Isomeric states in 253No

Isomeric states in ²⁵³No have been investigated by conversion electron and γ -ray spectroscopy with the GABRIELA detection system. The 31μs isomer reported more than 30 years ago is found to decay to the ground state of ²⁵³No by the emission of a 167keV M2 transition. The spin and parity of this low-lying isomeric state are established to be 5/2⁺ . The presence of another longer-lived isomeric state is also discussed.     

Competitive adsorption equilibria of CO2 and CH4 on a dry coal

Gases like CO₂ and CH₄ are able to adsorb on the coal surface, but also to dissolve into its structure causing the coal to swell. In this work, the binary adsorption of CO₂ and CH₄ on a dry coal (Sulcis Coal Province, Italy) and its swelling behavior are investigated. The competitive adsorption measurements are performed at 45?°C and up to 190 bar for pure CO₂, CH₄ and four mixtures of molar feed compositions of 20.0, 40.0, 60.0 and 80.0% CO₂ using a gravimetric-chromatographic technique. The results show that carbon dioxide adsorbs more favorably than methane leading to an enrichment of the fluid phase in CH₄. Coal swelling is determined using a high-pressure view cell, by exposing a coal disc to CO₂, CH₄ and He at 45 and 60?°C and up to 140 bar. For CO₂ and CH₄ a maximum swelling of about 4 and 2% is found, whereas He shows negligible swelling. The presented adsorption and swelling data are then discussed in terms of fundamental, thermodynamic aspects of adsorption and properties which are crucial for an ECBM operation, i.e. the CO₂ storage capacity and the dynamics of the replacement of CH₄ by CO₂.     

A note on Ramsey numbers for books

The book with n pages B_n is the graph consisting of n triangles sharing an edge. The book Ramsey number r(B_m,B_n) is the smallest integer r such that either B_m ? G or B_n ? G for every graph G of order r. We prove that there exists a positive constant c such that r(B_m,B_n) = 2n + 3 for all n ≥ cm. Our proof is based mainly on counting; we also use a result of Andrásfai, Erd?s, and Sós stating that triangle‐free graphs of order n and minimum degree greater than 2n/5 are bipartite. © 2005 Wiley Periodicals, Inc. J Graph Theory     

Interior point stabilization for column generation

Interior point stabilization is an acceleration method for column generation algorithms. It addresses degeneracy and convergence difficulties by selecting a dual solution inside the optimal space rather than retrieving an extreme point. The method is applied to the case of the vehicle routing problem with time windows.     

Analytical X-Ray Microscopy on Psaronius sp. – A Contribution to Permineralization Process Studies

 290 Million years old petrifactions from the Lower Permian Rotliegend of Chemnitz were examined by analytical X-ray microscopy to determine their chemical composition. Mappings show the inhomogeneous distribution of the involved elements, which may reflect the former plant anatomy, as well as some contemporaneous processes of permineralization (with silica and fluorite) and agate-formation. Most prominent advantages of the analytical X-ray microscopy are the low preparation expense of the museum samples, the analysis scanning range and the X-ray spot diameter suitable with the dimension of the fossil plants.     

14-fs high temporal quality injector for ultra-high intensity laser

We present a chirped pulse amplification (CPA) Ti:Sa laser generating sub-15 fs pulses with expected high temporal quality. Gain-narrowing in the pre-amplifier is balanced by a variable spectral reflectivity mirror and by a fine adaptation of the saturation conditions. A crossed polarized wave generation (XPW) filter is introduced to enhance the contrast, reduce the pulse duration and improve the spectral quality. The pulses are generated at 10 Hz repetition rate, with pulse energy of 110 μJ and very clean Gaussian spectrum. The temporal contrast is evaluated by a measurement before the XPW filter and calculations of the enhancement by the filter. The potential temporal incoherent contrast is 10¹² and the coherent contrast 10¹⁰. The performance of the system makes it suitable as an injector for petawatt lasers operating in the double-CPA scheme.     

Intracerebral delivery of 5‐iodo‐2′‐deoxyuridine in combination with synchrotron stereotactic radiation for the therapy of the F98 glioma

Iodine‐enhanced synchrotron stereotactic radiotherapy takes advantage of the radiation dose‐enhancement produced by high‐Z elements when irradiated with mono‐energetic beams of synchrotron X‐rays. In this study it has been investigated whether therapeutic efficacy could be improved using a thymidine analogue, 5‐iodo‐2′‐deoxyuridine (IUdR), as a radiosentizing agent. IUdR was administered intracerebrally over six days to F98 glioma‐bearing rats using Alzet osmotic pumps, beginning seven days after tumor implantation. On the 14th day, a single 15 Gy dose of 50 keV synchrotron X‐rays was delivered to the brain. Animals were followed until the time of death and the primary endpoints of this study were the mean and median survival times. The median survival times for irradiation alone, chemotherapy alone or their combination were 44, 32 and 46 days, respectively, compared with 24 days for untreated controls. Each treatment alone significantly increased the rats' survival in comparison with the untreated group. Their combination did not, however, significantly improve survival compared with that of X‐irradiation alone or chemotherapy alone. Further studies are required to understand why the combination of chemoradiotherapy was no more effective than X‐irradiation alone.     

Novel synthesis of polyimide–polyhybridsiloxane block copolymers via polyhydrosilylation: Characterization and physical properties

The insertion of soft polysiloxane segments into a polyimide backbone introduces changes in its properties (processability, low surface tension, gas permeability, and lower dielectric constant). Generally, these polyimide–polysiloxane copolymers are synthesized by the condensation of a dianhydride with an aromatic diamine and an amine telechelic polysiloxane, or by transimidization between an aminopyridine‐terminated oligoimide and an amine end‐capped oligosiloxane. This study investigated another route to obtain perfectly alternating polyimide–polyhybridsiloxane (PI–PHSX) block copolymers. The hydrosilylation, widely studied previously, was performed to elaborate copolymers from an allyl telechelic polyimide and a hydrosilane telechelic polyhybridsiloxane. The use of a telechelic polyhybridsiloxane as a soft segment brought better thermostability and better chemical resistance in comparison with an oligosiloxane based on ? Si(CH₃)₂? O? units. Using the same allyl telechelic polyimide moiety but varying the size of the hybrid siloxane part, we obtained different PI–PHSX block copolymers, leading to thermoplastic elastomers (TPE). We investigated the effect of the soft‐segment length on the thermal resistance, activation energy of thermal degradation, mechanical behavior, and surface properties of a series three PI–PHSX block copolymers containing 36, 54, and 75 wt % polyimide. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2414–2425, 2001     

An adaptive discretization for Tikhonov-Phillips regularization with a posteriori parameter selection

Summary. The aim of this paper is to describe an efficient adaptive strategy for discretizing ill-posed linear operator equations of the first kind: we consider Tikhonov-Phillips regularization with a finite dimensional approximation instead of A. We propose a sparse matrix structure which still leads to optimal convergences rates but requires substantially less scalar products for computing compared with standard methods. Received September 16, 1998 / Revised version received August 4, 1999 / Published online August 2, 2000