Fluctuating geometries, q-observables, and infrared growth in inflationary spacetimes

Infrared growth of geometrical fluctuations in inflationary spacetimes is investigated. The problem of gauge-invariant characterization of growth of perturbations, which is of interest also in other spacetimes such as black holes, is addressed by studying evolution of the lengths of curves in the geometry. These may either connect freely falling "satellites," or wrap non-trivial cycles of geometries like the torus, and are also used in diffeomorphism- invariant constructions of two-point functions of field operators. For spacelike separations significantly exceeding the Hubble scale, no spacetime geodesic connects two events, but one may find geodesics constrained to lie within constant-time spatial slices. In inflationary geometries, metric perturbations produce significant and growing corrections to the lengths of such geodesics, as we show in both quantization on an inflating torus and in standard slow-roll inflation. These become large, signaling breakdown of a perturbative description of the geometry via such observables, and consistent with perturbative instability of de Sitter space. In particular, we show that the geodesic distance on constant time slices during inflation becomes non-perturbative a few e-folds after a given scale has left the horizon, by distances \sim 1/H^3 \sim RS, obstructing use of such geodesics in constructing IR-safe observables based on the spatial geometry. We briefly discuss other possible measures of such geometrical fluctuations.Comment: 33 pages, 2 figures, latex; v2: typos corrected, references improve

On the divergences of inflationary superhorizon perturbations

We discuss the infrared divergences that appear to plague cosmological perturbation theory. We show that within the stochastic framework they are regulated by eternal inflation so that the theory predicts finite fluctuations. Using the $\Delta N$ formalism to one loop, we demonstrate that the infrared modes can be absorbed into additive constants and the coefficients of the diagrammatic expansion for the connected parts of two and three-point functions of the curvature perturbation. As a result, the use of any infrared cutoff below the scale of eternal inflation is permitted, provided that the background fields are appropriately redefined. The natural choice for the infrared cutoff would of course be the present horizon; other choices manifest themselves in the running of the correlators. We also demonstrate that it is possible to define observables that are renormalization group invariant. As an example, we derive a non-perturbative, infrared finite and renormalization point independent relation between the two-point correlators of the curvature perturbation for the case of the free single field.Comment: 12 page

Identification of early stage and metastatic prostate cancer using electrochemical detection of beta-2-microglobulin in urine samples from patients

Abstract To improve prostate cancer (PCa) diagnosis, it is imperative to identify novel biomarkers and establish effective screening techniques. Here, we introduce electrochemical biosensing of β-2-Microglobulin (β2M) in urine as a potential diagnostic tool for PCa. The immunosensor is composed of a screen-printed graphene electrode coated with anti β2M antibodies. The sensor is capable of detecting the protein directly in urine without any sample pretreatment within 45 min including sample incubation and a lower limit of detection of 204 µg/L. The sensor demonstrated a significant difference in the β2M-creatinine ratio in urine between control and both local- and metastatic PCa (mPCa) (P = 0.0302 and P = 0.0078 respectively), and between local- and mPCa (P = 0.0302). This first example of electrochemical sensing of β2M for the diagnosis of PCa may set the stage for an affordable, on-site screening technique for PCa

Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food : Outcome of the collaborative trial IMEP-41

Peer reviewedPublisher PD

The Kramers-Moyal Equation of the Cosmological Comoving Curvature Perturbation

Fluctuations of the comoving curvature perturbation with wavelengths larger than the horizon length are governed by a Langevin equation whose stochastic noise arise from the quantum fluctuations that are assumed to become classical at horizon crossing. The infrared part of the curvature perturbation performs a random walk under the action of the stochastic noise and, at the same time, it suffers a classical force caused by its self-interaction. By a path-interal approach and, alternatively, by the standard procedure in random walk analysis of adiabatic elimination of fast variables, we derive the corresponding Kramers-Moyal equation which describes how the probability distribution of the comoving curvature perturbation at a given spatial point evolves in time and is a generalization of the Fokker-Planck equation. This approach offers an alternative way to study the late time behaviour of the correlators of the curvature perturbation from infrared effects.Comment: 27 page

Classicality of the primordial perturbations

We show that during inflation, a quantum fluctuation becomes classical at all orders if it becomes classical at first order. Implications are discussed.Comment: 4 pages, uses RevTeX4 LaTeX document class. v2: More details of the classicality argument, and an improved discussion of its implications. v3: matches version published in PL

Urinary tract infections and post-operative fever in percutaneous nephrolithotomy

To review the incidence of UTIs, post-operative fever, and risk factors for post-operative fever in PCNL patients. Between 2007 and 2009, consecutive PCNL patients were enrolled from 96 centers participating in the PCNL Global Study. Only data from patients with pre-operative urine samples and who received antibiotic prophylaxis were included. Pre-operative bladder urine culture and post-operative fever (>38.5°C) were assessed. Relationship between various patient and operative factors and occurrence of post-operative fever was assessed using logistic regression analyses. Eight hundred and sixty-five (16.2%) patients had a positive urine culture; Escherichia coli was the most common micro-organism found in urine of the 350 patients (6.5%). Of the patients with negative pre-operative urine cultures, 8.8% developed a fever post-PCNL, in contrast to 18.2% of patients with positive urine cultures. Fever developed more often among the patients whose urine cultures consisted of Gram-negative micro-organisms (19.4-23.8%) versus those with Gram-positive micro-organisms (9.7-14.5%). Multivariate analysis indicated that a positive urine culture (odds ratio [OR] = 2.12, CI [1.69-2.65]), staghorn calculus (OR = 1.59, CI [1.28-1.96]), pre-operative nephrostomy (OR = 1.61, CI [1.19-2.17]), lower patient age (OR for each year of 0.99, CI [0.99-1.00]), and diabetes (OR = 1.38, CI [1.05-1.81]) all increased the risk of post-operative fever. Limitations include the use of fever as a predictor of systemic infection. Approximately 10% of PCNL-treated patients developed fever in the post-operative period despite receiving antibiotic prophylaxis. Risk of post-operative fever increased in the presence of a positive urine bacterial culture, diabetes, staghorn calculi, and a pre-operative nephrostom