bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical realism: what you should know and how to apply it
Authors: Lawani Ama
Published: December 2020

Purpose

The purpose of this paper is to discuss the critical realism (CR) philosophical viewpoint and how it can be applied in qualitative research. CR is a relatively new and viable philosophical paradigm proposed as an alternative to the more predominant paradigms of positivism, interpretivism and pragmatism. This paper reviews the concept, its benefits and limitation. It goes further to provide an example of how CR is used as a philosophical and methodological framework with the systems thinking theory to applied qualitative research.

Design/methodology/approach

A study of project management challenges in a Nigerian government organisation is used to demonstrate a qualitative research approach, which includes a coding process and data analysis that is consistent with CR ontology and epistemology.

Findings

CR focuses primarily on closed systems. However, a more accurate explanation of reality is obtained in addition to the identification of contextual causal mechanisms in the context of study when a general systems theory is applied.

Research limitations/implications

The knowledge about the nature of relationships obtained in the context of study may not necessarily be replicated in another context. However, this paper elucidates a CR process that is generalisable by demonstrating how a theory is applied in a different context.

Originality/value

The paper demonstrates how systems theory is used to understand interactions in a CR paradigm. It engages with CR approach critically and illustrates a clear example of how CR can be applied in social research.
Cancer in pregnancy increases the risk of venous thromboembolism: a nationwide cohort study
Authors: Greiber IK , Mikkelsen AP , Karlsen MA , Storgaard L , Viuff JH , Mellemkjær L , Hjortshøj CS , Lidegaard Ø
Published: December 2020

Objective

To investigate if cancer in pregnancy causes a higher risk of venous thromboembolism (VTE) during pregnancy and postpartum compared with pregnant women without cancer.

Design

A historical prospective cohort study using data from nationwide registries.

Setting and population

We assessed all pregnancies in Denmark between 1 January 1977 and 31 December 2017.

Methods

We linked information concerning cancer diagnosis, pregnancy and VTE diagnosis and potential confounders. Event rates of VTE for women with pre‐pregnancy cancer, cancer in pregnancy and without cancer were calculated per 10 000 pregnancies and compared using logistic regression analysis.

Main outcome measures

Occurrence of VTE during pregnancy or the postpartum period.

Results

A total of 3 581 214 pregnancies were included in the study and we found 1330 women with cancer in pregnancy. In pregnant women with cancer, the event rate of VTE was 75.2 per 10 000 pregnancies compared with 10.7 per 10 000 pregnancies in the no cancer group. The findings correspond to an increased adjusted odds ratio of 6.50 (95% CI3.5–12.1) in the cancer in pregnancy group in comparison with the no cancer group.

Conclusions

Women with cancer in pregnancy have a markedly higher risk of pregnancy‐associated VTE compared with women without cancer. In pregnancy‐related VTE risk assessment, the presence of cancer alone may be sufficient to indicate thromboprophylaxis.

Tweetable abstract

Cancer in pregnancy increases the risk of VTE during pregnancy and the postpartum period.
Camera trap detection of mycophagy among co‐occurring vertebrates
Authors: Elliott Todd F. , Vernes Karl
Published: December 2020

Thirty camera traps were deployed for a total of 4179 trap‐nights between January and June 2020 as part of a project assessing post‐fire recovery of pademelons (Thylogale spp.) in northern New South Wales. By chance, one camera documented a site that was highly productive for the ectomycorrhizal fungal genus Amanita. This camera provided a rare opportunity to document a diversity of co‐habitating vertebrates that utilise these ectomycorrhizal fungi for food and in turn perform an important ecosystem function through the dispersal of their spores. Our camera recorded eleven vertebrate species; of these, we captured photographic evidence of Australian brush‐turkeys (Alectura lathami), a parma wallaby (Notamacropus parma), long‐nosed bandicoots (Perameles nasuta), red‐legged pademelons (Thylogale stigmatica) and red‐necked pademelons (T. thetis) feeding on fungal fruiting bodies.
Toll‐like receptor 10 rs10004195 variation may be protective against Bacillus Calmette‐Guérin osteitis after newborn vaccination
Authors: Korppi Matti , Teräsjärvi Johanna , Lauhkonen Eero , Huhtala Heini , Nuolivirta Kirsi , He Qiushui
Published: December 2020

Aim

Toll‐like receptor 1 (TLR1), TLR2, TLR6 and TLR10 form the TLR2 subfamily. In our previous controlled studies in 132 subjects with osteitis after newborn Bacillus Calmette‐Guérin (BCG) vaccination, TLR1, TLR2 and TLR6 variations were associated with the risk of BCG osteitis. Now, we evaluated the role of ten single nucleotide polymorphisms (SNP) of the TLR10 gene in this cohort.

Methods

Five synonymous TLR10 SNPs (rs10004195, rs10856837, rs10856838, rs1109695 and rs11466652), and five missense TLR10 SNPs (rs11096955, rs11096957, rs11466649, rs11466653 and rs11466658) were determined by polymerase chain reaction (PCR)‐based sequencing in 132 former BCG osteitis patients.

