Frailty as a trigger for goals-of-care discussions in rapid response calls: A single-centre retrospective cohort study.

BACKGROUND: Timely goals-of-care (GOC) discussions are essential for end-of-life planning, particularly during acute hospital admissions, where ambiguity often persists. Frailty, prevalent in the ageing population and linked to adverse outcomes, underscores the need to align treatment strategies with quality of life. Recognising frailty as a trigger for GOC discussions during rapid response calls (RRCs) is critical for efficient resource management and improving patient outcomes. METHODS: This single-centre retrospective cohort study included all hospitalised patients aged ≥65 years admitted between September 2021 and June 2023 who experienced an RRC. Frailty was assessed using the Clinical Frailty Scale (CFS) during the RRC. The primary outcome was to investigate whether frailty, specifically assessed by the CFS as screened during an RRC, could be a suitable clinical trigger for initiating GOC discussions. We also aimed to identify the proportion of patients with frailty (CFS score: ≥5) and predictors at the time of RRC, resulting in recommendations for GOC discussions. RESULTS: Among 4954 patients, 1685 (34.0%) were classified as frail (CFS score: ≥5). Recommendations increased with frailty levels (nonfrail [CFS score: 1-4]: 6.6%, mildly frail [CFS score: 5]: 19.3%, moderate-to-severely frail [CFS score: 6-9]: 32.2%; p < 0.001). Frailty independently increased the probability of GOC recommendations during an RRC (area under the receiver operating characteristic curve = 0.71). The CFS cut-off point for GOC recommendations was ≥5. The presence of frailty was associated with higher odds of receiving GOC recommendations for mildly frail (CFS score: 5; odds ratio [OR] = 2.53; 95% confidence interval: 1.96-3.27) and moderate-to-severely frail (CFS score: 6-9; OR = 4.69; 95% confidence interval: 3.81-5.78) compared to nonfrail patients. CONCLUSION: Frailty, identified during an RRC, served as a robust trigger for GOC recommendations, highlighting the importance of tailored proactive discussions before episodes of deterioration. Higher levels of frailty (CFS score: ≥5) demonstrate practical markers for aiding clinicians with proactive GOC discussions.

A novel protocol for rapid deployment of heart rate data storage tags in Atlantic bluefin tuna Thunnus thynnus reveals cardiac responses to temperature and feeding.

The Atlantic bluefin tuna (ABFT) is a highly prized species of large pelagic fish. Studies of their environmental physiology may improve understanding and management of their populations, but this is difficult for mature adults because of their large size. Biologging of heart rate holds promise in investigating physiological responses to environmental conditions in free-swimming fishes but it is very challenging to anesthetize large ABFT for invasive surgery to place a tag in the body cavity near to the heart. We describe a novel method for rapid deployment of a commercially available heart-rate tag on ABFT, using an atraumatic trocar to implant it in the musculature associated with the cleithrum. We performed three sequential experiments to show that the tagging method (1) is consistently repeatable and reliable, (2) can be used successfully on commercial fishing boats and does not seem to affect fish survival, and (3) is effective for long-term deployments. In experiment 3, a tag logged heart rate over 80 days on a 60-kg ABFT held in a farm cage. The logged data showed that heart rate was sensitive to prevailing seasonal temperature and feeding events. At low temperatures, there were clear responses to feeding but these all disappeared above a threshold temperature of 25.5°C. Overall, the results show that our method is simple, rapid, and repeatable, and can be used for long-term experiments to investigate physiological responses by large ABFT to environmental conditions.

Thermodynamic Interpretation of the Meyer-Neldel Rule Explains Temperature Dependence of Ion Diffusion in Silicate Glass.

