bluuebunny/crossref_metadata_2025 huggingface dataset:
Are parent‐reported sleep logs essential? A comparison of three approaches to guide open source accelerometry‐based nocturnal sleep processing in children
Authors: Burkart Sarah , Beets Michael W. , Pfledderer Christopher D. , von Klinggraeff Lauren , Zhu Xuanxuan , St. Laurent Christine W. , van Hees Vincent T. , Armstrong Bridget , Weaver R. Glenn , Adams Elizabeth L.
Published: November 2023

We examined the comparability of children's nocturnal sleep estimates using accelerometry data, processed with and without a sleep log. In a secondary analysis, we evaluated factors associated with disagreement between processing approaches. Children (n = 722, age 5–12 years) wore a wrist‐based accelerometer for 14 days during Autumn 2020, Spring 2021, and/or Summer 2021. Outcomes included sleep period, duration, wake after sleep onset (WASO), and timing (onset, midpoint, waketime). Parents completed surveys including children's nightly bed/wake time. Data were processed with parent‐reported bed/wake time (sleep log), the Heuristic algorithm looking at Distribution of Change in Z‐Angle (HDCZA) algorithm (no log), and an 8 p.m.–8 a.m. window (generic log) using the R‐package ‘GGIR’ (version 2.6‐4). Mean/absolute bias and limits of agreement were calculated and visualised with Bland–Altman plots. Associations between child, home, and survey characteristics and disagreement were examined with tobit regression. Just over half of nights demonstrated no difference in sleep period between sleep log and no log approaches. Among all nights, the sleep log approach produced longer sleep periods (9.3 min; absolute mean bias [AMB] = 28.0 min), shorter duration (1.4 min; AMB = 14.0 min), greater WASO (11.0 min; AMB = 15.4 min), and earlier onset (13.4 min; AMB = 17.4 min), midpoint (8.8 min; AMB = 15.3 min), and waketime (3.9 min; AMB = 14.8 min) than no log. Factors associated with discrepancies included smartphone ownership, bedroom screens, nontraditional parent work schedule, and completion on weekend/summer nights (range = 0.4–10.2 min). The generic log resulted in greater AMB among sleep outcomes. Small mean differences were observed between nights with and without a sleep log. Discrepancies existed on weekends, in summer, and for children with smartphones and screens in the bedroom.
Putative prefoldin complex subunit 5 of Plasmodium berghei is crucial for microtubule formation and parasite development in the mosquito
Authors: Beyeler Raphael , Jordan Melanie , Dorner Lilian , He Buyuan , Cyrklaff Marek , Roques Magali , Stanway Rebecca , Frischknecht Friedrich , Heussler Volker
Published: November 2023

Plasmodium sporozoite development in and egress from oocysts in the Anopheles mosquito remains largely enigmatic. In a previously performed high‐throughput knockout screen, the putative subunit 5 of the prefoldin complex (PbPCS5, PBANKA_0920100) was identified as essential for parasite development during mosquito and liver stage development. Here we generated and analyzed a PbPCS5 knockout parasite line during its development in the mosquito. Interestingly, PbPCS5 deletion does not significantly affect oocyst formation but leads to a growth defect resulting in aberrantly shaped sporozoites. Sporozoites produced in the absence of PbPCS5 were thinner, markedly elongated, and did, in most cases, not contain a nucleus. Sporozoites contained fewer subpellicular microtubules, which reached deep into the sporoblast during sporogony where they contacted and indented nuclei. These aberrantly shaped sporozoites did not reach the salivary glands, and we, therefore, conclude that PbPCS5 is essential for sporogony and the life cycle progression of the parasite during its mosquito stage.
Clinical profile of re‐hospitalizations in pediatric kidney and liver transplant recipients
Authors: Shohet Adi , Ziv Noa , Gavish Rachel , Haskin Orly , Alfandary Hadas , Waisbourd‐Zinman Orith , Mozer‐Glassberg Yael , Krause Irit
Published: November 2023

Background

Solid organ transplantation has evolved in recent decades, resulting in a rise in patient and graft survival. Frequent hospitalizations affect graft function, patients' health, and quality of life. This study characterizes the frequency and causes of post‐transplant hospitalizations among pediatric recipients.

Methods

This is a retrospective observational study evaluating pediatric kidney transplant recipients (KTR) and liver transplant recipients (LTR) aged 0–21 years, followed at a tertiary pediatric center in Israel from 2012 to 2017. Data were collected starting at 60 days post‐transplantation. Diagnoses of admissions were based on clinical, laboratory, and radiographic findings.

Results

Forty‐nine KTR experienced 199 all‐cause re‐hospitalizations (median number of re‐hospitalizations per patient – 3 (IQR [interquartile range] 1–5.5), while 351 re‐hospitalizations were recorded in 56 LTR (median – 5 [IQR 2–8.8]). Median follow‐up time was 2.2 years for KTR (IQR 1–3.9) and 3 years for LTR (IQR 2.1–4.1). The most common cause for hospitalization for both cohorts was infection (50.8% and 62%, respectively). Gram‐negative bacteria were the most common pathogens identified in KTR, while viral pathogens were more common in LTR (51% and 57% of pathogen‐identified cases, respectively).

