scholarly journals Terahertz Dielectric Spectroscopic Analysis of Polypropylene Aging Caused by Exposure to Ultraviolet Radiation

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2001 ◽  
Author(s):  
Tianying Chang ◽  
Xiansheng Zhang ◽  
Hong-Liang Cui
Keyword(s):  
Refractive Index ◽  
Ultraviolet Radiation ◽  
Aging Process ◽  
Accelerated Aging ◽  
Terahertz Frequency ◽  
Terahertz Time Domain Spectroscopy ◽  
Ultraviolet Exposure ◽  
Data Processing Method ◽  
Spectroscopic Feature ◽  
Ultraviolet Aging

Terahertz dielectric spectroscopy is shown to be an effective tool for bench-marking ultraviolet aging of polypropylene. In this, thin-film polypropylene samples exposed to standard artificial ultraviolet radiation in accelerated aging from 1 day to 30 days are closely monitored by a terahertz time-domain spectroscopy system and analyzed using an effective data processing method. It is found that the terahertz absorption of the polypropylene samples is generally weak and the terahertz dielectric constant varies slightly though discernibly during the aging process, with the refractive index decreasing slightly with increasing length of ultraviolet exposure. Nonetheless, the rate of variation of the polypropylene refractive index with increasing terahertz frequency exhibits a drastic inflection around the 15-days aging point and the rate changes suddenly from positive value to negative value. Based on this prominent and consistent THz dielectric spectroscopic feature of the aging process, an efficient judging criterion is established to distinguish the early-term, mid-term, and late-term phases as well as the degree of polypropylene ultraviolet aging, corresponding to the fundamental transformation of the polymer material from a nonpolar to a polar substance at a critical level of oxidation induced by ultraviolet radiation.

scholarly journals Complex Refractive Index of Strontium Titanate in the Terahertz Frequency Range

2019 ◽  
Vol 7 (4) ◽  
pp. 71-80 ◽  
Author(s):  
V. R. Bilyk ◽  
K. A. Grishunin
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Strontium Titanate ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Complex Dielectric Constant ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Terahertz Frequency Range

The recent progress in terahertz time-domain spectroscopy enables the accurate and reliable measurements of dielectric properties in comparison with the traditional far-infrared spectroscopy using an incoherent light source. The broadband THz-TDS is a powerful tool to determine the real and imaginary parts of a complex dielectric constant by the transmission which allows to detect the parameters of the soft modes in ferroelectrics. In this work, the terahertz time-domain spectroscopy was used to investigate the dependence of the complex refractive index of a single-crystal quantum paraelectric strontium titanate in the terahertz frequency range from 0.3 to 2 THz. It was shown that the low-frequency terahertz response of the material is determined by the soft phonon mode TO1. The measured experimental dependences showed a good agreement with the theoretical curves obtained from the analysis of the Lorentz oscillator model for the complex dielectric constant of strontium titanate. The obtained results are necessary for understanding the principle of possibility to manipulate the order parameter in ferroelectric materials and can be used to create energy-efficient memory devices with a speed of recording information close to the theoretical limit.

Active modulation of refractive index by stress in the terahertz frequency range

2013 ◽  
Vol 52 (25) ◽  
pp. 6364 ◽  
Author(s):  
Lin’an Li ◽  
Wei Song ◽  
Zhiyong Wang ◽  
Shibin Wang ◽  
Mingxia He ◽  
...  
Keyword(s):  
Refractive Index ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range

scholarly journals Laboratory Study of the Ultraviolet Radiation Effect on an HDPE Geomembrane

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 390
Author(s):  
Fernando Luiz Lavoie ◽  
Marcelo Kobelnik ◽  
Clever Aparecido Valentin ◽  
Érica Fernanda da Silva Tirelli ◽  
Maria de Lurdes Lopes ◽  
...  
Keyword(s):  
Ultraviolet Radiation ◽  
Morphological Changes ◽  
Field Performance ◽  
Melt Flow Index ◽  
Flow Index ◽  
Test Results ◽  
Upward Trend ◽  
Scanning Calorimetry ◽  
Ultraviolet Exposure ◽  
Brittle Behavior

High-density polyethylene (HDPE) geomembranes are polymeric geosynthetic materials usually applied as a liner in environmental facilities due to their good mechanical properties, good welding conditions, and excellent chemical resistance. A geomembrane’s field performance is affected by different conditions and exposures, including ultraviolet radiation, thermal and oxidative exposure, and chemical contact. This article presents an experimental study with a 1.0 mm-thick HDPE virgin geomembrane exposed by the Xenon arc weatherometer for 2160 h and the ultraviolet fluorescent weatherometer for 8760 h to understand the geomembrane’s behavior under ultraviolet exposure. The evaluation was performed using the melt flow index (MFI) test, oxidative-induction time (OIT) tests, tensile test, differential scanning calorimetry (DSC) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. The sample exposed in the Xenon arc equipment showed a tendency to increase the MFI values during the exposure time. This upward trend may indicate morphological changes in the polymer. The tensile behavior analysis showed a tendency of the sample to lose ductility, without showing brittle behavior. The samples’ OIT test results under both device exposures showed faster antioxidant depletion for the standard OIT test than the high-pressure OIT test. The DSC and FTIR analyses did not demonstrate the polymer’s changes.

