Terahertz time-domain spectroscopy and application on peanut oils

Oil was extracted from the seeds of groundnut, melon and Moringa oleifera. The physicochemical properties of groundnut oil, melon oil and moringa oil were determined. The acid value obtained was 9.76 mgKOH/g, 7.85 mgKOH/g and 1.91 mgKOH/g for moringa, melon and groundnut oil respectively. The Iodine value was found to be 35.85 mg/g, 83.75 mg/g and 59.64 mg/g for moringa, melon and groundnut oil respectively. The Peroxide values were moringa oil - 13.80 meq/kg, melon oil - 5.60 meq/kg and groundnut oil - 10.80 meq/kg. Unsaponifiable matter values were moringa oil - 8.59 g/kg, melon oil - 2.18 g/kg, groundnut oil - 5.77 g/kg while the saponification values were moringa oil - 155.68 mgKOH/g, melon oil - 180.92 mgKOH/g and groundnut oil - 168.30 mgKOH/g. The volatile matter in the oils was found to be 0.06. 0.07 And 0.04 in groundnut, melon and moringa oil respectively. All the oils were pale yellow in colour and liquids at room temperature. The results obtained from the physicochemical characterization of the oils shows that moringa oleifera seed oil compares favourably with the other oils and has high potentials for use both as domestic oil and as industrial oil. Keywords : Groundnut, Melon, Moringa Oleifera, Oil, Physicochemical.

The spectral characteristics of corn oil after five minutes and ten minutes of boiling in the rang from 0.2THz to 1.5THz have been measured with THz time-domain spectroscopy (THz-TDS) at room temperature in nitrogen atmosphere. A novel iterative algorithm is employed to determinate the optical properties considering the effect of the cuvette. The refractive indices of the two corn oil samples show slow a decrease as the terahertz wave frequency increases. The power absorption coefficients increase as the frequency increases within the investigated terahertz wave frequency range. The results provided in this paper will help us to study the THz application to seed oil quality and safety detection further.

Human clinical trials have demonstrated the cardiovascular protective properties of peanuts and peanut oil in decreasing total and low density lipoprotein cholesterol (LDL-C) without reducing high density lipoprotein cholesterol (HDL-C). The cardiovascular effects of the nonlipid portion of peanuts has not been evaluated even though that fraction contains arginine, flavonoids, folates, and other compounds that have been linked to cardiovascular health. The objective of this study was to evaluate the effects of fat free peanut flour (FFPF), peanuts, and peanut oil on cardiovascular disease (CVD) risk factors and the development of atherosclerosis in male Syrian golden hamsters. Each experimental diet group was fed a high fat, high cholesterol diet with various peanut components (FFPF, peanut oil, or peanuts) substituted for similar metabolic components in the control diet. Tissues were collected at week 0, 12, 18, and 24. Total plasma cholesterol (TPC), LDL-C, and HDL-C distributions were determined by high-performance gel filtration chromatography, while aortic total cholesterol (TC) and cholesteryl ester (CE) were determined by gas liquid chromatography. Peanuts, peanut oil, and FFPF diet groups had significantly (P < 0.05) lower TPC, non-HDL-C than the control group beginning at about 12 wk and continuing through the 24-wk study. HDL-C was not significantly different among the diet groups. Peanut and peanut component diets retarded an increase in TC and CE. Because CE is an indicator of the development of atherosclerosis this study demonstrated that peanuts, peanut oil, and FFPF retarded the development of atherosclerosis in animals consuming an atherosclerosis inducing diet.

By using terahertz time domain spectroscopy (THz-TDS) system, the terahertz dielectric properties of various gallium arsenides were tested in the frequency range extending from 0.2 to 1.5 THz. The power absorption coefficient and refractive index of various resistivity gallium arsenides were measured and compared. The refractive index of the high resistivity and ultra-high resistivity GaAs are equal to be 6.53 and 5.9, respectively. The variation of the refractive index of the GaAs was less than 1%, ranging from 0.2 to 1.5THz, but the absorption coefficient of the ultra-resistivity GaAs showed very different frequency-dependent behaviors, ranging from 0.02cm−1 to 2.21cm−1, within the investigated frequency range. The results show that the ultra-resistivity GaAs will be a good candidate material for terahertz transmission waveguide.

