Theoretical and experimental investigations of easy made fishnet metamaterials at microwave frequencies

In this work, we demonstrate theoretically and experimentally a left handed behaviour of a planar fishnet type metamaterial in the microwave regime. The fabrication procedure based on printed circuit board technology and mechanical micromachining technique is easy, unique and doesn’t involve optical lithography. The effective parameters have been extracted using the S parameter retrieval method and show a very good agreement between simulation and experiment. Using finite-element method based simulations and W-band (75 GHz–110 GHz) experiments. We measured a negative index of refraction of −4 at 85 GHz. The demonstrated left handed materials represent a step towards the easy fabrication of metamaterials with a negative refractive index that open a new path for the active manipulation of millimetre wavelengths.     

New Synthesis of Substituted Difuryl or Dithienyl Methanes

New trisubstituted methanes derivatives are quantitatively and selectively obtained by condensation of 2-methylfuran or 2-methylthiophene with diverse aldehydes using macroporous ion-exchange resins as catalyst. Hydration rate of organic phase and sulfonic sites of catalyst determines a proper reaction progress.     

Vectorial Form of the Successive Lorentz Transformations. Application: Thomas Rotation

A complete treatment of the Thomas rotation involves algebraic manipulations of overwhelming complexity. In this paper, we show that a choice of convenient vectorial forms for the relativistic addition law of velocities and the successive Lorentz transformations allows us to obtain straightforwardly the Thomas rotation angle by three new methods: (a) direct computation as the angle between the composite vectors of the non-collinear velocities, (b) vectorial approach, and (c) matrix approach. The new expression of the Thomas rotation angle permits us to simply obtain the Thomas precession. Original diagrams are given for the first time.     

The Effect of Different Ethoxylations for Sorbitan Monolaurate on Enhancing Simultaneous Saccharification and Fermentation (SSF) of Wheat Straw to Ethanol

In this paper, four nonionic surfactants with different hydrophilic–lipophilic balance (HLB) based on sorbitan monolaurate were synthesized by introducing ethylene oxide gas (n = 20, 40, 60, and 80 ethylene oxide units). The chemical structure of the prepared ethoxylated surfactants was confirmed using Fourier transform-infrared and ¹H NMR spectroscopes. The surface tension and thermodynamic properties of the prepared surfactants have been studied. The simultaneous saccharification and fermentation (SSF) process for ethanol production from microwave/alkali pretreated wheat straw has been assayed using nonionic surfactants have different ethylene oxide units. Ethanol yield was 82% and 61% for Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively, with the addition of 2.5 g/l of the prepared nonionic surfactant (HLB = 18.2). Results show that the production of ethanol from microwave/alkali pretreated wheat straw increased with increasing the (HLB) value of the nonionic surfactant.     

Chemical properties and cytotoxic activity of complexes of platinum(II) and palladium(II) containing dmso and various anions; synthesis and structural characterization of [Pt(dmso)2{O2(CO)2CCH2CH2CH2}]

Treatment of cis-[Pt(dmso)₂Cl₂] with 2 mol of KBr or KI leads to the formation of the analogous dibromide or diiodide complexes. Treatment of [M(dmso)₂Cl₂] [M = Pt (cis-) or Pd (trans-)] with AgNO₃ (2 mol) in H₂O followed by 1mol of potassium oxalate, maleate, cyclobutane dicarboxylate (CBDC), malonate or 2mol of potassium cyclohexane carboxylate or pivalate leads to the formation of the corresponding Pt^II and Pd^II carboxylate complexes. The single crystal X-ray structure determination of [Pt(dmso)₂(CBDC)] has been discussed and compared with data on other related complexes. The in vitro cytotoxic activity of some of these complexes against eight tumour cell lines has been examined using the MTT-colorimetric assay.     

Spectrofluorimetric determination of warfarin sodium by using N1-methylnicotinamide chloride as a fluorigenic agent

A spectrofluorimetric method is described for the determination of drugs containing active methylene groups adjacent to carbonyl groups. The method was applied successfully to the determination of warfarin sodium in laboratory-prepared mixtures, in commercial tablets, and in spiked human plasma samples. Finally, the method was applied to the determination of the steady-state concentration of warfarin sodium in the blood of a hospitalized patient. The method involves the reaction of warfarin sodium with 0.2 ml (0.4 x 10(-3)M) N1-methylnicotinamide chloride reagent in the presence of 3 mL 1.0N NaOH and cooling in ice for 8 min, followed by adjustment of the pH to 2.0, using formic acid and heating for 4 min, whereby a highly fluorescent reaction product is produced. The optimal wavelengths of excitation and emission were determined by using a synchronous wavelength search and found to be 284 and 354 nm, respectively. The standard curves were linear over a concentration range of 50-1500 ng/mL in both aqueous solutions and spiked human plasma samples. The mean recoveries (+/- standard deviation) were 101.157 (+/-1.33) and 95.73 (+/-1.88%) for aqueous solutions and spiked human plasma samples, respectively. The method showed good specificity and precision. The proposed method is simple and economical because of its minimal instrumentation and chemicals requirements. Nevertheless, it is highly sensitive, specific, and reproducible. Accordingly, it is suitable for quality-control applications, drug monitoring, and bioavailability and bioequivalency studies.     

Analogies Photochimiques. III—Diméthyl-4,4 allyl-2 Cyclohexanone. Elimination Inattendue de C2H4O et Perte de 15 Unités de Masse

The mass spectrum of 4,4-dimethyl 2-allyl cyclohexanone shows an ion at m/z 122 resulting from the elimination of a neutral acetaldehyde molecule direct from the molecular ion. Deuterium labelling results show a complex decomposition pathway during which four hydrogen atoms transfer to the eliminated acetaldehyde molecule. The molecular ion of this compounds also loses a methyl group originating from the allyl substituent. The mechanisms are discussed in terms of photochemical analogies.     

Understanding how the herpes thymidine kinase orchestrates optimal sugar and nucleobase conformations to accommodate its substrate at the active site: a chemical approach

The herpes virus thymidine kinase (HSV-tk) is a critical enzyme for the activation of anti-HSV nucleosides. However, a successful therapeutic outcome depends not only on the activity of this enzyme but also on the ability of the compound(s) to interact effectively with cellular kinases and with the target viral or cellular DNA polymerases. Herein, we describe the synthesis and study of two nucleoside analogues built on a conformationally locked bicyclo[3.1.0]hexane template designed to investigate the conformational preferences of HSV-tk for the 2'-deoxyribose ring. Intimately associated with the conformation of the 2'-deoxyribose ring is the value of the C-N torsion angle chi, which positions the nucleobase into two different domains (syn or anti). The often-conflicting sugar and nucleobase conformational parameters were studied using North and South methanocarbadeoxythymidine analogues (6 and 7), which forced HSV-tk to make a clear choice in the conformation of the substrate. The results provide new insights into the mechanism of action of this enzyme, which cannot be gleaned from a static X-ray crystal structure.     

Synthetic approaches to bicyclomycin I. Prepration of monocylic intermediates by retrograde Michael cleavage of 6-alkyl-6-methoxyhexahydro-3H-thiazolo [3,4-a]pyrazine-5,8-diones.

The syntheses of N-protected-3-(hydroxypropyl)-3-methoxy-6-alkylidine piperazine-2,5-diones are described, in relation to an approach to bicyclomycin. A chemoselective Grignard reaction and a novel diastereoselective retrograde Michael cleavage highlight the sequence.