bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Ca2+ on the microtubule‐severing enzyme p60‐katanin. Insight into the substrate‐dependent activation mechanism
Authors: Iwaya Naoko , Akiyama Kohei , Goda Natsuko , Tenno Takeshi , Fujiwara Yoshie , Hamada Daizo , Ikura Teikichi , Shirakawa Masahiro , Hiroaki Hidekazu
Published: February 2012

Katanin p60 (p60‐katanin) is a microtubule (MT)‐severing enzyme and its activity is regulated by the p80 subunit (adaptor‐p80). p60‐katanin consists of an N‐terminal domain, followed by a single ATPase associated with various cellular activities (AAA) domain. We have previously shown that the N‐terminal domain serves as the binding site for MT, the substrate of p60‐katanin. In this study, we show that the same domain shares another interface with the C‐terminal domain of adaptor‐p80. We further show that Ca2+ ions inhibit the MT‐severing activity of p60‐katanin, whereas the MT‐binding activity is preserved in the presence of Ca2+. In detail, the basal ATPase activity of p60‐katanin is stimulated twofold by both MTs and the C‐terminal domain of adaptor‐p80, whereas Ca2+ reduces elevated ATPase activity to the basal level. We identify the Ca2+‐binding site at the end of helix 2 of the N‐terminal domain, which is different from the MT‐binding interface. On the basis of these observations, we propose a speculative model in which spatial rearrangement of the N‐terminal domain relative to the C‐terminal AAA domain may be important for productive ATP hydrolysis towards MT‐severing. Our model can explain how Ca2+ regulates both severing and ATP hydrolysis activity, because the Ca2+‐binding site on the N‐terminal domain moves close to the AAA domain during MT severing.

Structured digital abstract

 p80‐CTD binds to p60‐vMIT by pull down (View interaction)

 p80‐CTD and p60‐vMIT bind by nuclear magnetic resonance (View interaction)
Splice variants of the condensin II gene Ncaph2 include alternative reading frame translations of exon 1
Authors: Theodoratos Angelo , Wilson Laurence O. W. , Gosling Katharine M. , Fahrer Aude M.
Published: February 2012

Condensins I and II are five‐protein complexes that are important for the condensation of chromatin. They are essential for mitosis and important for regulating gene expression during interphase. Here, we investigated the transcription and translation of the mouse Ncaph2 gene, which encodes a subunit of condensin II. We identified three splice variants within the first exon, a NAGNAG splice variant at the beginning of exon 16 and alternative 3′‐UTRs. In total, Ncaph2 is potentially capable of generating 12 unique mRNA transcripts and six unique proteins. We confirm that Ncaph2 can generate three different N‐termini, all encoded by exon 1, one of which is translated from an alternative reading frame. This alternative reading frame splice variant appears to be a novel outcome of splicing. If this is applicable to other genes, it would account for a previously unappreciated level of eukaryotic protein diversity.
Polyclonal antibody‐based ELISA in combination with specific PCR amplification of internal transcribed spacer regions for the detection and quantitation of Lasiodiplodia theobromae, causal agent of gummosis in cashew nut plants
Authors: Muniz C.R. , Freire F.C.O. , Viana F.M.P. , Cardoso J.E. , Correia D. , Jalink H. , Kema G.H.J. , da Silva G.F. , Guedes M.I.F
Published: February 2012

Members of Botryosphaeriaceae family are associated with serious diseases in different plants across the world. In cashew nut plants (Anacardium occidentale), the fungus Lasiodiplodia theobromae causes a severe group of symptoms related to gummosis that results in decreased nut production. The aim of this work was to develop an indirect enzyme‐linked immunosorbent assay (ELISA) with sufficient sensitivity and specificity to detect the fungus both in vitro and in planta (artificially and naturally infected) and to increase the detection specificity within the fungi group using primers specific for the internal transcribed spacer (ITS) sequences. A collection of L. theobromae isolates was obtained, and antisera against the fungus were raised in rabbits. Cross‐reactivity against Neofusicoccum sp., Colletotrichum gloeosporioides, Phomopsis anacardii and Pestalotiopsis guepinii was examined. Naturally and artificially infected vegetal material were employed in the ELISAs. The fungi ITS sequences were determined, and single nucleotide polymorphisms were identified and used for primer design. For the naturally infected plants, there was an approximately fourfold variation in the absorbance values. Some positive readings for asymptomatic samples were detected. For the artificially infected samples, an ELISA‐based weekly time‐course analysis was conducted, and the values for samples from 0 and 7 days were lower than the threshold value. Beginning on day 14, the infection could be detected, with rates varying from 40% on day 14 to 80% on day 21 and 100% by the end of the experiment. The ITS sequencing revealed few polymorphisms among the L. theobromae isolates, but for C. gloeosporioides, P. anacardii, P. guepinii and Neofusicoccum sp., the sequences were sufficient to permit reliable discrimination. The feasibility of ELISA as an early detection technique to assist in gummosis management was demonstrated. PCR amplification based on ITS regions increases and complements serological specificity.
MODELING OF THE ADHESION OF BACILLUS CEREUS ISOLATED FROM A DAIRY PLANT AS A FUNCTION OF TIME AND TEMPERATURE
Authors: BERNARDES PATRÍCIA CAMPOS , ANDRADE NÉLIO JOSÉ DE , PENÃ WILMER EDGARD LUERA , MINIM LUÍS ANTÔNIO , SÁ JOÃO PAULO NATALINO , FERNANDES PATRÍCIA ÉRICA , COLOMBARI DANIELE DOS SANTOS
Published: February 2012

