Linear phase-and-frequency-modulated photonic links using optical discriminators.

We report our experimental results for linear analog optical links that use phase or frequency modulation and optical discrimination. The discriminators are based on two architectures: a cascaded MZI FIR lattice filter and a ring assisted MZI (RAMZI) IIR filter. For both types of discriminators, we demonstrate > 6 dB improvement in the link's third-order output intercept point (OIP3) over a MZM link. We show that the links have low second-order distortion when using balanced detection. Using high optical power, we demonstrate an OIP3 of 39.2 dBm. We also demonstrate 4.3dB improvement in signal compression.

The operational mental health consequences of deployment to Iraq for UK Forces.

UK Forces are currently engaged in high tempo, high intensity operations in both Iraq and Afghanistan. Concern has been raised about the impact of current operations upon the mental health of Service personnel. Using data gathered from deployed Field Mental Health Teams, a random sample of UK based non-deployed Community Mental Health Teams and services dedicated to mobilising, de-mobilising and to de-mobilised Reserve Forces, this paper explores the current mental health burden for UK Forces. At present, operationally related psychological disorders do not appear to be a substantial concern for Regular Forces, although for the minority that suffer such problems they are both distressing and of occupational relevance. Proportionately there are more mobilised Reserve Forces seeking help for mental health problems than Regular Forces on operations, but the overall burden that they currently place upon the Defence Mental Health Services is small. There is at present no evidence of an epidemic of mental health problems amongst either Regular or Reserve Forces veterans of the Op TELIC deployment, however, this may change in the future given the evolving nature and fluctuating intensity of operational activity.

A hybrid electroabsorption modulator device for generation of high spectral-efficiency optical modulation formats.

We report a novel hybrid integrated optic device consisting of AlGaInAs/InP electroabsorption modulators and a four-arm silica-on-silicon planar lightwave circuit optical interferometer. The device is designed for generation of high spectral efficiency optical modulation formats. We demonstrate generation of 21.4 Gb/s quadrature phase shift keyed optical signals with electrical data drives of 2V(pp) amplitudes, achieving a bit error rate of 10(-9) with the required optical signal to noise ratio of ~18 dB in a 0.1 nm resolution bandwidth.

Risk factors for post-traumatic stress disorder among UK Armed Forces personnel.

BACKGROUND: There is considerable interest in understanding further the factors that increase the risk of post-traumatic stress disorder (PTSD) for military personnel. This study aimed to investigate the relative contribution of demographic variables; childhood adversity; the nature of exposure to traumatic events during deployment; appraisal of these experiences; and home-coming experiences in relation to the prevalence of PTSD 'caseness' as measured by a score of 50 on the PTSD Checklist (PCL) in UK Armed Forces personnel who have been deployed in Iraq since 2003. METHOD: Data were drawn from the first stage of a retrospective cohort study comparing UK military personnel who were deployed to the 2003 Iraq War with personnel serving in the UK Armed Forces on 31 March 2003 but who were not deployed to the initial phase of war fighting. Participants were randomly selected and invited to participate. The response rate was 61%. We have limited these analyses to 4762 regular service individuals who responded to the survey and who have been deployed in Iraq since 2003. RESULTS: Post-traumatic stress symptoms were associated with lower rank, being unmarried, having low educational attainment and a history of childhood adversity. Exposure to potentially traumatizing events, in particular being deployed to a 'forward' area in close contact with the enemy, was associated with post-traumatic stress symptoms. Appraisals of the experience as involving threat to one's own life and a perception that work in theatre was above an individual's trade and experience were strongly associated with post-traumatic stress symptoms. Low morale and poor social support within the unit and non-receipt of a home-coming brief (psycho-education) were associated with greater risk of post-traumatic stress symptoms. CONCLUSIONS: Personal appraisal of threat to life during the trauma emerged as the most important predictor of post-traumatic stress symptoms. These results also raise the possibility that there are important modifiable occupational factors such as unit morale, leadership, preparing combatants for their role in theatre which may influence an individual's risk of post-traumatic stress symptoms. Therefore interventions focused on systematic preparation of personnel for the extreme stress of combat may help to lessen the psychological impact of deployment.