We study the temperature-dependent diffusion of many types of metal and semimetal ions in soda-lime glass using thermal relaxation ion spectroscopy, a technique that provides an electrical readout of thermally activated diffusion of charge carriers driven by built-in concentration gradients and electric fields. We measure the temperature of the onset of the motion, relevant to the long term storage of radioactive elements. We demonstrate the unique behavior of silver in soda-lime glass, enabling a thermal battery with rapid discharge of stored energy above a threshold temperature. We show that the Meyer-Neldel rule applies when comparisons of temperature-dependent diffusion rates are made between related measurements on one sample or between the same measurements on related samples. The results support a thermodynamic interpretation of the Meyer-Neldel rule as an enthalpy-entropy correlation where the Meyer-Neldel temperature (T_{MN}) is the temperature that enables liquidlike, barrier-free motion of the ions, with an upper limit set by the melting point of the host medium. This interpretation explains the observed reduction in T_{MN} by built-in electric fields in depletion layers and why the upper limit for T_{MN} for all ions is set by the glass transition temperature.

Real-world clinical and cost analysis of CT coronary angiography and CT coronary angiography-derived fractional flow reserve (FFRCT)-guided care in the National Health Service.

AIM: To quantify the real-world clinical and cost impact of computed tomography (CT) coronary angiography (CTCA)-derived fractional flow reserve (FFRCT) in the National Health Service (NHS). MATERIALS AND METHODS: Consecutive clinical CTCA examinations from September to December 2018 with ≥1 stenosis of ≥25% underwent FFRCT analysis. The Heart Team reviewed clinical data and CTCA findings, blinded to FFRCT values, and documented hypothetical consensus management. FFRCT results were then unblinded and hypothetical consensus management re-recorded. Diagnostic waiting times for management pathways were estimated. A per-patient cost analysis for diagnostic certainty regarding coronary artery disease (CAD) management was performed using 2014-2020 NHS tariffs for pre- and post-FFRCT pathways. RESULTS: Two hundred and fifty-one CTCAs were performed during the study period. Fifty-seven percent (145/251) had no CAD or stenosis <25%. One study was non-diagnostic. Of the remaining 42% (105/251), two were ineligible for FFRCT and there was a 5% (5/103) failure rate. FFRCT led to a change in hypothetical management in 65% (64/98; p<0.001) patients with a functional imaging test cancelled in 17% (17/98) and a diagnostic angiogram cancelled in 47% (46/98). FFRCT-guided management had a reduced mean time to definitive investigation compared with CTCA alone (28 ± 4 versus 44 ± 4 days; p=0.004). Using the proposed 2020/21 tariff, CTCA + FFRCT for stenosis ≥50% resulted in a diagnostic pathway £44.97 more expensive per patient than usual care without FFRCT. CONCLUSIONS: In the real-world NHS setting, FFRCT-guided management has the potential to rationalise patient management, accelerate diagnostic pathways, and depending on the stenosis severity modelled, may be cost-effective.

Graphitization of Glassy Carbon after Compression at Room Temperature.

Glassy carbon is a technologically important material with isotropic properties that is nongraphitizing up to ∼3000 °C and displays complete or "superelastic" recovery from large compression. The pressure limit of these properties is not yet known. Here we use experiments and modeling to show permanent densification, and preferred orientation occurs in glassy carbon loaded to 45 GPa and above, where 45 GPa represents the limit to the superelastic and nongraphitizing properties of the material. The changes are explained by a transformation from its sp^{2} rich starting structure to a sp^{3} rich phase that reverts to fully sp^{2} bonded oriented graphite during pressure release.

Latent class analysis differentiation of adjustment disorder and demoralization, more severe depressive and anxiety disorders, and somatic symptoms in patients with cancer.

