bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology, Morphometrics, and Molecular Characterization of Bryophrya gemmea n. sp. (Ciliophora, Colpodea): Implications for the Phylogeny and Evolutionary Scenario for the Formation of Oral Ciliature in the Order Colpodida
Authors: BOURLAND WILLIAM A. , VĎAČNÝ PETER , DAVIS MICHAEL C. , HAMPIKIAN GREG
Published: December 2010

ABSTRACT. We studied the morphology, morphometry, resting, and reproductive cysts, as well as the molecular phylogeny of Bryophrya gemmea n. sp., a colpodid ciliate that was discovered in ephemeral puddles in Idaho, northwest United States. This new species is distinguished from congeners by the irregularly pentagonal adoral organelles, four to five vestibular kineties, the single micronucleus, and one to three rows of brightly refractive protuberant interkinetal cortical granules to the right of the preoral suture. Resting cysts have two distinct membranes and an outer mucous coat. As typical for most colpodids, reproduction occurs in division cysts but details of ontogenesis are unknown. The 18S rRNA gene sequence shows only weak support for the phylogenetic relationship between Bryophrya and the bryophryid genus Notoxoma previously inferred from morphologic characters. Further, our molecular phylogenies classify bryophryids rather basal within the order Colpodida, not supporting ordinal status suggested by morphologists. Based on molecular data and morphologic characters, the colpodid genus Ilsiella is removed from the family Marynidae and placed in a new family, Ilsiellidae. Considering the molecular data, an evolutionary scenario for the formation of colpodid oral structures from a cyrtolophosidid ancestor through a bryophryid intermediate is proposed.
Increased Hematocrit After Applications of Conducted Energy Weapons (Including TASER® Devices) to Sus scrofa*
Authors: Jauchem James R.
Published: December 2010

Abstract:  Conducted energy weapons (CEWs) are used by law enforcement personnel to incapacitate individuals quickly and effectively, without intending to cause lethality. CEWs have been deployed for relatively long or repeated exposures in some cases. In laboratory animal models, central venous hematocrit has increased significantly after CEW exposure. Even limited applications (e.g., three 5‐sec applications) resulted in statistically significant increases in hematocrit. Preexposure hematocrit was significantly higher in nonsurvivors versus survivors after more extreme CEW applications. The purpose of this technical note is to address specific questions that may be generated when examining these results. Comparisons among results of CEW applications, other electrical muscle stimulation, and exercise/voluntary muscle contraction are included. The anesthetized swine appears to be an acceptable animal model for studying changes in hematocrit and associated red blood cell changes. Potential detrimental effects of increased hematocrit, and considerations during law enforcement use, are discussed.
Mechanisms and Effects of Retention of Over‐Expressed Aquaporin AtPIP2;1 in the Endoplasmic Reticulum
Authors: Sorieul Mathias , Santoni Véronique , Maurel Christophe , Luu Doan‐Trung
Published: December 2010

Plasma membrane intrinsic proteins (PIPs) are aquaporins that mediate water transport across the plant plasma membrane (PM). The present work addresses, using Arabidopsis AtPIP2;1 as a model, the mechanisms and significance of trafficking of newly synthesized PIPs from the endoplasmic reticulum (ER) to the Golgi apparatus. A functional diacidic export motif (Asp4‐Val5‐Glu6) was identified in the N‐terminal tail of AtPIP2;1, using expression in transgenic Arabidopsis of site‐directed mutants tagged with the green fluorescent protein (GFP). Confocal fluorescence imaging and a novel fluorescence recovery after photobleaching application based on the distinct diffusion of PM and intracellular AtPIP2;1‐GFP forms revealed a retention in the ER of diacidic mutated forms, but with quantitative differences. Thus, the individual role of the two acidic Asp4 and Glu6 residues was established. In addition, expression in transgenic Arabidopsis of ER‐retained AtPIP2;1‐GFP constructs reduced the root hydraulic conductivity. Co‐expression of AtPIP2;1‐GFP and AtPIP1;4‐mCherry constructs suggested that ER‐retained AtPIP2;1‐GFP may interact with other PIPs to hamper their trafficking to the PM, thereby contributing to inhibition of root cell hydraulic conductivity.
Episodic disc accretion in the halo of the ‘old’ pre-main-sequence
cluster η Chamaeleontis
Authors: Murphy Simon J. , Lawson Warrick A. , Bessell Michael S. , Bayliss Daniel D. R.
Published: December 2010

We present multi-epoch medium-resolution observations of two M4.5 candidate members in the halo of the ∼8 Myr η Chamaeleontis open cluster. During six months of observations, both stars exhibited variations in their Hα line profiles on time-scales of days to months, with at least one episode of substantial activity attributable to accretion from a circumstellar disc. We derive an accretion rate of ∼10−8.7 M⊙ yr−1 for this event, with a rate of ∼10−10.6 M⊙ yr−1 in quiescence. Episodic accretion like that observed here suggests existing surveys of accreting weak-lined T Tauri stars in young clusters are likely incomplete and that gas dissipation time-scales calculated from the fraction of accreting objects are underestimates.
The Value of Reputation in Corporate Finance and Investment Banking (and the Related Roles of Regulation and Market Efficiency)
Authors: Macey Jonathan
Published: December 2010

This article explores the roles of reputation, efficient capital markets, and capital market regulation in preserving and creating economic value. Each of these three mechanisms serves as a substitute for the other two, with each playing a role in maintaining the credibility and reliability of markets.

