bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and properties of wear‐resistant carbonized‐ceramic composite coating on pure aluminum surface
Authors: Shao Zhonglei , Chen Lu , Lu Hailin , Fan Fulin
Published: September 2022

In this paper, a new composite coating was prepared on the surface of pure aluminum (Al) by combining the micro‐arc oxidation (MAO) technology with the polyethylene glycol (PEG 400) carbonization technology. The composite coating and the single MAO coating were observed by a scanning electron microscope, and an energy‐dispersive spectrometer, finding that the single MAO coating surface with volcano‐like pores and microcracks, was covered by the carbonized layer of the composite coating where the overall coating thickness was around 19.5 µm, including 17.5 µm of inner MAO coating. The material properties of the composite coating were characterized by X‐ray diffraction and X‐ray photoelectron spectroscopy. The wear resistance of the composite coating was tested under dry friction conditions, finding that the wear width on the composite coating surface was 909.6 µm only, which was around 55.7%, 50.4%, and 58.2% of those for pure Al substrate, single carbonized coating, and single MAO coating, respectively. Then the comprehensive wear resistance of the composite coating was explored under different sliding speeds and lubrication mediums. Finally, the wear‐resisting mechanism of the composite coating was discussed, concluding that the composite coating could effectively reduce adhesive wear and abrasive wear of the Al substrate.
The effects of assessment design on academic dishonesty, learner engagement, and certification rates in MOOCs
Authors: Alexandron Giora , Wiltrout Mary Ellen , Berg Aviram , Gershon Sa'ar Karp , Ruipérez‐Valiente José A.
Published: September 2022

Background

Massive Open Online Courses (MOOCs) have touted the idea of democratizing education, but soon enough, this utopian idea collided with the reality of finding sustainable business models. In addition, the promise of harnessing interactive and social web technologies to promote meaningful learning was only partially successful. And finally, studies demonstrated that many learners exploit the anonymity and feedback to earn certificates unethically. Thus, establishing MOOC pedagogical models that balance open access, meaningful learning, and trustworthy assessment remains a challenge that is crucial for the field to achieve its goals.

Objectives

This study analysed the influence of an MOOC assessment model, denoted the Competency Exam (CE), on learner engagement, the level of cheating, and certification rates. At its core, this model separates learning from for‐credit assessment, and it was introduced by the MITx Biology course team in 2016.

Methods

We applied a learning analytics methodology to the clickstream data of the verified learners (N = 559) from four consecutive runs of an Introductory Biology MOOC offered through edX. The analysis used novel algorithms for measuring the level of cheating and learner engagement, which were developed in the previous studies.

Results and Conclusions

On the positive side, the CE model reduced cheating and did not reduce learner engagement with the main learning materials – videos and formative assessment items. On the negative side, it led to procrastination, and certification rates were lower.

Implications

First, the results shed light on the fundamental connection between incentive design and learner behaviour. Second, the CE provides MOOC designers with an ‘analytically verified’ model to reduce cheating without compromising on open access. Third, our methodology provides a novel means for measuring cheating and learner engagement in MOOCs.
The H3K9me2‐binding protein AGDP3 limits DNA methylation and transcriptional gene silencing in Arabidopsis
Authors: Zhou Xuelin , Wei Mengwei , Nie Wenfeng , Xi Yue , Peng Li , Zheng Qijie , Tang Kai , Satheesh Viswanathan , Wang Yuhua , Luo Jinyan , Du Xuan , Liu Rui , Yang Zhenlin , La Honggui , Zhong Yingli , Yang Yu , Zhu Jian‐Kang , Du Jiamu , Lei Mingguang
Published: September 2022

DNA methylation, a conserved epigenetic mark, is critical for tuning temporal and spatial gene expression. The Arabidopsis thaliana DNA glycosylase/lyase REPRESSOR OF SILENCING 1 (ROS1) initiates active DNA demethylation and is required to prevent DNA hypermethylation at thousands of genomic loci. However, how ROS1 is recruited to specific loci is not well understood. Here, we report the discovery of Arabidopsis AGENET Domain Containing Protein 3 (AGDP3) as a cellular factor that is required to prevent gene silencing and DNA hypermethylation. AGDP3 binds to H3K9me2 marks in its target DNA via its AGD12 cassette. Analysis of the crystal structure of the AGD12 cassette of AGDP3 in complex with an H3K9me2 peptide revealed that dimethylated H3K9 and unmodified H3K4 are specifically anchored into two different surface pockets. A histidine residue located in the methyllysine binding aromatic cage provides AGDP3 with pH‐dependent H3K9me2 binding capacity. Our results uncover a molecular mechanism for the regulation of DNA demethylation by the gene silencing mark H3K9me2.
Construction and validation of Rejection Sensitive Expectation, Perception, and Reaction Questionnaire—Partner (RSEPR‐P)
Authors: Natarajan Gitanjali , Prasad Aswathi
Published: September 2022

