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PubMed2003

Constrained optimization for green engineering decision-making.

Green engineering requires the designer to consider a very extensive set of environmental impacts. To minimize these impacts, the designer must significantly expand his or her "toolset" of product design concepts, alternative materials, manufacturing systems, and analytic methods for addressing life cycle impacts. This can overwhelm a designer, who then resorts to overly simplistic rules or checklists out of necessity. The central issue is how to identify all "pollution prevention pays" opportunities and then how to deal with the unavoidable tradeoffs that arise after all these opportunities have been exhausted. This paper presents a framework for employing mathematical decision modeling toward this end. A domain-independent constrained optimization formulation is presented. A multiattribute utility function reflects the willingness to pay for environmental improvement and is the basis of the objective function. The feasibility constraints reflect the unavoidable tradeoffs. Several case studies are presented, including power systems, floor tile manufacturing, and computer systems.

Computers↗

PubMedDate not supplied

A finite element approach for modeling photon transport in tissue.

The use of optical radiation in medical physics is important in several fields for both treatment and diagnosis. In all cases an analytic and computable model of the propagation of radiation in tissue is essential for a meaningful interpretation of the procedures. A finite element method (FEM) for deriving photon density inside an object, and photon flux at its boundary, assuming that the photon transport model is the diffusion approximation to the radiative transfer equation, is introduced herein. Results from the model for a particular case are given: the calculation of the boundary flux as a function of time resulting from a delta-function input to a two-dimensional circle (equivalent to a line source in an infinite cylinder) with homogeneous scattering and absorption properties. This models the temporal point spread function of interest in near infrared spectroscopy and imaging. The convergence of the FEM results are demonstrated, as the resolution of the mesh is increased, to the analytical expression for the Green's function for this system. The diffusion approximation is very commonly adopted as appropriate for cases which are scattering dominated, i.e., where mu s >> mu a, and results from other workers have compared it to alternative models. In this article a high degree of agreement with a Monte Carlo method is demonstrated. The principle advantage of the FE method is its speed. It is in all ways as flexible as Monte Carlo methods and in addition can produce photon density everywhere, as well as flux on the boundary. One disadvantage is that there is no means of deriving individual photon histories.

Health Physics↗

PubMed1984

Intercomparison of seven radioimmunoassay kits and a fluorescence polarization immunoassay kit for digoxin.

Samples from 33 patients being treated with digoxin and three concentrations of control material were analyzed for this drug by use of seven radioimmunoassay (RIA) kits and an automated fluorescence polarization immunoassay (FPIA) system. CVs ranged from 2.4 to 6.4% for the FPIA system and from 4.6 to 7.4% for two RIA methods. In the analysis of between-method variability of RIA kits, CVs ranged from 6.1 to 33.2%. We compared each RIA kit with the other six RIA kits (I), as well as each RIA kit with the FPIA system (II). Correlation coefficients were greater than or equal to 0.96 in all cases. Slopes ranged from 0.82 to 1.20 for comparison I and from 0.86 to 1.01 for comparison II. For the FPIA system, analytical recovery of digoxin ranged from 94 to 104%. For the RIA methods we examined, analytical recoveries ranged from 113 to 135%. Analysis time is shorter and precision is greater for the FPIA system than for the RIA methods.

Digoxin↗

PubMed2006

SK3 trafficking in hippocampal cells: the role of different molecular domains.

The regulative steps that control trafficking of ion channels are fundamental determinants of their qualitative and quantitative expression on the cell membrane. In this work the trafficking of the small conductance calcium-activated potassium channel, SK3 was studied in neurons in order to identify relevant molecular domains involved in this process. Hippocampal cell cultures were transfected with fusion proteins of green fluorescent protein (GFP) and different SK3 subunit truncations. The differential distribution of the mutants was analyzed by confocal microscopy and compared to the localization of the control fusion protein with full length SK3. The transport of chimeric proteins was quantified from fluorescence images by developing a morphometric analytical method. We found that the full length SK3 was distributed in cell body, axon and dendrites, whereas the deleted forms GFPDelta578-736 (deletion of the entire C-terminal domain), GFPDeltaCaMBD (deletion of the calmodulin-binding site) and GFPDeltaN (deletion of the N-terminal domain) were not transported into cell processes but accumulated in the cell body. The GFPDelta640-736 (deletion of the distal C-terminal domain) showed a distribution similar to control. The quantification and statistical analysis confirmed the differences in distribution across the three groups. In conclusion, the current work provides evidence for a fundamental role of the N-terminal domain and the calmodulin binding domain in SK3 trafficking in neurons.

Animals↗

PubMed1975

Collaborative study of the 2,4-dinitrophenyl ether multiresidue method for use in determining four carbamate pesticides.

