bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating Facies Fields by Use of the Ensemble Kalman Filter and Distance Functions—Applied to Shallow-Marine Environments
Authors: Lorentzen Rolf J. , Nævdal Geir , Shafieirad Ali
Published: January 2013

The ensemble Kalman filter (EnKF) is one of the most promising tools for assisted history matching of reservoir models, but challenges remain for applications on complex geological structures (facies fields). In this paper, we propose a method that uses distance functions to estimate such fields. The definition of a distance function is “the shortest distance between a given position in the field and the boundary separating facies types.” The idea behind this approach is that distances have smooth properties, and the distribution of the ensemble in a given gridblock is without multimodality and in better agreement with the EnKF Gaussianity assumptions. The distances are then updated by use of the EnKF and converted to petrophysical parameters when the reservoir simulator is run to the next assimilation time. The approach is flexible and simple and possesses several advantages compared with other existing methods: The input items for the method are facies realizations that can be generated with any preferred geostatistical tool; we ensure that the updated fields always are facies realizations; we ensure the conditioning of the correct facies types at the well location, both initially and during the assimilation steps; and the method does not involve complex modifications of the standard EnKF equations.

The approach presented here is based on an extension of previous work performed by the authors. The novelty of the extension is summarized by the following: Any number of specified facies types can be estimated; one distance function is used for each facies type—at each gridblock, the facies type that corresponds to the distance function with maximal value is selected; there are no restrictions on the structure of the facies field to be estimated; and the methodology is extended to update variations in the petrophysical parameters within each facies type. The first of these extensions is considered the most important because the flexibility regarding the number of facies types is necessary for every real industrial application.

We demonstrate the methodology on a field with shallow-marine-environment characteristics. The conclusions from the example are that the history match is improved, uncertainty is reduced, and the method always returns facies realizations with geological authenticity.
Reduction of Fines Migration by Nanofluids Injection: An Experimental Study
Authors: Habibi A.. , Ahmadi M.. , Pourafshary P.. , Ayatollahi Sh.. , Al-Wahaibi Y..
Published: January 2013

Formation damage of oil reservoirs as a result of fines migration is a major reason for productivity decline. Formation fines are defined as unconfined solid particles present in the pore spaces of formations. Their migration, caused by fluid flow in the reservoir, can cause pore plugging and permeability reduction. In the last 3 decades, many studies have characterized fines and their migration effect on permeability reduction. There are many techniques in the industry to remediate the damage, especially in the near-wellbore region. Nanofluids (NFs) that contain nanoparticles (NPs) exhibit specific properties, including a high tendency for adsorption and being good candidates for injection into the near-wellbore region, because of the small nanoparticle sizes. In this paper, a packed column is used to study the use of different types of NPs to reduce fines migration in synthetic porous materials. Three types of NPs—MgO, SiO2, and Al2O3—are used here to investigate their effects on fines movement. The results indicate that fines may adhere to the matrix grains, hindering their migration, when the porous materials are soaked with NFs. Furthermore, to check the mechanisms of this remediation technique, the effect of nanoparticle concentration and fluid flow rates in the medium on fines detachment was studied. A theoretical model was used to calculate total energy of interaction for the surfaces to check experimental results, which was also validated with scanning electron microscopy (SEM) pictures for samples from synthetic cores. The results showed that addition of 0.1 wt% of MgO and SiO2 NPs reduced fines migration by 15% compared with the reference state. MgO NPs were found to be more effective, even at high fluid rates, when used at a higher concentration, as noticed in the macroscopic and microscopic results.
Numerical Simulation of Steam-Assisted Gravity Drainage With Vertical Slimholes
Authors: Chang J.. , Ivory J.. , Tunney C..
Published: January 2013

Steam-assisted gravity drainage (SAGD) is the primary in-situ recovery method for bitumen from the large Athabasca deposit in Alberta, Canada. SAGD field operations encounter a significant decrease in production performance when low-permeability shale barriers are present in the formation. These layers can reduce SAGD performance and impede the growth of the steam chamber. They also significantly limit the percentage of the deposit from which bitumen can be economically recovered with SAGD. The concept of drilling vertical slimholes to create flow paths through barriers was conceived and investigated at Alberta Innovates-Technology Futures (AITF), formerly the Alberta Research Council. The use of slimholes has the potential to significantly increase the amount of recoverable bitumen (reserves) and the rate at which it is produced during SAGD. For shallow reservoirs, the slimholes could be drilled from the surface at a relatively low cost. It is believed that the process can be economically viable after its technical operation has been optimized with improvements in drilling technology, slimhole size and spacing, and enhanced usage of the slimholes in the development of steam chambers above the shale layers. Alternatively, the slimholes could be drilled from the horizontal wellbores (to avoid surface disturbance) as either horizontal slimholes from the producer or as horizontal/vertical slimhole combinations from the injector.

