bluuebunny/crossref_metadata_2025 huggingface dataset:
The NLRP6 inflammasome
Authors: Zheng Danping , Kern Lara , Elinav Eran
Published: December 2020

The NOD‐like receptor family pyrin domain containing 6 (NLRP6), a member of the NOD‐like receptor (NLR) family, acts as a cytosolic innate immune sensor that recognizes microbe‐associated molecular patterns. In some circumstances upon activation, NLRP6 recruits the adaptor apoptosis‐associated speck‐like protein (ASC) and the inflammatory caspase‐1 or caspase‐11 to form an inflammasome, which mediates the maturation and secretion of the pro‐inflammatory cytokines IL‐18 and IL‐1β. In other contexts, NLRP6 can exert its function in an inflammasome‐independent manner. Tight regulation of the NLRP6 inflammasome is critical in maintaining tissue homeostasis, while improper inflammasome activation may contribute to the development of multiple diseases. In intestinal epithelial cells, the NLRP6 inflammasome is suggested to play a role in regulating gut microbiome composition, goblet cell function and related susceptibility to gastrointestinal inflammatory, infectious and neoplastic diseases. Additionally, NLRP6 may regulate extra‐intestinal diseases. In this review, we summarize current knowledge on the NLRP6 inflammasome and its activation and regulation patterns, as well as its effector functions contributing to disease modulation. We discuss current challenges in NLRP6 research and future prospects in harnessing its function into potential human interventions.
Distance Artist: Building the Skills of Future Creatives. Developing Evidence‐Based Criteria for Global Virtual Team Tutoring and Management in Art and Design Education
Authors: Adiloğlu Fatoş , Fragiacomo Fabio , Petricone Fabiano
Published: December 2020

This article reflects on six years of research activities in the field of long‐distance collaboration and more specifically on how creative virtual teams operate and respond to challenges set by emerging and developing technologies. Furthermore, it considers how to build, manage and shape a more inclusive virtual team, documenting the methodologies applied in each activity, the experiences of both tutors and students and the educational context in which the international study took place. The project set out with a methodology for observing, managing and developing the interaction dynamics between each creative team member involved in the design of activities and practice of delocalized teams. The project is positioned within the field of educational technology and identifies a set of operative recommendations aimed at educators so that remote creative collaborative work can result most effective. The article explores the potential of virtual teams supporting communication and design.
Local delivery of simvastatin maintains tooth anchorage during mechanical tooth moving via anti‐inflammation property and AMPK/MAPK/NF‐kB inhibition
Authors: Xu Lianyi , Sun Xiaojuan , Zhu Guangxun , Mao Jing , Baban Babak , Qin Xu
Published: December 2020

Simvastatin (SMV) could increase tooth anchorage during orthodontic tooth movement (OTM). However, previous studies on its bone‐specific anabolic and anti‐inflammation properties were based on static in vitro and in vivo conditions. AMPK is a stress‐activated kinase that protects tissue against serious damage from overloading inflammation. Rat periodontal ligament cells (PDLCs) were subjected to a serial of SMV concentrations to investigate the optimization that promoted osteogenic differentiation. The PDLCs in static and/or tensile culturing conditions then received the proper concentration SMV. Related factors expression was measured by the protein array, real‐time PCR and Western blot. The 0.05UM SMV triggered osteogenic differentiation of PDLCs. The inhibition of AMPK activation through a pharmacological approach (Compound C) caused dramatic decrease in osteogenic/angiogenic gene expression and significant increase in inflammatory NF‐κB phosphorylation. In contrast, pharmacological activation of AMPK by AICAR significantly inhibited inflammatory factors expression and activated ERK1/2, P38 MAPK phosphorylation. Moreover, AMPK activation induced by SMV delivery significantly attenuated the osteoclastogenesis and decreased the expression of pro‐inflammatory TNF‐α and NF‐κB in a rodent model of OTM. The current studies suggested that SMV could intrigue intrinsic activation of AMPK in PDLCs that promote attenuate the inflammation which occurred under tensile irritation through AMPK/MAPK/NF‐kB Inhibition.
The PKM2 activator TEPP‐46 suppresses kidney fibrosis via inhibition of the EMT program and aberrant glycolysis associated with suppression of HIF‐1α accumulation
Authors: Liu Haijie , Takagaki Yuta , Kumagai Asako , Kanasaki Keizo , Koya Daisuke
Published: December 2020

Aims/Introduction

Tubulointerstitial fibrosis is a hallmark of diabetic nephropathy and is associated with an epithelial‐to‐mesenchymal transition (EMT) program and aberrant glycolysis. Dimeric pyruvate kinase (PK) M2 (PKM2) acts as a key protein kinase in aberrant glycolysis by promoting the accumulation of hypoxia‐inducible factor (HIF)‐1α, while tetrameric PKM2 functions as a pyruvate kinase in oxidative phosphorylation. The aim of the research is to study the effect of PKM2 tetramer activation on preventing kidney fibrosis via suppression of aberrant glycolysis and the EMT program.

