Inverse CO2/C2H2 Separation with MFU-4 and Selectivity Reversal via Postsynthetic Ligand Exchange

Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C₂H₂ in C₂H₂/CO₂ separation processes, CO₂-selective sorbents are much less common. Here, we report the remarkable performance of MFU-4 (Zn₅Cl₄(bbta)₃, bbta=benzo-1,2,4,5-bistriazolate) toward inverse CO₂/C₂H₂ separation. The MOF facilitates kinetic separation of CO₂ from C₂H₂, enabling the generation of high purity C₂H₂ (>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C₂H₂ is excluded from MFU-4 by narrow pore windows formed by Zn−Cl groups. Postsynthetic F⁻/Cl⁻ ligand exchange was used to synthesize an analogue ( MFU-4-F ) with expanded pore apertures, resulting in equilibrium C₂H₂/CO₂ separation with reversed selectivity compared to MFU-4 . MFU-4-F also exhibits a remarkably high C₂H₂ adsorption capacity (6.7 mmol g⁻¹), allowing fuel grade C₂H₂ (98 % purity) to be harvested from C₂H₂/CO₂ mixtures by room temperature desorption.     

Two-dimensional transport behavior in PbTeBi superlattices

We report on the 2D charge transport behavior observed in PbTeBi superlattice films. The logarithmic behavior with temperature and magnetic field was observed for the samples having the thickness of the PbTe layers larger than 45 A. This 2D behavior disappeared with annealing and, eventually, the sample showed a 3D nature for the fully annealed case.     

Using Bioconjugated Nanoparticles To Monitor E. coli in a Flow Channel

A simple and portable flow channel optical detection system combined with bioconjugated luminescent nanoparticles allows the rapid detection of single bacterial cells without sample enrichment. The optical system is designed to have single‐molecule‐detection capability in a microcapillary flow channel by decreasing the laser excitation probe volume to a few picoliters, which consequently results in a low background. Specific monoclonal antibodies were immobilized on nanoparticles to form nanoparticle–antibody conjugates. The bioconjugated nanoparticles bind to the target bacteria when they recognize the antigen on the bacterium surface, thus providing a bright luminescent signal for the detection of individual bacteria cells. The high sensitivity provided by the luminescent and photostable silica nanoparticles eliminates the need for further enrichment of bacteria samples and signal amplification. This flow channel detection system is convenient and allows the detection of single bacterial cells within a few minutes.     

The good,the bad,and the tiny: a review of microflow cytometry

Recent developments in microflow cytometry have concentrated on advancing technology in four main areas: (1) focusing the particles to be analyzed in the microfluidic channel, (2) miniaturization of the fluid-handling components, (3) miniaturization of the optics, and (4) integration and applications development. Strategies for focusing particles in a narrow path as they pass through the detection region include the use of focusing fluids, nozzles, and dielectrophoresis. Strategies for optics range from the use of microscope objectives to polymer waveguides or optical fibers embedded on-chip. While most investigators use off-chip fluidic control, there are a few examples of integrated valves and pumps. To date, demonstrations of applications are primarily used to establish that the microflow systems provide data of the same quality as laboratory systems, but new capabilities-such as automated sample staining-are beginning to emerge. Each of these four areas is discussed in detail in terms of the progress of development, the continuing limitations, and potential future directions for microflow cytometers.     

Genetic algorithms: Foundations and applications

Genetic algorithms are defined. Attention is directed to why they work: schemas and building blocks, implicit parallelism, and exponentially biased sampling of the better schema. Why they fail and how undesirable behavior can be overcome is discussed. Current genetic algorithm practice is summarized. Five successful applications are illustrated: image registration, AEGIS surveillance, network configuration, prisoner's dilemma, and gas pipeline control. Three classes of problems for which genetic algorithms are ill suited are illustrated: ordering problems, smooth optimization problems, and totally indecomposable problems.     

