bluuebunny/crossref_metadata_2025 huggingface dataset:
Forest patch characteristics affect reptile occurrence in north‐western Madagascar
Authors: Evans Alexandra M. , Marshal Jason P. , Alexander Graham J.
Published: February 2021

Characterising species–landscape associations is relevant for conservation planning and management in response to environmental transformation. The occurrence of reptiles is linked to landscape structure that allows for thermoregulation, shelter and feeding, but the relative importance of these factors is unknown for many tropical and subtropical species. We used community‐level occupancy modelling and remote sensing to investigate the effects of vegetation structure and anthropogenic development on reptile occurrence in a Malagasy dry forest during the dry season (June and July). The occupancy estimates for some species revealed that species occupancy increased for more densely vegetated sites situated closer to the forest edge. The proximity of anthropogenic transformation did not significantly affect the occurrence of species except for Uroplatus guentheri which showed preference for sites away from settlements. Because most species and those most sensitive to habitat transformation were associated with edges of intact forest patches with denser green vegetation, these areas should form the focus of efforts to conserve reptiles in tropical dry forests. We also demonstrate how setting and scale can affect how habitat‐use patterns are interpreted and the importance of local, species‐specific studies.
Treatment of steroid‐refractory chronic graft‐versus‐host disease with imatinib: Real‐life experience of the Spanish group of hematopoietic transplantation (GETH)
Authors: Parra Salinas Ingrid , Bermudez Aranzazu , López Corral Lucia , Lopez Godino Oriana , Móles‐Poveda Paula , Martín Guillermo , Costilla Barriga Lissette , Ferrá Coll Christelle , Márquez‐Malaver Francisco , Ortí Guillermo , Zudaire Ripa Maria Teresa , Rifon Jose , Martinez Carmen ,   the Spanish Group of Hematopoietic Transplantation (GETH)
Published: February 2021

Treatment of steroid‐refractory chronic graft‐versus‐host disease (cGVHD) is a challenge. Here, we describe a retrospective analysis of 66 patients with steroid‐refractory cGVHD treated with imatinib (starting dose of 100 mg in 70% of patients; maximum dose of 100‐200 mg in 74%). Most patients had multi‐organ involvement (≥2 organs, 83%), with the most affected being skin (85%), oral mucosa (55%), eyes (42%), and lungs (33%). The overall response rate was 41% (21 partial and three complete responses). The organ with the best response rate was the skin (46%), followed by gastrointestinal tract (43%), liver (41%), the oral mucosa (36%), eyes (29%), and lungs (18%). Imatinib led to steroid tapering in 17/38 patients. Twenty‐five (38%) patients experienced imatinib‐related adverse events, comprising extra‐hematologic toxicity (n = 24, 36%) and hematologic toxicity (n = 6, 9%). No cases of grade 4‐5 toxicity were reported. The main causes of imatinib discontinuation were treatment failure (52%) and toxicity (9%). After a median follow‐up of 41 months, the 3‐year overall survival was 81%, with no difference between imatinib responders and non‐responders. These real‐life results show that imatinib is safe and has moderate efficacy in patients with heavily pre‐treated cutaneous sclerotic cGVHD; however, activity against lung cGVHD is very limited.
How beliefs influence behaviour: Confucianism and innovation in China
Authors: Feng Xunan , Jin Zhi , Johansson Anders C.
Published: February 2021

Previous studies have analysed how religious beliefs may affect economic activity. We extend this literature by examining how Confucianism is linked to innovation activity at the firm level in China. We analyse the relationship between Confucianism and several proxies for input and outputs of innovation activities. Our results show that Confucianism is significantly related to lower levels of innovation activity regardless of which measure for firm‐level innovation we use. We also find that the nature of ultimate ownership influences this relationship, with innovation among state‐controlled firms being significantly more affected by Confucianism. This study thus adds to the understanding of how traditional belief systems influence behaviour among economic actors.
School teachers’ knowledge and experience about emergency management of traumatic dental injuries: A questionnaire‐based online cross‐sectional survey
Authors: Ivanda Stipe , Gavic Lidia , Galic Tea , Tadin Antonija
Published: February 2021

Background/Aim

Dental trauma is one of the critical oral health problems in childhood and adolescence that can affect an individual's quality of life. Teachers may witness a dental injury on many occasions, and they are likely to be involved at the site of an accident. Hence, they should be capable of managing prompt and correct emergency treatment at the accident site. The aim of this cross‐sectional study was to assess the level of knowledge and experience of Croatian elementary and high school teachers concerning dental trauma.

Materials and Methods

A questionnaire‐based cross‐sectional online survey was conducted to determine knowledge and experience about traumatic dental injuries among 803 full‐time working elementary and high school teachers. The inclusion criteria were full‐time employment at the time of data collection with at least 1 year of teaching experience. Retirement (teachers aged ≥65 years) and unwillingness to participate in the survey were the exclusion criteria. The Student t test or one‐way ANOVA, with Tukey's post hoc was used to evaluate the obtained data. The level of significance was set at p ≤ .05.