OBJECTIVES: Demoralization as a form of existential distress involves poor coping, low morale, hopelessness, helplessness, and meaninglessness. In a secondary analysis of a cohort of German cancer patients, we aimed to explore latent class structure to assess the contribution that symptoms of demoralization make to anhedonic depression, anxiety, adjustment, and somatic disorders. METHODS: Measures of demoralization, depression, anxiety, physical symptoms, and functional impairment had been completed cross-sectionally by 1527 patients with early or advanced cancer. Latent class analysis used maximum likelihood techniques to define the unobserved latent constructs that can be predicted as symptom clusters. Individual patients were assigned to the most probable class. Classes were compared on demographics, and logistic regression assessed the odds of individual items predicting each class. RESULTS: A 4-class model provided the best fit. Class 1 (n = 829, 54.3%) was defined by the absence of distress; Classes 2 to 4 all carried functional impairment. Class 2 (n = 333, 21.8%) was differentiated by somatic symptoms (sleep, tiredness, and appetite); Class 3 (n = 163, 10.7%) by anhedonia, anxiety, and severe demoralization; and Class 4 (n = 202, 13.2%) by adjustment and moderate demoralization. Members of Class 3 were more likely to be younger, female, anhedonic, depressed, and anxious. In both Classes 3 and 4, functional impairment, physical symptom burden, and suicidal ideation were present. CONCLUSIONS: In contrast with the severe symptom cluster carrying anhedonia, anxiety, and demoralization, the moderate symptom cluster was formed by patients with demoralization and impaired functioning, a clinical picture consistent with a unidimensional model of adjustment disorder.

Effect of aerobic exercise on cancer-associated cognitive impairment: A proof-of-concept RCT.

BACKGROUND: Change in cognitive ability is a commonly reported adverse effect by breast cancer survivors. The underlying etiology of cognitive complaints is unclear and to date, there is limited evidence for effective intervention strategies. Exercise has been shown to improve cognitive function in older adults and animal models treated with chemotherapy. This proof-of-concept randomized controlled trial tested the effect of aerobic exercise versus usual lifestyle on cognitive function in postmenopausal breast cancer survivors. METHODS: Women, aged 40 to 65 years, postmenopausal, stages I to IIIA breast cancer, and who self-reported cognitive dysfunction following chemotherapy treatment, were recruited and randomized to a 24-week aerobic exercise intervention (EX; n = 10) or usual lifestyle control (CON; n = 9). Participants completed self-report measures of the impact of cognitive issues on quality of life (Functional Assessment of Cancer Therapy-Cognitive version 3), objective neuropsychological testing, and functional magnetic resonance imaging at baseline and 24 weeks. RESULTS: Compared to CON, EX had a reduced time to complete a processing speed test (trail making test-A) (-14.2 seconds, P < .01; effect size 0.35). Compared to CON, there was no improvement in self-reported cognitive function and effect sizes were small. Interestingly, lack of between-group differences in Stroop behavioral performance was accompanied by functional changes in several brain regions of interest in EX compared to CON at 24 weeks. CONCLUSION: These findings provide preliminary proof-of-concept results for the potential of aerobic exercise to improve cancer-related cognitive impairment and will serve to inform the development of future trials.

The impact of sexual orientation on body image, self-esteem, urinary and sexual functions in the experience of prostate cancer.

Prostate cancer (PCa) poses a large health burden globally. Research indicates that men experience a range of psychological challenges associated with PCa including changes to identity, self-esteem and body image. The ways in which sexual orientation plays a role in the experience of PCa, and the subsequent impact on quality of life (QoL), body image and self-esteem have only recently been addressed. By addressing treatment modality, where participant numbers were sufficient, we also sought to explore whether gay (homosexual) men diagnosed with PCa (PCaDx) and with a primary treatment modality of surgery would report differences in body image and self-esteem compared with straight (heterosexual) men with PCaDx with a primary treatment modality of surgery, compared with gay and straight men without PCaDx. The results of our study identified overall differences with respect to PCaDx (related to urinary function, sexual function and health evaluation), and sexual orientation (related to self-esteem), rather than interactions between sexual orientation and PCaDx. Gay men with PCaDx exhibited higher levels of urinary functioning than straight men with PCaDx, the difference being reversed for gay and straight men without PCaDx; but this result narrowly failed to achieve statistical significance, suggesting a need for further research, with larger samples.

