having adjunct endoscopic therapy: 10.3% (95% CI: 6.7–13.8%) and 15.2% (11.1–19.3%) (OR 0.59; 95% CI: 0.36–0.97). Moreover, the significance disappeared in this group when a single outlier study was excluded.〈section xml:id="abs1-8"〉〈title type="main"〉Conclusions:Proton pump inhibitors are more effective than H2-A in preventing persistent or recurrent bleeding from peptic ulcer, although this advantage seems to be more evident in patients not having adjunct sclerosis therapy. This beneficial effect seems to be similar or even more marked in patients with Forrest Ia, Ib or IIa ulcers. However, proton pump inhibitors are not more effective than H2-A for reducing surgery or mortality rates. Nevertheless, the data are too scarce and heterogeneous to draw definitive conclusions, and further comparative trials are clearly warranted.

Notes: [Auszug] Stars that explode as supernovae come in two main classes. A type Ia supernova is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectrum; this class of supernova is thought to produce the majority of iron-peak elements in the Universe. ...