Lower Mississippian Chert Development, Southern Midcontinent Region

The Lower Mississippian Boone Formation is a chert-bearing, fossiliferous limestone typically 100-115m. thick forming the Springfield Plateau across the tri-state region of northwestern Arkansas, southwestern Missouri, and northeastern Oklahoma. The Boone represents the maximum flooding, highstand, and regressive intervals of a single, third order transgressive-regressive carbonate cycle bounded by regional unconformities. Two types of chert occur in this formation, and provide the basis for subdivision of the Boone into informal lower and upper members in northern Arkansas. The lower Boone represents early Osagean maximum flooding conditions and consists of calcisiltites with interbedded dark, nodular chert. This chert exhibits compaction phenomena and shrinkage fractures, indicating a penecontemporaneous origin from reorganization of silica immediately below the sediment water interface prior to lithification of the carbonate sediments (Manger et al. 1988a). The upper Boone represents late Osagean highstand and regression and consists primarily of carbonate grainstones and packstones (Shelby 1986). This interval contains white, later diagenetic chert, interpreted as a groundwater phenomenon in which silica has replaced lithified carbonate along its bedding planes, replicating the fabric of the limestone (Manger and Shelby 2000). This later diagenetic chert replacement favors the finer grained intervals and replicates the fabric of the limestone being replaced. Previous studies have shown that the penecontemporaneous chert typically comprises 40-50% of the lower Boone interval, while the later diagenetic chert contribution to the upper Boone ranges from 30-95% (Liner 1979). Understanding chert development is unsettled, and has been the subject of debate, primarily involving the source of the silica producing the chert, and the mode of formation of the chert-bearing intervals. Geochemical analyses suggest a volcanic rather than biogenic source for the silica in the Boone Formation

Crystal Nucleation by Laser-Induced Cavitation\ud

High-speed and high-resolution photography have been used to investigate the relationship between creation, expansion, and collapse of a vapor cavity induced by a 6 ns laser pulse and the subsequent nucleation of crystals. A thin layer of supersaturated aqueous solutions of (NH4)2SO4 and KMnO4 was confined between two glass plates with a separation of 50 and 100 μm. The expansion and collapse of the laser-induced vapor bubble occurred over a total time scale of 200 μs, while the first identifiable crystal appears one second after the laser pulse. Crystals were observed to form on a ring with a diameter of 70 μm centered in the focal point of the laser. The ring is preceded by an optical disturbance observed through the cavity around 30–50 μs after the laser pulse and vapor cavity formation. This ring-shaped optical disturbance originates from changes in refractive index induced by crystal nuclei formation. The formation of the nuclei most probably coincides with the formation of the bubble, when the rate of evaporation and the supersaturation are at their maxima. Apparently, it takes the nuclei around 30–50 μs to grow to a particle size with a visible optical disturbanc

Agrp neuron activity is required for alcohol-induced overeating

Alcohol intake associates with overeating in humans. This overeating is a clinical concern, but its causes are puzzling, because alcohol (ethanol) is a calorie-dense nutrient, and calorie intake usually suppresses brain appetite signals. The biological factors necessary for ethanol-induced overeating remain unclear, and societal causes have been proposed. Here we show that core elements of the brain’s feeding circuits—the hypothalamic Agrp neurons that are normally activated by starvation and evoke intense hunger—display electrical and biochemical hyperactivity on exposure to dietary doses of ethanol in brain slices. Furthermore, by circuit-specific chemogenetic interference in vivo, we find that the Agrp cell activity is essential for ethanol-induced overeating in the absence of societal factors, in single-housed mice. These data reveal how a widely consumed nutrient can paradoxically sustain brain starvation signals, and identify a biological factor required for appetite evoked by alcohol

Aerosol growth processes in an atmosphere containing dilute reacting gas

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Animal Assisted Therapy

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ϕ\phi meson production in sNN\sqrt{s_{NN}} = 200 GeV Au+Au and pp collisions at RHIC

