bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk Management, Corporate Governance, and the Search for Long‐Term Investors
Authors: Bauguess Scott , Dunigan Jim , Park Damien , McGurn Patrick , Chew Don , Walkling Ralph
Published: December 2010

This discussion explores a number of ways that more effective risk management, corporate governance, and communication with investors can help companies increase their effciency and long‐run value.

According to one of the panelists, recent surveys of corporate directors suggest that companies should devote more time and attention to three issues—strategy, risk management, and succession planning—and that strategy and risk are the “flipsides of the same coin.” As the panelist argues, “You can't talk about strategy without talking about what risks you're going to take—and what risks you decide to take has to depend on the core competencies that drive the corporate strategy.”

In addition to making risk management a critical part of corporate strategy, another notable recommendation is to communicate a company's strategy and business plan as clearly as possible to investors, with the aim of attracting more sophisticated, long‐term shareholders. Contrary to popular belief, such a group may well include some hedge funds and other activist shareholders. According to a newly released report on shareholder activism (produced and cited by another panelist), corporate boards should work harder to identify and engage the “largest 10 shareholders in the organization,” with the ultimate goal of cultivating a shareholder base that buys into the company's strategy.
Should Asset Managers Hedge Their “Fees at Risk”?
Authors: Scherer Bernd
Published: December 2010

Although the recent financial crisis afflicted all asset managers, the problem of general market exposure was in some respects worse for the long‐only funds that rely almost completely on asset‐based fees than for the “absolute return” and other kinds of hedge funds that also receive performance‐based fees. While the revenue generated by performance‐based fees is expected to be volatile, asset‐based fees tend to be viewed as an “annuity” stream that involves little or no earnings risk. But, especially in the case of long‐only funds, large shortfalls in asset fees were caused by the combination of significant redemptions and sharp reductions in assets under management that accompanied the plunge in asset prices.

In this article, the author attempts to quantify the expected effect of market fluctuations on the asset fees and profitability of long‐only asset managers. Having done so, he then argues that traditional long‐only asset managers—managers whose only reason for being is their ability to generate above‐market returns (or “alpha”) on a fairly consistent basis—routinely retain too much beta risk in their primarily asset‐based fee structures.

The author offers two main reasons for long‐only asset managers to hedge beta risk: (1) it would reduce the need for fund management firms to hold liquid capital to ensure solvency and fund important projects during market downturns; (2) it would provide the firm's current and prospective clients with a clearer signal of whether its managers are succeeding in the firm's mission of generating alpha, as well as the possibility of more equity‐like and cost‐effective incentive compensation systems for those managers.
The Riks-Stroke Story: Building a Sustainable National Register for Quality Assessment of Stroke Care
Authors: Asplund Kjell , Hulter Åsberg Kerstin , Appelros Peter , Bjarne Daniela , Eriksson Marie , Johansson Åsa , Jonsson Fredrik , Norrving Bo , Stegmayr Birgitta , Terént Andreas , Wallin Sari , Wester Per-Olov
Published: December 2010

Background

Riks-Stroke, the Swedish Stroke Register, is the world's longest-running national stroke quality register (established in 1994) and includes all 76 hospitals in Sweden admitting acute stroke patients. The development and maintenance of this sustainable national register is described.

Methods

Riks-Stroke includes information on the quality of care during the acute phase, rehabilitation and secondary prevention of stroke, as well as data on community support. Riks-Stroke is unique among stroke quality registers in that patients are followed during the first year after stroke. The data collected describe processes, and medical and patient-reported outcome measurements. The register embraces most of the dimensions of health-care quality (evidence-based, safe, provided in time, distributed fairly and patient oriented).

Result

Annually, approximately 25 000 patients are included. In 2009, approximately 320 000 patients had been accumulated (mean age 76-years). The register is estimated to cover 82% of all stroke patients treated in Swedish hospitals. Among critical issues when building a national stroke quality register, the delicate balance between simplicity and comprehensiveness is emphasised. Future developments include direct transfer of data from digital medical records to Riks-Stroke and comprehensive strategies to use the information collected to rapidly implement new evidence-based techniques and to eliminate outdated methods in stroke care.

Conclusions

It is possible to establish a sustainable quality register for stroke at the national level covering all hospitals admitting acute stroke patients. Riks-Stroke is fulfilling its main goals to support continuous quality improvement of Swedish stroke services and serve as an instrument for following up national stroke guidelines.
Reperfusion and Outcomes in Penumbra Vs. Systemic Tissue Plasminogen Activator Clinical Trials
Authors: Alexandrov Andrei V. , Schellinger Peter D. , Saqqur Maher , Barreto Andrew , Demchuk Andrew M. , Ribo Marc , Rubiera Marta , Sharma Vijay K. , Heliopoulos Ioannis , Alexandrov Anne W. , Molina Carlos A. , Tsivgoulis Georgios ,   for the CLOTBUST and TUCSON Investigators
Published: December 2010

Background

An uncontrolled clinical study of the Penumbra™ system showed high rates of recanalisation and relatively poor functional outcomes that were inadequately compared with historic controls. We aimed to compare the findings in Penumbra with intravenous tissue plasminogen activator trials that determined recanalisation (Combined Lysis Of Thrombus in Brain ischaemia using transcranial Ultrasound and Systemic tissue plasminogen activator and Transcranial Ultrasound in Clinical Sonothrombolysis).