Adhesion of Bacillus cereus to stainless steel 304 #4 was evaluated after different times and temperatures of contact. Mathematical model was obtained, which was capable of predicting the adhesion of B. cereus to stainless steel as a function of temperature (4–35C) and time (1–10 days). The increase in temperature from 4 to 35C resulted in an increased number of B. cereus cells attached more than 3 log cycles for an adhesion time of 1 day and more than 4 log cycles for an adhesion time of 10 days, indicating the importance of temperature in adhesion. The maximum number of cells attached to coupons incubated at 35C for 10 days (4.43 log cfu/cm2) was close to the number of cells attached to coupons incubated at 35C for 1 day (4.01 log cfu/cm2). The model obtained represents well the relationship between temperature and rate of adhesion, which is indicated by the statistical indices calculated.

PRACTICAL APPLICATIONS

This research shows important information for people dealing with food quality control, quality management, risk assessment, risk management hazard analysis by critical point control and good manufacturing practices, which are well‐recognized food safety tools. The number of manufactured foods has widely increased to meet the increasing number of consumers and, sometimes, the hygiene procedures in the food industry are poor or overlooked. It is essential that those responsible for producing food be knowledgeable about the characteristics of the material surfaces used to make the equipment, utensils and conveyors to help in the control of foodborne diseases. The viable alternatives to avoid or minimize food contamination are (1) improving surface quality related to microtopography by improving surface production process; (2) choosing surfaces with better characteristics concerning microtopography to control the adherence process and biofilm formation; and (3) implementing effective controls of cleaning and sanitizing procedures.
Mass Discharge in a Tracer Plume: Evaluation of the Theissen Polygon Method
Authors: Mackay Douglas M. , Einarson Murray D. , Kaiser Phil M. , Nozawa‐Inoue Mamie , Goyal Sham , Chakraborty Irina , Rasa Ehsan , Scow Kate M.
Published: February 2012

A tracer plume was created within a thin aquifer by injection for 299 d of two adjacent “sub‐plumes” to represent one type of plume heterogeneity encountered in practice. The plume was monitored by snapshot sampling of transects of fully screened wells. The mass injection rate and total mass injected were known. Using all wells in each transect (0.77 m well spacing, 1.4 points/m2 sampling density), the Theissen Polygon Method (TPM) yielded apparently accurate mass discharge (Md) estimates at three transects for 12 snapshots. When applied to hypothetical sparser transects using subsets of the wells with average spacing and sampling density from 1.55 to 5.39 m and 0.70 to 0.20 points/m2, respectively, the TPM accuracy depended on well spacing and location of the wells in the hypothesized transect with respect to the sub‐plumes. Potential error was relatively low when the well spacing was less than the widths of the sub‐plumes (>0.35 points/m2). Potential error increased for well spacing similar to or greater than the sub‐plume widths, or when less than 1% of the plume area was sampled. For low density sampling of laterally heterogeneous plumes, small changes in groundwater flow direction can lead to wide fluctuations in Md estimates by the TPM. However, sampling conducted when flow is known or likely to be in a preferred direction can potentially allow more useful comparisons of Md over multiyear time frames, such as required for performance evaluation of natural attenuation or engineered remediation systems.
Examining Consumers' Perceptions of the Health Benefits of Products with Fiber Claims
Authors: ZANK GAIL M. , KEMP ELYRIA
Published: February 2012

Many foods, including margarines and sugary cereals that were once viewed as unhealthy, are being reformulated and repositioned as healthier. A number of companies have launched new products touting fiber. Critics express concern that the increased interest in fiber as a marketing claim is not necessarily a good thing for consumers because many companies are using isolated fiber that does not have all the health benefits as naturally occurring fiber. This research examines whether consumers understand information related to fiber claims by specifically examining their perceptions of the nutrition level and health benefits of products with these claims. Additionally, consumption frequency of these products and consumer knowledge about fiber is assessed. Direction for public policy is provided.
Expression and Function of Macrophage Migration Inhibitory Factor in the Pathogenesis of UV‐Induced Cutaneous Nonmelanoma Skin Cancer†
Authors: Heise Ruth , Vetter‐Kauczok Claudia S. , Skazik Claudia , Czaja Katharina , Marquardt Yvonne , Lue Hongqi , Merk Hans F. , Bernhagen Jürgen , Baron Jens M.
Published: February 2012

