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Each year the GSA publications team sponsors a symposium to assist authors who wish to publish in GSA’s high impact and influential journals. The first part of the session will include five brief presentations from the editors of The Gerontologist, Innovation in Aging, and the Journals of Gerontology Series A and B plus journal managing editors. We will integrate practical tips with principles of publication ethics and scholarly integrity. The topics will be as follows: (1) Preparing your manuscript: strong and ethical scholarly writing for multidisciplinary audiences, (2) common problems that affect peer review, (3) addressing translational significance and fit to journal expectations, (4) transparency, documentation, and Open Science; and (5) working with Scholar One. Following these presentations, we will hold round table discussions with editors from the GSA journals portfolio. At these round tables, editors will answer questions related to the podium presentations and other questions specific to each journal. Intended audiences include emerging and international scholars, and authors interested in learning more about best practices and tips for getting their scholarly work published.

Informed by the Ecological and Health Belief models, the manualized Stroll Safe program addresses the unmet need of a targeted outdoors falls prevention program. We examined the efficacy of the program in partnership with eight Naturally Occurring Retirement Community program sites in one U.S city (N=86). Participants age 60 and older with a history of falls or a fear of falling were recruited. Community sites were randomly assigned to the treatment or wait list control group. Results of independent samples t-tests reveal a statistically significant improvement in knowledge of outdoor fall risks and safe community mobility strategy use for the treatment group as compared to the wait list control group on the Outdoor Falls Questionnaire (OFQ) and Falls Behavioral Scale for the Older Person (FaB) (ps

Community health workers (CHWs) play essential roles in implementing community-based behavioral lifestyle interventions. This qualitative analysis aimed to explore what program factors and CHW characteristics would help improve CHW performance in the Mobility and Vitality Lifestyle Program (MOVE UP), a community-based behavioral weight-management intervention for improving mobility among overweight or obese older adults. The MOVE UP program was implemented from January 2015 to June 2019 at 23 community-based sites in Pittsburgh, Pennsylvania. Trained and supported CHWs delivered 32 group sessions over 13 months. We collected data from semi-structured interviews with 21 CHWs and 14 community key informants (community site directors or coordinators); seven focus group discussions with participants from 9 sites, and 124 pieces of graduation advice provided by MOVE UP graduates for future participants; onsite CHW performance observation at 18 sites, and 124 meeting memos of support phone calls with CHWs. Interviews and focus groups were audio-recorded and transcribed verbatim. All data were thematically analyzed in a deductive approach, using the CHW generic logic model. Emerging themes were: Trained CHWs still require onsite support by experienced CHWs or training staff to deliver the first session; Participants need a Q&A session by specialists to address their questions beyond CHWs’ knowledge; Desirable CHW characteristics could increase CHWs’ relation and accessibility to participants, such as the same age group, similar weight loss experience, and living or working in the same community. These findings provide important insight as to recruiting and supporting CHWs in a community-based behavioral lifestyle intervention for older adults.

Of the approximately 716 bird species that breed in North America, 386 (54%) are considered Nearctic–Neotropical migrants by the U.S. Fish and Wildlife Service. In the past 50 yr, scores of these migratory species, including some once considered common, have declined dramatically. Nearctic–Neotropical migrants normally spend 6–8 months in tropical habitats, making the identification, availability, and management of Neotropical habitats critical issues for their conservation. Yet, for most species, complete and nuanced information about their use of tropical habitats and the relative effects of breeding vs. wintering conditions on survival, productivity, and population trends is not available, though many studies point to Neotropical overwintering habitats as being a strong driver of population change. Particularly important for long-distance Nearctic–Neotropical migrants is an understanding of how “carry-over effects” arise and influence population trends when conditions on wintering grounds and tropical stopover areas affect subsequent reproductive performance on breeding grounds. For example, why some species show strong carry-over effects from tropical habitats while others do not is not fully understood. In recent years, many studies have offered insights into these issues by taking advantage of new scientific methods and technological innovations. In this review, we explore threats facing North American breeding birds that migrate to the Neotropics, summarize knowledge of habitat selection and use on the wintering grounds, describe how conditions at one point in the annual cycle may manifest in subsequent seasons or life history stages, and discuss conservation concerns such as climate change and the potential for phenological mismatch.LAY SUMMARYMore than half of the bird species that breed in North America, representing billions of birds, migrate to the Neotropics.In the past 50 years, scores of these species have declined dramatically.Migratory birds normally spend 6–8 months in tropical habitats, making the conservation of these species an international challenge. Yet, for most species, complete and nuanced information about their use of tropical habitats and the relative effects of breeding vs. wintering conditions on survival, productivity, and population trends is not available.Accelerating climate change is adding to the urgency of our gaining an understanding of the full annual and migratory cycle of these birds.In recent years, many studies have offered insights into these issues by taking advantage of new scientific methods and technological innovations.

