bluuebunny/crossref_metadata_2025 huggingface dataset:
Recruitment and Retention of Older People in Clinical Research: A Systematic Literature Review
Authors: Forsat Noah D. , Palmowski Andriko , Palmowski Yannick , Boers Maarten , Buttgereit Frank
Published: October 2020

OBJECTIVE

To identify barriers and solutions for the recruitment and retention of older (aged ≥65 years) people in clinical trials.

DESIGN

Systematic literature review.

METHODS

Three databases (Medline, Embase, and CENTRAL) were searched for articles reporting on barriers or solutions regarding the recruitment or retention of older people. Only original research articles were included.

RESULTS

Fifty eligible articles were identified. Exclusion criteria were the most common cause of poor recruitment of older adults (mainly age and comorbidities). Patients' families or physicians often advised against participation (22% of included studies). Lack of interest (18%) and problems with transportation (18%) were also commonly cited as challenges. Fourteen trials (28%) reported that monitoring and adapting their recruitment methods helped, along with a flexible research team (26%) and provision of transportation (24%). Retention was impaired by death (12%), illness (8%), and loss of interest (6%). Methods with a positive effect on retention included financial incentives and regular information about the progress of the study (12%), a low staff turnover (12%), flexibility in appointment making (10%), and expression of appreciation by the staff through letters, gifts, and cards to the participants (10%).

CONCLUSION

We identified several barriers and have listed potential solutions that may improve recruitment and lead to fewer dropouts in trials involving older populations. Implementation of our findings may help mitigate the manifold challenges that come with running a trial with older people.
ANNEXIN 8 negatively regulates RPW8.1‐mediated cell death and disease resistance in Arabidopsis
Authors: Zhao Zhi‐Xue , Xu Yong‐Ju , Lei Yang , Li Qin , Zhao Ji‐Qun , Li Yan , Fan Jing , Xiao Shunyuan , Wang Wen‐Ming
Published: October 2020

Study on the regulation of broad‐spectrum resistance is an active area in plant biology. RESISTANCE TO POWDERY MILDEW 8.1 (RPW8.1) is one of a few broad‐spectrum resistance genes triggering the hypersensitive response (HR) to restrict multiple pathogenic infections. To address the question how RPW8.1 signaling is regulated, we performed a genetic screen and tried to identify mutations enhancing RPW8.1‐mediated HR. Here, we provided evidence to connect an annexin protein with RPW8.1‐mediated resistance in Arabidopsis against powdery mildew. We isolated and characterized Arabidopsis b7‐6 mutant. A point mutation in b7‐6 at the At5g12380 locus resulted in an amino acid substitution in ANNEXIN 8 (AtANN8). Loss‐of‐function or RNA‐silencing of AtANN8 led to enhanced expression of RPW8.1, RPW8.1‐dependent necrotic lesions in leaves, and defense against powdery mildew. Conversely, over‐expression of AtANN8 compromised RPW8.1‐mediated disease resistance and cell death. Interestingly, the mutation in AtANN8 enhanced RPW8.1‐triggered H2O2. In addition, mutation in AtANN8 led to hypersensitivity to salt stress. Together, our data indicate that AtANN8 is involved in multiple stress signaling pathways and negatively regulates RPW8.1‐mediated resistance against powdery mildew and cell death, thus linking ANNEXIN's function with plant immunity.
Serum fibroblast growth factor 21 level is increased in pre‐eclampsia patients: Association with blood pressure and lipid profile
Authors: Jiang Lin , Zhou Yang , Huang Qin
Published: October 2020

Background

Pre‐eclampsia (PE) is dangerous complication, which leads to adverse pregnancy outcomes.

Aims

The study was to explore the correlation between serum level of fibroblast growth factor (FGF) 21 and PE.

Methods

A total of 80 cases were involved in this study containing PE group (49 cases) and control group (31 cases, normal pregnancy). PE group was divided into early‐onset PE (EOPE) and late‐onset PE (LOPE). Serum level of FGF21 and biochemical parameters were measured before delivery.

Results

Maternal serum FGF21 level was higher in PE especially in EOPE than that in control groups (P < 0.05). In PE patients, serum FGF21 level was positively correlated with mean arterial pressure, diastolic blood pressure and low‐density lipoprotein cholesterol (P < 0.05). Levels of FGF21, uric acid and low‐density lipoprotein cholesterol were risk factors for PE.

Conclusion

Maternal serum FGF21 level in PE particularly in EOPE was higher and was associated with blood pressure and lipid profile.
Police and mental health in elementary and secondary schools: A systematic review of the literature and implications for nursing
Authors: Muller Rebecca , Morabito Melissa S. , Green Jennifer Greif
Published: October 2020

Accessible summary

What is known on this subject?

Police are often called on to respond to student mental health needs in schools.

School nurses, who are part of interdisciplinary mental health teams, may collaborate with responding police officers.

Currently, there are no reviews of the literature describing the use of police to respond to mental health crises in schools.

What this paper adds to existing knowledge?

This systematic review found six articles addressing police response to student mental health needs in elementary and secondary schools.

Articles primarily focused on the School Resource Officer programme; however, there was a lack of research on the effectiveness of this and other programmes in addressing the mental health needs of students.

