Scale Coverage Research Articles

Kinetics of gypsum crystal growth on a reverse osmosis membrane

The development of calcium sulfate dihydrate (gypsum) mineral scale in reverse osmosis (RO) membrane desalting was investigated by direct real-time observation of crystal growth. Gypsum scaling studies were conducted in a specially modified plate-and-frame reverse osmosis cell fitted with an optical window, with dark-field membrane lighting arrangement within the membrane cell to enhance crystal boundaries and allow recording of digital surface images magnified through an optical microscope. The evolution of the surface number density (SND) of gypsum crystals resembled a sigmoidal population growth process with an increasing rate of crystal formation at higher solution supersaturation (with respect to gypsum) at the membrane surface. The rate of formation of new crystals declined as the surface scale coverage increased, with surface scale progressing by diffusion-controlled growth of existing crystals as the gypsum crystal SND approached its plateau. The apparent crystallization induction time (i.e., observation time for the appearance of surface crystals) decreased with increased supersaturation, with single crystals growth reasonably characterized by a diffusion-growth model and a single crystal fluid mass transfer coefficient that was generalized by a Sherwood number type correlation. The present approach provides a convenient method of characterizing the kinetics of gypsum scale formation via quantification of single crystal mass transfer coefficient and evolution of the crystal SND. Such information can guide the development of comprehensive RO membrane scale formation models and characterization of mineral scaling propensities of RO membranes and source water where mineral salt scaling is of concern.

Reverse Osmosis Desalting of Inland Brackish Water of High Gypsum Scaling Propensity: Kinetics and Mitigation of Membrane Mineral Scaling

The potential for mineral scaling that may limit the generation of new potable water resources by reverse osmosis (RO), from inland brackish water of high gypsum scaling propensity, was experimentally explored via flux decline measurements and real-time RO membrane surface imaging. Antagonistic gypsum and calcium carbonate scaling kinetics were demonstrated for high-sulfate brackish water desalting. RO scaling studies with brackish water from the California San Joaquin Valley (approximately 10 000 mg/L total dissolved solids) revealed that membrane gypsum scaling was increasingly retarded with rising bicarbonate concentrations. Crystal growth rate, fractional membrane scale coverage, and flux decline decreased by up to about 63, 78, and 73%, respectively, as the bicarbonate concentration increased, at the membrane surface, from < 0.01 to 7.81 mM, for a gypsum saturation index of 2. Inhibition of gypsum crystal growth was attributed to bicarbonate adsorption onto the crystal surfaces, and CaCO3 scaling was undetected even up to a calcite saturation index of approximately 16. Given the suppression of gypsum scaling by bicarbonate, it is essential to considerthis effect in the conventional practice of pH adjustment to suppress CaCO3 scaling. The present results suggest that antagonistic and synergistic mineral crystallization kinetics effects are important for optimizing scale-control strategies (e.g., acid and antiscalants addition to the RO feed).

Vegetation Growth Monitoring Under Coal Exploitation Stress by Remote Sensing in the Bulianta Coal Mining Area

Abstract Coal exploitation inevitably damages the natural ecological environment through large scale underground exploitation which exhausts the surrounding areas and is the cause of surface subsidence and cracks. These types of damage seriously lower the underground water table. Deterioration of the environment has certainly an impact on and limits growth of vegetation, which is a very important indicator of a healthy ecological system. Dynamically monitoring vegetation growth under coal exploitation stress by remote sensing technology provides advantages such as large scale coverage, high accuracy and abundant information. A scatter plot was built by a TM (Thematic Mapper) infrared and red bands. A detailed analysis of the distributional characteristics of vegetation pixels has been carried out. Results show that vegetation pixels are affected by soil background pixels, while the distribution of soil pixels presents a linear pattern. Soil line equations were obtained mainly by linear regression. A new band, reflecting vegetation growth, has been obtained based on the elimination of the soil background. A grading of vegetation images was extracted by means of a density slice method. Our analysis indicates that before the exploitation of the Bulianta coal mining area, vegetation growth had gradually reduced; especially intermediate growth vegetation had been transformed into low vegetation. It may have been caused by the deterioration of the brittle environment in the western part of the mining area. All the same, after the start of coal production, vegetation growth has gradually improved, probably due to large scale aerial seeding. Remote sensing interpretation results proved to be consistent with the actual situation on the ground. From our research results we can not conclude that coal exploitation stress has no impact on the growth of vegetation. More detailed research on vegetation growth needs to be analyzed.

