bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of 25‐hydroxy‐vitamin D and parathyroid hormone in Callithrix penicillata primates living in their natural habitat in Brazil
Authors: Teixeira Danilo Simonini , Nobrega Yanna Karla M. , Valencia Carlos Enrique Uribe , Gandolfi Lenora , Pratesi Riccardo , Castro Luiz Claudio G.
Published: October 2012

Background

Vitamin D is a secosteroid hormone with important roles in the control of bone and mineral metabolism of vertebrates and in the maintenance of systemic homeostasis. This study aimed (i) to evaluate the serum concentrations of 25‐hydroxy‐vitamin D levels [25(OH)D], parathyroid hormone (PTH) and ionized calcium (iCa) of wild Callithrix penicillata (black‐tufted marmosets) and (ii) to propose reference ranges for those analytes for free‐living marmosets.

Methods

Blood samples were collected from 15 wild animals and analyzed for 25(OH)D, PTH and iCa. Reference values were calculated following standard analytical criteria.

Results

The observed mean serum levels (±standard deviation) were 25(OH)D, 61.7 (±20.8) ng/ml; PTH, 275.2 (±34.1) pg/ml; iCai 4.0 (±0.6) mg/dl.

Conclusions

For free‐living marmosets, the proposed physiological range for 25(OH)D is 20.1–103.3 ng/ml and for PTH is 207.0–343.3 pg/dl, with a confidence interval of 95%.
Pollen diversity matters: revealing the neglected effect of pollen diversity on fitness in fragmented landscapes
Authors: Breed Martin F. , Marklund Maria H. K. , Ottewell Kym M. , Gardner Michael G. , Harris J. Berton C. , Lowe Andrew J.
Published: October 2012

Few studies have documented the impacts of habitat fragmentation on plant mating patterns together with fitness. Yet, these processes require urgent attention to better understand the impact of contemporary landscape change on biodiversity and for guiding native plant genetic resource management. We examined these relationships using the predominantly insect‐pollinated Eucalyptus socialis. Progeny were collected from trees located in three increasingly disturbed landscapes in southern Australia and were planted out in common garden experiments. We show that individual mating patterns were increasingly impacted by lower conspecific density caused by habitat fragmentation. We determined that reduced pollen diversity probably has effects over and above those of inbreeding on progeny fitness. This provides an alternative mechanistic explanation for the indirect density dependence often inferred between conspecific density and offspring fitness.
sarA‐mediated repression of protease production plays a key role in the pathogenesis of Staphylococcus aureusUSA300 isolates
Authors: Zielinska Agnieszka K. , Beenken Karen E. , Mrak Lara N. , Spencer Horace J. , Post Ginell R. , Skinner Robert A. , Tackett Alan J. , Horswill Alexander R. , Smeltzer Mark S.
Published: October 2012

Mutation of staphylococcal accessory regulator (sarA) results in increased production of extracellular proteases in Staphylococcus aureus, which has been correlated with decreased biofilm formation and decreased accumulation of extracellular toxins. We used murine models of implant‐associated biofilm infection and S. aureus bacteraemia (SAB) to compare virulence of USA300 strain LAC, its isogenic sarA mutant, and derivatives of each of these strains with mutations in all 10 of the genes encoding recognized extracellular proteases. The sarA mutant was attenuated in both models, and this was reversed by eliminating production of extracellular proteases. To examine the mechanistic basis, we identified proteins impacted by sarA in a protease‐dependent manner. We identified 253 proteins where accumulation was reduced in the sarA mutant compared with the parent strain, and was restored in the sarA/protease mutant. Additionally, in SAB, the LAC protease mutant exhibited a hypervirulent phenotype by comparison with the isogenic parent strain, demonstrating that sarA also positively regulates production of virulence factors, some of which are subject to protease‐mediated degradation. We propose a model in which attenuation of sarA mutants is defined by their inability to produce critical factors and simultaneously repress production of extracellular proteases that would otherwise limit accumulation of virulence factors.
The histone acetyltransferase Hat1 facilitates DNA damage repair and morphogenesis in Candida albicans
Authors: Tscherner Michael , Stappler Eva , Hnisz Denes , Kuchler Karl
Published: October 2012

Chromatin assembly and remodelling is an important process during the repair of DNA damage in eukaryotic cells. Although newly synthesized histone H4 is acetylated prior to nuclear import and incorporation into chromatin during DNA damage repair, the precise role of acetylation in this process is poorly understood. Here, we identify the histone acetyltransferase 1 (Hat1) catalysing the conserved acetylation pattern of histone H4 preceding its chromatin deposition in the fungal pathogen Candida albicans. Surprisingly, Hat1 is required for efficient repair of not just exogenous but also endogenous DNA damage. Cells lacking Hat1 rapidly accumulate DNA damages and switch from yeast‐like to pseudohyphal growth. In addition, reduction of histone H4 mimics lack of Hat1, suggesting that inefficient H4 supply for deposition into chromatin is the key functional consequence of Hat1 deficiency. Thus, remarkably, we demonstrate that C. albicans is the first organism known to require histone H4 processing for endogenous DNA damage repair and morphogenesis. Strikingly, we also discover that hat1Δ/Δ cells are hypersusceptible to caspofungin due to intracellular reactive oxygen species induced by this drug. Hence, we propose that targeting this class of histone acetyltransferases in fungal pathogens may have potential in antifungal therapy.
Spatial tethering of kinases to their substrates relaxes evolutionary constraints on specificity
Authors: Capra Emily J. , Perchuk Barrett S. , Ashenberg Orr , Seid Charlotte A. , Snow Hana R. , Skerker Jeffrey M. , Laub Michael T.
Published: October 2012

