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Abstract: Nanoparticles of the single spinel phase Co1−x Zn x Fe2O4+γ of mean size 3–23nm, as determined by X-ray diffraction analysis, were synthesized by the co-precipitation method followed by a temperature treatment. Magnetic studies carried out in the range of 4.5–550K revealed gradual transition from ferrimagnetic to superparamagnetic to paramagnetic behaviour depending on the composition and particle size. The observed behaviour indicates a broad distribution of volume sizes of the nanoparticles. Particular importance can be ascribed to the composition of x=0.6 where the observed transition temperature to the paramagnetic state at 310–334K suggests applicability of this material for magnetic fluid hyperthermia in a self-controlled regime. [Copyright &y& Elsevier]

Temperate mountain forests have experienced an increase in frequency and severity of natural disturbances (e.g., droughts, fires, windstorms and insect outbreaks) in recent decades due to climate and environmental change. Outbreaks of bark beetles have caused significant dieback of conifer forests in Central Europe and it is essential to model and predict the potential severity of future bark beetle outbreaks. However, to predict future bark beetle activity, historical baseline information is required to contextualize the magnitude of current and potential future outbreaks. A fossil beetle record from a forest hollow in the Tatra Mountains, Slovakia; one of the best-preserved national parks in Central Europe, was produced to identify insect outbreaks during the last millennia. Sub-fossil bark beetle remains were compared with parallel pollen and charcoal to assess whether peaks in conifer bark beetle remains correspond with indications of disturbance documented in historical or sedimentary fossil records. Three peaks in bark beetle remains were detected (1) post-2004, (2) AD 1140–1440, and (3) AD 930–1030. The abundance of species Pityogenes chalcographus and Pityophthorus pityographus in the two top samples can be linked directly to large bark beetle outbreaks in the High Tatra Mountains after 2004. P. chalcographus and P. pityographus are also the abundant species in the second peak (AD 1140–1440) while the third peak (AD 930–1030) consists of the species Polygraphus poligraphus. The most prominent conifer bark beetle in Central Europe, Ips typographus , was found to be present in most of the samples but always at very low numbers. It is plausible that P. chalcographus and P. pityographus fossils might be useful proxies for past conifer bark beetle outbreaks in Central Europe, as they occur together with fossils of I. typographus but appear to be well-preserved. A significant correlation was found between primary bark beetles and macroscopic charcoal densities in the sediment, highlighting the complex interactions between disturbance agents, bark beetles and fire, in this long-term regime of natural disturbances. Our 1400-year disturbance record shows how bark beetle outbreaks have been an important component of the regional natural disturbance regime for over a millennium and have intensified with increasing anthropogenic activity. Bark beetle outbreaks are likely one of the drivers promoting the future ecological stability of the temperate conifer ecosystem over decades to centuries. • Historical baseline info is required to predict future bark beetle outbreaks. • A fossil record from the High Tatras provides abundant bark beetle fossils. • Three distinct bark beetle peaks are recorded between 1400 BP and present. • Subfossil bark beetle abundances correlate to charcoal concentrations. • Bark beetle outbreaks were originally part of the disturbance regime in this region. [ABSTRACT FROM AUTHOR]

Abstract: Metabolic abnormalities frequently associated with type 2 diabetes, feature besides endothelial dysfunction a novel factor of low cholesterol absorption and high cholesterol synthesis. We hypothesized an association between endothelial dysfunction and disturbances in cholesterol turnover, predisposing advanced atherosclerosis in patients with type 2 diabetes. We studied 75 patients: 30 with type 2 diabetes, 30 non-diabetic subjects with a history of cardiovascular disease, and 15 healthy subjects. Plasma sterols, soluble adhesion molecules sCD14, sCD40 Ligand, monocyte chemo-attractant protein-1 (MCP-1), sE- and sP-selectins were measured with and without atorvastatin therapy. The diabetic patients showed significantly higher levels of lathosterol and lower levels of sitosterol and campesterol. Non-diabetic subjects showed no significant differences in non-cholesterol based sterols. Plasma levels of hsCRP, sE- and sP-selectins and MCP-1 were significantly increased in patients with diabetes. The plasma levels of sCD40L correlate significantly with clinical parameters of BMI and glycaemia, and the plasma levels of sP-selectin correlate significantly with parameters of glycaemia and HbA1c. The diabetic patients without statin therapy showed a significant correlation of sE-selectin with the marker of cholesterol absorption—sitosterol and sitosterol/cholesterol ratio. The diabetic patients without statin therapy showed a significant inverse correlation of sP-selectin with the marker of cholesterol synthesis—lathosterol. Both relationships disappeared with statin treatment. We conclude that endothelial dysfunction in obese patients with type 2 diabetes mellitus and cardiovascular disease associates with obesity and glycaemic control. The relation of parameters of endothelial dysfunction (such as sP-selectin and sE-selectin) with cholesterol synthesis and absorption may be influenced by reverse cholesterol transport. [Copyright &y& Elsevier]