Global satellite measurements of HDO and implications for understanding the transport of water vapour into the stratosphere

AbstractThe deuterium content of water vapour in a given air mass is sensitive to its temperature and condensation history. Isotopic measurements therefore have the potential to shed light on the transport of air and water vapour into the stratosphere. Previous measurements of the isotopic composition in the upper troposphere and stratosphere have been sparse in terms of both spatial and temporal coverage. Presented here are retrievals of the deuterium content of water vapour (HDO or δD) from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite instrument. These retrievals offer the first global scale coverage of the isotopic composition of water vapour in this altitude region and span a time period of almost two years. The spatial coverage and the time span of the dataset offer previously unattainable insight into the mean seasonal and spatial distributions of the isotopic composition of water vapour in the upper troposphere and stratosphere. Measurements of HDO are extremely challenging due to low sensitivity in the spectra at low temperatures and water vapour amounts. Nonetheless, the data show a number of interesting results. Zonal mean profiles show the greatest depletion in δD in the tropical upper troposphere, with decreasing depletion with altitude in the stratosphere due to the influence of methane oxidation. Seasonal zonal means also show a strong depletion in the southern polar spring at around 300 mbar, which is thought to be related to the occurrence of polar stratospheric clouds and dehydration events in the polar vortex. Geographically, the regions and time periods where the greatest depletions are observed in the tropical upper troposphere are those associated with strong convective activity. Results confirm that temporal variability is central to the transport of water vapour into the tropical tropopause layer (TTL) and stratosphere. The data presented here show an annual cycle in δD in the TTL which is tied to temperature and suggests that this signature propagates upwards into the stratosphere. The data also show a number of points where extremely dry air is associated with relatively enriched δD values. We postulate that these points are evidence of ice lofting. Copyright © 2007 Royal Meteorological Society

Development and Validation of a Behavioral Screener for Preschool-Age Children

The purpose of this study was to document the development of a short behavioral scale that could be used to assess preschoolers' behavior while still retaining adequate scale coverage, reliability, and validity. Factor analysis and item analysis techniques were applied to data from a nationally representative, normative database to create a 23-item behavioral screener to be used to identify children at risk. Screener sum scores were created and correlated with kindergarten and second-grade measures to assess validity evidence. Additionally, a receiver operating curve analysis created a cut score for making decisions about the need for further assessment. Based on the information collected, the 23-item screener was useful for assessing preschool-age students' behavior characteristics.

Evidence for deceleration in the radio jets of GRS 1915+105?

There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than were subsequently found from higher resolution observations made with the Very Long Baseline Array and the Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign to use all three arrays to attempt to track the motion of the jet knots from the 2006 February outburst of the source, giving us unprecedented simultaneous coverage of all angular scales, from milliarcsecond scales out to arcsecond scales. The derived proper motion, which was dominated by the VLA measurements, was found to be 17.0masd-1, demonstrating that there has been no significant permanent change in the properties of the jets since 1994. We find no conclusive evidence for deceleration of the jet knots, unless this occurs within 70mas of the core. We discuss possible causes for the varying proper motions recorded in the literature.

CONFIDENCE INTERVALS FOR PROPORTION ESTIMATES IN COMPLEX SAMPLES

Confidence intervals are an important tool to indicate uncertainty of estimates and to give an idea of probable values of an estimate if a different sample from the population was drawn or a different sample of measures was used. Standard symmetric confidence intervals for proportion estimates based on a normal approximation can yield bounds outside the [0,1] scale and poor coverage, because such approximations are generally inappropriate. Many alternative intervals have been proposed to address these issues. This paper discusses a selection of intervals based on scale transformations and continuity corrections and adapts these for use in complex samples. The study expands on the work of Brown, Cai, and DasGupta (2001) and Korn and Graubard (1998) using educational survey designs and complex sample data. Results based on a National Assessment of Educational Progress (NAEP) data resampling study showed that the theoretically appealing Wilson interval yields appropriate coverage with short intervals in most situations.

Diagnostic characterization of gypsum scale formation and control in RO membrane desalination of brackish water

The utility of a laboratory diagnostic approach was investigated for a systematic evaluation of the impact of operating conditions, membrane type, and antiscalant effectiveness on membrane mineral salt scale formation. The study focused on low-pressure reverse osmosis (RO) membrane desalting of brackish water with high potential for scaling by calcium sulfate dihydrate (gypsum). Gypsum scale formation, in the surface crystallization regime, was studied in a plate-and-frame RO system via flux decline measurements and membrane surface imaging. Membrane scale coverage increased with increasing level of surface gypsum supersaturation. However, membrane scaling propensity, as quantified by both the surface scale coverage and flux decline, indicated that there were measurable differences among the four commercial membranes studied, particularly in response to antiscalant treatment. Axial development of scale coverage indicated higher scale coverage as the membrane channel exit was approached, consistent with increased level of gypsum supersaturation along the membrane. As a result, antiscalant effectiveness, at a given dosage, was also location dependent. The present study illustrates a practical approach of combining flux decline and surface scale coverage measurements as a means of quantifying the impact of scale formation and its dependence on operating conditions and membrane type. Clearly, further studies are needed to elucidate the impact of membrane surface roughness and charge as well as module geometry on surface mineral salt scale formation and its mitigation.

