bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between coffee consumption, oxidant status, and antioxidant potential in the Japanese general population
Authors: Ishizaka Yuko , Yamakado Minoru , Toda Akiko , Tani Mizuki , Ishizaka Nobukazu
Published: April 2013

Background:Several previous studies have demonstrated an association between habitual coffee intake and reduced risk of diabetes, cardiovascular morbidity and total mortality. Although the cause and effect relationship could not be determined through epidemiological data, antioxidant properties of coffee ingredients are presumed.

Methods:In the current study, by analyzing the data from 9877 subjects (mean age 59.2±10.4 years) who underwent general health screening, we evaluated the extent of in vivo oxidative stress by measuring derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP).

Results:The mean levels of d-ROM and BAP were significantly lower in women than in men. By univariate analysis (ANOVA), coffee consumption showed a graded negative association with d-ROM value in men, but not in women. Coffee consumption was unrelated to BAP levels in men and women. Smoking was significantly associated with increased d-ROM and decreased BAP values in men. Multivariate-adjusted analysis showed that coffee intake of three or more cups per day was an independent negative correlate of d-ROM value in men. Sugar use was negatively associated with d-ROM and BAP values in women.

Conclusions:Among an essentially healthy population, coffee intake was negatively associated with d-ROMs in men, but not in women. Whether the favorable effect of coffee, if present, is related to lower oxidative stress levels needs further investigation.
Prenatal diagnosis of inherited diseases: 20 years’ experience of an Italian Regional Reference Centre
Authors: Maruotti Giuseppe Maria , Frisso Giulia , Calcagno Giuseppe , Fortunato Giuliana , Castaldo Giuseppe , Martinelli Pasquale , Sacchetti Lucia , Salvatore Francesco
Published: April 2013

Background: The demand for molecular prenatal diagnosis (PD) of inherited diseases to help high-risk couples make informed reproductive decisions has increased in the past decade.

Methods: We provided multidisciplinary pre-test counselling to 1248 couples at high risk of having a child affected by an inherited disease.

Results: After multidisciplinary counselling, 1171 couples requested PD for one of 73 inherited diseases. Of these, 995 (85.0%) were performed on DNA from chorionic villi (CV) and 176 (15.0%) on samples from amniocentesis. The occurrence of pregnancy loss (0.6%) and major complications did not differ significantly between the two groups. We made a diagnosis in all cases (including 8 twin pregnancies) except in 4/995 cases of CV sampling (0.4%) and in 3/176 of amniocentesis (1.7%) due to insufficient DNA. In 15 cases, molecular analysis revealed non-paternity.

Conclusions: PD by analysis of foetal DNA from CV is a reliable aid in reproduction decision-making for couples at high risk of inherited diseases. The complexity of experimental procedures and the specific expertise required for the pre- and post-test multidisciplinary counselling suggest that PD be performed in reference centres also within the framework of supranational networks.
Central sequence C*
-algebras and tensorial absorption of the Jiang–Su algebra
Authors: Kirchberg Eberhard , Rørdam Mikael
Published: April 2013

We study properties of the central sequence algebra

A
ω

∩

A
'

${A_\omega \cap A^{\prime }}$

of a C*
-algebra A, and we present an alternative approach to a recent result of Matui and Sato. They prove that every unital separable simple nuclear C*
-algebra, whose trace simplex is finite-dimensional, tensorially absorbs the Jiang–Su algebra if and only if it has the strict comparison property. We extend their result to the case where the extreme boundary of the trace simplex is closed and of finite topological dimension. We are also able to relax the assumption on the C*
-algebra of having the strict comparison property to a weaker property that we call local weak comparison. Namely, we prove that a unital separable simple nuclear C*
-algebra, whose trace simplex has finite-dimensional closed extreme boundary, tensorially absorbs the Jiang–Su algebra if and only if it has the local weak comparison property.

We can also eliminate the nuclearity assumption if instead we assume the (SI) property of Matui and Sato, and, moreover, that each II
1
-factor representation of the C*
-algebra is a McDuff factor.
Tropical geometry over higher dimensional local fields
Authors: Banerjee Soumya D.
Published: April 2013

We introduce the tropicalization of closed sub-schemes of a torus defined over a higher dimensional local field. We study the basic invariants of such tropicalizations. This is a generalization of the fundamental theorem of tropical geometry to higher dimensional local fields.
Double solid twistor spaces II: General case
Authors: Honda Nobuhiro
Published: April 2013

In this paper we investigate Moishezon twistor spaces
which have a structure of double covering over
a very simple rational threefold.
These spaces can be regarded as a direct generalization of
the twistor spaces studied
in [J. Differential Geom. 36 (1992), 451–491]
and [Compos. Math. 82 (1992), 25–55] to the case of arbitrary signature.
In particular, the branch divisor of the double covering is a cut of the rational threefold by
a single quartic hypersurface.
We determine a defining equation of the hypersurface in an explicit form.
We also show that these twistor spaces interpolate
LeBrun twistor spaces and the twistor spaces constructed
in [J. Differential Geom. 82 (2009), 411–444].
On the Kähler–Ricci flow near a Kähler–Einstein metric
Authors: Sun Song , Wang Yuanqi
Published: April 2013

