bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of rice husk ash to the performance of polymer mortar and polymer concrete
Authors: Rahman Md. Mostafizur , Islam Md. Akhtarul 
Published: June 2013

Abstract
This paper presents the effect of rice husk ash (RHA) as fine filler, partially replacing sand (fine aggregate) in the composition of epoxy resin based polymer mortar (PM) and polymer concrete (PC), to make them advantageous and lessen their adverse effects on the environment. Assessment was carried out on the basis of the mechanical (compressive, flexural, tensile strength), physical (water sorption, chloride ion penetration) and morphological (porosity) properties of polymer mortar and polymer concrete. The microstructure of the PM specimens (with RHA and without RHA) is examined by scanning electron microscopy (SEM). The amount of RHA in the composition of PM and PC is optimized. The experimental result shows that the optimum replacement of sand by RHA in the composition of PM and PC has a favorable influence on mechanical, physical and morphological properties of the mortar and concrete.
First insights into structure-function relationships of alkylglycerol monooxygenase
Authors: Watschinger Katrin , Fuchs Julian E. , Yarov-Yarovoy Vladimir , Keller Markus A. , Golderer Georg , Hermetter Albin , Werner-Felmayer Gabriele , Hulo Nicolas , Werner Ernst R. 
Published: June 2013

Abstract
Alkylglycerol monooxygenase is a tetrahydrobiopterin-dependent enzyme that cleaves the O-alkyl-bond of alkylglycerols. It is an exceptionally unstable, hydrophobic membrane protein which has never been purified in active form. Recently, we were able to identify the sequence of alkylglycerol monooxygenase. TMEM195, the gene coding for alkylglycerol monooxygenase, belongs to the fatty acid hydroxylases, a family of integral membrane enzymes which have an 8-histidine motif crucial for catalysis. Mutation of each of these residues resulted in a complete loss of activity. We now extended the mutational analysis to another 25 residues and identified three further residues conserved throughout all members of the fatty acid hydroxylases which are essential for alkylglycerol monooxygenase activity. Furthermore, mutation of a specific glutamate resulted in an 18-fold decreased affinity of the protein to tetrahydrobiopterin, strongly indicating a potential important role in cofactor interaction. A glutamate residue in a comparable amino acid surrounding had already been shown to be responsible for tetrahydrobiopterin binding in the aromatic amino acid hydroxylases. Ab initio modelling of the enzyme yielded a structural model for the central part of alkylglycerol monooxygenase where all essential residues identified by mutational analysis are in close spatial vicinity, thereby defining the potential catalytic site of this enzyme.
Properties of orchard pruning and suitability for composite production
Authors: Sahin Halil Turgut , Arslan Mustafa Burak 
Published: June 2013

Abstract
Apple and cherry pruning with red pinewood particles in various proportions were used as the raw material for the experimental particleboard manufacturing in laboratory conditions. The results showed that there were no considerable differences in the main chemical constituents of carbohydrate and lignin content, although there were some differences found for extractives that are considerably higher for both cherry and apple pruning. The mean modulus of rupture values of boards were found to ranged from 12.4 to 18.48 MPa. These indicated that all the boards, except for the board type F (prepared from 100% apple pruning), met the minimum bending strength required in standard for general-purpose particleboards. The modulus of elasticity and internal bond of the experimental particleboards usually decreased as red pinewood particle content decreases in proportion. However, all the boards produced in this study met the minimum modulus of elasticity, internal bond, and surface strength required in standard for general-purpose particleboards. However, the thickness swelling for 24 h was considerably higher than the required in standard value of 14% for all boards.
Prevalence of subclinical contributors to low bone mineral density and/or fragility fracture
Authors: Eller-Vainicher Cristina , Cairoli Elisa , Zhukouskaya Volha V , Morelli Valentina , Palmieri Serena , Scillitani Alfredo , Beck-Peccoz Paolo , Chiodini Iacopo 
Published: June 2013