Results

The overall mean level of teachers’ knowledge regarding emergency management of dental trauma was 6.6 ± 2.5 points, out of a maximum possible score of 14. There were no significant differences in knowledge among teachers from lower elementary, upper elementary, and high school education (6.9 ± 2.5, 6.5 ± 2.4 vs 6.4 ± 2.6 points, respectively; p = .140). Teachers who had personally experienced dental trauma showed better knowledge (7.2 ± 2.6 vs 6.4 ± 2.5 points; p ≤ .001).

Conclusion

The knowledge of emergency management of dental trauma among elementary and high school teachers in Croatia is low. Since most of the participants expressed willingness for future education regarding this subject, educational programs are recommended.
Preference and performance of the rice leaf folder, Cnaphalocrocis medinalis, in relation to rice developmental stage
Authors: Liu Huan , Han Yongqiang , Zhong Yuqi , Ali Asad , Hou Maolin
Published: February 2021

The relationship between oviposition preference and offspring performance is critical to an understanding of the interaction between herbivores and host plants. Although the topic has been addressed widely in plant species‐herbivore systems, it has rarely been investigated in plant stage‐herbivore systems. In this study, we evaluated oviposition preference and offspring performance of the rice leaf folder (RLF), Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), on rice plants at the seedling (SS), tillering (TS), and booting (BS) stages. In preference assays, females deposited more eggs on TS and BS than on SS plants in cage tests, and preferred TS and BS odors over SS odors in Y‐tube olfactometer tests. Offspring performance was affected by plant stage. The RLF offspring performed well when the larvae fed on BS leaves, as indicated by the highest larval survival and pupation rate and the greatest adult longevity. RLF offspring performed also well when the larvae fed on TS leaves, where fecundity was the highest. The high RLF offspring performance on TS and BS plants coincided with high larval consumption of TS and BS leaf mass relative to SS leaf mass. Our findings confirm the prediction of the preference–performance hypothesis. The results explain the pest damage patterns in mixed croppings of one‐ and two‐season rice and are of significance for management of the pest through synchronization of rice planting.
Issues in world language teacher preparation: ACTFL/CAEP standards and oral proficiency
Authors: Huhn Christina , Bell Teresa R. , Chambless Krista
Published: February 2021

The purpose of this article is to provide a review of current research on two of the original ACTFL (American Council on the Teaching of Foreign Languages) research priorities areas, model teacher preparation programs and teacher oral proficiency, as well as a look at future directions for research in these areas. Driven by the call for continued research in the original articles, this article lays the foundation for future research on effective world language (WL) teacher preparation programs. Despite the premise from the original articles and the growth of teacher preparation programs built around the ACTFL/CAEP Standards, further research is necessary to fully realize the effects of teacher's proficiency levels on teacher effectiveness and student outcomes.
Gender equality without democracy? Higher education expansion and authoritarian values
Authors: Wang Suen
Published: February 2021

How does social policy affect authoritarian values? Leveraging exogenous variation, I evaluate how higher education expansion as a social policy program in China has influenced authoritarian support and traditional gender attitudes. I use an instrumental variable approach and regression analyses with marginal effects to assess multiple waves of Chinese national representative surveys coupled with regional statistics. The study differentiates between two types of authoritarian support: specific support (authoritarian support based on evaluation of recent policies) and diffuse support (long‐term authoritarian traits independent of recent policies). I find that education expansion has significantly decreased specific authoritarian support; however, it has not influenced diffuse authoritarian support. Moreover, a decrease in traditional gender attitudes is driven by a cohort effect rather than an education expansion effect. The findings have broader implications for understanding the effects of social policy on attitudinal change in an authoritarian context.
The efficacy and safety of acid suppressants for gastrointestinal bleeding prophylaxis in cardiac care unit patients
Authors: Chen Chen , Liu Hui , Duan Ruqiao , Wang Fangfang , Duan Liping
Published: February 2021

Background and Aim

Concerns regarding adverse events associated with proton pump inhibitors (PPIs) and histamine‐2 receptor antagonists (H2RAs) for gastrointestinal bleeding (GIB) prophylaxis in the intensive care unit have increased in recent years. Few studies have focused on acid suppressant use in the cardiac care unit (CCU) setting exclusively. We performed a cohort study to determine the efficacy and safety of acid suppressants for GIB prophylaxis in CCU patients.

Methods

This retrospective cohort study included adults who were admitted directly to the CCU for more than 2 days from January 1, 2014, to April 30, 2019. The Crusade score was calculated to evaluate the risk of GIB. The primary outcomes were clinically important gastrointestinal bleeding (CIGIB), hospital‐acquired pneumonia (HAP), and in‐hospital mortality.

