Feedforward control of the lateral position of a moving web using system identification

Many mathematical models have been developed to describe the lateral dynamics of a moving web, including Shelton's model. Experimental results in this study showed that the existing model does not fully describe the characteristic of the lateral dynamics for some typical operating conditions. An experimental model was derived by means of system identification using a well-known least-square method to improve the prediction capability of the lateral dynamics. A commercial guidance system usually has the proportional and integral control structure. Sometimes it may not eliminate the effect of periodic lateral disturbances efficiently which are transferred from upstream spans because the controller relying solely on feedback generates control action only when an output measurement signal differs from a reference value. However, if the disturbance is deterministic, a feedforward control structure may offer simple and effective disturbance rejection performance. In this paper, the lateral position of a web at the upstream span and the identified model of lateral dynamics for the span were used to estimate the effect of disturbance on the lateral dynamics of a moving web at the exit span of the guidance system. A feedforward controller was designed to reject the deterministic disturbance of lateral dynamics of a moving web. The disturbance rejection performance of the proposed controller was verified by computer simulation and experiments. These results showed that the proposed feedforward scheme with an improved mathematical model greatly improved control performance in overcoming the dynamic disturbance.     

Junior doctors and clinical audit

OBJECTIVES: To assess the extent of junior doctor involvement in clinical audit, the degree of support from audit staff, and the perceived value of the resulting audits. DESIGN: Postal survey of National Health Service (NHS) junior doctors. SUBJECTS AND SETTINGS: 704 junior doctors in central Leeds hospitals, June 1996. RESULTS: Questionnaires were returned by 232 respondents (33%), 211 (31%) were completed; 157 respondents (74%) had personally performed audit. Mean (+/- SD) duration since last audit project was 14.9 (14.1) (range 0-84) months. Of the respondents who had personally performed audit, 88 (56%) did not use the hospital audit department, 60 (38%) received no guidance and only 19 (12%) were involved in re-auditing the same project. Mean (+/- SD) time spent per audit project was 27.8 (37.7), (range 2-212) hours. Seventy-five junior doctors (48%) were aware of subsequent change in clinical practice, 41 (26%) perceived a negative personal benefit from audit, 33 (21%) perceived a negative departmental benefit, and 42 (27%) felt that audit was a waste of time. CONCLUSIONS: A large proportion of junior doctors are involved in audit projects that do not conform to established good practice and which have a low impact on clinical behaviour. Although junior doctors feel that there is inadequate assistance and poor supervision whilst performing audit, they still support the principle of audit. There is a need to improve the quality and supervision of audit projects performed by junior doctors.     

Beta1B subunit of voltage-dependent Ca2+ channels is predominant isoform expressed in human neuroblastoma cell line IMR32

BACKGROUND: In adults, Helicobacter pylori infection is always associated with gastritis or ulcer. However, very active gastritis and ulcers are rarely seen in children. The aim of the present work was to study the relationships between H. pylori and gastric mucosa in children. METHODS: Eighty infected children and adolescents including 48 (60%) neurologically impaired institutionalized patients, aged 2 months-22 years (mean 11.7 +/- 5.2 years) were studied retrospectively. All the patients underwent gastroscopy, and three antral and two fundic biopsy specimens were taken for histology and bacteriology. RESULTS: A normal gastric mucosa was found in 22 of 80 patients (27.5%), whereas the others had gastritis (n = 58, 72.5%). There were no statistical differences between patients with normal histology and those presenting with gastritis for age, sex, ethnic background, symptoms, and the degree of bacterial colonization. The macroscopic aspect of gastritis was less frequently found in children with a normal histology compared with those with histological gastritis (p < 0.001). CONCLUSIONS: These data show that H. pylori infection can be associated with a normal gastric histology in children.     

