The Association Between Perceived Discrimination, Age and Proportion of Lifetime in the United States Among Somali Immigrants: A Cross-Sectional Analysis

Discrimination is detrimental to health. Little is known about perceived discrimination among Somali immigrants. We examined whether age or proportion of lifetime in the United States was associated with perceived discrimination among Somali immigrants. Guided by Intersectionality, we described a secondary analysis of Everyday Discrimination Scale (EDS) survey data from the Healthy Immigrant Community study. Younger participants ( ≤40 years) experienced more discrimination than older participants ( >40 years). Higher education, being male, and earning $20,000-$39,999 was associated with more perceived discrimination. These findings suggest that Somali immigrants who are younger, more formally educated, male, and/or earn $20,000-$39,000 report more discrimination than their counterparts. Possible explanations include exposure to discrimination outside the Somali community or more awareness about racism. Alternatively, the EDS may not capture the discrimination experienced by Somali women or older adults. Further research is needed to address the discrimination experienced by Somali immigrants. Clinical Trial Registration: NCT05136339, November 29,2021.

Healthy immigrant community study protocol: A randomized controlled trial of a social network intervention for cardiovascular risk reduction among Hispanic and Somali adults

BACKGROUND

Immigrants to the United States face structural barriers that contribute to rising cardiovascular risk factors and obesity after immigration. This manuscript describes the development of the Healthy Immigrant Community protocol and baseline measures for a stepped wedge cluster randomized trial to test the effectiveness of a social network intervention for cardiovascular risk reduction among two immigrant populations.

METHODS

We developed a social network-informed, community-based, participatory research-derived health promotion intervention with Hispanic and Somali immigrant communities in Minnesota consisting of mentoring, educational and motivational sessions, group activities, and a community toolkit for healthy weight loss delivered by culturally concordant health promoters (HPs) to their social networks. Using a stepped wedge cluster randomized design, social network-based groups were randomly assigned to receive the intervention either immediately or after a delay of one year. Outcomes, measured at baseline, 6 months, 12 months, and 24 months, were derived from the American Heart Association's "Life's Simple 7": BMI and waist circumference, blood pressure, fasting blood glucose, total cholesterol, physical activity level, and dietary quality.

RESULTS

A total of 51 HPs were enrolled and randomized (29 Hispanic; 22 Somali). There were 475 participants enrolled in the study, representing a mean social network group size of 8 (range, 5-12). The mean BMI of the sample (32.2) was in the "obese" range.

CONCLUSION

Processes and products from this Healthy Immigrant Community protocol are relevant to other communities seeking to reduce cardiovascular risk factors and negative health behaviors among immigrant populations by leveraging the influence of their social networks.

Efficient CuO/Ag2WO4 photoelectrodes for photoelectrochemical water splitting using solar visible radiation

Water splitting energy production relies heavily on the development of high-performance photoelectrochemical cells (PECs). Among the most highly regarded semiconductor materials, cupric oxide (CuO) is an excellent photocathode material. Pristine CuO does not perform well as a photocathode due to its tendency to recombine electrons and holes rapidly. Photocathodes with high efficiency can be produced by developing CuO-based composite systems. The aim of our research is to develop an Ag₂WO₄/CuO composite by incorporating silver tungstate (Ag₂WO₄) nanoparticles onto hydrothermally grown CuO nanoleaves (NLs) by successive ionic layer adsorption and reaction (SILAR). To prepare CuO/Ag₂WO₄ composites, SILAR was used in conjunction with different Ag₂WO₄ nanoparticle deposition cycles. Physicochemical characterization reveals well-defined nanoleaves morphologies with tailored surface compositions. Composite CuO/Ag₂WO₄ crystal structures are governed by the monoclinic phase of CuO and the hexagonal phase of Ag₂WO₄. It has been demonstrated that the CuO/Ag₂WO₄ composite has outstanding performance in the PEC water splitting process when used with five cycles. In the CuO/Ag₂WO₄ photocathode, water splitting activity is observed at low overpotential and high photocurrent density, indicating that the reaction takes place at low energy barriers. Several factors contribute to PEC performance in composites. These factors include the high density of surface active sites, the high charge separation rate, the presence of favourable surface defects, and the synergy of CuO and Ag₂WO₄ photoreaction. By using SILAR, silver tungstate can be deposited onto semiconducting materials with strong visible absorption, enabling the development of energy-efficient photocathodes.