The Rejection Sensitive Expectation, Perception, and Reaction Questionnaire—Partner (RSEPR‐P) was developed to assess rejection expectation, perception of rejection, and reactions to perceived rejection among intimate partners. This article details the construction and validation procedures, including item pool generation, factor analysis, and the estimation of reliability and validity. The researchers examined the psychometric properties of RSEPR‐P in a community sample of 151 participants. Confirmatory factor analysis (CFA) with the final 24 items suggested four‐factor loading with each subscale loading on a separate factor. The subscales had good to excellent internal consistency. In support of the convergent validity, RSEPR‐P exhibited robust correlations with rejection sensitivity‐personal, mindfulness, marital adjustment, and self‐esteem measures. A 6‐month test–retest reliability was established. RSEPR‐P is proposed to have potential therapeutic and research utility.
Differences by sexual orientation in romantic relationship attitudes and skills among adolescents
Authors: Perry Nicholas S. , Huntington Charlie , Rhoades Galena K.
Published: September 2022

Objective

This study examined differences by sexual orientation in romantic relationship and marriage attitudes, and relationship skills, among a large, diverse sample of high school youth.

Background

The romantic relationships of sexual minority youth have been understudied, particularly factors related to their relationship quality, such as attitudes and skills. Sweeping changes in social and legal equality (e.g., same‐sex marriage) have promoted a paradigm shift in relationship possibilities for sexual minority youth.

Methods

Data were drawn from the baseline survey of a study of school‐based relationship education for adolescents. Adolescents (N = 979) completed a self‐report survey of their demographics, attitudes regarding romantic relationships and marriage, and their romantic relationship skills. Regression models examined differences by sexual orientation identity in relationship outcomes, controlling for relevant demographics.

Results

Sixteen percent of youth identified as sexual minority. Sexual minority youth, relative to heterosexual youth, did not differ in their attitudes regarding qualities of healthy romantic relationships. However, sexual minority youth endorsed less traditional views of marriage and held less traditional expectations of marriage for themselves. They also perceived themselves to have fewer romantic relationship skills than heterosexual youth.

Conclusions

Today's sexual minority youth hold less traditional views of marriage as a future for themselves, although legalized same‐sex marriage is now available. They perceived themselves as less skilled in romantic relationships, which are critical in adolescence for social and emotional development. Scientific efforts are needed to understand contributors to these differences and inform evidence‐based practices to support strong, healthy romantic bonds for all teens.
Digital gravity? Firm birth and relocation patterns of young digital firms in Germany
Authors: Hellwig Vanessa
Published: September 2022

This paper analyses the spatial patterns of young (<10 years) digital firms in Germany between 2008 and 2017 on county level. Determinants of firm birth locations as well as relocations are considered jointly to understand differences in location choices within firms' life cycles. I match commercial register data of 107,321 firms with county‐level administrative data to capture local characteristics. Using an OLS model with fixed effects, I find that the local knowledge base—that is, universities, research institutes, and colocated incumbents—are significant key determinants of digital firm birth when controlling for a host of local characteristics. My results indicate that for five firms per 1000 inhabitants, there is around one firm birth. Second, using a fixed effects gravity model for the analysis of relocations, I find that the most dominant explanatory factor for firm relocation across specifications is distance, that is, relocation costs. Relocation flows are more than twice as high to neighboring counties relative to other locations which shows that digital firms are not as footloose as their business model may suggest. Jointly, my results reflect economic activity's regional persistence, particularly for new firms. My paper provides evidence for policies targeting homogenous digital clusters based on strong colocation and that digital economic activity is not shifted over long distances, but the regional entrepreneurship capital is crucial for local growth.
Strategic climate policy with endogenous plant location: The role of border carbon adjustments
Authors: Elboghdadly Noha , Finus Michael
Published: September 2022

Carbon leakage and the relocation of firms is one of the main concerns of governments when choosing their climate policy. In a strategic trade model with endogenous plant location, we study the effect of border carbon adjustments (BCAs) on global welfare and emissions in an emission tax competition game between two asymmetric countries for two games: a simultaneous and a sequential game. Without BCAs, a ruinous “race to the bottom” with no relocation of firms is the only Nash equilibrium in a simultaneous game. In a sequential game, additionally, a “wise chicken” equilibrium may emerge where the Stackelberg leader gives in, letting all his/her plants relocate to avoid being stuck at the bottom. With BCAs, equilibrium emission taxes in both countries are higher, implying lower global emissions and usually higher global welfare in both games. With BCAs, the environmental more concerned country accepts that its firm partially relocates abroad, as it is rewarded with better control of global emissions, tariff revenues and higher net profits (profits minus taxes). This avoids high environmental damages and that either net profits are zero because of high subsidy levels in a “race to the bottom” or because all production plants have moved abroad.
Effect of relative humidity, storage days, and packaging on pecan kernel texture: Analyses and modeling
Authors: Prabhakar Himanshu , Kerr William L. , Bock Clive H. , Kong Fanbin
Published: September 2022

