An algorithmic method for the selection of multivariable process control structures

In process systems, the selection of suitable sets of manipulated and controlled variables and the design of their interconnection, known as the control structure selection problem, is an important structural optimisation problem. The operating performance of a plant depends on the control structure selected as well as the characteristics of the disturbances acting on the plant. The economic penalty associated with the variability of main process variables close to active constraints is used in this work in order to develop a quantitative measure for the ranking of alternative control structures. Based on this measure, a general methodology is presented for the generation of promising control structures where general centralised, linear time invariant, output feedback controllers are used to form the closed loop system. The special case of optimal static output feedback controllers is further investigated in this paper. Furthermore, the problem of selecting proper weights in forming quadratic integral performance indices in designing optimal multivariable controllers is addressed. The validity and usefulness of the method is demonstrated through a number of case studies.     

Control of leg-powered paraplegic cycling using stimulation of the lumbo-sacral anterior spinal nerve roots

We investigated leg-powered cycling in a recumbent tricycle for a paraplegic using functional electrical stimulation (FES) with the lumbo-sacral anterior root stimulator implant (LARSI). A female complete T9 paraplegic had a stimulator for the anterior L2 to S2 spinal roots (bilaterally) implanted in 1994. She was provided with equipment for daily FES cycling exercise at home. The cycling controller applies a pattern of stimulation in each of 16 crank angle phases. A 7-bit shaft encoder measures the crank angle with adequate precision. Each pattern was originally chosen to give the greatest propulsive force in that position when there was no motion. However, dynamically, some reduction in co-contraction is needed; also the patterns are applied with a preset advance time. Maximal power is obtained with an advance of 250 ms, which compensates for muscle response delay and accommodates changes in cadence (from about 25 to 85 rpm). With this system, she has cycled 1.2 km at a time on gently undulating road. We found that spinal root stimulation gives sufficient control over the muscles in the legs to produce a fluid cycling gait. We propose that root stimulation for leg cycling exercise may be a practicable and valuable function for paraplegics following spinal cord injury.     

Stomach implant for long-term erythropoietin expression in rats

Caveolae are small microdomains of the plasma membrane that are thought to play important roles in signal transduction processes. In this work, we have investigated the association of Rho proteins with caveolae-enriched membrane domains isolated from cultured endothelial cells. Fractionation of ECV304 cells by sucrose gradient density centrifugation in the absence of detergent resulted in the co-sedimentation of a significant proportion of RhoA and Cdc42 with known caveolae marker proteins, including caveolin, but not with other non-caveolae membrane proteins such as the angiotensin-converting enzyme. Immunoprecipitation experiments carried on crude endothelial cell lysates as well as with solubilized caveolae-enriched membrane domains showed the coimmunoprecipitation of caveolin with RhoA but not with Cdc42. Incubation of endothelial cell lysates with a glutathione-S-transferase (GST)-RhoA fusion protein resulted in the specific precipitation of caveolin, while addition of GST-caveolin-1 to the lysates promoted the precipitation of RhoA. Moreover, incubation of bacterially expressed RhoA with GST-caveolin-1 resulted in the precipitation of RhoA, indicating that RhoA directly interacts with caveolin-1. This interaction was found to be nucleotide-independent and was not affected by prior modification of RhoA with the C3 exoenzyme from C. botulinium or with the cytotoxic necrotinizing factor from E. coli. Taken together, these results suggest the association of RhoA with endothelial caveolae-enriched membrane domains, likely through physical interaction with caveolin-1. These findings may provide new insights into the functions played by Rho proteins and caveolae in signal transduction events.     

Anatomy of the cranial nerves

The anatomy of cranial nerves I and III through XII are presented. Each nerve is diagrammatically illustrated from its nuclear or its sensory origin and correlated with magnetic resonance and computed tomography images. The important identifying anatomical landmarks are demonstrated along the course of each nerve. Peripheral motor and sensory components are also discussed.     

Systemic hypothermia after spinal cord compression injury in the rat: does recorded temperature in accessible organs reflect the intramedullary temperature in the spinal cord?

This article addresses one basic issue regarding the use of systemic hypothermia in the acute management of spinal cord injury, namely, how to interpret temperature recordings in accessible organs such as the rectum or esophagus with reference to the spinal cord temperature. Thirty-six rats, divided into six groups, were randomized to laminectomy or to severe spinal cord compression trauma, and were further randomized to either a cooling/rewarming procedure or continuous normothermia (esophageal temperature 38 degrees C) for 90 min. The first procedure comprised normothermia during the surgical procedure, followed by lowering of the esophageal temperature from 38 degrees C to 30 degrees C (the hypothermic level), a 20-min steady-state period at 30 degrees C, rewarming to 38 degrees C, and finally a 20-min steady-state period at 38 degrees C. The esophageal, rectal, and epidural temperatures were recorded in all animals. The intramedullary temperature was also recorded invasively in four of the six groups. We conclude that the esophageal temperature is safe and easy to record and, in our setting, reflects the epidural temperature. The differences registrated may reflect a true deviation of the intramedullary temperature due to initial environmental exposure and secondary injury processes. Our results indicate that the esophageal temperature exceeds the intramedullary temperature during the initial recording and final steady state following rewarming, but not during the most crucial part of the experiment, the hypothermic period. The core temperature measured in the esophagus can therefore be used to evaluate the intramedullary temperature during alterations of the systemic temperature and during hypothermic periods.     