On a Fano manifold, we prove that the Kähler–Ricci flow starting from a Kähler metric in the anti-canonical class which is sufficiently close to a Kähler–Einstein metric
must converge in a polynomial rate to a Kähler–Einstein metric. The convergence cannot happen in general if we study the flow on the level of Kähler potentials. Instead we exploit the interpretation of the Ricci flow as the gradient flow of Perelman's μ functional. This involves modifying the Ricci flow by a canonical family of gauges. In particular, the complex structure of the limit could be different in general. The main technical ingredient is a Lojasiewicz type inequality for Perelman's μ functional near a critical point.
Energy inequalities for cutoff functions and some applications
Authors: Andres Sebastian , Barlow Martin T.
Published: April 2013

Let (𝒳,d,m) be a metric measure space with a local regular Dirichlet form. We establish necessary and sufficient conditions for upper heat kernel
bounds with sub-diffusive space-time exponent to hold. This characterization is
stable under rough isometries, that is it is preserved under bounded perturbations
of the Dirichlet form. Further, we give a criterion for stochastic completeness in terms of a Sobolev
inequality for cutoff functions. As an example we show that this criterion applies
to an anomalous diffusion on a geodesically incomplete fractal space, where the
well-established criterion in terms of volume growth fails.
Splitting theorems for Finsler manifolds of nonnegative Ricci curvature
Authors: Ohta Shin-ichi
Published: April 2013

We investigate the structure of a Finsler manifold
of nonnegative weighted Ricci curvature including a straight line,
and extend the classical Cheeger–Gromoll–Lichnerowicz Splitting Theorem. Such a space admits a diffeomorphic, measure-preserving splitting in general. As for a special class of Berwald spaces, we can perform the isometric splitting
in the sense that there is a one-parameter family of isometries
generated from the gradient vector field of the Busemann function. A Betti number estimate is also given for Berwald spaces.
Hecke algebras associated to Λ-adic modular forms
Authors: Wake Preston
Published: April 2013

We show that if an Eisenstein component of the p-adic Hecke algebra associated to modular forms is Gorenstein, then it is necessary that the plus-part of a certain ideal class group is trivial. We also show that this condition is sufficient whenever a conjecture of Sharifi holds.
Silibinin hemisuccinate binding to proteins in plasma and blood cell/plasma partitioning in mouse, rat, dog and man in vitro
Authors: Persiani Stefano , Sala Federica , Cole Richard , Webber Guy , Caselli Gianfranco , Vaghi Paola , Rovati Lucio C.
Published: April 2013

Background: The determination of plasma protein binding and blood cell/plasma partitioning is important when prescribing silibinin hemisuccinate to patients concomitantly receiving other drugs and to estimate the safety margins of exposure at the no observed adverse events levels determined from toxicity studies conducted in rats and dogs.

Methods: Protein binding of [3′-14C]silibinin hemisuccinate (1, 10, 100, 1000 and 4000 μM) was evaluated in human, dog, rat and mouse plasma by ultrafiltration. Blood cell/plasma partitioning in all these species was also determined.

Results: Silibinin hemisuccinate is highly bound to plasma proteins with percentage binding ranging from 94.3% to 97.8%. Its association with blood cells was negligible (<7%) in all species. The degree of protein binding was concentration independent up to the pharmacologically effective concentration of 100 μM. The blood cell/plasma partitioning indicates that distribution into blood cells is not an important feature for the disposition of silibinin hemisuccinate.

Conclusions: No corrections for fraction unbound are needed when comparing human and preclinical pharmacokinetic and pharmacodynamic data at pharmacological doses, and it is appropriate to analyze plasma as opposed to whole blood for the determination of silibinin hemisuccinate concentrations.
Lawson homology for abelian varieties
Authors: Hu Wenchuan
Published: April 2013

In this paper we study the action of the Fourier–Mukai transform on the Lawson homology of abelian varieties and
a Beauville-type eigenspace decomposition of Lawson homology with rational coefficients.
On some new model category structures from old,
on the same underlying category
Authors: Stanculescu Alexandru E.
Published: April 2013

We make a study of ℓℓ-extensions of
model category structures. We prove an
existence result of ℓℓ-extensions, present some
specific and some rather formal results
about them and give an application
of the existence result to the homotopy
theory of categories enriched over a
monoidal model category.
Synthesis of dihydropyrrolo[2,1-a]isoquinolines via isocyanide-based four-component reaction
Authors: Aminkhani Ali
Published: April 2013

Synthesis of 3-(t-butylimino or cyclohexylimino)-2-aryl-2,3-dihydropyrrolo[2,1-a]isoquinoline-1,1(10bH)-dicarbonitriles was developed through a one-pot four- component high-yield reaction of malononitrile, an aldehyde, isoquinoline and t-butylisocyanide or cyclohexylisocyanide. The simple, mild, and efficient reaction is conducted in dichloromethane at room temperature.
Drying of beech (Fagus sylvatica L.) timber in oscillation climates: drying time and quality
Authors: Milić Goran , Kolin Branko , Lovrić Aleksandar , Todorović Nebojša , Popadić Ranko
Published: April 2013

