Inert Systems Research Articles

Polymerization-based signal amplification under ambient conditions with thirty-five second reaction times

Although polymerization-based amplification (PBA) has demonstrated promise as an inexpensive technique for use in molecular diagnostics, oxygen inhibition of radical photopolymerization has hindered its implementation in point-of-care devices. The addition of 0.3-0.7 μM eosin to an aqueous acrylate monomer solution containing a tertiary amine allows an interfacial polymerization reaction to proceed in air only near regions of a test surface where additional eosin initiators coupled to proteins have been localized as a function of molecular recognition events. The dose of light required for the reaction is inversely related to eosin concentration. This system achieves sensitivities comparable to those reported for inert gas-purged systems and requires significantly shorter reaction times. We provide several comparisons of this system with other implementations of polymerization-based amplification.

Coordinated Movements Prevent Jamming in an Emperor Penguin Huddle

For Emperor penguins (Aptenodytes forsteri), huddling is the key to survival during the Antarctic winter. Penguins in a huddle are packed so tightly that individual movements become impossible, reminiscent of a jamming transition in compacted colloids. It is crucial, however, that the huddle structure is continuously reorganized to give each penguin a chance to spend sufficient time inside the huddle, compared with time spent on the periphery. Here we show that Emperor penguins move collectively in a highly coordinated manner to ensure mobility while at the same time keeping the huddle packed. Every 30–60 seconds, all penguins make small steps that travel as a wave through the entire huddle. Over time, these small movements lead to large-scale reorganization of the huddle. Our data show that the dynamics of penguin huddling is governed by intermittency and approach to kinetic arrest in striking analogy with inert non-equilibrium systems, including soft glasses and colloids.

Förster Resonance Energy Transfer in Quantum Dot–Dye‐Loaded Zeolite L Nanoassemblies

AbstractNanoassemblies formed by coating a dye‐loaded zeolite L surface with CdSe/ZnS core/shell quantum dots (QDs) is described. A photoinduced energy transfer is observed from the excited QDs, which are on the surface of the zeolite crystals, to dye molecules (energy acceptors) encapsulated and aligned in the 1D channels of the aluminosilicate host. Steady‐state and time‐resolved spectroscopy and microscopy are used to quantify the Förster resonance energy transfer occurring through electronic transition dipole interactions between the QDs and the oxonine‐loaded zeolite L crystals. For the first time the energy transfer in artificial antenna systems based on quantum dots and molecules hosted in inert systems is described.

Space Cannot Be Cut—Why Self-Identity Naturally Includes Neighbourhood

Psychology is not alone in its struggle with conceptualizing the dynamic relationship between space and individual or collective identity. This general epistemological issue haunts biology where it has a specific focus in evolutionary arguments. It arises because of the incompatibility between definitive logical systems of 'contradiction or unity', which can only apply to inert material systems, and natural evolutionary processes of cumulative energetic transformation. This incompatibility makes any attempt to apply definitive logic to evolutionary change unrealistic and paradoxical. It is important to recognise, because discrete perceptions of self and group, based on the supposition that any distinguishable identity can be completely cut free, as an 'independent singleness', from the space it inescapably includes and is included in, are a profound but unnecessary source of psychological, social and environmental conflict. These perceptions underlie Darwin's definition of 'natural selection' as 'the preservation of favoured races in the struggle for life'. They result in precedence being given to striving for homogeneous supremacy, through the competitive suppression of others, instead of seeking sustainable, co-creative evolutionary relationship in spatially and temporally heterogeneous communities. Here, I show how 'natural inclusion', a new, post-dialectic understanding of evolutionary process, becomes possible through recognising space as a limitless, indivisible, receptive (non-resistive) 'intangible presence' vital for movement and communication, not as empty distance between one tangible thing and another. The fluid boundary logic of natural inclusion as the co-creative, fluid dynamic transformation of all through all in receptive spatial context, allows all form to be understood as flow-form, distinctive but dynamically continuous, not singularly discrete. This simple move from regarding space and boundaries as sources of discontinuity and discrete definition to sources of continuity and dynamic distinction correspondingly enables self-identity to be understood as a dynamic inclusion of neighbourhood, through the inclusion of space throughout and beyond all natural figural forms as configurations of energy. Fully to appreciate and communicate the significance of this move, it is necessary to widen the linguistic, mathematical and imaginative remit of conventional scientific argument and explication so as to include more poetic, fluid and artistic forms of expression.