Abstract P650: Addressing Cardiovascular Disease Inequities: Qualitative Process Evaluation From a Co-Investigation With Im/Migrants Exploring How to Sustain a Community-Driven, Social Network Intervention Using a Racism-Conscious Approach

Introduction: Health promotion programs focused on cardiovascular disease are underutilized with im/migrants. The one-time referral to group-based interventions model ignores (1) the complex sociocultural influences on behavior change and (2) the socio-historical context of migration, racialization of immigrants and refugees, and the roles these play in differential social integration of refugees. One solution may be to apply community-based participatory research (CBPR) and Public Health Critical Race Praxis (PHCRP) to social network interventions with opinion leaders. Yet, these interventions are challenging to scale. There is a critical need to understand how to scale community-driven social network interventions to effectively address cardiovascular disease inequities resulting from systemic racism experienced by im/migrant populations. Developed using CBPR and informed by PHCRP, this work builds upon Healthy Immigrant Community (HIC), a collaborative effort between Latinx and Somali im/migrant partners and Rochester Healthy Community Partnership. Our aim is to explore opinion leader recruitment, their characteristics, and expectations for HIC scale-up.

Qualitative Hypothesis: Learning more about the opinion leaders’ background and experience in the Healthy Immigrant Community social network intervention will prepare us for a future efficacy study.

Methods: We conducted a process evaluation by: (1) interviewing community partners who recruited opinion leaders (n=8) and (2) conducting three pre-intervention focus groups with opinion leaders (Latinx n=4; Somali women n=8; Somali men n=8). We used PHCRP to deductively form codes yet allowed for new ideas that arose from the data by inductively generating additional codes.

Results: Interview participants described their decision-making process, qualities considered, recruitment strategies, and expectations for an implementation study. Focus group participants discussed their personal motivations for participation, how they hoped the study would help their community, and the barriers to health they experience because of structural determinism (macro-level forces that sustain inequities).

Conclusions: This work will enhance our ability to translate HIC to other communities by expanding our knowledge of opinion leader characteristics that are important in a community-driven, social network intervention. Because social network interventions have been demonstrated to cause positive behavior change, further adapting these interventions in a community setting would be expected to provide a more effective approach compared to individually targeted behavior change strategies. Additionally, selecting OLs is neither time nor resource intensive and could enhance organizational strategies for implementing health promotion programming.

Rochester Healthy Community Partnership: Then and now

Community-engaged research partnerships promote health equity through incorporation of regional contexts to inform partnership dynamics that shape research and interventions that reflect community voice and priorities. Long-term partnerships build trusted relationships and promote capacity building among community and academic partners, but there are many structural barriers to sustaining long-term partnerships. Here we describe lessons learned from sustaining Rochester Healthy Community Partnership (RHCP), an 18-year community-based participatory research (CBPR) partnership in Southeast Minnesota. RHCP collaborates with immigrant and refugee populations to co-create interventions that promote health equity for community health priorities. Challenges to sustainability include a tension between project-based funding and the needs of long-term community-based research infrastructure. These challenges can be met with a focus on shared CBPR principles, operating norms, partnership dynamics, and governance. RHCP began in 2004 through identification of a community health priority, defining the community, and establishment of CBPR principles. It grew through identification of broader community health priorities, capacity building for community and academic partners, and integration of diverse learners. We describe the capacity for RHCP to respond to new societal contexts, the importance of partnership dynamics as a barometer for partnership health, and lessons learned about sustainability of the CBPR partnership.

The Recruitment to Dissemination Continuum in Community-based Participatory Research

BACKGROUND

Dissemination of research findings to participants and communities, particularly among traditionally marginalized groups, is a systemic challenge. In community-based participatory research (CBPR), long-term partnerships may foster a link between recruitment to research studies, dissemination of results, and recruitment to future studies.