Results

TLR10 rs10004195 polymorphism was associated with the risk of BCG osteitis, compared to Finnish population controls. The variant genotype (AT/AA) was present in 13.6% of cases versus 26.2% of controls (p = 0.024). Correspondingly, the minor allele frequency (MAF) was lower (0.075) in cases than in controls (0.152; p = 0.009). There were no significant differences in the genotypes of the other nine studied TLR10 SNPs or in the corresponding MAFs between cases and controls.

Conclusion

Among ten studied TLR10 gene polymorphisms, the variation only in the TLR10 rs10004195 was associated with the BCG osteitis risk after newborn BCG vaccination.
Sex‐dependent effects of endocannabinoid modulation of conditioned fear extinction in rats
Authors: Morena Maria , Nastase Andrei S. , Santori Alessia , Cravatt Benjamin F. , Shansky Rebecca M. , Hill Matthew N.
Published: December 2020

Background and Purpose

Women are twice as likely as men to develop post‐traumatic stress disorder (PTSD) making the search for biological mechanisms underlying these gender disparities especially crucial. One of the hallmark symptoms of PTSD is an alteration in the ability to extinguish fear responses to trauma‐associated cues. In male rodents, the endocannabinoid system can modulate fear extinction and has been suggested as a therapeutic target for PTSD. However, whether and how the endocannabinoid system may modulate fear expression and extinction in females remains unknown.

Experimental Approach

To answer this question, we pharmacologically manipulated endocannabinoid signalling in male and female rats prior to extinction of auditory conditioned fear and measured both passive (freezing) and active (darting) conditioned responses.

Key Results

Surprisingly, we found that acute systemic inhibition of the endocannabinoid anandamide (AEA) or 2‐arachidonoyl glycerol (2‐AG) hydrolysis did not significantly alter fear expression or extinction in males. However, the same manipulations in females produced diverging effects. Increased AEA signalling at vanilloid TRPV1 receptors impaired fear memory extinction. In contrast, inhibition of 2‐AG hydrolysis promoted active over passive fear responses acutely via activation of cannabinoid1 (CB1) receptors. Measurement of AEA and 2‐AG levels after extinction training revealed sex‐ and brain region‐specific changes.

Conclusion and Implications

We provide the first evidence that AEA and 2‐AG signalling affect fear expression and extinction in females in opposite directions. These findings are relevant to future research on sex differences in mechanisms of fear extinction and may help develop sex‐specific therapeutics to treat trauma‐related disorders.
Suing Canadian governments: Core public policy and operational decisions
Authors: Marland Alex , Osborne Philip , Levesque Mario
Published: December 2020

Challenges in distinguishing between core policy and operational decisions in the public policy process have spawned a legal grey area in Canadian public administration. Governments are immune from civil liability for policy decisions made by the cabinet yet they remain exposed to liability for operational decisions by public servants. We seek to raise awareness of this nexus within the Canadian public administration community by drawing on key interviews with lawyers, former attorneys general, a former premier, a former judge and a legal scholar. We explain that demarcating policy from operational decisions relies on written documentation that is difficult to locate and may not exist. Clarity is desired, but Canadian courts are reluctant to overrule a public authority’s opinion, which is based on socio‐economic and political considerations. We conclude with observations for public administrators.
Tension in the Emergency Department? The Impact of Flow Stage Times on Managing Patient‐Reported Experiences and Financial Productivity
Authors: Smith Jeffery S. , Shockley Jeff , Anderson Sidney , Liu Xiaojin (Jim)
Published: December 2020

Healthcare providers are expected to compete across multiple performance dimensions, thereby managing both their financial productivity and the patients’ “in process” experiences. This fact creates tensions in some healthcare settings, as providers need to provide high‐quality care and positive customer experiences while still being financially responsible. Increasingly, these goals create pressures that require emergency departments (EDs) to generate operational efficiencies to improve how healthcare providers manage patient flow at different service stages and to deliver better care for an increasing number of patients at a more reasonable cost. From the perspective of managing patient process flow stage times, this article uses online ratings and secondary source data to examine how EDs can simultaneously improve both experiential and financial productivity performance. Our findings strongly indicate that EDs may be able to leverage the physician‐directed evaluation time stage to improve departmental efficiencies in both performance areas. However, the diminishing value of evaluation time and the time a patient spends in pre‐care for ED services are necessary contingencies to consider. Finally, to illustrate the practical relevance of these findings, we explore the perceived tradeoffs of managing the different patient flow time stages.
Normally functioning quadricuspid aortic valve mistaken for bicuspid valve in a septuagenarian
Authors: Molinary Michelle C. , Martin Amy B. , Asevedo Erin E. , McIlwain Elizabeth F. , Cospolich Brian , Kerut Edmund K.
Published: December 2020

A 70‐year‐old male underwent transthoracic (TTE) and transesophageal (TEE) echocardiography for a stroke. A bicuspid aortic valve was suspected by TTE, but TEE revealed a normally functioning quadricuspid aortic valve. A quadricuspid aortic valve may be more common than generally thought, as it may not be readily diagnosed by TTE, and may remain functionally normal.
Temporary Competitive Advantage: A State‐of‐the‐Art Literature Review and Research Directions
Authors: Dagnino Giovanni Battista , Picone Pasquale Massimo , Ferrigno Giulio
Published: December 2020

