bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure of the transcriptional repressor PagR of Bacillus anthracis
Authors: Zhao Haiyan , Volkov Arsen , Veldore Vidya Harini , Hoch James A. , Varughese Kottayil I.
Published: November 2009

PagR is a transcriptional repressor in Bacillus anthracis that controls the chromosomal S-layer genes eag and sap, and downregulates the protective antigen pagA gene by direct binding to their promoter regions. The PagR protein sequence is similar to those of members of the ArsR repressor family involved in the repression of arsenate-resistance genes in numerous bacteria. The crystal structure of PagR was solved using multi-wavelength anomalous diffraction (MAD) techniques and was refined with 1.8 å resolution diffraction data. The PagR molecules form dimers, as observed in all SmtB/ArsR repressor family proteins. In the crystal lattice four PagR dimers pack together to form an inactive octamer. Model-building studies suggest that the dimer binds to a DNA duplex with a bend of around 4 °.
Systematic review: maintenance treatment of gastro‐oesophageal reflux disease with proton pump inhibitors taken ‘on‐demand’
Authors: PACE F. , TONINI M. , PALLOTTA S. , MOLTENI P. , PORRO G. B.
Published: November 2009

Background Proton pump inhibitors (PPI) therapy ‘on‐demand’ is often used as an alternative to continuous maintenance therapy in gastro‐oesophageal reflux disease (GERD).

Aim We conducted a systematic review with the specific objectives to ascertain whether on‐demand PPI therapy was effective in preventing symptomatic relapse and to assess the relative efficacy of on‐demand vs. continuous PPI maintenance strategy.

Methods Randomized‐controlled clinical trials comparing on‐demand PPI vs. placebo or on‐demand vs. continuous PPI therapy in GERD patients were identified by searching the Medline database and the Cochrane Controlled Trials Register.

Results Seventeen studies were found which met inclusion criteria. Out of the 17 studies: five investigated exclusively patients with non‐erosive reflux disease (NERD), four patients with NERD and mild oesophagitis, two patients with erosive oesophagitis only, and two patients with uninvestigated GERD symptoms, respectively. Four further studies were not investigating the effectiveness of the therapies but primarily pharmacoeconomic or quality of life parameters.

Conclusions On the basis of the analysis of 17 studies, we can conclude that on‐demand therapy with currently available PPI appears to be effective in the long‐term management of patients with NERD or mild and uninvestigated forms of GERD, but not in patients with (severe) erosive oesophagitis.
Reproductive system, social organization, human disturbance and ecological dominance in native populations of the little fire ant, Wasmannia auropunctata
Authors: FOUCAUD JULIEN , ORIVEL JÉRÔME , FOURNIER DENIS , DELABIE JACQUES H. C. , LOISEAU ANNE , LE BRETON JULIEN , CERDAN PHILIPPE , ESTOUP ARNAUD
Published: November 2009

The invasive ant species Wasmannia auropunctata displays both ecologically dominant and non‐dominant populations within its native range. Three factors could theoretically explain the ecological dominance of some native populations of W. auropunctata: (i) its clonal reproductive system, through demographic and/or adaptive advantages; (ii) its unicolonial social organization, through lower intraspecific and efficient interspecific competition; (iii) the human disturbance of its native range, through the modification of biotic and abiotic environmental conditions. We used microsatellite markers and behavioural tests to uncover the reproductive modes and social organization of dominant and non‐dominant native populations in natural and human‐modified habitats. Microsatellite and mtDNA data indicated that dominant and non‐dominant native populations (supercolonies as determined by aggression tests) of W. auropunctata did not belong to different evolutionary units. We found that the reproductive system and the social organization are neither necessary nor sufficient to explain W. auropunctata ecological dominance. Dominance rather seems to be set off by unknown ecological factors altered by human activities, as all dominant populations were recorded in human‐modified habitats. The clonal reproductive system found in some populations of W. auropunctata may however indirectly contribute to its ecological dominance by allowing the species to expand its environmental niche, through the fixation over time of specific combinations of divergent male and female genotypes. Unicoloniality may rather promote the range expansion of already dominant populations than actually trigger ecological dominance. The W. auropunctata model illustrates the strong impact of human disturbance on species’ ecological features and the adaptive potential of clonal reproductive systems.
Pharmacy students' intention to practise in a rural setting: Measuring the impact of a rural curriculum, rural campus and rural placement on a predominantly metropolitan student cohort
Authors: Taylor Susan J. , Maharaj Praveen , Williams Kylie , Sheldrake Carol
Published: November 2009

Objective:  To compare pharmacy students' intention to practise in a rural setting expressed in their first year of university with that expressed during their final year.

Design:  Longitudinal survey of students in their first and final years.

Setting:  Tertiary educational institution.

Participants:  Predominantly metropolitan pharmacy students.

Interventions:  Students were exposed to a rural curriculum, rural campus and rural placement or rural placement alone during their degree.

Main outcome measure:  Change in proportion of students expressing an intention to practise in a rural setting following registration.