• Two ammonia spectra are recorded in the 11000 – 14500 cm-1 region. • 278 lines are assigned using combination differences and variational nuclear motion calculations. • 119 new energy levels belonging to 16 vibrational states are determined. Two sets of NH 3 absorption spectra covering the 0.793 μ m region are recorded using two Bruker IFS 125 HR Fourier transform spectrometers. Three unapodized absorption spectra are recorded in Brussels over the range 11000 − 14500 cm − 1 and the positions and intensities of 1114 ammonia lines observed in the 12491 − 12810 cm − 1 region are measured using a multi-spectrum least squares fitting algorithm. 367 additional lines are identified in an ammonia absorption spectrum recorded in two steps at the J. Heyrovsky Institute of Physical Chemistry in Prague, using two different interference filters covering the 12000 − 12500 and 12400 − 13000 cm − 1 ranges. The 1481 measured ammonia lines are analyzed using an empirical line list computed using variational nuclear motion calculations and ground state combination differences. Transitions are assigned to vibrational states with 4 ν N H stretching excitation (v 1 + v 3 = 4). 278 out of the 1481 measured lines are assigned to 300 transitions and 119 upper state energy levels are derived from the frequencies of the assigned transitions. [ABSTRACT FROM AUTHOR]

Iron sulphide Fe 3 S 4 , known as the mineral greigite, has been prepared in two distinct nanocrystalline forms with the mean crystallite size of d XRD ≈ 30 and 80 nm via hydrothermal synthesis by using two different surfactants (oleic acid and cetyltrimethylammonium bromide). Their crystallinity and phase purity are probed by X-ray diffraction and Mössbauer spectroscopy. For detailed characterization of the ferrimagnetic state and its temperature evolution, the SQUID magnetometry, ferromagnetic resonance and the temperature dependence of 57Fe Mössbauer spectra are used. The blocking behaviour of the nanocrystalline samples is discussed with respect to magnetic and Mössbauer data. Moreover, special attention is given to the analysis of temperature-dependent data, which reveals that: first, spin reorientation associated with the change in easy axis from 110 to 111 on cooling occurs at ≈100 K, secondly, Verwey-like transition is not present. • Greigite crystallites with d XRD ≈30 and 80 nm were prepared by hydrothermal method. • Ferrimagnetic order was characterized by spontaneous moments 3.08 and 3.28 μ B per formula unit. • Ferromagnetic resonance showed different behaviour of the two samples. • Temperature-dependent Mössbauer spectroscopy indicated spin-reorientation transition. [ABSTRACT FROM AUTHOR]

Abstract: A systematic study of LaMn1− x Co x O3 perovskite series by means of X-ray absorption spectroscopy in the extended X-ray absorption fine structure (EXAFS) range of the K-absorption edge of Mn is reported. The Mn–K edge absorption measurements in the EXAFS region were performed to study the local surrounding of Mn ions. Polycrystalline powder samples of LaMn1− x Co x O3 (x=0, 0.02; 0.2; 0.4; 0.5; 0.6; 0.8) prepared by solid-state reaction were used. The EXAFS spectra were analyzed with the FEFF8 computer program. The Mn–O distances of Mn to the nearest oxygen surroundings were evaluated for the samples in the series and compared with the Co–O distances obtained by EXAFS in V. Procházka et al., JMMM 310 (2007) 197 and with results of X-ray powder diffraction in C. Autret, J. Phys. Condens. Matter 17 (2005) 1601. [Copyright &y& Elsevier]

