bluuebunny/crossref_metadata_2025 huggingface dataset:
Qualifying Proppant Performance
Authors: Freeman E. R. , Anschutz D. A. , Renkes J. J. , Milton-Tayler David
Published: March 2009

Qualifying proppant performance of the delivered proppant before a frac job, or verifying proppant performance after a frac job, can add significant value to propped-fracture stimulations. Current field-testing protocol typically ensures that a proppant meets certain criteria with a simple yes or no answer. Seldom are strict collection and testing guidelines followed, as outlined by the American Petroleum Institute (API) and the International Organi-zation for Standardization (ISO). Qualifying proppant performance requires taking quality control a step further by considering the role that proppant characteristics play in the performance of proppant in the fracture. Applying a blend of established practices and new technology, quality-control data can be generated at the wellsite for comparison with the public domain (literature, websites, or fracturing simulators). These scientific data give an engineer insight into how delivered proppants are designed to perform and whether they do so. This eliminates the need to run expensive and time-consuming conductivity and permeability tests on every job. However, because proppant flow capacity or conductivity is a key measure of performance, some empirical results have been assimilated for wellsite and public data. Any differences in delivered proppant performance can be attributed to mining anomalies, manufacturing defects, transportation abuse, and/or contamination.

This paper also introduces new patent-pending technology that enables wellsite-proppant sampling and evaluation before the fracturing treatment. Having prefrac data gives one the opportunity to make any necessary changes in fracture design and implementation to get the most from available proppant. It also provides for a detailed inspection of the wellsite-delivered prop-pant supply. For instance, one can isolate and sample each pneumatic trailer and monitor associated pneumatic discharge pressures. Case histories, onshore and offshore, support qualifying proppant performance.
Friction Loss of Fracturing Fluids
Authors: Bundrant C.O. , Matthews Thomas A.
Published: March 2009

Introduction

For many years thickened fluids have been used in fracturing work. These fluids have included heavy oils, gels, and emulsions. It has long been recognized that it would be desirable to know the pressure losses due to friction while pumping, in order that the formation injection pressure could be known. Heretofore, all attempts to calculate pressure drop of emulsions and gels by standard engineering formulas have resulted in failure. The reason for this is that the apparent viscosity of gels and emulsions falls off sharply with an increase in shear rate [pumping rate], so that calculations based on laboratory viscosities usually give unrealistically high friction losses.

The relationship between shear rate and viscosity has been thoroughly investigated in this paper. The gels and emulsions used in oil well fracturing were found to fall into a general class of fluids known as pseudoplastics. The name is derived from the property of these fluids to exhibit plastic flow at low rates of shear, yet behave as low-viscosity liquids at high rates of flow. These gels and emulsions will be referred to as pseudoplastics in this paper.

General Correlation

The pseudoplastic properties of these gels and emulsions can be characterized in the laboratory by a log-log plot of measured viscosity vs. shear rate. In this case, measured viscosity is that obtained on the Brookfield viscometer, and shear rate is represented by spindle rpm. This data is shown plotted in Graph 1 and in Table 1.
Human-Factors Implications of Remote Drilling Operations: A Case Study From the North Sea
Authors: Lauche K. , Sawaryn S. J. , Thorogood J. L.
Published: March 2009

Improved capabilities for real-time data transfer have given rise to remote monitoring and support for drilling operations, providing faster access to information onshore and reducing personnel on board (POB) and cost. The challenge lies not so much with the technical feasibility but with the impact on work processes, which is still poorly understood. This paper presents a case study of the human-factors implications of onshore operation centers (OOCs) in the North Sea. The authors first investigated work conducted in the Norwegian sector and then followed the implementation of a pilot OOC for the Andrew low-cost-drilling project in Aberdeen. All delivered wells successfully but addressed different strategic aims.

For the case study of the Andrew project, the sample comprised 13 semistructured interviews conducted over 3 months and a longitudinal-attitude study with 33 participants from the onshore drilling team, OOC staff, and drilling representatives from offshore. Results were content analyzed by a team of industrial psychologists. The findings show that remote operations in drilling produce effects similar to those of virtual teams and computer-mediated process control in other industries; the monitoring work in the OOC was deprived of some of the physical activity, sensory information, and informal interaction. Potentially, some of these tasks could be automated further, while more cross-trained staff would be required offshore. Different user groups responded differently to the OOC implementation. Onshore teams generally approved of the concept because the OOC helped to create more situation awareness and presented an ideal environment for collaborative decision making and learning. The offshore response was mixed, with strong support for its innovative potential, but also critical voices about system reliability, contractual concerns, and the impact on work/life balance.

