Controlled Release of Agrochemicals Intercalated into Montmorillonite Interlayer Space

Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil.

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Dynamic RCS Estimation according to Drone Movement Using the MoM and Far-Field Approximation

Journal of Electromagnetic Engineering and Science ◽

10.26866/jees.2021.4.r.40 ◽

2021 ◽

Vol 21 (4) ◽

pp. 322-328

Author(s):

Dong-Yeob Lee ◽

Jae-In Lee ◽

Dong-Wook Seo

Keyword(s):

Fourier Transform ◽

Cross Section ◽

Method Of Moments ◽

Iterative Process ◽

Rotation Angle ◽

Field Approximation ◽

Far Field ◽

Impedance Matrix ◽

The Matrix ◽

The Fourier Transform

Micro-Doppler signatures from the rotating propellers of a drone can be utilized to distinguish the drone from clutter or airborne organisms with similar radar cross section (RCS) levels, such as birds and bats. To obtain the micro-Doppler signatures of a drone, calculation or measurement of the electric field scattered from the rotating propellers is essential. In this paper, using the relative angle concept and far-field approximation, we propose a way to rapidly estimate the dynamic RCS of a drone with several propellers according to its movement. In addition, based on the fact that the shape of the propeller does not change even if it rotates, we construct an impedance matrix only once and apply the matrix to the method of moments instead of the iterative process of calculating the impedance matrix and inverse matrix for each rotation angle of the propeller. Finally, by using the Fourier transform of the results from the proposed method, the rotation frequencies of the propellers according to the movement of the drone can be obtained.

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Spectral Functions for the Vector-Valued Fourier Transform

Journal of Function Spaces ◽

10.1155/2018/9584150 ◽

2018 ◽

Vol 2018 ◽

pp. 1-17

Author(s):

Vadim Mogilevskii

Keyword(s):

Distribution Function ◽

Fourier Transform ◽

Spectral Function ◽

Vector Function ◽

Finite Interval ◽

Spectral Functions ◽

The Matrix ◽

The Fourier Transform ◽

Vector Valued

A scalar distribution function σ(s) is called a spectral function for the Fourier transform φ^(s)=∫Reitsφ(t)dt (with respect to an interval I⊂R) if for each function φ∈L2(R) with support in I the Parseval identity ∫Rφ^s2dσ(s)=∫Rφt2dt holds. We show that in the case I=R there exists a unique spectral function σ(s)=(1/2π)s, in which case the above Parseval identity turns into the classical one. On the contrary, in the case of a finite interval I=(0,b), there exist infinitely many spectral functions (with respect to I). We introduce also the concept of the matrix-valued spectral function σ(s) (with respect to a system of intervals {I1,I2,…,In}) for the vector-valued Fourier transform of a vector-function φ(t)={φ1(t),φ2(t),…,φn(t)}∈L2(I,Cn), such that support of φj lies in Ij. The main result is a parametrization of all matrix (in particular scalar) spectral functions σ(s) for various systems of intervals {I1,I2,…,In}.

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ENCAPSULATION OF IBUPROFEN INTO SOLID LIPID NANOPARTICLES FOR CONTROLLED AND SUSTAINED RELEASE USING EMULSIFICATION SOLVENT EVAPORATION TECHNIQUE

Asian Journal of Pharmaceutical and Clinical Research ◽

10.22159/ajpcr.2019.v12i18.33652 ◽

2019 ◽

pp. 74-81

Author(s):

WESLEY N OMWOYO ◽

MAKWENA J MOLOTO

Keyword(s):

Fourier Transform ◽

Infrared Spectroscopy ◽

Controlled Release ◽

Drug Release ◽

Solid Lipid Nanoparticles ◽

Release Kinetics ◽

Lipid Nanoparticles ◽

The Matrix ◽

Evaporation Technique ◽

Emulsification Solvent Evaporation

Objective: The objective of the study was to encapsulate ibuprofen (IBU) into solid lipid nanoparticles (SLNs) for enhanced dissolution and achieving a sustained and controlled release of the drug from the nanocarrier. Methods: IBU loaded nanoparticles were prepared by emulsification solvent evaporation technique and characterized by Fourier Transform Infrared spectroscopy, Thermogravimetric Analysis, X-ray diffraction (XRD), and transmission electron microscopy. Release kinetics on the drug-loaded nanoparticles was carried out in phosphate buffer pH 6.8 using pharma test dissolution apparatus adopting shaking basket method at 37°C. Results: The optimized IBU-loaded SLNs had a particle size of 76.40 nm, polydispersity index of 0.275, and zeta potential of −41.3 mV. The encapsulation efficiency (EE) and DL were 99.73% and 2.31%, respectively. The Fourier transform infrared spectroscopy (FTIR) spectra confirmed successful encapsulation of the drug inside the nanocarrier as only peaks responsible for the emulsifier and the binder could be identified. This corroborated well with XRD spectra which showed a completely amorphous state of the drug-loaded nanoparticles as compared to the crystalline nature of the pure drug. The IBU-SLNs showed a release profile of up to 8 h which is a great improvement from other reported works. The drug release pattern of IBU-SLNs was best fitted with Higuchi square root model and followed the Higuchi drug release kinetics. Korsmeyer-Peppas model confirmed a non-Fickian diffusion model for the release of the drug from the matrix system. Conclusion: IBU-loaded SLNs were successfully prepared which had a sustained and controlled release. It was observed that the release of the drug from the matrix was diffusion controlled and time dependent.

