bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of furans from hemicellulosic saccharides in biphasic reaction systems
Authors: Rivas Sandra , González-Muñoz María Jesús , Santos Valentín , Parajó Juan Carlos
Published: April 2013

Furans (furfural and hydroxymethylfurfural) are the results of dehydration of monosaccharides, which can be obtained by acid hydrolysis of wood or other lignocellulosic materials. In this work, Pinus pinaster wood was subjected to aqueous autohydrolysis processing to obtain dissolved hemicellulose-derived polymeric or oligomeric saccharides made up of mannosyl, glucosyl, galactosyl, xylosyl, and arabinosyl structural units. The aqueous liquors were then heated in the presence of sulfuric acid and methyl isobutyl ketone to obtain furans. The effects of selected operational variables, such as the ratio of organic to aqueous phase, temperature, and reaction time, were assessed by empirical modeling in terms of the conversion into furans and levulinic acid. The maximum furfural conversion (71.4%) was predicted to occur operating at 165°C and a ratio of organic to aqueous phase of 2 for 68.5 min. In additional experiments, dimethyl sulfoxide and/or 1-butanol were added to the aqueous phase and the change in furan conversion rates was observed.
Galectins: new agonists of platelet activation
Authors: Schattner Mirta , Rabinovich Gabriel A.
Published: April 2013

Platelet activation at sites of vascular injury leads to the formation of a hemostatic plug and is crucial for hemostasis. However, uncontrolled platelet activation may lead to the formation of occlusive thrombi. Several soluble or matricellular proteins can activate platelets. In this article, we review recent advances in knowledge of the role of galectins in platelet physiology. In soluble or immobilized form, these endogenous glycan-binding proteins trigger platelet activation through the modulation of discrete signaling pathways. We discuss the role of platelet–galectin interactions not only in hemostasis, but also in chronic inflammation, atherosclerosis and cancer.
Antitumor effects of energy restriction-mimetic agents: thiazolidinediones
Authors: Omar Hany A. , Salama Samir A. , Arafa El-Shaimaa A. , Weng Jing-Ru
Published: April 2013

Distinct metabolic strategies used by cancer cells to gain growth advantages, such as shifting from oxidative phosphorylation to glycolysis, constitute a basis for their selective targeting as a novel approach for cancer therapy. Thiazolidinediones (TZDs) are ligands for the nuclear transcription factor peroxisome proliferator-activated receptor gamma (PPARγ) and they are clinically used as oral hypoglycemic agents. Accumulating evidence suggests that the ability of TZDs to suppress cancer cell proliferation through the interplay between apoptosis and autophagy was, at least in part, mediated through PPARγ-independent mechanisms. This review highlights recent advances in the pharmacological exploitation of the PPARγ-independent anticancer effects of TZDs to develop novel agents targeting tumor metabolism, including glucose transporter inhibitors and adenosine monophosphate-activated protein kinase, which have translational potential as cancer therapeutic agents.
Thermal Fatigue Crack Initiation of Laser Deposited High-temperature Titanium Alloy Ti60A in 20–700 °C
Authors: Zhang A.L. , Liu D. , Wang H.M.
Published: April 2013

Thermal fatigue damage of high-temperature titanium alloys is of great concern for severe temperature-fluctuating environment, and the thermal fatigue crack initiation stage plays a crucial role in thermal fatigue life. In present study, thermal fatigue tests keeping 55 seconds at 700 °C followed by water cooling 15 seconds at 20 °C were performed for the laser deposited high-temperature titanium alloy Ti60A (Ti5.54Al3.38Sn3.34Zr0.37Mo0.46Si). Thermal fatigue cracks initiate after 800 thermal fatigue cycles with a length of 20 µm. Subsequently numerous cracks grow to 500 µm and cause severe degradation after 1000 cycles. To investigate the crack initiation behavior, microstructural changes during thermal fatigue process were examined by OM, SEM, EPMA and TEM. Thermal fatigue cracks initiate preferably at grain boundaries, α/β interfaces, microvoids, and abnormal coarsened α produced by oxygen interstitial solution. Mechanisms of thermal fatigue crack initiation are related to compatibility of local deformation and microstructural changes during thermal fatigue process.
Temperature Dependencies of the Permittivities and Microwave Shielding Effectiveness of a Carbon-containing Electrically Conductive Concrete
Authors: Chambers B. , Pickles C. A. , Tumidajski P. J.
Published: April 2013

Conductive concrete is a construction material that can be utilized for a number of applications: in particular, electromagnetic shielding. In this research, the microwave shielding effectiveness of a carbon containing electrically conductive concrete was determined from both the real and the imaginary permittivities. Also, the permittivities and the shielding effectiveness of a normal concrete were determined for comparison purposes. It was shown that the permittivities of the conductive concrete were significantly higher than those of the normal concrete. The shielding abilities of both of the concretes were determined as a function of concrete thickness and temperature, and the conductive concrete had a superior shielding effectiveness. For the normal concrete, at room temperature and a frequency of 912 MHz, a shielding effectiveness of 30 dB was achieved for a thickness of about 400 cm. For the conductive concrete, under the same conditions, a thickness of only about 3 cm was required to achieve the same shielding effectiveness.
High-Temperature Oxidation Behavior of Cu-Si-Y Alloys
Authors: Liu Qun , Fu Guangyan , Su Yong , Zhang Zhigang , Xiong Qi
Published: April 2013