The influence of oscillating climate conditions during the conventional drying of beech timber on drying time and drying quality has been analyzed. Three conventional drying cycles were carried out as well as nine cycles, in which the oscillations of equilibrium moisture content (EMC), temperature, and their combination were applied. The combinations of two amplitudes (10% or 20%) and two frequencies (3 or 6 h) were used in different test runs. Higher drying quality regarding casehardening was achieved both in runs with oscillations of EMC (gap values 2.2–2.4 mm) and in runs with temperature oscillations (gap values 2.3–2.4 mm) compared with conventional runs (gap values 2.5–2.9 mm). The oscillations of both temperature and EMC did not improve any of the observed parameters.
Chemistry and water-repelling properties of phenyl-incorporating wood composites
Authors: Van Opdenbosch Daniel , Dörrstein Jörg , Klaithong Somruedee , Kornprobst Tobias , Plank Johann , Hietala Sami , Zollfrank Cordt
Published: April 2013

The properties of materials are presented, which are resulting from a combined inorganic-organic modification of wood with phenyltrimethoxysilane or phenyltriethoxysilane in a simple one-step impregnation treatment. The permanent swelling of the wood showed that the precursors entered the cell walls. The inclusion of phenyl groups, manifest by nuclear magnetic resonance spectroscopy, made the resulting wood composites highly hydrophobic, as evidenced by their low wettability and antishrink efficiencies of up to 44%. Impedance spectroscopy indicated that wood methylol groups took part in the condensation reactions with hydrated siloxanes, contributing to the high hydrophobicity and making the added phase resistant to leaching. The composites exhibited high weight percentage gains of up to 52% and ash contents up to 19%. The thermal properties of precursor solutions and products were assessed by differential scanning calorimetry and thermogravimetric analysis and compared with the more common silica precursor, tetraethyl orthosilicate.
Potential importance of Maackia amurensis agglutinin in non-small cell lung cancer
Authors: Mehta Sangeeta , Chhetra Rakhee , Srinivasan Radhika , Sharma Suresh C. , Behera Digambar , Ghosh Sujata
Published: April 2013

Maackia amurensis agglutinin is a NeuNAcα (2–3) Galβ (1–4) GlcNAc/Glc-specific lectin, which was shown to have diagnostic potential in cancers of different origin. In a previous report, we demonstrated that GM3 specific IgG from bronchoalveolar lavage fluid (BALF) of non-small cell lung cancer (NSCLC) patients interacted with ∼66kDa membrane glycoprotein band of NSCLC cell lines, which was also recognised by this lectin. This observation prompted us to assess the potential of Maackia amurensis agglutinin in NSCLC. Accordingly, we examined the reactivity of this lectin with NSCLC cell lines as well as the tissue biopsies and cells obtained from fine needle aspirations of NSCLC patients. Maackia amurensis agglutinin showed strong reactivity, specifically with cells and biopsy samples of NSCLC origin. Furthermore, this lectin was found to induce apoptosis in NSCLC cells. The mechanism of this lectin-induced apoptosis involved downregulation of Bcl-XL, upregulation of Bax, release of cytochrome c and activation of procaspase-3. Collectively our results have suggested that Maackia amurensis agglutinin may have the potential to serve as a unique probe for detection of NSCLC and also as a specific apoptosis-inducing agent in NSCLC cells.
Kinin B1 receptor gene ablation affects hypothalamic CART productionb
Authors: Torres Hugo A.M. , Louise Motta Fabiana , Sales Vicencia Micheline , Batista Carolina , da Silva Joelcimar M. , Vignoli Thiago , Barnabé Gabriela F. , Goeldner Francine O. , D’Almeida Vânia , Bittencourt Jackson C. , Sinigaglia-Coimbra Rita , Bader Michael , Mello Luiz Eugênio A.M. , Pesquero João Bosco
Published: April 2013

A role for the kinin B1 receptor in energy-homeostatic processes was implicated in previous studies; notably, the studies where kinin B1 receptor knockout mice (B1-/-) were shown to have impaired adiposity, impaired leptin and insulin production, lower feed efficiency, protection from liver steatosis and diet-induced obesity when fed a high fat diet (HFD). In particular, in a model where the B1 receptor is expressed exclusively in the adipose tissue, it rescues the plasma insulin concentration and the weight gain seen in wild type mice. Taking into consideration that leptin participates in the formation of hypothalamic nuclei, which modulate energy expenditure, and feeding behavior, we hypothesized that these brain regions could also be altered in B1-/- mice. We observed for the first time a difference in the gene expression pattern of cocaine and amphetamine related transcript (CART) in the (lateral hypothalamic area (LHA) resulting from the deletion of the kinin B1 receptor gene. The correlation between CART expression in the LHA and the thwarting of diet-induced obesity corroborates independent correlations between CART and obesity. Furthermore, it seems to indicate that the mechanism underlying the ‘lean’ phenotype of B1-/- mice does not stem solely from changes in peripheral tissues but may also receive contributions from changes in the hypothalamic machinery involved in energy homeostasis processes.
Progress in demystification of adhesion G protein-coupled receptors
Authors: Liebscher Ines , Schöneberg Torsten , Prömel Simone
Published: April 2013

