Sugar Cane Bagasse is a by-product of the sugar agroindustry; it is partly used as fuel. However, bagasse ash (SCBA) is considered waste, which creates a disposal problem. Furthermore, if sugar cane ...bagasse is burned under controlled conditions, the SCBA can be potentially reused. This paper considers the technical viability of using SCBA as a partial replacement for cement. Two samples of SCBA from a Colombian sugar industry were characterized. The chemical composition of the samples shows high percentages of silica, 76.3% and 63.2%. The mineralogical and morphological characteristics of the waste were determined by X-ray diffraction patterns (XRD), thermal analysis (TG/DTA) and scanning electron microscopy (SEM). The pozzolanic activity of SCBA was evaluated using the Frattini test and the strength activity index test (SAI). The ASTM C618 defines an SAI of at least 75% as a requirement for classifying material as a pozzolan. This condition was achieved in the experiments performed. The results indicate that SCBA produced in the manufacture of commercial cements can be recycled for use as pozzolanic material. This supplementary material can partially replace cement and therefore reduce CO2 emissions.
Purpose:
Partial scan reconstruction (PSR) artifacts are present in myocardial perfusion imaging using dynamic multidetector computed tomography (MDCT). PSR artifacts appear as temporal CT number ...variations due to inconsistencies in the angular data range used to reconstruct images and compromise the quantitative value of myocardial perfusion when using MDCT. The purpose of this work is to present and evaluate a technique termed targeted spatial frequency filtration (TSFF) to reduce CT number variations due to PSR when applied to myocardial perfusion imaging using MDCT.
Methods:
The TSFF algorithm requires acquiring enough X-ray projections to reconstruct both partial (π + fan angle α) and full (2π) scans. Then, using spatial linear filters, the TSFF-corrected image data are created by superimposing the low spatial frequency content of the full scan reconstruction (containing no PSR artifacts, but having low spatial resolution and worse temporal resolution) with the high spatial frequency content of the partial scan reconstruction (containing high spatial frequencies and better temporal resolution). The TSFF method was evaluated both in a static anthropomorphic thoracic phantom and using an in vivo porcine model and compared with a previously validated reference standard technique that avoids PSR artifacts by pacing the animal heart in synchrony with the gantry rotation. CT number variations were quantified by measuring the range and standard deviation of CT numbers in selected regions of interest (ROIs) over time. Myocardial perfusion parameters such as blood volume (BV), mean transit time (MTT), and blood flow (BF) were quantified and compared in the in vivo study.
Results:
Phantom experiments demonstrated that TSFF reduced PSR artifacts by as much as tenfold, depending on the location of the ROI. For thein vivo experiments, the TSFF-corrected data showed two- to threefold decrease in CT number variations. Also, after TSFF, the perfusion parameters had an average difference of 13.1% (range 4.5%–25.6%) relative to the reference method, in contrast to an average difference of 31.8% (range 0.3%–54.0%) between the non-TSFF processed data with the reference method.
Conclusions:
TSFF demonstrated consistent reduction in CT number variations due to PSR using controlled phantom andin vivo experiments. TSFF-corrected data provided quantitative measures of perfusion (BV, MTT, and BF) with better agreement to a reference method compared to noncorrected data. Practical implementation of TSFF is expected to incur in an additional radiation exposure of 14%, when tube current is modulated to 20% of its maximum, to complete the needed full scan reconstruction.
To describe, using a three-dimensional finite element (FE) model, the initial force system generated during bodily movement of upper canines with plastic aligners with and without composite ...attachments.
A CAD model of an upper right canine, its alveolar bone and periodontal ligament, thermoformed plastic aligner, and two light-cured composite attachments were constructed. A FE model was used to analyze the effects of imposing a distal movement condition of 0.15 mm on the aligner (simulating the mechanics used to produce a distal bodily movement) with and without composite attachments.
In terms of tension and compression stress distribution, without composite attachments a compression area in the cervical third of the distal root surface and a tension area in the apical third of the mesial surface were observed. With composite attachments, uniform compression areas in the distal root surface and uniform tension area in the mesial root surface were observed. Compression areas in the active surfaces of the composite attachments were also observed. In terms of movement patterns, an uncontrolled distal inclination, with rotation axis between the middle and cervical root thirds, was observed without composite attachment. Distal bodily movement (translation) was observed with composite attachment.
In a three-dimensional FE analysis of a plastic aligner system biomechanically supplementary composite attachments generate the force system required to produce bodily tooth movement; the absence of biomechanically supplementary composite attachments favors the undesired inclination of the tooth during the translation movements.
