Emptying Process Research Articles

Efficacy of the entomopathogenic nematode Steinernema riobrave against the stored-product insect pests Tribolium castaneum and Plodia interpunctella

Persistence of stored-product insects in hidden refugia and their subsequent movement into stored commodities resulting in product infestation contributes to their pest status and represents a potential target for biological control agents. Entomopathogenic nematodes have not been previously tested against stored-product insects in environments such as empty grain bins or food processing and warehouse facilities, but their eVectiveness at Wnding and infecting hosts in other cryptic habitats has been demonstrated. In laboratory bioassays, Steinernema riobrave reduced survival of red Xour beetle, Tribolium castaneum, larvae, pupae and adults from 77.9 § 3.2% in the controls to 27.4 § 2.5% in treatments. Temperature (25 and 30 °C) and relative humidity (43, 56–57, 75, and 100%) did not signiWcantly inXuence S. riobrave eYcacy in this experiment. Field trials simulating empty grain bin treatments were conducted using red Xour beetle and the Indian meal moth, Plodia interpunctella. Total survival of mixed stages (larvae, pupae and adults) of T. castaneum was 42% of that in the control and total survival of mixed stages of P. interpunctella was 27% of the control. Larval stages were the most susceptible to S. riobrave for both insect species with P. interpunctella larvae having 99% mortality and T. castaneum larvae having 80% mortality. S. riobrave shows promise as a biological control agent for stored-product insects, particularly Indian meal moth, but further studies looking at combinations of treatments may further enhance eYcacy. Published by Elsevier Inc.

Linearization of hybrid processes

HyPA is a formalism that is suitable for the algebraic analysis of hybrid systems, i.e., systems with continuous (physical) as well as discrete (computational) components. Linearization is a useful first step in this analysis, because it reduces the complexity of model descriptions by transforming them into so-called linear form. We present an algorithm for the linearization of hybrid processes modeled in a subset of hybrid process algebra (HyPA) and prove its correctness. This algorithm is able to linearize most HyPA constructs, except recursive parallelism, the empty process, and disrupts that are not a flow prefix. We also extend HyPA with an abstraction operator, which is used in the linearization algorithm.

Chemical mediators of gallbladder dysmotility.

In order to accomplish its contribution to the digestive process, the gallbladder must contract appropriately during its emptying phases and it must be able to relax adequately for filling to occur. A variety of neuro-hormonal inputs to gallbladder smooth muscle coordinate the gallbladder emptying process with other events occurring in the bowel. Gallbladder dysmotility can disrupt the normal flow of bile to the small bowel, resulting in digestive dysfunction. In addition to this, alterations in gallbladder motility may play a role in pathological conditions, such as cholesterol gallstone formation and cholecystitis. It is still not entirely clear whether impaired gallbladder emptying is a cause or consequence of cholesterol gallstones, but recent experimental evidences demonstrate that cholesterol can directly affect the plasma membrane of gallbladder smooth muscle cells to cause impaired contraction. In addition, gallbladder emptying is impaired in acute gallbladder inflammation, probably as the result of the deleterious neural and muscular actions of inflammatory mediators such as reactive oxygen species, prostaglandins and histamine. It should also be noted that opiate treatments in critically ill patients can reduce gallbladder motility by inhibiting neurotransmitter release, and may contribute to the onset of acalculous cholecystitis, which is associated with significant morbidity in these patients.

The effect of bacterial lipopolysaccharide on the gastric emptying of rats: a pretreatment evaluation using dexamethasone and methylene blue

The nitric oxide might be a putative mediator of the decrease in gastric emptying induced by bacterial lipopolysaccharide in rats. For that, we evaluated the effect of the pretreatment intravenous with dexamethasone and methylene blue in the retardation process of gastric emptying induced by intravenous application of lipopolysaccharide in rats. Dexamethasone has been shown to inhibit the induction of NOS II (induced NO-synthase) while the methylene blue, that blocks the soluble guanylyl cyclase, inhibits nitric oxide synthases and, in addition, inactivates nitric oxide directly. Male Wistar rats, specific patogenic free, were used after a 24 hour fast and 1 hour-water withdrawn. The pretreatment was performed using dexamethasone solutions (3 and 6 mg/kg), methylene blue (2 mg/kg) or sterile vehicle. The treatment consisted in the application of lipopolysaccharide (50 mug/kg) or vehicle. The time period between the pretreatment and treatment was 10 minutes, excluding the study with dexamethasone 6 mg/kg that was 1 hour. The gastric emptying was evaluated 1 hour after the lipopolysaccharide application, except for two studies with dexamethasone 3 mg/kg in which the time periods were 2 and 8 hours. A saline solution containing phenol red was used as the test meal. The gastric emptying was determined by measuring gastric retention 10 minutes after the orogastric infusion of the test meal. The pretreatment with dexamethasone or methylene blue and treatment with vehicle did not have effect in the gastric emptying comparing to the control group. We found that pretreatment with dexamethasone in the studies for 1 hour and 2 hours did not interfere in the retardation of the gastric emptying produced by endotoxin. Nevertheless, in the eighth period study with this drug there was a significant reduction of gastric retention in the endotoxin-treated animals in relation to the unpretreated ones. Meanwhile, the pretreatment with the methylene blue completely blocked the action of endotoxin on the gastric emptying in rats. These results suggest a possible involvement of nitric oxide on the effect of lipopolysaccharide in rat gastric emptying.

