Estimation and extrapolation of optimal treatment and testing strategies

We review recent developments in the estimation of an optimal treatment strategy or regime from longitudinal data collected in an observational study. We also propose novel methods for using the data obtained from an observational database in one health-care system to determine the optimal treatment regime for biologically similar subjects in a second health-care system when, for cultural, logistical, or financial reasons, the two health-care systems differ (and will continue to differ) in the frequency of, and reasons for, both laboratory tests and physician visits. Finally, we propose a novel method for estimating the optimal timing of expensive and/or painful diagnostic or prognostic tests. Diagnostic or prognostic tests are only useful in so far as they help a physician to determine the optimal dosing strategy, by providing information on both the current health state and the prognosis of a patient because, in contrast to drug therapies, these tests have no direct causal effect on disease progression. Our new method explicitly incorporates this no direct effect restriction.

Immobilized artificial membrane chromatography : quantitative structure-retention relationships of structurally diverse drugs

The chromatographic capacity factors (log k‘) for 32 structurally diverse drugs were determined by high performance liquid chromatography (HPLC) on a stationary phase composed of phospholipids, the so-called immobilized artificial membrane (IAM). In addition, quantitative structure-retention relationships (QSRR) were developed in order to explain the dependence of retention on the chemical structure of the neutral, acidic, and basic drugs considered in this study. The obtained retention data were modeled by means of multiple regression analysis (MLR) and partial least squares (PLS) techniques. The structures of the compounds under study were characterized by means of calculated physicochemical properties and several nonempirical descriptors. For the carboxylic compounds included in the analysis, the obtained results suggest that the IAM-retention is governed by hydrophobicity factors followed by electronic effects due to polarizability in second place. Further, from the analysis of the results obtained of two developed quantitative structure-permeability studies for 20 miscellaneous carboxylic compounds, it may be concluded that the balance between polarizability and hydrophobic effects is not the same toward IAM phases and biological membranes. These results suggest that the IAM phases could not be a suitable model in assessing the acid-membrane interactions. However, it is not possible to generalize this observation, and further work in this area needs to be done to obtain a full understanding of the partitioning of carboxylic compounds in biological membranes. For the non-carboxylic compounds included in the analysis, this work shows that the hydrophobic factors are of prime importance for the IAM-retention of these compounds, while the specific polar interactions, such as electron pair donor−acceptor interactions and electrostatic interactions, are also involved, but they are not dominant.

Examination of the effect of mental reinstatement of context acress developmental level, retention interval and type of mnemonic instruction

The effect of mental reinstatement of context was examined using a 4*5*2 factorial design incorporating four age groups (6-year-olds, 8-year-olds, 11-year-olds and adults), two retention intervals (1 day and 2 weeks after the stimulus event) and five interview conditions. The interview conditions included; free recall, mental reinstatement-environment (where the setting was reinstated but no event-related detail was provided in the mnemonic instruction), mental reinstatement-event (where specific event-related content was provided), mental reinstatement-combined (a combination of the two above-mentioned methods) and specific questions. Overall, mental reinstatement (irrespective of the type) was found to enhance correct recall performance compared to free recall and (unlike specific questions) it did not lead to greater number of commission errors. Contrary to our initial predictions, however, there was no evidence of any special benefit of mental reinstatement for children and the effect of the technique did not vary consistently as a function of retention interval.

Development of a retention model for child protection workers

This thesis addressed the critical issue of retention in the child protection workforce. Key predictors of a workers 'intention to stay' or the 'likelihood of staying' were lifestyle factors and whether a worker had contemplated leaving the organisation. The degree of satisfaction was not in itself predictive of either intentions to stay or the actual 'likelihood of staying'.

The effect of transition to specialty practice programs on Australian emergency nurses' professional development, recruitment and retention

BACKGROUND: To date, emergency nursing Transition to Specialty Practice Program (TSPP) evaluations have been single-site observational studies. The aim of this paper was to examine the professional development, recruitment and retention outcomes of Australian emergency nursing TSPPs. METHODS: An explanatory sequential design was used. Data were collected via online surveys and interviews of emergency Nurse Unit Managers and Nurse Educators. Survey data from EDs with TSPPs and EDs without TSPPs were compared. Qualitative data were analysed using content analysis. RESULTS: Data were collected from 118 EDs, and 13 interviews. TSPPs were offered in 72.1% of EDs. EDs with TSPPs had higher proportions of nurses with postgraduate qualifications (Mdn 28.3% vs. 22.1%, p=0.45) and Clinical Specialists (Mdn 16.4% vs. 6.3%, p=0.04). The median proportion of currently rostered nurses with TSPP completion was 34.2% in EDs with TSPPs introduced in 2000-2005 indicating ED high levels of retention. CONCLUSION: Emergency nursing TSPPs have had a positive effect on nursing professional development, recruitment and retention. To ensure consistency in outcomes and optimise reliability of emergency nursing skills and knowledge, a national emergency nursing TSPP framework is needed.

