3,908 research outputs found
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Recommendations are given regarding National Science Foundation (NSF) astronomy programs and the NASA Space Astrophysics program. The role of ground based astronomy is reviewed. The role of National Optical Astronomy Observatories (NOAO) in ground-based night-time astronomical research is discussed. An enhanced Explored Program, costs and management of small and moderate space programs, the role of astrophysics within NASA's space exploration initiative, suborbital and airborne astronomical research, the problems of the Hubble Space Telescope, and astronomy education are discussed. Also covered are policy issues related to the role of science advisory committees, international cooperation and competition, archiving and distribution of astronomical data, and multi-wavelength observations of variable sources
Seasonal patterns of estuarine acidification in seagrass beds of the Snohomish Estuary, WA
Recent studies have begun to explore physical and biogeochemical mechanisms of carbonate chemistry variability in a variety of coastal habitats, including coral reefs, upwelling margins, and inland seas. To our knowledge, there have been limited mechanistic studies of annual carbonate chemistry variability in nearshore estuarine environments. Here, we present autonomous sensor and grab sample data of carbonate chemistry covering a 10 month period from two subtidal seagrass bed sites in Possession Sound, WA. Simple mass balance stoichiometric models are used to evaluate seasonal drivers of carbonate system parameters in the seagrass beds. Simulations of increasing anthropogenic carbon (Canth) burdens in the habitats reveal seasonal differences in the magnitude of carbonate system responses. The addition of Canth alters the thermodynamic buffer factors (e.g. the Revelle factor) of the carbonate system, decreasing the system’s ability to buffer natural variability in the seagrass habitat on high-frequency (e.g. tidal, diel) and seasonal timescales. As a result, the most harmful carbonate system indices for many estuarine organisms (minimum pHT, minimum Ωarag, and maximum pCO2(s.w.)) change most rapidly with increasing Canth. We highlight how the observed seasonal climatology and non-linear response of the carbonate system to increasing Canth drive the timing of the crossing of established physiological stress thresholds for endemic organisms, as well as thresholds relevant for water quality management. In this system, the relative benefits of the seagrass beds in locally mitigating ocean acidification during the growing season increase with the higher atmospheric CO2 levels predicted toward 2100. Presently however, these mitigating effects are mixed due to intense diel cycling of CO2 driven by community metabolism
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. I. ASCA Observations and the Variability of the X-ray Spectral Components
We present a 35 day ASCA observation of the NLS1 Akn 564, which was part of a
multiwavelength AGN Watch monitoring campaign. Akn 564 shows a photon index
varying across the range 2.45--2.72. The presence of the soft hump component
below 1 keV, previously detected in ASCA data, is confirmed. Time-resolved
spectroscopy with ~daily sampling reveals a distinction in the variability of
the soft hump and power-law components over a timescale of weeks, with the hump
varying by a factor of 6 across the 35-day observation compared to a factor 4
in the power-law. Flux variations in the power-law component are measured down
to a timescale of ~1000s and accompanying spectral variability suggests the
soft hump is not well-correlated with the power-law on such short timescales.
We detect Fe Ka and a blend of Fe Kb plus Ni Ka, indicating an origin in highly
ionized gas. Variability measurements constrain the bulk of the Fe Ka to
originate within a light week of the nucleus. The large EW of the emission
lines may be due to high metallicity in NLS1s, supporting some evolutionary
models for AGN.Comment: 41 pages, 15 figures. Accepted for publication in the Astrophysical
Journal (v3 has final fixes for publication
On the formation of glycolaldehyde in dense molecular cores
Glycolaldehyde is a simple monosaccharide sugar linked to prebiotic chemistry. Recently, it was detected in a molecular core in the star-forming region G31.41+0.31 at a reasonably high abundance. We investigate the formation of glycolaldehyde at 10 K to determine whether it can form efficiently under typical dense core conditions. Using an astrochemical model, we test five different reaction mechanisms that have been proposed in the astrophysical literature, finding that a gas-phase formation route is unlikely. Of the grain-surface formation routes, only two are efficient enough at very low temperatures to produce sufficient glycolaldehyde to match the observational estimates, with the mechanism culminating in CH3OH + HCO being favored. However, when we consider the feasibility of these mechanisms from a reaction chemistry perspective, the second grain-surface route looks more promising, H3CO + HCO
Interactions between neurokinin B and kisspeptin in mediating estrogen feedback in healthy women
CONTEXT: Kisspeptin and neurokinin B (NKB) are obligate for normal gonadotropin secretion, but their hierarchy is unexplored in normal women. OBJECTIVE: To investigate the interaction between kisspeptin and NKB on estrogen-regulated LH secretion. DESIGN: Women were treated with neurokinin-3 receptor (NK3R) antagonist followed by transdermal estradiol to induce LH secretion 48 hours later, with kisspeptin-10 or vehicle infusion during estrogen administration in a 2-way crossover study. SETTING: Clinical research facility. PATIENTS OR OTHER PARTICIPANTS: Healthy females with regular menses. INTERVENTION(S): NK3R antagonist AZD4901 40 mg twice daily orally was taken from cycle day 4–6 for 6 days (n = 10, with 10 no treatment controls). Transdermal estradiol patches (200 μg/d) were applied after 5 days of NK3R antagonist treatment. At 24-hour estradiol treatment, women were randomized to 7-hour kisspeptin-10 (4 μg/kg/h) or vehicle iv infusion, with the alternate infusion in a subsequent cycle. MAIN OUTCOME MEASURE(S): Plasma gonadotropin and estradiol secretion. RESULTS: After an initial suppression, LH secretion was increased 48 hours after estradiol treatment. Kisspeptin-10 increased LH secretion during the inhibitory phase, and LH remained elevated beyond the discontinuation of kisspeptin-10 infusion. NK3R antagonist decreased LH pulse frequency (0.5 ± 0.2 vs 0.7 ± 0.2 pulses/h, P < .05) and stimulated FSH response to kisspeptin-10 infusion (10.7 ± 11.0 vs 5.0 ± 3.6 IU/L, P < .05) with a nonsignificant rise in LH. The duration of LH response was blunted, with LH being lower at 48 hours (7.5 ± 4.8 vs 15.0 ± 11.4 IU/L, P < .05). CONCLUSIONS: These data demonstrate that NKB signaling regulates GnRH/LH secretion in normal women, and is predominantly proximal to kisspeptin in mediating estrogenic positive and negative feedback on LH secretion