An explicit reduced mechanism for [formula omitted]–air combustion

For hydrogen–oxygen–inert systems, just as for other fuel–oxidizer mixtures, systematically reduced chemistry has in the past been developed separately for premixed and diffusion flames and for autoignition. In computational work that addresses turbulent combustion or the transition from deflagration to detonation, however, autoignition and flames both may occur, and reduced chemistry may be required because of computer limitations. To fill that need, systematically reduced chemistry is presented here that encompasses autoignition and flames. The description involves three global steps among five reacting species, H2,O2,H2O,H and HO2, being based on approximations to chemical-kinetic steady states for O, OH and H2O2. These steady states apply well under all conditions except during autoignition in lean and stoichiometric mixtures, where they underpredict induction times substantially. To remedy this deficiency, which occurs only when HO2 is not in steady state, an autoignition analysis is employed to derive a correction factor that reduces the value of the reaction rates to produce agreement of calculated ignition delays. Introduction of a criterion for inclusion of this correction factor, based on a test for the HO2 steady state, results in a generally applicable three-step chemical-kinetic description for hydrogen–air combustion that possesses reasonable accuracy for most computational purposes.

Collective motion and density fluctuations in bacterial colonies

Flocking birds, fish schools, and insect swarms are familiar examples of collective motion that plays a role in a range of problems, such as spreading of diseases. Models have provided a qualitative understanding of the collective motion, but progress has been hindered by the lack of detailed experimental data. Here we report simultaneous measurements of the positions, velocities, and orientations as a function of time for up to a thousand wild-type Bacillus subtilis bacteria in a colony. The bacteria spontaneously form closely packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail. The probability of finding clusters with large numbers of bacteria grows markedly as the bacterial density increases. The number of bacteria per unit area exhibits fluctuations far larger than those for populations in thermal equilibrium. Such "giant number fluctuations" have been found in models and in experiments on inert systems but not observed previously in a biological system. Our results demonstrate that bacteria are an excellent system to study the general phenomenon of collective motion.

Online measurement of particle size distribution during crystallization using ultrasonic spectroscopy

Particle growth during crystallization of paracetamol was monitored on-line using a new modified method based on ultrasonic spectroscopy. The model was earlier developed and tested with inert particles systems and accounts for low angle scattering and probe geometry. A graphic user interface was developed and integrated with the model based deconvolution algorithm for real-time data acquisition, analysis and display of results. The crystal growth and changes in size distribution were measured during the crystallization of paracetamol from paracetamol–isopropanol–water solution. A simplified pre-calibration procedure using acoustic velocity to estimate solution properties was established. The model based particle size distribution showed good agreement with offline measurements using laser diffraction analysis of a sample retrieved from the crystallizer.

SET‐LRP of acrylates in air

AbstractSingle Electron Transfer‐Living Radical Polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with well defined topology. In SET‐LRP, certain combinations of solvents and ligands facilitate the disproportionation of in situ generated Cu(I) species into “nascent” Cu(0) and Cu(II) species. A combination of heterogeneous and “nascent” Cu(0) activation yields polymers with very high chain end functionality. Under suitable conditions the tolerance toward oxygen must be increased since Cu(0), the activator in SET‐LRP, acts as an oxygen scavenger in all inert gas purification systems. Here we demonstrate that SET‐LRP of methyl acrylate can be conducted in the presence of air. The addition of a small amount of reducing agent hydrazine hydrate to the reaction mixture reduces Cu2O generated by the oxidation of Cu(0) with air, regenerating Cu(0) and allowing for the synthesis of polymers with predictable molecular weight and perfect retention of chain end functionality. The kinetics plots obtained under these conditions were identical to these generated by degassed samples. High conversions were achieved within a very short reaction time. In these SET‐LRP experiments, the reagents were not deoxygenated or subjected to standard degassing procedures such as freeze‐pump‐thaw or nitrogen sparging. This simple SET‐LRP procedure provides an efficient and economical approach to the synthesis of functional macromolecules. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1190–1196, 2010