Climate-driven impacts on marine trophic pathways worldwide are compounded by sea-ice loss at northern latitudes. For the Arctic, current information describing food-web linkages is fragmented, and ...there is a need for tools that can describe overarching trophic structure despite limited species-specific data. Here, we tested the ability of a mass-balanced ecosystem model (Ecopath with Ecosim, EwE) to reconstruct the trophic hierarchy of 31 groups, from primary producers to polar bears, in the Canadian Beaufort Sea continental shelf. Trophic level (TL) estimates from EwE were compared with those derived from two nitrogen stable isotope (SI) modelling approaches (SI linear and scaled) to assess EwE accuracy, using a data set of 642 δ
15
N observations across 282 taxa. TLs from EwE were strongly, positively related to those from both SI models (R
2
> 0.80). EwE performed well (within 0.2 TL) for groups with relatively well-known diets or for taxa characterized by fewer trophic connections (e.g., primary consumers). Performance was worse (>0.5 TL) for species groups aggregated at coarse taxonomic levels, those with poorly documented diets, and for anadromous fishes. Comparisons with SI models suggested that the scaled approach can overestimate the TL of top predators if ecosystem-specific information is not considered.
Objectives
To assess the effect of automatic tube potential selection (ATPS) on radiation dose, image quality, and lesion detectability in paediatric abdominopelvic CT and CT angiography (CTA).
...Methods
A paediatric modular phantom with contrast inserts was examined with routine pitch (1.4) and high pitch (3.0) using a standard abdominopelvic protocol with fixed 120 kVp, and ATPS with variable kVp in non-contrast, contrast-enhanced, and CTA mode. The volume CT dose index (CTDI
vol
), contrast-to-noise ratio (CNR) and lesion detectability index (d’) were compared between the standard protocol and ATPS examinations.
Results
CTDI
vol
was reduced in all routine pitch ATPS examinations, with dose reductions of 27–52 % in CTA mode (
P
< 0.0001), 15–33 % in contrast-enhanced mode (
P
= 0.0003) and 8–14 % in non-contrast mode (
P
= 0.03). Iodine and soft tissue insert CNR and d’ were improved or maintained in all ATPS examinations. kVp and dose were reduced in 25 % of high pitch ATPS examinations and in none of the full phantom examinations obtained after a single full phantom localizer.
Conclusions
ATPS reduces radiation dose while maintaining image quality and lesion detectability in routine pitch paediatric abdominopelvic CT and CTA, but technical factors such as pitch and imaging range must be considered to optimize ATPS benefits.
Key Points
•
ATPS automatically individualizes CT scan technique for each patient
.
•
ATPS lowers radiation dose in routine pitch pediatric abdominopelvic CT and CTA
.
•
There is no loss of image quality or lesion detectability with ATPS
.
•
Pitch and scan range impact the effectiveness of ATPS dose reduction
.
BackgroundAdvances in CT and machine learning have enabled on-site non-invasive assessment of fractional flow reserve (FFRCT).PurposeTo assess the interoperator and intraoperator variability of ...coronary CT angiography-derived FFRCT using a machine learning-based postprocessing prototype.Materials and methodsWe included 60 symptomatic patients who underwent coronary CT angiography. FFRCT was calculated by two independent operators after training using a machine learning-based on-site prototype. FFRCT was measured 1 cm distal to the coronary plaque or in the middle of the segments if no coronary lesions were present. Intraclass correlation coefficient (ICC) and Bland-Altman analysis were used to evaluate interoperator variability effect in FFRCT estimates. Sensitivity analysis was done by cardiac risk factors, degree of stenosis and image quality.ResultsA total of 535 coronary segments in 60 patients were assessed. The overall ICC was 0.986 per patient (95% CI 0.977 to 0.992) and 0.972 per segment (95% CI 0.967 to 0.977). The absolute mean difference in FFRCT estimates was 0.012 per patient (95% CI for limits of agreement: −0.035 to 0.039) and 0.02 per segment (95% CI for limits of agreement: −0.077 to 0.080). Tight limits of agreement were seen on Bland-Altman analysis. Distal segments had greater variability compared with proximal/mid segments (absolute mean difference 0.011 vs 0.025, p<0.001). Results were similar on sensitivity analysis.ConclusionA high degree of interoperator and intraoperator reproducibility can be achieved by on-site machine learning-based FFRCT assessment. Future research is required to evaluate the physiological relevance and prognostic value of FFRCT.
