bluuebunny/crossref_metadata_2025 huggingface dataset:
N‐Acylethanolamine acid amidase (NAAA) is dysregulated in colorectal cancer patients and its inhibition reduces experimental cancer growth
Authors: Romano Barbara , Pagano Ester , Iannotti Fabio A. , Piscitelli Fabiana , Brancaleone Vincenzo , Lucariello Giuseppe , Nanì Maria Francesca , Fiorino Ferdinando , Sparaco Rosa , Vanacore Giovanna , Di Tella Federica , Cicia Donatella , Lionetti Ruggero , Makriyannis Alexandros , Malamas Michael , De Luca Marcello , Aprea Giovanni , D'Armiento Maria , Capasso Raffaele , Sbarro Bernardo , Venneri Tommaso , Di Marzo Vincenzo , Borrelli Francesca , Izzo Angelo A.
Published: November 2021

Background and Purpose

N‐Acylethanolamine acid amidase (NAAA) is a lysosomal enzyme accountable for the breakdown of N‐acylethanolamines (NAEs) and its pharmacological inhibition has beneficial effects in inflammatory conditions. The knowledge of NAAA in cancer is fragmentary with an unclarified mechanism, whereas its contribution to colorectal cancer (CRC) is unknown to date.

Experimental Approach

CRC xenograft and azoxymethane models were used to assess the in vivo effect of NAAA inhibition. Further, the tumour secretome was evaluated by an oncogenic array, CRC cell lines were used for in vitro studies, cell cycle was analysed by cytofluorimetry, NAAA was knocked down with siRNA, human biopsies were obtained from surgically resected CRC patients, gene expression was measured by RT‐PCR and NAEs were measured by LC–MS.

Key Results

The NAAA inhibitor AM9053 reduced CRC xenograft tumour growth and counteracted tumour development in the azoxymethane model. NAAA inhibition affected the composition of the tumour secretome inhibiting the expression of EGF family members. In CRC cells, AM9053 reduced proliferation with a mechanism mediated by PPAR‐α and TRPV1. AM9053 induced cell cycle arrest in the S phase associated with cyclin A2/CDK2 down‐regulation. NAAA knock‐down mirrored the effects of NAAA inhibition with AM9053. NAAA expression was down‐regulated in human CRC tissues, with a consequential augmentation of NAE levels and dysregulation of some of their targets.

Conclusion and Implications

Our results show novel data on the functional importance of NAAA in CRC progression and the mechanism involved. We propose that this enzyme is a valid drug target for the treatment of CRC growth and development.
CHA2DS2‐VASc impact on risk following percutaneous coronary intervention in atrial fibrillation
Authors: Jensen Thomas , Thrane Pernille Gro , Olesen Kevin Kris Warnakula , Würtz Morten , Nielsen Jens Cosedis , Jensen Lisette Okkels , Madsen Morten , Thim Troels , Dalby Kristensen Steen , Lip Gregory Y. H. , Maeng Michael
Published: November 2021

Aims

In 2010, the European Society of Cardiology Guidelines on atrial fibrillation (AF) introduced the CHA2DS2‐VASc score to guide initiation of oral anticoagulation. In patients with AF undergoing percutaneous coronary intervention (PCI), triple therapy with oral anticoagulation and dual antiplatelet therapy was recommended to reduce ischaemic risk. We examined how the CHA2DS2‐VASc score impacted oral anticoagulation use and risks of ischaemic and hospitalized bleeding events in patients with AF undergoing PCI.

Methods

We included 6,014 patients with AF undergoing first‐time PCI in Western Denmark between 2003 and 2017. We divided patients into four groups based on year of PCI and estimated 1‐year risks of major adverse cardiac events (MACE) and hospitalization for bleeding.

Results

The proportion of oral anticoagulation users was 48% in 2003–2006 and 49% in 2006–2010. Following the CHA2DS2‐VASc score implementation, the proportion increased to 59% in 2011–2014 and 77% in 2015–2017. Using 2003–2006 as reference, risks of MACE were similar in 2007–2010 (adjusted relative risk [RRadj] 0.99, 95% confidence interval [CI] 0.83–1.18) and 2011–2014 (RRadj 0.92, 95% CI 0.78–1.09), but declined by 23% in 2015–2017 (RRadj 0.77, 95% CI 0.65–0.92). Hospitalizations for bleeding did not increase despite wider use of triple therapy.

Conclusion

Implementation of the CHA2DS2‐VASc score in the 2010 European guidelines on AF was associated with an increased utilization of oral anticoagulation and triple therapy among AF patients undergoing PCI. These changes were associated with a gradual decline in the risk of MACE, while the risk of hospitalized bleeding remained unchanged.
Geographical homogenization but little net change in the local richness of Canadian butterflies
Authors: Lewthwaite Jayme M. M. , Mooers Arne Ø.
Published: November 2021

Aim

Recent studies have found that local‐scale plots measured through time exhibit marked variation in the change in species richness. However, the overall effect often reveals no net change. Most studies to date have been agnostic about the identities of the species lost/gained and about the processes that might lead to these changes. Generalist traits might be crucial in allowing species to colonize new plots or remain resilientin situ, whereas environmental filtering might remove specialists. We test whether plots are changing in species richness, whether they are becoming more similar (i.e., becoming homogenized) through time and whether several generalist traits can predict gains or losses from local plots.