Conclusions

This is the largest study to describe rehospitalizations for pediatric solid organ recipients. The hospital admission rate was higher in LTR in comparison to KTR. Infections were the most common cause of hospitalization throughout the whole study period in both populations. Frequent hospitalizations impose a heavy burden on patients and their families; better understanding of hospitalization causes may help to minimize their frequency.
Chemoselective light‐induced reactivity of β‐enaminones
Authors: Valloli Lakshmy Kannadi , Manal Kavyasree , Lewis Brieanna , Jockusch Steffen , Sivaguru Jayaraman
Published: November 2023

The irradiation of β‐enaminones, generated in situ from cyclic 1,3‐diketones and activated alkenes leads to polyheterocyclic skeletons. The photoproduct chemoselectivity depends on the type of cyclic 1,3‐diketones employed viz., 2‐acetylcyclopentanone and 2‐acetylcyclohexanone. The observed chemoselectivity was rationalized based on the Dieckmann‐Kon rule.
Association between cumulative maternal exposures related to inflammation and child attention‐deficit/hyperactivity disorder: A cohort study
Authors: Nielsen Timothy C. , Nassar Natasha , Shand Antonia W. , Jones Hannah F. , Han Velda X. , Patel Shrujna , Guastella Adam J. , Dale Russell C. , Lain Samantha J.
Published: November 2023

Background

Preclinical studies suggest synergistic effects of maternal inflammatory exposures on offspring neurodevelopment, but human studies have been limited.

Objectives

To examine the cumulative association and potential interactions between seven maternal exposures related to inflammation and child attention‐deficit/hyperactivity disorder (ADHD).

Methods

We conducted a population‐based cohort study of children born from July 2001 to December 2011 in New South Wales, Australia, and followed up until December 2014. Seven maternal exposures were identified from birth data and hospital admissions during pregnancy: autoimmune disease, asthma, hospitalization for infection, mood or anxiety disorder, smoking, hypertension, and diabetes. Child ADHD was identified from stimulant prescription records. Multivariable Cox regression assessed the association between individual and cumulative exposures and ADHD and potential interaction between exposures, controlling for potential confounders.

Results

The cohort included 908,770 children, one‐third (281,724) with one or more maternal exposures. ADHD was identified in 16,297 children (incidence 3.5 per 1000 person‐years) with median age of 7 (interquartile range 2) years at first treatment. Each exposure was independently associated with ADHD, and risk increased with additional exposures: one exposure (hazard ratio (HR) 1.59, 95% confidence interval (CI) 1.54, 1.65), two exposures (HR 2.25, 95% CI 2.13, 2.37), and three or more exposures (HR 3.28, 95% CI 2.95, 3.64). Positive interaction was found between smoking and infection. The largest effect size was found for cumulative exposure of asthma, infection, mood or anxiety disorder, and smoking (HR 6.12, 95% CI 3.47, 10.70).

Conclusions

This study identifies cumulative effects of multiple maternal exposures related to inflammation on ADHD, most potentially preventable or modifiable. Future studies should incorporate biomarkers of maternal inflammation and consider gene–environment interactions.
Omega‐3 long‐chain polyunsaturated fatty acids in Atlantic salmon: Functions, requirements, sources, de novo biosynthesis and selective breeding strategies
Authors: Zhang Zeyu , Miar Younes , Huyben David , Colombo Stefanie M.
Published: November 2023

The aquaculture industry is a substantial user of wild‐sourced fish oil to supply omega‐3 (n‐3) long‐chain polyunsaturated fatty acids (LC‐PUFAs) in fish diets, which are required by many economically important farmed fish species, particularly Atlantic salmon (Salmo salar L.). Fish oil is commonly replaced with plant‐based oils as more environmentally and economically sustainable substitutes due to concerns regarding over‐fishing of wild stocks and increasing demand. One potential strategy to meet the physiological requirement for n‐3 LC‐PUFA is to improve n‐3 LC‐PUFA biosynthesis in salmon through selective breeding and strain enhancement. The objective of this review is to discuss strategies to supply sufficient levels of n‐3 LC‐PUFA to Atlantic salmon through the diet and de novo biosynthesis through selective breeding and salmon strain enhancement. This review provides an overview on the functions of n‐3 LC‐PUFA in Atlantic salmon, dietary requirements, source and supply of n‐3 LC‐PUFA in aquaculture feeds, and biosynthesis of n‐3 LC‐PUFA in fish. Several relevant studies have revealed the genetic influences on n‐3 LC‐PUFA biosynthesis and storage in Atlantic salmon. The results of the present review show that selective breeding of high n‐3 PUFA‐producing Atlantic salmon could be an effective strategy to improve the amount of EPA and DHA stored in tissues and reduce reliance on dietary sources of n‐3 LC‐PUFA such as fish oil.
Investigating rates and predictors of viral blips, low‐level viraemia and virological failure in the Australian HIV observational database
Authors: Han Win Min , Broom Jennifer , Bopage Rohan , Templeton David J. , Edmiston Natalie , Petoumenos Kathy ,   the Australian HIV Observational Database
Published: November 2023

Objectives

Australia has made significant progress towards achieving the UNAIDS's 95‐95‐95 cascade targets including HIV viral suppression. To investigate the burden of HIV viraemia, we assessed viral blips, low‐level viraemia (LLV) and virologic failure (VF) in an Australian cohort.

