Alvin titanium electrical penetrator design, manufacture, and testing : interim report

Under the U.S. Navy's Project TITANES a new titanium alloy pressure hull has been designed, built, and installed for use in the deep-submersible ALVIN. The Woods Hole Oceanographic Institution was assigned the task of designing, procuring and testing the through-hull electrical penetrators for the new sphere. This interim report traces the progress of this Woods Hole program from the initial design stage, through the various phases of manufacture and electrical testing, to the installation of the units in the completed hull, and the numerous laboratory~ pressure tank, and at-sea tests conducted to verify the satisfactory performance of the new penetrators. The results of all laboratory and in-service testing done to date support the conclusion that the performance of the titanium penetrators meets all of the original specifications.Office of Naval Research Contract No. NOr014-73-C-0097 NR 265-10

The impact of phages on interspecific competition in experimental populations of bacteria

BACKGROUND: Phages are thought to play a crucial role in the maintenance of diversity in natural bacterial communities. Theory suggests that phages impose density dependent regulation on bacterial populations, preventing competitive dominants from excluding less competitive species. To test this, we constructed experimental communities containing two bacterial species (Pseudomonas fluorescens and Pseudomonas aeruginosa) and their phage parasites. Communities were propagated at two environmental temperatures that reversed the outcome of competition in the absence of phage. RESULTS: The evenness of coexistence was enhanced in the presence of a phage infecting the superior competitor and in the presence of phage infecting both competitors. This occurred because phage altered the balance of competitive interactions through reductions in density of the superior competitor, allowing concomitant increases in density of the weaker competitor. However, even coexistence was not equally stable at the two environmental temperatures. CONCLUSION: Phage can alter competitive interactions between bacterial species in a way that is consistent with the maintenance of coexistence. However, the stability of coexistence is likely to depend upon the nature of the constituent bacteria-bacteriophage interactions and environmental conditions

Synthesis of Silver Nanoparticles by a Bryophilous Rhizoctonia species

We demonstrate the synthesis of silver nanoparticles by a potentially benign species of bryophilous Rhizoctonia in two different media. The first medium supports fungal growth and the up‐regulation of nitrate reductase, while the second medium supports fungal growth and the repression of nitrate reductase. For both media, the resulting silver nanoparticles were ca. 25‐50nm and were subglobose to broadly ellipsoidal in shape. The optical analysis of the silver nanoparticles from both media demonstrated plasmon resonance at 415nm, confirming their metallic properties. The liquid colour change typically observed for extracellular silver nanoparticle formation was absent in both media. The silver nanoparticles in the two different media displayed different chemical associations; fewer associated chemicals were found with the media, which supported the up‐regulation of nitrate reductase. Another difference included plate‐like silver nanoparticle conglomerations, which were only encountered on hyphae from the medium that repressed nitrate reductase. There was also a noticeable difference in the capping agent formations between each media. The Rhizoctonia isolate examined in this study is suitable for large‐scale industrial applications because it does not produce spores and would have minimal impact on air quality

Ferrimicrobium acidiphilum gen. nov., sp. nov. and Ferrithrix thermotolerans gen. nov., sp. nov.: heterotrophic, iron-oxidizing, extremely acidophilic actinobacteria

Two novel extremely acidophilic, iron-oxidizing actinobacteria were isolated, one from a mine site in North Wales, UK (isolate T23T), and the other from a geothermal site in Yellowstone National Park, Wyoming, USA (Y005T). These new actinobacteria belong to the subclass Acidimicrobidae, and in contrast to the only other classified member of the subclass (Acidimicrobium ferrooxidans), both isolates were obligate heterotrophs. The mine site isolate was mesophilic and grew as small rods, while the Yellowstone isolate was a moderate thermophile and grew as long filaments, forming macroscopic flocs in liquid media. Both isolates accelerated the oxidative dissolution of pyrite in yeast extract-amended cultures, but neither was able to oxidize reduced forms of sulfur. Ferrous iron oxidation enhanced growth yields of the novel mesophilic actinobacterium T23T, though this was not confirmed for the Yellowstone isolate. Both isolates catalysed the dissimilatory reduction of ferric iron, using glycerol as electron donor, in oxygen-free medium. Based on comparative analyses of base compositions of their chromosomal DNA and of their 16S rRNA gene sequences, the isolates are both distinct from each other and from Acidimicrobium ferrooxidans, and are representatives of two novel genera. The names Ferrimicrobium acidiphilum gen. nov., sp. nov. and Ferrithrix thermotolerans gen. nov., sp. nov. are proposed for the mesophilic and moderately thermophilic isolates, respectively, with the respective type strains T23T (5DSM 19497T5ATCC BAA-1647T) and Y005T (5DSM 19514T5ATCC BAA-1645T).info:eu-repo/semantics/publishedVersio