Chronic skin exposure to ultraviolet light stimulates the production of cytokines known to be involved in the initiation of skin cancer. Recent studies in mouse models suggested a role for macrophage migration inhibitory factor (MIF) in the UVB‐induced pathogenesis of nonmelanoma skin cancer (NMSC). Our studies aimed at defining the pathophysiological function of MIF in cutaneous inflammatory reactions and in the development and progression of NMSC. Immunohistochemical analysis revealed a moderate expression of MIF in normal human skin samples but an enhanced expression of this cytokine in lesional skin of patients with actinic keratosis or cutaneous SCC. Enzyme‐linked immunosorbent assay studies showed a time‐dependent increase in MIF secretion after a moderate single‐dose UVB irradiation in NHEKs and SCC tumor cells. MIF is known to interact with CXCR2, CXCR4 and CD74. These receptors are not constitutively expressed in keratinocytes and HaCaT cells and their expression is not induced by UVB irradiation either. However, stimulation with IFNγ upregulated CD74 surface expression in these cells. Affymetrix® Gene Chip analysis revealed that only keratinocytes prestimulated with IFNγ are responsive to MIF. These findings indicate that MIF may be an important factor in the pathogenesis of NMSC tumorigenesis and progression in an inflammatory environment.
Inherited variants in the MC1R gene and survival from cutaneous melanoma: a BioGenoMEL study
Authors: Davies John R. , Randerson‐Moor Juliette , Kukalizch Kairen , Harland Mark , Kumar Rajiv , Madhusudan Srinivasan , Nagore Eduardo , Hansson Johan , Höiom Veronica , Ghiorzo Paola , Gruis Nelleke A. , Kanetsky Peter A. , Wendt Judith , Pjanova Dace , Puig Susana , Saiag Philippe , Schadendorf Dirk , Soufir Nadem , Okamoto Ichiro , Affleck Paul , García‐Casado Zaida , Ogbah Zighereda , Ozola Aija , Queirolo Paola , Sucker Antje , Barrett Jennifer H. , van Doorn Remco , Bishop D. Timothy , Newton‐Bishop Julia
Published: February 2012

Inherited MC1R variants modulate MITF transcription factor signaling, which in turn affects tumor cell proliferation, apoptosis, and DNA repair. The aim of this BioGenoMEL collaborative study in 10 melanoma cohorts was to test the hypothesis that inherited variants thereby moderate survival expectation. A survival analysis in the largest cohort (Leeds) was carried out adjusting for factors known to impact on survival. The results were then compared with data from nine smaller cohorts. The absence of any consensus MC1R alleles was associated with a significantly lower risk of death in the Leeds set (HR, 0.64; 95% CI, 0.46–0.89) and overall in the 10 data sets (HR, 0.78; 95% CI, 0.65–0.94) with some support from the nine smaller data sets considered together (HR, 0.83; 95% CI, 0.67–1.04). The data are suggestive of a survival benefit for inherited MC1R variants in melanoma patients.
QUALITY OF LIFE AT END OF LIFE
Authors: Brown Edwina A.
Published: February 2012

Patients with chronic kidney disease, particularly those with diabetes, often have a heavy burden of vascular comorbidity and hence a poor overall prognosis. Unfortunately, patients and their healthcare teams often have unrealistic expectations about outcomes and receive ineffective and often harmful interventions towards their end of life. We need to move away from death being perceived as a failure and realise, instead, that our goal of care at the end of life is to achieve as good a quality of life for the patient as possible. To be able to achieve this, it is important to be realistic about prognosis, be able to recognise predictors of poor outcome and then be able to discuss these with the patient and their family to ensure symptom control, avoid interventions that could do harm and then as the end approaches, determine the wishes of the patient regarding preferred place of care for their inevitable death.
HOW TO IDENTIFY AND MANAGE DIABETES MELLITUS AFTER RENAL TRANSPLANTATION
Authors: Stevens Kathryn K. , Patel Rajan K. , Jardine Alan G.
Published: February 2012

New‐onset diabetes after transplantation (NODAT) has serious consequences for the patient in terms of overall survival, graft function and graft survival. The incidence of NODAT and impaired glucose tolerance has probably been underestimated previously because of lack of a universal diagnostic definition. Many risk factors have been identified, a proportion of which are modifiable. Early identification of those who are at high risk of NODAT and strategies to reduce risk will help to reduce the morbidity and mortality resulting from this condition. Where prevention is not possible, stringent management strategies are essential. Although, this article focuses on NODAT in the renal transplant recipient and considers the scale of the problem, impact on patient and transplant survival, determinants and risk factors for, and the management of, impaired glucose tolerance and NODAT, much of it will also be applicable to other types of solid organ transplantation.
Microalgae for phosphorus removal and biomass production: a six species screen for dual‐purpose organisms
Authors: Patel Anil , Barrington Suzelle , Lefsrud Mark
Published: February 2012

Microalgae biofuel production can be feasible when a second function is added, such as wastewater treatment. Microalgae differ in uptake of phosphorus (P) and growth, making top performer identification fundamental. The objective of this screen was to identify dual‐purpose candidates capable of high rates of P removal and growth. Three freshwater – Chlorella sp., Monoraphidium minutum sp., and Scenedesmus sp. – and three marine – Nannochloropsis sp., N. limnetica sp., and Tetraselmis suecica sp. – species were batch cultured in 250 mL flasks over 16 days to quantitate total phosphorus (TP) removal and growth as a function of P loads (control, and 5, 10, and 15 mg L−1 enrichment of control). Experimental design used 100 μmol m−2 s−1 of light, a light/dark cycle of 14/10 h, and no CO2 enrichment. Phosphorus uptake was dependent on species, duration of exposure, and treatment, with significant interaction effects. Growth was dependant on species and treatment. Not all species showed increased P removal with increasing P addition, and no species demonstrated higher growth. Nannochloropsis sp and N. limnetica sp. performed poorly across all treatments. Two dual‐purpose candidates were identified. At the 10 mg L−1 treatment Monoraphidium minutum sp. removed 67.1% (6.66 mg L−1 ± 0.60 SE) of TP at day 8, 79.3% (7.86 mg L−1 ± 0.28 SE) at day 16, and biomass accumulation of 0.63 g L−1 ± 0.06 SE at day 16. At the same treatment Tetraselmis suecica sp. removed 79.4% (6.98 mg L−1 ± 0.24 SE) TP at day 8, 83.0% (7.30 mg L−1 ± 0.60 SE) at day 16, and biomass of 0.55 g L−1 ± 0.02 SE at day 16. These species merit further study using high‐density wastewater cultures and lipid profiling to assess suitability for a nutrient removal and biomass/biofuel production scheme.
Evaluation of the impedance analyzer PocH‐100iV Diff for analysis of canine and feline blood
Authors: Bauer Natali B. , Nakagawa Julia , Dunker Cathrin , Failing Klaus , Moritz Andreas
Published: February 2012

