bluuebunny/crossref_metadata_2025 huggingface dataset:
Altering Light and Soil N to Limit Phalaris arundinacea Reinvasion in Sedge Meadow Restorations
Authors: Iannone Basil V. , Galatowitsch Susan M.
Published: November 2008

Efforts to eradicate invasive plants in restorations can unintentionally create conditions that favor reinvasion over the establishment of desired species, especially when remnant invasive propagules persist. Reducing resources needed by the invader for seedling establishment, however, may be an effective strategy to prevent reinvasion. Propagules of Phalaris arundinacea persist after removal from sedge meadow wetlands and reestablish quickly in posteradication conditions, hindering community restoration. A study was conducted in two experimental wetlands with controlled hydrologic regimes to determine if reducing light by sowing short‐lived, nonpersistent native cover crops or immobilizing soil N by incorporating soil–sawdust amendments can prevent Phalaris reinvasion, allowing native communities to recover. A 10‐species perennial target community and Phalaris were sown with high‐diversity, low‐diversity, or no cover crops in soils with or without sawdust, and seedling emergence, establishment, and growth were measured. High‐diversity cover crops reduced light, decreasing Phalaris and target community seedling establishment by 89 and 57%, respectively. Short‐term nitrogen reduction in sawdust‐amended soils delayed Phalaris seedling emergence and decreased Phalaris seedling establishment by 59% but did not affect total target community seedling establishment. The target community reduced Phalaris seedling establishment as effectively as cover crops did. In plots where the target community was grown, amending soils with sawdust further reduced Phalaris seedling growth but not establishment. Results show that use of cover crops can reduce seedling establishment of desired species and is counterproductive to restoration goals. Further, establishing target species is more important and practical for limiting Phalaris reinvasion than is immobilizing nitrogen.
HIDDEN AND FALSE “PREFERENCES” ON THE STRUCTURED 9‐POINT HEDONIC SCALE
Authors: VILLEGAS‐RUIZ XADENI , ANGULO OFELIA , O'MAHONY MICHAEL
Published: November 2008

An unspecified number of consumers who used a 9‐point hedonic scale were frustrated because they could not express preferences for products with the same ratings. Accordingly, consumers were required to rate samples of yogurt on a 9‐point structured hedonic scale. Consumers were able to express preference judgments because the testing was performed one‐on‐one with the experimenter. Thus, it was possible to determine the proportion of consumers who had given the same hedonic response to yogurts but still had preferences for one or other of the stimuli. Further testing, which included a pair of identical yogurts among the stimuli, allowed the proportion of preference and no preference responses elicited by identical stimuli to be determined in this context. Such data are useful as a control condition in preference testing, to assess the proportion of false preferences induced by the experimental conditions.

PRACTICAL APPLICATIONS

Consumer liking for various products is typically measured using the 9‐point structured hedonic scale. Sometimes, consumers will give the same score to two products yet prefer one to the other. Such preferences are not recorded if the consumer is isolated from the experimenter and has no means of reporting them. However, the situation is easily rectified if the experimenter interacts one‐on‐one with the consumer. Sometimes, false preferences can be obtained from a hedonic scale. This tendency can be monitored by including identical stimuli in the measurements. The present study investigated the extent of such problems so that methods could be devised to address the problem.
DECISION STRATEGIES DETERMINED FROM THE SHAPE OF THE SAME–DIFFERENT ROC CURVE: WHAT ARE THE EFFECTS OF INCORRECT ASSUMPTIONS?
Authors: HAUTUS MICHAEL J. , O'MAHONY MICHAEL , LEE HYE‐SEONG
Published: November 2008

The literature includes many studies that use the shape of the receiver operating characteristic (ROC) curve derived from the same–different test to ascertain the decision strategy used by the judge: a symmetrical ROC curve indicates a β ‐decision strategy, and an asymmetrical ROC curve indicates a τ ‐decision strategy. These studies have not considered the effect that breaches of the assumptions that underlie the standard same–different model would have on inferences drawn from the shape of the ROC curve. Three such assumptions are investigated: the equal‐variance assumption; the assumption of no stimulus order effects; and the assumption that the discriminability of the two stimuli is the same when presented first or second in the test sequence. Simulations indicate that the shape of the ROC curve is very tolerant of the breach of these assumptions. Consequently, inferences about the decision strategy used by a judge are fairly robust, and confidence in published results is upheld.

PRACTICAL APPLICATIONS

The same–different test is frequently used to determine the decision strategy adopted by judges. There are several assumptions made about the same–different test that may, if they were breached, undermine this test's ability to indicate the judge's decision strategy. The simulations conducted in this research indicate that the shape of the same–different ROC curve is very robust to breaches of these assumptions. Consequently, food scientists can maintain their confidence in the inferences made in the research already published on this topic, and in their own future research and development of sensory testing methods.
A PROCEDURE OF SENSORY EVALUATION FOR DESCRIBING THE AROMA PROFILE OF SINGLE GRAPE VARIETY WINES
Authors: CARLUCCI ANGELA , MONTELEONE ERMINIO
Published: November 2008

In order to describe the aroma “fingerprint” of single grape variety wines, a suitable procedure of aroma description was defined. The procedure consisted of two main steps based on panel training and term generation with aroma profile analysis. Training was divided in two parts: (1) aroma identification and learning and (2) intensity evaluation of aroma descriptors. In the second step, assessors generated attributes and measured their intensity on wine samples obtained from “Falanghina” variety grapes. After validation, this procedure was applied so that the aromatic profile of other five single variety wines could be defined.

