The microwave spectrum,structure and nuclear quadrupole coupling constants for stibabenzene

The microwave spectrum of 121-SbC₅H₅, 123-SbC₅H₅, β-dideutero 121-SbC₅H₃D₂ and 123-SbC₅H₃D₂ has been assigned in the region 26.5–40.0 GHz. The respective rotational constants and uncertainties are: A = 4512.69 ± 0.42, B = 1738.00 ± 0.01, C = 1254.51 ± 0.01; A = 4512.84 ± 0.30, B = 1729.80 ± 0.01, C = 1250.22 ± 0.01; A = 4176.18 ± 0.33, B = 1660.94 ± 0.01, C = 1188.15 ± 0.01; A = 4176.60 ± 0.61, B = 1652.94 ± 0.03, C = 1184.03 ± 0.03 (in MHz units). The structure is found to be planar, C_2v in symmetry. The $\text{d(}\text{Sb-C}\text{) = 2.050 ± 0.005}\text{A}\text{?}$ and ∠CSbC = 92.9° ± 1.0°. The nuclear quadrupole coupling constants for the 121 and 123 antimony isotopes are χ_aa = 456.4 ± 4.1 MHz, η = 0.396 ± 0.008, and χ_aa = 583.00 ± 5.3 MHz, η = 0.399 ± 0.008, respectively. Several alternate techniques using the coupling constants as data support a σ-donating property for antimony.     

Aliasing Effects and Sampling Theorems of Spherical Random Fields when Sampled on a Finite Grid

Aliasing effects are investigated for spherical random fields sampled on a finite grid. Using the spherical harmonics expansion, it is shown that for a band-limited spherical random field its trend and spectrum can be uniquely reconstructed from the sampled field if the sampling points are judiciously designed. Analytical expressions are also obtained for aliasing errors in the trend and the spectrum when the field is not band-limited.     

A millimeter wave dielectric waveguide antenna

This paper describes the theoretical and experimental results of a novel leaky-wave antenna incorporating a homogeneous dielectric transmission line and radiating aperture into a single structure. The primary objective of this investigation is to demonstrate the ability to control aperture radiation by simply cutting slots into a metal-free dielectric transmission line. Experimental line source antennas with identical periodic slots were designed to operate in the 35 GHz frequency region. The successful performance of these antennas resulted in the design of a dielectric line source antenna with a symmetrical amplitude taper which provided a lower sidelobe level. The design represents a significant breakthrough in achieving affordable, low-loss, lightweight antennas in the millimeter wave region. The most significant applications for this type of antenna include radar surveillance and tactical missile-seeker terminal guidance.     

Switching the Switch: Ligand Induced Disulfide Formation in HDAC8

Human histone deacetylase 8 is a well-recognized target for T-cell lymphoma and particularly childhood neuroblastoma. PD-404,182 was shown to be a selective covalent inhibitor of HDAC8 that forms mixed disulfides with several cysteine residues and is also able to transform thiol groups to thiocyanates. Moreover, HDAC8 was shown to be regulated by a redox switch based on the reversible formation of a disulfide bond between cysteines Cys₁₀₂ and Cys₁₅₃. This study on the distinct effects of PD-404,182 on HDAC8 reveals that this compound induces the dose-dependent formation of intramolecular disulfide bridges. Therefore, the inhibition mechanism of HDAC8 by PD-404,182 involves both, covalent modification of thiols as well as ligand mediated disulfide formation. Moreover, this study provides a deep molecular insight into the regulation mechanism of HDAC8 involving several cysteines with graduated capability to form reversible disulfide bridges.     

Cycloaddition Reactions of an Active Cyclic Phosphane/Borane Pair with Alkenes,Alkynes, and Carbon Dioxide

The active six-membered cyclo-FLP 6 undergoes a rapid P/B addition reaction to carbon dioxide. At elevated temperature, the resulting heterobicyclo[2.2.2]octane derived product 7 undergoes ring opening and equilibrates with the cyclotetramer (7)₄ . In the large macrocyclic structure, four monomeric six-membered cyclo-FLP units are connected by four CO₂ molecules to form the supramolecular ring system. The P/B cyclo-FLP 6 undergoes a variety of additional cycloaddition reactions.     

Computational experience with a bundle approach for semidefinite cutting plane relaxations of Max-Cut and Equipartition

We propose a dynamic version of the bundle method to get approximate solutions to semidefinite programs with a nearly arbitrary number of linear inequalities. Our approach is based on Lagrangian duality, where the inequalities are dualized, and only a basic set of constraints is maintained explicitly. This leads to function evaluations requiring to solve a relatively simple semidefinite program. Our approach provides accurate solutions to semidefinite relaxations of the Max-Cut and the Equipartition problem, which are not achievable by direct approaches based only on interior-point methods. Received: April, 2004 The last author gratefully acknowledges the support from the Austrian Science Foundation FWF Project P12660-MAT.     

Study on a Cross Diffusion Parabolic System

This paper considers a kind of strongly coupled cross diffusion parabolic system,which can be usedas the multi-dimensional Lyumkis energy transport model in semiconductor science.The global existence andlarge time behavior are obtained for smooth solution to the initial boundary value problem.When the initialdata are a small perturbation of an isothermal stationary solution,the smooth solution of the problem under theinsulating boundary condition,converges to that stationary solution exponentially fast as time goes to infinity.     

Vehicle routing problems with time windows and multiple service workers: a systematic comparison between ACO and GRASP

This paper systematically compares an ant colony optimization (ACO) and a greedy randomized adaptive search procedure (GRASP) metaheuristic. Both are used to solve the vehicle routing problem with time windows and multiple service workers. In order to keep the results comparable, the same route construction heuristic and local search procedures are used. It is shown that ACO clearly outperforms GRASP in the problem under study. Additionally, new globally best results for the used benchmark problems are presented.     

Uniqueness for inverse Sturm–Liouville problems with a finite number of transmission conditions

We establish various uniqueness results for inverse spectral problems of Sturm–Liouville operators with a finite number of discontinuities at interior points at which we impose the usual transmission conditions. We consider both the cases of classical Robin and of eigenparameter dependent boundary conditions.