Solar particle event storm shelter requirements for missions beyond low Earth orbit.

Protecting spacecraft crews from energetic space radiations that pose both chronic and acute health risks is a critical issue for future missions beyond low Earth orbit (LEO). Chronic health risks are possible from both galactic cosmic ray and solar energetic particle event (SPE) exposures. However, SPE exposures also can pose significant short term risks including, if dose levels are high enough, acute radiation syndrome effects that can be mission- or life-threatening. In order to address the reduction of short term risks to spaceflight crews from SPEs, we have developed recommendations to NASA for a design-standard SPE to be used as the basis for evaluating the adequacy of proposed radiation shelters for cislunar missions beyond LEO. Four SPE protection requirements for habitats are proposed: (1) a blood-forming-organ limit of 250 mGy-equivalent for the design SPE; (2) a design reference SPE environment equivalent to the sum of the proton spectra during the October 1989 event series; (3) any necessary assembly of the protection system must be completed within 30 min of event onset; and (4) space protection systems must be designed to ensure that astronaut radiation exposures follow the ALARA (As Low As Reasonably Achievable) principle.

Thrombosis in ovarian cancer: a case control study.

BACKGROUND: Thrombotic events are common in cancer patients and have been associated with an adverse prognosis in large registry-based studies. METHODS: A retrospective cohort of 417 patients with ovarian cancer treated at a tertiary cancer centre between 2006 and 2009 was studied to identify the incidence and risk factors for thrombotic events and the prognostic impact of thrombosis. Patient outcomes were evaluated against a matched control group without thrombosis. RESULTS: Ninety-nine thrombotic events occurred in 90 patients (21.6%) from 8 months before diagnosis to 56 months following diagnosis, peaking in the 4 months following diagnosis. Patients with thrombosis were older (mean 65 vs 61 years, P=0.007), had a worse performance status (PS ≥2: 29.9% vs 9.5%, P<0.0001) and had a more advanced FIGO stage (FIGO III/IV 75.6% vs 56.9%, P<0.0001) than patients without thrombosis. Shorter overall survival was seen in patients with pulmonary embolism and pelvic/lower limb deep vein thrombosis than without thrombosis (P=0.001). When the control group was matched for stage and PS, no survival difference was seen (P=0.91). CONCLUSION: Ovarian cancer patients with thrombotic events had a shorter survival. However, when matched for prognostic factors (PS and FIGO stage), thrombosis did not impact upon prognosis.

Rheology of concentrated carbon nanotube suspensions.

The rheological properties of non-Brownian carbon nanotube suspensions are measured over a range of nanotube volume fractions spanning the transition from semidilute to concentrated. The polymer-stabilized nanotubes are "sticky" and form a quiescent elastic network with a well-defined shear modulus and yield stress that both depend strongly on nanotube volume fraction with different but related critical exponents. We compare controlled-strain-rate and controlled-stress measurements of yielding in shear flow, and we study the effect of slow periodic stress reversal on yielding and the arrest of flow. Our measurements support a universal scaling of both the linear viscoelastic and steady-shear viscometric response. The former allows us to extract the elastic shear modulus of semidilute nanotube networks for values that are near or below the resolution limit of the rheometers used, while the latter provides a similar extrapolation of the yield stress. A simple scaling argument is used to model the dependence of yield stress and elastic modulus on concentration.

Nonequilibrium phase diagram of sticky nanotube suspensions.

We report a universal phase diagram describing the evolution from solidlike networks to flowing nematics for "sticky" nanotube suspensions under an applied shear stress. Although the nanotubes are strongly non-Brownian, we find features characteristic of first-order phase transitions, including a discontinuity in the nematic order parameter at the isotropic-(para)nematic phase boundary. Using simple physical arguments, we account for the shape of the coexistence curves, as well as the dependence of the order parameter on concentration and stress.

Quantitative exposure assessment for the combustion of meat and bone meal derived from specified risk material in the context of BSE in Ireland.

The probability and severity of an adverse event can be analyzed by quantitative exposure assessment (QEA). This methodology was applied to model the human health risks associated with the combustion of specified risk material (SRM) derived meat and bone meal (MBM) in a combustion facility. The identification of MBM and SRM as significant factors in the spread of bovine spongiform encephalopathy (BSE) has resulted in restrictions on their use and movement, and this has led to a requirement for alternative end-uses for these products. A stochastic (Latin Hypercube sampling) simulation model was developed to assess the exposure and hence the risks associated with the use of SRM-derived MBM in a combustion facility. The model simulates the potential infectivity pathways that SRM-derived MBM follows, including its production from animals potentially infected with sub-clinical BSE and subsequent processing of the material with segregation and heat treatments. A failure probability was included to take account of sub-optimal operating conditions. Two scenarios, reflecting the infectivity risk in different animal tissues as defined by the European Commission's scientific steering committee (SSC), were performed with 100,000 iterations of the model. Model results showed that the societal exposure to humans resulting from the combustion of SRM-derived MBM is extremely small (mean values ranging from 7.57 x 10(-6) ID50/year to 8.38 x 10(-5) ID50/year). The resulting societal risks are significantly less than the background societal risk of approximately 2.5 cases of sporadic CJD in Ireland each year. A sensitivity analysis revealed that the species barrier had a large impact on exposure calculations and hence should be the focus of further scientific investigation to reduce our uncertainty about this parameter. The model predicts that material spillage into untreated effluent represents the biggest risk to humans, indicating that efforts for risk mitigation should be focused on reducing the potential for spillage.