Results

Of the 3318 patients enrolled, 2284 (68.8%) patients received PPIs, 515 (15.5%) received H2RAs, and 519 (15.7%) received no acid suppressants. After adjusting for potential confounders, utilization of PPIs (2.69, 95% confidence interval [0.62–11.73]) and H2RAs (1.41, 95% confidence interval [0.19–10.36]) were not associated with a lower risk of CIGIB than the control. Sensitivity analyses revealed that PPI use was an independent risk factor for in‐hospital mortality in patients over 75 years old, with an adjusted odds ratio of 4.08 (1.14–14.63). PPIs increased the risk of HAP in patients over 75 years old and in those with heart failure, with adjusted odds ratios of 2.38 (1.06–5.34) and 2.88 (1.34–7.28), respectively.

Conclusions

Proton pump inhibitors and H2RAs for GIB prophylaxis in CCU patients were not associated with a lower risk of CIGIB than the controls. PPI therapy is associated with increased risks of HAP and in‐hospital mortality in patients over 75 years old. PPIs may increase the risk of HAP in patients with heart failure.
The Phytophthora effector Avh241 interacts with host NDR1‐like proteins to manipulate plant immunity
Authors: Yang Bo , Yang Sen , Guo Baodian , Wang Yuyin , Zheng Wenyue , Tian Mengjun , Dai Kaixin , Liu Zehan , Wang Haonan , Ma Zhenchuan , Wang Yan , Ye Wenwu , Dong Suomeng , Wang Yuanchao
Published: February 2021

Plant pathogens rely on effector proteins to suppress host innate immune responses and facilitate colonization. Although the Phytophthora sojae RxLR effector Avh241 promotes Phytophthora infection, the molecular basis of Avh241 virulence remains poorly understood. Here we identified non‐race specific disease resistance 1 (NDR1)‐like proteins, the critical components in plant effector‐triggered immunity (ETI) responses, as host targets of Avh241. Avh241 interacts with NDR1 in the plasma membrane and suppresses NDR1‐participated ETI responses. Silencing of GmNDR1s increases the susceptibility of soybean to P. sojae infection, and overexpression of GmNDR1s reduces infection, which supports its positive role in plant immunity against P. sojae. Furthermore, we demonstrate that GmNDR1 interacts with itself, and Avh241 probably disrupts the self‐association of GmNDR1. These data highlight an effective counter‐defense mechanism by which a Phytophthora effector suppresses plant immune responses, likely by disturbing the function of NDR1 during infection.
Understanding perceptions of health, lifestyle risks and chronic disease in middle age
Authors: Halcomb Elizabeth , Ashley Christine , Middleton Rebekkah , Lucas Elizabeth , Robinson Karin , Harvey Sue , Charlton Karen , McInnes Susan
Published: February 2021

Aim

The aim of this paper is to explore the perceptions, attitudes and beliefs of middle‐aged Australians around their health, lifestyle risks and chronic disease.

Background

Health promotion and risk reduction are important to stem the rising prevalence of chronic disease. While there has been much emphasis on supporting these strategies in older Australians, there has been less attention on those in middle age. However, as this group age, their health will inevitably be impacted by lifestyle risk.

Design

A qualitative descriptive study using semi‐structured interviews. Reporting was guided by the COREQ checklist.

Methods

Thirty‐four participants aged 40–65 years were recruited across South Eastern New South Wales, Australia, using convenience sampling. Semi‐structured interviews were conducted by four registered nurses with qualitative research experience. Verbatim transcripts were analysed using thematic analysis.

Results

Sixteen women and 18 men participated in the interviews. Four themes emerged, namely: adopting healthy lifestyles; denial; an impetus for change; and sustaining change. Perceptions about what constituted good health varied, with male participants being more ambivalent about their health. Impetus for change was mostly influenced by family history, awareness of health risks and identification of risks by health professionals. Participants found sustaining change challenging, particularly with regard to smoking cessation and dietary modifications.

Conclusions

Understanding the perceptions of health of middle‐aged people is important and enables health professionals to engage in early behavioural change conversations that consider perceived barriers to lifestyle modification. Findings from this study emphasise the importance of discussions about lifestyle risk to reduce the future burden of chronic disease.