The GnRH system of seasonal breeders: anatomy and plasticity

Seasonal breeders, such as sheep and hamsters, by virtue of their annual cycles of reproduction, represent valuable models for the study of plasticity in the adult mammalian neuroendocrine brain. A major factor responsible for the occurrence of seasonal reproductive transitions is a striking change in the responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the inhibitory effects of gonadal steroids. However, the neural circuitry mediating these seasonal changes is still relatively unexplored. In this article, we review recent findings that have begun to define that circuitry and its plasticity in a well-studied seasonal breeder, the ewe. Tract tracing studies and immunocytochemical analyses using Fos and FRAs as markers of activation point to a subset of neuroendocrine GnRH neurons in the MBH as potential mediators of pulsatile GnRH secretion. Because the vast majority of GnRH neurons lack estrogen receptors, seasonal changes in responsiveness to estradiol are most probably conveyed by afferents. Two possible mediators of this influence are dopaminergic cells in the A14/A15 cell groups of the hypothalamus, and estrogen receptor-containing cells in the arcuate nucleus that project to the median eminence. The importance of GnRH afferents in the regulation of season breeding is underscored by observations of seasonal changes in the density of synaptic inputs onto GnRH neurons. Thyroid hormones may participate in this remodeling, because they are important in seasonal reproduction, influence the morphology of other brain systems, and thyroid hormone receptors are expressed within GnRH neurons. Finally, in the hamster, neonatal hypothyroidism affects the number of caudally placed GnRH neurons in the adult brain, suggesting that thyroid hormones may influence development of the GnRH system as well as its reproductive functions in the adult brain.     

Serum LH concentrations in hypogonadal men during transdermal testosterone replacement through scrotal skin: further evidence that ageing enhances testosterone negative feedback. The Testoderm Study Group

As a trial of the provision of community-service information to family carers, general practitioners and pharmacists from the Western region of Melbourne were supplied with tear-off pads listing suburb-specific community services, and were encouraged to discuss service needs with carers of people with disabilities and distribute the lists to carers accordingly. One hundred and nine general practitioners and 58 pharmacists participated in pretrial and post-trial interviews assessing their knowledge of community services and frequency of discussion with carers. Before the trial, general practitioners had significantly higher self-rated knowledge of community services and reportedly discussed these with carers more often than did pharmacists. After the five-month trial period, pharmacists showed a significant increase in self-rated knowledge and frequency of discussion. General practitioners' knowledge and discussion showed a nonsignificant increase. After the trial, the two did not differ in knowledge of services; however, general practitioners maintained a higher reported frequency of discussion about services with carers. General practitioners and pharmacists appear to be well placed to act as a service link for family carers. However, additional high-intensity strategies are needed to assist them in this role.     

Neuroprotection: the next breakthrough in glaucoma? Proceedings of the Third Annual Optic Nerve Rescue and Restoration Think Tank

OBJECTIVES: To document the efficacy of combined epidural steroid injection (ESI) and manipulation to the lumbar spine in patients suffering from chronic low back pain (LBP). SUMMARY OF BACKGROUND DATA: The use of ESI in conjunction with lumbar manipulation has seldom been reported in the literature but has offered promising results when studied. STUDY DESIGN: Retrospective repeated-measures analysis of patients with chronic LBP who received ESIs combined with spinal manipulation. METHODS: A retrospective analysis using a repeated-measures format was performed on 17 cases of patients who had received ESI and manipulation to the lumbar spine. All patients were medically stable for chronic mechanical LBP and had experienced a suboptimal response to conventional care. The principle investigator was blinded from data outcomes when determining patient eligibility for the study. A subjective patient improvement scale was used to monitor degree of success. RESULTS: Ten of the 17 patients were eligible for the study. Patients were eliminated for lack of consistency of data collection, having received an additional procedure after conventional care, involvement of the cervical spine; one patient experienced an unrelated medical problem. After 1 yr of conventional care, the patients reported a 25.5% improvement. (Conventional care included ESI and manipulation done at separate times.) After on ESI with subsequent manipulation, these same patients reported a 50.5% improvement. Mean improvement was 25.00% (SD = 19.51, SEM 6.19, t = 4.04 and p = .0015). CONCLUSION: The use of ESI performed with manipulation seems to offer promise for a carefully selected group of patients. ESI combined with manipulation should be considered in patients who do not respond to conventional forms of care.     

Prognostic significance of fluorescence intensity of surface marker expression in childhood B-precursor acute lymphoblastic leukemia. A Pediatric Oncology Group Study