As the global human population increases, and many bird populations in the Neotropics and the rest of the world continue to decline, the study of the intersection of humans, birds, and conservation has become more relevant than ever. The field of conservation social science is an interdisciplinary field that applies the social sciences and humanities to examine research questions that have implications for biodiversity conservation, and encompasses disciplines as diverse as psychology, economics, and political ecology. An understanding of the human dimensions of biodiversity conservation issues can be an essential element in the success or failure of a conservation initiative, policy, or practice. The purpose of this article is to provide an understanding of the growing body of conservation social science relevant to Neotropical bird conservation research and to demonstrate its importance. We discuss how this research can contribute to addressing 5 major threats to bird conservation in the Neotropics, including future research needs, and we provide 3 case studies of bird conservation social science projects, demonstrating the insights that can be gained. We close with a discussion of how conservation biologists and ornithologists can most effectively work with conservation social scientists.

This research focuses on how surface structures can influence the behaviour of cells. There is a great diversity of surface structures, which makes the identification of an optimal physical environment for a specific phenotype difficult. Therefore, platforms that allow screening of many different designs at the same time facilitate the identification of an optimal cultural environment. Using the TopoChip, which contains 2176 unique microtopographies, structures have been identified that support the tenocyte phenotype, the primary cell type of the tendon. In addition, this also applies to mesenchymal stem cells (MSCs), which experience an activation of tendon-related genes. Furthermore, the library has been creatively expanded by using natural surface topographies that cause unique cell behaviour, such as promoting osteogenesis.

Researchers examined how nozzle design influences the combustion and emissions of a 10 kW, pure fast pyrolysis oil (FPO) flame from a swirl burner within an insulated combustor using an internally mixed air-blast nozzle. No other studies are known that conducted a detailed investigation of the effect of nozzle design on the combustion and emissions of a pure FPO spray flame. FPO (also called bio-oil or pyrolysis liquid biofuel) is a biofuel made from waste wood, but its properties, especially its high water content, make efficient combustion challenging. Combustion experiments showed how carbon monoxide (CO) emissions, nitric oxide (NO) emissions, carbonaceous residue, flame stability and nozzle coking were influenced by the nozzle's mixing chamber diameter and outlet number/diameter, angle and total area. Ultimately, an optimized nozzle was designed that achieved a self-sustaining FPO flame with excellent stability, low emissions and low coking; it also operated under "cold-start" conditions and at steady-state conditions, did not require a pilot flame to maintain a stable, seated flame. The results show that with careful nozzle design, FPO is able to perform very effectively in burners and can therefore help to facilitate the replacement of fossil fuels.

Drought stress is an important consideration for wildlife in arid and semiarid regions under climate change. Drought can impact plant and animal populations directly, through effects on their physiology, as well as indirectly through effects on vegetation productivity and resource availability, and by creating conditions conducive to secondary disturbance, such as wildfire. We implemented a novel approach to understanding community-level demographic responses of birds and their habitats to these stressors in the context of climate change at 14 study sites in the Four Corners region of the southwestern United States. A large wildfire affecting three of the sites provided a natural experiment for also examining fire effects on vegetation and the bird community. We assessed (1) trends in drought and end-of-century (2071-2100) predicted average drought conditions under mid-range and high greenhouse gas concentration trajectory scenarios; (2) effects of drought and fire on habitat (vegetation greenness); and (3) effects of drought and fire on community-level avian productivity and adult apparent survival rates. Drought has increased and is expected to increase further at our study sites under climate change. Under spring drought conditions, vegetation greenness and avian productivity declined, while summer drought appeared to negatively affect adult apparent survival rates. Response to fire was mixed; in the year of the fire, avian productivity declined, but was higher than normal for several years post-fire. Our results highlight important links between environmental stressors and avian vital rates that will likely affect population trajectories in this region under climate change. We suggest that the use and continued development of community-level demographic models will provide useful tool for leveraging sparse species-level data to provide multi-species inferences and inform conservation.

Innovation in Aging requires a statement from authors on translational significance. This requirement forces authors to consider the implications of their research for changing some component of aging. How does the research address a challenge posed by aging bodies, minds, relationships, or societies? The editorial board has developed criteria for assessing translational significance. Translational research must meet at least one of three criteria. It (i) must predict or explain a health or behavioral outcome, (ii) be advanced enough in deployment or development to assess these effects, and (iii) have a clear pathway to large-scale program delivery or change in clinical practice. The criteria rule out some kinds of submissions, such as scale development, single-case studies, or reviews of literature. We use these criteria to structure each article’s required translational significance statement. Rethinking translation may help focus research across the full set of GSA journals.