Adhesion G protein-coupled receptors (aGPCR) form the second largest class of GPCR. They are phylogenetically old and have been highly conserved during evolution. Mutations in representatives of this class are associated with severe diseases such as Usher Syndrome, a combined congenital deaf-blindness, or bifrontal parietal polymicrogyria. The main characteristics of aGPCR are their enormous size and the complexity of their N termini. They contain a highly conserved GPCR proteolytic site (GPS) and several functional domains that have been implicated in cell-cell and cell-matrix interactions. Adhesion GPCR have been proposed to serve a dual function as adhesion molecules and as classical receptors. However, until recently there was no proof that aGPCR indeed couple to G proteins or even function as classical receptors. In this review, we have summarized and discussed recent evidence that aGPCR present many functional features of classical GPCR, including multiple G protein-coupling abilities, G protein-independent signaling and oligomerization, but also specific signaling properties only found in aGPCR.
The unresolved puzzle why alanine extensions cause disease
Authors: Winter Reno , Liebold Jens , Schwarz Elisabeth
Published: April 2013

The prospective increase in life expectancy will be accompanied by a rise in the number of elderly people who suffer from ill health caused by old age. Many diseases caused by aging are protein misfolding diseases. The molecular mechanisms underlying these disorders receive constant scientific interest. In addition to old age, mutations also cause congenital protein misfolding disorders. Chorea Huntington, one of the most well-known examples, is caused by triplet extensions that can lead to more than 100 glutamines in the N-terminal region of huntingtin, accompanied by huntingtin aggregation. So far, nine disease-associated triplet extensions have also been described for alanine codons. The extensions lead primarily to skeletal malformations. Eight of these proteins represent transcription factors, while the nuclear poly-adenylate binding protein 1, PABPN1, is an RNA binding protein. Additional alanines in PABPN1 lead to the disease oculopharyngeal muscular dystrophy (OPMD). The alanine extension affects the N-terminal domain of the protein, which has been shown to lack tertiary contacts. Biochemical analyses of the N-terminal domain revealed an alanine-dependent fibril formation. However, fibril formation of full-length protein did not recapitulate the findings of the N-terminal domain. Fibril formation of intact PABPN1 was independent of the alanine segment, and the fibrils displayed biochemical properties that were completely different from those of the N-terminal domain. Although intranuclear inclusions have been shown to represent the histochemical hallmark of OPMD, their role in pathogenesis is currently unclear. Several cell culture and animal models have been generated to study the molecular processes involved in OPMD. These studies revealed a number of promising future therapeutic strategies that could one day improve the quality of life for the patients.
When stable RNA becomes unstable: the degradation of ribosomes in bacteria and beyond
Authors: Maiväli Ülo , Paier Anton , Tenson Tanel
Published: April 2013

This review takes a comparative look at the various scenarios where ribosomes are degraded in bacteria and eukaryotes with emphasis on studies involving Escherichia coli and Saccharomyces cerevisiae. While the molecular mechanisms of degradation in bacteria and yeast appear somewhat different, we argue that the underlying causes of ribosome degradation are remarkably similar. In both model organisms during ribosomal assembly, partially formed pre-ribosomal particles can be degraded by at least two different sequentially-acting quality control pathways and fully assembled but functionally faulty ribosomes can be degraded in a separate quality control pathway. In addition, ribosomes that are both structurally- and functionally-sound can be degraded as an adaptive measure to stress.
Molecular function of the prolyl cis/trans isomerase and metallochaperone SlyD
Authors: Kovermann Michael , Schmid Franz X. , Balbach Jochen
Published: April 2013

SlyD is a bacterial two-domain protein that functions as a molecular chaperone, a prolyl cis/trans isomerase, and a nickel-binding protein. This review summarizes recent findings about the molecular enzyme mechanism of SlyD. The chaperone function located in one domain of SlyD is involved in twin-arginine translocation and increases the catalytic efficiency of the prolyl cis/trans isomerase domain in protein folding by two orders of magnitude. The C-terminal tail of SlyD binds Ni2+ ions and supplies them for the maturation of [NiFe] hydrogenases. A combined biochemical and biophysical analysis revealed the molecular basis of the delicate interplay of the different domains of SlyD for optimal function.
Confucian virtues and Chinese adolescent development: a conceptual review
Authors: Shek Daniel T.L. , Yu Lu , Fu Xiao
Published: April 2013

Despite the fact that different Chinese communities have already undergone industrialization and urbanization, Confucian virtues are still regarded as developmental ideals in Chinese culture. Unfortunately, while Confucian virtues are commonly discussed under Chinese philosophies, they are rarely examined in the context of developmental research. In this paper, several key Confucian virtues are discussed, including loyalty (“zhong”), filial piety (“xiao”), benevolence (“ren”), affection (“ai”), trustworthiness (“xin”), righteousness (“yi”), harmony (“he”), peace (“ping”), propriety (“li”), wisdom (“zhi”), integrity (“lian”) and shame (“chi”). These Chinese traditional virtues are also linked to the concepts of character strengths and positive youth development constructs highlighted in Western culture. It is argued that Confucian virtues provide an indigenous conceptual framework to understand character strengths and positive youth development in Chinese culture. Furthermore, when service leadership is considered in Chinese contexts, these virtues should be regarded as important cornerstones.
A heat source reconstruction formula from single internal measurements using a family of null controls
Authors: Garcia Galina C. , Osses Axel , Tapia Marcelo
Published: April 2013