We present the results for the measurement of $\phi$ meson production in $\sqrt{s_{NN}}$ = 200 GeV Au+Au and pp collisions at the Relativistic Heavy Ion Collider (RHIC). Using the event mixing technique, spectra and yields are obtained from the $\phi\to K^{+}K^{-}$ decay channel for different centrality bins in Au+Au collisions and in pp collisions. We observe that the spectrum shape in Au+Au collisions depends weakly on the centrality and the shape of the spectrum in pp collisions is significantly different from that in Au+Au collisions. In Au+Au collisions, the extracted yield of $\phi$ meson is flat as a function of rapidity; The $$ of $\phi$, extracted from the fit function to the spectra, shows a different behavior as a function of centrality than that of $\pi^-$, $K^-$ and $\bar{p}$Comment: Proceedings for the 7th International Conference on Strangeness in Quark Matte

Sedimentary Provenance of the Wedington Member, Fayetteville Shale, From Age Relations of Detrital Zircons

U-Pb geochronology of detrital zircons collected from the Chesterian Wedington Sandstone allows interpretation of sediment provenance and dispersal patterns in the southern midcontinent during the Late Mississippian. Detrital zircons analyzed from six samples of Wedington Sandstone yielded a final result of 565 concordant analyses used for interpretation. Results are plotted as Probability-Density Plots to interpret the spectrum of ages. Significant peaks occurred at 350-500 Ma, 950-1250 Ma, 1300-1500 Ma, 1600-1800 Ma, 1800-2300 Ma, and \u3e2500 Ma. These peaks are interpreted as sourced by crystalline rocks within the Laurentian craton from Taconic-Acadian, Grenville, Midcontinent Granite-Rhyolite, Yavapai-Mazatzal, Paleoproterozoic, and Superior Provinces. The high percentage of grains derived from Acadian, Taconic, and Grenville Provinces indicate the Appalachian Mountains were the primary source of sediment during the Chesterian. The Midcontinent Granite-Rhyolite and Yavapai-Mazatzal Provinces were the second most prevalent source terranes, indicating the Nemaha Ridge was uplifted and supplying a significant amount of sediment by the Late Mississippian. Sediments were likely transported from both eastern and western sources into a drainage basin moving sediments south into northwest Arkansas, where they were deposited on the Arkoma shelf as a small constructive delta complex

Geochemical Analysis of Mississippian Cherts and Devonian-Mississippian Novaculites, Southern Midcontinent Region

This study uses trace elements and radiogenic isotopes (Pb, Sr, and Nd) to investigate the origin and mode of formation for the siliceous deposits in the Lower Mississippian Boone Formation and the Devonian-Mississippian Arkansas Novaculite in the southern midcontinent. Mississippi Valley-type Pb-Zn ore deposits in the Tri-State District and the Northern Arkansas District were deposited by hydrothermal fluids, and highly radiogenic Pb isotope ratios suggest a genetic relationship between the Boone Formation chert (206Pb/204Pb ~ 21.59, 207Pb/204Pb ~ 15.87, 208Pb/204Pb ~ 40.10) and the MVT ores. Due to the very low concentration of Pb in the Boone chert (~2 ppm) and the close proximity of samples containing radiogenic Pb to the tripolitic chert interval, the Boone Formation is interpreted to have been contaminated with radiogenic Pb by the hydrothermal fluids that emplaced the ores. Calculated epsilon values for Nd reveal a small positive shift in the Boone samples (epsilon Nd ~ -5.5) relative to other measured stratigraphic intervals in the southern midcontinent (epsilon Nd ~ -15.2), potentially indicating volcanic contribution of Nd. Upper Boone cherts (epsilon Nd ~ -4.6) and Hatton Tuff (epsilon Nd ~ -3.8) values are remarkably similar, indicating the same Nd source. Sr isotope ratios of the Boone samples (87Sr/86Sr ~ 0.7089) largely reflect Mississippian seawater Sr (87Sr/86Sr ~ 0.7080), while the novaculite samples contain more radiogenic Sr (87Sr/86Sr ~ 0.7121), likely reflecting Sr exchange from the detrital component within the Arkansas Novaculite stratigraphic interval. Rare earth element (REE) concentrations normalized to average continental arcs plot near one for the upper Boone chert samples, indicating similar compositions, while the lower Boone and Arkansas Novaculite have lower normalized values. Rare earth element plus yttrium (REY) concentrations normalized to Post-Archean Australian Shales (PAAS) reveal a negative cerium (Ce) anomaly and a positive yttrium (Y) anomaly, which is a signature of seawater, indicating that the Boone cherts may retain a depositional seawater REY signature

