Determination of macro and trace elements in canned marine products by inductively coupled plasma—optical emission spectrometry (ICP-OES) and ICP—mass spectrometry (ICP-MS)

This study determined the concentration of eight macroelements (Na, K, Mg, P, S, Ca, Fe, Zn) and nineteen trace elements (Li, Be, Cr, Mn, Co, Ni, V, Cu, Ga, Se, Rb, Sr, In, Sn, Cs, Ba, Tl, Bi, U) in commonly consumed canned marine products from South Korea. The samples were wet-digested using nitric acid and hydrogen peroxide by a microwave system and analyzed for macroelements using inductively coupled plasma—optical emission spectrometry (ICP-OES) and for trace elements by inductively coupled plasma—mass spectrometry (ICP-MS). The analytical methods were validated by the correlation coefficients, limits of detection and quantification, correlation variance, spiking recovery tests, and analyzing a NIST 1566?b oyster tissue certified reference material. The concentrations of macro and trace elements varied among the canned marine products. The macroelements were present in the order of Na?>?K?>?P?>?S> Mg?>?Ca?>?Fe?>?Zn. In general, the concentrations of macro and trace elements were within the specified limits of Food and Nutrition Board, Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives, and Ministry of Food and Drug Safety, Korea. The results suggest that the analyzed canned marine products are safe in terms of the analyzed elements and their consumption therefore does not cause any threat to human health.     

Convergence of proximal algorithms with stepsize controls for non-linear inverse problems and application to sparse non-negative matrix factorization

Numerical Algorithms - We consider a general ill-posed inverse problem in a Hilbert space setting by minimizing a misfit functional coupling with a multi-penalty regularization for stabilization....     

Novel additives for accelerating radiation grafting and curing reactions

The value of additives for increasing yields in radiation grafting reactions is discussed. The possible significance of the work in concurrent grafting during radiation curing is evaluated. Additives previously found to be effective in radiation grafting and reviewed here include acids, inorganic salts, organic inclusion compounds like urea, multifunctional acrylates and methacrylates. Synergistic effects in performance between the first three groups and the latter two have also been observed. Two new classes of compounds as additives in radiation grafting are reported and their reactivities compared with the earlier series. These new additives are oligomer acrylates and photoinitiators. In a mechanistic discussion related to these additives, a novel proposal involving partitioning phenomena is outlined to explain their modes of action.     

Electrotelluration: a new approach to tri- and tetrasubstituted alkenes

A novel electrotelluration process is described in which a Michael addition of an alkyl or aryl tellurolate anion occurs onto an activated alkyne with subsequent trapping of a vinyl anion with electrophiles (aldehydes and ketones) other than a proton. This process provides an efficient regio- and stereospecific route to tri- and tetrasubstituted alkenes. Methodologically significant examples of this chemistry were studied in which aryl and alkyl tellurolate anions were added to omega-keto alkynyl esters in a Michael reaction, and the incipient vinyl anions were trapped intramolecularly by the internal aldehydes. The reactive centers were tethered by different lengths of alkyl chains to form highly functionalized five-, six-, seven-, and eight-membered rings in modest to good yields.     

Novel preparation of functionalized iodotetrahydronaphthyridine, iodoazaindoline, and iodotetrahydropyridoazepine systems

A novel method, which utilizes a key halogen dance step for the preparation of iodotetrahydronaphthyridine, iodoazaindoline, and iodotetrahydropyridoazepine ring-systems is described. A variety of transformations of the iodo-functional group are also reported to demonstrate the utility of this method.     

The first general palladium catalyst for the Suzuki-Miyaura and carbonyl enolate coupling of aryl arenesulfonates

The first general method for the palladium-catalyzed Suzuki-Miyaura and carbonyl enolate coupling of unactivated aryl arenesulfonates was developed utilizing XPhos, 1, and Pd(OAc)2. This is of significant interest because aryl tosylates and aryl benzenesulfonates are more easily handled and considerably less expensive than aryl triflates. This catalyst system effects the coupling of a variety of aryl, heteroaryl, and extremely hindered arylboronic acids with different aryl tosylates, under mild conditions. The same catalyst was employed in the first carbonyl enolate coupling of aryl arensulfonates.     

A mollification method for ill-posed problems

Summary. A mollification method for a class of ill-posed problems is suggested. The idea of the method is very simple and natural: if the data are given inexactly then we try to find a sequence of ``mollification operators" which map the improper data into well-posedness classes of the problem (mollify the improper data). Within these mollified data our problem becomes well-posed. And when these facts are in hand we try to obtain error estimates and optimal or ``quasi-optimal" mollification parameters. The method is working not only for problems in Hilbert spaces, but also for problems in Banach spaces. Applications of the method to concrete problems, like numerical differentiation, parabolic equations backwards in time, the Cauchy problem for the Laplace equation, one- and multidimensional non-characteristic Cauchy problems for parabolic equations (in infinite or finite domains),... give us very sharp stability estimates of H\"older continuous type. In these cases the method is optimal in the sense that it gives the same order of H\"older continuous dependence on the data as for the regularized problems. Furthermore, the method may be implemented numerically using fast Fourier transforms. For the first time a uniform stability estimate of H\"older continuous type of the solution of the heat equation backwards in time in the space for all could be established by our mollification method. A new simple sharp pointwise estimate of H\"older type for the weak solution of a non-characteristic Cauchy problem for parabolic equations in a finite domain is established. Received June 25, 1993 / Revised version received February 18, 1994     

A non-local boundary value problem method for parabolic equations backward in time

The ill-posed parabolic equation backward in time

     

Determination of Essential and Toxic Elements in Vegetables from South Korea

This study reports the determination of trace essential (Co, Cr, Cu, Se, and Zn) and toxic (Al, As, Cd, Hg, and Pb) elements in greenhouse tomatoes, peppers, and cucumbers from supermarkets of Seoul, Busan, Gangneung, Daegu, Daejeon, and Gwangju, South Korea using inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectroscopy, and direct mercury analysis. The methods were validated by linearity, limits of detection and quantification, precision, accuracy, and recovery measurements that provided satisfactory results in all cases. Among the essential trace elements, Zn was found to have the highest concentrations (0.84–2.5?mg/kg) followed by Cu (0.21–0.62?mg/kg) and Cr (0.01–0.06?mg/kg). The mean concentrations (mg/kg) of the toxic elements were in the order Al?>?Pb?>?As?>?Cd?>?Hg for tomatoes and cucumbers and Al?>?Pb?>?Cd?>?As?>?Hg for peppers; all were below the permissible limits set by World Health Organization for human consumption. The estimated dietary intake, target hazard quotients (THQs), and hazard indices of the samples were within safe levels. The combined THQ values for the toxic elements in the vegetables were from 0.002 to 0.012 with significant contribution from arsenic, aluminum, cadmium, and mercury. The results of this study show that trace and toxic elements in the analyzed vegetables do not impose any serious health harmful effects for the population upon consumption.     

The Cauchy problem for Laplace's equation via the conjugate gradient method

A variational formulation of the Cauchy problem for the Laplaceequation is studied. An efficient conjugate gradient method based on an optimal-order stopping criterion is presented together with its numerical implementation based on the boundary-element method. Several numerical examples involving smooth or non-smooth geometries and over-, equally, or under-specified Cauchy dataare discussed. The numerical results show that the numericalsolution is convergent with respect to increasing the numberof boundary elements and stable with respect to decreasingthe amount of noise included in the input Cauchy data. Received 2 November, 1999. Revised 4 March, 2000.