Frequency-dependent photothermal measurement of thermal diffusivity for opaque and non-opaque materials; Application to crystals of TIPS-pentacene

We propose the use of a frequency-dependent photothermal measurement as a complement to light-flash, i.e. time-dependent, measurements to determine the through-plane thermal diffusivity of small, thin samples, e.g. semiconducting polymers and small organic molecule crystals. The analysis is extended from its previous use with some opaque conducting polymers to materials with finite absorption coefficients, such as crystals of 6,13-bis(triisopropylsilylethynyl pentacene ("TIPS-pentacene"). Taking into account the finite absorption coefficients of the latter gives a value of diffusivity, D=0.10 mm2/s, much smaller than previously estimated and more consistent with its expected value. We also briefly discuss the effects of coating samples for the measurement to improve their optical properties.Comment: 11 pages, 6 figures, to be published in Journal of Applied Physic

TRANSVERSE AND LONGITUDINAL THERMAL DIFFUSIVITY MEASUREMENTS OF POLYMER AND SMALL MOLECULE ORGANIC SEMICONDUCTORS WITH DIFFERENT TECHNIQUES

The main thrust of this research was to develop new probes to measure thermal conductivities (κ) of small-molecule crystals, as well as polymer blends of organic semiconductors, both to screen these for possible applications, e.g. as thermoelectric power generators, and to gain an understanding of thermal transport in them. Emphasis has been on the crystals of “TIPS pentacene” [TIPS = 6,13 bis(triisopropylsilylethynyl), and free-standing films of PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] for different electrochemical and thermoelectric applications. Separate techniques were used for in-plane and transverse thermal conductivities in which is determined indirectly from measurements of the thermal diffusivity (D ≡ κ/ρc, where ρ is the density and c the specific heat). For in-plane measurements, we used a position dependent ac-calorimetric technique in which, long, thin samples are illuminated with light chopped at a low frequency along part of their length, and the temperature oscillations on the opposite surface measured with a thermocouple. For the transverse, we have developed a simplified ac-photothermal apparatus for measurement of the transverse thermal (i.e through-plane) diffusivity of small samples with a typical area of 7 2. Our technique is essentially the Fourier transform of the laser flash method. The sample is heated on its front side with chopped light, and we measure the frequency-dependence of thermal radiation from the sample by mounting it in front of a mercury-cadmium-telluride (MCT) infrared detector inside the detector dewar. For optically opaque samples, a simple analysis of the complex frequency dependence of the detector signal gives the transverse diffusivity. For samples which are not opaque, the same analysis, overlooking the finite optical absorption length, can lead to a very large overestimate of the diffusivity. We have shown in this research how the technique can be adapted and present a more complete analysis for less absorbing samples. Since new electrically conducting and mechanically robust fibers and yarns are needed as building blocks for emerging textile devices, we have measured the longitudinal thermal conductivities of PEDOT:PSS fibers fabricated by a continuous wet-spinning process. These fibers have high electrical conductivity, excellent mechanical properties, and moderate thermoelectric performance by including a stage in which they are drawn through dimethyl sulfoxide. Drawing the fibers induces preferential orientation of the polymer chains in the fiber axis direction. A self-heating technique is used to conduct direct measurements on the thermal conductivity of the fibers and the result indicates drawn fibers have thermal conductivities several times larger than most films, consistent with better alignment of the polymer strands and grains. For all samples, the measured total thermal conductivity was about a factor of 20 larger than the electronic thermal conductivity calculated from the Wiedemann−Franz law using the Sommerfeld value for 0, which could be indicating that the lattice contribution dominated despite the large electrical conductivities observed. This result suggests that drawing the material not only aligns the conducting grains but also improves conduction through the PSS matrix

Frequency-Dependent Photothermal Measurement of Thermal Diffusivity for Opaque and Non-Opaque Materials: Application to Crystals of TIPS-Pentacene

We propose the use of a frequency-dependent photothermal measurement as a complement to light-flash, i.e., time-dependent, measurements to determine the through-plane thermal diffusivity of small, thin samples, e.g., semiconducting polymers and small organic molecule crystals. The analysis is extended from its previous use with some opaque conducting polymers to materials with finite absorption coefficients, such as crystals of 6,13-bis(triisopropylsilylethynyl)pentacene. Taking into account the finite absorption coefficients of the latter gives a value of diffusivity, D ≈ 0.10 mm2/s, much smaller than previously estimated and more consistent with its expected value. We also briefly discuss the effects of coating samples for the measurement to improve their optical properties

In vitro study of antimicrobial effects of Rosmarinus officinalis and Glycyrrhiza glabra extracts against some pathogens

