A new river sediment standard reference material

The collection, processing and certification of a new sediment Standard Reference Material (SRM), SRM 2704, is described. Collected from the bottom of the Buffalo River in New York State during the fall of 1986, SRM 2704 is certified for 25 elements with information provided on another 22 elements. Improvements in analytical methods as well as the application of well-defined quality-control procedures for collection, processing and analysis have resulted in a reference material that is more completely characterized than previous NIST sediment reference materials.     

A theoretical model for bubble formation during horizontal gas injection into liquid flow in vertical tubes

Bubble formation in flowing liquid is an important process for wastewater treatment, processing of molten metals, and biological processes. Based on a global balance of force on the bubble, this report describes a new theoretical model for bubble formation during horizontal gas injection into turbulent liquid flow in a vertical tube. This work highlights the importance of choosing the correct drag law in accordance with the bubble size. Five models for drag coefficient are compared, and of these, model III is recommended. Modified detachment criteria are applicable, depending on the liquid velocity. The new analytical model yields good predictions compared with experimental data. Based on the theoretical model, this study investigates the effects of the direction of liquid flow, liquid velocity, gas velocity, and orifice diameter on the bubble formation behavior.     

Optimization of enzymatic biochemical logic for noise reduction and scalability: how many biocomputing gates can be interconnected in a circuit?

We report an experimental evaluation of the "input-output surface" for a biochemical AND gate. The obtained data are modeled within the rate-equation approach, with the aim to map out the gate function and cast it in the language of logic variables appropriate for analysis of Boolean logic for scalability. In order to minimize "analog" noise, we consider a theoretical approach for determining an optimal set for the process parameters to minimize "analog" noise amplification for gate concatenation. We establish that under optimized conditions, presently studied biochemical gates can be concatenated for up to order 10 processing steps. Beyond that, new paradigms for avoiding noise buildup will have to be developed. We offer a general discussion of the ideas and possible future challenges for both experimental and theoretical research for advancing scalable biochemical computing.     

QSIMPS: A response to the analytical challenge of the pharmacokinetic revolution

Pharmacokinetics is a collection of equations (and concepts) which can transform blood and/or urine concentration—time data for a drug into numerical parameters that are useful as practical instruments for deciding certain questions concerning the efficacy and safety of the drug. To generate the parameters requires the analysis of hundreds of samples; experiments to compare parameters require the analysis of thousands of samples. Typically, tens of thousands of analyses are needed to generate the pharmacokinetic data required to bring a new drug on the market. This paper describes QSIMPS, a collection of software and hardware for the rapid, automated collection, processing and analysis of gas chromatography—mass spectrometry—selected ion monitoring data acquired for use in pharmacokinetic studies.     

Modeling liquid porosimetry in modeled and imaged 3-D fibrous microstructures

In this paper, an analysis to distinguish the geometric and porosimetric pore size distributions of a fibrous material is presented. The work is based on simulating the intrusion of nonwetting fluid in a series of 3-D fibrous microstructures obtained from 3-D image reconstruction or virtual geometries mathematically generated according to the properties of the media. We start our study by computing the pore size distribution of two typical hydroentangled nonwoven materials and present a theoretical model for their geometric pore size distributions based on Poisson line network model of the fibrous media. It is shown that the probability density function of the geometric pore size distribution can be approximated by a two-parametric Gamma distribution. We also study connectivity of the pore space in fibrous media by computing and comparing the accessible and allowed pore volumes in the form access function graphs. It is shown that the so-called ink-bottle effect can significantly influence the fluid intrusion in a porous material. The pore space connectivity of a homogeneous fibrous media is observed to be a function of thickness, solid volume fraction (SVF), and fiber diameter. It is shown that increasing the materials' thickness or SVF, while other properties are kept constant, reduces the pore space connectivity. On the other hand, increasing the fiber diameter enhances the connectivity of the pores if all other parameters are fixed. Moreover, modeling layered fibrous microstructures; it is shown that the access function graphs can be used to detect the location of the bottle neck pores in a layered/composite porous material.     