Highest number of generating attributes compared with the conventional sensory method, sample discrimination ability and panel performance confirm the validity of the procedure, which allows the analysis of single grape variety wines one by one in turns so that a large number of single variety wines can be analyzed in a simple, effective and rapid manner.

PRACTICAL APPLICATIONS

In this study, a procedure in sensory evaluation capable of describing the aromatic profile of a large number of single variety wines was defined. The proposed procedure permits a simple and effective definition of the aromatic “fingerprint” of wines, and an effective and quick quantification of this could fit very well in experimental studies aiming to test the response of different grape variety to particular agronomic or technological conditions.
MANGO SOY FORTIFIED PROBIOTIC YOGURT: EFFECT OF CULTURE ADDITION AND TEMPERATURE ON TEXTURAL CHARACTERISTICS
Authors: KAUR HARBINDER , KUMAR PRADYUMAN
Published: November 2008

Mango soy fortified probiotic yogurt (MSFPY) samples were prepared by using blends of toned milk (78.3%; 3% milk fat and 8.5% milk solid not fat), soy milk (14.5%) and mango pulp (7.2%) using yogurt bacteria and probiotic bacteria, namely, Bifidobacterium bifidus and Lactobacillus acidophilus. This work was conducted to see the effect of varied levels (0.5, 1, 1.5, 2 and 2.5%) of inoculum of yogurt and probiotic culture and the effect of different temperatures (10, 20 and 30C) on textural profile (hardness, cohesiveness, adhesiveness, springiness and gumminess). As per central composite rotatable design for four variables and five levels, 31 experiments were conducted. Textural profile data obtained at different temperatures of MSFPY were used to calculate temperature coefficients of all the textural properties, which were fitted into the second‐order polynomial model. Hardness temperature coefficients ranged from−0.92 to−1.97% per C, cohesiveness temperature coefficients ranged from−0.42 to 0.53% per C, adhesiveness temperature coefficients ranged from−2.74 to−3.73% per C, springiness temperature coefficients ranged from−1.47 to 5.07% per C and gumminess temperature coefficients ranged from−0.94 to−1.92% per C.

PRACTICAL APPLICATIONS

Yogurt has been attributed nutraceutical, therapeutic and probiotic effects such as digestion enhancement, immune system boosting, anticarcinogenic activity and reduction in serum cholesterol. This study showed the effect of addition of yogurt bacteria and probiotic bacteria in combination andtemperature on textural properties. As health awareness increases among consumers, they also want the texture of the product to remain the same. If the product has to be consumed at either low or room temperature, one may predict the textural parameters of the mango soy fortified probiotic yogurt at different temperatures.
Root canal treatment of three‐rooted maxillary second premolars: Report of four cases
Authors: Barros Danilo Barbosa , Guerreiro Tanomaru Juliane Maria , Tanomaru‐Filho Mário
Published: November 2008

The aim of this report is to contribute to a better understanding of the radiographic, clinical and anatomic findings in maxillary second premolars. This paper reports the endodontic treatment of two cases of three‐rooted three‐canal maxillary second premolars in different patients, and two sound maxillary second premolars also with three canals and three independent roots in a sibling of one of the patients. Although the presence of maxillary second premolars with one or two canals and one root is much more common, other anatomic conditions can be found. A correct clinical and radiographic diagnosis based on knowledge of root canal anatomy and critical interpretation of radiographs is necessary for a safer and successful endodontic treatment of these teeth.
Postoperative pain and associated factors in adolescent patients undergoing two‐visit root canal therapy
Authors: De Andrade Risso Patrícia , Da Cunha Antonio José Ledo Alves , De Araujo Marcos César Pimenta , Luiz Ronir Raggio
Published: November 2008

This prospective study investigated the frequency and intensity of postoperative pain and identified associated factors in adolescents undergoing two‐visit root canal therapy. Sixty‐four patients aged 11 to 18 years old presenting with molars with pulp necrosis were assigned consecutively to two visits (plus an interappointment dressing using calcium‐hydroxide paste). Pain intensity was recorded on a visual analogue scale (VAS) of 0–5. Data were analysed using multivariate logistic regression. The frequency of postoperative pain was 32.8% (21/64), with intensities of VAS 1 and VAS 2 in 81%, VAS 3 in 14.3% and VAS 4 in 4.7% of the 21 cases in which it was experienced. Spontaneous preoperative pain (odds ratio (OR) = 6.60; 95% confidence interval (CI) = 1.61–26.97; P = 0.009) and absence of apical perodontitis (OR = 5.65; 95% CI = 1.34–23.87; P = 0.01) were associated with postoperative pain. The frequency of postoperative pain was high, but the intensity, in general, was low, including flare‐ups. The presence of spontaneous preoperative pain and absence of apical periodontitis increase the probability of suffering from postoperative pain.
Serological responses to two serovar‐independent ELISA antigens of Actinobacillus pleuropneumoniae in Australian commercial pig herds
Authors: Eamens GJ , Gonsalves JR , Whittington A‐M , Turner B
Published: November 2008

Objective  To compare serological responses in pig herds classified as low or high risk for disease caused by Actinobacillus pleuropneumoniae, using two ELISA tests based on serovar‐independent antigens.