The effect of rare-earth element Y on high-temperature oxidation behavior of Cu-Si alloys at 973 and 1073 K in 0.1 MPa flowing pure O2 has been investigated. Results show at the two temperatures the mass gain of the alloys with different compositions follows the following sequence, Cu-3Si-1.0Y > Cu-3Si-0Y > Cu-3Si-0.5Y alloy. As the Y content increases, the grain size of the alloys decreases, which accelerates the diffusion rate of the alloying elements in the alloys and oxygen under the experimental conditions, increases the ratio of short-path diffusion, and promotes the formation of SiO2 and Y2O3. The three alloys do not form continuous oxide scales of SiO2 or Y2O3, but their rapid formation and dispersed distribution due to the grain-size reduction may also hinder the diffusion of alloying elements and oxygen, which is beneficial to improve the oxidation resistance of the Y-containing alloys. Thereby, the Cu-3Si-0.5Y alloy has good oxidation resistance. The Cu-3Si-1.0Y alloy exhibits largest mass gain among the three alloys, which is due to the fact that in the alloy with higher Y contend and finer grain size, more amount of Y2O3 is more quickly formed, whose mass occupy a more proportion in the whole mass gain of the alloy.
Determination of Direct Reduction Conditions of Mill Scale
Authors: Yucel Onuralp , Demirci Fahri , Turan Ahmet , Alkan Murat
Published: April 2013

In this study, experiments were conducted to understand the optimum direct reduction conditions of mill scale which is formed on the surface of the materials produced by continuous casting and which contains iron (II) and iron (III) oxides. Experiments were performed in a rotary kiln and anthracite and metallurgical coke were used as carbon source. The eligible parameters like process temperature, process duration, reductant type and quantity were tried to determine. Obtained reduced iron pellets were characterized by using EPMA, XRD and chemical analysis techniques. The highest metallization degrees were observed as 97.4% for the stoichiometrically 200% anthracite added experiments and as 95.5% for the stoichiometrically 200% metallurgical coke added experiments at 1423 K.
The disability gap in happiness across welfare regimes
Authors: Penner Anna
Published: April 2013

This article uses data from the 2008 International Social Survey Programme to examine the disability gap in happiness in 14 countries. This study builds on previous research linking disability to depression by exploring whether there are significant differences in the gap between disabled and non-disabled people’s happiness internationally and if differences in happiness systematically vary across welfare state regimes. Disabled respondents were found to be significantly less happy than non-disabled respondents from the same nation in all 14 countries and that the levels of happiness between disabled people and unemployed people were similar by welfare regime except in the conservative welfare regime. The disability gap in happiness varied across welfare state regimes, and social democratic countries generally had significantly smaller disability gaps than countries with conservative welfare regimes. These findings highlight the international scope of the disability gap and underscore the important role that welfare regimes have in shaping these differences.
Estimation of Panel Data Regression Models with Two-Sided Censoring or Truncation
Authors: Alan Sule , Honoré Bo E. , Hu Luojia , Leth-Petersen Søren
Published: April 2013

This paper constructs estimators for panel data regression models with individual specific heterogeneity and two-sided censoring and truncation. Following Powell the estimation strategy is based on moment conditions constructed from re-censored or re-truncated residuals. While these moment conditions do not identify the parameter of interest, they can be used to motivate objective functions that do. We apply one of the estimators to study the effect of a Danish tax reform on household portfolio choice. The idea behind the estimators can also be used in a cross sectional setting.
Tony Weir and the Law of Tort
Authors: Giliker Paula
Published: April 2013

Tony Weir was a leading figure in UK tort law who sadly passed away in December 2011. This paper examines his lasting contribution to English tort law as a scholar unafraid to speak his mind and whose incisive commentaries continue to be read by students and Supreme Court justices alike. It will focus on two areas in which Weir’s contribution was particularly significant: the treatment of claims for negligently-incurred pure economic loss and the degree to which tort law should provide a remedy for injuries resulting from risks which individuals have freely incurred. Weir’s contribution was distinctive and forcefully argued, encouraging his audience to reflect on the policy choices underlying any system of tort law.
French Tort Law Facing Reform
Authors: Brun Philippe , Quézel-Ambrunaz Christophe
Published: April 2013

The authors, both active members of the Groupe de Recherche Européen sur la Responsabilité Civile et l’Assurance, report on its research project into the compatibility with French law of recent proposals for a harmonised European tort law.
Degenerate first-order differential equations via projections
Authors: Al Horani Mohammed
Published: April 2013