Induction and stability of somaclonal variation in growth, leaf phenotype and gas exchange characteristics of poplar regenerated from callus culture.

Populus trichocarpa Torr. and Grey x P. balsamifera L. TT32 lines were regenerated from calli that had been maintained under differing in vitro conditions for sixteen months. In the final months, calli were maintained with one of six concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6 mg l(-1))and regenerated with 0.25, 0.50 or 1.0 mg l(-1) benzylaminopurine (BA). Regenerant lines were obtained from 15 of these 18 treatments. The spectrum of variation in several morphological, physiological and leaf gas exchange traits was evaluated in the primary regenerants in 1986, and in their secondary vegetative propagules in the two subsequent years, in relation to differences in the original culture conditions. The results indicate that somoclonal variation was induced largely as a result of prolonged culture in the presence of 2,4-D, but that the terminal maintenance and regeneration phases also induced changes in the regenerants. Qualitative differences among the regenerant lines were detected by the end of 1986. For most traits, these differences were statistically confirmed within the 3-year period. The treatment lines ultimately diverged sufficiently to produce lines showing general performance that was either above or below that of the original TT32 clone. An early visible indicator of this divergence was variation in leaf shape (leaf length/width ratio), which could be related to 2,4-D-BA interactions in the final stages of culture. Graphic illustration of the independent effects of either 2,4-D or BA on stem height and gas exchange parameters suggested an inverse relationship with BA concentration and a complex interaction with 2,4-D. Significant correlations were detected between gas exchange parameters and morphological characteristics representing leaf form and stem development. Overall, the results indicate the presence of somaclonal lines that offer potential for the selective improvement of growth using morphological and gas exchange parameters as screening tools.

Somaclonal variation in growth, leaf phenotype and gas exchange characteristics of poplar: utilization of leaf morphotype analysis as a basis for selection.

Populus hybrid TT32 lines produced from 15 treatment tissue culture regimes exhibited somaclonal variation in morphological and gas exchange parameters. Within four years of regeneration, discrete lines showing statistically validated superior, or inferior, growth performance relative to the parental reference clone were identified. Significant differences in the ratio of leaf length/width between treatment lines provided the earliest reliable indicator of the divergence in overall growth performance. Despite discernible variation in leaf phenotype among primary regenerants and secondary propagules within individual lines, the leaf length/width ratio was identified as a potential parameter for predicting growth performance. Its subsequent use led to the recognition of four distinct leaf morphotypes; cordate, ovate, reniform and oval. Two or more of these morphotypes were distributed within each of the original 15 treatment lines. Regrouping the data on the basis of leaf morphotype resulted in a clear segregation of the morphological traits, and revealed differences that were not readily apparent by statistical analysis based on treatment groups. The demonstration of similar relative performances by individual morphotypes with respect to a range of growth and gas exchange parameters confirmed that variation in leaf morphology was indicative of differential photosynthetic performance. Somaclonal variants with a leaf morphology was indicative of differential photosynthetic performance. Somaclonal variants with a leaf morphotype closest to that of the parental line showed the highest overall potential for selection, suggesting that the greatest benefits accrue from a minimal disturbance of the parental leaf phenotype.

Evidence from rat liver nuclear preparations that latency of microsomal UDP-glucuronosyltransferase is associated with vesiculation.

1. Nuclear, nuclear-envelope and microsomal preparations were prepared from rat liver, and their purity and morphology monitored by electron microscopy. 2. UDP-glucuronosyltransferase activity in microsomal preparations, but not in standard nuclear or nuclear-envelope preparations, displays latency from the criterion of being enhanced ('activated') by a range of detergents or the endogenous activator UDP-N-acetyl-glucosamine. 3. Nuclear preparations resemble activated rather than native microsomal preparations in failing to transfer glucuronic acid from 4-nitrophenyl glucuronide to 2-aminophenol. 4. Electron microscopy indicates that membranes of nuclear preparations and of our standard nuclear-envelope preparations remain, as in vivo, in a cisternal arrangement, whereas those of microsomal preparations are vesiculated. 5. In nuclear-envelope preparations in which vesiculation has been encouraged, the transferase can be activated by detergents. 6. We suggest that latency of UDP-glucuronosyltransferase results from vesiculation of membranes during preparation and that the latency of the microsomal transferase is largely a preparative artefact.

Photosynthesis of Conifers in Relation to Annual Growth Cycles and Dry Matter Production: I. Some C4 Characteristics in Photosynthesis of Japanese Larch (Larix leptolepis).