Background and aims: Disease causing bacteria have always been considered a major cause of morbidity and mortality in humans. The appearance of resistant microorganisms paved the way to the occurrence of infections that are only treated by a limited number of antimicrobial agents. The present study was, the antimicrobial effects of Rosmarinus officinalis and Glycyrrhiza glabra extract against some pathogens. Methods: In this study, the antibacterial activity using 9 Gram-positive and Gram-negative bacterial strains includes: Streptococcus pyogenes ATCC® 19615, Streptococcus pneumoniae ATCC 49619, S. saprophyticus ATCC®15305, Hafnia alvei ATCC 51873, Acinetobacter baumannii ATCC 19606, Enterococcus faecalis ATCC 29212, Proteus mirabilis ATCC 35659, Serratia marcescens ATCC 274 and Staphylococcus aureus ATCC® 25923 with micro dilution methods was studied. The MIC, MBC were studied also, resistance of these bacteria to standard antibiotics such as erythromycin, cefixime, ceftazidime, tetracycline, ampicillin and amikacin were compared. Results: In this study, the minimum inhibitory concentration (MIC) was used. The levels of MIC of R. officinalis were in ranges from 6.25 to 25 mg/ml. The highest MIC value was observed at 25 ppm against S. pyogenes, S. pneumoniae and P. mirabilis and the levels of MIC of G. glabra were in ranges from 6.25 to 12.5 ppm. The highest MIC value was observed at 12.5 ppm against S. pyogenes, S. pneumoniae, P. mirabilis and S. marcescens. Conclusion: In important human pathogens, drug resistance is increasing according to the results of this study, and may be proposed that this plant can be used as a drug. It can be a good way to replace herbs with chemical drugs

Regulation of Bone Metabolism

Bone is formed through the processes of endochondral and intramembranous ossification. In endochondral ossification primary mesenchymal cells differentiate to chondrocytes and then are progressively substituted by bone, while in intramembranous ossification mesenchymal stem cells (MSCs) differentiate directly into osteoblasts to form bone. The steps of osteogenic proliferation, differentiation, and bone homeostasis are controlled by various markers and signaling pathways. Bone needs to be remodeled to maintain integrity with osteoblasts, which are bone-forming cells, and osteoclasts, which are bone-degrading cells. In this review we considered the major factors and signaling pathways in bone formation; these include fibroblast growth factors (FGFs), bone morphogenetic proteins (BMPs), wingless-type (Wnt) genes, runt-related transcription factor 2 (RUNX2) and osteoblast-specific transcription factor (osterix or OSX). Keywords: BMP, FGF, Osteogenesis, OSX, RUNS2, Wn

Prevalência de parasitas intestinais em população no sul do Teerã, Irã

The aim of this study was to describe epidemiologic characteristics of intestinal parasites in a population in south of Tehran, Iran. A retrospective cross-sectional study of patients with suspicious intestinal parasitic infections referred to the Zakaria Razi Laboratory in Shahre-Ray, southern Tehran, Iran, was conducted from April 21, 2004 to October 20, 2005. All stool samples were examined and socio-demographic informations were retrieved. Of 4,371 referred patients, 466 (239 males and 227 females) were laboratory diagnosed with intestinal parasites, with a period prevalence of 10.7%. Blastocystis hominis (B. hominis) and Giardia lamblia (G. lamblia) were the most frequent intestinal parasites. More than half of patients aged ³ 18 years had a low level of educational attainment (e.g. illiterate, primary school, high school) (170/331, 54.1%). Further, majority of patients were homemakers (42.3%, 140/331) or workers (28.1%, 93/331) employed in various business settings such as food industry and construction. Findings of this study showed that intestinal parasitic infections are still a major public health challenge in Iran that needs to be addressed. We believe that public education, improving sanitation conditions of underdeveloped areas/communities, community involvement, and supporting evidence-based practice/programs are the major keys to success in preventing the spread of intestinal parasitic infections in Iran.O própósito deste estudo foi descrever as características epidemiológicas dos parasitas intestinais em população do sul de Teerã, Irã. Um estudo retrospectivo seccional cruzado de pacientes com suspeita de infecções parasitárias intestinais enviados ao Laboratório Zakaria Razi em Shahre-Ray, sul do Teerã, Irã foi conduzido de 21 de abril de 2004 a 20 de outubro de 2005. Todas as amostras de fezes foram examinadas e as informações sócio-demográficas recuperadas. De 4371 pacientes enviados, 466 (239 homens e 227 mulheres) foram diagnosticados laboratorialmente como portadores de parasitas intestinais com prevalência no período de 10,7%. Blastocystis hominis (B. hominis) e Giardia lamblia (G. lamblia) foram os parasitas intestinais mais frequentes. Mais da metade dos pacientes ³ 18 anos tinham baixo nível educacional (por exemplo: analfabetos, escola primária, 2º grau completo) (170/331, 54,1%). Mais ainda, a maioria dos pacientes eram empregados domésticos (42,3%, 140/331) ou trabalhadores (28,1%, 93/331) empregados em diversos tipos de serviços, tais como a indústria de alimentos e construção. Achados deste estudo mostraram que as infecções parasitárias intestinais são ainda um desafio importante em saúde pública no Irã que necessita ser resolvido. Acreditamos que a educação pública, a melhoria das condições sanitárias em áreas pouco desenvolvidas/comunidades, envolvimento da comunidade, e programas práticos baseados nas evidências, são as principais chaves do sucesso na prevenção da disseminação das infecções parasitárias no Irã