The 2D and 3D field-scale numerical simulations were performed by use of reservoir properties and operating conditions based on published information for the MacKay River SAGD operation in the Athabasca deposit. The reservoir depth was 135 m, the initial pressure 500 kPaa, the initial temperature 7.5°C, and the initial oil saturation (SO) 0.8. The simulations explored the effect of vertical slimholes, which were laterally offset 7 m from the horizontal well-pair in reservoirs with and without shale layers or shale lenses. The effects on SAGD performance that were investigated were slimhole cross section (25 cm × 25 cm or 50 cm × 50 cm), the distance between slimholes (12 or 24 m) in the direction parallel to the well pair, the permeability of the reservoir and the vertical slimholes, and horizontal slimholes from the injector or producer. The slimhole cross section represents the disturbed area adjacent to the drilled slimhole and the drilled hole itself and is therefore relatively large. The slimholes were represented as high-permeability vertical channels by use of refined grids. For a reservoir with a continuous shale layer, SAGD performance was improved by vertical slimholes because of the recovery of previously inaccessible oil from above the shale layer, where a secondary steam chamber was formed.
A New Unified Diffusion—Viscous-Flow Model Based on Pore-Level Studies of Tight Gas Formations
Authors: Rahmanian Mohammad R. , Aguilera Roberto , Kantzas Apostolos
Published: January 2013

In this study, single-phase gas-flow simulation that considers slippage effects through a network of slots and microfractures is presented. The statistical parameters for network construction were extracted from petrographic work in tight porous media of the Nikanassin Group in the Western Canada Sedimentary Basin (WCSB). Furthermore, correlations between Klinkenberg slippage effect and absolute permeability have been developed as well as a new unified flow model in which Knudsen number acts implicitly as a flow-regime indicator. A detailed understanding of fluid flow at microscale levels in tight porous media is essential to establish and develop techniques for economic flow rate and recovery. Choosing an appropriate equation for flow through a single element of the network is crucial; this equation must include geometry and other structural features that affect the flow as well as all variation of fluid properties with pressure. Disregarding these details in a single element of porous media can easily lead to flow misinterpretation at the macroscopic scale. Because of the wide flow-path-size distribution in tight porous media, a variety of flow regimes can exist in the equivalent network. Two distinct flow regimes, viscous flow and free molecular flow, are in either side of this flow-regime spectrum. Because the nature of these two types of flow is categorically different, finding/adjusting a unified flow model is problematic. The complication stems from the fact that the viscosity concept misses its meaning as the flow regime changes from viscous to free molecular flow in which a diffusion-like mechanism dominates. For each specified flow regime, the appropriate equations for different geometries are studied. In addition, different unified flow models available in the literature are critically investigated. Simulation of gas flow through the constructed network at different mean flow pressures leads to investigating the functionality of the Klinkenberg factor with permeability of the porous media and pore-level structure.
A Novel and Comprehensive Study of Polymeric and Traditional Phosphonate Inhibitors for High-Temperature Scale Control
Authors: Wang Wei , Kan Amy T. , Tomson Mason B.
Published: January 2013

A novel barite-inhibition assay based on the nucleation and inhibition model has been proposed and used to evaluate the thermal stability of phosphonates and polymeric scale inhibitors with regard to their potential application in high-temperature wells. Systematic experiments have been conducted to investigate the time (minutes to days) and temperature (up to 200°C) dependence of inhibitor thermal degradation, the impact of stainless steel and iron on the degradation of inhibitors at high temperatures, and the difference between aging tests with inhibitors in solution and with those inhibitors adsorbed on core materials. The results not only enable a more accurate understanding of the thermal degradation of scale inhibitors but also facilitate the selection and placement of scale inhibitors for high-temperature oil and gas production.
Nanopore-Structure Analysis and Permeability Predictions for a Tight Gas Siltstone Reservoir by Use of Low-Pressure Adsorption and Mercury-Intrusion Techniques
Authors: Clarkson C.R.. R. , Wood J.M.. M. , Burgis S.E.. E. , Aquino S.D.. D. , Freeman M..
Published: January 2013

The pore structure of unconventional gas reservoirs, despite having a significant impact on hydrocarbon storage and transport, has historically been difficult to characterize because of a wide pore-size distribution (PSD), with a significant pore volume (PV) in the nanopore range. A variety of methods is typically required to characterize the full pore spectrum, with each individual technique limited to a certain pore size range.

In this work, we investigate the use of nondestructive, low-pressure adsorption methods, in particular low-pressure N2 adsorption analysis, to infer pore shape and to determine PSDs of a tight gas silt-stone reservoir in western Canada. Unlike previous studies, core-plug samples, not crushed samples, are used for isotherm analysis, allowing an undisturbed pore structure (i.e., uncrushed) to be analyzed. Furthermore, the core plugs used for isotherm analysis are subsamples (end pieces) of cores for which mercury-injection capillary pressure (MICP) and permeability measurements were previously performed, allowing a more direct comparison with these techniques. PSDs, determined from two isotherm interpretation methods [Barrett-Joyner-Halenda (BJH) theory and density functional theory (DFT)], are in reasonable agreement with MICP data for the portion of the PSD sampled by both. The pore geometry is interpreted as slot-shaped, as inferred from isotherm hysteresis loop shape, the agreement between adsorption- and MICP-derived dominant pore sizes, scanning-electron-microscope (SEM) imaging, and the character of measured permeability stress dependence. Although correlations between inorganic composition and total organic carbon (TOC) and between dominant pore-throat size and permeability are weak, the sample with the lowest illite clay and TOC content has the largest dominant pore-throat size and highest permeability, as estimated from MICP. The presence of stress relief-induced microfractures, however, appears to affect laboratory-derived (pressure-decay and pulse-decay) estimates of permeability for some samples, even after application of confining pressure.