ObjectiveThe prevalence of subclinical contributors to low bone mineral density (BMD) and/or fragility fracture is debated. We evaluated the prevalence of subclinical contributors to low BMD and/or fragility fracture in the presence of normal 25-hydroxyvitamin D (25OHVitD) levels.DesignProspective observational study.MethodsAmong 1095 consecutive outpatients evaluated for low BMD and/or fragility fractures, 602 (563 females, age 65.4±10.0 years) with apparent primary osteoporosis were enrolled. A general chemistry profile, phosphate, 25OHVitD, cortisol after 1-mg overnight dexamethasone suppression test, antitissue transglutaminase and endomysial antibodies and testosterone (in males) were performed. Serum and urinary calcium and parathyroid hormone levels were also evaluated after 25OHVitD levels normalization. Vertebral deformities were assessed by radiograph.ResultsIn total, 70.8% of patients had low 25OHVitD levels. Additional subclinical contributors to low BMD and/or fragility fracture were diagnosed in 45% of patients, with idiopathic hypercalciuria (IH, 34.1%) and primary hyperparathyroidism (PHPT, 4.5%) being the most frequent contributors, apart from hypovitaminosis D. Furthermore, 33.2% of IH and 18.5% of PHPT patients were diagnosed only after 25OHVitD levels normalization. The subclinical contributors to low BMD and/or fragility fracture besides hypovitaminosis D were associated inversely with age (odds ratio (OR) 1.02, 95% CI 1–1.04,P=0.04) and BMI (OR 1.1, 95% CI 1.05–1.17,P=0.0001) and directly with fragility fractures (OR 1.89, 95% CI 1.31–2.73,P=0.001), regardless of BMD.ConclusionsSubclinical contributors to low BMD and/or fragility fracture besides hypovitaminosis D are present in more than 40% of the subjects with apparent primary osteoporosis. Hypovitaminosis D masks a substantial proportion of IH and PHPT patients.
Increased Glyoxalase-1 Levels in Fkbp5 Knockout Mice Caused by Glyoxalase-1 Gene Duplication
Authors: Kollmannsberger Lorenz K , Gassen Nils C , Bultmann Andrea , Hartmann Jakob , Weber Peter , Schmidt Mathias V , Rein Theo 
Published: June 2013

Abstract
Fkbp5 is genetically linked to stress-related diseases. Fkbp5 knockout mice are available and widely used to explore the role of Fkbp5 in health and disease. We found that these mice carry a gene duplication of glyoxylase-1, which explains why glyoxylase-1 levels are increased in the Fkbp5 knockout mice.
Targeting of Painting of fourth to roX1 and roX2 Proximal Sites Suggests Evolutionary Links Between Dosage Compensation and the Regulation of the fourth Chromosome in Drosophila melanogaster
Authors: Lundberg Lina E , Kim Maria , Johansson Anna-Mia , Faucillion Marie-Line , Josupeit Rafael , Larsson Jan 
Published: June 2013

Abstract
In Drosophila melanogaster, two chromosome-specific targeting and regulatory systems have been described. The male-specific lethal (MSL) complex supports dosage compensation by stimulating gene expression from the male X-chromosome, and the protein Painting of fourth (POF) specifically targets and stimulates expression from the heterochromatic 4th chromosome. The targeting sites of both systems are well characterized, but the principles underlying the targeting mechanisms have remained elusive. Here we present an original observation, namely that POF specifically targets two loci on the X-chromosome, PoX1 and PoX2 (POF-on-X). PoX1 and PoX2 are located close to the roX1 and roX2 genes, which encode noncoding RNAs important for the correct targeting and spreading of the MSL-complex. We also found that the targeting of POF to PoX1 and PoX2 is largely dependent on roX expression and identified a high-affinity target region that ectopically recruits POF. The results presented support a model linking the MSL-complex to POF and dosage compensation to regulation of heterochromatin.
Charge transport in nanocrystalline germanium/hydrogenated amorphous silicon mixed-phase thin films
Authors: Bodurtha Kent E. , Kakalios J. 
Published: June 2013