In this paper we study an inverse problem for
a singular differential equation in a Banach space. We use two
projections to reduce the problem to a regular
abstract inverse problem. In order to solve the problem, some conditions
on the space and the operators are assumed. As a possible
application of the abstract theorems, some examples of partial
differential equations are given.
Conservation laws in differential geometry of plane curves
and for eikonal equation and inverse problems
Authors: Megrabov Alexander G.
Published: April 2013

We derive the new conservation laws for a set of
arbitrary smooth plane curves. In these laws a solenoidal field is
expressed in terms of the Frenet unit vectors or in terms of the
curvature vectors. When curves are vector lines of an arbitrary
smooth vector field, these laws have identical form in terms of
this field or its field of directions. Also, a series of vector
analysis formulas as differential identities relating the modulus
and direction of a vector field is obtained. It is based on these
general formulas, the conservation laws for the kinematic seismics
(geometrical optics) for a scalar time field, i.e., for the
solutions of the eikonal equation are found. Some other formulas
relating the time field and a characteristic of a medium
(refractive index) are also given. In particular, we present the
formula for determining an integral characteristic of a medium in
the inverse problem formulation. All the formulas obtained
originate from studying the differential invariants of a Lie group
(an extension of the group of conformal transformations) which is
realized as the equivalence group admitted by the eikonal equation
and some other equations of mathematical physics.
Determinants of successful breastfeeding initiation in healthy term singletons: a Swiss university hospital observational study
Authors: Gubler Tabea , Krähenmann Franziska , Roos Malgorzata , Zimmermann Roland , Ochsenbein-Kölble Nicole
Published: April 2013

Aims: Breastfeeding significantly benefits mothers and infants. We aimed to identify the determinants of its successful initiation.

Methods: A retrospective study of 1893 mothers delivering healthy term singletons at a Swiss university hospital from 1/2008 to 3/2009 determined the associations between multiple breastfeeding and early postpartum parameters by univariate and multiple regression analysis.

Results: Multiparity was associated with nursing exclusively at the breast at discharge (P<0.001), less use of maltodextrin supplement (P<0.05), bottle/cup (both P<0.001), but more pacifier use (P<0.05). Among obese mothers, nursing exclusively at the breast at discharge was less frequent, and use of all feeding aids more frequent, than among normal-weight women (both P<0.001). Neuraxial anesthesia was associated with use of maltodextrin and bottle (both P<0.05) compared to no anesthesia. Delayed first skin-to-skin contact and rooming-in for <24 h/day were each associated with maltodextrin and cup (P<0.05). Nursing exclusively at the breast at discharge was less frequent (P<0.001), and bottle use more frequent (P<0.05), in women with sore nipples than in those without.

Conclusions: Obesity is a potent inhibitor of breastfeeding initiation. Delivery without anesthesia by a multiparous normal-weight mother, followed by immediate skin-to-skin contact, rooming-in for 24 h/day, and dedicated nipple care, provides the best conditions for successful early postpartum breastfeeding without the need for feeding aids or nutritional supplements.
Habitat selection, philopatry and spatial segregation in rural Irish hedgehogs (Erinaceus europaeus)
Authors: Haigh Amy , O’Riordan Ruth M. , Butler Fidelma
Published: April 2013

As a non-territorial species with no known dispersal period, there are no obvious factors that regulate hedgehog numbers in an area. This study aimed to examine these factors and involved the radio-tracking of rural hedgehogs over a 3-year period. Males had a significantly larger mean annual home range (56 ha) than females (16.5 ha), which was at its maximum during the breeding season. Outside of the breeding season, the home range was relatively small (4–5 ha) in both sexes. The home ranges of males completely overlapped both each other and all of the females. In contrast, females occupied more exclusive areas with little overlap between one another. On a nightly basis, both sexes occupied spatially independent areas with little overlap. Compositional analysis of the data showed that habitats were not used in proportion to their availability but were selected, and this changed seasonally, with the highest preference being for garden and arable land. Hedgehogs tagged for consecutive years exhibited site philopatry and followed the same pattern of habitat selection annually. It is suggested that the spatial separation observed amongst individual hedgehogs could restrict numbers in an area and that female numbers reach a carrying capacity before that of males.
Self-assembled plasmonic metamaterials
Authors: Mühlig Stefan , Cunningham Alastair , Dintinger José , Scharf Toralf , Bürgi Thomas , Lederer Falk , Rockstuhl Carsten
Published: April 2013

Nowadays for the sake of convenience most plasmonic nanostructures are fabricated by top-down nanofabrication technologies. This offers great degrees of freedom to tailor the geometry with unprecedented precision. However, it often causes disadvantages as well. The structures available are usually planar and periodically arranged. Therefore, bulk plasmonic structures are difficult to fabricate and the periodic arrangement causes undesired effects, e.g., strong spatial dispersion is observed in metamaterials. These limitations can be mitigated by relying on bottom-up nanofabrication technologies. There, self-assembly methods and techniques from the field of colloidal nanochemistry are used to build complex functional unit cells in solution from an ensemble of simple building blocks, i.e., in most cases plasmonic nanoparticles. Achievable structures are characterized by a high degree of nominal order only on a short-range scale. The precise spatial arrangement across larger dimensions is not possible in most cases; leading essentially to amorphous structures. Such self-assembled nanostructures require novel analytical means to describe their properties, innovative designs of functional elements that possess a desired near- and far-field response, and entail genuine nanofabrication and characterization techniques. Eventually, novel applications have to be perceived that are adapted to the specifics of the self-assembled nanostructures. This review shall document recent progress in this field of research. Emphasis is put on bottom-up amorphous metamaterials. We document the state-of-the-art but also critically assess the problems that have to be overcome.
Nanostructures for photon management in solar cells
Authors: Narasimhan Vijay Kris , Cui Yi
Published: April 2013

