Cyanobacteria in CELSS: Growth strategies for nutritional variation and nitrogen cycling

Cyanobacteria (blue-green algae) are versatile organisms which are capable of adjusting their cellular levels of carbohydrate, protein, and lipid in response to changes in the environment. Under stress conditions there is an imbalance between nitrogen metabolism and carbohydrate/lipid synthesis. The lesion in nitrogen assimilation is at the level of transport: the stress condition diverts energy from the active accumulation of nitrate to the extrusion of salt, and probably inhibits a cold-labile ATP'ace in the case of cold shock. Both situations affect the bioenergetic status of the cell such that the nitrogenous precursors for protein synthesis are depleted. Dispite the inhibition of protein synthesis and growth, photosynthetic reductant generation is relatively unaffected. The high O2 reductant would normally lead to photo-oxidative damage of cellular components; however, the organism copes by channeling the 'excess' reductant into carbon storage products. The increase in glycogen (28 to 35 percent dry weight increase) and the elongation of lipid fatty acid side chains (2 to 5 percent dry weight increase) at the expense of protein synthesis (25 to 34 percent dry weight decrease) results in carbohydrate, lipid and protein ratios that are closer to those required in the human diet. In addition, the selection of nitrogen fixing mutants which excrete ammonium ions present an opportunity to tailor these micro-organisms to meet the specific need for a sub-system to reverse potential loss of fixed nitrogen material

Application of photosynthetic N2-fixing cyanobacteria to the CELSS program

Commercially available air lift fermentors were used to simultaneously monitor biomass production, N2-fixation, photosynthesis, respiration, and sensitivity to oxidative damage during growth under various nutritional and light regimes, to establish a data base for the integration of these organisms into a Closed Ecological Life Support System (CELSS) program. Certain cyanobacterial species have the unique ability to reduce atmospheric N2 to organic nitrogen. These organisms combine the ease of cultivation characteristics of prokaryotes with the fully developed photosynthetic apparatus of higher plants. This, along with their ability to adapt to changes in their environment by modulation of certain biochemical pathways, make them attractive candidates for incorporation into the CELSS program

A simulation study of two major events in the heliosphere during the present sunspot cycle

The two major disturbances in the heliosphere during the present sunspot cycle, the event of June to August, 1982, and the event of April to June, 1978, are simulated by the method developed by Hakamada and Akasofu (1982). Specifically, an attempt was made to simulate the effects of six major flares from three active regions in June and July, 1982, and April and May, 1978. A comparison of the results with the solar wind observations at Pioneer 12 (approximately 0.8 au), ISEE-3 (approximately 1 au), Pioneer 11 (approximately 7 to 13 au) and Pioneer 10 (approximately 16 to 28 au) suggests that some major flares occurred behind the disk of the sun during the two periods. The method provides qualitatively some information as to how such a series of intense solar flares can greatly disturb both the inner and outer heliospheres. A long lasting effect on cosmic rays is discussed in conjunction with the disturbed heliosphere

Large-scale structure and the redshift-distance relation

In efforts to demonstrate the linear Hubble law v = Hr from galaxy observations, the underlying simplicity is often obscured by complexities arising from magnitude-limited data. In this paper we point out a simple but previously unremarked fact: that the shapes and orientations of structures in redshift space contain in themselves independent information about the cosmological redshift-distance relation. The orientations of voids in the CfA slice support the Hubble law, giving a redshift-distance power index p = 0.83 +/- 0.36 (void data from Slezak, de Lapparent, & Bijoui 1993) or p = 0.99 +/- 0.38 (void data from Malik & Subramanian 1997).Comment: 11 pages (AASTeX), 4 figures, to appear in the Astrophysical Journal Letter

Anxiety Associated With Increased Risk for Emergency Department Recidivism in Patients With Low-Risk Chest Pain

Anxiety contributes to the chest pain symptom complex in 30% to 40% of patients with low-risk chest pain seen in the emergency department (ED). The validated Hospital Anxiety Depression Scale-Anxiety subscale (HADS-A) has been used as an anxiety screening tool in this population. The objective was to determine the prevalence of abnormal HADS-A scores in a cohort of low-risk chest pain patients and test the association of HADS-A score with subsequent healthcare utilization and symptom recurrence. In a single-center, prospective, observational cohort study of adult ED subjects with low-risk chest pain, the HADS-A was used to stratify participants into 2 groups: low anxiety (score <8) and high anxiety (score ≥8). At 45-day follow-up, chest pain recurrence was assessed by patient report, whereas ED utilization was assessed through chart review. Of the 167 subjects enrolled, 78 (47%) were stratified to high anxiety. The relative risk for high anxiety being associated with at least one 30-day ED return visit was 2.6 (95% confidence interval 1.4 to 4.7) and this relative risk increased to 9.1 (95% confidence interval 2.18 to 38.6) for 2 or more ED return visits. Occasional chest pain recurrence was reported by more subjects in the high anxiety group, 68% vs 47% (p = 0.029). In conclusion, 47% of low-risk chest pain cohort had abnormal levels of anxiety. These patients were more likely to have occasional recurrence of their chest pain and had an increased risk multiple ED return visits

Fermion Determinants

The current status of bounds on and limits of fermion determinants in two, three and four dimensions in QED and QCD is reviewed. A new lower bound on the two-dimensional QED determinant is derived. An outline of the demonstration of the continuity of this determinant at zero mass when the background magnetic field flux is zero is also given.Comment: 10 page

Failure of the Standard Coupled-Channels Method in Describing the Inelastic Reaction Data: On the Use of a New Shape for the Coupling Potential

We present the failure of the standard coupled-channels method in explaining the inelastic scattering together with other observables such as elastic scattering, excitation function and fusion data. We use both microscopic double-folding and phenomenological deep potentials with shallow imaginary components. We argue that the solution of the problems for the inelastic scattering data is not related to the central nuclear potential, but to the coupling potential between excited states. We present that these problems can be addressed in a systematic way by using a different shape for the coupling potential instead of the usual one based on Taylor expansion.Comment: 10 pages, 4 figures, 1 table, Latex:RevTex4 published in J. Phys. G: Nucl. Part. Phy

A New Coupling Potential for the Scattering of Deformed Light Heavy-Ions

This letter introduces a new coupling potential to explain the experimental data over wide energy ranges for a number of systems. Within the coupled-channels formalism, this letter first shows the limitations of the standard coupled-channels theory in the case where one of the nuclei in the reaction is strongly deformed and then, demonstrates that a global solution to the problems of light heavy-ion reactions such as $^{12}$C+$^{12}$C, $^{16}$O+$^{28}$Si and $^{12}$C+$^{24}$Mg can be found using a new second-derivative coupling potential in the coupled-channels formalism. This new approach consistently improves the agreement with the experimental data for the elastic and inelastic scattering data as well as for their excitation functions using constant or slightly energy-dependent parameters.Comment: 4 Pages, 5 Figures, submitted to the Phys. Lett.

Multiple zero modes of the Dirac operator in three dimensions

One of the key properties of Dirac operators is the possibility of a degeneracy of zero modes. For the Abelian Dirac operator in three dimensions the construction of multiple zero modes has been sucessfully carried out only very recently. Here we generalise these results by discussing a much wider class of Dirac operators together with their zero modes. Further we show that those Dirac operators that do admit zero modes may be related to Hopf maps, where the Hopf index is related to the number of zero modes in a simple way.Comment: Latex file, 20 pages, no figure