Effectiveness of Workplace Interventions in Return-to-Work for Musculoskeletal, Pain-Related and Mental Health Conditions: An Update of the Evidence and Messages for Practitioners.

Purpose The objective of this systematic review was to synthesize evidence on the effectiveness of workplace-based return-to-work (RTW) interventions and work disability management (DM) interventions that assist workers with musculoskeletal (MSK) and pain-related conditions and mental health (MH) conditions with RTW. Methods We followed a systematic review process developed by the Institute for Work & Health and an adapted best evidence synthesis that ranked evidence as strong, moderate, limited, or insufficient. Results Seven electronic databases were searched from January 1990 until April 2015, yielding 8898 non-duplicate references. Evidence from 36 medium and high quality studies were synthesized on 12 different intervention categories across three broad domains: health-focused, service coordination, and work modification interventions. There was strong evidence that duration away from work from both MSK or pain-related conditions and MH conditions were significantly reduced by multi-domain interventions encompassing at least two of the three domains. There was moderate evidence that these multi-domain interventions had a positive impact on cost outcomes. There was strong evidence that cognitive behavioural therapy interventions that do not also include workplace modifications or service coordination components are not effective in helping workers with MH conditions in RTW. Evidence for the effectiveness of other single-domain interventions was mixed, with some studies reporting positive effects and others reporting no effects on lost time and work functioning. Conclusions While there is substantial research literature focused on RTW, there are only a small number of quality workplace-based RTW intervention studies that involve workers with MSK or pain-related conditions and MH conditions. We recommend implementing multi-domain interventions (i.e. with healthcare provision, service coordination, and work accommodation components) to help reduce lost time for MSK or pain-related conditions and MH conditions. Practitioners should also consider implementing these programs to help improve work functioning and reduce costs associated with work disability.

A prospective examination of Axis I psychiatric disorders in the first 5 years following moderate to severe traumatic brain injury.

BACKGROUND: Psychiatric disorders commonly emerge during the first year following traumatic brain injury (TBI). However, it is not clear whether these disorders soon remit or persist for long periods post-injury. This study aimed to examine, prospectively: (1) the frequency, (2) patterns of co-morbidity, (3) trajectory, and (4) risk factors for psychiatric disorders during the first 5 years following TBI. METHOD: Participants were 161 individuals (78.3% male) with moderate (31.2%) or severe (68.8%) TBI. Psychiatric disorders were diagnosed using the Structured Clinical Interview for DSM-IV, administered soon after injury and 3, 6 and 12 months, and 2, 3, 4 and 5 years post-injury. Disorder frequencies and generalized estimating equations were used to identify temporal relationships and risk factors. RESULTS: In the first 5 years post-injury, 75.2% received a psychiatric diagnosis, commonly emerging within the first year (77.7%). Anxiety, mood and substance-use disorders were the most common diagnostic classes, often presenting co-morbidly. Many (56.5%) experienced a novel diagnostic class not present prior to injury. Disorder frequency ranged between 61.8 and 35.6% over time, decreasing by 27% [odds ratio (OR) 0.73, 95% confidence interval (CI) 0.65-0.83] with each year post-injury. Anxiety disorders declined significantly over time (OR 0.73, 95% CI 0.63-0.84), whilst mood and substance-use disorder rates remained stable. The strongest predictors of post-injury disorder were pre-injury disorder (OR 2.44, 95% CI 1.41-4.25) and accident-related limb injury (OR 1.78, 95% CI 1.03-3.07). CONCLUSIONS: Findings suggest the first year post-injury is a critical period for the emergence of psychiatric disorders. Disorder frequency declines thereafter, with anxiety disorders showing greater resolution than mood and substance-use disorders.

Reaction paths of phosphine dissociation on silicon (001).

Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

The meaning of a high plasma free haemoglobin: retrospective review of the prevalence of haemolysis and circuit thrombosis in an adult ECMO centre over 5 years.