Influence of sexually transmitted infections on the cervical cytological abnormalities among Iranian women: A cross-sectional study

Background: Sexually transmitted infections (STIs) are one of the world’s most severe health challenges. The existence of STIs such as human papillomavirus (HPV) might cause cervical cell changes leading to cervical cancer. Objective: This study aims to assess the association of STIs with cervical cytological abnormalities and genital warts among women in northeastern Iran. Materials and Methods: This cross-sectional study was carried out on 190 women referred to the central laboratory of Academic Center for Education, Culture, and Research, Mashhad, Iran from March to July 2022. The presence of genital infections caused by Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, and Herpes simplex viruses (1 and 2) were assessed using the real-time polymerase chain reaction method. HPV genital infection was detected based on the principles of reverse hybridization, and cellular changes in the cervix were examined by the liquid-based cytology technique. Results: The mean age of participants was 35.33 ± 8.9 yr. 34 different HPV genotypes were detected in all HPV-positive cases, and the most common genotype was low-risk HPV6. No significant association was found between STIs and cervical cytology abnormalities. The prevalence rates of sexually transmitted pathogens among HPV-positive and HPV-negative individuals were 10.9 and 1.6%, respectively. The frequency of genital warts was significantly higher in cases with multiple infections of high- and low-risk HPV genotypes. Conclusion: High percentages of the participants with non-HPV STIs and HPV infection had normal cervical cytology. It is advised to use STIs and HPV diagnostic tests along with cytology examinations for cervical cancer screening. Key words: Sexually transmitted infections, Human papillomavirus, Cervical cancer, Genital wart, Genotypes

Knowledge and attitude of post-graduate dentistry students regarding HIV-positive patients

BACKGROUND AND AIM: Human immunodeficiency virus (HIV) can cause a hazardous disease and has severe fatal consequences. The problem of dental treatment in affected patients has still remained a big debate. The objective of this study was to evaluate the knowledge and attitude of post-graduate dentistry students regarding treatment and education of HIV-positive patients. METHODS: This was a cross-sectional descriptive study on the post-graduate students of dentistry in Iran. Samples were collected using consensus method. A valid questionnaire comprising three parts was designed according to previous studies. The questionnaire comprised of a demographic part, general questions and questions regarding knowledge and attitude of the subjects. Answers were collected and Student’s t-test and Fischer’s exact test was used to analyze the data. RESULTS: A total of 380 subjects took part in this study (164 male, 216 female). There were 92 HIV-positive patients. The average score of knowledge was 14.5 ± 2.8 (range = 0-24). The average score of knowledge in male and female participants was 14.5 ± 2.8 and 14.6 ± 2.7 respectively (range = 0-65). There was no significant relationship between knowledge and gender (P = 0.70). The average score of attitude was 44.8 ± 5.25 and male residents had a positive attitude in comparison to female residents. Male participants had a significantly more negative attitude toward high risk and HIV-positive patients compared to female residents (P = 0.04). CONCLUSION: The results of this study showed that post-graduate students had a positive attitude toward treatment of HIV-positive patients. Also, this study showed that post-graduate students had a good knowledge about the HIVpositive patients. This study shows that post-graduate students of dentistry were eager to learn more about the treatment of HIV-positive patients. Findings of this study also add new concepts to the oral hygiene maintenance of HIV-positive patients and decision making for them. KEYWORDS: Knowledge; Attitude; Dentistry; Human Immunodeficiency Virus (HIV

The Effect of Different Mixing Methods on the pH and Solubility of Mineral Trioxide Aggregate and Calcium-Enriched Mixture

Introduction: The aim of this study was to evaluate the effect of different mixing techniques on the pH and solubility of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM). Methods and Materials: Five samples were prepared from each biomaterial with different mixing techniques including hand-, amalgamator- or ultrasonic-mixing and were then placed in pre-weighted plastic tubes to determine their pH values. Each tube was then incubated in 10 mL deionized distilled water for 1 h at 37ºC. An electrode was placed in the fluid in each flask at 24ºC and the pH was recorded. In the next stage, six samples from each mixing technique/material were separately placed in glass bottles containing 50 mL of distilled water at 37ºC for 1 h and were let dry for 1 h at 37ºC. The samples’ weights were measured and recorded twice. The procedure was repeated at 1-, 7- and 21-day intervals. Data were analyzed with the repeated measures ANOVA (for solubility) and two-way ANOVA (for pH) and then the post-hoc Tukey’s test was done. Results: The pH of the materials was not significantly affected by mixing methods (P=0.8 for CEM and P=0.1 for MTA). The solubility of all test groups was within the acceptable range (≤3%). However, the solubility of CEM at 1- and 21-day intervals was significantly different (P=0.03 for 1 day and P=0.001 for 21 days). Different mixing techniques had significant effects on the solubility of MTA at the three time points (P=0.004, 0.003 and 0.002 for 1-, 7- and 21-day intervals, respectively). Conclusion: The pH of biomaterials was not influenced by the mixing technique and their solubility was within the acceptable range