Distinguishing seawater from geologic brine in saline coastal groundwater using radium-226; an example from the Sabkha of the UAE

This paper is not subject to U.S. copyright. The definitive version was published in Chemical Geology 371 (2014): 1-8, doi:10.1016/j.chemgeo.2014.01.018.Sabkhat (Salt flats) are common geographic features of low-lying marine coastal areas that develop under hyper-arid climatic conditions. They are characterized by the presence of highly concentrated saline solutions and evaporitic minerals, and have been cited in the geologic literature as present-day representations of hyper-arid regional paleohydrogeology, paleoclimatology, coastal processes, and sedimentation in the geologic record. It is therefore important that a correct understanding of the origin and development of these features be achieved. Knowledge of the source of solutes is an important first step in understanding these features. Historically, two theories have been advanced as to the main source of solutes in sabkha brines: an early concept entailing seawater as the obvious source, and a more recent and dynamic theory involving ascending geologic brine forced upward into the base of the sabkha by a regional hydraulic gradient in the underlying formations. Ra-226 could uniquely distinguish between these sources under certain circumstances, as it is typically present at elevated activity of hundreds to thousands of Bq/m3 (Becquerels per cubic meter) in subsurface formation brines; at exceedingly low activities in open ocean and coastal water; and not significantly supplied to water from recently formed marine sedimentary framework material. The coastal marine sabkha of the Emirate of Abu Dhabi was used to test this hypothesis. The distribution of Ra-226 in 70 samples of sabkha brine (mean: 700 Bq/m3), 7 samples of underlying deeper formation brine (mean: 3416 Bq/m3), the estimated value of seawater (< 16 Bq/m3) and an estimate of supply from sabkha sedimentary framework grains (<~6 Bq/m3) provide the first direct evidence that ascending geologic brine contributes significantly to the solutes of this sabkha system

Balloon dilation of mitral stenosis in adult patients: Postmortem and percutaneous mitral valvuloplasty studies

Preliminary reports have documented the utility of percutaneous balloon valvuloplasty of the mitral valve in adult patients with mitral stenosis, but the mechanism of successful valve dilation and the effect of mitral valvuloplasty on cardiac performance have not been studied in detail. Accordingly, mitral valvuloplasty was performed in five postmortem specimens and in 18 adult patients with rheumatic mitral stenosis, using either one (25 mm) or two (18 and 20 mm) dilation balloons. Postmortem balloon dilation resulted in increased valve orifice area in all five postmortem specimens, secondary to separation of fused commissures and fracture of nodular calcium within the mitral leaflets. In no case did balloon dilation result in tearing of valve leaflets, disruption of the mitral ring or liberation of potentially embolic debris.Percutaneous mitral valvuloplasty in 18 patients with severe mitral stenosis (including 9 with a heavily calcified valve) resulted in an increase in cardiac output (4.3 ± 1.1 to 5.1 ± 1.5 liters/min, p < 0.01) and mitral valve area (0.9 ± 0.2 to 1.6 ± 0.4 cm2, p < 0.0001), and a decrease in mean mitral pressure gradient (15 ± 5 to 9 ± 4 mm Hg, p < 0.0001), pulmonary capillary wedge pressure (23 ± 7 to 18 ± 7 mm Hg, p < 0.0001) and mean pulmonary artery pressure (36 ± 12 to 33 ± 12 mm Hg, p < 0.01). Left ventriculography before and after valvuloplasty in 14 of the 18 patients showed a mild (≤1 +) increase in mitral regurgitation in five patients and no change in the remainder. Embolic phenomena were not observed in any patient.Serial radionuclide ventriculography showed an increase in left ventricular peak filling rate (2.20 ± 1.20 to 2.50 ± 1.20 end-diastolic volumes per second [EDV/s], p < 0.05). Serial echocardiography/phonocardiography showed improvement in mitral valve excursion (11 ± 6 to 14 ± 6 mm, p < 0.001), mitral EF slope (7 ± 4 to 13 ± 5, p < 0.001), left atrial diameter (5.7 ± 0.9 to 5.3 ± 0.8 cm, p < 0.001), S2-opening snap interval (0.07 ± 0.03 to 0.08 ± 0.02 second, p < 0.02) and mitral valve area (0.9 ± 0.2 to 1.5 ± 0.4 cm2, p < 0.0001). All patients were discharged from the hospital with de- creased symptoms after valvuloplasty.It is concluded that percutaneous mitral valvuloplasty can be performed in adult patients with mitral stenosis, including patients with calcific disease, and can result in significant improvement in valvular function. The mechanisms of successful dilation include commissural separation and fracture of nodular calcium