Location

Canada.

Time period

1945–2015.

Major taxa studied

Two hundred and sixty‐five species of butterflies.

Methods

We measured change in species richness and pairwise beta diversity across 96 well‐sampled 10 km × 10 km plots across Canada between two time periods: 1945–1975 and 1985–2015. We looked at the effects of wing span, mobility, dietary breadth and range size on the number of grid cells each species gained and lost between time periods.

Results

We observed a slight increase in plot‐level species richness, and that these communities are becoming homogenized through time. We note that most butterfly species in Canada have large North American ranges. The species with the widest ranges are better able to colonize new plots than species with narrower ranges, but also experience higher frequencies of local extinctions. In sum, the median range size of species within a plot increased through time.

Main conclusions

We highlight that, even when local species richness exhibits very little change, other potentially important changes in biodiversity can occur, such as geographical homogenization attributable to the colonization dynamics of species that are already widely distributed. Such patterns can reconcile observed global losses of species with the simultaneous lack of change in local diversity.
Embedded librarians: An innovative experience in health and wellness communication
Authors: Barbaro Annarita , Amicarella Sofia Enrica , Ferrari Paola , Sorcini Ilaria , Zedda Monica
Published: November 2021

The article discusses the experiences of Italian librarians taking part in an institutional project to produce a new general‐public‐oriented health web portal. The web portal was set up to provide verified and easily understandable health information, and to debunk health‐related fake news circulating on the internet. The different roles, knowledge and skills acquired in during the project this are discussed and show how the librarian’s knowledge and skills were of fundamental importance for the success of the Web Portal. By collaborating with other professions new skills such as social media management, video creation and Search Engine Optimization were gained, which enhanced the information literacy role of the service.
Using an artificial intelligence tool can be as accurate as human assessors in level one screening for a systematic review
Authors: Burns Joseph K. , Etherington Cole , Cheng‐Boivin Olivia , Boet Sylvain
Published: November 2021

Background

Artificial intelligence (AI) offers a promising solution to expedite various phases of the systematic review process such as screening.

Objective

We aimed to assess the accuracy of an AI tool in identifying eligible references for a systematic review compared to identification by human assessors.

Methods

For the case study (a systematic review of knowledge translation interventions), we used a diagnostic accuracy design and independently assessed for eligibility a set of articles (n = 300) using human raters and the AI system DistillerAI (Evidence Partners, Ottawa, Canada). We analysed a series of 64 possible confidence levels for the AI’s decisions and calculated several standard parameters of diagnostic accuracy for each.

Results

When set to a lower AI confidence threshold of 0.1 or greater and an upper threshold of 0.9 or lower, DistillerAI made article selection decisions very similarly to human assessors. Within this range, DistillerAI made a decision on the majority of articles (93–100%), with a sensitivity of 1.0 and specificity ranging from 0.9 to 1.0.

Conclusion

DistillerAI appears to be accurate in its assessment of articles in a case study of 300 articles. Further experimentation with DistillerAI will establish its performance among other subject areas.
Sublingual immunotherapy with Dermatophagoides farinae drops for pediatric atopic dermatitis
Authors: Huang Chaodi , Tang Jianping
Published: November 2021

Background

We evaluated the clinical effect and safety of sublingual immunotherapy (SLIT) with Dermatophagoides farinae drops for pediatric atopic dermatitis (AD).

Methods

We enrolled children aged 4–13 years with AD and grouped them into the SLIT and control groups using the random number table method. We subdivided each group based on treatment duration (1‐, 2‐, and 3‐year subgroups). The SLIT group received Dermatophagoides farinae drops, and both groups received conventional treatment (topical glucocorticoids, skin moisturizers, oral antihistamines, and allergen avoidance). Effective rate and effect were compared between groups after 1, 2, and 3 years of treatment.

Results

We assessed 309 SLIT cases (male, 192; age, 4–13 years) and 131 controls (male, 79; age 4–13 years). The effective rate and curative effect after 2 and 3 years of treatment were significantly different between the groups (P < 0.05). The effect and effective rates between corresponding SLIT and control group treatment duration subgroups were significantly different (P < 0.05). SLIT group duration subgroups showed significant differences in the effect and effective rates (P < 0.05). Posttreatment Scoring Atopic Dermatitis (SCORAD) scores in the SLIT group duration subgroups were significantly lower than those of the corresponding control subgroups (P < 0.05). Upon follow‐up at 1 year post treatment completion, the SLIT group’s SCORAD score was significantly lower than its baseline score and the control group’s follow‐up score (P < 0.05).