Eight laboratories tested the 2,4-dinitrophenyl ether method for determining carbamate pesticide residues by gas-liquid chromatography. Propoxur, carbofuran, carbanolate, and carbaryl in apples, corn, green beans, and a leafy vegetable (kale, collards, cabbage, or turnip greens) were determined at the fortification levels of 0.1, 0.2, and 0.5 ppm. Average recoveries of propoxur were 87-95%; carbofuran, 87-100%; carbanolate, 89-102%; and carbaryl, 77-92%. No serious background problems were encountered, other than that from field-incurred carbaryl residues in apples. The study revealed the need for certain precautions in determining carbaryl because of its instability in analytical operations. The method has been adopted as official first action.

Carbamates↗

PubMed1999

Quantitation of fluorescent nucleotide incorporation by capillary gel electrophoresis and laser-induced fluorescence detection.

A method has been developed by which enzymatically incorporated fluorophore-labeled nucleotide sites in nucleic acid can be quantitated by degradation of nanogram quantities of DNA followed by capillary gel electrophoretic analysis with fluorescence detection. In this way the differing relative labeling densities achieved using either C5-substituted dUTP's or N4-substituted dCTP's were determined. The method has proven to be very useful in obtaining quantitative analytical data from the small quantities of complex molecules produced in nick translations. Various polymerization conditions using DNA polymerase I were examined to determine optimal labeling density. Simultaneous copolymerization of green fluorescing dCTP and dUTP nucleotides were undertaken in an attempt to maximize labeling density.

DNA↗

PubMed1987

Lateral interactions among membrane proteins. Valid estimates based on freeze-fracture electron microscopy.

We consider the lateral distribution of intrinsic membrane proteins from the viewpoint of the statistical-mechanical theory of liquids. We connect the information in freeze-fracture electron micrographs--positions of proteins but not lipids or aqueous species--to a well developed theory of liquid mixtures. An algorithm, based on the Born-Green-Yvon integral equation, is presented for deducing forces between proteins from correlations among protein positions that are observed in micrographs. The algorithm is tested on simulated micrographs, obtained by Monte-Carlo methods, where forces between proteins are known analytically. We conclude that valid estimates of such forces, both attractions and repulsions, can be obtained from the positions of a few thousand proteins.

Algorithms↗

PubMed2002

Determining eight colorants in milk beverages by capillary electrophoresis.

Milk beverages are popular because of their high nutritional value, and milk products that are enhanced with various fruit flavors are especially in high demand in Asia. Colorants are usually added to fruit flavored milk in order to increase its attraction and appearance, therefore, the detection and measurement of colorants in this type of beverage are relatively important for health issue reasons. Carminic acid, a natural colorant, along with tartrazine, Fast green FCF, Brilliant blue FCF, Allura Red AC, Indigo carmine, Sunset yellow FCF, and New coccine, which are seven different synthetic food colorants, are commonly used as food additives, therefore, this study would focus on the development of an analytical method for the detection of these common colorants in milk beverages. A high efficiency capillary electrophoresis separation method was finished by a pH 10.0 running buffer containing 7.0 mM beta-cyclodextrin, and the eight colorants were separated with baseline resolution within 9 min. In order to reduce the matrix interference resulting from the constituents of milk, a suitable polyamide column solid-phase extraction (SPE) was also investigated for milk sample pretreatment. The combination of the simple SPE pretreatment and the fast separation method of capillary electrophoresis, was able to determine successfully without matrix interference the content of these colorant additives in commercial milk beverages. The recoveries of the eight food colorants in milk beverages were better than 85% and the detection limits were also lower than 0.5 microg/ml by the developed method.

Ammonia↗

PubMed1999

Improved validated assay for the determination of mefloquine and its carboxy metabolite in plasma, serum and whole blood using solid-phase extraction and high-performance liquid chromatography.

An improved high-performance liquid chromatography method using a low silanol activity octadecylsilica column and a solid-phase extraction technique is validated for the simultaneous analysis of mefloquine and its carboxy metabolite in whole blood, plasma and serum. An octadecylsilica column with high silanol activity is compared to a column of low activity in terms of pH dependent variability of chromatographic retention times for mefloquine and its carboxy metabolite. The low silanol activity column showed a relatively large mobile phase pH range where retention times for both components are consistent. The solid-phase extraction procedure consists of a simple protein precipitation step followed by sample concentration and extraction using a C18 membrane disk. The inter- and intra-assay variability for a therapeutic concentration of mefloquine (1000 ng/ml) is less than 2% in whole blood, plasma and serum while carboxymefloquine (1000 ng/ml) is 2.3% or less. At concentrations as low as 100 ng/ml the inter-assay variability is 6.2% or less for both analytes. This method shows a robust analytical procedure for the simultaneous analysis of mefloquine and its carboxy metabolite where precise measurements are useful in pharmacokinetic studies and in estimating drug compliance.

