bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Stage Upscaling of Two-Phase Flow: From Core to Simulation Scale
Authors: Lohne Arild , Virnovsky George , Durlofsky Louis J.
Published: September 2006

In the coarse-scale simulation of heterogeneous reservoirs, effective or upscaled flow functions (e.g., oil and water relative permeability and capillary pressure) can be used to represent heterogeneities at subgrid scales. The effective relative permeability is typically upscaled along with absolute permeability from a geocellular model. However, if no subgeocellular-scale information is included, the potentially important effects of smaller-scale heterogeneities (on the centimeter to meter scale) in both capillarity and absolute permeability will not be captured by this approach.

In this paper, we present a two-stage upscaling procedure for two-phase flow. In the first stage, we upscale from the core (fine) scale to the geocellular (intermediate) scale, while in the second stage we upscale from the geocellular scale to the simulation (coarse) scale. The computational procedure includes numerical solution of the finite-difference equations describing steady-state flow over the local region to be upscaled, using either constant pressure or periodic boundary conditions. In contrast to most of the earlier investigations in this area, we first apply an iterative rate-dependent upscaling (iteration ensures that the properties are computed at the appropriate pressure gradient) rather than assume viscous or capillary dominance and, second, assess the accuracy of the two-stage upscaling procedure through comparison of flow results for the coarsened models against those of the finest-scale model.

The two-stage method is applied to synthetic 2D reservoir models with strong variation in capillarity on the fine scale. Accurate reproduction of the fine-grid solutions (simulated on 500×500 grids) is achieved on coarse grids of 10×10 for different flow scenarios. It is shown that, although capillary forces are important on the fine scale, the assumption of capillary dominance in the first stage of upscaling is not always appropriate, and that the computation of rate-dependent effective properties in the upscaling can significantly improve the accuracy of the coarse-scale model. The assumption of viscous dominance in the second upscaling stage is found to be appropriate in all of the cases considered.
Limits of 2D NMR Interpretation Techniques to Quantify Pore Size, Wettability, and Fluid Type: A Numerical Sensitivity Study
Authors: Toumelin Emmanuel , Torres-Verdín Carlos , Sun Boqin , Dunn Keh-Jim
Published: September 2006

Two-dimensional (2D) NMR techniques have been proposed as efficient methods to infer a variety of petrophysical parameters, including mixed fluid saturation, in-situ oil viscosity, wettability, and pore structure. However, no study has been presented to quantify the petrophysical limitations of such methods. We address this problem by introducing a pore-scale framework to accurately simulate suites of NMR measurements acquired in complex rock/ fluid models. The general pore-scale framework considered in this paper is based on NMR random walks for multiphase fluid diffusion and relaxations, combined with Kovscek's pore-scale model for two-phase fluid saturation and wettability alteration. We use standard 2D NMR methods to interpret synthetic data sets for diverse petrophysical configurations, including two-phase saturations with different oil grades, mixed wettability, or carbonate pore heterogeneity.

Results from our study indicate that for both water-wet and mixed-wet rocks, T2 (transverse relaxation)/D (diffusion) maps are reliable for fluid typing without the need for independently determined cutoffs. However, significant uncertainty exists in the estimation of fluid type, wettability, and pore structure with 2D NMR methods in cases of mixed-wettability states. Only light oil wettability can be reliably detected with 2D NMR interpretation methods. Diffusion coupling in carbonate rocks introduces additional problems that cannot be circumvented with current 2D NMR techniques.
Rate Superposition for Generating Pressure Falloff Solutions
Authors: Peres Alvaro M. M. , Boughrara Amina A. , Reynolds Albert C.
Published: September 2006

Although the Thompson-Reynolds steady-state theory has proved useful for explaining the relation between reservoir physics and the pressure/pressure derivative response for both injection and falloff tests, until now, we have been unable to apply this method to construct analytical solutions for the falloff response. In this work, we remedy this deficiency by constructing approximate analytical solutions for the pressure falloff response sub sequent to water injection at a vertical or horizontal well. By comparison with a finite-difference simulator using grid refinement and a hybrid grid, it is shown that our multiphase flow solutions are accurate.

The falloff solution can be written as the sum of the single-phase falloff solution based on oil properties at initial water saturation plus a multiphase flow term, which reflects the deviation of the total mobility (in the region contacted b y injected water) from oil mobility at initial water saturation. The multiphase term is presented as an integral in the vertical w ell case and a sum of one to three integrals in the horizontal w ell case. For the purpose of constructing an accurate estimate of the falloff multiphase pressure change term, one can use a series of 1D Buckley-Leverett solutions (one for each integral in the multiphase term) and assume that, throughout the falloff period, the total mobility profile in the reservoir is equal to the total mobility profile that existed at the instant of shut-in. Evaluation of each integral in the multiphase term requires the 1D mobility profile constructed from the Buckley-Leverett solution and a corresponding 1D flow rate profile during falloff.

For linear single-phase flow, it is shown that rate superposition applies and w e use this concept in a reasonable but adhoc w ay to estimate the rate profiles needed to compute the multiphase pressure term.

It is show n that even in cases w here falloff data allow one to accurately estimate the properties of the oil zone, k now ledge of the multiphase term is critical in order to ob tain an accurate estimate of the mechanical skin factor.
Preventing Lost Circulation by Use of Lightweight Slurries with Reticular Systems: Depleted Reservoirs in Southern Mexico
Authors: Romero S. N. , Monroy R. R. , Johnson C. , Cardenas F. , Abraham G. A. T.
Published: September 2006

In southern Mexico, 65% of the oil and 74% of the gas production comes from Mesozoic formations—naturally fractured carbonates—with a high potential for loss of circulation. Lost circulation during drilling and cementing often leads to formation damage and can severely impact well costs.