Conclusion

SLIT with Dermatophagoides farinae drops for pediatric AD is safe and effective; effectiveness is maintained after treatment cessation, and prolonged treatment improves efficacy.
Will wind always boost early‐age shrinkage of cement paste?
Authors: Zhang Lifeng , Ruan Shaoqin , Qian Kuangliang , Gu Xuliang , Qian Xiaoqian
Published: November 2021

Immediately after casting, the occurrence of early age shrinkage is sensitive to internal stresses, degree of hydration, and tensile strength, which is of concern to engineers. This study investigated the influences of wind speeds on early‐age shrinkage and tensile strength (strain) of cement paste, and the results were further interpreted by an investigation of hydration degree and capillary water. The outcomes show that as the wind speed increased, the shrinkages (i.e., drying, chemical, and autogenous shrinkage) experienced various trends depending on several factors. Meanwhile, a variety of wind speeds altered the proportion of the evaporation in the capillary water, the inner moisture distribution, and the humidity difference between specimens’ surface and their interior sections. Further, tensile strength and elastic modulus were deteriorated by wind, whereas with the growth of the wind speed, the ultimate tensile strain of specimens exhibited various scenarios within and after 24 h.
Quo vadis, esthetic dentistry? Ceramic veneers and overtreatment—A cautionary tale
Authors: Hirata Ronaldo , Sampaio Camila S. , de Andrade Oswaldo Scopin , Kina Sidney , Goldstein Ronald E. , Ritter Andre V.
Published: November 2021

The increased emphasis on orofacial esthetics, experienced both by dental professionals and the lay public, results in an environment where overtreatment can easily occur. Patients on the one hand feel pressure from esthetic norms that are often unrealistic, while dental professionals are compelled to deliver immediate results many times without considering what is best for the ill‐informed patient. This article is an illustrated cautionary tale against overtreatment disguised as esthetic dentistry. Representative clinical examples illustrate how porcelain veneers are used without following sound operatory principles, as well as how these cases have been resolved.
Alertness during working hours among eight‐hour rotating‐shift nurses: An observational study
Authors: Min Ari , Hong Hye Chong , Son Sungtaek , Lee Tae Hee
Published: November 2021

Purpose

The aim of this study was to identify the patterns of the decline in the alertness of rotating‐shift nurses during working hours across different shift types (day, evening, and night) using an objective measure.

Design

An observational study using ReadiBand wrist actigraphs was conducted.

Methods

Data were collected from June 2019 to February 2020. Participants were rotating‐shift nurses (N = 82) who provided direct nursing care for patients in acute care hospitals in South Korea. Nurses wore actigraphs continuously for 14 days on their non‐dominant hand to identify sleep–wake cycles and predict their alertness scores hourly. All participants completed a sleep diary.

Findings

Nurses working during night shifts had lower average alertness scores (mean = 77.12) than nurses working during day (mean = 79.05) and evening (mean = 91.21). Overall, alertness showed a declining trend and the specific patterns of decline differed across shifts. Participants with alertness scores less than 70 or 80 demonstrated a significant decline in alertness across all shifts.

Conclusions

Distinct patterns of decline in alertness per nursing shift were revealed. Each shift feature should be considered when developing interventions to increase nurses’ alertness, promote high‐quality care provision, and ensure patient safety.

Clinical relevance

The implementation of interventions to increase alertness among shift nurses is needed at the organizational level, and the cooperation of nursing managers and administrators is required.
The bicycle as ‘constructive hope’: Children, climate and active transport
Authors: Wild Kirsty , Woodward Alistair
Published: November 2021

Children are experiencing an increase in so‐called ‘eco‐anxiety’. Along with others, we argue that children need more concrete, meaningful opportunities to feel they can make a difference in climate. In this article, we contend that bringing back the bicycle, and the opportunities for independent and active mobility that it affords children, is an important form of climate action for young people. We assert that as well as providing sustainability and wellbeing co‐benefits for children, cycling can help bolster the neighbourhood resilience and social cohesion that will be key resources for communities adapting to new climate risks.
One planet one health: What about the kids?
Authors: Walton Merrilyn , Guest David , Raynes‐Greenow Camille
Published: November 2021

Humans in their increasing numbers and wealth are changing ecosystems through accelerated consumption of food, natural resources and energy which continue to cause significant damage to the planet. Using ‘stunting in children’ as a case study, we show how the traditional siloed (specialist) approaches have failed to reduce stunting world‐wide. Despite significant effort, traditional approaches fail to appreciate the interconnectedness of the multiple factors that underpin stunting. We will not improve the lives of the millions of children living in poverty by doing the same things we have always done, rather we need to adopt approaches that recognise the interconnectedness of all the component parts and apply One Health methods designed to solve these intractable problems.
The signaling function of sharing fake stories
Authors: Bergamaschi Ganapini Marianna
Published: November 2021

Why do people share or publicly engage with fake stories? Two possible answers come to mind: (a) people are deeply irrational and believe these stories to be true; or (b) they intend to deceive their audience. Both answers presuppose the idea that people put the stories forward as true. But I argue that insomecases, these outlandish (yet also very popular) stories function as signals of one's group membership. This signaling function can make better sense of why, despite their unusual nature or lack of a factual basis, some of these stories are so widespread.
The baby‐led weaning method: A focus on mealtime behaviours, food acceptance and fine motor skills
Authors: Campeau Meghan , Philippe Sarah , Martini Rose , Fontaine‐Bisson Bénédicte
Published: November 2021