OOCs can add value to drilling operations by enabling better-informed decisions, but the findings show that success depends on how well the introduction of organizational change is managed. The study provides evidence on how prospective users can be involved in the change process in this dispersed and fluctuating industry and which social and cognitive skills are important for effective collaboration in e-operations.
Evaluation of Factors Restricting Distribution of the Endangered Key Largo Woodrat
Authors: WINCHESTER CHRISTOPHER , CASTLEBERRY STEVEN B. , MENGAK MICHAEL T.
Published: March 2009

ABSTRACT  We examined a suite of models in an information theoretic framework to identify factors restricting presence of the endangered Key Largo woodrat (Neotoma floridana smalli) throughout its remaining habitat. Models containing variables related to availability of nest sites and mammalian predator abundances were supported by our data. Abundance of natural (large overstory trees) and artificial (rock and debris piles) nest substrate were the most important predictor variables, followed by indices of feral cat and raccoon (Procyon lotor) abundance. We recommend increasing abundance of nest substrate in the short term through addition of artificial nest substrate and in the long term through continued protection of remaining forest habitat.
Crop, Native Vegetation, and Biofuels: Response of White‐Tailed Deer to Changing Management Priorities
Authors: WALTER W. DAVID , VERCAUTEREN KURT C. , GILSDORF JASON M. , HYGNSTROM SCOTT E.
Published: March 2009

ABSTRACT  The expansion of the cellulosic biofuels industry throughout the United States has broad‐scale implications for wildlife management on public and private lands. Knowledge is limited on the effects of reverting agriculture to native grass, and vice versa, on size of home range and habitat use of white‐tailed deer (Odocoileus virginianus). We followed 68 radiocollared female deer from 1991 through 2004 that were residents of DeSoto National Wildlife Refuge (DNWR) in eastern Nebraska, USA. The refuge was undergoing conversion of vegetation out of row‐crop agriculture and into native grass, forest, and emergent aquatic vegetation. Habitat in DNWR consisted of 30% crop in 1991 but removing crops to establish native grass and wetland habitat at DNWR resulted in a 44% reduction in crops by 2004. A decrease in the amount of crops on DNWR contributed to a decline in mean size of annual home range from 400 ha in 1991 to 200 ha in 2005 but percentage of crops in home ranges increased from 21% to 29%. Mean overlap for individuals was 77% between consecutive annual home ranges across 8 years, regardless of crop availability. Conversion of crop to native habitat will not likely result in home range abandonment but may impact disease transmission by increasing rates of contact between deer social groups that occupy adjacent areas. Future research on condition indices or changes in population parameters (e.g., recruitment) could be incorporated into the study design to assess impacts of habitat conversion for biofuel production.
Subprime Mortgages, Foreclosures, and Urban Neighborhoods
Authors: Gerardi Kristopher , Willen Paul
Published: March 2009

This paper analyzes the impact of the subprime crisis on urban neighborhoods in Massachusetts. The topic is explored using a dataset that matches race and income information from HMDA data with property-level transaction data from Massachusetts Registry of Deeds offices. With this data, we show that much of the subprime lending in the state was concentrated in urban neighborhoods, and that minority homeownerships created with subprime mortgages have proven exceptionally unstable in the face of rapid price declines. The evidence, in Massachusetts, suggests that subprime lending did not, as is commonly believed, lead to a substantial increase in homeownership by minorities, but instead generated turnover in properties owned by minority residents. Furthermore, we argue that the particularly dire foreclosure situation in urban neighborhoods actually makes it somewhat easier for policymakers to provide remedies.
Proportion and characteristics of patients who measure their blood pressure at home: Nationwide survey in Slovenia
Authors: Petek-Ster Marija , Svab Igor , Klancic Dean
Published: March 2009

Introduction. Home blood pressure monitoring has several advantages over blood pressure monitoring at a physician's office, and has become a useful instrument in the management of hypertension. Objective. To explore the rate and characteristics of patients who measure their blood pressure at home. Methods. A sample of 2,752 patients with diagnosis of essential arterial hypertension was selected from 12596 consecutive office visitors. Data of 2,639 patients was appropriate for analysis. The data concerning home blood pressure measurement and patients' characteristics were obtained from the patients' case histories. Results 1,835 (69.5%) out of 2,639 patients measured their blood pressure at home. 1,284 (70.0%) of home blood pressure patients had their own blood pressure measurement device. There were some important differences between these two groups: home blood pressure patients were more frequently male, of younger age, better educated, from urban area, mostly non-smokers, more likely to have diabetes mellitus and ischemic heart disease and had higher number of co-morbidities and were on other drugs beside antihypertensive medication. Using the logistic regression analysis we found that the most powerful predictors of home blood pressure monitoring had higher education level than primary school OR=1.80 (95% CI 1.37-2.37), non-smoking OR=2.16 (95% CI 1.40-3.33) and having a physician in urban area OR=1.32 (95% CI 1.02-1.71). Conclusion. Home blood pressure monitoring is popular in Slovenia. Patients who measured blood pressure at home were different from patients who did not. Younger age, higher education, non-smoking, having a physician in urban area and longer duration of hypertension were predictors of home blood pressure monitoring.
Meconium Aspiration in the Midtrimester Fetus: An Autopsy Study
Authors: Mortensen Elin , Kearney Michael Shelley
Published: March 2009