In many industries, the traditional sources of competitive advantage tend to evaporate fairly rapidly. Therefore, managers need to continually rethink and reformulate their firm strategies. Likewise, scholars have felt compelled to shift the traditional centre of attention from competitive advantage that is sustainable over time to a focus on how firms compete by achieving a series of temporary advantages. However, the proliferation of research on temporary competitive advantage, far from building a solid body of literature, has produced a series of fragmented studies. This condition calls for detecting the state of knowledge in this realm of strategic inquiry. By leveraging the present status of the literature on temporary competitive advantage, we offer a conceptual map of the current inquiry of the antecedents, management, and consequences of temporary competitive advantage. Then, we identify the key implications for strategy theory and discuss the major challenges for cultivating fertile territories in this intriguing area of research.
From Bronze Age Hillfort to Capital City New Radiocarbon Dates and the First Archaeobotanical Investigation at the Vilnius Castle Hill
Authors: Motuzaitė Matuzevičiūtė Giedrė , Rusteikytė Auksė , Minkevičius Karolis , Žėkaitė Monika , Tamulynas Linas
Published: December 2020

The ‘Castle Hill’ represents the core territory of Vilnius, around which gravitated urban development, eventually culminating in the foundation of the capital of Lithuania. However, we know very little about the earliest occupation on Castle Hill - how it developed over time, and what the activities were of the people that inhabited the site. While the study of plant remains can provide a crucial insight into human staple foods, agricultural activities and the palaeoenvironment, previous attempts of archaeobotanical investigations of such an important cultural heritage site was cut short due to the outbreak of World War II.

Here is presented the first archaeobotanical analyses from the territory of Castle Hill together with new radiocarbon dates stretching from the 8thcentury BC until the 14thcentury AD. The primary archaeobotanical analyses in combination with published datasets from adjacent regions around Castle Hill show that the diversification of crops and the introduction of various crop rotation practises during the 8-13thcenturies AD. Here, for the first time, attention is drawn to the agricultural strategies in medieval Vilnius that likely played a pivotal role in the formation and development of the city.
Participation in employment and day care for adults with intellectual disabilities: Equal access for all?
Authors: Engeland Jeanette , Strand Bjørn Heine , Innstrand Siw Tone , Langballe Ellen Melbye
Published: December 2020

Background

The employment rate for people with intellectual disabilities is low. This study aims to increase the knowledge about the association between age, gender, diagnosis, functional level, educational level, and daily activities for adults with intellectual disabilities.

Method

A multinomial logistic analysis was applied to registry data on 12,735 adults with intellectual disabilities from the Norwegian Information System for the Nursing and Care Sector (IPLOS) and Statistics Norway (SSB).

Results

Higher likelihood of employment and day care participation were associated with younger age but differed between genders and diagnoses. High functional level and lack of a registered functional level decreased the likelihood for employment. Educational level was not associated with employment.

Conclusions

The systematic differences in employment and day care participation among people with intellectual disabilities indicate that actions are needed to prevent inequalities. Improved individual assessment of personal resources and wishes might promote participation in employment and day care.
Quantitative evaluation of facial sagging in different body postures using a three‐dimensional imaging technique
Authors: Park June Whan , Lee Myeongryeol , Kim Jihyun , Kim Eunjoo
Published: December 2020

Background

The possible contribution of head flexion posture while using a smartphone to the formation of “smartphone face,” is an increasing concern. Smartphone face describes the facial changes in a stooped posture receiving more gravitational pull on the jowl area.

Aims

In this study, we quantified facial sagging in different postural changes using a three‐dimensional imaging technique.

Methods

Faces of 21 young (30.45 ± 2.81 yo, n = 11) and old (59.50 ± 3.37 yo, n = 10) Korean female subjects were scanned in different body postures including standing, supine, and head flexion (30°, 45°). The landmark displacements and volumetric changes in facial areas were assessed and correlated with skin elasticity. In addition, 22 Korean female subjects (45.45 ± 3.81 yo) were recruited to test the anti‐gravity effect of facial cream A, which was formulated with Stem III complex™, for 8 weeks.

Results

The landmarks shifted inferior‐laterally with the supine posture, while the upper face shifted more laterally and the lower face shifted more inferiorly. With a head flexion posture, facial sagging occurred mainly toward the anterior direction with more prominent changes in the lower face. The changes were greater in the older group, and skin elasticity exhibited negative correlation with the shifting distances. A significant decrease in facial sagging was noted after an 8‐week treatment of facial cream A.

Conclusion

The use of a three‐dimensional imaging technique could accurately assess the gravity‐induced facial changes in different postures. The head flexion posture particularly gives more gravitational pull to the lower face, which could contribute to the drooping jawline.
Exploring Knowledge and Attitudes About Human Papillomavirus Vaccination Among School Nurses in an Urban School District
Authors: Selvan Preethi , Kearney Matthew , Cognetti David , Massey Philip , Leader Amy
Published: December 2020

BACKGROUND

Nurses in an urban school district completed a brief survey about their knowledge, attitudes, and practices related to human papillomavirus (HPV) vaccination.

METHODS

Descriptive and bivariate analyses examined trends and differences.

RESULTS

Among 208 nurses, only 3% correctly answered all 5 knowledge questions. Nurses with greater than 10 years of experience were more confident about where to refer a student for vaccination (p < .01) and less likely to be interested in providing the vaccine at their school (p < .001) compared to those with less than 10 years of experience. Almost one third (32%) of nurses reported having access to educational material about the HPV vaccine at their schools.