Baby‐led weaning (BLW) is an alternative complementary feeding method by which children feed themselves starting at 6 months with suitable solid finger foods. Despite its increasing popularity worldwide, research is limited on its effects on diet‐related behaviours and no study has yet addressed its association with fine motor skills. This cross‐sectional study aimed to compare 10‐ to 14‐month‐old children's mealtime behaviours, food acceptance and fine motor skills between the BLW and traditional spoon‐feeding (TSF) methods (n = 82; 41 per group). Parents completed three online questionnaires regarding feeding practices, eating behaviours and food consumption acceptance, and the Peabody developmental motor scale test was performed in person with each child. Compared to the TSF method, BLW was associated with a higher satiety responsiveness score (mean ± SEM: BLW 13.6 ± 0.5 vs. TSF 11.6 ± 0.5, p = 0.005), a slower eating pace (BLW 10.0 ± 0.5 vs. TSF 11.4 ± 0.5, p = 0.04), and a marginally higher grasping skill score and fine motor quotient (p = 0.05 for both). There was no difference in food acceptance between the two feeding methods. Parental pressure was negatively associated with some food acceptance and mealtime behaviours. BLW is associated with beneficial mealtime behaviours and possibly with fine motor skills development. This study reiterates the importance of avoiding pressuring infants while eating.
Seeking and maintaining connections: A grounded theory study of maintaining spirituality in residential aged care facilities
Authors: Gautam Sital , Montayre Jed , Neville Stephen
Published: November 2021

Background

Moving to a residential aged care facility involves living far from family and a familiar environment, and leaving behind the social support system of relatives, friends, and society. The pressure to find and develop new and meaningful connections in a residential aged care facility can be significant for older adults.

Objective

To provide a theoretical explanation of how older adults seek and maintain connections in a residential aged care facility.

Methods

A grounded theory study was conducted. A total of 17 residents were recruited from two Nepalese residential aged care facilities using theoretical sampling. Face to face in‐depth, semi‐structured interviews and observation within interviews were conducted. Data analysis included the process of open, axial, selective coding, and constant comparative analysis as per Corbin and Strauss’ variant of grounded theory.

Results

This study identified that the process of seeking connections in a residential aged care facility was forward‐moving, and involved “identifying sources,” “developing connections,” and “appraising responses.” By seeking connections, residents built new connections. Similarly, the study found that maintaining connections was a continuous process of “sustaining connections with co‐residents,” “preserving connections with nurses/caregivers,” and “continuing connections with inner‐self and higher being/s.” Maintaining connections led residents to balance shifting connections. Furthermore, it was found that the process of seeking and maintaining connections was conditional on facility arrangement i.e. the way residents were placed, rules, regulations, co‐residents’ language, gender, religious affiliation, attitudes, the attitudes and practices of nurses/caregivers, decreasing physical abilities of residents, increasing illness of residents, illness or death of co‐residents, and retirement or resignation of nurses/caregivers.

Conclusion

The current study provides unique insights into the process of seeking and maintaining connections in a residential aged care facility. Facility arrangement, rules, regulations, and caregiving practices should resonate with residents’ socio‐cultural expectations and spiritual belief system to support their process of seeking and maintaining connections.

Implications for practice

The findings can be beneficial for managers, nurses, caregivers, and spiritual advisors in developing interventions that promote the development of meaningful connections in a residential aged care facility.
A Remorseful Criminal: Searching for Guilt in Aristotle
Authors: Zavaliy Andrei G.
Published: November 2021

While instances of shame are plenty in Ancient Greek sources, it is notoriously difficult to identify a case of a wrongdoer who exhibits a reaction approximating our modern concept of guilt. Adopting a behavioural criterion for demarcating shame from guilt, I examine the most promising description of a guilt‐feeling from Aristotle’s Ethics. The description stands out from the earlier tradition by reversing the pattern of the behavioural tendencies of a wrongdoer, but fits well with the phenomenon of inner shame. The condition described by Aristotle can thus be conceived as self‐shaming, but one that exhibits some of the features that have more in common with guilt.
Dental treatment under intravenous sedation prolongs longevity of a fixed prosthesis in patients with intellectual disabilities
Authors: Yamaguchi‐Komeyama Kaori , Tanoue Naomi , Kurata Shinji , Ayuse Takao
Published: November 2021

Aims

This study aimed to assess the longevity of a fixed prosthesis in patients with intellectual disability (ID) and to investigate the risk factors associated with the failure of a prosthesis due to abutment tooth extraction or prosthesis dislodgement or removal.

Methods

We studied past medical records to evaluate the longevity of 315 prostheses that were luted in 76 patients with ID. We calculated the survival rates and assessed 15 variables potentially associated with prosthetic failure using multivariate Cox regression analyses with shared frailty for patients.

Results

Three‐quarters of our sample population had severe or profound ID. The maximum observation period was 31.0 years, and the corresponding survival ratio was 32.5%; the survival ratio at 10 years was 59.4%. The use of intravenous sedation significantly influenced the success of the prosthesis, with the hazard ratio (HR) being 0.49 times that of conventional treatment without behavior‐altering drug therapy. The most significant risk factor for prosthetic failure was age at placement; the HR for patients aged ≥31 years was 2.82 times that for patients aged ≤ 20 years.

