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Notes: We report on reflected high-energy electron-diffraction and transmission electron microscopy plane-view investigation of the dislocation structure in doped and undoped ZnSe/GaAs(001) grown by molecular-beam epitaxy and metal-organic vapor-phase epitaxy. The thicknesses of the investigated layers vary between 60 and 900 nm. Several stages of dislocation formation are found which occur at distinct layer thicknesses. Frank partial dislocations (up to 500 nm), Shockley partial dislocations (between 130 and 400 nm) with a maximum density at 300 nm, and perfect 60° dislocations (above 300 nm) are observed in samples with perfectly smooth surface. The formation of Shockley partial dislocations is strongly anisotropic which might be due to the higher mobility of α-type dislocations. An increased roughness of the growing surface yields a suppression of Shockley partial dislocations and an irregular dislocation network with dislocations inclined to the 〈110〉 directions. A regular dislocation network with straight dislocations is found in Cl-doped samples. © 1996 American Institute of Physics.

Notes: The electrical and interfacial properties of gold-polyimide-silicon structures were studied experimentally by measuring the capacitance-voltage (C-V) characteristics. Two different polyimides of PMDA-ODA (synthesized from pyromellitic dianhydride and oxydianiline) and BTDA-ODA (from benzophenone tetracarboxylic dianhydride and oxydianiline), respectively, were employed. Polyimide coatings on n-type silicon (with a doping level N=5×1014 cm−3) were prepared by spin coating followed by thermal cure to range from 0.4 to 2.1 μm in thickness. The resulting high frequency C-V plots of these structures were well defined and could be described by the basic theory on metal-insulator-semiconductor (MIS) devices. Distinct differences in the C-V characteristics were observed, depending upon the polyimides. PMDA-ODA dielectrics resulted in C-V hysteresis, believed to be caused by charge injection. On the other hand, BTDA-ODA showed much smaller hysteresis, but some stretch-out in the C-V curve. These differences are attributed to the different interfacial properties of these polyimides in contact with silicon substrates.

Notes: Electrical conduction phenomena in polyimide (Kapton) films were studied with particular attention devoted to the separation of interface and bulk phenomena. The measurements were carried out with a variety of methods in the temperature range of 50 to 270 °C at electrical fields of 104 to 6×105 V/cm and at time intervals of up to 2×104 s after voltage application. Biased, two-side metallized samples yield, after sufficiently long voltage application, interface-controlled steady-state currents described by Schottky injection, modified by space-charge layers in the vicinity of the electrodes. The effective work function for aluminum-polyimide is estimated to be 1.7 eV in the temperature range between 100 and 270 °C. A distinct dependence of these currents on electrode material is observed. Bulk phenomena were studied on one-side metallized samples subject to positive-corona charge injection. At temperatures below 200 °C, significantly larger currents than those for biased, two-side metallized samples were observed. The current-voltage characteristics are ohmic at low fields and space-charge limited at high fields. From these data, trap modulated mobilities for positive carriers of 4×10−12 cm2/V s at 50 °C and 10−9 cm2/V s at 200 °C, ohmic bulk conductivities of 10−16 (Ω cm)−1 at 100 °C and 10−14 (Ω cm)−1 at 200 °C and an intrinsic carrier density of 5×1013 cm−3 independent of temperature are obtained. Activation energies for the mobility are between 0.2 and 0.8 eV for the temperature range between 50 and 200 °C.

Notes: Second harmonic generation is investigated in a ZnSe/ZnS0.22Se0.78 waveguide grown by metal organic vapor phase epitaxy on (001) GaAs substrate. Phase matching is achieved by a first order periodic modulation of the nonlinear susceptibility χ(2) within the waveguide structure. The modulation is generated by a focused ion beam implantation technique, resulting in a well confined damage of the crystalline structure. The observed phase matching wavelengths corresponding to various modulation periods between 1.6 and 1.9 μm agree with those predicted by calculations. © 1998 American Institute of Physics.