Methods

Control patients treated with intravenous tissue plasminogen activator and intermittent ultrasound surveillance had National Institutes of Health Stroke Scale scores >7. The Penumbra trial definition of symptomatic intracranial haemorrhage was used. Revascularisation was defined using thrombolysis in brain ischaemia scores predictive of thrombolysis in myocardial infarction flow grades and compared with thrombolysis in myocardial infarction data from Penumbra. Favourable functional outcomes was defined as a modified Rankin Scale of 0–2.

Results

Pretreatment stroke severity (National Institutes of Health Stroke Scale score) was 17·6 ± 5·2 points in Penumbra patients ( n=125) and 16·3 ± 5·3 in controls ( n=68; P=0·101). The control group was older compared with Penumbra (68·8 ± 13·4 vs. 63·5 ± 13·5-years; P=0·010). Time-to-treatment initiation was on average 2 h later (2·3 ± 0·6 vs. 4·3 ± 1·5 h; P<0·001) in Penumbra. The rate of any revascularisation after treatment with Penumbra was higher than that following intravenous thrombolysis: 82% (54% thrombolysis in myocardial infarction II and 27% thrombolysis in myocardial infarction III) vs. 40% (25% partial, 15% complete revascularisation), P<0·001. Symptomatic intracranial haemorrhage tended to be higher with Penumbra (11·2% vs. 4·4%; P=0·182, Fisher's exact test). At three-months, mortality with Penumbra was higher (32·8%) than controls (14·1%; P=0·006). Favourable functional outcomes were higher in historic controls (39% vs. 25%; P=0·046).

Conclusions

Despite lower revascularisation rates, patients treated with systemic thrombolysis achieved better functional outcomes likely due to earlier treatment initiation. These data indicate that it is unrealistic to expect primary intraarterial revascularisation to be any better than systemic plasminogen activator within the 3-h time window. Improvements in the speed of delivery and performance of intraarterial reperfusion are needed.
Alcoholic liver disease and exacerbation by malnutrition and infections: what animal models are currently available?
Authors: Bergheim Ina , Eagon Patricia K. , Dooley Steven , Breitkopf‐Heinlein Katja
Published: December 2010

Alcoholic liver disease remains a frequent and serious problem for increasing numbers of patients. Research has expanded our molecular understanding of the cellular basis of disease progression; however, translation into therapy is still hampered by a lack of suitable animal models for alcoholic liver disease, as well as from consequences of related liver damage due to malnutrition, hepatitis C virus infection, or abuse of other substances. Many patients with liver disease do not simply consume too much alcohol; they also suffer from comorbidities such as obesity or viral hepatitis, and/or may be addicted to other drugs besides alcohol. This review will summarize the currently available animal models to study liver disease due to either single causes or combinations of liver toxic substances/infections and alcohol.
Human category learning 2.0
Authors: Ashby F. Gregory , Maddox W. Todd
Published: December 2010

During the 1990s and early 2000s, cognitive neuroscience investigations of human category learning focused on the primary goal of showing that humans have multiple category‐learning systems and on the secondary goals of identifying key qualitative properties of each system and of roughly mapping out the neural networks that mediate each system. Many researchers now accept the strength of the evidence supporting multiple systems, and as a result, during the past few years, work has begun on the second generation of research questions—that is, on questions that begin with the assumption that humans have multiple category‐learning systems. This article reviews much of this second generation of research. Topics covered include (1) How do the various systems interact? (2) Are there different neural systems for categorization and category representation? (3) How does automaticity develop in each system? and (4) Exactly how does each system learn?
Photoreduction and Ketone‐sensitized Reduction of Alkaloids
Authors: Görner Helmut , Miskolczy Zsombor , Megyesi Mónika , Biczók László
Published: December 2010

The photoprocesses of berberine, palmatine, coralyne, sanguinarine, flavopereirine and ellipticine were studied in several solvents. The quantum yields ΦΔ of singlet molecular oxygen formation of berberine, palmatine and sanguinarine are moderate in dichloromethane (0.2–0.6) and much smaller in acetonitrile or trifluoroethanol. For the other alkaloids examined, ΦΔ is rather independent of solvent polarity. The direct and ketone‐sensitized photolysis, using steady‐state irradiation at 313 nm or 248/308 nm laser pulses, was studied by absorption and fluorescence spectroscopy. Thereby, radicals were observed yielding eventually dihydro derivatives as major products, which are thermally back‐converted on admission of oxygen. The quantum yield of conversion of alkaloids to dihydroalkaloids is enhanced in the presence of triethylamine. The reaction in the presence of ketones and electron or H‐atom donors has a quantum yield of close to unity.
Intranasal Phototherapy Is More Effective Than Fexofenadine Hydrochloride in the Treatment of Seasonal Allergic Rhinitis: Results of a Pilot Study
Authors: Garaczi Edina , Boros‐Gyevi Márta , Bella Zsolt , Csoma Zsanett , Kemény Lajos , Koreck Andrea
Published: December 2010