We studied the incidence, severity, and significance of intrauterine meconium aspiration (IUMA) in the midtrimester fetus. Lung sections from 219 midtrimester fetuses were examined for meconium, identified by finding meconium corpuscles. There were 21 cases (9.6%) with IUMA. Gestational age ranged from 13 to 23 weeks (mean 18.7 weeks); 11 were female, and 10 were male. Eighteen were spontaneous abortions, 11 of which were macerated, and 1 of these was associated with an intrauterine contraceptive device. There were 3 terminations of pregnancy, 2 for fetal abnormality and 1 for severe preeclampsia. One fetus was conceived by in vitro fertilization. Fifteen cases (71.4%) showed slight IUMA, 5 cases (23.8%) showed moderate IUMA, and in 1 case (4.8%) IUMA was massive. The incidence of IUMA in an autopsy series of midtrimester fetuses was 9.6%. The amount of aspirated meconium was usually small and possibly physiologic. When IUMA was moderate or massive, it was associated with severe abnormality of the umbilical cord or placenta, particularly subchorionic hematoma.
Histologic Resolution of Pulmonary Interstitial Glycogenosis
Authors: Deutsch Gail H. , Young Lisa R.
Published: March 2009

Pulmonary interstitial glycogenosis (PIG) is an enigmatic lung disorder of unknown etiology that presents with neonatal respiratory distress. Despite its dramatic clinical presentation, the diagnosis of PIG has a favorable prognosis with rare mortality in the absence of comorbid conditions. In this report, we describe changes in successive lung biopsies in a neonate who presented with respiratory failure and pulmonary hypertension. Diagnostic lung biopsy at 10 days of age exhibited classic histologic and ultrastructural findings of PIG with diffuse expansion of the alveolar interstitium by glycogenated mesenchymal cells. Subsequent to the patient's clinical improvement, a repeat biopsy at 49 days of age showed significant resolution of the disorder. Colocalization of vimentin-immunopositive cells with both phospho-histone H3 and cleaved caspase-3 demonstrated prominent attenuation of mesenchymal cell proliferation and apoptosis in the second biopsy. Although the self-limited nature of PIG has been described clinically, it has never been documented histologically. We present this case to illustrate the clinical and pathologic resolution of the disorder and speculate that the lesional mesenchymal cells may have transient proliferative capacity.
Multilevel Modeling: A Review of Methodological Issues and Applications
Authors: Dedrick Robert F. , Ferron John M. , Hess Melinda R. , Hogarty Kristine Y. , Kromrey Jeffrey D. , Lang Thomas R. , Niles John D. , Lee Reginald S.
Published: March 2009

This study analyzed the reporting of multilevel modeling applications of a sample of 99 articles from 13 peer-reviewed journals in education and the social sciences. A checklist, derived from the methodological literature on multilevel modeling and focusing on the issues of model development and specification, data considerations, estimation, and inference, was used to analyze the articles. The most common applications were two-level models where individuals were nested within contexts. Most studies were non-experimental and used nonprobability samples. The amount of data at each level varied widely across studies, as did the number of models examined. Analyses of reporting practices indicated some clear problems, with many articles not reporting enough information for a reader to critique the reported analyses. For example, in many articles, one could not determine how many models were estimated, what covariance structure was assumed, what type of centering if any was used, whether the data were consistent with assumptions, whether outliers were present, or how the models were estimated. Guidelines for researchers reporting multilevel analyses are provided.
The Effectiveness of Volunteer Tutoring Programs for Elementary and Middle School Students: A Meta-Analysis
Authors: Ritter Gary W. , Barnett Joshua H. , Denny George S. , Albin Ginger R.
Published: March 2009

This meta-analysis assesses the effectiveness of volunteer tutoring programs for improving the academic skills of students enrolled in public schools Grades K–8 in the United States and further investigates for whom and under what conditions tutoring can be effective. The authors found 21 studies (with 28 different study cohorts in those studies) reporting on randomized field trials to guide them in assessing the effectiveness of volunteer tutoring programs. Overall, the authors found volunteer tutoring has a positive effect on student achievement. With respect to particular subskills, students who work with volunteer tutors are likely to earn higher scores on assessments related to letters and words, oral fluency, and writing as compared to their peers who are not tutored.
A Review of the Racial Identity Development of African American Adolescents: The Role of Education
Authors: DeCuir-Gunby Jessica T.
Published: March 2009

The purpose of this article is to provide a review and etiology of research on racial identity development of African American adolescents in the field of education. This review explores the Black racial identity (BRI) literature, focusing on how BRI has been examined. In particular, the review concentrates on the literature’s use of surveying instruments, the instruments’ psychometric evidence, and the instruments’ use in education. This article ends with a discussion of BRI research, offering implications for adolescents in education and future directions for research.
Models of Cognition for Students With Significant Cognitive Disabilities: Implications for Assessment
Authors: Kleinert Harold L. , Browder Diane M. , Towles-Reeves Elizabeth A.
Published: March 2009

This article addresses the application of the assessment triangle developed by the National Research Council ( Pellegrino, Chudowsky, & Glaser, 2001 ), most specifically the cognition vertex of that triangle, to the unique learning characteristics of students with significant cognitive disabilities in developing and demonstrating academic competence. Given the inclusion of all students, including students with significant cognitive disabilities, in measures of large-scale educational assessment and accountability under the No Child Left Behind Act, it is essential to examine how the primary elements of knowledge representation and competence identified by Pellegrino et al. for all students have special ramifications for students with significant cognitive disabilities. It is only in the development of such a model of competence that it is possible to construct alternate assessments for these students that validly represent what these students know and can do.
The Work of Multicultural Teacher Education: Reconceptualizing White Teacher Candidates as Learners
Authors: Lowenstein Karen L.
Published: March 2009

