Hasil untuk "Chemistry"

J. BeMiller, R. Whistler

S. Sarathy, P. Oßwald, N. Hansen et al.

P. Metrangolo, F. Meyer, T. Pilati et al.

C. Winterbourn, M. Hampton

J. Lehn

W. Binder, R. Sachsenhofer

D. Sherrington

P. Dutta, J. Dutta, V. Tripathi

J. P. McEvoy, G. Brudvig

J. R.

A. West

J. Speight

J. Logan, M. Prather, S. Wofsy et al.

A model for the photochemistry of the global troposphere constrained by observed concentrations of H2O, O3, CO, CH4, NO, NO2, and HNO3 is presented. Data for NO and NO2 are insufficient to define the global distribution of these gases but are nonetheless useful in limiting several of the more uncertain parameters of the model. Concentrations of OH, HO2, H2O2, NO, NO2, NO3, N2O5, HNO2, HO2NO2, CH3O2, CH3OOH, CH2O, and CH3CCl3 are calculated as functions of altitude, latitude, and season. Results imply that the source for nitrogen oxides in the remote troposphere is geographically dispersed and surprisingly small, less than 107 tons N yr−1. Global sources for CO and CH4 are 1.5 × 109 tons C yr−1 and 4.5 × 108 tons C yr−1, respectively. Carbon monoxide is derived from combustion of fossil fuel (15%) and oxidation of atmospheric CH4 (25%), with the balance from burning of vegetation and oxidation of biospheric hydrocarbons. Production of CO in the northern hemisphere exceeds that in the southern hemisphere by about a factor of 2. Industrial and agricultural activities provide approximately half the global source of CO. Oxidation of CO and CH4 provides sources of tropospheric O3 similar in magnitude to loss by in situ photochemistry. Observations of CH3CCl3 could offer an important check of the tropospheric model and results shown here suggest that computed concentrations of OH should be reliable within a factor of 2. A more definitive test requires better definition of release rates for CH3CCl3 and improved measurements for its distribution in the atmosphere.

L. Morss, N. Edelstein, J. Fuger

W. L. Jorgensen

J. Buriak

J. Noack, N. Roznyatovskaya, Tatjana Herr et al.

Kalayou Hiluf Gebremdhin, Mebrahtom Gebrelibanos Hiben, Hagos Feleke Gebremariam et al.

Benzo[a]phenoxazine (BPO) based molecules have been recently emerged as a new class of near-infrared (NIR) fluorophore for image-guided diagnosis in cancer research. The successful application of BPOs as NIR fluorophore in biomedical research has led to explore their potential application in lipid-based staining, subcellular organelle profile labeling; bioimaging hypoxic tumor cells, and detection of small molecules. In this review, the development of novel NIR-activated fluorescent molecules based on BPO scaffold in cancer research are summarized and highlighted. BPOs are heterocyclic dye molecule consisting of an phenoxazine core with further elongation of another benzene ring fused along a-faces, which consists of freely electron donating and/or electron accepting substituents on BPOs core structure. The chemical synthesis and molecular design of these structures, unique optical, and photochemical properties are also discussed. We hope that this review will inspire and motivate research interest around BPO dyes and promote further development for the rational design of BPO-based fluorescent probes.

Modar Sadek, Nazira Sarkis, George Jangi

This work presents the development and application of an innovative green supramolecular deep eutectic solvent (SUPRADES)-based DLLME approach for the extraction and quantification of melamine in milk matrices. For this purpose, thymol and nonanoic acid were combined to create a hydrophobic DES, which was then utilized as the extraction solvent. Additionally, a ternary SUPRADES based on a hydrophilic DES composed of choline chloride and ethylene glycol and doped with β-cyclodextrin (β-CD) was prepared and applied as the disperser solvent. Critical parameters were optimized systematically, yielding the following optimal conditions: Extraction solvent volume: 150 μL; disperser solvent: 600 μL; β-CD: 1% (w/v); pH: 7; extraction time: 1 min; and sample solution volume: 5 mL. Interestingly, the salting-out step did not affect the extraction efficiency. The optimized approach showed good linearity (100–900 ng/mL) with R2 = 0.998 when validated with matrix-matched calibration standards. The LOD and LOQ were 27 and 81 ng/mL, respectively, and the enrichment factor was 41. Method accuracy and precision were evaluated through recovery studies using milk samples fortified with melamine at three concentration levels (200, 500, and 800 ng/mL), and the recovery values were obtained in the range of 92–107%, with RSD < 5%. A greenness score of 79 was attained by the method, as quantified by the advanced ComplexMoGAPI. Lastly, this technique was successfully applied to extract and determine melamine in real samples of powdered milk, infant formula, and raw milk with acceptable and satisfactory results.