We recently showed that intranasal phototherapy represents an efficient therapeutic modality for the treatment of patients with seasonal allergic rhinitis (SAR). The aim of this pilot study was to compare the efficacy of intranasal phototherapy with that of the new generation antihistamine fexofenadine HCl in SAR. A randomized open study was conducted in patients with a history of moderate‐to‐severe ragweed‐induced SAR. Thirty‐one patients were randomly assigned to receive either intranasal irradiation three times a week for 2 weeks, or 180 mg fexofenadine HCl per day for 2 weeks. Each patient kept a diary of symptoms for nasal obstruction, nasal itching, rhinorrhea, sneezing and palate itching. Total nasal score (TNS), a sum of scores for nasal symptoms, was also calculated. In the rhinophototherapy group the individual scores significantly decreased compared with baseline for all of the parameters. In the fexofenadine HCl group none of the scores improved significantly at the end of the treatment except sneezing. TNS was significantly decreased in the rhinophototherapy group, but no significant change was observed in the fexofenadine HCl group after 2 weeks of treatment. In conclusion, we found that intranasal phototherapy is more efficient than fexofenadine HCl in reducing clinical symptoms for SAR.
Is Ciprofloxacin a Substrate of P‐glycoprotein?
Authors: Park Miki Susanto , Okochi Hideaki , Benet Leslie Z.
Published: December 2010

Introduction. Studies using MDCKII and LLC‐PK1 cells transfected with MDR1 cDNA indicate that ciprofloxacin is not a substrate of P‐glycoprotein. However, our data has shown that transport studies done using different P‐gp overexpressing cell lines (MDCKI‐MDR1, MDCKII‐MDR1 and L‐MDR1), could lead to contradictory conclusion on whether a compound is a substrate of P‐gp. The aim of our study was to determine if ciprofloxacin is indeed not a P‐glycoprotein substrate using MDCKI cells transfected with human MDR1 cDNA.

Methods. Semi‐quantitative RT‐PCR was used to determine the mRNA level of MDR1 while Western blot was performed to determine the protein expression level of P‐gp, MRP1 and MRP2 in various cells. Ciprofloxacin bidirectional transport studies were performed in MDCKI, MDCKI‐MDR1, MDCKII, MDCKII‐MDR1, MDCKII‐MRP2, LLC‐PK1, L‐MRP1 and L‐MDR1 cells.

Results. Ciprofloxacin showed net secretion in MDCKI‐MDR1 but net absorption in MDCKI cells. Various P‐gp inhibitors decreased the B to A and increased the A to B transport of ciprofloxacin in MDCKI‐MDR1 cells while having no effect in MDCKI cells. The B to A transport of ciprofloxacin in MDCKI‐MDR1 cells was not affected by non‐P‐gp inhibitors. In the presence of indomethacin, ciprofloxacin showed net secretion instead of net absorption in MDCKI cells while in the presence of probenecid and sulfinpyrazone, there was no net secretion and absorption. There was no difference in ciprofloxacin transport between MDCKII and MDCKII‐MDR1, LLC‐PK1 and L‐MDR1, LLC‐PK1 and L‐MRP1 and MDCKII and MDCKII‐MRP2.

Conclusions. Transport data in MDCKI and MDCKI‐MDR1 cells indicate that ciprofloxacin is a substrate of P‐gp but data from MDCKII, MDCKII‐MDR1, LLC‐PK1 and L‐MDR1 cells indicate that ciprofloxacin is not a substrate of P‐gp. Vinblastine, a well‐known P‐gp substrate, also did not show differences between LLC‐PK1 and L‐MDR1 cells. Further studies need to be performed to characterize these P‐gp overexpressing cell lines and the transport of ciprofloxacin.
Clinicopathological features of severe forms of low gamma‐glutamyltranspeptidase familial intrahepatic cholestasis in Korean pediatric patients
Authors: Kwon Hyeong Ju , Go Heounjeong , Kim Soo Hee , Ko Jae Sung , Seo Jeong Kee , Kang Gyeong Hoon
Published: December 2010