Relevance to Clinical Practice

These findings illustrate the importance of understanding perceptions of health to guide primary health care nurses to develop person‐centred health promotion and chronic disease prevention strategies in this age group.
Telomere heritability and parental age at conception effects in a wild avian population
Authors: Sparks Alexandra M. , Spurgin Lewis G. , van der Velde Marco , Fairfield Eleanor A. , Komdeur Jan , Burke Terry , Richardson David S. , Dugdale Hannah L.
Published: February 2021

Individual variation in telomere length is predictive of health and mortality risk across a range of species. However, the relative influence of environmental and genetic variation on individual telomere length in wild populations remains poorly understood. Heritability of telomere length has primarily been calculated using parent–offspring regression which can be confounded by shared environments. To control for confounding variables, quantitative genetic “animal models” can be used, but few studies have applied animal models in wild populations. Furthermore, parental age at conception may also influence offspring telomere length, but most studies have been cross‐sectional. We investigated within‐ and between‐parental age at conception effects and heritability of telomere length in the Seychelles warbler using measures from birds caught over 20 years and a multigenerational pedigree. We found a weak negative within‐paternal age at conception effect (as fathers aged, their offspring had shorter telomeres) and a weak positive between‐maternal age at conception effect (females that survived to older ages had offspring with longer telomeres). Animal models provided evidence that heritability and evolvability of telomere length were low in this population, and that variation in telomere length was not driven by early‐life effects of hatch period or parental identities. Quantitative polymerase chain reaction plate had a large influence on telomere length variation and not accounting for it in the models would have underestimated heritability. Our study illustrates the need to include and account for technical variation in order to accurately estimate heritability, as well as other environmental effects, on telomere length in natural populations.
Genetic Creutzfeldt–Jakob disease‐M232R with the cooccurrence of multiple prion strains, M1 + M2C + M2T: Report of an autopsy case
Authors: Shintaku Masayuki , Nakamura Takeshi , Kaneda Daita , Shinde Akiyo , Kusaka Hirofumi , Takeuchi Atsuko , Kitamoto Tetsuyuki
Published: February 2021

Genetic Creutzfeldt‐Jakob disease (gCJD) with a methionine to arginine substitution at codon 232 of the prion protein gene (gCJD‐M232R) is rare and has only been reported in Japan. We report an autopsy case of gCJD‐M232R showing alleles of codon 129 that were homozygous for methionine and the presence of multiple strains of the protease‐resistant, abnormal isoform of prion protein (PrPSc), M1 + M2C + M2T. The patient, a 54‐year‐old Japanese man, died after a clinical course of 21 months characterized by slowly progressive dementia and sleep disturbance. At autopsy, the neuropil of the cerebral neocortex showed a widespread and severe spongiform change. Grape‐like clusters of large confluent vacuoles were admixed with fine vacuoles. Neuronal loss was moderate, but reactive astrocytosis was mild. The dorsomedial nucleus of the thalamus and the inferior olivary nucleus showed moderate and severe neuronal loss, respectively. Many amyloid plaques were present in the cerebellar molecular layer. PrPSc deposition pattern was predominantly the synaptic type in the cerebrum and corresponded to the plaques in the cerebellum. Perivacuolar deposition was also seen. Western blot analysis of PrPSc revealed the predominance of type 2. Moreover, by employing Western blot analysis in combination with the protein misfolding cyclic amplification (PMCA) method, which selectively amplifies the minor M2T prion strain, we demonstrated the presence of M2T, in addition to M1 and M2C strains, in the brain of the patient. PMCA was a powerful method for demonstrating the presence of the M2T strain, although the amount is often small and the transmission is difficult.
Fine‐root functional trait responses to experimental warming: a global meta‐analysis
Authors: Wang Jinsong , Defrenne Camille , McCormack M. Luke , Yang Lu , Tian Dashuan , Luo Yiqi , Hou Enqing , Yan Tao , Li Zhaolei , Bu Wensheng , Chen Ye , Niu Shuli
Published: February 2021

Whether and how warming alters functional traits of absorptive plant roots remains to be answered across the globe. Tackling this question is crucial to better understanding terrestrial responses to climate change as fine‐root traits drive many ecosystem processes.

We carried out a detailed synthesis of fine‐root trait responses to experimental warming by performing a meta‐analysis of 964 paired observations from 177 publications.

Warming increased fine‐root biomass, production, respiration and nitrogen concentration as well as decreased root carbon : nitrogen ratio and nonstructural carbohydrates. Warming effects on fine‐root biomass decreased with greater warming magnitude, especially in short‐term experiments. Furthermore, the positive effect of warming on fine‐root biomass was strongest in deeper soil horizons and in colder and drier regions. Total fine‐root length, morphology, mortality, life span and turnover were unresponsive to warming.

Our results highlight the significant changes in fine‐root traits in response to warming as well as the importance of warming magnitude and duration in understanding fine‐root responses. These changes have strong implications for global soil carbon stocks in a warmer world associated with increased root‐derived carbon inputs into deeper soil horizons and increases in fine‐root respiration.
Safety and efficacy of transvenous lead extraction in octogenarians using powered extraction sheaths
Authors: Burger Heiko , Hakmi Samer , Petersen Johannes , Yildirim Yalin , Choi Yeong‐Hoon , Willems Stephan , Reichenspurner Hermann , Ziegelhoeffer Tibor , Pecha Simon
Published: February 2021

Background

In the aging population equipped with cardiac implantable electronic devices, an increasing number of octogenarians require lead extractions. This patient population is often considered as a high‐risk group for surgical procedures. We, therefore, investigated the safety and efficacy of transvenous lead extraction in octogenarians using powered extraction sheaths.