Abstract: The electric transport and magnetic susceptibility of double perovskites La2− x Sr x CoRuO6 have been studied over a temperature range up to 800–1000K. The crystal and magnetic structure has been determined by neutron diffraction on two samples of the series, x=0.6 and 1.4, which represent the electron- and hole-doped systems with respect to “ideal” single-valent insulator x=1. The study shows that spins in both the Co and Ru f. c. c. like sublattices exhibit a long-range ordering of the antiferromagnetic type II (T N=60K for x=0.6 and T N=60–80K for x=1.4). [Copyright &y& Elsevier]

• Natural and synthetic chalcopyrites were combined to obtain nanocomposite. • Nanocomposite was obtained via mechanochemical treatment and subsequent sintering. • Thermoelectric performance of CuFeS 2 can find application in large-scale production. Chalcopyrite CuFeS 2 was shown to be a promising thermoelectric material. Considering thermoelectric efficiency, its relatively high and temperature weakly dependent power factor, economic affordability and ecological benignity is counterbalanced by a high lattice thermal conductivity. Thus it is highly desirable to lower the thermal conductivity of chalcopyrite thermoelectric material without deterioration of other thermoelectric characteristics. In our study, we demonstrate that mechanosynthesis followed by appropriate sintering enables to prepare such nanostructured ceramics with a favourable thermoelectric response. Our study shows that mechanosynthesis is a low-cost technological route for the production of thermoelectric chalcopyrite ceramics. [ABSTRACT FROM AUTHOR]

The main objective of this study is to provide data on the bulk elemental composition, mineralogy and the possible origin of the Porangaba meteorite, whose fall was observed at 17:35 UT on 9 January 2015 on several sites of the state of São Paulo in Brazil. The surface of the meteorite was mapped by Scanning Electron Microscopy (SEM) and optical microscopy. The mineralogy and the bulk elemental composition of the meteorite were studied using Energy-Dispersive and Wavelength-Dispersive X-ray Spectroscopy (EDS/WDS) together with Electron Back Scatter Diffraction (EBSD). The bulk elemental composition was also independently analysed by Atomic Absorption Spectrometry (AAS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Laser Ablation ICP MS (LA ICP-MS) and Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS). Based on the available visual camera records of the Porangaba meteorite fall, its orbit was tentatively calculated, and possible candidates for the source bodies in the Solar system were proposed. We also present a laboratory simulation of a Porangaba-like (L4 Ordinary Chondrite) meteor emission spectra. These can be used as benchmark spectra for the identification of meteor rock types through their comparison with meteor spectra recorded by high-speed video-cameras equipped with simple grating spectrographs. • Complete study of Porangaba meteorite using a wide range of techniques • Calculations of Porangaba orbital parameters • Porangaba becomes one of rare examples of meteorites with complete lineage. • Porangaba was identified as relatively iron rich L4 type. [ABSTRACT FROM AUTHOR]

Abstract: The perovskite compounds of have been studied by means of NMR spectroscopy in powder samples prepared by the solid state reaction and sol–gel methods. The NMR signals were observed in the frequency range 250–650MHz at 4.2K in zero external magnetic field. A relatively narrow spectral line assigned to 55Mn in is situated around 270–320MHz in all spectra. Additional spectral lines are observed at higher frequencies. Line intensities and forms are dependent on the cobalt concentration and preparation techniques. [Copyright &y& Elsevier]

Abstract: The perovskite cobaltite Pr0.5Ca0.5CoO3 has been characterized by the magnetic and electric transport measurements, and structurally studied by neutron diffraction. The sample is a metallic-like conductor in a broad temperature range. On cooling, it undergoes at 75K an incomplete transition to the ferromagnetic phase of enhanced metallic character. The residual paramagnetic regions exhibit at about 30K a metal–insulator (M–I) transition, which is interpreted as a change from the t 2g 5 σ *0.5 cobalt states with collective e g electrons to a mixture of localized Co3+(t 2g 6 ) and Co4+(t 2g 5 ) low-spin states. The new insulating phase is of the same orthoperovskite type but distinguished by about 2% smaller unit cell volume compared to the ferromagnetic phase. The lattice contraction is caused by significant shortening of Pr,Ca–O bonding distances while the Co–O bond lengths remain nearly constant. [Copyright &y& Elsevier]

