Presence Of Crystalline Structure Research Articles

Volatile Organic Compound (VOC) Reduction from Face Mask Wastes via a Microwave Plasma Reactor

Since the outbreak of the COVID-19 pandemic, the driven of face masks as personal protective equipment has increased significantly. Thus, disposed face masks from users should be handled properly for preventing the contamination of medical waste and the potential spread of viruses to the environment. This study gives information for dealing with face masks and assessing the volatile organic compounds (VOCs) concentrations via an atmospheric-pressure microwave plasma reactor. Face mask samples were mixed with the flux agents, namely cullet/glass, Al2O3, SiO2 and CaCO3. Samples were compared with control (no addition of flux agents) and the addition of only cullet. Moreover, microwave power, gas flow rate and pyrolysis duration were controlled at 1000 W, 9 standard liter per minute (SLM) and 5 min, respectively. The total concentration of VOC with the absence of flux agents was 448.04 ppm. Furthermore, the fuse of cullet and SiO2-Al2O3-cullet in the mask reduced the concentration of VOCs by 314.77 ppm and 54.7 ppm, respectively. Furthermore, the combination of CaCO3-SiO2-Al2O3-cullet creates the vitrification of material with the presence of crystalline structure, where the compositions of Ca and Si were 13.55% and 19.12%, respectively. Moreover, the final composition of carbon from the flux agents was 17.92 ± 10.08%. This study confirms that the fuse of CaCO3-SiO2-Al2O3-glass/cullet reduced the VOC via plasma technology, which is a promising method to be implemented in order to reduce the concentration of VOC from the face mask waste.

Influence of vegetable oil, monoglycerides and polyglycerol polyricinoleate into the physical stability of organogel-emulsion (w/o) systems

The objective of the present investigation was to evaluate the physical stability of emulsions (w/o) with a gel as an oil phase. Two oil phases (canola and coconut oil) were used to assess the impact of the different vegetable oils. Monoglycerides were used as the gelling agent and polyglycerol polyricinoleate as the surfactant. Micrographs, differential scanning calorimetry, and rheology tests were performed. The presence of crystalline structures was observed in the continuous phase characteristic of some organogels and a smaller distribution of sizes as a function of time. Also, a change in the crystallization profile of the aqueous and oily phases concerning to time was also found, the crystallization signals coinciding (≈ − 40 °C), indicating a better organization by the phases. No variability was found in modules G′ and G″, so these systems have good mechanical stability. The properties of the organogelated emulsions are explained by the interface-interface interactions present between the particles and the reduced mobility, which slows the phase separation.

ELECTROPHYSICAL PROPERTIES OF ZINC OXIDE THIN FILMS OBTAINED BY CHEMICAL METHODS

The electrophysical characteristics comparative studies were carried out for ZnO films obtained by chemical precipitation from zinc acetate solutions and thermal oxidation of zinc films. The ZnO films showed optical absorption and band gap (2.9 to 3.2 eV) specific for this material, which indicates the presence of crystalline structure in them. The use of polyvinyl alcohol made it possible to obtain samples with the highest values of E g and electrical resistance, which is caused by the nanosize crystallites of the films. The investigated electrophysical characteristics of the ZnO films made it possible to establish the contribution of their own defects and surface states to the conductivity.

Structural and thermal properties of silk fibroin films obtained from cocoon and waste silk fibers as raw materials

This study compares the structural and thermal properties of silk fibroin (SF) films obtained from different raw materials: silk coccons (SC) and silk fibrous wastes (SW). Samples were processed by solution casting (SFC and SFW), and casting with a subsequent water annealing treatment (WA-SFC and WA-SFW). The presence of crystalline (silk I and silk II) and amorphous structures was evaluated using X-ray diffraction (XRD) and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Thermal properties of SF films were studied by DSC measurements. Accordingly, to FTIR and XRD results, the presence of silk I structure is greater in SFW that in SFC. Differences in enthalpy of crystallization peaks in DSC curves reveals that SFC presents a higher content of amorphous structures than SFW. The analysis also point that water annealing treatment induces conformational changes in secondary structures of SF films. It can be concluded that the presence of crystalline structures in SF films varies with the raw material and water annealing treatment. This fact represents a progress in the development of processing alternatives to control SF materials structure and properties.

