Potential markets for a satellite-based mobile communications system

The objective of the study was to define the market needs for improved land mobile communications systems. Within the context of this objective, the following goals were set: (1) characterize the present mobile communications industry; (2) determine the market for an improved system for mobile communications; and (3) define the system requirements as seen from the potential customer's viewpoint. The scope of the study was defined by the following parameters: (1) markets were confined to U.S. and Canada; (2) range of operation generally exceeded 20 miles, but this was not restrictive; (3) the classes of potential users considered included all private sector users, and non-military public sector users; (4) the time span examined was 1975 to 1985; and (5) highly localized users were generally excluded - e.g., taxicabs, and local paging

Modulation of the equilibrative nucleoside transporter by inhibitors of DNA synthesis.

Expression of the equilibrative, S-(p-nitrobenzyl)-6-thioinosine (NBMPR)-sensitive nucleoside transporter (es), a component of the nucleoside salvage pathway, was measured during unperturbed growth and following exposure to various antimetabolites at growth-inhibitory concentrations. The probe 5-(SAENTA-x8)-fluorescein is a highly modified form of adenosine incorporating a fluorescein molecule. It binds. with high affinity and specificity to the (es) nucleoside transporter at a 1:1 stoichiometry, allowing reliable estimates of es expression by flow cytometry. Using a dual labelling technique which combined the vital DNA dye Hoechst-33342 and 5-(SAENTA-x8)-fluorescein, we found that surface expression of es approximately doubled between G1 and G2 + M phases of the cell cycle. To address the question of whether es expression could be modulated in cells exposed to drugs which inhibit de novo synthesis of nucleotides, cells were exposed to antimetabolite drugs having different modes of action. Hydroxyurea and 5-fluorouracil (5-FU), which inhibit the de novo synthesis of DNA precursors, produced increases in the expression of es. In contrast, cytosine arabinoside (ara-C) and aphidicolin, which directly inhibit DNA synthesis, produced no significant increase in es expression. Thymidine (TdR), which is an allosteric inhibitor of ribonucleotide reductase that depletes dATP, dCTP and dGTP pools while repleting the dTTP pool, had no significant effect on es expression. These data suggest that surface expression of the es nucleoside transporter is regulated by a mechanism which is sensitive to the supply of deoxynucleotides. Because 5-FU (which specifically depletes dTTP pools) causes a large increase in expression whereas TdR (which depletes all precursors except dTTP) does not, this mechanism might be particularly sensitive to dTTP pools

Disentangling the exchange coupling of entangled donors in the Si quantum computer architecture

We develop a theory for micro-Raman scattering by single and coupled two-donor states in silicon. We find the Raman spectra to have significant dependence on the donor exchange splitting and the relative spatial positions of the two donor sites. In particular, we establish a strong correlation between the temperature dependence of the Raman peak intensity and the interdonor exchange coupling. Micro-Raman scattering can therefore potentially become a powerful tool to measure interqubit coupling in the development of a Si quantum computer architecture.Comment: Title changed. Other minor change

The variable phase method used to calculate and correct scattering lengths

It is shown that the scattering length can be obtained by solving a Riccati equation derived from variable phase theory. Two methods of solving it are presented. The equation is used to predict how long-range interactions influence the scattering length, and upper and lower bounds on the scattering length are determined. The predictions are compared with others and it is shown how they may be obtained from secular perturbation theory.Comment: 7 pages including 3 figure

Self-aligned fabrication process for silicon quantum computer devices

We describe a fabrication process for devices with few quantum bits (qubits), which are suitable for proof-of-principle demonstrations of silicon-based quantum computation. The devices follow the Kane proposal to use the nuclear spins of 31P donors in 28Si as qubits, controlled by metal surface gates and measured using single electron transistors (SETs). The accurate registration of 31P donors to control gates and read-out SETs is achieved through the use of a self-aligned process which incorporates electron beam patterning, ion implantation and triple-angle shadow-mask metal evaporation