CONCLUSIONS

Whereas most nurses had positive attitudes about the vaccine, fewer were interested in administering the HPV vaccine in school. Educational resources for school nurses could increase awareness of the vaccine and promote linkages to care outside of school.
Intra‐and Interpersonal Factors Buffer the Relationship Between Food Insecurity and Mental Well‐Being Among Middle Schoolers
Authors: Brinkman Jesse , Garnett Bernice , Kolodinsky Jane , Wang Weiwei , Pope Lizzy
Published: December 2020

BACKGROUND

Food insecurity (FI) is a significant predictor of feelings of isolation in children, as well as suicide ideation and depression. Using a census of public middle school‐aged children, we seek to determine whether FI is associated with suicide ideation and feelings of hopelessness and how individual and school community factors can alleviate or exacerbate this relationship.

METHODS

We analyzed data from the 2015 Youth Risk Behavior Surveillance Survey, conducted statewide by the Vermont Department of Health and administered to all public middle schoolers (N = 13,648). Questions were asked about FI, suicidal thoughts, feelings of hopelessness, perceptions of teaching and community care, physical activity, breakfast consumption, and demographics. Bivariate and cross‐tabular analyses were conducted in SPSS, and regressions and Sobel tests were conducted in STATA.

RESULTS

Results show that FI is associated with decreases in psychological well‐being as measured by suicide ideation and feelings of hopelessness in students. However, students who reported eating breakfast regularly, feeling connected to their community or having a positive relationship with a teacher had significantly lower instances of suicide ideation and hopelessness.

CONCLUSION

Suicide prevention programs should focus on enhancing community connection and student‐teacher relationships and increasing funding for breakfast programs in schools.
Addition of palm olein to lard‐supplemented diet indicates myocardial dysfunction and augments oxidative stress by authophagy‐lysosome pathway in rats
Authors: Kurhaluk Natalia , Bojková Bianka , Kajo Karol , Macháleková Katarína , Kisková Terézia
Published: December 2020

This study evaluated a prolonged effect of palm oil addition to lard‐supplemented diet (PLD) on the oxidative status, lysosomal enzyme activities, markers of hepatotoxicity and basic lipid profile in female rats. Female Sprague‐Dawley rats received PLD (10% of total fat: 7.5% from palm oil and 2.5% from lard), and the control group received lard‐supplemented diet (2.5% fat) from 28 days of age for 14 weeks. Histopathological evaluation of the liver from animals fed the PLD showed slight steatosis and signs of mild chronic inflammation. Reduction of extramedullary hematopoiesis and an increased ratio of red/white pulp were observed in the spleen. PLD induced oxidative stress (evaluated in the liver, heart, spleen, muscle and kidney) evidenced by an increase in conjugated dienes and malondialdehyde in all tissues except the muscle; protein carbonyl derivatives were increased as well. The changes in the antioxidant enzyme activities in the evaluated tissues were ambiguous except for the prominent increase in the heart. Lysosomal enzyme activities showed a tendency to increase in the heart and kidney and to decrease in the muscle and spleen. The De Ritis ratio, which is a biomarker of hepatotoxicity, was higher in the heart from animals fed the PLD. The palm oil addition to the lard‐supplemented diet‐induced prominent oxidative stress, particularly in myocardial tissue with involvement of the authophagy‐lysosome pathway.
Prenatal maternal sleep and trajectories of postpartum depression and anxiety symptoms
Authors: Gueron‐Sela Noa , Shahar Golan , Volkovich Ella , Tikotzky Liat
Published: December 2020

Postpartum emotional distress is very common, with 10%–20% of postpartum women reporting depressive or anxiety disorders. Sleep is a modifiable risk factor for emotional distress that has a pivotal role in postpartum adjustment. The present study aimed to examine whether sleep duration and quality during pregnancy predict trajectories of emotional distress in the postpartum period. Participants were 215 women that were assessed from the third trimester of pregnancy to 18‐months postpartum. At all five time points (third trimester, 3‐, 6‐, 12‐, and 18‐months postpartum), measures of sleep duration and quality (measured by wake time after sleep onset; WASO) were derived from both actiography and diary‐based measures. Repeated measures of depression and anxiety symptoms were collected using self‐report measures. Results indicated four bivariate postpartum depression and anxiety growth trajectories, including (a) high comorbidity (5.4%); (b) moderate comorbidity (19.4%); (c) low anxiety and decreasing depression symptomology (18.6%); and (d) low symptomology (56.6%). Multinomial logistic regression analyses showed that mothers with shorter sleep durations during pregnancy were more likely to belong to the high comorbidity or moderate symptoms classes compared to the low symptomology class. In addition, mothers with higher WASO (i.e. lower sleep quality) at 3‐months postpartum were more likely to belong to the moderate class compared to the low symptomology class. Given the potential negative implications of disrupted sleep in the perinatal period, the present study may inform future intervention studies that target sleep problems during pregnancy.
Parsimonious time series modeling for high frequency climate data
Authors: Anderson Paul L. , Sabzikar Farzad , Meerschaert Mark M.
Published: December 2020

