An evidence-based system for health surveillance of occupational divers.

BACKGROUND: The value of the commonly required routine annual medical examination of occupational divers has been questioned, and there is a need for a robust, evidence-based system of health surveillance for this group of workers. AIMS: To determine whether the medical examination and investigation component of occupational divers' routine comprehensive health surveillance adds significantly to the information gained from the questionnaire component in determining fitness for diving. METHODS: An occupational diver database was interrogated to identify divers issued with a 'limited' medical clearance or considered 'unfit' for diving over a 5-year period. Reasons for the 'unfit' or 'limited' designation and the source of the critical information, whether the annual health questionnaire or the medical examination or questionnaire component (or both) of the initial or 5-yearly comprehensive medical evaluation, was recorded. For divers completing the 5-yearly repeat comprehensive medical evaluation, the sensitivity and specificity of the questionnaire alone for determining unfitness for diving was compared with that of a nominal 'gold standard'. RESULTS: Of 5178 certificates issued to 2187 divers over a 5-year period, 158 (3%) were provisionally designated as either 'limited' or 'unfit'. Of nine divers identified by the examination component of the 5-yearly comprehensive medical evaluation, four were eventually designated 'fit', two 'limited', and three were lost to follow up. None who had completed subsequent investigations remained 'unfit'. The sensitivity and specificity of the questionnaire to detect unfit divers compared with the gold standard were 84.6 and 99.3%, respectively, and its accuracy was 98.9%. CONCLUSION: The current New Zealand occupational diver medical certification process, comprising annual health questionnaires and 5-yearly full examinations, detects all health issues critical to the determination of fitness to dive.

Arm bone loading index predicts DXA musculoskeletal outcomes in two samples of post-menarcheal girls.

OBJECTIVE: A site-specific bone loading index was developed to predict post-menarcheal arm bone mass, geometry, areal density and non-bone lean mass using organized activity records. METHODS: Two cohorts of post-menarcheal girls (A= 55, B= 48) met analysis inclusion criteria: (1) Whole body and non-dominant radius DXA scans +1.0 to +2.6 years post-menarche; (2) detailed, organized activity records available for 36 months prior to the focal DXA scan; (3) accompanying anthropometric data. DXA non-dominant arm and radius regions of interest (1/3, Ultradistal (UD)) were evaluated. An arm bone loading index (arm totBLI) was developed and refined to describe >50 activities. Separate regression analyses for Cohorts A&B tested explanatory value of arm totBLI for DXA outcomes, accounting for gynecological age, height and whole body non-bone lean mass. RESULTS: In both cohorts, arm totBLI reflecting 3 years of peri-menarcheal activity exposure exhibited strong explanatory value for post-menarcheal radius and arm outcomes (squared semi-partial r =0.07-0.34, p<0.05), except Arm Area. For both cohorts and most outcomes, arm totBLI explained significant variance, even after adjusting for local muscle mass. CONCLUSIONS: In two independent cohorts, arm totBLI may consistently indicate osteogenic and sarcogenic properties of represented activities; additional research is necessary for further refinement and validation.

Antiresonance phase shift in strongly coupled cavity QED.

We investigate phase shifts in the strong coupling regime of single-atom cavity quantum electrodynamics. On the light transmitted through the system, we observe a phase shift associated with an antiresonance and show that both its frequency and width depend solely on the atom, despite the strong coupling to the cavity. This shift is optically controllable and reaches 140°--the largest ever reported for a single emitter. Our result offers a new technique for the characterization of complex integrated quantum circuits.

Observation of squeezed light from one atom excited with two photons.

Single quantum emitters such as atoms are well known as non-classical light sources with reduced noise in the intensity, capable of producing photons one by one at given times. However, the light field emitted by a single atom can exhibit much richer dynamics. A prominent example is the predicted ability of a single atom to produce quadrature-squeezed light, which has fluctuations of amplitude or phase that are below the shot-noise level. However, such squeezing is much more difficult to observe than the emission of single photons. Squeezed beams have been generated using macroscopic and mesoscopic media down to a few tens of atoms, but despite experimental efforts, single-atom squeezing has so far escaped observation. Here we generate squeezed light with a single atom in a high-finesse optical resonator. The strong coupling of the atom to the cavity field induces a genuine quantum mechanical nonlinearity, which is several orders of magnitude larger than in typical macroscopic media. This produces observable quadrature squeezing, with an excitation beam containing on average only two photons per system lifetime. In sharp contrast to the emission of single photons, the squeezed light stems from the quantum coherence of photon pairs emitted from the system. The ability of a single atom to induce strong coherent interactions between propagating photons opens up new perspectives for photonic quantum logic with single emitters.