Real meromorphic functions and linear differential polynomials

We determine all real meromorphic functions f in the plane such that f has finitely many zeros, the poles of f have bounded multiplicities, and f and F have finitely many non-real zeros, where F is a linear differential polynomial given by F = f (k) +Σk-1j=0ajf(j) , in which k≥2 and the coefficients aj are real numbers with a0≠0.     

Synthesis, purification, and characterization of phosphine oxides and their hydrogen peroxide adducts

Reactions of the tertiary phosphines R(3)P (R = Me, Bu, Oct, Cy, Ph) with 35% aqueous H(2)O(2) gives the corresponding oxides as the H(2)O(2) adducts R(3)P=O·(H(2)O(2))(x) (x = 0.5-1.0). Air oxidation leads to a mixture of products due to the insertion of oxygen into one or more P-C bonds. (31)P NMR spectroscopy in solution and in the solid state, as well as IR spectroscopy reveal distinct features of the phosphine oxides as compared to their H(2)O(2) adducts. The single crystal X-ray analyses of Bu(3)P=O and [Cy(3)P=O·(H(2)O(2))](2) show a P=O stacking motif for the phosphine oxide and a cyclic structure, in which the six oxygen atoms exhibit a chair conformation for the dimeric H(2)O(2) adduct. Different methods for the decomposition of the bound H(2)O(2) and the removal of the ensuing strongly adsorbed H(2)O are evaluated. Treating R(3)P=O·(H(2)O(2))(x) with molecular sieves destroys the bound H(2)O(2) safely under mild conditions (room temperature, toluene) within one hour and quantitatively removes the adsorbed H(2)O from the hygroscopic phosphine oxides within four hours. At 60 °C the entire decomposition/drying process is complete within one hour.     

Subjective response of people to simulated sonic booms in their homes

In order to determine the effect of the number of sonic boom occurrences on annoyance, a computer-based system was developed for studying the subjective response of people to the occurrence of simulated sonic booms in their homes. The system provided a degree of control over the noise exposure not found in community surveys and a degree of situational realism not available in the laboratory. A system was deployed for eight weeks in each of 33 homes. Each day from 4 to 63 sonic booms were played as the test subject went about his or her normal activities. At the end of the day, the test subjects rated their annoyance to the sonic booms heard during the day. The sonic booms consisted of different combinations of waveforms, levels, and occurrence rates. The experiment confirmed that the increase in annoyance resulting from multiple occurrences can be modeled by the addition of the term "10 * log(number of occurrences)" to the sonic boom level. Of several noise metrics considered, perceived level was the best annoyance predictor. Comparisons of the subjective responses to the different sonic boom waveforms found no differences that were not accounted for by the noise metrics.     

Structures and Unexpected Dynamic Properties of Phosphine Oxides Adsorbed on Silica Surfaces

Solid‐state NMR spectroscopy of selected phosphine oxides adsorbed on silica surfaces establishes the surface mobilities, even of phosphine oxides with high melting points. Crystal structures of the adducts Ph₃PO ? HOSiPh₃ and Cy₃PO ? H₂O indicate that the interactions with silica involve hydrogen bonding of the P?O group to adsorbed water and surface silanol groups.     

Two simple and rugged designs for creating microfluidic sheath flow

A simple design capable of 2-dimensional hydrodynamic focusing is proposed and successfully demonstrated. In the past, most microfluidic sheath flow systems have often only confined the sample solution on the sides, leaving the top and bottom of the sample stream in contact with the floor and ceiling of the channel. While relatively simple to build, these designs increase the risk of adsorption of sample components to the top and bottom of the channel. A few designs have been successful in completely sheathing the sample stream, but these typically require multiple sheath inputs and several alignment steps. In the designs presented here, full sheathing is accomplished using as few as one sheath input, which eliminates the need to carefully balance the flow of two or more sheath inlets. The design is easily manufactured using current microfabrication techniques. Furthermore, the sample and sheath fluid can be subsequently separated for recapture of the sample fluid or re-use of the sheath fluid. Designs were demonstrated in poly(dimethylsiloxane) (PDMS) using soft lithography and poly(methyl methacrylate) (PMMA) using micromilling and laser ablation.