Signal transduction proteins are often multi‐domain proteins that arose through the fusion of previously independent proteins. How such a change in the spatial arrangement of proteins impacts their evolution and the selective pressures acting on individual residues is largely unknown. We explored this problem in the context of bacterial two‐component signalling pathways, which typically involve a sensor histidine kinase that specifically phosphorylates a single cognate response regulator. Although usually found as separate proteins, these proteins are sometimes fused into a so‐called hybrid histidine kinase. Here, we demonstrate that the isolated kinase domains of hybrid kinases exhibit a dramatic reduction in phosphotransfer specificity in vitro relative to canonical histidine kinases. However, hybrid kinases phosphotransfer almost exclusively to their covalently attached response regulator domain, whose effective concentration exceeds that of all soluble response regulators. These findings indicate that the fused response regulator in a hybrid kinase normally prevents detrimental cross‐talk between pathways. More generally, our results shed light on how the spatial properties of signalling pathways can significantly affect their evolution, with additional implications for the design of synthetic signalling systems.
Urocanate reductase: identification of a novel anaerobic respiratory pathway in Shewanella oneidensisMR‐1
Authors: Bogachev Alexander V. , Bertsova Yulia V. , Bloch Dmitry A. , Verkhovsky Michael I.
Published: October 2012

Interpretation of the constantly expanding body of genomic information requires that the function of each gene be established. Here we report the genomic analysis and structural modelling of a previously uncharacterized redox‐metabolism protein UrdA (SO_4620) of Shewanella oneidensis MR‐1, which led to a discovery of the novel enzymatic activity, urocanate reductase. Further cloning and expression of urdA, as well as purification and biochemical study of the gene's product UrdA and redox titration of its prosthetic groups confirmed that the latter is indeed a flavin‐containing enzyme catalysing the unidirectional reaction of two‐electron reduction of urocanic acid to deamino‐histidine, an activity not reported earlier. UrdA exhibits both high substrate affinity and high turnover rate (Km << 10 μM, kcat = 360 s−1) and strong specificity in favour of urocanic acid. UrdA homologues are present in various bacterial genera, such as Shewanella, Fusobacterium and Clostridium, the latter including the human pathogen Clostridium tetani. The UrdA activity in S. oneidensis is induced by its substrate under anaerobic conditions and it enables anaerobic growth with urocanic acid as a sole terminal electron acceptor. The latter capability can provide the cells of UrdA‐containing bacteria with a niche where no other bacteria can compete and survive.
Opposite responses by different chemoreceptors set a tunable preference point in Escherichia colipH taxis
Authors: Yang Yiling , Sourjik Victor
Published: October 2012

In bacterial habitats, the ability to follow spatial gradients of environmental factors that affect growth and survival can be largely advantageous. The bacterial strategy for unidirectional chemotactic movement in gradients of typical attractants or repellents, such as nutrients or toxins, is well understood. Optimal levels of other factors, however, may be found at intermediate points of a gradient and thus require a bidirectional tactic movement towards the optimum. Here we investigate the chemotactic response of Escherichia coli to pH as an example of such bidirectional taxis. We confirm that E. coli uses chemotaxis to avoid both extremes of low and high pH and demonstrate that the sign of the response is inverted from base‐seeking to acid‐seeking at a well‐defined value of pH. Such inversion is enabled by opposing pH sensing by the two major chemoreceptors, Tar and Tsr, such that the relative strength of the response is modulated by adaptive receptor methylation. We further demonstrate that the inversion point of the pH response can be adjusted in response to changes in the cell density.
Oral delivery of bioencapsulated exendin‐4 expressed in chloroplasts lowers blood glucose level in mice and stimulates insulin secretion in beta‐TC6 cells
Authors: Kwon Kwang‐Chul , Nityanandam Ramya , New James S. , Daniell Henry
Published: October 2012