This paper highlights a significant gap in knowledge about how police are involved in responding to student mental health crises within schools.

What are the implications for practice?

Understanding how police respond to mental health crises on school campuses will help nurses serve in collaborative roles with responding officers.

This study highlights gaps in research that need to be addressed for researchers and policymakers to best support students in crisis.

Introduction

Response to student mental health crises involves interdisciplinary school–community teams, which can include police officers. This paper presents the first systematic review of literature on how police address mental health in school settings. Results have implications for school nurses interacting with responding police.

Question/Aim

How are police involved in responding to student mental health needs in elementary and secondary schools?

Method

Using the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) framework, six articles met criteria for inclusion in this review.

Results

Two themes were identified: (1) descriptions of roles of police in schools and (2) studies presenting programmes or models of police engagement. The most common use of police in schools is through the School Resource Officer model.

Discussion

There are very few studies examining police involvement in mental health response in schools and little data available on whether prevailing models are effective. We are therefore unable to ascertain what impact school police have in responding to mental health crises or the extent to which they interact with school nurses.

Implications for practice

Understanding mental health crisis responses in schools can inform policy, practice, research and education for police and school providers, including nurses.
Spatial partial identity model reveals low densities of leopard and spotted hyaena in a miombo woodland
Authors: Davis R. S. , Stone E. L. , Gentle L. K. , Mgoola W. O. , Uzal A. , Yarnell R. W.
Published: October 2020

Decline in global carnivore populations has led to increased demand for assessment of carnivore densities in understudied habitats. Spatial capture–recapture (SCR) is used increasingly to estimate species densities, where individuals are often identified from their unique pelage patterns. However, uncertainty in bilateral individual identification can lead to the omission of capture data and reduce the precision of results. The recent development of the two‐flank spatial partial identity model (SPIM) offers a cost‐effective approach, which can reduce uncertainty in individual identity assignment and provide robust density estimates. We conducted camera trap surveys annually between 2016 and 2018 in Kasungu National Park, Malawi, a primary miombo woodland and a habitat lacking baseline data on carnivore densities. We used SPIM to estimate density for leopard (Panthera pardus) and spotted hyaena (Crocuta crocuta) and compared estimates with conventional SCR methods. Density estimates were low across survey years, when compared to estimates from sub‐Saharan Africa, for both leopard (1.9 ± 0.19 sd adults/100 km2) and spotted hyaena (1.15 ± 0.42 sd adults/100 km2). Estimates from SPIM improved precision compared with analytical alternatives. Lion (Panthera leo) and wild dog (Lycaon pictus) were absent from the 2016 survey, but lone dispersers were recorded in 2017 and 2018, and both species appear limited to transient individuals from within the wider transfrontier conservation area. Low densities may reflect low carrying capacity in miombo woodlands or be a result of reduced prey availability from intensive poaching. We provide the first leopard density estimates from Malawi and a miombo woodland habitat, whilst demonstrating that SPIM is beneficial for density estimation in surveys where only one camera trap per location is deployed. The low density of large carnivores requires urgent management to reduce the loss of the carnivore guild in Kasungu National Park and across the wider transfrontier landscape.
Modelling nonlinear dynamics of Crassulacean acid metabolism productivity and water use for global predictions
Authors: Hartzell Samantha , Bartlett Mark S. , Inglese Paolo , Consoli Simona , Yin Jun , Porporato Amilcare
Published: October 2020

Crassulacean acid metabolism (CAM) crops are important agricultural commodities in water‐limited environments across the globe, yet modelling of CAM productivity lacks the sophistication of widely used C3 and C4 crop models, in part due to the complex responses of the CAM cycle to environmental conditions. This work builds on recent advances in CAM modelling to provide a framework for estimating CAM biomass yield and water use efficiency from basic principles. These advances, which integrate the CAM circadian rhythm with established models of carbon fixation, stomatal conductance and the soil–plant‐atmosphere continuum, are coupled to models of light attenuation, plant respiration and biomass partitioning. Resulting biomass yield and transpiration for Opuntia ficus‐indica and Agave tequilana are validated against field data and compared with predictions of CAM productivity obtained using the empirically based environmental productivity index. By representing regulation of the circadian state as a nonlinear oscillator, the modelling approach captures the diurnal dynamics of CAM stomatal conductance, allowing the prediction of CAM transpiration and water use efficiency for the first time at the plot scale. This approach may improve estimates of CAM productivity under light‐limiting conditions when compared with previous methods.
Preoperative echocardiographic parameters predict primary graft dysfunction following pediatric lung transplantation
Authors: Himebauch Adam S. , Wong Wai , Wang Yan , McGowan Francis X. , Berg Robert A. , Mascio Christopher E. , Kilbaugh Todd J. , Lin Kimberly Y. , Goldfarb Samuel B. , Kawut Steven M. , Mercer‐Rosa Laura , Yehya Nadir
Published: October 2020