OBJECTIVES

To analyze the recruitment to dissemination continuum of a CBPR study and its potential impact on partnership processes and future research.

METHODS

We conducted a qualitative study with four focus groups with community members and academic partners who participated in the recruitment and the dissemination of research findings from a study of Hispanic and Somali social networks in Rochester, Minnesota. Thematic analysis and coding of focus group transcripts was conducted by investigators. The CBPR conceptual model for this partnership guided the analysis.

RESULTS

Trust, relationship building, and capacity building were key features for successful participant recruitment and research dissemination strategies. Strategies, resources, and relationships used or developed during the recruitment phase of research were directly applied to planning a dissemination event. Participants and members of their communities said they were more likely to participate in future research studies as a result of attending a dissemination event.

CONCLUSIONS

This study demonstrated the ways in which recruitment of marginalized populations to research studies and dissemination of study results can manifest as a continuum. This continuum is nurtured by trust, longitudinal relationships, and robust partnership dynamics. These factors fit well within an existing CBPR conceptual model.

An Assessment of Health Priorities Among a Community Sample of Somali Adults

Somali immigrants are one of the largest African populations to resettle in the United States since 1990. There is an emerging literature base of disease-specific studies among Somali immigrants. However, we are aware of no studies on the health priorities for Somalis from the community's perspective. Somali adults in Minnesota completed a survey conducted by a community-based participatory research partnership on individual and community health priorities. Data were reported as counts and frequencies. 646 participants completed the survey. The most important health issues for individuals and their families were health behaviors (22.7%), diabetes (18.2%), and hypertension (14.4%), while those of the community were diabetes (22.5%), hypertension (18.8%) and weight (15.9%). This study found a significant overlap of health priorities among Somali individuals and their families compared to the community. These health priorities underscore the need to focus on non-communicable diseases among Somali immigrants.

Community-Engaged Bidirectional Crisis and Emergency Risk Communication With Immigrant and Refugee Populations During the COVID-19 Pandemic

OBJECTIVES

This study was conducted to assess an intervention that was created by a community-academic partnership to address COVID-19 health inequities. We evaluated a community-engaged bidirectional pandemic crisis and emergency risk communication (CERC) framework with immigrant and refugee populations during the COVID-19 pandemic.

METHODS

A 17-year community-engaged research partnership adopted a CERC framework in March 2020 to address COVID-19 prevention, testing, and socioeconomic impacts with immigrant and refugee groups in southeast Minnesota. The partnership used bidirectional communication between communication leaders and their social networks to refine messages, leverage resources, and advise policy makers. We conducted a mixed-methods evaluation for intervention acceptability, feasibility, reach, adaptation, and sustainability through multisource data, including email communications, work group notes, semistructured interviews, and focus groups.

RESULTS

The intervention reached at least 39 000 people in 9 months. It was implemented as intended and perceived efficacy was high. Frequent communication between community and academic partners allowed the team to respond rapidly to concerns and facilitated connection of community members to resources. Framework implementation also led to systems and policy changes to meet the needs of immigrant and refugee populations.

CONCLUSIONS

Community-engaged CERC is feasible and sustainable and can reduce COVID-19 disparities through shared creation and dissemination of public health messages, enhanced connection to existing resources, and incorporation of community perspectives in regional pandemic mitigation policies.

Plasmon-Enhanced Light Absorption in (p-i-n) Junction GaAs Nanowire Solar Cells: An FDTD Simulation Method Study

A finite-difference time-domain method is developed for studying the plasmon enhancement of light absorption from vertically aligned GaAs nanowire arrays decorated with Au nanoparticles. Vertically aligned GaAs nanowires with a length of 1 µm, a diameter of 100 nm and a periodicity of 165-500 nm are functionalized with Au nanoparticles with a diameter between 30 and 60 nm decorated in the sidewall of the nanowires. The results show that the metal nanoparticles can improve the absorption efficiency through their plasmonic resonances, most significantly within the near-bandgap edge of GaAs. By optimizing the nanoparticle parameters, an absorption enhancement of almost 35% at 800 nm wavelength is achieved. The latter increases the chance of generating more electron-hole pairs, which leads to an increase in the overall efficiency of the solar cell. The proposed structure emerges as a promising material combination for high-efficiency solar cells.