Glucagon‐like peptide (GLP‐1) increases insulin secretion but is rapidly degraded (half‐life: 2 min in circulation). GLP‐1 analogue, exenatide (Byetta) has a longer half‐life (3.3–4 h) with potent insulinotropic effects but requires cold storage, daily abdominal injections with short shelf life. Because patients with diabetes take >60 000 injections in their life time, alternative delivery methods are highly desired. Exenatide is ideal for oral delivery because insulinotropism is glucose dependent, with reduced risk of hypoglycaemia even at higher doses. Therefore, exendin‐4 (EX4) was expressed as a cholera toxin B subunit (CTB)–fusion protein in tobacco chloroplasts to facilitate bioencapsulation within plant cells and transmucosal delivery in the gut via GM1 receptors present in the intestinal epithelium. The transgene integration was confirmed by PCR and Southern blot analysis. Expression level of CTB‐EX4 reached up to 14.3% of total leaf protein (TLP). Lyophilization of leaf material increased therapeutic protein concentration by 12‐ to 24‐fold, extended their shelf life up to 15 months when stored at room temperature and eliminated microbes present in fresh leaves. The pentameric structure, disulphide bonds and functionality of CTB‐EX4 were well preserved in lyophilized materials. Chloroplast‐derived CTB‐EX4 showed increased insulin secretion similar to the commercial EX4 in beta‐TC6, a mouse pancreatic cell line. Even when 5000‐fold excess dose of CTB‐EX4 was orally delivered, it stimulated insulin secretion similar to the intraperitoneal injection of commercial EX4 but did not cause hypoglycaemia in mice. Oral delivery of the bioencapsulated EX4 should eliminate injections, increase patient compliance/convenience and significantly lower their cost.
Regulating an Experience Good Produced in the Formal Sector of a Developing Country when Consumers Cannot Identify Producers
Authors: McQuade Timothy , Salant Stephen , Winfree Jason
Published: October 2012

In developing countries, consumers can buy many goods either in formal markets or in informal markets and decide where to purchase based on the product's price and anticipated quality. This pape assumes consumers cannot assess quality prior to purchase and cannot, at reasonable cost, identify who produced the good they are considering. Many products (meats, fruits, vegetables, fish, grains) sold both in formal groceries and, less formally, on the street fit this description. This paper also assumes that producers can adjust quality at a cost and only firms in the formal sector are subject to government regulation. In the long run, producers migrate to the sector that is more profitable. Using this model, we demonstrate how regulations in the formal sector can lead to a quality gap between formal and informal sector goods. Moreover, the paper investigates how changes in regulation affect quality, price, aggregate production, and the number of firms in each sector.
Shadow Economy and Entrepreneurial Entry
Authors: Estrin Saul , Mickiewicz Tomasz
Published: October 2012

The impact of the shadow economy on entrepreneurial entry across countries is analyzed utilising 1998–2005 individual‐level Global Entrepreneurship Monitor data and national macro‐economic variables. A simple correlation coefficient suggests a positive relationship between the size of the shadow economy and the likelihood of entrepreneurial entry. However, this masks more complex relationships, if, as argued, the shadow economy is an embedded social phenomenon. With appropriate controls and instrumenting for potential endogeneity, the impact of the shadow economy on entry in a linear specification is found to be negative. Further, there is evidence of a U‐shaped relationship: entrepreneurial entry is least likely when the shadow economy amounts to about a quarter of gross domestic product (GDP). At the individual level, an extensive shadow economy has a more negative impact on respondents who are risk averse. In addition, in the economies where property rights are stronger, the negative impact of the shadow economy is weaker.
Association study of FUT2 (rs601338) with celiac disease and inflammatory bowel disease in the Finnish population
Authors: Parmar A. S. , Alakulppi N. , Paavola‐Sakki P. , Kurppa K. , Halme L. , Färkkilä M. , Turunen U. , Lappalainen M. , Kontula K. , Kaukinen K. , Mäki M. , Lindfors K. , Partanen J. , Sistonen P. , Mättö J. , Wacklin P. , Saavalainen P. , Einarsdottir E.
Published: October 2012

Homozygosity for a nonsense mutation in the fucosyltransferase 2 (FUT2) gene (rs601338G>A) leads to the absence of ABH blood groups (FUT2 non‐secretor status) in body fluids. As the secretor status has been shown to be a major determinant for the gut microbial spectrum, assumed to be important in the gut immune homeostasis, we studied the association of rs601338‐FUT2 with celiac disease (CelD) and inflammatory bowel disease (IBD) in the Finnish population. Rs601338 was genotyped in CelD (n = 909), dermatitis herpetiformis (DH) (n = 116), ulcerative colitis (UC) (n = 496) and Crohn's disease (CD) (n = 280) patients and healthy controls (n = 2738). CelD showed significant genotypic [P = 0.0074, odds ratio (OR): 1.28] and recessive (P = 0.015, OR: 1.28) association with the rs601338‐AA genotype. This was also found in the combined CelD+DH dataset (genotype association: P = 0.0060, OR: 1.28; recessive association: P < 0.011, OR: 1.28). The A allele of rs601338 showed nominal association with dominant protection from UC (P = 0.044, OR: 0.82) and UC+CD (P = 0.035, OR: 0.84). The frequency of non‐secretors (rs601338‐GG) in controls, CelD, DH, UC and CD datasets was 14.7%, 18%, 18.1%, 14.3% and 16.1%, respectively. No association was evident in the DH or CD datasets alone. In conclusion, FUT2 non‐secretor status is associated with CelD susceptibility and FUT2 secretor status may also play a role in IBD in the Finnish population.
The Rate (Time)-Dependent Mechanical Behavior of the PMR-15 Thermoset Polymer at Temperatures in the 274–316 °C Range: Experiments and Modeling
Authors: Ryther C. E. C. , Ruggles-Wrenn M. B.
Published: October 2012