While efficient markets and effective regulation are market‐wide phenomena that affect all firms, reputation is a firm‐specific corporate asset. Companies develop reputational capital by treating customers and counterparties fairly (while forgoing the temptation to achieve short‐term profits at their expense). At the same time, companies seeking access to the capital markets but lacking a reputation must typically employ reputational intermediaries. Investment banks, credit rating agencies, accounting firm s, law firms, and organized stock exchanges have all served as reputational intermediaries at various times during the last 200 years.

One contributor to the recent financial crisis was a kind of experimentation by some reputational intermediaries with an opportunistic and two‐tiered “customer differentiation” strategy in which some customers were treated very well, while others were treated with little or no regard for their legitimate expectations as to how they would be treated. This strategy has proved to be a failure, imposing significant costs on those organizations as well as their customers. The available substitutes for reputation, capital market effciency and effective regulation, did not provide sufcient offsetting protection for investors.

While the two‐tiered “customer differentiation” strategy has failed, the central message of the economic theory of reputation remains intact. This message is that a company's reputation is a valuable asset that must be preserved to ensure the future of the organization. For all financial intermediaries that rely heavily on their reputations when selling their products and services, the author recommends large and continuous investment in maintaining those reputations. For investment banks in particular—a group whose reputations have held up reasonably well—the author suggests that they continue to view their role as reputational intermediaries as a core part of their businesses.
Blockholders Are More Common in the United States Than You Might Think*
Authors: Holderness Clifford G.
Published: December 2010

Finance scholars have long characterized the large publicly traded U.S. company as having a fragmented ownership structure with a diffuse shareholder base—significantly more diffuse than comparable companies in most other countries. But the findings of the author's recent study, which incluudes large amounts of “hand‐collected data” on the share ownership of U.S. companies, are strikingly at odds with this characterization.

As reporteed in the study, 96% of a sample of 375 randomly chosen, publicly traded U.S. corporations—including companies like American Express and McDonald's—had at least one shareholder who owned at least 5% of the firm's common stock. In fact, such blockholders as a group owned almost 40% of the typical U.S. company. There was, to be sure, an inverse relation between ownership concentration and firm size, but ownership was unexpectedly concentrated even among the largest companies, with 89% of the S&P 500 companies in the sample having at least one 5% blockholder.

What's more, the ownership concentration of U.S. public companies turned out to be remarkably similar to the average ownership concentration of large samples of listed companies from 22 European and East Asian countries. More specifically, the ownership structure of U.S. companies—after controlling for differences in company size—appears to all in the middle of the distribution of those countries, whether one looks at the proportion of companies with block‐holders or the blockholders' average percentage holdings.
Private Equity in the U.S.: Building a New Future
Authors: Wright Mike , Jackson Andrew , Frobisher Steve
Published: December 2010

Despite the recent downturn, private equity firms still have an important role to play in the global economy. At the same time, many PE firms may need to rethink their strategies. Practices that have been worked in the past may not produce acceptable returns in a future, particularly given the current constraints on financing and leverage.

One source of PE's comparative advantage, as demonstrated during the recent crisis, has been the ability of the best and most experienced firms to reorganize their portfolio companies when they get into financial trouble. But in addition to their financial management skills, specialized operating expertise has become more critical to success, and those PE firms that have not acquired it are especially likely to find that past success in raising capital is no guarantee of success in the future.

The authors begin by providing a brief overview of the past three decades of global private equity to identify how the market arrived at its current position. Using the findings of academic research together with case studies and interviews with PE practitioners in the U.K., the authors suggest a number of building blocks for the future that reflect the considerable success of the most reputable and experienced PE firms in increasing the value of their portfolio companies.
Measuring Corpotate Liquidity Risk
Authors: Jankensgård Håkan
Published: December 2010

This article presents the outline of a framework for evaluating liquidity risk (at the corporate level) with risk measures that are intuitive and economically relevant. In particular, the risk measures are designed explicitly to show the effectiveness of a company's risk management program in helping the firm to (1) avoid financial distress or default and (2) ensure its ability to undertake all strategic investments.

For managers attempting to quantify liquidity risks, this paper proposes that the risk measures have two important features: One is to make the liquidity risk estimate depend on some measure of the firm's balance sheet strength, one that reflects the role of the balance sheet as a risk buffer. The second is to provide a useful estimate of the opportunity costs associated with a given liquidity shortage—one that reflects the value of the investment opportunities that liquidity problems could jeopardize.