Background

An automated impedance‐based in‐house hematology analyzer, the PocH‐100iV Diff, which provides a 3‐part leukocyte differential count that includes eosinophils, recently has been introduced.

Objectives

The aims of this study were to validate results from the PocH‐100iV Diff for dogs and cats and evaluate the impact of the anticoagulant used and sample storage conditions.

Methods

Blood samples collected in K3EDTA from 153 cats and 150 dogs were included in the comparison study. The reference analyzer was the ADVIA 2120 hematology analyzer, and manual differential leukocyte counts and PCV were the manual reference methods.

Results

Coefficients of variation were < 3% except for platelet counts and feline differential and eosinophil counts. Correlation between analyzers was good to excellent except for hemoglobin (HGB) concentration in dogs and RBC indices for both species. Biases were close to 0 except for MCHC and platelet counts. Correlation with manual counts was good for lymphocytes and OTHR cells (combined neutrophil and monocyte counts) and fair and poor for feline and canine eosinophil counts, respectively. Estimated sensitivity and specificity for detection of eosinophilia were, respectively, 50% and 98% for cats and 34% and 77% for dogs. A significant anticoagulant effect was seen for MCV in cats and for HCT, MCH, MCHC, and platelet, OTHR, and eosinophil counts in dogs. RBC and WBC counts, HGB concentration, and MCH were stable for 72 h. HCT, MCV, MCHC, and platelet counts were affected by sample storage (dogs > cats; 22°C > 4°C).

Conclusions

The PocH‐100iV Diff is a suitable in‐house instrument. A strength is its specific, but moderately sensitive, detection of feline eosinophils.
Twice‐weekly, in‐school jumping improves lean mass, particularly in adolescent boys
Authors: Weeks B. K. , Beck B. R.
Published: February 2012

Objective

To determine the effect of a twice‐weekly, school‐based, 10‐min jumping regime on muscle and fat tissue in healthy adolescent boys and girls.

Methods

We replaced regular warm‐up activities with jumping in physical education (PE) classes of early high school students for 8 months to observe the effect on muscle and fat tissue. A total of 99 adolescents (46 boys, 53 girls; 13.8 ± 0.4 years) volunteered to participate. Intervention group subjects performed 10 min of varied jumping activity, while control subjects performed a regular PE warm‐up. Biometrics, Tanner staging, age of peak height velocity (PHV), vertical jump, whole body lean tissue and fat mass (dual‐energy X‐ray absorptiometry‐derived) were measured at baseline and follow‐up. Physical activity was determined by questionnaire.

Results

There were no differences in any measured variable between control and intervention groups at baseline. Boys had a significantly older age of PHV than girls (p = 0.02). No group differences were detected for 8‐month change in height, weight or maturity measures for the combined sample; however, at 8 months, jumpers had accrued greater lean tissue mass than controls (p = 0.002). Sex‐specific analysis revealed that intervention group boys had gained more lean tissue mass than controls (p = 0.016) and experienced significant fat loss (p = 0.010) than controls, an effect that was not observed in the girls.

Conclusion

Regular, short‐duration, jumping activity during adolescence increased lean tissue mass and boys additionally lost fat mass. Sex‐specific and/or maturation‐specific factors may explain the disparity in effect.
Muscle contraction duration and fibre recruitment influence blood flow and oxygen consumption independent of contractile work during steady‐state exercise in humans
Authors: Richards Jennifer C. , Crecelius Anne R. , Kirby Brett S. , Larson Dennis G. , Dinenno Frank A.
Published: February 2012

We tested the hypothesis that, among conditions of matched contractile work, shorter contraction durations and greater muscle fibre recruitment result in augmented skeletal muscle blood flow and oxygen consumption (
) during steady‐state exercise in humans. To do so, we measured forearm blood flow (FBF; Doppler ultrasound) during 4 min of rhythmic hand‐grip exercise in 24 healthy young adults and calculated forearm oxygen consumption (
) via blood samples obtained from a catheter placed in retrograde fashion into a deep vein draining the forearm muscle. In protocol 1 (n= 11), subjects performed rhythmic isometric hand‐grip exercise at mild and moderate intensities during conditions in which time–tension index (isometric analogue of work) was held constant but contraction duration was manipulated. In this protocol, shorter contraction durations led to greater FBF (184 ± 25 versus 164 ± 25 ml min−1) and
(23 ± 3 versus 17 ± 2 ml min−1; both P < 0.05) among mild workloads, whereas this was not the case for moderate‐intensity exercise. In protocol 2 (n= 13), subjects performed rhythmic dynamic hand‐grip exercise at mild and moderate intensities in conditions of matched total work, but muscle fibre recruitment was manipulated. In this protocol, greater muscle fibre recruitment led to significantly greater FBF (152 ± 15 versus 127 ± 13 ml min−1) and
(20 ± 2 versus 17 ± 2 ml min−1; both P < 0.05) at mild workloads, and there was a trend for similar responses at the moderate intensity but this was not statistically significant. In both protocols, the ratio of the change in FBF to change in
was similar across all exercise intensities and manipulations, and the strongest correlation among all variables was between
and blood flow. Our collective data indicate that, among matched workloads, shorter contraction duration and greater muscle fibre recruitment augment FBF and
during mild‐intensity forearm exercise, and that muscle blood flow is more closely related to metabolic cost (
) rather than contractile work per se during steady‐state exercise in humans.
Ontogeny of the renal urotensin II system in the rat
Authors: Forty Ellen J. , Ashton Nick
Published: February 2012

