On the uniqueness of bivariant Chern class and bivariant Riemann–Roch transformations

The existence of bivariant Chern classes was conjectured by W. Fulton and R. MacPherson and proved by J.-P. Brasselet for cellular morphisms of analytic varieties. However, its uniqueness has been unsolved since then. In this paper we show that restricted to morphisms whose target varieties are possibly singular but (rational) homology manifolds (such as orbifolds), the bivariant Chern classes (with rational coefficients) are uniquely determined. We also discuss some related results and problems.     

Atomic states of lithium by the beam-foil technique in the spectral range 400–1900 Å

⁶Li⁺-ions accelerated electrostatically to energies of 200–390 keV are electronically excited by the beam-foil technique. The emitted light is analyzed with a Seya-Namioka VUV monochromator in the wavelength range 400–1900 å. All Li II and Li III lines known from theory — in one case emitted by an=9 level — are detected, several of them for the first time. Lifetimes of 20 Li II levels, some not measured previously, are determined after correction for cascades. The accuracy of the experimental values for several lifetimes is better than that of theoretical predictions.     

Microscopic transport theory of heavy-ion collisions

Drift and diffusion coefficients for the variables of mass fragmentation and excitation energy are studied for deeply inelastic collisions. The transport coefficients are obtained in closed form as functions of the parameters of the interaction matrix elements between nucleonic states and as functions of the binding energy of the intermediate rotating quasimolecular configuration. Drift and diffusion coefficients for excitation and mass transfer are related (dissipation fluctuation theorem). In good approximation these relations take the simple form of Einstein's relation between the mobility and the diffusion coefficient of a particle in a medium. For the total mass numbers 100, 250 and 500 the results are discussed in detail. The transport coefficients are compared with experimental results. Within the uncertainties of determination from experimental data, the drift and diffusion coefficients are well described by two previously adjusted parameters of the mean interaction matrix elements. Consequences for the production of superheavy elements in deeply inelastic collisions of U on U or Cf are discussed.     

Solvent-controlled assembling by hydrogen bridges and halogen-halogen interactions of novel organotin oxo clusters

The crystal structure of the novel methylene-bridged tetraorganodistannoxane ([Ph(HO)SnCH2Sn(I)Ph]O)4 (1) depends on the solvent it is crystallised from and is controlled by hydrogen bridges and interhalogen interactions.     

Investigating the underlying Markovian dynamics of ECG rhythms by information flow

Several approaches have been recently introduced to characterize and classify signals based on the underlying hidden dynamic. Markov models represent a natural choice for describing the dynamic evolution of a signal. However, the right selection of the memory of the process is essential for the correctness of the Markov model and a mathematically well-founded criterion is necessary to establish when the Markov model is a good approximation of the process. We review an information-theoretic based method that introduces the concept of information flow as such a criterion. The information flow describes the progressive loss of statistical dependence between the entire past and a point ahead in the future, which is indirectly related with the hidden dynamic of the signal. An approximated measure of information flow can be used as the discriminating statistic for selecting the optimal Markov model in terms of the shortest memory required. This technique is applied to investigate the underlying Markovian dynamics of the heart rate variability (HRV) for subjects in different patho-physiological conditions. Markov models with different memories seem to be associated with the circadian cycle and with different pathologies. Furthermore, the precursor character of the information flow for predicting ventricular tachycardia (VT) is discussed.     

Highly Efficient Synthesis of Globular (Bola)amphiphilic [5:1]Hexakisadducts of C60

We report on the very facile access of a new family of amphiphilic and bola‐amphiphilic fullerene [5:1]hexakisadducts 9 a – f and 11 a – e . The key point for this successful approach is the use of C_2v‐symmetrical fullerene pentakisadduct precursors 2 b – f allowing for the completely regioselective addition of a sixth malonate addend to complete the octahedral [5:1] addition pattern. For the synthesis of the new amphiphiles we first developed a new second‐generation dendrimer containing 9 tert‐butoxycarbonyl (Boc)‐protected amino functions at the periphery and two new malonates containing 6 or 18 Boc‐protected amino termini, respectively. The hexakisadducts contain up to 18 positive or negative charges at the dendritic moiety and either no or ten positive or negative charges at the unbranched malonate positions after deprotection with trifluoroacetic acid (TFA). The charge state at the termini is pH‐dependent. Complete structural characterization of the new compounds was carried out by ESI mass spectrometry and by UV/Vis, FTIR, ¹H NMR and ¹³C NMR spectroscopy. We were also able to obtain the first X‐ray crystal structure of pentakisadduct ( 2 a ) with a C_2v‐symmetrical addition pattern. The new amphiphilic hexakisadducts show interesting solubility properties in water. Initial investigations on the aggregation properties of the amphiphilic hexakisadduct 12 c by using dynamic light scattering (DLS) and conductivity measurements, show aggregates with a radius up to 200 nm and a critical micelle concentration (CMC) of approximately 8 mg L^?1.     

NEWS ABOUT FOUR-MEMBERED RINGS IN THE CHEMISTRY OF ORGANOSILICON, -GERMANIUM,AND -TIN COMPOUNDS

The synthesis of the cyclic tin-modified silanes 1–6 are described by the reaction of ^t Bu₂SnCl₂ with different dichloromono- and -disilanes in the presence of magnesium. Reacting dimethyldichlorosilane with diphenyldichlorosilane and magnesium yielded the 1,1-dimethylhexaphenylcyclotetrasilane 8 in reasonably good yields.     

Measurement of the isolated prompt photon production cross section in pp collisions at √s=7 TeV

The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E(T)(γ) in pp collisions at √s=7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9 pb(-1). Photons are required to have a pseudorapidity |η(γ)|<1.45 and E(T)(γ)>21 GeV, covering the kinematic region 0.006相似文献