Photosynthetic pathway, chilling tolerance and cell sap osmotic potential values of grasses along an altitudinal gradient in Papua New Guinea.

A total of 22 grass species were examined from 5 sites spanning the altitudinal range 1550-4350 m.a.s.l. The presence of the C3 or C4 photosynthetic pathway was determined from δ13C values and chilling tolerance was assessed on the basis of electrolyte leakage from leaf slices incubated on melting ice. Most of the grasses studied at the lower altitude sites of 1550 m.a.s.l. (annual mean of daily minimum temperature, 14.6° C) and 2600 m.a.s.l. (9.4° C) possessed C4 photosynthesis and were chill-sensitive. The single except ion was Agrostis avenacea, a montane chill-resistant C3 species which occurred at 2600 m.a.s.l. The three species apparently most sensitive to chilling were Ischaemum polystachyum, Paspalum conjugatum and Saccharum robustum, all occurring at 1550 m.a.s.l. At the higher altitude sites of 3280 (5.6° C), 3580 (4.0° C) and 4350 (-0.7°C) m.a.s.l., most of the grasses exhibited C3 photosynthesis and were chill-resistant. However, an Upland population of the C4 species, Miscanthus floridulus was found at 3280 m.a.s.l. which had acquired chill-resistance as confirmed by additional in vivo variable chlorophyll fluorescence measurements. Cell sap osmotic potential values of the upland grasses at altitudes of 3280-4350 m.a.s.l. were lower (-8.1 to -19.8 bars) than values in grasses from 1550 and 2600 m.a.s.l. (-3.9 to -7.5 bars) due mainly to the presence of non-electrolyte osmoticants, which may be involved in frost avoidance mechanism(s).

Failure of mebendazole to cure trichomonal vaginitis resistant to metronidazole: case reports.

After a recent report showing the in vitro susceptibility to mebendazole of a strain of Trichomonas vaginalis that was resistant to metronidazole, we present two cases of metronidazole resistant infection, both of which failed to respond to oral mebendazole.

Temperature dependent factors influencing nutrient uptake: an analysis of responses at different levels of organization.

Ion fluxes show a characteristically biochemical dependence on temperature when observed at the membrane level and over short periods after a perturbation of temperature. The primary active transport systems are enzymic and are dependent both on substrate supply and on changes in protein conformation. The hydrophobic parts of the proteins are surrounded by lipid molecules whose physical state may crucially affect conformation changes. These lipids may undergo transitions from a fluid to a gel state at temperatures occurring in the natural environment. It will be noted that the concepts developed in model systems of pure phospholipid/protein interactions cannot be very readily applied to the spatially heterogeneous assemblies of lipid molecules and transport proteins in real cell membranes. While it is obvious that ion transport rates are responsive to temperature changes in a given cell, it is difficult to explain exactly which components of the transport process become limiting. We will show that, on cooling, the membrane potential can initially be greatly disturbed when temperature is changed and that this may be related to ATP supply to H+-translocating ATPase. This affects the driving force for all other solutes. When temperature is lowered the permeability coefficients for most ions are reduced and yet it is commonly found that diffusive efflux of ions increases in the cold. We attempt to explain this paradox on the basis of driving forces and metabolic regulation of ion transport. Acclimatory changes occur on extended exposure of a cell or an organism to a reduced growth temperature. Some of these changes occur at the membrane level and relate to lipid composition and modulation of carrier activity. Others involve changes in the relative size and sometimes the morphology of the root system. We will show that these processes lessen the temperature dependence of ion transport and ensure that the intake of nutrients does not limit growth at low temperatures. These acclimatory changes are seen as part of the general process of regulation of nutrient uptake.

Short-term studies on the use of amino acids as an osmotic agent in continuous ambulatory peritoneal dialysis.

