896 research outputs found
An automatic reagent dispenser for shipboard use
Recent work on modification of the molybdenum-blue method for determination of dissolved inorganic phosphate in sea water (Wooster and Rakestraw, 1951) showed the need for a simple rugged device sui table for rapid and precise delivery of small quantities of reagents at sea. The two reagents used for phosphat e determination impose addit ional requirements on this device. Molybdic acid solution must be protected from the light and must not be allowed to come in contact with rubber;·stannous chloride solution must be protected from contact with the atmosphere
Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean
Aeolian dust transport from the Saharan/Sahel desert regions is considered the dominant external input of iron (Fe) to the surface waters of the eastern (sub-) tropical North Atlantic Ocean. To test this hypothesis, we investigated the sources of dissolved Fe (DFe) and quantified DFe fluxes to the surface ocean in this region. In winter 2008, surface water DFe concentrations varied between <0.1 nM and 0.37 nM, with an average of 0.13 ± 0.07 nM DFe (n = 194). A strong correlation between mixed layer averaged concentrations of dissolved aluminum (DAl), a proxy for dust input, and DFe indicated dust as a source of DFe to the surface ocean. The importance of Aeolian nutrient input was further confirmed by an increase of 0.1 nM DFe and 0.05 ?M phosphate during a repeat transect before and after a dust event. An exponential decrease of DFe with increasing distance from the African continent, suggested that continental shelf waters were a source of DFe to the northern part of our study area. Relatively high Fe:C ratios of up to 3 à 10?5 (C derived from apparent oxygen utilization (AOU)) indicated an external source of Fe to these African continental shelf waters. Below the wind mixed layer along 12°N, enhanced DFe concentrations (>1.5 nM) correlated positively with apparent oxygen utilization (AOU) and showed the importance of organic matter remineralization as an DFe source. As a consequence, vertical diffusive mixing formed an important Fe flux to the surface ocean in this region, even surpassing that of a major dust event
The Robertson v. Princeton Case: Too Important to Be Left to the Lawyers
Offers comments from eleven contributors on the Robertson family's donor rights suit against the Woodrow Wilson School of Public and International Affairs for violation of donor intent. Explores its effects on and implications for the nonprofit sector
Mars-back Approach to Moon-Mars Exploration System Commonality
This conference features the work of authors from: Georgia Techâs Space Systems Design Lab, Aerospace Systems Design Lab, School of Aerospace Engineering, Georgia Tech Research Institute; NASAâs Jet Propulsion Laboratory, Marshall Space Flight Center, Goddard Space Flight Center, Langley Research Center; and other aerospace industry and academic institutionsThe Mars-back approach entails the development of a common system for the exploration
of Moon and Mars by first looking at the requirements placed upon the system by the
Mars exploration case and then projecting the system capabilities back to the Moon. By
developing a common system for the exploration of both destinations, overall
development cost is decreased and any gap between Moon and Mars is either eliminated
or significantly reduced. As elements needed for lunar exploration are a sub-set of those
utilized in Mars exploration, lunar exploration directly demonstrates and validates the
elements prior to Mars exploration and lunar exploration can continue during the
exploration of Mars. Through directly linking lunar exploration to the exploration of
Mars, Mars exploration can be significantly accelerated and greater public support can be
maintained in order to sustain the Vision for Space Exploration. In designing elements for
a common Moon-Mars exploration system, our analysis indicates that through proper
upfront systems engineering and appropriate use of platforming and modularity, the
performance overheads associated with each particular use case can be kept low while the
affordability of the overall system can be significantly improved.AIAA Space Systems Technical Committee ; AIAA Space Transportation Systems Technical Committee ; Space Technology Advanced Research Cente
Survival Outcomes of Patients Treated with Hypofractionated Stereotactic Body Radiation Therapy for Parotid Gland Tumors: a Retrospective Analysis