Methods

Between January 2013 and March 2017, 403 patients underwent lead extraction at two high‐volume lead extraction centers. A total of 71 octogenarians were treated with laser lead extraction and were included in this analysis. Primary extraction method was laser lead extraction, with additional use of mechanical rotational sheaths or femoral snares, if necessary. Patient‐based and procedural data were collected and analyzed retrospectively.

Results

Mean age was 83.5 ± 3.3 years, 64.7% were males. A total of 152 leads were extracted. The mean lead dwell time of treated leads was 10.2 ± 5.2 years. Complete procedural success rate was 92.9%, while clinical success was achieved in 98.6%. Failure of extraction occurred in one patient (1.4%). In six (7.7%) patients, additional mechanical rotational sheaths or femoral snares were used. Overall complication rate was 4.2%, including one (1.4%) major (RA perforation) and two (2.8%) minor complications. No procedure‐related mortality was observed in any of the patients.

Conclusion

Transvenous lead extraction in octogenarians with old leads is safe and effective when performed in experienced centers. Patient's age should therefore not be considered as contraindication for lead extraction using powered extraction sheaths.
Asymptotics of Selective Inference
Authors: Tian Xiaoying , Taylor Jonathan
Published: February 2021

In this paper, we seek to establish asymptotic results for selective inference procedures removing the assumption of Gaussianity. The class of selection procedures we consider are determined by affine inequalities, which we refer to as affine selection procedures. Examples of affine selection procedures include selective inference along the solution path of the least absolute shrinkage and selection operator (LASSO), as well as selective inference after fitting the least absolute shrinkage and selection operator at a fixed value of the regularization parameter. We also consider some tests in penalized generalized linear models. Our result proves asymptotic convergence in the high‐dimensional setting where n<p, and n can be of a logarithmic factor of the dimension p for some procedures.
Acumulación primitiva y acaparamiento de tierras en Colombia.
Authors: TORRES MORA ALVARO GERMAN
Published: February 2021

En este artículo abordo la relación entre el acaparamiento de tierras, el cultivo de palma de aceite y el paramilitarismo en Colombia desde la óptica de la acumulación primitiva. Para el efecto hago un análisis de tres casos concretos: el Bajo Atrato en Chocó, Mapiripán en Meta y Las Pavas en el sur de Bolívar, todos en Colombia, en los que se han presentado hechos de violencia que incluyen desplazamiento forzado y despojo de tierras, con subsecuentes proyectos de cultivo de palma de aceite a gran escala. La discusión trae a colación el mercado internacional de agrocombustibles y la necesidad del Estado colombiano de copar territorios que antes le resultaban hostiles.
La influencia de la teoría de la dependencia en los discursos de desarrollo de América Latina
Authors: Zambrano Marquez Diego Miguel
Published: February 2021

La teoría de la dependencia ha sido considerada como una perspectiva obsoleta para el estudio de la realidad latinoamericana. El éxito de otras áreas geográficas periféricas al posicionarse en el centro de la economía mundial al final del siglo veinte significó el aparente final de la validez de la teoría de la dependencia. Sin embargo, los Estados de América Latina siguen sin ser capaces de corregir las deficiencias estructurales que inspiraron la incepción de la dependencia, ya que continúan siendo significativamente dependientes a la comercialización de materias primas. Este artículo busca reabrir el debate sobre la teoría de la dependencia, con el objetivo de recuperar sus valiosos análisis para la reflexión sobre las tendencias socioeconómicas actuales de la región. A su vez, busca redefinir los aspectos teóricos más rígidos y obsoletos de la teoría de la dependencia, para resaltar su influencia en discursos de desarrollo actuales. En este sentido, este artículo resalta los paralelismos entre la teoría de la dependencia y la literatura académica sobre el desarrollo y los recursos primarios.
Investigations of the Turbulent Mixing Regions Formed by Jets
Authors: Kuethe Arnold M.
Published: February 2021

The turbulent mixing of two jets of fluid of the same density is investigated theoretically by means of Prandtl’s theory of turbulence and the results compared with experiment.

A solution obtained by Tollmien for the mixing region of a plane jet, in which he considers the fluid bounding the jet at rest, is extended to the general case of the mixing of two parallel streams of different velocities. Distributions of the tangential and normal velocities in the mixing region are given. The solution is worked out for two different conditions imposed on the normal velocity at the boundary of the mixing region.

Next, the turbulent mixing region surrounding an axially symmetrical jet issuing into fluid at rest is considered. The problem is solved, as far as the core of potential flow extends, by the application of a new method of approximation. The velocity field, as determined by a second approximation to the velocity profiles, is given. An extension of the method of solution, applicable to problems in which the velocity profiles differ widely, is mentioned.

