Hydrogenated and deuterated iron clusters: Infrared spectra and density functional calculations

Iron clusters react sequentially with hydrogen molecules to form multiply hydrogenated products. The increases in cluster ionization potential upon reaction verify that hydrogen chemisorbs dissociatively to form iron cluster–hydride complexes, FenHm. At low source temperatures, the cluster–hydride complexes take up additional hydrogen molecules which are shown to be physisorbed onto the underlying FenHm complexes to form FenHm(H2)p species. The infrared spectra of FenHm and FenDm (n = 9–20) were obtained by the photodissociation action spectroscopic method in which depletion of the FenHm(H2)p and FenDm(D2)p species was the signature of absorption. The spectra, recorded in the 885–1090 cm−1 region, consist of several overlapping bands, each approximately 20 cm−1 in width. The dissimilarity of each FenHm(H2)p spectrum with the corresponding FenDm(D2)p spectrum indicates that the carrier involves hydrogen and is not merely due to absorption by the underlying iron cluster. Density functional calculations were performed on model complexes, Fe13H14 and Fe13D14, the iron portion of which was assumed to have Th symmetry. The infrared-active vibrational frequencies involving hydrogen bending and deuterium stretching are predicted to lie within the experimental frequency range of the experiment, well removed from the skeletal modes of the underlying iron cluster. The complexity of the observed spectra as compared to simulations based on the assumed (high-symmetry) model imply that the experimentally produced complexes possess low symmetry

Application of the Program-Targets Method in the Formation of the Advanced Development Strategy of the Modern Library

The coming era of digital transformation, from the point of view of the consumer of information services, has a dual character. On the one hand, there is an excess of information, and on the other hand, its absence in the form ready for adequate perception by the vast majority of citizens. The ongoing «information overload» causes the effect of reducing the motivation to use information, which entails the closure of libraries and the reduction of the library stock. Integrating modern technologies into library activities, providing the relationship between the physical and virtual worlds, will bring the library to a completely new level of relationships with readers and significantly increase the efficiency of information use. The article deals with the issues of innovative activities of the library, aimed at developing and implementing the provisions of the digital development strategy, which provides for digital transformation, which implies a significant increase in efficiency through the introduction of new user service technologies. It is substantiated that the methodology of Academician V. L.Kvint, according to which strategy is defined as a system of search, formulation and development of doctrine, which ensures long-term success with its consistent and complete implementation; in accordance with the stated principles of strategizing, the scheme for developing a strategy for the advanced development of a modern library is formalized and described. It is shown that the methodology of program-target management makes it possible to synchronize the process of strategizing with the processes of «substantiating goals in terms of their achievability in time and consistency with resource capabilities», such synchronization is provided by the logical scheme of the method: «goals — ways to achieve — means», in accordance with which the goals set for the digital development of the object of strategizing are implemented by a set of organizational and technical measures provided with the resources required for this

Investigation of radiation effects in water solutions during exposure with laser or LEDs light

Abstract only.The installation for gamma-, X-ray and neutron registration in water solutions (600 ml LiOH, or NaOH, or Na2CO3) during exposure with red light (λ=645+/-20 nm) of laser or light-emission devises (LEDs) was created. The laser light power was 5 mW and the LEDs - from 600 mW up to 10 W. Neutrons were measured with help of tow 3He counters, placed in paraphine barrel. Small neutron emission (up to 100 neutrons) has been registered in the form of series of short (ms) bursts during some minutes. Tritium production has also been detected in water solution probes. The gamma-ray and X-ray radiation measured by NaI scintillation detector & Geiger counters was not detected. Received results are discussed

Work functions, ionization potentials, and in-between: Scaling relations based on the image charge model

We revisit a model in which the ionization energy of a metal particle is associated with the work done by the image charge force in moving the electron from infinity to a small cut-off distance just outside the surface. We show that this model can be compactly, and productively, employed to study the size dependence of electron removal energies over the range encompassing bulk surfaces, finite clusters, and individual atoms. It accounts in a straightforward manner for the empirically known correlation between the atomic ionization potential (IP) and the metal work function (WF), IP/WF$\sim$2. We formulate simple expressions for the model parameters, requiring only a single property (the atomic polarizability or the nearest neighbor distance) as input. Without any additional adjustable parameters, the model yields both the IP and the WF within $\sim$10% for all metallic elements, as well as matches the size evolution of the ionization potentials of finite metal clusters for a large fraction of the experimental data. The parametrization takes advantage of a remarkably constant numerical correlation between the nearest-neighbor distance in a crystal, the cube root of the atomic polarizability, and the image force cutoff length. The paper also includes an analytical derivation of the relation of the outer radius of a cluster of close-packed spheres to its geometric structure.Comment: Original submission: 8 pages with 7 figures incorporated in the text. Revised submission (added one more paragraph about alloy work functions): 18 double spaced pages + 8 separate figures. Accepted for publication in PR

MRI sensing based on the displacement of paramagnetic ions from chelated complexes