Notes: The thermal outdiffusion of hydrogen from undoped ZnSe layers grown by metalorganic vapor phase epitaxy has been investigated. The samples were grown using dimethyl-zinc-triethylamine, di-tert.-butylselenide as precursors with hydrogen and nitrogen as carriergas. The typical atomic hydrogen concentrations of the samples is nH=1018 cm−3, which originates from pyrolysis products of the organometallic precursors. The incorporation from the carrier gas is negligible. Control samples grown by molecular beam epitaxy in the presence of atomic and molecular hydrogen in the growth chamber showed no hydrogen incorporation. The outdiffusion process was investigated using transient effusion experiments. The experiments are explained by diffusion controlled effusion with a diffusion coefficient of D(T)=1.4×10−11 exp[−0.33(±0.03) eV/(kBT)]cm2/s. © 1998 American Institute of Physics.

Notes: The ubiquitous nature of irritable bowel syndrome (IBS), coupled with a lack of good treatment options, has created the impression that the condition must represent a large drain on health-care resources. The literature certainly appears to support this view but is largely based on patients seen in referral centres (10–15%) and it may not be appropriate to extrapolate these data to the IBS population as a whole (85–90%).In addition to reviewing such literature that exists on the economics of IBS, this paper contains some new data, which suggest that the direct costs of the condition, certainly in the UK, may not be quite as high as has previously been assumed. This may be partly due to factors such as the low cost of the drugs used to treat the condition and the tendency for many patients to stop consulting because of disenchantment with the inadequacies of current therapy. Conversely, the indirect and intangible costs of the disorder appear to be much greater, but these burdens obviously do not have such an impact on those responsible for purchasing and providing health care for IBS sufferers.Paradoxically, if a new, effective therapy for IBS were forthcoming, the situation could change dramatically, especially if it involved a new drug. Any such agent would inevitably be more expensive than anything available today, leading to a potentially dramatic escalation in the direct costs of this disorder.

Notes: We describe the development and evaluation of a new disease-specific instrument, the Irritable Bowel Syndrome Quality of Life Questionnaire (IBSQOL), which was designed for use in patients with irritable bowel syndrome. The IBSQOL measures 10 domains found to be relevant to patients with irritable bowel syndrome: emotional health, mental health, health belief, sleep, energy, physical functioning, diet, social role, physical role, and sexual relations.〈section xml:id="abs1-2"〉〈title type="main"〉Methods:During its development and evaluation, the IBSQOL was administered to over 500 patients with irritable bowel syndrome—two groups of patients from tertiary care centres, three focus groups of 8–12 patients each, and 287 patients in a national irritable bowel syndrome support network. As a control, the IBSQOL was also administered to 37 patients who did not have irritable bowel syndrome but had other gastrointestinal disorders. Statistical analyses to test the reliability and validity of the IBSQOL were performed using Cronbach's α coefficient.〈section xml:id="abs1-3"〉〈title type="main"〉Results:Responses from the focus groups indicated that the IBSQOL was easy to complete and did not require too much time to fill out (≈ 25 min). Statistical analyses of the final 30-item version of the IBSQOL demonstrated that it had both adequate validity and reliability (α ≥ 0.60). A comparison of mean IBSQOL scores of persons with and without irritable bowel syndrome (but with other gastrointestinal conditions) showed no difference between the two groups with irritable bowel syndrome; however, scores for both irritable bowel syndrome groups were considerably lower than for the non-irritable bowel syndrome group, suggesting better health-related quality of life in patients who do not have irritable bowel syndrome. This further demonstrated the validity of the IBSQOL in targeting questions and domains specific to patients with irritable bowel syndrome.〈section xml:id="abs1-4"〉〈title type="main"〉Conclusions:Evaluation of the IBSQOL included testing the questionnaire in a large number of patients, which resulted in a revised and well-constructed instrument that demonstrated both adequate validity and reliability. The IBSQOL is currently being used in large-scale clinical trials to measure changes in quality of life in patients with irritable bowel syndrome following treatment intervention.