Leadership Implementation of a 12 Pathways Model (GIW-12P) to Promote Schoolwide Wellbeing

This research investigated how a leadership team enacted wellbeing promotion in a Catholic Preparatory to Year 12 all-girls school using the Growing Inclusive Wellbeing 12 Pathways Model (GIW-12P). This qualitative case study purposively selected participants (n = 25) and collected data over an eight-week period using surveys and semi-structured focus group discussions. Thematic analysis was conducted in four phases with three key findings. Firstly, the GIW-12P as a tool proved highly effectual as a model. Secondly, applying the model surfaced areas of effectual wellbeing promotion while also illuminating gaps in practices and drawing attention to areas for further action. Thirdly, the “how” of the application surfaced as an opportunity for school-wide collaboration linked to core beliefs and quality outcomes for students, teachers, and all participants. Using the GIW-12P model provides new knowledge to policymakers and researchers in the field of practice. When collaboratively used as an analysis tool, the GIW-12P created an intersectionality with the concept of wellbeing within this community. When applied by a team to investigate wellbeing promotion, the GIW-12P surfaces information key to effective decision-making for leaders regarding the utilisation (i.e., allocation and deployment) of human and financial resources and educational policy to drive school-wide wellbeing promotion

Dichotomous Effects of Mu Opioid Receptor Activation on Striatal Low-Threshold Spike Interneurons

Striatal low-threshold spike interneurons (LTSIs) are tonically active neurons that express GABA and nitric oxide synthase and are involved in information processing as well as neurovascular coupling. While mu opioid receptors (MORs) and their ligand encephalin are prominent in the striatum, their action on LTSIs has not been investigated. We addressed this issue carrying out whole-cell recordings in transgenic mice in which the NPY-expressing neurons are marked with green fluorescent protein (GFP). The MOR agonist (D-Ala(2), N-MePhe(4), Gly-ol)-enkephalin (DAMGO) produced dual effects on subpopulations of LTSIs. DAMGO caused inhibitory effects, accompanied by decreases of spontaneous firing, in 62% of LTSIs, while depolarizing effects (accompanied by an increase in spontaneous firing) were observed in 23% of LTSIs tested. The dual effects of DAMGO persisted in the presence of tetrodotoxin (TTX), a sodium channel blocker or in the presence of the nicotinic acetylcholine receptor antagonist mecamylamine. However, in the presence of either the GABAA receptor antagonist picrotoxin or the muscarinic cholinergic receptor antagonist atropine, DAMGO only elicited inhibitory effects on LTSIs. Furthermore, we found that DAMGO decreased the amplitude and frequency of spontaneous GABAergic events. Unexpectedly, these effects of DAMGO on spontaneous GABAergic events disappeared after blocking of the muscarinic and nicotinic cholinergic blockers, showing that GABA inputs to LTSIs are not directly modulated by presynaptic MORs. These finding suggest that activation of MORs affect LTSIs both directly and indirectly, through modulation of GABAergic and cholinergic tones. The complex balance between direct and indirect effects determines the net effect of DAMGO on LTSIs