How does medical and healthcare decision-making among the very old people change in their last year before death? We explored patterns of decision-making in the Health ABC cohort study in 2011-14 (years 15-17), which involved 12 waves of quarterly phone interviews. When the participant was unable to do the interview, a proxy completed it instead. We identified a sample of 291 decedents (aged 90.0±2.9 at death, 35.7% Black, 52.6% female) with at least 1-year follow-up before death. Percentages of decedents who have made medical or healthcare decisions in the last four quarters before death were 32.0%, 31.2%, 32.6%, 41.9%, respectively. Decedents made more healthcare decisions in the last quarter before death (P

Bio-oil, also called pyrolysis liquid biofuel, is made from the pyrolysis of waste biomass and provides a carbon-neutral alternative fuel. This study focuses on optimizing swirl burners for use with bio-oil. Spray combustion of bio-oil/ethanol blends was previously studied using a 10 kW swirl burner. The previous burner had a small combustion chamber with no refractory lining. It was not feasible to stabilize flames of bio-oil without blending with ethanol, and the pollutant emissions were relatively high. In this study, the burner is upgraded by implementing a refractory-lined combustion chamber and increasing the size of the chamber to investigate the relationship between the burner design and combustion performance of bio-oil. The main reasons for upgrading the burner are to eliminate ethanol addition to bio-oil, stabilize the pure bio-oil flame, achieve lower pollutant emissions, and make the burner more comparable to industrial bio-oil burners. In addition to flame stability, fuel boiling inside the ...

A Primary trading commodity in fishing industry is Tuna. However, catching this fish is not easy. It clearly requires adequate equipment. On the other hand, Indonesia as an archipelago country has very high fisheries potential. Moreover, Indonesia openly publish to the public data of Vessel Monitoring System (VMS) in indonesia teritory. However, this VMS data has not used optimally with the fisherman. This paper proposed a website so that user can predict the location of Tuna in Indonesia teritory through over the year. This will reduce fishing costs for Indonesia tuna fishermen such as fuel and labor costs. This study does four things. Firstly, conduct tracking modeling of fishing tuna vessel only. Secondly, develop visualization techniques resulting from algorithms by programming Python Dash. Thirdly, develop fish position prediction techniques using the Machine Learning ensemble by Support Vector Machine technology. Lastly, integrating all steps into a website. It concludes that system can predict the location of tuna correctly 97.6%.

Indonesian waters are very wide and have very high fisheries potential. This clearly benefits the Indonesian fishing industry. Tuna is a primary trading commodity in this industry, but catching this fish is not easy. In addition, the movement of tuna follows the pattern of changes in Earth's temperature, so determining its position clearly requires adequate equipment. The original purpose of Vessel Monitoring System (VMS) is for enforcement and control of vessel sailing. In this paper, we use VMS to find the position of tuna to reduce fishing costs for Indonesia tuna fishermen such as fuel and labor costs. This study does three things. Firstly, conduct tracking modeling of the movements of each type of fishing vessel in Indonesian waters, and use cross-reference with weather data and earth conditions, then filtering the data for fishing tuna vessel only. Secondly, develop visualization techniques resulting from algorithms by programming Python Dash. Finally, develop fish position prediction techniques using the Machine Learning ensemble by Support Vector Machine technology. It concludes that system can predict the location of tuna correctly 97.6%.

This work reports on the effects of air exposure on the photoluminescence intensity of GaN nanocolumns, with diameters ranging from below 40 nm up to around 230 nm, grown selectively on GaN/sapphire and GaN/Si(111). The high control of dimensions provided by selective area growth epitaxy allowed for a better study of the relationship between the observed phenomena, namely the photoluminescence intensity quenching due to oxygen photo-adsorption, and the nanocolumns properties (morphology and dimensions). For nanocolumns with diameters below 120 nm and lengths of about 300 nm, photoluminescence intensity dropped by more than 90% of the initial value, while for shorter nanocolumns a reduced drop value was found.

This article provides a comprehensive review of the spray combustion of fast pyrolysis bio-oil (FPBO, also called bio-oil, pyrolysis oil or pyrolysis liquid biofuel), which is widely regarded as one of the most economically feasible renewable resources to facilitate the replacement of fossil oils. The utilization of FPBO as a fuel is challenging due to its unique atomization and combustion characteristics but it is important given the need to develop a more sustainable energy infrastructure. Significant efforts have been made in utilizing FPBO as a practical alternative fuel and the first FPBO facilities for heat and/or power generation have been brought online in recent years. FPBO-fueled burners, boilers, and furnaces are ready from a technical perspective for large-scale industrial use, and even small-scale systems show excellent flame stability, low emissions, and minimal requirements for secondary fuel usage. FPBO applications in gas turbine and compression-ignition engines are technically more challenging, currently having had only limited successes in larger-scale units and for short time intervals in smaller ones. With recent research and technological advances, however, FPBO use in small-scale combustion engines appears to be technically feasible. In the literature, extensive research efforts have been dedicated to this topic either as a fuel itself or its utilization for practical applications. Nonetheless, inadequate considerations have been given to the critical role of FPBO atomization and its subsequent fuel/air mixing, which in turn controls the combustion efficiency and emission characteristics of a system. Understanding the spray combustion properties of FPBO is especially important because of the fuel's unfavorable properties compared to fossil oils including low energy density, high viscosity, high water content, containing suspended solid particulates and non-volatile residue, chemical instability, and an incompatibility with conventional fossil oils. The information presented herein, therefore, focuses on understanding the challenges and constraints that are unique to FPBO applications, along with proposing several strategies to properly atomize and combust this fuel in order to enhance combustion efficiency and reduce pollutant emissions in practical systems. Although substantial progress has been made in understanding the FPBO spray combustion as revealed by this review, better standardization of FPBO properties, more efficient techniques for optimizing atomization and combustion for different applications, and more studies to understand the long-term reliability of devices running on FPBO are needed.