Procedure  Cross‐sectional sampling was undertaken in 13 commercial herds, the clinical and slaughter histories of which indicated either freedom from (n = 5) or prior confirmed cases of A. pleuropneumoniae (n = 8). In nine herds, approximately 40 pigs each were sampled at 4, 8, 12, 16 and 20 weeks. Three of the remaining four herds were sampled between 6 and 30 weeks of age, and the last was sampled only prior to slaughter, at approximately 24 weeks. Sera were tested in ELISA based on two antigens common among A. pleuropneumoniae serovars: a 39‐kDa outer membrane protein and a recombinant ApxIVA‐N terminus protein.

Results  Sampling of 1 and 5 to 6‐month‐old pigs provided the most useful information on herd status. The 39‐kDa ELISA was sensitive in detecting infected herds, but had evidence of cross‐reactivity with high seroreactivity rates in older pigs in some low‐risk herds. The ApxIVA‐N ELISA was less seroreactive in high‐risk herds and had higher specificity in low‐risk herds.

Conclusion  ELISA based on the 39‐kDa subunit are of limited use, because of possible cross‐reactivity, but a high negative predictive value may be useful for risk assessment in suspect herds. Maternal antibody to ApxIVA‐N may be of value in detecting high‐risk herds, but 5% of 4‐week‐old pigs in low‐risk herds were also seropositive in this assay.
The role of the cell wall in fungal pathogenesis
Authors: Arana David M. , Prieto Daniel , Román Elvira , Nombela César , Alonso‐Monge Rebeca , Pla Jesús
Published: November 2008

Fungal infections are a serious health problem. In recent years, basic research is focusing on the identification of fungal virulence factors as promising targets for the development of novel antifungals. The wall, as the most external cellular component, plays a crucial role in the interaction with host cells mediating processes such as adhesion or phagocytosis that are essential during infection. Specific components of the cell wall (called PAMPs) interact with specific receptors in the immune cell (called PRRs), triggering responses whose molecular mechanisms are being elucidated. We review here the main structural carbohydrate components of the fungal wall (glucan, mannan and chitin), how their biogenesis takes place in fungi and the specific receptors that they interact with. Different model fungal pathogens are chosen to illustrate the functional consequences of this interaction. Finally, the identification of the key components will have important consequences in the future and will allow better approaches to treat fungal infections.
Utilisation of introduced Brazilian pastures ecosystems by native dung beetles: diversity patterns and resource use
Authors: LOUZADA JÚLIO N.C. , CARVALHO E SILVA PAULO R.
Published: November 2008

Abstract. 

Cattle pastures dominated by introduced grasses are a characteristic component of many tropical landscapes in Brazil, yet little information is available concerning the insect communities that inhabit these novel ecosystems.

Dung beetles are a conspicuous element of pasture insect communities, and make a significant contribution to dung decomposition, parasitic fly control, and soil bioturbation.

We sampled dung beetle assemblages in twelve introduced pastures near Viçosa, Minas Gerais, Brazil. We used pitfall traps baited separately with cow and horse dung, and collected a total of 456 dung beetles, comprising 23 species from 13 different genera. We analysed patterns of alpha and beta diversity, community structure, and species composition among pastures and bait types.

Cow dung harboured significantly more species, but a similar abundance of dung beetles compared with horse dung. However, both dung types supported species exclusive to that type, and hosted a distinct dung beetle community structure and composition.

Although livestock (cattle and horses) was introduced to Brazil less than 500 years ago, our data suggest that novel and well‐structured dung beetle communities are actively exploiting these novel food resources in Brazilian pasturelands.
The Making of Customary Territories: Social Change at the Intersection of State and Indigenous Territorial Politics on Lake Titicaca, Peru
Authors: Kent Michael
Published: November 2008

Este artículo explora la relación entre la política indigena, el manejo de áreas protegídas y formas consuetudinarias de territorialidad en los Andes, mediante el análisis de un conflicto relacionado con la Reserva Nacional del Titicaca en Perú. Cuestiona la literatura académica que supone la pre‐existencia de los territorios consuetudinarios, cuya defensa desencadenaría conflictos entre los moviementos indígenas y los actores externos. En contraste, este artículo demuestra como la conformación de territorios consuetudinarios ha sido el resultado corolario del conflicto entre las autoridades de la Reserva y varios grupos indígenas. Durante este proceso, territorios flexibles, vagamente definidos y compartidos, se han transformado en territorios “consuetudinarios” fijos, claramente definidos y exclusivos.