Background and aim: Low gamma‐glutamyltranspeptidase (γ‐GTP) familial intrahepatic cholestasis is a broad‐spectrum condition that ranges from mild to severe. Severe forms of low γ‐GTP familial intrahepatic cholestasis, including progressive familial intrahepatic cholestasis type‐1 and ‐2 (PFIC‐1 and PFIC‐2), present with symptoms of cholestasis early in life and may progress to cirrhosis. Methods: We included five patients with low γ‐GTP, cholestasis and hyperbilirubinemia. We analyzed clinicopathological features of these five cases. Results: The age of the patients at diagnosis ranged from 1 month to 1 year old. All patients presented with jaundice, and one experienced pruritus. In contrast to hyperbilirubinemia, serum γ‐GTP levels were relatively low, or within normal range. Microscopically, intracanalicular cholestasis, bile duct loss or atrophy and varying degrees of fibrosis were found in all of the cases, whereas giant cell formation of hepatocytes was detected in three cases. Anti‐ABCB11 immunostaining revealed loss of expression in three cases with diffuse giant cell transformation of hepatocytes but retained expression in one case with no giant cell transformation. Conclusions: Low γ‐GTP familial intrahepatic cholestasis (PFIC‐1 and PFIC‐2) should be considered a differential diagnosis when pediatric patients with cholestatic liver diseases associated with normal to low serum γ‐GTP levels relative to the extent of cholestasis.
Apoptosis status from rat heart submitted to foot shock stress
Authors: Spadari‐Bratfisch Regina Célia , de Menezes Cáceres Viviane , Ortolani Daniela , Carlin Viviane , Ribeiro Daniel Araki
Published: December 2010

Background and aim:The goal of this study was to investigate whether physical stress is able to modulate apoptotic response in rat myocardial tissue. The effects of foot shock stress on the histopatological changes and immunohistochemistry for p53,bcl‐2andbaxwere evaluated.Methods:Male Wistar rats (n= 10) were distributed into two groups: group 1, control and group 2, stress. The stress protocol consisted of one daily foot‐shock session applied on three consecutive days.Results:The results pointed out no remarkable changes of myocardial tissue between groups. Also, the foot shock stress was not able to modulate p53,bcl‐2orbaxexpression, as depicted by no significant statistically differences (P> 0.05) between groups for all immunomarkers evaluated.Conclusions:Taken together, our results suggest that foot shock stress did not induce histopathological changes in rat myocardial tissue. It seems that physical stress is not able to modulate apoptotic response in rats. Certainly, this finding offers new insights into the mechanisms underlying the relation between apoptosis and cardiac injury after stress.
Application of the Analytic Hierarchy Process for Selecting and Modeling Stormwater Best Management Practices
Authors: Young Kevin D. , Younos Tamim , Dymond Randel L. , Kibler David F. , Lee David H.
Published: December 2010

Engineers are increasingly expected to consider several influential criteria when selecting a single best management practice (BMP) for stormwater management. These criteria include site physical characteristics; local, state, and federal pollution control ordinances; stakeholder input, and BMP implementation and long‐term maintenance costs. This paper discusses the development of a software‐aided approach based on the Analytic Hierarchy Process (AHP) as a decision‐making tool for selecting stormwater management BMPs. Supported with input from a geographic information system, the AHP can provide an objective, mathematically‐based alternative to the existing, often subjective BMP selection approaches. In this study, the developed AHP decision support software was applied in a demonstration site in the Town of Blacksburg, Virginia. First, the AHP decision support algorithm was applied to evaluate and rank BMP options for the demonstration site. Second, the EPA Storm Water Management Model (SWMM) was used to effectively model the BMPs recommended by the AHP software. Results indicate potential advantages over traditional BMP selection methods.
Watershed Retrofit and Management Evaluation for Urban Stormwater Management Systems in North Carolina
Authors: DeBusk Kathy M. , Hunt William F. , Hatch Upton , Sydorovych Olha
Published: December 2010

In response to water quality concerns in the Jordan Lake Reservoir and state and federal mandates, several cities in North Carolina are being required for the first time to reduce nutrient loads in stormwater from previously developed lands; that is, install retrofits. It is anticipated that similar requirements will become necessary for other urban areas in North Carolina. The goal of this study is to evaluate the feasibility of alternative approaches to stormwater management for existing developments within North Carolina cities. Geographic coverage of the study included a portion of the New Hope Creek watershed, located within the City of Durham in central North Carolina. The watershed was analyzed to identify potential retrofit opportunities that could be implemented to reduce pollutant loadings entering New Hope Creek and, ultimately, Jordan Lake. Current pollutant loadings generated by the watershed, as well as reductions in annual loadings of total suspended solids, total nitrogen and total phosphorus that could be achieved by implementing the identified retrofits, were estimated. Trends and relationships between land use type and the quantity and type of retrofit opportunities were identified and conclusions were drawn as to the most appropriate types of retrofits for certain land uses.
Stormwater Management for a Record Rainstorm at Chicago
Authors: Changnon Stanley A.
Published: December 2010

A record setting 24‐hour rainstorm hit Chicago in September 2008. It created an opportunity to assess its impacts and to compare the storm water management with that used in other recent rainstorms. Flooding impacted all forms of transportation and thousands of homes and businesses, 10,000 homes had to be evacuated. One lesson learned is that this storm's magnitude was enhanced by urban and lake influences on the atmosphere that extended over the large suburban areas west of the city. This helped intensify the rainfall over a large area. A second lesson learned is when 6‐hour and 24‐hour rainfall amounts exceed once‐in‐25‐years recurrence values, the water management facilities cannot handle the large volume of water. Hence, major diversions of flood waters were needed to be made into Lake Michigan and the Illinois River.
Comparison of Computed Tomography and Routine Radiography of the Tympanic Bullae in the Diagnosis of Otitis Media in the Calf
Authors: Finnen A. , Blond L. , Francoz D. , Parent J.
Published: December 2010

Background:Otitis media is difficult to diagnose antemortem. Case reports have described computed tomography (CT) in the diagnosis, but not all cases were confirmed.