Improving the precision of the accumulated oxygen deficit using VO2-power regression points from below and above the lactate threshold

The accumulated oxygen deficit (AOD) method assumes a linear VO₂-power relationship for exercise intensities increasing from below the lactate threshold (BLT) to above the lactate threshold (ALT). Factors that were likely to effect the linearity of the VO₂-power regression and the precision of the estimated total energy demand (ETED) were investigated. These included the slow component of VO₂ kinetics (SC), a forced resting y-intercept and exercise intensities BLT and ALT. Criteria for linearity and precision included the Pearson correlation coefficient (PCC) of the VO₂-power relationship, the length of the 95% confidence interval (95% CI) of the ETED and the standard error of the predicted value (SEP), respectively. Eight trained male and one trained female triathlete completed the required cycling tests to establish the AOD when pedalling at 80 rev/min. The influence of the SC on the linear extrapolation of the ETED was reduced by measuring VO₂ after three min of exercise. Measuring VO₂ at this time provided a new linear extrapolation method consisting of ten regression points spread evenly from BLT and ALT. This method produced an ETED with increased precision compared to using regression equations developed from intensities BLT with no forced y-intercept value; (95%CI (L), 0.70±0.26 versus 1.85±1.10, P<0.01; SEP(L/Watt), 0.07±0.02 versus 0.28±0.17; P<0.01). Including a forced y-intercept value with five regression points either BLT or ALT increased the precision of estimating the total energy demand to the same level as when using 10 regression points, (5 points BLT + y-intercept versus 5 points ALT + y-intercept versus 10 points; 95%CI(l), 0.61±0.32, 0.87±0.40, 0.70±0.26; SEP(L/Watt), 0.07±0.03, 0.08±0.04, 0.07±0.02; p>0.05). The VO₂-power regression can be designed using a reduced number of regression points... ABSTRACT FROM AUTHOR

Does the concept of ″altered states of consciousness″ rest on a mistake?

Block (2002) has argued that the multiplicity of meanings ascribed to consciousness is due to the erroneous treatment of very different concepts as a single concept. Block distinguished four notions of consciousness intended to encapsulate the various meanings attributed to the term: phenomenal, access, self, and monitoring consciousness. We argue that what is common to all of these definitions is the implicit distinction between consciousness and the content of consciousness. We critically examine the term “altered state of consciousness” and argue that affixing the qualifier “altered state” to consciousness results in a theoretical confusion of consciousness and its content, that is, consciousness is mistaken for the content of consciousness. We refer to this as the consciousness/content fallacy and argue that it may be avoided if one supplants “altered states of consciousness” with “altered pattern of phenomenal properties,” an extrapolation of the term “phenomenal field.” Implications of the consciousness/content fallacy for theory and research are also considered.

1-14C-Linoleic Acid distrubution in various tissue lipids of guinea pigs following an oral dose

A recent study on the metabolism of 1-¹⁴C-α-linolenic acid in the guinea pig revealed that the fur had the highest specific activity of all tissues examined, 48 h after dosing. The present study investigated the pattern of tissue lipid labeling following an oral dose of 1-¹⁴C-linoleic acid after the animals had been dosed for the same time as above. Guinea pigs were fed one of two diets with a constant linoleic acid content (18% total fatty acids) and a different content of α-linolenic acid (0.3 or 17.3%) from weaning for 3 wk and 1-¹⁴C-linoleic acid was given orally to each animal for 48 h prior to sacrifice. The most highly labeled tissues (dpm/mg of linoleic acid) were liver, followed by brain, lung and spleen, heart, kidney and adrenal and intestines, in both diet groups. The liver had almost a three-fold higher specific activity than skin and fur which was more extensively labeled than the adipose and carcass. Approximately two-thirds of the label in skin plus fur was found in the fur which, because of a low lipid mass, would indicate that the fur was highly labeled. All tissues derived from animals on the diet with the low α-linolenic acid level were significantly more labeled than the tissues from the animals on the high α-linolenic acid diet, by a factor of 1.5 to 3. The phospholipid fraction was the most highly labeled fraction in the liver, free fatty acids were the most labeled fraction in skin & fur, while triacyglycerols were the most labeled in the carcass and adipose tissue. In these tissues, more than 90% of the radioactivity was found in fatty acids with 2-double bonds in the tissue lipids. These data indicate that the majority of label found in guinea pig tissues 48 h after dosing was still associated with a fatty acid fraction with 2-double bonds, which suggests there was little metabolism of linoleic acid to more highly unsaturated fatty acids in this time frame. In this study, the labeling of guinea pig tissues with linoleic acid, 48 h after dosing, was quite different from the labeling with α-linolenic acid reported previously. The retention of the administered radioactivity from ¹⁴C-linoleic acid in the whole body lipids was 1.6 times higher in the group fed the low α-linolenic acid diet (diet contained a total of 1.8 g PUFA/100 g diet)compared with the group fed the high α-linolenic acid diet (diet contained 3.6 g PUFA/100 g diet). The lack of retention of ¹⁴C-labeled lipids in the whole body would be consistent with an increased rate of β-oxidation of the labeled fatty acid on the diet rich in PUFA, a result supported by other studies using direct measurement of labeled carbon dioxide.