The studies expounding on the effects of storage conditions on texture changes are limited. The researchers have been proposing methods to measure pecan texture instrumentally. But current protocols and/or attributes fail to address huge variability during experimentation. Additionally, there are no predictive models to estimate changes in pecan texture during storage. This study addresses all the above concerns and investigates the effects of different relative humidity (RH, 30–90%) and packaging material (Polyethylene‐Nylon [PEN], polypropylene [PP], low density polyethylene [LDPE], and metallic laminates [ML]) on pecan texture, introducing a rift ratio (F/H or fracturability to hardness ratio) to address variability in the data and predictive model to estimate changes in the textural attribute of pecans during storage. The textural analysis was conducted on pecan cores and intact pecans to measure the area under curve, fracturability, hardness, cohesiveness, chewiness, springiness, and rift ratio. It was observed that values for the rift ratio obtained using the intact pecan method had high R2 (0.72) as compared to the rest of the textural attributes. A three‐parameter logistic model was employed to predict pecan texture during storage. The pecans stored at 75, 80, and 90% reached the rift ratio (F/H) of 0.5 at approx. 115, 3, and 0.15 days (~ 4 hr), respectively. Similarly, pecans stored in LDPE, PP, and PEN packs at 80% reached rift ratio (F/H) of 0.5 at approx. 26, 57, and 78 days, respectively. The presence of any kind of package delayed fracturability loss by at least eight folds at 80% RH. The pecans stored in ML did not experience a significant change in textural attributes
The influence of household structure and composition on the introduction of solid, semisolid and soft foods among children aged 6–8 months: An analysis based on Ethiopia Demographic and Health Surveys
Authors: Irenso Asnake Ararsa , Zheng Miaobing , Campbell Karen J. , Chamberlain Dan , Laws Rachel
Published: September 2022

The early and late introduction of complementary food, both prevalent in Ethiopia, are associated with morbidities, growth faltering and developmental risks in children. The interhousehold network around the primary caregiver's intrahousehold network is critical in influencing the age of introducing complementary foods. This study examined the influence of household composition and structures on complementary food introduction. This is a secondary data analysis of four Ethiopian Demographic and Health Surveys conducted between 2000 and 2016. The household structure and composition variables were calculated from household members' kinship status and attribute, respectively. The introduction of solid, semisolid or soft foods was dichotomised as whether the children within 6 to 8 months have been given complementary foods. Multivariable logistic regression with adjustment for the primary caregiver and household characteristics was run to examine the associations between household structure and composition variables and the introduction of complementary foods. The marginal effects (ME) were calculated to facilitate the practical interpretation of the study findings. Large households (>3 nonredundant contacts) with extended family or unrelated people (high effective size, ME = 6.01%, 95% confidence interval [CI]: −8.53, −3.49) lowered the proportion of children starting food within the recommended 6–8 months. Households with close kins (high constraint) (ME = 7.22%, 95% CI: −13.65, 28.09) and greater age diversity (ME = 0.65%, 95% CI: 0.15, 1.15) increased the proportion of children receiving complementary food at an appropriate age. This study revealed that interhousehold structure and composition influence the age of introduction of complementary foods. These factors, therefore, need to be considered in designing interventions to improve age at the introduction of complementary foods.
Remote sensing and field information aid in predicting the presence of the terrestrial orchidCyclopogon luteo‐albus
Authors: Díaz‐Toribio Milton H. , Flores‐Palacios Alejandro , Pérez Maqueo Octavio , Lira‐Noriega Andrés , García‐Franco José G.
Published: September 2022

Tropical montane cloud forest is one of the most threatened ecosystems, in central Veracruz, Mexico. Within this ecosystem, terrestrial orchids are strongly dependent on forest conditions and may be sensitive to environmental change. We applied field surveys of abiotic and biotic factors associated with the presence of the terrestrial orchidCyclopogon luteo‐albusand combined this with correlative niche modeling approaches to evaluate its potential distribution under two different environmental sets and two different extents. Layers of environmental information were obtained from Landsat imagery and interpolated bioclimatic and soil property layers. Existing species records were used as training data by sampling five forest fragments in central Veracruz, utilizing herbarium and global biodiversity information facility databases. The resulting predictions were tested by sampling at 15 sites of potential distribution. The model predicted the presence ofC. luteo‐albuswith a reliability of 80%. The most important variables of models derived from interpolated layers coincide with site‐relevant parameters suggesting the utility of these tools to further explore species suitabilities at larger geographic extents. Potential distribution mapping is an important tool to identify key areas for conservation and priority areas for future studies of species and partially resolves the lack of records of many orchid species.
Cell‐intrinsic melanin fails to protect melanocytes from ultraviolet‐mutagenesis in the absence of epidermal melanin
Authors: Weiss Tirzah J. , Crawford Emma R. , Posada Valentina , Rahman Hafeez , Liu Tong , Murphy Brandon M. , Arnold Tiffany E. , Gray Shannon , Hu Zhexuan , Hennessey Rebecca C. , Yu Lianbo , D'Orazio John A. , Burd Craig J. , Zippin Jonathan H. , Grossman Douglas , Burd Christin E.
Published: September 2022