Results:  The proportion of respondents who indicated an intention to practise in a rural setting was 21.6% (27/125) in 2006 compared with 11.2% (14/125) in 2003. This was a statistically significant increase of 10.4% (P = 0.001) over the four years. Positive influences on students' intention to practise in a rural setting were: rural background (P = 0.012); rural placement (either two weeks or 12 weeks) (P = 0.002); having been enrolled in the BPharm (Rural) (P = 0.001).

Conclusions:  This study confirmed the work of others in that the students most likely to express an intention to practise in a rural setting were those from a rural background who elected to undertake and complete a rural degree involving a rural placement. A follow‐up survey will be conducted to establish whether their stated intention as students has translated to rural practice in reality.
Dissecting large earthquakes in Japan: Role of arc magma and fluids
Authors: Zhao Dapeng , Santosh M. , Yamada Akira
Published: November 2009

We synthesized information from recent high‐resolution tomographic studies of large crustal earthquakes which occurred in the Japanese Islands during 1995–2008. Prominent anomalies of low‐velocity and high Poisson's ratio are revealed in the crust and uppermost mantle beneath the mainshock hypocenters, which may reflect arc magma and fluids that are produced by a combination of subducting slab dehydration and corner flow in the mantle wedge. Distribution of 164 crustal earthquakes (M 5.7–8.0) that occurred in Japan during 1885–2008 also shows a correlation with the distribution of low‐velocity zones in the crust and uppermost mantle. A qualitative model is proposed to explain the geophysical observations recorded so far in Japan. We consider that the nucleation of a large earthquake is not entirely a mechanical process, but is closely related to the subduction dynamics and physical and chemical properties of materials in the crust and upper mantle; in particular, the arc magma and fluids.
Asian perspectives in the management of inflammatory bowel disease: Findings from a recent survey
Authors: Sung Joseph JY , Kamm Michael A , Marteau Philippe
Published: November 2009

Background and Aim:  The prevalence and incidence of inflammatory bowel disease (IBD) differs worldwide. While the prevalence of IBD has stabilized in Europe, the USA and Japan, an increasing trend has been observed in Asia. However, there are no data on the current clinical practice for the management of IBD in the region. The present study aims to investigate the number of existing and new cases of IBD and to understand the current practice of diagnosis and treatment of IBD in different Asian countries.

Methods:  A self‐administered questionnaire, designed according to European and US guidelines, was distributed to IBD specialists throughout Asia. The questionnaire estimated the annual incidence of existing and new IBD cases in physicians' clinical practices and evaluated their procedures of diagnosis and preference for therapeutic treatment and maintenance treatment.

Results:  Eighty‐seven questionnaires were received out of the 107 distributed. In the clinical practices of these 87 respondents, there were 502 existing and 73 new cases per year for ulcerative colitis (UC) and 202 existing and 32 new cases per year for Crohn's disease (CD). Colonoscopy and histology were the most commonly used methods for the diagnosis of UC and CD, but clinical practice regarding the diagnosis of IBD varied. The treatment of choice for mild‐to‐moderate UC and CD was 5‐aminosalicylic acid (5‐ASA), which is also the preferred choice for the maintenance treatment of UC and CD.

Conclusion:  Clinical practice with regards to IBD diagnosis and management varies within Asia.5‐ASA is the preferred treatment and maintenance therapy for mild‐to‐moderate IBD.
TLR4 monoclonal antibody blockade suppresses dextran‐sulfate‐sodium‐induced colitis in mice
Authors: Liu Yi , Zhang Zhijun , Wang Lei , Li Juan , Dong Le , Yue Wenjie , Chen Jian , Sun Xu , Zhong Liang , Sun Dayu
Published: November 2009

Background and Aim:  Ulcerative colitis (UC) refers to a kind of inflammatory bowel disease, of which the accurate pathogenesis is not yet well understood. Recently, the toll‐like receptor 4 (TLR4) and the TLR4 signaling pathway have been proved as playing an important role in the pathogenesis of UC. The objective of this study was to evaluate the effect of TLR4 monoclonal antibody on dextran‐sulfate‐sodium‐induced colitis in a mouse model.

Methods:  We evaluated the effects of the TLR4 monoclonal antibody (TLR4mAb) on the development of dextran‐sulfate‐sodium‐(DSS)‐induced colitis. Tissue samples were evaluated by the disease activity index and histopathological score. Meanwhile, the mucosal mRNA expression of cytokines, tumor necrosis factor‐α, interferon‐γ and interleukin‐1β were analyzed by semiquantitative reverse transcription polymerase chain reaction. The mucosal protein P38‐MAPK, c‐jun and c‐fos expressions of the TLR4‐P38MAPK pathway were analyzed using Western blot.

Results:  After the treatment with TLR4mAb against DSS‐induced colitis, the bodyweight was significantly increased and both disease activity index and histopathological score were decreased significantly. Furthermore, the mucosal expression of messenger RNA of tumor necrosis factor‐α, interferon‐γ and interleukin‐1β were observed to be 8–15‐fold more than the baseline, whereas the mucosal expressions of P38MAPK and c‐jun were found to be decreased.