AIMS: In adults requiring extracorporeal membrane oxygenation (ECMO), we wanted to determine; i) the frequency of elevated plasma free haemoglobin (PFHb), ii) the reasons for circuit changes and iii) whether elevated PFHb was associated with higher in-hospital mortality. MATERIALS AND METHODS: Patients requiring ECMO between January 2010 and August 2014 were identified from a prospectively collected ECMO database. Their scanned medical records and pathology results were reviewed. Relevant patient, biochemical and circuit data were collected on an Excel spreadsheet and analysed using Stata 13 (StataCorp, College Station, TX). The patients were analysed in three groups, depending on their peak PFHb during ECMO: 'Normal PFHb' (<0.1 g/L), 'Low level PFHb' (0.1 - 0.5 g/L), 'High level PFHb' (>0.5 g/L). MAIN RESULTS: There were 184 ECMO runs (56 VV, 128 VA) - 61 'Normal PFHb', 99 'Low level PFHb', 24 'High level PFHb'. Circuit thrombosis (pump, oxygenator) or haemolysis requiring exchanges were significantly more common in VV ECMO compared to VA ECMO - 23.21% (13/56) vs. 0.78% (1/128), p<0.001. Elevated PFHb was associated with a longer duration of haemofiltration (p<0.001) and ECMO support (p<0.001). In-hospital mortality rates for the 'Normal PFHb', 'Low level PFHb' and 'High level PFHb' groups were 16.39% (10/61), 30.30% (30/99) and 37.50% (9/24), respectively, p=0.067. CONCLUSION: Elevated PFHb values during adult ECMO were common. Severe haemolysis or thrombosis requiring circuit changes were uncommon and occurred almost exclusively on VV ECMO. There was a non-statistically significant increase in in-hospital mortality with elevated PFHb and studies of larger registry data may clarify the prognostic value of PFHb in adult patients.

Measuring oxygen uptake in fishes with bimodal respiration.

Respirometry is a robust method for measurement of oxygen uptake as a proxy for metabolic rate in fishes, and how species with bimodal respiration might meet their demands from water v. air has interested researchers for over a century. The challenges of measuring oxygen uptake from both water and air, preferably simultaneously, have been addressed in a variety of ways, which are briefly reviewed. These methods are not well-suited for the long-term measurements necessary to be certain of obtaining undisturbed patterns of respiratory partitioning, for example, to estimate traits such as standard metabolic rate. Such measurements require automated intermittent-closed respirometry that, for bimodal fishes, has only recently been developed. This paper describes two approaches in enough detail to be replicated by the interested researcher. These methods are for static respirometry. Measuring oxygen uptake by bimodal fishes during exercise poses specific challenges, which are described to aid the reader in designing experiments. The respiratory physiology and behaviour of air-breathing fishes is very complex and can easily be influenced by experimental conditions, and some general considerations are listed to facilitate the design of experiments. Air breathing is believed to have evolved in response to aquatic hypoxia and, probably, associated hypercapnia. The review ends by considering what realistic hypercapnia is, how hypercapnic tropical waters can become and how this might influence bimodal animals' gas exchange.

Postnatal demoralisation among women admitted to a hospital mother-baby unit: validation of a psychometric measure.

Demoralisation is a psychological state characterised by experiences of distress and sadness, helplessness, subjective incompetence and hopelessness, in the context of a stressful situation. Experiences of demoralisation may be particularly relevant to women who have recently given birth, who can feel incompetent, isolated and helpless. The psychometric properties of the Demoralisation Scale among women in the postnatal period participating in a clinical program were examined. Women admitted with their infants to a hospital mother-baby unit in Australia for five nights were recruited consecutively (N = 209) and assessed at admission and discharge. The Demoralisation Scale was perceived as relevant and exhibited high reliability, acceptable construct validity and good sensitivity to change. The mean demoralisation score was high (M = 30.9, SD = 15.5) and associated with negative experiences of motherhood and functional impairment, independent of depression and anxiety symptoms. Mean demoralisation decreased significantly after program completion (M = 18.4, SD = 12.4). More participants showed a significant improvement in demoralisation (57.5 %) than in depression (34.8 %) and anxiety (9.8 %) symptoms. Demoralisation can provide a useful framework for understanding and measuring the experiences of women participating in postnatal clinical programs and in directing treatment towards helping women to acquire the necessary caregiving skills and increasing parental efficacy. The Demoralisation Scale is a useful clinical tool for assessing intervention effects.