In the theory applied in this paper, the mixing length is assumed proportional to the breadth of the mixing region. The proportionality factor which is the only empirical quantity in the theory was experimentally evaluated. Velocity profiles in the mixing region of an axially symmetrical jet were measured by means of a pitot tube and good agreement is found between theory and experiment.

Measurements of velocity fluctuations in the core of potential flow near the jet mouth and in the mixing region at a distance of 9.3 diameters were made by means of the hot-wire anemometer.
Effect of Surface Rolling on the Fatigue Strength of Steel
Authors: Horger O. J.
Published: February 2021

The investigation discussed in this paper was made to determine the effect of cold-working on the endurance limit and other related physical properties of steel. This cold-working was of a surface nature resulting in an almost negligible reduction in area. The preliminary work conducted in this field, for the most part, has been a laboratory development in so far as the technical and mechanical details of the surface-rolling process is concerned, but it has been sufficient to show the advantageous effect of this process on the endurance limit of steel, thereby justifying further study. Therefore, the investigation discussed in this paper was inaugurated to determine the various factors involved in the immediate application of this surface-rolling process in practice. As a result this paper is in the nature of a progress report covering principally tests made on 0.3-in, and 1-in. diameter cold-worked specimens without stress concentration. Further fatigue tests are being conducted on 1-in. and 2-in. diameter surface-rolled specimens with and without stress concentration and on 0.080-in. diameter fatigue specimens machined from various layers of 2-in. diameter surface-rolled specimens.
Flow Physics During Surge and Recovery of a Multi-Stage High-Speed Compressor
Authors: Zhao Fanzhou , Dodds John , Vahdati Mehdi
Published: February 2021

Stall followed by surge in a high-speed compressor can lead to violent disruption of the flow, damage to the blade structures and eventually engine shutdown. Knowledge of unsteady blade loading during surge is crucial for compressor design such as axial gap optimization. The aim of this paper is to demonstrate the feasibility of using three-dimensional full assembly unsteady Reynolds-averaged Navier–Stokes (URANS) CFD for modeling surge cycles of an eight-stage high-speed compressor rig. Results from this work show stalling of the mid-stages is the surge trigger. During the flow reversal, a strong acoustic reflection occurs when the convected entropy perturbations reach the intake opening, which increase the blade loading significantly. During recovery, a hysteresis loop was recorded due to hot air re-ingestion, which led to a strong shear at mid-span of the inlet guide vane (IGV)/R1 domain and the formation of rotating helical flow structures. The final phase of recovery was accompanied by a four-cell multi-row tip rotating stall, which was cleared as the compressor recovered to the forward flow characteristic. It was also shown that the single passage model, despite its limitations and shortcomings in modeling recovery, can predict reasonably accurate transient flow features during surge and thus provide considerable insight to the flow behavior, which can be used to obtain a first approximation of casing and blade loading.
Analysis of Liner Deformation Behaviour in Transtibial Prosthesis
Authors: Regalla Srinivasa Prakash , Prashant Kirange Piyush , Dhake Harshal Vinayak , Shrivastava Prakash Narayan
Published: February 2021

The problems associated with the prostheses for transtibial amputees are related mainly to the fit and comfort. There has been a steady effort to improve the wearability, stability, and durability of the below-knee prosthesis. The liner in the below-knee prosthesis plays a crucial role in ensuring these quality characteristics. Isotropic liner material either acts hard and hence result in discomfort or deforms too much and results in eventual loosening of the prosthetic socket. The material hyper-elastic behavior and thickness are both critical in the design of the liner with optimum comfort. A generalized deformation model taking into account the interaction of the socket, liner, muscle, and tissue becomes cumbersome. In the literature, numerous hyper-elastic models have been applied. Studies on suitability and application of hyper-elastic materials for liner material has not been sufficiently carried out. In this paper, the suitability of liner materials in terms of their ability to allow sufficient elastic deformation in the normal direction for the cushioning effect while undergoing limited shear deformation has been investigated. The hyper-elastic liner and rigid socket pair have been idealized as adhesively bonded flat layers of suitable thicknesses subjected to various combinations of normal and shear loads. The deformations for a normal load and varied range of shear loads have been compared to conclude on the best-suited material model. The low shear deformation observed for all three liner materials implies that the shear loading will not affect the adhesive bond between the liner and socket and hence will not cause loosening with prolonged usage of the prosthetics. The deformation observed was maximum with Ogden 3-parameter hyper-elastic model, whereas it was least in the case when Mooney Rivlin 3-parameter hyper-elastic model. The results obtained for the Mooney-Rivlin 3-parameter model and Neo-Hookean model are very close to each other.
Effect of Metal-Composite Layer Thickness on Springback After U-Bending
Authors: Nikhare Chetan P.
Published: February 2021

