Ice-dammed lateral lake and epishelf lake insights into Holocene dynamics of Margeurite Trough Ice Stream and George VI Ice Shelf, Alexander Island, Antarctic Peninsula

Funded by NERC grant NE/F0128961/1We present new data regarding the past dynamics of Marguerite Trough Ice Stream, George VI Ice Shelf and valley glaciers from Ablation Point Massif on Alexander Island, Antarctic Peninsula. This ice-free oasis preserves a geological record of ice stream lateral moraines, ice-dammed lakes, ice-shelf moraines and valley glacier moraines, which we dated using cosmogenic nuclide ages. We provide one of the first detailed sediment-landform assemblage descriptions of epishelf lake shorelines. Marguerite Trough Ice Stream imprinted lateral moraines against eastern Alexander Island at 120 m at Ablation Point Massif. During deglaciation, lateral lakes formed in the Ablation and Moutonn?e valleys, dammed against the ice stream in George VI Sound. Exposure ages from boulders on these shorelines yielded ages of 13.9 to 9.7 ka. Following recession of the ice stream, George VI Ice Shelf formed in George VI Sound. An epishelf lake formed at 15?20 m asl in Ablation and Moutonn?e valleys, dated from 9.4 to 4.6 ka, suggesting that the lake was stable and persistent for some 5000 years. Lake-level lowering occurred after this, with the lake level at 12 m at 3.1 ? 0.4 ka and at 5 m asl today. A readvance of the valley glaciers on Alexander Island at 4.4 ? 0.7 ka is recorded by valley glacier moraines overlying epishelf lake sediments. We speculate that the glacier readvance, which occurred during a period of warmth, may have been caused by a dynamic response of the glaciers to a lowering in surface elevation of George VI Ice ShelfpublishersversionPeer reviewe

Community screening for left ventricular systolic dysfunction using plasma and urinary natriuretic peptides

ObjectivesWe sought to compare urinary and plasma N-terminal pro-brain natriuretic peptide (N-BNP) in left ventricular systolic dysfunction (LVSD) diagnosis.BackgroundPlasma N-BNP is elevated in LVSD. Renal tubule cells produce BNP. We tested the incremental value of urinary N-BNP in LVSD diagnosis.MethodsIn this prospective, community-screening study of undiagnosed LVSD, 1,360 subjects (45 to 80 years of age) were invited, and 1,308 had analyzable echocardiographic scans and urine and plasma specimens. The criterion standard for LVSD was defined as a wall motion score over 1.8 (ejection fraction ≤40%).ResultsTwenty-eight patients with LVSD had elevated urinary and plasma N-BNP levels compared with normal subjects (p < 0.0005). Receiver-operating characteristic (ROC) areas under the curve (AUCs) for urinary and plasma N-BNP were 0.831 and 0.840, respectively. Both tests had high negative predictive values (>99%) for excluding LVSD. Urinary N-BNP was more specific (67.2%) than plasma N-BNP (41%). The plasma/urinary N-BNP product yielded a higher ROC-AUC (0.923) and specificity (78%), reducing the number of cases to scan to detect one case of LVSD to 11.4 (compared with 16.6 [urinary N-BNP] and 29.0 [plasma N-BNP]). Sequential application of tests (urinary N-BNP, then plasma N-BNP in the urine-“positive” cases) achieved similar reductions in the number of cases to scan (10.8), while limiting the number of N-BNP tests to be performed. Urinary N-BNP performed poorly in detection of other cardiac abnormalities with preserved systolic function. It was less costly to test urinary N-BNP in the whole population as compared with other strategies, including scanning high-risk cases with N-BNP testing in the remainder.ConclusionsUrinary N-BNP used together with plasma N-BNP could reduce the echocardiographic burden in screening programs

Gender and renal function influence plasma levels of copeptin in healthy individuals