Community-acquired pneumonia: why aren't national antibiotic guidelines followed?

AIMS: Adherence to guidelines for the management of community-acquired pneumonia (CAP) has been shown to improve patients' clinical outcomes. This study aimed to assess adherence to the Australian Therapeutic Guidelines (TG14) for the empirical management of CAP, and explore the potential barriers affecting adherence to these guidelines. METHODS: Medical records were reviewed for all patients who were diagnosed with CAP within 24 h of presentation at the Royal Hobart Hospital, the main teaching hospital in Tasmania, Australia, between July 2010 and March 2011. A survey of emergency department and medical team prescribers was also undertaken to identify potential barriers to adhere with the guidelines. χ(2) and Fisher's exact tests were used to test the significance between categorical data. To compare categorical and scale data, the Mann-Whitney U-test was used. RESULTS: A total of 193 patient records were assessed. The overall adherence to TG14 for the empirical antibiotic management of CAP was 16.1% (3.1%, 20.7% and 25.4% for patients with mild, moderate and severe CAP, respectively). Ceftriaxone was prescribed to 34.4%, 26.8% and 57.4% of patients with mild, moderate and severe CAP, respectively. The response rate to the barrier survey was 43.1%; of those who responded, 46.4% thought the influence of senior doctors on junior doctors could be a factor affecting adherence to the guidelines. Other barriers noted were a lack of guideline awareness (39.3%), the requirement to calculate the severity of CAP (35.7%), and the existence of other guidelines that conflict with TG14 (28.6%). CONCLUSIONS: Adherence to CAP treatment guidelines was poor, especially in patients with mild disease. Prescribing was mainly influenced by senior doctors. Efforts to improve compliance with CAP treatment guidelines should consider the potential barriers that hinder adherence.

Solid organ transplant recipients: clinical considerations in the application of exercise.

Over 100 000 solid organ transplants are performed worldwide each year and this has a significant impact on physical function and quality of life. However, the capacity for exercise in solid-organ recipients is reduced. Regular physical activity improves most of the indices of fitness in these patients but, with few exceptions, they do not reach the values seen in healthy controls. The reason for the 40-60% reduction in maximal exercise capacity is not clear; the disease process, need for life long immunosuppression and sedentary lifestyle all contribute. The interaction between exercise and immunosuppressing medication merits research as does the specifics of the exercise prescription for these patients. This paper reviews important features of this rapidly expanding group of patients and suggests clinical considerations in the application of exercise in this population.

Subgroup effects in a randomised trial of different types and doses of exercise during breast cancer chemotherapy.

BACKGROUND: The Combined Aerobic and Resistance Exercise Trial tested different types and doses of exercise in breast cancer patients receiving chemotherapy. Here, we explore potential moderators of the exercise training responses. METHODS: Breast cancer patients initiating chemotherapy (N=301) were randomly assigned to three times a week, supervised exercise of a standard dose of 25-30 min of aerobic exercise, a higher dose of 50-60 min of aerobic exercise, or a higher dose of 50-60 min of combined aerobic and resistance exercise. Outcomes were patient-reported symptoms and health-related fitness. Moderators were baseline demographic, exercise/fitness, and cancer variables. RESULTS: Body mass index moderated the effects of the exercise interventions on bodily pain (P for interaction=0.038), endocrine symptoms (P for interaction=0.029), taxane/neuropathy symptoms (P for interaction=0.013), aerobic fitness (P for interaction=0.041), muscular strength (P for interaction=0.007), and fat mass (P for interaction=0.005). In general, healthy weight patients responded better to the higher-dose exercise interventions than overweight/obese patients. Menopausal status, age, and baseline fitness moderated the effects on patient-reported symptoms. Premenopausal, younger, and fitter patients achieved greater benefits from the higher-dose exercise interventions. CONCLUSIONS: Healthy weight, fitter, and premenopausal/younger breast cancer patients receiving chemotherapy are more likely to benefit from higher-dose exercise interventions.