Melanin is a free‐radical scavenger, antioxidant, and broadband absorber of ultraviolet (UV) radiation which protects the skin from environmental carcinogenesis. However, melanin synthesis and UV‐induced reactive melanin species are also implicated in melanocyte genotoxicity. Here, we attempted to reconcile these disparate functions of melanin using a UVB‐sensitive, NRAS‐mutant mouse model, TpN. We crossed TpN mice heterozygous for an inactivating mutation in Tyrosinase to produce albino and black littermates on a C57BL/6J background. These animals were then exposed to a single UVB dose on postnatal day three when keratinocytes in the skin have yet to be melanized. Approximately one‐third (35%) of black mice were protected from UVB‐accelerated tumor formation. However, melanoma growth rates, tumor mutational burdens, and gene expression profiles were similar in melanomas from black and albino mice. Skin from albino mice contained more cyclobutane pyrimidine dimer (CPD) positive cells than black mice 1‐h post‐irradiation. However, this trend gradually reversed over time with CPDs becoming more prominent in black than albino melanocytes at 48 h. These results show that in the absence of epidermal pigmentation, melanocytic melanin limits the tumorigenic effects of acute UV exposure but fails to protect melanocytes from UVB‐induced mutagenesis.
Neurological post‐acute sequelae of SARS‐CoV‐2 infection
Authors: Takao Masaki , Ohira Masayuki
Published: September 2022

The novel coronavirus disease 19 (COVID‐19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), can have two phases: acute (generally 4 weeks after onset) and chronic (>4 weeks after onset). Both phases include a wide variety of signs and symptoms including neurological and psychiatric symptoms. The signs and symptoms that are considered sequelae of COVID‐19 are termed post‐COVID condition, long COVID‐19, and post‐acute sequelae of SARS‐CoV‐2 infection (PASC). PASC symptoms include fatigue, dyspnea, palpitation, dysosmia, subfever, hypertension, alopecia, sleep problems, loss of concentration, amnesia, numbness, pain, gastrointestinal symptoms, depression, and anxiety. Because the specific pathophysiology of PASC has not yet been clarified, there are no definite criteria of the condition, hence the World Health Organization's definition is quite broad. Consequently, it is difficult to correctly diagnose PASC. Approximately 50% of patients may show at least one PASC symptom up to 12 months after COVID‐19 infection; however, the exact prevalence of PASC has not been determined. Despite extensive research in progress worldwide, there are currently no clear diagnostic methodologies or treatments for PASC. In this review, we discuss the currently available information on PASC and highlight the neurological sequelae of COVID‐19 infection. Furthermore, we provide clinical suggestions for diagnosing and caring for patients with PASC based on our outpatient clinic experience.
The legal components of benefit‐sharing in transboundary watercourses: An analysis of China's approach
Authors: Huang Xisheng , Devlaeminck David J.
Published: September 2022

Transboundary water resources are governed under the rules of equitable and reasonable utilization and the due diligence obligation not to cause significant harm, widely recognized as customary international law. In meeting their obligations, States could allocate water resources between riparian States, but they may also share the benefits of utilization. Although not well defined, benefit‐sharing has received significant attention around the world, particularly in China, a primarily upstream State that prefers bilateral agreements and soft law instruments. This article explores benefit‐sharing through its base legal components, analysing China's transboundary water treaties and instruments to determine if they can act as a foundation for benefit‐sharing, while drawing out lessons for implementing benefit‐sharing globally.
Application of mevalonolactone prevents deterioration of epidermal barrier function by accelerating the lamellar granule lipid transport system
Authors: Chen Bin , Lu Nan , Lee KeeSuh , Ye Lei , Hasegawa Chiho , Maeda Kazuhisa
Published: September 2022

Background

Fatty acids increase ATP‐binding cassette ABC transporter A12 (ABCA12) levels via an increase in peroxisome proliferator‐activated receptor β/δ (PPAR β/δ). Promoting lipid transport to lamellar granules has been suggested to improve epidermal barrier function in patients with dry skin.

Objective

We investigated whether mevalonolactone (MVL) produced by Saccharomycopsis fibuligera improves dry skin by promoting ABCA12 expression and the amount of free fatty acids in epidermal keratinocytes.

Methods

We examined whether MVL increases ABCA12 mRNA and protein levels and the amount of Nile red‐positive lipids in cultured epidermal keratinocytes and in a three‐dimensional epidermal model by cell staining. Promotion of fatty acid production by MVL was analyzed by liquid chromatography‐mass spectrometry. We also evaluated whether MVL addition increases PPAR β/δ mRNA expression in cultured keratinocytes. Based on the results, a randomized controlled trial was conducted in which milky lotions containing MVL and placebo were applied to dry facial skin of healthy female volunteers in winter.