Hypothesis:CT is a sensitive and specific imaging modality of the tympanic bullae and can be used as the gold standard for the diagnosis of otitis media.

Animals:Sixteen Holstein calves 5–7 weeks of age were included.

Methods:Prospective study. All calves were sedated with IV xylazine (0.05–0.15 mg/kg) for routine radiography (3 views) and CT of the tympanic bullae followed by necropsy.

Results:Based upon necropsy findings, 10 of 16 calves were affected with otitis media, 4 unilaterally and 6 bilaterally. Imaging changes associated with otitis media included increased soft tissue opacity within the bulla, thickening of the bulla wall, enlarged bulla, and osteolysis of the bulla wall and trabeculations. The most frequent radiographic changes were lysis of trabeculations and increased soft tissue opacity, which were present in 56.3% of affected bullae. On CT, increased soft tissue opacity within the bulla was present in 93.8% of affected bullae. Sensitivity of radiography and CT was 68.8 and 93.8% and specificity was 50 and 100%, respectively. The κ value between radiography and CT with necropsy diagnosis was 0.19 for radiography, indicating poor agreement, and 0.94 for CT, indicating excellent agreement.

Conclusion:CT is more specific, more sensitive, and easier to interpret than radiography and can be used as the gold standard in the diagnosis of otitis media in the calf.
Buckling Design of Confined Steel Cylinders Under External Pressure
Authors: Vasilikis Daniel , Karamanos Spyros A.
Published: December 2010

Thin-walled steel cylinders surrounded by an elastic medium, when subjected to uniform external pressure may buckle. In the present paper, using a two-dimensional model with nonlinear finite elements, which accounts for both geometric and material nonlinearities, the structural response of those cylinders is investigated, toward developing relevant design guidelines. Special emphasis is given on the response of the confined cylinders in terms of initial imperfections; those are considered in the form of initial out-of-roundness of the cylinder and as an initial gap between the cylinder and the medium. Furthermore, the effects of the deformability of the surrounding medium are examined. The results indicate significant imperfection sensitivity and a strong dependency on the medium stiffness. The numerical results are employed to develop a simple and efficient design methodology, which is compatible with the recent general provisions of European design recommendations for shell buckling and could be used for design purposes.
The New Framework for Shell Buckling Design and the European Shell Buckling Recommendations Fifth Edition
Authors: Rotter J. Michael
Published: December 2010

This paper outlines key aspects of the new European Standard on the Strength and Stability of Metal Shells EN 1993-1-6 with its extended commentary and expansion in the fifth edition of the European Recommendations on Shell Buckling. This European design standard is the first to be strongly oriented toward numerical analyses in design, with clear distinctions between different classes of both analysis and fabrication. It presents a different style of standard: Each limit state is defined in a separate chapter, but all shell geometries are treated and all analysis types are used within each chapter. The strength evaluation criteria differ according to the calculation that has been made. This new structure, with its new paradigm that permits generalization of the design procedure for all thin shells, geometries, load cases, boundary conditions, and qualities, represents a major step forward. It also offers the opportunity for future research studies of shell structures to be undertaken within a coherent conceptual framework that is completely general. The EN 1993-1-6 standard goes a long way toward bridging the gap between the computational engineering mechanics and structural engineering design communities. Unfortunately, this European standard EN 1993-1-6 has a complex and extensive background that cannot be stated within the document so the European Recommendations on Shell Stability, now published in its fifth edition, gives an extensive commentary, many expanded rules, and many additional geometries and load cases that are not formally presented within the standard itself. The development of both EN 1993-1-6 and the recommendations has been the work of the Eurocode shell structures development committee CEN/TC250/SC3/PT4 and the European Convention for Constructional Steelwork committee (ECCS) TWG 8.4. It is presented here by the convener of these two committees. This paper explains the reasoning behind several particular choices that have been taken in developing the standard, occasionally running counter to traditional views. It also identifies several tricky issues that have not been addressed well in the shell buckling literature but that have arisen through the attempts to achieve completely general rules and which need imaginative answers to ensure a fully consistent treatment of all systems. It is hoped that this paper will assist researchers and designers to understand the rules and recommendations and will encourage researchers to undertake and present their work in a manner that permits its rapid adoption into the new standardized design procedures.
Accurate Determination of Plastic Collapse Loads From Finite Element Analyses
Authors: Doerich C. , Rotter J. M.
Published: December 2010

