Einstein gravity as a 3D conformally invariant theory

We give an alternative description of the physical content of general relativity that does not require a Lorentz invariant spacetime. Instead, we find that gravity admits a dual description in terms of a theory where local size is irrelevant. The dual theory is invariant under foliation preserving 3-diffeomorphisms and 3D conformal transformations that preserve the 3-volume (for the spatially compact case). Locally, this symmetry is identical to that of Horava-Lifshitz gravity in the high energy limit but our theory is equivalent to Einstein gravity. Specifically, we find that the solutions of general relativity, in a gauge where the spatial hypersurfaces have constant mean extrinsic curvature, can be mapped to solutions of a particular gauge fixing of the dual theory. Moreover, this duality is not accidental. We provide a general geometric picture for our procedure that allows us to trade foliation invariance for conformal invariance. The dual theory provides a new proposal for the theory space of quantum gravity.Comment: 27 pages. Published version (minor changes and corrections

Jacobi's Principle and the Disappearance of Time

Jacobi's action principle is known to lead to a problem of time. For example, the timelessness of the Wheeler-DeWitt equation can be seen as resulting from using Jacobi's principle to define the dynamics of 3-geometries through superspace. In addition, using Jacobi's principle for non-relativistic particles is equivalent classically to Newton's theory but leads to a time-independent Schrodinger equation upon Dirac quantization. In this paper, we study the mechanism for the disappearance of time as a result of using Jacobi's principle in these simple particle models. We find that the path integral quantization very clearly elucidates the physical mechanism for the timeless of the quantum theory as well as the emergence of duration at the classical level. Physically, this is the result of a superposition of clocks which occurs in the quantum theory due to a sum over all histories. Mathematically, the timelessness is related to how the gauge fixing functions impose the boundary conditions in the path integral.Comment: Published version. Significant amendments to presentation. 27 page

Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake

NSERC Grant No. CRDPJ 476388; NSERC Grant No. IRCPJ 428588–11Peer ReviewedFluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)—the first full-scale demonstration oil sands end pit lake (EPL)—contains approximately 1.9 3 108 m^3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m^3 m^-2 d^-1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy

Quantum Machian Time in Toy Models of Gravity

General Relativity on closed spatial topologies can be derived, using a technique called "best-matching", as an evolving 3-geometry subject to constraints. These constraints can be thought of as a way of imposing temporal and spatial relationalism. The same type of constraints can be used in non-relativistic particle models to produce relational theories that suffer from the same Problem of Time as that encountered in General Relativity. As a result, these simple toy models are well suited for studying the Problem of Time in quantum gravity. In this paper, a version of these particle models is studied where we "best-match" the time translational invariance of the theory. Using insights gained from this procedure, we can move back and forth between absolute and relational time by changing the way in which the relational fields are varied. We then proceed to quantize this theory using Dirac and path integral quantizations. We discover that one of the constraints of the theory, which we call the Mach constraint, is responsible for removing the dependence of the theory on a background structure. It is this Mach constraint that is responsible for making the theory temporally relational. Because of the deep relationship between these models and General Relativity, this work may shed new light on the Problem of Time in quantum gravity and how one might expect time to emerge on quantum subsystems of the universe.Comment: 27 pages, references added, typos fixed, additional comments added to abs/intro/concl, journal ref adde

The role of growth and maturation during adolescence on team-selection and short-term sports participation