This article explores the relation between indigenous politics, protected area management, and customary forms of territoriality in the Andes, by analyzing a conflict over the Titicaca National Reserve, Peru. It questions academic literature that assumes the pre‐existence of customary territories, the defence of which supposedly leads to conflicts between indigenous movements and external actors. Instead, this article shows how theproductionof customary territories has been the corollary result of the conflict between the Reserve's authorities and a variety of indigenous groups. In the process, flexible, vaguely defined, and shared territories have transformed into fixed, clearly defined, and exclusive “customary” territories.
Boundary Layer Influence on the Unsteady Horseshoe Vortex Flow and Surface Heat Transfer
Authors: Sabatino D. R. , Smith C. R.
Published: November 2008

The spatial-temporal flow field and associated surface heat transfer within the leading edge, end-wall region of a bluff body were examined using both particle image velocimetry and thermochromic liquid crystal temperature measurements. The horseshoe vortex system in the end-wall region is mechanistically linked to the upstream boundary layer unsteadiness. Hairpin vortex packets, associated with turbulent boundary layer bursting behavior, amalgamate with the horseshoe vortex resulting in unsteady strengthening and streamwise motion. The horseshoe vortex unsteadiness exhibits two different natural frequencies: one associated with the transient motion of the horseshoe vortex and the other with the transient surface heat transfer. Comparable unsteadiness occurs in the end-wall region of the more complex airfoil geometry of a linear turbine cascade. To directly compare the horseshoe vortex behavior around a turning airfoil to that of a simple bluff body, a length scale based on the maximum airfoil thickness is proposed.
Location and Magnitude of Heat Sources in Solid Oxide Fuel Cells
Authors: Fischer Katharina , Seume Joerg R.
Published: November 2008

The correct prediction of the temperature distribution is a prerequisite for the reliable determination of species and current distributions in any solid oxide fuel cell (SOFC) model. It is even more crucial if the model is intended for the analysis of thermo-mechanical stresses. This paper addresses the different mechanisms of heat generation and absorption in the fuel cell. Particular attention is paid to the heating associated with the oxidation of hydrogen, which is commonly assigned to the interface between electrolyte and anode in SOFC modeling. However, for a detailed determination of the temperature profile in the fuel cell solid components, the separate consideration of the cathodic and anodic half-reactions is required. A method for determining the specific entropy change of the half-reactions based on Seebeck-coefficient data is adopted from the literature and applied to the SOFC. In order to exemplarily demonstrate the contribution of the various heat sources to the overall heat generation as well as the influence of their location, a spatially discretized model of a tubular SOFC is used. Temperature profiles obtained with and without separate consideration of the electrode reactions are compared. The comparison shows that the spatially discretized reaction model is indeed necessary for the reliable assessment of temperature gradients in the ceramic SOFC components.
Sensitivity Analysis of a 2.5kW Proton Exchange Membrane Fuel Cell Stack by Statistical Method
Authors: Rajalakshmi N. , Velayutham G. , Dhathathreyan K. S.
Published: November 2008

This paper describes the application of statistical analysis to a 2.5kW proton exchange membrane fuel cell stack operation, by experimental design methodology, whereby robust design conditions were identified for the operation of fuel cell stacks. The function is defined as the relationship between the fuel cell power and the operating pressure and stoichiometry of the reactants. Four types of control factors, namely, the pressures of the fuel and oxidant and the flow rates of the fuel and oxidant, are considered to select the optimized conditions for fuel cell operation. All the four factors have two levels, leading a full factorial design requiring 24 experiments leading to 16 experiments and fractional factorial experiments, 24−1, leading to 8 experiments. The experimental data collected were analyzed by statistical sensitivity analysis by checking the effect of one variable parameter on the other. The mixed interaction between the factors was also considered along with main interaction to explain the model developed using the design of experiments. The robust design condition for maximum fuel cell performance was found to be air flow rate, and the interaction between the air pressure and flow rate compared to all other factors and their interactions. These fractional factorial experiments, presently applied to fuel cell systems, can be extended to other ranges and factors with various levels, with a goal to minimize the variation caused by various factors that influence the fuel cell performance but with less number of trials compared to full factorial experiments.
Stress-Strain Behavior of Perfluorosulfonic Acid Membranes at Various Temperatures and Humidities: Experiments and Phenomenological Modeling
Authors: Kusoglu Ahmet , Tang Yaliang , Santare Michael H. , Karlsson Anette M. , Cleghorn Simon , Johnson William B.
Published: November 2008

The constitutive response of perfluorinated sulfonic acid (PFSA) membranes based on tensile testing is investigated, and a phenomenological constitutive model for the elastoplastic flow behavior as a function of temperature and humidity is proposed. To this end, the G’Sell–Jonas (1979, “Determination of the Plastic Behavior of Solid Polymers at Constant True Strain Rate,” J. Mater. Sci., 14, pp. 583–591) constitutive model for semicrystalline polymers is extended by incorporating, in addition to temperature, relationships between the material constants of this model and the measured relative humidity. By matching the proposed constitutive model to the experimental stress-strain data, useful material constants are found. Furthermore, correlations between these material constants and Young’s modulus and proportional limit stress are investigated. The influence of material orientation, inherited from processing conditions, on the stress-strain behavior is also studied. The proposed model can be used to approximate the mechanical behavior of PFSA membranes in numerical simulations of a fuel cell operation.
Surface Scale Formation on Solid Oxide Fuel Cell Proximal Balance of Plant Components
Authors: Gerdes Kirk , Johnson Christopher
Published: November 2008

