1,114 research outputs found
Thermochemical and Continuum Modeling to Understand the Chemical Composition of PWR Fuel CRUD
Computational modeling of Chalk River Undesirable Deposits (CRUD) allows for the prediction of associated phenomena that impact nuclear power plant performance, reliability, and safety. It also provides insight into the physical mechanisms by which CRUD forms and affects plant performance. A major concern in pressurized water reactors (PWRs) is Axial Offset Anomaly (AOA) which is caused by CRUD’s proficiency at trapping boron within the reactor core. The ability to predict AOA and other phenomena requires a detailed explanation of the chemical composition of CRUD. By pairing computational models that can simulate the structure and species trapping with detailed thermochemical models, the compounds that makeup CRUD are determined. Among these thermodynamically predicted compounds is Ni2FeBO5, a mineral named bonaccordite, the formation of which provides a boron retention mechanism. Accordingly, bonaccordite has been found in CRUD samples from fuel linked to very extreme AOA. In this dissertation, thermochemical models are detailed for PWR primary loop chemistry up to the saturation temperature and are implemented using CALPHAD modeling. Likely solid precipitation reactions are identified, and those reactions are incorporated into the multiphysics continuum modeling code MAMBA. An assessment of the kinetic rates of the reactions are determined by Bayesian calibration of the MAMBA model using observational data from CRUD samples. The modeling is able to demonstrate the composition of CRUD scrapes obtained from plant data. This model contributes to the understanding of CRUD formation and composition and allows for the prediction of phenomena such as AOA
Privacy enhanced interface identifiers in IPv6
The Internet Protocol Version 6 (IPV6) proposed to
replace IPV4 to solve scalability challenges and improve
quality of service and security. Current implementation of IPv6
uses static value that is determined from the Media Access
Control (MAC) address as the Interface Identifier (IID). This
results in a deterministic IID for each user that is the same
regardless of any network changes. This provides an
eavesdropper with the ability to easily track the physical
location of the communicating nodes using simple tools, such
as ping and traceroute. Moreover, this address generation
method provides a means to correlate network traffic with a
specific user which can be achieved by filtering the IID and
traffic analysis. These serious privacy breaches need to be
addressed before widespread deployment of IPv6. In this paper
we propose a privacy-enhanced method for generating IID
which combines different network parameters. The proposed
method generates non-deterministic IIDs that is resistance
against correlation attack. We validate our approach using
Wireshark, ping and traceroute tools and show that our
proposed approach achieves better privacy compared to the
existing IID generation methods
Effect of Bioactive and Antimicrobial Nanoparticles on Properties and Applicability of Dental Adhesives
The aim of the study was to examine the applicability of bioactive and antibacterial nanoparticles to an experimental adhesive. The adhesive (60 wt% BisGMA, 15 wt% TEGDMA, 25 wt% HEMA) was mixed with combinations of 5 wt% methacryl-functionalized polyhedral oligomeric silsesquioxane (MA-POSS) and one kind of bioactive/antibacterial nanoparticles: 1 wt% core-shell silica-silver nanoparticle (SiO2@Ag), 1 wt% bioactive glass with bismuth (BAG-Bi) or 1 wt% calcium phosphate (CAP). Pure adhesive served as control. The physicochemical (degree of conversion (DC), linear shrinkage (LS), shear and complex viscosity, water sorption (WS), sol fraction (SF)), biological (antimicrobial effect) and bioactive (mineral precipitation) properties were investigated. DC and LS remained unchanged. The combination of BAG-Bi/MA-POSS resulted in a significantly increased WS and SF compared to control. In addition, the combination of CAP/MA-POSS slightly increased the shear viscosity of the adhesive. The addition of the nanoparticles did not influence the antimicrobial effects compared to the pure adhesive. Improved mineral inducing capacity could be detected in all nanoparticle combinations. The combination of bioactive and/or antibacterial nanoparticles showed improved mineral inducing capacity, but no antibacterial properties. The material properties were not or only slightly affected.
