Automated image analysis to characterize the melt densification stage of polymer sintering processes

Knowledge of melt densification during sintering is generally acquired by visualization methods, recording bubble formation and dissolution with time. Only manual visualization methods have been reported for polymer studies, which restrict the availability of data to a few discrete moments in time for the overall process. An automated vision system is presented in this paper to provide an improved level of analysis on densification, validated against a manual method. The machine vision technique was applied in the analysis of sintering for various polyethylenes of differing melt flow index and particle size. The automated technique was found to be very accurate and capable of collecting bubble size distributions on a timescale of seconds, which is an improvement in data collection. The method was prone to underestimate bubble numbers (∼20% error), especially those less than 100 μm in size, till the bed temperature rose significantly above the melting temperature of the polymer.     

PCR-based detection of gene transfer vectors: application to gene doping surveillance

Athletes who illicitly use drugs to enhance their athletic performance are at risk of being banned from sports competitions. Consequently, some athletes may seek new doping methods that they expect to be capable of circumventing detection. With advances in gene transfer vector design and therapeutic gene transfer, and demonstrations of safety and therapeutic benefit in humans, there is an increased probability of the pursuit of gene doping by athletes. In anticipation of the potential for gene doping, assays have been established to directly detect complementary DNA of genes that are top candidates for use in doping, as well as vector control elements. The development of molecular assays that are capable of exposing gene doping in sports can serve as a deterrent and may also identify athletes who have illicitly used gene transfer for performance enhancement. PCR-based methods to detect foreign DNA with high reliability, sensitivity, and specificity include TaqMan real-time PCR, nested PCR, and internal threshold control PCR.     

Detection,characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

The increasing demand of analytical information related to inorganic engineered nanomaterials requires the adaptation of existing techniques and methods, or the development of new ones. The challenge for the analytical sciences has been to consider the nanoparticles as a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g. size, shape, aggregation). Moreover, information about the species derived from the nanoparticles themselves and their transformations must also be supplied. Whereas techniques commonly used for nanoparticle characterization, such as light scattering techniques, show serious limitations when applied to complex samples, other well-established techniques, like electron microscopy and atomic spectrometry, can provide useful information in most cases. Furthermore, separation techniques, including flow field flow fractionation, capillary electrophoresis and hydrodynamic chromatography, are moving to the nano domain, mostly hyphenated to inductively coupled plasma mass spectrometry as element specific detector. Emerging techniques based on the detection of single nanoparticles by using ICP-MS, but also coulometry, are in their way to gain a position. Chemical sensors selective to nanoparticles are in their early stages, but they are very promising considering their portability and simplicity. Although the field is in continuous evolution, at this moment it is moving from proofs-of-concept in simple matrices to methods dealing with matrices of higher complexity and relevant analyte concentrations. To achieve this goal, sample preparation methods are essential to manage such complex situations. Apart from size fractionation methods, matrix digestion, extraction and concentration methods capable of preserving the nature of the nanoparticles are being developed. This review presents and discusses the state-of-the-art analytical techniques and sample preparation methods suitable for dealing with complex samples. Single- and multi-method approaches applied to solve the nanometrological challenges posed by a variety of stakeholders are also presented.     

Benchmarking the ACEnano Toolbox for Characterisation of Nanoparticle Size and Concentration by Interlaboratory Comparisons

ACEnano is an EU-funded project which aims at developing, optimising and validating methods for the detection and characterisation of nanomaterials (NMs) in increasingly complex matrices to improve confidence in the results and support their use in regulation. Within this project, several interlaboratory comparisons (ILCs) for the determination of particle size and concentration have been organised to benchmark existing analytical methods. In this paper the results of a number of these ILCs for the characterisation of NMs are presented and discussed. The results of the analyses of pristine well-defined particles such as 60 nm Au NMs in a simple aqueous suspension showed that laboratories are well capable of determining the sizes of these particles. The analysis of particles in complex matrices or formulations such as consumer products resulted in larger variations in particle sizes within technologies and clear differences in capability between techniques. Sunscreen lotion sample analysis by laboratories using spICP-MS and TEM/SEM identified and confirmed the TiO₂ particles as being nanoscale and compliant with the EU definition of an NM for regulatory purposes. In a toothpaste sample orthogonal results by PTA, spICP-MS and TEM/SEM agreed and stated the TiO₂ particles as not fitting the EU definition of an NM. In general, from the results of these ILCs we conclude that laboratories are well capable of determining particle sizes of NM, even in fairly complex formulations.     

Comparative studies on some methods for handling quantitative data generated by analytical pyrolysis

A number of multivariable statistical techniques have been prepared for handling programs or mass spectra. The more widely used methods are reviewed and their application, the microbiological data set compared. The results are drawn together to formulate a XXXXX data handling rationale capable of processing a variety of pyrolyses applications.     