The concurrent development of high-performance materials, new device and system architectures, and nanofabrication processes has driven widespread research and development in the field of nanostructures for photon management in photovoltaics. The fundamental goals of photon management are to reduce incident light reflection, improve absorption, and tailor the optical properties of a device for use in different types of energy conversion systems. Nanostructures rely on a core set of phenomena to attain these goals, including gradation of the refractive index, coupling to waveguide modes through surface structuring, and modification of the photonic band structure of a device. In this review, we present recent developments in the field of nanostructures for photon management in solar cells with applications across different materials and system architectures. We focus both on theoretical and numerical studies and on progress in fabricating solar cells containing photonic nanostructures. We show that nanoscale light management structures have yielded real efficiency gains in many types of photovoltaic devices; however, we note that important work remains to ensure that improved optical performance does not come at the expense of poor electrical properties.
Metal nanoantimicrobials for textile applications
Authors: Giannossa Lorena Carla , Longano Daniela , Ditaranto Nicoletta , Nitti Maria Angela , Paladini Federica , Pollini Mauro , Rai Mahendra , Sannino Alessandro , Valentini Antonio , Cioffi Nicola
Published: April 2013

Research on the nanomaterials containing one or more transition metals is growing tremendously, thanks to the large number of preparation processes available and to the novel applications that can be envisaged in several fields. This review presents an overview of the selected studies in the field of antimicrobial textiles, employing bioactive nanophases of elements/compounds such as silver, copper, or zinc oxide. In addition, the history of use of these antimicrobials and their mechanism of action are shortly reported. Finally, a short description is provided of the deposition/preparation methods, which are being used in the authors’ labs for the development of the textiles modified by the novel nanoantimicrobials.
Archiving Aggregates of Individually Created Digital Content: Lessons from Archiving the Occupy Movement
Authors: Besser Howard
Published: April 2013

With the ubiquity of digital phones and cameras, our memory institutions will need to ingest an increasingly large number of born-digital media, much of it coming from personal archives. The high volume of this material will force collections to find smart ways to automate appraisal/selection, metadata assignment, and standardization of formats, or to convince contributors to do so. This article reports on ideas and methods developed by the group Activist Archivists to automate selection, metadata collection, and standardization of the born-digital media documenting the Occupy movement. Techniques include employing automatic time/date/location stamping, analyzing social media sites, producing guidelines for contributors, and asking for community involvement in selecting the material perceived as having the most enduring value.
Fluorescence diagnosis using 5-aminolevulinic acid in coloproctology/Fluoreszenz-Diagnostik in der Koloproktologie mittels 5-Aminolävulinsäure
Authors: Filonenko Elena V. , Urlova Antonina N. , Raszhivina Antonina A. , Sotnikov Veniamin N. , Nechipai Andrei M.
Published: April 2013

Methods of fluorescence diagnosis (FD) with 5-aminolevulinic acid (5-ALA) have frequently been used for the detection of early cancer on the surface of the mucosa and skin. The objective of this study was to estimate the effectiveness of FD using Alasens (5-ALA) for the detection of malignant lesions in the colon.

In the article, our experience of fluorescence colonoscopy is represented using Alasens (5-ALA) in 78 patients with colonic polyps. FD was performed using the visual assessment of fluorescence images in combination with local fluorescence spectroscopy.

The sensitivity and specificity of FD with Alasens was 94.9% and 62.5%, respectively. The application of local fluorescence spectroscopy as a step of the combined approach allows the specificity to be increased from fluorescence colonoscopy from 62.5% up to 93.7%.
The effects of magnesium oxide on the thermal, morphological, and crystallinity properties of metallocene linear low-density polyethylene/rubbers composite
Authors: Alwaan Ismaeel M. , Hassan Azman
Published: April 2013

The effects on the thermal, morphological, and crystallinity properties of the different loadings of magnesium oxide (MgO) blended with 10% rubbers [9:1 natural rubber (NR)/epoxidized NR] and metallocene linear low-density polyethylene (mLLDPE) in the presence of N,N-m-phenylenebismaleimide (HVA-2) compatibilizer were investigated. Fourier transform infrared spectroscopy showed that the epoxy and double-bond groups were absent in the blends. The crystallinity degree of mLLDPE composites were determined based on the results of differential scanning calorimetry. The crystallinity of the blends was continuously increased by the loading of MgO compared with blend of 0 phr MgO. Based on thermogravimetric analysis, the degradation temperature of NR in the blends with MgO is significantly enhanced compared with a pure NR and 0 phr MgO blend. The observations of the scanning electron micrographs indicate that the HVA-2 had caused a cross-linking reaction in the rubber phase and the domains of the MgO are separated from the continuous phase (mLLDPE).
Topochemical modifications of mixed metal oxide compounds by low-temperature fluorination routes
Authors: Clemens Oliver , Slater Peter R.
Published: April 2013