Observations that deciduous larch species can show annual growth increments equal to or greater than evergreen conifers, and that the saturating light intensity for photosynthesis in needles of Larix leptolepis was almost twice those for several evergreen conifers, led to a study of the photosynthetic mechanism in L. leptolepis. Several features of photosynthesis in L. leptolepis placed this species in an intermediate position between classical C3 and C4 plants. Incorporation of 14 C from 14 CO2 by enzyme preparations of larch needles was eight times greater with PEP as substrate than with ribulose bis phosphate; a chlorophyll a/b ratio of 3.5 was obtained; needles possessed a green starch-containing endodermis but with little orientation of mesophyll cells to this "bundle sheath"; no clear ultrastructural dimorphism was observed between chloroplasts of mesophyll and endodermal cells; a CO2 -compensation point of 20 µl-l-1 was recorded; and the first measurable product of photosynthesis appeared to be malate rather than phospho-glyceric acid. These results are discussed in relation to the deciduous habit of L. leptolepis and its high productivity in comparison with other conifers.

Sodium fluxes in single amphibian oocytes: further studies and a new model.

1. The kinetics of Na efflux were studied in oocytes of Bufo bufo, Rana temporaria and R. pipiens. 2. Rate constants for Na efflux into Ringer solution varied from 0-002 min-minus 1 to 0-017 min-minus 1 and did not vary significantly from one species to another. 3. Na efflux is rapidly reduced by 30-50% on removing external K or applying ouabain but is reduced by 90% on cooling to 0 degrees C. The effects of K and cooling are also rapidly reversible. 4. Substitution of external Na by Li produces a slow decline of Na efflux. Reversal on restoring external Na is, however, rapid even in the presence of ouabain. 5. When external Na is replaced by Li in the presence of ouabain, the normal decline in Na efflux does not occur. 6. When external Na has been replaced by Li, application of ouabain causes little or no further decline in Na efflux. 7. These results are interpreted quantitatively by means of a model which proposes that intracellular membrane-bounded channels (IMBC) contain 10-30% of the intracellular Na and provide a channel for its expulsion from the cell via connexions with the cell surface. It is supposed that Na is expelled actively from the cytoplasm into the IMBC as well as at the cell surface. Na expulsion via the IMBC is supposed to be insensitive to external K or ouabain. This model accounts for the results using parameters consistent with other investigations by autoradiography and Na-sensitive micro-electrodes. 8. Preliminary electron micrographic evidence shows channels which appear to lead from the cell surface into the cytoplasm and which may correspond with the proposed IMBC of the model.

Location of inexchangeable sodium in the nucleus and cytoplasm of oocytes of Bufo bufo exposed to sodium-free solutions.

1. In oocytes exposed to Ringer solution in which Li substitutes for Na, 13-62% Na is inexchangeable with Li.2. Nuclei of oocytes isolated by dissection in salt solutions swell irrespective of the concentration or ionic components of the solution. When isolated in 4% bovine albumin solutions, swelling is negligible.3. When the nuclei of cells exposed to Li are isolated in 4% albumin solution, less than 6% of the inexchangeable Na is found in the nucleus, while 36-88% of it is found in the cytoplasmic fragments remaining after removal of the nucleus.4. When a Li-exposed cell is crushed in a cellophane bag and dialysed against Ringer or Li-substituted Ringer, 86-92% of the inexchangeable Na diffuses out.5. It thus appears that the inexchangeable Na is located almost entirely in the cytoplasm and hardly at all in the nucleus, and is not bound to macromolecules within the cell.

Autoradiographic demonstration of inhomogeneous distribution of sodium in single oocytes of Bufo bufo.

1. Autoradiography of frozen cells labelled with (22)Na has been used to locate a sequestered fraction of internal Na in the oocyte which exchanges very slowly or not at all with external Li.2. Relative grain density in nucleus and cytoplasm, measured photometrically, was used as an indication of (22)Na distribution within the oocyte. In test experiments grain density fell to 50% within 19 mum of the edge of the section. Owing to the large diameter of the oocyte (> 600 mum) and its nucleus (> 200 mum), this resolution was adequate to determine cytoplasmic/nuclear (C/N) ratios of grain density.3. In oocytes fully loaded with (22)Na, the mean C/N ratio was 0.92 +/- 0.03 (n = 11). After 5 hr exchange in Li-substituted Na-free Ringer solution, the mean C/N ratio was 2.18 +/- 0.04 (n = 11). After 5 hr exchange in Ringer solution as a control, the mean C/N ratio was 1.39 +/- 0.18 (n = 7). The cytoplasm thus contained a fraction of (22)Na inexchangeable with Li, and more slowly exchangeable with Na than that in the nucleus.4. The non-Li-exchangeable fraction of internal Na thus revealed appeared to be quantitatively similar to that already demonstrated by studies of (22)Na fluxes and of internal Na activity by means of Na-sensitive micro-electrodes.