Background: to review a single-institution experience with the management of parotid malignancies treated by fractionated stereotactic body radiosurgery (SBRT). Findings: Between 2003 and 2011, 13 patients diagnosed with parotid malignancies were treated with adjuvant or definitive SBRT to a median dose of 33âGy (range 25â40âGy). There were 11 male and two female patients with a median age of 80. Ten patients declined conventional radiation treatment and three patients had received prior unrelated radiation therapy to neighboring structures with unavailable radiation records. Six patients were treated with definitive intent while seven patients were treated adjuvantly for adverse surgical or pathologic features. Five patients had clinical or pathologic evidence of lymph node disease. Conclusion: at a median follow-up of 14âmonths only one patient failed locally, and four failed distantly. The actuarial 2-year overall survival, progression-free survival, and local-regional control rates were 46, 84, and 47%, respectively. Statistical analysis revealed surgery as a positive predictor of overall survival while presence of gross disease was a negatively correlated factor (pâ<â0.05)
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Effects of water withdrawals on macroinvertebrate emergence: Unexpected results for three holometabolous species
Small, low-head diversion dams are capable of withdrawing much of the flow of a river, often resulting in elevated water temperatures. Accelerated growth and development of aquatic invertebrates has been demonstrated in warmer temperatures, suggesting that the timing of insect emergence and adult body size may be significantly altered by water withdrawals. To examine the influence of summer water withdrawals on aquatic invertebrate life histories, emergence timing and adult body mass of three holometabolous species were monitored continuously for 9â10 weeks on the Umatilla and Walla Walla Rivers in arid northeastern Oregon. On each river, multiple sample sites were located along gradients of decreasing discharge and increasing water temperatures caused by successive diversions.
Despite reductions in discharge of up to 93% and increases in average water temperature of up to 4.6°C from upstream to downstream, timing of median emergence was unaltered for Helicopsyche borealis, Petrophila confusalis and Glossosoma traviatum. However, in a laboratory experiment, higher temperatures led to earlier emergence for H. borealis. Water temperature in the field study was not significantly correlated with reduced adult body size of these species, though female P. confusalis were 31% smaller at the warmest sample site. Holometabolous life histories and high temperature tolerances are possible explanations for the observed resistance of these species to life history alteration.Keywords: water abstraction,
Petrophila,
life history,
agriculture,
Glossosoma,
Helicopsyche,
discharge,
temperatur
Trigeminal neuralgia treatment outcomes following Gamma Knife radiosurgery with a minimum 3-year follow-up
OBJECTIVE: Effective short-term outcomes have been well documented for trigeminal neuralgia (TN) patients treated with Gamma Knife radiosurgery (GKRS) with reported success rates of 70â90Â % with median follow-up intervals of 19â75Â months. Fewer series, however, have described uniform long-term follow-up data. In this study, we report our long-term institutional outcomes in patients treated with GKRS after a minimum follow-up of 36Â months. METHODS: Thirty-six consecutive patients with medically intractable TN received a median radiation dose of 45Â Gy applied with a single 4-mm isocenter to the affected trigeminal nerve. Follow-up data were obtained by clinical examination and telephone questionnaire. Outcome results were categorized based on the Barrow Neurological Institute (BNI) pain scale with BNI IâIII considered to be good outcomes and BNI IVâV considered as treatment failure. BNI facial numbness score was used to assess treatment complications. RESULTS: The incidence of early pain relief was high (80.5Â %) and relief was noted in an average of 1.6Â months after treatment. At minimum follow-up of 3Â years, 67Â % were pain free (BNI I) and 75Â % had good treatment outcome. At a mean last follow-up of 69Â months, 32Â % were free from any pain and 63Â % were free from severe pain. Bothersome posttreatment facial numbness was reported in 11Â % of the patients. A statistically significant correlation was found between age and recurrence of any pain with age >70 predicting a more favorable outcome after radiosurgery. CONCLUSION: The success rate of GKRS for treatment of medically intractable TN declines over time with 32Â % reporting ideal outcome and 63Â % reporting good outcome. Patients older than age 70 are good candidates for radiosurgery. This data should help in setting realistic expectations for weighing the various available treatment options
Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus.
Idiopathic congenital nystagmus is characterized by involuntary, periodic, predominantly horizontal oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 singleton cases of idiopathic congenital nystagmus (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina, suggesting a specific role in the control of eye movement and gaze stability
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