This paper describes the implementation of lightweight (9.17 lbm/gal) slurries and a reticular-product technology to avoid losses while cementing and to improve zonal isolation and post-cement job evaluation. Applying this combination of technologies improved the success ratio of primary isolation of the wells.

Lightweight cementing slurries with reticular systems were used in two wells in Mexico: a development well (Copano 32) and an exploration well (Malva 201). The wells were drilled underbalanced, and in both cases, lost circulation was a problem during drilling and cementing. Using this technology, circulation of the slurry was regained while cementing and returns reached the designed cement top, avoiding an anticipated remedial cementing job. The pressure behavior during cementing clearly showed the plugging effect of the fiber-laden slurry in the formation; periodic low-pressure intervals were encountered before the final constant increase in pressure, which indicated that the designed-cement job objectives had been achieved.

In these wells, implementation of lightweight slurries and reticular-product technology prevented further cement invasion into the production zone. Savings in rig downtime and improved zonal isolation led to a significant reduction in costs during the construction of the wells.

The cementing solution represented at least a 300% cost savings related to the cementing process. He also confirmed that lightweight cement slurries with reticular products are a viable solution for the depleted reservoirs, in southern Mexico and similar wells around the world, in which lost-circulation problems of this kind exist.
Exhuberance Over Exubera
Authors: Hite Pamela F. , Barnes Ann M. , Johnston Philip E.
Published: September 2006

IN BRIEF

The isolation, purification, and clinical use of insulin has been enhanced many times in the past 80 years. This article outlines the development of insulin and describes the formulation, activity, and practical use of a newly approved inhaled form of insulin sold under the trade name Exubera.
Clinical Use of the Metabolic Syndrome: Why the Confusion?
Authors: Blaha Michael , Elasy Tom A.
Published: September 2006

IN BRIEF

The term “metabolic syndrome” refers to a cluster of risk factors for cardiovascular disease and type 2 diabetes that occurs as a result of obesity and insulin resistance. Considerable confusion surrounding the precise use of this term in the clinical setting has led to difficulty in assessing the utility of this concept. This article provides a simple framework for understanding the disparate approaches to this syndrome. This understanding will facilitate decision-making regarding the role of the metabolic syndrome in everyday clinical practice.
The Diabetes Patient Portal: Patient Perspectives on Structure and Delivery
Authors: Hess Rachel , Bryce Cindy L. , McTigue Kathleen , Fitzgerald Katharine , Zickmund Susan , Olshansky Ellen , Fischer Gary
Published: September 2006

In Brief

This article describes the recent development of a diabetes-specific patient portal that is linked to an existing electronic medical record system. The portal was designed to provide patients with a secure means of electronic access to preventive health care reminders, information concerning their medications and health histories, educational materials, and self-management resources concerning diabetes-related risks. The authors briefly describe their work on the portal to date and discuss future directions for their research.
Educating Medical Office Staff: Enhancing Diabetes Care in Primary Care Offices
Authors: Celeste-Harris Sonya , Maryniuk Melinda
Published: September 2006

In Brief

This article describes Joslin Diabetes SmartStart, a program through which the provision of educational materials and training to the office staff of primary care providers has resulted in improved clinical and behavioral patient outcomes. Certified diabetes educators provided participating clinics with basic diabetes education for clinical staff; a set of diabetes patient education flipcharts, booklets, and handouts in English and Spanish; and patient access to a call center. Positive outcomes included decreases in hemoglobin A1c and blood pressure levels and increases in patient-reported quality of life and confidence in diabetes self-management ability.
Group Education Strategies for Diabetes Self-Management
Authors: Tang Tricia S. , Funnell Martha M. , Anderson Robert M.
Published: September 2006

In Brief

Empowerment-based diabetes group education emphasizes strategies that are patient centered, problem based, culturally relevant, integrative, and evidence based. These programs and strategies can be conducted across a variety of educational and clinical settings with the goal of responding to the unique diabetes-related needs of each patient.
Diabetes Control in Thyroid Disease
Authors: Johnson Jennal L.
Published: September 2006

In Brief

Thyroid disease is commonly found in most types of diabetes. This article defines the prevalence of thyroid disease in diabetes and elucidates through case studies the assessment, diagnosis, and clinical management of thyroid disease in diabetes.
Diabetic Nephropathy: Where We Have Been and Where We Are Going
Authors: Ossman Sherry Smith
Published: September 2006

In Brief

This article provides an overview of renal disease in diabetes, preventive treatment options, and the effect of diabetes on renal function. New treatment strategies used to slow progression of diabetic nephropathy are also discussed.
Hyperglycemia in HIV/AIDS
Authors: Spollett Geralyn R.
Published: September 2006

In Brief

For patients with diabetes, the additional diagnosis of HIV increases the challenge of self-care management. However, in patients with HIV who develop hyperglycemia, the added responsibilities can be overwhelming. This article describes the research studies that link treatment of HIV with the development of diabetes and offers suggestions for screening patients with HIV for diabetes.
Patterned Color and Fluorescent Images with Polydiacetylene Supramolecules Embedded in Poly(vinyl alcohol) Films
Authors: Kim J.‐M. , Lee Y. B. , Chae S. K. , Ahn D. J.
Published: September 2006