Role of pure and mixed cultures of gram-positive eubacteria in mineral leaching

Research on the biooxidation of sulfidic minerals has tended to be heavily biased towards Gram-negative bacteria, such as Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans. Currently, just three species of mineral-oxidising Gram-positive bacteria are recognised: Sulfobacillus thermosulfidooxidans, Sulfobacillus acidophilus and Acidimicrobium (Am.) ferrooxidans, all of which are thermotolerant prokaryotes. We have isolated and characterised a number of phylogenetically distinct Gram-positive ironmetabolising bacteria, including mesophilic and moderately thermophilic strains. Mesophilic isolates include (i) novel Sulfobacillus spp., some of which are the more acidophilic than all known iron-oxidising bacteria, (ii) "Ferrimicrobium acidiphilum", an actinobacterium most closely related to Am. ferrooxidans, and (iii) a group of low GC Gram-positives which appear to represent a novel genus. Moderately thermophilic isolates include a novel Sulfobacillus sp., an Alicyclobacillus spp. that, in contrast to currently recognised species, grows anaerobically by reduction of ferric iron and thrives in mineral leaching environments, and a new genus/species of iron- and sulfur-oxidising bacterium with the proposed name "Caldibacillus ferrivorus". These novel prokaryotes exhibited varying degrees of mineral leaching efficiencies, with the mesophilic Sulfobacillus spp. being particularly adept at solubilising pyrite at very low (<1) pH values. All novel Gram-positive isolates catalysed the oxidative dissolution of pyrite at lower redox potentials than Gram-negative mesophiles. Mixed cultures of Gram-positive bacteria, either with other Gram-positives or with Gram-negative bacteria, were often more effective mineral-leaching systems than corresponding pure cultures.info:eu-repo/semantics/publishedVersio

Adaptive self-organization in a realistic neural network model

Information processing in complex systems is often found to be maximally efficient close to critical states associated with phase transitions. It is therefore conceivable that also neural information processing operates close to criticality. This is further supported by the observation of power-law distributions, which are a hallmark of phase transitions. An important open question is how neural networks could remain close to a critical point while undergoing a continual change in the course of development, adaptation, learning, and more. An influential contribution was made by Bornholdt and Rohlf, introducing a generic mechanism of robust self-organized criticality in adaptive networks. Here, we address the question whether this mechanism is relevant for real neural networks. We show in a realistic model that spike-time-dependent synaptic plasticity can self-organize neural networks robustly toward criticality. Our model reproduces several empirical observations and makes testable predictions on the distribution of synaptic strength, relating them to the critical state of the network. These results suggest that the interplay between dynamics and topology may be essential for neural information processing.Comment: 6 pages, 4 figure

Pancreas Transplantation: Does Age Increase Morbidity?

Introduction. Pancreas transplantation (PTx) is the only definitive intervention for type 1 diabetes. Medical advancements in diabetes care have led to an aging PTx candidate pool. We report our experience with patients ≥50 years of age undergoing PTx. Methods. We reviewed 136 consecutive PTx patients at our institution from 1996–2010; 17 were ≥50 years of age. We evaluated demographics, surgical complications, acute rejection (AR) rates, nonsurgical infections, and survival outcomes. Results. Demographic data was similar (P > .05) between groups, excluding age. The two groups had comparable major and minor surgical complication rates (P = .10 and P = .25, resp.). The older group had a lower 1-year and overall AR rate (P = .04 and P = .03, resp.). The incidence of non-surgical infections and overall patient and graft survival was similar between groups (P > .05). Conclusion. Older patients with type 1 diabetes are feasible candidates for PTx, as surgical morbidity, incidence of infections, and AR rates are low