Urotensin II (UII), a peptide hormone which influences glomerular filtration rate and urine concentration, and its receptor, UT, are expressed in the adult rat kidney. The ability of the kidney to reabsorb sodium and water starts to develop in utero and matures during early postnatal life in the rat, yet little is known about the ontogeny of the renal UII system. This study mapped renal expression of the urotensin system during the fetal and postnatal periods and determined renal activity of UII in the immature rat. Urotensin II peptide and mRNA were present in Sprague–Dawley (SD) rat metanephroi from the earliest stage examined, embyonic day 19 (E19; rat gestation 22 days); levels increased to peak at 4 weeks of age. In contrast, UT protein and mRNA expression declined rapidly between E19 and birth and remained at a similar level postnatally. Infusion of rat UII [6–60 pmol min−1 (100 g body weight)−1] or rat urotensin‐related peptide [6 pmol min−1 (100 g body weight)−1] in anaesthetized 4‐week‐old SD rats had no influence on measured renal parameters; however, infusion of UT antagonist, SB‐706375 (0.01 mg kg−1 min−1), provoked a pronounced diuresis [vehicle 23.5 ± 1.9 versus antagonist 75.3 ± 12.5 μl min−1 (100 g body weight)−1; P < 0.001] and natriuresis, accompanied by modest increases in effective renal blood flow and glomerular filtration rate [vehicle 0.4 ± 0.1 versus antagonist 1.1 ± 0.2 ml min−1 (100 g body weight)−1; P < 0.0001] and a significant increase in fractional sodium excretion. These results indicate that the endogenous rat UII system may influence renal sodium and water excretion before the onset of full urine concentrating capacity in the SD rat.
A single bout of exercise activates skeletal muscle satellite cells during subsequent overnight recovery
Authors: Snijders Tim , Verdijk Lex B. , Beelen Milou , McKay Bryon R. , Parise Gianni , Kadi Fawzi , van Loon Luc J. C.
Published: February 2012

Skeletal muscle satellite cell (SC) content has been reported to increase following a single bout of exercise. Data on muscle fibre type‐specific SC content and/or SC activation status are presently lacking. The objective of the study was to determine the impact of a single bout of exercise on muscle fibre type‐specific SC content and activation status following subsequent overnight recovery. Eight healthy men (age, 20 ± 1 years) performed a single bout of combined endurance‐ and resistance‐type exercise. Muscle biopsies were collected before and immediately after exercise, and following 9 h of postexercise, overnight recovery. Muscle fibre type‐specific SC and myonuclear content and SC activation status were determined by immunohistochemical analyses. Satellite cell activation status was assessed by immunohistochemical staining for both Delta‐like homologue 1 (DLK1) and Ki‐67. Muscle fibre size and fibre area per nucleus were greater in type II compared with type I muscle fibres (P < 0.05). At baseline, no differences were observed in the percentage of SCs staining positive for DLK1 and/or Ki67 between fibre types. No significant changes were observed in SC content following 9 h of postexercise, overnight recovery; however, the percentage of DLK1‐positive SCs increased significantly during overnight recovery, from 22 ± 5 to 41 ± 5% and from 24 ± 6 to 51 ± 9% in the type I and II muscle fibres, respectively. No changes were observed in the percentage of Ki‐67‐positive SCs. A single bout of exercise activates both type I and II skeletal muscle fibre SCs within a single night of postexercise recovery, preceding the subsequent increase in SC content.
Gear Tribology Aspects in Aircraft High-Lift Actuation Systems
Authors: Wang Anngwo , El-Bayoumy Lotfi
Published: February 2012

Gears are extensively used in aircraft high-lift actuation systems in which the loading is high and the speed is relatively slow. The specific lubrication film thickness falls into the boundary lubrication regime. In case of lubrication failure, it will cause pitch-line pitting, scoring or micropitting. Many tests have been performed to examine the root cause of these problems. The sliding and rolling action between mating gears in a compound planetary rotary actuator is the source of variation in efficiency. This efficiency variation can be smooth or fluctuating depending on the combination and timing of ring, planet and sun gears. The instantaneous efficiency characteristics of synchronous and non-synchronous actuators under forward-driving with opposing load and reverse-driving with aiding load are investigated. These are some of the gear tribological topics discussed in this paper.
Large-Scale Simulation of Fluid Flows in Mixed Lubrication
Authors: Brunetiere Noe¨l , Wang Q. Jane
Published: February 2012