1. A 1% amino acid dialysis solution with a high concentration of the branched-chain amino acids has been compared with 1.36% glucose in short-term studies. 2. The 1% amino acid solution was as effective an agent as 1.36% glucose with respect to ultrafiltration and clearance of creatinine, urea and potassium. 3. Levels of branched-chain amino acids rose to the upper end of the normal range within 1 h and remained at this level over the entire period of the study. Total and non-essential amino acids had returned to baseline by the end of the cycle. 4. Blood glucose rose to significantly greater levels during the 1.36% glucose exchange than during the 1% amino acid exchange. There was an increase in serum insulin levels during both cycles; this was significantly greater with the 1% amino acid solution than the 1.36% glucose. 5. There was no evidence of short-term metabolic complications with the 1% amino acid solution.

Acclimation of potassium influx in rye (Secale cereale) to low root temperatures.

The influx of K(+)((86)Rb(+)) into intact roots of rye (Secale cereale L. cv. Rheidal) exposed to a differential temperature (DT) between the root (8° C) and shoot (20° C) is initially reduced compared with warm-grown (WG) controls with both shoot and root maintained at 20° C. Over a period of 3 d, however, K(+)-influx rates into DT plants are restored to levels similar to or greater than those of the WG controls, the absolute rates of K(+) influx being strongly dependent upon the shoot/root ratio. Acclimation in DT plants results in a reduction of K(+) influx into the apical (0-2 cm) region of the seminal root which is associated with a compensatory increase in K(+) influx into the more mature, basal regions of the root. Values of V max and apparent K m for K(+) influx into DT plants were similar to those for WG plants at assay temperatures of 8° C and 20° C except for an increase in the apparent K m at 8° C. The influx of K(+) from solutions containing 0.6 mol·m(-3) K(+) into both WG and DT plants was found to be linearly related to assay temperature over the range 2-27° C, and the temperature sensitivity of K(+) influx to be dependent upon shoot/root ratio. At high shoot/root ratios, the ratio of K(+) influx at 20° C:K(+) influx at 8° C for WG plants approached a minimum value of 1.9 whereas that for DT plants approached unity indicating that K(+) influx into DT plants has a large temperature-insensitive component. Additionally, when plants were grown in solutions of low potassium concentration, K(+) influx into DT plants was consistently greater than that into WG plants, in spite of having a greater root potassium concentration ([K(+)]int). This result indicates some change in the regulation of K(+) influx by [K(+)]int in plants exposed to low root temperatures. We suggest that K(+) influx into rye seedlings exposed to low root temperatures is regulated by the increased demand placed on the root system by a proportionally larger shoot and that the acclimation of K(+) influx to low temperatures may be the result of an increased hydraulic conductivity of the root system.

Leaf anatomy, water relations and crassulacean acid metabolism in the chlorenchyma and colourless internal water-storage tissue of Carpobrotus edulis and Senecio ?mandraliscae.

Both Carpobrotus edulis and Senecio ?mandraliscae possess leaves with a peripheral chlorenchyma and colourless internal water-storage tissue. Water stress in C. edulis growing under semi-natural conditions resulted in the induction of weak Crassulacean acid metabolism (CAM) whereas well-watered plants of S. ?mandraliscae exhibited a similar degree of CAM. Titratable acidity in the separated water-storage tissue was substantially lower than in the chlorenchyma in both species but, nevertheless, increased during the night and decreased during the day either when sampled from the intact plant or from incubated tissue slices. Indeed, the increase in nocturnal titratable acidity produced by the water-storage tissue in situ accounted for approx. 30% of total acidification on a per-leaf basis. It appears that during the night the water-storage tissue in these species is able to fix CO2 which is subsequently released during the day to enter the photosynthetic carbon-reduction cycle of the chlorenchyma. Diurnal rhythms of water potential (Ψ) and osmotic potential (Ψs) were measured in separated chlorenchyma and water-storage tissue by thermocouple psychrometry. Both parameters increased during the latter part of the daytime and initial nocturnal period and decreased during the rest of the night and into the post-dawn period. The chlorenchyma of water-stressed plants of C. edulis appeared to possess a marked negative turgor pressure (as determined from Ψ-Ψs) but this was caused by a severe underestimation in the measurement of the chlorenchyma Ψ. It is suggested that this artefact arose from release of colloidal polysaccharide mucilage, or possibly tannins, from broken tannin cells producing a lowering of water activity when measured using thermocouple psychrometry.

