Thermomechanical surface instability at the origin of surface fissure patterns on heated circular MDF samples

When a flat sample of medium density fibreboard (MDF) is exposed to radiant heat in an inert atmosphere, primary crack patterns suddenly start to appear over the entire surface before pyrolysis and any charring occurs. Contrary to common belief that crack formation is due to drying and shrinkage, it was demonstrated for square samples that this results from thermomechanical instability. In the present paper, new experimental data are presented for circular samples of the same MDF material. The sample was exposed to radiant heating at 20 or 50 kW/m2, and completely different crack patterns with independent Eigenmodes were observed at the two heat fluxes. We show that the two patterns can be reproduced with a full 3-D thermomechanical surface instability model of a hot layer adhered to an elastic colder foundation in an axisymmetric domain. Analytical and numerical solutions of a simplified 2-D formulation of the same problem provide excellent qualitative agreement between observed and calculated patterns. Previous data for square samples together with the results reported in the present paper for circular samples confirm the validity of the model for qualitative predictions, and indicate that further refinements can be made to improve its quantitative predictive capability.Comment: 9 pages, 13 figures. New title and abstract, added experimental and simulation details and figures, conclusions unchanged. Matches the version published in Fire And Material

Potencial ação de extratos de plantas na onicomicose causada por Trichophyton rubrum: Uma revisão integrativa / Potential action of plant extracts in onychomycosis caused by Trichophyton rubrum: An integrative review

Introdução: As dermatomicoses são doenças cutâneas, causadas por diferentes espécies de fungos dermatófitos, leveduras e fungos filamentosos não dermatófitos. Eles podem degradar queratina, tendo como alvo regiões do corpo como estrato córneo da pele, unhas e couro cabeludo, e são comumente ocasionadas por Trichophyton rubrum. A onicomicoses, que atinge as unhas e/ou leito subungueal, é uma patologia de difícil tratamento. Um dos obstáculos para o tratamento convencional é a redução da eficiência dos fármacos devido ao aumento da resistência microbiana aos agentes antifúngicos, sendo assim a utilização de produtos naturais é uma alternativa favorável por ser fonte de agentes terapêuticos inovadores.  Objetivo: avaliar o potencial antifúngico de extratos de plantas para possível desenvolvimento de novas alternativas medicamentosas. Metodologia: Trata-se de uma revisão do tipo integrativa, que utilizou as palavras-chaves “plant extract and onychomycosis” e “Trichophyton rubrum and plant extract”, para pesquisa nas bases de dados PubMed e LILACS. A seleção de artigos foi realizada entre os meses de agosto e setembro de 2020. Resultados: Os artigos selecionados mostram que extratos de plantas apresentam atividade antifúngica contra T. rubrum, inibindo seu crescimento, a germinação de conídios e crescimento radial do micélio in vitro. Conclusão: as plantas medicinais podem ser uma alternativa para o tratamento da onicomicose, porém mais estudo são necessários para que a eficácia antifúngica possa ser verdadeiramente comprovada e suprir as limitações encontradas nas terapias atuais

Cold Atmospheric Plasma Jet as a Possible Adjuvant Therapy for Periodontal Disease

Due to the limitations of traditional periodontal therapies, and reported cold atmospheric plasma anti-inflammatory/antimicrobial activities, plasma could be an adjuvant therapy to periodontitis. Porphyromonas gingivalis was grown in blood agar. Standardized suspensions were plated on blood agar and plasma-treated for planktonic growth. For biofilm, dual-species Streptococcus gordonii + P. gingivalis biofilm grew for 48 h and then was plasma-treated. XTT assay and CFU counting were performed. Cytotoxicity was accessed immediately or after 24 h. Plasma was applied for 1, 3, 5 or 7 min. In vivo: Thirty C57BI/6 mice were subject to experimental periodontitis for 11 days. Immediately after ligature removal, animals were plasma-treated for 5 min once-Group P1 (n = 10); twice (Day 11 and 13)-Group P2 (n = 10); or not treated-Group S (n = 10). Mice were euthanized on day 15. Histological and microtomography analyses were performed. Significance level was 5%. Halo diameter increased proportionally to time of exposure contrary to CFU/mL counting. Mean/SD of fibroblasts viability did not vary among the groups. Plasma was able to inhibit P. gingivalis in planktonic culture and biofilm in a cell-safe manner. Moreover, plasma treatment in vivo, for 5 min, tends to improve periodontal tissue recovery, proportionally to the number of plasma applications

