Synthesis and characterisation of main-chain hydrogen-bonded supramolecular liquid crystalline complexes formed by azo-containing compounds

A series of azopyridine-containing hydrogen bonding acceptors (4a-c) with flexible spacers of oligo(methylene) were synthesised. Hydrogen-bonded polymeric complexes 4/5 and trimeric complexes 4/6₂ , where 5 and 6 are aromatic dicarboxylic acids and monocarboxylic acids, respectively, were prepared and their liquid crystallinity was examined using differential scanning calorimetry and polarising optical microscopy. The study showed that most of the complexes displayed reversible thermotropic nematic phase. The isotropic to nematic phase transition temperatures of polymeric complexes 4/5 and trimeric complexes 4/6₂ in general decreased with the increase in length of spacers and terminal groups in the corresponding proton acceptors 4 and the proton donors 5 and 6, respectively. Hydrogen bonding interactions in complexes 4/5 and 4/6₂ were studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.     

Configuration-dependent bands in 169Re

High-spin states in ¹⁶⁹Re were studied and resulted in the identification of a strongly coupled band based on the 9/2^-[514] Nilsson state and a decoupled band built on the h _9/2 1/2^-[541] intruder proton orbit. The cranked-shell-model calculations present configuration-dependent deformations that can explain the different band crossing frequencies. The 9/2^-[514] band in ¹⁶⁹Re shows the largest signature splitting at low spin among the known odd-mass Re isotopes. After the alignment of a pair of i _13/2 neutrons, the phase of the splitting is inverted with a significantly reduced amplitude. For the 9/2^-[514] bands in light odd-A Re isotopes, the signature splitting of the Routhians and its relation with the signature dependence of M1 transition matrix elements are investigated in connection with the deviation of nuclear shape from axial symmetry, suggesting an appreciable negative deformation for the very neutron-deficient odd-A Re isotopes. Additionally, a three-quasipariticle band was observed and assigned to be built likely on the configuration.Received: 9 May 2003, Published online: 18 December 2003PACS: 21.10.Re Collective levels - 23.20.-g Electromagnetic transitions - 23.20.Lv transitions and level energies - 27.70. + q      

A new isomer in 136 Ba populated by deep inelastic collisions

Excited states in ¹³⁶Ba, populated in deep inelastic collisions by the interaction of 450 MeV ⁸²Se ions with a ¹³⁹La target, have been studied by means of in-beam -ray spectroscopy. A new isomer with has been identified at an excitation energy E_x = 3.357 MeV. The half-life was determined as ns. The extracted B(E2) value is much smaller than those in ¹³²Te and ¹³⁴Xe. This hindrance is investigated by a shell model calculation.Received: 22 September 2003, Revised: 11 November 2003, Published online: 6 April 2004PACS: 21.10.Tg Lifetimes - 23.20.Lv transitions and level energies - 27.60. + j      

High-spin states in 190Pt

The level structure of 190Pt has been studied experimentally using the 176Yb (18O, 4n) reaction at beam energies of 88 and 95 MeV. γ-γ-t coincidence measurements were carried out. Based onthe analysis of γ-γ coincidence relationships, the level scheme of 190Pt is extended to high-spin states. A new structure built on the 3413.6 keV 14+ state has been observed, and the vi1-213/2 vh-19/2 vj (j = p3/2 or f5/2) configuration is tentatively assigned to it.     

120-W continuous-wave diode-pumped Tm:YAG laser

We present a 120-W cw diode-pumped Tm:YAG laser. The Tm:YAG rod is side pumped by three diode arrays whose radiation is coupled through compound parabolic concentrators. The maximum optical-to-optical conversion efficiency of the 2.02-mum laser output is 25.2%, with a slope efficiency of 31.2%.     

Global Optimization by Monotonic Transformation

This paper addresses the problem of global optimization by means of a monotonic transformation. With an observation on global optimality of functions under such a transformation, we show that a simple and effective algorithm can be derived to search within possible regions containing the global optima. Numerical experiments are performed to compare this algorithm with one that does not incorporate transformed information using several benchmark problems. These results are also compared to best known global search algorithms in the literature. In addition, the algorithm is shown to be useful for several neural network learning problems, which possess much larger parameter spaces.     

Rotational bands and signature inversion phenomena in πh9/2⊗νi13/2 and πi13/2⊗νi13/2 structures in odd-odd 176Ir

The ^109,111,113Rh nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85 MeV. Their level schemes have been built from gamma-rays detected using the Euroball IV array. High-spin states of the neutron-rich ^111,113Rh nuclei have been identified for the first time. Several rotational bands with the odd proton occupying the πg _9/2, πp _1/2 and π(g _7/2/d _5/2) sub-shells have been observed. A band of low-energy transitions has been identified at excitation energy around 2 MeV in ^109,111Rh, which can be interpreted in terms of three-quasiparticle excitation, πg _9/2νh _11/2νg _7/2/d _5/2. In addition another structure built on states located at low excitation energy (608 keV in ¹¹¹Rh, 570 keV in ¹¹³Rh) points out that, as already observed in the lighter isotopes ^107,109Rh, triaxial deformation plays a role in the neutron-rich Rh isotopes well beyond the mid-shell. Received: 15 July 2002 / Accepted: 9 October 2002 / Published online: 3 December 2002 RID="a" ID="a"e-mail: porquet@csnsm.in2p3.fr RID="b" ID="b"Present address: CSNSM IN2P3-CNRS and Université Paris-Sud 91405 Orsay, France. RID="c" ID="c"Present address: CEA/Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, France. Communicated by D. Schwalm     

Laser-induced vibrations of micro-beams under different boundary conditions

In this study, the vibration phenomenon during pulsed laser heating of a micro-beam is investigated. The beam is made of silicon and is heated by a non-Gaussian laser beam with a pulse duration of 2 ps, which incites vibration due to the thermoelastic damping effect. The coupling between the temperature field and stress field induces energy dissipation and converts mechanical energy into heat energy, which is irreversible. An analytical–numerical technique based on the Laplace transform is used to calculate the vibration of the deflection and thermal moment. A general algorithm of the inverse Laplace transform is developed. The validation of this algorithm is obtained through comparison with numerical results obtained by the FEMLAB software package. The effect of laser pulse energy absorption depth is studied. The size effect and the effect of different boundary conditions are also analyzed. Finally, the damping ratio and resonant frequency shift ratio of beams due to the air damping effect and the thermoelastic damping effect are compared.     

The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measuring the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular grating that is projected onto the mirror surface is a simple function of the angular rotation of the mirror. The circular grating may readily be generated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surface, the diameter of the optical grating may be varied. Furthermore, the additional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 μm is achieved for use on micro-systems. With the use of more sophisticated optical elements, the angular rotation of even smaller micro-mirrors may be measured.