Factors affecting the intensity of epidermal papillomatosis in populations of roach,Rutilus rutilus(L.), estimated as scale coverage

Studies of epidermal papillomatosis in fish populations have only rarely focused on the intensity of the disease, i.e. the number and size of papillomas. Furthermore, the methods used to evaluate the intensity of papillomatosis have not been standardized. We tested the reliability of a method based on counting of scales covered by papilloma tumours in roach, Rutilus rutilus (L). In addition, we studied the frequency distributions of the number of scales covered by papillomas within populations, evaluated the correlation between the prevalence and mean intensity of the disease among populations and examined the intensity of papillomatosis in roach with respect to sex and size of fish. Reliability of the scale coverage method was high. Therefore, the method could offer an effective way to determine the intensity of papillomatosis in fish species with large scales. The frequency distribution of the scale coverage of papillomas was highly aggregated within all populations studied. The mean intensity of papillomatosis increased with the size of the fish and was higher in males than in females. However, there was no correlation between the mean intensity and prevalence of the disease among the 19 roach populations studied.

Morphometric characterization of calcium sulfate dihydrate (gypsum) scale on reverse osmosis membranes

The axial development of calcium sulfate dihydrate (gypsum) scaling on selected reverse osmosis (RO) membrane surfaces was investigated experimentally in a plate-and-frame RO system. Scaling experiments with model solutions demonstrated progressive axial development of surface gypsum crystals along the membrane surface. The impact of surface crystallization was characterized via flux decline measurements and by both optical and high-resolution scanning electron microscopy (SEM) surface imaging. Surface coverage by gypsum scale (percent area covered and gypsum surface mass density) increased along the membranes (towards the membrane exit), consistent with the increase in concentration polarization. At the membrane channel entry, surface gypsum crystals were at their initial growth stage formed as primarily needle-like structures. With increasing axial distance from the entry, surface crystallization resulted in crystal structures that transitioned from the needle and plate-like structures, in the submicron size range, to partial rosettes to complete rosette structures in the mm size range. Significant differences were observed in the extent of surface scale coverage and surface crystal size among the membrane studied. Antiscalant addition to the feed solution led to progressive decline in the percent of area covered by scale with increasing antiscalant dosage and corresponding decrease in flux decline. Antiscalant addition resulted in perturbed surface crystal morphology of flattened and/or fused rosette crystal arms and to complete elimination of surface crystals at a sufficiently high antiscalant dosage. The present study demonstrates that gypsum scale development is affected by the formation of surface crystals on the membrane surface, thereby suggesting that there is merit to expanded research on the direct impact of surface topology and chemistry on surface crystallization of mineral salts.

Extension of SuperDARN at Dome C

The SuperDARN (Super Dual Auroral Radar Network) experiment is a multinational effort to develop chains of coherent HF radars world wide in order to obtain instantaneous large scale coverage of the magnetospheric plasma convection at high spatial and temporal resolution. We will review the scientific context of the experiment. The role of SuperDARN in our understanding of Sun-Earth relations will be emphasized through its numerous scientific objectives. The principle of the experiment will be described and specific capabilities and achievements presented, as well as its implication in the Space Weather program. Finally, the implementation of SuperDARN radars at Dome C is presented together with the prospective global extension of the network in both hemispheres.

Analytic marginalization over CMB calibration and beam uncertainty

With the increased accuracy and angular scale coverage of the recent CMB experiments it has become important to include calibration and beam uncertainties when estimating cosmological parameters. This requires an integration over possible values of the calibration and beam size, which can be performed numerically but greatly increases computation times. We present a fast and general method for marginalization over calibration-type errors by analytical integration. This is worked through for the specific example of CMB calibration and beam uncertainties and the resulting formulae are practical to implement. We show how cosmological parameter constraints from the latest CMB data are changed when calibration/beam uncertainties are taken into account: typically the best-fitting parameters are shifted and the errors bars are increased by up to 50 per cent for e.g. n s and Ω b h 2 ; although as expected there is no change for Ω K , because it is constrained by the positions of the peaks.