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The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: Implications for near-term ocean acidification effects
We report results from an oyster hatchery on the Oregon coast, where intake waters experienced variable carbonate chemistry (aragonite saturation state 3.2; pH 8.2) in the early summer of 2009. Both larval production and midstage growth (∼ 120 to ∼ 150 µm) of the oyster Crassostrea gigas were significantly negatively correlated with the aragonite saturation state of waters in which larval oysters were spawned and reared for the first 48 h of life. The effects of the initial spawning conditions did not have a significant effect on early-stage growth (growth from D-hinge stage to ∼ 120 µm), suggesting a delayed effect of water chemistry on larval development.This is the publisher’s final pdf. The published article is copyrighted by the Association for the Sciences of Limnology and Oceanography, Inc. and can be found at: http://www.aslo.org/lo
MYCN expression induces replication stress and sensitivity to PARP inhibition in neuroblastoma
This study investigates the influence expression of the MYCN oncogene has on the DNA damage response, replication fork progression and sensitivity to PARP inhibition in neuroblastoma. In a panel of neuroblastoma cell lines, MYCN amplification or MYCN expression resulted in increased cell death in response to a range of PARP inhibitors (niraparib, veliparib, talazoparib and olaparib) compared to the response seen in non-expressing/amplified cells. MYCN expression slowed replication fork speed and increased replication fork stalling, an effect that was amplified by PARP inhibition or PARP1 depletion. Increased DNA damage seen was specifically induced in S-phase cells. Importantly, PARP inhibition caused a significant increase in the survival of mice bearing MYCN expressing tumours in a transgenic murine model of MYCN expressing neuroblastoma. Olaparib also sensitized MYCN expressing cells to camptothecin- and temozolomide-induced cell death to a greater degree than non-expressing cells. In summary, MYCN expression leads to increased replication stress in neuroblastoma cells. This effect is exaggerated by inhibition of PARP, resulting in S-phase specific DNA damage and ultimately increased tumour cell death. PARP inhibition alone or in combination with classical chemotherapeutics is therefore a potential therapeutic strategy for neuroblastoma and may be more effective in MYCN expressing tumours
Effects of 12 Months of Vagus Nerve Stimulation in Treatment-Resistant Depression: A Naturalistic Study
Background: The need for effective, long-term treatment for recurrent or chronic, treatment-resistant depression is well established.
Methods: This naturalistic follow-up describes outpatients with nonpsychotic major depressive (n = 185) or bipolar (I or II) disorder, depressed phase (n = 20) who initially received 10 weeks of active (n = 110) or sham vagus nerve stimulation (VNS) (n = 95). The initial active group received another 9 months, while the initial sham group received 12 months of VNS. Participants received antidepressant treatments and VNS, both of which could be adjusted.
Results: The primary analysis (repeated measures linear regression) revealed a significant reduction in 24-item Hamilton Rating Scale for Depression (HRSD24) scores (average improvement, .45 points [SE = .05] per month (p \u3c .001). At exit, HRSD24 response rate was 27.2% (55/202); remission rate (HRSD24 ≤ 9) was 15.8% (32/202). Montgomery Asberg Depression Rating Scale (28.2% [57/202]) and Clinical Global Impression-Improvement (34.0% [68/200]) showed similar response rates. Voice alteration, dyspnea, and neck pain were the most frequently reported adverse events.
Conclusions: These 1-year open trial data found VNS to be well tolerated, suggesting a potential long-term, growing benefit in treatment-resistant depression, albeit in the context of changes in depression treatments. Comparative long-term data are needed to determine whether these benefits can be attributed to VNS
Effects of 12 Months of Vagus Nerve Stimulation in Treatment-Resistant Depression: A Naturalistic Study
Background: The need for effective, long-term treatment for recurrent or chronic, treatment-resistant depression is well established.
Methods: This naturalistic follow-up describes outpatients with nonpsychotic major depressive (n = 185) or bipolar (I or II) disorder, depressed phase (n = 20) who initially received 10 weeks of active (n = 110) or sham vagus nerve stimulation (VNS) (n = 95). The initial active group received another 9 months, while the initial sham group received 12 months of VNS. Participants received antidepressant treatments and VNS, both of which could be adjusted.
Results: The primary analysis (repeated measures linear regression) revealed a significant reduction in 24-item Hamilton Rating Scale for Depression (HRSD24) scores (average improvement, .45 points [SE = .05] per month (p \u3c .001). At exit, HRSD24 response rate was 27.2% (55/202); remission rate (HRSD24 ≤ 9) was 15.8% (32/202). Montgomery Asberg Depression Rating Scale (28.2% [57/202]) and Clinical Global Impression-Improvement (34.0% [68/200]) showed similar response rates. Voice alteration, dyspnea, and neck pain were the most frequently reported adverse events.
Conclusions: These 1-year open trial data found VNS to be well tolerated, suggesting a potential long-term, growing benefit in treatment-resistant depression, albeit in the context of changes in depression treatments. Comparative long-term data are needed to determine whether these benefits can be attributed to VNS
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