This article explores and challenges a widely held and often unexamined conception of White teacher candidates as learners about issues of diversity and equity in teacher education. This conception suggests that most White teacher candidates are deficient learners who lack resources for learning about diversity. This review reframes this conception through an examination of three bigger pictures of White teacher candidates, of the lack of research regarding pedagogies for multicultural teacher education, and of insights from those who describe pedagogies that build on what students bring. Ultimately, if teacher educators hope that teacher candidates view their future K–12 students as having resources and capabilities for learning, then teacher educators must critically examine and dialogue about what they model through their own pedagogies.
Advancements in Research Synthesis Methods: From a Methodologically Inclusive Perspective
Authors: Suri Harsh , Clarke David
Published: March 2009

The dominant literature on research synthesis methods has positivist and neo-positivist origins. In recent years, the landscape of research synthesis methods has changed rapidly to become inclusive. This article highlights methodologically inclusive advancements in research synthesis methods. Attention is drawn to insights from interpretive, critical, and participatory traditions for enhancing trustworthiness, utility, and/or emancipatory potential for research syntheses. Also noted is a paucity of the literature that builds connections between methodologically diverse segments of the literature on research synthesis methods. Salient features of a methodologically inclusive research synthesis (MIRS) framework are described. The MIRS framework has been conceptualized by distilling and synthesizing ideas, theories, and strategies from the extensive literatures on research synthesis methods and primary research methods. Rather than prescribe how a research synthesis should be conducted or evaluated, this article attempts to open spaces, raise questions, explore possibilities, and contest taken-for-granted practices.
Correlation Between Static Foot Type Measurements and Clinical Assessments
Authors: Chuckpaiwong Bavornrit , Nunley James A. , Queen Robin M.
Published: March 2009

Background: An accurate and consistent differentiation of foot type is needed to assess appropriate treatments and to examine potential risk factors for acute and overuse injuries. Materials and Methods: One hundred forty-seven members of the American Orthopaedic Foot and Ankle Society were asked to complete a questionnaire related to clinical assessments of foot type and to examine 30 photographs of healthy feet taken on the mirrored foot photo box (MFPB). Responders were asked to categorize each image into one of five categories (pes planus, low arch, normal, high arch, and pes cavus). Different static measurements were obtained from each image. Pearson correlations were calculated between the static foot measures and the clinical grade. Significantly correlated parameters were analyzed via regression analysis. Results: Clinical assessment was reported to be the most important tool in defining foot type (69.9%) followed by standing radiographs and foot print measurements. Clinicians stated that arch height (56.2%) was the most used physical characteristic, while the lateral talo-first metatarsal angle (64.4%) was the most used radiographic assessment. Foot measurements were correlated with the clinical grade ( r = 0.511 to 0.780). Regression analysis revealed that rearfoot angle, foot print index and truncated arch index were significant predictors of clinically defined foot type. Rearfoot angle accounted for 78% of the variance in clinically assessed foot type. Conclusion: The results of this study indicate the need to measure multiple parameters to assess foot type. However, if only one parameter can be collected, it appears that rearfoot angle explains the majority of variance in the clinically assessed foot type.
Single Transverse, Dorsal Incision for Lesser Metatarsophalangeal Exposure
Authors: Dalal Rakesh , Mahajan Ravindra H.
Published: March 2009

Background: The exposure of the lesser metatarsophalangeal joints is often difficult and inadequate in the presence of rheumatoid arthritis and associated deformities. We describe our results following the use of a single curved transverse, dorsal incision for the Mann-Thompson type of forefoot arthroplasty, 5 , 9 multiple Weil osteotomies, 1 , 2 , 7 , 11 and other forefoot procedures. Materials and Methods: One hundred thirty-nine consecutive patients (163 feet) were included in the study. Wound healing, and patient and surgeon satisfaction were assessed. Results: Ease of exposure and visualization of the target area was good-to-excellent in all patients. There were eight minor wound complications. There were no neurovascular complications. Conclusion: A single transverse incision offers adequate exposure of lesser metatarsophalangeal joints and good cosmesis.

Level of Evidence: IV, Case Series
Accuracy of Ultrasound Guided Injections in the Foot and Ankle
Authors: Reach John S. , Easley Mark E. , Chuckpaiwong Bavornrit , Nunley James A.
Published: March 2009

Background: Ultrasonography is an emerging imaging modality which affords dynamic, real-time, cost-effective and surgeon controlled visualization of the foot and ankle. The purpose of this study was to evaluate the accuracy of ultrasound guided injections for common injection sites in the foot and ankle. Materials and Methods: In 10 fresh cadaver feet, ultrasound guidance was utilized to inject a methylene blue-saline mixture into (1) the first MTP joint, (2) the second MTP joint, (3) the tibiotalar joint, (4) the Achilles peritendinous space, (5) the flexor hallucis longus sheath, (6) the posterior tibial tendon sheath, and (7) the subtalar joint. Dissection was then undertaken to assess injection accuracy. Results: Ultrasound guidance allowed the avoidance of intervening neurovascular and tendinous structures. Ultrasound guided MTP, ankle, Achilles, PTT and FHL peritendinous injections were 100% accurate. Ultrasound guided subtalar injection was 90% accurate. Conclusion: Ultrasound appears to be a highly accurate method of localizing injections into a variety of locations in the foot and ankle. Clinical Relevance: Ultrasound's ability to display soft-tissue structures may be an advantage over blind injection and fluoroscopic injection techniques.
Biomechanical Evaluation of Plate Osteosynthesis of Distal Fibula Fractures with Biodegradable Devices
Authors: Klos Kajetan , Sauer Stefanie , Hoffmeier Konrad , Gras Florian , Fröber Rosemarie , Hofmann Gunther O. , Mückley Thomas
Published: March 2009