Antimalarials↗

PubMedDate not supplied

Proteomics: theoretical and experimental considerations.

Cellular engineering relies on the ability to decipher the genetic basis of various phenotypes. Emerging technologies for analyzing the biological function of the information encoded in the genome of particular organisms and/or tissues focus on the monitoring of transcription (mRNA) and translation (protein) processes. Elementary theoretical considerations presented in this article strongly suggest that a combination of mRNA and protein expression patterns should be simultaneously considered to fully develop a conceptual understanding of the functional architecture of genomes and gene networks. We propose a framework of experimental and mathematical methods for acquiring and analyzing quantitative proteomic information and discuss recent developments in proteome analytical technology.

Bacterial Proteins↗

PubMed2005

Recommendations for improving serum creatinine measurement: a report from the Laboratory Working Group of the National Kidney Disease Education Program.

BACKGROUND: Reliable serum creatinine measurements in glomerular filtration rate (GFR) estimation are critical to ongoing global public health efforts to increase the diagnosis and treatment of chronic kidney disease (CKD). We present an overview of the commonly used methods for the determination of serum creatinine, method limitations, and method performance in conjunction with the development of analytical performance criteria. Available resources for standardization of serum creatinine measurement are discussed, and recommendations for measurement improvement are given. METHODS: The National Kidney Disease Education Program (NKDEP) Laboratory Working Group reviewed problems related to serum creatinine measurement for estimating GFR and prepared recommendations to standardize and improve creatinine measurement. RESULTS: The NKDEP Laboratory Working Group, in collaboration with international professional organizations, has developed a plan that enables standardization and improved accuracy (trueness) of serum creatinine measurements in clinical laboratories worldwide that includes the use of the estimating equation for GFR based on serum creatinine concentration that was developed from the Modification of Diet in Renal Disease (MDRD) study. CONCLUSIONS: The current variability in serum creatinine measurements renders all estimating equations for GFR, including the MDRD Study equation, less accurate in the normal and slightly increased range of serum creatinine concentrations [<133 micromol/L (1.5 mg/dL)], which is the relevant range for detecting CKD [<60 mL.min(-1).(1.73 m2)(-1)]. Many automated routine methods for serum creatinine measurement meet or exceed the required precision; therefore, reduction of analytical bias in creatinine assays is needed. Standardization of calibration does not correct for analytical interferences (nonspecificity bias). The bias and nonspecificity problems associated with some of the routine methods must be addressed.

Calibration↗

PubMedDate not supplied

Comparative validation study to demonstrate the equivalence of a minor modification to AOAC methods 996.09, Vip for EHEC and 996.10, assurance Eia EHEC with the reference culture method for the detection of Escherichia coli O157:H7 in beef.

The Visual Immunoprecipitate Assay (VIP) method for the detection of enterohemorrhagic Escherichia coli O157:H7 (VIP for EHEC) and Assurance Enzyme Immunoassay (EIA) method for the detection of EHEC (EHEC EIA) are AOAC INTERNATIONAL Official Methods 996.09 and 996.10, respectively. A minor modification to the enrichment medium used in both methods has been developed. This modification, the BioControl modified EHEC medium (BioControl mEHEC) provides a more cost-effective procedure with performance equivalent to that of the cultural method for detection of E. coli O157:H7 in beef.

Animals↗

PubMed1979

Improved detection of coliforms and Escherichia coli in foods by a membrane filter method.

Analytical procedures based on filtration of homogenates through membrane filters, and particularly hydrophobic grid-membrane filters (HGMF), offer definite improvements in the enumeration of Escherichia coli and coliforms in foods. Whereas the counted specimen in pour plates may not usually be greater than 0.1 g, up to 1.0 g of ground beef, green beans, potato, cod, strawberries, or grapes could be filtered and counted on HGMF. Greatly improved limit of detection, reduced interference by noncoliforms, and complete removal of growth inhibitors such as polyphenols were demonstrated for HGMF, using violet red bile and mFC agars. In addition, counting on HGMF eliminated a false-positive reaction caused by sucrose in ice cream.

Escherichia coli↗

PubMed2005

Efficient integral-equation-based method for accurate analysis of scattering from periodically arranged nanostructures.

