Infrared spectra of C2H4 dimer and trimer

Spectra of ethylene dimers and trimers are studied in the nu11 and (for the dimer) nu9 fundamental band regions of C2H4 (~2990 and 3100 cm-1) using a tunable optical parametric oscillator source to probe a pulsed supersonic slit jet expansion. The deuterated trimer has been observed previously, but this represents the first rotationally resolved spectrum of (C2H4)3. The results support the previously determined cross-shaped (D2d) dimer and barrel-shaped (C3h or C3) trimer structures. However, the dimer spectrum in the nu9 fundamental region of C2H4 is apparently very perturbed and a previous rotational analysis is not well verified.Comment: 21 pages, 4 figure

Structural and physical properties of Sm3+ doped magnesium zinc sulfophosphate glass

Samarium (Sm3+ ) doped magnesium zinc sulfophosphate glass system of composition (60-x)P2O5-20MgO-20ZnSO4-xSm2O3 (x = 0.0, 0.5, 1.0, 1.5 and 2.0 mol%) were synthesized using melt-quenching technique. The structure and physical properties of prepared glass samples were characterized. The X-ray diffraction pattern verified their amorphous nature. The physical properties such as density, refractive index, molar volume, rare earth ion concentration, etc. were calculated. The decrease in the optical bandgap energy with increasing Sm2O3 contents was attributed to the alteration in the glass network structures. Fourier transformed infrared spectra and Raman analyses manifested the depolymerization of ZnSO4 in the phosphate host matrix. The present findings may be beneficial for the advancement of functional glasses

Quantum gravitational optics: Effective Raychaudhuri equation

Vacuum polarization in QED in a background gravitational field induces interactions which {\it effectively} modify the classical picture of light rays, as the null geodesics of spacetime. These interactions violate the strong equivalence principle and affect the propagation of light leading to superluminal photon velocities. Taking into account the QED vacuum polarization, we study the propagation of a bundle of rays in a background gravitational field. To do so we consider the perturbative deformation of Raychaudhuri equation through the influence of vacuum polarization on photon propagation. We analyze the contribution of the above interactions to the optical scalars namely, shear, vorticity and expansion using the Newman-Penrose formalism.Comment: 17 pages, 1 figure, RevTex format, Replaced with the published versio

Solvent effect on 14N NMR shielding of glycine, serine, leucine, and threonine: comparison between chemical shifts and energy versus dielectric constant

The polarizable continuum model (PCM) is employed to describe the system in the condensed phase. The performance of DFT and PCM in describing high order nonlinear mixed electric and magnetic effects in condensed phase are described. In this paper we consider the effect of 10 solvents with a wide range of dielectric constants on 4 amino acids. NMR shielding values (ppm), isotropic and anisotropic effects, energy interaction between solute and solvent, and the effect of hydrogen bond on shielding are described. Direct and indirect solvent effects on shielding are also calculated. The observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than on the change of molecular geometry induced by the solvent. KEY WORDS: Solvent effect, 14N NMR shielding, Solvent-induced shielding, Polarizable continuum model, Amino acids   Bull. Chem. Soc. Ethiop. 2007, 21(1), 111-116

Combined efficacy of silver nanoparticles and commercial antibiotics on different phylogenetic groups of Escherichia coli

NO ABSTRACT AVAILABLESilver nanoparticles (Ag-NPs) can attach to flexible polymeric chains of antibiotics, hence it can be used in combination with antibiotics against resistant bacteria. In this study, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and MBC/MIC ratio of Ag-NPs and antibiotics (gentamicin, tetracycline, erythromycin, ciprofloxacin, nalidixic acid, cefixime, cephalexin, amoxicillin, ampicillin, and penicillin) were quantified against 50 Escherichia coli isolates (25 human urinary tract infection and 25 avian colibacillosis). All isolates had been assigned as four phylogenetic groups A, B1, B2, and D. The results showed that the majority of the human and broiler isolates belonged to phylogenetic groups A and B2. MBC/MIC ratio of Ag-NPs in combination with antibiotics was assessed. It was found that the MIC of the majority of broiler isolates to Ag-NPs was equal to or greater than 50 μg/ml. To conclude, a combination of penicillin and ciprofloxacin with Ag-NPs exhibited profound impact against isolates, the combinations might be applicable for treating multidrug-resistant bacteria

Saponifikasi dan Ekstraksi Satu Tahap untuk Ekstraksi Minyak Tinggi Linoleat dan Linolenat dari Kedelai Varietas Lokal

Asam linoleat (LA, linoleic acid, C18:2ω-6) dan asam alfa linolenat (ALA, alpha linolenic acid, C18:3ω-3) merupa- kan asam lemak tidak jenuh majemuk (PUFA, polyunsaturated fatty acid) esensial. Penelitian tentang kedelai varietas lokal sebagai sumber LA dan ALA sangat penting dalam rangka mengurangi ketergantungan terhadap produk minyak tinggi LA dan ALA impor. Akan tetapi, penelitian tentang ekstraksi LA dan ALA dari kedelai varietas lokal yang ada di Indonesia masih sangat terbatas. Teknik ekstraksi yang efisien diperlukan untuk meningkatkan kadar PUFA. Salah satu teknik untuk mengekstrak minyak tinggi LA dan ALA adalah kombinasi saponifikasi dan ekstraksi simultan atau saponifikasi-ekstraksi satu tahap.Penelitian ini bertujuan untuk mengungkap potensi kedelai varietas lokal sebagai sumber LA dan LA, dan untuk mengembangkan teknik saponifikasi-ekstraksi satu tahap. Kedelai varietas lokal, yaitu Panderman, Wilis, Kaba, Burangrang, dan Anjasmara, dianalisis profil asam lemaknya. Varietas yang digunakan lebih lanjut untuk saponifikasi- ekstraksi satu tahap didasarkan pada kadar LA dan ALA tertinggi. Selanjutnya, kondisi saponifikasi-ekstraksi satu tahap dioptimasi dengan menggunakan metodelogi permukaan respon dengan tiga faktor yaitu rasio air:tepung kedelai, suhu saponifikasi, dan lama saponifikasi. Respon yang dikaji adalah kadar LA dan ALA dalam minyak yang terekstrak. Hasil penelitian menunjukkan bahwa diantara kedelai varietas lokal yang diteliti, varietas Burangrang mempunyai kadar LA+ALA tertinggi (60,43 %). Varietas yang berbeda menunjukkan profil asam lemak yang berbeda dan kadar minyak (dalam bentuk asam lemak bebas) yang berbeda pula. LA merupakan asam lemak yang dominan untuk seluruh varietas kedelai. Rasio air:tepung kedelai, suhu saponifikasi, dan lama saponifikasi mempengaruhi respon yang bersifat kuadratik. Kondisi optimum tercapai pada rasio air:tepung kedelai 2,03:1, suhu saponifikasi 58,86 °C, dan lama sapon- ifikasi 92,27 menit. Respon kadar LA dan ALA (%) pada kondisi optimum berdasarkan prediksi adalah 68,47 % dan respon aktual 68,89 %. Minyak yang diperoleh mempunyai tingkat oksidasi yang rendah

Exact solutions of Dirac equation on (1+1)-dimensional spacetime coupled to a static scalar field

We use a generalized scheme of supersymmetric quantum mechanics to obtain the energy spectrum and wave function for Dirac equation in (1+1)-dimensional spacetime coupled to a static scalar field.Comment: 7 pages, Late