Coalescence Method Research Articles

A versatile method for preparation of hydrated microbial–latex biocatalytic coatings for gas absorption and gas evolution

We describe a latex wet coalescence method for gas-phase immobilization of microorganisms on paper which does not require drying for adhesion. This method reduces drying stresses to the microbes. It is applicable for microorganisms that do not tolerate desiccation stress during latex drying even in the presence of carbohydrates. Small surface area, 10-65 μm thick coatings were generated on chromatography paper strips and placed in the head-space of vertical sealed tubes containing liquid to hydrate the paper. These gas-phase microbial coatings hydrated by liquid in the paper pore space demonstrated absorption or evolution of H₂, CO, CO₂ or O₂. The microbial products produced, ethanol and acetate, diffuse into the hydrated paper pores and accumulate in the liquid at the bottom of the tube. The paper provides hydration to the back side of the coating and also separates the biocatalyst from the products. Coating reactivity was demonstrated for Chlamydomonas reinhardtii CC124, which consumed CO₂ and produced 10.2 ± 0.2 mmol O₂ m⁻² h⁻¹, Rhodopseudomonas palustris CGA009, which consumed acetate and produced 0.47 ± 0.04 mmol H₂ m⁻² h⁻¹, Clostridium ljungdahlii OTA1, which consumed 6 mmol CO m⁻² h⁻¹, and Synechococcus sp. PCC7002, which consumed CO₂ and produced 5.00 ± 0.25 mmol O₂ m⁻² h⁻¹. Coating thickness and microstructure were related to microbe size as determined by digital micrometry, profilometry, and confocal microscopy. The immobilization of different microorganisms in thin adhesive films in the gas phase demonstrates the utility of this method for evaluating genetically optimized microorganisms for gas absorption and gas evolution.

Large‐scale species delimitation method for hyperdiverse groups

Accelerating the description of biodiversity is a major challenge as extinction rates increase. Integrative taxonomy combining molecular, morphological, ecological and geographical data is seen as the best route to reliably identify species. Classic molluscan taxonomic methodology proposes primary species hypotheses (PSHs) based on shell morphology. However, in hyperdiverse groups, such as the molluscan family Turridae, where most of the species remain unknown and for which homoplasy and plasticity of morphological characters is common, shell-based PSHs can be arduous. A four-pronged approach was employed to generate robust species hypotheses of a 1000 specimen South-West Pacific Turridae data set in which: (i) analysis of COI DNA Barcode gene is coupled with (ii) species delimitation tools GMYC (General Mixed Yule Coalescence Method) and ABGD (Automatic Barcode Gap Discovery) to propose PSHs that are then (iii) visualized using Klee diagrams and (iv) evaluated with additional evidence, such as nuclear gene rRNA 28S, morphological characters, geographical and bathymetrical distribution to determine conclusive secondary species hypotheses (SSHs). The integrative taxonomy approach applied identified 87 Turridae species, more than doubling the amount previously known in the Gemmula genus. In contrast to a predominantly shell-based morphological approach, which over the last 30 years proposed only 13 new species names for the Turridae genus Gemmula, the integrative approach described here identified 27 novel species hypotheses not linked to available species names in the literature. The formalized strategy applied here outlines an effective and reproducible protocol for large-scale species delimitation of hyperdiverse groups.

Neutral communities in fragmented landscapes

Habitat fragmentation displays a crucial role in conservation biology. Despite this, little is known about the detailed ecological consequences of habitat fragmentation due to the scarce number of controlled experimental surveys. The species–area relationship, a fundamental concept in ecology, requires the understanding of the fragmentation effects in a long term perspective, which turns this task even harder. Here we address the spatial patterns of species distribution in fragmented landscapes, assuming a neutral community model. We study the species area relationship and how its shape changes as the landscape becomes more fragmented. Recent investigations, based on extensive computer simulation, have contributed to establish some definite conclusions in the study of non‐fragmented landscapes: the existence of a three‐regime or two‐regime scenario for the species–area relationship, the emergence of a power‐law regime at intermediate scales and the augment of the species–area exponent z with the speciation rate. Despite the recent efforts, some other questions remain, such as the dependence of z in the whole range of the speciation rate. Questions like these are currently debated but generalizations cannot be drawn. This is the first paper, to our knowledge, that uses the coalescence method and neutral theory to examine biodiversity on more complex spatial structures. Our simulation results corroborate that the fragmentation plays a crucial role in shaping the species–area relationship, by determining the existence and extension of the power‐law regime associated with small and intermediate areas. On the other hand, when individuals are allowed to disperse over longer distances the species–area relationship now displays the classic triphasic pattern, and the intermediate regime, which is well described by a power‐law, is established even for highly fragmented landscapes.