Conclusion:  Blocking TLR4 by TLR4mAb can prevent the development of DSS‐induced colitis through the TLR4‐P38MAPK‐c‐jun pathway.
The Development of Conditional Reasoning and the Structure of Semantic Memory
Authors: Markovits Henry , Fleury Marie‐Léda , Quinn Stéphane , Venet Michèle
Published: November 2009

The present article examines 2 predictions concerning conditional reasoning in children derived from a revised version of Markovits's model of conditional reasoning. The first study examined the prediction that younger children (8 years of age) would have greater difficulty in responding correctly to premises where the antecedent was strongly associated with the consequent than to premises where the association was weaker; for example, “If something is a car, then it has a motor” should be more difficult than “If something is a refrigerator, then it has a motor.” A total of 55 children in grades 2 and 3 (average age: 8 years) and 49 children in grades 5 and 6 (average age: 11 years) were given either 2 strongly associated problems or weakly associated counterparts. Results indicated that 8‐year‐olds did better on the weakly associated problems than on the strongly associated problems, but there was no difference among the 11‐year‐olds. The second study examined the prediction that younger children (8 years of age) would have greater difficulty in responding correctly to causal premises (“If a rock is thrown at a window, the window will break”) than to corresponding ad hoc premises (“A rock is something that can be used to break a window”). A total of 53 children in grades 2 and 3 (average age: 8 years) and 49 children in grades 5 and 6 (average age: 11 years) were given either 2 causal problems or ad hoc counterparts. Results indicated that 8‐year‐olds did better on the ad hoc problems than on the causal problems, but there was no difference among the 11‐year‐olds. These studies are interpreted as consistent with the idea that 1 major factor in the development of reasoning in this age level is the development of children's ability to explore their own knowledge base.
LINNAEUS AS A SECOND ADAM? TAXONOMY AND THE RELIGIOUS VOCATION
Authors: Harrison Peter
Published: November 2009

Swedish naturalist Carl von Linné (1707–1778) became known during his lifetime as a “second Adam” because of his taxonomic endeavors. The significance of this epithet was that in Genesis Adam was reported to have named the beasts—an episode that was usually interpreted to mean that Adam possessed a scientific knowledge of nature and a perfect taxonomy. Linnaeus's soubriquet exemplifies the way in which the Genesis narratives of creation were used in the early modern period to give religious legitimacy to scientific activities and to taxonomy in particular. Allusions to Adam's work in the Garden of Eden thus became a way of investing the vocation of the naturalist with religious significance.
Tissue and blood superoxide dismutase activity and malondialdehyde level in leprosy
Authors: Abdel‐Hafez HZ , Mohamed E‐EM , Abd‐Elghany AA
Published: November 2009

Background  Oxidative stress (OS) results from an imbalance between free radical generating and scavenging systems. The end product of lipid peroxidation, malondialdehyde (MDA) serves as a marker of cellular damage. Superoxide dismutase (SOD) traps free radicals and acts as a free radical scavenging system.

Objective  To study OS indices in paucibacillary (PB) and multibacillary (MB) leprosy in tissues and blood.

Materials and methods  The study group comprised untreated PB patients (n = 14), untreated MB patients (n = 18) and normal human volunteers (n = 20). SOD activity, MDA level and MDA/SOD ratio were estimated in both blood and tissue.

Results  Compared with controls, SOD activity in tissues decreased significantly in both PB and MB patients, while SOD activity in erythrocytes decreased significantly only in MB. In addition, MDA levels increased significantly in tissues of both PB and MB patients. Moreover, the mean level of MDA in plasma of MB patients was significantly higher, whereas there was no significant difference in that of PB patients. This study showed significant increase in OS index (MDA/SOD ratio) in tissue of PB and MB patients and in blood of MB patients only, whereas there was no significant difference in OS index in blood of PB patients compared with that in the controls.

Conclusion  Oxidative stress was observed in both tissues and blood of MB patients and in tissues of PB patients, denoting its crucial involvement in the pathogenesis of leprosy. This can constitute an important tool in prognosis, treatment and control of leprosy.
TRANSPLANTATION AND CELLULAR ENGINEERING: Association of stress‐related perinatal factors and cord blood unit hematopoietic progenitors is dependent on delivery mode
Authors: Juutistenaho Sari , Eskola Mikko , Sainio Susanna , Aranko Kari , Kekomäki Riitta
Published: November 2009

BACKGROUND: Perinatal characteristics, variably utilized in cord blood (CB) selection for banking, affect CB hematopoietic progenitor cells (HPCs). The association between perinatal stress factors and CB unit HPCs was evaluated.

STUDY DESIGN AND METHODS: Umbilical arterial (UA) pH, absolute and relative birth weight (BW) and placental weight (PW), and PW/BW ratio of 167 healthy, full‐term infants were compared with CB unit prefreeze total nucleated cells (TNCs), total CD34+ (TCD34+) cells, and total colony‐forming unit (CFU‐TOT) number. Cesarean section (C‐section, n = 104) and vaginal delivery subgroups were also analyzed.