Gas-freeing of crude oil tanks – analysis using numerical simulation

Marine gas-freeing is a seldom-examined operation that takes place on board oil tankers ahead of some cargo transitions and tank maintenance/inspection cycles. Since the introduction of inert gas systems (IGS), tanker explosions have been minimised, but the issue of toxic vapours inside the tank still exists. Another issue relating to gas-freeing concerns the actual time required to ensure gas-free conditions; there are no regulatory considerations for the minimum times for gas-freeing, which stands in contrast to regulations concerning other areas on board a vessel.Through the use of modern computational methods, gas-freeing processes have been modelled and simulated in order to determine the progression of gas-freeing with regards to examining the concentration and distribution of vapours inside the tank during the procedure, as well as studying the decrease in total average concentration with regards to forming a simple qualitative model to predict the time required to gas-free given certain initial conditions.

Eliminating explosions [aircraft safety

The paper presents the new onboard inert gas generator systems (OBIGGS), which prevent the ignition of fuel tank vapours in aircraft by inerting the tank with nitrogen enriched air. This nitrogen generation technology helps airlines comply with new FAA rules aimed at increasing safety in the air.

Modeling and measurement of glass transition temperatures of energetic and inert systems

AbstractIn this article, measurements of glass transition temperature (Tg) changes of two energetic material blend systems were carried out using the differential scanning calorimetry (DSC) technique. On one hand, experimental Tg values were compared to those predicted by the additivity model, Fox and Pochan equations, and, on other hand, to atomistic molecular dynamics simulation results performed in this work. The two blend systems studied were both composed of a polymer, either the inert hydroxyl‐terminated polybutadiene (HTPB) or the energetic polyglycidylazide (GAP), and smaller molecules, which acted as plasticizers, dioctyl adipate (DOA), or glycidylazide oligomers (Gp1). Modeling results show deviations from experimental data, which varied from 5 to 20 K over an absolute scale for pure components and blends. A good fit was found when predicting the effect of adding smaller molecules to HTPB. Simulations were particularly useful for the blend in which the glass transition temperature of one component, DOA, was not experimentally measurable, due to the high crystallinity of the small DOA molecule. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.

Wetting kinetics of a hypo-eutectic Al–Si system

This study is devoted to investigation of spreading of a hypo-eutectic Al 8Si system over a flat Al surface. Wetting kinetics was studied using a real time in situ monitoring of the triple line movement facilitated by a hot-stage microscopy system under controlled atmosphere. Analysis of the validity of the classic Tanner's law correlation developed for inert wetting systems is performed. A good agreement of the power relationship between the triple line location and time was established. The dispersion of the n-power exponent magnitude is between 9 and 13, with an average value of 11.

Comparison of Wicke–Kallenbach and Graham's diffusion cells for obtaining transport characteristics of porous solids

Counter-current gas diffusion measurements on a series of porous solids covering a broad range of pore sizes (mean pore radii between 78 nm and 10 μ m ) were performed in the Wicke–Kallenbach and Graham's diffusion cells. Mutual agreement of diffusion fluxes from both cells was found in the whole range of tested pore radii and inert gas systems. For pore materials with mean pore radii exceeding 5 μ m the experimentally unavoidable tiny total pressure gradient induces additional permeation flow which precludes the use of Graham's law for evaluation of transport parameters of the porous solids. Transport parameters together with 95% confidence regions were determined for porous materials with pore radii up to 5 μ m and the prevailing diffusion mechanism, intimately connected with the shape of confidence regions, was estimated.