Methods

We studied the proportion of people with viral suppression, viral blips, LLV and VF in the Australian HIV observational database (AHOD) between 2010 and 2021. The association between blips or LLV, and VF was investigated using Cox regression, and predictors of viral blips and LLV were assessed using repeated‐measured logistic regression.

Results

Among 2544 AHOD participants who were in follow‐up and on antiretroviral therapy (ART) from 1 January 2010 (88.7% male), 444 had experienced VF (incidence rate: 2.45 [95% CI: 2.23–2.69] per 100 person‐years [PY]) during 18,125 PY of follow‐up (a median of 7.6 years). The proportion of people with VF decreased over time, whereas rates of blips and LLV remained stable. Participants with blips (hazard ratio, 2.89; 95% CI: 2.31–3.61) and LLV (4.46; 95% CI: 3.38–5.89) were at increased risk of VF. Hepatitis B co‐infection, longer documented treatment interruption duration, younger age and lower CD4 at ART initiation, and protease inhibitors‐based initial regimen were associated with an increased risk of VF. Common predictors of blips and LLV such as higher HIV‐1 RNA and lower CD4 at ART initiation, longer treatment interruption, more VL testing and types of care settings (hospitals vs. sexual health services) were identified.

Conclusions

Blips and LLV predict subsequent VF development. We identified important predictors of HIV viraemia including VF among individuals on INSTI‐based regimens to help direct HIV management plans.
Responding to avian influenza A H5N1 detection on a hospital property in Maine—An interdisciplinary approach
Authors: Krueger Anna , Myles Devin J. F. , Rice Carrie P. , Taylor Tegwin K. , Hurwitz Carolyn , Morris Jesse , Robinson Sara
Published: November 2023

Background

The risk of infection with avian influenza A viruses currently circulating in wild and domestic birds in the Americas is considered low for the general public; however, detections in humans have been reported and warning signs of increased zoonotic potential have been identified. In December 2022, two Canada geese residing on the grounds of an urban hospital in Maine tested positive for influenza A H5N1 clade 2.3.4.4b.

Aims

Given the opportunity for exposure to staff and hospital visitors through potentially infected faeces on the property, public health authorities determined mitigation efforts were needed to prevent the spread of disease. The ensuing response relied on collaboration between the public health and animal health agencies to guide the hospital through efforts in preventing possible zoonotic transmission to humans.

Materials and Methods

Mitigation efforts included staff communication and education, environmental cleaning and disinfection, enhanced illness surveillance among staff and patients, and exposure and source reduction.

Results

No human H5N1 cases were identified, and no additional detections in birds on the property occurred. Hospital staff identified barriers to preparedness resulting from a lack of understanding of avian influenza A viruses and transmission prevention methods, including avian influenza risk in resident wild bird populations and proper wildlife management methods.

Conclusion

As this virus continues to circulate at the animal‐human interface, this event and resulting response highlights the need for influenza A H5N1 risk awareness and guidance for facilities and groups not traditionally involved in avian influenza responses.
Prioritisation of Needs and Opportunities for Promoting Circular Economy When Managing Materials and Waste Arising From Nuclear Decommissioning
Authors: Pancotti Federica , Bruno Aina , Wasselin Virginie , Maitre Melanie , Kennes Christian , Vaillant Ludovic , Larsson Arne , Harvey Elizabeth , Szőke Réka , Aldave De Las Heras Laura , Poškas Gintautas , Banford Anthony , Meteyer Alison , Jacops Elke , Oxberry David , Mikšová Jitka , Sciacqua Rossella
Published: November 2023

The Euratom HARPERS (HARmonised PracticEs, Regulations and Standards in waste management and decommissioning) project aims to establish and clarify the benefits and added value of a more aligned practices, methodologies and approaches for prioritised topics related to decommissioning and initial phases of radioactive waste handling, including shared processing facilities between Member States (MS).

The HARPERS project has a two-phase approach: the first phase involves engaging with Stakeholders to assess needs and pros/cons for harmonisation and to identify priority areas for deeper analysis. The second phase will pursue deeper engagement with Stakeholders to further assess the highest ranked priority areas in the three technical Work Packages. In Phase 2 the industry and business impacts resulting from the project findings will be also evaluated.

Work Package 4 (WP4) of HARPERS project is focused on addressing the most important conditions and opportunities for promoting Circular Economy approaches when managing materials and waste arising from nuclear decommissioning across Europe.

For the prioritisation of needs and opportunities for Circular Economy considerations, a detailed list of topics (challenges/needs - related to alignment of practices and approaches) has been developed. Topics were clustered into 7 main categories and discussed with interested external stakeholders during dedicated on-line workshops conducted in January and February 2023.

Criteria for the prioritisation of topics, based on drivers relating to societal impacts, actor-specific impacts, scientific impacts and financial impacts, have been developed and discussed during the workshops too.