Light-induced high-spin state in ZnO nanoparticles

The effects of white-light irradiation on ∼15 nm diameter ZnO nanoparticles are investigated by means of electron paramagnetic resonance, near liquid-nitrogen and liquid-helium temperatures. Under dark conditions, usual core- and surface-defects are detected, respectively, at g = 1.960 and g = 2.003. Under white-light illumination, the core-defect signal intensity is strongly increased, which is to be correlated to the light-induced conductivity's augmentation. Beside, a four-lines structure appears, with the same gravity center as that of the surface defects. Simulations and intensity power-dependence measurements show that this four-line-structure is very likely to arise from a localized high spin S = 2, induced by light irradiation, and subjected to a weak axial anisotropy. At 85 K, this high-spin state can last several hours after the light-irradiation removal, probably due to highly spin-forbidden recombination process. The possible excited resonant complexes at the origin of this signal are discussed. Other light-induced S = 1/2-like centers are detected as well, which depend on the nanoparticles growth conditions.

Social networks and obesity among Somali immigrants and refugees

BACKGROUND

Somali immigrants and refugees to the United States are at high risk for obesity and related cardiovascular risk. Social network factors influence health behaviors and are important contributors to the obesity epidemic. The objective of this study was to describe social networks and obesity-related characteristics among adult Somali immigrants in a Minnesota city in order to inform a community-based, participatory, research-derived, social network intervention to decrease obesity rates.

METHODS

Survey data (demographics, general health measures, and sociobehavioral and network measures) and height and weight measures (for calculating body mass index) were collected from adult Somali immigrants by bilingual study team members at community locations. Descriptive statistics were used to report the survey and biometric data. Logistic regression models were used to describe the basic associations of participants and network factors. Network data were analyzed to identify nodes and ties, to visualize the network, and to identify potential interventionists for a future social network intervention.

RESULTS

Of the 646 participants, 50% were overweight or affected by obesity. The network had 1703 nodes with 3583 ties between nodes, and modularity was high (0.75). Compared with respondents of normal weight, participants who were overweight or affected by obesity had more network members who were also overweight or obese (odds ratio [OR], 2.90; 95% CI, 1.11-7.56; P = .03); this was most notable for men (OR, 4.58; 95% CI, 1.22-17.22; P = .02) and suggestive for those 50 years or older (OR, 24.23; 95% CI, 1.55-377.83; P = .03). Weight loss intention among participants who were overweight or affected by obesity was associated with number of family members and friends trying to lose weight, enabling functional network factors (social norms for weight loss, social support for healthy eating, and social cohesion), and less favorable obesogenic social norms.

CONCLUSIONS

In this community sample of Somali immigrants, distinct social networks are clustered by weight status, and social contacts and functional network characteristics are related to individuals' weight loss intentions. These factors should be considered in weight loss interventions and programs. A social network intervention targeting weight loss, within a community-based participatory research framework, is feasible in this vulnerable population.

Core-defect reduction in ZnO nanorods by cobalt incorporation

Zinc oxide (ZnO) nanorods grown by the low-temperature (90 °C) aqueous chemical method with different cobalt concentration within the synthesis solution (from 0% to 15%), are studied by electron paramagnetic resonance (EPR), just above the liquid helium temperature. The anisotropic spectra of substitutional Co²⁺ reveal a high crystalline quality and orientation of the NRs, as well as the probable presence of a secondary disordered phase of ZnO:Co. The analysis of the EPR spectra indicates that the disappearance of the paramagnetic native core-defect (CD) at [Formula: see text] is correlated with the apparition of the Co²⁺ ions lines, suggesting a gradual neutralization of the former by the latter. We show that only a little amount of cobalt in the synthesis solution (about 0.2%) is necessary to suppress almost all these paramagnetic CDs. This gives insight in the experimentally observed improvement of the crystal quality of diluted ZnO:Co nanorods, as well as into the control of paramagnetic defects in ZnO nanostructures.