scholarly journals Optical Properties of Crystalline Lactose Fluidized with Dilutions of Various Substances in the Terahertz Frequency Range

Pharmaceutics ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 32
Author(s):  
Anna Baranova ◽  
Anastasiya Lykina ◽  
Daria Antonova ◽  
Olga Smolyanskaya
Keyword(s):  
Optical Properties ◽  
Interferon Gamma ◽  
Fluidized Beds ◽  
Principal Component ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Terahertz Frequency Range ◽  
Glycine Buffer ◽  
Diluted Solution

Lactose is a commonly used component of pharmaceutical medications in tablet form. It was previously shown that lactose changes conformationally after saturation in fluidized beds with active pharmaceutical ingredients obtained by repeated dilution of antibodies to interferon-gamma in combination with an external intensive vibration treatment. Moreover, it was revealed that these solutions are self-organized dispersed systems in which nano-objects are formed. Their biological activity and mechanism of action were previously established as well. The current work was dedicated to investigating the optical properties of fluidized lactose powders in the terahertz frequency range. Spectral analyses of powders of crystalline lactose saturated in fluidized beds with a diluted solution of either glycine buffer, antibodies to interferon-gamma, or water were carried out, intact lactose served as a control. All powders were tableted before testing. In the course of the study, the macroscopic parameters of the tablets were established, at which they had a stable shape and their THz optical properties had no parasitic diffraction losses. These tablets were analyzed using terahertz time-domain spectroscopy in the frequency range of 0.2–2.6 THz. The differentiation between the spectra was conducted using a principal component analysis. The differences between intact lactose and the lactose saturated with any of studied solutions were demonstrated. Additionally, lactose saturated with solutions of multiple dilutions of a substance (antibodies or glycine buffer) differed not only from intact lactose, but also from lactose saturated with a diluted solution of water. Moreover, discrimination of lactose formulations saturated with different substances (antibodies or glycine buffer) was also possible. Additionally, intact lactose differed from lactose saturated with diluted water. The methods reported could be useful for the quality control of the medications based on the technology of repeated dilution of an original substance.

scholarly journals Largely accelerated arterial aging in rheumatoid arthritis is associated with inflammatory activity and smoking in the early stage of the disease

2020 ◽  
Author(s):  
Nikolett Mong ◽  
Zoltan Tarjanyi ◽  
Laszlo Tothfalusi ◽  
Andrea Bartykowszki ◽  
Aniko Ilona Nagy ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Cardiovascular Events ◽  
Aging Process ◽  
Reference Group ◽  
Early Stage ◽  
Accelerated Aging ◽  
Contributing Factors ◽  
Atherosclerosis Progression ◽  
Arterial Aging

Abstract Background: Rheumatoid arthritis (RA) patients have a shorter life expectancy than the general population primarily due to cardiovascular comorbidities.Objectives: To characterize arterial aging in RA.Patients and methods: Coronary calcium scores (CCS) were available from 112 RA patients; out of these patients, follow-up CCS were measured of 54 randomly selected individuals. Control CCS were obtained from the MESA database (includes 6000< participants); arterialage was calculated from CCS.Results: RA patients were significantly older (10.45±18.45 years, p<0.001) in terms of the arterial age compared to the age, gender and race matched controls. The proportion of RA patients who had zero CCS was significantly less (p<0.01) than in the MESA reference group. Each disease year contributed an extra 0.395 years (p<0.01) on the top of the normal aging process. However, the rate of the accelerated aging is not uniform, in the first years of the disease it is apparently faster. Smoking (p<0.05), previous cardiovascular events (p<0.05) and high blood pressure (p<0.05) had additional significant effect on the aging process. In the follow-up study, inflammatory disease activity (CRP>5 mg/L, p<0.05) especially in smokers and shorter than 10 years disease duration (p=0.05) had the largest impact.Conclusions: Arterial aging is faster in RA patients compared to control subjects, particularly in the first 10 years of the disease. Inflammation, previous cardiovascular events and smoking are additional contributing factors to the intensified coronary atherosclerosis progression. These data support that optimal control of inflammation is essential to attenuate the cardiovascular risk in RA.

Effect of Accelerated Aging Process on Seed Quality and Biochemical Changes in Sweet Pepper (Capsicum annuum Linn.) Seeds

2011 ◽  
Vol 10 (2) ◽  
pp. 175-182 ◽  
Author(s):  
P. Kaewnaree ◽  
S. Vichitphan ◽  
P. Klanrit ◽  
B. SIRI ◽  
K. Vichitphan
Keyword(s):  
Capsicum Annuum ◽  
Aging Process ◽  
Seed Quality ◽  
Accelerated Aging ◽  
Sweet Pepper ◽  
Biochemical Changes
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