Chromium containing alloys used as solid oxide fuel cell (SOFC) interconnects can generate volatile chrome species that deposit as Cr2O3(s) at the SOFC cathode/electrolyte interface under modest current densities (∼0.5 A/cm2). Deposition of chromic oxide at this interface increases overpotential losses, thereby degrading fuel cell performance and efficiency. Balance of plant components have not received attention as a chromium source but can produce volatile Cr species through direct thermal contact with the hot cell stack. In this work, materials representative of BoP component alloys were exposed to dry air at temperatures between 600°C and 800°C for 72 h. The material classes tested include austenitic steel, ferritic steel, alumina formers, silica formers, and a specialty ferritic with elevated alumina and silica content. The surface scales formed on each alloy were identified using X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Thin surface scales were formed that included Cr-, Fe-, Al-, and Si-oxides as well as Mn–Cr spinel. The surface composition estimated from the analytical data is used to thermodynamically calculate the abundance of volatile chromium species over the alloys. Using the calculated vapor composition and assumed rate efficiencies, it is possible to calculate the mass of Cr2O3 that will deposit on the SOFC surface. Up to 4.3 cm2 of SOFC active area can be deactivated in 2000 h of operation assuming a 1% efficiency of volatilization of chrome species and a 1% efficiency of deposition of Cr2O3. This is estimated to be approximately 5% of the starting active area of an ∼20 W SOFC. Degradation of SOFC performance is expected to scale almost linearly with stack size.
Interactive Haptic Refinement of a Five-Axis Finishing Cut
Authors: Chen Kun , Tang Kai
Published: November 2008

This paper describes the design of a haptic system that allows the interactive modification of cutter orientation during five-axis finishing cuts with the aim of improving the surface finish quality and collision avoidance strategies. The system supports two haptic models that provide three degree of freedom (DOF) force feedback and 6DOF posture sensing. Details of five key functions of the system are given: (1) a rendering conversion that uses 3DOF (instead of five) force feedback haptic representation, (2) an efficient force feedback design that allows accurate results to be obtained from the user’s manipulation, (3) a fast collision detection scheme that achieves real-time feedback, (4) use of active haptic guidance to assist cutter-path generation, and (5) a design that supports both ball-end and flat-end tools with partial optimization.
An Experimental Study of Haptic Feedback in a Teleoperated Assembly Task
Authors: Christiansson Göran A. V.
Published: November 2008

Haptic feedback is known to improve teleoperation task performance for a number of tasks, and one important question is which haptic cues are the most important for each specific task. This research quantifies human performance in an assembly task for two types of haptic cues: low-frequency (LF) force feedback and high-frequency (HF) force feedback. A human subjects study was performed with those two main factors: LF force feedback on/off and HF force (acceleration) feedback on/off. All experiments were performed using a three degree-of-freedom teleoperator where the slave device has a low intrinsic stiffness, while the master device on the other hand is stiff. The results show that the LF haptic feedback reduces impact forces, but does not influence low-frequency contact forces or task completion time. The HF information did not improve task performance, but did reduce the mental load of the teleoperator, but only in combination with the LF feedback.
Characterization of Tactors Used in Vibrotactile Displays
Authors: Jones Lynette A. , Held David A.
Published: November 2008

A series of experiments was conducted to evaluate the operating characteristics of small DC motors that are often in tactile displays. The results indicated that these motors are reliable in terms of their frequency and amplitude of oscillation, but that the frequency varies across motors. A simulated skin material was developed to provide a substrate for evaluating the performance of the motors. There was a marked attenuation in frequency when the tactors were on this material and the surface waves could be detected 60 mm from the site of activation. These findings suggest that the spacing between tactors should be at least 60–80 mm if tactile cues are used to locate events in the environment.
A Rigorous Dynamical-Systems-Based Analysis of the Self-Stabilizing Influence of Muscles
Authors: Eriten Melih , Dankowicz Harry
Published: November 2008

In this paper, dynamical systems analysis and optimization tools are used to investigate the local dynamic stability of periodic task-related motions of simple models of the lower-body musculoskeletal apparatus and to seek parameter values guaranteeing their stability. Several muscle models incorporating various active and passive elements are included and the notion of self-stabilization of the rigid-body dynamics through the imposition of musclelike actuation is investigated. It is found that self-stabilization depends both on muscle architecture and configuration as well as the properties of the reference motion. Additionally, antagonistic muscles (flexor-extensor muscle couples) are shown to enable stable motions over larger ranges in parameter space and that even the simplest neuronal feedback mechanism can stabilize the repetitive motions. The work provides a review of the necessary concepts of stability and a commentary on existing incorrect results that have appeared in literature on muscle self-stabilization.
A Novel Theoretical Framework for the Dynamic Stability Analysis, Movement Control, and Trajectory Generation in a Multisegment Biomechanical Model
Authors: Iqbal Kamran , Roy Anindo
Published: November 2008