Background: This study compared fixation with a titanium one-third tubular plate and one lag-screw vs. fixation with biodegradable plates with one lag-screw applied with two different plate-screw patterns. Materials and Methods: Ten pairs of fibulas were osteotomied, plated (titanium plate with one lag screw vs. absorbable 2/8 plate-screws crossing vs. 0/8 plate-screws crossing the osteotomy gap). and tested in torsion and bending to obtain stiffness and neutral-zone (NZ) data. Tests were performed using 5 load cycles. No load to failure was performed. Biodegradation was simulated by 6 week immersion in phosphate-buffered saline after which the testing protocol was repeated. The specimens were then loaded with 100 N in bending. Results: Post-implantation, there were no significant differences, in torsion and bending, regarding the NZ or the stiffness, between the 2/8 biodegradable plate and the titanium plate. The 0/8 pattern performed significantly less well in terms of stiffness and NZ in the initial torsion test, and significantly less well in terms of stiffness in the initial bending test. After 6 weeks’ immersion, all biodegradable constructs showed a significantly larger NZ and significantly reduced bending and torsional stiffness. When loaded with 100 N, four of the six 0/8 osteosyntheses failed. There were no significant differences between the 2/8 pattern and the titanium plates. Conclusion: In a model of a Weber-B fracture, the use of a 2/8 biodegradable plate construct initially did not differ statistically to that obtained with a one-third tubular titanium plate. After immersion the 2/8 construct withstood some physiological load. Clinical Relevance: For the fixation of ankle fractures with a biodegradable plate of the type employed in this study, the use of fracture-gap-crossing screws is recommended.
Open Midfoot Blast Trauma Treated with Ring External Fixation: Case Report
Authors: Keeling John J. , Beer Robert , Forsberg Jonathan A. , Andersen Romney C. , Mazurek Michael T. , Shawen Scott B.
Published: March 2009

Level of Evidence: V, Case Report
Narratives of Emergence:Jean Paul on the Inner Life
Authors: Coker William N.
Published: March 2009

Poetry is the only peace-goddess of the earth and of the angels, who leads us, and if only for a matter of hours, out of prisons and onto stars.—Jean Paul, Pre-School of Aesthetics [Vorschule der Ästhetik] (1804) 1
Mechanical anisotropy and ideal strength in a multifunctional Ti–Nb–Ta–Zr–O alloy (Gum Metal)
Authors: Hara Masashi , Shimizu Yusuke , Yano Takeshi , Takesue Naohisa , Furuta Tadahiko , Kuramoto Shigeru
Published: March 2009

An ideal shear strength of Gum Metal, a newly developed set of beta-type titanium alloys with the nominal composition Ti-24(Nb + V + Ta) – (Zr, Hf) – O (at.%) believed to deform without motion of crystal dislocations, has been investigated experimentally for precise determination. Tensile tests of single crystals of Gum Metal along the <100>, <110>, and <111> directions showed that the Young' moduli were 40, 60, and 86 GPa, respectively. The elastic constants were estimated as c11 – c12 = 25 – 27 GPa and c44 = 29 – 36 GPa. In terms of these values, the anisotropy factor and the ideal strength were evaluated as 2.3 – 2.6 and 1.7 – 1.9 GPa, respectively. It was found that a ratio of the actual ultimate tensile strength to the ideal strength for Gum Metal was much higher than for other bcc metals.
Directional crystallisation of Ti–Al–Si in-situ composites
Authors: Kopeček Jaromír , Novák Michal , Vojtěch Dalibor , Lejček Pavel
Published: March 2009

The study of unidirectional crystallisation of a Ti-19Al-11Si (at.%) alloy by the floating zone method with optical heating is described. While the homogeneous eutectic composites with rod-shaped Ti5Si3 precipitates grow at a rate of 5 mm · h– 1, an inhomogeneous structure of the composite with primarily crystallised Ti5Si3 silicides was obtained at the rate of 18.8 mm · h– 1. The cracking of the reinforcing Ti5Si3 silicides is followed by cracking of the Ti3Al matrix phase due to a large difference between the coefficients of thermal expansion of both phases.
Low-cycle fatigue properties of TiAl alloy with high Nb content
Authors: Kruml Tomáš , Obrtlík Karel , Petrenec Martin , Polák Jaroslav
Published: March 2009