Conclusions

In patients with severe ID, appropriate intravenous sedation was effective in prolonging the longevity of a fixed prosthesis.
Examining the effects of undergraduate STEM teacher recruitment and teacher education programs on preservice secondary science and mathematics teacher readiness and teacher performance assessment (edTPA) scores
Authors: Moon Sungmin , Carpenter Stacey L. , Hansen Alexandria K. , Bushong Leslie , Bianchini Julie A.
Published: November 2021

We examined the effects of teacher education on preservice secondary science and mathematics teacher readiness. The construct of teacher readiness consisted of three dimensions: (a) preservice teachers’ understanding of how to implement current standards, (b) their understanding of how to teach multilingual learners (MLs), and (c) their beliefs about their abilities and skills as educators. To determine teacher readiness, a subset of preservice teachers enrolled in six teacher education programs (TEPs) completed a pre‐ and post‐survey. We found that the undergraduate STEM teacher recruitment program was associated with developing preservice teachers’ understanding of standards‐based instruction but was not associated with the other two dimensions of teacher readiness. We also found that the post‐baccalaureate TEPs were effective in developing preservice teachers’ understanding of ML instruction, whereas the experimental baccalaureate program was not. Further, we found that teacher readiness did not predict participants’ performance assessment (edTPA) scores. Findings suggest that teacher educators and curriculum developers involved in undergraduate STEM teacher recruitment programs should better address language, literacy, and ML instruction. Both teacher recruitment and TEPs should consider ways to strengthen teacher efficacy. Finally, teacher educators should carefully consider how their coursework and field experiences help preservice teachers prepare for the edTPA.
A Highly Efficient Approach for Bi-Level Programming Problems Based on Dominance Determination
Authors: Wang Guan , Zou Qiang , Zhao Chuke , Liu Yusheng , Ye Xiaoping
Published: November 2021

Bi-level programming, where one objective is nested within the other, is widely used in engineering design, e.g., structural optimization and electronic system design. One major issue of current solvers for these bi-level problems is their low computational efficiency, especially for complex nonlinear problems. The existing methods usually applied time-consuming nested computational structure, which requires an amount of function evaluations (FEs) since a lower-level (LL) optimization needs to be constructed for each upper-level (UL) solution. To solve this issue, a new method based on bi-level grey wolf optimizer (BLGWO) is proposed in this paper. The basic idea is to drop the conventional nested computational structure and instead use a simultaneous computational structure. The simultaneous structure is built on top of a dominance determination process for the grey wolf optimizer, so that the upper-level and lower-level problems can be optimized simultaneously, which greatly improves the efficiency of solving the bi-level problems. The effectiveness of this new method has been validated with ten benchmark functions and two engineering design examples, as well as comparisons with three important existing methods in the bi-level programming domain.
Comparison of Under-Actuated and Fully Actuated Serial Robotic Arms: A Case Study
Authors: Bottin Matteo , Rosati Giulio
Published: November 2021

Under-actuated robots are very interesting in terms of cost and weight since they can result in a state-controllable system with a number of actuators lower than the number of joints. In this paper, a comparison between an under-actuated planar three-degrees-of-freedom (DOF) robot and a comparable fully actuated two-degrees-of-freedom robot is presented, mainly focusing on the performances in terms of trajectories, actuator torques, and vibrations. The under-actuated system is composed of two active rotational joints followed by a passive rotational joint equipped with a torsional spring. The fully actuated robot is inertial equivalent to the under-actuated manipulator: the last link is equal to the sum of the last two links of the under-actuated system. Due to the conditions on the inertia distribution and spring placement, in a simple point-to-point movement the last passive joint starts and ends in a zero-value configuration, so the three DOF robot is equivalent, in terms of initial and final configuration, to the two DOF fully actuated robot, thus they can be compared. Results show how while the fully actuated robot is better in terms of reliable trajectory and actuator torques, the under-actuated robot wins in flexibility and in vibrations at a given configuration.
Numerical Investigation of a Phase Change Material Building Integrating Solar Thermal Collector PCM-BST
Authors: Benkaddour Ayman , Faraji Mustapha
Published: November 2021

Sensible thermal energy storage (TES) systems can reduce energy environmental fluctuation dependency with the nocturnal energy needs usage in maintaining the building's comfort levels. In the present paper, phase change material (PCM) is introduced to improve the thermal energy storage capacity of a solar collector integrating a novel composite PCM/concrete wall. A mathematical model based upon the conservation and heat transfer equations has been developed using the enthalpy method. The equations that govern the problem were discretized with the control volume scheme and solved iteratively using the tridiagonal matrix algorithm (TDMA). The numerical investigation has been implemented into a personal fortran code. Many series of simulation runs were executed. The position of the PCM layer within the wall and the PCM melting temperature are varied in the range 0 cm ≤ xm ≤ 7.5 cm and 15 °C ≤ Tm ≤ 35 °C, respectively. The objective is to let inner temperature Tin swing close to a comfort threshold. The position of PCM close to the absorber improves the efficiency of the room heating with good nocturnal use of latent heat stored during the day. PCM melting temperature affects deeply the composite PCM/concrete wall/solar collector behavior. Lastly, PCM gained the system an important benefit which is the solar collector high-temperature isolation as to not reach the room and disturb the inside comfort zone by melting and solidifying. Those parameters can be considered as the primary pointers for PCM/wall integrated solar collector design. Also, a daily heating potential, Qh, and thermal load leveling, TLL, are introduced to evaluate the system performance.
Thermal Design of Variable Frequency Drives for Hybrid and Electric Transport Applications
Authors: Lakhkar Nikhil R.
Published: November 2021