Poly(vinyl alcohol) (PVA) films embedded with functional polydiacetylene (PDA) are efficiently prepared for color and fluorescence imaging. Intensely blue films are obtained by mixing and drying solutions containing PDA vesicles and PVA. A blue‐to‐red color transition is observed upon heating the polymer films. In addition, selective UV irradiation (through a photomask) of PVA films containing diacetylene monomer results in the generation of micropatterned color (without heating) and both color and fluorescent images (after heating the films at 120 °C for 10 s). Patterned two‐color (blue and red) images in the polymer film are readily obtained by a sequential process of photomasked irradiation, heating, and unmasked irradiation.
Physical fitness indices and anthropometrics profiles in schoolchildren with sickle cell trait/disease
Authors: Moheeb Hisham , Wali Yasser A. , El‐Sayed Mahmoud S.
Published: September 2006

The current studies aimed at determining physical fitness indices and anthropometrics profiles of school children with sickle cell trait (SCT) and sickle cell disease (SCD). Male school children (150) comprising 3 Groups participated in the studies. Group 1 has 50 normal healthy controls, while Groups 2 and 3 each has 50 children who were suffering from SCT and SCD, respectively. Anthropometrics measurement and parameters of physical fitness were assessed in all subjects. All children were also subjected to a 5‐min running exercise test on a flat motorized treadmill at speed corresponding to 5 km/hr. Throughout the test, heart rate was monitored and recoded during exercise and for 10‐min during recovery. Blood lactate was measured before and 5 min following the completion of test. The mean values of lean body mass and height were lower in the SCD children (P < 0.05) compared with the healthy subjects and SCT individuals. Children with SCD exhibited a higher mean value (P < 0.05) for percent body fat and fat mass than the normal healthy subjects and SCT individuals. Although all groups tolerated well the treadmill exercise protocol, the SCD group exhibited higher (P < 0.05) mean values of heart rate during exercise than those observed in the SCT and normal control children. In addition, SCD children showed higher serum lactate values before and after treadmill exercise compared to the other groups. Children with SCD exhibit high level of adiposity; low level of fitness and their exercise performance appears to be physiologically more stressful as indicated by heart rate and blood lactate concentration responses. Am. J. Hematol., 2006. © 2006 Wiley‐Liss, Inc.
On the Unpredictability of Odor
Authors: Sell C. S.
Published: September 2006

The relationship between molecular structure and odor has fascinated and puzzled chemists for more than a century. Despite a great deal of research on structure–odor relationships, prediction of the odor of a novel molecule remains a statistical exercise and models only provide a probability of the character, threshold, and intensity. Surprises are still commonplace, and serendipity continues to be an important factor in the discovery of novel fragrant molecules. Recent advances in our understanding of the mechanism of olfaction provide an explanation for this and suggest that our ability to predict odor properties of molecules will not improve significantly in the near future.
A sidelong look at storm tracks
Authors: James I. N. , Burkhardt Ulrike
Published: September 2006

The three‐dimensional structure of time‐mean eddy statistics and the time evolution of longitude‐height sections suggest that the storm tracks form a single structure in the upper troposphere and indicate that eddies regularly propagate from the Pacific to the Atlantic. The model of storm tracks as independent meta‐systems is inadequate. Copyright © 2006 Royal Meteorological Society
Algen unter Strom: Das Experiment
Authors: Lühring Hinrich
Published: September 2006

Die Methode der lokalen ‘Anästhetisierung’ eines definierten Abschnitts einer riesigen Internodialzelle von Characeen ist geeignet, sich im Schulunterricht auch experimentell der Membranphysiologie anzunehmen. Characeen sind robuste Systeme, die leicht in einfach herzustellenden Lösungen akklimatisieren. Experimente zu den meisten Fragestellungen wie Membranspannung und ‐widerstand, Erregbarkeit, elektrogene Ionenpumpen oder Cotransportsysteme etc. können innerhalb von 45 Minuten mit geringer Vorbereitung durchgeführt werden.
Proteinspleißen: Inteine – die “Introns” der Proteine und ihre biotechnologische Anwendung
Authors: Elleuche Skander , Pöggeler Stefanie
Published: September 2006

Ein Intein ist eine Sequenz, die sich posttranslational und autokatalytisch aus einem Vorläuferprotein herausgespleißt. Inteine kommen in allen drei Bereichen des Lebens (Prokaryoten, Eukaryoten, Archaea) vor und werden auch als “Proteinintrons” bezeichnet. Im Gegensatz zu Introns, bei denen die Spleißreaktion auf RNA‐Ebene stattfindet, schneiden sich Inteine aus Proteinen heraus und verknüpfen die flankierenden Proteinbereiche (Exteine) über eine neue Peptidbindung. Viele Inteine besitzen außerdem noch eine Endonuklease, die sie nutzen, um sich durch horizontalen Gentransfer zu verbreiten. Das Intein‐Spleißen kann an verschiedenen Reaktionsschritten beeinflusst und reguliert werden. Dies macht Inteine zu einem vielseitig einsetzbaren Werkzeug in der molekularen Biotechnologie und ermöglicht die Zusammensetzung verschiedener Proteinfragmente in vitro.
Das gläserne Insekt: Einblick in die inneren Organe von Arthropoden
Authors: Kühmstedt Joachim , Melzer Roland R.
Published: September 2006

Die durchsichtigen Larven der Büschelmücke (Chaoborus crystallinus) eignen sich hervorragend, um im Biologieunterricht einen Blick auf die inneren Organe von Insekten zu werfen. Strickleiternervensystem und Gastransport, aber auch ethische Fragestellungen zum Umgang mit Versuchstieren lassen sich beispielsweise anhand des “gläsernen Insektes” diskutieren. Ein Arbeitsblatt zum Download bietet eine praktische Anregung für den Unterricht.
Virtuelle Wildbiene im Netz
Authors: Ulbrich Karin
Published: September 2006

