bluuebunny/crossref_metadata_2025 huggingface dataset:
Auricular Tissue Engineering Using Osteogenic Differentiation of Adipose Stem Cells with Small Intestine Submucosa
Authors: Lin Chih-Hsun , Yang I-Chen , Tsai Chi-Han , Fang Hsu-Wei , Ma Hsu
Published: July 2017

Background:

Ear reconstruction remains a challenge for plastic surgeons. A tissue-engineering approach could provide another route for obtaining shape maintenance in neoauricular tissue.

Methods:

The authors designed a novel tissue-engineering auricular construct by culturing human adipose stem cells, which differentiated into osteocytes but not chondrocytes, in small intestine submucosa scaffolds. The authors evaluated cell growth potential and mechanical properties. An ear-shaped construct was created in vitro and then implanted in the backs of nude mice. The histology, cellularity, neovascularization, mechanical properties, and ear shape maintenance were investigated.

Results:

In vitro, human adipose stem cells could be successfully seeded in the small intestine submucosa and differentiated toward osteogenesis. The ear-shaped human adipose stem cell/small intestine submucosa construct could maintain its shape in vivo up to 1 year. Alizarin Red S staining confirmed osteogenic differentiation. CD31 stain showed prominent angiogenesis in the human adipose stem cell/small intestine submucosa construct at 6 months and persistence up to 1 year. h-MHC stain revealed the maintenance of cellularity at 6 months and persistence up to 1 year. The mechanical properties were similar to those of native ear cartilage.

Conclusion:

The authors’ study found that the combination of human adipose stem cells and small intestine submucosa could provide a more durable ear-shaped construct in vivo. The mechanical properties, shape, and cellularity were maintained in the constructs for up to 12 months.

CLINICAL QUESTION/LEVEL OF EVIDENCE:

Therapeutic, V.
Male-to-Female Sex Reassignment Surgery Using the Combined Technique Leads to Increased Quality of Life in a Prospective Study
Authors: Papadopulos Nikolaos A. , Zavlin Dmitry , Lellé Jean-Daniel , Herschbach Peter , Henrich Gerhard , Kovacs Laszlo , Ehrenberger Benjamin , Machens Hans-Günther , Schaff Jürgen
Published: July 2017

Background:

The authors’ previous research showed that various plastic surgical procedures can increase a patient’s quality of life in its different aspects. In a prospective setting, they evaluated whether sex reassignment surgery has similar effects for male-to-female transgender patients compared to baseline data before sex reassignment surgery.

Methods:

All 39 patients who underwent their first-stage male-to-female sex reassignment surgery between October of 2012 and January of 2014 received one set of questionnaires preoperatively (time 0) and approximately 6 months after their final operation (time 1). Each set contained self-developed, indication-specific questions combined with the standardized validated Questions on Life Satisfaction, Modules (German version) questionnaire, the Freiburg Personality Inventory, the Rosenberg Self-Esteem Scale, and the Patient Health Questionnaire, which were compared to available norm data.

Results:

The mean patient age was 38.6 years. The majority of the patients were highly educated, childless, and single. Significant improvements were found in the Questions on Life Satisfaction, Modules (German version), especially for the items “partnership,” “ability to relax,” “energy,” “freedom from anxiety,” “hair,” “breast,” and “penis/vagina” (p < 0.01). Furthermore, the patients appeared more emotionally stable (p = 0.03), showed higher self-esteem (p = 0.01), and showed much lower depression/anxiety (p < 0.01).

Conclusions:

The positive study findings were confirmed with the results from prior retrospective studies. However, medical literature focuses largely on surgical and functional satisfaction and not overall quality of life. In addition, standardized questionnaires are used rarely and solely retrospectively, with the risk of recall bias. The increased quality of life of transgender women postoperatively endorses sex reassignment surgery as a valuable option for these patients.

CLINICAL QUESTON/LEVEL OF EVIDENCE:

Therapeutic, IV.
Facial Assessment and Injection Guide for Botulinum Toxin and Injectable Hyaluronic Acid Fillers: Focus on the Upper Face
Authors: de Maio Maurício , Swift Arthur , Signorini Massimo , Fagien Steven
Published: July 2017

Techniques for the administration of injectable fillers and neuromodulators for facial aesthetic rejuvenation and enhancement continue to evolve. As the number of physicians with limited experience in providing aesthetic treatments expands, the need for guidance and training from more experienced injectors has become apparent. The use of a slow, careful, and methodical injection technique is imperative in all treatment settings and for all facial areas. Constant attention to local anatomy, particularly arteries, veins, and nerve bundles, is critical for minimizing complications. This first article of a three-part series addresses techniques and recommendations for aesthetic treatment of the upper face. Traditionally, the upper face has been considered a basic area for treatment with neuromodulators but an advanced area for treatment with fillers. Injectable fillers may be used for temple volumization, eyebrow shaping, and forehead contouring. Neuromodulators are well suited for diminishing the appearance of dynamic facial lines such as forehead, glabellar, and crow’s feet lines, and eyebrow lifting and eye-aperture widening. These techniques may be used independently or together, sequentially or concurrently, to address rejuvenation of individual or multiple facial regions. Overall, this series provides a practical framework of techniques for physicians who desire to perform safe and effective aesthetic treatments using a multimodal approach.
101 Consecutive Profunda Artery Perforator Flaps in Breast Reconstruction: Lessons Learned with Our Early Experience
Authors: Haddock Nicholas T. , Gassman Andrew , Cho Min-Jeong , Teotia Sumeet S.
Published: July 2017