This work presents the preliminary outcomes of the two online workshops.
Decreasing Level Activities and Releasing Wastes: It’s Now Possible Thanks to a New Electrodecontamination Implementation
Authors: Gal Michaël , Reuter Olaf , Damerval Frédérique
Published: November 2023

The ORANO la Hague plant (Manche) must be innovative in dismantling its old facilities.

In particularly, the dismantling HAO’s cells (High Activities Oxides building) involves the clean-up of equipment in cells that was used to shear and dissolve spent fuel.

Electro chemical Decontamination (ED) was extensively used in the pre-maintenance job decontamination for its high efficiency and innocuousness towards the components treated. It generates low amount of effluent, usually exhibit high contamination and dose rate as DF high as 1000 were commonly obtained.

Its ventures in the D&D areas were rare, because of the complex set-up.

Addressing a recurrent implementation issue, ORANO DS is developing, from an equipment developed by the company REUTER GmbH, a simple solution to be able to use ED to treat metal waste which, after clean-up operations, has an activity not compatible with surface waste disposal. Electro-decontamination will also be used to reduce the level of radiological exposure, to allow human access and to keep compatible conditions for the nuclear measure in Zone 4 (e.g. cell 916 HAO).

The purpose of this technical development in collaboration with REUTER GmbH is to adapt an ED equipment to allow its use in a specific nuclear environment: work in zone 4, where access is forbidden to humans and interventions are carried out by remote handling.
PREDIS Collaboration to Advance the Predisposal Management of Radioactive Waste
Authors: Oksa Maria
Published: November 2023

PREDIS - Predisposal management of radioactive waste is a European Commission funded project to develop predisposal activities on treatment and conditioning methodologies. The target is for wastes, which yet haven’t adequate or industrially mature solutions, including metallic materials, liquid organic and solid organic waste. PREDIS project also addresses testing and evaluating innovations and digitalization solutions for cemented waste handling and pre-disposal storage. The scope of the PREDIS project includes characterization, treatment and conditioning of the waste streams, demonstrations and performance evaluation of the waste streams to verify safety and effectiveness of the new solutions. Environmental assessment of the processes and residual products, economic assessment of the treatment processes and finally guidelines for use, to ensure deployment of the new solutions are also in focus of the project.

The four-year PREDIS project that started in September 2020 with 47 seven partners in 17 countries has been strong in development, collaboration and sharing information on predisposal activities both in technical issues and in strategic research agenda, waste acceptance criteria and life cycle assessment. One target of the project has been to develop the knowledge management programme and support training and mobility activities in collaboration with EJP EURAD. PREDIS project has close collaboration with stakeholders and end users, having an End User Group of 25 organisations. PREDIS project has already widely disseminated the project results via webinars, open workshops and international conferences, and had close dialogue with the stakeholders to share the relevant information on predisposal issues. This paper will present the main achievements in the research and development collaboration aspect of the PREDIS project.
Lessons Learned From Implementing Training and Mobility Programmes Within EC H2020 Projects EURAD and PREDIS
Authors: Miksova Jitka , Belmans Niels , Carbol Paul , Holt Erika , Valls Alba , Faltejsek Jiří , Coeck Michele
Published: November 2023

Both EURAD and PREDIS are addressing research, strategic studies and knowledge management (KM) in the field of radioactive waste management (RWM). PREDIS is focusing on radioactive waste predisposal, while EURAD on overall aspects of RWM with s special focus on geological disposal of radioactive waste. Both are partially financially supported by the European Commission.

Since inception, the KM activites are essential to ensure efficient knowledge transfer among the community. The projects contribute training amd mobility aspects, also including the ‘School of Radioactive Waste Management’, while using available research infrastructures and providing a platform for knowledge exchange.

Besides training courses, both projects regularly organize topical webinars with worldwide participant and facilitate exchange of students and experts between institutes. A number of initiatives are taken to give visibility to students in the R&D programmes, thus supporting their networking and possibilities for mentoring.
Viewing of Radioactive Material Including Vitrification Processes
Authors: Canty Christopher , Canty Tod
Published: November 2023

High Temperature cameras allow ideal visual inspection and verification in extreme temperature environments. A unique fused glass seal provides an impenetrable safety barrier between the camera electronics and the harsh process environments. The camera is protected from high temperatures, fumes and radiation. The dynamic imaging system provides a live view of the process, and analyzes the process by generating critical real time measurement data.

In nuclear waste vitrification, radioactive material is heated with glass forming additives and poured into a containment vessel to cool into a uniform glass product. The use of high temperature camera systems allows verification that the melting and cooling processes are uniform and repeatable, by providing a live view and analysis of the process. This allows for maximum efficiency and safety, while maximizing the percentage of waste that can be immobilized in the glass product.

