Semidefinite optimization in discrepancy theory

Recently, there have been several new developments in discrepancy theory based on connections to semidefinite programming. This connection has been useful in several ways. It gives efficient polynomial time algorithms for several problems for which only non-constructive results were previously known. It also leads to several new structural results in discrepancy itself, such as tightness of the so-called determinant lower bound, improved bounds on the discrepancy of the union of set systems and so on. We will give a brief survey of these results, focussing on the main ideas and the techniques involved.     

Dense wavelength division demultiplexing using photonic crystal waveguides based on cavity resonance

We demonstrated a photonic crystal waveguide based dense wavelength division multiplexing device using the resonances in the cavities. The demultiplexing is achieved through filtering. This filtering is achieved by varying the radii of the surrounding holes of the cavity, which in turn changes the resonant wavelength of the cavity. The four wavelengths demultiplexed in the design are 0.8 nm apart in the optical region centered on 1.55 and 1.56 μm. The device designed and simulated has easy to realize structure as well as high quality factor. Two-dimensional Finite Difference Time Domain (FDTD) is chosen to do the simulation of this work.     

Carbon nanofiber reinforced syntactic foams: Degradation mechanism for long term moisture exposure and residual compressive properties

Hollow particle filled polymer matrix composites, called syntactic foams, are challenging for studies related to environmental exposure and degradation mechanisms due to the possible role of matrix, particle–matrix interface, and particle material and wall thickness. In the current study, syntactic foams reinforced with 1 wt.% vapor grown carbon nanofibers (CNFs) are subjected to water immersion and characterized for residual compressive properties under quasi-static and high strain rates. The testing is conducted on four different types of syntactic foams, fabricated with glass hollow particles of two different densities: 220 and 460 kg/m³ in 30 and 50 vol.% quantities. After a period of 6 months, a maximum of 7% weight gain is observed in the worst performing syntactic foam. The exposed specimens are tested for residual compressive properties and the results are compared with the properties of dry specimens. The quasi-static compressive strength of CNF reinforced syntactic foams is found to decrease and the modulus remained unaffected due to the moisture exposure. The high strain rate compressive strength was 1.3–2.2 times higher for wet and dry specimens compared to the quasi-static strength of the same type of syntactic foams.     

Efficient,Three-Component Synthesis of Pyrrole Derivatives Catalyzed by Iodobenzene and Oxone

A simple and highly efficient three-component method using easily available amines, nitrostyrene, and diketones in one pot has been developed for synthesis of pyrroles in the presence of catalytic amounts of iodobenzene and Oxone as oxidant. The protocol has been used to afford wide range of pyrroles in moderate to good yields.     

Novel and cost‐effective 6‐plex isobaric tagging reagent,DiART, is effective for identification and relative quantification of complex protein mixtures using PQD fragmentation

Deuterium isobaric Amine Reactive Tag (DiART) reagents facilitate relative quantification during proteomic analysis in a functionally similar manner to commercially available isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass tag (TMT) reagents. In contrast to iTRAQ and TMT, DiART reagents incorporate deuterium isotopes which significantly reduce the number of required synthesis steps and hence have potential to significantly reduce reagent production cost. We examined the capability of DiART for performing quantitative proteomic experiments using a linear ion‐trap mass spectrometer with Pulsed Q Dissociation (PQD) fragmentation. Using a synthetic peptide tagged with DiART reagent, we observed a precise mass shift of 144.79 Da on the triply charged precursor ion, which shows complete derivatization of the N‐terminus and ε‐amino group of lysine. A DiART tagged tryptic digest of bovine serum albumin showed a sequence coverage of 57.99% which was very comparable to that showed by iTRAQ, 54.77%. Furthermore, a ten protein mixture tagged with DiART reagents and mixed in 1:1:1:1:1:1 exhibited < 15% error, whereas a linear trend (slope of 1.085) was observed when tagged proteins were mixed in the ratio 2:1:2:4:10:14 and plotted against theoretical ratios. Finally, when complex cell‐wall protein mixtures from the model fungus A. nidulans were tagged with DiART reagents and mixed in different ratios, they exhibited similar trends. We conclude that DiART reagents are capable of performing quantitative proteomic experiments using PQD on a linear ion trap mass spectrometer. Copyright © 2013 John Wiley & Sons, Ltd.     

Excited State Lactim to Lactam Type Tautomerization Reaction in 5-(4-Fluorophenyl)-2-Hydroxypyridine: Spectroscopic Study and Quantum Chemical Calculation

The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) have been studied by steady state and time resolved spectroscopy in combination with quantum chemical calculations. The molecule FP2HP exists as lactim and lactam form in the ground state due to small stability difference but does not undergo lactim to lactam isomerisation due to high barrier energy. Whereas in the excited state the lactim form undergoes tautomerization producing red shifted emission of the lactam tautomer along with the local emission of the lactim form. In polar protic solvents, the barrier for lactim-lactam tautomerization rapidly decreases forming the lactam tautomer only. Temperature has pronounced effect on the excited state tautomerization equilibrium and is clearly reflected in the measured equilibrium constant (K _tau ⁰ ) and free energy change (??G⁰). Structural calculations at Hartree Fock and Density Functional Theory levels, calculated stability of the isomers in different solvents using Polarized Continuum Model and the theoretical potential energy surfaces for the ground and excited states along the proton transfer coordinate are reported for the tautomeric equilibrium of FP2HP.     

Minimizing flow time on a constant number of machines with preemption

We consider offline algorithms for minimizing the total flow time on O(1) machines where jobs can be preempted arbitrarily but migrations are disallowed. Our main result is a quasi-polynomial time approximation scheme for minimizing the total flow time. We also consider more general settings and give some hardness results.     

Chemical imaging of the surface of self-assembled polystyrene-b-poly(methyl methacrylate) diblock copolymer films using apertureless near-field IR microscopy

The nanoscale chemical composition variations of the surfaces of thin films of polystyrene- b-poly(methyl methacrylate) (PS- b-PMMA) diblock copolymers are investigated using apertureless near-field IR microscopy. The scattering of the incident infrared beam from a modulated atomic force microscopy (AFM) tip is probed using homodyne detection and demodulation at the tip oscillation frequency. An increase in the IR attenuation is observed in the PMMA-rich domains with a wavenumber dependence that is consistent with the bulk absorption spectrum. The results indicate that even though a small topography-induced artifact can be observed in the near-field images, the chemical signature of the sample is detected clearly.