We introduce a mechanism for ion sensing by MRI in which analytes compete with paramagnetic ions for binding to polydentate chelating agents. Displacement of the paramagnetic ions results in alteration of solvent interaction parameters and consequent changes in relaxivity and MRI contrast. The MRI changes can be tuned by the choice of chelator. As an example, we show that calcium-dependent displacement of Mn[superscript 2+] ions bound to EGTA and BAPTA results in a T[subscript 1]-weighted MRI signal increase, whereas displacement from calmodulin results in a signal decrease. The changes are ion selective and can be explained using relaxivity theory. The ratio of T[subscript 2] to T[subscript 1] relaxivity is also calcium-dependent, indicating the feasibility of “ratiometric” analyte detection, independent of the probe concentration. Measurement of paramagnetic ion displacement effects could be used to determine analyte ion concentrations with spatial resolution in opaque specimens.National Institutes of Health (U.S.) (grant DP2-OD2441)National Institutes of Health (U.S.) (grant R01-GM65519)McGovern Institute for Brain Research at MIT. Neurotechnology (MINT) Progra

Evaluating the Developed Model of Experimental Rhinitis in Laboratory Rats: Pre-Clinical Experimental Randomized Study

Background. Among the damaging factors affecting the mucociliary system of the nasal cavity, surgical wound is of particular relevance in the practice of an otorhinolaryngologist. The clinical assessment of regeneration of the mucociliary system is associated with certain diffi culties, since the intravital morphological examination of the nasal mucosa in patients is traumatic. Therefore, the development of animal models of experimental rhinitis is considered to be highly relevant in order to study the dynamics of mucociliary pathomorphological changes and assess the epithelium regeneration.Objectives. To evaluate the developed model of experimental rhinitis in laboratory rats by studying clinical, morphological and biochemical changes in the infl ammatory process.Methods. The experimental rhinitis model was developed and tested on 60 mature male Wistar rats. All animals were randomized into two groups: experimental group #1 (n = 30) — rats in which experimental rhinitis modeling was performed and group #2 (n = 30) — control, intact animals. In the course of the experiment, the authors examined the content of CRP in blood, evaluated the differential blood cell count, and studied a morphology of the nasal septum mucosa in 2, 5, 10 days after the injury to assess the dynamics of the infl ammatory process in rats of both groups. Statistical analysis of the study results was carried out by means of Statistica 8.0 (StatSoft Inc., USA).Results. After injury, the rats from group #1 developed acute rhinitis, which was clinically manifested by the release of mucous or mucopurulent secretion from the nostrils, sneezing and scratching the nose. An increase in CRP, band and segmented neutrophils, and a decrease in lymphocytes were observed in blood of the rats from group #1 in comparison with the control group. Microscopic analysis of changes in the nasal septum mucosa showed that the acute phase of exudative infl ammation developed on the second day: vascular congestion, edema, neutrophilic infl ammatory infi ltration of the submucosal membrane were observed against the background of foci of epithelial necrosis. The proportion of lymphocytes and macrophages in the infl ammatory infi ltrate increased by the fi fth day, initial signs of restoration of epithelial tissue — the formation of an undifferentiated regenerating epithelium — appeared by the tenth day.Conclusion. The results of the study show that an adequate experimental model of acute rhinitis in laboratory animals have been obtained. An acute infl ammatory process is characterized by clinical manifestations and changes in blood parameters. Particular destructive and reparative-proliferative changes develop in the mucous membrane of the nasal septum of experimental animals as a result of a surgical wound

Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)

BACKGROUND: Seasonal changes in pore water and sediment redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability. RESULTS: Seasonal trends in pore water and sediment geochemistry are assessed in the upper 50 cm of littoral kettle lake sediments. Pore waters are always redox stratified, with the least compressed redox stratification observed during fall and the most compressed redox stratification observed during summer. A 2-step sequential sediment extraction yields much more Fe in the first step, targeted at amorphous Fe(III) (hydr)oxides (AEF), then in the second step, which targets Fe(II) monosulfides. Fe extracted in the second step is relatively invariant with depth or season. In contrast, AEF decreases with sediment depth, and is seasonally variable, in agreement with changes in redox stratification inferred from pore water profiles. A 5-step Tessier extraction scheme was used to assess metal association with operationally-defined exchangeable, carbonate, iron and manganese oxide (FMO), organic/sulfide and microwave-digestible residual fractions in cores collected during winter and spring. Distribution of metals in these two seasons is similar. Co, As, Cd, and U concentrations approach detection limits. Fe, Cu and Pb are mostly associated with the organics/sulfides fraction. Cr and Zn are mostly associated with FMO. Mn is primarily associated with carbonates, and Co is nearly equally distributed between the FMO and organics/sulfide fractions. CONCLUSION: This study clearly demonstrates that near-surface lake sediment pore water redox stratification and associated solid phase geochemistry vary significantly with season. This has important ramifications for seasonal changes in the bioavailability and mobility of trace elements. Without rate measurements, it is not possible to quantify the contribution of various processes to natural organic matter degradation. However, the pore water and solid phase data suggest that iron reduction and sulfate reduction are the dominant pathways in the upper 50 cm of these sediments