Altitudinal changes in the incidence of crassulacean acid metabolism in vascular epiphytes and related life forms in Papua New Guinea.

The occurrence of Crassulacean acid metabolism (CAM), as judged from δ13C values, was investigated in epiphytes and some related plant species at a series of sites covering the approximate altitudinal range of epiphytes in Papua New Guinea. Comprehensive collections were made at each site and the occurrence of water storage tissue and blade thickness was also determined. Some 26% of epiphytic orchids from a lowland rainforest (2-300 m.a.s.l) showed δ13C values typical of obligate CAM and possessed leaves thicker than 1 mm. A second group of orchids, mostly with succulent leaves, possessed intermediate δ13C values between -23 and -26% and accounted for 25% of the total species number. Some species of this group may exhibit weak CAM or be facultative CAM plants. The remainder of the lowland rainforest species appeared to be C3 plants with δ13C values between -28 and -35%. and generally possessed thin leaves. Obligate CAM species of orchids from a lower montane rainforest (1175 m.a.s.l) comprised 26% of the species total and mostly possessed thick leaves. The remainder of the species were generally thin-leaved with δ13C values between -26 and -35%. largely indicative of C3 photosynthesis. Orchids with intermediate δ13C values were not found in the lower montane rainforest. Obligate CAM appeared to be lacking in highland epiphytes from an upper montane rainforest and subalpine rainforest (2600-3600 m.a.s.l). However the fern, Microsorium cromwellii had a δ13C value of -21.28%. suggesting some measure of CAM activity. Other highland ferns and orchids showed more negative °13C values, up to-33%., typical of C3 photosynthesis. The highland epiphytic orchids possessed a greater mean leaf thickness than their lowland C3 counterparts due to the frequent occurrence of water storage tissue located on the adaxial side of the leaf. It is suggested that low daytime temperatures in the highland microhabitats is a major factor in explaining the absence of CAM. The increased frequency of water storage tissue in highland epiphytes may be an adaptation to periodic water stress events in the dry season and/or an adaptation to increased levels of UV light in the tropicalpine environment.

Comparative effects of alfacalcidol and parathyroidectomy with vitamin D in hyperparathyroid renal bone disease.

Parathyroidectomy is now rarely undertaken for hyperparathyroid bone disease in chronic uraemia unless treatment with 1 alpha-hydroxylated vitamin D3 derivatives is unsuccessful. However, no comparisons have been reported of the use of parathyroidectomy with 1 alpha-hydroxylated vitamin D3 derivatives in patients with bone disease of comparative severity. We studied 14 uraemic patients on maintenance haemodialysis treatment before and after treatment with 1 alpha-hydroxyvitamin D3 (alfacalcidol) and compared the findings with those from 12 patients studied before and after parathyroidectomy followed by treatment with vitamin D. The initial severity of the bone disease in the two groups was similar as judged by biochemical, radiographic and histological findings. Both groups demonstrated significant falls in plasma alkaline phosphatase (p less than 0.005) and healing of radiographic erosions after treatment. The histological changes in bone, however, were more marked in patients after parathyroidectomy. Significant reductions were observed in the active osteoblastic surface (p less than 0.005), the total resorption surface (p less than 0.05), the active resorption surface (p less than 0.02) and the index of marrow fibrosis (p less than 0.001), but these indices did not change significantly in the alfacalcidol-treated patients. We concluded that the responses to alfacalcidol in bone are less complete than those obtained with parathyroidectomy despite similar biochemical and radiographic responses.

The action of heavy metals on the gametes of the marine mussel, Mytilus edulis (L.)--I. Copper-induced uncoupling of respiration in the unfertilized egg.