Differential Requirement for LAT and SLP-76 in GPVI versus T Cell Receptor Signaling

Mice deficient in the adaptor Src homology 2 domain-containing leukocyte phosphoprotein of 76 kD (SLP-76) exhibit a bleeding disorder and lack T cells. Linker for activation of T cells (LAT)-deficient mice exhibit a similar T cell phenotype, but show no signs of hemorrhage. Both SLP-76 and LAT are important for optimal platelet activation downstream of the collagen receptor, GPVI. In addition, SLP-76 is involved in signaling mediated by integrin αIIbβ3. Because SLP-76 and LAT function coordinately in T cell signal transduction, yet their roles appear to differ in hemostasis, we investigated in detail the functional consequences of SLP-76 and LAT deficiencies in platelets. Previously we have shown that LAT−/− platelets exhibit defective responses to the GPVI-specific agonist, collagen-related peptide (CRP). Consistent with this, we find that surface expression of P-selectin in response to high concentrations of GPVI ligands is reduced in both LAT- and SLP-76–deficient platelets. However, platelets from LAT−/− mice, but not SLP-76−/− mice, aggregate normally in response to high concentrations of collagen and convulxin. Additionally, unlike SLP-76, LAT is not tyrosine phosphorylated after fibrinogen binding to integrin αIIbβ3, and collagen-stimulated platelets deficient in LAT spread normally on fibrinogen-coated surfaces. Together, these findings indicate that while LAT and SLP-76 are equally required for signaling via the T cell antigen receptor (TCR) and pre-TCR, platelet activation downstream of GPVI and αIIbβ3 shows a much greater dependency on SLP-76 than LAT

If the real world were irrelevant, so to speak: The role of propositional truth-value in counterfactual sentence comprehension

Propositional truth-value can be a defining feature of a sentence’s relevance to the unfolding discourse, and establishing propositional truth-value in context can be key to successful interpretation. In the current study, we investigate its role in the comprehension of counterfactual conditionals, which describe imaginary consequences of hypothetical events, and are thought to require keeping in mind both what is true and what is false. Pre-stored real-world knowledge may therefore intrude upon and delay counterfactual comprehension, which is predicted by some accounts of discourse comprehension, and has been observed during online comprehension. The impact of propositional truth-value may thus be delayed in counterfactual conditionals, as also claimed for sentences containing other types of logical operators (e.g., negation, scalar quantifiers). In an event-related potential (ERP) experiment, we investigated the impact of propositional truth-value when described consequences are both true and predictable given the counterfactual premise. False words elicited larger N400 ERPs than true words, in negated counterfactual sentences (e.g., “If N.A.S.A. had not developed its Apollo Project, the first country to land on the moon would have been Russia/America”) and real-world sentences (e.g., “Because N.A.S.A. developed its Apollo Project, the first country to land on the moon was America/Russia”) alike. These indistinguishable N400 effects of propositional truth-value, elicited by opposite word pairs, argue against disruptions by real-world knowledge during counterfactual comprehension, and suggest that incoming words are mapped onto the counterfactual context without any delay. Thus, provided a sufficiently constraining context, propositional truth-value rapidly impacts ongoing semantic processing, be the proposition factual or counterfactual

Bostonia: The Boston University Alumni Magazine. Volume 6

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Review Section : Nature/Nurture Revisited I

Biologically oriented approaches to the study of human conflict have thus far been limited largely to the study of aggression. A sample of the literature on this topic is reviewed, drawing upon four major approaches: comparative psychology, ethology (including some popularized accounts), evolutionary-based theories, and several areas of human physiology. More sophisticated relationships between so-called "innate" and "acquired" determinants of behavior are discussed, along with the proper relevance of animal behavior studies for human behavior. Unless contained in a comprehensive theory which includes social and psychological variables, biolog ically oriented theories (although often valid within their domain) offer at best severely limited and at worst highly misleading explanations of complex social conflicts. The review concludes with a list of several positive contributions of these biological approaches and suggests that social scientists must become more knowledgeable about them.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68270/2/10.1177_002200277401800206.pd

Sequencing three crocodilian genomes to illuminate the evolution of archosaurs and amniotes

The International Crocodilian Genomes Working Group (ICGWG) will sequence and assemble the American alligator (Alligator mississippiensis), saltwater crocodile (Crocodylus porosus) and Indian gharial (Gavialis gangeticus) genomes. The status of these projects and our planned analyses are described

Bostonia: The Boston University Alumni Magazine. Volume 16

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs