Classes Of Analytes Research Articles

Higher-order synchronization for a data assimilation algorithm for the 2D Navier–Stokes equations

We consider the two-dimensional (2D) Navier–Stokes equations (NSE) with space periodic boundary conditions and an algorithm for continuous data assimilation developed by Azouani et al. (2014). The algorithm is based on the observation that existence of finite determining parameters for nonlinear dissipative systems can be exploited as a feedback control mechanism for a companion system into which observables, e.g, modes, nodes, or volume elements, are input directly for the purpose of assimilation. It has been shown that in the case of the 2D NSE, the approximating solution induced by the algorithm synchronizes with the exact solution of the 2D NSE in the topology of the Sobolev space, H1, provided that the number of observed modes, nodes, or volume elements is sufficiently large in terms of the Grashof number. In this article, we adapt a technique, introduced by Grujić and Kukavica (1998) and Kukavica (1999) to obtain good estimates of the analyticity radius for the 2D NSE, and show that one can in fact obtain synchronization in the analytic Gevrey class in the case of modal observables, given sufficiently many, but fixed number of such observables. For these types of observables, we additionally show that synchronization in the uniform norm, L∞, can be achieved by assuming the same number of modal observables (in terms of the order of the Grashof number) as is required for the H1 synchronization.

Universal Biotin-PEG-Linked Gold Nanoparticle Probes for the Simultaneous Detection of Nucleic Acids and Proteins.

Novel biotin-polyethylene glycol (biotin-PEG) gold nanoparticle probes have been synthesized and used as universal constructs for the detection of protein (prostate-specific antigen, PSA) and nucleic acid targets (microRNAs) from a single sample. Microarray assays based upon these probes enabled sensitive detection of biomarker targets (50 fM for nucleic acid targets and 1 pg/μL for the PSA target). Ways of detecting biomarkers, including nucleic acids and proteins, are necessary for the clinical diagnosis of many diseases, but currently available diagnostic platforms rely primarily on the independent detection of proteins or nucleic acids. In addition to the economic benefits associated with the use of a single platform to detect both classes of analytes, studies have shown that the simultaneous identification of multiple classes of biomarkers in the same sample could be useful for the detection and management of early stage diseases, especially when sample amounts are limited. Therefore, these new probes and the assays based upon them open the door for high-sensitivity combination-target assays for studying and tracking biological pathways and diseases.

Introducing mass spectrometry to first-year undergraduates: Analysis of caffeine and other components in energy drinks using paper-spray mass spectrometry

We describe the use of ambient ionization mass spectrometry in a freshman-level undergraduate class for the detection of caffeine and other components in several commercially available energy drinks (5-hour Energy, Starbucks Refreshers, Red Bull Sugarfree, and Coca Cola Classic). We use the technique of paper-spray mass spectrometry where a filter paper is used as a substrate on which a sample is directly applied and a high voltage is used to generate an electrospray of ions in ambient conditions which are then detected by a mass spectrometer. The purpose of this laboratory exercise is twofold: 1) to use the paper-spray method to determine the chemical composition of different types of commercially available energy drinks and 2) to perform tandem mass spectrometry (MS/MS) to demonstrate that the mass spectrometer can be used for structural analysis. This laboratory serves as an excellent means of introducing the beginning student to the concepts of charge, mass, and molecular structure. In addition to the freshmen general chemistry class, we also incorporated this lab into the introductory analytical chemistry class taught at the sophomore level with the inclusion of a third exercise where the usefulness of mass spectrometry for quantitative analysis is demonstrated by determining the concentration of caffeine in the energy drinks with deuterated caffeine as an internal standard.

Analytical Thinking, Analytical Action: Using Prelab Video Demonstrations and e-Quizzes To Improve Undergraduate Preparedness for Analytical Chemistry Practical Classes

This project utilizes visual and critical thinking approaches to develop a higher-education synergistic prelab training program for a large second-year undergraduate analytical chemistry class, directing more of the cognitive learning to the prelab phase. This enabled students to engage in more analytical thinking prior to engaging in the analytical action in the laboratory, motivating students to arrive at classes prepared to engage in the material rather than the mechanics (physical processes) of the practical exercises. This reduced the likelihood of cognitive overload at the beginning of the class. Video demonstrations were developed providing both visual demonstrations with audio explanations to reinforce each concept, and students were guided to these through compulsory prelab e-quizzes. The effectiveness of the program was evaluated by academic performance and an attitudinal survey. Attitudes toward the prelab program were very positive, particularly for the e-quizzes. There was no improvement on a...

Growth, distribution, and sectoral heterogeneity: Reading the Kaleckians in Latin America

Abstract The aim of this paper is to explore a parallelism between two episodes in the history of economic thought in order to suggest that the interaction between them can contribute to the research on Kaleckian growth and distribution models. First, a brief summary of the theoretical development from Steindl's stagnationist claims to the debate about demand regimes is offered. Then, a more detailed account is provided of the Latin American debate that began with Furtado's stagnationist claims and resulted in the formulation of models of social articulation and disarticulation. Finally, an analytical classification of Kaleckian and Latin American growth and distribution models is provided, indicating the way in which sectoral heterogeneity and demand composition can act as a plausible link between growth and distribution.

Large-Scale Metabolite Analysis of Standards and Human Serum by Laser Desorption Ionization Mass Spectrometry from Silicon Nanopost Arrays.

The unique challenges presented by metabolomics have driven the development of new mass spectrometry (MS)-based techniques for small molecule analysis. We have previously demonstrated silicon nanopost arrays (NAPA) to be an effective substrate for laser desorption ionization (LDI) of small molecules for MS. However, the utility of NAPA-LDI-MS for a wide range of metabolite classes has not been investigated. Here we apply NAPA-LDI-MS to the large-scale acquisition of high-resolution mass spectra and tandem mass spectra from a collection of metabolite standards covering a range of compound classes including amino acids, nucleotides, carbohydrates, xenobiotics, lipids, and other classes. In untargeted analysis of metabolite standard mixtures, detection was achieved for 374 compounds and useful MS/MS spectra were obtained for 287 compounds, without individual optimization of ionization or fragmentation conditions. Metabolite detection was evaluated in the context of 31 metabolic pathways, and NAPA-LDI-MS was found to provide detection for 63% of investigated pathway metabolites. Individual, targeted analysis of the 20 common amino acids provided detection of 100% of the investigated compounds, demonstrating that improved coverage is possible through optimization and targeting of individual analytes or analyte classes. In direct analysis of aqueous and organic extracts from human serum samples, spectral features were assigned to a total of 108 small metabolites and lipids. Glucose and amino acids were quantitated within their physiological concentration ranges. The broad coverage demonstrated by this large-scale screening experiment opens the door for use of NAPA-LDI-MS in numerous metabolite analysis applications.

Class origin and sibling similarities in long-term income

Sibling correlations have gained increasing prominence in inequality studies as a measurement of the total impact of family background on individual outcomes. Whilst previous studies have tended to use traditional socio-economic measures such as parent’s income or education, this paper introduces an analytical class approach to sibling studies by analysing how much of the influence that siblings share in their long-term income results from class origin. Data are from Statistics Denmark and consist of 290,399 individuals born between 1963 and 1973. Models are estimated which – in addition to parents’ education and income – include modifications of the Erikson–Goldthorpe–Portocarero schemes ranging from 3 to 15 classes and Grusky’s micro-class scheme of 72 classes. The results show that although class adds to explanations of the family influence on children’s income, most of the sibling similarities are not explained by parental education, income or class. Depending on gender, the class schemes explain between 8 and 13 per cent of the sibling similarities and 15 to 20 per cent when parents’ income and educations are also included. Models with different class schemes demonstrate that elaborated versions of the EGP class scheme add little to the explanation of similarities between brothers, sisters and mixed siblings.

INCLUSION PROPERTIES OF A CLASS OF FUNCTIONS INVOLVING THE DZIOK-SRIVASTAVA OPERATOR

In this work, we first introduce a class of analytic functions involving the Dziok-Srivastava linear operator that generalizes the class of uniformly starlike functions with respect to symmetric points. We then establish the closure of certain well-known integral transforms under this analytic function class. This behaviour leads to various radius results for these integral transforms. Some of the interesting consequences of these results are outlined. Further, the lower bounds for the ratio between the functions $f(z)$ in the class under discussion, their partial sums $f_m(z)$ and the corresponding derivative functions $f'(z)$ and $f'_m(z)$ are determined by using the coefficient estimates.

Contact printing of a quantum dot and polymer cross-reactive array sensor

Contact printing of Quantum Dot (QD) and organic polymer (OP) composites is explored as an alternate method of fabricating a cross-reactive chemical sensor array. Sensing layers fabricated by inkjet printing and contact printing methods are compared, showing that contact printing methods demonstrate a more uniform distribution of the QDs and higher signal to noise ratios (SNRs) when exposed to chemical vapors. A cross-reactive array was then fabricated with CdSe QDs and five OPs and exposed to the vapor of 15 common laboratory solvents. Principal component analysis (PCA) of the data showed high dimensionality of the sensor array response and linear discriminant analysis (LDA) produced correct classification of the target analytes in 100% of test cases.

On-Tissue Derivatization via Electrospray Deposition for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging of Endogenous Fatty Acids in Rat Brain Tissues.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is used for the multiplex detection and characterization of diverse analytes over a wide mass range directly from tissues. However, analyte coverage with MALDI MSI is typically limited to the more abundant compounds, which have m/z values that are distinct from MALDI matrix-related ions. On-tissue analyte derivatization addresses these issues by selectively tagging functional groups specific to a class of analytes, while simultaneously changing their molecular masses and improving their desorption and ionization efficiency. We evaluated electrospray deposition of liquid-phase derivatization agents as a means of on-tissue analyte derivatization using 2-picolylamine; we were able to detect a range of endogenous fatty acids with MALDI MSI. When compared with airbrush application, electrospray led to a 3-fold improvement in detection limits and decreased analyte delocalization. Six fatty acids were detected and visualized from rat cerebrum tissue using a MALDI MSI instrument operating in positive mode. MALDI MSI of the hippocampal area allowed targeted fatty acid analysis of the dentate gyrus granule cell layer and the CA1 pyramidal layer with a 20-μm pixel width, without degrading the localization of other lipids during liquid-phase analyte derivatization.

The utmost rigidity property for quadratic foliations on $$\mathbb {P}^2$$ P 2 with an invariant line

In this work we consider holomorphic foliations of degree two on the projective plane $\mathbb{P}^2$ having an invariant line. In a suitable choice of affine coordinates these foliations are induced by a quadratic vector field over the affine part in such a way that the invariant line corresponds to the line at infinity. We say that two such foliations are topologically equivalent provided there exists a homeomorphism of $\mathbb{P}^2$ which brings the leaves of one foliation onto the leaves of the other and preserves orientation both on the ambient space and on the leaves. The main result of this paper is that in the generic case two such foliations may be topologically equivalent if and only if they are analytically equivalent. In fact, it is shown that the analytic conjugacy class of the holonomy group of the invariant line is the modulus of both topological and analytic classification. We obtain as a corollary that two generic orbitally topologically equivalent quadratic vector fields on $\mathbb{C}^2$ must be affine equivalent. This result improves, in the case of quadratic foliations, a well-known result by Ilyashenko that claims that two generic and topologically equivalent foliations with an invariant line at infinity are affine equivalent provided they are close enough in the space of foliations and the linking homeomorphism is close enough to the identity map on $\mathbb{P}^2$.

Power Analysis and Sample Size Determination in Metabolic Phenotyping.

Estimation of statistical power and sample size is a key aspect of experimental design. However, in metabolic phenotyping, there is currently no accepted approach for these tasks, in large part due to the unknown nature of the expected effect. In such hypothesis free science, neither the number or class of important analytes nor the effect size are known a priori. We introduce a new approach, based on multivariate simulation, which deals effectively with the highly correlated structure and high-dimensionality of metabolic phenotyping data. First, a large data set is simulated based on the characteristics of a pilot study investigating a given biomedical issue. An effect of a given size, corresponding either to a discrete (classification) or continuous (regression) outcome is then added. Different sample sizes are modeled by randomly selecting data sets of various sizes from the simulated data. We investigate different methods for effect detection, including univariate and multivariate techniques. Our framework allows us to investigate the complex relationship between sample size, power, and effect size for real multivariate data sets. For instance, we demonstrate for an example pilot data set that certain features achieve a power of 0.8 for a sample size of 20 samples or that a cross-validated predictivity QY(2) of 0.8 is reached with an effect size of 0.2 and 200 samples. We exemplify the approach for both nuclear magnetic resonance and liquid chromatography-mass spectrometry data from humans and the model organism C. elegans.

Automated screening of reversed-phase stationary phases for small-molecule separations using liquid chromatography with mass spectrometry.