Cold Atmospheric Pressure Plasma Is Effective against P. gingivalis (HW24D-1) Mature Biofilms and Non-Genotoxic to Oral Cells

The effects of helium cold atmospheric pressure plasma (He-CAPP) jet on Porphyromonas gingivalis (HW24D-1) biofilm, on human gingival fibroblasts (HGF) and human gingival keratinocytes (OBA-9) were assessed. Standardized suspension of P. gingivalis was obtained, and biofilms were grown anaerobically for 48 h. After exposition to He-CAPP, the biofilm viability was evaluated by XTT assay. HGF were grown at 37 °C, in an CO2 chamber in DMEM, while OBA-9 cells were cultured in keratinocyte serum-free medium. After 24 h, plates were exposed to He-CAPP for 1 to 7 min. Plasma was generated using a commercial AC power supply with amplitude modulated signal (voltage amplitude of 20 kVp-p, frequency of 31.0 kHz and duty cycle of 22%). The corresponding discharge power was 0.6W at He flow rate of 1 L/min. DNA damage was accessed by static cytometry. Data were analyzed by GraphPad Prism (p < 0.05). Significant reductions in P. gingivalis viability in relation to non-treated groups were detected (p < 0.0001), directly proportional to exposure time. Treated groups were slightly aneuploid after 5- and 7-min treatment in HGF, and for 3 min in OBA-9 cells, with 1.2 DNA index mean. Helium cold atmospheric pressure plasma jet showed inhibitory effect on P. gingivalis mature biofilm and was not genotoxic for epithelial gingival cells and human oral fibroblasts

Amplitude-modulated cold atmospheric pressure plasma jet for treatment of oral candidiasis: In vivo study.

The aim of this study was to establish an effective and safe protocol for in vivo oral candidiasis treatment with atmospheric plasma jets. A novel amplitude-modulated cold atmospheric pressure plasma jet (AM-CAPPJ) device, operating with Helium, was tested. In vitro assays with Candida albicans biofilms and Vero cells were performed in order to determine the effective parameters with low cytotoxicity. After the determination of such parameters, the protocol was evaluated in experimentally induced oral candidiasis in mice. AM-CAPPJ could significantly reduce the viability of C. albicans biofilms after 5 minutes of plasma exposure when compared to the non-exposed group (p = 0.0033). After this period of exposure, high viability of Vero cells was maintained (86.33 ± 10.45%). Also, no late effects on these cells were observed after 24 and 48 hours (83.24±15.23% and 88.96±18.65%, respectively). Histological analyses revealed significantly lower occurrence of inflammatory alterations in the AM-CAPPJ group when compared to non-treated and nystatin-treated groups (p < 0.0001). Although no significant differences among the values of CFU/tongue were observed among the non-treated group and the groups treated with AM-CAPPJ or nystatin (p = 0.3201), histological analyses revealed marked reduction in candidal tissue invasion. In conclusion, these results point out to a clinical applicability of this protocol, due to the simultaneous anti-inflammatory and inhibitory effects of AM-CAPPJ with low cytotoxicity

