Factores de crecimiento y páncreas exocrino

The exocrine pancreatic secretion is the final result of multiple extracellular messengers acting simultaneously on acinar and ductular cells. The overall process is mediated by a number at intracellular messengers including cyclic cAMP, IP3, IP4 or diacylglycerol. Hormones such as histamine and insuline can also participate as regulatory agents in the modulation of pancreatic secretion. Histamine has been shown to exert a mild secretagogue-like effect through modulation of the secretory responses evoked by classical secretagogues. Insuline can markedly potentiate the secretory responses to acetylcholine and cholecystokinin In addition, other peptides released from the islets of Langerhans, i.e. glucagon, somatostatin and pancreatic polypeptide can attenuate the secretory responses induced by cholecystokinin and acetylcholine. Growth factors participate in the control of cell growth, replication and differentiation. They are also involved in the exocrine pancreatic secretion. Numerous studies have demonstrated that growth factors are coupled to activation of G proteins. Thus, EGF can stimulate or inhibit adenyl cyclase by activating Gs or Gi type G proteins It has been shown a relationship between EGF and cholecystokinin levels. Moreovera a dual mode of action for EGFon pancreatic acini has been postulatedLa secreción pancreática exocrina es el resultado final de la acción simultánea de múltiples mensajeros extracelulares sobre las células acinares y ductulares. El proceso global está mediado por un grupo de mensajeros intracelulares como cAMP, IP3, IP4 o diacilglicerol. Hormonas como histamina e insulina pueden participar también como agentes reguladores moduladores de la secreción pancreática. Se ha demostrado que la histamina ejerce un efecto secretagogo moderado a través de la modulación de la respuesta secretora inducida por los secretagogos clásicos. La insulina puede potenciar acusadamente la respuesta secretora a acetilcolina y colecistoquinina. Además, otros péptidos liberados de los islotes de Langerhans como glucagon, somatostatina y polipéptido pancreático, pueden atenuar las respuestas secretoras inducidas por colecistoquinina y acetilcolina. Los factores de crecimiento participan en el control del crecimiento, replicación y diferenciación celular. También están implicados en la secreción pancreática exocrina. Numerosos estudios han demostrado que los factores de crecimiento están asociados a la activación de la proteína G. Así, EGF puede estimular o inhibir la adenilato ciclasa por activación de las proteínas G de tipo Gs o Gi. Se ha mostrado una relación entre EGF y los niveles de colecistoquinina, postulándose un modo dual de acción del EGF sobre los acinos pancreáticos.This work was supported by DGICYT PB94-1416-CO2-02, the British Council and the Wellcome Trust

A Multi segment Morphing System for a Micro Air Vehicle using Shape Memory Alloy Actuators

A configurable multi-segment morphing system for a micro air vehicle (MAV) is presented in this study. One of the novelties is the development of an adaptive control allocation algorithm that provides fast, simultaneous and independent operation of four morphing segments using shape memory alloy (SMA) actuators. The SMA operation is time-staggered in microsecond resolution to ensure that only one SMA draws power from the MAV battery at a time. The other novelties are the in-flight measurement of morphing angle using dual flex-sensors and morphing of leading edges such that the ‘morphing-line’ is diagonal (45º) to the MAV’s lateral axis. The system was implemented on an open source autopilot controller and operated using the MAV battery. It was ground-tested under propeller ON conditions and a droop rate of 35º/s and ability to track a 1 Hz sinusoidal variation of droop angle were realised

Accessory belly of flexor digitorum superficialis - case report of a rare variant

Variations of the muscles pose a challenge to diagnosis and knowledge about them is important during surgeries and other interventions. At times these variations may cause symptoms per se. Variations of the Flexor digitorum superficialis: a muscle of the anterior compartment of forearm, are not very common. We present a rare variation of this muscle in the right upper limb of a male cadaver. The variant was an accessory belly arising from and under the Flexor digitorum superficialis and inserting into the base of proximal phalanx of the index finger. We also review the evolutionary and embryological concepts of such variations

Integrated electrical and mechanical modelling of integrated-full-electric-propulsion systems

Integrated Full Electric Propulsion (IFEP) systems are the subject of much interest at present. Current research is focused on analysing and improving aspects of subsystem and system performance. However, there is a great need to look more widely at the `multi-physics' problem of characterising the dynamic interactions between the electrical and mechanical systems. This paper will discuss the changing nature of modelling and simulation to aid research into IFEP systems, outlining the alternative angle taken by the Advanced Marine Electrical Propulsion Systems (AMEPS) project to characterise and investigate electrical-mechanical system interactions. The paper will describe this approach and highlight the unique challenges associated with the problem, discussing the suitable methods that will be adopted to address these challenges. Finally, an overview of the present and future research opportunities facilitated via the AMEPS project will be presented