Materials and methods

In vivo: Streptozotocin (STZ) was utilized to induce diabetes in 8‐week‐old CD‐1 mice; 4 weeks after diabetes induction, proteinuria‐induced kidney fibrosis was developed by intraperitoneal injection of bovine serum albumin (BSA: 0.3 g/30 g BW) for 14 days; The PKM2 activator TEPP‐46 was also administered orally simultaneously. In vitro: HK2 cells were co‐treated with high‐glucose media or/and TGF‐β1 and TEPP46 for 48 h, cellular protein was extracted for evaluation.

Results

Diabetic mice developed kidney fibrosis associated with aberrant glycolysis and EMT; BSA injection accelerated kidney fibrosis in both the control and diabetic mice; TEPP‐46 rescued the kidney fibrosis. In HK2 cells, TEPP‐46 suppressed the EMT program induced by TGF‐β1 and/or high‐glucose incubation. TEPP‐46‐induced PKM2 tetramer formation and PK activity resulted in suppression of HIF‐1α and lactate accumulation. Specific siRNA‐mediated knockdown of HIF‐1α expression diminished high glucose‐induced mesenchymal protein levels.

Conclusion

PKM2 activation could restore the tubular phenotype via suppression of the EMT program and aberrant glycolysis, providing an alternative target to mitigate fibrosis in diabetic kidneys.
Immersion challenge of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. did not increase the severity of Neoparamoeba perurans‐induced amoebic gill disease (AGD)
Authors: English Chloe J. , Botwright Natasha A. , Adams Mark B. , Barnes Andrew C. , Wynne James W. , Lima Paula C. , Cook Mathew T.
Published: December 2020

Amoebic gill disease (AGD) is one of the main health issues impacting farmed Atlantic salmon. Neoparamoeba perurans causes AGD; however, a diversity of other amoeba species colonizes the gills and there is little understanding of whether they are commensal or potentially involved in different stages of gill disease development. Here, we conduct in vivo challenges of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. to investigate their pathogenicity to Atlantic salmon gills. Additionally, we assessed whether the presence of Nolandella sp. and Pseudoparamoeba sp. influences the onset and/or severity of N. perurans‐induced AGD. All three strains attached and multiplied on the gills according to qPCR analysis. Furthermore, minor gross gill lesions and histological changes were observed post‐exposure. While N. perurans was found associated with classical AGD lesions, Nolandella sp. and Pseudoparamoeba sp. were not found associated with lesion sites and these lesions did not meet the expected composite of histopathological changes for AGD. Moreover, the presence of these non‐N. perurans species did not significantly increase the severity of AGD. This trial provides evidence that cultured Nolandella sp. and Pseudoparamoeba sp. do not induce AGD and do not influence the severity of AGD during the early stages of development.
The importance of family‐focused and strengths‐based approaches to interventions for grandfamilies
Authors: Fruhauf Christine A. , Yancura Loriena A. , Greenwood‐Junkermeier Heather , Riggs Nathaniel R. , Fox Aimee L. , Mendoza A. Nancy , Ooki Nancy
Published: December 2020

Critical to maintaining and improving physical and mental health is self‐care, yet interventions for grandfamilies (i.e., skipped‐generation households) minimally address such practices. Grounded by family resilience theory and strengths‐based approaches, this article introduces our rationale for an intervention addressing grandparents' and grandchildren's self‐care practices. The GRANDcares intervention is a tripartite intervention for grandparents, grandchildren, and service providers who work with grandfamilies. Following the National Institutes of Health's stage model for behavioral interventions, we briefly outline the literature on promoting self‐care and resilience in grandfamilies and meeting service providers' needs when working with grandfamilies. Next, we apply these theories to the development of the GRANDcares intervention. We close with a discussion of the GRANDcares programming and a synopsis of our efforts thus far, including recommendations for future research on strengths‐based interventions for grandfamilies.
The state of theory in elder family financial exploitation: A systematic review
Authors: Chan Athena C. Y. , Stum Marlene S.
Published: December 2020

Calls to address theoretical gaps in elder abuse as a field have been made over time. In this systematic review, the state of theory in elder family financial exploitation (EFFE), one of the most prevalent types of elder abuse, is examined. A synthesis of the scope and use of theories and constructs in 15 identified peer‐reviewed EFFE empirical articles published between 1990 and 2019 confirms a field in its infancy. Findings identified theoretical gaps in almost half of the studies utilizing a grand or middle‐range theory (8 of 15)—four focused on culture as a single concept, and three did not mention theory or constructs. Five interdisciplinary theoretical lenses have been used to examine EFFE, offering little depth and breadth in any one theory. To move EFFE forward theoretically, we discuss building on identified theories, integrating culture as a concept, and adding a focus on family systems using relevant family‐focused theories.
A new method to estimate the lifetime of long‐life product categories
Authors: Dunant Cyrille F. , Shah Trishla , Drewniok Michał P. , Craglia Matteo , Cullen Jonathan M.
Published: December 2020

