Stability borders of feedback control of delayed measured systems

When stabilization of unstable periodic orbits or fixed points by the method given by Ott, Grebogi and Yorke (OGY) has to be based on a measurement delayed by $\tau$ orbit lengths, the performance of unmodified OGY method is expected to decline. For experimental considerations, it is desired to know the range of stability with minimal knowledge of the system. We find that unmodified OGY control fails beyond a maximal Ljapunov number of $\lambda_{max}=1+\frac{1}{\tau}$. In this paper the area of stability is investigated both for OGY control of known fixed points and for difference control of unknown or inaccurately known fixed points. An estimated value of the control gain is given. Finally we outline what extensions have to be considered if one wants to stabilize fixed points with Ljapunov numbers above $\lambda_{max}$.Comment: 5 pages LaTeX using revtex and epsfig (4 figs included). Revised versio

Establishing links between organizational climate, employee well-being and historical patient outcomes

This research undertaken in collaboration with Queensland Health analysed the links between dimensions of workplace climate/employee well-being contained in a number of Queensland Health databases, including the Patient Satisfaction Survey, the Clinical Incident database, the compliments and complaints database, the Variable Life Adjusted Display (VLAD) Database and the Better Workplaces Staff Opinion Survey database. Queensland Health sought to identify in what ways workplace climate is related to patient outcomes using existing datasets collected within the Queensland Health Centre for Healthcare Improvement. The process of establishing links involved matching aggregated data for specific facilities (where possible), or failing that, larger facilities (e.g. Hospital), or the Health Service District. Once the datasets had been matched on location or facility, correlations were calculated between the aggregated scores. The results demonstrated links between the data sets. These links showed that a better workplace climate is associated with greater reported numbers of clinical incidents, especially “no harm” clinical incidents. There was also a link between workplace climate and patient compliments/complaints which show that unsolicited compliments received from patients and their families are clearly related to a number of positive aspects of workplace climate (workplace morale, role clarity, and appraisal and recognition) and individual morale. The results linking workplace climate and patient satisfaction showed that there is a strong positive relationship between overall patient satisfaction and role clarity, and a negative relationship between overall patient satisfaction and both workplace distress and excessive work demands. While these results relate to historical data and therefore should not be construed to reflect the current state of operation within Queensland Health, they are still indicative of some very important relationships. This is the first study to demonstrate that more positive clinical management practices, better perceptions of the workplace climate and better employee well-being are a reflection of a better incident reporting and learning culture in a health care organization, ultimately resulting in improved patient outcomes

Temporal extensivity of Tsallis' entropy and the bound on entropy production rate

The Tsallis entropy, which is a generalization of the Boltzmann-Gibbs entropy, plays a central role in nonextensive statistical mechanics of complex systems. A lot of efforts have recently been made on establishing a dynamical foundation for the Tsallis entropy. They are primarily concerned with nonlinear dynamical systems at the edge of chaos. Here, it is shown by generalizing a formulation of thermostatistics based on time averages recently proposed by Carati [A. Carati, Physica A 348, 110 (2005)] that, whenever relevant, the Tsallis entropy indexed by $q$ is temporally extensive: linear growth in time, i.e., finite entropy production rate. Then, the universal bound on the entropy production rate is shown to be $1/|1-q|$ . The property of the associated probabilistic process, i.e., the sojourn time distribution, determining randomness of motion in phase space is also analyzed.Comment: 25 pages, no figure

Differential peripheral B cell phenotype in patients with primary Sjögren’s syndrome (pSS) compared to secondary Sjögren’s syndrome associated with systemic lupus erythematosus (SS/SLE)

