High order multiple births in the Maltese population

Triplets are a relatively rare occurrence being encountered in the Maltese Islands with an overall incidence of about 0.1 per 1000 maternities. The incidence appears to be on the increase over the last twenty years rising from the 0.08 per 1000 maternities in the decade 1960-69 to 0.11 per 1000 maternities in the following two decades. This increase has been correlated with the increasing use of ovulation induction agents, as has the occurrence of two quadruplets and one octuplet pregnancies in 1988-90. Triplets are shown to occur more frequently in elderly mothers, but no relationship to parity could be identified. Higher order births are shown to have a high incidence of antenatal and intrapartum problems, and are associated with a higher fetal loss than singleton pregnancies.peer-reviewe

Anodic Aluminum Oxide (AAO) Membranes for Cellular Devices

Anodic Aluminum Oxide (AAO) membranes can be fabricated with a highly tunable pore structure making them a suitable candidate for cellular hybrid devices with single-molecule selectivity. The objective of this study was to characterize the cellular response of AAO membranes with varying pore sizes to serve as a proof-of-concept for an artificial material/cell synapse system. AAO membranes with pore diameters ranging from 34-117 nm were achieved via anodization at a temperature of -1̊C in a 2.7% oxalic acid electrolyte. An operating window was established for this setup to create membranes with through-pore and disordered pore morphologies. C17.2 neural stem cells were seeded onto the membranes and differentiated via serum withdrawal. The data suggests a highly tunable correlation between AAO pore diameter and differentiated cell populations. Analysis of membranes before and after cell culture indicated no breakdown of the through-pore structure. Immunocytochemistry (ICC) showed that AAO membranes had increased neurite outgrowth when compared to tissue culture treated (TCT) glass, and neurite outgrowth varied with pore diameter. Additionally, lower neuronal percentages were found on AAO as compared to TCT glass; however, neuronal population was also found to vary with pore diameter. Scanning electron microscopy (SEM) and ICC images suggested the presence of a tissue-like layer with a mixed-phenotype population. AAO membranes appear to be an excellent candidate for cellular devices, but more work must be completed to understand the surface chemistry of the AAO membranes as it relates to cellular response

Microstructural Evolution and Mechanical Property Development of Selective Laser Melted Copper Alloys

Selective Laser Melting (SLM) is an additive manufacturing technology that utilizes a high-power laser to melt metal powder and form a part layer-by-layer. Over the last 25 years, the technology has progressed from prototyping polymer parts to full scale production of metal component. SLM offers several advantages over traditional manufacturing techniques; however, the current alloy systems that are researched and utilized for SLM do not address applications requiring high electrical and thermal conductivity. This work presents a characterization of the microstructural evolution and mechanical property development of two copper alloys fabricated via SLM and post-process heat treated to address this gap in knowledge. Tensile testing, conductivity measurement, and detailed microstructural characterization was carried out on samples in the as-printed and heat treated conditions.A single phase solid solution strengthened binary alloy, Cu-4.3Sn, was the first alloy studied. Components were selectively laser melted from pre-alloyed Cu-4.3Sn powder and heat treated at 873 K (600 °C) and 1173 K (900 °C) for 1 hour. As-printed samples were around 97 percent dense with a yield strength of 274 MPa, an electrical conductivity of 24.1 %IACS, and an elongation of 5.6%. Heat treatment resulted in lower yield strength with significant increases in ductility due to recrystallization and a decrease in dislocation density. Tensile sample geometry and surface finish also showed a significant effect on measured yield strength but a negligible change in measured ductility. Microstructural characterization indicated that grains primarily grow epitaxially with a sub-micron cellular solidification sub-structure. Nanometer scale tin dioxide particles identified via XRD were found throughout the structure in the tin-rich intercellular regions.The second alloy studied was a high-performance precipitation hardening Cu-Ni-Si alloy, C70250. Pre-alloyed powder was selectively laser melted to produce components around 98 percent dense with high mechanical strength and electrical conductivity. Aging heat treatments were carried out at 723 K (450 °C) directly on as-printed samples up to 128 hours. A peak yield strength of around 590 MPa could be attained with an electrical conductivity of 34.2 %IACS after 8 hours of aging. Conductivity continues to increase with further aging while the peak strength appears to be less sensitive to aging time exhibiting a broad range of time where near-peak properties exist. Nanometer-scale silicon-rich oxide particles exist throughout the material and persist during aging. Deformation twinning is observed in the peak age condition after tensile testing and several strengthening mechanisms appear to be active to varying degrees throughout aging, which accounts for the broad range of aging time where nearly the peak mechanical properties exist. The findings of this research are integral to understanding SLM copper alloys and serve as a foundation for future development of new copper alloys tailored to the SLM process