RESULTS: UA pH (median, 7.28; range, 7.04‐7.40) correlated with CB unit CFU‐TOT number (n = 166; r = −0.32, p < 0.0001), TCD34+ cells (r = −0.31, p < 0.0001), and TNCs (r = −0.29, p = 0.0002). Similarly, BW, PW, and PW/BW ratio correlated with HPCs. In multiple linear regression analysis, CFU‐TOT number was predicted by collected CB TNCs and UA pH in vaginal deliveries (R2 = 0.53), in contrast with TNCs, PW, and BW in C‐sections (R2 = 0.37). TCD34+ cells were predicted by adding UA pH (vaginal deliveries, R2 = 0.75) or PW (C‐sections, R2 = 0.36) to collected CB TNCs.

CONCLUSIONS: Stress‐related perinatal factors, particularly UA pH, are associated with CB unit HPCs and may improve unit selection. Multiple linear regression models may prove useful for predicting HPCs. Mode of delivery affects model choice; UA pH has a strong effect on HPCs in vaginal deliveries.
Geochemistry of Some Marine Fe–Mn Nodules and Crusts with Respect to Pt Contents
Authors: Cabral Alexandre Raphael , Sattler Carl‐Diedrich , Lehmann Bernd , Tsikos Harilaos
Published: November 2009

Bulk chemical analyses for Pt and Pd in marine Fe–Mn nodules and crusts from different provenances are presented, together with a wide range of elements. Platinum contents vary from 70–328 ppb, whereas Pd contents extend from 0.6–4.7 ppb only. Bromine and Pb show strong positive correlations with Pt. Lead is remarkably enriched in Fe–Mn precipitates over seawater, but Br is a conservative‐type element in seawater and shows no enrichment in Fe–Mn precipitates. Hence, the Pt–Br–Pb element association combines two elements, Br and Pb, of extremely contrasting enrichment factors in Fe–Mn precipitates.
Architecture and gating of Hv1 proton channels
Authors: Tombola Francesco , Ulbrich Maximilian H. , Isacoff Ehud Y.
Published: November 2009

Voltage‐gated proton channels have been described in different cells and organisms since the early ’80s, but the first member of the family, Hv1, was cloned only recently. The Hv1 channel was found to contain a voltage‐sensing domain (VSD), similar to those of voltage‐gated sodium, potassium and calcium channels. All these other channels also contain a pore domain, which forms a central pore at the interface of the four subunits. The pore domain is missing in Hv1. This raised several questions on the location of the proton pore and on the mechanism of gating. Here, we briefly review our effort to understand the structural organization of Hv1 channels and discuss the relationship between the gating of Hv1 and the gating of ion‐conducting pores recently discovered in the VSDs of mutant voltage‐gated potassium and sodium channels.
Thermal Convection in Short-Bearing Films
Authors: Georgopoulos E. , Burton R. A.
Published: November 2009

A solution for the temperature distribution in a short-bearing film, is obtained, when convection is included. The solution shows that for some cases convection is indeed small compared to conduction and can be discarded from the energy equation. It also shows that convection becomes important in some extreme cases and, thus, it should be retained in the energy equation.
Dynamic and Static Properties of Recessed Hydrostatic Journal Bearings by Small Displacement Analysis
Authors: Rowe W. B.
Published: November 2009

Coefficients are presented for hydrostatic stiffness, hydrodynamic stiffness and squeeze damping for capillary, orifice and constant flow control. Due to the linear behaviour of such bearings these coefficients may be used for conservative design and with reasonable accuracy where the displacements are less than half the clearance. The dynamic coefficients may also be employed to predict the onset of whirl. The results are illustrated by application to rotating and non-rotating load situations. It is demonstrated that the squeeze damping constant for the concentric condition may be obtained from a steady loading test for hydrodynamic stiffness since Csq = λhd/(πN). It is argued that this relationship may be generalised for all types of bearings capable of exhibiting half-speed whirl operating at any speed.
Load Support System Analysis-High Speed Input Pinion Configuration
Authors: Gassel S. S. , Pirvics J.
Published: November 2009

Structural assemblies which transmit power, helicopter gearboxes for example, require accurate evaluation of load and displacement distributions to ensure system design optimization. Particular performance parameters which depend on detailed understanding of the distributions are operating life and rigidity. The coupling complexity of system components; gears, shafts, bearings and the housing itself, prevents meaningful evaluation of performance from the study of isolated components. The entire load support system has to be examined in its interacting entirety. In this paper a theoretical study has been made to determine the performance of a load support system, consisting of a shaft and two taper roller bearings for the high-speed input pinion of an advanced helicopter transmission. SHABERTH, a computer program designed to perform thermo-mechanical analyses of arbitrarily configured rolling element bearing-shaft systems, was employed to analyze, both, a straddle arrangement where the spiral bevel pinion gear is located axially between the two bearings, and a cantilevered arrangement where the pinion is outboard of the bearings. The effects of preload, shaft wall thickness, bearing spacing and misalignment of bearing races were examined. Their influence on load distributions and bearing rating lives including simulation of bearing and shaft elastic deformations were evaluated for both support geometries. Additional effort was expended to detail the performance of the pinion designs over a range of shaft rotational speeds. Lubrication and friction effects were included. Particular attention was directed to local as well as global heat generation rates (HGR) to provide design information for proper lubrication of the bearings. The results provide guidance for improved design of transmissions and the load vector control within them. In particular, the relative merits of the straddle versus the cantilever design have been exposed so that their individual characteristics may be exploited to increase system survivability.
Analysis of Dynamically Loaded Floating-Ring Bearings for Automotive Applications
Authors: Rohde Steve M. , Ezzat Hazem A.
Published: November 2009