Effect of different crystalline structures on W/O and O/W/O wax emulsion stability

Abstract The possibility of emulsion stabilization using mineral and vegetable wax particles only (without surfactant) was investigated. Mineral waxes, paraffin wax and ceresin, and a vegetable wax, carnauba wax, were used. The content of the wax particles and the water to oil proportion were found crucial for the stability of all emulsions. Some emulsions were also produced with a liquid wax (i.e. jojoba oil). The multiple light scattering method was used to determine the stability of emulsion systems during storage. The presence of crystalline structures were confirmed by microscopic analysis. The results show that all tested waxes can independently stabilize emulsion systems. The wax crystallization directly on the droplet surface provided stability against droplet coalescence while the continuous phase wax crystals reduced inter-droplet collisions. However, the effective protection against coalescence and the phase separation takes only place in the presence of appropriate amounts of different waxes and with specific proportions of water to oil phases. The emulsions type was denoted as W/O in the presence of mineral waxes and O/W/O in systems with vegetable wax. Emulsions with jojoba oil and mineral waxes had a similar stability compare to emulsions with the same composition but without the liquid wax. In contrast, phase separation were observed in emulsions obtained with two vegetable components (jojoba oil and carnauba wax). It might have been associated with a high wettability of the carnauba wax surface by jojoba oil that could have made the wax particles unsuitable for Pickering stabilization of emulsion.

Crystalline Structures as the Only Dermoscopic Clue for the Diagnosis of Basal Cell Carcinoma

T HE PRESENCE OF CRYSTALLINE STRUCTURES on polarized light dermoscopy has been described in lesions with an increased amount of collagen, such as dermatofibroma, scars, melanoma, Spitz nevi, and basal cell carcinoma (BCC). These structures are not visible to the unaided eye, and they do not appear in nonpolarized contact dermoscopic images. The lesions shown in this article correspond to histologically confirmed superficial BCCs. They were located on the upper back area of a 53-year-old woman (Figure, A), the lower back of a 76-year-old man (Figure, B), and the neck of a 46-year-old woman (Figure, C). Clinically, in all 3 cases, the lesions were slightly raised, with a shiny surface and mild erythema. Dermoscopic evaluation revealed the presence of orthogonal, linear, bright white structures that corresponded to crystalline structures (circles) in the absence of the classic dermoscopic criteria of BCC. In Figure, C, the rosette sign was also observed. When the diagnosis is uncertain, a biopsy should be considered to rule out melanoma or BCC in any case involving a lesion that displays crystalline structures.

Dermoscopy: An Aid to the Detection of Amelanotic Cutaneous Melanoma Metastases

The recognition of amelanotic cutaneous melanoma metastases (ACMM) remains a diagnostic challenge. To describe and analyze the clinical and dermoscopic characteristics of ACMM. Cases of ACMM were retrospectively selected from the image databases of three dermatology centers. The clinical and dermoscopic images were combined into one database for analysis. Forty-seven ACMM were observed in 18 patients. All lesions were erythematous, symmetric, dome-shaped papules or nodules appearing an average of 17 months after the diagnosis of the primary melanoma. ACMM presented as clinical outliers or as nonspecific papules found by palpation of the skin. The predominant dermoscopic feature was the presence of vascular structures, including serpentine (45%), glomerular (30%), irregular hairpin (23%) and corkscres-like vessels (19%). A few lesions also revealed crystalline (or shiny white lines) when viewed using polarized dermoscopy. ACMM should be considered in the differential diagnosis of new or persistent skin-colored or pink papules in patients with a previous history of invasive melanoma, especially if the lesions reveal atypical vessels under dermoscopy. The presence of crystalline structures may be another clue for the detection of some ACMM.

Determination of the wear resistance of traditional ceramic tile glazes using a pin-on-disk tribometer

Wear resistance is a key ceramic tile property when it comes to determining foreseeable tile response to mechanical aggressions (scratching and wear) under intended service conditions. The main purpose of the present study consists of subjecting materials of a ceramic nature to wear in a pin-on-disk tribometer in order to characterise these and subsequently to correlate the results with those obtained using other standard techniques, as well as with the microstructure of the materials. The results obtained for the different materials indicated that the presence of crystalline structures in the fired glaze coating raised the wear resistance of these materials, this being greater when the crystals present were smaller. The presence of these crystals in the fired glaze modifies glaze mechanical properties (microhardness, modulus of elasticity, and toughness), microstructure, and wear resistance.