When computational modeling is used to evaluate the true strength of an imperfect elastic-plastic shell structure, the current European standard on shell structures requires that two reference strengths are always determined: the linear bifurcation load and the plastic limit (plastic collapse) load. These two loads are used in more than one way to characterize the strength of all imperfect elastic-plastic systems. Where parametric studies of a problem are being undertaken, it is particularly important that these two loads are accurately defined, since all other strengths will be related to them. For complex problems in shell structures, it is not possible to develop analytical solutions for the plastic collapse strength, and finite element analysis must be used. Unfortunately, because a collapse mechanism often requires the development of very extensive plasticity involving large local strains, and the collapse load is simply at the end of a slowly rising load-deflection curve, it is sometimes difficult for the analyst to accurately determine this plastic collapse strength. This paper describes two methods, based on modifications of the Southwell plot, of obtaining very accurate evaluations of the plastic limit load, irrespective of whether a fairly complete plastic strain field has developed or not. These two methods allow plastic collapse limit loads to be reported with great precision.
Buckling of Thin Cylindrical Shells Under Locally Elevated Compressive Stresses
Authors: Rotter J. Michael , Cai Minjie , Holst J. Mark F. G.
Published: December 2010

Thin cylindrical shells used in engineering applications are often susceptible to failure by elastic buckling. Most experimental and theoretical research on shell buckling relates only to simple and relatively uniform stress states, but many practical load cases involve stresses that vary significantly throughout the structure. The buckling strength of an imperfect shell under relatively uniform compressive stresses is often much lower than that under locally high stresses, so the lack of information and the need for conservatism have led standards and guides to indicate that the designer should use the buckling stress for a uniform stress state even when the peak stress is rather local. However, this concept leads to the use of much thicker walls than is necessary to resist buckling, so many knowledgeable designers use very simple ideas to produce safe but unverified designs. Unfortunately, very few scientific studies of shell buckling under locally elevated compressive stresses have ever been undertaken. The most critical case is that of the cylinder in which locally high axial compressive stresses develop extending over an area that may be comparable with the characteristic size of a buckle. This paper explores the buckling strength of an elastic cylinder in which a locally high axial membrane stress state is produced far from the boundaries (which can elevate the buckling strength further) and adjacent to a serious geometric imperfection. Care is taken to ensure that the stress state is as simple as possible, with local bending and the effects of internal pressurization eliminated. The study includes explorations of different geometries, different localizations of the loading, and different imperfection amplitudes. The results show an interesting distinction between narrower and wider zones of elevated stresses. The study is a necessary precursor to the development of a complete design rule for shell buckling strength under conditions of locally varying axial compressive stress.
Buckling of Thin-Walled Long Steel Cylinders Subjected to Bending
Authors: Houliara Sotiria , Karamanos Spyros A.
Published: December 2010

The present paper investigates structural response and buckling of long unstiffened thin-walled cylindrical steel shells, subjected to bending moments, with particular emphasis on stability design. The cylinder response is characterized by cross-sectional ovalization, followed by buckling (bifurcation instability), which occurs on the compression side of the cylinder wall. Using a nonlinear finite element technique, the bifurcation moment is calculated, the post-buckling response is determined, and the imperfection sensitivity with respect to the governing buckling mode is examined. The results show that the buckling moment capacity is affected by cross-sectional ovalization. It is also shown that buckling of bent elastic long cylinders can be described quite accurately through a simple analytical model that considers the ovalized prebuckling configuration and results in very useful closed-form expressions. Using this analytical solution, the incorporation of the ovalization effects in the design of thin-walled cylinders under bending is thoroughly examined and discussed, considering the framework of the provisions of the new European Standard EN1993-1-6.
Thermal Performance Model for Spacesuit Waste Heat Rejection Using Water Membrane Evaporators
Authors: Janeborvorn Y. , Filburn T. P. , Yavuzturk C. C. , Ungar E. K.
Published: December 2010

Hydrophobic, micropore membrane evaporators are studied for use in waste heat rejection in new generation spacesuits developed by the U.S. National Aeronautics and Space Administration (NASA). The waste heat rejection is accomplished via evaporation of liquid water through membrane pores, whereby the hydrophobic membrane allows only water vapor to pass through and retains the liquid phase inside the membrane water channel, allowing the waste heat rejection through the proposed spacesuit water membrane evaporator (SWME) system to be significantly less sensitive to contamination while improving the overall contaminant and system control. Although SWME uses the same heat transport loop as used in current NASA sublimator systems, thus eliminating the need for a separate feedwater system, it permits the system configuration to be simpler and more compact while also eliminating corrosion problems and reducing system freeze-up potential. An improved thermal performance model based on membrane segment energy balances is presented, which is a spacesuit water membrane evaporator for a single circular annulus water channel bounded by two annular vapor channels. The model allows for the investigation of the local heat transfer characteristics along the annulus including temperature gradients in the membrane wall and the water channel using a steady-state approach. The model also accounts for the effects of thermal and hydraulic entry lengths, far field radiation, and energy carried away by the mass of water evaporation. The local heat transfer analysis enables the straightforward calculation of the overall magnitude of heat transfer from the SWME. A model validation is presented via the sum of the squares error analyses between the model predictions and the experimental results.
Enhancement of Temperature Blending in Convective Heat Transfer by Motionless Inserts With Variable Segment Length
Authors: Rahmani Ramin K. , Ayasoufi Anahita , Tanbour Emad Y. , Molavi Hosein
Published: December 2010

