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Metasurfaces are two-dimensional artificial structures, which have extraordinary electromagnetic properties. They have been used in a myriad of devices such as nano-antennas, cloaking coatings, imaging devices, at lenses, and polarization converters over a wide range of frequencies. Due to high dependency of many devices on incident wave polarization, manipulating the polarization of electromagnetic waves would be useful, especially in the Terahertz (THz) regime. In this study, we propose a Linear To Circular Polarization Converter (LTC-PC) based on a THz reflective metasurface. For a TE linear polarization incident wave, this structure has two distinct bands; the first one lies in a wideband frequency range of 0.5{1.41 THz, in which the reflected wave will be a Left- Handed Circular Polarization (LHCP) with minimum efficiency of 89% and maximum efficiency of more than 95% in 80% of the bandwidth. The second band lies in the narrowband frequency range of 1.45-1.55 THz, resulting in a Right-Handed Circular Polarization (RHCP) wave with a minimum efficiency of 82%. The proposed polarization converter can be used in optical communication and electronic devices. [ABSTRACT FROM AUTHOR]

Background and Aim: Incomplete root development caused by trauma ,caries, or pulpal pathosis requires special attention and treatment . Although calcium hydroxide apexification has been used successfully for years but it requires patient cooperation and multiple appointments . Single visit apexification with MTA has been used in recent years. The purpose of this study was to compare bacterial microleakage of two types of MTA (Made in Iran and Brazil) applied as apical barrier in open apex teeth.Materials and Methods: 48 single root teeth were used in this experimental in vitro study. Teeth apices were prepared as open apex teeth. For canal obturation the 4mm of root end was filled with 2 types of MTA (white Iranian MTA salami co. Iran and Angelus MTA Angelus Brazil) from coronal access. Teeth were mounted in self-cured acryl and put in BHI microbial culture. A suspension of Staphylococcus epidermidis was injected from coronal area into the root canals.The teeth were incubated and examined every 24 hours for microbial microleakage, indicated as turbidity in culture. Data were analyzed using Fisher exact test with p

Background: The antibiotic resistance is considered as one of the biggest public health concerns in most countries. The aim of this study was to determine antibiotic resistance pattern of Escherichia coli isolated from chickens with colibacillosis in Yazd, Iran. Methods: A total of 200 carcasses of Ross chickens with colibacillosis were collected from farms located around Yazd, central Iran. After autopsy, specimens were collected from air bags of carcasses using sterile swaps and transferred immediately to the laboratory. After microbiological culture, the isolates were confirmed by the conventional Polymerase Chain Reaction (PCR) assay. Antimicrobial susceptibility of E. coli isolates were determined by disk diffusion method. Results: Out of 200 specimens, 100 (50%) E. coli isolates were identified and confirmed by PCR method. The results of antimicrobial susceptibility tests showed the highest resistance against nalidixic acid (100%), enrofloxacin (87%), ciprofloxacin (86%), and erythromycin (82%), respectively. Also, the highest susceptibility was seen for colistin (100%), meropenem (94%), and gentamicin (93%), respectively. Conclusion: In this study, multidrug resistance was observed in avian pathogenic E. coli isolates that represents the heavy usage of these drugs in poultry flocks in Yazd, central Iran. Improper or overuse of antibiotics usage for treatment of the poultry diseases could play an important role in spreading of the antimicrobial resistance genes among pathogenic bacteria from human and animals especially through food chain. [ABSTRACT FROM AUTHOR]

Irradiation is a new technology which can be used for foods especially for the ones which common methods such as thermal method cannot be applied. Traditional ice cream samples were purchased from a local market. After applying a 15 kGy dose for sterilization, B rucella abortus and B rucella melitensis were inoculated to samples and then treated with four doses of 1, 2, 3 and 5 kGy electron beam irradiation at −18C storage temperature. Microbial examinations were performed in 3, 7, 14 and 21 days after treatment with electron beam irradiation. Results showed that no bacteria were observed in the initial test after use of 5 kGy dose. Applying 2 and 3 kGy reduced significantly ( P < 0.05) the microbial population but could not eliminate it completely. This study confirmed that electron beam irradiation is a reliable way to reduce microbial population of B rucella spp. in traditional ice cream and therefore improve food safety. Practical Applications To maintain palatability of traditional ice cream, milk must not be too heated or else pasteurization is not achieved. So, electron beam irradiation could ensure the safety of ice cream, instead of heat treatment. [ABSTRACT FROM AUTHOR]