Multiple-choice question (MCQ) test is a very common and popular test instrument among educators utilized for assessing student performance, particularly in large size classes, in an objective manner. Despite its popularity and the advantages it offers, any automated test grading application designed for handling MCQ test is challenged with scoring time efficiency and accuracy issues. Between both, achieving higher accuracy is still of greater interest as reflected in many research works. Furthermore, recognizing student's answers appear in handwritten form is not an easy task to accomplish. When a single column answer sheet is used, then any attempt to recognize student's answer written outside the determined area will obviously create an additional cost to the application. Not only it will affect the time required for locating and processing the corrected answer, but the non-standard handwritten answer may decline the accuracy level also. A three-column answer sheet is proposed then as a solution to accommodating students' need for putting their corrected answer. The computational cost of recognizing at most three consecutive answers in the designated area is shown to follow a linear growth. Therefore, it can be concluded that the three-column answer sheet offers advantages to time efficiency and indirectly, recognition accuracy issues.

In this paper, design and implementation of automated scoring of multiple-choice test using template matching technique is reported. In the proposed method an Android based smart-phone is used to identify the presence of X-mark in the answer sheet, instead of identify which circle in the answer sheet is blackened as usually do in the widely known solution using Optical Mark Reader (OMR). Cost and practicality wise, the usage of smart-phone compared to OMR is expected to increase the accessibility to automated scoring of multiple-choice test. Furthermore, the identification of X-mark opens the possibility for students to change their answer easier by making corrected X-mark and then placing a new X-mark in another blank square compared to wipe a blackened circle and filling a new circle. Four main stages are involved in the implementation, namely image preparation stage, blank squares position determination stage, X-mark detection stage, and evaluation stage. After those stages are implemented, tests are conducted to find the best distance and angle of the smart phone to the answer sheet in taking the answer sheet's images, and to evaluate the accuracy in identifying right answers and gives valid scoring. The success rate of recogntion the answer is at least 99%.

This work reports on the growth of (In, Ga)N core–shell micro pillars by plasma-assisted molecular beam epitaxy using an ordered array of GaN cores grown by metal organic vapor phase epitaxy as a template. Upon (In, Ga)N growth, core–shell structures with emission at around 3.0 eV are formed. With spatially resolved cathodoluminescence, an increasing In content toward the pillar top is found to be present in the (In, Ga)N shell, as indicated by a shift of CL peak position from 3.2 eV at the shell bottom to 3.0 eV at the shell top. Further, the fabrication of a core–shell pin structure is demonstrated. Spatially resolved electroluminescence measurements performed on individual pillars confirm electroluminescence from the (In, Ga)N shell (lateral diode) at around 3.0 eV, as well as from the pillar top facet (axial diode) at around 2.3 eV.

This work reports on the selective area growth mechanism of green-emitting InGaN/GaN nanocolumns with long InGaN sections (330–410 nm) grown by molecular beam epitaxy on GaN/sapphire. The evolution of the morphology of the InGaN segment is found to depend critically on the nominal III/V ratio as well as the diameter of the GaN section, both affecting the local III/V ratio at the top of the nanocolumn. Depending on the local III/V ratio, either metal or nitrogen rich, the diameter of the InGaN segment increases or decreases, respectively, compared to the initial diameter of the GaN segment. In addition, the In distribution inside the InGaN segment is found to depend on the local III/V and In/Ga ratios, i.e., increasing In content toward the top under local metal rich conditions and decreasing In content toward the top under locally N rich conditions.

Despite the strong interest in optoelectronic devices working in the deep ultraviolet range, no suitable low cost, large-area, high-quality AlN substrates have been available up to now. The aim of this work is the selective area growth of AlN nanocolumns by plasma assisted molecular beam epitaxy on polar (0001) and semi-polar (11-22) GaN/sapphire templates. The resulting AlN nanocolumns are vertically oriented with semi-polar {1-103} top facets when grown on (0001) GaN/sapphire, or oriented at 58° from the template normal and exposing {1-100} non-polar top facets when growing on (11-22) GaN/sapphire, in both cases reaching filling factors ≥80%. In these kinds of arrays each nanostructure could function as a building block for an individual nano-device or, due to the large filling factor values, the overall array top surfaces could be seen as a quasi (semi-polar or non-polar) AlN pseudo-template.