Background:

Free and local flaps based on the profunda artery perforators were first used for reconstruction of pressure sores, burn contractures, and extremity wounds. Recently, a revised profunda artery perforator flap was introduced for breast reconstruction. However, despite increasing reports of the use of the flap, it remains a rarely used option. The authors present their early experience with the first 101 profunda artery perforator flaps used for breast reconstruction at their institution.

Methods:

The authors conducted a retrospective review of the first 101 profunda artery perforator flaps at their institution. Patient demographics, perioperative data, and postoperative complications were recorded and analyzed.

Results:

One hundred one consecutive profunda artery perforator flaps were used to reconstruct 96 breasts in 56 patients. In 42 breasts, the flap was used in conjunction with another flap—with a deep inferior epigastric perforator flap (n = 36), a superior gluteal artery perforator flap (n = 1), or as stacked profunda artery perforator flaps (n = 5). Mean flap weight was 425 g (range, 170 to 815 g), and mean patient body mass index was 26.8 kg/m2 (range, 18.2 to 42.3 kg/m2). Complications included total flap loss (2 percent), donor-site cellulitis (5.9 percent), and donor-site wound dehiscence (10.9 percent).

Conclusions:

The profunda artery perforator flap is a safe and reliable option for breast reconstruction. Flap size is adequate for breast reconstruction in appropriately selected patients. Furthermore, it can be combined with other flaps when additional volume or skin requirements are present. Flap and donor-site complications are comparable to those of other free tissue breast reconstruction options. It is a clear second option to the deep inferior epigastric perforator flap for autologous tissue reconstruction.

CLINICAL QUESTION/LEVEL OF EVIDENCE:

Therapeutic, IV.
Rates of Primary and Secondary Syphilis Among White and Black Non-Hispanic Men Who Have Sex With Men, United States, 2014
Authors: Grey Jeremy A. , Bernstein Kyle T. , Sullivan Patrick S. , Kidd Sarah E. , Gift Thomas L. , Hall Eric W. , Hankin-Wei Abigail , Weinstock Hillard S. , Rosenberg Eli S.
Published: July 2017

Background:

Men who have sex with men (MSM) in the United States experience an approximately 100-fold greater rate of primary and secondary (P&S) syphilis diagnoses compared with men who have sex with women only. As in the general population, racial/ethnic disparities in P&S syphilis diagnosis rates may exist among MSM, but MSM-specific P&S syphilis rates by race/ethnicity are unavailable. We enhanced a published modeling approach to estimate area-level MSM populations by race/ethnicity and provide the first estimates of P&S syphilis among black and white non-Hispanic MSM.

Methods:

We used data from the American Community Survey (ACS), published findings from the National Health and Nutrition Examination Survey (NHANES), and national syphilis surveillance data to estimate state-level rates of P&S syphilis diagnoses among MSM, overall and for black and white non-Hispanic MSM. We also used variability around ACS and NHANES estimates to calculate 95% confidence intervals for each rate.

Results:

Among 11,359 cases of P&S syphilis among MSM with known race/ethnicity in 2014, 72.5% were among white (40.3%) or black (32.2%) MSM. The national rate of P&S syphilis diagnosis was 168.4/100,000 for white MSM and 583.9/100,000 for black MSM. Regional rates for black MSM ranged from 602.0/100,000 (South) to 521.5/100,000 (Midwest) and were consistently higher than those for white MSM.

Conclusions:

Although white MSM accounted for more P&S syphilis diagnoses than black MSM in 2014, when evaluating diagnoses based on rate per 100,000, black MSM had consistently and markedly higher rates than white MSM, with the highest impacted states located in the US South.
Missed Opportunities: Adapting the HIV Care Continuum to Reduce HIV-Related Deaths
Authors: Braunstein Sarah L. , Robbins Rebekkah S. , Daskalakis Demetre C.
Published: July 2017

Introduction:

With advances in HIV care, persons with HIV/AIDS (PWHA) can lead healthy lives, but avoidable HIV-related deaths continue to occur in New York City (NYC).

Methods:

We selected PWHA from our surveillance registry who died between 2007 and 2013, resided in NYC, and survived ≥15 months after diagnosis to generate an HIV Mortality Reduction Continuum of Care (HMRCC) describing predeath care patterns among PWHA. We used HIV laboratory test reports to measure care outcomes during an “intervenable period” during which deaths may have been avoided. The continuum was stratified by the underlying cause of death (HIV-related vs. other), and the HIV-related HMRCC was stratified by demographic characteristics.