The Electrification of commercial vehicles is happening at a rapid pace. Most of the major automotive corporations are pursuing this opportunity to include electric vehicles in their portfolios. The commercial trucking industry has also been exploring the use of electric vehicles for goods transport including perishables. The transition to electrically driven vehicles has led to the need for electrically driven HVAC systems. To support this evolving commercial market, we developed an electrically driven variable speed compressor platform comprising of compressor and variable frequency drive (VFD). The product platform addresses two categories of vehicles: 1) Hybrid vehicle – the vehicle in this category uses conventional IC engine and has traditional batteries that output 48VDC. 2) Electric vehicle – the vehicle in this category is electrically driven using battery bank or traction drive that gives 650VDC as output. Hence, 650V DC is input to VFD. Both these applications were addressed with two drive designs.

In this paper, we discuss the thermal design aspects of both 48V and 650V variable frequency drives. In this publication, the product development process is described from product conception, to final product. The mechanical / environmental design considerations while designing these drives were, (1) The drive was expected to be mounted under the vehicle bed and hence should be strong enough to withstand shock and vibration, (2) the drive was decided to be air cooled (4) the drive was designed to be IP67 so that it can withstand harsh road conditions, (5) the desired operating temperature range was between −40°C to 85°C for 48V and −40°C to 65°C for 650V and (6) the estimated time of service was expected to be 10 years. We were able to achieve an operating margin of −40°C to 70°C at full load for hybrid vehicle drive (48VDC) and −40°C to 65°C for electric vehicle drive (650VDC) using air cooling.
Thermal Performance of Different Carbonaceous Nanoparticles as Additives to Thermal Paste as an Interface Material
Authors: Bharadwaj Bharath , Singh Prashant , Mahajan Roop L.
Published: November 2021

With increased focus on miniature high power density electronic packages, there is a need for the development of new interface materials with lower thermal resistance. To this end, high conductivity thermal paste or similar thermal interface materials (TIMs), reinforced with superior thermal conductivity materials such as multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), graphite-derived multilayer graphene (g-MLG) offer an effective strategy to provide efficient paths for heat dissipation from heat source to heat sink. In an earlier paper, we had demonstrated that multilayer graphene derived from coal (coal-MLG) synthesized using our in-house developed one-pot process, has increased presence of phenolic groups on its surfaces, which translates into better dispersion of coal-MLG in silicone thermal paste. In this paper, we first compare the thermal conductance of a high conductivity thermal paste (k = 8.9 W/mK) using coal-MLG as an additive with that realized with other nano additives — MWCNTs, GNPs, and g-MLG. The data shows that coal-MLG as an additive outperforms all the other investigated nano additives in enhancing the thermal performance of the paste. With the coal-MLG as an additive, ∼70% increase in thermal performance was observed as compared to the base thermal paste used. This increase is about 2.5 times higher than that obtained using g-MLG as an additive. We also measured the thermal performance of coal-MLG-based TIM with its different wt.% fractions. The data confirmed our hypothesis that the optimum level of the loading fraction of the additive that can be dispersed in the matrix (paste in this case) before the onset of agglomeration is higher for the coal-MLG (3%) than for the other additives (2%). The implication is further improvement thermal performance with coal-MLG. The data shows the additional thermal enhancement to ∼2X. Finally, since coal-MLG produced by our in-house process is relatively cheaper and more environmentally friendly, we believe that these results would pave the path for enhanced thermal performance with non-silicone thermal pastes at a significantly lower cost. We also expect similar benefits for the silicone-based thermal pastes.
Epoxy Die Attach Combined With Face-Up Die Bonding for Improved XYZ Placement Accuracy
Authors: Avanessian Tadeh , Clatterbaugh Jim , Zinsmaster Robin L. , Hashemi Leyla
Published: November 2021

Epoxy die attach is widely used in microcircuit assembly and enjoys advantages such as ease of deposition, fast curing, reworkability, and non-toxicity. These qualities also make it suitable for automated mass production. However, this method falls short when high placement accuracy is desired as the die can shift on uncured epoxy leading to die displacement from its original location. Gold to gold face-up bonding is another method utilized in microelectronics packaging given its proven bonding reliability and high placement accuracy for small devices. Nevertheless, it is difficult to achieve a reliable bond using this method for relatively larger devices. The nonplanarity of the bonding collet or the variation in the height of the gold bumps results in a tilted die attach and/or a weak bond between the die and the substrate. Moreover, CTE (Coefficient of Thermal Expansion) mismatch between the die, the gold bumps, and/or the substrate leads to bond failure due to temperature fatigue. This paper discusses a hybrid method to take advantage of the strengths of both methods mentioned above, culminating in a reliable process with high XYZ placement accuracy. To apply this method, epoxy is first dispensed on a gold-plated substrate. Using a flip chip machine, samples with plated gold bumps on their ground side are then placed on the substrate. The gold bumps are mainly used as targets and stand-offs to improve the placement accuracy and to control epoxy glue-line thickness. The force applied on the die, the time the force is applied, and the substrate temperature are controlled for optimum die attach. Moreover, along with the force applied by the vacuum tip, epoxy is partially cured on the flip chip machine heated stage before it is moved to an oven to complete the cure process. Die shear test results before and after temperature conditioning are compared with standard epoxy die attach and gold to gold face-up bonding for identical samples and the advantages are discussed.
Module-Level TIM Degradation in HALT
Authors: Tompkins Joshua , Huitink David
Published: November 2021

