Velocity-independent microfluidic flow cytometry

Pressure-driven flow in microfluidic channels is characterized by a distribution of velocities. This distribution makes it difficult to implement conventional flow cytometry data analysis. We have demonstrated a method to measure velocity as an independent parameter when performing microfluidic flow cytometry. This method allows velocity-independent analysis of particles such as beads or cells, and allows flow cytometry analysis of extended objects, such as long DNA molecules. It allows accurate flow cytometry in transient and nonuniform flows. This general measurement method could be used in the future to measure the velocity of particles in a variety of existing microfluidic devices without the need for changes in their design.     

Transfer reactions induced by 17, 18O on 12, 13C at c.m. energies between 12.6 TO 14.0 MeV

Angular distributions for one-neutron and many-nucleon transfer reactions were measured in the systems ^{17, 18}O and ^{12, 13}C at c.m. energies between 12.6 to 14.0 MeV. All the cross sections were analyzed in terms of the full-recoil finite-range DWBA model. For multi-nucleon transfer processes an inert cluster transfer was assumed. The sensitivity of DWBA calculations to various parameter sets is discussed, and the effect of the no-recoil approximation on the phase and magnitude of the transfer amplitude is studied. For one-neutron transfer reactions the forward part of the angular distributions was reproduced reasonably well by the DWBA model, yielding satisfactory spectroscopic information. The rise of the cross section at the backward angles was not reproduced by the DWBA model. Possible contributions of cluster-exchange and compound-nucleus reactions are discussed. For multi-nucleon transfer reactions poorer fits were obtained, particularly in the ¹⁸O+¹²C system.     

Formation of inclusion organoactinide complexes with boron-containing macrocycles

Reaction of the organoactinide complexes (C5Me5)2AnMe2 (An = Th, U) with catecholborane yields an inclusion complex where the actinide is encapsulated inside a 15-membered, hexaoxo, trianionic macrocycle built from alternating catechol and catecholborate fragments. In the presence of LiOH, a dimer of two encapsulated actinide macrocycles is formed. The X-ray molecular structure for all the complexes is presented.     

Experimental measurement of the strength of a C alpha-H...O bond in a lipid bilayer

Due to the apolar nature of the lipid bilayer, the weak Calpha-H...O H-bond is thought to contribute significantly toward the stability of transmembrane helical bundles such as glycophorin A (GPA). Here for the first time we measured the strength of such a bond, using vibrational frequency shifts of a dimeric and nondimeric variants of GPA containing a Gly CD2 label. Although the resulting estimated bond strength of 0.88 kcal/mol is relatively weak, several such bonds could contribute significantly toward bundle stabilization.     

Testing monotonicity over graph products

We consider the problem of monotonicity testing over graph products. Monotonicity testing is one of the central problems studied in the field of property testing. We present a testing approach that enables us to use known monotonicity testers for given graphs G₁, G₂, to test monotonicity over their product G₁ × G₂. Such an approach of reducing monotonicity testing over a graph product to monotonicity testing over the original graphs, has been previously used in the special case of monotonicity testing over [n]^d for a limited type of testers; in this article, we show that this approach can be applied to allow modular design of testers in many interesting cases: this approach works whenever the functions are boolean, and also in certain cases for functions with a general range. We demonstrate the usefulness of our results by showing how a careful use of this approach improves the query complexity of known testers. Specifically, based on our results, we provide a new analysis for the known tester for [n]^d which significantly improves its query complexity analysis in the low‐dimensional case. For example, when d = O(1), we reduce the best known query complexity from O(log ²n/ε) to O(log n/ε). © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008     

Evolution of the mean instantaneous intensity in fibers affected by polarization mode dispersion

It is shown that the mean instantaneous intensity (MII) of a pulse propagating in an optical fiber affected by polarization mode dispersion is related to the frequency autocorrelation of the fiber's Jones matrix through a Fourier transform. A simple derivation of the diffusion equation satisfied by the MII and the autocorrelation function of a Jones matrix is described.     

Electrospinning of ultrahigh‐molecular‐weight polyethylene nanofibers

The electrospinning method has been employed to fabricate ultrafine nanofibers of ultrahigh‐molecular‐weight polyethylene for the first time with a mixture of solvents of different dielectric constants and conductivities. The possibility of producing highly oriented nanofibers from ultrahigh‐molecular‐weight polymers suggests new ways of fabricating ultrastrong, porous, and single‐component nanocomposite fibers with improved properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 766–773, 2007     

Polyoxometalate-Engineered Building Blocks with Gold Cores for the Self-Assembly of Responsive Water-Soluble Nanostructures

The controlled assembly of gold nanoparticles (AuNPs) with the size of quantum dots into predictable structures is extremely challenging as it requires the quantitatively and topologically precise placement of anisotropic domains on their small, approximately spherical surfaces. We herein address this problem by using polyoxometalate leaving groups to transform 2 nm diameter gold cores into reactive building blocks with hydrophilic and hydrophobic surface domains whose relative sizes can be precisely tuned to give dimers, clusters, and larger micelle-like organizations. Using cryo-TEM imaging and ¹H DOSY NMR spectroscopy, we then provide an unprecedented “solution-state” picture of how the micelle-like structures respond to hydrophobic guests by encapsulating them within 250 nm diameter vesicles whose walls are comprised of amphiphilic AuNP membranes. These findings provide a versatile new option for transforming very small AuNPs into precisely tailored building blocks for the rational design of functional water-soluble assemblies.