Stationary spiral inserts can effectively enhance heat transfer and temperature blending in the heat convection systems. In this paper, the impact of the segment length on the performance of a stationary insert is studied for flow Re numbers from ∼80 to ∼7900 through numerical simulation of heat transfer in streams of cold and hot gases flowing across it. The segment length to width ratio is from 1.11 to 2.33. The temperature of the studied gas is from 300 K to 1300 K. It is shown that the insert with variable segment length is more effective in temperature blending for two compressible streams compared with an insert with constant segment length, especially for low-Re-number turbulent flows.
A Microreactor System
for the Analysis of the Fast Pyrolysis of
Biomass
Authors: Williams Alexander , Mayor J.
Rhett
Published: December 2010

A novel fast pyrolysis microreactor was developed to facilitate control over feedstock dwell time, pyrolysis temperature, and the individual collection of pyrolysis liquid and solid products. The design process followed is presented including design requirements, functional decomposition, commissioning tests, and the final microreactor design. A vibratory assisted spreading study was performed as particle agglomeration was a key challenge within the reactor design. The study results and analysis of variance are presented identifying the most significant factor and a best operating point. Analytical and experimental heat transfer analyses are also presented to validate the reactor’s thermal performance. Through the pairing of the analyses, projections for thin biomass layer heating rates are made resulting in estimates on the order of 400°C/s. Finally, experimental pyrolysis results are given showing fast pyrolysis conversion as a function of time and the process by which kinetic descriptors could be derived using this system’s results. Yield results are compared with literature and are found to be in good agreement with published fast pyrolysis results.
Experimental Observation of Inertia-Dominated Squeeze Film Damping in Liquid
Authors: Fornari Antoine , Sullivan Matthew , Chen Hua , Harrison Christopher , Hsu Kai , Marty Frederic , Mercier Bruno
Published: December 2010

We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit.
Computational Investigations Into Draining in an Axisymmetric Vessel
Authors: Robinson Adam , Morvan Hervé , Eastwick Carol
Published: December 2010

Within an aero-engine, bearing chamber oil is provided for components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure that it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper, a simplified physical situation related to bearing chamber scavenge is computationally modeled. The volume of fluid (VOF) model of Hirt and Nichols (1981, “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries,” J. Comput. Phys., 39, pp. 201–225), implemented within the commercial computational fluid dynamics (CFD) code FLUENT (Fluent, 2006, Fluent 6.3 User’s Guide, 10 Cavendish Court, Lebanon, NH 03766), has been applied to investigate the case of transient draining in an axisymmetric vessel. The model is setup to match the experimental work of Lubin and Springer (1967, “The Formation of a Dip on the Surface of a Liquid Draining From a Tank,” J. Fluid Mech., 29(2), pp. 385–390). First, a comparison of the computational predictions with the experimental results for free draining is presented. Second, a comparison between the free surface positions obtained the developed VOF methodology and the results obtained by Zhou and Graebel (1990, “Axisymmetric Draining of a Cylindrical Tank With a Free Surface,” J. Fluid Mech., 221, pp. 511–532) using a boundary integral method is reported. When comparing the results with the observations of Lubin and Springer some differences are noted. These differences, which relate to the effect of initial height and outflow history, may have arisen due to the experimental procedure used by Lubin and Springer. This paper shows that CFD is a promising approach to analyzing these simple draining situations in terms of predicting bulk quantities, transitions, and free-surface shape and position.
An Electrodiffusion Model for the Blood-Brain Barrier Permeability to Charged Molecules
Authors: Li Guanglei , Fu Bingmei M.
Published: December 2010

The endothelial surface glycocalyx layer (SGL) and the basement membrane (BM) are two important components of the blood-brain barrier (BBB). They provide large resistance to solute transport across the BBB in addition to the tight junctions in the cleft between adjacent endothelial cells. Due to their glycosaminoglycan compositions, they carry negative charge under physiological conditions. To investigate the charge effect of the SGL and BM on the BBB permeability to charged solutes, we developed an electrodiffusion model for the transport of charged molecules across the BBB. In this model, constant charge densities were assumed in the SGL and in the BM. Both electrostatic and steric interaction and exclusion to charged molecules were considered within the SGL and the BM and at their interfaces with noncharged regions of the BBB. On the basis of permeability data for the positively charged ribonuclease (+4,radius=2.01 nm) and negatively charged α-lactalbumin (−10,radius=2.08 nm) measured in intact rat mesenteric and pial microvessels, our model predicted that the charge density in both SGL and BM would be ∼30 mEq/L, which is comparable to that in the SGL of mesenteric microvessels. Interestingly, our model also revealed that due to the largest concentration drop in the BM, there is a region with a higher concentration of negatively charged α-lactalbumin in the uncharged inter-endothelial cleft, although the concentration of α-lactalbumin is always lower than that of positively charged ribonuclease and that of a neutral solute in the charged SGL and BM.
Wall Shear Stresses Remain Elevated in Mature Arteriovenous Fistulas: A Case Study
Authors: Carroll G. T. , McGloughlin T. M. , Burke P. E. , Egan M. , Wallis F. , Walsh M. T.
Published: December 2010