The low-cycle fatigue properties of TiAl alloy with 8 at.% of Nb with nearly fully lamellar microstructure were studied at room temperature and 750 °C and compared with those reported in literature for a previous class of TiAl alloys with 2 at.% of Nb. Hardening/softening curves, cyclic stress – strain curves (CSSC) and fatigue life curves were obtained at both temperatures. The material shows stable cyclic stress – strain response. Parameters of the CSSC, of the Manson – Coffin law and of the Basquin law were determined. Bilinear dependence is used to approximate the Manson – Coffin plot and the Basquin plot at 750 °C.
Structural and phase transformations in Zr and Zr–Nb alloys under loading by spherical converging stress waves
Authors: Taluts Nina , Dobromyslov Arkadiy , Kozlov Evgeniy
Published: March 2009

X-ray diffraction, optical and transmission electron microscopy, and measurement of microhardness were used to study zirconium and Zr – Nb alloys loaded by spherical converging stress waves of different intensity. It is revealed that the phase and structural states of the specimens depend on the loading intensity, the niobium content and the depth of the layer in the sphere. The ω-phase (high pressure phase) is retained in a metastable state only after low-intensity loading, and the quantity of the ω-phase increases with increase in niobium content in the alloy. The ω-phase is not retained after high-intensity loading because of high remaining temperatures. It was established that various defects (deformation twins, dislocations, adiabatic shear bands, regions of unstable plastic flow and cracks) are produced during loading.
Energetic formulation of nonlocal crystal plasticity
Authors: Kratochvíl Jan , Kružík Martin , Sedláčček Radan
Published: March 2009

We review an energetic solution to a problem of the rate-independent evolution of elasto-plastic materials subjected to external loads in the framework of large deformations and multiplicative plasticity. Our model includes gradients of the plastic strain and of hardening variables.
The influence of dispersoids on the recrystallization of aluminium alloys
Authors: Poková Michaela , Cieslar Miroslav , Slámová Margarita
Published: March 2009

The influence of dispersoids on the softening processes in twin-roll cast and cold-rolled Al – Fe – Mn – Si aluminium alloy was studied. Before rolling, the specimens were thermo-mechanically pre-treated in order to create a different second-phase dispersion. The influence of the initial microstructure was studied by means of electrical resistivity, light and electron microscopy. The evolution of softening was monitored by microhardness measurements. The depletion of the Al matrix from solutes connected with formation of a dense dispersion of precipitates results in the enhancement of (sub)grain-boundary mobility. As a consequence, full recrystallization occurs at lower temperatures in pre-annealed specimens with low solute concentrations. The presence of coarser precipitates formed during the pre-treatment results in the formation of a fine-grained microstructure.
Microstructural investigation of the failure mechanisms after creep exposure of Mg–Y–Nd–Zn–Mn alloy
Authors: Janík Vít , Hnilica František , Smola Bohumil , Stulíková Ivana , Očenášek Vladivoj
Published: March 2009

Tensile creep tests of squeeze-cast Mg-3Y-2Nd-1Zn-1Mn (wt.%) magnesium alloy were performed at constant load. Measurement of grain-boundary sliding by observation of the offset of marker lines was carried out. The role of mutual orientation of neighbor dendrites and possible influence of active slip systems inside dendrites on the cavity nucleation was investigated by electron backscatter diffraction.

Experimental results show that creep failure in this alloy takes place by continuous nucleation, growth, and coalescence of cavities on dendritic boundaries. A nucleation mechanism involving stress concentrations due to slip inside the grains is not probable. Additionally, although the total extent of deformation due to grain boundary sliding is small, the contribution of sliding to the origin of required stress concentrations necessary for cavity nucleation cannot be excluded.
Changes in structure and properties of carbide-steel cermets resulted from a heat treatment
Authors: Frage Naum R. , Dariel Moshe P. , Kaputkina Liudmila M. , Prokoshkina Vera G. , Kaputkin Dmitry E. , Sverdlova Natalja R.
Published: March 2009

Cermets were produced by a technology including pressing and sintering of titanium carbide TiCx (0.7 < × < 0.98) preforms and molten tool steel infiltration. So-called “graded” cermets were produced using a controlled distribution of TiCx with different x. The resultant redistribution of alloying elements between the steel and TiCx during both the infiltration and following heat treatment was very essential. The changes of both steel and TiCx compositions produce changes in the process of austenitization, carbide dissolution and precipitation, and martensitic transformation. Both the strength of the material and the gradient of properties in graded cermets can be controlled using both kinetic factors of element redistribution and structure changes caused by the heat treatment.
Rapid techniques for determining annual accumulation applied at Summit, Greenland
Authors: Hawley Robert L. , Morris Elizabeth M. , McConnell Joseph R.
Published: March 2009

We have determined accumulation histories by identifying annual-layer horizons in records obtained by three independent methods: (1) glaciochemical analysis on a core, (2) density profiling in the borehole from which the core was taken, using the neutron-probe (NP) technique, and (3) borehole optical stratigraphy (BOS), again in the same borehole. We also used three different techniques for determining density to convert annual-layer thickness to accumulation: (1) gravimetric measurements on core samples, (2) measurement of density using NP and (3) a simple empirical model based on regional climatology. The result is nine different accumulation time series, three of which are completely independent. The chemical-analysis- and NP-derived accumulation time series are correlated, and the ∼70 year means are in agreement. The BOS-derived accumulation ∼70 year mean is slightly lower, probably due to a combination of the empirical density model’s underestimate of the density profile and the misidentification of sub-annual events in the shallow part of the borehole as annual horizons.
The transfer of mass-balance profiles to unmeasured glaciers
Authors: Kuhn Michael , Abermann Jakob , Bacher Michael , Olefs Marc
Published: March 2009