We consider the inverse problem of determining the spatial dependence of the source term in a heat equation in assuming known,
from a single internal measurements of the solution in . The purpose of this paper is to
establish a reconstruction formula for similar to the one obtained by M. Yamamoto in “Stability, Reconstruction formula and regularization for an inverse source hyperbolic
problem by a control method”, Inverse Problems 11 (1995), 481–496, for hyperbolic equations using exact controls, and generalized here for parabolic equations. The reconstruction formula is
associated to a family of exact controls indexed by . We perform numerical
simulations in order to illustrate the feasibility, accuracy and stability of the proposed reconstruction formula.
A numerical study of
heuristic parameter choice rules for
total variation regularization
Authors: Kindermann Stefan , Mutimbu Lawrence D. , Resmerita Elena
Published: April 2013

We present a numerical study of heuristic (noiselevel-free)
regularization parameter choice rules for linear inverse problems with total variation regularization. Such type of
regularization is frequently employed in image and signal processing tasks, such as denoising or
deblurring. We review convergence results for total variation regularization and
propose some generalizations of two well-known heuristic parameter choice rules, the
quasi-optimality principle and the Hanke–Raus rules. We investigate the feasibility of these rules using different concepts of convergence such as
convergence in the Bregman distance and strict convergence in one and two dimensions by numerical simulation.
Diagnostic problems in case of twin pregnancies: US vs. MRI study
Authors: Bekiesinska-Figatowska Monika , Herman-Sucharska Izabela , Romaniuk-Doroszewska Anna , Jaczynska Renata , Furmanek Mariusz , Bragoszewska Hanna
Published: April 2013

Aim: To present an experience with twin pregnancies underlining the impact of magnetic resonance imaging (MRI) on diagnosis and management.

Methods: There were 17 cases of twin pregnancies: nine monochorionic [including four monochorionic diamniotic and five monochorionic monoamniotic (conjoined twins)] and eight dichorionic. The MRI examinations were performed between 19 and 39 weeks of gestational age in two centers using 1.5 T scanners (GE Signa Excite and GE Signa HDxt; GE Healthcare, Waukesha, WI, USA), always after ultrasound (US). In the first period of our activity, SSFSE sequence in T2-weighted images (SSFSE/T2WI) was the main diagnostic tool supported by TSE or GRE T1-weighted images (T1WI). After upgrading the scanners, diffusion-weighted imaging (DWI), steady-state free precession (FIESTA), and echoplanar GRE imaging (EPIGRE) became available.

Results: In 11 cases (64.7%), MRI was superior to US and supplied additional information, including two cases in which pathology of the second twin suspected on US was ruled out on the basis of MRI. In six cases (35.3%) MRI confirmed US diagnosis and brought no new data.

Conclusion: MRI offers more detailed assessment of fetal pathology in cases of twin pregnancies, including conjoined twins, in which sonographic evaluation is more difficult than in single cases.
Of the rookery distribution differences in northern fur seals and Steller sea lions in the waters of the Russian far east
Authors: Wada Kazuo , Hoshino Hiroshi , Kuboshima Emi , Wada Akihiko
Published: April 2013

We investigated factors influencing differences in the rookery distribution patterns between northern fur seals and Steller sea lions in the waters of the Russian far east. The limited distribution of northern fur seal rookeries observed during 1991–2001 resulted from the need for shallow tide pools near the shore for pups to practice swimming. In addition, the large and concentrated populations of the seals required large flat areas and a high degree of natal site fidelity. In contrast, in the case of Steller sea lion rookeries observed along the Kuril islands in 2001, the pups were able to swim under maternal care, and their populations were smaller and had a lower degree of natal site fidelity. So, from our observations, their rookeries, unlike those of northern fur seals, are therefore widely distributed across diverse topographical conditions in the waters of Russian far east.
Crystal and molecular structure of bis(4-dimethylamino-3-nitrophenyl)tellurium dichloride
Authors: Beckmann Jens , Dakternieks Dainis , Duthie Andrew , Mitchell Cassandra
Published: April 2013

Single crystal X-ray crystallography revealed that the title compound [(4-Me2N)(3-O2N)C6H3]2TeCl2 is associated in the solid state mainly by intermolecular secondary Te‧‧‧O contacts.
Effect of reinforcement percentage on wear behavior of SiCp reinforced ZA43 alloy metal matrix composites
Authors: Marigoudar Rajaneesh N. , Sadashivappa Kanakuppi
Published: April 2013

