Photoluminescence characteristics of zinc blende InAs nanowires

A detailed understanding of the optical properties of self-catalysed (SC), zinc blende (ZB) dominant, nanowires (NWs) is crucial for the development of functional and impurity-free nanodevices. Despite the fact that SC InAs NWs mostly crystallize in the WZ/ZB phase, there are very limited reports on the photoluminescence (PL) properties of ZB InAs NWs. Here, we report on the PL properties of Molecular Beam Epitaxy grown, SC InAs NWs. The as-grown NWs exhibit a dominant band to band (BtB) peak associated with ZB, InAs with an emission energy of ~0.41 eV in good agreement with the band gap energy of ZB InAs and significantly lower than that of the wurtzite phase (~0.48 eV). The strong BtB peak persists to near room temperature with a distinct temperature-dependent red-shift and very narrow spectral linewidth of ~20 meV (10 K) which is much smaller than previously reported values. A narrowing in PL linewidth with increasing NWs diameter is correlated with a decline in the influence of surface defects resulting from an enlargement in NWs diameter. This study demonstrates the high optical property of SC InAs NWs which is compatible with the Si-complementary metal-oxide-semiconductor technology and paves the way for the monolithic integration of InAs NWs with Si in novel nanodevices

Prognosis of non traumatic coma: The role of some socio-economic factors on its outcome in Ibadan, Nigeria

Background : Coma occurring in the course of an illness, irrespective of cause, traditionally implies a poor prognosis and many factors may determine its outcome. These factors must be identified and possibly stratified in their order of importance. This research seeks to identify these factors and how they influenced the outcome of non-traumatic coma in our environment. Methods : Two hundred consecutive patients, aged 18-79 years who met the inclusion criteria, the Glasgow coma scale (GCS) score of < 8, history and physical findings suggestive of medical illness, no head trauma or sedation, were recruited into the study from August 2004 to March 2005 at the University College Hospital (UCH), Ibadan, after obtaining institutional ethical clearance and consent from patients\u2032 guardians. Detailed history of illness including the bio-data and time to present to the hospital and treatments given were noted. Thereafter, the clinical course of the patients was monitored daily for a maximum of 28 days during which the support of the family and/ or the hospital social welfare was evaluated. Results : During the 8-month period of the study, 76% (152) of the patients died while 24% (48) survived. The following factors were associated with high mortality rate: inability to confirm diagnosis (100%), poor family support (97.1%), delay in making a diagnosis within 24 h (85.4%), poor family understanding of disease (84.1%), need for intensive care admission and management (83.3%), poor hospital social welfare support (82.4%), presentation to UCH after 6 h of coma (76.7%), and referral from private health facilities (75.7%). Others include substance abuse (100%) and seropositivity to HIV (96%) and hepatitis B surface antigen (92%) antibodies, among others. Conclusion : This study has demonstrated that socio-economic factors such as gender, occupation, risky lifestyle behaviors, late presentation or referral to hospital, late diagnosis and treatment, and poor family support contributed to poor outcome of nontraumatic coma. It is hoped that improvement, modification, or correction of these factors may improve coma outcome

Realization of vertically aligned, ultra-high aspect ratio InAsSb nanowires on graphite

The monolithic integration of InAs1–xSbx semiconductor nanowires on graphitic substrates holds enormous promise for cost-effective, high-performance, and flexible devices in optoelectronics and high-speed electronics. However, the growth of InAs1–xSbx nanowires with high aspect ratio essential for device applications is extremely challenging due to Sb-induced suppression of axial growth and enhancement in radial growth. We report the realization of high quality, vertically aligned, nontapered and ultrahigh aspect ratio InAs1–xSbx nanowires with Sb composition (xSb(%)) up to ∼12% grown by indium-droplet assisted molecular beam epitaxy on graphite substrate. Low temperature photoluminescence measurements show that the InAs1–xSbx nanowires exhibit bright band-to-band related emission with a distinct redshift as a function of Sb composition providing further confirmation of successful Sb incorporation in as-grown nanowires. This study reveals that the graphite substrate is a more favorable platform for InAs1–xSbx nanowires that could lead to hybrid heterostructures possessing potential device applications in optoelectronics

Optical and structural investigation of a 10 μm InAs/GaSb type-II superlattice on GaAs