Results:

Eleven thousand one hundred eighty-seven analysis-eligible PWHA died during 2007–2013. Ninety-eight percent linked to care; 80% were retained in care during the intervenable period; 66% were prescribed antiretroviral therapy; 47% had viral load ≤1500 copies/mL; and 40% achieved viral suppression (VS). Half (47%) of the deaths were HIV-related. Retention was higher among HIV-related cause of death (83% vs. 78%) but VS was lower (34% vs. 46%). The HIV-related HMRCC revealed disparities in VS. Despite comparable retention rates, whites had the highest VS (42%, vs. 32% blacks and 33% Latinos/Hispanics). In addition, retention and VS increased with increasing age. People with a history of injection drug use had relatively high rates of retention (88%) and VS (37%).

Discussion:

The HMRCC is a novel framework for evaluating predeath care patterns among PWHA and identifying opportunities to reduce preventable deaths. In NYC, reducing mortality will require increasing VS among those already in care, particularly for blacks and Latinos/Hispanics.
P53 toxicity is a hurdle to CRISPR/CAS9 screening and engineering in human pluripotent stem cells
Authors: Ihry Robert J. , Worringer Kathleen A. , Salick Max R. , Frias Elizabeth , Ho Daniel , Theriault Kraig , Kommineni Sravya , Chen Julie , Sondey Marie , Ye Chaoyang , Randhawa Ranjit , Kulkarni Tripti , Yang Zinger , McAllister Gregory , Russ Carsten , Reece-Hoyes John , Forrester William , Hoffman Gregory R. , Dolmetsch Ricardo , Kaykas Ajamete
Published: July 2017

CRISPR/Cas9 has revolutionized our ability to engineer genomes and to conduct genome-wide screens in human cells. While some cell types are easily modified with Cas9, human pluripotent stem cells (hPSCs) poorly tolerate Cas9 and are difficult to engineer. Using a stable Cas9 cell line or transient delivery of ribonucleoproteins (RNPs) we achieved an average insertion or deletion efficiency greater than 80%. This high efficiency made it apparent that double strand breaks (DSBs) induced by Cas9 are toxic and kill most treated hPSCs. Cas9 toxicity creates an obstacle to the high-throughput use CRISPR/Cas9 for genome-engineering and screening in hPSCs. We demonstrated the toxic response istp53-dependent and the toxic effect oftp53severely reduces the efficiency of precise genome-engineering in hPSCs. Our results highlight that CRISPR-based therapies derived from hPSCs should proceed with caution. Following engineering, it is critical to monitor fortp53function, especially in hPSCs which spontaneously acquiretp53mutations.
A GAL80 collection to inhibit GAL4 transgenes inDrosophilaolfactory sensory neurons
Authors: Eliason Jessica , Afify Ali , Potter Christopher , Matsumura Ichiro
Published: July 2017

Fruit flies recognize hundreds of ecologically relevant odors and respond appropriately to them. The complexity, redundancy and interconnectedness of the olfactory machinery complicate efforts to pinpoint the functional contributions of any component neuron or receptor to behavior. Some contributions can only be elucidated in flies that carry multiple mutations and transgenes, but the production of such flies is currently labor-intensive and time-consuming. Here, we describe a set of transgenic flies that express theSaccharomyces cerevisiaeGAL80 in specific olfactory sensory neurons (OrX-GAL80s). The GAL80s effectively and specifically subtract the activities of GAL4-driven transgenes that impart anatomical and physiological phenotypes.OrX-GAL80scan allow researchers to efficiently activate only one or a few types of functional neurons in an otherwise nonfunctional olfactory background. Such experiments will improve our understanding of the mechanistic connections between odorant inputs and behavioral outputs at the resolution of only a few functional neurons.
Mathematical modeling of tumor-tumor distant interactions supports a systemic control of tumor growth
Authors: Benzekry Sebastien , Lamont Clare , Barbolosi Dominique , Hlatky Lynn , Hahnfeldt Philip
Published: July 2017

Interactions between different tumors within the same organism have major clinical implications, especially in the context of surgery and metastatic disease. Three main explanatory theories (competition, angiogenesis inhibition and proliferation inhibition) have been proposed but precise determinants of the phenomenon remain poorly understood. Here we formalized these theories into mathematical models and performed biological experiments to test them with empirical data. In syngeneic mice bearing two simultaneously implanted tumors, growth of only one of the tumors was significantly suppressed (61% size reduction at day 15, p<0.05). The competition model had to be rejected while the angiogenesis inhibition and proliferation inhibition models were able to describe the data. Additional models including a theory based on distant cytotoxic log-kill effects were unable to fit the data. The proliferation inhibition model was identifiable and minimal (4 parameters), and its descriptive power was validated against the data, including consistency in predictions of single tumor growth when no secondary tumor was present. This theory may also shed new light on single cancer growth insofar as it offers a biologically translatable picture of how local and global action may combine to control local tumor growth, and in particular, the role of tumor-tumor inhibition. This model offers a depiction of concomitant resistance that provides an improved theoretical basis for tumor growth control and may also find utility in therapeutic planning to avoid post-surgery metastatic acceleration.
Trade-off and flexibility in the dynamic regulation of the cullin-RING ubiquitin ligase repertoire
Authors: Straube Ronny , Flockerzi Dietrich , Wolf Dieter A.
Published: July 2017

