Plasma degradation of trichloroethylene: Process optimization and reaction mechanism analysis

In this study, a multi-pin-to-plate negative glow discharge reactor was employed to degrade the hazardous compound, trichloroethylene (TCE). The response surface methodology (RSM) was applied to examine the influences of various process factors (relative humidity (RH), gas flow rate, and discharge power) on the TCE decomposition process, with regard to the TCE removal efficiency, CO2 and CO selectivities. The variance analysis was used to estimate the significance of the single process factors and their interactions. It has been proved that the discharge power had the utmost influential impact on the TCE removal efficiency, CO2 and CO selectivities, subsequently the gas flow rate, and finally RH. Under the optimal conditions with 20.83% RH, 2 W discharge power and 0.5 L·min–1 gas flow rate, the optimal TCE removal efficiency (86.05%), CO2 selectivity (8.62%), and CO selectivity (15.14%) were achieved. In addition, a possible TCE decomposition pathway was proposed based on the investigation of byproducts identified in the exhaust gas of the NTP reactor. This work paves a way for the control of chlorinated volatile organic compounds.

Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-Imides

The vapor deposition of many molybdenum-containing films relies on the delivery of volatile compounds with the general bis(tert-butylimido)molybdenum(VI) framework, both in atomic layer deposition and chemical vapor deposition. We have prepared a series of (tBuN)2MoCl2 adducts using neutral N,N’-chelates and investigated their volatility, thermal stability, and decomposition pathways. Volatility has been determined by thermogravimetric analysis, with the 1,4-di-tert-butyl-1,3-diazabutadiene adduct (5) found to be the most volatile (1 Torr of vapor pressure at 135 ºC). Thermal stability was measured primarily using differential scanning calorimetry, and the 1,10-phenanthroline adduct (4) was found to be the most stable, with an onset of decomposition of 303 ºC. We have also investigated molybdenum compounds with other alkyl-substituted imido groups: these compounds all follow a similar decomposition pathway, γ-H activation, with varying reaction barriers. The tert-pentyl, 1-adamantyl, and a cyclic imido (from 2,5-dimethylhexane-2,5-diamine) were systematically studied to probe the kinetics of this pathway. All of these compounds have been fully characterized, including via single-crystal X-ray diffraction, and a total of 19 unique structures are reported.

Variation in Downed Deadwood Density, Biomass, and Moisture during Decomposition in a Natural Temperate Forest

Deadwood is a resource of water, nutrients, and carbon, as well as an important driving factor of spatial pedocomplexity and hillslope processes in forested landscapes. The applicability of existing relevant studies in mountain forests in Central Europe is limited by the low number of data, absence of precise dating, and short time periods studied. Here, we aimed to assess the decomposition pathway in terms of changes and variability in the physical characteristics of deadwood (wood density, biomass, and moisture) during the decomposition process, and to describe differences in decomposition rate. The research was carried out in the Žofínský Primeval Forest, one of the oldest forest reserves in Europe. Samples were taken from sapwood of downed logs of the three main tree species: Fagus sylvatica L., Abies alba Mill., and Picea abies (L.) Karst. The time since the death of each downed log was obtained using tree censuses repeated since 1975 and dendrochronology. The maximal time since the death of a log was species-specific, and ranged from 61–76 years. The rate of change (slope) of moisture content along the time since death in a linear regression model was the highest for F. sylvatica (b = 3.94) compared to A. alba (b = 2.21) and P. abies (b = 1.93). An exponential model showing the dependence of biomass loss on time since death revealed that F. sylvatica stems with a diameter of 50–90 cm had the shortest decomposition rate—51 years—followed by P. abies (71 years) and A. alba (72 years). Our findings can be used in geochemical models of element cycles in temperate old-growth forests, the prediction of deadwood dynamics and changes in related biodiversity, and in refining management recommendations.

