A new μs isomer in 136Sb produced in the projectile fission of 238U

Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed. Received: 30 March 2001 / Accepted: 18 September 2001     

Dextramabs: A Novel Format of Antibody-Drug Conjugates Featuring a Multivalent Polysaccharide Scaffold

Antibody-drug conjugates (ADCs) are multicomponent biomolecules that have emerged as a powerful tool for targeted tumor therapy. Combining specific binding of an immunoglobulin with toxic properties of a payload, they however often suffer from poor hydrophilicity when loaded with a high amount of toxins. To address these issues simultaneously, we developed dextramabs, a novel class of hybrid antibody-drug conjugates. In these architectures, the therapeutic antibody trastuzumab is equipped with a multivalent dextran polysaccharide that enables efficient loading with a potent toxin in a controllable fashion. Our modular chemoenzymatic approach provides an access to synthetic dextramabs bearing monomethyl auristatin as releasable cytotoxic cargo. They possess high drug-to-antibody ratios, remarkable hydrophilicity, and high toxicity in vitro.     

En route to Background Independence: Broken split-symmetry,and how to restore it with bi-metric average actions

The most momentous requirement a quantum theory of gravity must satisfy is Background Independence, necessitating in particular an ab initio derivation of the arena all non-gravitational physics takes place in, namely spacetime. Using the background field technique, this requirement translates into the condition of an unbroken split-symmetry connecting the (quantized) metric fluctuations to the (classical) background metric. If the regularization scheme used violates split-symmetry during the quantization process it is mandatory to restore it in the end at the level of observable physics. In this paper we present a detailed investigation of split-symmetry breaking and restoration within the Effective Average Action (EAA) approach to Quantum Einstein Gravity (QEG) with a special emphasis on the Asymptotic Safety conjecture. In particular we demonstrate for the first time in a non-trivial setting that the two key requirements of Background Independence and Asymptotic Safety can be satisfied simultaneously. Carefully disentangling fluctuation and background fields, we employ a ‘bi-metric’ ansatz for the EAA and project the flow generated by its functional renormalization group equation on a truncated theory space spanned by two separate Einstein–Hilbert actions for the dynamical and the background metric, respectively. A new powerful method is used to derive the corresponding renormalization group (RG) equations for the Newton- and cosmological constant, both in the dynamical and the background sector. We classify and analyze their solutions in detail, determine their fixed point structure, and identify an attractor mechanism which turns out instrumental in the split-symmetry restoration. We show that there exists a subset of RG trajectories which are both asymptotically safe and split-symmetry restoring: In the ultraviolet they emanate from a non-Gaussian fixed point, and in the infrared they loose all symmetry violating contributions inflicted on them by the non-invariant functional RG equation. As an application, we compute the scale dependent spectral dimension which governs the fractal properties of the effective QEG spacetimes at the bi-metric level. Earlier tests of the Asymptotic Safety conjecture almost exclusively employed ‘single-metric truncations’ which are blind towards the difference between quantum and background fields. We explore in detail under which conditions they can be reliable, and we discuss how the single-metric based picture of Asymptotic Safety needs to be revised in the light of the new results. We shall conclude that the next generation of truncations for quantitatively precise predictions (of critical exponents, for instance) is bound to be of the bi-metric type.     

Optimization of an rf-powered magnetron glow discharge for the trace analysis of glasses and ceramics

A radiofrequency (rf) powered planar magnetron glow discharge ion source has been designed and coupled to a double-focusing mass spectrometer. Superposition of the electrical field of the plasma in the cathode dark space and the magnetic field obtained from a ring-shaped magnet located directly behind the sample (cathode) form the electron traps and enhance the sputtering and ionization efficiency of the ion source. In order to establish optimum conditions for the trace analysis of nonconducting materials, mass spectrometric studies have been carried out on the ion signal intensities and energy distributions of analyte and discharge gas ions depending on pressure.     

How chromophore shape determines the spectroscopy of phenylene-vinylenes: origin of spectral broadening in the absence of aggregation

Single oligo(phenylene-vinylene) molecules constitute model systems of chromophores in disordered conjugated polymers and can elucidate how the actual conformation of an individual chromophore, rather than that of an overall polymer chain, controls its photophysics. Single oligomers and polymer chains display the same range of spectral properties. Even heptamers support pi-electron conjugation across approximately 80 degrees curvature, as revealed by the polarization anisotropy in excitation and supported by quantum chemical calculations. As the chain becomes more deformed, the spectral linewidth at low temperatures, often interpreted as a sign of aggregation, increases up to 30-fold due to a reduction in photophysical stability of the molecule and an increase in random spectral fluctuations. The conclusions aid the interpretation of results from single-chain Stark spectroscopy in which large static dipoles were only observed in the case of narrow transition lines. These narrow transitions originate from extended chromophores in which the dipoles induced by backbone substituents do not cancel out. Chromophores in conjugated polymers are often thought of as individual linear transition dipoles, the sum of which make up the polymer's optical properties. Our results demonstrate that, at least for phenylene-vinylenes, it is the actual shape of the individual chromophore rather than the overall chromophoric arrangement and form of the polymer chain that dominates the spectroscopic properties.     