This paper presents a novel method to compute the lubricant pressure distribution between a rough and a smooth surface in relative motion. The originality of this method is to combine a deterministic approach for the large scales and a stochastic model for the small scales of the problem. As a result, the new method allows a significant mesh reduction while maintaining an accurate prediction of the generated load.
Simulation of Hydrodynamic Forces on Passenger Car Synchronizer Rings During Rattling
Authors: Fietkau Peter , Baumann Axel , Bertsche Bernd
Published: February 2012

This paper presents a model to calculate hydrodynamic forces on a rattling synchronizer ring, i.e. a ring which is excited by rotational speed irregularities and therefore moves within its functional clearance. Based on the Reynolds Equation an analytical and a numerical solution for determination of the forces resulting from oil films on the ring are derived. The model is implemented in a user force element for the multi-body simulation environment SIMPACK and sample simulations with a simple experimental transmission are presented. The results show that the model is capable of representing the rattle characteristic of a synchronizer ring.
A 3D Multigrid Solver for the Elastic Contact Problem: Application to Graded Materials
Authors: Boffy H. , Baietto M. C. , Sainsot P. , Lubrecht T.
Published: February 2012

The actual contact between solid surfaces is generally rough and time dependent. The stresses induced by the rough contact can only be correctly described using a detailed 3D model. Even finer details are required in the case of surface coatings. Consequently, the rough coated contact problem is strongly multi-scale: the characteristic dimensions of the contact, the coating and the roughness range from the millimeter to the nanometer. A straightforward discretisation of this multi-scale problem would exceed the memory and CPU capacity of current (and next generation) computers. This paper proposes an efficient numerical model that can handle this multi-scale problem: using 109 points and locally refined grids. The proposed model is based on multigrid techniques within a finite difference frame work. Localised refinement is implemented to optimize memory requirement and computing time. Validation of the solver is performed through a comparison with analytical results for simple cases. The algorithm performance is analyzed through a parametric study describing the influence of layer thickness (0.01 < t/a < 10) and mechanical properties (0.005 < Ec/Es < 10) of the coating on the contact parameters (Ph, a). A linear graded coating, used as a solution to avoid interfacial problems, is then compared to a coating with constant properties. A quantitative analysis of the evolution of the maximum tensile stress with depth is conducted in both cases.
Slider Air Bearing Design in Consideration of the Pumping Effect
Authors: Zhang Bo , Mawatari Toshifumi , Nakajima Akira
Published: February 2012

The pumping effect proposed by the authors is used to analyze the contamination of the air bearing in hard disk drive. Three different types of air bearing surface are considered in the focus on the accumulation of the contamination at the rear pad where the minimum spacing is located. It is found that the contamination tends to accumulate at both the front and the rear ends of the air bearing surface pad where the shear stress of air film is interrupted due to due to the dramatic change in the spacing. The accumulation at the tailing edge of the air bearing is the most detrimental. The thickness of adsorbed film at the tailing edge increases suddenly when the terrace length at the tailing edge exceeds a critical value, which is in between 15 μm and 35 μm in this article.
Nonlinear Dynamic Oil-Film Forces in Infinite-Short Journal Bearings
Authors: Yang Lihua , Wang Weimin , Yu Lie
Published: February 2012

In this paper, the analytic solutions of oil-film forces in infinite-short cylindrical journal bearing are calculated by solving its corresponding Reynolds equation. On this base, the linear and nonlinear dynamic coefficients of the bearing are predicted. By comparing the dynamic oil-film forces approximately represented by dynamic coefficients with the analytic solutions, the accuracy of this representation model is investigated. The results show that more orders of dynamic coefficients are included in representation model, the obtained approximate oil-film forces are more close to their analytic solutions. This can be a reference to illustrate the feasibility and applicability of representing oil-film forces by applying the dynamic coefficients of bearings.
Modeling of Eddy Current Loss for Magnetic Thrust Bearings
Authors: Tian Yongsheng , Sun Yanhua , Yu Lie
Published: February 2012

In this paper, an analytical model for calculating eddy current loss in magnetic thrust bearings (MTBs) is presented. The surface magnetic field intensity, considering the skin effect of eddy current, is varying with the frequency and can be calculated by effective reluctance method. The magnetic field distribution and eddy current loss can be obtained from it. Finally, the validity of the model is verified by the finite element method (FEM) simulation and experimental results.
Friction and Wear Characteristics of Diamond-Like Carbon (DLC) Coating Used for Machine Elements
Authors: Kim D. W. , Kim K. W.
Published: February 2012

In this study, friction and wear tests were performed in order to investigate the effect of sliding velocity and normal load on the friction and wear characteristics of multi-layered diamond-like carbon (DLC) coating used for machine elements (automotive engine tappet, etc). Friction and wear tests against AISI 52100 bearing steel ball were performed under various sliding velocities (0.25, 0.5, 1 and 2 m/s) and normal loads (6.13, 20.7 and 49.0 N). As a result of test, kinetic friction coefficients and wear rates of multi-layered DLC coating and AISI 52100 bearing steel were obtained under each test condition. The result showed that the kinetic friction coefficients and wear rates generally decreased with the increase in sliding velocity and normal load.
Elements of a Successful Quality Control Department in a Grease Plant
Authors: Milligan Kimberly
Published: February 2012

The Quality Control (QC) Department in a grease plant is vital to product compliance and customer satisfaction. QC provides the initial inspection of raw materials and finished goods which determines whether the material is acceptable for manufacture or sale. In other words, the QC department is the gateway to customer satisfaction and future accounts. In order to have a successful QC department, the following key factors must be met: properly trained personnel, suitable inspection equipment and a functioning management system. If these three factors are established and continually improved, the QC Department will be effective.
An Elastic-Plastic Spherical Contact Model Under Combined Normal and Tangential Loading
Authors: Wu Aizhong , Shi Xi , Polycarpou Andreas A.
Published: February 2012