The inflammatory accumulation of lipids and ROS in human Nrf1α-deficient hepatoma cells is ameliorated by 2-bromopalmitate

Since Nrf1 and Nrf2 are essential for regulating the lipid metabolism pathways, their dysregulation was also shown to be critically involved in the non-controllable inflammatory pathology into cancer development. However, it is unknown that the interaction between Nrf1 and Nrf2 in the regulation of lipid metabolism, especially in hepatoma cells. Here, we have further explored the molecular mechanisms underlying their distinct regulation of lipid metabolism, by comparative analysis of changes in those lipid metabolism-related genes in Nrf1α-/- and/or Nrf2-/- cell lines relative to wild-type controls. The results revealed that loss of Nrf1 leads to disordered lipid metabolism; its lipid synthesis pathway was up-regulated by JNK-Nrf2-AP1 signaling, while its lipid decomposition pathway was down-regulated by the nuclear receptor PPAR-PGC1 signaling, resulting in severe accumulation of lipids as deposited in lipid droplets. By contrast, knockout of Nrf2 gave rise to decreases in lipid synthesis and uptake capacity. These demonstrate that Nrf1 and Nrf2 contribute to significant differences in the cellular lipid metabolism regulatory profiles and relevant pathological responses. Further experiments unraveled that lipid deposition in Nrf1α-/- cells was resulted from CD36 upregulation by activating the PI3K-AKT-mTOR pathway, leading to induction of the inflammatory response. Following treatment of Nrf1[alpha]-/- cells with 2-bromopalmitate (2BP), it enabled the yield of lipid droplets to be strikingly alleviated, as companied by substantial abolishment of CD36 and critical inflammatory cytokines. Such Nrf1[alpha]-/--led inflammatory accumulation of lipids and ROS was significantly ameliorated by 2BP. Overall, this study provides a potential strategy for cancer prevention and treatment by precision targeting of Nrf1, Nrf2, or both.

Atomic-scale imaging of CH3NH3PbI3 structure and its decomposition pathway

Understanding the atomic structure and structural instability of organic-inorganic hybrid perovskites is the key to appreciate their remarkable photoelectric properties and understand failure mechanism. Here, using low-dose imaging technique by direct-detection electron-counting camera in a transmission electron microscope, we investigate the atomic structure and decomposition pathway of CH3NH3PbI3 (MAPbI3) at the atomic scale. We successfully image the atomic structure of perovskite in real space under ultra-low electron dose condition, and observe a two-step decomposition process, i.e., initial loss of MA+ followed by the collapse of perovskite structure into 6H-PbI2 with their critical threshold doses also determined. Interestingly, an intermediate phase (MA0.5PbI3) with locally ordered vacancies can robustly exist before perovskite collapses, enlightening strategies for prevention and recovery of perovskite structure during the degradation. Associated with the structure evolution, the bandgap gradually increases from ~1.6 eV to ~2.1 eV. In addition, it is found that C-N bonds can be readily destroyed under irradiation, releasing NH3 and HI and leaving hydrocarbons. These findings enhance our understanding of the photoelectric properties and failure mechanism of MAPbI3, providing potential strategies into material optimization.

Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

Using Nematode Community to Evaluate Banana Soil Food Web in Mekargalih, Cianjur, West Java

Soil biota is very diverse and contributes widely to ecosystem services that are important in the sustainable function of natural and managed ecosystems. Knowing the condition of the soil food web through the communities that inhabit it is necessary to assess the productivity of the soil. Nematode communities in the soil food web can be used as indicators because of their high abundance, and they inhabit various trophic levels, and participate in several important processes in the soil. The soil food web condition from three locations (Agr1, Agr2, Agr3) through the nematode functional index was evaluated using the maturity index (MI), the maturity index 2-5 (MI-25), the plant-parasitic index (PPI), the channel index (CI), the enrichment index (EI), the structure index (SI), and the basal index (BI). Nematode diversity was evaluated using Simpson’s index of diversity, dominance, and evenness. The MI and MI2-5 scores indicated that Agr3 (3.81) had an undisturbed food web, while Agr2 (2.88 and 3.0) and Agr1 (2.5 and 2.51) were in a moderate condition with minor disturbances. Fauna profile analysis using SI and EI shows that Agr3 and Agr1 had an undisturbed soil food web, and Agr2 was in enriched conditions. CI results found that Agr1 and Agr3 had a fungal decomposition pathway while Agr2 had a bacterial decomposition pathway. We concluded from this research, that prospect of the nematode community to serve as a collection of biological indicator data in assessing soil or ecosystem health can be considered in further research.