Terahertz Spectroscopy Tracks Proteolysis by a Joint Analysis of Absorptance and Debye Model

The study aims at assessing the physicochemical properties, heavy metals, and aflatoxins content of crude palm and groundnut oils produced and sold in the Adikpo, Wadata, and Otukpa areas of Benue state, Nigeria. Specific gravity, refractive index, acid value, saponification value, peroxide value, moisture content, and smoke point are the physicochemical properties evaluated. The heavy metals analyzed include; Lead, Nickel, Copper, Iron, Arsenic, and Iron. Total aflatoxins were determined by Enzyme-linked immunosorbent assay (ELISA). Findings revealed that most of the physicochemical properties of palm and groundnut oils from these areas deviated from the Food and Agricultural Organization/World Health Organization (FAO/WHO) standard range. A high amount of Cadmium (0.89 mg/kg, 1.01 mg/kg, and 0.92 mg/kg) was detected in the local groundnut oil samples but lesser in palm oils from Adikpo, Wadata, and Otukpa respectively, while Copper content was within the FAO/WHO safe limits. The arsenic content of palm oil produced in the region was not as high as those in groundnut oil but was higher than the recommended maximum limit of 0.1 mg/kg. The Nickel content in the oil samples was higher than the 0.50 mg/kg permissible limit, but Lead was within the safe limits. Total Aflatoxin content in crude groundnut oil was within the range of 9.05 ppm to 10.13 ppm, while a range of 2.03 ppm to 2.74 ppm was recorded in crude palm oil. The locally produced oils are of lower quality, suggesting that refining should be adopted and quality seeds should be used for the extraction of oils.

The surface of a topological insulator harbors exotic topological states, protected against backscattering from disorder by time reversal symmetry. The study of these exotic quantum states not only provides an opportunity to explore fundamental phenomena in condensed matter physics, such as the spin Hall effect, but also lays the foundation for applications from quantum computing to spintronics. Conventional electrical measurements suffer from substantial bulk interference, making it difficult to clearly distinguish topological surface states from bulk states. Employing terahertz time-domain spectroscopy, we study the temperature-dependent optical behavior of a 23-quintuple-thick film of bismuth selenide (Bi2Se3) allowing for the deconvolution of the surface state response from the bulk. Our measurement of carrier dynamics give an optical mobility exceeding 2100 cm2/V•s at 4 K, indicative of a surface-dominated response, and a scattering lifetime of ~0.18 ps and a carrier density of 6×1012 cm-2 at 4 K for the Bi2Se3 film. The sample was further processed into a Hall bar device using two different etching techniques, a wet chemical etching and Ar+ ion milling, which resulting in a reduced Hall mobility. Even so, the magneto-conductance transport reveals weak antilocalization behavior in our Bi2Se3 sample, consistent with the presence of a single topological surface state mode.

Experimental and theoretical study of fingerprint spectra of 2-(4-fluorophenyl)benzimidazole and 2-(4-chlorophenyl)benzimidazole in terahertz range

Terahertz time domain spectroscopy (THz-TDS) is a new kind of nondestructive detection method, frequency of terahertz wave spans from a few tens of GHz to several THz, which is used to detect material because of its strong identification, it can supply rich vibration information caused by intermolecular and large intra-molecular. Ammonium sulfamate (AMS) is a kind of herbicide, it has special value for many woody plants, which can prevent annual weeds. The excess use of pesticide is a huge threaten for human health in recent years, thus the research on detection of pesticide has absolutely important meaning, in this paper, pure AMS and mixture samples of AMS and orange are measured using THz-TDS, and their absorption coefficient are calculated by the model, which is put forward based on Fresnel equation. We qualitatively analyze the absorption coefficient spectra of pure AMS, which is useful for us to identify the pesticide in agriculture products. Meanwhile, we measured 14 mixture samples of AMS and orange, the weight ratio of mixtures are from 0% to 59.9%. Nine samples are considered as calibration set and the other five samples are regarded as prediction set, to quantitatively analyze the concentration of AMS by the partial least squares (PLS), the result shows that the prediction error is less then 4.5%, in addition, the relationship of the average absorption and weight ratio are absolutely linear. The experiment demonstrates that THz-TDS is promising and efficient to quantitatively detect the component of mixtures, and it has important reference value for the detection of pesticide in agriculture food.