The importance of preoperative cardiac function in pediatric lung transplantation is unknown. We hypothesized that worse preoperative right ventricular (RV) systolic and worse left ventricular (LV) diastolic function would be associated with a higher risk of primary graft dysfunction grade 3 (PGD 3) between 48 and 72 hours. We performed a single center, retrospective pilot study of children (<18 years) who had echocardiograms <1 year prior to lung transplantation between 2006 and 2019. Conventional and strain echocardiography parameters were measured, and PGD was graded. Area under the receiver operating characteristic (AUROC) curves and logistic regression were performed. Forty‐one patients were included; 14 (34%) developed PGD 3 and were more likely to have pulmonary hypertension (PH) as the indication for transplant (P = .005). PGD 3 patients had worse RV global longitudinal strain (P = .01), RV free wall strain (FWS) (P = .003), RV fractional area change (P = .005), E/e’ (P = .01) and lateral e’ velocity (P = .004) but not tricuspid annular plane systolic excursion (P = .61). RV FWS (AUROC 0.79, 95% CI 0.62‐0.95) and lateral e’ velocity (AUROC 0.87, 95% CI 0.68‐1.00) best discriminated PGD 3 development and showed the strongest association with PGD 3 (RV FWS OR 3.87 [95% CI 1.59‐9.43], P = .003; lateral e’ velocity OR 0.10 [95% CI 0.01‐0.70], P = .02). These associations remained when separately adjusting for age, weight, primary PH diagnosis, ischemic time, and bypass time. In this pilot study, worse preoperative RV systolic and worse LV diastolic function were associated with PGD 3 and may be modifiable recipient risk factors in pediatric lung transplantation.
Use of low cell dose for unmanipulated donor lymphocyte for management of cytomegalovirus infection: A single‐center experience
Authors: Uygun Vedat , Karasu Gülsün , Daloğlu Hayriye , Öztürkmen Seda , Yalçın Koray , Çelen Safiye Suna , Yeşilipek Akif
Published: October 2020

Although advancements have been made in monitoring and preventing viral infections in HSCT patients, CMV reactivation still remains a critical post‐transplant complication. Adoptive cell therapy is an alternative to pharmacotherapy of CMV infection in refractory patients. We retrospectively reviewed CMV infection cases after allogeneic HSCT who received U‐DLI as treatment. In total, five pediatric patients between the ages of 0.5‐16 years that received U‐DLI for a post‐HSCT CMV infection were evaluated. The dose of CD3+ lymphocytes administered in DLI was 5 × 104/kg, except in one patient transplanted from his sibling. One patient, who was transplanted from an unrelated donor, received U‐DLI from his haploidentical mother. CMV titers dramatically reduced after U‐DLI. If the availability of CMV‐specific CTL is an issue, we propose that one should consider using the U‐DLI therapy with low cell dose from a seropositive donor. In case the stem cell donor is seronegative and a seropositive donor is unavailable, using the U‐DLI therapy from seropositive, haploidentical donors is a promising way of treatment. More studies need to be conducted to further confirm the safety and efficacy of this treatment procedure.
Stromal metalloproteinases: Crucial contributors to the tumor microenvironment
Authors: Shimoda Masayuki , Ohtsuka Takashi , Okada Yasunori , Kanai Yae
Published: October 2020

Proteolytic balance is crucial for the maintenance of tissue homeostasis. In cancer, dysregulated proteolysis is involved in unregulated tissue remodeling and inflammation, leading to the promotion of tumor growth, local invasion, and metastasis. Metalloproteinases, which were first identified as collagen cleaving enzymes, have been shown to extensively degrade extracellular matrix proteins or selectively release cell surface‐bound cytokines, growth factors, or their receptors, thereby impacting extracellular matrix integrity, immune cell recruitment and tissue turnover. Although tumor cells produce various metalloproteinases, the major source is thought to be stromal cells infiltrating the tumor. Different types of stromal cells express specific sets of metalloproteinases and their inhibitors, which specifically alter the milieu within the tumor. In this review, recent findings and knowledge regarding metalloproteinases derived from stromal cells during the creation of the tumor microenvironment are described and their contribution to the tumor progression and metastasis discussed.
Adaptability of winter wheat Dongnongdongmai 1 (Triticum aestivum L.) to overwintering in alpine regions
Authors: Bao Y. , Yang N. , Meng J. , Wang D. , Fu L. , Wang J. , Cang J.
Published: October 2020

Long winters led to a one‐crop‐a‐year cultivation system until the winter wheat Dongnongdongmai 1 (Dn1) was successfully cultivated in northeast China. This crop variety is resistant to extremely low temperatures (−35 °C).

To better understand the adaptability of winter wheat Dn1 to low temperatures, gas chromatography time‐of‐flight mass spectrometry (GC‐TOF/MS) and metabolomics analysis was conducted on the tillering nodes of winter wheat during the overwintering period. Enzyme‐regulating genes of the metabolic products were also quantitatively analysed.

The metabolomic results for the tillering nodes in the overwintering period showed that disaccharides had a strong protective effect on winter wheat Dn1. Amino acid metabolism (i.e. proline, alanine and GABA) changed significantly throughout the whole wintering process, whereas organic fatty acid metabolism changed significantly only in the late stage of overwintering. This result indicates that the metabolites used by winter wheat Dn1 differ in different overwintering stages.

