New generalized Halanay inequalities with applications to stability of nonlinear non-autonomous time-delay systems

In this paper, a general class of Halanay-type non-autonomous functional differential inequalities is considered. A new concept of stability, namely global generalized exponential stability, is proposed. We first prove some new generalizations of the Halanay inequality. We then derive explicit criteria for global generalized exponential stability of nonlinear non-autonomous time-delay systems based on our new generalized Halanay inequalities. Numerical examples and simulations are provided to illustrate the effectiveness of the obtained results.

Determinants of mastitis in women in the CASTLE study: a cohort study

BACKGROUND: Mastitis is an acute, debilitating condition that occurs in approximately 20 % of breastfeeding women who experience a red, painful breast with fever. This paper describes the factors correlated with mastitis and investigates the presence of Staphylococcus aureus in women who participated in the CASTLE (Candida and Staphylococcus Transmission: Longitudinal Evaluation) study. The CASTLE study was a prospective cohort study which recruited nulliparous women in late pregnancy in two maternity hospitals in Melbourne, Australia in 2009-2011.

METHODS: Women completed questionnaires at recruitment and six time-points in the first eight weeks postpartum. Postpartum questionnaires asked about incidences of mastitis, nipple damage, milk supply, expressing practices and breastfeeding problems. Nasal and nipple swabs were collected from mothers and babies, as well as breast milk samples. All samples were cultured for S. aureus. "Time at risk" of mastitis was defined as days between birth and first occurrence of mastitis (for women who developed mastitis) and days between birth and the last study time-point (for women who did not develop mastitis). Risk factors for incidence of mastitis occurring during the time at risk (Incident Rate Ratios [IRR]) were investigated using a discrete version of the multivariable proportional hazards regression model.

RESULTS: Twenty percent (70/346) of participants developed mastitis. Women had an increased risk of developing mastitis if they reported nipple damage (IRR 2.17, 95 % CI 1.21, 3.91), over-supply of breast milk (IRR 2.60, 95 % CI 1.58, 4.29), nipple shield use (IRR 2.93, 95 % CI 1.72, 5.01) or expressing several times a day (IRR 1.64, 95 % CI 1.01, 2.68). The presence of S. aureus on the nipple (IRR 1.72, 95 % CI 1.04, 2.85) or in milk (IRR 1.78, 95 % CI 1.08, 2.92) also increased the risk of developing mastitis.

CONCLUSIONS: Nipple damage, over-supply of breast milk, use of nipple shields and the presence of S. aureus on the nipple or in breast milk increased the mastitis risk in our prospective cohort study sample. Reducing nipple damage may help reduce maternal breast infections.

A novel approach to exponential stability of nonlinear non-autonomous difference equations with variable delays

In this paper, by using a novel approach, we first prove a new generalization of discrete-type Halanay inequality. Based on our new generalized inequality, a novel criterion for the exponential stability of a certain class of nonlinear non-autonomous difference equations is proposed. Numerical examples are given to illustrate the effectiveness of the obtained results.

M-learning in an off-campus environment : using iPods in accounting education

The widening availability of the internet and the popularity of handheld devices such as Apple’s iPod are creating a generation of tech-savvy students who are becoming more demanding for innovative ways of accessing information. In this study thirty iPods were distributed to students studying an exclusively online graduate level accounting program at a mid-sized Australian university. The students were required to use their iPods as part of the course’s online learning environment. At the end of the semester students were given two questionnaires: (1) to illicit their opinions on the usefulness of the iPod as a learning tool, and (2) to establish their learning styles (using a VARK© questionnaire). The findings indicate that flexibility the perceived benefit of using iPods allowing more efficient and effective study time. In particular the mobility (m-learning) that allowed students to take advantage of what would otherwise be down-time such as travelling on public transport. Disadvantages related to the difficulty in reading text on a small screen and the ability to move to particular parts of a recorded lecture with precision. These comments were consistent for all demographics however students with a more visual learning style rated the iPod more important to their learning than other students. This study involved a small sample but the generally positive response to the use of iPods indicates that there would be value in further studies with larger groups.

Client-reported reasons for non-engagement in drug and alcohol treatment

Introduction and Aims.To examine client-reported reasons for missed early appointments at a drug and alcohol treatment service and to compare characteristics of those who missed appointments with those who attended. Design and Methods. Clients who missed a first or second appointment between 1 May and 31 August 2007 at a public community-based outpatient treatment facility were invited to participate in a semistructured telephone interview.This consisted of an open-ended question asking the reason(s) for nonattendance, followed by a questionnaire of items for therapeutic alliance and service satisfaction, perceived impact of substance use and previous treatment experience, mostly rated on Likert scales. Database information on demographic and clinical variables was gathered for all clients who were accepted for treatment within the study time frame. Characteristics of those who missed a first or second appointment (n = 66) were compared with those who attended at least their first two appointments (n = 97). Results. Of clients who missed their appointments, 80.6% provided reasons for nonattendance, which included extraneous factors (50.0%), service shortcomings (29.7%), no further need for service (16.2%) and motivational ambivalence (4.1%). They generally had high ratings of therapeutic alliance and service satisfaction and identified their substance use as having a negative impact on their lives. Clients who missed appointments were more likely to be male, unmarried and have a history of polysubstance use. Discussion and Conclusions. Extraneous issues relating to the client may be a dominant obstacle in early treatment engagement. Efforts to overcome these issues may therefore improve early engagement.