Wildbienen sind wichtige Bestäuber. Sie sind jedoch weit weniger bekannt als Honigbienen. Simulationen mit einem neuen Internet‐Tool fördern das Verständnis für ihre Habitatansprüche.
Was ist ein Gen?
Authors: Kronberg Inge
Published: September 2006

Der Begriff “Gen” hat eine wechselvolle Geschichte: Nach klassischer Vorstellung handelt es sich um eine Vererbungseinheit, über die Anlagen für ein Merkmal von einer Generation an die nächste weitergegeben werden. Molekularbiologische Erkenntnisse verknüpfen das Gen mit der Codierung von Proteinen. Ein Gen ist demnach der Abschnitt eines DNAMoleküls, der für ein RNA‐Molekül codiert. Die RNA schreibt die in der DNA‐Basensequenz verschlüsselte genetische Information ab und bringt sie an die Stätten der Proteinsynthese. Dieses relativ einfache Bild eines Gens hat viel von der tatsächlichen Komplexität verhüllt und musste in den vergangenen Jahren zunehmend abgewandelt werden.
Genetik der Alkoholabhängigkeit
Authors: Treutlein Jens , Schumann Gunter
Published: September 2006

Dass Menschen unterschiedliche Alkoholtrinkgewohnheiten haben, ist in den Genen verankert. Im Rahmen eines Forschungsprojektes im Nationalen Genomforschungsnetz (NGFN) entdeckten Forscher zwei Varianten im Gen CRHR1, die einen Einfluss darauf haben, ob man es bei mäßigem Alkoholkonsum belässt oder nicht. Betroffene trinken nicht häufiger als andere, dafür aber bei jedem Anlass im Schnitt wesentlich mehr.
Zugvögel: Kompass im Kopf
Authors: Irsch Wilhelm
Published: September 2006

Zugvögel navigieren nach dem Stand der Sonne, den Sternen und dem Erdmagnetfeld. Ein Forscherteam am Institut für Biologie und Umweltwissenschaften der Universität Oldenburg ist der Lokalisierung des rätselhaften Magnetsinns nun ein gutes Stück näher gekommen.
Long-term results of a randomized trial comparing preoperative short-course radiotherapy with preoperative conventionally fractionated chemoradiation for rectal cancer
Authors: Bujko K , Nowacki M P , Nasierowska-Guttmejer A , Michalski W , Bebenek M , Kryj M
Published: September 2006

Background

Neoadjuvant chemoradiotherapy does not alter anal sphincter preservation or postoperative complications compared with short-course radiotherapy alone in patients with clinical stage T3 or T4 resectable rectal cancer. The aim of this study was to compare survival, local control and late toxicity in the two treatment groups.

Methods

The study randomized 312 patients to receive either preoperative irradiation (25 Gy in five fractions of 5 Gy) and surgery within 7 days or chemoradiation (50·4 Gy in 28 fractions of 1·8 Gy, bolus 5-fluorouracil and leucovorin) and surgery 4–6 weeks later. The median follow-up of living patients was 48 (range 31–69) months.

Results

Early radiation toxicity was higher in the chemoradiation group (18·2 versus 3·2 per cent; P < 0·001). The actuarial 4-year overall survival was 67·2 per cent in the short-course group and 66·2 per cent in the chemoradiation group (P = 0·960). Disease-free survival was 58·4 versus 55·6 per cent (P = 0·820), crude incidence of local recurrence was 9·0 versus 14·2 per cent (P = 0·170) and severe late toxicity was 10·1 versus 7·1 per cent (P = 0·360) respectively.

Conclusion

Neoadjuvant chemoradiation did not increase survival, local control or late toxicity compared with short-course radiotherapy alone.
A Ring‐Fusion/Ring‐Fission Mechanism for the Metathesis Reaction of Macrocyclic Formaldehyde Acetals
Authors: Cacciapaglia Roberta , Di Stefano Stefano , Mandolini Luigi
Published: September 2006

Important insight has been obtained into the mechanism of the reversible acid‐catalysed transacetalation of cyclophane formaldehyde acetals (formals) Ci in CDCl3, at 25 °C. The order of appearance of the lowest oligomers in the early stages of the equilibration reaction is fully consistent with ring‐fusion/ring‐fission processes in which oxonium ion intermediates undergo SN2 reactions, according to an acid‐catalysed bimolecular (A2) mechanism. The alternative acid‐catalysed monomolecular (A1) reaction path, based on “back‐biting” processes of carbenium ions generated by SN1‐type cleavage of oxonium ion intermediates, predicts sequences that are in marked contrast with experimental findings.
A new approach to study fibroblast migration
Authors: Thampatty Bhavani P. , Wang James H.‐C.
Published: September 2006

This paper presents a new approach to study cell migration. Human tendon fibroblasts were plated on silicone membranes coated with 10 μg/ml ProNectin‐F. The silicone surfaces were micro‐fabricated with parallel microgrooves, with 10 μm ridge and groove width, and 3 μm groove depth. Fibroblasts grown in the microgrooves had an elongated shape and oriented along the microgroove direction. They also moved along the same direction instead of “random walk” when cells migrate on smooth culture surfaces. In response to TGF‐β1 (5 ng/ml) treatment, these fibroblasts on the microgrooved surfaces were differentiated into myofibroblasts, as judged by an elevated expression of α‐smooth muscle actin (α‐SMA), a specific marker for myofibroblasts. Moreover, these myofibroblasts were found to be ∼30% less motile compared to that of untreated fibroblasts. Thus, use of microgrooved surface may be an effective approach to detect difference in cell motility because cell migration on the microgrooved surface is one dimensional and hence easier to be quantified than two‐dimensional random movement on conventional smooth culture surfaces. Cell Motil. Cytoskeleton 2006. © 2006 Wiley‐Liss, Inc.
An efficient Green's function for acoustic waveguide problems
Authors: Santiago J. A. F. , Wrobel L. C.
Published: September 2006