In this work, by utilizing the shear strength criterion for the sliding inception, a finite element model for obliquely loaded spherical contact has been developed, which realized a friction transition from perfect slip case to full stick case with increasing normal approach. Both tangential force and normal force during tangential loading were investigated using different models. It was found that with elastic-plastic normal displacement preload, there is an obvious normal force release during tangential loading. Furthermore, both Coulomb friction model and the proposed model predict a lower tangential force at the same tangential displacement compared to the full stick model. However, the Coulomb friction is more empirically determined with some arbitrary friction coefficient whereas the proposed model is based on physics parameters.
Dynamic Characteristics of the Combined Smart Bearing
Authors: Lee Yong Bok , Lee Kyung Min , Chung Jin-Taek , Kim Seung Jong , Jeong Se Na
Published: February 2012

The stability, reliability, efficient performance of high speed turbo machinery is very important, and accordingly has increased the demand for advanced bearings. In order to meet the advanced bearing needs, Heshmat proposed a hybrid foil-magnetic bearing [1]. The hybrid bearing combining the two bearings takes advantage of the strengths of each while compensating for each other’s weaknesses. This paper presents dynamic characteristics of the combined smart bearing (CSB) of different structure from Heshmat’s bearing. The CSB and test rig were designed, fabricated and carried out the test. Numerical predictions of Air foil bearing (AFB) and CSB were compared the dynamic force performance, and analysis of bearings are performed by finite element method (FEM). Experiments were conducted to determine the structural static and dynamic characteristics of AFB. The dynamic characteristics of AFB and CSB compared depending on the rotating speed change. The experimental results were obtained the dynamic characteristics of the CSB 50% higher than value of the stiffness effect. In addition to, the CSB 100% higher than value of the damping effect.
Surface Texturing Effect, Characterization and Optimization for Boundary and Mixed Lubrication
Authors: Podgornik B. , Sedlacˇek M.
Published: February 2012

Under boundary and mixed lubrication surface roughness and topography have significant influence on the tribological behaviour of contact surfaces, where even a small change in surface topography can lead to a considerable change in tribological behaviour. In recent years an effort for better controlling friction and wear has been focused also on the surface topography modification, especially on surface texturing. The aim of the present research work was to investigate the possibility of using roughness parameters kurtosis and skewness as design parameters for optimizing texturing pattern in boundary and mixed lubricated contacts. Results of the investigation performed on groove and dimple textured surfaces under low load low sliding speed conditions confirm correlation between kurtosis and skewness parameters and coefficient of friction. For textured surfaces increase in kurtosis and more negative skewness, obtained by reducing cavity size, increasing cavity depth and decreasing texturing density were found to yield lower friction. Furthermore, kurtosis and skewness were recognized as suitable parameters for textured surfaces optimization. Through virtual texturing effect of different texturing parameters on kurtosis and skewness parameters can be identified and then optimized to result in reduced friction under boundary and mixed lubrication.
Mechanisms of Lubricated and Unlubricated Friction and Wear
Authors: Marais G. , de Vaal P. L.
Published: February 2012

A study was undertaken to analyse results obtained with the HFRR instrument by identifying crucial factors contributing to friction and wear mechanisms. For lubricated tests a mixture of n-hexadecane (cetane) as base fluid and palmitic acid as lubricity additive was used. Experimental results, including results obtained by running unlubricated (dry) tests and results obtained from literature were all considered to formulate the hypothesis that a fully functional additive film will not survive the full duration of the lubricity test, which is 75 minutes [5]. Friction values obtained in the experiments conducted were much higher than what is expected for boundary films formed by long chain carboxylic acids. Comparable friction values were obtained in the first few seconds of the tests, but the friction values increased indicating the destruction of the boundary film. Metal oxide lubrication dominates for the remainder of the test.
Analysis of the Contribution of Adhesion and Ploughing to Shoe-Floor Lubricated Friction in the Boundary Lubrication Regime
Authors: Moore Caitlin , Beschorner Kurt , Menezes Pradeep L. , Lovell Michael R.
Published: February 2012

Slip and fall accidents cost billions of dollars each year. Shoe-floor-lubricant friction has been shown to follow the Stribeck effect, operating primarily in the boundary and mixed-lubrication regimes. Two of the most important factors believed to significantly contribute to shoe-floor-lubricant friction in the boundary lubrication regime are adhesion and ploughing. Experiments were conducted using a pin-on-disk tribometer to quantify adhesion and ploughing contributions to shoe-floor friction in dry and lubricated conditions. The coefficient of friction between three shoe materials and two floor materials of different hardness and roughness were considered. Experiments were conducted under six lubricants for a sliding speed of 0.01 m/sec at ambient conditions. It was found that the contribution of adhesion and ploughing to shoe-floor-lubricant friction was significantly affected by material hardness, roughness, and lubricant properties. Material hardness and roughness are known to affect adhesion, with increased hardness or increased roughness typically resulting in decreased adhesion. The smoothest shoe material, while also being the hardest, resulted in the greatest adhesional contribution to friction. The roughest material, while also being the softest, resulted in the lowest adhesional contributions under dry conditions. Canola oil consistently resulted in the lowest percent of full adhesion and water consistently resulted in the highest percent of full adhesion, presumably due to the thickness, of the boundary lubrication layer. Ploughing contribution was dependent upon the hardness of the shoe and floor materials. A positive correlation was found between the shoe and floor hardness ratio and ploughing coefficient of friction.
Friction and Wear of Bronze Filled PTFE and Graphite Filled PTFE in 40 MPA Hydrogen Gas
Authors: Sawae Yoshinori , Miyakoshi Eiichi , Doi Shunichiro , Watanabe Hideki , Kurono Yoshie , Sugimura Joichi
Published: February 2012