EPR investigation of pure and Co-doped ZnO oriented nanocrystals

Pure and cobalt-doped zinc oxide aligned nanorods have been grown by the low-temperature (90 °C) aqueous chemical method on amorphous ZnO seed layer, deposited on a sapphire substrate. High crystallinity of these objects is demonstrated by the electron paramagnetic resonance investigation at liquid helium temperature. The successful incorporation of Co²⁺ ions in substitution of Zn²⁺ ones in the ZnO matrix has also been confirmed. A drastic reduction of intrinsic ZnO nanorods core defects is observed in the Co-doped samples, which enhances the structural quality of the NRs. The quantification of substitutional Co²⁺ ions in the ZnO matrix is achieved by comparison with a reference sample. The findings in this study indicate the potential of using the low-temperature aqueous chemical approach for synthesizing material for spintronics applications.

Low-Frequency Self-Powered Footstep Sensor Based on ZnO Nanowires on Paper Substrate

In this work, we design and fabricate a wireless system with the main operating device based on zinc oxide (ZnO) nanowires. The main operating device is based on piezoelectric nanogenerator (NG) achieved using ZnO nanowires grown hydrothermally on paper substrate. The fabricated NG is capable of harvesting ambient mechanical energy from various kinds of human motion, e.g., footsteps. The harvested electric output has been used to serve as a self-powered pressure sensor. Without any storage device, the signal from a single footstep has successfully triggered a wireless sensor node circuit. This study demonstrates the feasibility of using ZnO nanowire piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks.

A flexible anisotropic self-powered piezoelectric direction sensor based on double sided ZnO nanowires configuration

We have successfully synthesized highly dense and well aligned zinc oxide nanowires (NWs) on the two sides of a PEDOT: PSS substrate by a single step low temperature hydrothermal method. The grown sample was used to fabricate a double sided piezoelectric nanogenerator (NG). The maximum harvested output power density from the fabricated double sided NG configuration was about 4.44 mW cm(-2). The results obtained from the present double sided NG were approximately double the output from a single side. In addition to that, the voltage polarity of the harvested voltage from the two sides of the NG has been investigated. The results showed that upon bending, an anisotropic voltage polarity is generated on the two sides. Indicating that, this double sided NG can be used as a self-powered voltage polarity based direction sensor. The results of the present flexible double sided NG is very promising for harvesting energy from irregular mechanical energy sources in the surrounding environment. In addition, the fabricated configuration showed stability for sensing and can be used in surveillance and security applications.

A selective potentiometric copper (II) ion sensor based on the functionalized ZnO nanorods

In this work, ZnO nanorods were hydrothermally grown on the gold-coated glass substrate and characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques. The ZnO nanorods were functionalized by two different approaches and performance of the sensor electrode was monitored. Fourier transform infrared spectroscopy (FTIR) was carried out for the confirmation of interaction between the ionophore molecules and ZnO nanorods. In addition to this, the surface of the electrode was characterized by X-ray photoelectron spectroscopy (XPS) showing the chemical and electronic state of the ionophore and ZnO nanorod components. The ionophore solution was prepared in the stabilizer, poly vinyl chloride (PVC) and additives, and then functionalized on the ZnO nanorods that have shown the Nernstian response with the slope of 31 mV/decade. However, the Cu2+ ion sensor was fabricated only by immobilizing the selective copper ion ionophore membrane without the use of PVC, plasticizers, additives and stabilizers and the sensor electrode showed a linear potentiometric response with a slope of 56.4 mV/decade within a large dynamic concentration range (from 1.0 x 10(-6) to 1.0 x 10(-1) M) of copper (II) nitrate solutions. The sensor showed excellent repeatability and reproducibility with response time of less than 10 s. The negligible response to potentially interfering metal ions such as calcium (Ca2+), magnesium (Mg2+), potassium (K+), iron (Fe3+), zinc (Zn2+), and sodium (Na+) allows this sensor to be used in biological studies. It may also be used as an indicator electrode in the potentiometric titration.