The inelastic deformation behavior of the PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at temperatures in the 274–316 °C range. The experimental program was designed to explore the influence of strain rate on monotonic loading at various temperatures. In addition, the effects of prior strain rate on relaxation response and on creep behavior following strain-controlled loading were examined at temperatures in the range of interest. Positive, nonlinear strain rate sensitivity is observed in monotonic loading at all temperatures investigated. Both relaxation behavior and creep are profoundly influenced by prior strain rate at all temperatures. The time-dependent mechanical behavior of the PMR-15 polymer is also strongly affected by temperature. The elastic modulus decreases and the departure from quasi-linear behavior is accelerated with increasing temperature. Stress levels in the region of inelastic flow decrease as the temperature increases. The relaxation behavior as well as the creep response is strongly influenced by temperature. The viscoplasticity theory based on overstress for polymers (VBOP) is augmented to model the effects of temperature on the inelastic deformation behavior of PMR-15. VBOP is a unified state variable theory with growth laws for three state variables: the equilibrium stress, the kinematic stress, and the isotropic stress. Based on the experimental findings several VBOP model parameters are developed as functions of temperature. The augmented model is employed to predict the response of the material under both strain- and stress-controlled loading histories at temperatures in the range of interest. Comparison with experimental data demonstrates that the augmented VBOP successfully predicts the inelastic deformation behavior of PMR-15 polymer under various loading histories at temperatures between 274 and 316 °C.
Experimental Investigation on Freezing of Water Falling Film on Vertical Bank of Cold Horizontal Tubes
Authors: Sait Hani H. , Hussain Ahmed , Selim Abduzahir M.
Published: October 2012

The heat exchangers for ice formation on tube essentially consists of cold pipes submersed in stagnant water or in a cross flow of water. The heat exchanger considered here is a falling film one. Water falling film falls down over a set of vertical in-line cold horizontal tubes. The falling film main modes are droplets, jets, and sheet depending on its flow rate. The tubes are internally cooled by a controlled subzero temperature coolant. The coolant passes through the pipes in parallel. Water falling film freezes gradually outside the test tubes. The quantity of ice formed on the test tubes is observed, photographed, and measured at different times for different falling film modes. It has been noticed that the rate of ice formation decreases with time as ice accumulates on the test tubes. The overall heat transfer coefficient decreases as more ice accumulates on the test tubes.
The Simulation and Assessment of Compressed Natural Gas Storage Well With Defects
Authors: Tan Wei , Zhang JinJun , Niu WeiFei , Wang ZeJun , Wang ShiLai , Xiao YanTong
Published: October 2012

Compressed natural gas (CNG) is a fossil fuel substitute for gasoline (petrol), diesel, or propane/LPG (liquefied petroleum gas). Nowadays, there are three ways used to store CNG: gas bottles group, jumbo tubes trailer, and CNG storage well. The technology of storage well came into use in the early 1990s in China and nowadays, there are more than 5000 CNG storage wells in use. In this paper, the CNG storage well is introduced with the structure, advantages, and the technology of construction. Compared with other CNG containers, storage well has the following advantages: safer and more reliable, accident-preventive, space-saving, and longer life expectancy. The feasibility of IRIS (internal rotary system) used for storage well NDT (Nondestructive testing) is also studied. And the CNG well with defects are assessed as well. To investigate the validity of IRIS in detecting the storage well, an interval casing with man-made defects is tested. FEM (finite element method), combined with the method in JB4732 (Chinese industry standard) is used to analyze the storage well with inner corrosion pits, and evaluate the fatigue life. The linear elastic FEA (finite element analysis) of storage with single, two, and three defects is performed. The limit load analysis is also discussed with two different iterative methods. The result shows that IRIS can be used in detecting internal and external defects and recording the information. The simulation indicates that the pit along the axis direction is more dangerous than the one on any other direction and the influence radius of pit is the length of defect. The two different iterative methods used in limit load analysis finally lead to a consensus. The IRIS can be adopted in storage well. It can detect the defects on the internal and external surface of casing and record the detailed information. A database should be built to record defect information for each storage well. On the basis of IRIS detection and FEM analysis, determines whether a well can survive or not until next detection carried on by the method proposed in this paper.
Transition Mechanisms in Laminar Separated Flow Under Simulated Low Pressure Turbine Aerofoil Conditions
Authors: Dähnert Jerrit , Lyko Christoph , Peitsch Dieter
Published: October 2012

Based on detailed experimental work conducted at a low speed test facility, this paper describes the transition process in the presence of a separation bubble with low Reynolds number, low free-stream turbulence, and steady main flow conditions. A pressure distribution has been created on a long flat plate by means of a contoured wall opposite of the plate, matching the suction side of a modern low-pressure turbine aerofoil. The main flow conditions for four Reynolds numbers, based on suction surface length and nominal exit velocity, were varied from 80,000 to 300,000, which covers the typical range of flight conditions. Velocity profiles and the overall flow field were acquired in the boundary layer at several streamwise locations using hot-wire anemometry. The data given is in the form of contours for velocity, turbulence intensity, and turbulent intermittency. The results highlight the effects of Reynolds number, the mechanisms of separation, transition, and reattachment, which feature laminar separation-long bubble and laminar separation-short bubble modes. For each Reynolds number, the onset of transition, the transition length, and the general characteristics of separated flow are determined. These findings are compared to the measurement results found in the literature. Furthermore, the experimental data is compared with two categories of correlation functions also given in the literature: (1) correlations predicting the onset of transition and (2) correlations predicting the mode of separated flow transition. Moreover, it is shown that the type of instability involved corresponds to the inviscid Kelvin-Helmholtz instability mode at a dominant frequency that is in agreement with the typical ranges occurring in published studies of separated and free-shear layers.
The Influence of Leading Edge Diameter on Stagnation Region Heat Transfer Augmentation Including Effects of Turbulence Level, Scale, and Reynolds Number
Authors: Gandavarapu Preethi , Ames Forrest E.
Published: October 2012