Cullin-RING ubiquitin ligases (CRLs) catalyze the ubiquitylation of substrates many of which are degraded by the 26S proteasome. Their modular architecture enables recognition of numerous substrates via exchangeable substrate receptors that competitively bind to a cullin scaffold with high affinity. Due to the plasticity of these interactions there is ongoing uncertainty how cells maintain a flexible CRL repertoire in view of changing substrate loads. Based on a series of invivoandin vitrostudies, different groups proposed that the exchange of substrate receptors is mediated by a protein exchange factor named cullin-associated and neddylation-dissociated 1 (Cand1). Here, we have performed quantitative mathematical modeling to support this hypothesis. To this end we first show that the exchange activity of Cand1 necessarily leads to a trade-off between high ligase activity and fast receptor exchange. Supported by previousin vivostudies we argue that this trade-off yields an optimal Cand1 concentration where the time scale for substrate degradation becomes minimal. In a second step we show through simulations that (i) substrates bias the CRL repertoire leading to preferential assembly of ligases for which substrates are available and (ii) differences in binding affinities create a temporal hierarchy for the degradation of substrates. Together, our results provide general constraints for the operating regimes of molecular exchange systems and suggest that Cand1 endows the CRL network with the properties of an “on demand” system allowing cells to dynamically adjust their CRL repertoire to fluctuating substrate abundances.

Author summary

Cullin-RING ubiquitin ligases (CRLs) are multisubunit protein complexes where exchangeable substrate receptors (SRs) assemble on a cullin scaffold to mediate ubiquitylation and subsequent degradation of a large variety of substrates. In humans there are hundreds of different CRLs having potentially thousands of substrates. Due to the high affinity of cullin-SR interactions, it has long been a mystery how cells would maintain flexibility to sample the entire SR repertoire in order to match fluctuating substrate loads. Recent experiments indicate that the exchange of different SRs is mediated by a novel protein exchange factor (Cand1). However, the proposed biochemical function of Cand1 as a promoter of CRL activity remained difficult to reconcile with previous reports of Cand1 acting as an inhibitor of CRL activityin vitro. Here we show that these two findings are not contradictory, but that the exchange activity of Cand1 necessarily leads to a trade-off between high ligase activity and fast receptor exchange which leads us to predict an optimal Cand1 concentration and a temporal hierarchy for substrate degradation. Our results support the view that Cand1 endows the CRL network with the flexibility of an “on demand” system where relative CRL abundances are dictated by substrate availability.
A compartmentalized, self-extinguishing signaling network mediates crossover control in meiosis
Authors: Zhang Liangyu , Köhler Simone , Rillo-Bohn Regina , Dernburg Abby F.
Published: July 2017

Meiotic recombination between homologous chromosomes is tightly regulated to ensure proper chromosome segregation. Each chromosome pair typically undergoes at least one crossover event (crossover assurance) but these exchanges are also strictly limited in number and widely spaced along chromosomes (crossover interference). This has implied the existence of chromosome-wide signals that regulate crossovers, but their molecular basis remains mysterious. Here we characterize a family of four related RING finger proteins inC. elegans. These proteins are recruited to the synaptonemal complex between paired homologs, where they act as two heterodimeric complexes, likely as E3 ubiquitin ligases. Genetic and cytological analysis reveals that they act with additional components to create a self-extinguishing circuit that controls crossover designation and maturation. These proteins also act at the top of a hierarchical chromosome remodeling process that enables crossovers to direct stepwise segregation. Work in diverse phyla indicates that related mechanisms mediate crossover control across eukaryotes.
Avoidance of toxic misfolding and protein stability do not explain the sequence constraints of highly expressed proteins
Authors: Plata Germán , Vitkup Dennis
Published: July 2017

The avoidance of cytotoxic effects associated with protein misfolding has been proposed as a dominant constraint on the sequence evolution and molecular clock of highly expressed proteins. Recently, Leuenbergeret al.developed an elegant experimental approach to measure protein thermal stability at the proteome scale. The collected data allow us to rigorously test the predictions of the misfolding avoidance hypothesis that highly expressed proteins have evolved to be more stable, and that maintaining thermodynamic stability significantly constrains their evolution. Notably, careful re-analysis of the Leuenbergeret al.data across four different organisms reveals no substantial correlation between protein stability and protein abundance. Therefore, the key predictions of the misfolding toxicity and related hypotheses are not supported by available empirical data. The data also suggest that, regardless of protein expression, protein stability does not substantially affect the protein molecular clock across organisms.
Polar-angle representation of saccadic eye movements in human superior colliculus
Authors: Savjani Ricky R , Halfen Elizabeth , Kim Jung Hwan , Ress David
Published: July 2017