Results

MVL increased ABCA12 mRNA and protein levels and lamellar granule number and size. Fatty acid analysis revealed that MVL elevated myristic acid, palmitic acid, and palmitoleic acid levels as well as PPAR β/δ mRNA expression. In human tests, milky lotions containing MVL were shown to significantly improve transepidermal water loss (TEWL) in the stratum corneum compared to placebo.

Conclusion

The results suggest that MVL increases fatty acid uptake and ABCA12, promotes fatty acid transport to lamellar granules, and improves epidermal barrier function in dry skin through increased expression of PPAR β/δ.
The curse of knowledge when teaching statistics
Authors: Shatz Itamar
Published: September 2022

When teaching statistics, educators sometimes overestimate their students' knowledge and abilities. This is due to the curse of knowledge, a cognitive bias that causes people—especially experts—to overestimate how likely others are to know and understand the same things as them. This can lead to various issues, including struggling to communicate with students, and making students feel less comfortable in the classroom. To address this, educators should first identify situations where this bias can affect their teaching. In doing so, they should consider relevant risk factors, and potentially also solicit feedback from relevant individuals. Then, educators can reduce this bias and its impact on their teaching by using techniques such as keeping the curse of knowledge and their audience in mind, assessing students' knowledge, assuming lack of knowledge unless there is strong evidence to the contrary, and avoiding saying that things are obvious.
Automated preparation of washed platelet concentrates through spinning‐membrane filtration
Authors: Mitsuhashi Hisako , Ochi Yosuke , Fuchizaki Akihiro , Ooba Ryuunosuke , Hayashi Tomoya , Horie Yoshinori , Kawamura Tomoko , Tanaka Mitsunobu , Takihara Yoshihiro , Shimogaki Kazushige , Kimura Takafumi
Published: September 2022

Background

Washed platelet concentrates (WPC), prepared with an automated system cell processor (ACP), have recently been approved to be manufactured and marketed in Japan. From the perspective of risk management, it is preferable to secure alternative technologies for ACP. Here, we conducted a study to evaluate the quality of WPC prepared using an automated membrane filtration‐based system, Lovo.

Study design and methods

Replaced PCs prepared from apheresis PCs were equally divided into control and test units, and subsequently washed using ACP and Lovo respectively. Work and operational efficiencies were evaluated by in vitro analyses, including total handling time, platelet recovery, and plasma protein removal rate. Product quality, including a set of biochemical and physiological indicators of platelets and supernatants, were assessed before and 3 days after washing.

Results

In vitro platelet recovery rates and plasma protein removal rates were >85% and >95%, respectively, in both groups. The pH values on day 0 were significantly high (6.97 vs. 6.86) due to low pCO2 in the test group, while no significant differences in glucose consumption and lactate production were observed between the two groups. The levels of hypotonic shock responses, aggregation response, platelet shape, CD62P expression, and sCD62P concentration were similar in both groups during the 3‐day storage period.

Conclusion

Platelet washing with Lovo provides platelet quality equivalent to, or better than, conventional washing with ACP. Thus, the new automated system, Lovo, can be considered as an alternative to ACP for WPC preparation.
THE STEREO‐SPECIFICITY AND TEMPERATURE‐DEPENDENCE OF THE PERMEABILITY OF HUMAN ERYTHROCYTES TO ALDOSES
Authors: Fisher R. B. , Nimmo I. A.
Published: September 2022

Time‐courses have been determined between 2·0°C and 25·5°C for the uptake of D(+) glucose, D(+) xylose and L(+) arabinose by human erythrocytes. They can be explained by assuming uptake is governed by a mobile carrier of the Widdas type. Since at any temperature the three aldoses have the same maximum rate of permeation but different half‐saturation concentrations for the carrier, it is argued that they have a common carrier, and that the rate‐limiting step in permeation is the translocation across the membrane of the carrier or carrier‐aldose complex. Data are also given which suggest that α‐ and β‐glucose have different half‐saturation concentrations for the carrier.
THE ACTION OF GASTRIN AND CHOLECYSTOKININ‐RELATED PEPTIDES ON PANCREATIC SECRETION IN THE RAT
Authors: Dockary G. J.
Published: September 2022

The responses of the rat pancreas to porcine gastrins I and II and to six synthetic peptides, with structures related to gastrin and cholecystokinin, have been studied. All the peptides stimulated both the rate of flow and rate of protein secretion from the pancreas. The observed and the calculated maximal responses to gastrins I and II, and to pentagastrin and the C‐terminal octapeptide of cholecystokinin, were similar. There were, however, marked differences in potency between the various peptides. Those peptides in which the tyrosine residue was sulphated and was at position 7 from the C‐terminus were considerably more potent in stimulating both flow and protein responses of the pancreas, than those peptides in which the tyrosine was either absent, unsulphated, or at position 6 from the C‐terminus.
THE BLOOD VOLUMES OF FETAL AND NEWBORN SHEEP
Authors: Pipkin Fiona Broughton , Margaret S. , Kirkpatrick L.
Published: September 2022