Prediction of Thermal Damage upon Ultrafast Laser Ablation of Metals

Ultrafast lasers micromachining results depend on both the processing parameters and the material properties. The obtained thermal effects are negligible if a good combination of processing parameters is chosen. However, optimizing the processing parameters leading to the required surface quality on a given material can be quite complex and time consuming. We developed a semi-empirical model to estimate the heat accumulation on a surface as a function of the laser fluence, scanning speed and repetition rate. The simulation results were correlated with experimental ones on different materials, and compared with the transient temperature distributions calculated using an analytical solution to the heat transfer equation. The predictions of the proposed model allow evaluating the heat distribution on the surface, as well as optimizing the ultrafast laser micromachining strategy, yielding negligible thermal damage.     

Effect of homogenization (microfluidization) process parameters in mechanical production of micro- and nanofibrillated cellulose on its rheological and morphological properties

The rheological properties of microfibrillated cellulose (MFC)/nanofibrillated cellulose (NFC) suspensions have an important role during processing and mixing. In this work, the process parameters for MFC/NFC production within a microfluidizer (i.e., the size of interaction chamber and number of passes) were varied to investigate the influences on morphology, zeta potential, chemical properties and rheological features including viscosity, creep, strain recovery and yield stress behavior. The stability and appropriate viscosity of the fiber suspensions can be controlled by optimizing the processing conditions, resulting in a reduction in fiber diameter and most negative zeta potential value. The viscosity increased with higher amount of fibrillation by using a smaller chamber or higher number of passes, but intermediate plateau values are characteristic for temporary aggregation and breaking-up of the fiber network. The creep response and yield stress have been described by parameters of the Burger model and Herschel–Bulkley model, respectively, showing a more prominent effect on yield stress of chamber size than number of passes. The network formation leads to lower creep compliance and step-like strain recovery. The transition from gel-like to liquid-like behavior as characterized by the dynamic yield point at a specific strain, is almost independent of the processing conditions. Most important, the total number of passes applied in production can be directly related to the rotational Péclet number, which combines rheological and morphological data.     

Investigation on the machine calibration effect on the optimization through design of experiments (DOE) in injection molding parts

Achieving production quality is a key issue faced in injection molding. Before mass production, ensuring good production quality is one of the crucial factors in injection molding. To achieve good quality, CAE technology is beneficial to assist us either to make the process window approach or to integrate with optimization strategies to improve the quality. However, there are still some questions or challenges existed. For example, for general injection molding, the difference between CAE simulation prediction and real experimental observation is very often encountered. But its mechanism of this difference is not fully understood yet. When design of experiments (DOE) procedure is performed using CAE simulation, the optimal parameters obtained from CAE prediction are expected to be forwarded into the real molding trial. However, there is no guarantee to get results with good accuracy based on those optimal parameters. In this study, we have proposed a feasible methodology to uncover the difference and its internal mechanism between CAE simulation prediction and real experimental observation. It also includes the method to reduce that difference by calibrating the machine performance. Specifically, a standard procedure to calibrate the real performance of the injection machine using CAE technology has been constructed. Moreover, to realize the integration of CAE and DOE optimization strategy, the quality difference between the virtual CAE-DOE and the physical DOE optimization has been investigated before doing the machine calibration. The result showed that the difference between the virtual CAE-DOE and the physical DOE is almost same as that of the original injection molding design. However, after the machine calibration, the quality difference between the virtual CAE-DOE and the physical DOE optimization is reduced by 67%. It is noted that the machine calibration effect is quite significant in injection molding process development.     

Global optimization of the infrared matrix-assisted laser desorption electrospray ionization (IR MALDESI) source for mass spectrometry using statistical design of experiments

Design of experiments (DOE) is a systematic and cost-effective approach to system optimization by which the effects of multiple parameters and parameter interactions on a given response can be measured in few experiments. Herein, we describe the use of statistical DOE to improve a few of the analytical figures of merit of the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source for mass spectrometry. In a typical experiment, bovine cytochrome c was ionized via electrospray, and equine cytochrome c was desorbed and ionized by IR-MALDESI such that the ratio of equine:bovine was used as a measure of the ionization efficiency of IR-MALDESI. This response was used to rank the importance of seven source parameters including flow rate, laser fluence, laser repetition rate, ESI emitter to mass spectrometer inlet distance, sample stage height, sample plate voltage, and the sample to mass spectrometer inlet distance. A screening fractional factorial DOE was conducted to designate which of the seven parameters induced the greatest amount of change in the response. These important parameters (flow rate, stage height, sample to mass spectrometer inlet distance, and laser fluence) were then studied at higher resolution using a full factorial DOE to obtain the globally optimized combination of parameter settings. The optimum combination of settings was then compared with our previously determined settings to quantify the degree of improvement in detection limit. The limit of detection for the optimized conditions was approximately 10 attomoles compared with 100 femtomoles for the previous settings, which corresponds to a four orders of magnitude improvement in the detection limit of equine cytochrome c.     