The superior colliculus (SC) is a layered midbrain structure involved in directing eye movements and coordinating visual attention. Electrical stimulation and neuronal recordings in the intermediate layers of monkey SC have shown a retinotopic organization for the mediation of saccadic eye-movements. However, in human SC the topography of saccades is unknown. Here, a novel experimental paradigm and highresolution (1.2-mm) functional magnetic resonance imaging methods were used to measure activity evoked by saccadic eye movements within SC. Results provide three critical observations about the topography of the human SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical eye-movement mechanisms.

Highlights

High-resolution functional MRI enabled imaging from intermediate layers of human SC

Saccades along superior-inferior visual field are mapped across medial-lateral SC

Saccadic eye movement maps lie deeper in SC and are in alignment with retinotopy

eTOC Blurb

Savjani et al. found the polar angle representation of saccadic eye movements in human SC. The topography is similar in monkey SC, is in register with the retinotopic organization evoked by visual stimulation, but lies within deeper layers. These methods enable investigation of human subcortical eye-movement organization and visual function.
Characterization ofAIIIBVsuperlattices by means of synchrotron diffraction topography and high-resolution X-ray diffraction
Authors: Wierzchowski Wojciech , Wieteska Krzysztof , Gaca Jarosław , Wójcik Marek , Możdżonek Małgorzata , Strupiński Włodzimierz , Wesołowski Marek , Paulmann Carsten
Published: July 2017

New possibilities are presented for the characterization ofAIIIBVmixed superlattice compounds by the complementary use of synchrotron diffraction topography and rocking curves. In particular, using a synchrotron white beam and the section diffraction pattern of a 5 µm slit taken at a 10 cm film-to-crystal distance, it was possible to reproduce a set of stripes corresponding to interference fringes. These are analogous to the interference maxima revealed in high-resolution rocking curves, but are created by the changes in orientation of the planes inclined to the surface which are induced by unrelaxed strain. The section diffraction topographic method enabled examination of the sample homogeneity along the narrow intersecting beam. This was important in the case of the present sample containing a twin lamella in the InP substrate wafer. Both the section and projection Bragg case topographic methods enabled the crystallographic identification of the twin lamella. Another characteristic feature indicated in the section topography was the bending of the stripes corresponding to the superlattice peaks close to the boundaries of the twin lamella. The most probable interpretation of this phenomenon is an increase in the thickness of the deposited layers close to the lamella, together with possible changes in the chemical composition, leading to a decrease in the mean lattice parameter in the superlattice.
The impact of flipped classroom in MBA’s evaluation
Authors: Scafuto Isabel , Serra Fernando , Mangini Eduardo , Maccari Emerson Antonio , Ruas Roberto
Published: July 2017

Purpose

The purpose of this paper is to evaluate the perceived quality of the service environment, regarding the use of the flipped classroom, through a survey of MBA students.

Design/methodology/approach

Four hypotheses were developed from the literature in marketing and quality services in higher education. The hypotheses were tested using linear regressions. The data were collected using a structured questionnaire. The sample had 981 effective responses.

Findings

The results of the statistical analysis show that the evaluation of the perceived quality of the educator and course are positively affected by the use of the flipped classroom.

Research limitations/implications

Only one higher education organisation was studied. The variables analysed have no mediation and moderation, which is a suggestion for future studies.

Originality/value

This paper contributes to studies of higher education services and quality, as it shows the influence of the process on the educator. In higher education, the educator is usually considered independent, having a strong influence on perceived quality. The study contributes to the theme by showing the flipped classroom as an effective teaching strategy that requires further empirical study.
The soot handling ability requirements and how to solve soot related viscosity increases of heavy duty diesel engine oil
Authors: Tang Zhongping , Feng Zhengwen , Jin Peng , Fu Xisheng , Chen Hua
Published: July 2017

Purpose

The purpose of this paper is to identify the feature of soot in diesel engine oil and provide a method to stably disperse these soots using effect additives which is benefical for lubricants to pass related engine tests.

Design/methodology/approach

This paper designed experiments to investigate the dispersant type, treat level and different dispersant interactions which influence on lubricant soot-related viscosity increase. The research work developed an effective dispersant package which can well solve the soot-related viscosity increase, allowing pass Mack T-11 and Mack T-8 engine tests and demonstrated the helpfulness of using a quickly screening method developed by a steel piston diesel engine CA 6DL2-35.

Findings

The effect of dispersant treat level on the viscosity increase of the oil samples was negligible. Dispersant booster can effectively improve the soot handling ability of heavy-duty diesel engine oils (HDDEO), and the appropriate treat level of dispersant booster can help HDDEO pass Mack T-8 and Mack T-11 engine tests.