Climate data often provides a periodically stationary time series, due to seasonal variations in the mean and covariance structure. Periodic ARMA models, where the parameters vary with the season, capture the nonstationary behavior. High frequency data collected weekly or daily results in a large number of model parameters. In this article, we apply discrete Fourier transforms to the parameter vectors, and develop a test for the statistically significant harmonics. An example of daily high temperatures illustrates the method, whereby a periodic autoregressive model with 1095 parameters is reduced to a parsimonious 12 parameter version without any apparent loss of fidelity.
The End of Liberal Engagement with China and the New US–Taiwan Focus
Authors: Chen Dean P.
Published: December 2020

Using neoclassical realist theory, this paper focuses on how the liberal logic underpinning the US engagement policy with the People's Republic of China (PRC) – to promote the PRC's greater marketization, internationalization, political opening, and even democratization – has shaped Washington's One‐China/strategic ambiguity policy since 1972. This approach is used to deal carefully with the Taiwan Strait impasse. However, as strategic competitions intensify between the United States and PRC, the Donald Trump administration is strengthening Washington–Taipei ties, in line with conservative nationalism, to counter a more assertive and authoritarian China. Declaring the failure of past engagement upheld by presidents following Nixon, the Trump government is less cautious about upsetting Beijing through the United States' more explicit backing of the island democracy. The United States’ bolstering of Taiwan's status, though short of recognizing its sovereignty, has received strong bipartisan support in Washington and is unlikely to be changed even if Joe Biden, the Democratic nominee, is elected president in November 2020.
Novel neonatal presentation of megalencephaly‐polymicrogyria‐pigmentary mosaicism syndrome (MPPM) related to MTOR mutation: Report of a case
Authors: Taylor Dustin L. , Wildin Robert S. , Morley Keith W.
Published: December 2020

The PI3K/AKT/mTOR signaling pathway is a critical mediator of cell functions. Activating mutations of this pathway are known to disturb normal growth and development, leading to a range of overgrowth and neurologic syndromes. We report a case of megalencephaly‐polymicrogyria‐pigmentary mosaicism syndrome (MPPM) in novel association with MTOR pathogenic variant c.6644C>A (p.Ser2215Tyr) and neonatal evanescent skin findings. This case highlights the importance of a thorough newborn cutaneous examination, as this initial window offers a critical opportunity for potential prognostication and surveillance for neurological sequelae.
Identification of the AG afterglow thermoluminescence band in the cyanobacterium Synechocystis PCC 6803
Authors: Kodru Sandeesha , Sass László , Patil Priyanka , Szabó Milán , Vass Imre
Published: December 2020

The so‐called afterglow, AG, thermoluminescence (TL) band is a useful indicator of the presence of cyclic electron flow (CEF), which is mediated by the NADH dehydrogenase‐like (NDH) complex in higher plants. Although NDH‐dependent CEF occurs also in cyanobacteria, the AG band has previously not been found in these organisms. In the present study, we tested various experimental conditions and could identify a TL component with ca. +40°C peak temperature in Synechocystis PCC 6803 cells, which were illuminated by far‐red (FR) light at around −10°C. The +40°C band could be observed when WT cells were grown under ambient air level CO2, but was absent in the M55 mutant, which is deficient in the NDH‐1 complex. These experimental observations match the characteristics of the AG band of higher plants. Therefore, we conclude that the newly identified +40°C TL component in Synechocystis PCC 6803 is the cyanobacterial counterpart of the plant AG band and originates from NDH‐1‐mediated CEF. The cyanobacterial AG band was most efficiently induced when FR illumination was applied at −10°C and its contribution to the total TL intensity declined when cells were illuminated above and below this temperature. Based on this phenomenon we also conclude that CEF is blocked by low temperatures at two different sites in Synechocystis PCC 6803: (1) Below −10°C at the level of NDH‐1 and (2) below −30°C at the donor or acceptor side of Photosystem I.
Biomechanical properties of a novel locking compression plate to stabilize oblique tibial osteotomies in buffaloes
Authors: Ahmad Raja A. , Aithal Hari Prasad , Amarpal  , Kinjavdekar Prakash , Gope Prakash Chandra , Madhu Doddadasarahalli N.
Published: December 2020

Objective

Quantitation of mechanical properties of a novel locking compression plate (LCP) for bovine tibia.

Study design

Prospective in vitro study.

Sample population

Adult Murrah buffalo (250‐350 kg) tibiae.

Methods

Forty tibiae were randomly assigned to five treatment groups (n = 8/group): intact bone and bone constructs with a standard nonlocking plate, single LCP, double LCP, and novel LCP. During implant application, a mid‐diaphyseal, oblique osteotomy was performed in all constructs, which were subsequently tested in axial compression (n = 4 each) or three‐point craniocaudal bending (n = 4 each). Novel LCP alone (n = 4) was tested only in bending. Stiffness, yield load, ultimate failure load, and bending moment were determined from the load deformation curves and compared among different treatment groups (P < .05).