The author illustrates the application of the proposed risk measures with an example of a company evaluating a hedging strategy designed to accompany a substantial increase in its investment budget. Using the risk measures discussed in this paper, the author shows how to assess the effectiveness of a proposed hedge in terms of its expected ability to reduce costly cash shortfalls in scenarios in which the firm's debt capacity is also expected to be depleted.
Small Intracerebral Haemorrhages are Associated with Less Haematoma Expansion and Better Outcomes
Authors: Dowlatshahi Dar , Smith Eric E. , Flaherty Matthew L. , Ali Myzoon , Lyden Patrick , Demchuk Andrew M. ,   on behalf of the VISTA Collaborators
Published: December 2010

Background and purpose

Haematoma expansion following intracerebral haemorrhage is a major determinant of early neurological worsening and poor clinical outcome. This has created interest in improving patient selection for therapies targeting haematoma expansion. Based on prior observations, we hypothesised that intracerebral haemorrhage volumes under 10 ml would be less likely to expand. We additionally sought to define a baseline haematoma volume below which significant growth was not observed.

Methods

Patient data were obtained from the Virtual International Stroke Trials Archive. Patients with intracerebral haemorrhage presented within six-hours of symptom onset had baseline clinical, radiological and laboratory data, and computed tomographic scan at 72 h and three-month follow-up. The predictor of interest was baseline haematoma volume. Primary outcomes were absolute and relative haematoma growth. Secondary outcomes were early neurological worsening, good functional outcome, and 90-day mortality.

Results

The final dataset consisted of 496 patients. Baseline haematoma volumes under 10 ml were associated with much lower odds of absolute expansion compared to larger haematomas. Smaller haematomas were associated with significantly decreased odds of early neurological worsening and three-month mortality, and increased odds of good functional outcome. The smallest haematoma to double in size was 3·97 ml. Among the 34 subjects with very small haematomas (<3 ml), none had early neurological worsening and most had good three-month outcome (73·5%, mRS≤3).

Conclusions

This study provides observational evidence that very small haematomas are unlikely to expand, by commonly used absolute growth definitions, and may represent a subgroup of patients with intracerebral haemorrhage destined towards good clinical outcomes.
Timeframes of UVA‐induced Bystander Effects in Human Keratinocytes
Authors: Whiteside James R. , Allinson Sarah L. , McMillan Trevor J.
Published: December 2010

The bystander effect is defined as the induction of cellular damage in unirradiated cells, induced by irradiated cells in the surrounding area. Our laboratory has previously identified that an environmentally relevant dose of UVA is able to induce the effect in human keratinocytes and fibroblasts, seen as reduced clonogenic survival. Here we report on our investigations into the periods over which the bystander signals are released by the irradiated cells and for how long unirradiated cells need to be exposed to them for the effect to be induced. Using a coincubation system we have identified that irradiated cells do not release the signals immediately following irradiation but have a time lag of over 24 h before levels are sufficient to induce the effect, with the signals being released for a minimum of 3 days following irradiation. We have also found that the recipient cells only require at most 24 h of exposure to these signals for induction of the effect. These data indicate that a single exposure to UVA can exert an effect for several days postirradiation, thus amplifying the deleterious effects of exposure.
Histopathologic changes in the gills and skin of adult Clarias gariepinus exposed to ethanolic extract of Parkia biglobosa pods
Authors: Abalaka Samson Eneojo , Fatihu Muhammad Yakasai , Ibrahim Najume Doguwar Giginya , Kazeem Haruna Makonjuola
Published: December 2010

Background and aim: Fish live in direct contact with their immediate external environment and, therefore, are highly vulnerable to aquatic pollutants. We aimed to investigate histopathologic changes in the gills and skin of fish exposed to plant extracts. Methods: Clarias gariepinus adults were exposed to 0 mg/L, 85 mg/L, 100 mg/L, 115 mg/L, 130 mg/L and 145 mg/L concentrations of ethanolic extracts of Parkia biglobosa pods over a 96‐h period. Results: Gills from exposed fish showed hyperemia and severe edema with fusion of secondary lamellae. The skin from exposed fish showed hyperplasia of mucus producing cells, epidermal and dermal polymorphonuclear leukocytic infiltrations with areas of dermal necrosis and aggregation of melanin pigments. Fish from the control group showed no histopathologic changes. Conclusions: Ethanolic extract of P. biglobosa pods is toxic to adult C. gariepinus. Therefore, extensive use of this tree to harvest fish for human consumption should be discouraged pending further investigations to determine the safety of such practices to human health.
HER2 expression in breast cancer: Comparisons of fluorescence in situ hybridization and silver in situ hybridization, and immunohistochemical staining using monoclonal antibody and polyclonal antibody
Authors: Jang Jung Sik , Jang Eun Jeong , Park Ji‐Young
Published: December 2010