Keywords: POSS; SiO2@Ag; antimicrobial nanoparticles; bioactive glass; bioactive nanoparticles; calcium phosphate; dental adhesive
Data-driven methods for diffusivity prediction in nuclear fuels
The growth rate of structural defects in nuclear fuels under irradiation is
intrinsically related to the diffusion rates of the defects in the fuel
lattice. The generation and growth of atomistic structural defects can
significantly alter the performance characteristics of the fuel. This
alteration of functionality must be accurately captured to qualify a nuclear
fuel for use in reactors. Predicting the diffusion coefficients of defects and
how they impact macroscale properties such as swelling, gas release, and creep
is therefore of significant importance in both the design of new nuclear fuels
and the assessment of current fuel types. In this article, we apply data-driven
methods focusing on machine learning (ML) to determine various diffusion
properties of two nuclear fuels, uranium oxide and uranium nitride. We show
that using ML can increase, often significantly, the accuracy of predicting
diffusivity in nuclear fuels in comparison to current analytical models. We
also illustrate how ML can be used to quickly develop fuel models with
parameter dependencies that are more complex and robust than what is currently
available in the literature. These results suggest there is potential for ML to
accelerate the design, qualification, and implementation of nuclear fuels
Preoperative systemic inflammation predicts postoperative infectious complications in patients undergoing curative resection for colorectal cancer
The presence of systemic inflammation before surgery, as evidenced by the glasgow prognostic score (mGPS), predicts poor long-term survival in colorectal cancer. The aim was to examine the relationship between the preoperative mGPS and the development of postoperative complications in patients undergoing potentially curative resection for colorectal cancer. Patients (n=455) who underwent potentially curative resections between 2003 and 2007 were assessed consecutively, and details were recorded in a database. The majority of patients presented for elective surgery (85%) were over the age of 65 years (70%), were male (58%), were deprived (53%), and had TNM stage I/II disease (61%), had preoperative haemoglobin (56%), white cell count (87%) and mGPS 0 (58%) in the normal range. After surgery, 86 (19%) patients developed a postoperative complication; 70 (81%) of which were infectious complications. On multivariate analysis, peritoneal soiling (P<0.01), elevated preoperative white cell count (P<0.05) and mGPS (P<0.01) were independently associated with increased risk of developing a postoperative infection. In elective patients, only the mGPS (OR=1.75, 95% CI=1.17-2.63, P=0.007) was significantly associated with increased risk of developing a postoperative infection. Preoperative elevated mGPS predicts increased postoperative infectious complications in patients undergoing potentially curative resection for colorectal cancer
Real-time volumetric lipid imaging in vivo by intravascular photoacoustics at 20 frames per second
Lipid deposition can be assessed with combined intravascular photoacoustic/ultrasound (IVPA/US) imaging. To date, the clinical translation of IVPA/US imaging has been stalled by a low imaging speed and catheter complexity. In this paper, we demonstrate imaging of lipid targets in swine coronary arteries in vivo, at a clinically useful frame rate of 20 s−1. We confirmed image contrast for atherosclerotic plaque in human samples ex vivo. The system is on a mobile platform and provides real-time data visualization during acquisition. We achieved an IVPA signal-to-noise ratio of 20 dB. These data show that clinical translation of IVPA is possible in principle
NEGATIVE INTERRELATIONSHIP BETWEEN NUMBER OF BERSEEM CUTS AND COTTON YIELD AS A FOLLOWING CROP
The present investigation was carried out at the Experimental Farm of the Faculty of Agriculture at Fayoum, Cario University at Dalla, Fayoum Governorate during the two seasons 2000/2001 and 2001/2002. The aim of this investigation was to study the effect of organic manure and number of berseem cuts on cotton yield and its components and fiber traits. The obtained results indicate that only plant height at harvest, number of fruiting branches / plant and the height of the 1st fruiting branch were significantly affected by organic manure (O.M.) application. On the other hand, organic manure did not affect significantly the seed cotton yield, yield components and fiber quality traits. Cotton planting dates affected significantly all studied vegetative growth, seed cotton yield, yield components and fiber quality traits. Early planting date (1st week of March) showed significant superiority over the other two planting dates (1st week of April & May) in number of fruiting branches/ plant, number of days to 1st flower appearance and 1st boll opening, number and weight of open bolls/ plant in the 1st& 2nd pickings, seed cotton yield, lint percentages and studied fiber quality traits. The decreases in the total seed cotton yield attributed to the late planting dates (1st week of April & May) amounted 26.4 and 84.8% and 30.6 and 84.1% of March planting with the treatments of 10 and 20 m3/ fad organic manure, respectively
A Novel Fluorescent Clinical Method to Rapidly Quantify Plasma Volume
Objectives
To determine the performance of a rapid fluorescent indicator technique for measuring plasma volume (PV).
Methods
This was an open-label, observational evaluation of a two-component intravenous visible fluorescent dye technique to rapidly measure PV in 16 healthy subjects and 16 subjects with chronic kidney disease (8 stage 3 and 8 stage 4 CKD), at 2 clinical research sites. The method consisted of a single intravenous injection of 12 mg of a large 150-kDa carboxy-methyl dextran conjugated to a fluorescent rhodamine-derived dye as the PV marker (PVM), and 35 mg of a small 5-kDa carboxy-methyl dextran conjugated to fluorescein, the renal clearance marker. Dye concentrations were quantified 15 min after the injections for initial PV measurements using the indicator-dilution principle. Additional samples were taken over 8 h to evaluate the stability of the PVM as a determinant of PV. Blood volumes (BV) were calculated based on PV and the subject’s hematocrit. Pharmacokinetic parameters were calculated from the plasma concentration data taken over several days using noncompartmental methods (Phoenix WinNonlin®). Linear correlation and Bland-Altman plots were used to compare visible fluorescent injectate-measured PV compared to Nadler’s formula for estimating PV. Finally, 8 healthy subjects received 350 mL infusion of a 5% albumin solution in normal saline over 30 min and a repeat PV determination was then carried out.
Results
PV and BV varied according to weight and body surface area, with PV ranging from 2,115 to 6,234 mL and 28.6 to 41.9 mL/kg when weight adjusted. Both parameters were stable for > 6 h with repeated plasma measurements of the PVM. There was no difference between healthy subjects and CKD subjects. Overall, there was general agreement with Nadler’s estimation formula for the mean PV in subjects. A 24-h repeat dose measurement in 8 healthy subjects showed PV variability of 98 ± 121 mL (mean = 3.8%). Additionally, following an intravenous bolus of 350 mL of a 5% albumin solution in normal saline in 8 healthy subjects, the mean (SD) measured increase in PV was 356 (±50.0) mL post-infusion. There were no serious adverse events reported during the study.
Conclusions
This minimally invasive fluorescent dye approach safely allowed for rapid, accurate, and reproducible determination of PV, BV, and dynamic monitoring of changes following fluid administration
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