On the basis of the premise of slot-shaped pore geometry, fractured rock models (matchstick and cube) were used to predict absolute permeability, by use of dominant pore-throat size from MICP/adsorption analysis and porosity measured under confining pressure. The predictions are reasonable, although permeability is mostly overpredicted for samples that are unaffected by stress-release fractures. The conceptual model used to justify the application of these models is slot pores at grain boundaries or between organic matter and framework grains.
Blockage Detection and Characterization in Natural Gas Pipelines by Transient Pressure-Wave Reflection Analysis
Authors: Adeleke Najeem , Ityokumbul Mku T. , Adewumi Michael
Published: January 2013

Pipeline blockage is a major problem in gas production and transportation processes. Safety and economic costs of pipeline blockages are compelling the industry to design innovative means for early detection of partial blockages along pipe systems as a preventive measure. This paper presents a simple numerical model to be used for accurate blockage characterization in natural gas pipelines. The transport phenomenon is modeled with a quasi-1D set of partial differential equations for isothermal natural gas flow in pipes. The variable area formulation maintains the simplicity of a 1D formulation and yet allows for the complex geometries associated with natural gas pipeline blockages. Viscous effects are also included in the formulation of the governing equations, and a cubic equation of state is incorporated into the model to provide the quasi-compositional effect of real gases without the complexities of a fully compositional model. The generalized Newton-Raphson technique is used to solve the piece-wise finite-volume formulation iteratively as an optimization problem with pressure and velocity as perturbed variables. Reflected pressure waves observed at the pipe inlet node were analyzed for blockage characterization. It was observed that viscous losses have no effect on blockage length and location prediction accuracy, but has significant impact on the accuracy of blockage severity predictions.
Surface Complexation Modeling for Waterflooding of Sandstones
Authors: Brady Patrick V. , Krumhansl James L.
Published: January 2013

A theoretical surface coordination model of oil attraction to sandstone-reservoir surfaces confirms the two primary oil/mineral coordination reactions to be electrostatic linking of anionic kaolinite-edge sites to protonated nitrogen bases at pH < 6 and calcium carboxylate groups at pH > 6. Kaolinite basal planes are calculated to link to oil through oil –NH+ groups at pH < 6–7 and through oil –COOCa+ groups at pH > 6–7, and may be important to oil attraction where basal planes are more exposed than edges (the ranges shift, depending on the oil, acid, and base numbers). Model predictions are most sensitive to the dissociation constant of oil surface carboxylate groups but are relatively insensitive to other surface equilibria and temperature. The model shows that, although low-salinity, low-Ca waterfloods can enhance oil recovery by decreasing the number of Ca2+ bridges and anionic kaolinite-edge sites, dissolution of sandstone carbonate minerals dampens the low-salinity effect by buffering decreases in waterflood Ca2+ levels. Better model predictions require more-accurate predictions of Ca2+ levels during waterflooding, high-temperature sulfate-adsorption analyses, and more-precise measurements of oil acidity and basicity.
Simultaneous Continuous Monitoring of the Drilling-Fluid Friction Factor and Density
Authors: Carlsen Liv A. , Rolland Nils Lennart , Nygaard Gerhard , Time Rune
Published: January 2013

This paper introduces a method to enable continuous automatic online updates of the density and frictional effects of the drilling fluid during drilling operations. The placement of differential-pressure sensors along the circulation path from the rig pump to the connection to the drillstring enables the fluid properties to be examined more thoroughly at various flow rates, pressures, and temperatures. The paper presents results from a full-scale test in which different fluids were examined. The results show that the method may give reliable data on the main drilling-fluid properties, which are important in all drilling operations, and especially in automatic modes.
Methods for division of road traffic network for distributed simulation performed on heterogeneous clusters
Authors: Potuzak Tomas
Published: January 2013

The computer simulation of road traffic is an important tool for control and
analysis of road traffic networks. Due to their requirements for computation
time (especially for large road traffic networks), many simulators of the
road traffic has been adapted for distributed computing environment where
combined power of multiple interconnected computers (nodes) is utilized. In
this case, the road traffic network is divided into required number of
sub-networks, whose simulation is then performed on particular nodes of the
distributed computer. The distributed computer can be a homogenous (with
nodes of the same computational power) or a heterogeneous cluster (with nodes
of various powers). In this paper, we present two methods for road traffic
network division for heterogeneous clusters. These methods consider the
different computational powers of the particular nodes determined using a
benchmark during the road traffic network division.
Support for end-to-end response-time and delay analysis in the industrial tool suite: Issues, experiences and a case study
Authors: Mubeen Saad , Mäki-Turja Jukka , Sjödin Mikael
Published: January 2013