We report on a 10 μm InAs/GaSb type-II superlattice (T2SL) grown by molecular beam epitaxy on a GaAs substrate using an interfacial misfit (IMF) array and investigate the optical and structural properties in comparison with a T2SL grown on a GaSb substrate. The reference T2SL on GaSb is of high structural quality as evidenced in the high-resolution x-ray diffraction (HRXRD) measurement. The full width at half maximum (FWHM) of the HRXRD peak of the T2SL on GaAs is 5 times larger than that on GaSb. The long-wave infrared (LWIR) emission spectra were analyzed, and the observed transitions were in good agreement with the calculated emission energies. The photoluminescence (PL) intensity maxima (Imax) of ∼10 μm at 77 K is significantly reduced by a factor of 8.5 on the GaAs substrate. The peak fitting analysis of the PL profile indicates the formation of sub-monolayer features at the interfaces. PL mapping highlights the non-uniformity of the T2SL on GaAs which corroborates with Nomarski imaging, suggesting an increase in defect density

Anti-trypanosomal Activity of Bufonidae (Toad) Venom Crude Extract on Trypanosoma brucei brucei in Swiss Mice

Trypanosomiasis afflicts about 6 ~ 7 million people globally and to a large extent impedes livestock production in Africa. Naturally, trypanosomal parasites undergo genetic mutation and have developed resistance over a wide range of therapies. The utilization of animals and plants products has presented therapeutic potential for identifying novel anti-trypanosomal drugs. This study evaluated toad venom for anti-trypanosomal potency invivo in Swiss mice. Toads were collected from July to August 2019. The acute oral toxicity and biochemical characterization of the toad venom were determined. The experimental mice were administered various doses (130 mg/kg, 173 mg/kg and 217 mg/kg) of the toad venom crude extract and 0.75 mg/mL of Diamizan Plus standard drug for the treatment of trypanosomiasis, once daily for 3 days. The in-vivo anti-trypanosomal activity was evaluated by a curative test, after infecting the mice with Trypanosoma brucei brucei. The pre-patent period was 72 hours before treatment commenced. The overall results showed that trypanosomal load was highest in the control group while the group treated with Diamizan drug had the least trypanosomal load. As such, the mean trypanosomal load in relation to treatments showed a very high significant difference (P0.05) across treatment groups. The over 50% reduction in the trypanosomal load in the 130 mg/kg group in comparison with the control group brings to bare the anti-trypanosomal potency of the toad venom. The anti-trypanosomal activity demonstrated by the toad venom has provided basis for development of new therapeutic agents from different toad species. The study recommends further studies (both in-vivo and invitro) followed by the characterization of the active compounds present in the toad venom responsible for the anti-tyrpanosomal activity observed alongside the management and conservation of these species

Prognosis of non traumatic coma: The role of some socio-economic factors on its outcome in Ibadan, Nigeria

Background : Coma occurring in the course of an illness, irrespective of cause, traditionally implies a poor prognosis and many factors may determine its outcome. These factors must be identified and possibly stratified in their order of importance. This research seeks to identify these factors and how they influenced the outcome of non-traumatic coma in our environment. Methods : Two hundred consecutive patients, aged 18-79 years who met the inclusion criteria, the Glasgow coma scale (GCS) score of < 8, history and physical findings suggestive of medical illness, no head trauma or sedation, were recruited into the study from August 2004 to March 2005 at the University College Hospital (UCH), Ibadan, after obtaining institutional ethical clearance and consent from patients′ guardians. Detailed history of illness including the bio-data and time to present to the hospital and treatments given were noted. Thereafter, the clinical course of the patients was monitored daily for a maximum of 28 days during which the support of the family and/ or the hospital social welfare was evaluated. Results : During the 8-month period of the study, 76% (152) of the patients died while 24% (48) survived. The following factors were associated with high mortality rate: inability to confirm diagnosis (100%), poor family support (97.1%), delay in making a diagnosis within 24 h (85.4%), poor family understanding of disease (84.1%), need for intensive care admission and management (83.3%), poor hospital social welfare support (82.4%), presentation to UCH after 6 h of coma (76.7%), and referral from private health facilities (75.7%). Others include substance abuse (100%) and seropositivity to HIV (96%) and hepatitis B surface antigen (92%) antibodies, among others. Conclusion : This study has demonstrated that socio-economic factors such as gender, occupation, risky lifestyle behaviors, late presentation or referral to hospital, late diagnosis and treatment, and poor family support contributed to poor outcome of nontraumatic coma. It is hoped that improvement, modification, or correction of these factors may improve coma outcome