Discrete Bubble Model for Prediction of Bubble Behavior in 3D Fluidized Beds

AbstractA discrete bubble model has been developed taking into account multiple bubble‐bubble interactions and a delayed coalescence method. The obtained simulation results were compared with experimental data reported in literature. The simulation results predicted by the developed model indicate clearly that the multiple interactions of bubbles lead to more reasonable results than those predicted by a binary interaction model. In addition, two types of interaction models were applied and predicted results were compared. The frequency of gas bubbles passing through the bed cross section versus bed height follows the same trend as the experimental data.

VCO Production from Fresh Old Coconut Bunch by Circulating and Pumping Method

VCO (Virgin Coconut Oil) is one of coco-diesel source, made without high heating and chemicals. Commercial processes production, such fermentation and centrifugation usually need more time and expensive in cost and investment. Circulating by pumping through a nozzle is a new process method invented to produce VCO. The process followed by coalescence method, breaking emulsion by hitting particles through pipe and nozzle. The problem of this method was that the product gave lower yield than another method and not yet qualified. This research was purposed to discover correlation between pressure and time of circulation variables against yield and content (FFA, Peroxide, water content) represented by SNI (national Indonesian standard). Producing VCO initiated by producing coconut milk from fresh old coconut, then each 1 litre milk were pumped through the pipe and nozzle with variation of circulations pressures and time. The results were decanted for 10 hours so the oil and water would be separated. The oil at upper layer was taken as final product. Then the last step was analysed the oils and oil cake (blondo). The results showed that pressure and time of circulating variables gave impact to the yield. On optimum variables, 2 atm pressure and 15 minutes of circulating gave better results with 97% yield. This operating variables also affecting oil quality. The minimum water content is 0.1%, free fatty acid is 0.18% and peroxide value is 2 mg/kg eq. The results showed that all of parameters meet the SNI standard.

Ab Initio Study of Lithiathion of the Si4– Cluster

The potential energy surfaces of the Li(n)Si(4)(-) (n = 0-5) clusters were explored using the Kick Coalescence method. We found that, for those systems with n ≤ 2, the butterfly and parallelogram Si(4)(2-) kernels prevail as building blocks; however, when n ≥ 3, the Si(4)(4-) tetrahedral kernel, which is commonly found in heavier alkali monosilicides, MSi (M = Na, K, Rb, Cs), arises as the prevailing building block. In addition, by a natural population analysis (NPA) we found that the maximum charge transfer -4 from Li atoms to Si atoms is attained when n = 3. The addition of more Li atoms to the Si(4)(4-) system does not increase the charge transfer, but keeps it almost constant at the maximum value. We also calculated theoretical vertical electron detachment energies (VDEs) for low-lying isomers of the Li(n)Si(4)(-) (n = 0-4) clusters in order to facilitate their experimental identification.

Directed Calcium Chloride Coalescence Method for Preparation of Silver Nanocubes

Controlling the size, shape, and structure of metal nanoparticles is very important because of the strong correlation between these parameters and their resulting optical, electrical, and catalytic properties. This paper describes a directed calcium chloride coalescence method, based upon incubating a silver colloid with an aqueous solution of CaCl(2), for preparation of silver nanocubes with a particle size of 270 to 950 nm. The method avoids the use of nonvolatile surfactants and polymers, which may be adsorbed onto the silver nanocubes and interfere with their possible applications in catalysis and analytical devices based on surface-enhanced Raman scattering (SERS) spectroscopy. The nanocubes show good SERS activity in the presence of adsorbed 4-mercaptobenzoic acid (4-MBA) with excitation at 632.8 nm, and the enhancement factor reaches approximately 7 x 10(5). The nanocubes are produced in a simple and cost-effective way, and they are expected to play an important role in the development of SERS-based analytical devices. The method may represent a novel route for preparation of metal nanocubes, which is a subject of intense interest.

