Limited Data Quality Research Articles

Pipeline Reduction of Binary Light Curves from Large–Scale Surveys

AbstractOne of the most important changes in observational astronomy of the 21st Century is a rapid shift from classical object-by-object observations to extensive automatic surveys. As CCD detectors are getting better and their prices are getting lower, more and more small and medium-size observatories are refocusing their attention to detection of stellar variability through systematic sky-scanning missions. This trend is aditionally powered by the success of pioneering surveys such as ASAS, DENIS, OGLE, TASS, their space counterpart Hipparcos and others. Such surveys produce massive amounts of data and it is not at all clear how these data are to be reduced and analysed. This is especially striking in the eclipsing binary (EB) field, where most frequently used tools are optimized for object-by-object analysis. A clear need for thorough, reliable and fully automated approaches to modeling and analysis of EB data is thus obvious. This task is very difficult because of limited data quality, non-uniform phase coverage and solution degeneracy. This paper reviews recent advancements in putting together semi-automatic and fully automatic pipelines for EB data processing. Automatic procedures have already been used to process Hipparcos data, LMC/SMC observations, OGLE and ASAS catalogs etc. We discuss the advantages and shortcomings of these procedures.

Commentary: Utilizing information on causes of neonatal deaths in less-developed countries

Using rigorous and transparent methods, Lawn et al. 3 have provided, for 193 countries in the year 2000, systematic estimates, with associated uncertainty, of the distribution of neonatal deaths for programme-relevant causes. Only 2.5% of neonatal deaths had reliable cause-of-death information available through vital registration systems, primarily in well-developed countries. The distribution of reported causes of deaths varied substantially between countries and across studies. The major direct causes of neonatal deaths globally were estimated to be infections (sepsis, pneumonia, tetanus, and diarrhoea; 35%), preterm birth (28%), and birth asphyxia (23%). There was substantial uncertainty around these estimates owing to the limited quantity and quality of data from settings in which the great majority (97.5%) of neonatal deaths had occurred. It is obvious that complex statistical models are not a panacea, and collecting reliable information on the causes of deaths should receive due attention. Simultaneously, it would be pertinent to highlight other important limitations and practical implications of this review. Several studies included in this review, primarily from low-income and middle-income countries, used verbal autopsy (lay reporting) tools to determine the causes of deaths. The neonate, especially in the first week of life, offers a limited symptomatic response to different insults resulting in substantial overlap of clinical manifestations of several diseases. The sensitivity and specificity of verbal autopsy technique in correctly identifying various causes of deaths is, therefore, sub-optimal. Validation studies suggest that although major congenital malformations and neonatal tetanus have high levels of sensitivity (0.79–0.98 for tetanus) and specificity (>0.9), the performance for other important conditions like septicaemia is poor. 4,5 The instrument using both open-ended

Human Immunodeficiency Virus Acquired Heterosexually Abroad: Expert Panel Assessment of the “Indigenous/Nonindigenous to the United Kingdom Status” of Cases

In Scotland the proportion of human immunodeficiency virus (HIV)-diagnosed patients who were presumed to have acquired their infection abroad increased from 4% (12/269) in 1985 to 34% (53/154) in 2000. Several journalists and health professionals assumed that this increase in diagnosis rate reflected HIV among persons from Scotland who had acquired their infection while traveling abroad. Because of limitations in HIV surveillance data quality, no attempt had been made to distinguish diagnosed persons who were indigenous to the United Kingdom from those who were not. To address this problem, the investigators set out to interpret the existing surveillance data using a probability-based judgment approach. A panel of travel medicine experts was employed to generate a judgment on reported heterosexual cases, presumed to have acquired HIV abroad and diagnosed before 2001, as to their likelihood of being indigenous to the United Kingdom (I) or not (NI). Median score thresholds were set to produce a range of possible values of I as a proportion of I + NI. For diagnoses made during 1991 to 1995, the possible value of I as a proportion of I + NI ranged between 17% (5/29) and 34% (23/68); for 1996 to 2000, the range was 32% (39/123) to 33% (43/130). Overall, 15% of cases were unclassifiable. Thus, up to one-third of HIV-diagnosed heterosexuals who likely acquired their HIV abroad originated in Scotland. Amid current publicity about infections among immigrants, the distinction between I and NI group sizes should better inform public health professionals for resource allocation to prevent new HIV infection among indigenous persons, and for the health care of nonindigenous persons entering Scotland with HIV. Using classification criteria derived from this study, there are plans to publish such data routinely in the context of national surveillance.