The aim of this work is to gain insight into the selective area growth (SAG) of InGaN nanostructures by plasma-assisted molecular beam epitaxy, focusing on their potential as building blocks for next-generation LEDs. Several nanocolumn (NC)-based approaches such as standard axial InGaN/GaN structures and InGaN/GaN core–shell structures are discussed. The first section reports on the growth and characterization of ordered InGaN NCs as well as light-emitting diodes grown on c-plane GaN/sapphire templates. In particular, the growth mechanism of green-emitting InGaN/GaN NCs is discussed. In order to enable white light emission the stacking of red, green, and blue emitting segments is used to achieve the monolithic integration of these structures in one single InGaN NC allowing for the fabrication of ordered broad spectrum emitters. As alternative to axial InGaN/GaN nanostructures, the next section reports on the growth and characterization of InGaN/GaN core–shell structures with emission at around 3.0 eV. Furthermore, the successful fabrication of a core–shell pin diode structure is demonstrated. Finally, the SAG of In(Ga)N/GaN NCs on Si(111) substrates is presented. Ordered In(Ga)N/GaN NCs emitting from ultraviolet (3.2 eV) to infrared (0.78 eV) were grown on top of GaN-buffered Si substrates.

This work reports on the growth and characterization of InGaN/GaN core–shell structures by plasma-assisted molecular beam epitaxy on an ordered array of top-down patterned GaN microrods fabricated on a GaN/sapphire substrate. Growth of InGaN/GaN is conformal, with axial and radial growth components leading to core–shell structures with clear hexagonal facets. The radial InGaN growth (shell) was confirmed by spatially resolved cathodoluminescence performed using scanning electron microscopy as well as scanning transmission electron microscopy. The In content of the InGaN shell is controlled by means of the growth temperature and the III/V ratio.

The purpose of this study was to develop a safe, inexpensive, and practical method for estimating the force on the human spine during simulated fall landings for forensic investigations. Although the injury tolerances for the spine are known, the mechanics of spinal loading during fall landing are not well-established and thus limit the use of injury tolerances in establishing risk in landing injury cases. Measuring these spinal forces directly using live subjects would be invasive and unsafe; cadaver and animal models are expensive and do not capture the true mechanics of human spinal loading. As an alternative, this study proposed the use of a heavy duty punching bag to simulate the semi-rigid properties of the human body during a fall landing. The heavy bag was instrumented with accelerometers and dropped from various heights to measure impact acceleration. A live test subject instrumented with accelerometers on the foot and low back performed feet-first fall landings at relatively low heights to establish data for comparison. The impact acceleration for the heavy bag and back acceleration of the live subject matched well at corresponding heights. The measured foot accelerations did not correlate directly with those of the bag, possibly due to additional limb acceleration during landing. These preliminary results suggest that a heavy bag could be used to estimate the acceleration experienced by the back during simulated fall landings in forensic investigations.

International audience; E-beam lithography was used to pattern a titanium mask on a GaN substrate with ordered arrays of nanoholes. This patterned mask served as a template for the subsequent ordered growth of GaN/InGaN nanorods by plasma-assisted molecular beam epitaxy. The mask patterning process was optimized for several holes configurations. The smallest holes were 30 nm in diameter with a pitch (center-to-center distance) of 100 nm only. High quality masks of several geometries were obtained that could be used to grow ordered GaN/InGaN nanorods with full selectivity (growth localized inside the nanoholes only) over areas of hundreds of microns. Although some parasitic InGaN growth occurred between the nanorods during the In incorporation, transmission electron microscopy and photoluminescence measurements demonstrated that these ordered nanorods exhibit high crystal quality and reproducible optical properties.