Practical implications

The test results are useful for formulators to select the appropriate dispersants or dispersant booster to develop the HDDEO packages which can meet the modern diesel engine lubrication requirements.

Originality/value

Most previous studies in this field were carried out on soot formation mechanism and soot-related wear rather than how to solve the soot-related viscosity increasing of HDDEO. This paper describes the soot dispersing requirements of different HDDEO specifications and developed an effective dispersant package which can well deal with Mack T-11 and Mack T-8E standard engine tests soot handling ability requirements.
Preparation and performance evaluation of mPAO8 using olefin from coal as raw material
Authors: Ma Yuefeng , Xu Jian , Zeng Xiangqiong , Jiang Haizhen , Li Jiusheng
Published: July 2017

Purpose

The purpose of this paper is to prepare metallocene polyalphaolefin 8 (mPAO8) by the oligomerization of olefin from coal with metallocene catalyst system and compare it with commercially available polyalphaolefin 8 (PAO8) from Chevron.

Design/methodology/approach

Molecular structures, component and mass were determined by nuclear magnetic resonance spectroscopy, gas chromatography and gel permeation chromatography, respectively. The physico-chemical properties, including Noack volatility, viscosity index and elemental analyses, were studied. The oxidative stability was evaluated by pressurized differential scanning calorimetry, whereas the thermal stability was studied by thermo-gravimetric analysis.

Findings

The produced mPAO8 consisted of a large part of tetramer, pentamer and a small part of trimer and hexamer. Additive T501 significantly improved the oxidation stability of PAO8 from Chevron and the synthesized mPAO8. Both samples had similar properties, such as oxidative stability, additive response, pour point and Noack volatility loss. But mPAO8 possessed a higher thermal stability, better viscosity index and flash point than PAO8. Therefore, the mPAO8 prepared by the oligomerization of olefin from coal could be used as base oil for lubricant development.

Originality/value

The mPAO8 base oil was successfully prepared by successive carbon numbers and shows similar properties with commercially available PAO8 products from Chevron. The findings can cover the shortage of the synthesis lubricants market in China.
Experimental and numerical investigation on single dent with marginal bump in EHL point contacts
Authors: Wang Xue-feng , Hu R.F. , Shang Weiyan , Zhao Fuzhou
Published: July 2017

Purpose

The dent is one of typical surface defects on the surfaces of the machine elements and it is not in fact inerratic. This work aims to investigate the effect of a single dent with a marginal bump on the film shape in elastohydrodynamic lubrication (EHL) point contacts.

Design/methodology/approach

The experimental investigations of a single dent with marginal bump were carried out using multi-beam interferometry in EHL point contacts. In the meantime, its numerical simulation was also finished using multi-level method and multilevel multi-integration method. The effects of the entrainment velocity and the applied load as well as the slide-roll ratio on the film were chiefly discussed. Meanwhile, the comparison of films between smooth and dented surfaces was conducted under simple sliding conditions.

Findings

Under pure sliding conditions, the minimum film thickness presents itself near the marginal bump at lower entrainment velocity. The inlet dimple before the marginal bump is subjected to the operating conditions. Under pure rolling conditions, the shape of the dent is almost unchanged when it is passing through the contact region at lower entrainment velocity. The dent depth hardly depends on the applied load under static conditions. However, larger load enhances the inlet dimple and the elastic deformation of the dent with the marginal bump under pure sliding conditions.

Originality/value

This work is helpful to understanding the effect of the marginal bump before the single dent on point contact EHL films.
Rheological behaviour of lubrication oils used in two-stroke marine engines
Authors: Ravendran Rathesan , Jensen Peter , de Claville Christiansen Jesper , Endelt Benny , Appel Jensen Erik
Published: July 2017

Purpose

The purpose of this study is to investigate the rheological behaviour of commercial lubrication oils used for cylinder lubrication in two-stroke marine diesel engines. Furthermore, it is of interest to investigate whether the viscosity of lubrication oils is affected by different levels of alkalinity.

Design/methodology/approach

Viscosity measurements are performed using both rotational and capillary rheometry. It was possible to measure oil viscosity in the shear rate from 0.1 to 3,000 s−1 using rotational rheometry, whereas capillary rheometry allowed measurements in higher shear rates from 5 × 105 to 1.3 × 106 s−1 at 50°C.

Findings

The viscosity measurements show that the studied lubrication oils behave as a Newtonian fluid and that the viscosities are insensitive to the level of alkalinity. Furthermore, the viscosity/temperature dependency for the lubrication oils was found to fit the Arrhenius model.

Originality/value

This study presents useful information about the rheological behaviour of lubrication oils, more precisely how the oil properties are affected by shear rate, temperature and level of alkalinity. The value of this research is considered to be important for designing two-stroke diesel engines and cylinder lubrication systems.
Behavior evaluation and effects of different lubricants in ECAP process
Authors: Hasani Najafabadi Seyed Husein , Lotfi Neyestanak Ali Akbar , Daneshmand Saeed
Published: July 2017

Purpose

The purpose of equal channel angular pressing (ECAP) is producing ultra-fine grain materials. In practical applications, it is important to understand and predict effect of different process parameters on deformed parts. One of the most important process parameters is friction coefficient. Behavior evaluation of different lubricants in the ECAP process is the aim of this research.