The relationship between field temperature and metabolite changes in winter wheat Dn1 during overwintering periods is discussed, and disaccharides were identified as the osmotic stress regulators for winter wheat Dn1 during the overwintering process, as well as maintenance of the carbon and nitrogen balance by monosaccharides, amino acids and lipids for cold resistance.
Sedimentology of the Upper Pennsylvanian organic‐rich Cline Shale, Midland Basin: From gravity flows to pelagic suspension fallout
Authors: Peng Junwen
Published: October 2020

Although deep‐water fine‐grained sedimentary rocks comprise approximately two‐thirds of the stratigraphic record, the transportation and depositional processes are poorly understood compared with their shelf counterparts. This study reports the range of fine‐grained sedimentary rock lithofacies, transport, and depositional processes and cyclicities recorded in deep‐water deposits on the basis of three continuous cored wells from the Upper Pennsylvanian Cline Shale, Midland Basin, USA, with the goal of elucidating general principles that can inform synthesis depositional models for deep‐water fine‐grained sedimentary systems. A combination of sedimentological, petrographic and bulk geochemical analysis has defined seven lithofacies that stack in a repeated pattern to constitute ca 8 to 20 m thick composite cycle sets. The lower unit of each composite cycle set is characterized by basal siliciclastic‐rich lithofacies interpreted to record dilute, low‐density turbidity currents, potentially derived from hyperpycnal input which grade upward into carbonate‐rich lithofacies interpreted as debris‐flow deposits or pelagic suspension deposits. The upper unit of each composite cycle set is characterized by basal carbonate‐rich lithofacies interpreted as debris‐flow deposits or pelagic suspension deposits which grades upward into siliciclastic‐rich lithofacies interpreted to record dilute, low‐density turbidity currents, potentially derived from hyperpycnal input. The cyclicities recorded in the Cline Shale are believed to be controlled by high‐amplitude glacioeustatic sea‐level fluctuation (mean: ca 100 m). The siliciclastic‐rich lithofacies, potentially derived from hyperpycnal turbidity flows, were deposited during sea‐level lowstand, when siliciclastic sediment‐transport systems extended across the wide Eastern Shelf and deltas developed at the shelf margin. Carbonate‐rich lithofacies are interpreted to be deposited from debris flows or pelagic suspension fallout during sea‐level highstand when carbonate platforms were developed on the surrounding shelves. The prevalence of sediment density flow deposits, even in distal basin floor environments, challenges the conventional model that deep‐water fine‐grained sedimentary rocks are dominantly background sedimentation.
Consociational Power‐Sharing in the Arab World as Counter‐Revolution
Authors: Halawi Ibrahim
Published: October 2020

This paper argues that consociational power‐sharing in the Arab world is intrinsically counter‐revolutionary. The academic debate on consociational power‐sharing has largely overlooked this because 1) it pre‐supposes class inequalities and over‐emphasizes state stability; and 2) it is limited by a broader misunderstanding of counter‐revolution, in which the concept is reduced to momentary reactions to revolution. By critiquing class and state assumptions in the consociational power‐sharing literature and presenting a nuanced conceptualization of counter‐revolution, this paper seeks to bring the debate closer to the concurrent revolutionary episodes against the consociational arrangements of Lebanon and Iraq, and to inspire more inclusionary state‐(re)building arrangements in the Arab world.
The Syrian Conflict: Proxy War, Pyrrhic Victory, and Power‐Sharing Agreements
Authors: Heydemann Steven
Published: October 2020

The Syrian conflict presents as a case that has been well‐studied in the power‐sharing literature. It is typically coded as an ethno‐sectarian civil war moving towards a decisive military victory by an authoritarian regime and thus unlikely to end in a power‐sharing agreement. Yet Syria's experience offers important insights into the effects of new conflict environments on prospects for power‐sharing in ‘hard’ cases. Syria's conflict exhibits attributes and is unfolding in an environment that requires rethinking simplistic correlations between the military and political outcomes of civil wars. Moreover, the form of political settlement that emerges in Syria may also complicate assumptions about the ability of victors to shape the terms of post‐war settlements unilaterally. Whether a power‐sharing agreement is reached in Syria – however remote the prospects for that might be – will be determined by factors that underscore the impact changing conflict contexts can have on how civil wars end.
Detection of adenovirus hepatitis and acute liver failure in allogeneic hematopoietic stem cell transplant patients
Authors: Onda Yoshiyuki , Kanda Junya , Sakamoto Soichiro , Okada Mutsumi , Anzai Naoyuki , Umadome Hiroshi , Tashima Masaro , Haga Hironori , Watanabe Chihiro , Hanaoka Nozomu , Fujimoto Tsuguto , Takaori‐Kondo Akifumi
Published: October 2020

Human adenovirus (HAdV) is an important cause of the common cold and epidemic keratoconjunctivitis in immunocompetent individuals. In immunocompromised patients, HAdV can sometimes cause severe infection such as cystitis, gastroenteritis, pneumonia, encephalitis, hepatitis, or disseminated disease, resulting in significant morbidity and also mortality. In particular, severe cases have been reported in patients after allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Indeed HAdV has been recognized as a pathogen that requires careful monitoring in allo‐HSCT patients. While HAdV hepatitis leading to severe acute liver failure is rare, such liver failure progresses rapidly and is often fatal. Unfortunately, HAdV hepatitis has few characteristic symptoms and physical findings, which makes it difficult to promptly confirm and start treatment. We report here four cases of HAdV hepatitis after allo‐HSCT and their autopsy findings.
Whole Field Measurements to Understand the Role of Varying Depths of Nucleation Site on Vapor Bubble Dynamics and Heat Transfer Rates
Authors: Narayan L Surya , Vijaykumar Pasi , Srivastava Atul
Published: October 2020