El objetivo de este trabajo es un estudio profundo del crecimiento selectivo de nanoestructuras de InGaN por epitaxia de haces moleculares asistido por plasma, concentrandose en el potencial de estas estructuras como bloques constituyentes en LEDs de nueva generación. Varias aproximaciones al problema son discutidas; desde estructuras axiales InGaN/GaN, a estructuras core-shell, o nanoestructuras crecidas en sustratos con orientaciones menos convencionales (semi polar y no polar). La primera sección revisa los aspectos básicos del crecimiento auto-ensamblado de nanocolumnas de GaN en sustratos de Si(111). Su morfología y propiedades ópticas son comparadas con las de capas compactas de GaN sobre Si(111). En el caso de las columnas auto-ensambladas de InGaN sobre Si(111), se presentan resultados sobre el efecto de la temperatura de crecimiento en la incorporación de In. Por último, se discute la inclusión de nanodiscos de InGaN en las nanocolumnas de GaN. La segunda sección revisa los mecanismos básicos del crecimiento ordenado de nanoestructuras basadas en GaN, sobre templates de GaN/zafiro. Aumentando la relación III/V localmente, se observan cambios morfológicos; desde islas piramidales, a nanocolumnas de GaN terminadas en planos semipolares, y finalmente, a nanocolumnas finalizadas en planos c polares. Al crecer nanodiscos de InGaN insertados en las nanocolumnas de GaN, las diferentes morfologias mencionadas dan lugar a diferentes propiedades ópticas de los nanodiscos, debido al diferente carácter (semi polar o polar) de los planos cristalinos involucrados. La tercera sección recoge experimentos acerca de los efectos que la temperatura de crecimiento y la razón In/Ga tienen en la morfología y emisión de nanocolumnas ordenadas de InGaN crecidas sobre templates GaN/zafiro. En el rango de temperaturas entre 650 y 750 C, la incorporacion de In puede modificarse bien por la temperatura de crecimiento, o por la razón In/Ga. Controlar estos factores permite la optimización de la longitud de onda de emisión de las nanocolumnas de InGaN. En el caso particular de la generación de luz blanca, se han seguidos dos aproximaciones. En la primera, se obtiene emisión amarilla-blanca a temperatura ambiente de nanoestructuras donde la región de InGaN consiste en un gradiente de composiciones de In, que se ha obtenido a partir de un gradiente de temperatura durante el crecimiento. En la segunda, el apilamiento de segmentos emitiendo en azul, verde y rojo, consiguiendo la integración monolítica de estas estructuras en cada una de las nanocolumnas individuales, da lugar a emisores ordenados con un amplio espectro de emisión. En esta última aproximación, la forma espectral puede controlarse con la longitud (duración del crecimiento) de cada uno de los segmentos de InGaN. Más adelante, se presenta el crecimiento ordenado, por epitaxia de haces moleculares, de arrays de nanocolumnas que son diodos InGaN/GaN cada una de ellas, emitiendo en azul (441 nm), verde (502 nm) y amarillo (568 nm). La zona activa del dispositivo consiste en una sección de InGaN, de composición constante nominalmente y longitud entre 250 y 500 nm, y libre de defectos extendidos en contraste con capas compactas de InGaN de similares composiciones y espesores. Los espectros de electroluminiscencia muestran un muy pequeño desplazamiento al azul al aumentar la corriente inyectada (desplazamiento casi inexistente en el caso del dispositivo amarillo), y emisiones ligeramente más anchas que en el caso del estado del arte en pozos cuánticos de InGaN. A continuación, se presenta y discute el crecimiento ordenado de nanocolumnas de In(Ga)N/GaN en sustratos de Si(111). Nanocolumnas ordenadas emitiendo desde el ultravioleta (3.2 eV) al infrarrojo (0.78 eV) se crecieron sobre sustratos de Si(111) utilizando una capa compacta (“buffer”) de GaN. La morfología y eficiencia de emisión de las nanocolumnas emitiendo en el rango espectral verde pueden ser mejoradas ajustando las relaciones In/Ga y III/N, y una eficiencia cuántica interna del 30% se deriva de las medidas de fotoluminiscencia en nanocolumnas optimizadas. En la siguiente sección de este trabajo se presenta en detalle el mecanismo tras el crecimiento ordenado de nanocolumnas de InGaN/GaN emitiendo en el verde, y sus propiedades ópticas. Nanocolumnas de InGaN/GaN con secciones largas de InGaN (330-830 nm) se crecieron tanto en sustratos GaN/zafiro como GaN/Si(111). Se encuentra que la morfología y la distribución espacial del In dentro de las nanocolumnas dependen de las relaciones III/N e In/Ga locales en el frente de crecimiento de las nanocolumnas. La dispersión en el contenido de In entre diferentes nanocolumnas dentro de la misma muestra es despreciable, como indica las casi identicas formas espectrales de la catodoluminiscencia de una sola nanocolumna y del conjunto de ellas. Para las nanocolumnas de InGaN/GaN crecidas sobre GaN/Si(111) y emitiendo en el rango espectral verde, la eficiencia cuántica interna aumenta hasta el 30% al disminuir la temperatura de crecimiento y aumentar el nitrógeno activo. Este comportamiento se debe probablemente a la formación de estados altamente localizados, como indica la particular evolución de la energía de fotoluminiscencia con la temperatura (ausencia de “s-shape”) en muestras con una alta eficiencia cuántica interna. Por otro lado, no se ha encontrado la misma dependencia entre condiciones de crecimiento y efiencia cuántica interna en las nanoestructuras InGaN/GaN crecidas en GaN/zafiro, donde la máxima eficiencia encontrada ha sido de 3.7%. Como alternativa a las nanoestructuras axiales de InGaN/GaN, la sección 4 presenta resultados sobre el crecimiento y caracterización de estructuras core-shell de InGaN/GaN, re-crecidas sobre arrays de micropilares de GaN fabricados por ataque de un template GaN/zafiro (aproximación top-down). El crecimiento de InGaN/GaN es conformal, con componentes axiales y radiales en el crecimiento, que dan lugar a la estructuras core-shell con claras facetas hexagonales. El crecimiento radial (shell) se ve confirmado por medidas de catodoluminiscencia con resolución espacial efectuadas en un microscopio electrónico de barrido, asi como por medidas de microscopía de transmisión de electrones. Más adelante, el crecimiento de micro-pilares core-shell de InGaN se realizó en pilares GaN (cores) crecidos selectivamente por epitaxia de metal-orgánicos en fase vapor. Con el crecimiento de InGaN se forman estructuras core-shell con emisión alrededor de 3 eV. Medidas de catodoluminiscencia resuelta espacialmente indican un aumento en el contenido de indio del shell en dirección a la parte superior del pilar, que se manifiesta en un desplazamiento de la emisión de 3.2 eV en la parte inferior, a 3.0 eV en la parte superior del shell. Este desplazamiento está relacionado con variaciones locales de la razón III/V en las facetas laterales. Finalmente, se demuestra la fabricación de una estructura pin basada en estos pilares core-shell. Medidas de electroluminiscencia resuelta espacialmente, realizadas en pilares individuales, confirman que la electroluminiscencia proveniente del shell de InGaN (diodo lateral) está alrededor de 3.0 