Mathematical constraints on a theory of human memory - Response

Colonius suggests that, in using standard set theory as the language in which to express our computational-level theory of human memory, we would need to violate the axiom of foundation in order to express meaningful memory bindings in which a context is identical to an item in the list. We circumvent Colonius's objection by allowing that a list item may serve as a label for a context without being identical to that context. This debate serves to highlight the value of specifying memory operations in set theoretic notation, as it would have been difficult if not impossible to formulate such an objection at the algorithmic level.

Analysis of dynamic process models for structural insight and model reduction .1. Structural identification measures

An important consideration in the development of mathematical models for dynamic simulation, is the identification of the appropriate mathematical structure. By building models with an efficient structure which is devoid of redundancy, it is possible to create simple, accurate and functional models. This leads not only to efficient simulation, but to a deeper understanding of the important dynamic relationships within the process. In this paper, a method is proposed for systematic model development for startup and shutdown simulation which is based on the identification of the essential process structure. The key tool in this analysis is the method of nonlinear perturbations for structural identification and model reduction. Starting from a detailed mathematical process description both singular and regular structural perturbations are detected. These techniques are then used to give insight into the system structure and where appropriate to eliminate superfluous model equations or reduce them to other forms. This process retains the ability to interpret the reduced order model in terms of the physico-chemical phenomena. Using this model reduction technique it is possible to attribute observable dynamics to particular unit operations within the process. This relationship then highlights the unit operations which must be accurately modelled in order to develop a robust plant model. The technique generates detailed insight into the dynamic structure of the models providing a basis for system re-design and dynamic analysis. The technique is illustrated on the modelling for an evaporator startup. Copyright (C) 1996 Elsevier Science Ltd

Inflammatory Cytokines during Liver Transplantation: Prospective Randomized Trial Comparing Conventional and Piggyback Techniques

Background/Aims: Cytokines have a significant role in the response to injury following liver transplantation, but the origin and course of such molecules are not completely known. The aim of this study was to evaluate the production and liver metabolism of the inflammatory cytokines interleukin (IL)-1 beta, IL-6, IL-8, interferon (IFN)-Y and tumor necrosis factor (TNF)-alpha in orthotopic liver transplantation (OLT), comparing the conventional and the piggyback methods. Methodology: We performed a study of 30 patients who underwent elective OLT and were randomized for the conventional or piggyback techniques at the beginning of the operation. The amount of cytokines and their hepatic metabolism were calculated based on plasma concentrations and vascular blood flow at 2, 5, 10, 15, 30, 60, 90, and 120 minutes after revascularization. Results: The amount of IL-1 beta in portal blood was higher in patients who underwent surgery using the conventional technique (estimate interest = 63,783.9 +/- 16,586.1 pg/min, versus 11,979.6 +/- 16,585.7 pg/min in the piggyback group, p=0.035). There were no significant differences between the two operative`s methods for IL-6, IL-8, IFN-Y and TNF-alpha production. The hepatic metabolism of cytokines was not different between groups. Although all the curves showed higher amounts of cytokines with the conventional technique, these were not statistically significant. Conclusion: The study shows the similarity between the two techniques concerning the stimuli for the production of inflammatory molecules.

Analysis of Different Staining Techniques for C4d Detection in Renal Allograft Biopsies

Capillary C4d deposition has been recognized as a marker of antibody-mediated rejection (AMR). Although the detection of capillary C4d by means of immunofluorescence (IF) in cryostat sections is well established, frozen tissue is not always available, thus limiting the diagnosis of AMR. The aim of the present study was to analyze different techniques for C4d staining and the prevalence of C4d in renal allograft biopsies. Detection of C4d was carried out using IF or immunohistochemistry (IHC) on frozen and paraffin sections of renal allograft biopsies available from the same patients. Biopsies obtained from 20 patients were classified into 3 groups: no rejection, acute rejection, and chronic allograft nephropathy (CAN). The capillary C4d deposition prevalence in frozen-IF, considered the gold standard technique for C4d detection, was 45% (9/20 cases). Compared with frozen-IF, the frozen-IHC technique presented an 85% concordance rate (17/20 cases; r =.70; P <.001; sensitivity = 77.8%; specificity = 90.9%). The paraffin-IF technique showed similar results, with an 80% concordance rate (16/20 cases; r =.64; P <.005; sensitivity = 55.6%; specificity = 100%), whereas C4d detection occurred in only 65% of paraffin-IHC cases (13/20; r =.30; not significant; sensitivity = 66.7%; specificity = 63.6%). No capillary C4d deposition was detected in cases without evidence of rejection. However, 4/7 cases (57%) of acute rejection were C4d positive. In the CAN group, 5111 cases (45%) were C4d positive. In conclusion, these results demonstrated that frozen-IHC and paraffin-IF can be considered alternative techniques to frozen-IF for C4d detection. The paraffin-IHC technique displayed the lowest concordance rate for C4d detection.