The infrared spectra and theoretical calculations of frequencies of fac-tricarbonyl octahedral complexes of manganese(I)

The carbonyl stretching frequencies in the infrared spectra of 38 fac-tricarbonyl octahedral complexes of manganese(I) prepared in this laboratory were determined. These complexes may be grouped into three types: (a) neutral complexes of the structure (CO)(3)Mn(P-P)Z where P-P represents depe, dppe, or dppp, and Z represents various anionic functional groups bonded to the manganese; (b) ionic complexes of the structure [(CO)(3)Mn(P-P)Z](+)BF(4)(-) where Z represents various neutral molecules possessing one phosphorous, nitrogen, or oxygen atom coordinated to the manganese; (c) complexes of the structure (CO)(3)Mn(pn)Z where the chelating pn represents 1,1-diphenylphosphino-2,2-dimethylaminoethane, Ph(2)PCH(2)CH(2)NMe(2). All of these complexes show three carbonyl stretching modes (2A' + A"). The effects on the frequencies of these modes induced by both the various Z groups and the various ligands are discussed. Theoretical calculations (B3LYP/6-31G) with optimization of the full molecule make it possible to distinguish between the three stretching modes and to make unambiguous assignments of appropriate symmetry species to each.     

Watching nanoparticles form: an in situ (small-/wide-angle X-ray scattering/total scattering) study of the growth of yttria-stabilised zirconia in supercritical fluids

Understanding nanoparticle-formation reactions requires multi-technique in situ characterisation, since no single characterisation technique provides adequate information. Here, the first combined small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering (WAXS)/total-scattering study of nanoparticle formation is presented. We report on the formation and growth of yttria-stabilised zirconia (YSZ) under the extreme conditions of supercritical methanol for particles with Y(2)O(3) equivalent molar fractions of 0, 4, 8, 12 and 25 %. Simultaneous in situ SAXS and WAXS reveals a quick formation (seconds) of sub-nanometre amorphous material forming larger agglomerates with subsequent slow crystallisation (minutes) into nanocrystallites. The amount of yttria dopant is shown to strongly affect the crystallite size and unit-cell dimensions. At yttria-doping levels larger than 8 %, which is known to be the stoichiometry with maximum ionic conductivity, the strain on the crystal lattice is significantly increased. Time-resolved nanoparticle size distributions are calculated based on whole-powder-pattern modelling of the WAXS data, which reveals that concurrent with increasing average particle sizes, a broadening of the particle-size distributions occur. In situ total scattering provides structural insight into the sub-nanometre amorphous phase prior to crystallite growth, and the data reveal an atomic rearrangement from six-coordinated zirconium atoms in the initial amorphous clusters to eight-coordinated zirconia atoms in stable crystallites. Representative samples prepared ex situ and investigated by transmission electron microscopy confirm a transformation from an amorphous material to crystalline nanoparticles upon increased synthesis duration.     

Wavelength dependence of the suppressed ionization of molecules in strong laser fields

We study ionization of molecules by an intense laser field over a broad wavelength regime, ranging from 0.8 to 1.5 μm experimentally and from 0.6 to 10 μm theoretically. A reaction microscope is combined with an optical parametric amplifier to achieve ionization yields in the near-infrared wavelength regime. Calculations are done using the strong-field S-matrix theory and agreement is found between experiment and theory, showing that ionization of many molecules is suppressed compared to the ionization of atoms with identical ionization potentials at near-infrared wavelengths at around 0.8 μm, but not at longest wavelengths (10 μm). This is due to interference effects in the electron emission that are effective at low photoelectron energies but tend to average out at higher energies. We observe the transition between suppression and nonsuppression of molecular ionization in the near-infrared wavelength regime (1-5 μm).     

Modulation versus Templating: Fine‐Tuning of Hierarchally Porous PCN‐250 Using Fatty Acids To Engineer Guest Adsorption

Modulation and templating are two synthetic techniques that have garnered significant attention over the last several years for the preparation of hierarchically porous metal–organic frameworks (HP‐MOFs). In this study, by using fatty acids with different lengths and concentrations as dual‐functional modulators/templates, we were able to obtain HP‐MOFs with tunable mesopores that exhibit different pore diameters and locations. We found that the length and concentration of the fatty acids can determine if micelle formation occurs, which in turn dictates the porosity of the resulting HP‐MOFs. The HP‐MOFs with different mesopores differed in their performance in gas uptake and dye adsorption, and the structure–performance relationships were ascribed to the pore diameters and locations. This approach could provide a potentially universal method to efficiently introduce hierarchal mesopores into existing microporous MOF adsorbents with tunable properties.