[en] Manganese dioxide has been used to scavenge radionuclides from water solutions. In this work the behaviour of MnO₂ with uranium and plutonium has been studied by batch equilibration experiments, column experiments and cartridge experiments. 8 refs.; 2 figs.; 3 tabs

[en] We present a band-selective NMR method to probe the constituent electronic bands separately in the condensed molecular matter. This method is applied to an organic-inorganic π-d hybrid metal, and its utility to give the static and dynamic spin susceptibilities for the constituent bands is demonstrated. The analysis of the results uncovers an exotic feature; the antiferromagnetic and ferromagnetic correlations are enhanced in separate bands in a single material. This finding provides a novel scope connecting the metal-insulator transitions in this system and the manganese oxides

[en] A simple method based on a conventional solid-state process is proposed for synthesis of manganese oxide nanowires. This method provides an opportunity for bunching the nanowires synthesized, since the nanowires form in one direction. Thus, aligned bunches (e.g. >100 μm long and about 50 μm in diameter) consisting of individual nanowires (diameters ranging between 50 and 200 nm) can be prepared simply. The phenomenon of simultaneous alignment of the nanowires in one direction to form ordered bunches is indeed an interesting development in the realm of nanotechnology. It can be considered as an alternative to conventional template-based methods

[en] Polycrystalline CuMn₂O₄ is synthesized by solid state reaction method. Structural and magnetization studies reveal that the sample is multiphase with CuMn₂O₄ as primary phase and Mn₃O₄ as secondary phase. Magnetocaloric properties such as isothermal magnetic entropy change (−ΔS _M) and refrigerant capacity (RC) are evaluated from isothermal magnetization data. Value of isothermal magnetic entropy change ($|\mathrm{\Delta <!--\; ??\; -->}{S}_M|$) in the 40–80 K temperature range is 3.5–4.6 J kg⁻¹K⁻¹, for a field change of ΔH = 70 kOe. Value of refrigeration capacity (RC) evaluated for the same field change (ΔH = 70 kOe) is ∼190 J/kg for the T _cold and T _hot pair of 40 and 90 K respectively. Also value of $|\mathrm{\Delta <!--\; ??\; -->}{S}_M|$ remains almost constant over a broad temperature range of 60–80 K. (paper)

[en] We investigate the influence of MnO₂ polymorphism form on MnO₂/Ag₂O hydrogen getter. The results show that the performances strongly depend on the polymorphism form of manganese oxide. The nsutite γ-MnO₂ phase, which consists of a random intergrowth of MnO₂–ramsdellite and MnO₂–pyrolusite building blocks, shows the more promising performances to trap H₂ via the formation of hydroxyl groups. This observation is especially relevant for compounds with a low pyrolusite/ramsdellite ratio and a high rate of microtwinnings

[en] In 1986 Alex Mueller and Georg Bednorz of IBM Zurich discovered high-temperature superconductivity in copper-based oxides. This finding, which was rewarded with the Nobel Prize for Physics in the following year, triggered intense research into the properties of the transition metal oxides. Since then scientists have questioned the very nature of the metallic state in these materials. A few years after the initial discovery, in 1993, more excitement greeted reports that certain manganese oxides showed a huge change in electrical resistivity when a magnetic field was applied. This effect is generally known as magnetoresistance, but the resistivity change observed in these oxides was so large that it could not be compared with any other forms of magnetoresistance. The effect observed in these materials the manganese perovskites was therefore dubbed ''colossal'' magnetoresistance to distinguish it from the giant magnetoresistance observed in magnetic multilayers. In this article the author explains why magnetoresistance is an expanding field of physics research. (UK)

[en] In the present report the sorption character of uranium (IV) in the static conditions on the thin layer sorbents with application of the clinoptilolite of the Chankan deposit of the Republic of Kazakhstan is shown. A wide circle of metal hydroxides - in both the individual form and in the their mixture - is used. It is shown that the most sorptive capacity against the uranium (IV) has the modified clinoptilolite of MnO₂

[en] Periodically ordered mesoporous manganese oxides were synthesized in a single and double replication procedure. Mesoporous SBA-15 and -16 silica and their reverse replica carbons were successively used as hard templates. The silica and carbon pore systems were infiltrated with Mn(NO₃)₂·xH₂O or Mn(AcAc)₂, which was then converted to Mn₂O₃ at 873 K: the silica and carbon matrix were finally removed by NaOH solution or calcinations in air. The structure of the mesoporous Mn₂O₃, using a carbon template, corresponds to that of the original SBA-15 and SBA-16 silica. The products consist of hexagonally arranged cylindrical mesopores with crystalline pore walls or cubic mesoporous pores. The structure of replica has been confirmed by XRD, TEM analysis, and its electrochemical properties were tested with cyclic voltammetry. Formation of Mn₂O₃ inside the mesoporous carbon pore system showed much improved electrical properties

[en] Tetracycline antibiotics including tetracycline (TTC), oxytetracycline (OTC) and chlorotetracycline (CTC) undergo rapid transformation to yield various products in the presence of MnO₂ at mild conditions (pH 4-9 and 22 ^oC). Reaction rates follow the trend of CTC > TTC > OTC, and are affected by pH and complexation of TCs with Mg²⁺ or Ca²⁺. Experimental results of TTC indicate that MnO₂ promotes isomerization at the C ring to form iso-TTC and oxidizes the phenolic-diketone and tricarbonylamide groups, leading to insertion of up to 2 O most likely at the C9 and C2 positions. In contrast, reactions of OTC with MnO₂ generate little iso-OTC, but occur mainly at the A ring's dimethylamine group to yield N-demethylated products. CTC yields the most complicated products upon reactions with MnO₂, encompassing transformation patterns observed with both TTC and OTC. The identified product structures suggest lower antibacterial activity than that of the parent tetracyclines. - Highlights: → Tetracyclines transform rapidly by MnO₂ to yield complicated products. → Isomerized, (hydr)oxygenated and N-demethylated products are formed. → Transformation product structures may suggest lowered antibacterial activity. - The complex transformation pathways of three popular tetracycline antibiotics (tetracycline, oxytetracycline and chlorotetracycline) with MnO₂ under environmental conditions are systematically evaluated and elucidated.

[en] Birnessite-type MnO₂ materials are widely studied as electrodes for pseudocapacitors. However, the poor cycling stability limits their applications. Here, wrinkle birnessite-type MnO₂ nanosheet array has been synthesized and taken as an example to discover the reason of capacity fading for pseudocapacitors. It is discovered that in the the galvanostatic charge-discharge process, the smalle nanosheets blocking the macropores of the array framework have been dissolved and recrystallized on the large wrinkle birnessite nanosheet array framework, finally forming a hierarchical structure of nanosheets@nanosheets of birnessite. The recrystallizaion of the small birnessite nanosheets may decrease the specific capacity through the decreasement of the surface area of the electrode. (paper)