Single nanowire-based UV photodetectors for fast switching

Relatively long (30 µm) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

Influence of pH, Precursor Concentration, Growth Time, and Temperature on the Morphology of ZnO Nanostructures Grown by the Hydrothermal Method

We investigated the influence of the pH value, precursor concentration (C), growth time and temperature on the morphology of zinc oxide (ZnO) nanostructures. The pH of the starting solution was varied from 1.8 to 12.5. It was found that the final pH reaches an inherent value of 6.6 independently of the initial pH solution. Various ZnO structures of nanotetrapod-like, flower-like, and urchin-like morphology were obtained at alkaline pH (8 to 12.5) whereas for pH solution lower than 8 rod-like nanostructures occurred. Moreover, we observed the erosion of the nanorods for a pH value less than 4.6. By changing the concentrations the density and size were also varied. On going from a high (C>400 mM) to lower (C<25 mM)C, the resulted ZnO nanostructures change from a film to nanorods (NRs) and finally nanowires (NWs). It was also found that the length and diameter of ZnO NRs follow a linear relation with time up to 10 hours, above which no further increase was observed. Finally the effect of growth temperature was seen as an influence on the aspect ratio.

Intracellular ZnO Nanorods Conjugated with Protoporphyrin for Local Mediated Photochemistry and Efficient Treatment of Single Cancer Cell

ZnO nanorods (NRs) with high surface area to volume ratio and biocompatibility is used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light needed to achieve cancer cell necrosis. In this letter, ZnO nanorods used for the treatment of breast cancer cell (T47D) are presented. To adjust the sample for intracellular experiments, we have grown the ZnO nanorods on the tip of borosilicate glass capillaries (0.5 μm diameter) by aqueous chemical growth technique. The grown ZnO nanorods were conjugated using protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods. Mechanism of cytotoxicity appears to involve the generation of singlet oxygen inside the cell. The novel findings of cell-localized toxicity indicate a potential application of PPDME-conjugated ZnO NRs in the necrosis of breast cancer cell within few minutes.

Stable White Light Electroluminescence from Highly Flexible Polymer/ZnO Nanorods Hybrid Heterojunction Grown at 50 degrees C

Stable intrinsic white light-emitting diodes were fabricated from c-axially oriented ZnO nanorods (NRs) grown at 50 degrees C via the chemical bath deposition on top of a multi-layered poly(9,9-dioctylfluorene-co-N-(4-butylpheneylamine)diphenylamine)/poly(9,9dioctyl-fluorene) deposited on PEDOT:PSS on highly flexible plastic substrate. The low growth temperature enables the use of a variety of flexible plastic substrates. The fabricated flexible white light-emitting diode (FWLED) demonstrated good electrical properties and a single broad white emission peak extending from 420 nm and up to 800 nm combining the blue light emission of the polyflourene (PFO) polymer layer with the deep level emission (DLEs) of ZnO NRs. The influence of the temperature variations on the FWLED white emissions characteristics was studied and the devices exhibited high operation stability. Our results are promising for the development of white lighting sources using existing lighting glass bulbs, tubes, and armature technologies.

White Electroluminescence Using ZnO Nanotubes/GaN Heterostructure Light-Emitting Diode

We report the fabrication of heterostructure white light-emitting diode (LED) comprised of n-ZnO nanotubes (NTs) aqueous chemically synthesized on p-GaN substrate. Room temperature electroluminescence (EL) of the LED demonstrates strong broadband white emission spectrum consisting of predominating peak centred at 560 nm and relatively weak violet-blue emission peak at 450 nm under forward bias. The broadband EL emission covering the whole visible spectrum has been attributed to the large surface area and high surface states of ZnO NTs produced during the etching process. In addition, comparison of the EL emission colour quality shows that ZnO nanotubes have much better quality than that of the ZnO nanorods. The colour-rendering index of the white light obtained from the nanotubes was 87, while the nanorods-based LED emit yellowish colour.

Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers

Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes

Hybrid light emitting diodes (LEDs) based on n-ZnO nanorods and blended polymers were fabricated and characterized. The blended polymers consisted of a blue emitting polymer and a charge transport polymer. The effect of the interlayer design on the electrical and electroluminescent characteristics of these hybrid LEDs was investigated. We demonstrated that by adding a calcium (2) acetylacetonate [Ca(acac)(2)] layer between the blended polymer layer and the ZnO nanorods, an increase in device performance was observed. The purpose of the extra layer was to act as a band offset stepping layer (offset divider). Moreover, the effect of the stepper layer thickness for this offset stepping layer was studied. The results indicate that LED performance is greatly affected by the presence and thickness of this band offset stepping layer.