Drug‐induced pancreatitis: lessons in data mining

Drug‐induced pancreatitis: lessons in data mining

Experiences of environmental performance evaluation in the cement industry. Data quality of environmental performance indicators as a limiting factor for Benchmarking and Rating

Although ISO 14031 gives guidelines for environmental performance evaluation, there is limited experience of applying the standard in the area of benchmarking and external rating, especially when limitations of data quality are considered. This paper evaluates the importance of the data quality of operational performance indicators (OPIs, in this case emission factors) as a limiting factor for benchmarking and external rating between six cement plants in Sweden, Norway and Finland for three types of emissions, dust, NO x and SO 2. Monthly emission factors for 1993–1999 were collected for these plants and a quality assurance process was undertaken to eliminate factors that decreased comparability. The data were tested against six hypotheses concerning different aspects of the variation of the emission factors. One of the findings was that there is no sharp limit when the quality of emission factors is high enough to make it possible to compare, since quality is a qualitative conception in itself. Instead, organisations using emission factors should strive to adapt a system with quality assurance of emission factors, resulting in widely accpeted emission factors suitable for comparison between plants. This is achieved with a sector specific methodology which can handle irrelevant differences and reflects real differences in environmental performance.

Management of neurocysticercosis.

Neurocysticercosis is a common cause of neurological disease in developing countries and a major cause of epilepsy worldwide. A unique characteristic of human neurocysticercosis is that the living parasite is very well tolerated in human brain, so symptoms and clinical disease primarily result from death of the organism and accompanying inflammatory reaction in the human CNS. Among the diverse clinical manifestations of human neurocysticercosis, seizures are the most common, but other clinical problems occur, depending upon the localisation and viability of the parasite. Although both praziquantel and albendazole are effective agents, there is controversy about their role in several forms of the disease. Systematic reviews have pointed out the limited quality of available data on therapy. At a recent international conference convened to develop guidelines for treatment of this disease, areas of consensus and disagreement on the role of antiparasitic therapy were discussed. It was clear to all that cysticercosis cannot be regarded as a single disorder; treatment needs to be modified based on the location and number of cysticerci and the host response. There was a strong consensus that there is no role for antiparasitic drugs in patients with only calcified lesions. Studies suggest that patients with single enhancing lesions will do well regardless of antiparasitic therapy. Antiparasitic drugs are contraindicated in patients with cerebral oedema (cysticercal encephalitis). Most experts strongly recommend antiparasitic therapy in patients with multiple subarachnoid cysticerci or giant cysticerci. In patients with ventricular cysticerci, endoscopic removal is the preferred therapy. However, recent evidence suggests that placement of a ventricular shunt followed by antiparasitic therapy is an acceptable alternative. Standard treatment for localization-related epilepsy is effective for seizures caused by cysticercosis. In general, seizures are easily controlled in this illness. While many controversies regarding the treatment of patients with neurocysticercosis were not resolved at the international consensus conference, participants did conclude that controlled prospective studies are required to define optimal therapy for the infection and that treatment of infected individuals must be individualised.