Inactivation of candida albicans by cold atmospheric pressure plasma jet

Nonthermal atmospheric pressure plasma jets (APPJs) are characterized by very reactive chemistry without the need of elevated temperatures. Also, plasma jets are capable of producing cold plasma plumes that are not spatially confined by electrodes, which makes them very attractive for biomedical applications. In this paper, we investigate the antimicrobial efficiency of a simple plasma jet device operating with pure He as working gas. The device was driven by an ac power supply operated at 31.0 kHz, 13.0 kV amplitude with mean power around 1.8 W. The jet was directed perpendicularly on a standard Petri dish (O90 mm x 15 mm) filled with agar. The jet fungicidal efficiency was tested against Candida albicans (reference strains SC 5314 and ATCC 18804) and five clinical isolates from previously obtained denture stomatitis lesions. In this paper, the effects of treatment time and distance to the target were evaluated. In most treatments the samples did not have direct contact with the plasma plume; therefore, the reactive oxygen species produced by interaction between the plasma jet and ambient air were the principal inactivate agent.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Influence of photodegradation with UV radiation in biotreatment with Paecilomyces variotti on PHBV/GNS nanocomposites

Graphite nanosheets (GNSs) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites were prepared by solution casting method. This study aimed to evaluate the effects of previously phototreatment with ultraviolet (UV) radiation on the biotreatment with Paecilomyces variotti of neat PHBV and PHBV/GNS nanocomposites. Some samples of PHBV film were submitted only to biotreatment with P. variotti during 120 daysother samples were subjected to phototreatment (UV radiation) for 30h followed by biodegradation assessment with P. variotti for a period of 120 days. The effects of biotreatments on thermal properties were studied through differential scanning calorimetry. The PHBV films were monitored by weight changes as a function of time. Also, their surfaces were examined after the tests using scanning electron microscopy, contact angle and roughness measurements. The level of oxidation was recorded by means of carbonyl index evaluation by Fourier transformed infrared spectroscopy spectroscopy. The phototreatment of PHBV films influenced the process of adhesion and colonisation by P. variotti on the surface of the films, and enhanced morphological and structural changes.CNPqFAPESP (Brazil)CAPES/PVNSFed Univ Sao Paulo UNIFESP, Inst Sci & Technol, Technol Lab Polymers & Biopolymers TecPBio, Talim 330, Sao Jose Dos Campos, SP, BrazilSao Paulo State Univ UNESP, Inst Sci & Technol, Dept Environm Engn, Rodovia Presidente Dutra,Km 137-8, Sao Jose Dos Campos, SP, BrazilFed Univ Sao Paulo UNIFESP, Inst Sci & Technol, Technol Lab Polymers & Biopolymers TecPBio, Talim 330, Sao Jose Dos Campos, SP, BrazilCNPq: 158961/2014-5CNPq: 303287/2013-6Web of Scienc

Cymbopogon citratus essential oil: effect on polymicrobial caries-related biofilm with low cytotoxicity

<div><p>Abstract The objective of this study was to evaluate the effects of Cymbopogon citratus essential oil and its main compound (citral) against primary dental colonizers and caries-related species. Chemical characterization of the essential oil was performed by gas chromatography/mass spectroscopy (GC/MS), and the main compound was determined. Antimicrobial activity was tested against Actinomyces naeslundii, Lactobacillus acidophilus, S. gordonii, S. mitis, S. mutans, S. sanguinis and S. sobrinus. Minimum inhibitory and bactericide concentrations were determined by broth microdilution assay for streptococci and lactobacilli reference, and for clinical strains. The effect of the essential oil on bacterial adhesion and biofilm formation/disruption was investigated. Negative (without treatment) and positive controls (chlorhexidine) were used. The effect of citral on preformed biofilm was also tested using the same methodology. Monospecies and microcosm biofilms were tested. ANOVA or Kruskal-Wallis tests were used (α=0.05). Cytotoxicity of the essential oil to human keratinocytes was performed by MTT assay. GC/MS demonstrated one major component (citral). The essential oil showed an inhibitory effect on all tested bacterial species, including S. mutans and L. acidophilus. Essential oil of C. citratus (10X MIC) reduced the number of viable cells of lactobacilli and streptococci biofilms (p < 0.05). The essential oil inhibited adhesion of caries-related polymicrobial biofilm to dental enamel (p < 0.01). Citral significantly reduced the number of viable cells of streptococci biofilm (p < 0.001). The essential oil showed low cytotoxicity to human keratinocytes. Based on these findings, this study can contribute to the development of new formulations for products like mouthwash, against dental biofilms.</p></div