ABSTRACTMixed phase thin films consisting of hydrogenated amorphous silicon (a-Si:H) in which germanium nanocrystals (nc-Ge) are embedded have been synthesized using a dual-chamber co-deposition system. Raman spectroscopy and x-ray diffraction measurements confirm the presence of 4 - 4.5 nm diameter nc-Ge homogenously embedded within the a-Si:H matrix. The conductivity and thermopower are studied as the germanium crystal fraction XGe is systematically increased. For XGe < 10%, the thermopower is n-type (as in undoped a-Si:H) while for XGe > 25% p-type transport is observed. For films with 10 < XGe < 25% the thermopower shifts from p-type to n-type as the temperature is increased. This transition is faster than expected from a standard two-channel model for charge transport.
Multi-geophysical Investigation of Geological Structures in a Pre-selected High-level Radioactive Waste Disposal Area in Northwestern China
Authors: An Zhiguo , Di Qingyun , Wang Ruo , Wang Miaoyue 
Published: June 2013

A potential high-level radioactive waste (HLRW) disposal site in northwestern China was investigated to determine its suitability for such a use. The site is primarily covered with well-developed metamorphic granite rocks. The primary targets for geological repositories are three granite rock masses (I, II, and III). Only surface geological data were available from previous studies. The objective of this study was to evaluate the quality of the rock mass and identify any weak geological structures that could jeopardize this future underground repository. We used gravity and aeromagnetic data on a large scale to study the regional geological structures within and around the three rock masses. Subsequently, in 2009, a controlled source audio-frequency magnetotelluric (CSAMT) survey was conducted to study rock mass I in more detail. This paper introduces three-dimensional (3-D) tomography imaging of gravity and aeromagnetic data. 3-D tomography imaging was carried out on previously collected gravity and aeromagnetic data and, using the results of different depth slices, we evaluated the rock mass quality and interpreted the geology. The aeromagnetic depth slices show that at about 1-km deep in rock masses I and III there is a high magnetic susceptibility body, possibly caused by an early granite intrusion. The deep granite or metamorphic rocks appear as weak `magnetic anomalies in the magnetic slices. The results also indicate that rock mass II is more deeply buried and smaller than rock masses I and III. In the upper crust, inhomogeneous density variations have a strike direction consistent with that of the structure revealed in the aeromagnetic data. For rock mass I, we designed a CSAMT line to map small-scale outcropped faults to depth, and identify any hidden faults or weakened zones in the subsurface. Because of the highly resistive ground, we improved the electrode contact conditions by pouring salt water on both the transmitting and receiving electrodes. During data processing, we applied Hanning filtering to reduce static effects from lack of electrical homogeneity near the ground surface, and through experimentation found an optimum filter length to achieve maximum static effect reduction. Sounding data were inverted for geoelectrical cross sections using a two-dimensional smooth-model inversion method. Inversion artifacts were suppressed by imposing the model smoothness constraint. Several important results were revealed by the inversion: the inversion section correctly recognized two fractures at the surface, and also identified two new faults that were not observed during the previous geological survey. The inversion profile suggests that the narrow factures and deformation bands extend to a great depth. With further drilling confirmation, this interpretation will enhance understanding of the deep geological structures at the HLRW disposal site.
Hydraulic Fracturing with Water-Based Fluids in Water-Sensitive Formations
Authors: Salazar F. , Rachid R. , Jimenez J. , Milne A. , Ali Syed 
Published: June 2013