Increased recycling and reuse rates are a central part of the objectives laid out by the COP21. Nonetheless, the practical implementation of what has been called the circular economy, as well as its true potential, are not easily established. This is because the impact and implementation time scales of any intervention depend on knowing the lifetime of products, which is frequently unknown. This is particularly true in construction, responsible for 39% of worldwide emissions, 11% of which are embodied. Most material flow analysis (MFA) models will simply assume a range of plausible life expectancies when bottom‐up data are lacking. In this work, we propose a novel method of identification using the high quality but highly aggregated trade data available and use it to establish a “mortality curve” for buildings and other long‐lasting products. This identification method is intended to provide more reliable inputs to existing MFA models. It is widely applicable because of the general availability of the underlying data. Using it on United Kingdom trade data, we identify product classes at 1 year for packaging/home scrap, 1 to around 10 years for vehicles/equipment, and around 50 years for construction. The identification approach was then validated by using classical approaches using bottom‐up data for vehicles.
Neuroprotection offered by mesenchymal stem cells in perinatal brain injury: Role of mitochondria, inflammation, and reactive oxygen species
Authors: Nair Syam , Rocha‐Ferreira Eridan , Fleiss Bobbi , Nijboer Cora H , Gressens Pierre , Mallard Carina , Hagberg Henrik
Published: December 2020

Preclinical studies have shown that mesenchymal stem cells have a positive effect in perinatal brain injury models. The mechanisms that cause these neurotherapeutic effects are not entirely intelligible. Mitochondrial damage, inflammation, and reactive oxygen species are considered to be critically involved in the development of injury. Mesenchymal stem cells have immunomodulatory action and exert mitoprotective effects which attenuate production of reactive oxygen species and promote restoration of tissue function and metabolism after perinatal insults. This review summarizes the present state, the underlying causes, challenges and possibilities for effective clinical translation of mesenchymal stem cell therapy.

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Air‐to‐Air Meeting Technique in Radiofrequency Thermocoagulation of Trigeminal Neuralgia: A Case Report
Authors: Du Chao , Wang Zhijia , Gao Yufei , Li Kai , Wang Zhengming , Tian Yu
Published: December 2020

Background

In a minority of cases, foramen ovales (FOs) are difficult to access due to single confounding anatomical variations. However, there is no method reported where the FO has been successfully targeted via a single puncture in the presence of two or more anatomical variations.

Objectives

To observe the effect of a new stereotactic bidirectional approach guiding technique utilized in a patient who harbored a particularly difficult‐to‐access FO due to multiple anatomical variations.

Methods

During operation of a unique facial entry point’s trigeminal neuralgia patient, make one plane which identified by a three‐dimensional (3D) coordinates of the FO target and arc angle value on stereotactic frame, make this plane intersected with another plane which determined by the 3D CT‐reconstruction’s facial entry point data on a ruler, so as to elucidate the appropriate trajectory. The authors coined the approach “Air‐to‐air meeting” method.

Results

We completed the radiofrequency thermocoagulation (RFT) with a single puncture to successfully target the FO according to the preoperative plan confirmed by C‐arm radiography. Postoperative pain scores using a visual analog scale decreased from 10 to 3 by the first day after the procedure. There were no permanent complications or morbidity from the surgery.

Conclusions

To the authors’ knowledge, this is the first report describing a unique facial entry point determined by this technique for the treatment of a patient with trigeminal neuralgia.
Comprehensive analysis of the isomiRome in the vegetative organs of the conifer Pinus pinaster under contrasting water availability
Authors: Perdiguero Pedro , Rodrigues Andreia Santos , Chaves Inês , Costa Bruno , Alves Ana , de María Nuria , Vélez María Dolores , Díaz‐Sala Carmen , Cervera María Teresa , Miguel Célia Maria
Published: December 2020

An increasing number of microRNAs (miRNAs) and miRNA‐related sequences produced during miRNA biogenesis, comprising the isomiRome, have been recently highlighted in different species as critical mediators of environmental stress responses. Conifers have some of the largest known genomes but an extensive characterization of the isomiRome from any conifer species has been lacking. We provide here a comprehensive overview of the Pinus pinaster isomiRome expressed in roots, stem and needles under well‐watered and drought conditions. From the 13,441 unique small RNA sequences identified, 2,980 were annotated as canonical miRNAs or miRNA* and the remaining were classified as isomiRNA or miRNA‐like sequences. A survey of their expression patterns highlighted roots as the most responsive organ under drought, where specific sequences of which a 24‐nt novel miRNA stood out, were strongly down‐regulated. Given the putative roles of the miRNA‐targeted transcripts validated specifically in root tissues, some of the miRNAs, conserved and novel, are shortlisted as potential regulators of drought response. These results provide a valuable resource for comparative studies between gymnosperms and angiosperms. Furthermore, it evidences high transferability of the isomiRome between pine species being a useful basis for further molecular regulation and physiological studies, and especially those focused on adaptation to drought conditions.
Management and outcome of hepatic artery thrombosis after pediatric liver transplantation
Authors: Channaoui Aniss , Tambucci Roberto , Pire Aurore , de Magnée Catherine , Sokal Etienne , Smets Françoise , Stephenne Xavier , Scheers Isabelle , Reding Raymond
Published: December 2020

Background

Pediatric LT are at particular risk of HAT, and its management still constitutes a matter of debate. Our purpose was to study predisposing factors and outcome of HAT post‐LT, including the impact of surgical revisions on survival and biliary complications.