Stagnation region heat transfer measurements have been acquired on two large cylindrical leading edge test surfaces having a four to one range in leading edge diameter. Heat transfer measurements have been acquired for six turbulence conditions including three grid conditions, two aero-combustor conditions, and a low turbulence condition. The data have been run over an eight to one range in Reynolds numbers for each test surface with Reynolds numbers ranging from 62,500 to 500,000 for the large leading edge and 15,625 to 125,000 for the smaller leading edge. The data show augmentation levels of up to 110% in the stagnation region for the large leading edge. However, the heat transfer results for the large cylindrical leading edge do not appear to infer a significant level of turbulence intensification in the stagnation region. The smaller cylindrical leading edge shows more consistency with earlier stagnation region heat transfer results correlated on the TRL parameter. These results indicate that the intensification of approaching turbulence is more prevalent with the more rapid straining of the smaller leading edge. The downstream regions of both test surfaces continue to accelerate the flow but at a much lower rate than the leading edge. Bypass transition occurs in these regions providing a useful set of data to ground the prediction of transition onset and length over a wide range of Reynolds numbers and turbulence intensity and scales.
Failure Mechanism of Laser Welds in Lap-Shear Specimens of a High Strength Low Alloy Steel
Authors: Lee Jaewon , Asim Kamran , Pan Jwo
Published: October 2012

In this study, the failure mechanism of laser welds in lap-shear specimens of a high strength low alloy (HSLA) steel under quasi-static loading conditions is examined based on the experimental and computational results. Optical micrographs of the welds in the specimens before tests were examined to understand the microstructure near the weld. A micrographic analysis of the failed welds in lap-shear specimens indicates a ductile necking/shear failure mechanism near the heat affected zone. Micro-hardness tests were conducted to provide an assessment of the mechanical properties of the joint area which has varying microstructure due to the welding process. A finite element analysis was also carried out to identify the effects of the weld geometry and different mechanical properties of the weld and heat affected zones on the failure mechanism. The results of the finite element analysis show that the geometry of the weld protrusion and the higher effective stress–plastic strain curves of the heat affected and weld zones result in the necking/shear failure of the load carrying sheet. The deformed shape of the finite element model near the weld matches well with that near a failed weld. A finite element analysis based on the Gurson yield function with consideration of void nucleation and growth was also carried out. The results of the finite element analysis indicate that the location of the material elements with the maximum void volume fraction matches well with that of the initiation of ductile fracture as observed in the experiments.
Experimental and Numerical Investigation of the Gas Side Heat Transfer and Pressure Drop of Finned Tubes—Part I: Experimental Analysis
Authors: Hofmann Rene , Walter Heimo
Published: October 2012

In this study, a heat transfer and pressure drop correlation are determined for helically I- and U-shaped finned tubes as well as for solid I-finned tubes at constant transverse and longitudinal spacing. In the heat transfer correlation, the influence of the number of tube rows arranged in flow direction is taken into consideration. A detailed description of the test rig and the data reduction procedure is presented. A thorough uncertainty analysis was performed to validate the results. The investigation has shown that the influence of the fin geometry on the heat transfer of the helically segmented I- and U-shaped tubes can be disregarded. The heat transfer correlation, which is valid for the helically segmented I- and U-shaped tubes in a staggered arrangement, can describe 90% of all measurement data within ±15%. All measurements are performed for constant transverse and longitudinal spacing. For the pressure drop coefficient, two new correlations, which are only valid for helically segmented U shaped finned tubes in a staggered arrangement, show an average deviation of approximately ±13% for 90% of all measurement results. All new correlations are compared with correlations from open and established literature for industrial boiler applications. The new heat transfer and pressure drop correlations show a relative deviation of ±20% in comparison with correlations in open literature. The new pressure drop correlations show the same characteristic as most correlations in the open literature.
Thermomechanical Simulation of the Solar One Thermocline Storage Tank
Authors: Flueckiger Scott M. , Yang Zhen , Garimella Suresh V.
Published: October 2012