The [Pd(bipy)]2+ “merry-go-round”: Insights into the lability of the Pd–N bond

Abstract Two tripods (1 and 2) featuring pyrimidinyl pendant arms have been synthesized from 5-(1H-pyrazol-3-yl)-pyrimidine (5) and 1,3,5-tribromomethylbenzene derivatives. Reaction with three equivalents of [Pd(bipy)](NO3)2 to form a macrotricycle closed by palladium coordination unexpectedly afforded the mononuclear species [Pd(1)(bipy)]2+ and [Pd(2)(bipy)]2+. These complexes show fluxional behavior on the 1H NMR timescale, the [Pd(bipy)]2+ fragment hopping between the pyrimidinyl coordinating moieties. The ΔGc‡’s estimated by the coalescence method are temperature independent, which means that ΔSc‡ = 0. This indicates that the “merry-go-round” process of [Pd(bipy)]2+ occurs intramolecularly, presumably by nucleophilic attack of the free pyrimidinyl arm to the bound Pd2+ center. This phenomenon permits to quantify the lability of the Pd–N coordination bond, the average ΔGc‡ ≈ ΔHc‡ value being 70 kJ mol–1.

Functionally Rigid and Degenerate Molecular Shuttles

The preparation and dynamic behavior of two functionally rigid and degenerate [2]rotaxanes (14 PF(6) and 24 PF(6)) in which a pi-electron deficient tetracationic cyclophane, cyclobis(paraquat-p-phenylene) (CBPQT(4+)) ring, shuttles back and forth between two pi-electron-rich naphthalene (NP) stations by making the passage along an ethynyl-phenylene-(PH)-ethynyl or butadiyne rod, are described. The [2]rotaxanes were synthesized by using the clipping approach to template-directed synthesis, and were characterized by NMR spectroscopic and mass spectrometric analyses. (1)H NMR spectra of both [2]rotaxanes show evidence for the formation of mechanically interlocked structures, resulting in the upfield shifts of the resonances for key protons on the dumbbell-shaped components. In particular, the signals for the peri protons on the NP units in the dumbbell-shaped components experienced significant upfield shifts at low temperatures, just as has been observed in the flexible [2]rotaxanes. Interestingly, the resonances for the same protons did not exhibit a significant upfield shift at 298 K, but rather only a modest shift. This phenomenon arises from the much reduced binding of the ethynyl-NP unit compared to the 1,5-dioxy-NP unit. This effect, in turn, increases the shuttling rate when compared to the 1,5-dioxy-NP-based rotaxane systems investigated previously. The kinetic and thermodynamic data of the shuttling behavior of the CBPQT(4+) ring between the NP units were obtained by variable-temperature NMR spectroscopy and using the coalescence method to calculate the free energies of activation (DeltaG(c) ( not equal)) of 9.6 and 10.3 kcal mol(-1) for 14 PF(6) and 24 PF(6), respectively, probed by using the rotaxane's alpha-bipyridinium protons. The solid-state structure of the free dumbbell-shaped compound (3) shows the fully rigid ethynyl-PH-ethynyl linker with a length (8.1 A) twice as long as that (3.8 A) of the butadiyne linker. Full-atomistic simulations were carried out with the DREIDING force field (FF) to probe the degenerate molecular shuttling processes, and afforded shuttling energy barriers (DeltaG( not equal)=10.4 kcal mol(-1) for 14 PF(6) and 24 PF(6)) that are in good agreement with the experimental values (DeltaG(c) ( not equal)=9.6 and 10.3 kcal mol(-1) for 14 PF(6) and 24 PF(6), respectively, probed by using their alpha-bipyridinium protons).

Production of fragments with and without strangeness within a combined BUU + SMM approach

The formation of hypernuclei in hadron-induced reactions and in heavy-ion collisions within a combination of a covariant transport model and a statistical fragmentation approach is investigated. We study the applicability and limitations of such a hybrid approach by comparing fragmentation data in heavy-ion collisions and proton-induced reactions. It turns out that the combined approach describes fairly well multiplicities and momentum spectra of fragments. We thus extend the model by including strangeness degrees of freedom in the fragmentation process, modeled by a phase-space coalescence method. We provide theoretical predictions on spectra and on inclusive cross sections of light hypernuclei for the future experiments on hypernuclear physics at the new GSI facility.