Design/methodology/approach

The present study concerns the experimental measurements of the effective strain by means of gridded parts for three different lubricants, graphite, molybdenum disulfide and zinc stearate, to evaluate friction coefficient in ECAP process. Mesh size was 2 × 2 mm2 and embedded in parts made of AL2024; process was done in ambient temperature, and parts were in annealed situation. After the process, strain measured by optical and analytical methods for evaluation of lubricants’ behavior with different friction coefficients.

Findings

This study shows that zinc stearate has better effects rather than other lubricants in ECAP process and ECAPed parts.

Originality/value

The fatal challenge for researchers and industrial applications of ECAP process is lubrication. This research is a guide for scientists and engineers (in the future applications) to reduce and control bad frictional effects, produce better parts (more strain homogenous parts), prevent die failures and decrease press tonnage in ECAP process.
The effect of dimple size on the tribological performances of a laser surface textured palm kernel activated carbon-epoxy composite
Authors: Mohmad Martini , Abdollah Mohd Fadzli Bin , Tamaldin Noreffendy , Amiruddin Hilmi
Published: July 2017

Purpose

The purpose of this study is to investigate the effect of dimple size on the tribological performances of laser surface-textured palm kernel-activated carbon-epoxy (PKAC-E) composite.

Design/methodology/approach

A PKAC-E disc 74 mm in diameter was fabricated using the hot compression moulding technique. Five different types of surface contacts were prepared using a CO2 laser surface-texturing machine: a non-textured surface, and surfaces with dimples between 500 and 1,200 μm in diameter. The area density, contact ratio and depth were kept constant. A sliding test was carried out using a ball-on-disc tribometer under boundary lubricated conditions with constant sliding speed, sliding distance and applied load.

Findings

In general, the results showed that the friction coefficient decreased with an increasing dimple diameter of surface-textured PKAC-E composite. However, the appropriate dimple diameter for maintaining low friction coefficient is proposed in the range of 800 to 1,000 μm.

Originality/value

This is the first study, to the authors’ knowledge, to investigate the effects of dimple size, which is larger than 500 μm, on the tribological performances of laser surface-textured PKAC-E composite.
Hydrodynamic journal bearing lubricated with a ferrofluid
Authors: Patel Nimeshchandra S. , Vakharia Dipak , Deheri Gunamani
Published: July 2017

Purpose

This paper aims to investigate the performance of a ferrofluid-based hydrodynamic journal bearing system.

Design/methodology/approach

This paper presents a new design of ferrofluid-based hydrodynamic journal bearing. An experimental set-up consisting of a magnetic shaft along with a brass bearing was modified and developed. A permanent magnet was used to make the selected shaft material magnetic. The load and speed were varied to conduct the analyses for different test conditions.

Findings

The paper provides information about a design of ferrofluid-based journal bearing and its improved performances. For moderate to higher loads at different shaft speeds, it was found that because of the magnetization effect, the maximum film pressure in case of a ferrofluid lubricant increased up to approximately 60 per cent, compared with that of the conventional lubricant-based journal bearing system. Besides, the temperature rise was found smaller for ferrofluid lubricants, thus making the system cooler while running.

Originality/value

This paper offers a new design of magnetic bearing system for the experimental analysis by utilizing a magnetic shaft with a non-magnetic bearing. The present ferrofluid-based bearing design is less complicated from manufacturing point of view.
Quantitative analysis of wear particles generated by cavitation erosion in glycerol-water mixtures
Authors: Saleh Bahaa , Abouel-Kasem A. , Ahmed Shemy
Published: July 2017

Purpose

This paper aimed to analyze removed particles from stationary specimen-aluminum (Al-99.92) produced by vibratory cavitation erosion tests in distilled water and glycerol-water mixtures.

Design/methodology/approach

The particle morphology which include particle surface topography, size distribution, particle size parameters and particle shape parameters were examined for distilled water and glycerol-water mixtures having different viscosities.

Findings

The results showed that the variation of size parameters with viscosity was very similar to the variation of weight loss with viscosity. Both the size parameters and weight losses show a monotonic decrease in going from distilled water to glycerol-water mixtures having viscosity about 10.1 cSt, beyond which the change is very small. On the other hand, the shape parameters were much less sensitive to distinguish between the particles produced in water and glycerol-water mixtures. The mechanism of cavitation erosion is investigated in detail through observations of the removed particles. The particle surfaces topography demonstrated that the mechanism in water and glycerol-water mixtures was fatigue failure.