This study deals with the frictional performance of dynamically loaded floating-ring journal bearings and investigates their feasibility for automotive applications. An analysis of the performance of floating-ring journal bearings in conducted. The bearing loads and speeds considered simulate those experienced in automotive engines. The potential contribution of the floating-ring design concept to reduced engine friction is assessed, and its compliance with current bearing durability criteria is evaluated. The results indicate that the adoption of the floating-ring design concept has the potential for reducing power loss in automotive engine bearings. It is shown that this can be accomplished without violating minimum film thickness constraints currently accepted as criteria for successful engine bearing operation.
A New Method for Etching Surfaces of Bearings and Other Machine Elements
Authors: Hirs G. G. , Sonneveld J. IJ.
Published: November 2009

The method relates to the production of shallow recesses in surfaces by etching. Recesses in metal surfaces are particularly suitable for use in sliding bearings for rotating components and in some other machine elements. Frequently, such recesses have a depth of 10 microns or more and are made in the form of intricate groove patterns on curved surfaces. According to the new method, etching fluid is caused to flow by means of a flow guiding template onto areas determined by this template along the surface to be etched. The etching rate on the areas to be etched is controlled by adjustment of the flow velocity of the etching fluid and the slit height of the flow guiding template. The recesses or grooves are deeper when the flow velocity of the etching fluid and the slit height are both higher. The paper gives a brief description of the new etching method and a comparison with other fabrication methods such as photochemical etching and electro-chemical machining. The new method appears to be preferable to others for large series production. The paper concludes with theoretical work in which the etching process is explained in terms of mass transfer by connective diffusion and with some experimental results using a simplified flow guiding template design.
Nonlinear Shear Stress and Thermal Effects in Fully Flooded Elastohydrodynamic Line Contacts
Authors: Heyes D. M. , Montrose C. J.
Published: November 2009

A nonlinear viscoelastic model for lubricant behavior under elastohydrodynamic conditions is derived which incorporates temperature changes in the contact. The formalism is written primarily in terms of convolution integrals. Calculations of temperature distributions in the contact and the variation of traction coefficient with shear rate are in qualitative agreement with experiment.
Self-Centering Film Dividers
Authors: Wilcock D. F.
Published: November 2009

One rather effective way to reduce the frictional drag of fluid film journal or thrust bearings, when operating in the turbulent regime, is to introduce a “floating” member dividing the fluid film into two roughly equal parts. The average shear rate is unchanged, but the effective Reynolds number is reduced, with a corresponding reduction in friction power. Such dividers have been widely used in floating sleeve journal bearings of the small high speed type. Use in thrust bearings is not known. In either application, it is essential that the self-centering divider center itself under all conditions after shaft rotation is initiated. This paper describes and analyzes a divider design that has such a property.
An Experimental Investigation of the Effect of Inter-Orifice Variations on the Performance of an Externally-Pressurized, Orifice-Compensated Air Journal Bearing
Authors: Stowell T. B. , Markho P. H. , Grewal S. S.
Published: November 2009

The performance of an externally-pressurized, orifice-compensated air journal bearing fitted with various combinations of nonuniform supply orifices of known size is compared with the performance of the same bearing fitted with uniform orifices. In general, it is found that even a substantial amount of scatter in orifice size about a mean, design value does not result in a marked deterioration in bearing performance. Furthermore, the bearing load capacity at a given eccentricity may actually be enhanced (at the expense of a relatively smaller reduction in radial stiffness) by using nonuniform orifices, the best arrangement being one where there is a progressive, circumferential variation of orifice size.
Tool Wear Investigations on Some Cutting Tool Materials
Authors: Venkatesh V. C.
Published: November 2009

Tool life curves were plotted for HSS, cemented tungsten carbides, coated carbides, and cemented titanium carbides. HSS tools showed a distinct inflection coinciding with the formation of a white diffusion layer. Crater wear propagation studies were carried out on all tools and in addition on laminated carbides. HSS, laminated carbide, and cemented titanium carbide show a tendency to form a closed crater, revealing that in these tools diffusion is a mode of wear.
A Force System Synthesis Algorithm for Use as a Companion to Mechanism Dynamic Analysis Programs
Authors: Carson W. L. , Lee C.-S. I.
Published: November 2009

The set of equations and algorithm described in this paper can be used to develop force system synthesis programs which utilize existing mechanism dynamic analysis programs as a host. The algorithm can be used for any planar mechanism. Also it can be used on smart microprocessor-based interactive graphic terminals since it does not require having to reaccess the host computer program during the force system synthesis process.
Degeneracy, Singularity, and Multiplicity in Least-Squares Design of a Function-Generating Mechanism
Authors: Wilde D. J.
Published: November 2009

