It is proved that the unit sphere S in a Banach space E has the fixed-point property with respect to a large class, C, of noncompact upper-semicontinuous set-valued maps. The result is combined with an extension of the famous Borsuk-Ulam theorem to vector fields, , where the perturbation of the identity is an element of C.To Stan Ulam, teacher and friend.Supported by FCAC Québec and CRSNG Canada grants. 相似文献
We have begun to use 350–500 kJ of 1/3-micron laser light from the National Ignition Facility (NIF) laser to create millimeter-scale, bright multi-keV x-ray sources. In the first set of shots we achieved 15%–18% x-ray conversion efficiency into Xe M-shell (∼1.5–2.5 keV), Ar K-shell (∼3 keV) and Xe L-shell (∼4–5.5 keV) emission (Fournier et al., Phys. Plasmas 17, 082701, 2010), in good agreement with the emission modeled using a 2D radiation-hydrodynamics code incorporating a modern Detailed Configuration Accounting atomic model in non-LTE (Colvin et al., Phys. Plasmas, 17, 073111, 2010). In this paper we first briefly review details of the computational model and comparisons of the simulations with the Ar/Xe NIF data. We then discuss a computational study showing sensitivity of the x-ray emission to various beam illumination details (beam configuration, pointing, peak power, pulse shape, etc.) and target parameters (size, initial density, etc.), and finally make some predictions of how the x-ray conversion efficiency expected from NIF shots scales with atomic number of the emitting plasma. 相似文献
The paper proposes a rapid screening method for a first step improvement of an animal component-free medium dedicated to the
growth of the anchorage-dependent Vero cell line. A new, rapid, and non-invasive technique is presented to specifically monitor
cultures of adherent cells in 96-well plates. The operating conditions of an image analyzer are adapted to take into account
the decrease of cell size when the attached cell density increases. An experimental design is carried out to assess the influence
of ten component groups in the original medium. Two groups including protein extracts, growth factor, insulin, glucose, and
pyruvate show significant positive effects. The groups with vitamins and molecules related to nitrogenous bases display a
less pronounced influence. The mixture of amino acids, B1 vitamin, magnesium sulfate, and sodium phosphate as well as the couple sodium citrate and ferric chloride lead to a downward
trend. The screening results are proved to be scalable in stirred cultures with cells on microcarriers. An improved serum-free
medium, with some component groups being removed or added, can be rapidly formulated to reach respectively similar or 1.6
times higher cell density than in the original medium. The results from this global approach could be helpful to further focus
experiments on identified medium components. 相似文献
Abstract A genetically engineered periodic polypeptide consisting of 36 repeats of the octapeptide sequence -(AlaGly)3GluGly- has been crystallized from solution in aqueous lithium bromide. Analysis by solid-state nuclear magnetic resonance spectroscopy, vibrational spectroscopy, and wide-angle x-ray diffraction reveals a crystal structure analogous to that obtained when silk solutions are allowed to dry under quiescent conditions, i.e., the silk I structure. Previous analyses of the same polymer have demonstrated an antiparallel β-sheet architecture (silk II structure) in samples crystallized from formic acid. These results illustrate the potential for controlling the solid-state structures and properties of genetically engineered materials through selection of appropriate processing and crystallization conditions. 相似文献
MALDI imaging mass spectrometry (MALDI-IMS) has become a powerful tool for the detection and localization of drugs, proteins, and lipids on-tissue. Nevertheless, this approach can only perform identification of low mass molecules as lipids, pharmaceuticals, and peptides. In this article, a combination of approaches for the detection and imaging of proteins and their identification directly on-tissue is described after tryptic digestion. Enzymatic digestion protocols for different kinds of tissues—formalin fixed paraffin embedded (FFPE) and frozen tissues—are combined with MALDI-ion mobility mass spectrometry (IM-MS). This combination enables localization and identification of proteins via their related digested peptides. In a number of cases, ion mobility separates isobaric ions that cannot be identified by conventional MALDI time-of-flight (TOF) mass spectrometry. The amount of detected peaks per measurement increases (versus conventional MALDI-TOF), which enables mass and time selected ion images and the identification of separated ions. These experiments demonstrate the feasibility of direct proteins identification by ion-mobility-TOF IMS from tissue. The tissue digestion combined with MALDI-IM-TOF-IMS approach allows a proteomics “bottom-up” strategy with different kinds of tissue samples, especially FFPE tissues conserved for a long time in hospital sample banks. The combination of IM with IMS marks the development of IMS approaches as real proteomic tools, which brings new perspectives to biological studies. 相似文献
DNA hybrid catalysis goes organometallic : A DNA strand functionalized with diene ligands forms iridium(I) complexes that can efficiently catalyze an allylic amination in aqueous medium (see scheme). The DNA‐based complexes show high stability and activity, and their secondary structure influences the stereoselectivity of the reaction.
Intact noncovalent complexes were studied in the gas phase using negative ion nano-ESI mass spectrometry. Among various noncovalent systems studied in the gas phase, the interaction of DNA strands with peptide nucleic acids (PNAs) presents a strong interest as biologically relevant systems. PNAs originally described by Nielsen are used as DNA mimics as possible medical agents by imprisoning DNA single strands into stable noncovalent complexes. Two types of PNAs were investigated in the PNA/DNA multiplex: the original Nielsen's PNA and a modified backbone PNA by the introduction of syn- and anti-(aminoethyl)thiazolidine rings. We first investigated the stoichiometry of PNA/DNA multiplexes formed in solution and observed them in the gas phase via qualitative kinetics of complementary strand associations. It resulted in observing PNA2/DNA triplexes (ts) as the multiply deprotonated species, most stable in both the solution and gas phase. Second, charge-dependant decompositions of these species were undertaken under low-energy collision conditions. It appears that covalent bond cleavages (base releasing or skeleton cleavage) occur from lower ts charge states rather than ts unzipping, which takes place from higher charge states. This behavior can be explained by considering the presence of zwitterions depending on the charge state. They result in strong salt-bridge interactions between the positively charged PNA side chain and the negatively charged DNA backbone. We propose a general model to clearly display the involved patterns in the noncovalent triplex decompositions. Third, the relative stability of three PNA2/DNA complexes was scrutinized in the gas phase by acquiring the breakdown curves of their ts(6-) form, corresponding to the ts unzipping. The chemical structures of the studied PNAs were chosen in order to evidence the possible influence of backbone stereochemistry on the rigidity of PNA2/DNA complexes. It provided significantly different stabilities via V(m) measurements. The relative gas-phase stability order obtained was compared to that found in solution by Chassaing et al., and shows qualitative agreement. 相似文献