The growing interest in large-scale solar power production has led to a renewed exploration of thermal storage technologies. In a thermocline storage system, heat transfer fluid (HTF) from the collection field is simultaneously stored at both excited and dead thermal states inside a single tank by exploiting buoyancy forces. A granulated porous medium included in the tank provides additional thermal mass for storage and reduces the volume of HTF required. While the thermocline tank offers a low-cost storage option, thermal ratcheting of the tank wall (generated by reorientation of the granular material from continuous thermal cycling) poses a significant design concern. A comprehensive simulation of the 170 MWht thermocline tank used in conjunction with the Solar One pilot plant is performed with a multidimensional two-temperature computational fluid dynamics model to investigate ratcheting potential. In operation from 1982 to 1986, this tank was subject to extensive instrumentation, including multiple strain gages along the tank wall to monitor hoop stress. Temperature profiles along the wall material are extracted from the simulation results to compute hoop stress via finite element models and compared with the original gage data. While the strain gages experienced large uncertainty, the maximum predicted hoop stress agrees to within 6.8% of the maximum stress recorded by the most reliable strain gages.
A Generalized Analytical Model of the Cutting Angles of a Biopsy Needle Tip
Authors: Ehmann Kornel , Malukhin Kostyantyn
Published: October 2012

A general analytical model of the geometry of a biopsy needle tip is formulated. The model is then used to derive the correlations for the characteristic cutting mechanics angles and for their respective distribution along the active cutting edges of the needle tip. The angles are defined in analogy to the definitions used in cutting tool design for material removal operations. Specifically, analytical expressions for the inclination and rake angles of the tip are derived. The validity of the models was confirmed through their application to plausible needle tip geometries such as: flat, cylindrical and helical tips. The knowledge of the tip geometry and of the relevant angles is a prerequisite for the understanding of tissue cutting mechanics.
Selection of Compliant Constant-Force Mechanisms Based on Stress and Force Criteria
Authors: Weight Brent L. , Magleby Spencer P. , Howell Larry L.
Published: October 2012

Recent developments have made possible simple, compressive, constant force mechanisms (CFM) using compliant mechanism approaches. In order to reliably design such mechanisms for particular applications it is essential to understand the feasibilities of various configurations in terms of output force magnitude and allowable stresses. This paper first reviews past work done in the area of CFMs and then develops new non-dimensionalized parameters. While these new parameters simplify the calculations required to design a CFM, they will be utilized in future work to develop improved configurations and a detailed design methodology. The paper concludes by presenting an example that shows the usefulness of the new parameters.
Dynamics of a Class of Parallel Wrists
Authors: Di Gregorio Raffaele , Parenti-Castelli Vincenzo
Published: October 2012

This paper presents a dynamic model of parallel wrists with all links constrained to have a spherical motion with the same center. The model can also be applied to serial wrists. The model, based on Lagrangian formulation of dynamics, exploits the feature that all the links have the same fixed point. Three parameters defining the platform orientation are used as generalized coordinates. This choice allows the use of the generalized inertia matrix (GIM) appearing in the model to calculate effective dynamic performance indices proposed in a previous paper. The model can solve both the direct and the inverse dynamic problems. It also contains the Jacobian matrix useful to characterize the kinematic behavior of parallel manipulators. By the model it is shown that the best performances are reached in the workspace regions where the manipulator has a good kinematic and dynamic isotropy, whereas the incidence of non-linear forces on performances is relevant at high end-effector speed. A numerical example is provided.
Reduction of Impact and Vibration in an Industrial Cam-Follower System Using the Splinedyne Method: A Case Study
Authors: Gordon Robert P. , Norton Robert L.
Published: October 2012

The splinedyne method of cam design is a variation on the poly-dyne method that uses B-spline functions to obtain superior control of follower motion and its derivatives in combination with a dynamic model of the follower train to minimize vibration in the follower at any one design speed. This paper presents the results of the application of this technique to an automated assembly machine cam-follower train whose vibratory behavior before redesign was limiting machine speed and causing increased product scrap rate due to impacts and vibrations. The improved splinedyne system contributed to a measured 14% increase in production rate in combination with a 1% reduction in scrap rate from that station.
Modified 6-

P

SU Platform
Authors: Hopkins Brian R. , Williams Robert L.
Published: October 2012

The Department of Mechanical Engineering at Ohio University has designed, constructed, and controlled a new 6-dof in-parallel-actuated platform, a combination and modification of existing designs. The 6-PSU platform consists of 6 legs with a prismatic joint, spherical joint, and universal joint connecting links in each leg which move the platform in the six Cartesian freedoms with respect to the base. The prismatic joint is actuated while the other two joints in each leg are passive. The six prismatic joints move vertically with respect to the base, which appears to be a big improvement over the standard Gough/Stewart platform. Experimental results from the Ohio University manipulator are presented.
Motion Generation of a Casting Manipulator With a Large Working Space
Authors: Izumi Shinsuke , Takeda Yukio , Higuchi Masaru , Funabashi Hiroaki , Arisumi Hitoshi
Published: October 2012

Casting manipulator has a potential to achieve far larger working space with simple mechanism by casting its gripper than the conventional types of robot. In order to enlarge the working space of the manipulator, the gripper must be cast at a high-speed. In casting the gripper at a high-speed, the motion of the manipulator must be generated which makes the best use of the actuator power while the posture of the gripper is kept stable. The present paper proposes new methods to cast the gripper at higher-speed. In proposed methods, transient swinging motion of which amplitude ranges from 90° to 180° or rotating motion of the manipulator are generated before casting the gripper by modifying the method previously proposed by Arisumi et al.. For generating a rotating motion, a new approach is also proposed that varies the length of the flexible link while generating the motion. Numerical simulations have been carried out to evaluate the methods from the criteria of the casting speed of the gripper, the required time for generating motion, and the stability of the posture of the gripper.
A Numerically Robust Algorithm to Solve the Five-Pose Burmester Problem
Authors: Al-Widyan Khalid , Angeles Jorge , Cervantes-Sa´nchez J. Jesu´s
Published: October 2012