Metal matrix composites (MMCs) are characterized by high specific strength and stiffness. Light metal alloys are reinforced with hard ceramic particles, which show better properties compared to monolithic alloys. ZA43 MMCs are fabricated by stir casting technique by reinforcing preheated silicon carbide particles (SiCp). Wear behavior of ZA43 MMCs is evaluated by conducting dry sliding wear test using a pin-on-disc wear test rig. The tests were conducted for varying loads of 9.81, 19.62, 29.43 and 39.24 N and sliding disc speeds of 2.12, 2.93, 3.66, 4.39 and 5.13 m/s at constant time of 15 min. The results reveal that the wear resistance property of the composite increases as the percentage of reinforcement increases. It was also observed that volume loss increases with increasing applied load and sliding speed. The tested samples were examined and analyzed by taking scanning electron micrographs. The dominating wear mechanisms observed were delamination, scissoring of the abrasive particle, pullout of particle, smearing of the surface and abrasion.
Structure-Electrical Transport Property Relationship of Anisotropic iPP/CNT Films
Authors: Kalakonda Parvathalu , Daly Michael , Xu Kaikai , Cabrera Yaniel , Judith Robert , Iannacchione Germano S. , Georgiev Georgi Y. , Cebe Peggy
Published: April 2013

The internal micro/nano-structure of anisotropically oriented polymer/CNTs composites determines their macroscopic properties. However, the connections between the two are not fully understood. The varying of CNT concentration, preparation method, and a thermodynamic parameter (e.g. temperature) can all play interconnected role. In this work, the macroscopic electrical conductivity was measured perpendicular to the film thickness of an insulating polymer (isotactic PolyPropylene, iPP) and a nano-composite of iPP with 5 weight percent of CNT. The thin films studied were sheared (anisotropically nano-structured) and non-sheared (with random internal structure). In general the effect of melt shearing induces anisotropy on the electrical transport properties of the iPP/CNT films in directions parallel and perpendicular to the direction of orientation. Our results show that for the pure iPP, resistivity slightly increases with shear at higher temperatures. When CNTs are introduced, there is a large difference between the resistivity of the sheared and non-sheared nanocomposite. The sheared PNCs when the CNTs are aligned parallel to each other, have higher resistivity, which is possibly due to the higher concentration at which the percolation threshold occurs in this arrangement. The resistivity decreases overall, as the temperature increases from 0 to 50 °C. These results show that CNTs can be used to control and fine tune the desired macroscopic physical properties of nanocomposites, by concentration and orientation, such as electrical conductivity, for applications where such properties are necessary.
Predation inhibits the positive effect of dispersal on intraspecific and interspecific synchrony in pond metacommunities
Authors: Howeth Jennifer G. , Leibold Mathew A.
Published: April 2013

Recent interest in the ecological drivers of compensatory and synchronous population dynamics has provided an improved yet incomplete understanding of local and regional population oscillations in response to variable environments. Here, we evaluate the effect of dispersal rate and spatiotemporal heterogeneity in predation by the selective planktivore, bluegill sunfish (Lepomis macrochirus), on local and regional dynamics of zooplankton in pond metacommunities. A metacommunity consisted of three pond mesocosm communities, one with constant presence of predators, one without predators, and one with alternating presence–absence of predators. The three communities were connected at either no, low (0.7% per day), or high (20% per day) planktonic dispersal. Results demonstrate that heterogeneous predation (1) prevents spatial synchrony among prey populations across local communities, (2) disrupts the synchronous population dynamics within communities produced by dispersal, and (3) induces local compensatory dynamics between species within communities regardless of dispersal rate. Taken together, the results emphasize that spatiotemporal heterogeneity in selective predation can inhibit both intraspecific and interspecific synchrony in metacommunities.
Formation Testing and Sampling in Low Mobility Heavy Oil Formations of the Eastern Desert, Egypt
Authors: Edelman Jeff , Shah Shabbir H. , Weinheber Peter , Ahmed Ramy , Roumani Izzat , Maghrabia Karim
Published: April 2013

The Arta fields of Egyptian Eastern Desert are operated by Petrodara, a joint venture of Transglobe Energy and Egyptian General Petroleum Corporation (EGPC). The main producing horizon is the Nukhul and formation pressure measurements are critical in this poorly sorted conglomerated marl in order to understand and model depletion. However, low permeability and high viscosity oils contributed to a very low mobility environment that presented considerable challenges to Wireline Formation Tester (WFT) tools. Extensive testing programs resulted in an excessive amount of tests that were unusable, being classified as ‘dry’, ‘tight’ or ‘supercharged’. This low mobility environment also complicated the requirement for PVT samples acquired with the WFT tools. Normal testing operations resulted in very high drawdowns that sampled below formation pressure and caused emulsions with the filtrate of the water based drilling fluid.

In this paper we discuss how the Operator and the Service Company combined to employ fit for purpose WFT techniques to acquire accurate formation pressure data and PVT quality oil samples. Most of our discussion will be based on understanding the dynamics of pretesting in low permeability formations and how the optimal tool and pretest design can produce results where previous attempts have failed. Specifically we consider the newest ‘pretest only’ WFT that provides very fine control over pretest rate and volume and allows precise test design that is not possible with conventional WFT tools. Additionally, we demonstrate the application of best practices and lessons learned from worldwide sampling operation to acquire PVT quality heavy oil samples.
Application of a Numerical Simulation Model for Work over Plans Assessment Prior Operations and Determination of Best Well Intervention Technique for Production Enhancement
Authors: Abugren Yosra Yousef , Joshi Sameer , Steene Marie V. , Thabet Enas
Published: April 2013

This paper describes the application of a new numerical model to simulate any work over plans in order to assess the work over efficiency and the well productivity enhancement, prior to operations commencement.