In Vivo Electrochemical Biosensors for Reactive Oxygen Species Detection: A Mini-Review

Due to the significance of reactive oxygen species (ROS) in numerous physiological processes including pathogen response, apoptosis, and induction of defense genes, various methods have been developed for their quantitative analysis. However, the conventional methods using exogenous tracers lack the capability to conduct real-time in vivo measurements. The electrochemical biosensors have shown their potentials for in vivo applications with the rapid and reagentless detection processes. In this article, electrochemical biosensors that are capable of making in vivo ROS detections are reviewed. The different configurations of these biosensors with corresponding strategies to enhance sensitivity and selectivity are discussed in detail. With further studies to promote the biosensor performance, these devices promise to provide more facile ways for ROS research in life sciences.     

Advances in numerical methods for the solution of population balance equations for disperse phase systems

Accurate prediction of the evolution of particle size distribution is critical to determining the dynamic flow structure of a disperse phase system. A population balance equation (PBE), a non-linear hyperbolic equation of the number density function, is usually employed to describe the micro-behavior (aggregation, breakage, growth, etc.) of a disperse phase and its effect on particle size distribution. Numerical solution is the only choice in most cases. In this paper, three different numerical methods (direct discretization methods, Monte Carlo methods, and moment methods) for the solution of a PBE are evaluated with regard to their ease of implementation, computational load and numerical accuracy. Special attention is paid to the relatively new and superior moment methods including quadrature method of moments (QMOM), direct quadrature method of moments (DQMOM), modified quadrature method of moments (M-QMOM), adaptive direct quadrature method of moments (ADQMOM), fixed pivot quadrature method of moments (FPQMOM), moving particle ensemble method (MPEM) and local fixed pivot quadrature method of moments (LFPQMOM). The prospects of these methods are discussed in the final section, based on their individual merits and current state of development of the field. Supported by the National Basic Research Program of China (Grant No. 2004CB720208), the National Natural Science Foundation of China (Grant Nos. 40675011 & 10872159), and the Key Laboratory of Mechanics on Disaster and Environment in Western China     

Underwater life support based on immobilized oxygen carriers

One of the primary problems that hinders humans in their efforts to explore and develop the ocean realms is the lack of a ready supply of oxygen. Practical methods have not yet been devised for using the vast amount of oxygen dissolved in ocean waters for human life support in an undersea environment. Fish and other water-breathing animals have solved this problem by utilizing hemoglobin as a molecular oxygen pump. To achieve a similar oxygen extraction capability, we have explored various methods of oxygen extraction that are based on immobilized forms of hemoglobin. Improved methods for immobilizing hemoglobin or other oxygen carrying molecules and a method for extracting the available dissolved oxygen from natural waters and other fluids are described. The techniques that have been developed allow for immobilization of oxygen carriers at high concentration in a state where they are capable of reversible oxygen binding, and also allow for regeneration of the carrier in the event of oxidation of the oxygen-binding site.     

Field-theoretic simulations of polymer solutions: finite-size and discretization effects

In this work we analyze the finite-size and discretization effects that occur in field-theoretic polymer simulations. Following our previous work, we study these effects for a polymer solution in the canonical ensemble confined to a slit (with nonadsorbing walls) of width L, and focus on the behavior of two quantities: the chemical potential mu, and the correlation length xi. Our results show that the finite-size effects disappear for both quantities once the lateral size of the system L is larger than approximately 2xi. On the other hand, the chemical potential is dominated by the lattice discretization Deltax. The origins of this dependence are discussed in detail, and a scheme is proposed in which this effect is avoided. Our results also show that the density profiles do not depend on the lattice discretization if Deltax < approximately xi/4. This implies that the correlation length xi, extracted from the density profiles, is free of lattice size and lattice discretization artifacts once L is > approximately 2xi and Deltax < approximately xi/4.     

Enzymatic Macrocyclization of 1,2,3‐Triazole Peptide Mimetics

The macrocyclization of linear peptides is very often accompanied by significant improvements in their stability and biological activity. Many strategies are available for their chemical macrocyclization, however, enzyme‐mediated methods remain of great interest in terms of synthetic utility. To date, known macrocyclization enzymes have been shown to be active on both peptide and protein substrates. Here we show that the macrocyclization enzyme of the cyanobactin family, PatGmac, is capable of macrocyclizing substrates with one, two, or three 1,4‐substituted 1,2,3‐triazole moieties. The introduction of non‐peptidic scaffolds into macrocycles is highly desirable in tuning the activity and physical properties of peptidic macrocycles. We have isolated and fully characterized nine non‐natural triazole‐containing cyclic peptides, a further ten molecules are also synthesized. PatGmac has now been shown to be an effective and versatile tool for the ring closure by peptide bond formation.     

