Alfredo Bautista

UTP and diadenosine tetraphosphate accelerate wound healing in the rabbit cornea.

Nucleotides are naturally occurring substances present in tear film that can stimulate tear secretion in animals and humans. We investigated whether certain nucleotides can affect the rate of wound healing in the cornea of white rabbits. In the absence of any added compound, the rate of healing was 72.4 ± 2.2 μm h−1. Of all the tested nucleotides, UTP and Ap4A were the most active ones, maximally increasing the rate of healing to 121.6 ± 3.7 and 93.7 ± 3.2 μm h−1, respectively. Responses to UTP were dose dependent. UTP had a pD2 value of 8.9 ± 0.1 (EC50: 1.25 nM). P2 purinoceptor antagonists such as suramin and reactive blue‐2, inhibited the effect of UTP indicating the involvement of P2Y receptors. Mitogen‐activated protein kinase (MAPK) cascade inhibitors also abolished the effects of UTP, suggesting that P2Y receptors are coupled to the MAPK cascade, and that this is involved in controlling the rate of epithelial cell migration.

An explicit finite differences scheme over hexagonal tessellation

Abstract We introduce a new numerical method inspired in the cellular automata methodology to study the transmission of waves in two-dimensional solids. The stability of the second-order method is investigated and compared with that of a classical finite differences method for both wave and elastic equations.

Database Concurrent Processor

The organization of an autonomous processor supporting database management functions is presented. The DataBase Concurrent Processor (DBCP) can be thought as a back-end data management machine of a general purpose host computer; it supports relational data model directly in hardware, and is able to run concurrently a number of programs written with a relationally complete instruction set. DBCP is composed of a parallel organization of cells and a Coordination Unit (CU). Each cell supports and processes tuples of an unique relation and consists of a special purpose microprocessor and a circulating serial memory. Along a full. memory revolution each microprocessor accomplishes an access on its own memory block while, at the same time, the CU transmits all necessary information to the access to be made in the next revolution. CU is allowed by microprocessor functional independence to organize different concurrency control strategies, trying to make maximum use of cellular organization processing capability. This concurrent processing capability at backend level fits better to the database system multiuser nature (shared resources) and consequently higher capabilities and performance rates are hoped to be achieved.

Dynamic load balancing in a heterogeneous environment under PVM

An algorithm for dynamic load balancing in an heterogeneous workstations net is presented in this paper. Workstations are not usually a private resource, but a shared one. So, the computational load, and thus, the computational speed, of each workstation in the net is not predictable. Moreover for some problems the generated load could be variable in execution time. If former conditions appear, static load balancing is not a good approach. The method described in this paper is able to maintain a very good efficiency when the load in the workstations varies on time, or when the computational requirements of the problem are not constants.

Distributed parallel computers versus PVM on a workstation cluster in the simulation of time dependent partial differential equations

In the present paper, we present some experimental results about the parallel numerical simulation of a time dependent partial differential equation, the two dimensional nonlinear Schrodinger equation, on a message passing parallel machine and using PVM on a cluster of Sparc-stations. An implicit finite difference method has been used to carry out the simulation. Some features about the different scaling models are explained. In spite of the fact that it is difficult to compare the two parallel computing environments, we give some results of the two implementations. We reach the conclusion that PVM on a workstation cluster is a good solution to solve large-scale problems.<<ETX>>

An architectural design for simultaneous microdiagnostic

Abstract Simultaneous microdiagnostic is the execution of diagnosis microroutines by a system while performing its normal tasks. This paper deals with providing a monoprocessor architecture with minimal redundancies to enable simultaneous execution of two microprograms on different modules in the system in a conflict-free manner. Concurrent execution of several independent microdiagnostics is proposed so that the necessary compatibility between normal processing and a sole diagnostic could be diversified among several test alternatives. Consequently, a higher checking rate and, therefore, shorter fault latency times and quicker recovery actions are expected to be achieved. In order to keep the additional complexity introduced reasonable, some factors like — for example — the number of different test alternatives, are assayed by programmed simulation. Microdiagnostic is driven by an auxiliary control unit where there are a micro-address and data registers pair for every test alternative.

Microprocessor-based approach to industrial devices quality control

An industrial devices quality control inspection system based on a general purpose microprocessor is proposed. The system employs a microprocessor CPU, timer, ROM and peripheral interfaces in the hardware portion. Software includes an algorithm incorporating data acquisition, statistical computation and command interpreting functions, plus arithmetic and conversion subroutines. Two applications have been developed and are briefly described.

Efficiency on clusters of parallel simulation of sine-Gordon equation over hexagonal tessellation

Experiences in the parallel execution of a numerical method to simulate the sine-Gordon equation over two different clusters are presented in this paper. The nonlinear sine-Gordon equation has been discretized in a finite differences method based on hexagonal tesselation, and then parallelized using MPI for parallel execution on three workstation clusters, a Pentium III PC based cluster using Gigabit Ethernet and Myrinet as interconnection networks, an Itanium2 based HP RX2600 cluster with Gigabit Ethernet, and a Prescott based PC cluster. Efficiency measurements over these clusters are also studied and compared.

Parallel Simulation of Non-linear Phenomena with Cellular Automata

This paper presents a new approach to the problem of simulating wave propagation in elastic solids, using Cellular Automata. The main objective of this work is to develop a cellular automaton model which allows to understand several complex or non-linear phenomena that occur in the propagation of stress waves. These phenomena, such as soliton propagation, viscoelasticity, discontinuities, fracture mechanics and many others, are often hardly expressed by means of differential equations, or, if they do, it is very difficult to solve the final equations analytically. By the use of CA, where a microscopical description of the behaviour of each element is made, it is intended to prove that complex phenomena such as plasticity, energy losses and so on can be worthily simulated. This kind of description makes easier the experimentation with many different systems, since the number of characteristic parameters is small.

RDBAS: a relational database system for non-experienced users

Abstract In the last years, the relational approach has developed into a very interesting foundation to the implementation of database management systems oriented towards small computers. This paper deals with a software tool for assisted access to databases using the relational model (RDBAS). A main design goal has been the elaboration of a system whose utilization by unexperienced users requires only a bit of learning effort. Working towards this goal, a non-procedural semi-graphic query language with relational processing capability has been implemented. This language is based on the domain relational calculus and can be used in an interactive way. An interesting feature of this system is the extensibility of its command repertory. Specific purpose new commands can be defined to be used, even by people who are unaware of the query language. Information structures and techniques used in implementation are also discussed.