Efficient implementations of the boundary element method for underwater acoustics should employ Green's functions which directly satisfy the boundary conditions on the free surface and the horizontal parts of the bottom boundary. In the present work, these Green's functions are constructed by using either eigenfunction expansions or Ewald's method. This method is discussed in detail, including an attempt to optimize the value of the parameter b, which splits the integral employed in Ewald's representation.

A numerical analysis of the infinite series used in the two‐dimensional acoustic waveguide problem is described, considering the following simplifications: the source of acoustic disturbance is time‐harmonic, the velocity of sound is constant and the medium in the absence of perturbations is quiescent. Copyright © 2006 John Wiley & Sons, Ltd.
Cell death and thymic export during fetal life
Authors: Holder Joanne E. , Washington Elizabeth A. , Cunningham Craig P. , Cahill Ross N. P. , Kimpton Wayne G.
Published: September 2006

In the fetus the peripheral T cell pool expands as the fetus grows, but the mechanisms that regulate T cell homeostasis during fetal life are unknown. Here, we show that the peripheral T cell pool in the sheep fetus is established by the export from the fetal thymus of twice as many CD8+ as CD4+ thymic emigrants every day. Clonal deletion of CD4+ thymocytes in the fetal thymus appeared to be more stringent than was the case for CD8+ thymocytes because only 1 in 35 single‐positive CD4 (SPCD4) thymocytes was exported from the thymus whereas the majority (2/3) of the single‐positive CD8 (SPCD8) thymocytes were exported from the fetal thymus each day. Furthermore, within the thymus, the number of apoptotic SPCD4 thymocytes was 40 times greater than the number of apoptotic SPCD8 thymocytes. A tissue‐specific migration of CD8+ emigrants localizing in the spleen was also established in the fetus in contrast to CD4+ emigrants, which migrated randomly to spleen and LN.
More intrinsically knotted graphs
Authors: Foisy Joel
Published: September 2006

We demonstrate four intrinsically knotted graphs that do not contain each other, nor any previously known intrinsically knotted graph, as a minor. © 2006 Wiley Periodicals, Inc. J Graph Theory 54: 115–124, 2007
Pentagons and cycle coverings
Authors: Wang Hong
Published: September 2006

Let G be a graph of order n ≥ 5k + 2, where k is a positive integer. Suppose that the minimum degree of G is at least ⌈(n + k)/2⌉. We show that G contains k pentagons and a path such that they are vertex‐disjoint and cover all the vertices of G. Moreover, if n ≥ 5k + 7, then G contains k + 1 vertex‐disjoint cycles covering all the vertices of G such that k of them are pentagons. © 2006 Wiley Periodicals, Inc. J Graph Theory 54: 194–208, 2007
A bound on the chromatic number using the longest odd cycle length
Authors: Kenkre Sreyash , Vishwanathan Sundar
Published: September 2006

Let G be a non‐bipartite graph with ℓ as the length of the longest odd cycle. Erdös and Hajnal proved that χ(G) ≤ ℓ + 1. We show that the only graphs for which this is tight are those that contain Kℓ + 1 and further, if G does not contain Kℓ then χ(G) ≤ ℓ −1. We then extend these results and show that if we exclude a large clique, we can prove better bounds for χ(G) as a function of ℓ. Specifically, we show that if ω(G) ≤ ⌈ℓ(1 − ϵ)⌉ for ϵ ≤ 4/15, then χ(G) ≤ ⌈ℓ(1 − ϵ/2)⌉. © 2006 Wiley Periodicals, Inc. J Graph Theory 54: 267–276, 2007
Collision‐induced fragmentation pathways including odd‐electron ion formation from desorption electrospray ionisation generated protonated and deprotonated drugs derived from tandem accurate mass spectrometry
Authors: Williams Jonathan P. , Nibbering Nico M. M. , Green Brian N. , Patel Vibhuti J. , Scrivens James H.
Published: September 2006

The rapid desorption electrospray ionisation (DESI) of some small molecules and their fragmentation using a triple‐quadrupole and a hybrid quadrupole time‐of‐flight mass spectrometer (Q‐ToF) have been investigated. Various scanning modes have been employed using the triple‐quadrupole instrument to elucidate fragmentation pathways for the product ions observed in the collision‐induced dissociation (CID) spectra. Together with accurate mass tandem mass spectrometry (MS/MS) measurements performed on the hybrid Q‐ToF mass spectrometer, unequivocal product ion identification and fragmentation pathways were determined for deprotonated metoclopramide and protonated aspirin, caffeine and nicotine. Ion structures and fragmentation pathway mechanisms have been proposed and compared with previously published data. The necessity for elevated resolution for the differentiation of isobaric ions are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Investigation of the mechanism of lubrication in starch–oil composite dry film lubricants
Authors: Biresaw G. , Kenar J. A. , Kurth T. L. , Felker F. C. , Erhan S. M.
Published: September 2006