eV, mientras que la emisión desde la parte superior del pilar (diodo axial) está alrededor de 2.3 eV. Para finalizar, se presentan resultados sobre el crecimiento ordenado de GaN, con y sin inserciones de InGaN, en templates semi polares (GaN(11-22)/zafiro) y no polares (GaN(11-20)/zafiro). Tras el crecimiento ordenado, gran parte de los defectos presentes en los templates originales se ven reducidos, manifestándose en una gran mejora de las propiedades ópticas. En el caso de crecimiento selectivo sobre templates con orientación GaN(11-22), no polar, la formación de nanoestructuras con una particular morfología (baja relación entre crecimiento perpedicular frente a paralelo al plano) permite, a partir de la coalescencia de estas nanoestructuras, la fabricación de pseudo-templates no polares de GaN de alta calidad. ABSTRACT The aim of this work is to gain insight into the selective area growth of InGaN nanostructures by plasma assisted molecular beam epitaxy, focusing on their potential as building blocks for next generation LEDs. Several nanocolumn-based approaches such as standard axial InGaN/GaN structures, InGaN/GaN core-shell structures, or InGaN/GaN nanostructures grown on semi- and non-polar substrates are discussed. The first section reviews the basics of the self-assembled growth of GaN nanocolumns on Si(111). Morphology differences and optical properties are compared to those of GaN layer grown directly on Si(111). The effects of the growth temperature on the In incorporation in self-assembled InGaN nanocolumns grown on Si(111) is described. The second section reviews the basic growth mechanisms of selectively grown GaNbased nanostructures on c-plane GaN/sapphire templates. By increasing the local III/V ratio morphological changes from pyramidal islands, to GaN nanocolumns with top semi-polar planes, and further to GaN nanocolumns with top polar c-planes are observed. When growing InGaN nano-disks embedded into the GaN nanocolumns, the different morphologies mentioned lead to different optical properties, due to the semipolar and polar nature of the crystal planes involved. The third section reports on the effect of the growth temperature and In/Ga ratio on the morphology and light emission characteristics of ordered InGaN nanocolumns grown on c-plane GaN/sapphire templates. Within the growth temperature range of 650 to 750oC the In incorporation can be modified either by the growth temperature, or the In/Ga ratio. Control of these factors allows the optimization of the InGaN nanocolumns light emission wavelength. In order to achieve white light emission two approaches are used. First yellow-white light emission can be obtained at room temperature from nanostructures where the InGaN region is composition-graded by using temperature gradients during growth. In a second approach the stacking of red, green and blue emitting segments was used to achieve the monolithic integration of these structures in one single InGaN nanocolumn leading to ordered broad spectrum emitters. With this approach, the spectral shape can be controlled by changing the thickness of the respective InGaN segments. Furthermore the growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN layers (planar) of similar composition and thickness. Electroluminescence spectra show a very small blue shift with increasing current, (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells. Next the selective area growth of In(Ga)N/GaN nanocolumns on Si(111) substrates is discussed. Ordered In(Ga)N/GaN nanocolumns emitting from ultraviolet (3.2 eV) to infrared (0.78 eV) were then grown on top of GaN-buffered Si substrates. The morphology and the emission efficiency of the In(Ga)N/GaN nanocolumns emitting in the green could be substantially improved by tuning the In/Ga and total III/N ratios, where an estimated internal quantum efficiency of 30 % was derived from photoluminescence data. In the next section, this work presents a study on the selective area growth mechanisms of green-emitting InGaN/GaN nanocolumns and their optical properties. InGaN/GaN nanocolumns with long InGaN sections (330-830nm) were grown on GaN/sapphire and GaN-buffered Si(111). The nanocolumn’s morphology and spatial indium distribution is found to depend on the local group (III)/N and In/Ga ratios at the nanocolumn’s top. A negligible spread of the average indium incorporation among different nanostructures is found as indicated by similar shapes of the cathodoluminescence spectra taken from single nanocolumns and ensembles of nanocolumns. For InGaN/GaN nanocolumns grown on GaN-buffered Si(111), all emitting in the green spectral range, the internal quantum efficiency increases up to 30% when decreasing growth temperature and increasing active nitrogen. This behavior is likely due to the formation of highly localized states, as indicated by the absence of a complete s-shape behavior of the PL peak position with temperature (up to room temperature) in samples with high internal quantum efficiency. On the other hand, no dependence of the internal quantum efficiency on the growth conditions is found for InGaN/GaN nanostructures grown on GaN/sapphire, where the maximum achieved efficiency is 3.7%. As alternative to axial InGaN/GaN nanostructures, section 4 reports on the growth and characterization of InGaN/GaN core-shell structures on an ordered array of top-down patterned GaN microrods etched from a GaN/sapphire template. Growth of InGaN/GaN is conformal, with axial and radial growth components leading to core-shell structures with clear hexagonal facets. The radial InGaN growth (shell) is confirmed by spatially resolved cathodoluminescence performed in a scanning electron microscopy as well as in scanning transmission electron microscopy. Furthermore the growth of InGaN core-shell micro pillars using an ordered array of GaN cores grown by metal organic vapor phase epitaxy as a template is demonstrated. Upon InGaN overgrowth core-shell structures with emission at around 3.0 eV are formed. With spatially resolved cathodoluminescence, an increasing In content towards the pillar top is found to be present in the InGaN shell, as indicated by a shift of CL peak position from 3.2 eV at the shell bottom to 3.0 eV at the shell top. This shift is related to variations of the local III/V ratio at the side facets. Further, the successful fabrication of a core-shell pin diode structure is demonstrated. Spatially resolved electroluminescence measurements performed on individual micro LEDs, confirm emission from the InGaN shell (lateral diode) at around 3.0 eV, as well as from the pillar top facet (axial diode) at around 2.3 eV. Finally, this work reports on the selective area growth of GaN, with and without InGaN insertion, on semi-polar (11-22) and non-polar (11-20) templates. Upon SAG the high defect density present in the GaN templates is strongly reduced as indicated by TEM and a dramatic improvement of the optical properties. In case of SAG on non-polar (11-22) templates the formation of nanostructures with a low aspect ratio took place allowing for the fabrication of high-quality, non-polar GaN pseudo-templates by coalescence of the nanostructures.