Error Linearization (EL), an iterative curve-fitting procedure recently proposed for designing minimum squared error four-bar function generating mechanisms, suffers from frequent instability. The cause seems to be the near singularity of a certain 3×3 matrix, which produces artificially large steps, usually toward designs with unrealistically short driver and follower. This degenerate case proves unfortunately to be the true global minimum. To bring this behavior under control, the coupler length, formerly regarded as an independent design variable, is made to depend on the driver and follower lengths. They are determined by solving a now well-conditioned 2×2 set of error linearization equations. In an example this Stabilized EL procedure (SEL) located five reasonable locally minimal designs which would have been missed by the unstabilized version.
A Finite Element Stress Analysis of Spur Gears Including Fillet Radii and Rim Thickness Effects
Authors: Chang S. H. , Huston R. L. , Coy J. J.
Published: November 2009

Spur gear stress analysis results are presented for a variety of loading conditions, support conditions, fillet radii, and rim thickness. These results are obtained using the SAP IV finite-element code. The maximum stresses, occurring at the root surface, substantially increase with decreasing rim thickness for partially supported rims (that is, with loose-fitting hubs). For fully supported rims (that is, with tight-fitting hubs), the root surface stresses slightly decrease with decreasing rim thickness. The fillet radius is found to have a significant effect upon the maximum stresses at the root surface. These stresses increase with decreasing fillet radius. The fillet radius has little effect upon the internal root section stresses.
Experimental Determination of the Roller Chain Load Distribution
Authors: Naji M. R. , Marshek K. M.
Published: November 2009

An experimental study was conducted to determine the effect of elastic properties, geometric variations, and lubrication on roller chain load distribution. Comparison was made with the theoretical results for a test chain on a 20-tooth sprocket. The load distribution was found for a large number of cases to be independent of the elastic properties of the chain and the sprocket. The load distribution for the chain on a driver sprocket differed from that for a chain on a driven sprocket because of the change in direction of the friction force. Lubrication had no noticeable effect. A large pitch for the sprocket teeth was found to amplify the tension in the chain link.
Surface Durability of Forged and Machined Steel Gears
Authors: Lehnhoff T. F. , Chen Hen-Li , Ardayfio D. D.
Published: November 2009

Forged and machined straight bevel gears have been tested in order to compare the surface durability or pitting fatigue characteristics. The gears were prepared with identical geometric properties to the extent possible with two different manufacturing processes. The machined gears were cut with a two-tool generator. A static torque four-square recycling power gearbox apparatus was used for the tests. The simulated transmitted power was 22.4 kW (30 hp) for a constant life of 201 hours or 14.5 × 106 cycles. The damage was compared based on the number of pitted teeth per gear and the pits per tooth. Eight straight bevel gears with nineteen teeth each or a total of 152 teeth were used for each of the ten tests. The machined gears had 30.6 percent more pitted teeth per gear and 38.5 percent more pits per tooth than the forged gears. The improvement in the forged gears may in part be due to slightly better microstructural characteristics resulting during the heat treatment operation. However, the strongest evidence would attribute the difference to the surface roughness. Without special processing, machined gears have more adversely oriented pitting nucleation sites resulting from tool marks.
Optimal Allocation of Antenna Structural Tolerances Based on Reliability
Authors: Wang S. H. , Ragsdell K. M.
Published: November 2009

Surface accuracy of antenna structures which are widely used in communication, space exploration, and radio astronomy will be different from that which is desired, because of a variety of random factors, including operating altitude variation, structural member size tolerance, material property variation, assembly error, and dead load variation. In this paper a first-order second-moment approach is given for the prediction of the surface accuracy reliability. A synthesis procedure, using nonlinear programming techniques, of allocating tolerances in antenna structures to achieve the minimum cost for specified reliability and tolerance bounds is presented. The formulated optimal tolerance allocation problem is solved using the Generalized Reduced Gradient code, OPT, and numerical results are given for specific applications.
A Compact Approach To Planar Kinematic Analysis
Authors: Fallahi B. , Ragsdell K. M.
Published: November 2009

The automatic analysis of kinematic chains is today an important practical problem. The widespread use of CAD/CAM systems for mechanical design increases the potential utility of such an analysis procedure. In this paper, we describe a Mechanism Analysis Procedure (MAP) which should be of practical value in modern CAD/CAM computing environments which employ minicomputers, since it seeks to minimize the required computer storage for a problem of given size. Numerical results are given which compare MAP to DRAM, a very widely used program of similar capability.
The Dual Torus and Associated Linkages
Authors: Davidson J. K. , Hunt K. H.
Published: November 2009

A transformation for plane coordinates is presented and is used to derive the equation, in plane coordinates, for the dual torus, which is the envelope of two-freedom motion of a plane. Five distinct forms of the dual torus are described. Two kinds of nodal points are found which relate to linkage motion. The principle of identical surface-enveloping by four cognate spatial dyad linkages is developed, and the existence of all forms of spatial ERRR linkages is confirmed. Finally, some comments are made about duality of the dual torus and the point torus.
Instantaneous Kinematics of a Plane in Spherical Motion
Authors: Ting K.-L. , Soni A. H.
Published: November 2009

