One of the most important atomic properties governing an element's chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the ...heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626 21±0.000 05 eV. This work provides a stringent benchmark for state-of-the-art many-body atomic modeling that considers relativistic and quantum electrodynamic effects and paves the way for high-precision measurements of atomic properties of elements only available from heavy-ion accelerator facilities.
The transformation of organic matter in the soil is largely determined by hydrolytic enzymes. Under the conditions of climate change, understanding the mechanisms of microbial response is of ...particular importance for predicting the carbon cycle. Until now, the effect of drought duration and frequency on soil hydrolytic enzymes has been little studied. A multifactorial field manipulation experiment was carried out, simulating in the presence of plants and without them: two short-term droughts, a long-term drought, and an optimal level of soil moisture. The maximum reaction rate
V
max
, Michaelis constant
K
m
, and catalytic efficiency
K
a
of five groups of enzymes involved in the carbon cycle (cellobiase, glucosidase, xylanase), phosphorus (phosphatase), and nitrogen (chitinase) were determined. In phosphatases, glucosidases, and xylanases,
V
max
decreased during short-term drought. During prolonged drought, the
V
max
value of phosphatases, cellobiohydrolases, and xylanases decreased and increased in chitinases, while remaining unchanged in glucosidases. Both long-term and short-term droughts led to an increase in
K
m
and a decrease in catalytic efficiency (
K
a
) for almost all enzymes. Short-term droughts were not a “weakened version” of a long-term drought, but had their own specifics—a decrease in
K
m
of glucosidases, which led to an increase in
K
a
. Long-term drought was characterized by an increase in
V
max
of chitinases and spatial variability of
V
max
of phosphatases and glucosidases. The influence of the presence of plants was secondary and manifested itself only during short droughts. The reversibility of the effect of drought on
V
max
,
K
m
, and
K
a
decreased in the series first short-term drought > second short-term drought > long-term drought due to an increase in the total duration of the stress impact.
Atrial macro reentry tachycardias are the most common tachyarrhythmias in the structure of cardiac arrhythmias in the elderly. Catheter ablations are the gold standard for the treatment of atrial ...macro reentry arrhythmias, but in the elderly group, the risks of complex ablations often outweigh the benefits.
Aim: to determine the optimal volume of catheter ablation in atrial tachyarrhythmia using an implanted pacemaker in elderly patients.
Materials and methods. The work is based on a retrospective analysis of the results of surgical treatment of (n = 45) elderly patients (75–90 years) with atrial macro reentry tachycardia, who were previously identified as an artificial pacemaker at the National M. Amosov Institute of Cardiovascular Surgery Affiliated to National Academy of Medical Sciences of Ukraine. Patients were divided into 3 groups depending on the response of the reentry tachycardia to electrical pacing (assessed by the difference between postpacing interval (PPI) and tachycardia cycle lens (CL): group І – PPI-CL 20–40 ms; group ІІ – PPI–CL 20–40 ms; group ІІІ – PPI-CL 60 ms and more.
Results. In the group I (n = 20) in 100 % of the patients isthmus-dependent reentry tachyarrhythmia was diagnosed and cava-tricuspid isthmus was ablated. In the group ІІ (n = 12) 4 (33 %) patients were diagnosed with reentry tachycardia around the right pulmonary veins, in 8 (67 %) patients – reentrant tachycardia around the mitral valve. In the group ІІІ (n = 13) in 8 (62 %) patients macro reentry around the mitral valve was found, in 3 (23 %) – reentry around the left pulmonary veins, in another 2 (15 %) of the patients – reentry of the left atrial roof.
Conclusions. Non-invasive electrophysiological study with pacemaker can be an effective way to study atrial macro reentry tachyarrhythmias. Electrophysiological PPI-SI criteria less than 20 ms can be used as an additional diagnostic criterion for the selection of patients for surgical treatment. Catheter ablation is recommended for elderly patients when the reentry circle is located in the right atrium.
Two heteroleptic NiII complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer ...(LL’CT, HOMOcatecholate → LUMOα-diimine). A molecular design of compound NiII(3,6-Cat)(bipy)∙CH3CN (1) on the base of bulky 3,6-di-tert-butyl-o-benzoquinone (3,6-DTBQ) was an annelation of the ligand with an electron donor glycol fragment, producing derivative NiII(3,6-Catgly)(bipy)∙CH2Cl2 (2), in order to influence the energy of LL’CT transition. A substantial longwave shift of the absorption peak was observed in the UV-Vis-NIR spectra of 2 compared with those in 1. In addition, the studied NiII derivatives demonstrated a pronounced negative solvatochromism, which was established using a broad set of solvents. The molecular geometry of both compounds can be ascribed as an insignificantly distorted square-planar type, and the π–π intermolecular stacking of the neighboring α-diimines is realized in a crystal packing. There is a lamellar crystal structure for complex 1, whereas the perpendicular T-motifs with the inter-stacks attractive π–π interactions form the packing of complex 2. The redox-active nature of ligand systems was clearly shown through the electrochemical study: a quasi-reversible one-electron reduction of 2,2′-bipyridine and two reversible successive one-electron oxidative conversations (“catecholate dianion—o-benzosemiquinonato radical anion—neutral o-benzoquinone”) were detected.
The paper presents petrochemical, geochemical, and mineralogical data on rocks of the phoscorite–carbonatite complex in the Kovdor alkaline–ultramafic massif, Kola Peninsula, Russia. In contrast to ...what is usually thought, trace elements were determined to be concentrated not in the carbonatites themselves but in the related phoscorites. The paper presents data on the evolution of the compositions and zoning of minerals in successive generations of both rock types as a result of the fractional crystallization of their parental magmas, and data on general trends in the concentrations of trace elements. The Fe-rich phosphate–carbonate melt seems to have separated from the primitive alkaline–ultramafic silicate melt during its advanced differentiation. The Fe-rich phosphate–carbonate magma was parental for the phoscorite–carbonatite complex. The possibility of its splitting into immiscible Fe-rich phosphate and carbonatite melts is discussed.
The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The ...radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."
We report the synthesis, structural investigation, and thermal behavior for three zinc-based 1D-coordination polymers with 3,6-di-tert-butyl-2,5-dihydroxy-p-benzoquinone, which were synthesized in ...the presence of different glycols. The interaction of zinc nitrate with glycols, followed by using the resulting solution in solvothermal synthesis with the anilate ligand in DMF, makes it possible to obtain linear polymer structures with 1,2-ethylene or 1,2-propylene glycols coordinated to the metal. The reaction involving 1,3-propylene glycol under similar conditions gives a crystal structure that does not contain a diol. The crystal and molecular structures of the synthesized compounds were determined using single crystal by X-ray structural analysis. The influence of glycol molecules coordinated to the metal on the thermal destruction of synthesized compounds is shown.
Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with ...modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of ^{252,253,254}No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in ^{252,254}No isotopes. Finally, the hyperfine splitting of ^{253}No was evaluated, enabling a complementary measure of its (quadrupole) deformation, as well as an insight into the neutron single-particle wave function via the nuclear spin and magnetic moment.
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