Methods

Among 882 primary pediatric LT performed between 1993 and 2015, 36 HAT were encountered (4.1%, 35 fully documented). Each HAT case was retrospectively paired with a LT recipient without HAT, according to diagnosis, age at LT, type of graft, and era.

Results

Five‐year patient survivals were 77.0% versus 83.9% in HAT and non‐HAT paired groups, respectively (P = .321). Corresponding graft survivals were 20.0% versus 80.5% (P < .001), and retransplantation rates 77.7% versus 10.7%, respectively (P < .001). One‐year biliary complication‐free survivals were 16.6% versus 83.8% in the HAT and non‐HAT groups, respectively (P < .001). Regarding chronology of surgical re‐exploration, only HAT cases that occurred within 14 days post‐LT were re‐operated, fourteen of them being explored within 7 days post‐LT (revascularization rate: 6/14), versus two beyond 7 days (no revascularization). When revascularization was achieved, graft and biliary complication‐free survival rates at 1 year were 33.3% and 22.2%, respectively, both rates being 0.0% in case of failure.

Conclusions

The pejorative prognosis associated with HAT in terms of graft survival is confirmed, whereas patient survival could be preserved through retransplantation. Results suggest that HAT should be re‐operated if occurring within 7 days post‐LT, but not beyond.
The role of extracorporeal membrane oxygenation in pediatric abdominal transplant patients: A qualitative systematic review of literature
Authors: Reid Trista D. , Kratzke Ian , Dayal Diana , Raff Lauren , Kumar Aman , Phillips Michael R. , Carlson Rebecca , Desai Chirag S.
Published: December 2020

Background

Advances in ECMO have made it a useful adjunct in critically ill pediatric patients; however, a dearth of evidence exists regarding risks and benefits in pediatric abdominal transplantation. The purpose of this study was to perform a qualitative systematic review of outcomes in pediatric patients undergoing ECMO support pre– or post–abdominal organ transplantation.

Methods

This was a systematic review conducted from Jan 1, 1989, to April 24, 2020, via PubMed, Embase, Scopus, Web of Science, the Cochrane Library, and ClinicalTrials.gov of all pediatric solid abdominal organ transplant recipients (pre‐ and post‐transplant) and donors who underwent V‐A or V‐V ECMO cannulation. Death was the primary outcome, with graft function and complications as secondary outcomes.

Results

Fourteen articles were identified that fit criteria, with 88% being case reports. Three patients were donors placed on ECMO, with no mortality among the 8 recipients of organs from these donors. Nineteen recipients were placed on ECMO. All were liver transplants. Most patients experienced at least one complication (84%), with bleeding as the most common cause (44%). Mortality was 26%. Causes of death included multiorgan system failure (n = 3), heart failure (n = 1), Systemic inflammatory response syndrome (n = 1), abdominal compartment syndrome (n = 3), bleeding (n = 1), septic shock from aspergillus (n = 1), and hepatic artery thrombosis (n = 2).

Conclusions

The data are poor on ECMO usage in pediatric abdominal transplantation. While complications were high, mortality did not appear to be related to ECMO usage and was relatively low given the severity of patient illness.
Roy Holland and Henri Bergson
Authors: Mounce H. O.
Published: December 2020

I argue that while there is no evidence that Roy Holland was influenced by Henri Bergson, their views of morality nevertheless reveal an interesting similarity.
Nucleolar rDNA folds into condensed foci with a specific combination of epigenetic marks
Authors: Kutashev Konstantin O. , Franek Michal , Diamanti Klev , Komorowski Jan , Olšinová Marie , Dvořáčková Martina
Published: December 2020

Arabidopsis thaliana 45S ribosomal genes (rDNA) are located in tandem arrays called nucleolus organizing regions on the termini of chromosomes 2 and 4 (NOR2 and NOR4) and encode rRNA, a crucial structural element of the ribosome. The current model of rDNA organization suggests that inactive rRNA genes accumulate in the condensed chromocenters in the nucleus and at the nucleolar periphery, while the nucleolus delineates active genes. We challenge the perspective that all intranucleolar rDNA is active by showing that a subset of nucleolar rDNA assembles into condensed foci marked by H3.1 and H3.3 histones that also contain the repressive H3K9me2 histone mark. By using plant lines containing a low number of rDNA copies, we further found that the condensed foci relate to the folding of rDNA, which appears to be a common mechanism of rDNA regulation inside the nucleolus. The H3K9me2 histone mark found in condensed foci represents a typical modification of bulk inactive rDNA, as we show by genome‐wide approaches, similar to the H2A.W histone variant. The euchromatin histone marks H3K27me3 and H3K4me3, in contrast, do not colocalize with nucleolar foci and their overall levels in the nucleolus are very low. We further demonstrate that the rDNA promoter is an important regulatory region of the rDNA, where the distribution of histone variants and histone modifications are modulated in response to rDNA activity.
The DRBEM solution of Cauchy MHD duct flow with a slipping and variably conducting wall using the well-posed iterations
Authors: Aydin Cemre , Tezer-Sezgin Münevver
Published: December 2020