Macroscale water fluxes 1. Quantifying errors in the estimation of basin mean precipitation

Developments in analysis and modeling of continental water and energy balances are hindered by the limited availability and quality of observational data. The lack of information on error characteristics of basin water supply is an especially serious limitation. Here we describe the development and testing of methods for quantifying several errors in basin mean precipitation, both in the long‐term mean and in the monthly and annual anomalies. To quantify errors in the long‐term mean, two error indices are developed and tested with positive results. The first provides an estimate of the variance of the spatial sampling error of long‐term basin mean precipitation obtained from a gauge network, in the absence of orographic effects; this estimate is obtained by use only of the gauge records. The second gives a simple estimate of the basin mean orographic bias as a function of the topographic structure of the basin and the locations of gauges therein. Neither index requires restrictive statistical assumptions (such as spatial homogeneity) about the precipitation process. Adjustments of precipitation for gauge bias and estimates of the adjustment errors are made by applying results of a previous study. Additionally, standard correlation‐based methods are applied for the quantification of spatial sampling errors in the estimation of monthly and annual values of basin mean precipitation. These methods also perform well, as indicated by network subsampling tests in densely gauged basins. The methods are developed and applied with data for 175 large (median area of 51,000 km2) river basins of the world for which contemporaneous, continuous (missing fewer than 2% of data values), long‐term (median record length of 54 years) river discharge records are also available. Spatial coverage of the resulting river basin data set is greatest in the middle latitudes, though many basins are located in the tropics and the high latitudes, and the data set spans the major climatic and vegetation zones of the world. This new data set can be applied in diagnostic and theoretical studies of water balance of large basins and in the evaluation of performance of global models of land water balance.

Iron abundance in hot hydrogen-deficient central stars and white dwarfs from FUSE, HST, and IUE spectroscopy

We present a rst systematic investigation of the iron abundance in very hot (Te 50 000 K) hydrogen- decient post-AGB stars. Our sample comprises 16 PG 1159 stars and four DO white dwarfs. We use recent FUSE observations as well as HST and IUE archival data to perform spectral analyses with line blanketed NLTE model atmospheres. Iron is not detected in any PG 1159 star. In most cases this is compatible with a solar iron abundance due to limited quality of HST and IUE data, although the tendency to an iron underabundance may be recognized. However, the absence of iron lines in excellent FUSE spectra suggests an underabundance by at least 1 dex in two objects (K 1-16, NGC 7094). A similar result has been reported recently in the (WC)-PG 1159 transition object Abell 78 (Werner et al. 2002). We discuss dust fractionation and s-process neutron-captures as possible origins. We also announce the rst identication of sulfur in PG 1159 stars.

Survey of approaches to improve reliability in lca

Limitations of data quality and difficulties to assess uncertainty are long since acknowledged problems in LCA. During recent years a range of tools for improvement of reliability in LCA have been presented, but despite this there is still a lack of consensus about how these issues should be handled. To give basic understanding of data quality and uncertainty in LCA, key concepts of data quality and uncertainty in the context of LCA are explained. A comprehensive survey of methods and approaches for data quality management, sensitivity analysis, and uncertainty analysis published in the LCA literature is presented. It should serve as a guide to further reading for LCA practitioners interested in improving data quality management and uncertainty assessment in LCA projects. The suitability of different tools for addressing different types of uncertainty and future needs in this field is discussed.

Setting health priorities: the development of cost-effectiveness league tables.