Introduced in this paper is a robust algorithm to solve the five-pose planar Burmester problem. The proposed algorithm functions even in the presence of special conditions of the prescribed poses that lead to algorithmic singularities otherwise. In order to show the applicability and to validate the robustness of the proposed algorithm, some examples are included.
Static Analysis of Tensegrity Structures: Part 1 — Equilibrium Equations
Authors: Crane Carl D. , Duffy Joseph , Correa Julio C.
Published: October 2012

In this paper the mathematical model to perform the static analysis of an antiprism tensegrity structure subjected to a wide variety of external loads is addressed. The virtual work approach is used to deduce the equilibrium equations and a method based on the Newton’s Third Law to verify the numerical results is presented. In the second part of the paper several numerical examples are given.
Development of Steerable Endoscopes to Improve Depth Perception During Laparoscopic Surgery
Authors: Breedveld Paul , Hirose Shigeo
Published: October 2012

Laparoscopic surgery is carried out by using an endoscope with a camera that is inserted through a small incision in the abdominal wall. The camera pictures are presented on a monitor. The movements of the endoscope are limited by the incision point. This results in a restricted ability to observe organs from different sides, which complicates the surgeon’s depth perception. This paper describes the development of two new steerable endoscopes that are the product of a close co-operation between the Man-Machine Systems Group of the Delft University of Technology and the Hirose & Yoneda Laboratory of the Tokyo Institute of Technology. Both endoscopes contain a new spatial parallelogram-mechanism to transform the handgrip movements into movements of the steerable tip. The handgrips contain an arrow that points always in the direction of the line-of-sight of the tip-camera. This provides intuitive control of the tip, showing how the camera is oriented in the abdominal cavity. The tip-cameras can be moved in six degrees of freedom, thus enabling the surgeon to observe organs from different sides. Part of the parallelogram-mechanism is a new kind of spring that combines high torsion stiffness with a low, asymmetric bending stiffness. The endoscopes and the spring have been applied for two international patents.
Mechanism Design Issues of the Materials Processing Research Centrifuge of Auburn University
Authors: Simionescu Petru-Aurelian , Beale David G. , Overfelt Ruel A.
Published: October 2012

Some of the design issues of the 7feet radius materials processing research centrifuge of the Solidification Design Center of Auburn University are presented. The centrifuge consists of a modified rear axle of a 6 ton truck disposed vertically on a steel structure, the wheel-hub of which rotates a horizontal arm. The two-stage gearbox and the angle alignment system of the experiment container are some of the mechanism design issues detailed in the paper.
Developing Classifications for Synthesizing, Refining, and Animating Planar Mechanisms
Authors: Martin David T. , Murray Andrew P.
Published: October 2012

In this paper we classify several planar single degree-of-freedom mechanisms for developing features in kinematic synthesis software. The goal of the classification scheme is to identify all mechanisms that behave similarly. Roughly speaking, a mechanism’s behavior is assessing whether the input and output links of the mechanisms are capable of a full rotation. The features we use this for are to help identify t he range of motion of the input link of a mechanism, to guide the design of a mechanism to result in a desired classification, and to alter the mechanism such that the classification remains unchanged.
VRSPATIAL: Designing Spatial Mechanisms Using Virtual Reality
Authors: Vance Judy M. , Larochelle Pierre , Dorozhkin Denis
Published: October 2012

The traditional computer interface provides a two-dimensional (2D) interface to design. The monitor is a two-dimensional visual display and the desktop mouse is a two-dimensional input device. These tools are sufficient for designing 2D products such as planar linkages. When these tools are used to design three-dimensional (3D) products however, the designer must learn how to use the 2D tools to interact with objects defined in three-dimensional space. Virtual reality technology provides truly three-dimensional tools, with position tracked visual displays and input devices, that allow interaction with 3D digital products. Over the last few years we have developed a virtual environment for spatial mechanism design [1–4]. This paper describes the differences between designing a spatial mechanism using traditional computer interfaces and designing using the VRSpatial application.
The “rainbow” in the drop
Authors: Casini Giovanni , Covello Antonio
Published: October 2012

We describe an apparatus that can visualize the creation of rainbows using a cylinder of acrylic glass. The apparatus allows one to observe rainbows up to the sixth order. A brief theoretical introduction and a method to quantitatively analyze the observation are discussed. A simple lighting system is described and its divergence is computed. The effect of light divergence on rainbow formation is analyzed.
Inclined Levitron experiments
Authors: Michaelis Max M.
Published: October 2012