Introducing Russell Graphically

Reviews 75 INTRODUCING RUSSELL GRAPHICALLY Stefan Andersson Theology and Religious Studies / U. of Lund s–223 62, Lund, Sweden butterflyandeson@hotmail.com Dave Robinson and Judy Groves. Introducing Bertrand Russell. Cambridge, uk: Icon Books Ltd., 2002. Pp. 176. us$11.95; cdn$16.99; £9.99. ntil now there have appeared at least 20 short books in different languages Uwith the aim of introducing the life and work—or both—of Bertrand Russell . With the publication of Introducing Bertrand Russell written by Dave Robinson , illustrated by Judy Groves and edited by Richard Appignanesi we have the first attempt to introduce the life and thought of Russell with the help of 76 Reviews cartoon-like illustrations and easy-to-follow diagrams. This particular genre of presenting a topic or a thinker started some 30 years ago, but it is not until now that Russell has been blessed with an attempt to present the most important aspects of his life and thinking in this particular way. After first telling us a little bit about Russell’s upbringing and his fear of madness, Robinson in Introducing Bertrand Russell uses Russell’s passionate search for certainty in mathematics as the starting-point for his description of Russell’s philosophical odyssey. The 170 pages are divided into 117 short sections in which the author tries to convey the most interesting aspects of Russell’s life and thinking. Starting with the fourth “The Geometry Lesson” and ending 26 sections later with “What is Logic?”, where Russell reluctantly admits that “Logic, in other words, is an empty process of linguistic analysis” (p. 43), we get a quick but fair description of the development of Russell’s thinking about mathematics and logic. The rest of the book is much more impressionistic and jumps from one topic to another with Wittgenstein showing up in different parts of the book without being allowed to steal the show. Robinson’s intentions have obviously been to give a brief introduction to and assessment of Russell’s thinking and political activities, but the book starts with a well-intended exaggeration: “Everyone has heard of Bertrand Russell. He was a great thinker, an agitator imprisoned for his beliefs, and a man who changed Western philosophy for ever” (p. 3). Unfortunately, far from everyone has heard about Bertrand Russell, but what follows is true. What surprises me is that a person who holds Russell in such high esteem should not be able to get some fundamental facts right. The work on publishing The Collected Papers of Bertrand Russell is being pursued at McMaster University in Hamilton and not at some non-existing institution called MacMaster University in Toronto. Russell’s famous essay “A Free Man’s Worship” was not written and published in 1923 for the first time, but twenty years earlier. Robinson describes it as a “kind of gospel to agnosticism” (p. 143), which is not totally misleading, but by misdating it by twenty years, he creates a very confusing picture of the development of Russell’s personal religious beliefs as well as his views on religion. The section “Russell on Religion” (pp. 142–3) starts with the sentence: “Russell lost his Christian faith at an early age but often admitted to mysterious spiritual longings.” This is vague, but it is acceptable. Then we get to know a little about “a personal epiphany” that Russell had on 10 February 1901. Russell used different expressions to refer to this very important experience of “mystic illumination” or even “first conversion”. The ballooncontains—asoften—adirectquotationfromRussell;inthiscase,thefirst volume of his Autobiography, where he talks about the insights that he gained Reviews 77 from this experience: “that the loneliness of the human soul is unendurable; nothing can penetrate it except the highest intensity of the sort of love that religious teachers have preached.” This description of Russell’s most important “religious”, “mystical” or “spiritual” experience was actually written in 1931. Robinson seems happily unaware of all these things. The confusion gets worse when we turn to the following section, “No Proof or Disproof of God”, where the first sentence states: “Russell had not lost his faith in Christianity but had long stopped believing in God...