In this paper we discuss the implementation of the state-of-theart end-to-end
response-time and delay analysis as two individual plug-ins for the existing
industrial tool suite Rubus-ICE. The tool suite is used for the development
of software for vehicular embedded systems by several international
companies. We describe and solve the problems encountered and highlight the
experiences gained during the process of implementation, integration and
evaluation of the analysis plug-ins. Finally, we provide a proof of concept
by modeling the automotive-application case study with the existing
industrial model (the Rubus Component Model), and analyzing it with the
implemented analysis plug-ins.
Dual-Cured Etch-and-Rinse Adhesive Systems Increase the Bond Durability of Direct Coronal Dentin Restorations
Authors: Borges BCD , Vilela ARRC , da Silva-Junior CA , Souza-Junior EJ , Sinhoreti MAC , Pinheiro FHSL , Braz R , Montes MAJR
Published: January 2013

This study aimed to evaluate the bond durability of dentin restorations bonded with light- or dual-cured etch-and-rinse adhesive systems. A three-step adhesive system (Scotchbond Multipurpose Plus), an acetone-based two-step adhesive system (Prime & Bond 2.1), and an ethanol-based two-step adhesive system (Excite) were tested. Both the light- and the dual-cured versions were evaluated. High C-factor dentin cavities were prepared on 120 bovine incisors, which were then restored with resin composite (n=10). The samples were stored in water for 24 hours, and half of them were subjected to additional degradation with 10% NaOCl for five hours. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were evaluated by scanning electron microscopy. Data were analyzed by three-way analysis of variance and Tukey tests (p<0.05). The dual-cured adhesive system presented a higher immediate bond strength and durability than those that were light cured. The three-step adhesive system produced the highest values, whereas the acetone-based adhesive system produced the lowest result. Therefore, the use of dual-cured etch-and-rinse adhesive systems can induce increased bond durability to direct coronal dentin restorations.
Evaluation of portable blood glucose meters for measurement of blood glucose concentration in ferrets (Mustela putorius furo)
Authors: Petritz Olivia A. , Antinoff Natalie , Chen Sue , Kass Philip H. , Paul-Murphy Joanne R.
Published: January 2013

Objective—To evaluate agreement of 3 models of portable blood glucose meters (PBGMs; 2 designed for use with human samples and 1 designed for veterinary use) with a laboratory analyzer for measurement of blood glucose concentrations in ferrets (Mustela putorius furo).

Design—Evaluation study.

Animals—52 ferrets.

Procedures—Samples were analyzed with 4 PBGMs (whole blood) and a laboratory analyzer (plasma). Two PBGMs of the model designed for veterinary use were tested; each was set to a code corresponding to canine or feline sample analysis throughout the study. Agreement and bias between measurements obtained with the PBGMs and the laboratory analyzer were assessed with Bland-Altman plots. Linear regression analysis was performed to evaluate associations with venipuncture site by comparison of central (jugular) and peripheral (lateral saphenous or cephalic) venous blood samples.

Results—Plasma glucose concentrations measured with the laboratory analyzer ranged from 41 to 160 mg/dL. Results from the PBGM for veterinary use coded to test a canine blood sample had the greatest agreement with the laboratory analyzer (mean bias, 1.9 mg/dL); all other PBGMs significantly underestimated blood glucose concentrations. A PBGM designed for use with human samples had the least agreement with the laboratory analyzer (mean bias, −34.0 mg/dL). Blood glucose concentration was not significantly different between central and peripheral venous blood samples for any analyzer used.

Conclusions and Clinical Relevance—Significant underestimation of blood glucose concentrations as detected for 3 of the 4 PBGMs used in the study could have a substantial impact on clinical decision making. Verification of blood glucose concentrations in ferrets with a laboratory analyzer is highly recommended.
A novel active contour model for unsupervised low-key image segmentation
Authors: Mei Jiangyuan , Si Yulin , Karimi Hamid , Gao Huijun
Published: January 2013

Unsupervised image segmentation is greatly useful in many vision-based applications. In this paper, we aim at the unsupervised low-key image segmentation. In low-key images, dark tone dominates the background, and gray level distribution of the foreground is heterogeneous. They widely exist in the areas of space exploration, machine vision, medical imaging, etc. In our algorithm, a novel active contour model with the probability density function of gamma distribution is proposed. The flexible gamma distribution gives a better description for both of the foreground and background in low-key images. Besides, an unsupervised curve initialization method is designed, which helps to accelerate the convergence speed of curve evolution. The experimental results demonstrate the effectiveness of the proposed algorithm through comparison with the CV model. Also, one real-world application based on our approach is described in this paper.
Examination of Roller-Integrated Continuous Compaction Control on Colorado Test Site
Authors: Rinehart Robert V. , Mooney Michael A. , Facas Norman F. , Musimbi Odon M.
Published: January 2013

