Essential oil composition of five collections of Achillea biebersteinii from central Turkey and their antifungal and insecticidal activity

The composition of the essential oils hydrodistilled from the aerial parts of five Achillea biebersteinii Afan samples, collected in central Turkey from Konya, Isparta and Ankara, were analyzed both by gas chromatography (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Eighty-four components were identified, representing 87 to 99% of the total oil composition. The identified major components were 1,8-cineole (9-37%), camphor (16-30%) and p-cymene (1-27%). Two samples differed in piperitone (11%) and ascaridol (4%) content. The five A. biebersteinii essential oils were subsequently evaluated for their antifungal activity against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides using the direct overlay bioautography assay. The essential oils showed no antifungal activity at 80 and 160 microg/spot. In addition, A. biebersteinii oils and their major compounds were subsequently investigated against Aedes aegypti first instar larvae in a high throughput bioassay. Among the oils, only one sample from Ankara showed a notable larvacidal effect on Ae. aegypti larvae. The major compounds, 1,8-cineole, camphor and p-cymene, exhibited low mosquito larval activity, and thus the minor compounds are probably responsible for the observed activity against Ae. aegypti larvae. The oils showed weak activity against adult Ae. aegypti.     

Removal of an azo-metal complex textile dye from colored aqueous solutions using an agro-residue

The pine leaves which are an agricultural residue were used in its natural form as biosorbent for the removal of Acid Yellow 220 (AY 220) dye from aqueous solutions. The sorption experiments were carried out as a function of solution pH, biosorbent dosage, biosorbent size, dye concentration, temperature, contact time and ionic strength. The sorption isotherms closely followed the Langmuir model. The monolayer sorption capacity of the pine leaves for AY 220 was found as 40.00 mg g^{− 1}. It was shown that pseudo-second order equation could best describe the sorption kinetics. The thermodynamic data indicated that the sorption system was spontaneous, endothermic and physical process. Based on the results of present investigation, the pine leaves could be used as a suitable alternative biosorbent for the elimination of AY 220 from aqueous solutions.     

Simulated and experimental studies of a multi-band symmetric metamaterial absorber with polarization independence for radar applications

We develop a simple new design for a multi-band metamaterial absorber (MTMA) for radar applications. Computer Simulation Technology (CST) Studio Suite 2018 was used for the numerical analysis and absorption study. The simulated results show four high peaks at 5.6 GHz, 7.6 GHz, 10.98 GHz, and 11.29 GHz corresponding to absorption characteristics of 100%, 100%, 99%, and 99%, respectively. Furthermore, two different structures were designed and compared with the proposed MTMA. The proposed structure remained insensitive for any incident angle and polarization angle from 0° to 60°. Moreover, negative constitutive parameters were retrieved numerically. To support the simulated results, the proposed design was fabricated by using a computer numerical control-based printed circuit board prototyping machine and tested experimentally in a microwave laboratory. The absorption mechanism of the proposed MTMA is presented through the surface current and electric field distributions. The novelties of the proposed structure are a simple and new design, ease of fabrication, low cost, durability, suitability for real-time applications and long-term stability given the fabrication technique and non-destructive measurement method and very high absorption. The proposed structure has potential applications in C and X band frequency ranges.     

An amperometric urea biosensor based on covalent immobilization of urease on copolymer of glycidyl methacrylate and vinylferrocene

A unique urea biosensor construction based on the direct covalent attachment of urease onto a polymeric electron transfer mediator, poly(glycidyl methacrylate-co-vinylferrocene)-coated electrode is described. Amperometric response was measured as a function of urea concentration, at a fixed potential of +0.35 V vs. Ag/AgCl in phosphate-buffered saline (pH 7.0). Covalent immobilization of the urease directly to the functionalized ferrocene copolymer surface produced biosensors with a short response time (about 3 s) and provided low detection limits. The stability, reusability, pH, and temperature response of the biosensor, besides its kinetic parameter, were also studied.     

Incorporation of a 2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione unit into a donor–acceptor triad: synthesis and ion recognition features

A novel directly-linked donor–acceptor–donor (D–A–D) type system, which is based on 2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione as the A unit and thiophene as the D units, respectively, is designed, synthesized, and characterized by spectroscopic methods. This novel D–A–D system can be used for the fluorogenic detection of Cu²⁺ among other ions.     