Abstract
Ecuador is producing oil today from mature fields with increasing water cut, and most of the reservoirs are subhydrostatic with permeability ranging from 10 to 1000 md and significant clay content (mainly kaolinite and glauconite) in the formation matrix. As a consequence of the increasing workover interventions and fluid invasion due to the depleted reservoir conditions, there was need to stimulate the wells to be able to bypass the damage zone. In the past, it was common to lose completion fluid into the reservoir, resulting in a 20% to 50% reduction in production or even in extreme cases killing the well when the completion fluid was incompatible with either reservoir fluids or formation clays.
Historically matrix acidizing treatments have been perfomed in an attempt to remove formation damage or to increment production, with limited success. Matrix acidizing treatments are not sufficient to fully remove the damage because of the high clay content, and in many cases, the damage cannot be removed by just treating the critical matrix. Conventional hydraulic fracturing treatments were then tried as a means to bypass the damage. However, some of the wells treated showed positive skin factors following the fracture treatments.
The wells in which hydraulic fracturing had proved unsuccessful were studied in more detail to understand the reason why hydraulic fracturing resulted in a positive skin. It was concluded from the formation mineralogy and core flow testing that the fracturing treatments were unsuccessful due to a reduction in the formation permeability due to the mechanical plugging and movement of the kaolinite or disrupted mica in the pore throats. The reduction in the matrix permeability results in skin damage in the faces of the fracture. The fracture-face damage or skin can also be caused by fluid loss from the fracturing fluid through the fracture faces, which creates an additional drop in pressure that may further reduce the productivity of the well. The impact of these effects on the productivity of a treated well depends on the reservoir characteristics and mineralogy, fracture geometry, extent of fluid leakoff into the reservoir, and the viscosity of the fracturing fluid filtrate. The magnitude of these effects and resulting additional pressure drop generally increases with increasing reservoir permeability.
To eliminate or mitigate the fracture-face skin effect in water-sensitive formations, a new treatment incorporating a prepad of a viscosified blend of chelants and acid was field tested. By adding this stage into the fracturing treatment design, the retained matrix permeability was increased to +/- 70% of the undamaged matrix permeability, resulting in negligible fracture-face skin. The productivity of fracturing treatments performed using this innovative technique resulted in negative skin factors and production ratios that exceeded expectations in water-sensitive and high clay content reservoirs.
Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures
Authors: Zhou L. , Nasr-El-Din H. A. 
Published: June 2013

Abstract
Regular mud acid mixtures have been extensively used to stimulate sandstone formations; however, the use of this acid in a deep well has some major drawbacks, including high and uncontrolled reaction rate and corrosion to well tubulars. A single stage sandstone acid system (HF and a phosphonic acid) has been developed as an alternative to mud acid. Carbonate minerals in sandstone formations can cause formation damage. Therefore, there is a need to remove the carbonates to enhance the performance of this sandstone acid system.
In this study, the single stage sandstone acid systems with different HF concentration were examined to stimulate sandstone formation at high temperature. Berea (5 wt% clays) and Bandera (11 wt% clays) sandstone cores were used in the coreflood experiments. Coreflood experiments on sandstone cores were conducted at 300 °F at a flow rate of 2 cm3/min. The concentrations of Si, Ca, Al, Mg, and Fe in the core effluent samples were analyzed using Inductively Coupled Plasma (ICP). 0.6M GLDA (pH= 3.8), 0.6M HEDTA (pH =3.8), and 9 wt% formic acid solution were evaluated to remove the carbonate minerals from Bandera sandstone cores.
Coreflood experiments showed the sandstone acid systems enhanced the permeability of Berea sandstone cores, and the optimum injection volume is 2.5 PV to keep the integrity of the cores at 2 cm3/min and 300°F. This acid system damaged Bandera sandstone cores severely at 300°F, which contain 16 wt% dolomite, and 10 wt% illite. Analysis of core effluent samples indicated that there was CaF2 precipitate in the core when the acid systems were pumped without preflush. Therefore, calcium carbonate in Bandera sandstone cores should be removed with preflush. GLDA, HEDTA and formic acid (9 wt%) were compatible with Bandera sandstone cores at low pH value, and formic acid was much more effective in remove carbonate in Bandera sandstone cores.
Effects of Total Suspended Solids on Permeability of Proppant Pack
Authors: Ye X. , Tonmukayakul N. , Lord P. , LeBas R. 
Published: June 2013