Background and aim: The human epidermal growth factor receptor 2 (HER2) gene is an important tumor marker in breast cancer. The silver in situ hybridization (SISH) has been recently introduced for measuring the HER2 amplification status. We evaluated the concordance between HER2 gene amplification in invasive breast cancer as determined by the fluorescence in situ hybridization (FISH) and SISH techniques and we compared the results to that of immunohistochemical (IHC) staining with using polyclonal c‐erbB‐2 antibody and monoclonal HER2 antibody. Methods: A total of 90 cases were analyzed by direct‐labeled manual FISH and bright field automated SISH. All the specimens underwent IHC staining using c‐erbB‐2 and PATHWAY 4B5. The evaluation was performed by following the recommendation of the manufacturer and the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines. Results: The overall concordance rate between FISH and SISH was 98.8% (Kappa index: 0.96). There was no significant difference in estimating the HER2 status using polyclonal and monoclonal antibody. Conclusions: The 98.8% concordance of FISH fulfills the ASCO/CAP requirement of greater than 95% concordance for the amplified cases versus the non‐amplified cases. The HER2 gene copy status can be reliably determined by SISH.
Three new species of Dactylicapnos (Fumariaceae) and a synopsis of the D. macrocapnos complex
Authors: Lidén Magnus
Published: December 2010

The Dactylicapnos macrocapnos complex is revised, and D. platycarpa Lidén, D. odontocarpa Lidén and D. macrocapnos subsp. echinosperma Lidén are recognised as new taxa. The complex consists of a chain of 4 vicariant taxa from northwestern India (Garhwal) to western Bhutan (Thimphu). Dactylicapnos cordata Lidén (eastern Nepal, Darjeeling) is described and contrasted with its close relative, the geographically disjunct D. burmanica (western Yunnan, Burma).
Nomenclatural novelties in miscellaneous Asian Brassicaceae (Cruciferae)
Authors: German Dmitry A. , Al‐Shehbaz Ihsan A.
Published: December 2010

The new tribe Crucihimalayeae and three new genera Schrenkiella, Leiocarpaea and Ladakiella are described, and their diagnostic characters are discussed. Spirorhynchus is reduced to synonymy of Goldbachia, Ptilotrichum and Berteroella are merged with Stevenia, and Phaeonychium and Eurycarpus are merged with Solms‐laubachia. Thirteen new combinations are proposed: Goldbachia sabulosa (Kar. & Kir.) D. German & Al‐Shehbaz, Ladakiella klimesii (Al‐Shehbaz) D. German & Al‐Shehbaz, Leiocarpaea cochlearioides (Murr.) D. German & Al‐Shehbaz, Schrenkiella parvula (Schrenk) D. German & Al‐Shehbaz, Stevenia dahurica (Peschkova) D. German & Al‐Shehbaz, Stevenia maximowiczii (Palib.) D. German & Al‐Shehbaz, Solms‐laubachia albiflora (T. Anderson) D. German & Al‐Shehbaz, Solms‐laubachia kashgarica (Botsch.) D. German & Al‐Shehbaz, Solms‐laubachia lanuginosa (Hook. f. & Thomson) D. German & Al‐Shehbaz, Solms‐laubachia marinellii (Pamp.) D. German & Al‐Shehbaz, Solms‐laubachia parryoides (Kurz ex Hook. f. & T. Anderson) D. German & Al‐Shehbaz, Solms‐laubachia surculosa (N. Busch) D. German & Al‐Shehbaz, and Solms‐laubachia villosa (Maxim.) D. German & Al‐Shehbaz.
The Runoff Reduction Method
Authors: Battiata Joseph , Collins Kelly , Hirschman David , Hoffmann Greg
Published: December 2010

The Runoff Reduction Method (RRM) provides an innovative approach to crediting the total performance of stormwater best management practices (BMPs). Total BMP performance refers to the pollutant removal and runoff volume reduction capabilities. The RRM tracks the implementation of stormwater BMPs, including Low Impact Development (LID) strategies such as permeable pavement, rainwater harvesting, downspout disconnection, soil amendments, etc., and credits the appropriate runoff volume reduction, pollutant concentration reduction, or both towards compliance with stormwater quality and quantity requirements. By providing a mechanism to credit the volume reduction associated with these LID strategies the RRM also documents an allowable reduction of the overall size and footprint of structural detention practices, thereby providing an economic incentive for the development community to implement LID providing a better overall solution for minimizing the impact of development on the hydrologic cycle.
Wetlands and Ponds for Stormwater Treatment in Subtropical Australia: Their Effectiveness in Enhancing Biodiversity and Improving Water Quality?
Authors: Greenway Margaret
Published: December 2010

Stormwater best management practice is aimed at reducing potential downstream impacts on aquatic ecosystem health. Sediment basins, wetlands and ponds are commonly used in subtropical Australia for water‐quality improvement; they also have the potential to enhance aquatic biodiversity in urbanised catchments. Two retrofit field sites in Brisbane, Australia were monitored for water quality and ecosystem health. The Golden Pond “wetland system” treatment train consisted of a sediment basin and two wetlands. The Bridgewater Creek “pond system”, consisted of a sediment basin and five ponds. Suspended solids were reduced during wet weather, but increased during dry weather due to resuspension by ducks. NO3‐N decreased in both wet and dry weather. NH4‐N increased probably due to ammonification of organic matter. PO4‐P decreased. The removal of soluble NO3 and PO4 is indicative of biological uptake by phytoplankton submerged pond weeds and periphyton attached to aquatic macrophytes. Macroinvertebrate species richness increased, and mosquitoes were not a problem due to predation of larvae by macroinvertebrates. Macrophyte survival was adversely affected by flash flooding and increased inundation. Although water quality objectives were not consistently achieved, both systems were effective in reducing suspended solids and nutrients from stormwater runoff and provided a habitat for aquatic organisms.
Integration of Education, Scholarship, and Service through Stormwater Management
Authors: Welker Andrea L. , Wadzuk Bridget M. , Traver Robert G.
Published: December 2010