In this study, TIM degradation is driven through HALT using temperature cycling and random vibration for two commercially available materials providing thermal conductivities of 6.5 and 8.0 W/m-K. HALT specimen were prepared by applying TIM through a 4-mil stencil over AlSiC baseplates in the shape of those used in Wolfspeed CAS325M12HM2 power electronics modules. Baseplates were mounted onto aluminum carrier blocks with embedded thermocouples to characterize the thermal resistance across the baseplate and TIM layer. Thermal dissipation into the top of the baseplates was provided by a custom heating block, which mimics the size and placement of the die junctions in CAS325 modules, applying power loads of 200, 300, and 400W. After initial characterization, samples were transferred to the HALT chamber with one set of samples exposed to temperature cycling only (TCO) and the other temperature cycling and vibration (TCV). Both sample sets were cycled between temperature extremes of −40 and 180 °C with random vibrations applied at a peak acceleration of 3.21 Grms. After hundreds of cycles, samples were reevaluated to assess changes in thermal resistance to provide an accelerated measure of TIM degradation. This will allow for reliability calculations of useful lifetime, provide a basis for developing accelerated testing method to related temperature cycling to faster methods of degradation, and additionally provide a means by which to develop a maintenance schedule for servicing the power modules which will enhance cooling and lifetime operation.
Mechanical Behavior of Heat Activated Film Adhesives
Authors: Janamanchi Prabhat , Dasgupta Abhijit , Singh Narendra
Published: November 2021

Heat activated film (HAF) adhesives enable the bonding of materials that are difficult to bond with conventional adhesives where one of the substrates is flexible. Although they are traditionally found in the context of industrial and structural applications, they are increasingly finding use in in electronic products.

This paper provides a preliminary evaluation of the mechanical behavior of HAFs. Two commercial polyurethane HAF formulations (designated as HAF-II and HAF-III, for the purpose of this paper) were evaluated to assess the dependence of the mechanical properties on phase transitions and on the thermal exposure history of the material. Both factors were found to play a significant role in determining the overall usability of the materials. The melting transition occurs under 50°C for both materials, after which their stiffness drops significantly. Among the two, HAF-III is preferable as it undergoes a delayed melting transition, effectively extending the usable operating temperature range.

As with any adhesive, there are several other factors that can influence the performance of adhesives such as post-curing age, storage, and curing conditions to name a few. The impact of these factors on the material’s strength is also discussed in brief and a recommendation for favorable conditions is provided.
Design and Application of Innovative 3DVC in AI Server System
Authors: Tan Xianguang , He Yongzhan , Liu Bin , Yu Jiang , Nishi Ahuja , Tian Wenbin
Published: November 2021

With the accelerated application of cloud computing and artificial intelligence, the computing power and power consumption of chips are greatly enhanced, which brings severe challenges to heat dissipation. Based on this, Baidu has adopted advanced phase change cooling technology and successfully developed an innovative 3dvc air cooling scheme for AI server system. This paper introduces the design, test and verification of the innovative scheme in detail. The results show that the scheme can reduce the GPU temperature by more than 5 °C compared with the traditional heat pipe cooling scheme, save 30%+ of the fan power consumption, and achieve good cooling and energy saving effect.
Electromigration Analysis of Solder Joints for Power Modules Using an Electrical-Thermal-Stress-Atomic Coupled Model
Authors: Kato Mitsuaki , Omori Takahiro , Goryu Akihiro , Fumikura Tomoya , Hirohata Kenji
Published: November 2021

Numerical analysis of electromigration in solder joints has mainly examined ball grid arrays (BGAs) in flip-chip packages, and few numerical study has been reported on solder joints in power modules. This report describes an electromigration analysis of solder joints for power modules with a Si-based power device, which are still widely used today, using an electrical-thermal-stress-atomic coupled analysis. To evaluate electromigration, a solder joint with a power device and a substrate as used in power modules was simulated. Due to current crowding, the current density at the edge of the solder joint exceeded the electromigration threshold even in Si-based power modules. Unlike general electromigration phenomena, the vacancy concentration increased at the center and decreased at the edges of the solder joint, regardless of whether it was on the cathode side or anode side. The vacancy concentration clearly increased with increasing current density and size ratio. Creep strain increased significantly with increasing current density, temperature, and size ratio. The largest change in vacancy concentration and creep strain was at the anode edge where current crowding occurred. In addition, we modeled the two-dimensional behavior of metal atoms passing through the interface of the solder joint. The expansion of intermetallic compound was accelerated by increasing the temperature and current density.
Thermal Conductivity Prediction Model for Composite Thermal Interface Materials Using Copper Metal Foam
Authors: Kawakita Shinya , Ishizaka Yuki , Fushinobu Kazuyoshi
Published: November 2021