Roller-integrated continuous compaction control can improve earthwork quality assurance in the United States; therefore, it is receiving considerable attention. Most preliminary specifications that are being evaluated are based on specifications from Austria, Germany, and Sweden. In general, the European specifications encompass either of two approaches: (a) spot testing in roller-identified weak areas or (b) calibrating roller-measured values to spot test values. A pilot implementation on an active earthwork construction site in Colorado showed spot testing roller-identified weak zones represented an incremental progression from the current methods employed in the United States. The calibration option was shown to be labor intensive, and the results presented here indicate that the initial time investment may not be justifiable. Implementation of the calibration option is further complicated because it is a significant departure from current methods. An analysis of the spot-testing option showed that if a similar level of quality acceptance is desired, then current requirements for quality assurance based on density spot testing may have to be lowered for quality assurance to be based on continuous compaction control.
Locating Soil Tests with Intelligent Compaction Data and Geographic Information System Technology
Authors: Graettinger Andrew J. , Doherty William B. , Herron Michael , Siekmeier John , Petersen Lee
Published: January 2013

Intelligent compaction is gaining popularity as a tool for evaluating soil compaction. Unfortunately, intelligent compaction equipment collects an overwhelming amount of data, especially for an inspector who is making decisions in the field. The goal of this approach is to identify optimal places to perform field compaction tests on the basis of relative compaction values. This paper presents a geographic information system application that analyzes and views intelligent compaction data to support in-field decision making. To facilitate the analysis, intelligent compaction data were converted from geographic coordinates into a regularized station and offset coordinate system. A grid of points at 1-ft intervals was placed over the intelligent compaction data, and spatial analysis tools were used to average the compaction values within various distances of the grid points. On the assumption that 95% of a soil lift must be compacted correctly, statistical analyses were performed to identify points that fell between the 4th and 6th percentiles of the compaction value. A positive outcome from field compaction tests at these locations would indicate that at least 95% of the lift was properly compacted; a negative outcome would indicate that less than 95% of the lift was compacted adequately and that additional compaction work was required.
Full-Scale Evaluation of Geogrid-Reinforced Thin Flexible Pavements
Authors: Jersey Sarah R. , Tingle Jeb S. , Norwood Gregory J. , Kwon Jayhyun , Wayne Mark
Published: January 2013

A full-sale test section was constructed and subjected to traffic loading at the U.S. Army Engineer Research and Development Center to evaluate the performance of a geogrid that was used for base reinforcement in a thin flexible pavement. Three test items—a geogrid-reinforced test item and two unreinforced control test items—were constructed under controlled conditions. The test pavements were subjected to accelerated traffic loading to evaluate the relative performance of the pavement structures. Pavement stiffness and permanent surface deformations were measured periodically throughout the testing. The study results showed that the geogrid-reinforced pavement performed better than the unreinforced control pavements did. The results were used to develop traffic benefit ratios and effective base course structural coefficients to enable comparison of the pavement structures.
Avoiding Sulfate Heave in Subgrades with a Little Help from Precision Agriculture
Authors: Harris Pat , Harvey Omar , Sebesta Stephen
Published: January 2013

In recent years, the Texas Department of Transportation has observed the heaving of gypsum- or sulfate-bearing subgrade soil when it has been chemically stabilized with calcium-based additives. The occurrence of sulfate or gypsum deposits in these soils is unpredictable and often localized in small areas. Current testing procedures, in which samples are collected at specified intervals for sulfate measurements, often miss these localized concentrations. A method that provides rapid and continuous mapping of sulfate content in subgrades to a depth of at least 1 m is needed. Researchers in precision agriculture have used several devices that rapidly and continuously measure the bulk electrical conductivity of the soil at high spatial resolutions (<10 ft) and depths (≥2 ft). For the research described in this paper, the Veris 3150 was used to measure spatial variability in bulk electrical conductivity across three sulfate-bearing subgrades in Texas. The data were used to construct high-resolution maps of the subgrade conductivity and were compared with soil properties to identify potentially high-risk areas for sulfate heaving. The bulk electrical conductivity, the sulfate content, and the soil plasticity varied in tandem throughout the subgrades. This research identified areas with an electrical conductivity of >100 mS/m as having the greatest potential for sulfate problems of the subgrades tested. It also identified a technique that could be used to rapidly and effectively screen large projects for potential sulfate problems and to map the distribution of high- and low-clay subgrade soils.
Seasonal and interannual variability of elemental carbon in the snowpack of Storglaciären, northern Sweden
Authors: Ingvander Susanne , Rosqvist Gunhild , Svensson Jonas , Dahlke Helen E.
Published: January 2013