Education, scholarship, and service are the cornerstones of academia. This paper describes how the design, construction, and research of stormwater control measures on the campus of Villanova University has been used to integrate these three facets of academic life. To date, eleven stormwater control measures have been constructed on Villanova's campus. This paper will focus on how the authors have successfully used three of these stormwater control measures, a constructed stormwater wetland, a rain garden, and a porous asphalt/pervious concrete comparison study, to fulfil the university's commitments to education, scholarship, and service.
Collapse of Nuclear Reactor SG Tubes Pressurized From Outside: The Influence of Imperfections
Authors: Luzzi Lelio , Di Marcello Valentino
Published: December 2010

Some innovative nuclear power plant proposals consider for the design tubes of considerable thickness subjected to external pressure (e.g., steam generators tubes). The collapse of thick tubes is expected to be dominated by yielding but, because of the decreasing nature of the postcollapse evolution, interaction with buckling is likely to be significant enough to demand consideration. At the present, few studies have been carried out both experimentally and numerically, as witnessed by the really conservative attitude that codes assume for thick tubes. A numerical investigation has been performed in this context at the Politecnico di Milano, which was originally intended as a support for requesting a relaxation of American Society of Mechanical Engineers (ASME) regulations. Actually, in 2007, ASME code case N-759 was approved, permitting significant thickness saving in the tube design. Nevertheless, the numerical investigation was pursued to assess the influence of different parameters, such as eccentricity, initial stresses, and material hardening, on the collapse of tubes with diameter to thickness ratios D/t<20. Results are thought to be useful under at least two respects: first, providing some understanding on the collapse behavior in a thickness range so far unexplored; second, giving an indication on the assumptions on which computer codes ought to be based when numerical analyses are required.
Partially Averaged Navier–Stokes (PANS) Method for Turbulence Simulations: Flow Past a Circular Cylinder
Authors: Lakshmipathy Sunil , Girimaji Sharath S.
Published: December 2010

The objective of this study is to evaluate the capability of the partially averaged Navier–Stokes (PANS) method in a moderately high Reynolds number (ReD 1.4×105) turbulent flow past a circular cylinder. PANS is a bridging closure model purported for use at any level of resolution ranging from Reynolds-averaged Navier–Stokes to direct numerical simulations. The closure model is sensitive to the length-scale cut-off via the ratios of unresolved-to-total kinetic energy (fk) and unresolved-to-total dissipation (fε). Several simulations are performed to study the effect of the cut-off length-scale on computed closure model results. The results from various resolutions are compared against experimental data, large eddy simulation, and detached eddy simulation solutions. The quantities examined include coefficient of drag (Cd), Strouhal number (St), and coefficient of pressure distribution (Cp) along with the mean flow statistics and flow structures. Based on the computed results for flow past circular cylinder presented in this paper and analytical attributes of the closure model, it is reasonable to conclude that the PANS bridging method is a theoretically sound and computationally viable variable resolution approach for practical flow computations.
A Finite Element Model of Cell-Matrix Interactions to Study the Differential Effect of Scaffold Composition on Chondrogenic Response to Mechanical Stimulation
Authors: Appelman Taly P. , Mizrahi Joseph , Seliktar Dror
Published: December 2010

Mechanically induced cell deformations have been shown to influence chondrocyte response in 3D culture. However, the relationship between the mechanical stimulation and cell response is not yet fully understood. In this study a finite element model was developed to investigate cell-matrix interactions under unconfined compression conditions, using a tissue engineered encapsulating hydrogel seeded with chondrocytes. Model predictions of stress and strain distributions within the cell and on the cell boundary were shown to exhibit space-dependent responses that varied with scaffold mechanical properties, the presence of a pericellular matrix (PCM), and the cell size. The simulations predicted that when the cells were initially encapsulated into the hydrogel scaffolds, the cell size hardly affected the magnitude of the stresses and strains that were reaching the encapsulated cells. However, with the inclusion of a PCM layer, larger cells experienced enhanced stresses and strains resulting from the mechanical stimulation. It was also noted that the PCM had a stress shielding effect on the cells in that the peak stresses experienced within the cells during loading were significantly reduced. On the other hand, the PCM caused the stresses at the cell-matrix interface to increase. Based on the model predictions, the PCM modified the spatial stress distribution within and around the encapsulated cells by redirecting the maximum stresses from the periphery of the cells to the cell nucleus. In a tissue engineered cartilage exposed to mechanical loading, the formation of a neo-PCM by encapsulated chondrocytes appears to protect them from initially excessive mechanical loading. Predictive models can thus shed important insight into how chondrocytes remodel their local environment in order to redistribute mechanical signals in tissue engineered constructs.
Online Estimation Algorithm for a Biaxial Ankle Kinematic Model With Configuration Dependent Joint Axes
Authors: Tsoi Y. H. , Xie S. Q.
Published: December 2010