Introduction: Peripheral B-cell abnormalities, a feature of both systemic lupus erythematosus (SLE) and primary Sjogren’s syndrome (pSS), are implicated in the pathogenesis of both diseases and correlate with disease activity. This study aims to investigate how the defective B-cell phenotype in pSS patients compares to patients with SS and SLE (SS/SLE), and whether abnormalities in B-cell phenotype could be related to differential B-cell lipid-raft expression and B-cell activating factor (BAFF) receptor function in patients with pSS and SLE and secondary SS (SS/SLE). Methods: Blood samples and clinical and laboratory parameters from 32 patients with pSS and SS/SLE and 13 age/sex matched HC were obtained. We used flow-cytometry to perform B-cell immunophenotyping and analysed lipid-raft expression (marker of B-cell activation). In vitro cultures were also used to assess lipid-raft expression in response to BAFF. Results: Patients with SS/SLE had a significantly decreased Bm1 and Bm5 and increased Bm2 populations compared to HC (p=0.031, p=0.035 and p=0.01, respectively), and increased Bm2 compared to pSS (p=0.027). Bm1-cells were decreased in both pSS and SS/SLE patients compared to HC (p=0.028 and p= 0.031, respectively). Both age and disease duration correlated strongly with Bm2’ cells in SS/SLE patients (r=0.9572, p= 0.0428), and the immunosuppressive treatment correlated negatively with the number of circulating Bm2 and Bm2’ cell in pSS (r = -0.54, p=0.01 and r = -0.56, p=0.008, respectively). B-cells from patients with pSS had a significant increase in lipid-raft expression compared to HC (p=0.01) and patients with SS/SLE (p<0.05). Lipid-raft levels correlated with BAFF-receptor expression in HC and SS/SLE B-cells (p=0.17, r=0.694) but not in pSS patients. Both disease activity score (ESSDAI) and IgG level correlated positively with lipid rafts expression in B cells from patients with pSS (r = 0.79, p=0.004 and r =0.53, p=0.04, respectively). Conclusion: Patients with SS/SLE had more significant B-cell abnormalities compared to HC and pSS, detectable even in a small number of patients. Also the relationship between lipid-raft and BAFF-receptor expression was altered between pSS and SS/SLE patients, and correlated with the disease activity and IgG levels in pSS group, suggesting that therapies targeting BAFF might be particularly successful in the SS/SLE sub-group of patients

The fractional integrated bi- parameter smooth transition autoregressive model

This paper introduces the fractionally integrated Bi-parameter smooth transition autoregressive model (FI-BSTAR model) as an extension of BSTAR model proposed by Siliverstovs (2005) and the fractionally integrated STAR model (FI-STAR model) proposed by van Dijk et al. (2002). Our FI-BSTAR model is able to simultaneously describe persistence and asymmetric smooth structural change in time series. An empirical application using monthly growth rates of the American producer price index is provided.Long Memory, Nonlinearity, Asymmetry, STAR models.

Coastal sea surface temperature variability along the south coast of South Africa and the relationship to regional and global climate

The southern coastline of South Africa is approximately zonal, with a wide (up to 270 km) shelf region. Intense thermoclines are known to be established by insolation on the inner shelf region during summer, upwelling is generated by easterly-component winds, and occasionally Agulhas Current water can be advected close to the coast, particularly in the east. These processes induce daily and seasonal fluctuations of coastal sea-surface temperature (SST), but their influence over longer time scales (interannual) has not yet been tested. Here time series of SST ranging from 12 to 31 years are examined for inter-relationships with local and regional winds, and the southern oscillation index (SOI). The emphasis is on the summer period, and it is found that the correlation between SST and major axis wind anomalies can be improved substantially by considering the frequency of occurrence of winds above given thresholds. Moreover, winds and SSTs are also correlated with the SOI, such that fewer easterly-component winds are experienced at low phases (El Nino) with consequent increases in coastal SST, and correspondingly more easterly-component winds at high phases (La Nina) result in decreased coastal SST; however, these relationships did not hold for a measuring site within a large open bay area. Long-term trends are also established, with substantial increases in SST (0.25°C/decade) in association with greater increases in air temperature (0.36°C/ decade)

Challenges in implementing cardiovascular risk scores for assessment of young people with childhood-onset autoimmune rheumatic conditions

Cardio-vascular risk (CVR) stratification tools have been implemented in clinical practice to guide management decision for primary prevention of cardiovascular disease. Less is known about how we can optimally estimate the CVR in children and adolescents or about the reliability of the risk stratification tools validated in adult populations. Chronic inflammation associated with autoimmune rheumatic disease (ARD) drives an increased risk for accelerated atherosclerosis in patients of all ages. Although the research is less advanced than in adult populations, it is recognized that young people with ARDs with childhood-onset have increased CVR compared to age-matched healthy controls, as supported by studies investigating lipid biomarker profile and markers of endothelial dysfunction. Further research is needed to address the unmet need for adequate CVR identification and management strategies in young people in general, and in those with underlying chronic inflammation in particular. This perspective paper explores various challenges in adequately identifying and managing CVR in younger populations and potential directions for future research

Noncommutative partially convex rational functions

Motivated by classical notions of bilinear matrix inequalities (BMIs) and partial convexity, this article investigates partial convexity for noncommutative functions. It is shown that noncommutative rational functions that are partially convex admit novel butterfly-type realizations that necessitate square roots. The notion of xy-convexity, a strengthening of partial convexity arising in connection with BMIs, is also considered. A characterization of xy-convex polynomials is given