Blood volumes were measured in fetal and newborn lambs using 51Cr tagged red cells. Absolute blood volume was strongly correlated with body weight in both groups. Gestation age was also a highly significant determinant of absolute blood volume in fetuses. Since body weight at a given gestation age in sheep was significantly influenced by the size of the breed concemed, all three variables (breed, gestation age and body weight) should be taken into account when considering fetoplacental blood volumes.
Unsteady Investigation of the Effect of Purge Air on the Flow Field Inside a Turbine Vane Frame Using Particle Image Velocimetry
Authors: Schien Malte , Hafizovic Asim , Planck Florian , Merli Filippo , Woisetschläger Jakob , Göttlich Emil
Published: September 2022

Reducing greenhouse gas emissions and high fuel expenses motivates manufacturers to design more efficient aircraft engines. For directly driven jet engines, this is possible through increased by-pass ratios for high propulsive efficiencies. This implies a change in the operating condition of the low-pressure turbine (LPT) toward lower rotational speeds at larger diameters. Turbine vane frames (TVFs) guide the airflow from the high-pressure turbine (HPT) to the LPT in radial and circumferential direction. The TVF setup integrates turning vanes and thus removes the need for a vane blade row in the first LPT stage. Consequently, the TVF yields a benefit for overall engine weight and length, resulting in overall efficiency gains. Experimental measurements have been conducted at the two-spool test rig at the Graz University of Technology, consisting of a single-stage HPT, the TVF, and the first LPT rotor. Engine-relevant flow conditions are achieved at the TVF inlet, including HPT tip clearance and purge air effects. Particle image velocimetry (PIV) was used to capture the flow field in between two struts of the TVF upstream of the splitter vanes. Flow data in the area of strong transient interactions between the HPT and the TVF are recorded and discussed in terms of aerodynamic performance. To reveal the unsteady behavior of the fluid, the flow field has been recorded at six serial stator–rotor positions. Two data sets of varying HPT purge flows were obtained to characterize the effect of purge air inside the measurement domain.
Processing Multicomponent Blade Tip Timing Experimental Data by Independent Component Analysis
Authors: Rizzetto Elena , Carassale Luigi
Published: September 2022

Blade tip timing (BTT) is a simple, robust, and nonintrusive method for measuring the rotor blade vibrations in turbomachinery. Using this method, the analysis of vibrations characterized by multiple spectral components typical, for example, of flutter is challenging. This chapter proposes a probabilistic method able to separate and identify multiple harmonic components sampled according to a BTT-like schema. The data are divided into batches of fixed length called snapshots, which are interpreted as realization of random vectors. The statistical properties of the subspace spanned by such random vectors is used to identify the number of components present in the signal (i.e., number of active modes), to separate the components and estimate their frequency and amplitude. These results are obtained by applying sequentially the principal component analysis (PCA), the independent component analysis (ICA), and the harmonic matching (HM). The proposed technique is applied to experimental data obtained from a test rig with fixed disk and traveling load. The time-resolved measurements are resampled according to the sampling pattern induced by specified sensor spacing.
Viscoelastic Properties of Bioprinted Alginate Microbeads Compared to Their Bulk Hydrogel Analogs
Authors: Roberge Cassandra L. , Kingsley David M. , Cornely Lexie R. , Spain Connor J. , Fortin Aiyana G. , Corr David T.
Published: September 2022

Hydrogel microbeads are engineered spherical microgels widely used for biomedical applications in cell cultures, tissue engineering, and drug delivery. Their mechanical and physical properties (i.e., modulus, porosity, diffusion) heavily influence their utility by affecting encapsulated cellular behavior, biopayload elution kinetics, and stability for longer term cultures. There is a need to quantify these properties to guide microbead design for effective application. However, there are few techniques with the μN-level resolution required to evaluate these relatively small, compliant constructs. To circumvent mechanically testing individual microbeads, researchers often approximate microbead properties by characterizing larger bulk gel analogs of the same material formulation. This approach provides some insight into the hydrogel properties. However, bulk gels possess key structural and mechanical differences compared to their microbead equivalents, which may limit their accuracy and utility as analogs for estimating microbead properties. Herein, we explore how microbead properties are influenced by hydrogel formulation (i.e., alginate concentration, divalent cation crosslinker, and crosslinker concentration), and whether these trends are accurately reflected in bulk gel analogs. To accomplish this, we utilize laser direct-write bioprinting to create 12 × 12 arrays of alginate microbeads and characterize all 144 microbeads in parallel using a commercially available microcompression system. In this way, the compressive load is distributed across a large number of beads, thus amplifying sample signal. Comparing microbead properties to those of their bulk gel analogs, we found that their trends in modulus, porosity, and diffusion with hydrogel formulation are consistent, yet bulk gels exhibit significant discrepancies in their measured values.
Comparing Instrumentation Selection Techniques for Vibration Testing
Authors: Khan Moheimin , Wilbanks Justin , Smith Chandler , Walsh Timothy , Owens Brian
Published: September 2022