Spinel ferrite has the excellent characteristics of high saturation magnetization, high resistivity and low dielectric loss. It plays an important role in signal isolation, circulation, phase shift, frequency limiting, filtering, delay and amplification. So it is of great significance to study the spectral characteristics of spinel ferrite at different temperatures by using terahertz time-domain spectroscopy. The terahertz spectral characteristics of spinel ferrite under the different temperature condition were measured by terahertz time domain spectroscopy system. The transmittance of the power, absorption rate, absorption coefficient and refractive index of spinel ferrite were obtained by calculation. The experimental results show that the transmittance is positively correlated with temperature and the absorption spectrum of the samples increases with the increase of frequency in the 0-1THz band, and the refractive index of spinel ferrite increases with the increase of temperature.

This paper presents an experimental study on the physicochemical properties of rice oil, peanut oil, corn oil and Kraft paper immersed in these oils in the presence of antioxidants (butylated hydroxytoluene, tertiary butyl hydroquinone and Naugalube¯ 750). The experiments are performed on new and aged conditions. Ageing of oils is carried at 115 °C for 96 hours while Kraft paper is aged in oils at 130 °C for 164 hours. Both closed and open cup methods are used for ageing. The results show that ageing insignificantly affects the breakdown voltage, but markedly increases the acid number and the viscosity of the vegetable oils. The combination of tertiary butyl hydroquinone and either butylated hydroxytoluene or Naugalube¯ 750 slightly increases the breakdown voltage, but significantly raises the oxidation stability of the vegetable oils. This results in a reduction in the viscosity and the acid number of the vegetable oils. Moisture significantly affects the breakdown voltage of both vegetable and mineral oil. High moisture content results in low breakdown voltage. The results also show that ageing insignificantly affects the breakdown voltage, but markedly decreases the tensile strength of oil-impregnated paper. Although the presence of antioxidants does not increase the breakdown voltage of aged paper, these additives slow down the ageing process. This results in an increase in tensile strength of the paper.

ObjectiveLaryngeal cancer is a common malignancy in otorhinolaryngological head and neck surgery, accounting for approximately one-third of all head and neck malignancies. Terahertz time-domain spectroscopy (THz-TDS) has recently been found to be useful for the detection of tumors. This study was conducted to investigate the application of THz-TDS in the diagnosis of pathological resection margins of laryngeal cancer.MethodsFresh laryngeal cancer tissues from 10 patients with laryngeal cancer were extracted, and after simultaneous HE staining and terahertz imaging, the tumor area, paracancerous area, and normal tissue area of each laryngeal cancer tissue sample were located under a microscope according to the pathological results of HE staining.ResultsThe shape contours of the tumor region revealed by terahertz imaging maps and HE staining were similar. In the terahertz spectrum in the frequency range of 0.5–1.9 THz, both the absorption coefficient and refractive index values followed the order tumor > para cancer > normal tissue, with statistically significant differences (P < 0.01). When the terahertz frequency was 1.5 THz, the absorption coefficient of terahertz light waves by laryngeal cancer tissue and the percentage of nuclei showed an extremely high positive correlation (P < 0.01, r = 0.971). In the frequency ranges of 0.5–1.2 THz and 1.6–1.9 THz, the absorption coefficients of the highly differentiated group were higher than those of the moderately differentiated group. In the frequency range of 1.2–1.6 THz, the results were reversed, with statistically significant differences (P < 0.05). In the frequency range of 0.5–1.9 THz, the highly differentiated group had a higher refractive index than the moderately differentiated group, with a statistically significant difference (P < 0.05).ConclusionsTHz-TDS can be used to determine the pathological margins of laryngeal cancer based on the absorption coefficient and refractive index, and the magnitudes of the absorption coefficient and refractive index are related to the percentage of nuclei. The degree of differentiation of laryngeal cancer tissue can be assessed by THz-TDS. The study shows that the terahertz time-domain system is promising for applications in the diagnosis of laryngeal cancer, especially for the more accurate identification of intraoperative margins.