In this paper, an analytical method to study the instantaneous motion of a plane subjected to a space motion is investigated. As a point traces a point-path, a plane under a one-parameter space motion generates a plane-path which envelops a developable ruled surface. A plane-envelope is characterized through its edge of regression by a set of curvature-like dimensionless numbers. For a spherical motion, the families of planes whose envelops have the common characteristic numbers are found. Some special cases which are analogous to the subjects in the infinitesimal Burmester theory are also examined.
Nanocrystalline cobalt-based films with high thermal stability from a single molecule
Authors: Henderson Lucas B. , Rivers Joseph H. , Bost Daniel E. , Jones Richard A. , Ekerdt John G.
Published: November 2009

Thin nanocrystalline hcp Co-based films are grown by chemical vapor deposition on SiO2. Tetrakis(trimethylphosphine)cobalt(0), ((CH3)3P)4Co, is a single-source precursor that forms Co films that incorporate both P and C when the substrate temperature ranges from 225 to 325 °C, and feature crystallites sized <15 nm. The P within the deposited film is mostly elemental with some being phosphidic, and the C exists mostly in the carbidic form along with some being graphitic. The Co is correspondingly predominantly metallic. Upon annealing to 400 °C for 3 h, some extent of both Co2P crystallite precipitation and minimal allotropic transformation to fcc Co is observed, and the amount of carbidic C is reduced relative to graphitic C, but the nanocrystalline microstructure of the film is preserved, still primarily composed of hcp Co-based crystallites.
Paternal Dominance of Trans-eQTL Influences Gene Expression Patterns in Maize Hybrids
Authors: Swanson-Wagner Ruth A. , DeCook Rhonda , Jia Yi , Bancroft Tim , Ji Tieming , Zhao Xuefeng , Nettleton Dan , Schnable Patrick S.
Published: November 2009

A-Maize-ing

Maize is one of our oldest and most important crops, having been domesticated approximately 9000 years ago in central Mexico.

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et al.

(p.
1112
; see the cover) present the results of sequencing the B73 inbred maize line. The findings elucidate how maize became diploid after an ancestral doubling of its chromosomes and reveals transposable element movement and activity and recombination.

Vielle-Calzada
et al.

(p.
1078
) have sequenced the
Palomero Toluqueño
(
Palomero
) landrace, a highland popcorn from Mexico, which, when compared to the B73 line, reveals multiple loci impacted by domestication.

Swanson-Wagner
et al.

(p.
1118
) exploit possession of the genome to analyze expression differences occurring between lines. The identification of single nucleotide polymorphisms and copy number variations among lines was used by

Gore
et al.

(p.
1115
) to generate a Haplotype map of maize. While chromosomal diversity in maize is high, it is likely that recombination is the major force affecting the levels of heterozygosity in maize. The availability of the maize genome will help to guide future agricultural and biofuel applications (see the Perspective by

Feuillet and Eversole

).
A Periplasmic Reducing System Protects Single Cysteine Residues from Oxidation
Authors: Depuydt Matthieu , Leonard Stephen E. , Vertommen Didier , Denoncin Katleen , Morsomme Pierre , Wahni Khadija , Messens Joris , Carroll Kate S. , Collet Jean-François
Published: November 2009

Periplasmic Redox Regulation

The oxidation state of intracellular and extracellular proteins are carefully managed by cellular redox machineries.

Depuydt
et al.

(p.
1109
) discovered a reducing system that protects single cysteine residues from oxidation in the bacterial periplasm. DsbG, a thioredoxin-related protein, appears to be a key player in that system and is the first reductase identified in the periplasm of
Escherichia coli
. Together with DsbC, DsbG controls the global sulfenic acid content of this compartment. Sulfenic acid formation is a major posttranslational modification in the periplasm, and three homologous L,D-transpeptidases are substrates of DsbG. Sulfenic acid formation is not restricted to
E. coli
, but is ubiquitous. Because proteins from the thioredoxin superfamily are widespread, similar thioredoxin-related proteins may control cellular sulfenic acid more widely.
Research Centers Promise a Break on Medical Patents in Developing Countries
Authors: Kean Sam
Published: November 2009

More than a half-dozen major U.S. universities and institutes pledged last week to lean on biotech companies when licensing intellectual property to secure more favorable terms for countries in the developing world.
Did Neandertals Dine In?
Authors: Balter Michael
Published: November 2009

Researchers have long debated whether the highly carnivorous Neandertals sometimes ate each other. In recent years, new evidence for this macabre hypothesis has emerged.
Teratogenesis in Lake Trout (Salvelinus namaycush) in an Experimentally Acidified Lake
Authors: Kennedy L. A.
Published: November 2009

Embryonic mortality and morbidity were seen in an indigenous population of lake trout (Salvelinus namaycush) inhabiting a lake experimentally acidified over a period of 3 yr to a mean summer epilimnion pH of 5.84. The pH of the hypolimnetic zone where trout spend the summer and undergo gametogenesis was 6.2. Although fertilization appeared to be successful, 59% of eggs incubated in the acidified lake had died or failed to gastrulate by 15 d, and 60% of the surviving embryos displayed gross anatomical malformations. Prior to hatching only 6% of the eggs contained embryos and all were anomalous. In a control lake, 92.9% of eggs contained normal embryos prior to hatching. Both the volume and dry weight of eggs of fish inhabiting the acidified lake were significantly less than eggs from the control lake. When gametogenesis and fertilization occurred in the acid lake but embryogenesis occurred in untreated water in the laboratory, there was a 50% reduction in the viability of eggs of one fish by day 31, compared to controls.Key words: lake acidification, teratogenesis, lake trout
Effects of Chronic Zinc Exposure on the Growth, Sexual Maturity, Reproduction, and Bioaccumulation of the Guppy, Poecilia reticulata
Authors: Pierson Keith B.
Published: November 2009