Vibration testing of complex aerospace structures requires substantial pretest planning. Ground and flight testing of structures can be costly to execute in terms of time and money, so it is pertinent that tests are properly set up to capture mode shapes or dynamics of interest. One of the most important planning tasks is the placement of sensors to acquire measurements for control and characterization of the results. In this paper, we will examine two techniques that can leverage available output from finite element modeling to intelligently place accelerometers for a vibration test to capture the structural dynamics throughout a specified frequency range with a data acquisition channel budget. These two techniques are effective independence (EI) and optimal experimental design (OED). Both methods will be applied to an aerospace structure. Effects of the chosen sets on system equivalent reduction and expansion process (SEREP) are detailed alongside simpler comparison metrics, like the auto-modal assurance criterion (auto-MAC). In addition to comparing the resulting instrumentation sets, the application of the two approaches will be compared in terms of the inputs required, the information obtained from their application, and the computation time requirements. Both OED and EI offer an effective method for selecting an instrumentation set for a given vibration test. EI is a straightforward, computationally inexpensive approach that provides effective instrumentation sets. OED provides an effective alternative that is less sensitive to the impact of local modes and leads to a natural ranking of importance for each chosen degree-of-freedom (DOF).
The Characteristics of a Novel After-Burner Used for Metal-Supported Planar SOFC System
Authors: Li Siyuan , Zhang Zhe , Li Guoxiang , Bai Shuzhan
Published: September 2022

A novel after-burner used for the heat-up and normal operating conditions of a metal-supported planar solid oxide fuel cell (SOFC) system, is designed and experimentally studied in this paper. The burner construction and the calculation of maximum burner power are shown in detail. Meanwhile, its static characteristics are researched through the influence of excess air ratio (ER), air velocity, inlet air temperature, and fuel utilization rate (Uf) and its transient characteristics are researched through the processes of burner start-up, burner operating state switch, and stack start-up. The results suggest that the best ER value gets larger with the increased burner power. The air velocity is better controlled within 3 m/s to prevent the influence of a lifted flame. High inlet air temperature can extend the lean combustion range and reduces incomplete combustion products, but large ER mutations should still be avoided. In the case of anode off-gas combusting with cathode off-gas, there are nearly zero emissions. Meanwhile, the flue gas temperature decreases to about 760 °C because of enlarged heat loss, but it is minimally influenced by Uf. Under the static condition, the optimal point with both controlled temperature and lowest emissions can be obtained in a wide range, and the after-burner can well adapt to various operating states of the stack. Under the transient condition, the after-burner has good response performance with much shorter time in burner start-up and burner operating state switch than conventional porous media ones. It can start up the stack in 1715 s.
Effect of Hydraulic Diameter and Surface Roughness on Additively-Manufactured Offset Strip Fin Heat Exchanger Performance
Authors: Baker T. M. , Manahan M. P. , Lynch S. P. , Reutzel E. W.
Published: September 2022

Compact heat exchangers with air-side offset strip fins are commonly used where liquid-to-air heat transfer is required. The fins provide increased surface area for the air-side heat transfer, and the liquid is pumped through channels that are transverse to the air-flow direction. Traditionally-manufactured offset strip fin (OSF) heat exchangers are typically made by stamping sheet metal to produce fins with a sinusoidal or near square-wave fashion. These stamped sheets are then brazed or welded to the liquid channels. A plethora of empirical data and correlations exists to predict the heat transfer and pressure drop on the air-side of traditionally manufactured offset strip fin heat exchangers. Recently, additively-manufactured (AM) offset strip fin heat exchangers have been shown to provide manufacturing benefits, such as the ability to remove complicated liquid manifold welds as well as enhanced fin and oil channel features. Furthermore, they provide a convenient reference point for comparing the heat exchanger performance to that of a traditionally-manufactured equivalent. The present investigation shows empirical data from six additively-manufactured offset strip fin coupons of varying fin spacing and fin height to produce two groups of hydraulic diameters: 2.6 mm and 4.1 mm. The surface roughness of these coupons is notably different than traditionally-manufactured offset strip fins. The heat transfer and pressure drop behavior are compared to the correlations for traditionally-manufactured heat exchangers as well as ones derived specifically for ones that were additively manufactured.
Aberration control in quantitative widefield quantum microscopy
Authors: Scholten S. C. , Robertson I. O. , Abrahams G. J. , Singh Priya , Healey A. J. , Tetienne J.-P.
Published: September 2022