We studied the variability of elemental carbon (EC) over 3 years (2009–11) in the winter snowpack of Storglaciären, Sweden. The goal of this study was to relate the seasonal variation in EC to specific snow accumulation events in order to improve understanding of how different atmospheric circulation patterns control the deposition of EC. Specifically, we related meteorological parameters (e.g. wind direction, precipitation) to snow physical properties, EC content, stable-isotope δ18O ratios and anion concentrations in the snowpack. The distribution of EC in the snowpack varied between years. Low EC contents corresponded to a predominance of weather systems originating in the northwest, i.e. North Atlantic. Analysis of single layers within the snowpacks showed that snow layers enriched in heavy isotopes coincided predominantly with low EC contents but high chloride and sulfate concentration. Based on this isotopic and geochemical evidence, snow deposited during these events had a strong oceanic, i.e. North Atlantic, imprint. In contrast, snow layers with high EC content coincided with snow layers depleted in heavy isotopes but high anion concentrations, indicating a more continental source of air masses and origin of EC from industrial emissions.
A Study of Serum Zinc level in Cirrhosis of Liver
Authors: Atia F , Sultana N , Ahmed S , Ferdousi S , Sultana R , Atiquzzaman M
Published: January 2013

Cirrhosis is a consequence of chronic liver diseases. Zinc is a micronutrient that plays an important role in the function of liver. This cross-sectional study was carried out in the Department of Biochemistry, Dhaka Medical College, from July 2010 to June 2011 to observe the association of serum zinc level with liver cirrhosis. A total of 100 adults, both males and females with age range of 18-60 years, of which 50 were healthy subjects and 50 adult hospitalised cirrhotic patients were selected purposively for the study according to selection crieteria. Fasting serum zinc level was measured with atomic absorption spectrophotometer. Serum zinc level was found to be low in 72% patients. Mean ±SD of serum zinc levels (?g/L) were 610.32 ± 169.60 and 827.66 ± 267.32 in cases and controls respectively. In cirrhotic patients serum zinc level was significantly lower than that of healthy controls (P<0.001). Though, it is difficult to draw any definite conclusion from this study, because of reduced level serum of zinc found in cirrhotics, Zn may be supplemented to them with a hope of better treatment response. DOI: http://dx.doi.org/10.3329/bjmb.v5i2.13340 Bangladesh J Med Biochem 2012; 5(2): 44-47
Donor Site Evaluation After Lingual Mucosal Graft Harvest for Urethroplasty
Authors: Asaduzzaman M , Quddus MR , Islam MS , Ahmed K , Rosy SK , Bhuiyan AKMZI
Published: January 2013

This study was carried out in the Department of Urology, National Institute of Kidney Diseases and Urology, (NIKDU), during the period from Jan' 09 to Dec' 10 to assess the complications at donor site after lingual mucosal graft harvesting for urethroplasty. A total of 30 patients with mean age of 36.6 years (rang 21 to 56 years) and mean urethal stricture length of 36 mm (range 22 to 59 mm) who underwent urethroplasty for anterior urethral strictures using dorsal onlay of a lingual mucosal graft (LMG) were selected for the study. The site of the harvest graft was ventrolateral mucosal lining of the tongue. Donor site complications like pain, numbness, tightness, slurring of speech, salivatory changes and difficulty in protrusion of tongue were noted. The mean period of follow-up was 14 months (range 6-18 months). At the first postoperative day, 96% of the patients experienced pain at donor site and 26% had slurring of speech. Pain was mild to discomforting in 60% and distressing to excruciating in 37% of the patients. By third postoperative day, 22 (73%) patients were pain free, 06 (20%) suffered from mild pain and 02 (6%) suffered from discomforting pain only and none had slurring of speech. On the fifth postoperative day, only 02 (6%) patient suffered pain. By day 6 of surgery, all patients were pain free. Only 01 (3.3%) patients reported numbness which persisted during the whole period of follow up. The study showed that LMG is easy to harvest and associated with less postoperative pain, minor risk of donor site complications and without any functional or esthetic deficiency. So tongue may be the best alternative donor site for anterior urothroplasty. DOI: http://dx.doi.org/10.3329/bjmb.v5i2.13341 Bangladesh J Med Biochem 2012; 5(2): 48-52
Effect of Nitrendipine, Diltiazem and Verapamil on psychomotor performance in human volunteers
Authors: Tamboli Saleem Basha
Published: January 2013