Results

Under compression, yield load of the novel LCP (24.07 ± 3.45 kN) was greater than that of the nonlocking plate (11.10 ± 2.46 kN) and the single LCP (18.01 ± 2.07 kN) but less than that of the double LCP (30.61 ± 1.95 kN), and ultimate failure load of the novel LCP (25.85 ± 4.32 kN) was greater than that of the nonlocking plate (13.18 ± 2.91 kN) but similar to that of the single LCP (21.17 ± 2.33 kN) and the double LCP (32.40 ± 1.46 kN). Bending moment, yield load, and ultimate failure load of the novel LCP were 565.37 ± 79.30 Nm, 7.90 ± 1.14 kN, 9.83 ± 1.38 kN, respectively, which were greater than those of the nonlocking plate and the single LCP but comparable to those of the double LCP.

Conclusion

The novel LCP developed for bovine tibia was mechanically superior to the standard nonlocking plate or the single LCP and comparable to the double LCP.

Clinical significance

The novel LCP may provide rigid fixation of tibial diaphyseal fractures in buffaloes and cattle weighing 250 to 350 kg.
Full-Dimensional Intuitive Motion Mapping Strategy for Minimally Invasive Surgical Robot With Redundant Passive Joints
Authors: Kong Kang , Wang Shuxin , Li Jianmin , Su He
Published: December 2020

Adding redundant passive joints to a robotic arm is an effective way to make the robot overcome the inherent incision constraint of minimally invasive surgery (MIS). However, due to the limited motion accuracy, it is difficult to realize full-dimensional intuitive motion based on traditional multi-axis coordinated control technology in this kind of MIS robots. To solve this problem, a separated position and orientation mapping strategy for MIS robot with redundant passive joints is proposed in the paper. The position and orientation mapping of the strategy are realized by coordinate motion control and joint direct control technique, respectively. To realize the intuitive motion under this condition, an inverse motion mapping method is further proposed. Compared with the existing mapping strategy, the proposed strategy is much more compact as the orientation mapping is greatly simplified. A large number of in vivo trials based on the newly developed prototype have been conducted and results fully verify the effectiveness of the proposed strategy.
A New Deterministic Model for Mixed Lubricated Point Contact With High Accuracy
Authors: Zhang Shuowen , Zhang Chenhui
Published: December 2020

Mixed lubrication is a major lubrication regime in the presence of surface roughness. A deterministic model is established to solve mixed lubricated point contact in this paper, using a new method to solve the asperity contact region in mixed lubrication. Treatment of pressure boundary conditions between elastohydrodynamic lubrication region and asperity contact region is discussed. The new model is capable of calculating the typical Stribeck curve and analyzing the transition of lubrication regime, from full film lubrication to boundary lubrication. Moreover, the final result of the model is independent of pressure initialization. High performance in accuracy and convergence has been achieved, which is of great importance for further lubrication modeling with consideration of nano-scale roughness, intermolecular, and surface forces.
The Relationship Between Steady-State Cetane Combustion Changes and Cold Start Engine Performance
Authors: Simms Gretchen , Fischer Sean , Cooke Jay , Hamilton Len , Luning Prak Dianne , Cowart Jim
Published: December 2020

In the past, the Navy has investigated new renewable diesel engine fuels in comparison to conventional petroleum-based fuels using some previously published combustion metrics based on ignition delay, maximum rate of heat release and combustion phasing. These metrics quantify new fuel combustion changes using a conventional heat release analysis as compared to the base fuel. When combustion changes exceed established levels, fuel may be deemed marginal or unacceptable. In this study, these metrics are applied to Primary Reference diesel Fuel (PRF) mixtures in the range from 35 to 65. As expected, significant combustion variations are observed with lengthening ignition delay and increasing maximum heat release rate resulting from lower Cetane Number (CN) fuel. In this work, these steady-state metrics were then applied to predict the worsening of cold start engine performance. It is seen that the acceptable (‘green’) range of combustion change variations provides for acceptable cold engine starting performance. As the steady-state combustion changes become moderately more significant (‘yellow’), the cold start performance degrades. With very substantial steady-state combustion metric changes (‘red’), the cold start nature becomes unacceptable. This study shows that excellent correlation between steady-state engine performance and cold start behavior is possible.
An Experimental and Numerical Study of a Hydrogen Fueled, Directly Injected, Heavy Duty Engine at Knock-Limited Conditions
Authors: Mortimer Joel , Yoannidis Stephen , Poursadegh Farzad , Lu Zhewen , Brear Michael , Yang Yi , Etherington David , Heijkoop Marcel , Lacey Joshua
Published: December 2020

This paper presents an experimental and numerical study of a directly injected, spark-ignited (DI SI), heavy duty hydrogen fueled engine at knock-limited conditions. The impact of air-fuel ratio and ignition timing on engine performance is first investigated experimentally. Two-zone combustion modeling of the hydrogen fueled cylinder is then used to infer burn profiles and unburned, end-gas conditions using the measured in-cylinder pressure traces. Simulation of the autoignition chemistry in this end-gas is then undertaken to identify key parameters that are likely to impact knock-limited behavior.