The present study focuses on the numerical investigation of the Cauchy Magnetohyrodynamic (MHD) duct flow in the presence of an externally applied oblique magnetic field, with a slipping and variably conducting wall portion of the duct walls. The underspecified and overspecified boundary informations for the velocity of the fluid and the induced magnetic field on both slipping and variably conducting duct wall and its opposite part, respectively, constitutes the Cauchy MHD duct flow problem. This study aims to recompute the velocity of the fluid and induced magnetic field with specified slip length and conductivity constant, respectively, on the underspecified wall which is both slipping and variably conducting. The governing coupled convection-diffusion type MHD equations for the direct and inverse formulations are solved in one stroke using the dual reciprocity boundary element method (DRBEM). Both the velocity and induced magnetic field and their normal derivatives to be used as overspecified boundary conditions for the construction of Cauchy problem are obtained through the direct formulation of the problem. The well-posed iterations are used in the regularization of the ill-conditioned systems of linear algebraic equations resulting from the DRBEM discretization of Cauchy problem (inverse problem). Numerical solutions for the slip velocity and induced magnetic field are obtained for Hartmann number values $M$=5, 10, 50. The main advantages of the DRBEM are its boundary only nature and the capability of providing both the unknowns and their normal derivatives on the underspecified walls so that the conductivity constant and the slip length between them can be recovered at a low computational expense.
Fuzzy control of dual storage system of an electric drive vehicle considering battery degradation
Authors: Keskin Kemal , Urazel Burak
Published: December 2020

In this manuscript, fuzzy logic energy management strategy for dual storage system inclu\-ding supercapacitors and battery is proposed in order to prolong battery lifespan and enhance the range of electric drive vehicle (EDV). First an EDV model and three drive cycles (NEDC, UDDS, and NREL) are established in Matlab/Simulink. Then a fuzzy inference system is designed considering three inputs: power demand, state of charge (SOC) of battery and SOC of supercapacitors. An output, which refers to split ratio between supercapacitors and battery power, is determined. Fuzzy rules are constituted in order to decrease not only high level battery current but also number of charge/discharge cycle of battery which are the main factors of battery deterioration. For a performance verification of the proposed method, three drive cycles with different characteristics are considered. Obtained results are compared to two other strategies; one of them is battery only system and the other one is dual storage system managed by logic threshold method. It is shown that the proposed method delivers better and robust performance to prolong battery lifespan.
Influence of Ambient Pressure and Heating Power on the Thermal Runaway Features of Lithium-Ion Battery
Authors: Chen Xiantao , Zhang Xu , Wang Haibin , Jia Jingyun , Xie Song , Zhi Maoyong , Fu Ju , Sun Qiang
Published: December 2020

The thermal runaway hazards pose a serious threat to the application and transport of lithium-ion batteries on the aircraft. Hence, the researches of thermal safety in flight condition are necessary. In this study, the tests were conducted in a dynamic pressure chamber to study the effects of ambient pressure and heating power on the thermal runaway characteristics. The results show that the fierce behaviors of jet fire, deflagration, and explosion only were observed in high ambient pressure with high heating power. The open time of the safety valve is advanced as pressure from 95 kPa to 20 kPa. The parameters of heat release rate (HRR), total heat release (THR), cell surface temperature, peak concentration of CO2, and mass loss decrease as the descend of external pressure or heating power. The peak values of hydrocarbon (CHx) and CO increase with the descent of pressure but decrease as the reduction of heating power. The effects of ambient pressure on the thermal runaway (TR) fire behaviors mainly attribute to the low oxygen density. The time of heating and smoking may account for the difference of TR behaviors with various heating power. It is revealed that the fire risk and the hazards of toxic/flammable gas emissions are tightly relative to the TR behaviors. These results provide valuable proposals and inspiration for the safety warning and hazard reduction under low pressure.
Liquid-Cooled Heat Sink Optimization for Thermal Imbalance Mitigation in Wide-Bandgap Power Modules
Authors: Sahu Raj , Gurpinar Emre , Ozpineci Burak
Published: December 2020

Power semiconductor die layout in substrates used in power modules is generally optimized for minimum electrical parasitics (e.g., stray inductance) by considering the minimum spacing between dies for thermal decoupling. The layout assumes sufficient heat spreading and transfer from dies to the cooling structure. For module designs using a direct substrate cooling method, the base plate is removed, leading to a steady-state thermal asymmetry in the power module due to insufficient heat spreading/transfer. This causes significant temperature differences among the devices. Such unintentional thermal asymmetries can lead to undesirable asymmetries in power conversion among semiconductor devices, which impact reliability. This article proposes a thermal imbalance mitigation method that uses evolutionary optimized liquid-cooled heat sinks to improve the thermal loading among devices.
Design of Accelerated Degradation Test Method and Failure Analysis of Flexible Hybrid Electronic Devices
Authors: Davila-Frias Alex , Marinov Val , Yadav Om Prakash , Atanasov Yuriy
Published: December 2020