Inter-subnet localized mobility support for host identity protocol

Host identity protocol (HIP) has security support to enable secured mobility and multihoming, both of which are essential for future Internet applications. Compared to end host mobility and multihoming with HIP, existing HIP-based micro-mobility solutions have optimized handover performance by reducing location update delay. However, all these mobility solutions are client-based mobility solutions. We observe that another fundamental issue with end host mobility and multihoming extension for HIP and HIP-based micro-mobility solutions is that handover delay can be excessive unless the support for network-based micro-mobility is strengthened. In this study, we co-locate a new functional entity, subnet-rendezvous server, at the access routers to provide mobility to HIP host. We present the architectural elements of the framework and show through discussion and simulation results that our proposed scheme has achieved negligible handover latency and little packet loss

Distributed mobility management with mobile Host Identity Protocol proxy

The architectural evolution from hierarchical to flatter networks creates new challenges such as single points of failure and bottlenecks, non-optimal routing paths, scalability problems, and long handover delays. The cellular networks have been hierarchical so that they are largely built on centralized functions based on which their handover mechanisms have been built. They need to be redesigned and/or carefully optimized. The mobility extension to Host Identity Protocol (HIP) proxy, mobile HIP Proxy (MHP), provides a seamless and secure handover for the Mobile Host in the hierarchical network. However, the MHP cannot ensure the same handover performance in flatter network because the MHP has also utilized the features offered by the hierarchical architecture. This paper extends the MHP to distributed mobile HIP proxy (DMHP). The performance evaluation of the DMHP in comparison to MHP and other similar mobility solutions demonstrates that DMHP does indeed perform well in the flatter networks. Moreover, the DMHP supports both efficient multi-homing and handover management for many mobile hosts at the same time to the same new point of attachment

Disminución de los costos de operación en las cosechadoras de caña a través de un plan de mantenimiento en la empresa agroindustrial laredo S.A.A.

El presente trabajo de investigación tiene como objetivo fundamental proponer mejoras al plan de mantenimiento de las Cosechadoras de caña en la Empresa Agroindustrial Laredo S.A.A., con el fin de disminuir los costos de operación y al mismo tiempo aumentar la disponibilidad de cada una de ellas, permitiendo formular estrategias para mejorar la planificación y ejecución del mantenimiento. Para el desarrollo de esta investigación, se contó con una data de Costos de Operación y Frecuencia de Fallas del año 2013, primero se procedió a describir el estado actual en el que se encuentra el área de Taller Agrícola con respecto al mantenimiento de las Cosechadoras de caña consultando con el software de mantenimiento para ver el historial de estos equipos, teniendo esa data se procedió a calcular el Tiempo Promedio entre Fallas (MTBF) y el Tiempo Promedio para Reparar (MTTR) para luego calcular la Disponibilidad de cada cosechadora. Seguidamente se propone un cambio del uso de aceite minerales por aceites sintéticos para los sistemas motor e hidráulico, ampliando los rangos de cambio de aceite, se propuso una organización del área por cargos y sus respectivas funciones del personal; implementar el uso de indicadores de mantenimiento y de gestión para la toma de decisiones acertadas según los datos obtenidos. Luego se realizó un análisis de los costos de operación con un mantenimiento inconsistente de cada cosechadora tomando solo como datos los costos de mano de obra, combustible, lubricantes, filtros y desgaste de neumáticos; para luego estimar los costos de operación con un mantenimiento responsable, con la implementación de aceites sintéticos y análisis de aceites. A esto se obtuvo los costos de operación totales con un mantenimiento responsable y comparándola con la gestión anterior (mantenimiento inconsistente) se comprobó un ahorró total de S/. 243,633.66 y un aumento de la producción total por todas las cosechadoras de caña en 1994429 Toneladas de caña en un periodo de 12 meses lo cual es un ahorro muy importante para la empresa