In this review, we discuss recent developments in the use of low-temperature fluorination routes for the topochemical modification of mixed metal oxide compounds. By applying such methods, material properties (such as magnetism, superconductivity, electrical conductivity, and ionic conductivity) can be tuned in a wide range. Furthermore, oxide fluoride compounds are interesting from a structural point of view, and while differentiating between oxide and fluoride ions has proved to be difficult using diffraction methods, strategies (e.g., bond valence sum calculations) to overcome this problem have been shown to be possible. In addition, this review concludes with an outlook on future prospects in the field of oxide fluoride compounds.
Vibration analysis of sandwich beams with variable cross section on variable Winkler elastic foundation
Authors: Demir Ersin , Çallioğlu Hasan , Sayer Metin
Published: April 2013

In this study, free vibration behavior of a multilayered symmetric sandwich beam made of functionally graded materials (FGMs) with variable cross section resting on variable Winkler elastic foundation are investigated. The elasticity and density of the functionally graded (FG) sandwich beam vary through the thickness according to the power law. This law is related to mixture rules and laminate theory. In order to provide this, a 50-layered beam is considered. Each layer is isotropic and homogeneous, although the volume fractions of the constituents of each layer are different. Furthermore, the width of the beam varies exponentially along the length of the beam, and also the beam is resting on an elastic foundation whose coefficient is variable along the length of the beam. The natural frequencies are computed for conventional boundary conditions of the FG sandwich beam using a theoretical procedure. The effects of material, geometric, elastic foundation indexes and slenderness ratio on natural frequencies and mode shapes of the beam are also computed and discussed. Finally, the results obtained are compared with a finite-element-based commercial program, ANSYS®, and found to be consistent with each other.
Utilization of water reed in production of various insulation panels
Authors: Karademir Arif , Yetis Ferhat , Imamoglu Sami , Varlıbas Hulya
Published: April 2013

Some panels and particleboards were made from reed mats and blends of reed-wood chips to be used inside buildings for sound and heat insulations. It was seen that the outer layers of the reed body (spike) was almost water resistant and exceptionally resistant to the penetration of common adhesives. Therefore, the panels from stitched reed mats exhibited very poor mechanical strength. The sound transmissions of such panels (1–3 km/s) made with various combinations, however, were recorded to be excellent compared with that of particleboards made of wood (17 km/s). Blends of reed chips (2 cm) and wood chips, however, gave particleboards with better mechanical properties (5–17 MPa) than that of panels made from reed mats (2 MPa). An increasing amount of reed chips in tested particleboards was recorded to be improving both sound and heat insulations from 17 to 6 km/s and from 0.34 to 0.27 W/mK, respectively. The bending strength of samples, however, was reduced from 26 to 5 MPa. Thickness swelling was also noted to increase from 18% to 85% due to reed chips addition. It was concluded that the outer layers of water reeds should be modified via chemical and/or enzymatic methods to increase the interfacial bounds between adhesives.
Management of Prominent Premaxilla in Bilateral Cleft Lip and Alveolus
Authors: Nemes Bálint , Fábián Gábor , Nagy Krisztián
Published: April 2013

Our aim was to describe the early management protocol of the prominent premaxilla in bilateral cleft lip and alveolus and its rationale, as used in the Cleft Centre at the 1st Department of Pediatrics and at the Department of Pedodontics and Orthodontics at the Semmelweis University Budapest. The non-surgical and surgical procedures included lip taping, nasoalveolar molding, lip adhesion and definitive one-stage lip closure. With this treatment sequence, arch management was satisfactory and at the time of the definitive lip closure the position of the premaxilla did not interfere with adequate surgical repair.
Fish foraging patterns, vulnerability to fishing, and implications for the management of ecosystem function across scales
Authors: Nash Kirsty L. , Graham Nicholas A. J. , Bellwood David R.
Published: April 2013