The experiments demonstrate knock-limited performance on this high compression ratio engine over a wide range of air-fuel ratios, λ. Other trends with λ are qualitatively similar to those shown in previous studies of hydrogen fueled engines. Kinetic simulations then suggest that some plausible combination of residual nitric oxide from previous cycles and locally high charge temperatures at intake valve closing can lead to autoignition at the knock-limited conditions identified in the experiments. This prompts a parametric study that shows how increased λ makes hydrogen less likely to autoignite, and suggests options for the design of high efficiency, directly injected, hydrogen fueled engines.
Influence of Low Ambient Temperatures on the Exhaust Gas and Deposit Composition of Gasoline Engines
Authors: Appel Dominik , Hagen Fabian P. , Wagner Uwe , Koch Thomas , Bockhorn Henning , Trimis Dimosthenis
Published: December 2020

To comply with future emission regulations for internal combustion engines, system-related cold-start conditions in short-distance traffic constitute a particular challenge. Under these conditions, pollutant emissions are seriously increased due to internal engine effects and unfavorable operating conditions of the exhaust aftertreatment systems. As a secondary effect, the composition of the exhaust gases has a considerable influence on the deposition of aerosols via different deposition mechanisms and on fouling processes of exhaust gas-carrying components. Also, the performance of exhaust gas aftertreatment systems may be affected disadvantageously.

In this study, the exhaust gas and deposit composition of a turbocharged three-cylinder gasoline engine is examined in-situ upstream of the catalytic converter at ambient and engine starting temperatures of −22 °C to 23 °C using a Fourier-transform infrared spectrometer and a particle spectrometer. For the cold start investigation, a modern gasoline engine with series engine periphery is used. In particular, the investigation of the behavior of deposits in the exhaust system of gasoline engines during cold start under dynamic driving conditions represents an extraordinary challenge due to an average lower soot concentration in the exhaust gas compared to diesel engines and so far, has not been examined in this form. A novel sampling method allows ex-situ analysis of formed deposits during a single driving cycle. Both, particle number concentration and the deposition rate are higher in the testing procedure of Real Driving Emissions (RDE) than in the inner-city part of the Worldwide harmonized Light vehicles Test Cycle (WLTC). In addition, reduced ambient temperatures increase the amount of deposits, which consist predominantly of soot and to a minor fraction of volatile compounds. Although the primary particle size distributions of the deposited soot particles do not change when boundary conditions change, the degree of graphitization within the particles increases with increasing exhaust gas temperature.
Evaluation of Soot Production Near a Cold Surface for an Impinged Diesel Spray Combustion
Authors: Zhao Zhihao , Zhao Le , Lee Seong-Young
Published: December 2020

Spray impingement in internal combustion engines has received great attentions. Such a phenomenon is especially important for diesel spray because the spray and combustion characteristics are significantly altered by the impingement. In this study, numerical investigations of impinged reacting spray jets in a constant volume combustion chamber were performed to understand the spray and flame structure under high pressure and high temperature conditions. The 3-D computational fluid dynamics (CFD) CONVERGE code was selected as the numerical tool to perform Large-eddy simulations (LES) to understand the process of spray combustion-wall interaction. CFD models were validated against experimental results in terms of spray penetration and ignition delay at inert and reacting spray conditions. The temperature and soot mass fraction profiles near the impinging plate were investigated for 900 and 1000 K ambient conditions. It was found that soot mass fraction is generally increased near the impinging plate as the temperature is decreased. The heat transfer from the flame to the plate makes the temperature close to the wall more favorable for soot formation. A dense soot core was observed at the leading edge when the injection was still happening because the vortex there took the opportunity from existing burned gas to new fuel to meet the ambient air. A soot layer was observed stick on the wall as the air was hard to entrain the flame all the way to the plate side.
Numerical Analysis of Fuel Effects on Advanced Compression Ignition Using a Virtual Cooperative Fuel Research Engine Model
Authors: Kalvakala Krishna C. , Pal Pinaki , Wu Yunchao , Kukkadapu Goutham , Kolodziej Christopher , Pulpeiro Gonzalez Jorge , Waqas Muhammad Umer , Lu Tianfeng , Aggarwal Suresh K. , Som Sibendu
Published: December 2020

Growing environmental concerns and demand for better fuel economy are driving forces that motivate the research for more advanced engines. Multi-mode combustion strategies have gained attention for their potential to provide high thermal efficiency and low emissions for light-duty applications. These strategies target optimizing the engine performance by correlating different combustion modes to load operating conditions. The extension from boosted SI mode at high loads to advanced compression ignition (ACI) mode at low loads can be achieved by increasing compression ratio and utilizing intake air heating. Further, in order to enable an accurate control of intake charge condition for ACI mode and rapid mode-switches, it is essential to gain fundamental insights into the autoignition process. Within the scope of ACI, homogeneous charge compression ignition (HCCI) mode is of significant interest. It is known for its potential benefits, operation at low fuel consumption, low NOx and PM emissions. In the present work, a virtual Cooperative Fuel Research (CFR) engine model is used to analyze fuel effects on ACI combustion. In particular, the effect of fuel Octane Sensitivity (S) (at constant RON) on autoignition propensity is assessed under beyond-RON (BRON) and beyond-MON (BMON) ACI conditions. The 3D CFR engine computational fluid dynamics (CFD) model employs finite-rate chemistry approach with multi-zone binning strategy to capture autoignition. Two binary blends with Research Octane Number (RON) of 90 are chosen for this study: Primary reference fuel (PRF) with S = 0, and toluene-heptane (TH) blend with S = 10.8, representing paraffinic and aromatic gasoline surrogates. Reduced mechanisms for these blends are generated from a detailed gasoline surrogate kinetic mechanism. Simulation results with the reduced mechanisms are validated against experimental data from an in-house CFR engine, with respect to in-cylinder pressure, heat release rate and combustion phasing. Thereafter, the sensitivity of combustion behavior to ACI operating condition (BRON vs BMON), air-fuel ratio (λ = 2 and 3), and engine speed (600 and 900rpm) is analyzed for both fuels. It is shown that the sensitivity of a fuel’s autoignition characteristics to λ and engine speed significantly differs at BRON and BMON conditions. Moreover, this sensitivity is found to vary among fuels, despite the same RON. This study also indicates that the octane index (OI) fails to capture the trend in the variation of autoignition propensity with S under BMON conditions.
Effect of Split Injection Timing on Combustion and Emissions of a DISI Optical Engine Under Lean Burn Condition
Authors: Sun Zhe , Cui Mingli , Wang Hongyu , Nour Mohamed , Li Xuesong , Xu Min , Hung David
Published: December 2020