Propuesta vial mediante diseño geométrico de carreteras en un sistema de evacuación para vehículos en el distrito de Salaverry, Trujillo 2021

La investigación se realizó en Trujillo, en la Universidad Privada del Norte. Así mismo, a través del objetivo principal, se determinó la propuesta vial mediante conceptos del diseño geométrico de carreteras para un sistema de evacuación para vehículos, a su vez, se definió que el diseño de investigación es no experimental de tipo transversal-descriptico propositivo, y considerando una población objetivo de todos los artículos sobre sistemas de evacuación vehicular y propuestas viales, donde se tomó una muestra de 50 investigaciones, se utilizó la técnica de recolección de datos denominada revisión documental utilizando como instrumento la ficha de registro, y por consiguiente, el análisis de datos mediante cuadros estadísticos y polígonos de frecuencias. El problema se enfoca en la exigencia física para evacuar zonas vulnerables ante riesgos de tsunamis, además de una deficiente zona segura, por ello, en los resultados se muestra una propuesta de infraestructura vial en ascenso al cerro del distrito y las nuevas idealizaciones de rutas de evacuación y zonas seguras. Por tanto, la incorporación de la propuesta vial permitirá la evacuación vehicular a las zonas seguras de manera rápida, eficiente y segura sin restricción alguna, a partir de un complemento para el sistema de evacuación

Motivación laboral en los colaboradores de la Empresa de Transportes Turismo Alvarado E.I.R.L y su relación con el clima organizacional Chiclayo, 2016-2017

La presente investigación se llevó a cabo con el objetivo de encontrar correlación entre las variables Motivación Laboral y Clima Organizacional dentro de la población de la Empresa de Transportes Turismo Alvarado E.I.R.L., para esto fue necesario la utilización de dos cuestionarios para recolectar datos de los 36 colaboradores pertinentes a sus distintas áreas , uno mide la Motivación Laboral y el otro el Clima Organizacional, estos son propuestos en los modelos ML-ORG de Julio Jaramillo (2011) y el de Litwin y Stringer (1968) respectivamente. Para la correlación de las dos variables se empleó el coeficiente Spearman, asimismo la validez y confiabilidad de los instrumentos fueron debidamente demostradas y los datos obtenidos se procesaron en el programa estadístico SPSS. Los resultados obtenidos según el objetivo general indican que la variable motivación influye en un (94,6%) en la de clima organizacional, por lo cual se concluye que para mejorar aspectos del Clima Organizacional de la Empresa de Transportes Turismo Alvarado E.I.R.L se tiene que trabajar en la Motivación Laboral de los colaboradores. Este estudio demuestra que la motivación de los colaboradores se encuentra en un nivel alto (54.8%) y la medición del clima organizacional de la empresa se encuentra en un nivel bueno (64.4%)

A Stromgren view of the multiple populations in globular clusters

We discuss a variety of photometric indices assembled from the uvby Stromgren system. Our aim is to examine the pros and cons of the various indices to find the most suitable one(s) to study the properties of multiple populations in globular clusters (GCs) discovered by spectroscopy. We explore in particular the capabilities of indices like m_1 and c_y at different metallicities. We define a new index delta_4=(u-v)-(b-y) to separate first and second stellar generations in GCs of any metal abundance, since it keeps the sensitivity to multiple stellar populations over all the metallicity range and at the same time minimizes the sensitivity to photometric errors. We detecte clear differences in the red giant branches of the GCs examined, like skewness or bi/multi-modality in color distribution. We connect the photometric information with the spectroscopic results on O, Na abundances we obtained in our survey of GCs. Finally, we compute the effects of different chemical composition on the Stromgren filters and indices using synthetic spectra.Comment: Accepted for publication on Astronomy and Astrophysics. Figures 1,3,5 degraded in resolutio