Background: During adolescence, deselection from sport occurs during team try-outs when month of birth, stage of growth and maturation may influence selection.Aim: The purpose of this study was to identify differences in growth and maturity related factors between those selected and deselected in youth sports teams and identify short-term associations with continued participation.Subjects and methods: Eight hundred and seventy participants, aged 11–17 years, were recruited from six sports try-outs in Saskatchewan, Canada: baseball, basketball, football, hockey, soccer and volleyball. Two hundred and forty-four of the initial 870 (28%) returned for follow-up at 36 months. Chronological (years from birth), biological (years from age at peak height velocity (APHV)) and relative (month of birth as it relates to the selection band) ages were calculated from measures of date of birth, date of test, height, sitting height and weight. Parental heights were measured or recalled and participant’s adult height predicted. Reference standards were used to calculate z-scores. Sports participation was self-reported at try-outs and at 36-month follow-up.Results: There was an over-representation of players across all sports born in the first and second quartiles of the selection bands (p < 0.05), whether they were selected or deselected. z-scores for predicted adult height ranged from 0.1 (1.1) to 1.8 (1.2) and were significantly different between sports (p < 0.05). Height and APHV differences (p < 0.05) were found between selected and deselected male participants. In females only weight differed between selected and deselected female hockey players (p < 0.05); no further differences were found between selected and deselected female participants. Four per cent of deselected athletes exited sports participation and 68% of deselected athletes remained in the same sport at 36 months, compared with 84% of selected athletes who remained in the same sport.Conclusions: It was found that youth who attended sports team’s try-outs were more likely to be born early in the selection year, be tall for their age, and in some sports early maturers. The majority of both the selected and deselected participants continued to participate in sport 36 months after try-outs, with the majority continuing to participate in their try-out sport

Conversion of Society for Maternal-Fetal Medicine abstract presentations to manuscript publications

To evaluate the rate of conversion of Society for Maternal Fetal Medicine (SMFM) Annual Meeting abstract presentations to full manuscript publications over time

Disease-specific risk of venous thromboembolic events is increased in idiopathic glomerulonephritis

The risk of venous thromboembolic events is thought to be highest in patients with membranous nephropathy. This association has been recently questioned, and it is not known whether this simply reflects the severity of proteinuria. To better understand the relationship between histologic diagnosis and the risk of venous thromboembolic events we evaluated patients in the Toronto Glomerulonephritis Registry. Of 1313 patients with idiopathic glomerulonephritis, 395 were diagnosed with membranous nephropathy, 370 with focal segmental glomerulosclerosis (FSGS), and 548 with immunoglobulin-A nephropathy (IgAN). Risk factors were evaluated by Cox proportional hazards for 53 image-confirmed venous thromboembolic events in 44 patients during a median follow-up of 63 months. The risk was highest in patients with membranous nephropathy and FSGS (hazard ratios of 22 and 7.8, respectively) referenced to patients with IgAN. Following adjustment for gender, cancer history, proteinuria, and serum albumin by multivariable analysis, the histologic subtype remained an independent risk for venous thromboembolic events. This risk was still highest in patients with membranous nephropathy followed by FSGS with adjusted hazard ratios of 10.8 and 5.9, respectively. Thus, in this large cohort, histologic diagnosis was an independent risk factor for venous thromboembolic events. Further studies are needed to discover mechanisms responsible for this high risk in patients with membranous nephropathy

Effects of dapagliflozin on volume status and systemic haemodynamics in patients with chronic kidney disease without diabetes:Results from DAPASALT and DIAMOND

Aims To assess the effect of sodium-glucose cotransporter-2 inhibitor dapagliflozin on natriuresis, blood pressure (BP) and volume status in patients with chronic kidney disease (CKD) without diabetes. Materials and methods We performed a mechanistic open-label study (DAPASALT) to evaluate the effects of dapagliflozin on 24-hour sodium excretion, 24-hour BP, extracellular volume, and markers of volume status during a standardized sodium diet (150 mmol/d) in six patients with CKD. In parallel, in a placebo-controlled double-blind crossover trial (DIAMOND), we determined the effects of 6 weeks of dapagliflozin on markers of volume status in 53 patients with CKD. Results In DAPASALT (mean age 65 years, mean estimated glomerular filtration rate [eGFR] 39.4 mL/min/1.73 m(2), median urine albumin:creatinine ratio [UACR] 111 mg/g), dapagliflozin did not change 24-hour sodium and volume excretion during 2 weeks of treatment. Dapagliflozin was associated with a modest increase in 24-hour glucose excretion on Day 4, which persisted at Day 14 and reversed to baseline after discontinuation. Mean 24-hour systolic BP decreased by -9.3 (95% confidence interval [CI] -19.1, 0.4) mmHg after 4 days and was sustained at Day 14 and at wash-out. Renin, angiotensin II, urinary aldosterone and copeptin levels increased from baseline. In DIAMOND (mean age 51 years, mean eGFR 59.0 mL/min/1.73 m(2), median UACR 608 mg/g), compared to placebo, dapagliflozin increased plasma renin (38.5 [95% CI 7.4, 78.8]%), aldosterone (19.1 [95% CI -5.9, 50.8]%), and copeptin levels (7.3 [95% CI 0.1, 14.5] pmol/L). Conclusions During a standardized sodium diet, dapagliflozin decreased BP but did not increase 24-hour sodium and volume excretion. The lack of increased natriuresis and diuresis may be attributed to activation of intra-renal compensatory mechanisms to prevent excessive water loss