Abstract: A systematic study of cobalt environment in the perovskite series by means of X-ray absorption spectroscopy in the EXAFS range is reported. The spectra were measured at the edge of Co on powder samples at room temperature and analysed using multiple scattering paths calculated with the FEFF8 computer program. The next neighbor oxygen shell of cobalt shows a decrease of the distance from the central ion with increasing Co doping. This corresponds to an increased oxidation level of 3d ions. An information on the distortion of the oxygen octahedra and the Debye–Waller factor is discussed. [Copyright &y& Elsevier]

Hydrogen cyanide (HCN), a key molecule of significant importance in contemporary perspectives on prebiotic chemistry, originates in planetary atmospheres from various processes, such as photochemistry, thermochemistry, and impact chemistry, as well as from delivery by impacts. The resilience of HCN during periods of heavy bombardment, a phenomenon caused by an influx of material on unstable trajectories after accretion, remains relatively understudied. This study extensively investigates the stability of HCN under impact conditions simulated using a laboratory Nd:YAG laser in the ELISE experimental setup. High-resolution infrared spectroscopy was employed to monitor the gas phase composition during these simulations. Impact chemistry was simulated in bulk nitrogen atmospheres with varying mixing ratios of HCN and water vapor. The probed range of compositions spans from ∼0 to 1.8% of HCN and 0 to 2.7% of H 2 O in a ∼1 bar nitrogen atmosphere. The primary decomposition products of HCN are CO and CO 2 in the presence of water and unidentified solid phase products in dry conditions. Our experiments revealed a range of initial HCN decomposition rates between 2.43 × 10 15 and 5.17 × 10 17 molec J -1 of input energy depending on the initial composition. Notably, it is shown that the decomposition process induced by the laser spark simulating the impact plasma is nonlinear, with the duration of the irradiation markedly affecting the decomposition rate. These findings underscore the necessity for careful consideration and allowance for margins when applying these rates to chemical models of molecular synthesis and decomposition in planetary atmospheres., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Recent ground-based observations of Venus have detected a single spectral feature consistent with phosphine (PH 3 ) in the middle atmosphere, a gas which has been suggested as a biosignature on rocky planets. The presence of PH 3 in the oxidized atmosphere of Venus has not yet been explained by any abiotic process. However, state-of-the-art experimental and theoretical research published in previous works demonstrated a photochemical origin of another potential biosignature-the hydride methane-from carbon dioxide over acidic mineral surfaces on Mars. The production of methane includes formation of the HC · O radical. Our density functional theory (DFT) calculations predict an energetically plausible reaction network leading to PH 3 , involving either HC · O or H· radicals. We suggest that, similarly to the photochemical formation of methane over acidic minerals already discussed for Mars, the origin of PH 3 in Venus' atmosphere could be explained by radical chemistry starting with the reaction of ·PO with HC·O, the latter being produced by reduction of CO 2 over acidic dust in upper atmospheric layers of Venus by ultraviolet radiation. HPO, H 2 P·O, and H 3 P·OH have been identified as key intermediate species in our model pathway for phosphine synthesis.

Examination of thermal decomposition of street samples of cocaine and methamphetamine shows that typical products detected in previous studies are accompanied by a wide palette of simple volatile compounds easily detectable by spectral techniques. These molecules increase smoke toxicity and their spectral detection can be potentially used for identification of drug samples by well-controlled laboratory thermolysis in temperature progression. In our study, street samples of cocaine and methamphetamine have been thermolyzed under vacuum over the temperature range of 350-650 °C. The volatile products (CO, HCN, CH 4 , C 2 H 4 , etc.) have been monitored by high-resolution Fourier-transform infrared (FTIR) spectrometry in this temperature range. The decomposition mechanism has been additionally examined theoretically by quantum-chemical calculations for the highest temperature achieved experimentally in our study and beyond. Prior to analysis, the street samples have also been characterized by FTIR, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and melting point determination., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Besides delivering plausible prebiotic feedstock molecules and high-energy initiators, extraterrestrial impacts could also affect the process of abiogenesis by altering the early Earth's geological environment in which primitive life was conceived. We show that iron-rich smectites formed by reprocessing of basalts due to the residual post-impact heat could catalyze the synthesis and accumulation of important prebiotic building blocks such as nucleobases, amino acids and urea.