Background
Biomaterial-associated infections are one of the most important complications in orthopedic surgery. The main goal of this study was to demonstrate the in vivo bactericidal effect of ...ultraviolet (UV) irradiation on Ti6Al4V surfaces.
Materials and methods
An experimental model of device-related infections was developed by direct inoculation of
Staphylococcus aureus
into the canal of both femurs of 34 rats. A UV-irradiated Ti6Al4V pin was press-fit into the canal by retrograde insertion in one femur and the control pin was inserted into the contralateral femur. To assess the efficacy of UV radiation, the mean colony counts after inoculation in the experimental subjects and the control group were compared at different times of sacrifice and at different inoculum doses.
Results
At 72 h, the mean colony counts after inoculation in experimental femurs were significantly lower than those of the control group, with a reduction percentage of 76 % (
p
= 0.041). A similar difference between control and experimental pins was observed at 24 h using an inoculum dose <10
4
colony-forming units (CFU), for which the reduction percentage was 70.48 % (
p
= 0.017).
Conclusion
The irradiated surface of Ti6Al4V is able to reduce early bacterial colonization of Ti6AlV pins located in the medullar channel and in the surrounding femur. The reductions depend on the initial inoculums used to cause infection in the animals and the greatest effects are detected for inoculums <10
4
CFU.
Level of evidence
Not applicable.
Photon-counting detector (PCD) CT has been shown to reduce radiation dose and improve image quality in adult chest CT examinations; its potential impact in pediatric CT is not well documented.
The ...purpose of our study was to compare radiation dose, objective image quality, and subjective image quality of PCD CT and energy-integrating detector (EID) CT in children undergoing high-resolution CT (HRCT) of the chest.
This retrospective study included 27 children (median age, 3.9 years; 10 girls, 17 boys) who underwent PCD CT between March 1, 2022, and August 31, 2022, and 27 children (median age, 4.0 years; 13 girls, 14 boys) who underwent EID CT between August 1, 2021, and January 31, 2022; all examinations comprised clinically indicated chest HRCT. The patients in the two groups were matched by age and water-equivalent diameter. Radiation dose parameters were recorded. One observer placed ROIs to measure objective parameters (lung attenuation, image noise, and SNR). Two radiologists independently assessed subjective measures (overall image quality and motion artifacts) using 5-point Likert scales (1 = highest quality). Groups were compared.
PCD CT, in comparison with EID CT, showed lower median CTDI
(0.41 vs 0.71 mGy,
< .001), DLP (10.2 vs 13.7 mGy × cm,
= .008), size-specific dose estimate (0.82 vs 1.34 mGy,
< .001), and tube current-exposure time product (48.0 vs 202.0 mAs,
< .001). PCD CT and EID CT showed no significant difference in right upper lobe (RUL) lung attenuation (mean, -793 vs -750 HU;
= .09), right lower lobe (RLL) lung attenuation (mean, -745 vs -716 HU;
= .23), RUL image noise (mean, 55 vs 51 HU;
= .27), RLL image noise (mean, 59 vs 57 HU;
= .48), RUL SNR (mean, -14.9 vs -15.8;
= .89), or RLL SNR (mean, -13.1 vs -13.6;
= .79). PCD CT and EID CT showed no significant difference in median overall image quality for reader 1 (1.0 vs 1.0,
= .28) or reader 2 (1.0 vs 1.0,
= .17) or median motion artifacts for reader 1 (1.0 vs 1.0,
= .07) or reader 2 (1.0 vs 1.0,
= .22).
PCD CT showed significantly reduced dose levels without a significant difference in objective or subjective image quality compared with EID CT.
These data expand understanding of the capabilities of PCD CT and support its routine use in children.
To cause plant diseases, pathogenic micro-organisms secrete effector proteins into host tissue to suppress immunity and support pathogen growth. Bacterial pathogens have evolved several distinct ...secretion systems to target effector proteins, but whether fungi, which cause the major diseases of most crop species, also require different secretory mechanisms is not known. Here we report that the rice blast fungus Magnaporthe oryzae possesses two distinct secretion systems to target effectors during plant infection. Cytoplasmic effectors, which are delivered into host cells, preferentially accumulate in the biotrophic interfacial complex, a novel plant membrane-rich structure associated with invasive hyphae. We show that the biotrophic interfacial complex is associated with a novel form of secretion involving exocyst components and the Sso1 t-SNARE. By contrast, effectors that are secreted from invasive hyphae into the extracellular compartment follow the conventional secretory pathway. We conclude that the blast fungus has evolved distinct secretion systems to facilitate tissue invasion.
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