Wavelet formulation of the polarizable continuum model

The first implementation of a wavelet discretization of the Integral Equation Formalism (IEF) for the Polarizable Continuum Model (PCM) is presented here. The method is based on the application of a general purpose wavelet solver on the cavity boundary to solve the integral equations of the IEF‐PCM problem. Wavelet methods provide attractive properties for the solution of the electrostatic problem at the cavity boundary: the system matrix is highly sparse and iterative solution schemes can be applied efficiently; the accuracy of the solver can be increased systematically and arbitrarily; for a given system, discretization error accuracy is achieved at a computational expense that scales linearly with the number of unknowns. The scaling of the computational time with the number of atoms N is formally quadratic but a N^1.5 scaling has been observed in practice. The current bottleneck is the evaluation of the potential integrals at the cavity boundary which scales linearly with the system size. To reduce this overhead, interpolation of the potential integrals on the cavity surface has been successfully used. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Monitoring chemical impacts on cell cultures by means of image analyses

Many chemical processes are involved in the interactions of living cells with their environment; however, monitoring such processes often requires sophisticated analyzers. In this study, a sensing strategy based on imaging techniques has been developed to (i) enable cell discrimination based on their physical appearance such as size and shape and (ii) to build predictive models that relate the measured cell appearance to chemical parameters in their environment. Both goals aim at innovative and straightforward sensing strategies for analyzing cell–environment interactions. Image analyses offer several advantages such as the use of simpler, more robust sensors and the omission of extensive sample/sensor preparations. Imaging can analyze numerous cells and thus gains a culture representative insight rather than a potentially nonrepresentative single‐cell response. As a proof‐of‐principle application, different species of microalgae cells have been exposed to various nutrient conditions. Microalgae are known to sensitively adapt to changing nutrient conditions and could potentially become biological “probes” for chemical shifts in ecosystems. Because of considerable spreads of cell size and shapes within one class, size and shape distributions have been derived from visible images of cell cultures. It is shown that the novel image analyses are capable of discriminating different cell species based on their cell shapes and sizes. It is also demonstrated that in conjunction with the recently introduced, nonlinear multivariate “predictor surfaces”, the nutrient availability has a quantifiable impact on the cell size distributions. In this application, predictor surfaces are somewhat more precise than partial least squares. Copyright © 2012 John Wiley & Sons, Ltd.     

A review on analytical performance of micro- and nanoplastics analysis methods

Micro- and nanoplastics have been detected in diverse matrices. Recent studies have suggested their health impact on humans, animals, plants, and environment which depends on the size, concentration, chemical nature, and the mode of interaction of the plastic particles. Detection and quantification of these particles are often challenging due to their small size and complexity of the matrix in which they exist. The concentration and size of the particles combined with the nature of the matrix determines an analytical method to be followed. In recent years, many review articles focusing on origin, fate, and health effects of micro- and nanoplastics are already published. A systemic review focusing on analytical performance of currently available micro- and nanoplastics analysis methods would be useful for the scientific community. In this article, we reviewed papers and reports published in recent decades focusing on the sampling, concentration, detection, and chemical identification methods. We also reviewed the emerging new methods for microplastic analysis. Finally, we provide advantages and limitations of the methods and future perspectives on microplastic analysis.     

Characterisation and determination of fullerenes: A critical review

A prominent sector of nanotechnology is occupied by a class of carbon-based nanoparticles known as fullerenes. Fullerene particle size and shape impact in how easily these particles are transported into and throughout the environment and living tissues. Currently, there is a lack of adequate methodology for their size and shape characterisation, identification and quantitative detection in environmental and biological samples. The most commonly used methods for their size measurements (aggregation, size distribution, shape, etc.), the effect of sampling and sample treatment on these characteristics and the analytical methods proposed for their determination in complex matrices are discussed in this review. For the characterisation and analysis of fullerenes in real samples, different analytical techniques including microscopy, spectroscopy, flow field-flow fractionation, electrophoresis, light scattering, liquid chromatography and mass spectrometry have been reported. The existing limitations and knowledge gaps in the use of these techniques are discussed and the necessity to hyphenate complementary ones for the accurate characterisation, identification and quantitation of these nanoparticles is highlighted.     