Originality/value

Cavitation often occurs in almost all machines that handle liquids, especially at high speeds, leading to irreparable damage of the components of these machines. Elucidation of such complex phenomenon demands full characterization of the erosion mechanism and controlling parameters inherent to it, so that cavitation erosion can be prevented or at least be reduced through adequate information and collection of relevant data under different operating conditions. Very few studies have been made to approach the viscosity effect upon cavitation erosion from the particle analysis standpoint. The aim of the present work is to identify the effect of liquid viscosity on the size, shape characteristics of the erosion particles and their morphological features. The prevailed mechanisms of wear and particle generation have been proposed based on the acquired information from particle analysis.
Differences between perceived usefulness of social media and institutional channels by undergraduate students
Authors: Sumida Garcia Leandro , Costa Silva Camila Mariane
Published: July 2017

Purpose

This research aims to compare the preference of social media sites and institutional communication channels of a higher education institution by confronting elements that form perceived usefulness and user satisfaction with the system. Social media technologies are a part of the routine of the modern society in many diverse ways, including the support and even substitution of software designed specifically for knowledge acquisition and sharing. If students do not see value in the use of virtual learning environments and learning platforms, such tools might be prone to obsolescence as well.

Design/methodology/approach

The study was applied in a Brazilian public university located in a major city near São Paulo. The paper shows the results of the analysis of a survey with 108 answers, testing a model based on the information system success and on the technology acceptance model. The perceived usefulness of information technology is also subject to test through a Studentt-test.

Findings

The paper shows that students perceive more value when using social media technologies to perform academic activities than in information systems provided by the university, mainly owing to the ease of use of the former. Service quality does not present a strong role as an antecedent variable in any case.

Practical implications

Students do not expect or do not see value in technical support during their general experience or usefulness for any of the analysed technologies. Thus, higher education institutions should focus their initiatives in providing availability, information quality and usability for institutional channels or, if they choose to do so, social media sites as well.

Originality/value

This study contributes to educational institutions by attaining better use of available IT tools for academic purposes. Previous studies looked for monitored or institutionalized use of social media tools in an educational context, but there was no in-depth analysis of spontaneous use by students to perform academic tasks.
Refactoring a CS0 course for engineering students to use active learning
Authors: Lokkila Erno , Kaila Erkki , Lindén Rolf , Laakso Mikko-Jussi , Sutinen Erkki
Published: July 2017

Purpose

The purpose of this paper was to determine whether applying e-learning material to a course leads to consistently improved student performance.

Design/methodology/approach

This paper analyzes grade data from seven instances of the course. The first three instances were performed traditionally. After an intervention, in the form of applying e-learning methodologies, more data were collected from four course instances. These data are then analyzed and compared.

Findings

The main finding of this paper is that the application of e-learning improved the overall grades and decreased the fail rates of students who took this course.

Originality/value

This paper demonstrates the efficacy of applying e-learning methods to an undergraduate course. This paper is of special interest to educators, who wish to improve and enhance their teaching.
An investigation into the Community of Inquiry model in the Malaysian ESL learners’ context
Authors: Annamalai Nagaletchimee
Published: July 2017

Purpose

This study aims to explore how the Community of Inquiry (CoI) model (2000) is used to categorize students’ and teachers’ interactions in an asynchronous discussion and how these interactions are able to help students add quality to their narrative writing.

Design/methodology/approach

The interactions were categorized based on teaching, social and cognitive presences suggested by the CoI model. Data collection included online archives and students’ narrative essays. Content analysis was performed based on the presences suggested by the CoI model. Scores for the narrative essays were based on Tribble’s (1996) assessment scale.

Findings

The findings indicated that the interactions were significantly related to the cognitive, teaching and social presences. However, the cognitive presence indicated a distinctive pattern. As this was a qualitative study, there were emerging themes. The study found that critical thinking was minimal, as the writing task was related to creative thinking.

Research limitations/implications

It is suggested that writing in the online environment should also consider different types of writing.

Originality/value

The emerging themes can be used to enhance and complement the CoI model when used in the Malaysian setting.
The effect of family business professionalization on dividend payout
Authors: Michiels Anneleen , Uhlaner Lorraine , Dekker Julie
Published: July 2017

Purpose

The topic of dividend policies of private family-controlled firms has aroused the interest of corporate finance and governance scholars and practitioners alike. However, a lot of questions concerning the dividends in privately held family firms remain unanswered. The purpose of this paper is to examine whether a private family firm’s dividend payout is influenced by its degree of professionalization.

Design/methodology/approach

The hypotheses are tested on a sample of 492 small to medium-sized Belgian family-controlled businesses with Tobit regression models.

Findings

The results show that professionalized family-controlled firms pay higher dividends to their shareholders than do less-professionalized firms. In particular, the use of financial control systems, non-family involvement in governance systems, and the use of human resource control systems have a positive significant impact on the average level of dividend payout.

Practical implications

This study may be of interest to family business consultants and (potential) investors, as the results contradict the assumption that family businesses (especially those privately held) will always have a no or low dividend policy.

Originality/value

Investigating dividend payout in the context of other components than family ownership (in this case, professionalization) can broaden our understanding of dividend payout.