The function of species has been recognized as critical for the maintenance of ecosystems within desired states. However, there are still considerable gaps in our knowledge of interspecific differences in the functional roles of organisms, particularly with regard to the spatial scales over which functional impact is exerted. This has implications for the delivery of function and the maintenance of ecosystem processes. In this study we assessed the allometric relationship between foraging movements and fish body length at three sites, for 20 species of herbivorous reef fishes within four different functional groups: browsers, farmers, grazer/detritivores, and scraper/excavators. The relationship between vulnerability of species to fishing and their scale of foraging was also examined. We present empirical evidence of the strong, positive, log‐linear relationship between the scale of foraging movement and fish body length. This relationship was consistent among sites and between the two different movement metrics used. Phylogeny did not affect these results. Functional groups foraged over contrasting ranges of spatial scales; for example, scraper/excavators performed their role over a wide range of scales, whereas browsers were represented by few species and operated over a narrow range of scales. Overfishing is likely not only to remove species operating at large scales, but also to remove the browser group as a whole. Large fishes typically have a significant role in removing algae on reefs, and browsers are key to controlling macroalgae and reversing shifts to macroalgal‐dominated states. This vulnerability to exploitation has serious consequences for the ability of fish assemblages to deliver their functional role in the face of anthropogenic impacts. However, identification of the scales at which herbivorous fish assemblages are susceptible to fishing provides managers with critical knowledge to design management strategies to support coral‐dominated reefs by maintaining function at the spatial scales at which vulnerable species operate.
Accurate Prediction of Dissociation Pressures of Natural Gas Hydrates Containing Carbon Dioxide and Hydrogen Sulfide for Efficient Flow Assurance Phenomena
Authors: Mekala Prathyusha , Sangwai Jitendra S.
Published: April 2013

Information on the phase behavior of gas hydrate is vital for several mitigation techniques to control their formation in pipelines and surface facilities for efficient flow assurance during the production and transportation of natural gas and reservoir fluids. The pipeline environment (high pressure and low temperature) favors the formation of natural gas hydrate, which is one of the main elements in the flow assurance issues and this has to be taken in to account very seriously. Depending upon the composition of the gas produced, hydrates can form different physical structures and thus require careful attention whole modeling their phase behavior. The better thermodynamic models are necessary to design and understand the phase behavior of produced trapped natural gas from natural gas hydrates from subsea environments. Most of the models available in an open literature are primarily applicable at relatively low pressure condition.

In this work, model of Chen and Guo along with the three famous Equation of States (EoS), namely, Peng-Robinson (PR), Peng-Robinson-Stryjek-Vera (PRSV) and Soave-Redlich-Kwong (SRK), are used to model the hydrate phase behavior at high pressure conditions. Their efficacy to model phase behavior for hydrates of pure natural gases and gas mixture containing H2S and CO2 is presented and tested against the experimental data available from open literature at high pressures conditions.

The developed model uses the published Lennard-Jones cell potentials of typical gas species that form hydrates assuming the adsorption would be carried out in the cavities of hydrate structures. We optimized the computed phase diagrams based on three EoS with experimental phase diagram data from literature and determined the model parameters with less percentage average deviation.

The present papers discusses about modeling of the phase behavior of binary gas mixture hydrates like CH4-C2H6, CH4-CO2 and CH4-H2S. Model predictions are validated against the experimental data from the literature, and observed to be in well agreement for high pressure range which helps in the flow assurance. Such models shows potential of their application in understanding flow assurance phenomena at higher pressure.
An Integration between Geological and Reservoir Engineering Data to Design a Conceptual Waterflood Program
Authors: Abu El Ela M.. , Samir M.. , Abdel Monem A.. , El Tayeb S.. , Sayyouh Helmy
Published: April 2013

Field development plan is a set of operations and decisions by which oil reservoirs are identified, evaluated and developed. Making smart reservoir development plan depends on the ability to analyze and integrate the available data.

In this work, a conceptual short-term study was performed with the objective of determining the optimum conditions for required application of waterflooding pilot project in Upper Bahariya Formation (Ferdaus field / Egypt) in order to maintain the pressure and increase the oil production rate.

The integration between the geological and engineering data identified the reservoir structure of Upper Bahariya formation which includes two isolated formations: Upper Baharia 2 and Upper Baharia 3. The original oil in place of Upper Baharia 2 is about 5 MMSTB, while for Upper Baharia 3 is about 11.9 MMSTB.

An efficient monitoring program design, for the waterflooding pilot, including three different injection scenarios with 12 response cases, to investigate the uncertainties of the static model are presented. The results of the pilot study scenarios are very encouraging to implement the waterflooding pilot. Recoverable amount of 2 MMSTB will be achieved upon performing the full scale waterflooding project. Such study is an original conceptual contribution to the knowledge of the integration between geological and reservoir engineering data to design of a comprehensive waterflood program.
The Polymer Flooding Technique Applied at High Water Cut Stage in Daqing Oilfield
Authors: Yuming Wang , Yanming Pang , Zhenbo Shao , Peihui Han , Rong Li , Ruibo Cao , Xianhua He
Published: April 2013