The boundary coefficient of friction (COF) of starch–oil composite dry film lubricants was investigated as a function of starch type (waxy vs. normal purified food grade corn starch), oil chemistry (hexadecane vs. oleic acid and various vegetable oils), and starch‐to‐oil ratio. Based on the results, a mechanism of starch–oil interaction in these composites was proposed. According to the proposed mechanism: (a) the oil in the composite is distributed between the bulk and the surface of the starch; and (b) the fraction of the oil trapped in the bulk and that adsorbed on the surface are related to each other by an equilibrium constant, and are functions of the total oil concentration in the composite. In line with the proposed mechanism, an adsorption model was used to quantify the free energy of adsorption (ΔGads) of the polar oils onto the starch surface. The analysis gave ΔGads values that were higher than those reported for the adsorption of the same polar oils onto steel surfaces. This result is consistent with the effect of the relative surface energies of steel and starch on the adsorption of polar oils. The adsorption property of the non‐polar hexadecane relative to the polar oils was estimated by comparing their interfacial tensions with starch. The result showed a higher interfacial tension for hexadecane–starch than that for the polar oil–starch composites. This result predicts a relatively poorer compatibility with, and, hence, poorer adsorption of hexadecane onto starch leading to higher COF, as was observed in the friction measurements. Published in 2006 by John Wiley & Sons, Ltd.
Camptocormia induced by atypical antipsychotics and resolved by electroconvulsive therapy
Authors: Vela Lydia , Jiménez Morón Diego , Sánchez Carmen , Pareja Juan Antonio , Barón Manuel
Published: September 2006

We present a depressive patient who developed mild parkinsonian signs and camptocormia after the introduction of olanzapine. She had been treated before with other antipsychotic drugs. When camptocormia was diagnosed, olanzapine was withdrawn and levodopa was introduced. Depressive symptoms got worse and electroconvulsive therapy was tried. When the treatment was completed, her depression substantially improved and her posture became completely upright. © 2006 Movement Disorder Society
Denoising of complex MRI data by wavelet‐domain filtering: Application to high‐b‐value diffusion‐weighted imaging
Authors: Wirestam Ronnie , Bibic Adnan , Lätt Jimmy , Brockstedt Sara , Ståhlberg Freddy
Published: September 2006

The Rician distribution of noise in magnitude magnetic resonance (MR) images is particularly problematic in low signal‐to‐noise ratio (SNR) regions. The Rician noise distribution causes a nonzero minimum signal in the image, which is often referred to as the rectified noise floor. True low signal is likely to be concealed in the noise, and quantification is severely hampered in low‐SNR regions. To address this problem we performed noise reduction (or denoising) by Wiener‐like filtering in the wavelet domain. The filtering was applied to complex MRI data before construction of the magnitude image. The noise‐reduction algorithm was applied to simulated and experimental diffusion‐weighted (DW) images. Denoising considerably reduced the signal standard deviation (SD, by up to 87% in simulated images) and decreased the background noise floor (by approximately a factor of 6 in simulated and experimental images). Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Nonlinear phase correction of navigated multi‐coil diffusion images
Authors: Atkinson David , Counsell Serena , Hajnal Joseph V. , Batchelor Philip G. , Hill Derek L.G. , Larkman David J.
Published: September 2006

Cardiac pulsatility causes a nonrigid motion of the brain. In multi‐shot diffusion imaging this leads to spatially varying phase changes that must be corrected. A conjugate gradient based reconstruction is presented that includes phase changes measured using two‐dimensional navigator echoes, coil sensitivity information, navigator‐determined weightings, and data from multiple coils and averages.

A multi‐shot echo planar sequence was used to image brain regions where pulsatile motion is not uniform. Reduced susceptibility artifacts were observed compared to a clinical single‐shot sequence. In a higher slice, fiber directions derived from single‐shot data show distortions from anatomical scans by as much as 7 mm compared to less than 2 mm for our multi‐shot reconstructions. The reduced distortions imply that phase encoding can be applied in the shorter left–right direction, enabling time savings through the use of a rectangular field of view. Higher resolution diffusion imaging in the spine permits visualization of a nerve root. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Determination of the maturity and functionality of tumor vasculature by MRI: Correlation between BOLD‐MRI and DCE‐MRI using P792 in experimental fibrosarcoma tumors
Authors: Baudelet Christine , Cron Gregory O. , Gallez Bernard
Published: September 2006

Using hypercapnia and carbogen as functional markers of vessel maturation and function, we compared blood oxygen level‐dependent (BOLD) contrast with standard dynamic contrast‐enhanced (DCE)‐MRI quantitative parameters in murine fibrosarcoma. Our results show that there was no correlation between vessel maturity and contrast‐agent uptake rate (KinTrans) or contrast agent efflux rate (kep). In addition, DCE‐MRI provided higher estimates of the fraction of functional tumor compared to BOLD‐MRI. The two putative markers of regional vascular density, i.e., the magnitude of BOLD signal change during carbogen challenge (VF) and the fractional plasma volume found by DCE‐MRI (Vp), were only weakly correlated (r2 = 0.02–0.14). Furthermore, VF showed no correlation with KinTrans. A positive correlation was observed (r2 = 0.75) between mean tumor VF and kep, but only when averaged over the whole tumor (which includes tumor regions completely unperfused by the gadolinium (Gd) contrast agent). This would merely reveal a relationship between perfusion status and the capacity to respond to carbogen breathing. In conclusion, characterizations of tumor microvasculature imaging using BOLD‐MRI and DCE‐MRI appear to be largely complementary, given the weak correlations between their corresponding derived parameters. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Dual vessel arterial spin labeling scheme for regional perfusion imaging
Authors: Zimine Ivan , Petersen Esben Thade , Golay Xavier
Published: September 2006