There are various reversed-phase stationary phases that offer significant differences in selectivity and retention. To investigate different reversed-phase stationary phases (aqueous stable C18 , biphenyl, pentafluorophenyl propyl, and polar-embedded alkyl) in an automated fashion, commercial software and associated hardware for mobile phase and column selection were used in conjunction with liquid chromatography and a triple quadrupole mass spectrometer detector. A model analyte mixture was prepared using a combination of standards from varying classes of analytes (including drugs, drugs of abuse, amino acids, nicotine, and nicotine-like compounds). Chromatographic results revealed diverse variations in selectivity and peak shape. Differences in the elution order of analytes on the polar-embedded alkyl phase for several analytes showed distinct selectivity differences compared to the aqueous C18 phase. The electron-rich pentafluorophenyl propyl phase showed unique selectivity toward protonated amines. The biphenyl phase provided further changes in selectivity relative to C18 with a methanolic phase, but it behaved very similarly to a C18 when an acetonitrile-based mobile phase was evaluated. This study shows the value of rapid column screening as an alternative to excessive mobile phase variation to obtain suitable chromatographic settings for analyte separation.

Development and analytical validation of a flexible multiplexing platform for cytokine assays.

Abstract Multiplex assays have advantages in being able to reduce time and sample volumes; however, multiplexing offers additional challenges, which include developing multiple assays that can be run with the same protocol, reagents, and sample dilution. Moreover, transferring reagents that work in one assay format to another without compromising performance and the integrity of sample measurement is difficult. The U-PLEX® platform enables flexible multiplexing of immunoassays using MSD’s MULTI-ARRAY® technology. Antibodies used in V-PLEX® kits were transferred to the U-PLEX platform by biotinylating the capture antibodies. The assays represented a variety of analyte classes (chemokine, interleukin, interferon), antibody types (monoclonal, polyclonal), and analytical properties (sensitivity, dynamic range, concentration-response slope). During development, antibody concentration, biotin and MSD SULFO-TAG™ label ratios, and calibrator concentrations were evaluated and optimized. Assays were readily transferred to the U-PLEX platform with calibration curves showing expected signals, sensitivity, precision, and accuracy. Controls for the assays showed CVs of <10% within runs. Sensitivities were <1 pg/mL for many assays. All assays used the same assay diluents. Non-specific binding between assays was typically <0.1%. We measured 40 human serum and 40 EDTA plasma samples, and demonstrated good correlation with V-PLEX assays (r2 > 0.9; slopes 0.8 – 1.2). The utility and convenience of the U-PLEX platform was demonstrated by easily transferring over 40 human cytokine assays onto the platform without compromising performance. When multiplexed, these assays enable multiple measurements from small amounts of human samples.

On the Analytic Type of Artin Algebras

In this paper we give a complete analytic classification of Artin Gorenstein almost stretched algebras, i.e., Artin Gorenstein algebras with Hilbert function {1, n, 2,…, 2, 1,…, 1}.

Expedited Selection of NMR Chiral Solvating Agents for Determination of Enantiopurity.

The use of NMR chiral solvating agents (CSAs) for the analysis of enantiopurity has been known for decades, but has been supplanted in recent years by chromatographic enantioseparation technology. While chromatographic methods for the analysis of enantiopurity are now commonplace and easy to implement, there are still individual compounds and entire classes of analytes where enantioseparation can prove extremely difficult, notably, compounds that are chiral by virtue of very subtle differences such as isotopic substitution or small differences in alkyl chain length. NMR analysis using CSAs can often be useful for such problems, but the traditional approach to selection of an appropriate CSA and the development of an NMR-based analysis method often involves a trial-and-error approach that can be relatively slow and tedious. In this study we describe a high-throughput experimentation approach to the selection of NMR CSAs that employs automation-enabled screening of prepared libraries of CSAs in a systematic fashion. This approach affords excellent results for a standard set of enantioenriched compounds, providing a valuable comparative data set for the effectiveness of CSAs for different classes of compounds. In addition, the technique has been successfully applied to challenging pharmaceutical development problems that are not amenable to chromatographic solutions. Overall, this methodology provides a rapid and powerful approach for investigating enantiopurity that compliments and augments conventional chromatographic approaches.

Analysis of polar urinary metabolites for metabolic phenotyping using supercritical fluid chromatography and mass spectrometry