Several kinds of Polytetrafluoroethylene (PTFE) composites are currently being used in reciprocating hydrogen gas compressors as seal material which should articulate against metal counterfaces in pressurized hydrogen gas. Although their friction and wear behavior has large impact on the efficiency and reliability of gas compressors, available information about tribological characteristics of PTFE composites in high pressure hydrogen gas is quite limited. In this study, friction and wear of graphite filled PTFE and bronze filled PTFE were evaluated in the 40 MPa hydrogen gas environment by using a pin-on-disk type apparatus enclosed in a high pressure vessel to supply experimental data for the design of gas compressors in hydrogen fuelling stations. AISI316L austenitic stainless steel disk was used as a sliding counterface. All experiments were conducted under dry condition with the average contact pressure of 1.8 MPa, the sliding speed of 100 mm/s and the gas temperature of 327 K. The friction force exerted between PTFE composites and stainless steel was evaluated by a load cell during the experiment and the wear rate of composites was evaluated from the weight loss of pin specimens. In addition, chemical analysis of the polymer transfer film formed on the disk surface were conducted by using X-ray photoelectron spectrometer. Friction and wear tests were also conducted in 40 MPa helium gas for comparison. Results indicated that bronze filled PTFE was more sensitive to the gas pressure and gas species; it showed good friction and wear behavior in high pressure hydrogen, although friction in high pressure helium became very high. On the other hand, the effects of high pressure gas environment were relatively small for the friction and wear of graphite filled PTFE.
Influence of Rock Mechanical Properties on the Formation of Rock Fragments During Cutting Operation
Authors: Menezes Pradeep L. , Lovell Michael R.
Published: February 2012

Mechanical rock cutting is a process encountered in different engineering applications including rock excavation, mining and deep oil well drilling. Rock mechanical properties vary with depth in the subsurface and also at different geographical locations due to different environmental conditions. Understanding of fragmentation mechanisms in specific rock materials allows the determination of optimum cutting parameters that improve cutting efficiency and increase tool life during cutting operations. In the present investigation, numerical models that accurately predict the rock fragmentation and stress profiles in the rock slab during cutting were developed using the explicit finite-element method (FEM). In the numerical models, a damage material model was utilized to capture the rock fragmentation process and a rigid steel cutter (at different rake angles) was displaced at different velocities against a stationary rock slab. Rock slabs with significantly different mechanical properties were incorporated with a constant friction factor and a cutting depth of 1 mm. The variation of cutting forces and stresses, and fragmentation of the rock slab were analyzed. The simulation results indicated that the explicit FEM is a powerful tool for simulating rock cutting as the formation of fragments were distinctly observed at different cutting conditions. The rock mechanical properties and tool rake angle were found to have the most significant effect on the rock fragmentation during cutting operations. The cutting forces were also influenced by mechanical properties of the rock and tool rake angle.
A Friction Inclusive Cellular Automata Approach for Modeling Kinetic and Transitional Granular Flows
Authors: Marinack Martin C. , Higgs C. Fred
Published: February 2012

Granular flows continue to be a complex problem in nature and industrial sectors where solid particles exhibit solid, liquid, and gaseous behavior in a manner which is often unpredictable locally or globally. In tribology, they have also been proposed as lubricants because of their liquid-like behavior in sliding contacts, and due to their ability to carry loads and accommodate surface velocities. The present work attempts to model a granular Couette flow in an annular shear cell using a lattice-based cellular automata (CA) computational modeling approach. The CA framework has the flexibility to employ rule-based mathematics and/or first-principle physics to rapidly model physical processes. The model developed in this work incorporates dissipative effects due to friction between particles and boundaries, in addition to particle spin. This new model also includes a rigorous treatment of boundary-particle interactions. Additional work has been done to account for the transfer of momentum through particle chains, allowing for the modeling of transitional granular flows, which consist of both kinetic and contact flow regimes.
Intensifying Weathering and Land Use in Iron Age Central Africa
Authors: Bayon Germain , Dennielou Bernard , Etoubleau Joël , Ponzevera Emmanuel , Toucanne Samuel , Bermell Sylvain
Published: February 2012

A Price of Civilization

Large expanses of rainforests in parts of Central Africa were abruptly replaced by savannas around 3000 years ago, presumably because of climate change. However, that succession occurred at a time of expansion by Bantu tribes, from near the border of present-day Cameroon and Nigeria to the south and east, in a migration that brought with it agriculture and iron-smelting technologies.

Bayon
et al.

(p.
1219
, published online 9 February; see the Perspective by

Dupont

) analyzed the nearby marine sedimentary record and found that chemical weathering in Central Africa also increased markedly at this time. This increase in weathering could have been caused by forest clearing by the Bantu to create arable land and to fuel their smelters, rather than climate change alone.