Background: Calcium channel blockers are amongst the commonly used drugs in the treatment of cardiovascular disorders. They produce their action by blocking voltage regulated calcium channels. Methodolgy: Present study evaluated the effects of three structurally dissimilar calcium channel blockers Nitrendipine (a dihydropyridine) in a single dose of 10 mg and 20 mg, Diltiazem (a benzothiazepine) in a single dose of 30 mg and 60 mg and Verapamil (a phenylalkylamine) in a single dose of 40 mg and 80 mg on psychomotor performance in human volunteers. For evaluation of psychomotor performance, the tests used were arithmetic ability, verbal learning, letter cancellation, digit symbol substitution and card sorting test. Results: Nitrendipine both in low dose (10mg) and high dose (20mg) as well as Diltiazem in high dose (60mg) and Verapamil in high dose (80mg) were found to impair the psychomotor performance in human volunteers to a statistically significant extent in all the tests employed except letter cancellation test. Whereas Diltiazem in low dose (30mg) and Verapamil in low dose (40mg) showed statistically significant impairment of psychomotor performance using arithmetic ability, verbal learning, and digit symbol substitution test. Conclusion: Thus calcium channel blockers namely Nitrendipine, Diltiazem and Verapamil significantly impaired the psychomotor performance of human volunteers in our study. DOI: http://dx.doi.org/10.3329/bjms.v12i1.11534 Bangladesh Journal of Medical Science Vol. 12 No. 01 January13 pp.43-48
Risk profile in asymptomatic first degree relatives of Coronary Artery Disease (CAD) patients
Authors: Chawla Omna , Matreja Prithpal Singh , Pramod John
Published: January 2013

Aim: Cardiovascular disease is on the rise and is expected to be a leading cause of death and disability worldwide. Identification of risk in asymptomatic individual in higher risk group could help to plan individual patients management. Positive family history is one of the risk factors and screening at this level may help in determining individual therapy. Studies have shown relation of positive family history but are lacking in this part of world, so we considered it worthwhile to assess FRS in asymptomatic sibling of CAD Patients Materials and methods: 75 volunteers were enrolled in the study and they underwent Bruce treadmill exercise protocol after their initial evaluation, these volunteers than also underwent biochemical test  Fasting blood sugar and lipid profile. These volunteers were divided into two groups based upon their Treadmill test results. Results: 31 out of 75 volunteers were TMT positive and they were kept in one group. These volunteers differed significantly (p<0.05) in higher age, fasting blood sugar and Low density lipoprotein level (LDL). This group also had a significantly lower metabolic equivalents and higher Framingham Risk Score. Conclusion: Our study showed that positive family history is associated with a higher Framingham risk score in asymptomatic volunteers. DOI: http://dx.doi.org/10.3329/bjms.v12i1.11825 Bangladesh Journal of Medical Science Vol. 12 No. 01 January13 pp.68-73
Stress among Parents of Children with Mental Retardation
Authors: Islam Md Ziaul , Farjana Sharmin , Shahnaz Runa
Published: January 2013

Mental retardation is one of the most prevalent developmental disabilities of the children globally. Family is the main source of support for those disable children in any society. Parents experience enormous physical and mental stress to tackle the mentally retarded children. This present comparative cross-sectional study tried to compare difference of mental and physical stress between the parents of children with mental retardation and the parents of children with no mental retardation. It included 220 parents, 110 of whom had children with mental retardation and another 110 parents of children with no mental retardation. To assess stress, A Quick Stress Assessment Test (QSAT) (Vaz, 1995) was used, which comprised two parts: physical and mental, former with 19 items and latter with 21 items. Data were collected with a self-administered questionnaire and analyzed by using SPSS software. To check differences of stress scores and gender differences of stress,t test and ?2 tests were applied as required. The study revealed that the parents of children with mental retardation (PCMR) shared significantly greater stress score (34.27) than the parents of children with no mental retardation (PCNR) (21.66), [t(218)= 2.63, p=0.001]. Mental stress score was significantly higher among PCMR (33.57) than the PCNR (26.46) [t(218)= 3.87; p=0.002] while physical stress score was insignificantly higher among PCMR (20.43) than the PCNR (18.66). Majority of the parents with mentally retarded children (71.4% mothers and 67.5% fathers) had higher mental stress than physical stress [?2 (1)=22 43, p=0.024]. Mothers had significantly higher mental stress score than the fathers of mentally retarded children [t(109), p=0.025]. Special measures like early diagnosis, prompt treatment and counseling for mental and physical stress of the parents along with provision of need based rehabilitation services for the mentally retarded children at different levels to reduce the stress burden of their parents. DOI: http://dx.doi.org/10.3329/bjms.v12i1.13354 Bangladesh Journal of Medical Science Vol. 12 No. 01 January13 pp.74-80
Emphysematous Pyelonephritis: Radiological Perspective
Authors: Ansari Sajid , Ahmad Kaleem , Dhungel Kanchan , Sah Panna Lal , Gupta Mukesh Kumar , Rauniyar RK
Published: January 2013

Emphysematous pyelonephritis (EPN) is an acute necrotizing parenchymal and perirenal infection and is caused by gas-forming organisms. Diabetes mellitus and ureteric obstruction are the predisposing factors for EPN. Computerized tomography (CT) scan is the modality of choice in diagnosing the disease, determining the extent of infection and helps in management. We report a case of emphysematous pyelonephritis in 52 years old man with emphasis on plain radiographic and CT scan findings. DOI: http://dx.doi.org/10.3329/bjms.v12i1.13358 Bangladesh Journal of Medical Science Vol. 12 No. 01 January13 pp.93-95
ℓ1 Major Component Detection and Analysis (ℓ1 MCDA): Foundations in Two Dimensions
Authors: Tian Ye , Jin Qingwei , Lavery John , Fang Shu-Cherng
Published: January 2013