For estimation of the mass balance of an unmeasured glacier, its area distribution with altitude, s (h), generally is the only available quantitative information. The appropriate specific balance profile, b (h), needs to be transferred from a measured glacier, where transfer means modification and adaptation to the topographic and climatic situation of the unmeasured glacier, such as altitude, exposure to sun and wind, or temperature. This study proposes the area median elevation, M, as a parameter of prime importance for the transfer. Using as an example ten Alpine glaciers, the similarity of M and equilibrium-line altitude is quantified and the effect of aspect and surrounding topography is qualitatively suggested. The transfer of b (h) between well-measured glaciers yielded differences in the mean specific balance of 150 mm in the mean of a 10 year period, which corresponds to a change in median altitude by 30 m. Transfer of b (h) with a shift according to median glacier elevation to a basin with 27 glaciers and 23 km2 ice cover agreed to within 10% with elevation changes converted from digital elevation models of 1969 and 1997.
Homogenization of long-term mass-balance time series
Authors: Huss Matthias , Bauder Andreas , Funk Martin
Published: March 2009

The re-analysis of long-term mass-balance time series is important to provide bias-corrected mass-balance data for climate-change impact studies. A method to homogenize time series of comprehensive mass-balance monitoring programmes is presented and applied to the nearly 50 year mass-balance records of Griesgletscher and Silvrettagletscher, Switzerland. Using a distributed mass-balance model in daily resolution we correct the mass-balance data for varying observation dates. Direct point measurements are combined with independent geodetic mass changes, a prerequisite for a thorough homogenization of mass-balance records. Differences between mass balance evaluated in the hydrological year or according to the measurement period and the stratigraphic system are analysed and may be up to ±0.5mw.e. a−1. Cumulative mass balance of both glaciers based on the glaciological method generally agrees well with geodetic mass change on the investigated glaciers. However, for Silvretta-gletscher a significant bias of +0.37mw.e. a−1 has been detected and corrected for since 1994.
Antarctic precipitation and climate-change predictions: horizontal resolution and margin vs plateau issues
Authors: Genthon C. , Krinner G. , Castebrunet H.
Published: March 2009

All climate models participating in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, as made available by the Program for Climate Model Diagnosis and Intercomparison (PCMDI) as the Coupled Model Intercomparison Project 3 (CMIP3) archive, predict a significant surface warming of Antarctica by the end of the 21st century under a moderate (SRESA1B) greenhouse-gas scenario. All models but one predict a concurrent precipitation increase but with a large scatter of results. The models with finer horizontal resolution tend to predict a larger precipitation increase. Because modeled Antarctic surface mass balance is known to be sensitive to horizontal resolution, extrapolating predictions from the different models with respect to model resolution may provide simple yet better multi-model estimates of Antarctic precipitation change than mere averaging or even more complex approaches. Using such extrapolation, a conservative estimate of the predicted precipitation increase at the end of the 21st century is +30 kg m–2 a–1 on the grounded ice sheet, corresponding to a >1m ma–1 sea-level rise. About three-quarters of this rise originates from the marginal regions of the Antarctic ice sheet with surface elevation below 2250 m. This is where field programs are most urgently needed to better understand and monitor accumulation at the surface of Antarctica, and to improve and verify prediction models.
The influence of drainage boundaries on specific mass-balance results: a case study of Engabreen, Norway
Authors: Elvehøy Hallgeir , Jackson Miriam , Andreassen Liss M.
Published: March 2009

Mass-balance measurements were initiated on Engabreen, an outlet glacier from the Svartisen ice cap, Norway, in 1970. The glacier boundary was defined based on where meltwater drained, as the interest in Engabreen was mainly hydrological. However, the apparent discrepancy between the calculated cumulative glacier mass balance since 1970 and changes in glacier geometry prompted a re-examination of the glacier boundary. The glaciological drainage boundary is defined by studying whether ice flow physically contributes to Engabreen tongue and corresponds to a glacier with an area of 27.2 km2, significantly smaller than that defined by the hydrological drainage boundary at 39.6 km2. This glaciological drainage boundary is here named the ice-flow perimeter. The area difference between this and the hydrological drainage boundary is largest for the altitudinal range 1300–1400ma.s.l. Generally, the ‘glaciological’ glacier is lower in mean altitude than the ‘hydrological’ glacier, and this affects the calculated specific mass balance. Using the glaciological boundary leads to reductions in mean annual winter and summer balance (when spatial differences are ignored) of 0.12 mw.e. (from 2.92 to 2.80mw.e.) and 0.15 mw.e. (from –2.32 to –2.47mw.e.), respectively. The reduction in mean net balance for the period 1970–2006 is 0.27mw.e. (from +0.59 to +0.32mw.e.) which is about 50% of the calculated mass surplus in this period. This illustrates that the choice of glacier outline can significantly influence the long-term cumulative mass balance and that results from outlet glaciers must be interpreted with care when used for regional estimates of glacier change.
Do climate models underestimate snow accumulation on the Antarctic plateau? A re-evaluation of/from in situ observations in East Wilkes and Victoria Lands
Authors: Genthon C. , Magand O. , Krinner G. , Fily M.
Published: March 2009