The direct addition of Cu2+ to unfertilized eggs of Mytilus edulis results in a stimulation of respiration with maximal stimulation occurring at a Cu2+ concentration of ca 0.5 mM. By contrast, the addition of Zn2+ has no effect on egg respiration. The uncoupler CCCP produces a 5/6 fold stimulation of egg respiration but the addition of ADP leads to only a small release of respiration. In contrast, sperm respiration is unaffected by Cu2+, inhibited by Zn2+ and CCCP produces only a small respiratory stimulation. The addition of Cu2+ to respiring Mytilus mantle tissue mitochondria produces an initial stimulation of State 4 oxidation which is then followed by a progressive inhibition. It is suggested that respiration in the unfertilized egg may be inhibited by a high ATP/ADP ratio in the cytosol. Respiration can, therefore, be released by either the addition of a H+-translocating uncoupler or by Cu2+ which may act by stimulating mitochondrial K+ influx.

Copper-stimulated respiration in the unfertilized egg of the Eurasian perch, Perca fluviatilis (L).

The addition of Cu2+ (0.1-1.0 mM) to respiring, unfertilized eggs produced a marked stimulation in the rate of respiration whereas Zn2+ had no effect over the same concentration range. In the absence of Cu2+, temperature had little effect on unfertilized egg respiration but the Cu2+ stimulated respiratory rate showed the more normal response with a Q10 of 1.86 (10-20 degrees C). It appears that perch egg respiration is rate-limited by a physical event and it is suggested that Cu2+ may act by dissipating an oxygen permeability barrier located at the chorion.

Vitamin A and hyperparathyroid bone disease in uremia.

The possible contribution of hypervitaminosis A to bone disease in uremia was examined in 50 dialysis-treated patients with end-stage chronic renal failure. None of the patients received dietary supplements of vitamin A. In common with previous investigations, plasma concentrations of total vitamin A and the retinol-binding protein (RBP) were increased in patients, but the molar ratio of vitamin A to RBP was significantly lower than control values. A significant correlation was noted between concentrations in plasma of vitamin A and RBP. No significant relationship was found between vitamin A or the vitamin A/RBP ratio, and the measured biochemical, radiographic, or histological indices of hyperparathyroidism and bone resorption. We conclude that the elevated plasma values of vitamin A in uremia are largely attributable to the high concentrations of RBP and do not contribute significantly to the pathogenesis of renal osteodystrophy.

The mechanism of calcium transport in mitochondria isolated from the marine mussel, Mytilus edulis (L.).

Isolated mussel mitochondria produced a less pronounced transient stimulation of respiration upon the addition of Ca2+ in a reaction medium containing Pi and a slower rate of Ca2+ transport compared to rat liver mitochondria. The initial rates of Ca2+ transport in the absence of Pi were more similar and both types of mitochondria possessed a sigmoidal relationship between the initial rate of Ca2+ transport and the free Ca2+ concentration ("Km" approximately 5 microM). Ruthenium red produced an equal maximal inhibition of the initial rate of Ca2+ transport in both types of mitochondria but mussel mitochondria were rather more resistant to the inhibitor. The major difference found was that approximately 15 nmoles La3+ mg protein-1 was required to produce maximal inhibition of the initial rate of Ca2+ transport in mussel mitochondria compared to approximately 1.0 nmole La3+ mg protein-1 in rat liver mitochondria. It is concluded that mussel mitochondria possess a comparable Ca2+ transporter to vertebrate mitochondria and possible reasons for resistance to La3+ are discussed.

Deterioration of renal bone disease in patients treated with salmon calcitonin.

Twelve patients with chronic renal failure and osteitis fibrosa were treated for periods of 1-9 months with thrice-weekly injections of 10-200 iu salmon calcitonin. Treatment had no significant effects on symptoms of bone disease and side effects were common. A transient fall in plasma alkaline phosphatase levels occurred in only three patients, and both plasma alkaline phosphatase and hydroxyproline levels rose in the majority of patients. Radiographic signs of hyperparathyroidism increased in seven of the nine patients treated for longer than 3 months. Paired bone biopsy specimens in nine patients showed significant increases in osteoblast counts, but no changes in the indices of resorption. These treatment-induced changes were reversed when treatment with 1,25-dihydroxyvitamin D3 was substituted for calcitonin. The use of this regimen of salmon calcitonin is not recommended in the long-term management of hyperparathyroid bone disease in chronic renal failure.