Embedding Untimed into Timed Process Algebra; the Case for Explicit Termination

In ACP-style process algebra, the interpretation of a constant atomic action combines action execution with termination. In a setting with timing, different forms of termination can be distinguished: some-time termination, termination before the next clock tick, urgent termination, being terminated. In a setting with the silent action τ, we also have silent termination.This leads to problems with the interpretation of atomic actions in timed theories that involve some form of the empty process or some form of the silent action.Reflection on these problems lead to a re-design of basic process algebra, where action execution and termination are separated. Instead of actions as constants, we have action prefix operators. Sequential composition remains a basic operator, and thus we have two basic constants for termination, δ for unsuccessful termination (deadlock) and ∊ for successful termination (skip). We can recover standard process algebras as subtheories of the new theory. The new approach has definite advantages over the standard approach.

Deformation Zones in Granular Materials in Hoppers During Filling and Emptying Processes

The present paper is concerned with the simplified analysis of deformation and stress states in converging hoppers during filling and discharge of a granular material. The equilibrium conditions and stress-strain relations are satisfied for cylindrical slice elements assuming dependence of displacement and stress on radial coordinate. The elastic or elasto-plastic material model is used with the Coulomb yield condition and non-associated flow rule. The paper presents a detailed analysis of pressure evolution of a granular material on a hopper wall during the emptying process when the initial active state of pressure is transformed into the passive state. The growth of wall pressure associated with this process is demonstrated. The analytical treatment presented in this paper can be compared with the respective finite element solution.

A Multi‐mechanistic Drug Release Approach in a Bead Dosage Form and In Vitro/In Vivo Correlations

An in vitro/in vivo relationship of a combined multi‐mechanistic dosage form has now been established in the literature. In our previous study, we successfully prepared a combination of immediate release, enteric coated, and controlled‐release (CR) beads and mathematically modeled in vitro and in vivo drug release characteristics of the combination based on the release profiles of individual beads. The objective of the present study is to develop in vitro/in vivo correlations (IVIVC) for three individual beads and the combination using theophylline as a model drug and the beagle dog as an animal model. In the study, an IVIVC correlation is estimated by two‐stage procedures: deconvolution followed by comparison of the fraction of drug absorbed to the fraction of drug dissolved. The Wagner–Nelson mass balance method was used to deconvolute plasma drug concentration—time curves. In vitro, a two‐stage medium (0.1 N HCl and pH 6.5 phosphate buffer) was used for the dissolution test; a 2h first stage (acidic) was selected based on the average gastric emptying time in a fasted dog. In vivo, tlag was used for the gastric emptying process for enteric coated beads and the combination, which contains enteric coated beads. A time‐scaling technique was used to consider the rate difference between in vitro dissolution and in vivo absorption in the process of IVIVC. As shown in the results, a point‐to‐point correlation was established for each formulation. The linear regression analysis of the correlation was r2 > 0.99 for all three individual beads and 0.97 for the combined bead dosage form. The results suggest level A IVIVCs indicating an appropriateness for the in vitro and in vivo models used in this study.

Rate of convergence to equilibrium of marked Hawkes processes

In this article we obtain rates of convergence to equilibrium of marked Hawkes processes in two situations. Firstly, the stationary process is the empty process, in which case we speak of the rate of extinction. Secondly, the stationary process is the unique stationary and nontrivial marked Hawkes process, in which case we speak of the rate of installation. The first situation models small epidemics, whereas the results in the second case are useful in deriving stopping rules for simulation algorithms of Hawkes processes with random marks.

Rate of convergence to equilibrium of marked Hawkes processes

In this article we obtain rates of convergence to equilibrium of marked Hawkes processes in two situations. Firstly, the stationary process is the empty process, in which case we speak of the rate of extinction. Secondly, the stationary process is the unique stationary and nontrivial marked Hawkes process, in which case we speak of the rate of installation. The first situation models small epidemics, whereas the results in the second case are useful in deriving stopping rules for simulation algorithms of Hawkes processes with random marks.

Floating dosage systems in drug delivery.