The paper outlines the critical steps in the disposal of nuclear waste, including the vitrification processes. The strategies used to ensure process safety and efficiency are examined and the critical measurements in each step are determined. It is demonstrated that High Temperature cameras are a useful tool for monitoring those critical measurements to improve the processes of nuclear waste vitrification.
Methodology to Characterize Row Manifolds for High Power Direct to Chip Liquid Cooling Data Centers
Authors: Shahi Pardeep , Heydari Ali , Eslami Bahareh , Radmard Vahideh , Hinge Chandraprakash , Modi Himanshu , Chinthaparthy Lochan Sai Reddy , Tradat Mohammad , Agonafer Dereje , Rodriguez Jeremy
Published: November 2023

Demand is growing for the dense and high-performing IT computing capacity to support artificial intelligence, deep learning, machine learning, autonomous cars, the Internet of things, etc. This led to an unprecedented growth in transistor density for high-end CPUs and GPUs, creating thermal design power (TDP) of even more than 700 watts for some of the NVIDIA existing GPUs. Cooling these high TDP chips with air cooling comes with a cost of the higher form factor of servers and noise produced by server fans close to the permissible limit. To overcome these issues for high TDP chips advanced cooling technologies, need to be investigated. Liquid cooling is becoming more mainstream to overcome the some of challenges mentioned above. Direct-to-chip cold plate-based liquid cooling is highly efficient and becoming more reliable as the advancement in technology is taking place. Several components are used in the liquid-cooled data centers for the deployment of cold plate based direct to chip liquid cooling like cooling loops, rack manifolds, CDUs, row manifolds, quick disconnects, flow control valves, etc. Row manifolds used in liquid cooling are used to distribute secondary coolant to the rack manifolds. Characterizing these row manifolds to understand the pressure drops and flow distribution for better data center design and energy efficiency is important. In this paper, the methodology is developed to characterize the row manifolds. Water-based coolant Propylene glycol 25% was used as the coolant for the experiments and experiments were conducted at 21 °C coolant supply temperature. Highly calibrated Pressure sensors were used at the supply port of the row manifolds and the inlet-outlet of the main hose to measure the supply pressure of ports and pressure drop across the row manifold respectively. Similarly, ultrasonic flow sensors were used to measure the flow rate at each supply port and the main entrance of the row manifold. Two, six-port row manifolds’ P-Q curves were generated, and the value of supply pressure and the flow rate were measured at each port. The results obtained from the experiments were validated by a technique called Flow Network Modeling (FNM). FNM is a 1-D simulation suited for the analysis of flow distribution in liquid cooling systems. The FNM technique uses the overall flow and thermal characteristics to represent the behavior of individual components. Therefore, the solution of conservation equations over the network enables efficient prediction of the flow rates, pressures, and temperatures in a complete liquid-cooling system.
Study of Reliable Chip Last Process for Fan Out Wafer Level Package
Authors: Liu Shuai-Lin , Kao Nicholas , Lin Vito , Zhang Ken , Wang Yu-Po
Published: November 2023

Package on Package (PoP) is one of packing technology to implement in mobile application. PoP is a stacking technology to integrate two or more separated packages. Specifically for application processor or baseband die of smartphone and tablets, the design to stack AP/BB chip and memory package is adopted generally in iOS or Android phones. One of PoP structure, substrate base of high bandwidth PoP (HBW-PoP), is a mature packaging type and has accessed to market in recent years. Seeking to the alternative PoP technologies, the demand is to reduce package dimension to cram more chip functions and expand battery capacity by size as larger as possible. Fan out wafer level package (FOWLP) efficiently enable higher I/O counts for high performance edge computing by re-distribution organic layers (RDL). In addition, the more advanced silicon node, the higher cost design houses bear in packaging development. Therefore, this study is that we propose a fan out package on package (FO-PoP) with chip last process, which features have higher process yield, shorter cycle time benefits than chip first platform. Organic RDL can miniaturize package height by replacing substrate base PoP. The total height can reach less than 0.5mm and meet up the market trend in wearable and smartphone applications. Known-good-die (KGD) feature of chip last process extremely control RDL process yield to reduce AP dies loss and further improve overall packaging yield. Then, the in-parallel process between bottom RDL and die micro-bumping process can shorten cycle time for production efficiency. In this paper, test vehicle verification includes warpage in the criteria and reliability validation passed by packaging level reliability and board level reliability.
L2A CDUs Performance and Considerations for Server Rooms Upgrade With Conventional Air Conditioning
Authors: Heydari Ali , Soud Qusai , Tradat Mohammad , Gharaibeh Ahmad , Fallahtafti Najmeh , Rodriguez Jeremy , Sammakia Bahgat
Published: November 2023

As the online frameworks and services are growing rapidly with the evolution of web-based Artificial Intelligence (AI) applications, server rooms are upgrading in computational capacity and size to keep up with these demands. Enterprise companies with their limited capacity server rooms struggle to keep up with these increasing computational demands. Hence, some of them end up outsourcing their servers to co-located facilities (Co-Lo) and the others choose to upgrade their existing server rooms. Correspondingly, the thermal load associated with such upgrades is typically tremendous. Approximately around 40% of the power consumed by datacentres is dissipated as heat. Conventional HVAC systems fail to satisfy the requirements of such server capacities. Not only do they struggle to fulfil the cooling load, but their maldistribution of cool air into the server room forms a major cause for hotspots formation. To tackle this issue, Liquid-to-Air (L2A) Coolant Distribution Units (CDUs) are being used as a liquid-based cooling solution for rack-level cooling. This type of CDUs provide efficient cooling for servers through liquid coolant that is distributed into cooling loops mounted on top of each server board. The generated heat is curried away using this liquid coolant back to the CDU, which then dissipates it into the surrounding air using dedicated pumps, fans, and heat exchanger, hence the name Liquid-to-Air.