The study of fluid inclusion is an important tool and method in mineral evolution research. The shape, number and size of fluid inclusions in halite crystals grown at different temperatures are different and can directly show the composition, temperature and pressure of the ore-forming fluids. Terahertz time-domain spectroscopy (THz-TDS) has been used to probe the inclusion of individual of the halite rock, exhibiting different spectral signals in the terahertz band. The relationship between absorption coefficient and temperature exhibited the nonlinear features at different frequencies, a fitted regression curve can present accordingly and the evolutionary regime of halite rock (early diagenetic phase, late diagenetic phase and approximate metamorphic phase) can be indicated by the absorption coefficient in the THz region. Furthermore, XRD and optical microscope as supplementary methods provide more information for us to understand the evolutionary regime of halite rock. The results show that under low temperature, the inclusion of individual is less but relatively large, arranged in relatively loose; at higher temperatures, the inclusion of individual were more, substantially along or parallel to the crystal surface, but individual size is relatively small. The present study of identification based on THz-TDS was in good agreement with X-ray diffraction (XRD) and optical microscopes, and the evolution is validated by theoretical simulations suggesting that the terahertz technology can act as a non-destructive, contact-free tool for the evolution of the geological diagenetic and metallogenic research. THz-TDS can be used as a complementary method for composition and characteristic analysis of ore-forming fluids in geological diagenetic research, realizing a lead in evolution of rock reservoir diagenetic systems study.

Terahertz Time-Domain Spectroscopy (THz-TDS) is a new technique in studying the conformational state of molecules. Cell membranes are important structures in the interaction with extra cellular entities. Their principal building blocks are lipids, amphiphilic molecules that spontaneously self-assemble when in contact with water. In this work we report the use of THz-TDS in transmission mode to examine the behavior of supported phospholipid bilayers (SPBs) within the frequency range of 0.2 THz to 3 THz. SPBs were obtained by vesicle adsorption method involving the spread of a suspension (50-100 &mu;l) of small unilamellar vesicles (SUVs) or multilamellar vesicles (MLVs) dissolved in PBS (phosphate buffer solution) on a support of silicon wafers. Both SUVs and MLVs were obtained from dipalmitoyl phosphatidylcholine (DPPC) and lecithin by using the thin-film hydration method. Broadband THz pulses are generated and detected using photoconductive antennas optically excited by a femtosecond laser pulse emitted from a self-mode locked fiber laser at a wavelength of 780 nm with a pulse widths of 150 fs. THz-TDS was proven to be a useful method in studying SPBs and their hydration states. The absorption coefficient and refractive index of the samples were calculated from THz measurements data. The THz absorption spectra for different lipids in SPBs indicate specific absorption frequency lines. A difference in the magnitude of the refractive index was also observed due to the different structure of supported lipid bilayers. The THz spectrum of DPPC was obtained by using theoretical simulations and then the experimental and theoretical THz spectra were compared.

Melamine is an organic base and a trimer of cyanamide, with a 1, 3, 5-triazine skeleton. It is usually used for the production of plastics, glue and flame retardants. Melamine combines with acid and related compounds to form melamine cyanurate and related crystal structures, which have been implicated as contaminants or biomarkers in protein adulterations by lawbreakers, especially in milk powder. This paper is focused on developing an available method for quantitative detection of melamine in the fields of security inspection and nondestructive testing based on THz-TDS. Terahertz (THz) technology has promising applications for the detection and identification of materials because it exhibits the properties of spectroscopy, good penetration and safety. Terahertz time-domain spectroscopy (THz-TDS) is a key technique that is applied to spectroscopic measurement of materials based on ultrafast femtosecond laser. In this study, the melamine and its mixture with polyethylene powder in different consistence are measured using the transmission THz-TDS. And we obtained the refractive index spectra and the absorption spectrum of different concentrations of melamine on 0.2-2.8THz. In the refractive index spectra, it is obvious to see that decline trend with the decrease of concentration; and in the absorption spectrum, two peaks of melamine at 1.98THz and 2.28THz can be obtained. Based on the experimental result, the absorption coefficient and the consistence of the melamine in the mixture are determined. Finally, methods for quantitative detection of materials in the fields of nondestructive testing and quality control based on THz-TDS have been studied.