The identification of new diseases and the resistance shown toward existing drugs calls for the introduction of new therapeutic molecules. In response, a large number of chemical entities have been introduced, of which some have absorption over the entire gastrointestinal tract (GIT), some have absorption windows (i.e., absorption sites, especially the upper part of the small intestine), and some have poor solubility in intestinal media altogether. The drugs belonging to the second and third categories, and the drugs required for local action in the stomach, require a specialized delivery system. All the above requirements can be met and effective delivery of the drugs to the absorption window, for local action and for treatment of gastric disorders such as gastro-esophageal reflux, can be achieved by floating dosage systems (FDS). To date, a number of FDS involving various technologies, carrying their own advantages and limitations, were developed, such as single- and multiple-unit hydrodynamically balanced systems (HBS), single- and multiple-unit gas-generating systems, hollow microspheres, and raft-forming systems. Various factors such as gastrointestinal physiology, dosage form characteristics, and patient-related factors control the behavior of FDS. This review discusses the anatomy and physiology of the stomach, the gastric emptying process, factors affecting the gastric retention of dosage forms, and various techniques adopted in the development of FDS.

Modeling drug absorption from enteric-coated granules.

A system-approach-based method is proposed for modeling drug absorption from enteric-coated granules. This method was exemplified using enteric-coated granules of aspirin given to healthy subjects. Based on the results obtained, it can be concluded that absorption of salicylate from the granules can be sufficiently described using a first-order linear model with an absorption rate constant of salicylate similar to that reported for an aqueous solution of aspirin administered orally to healthy subjects. The method proposed in this study may contribute to the working library of modeling techniques in pharmacokinetics since it allows direct modeling of the drug absorption process and estimates the absorption rate constant of a drug when its behavior in the body is significantly influenced by a gastric emptying process. i.e., when the absorption rate constant of the drug cannot be estimated on the basis of its cumulative absorption-time profile.

Adsorption in an ordered and non-interconnected mesoporous material: Single crystal porous silicon

Porous silicon is a network of parallel straight mesopores without lateral interconnection. The adsorption isotherm of nitrogen onto porous silicon exhibits a hysteresis loop of type H2 in the IUPAC classification, similar to those observed for highly interconnected mesoporous media. This shows that it is not possible to conclude from the observation of such a type of hysteresis whether a porous material is a network of interconnected or independent pores. Analysis of the adsorption and desorption branches according to the modified Kelvin equation does not account for the pore size distribution extracted from transmission electron micrographs. This suggests that the pore size dependence of the adsorbed layer thickness, prior to capillary condensation, needs to be considered. The steepness of the desorption branch cannot be explained in the framework of either the macroscopic Cohan model or the existing microscopic single pore models. It is believed that collective effects occur during the pore emptying process. Our experimental results bring strong arguments against the widely used application of the Barrett–Joyner–Halenda method to extract the pore size distribution from the desorption branch.

MICROSPHERES AS FLOATING DRUG-DELIVERY SYSTEMS TO INCREASE GASTRIC RETENTION OF DRUGS

Gastric emptying is a complex process, which is highly variable and makes in vivo performance of the drug-delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug-delivery systems for more than 12 h. The floating or hydrodynamically controlled drug-delivery systems are useful in such applications. The present review addresses briefly the physiology of the gastric emptying process with respect to floating drug-delivery systems. In recent years, the multiparticulate drug-delivery systems are used in the oral delivery of drugs. One of the approaches toward this goal is to develop the floating microspheres so as to increase the gastric retention time. Such systems have more advantages over the single-unit dosage forms. The development of floating microspheres involves different solvent evaporation techniques to create the hollow inner core. The present review addresses the preparation and characterization of the floating microspheres for the peroral route of administration of the drug.

Microprocessor-controlled movement of solid gastric content using sequential neural electrical stimulation

Background & Aims: Gastric electrical stimulation has been attempted for years without much success. The aim of this study was to determine if movement of solid gastric content could be achieved using microprocessor-controlled sequential electrical stimulation. Methods: The study was performed on 9 anesthetized dogs. The dogs underwent laparotomy, pyloroplasty, and implantation of 4–6 sets of bipolar stainless-steel wire electrodes. Each set consisted of 2–6 electrodes (10 × 0.25 mm, 3 cm apart) implanted circumferentially. The stomach was filled with solid food mixed with plastic pellets, and the process of gastric emptying was monitored. Artificial contractions were produced using microprocessor-controlled phase-locked bipolar trains of 50-Hz rectangular voltage with flexible amplitudes. Results: Using the above stimulating parameters, we were able to produce circumferential gastric contractions that were artificially propagated distally by embedding and phase-locking the stimulating voltage. The number of expelled pellets after the stimulation sessions was significantly higher than the number of pellets emptied during the nonstimulation sessions ( P < 0.01). Conclusions: Microprocessor-controlled electrical stimulation produced artificial peristalsis and markedly accelerated the movement of solid gastric content. GASTROENTEROLOGY 2000;118:258-263