Accelerated life testing (ALT) has been a common choice to study the effects of environmental stresses on flexible hybrid electronics (FHE), a promising technology to produce flexible electronic devices. Nevertheless, accelerated degradation testing (ADT) has proven to be a more effective approach, which does not require failure occurrences, allowing shorter testing times. Since FHE devices are expected to be highly reliable, ADT provides useful information in the form of degradation data for further analysis without actual failure data. In this paper, we present the design and experimental setup of ADT for FHE considering two stress factors simultaneously. We use daisy-chain resistance as a measurable degradation characteristic to periodically monitor the degradation of FHE products under accelerated stress conditions. Two stress factors, temperature and humidity, are considered and ADT was carried out considering four combinations of temperature and humidity simultaneously. Failure analysis was performed on failed units to investigate the failure process and location of the failure. The ADT data was used to fit in the appropriate mathematical degradation model representing the failure process. The data analysis showed faster degradation paths for higher stress combinations. Finally, we present insights and further research opportunities to expand the work.
Enabling Packaging Architectures and Interconnect Technologies for Image Sensors
Authors: Lu Mei-Chien
Published: December 2020

Image sensors have become a crucial technology platform for many applications in the past decades. Market demands continue to grow at a fast pace accelerated by innovations, performance improvement, and new applications. Efficient package architectures and advanced interconnect technologies are among the enablers for the commercialization of image sensors. This study examines how image sensor pixel electronics design and form factor drives innovations in chip stacking and high-density interconnects. 3D chip stacking architectures for CMOS image sensors are analyzed. Cases of image sensors for imaging at visible light, single photon avalanche photodiode (SPAD) for wide dynamic range, rolling shutter and global shutter, and depth sensing and light detection and ranging (LiDAR) are explored based on the pixel electronics requirements. Interconnect methods are also explored. Wafer direct bonding followed by through silicon via (TSV) and hybrid bonding technologies have recently been implemented in the image sensor industry. The preferences and challenges of these two interconnect technologies for image sensor chip stacking are discussed. As TSV technology is relatively mature, this study includes the process flow for one example of the hybrid bonding method. Challenges and future advancement are briefed along with the outlook of the technology and market momentum of image sensors.
Comparative Study of Effective Cooling in Microchannel Heat Sinks (MCHS) With Nanofluid and Hydrophobic Nanostructures Using Computational Fluid Dynamics
Authors: Jennings Darryl , Smith Sonya
Published: December 2020

The goal of this research is to present an analytical model of nanostructures and study the effects of their geometry on the performance of micro channels. The pressure drop experienced by micro channels is of interest as it presents a limit on forced convection heat transfer. This work will demonstrate how the presence of nanostructures primarily affects pressure drop as well as other cooling flow characteristics. Additional work in the impact of microchannel cross-sectional geometry and friction factor formulation is provided as well. Multiple transient analyses were performed in ANSYS FLUENT to ascertain performance characteristics of microchannels without the presence of hydrophobic nanostructures. The results were compared to the analytical model developed in this study.
Effective Thermal Conductivity of Phase Change Material-Based Composites for High Heat Flux Electronic Cooling
Authors: Singh Ayushman , Rangarajan Srikanth , Choobineh Leila , Sammakia Bahgat
Published: December 2020

This work presents a simplified approach to optimally designing a heat sink with metallic thermal conductivity enhancers infiltrated with phase change material for electronic cooling. In present study, thermal conductivity enhancers are in the form of a honeycomb structure. A benchmarked two-dimensional computational fluid dynamics model was employed to investigate the thermal performance of the phase change material-metallic thermal conductivity enhancer composite heat sinks. Metallic thermal conductivity enhancers are often used in conjunction with phase change material to enhance the conductivity of the composite heat sink. Under constrained heat sink volume, the higher volume fraction of thermal conductivity enhancers improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of heat sink for electronic cooling by resolving the stated tradeoff. In this study, the total volume of the heat sink and the interfacial heat transfer area between the phase change material and thermal conductivity enhancers are constrained for all design points. Furthermore, assuming conduction-dominated heat transfer, an effective numerical model that solves the single energy equation with the effective properties of the phase change material- metallic thermal conductivity enhancer composite has been developed. The temperature gradient-time history is compared and matched for both the models to arrive at the accurate effective thermal conductivity value. The relationship of effective thermal conductivity as a function of metal volume fraction and thermal conductivity of metallic thermal conductivity enhancer is obtained. The figure of merit (FOM) is used to define the balance between effective thermal conductivity and energy storage capacity. The FOM is maximized to find the optimal volume fraction for the present design. The results from the study reveals that there exists an optimal metal volume fraction that maximizes the thermal performance of the composite.
An Experimental Investigation Into Frost Accumulation Over Vertical Finned and Unfinned Surfaces During Impinging Air Flow
Authors: Oksuz E. A. , Saygin A. , Basol A. M. , Budakli M. , Arik M.
Published: December 2020