A mathematical model for Escherichia coli debris size reduction during high pressure homogenisation based on grinding theory

Experimental data for E. coli debris size reduction during high-pressure homogenisation at 55 MPa are presented. A mathematical model based on grinding theory is developed to describe the data. The model is based on first-order breakage and compensation conditions. It does not require any assumption of a specified distribution for debris size and can be used given information on the initial size distribution of whole cells and the disruption efficiency during homogenisation. The number of homogeniser passes is incorporated into the model and used to describe the size reduction of non-induced stationary and induced E. coil cells during homogenisation. Regressing the results to the model equations gave an excellent fit to experimental data ( > 98.7% of variance explained for both fermentations), confirming the model's potential for predicting size reduction during high-pressure homogenisation. This study provides a means to optimise both homogenisation and disc-stack centrifugation conditions for recombinant product recovery. (C) 1997 Elsevier Science Ltd.

Social adaptation of children with mild intellectual disability: Effects of partial integration within primary school classes

is study examined the social adaptation of children with mild intellectual disability who were either (a) partially integrated into regular primary school classes, or (b) full-time in separate classes, All of the children were integrated in sport and play activities with the whole school. Consistent with previous research, children with intellectual disability were less socially accepted than were a matched group of control children. Children in partially integrated classes received more play nominations than those in separate classes, brit there was no greater acceptance as a best friend. On teachers' reports, disabled children had higher levels of inappropriate social behaviours, but there was no significant difference in appropriate behaviours. Self-assessments by integrated children were more negative than those by children in separate classes, and their peer-relationship satisfaction was lower. Ratings by disabled children of their satisfaction with peer relationships were associated with ratings of appropriate social skills by themselves and their teachers, and with self-ratings of negative behaviour. The study confirmed that partial integration can have negative consequences for children with an intellectual disability.

Risk Estimates of Dengue in Travelers to Dengue Endemic Areas Using Mathematical Models

Dengue has emerged as a frequent problem in international travelers. The risk depends on destination, duration, and season of travel. However, data to quantify the true risk for travelers to acquire dengue are lacking. We used mathematical models to estimate the risk of nonimmune persons to acquire dengue when traveling to Singapore. From the force of infection, we calculated the risk of dengue dependent on duration of stay and season of arrival. Our data highlight that the risk for nonimmune travelers to acquire dengue in Singapore is substantial but varies greatly with seasons and epidemic cycles. For instance, for a traveler who stays in Singapore for 1 week during the high dengue season in 2005, the risk of acquiring dengue was 0.17%, but it was only 0.00423% during the low season in a nonepidemic year such as 2002. Risk estimates based on mathematical modeling will help the travel medicine provider give better evidence-based advice for travelers to dengue endemic countries.

Intracardiac Cavopulmonary Connection in Patients with Univentricular Heart Using Intra-atrial Lateral Tunnel and Intra-atrial Conduit Techniques

Background: In this study, we analyzed the time course of hemodynamic efficiency and follow-up in Fontan candidates who underwent the bidirectional Glenn procedure for staged intracardiac cavopulmonary connection (ICPC). Methods: Between 1991 and 2008, 52 patients with univentricular heart (mean age, 3.3 years; range, 2-8 years; 27 female patients [51.9%]) underwent ICPC. The cardiac malformations were as follows: tricuspid atresia, 25 cases (48.0%); common ventricle, 16 cases (30.7%); and pulmonary atresia with intact ventricular septum, 11 cases (21.1%). The intracardiac cavopulmonary procedure was indicated for all 52 cases. In 42 patients (80.7%), an intra-atrial lateral tunnel was constructed with a bovine pericardium patch. In the last 10 consecutive cases (19.3%), we performed a modified surgical technique in which we implanted an intra-atrial corrugated bovine pericardium tube sutured around the superior and inferior vena cava ostium. In all cases, a 4-mm fenestration was made to reduce the intratunnel pressure. All 52 patients had previously undergone a Glenn operation. Results: There were 2 hospital deaths (3.8%) and no recorded late deaths. During the follow-up, all patients were medicated with antiplatelet drugs. To evaluate the hemodynamic performance, we used Doppler echocardiography, computed tomography, and magnetic nuclear resonance studies. There were no prosthesis thromboses during this follow-up period. To evaluate cardiac arrhythmias, we conducted a Holter study. The last 10 patients with an intra-atrial conduit (IAC) presented with sinus rhythm and no arrhythmias during the last 4 years. The 50 surviving patients (96.1%) have been followed up for 6 to 204 months; all these patients are free of reoperation. Conclusion: The Glenn operation, which is performed at an early age, prepares the pulmonary bed to receive the ICPC. The midterm results of the intracardiac Fontan procedure seem to be good. The modified surgical procedure (IAC) can be a good alternative technique to the Fontan procedure in suitable patients.