Supercritical fluid chromatography (SFC) is frequently used for the analysis and separation of non-polar metabolites, but remains relatively underutilised for the study of polar molecules, even those which pose difficulties with established reversed-phase (RP) or hydrophilic interaction liquid chromatographic (HILIC) methodologies. Here, we present a fast SFC-MS method for the analysis of medium and high-polarity (−7≤cLogP≤2) compounds, designed for implementation in a high-throughput metabonomics setting. Sixty polar analytes were first screened to identify those most suitable for inclusion in chromatographic test mixtures; then, a multi-dimensional method development study was conducted to determine the optimal choice of stationary phase, modifier additive and temperature for the separation of such analytes using SFC. The test mixtures were separated on a total of twelve different column chemistries at three different temperatures, using CO2-methanol-based mobile phases containing a variety of polar additives. Chromatographic performance was evaluated with a particular emphasis on peak capacity, overall resolution, peak distribution and repeatability. The results suggest that a new generation of stationary phases, specifically designed for improved robustness in mixed CO2-methanol mobile phases, can improve peak shape, peak capacity and resolution for all classes of polar analytes. A significant enhancement in chromatographic performance was observed for these urinary metabolites on the majority of the stationary phases when polar additives such as ammonium salts (formate, acetate and hydroxide) were included in the organic modifier, and the use of water or alkylamine additives was found to be beneficial for specific subsets of polar analytes. The utility of these findings was confirmed by the separation of a mixture of polar metabolites in human urine using an optimised 7min gradient SFC method, where the use of the recommended column and co-solvent combination resulted in a significant improvement in chromatographic performance.

Riesz outer product Hilbert space frames: Quantitative bounds, topological properties, and full geometric characterization

Outer product frames are important objects in Hilbert space frame theory. But very little is known about them. In this paper, we make the first detailed study of the family of outer product frames induced directly by vector sequences. We are interested in both the quantitative attributes of these outer product sequences (in particular, their Riesz and frame bounds) and their independence and spanning properties. We show that Riesz sequences of vectors yield Riesz sequences of outer products with the same (or better) Riesz bounds. Equiangular tight frames are shown to produce Riesz sequences with optimal Riesz bounds for outer products. We provide constructions of frames which produce Riesz outer product bases with “good” Riesz bounds. We show that the family of unit norm frames which yield independent outer product sequences is open and dense (in a Euclidean-analytic sense) within the topological space ⊗i=1MSN−1 where M is less than or equal to the dimension of the space of symmetric operators on HN; that is to say, almost every frame with such a bound on its cardinality will induce a set of independent outer products. Thus, this would mean that finding the necessary and sufficient conditions such that the induced outer products are dependent is a more interesting question. For the coup de grâce, we give a full analytic and geometric classification of such sequences which produce dependent outer products.

(Invited) Porphyrins Based Gas Sensors and Their Applications

The role of porphyrins in life processes is well known. Iron complexes for instance are prostetic groups of important proteins such as hemoglobine and cytochromes. On the other hand, reduced porphyrins, as magnesium chlorin complexes, are fundamental in the photosynthetic processes. Such richness of properties is particularly attractive for chemical sensing. The molecular framework of porphyrins is a unique site for a wide range of interaction mechanisms useful for analyte binding. the interactions span from Van der Waals forces to hydrogen bond, to π interactions and to the coordination to the central metal ion. The concurrence of all these mechanisms makes difficult the development of selective sensors, even if selectivity can in some cases found or improved by a suitable design of the sensor. On the other hand, the sensitivity of porphyrins can be oriented, through a proper molecular design, towards different classes of analytes. This control is of great value for the design of sensor arrays where several sensors non-selective but different among them are considered together. We have been interested since about two decades to the use porphyrins to develop sensors for volatile compounds and gases. The physical properties of porphyrins restrict the transduction mechanisms that can be exploited to create an electric signal from the porphyrin-analyte interaction. It is important to recall that a chemical sensor actually measures a physical quantity of the sensing material that is affected by the interaction with the analyte. We developed sensors measuring the mass, the optical absorbance, the surface potential and the charge transferred either to or from an inorganic semiconductor. The sensing properties in all these devices can be related to the properties of the individual porphyrins, for instance the Hard and Soft Acids and Bases (HSAB) Pearson’s rule can be invoked to elucidate the sensitivity of porphyrins coated quartz microbalance sensors with regards to amines and alcohols. In this paper, we will provide a rationale for the development of porphyrins based gas sensors discussing the pros and the cons of each transduction principle. A review of the applications will also be illustrated with a special emphasis on medical diagnosis through the analysis of volatile compounds.

Parametric rigidness of germs of analytic unfoldings with a Hopf bifurcation

In this paper we prove that families of germs of one-parameter analytic differential equations with a Hopf bifurcation are rigid in the parameter. These systems are intrinsically real: the complex phase portrait is invariant under an antiholomorphic involution. The latter permits to identify the modulus of the analytic classification. The dynamics in the Siegel domain does not explain the existence of the real structure. Rather, these properties are meaningful in the Poincaré domain, where the fixed points are linearizable.