1S-2S Spectrum of a Hydrogen Bose-Einstein Condensate

We calculate the two-photon 1S-2S spectrum of an atomic hydrogen Bose-Einstein condensate in the regime where the cold collision frequency shift dominates the lineshape. WKB and static phase approximations are made to find the intensities for transitions from the condensate to motional eigenstates for 2S atoms. The excited state wave functions are found using a mean field potential which includes the effects of collisions with condensate atoms. Results agree well with experimental data. This formalism can be used to find condensate spectra for a wide range of excitation schemes.Comment: 13 pages, 4 figure

Microplastics and synthetic particles ingested by deep-sea amphipods in six of the deepest marine ecosystems on Earth

Funding Funding for the laboratory work and analysis was from Newcastle University internal support. This work was supported by the 2007–2010 HADEEP project, funded by the Nippon Foundation (2009765188) and the Natural Environmental Research Council (NE/E007171/1). The 2011–2013 Kermadec Trench sampling was supported by the TOTAL Foundation (France) through the projects ‘Multi-disciplinary investigations of the deepest scavengers on Earth’ (2010–2012) and ‘Trench Connection’ (2013–2015). The Mariana samples were derived from the ‘FISH2017’ expedition (RV Shinyo-Maru SY1615) supported by the Tokyo University for Marine Science and Technology. Acknowledgements We thank the captain, crew and company of the research expeditions who assisted in the collection of the amphipods between 2008 and 2017, namely the Japanese Hakuho-Maru, Tansei Maru and Shinyo-Maru, the German Sonne and the RV Kaharoa in New Zealand. The assistance of David Whitaker and Peter McParlin from The School of Marine Science and Technology at Newcastle University are much appreciated. We are extremely grateful to Bob Keighley and Dan Parnaby at Shimadzu UK Limited for facilitating the FTIR analysis and access to their material database. We also thank Heather Stewart from the British Geological Survey for calculating the distances between trenches.Peer reviewedPublisher PD

Preparation of anti-vicinal amino alcohols: asymmetric synthesis of D-erythro-Sphinganine, (+)-spisulosine and D-ribo-phytosphingosine

Two variations of the Overman rearrangement have been developed for the highly selective synthesis of anti-vicinal amino alcohol natural products. A MOM-ether directed palladium(II)-catalyzed rearrangement of an allylic trichloroacetimidate was used as the key step for the preparation of the protein kinase C inhibitor D-erythro-sphinganine and the antitumor agent (+)-spisulosine, while the Overman rearrangement of chiral allylic trichloroacetimidates generated by asymmetric reduction of an alpha,beta-unsaturated methyl ketone allowed rapid access to both D-ribo-phytosphingosine and L-arabino-phytosphingosine

Long-term Monitoring and Recovery of a Population of Alligator Snapping Turtles, Macrochelys temminckii (Testudines: Chelydridae), from a Northeastern Arkansas Stream

We conducted a mark-recapture study of Alligator Snapping Turtles, Macrochelys temminckii, on Salado Creek (Independence Co., Arkansas) during 10 trapping seasons, which spanned a 20-year period (1995–2015). We trapped a total of 163 Alligator Snapping Turtles during 416 trap nights and recorded a total of 35 recaptures during this study. Both the catch per unit effort (CPUE) and Jolly-Seber approaches demonstrated that this population benefitted from removal of harvest pressure, thus leading to an increase in abundance of Alligator Snapping Turtles in the lower ~5 km of the creek. The CPUE averaged slightly greater than 0.24 (317 trap nights) during the first 4 years (1995–1998). The CPUE also showed an increase to 0.64 by 2001 (only 14 trap nights), and then dramatically increased during the final 5 years to 0.92 (85 trap nights). The population size estimates during the early period of the study (1995–2001) ranged from 20 turtles in 1995 to as many as 88 turtles in 1998, whereas the population size estimates from 2011-2015 ranged from 105 turtles in 2011 to as many as 282 turtles in 2015. Within our sample, recaptured males grew faster on average than females or juveniles in both straight carapace length and mass. These data, however, should be used with caution as age was not known. Most of the recaptured Alligator Snapping Turtles exhibited some degree of site fidelity