Trapping and detection of single molecules in water

An innovative nanoprobe-based device that can measure and adjust the pH, can mimic biochemistry, can create microscale vortices in water, and can be used to trap single molecules is presented. Because the analytes in question to trap and detect are small in dimensions, we start by presenting scaling issues and challenging limitations for miniaturized chemical nanosensors. Advantages of using nanoprobes e.g., isolated nanowires, as the components in chemical sensing are discussed. How the observation of the physical property can beneficially change with isomorphic scaling is highlighted. Some of the technology-related constrains are presented for specific sensors. Solutions to overcome such problems are also given. Different aspects, e.g., sample size and sensitivity, for chemical sensing at the nanoscale are highlighted.

Electrical characteristics and stability of gold and palladium Schottky contacts on ZnO nanorods

The electrical characteristics and stability of Pd and Au Schottky contacts on ZnO nanorods grown on glass substrate have been investigated. The nanorods were grown using the aqueous chemical growth method. The nanorods were characterized with scanning electron microscopy (SEM), x-ray diffraction (XRD) and photoluminescence (PL). Prior to the metal contact deposition, an insulating PMMA layer was deposited between the nanorods. The best-produced Schottky contact was an as-deposited Pd/ZnO contact with an ideality factor of 1.74 ± 0.43 and a barrier height of 0.67 ± 0.09 eV. The relatively high ideality factor indicates that the current transport cannot be described by pure thermionic transport. The presence of surface states due to the high evaporation pressure is probably the reason for the high ideality factor. Post metal deposition annealing at 150 °C for 30 min in air lowered the barrier height and decreased the Au/ZnO ideality factor but increased it for Pd/ZnO. The current follows ohmic behavior when the applied forward bias, V(forward), is lower than 0.1 V, whereas for V(forward) between 0.1 and 0.45 V the current follows I∼exp(cV), and at higher forward biases the current-voltage characteristics follow the relation I∼V(2), indicating that the space-charge current-limiting mechanism is dominating the current transport.

Buckling and mechanical instability of ZnO nanorods grown on different substrates under uniaxial compression

Mechanical instability and buckling characterization of vertically aligned single-crystal ZnO nanorods grown on different substrates including Si, SiC and sapphire (α-Al(2)O(3)) was done quantitatively by the nanoindentation technique. The nanorods were grown on these substrates by the vapor-liquid-solid (VLS) method. The critical load for the ZnO nanorods grown on the Si, SiC and Al(2)O(3) substrates was found to be 188, 205 and 130 µN, respectively. These observed critical loads were for nanorods with 280 nm diameters and 900 nm length using Si as a substrate, while the corresponding values were 330 nm, 3300 nm, and 780 nm, 3000 nm in the case of SiC and Al(2)O(3) substrates, respectively. The corresponding buckling energies calculated from the force displacement curves were 8.46 × 10(-12), 1.158 × 10(-11) and 1.092 × 10(-11) J, respectively. Based on the Euler model for long nanorods and the J B Johnson model (which is an extension of the Euler model) for intermediate nanorods, the modulus of elasticity of a single rod was calculated for each sample. Finally, the critical buckling stress and strain were also calculated for all samples. We found that the buckling characteristic is strongly dependent on the quality, lattice mismatch and adhesion of the nanorods with the substrate.

The physiological effect of infant mortality in reproductive behavior in the Sudan

The present study examines the physiological effect of infant mortality on reproductive behavior for the Sudan using retrospective pregnancy history data for ever-married women, 15-49. The investigation has revealed that the death of an infant reduces the subsequent birth interval significantly, by about 6 months. This difference in the length of birth interval appears to be primarily a result of the interruption of lactation. When the birth intervals are examined by the fate of the two preceding children, the analysis shows insufficient evidence to indicate that infant mortality affects the length of birth intervals independently of the physiological effect.