Microencapsulation of hydrophilic solid powder as fire retardant agent with epoxy resin by droplet coalescence method

AbstractTo give water resistance to Bistetrazol–diammonium (BHT–2NH3) as a fire retardant agent, microencapsulation with epoxy resin was tried by the droplet coalescence method. In this method, two kinds of epoxy resin droplets were prepared; one is the larger epoxy resin droplet containing BHT–2NH3 as a core material and the other the smaller droplets containing Imidazole as a gelation agent. The larger epoxy resin droplets were made to coalesce with the many smaller droplets during the microencapsulation process to prepare microcapsules. In the experiment, the agitation velocities for preparation of the droplets and for coalescence were mainly changed. With increase in the impeller speed, the content of core material increased, became maximum because of increase in the coalescence frequency, and then decreased because of breakup of droplets. With increase in the impeller speed, the leakage ratio of core material decreased, became minimum, and then increased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.

Encapsulation of Protonated Diamines in a Water-Soluble, Chiral, Supramolecular Assembly Allows for Measurement of Hydrogen-Bond Breaking Followed by Nitrogen Inversion/Rotation

Amine nitrogen inversion, difficult to observe in aqueous solution, is followed in a chiral, supramolecular host molecule with purely rotational T-symmetry that reduces the local symmetry of encapsulated monoprotonated diamines and enables the observation and quantification of Delta G (++) for the combined hydrogen-bond breaking and nitrogen inversion/rotation (NIR) process. Free energies of activation for the combined hydrogen-bond breaking and NIR process inside of the chiral assembly were determined by the NMR coalescence method. Activation parameters for ejection of the protonated amines from the assembly confirm that the NIR process responsible for the coalescence behavior occurs inside of the assembly rather than by a guest ejection/NIR/re-encapsulation mechanism. For one of the diamines, N, N, N', N'-tetramethylethylenediamine, the relative energy barriers for the hydrogen-bond breaking and NIR process were calculated at the G3(MP2)//B3LYP/6-31++G(d,p) level of theory, and these agreed well with the experimental data.

Two computational methods for describing size selected nanocluster growth and obtaining accurate cluster size distributions

Describing nanocluster growth and obtaining size distributions of clusters near kinetically determined metastable states is a computationally difficult problem because of the slow convergence of size distributions near the metastable state. In this work, we examine the size selected growth of nanoclusters in such situations by using a mesoscopic reaction kinetic model (RKM), and introduce two effective computational schemes for describing the size selection and obtaining size distributions. The first method is based on the particle coalescence method (PCM), where the configuration space of clusters is sampled by using the rejection-free Bortz–Kalos–Lebowitz algorithm. The second method is based on direct numerical integration of the RKM by using the transformation referred to as the master equation discretization (MED) scheme. We compare the computational reliability of the PCM and RKM discretization methods in a typical case of 2D-nanocluster growth with size dependent energetics and show that both of these approaches allows us to study in detail the evolution of the size distribution in all stages of the growth.

Optimal conditions for submonolayer nanoisland growth in ion beam assisted deposition

We study the optimal conditions for nanoisland growth in ion beam assisted deposition (IBAD). This situation occurs when adatom islands remain small enough to prevent the onset of three-dimensional growth, while at the same time preventing ion-induced surface erosion. To this end, we develop a rate equation model of IBAD, which embodies continuous deposition of adatoms and creation of vacancies, recombination of vacancies at adatom island edges, as well as recombination of adatoms at vacancy island edges. These rate equations are solved by numerical simulations based on the particle coalescence method. To determine the optimal growth condition, we find the largest mean size of the vacancy islands leading to their survival. We show that at this onset between the rough and smooth layer-by-layer growth regimes there is a simple exponential relation between the largest size of the vacancy islands and the external control parameters of the growth.

Synthesis, X-ray crystallographic, and dynamic 1H NMR studies of crown-tetrathia[3.3.3.3]metacyclophanes—conformational control by cooperative intramolecular C–H⋯π interaction both in solid state and in solution

Crown-tetrathia[3.3.3.3]metacyclophanes 3a– c were synthesized via intermolcular coupling reaction in 22–30% yields. X-ray crystal analysis of 3b revealed that it adopted a perpendicular conformation ( 3b- B or 3b- C ) in which two aromatic rings were inclined to be perpendicular to the opposite aromatic rings, driving two internal methyl groups into the π-cloud of the corresponding benzene rings. Furthermore, this perpendicular structural feature led to benzylic protons of thia-bridges being in close proximity to the adjacent aromatic rings. As a result, the induced upfield shifts for the two internal methyl protons and four benzylic protons were clearly observed in dynamic 1H NMR spectra at low temperature, indicating that the intramolecular C–H⋯π interaction became increasingly important at low temperature. The energy barrier for inter-conversion between 3b- B and 3b- C was estimated to be 12.1 kcal mol −1 by using a coalescence method. The total stabilization enthalpy of the C–H⋯π interactions was quantitatively calculated to be 7.9±0.8 kcal mol −1 by the dynamic NMR spectroscopy. In contrast, 3a showed two non-interconvertible conformers at room temperature, which tended to interconvert at elevated temperature, however, many conformers co-existed at low temperature.