Lean combustion has proven to be an effective way to improve the efficiency and emissions of the direct injection spark ignition (DISI) engine. However, one of the main problems at the lean stability limit is the major decrease in flame temperature due to dilution, resulting in a low laminar flame speed, especially under low-speed engine operating conditions. The split injection is a potential technology to realize proper air-fuel mixing and achieve different spray distribution that can help in solving such problems. In this study, split injections with different secondary injection timings were tested to achieve homogeneous and homogeneous-stratified modes in a DISI optical engine under lean-burn mode. The split ratio of each strategy was 1:1. The engine was operated at 800 rpm, and a high-energy ignition system was utilized to realize lean combustion at a lambda of 1.55. Engine combustion performance and emissions were tested while performing high-speed color recording to study the characteristics of flame chemiluminescence through a quartz piston combined with a 45-degree mirror installed below. Flame structure during various combustion phases was compared under different selected conditions based on a digital image processing technique. The results show that the pressure and emissions vary with the second injection timing. Proper control of the split injection timing can improve lean combustion performance, including faster flame speed, increased indicated mean effective pressure (IMEP), and lower harmful emissions. Poor fuel evaporation and soot generation from spatial hot spots in the combustion process of split injection are the major challenges for further improvement.
Predicting the Cetane Number, Yield Sooting Index, Kinematic Viscosity, and Cloud Point for Catalytically Upgraded Pyrolysis Oil Using Artificial Neural Networks
Authors: Kessler Travis , Schwartz Thomas , Wong Hsi-Wu , Mack J. Hunter
Published: December 2020

The conversion of biomass using fast pyrolysis has the potential to be significantly less expensive at scale compared to alternative methods such as fermentation and gasification. Selective upgrading of the products of fast pyrolysis through chemical catalysis produces compounds with lower oxygen content and lower acidity; however, identifying the specific catalytic pathways for producing viable fuels and fuel additives often requires a trial-and-error approach. Specifically, key properties of the compounds must be experimentally tested to evaluate the viability of the resultant compounds. The present work proposes predictive models constructed with artificial neural networks (ANNs) for cetane number (CN), yield sooting index (YSI), kinematic viscosity (KV), and cloud point (CP), with blind test set median absolute errors of 5.14 cetane units, 3.36 yield sooting index units, 0.07 millimeters squared per second, and 4.89 degrees Celsius, respectively. Furthermore, the cetane number, yield sooting index, kinematic viscosity, and cloud point were predicted for over three hundred expected products from the catalytic upgrading of pyrolysis oil. It was discovered that 130 of these compounds have predicted cetane numbers greater than 40, with four of these compounds possessing predicted yield sooting index values significantly less than that of diesel fuel and predicted viscosities and cloud points comparable to that of diesel fuel.
Piston Bowl Geometry Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine
Authors: Tang Meng , Pei Yuanjiang , Guo Hengjie , Zhang Yu , Torelli Roberto , Probst Daniel , Fütterer Carsten , Traver Michael
Published: December 2020

A design optimization campaign was conducted to search for improved combustion profiles that enhance gasoline compression ignition in a heavy-duty diesel engine with a geometric compression ratio of 17.3. Three-dimensional computational fluid dynamics simulations were employed using the software package CONVERGE. A large-scale design of experiments (DoE) approach was used for the optimization. The main parameters explored include geometric features, injector specifications, and swirl motion. Both stepped-lip bowls and re-entrant bowls were included in the optimization effort in order to assess their respective performance implications. A total of 256 design candidates were prepared using the software package CAESES for automated and simultaneous geometry generation and combustion recipe perturbation. The design optimization was conducted for three engine load points representing light to medium load conditions. The design candidates were evaluated for fuel efficiency, emissions, fuel-air mixing characteristics, and global combustion behavior. Simulation results show that the optimum designs were all stepped-lip bowls, which exhibited better overall performance than re-entrant bowls due to improvements in fuel-air mixing, as well as reduced heat loss and emissions formation. Improvements in indicated specific fuel consumption of up to 3.2% were achieved while meeting engine-out NOx emission targets of 1–1.5 g/kW·hr. Re-entrant bowls performed worse compared to the baseline design, and significant performance variations occurred across the load points. Specifically, the re-entrant bowls were on par with the stepped-lip bowls under light load conditions, but significant deteriorations occurred under higher load conditions. As a final task, selected optimized designs were then evaluated under simulated full-load conditions.