Pinacol-Pinacolone Rearrangement of 1, 2-Di-(p-methoxyphenyl)-ethane-1, 2-diol and Bis-(4-methoxyphenyl)-acetaldehyde in Acid Media

1, 2-Di-(p-methoxyphenyl)-ethane-1, 2-diol gave in acid media bis-(4-methoxy-phenyl)-acetaldehyde, 4-4′-dimethoxy-deoxybenzoin, and 1, 2-di-(p-methoxyphenyl)-ethylene oxide; their respective yields being influenced by at least 3 factors: (i) the acid, (ii) its concentration, and (iii) the reaction period. Bis-(4-methoxyphenyl)-acetaldehyde rearranged to the deoxybenzoin in boiling sulfuric (50%) or phosphoric (75%) acids (w/w), and to two isomeric 1, 2-diacetoxy-1, 2-di-(p-methoxyphenyl) ethanes when it was heated with acetic anhydride. The mechanisms of these reactions are discussed.     

Constrained modeling for spectroscopic measurement of bi-exponential spin-lattice relaxation of water in vivo

The (1)H NMR water signal from spectroscopic voxels localized in gray matter contains contributions from tissue and cerebral spinal fluid (CSF). A typically weak CSF signal at short echo times makes separating the tissue and CSF spin-lattice relaxation times (T(1)) difficult, often yielding poor precision in a bi-exponential relaxation model. Simulations show that reducing the variables in the T(1) model by using known signal intensity values significantly improves the precision of the T(1) measurement. The method was validated on studies on eight healthy subjects (four males and four females, mean age 21 +/- 2 years) through a total of twenty-four spectroscopic relaxation studies. Each study included both T(1) and spin-spin relaxation (T(2)) experiments. All volumes were localized along the Sylvian fissure using a stimulated echo localization technique with a mixing time of 10 ms. The T(2) experiment consisted of 16 stimulated echo acquisitions ranging from a minimum echo time (TE) of 20 ms to a maximum of 1000 ms, with a repetition time of 12 s. All T(1) experiments consisted of 16 stimulated echo acquisition, using a homospoil saturation recovery technique with a minimum recovery time of 50 ms and a maximum 12 s. The results of the T(2) measurements provided the signal intensity values used in the bi-exponential T(1) model. The mean T(1) values when the signal intensities were constrained by the T(2) results were 1055.4 ms +/- 7.4% for tissue and 5393.5 ms +/- 59% for CSF. When the signal intensities remained free variables in the model, the mean T(1) values were 1085 ms +/- 19.4% and 5038.8 ms +/- 113.0% for tissue and CSF, respectively. The resulting improvement in precision allows the water tissue T(1) value to be included in the spectroscopic characterization of brain tissue.     

Molality as a unit of measure for expressing 1H MRS brain metabolite concentrations in vivo

Absolute concentrations of cerebral metabolite in in vivo 1H magnetic resonance spectroscopy studies (1H-MRS) are widely reported in molar units as moles per liter of tissue, or in molal units as moles per kilogram of tissue. Such measurements require external referencing or assumptions as to local water content. To reduce the scan time, avoid assumptions that may be invalid under specific pathologies, and provide a universally accessible referencing procedure, we suggest that metabolite concentrations from 1H-MRS measurements in vivo be reported in molal units as moles per kilogram of tissue water. Using internal water referencing, a two-compartment water model, a simulated brain spectrum for peak identification, and a spectroscopic bi-exponential spin-spin relaxation segmentation technique, we measured the absolute concentrations for the four common 1H brain metabolites: choline (Cho), myo-inositol (mIno), phosphocreatine + creatine (Cr), and N-acetyl-aspartate (NAA), in the hippocampal region (n = 26) and along the Sylvian fissure (n = 61) of 35 healthy adults. A stimulated echo localization method (20 ms echo time, 10 ms mixing time, 4 s repetition time) yielded metabolite concentrations, uncorrected for metabolite relaxation or contributions from macromolecule resonances, that were expectantly higher than with molar literature values. Along the Sylvian fissure the average concentrations (coefficient of variation (CV)) in mmoles/kg of tissue water were 17.6 (12%) for NAA, 14.2 (9%) for Cr, 3.6 (13%) for Cho, and 13.2 (15%) for mIno. Respective values for the hippocampal region were 15.7 (20%), 14.7 (16%), 4.6 (19%), and 17.7 (26%). The concentrations of the two regions were significantly different (p 相似文献   

