The absorption spectrum of H2: CRDS measurements of the (2-0) band, review of the literature data and accurate ab initio line list up to 35000 cm(-1)

Five very weak transitions-O(2), O(3), O(4), O(5) and Q(5)-of the first overtone band of H(2) are measured by very high sensitivity CW-Cavity Ring Down Spectroscopy (CRDS) between 6900 and 7920 cm(-1). The noise equivalent absorption of the recordings is on the order of α(min)≈ 5 × 10(-11) cm(-1) allowing for the detection of the O(5) transition with an intensity of 1.1 × 10(-30) cm per molecule, the smallest intensity value measured so far for an H(2) absorption line. A Galatry profile was used to reproduce the measured line shape and derive the line strengths. The pressure shift of the O(2) and O(3) lines was accurately determined from a series of recordings with pressure ranging between 10 and 700 Torr. From an exhaustive review of the literature data, the list of H(2) absorption lines detected so far has been constructed. It includes a total of 39 transitions ranging from the S(0) pure rotational line near 354 cm(-1) up to the S(1) transition of the (5-0) band near 18,908 cm(-1). These experimental values are compared to a highly accurate theoretical line list constructed for pure H(2) at 296 K (0-35,000 cm(-1), intensity cut off of 1 × 10(-34) cm per molecule). The energy levels and transition moments were computed from high level quantum mechanics calculations. The overall agreement between the theoretical and experimental values is found to be very good for the line positions. Some deviations for the intensities of the high overtone bands (V > 2) are discussed in relation with possible pressure effects affecting the retrieved intensity values. We conclude that the hydrogen molecule is probably a unique case in rovibrational spectroscopy for which first principles theory can provide accurate spectroscopic parameters at the level of the performances of the state of the art experimental techniques.     

Uniform PEO Star Polymers Synthesized in Water via Free Radical Polymerization or Atom Transfer Radical Polymerization

Amphiphilic star shaped polymers with poly(ethylene oxide) (PEO) arms and cross‐linked hydrophobic core were synthesized in water via either conventional free radical polymerization (FRP) or atom transfer radical polymerization (ATRP) techniques using a simple “arm‐first” method. In FRP, PEO based macromonomers (MM) were used as arm precursors, which were then cross‐linked by divinylbenzene (DVB) using 2,2′‐azoisobutyronitrile (AIBN). Uniform star polymers ( < 1.2) were achieved through adjustment of the ratio of PEO MM, DVB, and AIBN. While in case of ATRP, both PEO MM, and PEO based macroinitiator (MI) were used as arm precursors with ethylene glycol diacrylate as cross‐linker. Even more uniform star polymers with less contamination by low MW polymers were obtained, as compared to the products synthesized by FRP.

     

Adiabatic method for positronic atoms and molecules

The adiabatic separation of electronic and positronic degrees of freedom is proposed. The positronic charge in expressions for the potential energy is partitioned between the electronic and positronic Hamiltonians. This partitioning assures an acceptable electron density distribution around the positron. Our adiabatic method gives good values of binding energies and annihilation rates for model systems, in which the positron is weakly bound. On the other hand, it does not work well if the wave function contains a significant contribution of the positronium cluster.     

Fluorescent Properties of Vitamin a Derivative,Retinyl Palmitate,in Binary Solvents with Aqueous Phase

Fluorescence emission and fluorescence excitation spactra of retinyl palmitate molecules in binary water/p-dioxane and water/isopropyl alcohol solvents under different solvents polarities were studied. The binary solvents polarities were changed by changing the molar ratios of water to p-dioxane (or isopropyl alcohol). It was suggested that the observed changes of spectral properties were caused by the formation of different retinyl palmitate self- organised structures that were induced by environments of different polarity. The role of non (low) polar components of binary solvents in the process of resultant structures creation is also discussed.     

Overlap valence quarks on a twisted mass sea: A case study for mixed action lattice QCD

We discuss a lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like locality in the continuum limit. We also show that by adopting suitable matching conditions for the sea and valence theories a consistent continuum limit for the pion decay constant and light baryon masses can be obtained. Finally, we confront results for sea–valence mixed meson masses and the valence scalar correlator with corresponding expressions of chiral perturbation theory. This allows us to extract low energy constants of mixed action chiral perturbation which characterize the strength of unitarity violations in our mixed action setup.     

Spin polarization in a freely evolving sample of cold atoms

We have implemented and optimized a technique of spin polarization by optical pumping in a caesium atomic fountain, gaining a nearly fivefold increase in the useful cold atom signal in detection. This allows an improvement of the fountain clock stability without compromising its accuracy. We present a detailed study of optical pumping in a freely evolving cloud of cold caesium atoms: we have investigated theoretically and experimentally the dynamics of the pumping process and the associated heating due to random photon scattering. The heating limits the potential gain in the fountain signal due to an additional cloud expansion. A high degree of spin polarization was achieved with accumulation of up to 97 % of the population in a single magnetic (m _F  = 0) sublevel of the ground state. Factors affecting the achievable spin polarizations, such as the purity of the pumping light polarization and the shadowing effect in the cloud, were considered. This technique may also be used in atom interferometers and for other alkali metal systems.     

Magnetorheological damping and semi-active control of an autoparametric vibration absorber

A numerical study of an application of magnetorheological (MR) damper for semi-active control is presented in this paper. The damper is mounted in the suspension of a Duffing oscillator with an attached pendulum. The MR damper with properties modelled by a hysteretic loop, is applied in order to control of the system response. Two methods for the dynamics control in the closed-loop algorithm based on the amplitude and velocity of the pendulum and the impulse on–off activation of MR damper are proposed. These concepts allow the system maintaining on a desirable attractor or, if necessary, to change a position from one attractor to another. Additionally, the detailed bifurcation analysis of the influence of MR damping on the number of periodic solutions and their stability is shown by continuation method. The influence of MR damping on the chaotic behavior is studied, as well.     

Upper Bounds for Erdös–Hajnal Coefficients of Tournaments

A celebrated unresolved conjecture of Erdös and Hajnal (see Discrete Appl Math 25 (1989), 37–52) states that for every undirected graph H, there exists , such that every graph on n vertices which does not contain H as an induced subgraph contains either a clique or an independent set of size at least . In (Combinatorica (2001), 155–170), Alon et al. proved that this conjecture was equivalent to a similar conjecture about tournaments. In the directed version of the conjecture cliques and stable sets are replaced by transitive subtournaments. For a fixed undirected graph H, define to be the supremum of all ε for which the following holds: for some n₀ and every every undirected graph with vertices not containing H as an induced subgraph has a clique or independent set of size at least . The analogous definition holds if H is a tournament. We call the Erdös–Hajnal coefficient of H. The Erdös–Hajnal conjecture is true if and only if for every H. We prove in this article that:

• the Erdös–Hajnal coefficient of every graph H is at most ,
• there exists such that the Erdös–Hajnal coefficient of almost every tournament T on k vertices is at most , i.e. the proportion of tournaments on k vertices with the coefficient exceeding goes to 0 as k goes to infinity.