Principal Component Analysis (PCA) is widely used for identifying the major components of statistically distributed point clouds. Robust versions of PCA, often based in part on the ℓ1 norm (rather than the ℓ2 norm), are increasingly used, especially for point clouds with many outliers. Neither standard PCA nor robust PCAs can provide, without additional assumptions, reliable information for outlier-rich point clouds and for distributions with several main directions (spokes). We carry out a fundamental and complete reformulation of the PCA approach in a framework based exclusively on the ℓ1 norm and heavy-tailed distributions. The ℓ1 Major Component Detection and Analysis (ℓ1 MCDA) that we propose can determine the main directions and the radial extent of 2D data from single or multiple superimposed Gaussian or heavy-tailed distributions without and with patterned artificial outliers (clutter). In nearly all cases in the computational results, 2D ℓ1 MCDA has accuracy superior to that of standard PCA and of two robust PCAs, namely, the projection-pursuit method of Croux and Ruiz-Gazen and the ℓ1 factorization method of Ke and Kanade. (Standard PCA is, of course, superior to ℓ1 MCDA for Gaussian-distributed point clouds.) The computing time of ℓ1 MCDA is competitive with the computing times of the two robust PCAs.
Economies: An Open Access Journal for the Field of Development Macroeconomics
Authors: Fendel Ralf
Published: January 2013

Economies (ISSN 2227-7099) is a new international, peer-reviewed open access journal for the academic fields of development economics and macroeconomics. While the latter seems to be clearly defined, development economics is not, because it is related to nearly all traditional economic sub-disciplines such as macroeconomics, international trade and finance, as well as microeconomics and public finance. Typically, academic field journals of development economics cover all those economic sub-disciplines. Economies instead focuses mainly on the macroeconomic perspective of economic development and it intends to publish academic research that is of strong macroeconomic policy relevance. In general, contributions in Economies should foster understanding of the macroeconomic process of economic development, with the process of development not exclusively being reserved to what we typically call developing countries. Also, the group of developed economies is still developing in the sense of improving their living standards further. [...]
Allometric Scaling and Resource Limitations Model of Tree Heights: Part 1. Model Optimization and Testing over Continental USA
Authors: Shi Yuli , Choi Sungho , Ni Xiliang , Ganguly Sangram , Zhang Gong , Duong Hieu , Lefsky Michael , Simard Marc , Saatchi Sassan , Lee Shihyan , Ni-Meister Wenge , Piao Shilong , Cao Chunxiang , Nemani Ramakrishna , Myneni Ranga
Published: January 2013

A methodology to generate spatially continuous fields of tree heights with an optimized Allometric Scaling and Resource Limitations (ASRL) model is reported in this first of a multi-part series of articles. Model optimization is performed with the Geoscience Laser Altimeter System (GLAS) waveform data. This methodology is demonstrated by mapping tree heights over forested lands in the continental USA (CONUS) at 1 km spatial resolution. The study area is divided into 841 eco-climatic zones based on three forest types, annual total precipitation classes (30 mm intervals) and annual average temperature classes (2 °C intervals). Three model parameters (area of single leaf, α, exponent for canopy radius, η, and root absorption efficiency, γ) were selected for optimization, that is, to minimize the difference between actual and potential tree heights in each of the eco-climatic zones over the CONUS. Tree heights predicted by the optimized model were evaluated against GLAS heights using a two-fold cross validation approach (R2 = 0.59; RMSE = 3.31 m). Comparison at the pixel level between GLAS heights (mean = 30.6 m; standard deviation = 10.7) and model predictions (mean = 30.8 m; std. = 8.4) were also performed. Further, the model predictions were compared to existing satellite-based forest height maps. The optimized ASRL model satisfactorily reproduced the pattern of tree heights over the CONUS. Subsequent articles in this series will document further improvements with the ultimate goal of mapping tree heights and forest biomass globally.
Vegetation Index Differencing for Broad-Scale Assessment of Productivity Under Prolonged Drought and Sequential High Rainfall Conditions
Authors: Browning Dawn , Steele Caitriana
Published: January 2013

Spatially-explicit depictions of plant productivity over large areas are critical to monitoring landscapes in highly heterogeneous arid ecosystems. Applying radiometric change detection techniques we sought to determine whether: (1) differences between pre- and post-growing season spectral vegetation index values effectively identify areas of significant change in vegetation; and (2) areas of significant change coincide with altered ecological states. We differenced NDVI values, standardized difference values to Z-scores to identify areas of significant increase and decrease in NDVI, and examined the ecological states associated with these areas. The vegetation index differencing method and translation of growing season NDVI to Z-scores permit examination of change over large areas and can be applied by non-experts. This method identified areas with potential for vegetation/ecological state transition and serves to guide field reconnaissance efforts that may ultimately inform land management decisions for millions of acres of federal lands.