Potential impact of public access defibrillators on survival after out of hospital cardiopulmonary arrest: retrospective cohort study

Objective: To estimate the potential impact of public access defibrillators on overall survival after out of hospital cardiac arrest.Design: Retrospective cohort study using data from an electronic register. A statistical...

Dementia: Management of Behavioural and Psychological Symptoms

Back to table of contents Previous article Next article Book Forum: Geriatric PsychiatryFull AccessDementia: Management of Behavioural and Psychological SymptomsROBERT HOWARD, M.D., M.R.C.PSYCH., ROBERT HOWARDSearch for more papers by this author, M.D., M.R.C.PSYCH., London, U.K.Published Online:1 Sep 2002https://doi.org/10.1176/appi.ajp.159.9.1610AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail On November 25, 1901, Auguste D. Alzheimer’s now famous first case was admitted to a hospital in Frankfurt. Her presenting problem wasn’t cognitive deficit but a cluster of psychiatric symptoms that included unpredictable and challenging behavior, auditory hallucinations, and paranoia. Over the following century, psychiatrists and neurologists with an interest in Alzheimer’s disease somehow fostered a preoccupation with the neuropathology, neurochemistry, and molecular biology of impaired cognition that pushed study of the more psychological and psychopathological aspects of the disorder into the background. Most recently, the advent of the cholinesterase inhibitors has led to an unfortunate increase in the categorization of individuals with dementia in terms of their Mini-Mental State Examination (MMSE) score. For example, in the United Kingdom, access to these drugs is currently rationed on the basis of “guidance” from a government body that recommends stopping prescription when the MMSE score drops below 12.Through all of this, a huge, invisible army of Alzheimer’s disease patients and their informal and professional caregivers have struggled with problems that are often only indirectly related to cognitive deficit. What makes life difficult for the caregivers isn’t the fact that their husband or father can’t remember the date or the names of grandchildren. Rather, it is the problems that are considered by this book. Psychosis, depression, and aspects of behavior that arise out of agitation would probably be the simplest way to describe what the authors call behavioral and psychological symptoms.The book begins with an explanation of the methodologies used to identify and measure such symptoms in patients with dementia. The most widely used scales are reproduced in full in the text, there are helpful pointers toward which instrument to use for a particular target behavior or patient group, and the coverage of scales is comprehensive. Reading about some of the less well-known of these scales taught me an important lesson. To name a scale the Caretaker Obstreperous Behavior Rating Assessment shows just how dangerous the attraction of a catchy acronym can be. You can see why they did it—but Drachman and colleagues must flinch every time they see their adjective in print.This book provides a comprehensive and authoritative but, above all, balanced account of the strategies that have been used to manage distressing and challenging behaviors in dementia together with pertinent reviews of the evidence base for each. Strategically, the chapters considering pharmacological management are placed at the end of the book. To reach them, the reader has to pass accounts of behavioral and psychological therapies, interventions aimed at and delivered through caregivers, and alternative therapies.My guess is that the book will work for different readers in a variety of ways. Colleagues already open to the use of nondrug interventions in the first line of management of these problems will be delighted to find everything they could possibly want to know presented in a convincing and readable format within a single volume. More narrow-minded practitioners who rely solely on psychopharmacology to sort out their patients’ problems will find the information they need to minimize iatrogenic damage. (The secret is to start with the lowest available dose and not go above 1 mg/day of risperidone or 5 mg/day of olanzapine.) I hope that even hardened prescribers will dip into some of the earlier chapters and at least examine the evidence for the efficacy of the alternatives.It would be good to see a copy of this book in the office of every care facility with resident dementia patients. Even if they don’t read it from cover to cover, nursing and occupational therapy staff as well as family caregivers would find useful reference information here. Everyone in old age psychiatry knows of the Newcastle group’s reputation for research excellence. Here is a rather special example of how such a command of the research field can lead to clear guidance on how we can provide what is really most likely to help our patients and their caregivers. I predict classic status.Edited by Clive G. Ballard, John O’Brien, Ian James, and Alan Swann. New York, Oxford University Press, 2001, 316 pp., $45.00. FiguresReferencesCited byDetailsCited ByNone Volume 159Issue 9 September 2002Pages 1610-1610 Metrics PDF download History Published online 1 September 2002 Published in print 1 September 2002

Evaluation of the Extent of Carbon Steel Surface Damage by Calcium Carbonate Scale

Calcium carbonate scale damage in the allotropic forms of calcite and aragonite was selectively induced on freshly polished carbon steel surfaces in cooling system media. The damaged surfaces were submitted to cyclic voltammetry using a potassium ferrocyanide/sodium nitrate aqueous solution as the oxidizing medium to establish a method for evaluating the extent of scale coverage. © 2001 The Electrochemical Society. All rights reserved.