Nanostructured bioceramics for maxillofacial applications

Biomaterials science and technology have been expanding tremendously the recent years. The results of this evolution are obvious in maxillofacial applications especially with the contemporary development of Nanotechnology. Among biomaterials, bioceramics possess a specific field due to various interactions with the biological tissues. The combination of bioceramics and nanotechnology has resulted in enhanced skeletal interactions in maxillofacial applications. Nanotechnology secures better mechanical properties and more effective biological interactions with jaws. The main production methods for the synthesis of nanostructured materials include plasma arcing, chemical vapour deposition, sol-gel and precipitation. The bioceramics in Dentistry comprise inert, bioactive, resorbable and composite systems. The purpose of the present article is to describe the available nanotechnology methods and how these could be addressed to synthesise maxillofacial bioceramics with advanced properties for better biological applications. Additionally, it describes specific clinical applications in maxillofacial surgery of these biomaterials--either by themselves or in combination with others--that can be promising candidates for bone tissue engineering. Such applications include replacement of lost teeth, filling of jaws defects or reconstruction of mandible and temporomandibular joint.

Dissolutive wetting in the Bi–Sn system

The isothermal dissolutive wetting behavior of various Bi–Sn alloys on pure Bi substrates was studied at 250 °C using the sessile drop technique. Wetted radius and apparent dynamic contact angle were recorded as a function of time. Sequential quenching and metallographic cross-sectioning were employed to investigate the temporal evolution of the S/L interface and the complete configuration of the contact line region. The macroscopic total contact angle was found to be close to 90° during spreading for the majority of Bi–Sn alloys investigated. The contact line mobility relationship, based on apparent dynamic contact angle, showed certain similarities to a universal correlation for partially wetting inert systems. Additional discussions of grain boundary effects and mass transport are presented.

Micro ultrasonic welding: joining of chemically inert polymer microparts for single material fluidic components and systems

This paper presents a novel powerful micro joining process—the ultrasonic welding of real micro polymer parts. It seems to be especially suited for the manufacturing of single material, chemically inert plastic microfluidic components and systems for applications in the field of pharmaceutics, biotechnology and life sciences as well as for high temperature polymer fluidic microdevices. The performance of this ‘micro ultrasonic welding’ process, alone using a pneumatic standard ultrasonic welding machine, is demonstrated by the example of covering and sealing microchannels and assembling a piezo-driven micropump.

Collision Relaxation of Highly Vibrationally Excited SO2 by CO in A Supersonic Beam

AbstractCollision relaxation cross sections of a single, highly vibrationally excited level in the ground electronic state of SO2 at 44877.52 cm−1 above the zero‐point by the collision partner CO has been measured in a supersonic expansion using the kinetic quantum beat spectroscopic technique. The depopulation cross section at 14.5 K for this SO2*‐CO system has been determined to be 75 Å2, while the dephasing cross section is 22 Å2. Comparison with previously measured cross sections for the SO2*‐SO2, SO2*‐inert gases systems at room temperature using a similar spectroscopic approach reveals both the long range interaction and repulsive force contributions to the relaxation cross sections of highly vibrationally excited molecules.

Effect of drug particle size in ultrasound compacted tablets: Continuum percolation model approach

The main objective of this work is to study the influence of the drug particle size on the pharmaceutical availability of ultrasound compacted tablets. Inert matrix systems containing different drug particle sizes were prepared using both, an ultrasound-assisted press and a traditional eccentric machine. Potassium chloride was used as drug model and Eudragit ® RS-PM as matrix forming excipient. The excipient particle size was kept constant. The cross-sectional microphotographs of ultrasound tablets show the existence of a quasi-continuum medium. Keeping constant the drug load, US-tablets showed very similar release rates, whereas for traditional tablets, an increase in the particle size resulted in a clear decrease in the release rate. In these tablets, the excipient forms an almost continuum medium. In an infinite theoretical system of these characteristics, the size of the drug particles will not modify the percolation threshold. The percolation of the excipient in this system can be assimilated to a continuum percolation model. In accordance with the proposed model, a lower influence of the drug particle size on the drug release rate was obtained for the US-tablets in comparison with traditional tablets. This fact can be indicative of the similarity of the drug percolation thresholds in these systems.