Drying study of siloxane-PPG nanocomposites

This is a study of the structural transformations occurring in hybrid siloxane-polypropyleneglycol (PPG) nanocomposites, with different PPG molecular weight, along the drying process. The starting materials are wet gels obtained by the sol-gel procedure using as precursor the 3-(trietoxysilyl)propylisocyanate (IsoTrEOS) and polypropylenglycol bis(2-amino-propyl-ether) (NH2-PPG-NH2). The shrinkage and mass loss measurements were performed using a temperature-controlled chamber at 50°C. The nanostructural evolution of samples during drying was studied in situ by small angle x-ray scattering (SAXS). The experimental results demonstrate that the drying process is highly dependent on the molecular weight of polymer. After the initial drying stage, the progressive emptying of pores leads to the formation of a irregular drying front in gels prepared from PPG of high molecular weight, like 4000 g/mol. As a consequence, an increase of the SAXS intensity due to the increase of electronic density contrast between siloxane clusters and polymeric matrix is observed. For hybrids containing PPG of low molecular weight, the pore emptying process is fast, leading to a regular drying front, without isolated nanopockets of solvents. SAXS intensity curves exhibit a maximum, which was associated to the existence of spatial correlation of the silica clusters embedded in the polymeric matrix. The spatial correlation is preserved during drying. These results also reveal that the structural transformation during drying is governed by capillary forces and depends on the entanglement of polymer chains.

On the Two-Variable Fragment of the Equational Theory of the Max-Sum Algebra of the Natural Numbers

&lt;p&gt;This paper shows that the collection of identities in two variables&lt;br /&gt;which hold in the algebra N of the natural numbers with constant&lt;br /&gt;zero, and binary operations of sum and maximum does not have a&lt;br /&gt;finite equational axiomatization. This gives an alternative proof of the&lt;br /&gt;non-existence of a finite basis for N - a result previously obtained by&lt;br /&gt;the authors. As an application of the main theorem, it is shown that&lt;br /&gt;the language of Basic Process Algebra (over a singleton set of actions),&lt;br /&gt;with or without the empty process, has no finite omega-complete equational&lt;br /&gt;axiomatization modulo trace equivalence.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;AMS Subject Classification (1991): 08A70, 08B05, 03C05, 68Q70.&lt;br /&gt;ACM Computing Classification System (1998): F.4.1.&lt;br /&gt;Keywords and Phrases: Equational logic, varieties, complete axiomatizations,&lt;br /&gt;process algebra, trace equivalence.&lt;/p&gt;

Microprocessor controlled movement of liquid gastric content using sequential neural electrical stimulation

Background—Gastric electrical stimulation has been attempted for several years with little success.Aims—To determine whether movement of liquid gastric content could be achieved using microprocessor controlled sequential electrical stimulation.Methods—Eight anaesthetised dogs...

ANATOMY AND PHYSIOLOGY OF THE GASTROESOPHAGEAL JUNCTION

The gastroesophageal junction is a complex valve composed of a smooth muscle element (LES) and a diaphragmatic element. These normally supplement each other to maintain competence in a static condition and during dynamic stresses associated with increased intra-abdominal pressure or swallowing. These sphincteric components also interact with each other pathophysiologically. During swallowing, large hernias impair the process of esophageal emptying, thereby prolonging acid clearance. The susceptibility to stress reflux inherent during periods of diminished LES pressure is also dramatically increased by disabling the diaphragmatic sphincter. These functional impairments of the gastroesophageal junction associated with hiatus hernia lead to increased esophageal acid exposure and offer one explanation for the chronicity of reflux disease.

Finite Element Analysis of Bulk Solids Flow: Part 1, Development of a Model Based on a Secant Constitutive Relationship

Silos and bins are used in agriculture and many other industries for the storage and handling of bulk solids. This paper deals with a secant constitutive relationship for bulk solids for a transient finite element analysis of stresses, displacements and velocities in the solids during discharge of a silo filled with soybean. The constitutive relationship will be presented for the modelling of flow of cohesionless granular materials in a silo or bin. Stresses and strains are related by a secant relationship that has an elastic and a plastic component. The Drucker-Prager yield criterion is used to indicate the switch from elastic to plastic behaviour.Wall pressures in a model bin were measured and used to verify numerical results. Finite element analyses with the secant constitutive model proved to be very stable during the entire emptying process. Wall pressures predicted with the numerical model for the entire emptying process compared well with those measured in experiments.