Constraining the mass density of free-floating black holes using razor-thin lensing arcs

Strong lensing of active galactic nuclei in the radio can result in razor-thin arcs, with a thickness of less than a milli-arcsecond, if observed at the resolution achievable with very long baseline interferometry (VLBI). Such razor-thin arcs provide a unique window on the coarseness of the matter distribution between source and observer. In this paper, we investigate to what extent such razor-thin arcs can constrain the number density and mass function of `free-floating' black holes, defined as black holes that do not, or no longer, reside at the centre of a galaxy. These can be either primordial in origin or arise as by-products of the evolution of super-massive black holes in galactic nuclei. When sufficiently close to the line of sight, free-floating black holes cause kink-like distortions in the arcs, which are detectable by eye in the VLBI images as long as the black hole mass exceeds $\sim 1000$ Solar masses. Using a crude estimate for the detectability of such distortions, we analytically compute constraints on the matter density of free-floating black holes resulting from null-detections of distortions along a realistic, fiducial arc, and find them to be comparable to those from quasar milli-lensing. We also use predictions from a large hydrodynamical simulation for the demographics of free-floating black holes that are not primordial in origin, and show that their predicted mass density is roughly four orders of magnitude below the constraints achievable with a single razor-thin arc.Comment: 17 pages, 13 figures, 1 table, comments welcom

1994). Réflexions sur la modélisation de la propagation de polluants dans les hydrosystèmes souterrains

Les modèles de simulation de propagation de polluants dans les eaux souterraines sont de plus en plus utilisés comme outils de gestion de cette ressource. La qualité des simulations dépend étroitement des connaissances que l'on a des processus et des paramètres de transport nécessaires à la mise en application des modèles. La fiabilité des résultats repose sur: - le choix du bon modèle en fonction de l'échelle d'observation - la mesure des paramètres représentatifs du transport liée à l'échelle de discrétisation du site - la spatialisation de mesures locales. Compte tenu des spécificités des hydrosystèmes souterrains (invisibilité, accès coûteux), la connaissance du milieu restera trop fragmentaire pour réaliser des simulations fines. Seules les approches stochastiques permettent alors d'intégrer ces incertitudes dans les simulations.Groundwater quality modelling has become a tool for water management. The accuracy of the simulations closely depends on the available knowledge concerning the transport processes and the parameters used in the model. The accuracy of the results depends on the choice ofa suitable model adapted to the observation scale, the measurement of the effective parameters linked to the discretization of the field and the spatialization of the local measurements.The mathematical model used to describe mass transport in porous media is the dispersion-convection equation. The velocity is calculated by solving the flow equation. For heterogeneous media, numerical schemes which simultaneously solve heads and velocities have to be preferred to classical finite element or finite differences techniques. The dispersion coefficient represents the velocity fluctuations around the average velocity. Therefore, it strongly depends on the dimension and the scale of the discretization.A predictive simulation of the Twin Lake Tracer Test experiment has been done. After a very fine calibration of the flow (differences between measured and calculated heads less than 1 cm), the transport simulation did not succeed. The headgradients were not calculated with enough accuracy and the simulated plume travelled in a wrong direction.Due to the nature of groundwater (invisible, expensive rneasurements), knowledge of the structure of the aquifer will always be too incomplete to perform very detailed simulations. Stochastic computations may be the way to take into account uncertainities in groundwater modening

Textural and microstructural studies of zinc sulfide and associated phases in certain base metal deposits

A textural and microstructural study of a variety of zinc sulfide-containing ores has been undertaken, and the possible depositional and deformational controls of textural and microstructural development considered. Samples for the study were taken from both deformed and undeformed zinc ores of the Central U.S. Appalachians, and deformed zinc ores of the English Pennines. A variety of mineralogical techniques were employed, including transmitted and reflected light microscopy of etched and unetched material, transmission electron microscopy and electron microprobe analysis. For the Pennine zinc sulfides, spectroscopic, x-ray diffraction and fluid inclusion studies were also undertaken. Optical and electron optical examination of the Appalachian material confirmed the suitability of zinc sulfide for detailed study with such techniques. Growth and deformation-related microstructures could be distinguished from specimen-preparation induced artifacts. A deformationally-mduced lamelliform optical anisotropy is seen to be developed in areas hosting a dense planar microstructure of {111} twin- and slip-planes. The Pennine zinc sulfide texturally records a changing depositional environment. Thus, for example, delicately growth- zoned crystals are truncated and cross-cut by solution disconformities. Fluid inclusion studies indicate a highly saline (20-25 wt. % equiv. NaCl), low temperature (100-150°C.) fluid. Texturally, two varieties of zinc sulfide can be recognised; a widely developed, iron- banded variety, and a paragenetically early variety, banded due to horizons rich in crystal defects and microscopic inclusions. The zinc sulfide takes the form of a disordered 3C-polytype, with much of the disorder being deformational in origin. Twin- and slip-plane fabrics are developed . A deformation-related optical anisotropy is seen to overprint growth-related anisotropy, along with cuprian alteration of certain {111} deformation planes