Evaluation of the Chain Length Distribution in Free‐Radical Polymerization, 1. Bulk Polymerization

A method for the direct computation of the chain length distribution in a bulk polymerization is developed, based on the discretization procedure introduced by Kumar and Ramkrishna (Chem. Eng. Sci. 1996 , 51, 1311) in the context of particle size distribution. The overall distribution of chain lengths is partitioned into a finite number of classes which are supposed to be concentrated at some appropriate pivotal chain lengths. Several of the involved reactions lead to the formation of chain whose length differs from the pivotal values. Rules have been introduced in order to share chains between two contiguous classes, which have been designed so as to preserve two well‐defined properties of the distribution, such as, for example, two of its moments. The method has been applied to a polymerization system including propagation, bimolecular terminations and two different chain branching mechanisms: chain transfer to polymer and crosslinking. In addition, complex systems such as one with chain length‐dependent kinetic constants or a two‐dimensional distribution of chain length and number of branches have been considered.     

Capillary electrophoresis for the analysis of glycosaminoglycans and glycosaminoglycan-derived oligosaccharides

Glycosaminoglycans are a family of polydisperse, highly sulfated complex mixtures of linear polysaccharides that are involved in many life processes. Defining the structure of glycosaminoglycans is an important factor in elucidating their structure-activity relationship. Capillary electrophoresis has emerged as a highly promising technique consuming an extremely small amount of sample and capable of rapid, high-resolution separation, characterization and quantitation of analytes. Numerous capillary electrophoresis methods for analysis of intact glycosaminoglycans and glycosaminoglycan-derived oligosaccharides have been developed. These methods allow for both qualitative and quantitative analysis with a high level of sensitivity. This review is concerned with separation methods of capillary electrophoresis, detection methods and applications to several aspects of research into glycosaminoglycans and glycosaminoglycan-derived oligosaccharides. The importance of capillary electrophoresis in biological and pharmaceutical samples in glycobiology and carbohydrate biochemistry and its possible applications in disease diagnosis and monitoring chemical synthesis are described.     

Synthesis,Characterization, and Applications of Copper Nanoparticles

Copper nanoparticles with different structural properties and effective biological effects may be fabricated using new green protocols. The control over particle size and in turn size-dependent properties of copper nanoparticles is expected to provide additional applications. Various methods for the synthesis of copper nanoparticles have been reported including chemical methods, physical methods, biological methods, and green synthesis. Biological methods involve the use of plant extracts, bacteria, and fungi. Commendable work has been done regarding the synthesis and stability of copper nanoparticles. There is a need to summarize the behavior of copper nanoparticles in different media under various conditions. Here, a complete list of the literature on the synthesis of copper nanoparticles, their properties, stabilizing agents, factors affecting the morphology, and their applications is presented. The importance of copper nanoparticles compared to other metal nanoparticles are due to high conductivity. Methods for the synthesis of copper nanoparticles, including green protocols using plants and micro-organisms compared chemical methods, have also been reviewed.     

Signal Amplification Technologies for the Detection of Nucleic Acids: from Cell-Free Analysis to Live-Cell Imaging

Due to their unique properties, such as programmability, ligand-binding capability, and flexibility, nucleic acids can serve as analytes and/or recognition elements for biosensing. To improve the sensitivity of nucleic acid-based biosensing and hence the detection of a few copies of target molecule, different modern amplification methodologies, namely target-and-signal-based amplification strategies, have already been developed. These recent signal amplification technologies, which are capable of amplifying the signal intensity without changing the targets’ copy number, have resulted in fast, reliable, and sensitive methods for nucleic acid detection. Working in cell-free settings, researchers have been able to optimize a variety of complex and quantitative methods suitable for deploying in live-cell conditions. In this study, a comprehensive review of the signal amplification technologies for the detection of nucleic acids is provided. We classify the signal amplification methodologies into enzymatic and non-enzymatic strategies with a primary focus on the methods that enable us to shift away from in vitro detecting to in vivo imaging. Finally, the future challenges and limitations of detection for cellular conditions are discussed.     

Size separation of graphene oxide using preparative free‐flow electrophoresis

Graphene oxide nanosheets often bear a wide size distribution. However, it is critical to have nanosheets with narrow size distribution for their unique size‐dependent physiochemical properties, and nanosheets with a narrow size distribution are the cornerstones for application. Therefore, efficient separation methods of graphene nanosheets have been given considerable attention in many scientific areas recently. Free‐flow electrophoresis is extensively used in the separation and purification of biological molecules with continuous flow separation. The charged graphene oxide nanosheets to some extent are very close in size to biological molecules and share similarity in motion behavior in an electric field. Thus, in the present work, we present a new and simple means to separate graphene oxide nanosheets into more mono‐dispersed size groups by using the free‐flow electrophoresis technique. By optimizing the separation conditions, we were able to obtain graphene oxide sheets with narrow size distribution. The separated samples were characterized by atomic force microscopy, and the size measurements were made by using the software “Image Pro Plus.” In addition, a brief discussion is also given into the theoretic background of the separation of graphene oxide according to the size by the technique of preparative free‐flow electrophoresis.