Daqing Oilfield has complex geological conditions, multiple reservoir layers and severe areal and vertical heterogeneity. After feasibility study, polymer flooding is selected as the dominant EOR technique. Polymer flooding in Daqing Oilfield has experienced four stages: laboratory study, pilot tests, industrial field tests and commercial application. Reservoir engineering techniques, such as individual injection parameters design, separate layer polymer injection, in-depth profile modification and comprehensive adjustment, are discussed and the technical-economic effects of polymer flooding are evaluated. The result shows that due to the conversion from water injection to polymer flooding at the water cut of 90-95%, the recovery factor is raised by 13.3% (OOIP) at the water cut of 98% compared to water flooding. At the same time, production rate is increased and water injection volume is reduced. The average operation cost of polymer flooding is $0.1-2.83 /barrel lower than that of water flooding. The polymer flooding of Daqing Oilfield at high water cut stage has better technical-economic effects than full term water injection. Until the end of 2011, the oil production of polymer flooding has exceeded 1000×104 ton(7.31Mbbl) ten years in a roll, and the cumulative production has reached 1.58×108 ton (1.15Bbbl). Polymer flooding has become a major technique in the sustainable development of Daqing Oilfield.
New Approach for Pulse Test Analysis
Authors: El-Khatib Noaman
Published: April 2013

New concepts are introduced to define time lag and response amplitude. The points of extreme pressure values (maxima and minima) are used to define the time lag and pressure response amplitude. The points of maxima and minima are found by equating the pressure derivative to zero. This results in a more accurate solution of the governing equations. The developed method is based on well-defined and easily locatable points, making the method amenable to automatic analysis by computer procedures. It eliminates the need for manually plotting of parallel tangents to the pressure profiles which is subjective, less accurate and does not amend itself to automatic processing.

The solution is used to construct correlation charts for relative time lag and dimensionless pressure response amplitude vs. the dimensionless cycle time for different values of the pulse ratio. The correlation charts will be used to analyze results of pulse testing to obtain interwell reservoir properties, namely transmissibility kh/μ and storativity hϕct. Simulation examples are generated to validate the developed procedure. Results indicate the robustness of the developed method and its superiority over the conventional pulse test analysis method.

The developed correlations show that the relative time lad decreases linearly with the dimensionless cycle time on a log-log plot. Results also indicate that the relative time lag and dimensionless pressure response amplitude decrease with pulse ratio for odd pulses and increase for even pulses.
First Implementation of CRA Casing in Sour HPHT Reservoirs in Deep Wells in Kuwait
Authors: Al-Saeedi M. J. , Al-Enezi D.. , Sounderrajan M.. , Saxena A. K. , Gumballi G. K. , McKinnell D. C.
Published: April 2013

Kuwait Oil Company has embarked on an ambitious project of drilling development wells to exploit the Najmah-Sargelu and Middle Marrat reservoirs at depths of 14,000 to 17,000 ft. These Jurassic formations consist of layered shales and limestones, which can be heavily fractured and highly pressured. The wells drilled to these prospects are very challenging because of HPHT conditions, narrow pore/fracture pressure windows, and high levels of H2S and CO2.

During drilling and production high concentrations of H2S and CO2 have been recorded. Given the strategic importance of these gas prospects, a study was undertaken into the metallurgy of materials planned for these production wells. With high levels of toxic gases and HP conditions, the severity of sour service was evaluated to be within the most severe area when referencing NACE standards. Dependent on well bore fluid and onset of any water production, Stress Corrosion Cracking (SCC) and Weight Loss Corrosion could occur leading to material failure and lost production. After this study, the use of CRA materials was recommended in future wells to counter these challenges.

The application of CRA for down hole tubular and surface wellhead equipment has gained wide acceptance in sour fluid service in recent years especially in HPHT wells. CRA usage has increased to; eliminate intensive corrosion inhibition programs, reduce maintenance costs and enhance safety. Considering the key parameters influencing corrosion properties of CRA (temperature, partial pressure of H2S and CO2, pH environment, chloride concentrations), it was decided to specify the use of 28 Cr CRA material for these Jurassic gas wells. This paper will discuss the initial study of the material metallurgy, the well design, the specification of tubulars and wellhead, special procedures necessary to run these exotic materials plus details of actual operations in the first wells.
Geochemical Evaluation of Hydrocarbons and their Potential Sources in the Central and Meridional Atlas of Tunisia
Authors: Belhaj Mohamed A.. , Saidi M.. , Bendriss W.. , Mahmoudi S.. , Bouazizi I..
Published: April 2013

The Central and Meridional Atlas of Tunisia, contains significant accumulations of oil in early Cretaceous aged reservoirs. The active cretaceous hydrocarbon system is a product of unique paleogeographic and tectonic events that led to cretaceous deposition of organic-rich source rocks.

The analysis of different sources rocks from the Central and Meridional Atlas of Tunisia indicates that the Albian Lower Fahdene Fm has a substantial oil-generation potential. The Cenomanian-Turonian Bahloul Fm exhibits fair to high organic matter content and petroleum potential and is immature to mature. The Jurassic source rock, located in the Southern part of this area, exhibits fair to good organic matter content and petroleum potential.