Effects of the SGLT2 inhibitor dapagliflozin on proteinuria in non -diabetic patients with chronic kidney disease (DIAMOND):a randomised, double-blind, crossover trial

Background: SGLT2 inhibition decreases albuminuria and reduces the risk of kidney disease progression in patients with type 2 diabetes. These benefits are unlikely to be mediated by improvements in glycaemic control alone. Therefore, we aimed to examine the kidney effects of the SGLT2 inhibitor dapagliflozin in patients with proteinuric kidney disease without diabetes. Methods: DIAMOND was a randomised, double-blind, placebo-controlled crossover trial done at six hospitals in Canada, Malaysia, and the Netherlands. Eligible participants were adult patients (aged 18–75 years) with chronic kidney disease, without a diagnosis of diabetes, with a 24-h urinary protein excretion greater than 500 mg and less than or equal to 3500 mg and an estimated glomerular filtration rate (eGFR) of at least 25 mL/min per 1·73 m2, and who were on stable renin–angiotensin system blockade. Participants were randomly assigned (1:1) to receive placebo and then dapagliflozin 10 mg per day or vice versa. Each treatment period lasted 6 weeks with a 6-week washout period in between. Participants, investigators, and study personnel were masked to assignment throughout the trial and analysis. The primary outcome was percentage change from baseline in 24-h proteinuria during dapagliflozin treatment relative to placebo. Secondary outcomes were changes in measured GFR (mGFR; via iohexol clearance), bodyweight, blood pressure, and concentrations of neurohormonal biomarkers. Analyses were done in accordance with the intention-to-treat principle. This study is registered with ClinicalTrials.gov, NCT03190694. Findings: Between Nov 22, 2017, and April 5, 2019, 58 patients were screened, of whom 53 (mean age 51 years [SD 13]; 32% women) were randomly assigned (27 received dapagliflozin then placebo and 26 received placebo then dapagliflozin). One patient discontinued during the first treatment period. All patients were included in the analysis. Mean baseline mGFR was 58·3 mL/min per 1·73 m2 (SD 23), median proteinuria was 1110 mg per 24 h (IQR 730–1560), and mean HbA1c was 5·6% (SD 0·4). The difference in mean proteinuria change from baseline between dapagliflozin and placebo was 0·9% (95% CI −16·6 to 22·1; p=0·93). Compared with placebo, mGFR was changed with dapagliflozin treatment by −6·6 mL/min per 1·73 m2 (–9·0 to −4·2; p<0·0001) at week 6. This reduction was fully reversible within 6 weeks after dapagliflozin discontinuation. Compared with placebo, bodyweight was reduced by 1·5 kg (0·03–3·0; p=0·046) with dapagliflozin; changes in systolic and diastolic blood pressure and concentrations of neurohormonal biomarkers did not differ significantly between dapagliflozin and placebo treatment. The numbers of patients who had one or more adverse events during dapagliflozin treatment (17 [32%] of 53) and during placebo treatment (13 [25%] of 52) were similar. No hypoglycaemic events were reported and no deaths occurred. Interpretation: 6-week treatment with dapagliflozin did not affect proteinuria in patients with chronic kidney disease without diabetes, but did induce an acute and reversible decline in mGFR and a reduction in bodyweight. Long-term clinical trials are underway to determine whether SGLT2 inhibitors can safely reduce the rate of major clinical kidney outcomes in patients with chronic kidney disease with and without diabetes. Funding: AstraZeneca