Photon-by-photon feedback control of a single-atom trajectory.

Feedback is one of the most powerful techniques for the control of classical systems. An extension into the quantum domain is desirable as it could allow the production of non-trivial quantum states and protection against decoherence. The difficulties associated with quantum, as opposed to classical, feedback arise from the quantum measurement process-in particular the quantum projection noise and the limited measurement rate-as well as from quantum fluctuations perturbing the evolution in a driven open system. Here we demonstrate real-time feedback control of the motion of a single atom trapped in an optical cavity. Individual probe photons carrying information about the atomic position activate a dipole laser that steers the atom on timescales 70 times shorter than the atom's oscillation period in the trap. Depending on the specific implementation, the trapping time is increased by a factor of more than four owing to feedback cooling, which can remove almost all the kinetic energy of the atom in a quarter of an oscillation period. Our results show that the detected photon flux reflects the atomic motion, and thus mark a step towards the exploration of the quantum trajectory of a single atom at the standard quantum limit.

Utility of regular medical examinations of occupational divers.

The utility of regular medical fitness-for-diving examinations of occupational divers is unknown. The aim of this audit was to investigate the impact on the employment of occupational divers of a 5-yearly medical examination and an annual health surveillance questionnaire administered in intervening years. The medical records of all New Zealand occupational divers registered with the Department of Labour for at least 5 years were audited (n= 336). Each record included at least two full medical examinations (mean spacing of 5.6 years). An impact on career was defined as the diver being issued with either a conditional certificate of fitness or being graded as temporarily or permanently unfit for diving. The means by which the relevant medical issue was identified was recorded. Ten (3%) of 336 divers had an assessment outcome, which had a career impact. One was considered permanently unfit, four were temporarily unfit, and five were issued with conditional certification. Two were identified by respiratory function testing and eight by way of their responses to the questionnaire; none was found by the medical interview and examination process. The questionnaire system did not 'miss' any divers who developed a critically important health problem, and detected most of those with less important problems. Five yearly medical examinations have a low detection rate for important health problems, but remain useful for discussion of risk understanding, acceptance and mitigation.

A case of type 3 DCS with a radiologically normal spinal cord.

A subtype of cerebral arterial gas embolism arising in divers, in which apparent spinal cord disease follows early cerebral manifestations, is well known and has been described as type 3 DCS. A case that clinically conformed to the pattern of type 3 DCS was examined radiologically. Despite clinical signs of spinal disease, magnetic resonance imaging scans of the spinal cord did not demonstrate pathology.

Abdominal fat distribution in pre- and postmenopausal women: The impact of physical activity, age, and menopausal status.

Age-related increases in total body fat have been reported, but the impact of menopause on abdominal fat distribution is still unclear. The purpose of this study was to determine the impact of menopausal status on abdominal fat distribution using magnetic resonance imaging (MRI). In addition, we investigated the influence of abdominal fat distribution on blood lipid profiles and leptin concentrations. Twenty-three premenopausal (PRE), 27 postmenopausal (POST), and 28 postmenopausal women on estrogen replacement therapy (ERT) had measurements of regional abdominal fat, blood lipids, and serum leptin concentrations. The women were matched for body mass index (BMI) and total body fat mass. Age and menopausal status were not found to be significant predictors of total abdominal fat, visceral fat, or subcutaneous fat, while physical activity was a significant predictor (P <.01) for total abdominal fat (R(2) =.16), visceral fat (R(2) =.32) and percent visceral fat (R(2) =.25). There was a trend for a greater visceral fat content in the POST women compared with the PRE women (2,495.0 +/- 228.4 v 1,770.4 +/- 240.8 cm(2), respectively, P =.06). The percent visceral abdominal fat was significantly lower (P <.05) in the premenopausal women than in either postmenopausal group (PRE, 23.2% +/- 1.7%; POST, 28.9% +/- 1.8%; ERT, 28.9% +/- 1.6%). Menopausal status and age did not influence any of the blood lipid values. Abdominal fat distribution was a significant predictor of cholesterol concentrations and the cholesterol/high-density lipoprotein-cholesterol (HDL-C) ratio, but only accounted for approximately 15% of the variability in these levels. Total body fat and physical activity accounted for 47% of the variability in leptin concentrations, while abdominal fat distribution, age, and menopausal status were not significant predictors. In conclusion, in early postmenopausal women, the level of physical activity accounts for the variability in abdominal fat distribution observed, while menopausal status and age do not play a significant role. ERT was not associated with additional benefits in abdominal fat distribution compared with postmenopausal women not on ERT or in the blood lipid profile in these women.