Participatory ergonomics: Understanding the contributions of reflection groups in a hospital food service

Aim: To identify how the methodology of Reflection Groups (RG) can contribute to approach social-psychological problems, so often observed as obstacles in PE efforts. The objective was also to verify the contributions from RG to the implementation of ergonomics recommendations, which were a starting point and organized group discussions. Method: A concrete case was used as an illustration, and studied in depth: RG with administration and production workers` representatives from the Department of Nutrition and Dietetics of a cardiologic hospital in Sao Paulo, Brazil. RG are temporary thinking groups, taking place outside the workplace and having delegative and consultive participation. They make use of Operative Groups, an adapted form of tripartite group, activity as an instrumental resource, group dynamic techniques and videotaping. In 2007, 31 meetings took place during paid working hours with 7 groups of different composition, ranging from 1.5 h to 3 h. Results: Additionally to the positive effects in communication and psychosocial environment, RG could also contribute to changes in interpersonal relationships, cooperation, personal and work behaviours. By dealing with aspects which could hinder the explicit task: fears, conflicts, and stereotyped beliefs and behaviours; resistance to change could be broken and group members could learn. RG allowed input about new risks; continuous information and feedback about ongoing ergonomics interventions so that immediate corrective action could be taken. The main form of participation was in administrative, organizational, and psychosocial problems which required a better clarification and identification of their real causes, commitment, and elaboration of strategies and negotiation of different stakeholders in their solution. Conclusion: RG takes advantage of homogeneous and heterogeneous groups, in face to face communication. The interactions in the groups are task-oriented (explicit task) but attaining groups` goals depends on a relational interaction (implicit task). Relevance to industry: Reflection groups can bring important contributions to ergonomics and industry because they favour the discussion, disclosure of problems and incorporation of solutions, enabling interventions in working organization, psychosocial environment and relationships in a collective and participatory approach, promoting health and social integration. (C) 2010 Elsevier B.V. All rights reserved.

Effects of semen storage and separation techniques on sperm DNA fragmentation

Objective: To determine the effect of semen storage and separation techniques on sperm DNA fragmentation. Design: Controlled clinical study. Setting: An assisted reproductive technology laboratory. Patient(s): Thirty normoozospermic semen samples obtained from patients undergoing infertility evaluation. Intervention(s): One aliquot from each sample was immediately prepared (control) for the sperm chromatin dispersion assay (SCD). Aliquots used to assess storage techniques were treated in the following ways: snap frozen by liquid nitrogen immersion, slow frozen with Tris-yolk buffer and glycerol, kept on ice for 24 hours or maintained at room temperature for 4 and 24 hours. Aliquots used to assess separation techniques were processed by the following methods: washed and centrifuged in media, swim-up from washed sperm pellet, density gradient separation, density gradient followed by swim-up. DNA integrity was then measured by SCD. Main Outcome Measure(s): DNA fragmentation as measured by SCD. Result(s): There was no significant difference in fragmentation among the snap frozen, slow frozen, and wet-ice groups. Compared to other storage methods short-term storage at room temperature did not impact DNA fragmentation yet 24 hours storage significantly increased fragmentation. Swim-up, density gradient and density gradient/swim-up had significantly reduced DNA fragmentation levels compared with washed semen. Postincubation, density gradient/swim-up showed the lowest fragmentation levels. Conclusion(s): The effect of sperm processing methods on DNA fragmentation should be considered when selecting storage or separation techniques for clinical use. (Fertil Steril (R) 2010;94:2626-30. (C) 2010 by American Society for Reproductive Medicine.)

Re-integration into work

This is the first complete textbook designed for physiotherapists and occupational therapists on the topic of pain. It was developed for use in conjunction with the International Association for the Study of Pain's pain curriculum for OTs and PTs. The book addresses the nature of pain, the neuroanatomical and neurophysiological substrates of pain, the psychological... More aspects of pain, the lifespan approach to pain, pain measurement, pain and placebo, modalities for treating pain, and special topics in pain. It provides an overview of the physiological, psychosocial, and environmental aspects of pain experience across the lifespan. Aimed primarily at OTs and PTs the assessment and interventions issues pertaining to the perspectives of each profession are discussed in detail. The book is also relevant to the other health professions involved in pain management or intending to work in this area.