In the present work, one of the most popular liquid cooling strategies is explored based on various scenarios. the performance of a 24-kW liquid to Air (L2A) CDU is judged based on cooling effect, stability, and reliability. The study is curried out experimentally, in which a test rack with three thermal test vehicles (TTVs) are used to investigate various operation scenarios. Both liquid coolant and air sides of this experimental setup are equipped with the required instrumentations to monitor and analyse the tests. All test cases were taken in a room with limited air conditioning to resemble the environment of upgraded server rooms with conventional AC systems. Moreover, the impact of using such high-power density cooling unit on the server room environment with restricted HVAC system is also brought to light. Environmental and human comfort parameters such as noise, air velocity, and ambient temperature are measured under various operation conditions and benchmarked against their ranges for human comfort as listed in ASHREE standards. At the end of this research, recommendations for best practice are provided along with areas of enhancement for the selected system.
Thermal-Hydraulic Characterization of Thermosyphon Cooling System for Highly Compact Edge MicroDataCenter. Part I: Design and Experiments
Authors: Rouaze Gautier , Minazzo Enzo M. , Marcinichen Jackson B. , Thome John R. , Buining Fred
Published: November 2023

The delivery of computing services — including storage, databases, networking, software, analytics, artificial intelligence (AI) and more — has started with Cloud Computing (CC) over the Internet, delivered from off-premise datacenters, running infrastructure at scale with a pay as you go service to their end customers. As the Internet of Everything (IoE) continues to evolve, parts of these services are migrating from the centralized locations (Cloud) to more decentralized locations closer to the end-user, e.g. Fog Computing (FC), Edge Computing (EC) and only recently on to the end-user device itself, the Mist Computing (MC). By 2025, Gartner predicts 75% of the data will be processed at the Edge. Applications are characterized by big data and near real-time processes in various areas, such as: energy management, highways, buildings, plant automation, supply chain, visual security, signage, and mobile-EC. Unlike for Cloud systems, reference frameworks and standards for FC and EC are still in an early stage of development or non-existant for MC.

As part of the European project BRAINE (a 28-partner consortium), a novel type of Edge MicroDataCenter (EMDC) providing cost-effective, powerful computing resources close to endusers and specifically designed for AI elaborations is being developed with very efficient cooling that nears being completely passive.

The present study concentrates on experimental validations of a new highly efficient, passive thermosyphon cooling system (patent pending by October 2023) thermally managing the level and uniformity of temperature for all the electronics in the package (no air cooling at all within the computer chassis). The primary objective is the cooling of 11 nodes (which include CPUs, FPGAs, GPUs and Storage) considering one heat sink evaporator per node. Presently, a first prototype as a simplified EMDC with 4 slots (i.e 4 nodes) has been fabricated and the entire thermosyphon cooling system evaluated. The experimental results are presented. The working fluids used are the new environmentally friendly refrigerants R1233zd(E) and R1234ze(E).

It is highlighted that BRAINE’s overall aim is to boost the development of the Edge framework and specifically energy-efficient hardware and AI-empowered software systems, capable of processing Big Data at the Edge, performing AI functions, supporting security, data privacy and sovereignty. Then, cooling is one of the most important aspect in this new technological challenge. In fact, our cooling system has no moving parts inside computer (solid-state) and our thermosyphon has an energy efficiency ratio of heat dissipation-to-cooling fan power up to 64-to-1.
Prediction of Pad Cratering Performance at Copper-Resin Interfaces With Multiple Reflows
Authors: Lall Pradeep , Pandurangan Aathi Raja Ram , Choudhury Padmanava
Published: November 2023

Pad cratering is one of the major failure modes encountered during PCB assembly and operation. Fracture is generally mechanically induced between the outermost layer of board resin and copper foil, between the resin and the glass fibers, or in the bulk resin of the printed circuit board. Prior work on the reliability of printed circuit board assemblies focuses on solder joint fatigue. However, data on the reliability of pad cratering and predictive models on expected pad-crater propensity are scarce. Mechanical characteristics of the copper/resin interfaces and bulk resin material evolve with reflows. Pad cratering at copper-to-resin interfaces with respect to reflows has not been studied widely yet. Ten distinct bulk resin materials have been investigated to compute the evolution of bulk resin properties. Copper-to-resin interfacial samples have been tested under four-point bend loading with respect to reflow conditions. The evolution of bulk resin properties has been considered for computing the evolution of copper/resin interfacial properties. The steady-state energy release rate and Interfacial Fracture Toughness are determined for each testing condition. This research would be useful in proposing a copper/resin interface combination that is more reliable against pad cratering. Based on the data captured, a predictive regression model has been developed to predict the material combinations providing the best reliability against pad cratering.
Prediction of Failure at FCBGA Interfaces Under Thermo-Mechanical Loads Using a Competing Risk Cohesive Zone Model
Authors: Lall Pradeep , Pandurangan Aathi Raja Ram , Katsuri Madhu
Published: November 2023