This work studies the possible effects of varying depths of cavity on bubbling features and the associated heat transfer rates in nucleate pool boiling regime. A single vapor bubble has been generated on a substrate with a cylindrical cavity at its center that acts as the nucleation site. Experiments have been conducted for three cavity depths (250, 500, and 1000 μm), while keeping its throat diameter constant at 200 μm. With the bulk fluid maintained under saturated conditions, for each cavity depth, surface superheat level has been varied in the range of ΔTsuperheat = 8, 10 and 12 °C. A gradient-based visualization technique, coupled with a high speed camera, has been employed to simultaneously map the changes in thermal gradients during the formation of the vapor bubble as well as bubble dynamic parameters. The image sequence obtained has been qualitatively and quantitatively analyzed to elucidate the dependence of bubbling features and various heat transfer processes on cavity depth. With an increase in the depth of cavity, the net effect of reduction in the available thermal energy due to the increased convection effects and significant depletion of superheated layer are identified as the dominant heat transfer processes that influence the bubbling features. Furthermore, based on the statistics of bubble departure characteristics, the cavity with higher depth (1000 μm) showed a much stable bubble formation with minimal variation in the bubble departure frequency as compared to the bubbling features from a cavity with smaller depth (250 μm). Evaporative heat transfer process has been identified as the primary cause for increased inconsistency of bubbling features at high superheat conditions for experiments performed for low cavity depths.
On the Development of Correlations for Bubble Liftoff Parameters During Subcooled Nucleate Flow Boiling Using Nonintrusive Dynamic Measurements
Authors: Sinha Gulshan Kumar , Srivastava Atul
Published: October 2020

Accurate prediction of bubble dynamic parameters is essential to improve boiling heat transfer models. Considering the complexities and challenges associated with performing a large number of boiling experiments, researchers have realized the importance of experimental correlations for predicting bubble dynamic parameters. In this direction, we report an experimental work concerned with the development of correlations for various bubble liftoff parameters during nucleate flow boiling regime. As a definite advancement, the experimental measurements have been performed in a purely nonintrusive manner, thereby minimizing the errors arising due to the interaction of any external probe with the process under study. The measurement approach makes use of a gradient-based imaging technique to simultaneously map the bubbling features and thermal field around a single vapor bubble generated under subcooled flow boiling conditions. Experiments have been performed in a rectangular channel for a wide range of heat fluxes (q" = 20–50 kW/m2), subcooling level (ΔTsub = 2–9 K), and Reynolds numbers (Re = 600–6000) with water as the working fluid. Results show a strong dependence of bubble liftoff parameters on Reynolds number, subcooling level, and applied heat flux. Based on the experimental measurements, empirical correlations have been developed for various bubble liftoff parameters as a function of Jacob number and Reynolds number. Predictions made through the developed correlations are found to be in good agreement with the measured values as well as with the values reported in the available literature. Of all the bubble parameters, maximum deviation between the predicted and measured values (≈23%) was found to be in bubble release frequency.
Research on Natural Convection of Two-Layer Corium Pools
Authors: Luo Simin , Sun Hongping , Zhang Yapei , Wu Junmei , Qiu Suizheng , Su Guanghui
Published: October 2020

As a promising mitigation strategy, In-vessel-retention (IVR) has been an important research focus in realms of nuclear safety analysis. For IVR analysis, it’s of importance to study the natural convection behaviors of the corium pool formed in the lower plenum of the reactor vessel. Because of the different densities between corium compositions, typically the corium pool is believed to evolve to two-layer configurations, with a heavier oxide layer at bottom and a metal layer on top. To know better the convection behaviors of the layered corium pools, research was performed both experimentally and numerically. The test section for the experiment is a two-dimensional semi-ellipsoidal slice, which measures a span of 1.2m, a total pool depth of 0.75m and a thickness of 0.2m. Two immiscible fluid, i.e. fluorinert fluid FC-40 and water, were chosen to simulate the oxide layer and the metal layer respectively. Based on the experimental settings, numerical simulations were performed, and the results were compared with the experimental data. Further, discussions were made on the focusing effect, the relationship between the temperature and the velocity field, and also the coupling modes in the two-layer system. These results offer more details to the knowledge of layered corium pools and can be helpful for IVR analysis.
Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors: Project Overview and Progress Until 2018
Authors: Yamano Hidemasa , Takai Toshihide , Furukawa Tomohiro , Kikuchi Shin , Emura Yuki , Kamiyama Kenji , Fukuyama Hiroyuki , Higashi Hideo , Nishi Tsuyoshi , Ohta Hiromichi , Liu Xiaoxing , Morita Koji , Nakamura Kinya
Published: October 2020