Bulk Viscous LRS Biachi-I Universe with variable GG and decaying Λ\Lambda

The present study deals with spatially homogeneous and totally anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with variable $G$ and $\Lambda$ in presence of imperfect fluid. To get the deterministic model of Universe, we assume that the expansion $(\theta)$ in the model is proportional to shear $(\sigma)$. This condition leads to $A=\ell B^{n}$, where $A$,\;$B$ are metric potential. The cosmological constant $\Lambda$ is found to be decreasing function of time and it approaches a small positive value at late time which is supported by recent Supernovae Ia (SN Ia) observations. Also it is evident that the distance modulus curve of derived model matches with observations perfectly.Comment: 11 pages, 4 figures and 1 table, Accepted for publication in Astrophysics and Space Scienc

Wind energy resource assessment for Cook Islands with accurate estimation of Weibull parameters using frequentist and Bayesian methods

Wind energy resource assessments at two islands in the Cook Islands are carried out in the present work. The wind data were collected for a year from sites on Mauke and Rarotonga Islands in the Cook Islands and the daily, monthly and seasonal average wind speeds, the diurnal variations of the wind shear coefficient, average temperature and turbulence intensity were estimated. Eleven frequentist methods and a Bayesian technique were used to determine the Weibull parameters and the wind power density (WPD) for each site. The best method was determined using the goodness of fit test and error measures. The average wind speeds were 4.65 m/s and 3.86 m/s at 34 m above ground level for the sites on Mauke and Rarotonga respectively. Based on the goodness of fit tests and error measures, the Least Squares Method performed best for estimating the Weibull parameters at the Mauke site, while for the Rarotonga site, the median and quartiles method performed the best. For both the sites, the Bayesian method, which is being used for the first time for wind resource assessments, ranked second of the twelve methods, indicating good potential for this method. The annual energy production (AEP) was also determined which was calculated to be 2192.34 MWh from a total of ten Vergnet 275 kW turbines at the two sites. Finally, an economic analysis carried out for the two sites, indicated a payback period of 7.72 years

Future Armour Materials and Technologies for Combat Platforms

The ultimate goal of armour research is to create better armour for battle worthy combat plat forms such as main battle tanks, infantry combat vehicles and light combat vehicles. In each of these applications, the main aim boils down to one of the two things; either reduce the weight without sacrificing protection or enhance the performance at same or even reduced weight. In practice, these ambitions can be fulfilled only if we have with us, appropriate improved armour materials, advanced and innovative technologies and also improved designs, which enable us to use them for creating next generation armour modules. Armour systems have progressed through improvements in metallic, ceramic and lightweight (low areal density) composite materials. Similarly, the advances in development of explosive reactive armour (ERA) and non-explosive reactive armour (NERA) have generated efficient armour system against contemporary high explosive antitank ammunition and missile threats for the armoured vehicles. Yet, to achieve armour performance exceeding that of the current light combat vehicles and main battle tanks, further advancements in armour materials, systems, and survivability technologies are required for new vehicular systems that weigh significantly less than the present combat platforms. Various approaches and advancements in the metallic and composite armour materials, ERA and NERA systems to improve the survivability of armoured vehicles in the futuristic multi-spectral battlefield scenarios are described

Inflationary Cosmology and Quantization Ambiguities in Semi-Classical Loop Quantum Gravity

In loop quantum gravity, modifications to the geometrical density cause a self-interacting scalar field to accelerate away from a minimum of its potential. In principle, this mechanism can generate the conditions that subsequently lead to slow-roll inflation. The consequences for this mechanism of various quantization ambiguities arising within loop quantum cosmology are considered. For the case of a quadratic potential, it is found that some quantization procedures are more likely to generate a phase of slow--roll inflation. In general, however, loop quantum cosmology is robust to ambiguities in the quantization and extends the range of initial conditions for inflation.Comment: 15 pages, 8 figure

Influence of enhanced melt supply on upper crustal structure at a mid-ocean ridge discontinuity: A three-dimensional seismic tomographic study of 9°N East Pacific Rise

We present a three-dimensional upper crustal model of the 9°03′N overlapping spreading center (OSC) on the East Pacific Rise that assists in understanding the relationship between melt sills and upper crustal structure at a ridge discontinuity with enhanced melt supply at crustal levels. Our P wave velocity model obtained from tomographic inversion of ∼70,000 crustal first arrival travel times suggests that the geometry of extrusive emplacement are significantly different beneath the overlapping spreading limbs. Extrusive volcanic rocks above the western melt sill are inferred to be thin (∼250 m). More extensive accumulation of extrusives is inferred to the west than to the east of the western melt sill. The extrusive layer inferred above the eastern melt sill thickens from ∼350 (at the neovolcanic axis) to 550 m (to the west of the melt sill). Volcanic construction is likely to be significant in the formation of ridge crest morphology at the OSC, particularly at the tip of the eastern limb. On the basis of our interpretation of the velocity model, we propose that enhanced magma supply at crustal levels at the OSC may provide an effective mechanism for the migration of ridge discontinuities. This “dynamic magma supply model” may explain the commonly observed nonsteady migration pattern of ridge discontinuities by attributing this to the temporal fluctuations in melt availability to the overlapping spreading limbs