We consider a simplified characterization of the postural control system that embraces two broad components: one representing the musculoskeletal dynamics in the sagittal plane and the other representing proprioceptive feedback and the central nervous system (CNS). Specifically, a planar four-segment neuromusculoskeletal model consisting of the ankle, knee, and hip degrees-of-freedom (DOFs) is described in this paper. The model includes important physiological constructs such as Hill-type muscle model, active and passive muscle stiffnesses, force feedback from the Golgi tendon organ, muscle length and rate feedback from the muscle spindle, and transmission latencies in the neural pathways. A proportional-integral-derivative (PID) controller for each individual DOF is assumed to represent the CNS analog in the modeling paradigm. Our main hypothesis states that all stabilizing PID controllers for such multisegment biomechanical models can be parametrized and analytically synthesized. Our analytical and simulation results show that the proposed representation adequately shapes a postural control that (a) possesses good disturbance rejection and trajectory tracking, (b) is robust against feedback latencies and torque perturbations, and (c) is flexible to embrace changes in the musculoskeletal parameters. We additionally present detailed sensitivity analysis to show that control under conditions of limited or no proprioceptive feedback results in (a) significant reduction in the stability margins, (b) substantial decrease in the available stabilizing parameter set, and (c) oscillatory movement trajectories. Overall, these results suggest that anatomical arrangement, active muscle stiffness, force feedback, and physiological latencies play a major role in shaping motor control processes in humans.
Effects of Camera Switching on Fine Accuracy in a Motion Capture System
Authors: Kuxhaus Laurel , Schimoler Patrick J. , Vipperman Jeffrey S. , Miller Mark Carl
Published: November 2008

When using optical motion capture systems, increasing the number of cameras improves the visibility. However, the software used to deal with the information fusion from multiple cameras may compromise the accuracy of the system due to camera dropout, which can vary with time. In cadaver studies of radial head motion, increasing the number of cameras used by the motion capture system seemed to decrease the accuracy of the measurements. This study investigates the cause. The hypothesis was that errors in position can be induced when markers are obscured from and then restored to a camera’s viewable range, as can happen in biomechanical studies. Accuracy studies quantified the capabilities of the motion capture system with precision translation and rotation movements. To illustrate the effect that abrupt perceived changes in a marker’s position can have on the calculation of radial head travel, simulated motion experiments were performed. In these studies, random noise was added to simulated data, which obscured the resultant path of motion. Finally, camera-blocking experiments were performed in which precise movements were measured with a six-camera Vicon system and the errors between the actual and perceived motion were computed. During measurement, cameras were selectively blocked and restored to view. The maximum errors in translation and rotation were 3.7 mm and 0.837 deg, respectively. Repeated measures analysis of variance (ANOVAs) (α=0.05) confirmed that the camera-blocking influenced the results. Taken together, these results indicate that camera-switching can affect the observation of fine movements using a motion analysis system with a large number of cameras. One solution is to offer opportunity for user interaction in the software to choose the cameras used for each instant of time.
Gap Junctions and Osteoblast-like Cell Gene Expression in Response to Fluid Flow
Authors: Jekir Michael G. , Donahue Henry J.
Published: November 2008

Bone formation occurs in vivo in response to mechanical stimuli, but the signaling pathways involved remain unclear. The ability of bone cells to communicate with each other in the presence of an applied load may influence the overall osteogenic response. The goal of this research was to determine whether inhibiting cell-to-cell gap junctional communication between bone-forming cells would affect the ensemble cell response to an applied mechanical stimulus in vitro. In this study, we investigated the effects of controlled oscillatory fluid flow (OFF) on osteoblastic cells in the presence and the absence of a gap-junction blocker. MC3T3-E1 Clone 14 cells in a monolayer were exposed to 2h of OFF at a rate sufficient to create a shear stress of 20dynes∕cm2 at the cell surface, and changes in steady-state mRNA levels for a number of key proteins known to be involved in osteogenesis were measured. Of the five proteins investigated, mRNA levels for osteopontin (OPN) and osteocalcin were found to be significantly increased 24h postflow. These experiments were repeated in the presence of 18β-glycyrrhetinic acid (BGA), a known gap-junction blocker, to determine whether gap-junction intercellular communication is necessary for this response. We found that the increase in OPN mRNA levels is not observed in the presence of BGA, suggesting that gap junctions are involved in the signaling process. Interestingly, enzyme linked immunosorbent assay data showed that levels of secreted OPN protein increased 48h postflow and that this increase was unaffected by the presence of intact gap junctions.
Development of a Wearable Exoskeleton Haptic Interface Device
Authors: Sone Junji , Inoue Ryou , Yamada Katsumi , Nagae Takanori , Fujita Kinya , Sato Makoto
Published: November 2008

We developed a wearable exoskeleton haptic interface to fit the human body. We generated a force constituting a contrasting moment by pulling a wire using a dc motor. We also developed a control system, which included a motor controller, an interface, and a control software. We evaluated the performance of our interface by conducting a simple task experiment. To execute one task, the control data for each joint jaw must be prepared, and we used force control data generated by a rectified and filtered electromyogram (EMG) curve. From the force representation experiments, it was determined that a force curve based on the EMG data could be used for a haptic interface, and we confirmed that a suitable force curve could be obtained for each subject.
Effect of Walleye (Stizostedion vitreum vitreum) Predation on Juvenile Mortality and Recruitment of Yellow Perch (Perca flavescens) in Oneida Lake, New York
Authors: Nielsen Larry A.
Published: November 2008