A new method for resolving uncertainty of energy requirements in large water breathers: The 'mega-flume' seagoing swim-tunnel respirometer

Body size is a key determinant of metabolic rate, but logistical constraints have led to a paucity of energetics measurements from large water-breathing animals. As a result, estimating energy requirements of large fish generally relies on extrapolation of metabolic rate from individuals of lower body mass using allometric relationships that are notoriously variable. Swim-tunnel respirometry is the 'gold standard' for measuring active metabolic rates in water-breathing animals, yet previous data are entirely derived from body masses <10 kg - at least one order of magnitude lower than the body masses of many top-order marine predators. Here, we describe the design and testing of a new method for measuring metabolic rates of large water-breathing animals: a c. 26 000 L seagoing 'mega-flume' swim-tunnel respirometer. We measured the swimming metabolic rate of a 2·1-m, 36-kg zebra shark Stegostoma fasciatum within this new mega-flume and compared the results to data we collected from other S. fasciatum (3·8-47·7 kg body mass) swimming in static respirometers and previously published measurements of active metabolic rate measurements from other shark species. The mega-flume performed well during initial tests, with intra- and interspecific comparisons suggesting accurate metabolic rate measurements can be obtained with this new tool. Inclusion of our data showed that the scaling exponent of active metabolic rate with mass for sharks ranging from 0·13 to 47·7 kg was 0·79; a similar value to previous estimates for resting metabolic rates in smaller fishes. We describe the operation and usefulness of this new method in the context of our current uncertainties surrounding energy requirements of large water-breathing animals. We also highlight the sensitivity of mass-extrapolated energetic estimates in large aquatic animals and discuss the consequences for predicting ecosystem impacts such as trophic cascades.

Estimating mean exposures from censored data: exposure to benzene in the Australian petroleum industry

A retrospective assessment of exposure to benzene was carried out for a nested case control study of lympho-haematopoietic cancers, including leukaemia, in the Australian petroleum industry. Each job or task in the industry was assigned a Base Estimate (BE) of exposure derived from task-based personal exposure assessments carried out by the company occupational hygienists. The BEs corresponded to the estimated arithmetic mean exposure to benzene for each job or task and were used in a deterministic algorithm to estimate the exposure of subjects in the study. Nearly all of the data sets underlying the BEs were found to contain some values below the limit of detection (LOD) of the sampling and analytical methods and some were very heavily censored; up to 95% of the data were below the LOD in some data sets. It was necessary, therefore, to use a method of calculating the arithmetic mean exposures that took into account the censored data. Three different methods were employed in an attempt to select the most appropriate method for the particular data in the study. A common method is to replace the missing (censored) values with half the detection limit. This method has been recommended for data sets where much of the data are below the limit of detection or where the data are highly skewed; with a geometric standard deviation of 3 or more. Another method, involving replacing the censored data with the limit of detection divided by the square root of 2, has been recommended when relatively few data are below the detection limit or where data are not highly skewed. A third method that was examined is Cohen's method. This involves mathematical extrapolation of the left-hand tail of the distribution, based on the distribution of the uncensored data, and calculation of the maximum likelihood estimate of the arithmetic mean. When these three methods were applied to the data in this study it was found that the first two simple methods give similar results in most cases. Cohen's method on the other hand, gave results that were generally, but not always, higher than simpler methods and in some cases gave extremely high and even implausible estimates of the mean. It appears that if the data deviate substantially from a simple log-normal distribution, particularly if high outliers are present, then Cohen's method produces erratic and unreliable estimates. After examining these results, and both the distributions and proportions of censored data, it was decided that the half limit of detection method was most suitable in this particular study.

Why did they leave and what can they tell us? Allied health professionals leaving rural settings

The aim of this paper is to explore the lack of retention of allied health professionals in rural areas in Victoria, Australia. A structured telephone interview was used to elicit responses from 32 allied health professionals from south-west, central-west and north-east Victoria about their working experiences and reasons for resignation. The data revealed that work experiences in rural areas can be summarised within three domains: organisational, professional and personal/community. Under the organisational domain the participants were mainly focussed on the way in which their work arrangements require them to be both more generalist in their approach to day-to-day work, and more expansive in shouldering management style functions in the workplace. Under the professional domain there were three major issues; clinical, career and education/training. The personal/community domain focussed on issues to do with their affinity for their workplace as well as their location in a rural place. The attempts by government to address some of the leading factors for retention of allied health professionals are perhaps too narrowly focussed on the public sector and could encompass a wider approach.