One of the key issues in a core disruptive accident (CDA) evaluation in sodium-cooled fast reactors is eutectic reactions between boron carbide (B4C) and stainless steel (SS) as well as its relocation. Such behaviors have never been simulated in CDA numerical analyses in the past, therefore it is necessary to develop a physical model and incorporate the model into the CDA analysis code. This study focuses on B4C-SS eutectic melting experiments, thermophysical property measurement of the eutectic melt, and physical model development for the eutectic melting reaction. The eutectic experiments involve the visualization experiments, eutectic reaction rate experiments and material analyses. The thermophysical properties are measured in a range from solid to liquid state. The physical model is developed for a severe accident computer code based on the measured data of the eutectic reaction rate and the physical properties. This paper describes the project overview and progress of experimental and analytical studies conducted until 2018. Specific results in this paper are boron concentration distributions of solidified B4C-SS eutectic sample in the eutectic melting experiments, which would be used for the validation of the eutectic physical model implemented into the computer code.
A Fault Diagnosis Method Based on Signed Directed Graph and Correlation Analysis for Nuclear Power Plants
Authors: Liu Chongchong , Wu Guohua , Yang Congsong , Li Yunwen , Wu Qian
Published: October 2020

Fault detection and diagnosis (FDD) provides safety alarms and diagnostic functions for a nuclear power plant (NPP), which comprises large and complex systems. NPP has a large number of parameters which make it difficult achieve FDD. Now many diagnosis methods have lack of better explanation for faults and quantitative analysis. Therefore, to overcome the “black box” of FDD based on data-driven methods, this paper adopts signed directed graph (SDG) in knowledge graph for FDD. It can express the cause and effect of accidents through knowledge maps. At same time, this paper uses correlation analysis to conduct a quantitative analysis between parameters and faults.

It this paper, SDG is used to explain the reason of faults. In order to quickly achieve FDD, this paper introduces a quantitative analysis method. It combines expert system and correlation analysis method to analyze the weight of each parameter. On this basis, matrix reasoning is used to achieve the FDD, and the reason is shown in SDG model inference. This paper takes loss of coolant accident as the case study, the case shows that the proposed method is superior to the conventional SDG method and can diagnose the faults timely.
Study on On-Site Calibration Method of Stationary Neutron Dosimeter
Authors: Lv Jinxu , Lv Ning , Guo Huiping , Sun Mingyan , Zhao Kuo , Lv Wenhui , Wei Zhihao , Xiao Qizhan , Li Daji , Liu Yang
Published: October 2020

The on-site calibration system of stationary neutron ambient dose equivalent instrument is mainly comprised of a small controllable neutron source and a reference neutron ambient dose equivalent instrument. According to the principle of “relative calibration method”, a small controllable neutron source continuously emits neutrons at the calibration site to construct a neutron radiation field.

The calibration factor (NB) can be obtained by comparing the response numbers from two instrument, the instrument to be calibrated and the reference instrument, which are symmetrically placed in the neutron radiation field. In order to complete the transfer of the ambient dose equivalent calibration coefficient of the reference instrument from National Metrology Center (252CfStandard radiation field) to nuclear facility site, the calibration coefficient needs to be corrected, that is, multiplied by the “energy correction coefficient”. Energy correction coefficient includes: (1) “Instrument Energy Response Correction Coefficient” kε for neutron fluence to neutron counting of the instrument, (2) “Conversion Correction Coefficient” kΦ for neutron fluence to neutron ambient dose equivalent.

Tests have shown that the ambient dose equivalent rate measurement error of the instrument which have been calibrated but without energy correction was 16.5%, by contrast the measurement error was 2.9% with energy correction. It can be seen that the energy correction is necessary and effective for the measuring instrument of neutron ambient dose equivalent during the on-site calibration process.
Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors: Validation of a Multi-Phase Model for Eutectic Reaction Between Stainless Steel and Boron Carbide
Authors: Liu Xiaoxing , Morita Koji , Yamano Hidemasa
Published: October 2020

Investigation of the eutectic reaction in a core disruptive accident of sodium cooled reactor is of importance since reactor criticality will be affected by the change in reactivity after eutectic reaction. In our previous study, a two-dimensional fast reactor safety analysis code, SIMMER-III, was extended to include a physical model to simulate the eutectic reaction between stainless steel (SS) and B4C. Based on experimental knowledge on eutectic reaction, the growth of eutectic material was modeled according to a parabolic rate law. Heat and mass transfer behaviors among reactor materials including a eutectic composition in solid and liquid phases were also modeled considering both equilibrium and non-equilibrium processes in phase change. Physical properties of the eutectic composition were also formulated based on experimental measurements for 5 mass% B4C-SS composition. In this study, we extended the eutectic reaction model to SIMMER-IV, a three-dimensional counterpart of SIMMER-III. We performed validation analysis using SIMMER-III and SIMMER-IV with the developed model based on an experiment, where a B4C pellet was immersed into a molten SS pool. Boron concentration in the pool was measured at several time points and the boron concentration after solidification of the molten pool was compared with the experiment post analysis result. Simulation results of boron distribution are comparable to the experimental results.
Design Applicability of the Advanced Spectrum Method Assisted by Time History Analysis for Multiply Supported Piping System
Authors: Yoshida Ayaka , Takayama Yoshihiro , Shudo Hiromichi
Published: October 2020

The independent support motion response spectrum method (ISM) is currently used for seismic analysis to calculate the response of multiply supported piping system with independent inputs of support excitations. This approach may derive considerable overestimation in the combination of group responses under the absolute sum rule of NUREG-1061. To reduce the excessive overestimation, an advanced method named “Spectrum Method Assisted by Time History Analysis (SATH)” has been proposed. In the SATH method, modal responses by multiple excitations are combined with correlation coefficients which are calculated from the covariances and the standard deviations of time history responses of the oscillators having each of modal frequencies of piping system by each of the floor acceleration time history excitations.