A sudden increase in the usage of automotive vehicles results in sudden increases in the fuel consumption which results in an increase in air pollution. To cope up with this challenge federal government is implying the stricter environmental regulation to decrease air pollution. To save from the environmental regulation penalty vehicle industry is researching innovation which would reduce vehicle weight and decrease the fuel consumption. Thus, the innovation related to light-weighting is not only an option anymore but became a mandatory necessity to decrease fuel consumption. To achieve this target, the industry has been looking at fabricating components from high strength to ultra-high strength steels or lightweight materials. With the usage of advanced high strength steels, the lightweight was achieved by reducing a gage thickness without compromising the strength aspect. However due to their high strength property often challenges occurred are higher machine tonnage requirement, sudden fracture, geometric defect, etc. The geometric defect comes from the elastic recovery of a material, which is also known as a springback. Springback is commonly known as a manufacturing defect due to the geometric error in the part, which would not be able to fit in the assembly without secondary operation or compensation in the forming process. It is learned that the springback of the material increases with an increase in the material strength and/or decrease in material thickness. In advanced high strength steels, higher strength and lower gage thickness options make the part prone to higher springback. Due to these many challenges, other research route involved is composite material, where light materials can be used with high strength material to reduce the overall vehicle weight. This generally includes, tailor welded blanks, multilayer material, mechanical joining of dissimilar material, etc. Due to substantial use of dissimilar materials, these parts are also called as hybrid components. It was noted that the part weight decreases with the use of hybrid components without compromising the integrity and safety. In the previously published paper in IMECE2017 the study was focused on equal layer thickness of metal and composite in bilayer material. In this paper, a springback analysis was performed considering bilayer metal by varying the thickness of the metal as well as the composite. For this two dissimilar materials aluminum and composite was considered as bonded material. This material was then bent on a free bend die. The bilayer springback was compared with different layer thickness of metal and composite and in different condition like aluminum layer on punch side and then on die side. These results were then compared with the baseline springback of only aluminum thin and thick layer.
Force Controlled Electrical Pulse Assisted Forming
Authors: Grimm Tyler J. , Deshpande Amit B. , Mears Laine , Hu Jianxun
Published: February 2021

Electrically-assisted manufacturing refers to the direct application of electrical current to a workpiece during a manufacturing process. This assistance results in several benefits such as flow stress reduction, increased elongation, reduced springback, increased diffusion, and increased precipitation control. These effects are also associated with traditional thermal assistance. However, for over half a decade it has been argued whether or not these observed effects are due to electroplasticity, a term which describes effects that cannot be fully explained through resistive heating. Several theories have been proposed as to the mechanism responsible for these purported athermal effects. Conflicting results within literature have enabled this debate over electroplasticity since its discovery in the mid 20th century.

While the effects of electrically-assisted manufacturing are clearly characterized throughout literature, there is a lack of research related to control systems which may be used to take advantage of its effects. Typically, control systems are developed using an empirical approach, requiring extensive testing in order to fully characterize the stress-strain behavior at all conditions. Additionally, current research has primarily focused on reducing flow stresses during electrically-assisted processes without regard for the strength of the material subsequent to forming. Therefore, there is a strong need for a control system which can quickly be deployed for new materials and does not significantly reduce the subsequent strength of the material.

Herein, a novel control approach is developed in which electrical pulses are triggered by a predetermined stress level. This stress value would be set according to the manufacturer’s stamping die strength. Once the material reaches this stress value, current is deployed until a minimum stress level is reached. At that point, the electricity is turned off and the material allowed to cool; at that stage the stress begins to elevate and the cycle continues. This approach does not require extensive pre-testing and is robust to a range of strain rate. This type of implementation can also be adapted to different levels of capability. For example, since the current is controlled by force and not by time, a low-current power supply will stay on for each pulse longer than a power supply with higher capabilities; however, each will achieve a similar effect. This study investigates the effect of several different minimum stress levels and strain rates. The strain rates chosen are relatively similar to common stamping process. This system was experimentally tested using 1018 CR steel. This control approach was found to be a successful method of maintaining a desired stress level.
Displacement of the Residual Limb Within Transfemoral Sockets: A Literature Review
Authors: Salazar-Salgado Sara , Rendón-Vélez Elizabeth
Published: February 2021

According to the World Health Organization and the International Society for Prosthetics and Orthotics, between 0.5 to 0.8 percent of the global population has suffered limb amputations. In the last years, Colombia, Angola, Afghanistan, and Chechenia are the countries that have held the first places with the highest amount of landmine victims. In Colombia, this weapon has left more than 10.000 affected people, many of which have suffered traumatic lower limb amputation To recover some of the lost function, amputees are generally prescribed with a prosthesis. However, the adaptation of the user with this element depends on the comfort felt when using it and consequently, on the fit between the socket and the residual limb. The fit between these two elements is highly influenced by the relative motion between them (i.e. displacement, slip). Both excess of displacement or complete absence, have several negative consequences for the amputee. Thus, measuring displacement could be an important indicator of the quality of the socket and the suspension system, and could provide critical information to improve surgical interventions, the prescription of prosthetic elements and the design and development of new prosthetic components. Several authors have investigated this topic; however, the studies have been mostly conducted on transtibial amputees. Therefore, this review aims to summarize the gathered information about the displacement between the socket and residual limb in transfemoral amputees.