Abstract
Recently, interest in using produced water for hydraulic stimulation processes has greatly increased within the oilfield services industry. However, successful hydraulic fracturing operations using produced water have yet to reach their full potential. This is largely because of wide variance in water quality from such sources as bacterial content, suspended solids, scale, and precipitate potential. Among these, suspended solids are a major issue. Their presence can create severe problems by plugging the proppant's pore space. In this paper, the effects of total suspended solids (TSS) on proppant permeability using a novel benchtop device (Ye et al. 2009) are discussed. This apparatus imposes a controlled strain on the proppant pack while continually measuring its permeability up to a compressive stress of 7,100 psi. Another unique feature of this apparatus is the direct visualization of the proppant pack through a polycarbonate window. Images taken have been analyzed, which provides quantitative information about the relationship between relative permeability and fine particles invasion. Results using produced water samples revealed that electrocoagulation (EC) treatment would increase the permeability up to 40%, depending on the proppant and produced water source. Extensive data analyses and flow visualizations are presented, demonstrating the effects of TSS on the permeability of proppant packs.
Fracturing Fluid Conductivity Damage and Recovery Efficiency
Authors: Weaver J. D. , Liang F. , Schultheiss N. C. 
Published: June 2013

Abstract
The primary purpose of hydraulic fracturing is to provide highly conductive paths from the reservoir to the wellbore. This is accomplished by pumping fracturing fluids at extreme pressures to create fractures in the reservoir rock. In addition to creating the fractures, the fluid is used to carry proppant into the fractures to keep them open for flow after the pressure is relieved.
The performance of fracturing fluids is generally determined by their ability to 1) create fracture width and length with minimal loss of energy caused by friction, 2) efficiently transport proppant through the tubulars and deep into the fracture, 3) keep the proppant suspended to help distribute proppant vertically in the fracture, 4) break on a planned schedule to permit rapid and efficient flowback without producing back the proppant, and 5) perform all of these goals economically.
There are several good methods available to determine fluid efficiencies, proppant transport properties, and fluid break times that are important to a stimulation engineer when designing fracture treatments. However, there are few methods available that adequately simulate post-fracturing fluid recovery that provides the expected well cleanup rate, efficiency, and impairment of proppant pack conductivity.
This paper presents the development of a laboratory method that permits the determination of post-fracture cleanup parameters of a fluid system under realistic reservoir conditions. Fluid rheology and fluid recovery data are presented that compare commonly used fracturing fluid systems with a variety of breakers and proppant types. The use of this data should aid stimulation engineers in the selection of the optimum fluid system, breaker package, and proppant combination for specific reservoir conditions.
Self-Diverting Acid for Effective Carbonate Stimulation Offshore Brazil: A Successful History
Authors: Neto A. T. , Silva C. A. , Torres R. S. , Farias R. L. , Prata F. G. , Souza L. A. , Pereira A. Z. , Calderon A. , Sandes E. F. 
Published: June 2013

Abstract
The stimulation history in offshore Brazil is undergoing into a deep transformation. The requirements of technology, before focused on sandstone reservoirs demand, are being expanded by the need for techniques to stimulate carbonate reservoirs, specially the pre-salt carbonates. In this scenario, a self-diverting acid system based on a viscoelastic surfactant (VES) technology was introduced for carbonate reservoir stimulation.
The Self-Diverting VES (SD-VES) promotes viscosity development when the acid comes in contact with the carbonate formation. The mechanism of viscosity development is simple: In concentrated acid, the system presents low viscosity, which results in friction reduction while pumping; however, when the fluid reacts with the formation and the acid concentration decreases, the micelle spherical structures combine, transforming into rod-like micelles that convert to a 3-D structure, which increases the fluid viscosity. The high viscosity generates a temporary barrier across the high-injectivity zones, diverting the subsequent fluid to treat other reservoir zones.
Generally the SD-VES is associated with several placement techniques that aid in achieving good treatment distribution through the entire producer interval. Regardless of the placement technique applied, the SD-VES is generally used as the main acid fluid and is bullheaded into the well. Because of its rheological behavior, the SD-VES is pumped as a single fluid during bullheading, aiming to achieve formation stimulation and good treatment distribution throuth the entire productive interval.
Since the SD-VES was introduced in 2009 to treat carbonate reservoirs in offshore Brazil, more than 40 wells have been treated using the system in the various acid placement techniques presented in this paper. Three case histories are presented to better illustrate the different scenarios where the SD-VES was applied.