Detection of respiratory arousals using photoplethysmography (PPG) signal in sleep apnea patients

Respiratory events during sleep induce cortical arousals and manifest changes in autonomic markers in sleep disorder breathing (SDB). Finger photoplethysmography (PPG) has been shown to be a reliable method of determining sympathetic activation. We hypothesize that changes in PPG signals are sufficient to predict the occurrence of respiratory-event-related cortical arousal. In this study, we develop a respiratory arousal detection model in SDB subjects by using PPG features. PPG signals from 10 SDB subjects (9 male, 1 female) with age range 43-75 years were used in this study. Time domain features of PPG signals, such as 1) PWA--pulse wave amplitude, 2) PPI--peak-to-peak interval, and 3) Area--area under peak, were used to detect arousal events. In this study, PWA and Area have shown better performance (higher accuracy and lower false rate) compared to PPI features. After investigating possible groupings of these features, combination of PWA and Area (PWA + Area) was shown to provide better accuracy with a lower false detection rate in arousal detection. PPG-based arousal indexes agreed well across a wide range of decision thresholds, resulting in a receiver operating characteristic with an area under the curve of 0.91. For the decision threshold (PC(thresh) = 25%) chosen for the final analyses, a sensitivity of 68.1% and a specificity of 95.2% were obtained. The results showed an accuracy of 84.68%, 85.15%, 86.93%, and 50.79% with a false rate of 21.80%, 55.41%, 64.78%, and 50.79% at PC(thresh) = 25% or PPI, PWA, Area , and PWA + Area features, respectively. This indicates that combining PWA and Area features reduced the false positive rate without much affecting the sensitivity of the arousal detection system. In conclusion, the PPG-based respiratory arousal detection model is a simple and promising alternative to the conventional electroencephalogram (EEG)-based respiratory arousal detection system.

Quality of life related to oral versus subcutaneous iron chelation: a time trade-off study

Objective: To investigate the utility associated with subcutaneous infusion (deferoxamine) compared with once-daily oral administration (deferasirox) of iron chelation therapy.

Methods: Interviews using the time trade-off technique were used to estimate preferences (utility) for health states by finding the point at which respondents were indifferent between a longer but lower quality of life (QoL) and a shorter time in full health. Participants (n = 110) were community-based, 51% women, median age 35 years, from four regions in Sydney, Australia. Respondents rated three health states involving equal outcomes for people with thalassemia but with different treatment modalities for iron chelation; an "anchor state" describing a patient receiving iron chelation without administration mode specified, anchor state plus iron chelation via subcutaneous infusion, and anchor state plus iron chelation through once-daily oral medication.

Results: On an interval scale between 0 (death) and 1 (full health), median (interquartile range) utility of 0.80 (0.65–0.95) for the anchor state, 0.66 (0.45–0.87) for subcutaneous infusion, and 0.93 (0.80–0.97) for once-daily oral administration was obtained. The mean (median) difference of 0.23 (0.27) between the two treatments was statistically significant (Wilcoxon-signed rank test, P < 0.001). Subcutaneous infusion was associated with a mean (median) utility 0.13 (0.14) lower than the anchor state (P < 0.001), and once-daily oral treatment had a utility 0.10 (0.13) higher (P < 0.001).

Conclusion: Community respondents associate oral administration of an iron chelator such as deferasirox with enhanced QoL compared with subcutaneous treatment. Assuming equal safety and efficacy, QoL gains from once-daily oral treatment compared with subcutaneous infusion are significant.

Television viewing habits and time use in Australian preschool children : an exploratory study

The overall aim in this study was to investigate time use in Australian preschool children, paying close attention to the types of television programs and videos/DVDs they watch. Ninety-two mothers of preschool children completed five activity diaries, for three typical weekdays and two weekend days. On average, children spent around just over 1 hour per weekday watching television and 30 minutes watching videos/DVDs; on weekends they spent on average 1 hour watching television and the same amount of time watching videos/DVDs. On weekdays, children spent more time watching child informative television; on the weekend they spent more time watching child animated television programs. When not watching television, children were mainly engaged in general play or in outdoor play. Child informative television was associated positively with time spent outdoors and in general and pretend play on weekdays (and for general play also on weekend days), whereas overall television viewing was correlated negatively with reading. Our findings suggest that the content of television programs may play a critical role in the relationship between television and other daily activities.

Assessing Sleep during Pregnancy - a study across two time points examining the pittsburg sleep quality index and associations with depressive symptoms

Background and Purpose: Sleep quality seems to be an antecedent to depressive symptoms during pregnancy. We sought to 1) examine the psychometrics of the Pittsburgh Sleep Quality Index (PSQI) in pregnancy; 2) examine whether sleep quality predicted increases in depressive symptoms; and 3) compare PSQI scores across 3 or 2 levels of depressive symptoms.

Methods: Each of the 252 participants completed the Beck Depression Inventory (short form) and a sleep quality measure at mid and late pregnancy.

Results: PSQI total scores showed good internal consistency and construct validity. An improved model of the internal structure of the PSQI in pregnancy was found with 1 factor labeled Sleep Efficiency, a second labeled Night and Daytime Disturbances, and an Overall Sleep Quality component associated with, but separate from, both of these 2 factors. Although PSQI scores showed moderate stability over time, sleep disturbance scores increased in late pregnancy. Importantly, PSQI prospectively predicted increases in depressive symptoms.

Conclusions: Findings suggest that the PSQI is useful in pregnancy research. Findings also support the idea that sleep problems are prospective risk factors for increases in depressive symptoms during pregnancy. Practitioners are advised to screen for sleep quality during early pregnancy.