Widefield quantum microscopy based on nitrogen-vacancy (NV) centers in diamond has emerged as a powerful technique for quantitative mapping of magnetic fields with a sub-micrometer resolution. However, the accuracy of the technique has not been characterized in detail so far. Here, we show that optical aberrations in the imaging system may cause large systematic errors in the measured quantity beyond trivial blurring. We introduce a simple theoretical framework to model these effects, which extends the concept of a point spread function to the domain of spectral imaging. Using this model, the magnetic field imaging of test magnetic samples is simulated under various scenarios, and the resulting errors are quantified. We then apply the model to previously published data, show that apparent magnetic anomalies can be explained by the presence of optical aberrations, and demonstrate a post-processing technique to retrieve the source quantity with improved accuracy. This work presents a guide to predict and mitigate aberration induced artifacts in quantitative NV-based widefield imaging and in spectral imaging more generally.
Observation of interfacial strain relaxation and electron beam damage thresholds in Al0.3In0.7N/GaN heterostructures by transmission electron microscopy
Authors: Motoki Keisuke , Engel Zachary , Matthews Christopher M. , Ahmad Habib , McCrone Timothy M. , Harada Kohei , Doolittle W. Alan
Published: September 2022

The structural quality of indium-rich Al0.3In0.7N grown by metal modulated epitaxy (MME), previously demonstrating x-ray diffraction (XRD) figures of merit ∼11 times better than the previous literature is investigated to explain the origin of such a large quality improvement. Four-dimensional scanning transmission electron microscope was used to map the lattice parameter near the AlInN/GaN heterojunction and indicate a 5.4% lattice constant change, suggesting 75% relaxation within ∼2 nm from the interface. Cross-sectional TEM Moiré fringes are observed at the AlInN/GaN heterointerface, indicating that there are misfit dislocations between AlInN and GaN which, while rare, have been observed for other highly mismatched In-rich III-Nitrides. The TEM measurements show regions of contrast indicating larger scale variations in strain, but defect contrast associated with dislocations and/or intrinsic basal stacking faults was minimal, indicating a good quality AlInN film and confirming prior XRD results. Significant electron beam induced damage can occur and depended strongly on operational conditions. The damage threshold current density was estimated using time-dependent TEM to be ∼5.7 A/cm2, significantly lower than from prior studies of InGaN. Damage also strongly depends on the thickness of the TEM foil examined and occurred at thicknesses greater than found for InGaN. The present study suggests that the MME technique is an excellent candidate for growing high-quality indium-rich AlInN films as compared to the traditional molecular beam epitaxy or metal organic chemical vapor deposition techniques.
Lattice strain modulation toward efficient blue perovskite light-emitting diodes
Authors: Liu Baoxing , Li Junzi , Wang Gui , Ye Fanghao , Yan Huibo , Zhang Meng , Dong Shou-Cheng , Lu Lei , Huang Pu , He Tingchao , Xu Ping , Kwok Hoi-Sing , Li Guijun
Published: September 2022

The successful implementation of perovskite light-emitting diodes (PeLEDs) in advanced displays and lighting has proven to be challenging because of the inferior performance of blue devices. Here, we point out that a strained system would lead to the quasi-degenerate energy state to enhance the excited-state transition due to the formation of double-polarized transition channel. The tensile strained structure also brings about a synergetic control of the carrier dynamics in virtue of lattice structure deformation and reduced dimensional phase regulation to promote carrier population in large bandgap domains and to realize near-unit energy transfer from the large bandgap phases to the emitter phases. Accordingly, high external quantum efficiencies of 14.71 and 10.11% are achieved for the 488- and 483-nanometer PeLEDs. This work represents a versatile strategy using a strained system to achieve enhanced radiative emission for the development of efficient PeLEDs.
Best frequencies and temporal delays are similar across the low-frequency regions of the guinea pig cochlea
Authors: Burwood George , Hakizimana Pierre , Nuttall Alfred L , Fridberger Anders
Published: September 2022

The cochlea maps tones with different frequencies to distinct anatomical locations. For instance, a faint 5000-hertz tone produces brisk responses at a place approximately 8 millimeters into the 18-millimeter-long guinea pig cochlea, but little response elsewhere. This place code pervades the auditory pathways, where neurons have “best frequencies” determined by their connections to the sensory cells in the hearing organ. However, frequency selectivity in cochlear regions encoding low-frequency sounds has not been systematically studied. Here, we show that low-frequency hearing works according to a unique principle that does not involve a place code. Instead, sound-evoked responses and temporal delays are similar across the low-frequency regions of the cochlea. These findings are a break from theories considered proven for 100 years and have broad implications for understanding information processing in the brainstem and cortex and for optimizing the stimulus delivery in auditory implants.
Sugar, sugar: Glucose activates motion in pancreatic cilia
Authors: Sui Haixin
Published: September 2022

Pancreatic primary cilia are active and dynamic, not static antenna-like sensors as previously thought. This movement may be an important mechanism to glucose regulation.