Theoretical Analysis of Diffused Quantum-well Lasers and Optical Amplifiers

Diffused quantum-well (QW) distributed feedback (DFB) lasers and optical amplifiers will be theoretically analyzed in this paper. For DFB lasers, a design rule will be proposed and the validity of the design rule will be discussed with respect to changes in the injected carrier density. The range of grating period, which can be used in the design, is discussed. As a consequence, the maximum tuning range of the emission wavelength can be estimated without involving the time-consuming self-consistent simulation. The features of polarization independence of optical amplifiers achieved by using diffused QWs are also discussed. Our theoretical results successfully explain why polarization independence can achieve in the long-wavelength tail of the modal gain and absorption coefficient but not at photon energies above the transition edge. This explanation applies to other tensile-strained QWs for polarization-independent applications. The understanding is crucial for optimizing polarization-independent devices. To conclude, our analysis of the diffused QW optical devices demonstrates that QW intermixing technology is a practical candidate for not only realizing monolithic photonic integrated circuit, but also enhancing optical device performance.published_or_final_versio

Interdiffusion-induced polarization-independent optical gain of an InGaAs-InP quantum-well with carrier effects

A theoretical study of the polarization-independent optical gain using group V sublattice interdiffusion in InGaAs-InP quantum wells (QW's) is presented here. The reverse bias and carrier effects on the subband structures, transition energy, and optical gain of the interdiffused QW are discussed. The interdiffused QW structures are optimized in terms of their subband structure, carrier density, structural parameters, and properties of optical gain spectra. The results show that an optimized interdiffused QW structure can produce polarization-independent optical gain over a range of operation wavelengths around 1.5 μm, although the differential gain and linewidth enhancement factor are slightly degraded. The required tensile strain for the polarization-independent optical properties of a lattice-matched QW structure may be generated using interdiffusion. These results suggest that polarization-independent optical devices can be fabricated using interdiffusion in a lattice-matched InGaAsP QW structure.published_or_final_versio

Visible photoluminescence in ZnO tetrapod and multipod structures

The investigation of the properties of ZnO tetrapod and multipod structures using scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy was discussed. The ZnO samples were fabricated by heating a mixture of ZnO, GeO2 and graphite at 1100°C in order to modify the morphology of the fabricated structures. The room temperature of PL was measured by using a HeCd laser excitation source (325 nm). It was found that the green PL was due to transition between a shallow donor and deep acceptor in the absence of g ≈ 1.96 EPR signal and transition between the conduction band and deep acceptor in the absence of g ≈ 1.96 EPR signal.published_or_final_versio

Uncertainty assessment in river flow projections for Ethiopia’s Upper Awash Basin using multiple GCMs and hydrological models

Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios for the period 2071–2100. Hydrological models vary in their spatial distribution and process representations of unsaturated and saturated zones. Very good performance is achieved for 1975–1999 (NSE: 0.65–0.8; r: 0.79–0.93). GCM-related uncertainty dominates variability in projections of high and mean discharges (mean: –34% to +55% for RCP4.5,–2% to +195% for RCP8.5). Although GCMs dominate uncertainty in projected low flows, inter-hydrological model uncertainty is considerable (RCP4.5: –60% to +228%, RCP8.5: –86% to +337%). Analysis of variance uncertainty attribution reveals that GCM-related uncertainty occupies, on average, 68% of total uncertainty for median and high flows and hydrological models no more than 1%. For low flows, hydrological model uncertainty occupies, on average, 18% of total uncertainty; GCM-related uncertainty remains substantial (average: 28%)

Conditional targeting of MAD1 to kinetochores is sufficient to reactivate the spindle assembly checkpoint in metaphase

Fidelity of chromosome segregation is monitored by the spindle assembly checkpoint (SAC). Key components of the SAC include MAD1, MAD2, BUB1, BUB3, BUBR1, and MPS1. These proteins accumulate on kinetochores in early prometaphase but are displaced when chromosomes attach to microtubules and/or biorient on the mitotic spindle. As a result, stable attachment of the final chromosome satisfies the SAC, permitting activation of the anaphase promoting complex/cyclosome (APC/C) and subsequent anaphase onset. SAC satisfaction is reversible, however, as addition of taxol during metaphase stops cyclin B1 degradation by the APC/C. We now show that targeting MAD1 to kinetochores during metaphase is sufficient to reestablish SAC activity after initial silencing. Using rapamycin-induced heterodimerization of FKBP-MAD1 to FRB-MIS12 and live monitoring of cyclin B1 degradation, we show that timed relocalization of MAD1 during metaphase can stop cyclin B1 degradation without affecting chromosome-spindle attachments. APC/C inhibition represented true SAC reactivation, as FKBP-MAD1 required an intact MAD2-interaction motif and MPS1 activity to accomplish this. Our data show that MAD1 kinetochore localization dictates SAC activity and imply that SAC regulatory mechanisms downstream of MAD1 remain functional in metaphase. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00412-014-0458-9) contains supplementary material, which is available to authorized users

Acceptance of spousal death: The factor of time in bereaved older adults' search for meaning

Response to the death of a spouse was examined by focusing on acceptance, which was conceptualized as both a process and an outcome. Grounded theory was applied to analyze the experience of 15 bereaved Hong Kong Chinese older adults. The main theme that emerged was time. Acceptance of spousal death was found to be related to the search for meaning in 2 time-related themes: timing of spousal death and paradoxical time perception. For paradoxical time perception, 2 subthemes were identified: truncation and daily isolation in time. For bereaved older adults, time-related meaning seeking may be best fostered by self-transcendence, (e.g., participation in volunteer work and social activities). © Taylor & Francis Group, LLC.link_to_subscribed_fulltex

A cross-national comparison of Hong Kong and U.S. student beliefs and preferences in end-of-life care: Implications for social work education and hospice practice

In this mixed methods study, the authors explored differences and similarities in beliefs about death and dying as well as end-of-life care preferences among social work students in Hong Kong and the United States. A convenience sample of 176 social work students from Hong Kong and 58 from the United States was recruited to complete a quantitative questionnaire with three open-ended questions. Findings revealed differences as well as similarities in beliefs about death and dying and that a larger proportion of Hong Kong students as compared to U.S. students preferred curative rather than palliative care. Implications for social work education and hospice practice in both countries include the need for social work student and practitioner self-awareness in order to prepare for culturally competent practice and policies that are relevant across cultures. © Taylor & Francis Group, LLC.link_to_subscribed_fulltex

Family predictors of psychosocial outcomes among Hong Kong Chinese cancer patients in palliative care: Living and dying with the support paradox

A good death is universally desired. For Chinese patients, the family is believed to play a key role in making this possible. This study aims at exploring the relationship of family-related factors and psychosocial outcomes among Hong Kong Chinese cancer patients in palliative care. Clinical data mining was adopted as the research method. Nurses collected data from clinical interviews with incoming palliative care patients. A total of 935 patients from three years of deceased patient records was included. Stepwise regression analysis demonstrated that caregivers' support and acceptance predicted fewer psychosocial symptoms of patients, whereas depressed family response to patient's illness and family anxiety predicted a greater number of psychosocial symptoms of patients upon their admission to palliative care. The findings suggested two possible pathways toward enhancing the psychosocial experience of dying patients, that is, the family support pathway and the familial-altruistic pathway. Further reflections on the findings may suggest that these patients may be situated in a support paradox, in which they desire family support but also worry about the burden that support places on family members. Implications for practice were discussed in the cultural context.link_to_subscribed_fulltex