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Application of FTIR Method for the Assessment of Immobilization of Active Substances in the Matrix of Biomedical Materials

Materials ◽

10.3390/ma12182972 ◽

2019 ◽

Vol 12 (18) ◽

pp. 2972 ◽

Cited By ~ 9

Author(s):

Dorota Kowalczuk ◽

Monika Pitucha

Keyword(s):

Fourier Transform ◽

Fourier Transform Infrared ◽

Spectroscopic Technique ◽

Modification Process ◽

The Matrix ◽

Ideal Tool ◽

Reflectance Ftir ◽

The Fourier Transform ◽

Specific Reactions ◽

Active Substances

Background: The purpose of the study was to demonstrate the usefulness of the Fourier transform infrared spectroscopy (FTIR) method for the evaluation of the modification process of biomaterials with the participation of active substances. Methods: Modified catheter samples were prepared by activating the matrix with an acid, iodine, or bromine, and then immobilizing the active molecules. To carry out the modification process, the Fourier transform infrared-attenuated total reflectance (FTIR-ATR) method was used. Results: FTIR analysis indicated the presence of the immobilized substances in the catheter matrix and site-specific reactions. Conclusion: We surmise that the infrared spectroscopic technique is an ideal tool for the assessment of the drug immobilization and the changes occurring in the course of the modification process.

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Comparison between the Matrix Pencil Method and the Fourier Transform Technique for High-Resolution Spectral Estimation

Digital Signal Processing ◽

10.1006/dspr.1996.0011 ◽

1996 ◽

Vol 6 (2) ◽

pp. 108-125 ◽

Cited By ~ 24

Author(s):

José Enrique Fernández del Rı́o ◽

Tapan K. Sarkar

Keyword(s):

Fourier Transform ◽

High Resolution ◽

Spectral Estimation ◽

Matrix Pencil ◽

Matrix Pencil Method ◽

The Matrix ◽

The Fourier Transform

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The Study of the Morphology and Dielectric Properties of PVC + TiO2-Based Nanocomposites

Integrated Ferroelectrics ◽

10.1080/10584587.2019.1668701 ◽

2019 ◽

Vol 201 (1) ◽

pp. 178-182

Author(s):

M. A. Ramazanov ◽

A. M. Rahimli

Keyword(s):

Fourier Transform ◽

Infrared Spectroscopy ◽

Dielectric Properties ◽

Polymer Matrix ◽

Chemical Structure ◽

Sem Analysis ◽

The Matrix ◽

Agglomeration Of Nanoparticles ◽

The Fourier Transform

In given work, PVC + TiO2-based nanocomposites were synthesized and their structure and dielectric properties were investigated. SEM analysis of samples was performed to determine the distribution of nanoparticles in the polymer matrix. It was pointed out that the nanoparticles play the role of structure nucleation centers when they are distributed in the polymer matrix in small quantities. As the concentration of particles increases, changes in the supramolecular structure of the polymer occurs, as well as the agglomeration of nanoparticles in the matrix, which leads to an increase in their size. The Fourier transform infrared spectroscopy (FTIR) measurements for pure polymer and nanocomposites were carried out. It has been determined that, as the concentration of TiO2 nanoparticles increases, there is no change in the chemical structure of the polymer and only decreases the intensity of the maxima of the spectra. It has been shown that polymer matrix is only physically interacted with the nanoparticles and does not form any chemical bond with nanoparticles. It has also been established that the increase in the percentage of TiO2 nanoparticles in the polymer has increased the dielectric permittivity of nanocomposites and it has started to decline at a certain concentration.

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Efficient variations of the Fourier transform in applications to option pricing

The Journal of Computational Finance ◽

10.21314/jcf.2014.277 ◽

2014 ◽

Vol 18 (2) ◽

pp. 57-90 ◽

Cited By ~ 29

Author(s):

Svetlana Boyarchenko ◽

Sergei Levendorski˘ı

Keyword(s):

Fourier Transform ◽

Option Pricing ◽

The Fourier Transform

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Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

Applied Sciences ◽

10.3390/app11062582 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2582

Author(s):

Lucas M. Martinho ◽

Alan C. Kubrusly ◽

Nicolás Pérez ◽

Jean Pierre von der Weid

Keyword(s):

Fourier Transform ◽

Guided Waves ◽

Strain Level ◽

Energy Concentration ◽

Short Time Fourier Transform ◽

Time Frequency ◽

Frequency Representation ◽

The Fourier Transform ◽

Short Time ◽

Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

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