A B S T R A C T The present study sought to identify confounding factors for the interpretation of copeptin levels in healthy individuals. The natriuretic peptides are recognized as diagnostic and prognostic tools in HF (heart failure). Interpretation of BNP (brain natriuretic peptide) and NTproBNP (N-terminal pro-BNP) levels is multifaceted as their secretion is influenced by many variables. A newly identified glycopeptide called copeptin is comparable with the natriuretic peptides in the diagnosis and prognosis of HF and as a prognostic biomarker after AMI (acute myocardial infarction). Copeptin, derived from the C-terminal portion of the precursor to AVP (arginine vasopressin), is secreted stoichiometrically with vasopressin, hence it can be used as a surrogate marker of the AVP system. In the present study, 706 healthy volunteers were recruited from a local HF screening study. Participants with a history of cardiovascular disease and those with echocardiographic abnormalities were excluded from the study. Copeptin and NTproBNP levels were assayed using in-house immunoluminometric assays. Median copeptin levels were significantly higher in the male volunteers compared with the females [median (range): 4.3 (0.4 -44.3) compared with 3.2 (1.0-14.8) pmol/l; P &lt; 0.001]. In males, copeptin was correlated with eGFR (estimated glomerular filtration rate; r s = − 0.186, P &lt; 0.001). In females, the correlation of copeptin with eGFR was weak (r s = − 0.097, P = 0.095). DT (deceleration time) and left atrial size correlated with higher copeptin levels (r s = 0.085, P = 0.029 and r s = 0.206, P &lt; 0.001 respectively). Only gender (P &lt; 0.001), eGFR (P &lt; 0.001), left atrial size (P = 0.04) and DT (P = 0.02) remained independently predictive of plasma copeptin. The present study suggests that gender and renal function specific partition values should be used to interpret copeptin values in future studies of this biomarker in HF or ischaemic heart disease

Activation of a novel natriuretic endocrine system in humans with heart failure

Proguanylin and prouroguanylin are the inactive precursors of guanylin and uroguanylin, natriuretic peptides involved in the regulation of sodium balance. Urinary uroguanylin levels have been found previously to be elevated in patients with HF (heart failure). The aim of the present study was to investigate whether plasma proguanylin and prouroguanylin levels are increased in patients with HF and to evaluate their relationship with cardiac and renal function. In this prospective observational study, we recruited 243 patients with HF (151 men) and 72 healthy controls. In patients with HF, plasma levels of proguanylin [median, 7.2 (range, 0.9–79.0) μg/l] and prouroguanylin [8.3 (1.7–53.0 μg/l)] were both significantly (P<0.0005) higher compared with levels in healthy controls [5.5 (0.4–22.3 μg/l) for proguanylin and 6.3 (2.5–16.9) μg/l for prouroguanylin]. In patients with HF, increased age, a history of hypertension, diabetes and atrial fibrillation, use of diuretics, a higher NYHA (New York Heart Association) class and a lower eGFR (estimated glomerular filtration rate) were significant univariate predictors of proguanylin and prouroguanylin levels. In multivariate analysis, a history of hypertension and low eGFR both had strong independent associations with proguanylin and prouroguanylin levels. Proguanylin and prouroguanylin varied significantly between NYHA class with a trend of increasing plasma concentrations with worsening severity of symptoms. In conclusion, plasma proguanylin and prouroguanylin are elevated in patients with HF. Elevated plasma proguanylin and prouroguanylin levels are associated with hypertension, renal impairment and increasing severity of HF. This novel endocrine system may contribute to the pathophysiology of HF

Cosmological Constant Problems and Renormalization Group

The Cosmological Constant Problem emerges when Quantum Field Theory is applied to the gravitational theory, due to the enormous magnitude of the induced energy of the vacuum. The unique known solution of this problem involves an extremely precise fine-tuning of the vacuum counterpart. We review a few of the existing approaches to this problem based on the account of the quantum (loop) effects and pay special attention to the ones involving the renormalization group.Comment: 12 pages, LaTeX, based on the on the talk at IRGAC-2006 (Barcelona, July 11-15, 2006), misprints corrected, comment on anthropic approach modified, some references added, accepted in Journal of Physics