Swimming in air-breathing fishes.

Fishes with bimodal respiration differ in the extent of their reliance on air breathing to support aerobic metabolism, which is reflected in their lifestyles and ecologies. Many freshwater species undertake seasonal and reproductive migrations that presumably involve sustained aerobic exercise. In the six species studied to date, aerobic exercise in swim flumes stimulated air-breathing behaviour, and there is evidence that surfacing frequency and oxygen uptake from air show an exponential increase with increasing swimming speed. In some species, this was associated with an increase in the proportion of aerobic metabolism met by aerial respiration, while in others the proportion remained relatively constant. The ecological significance of anaerobic swimming activities, such as sprinting and fast-start manoeuvres during predator-prey interactions, has been little studied in air-breathing fishes. Some species practise air breathing during recovery itself, while others prefer to increase aquatic respiration, possibly to promote branchial ion exchange to restore acid-base balance, and to remain quiescent and avoid being visible to predators. Overall, the diversity of air-breathing fishes is reflected in their swimming physiology as well, and further research is needed to increase the understanding of the differences and the mechanisms through which air breathing is controlled and used during exercise.

Twisted pair of optic fibers for background removal in radiation fields.

In many situations in which an optic fiber carries a signal through a radiation field, an unwanted background signal is produced consisting of fluorescent and/or Cerenkov light. This presents a major problem in the measurement of the light signal, for example, in scintillation dosimetry of medical therapeutic beams. In this paper, we demonstrate a new method of measuring and removing the background signal through the use of a twisted pair of optic fibers. The twisted pair consists of a fiber carrying the scintillation signal that is twisted with a second optic fiber to form a double helix. The two twisted fibers will experience the same radiation environment provided the periodicity of the twist is correlated to the dose rate gradient. An expression for the required twist periodicity is presented. A scintillation dosimeter with a twisted pair optic fiber was tested in a megavoltage beam and found to accurately measure its beam characteristics. The twisted pair approach is not restricted to medical applications and can be used in many situations in which optical signals are carried through radiation fields.

Settleable atmospheric particulate matter affects the swimming performance and aerobic metabolic rate of Nile tilapia (Oreochromis niloticus).

Atmospheric particulate matter (APM) produced by the steel industry comprises a complex mixture of particles that includes a wide variety of metals and metallic nanoparticles. These particles settle out onto areas surrounding the industries. There is evidence that this 'settleable' APM (SePM) may cause air-to-water cross-contamination with significant effects on aquatic biota. Recent investigations have reported sublethal impacts on the gill structure and blood oxygen-carrying capacity of fishes, which raises the hypothesis that there will be consequences for gas exchange capacity and ability to support aerobic activities. Therefore, we investigated the effects of an environmentally relevant level of SePM contamination on swimming performance and associated aerobic metabolic rates in Nile tilapia, Oreochromis niloticus. Short-term exposure (96 h) to SePM reduced critical swimming speed, energetic efficiency of aerobic swimming, standard metabolic rate, maximum metabolic rate, and aerobic scope. The compromised swimming performance could have adverse ecological effects by limiting foraging ability, predator evasion, territorial protection, and migration. The impairments to aerobic capacity could also affect overall fish performance by influencing long-term energy balance and allocation to growth and reproduction. Thus, despite being sublethal, SePM contamination is considerably debilitating, and if its limiting effects are not compensated for in the longer term, this may reduce the survival and fitness of fish populations.