In this work, through a comparative study of self-assembled (SA) and selective area grown (SAG) (In)GaN nanocolumn (NC) ensembles, we first give a detailed insight into improved crystallographic uniformity (homogeneity of crystallographic tilts and twists) of the latter ones. The study, performed making use of: reflective high energy electron diffraction, X-ray diffraction and scanning electron microscopy, reveals that unlike their SA counterparts, the ensembles of SAG NCs show single epitaxial relationship to both sapphire(0001) and Si(111) underlying substrates. In the second part of the article, making use of X-ray diffraction, we directly show that the selective area growth leads to improved compositional uniformity of InGaN NC ensembles. This further leads to improved spectral purity of their luminescence, as confirmed by comparative macro-photoluminescence measurements performed on SA and SAG InGaN NC ensembles. An improved crystallographic uniformity of NC ensembles facilitates their integration into optoelectronic devices, whereas their improved compositional uniformity allows for their employment in single-color optoelectronic applications.

The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN layers (planar) of similar composition and thickness. The devices are driven under pulsed operation up to 1300 A/cm2 without traces of efficiency droop. Electroluminescence spectra show a very small blue shift with increasing current, (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

The aim of this work is to provide an overview on the recent advances in the selective area growth (SAG) of ( In ) GaN nanostructures by plasma assisted molecular beam epitaxy, focusing on their potential as building blocks for next generation LEDs. The first three sections deal with the basic growth mechanisms of GaN SAG and the emission control in the entire ultraviolet to infrared range, including approaches for white light emission, using InGaN disks and thick segments on axial nanocolumns. SAG of axial nanostructures is developed on both GaN /sapphire templates and GaN -buffered Si (111). As an alternative to axial nanocolumns, section 4 reports on the growth and characterization of InGaN / GaN core-shell structures on an ordered array of top-down patterned GaN microrods. Finally, section 5 reports on the SAG of GaN , with and without InGaN insertion, on semi-polar (11-22) and non-polar (11-20) templates. Upon SAG the high defect density present in the templates is strongly reduced as indicated by a dramatic improvement of the optical properties. In the case of SAG on non-polar (11-22) templates, the formation of nanostructures with a low aspect ratio took place allowing for the fabrication of high-quality, non-polar GaN pseudo-templates by coalescence of these nanostructures.

This paper consists of two case studies: the World Meteorological Organization's information/knowledge exchange on oceanic weather and The World Health Organization's information/knowledge exchange on influenza. In both cases the issues of context, codification and commodification arise. Most importantly, these exchanges have the power to save lives. The fact that they do so is evidence as to the importance of exchanging information/knowledge. Copyright © 2000 John Wiley & Sons, Ltd.

There are a disproportionate number of professional women working through temporary agencies. We develop a theory wherein this gender skewness in temporary-agency employment results from the differences in perceptions of control at work between men and women working through large traditional organizations. Our theory suggests that if control is perceived to be less for women than for men in large organizations, then women will tend to populate other work arrangements, like temporary agencies, in order to enhance their control. Propositions are tested via a unique data set comparing the responses of employees from both a London temporary accountancy agency and a large London accountancy firm. Our results are consistent with a lack of control driving professional women from large firms to temporary agencies, and neither rely on preference differences nor familial obligations.

Audiences choose to see films using information from previous films. A stochastic consumer choice process based on this assumption generates a particular distribution of financially successful films among film types. Movie stars can be used to mark these successful film types. Thus, their star power originates not only from “box-office appeal” but also from “marking power”. Evidence of 960 top 20 films released in the United States and Canada between 1940–1955 and 1960–1995 is consistent with this model.