The kinematics of the human ankle is commonly modeled as a biaxial hinge joint model. However, significant variations in axis orientations have been found between different individuals and also between different foot configurations. For ankle rehabilitation robots, information regarding the ankle kinematic parameters can be used to estimate the ankle and subtalar joint displacements. This can in turn be used as auxiliary variables in adaptive control schemes to allow modification of the robot stiffness and damping parameters to reduce the forces applied at stiffer foot configurations. Due to the large variations observed in the ankle kinematic parameters, an online identification algorithm is required to provide estimates of the model parameters. An online parameter estimation routine based on the recursive least-squares (RLS) algorithm was therefore developed in this research. An extension of the conventional biaxial ankle kinematic model, which allows variation in axis orientations with different foot configurations had also been developed and utilized in the estimation algorithm. Simulation results showed that use of the extended model in the online algorithm is effective in capturing the foot orientation of a biaxial ankle model with variable joint axis orientations. Experimental results had also shown that a modified RLS algorithm that penalizes a deviation of model parameters from their nominal values can be used to obtain more realistic parameter estimates while maintaining a level of estimation accuracy comparable to that of the conventional RLS routine.
A Mathematical Simulation of the Ureter: Effects of the Model Parameters on Ureteral Pressure/Flow Relations
Authors: Vahidi Bahman , Fatouraee Nasser , Imanparast Ali , Moghadam Abbas Nasiraei
Published: December 2010

Ureteral peristaltic mechanism facilitates urine transport from the kidney to the bladder. Numerical analysis of the peristaltic flow in the ureter aims to further our understanding of the reflux phenomenon and other ureteral abnormalities. Fluid-structure interaction (FSI) plays an important role in accuracy of this approach and the arbitrary Lagrangian–Eulerian (ALE) formulation is a strong method to analyze the coupled fluid-structure interaction between the compliant wall and the surrounding fluid. This formulation, however, was not used in previous studies of peristalsis in living organisms. In the present investigation, a numerical simulation is introduced and solved through ALE formulation to perform the ureteral flow and stress analysis. The incompressible Navier–Stokes equations are used as the governing equations for the fluid, and a linear elastic model is utilized for the compliant wall. The wall stimulation is modeled by nonlinear contact analysis using a rigid contact surface since an appropriate model for simulation of ureteral peristalsis needs to contain cell-to-cell wall stimulation. In contrast to previous studies, the wall displacements are not predetermined in the presented model of this finite-length compliant tube, neither the peristalsis needs to be periodic. Moreover, the temporal changes of ureteral wall intraluminal shear stress during peristalsis are included in our study. Iterative computing of two-way coupling is used to solve the governing equations. Two phases of nonperistaltic and peristaltic transport of urine in the ureter are discussed. Results are obtained following an analysis of the effects of the ureteral wall compliance, the pressure difference between the ureteral inlet and outlet, the maximum height of the contraction wave, the contraction wave velocity, and the number of contraction waves on the ureteral outlet flow. The results indicate that the proximal part of the ureter is prone to a higher shear stress during peristalsis compared with its middle and distal parts. It is also shown that the peristalsis is more efficient as the maximum height of the contraction wave increases. Finally, it is concluded that improper function of ureteropelvic junction results in the passage of part of urine back flow even in the case of slow start-up of the peristaltic contraction wave.
A Dilution-Filtration System for Removing Cryoprotective Agents
Authors: Zhou Xiaoming , Liu Zhong , Shu Zhiquan , Ding Weiping , Du Pingan , Chung JaeHyun , Liu Carolyn , Heimfeld Shelly , Gao Dayong
Published: December 2010

In most cryopreservation applications, the final concentrations of cryoprotective agents (CPAs) must be reduced to biocompatible levels. However, traditional methods for removing CPAs usually have disadvantages of operation complexity, time consumption, and ease of contamination, especially for the applications involving large volumes of cell suspensions. A dilution-filtration system, which involves pure ultrafiltration for separation, was developed for continuous, automatic, and closed process of removing CPAs. To predict the optimal protocols under given experimental conditions, a theoretical model was established first. Cell-free experiments were then conducted to investigate the variation in CPA concentration during the process, and the experimental data were compared with the theoretical values for the validation of the model. Finally, ten units (212.9 ml/unit±9.5 ml/unit) of thawed human red blood cells (cryopreserved with 40% (w/v) glycerol) were deglycerolized using the theoretically optimal operation protocols to further validate the effectiveness and advantage of the system. In the cell-free experiments, glycerol was continuously removed and the concentration variations fitted the simulated results quite well. In the in-vitro experiments, glycerol concentration in RBC suspension was reduced to 5.57 g/l±2.81 g/l within an hour, and the cell count recovery rate was 91.19%±3.57%, (n=10), which proves that the system is not only safe for removing CPAs, but also particularly efficient for processing large-scale samples. However, the operation parameters must be carefully controlled and the optimal protocols should be specialized and various from case to case. The presented theoretical model provides an effective approach to find out the optimal operation protocols under given experimental conditions and constrains.
Effect of Surgery to Implant Motion and Force Sensors on Vertical Ground Reaction Forces in the Ovine Model
Authors: Herfat Safa T. , Shearn Jason T. , Bailey Denis L. , Greiwe R. Michael , Galloway Marc T. , Gooch Cindi , Butler David L.
Published: December 2010