Barium Sulfate Deposition and Precipitation Using a Combined Electrochemical Surface and Bulk Solution Approach

Abstract Barium sulfate (BaSO4) deposition is a serious problem in many processing environments. Much of the work on BaSO4 scaling has concentrated on using beaker tests to analyze the formation of crystals in the bulk solution, and this technique has been used to assess scale control inhibitors. The present study reports results of a study comparing the characteristics of mineral scale formation (BaSO4) in a bulk solution and at a solid surface. An electrochemically based technique, in which the rate of oxygen-reduction reaction at a rotating disk electrode (RDE) surface is used to assess the extent of scale coverage, was used in conjunction with assessment of bulk precipitation measurements. Results from this study showed that the action of a commercial polyphosphinocarboxylic acid (PPCA) inhibitor was different in the bulk solution and at the surface. The addition of 25 ppm PPCA, although effective in retarding bulk precipitate formation, enhanced the level of surface scaling. Practical implications re...

Impedance techniques at partially blocked electrodes by scale deposition

By using electrochemical and EHD impedances, CaCO 3 accelerated deposition from carbonically pure waters on a rotating platinum disc electrode can be characterized through the kinetics of oxygen reduction on a partially blocked surface. An approximate model of the electrochemical impedance is proposed which explains the main features of the experimental data. The electrochemical impedance, measured during scale growth, allows two quantities, R HF and C HF obtained from its high frequency behaviour, to be determined. C HF can be related to the scale coverage of the surface and R HF to the morphology of the scale deposit. In addition SEM observations illustrate the scale deposit growth process at the electrode surface.

Galileo multispectral imaging of Earth

Nearly 6000 multispectral images of Earth were acquired by the Galileo spacecraft during its two flybys. The Galileo images offer a unique perspective on our home planet through the spectral capability made possible by four narrowband near-infrared filters, intended for observations of methane in Jupiter's atmosphere, which are not incorporated in any of the currently operating Earth orbital remote sensing systems. Spectral variations due to mineralogy, vegetative cover, and condensed water are effectively mapped by the visible and near-infrared multispectral imagery, showing a wide variety of biological, meteorological, and geological phenomena. Global tectonic and volcanic processes are clearly illustrated by these images, providing a useful basis for comparative planetary geology. Differences between plant species are detected through the narrowband IR filters on Galileo, allowing regional measurements of variation in the "red edge" of chlorophyll and the depth of the 1-micrometer water band, which is diagnostic of leaf moisture content. Although evidence of life is widespread in the Galileo data set, only a single image (at approximately 2 km/pixel) shows geometrization plausibly attributable to our technical civilization. Water vapor can be uniquely imaged in the Galileo 0.73-micrometer band, permitting spectral discrimination of moist and dry clouds with otherwise similar albedo. Surface snow and ice can be readily distinguished from cloud cover by narrowband imaging within the sensitivity range of Galileo's silicon CCD camera. Ice grain size variations can be mapped using the weak H2O absorption at 1 micrometer, a technique which may find important applications in the exploration of the moons of Jupiter. The Galileo images have the potential to make unique contributions to Earth science in the areas of geological, meteorological and biological remote sensing, due to the inclusion of previously untried narrowband IR filters. The vast scale and near global coverage of the Galileo data set complements the higher-resolution data from Earth orbiting systems and may provide a valuable reference point for future studies of global change.

The Projected Characteristics of a National Topographic Digital Databank

Comparatively little is known concerning the likely characteristics of projected national digital topographic data bases. This paper describes an estimation of these characteristics for Great Britain, based on a sample of over 400 Ordnance Survey digital maps at 1 : 1250 and 1 : 2500 scales. The sources of the considerable uncertainty in the projections are discussed and it is concluded that some 3000 km of line work at map scale needs to be encoded to provide basic scale coverage apart from contours. With present Ordnance Survey methods of storage, this would require about 580 magnetic tapes.

Topographic Maps From Computer Output on Microfilm

In excess of 210,000 map sheets constitute the basic scale coverage of topographic data in Great Britain. Photography based microfilm techniques have alleviated, to some extent, the problems associated with distribution and storage for such vast data quantities. With an increasing number of large scale plans being held in digital form, the use of computer output on microfilm could offer a more cost effective approach. This paper reports on research into the display of topographic information by COM and discusses the quality and usefulness of the results. It concludes that the initiation of a trial service should be integrated into the next phase of Ordnance Survey planning.