The water-silicas interfacial interaction energies

The water-silicas interfacial interaction energies were calculated for samples of quartz, silicas and silicas outgassed at high temperatures using own and published data of the spreading pressure of water, its surface tension, its contact angle and using formulas obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for 18 different samples were in the range 7.80-6.92 kJ mol⁻¹. Lower values of energies are for samples that contain relatively less amounts of water at P/P₀ = 0.25 and are characterized also by relatively low values of surface pressures.     

Beneficial Effects of Green Tea Catechins on Female Reproductive Disorders: A Review

Tea is one of the most widely consumed beverages worldwide after water, and green tea accounts for 20% of the total tea consumption. The health benefits of green tea are attributed to its natural antioxidants, namely, catechins, which are phenolic compounds with diverse beneficial effects on human health. The beneficial effects of green tea and its major bioactive component, (−)-epigallocatechin-3-gallate (EGCG), on health include high antioxidative, osteoprotective, neuroprotective, anti-cancer, anti-hyperlipidemia and anti-diabetic effects. However, the review of green tea’s benefits on female reproductive disorders, including polycystic ovary syndrome (PCOS), endometriosis and dysmenorrhea, remains scarce. Thus, this review summarises current knowledge on the beneficial effects of green tea catechins on selected female reproductive disorders. Green tea or its derivative, EGCG, improves endometriosis mainly through anti-angiogenic, anti-fibrotic, anti-proliferative and proapoptotic mechanisms. Moreover, green tea enhances ovulation and reduces cyst formation in PCOS while improving generalised hyperalgesia, and reduces plasma corticosterone levels and uterine contractility in dysmenorrhea. However, information on clinical trials is inadequate for translating excellent findings on green tea benefits in animal endometriosis models. Thus, future clinical intervention studies are needed to provide clear evidence of the green tea benefits with regard to these diseases.     

Quasi phase matching in GaAs--AlAs superlattice waveguides through bandgap tuning by use of quantum-well intermixing

We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs-AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient chi((2))(zxy), which we realized by periodically tuning the superlattice bandgap. Second-harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4microm . The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of ~110 nW was obtained for the second harmonic by use of an average launched pump power of ?2.3mW .     

SPE and HPLC monitoring of 17-β-estradiol in Egyptian aquatic ecosysetms

Solid-phase extraction and HPLC methods are described for monitoring of 17-β-estradiol residues in Egyptian aquatic ecosystems (water, fish, mollusks, sediment, and drinking water) at the Nile River, Suez Canal region, and northeast of Egypt. Molecular imprinted polymer was prepared and used in extraction. High performance liquid chromatography (HPLC) columns used were Supelcosil C₁₈ and Nucleosil C₁₈. The mobile phases used were different combinations of water and acetonitrile. The concentration of 17-β-estradiol in water, aquatic animals, and sediment samples were of 265.13–7988.12 µg/L, 0.503–96.167, and 0.775–11.884 µg/kg, respectively. Marine lake was contained with high levels of 17-β-estradiol (P < 0.05). Similarly, the Nile River downstream showed high levels of 17-β-estradiol. The detected concentrations in mollusks were significantly higher than those detected in fish. Tilapia fish did not show 17-β-estradiol. Contrarily, low concentrations were detected in the rivulet streams supplied by the Nile River. Besides, 17-β-estradiol was also detected in the sediments at low levels. Detection of 17-β-estradiol in the Egyptian ecosystems attracted attention toward heavy reliance on some esterogenic medicinal products in Egypt. The monitoring of 17-β-estradiol in other water bodies was recommended. Besides, the development of methodologies of bioremediation to eliminate 17-β-estradiol from the Egyptian and other water resources of the world was also suggested.