Analysis and Simulation of Fiber Dispersion in Water Using a Theoretical Analogous Model

The wet-lay nonwoven processing is divided into fiber dispersing and blending, web formation, drying, and finally, consolidating the formed web. Fiber dispersion is the most crucial step of this process. The required time and necessary agitation to separate and disperse fibers depends on fiber characteristics. In this work, theoretical and experimental studies were done to investigate the effects of fibers characteristics on their dispersion in water for wet-laid nonwoven. Two effective forces of drag and surface tension were modeled using linear spring and damper to analyze the fiber behaviors in a stirred mixing tank. Results show that when the fiber diameter is increased, the required time for breaking up of fiber bundles and clumps is increased. The effect of fiber types on fibers break up and dispersing time were also investigated. In the experimental work, an on-line vision system was developed to observe the dispersion behavior of polyester and glass fibers.     

Transport properties of electrospun nylon 6 nonwoven mats

In this work, we evaluate the physical properties of nylon 6 nonwoven mats produced from solutions with formic acid. Nonwoven electrospun mats from various solutions with different concentration are examined regarding their morphology, pore size, surface area, and gas transport properties. Each nonwoven mat with average fiber diameters from 90 to 500 nm was prepared under controlled electrospinning process parameters. From the results, it was observed that the fiber diameter was strongly affected by the polymer concentration (polymer viscosity). In additional the results showed that the pore size, Brunauer-Emmett-Teller (BET) surface area, and gas transport property of electrospun nylon 6 nonwoven mats were affected by the fiber diameter.     

Rheology and fiber degradation during shear flow of carbon-fiber-reinforced polypropylenes

The processing of fiber-reinforced thermoplastics is often accompanied by a significant fiber fracture. Therefore, it is important to assess the effect of processing variables on the extent of fiber damage occurring during product fabrication, such as extrusion or injection molding. The present paper discusses fiber damage caused by shear forces exerted on the composite by a molten matrix in both experimental and theoretical terms. The degradation process in carbon fiber-polypropylene composites is studied in a broad range of shear rates, although it occurs significantly only under high shearing in a capillary. Changes in fiber length and its distribution during the multi-flow through a capillary, as well as the materials’ rheological properties found in research after shearing, are discussed and the results are compared with a model of fiber-length analysis for the mixing-regrinding process. Published in Russian in Vysokomolekulyamye Soedineniya, Ser. A, 2006, Vol. 48, No. 9, pp. 1628–1639. The text was submitted by the authors in English.     

Discussion of challenges encountered during the collection and submission of wipe/leak test samples

Summary Collection and submission challenges are encountered during analysis of samples taken on devices containing radioactive materials. The sample analysis is for either gross alpha-counting by gas-flow proportional counting or low-level beta-counting by liquid scintillation counting. Technical manuals, safety and maintenance messages, provide established policies for the collection and submission of the samples. The analytical challenges range from incorrect sampling media to improper packaging and shipping of the samples. Since quality starts with sample collection and the samples are not being collected and/or submitted correctly, the counting laboratory may not be able to provide meaningful analytical results to the customer.     

Establishment and validation of a microfluidic capillary gel electrophoresis platform method for purity analysis of therapeutic monoclonal antibodies

Capillary and microfluidic chip electrophoresis technologies are heavily utilized for development, characterization, release, and stability testing of biopharmaceuticals. Within the biopharmaceutical industry, CE‐SDS and M‐CGE are commonly used for purity determination by separation and quantitation of size‐based variants. M‐CGE is used primarily as an R&D tool for product and process development, while cGMP release and stability testing applications are commonly reserved for CE‐SDS. This paper describes the establishment of an M‐CGE platform method to be used for R&D and cGMP applications, including release and stability testing, for monoclonal antibodies. The M‐CGE platform method enables testing for product development support and cGMP release and stability using the same method, and utilization of one CE technology for the entire lifecycle of a biopharmaceutical product. Critical method parameters were identified, and the analytical design space of those critical parameters was defined using design of experiments (DOE) studies. Once defined through DOE studies, the method design space was validated according to ICH Q2 (R1) guidelines. Additional molecules of the same validated class were verified for use in the method by experimental confirmation of accuracy, specificity, and stability indicating capabilities. The platform method model facilitates rapid utilization of the method in development and GMP testing environments, and eliminates the need for individual validations for assets of the same class entering early stage development.     