Molecular characterization indicates that most of the produced oils appear to be sourced from a predominantly shaly marine and mature source rock deposited in suboxic to oxic environment. Oil stains located in the northern part of the area seems to be sourced by a marly or argillaceous limestone. Oil-oil correlations and molecular characteristics of selected source rock samples and maturation models suggests that oils were generated from similar source rock and/or organic facies. The Lower Fahdene Fm is the best source candidate to generate these fluid samples. The integration of benzocarbazoles as geochemical molecules tracer has permitted a relative estimation of the lateral migration distance for the different accumulations of the area.
Thru-Tubing Inflatable Straddle Packer Assembly Enables Selective Treatment of Multiple Zones and Improves Productivity
Authors: Kothiyal M. D. , Parasher A.. , Qutob A. H. , Cooper R. J. , Forsyth G. R.
Published: April 2013

The subject well is an onshore oil producer located in Cairn Energy India's Rajasthan block. The well had stratified sand sections completed with 4-inch inflow control device (ICD) screens and isolated by swellable packer assemblies. The well was put into production at a rate of approximately 1,000 bopd; however, due to formation damage – notably paraffin and scale - the well could not sustain production and eventually ceased.

Our objective was to selectively stimulate 15 ICDs using coiled tubing. The well had a minimum restriction and a larger setting diameter which warranted the usage of coiled tubing deployed inflatable straddle packer system. This enabled passage through the restriction and setting in the larger outer diameter to selectively treat each zone by mechanically diverting the stimulation fluid.

The challenge was significant. Multiple zones required treatment in a single run by performing 15 multi-settings, maintaining seal integrity following each set, and returning the tool to its original outer diameter for retrieval. The well was deviated at 74 degree which challenged accessibility.

The assembly was run successfully and managed to selectively stimulate all required zones in one trip. Using this application, we confirmed that all treatment fluid was effectively sealed and treated by diverting the treatment fluid directly into the required zone, preventing more permeable sections absorbing most of the fluid, and ensuring the treatment chemicals were used in a cost effective manner. The single coiled tubing run avoided multiple runs to isolate sections using plugs. The well subsequently began to flow once lifted with nitrogen, positively indicating that the ICDs were effectively cleaned and the zones successfully treated.

This case demonstrates the innovative use of thru-tubing wellbore isolation techniques to effectively enhance production in wells with challenging configurations and operating parameters. This study further paves the way for similar interventions in wells with similar characteristics.
Normal Stress Rheology of Drilling Fluids and Potential in Lost Circulation Control
Authors: Kulkarni Sandeep D. , Savari Sharath , Maghrabi Shadaab , Jamison Dale E. , Kumar Arunesh
Published: April 2013

Investigating lost circulation in DEA 13 JIP has shown that it is difficult to arrest losses while drilling with non-aqueous drilling fluids (NAF) as compared to aqueous drilling fluids (AF). In an earlier work (Kulkarni 2012), a novel method was discussed to characterize the plugging (of LCM particles and Fibers) performance of non-aqueous and aqueous drilling fluids using viscoelastic parameters under shear stress (First Normal Stress Difference=N1). This paper discusses the modification of drilling fluids (particularly non-aqueous fluids) to combat lost circulation. N1 measured at low and moderate shear stresses for different aqueous and non-aqueous drilling fluids shows that the magnitude of N1 for AF was significantly higher than that for NAF; although, the FANN® 35 viscometer shear rheology of both was similar. Another important finding was that adding certain polar-organic compounds to the NAF improves its N1 magnitude remarkably, which in turn was found to improve the drilling fluid's performance in lost circulation applications. For representative AF and NAFs, with the same FANN 35 viscometer rheology properties and lost circulation materials, fracture plugging efficiency was probed on a Permeability Plugging Apparatus (PPA) using a tapered slot. The plugging performance of the LCM in the AF was significantly better than in the NAF for the same combination of LCM. This difference in plugging performance was attributed to the noticeable difference in N1 observed for these two drilling fluids. The relation between N1 and plugging efficiency became evident when the addition of polar-organic compounds to the NAF increased its N1 and improved its plugging efficiency. These findings could be used to tailor the NAF for LCM treatment during the mud design phase and help alleviate trial-and-error in the LCM design.
Gas Formation Testing in Exploration Phase
Authors: Hassan Rozlin , Haddad Sammy , Wa Wee Wei , Johan Zailily , Lim Lee Chin
Published: April 2013

Reservoir rock properties, fluids' type and pressure are fundamental parameters for the successful reservoir management in field development planning. Key reservoir parameters are namely horizontal permeability, vertical permeability, damage skin, radius of investigation and reservoir pressure. Together with the reservoir fluid properties, they form critical input to comprehensive production and reservoir engineering studies.

Exploration work done through a 3 wells campaign in three main gas fields offshore Malaysia is presented in this paper. The main objective for the operator is to acquire an early and quick identification of hydrocarbon prospects for appraisal wells' planning. Compared to the conventional full scale DST, the combination of Downhole fluid analysis and interval pressure transient test (IPTT) by wireline formation tester were deployed to achieve these objectives.

This paper illustrates the successful downhole reservoir fluid identification and formation testing in the reservoirs with the mobility range of 365 to 3020 md/cP. At the interval of interests with the presence of hydrocarbon, dual packer formation tester module offers selectively straddling reservoir sections to provide the capability to conduct controlled local production and interference for reservoir parameters estimation. The methodology, applications and suggested best practices applied throughout the campaign are presented in this paper.