A plethora of applications are grounded on the physics of electromagnetic interaction with a periodic arrangement of nanostructures. These range from metamaterials and negative index materials to photonic band-gap structures to surface plasmon polariton optics to nanofrequency selective surfaces. There is therefore a need for rigorous physics based methods that are both accurate and fast to enable rapid design and analysis. Difficulties that need to be overcome to realize such a simulation tool are twofold: (i) at wavelengths in the range 200-1300 nm metals behave as dielectrics with negative real permittivity. Their frequency response must be explicitly accounted for in the simulation. (ii) The computational cost to compute response over a broad band of frequencies is high. This paper develops an integral-equation-based analysis technique that addresses these challenges. This integral equation relies on a periodic layered medium formulation. The Green's dyad for this formulation is derived, and separated into a superposition of two contributions: direct and reflected components. The means to accelerate the computation of the Green's dyad and the evaluation of inner products is prescribed. The proposed technique is validated extensively against available analytical data for hypothetical materials as well as silver. It is shown that this solver can accurately predict the enhanced transmission from perforated silver films for several configurations. While the application domain in this paper is the study of enhanced transmission in perforated silver films, the method presented herein is sufficiently general and can be applied to several other application domains with little or no change.

Journal Article↗

PubMed2006

A confirmatory analysis of malachite green residues in rainbow trout with liquid chromatography-electrospray tandem mass spectrometry.

A quantitative liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed for the determination of malachite green (MG) and its metabolite leucomalachite green (LMG) in fish. Residues were extracted with an acetonitrile-acetate buffer and purified using the automated solid-phase extraction (ASPEC). Residues were analyzed with a reversed-phase LC-MS/MS using a positive-ion electrospray ionisation (ESI). Isotope-labelled leucomalachite green (LMG-D5) was used as an internal standard for the quantification of LMG residues. The related dye, brilliant green (BG) was used as an instrumental standard. Identification and quantification of analytes were based on the ion transitions monitored by multiple reaction monitoring (MRM). The decision limit (CCalpha) for MG and LMG was 0.13 and 0.16 microgkg(-1). The respective detection capabilities (CCbeta) were 0.22 and 0.27 microgkg(-1). The absolute recovery (repeatability SD(r)) was in the range of 58-65% (7.8-11.2%) for MG and 59-68% (9.7-16.9%) for LMG. LMG was quantified also based on the internal standard, giving a recovery (repeatability SD(r)) of 103-110% (4.8-9.3%). The method was further evaluated by analyzing a total of 34 fish residue monitoring samples, of which eight samples were found to be non-compliant containing low residues of LMG.

Animals↗

PubMedDate not supplied

[Effect of diet therapy on the changes of vitamin C content in the blood and urine of patients with chronic gastritis and peptic ulcer].

Estimation and analytical methods were employed to investigate real rations of patients with gastroduodenal ulcer. Chemical composition of diet N 1 was found unsatisfactory both by ascorbic acid and carbohydrates content responsible for low-caloric value of the diet. The ration correction with additional provision of vegetables, fruit, greens raised vitamin C intake by the patients though the deficiency was not abolished.

Ascorbic Acid↗

PubMed2001

Green/red dual fluorescence detection of total protein and alkaline phosphate-conjugated probes on blotting membranes.

A two-color fluorescence detection method is described based upon covalently coupling the succinimidyl ester of BODIPY FL-X to proteins immobilized on poly(vinylidene difluoride) (PVDF) membranes, followed by detection of target proteins using the fluorogenic substrate 9H-(1,3-dichloro-9,9-dimethylacridin-2-one-7-yl(DDAO)-phosphate in combination with alkaline-phosphatase-conjugated reporter molecules. This results in all proteins in the profile being visualized as green signal while those detected specifically with the alkaline-phosphatase conjugate appear as red signal. The dichromatic detection system is broadly compatible with a wide range of analytical imaging devices including UV epi- or transilluminators combined with photographic or charge-coupled device (CCD) cameras, xenon-arc sources equipped with appropriate excitation/emission filters, and dual laser gel scanners outfitted with a 473 nm second-harmonic generation or 488 nm argon-ion laser as well as a 633 nm helium-neon or 635 nm diode laser. The dichromatic detection method permits detection of low nanogram amounts of protein and allows for unambiguous identification of target proteins relative to the entire protein profile on a single electroblot, obviating the need to run replicate gels that would otherwise require visualization of total proteins by silver staining and subsequent alignment with chemiluminescent or colorimetric signals generated on electroblots.

Acridines↗

PubMed1987

Solid-phase extraction and high-performance liquid chromatographic method for chlorpromazine and thirteen metabolites.

A rapid and reliable procedure, based on a C8 bonded phase extraction and reversed-phase isocratic high-performance liquid chromatographic separation with internal standard quantitation, has been developed for the determination of the antipsychotic drug chlorpromazine and thirteen common metabolites. The method allows quantitation of these analytes at the ng/ml concentration range in human plasma. An evaluation of recovery, detection limits, and reproducibility is presented along with application of the method to patient samples.

Biotransformation↗