Regional perfusion imaging (RPI) based on pulsed arterial spin labeling and angulated inversion slabs has been recently proposed. The technique allows mapping of individual brain perfusion territories of the major feeding arteries and could become a valuable clinical tool for evaluation of patients with cerebrovascular diseases. Here we propose a new labeling scheme for RPI where lateral and posterior circulations are labeled simultaneously. Two scans instead of three are sufficient to obtain the same perfusion territories as in the original approach, allowing for a 33% reduction in the total RPI protocol time. Moreover, the position of the inversion slabs with respect to vascular anatomy facilitates the planning and allows potentially better labeling efficiency. The new approach was tested on seven healthy volunteers and compared to the original labeling scheme. The results showed that the same perfusion territories and regional CBF values can be obtained. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Bladder sensation in peripheral nerve lesions
Authors: Yamaguchi Chiharu , Sakakibara Ryuji , Uchiyama Tomoyuki , Liu Zhi , Yamamoto Tatsuya , Ito Takashi , Awa Yusuke , Yamamoto Kaori , Kinou Mika , Yamanishi Tomonori , Nomura Fumio , Hattori Takamichi
Published: September 2006

Objective

To present bladder sensory data of three common peripheral nerve lesions (e.g., distal, intermediate/focal, and proximal).

Methods

We measured first sensation (FS) and bladder capacity (BC) (not exceeding 600 ml) in 71 patients with peripheral nerve lesions: 35 diabetic neuropathy (D group), 6 post‐pelvic surgery (S), and 27 cauda equina syndrome due to lumbar spondylosis (L). We excluded those with detrusor overactivity or low compliance that might affect bladder sensation.

Results

The mean FS was 301.7 ml (D), 271.3 ml (S), and 189.4 ml (L), with the largest being in the D group (P < 0.05); the mean BC was 495.2, 475.4, and 391.4 ml, with the largest being in the D group (P < 0.05); who commonly had less frequent toileting. The mean post‐void residual volume was 106.5, 29.0, and 42.0 ml; the values tended to increase along with BC. In the D group, the mean FS in patients with skin hypoalgesia as detected by pin prick and in those without it was 407.8 and 210.0 ml. The percentage of patients with FS < 100 ml was 5.7%, 0%, and 7.4%, respectively, who commonly had urinary urgency and frequency.

Conclusions

Bladder sensation is affected in diabetic neuropathy more severely than in intermediate/proximal lesions, together with somatic sensory disturbance. Bladder sensory disturbance leads to less frequent toileting, resulting in bladder over‐distension and large post‐void residuals. A small proportion of patients with peripheral nerve lesions develop urinary urgency, presumably reflecting irritation of the afferent nerve fibers or the urothelium. Neurourol. Urodynam. 25:763–769, 2006. © 2006 Wiley‐Liss, Inc.
Magnetic resonance imaging of gadolinium‐labeled pancreatic islets for experimental transplantation
Authors: Biancone Luigi , Crich Simonetta Geninatti , Cantaluppi Vincenzo , Romanazzi Giuseppe Mauriello , Russo Simona , Scalabrino Elisa , Esposito Giovanna , Figliolini Federico , Beltramo Silvia , Perin Paolo Cavallo , Segoloni Giuseppe Paolo , Aime Silvio , Camussi Giovanni
Published: September 2006

New imaging techniques that couple anatomical resolution to sensitivity may greatly contribute to improving islet transplantation. In the present work, a report is given of the direct detection of islets by magnetic resonance imaging (MRI) after ex vivo cell labeling with the MRI T1 contrast agent GdHPDO3A. Experiments on mouse and human islets demonstrated well‐tolerated uptake of GdHPDO3A, based on morphology, viability, glucose‐dependent insulin response and apoptosis/toxicity gene array profile. GdHPDO3A loading was sufficient for in vitro MRI cell detection. In vivo isotransplanted mouse islets into the kidney capsule and xenotransplanted human islets within the mouse liver were detected. Imaging specificity was supported by the absence of signal in unlabeled islet transplants, its persistence upon using fat‐suppression MRI protocols and the colocalization with the transplanted islets. In conclusion, direct islet imaging with high spatial and contrast resolution after labeling with GdHPDO3A is demonstrated, allowing visualization of kidney subcapsular mouse islet grafts and intrahepatic human islet xenografts. Copyright © 2006 John Wiley & Sons, Ltd.
Use of information and communication technology (ICT) and perceived health in adolescence: The role of sleeping habits and waking‐time tiredness
Authors: Punamäki Raija‐Leena , Wallenius Marjut , Nygård Clase‐Håkan , Saarni Lea , Rimpelä Arja
Published: September 2006

The first aim for this paper was to examine gender and age differences in the intensity of usage of information and communication technology (ICT: computer for digital playing, writing and e‐mailing and communication, and Internet surfing, and mobile phone). Second, we modelled the possible mediating role of sleeping habits and waking‐time tiredness in the association between ICT usage and perceived health (health complaints, musculoskeletal symptoms, health status). The participants were 7292 Finns aged 12, 14, 16 and 18 years responding to a postal enquiry (response rate 70%). The results showed that boys played digital games and used Internet more often than girls, whose mobile phone usage was more intensive. Structural equation model analyses substantiated the mediating hypothesis: intensive ICT‐usage was associated with poor perceived health particularly or only when it negatively affected sleeping habits, which in turn was associated with increased waking‐time tiredness. The associations were gender‐specific especially among older adolescents (16‐ and 18‐year olds). Intensive computer usage forms a risk for boys’, and intensive mobile phone usage for girls’ perceived health through the mediating links. Girls were vulnerable to the negative consequences of intensive mobile phone usage, as it associated with perceived health complaints and musculoskeletal symptoms both directly and through deteriorated sleep and increased waking‐time tiredness. The results of gender‐specific ICT usage and vulnerability are discussed as reflecting gendered psychophysiological, psychological and social developmental demands.
Rational selection of small molecules that increase transcription through the GAA repeats found in Friedreich's ataxia
Authors: Grant LaKechia , Sun Jun , Xu Hongzhi , Subramony S.H. , Chaires Jonathan B. , Hebert Michael D.
Published: September 2006