AlanWilliams’swebsitedescribeshimasa‘‘pseudo-retired professor of economics still active inpromoting more explicit priority-setting based oncost-effectivenessapproachestobothhealthmaxim-isationandthereductionofhealthinequalities’’.Heiswidely acknowledged as the most influential ofBritishhealtheconomistsandindeedthefatherofthesub-discipline in the United Kingdom, as evidencedby respondents to a survey of British healtheconomists who, when asked about the paperdeemed most influential on both the discipline andpolicy,answered‘‘anythingwrittenbyAlanWilliams’’(1) and specifically his 1985 paper reproduced here.Atfirstsightitmayappearoddthateconomistsshould choose as ‘‘most influential’’ a paper aboutcoronary artery bypass grafting (CABG), and more-over one published in a medical journal. We believethat the following features account for the seminalnatureofthepaper:thecollectionofmethodologicalaspects that were innovative at that time; the closerelationship between analysis and policy; the frankacknowledgement of the limitations in data quality;andthevisionofafutureresearchagenda.However,the active involvement of its author in proselytisingand arguing for his overall vision that ‘‘an explicitapproachbasedoncost-effectivenessreasoningisonstrongermoralgroundthananyotherapproach’’hasalso been a key reason for the paper’s success instimulating the research and policy directions ofmany others (including economists).Williams’s paper introduced four specificmethodological ideas to the context of decision-making in the UK National Health Service (NHS):application of the quality-adjusted life year (QALY)as a measure of effectiveness of interventions;calculation of ratios of cost per QALY gained frominterventions; presentation of the first ‘league table’comparingtherelativecost-effectivenessofdifferentinterventions; and recognition that sub-groups ofpatients may have differential cost-effectivenessratios. Parts of these ideas had been developed andapplied in earlier publications in the USA (2, 3)butnever in the UK. The approach of combiningquantity and quality of life across different healthinterventions in the league table was particularlyinfluentialinmovingcost-effectivenessanalysisawayfrom only piecemeal decision-making to broadersectoral planning (4).In terms of policy implications, the paperconcluded that CABG compared extremely favour-ablywithhearttransplantsandtreatmentofend-stagerenal failure, favourably with valve replacement foraortic stenosis and implantation of pacemakers forheartblock,andlessfavourablywithhipreplacements.The more severe a case of angina, the more cost-effectiveitwastotreatwithCABG,andonlythemostsevere cases were judged to be ‘‘a fairly strongclaimant’’ on any extra resources. These werecontroversialconclusionsaimedatstimulatingfurtherdebate. The paper was published at an importantpoint: a consensus conference had recommended alarge increase in CABG operations; the UK Depart-ment of Health and Social Security had just signifi-cantlyextendedthehearttransplantprogramme;andadetailed report on the costs and benefits of the hearttransplantation programme had been completed (5).The paper was the first to compare directly theefficiency of very different types of health careinterventions and, by so doing, to challenge UKgovernmentpolicy.However,itwasalsoimportantforthefutureacceptanceoftheapproachthatseveralkeypeople involved in these debates had been part of the

Ghadames basin, southern Tunisia: A reappraisal of Triassic reservoirs and future prospectivity (E & P Notes)

Recent discoveries of oil and gas in Triassic reservoirs of the Ghadames basin, eastern Algeria, suggest that similar potential exists to the east, in the southern Tunisian part of the province. For decades, southern Tunisia has remained an underexplored part of the basin, in large part owing to older geological interpretations that focus on Paleozoic reservoirs and to limitations in seismic data quality, resulting from statics problems, that have rendered trap identification inaccurate or tenuous. New analyses of previously and recently acquired geological and geochemical data, as well as improvements in seismic data acquisition and processing, have begun to reverse older notions regarding limited hydrocarbon presence in southern Tunisia. Log correlations indicate that productive, sand-rich intervals of the major Triassic reservoir in the region, the Trias Argilo Greseux Inferieur (TAGI), can be correlated over large distances, suggesting significant continuity into lightly drilled and undrilled areas. Analyses of geochemical data reveal a more complex, multistage history of hydrocarbon maturation and migration than previously believed. Much greater volumes of petroleum have been generated and a larger variety of traps have been created than can be accounted for by older interpretations. Where added to the use of new field and processing parameters for seismic surveys, these factors have together led to important, upgraded evaluations of basin potential in southern Tunisia.

Stress coupling between earthquakes in northwest Turkey and the north Aegean Sea

We have investigated the Coulomb stress interactions of 29 earthquakes (Ms≥6.0) that have occurred in the region of northwest Turkey and north Aegean Sea since 1912. Of these events, 23 may be related to earlier events, and 16 are clearly related to earlier events. All events after 1967 are related to previous events. Events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified. In some cases, faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local Coulomb stress rise. Thus regions of Coulomb stress shadow can become regions where a damaging earthquake may occur. The relation between smaller events and the Coulomb stress distribution is less clear, but may be related to poor data quality and practical limitations of our modeling technique. Nonetheless, there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced. We discuss the contemporary distribution of Coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults.