Sintered silica colloidal crystals with fully hydroxylated surfaces

Silica colloidal crystals require multiple processing steps before they are useful materials in analytical applications, such as chemical separations, microarrays, sensors, and total internal reflection microscopy. These chemical processing steps include calcination, sintering, surface rehydroxylation, and chemical modification, but these steps have not been fully characterized for colloidal crystals. Silica particles of nominally 200 nm in diameter were prepared, and FTIR, SEM, UV-visible spectroscopy, and refractive index measurements were used to study the changes in chemical composition, particle size, and particle density throughout the process. The final material is shown to be a durable, crack-free crystal of solid particles bearing a fully hydroxylated surface of silanols, which can then be chemically modified.     

Performance of a parallel viscoelastic-viscoplastic model for a microcellular thermoplastic foam on wide temperature range

This paper is concerned with the experimental testing and the constitutive modelling of a thermoplastic microcellular polyethylene-terephthalate (MC-PET) foam on the temperature range of 21–210 °C in order to investigate the temperature-dependent performance of the applied parallel viscoelastic-viscoplastic material model. By means of carefully designed uniaxial mechanical tests in temperature chamber, the viscous, elastic and yielding behaviours of the investigated material are identified, which are then applied for selecting suitable viscoelastic-viscoplastic constitutive models. The material characterization process is conducted using finite-element-based fitting method, including also the analysis of the applied numerical optimization algorithm. The fitting results are used to analyse the parameter sensitivity and to propose closed-form analytical relations for the temperature dependency of the material parameters. Finally, the utilisation of the analytical temperature functions for speeding up the parameter-fitting process is also demonstrated.     

Theoretical analysis of texture dependent extensional viscosity of discotic mesophases

Rheological functions for uniaxial extensional flows predicted by a previously selected and validated constitutive equation (CE) for discotic mesophases are presented. The predicted relations between extensional viscosities, flow-induced microstructure, processing conditions, and material parameters of discotic mesophases are characterized and discussed. It is found that, in contrast to rod-like nematics, two distinct uniaxial extensional viscosities need to be defined to characterize the extensional rheological functions of discotic mesophases completely. The model predicts non-Troutonian extensional viscosities of discotic nematics, such as strain thinning and strain thickening, depending on the process temperature, and the ratio of viscous to elastic stress contributions. The uniaxial extensional viscosities are also found to depend strongly on the flow-induced microstructure. The rheological analysis is then used to characterize the relations between extensional flow viscosities and the classical microstructures that arise during the industrial fiber spinning of discotic mesophase pitches.     

The Preparation of Perovskite Nano Powder by Sol-gel from DTPA and the Mechanism of Thermal Decomposition

Dy0.8Sr0.2FeO3 nano powder, a synthetic oxide, is made by sol-gel method from metal nitrate and diethylenetriaminepentaaeetic acid (DTPA), and the processing parameters are optimized.The process of the preparation, thermal decomposition and the property of the powder are studied by TG-DTA, IR, TEM, and XRD. The diameter of the average grain is about 70 nm. This new technique can be used in the preparation and the studying of ha‘no materials in the complex oxide system.     

Détermination du modèle thermocinétique d'un phénomène par convolution avec la fonction d'appareil optimisation des paramètres de ce modèle

The analysis of experiments on thermal reaction kinetics is complicated by the deformation of the signal due to the inertia of the microcalorimeter.A method is presented which calculates the thermogram by optimizing the parameters of a theoretical model. This model introduces the characteristics of the apparatus by a convolution technique. Since an experimental determination of the deformation due to the apparatus is used, it is unnecessary to assume an analytical form of this function as in previous methods of analysis by deconvolution.