Activities of daily living (ADLs) generate complex, multidirectional forces in the anterior cruciate ligament (ACL). While calibration problems preclude direct measurement in patients, ACL forces can conceivably be measured in animals after technical challenges are overcome. For example, motion and force sensors can be implanted in the animal but investigators must determine the extent to which these sensors and surgery affect normal gait. Our objectives in this study were to determine (1) if surgically implanting knee motion sensors and an ACL force sensor significantly alter normal ovine gait and (2) how increasing gait speed and grade on a treadmill affect ovine gait before and after surgery. Ten skeletally mature, female sheep were used to test four hypotheses: (1) surgical implantation of sensors would significantly decrease average and peak vertical ground reaction forces (VGRFs) in the operated limb, (2) surgical implantation would significantly decrease single limb stance duration for the operated limb, (3) increasing treadmill speed would increase VGRFs pre- and post operatively, and (4) increasing treadmill grade would increase the hind limb VGRFs pre- and post operatively. An instrumented treadmill with two force plates was used to record fore and hind limb VGRFs during four combinations of two speeds (1.0 m/s and 1.3 m/s) and two grades (0 deg and 6 deg). Sensor implantation decreased average and peak VGRFs less than 10% and 20%, respectively, across all combinations of speed and grade. Sensor implantation significantly decreased the single limb stance duration in the operated hind limb during inclined walking at 1.3 m/s but had no effect on single limb stance duration in the operated limb during other activities. Increasing treadmill speed increased hind limb peak (but not average) VGRFs before surgery and peak VGRF only in the unoperated hind limb during level walking after surgery. Increasing treadmill grade (at 1 m/s) significantly increased hind limb average and peak VGRFs before surgery but increasing treadmill grade post op did not significantly affect any response measure. Since VGRF values exceeded 80% of presurgery levels, we conclude that animal gait post op is near normal. Thus, we can assume normal gait when conducting experiments following sensor implantation. Ultimately, we seek to measure ACL forces for ADLs to provide design criteria and evaluation benchmarks for traditional and tissue engineered ACL repairs and reconstructions.
Effect of Supraspinatus Tendon Repair Technique on the Infraspinatus Tendon
Authors: Andarawis-Puri Nelly , Kuntz Andrew F. , Ramsey Matthew L. , Soslowsky Louis J.
Published: December 2010

Supraspinatus tendon tears are common and often propagate into larger tears that include the infraspinatus tendon, resulting in loss of function and increased pain. Previously, we showed that the supraspinatus and infraspinatus tendons mechanically interact through a range of rotation angles, potentially shielding the torn supraspinatus tendon from further injury while subjecting the infraspinatus tendon to increased risk of injury. Surgical repair of torn supraspinatus tendons is common, yet the effect of the repair on the infraspinatus tendon is unknown. Since we have established a relationship between strain in the supraspinatus and infraspinatus tendons the success of a supraspinatus tendon repair depends on its effect on the loading environment in the infraspinatus tendon. More specifically, the effect of transosseous supraspinatus tendon repair in comparison to one that utilizes suture anchors, as is commonly done with arthroscopic repairs, on this interaction through these joint positions will be evaluated. We hypothesize that at all joint positions evaluated, both repairs will restore the interaction between the two tendons. For both repairs, (1) increasing supraspinatus tendon load will increase infraspinatus tendon strain and (2) altering the rotation angle from internal to external will increase strain in the infraspinatus tendon. Strains were measured in the infraspinatus tendon insertion through a range of joint rotation angles and supraspinatus tendon loads, for the intact, transosseous, and suture anchor repaired supraspinatus tendons. Images corresponding to specific supraspinatus tendon loads were isolated for the infraspinatus tendon insertion for analysis. The effect of supraspinatus tendon repair on infraspinatus tendon strain differed with joint position. Altering the joint rotation did not change strain in the infraspinatus tendon for any supraspinatus tendon condition. Finally, increasing supraspinatus tendon load resulted in an increase in average maximum and decrease in average minimum principal strain in the infraspinatus tendon. There is a significant difference in infraspinatus tendon strain between the intact and arthroscopically (but not transosseous) repaired supraspinatus tendons that increases with greater loads. Results suggest that at low loads neither supraspinatus tendon repair technique subjects the infraspinatus tendon to potentially detrimental loads; however, at high loads, transosseous repairs may be more advantageous over arthroscopic repairs for the health of the infraspinatus tendon. Results emphasize the importance of limiting loading of the repaired supraspinatus tendon and that at low loads, both repair techniques restore the interaction to the intact supraspinatus tendon case.
A Comparison of Uniaxial and Biaxial Mechanical Properties of the Annulus Fibrosus: A Porcine Model
Authors: Gregory Diane E. , Callaghan Jack P.
Published: December 2010