Gravitational Radiation from Coalescing Binary Neutron Stars

We calculate the gravitational radiation produced by the merger and coalescence of inspiraling binary neutron stars using 3-dimensional numerical simulations. The stars are modeled as polytropes and start out in the point-mass limit at wide separation. The hydrodynamic integration is performed using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the gravitational radiation is calculated using the quadrupole approximation. We have run several simulations, varying both the neutron star radius and the equation of state. The resulting gravitational wave energy spectra $dE/df$ are rich in information about the hydrodynamics of merger and coalescence. In particular, our results demonstrate that detailed information on both $GM/Rc^2$ and the equation of state can in principle be extracted from the spectrum.Comment: 33 pages, LaTex with RevTex macros; 21 figures available in compressed PostScript format via anonymous ftp to ftp://zonker.drexel.edu/papers/ns_coll_1 ; in press, Phys. Rev. D (Nov 15, 1994 issue

Exploring Human/Animal Intersections: Converging Lines of Evidence in Comparative Models of Aging

At a symposium convened on March 8, 2007 by the Institute on Aging at the University of Pennsylvania, researchers from the University’s Schools of Medicine and Veterinary Medicine explored the convergence of aging research emerging from the two schools. Studies in human patients, animal models, and companion animals have revealed different but complementary aspects of the aging process, ranging from fundamental biologic aspects of aging to the treatment of age-related diseases, both experimentally and in clinical practice. Participants concluded that neither animal nor human research alone will provide answers to most questions about the aging process. Instead, an optimal translational research model supports a bidirectional flow of information from animal models to clinical research

Open science in archaeology

No abstract available

Gravitational Radiation from the Coalescence of Binary Neutron Stars: Effects Due to the Equation of State, Spin, and Mass Ratio

We calculate the gravitational radiation produced by the coalescence of inspiraling binary neutron stars in the Newtonian regime using 3-dimensional numerical simulations. The stars are modeled as polytropes and start out in the point-mass regime at wide separation. The hydrodynamic integration is performed using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the gravitational radiation is calculated using the quadrupole approximation. We have run a number of simulations varying the neutron star radii, equations of state, spins, and mass ratio. The resulting gravitational waveforms and spectra are rich in information about the hydrodynamics of coalescence, and show characteristic dependence on GM/Rc^2, the equation of state, and the mass ratio.Comment: 39 pages, uses Latex 2.09. To be published in the Dec. 15, 1996 issue of Physical Review D. 16 Figures (bitmapped). Originals available in compressed Postscript format at ftp://zonker.drexel.edu/papers/PAPER2

Paediatric Investigators Collaborative Network on Infections in Canada (PICNIC) study of aseptic meningitis

BACKGROUND: The seasonality, clinical and radiographic features and outcome of aseptic meningitis have been described for regional outbreaks but data from a wider geographic area is necessary to delineate the epidemiology of this condition. METHODS: A retrospective chart review was completed of children presenting with aseptic meningitis to eight Canadian pediatric hospitals over a two-year period. RESULTS: There were 233 cases of proven enteroviral (EV) meningitis, 495 cases of clinical aseptic meningitis and 74 cases of possible aseptic meningitis with most cases occurring July to October. Headache, vomiting, meningismus and photophobia were more common in children ≥ 5 years of age, while rash, diarrhea and cough were more common in children < 5 years of age. Pleocytosis was absent in 22.3% of children < 30 days of age with proven EV meningitis. Enterovirus was isolated in cerebrospinal fluid (CSF) from 154 of 389 patients (39.6%) who had viral culture performed, and a nucleic acid amplification test for enterovirus was positive in CSF from 81 of 149 patients (54.3%). Imaging of the head by computerized tomography or magnetic resonance imaging was completed in 96 cases (19.7%) and 24 had abnormal findings that were possibly related to meningitis while none had changes that were definitely related to meningitis. There was minimal morbidity and there were no deaths. CONCLUSION: The clinical presentation of aseptic meningitis varies with the age of the child. Absence of CSF pleocytosis is common in infants < 30 days of age. Enterovirus is the predominant isolate, but no etiologic agent is identified in the majority of cases of aseptic meningitis in Canadian children