Maintaining vascular access (VA) patency continues to be the greatest challenge for dialysis patients. VA dysfunction, primarily due to venous neointimal hyperplasia development and stenotic lesion formation, is mainly attributed to complex hemodynamics within the arteriovenous fistula (AVF). The effect of VA creation and the subsequent geometrical remodeling on the hemodynamics and shear forces within a mature patient-specific AVF is investigated. A 3D reconstructed geometry of a healthy vein and a fully mature patient-specific AVF was developed from a series of 2D magnetic resonance image scans. A previously validated thresholding technique for region segmentation and lumen cross section contour creation was conducted in MIMICS 10.01, allowing for the creation of a 3D reconstructed geometry. The healthy vein and AVF computational models were built, subdivided, and meshed in GAMBIT 2.3. The computational fluid dynamic (CFD) code FLUENT 6.3.2 (Fluent Inc., Lebanon, NH) was employed as the finite volume solver to determine the hemodynamics and shear forces within the healthy vein and patient-specific AVF. Geometrical alterations were evaluated and a CFD analysis was conducted. Substantial geometrical remodeling was observed, following VA creation with an increase in cross-sectional area, out of plane curvature (maximum angle of curvature in AVF=30 deg), and angle of blood flow entry. The mean flow velocity entering the vein of the AVF is dramatically increased. These factors result in complex three-dimensional hemodynamics within VA junction (VAJ) and efferent vein of the AVF. Complex flow patterns were observed and the maximum and mean wall shear stress (WSS) magnitudes are significantly elevated. Flow reversal was found within the VAJ and efferent vein. Extensive geometrical remodeling during AVF maturation does not restore physiological hemodynamics to the VAJ and venous conduit of the AVF, and high WSS and WSS gradients, and flow reversal persist. It is theorized that the vessel remodelling and the continued non-physiological hemodynamics within the AVF compound to result in stenotic lesion development.
Biomechanical Validation of Finite Element Models for Two Silicone Metacarpophalangeal Joint Implants
Authors: Hussein A. I. , Stranart J. C. , Meguid S. A. , Bogoch E. R.
Published: December 2010

Silicone implants are used for prosthetic arthroplasty of metacarpophalangeal (MCP) joints severely damaged by rheumatoid arthritis. Different silicone elastomer MCP implant designs have been developed, including the Swanson and the NeuFlex implants. The goal of this study was to compare the in vitro mechanical behavior of Swanson and NeuFlex MCP joint implants. Three-dimensional (3D) finite element (FE) models of the silicone implants were modeled using the commercial software ANSYS and subjected to angular displacement from 0 deg to 90 deg. FE models were validated using mechanical tests of implants incrementally bent from 0 deg to 90 deg in a joint simulator. Swanson size 2 and 4 implants were compared with NeuFlex size 10 and 30 implants, respectively. Good agreement was observed throughout the range of motion for the flexion bending moment derived from 3D FE models and mechanical tests. From 30 deg to 90 deg, the Swanson 2 demonstrated a greater resistance to deformation than the NeuFlex 10 and required a greater bending moment for joint flexion. For larger implant sizes, the NeuFlex 30 had a steeper moment-displacement curve, but required a lower moment than the Swanson 4, due to implant preflexion. On average, the stress generated at the implant hinge from 30 deg to 90 deg was lower in the NeuFlex than in the Swanson. On average, starting from the neutral position of 30 deg for the preflexed NeuFlex implant, higher moments were required to extend the NeuFlex implants to 0 deg compared with the Swanson implants, which returned spontaneously to resting position. Implant toggling within the medullary canals was less in the NeuFlex than in the Swanson. The differential performance of these implants may be useful in implant selection based on the preoperative condition(s) of the joint and specific patient functional needs.
A High Throughput System for Long Term Application of Intermittent Cyclic Hydrostatic Pressure on Cells in Culture
Authors: Rottmar Markus , Ackerknecht Sabine , Wick Peter , Maniura-Weber Katharina
Published: December 2010

The process of bone remodeling is governed by mechanical stresses and strains. Studies on the effects of mechanical stimulation on cell response are often difficult to compare as the nature of the stimuli and differences in parameters applied vary greatly. Experimental systems for the investigation of mechanical stimuli are mostly limited in throughput or flexibility and often the sum of several stimuli is applied. In this work, a flexible system that allows the investigation of cell response to isolated intermittent cyclic hydrostatic pressure (icHP) on a high throughput level is shown. Human bone derived cells were cultivated with or without mechanical stimulus in the presence or absence of chemical cues triggering osteogenesis for 7–10 days. Cell proliferation and osteogenic differentiation were evaluated by cell counting and immunohistochemical staining for bone alkaline phosphatase as well as collagen 1, respectively. In either medium, both cell proliferation and level of differentiation were increased when the cultures were mechanically stimulated. These initial results therefore qualify the present system for studies on the effects of isolated icHP on cell fate and encourage further investigations on the details behind the observed effects.