A case study is discussed, where an operator in Egypt had a plan to improve the productivity of an oil well producing from a multi-layer reservoir, where a low productivity layer had been previously identified and characterized by multiple techniques.

It was critical for the operator to enhance the productivity across this layer and to identify the appropriate remedial action (water shut off, re-perforate, or stimulation) that could impact the whole field production performance. The operator had decided to re-perforate and add new perforations to the low productivity layer.

The numerical simulation model was hence applied to assess work over techniques and to determine the most suitable remedial action for implementation. The simulation result of reperforation and adding new perforations showed water cut drop by 6% with an increase in oil rate by 538 b/d and in water rate by 348 b/d compared to the initial profile identified by production logging. The result of the numerical simulation model suggests that the low productivity layer should be considered as a candidate for stimulation (fracturing/acidizing).

When the operator attempted to re-perforate the low productivity layer, the production performance after the re-perforation did not show a major improvement, as the water cut decreased by 6% only with a small gain in oil rate, which is in agreement with the simulation model outcome.

The operator understood the reason for the field wide low productivity from this layer and hence obtained a key to unlocking the reserves contained in this layer across the whole field in future field development plans.
Case Study in Upgrading Capability of a Crude Oil Pipeline for Maximum Transportation Capacity
Authors: Abdou Hesham A.
Published: April 2013

Since November 1984 The 406.4 mm x 166 km has run from Meleiha field at Egypt's Western Desert to El-Hamra terminal on the coast of the Mediterranean Sea (Figure 1). Its original capacity was 100,000 barrels oil per day (BOPD) using two pumping stations. Planned pumped flow rate increased to 177,000 BOPD when maximum allowable working pressure (MAWP) reduced from 1463 psi to 950 psi. This paper shows how to increase flow rates without reaching MAWP, two methods are recommended: 1) loop the existing pipeline using a 406.4 mm x 56 km pipe. 2) Use a drag reducing agent (DRA) to reduce hydraulic friction losses and total dynamic pressure (TDP) thereby pumping more with reduced initial pumping pressure at Meleiha. Mathematical models are designed to simulate pumping operation through the whole system, with TDP predicted for three pipeline cases: 1) Normal case without both looping and DRA. 2) Oil pumping without DRA and with looping. 3) Oil pumping with both looping and DRA.
Estimation of Annulus Pressure Fluids Kick for Vertical Well Using Moore Method and Integrated Numerical Simulation
Authors: Marbun B. T. , Shidiq A. M.
Published: April 2013

The pressure analysis in annulus to overcome well kick and the well control procedure execution are main concern, particularly when the top of influx reaches the casing shoe. Besides, time and gas volume determination when bubble of gas reaches the surface are importance in executing well control operation with conventional method. The data should be calculated and considered to determine the most appropriate killing well method.

Annulus pressure will increase continuously until eventually reach highest value and volume of pit gain and also reach the maximum at the time of influx reach the surface. Sometime, to circulate all of the influx, it is required sufficient time. Considering the worst circumstances, drilling crews should prepare their mental and the correct strategy to overcome it. There is a fatal risk when well control fails to do, not only loss of rig equipments, but also the life of drilling personel. Thus, the strategy must be done safely. The annulus pressure determination in this research uses the Moore equation. The result of the calculation will be compared to the result of the integrated numerical simulation. Driller Method and Wait & Weight Method will be applied in Moore equation and simulator. Based on comparison of the calculation result, the safer well control method can be chosen optimally.
Determination of Drainage Area and Shape Factor of Vertical Wells in Naturally Fracture Reservoir with Help Well testing and Developed IPR Curve
Authors: Sadeghi Mohammad , Shadizadeh Seyed Reza , Ahmadi Mohammad Ali
Published: April 2013

Shape Factor and drainage area in hydrocarbon reservoir are of the necessary and influencing factors on evaluation and optimization of drilling operation in oil fields. There are numerous methods to calculate the reservoir average pressure in conventional and sandstone reservoirs in that shape and drainage area of the reservoir are of important variables. On the other hand, these relations especially set for sandstone reservoirs and have limited usage in natural fracture reservoirs. This research demonstrates an approach to figure out shape factor and drainage area of wells in carbonated and naturally fractured reservoirs in all pressure and fluidity conditions. To assess this goal, results of well testing are carried out both for development of inflow performance curve and finding the drainage area. To make sure about the validity and preciseness of this method, it was investigated against the data from a well in a natural fracture field and the results were compared with those of other methods. Results dictated that the new approach can provide us with more precise and correct routes for the shape of the well in naturally fractured reservoirs. The suggested approach in this research needs production test data that has been optimized by well testing data for naturally fractured reservoirs. Additionally, this approach implemented to the draw down test and Tiab direct technique which is related to Warren and Root solution. What's more, this approach is reliable for all vertical wells in naturally fractured reservoirs (NFRs) with accessible production test data and well testing.
Dielectric Measurement Improves Formation Water Saturation Evaluation in Variable Water Salinity Conditions, Upper Bahariya Formation, Egypt
Authors: Van Steene M.. , Giussani M.. , Corbella M.. , Tornaghi M..
Published: April 2013

In Egypt's Western Desert, water saturation evaluation of the Upper Bahariya reservoirs is complicated by significant uncertainties in the resistivity-based saturation equation inputs, mainly the formation water salinity, but also the cementation factor and the clay cation exchange capacity (CEC).