What is known about the topic? Although recruitment and retention of allied health professionals in rural areas is widely discussed, the professionals have not been interviewed about their experiences once they have left rural employment.

What does this paper add? This paper provides detailed insights into the reasons why allied health professionals leave their positions in rural areas and the positive and negative aspects of living and working in a rural area. The results of this study contribute to the development of better policy models for recruitment and retention of allied health professionals in rural areas.

What are the implications for practitioners? The factors that influence whether allied health professionals stay or leave rural areas is of concern for health policy makers at state and federal levels. This paper provides information for the extension and development of programs to attenuate rural leakage of professionals.

Rematerialising heritage

The Rocks is one of Sydney’s premier tourist locations; its identity largely founded on the perception of it as a historically significant site. This perception is steeped in complex notions of the ‘authentic tourist experience offered at The Rocks, which arguably originates from the retention of some of the early streets and architectures of the area. However, implicit in the act of retention is also the act of deletion. Throughout the area of The Rocks, gaps exist. These are the spaces where buildings, houses, outhouses, lanes and indeed whole streets have been eradicated to make way for urban progress or to redefine areas of the city according to political or economic aims. Heritage here is constructed, not only from that which is retained and preserved but also from that which is deleted and destroyed. This paper seeks to examine the fate of one particular street in the Rocks – Princes Street – that was eradicated in 1927 to make way for the Sydney Harbour Bridge. The physical demolition of the street and subsequent erasure of any material sign of it has effectively allowed the street to disappear. The predominant historical narrative that results reveals the extent to which current notions of the past are fundamentally understood through the existence of the material artefact. Yet this paper argues that definitions of the past can be drawn, not only from the material or architectural object that operates as historical proof but also from the social, performative and touristic acts that might be undertaken around the object, the architecture or even its representation.

Retention of allied health professionals in the south-west of Victoria

The article reports on the research studies about the role of the allied health professionals in primary and preventive health care in Victoria. The studies shows that allied health practice in rural areas provide information on the strategies to maintain the health workforce. The results of the final report regarding the allied workforce issues in south-west Victoria was discussed. The details about the participants, methods and results of the survey regarding the retention of allied health professionals in south-west Victoria.

Engagement and retention of participants in a physical activity website

Background: Websites have the potential to deliver enhanced versions of targeted and tailored physical activity programs to large numbers of participants. We describe participant engagement and retention with a stage-based physical activity website in a workplace setting. Methods:  We analyzed data from participants in the website condition of a randomized trial designed to test the efficacy of a print- vs. website-delivered intervention. They received four stage-targeted e-mails over 8 weeks, with hyperlinks to the website. Both objective and self-reported website use data were collected and analyzed. Results: Overall, 327 were randomized to the website condition and 250 (76%) completed the follow-up survey. Forty-six percent (n = 152) visited the website over the trial period. A total of 4,114 hits to the website were recorded. Participants who entered the site spent on average 9 min per visit and viewed 18 pages. Website use declined over time; 77% of all visits followed the first e-mail. Conclusions: Limited website engagement, despite the perceived usefulness of the materials, demonstrates possible constraints on the use of e-mails and websites in delivering health behavior change programs. In the often-cluttered information environment of workplaces, issues of engagement and retention in website-delivered programs require attention.

Retention of essential amino acids during extrusion of protein and reducing sugars

This research investigates the retention of essential amino acid profiles of products during the extrusion of proteins and reducing sugars. Animal proteins (egg and milk protein at 10 and 30% levels) and reducing sugars (fructose and galactose at 0, 2, and 8% levels), with pregelatinized wheat flour, were extruded at 110 and 125 °C product temperatures and feed moistures of 19 and 23.5% for egg protein and 13.75 and 16% for milk protein. The nutritional property analyzed was essential amino acid retention, and sugar retention was also considered to understand the relationship of sugars with retention of amino acids. Lysine showed the lowest retention (up to 40%) of all the essential amino acids. Retention of other essential amino acids varied from 80 to 100% in most situations. Apart from lysine,  tryptophan, threonine, and methionine were found to be significantly changed (P < 0.05) with processing conditions. Increased protein and sugar levels resulted in a significant degradation of lysine. Greater lysine retention was found at a lower temperature and higher feed moisture. Results of sugar retention also showed similar patterns. The products made from fructose had greater lysine retention than products made from galactose with any type of protein. The outcomes of this research suggested that the combination of milk protein and fructose at a lower temperature and higher feed moisture is most favorable for developing high-protein extruded products.