Knowing Values and Public Inspection

We present a basic dynamic epistemic logic of "knowing the value". Analogous to public announcement in standard DEL, we study "public inspection", a new dynamic operator which updates the agents' knowledge about the values of constants. We provide a sound and strongly complete axiomatization for the single and multi-agent case, making use of the well-known Armstrong axioms for dependencies in databases

The development of food portion sizes suitable for 4–18‐year‐old children used in a theoretical meal plan meeting energy and nutrient requirements

Background: Healthy eating guidelines for school‐aged children are available but without advice on portion sizes. This is a concern because consuming large portions is associated with an increased risk of overweight/obesity. The present study aimed to calculate recommended portion sizes for school‐aged children based on weight for age and use them to develop a meal plan to meet nutritional needs within energy requirements. / Methods: Portion size data on foods consumed by school‐aged children (4–18 years) were extracted from two sources: (i) British National Diet and Nutrition Survey (1997) and (ii) Avon Longitudinal Study of Parents and Children (1997–2006). Foods were allocated to groups based on the UK Eatwell Guide and the US My Plate Model. Portion sizes were developed for a variety of foods. A meal plan that included portion size guidance and met healthy eating guidelines was developed based on the number of portions of each food group needed to meet dietary requirements. / Results: Portion sizes were developed for 131 foods that were commonly eaten by children in age groups 4–6, 7–10, 11–14 and 15–18 years. The meal plan met requirements for energy and nutrients as specified by UK dietary reference values, except for vitamin D for which there are few dietary sources. / Conclusions: Food portion sizes informed by usual intake in UK children can help inform dietary advice for a range of childhood settings and for parents. The meal plan included a wide variety of foods to encourage dietary diversity and meet energy and nutrient needs for school‐aged children

Knowledge, attitude and experiences of menopause in the postmenopausal women at a tertiary care center: a cross sectional study

Background: Menopause is an inevitable milestone in the reproductive life of every woman. The objective is to investigate menopausal knowledge, attitude, symptoms and management among the participants, to identify the differences according to their educational status and to examine correlations of knowledge, attitude and symptoms pertaining to menopause.Methods: This cross-sectional study was conducted for a period of 10 months in postmenopausal women attending a tertiary care center in Pondicherry, India with a structured questionnaire developed on the basis of the objective of the study.Results: 330 postmenopausal women were recruited, and all were aware of their postmenopausal status. Mean age at menopause was 45.91±2.66 years. 54.5% were aware about what menopause was while 5.5% were unaware. 12.1% had proper knowledge about cause of menopause, whereas 3.6% said it is due to god’s decision / turning point. Most prevalent symptoms were tiredness (89.6%) followed by vasomotor symptoms like hot flushes (88.5%) and night sweats (80.3%). Only 2.1% had used HRT for menopausal symptoms.Conclusions: Depth of knowledge is more important when concern is about greater health disrupter which tends to be imperceptible for a long time such as bone health and cardiovascular risk profile. Thus, the government could concentrate on providing health services to women in post reproductive age group also besides women in the reproductive age

SARCS strong lensing galaxy groups: I - optical, weak lensing, and scaling laws

We present the weak lensing and optical analysis of the SL2S-ARCS (SARCS) sample of strong lens candidates. The sample is based on the Strong Lensing Legacy Survey (SL2S), a systematic search of strong lensing systems in the photometric Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The SARCS sample focuses on arc-like features and is designed to contain mostly galaxy groups. We briefly present the weak lensing methodology that we use to estimate the mass of the SARCS objects. Among 126 candidates, we obtain a weak lensing detection for 89 objects with velocity dispersions of the Singular Isothermal Sphere mass model ranging from 350 to 1000 km/s with an average value of 600km/s, corresponding to a rich galaxy group (or poor cluster). From the galaxies belonging to the bright end of the group's red sequence (M_i<-21), we derive the optical properties of the SARCS candidates. We obtain typical richnesses of N=5-15 galaxies and optical luminosities of L=0.5-1.5e+12 Lsol (within a radius of 0.5 Mpc). We use these galaxies to compute luminosity density maps, from which a morphological classification reveals that a large fraction of the sample are groups with a complex light distribution, either elliptical or multimodal, suggesting that these objects are dynamically young structures. We finally combine the lensing and optical analyses to draw a sample of 80 most secure group candidates, i.e. weak lensing detection and over-density at the lens position in the luminosity map, to remove false detections and galaxy-scale systems from the initial sample. We use this reduced sample to probe the optical scaling relations in combination with a sample of massive galaxy clusters. We detect the expected correlations over the probed range in mass with a typical scatter of 25% in the SIS velocity dispersion at a given richness or luminosity, making these scaling laws interesting mass proxie