Cytoskeletal remodelling and slow dynamics in the living cell

The cytoskeleton (CSK) is a crowded network of structural proteins that stabilizes cell shape and drives cell motions. Recent studies on the dynamics of the CSK have established that a wide variety of cell types exhibit rheology in which responses are not tied to any particular relaxation times and are thus scale-free. Scale-free rheology is often found in a class of materials called soft glasses, but not all materials expressing scale-free rheology are glassy (see plastics, wood, concrete or some metals for example). As such, the extent to which dynamics of the CSK might be regarded as glassy remained an open question. Here we report both forced and spontaneous motions of microbeads tightly bound to the CSK of human muscle cells. Large oscillatory shear fluidized the CSK matrix, which was followed by slow scale-free recovery of rheological properties (aging). Spontaneous bead motions were subdiffusive at short times but superdiffusive at longer times; intermittent motions reflecting nanoscale CSK rearrangements depended on both the approach to kinetic arrest and energy release due to ATP hydrolysis. Aging, intermittency, and approach to kinetic arrest establish a striking analogy between the behaviour of the living CSK and that of inert non-equilibrium systems, including soft glasses, but with important differences that are highly ATP-dependent. These mesoscale dynamics link integrative CSK functions to underlying molecular events, and represent an important intersection of topical issues in condensed matter physics and systems biology.

Gold Glyconanoparticles as Probes to Explore the Carbohydrate‐Mediated Self‐Recognition of Marine Sponge Cells

Cell aggregation in the red-beard marine sponge Microciona prolifera is mediated by a 2 10 kDa proteoglycan-like macromolecular aggregation factor (MAF), and is based on two highly polyvalent functional properties; a Ca-dependent proteoglycan self-interaction and a Ca-independent cell-binding activity. MAF, the first circular proteoglycan described, is composed of two N-glycosylated proteins, MAFp3 and MAFp4, with twenty units of each glycoprotein forming the central ring and the radiating arms, respectively. Each MAFp3 carries one or two copies of a 200 kDa acidic glycan, g-200, whereas each MAFp4 carries about 50 copies of a 6 kDa glycan, g-6. The MAFp4 arms of the sunburst-like proteoglycan are linked to cell-surface binding receptors, while the MAFp3 ring exposes the g-200 glycans so that they can engage in the Ca-dependent self-association (for a detailed review, see ref. [4]). By making use of MAF-specific monoclonal antibodies, it could be demonstrated that the self-association of MAF occurs through highly repetitive epitopes on the g-200 glycan. One of these epitopes was shown to be the sulfated disaccharide GlcpNAc3S(b1–3)Fucp. To gain insight into the role of carbohydrate interactions in MAF self-aggregation, we designed a challenging system for mimicking the g-200 self-association. By using the synthetic sulfated disaccharide, multivalently presented as a bovine serum albumin conjugate, and surface plasmon resonance spectroscopy, it was shown that Ca-dependent carbohydrate self-recognition is a major force in the g-200 association phenomenon. Gold glyconanoparticles have been successfully used as inert multivalent systems to explore either carbohydrate self-interactions or carbohydrate binding to proteins. In the present study, water-soluble gold glyconanoparticles coated with synthetic carbohydrates related to the sulfated disaccharide fragment (Scheme 1) were used as multivalent systems to investigate the g-200 glycan–glycan interaction by transmission electron microscopy (TEM). Very recently, an NMR study of intact MAF glycans suggested the presence of a-Fuc residues. However, earlier structural analysis of oligosaccharide fragments obtained from a partial acid hydrolysate of the g-200 glycan could not identify the anomeric configuration of the fucose residue in these fragments. 16] Therefore, gold glyconanoparticles coated with the aor the b-anomer (Au-1a and Au-1b) of the native sulfated disaccharide epitope were used in the aggregation experiments. The importance of each of the two monosaccharide units for the self-recognition process of the disaccharide epitope was determined by studying the gold glyconanoparticles Au-2 and Au-3. The three gold glyconanoparticle systems Au-4 (a-l-Fucp replaced by a-l-Galp), Au-5 (bd-GlcpNAc3S replaced by b-d-GlcpNAc), and Au-6 (b-dGlcpNAc3S replaced by b-d-Glcp3S) were used to evaluate the relevance of the modified sites in the self-recognition process. Scheme 1. Gold glyconanoparticles Au-1a/b to Au-6, related to the MAF sulfated disaccharide epitope.