Automotive under-the-hood electronics may reside on-engine, on-transmission, or in-wheel-well. Several high I/O advanced packaging architectures, including the flip-chip ball grid arrays (FCBGAs), enable much of the functionality. Underhood electronics in automobiles are an integral part of the critical and safety operations of the vehicle. Underfills significantly reduce the amount of plastic work during temperature excursions and offer mechanical support to the solder connections. One of the most common failure modes at chip/UF interfaces has been delamination. A critical characteristic in evaluating the chip/UF interfacial reliability is the interfacial fracture toughness of the chip/UF interfaces. The interfacial crack could rapidly spread to the solder joints, leading to system failure. The chip/UF interface properties may change over time in response to high-temperature exposure. In this study, bi-material specimens of Chip/UF interfaces have been fabricated and exposed to high temperatures of 100°C and 150°C for 30 days, 60 days, 90 days, 120 days, 180 days, 240 days, 300 days, and 360 days. The aged samples are subjected to four-point bend fatigue and monotonic loading. The interfacial fracture toughness values have been determined for each loading condition. The Paris constants (A, n) are computed from fatigue loading interfaces, which directly represent the evolution of interfacial properties with respect to sustained high-temperature exposure. A predictive finite element model of the FCBGA interfaces has been created.
A Comparative Data Center Energy Efficiency and TCO Analysis for Different Cooling Technologies
Authors: Heydari Ali , Eslami Bahareh , Chowdhury Uschas , Radmard Vahideh , Shahi Pardeep , Miyamura Harold , Tradat Mohammad , Chen Peter , Tuholski Drew , Gray Kevin , Buell Tyler , Stover Greg , Rodriguez Jeremy
Published: November 2023

Growth of data centers’ demand for electricity with respect to the energy cost emerges the need for more effective cooling solutions. This requirement necessitates a comprehensive assessment of each cooling technology in terms of their energy efficiency and economic performance. Here we developed a comparative analysis for four different cooling methods for a 1.7MW data center to indicate how the type and scale of the cooling technology impacts the total efficiency and costs. IT load is kept constant among all the four studies and only the cooling infrastructure configuration has been changed. Both air and hybrid (air-liquid) cooling are examined and for the liquid-cooled section, liquid-to-liquid (L2L), and liquid-to-air (L2A) coolant distribution units (CDU) are assessed at two levels of rack and row scale. Total Usage Effectiveness (TUE) and Total Cost of Ownership (TCO) results are presented for all different designs. The TCO calculations are divided into some subsections where costs for the primary and secondary side of the data center are specified. The capital cost for equipment, cooling units, preparation inside and outside of the data center, plumbing, installation, commissioning, and servicing etc. are considered while preparing the total cost for a particular cooling technology. Here, we considered N+1 redundancy for the cooling equipment on the secondary side and UPS system. The operation cost calculation includes the energy usage of the components inside and outside of the data center. Comprehensive analysis has been performed while transitioning from air cooling to hybrid cooling as efficiency of the components play an important role in determining the total power consumption. In this analysis, TCO modeling is facilitated with TUE number for cases being studied and power consumption from auxiliary components are included in the analysis. Results demonstrate a drop of 8.5% and 3.4% in total cooling energy usage and operating costs respectively due to the transition from air towards hybrid cooling. In the next step, the sensitivity of the TCO model to the type of coolant fluid and relevant thermohydraulic properties has been evaluated and presented. In the concluding phase, an optimization study was undertaken to illustrate the appropriate utilization of liquid cooling in order to achieve a design that is more economically efficient. This analysis aims to provide insights regarding the technological opportunities for further power and cost reductions for data center owners and highlight the most impactful parameters on both operational and capital costs. The outcome of this research demonstrates the actual cost per MW of IT which is a simple yet effective metric for each cooling architecture.
Impact of Component Interconnectivity on Mechanical and Electrical Properties of Flexible Hybrid Electronics with Printed Water-based Silver Ink Circuits
Authors: Lall Pradeep , Musa Fatahi , Soni Ved , Miller Scott
Published: November 2023

Flexible Hybrid Electronics (FHE) have the potential to revolutionize the electronics industry by providing sustainable and efficient devices. However, the reliable interconnectivity between printed traces and surface-mount devices (SMD) remains a critical challenge for FHE. There is a need for more research on the use of printed water-based silver ink traces and bonding materials for component attachment in FHE, as the literature on this subject is limited. This study was conducted to compare the effects of different bonding materials on component attachment. The bonding materials investigated were electrically conductive adhesive (ECA) and low-temperature solder (LTS). The study used the direct write method to print silver pads, which were then used to attach components such as resistors, inductors, and capacitors using the bonding materials. Electrically conducted adhesive (ECA) results were compared to those of Low Temperature Solder (LTS). The interconnectivity of the attached components was evaluated by measuring their rating values before and after attachment. The findings of this study provide insights into the performance of different bonding materials for component attachment in FHE. Such insights can aid in the development of reliable and efficient interconnectivity methods for FHE, which can contribute to the widespread adoption of FHE in various industries.
Effects of Grain to Sample Volume Ratio on the Deformation Behavior of Polycrystal SAC Samples Subjected to Shear Loads
Authors: Mondal Debabrata , Suhling Jeffrey C. , Mirkoohi Elham , Lall Pradeep
Published: November 2023