A novel dielectric multifrequency measurement was able to clearly identify zones in which oil was present, regardless of these inputs. It provided a residual oil saturation and clear differentiation of oil-bearing zones from water-saturated zones. The measurement also permitted us to apply constraints to the conventional saturation interpretation from shallow and deep resistivities. This process highlighted the variability of formation water salinity across the well and the mixing of filtrate and formation waters in the zone investigated by microresistivity tools.

The dielectric tool also measures dielectric dispersion, from which a parameter (MN) related to the tortuosity of the conduction path can be extracted. This MN parameter was used to refine the water saturation computation from deep-resistivity logs. Variation of the MN parameter between 1.8 and 2 was observed in the reservoir zones. In the zone of interest, a water saturation difference of 7-8 % was observed in the cleanest zone between water saturation computed using the variable MN parameter and that computed using a fixed cementation factor of 1.9. The water saturation recomputed using the data from the dielectric log matches well the irreducible water computed from the nuclear magnetic resonance (NMR) data.

Dielectric dispersion was also used to derive the CEC, which was then input as a direct measure of shaliness in the deep-resistivity saturation equation.

The dielectric measurement increased the accuracy of the water saturation computation in this challenging environment and provided data that are not directly available with conventional logging.
New 16" PDC Bit Design with Improved Cutter Technology Delivers High Rate of Success and Increased Rate of Penetration Drilling in Deep Gas Field in the Arabian Peninsular
Authors: Teasdale P.. , Djaoui M.. , Ahmad R. T. , Markandeya S Holalkere , Roberts T
Published: April 2013

This paper details the step by step process undertaken by a dedicated focus group established to provide a solution to inconsistent drilling performance with the 16" section in a deep gas field on the Arabian Peninusular. The paper reviews the analysis undertaken as well as focusing on new design concepts and improved technology introduced.

Drilling in these deep gas fields, especially the 16" sections has always been a challenge for Polycrystalline Diamond Compact (PDC) drill bits due to the complex lithology that consists of a variety of carbonates with high interfacial severity, followed by a highly abrasive sandstone and dense dolomite formations. Despite improving the ability to consistently drill the 16" sections in a single run over the past few years, the new challenge is to make further improvements to the consistency while at the same time providing further improvements in rate of penetration.

Having experienced inconsistent performance and a series of premature PDC bit failures in these applications over the last few years the vendor assembled an integrated project team to investigate the issue. This team carried out an in depth analysis of all the available field data and identified several factors that were responsible for PDC bit damage, such as bit/BHA whirl, poor operating parameters with their associated vibrations and the limited ability of existing PDC cutters to drill such formations.

The findings led to the development of a new PDC bit design solution with high lateral and torsional stability capable of drilling with high drilling efficiency, the introduction of new cutter technology; along with optimised operating parameters. The successful implementation of the new drill bit and recommended drilling parameters has enabled the operator to more consistently drill these challenging 16" sections in a single run at higher ROPs than previously achieved. This has resulted in significant cost saving for the operator.
Novel Technique to Increase Production from Tight Reservoirs using Channel Fracturing Technique for the first time in the Middle East and North Africa
Authors: Samir M..
Published: April 2013

Hydrocarbon production from tight reservoirs with ultra-low permeabilities in commercial rates for extended periods is difficult to achieve with the current stimulation technologies used in the industry. Normal hydraulic fracturing with conventional techniques to enhance conductivity has been directed towards improving the ability of oil and gas to flow through a porous proppant pack. The industry has extended significant efforts towards the goal of increasing proppant pack permeability through the development of less damaging carrier fluids, higher strength man-made proppants, more efficient fracturing fluid breakers etc. but with no assurance of maintaining long-term production.

The concept of the novel channel fracturing technique is to create flow paths inside the proppant porous media to give infinite conductivity, which delivers a number of consequential benefits: better post-frac cleanup, lower pressure loss within the fracture, and longer effective fracture half-lengths, all of which contribute towards improved short and long-term production.

This new channel fracturing technique was applied and implemented in reservoirs located in the Egyptian western desert for the Abu Roash ‘G’ and Upper Bahariya formations, which usually undergo a steeper than normal decline in production even after hydraulic fracturing with conventional techniques.

This paper will discuss the results of four well stimulation treatments utilizing the channel fracturing technique proving the increase and stabilization of oil production over extended periods even with decreasing reservoir pressures around the wellbore.