Frost formation on evaporators negatively affects the cooling performance of refrigerators. It increases the thermal resistance between the refrigerant and air leading to a reduction in the system cooling capacity. In this study, the effect of frost accumulation over a bare and finned surface on the convective thermal resistances has been experimentally investigated under impinging flow conditions. The surfaces are vertically positioned in a horizontal wind tunnel. The convective resistances have been measured with an in-house developed heat flux measurement system. Finally, the effectiveness of the finned surface was derived from the measurements for dry, condensing flow and as well as for frosting conditions. Under frosting conditions, the effectiveness of the finned surface is measured as 1.4 that is by a factor of 2X lower compared to the effectiveness of the same finned surface operating under dry conditions. It has been observed that the frost accumulation initially takes place at the tip of the fins and leads to a 45% drop in the heat transfer rate when the fin tips are completely covered with frost. Further frost accumulation on the fin base does not result in an additional drop in the heat transfer rate. In this regard, the study emphasizes the importance of the fin tip design for the heat sinks operating under frosting conditions.
Multifunctional Magnetic Nanocomposite Encapsulant for EMI Shielding in Power Electronics
Authors: Carlton Hayden , Iradukunda Ange , Huitink David , Myane Sarah , Akey Noah , Imran Asif , Luo Fang
Published: December 2020

As power densities and switching frequencies dramatically increase, a potential area of advancement for encapsulant technologies is to utilize them to mitigate electromagnetic interference, which directly impacts device efficiency at high switching frequencies; one promising topic involves the creation of magnetic nanoparticle-enhanced encapsulants, with intrinsic sensitivity to electromagnetic fields that could provide additional noise shielding for power electronic devices. A nanocomposite encapsulant was created by directly incorporating magnetic iron oxide nanoparticles into a silicone matrix. The nanoparticles, with an average size of 100 nm, achieved excellent dispersion in the silicone polymer, even at high concentrations, with no additive or surfactants needed to improve stability. Material testing, including thermo mechanical analysis and thermal conductivity measurements were performed to determine if the addition of the nanoparticles altered the thermal or mechanical properties of the base silicone. The nanocomposites at different concentrations observed thermal conductivities of 0.5 W/m-K and coefficient of thermal expansions of 280 ppm/°C, which resembles that of normal silicone; however, the addition of the iron oxide reduced the dielectric breakdown strength of the silicone matrix exponentially with respect to concentration from 20 kV/mm to 3 kV/mm. Further efforts to optimize the dielectric properties of the nanocomposites with respect to the nanoparticle loading is necessary in order to directly apply this technology; however, the results indicate magnetic nanocomposites could be a potential avenue towards mitigating electromagnetic interference in power devices.
CFD Analysis on Liquid Cooled Cold Plate Using Copper Nanoparticles
Authors: Shahi Pardeep , Agarwal Sarthak , Saini Satyam , Niazmand Amirreza , Bansode Pratik , Agonafer Dereje
Published: December 2020

In today’s world, most data centers have multiple racks with numerous servers in each of them. The high amount of heat dissipation has become the largest server-level cooling problem for the data centers. The higher dissipation required, the higher is the total energy required to run the data center. Although still the most widely used cooling methodology, air cooling has reached its cooling capabilities especially for High-Performance Computing data centers. Liquid-cooled servers have several advantages over their air-cooled counterparts, primarily of which are high thermal mass, lower maintenance. Nano-fluids have been used in the past for improving the thermal efficiency of traditional dielectric coolants in the power electronics and automotive industry. Nanofluids have shown great promise in improving the convective heat transfer properties of the coolants due to a proven increase in thermal conductivity and specific heat capacity.

The present research investigates the thermal enhancement of the performance of de-ionized water-based dielectric coolant with Copper nanoparticles for a higher heat transfer from the server cold plates. Detailed 3-D modeling of a commercial cold plate is completed and the CFD analysis is done in a commercially available CFD code ANSYS CFX. The obtained results compare the improvement in heat transfer due to improvement in coolant properties with data available in the literature.
CFD Simulation of Two-Phase Immersion Cooling Using FC-72 Dielectric Fluid
Authors: Niazmand Amirreza , Chauhan Tushar , Saini Satyam , Shahi Pardeep , Bansode Pratik Vithoba , Agonafer Dereje
Published: December 2020