Background: Pseudomonas aeruginosa is a gram-negative, non-fermentative bacillus and one of the most common opportunistic human pathogen causing 10-15% of nosocomial and burn wound infections worldwide. These bacteria are resistant to most of the antibiotics. This study aimed to investigate the frequency of extended spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL) enzymes in P.aeruginosa strains isolated from burn wounds. Materials and Methods: In this descriptive cross-sectional study, 180 wound specimens were collected from patients hospitalized in burn hospital and then cultured. The suspected colonies were identified using the conventional biochemical methods. Susceptibility testing was performed using the Kirby-Bauer method. Moreover, the Combination Disk and E.test methods were used for the determination of ESBLs and MBL, respectively. Results: Fifty-four (30%) out of 180 cultured samples were identified as p.aeruginosa; 12 (22%) and 16 (29.5%) isolates were ESBLs and MBL producer, respectively. Overall, 42 (79%), 40 (74%), 40 (74%), 38 (70%), 35 (66%) and 34 (62%) isolates were resistant to ceftizoxime, imipenem, gentamycin, piperacillin, cefepime, meropenem and ertapenem, respectively. Conclusion: Results reveal that the antimicrobial resistance and prevalence of ESBLs and MBL producing P.aeruginosa strains is increasing in our hospital and it is necessary to perform susceptibility testing, control risk factors and reasonably prescribe the appropriate antibiotics. Considering the diversity of ESBL and MBL classes and their prevalence in different areas, performing molecular research is needed. [ABSTRACT FROM AUTHOR]

The effects of phosphorous atom on the stability, multiplicity, and reactivity of six-member cyclic silylenes are investigated at B3LYP/AUG-cc-pVTZ//B3LYP/6-31+G* and MP2/6-311++G**//B3LYP/6-31+G* coupled with appropriate isodesmic reactions. From a thermodynamic point of view, 1 H-2-silaphosphinine-2-ylidene ( 1a) and 1 H-4-silaphosphinine-4-ylidene ( 2a) are relatively the most stable with singlet-triplet energy gaps (Δ ES-T) of 37.0 and 28.1 kcal/mol, respectively. The calculated energy barrier for the 1,2- H shift of 1a to the corresponding 2-silapyridine ( 1) is 26.5 kcal/mol, which is lower than the 28.8 kcal/mol required for the 1,4- H shift of 2a to the corresponding 4-silapyridine ( 2). In contrast to the previous reports, isodesmic reactions indicate that π-donor/σ-donor phosphorous destabilizes the singlet while stabilizes the triplet state. Both 1a and 2a silylenes appear invulnerable to the head-to-head as well as the head-to-tail dimerization, inviting experimental explorations. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

α-Cyclopropyl stability impacts on singlet and triplet heterocyclic carbenes with acyclic, cyclic, and cyclic-unsaturated structures are compared and contrasted to di- t-butyl as well as t-butylcyclopropylcarbenes through appropriate isodesmic reactions at B3LYP/AUG-cc-pVTZ level. Substitution of one of the t-butyl groups of di- t-butylcarbene with a cyclopropyl alters the ground state multiplicity from triplet to singlet with a singlet-triplet energy separation (Δ Es-t) of 7.2 kcal/mol. Additional heteroatom substitution increases Δ Es-t values for the resulting α-heteroatom cyclopropylcarbenes in the following order: amino > oxy > thio > phophino. α-Cyclopropyl group stabilizes singlet states of all our carbenes two to three times more than their corresponding triplet states. The Δ Es-t values of all the carbenes are increased through cyclization, while the introduction of unsaturation in the rings causes small and rather random changes. To probe the kinetic stability of the species, we calculated the transition states for the opening of cyclopropyl through 1,2- C shift. Interestingly, the 4.1 kcal/mol energy barrier in cyclopropylcarbene is significantly increased in the presence of heteroatoms to 31.2 kcal/mol for aminocyclopropylcarbene. The reactivity of the species is discussed in terms of nucleophilicity and electrophilicity issues showing our carbenes, especially acyclic ones, more nucleophilic than the common N-heterocyclic carbenes. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides (LPSs) of 11 bacterial strains from the type species of the genera Bacteroides (B. fragilis), Prevotella (Pr. melaninogenica), Porphyromonas (Po. gingivalis), Campylobacter (C. fetus subsp. fetus), and Wolinella (W. succinogenes), and from the type strains of B. distasonis, B. forsythus, B. ureolyticus, Po. levii, Po. macacae, and C. gracilis, were extracted with hot water-phenol (Westphal method). S-form LPSs, obtained from all organisms, were well resolved with tricine-sodium-dodecyl-sulphate polyacrylamide gel electrophoresis and visualized by silver staining. Lipid A was not stained. Also profiles from LPS of Escherichia coli, serotypes 0111:B4 and 055:B5, could be distinguished. While W. succinogenes showed a relatively short S-form LPS on electrophoregrams, the other bacteria, including B. fragilis, exhibited long-ladder LPSs. Po. gingivalis displayed the largest number of bands and the longest O-chain. The long O-chain of this bacterium may be important for its virulence. [ABSTRACT FROM AUTHOR]