Friedreich's ataxia (FRDA) is an autosomal recessive trinucleotide repeat disease with no effective therapy. Expanded GAA repeats in the first intron of the FRDA gene are thought to form unusual non‐B DNA conformations that decrease transcription and subsequently reduce levels of the encoded protein, frataxin. Frataxin plays a crucial role in iron metabolism and detoxification. To discover small molecules that increase transcription through the GAA repeat region in FRDA, we have made stable cell lines containing a portion of expanded intron 1 fused to a GFP reporter. Small molecules identified using the competition dialysis method were found to increase FRDA‐intron 1‐reporter gene expression. One of these compounds, pentamidine, increases frataxin levels in patient cells. Thus our approach can be used to detect small molecules of potential therapeutic value in FRDA.
WFS1 protein modulates the free Ca2+ concentration in the endoplasmic reticulum
Authors: Takei Daisuke , Ishihara Hisamitsu , Yamaguchi Suguru , Yamada Takahiro , Tamura Akira , Katagiri Hideki , Maruyama Yoshio , Oka Yoshitomo
Published: September 2006

The WFS1 gene, encoding an endoplasmic reticulum (ER) membrane glycoprotein, is mutated in Wolfram syndrome characterized by diabetes mellitus and optic atrophy. Herein, Ca2+ dynamics were examined in WFS1‐knockdown and ‐overexpressing HEK293 cells. Studies using ER‐targeted Ca2+‐sensitive photoprotein aequorin demonstrated WFS1 protein to positively modulate ER Ca2+ levels by increasing the rate of Ca2+ uptake. Furthermore, Ca2+ imaging with Fura‐2 showed the magnitude of the store‐operated Ca2+ entry to parallel WFS1 expression levels. These data indicate that WFS1 protein participates in the regulation of cellular Ca2+ homeostasis, at least partly, by modulating the filling state of the ER Ca2+ store.
Muscle atrophy in transgenic mice expressing a human TSC1 transgene
Authors: Wan Min , Wu Xiaohui , Guan Kun-Liang , Han Min , Zhuang Yuan , Xu Tian
Published: September 2006

Muscle mass is regulated by a wide range of hormonal and nutritional signals, such as insulin and IGF. Tuberous sclerosis complex (TSC) is an inherited hamartoma disease with tumor growth in numerous organs. TSC is caused by mutation in either TSC1 or TSC2 tumor suppressor genes that negatively regulate insulin‐induced S6K activation and cell growth. Here we report that expression of human TSC1 (hTSC1) in mouse skeletal muscle leads to reduction of muscle mass. Expression of hTSC1 stabilizes endogenous TSC2 and leads to inhibition of the mTOR signaling. The hTSC1‐mTSC2 hetero‐complex and its downstream components remain sensitive to insulin stimulation and nutrition signals. This study suggests that an increase in the steady state level of resident TSC1–TSC2 complex is sufficient to reduce muscle mass and cause atrophy.
Modulation of LRP6‐mediated Wnt signaling by molecular chaperone Mesd
Authors: Li Yonghe , Lu Wenyan , He Xi , Bu Guojun
Published: September 2006

LRP6 is a Wnt coreceptor at the cell surface. Here, we report that a specialized molecular chaperone Mesd modulates LRP6‐mediated Wnt signaling and how different LRP6 mutants exhibit differential effects on Wnt signaling. We found that overexpression of increasing amounts of the full‐length LRP6 enhances Wnt signaling in a dose dependent manner only in the presence of a co‐expression of the molecular chaperone Mesd, which promotes LRP6 folding and maturation to the cell surface. We also demonstrated that LRP6 mutant lacking the intracellular domain impedes LRP6 cell surface expression and Wnt signaling in a dominant‐negative fashion by sequestering Mesd from promoting LRP6 folding. Our results present novel mechanisms by which Mesd and LRP6 modulate Wnt signaling.
Differential protein distributions define two sub‐compartments of the mitochondrial inner membrane in yeast
Authors: Wurm Christian A. , Jakobs Stefan
Published: September 2006

The mitochondrial inner membrane exhibits a complex topology. Its infolds, the cristae membranes, are contiguous with the inner boundary membrane (IBM), which runs parallel to the outer membrane. Using live cells co‐expressing functional fluorescent fusion proteins, we report on the distribution of inner membrane proteins in budding yeast. To this end we introduce the enlarged mitochondria of Δmdm10, Δmdm31, Δmdm32, and Δmmm1 cells as a versatile model system to study sub‐mitochondrial protein localizations. Proteins of the F1F0 ATP synthase and of the respiratory chain complexes III and IV were visualized in the cristae‐containing interior of the mitochondria. In contrast, proteins of the TIM23 complex and of the presequence translocase‐associated motor were strongly enriched at the IBM. The different protein distributions shown here demonstrate that the cristae membranes and the IBM are functionally distinct sub‐compartments.