Investigation of climate change and history of lead deposition using soil archives

Our study focused on the investigation of climate change and the fate of lead in soils from the Low Volga region of Russia over 3500 years. We used a comparative analysis of the modern soils and palaeosols preserved under burial mounds, which date back to the Middle Ages and the Early Iron and Bronze Ages. A climate reconstruction showed periodic changes, with the most humid climate conditions occurring during Golden Horde period. However, we could not find any consistent changes in Pb concentration and profile distribution following the climate change. We observed a clear difference in Pb isotopic ratios between the lower and upper horizons both for the modern and buried profiles, reflecting the influence of atmospheric lead depositions. However, there is no statistically significant difference in Pb isotopic ratios between the upper horizons of buried and modern soils (except modern soils collected in the vicinity of a motorway). This means that either anthropogenic input due to long range air transport was insignificant, or that airborne anthropogenic lead and natural airborne lead have similar isotopic composition

High gas velocity burner tests on silicon carbide and silicon nitride at 1200 C

Specimens of silicon carbide and silicon nitride were exposed to a Mach one gas velocity burner simulating a turbine engine environment. Cyclic tests up to 100 hour duration were conducted at specimen temperatures of 1200 C. A specimen geometry was used that develops thermal stresses during thermal cycling in a manner similar to blades and vanes of a gas turbine engine. Materials were compared on a basis of weight change, dimensional reductions, metallography, fluorescent penetrant inspection, X-ray diffraction analyses, failure mode, and general appearance. One hot pressed SiC, one reaction sintered SiC, and three hot pressed Si3N4 specimens survived the program goal of 100 one-hour cycle exposures. Of the materials that failed to meet the program goal, thermal fatigue was identified as the exclusive failure mode

High temperature mechanical properties of polycrystalline hafnium carbide and hafnium carbide containing 13-volume-percent hafnium diboride

High temperature mechanical properties of polycrystalline hafnium carbide containing 13- volume-percent hafnium diborid

Strontium as a tracer of weathering processes in a silicate catchment polluted by acid atmospheric inputs, Strengbach, France

This paper determines the weathering and atmospheric contributions of Ca in surface water from a small spruce forested silicate catchment (N–E France) receiving acid atmospheric inputs. The bedrock is a granite with K-feldspar and albite as dominant phases. The calcium content in plagioclase is low and the Ca/Na ratio in surface water is high, reflecting other sources of calcium from those expected from the weathering of major mineral phases. The biotite content is low. Only traces of apatite were detected while no calcite was found in spite of a major hydrothermal event having affected the granite. The strontium isotopic ratio 87Sr/86Sr and Sr content was used as a tracer of weathering and was determined in minerals and bulk bedrock, open field precipitation, throughfall, soil solution, spring and stream water. The Sr isotopic ratio of the reacting weathering end-member was predicted by simulating the alteration of the granite minerals by incorporating strontium into the water–rock interaction kinetic code KINDIS. In the early stages of water–rock interaction, K-feldspar and biotite strongly influence the isotopic composition of the weathering solution whereas, the Na-rich plagioclase appears to be the main long-term reactive weathering end-member. Approximately 50% of dissolved Sr in streamwater are atmospherically derived. The 87Sr/86Sr ratios of exchangeable Sr in the fine fraction at 1-m depth from a soil profile indicate that the amount of exchangeable Sr seems essentially controlled by atmospheric inputs. The exception is the deep saprolite where weathering processes could supply the Sr (and Ca). Na-Plagioclase weathering obviously control the chemistry and the isotopic composition of surface waters. The weathering of trace mineral plays a secondary role, the exception is for apatite when plagioclase is absent. Our hydrochemical, mineralogical and isotopic investigations show that a major part of the strong Ca losses detected in catchment hydrochemical budgets that result from the neutralization of acid precipitation has an atmospheric origin. Consequently, in the long term, in such areas, the availability of such an exchangeable base cation might be strongly limited and surface waters consequently acidified

Implementation of a Vestibular Disorder Screening Tool in an Urgent Care

Implementation of a Vestibular Disorder Screening Tool in an Urgent Care Kathleen A. Probst M.S.N., University of Missouri-Columbia, 2007 B.S.N., University of Missouri-Columbia, 2004 A Dissertation Submitted to The Graduate School at the University of Missouri-St. Louis in partial fulfillment of the requirements for the degree Doctor of Nursing Practice August 2023 Advisory Committee Susan Dean-Baar, PhD, RN, CENP, FAAN Chairperson Jennifer Vines, DNP, MSN, RN Troy Dinkel, MD Copyright, Kathleen A. Probst, 2023 Abstract Problem: Vestibular disorders disrupt everyday living and can cause reduced quality of life. Guidelines developed to screen for vestibular disorders are not efficient to use in the emergency department and are not utilized by some providers due to lack of confidence and training. Patients who present to the emergency department with vestibular disorder symptoms are often left undiagnosed, therefore leading to lack of referrals for vestibular therapy (VT). Methods: A vestibular screening tool (VST) was introduced to a convenience sample of providers working in an urgent care setting. This quality improvement project analyzed quantitative descriptive data, both retrospective and prospective, comparing the number of VT referrals in patients with a vestibular disorder diagnosis. This project also compared provider confidence levels to diagnosis and refer patients with vestibular disorders. Results: Comparison of the number of VT referrals made from the retrospective (n=121, 30.58%) and prospective (n=126, 34.92%) data suggest no significant relationship. There was a significant difference in the mean rank for provider confidence level from before and after the VST was introduced (U=838, z = -1.98, p = 0.047). Implications for Practice: Introduction of a VST in an urgent care setting can increase provider confidence level in diagnosing patients with a vestibular disorder and referring to VT