Discrete-time <Emphasis Type="Italic">MAP/G</Emphasis>/1/∞ system with inversive probabilistic servicing discipline

Consideration was given to the discrete-time MAP/G/1/∞ queuing system where the arriving customer is taken to the server with a certain probability depending only of the processed length of the customer in service and squeezes out its predecessor to the first place on the queue or, with the complementary probability, occupies the first place on the queue (inversive probabilistic servicing discipline). For this system, the main stationary operational characteristics were established.     

A Finite MAP K /G K /1 Queueing System with Generalized Foreground-Background Processor-Sharing Discipline

Queuing systems with Markov arrival process, several customer types, generalized foreground-background processor-sharing discipline with minimal served length or separate finite buffers for customers of different types, or a common finite buffer for customers of all types are studied. Mathematical relations are derived and used to compute the joint stationary distribution of the number of customers of all types in a system.     

Potential Use of Ascorbic Acid–Based Surfactants as Skin Penetration Enhancers

ABSTRACT

6-O-Ascorbic acid alkanoates (ASCn) are amphiphilic molecules having physical-chemical properties that depend on the alkyl chain length. The derivatives of low molecular weight (n < 11) have enough aqueous solubility to produce self-assemblies at room temperature (≈25°C), while those with longer alkyl chains possess a critical micellar temperature (CMT) higher than 30°C. At higher temperatures (T° > CMT), ASCn aqueous suspensions turn into either micellar solutions or gel phases, depending on the length of the hydrophobic chain. On cooling, coagels are produced, which possess a lamellar structure that exhibit sharp X-ray diffraction patterns and optical birefringence. The semisolid consistency of such coagels is an interesting property to formulate dermatological pharmaceutical dosage forms able to solubilize and stabilize different drugs. The objective of the present study was the evaluation of the enhancing permeation effect of ASCn with different chain lengths and to correlate permeability changes with histological effects. With this purpose, ASCn coagels containing anthralin (antipsoriasic drug) or fluorescein isothiocyanate (FITC, hydrophobic fluorescent marker) were assayed on rat skin (ex vivo) and mice skin (in vivo), respectively. Also, histological studies were performed aimed at detecting some possible side effects of ASCn. No inflammatory cellular response was observed in the skin when ASCn coagels were applied, suggesting non-irritating properties. Light microscopy indicated slight disruption and fragmentation of stratum corneum. The penetration of ASCn through rat skin epidermis was very fast and quantitatively significant. The permeation of anthralin was significantly increased when the drug was vehiculized in ASCn coagels, compared to other pharmaceutical systems. The results indicated that ASC12 seems to have the highest enhancing effect on FITC permeation. ASC12 appears to be the compound that possesses the highest capacity to enhance the penetration of the drugs. Furthermore, it has the highest permeation of the serie.     

A comparative study of the physico‐chemical properties affecting the organoleptic quality of fresh and thermally treated yellow tomato ecotype fruit

In recent years, yellow commercial tomatoes have attracted great interest from consumers. The goal of this work was to characterise the parameters of three yellow genotypes that affect the fruit quality, in comparison with those of a red fruit genotype. Compared to the other genotypes, the GiaGiù ecotype was characterised as having the highest titratable acidity, organic acids content and pectin content before and after a thermal treatment simulating industrial pasteurisation. Most of the analysed parameters influence the taste and aroma of fresh fruit and processed products, particularly the high glutamic acid content measured in the GiaGiù ecotype. This genotype was also distinctive for its higher pectin content, which influences the texture. These features might allow the development of new food products that require a specific viscosity, such as sauces and ketchup. Interestingly, the beneficial properties of GiaGiù were preserved after thermal processing.     

On a Retrial Single-Server Queueing System with Finite Buffer and Multivariate Poisson Flow

We consider a single-server queueing system with a finite buffer, K input Poisson flows of intensities _i , and distribution functions B _i (x) of service times for calls of the ith type, . If the buffer is overflowed, an arriving call is sent to the orbit and becomes a repeat call. In a random time, which has exponential distribution, the call makes an attempt to reenter the buffer or server, if the latter is free. The maximum number of calls in the orbit is limited; if the orbit is overflowed, an arriving call is lost. We find the relation between steady-state distributions of this system and a system with one Poisson flow of intensity where type i of a call is chosen with probability _i / at the beginning of its service. A numerical example is given.     

Analysis of the multi-server Markov queuing system with unlimited buffer and negative customers

Consideration was given to the multi-server queuing system with unlimited buffer, Markov input flow, and Markov (general) process of servicing all customers on servers with the number of process states and intensities of the inter-phase passage depending on the number of customers in the system. Additionally, a Markov flow of negative customers arrives to the system, the arriving negative customer killing the last queued positive customer. A recurrent algorithm to calculate the stationary probabilities of system states was obtained, and a method of calculation of the stationary distribution of the waiting time before starting servicing of a positive customer was proposed.     

The robustness of series-connected high power IGBT modules

The behaviour in terms of robustness of series-connected high power IGBT modules is presented, arranged in a topology which ensures voltage balance on IGBT’s and diodes by means of a simple auxiliary circuit applied directly on the high power devices, which are used in hard switching mode. Analyses in terms of IGBT and diode SOA (safe operating area), collector to emitter voltage gradient and short circuit condition are reported as well as an extended experimental characterisation. Both analyses confirm superior switching rating and system reliability, by using two series-connected IGBT in substitution of a single module, same current and double voltage rated. Moreover, thanks the auxiliary circuit presence, the robustness of total system is maintained also in extreme operating conditions.     

Hybridization of optimal control problems

Optimization problems for hybrid systems have attracted a lot of attention in recent years. This interest stimulated numerous scientific works and the development of tools to study optimal trajectories, such as necessary conditions. The idea of the present contribution is to use such results for hybrid systems to construct a hybridization of an optimal control problem. The approximation via a hybrid system was already considered in the literature, but using different methods to obtain a reduction to minimal path problems on a graph. Our procedure gives an efficient approximation, i.e. more efficient than standard discretization.     

Response of Male Domestic Rabbits (Oryctolagus cuniculus) to Inguinal Gland Secretion from Intact and Ovariectomized Females

European rabbits (Oryctolagus cuniculus) of both sexes possess a variety of skin glands important in chemical communication. These include sizable inguinal glands, the strong-smelling secretion from which accumulates in conspicuous pouches of skin on either side of the genital opening. To test the hypothesis that this secretion advertises sexual receptivity in females, inguinal gland secretions from nine intact and six ovariectomized females were presented on dummy rabbits or in a simultaneous choice paradigm, and the responses of nine stud males to these secretions were recorded. Although the males clearly perceived the stimuli, no differences in responses to secretions from the intact and ovariectomized does were observed, and no differences were found in the size, weight, or secretory activity of the does' glands. It is concluded that inguinal gland secretion plays little role in communicating sexual receptivity in female rabbits and that ovarian steroids play little part in regulating inguinal gland activity.