The abundance of 12 year-classes of yellow perch (Perca flavescens) in Oneida Lake, New York, was estimated at intervals between ages 0 and II from catch and area swept by trawls. Rankings of abundance of year-classes changed between the ends of the first and third growing seasons, suggesting that ultimate year-class strength was influenced strongly by mortality of age I and II fish. Predation by walleyes was probably the principal cause of mortality of age I and II perch. Although frequency of occurrence of age I and II perch in stomachs of walleyes was low, several lines of evidence suggested that density of juvenile perch also was low and that walleyes consumed a large proportion of each perch cohort. Rates of mortality were modified by perch length, perch density, and density of age 0 perch, all of which relate to intensity of walleye predation.Key words: yellow perch, walleye; mortality, predation; Oneida Lake
Terebellidae (Polychaeta) from the Northeast Pacific Ocean
Authors: Banse Karl
Published: November 2008

Betapista dekkerae, new genus and new species, is described. The generic diagnoses for Laphania and Scionides are improved after inspection of the holotypes of the type species. Eupolymnia heterobranchia (syn., E. crescentis) is redescribed. Additions to the descriptions, based on study of type material, are made for Laphania boecki (new record, Northeast Pacific), Neoamphitrite robusta (syn., Scionides dux), Neoleprea californica and N. spiralis, Pista brevibrunchiata (new record, British Columbia [B.C.], Washington [WA], Japan) and P. fratrella, and Polycirrus californicus (new record, B.C., WA, syn., P. perplexus). Other additions to the descriptions are provided for Amaeana occidentalis (new record, B.C.) and Pista cristata. Two further Pista species (one from the Skagerrak) and five Polycirrus species are charcterized but not named. Other new records are Lanassa venusta venusta (B.C.), Lysilla loveni, and Neoleprea japonica (the two latter for Northeast Pacific). Lysilla pacifica, Pista fasciata, and P. fratrella are shown not to be members of the fauna of British Columbia and Washington. Presumably, neither is Polycirrus caliendrum. New observations on the types of the Antarctic Polycirrus kerguelensis and Ereutho kerguelensis are noted.Key words: Betapista n.g., Neoleprea, new records, Northeast Pacific, Pista, Polycirrus, Scionides, Terebellidae
New and Rare Records of Canadian Fishes and the Influence of Hydrography on Resident and Nonresident Scotian Shelf Ichthyofauna
Authors: Markle Douglas F. , Scott W. B. , Kohler A. C.
Published: November 2008

A recently initiated ichthyoplankton survey of the Scotian Shelf has discovered large numbers of subtropical/tropical expatriated fishes, mostly larvae, and at least two previously unrecognized populations. Thirty-three species in 25 primarily subtropical families (Carcharhinidae, Engraulidae, Synodontidae, Chlorophthalmidae, Ogcocephalidae, Antennariidae, Carapidae, Ophidiidae, Exocoetidae, Syngnathidae, Scorpaenidae, Triglidae, Dactylopteridae, Serranidae, Apogonidae, Branchiostegidae, Rachycentridae, Sciaenidae, Labridae, Scaridae, Callionymidae, Gobiidae, Bothidae, Cynoglossidae, and Ostraciontidae), seven species in four deepwater families (Gonostomatidae, Sternoptychidae, Myctophidae, and Moridae) and two gadoids are reported as new or rare records from the Canadian Atlantic. The frequency and quantity of subtropical expatriates raise the question of their ultimate fate. The existence of eastern Atlantic populations of some of these raises the possibility of transatlantic dispersal. Juvenile or adult specimens of most of the expatriated forms have not been found on the Scotian Shelf but the complex hydrography on the shelf may allow temporary habitation especially in summer. Two species, red hake and Gulf Stream flounder, appear to have discrete, self-sustaining populations on the Scotian Shelf. Both species appear to represent northernmost populations which may be living near their lower thermal limit. Discrepancies between the literature on red hake and data reported herein are unresolved and require long-term observations.Key words: Scotian Shelf, ichthyoplankton, hydrography, zoogeography, western North Atlantic
Genetic Changes in Hatchery Stocks of Brown Trout (Salmo trutta)
Authors: Ryman Nils , Ståhl Gunnar
Published: November 2008

Preservation of the genetic characteristics of a population is one of the primary objectives of many fish stocking programs. Using starch gel electrophoresis we have tested for temporal gene frequency stability at two polymorphic loci coding for α-glycerophosphate dehydrogenase and creatine phosphokinase. Three Swedish hatchery stocks of brown trout (Salmo trutta) and field samples from natural populations corresponding to two of these stocks were analyzed. Highly significant allele frequency changes at both loci indicated considerable lack of intra-stock genetic homogeneity. In the light of these findings we emphasize the importance of using large numbers of actual as well as effective parents to avoid inadvertent genetic changes and inbreeding. No stock should be founded or perpetuated using less than approximately 30 parents of the least numerous sex in any generation.Key words: inbreeding, genetic drift, gene bank, electrophoresis, stocking, trout
Simulations of Energy Flow Through the Amictic Female Rotifer Brachionus rubens Ehrbg.
Authors: Majkowski J. , Pilarska J. , Klekowski R. Z.
Published: November 2008