It has been suggested that meteorological and climate models underestimate snow accumulation on the Antarctic plateau, because accumulation (or surface mass balance (SMB)) is dominated by clear-sky precipitation while this process is not properly taken into account in the models. Here, we show that differences between model and field SMB data are much reduced when the in situ SMB reports used to evaluate the models are filtered through quality-control criteria and less reliable reports are subsequently left out. We thus argue that, although not necessarily unsupported, model biases and their interpretations in terms of clear-sky vs synoptic precipitation on the Antarctic plateau may have been overstated in the past. To avoid such misleading issues, it is important that in situ SMB reports of insufficient or unassessed reliability are discarded, even at the cost of a strong reduction in spatial sampling and coverage.
Ground-based interferometric radar for velocity and calving-rate measurements of the tidewater glacier at Kronebreen, Svalbard
Authors: Rolstad C. , Norland R.
Published: March 2009

This paper presents the first attempt to measure the calving rate and flow velocity of the front of a glacier using ground-based high-range resolution interferometric radar at a high temporal rate (2 Hz). The radar, operating at 5.75 GHz, is located ∽4 km from the calving front of Kronebreen, Svalbard. The radar measures a horizontal width of ∽700m of the front, and a range of 300 m. The latter includes the calving front and 250m up-glacier. We find that the glacier surface provides permanent scatterers, so spatially continuous movements at the front and at locations further up-glacier can be tracked. For ∽8 hours we measured a large increase in velocity at the calving front, which extended 30 m up-glacier, while further up-glacier the velocity was stable (∽2.5md–1) during the entire period. Two large calving events were identified during this survey, removing 25m of ice in the radar range direction normal to the ice front. The velocity of the front slowed to a stable 2.5md–1 after the events. During another data series the velocities were stable (∽2.5md–1) and no calving events were identified. The method is promising for carrying out studies of processes at a calving front, as it provides spatially continuous, high-frequency accurate velocities from a safe distance to the glacier.
Mass balance of Glaciar Zongo, Bolivia, between 1956 and 2006, using glaciological, hydrological and geodetic methods
Authors: Soruco A. , Vincent C. , Francou B. , Ribstein P. , Berger T. , Sicart J.E. , Wagnon P. , Arnaud Y. , Favier V. , Lejeune Y.
Published: March 2009

The longest continuous glaciological mass-balance time-series in the intertropical zone of South America goes back to 1991 on Glaciar Zongo, Bolivia. Photogrammetric and hydrological data have been used to (1) check the specific net balance over long periods and (2) extend the mass-balance time series over the last 50 years. These data reveal a bias in the glaciological mass balance which can be explained by the field-measurement sampling network. Our study shows a large temporal variability of the surface mass balances in the ablation area and reveals strong relationships between independent surface mass-balance data coming from selected ablation areas with numerous data. It demonstrates the very large contribution (80%) of low-elevation ranges (one-third of the surface) to the specific mass balance and, consequently, the importance of the reduction of the area of the tongue. With these new results, Glaciar Zongo offers the longest and most accurate mass-balance series in any Andean country. The dataset shows that Glaciar Zongo experienced a relatively steady state over the period 1956–75, with even a slight mass gain over 1963–75, and a rapid and continuous decrease since then.
Oviposition Preference of Callosobruchus maculatus (F.) to Common Pulses and Potentiality of Triflumuron as their Protectant
Authors: Islam M Saiful , Akhter Fauzia , Laz Rezina , Parween Selina
Published: March 2009

Seeds of black grams, lentils, Bengal grams and green peas were soaked separately in aqueous solutions of Triflumuron at doses of 0.0 (control), 0.5, 1.0, 1.5 and 2.0 ppm. Three day -old adults of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) were allowed to oviposit on air-dried, treated or untreated pulses of each type and dose in âno-choice' and âfree-choice' tests. Maximum oviposition occurred in Bengal grams (61.00? 0.25) and green peas (33.67? 0.54) in âno-choice' and âfree-choice' tests, respectively. The beetles avoided egg laying on lentils. Maximum egg-hatching occurred on black grams (>90%) in both tests. Minimum developmental time was required in the Bengal grams (30? 0.5 days in âno-choice' test and 31.33? 1.23 days in âfree-choice' test). No adults emerged from green peas, while 54.79% and 86.15% emergence were recorded from untreated black grams in âno-choice' and âfree-choice' tests, respectively. Triflumuron reduced egg-laying significantly in green peas, where hatchability also reduced significantly to 35.99% at 2 ppm in âno-choice' test. Percentage of hatching decreased in all pulses with the increasing doses of triflumuron. No adults emerged from the treated green peas in any test, and at 2 ppm the adult emergence declined to < 50% in all pulses. Implications of these results are further discussed. Â Key words: Callosobruchus maculatus, Triflumuron, seed protectant, fecundity, hatchability, developmental period, adult emergence Â  doi: 10.3329/jbs.v15i0.2207 J. bio-sci. 15: 83-88, 2007