Simulated annealing and tabu search approaches for the Corridor Allocation Problem

In the Corridor Allocation Problem, we are given n facilities to be arranged along a corridor. The arrangements on either side of the corridor should start from a common point on the left end of the corridor. In addition, no space is allowed between two adjacent facilities. The problem is motivated by applications such as the arrangement of rooms in office buildings, hospitals, shopping centers or schools. Tabu search and simulated annealing algorithms are presented to minimize the sum of weighted distances between every pair of facilities. The algorithms are evaluated on several instances of different sizes either randomly generated or available in the literature. Both algorithms reached the optimal (when available) or best-known solutions of the instances with n ? 30. For larger instances with size 42 ? n ? 70, the simulated annealing implementation obtained smaller objective values, while requiring a smaller number of function evaluations.     

Photoswitching electron transport properties of an azobenzene containing thiol-SAM

The influence of conformational and electrical properties of azobenzene molecules on the electron transfer barrier properties of their SAMs was studied by SECM and ellipsometry.     

Cellulose nanocrystal submonolayers by spin coating

Dilute concentrations of cellulose nanocrystal solutions were spin coated onto different substrates to investigate the effect of the substrate on the nanocrystal submonolayers. Three substrates were probed: silica, titania, and amorphous cellulose. According to atomic force microscopy (AFM) images, anionic cellulose nanocrystals formed small aggregates on the anionic silica substrate, whereas a uniform two-dimensional distribution of nanocrystals was achieved on the cationic titania substrate. The uniform distribution of cellulose nanocrystal submonolayers on titania is an important factor when dimensional analysis of the nanocrystals is desired. Furthermore, the amount of nanocrystals deposited on titania was multifold in comparison to the amounts on silica, as revealed by AFM image analysis and X-ray photoelectron spectroscopy. Amorphous cellulose, the third substrate, resulted in a somewhat homogeneous distribution of the nanocrystal submonolayers, but the amounts were as low as those on the silica substrate. These differences in the cellulose nanocrystal deposition were attributed to electrostatic effects: anionic cellulose nanocrystals are adsorbed on cationic titania in addition to the normal spin coating deposition. The anionic silica surface, on the other hand, causes aggregation of the weakly anionic cellulose nanocrystals which are forced on the repulsive substrate by spin coating. The electrostatically driven adsorption also influences the film thickness of continuous ultrathin films of cellulose nanocrystals. The thicker films of charged nanocrystals on a substrate of opposite charge means that the film thickness is not independent of the substrate when spin coating cellulose nanocrystals in the ultrathin regime (<100 nm).     

NMR on the new phases of liquid 3He in contact with platinum powder

Liquid ³He has been cooled by adiabatic demagnetization of copper nuclei to 1.6 mK, well into the region of the superfluid phases. NMR measurements on ³He in a coil partly filled with platinum powder give results different from those expected for bulk liquid.     

Comparison of liquid chromatography-microchip/mass spectrometry to conventional liquid chromatography–mass spectrometry for the analysis of steroids

The feasibility of a microfluidic-based liquid chromatography-electrospray ionization/mass spectrometric system (HPLC-Chip/ESI/MS) was studied and compared to a conventional narrow-bore liquid chromatography-electrospray ionization/mass spectrometric (LC-ESI/MS) system for the analysis of steroids. The limits of detection (LODs) for oxime derivatized steroids, expressed as concentrations, were slightly higher with the HPLC-Chip/MS system (50–300 pM) using an injection volume of 0.5 μL than with the conventional LC-ESI/MS (10–150 pM) using an injection volume of 40 μL. However, when the LODs are expressed as injected amounts, the sensitivity of the HPLC-Chip/MS system was about 50 times higher than with the conventional LC-ESI/MS system. The results indicate that the use of HPLC-Chip/MS system is clearly advantageous only in the analysis of low-volume samples. Both methods showed good linearity and good quantitative and chromatographic repeatability. In addition to the instrument comparisons with oxime derivatized steroids, the feasibility of the HPLC-Chip/MS system in the analysis of non-derivatized and oxime derivatized steroids was compared. The HPLC-Chip/MS method developed for non-derivatized steroids was also applied to the quantitative analysis of 15 mouse plasma samples.     

Properties of the 13/2+ isomeric decay in201Hg

The isomeric decay of theT _1/2=94 us isomeric state in²⁰¹Hg was studied in beam via the reaction¹⁹⁸Pt(α, n). Gamma-ray and conversion-electron spectra were recorded. From the conversion coefficients, the multipolarities of the two depopulating transitions were determined to beM 2 + 10%E 3 andE 2, respectively. These assignments give the depopulating transitions to be 13/2⁺ → 9/2^? and 9/2^? → 5/2^?, and these thus substantiate the previous suggestion that the isomeric state hasJ ^π=13/2⁺. For the 13/2⁺ → 9/2^? M 2 transition a detailed study ofE 3 andM 4 admixed amplitudes was done. The microscopic properties of the 13/2⁺ and 9/2^? states are discussed, and a comparison to the corresponding ones in^199,203,205Hg is made.     

Stability and electrostatics of mercaptoundecanoic acid-capped gold nanoparticles with varying counterion size.

The solubility of charged nanoparticles is critically dependent on pH. However, the concentration range available with bases such as NaOH is quite narrow, since the particles precipitate due to compression of the electric double layer when the ionic strength is increased. The stability of mercaptoundecanoic acid-capped Au nanoparticles is studied at a set pH using the hydroxide as base and different cations of various sizes. The counterions used are sodium (Na(+)), tetramethylammonium (TMA(+)), tetraethylammonium (TEA(+)), and tetrabutylammonium (TBA(+)). The particles precipitate in the 70-90 mM range with Na(+) as the counterion, but with quaternary ammonium hydroxides the particles are stable even in concentrations exceeding 1 M. The change in solubility is linked to a strongly adsorbed layer on the surface of the ligand shell of the nanoparticles. The increased concentration range obtained with TEAOH is further used to facilitate thiol exchange which occurs at a greater extent than would be achieved in NaOH solution.     

Bis(6‐thioxo‐1,6‐dihydro­purinium) tetra­chloro­zincate(II)

The title salt, (C₅H₅N₄S)₂[ZnCl₄], consists of two 6‐thioxo‐1,6‐dihydro­purinium (6mpH₂⁺) cations (A and B) and a tetra­chloro­zincate anion, which are held together by N—H⋯Cl and C—H⋯Cl inter­actions. There is an anion–π inter­action between one Cl atom of the [ZnCl₄]⁻ anion and the pyrimidine ring of the 6mpH₂⁺(B) cation. Inter­molecular π–π stacking inter­actions allow 6mpH₂⁺(A) cations to form anti­parallel pairs. One inter­esting structural feature is the double N—H⋯N inter­molecular hydrogen bonds between two 6mpH₂⁺(A) cations. This kind of inter­action, mimicking that of natural nucleobases, can be very valuable in designing new therapeutic purine derivatives.