In this paper, the applicability of the SATH method to actual design which uses broadened Floor Response Spectra (FRS) was examined. Conservativeness of the SATH method is also discussed with presenting that responses derived from the SATH method tend to exceed responses by the time history analysis even when many different time intervals of acceleration time histories are used within the range of the FRS broadening.
Numerical Simulation of Liquid Jet Behavior in Shallow Pool by Interface Tracking Method
Authors: Suzuki Takayuki , Yoshida Hiroyuki , Horiguchi Naoki , Yamamura Sota , Abe Yutaka
Published: October 2020

In the severe accident (SA) of nuclear reactors, fuel and components melt, and melted materials fall to a lower part of a reactor vessel. In the lower part of a reactor vessel, in some sections of the SAs, it is considered that there is a water pool. Then, the melted core materials fall into a water pool in the lower plenum as a jet. The molten material jet is broken up, and heat transfer between molten material and coolant may occur. This process is called a fuel-coolant interaction (FCI). FCI is one of the important phenomena to consider the coolability and distribution of core materials.

In this study, the numerical simulation of jet breakup phenomena with a shallow pool was performed by using the developed method (TPFIT). We try to understand the hydrodynamic interaction under various, such as penetration, reach to the bottom, spread, accumulation of the molten material jet. Also, we evaluated a detailed jet spread behavior and examined the influence of lattice resolution and the contact angle. Furthermore, the diameters of atomized droplets were evaluated by using numerical simulation data.
Experimental Investigation of Behavior of Impinging Liquid Jet in a Shallow Pool by 3D-LIF
Authors: Yamamura Sota , Kimura Fumihito , Yoshida Hiroyuki , Kaneko Akiko , Abe Yutaka
Published: October 2020

In some scenarios of severe accidents, the core materials melt and fall into a water pool in the lower plenum as a jet. The molten material jet is broken up, and heat transfer between molten material and coolant occurs. The aim of this study is to clarify the behavior of liquid jet falling into a shallow pool. In a previous study, it is clarified that, in a shallow pool, the jet spread radially after bottoming, and the atomization occurs with high flow velocity in a shallow pool. the detail of atomization and the spreading of the jet cannot be measured by the limitation of a 2D visualization method.

In this study, a 3D-LIF method is used to obtain the detail 3D shape data of the jet. The 3D visualization of the jet is conducted. Using 3D shape data, the liquid film and the atomized droplet are measured. The initial jet velocity is selected as a parameter. As a result, following knowledge is obtained. The thickness of liquid film increases suddenly, and the radius of thin liquid flow increases with the increase of the initial jet velocity. The number of atomized droplets increases with the increase of the initial jet velocity. However, the size of the droplets are not influenced by the initial jet velocity.
Classification Analysis of Communication System of Nuclear Power Plant
Authors: Yun Yu , Shen Zheng , Jing Liu
Published: October 2020

The communication system of nuclear power plants in China is not a safety class system, but it plays an important role in the safe operation of nuclear power plants. Under emergency state, the communication system is a prerequisite for accident management. In order to ensure communication on-site and off-site, diverse communication sub-systems are designed throughout the nuclear power plant, including various communication means for voice, data and images. For an advanced generation II pressurized water reactor (PWR) nuclear power plant (NPP) in China, there are various subsystems, including normal telephone system, safety telephone system, grid telephone system and so on.

Although NPPs have designed diverse communication sub-systems, there is not any clear classification of the sub-systems, which is not enough for the reliability of communication sub-systems under accident conditions. Therefore, it can hardly ensure effective communications between different emergency response organizations and this will influence the mitigation of the accident. In order to identify the importance of different communication sub-systems, to optimize the design of communication system, and to improve the reliability and efficiency of nuclear power plant communication system, it’s necessary to analyze the function and operation of each sub-system, as well as to develop the classification method of nuclear power plant communication system.

Considering the availability and reliability of onsite and offsite communication under emergency conditions, slightly considering economic issue, this paper determines 7 assessment factors and develops a set of scoring methods for communication system classification. On this basis, this paper completes the classification of the communication system for an advanced generation II PWR NPP, which provides a reference for communication system classification and provides the technical basis for design modification of the communication system.
Walk-Away Safe Modular Small and Micro Reactors for Electricity Generation and Process Heat
Authors: El-Genk Mohamed S. , Schriener Timothy
Published: October 2020

The walk-away safe, SLIMM and VSLLIM small and micro reactor designs have recently been developed at the University of New Mexico’s Institute for Space and Nuclear Power studies. These passive operation reactors concepts could generate 10–100 MWth and 1.0–10 MWth without refueling for 6.3–68 full power years (FPYs) and 5.8–92 FPY, respectively. These factory constructed, assembled and sealed reactors would be transported to designated sites by truck, rail or barge, and installed below ground, to protect against impact by an airplane or a missile, and mounted on seismic insolation bearings, to resist earthquakes.