A computer-aided systematic literature search was performed by two independent reviewers using three databases. The selected papers were evaluated with regards to: sample characteristics, displacement measurement instrument, measured activity, displacement axis, surfaces in contact, type of socket and type of suspension system used.

Most of the studies were performed on less than five individuals with mature residual limbs and trauma caused amputation. The most common aspects of displacement were: imaging techniques (measurement instrument), gait (measured activity), vertical direction (displacement axis), bone/socket (surfaces in contact), quadrilateral (type of socket) and suction-based (suspension system).

The optimal range of motion is still unknown for transfemoral amputees. A marker-based optical tracking system is promising for research purposes, while electronic sensors would be optimal for clinical use. Volume change may be an indirect and, more straightforward option to measure displacement. Further research is needed to determine the effect of using a modified socket, to find a way to measure relative motion inside the socket using marker-based optical tracking systems and to define the influence of subject-specific characteristics in the amount of displacement. A better understanding of what happens inside the socket helps to optimize prosthetic designs and to improve the amputee’s quality of life.
Effect of the Number of Stages on the Performance of Savonius Vertical Axis Wind Turbines: Part I — Using Straight Semicircular Blades
Authors: Saad Ahmed S. , Ookawara Shinichi , Elwardany Ahmed , El-Sharkawy Ibrahim I. , Ahmed Mahmoud
Published: February 2021

The Savonius vertical axis wind turbine offers several benefits as simple construction, low manufacturing, installation and maintenance costs, low operating wind speed, and independence of wind direction. However, the conventional single-stage Savonius rotors have negative torque values at a certain range of rotor angles and large torque variation over the complete cycle which led to reduction of the power coefficient and the self-starting abilities. To overcome these drawbacks, a multi-stage Savonius wind rotor is proposed to obtain the optimum number of stages that enhances both the power coefficient and the self-starting capabilities. In the current study, one-, two-, three-, and four-stage Savonius wind rotors with straight semicircular blades are investigated. In two stages rotor, one single-stage rotor is mounted over another single stage with a phase shift of 90°. In the three stages rotor, the three singlestage rotors are mounted one above the other with a phase shift of 60° relative to one another while with a phase shift of 45° for the four stages. All rotors have overall rotor diameter (D) of 200 mm, a thickness of 2 mm, a stage aspect ratio of 1.0, and an overlap ratio (δ) of 0.0. The diameter of the circular end plates (Do) attached to the rotor tips is 1.1 of the rotor diameter (D). All studies are performed at a wind speed (V) of 6 m/s.

The variations of torque and power coefficients are estimated for all the studied multi-stages rotors. Therefore, 3D incompressible unsteady Reynolds-Averaged Navier-Stokes equations along with the k-ω shear-stress transport turbulence model is developed and numerically simulated using ANSYS Fluent. The numerical model is validated using the available measurements and numerical results.

The predicted flow field characteristics such as streamlines and pressure fields around the studied rotors with various numbers of stages are presented and analyzed. Accordingly, results indicated that with the increase in the number of stages, a significant enhancement of the torque and the power coefficients is attained. In addition, the rate of percentage gain in the torque and the power coefficients is higher for two stages rotor than that of three and four stages rotors. The maximum torque and power coefficients for the two stages rotor are 0.336 and 0.194, respectively. The power coefficient gain obtained by using the two stages Savonius rotor is 17.5 % compared to the conventional single stage which has a power coefficient of 0.165 at a wind velocity (V) of 6 m/s. Furthermore, using a multi-stage rotor significantly smooths the variations in the torque coefficient and produces positive static torque values at all rotational angles resulted in enhancing the self-starting capabilities of the Savonius rotor.
Investigating the Sensitivity of Particle Size Distribution on Part Geometry in Additive Manufacturing
Authors: Ramesh Sagar Vaishak , Lorin Samuel , Göhl Johan , Quist Johannes , Cromvik Christoffer , Mark Andreas , Jareteg Klas , Edelvik Fredrik , Wärmefjord Kristina , Söderberg Rikard
Published: February 2021

Selective laser melting process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the end product. This paper investigates the effect of PSD on deformation for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder distribution based on the different particle size distribution of the powder. The CFD is used as a virtual test bed to determine thermal parameters such as density, heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to test the sensitivity of the melted zone and distortion using Structural Mechanics. Results showed significant influence of particle size distribution on the packing density, surface height, surface roughness, the stress state and displacement of the melted zone. The results will serve as a catalyst in developing geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.