Oscar Raymond-Herrera

Bio: Oscar Raymond-Herrera is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Frequency domain & Ferroelectricity. The author has an hindex of 7, co-authored 15 publications receiving 110 citations.

Effect of antimicrobial nanocomposites on Vibrio cholerae lifestyles: Pellicle biofilm, planktonic and surface-attached biofilm.

Abstract: Vibrio cholerae is an important human pathogen causing intestinal disease with a high incidence in developing countries. V. cholerae can switch between planktonic and biofilm lifestyles. Biofilm formation is determinant for transmission, virulence and antibiotic resistance. Due to the enhanced antibiotic resistance observed by bacterial pathogens, antimicrobial nanomaterials have been used to combat infections by stopping bacterial growth and preventing biofilm formation. In this study, the effect of the nanocomposites zeolite-embedded silver (Ag), copper (Cu), or zinc (Zn) nanoparticles (NPs) was evaluated in V. cholerae planktonic cells, and in two biofilm states: pellicle biofilm (PB), formed between air-liquid interphase, and surface-attached biofilm (SB), formed at solid-liquid interfaces. Each nanocomposite type had a distinctive antimicrobial effect altering each V. cholerae lifestyles differently. The ZEO-AgNPs nanocomposite inhibited PB formation at 4 μg/ml, and prevented SB formation and eliminated planktonic cells at 8 μg/ml. In contrast, the nanocomposites ZEO-CuNPs and ZEO-ZnNPs affect V. cholerae viability but did not completely avoid bacterial growth. At transcriptional level, depending on the nanoparticles and biofilm type, nanocomposites modified the relative expression of the vpsL, rbmA and bap1, genes involved in biofilm formation. Furthermore, the relative abundance of the outer membrane proteins OmpT, OmpU, OmpA and OmpW also differs among treatments in PB and SB. This work provides a basis for further study of the nanomaterials effect at structural, genetic and proteomic levels to understand the response mechanisms of V. cholerae against metallic nanoparticles.

Resolution improvement of accelerometers measurement for drones in agricultural applications

Abstract: In agricultural tasks, monitoring of large fields is required. In the last years automatic/autonomous monitoring has been researched; where unmanned aerial vehicles (UAV)—commonly known as drones—are used. For these systems, constrains related with autonomy during flight arise. In order to control properly the UAVs during flight, they require to measure physical variables, in a fast and accurate way. Also, the weight of instruments must be reduced for improving autonomy. In general, aerial vehicles obtain parameters like position, velocity and acceleration using inertial navigation systems. Regarding to this concern, in this work application of a novel technique for measurements onboard UAVs—particularly inertial measurement unit or IMU—is proposed. There are accelerometers inside the IMU. These accelerometers have a frequency domain output. The speed and position are calculated by the INS from acceleration. The acceleration is obtained from frequency measurements of the accelerometers output. For this reason an accurate and fast frequency measurement method is required. In this work, for this particular application, frequency measurement using principle of rational approximations is proposed. This technique allows to measure frequency in short time and with high accuracy, using a few electronic components. Due this properties, it perfectly fits requirements for UAVs.

Synthesis and Complete Antimicrobial Characterization of CEOBACTER, an Ag-Based Nanocomposite

Abstract: The antimicrobial activity of silver nanoparticles (AgNPs) is currently used as an alternative disinfectant with diverse applications, ranging from decontamination of aquatic environments to disinfection of medical devices and instrumentation. However, incorporation of AgNPs to the environment causes collateral damage that should be avoided. In this work, a novel Ag-based nanocomposite (CEOBACTER) was successfully synthetized. It showed excellent antimicrobial properties without the spread of AgNPs into the environment. The complete CEOBACTER antimicrobial characterization protocol is presented herein. It is straightforward and reproducible and could be considered for the systematic characterization of antimicrobial nanomaterials. CEOBACTER showed minimal bactericidal concentration of 3 μg/ml, bactericidal action time of 2 hours and re-use capacity of at least five times against E. coli cultures. The bactericidal mechanism is the release of Ag ions. CEOBACTER displays potent bactericidal properties, long lifetime, high stability and re-use capacity, and it does not dissolve in the solution. These characteristics point to its potential use as a bactericidal agent for decontamination of aqueous environments.