This paper describes the design, operation and passive safety features of the SLIMM and VSLLIM reactors and presents estimates of operation lives and post-operational biological dose rates. Results of passive removal of decay heat by natural circulation of ambient air along the outer surface of the guard vessel wall will also presented and discussed.
A Real-Time Hard X-Ray Tomographic System Designed for HL-2A Fast Electron Bremsstrahlung Radiation
Authors: Yuan Chen , Wu Jun
Published: October 2020

A real-time hard X-ray (HXR) tomographic system is designed for HL-2A tokamak, which is dedicated to the real-time tomography of fast electron bremsstrahlung radiation during the lower hybrid (LH) driven mode within the energy range of 20keV to 200keV. This system has realized the investigation of HXR energy from 12 different chords on the equatorial plane of the reaction region. The spatial and temporal resolutions of the system are 2cm and 10ms, separately. HXR detection is accomplished by a self-designed detector array, with a structure of 12 arc arranged cadmium telluride (CdTe) semiconductors and their corresponding collimators. The real-time HXR acquisition and processing is achieved by the main electronic system, which is comprised of a high speed analog-to-digital module and a high performance signal processing unit. Due to high HXR flux and the real-time demand in measurement, the HXR tomography is accomplished by several customized digital processing algorithms based on FPGA logic resources, such as the digital real-time spectrum measurement, the trapezoidal shaper, the pile up filter, and the baseline restorer, etc. This system has been proved to be qualified as a dependable platform of fast electron bremsstrahlung radiation research during LH mode on HL-2A, which provides indispensable parameters for plasma state during fusion reaction.
Numerical Analysis of Single-Phase Thermal Hydraulic Parameters Along Nanostructured Coating Film
Authors: Al-Yahia Omar S. , Addad Yacine , Yoon Ho Joon , Cho Sung Oh
Published: October 2020

In typical pressurized water reactors, zirconium alloys are used as cladding material for the fuel. However, zircalloy is known to face problems with the high temperature steam, due to the chemical process of oxidation, the oxygen molecules will be separated from the water molecules of the coolant leading to hydrogen gas releases. Recently, a research team at KAIST, South Korea suggested a methodology to fabricate nanoporous oxide layer with the aim of preventing the zircalloy outer surface from reacting with the coolant. Although, this new proposal offers a better solution to prevent the potential hydrogen gas generation, it is still not well understood how the nanoporous-layer is going to affect the convective heat transfer rates between the coolant and the fuel. In fact, on one hand the low conductivity of the oxide layer is expected to reduce the conduction heat transfer within the cladding material; but on the other hand, the nanopores on the oxide layer might act as an effective surface roughness, hence affecting both the hydrodynamic and thermal fields within the coolant channels. In this study, a CFD analysis is carried out to investigate the influence of this nanoporous layer on the convective heat transfer rate and pressure drop coefficient. A detailed 2-D steady-state numerical analysis on single-phase model is performed using Star-CCM+ code. The study is conducted using pores with a diameter of 30 to 100 nm. The results obtained from these predictions are then compared with the ones obtained in the case of the smooth surface. Therefore, the main objectives of the present study are to examine the effect of this nanopourous layer on the thermal hydraulic parameters and to produce the corresponding correlations to be used in the system scale thermal-hydraulic codes.
Simulation Analysis on the Pressurizer Degassing Sub-System of Module Small Reactor (ACP100)
Authors: Zhiyun Cai , Yun Ren , Jianyong Lai , Yulong Zhang , Hang Liu , Xianghong Liu , Minghao Liu , Zhu Ye
Published: October 2020

A pressurizer degassing sub-system is designed in Module Small Reactor (ACP100), which can be used to vent the non-condensable gas dissolved in Reactor Coolant during plant shutdown period by opening the remote degassing valve installed on top of the pressurizer. In order to verify the transient characteristic during the whole degassing process, a dedicated transient degassing program is developed based on the improved non-equilibrium multi-region model and the transient degassing model, which is used then to carry out a simulation analysis on this process. Also, the boundary condition models including pressurizer heater power model, pressure spray model, surge line flow model and critical flow model for degassing valve are established. The simulation results show that, under ultimate condition of hot-zero power operation, during the whole degassing process, the Pressurizer’s pressure drops to a maximum 0.038MPa, and the water level is raised 0.0637m above the normal level, which means, both of the pressure and water level are within the normal operation band and shall not initiate any safety signal. Meanwhile, the whole transient process lasts about 16 minutes, and then it enters into the stable degassing period. The gas concentration vs time curve is very smooth. It takes about 5.8 hours to remove the gas dissolved in Reactor Coolant from 35 ml(STP)/kg to 15 ml(STP)/kg. The analysis shows the Pressurizer Degassing Sub-system is safety, effectively and reliable.