Spectrum measurement using discrete detector arrays

Modern spectrometers can produce highly resolved spectra, but this ability has not yet been matched by an ability to measure them efficiently and for instruments such as a spatially dispersive mass spectrometer it is in the development of high-performance focal plane detectors (FPDs) where there are enormous gains in efficiency to be achieved. In this paper two key questions are addressed: (a) how much information does a 1D spectrum or 2D image contain?; and (b) can a given FPD capture all this information? In answering these questions, issues of performance, data quality and technology limitations of 1D and 2D arrays of counters arise naturally. A procedure is evolved for comparing the performance of a detector and a spectrometer which is not limited to spatially dispersive instruments. © 1998 John Wiley & Sons, Ltd.

Data Quality Assessment for Perinatal Events in an On-line Obstetrical Database (O-DB) and a Health Records Database (HR-DB). † 1227

Background: Limited data quality research in the perinatal and other clinical fields suggests that the quality of different databases and of different data items within single databases is variable.

The underdetermined Earth

In the endeavour to achieve the goal of understanding the structure of the Earth in three dimensions, the limitations of the seismological probe for Earth structure have to be recognised. In geo-seismology there are high quality observations of a wide range of information on the seismic wavefield but only at a limited number of observation points around the globe. In contrast for the Sun, the other body for which seismological techniques have been routinely applied, there is the equivalent of a very high concentration of seismometers on one-hemisphere but very limited data quality. The restriction imposed by data quality is easily recognised but the restrictions imposed by the limited sampling of the globe are more subtle and have to be borne in mind in the interpretation of any images of seismic structure.

Exploratory research synthesis--methodological considerations for addressing limitations in data quality.

Exploratory meta-analysis or research synthesis has been advocated as a way of developing important hypotheses for further study. An exploratory research synthesis was conducted on the carotid endarterectomy (CE) literature to illustrate this method. The CE scientific literature is similar to that of many other new medical interventions because it contains numerous limitations to data quality. Exploratory research synthesis of such literature necessitates a number of methodological and statistical considerations to address these limitations, including the problems of missing data, appropriate unit of analysis, nonnormal distribution of outcomes, and lack of controlled studies. Strengths and limitations of the exploratory research synthesis approach are discussed within the context of public policy decisions for assessing medical technologies.

Effect of Hypertensive Diseases in Pregnancy on Birthweight, Gestational Duration, and Small-or-Gestational-Age Births

We measured the impact of hypertensive disorders in pregnancy (chronic hypertension, pregnancy-induced hypertension, and eclampsia) on birthweight, gestational duration, and small-for-gestational-age births. We employed a retrospective cohort design using North Carolina birth certificate data for the years 1988-1990, with the analyses based on nearly 300,000 pregnancies. Women noted to have eclampsia during pregnancy had a substantially greater risk of delivering very-low-birthweight infants (birthweight < or = 1,499 gm; risk difference (RD) = 6.7%) and moderately-low-birthweight infants (1,500-2,499 gm; RD = 14.6%), and very preterm (gestational age < 33 weeks; RD = 7.1%) and moderately preterm (33-36 weeks; RD = 9.3%) births, compared with women without hypertension. Corresponding risk differences for these outcomes were 1.9% and 5.1% for very low and moderately low birthweight, and 1.6% and 3.0% for very preterm and moderately preterm for women with chronic hypertension. Risk differences were of similar magnitude for women with pregnancy-induced hypertension for these outcomes. Hypertensive disorders in pregnancy were associated with small-for-gestational-age infants, with risk differences of 5.1%, 3.5%, and 9.2% for chronic hypertension, pregnancy-induced hypertension, and eclampsia, respectively. The patterns of risk were similar for preterm births due to spontaneous onset of labor and those due to other precipitating events. We observed similar patterns for black and white women. Control for confounders through multivariable logistic regression models did not alter the observed patterns. In spite of the limited data quality, we found that hypertensive disorders in pregnancy substantially increase the risk of low birthweight, preterm births, and small-for-gestational-age births.