A model is developed (i) to integrate a set of experimental observations concerning the energy flow through the amictic female rotifer Brachionus rubens Ehrbg.; (ii) to identify inconsistencies in the data; (iii) to understand better the energy dynamics of this organism and the impact of the environment on it; and (iv) to determine the direction of further experimental and theoretical studies. Simulations of energy flow through this organism are generated for various concentrations of food (the alga Chlorella vulgaris), constant during its life span. It is shown that the experimental data for the immature female are self-consistent but that the experimental instantaneous values of total production for the mature female are undervalued. Consequently, Pilarska's instantaneous values of food assimilation and the instantaneous coefficients of energy conversion efficiency are undervalued for the mature female. Using sensitivity analysis we find that the model is highly sensitive to changes in (listed in order of importance) (i) the instantaneous value of food consumption, (ii) the instantaneous coefficient of food assimilation efficiency, (iii) the life span, and (iv) the egg calorific value. The model is relatively insensitive to changes in (i) the initial body calorific value, (ii) the age at maturity, (iii) the time interval between two successive acts of reproduction, and (iv) the instantaneous value of respiration. Specific parameters are identified as needing remeasurement.Key words: model, simulation, bioenergetics, growth, reproduction, rotifer, Brachionus rubens, sensitivity
Interspecific Predation of Common Strait of Georgia Planktonic Coelenterates: Laboratory Evidence
Authors: Arai Mary Needler , Jacobs J. Roger
Published: November 2008

Among the common pelagic coelenterates of Departure Bay, B.C., Stomotoca atra, Eutonina indicans, Aequorea victoria, and Aurelia aurita show predation on other species under laboratory conditions. Selectivity is demonstrated in the diets of each of these predators.Key words: Stomotoca atra, Eutonina indicans, Aequorea victoria, medusae, feeding, Aurelia aurita
Identifying Pollution Related Changes in Chironomid Communities as a Function of Taxonomic Rank
Authors: Waterhouse J. C. , Farrell M. P.
Published: November 2008

This study compares specific- and generic-level analyses of chironomid presence/absence data along a heavy-metal gradient. Eighteen binary similarity coefficients were calculated for five sampling stations from a small Ohio stream that receives an effluent containing zinc, copper, and chromium from a metal-plating industry. In general, the specific- and generic-level values were highly correlated and showed similar patterns across the 10 station comparisons. The basis for this correlation was then investigated by an assessment of both the amount (average number of species per genus) and the pattern (species to genus ratio trend) of information loss along the pollution gradient. Trends in the species to genus ratio along the gradient are viewed as indicative of the similarity of congenerics in their response to the gradient. The lack of a significant trend in the species to genus ratio in our data indicates that the agreement between specific- and generic-level analyses was due to the ability of a robust species distribution pattern to withstand a limited amount of random information loss, rather than any inherent similarity among congenerics reflected in their species to genus ratio trends. Analyses based on only a few species (e.g. abundant or indicator species) cannot afford as much information loss and must rely more heavily on similarity of congeneric species.
Lake Michigan's Capacity to Support Lake Trout (Salvelinus namaycush) and Other Salmonines: An Estimate Based on the Status of Prey Populations in the 1970s
Authors: Eck G. W. , Brown Jr. Edward H.
Published: November 2008

We used a mass balance equation relating total mortality of age II and older alewives (Alosa pseudoharengus) to their removals by predatory fish and other sources of mortality as the basis for estimating that the forage base in Lake Michigan could support an additional 13 000 to 21 000 t of lake trout (Salvelinus namaycush) or a total lake trout biomass between 15 000 and 23 000 t. This biomass estimate is projected with biomasses of other trout and salmon held at 1979 levels. Major premises of this approach are that (1) the sustained availability of age II and older alewives to salmonines will ultimately limit the expansion of salmonine stocks, (2) the alewife population was oscillating without trend during 1973–80, and (3) additional limited predation on alewives would be compensated by a reduction in natural mortality caused by physiological stress and disease.
Morphological, Electrophoretic and Fecundity Characteristics of Atlantic Snow Crab, Chionoecetes opilio, and Implications for Fisheries Management
Authors: Davidson K. , Roff J. C. , Elner R. W.
Published: November 2008

For adult snow crabs (Chionoecetes opilio), from the western Gulf of St. Lawrence, eastern and western Cape Breton Island, and eastern Newfoundland, we compared morphometric, meristic, electrophoretic, and fecundity characteristics. Our morphometric, meristic, and fecundity data indicated that snow crabs from the four areas are morphologically and biologically distinct; therefore, they represent four "phenotypic" or "biological" stocks. We propose that the differences in morphology are due largely to environmental effects on growth during juvenile stages. The electrophoretic data indicate that Newfoundland and western Gulf of St. Lawrence snow crabs differ genetically from each other and from the Cape Breton Island snow crabs; therefore, they represent two different "genetic" stocks. Eastern and western Cape Breton Island snow crabs did not exhibit electrophoretic differences and, thus, they represent a single genetic stock. Genetic exchange between Atlantic Canadian snow crab populations appears possible through larval dispersal. There is a widely different degree of resilience to exploitation and response to the same management strategy between eastern and western Cape Breton Island snow crab populations; hence, a phenotypically and/or genotypically defined stock is not necessarily a useful management tool. Stocks may be subdivided into more meaningful management units that reflect intra-stock factors such as growth and recruitment patterns.