Atomic and Electronic Structure of Quaternary CdxZnySδOγ Nanoparticles Grown on Mordenite

Abstract: Atomic, electronic, and compositional structure of quaternary CdxZnySδOγ semiconductor nanoparticles grown on synthesized mordenite-type zeolite (MOR) is discussed in this work. Semiconductor–MOR composites were synthesized using two different methods: by Cd2+-Zn2+-ion exchange with synthesized sodium-mordenite, and by direct synthesis of zinc/cadmium-mordenite through a variant of the sol–gel technique, both followed by sulfidation treatment in H2S flow. We show that CdxZnySδOγ semiconductor nanoparticles grow strongly bonded, revealing a core–shell-type arrangement with a wide-open (a = 8.33 A) cubic fcc structure, and constrained by the MOR surface structure. Because of the core–shell-type nanoparticles and their observed structural and optical properties, these photoactive composites are promising candidates for applications in the fields of photocatalysis and optoelectronics.

Unmanned Aerial Vehicles in Agriculture: A Review of Perspective of Platform, Control, and Applications

Abstract: For agricultural applications, regularized smart-farming solutions are being considered, including the use of unmanned aerial vehicles (UAVs). The UAVs combine information and communication technologies, robots, artificial intelligence, big data, and the Internet of Things. The agricultural UAVs are highly capable, and their use has expanded across all areas of agriculture, including pesticide and fertilizer spraying, seed sowing, and growth assessment and mapping. Accordingly, the market for agricultural UAVs is expected to continue growing with the related technologies. In this study, we consider the latest trends and applications of leading technologies related to agricultural UAVs, control technologies, equipment, and development. We discuss the use of UAVs in real agricultural environments. Furthermore, the future development of the agricultural UAVs and their challenges are presented.

Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation

Abstract: An electrodeposited Cu2ZnSnS4 (CZTS) compact thin film modified with an In2S3/CdS double layer and Pt deposits (Pt/In2S3/CdS/CZTS) was used as a photocathode for water splitting of hydrogen production under simulated sunlight (AM 1.5G) radiation. Compared to platinized electrodes based on a bare CZTS film (Pt/CZTS) and a CZTS film modified with a CdS single layer (Pt/CdS/CZTS), the Pt/In2S3/CdS/CZTS electrode exhibited a significantly high cathodic photocurrent. Moreover, the coverage of the In2S3 layer was found to be effective for stabilization against degradation induced by photocorrosion of the CdS layer. Bias-free water splitting with a power conversion efficiency of 0.28% was achieved by using a simple two-electrode cell consisting of the Pt/In2S3/CdS/CZTS photocathode and a BiVO4 photoanode.

A review of integrated photocatalyst adsorbents for wastewater treatment

Abstract: Photocatalysis has the best potential to replace the conventional wastewater treatment technology due to its utilization of visible light to photo-degrade organic and inorganic contaminants. However, when applied in slurry form, agglomeration of nanoparticle will lead to serious decrease in photocatalytic performance due to hinderance effect. By combining the photocatalyst and adsorbents, which is designated as integrated photocatalyst adsorbent (IPCA), an adsorbent material which also degrades toxic organic compounds in the presence of UV/visible light irradiation could be produced. The compound does not only preserve all the interesting characteristics of both individual components, but also overcomes serious drawbacks, such as low absorptivity, rapid recombination of photogenerated electrons and hinderance effect of photocatalyst when applied in slurry form. There are several criteria that must be obeyed by the absorbent material used such as high absorption capacity to target compound, reasonable transparency to UV–vis light, high surface area, inhibition of photocatalyst leaching and good stability with dispersing solvent. In this review article, the authors presented an overview on the application of photocatalyst, adsorbents and integrated photocatalyst adsorbents for wastewater treatment. Moreover, the discussions were also focused on the major adsorbent which has been integrated with photocatalyst such as carbon, clays, zeolite matrix materials and others. Additionally, the mechanisms of the adsorption of emerging organic contaminants with adsorbents in IPCA were also discussed to clearly understand the possible interactions between organic contaminants and IPCA. Outlook on IPCA study were also discussed to further broaden the prospective of this technology.