The study of size effects in electronic structural components and solders is important when dimensions are being continually downsized. It is crucial to obtain a constitutive model that describes material behavior of electronic package solders at small scales. Ample studies are available to describe the deformation behavior of SAC alloys at bulk level. For instance, stress-strain, creep, and shear behaviors have been investigated for bulk SAC samples. Although solder joints are very small in dimensions, most researchers have not explained the solder deformation considering size effects. With further miniaturization of solder joints in high density packaging, the localized material behavior can influence significantly the overall system. For instance, knowledge of individual grain properties of a crystalline materials is essential in determining material behavior of miniaturized products.

Sn-Ag-Cu (SAC) alloys are the most widely used lead-free materials to fabricate solder interconnects in microelectronic packaging. For most of the SAC alloys, more than 95% weight percentage is β-Sn which is a highly anisotropic material in terms of elastic modulus (E) and coefficient of thermal expansion (CTE). Moreover, due to the crystalline nature of β-Sn material, plastic deformation beyond the elastic limit is described by various atomic planes and directions, which are termed as slip systems. Ten different slip families with 32 slip systems have been recognized for β-Sn body-centered tetragonal (BCT) crystals. When external loads are applied on solder joints, plastic deformation is dictated by the movement of dislocations and direction of deformation is defined by slip systems.

When structural components are miniature in dimensions, crystal plasticity theory can accurately predict the material response considering crystallographic deformation mechanisms. In this study, a crystal plasticity-based DAMASK code was used to explain the mesoscale deformation behavior of polycrystal beta-tin samples. Polycrystalline beta-tin samples were obtained using Voronoi tessellation in NEPER with random grain orientations, which is the case for real samples. Shear simulations were performed for a sample with reasonably large number of grains. The model was then calibrated with experimental stress-strain data for a reflowed SAC305 alloy to determine a set of beta-tin slip properties. Subsequently, multiple polycrystalline models were generated with varying number of Sn grains, and a spectral solver was used to determine the sample responses under shear loads on three orthogonal planes. Samples with large number of grains exhibited isotropic deformation behavior. However, samples with fewer number of grains demonstrated anisotropic behavior. This study determined the overall average grain size to sample size ratio at which isotropic behavior breaks down under the application of shear loads.
Assessment of Effect of Operating Temperature on SAC-R Solders at High Strain Rates After Prolonged Storage
Authors: Lall Pradeep , Saha Mrinmoy , Suhling Jeff , Locker David
Published: November 2023

Electronic components may be used continuously under high strain-rate loads, high ambient temperatures, and other conditions in the aerospace, military, automobile, space, and offshore oil industries. In addition, these components may be kept in uncontrolled climate enclosures before deployment. A long duration of storage has been found to cause the material characteristics of undoped SAC alloys to change, even at mild temperatures. To reduce the effects of aging, a number of dopants have been added to the compositions of SAC alloys. In this investigation, SAC-R, a doped SAC solder, has been stored at 50°C for a year before being put through high strain rate testing. Uniaxial tensile tests have been performed to determine the mechanical characteristics of SAC-R in samples that have aged for no aging and samples that have aged for up to 360 days. The experiment’s High and Low operating temperatures ranged from −65°C to 200°C. After computing the constants for the Anand Visco-Plasticity model using the experimental material data, the model’s predictions for the uniaxial tensile test were compared to the experimental data. In order to simulate the drop events using the Anand constitutive model, the material constitutive behavior has been implemented in a finite element framework. In order to track the course of damage in the solder interconnects, the plastic work per shock event has also been calculated. The shock event of a ball-grid array package on PCB assembly has been simulated using the constitutive model.
Evaluation of Additive Circuits Printed With Sustainable Aqueous Silver Inks Using Aerosol Jet Printing and Gravure Offset Printing and Investigation of Circuit Repairability
Authors: Lall Pradeep , Soni Ved , Miller Scott
Published: November 2023

Additive printed electronics, in particular, has been a rapidly advancing field, with applications that span from smart packaging to energy harvesting systems to healthcare devices to intelligent textiles. The basic building block of any flexible circuit created by these technologies is conductive ink. This ink typically comprises metal nanoparticles and several solvents. However, many of the solvents used in these inks are toxic substances or include volatile organic compounds (VOCs) that have a variety of negative effects on the environment and human health, including air pollution, smog, respiratory problems, health risks, and reduced air quality. Consequently, there is a strong push toward developing sustainable materials for use in products, including ink formulations with fewer toxic solvents. In this study, researchers investigate the use of two printing techniques, aerosol jet printing and gravure offset printing, to print full-wave rectifiers (AC to DC conversion) and Voltage bridge oscillators (DC to AC conversion) using commercially available aqueous silver ink. The performance of the additively printed circuits is compared to both theoretical values and to the same circuits printed using non-aqueous inks. Additionally, a switch-mode battery charging circuit has also been printed with a sustainable ink and its performance has been investigated.