The annulus fibrosus of the intervertebral disk experiences multidirectional tension in vivo, yet the majority of mechanical property testing has been uniaxial. Therefore, our understanding of how this complex multilayered tissue responds to loading may be deficient. This study aimed to determine the mechanical properties of porcine annular samples under uniaxial and biaxial tensile loading. Two-layer annulus samples were isolated from porcine disks from four locations: anterior superficial, anterior deep, posterior superficial, and posterior deep. These tissues were then subjected to three deformation conditions each to a maximal stretch ratio of 1.23: uniaxial, constrained uniaxial, and biaxial. Uniaxial deformation was applied in the circumferential direction, while biaxial deformation was applied simultaneously in the circumferential and compressive directions. Constrained uniaxial consisted of a stretch ratio of 1.23 in the circumferential direction while holding the tissue stationary in the axial direction. The maximal stress and stress-stretch ratio (S-S) moduli determined from the biaxial tests were significantly higher than those observed during both the uniaxial tests (maximal stress, 97.1% higher during biaxial; p=0.002; S-S moduli, 117.9% higher during biaxial; p=0.0004) and the constrained uniaxial tests (maximal stress, 46.8% higher during biaxial; S-S moduli, 82.9% higher during biaxial). These findings suggest that the annulus is subjected to higher stresses in vivo when under multidirectional tension.
Teaching Elementary Particle Physics: Part I1
Authors: Hobson Art
Published: December 2010

I'll outline suggestions for teaching elementary particle physics, often called high energy physics, in high school or introductory college courses for non-scientists or scientists. Some presentations of this topic simply list the various particles along with their properties, with little overarching structure. Such a laundry list approach is a great way to make a fascinating topic meaningless. Students need a conceptual framework from which to view the elementary particles. That conceptual framework is quantum field theory (QFT). Teachers and students alike tend to quake at this topic, but bear with me. We're talking here about concepts, not technicalities. My approach will be conceptual and suitable for non-scientists and scientists; if mathematical details are added in courses for future scientists, they should be simple and sparse. Introductory students should not be expected to do QFT, but only to understand its concepts. Those concepts take some getting used to, but they are simple and can be understood by any literate person, be she plumber, attorney, musician, or physicist.
Using the Wiimote in Introductory Physics Experiments
Authors: Ochoa Romulo , Rooney Frank G. , Somers William J.
Published: December 2010

The Wii is a very popular gaming console. An important component of its appeal is the ease of use of its remote controller, popularly known as a Wiimote. This simple-looking but powerful device has a three-axis accelerometer and communicates with the console via Bluetooth protocol. We present two experiments that demonstrate the feasibility of using the Wiimote in introductory physics experiments. The linear dependence of centripetal acceleration on the radial distance at constant angular velocity is verified and compared with data obtained using photogate timers. A second application to simple harmonic oscillators tests the capabilities of the Wiimote to measure variable accelerations.
Experiencing Light's Properties Within Your Own Eye
Authors: Mauser Michael
Published: December 2010

Seeing the reflection, refraction, dispersion, absorption, polarization, and scattering or diffraction of light within your own eye makes these properties of light truly personal. There are practical aspects of these within the eye phenomena, such as eye tracking for computer interfaces. They also offer some intriguing diversions, for example, being able to identify polarized light with the naked eye. Finally, some interesting features of the eye are revealed, like the presence of particles within the eye.
Chladni Patterns on Drumheads: A “Physics of Music” Experiment
Authors: Worland Randy
Published: December 2010

In our “Physics of Music” class for non-science majors, we have developed a laboratory exercise in which students experiment with Chladni sand patterns on drumheads. Chladni patterns provide a kinesthetic, visual, and entertaining way to illustrate standing waves on flat surfaces and are very helpful when making the transition from one-dimensional systems, such as string and wind instruments, to the two-dimensional membranes and plates of the percussion family. Although the sand patterns attributed to Ernst Florens Friedrich Chladni1 (1756–1827) are often demonstrated for this purpose using metal plates,2–4 the use of drumheads offers several pedagogical and practical advantages in the lab.
Apparatus Named After Our Academic Ancestors — II
Authors: Greenslade Thomas B.
Published: December 2010

In my previous article1 on apparatus named after physicists and physics teachers, I discussed five relatively common pieces of apparatus from the 1875–1910 era. Now I will go back to the 18th and early-19th centuries to discuss eponymous2 apparatus that we are still using in lecture demonstrations.
Using the Sound Card as a Timer
Authors: Aguiar C. E. , Pereira M. M.
Published: December 2010

Experiments in mechanics often involve measuring time intervals much smaller than one second, a task that is hard to perform with handheld stopwatches. This is one of the reasons why photogate timers are so popular in school labs. There is an interesting alternative to stopwatches and photogates, easily available if one has access to a personal computer with sound-recording capability. The idea is simple: a computer sound card can record audio frequencies up to several kilohertz, which means it has a time resolution of a fraction of a millisecond, comparable to that of photogate timers. Many experiments in mechanics can be timed by the sound they produce, and in these situations a direct audio recording may provide accurate measurements of the time intervals of interest. This idea has already been explored in a few cases,1–5 and here we apply it to an experiment that our students found very enjoyable: measuring the speed of soccer balls they kicked.