Synthesis and applications of polymer-nanoparticle composites : conjugated polymer- CdTe quantum dots and nitrocellulose-Ag nanoparticles

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Domain Generalisation via Risk Distribution Matching

We propose a novel approach for domain generalisation (DG) leveraging risk distributions to characterise domains, thereby achieving domain invariance. In our findings, risk distributions effectively highlight differences between training domains and reveal their inherent complexities. In testing, we may observe similar, or potentially intensifying in magnitude, divergences between risk distributions. Hence, we propose a compelling proposition: Minimising the divergences between risk distributions across training domains leads to robust invariance for DG. The key rationale behind this concept is that a model, trained on domain-invariant or stable features, may consistently produce similar risk distributions across various domains. Building upon this idea, we propose Risk Distribution Matching (RDM). Using the maximum mean discrepancy (MMD) distance, RDM aims to minimise the variance of risk distributions across training domains. However, when the number of domains increases, the direct optimisation of variance leads to linear growth in MMD computations, resulting in inefficiency. Instead, we propose an approximation that requires only one MMD computation, by aligning just two distributions: that of the worst-case domain and the aggregated distribution from all domains. Notably, this method empirically outperforms optimising distributional variance while being computationally more efficient. Unlike conventional DG matching algorithms, RDM stands out for its enhanced efficacy by concentrating on scalar risk distributions, sidestepping the pitfalls of high-dimensional challenges seen in feature or gradient matching. Our extensive experiments on standard benchmark datasets demonstrate that RDM shows superior generalisation capability over state-of-the-art DG methods.Comment: Accepted at 2024 IEEE/CVF Winter Conference on Applications of Computer Vision (WACV 2024

EFFICACY OF Ageratum LEAF EXTRACT ON POSTHARVEST ROT CAUSED BY Aspergillus niger AND Colletotrichum sp. ON CHILLI FRUITS

Abstract: The damage of chilli, an important spice fruit, comes from fungal diseases caused mainly by Aspergillus niger and Colletotrichum sp. The fungi on chilli fruits would directly harm consumers’ health. Plant extracts containing bio-active compounds with antimicrobial properties could be a good possible solution to deal with the fungi. This study aims to evaluate the in vitro and in vivo efficacy of aqueous extracts from the leaves of Ageratum plants against A. niger and Colletotrichum sp. The results show that the optimal efficacy of the treatment of Ageratum leaf extract is at a concentration of 6%, with the efficacy of Ageratum leaf extract on colonial diameter at approximately 43–44% for the two fungi at 96 hours after inoculation. The 6% Ageratum leaf extract has a high efficacy (~54.23%) on limiting the development of Aspergillus rot lesions on chilli fruits 4 days after inoculation. Meanwhile, the efficacy of the extract on Colletotrichum lesions is 11.34%, lower than that of Aspergillus rot.Keywords: Ageratum leaf extract, chilli fruit, rot lesio

Design and fabrication of the trapezoidal electrostatic comb-drive actuator

This paper reports the design, fabrication and characterization process of the trapezoidal Electrostatic Comb-drive Actuator (ECA) with the slope angle α=20. Together with the trapezoidal ones, the rectangular ECA with identical dimension was also designed and fabricated for comparison purpose. In order to reduce calculating deviation, the fringing effect was also taken into consider while carrying out theoretical analysis. The obtained results pointed out the fact, that the trapezoidal ECA excels the rectangular ones with the same numbers of teeth in electrostatic force and displacement generation, while requires relatively low driving voltage. But it is also observed that with higher driving voltage (larger than 50V), the trapezoidal ECA starts to lose its stability (the lateral pull-in phenomenon occurs)

Synthesis of microcrystalline cellulose from banana pseudo-stem for adsorption of organics from aqueous solution

In this study, we proposed and tested a green method for producing microcrystalline cellulose (MCC) with high quality from waste banana pseudo-stem (BPS) after fruit harvesting. The MCC was synthesized by treating BPS with sulfuric acid, sodium hydroxide, and H2O2solution.The produced MCC material was then characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis to explore its properties. The removal of methylene blue (MB) in aqueous solution was conducted by batch adsorption method to evaluate the applicability of MCC for wastewater treatment. The results showed that the adsorption using MCC reached equilibrium after 15 min. The highest MB adsorption capacity of MCC reached 16.6mg/g at pH 6. The adsorption kinetics data were best described by the pseudo second order rate equation. Equilibrium isotherm data of adsorption were well fitted to the linear Langmuir isotherm model. Affecting factors such as adsorbent dosage, initial concentration of MB, and temperature were also investigated. These results suggest a great potential use of MCC for advanced wastewater treatment

Study, Design and Construction of an Early Warning Environmental Radiation Monitoring Station

We report on the design and construction of an Early Warning Environmental Radiation Monitoring Station (EWERMS), used ONLINE in the environmental radiation monitoring and early warning network. It has a  high sensitivity and can send a prompt alarm signal via Internet to the emergency management office. It includes four gamma probes: one NaI(Tl) and three Geiger Mueller (GM) detectors. The NaI(TL) detector is used to monitor spectrum environmental radiation and measure the isotopic composition, the GM detectors are used to detect and measure high gamma ray rates. The instrument has been designed to be used outdoor and tolerate large and rapid temperature variations. The photomultiplier tubes (PMT), amplifiers and Analog To Digital (ADC) gains are stabilized using pulsed LEDs as precision reference light sources

Probiotic Beverage From Pineapple Juice Fermented With Lactobacillus and Bifidobacterium Strains

Pineapple is an economically significant plant and the third most important fruit crop in the tropical and subtropical regions of the world. In this study, fermentation of pineapple juice with probiotic bacteria Lactobacillus and Bifidobacterium strains as well as changes of some properties in the beverage during storage were investigated. All tested strains exhibited good growth properties on pineapple juice without supplementation of any nutrient compounds. After 24 h fermentation, the cell counts of lactobacilli passed the level of 5*109 cfu/ml, while the cell number of bifidobacteria reached a level of 109 cfu/ml. The highest volumetric productivity (3.5*108 cfu/ml*h) was observed in L. plantarum 299V. The ratios of lactic acids to acetic acids in the cases of L. plantarum 299V and L. acidophilus La5 were 5.37 and 9.91, respectively. In the case of B. lactis Bb-12, the concentrations of lactic acid and acetic acid were 6 mM and 23 mM in natural juices, and 15 and 21 mM in the case of supplementation with prebiotics at the 16th h of fermentation, respectively. Additionally, supplementation with prebiotics at the initiation of fermentation resulted 7 mM lactic acid and 23 mM acetic acid at the end of fermentation. Fructose was the most preferred sugar for both lactobacilli and bifidobacteria. Both total phenolic content and antioxidant capacity increased slightly during fermentation and dropped during the storage period. The microbial population did not change significantly during the first month of storage. After the storage period (2 months), the probiotic bacteria lost about 0.11 log cfu/ml viability after treatment with 0.3% pepsin for 135 min, and a further 0.1 log cfu/ml after treatment with 0.6% bile salts. These values were 10 times higher than data from the fresh fermented pineapple juice. Our results are very promising and may serve as a good base for developing probiotic pineapple juice