Children of affectively ill parents: a review of the past 10 years

OBJECTIVE: To review the literature investigating the effects of parental affective illness on children over the past decade. METHOD: A computerized search of articles published over the past 10 years was completed. Articles were reviewed and relevant studies are presented. RESULTS: Over the course of the past 10 years a number of longitudinal studies have confirmed that children of affectively ill parents are at a greater risk for psychiatric disorders than children from homes with non-ill parents. Life table estimates indicate that by the age of 20 a child with an affectively ill parent has a 40% chance of experiencing an episode of major depression. Children from homes with affectively ill parents are more likely to exhibit general difficulties in functioning, increased guilt, and interpersonal difficulties as well as problems with attachment. Marital difficulties, parenting problems, and chronicity and severity of parental affective illness have been associated with the increased rates of disorder observed in these children. CONCLUSION: The presence of depression in parents should alert clinicians to the fact that their children also may be depressed and therefore in need of services. J. Am. Acad. Child Adolesc.     

Identification and characterization of the PutP proline permease that contributes to in vivo survival of Staphylococcus aureus in animal models

Staphylococcus aureus is an important pathogen of humans and other animals, causing bacteremia, abscesses, endocarditis, and other infectious syndromes. A signature-tagged mutagenesis (STM) system was adapted for use in studying the genes required for in vivo survival of S. aureus. An STM library was ultimately created in S. aureus RN6390, with Tn917 being used to create the transposon mutations. Pools of S. aureus RN6390 mutants were screened in mouse abscess, bacteremia, and wound infection models for growth attenuation after in vivo passage. One of the mutants that was identified displayed marked attenuation following large-pool screening in all three animal models, which was confirmed in bacteremia and endocarditis models of infection with a smaller pool of mutants. Sequence analysis of the entire open reading frame showed a 99% identity to the high-affinity proline permease (putP) gene characterized in another strain of S. aureus. In wound and murine abscess infection models, the putP mutant was approximately 10-fold more attenuated than was wild-type strain RN6390. Another S. aureus strain transduced with the putP mutation also displayed an attenuated phenotype after passage in the wound model. A [3H]proline uptake assay showed that less proline was specifically transported into the putP mutant than into strain RN6390. The reduced viability of the bacteria possessing the mutation in the S. aureus high-affinity proline permease suggests that proline scavenging by the bacteria is important for in vivo growth and proliferation and that analogs of proline may serve as potential antistaphylococcal therapeutic agents.     

Chronobiology and chronotherapy of asthma

There is no doubt that many pathophysiologic conditions change over a 24-hour period and thus therapy needs to be directed at these changes. In particular, asthma has been one of the better-studied disease processes in regard to circadian changes in pathophysiology. As we continue to learn more about circadian changes, better approaches to treating the disease with the same medications will emerge. It should be remembered that many asthmatics do not perceive their degree of bronchoconstriction. This was brought forth in Turner-Warwick's epidemiologic study in that less than one half of the asthmatic individuals who had problems with their asthma every night describe their asthma as being severe. The majority stated they either had mild or moderate asthma. Therefore, it is important that we use objective criteria such as peak flow meters in determining an individual patient's day-to-night changes in lung function. Then, any therapeutic intervention can be objectively determined at home with both the patient and physician gaining knowledge about the ongoing asthmatic process.     

N-terminal heterogeneity of parenchymal and cerebrovascular Abeta deposits

The goals of this study were twofold: to determine whether species differences in Abeta N-terminal heterogeneity explain the absence of neuritic plaques in the aged dog and aged bear in contrast to the human; and to compare Abeta N-terminal isoforms in parenchymal vs cerebrovascular Abeta (CVA) deposits in each of the species, and in individuals with Alzheimer disease (AD) vs nondemented individuals. N-terminal heterogeneity can affect the aggregation, toxicity, and stability of Abeta. The human, polar bear, and dog brain share an identical Abeta amino acid sequence. Tissues were immunostained using affinity-purified polyclonal antibodies specific for the L-aspartate residue of Abeta at position one (AbetaN1[D]), D-aspartate at N1 (AbetaN1[rD]), and pyroglutamate at N3 (AbetaN3[pE]) and p3, a peptide beginning with leucine at N17 (AbetaN17[L]). The results demonstrate that each Abeta N-terminal isoform can be present in diffuse plaques and CVA deposits in AD brain, nondemented human, and the examined aged animal models. Though each Abeta N-terminal isoform was present in diffuse plaques, the average amyloid burden of each isoform was highest in AD vs polar bear and dog (beagle) brain. Moreover, the ratio of AbetaN3(pE) (an isoform that is resistant to degradation by most aminopeptidases) vs AbetaN17(L)-x (the potentially nonamyloidogenic p3 fragment) was greatest in the human brain when compared with aged dog or polar bear. Neuritic plaques in AD brain typically immunostained with antibodies against AbetaN1(D) and AbetaN3(pE), but not AbetaN17(L) or AbetaN1(rD). Neuritic deposits in nondemented individuals with atherosclerotic and vascular hypertensive changes could be identified with AbetaN1(D), AbetaN3(pE), and AbetaN1(rD). The presence of AbetaN1(rD) in neuritic plaques in nondemented individuals with atherosclerosis or hypertension, but not in AD, suggests a different evolution of the plaques in the two conditions. AbetaN1(rD) was usually absent in human CVA, except in AD cases with atherosclerotic and vascular hypertensive changes. Together, the results demonstrate that diffuse plaques, neuritic plaques, and CVA deposits are each associated with distinct profiles of Abeta N-terminal isoforms.