With more development in electronics system capable of having larger functional densities, power density is increasing. Immersion cooling demonstrates the highest power usage efficiency (PUE) among all cooling techniques for data centers and there is still interest in optimizing immersion cooling to use it to its full potential. The aim of this paper is to present the effect of inclination and thermal shadowing on two-phase immersion cooling using FC-72. For simulation of boiling, the RPI (Rensselaer Polytechnic Institute) wall boiling model has been used. Also, two empirical models were used for calculation of bubble departure diameter and nucleate site density. The boundary condition was assumed to be constant heat flux and the bath temperature was kept at boiling temperature of FC-72 and the container pressure is assumed to be atmospheric. this study showed that due to the thermal shadowing, boiling boundary layer can lay over the top chipset and increases vapor volume fraction over top chipsets. This ultimately causes increase in maximum temperature of second chip. The other main observation is with higher inclination angle of chip, maximum temperature on the chip decreases up to 3°C.
Development of a Novel Test Setup to Study the Combined Effects of Electromigration and Mechanical Stress in Solder Interconnects
Authors: Montazeri Mahsa , Huitink David R.
Published: December 2020

One key concern that arises from scaling of device interconnects with increasing power density requirements is electromigration (EM). On the other hand, thermal cycling fatigue has always been a reliability challenge in solder interconnects. Variations in device temperature caused by environmental or operating conditions induce stress in solders, as they usually connect two components with different coefficients of thermal expansion (CTE). These thermally induced stresses may lead to crack formation within the solders. The combination of EM effects and thermal cycling add to the complexity of the reliability estimation for high current density applications.

In this work, a novel test setup has been designed and developed to estimate the reliability of solder interconnects under high current density, while a constant tensile stress is also applied to the solder interconnect. The test set up offers the ability to test up to four samples at the same time. Additionally, the test samples are fabricated with two copper wires connected by Pb/Sn solder to imitate copper UBM in a flip-chip bonding connection. Strain in solder is measured by monitoring the elongation of the wire during testing, while failure of the connection is detected by continuous monitoring of the electrical resistance. The experiment is conducted for conditions including pure tensile stress, pure EM and coupled EM and tensile stress where a significant reduction in life-time is observed for the coupled degradation effects. Comparing the experimental results of different current densities at different stress levels will help in identifying the nature of degradation in solders, which will help inform the drive for miniaturization.
Experimental Characterization of Heat Transfer and Thermal Energy Storage Capability Using Swirling Two-Phase Flow in the Package Integrated Cyclone COoler (PICCO)
Authors: deBock Peter , Miorini Rinaldo , Hoel Cathleen , Sharar Darin , Whalen Bryan
Published: December 2020

The increasing demand for high power density wide-bandgap power electronics has propelled heat transfer research leading to a constant increase in the thermal performance of cold plates and heat sinks. Most of this research has focused on reducing thermal resistance of the package which can have a detrimental effect on transient thermal performance if thermal capacitance is reduced.

In order to provide both a low thermal resistance and a higher thermal capacitance integrated into the package and near the thermal junction, a new cold plate called the Package Integrated Cyclone COoler (PICCO) was developed. GE Research and the US Army Research Lab collaborated to explore and validate the potential of this concept.

The PICCO coldplate, which is enabled by 3D printing, establishes a swirling coolant flow field to remove heat. The swirling flow is anticipated to significantly aid in vapor removal from the surface and hence allow for the fluid to provide thermal capacitance through two-phase heat transfer efficiently.

This paper describes the experiment design and development for thermal storage and cooling performance characterization of PICCO. The test rig includes a high-pressure capability gear pump moving fluid first through a Coriolis flowmeter and then through PICCO, where the fluid is accelerated in the cyclone and heated by miniaturized ceramic heaters, simulating SiC power electronics. The coolant releases the accumulated enthalpy to a plate-fin heat exchanger that is connected to a chiller. Several absolute and differential pressure transducers and thermocouples monitor the state of FC-72. The experiments will provide empirical transfer functions characterizing the PICCO pressure drop, heat transfer coefficient, critical heat flux and thermal energy storage capability.
Real Time Prediction of Li-Ion Battery Pack Temperatures in EV Vehicles
Authors: Soleymani Azita , Maltz William
Published: December 2020

A semi-analytical digital twin model of a 90 kW.h li-ion battery pack was developed to capture thermal behavior of the pack in a real-time environment. The solution uses reduced-order models that minimize compute cost/time yet are accurate in predicting real-world operation. The real-time heat generation rate in the battery pack is calculated using 2RC equivalent circuit model. A series of HPPC tests were conducted to calibrate the equivalent circuit model in order to accurately calculate heat generation rate as a function of SOC, temperature, current, charge/discharge mode and pulse duration. In the paper, live-sensor data was integrated into the digital twin system level model of the battery pack to create a real-time environment. The generated tool was utilized to monitor the real-time temperature of the battery pack remotely and have a predictive maintenance solution. The model results for heat generation rate, terminal voltage, and temperature were found to be consistent with the test data across a wide range of conditions.

The generated model was used to accelerate battery pack design and development by enabling the evaluation of design feasibility and to conduct in-depth root causes analyses for various inputs and operating conditions, including initial SOC, temperature, coolant flow rate, different charge and discharge profiles. The resulting digital twin model provides additional data that cannot be measured offering the EV industry an opportunity to improve its safety record.