Suspended trapping is used to eject electrons in negative-ion Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometric experiments. In contrast to electron ejection by resonant excitation of the trapping motion, suspended trapping involves allowing the electrons to escape along the z-axis (perpendicular to the trap plates) while the trapping potential is briefly removed. The duration of this event is sufficiently short (~10 μs) so that ion losses are negligible; the overall effect is that of a ‘high-pass mass filter’. Suspended trapping is simpler to implement and more generally applicable to various cell geometries than resonant electron ejection. The effectiveness of the suspended trapping technique is not compromised by the anharmonicity of the potential well in ‘elongated’ ICR traps, but depends simply on the time it takes the electrons to escape the cell. Finally, a small, positive offset potential (~+0.25 V) applied to the trap plates during the suspended trapping event increases the efficiency of the ejection. 相似文献
The relationship between structures of protein ions, their charge states, and their original structures prior to ionization remains challenging to decouple. Here, we use cation-to-anion proton transfer reactions (CAPTR) to reduce the charge states of cytochrome c ions in the gas phase, and ion mobility to probe their structures. Ions were formed using a new temperature-controlled nanoelectrospray ionization source at 25 °C. Characterization of this source demonstrates that the temperature of the liquid sample is decoupled from that of the atmospheric pressure interface, which is heated during CAPTR experiments. Ionization from denaturing conditions yields 18+ to 8+ ions, which were each isolated and reacted with monoanions to generate all CAPTR products with charge states of at least 3+. The highest, intermediate, and lowest charge-state products exhibit collision cross-section distributions that are unimodal, multimodal, and unimodal, respectively. These distributions depend strongly on the charge state of the product, although those for the intermediate charge-state products also depend on that of the precursor. The distributions of the 3+ products are all similar, with averages that are less than half that of the 18+ precursor ions. Ionization of cytochrome c from native-like conditions yields 7+ and 6+ ions. The 3+ CAPTR products from these precursors have slightly more compact collision cross-section distributions that are indistinguishable from those for the 3+ CAPTR products from denaturing conditions. More broadly, these results indicate that the collision cross-sections of ions of this single domain protein depend strongly on charge state for charge states greater than ~4.
Motivated by the categorical notion of localizations applied to the quasi-category of abelian groups, we call a homomorphism
α: A → B a quasi-localization of abelian groups if for each ϕ ∈ Hom(A,B) there is an n ∈ ℕ and a unique ψ ∈ End(B) such that nϕ = ψ ∘ α. In this case we call B a quasi-localization of A. In this paper we investigate quasi-localizations of the integers ℤ. While it is well-known that localizations of ℤ are just
the E-rings, quasi-localizations of ℤ are much more abundant; an injection α: ℤ → M with M torsion-free, is a quasi-localization if and only if, for R = End(M), one has
. We call R the ring of the quasi-localization M. Some old results due to Zassenhaus and Butler show that all rings with free additive groups of finite rank are indeed rings
of quasi-localizations of ℤ. We will extend this result and show that there are also rings of infinite rank with this property.