This report describes the prognostic significance of the intensity of surface membrane antigen expression in a series of 1,231 children older than 1 year with newly diagnosed B-precursor acute lymphoblastic leukemia (ALL) treated on Pediatric Oncology Group (POG) treatment protocols. All patients had dual-color flow cytometric immunophenotyping performed at a central reference laboratory with a standard panel of monoclonal antibodies. The flow cytometers used in the study were calibrated with a standard fluorescence microparticle that permitted conversion of relative fluorescence channels to standard units of mean equivalents of soluble fluorochrome (MESF). In univariate analysis, fluorescence intensity of CD45 and CD20 was significantly associated with event-free survival (EFS), whereas other markers showed no significant correlation with outcome. Patients whose blasts were greater than the 75th percentile of intensity for CD45 (corresponding to 18,000 MESF units with CD45-FITC, or about 8% of the intensity of normal lymphocytes) fared significantly worse than those with lower-density CD45, and those whose blasts were greater than the 25th percentile of intensity for CD20 (corresponding to 17,900 MESF units with CD20-PE) had a poorer EFS. The intensity of both CD45 and CD20 was independently correlated with outcome. There was no significant correlation between intensity of expression of either antigen and traditional clinical risk factors, ploidy, or t(9;22) or t(1;19). All patients with t(4;11) had CD45 intensity greater than the 75th percentile, but CD45 intensity retained its prognostic significance after adjusting for t(4;11). In multivariate analysis, both CD45 intensity greater than the 75th percentile and CD20 intensity greater than the 25th percentile were significantly correlated with poor outcome independently of previously reported poor prognostic factors including National Cancer Institute (NCI) risk group, ploidy, trisomies of 4 and 10, and adverse translocations including t(1;19), t(9;22), and t(4;11). We conclude that in childhood B-precursor ALL, the intensity of expression of CD20 and CD45 provides prognostic information not available from simple consideration of antigen expression as positive or negative, and adds to that obtained from traditional clinical and biologic risk factors.     

The cystic fibrosis transmembrane conductance regulator as a marker of human pancreatic duct development

BACKGROUND & AIMS: The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a small conductance adenosine 3',5'-cyclic monophosphate (cAMP)-activated chloride ion channel found in the apical membranes of epithelia within the pancreas, airway, intestine, bile duct, sweat gland, and male genital ducts. Pancreatic insufficiency is a feature of about 85% of patients with cystic fibrosis and is believed to be caused by pancreatic autolysis after pancreatic duct obstruction. The aim of this study was to investigate the expression of CFTR in the pancreas from early development to postnatal life to establish whether the CFTR plays a key role in development of the pancreatic duct epithelium. METHODS: Expression of CFTR from the start of the mid-trimester of human development through term to adult life by messenger RNA (mRNA) in situ hybridization was examined. RESULTS: CFTR mRNA is detected throughout the pancreatic duct epithelium and its pattern of expression follows the differentiation of the duct system. CONCLUSIONS: CFTR is a valuable marker of human pancreatic duct cell development and differentiation.     

The learning curve for laparoscopic colorectal surgery. Preliminary results from a prospective analysis of 1194 laparoscopic-assisted colectomies

BACKGROUND: Laparoscopic-assisted colectomy is an emerging technology for patients with cancer, polyps, inflammation, and other types of pathologic conditions. While previous studies have shown better outcomes for laparoscopic cholecystectomies when surgeons perform more procedures, there is no information on the relationship between surgeon volume and outcomes for laparoscopic-assisted colectomy. OBJECTIVE: To evaluate whether better clinical outcomes are found for surgeons who perform higher numbers of laparoscopic-assisted colectomies and whether such a relationship, if it exists, applies to both intraoperative and postoperative outcomes. DESIGN: Analysis of a data set of 1194 patients, operated on by 114 surgeons, from a prospective registry sponsored by the American Society of Colon and Rectal Surgeons, from May 1991 to October 1994. MAIN OUTCOME MEASURES: Completion rate, intraoperative and postoperative complications, and length of hospital stay. RESULTS: In 75% of cases, surgery was completed laparoscopically, with no difference between high-volume surgeons (> or = 40 cases) and low-volume surgeons. Length of stay (average, 6 days) did not vary according to surgeon volume. Postoperative complications occurred in 15% of cases, with a significantly lower rate for high-volume surgeons (10% vs 19%; P < .001). Intraoperative complications occurred in 5% of cases, with a nonsignificant trend toward a lower rate for high-volume surgeons (3.7% vs 6.3%). A multivariate regression analysis, adjusting for type of disease (cancer vs inflammation vs polyps) and for level of difficulty of the procedure (high vs low) showed that for high-volume surgeons there is a lower probability of both intraoperative complications (adjusted odds ratio, 0.56; 95% confidence interval, 0.32-0.97; P = .04) and postoperative complications (adjusted odds ratio, 0.48; 95% confidence interval, 0.34-0.68; P < .001). CONCLUSIONS: There is a learning curve for laparoscopic-assisted colectomy with respect to intraoperative and postoperative outcomes. As with other laparoscopic procedures, surgeons who perform higher volumes of laparoscopic-assisted colectomy have lower rates of intraoperative and postoperative complications.