SR instrumentation for optimized anomalous scattering and high resolution structure studies of proteins and nucleic acids (invited)

Crystal structure solution by anomalous dispersion methods has been greatly facilitated using the rapidly tunable station 9.5 at the Daresbury SRS. Both SIROAS and MAD techniques, with IP data, have been used in the phasing of a brominated nucleotide and a seleno deaminase, respectively. The electron density maps in each case are interpretable. Throughput of projects could be improved upon with a better duty cycle detector. Another category of data collection is that at very high resolution. Detailed structure refinement pushes the limits of resolution and data quality. Station 9.5 has been used to collect high resolution (1.4 Å) native data for the protein concanavalin A. This utilized very short wavelengths (0.7 Å), the image plate, and crystal freezing. A total of 155 407 measurements from two crystals benefited from the on-line nature of the IP detector device, but a slow and quick pass are required to capture the full dynamic range of the data. There are data seen to 1.2 Å and beyond for a pure Mn substituted form of the protein, but a higher intensity still is required to actually record these data. By comparison, trials at CHESS, on a multipole wiggler (station A1) with a CCD (without image intensifier) system, yield native concanavalin A data to 0.98 Å and beyond. This demonstrates that the combination of yet higher intensity and the ease of use of a CCD offers worthwhile improvements; in this case an increase in the data by a factor of (1.4/0.98)3, thus at least doubling the data to parameter ratio for protein structure model refinement and potentially opening up direct structure determination of proteins of the size of concanavalin A (25 kDa). Finally, possibilities at ESRF and further detector developments, such as mosaic CCDs and scintillator coatings, offer further impetus for the field. These include more intense rapidly tunable beams for anomalous dispersion-based structure solution and ‘‘ideal’’ higher resolution data collection and reactivity studies. ESRF BL19 is described; facilities on BL19 will include a system for freezing and storing crystals at cryogenic temperatures, so that data can be recorded from the same crystal on different runs. Overall, there have been tremendous strides made in this field in the last 15 years, and yet further improvements are to come.

Determination of organic acids by ion chromatography in rain water in the State of Zulia, Venezuela

Ion-exchange chromatography with a Dionex Model QIC system was used to identify and determine formic and acetic acid in event rains collected at the La Esperanza site (Zulia, Venezuela). Pyruvic acid was observed infrequently and always at very low concentrations. The method can be adapted for the routine determination of these acids, giving results in less than 12 min (only the chromatogram without column clean-up). A set of calibration graphs for mixed standards with different concentration ranges (0.5–80 μM) with a good linear regression ( R 2 = 0.9992–1.0000) were used. The estimated limit of quantification was <0.2 μM for both acids. Replicate analyses of four different fractions of a certain sample taken and preserved with chloroform showed relatively good reproducibility (R.S.D. ca. 7%) for both acids, and the results were well within acceptable data quality limits. Both the absolute organic acid concentrations and the ratio of organic acid concentrations to inorganic acid concentrations were significantly lower in La Esperanza than those reported at other rural Venezuelan sites. Organic and inorganic anion balances revealed a low potential contribution ( ca. 7%) of formic and acetic acid to the acidity of the rain (volume-weighted average pH = 4.1). In other rural Venezuelan sites these acids contributed over 60% to the free acidity.

Shallow water reverberation, signal motion loss, and acoustic navigation: A preliminary study for autonomous underwater vehicle target detection

It is usually difficult to use autonomous underwater vehicles (AUV) for locating targets in shallow‐water ocean environments due to the strong wave surge and multipath acoustic reverberations. A preliminary study of some environmental effects unique for a shallow‐water sound channel helps place bounds on possible solutions and reduce program uncertainty. Accordingly, three interrelated issues are addressed in this paper: Signal masking by shallow‐water reverberation, signal loss caused by extreme platform motions, and shallow‐water acoustic navigation. A model estimating the signal motion loss and the average reverberation intensity in the shallow‐water environment is developed. The computer simulation of multisensor navigation serves not only as a precise vehicle‐positioning device but also as the platform motion data input for the model. As a result of the shallow‐water experiments and acoustic modeling, conclusions of this preliminary study are (1) SML is not the dominant factor for sonars in the frequency range of interest (≳200 kHz) with respect to target detectability, (2) beam patterns can be manipulated to effectively reject most interferences caused by surface reverberation and noise, and (3) a multisensor navigation filter is practical even with limited sensor data quality.