While there are many realization results of rings R as endomorphism rings of torsion-free abelian groups M in the literature, the group M is usually not contained in the divisible hull of R+, as is required here. We will use a particular case of a category of left R-modules M with a distinguished family
of submodules and thus
. We will restrict our discussion to the case M = R such that
, and in this case we call the family
of left ideals E-forcing, not to be confused with the notion of forcing in set theory. We will provide many examples of quasi-localizations
M of ℤ, among them those of infinite rank as well as matrix rings for various rings of finite rank. 相似文献
The complex [7,10-mu-H-7-CO-7,7-(PPh3)2-isonido-7,8,9-ReC2B7H9] has been synthesized by treatment of the complex salt [NHMe3][3,3-Cl2-3,3-(CO)2-closo-3,1,2-ReC2B9H11] with PPh3 in refluxing THF (tetrahydrofuran) and isolated as intensely colored orange-red microcrystals. Spectroscopic NMR and IR data have suggested that the product has a highly asymmetric structure with two inequivalent PPh3 ligands and a single CO ligand. Measurement of 11B NMR spectra in particular have indicated seven distinct boron vertexes, although the resulting cage degradation by removal of two BH vertexes was confirmed only following X-ray crystallographic analysis, which revealed the pentadecahedral isonido-7,8,9-ReC2B7 architecture. The 11B NMR resonances span an enormous chemical shift range (Deltadelta = 113), and this appears to be a direct consequence of the deshielding of the boron vertex directly opposite the quadrilateral |ReCCB| aperture. The new complex has been shown by electrochemical measurements to undergo a reversible one-electron oxidation. Digitally simulated cyclic voltammograms support a proposed square scheme (E(1/2) = 0.58, 0.69 V vs ferrocene) involving a reversible isonido-closo transition of the metallacarborane cage. Most unusually for a metallacarborane complex, ambient temperature solutions in CH2Cl2 and DMF have been shown to be intensely turquoise-blue fluorescent (lambda(em) = 442 nm, Phi = 0.012). Fluorescence spectroscopy measurements in MeTHF (2-methyltetrahydrofuran) glass at 77 K have indicated that the likely cause of such a broad emission is dual fluorescence (lambda(em) = 404, 505 nm), with both emissions displaying vibronic structure. Following excited-state lifetime decay analysis, the emissive behavior has been accredited to metal-perturbed 1IL states, with the lower energy emission arising from a slight geometric distortion of the initially excited complex. 相似文献
Let R be a ring with identity. We call a family ? of left ideals of R a Zassenhaus family if the only additive endomorphisms of R that leave all members of ? invariant are the left multiplications by elements of R. Moreover, if R is torsion-free and there is some left R-module M such that R ? M ? R??? and End?(M) = R we call R a “Zassenhaus ring”. It is well known that all Zassenhaus rings have Zassenhaus families. We will give examples to show that the converse does not hold even for torsion-free rings of finite rank. 相似文献
This paper introduces an indirect intelligent sliding mode controller (IISMC) for shape memory alloy (SMA) actuators, specifically a flexible beam deflected by a single offset SMA tendon. The controller manipulates applied voltage, which alters SMA tendon temperature to track reference bending angles. A hysteretic recurrent neural network (HRNN) captures the nonlinear, hysteretic relationship between SMA temperature and bending angle. The variable structure control strategy provides robustness to model uncertainties and parameter variations, while effectively compensating for system nonlinearities, achieving superior tracking compared to an optimized PI controller. 相似文献
The partitioning of reaction exothermicity into relative translational energy of the products of gas-phase SN2 (F? + CH3Cl) and nucleophilic aromatic substitution (F? + C6H5Cl) reactions has been investigated using kinetic energy release Fourier transform ion cyclotron resonance spectroscopy. The chloride product ion is observed to be highly translationally excited for the SN2 reaction, indicating a cold internal energy distribution for the products. For the chlorobenzene reaction the products are not generated with large translational energies. The results are compared with a statistical model. Ion-intensity profiles for the CH3Cl reaction deviate significantly from the statistical model whereas the chlorobenzene results are consistent with this model. The kinetic energy release for the CH3C1 reaction is compared with energy-disposal results for the photodissociation and dissociative electron-attachment processes of halomethanes. In all three cases a node in the molecular orbital between the carbon atom and the departing halogen results in a repulsive energy release. Ion-retention curves for the nucleophilic aromatic substitution reaction are consistent with the existence of a long-lived ion-dipole complex on the exit channel for this reaction. 相似文献
A Microsoft EXCEL 5.0 program was developed to evaluate data from biochemical and functional bioassays, an important step in drug discovery. The program accommodates both agonist and antagonist data. The program, written entirely in Visual Basic, is compatible with both Macintosh and PC platforms. Data are conveniently entered into a worksheet following only a few simple rules. The program performs complex data analysis and outputs calculated and graphic results to EXCEL worksheets. A set-up routine with a convenient dialog box offers the user controls regarding data analysis and results formats. After determining if the data are from an agonist or antagonist assay, the program automatically performs the analysis and outputs results in the proper format. Calculations support Schild analysis for antagonists. An agonist and antagonist were analyzed to illustrate program usage and results generated by the analysis. EXCEL-Visual Basic is a useful and convenient tool for evaluating bioassay data. Data entry is greatly simplified and custom reports can be generated with relative ease. Data are stored in a format that allows for easy editing re-analysis. 相似文献