A 134-d bioassay using sublethal quantities of zinc was conducted beginning with 5-d-old guppies, Poecilia reticulata. Five-day-old control fry had the highest whole body zinc concentrations (mg/g) which declined with growth; the zinc burden (mg/fish) increased primarily from 56 to 70 d during the onset of pregnancy. Uptake of zinc following zinc exposure occurred during logarithmic growth and pregnancy indicating that females actively transfer zinc to the embryo; 0.328 mg/L zinc triggered an apparent excretion process. Guppies exposed to 0.173 mg/L zinc for 70 d had significantly greater zinc body concentrations than controls. Acute sensitivity to zinc was correlated with the zinc body concentration. Growth in wet weight remained uniform for 28 d; however, after 134 d 0.607 mg/L zinc reduced the wet weight of females by 40%. The most sensitive indicator of toxicity was sexual maturity, after 70 d at 0.173 mg/L zinc, significantly fewer females had matured. At 0.607 mg/L zinc, fewer females (50%) gave birth and the time until birth of the first brood increased. Equal growth in wet weight of the second generation fry occurred at all zinc concentrations with growth in both generations being statistically equal implying that the second-generation guppies had become acclimated to zinc exposure. An application factor ranging from 0.030 to 0.099 was calculated. Comparison of growth, reproductive, and body concentration/burden data suggests that at least two modes of zinc regulation exist among fishes.Key words: zinc, bioaccumulation, growth, sexual maturity, reproduction, guppy, application factor
Determination of Corticosteroids in Fish Plasma by High Performance Liquid Chromatography: Evaluation of the Method Using Striped Bass (Morone saxatilis)
Authors: MacFarsane R. Bruce
Published: November 2009

A sensitive, specific, and reproducible technique for the simultaneous determination of cortisol, cortisone, and corticosterone in fish plasma was developed using high performance liquid chromatography (HPLC). Corticosteroids were extracted from plasma by methylene chloride and Sep-Pak cartridges for comparative purposes. The Sep-Pak method proved more convenient and efficient. Chromatography was accomplished on a nitrile bonded phase using a methanol–water mobile phase. Steroids were identified and quantified by monitoring absorbance at 254 and 280 nm simultaneously. Sensitivity is approximately 5 ng for each steroid. An evaluation of the technique using subadult striped bass (Morone saxatilis) revealed that cortisol was the only corticosteroid detected. Plasma cortisol concentrations increased in response to brief confinement and crowding, supporting the efficacy of this measurement as an evaluator of stress in striped bass. The HPLC technique provides specific determination of each corticosteroid (thus eliminating cross-reactivity problems inherent in radioimmunoassay methods), resolves corticosteroids from androgens and estrogens, and permits the isolation and purification of individual steroids.
QUANTIZATION OF NON-LAGRANGIAN SYSTEMS
Authors: KOCHAN DENIS
Published: November 2009

A novel method for quantization of non-Lagrangian (open) systems is proposed. It is argued that the essential object, which provides both classical and quantum evolution, is a certain canonical two-form defined in extended velocity space. In this setting classical dynamics is recovered from the stringy-type variational principle, which employs umbilical surfaces instead of histories of the system. Quantization is then accomplished in accordance with the introduced variational principle. The path integral for the transition probability amplitude (propagator) is rearranged to a surface functional integral. In the standard case of closed (Lagrangian) systems the presented method reduces to the standard Feynman's approach. The inverse problem of the calculus of variation, the problem of quantization ambiguity and the quantum mechanics in the presence of friction are analyzed in detail.
SIGNATURES OF SINGLET NEUTRINOS IN LARGE EXTRA DIMENSIONS AT THE LHC
Authors: GINGRICH DOUGLAS M.
Published: November 2009

It is a challenge to explain why neutrinos are so light compared to other leptons. Small neutrino masses can be explained if right-handed fermions propagate in large extra dimensions. Fermions propagating in the bulk would have implications on Higgs boson decays. If the Higgs boson is discovered at the Large Hadron Collider (LHC), a detailed analysis may reveal the presence of large extra dimensions. This paper reviews the status of large extra-dimensional models in the context of the current limits on Higgs boson masses and the fundamental Planck scale in extra dimensions.
Follicular origins of modern reproductive endocrinology
Authors: Stephens Sahar M. , Moley Kelle H.
Published: November 2009

This essay looks at the historical significance of the APS Classic Paper: Allen E, Doisy EA. The induction of a sexually mature condition in immature females by injection of the ovarian follicular hormone. Am J Physiol 69: 577–588, 1924 ( http://ajplegacy.physiology.org/cgi/reprint/69/3/577 ).