In the previous research, we prototyped the TIC in which a conventional TIM composed of silicone resin and filler was filled in pores of copper foam, and measured its thermal conductivity by a steady-state method. In addition, the effective thermal conductivity of TIC was predicted by Bhattacharya’s equation and Boomsma’s equation. As a result, it was reported that the experimental value and the predicted value match within 0.7 W/(m·K) by modifying the thermal conductivity of copper to 120 W/(m·K) in the Boomsma’s equation. The issue of that was to investigate the cause of the decrease in thermal conductivity of copper to 120 W/(m·K). In this paper, the effective thermal conductivity of TIC was predicted using the WP structure instead of the Kelvin structure, which is the basis of the Bhattacharya’s equation and Boomsma’s equation. As the result, it was clarified that the effective thermal conductivity predicted by the three-dimensional thermal conductivity calculation model based on the WP structure is more accurate than that predicted by the Kelvin model. And it was found that the experimental value and the predicted value match in the range of 0.4 W/(m·K) by considering the TIC surface structure without modifying the thermal conductivity of copper.
Machine Learning-Based Model for Optimal Operating Conditions of Thermosyphons for Electronic Cooling Applications
Authors: Kim John , Amalfi Raffaele L.
Published: November 2021

Two-phase cooling systems based on the thermosyphon operating principle exhibit excellent heat transfer performance, reliability, and flexibility, therefore can be applied to overcome thermal challenges in a wide range of electronic cooling applications and deployment scenarios. However, extremely complex nature of two-phase flow physics involving flow patterns and phase transitions has been the major challenge for technology adoption in industry. This paper demonstrates a machine learning (ML) based model for evaluating the thermal performance and refrigerant mass flow rate, of a thermosyphon cooling system for telecom equipment. Unlike conventional laboratory approach that requires numerous sensors attached to a cooling system to capture their thermal performance, the new model requires a minimum number of sensors to monitor the health of a thermal management solution. Using the proposed model, a system control module can be further developed which could identify optimal operating parameters in real-time under dynamically changing heat load conditions and actively maintain safety and thermal requirements.
A Novel Concept for Air Removal in Two-Phase Immersion Cooling Systems
Authors: Peterson Eric , Morris Seth , Alissa Husam , Keehn Nicholas , Ramakrishnan Bharath , Oruganti Vaidehi , Manousakis Ioannis , Mckay Noah
Published: November 2021

A 10 kW scale model of a decoupled immersion cooling rig is constructed in order to serve as a testbed for immersion cooling, using 3M FC3284 dielectric cooling fluid. A species separator is constructed and demonstrates an ability to remove air from the flowfield before the condensable gases enter the condenser vessel, verified with Schlieren photography. The condenser underperformed significantly compared to initial sizing calculations using the NTU method, and film thickness of FC3284 liquid on the surface of the condenser was determined to be the cause due to low thermal conductivity of the liquid. The average film thickness on the surface of the condenser is calculated. In addition to the performance detriment of the film, air is also shown to reduce the condenser’s performance. The height of a transient stratification line is measured and compared against condenser power. Condenser efficacy losses are large and variable based on the concentration of air in the condenser vessel. A low vs high-mounted boiler is investigated. The mounting of the boiler has an effect on how much vapor is lost during a maintenance event. Finally, a comparison of the test rig’s overall cooling efficiency is made with various air-cooled datacenters by tracking energy consumption to cool a given IT load. This also translates to a reduction in carbon emissions.
Rack-Level Thermosyphon Cooling and Vapor-Compression Driven Heat Recovery: Evaporator Model
Authors: Khalid Rehan , Amalfi Raffaele Luca , Wemhoff Aaron P.
Published: November 2021

An in-rack cooling system connected to an external vapor recompression loop can be an economical solution to harness waste heat recovery in data centers. Validated subsystem-level models of the thermosyphon cooling and recompression loops (evaporator, heat exchangers, compressor, etc.) are needed to predict overall system performance and to perform design optimization based on the operating conditions. This paper specifically focuses on the model of the evaporator, which is a finned-tube heat exchanger incorporated in a thermosyphon cooling loop. The fin-pack is divided into individual segments to analyze the refrigerant and air side heat transfer characteristics. Refrigerant flow in the tubes is modeled as 1-D flow scheme with transport equations solved on a staggered grid. The air side is modeled using differential equations to represent the air temperature and humidity ratio and to predict if moisture removal will occur, in which case the airside heat transfer coefficient is suitably reduced. The louver fins are modeled as individual hexagons and are treated in conjunction with the tube walls. A segment-by-segment approach is utilized for each tube and the heat exchanger geometry is subsequently evaluated from one end to the other, with air property changes considered for each subsequent row of tubes. Model predictions of stream outlet temperature and pressure, refrigerant outlet vapor quality and heat exchanger duty show good agreement when compared against a commercial software.