Central neurocytoma: proton MR spectroscopy and diffusion weighted MR imaging findings

Purpose

To present proton magnetic resonance spectroscopy and diffusion-weighted imaging (DWI) findings of central neurocytoma (CN).

Methods and Materials

Imaging findings of seven patients with the histopathological diagnosis of CN (five male and two female; age range, 21–28 years of age) were evaluated retrospectively. In addition to conventional magnetic resonance imaging features, we also assessed the metabolite ratios and tumor normalized apparent diffusion coefficient (NADC), which was calculated by dividing the tumor apparent diffusion coefficient (ADC) values by normal ADC. Approval from our institutional review board was obtained for this review.

Results

The tumor choline/creatine ratios were 5.17±2.38, while N-acetyl aspartate/choline and N-acetyl aspartate/creatine ratios were 0.33±0.15 and 1.84±1.38, respectively. On DWI, tumors had heterogeneous hyperintense appearances when compared with the contralateral parietal lobe white matter and tumor NADC values were 0.63±0.05.

Conclusion

Significantly increased choline/creatine and decreased N-acetyl aspartate/choline ratios with lower NADC values in CN resemble high-grade gliomas and complicate the diagnosis. Familarity its physiologic features would help to presurgical diagnosis of ventricular and exraventricular CNs.     

Analysis of multiple scattering iterations for high-frequency scattering problems. I: the two-dimensional case

We present an analysis of a recently proposed integral-equation method for the solution of high-frequency electromagnetic and acoustic scattering problems that delivers error-controllable solutions in frequency-independent computational times. Within single scattering configurations the method is based on the use of an appropriate ansatz for the unknown surface densities and on suitable extensions of the method of stationary phase. The extension to multiple-scattering configurations, in turn, is attained through consideration of an iterative (Neumann) series that successively accounts for further geometrical wave reflections. As we show, for a collection of two-dimensional (cylindrical) convex obstacles, this series can be rearranged into a sum of periodic orbits (of increasing period), each corresponding to contributions arising from waves that reflect off a fixed subset of scatterers when these are transversed sequentially in a periodic manner. Here, we analyze the properties of these periodic orbits in the high-frequency regime, by deriving precise asymptotic expansions for the “currents” (i.e. the normal derivative of the fields) that they induce on the surface of the obstacles. As we demonstrate these expansions can be used to provide accurate estimates of the rate at which their magnitude decreases with increasing number of reflections, which defines the overall rate of convergence of the multiple-scattering series. Moreover, we show that the detailed asymptotic knowledge of these currents can be used to accelerate this convergence and, thus, to reduce the number of iterations necessary to attain a prescribed accuracy.     

Synthesis,characterization, and antimicrobial activity of new benzoylthiourea ligands

In this study, new benzoylthiourea derivatives, (E)-N-[(2-benzamidomethyleneamino)ethylcarbamothioyl]benzamide H₃L′, N-(1-(3-benzoylthioureido)propan-2-ylcarbamothioyl)-benzamide H₄L″, (E)-N-[4-(benzamidomethyleneamino)phenylcarbamothioyl]benzamide H₃L‴, were synthesized. Structures of the compounds were identified by spectroscopic techniques. In addition, all synthesized compounds were evaluated for in vitro antibacterial and antifungal activity. Compound H₃L‴ exhibited antibacterial activity.     

Synthesis of a glutaraldehyde derivative of calix[4]arene as a cross-linker reagent for lipase immobilization

This article describes the synthesis of a new calix[4]arene 1,3-distal glutaraldehyde derivative 4 as a cross-linker-reagent for immobilization of Candida rugosa lipase (CRL). p-tert-Butylcalix[4]arene 1,3-distal diaminoalkyl derivative (3) synthesized via aminolysis reaction of 5,11,17,23-tert-butyl-25,27-ethoxycarbonylmethoxy-26,28-hydroxycalix[4]arene (2) with 1,8-diaminooctane. Compound 3 was converted to its aldehyde derivative (4) by the treatment with glutaraldehyde solution. 4 was used in lipase immobilization in order to see the role of calix[4]arene binding site on the lipase activity and stability. It was observed that the immobilized lipase activity was maintained at levels exceeding 95% of its original activity after 40 min.