Island size distributions in submonolayer growth in hyperthermal deposition

In ion beam assisted deposition (IBAD) and other related hyperthermal deposition techniques island growth is in clear contrast with growth obtained without bombardment, and a greatly enhanced density of small islands is observed. In this contribution we study the effects of island breakup and adatom detachment on growth during IBAD using computer simulations based on the particle coalescence method. It is shown that in both cases a quasi-stationary state occurs, and a new scaling behaviour appears. The scaling properties observed are different, which makes it possible to distinguish the dominant growth mode experimentally. Results support the conclusion that, in IBAD, fragmentation and detachment explain the enhanced island density and thus promote the layer-by-layer growth.

Island growth in submonolayer deposition with aggregation and fragmentation

Island growth is studied in the case of island aggregation and break-up during submonolayer deposition. It is demonstrated that the island size distributions are of the scaling form and the mean island size has a power-law behaviour corresponding to hyperthermal deposition conditions. The corresponding scaling exponents are analytically derived and compared with the simulations by the revised particle coalescence method developed here. The scaling exponents are found to depend only on the homogeneity exponents of aggregation and fragmentation kernels.

Atropisomerism of phosphorus-containing N-aryl carbamates. Experimental and computational data

Studies by 1H NMR spectroscopy and X-ray diffraction analysis revealed hindered rotation of the aromatic substituent about the CAr—N bond in ortho-substituted (except for o-fluorine-substituted) phosphorus-containing carbamates. The energy barriers to rotation (ΔGc≠) and coalescence temperatures (Tc) determined by the coalescence method increase with increasing volume of the ortho substituent. Conformations resulting from rotation of the ortho-substituted aryl group about the CAr—N bond were analyzed by quantum-chemical methods, potential curves were constructed, and differences between the conformational energies and the heights of rotation barriers were estimated. The theoretical rotation barriers change in parallel with the experimental values of ΔGc≠; however, the theoretical values are much smaller in magnitude.

Viscosity measurement using drop coalescence in microgravity

We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Homogeneous nucleation can also be avoided due to the rapidity of the measurement using this method. The technique relies on measurements from experiments conducted in near zero gravity environment as well as highly accurate analytical formulation for the coalescence process. The viscosity of the liquid is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity for two coalescing drops. Results are presented from two sets of validation experiments for the method which were conducted on board aircraft flying parabolic trajectories. In these tests the viscosity of a highly viscous liquid, namely glycerin, was determined at different temperatures using the drop coalescence method described in here. The experiments measured the free surface velocity of two glycerin drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The liquid viscosity was determined by adjusting the computed free surface velocity values to the measured experimental data. The results of these experiments were found to agree reasonably well with the known viscosity for the test liquid used.

Structure and activity of lipid membrane biosensor surfaces studied with atomic force microscopy and a resonant mirror

Three variants of the liposome fusion (coalescence) method to produce supported lipid bilayers, containing the ganglioside GM1 on silicon nitride surfaces, were studied. The first procedure involved attachment and fusion of liposomes containing DMPC, GM1 and a small amount of biotinylated lipid (Biotin-LC-DPPE) to a streptavidin coated surface. Direct fusion of liposomes composed of a mixture of DPPC, DPPG, DPPE, GM1 and cholesterol to the surface were the second variant. The final method utilised the second type of liposomes, fused onto a streptavidin layer with a small amount of exposed hydrophobic tails. The methods produced similar lipid layers, but with different ways of attachment to the surface. The binding of cholera toxin B-subunit (CTB) towards these sensor surfaces was measured in a resonant mirror biosensor instrument and the activity and longer-term stability of the layers were examined. The prepared surfaces were also imaged by atomic force microscopy (AFM) in liquid to characterise the topography of the lipid layers. The binding efficiency of CTB towards these surfaces was discussed in terms of lipid fluidity and surface roughness.