An inclined Levitron demonstration serves to illustrate macroscopically the basic non-quantum mechanical principle of nuclear magnetic resonance. By tuning a “rotary driver” to either the precession or the nutation frequency, the levitated top is made to precess or nutate visibly. By reflecting the beam from a laser-pointer off the Levitron, cycloidal pictures of the induced motion are obtained. Steady inclination at a steep angle is demonstrated in contrast to rotating inclination. Levitron traps are analogous to particle traps. Inclined or horizontal axis operation could lead to nearly frictionless bearings.
Ampère’s motor: Its history and the controversies surrounding its working mechanism
Authors: Assis A. K. T. , Chaib J. P. M. C.
Published: October 2012

In 1822 Ampère created a new kind of motor when he succeeded in spinning a cylindrical magnet around its axis by connecting it to a battery generating a steady current. Nowadays, it is easy to present such a motor in the classroom utilizing a neodymium magnet, a D battery, a steel nail, and a short piece of copper wire. Although it is very simple to observe the rotation, the explanation of this effect is still under dispute. This work presents the history of this motor including the controversy between Ampère and Faraday, as well as the modern explanation based on the field concept. We emphasize the positive outcomes to be gained in the classroom by presenting this device to students.
Matrix Numerov method for solving Schrödinger’s equation
Authors: Pillai Mohandas , Goglio Joshua , Walker Thad G.
Published: October 2012

We recast the well-known Numerov method for solving Schrödinger’s equation into a representation of the kinetic energy operator on a discrete lattice. With just a few lines of code in a high-level programming environment such as mathematica, it is simple to calculate and plot accurate eigenvalues and eigenvectors for a variety of potential problems. We illustrate the method by calculating high-accuracy solutions for the |x| potential.
Examples and comments related to relativity controversies
Authors: Boyer Timothy H.
Published: October 2012

Recently, Mansuripur has called into question the validity of the Lorentz force in connection with relativistic electromagnetic theory. Here, we present some very simple point-charge systems treated through order v2/c2 in order to clarify some aspects of relativistic controversies both old and new. In connection with the examples, we confirm the validity of the relativistic conservation laws. The relativistic examples make clear that external forces may produce a vanishing torque in one inertial frame and yet produce a non-zero torque in another inertial frame, and that the conservation of angular momentum will hold in both frames. We also discuss a relativistic point-charge model for a magnetic moment and comment on the interaction of a point charge and a magnetic moment. Mansuripur's claims of incompatibiltiy between the Lorentz force and relativity are seen to be invalid.
Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinning
Authors: Ćuk Matija , Stewart Sarah T.
Published: October 2012

Forming the Moon from Earth

It is thought that the Moon formed after a Mars-sized planet hit Earth about 4.5 billion years ago. Computer simulations of this event predict that the Moon was produced primarily from material from the impacting planet. However, the Moon has a similar composition to that of Earth, and the impacting planet would likely have had a different composition. Prior models assumed that the impact left the Earth-Moon system with the same angular momentum as it has today (see the Perspective by

Halliday

).
Ćuk and Stewart
(p.
1047
, published online 17 October; see the cover) show that the angular momentum of the Earth-Moon system could have decreased by half after the Moon-forming impact, opening the door to new impact models. For example, simulations suggest that high-velocity impacts onto a fast-spinning early Earth can lead to a Moon formed primarily from Earth's mantle.
Canup
(p.
1052
, published online 17 October) considered instead lower-velocity impacts by planets comparable in mass to the proto-Earth, which could generate a Moon and an Earth with similar compositions.
Forming a Moon with an Earth-like Composition via a Giant Impact
Authors: Canup Robin M.
Published: October 2012

Forming the Moon from Earth

It is thought that the Moon formed after a Mars-sized planet hit Earth about 4.5 billion years ago. Computer simulations of this event predict that the Moon was produced primarily from material from the impacting planet. However, the Moon has a similar composition to that of Earth, and the impacting planet would likely have had a different composition. Prior models assumed that the impact left the Earth-Moon system with the same angular momentum as it has today (see the Perspective by

Halliday

).
Ćuk and Stewart
(p.
1047
, published online 17 October; see the cover) show that the angular momentum of the Earth-Moon system could have decreased by half after the Moon-forming impact, opening the door to new impact models. For example, simulations suggest that high-velocity impacts onto a fast-spinning early Earth can lead to a Moon formed primarily from Earth's mantle.
Canup
(p.
1052
, published online 17 October) considered instead lower-velocity impacts by planets comparable in mass to the proto-Earth, which could generate a Moon and an Earth with similar compositions.
Pancreas Cancer Meets the Thunder God
Authors: Hingorani Sunil R. , Potter John D.
Published: October 2012

Natural product shows remarkable activity against pancreatic ductal adenocarcinoma across preclinical model systems.
Sisyphus and Translational Stroke Research
Authors: Lyden Patrick , Lapchak Paul
Published: October 2012

Testing of a stroke drug in cynomologus macaques and patients undergoing neurointervention may ultimately predict outcome in phase 2 or phase 3 clinical trials.
Come Together: Antibody Linkers to Combat Hemophilia
Authors: Baker Aaron B.
Published: October 2012

A bispecific antibody mimics the missing clotting factor in hemophilia and may allow improved treatment.
Transmission Favors HIV’s Ancestors
Authors: Barnabas Ruanne V.
Published: October 2012

HIV prevention strategies may be able to focus on founder strains of the virus that appear to be preferentially transmitted.