Explore the vast range of titles available.

Pure SnO2 and 1 at.% PdO–SnO2 materials were prepared using a simple hydrothermal method. The micromorphology and element valence state of the material were characterized using XRD, SEM, TEM, and XPS methods. The SEM results showed that the prepared material had a two-dimensional nanosheet morphology, and the formation of PdO and SnO2 heterostructures was validated through TEM. Due to the influence of the heterojunction, in the XPS test, the energy spectrum peaks of Sn and O in PdO–SnO2 were shifted by 0.2 eV compared with SnO2. The PdO–SnO2 sensor showed improved ethanol sensing performance compared to the pure SnO2 sensor, since it benefited from the large specific surface area of the nanosheet structure, the modulation effect of the PdO–SnO2 heterojunction on resistance, and the catalyst effect of PdO on the adsorption of oxygen. A DFT calculation study of the ethanol adsorption characteristics of the PdO–SnO2 surface was conducted to provide a detailed explanation of the gas-sensing mechanism. PdO was found to improve the reducibility of ethanol, enhance the adsorption of ethanol’s methyl group, and increase the number of adsorption sites. A synergistic effect based on the continuous adsorption sites was also deduced.

The accurate monitoring and detection of acetone vapor are essential for environmental and human safety. Consequently, fern-like Fe2O3 with hierarchical vein-like structures is synthesized via a concise hydrothermal method. Compared with pure fern-like Fe2O3, fern-like Pd/PdO-Fe2O3 shows the best acetone-sensing characteristics, in terms of lower operating temperature (180 °C), better selectivity and excellent long-term stability. More importantly, the response value of the Pd/PdO-Fe2O3 sensor to 100 ppm acetone reaches as high as 73, which is 55% higher than that of pristine fern-like Fe2O3. This enhanced sensing performance can be ascribed to the synergistic effect between Pd/PdO and fern-like Fe2O3. On the one hand, Pd/PdO nanoparticles show favorable catalytic activity toward ionized oxygen molecules; meanwhile, the formation of the heterojunction between PdO and fern-like Fe2O3 plays an important role. On the other hand, the hierarchical nature of fern-like Fe2O3 promotes efficient gas diffusion throughout the structure. Based on its advantages, fern-like Pd/PdO-Fe2O3 becomes a satisfactory candidate for acetone gas sensors.

A new index is developed for the Interdecadal Pacific Oscillation, termed the IPO Tripole Index (TPI). The IPO is associated with a distinct ‘tripole’ pattern of sea surface temperature anomalies (SSTA), with three large centres of action and variations on decadal timescales, evident in the second principal component (PC) of low-pass filtered global SST. The new index is based on the difference between the SSTA averaged over the central equatorial Pacific and the average of the SSTA in the Northwest and Southwest Pacific. The TPI is an easily calculated, non-PC-based index for tracking decadal SST variability associated with the IPO. The TPI time series bears a close resemblance to previously published PC-based indices and has the advantages of being simpler to compute and more consistent with indices used to track the El Niño–Southern Oscillation (ENSO), such as Niño 3.4. The TPI also provides a simple metric in physical units of °C for evaluating decadal and interdecadal variability of SST fields in a straightforward manner, and can be used to evaluate the skill of dynamical decadal prediction systems. Composites of SST and mean sea level pressure anomalies reveal that the IPO has maintained a broadly stable structure across the seven most recent positive and negative epochs that occurred during 1870–2013. The TPI is shown to be a robust and stable representation of the IPO phenomenon in instrumental records, with relatively more variance in decadal than shorter timescales compared to Niño 3.4, due to the explicit inclusion of off-equatorial SST variability associated with the IPO.

Nanocrystalline Pd@PdO core–shell ( a ) were synthesized by aqueous sol–gel transformations from precursor [Cl 2 PdL] ( 1 ) {where, L = 8-(2-pyridylmethoxy)quinoline}. Formation of the precursor ( 1 ) was confirmed by elemental analysis, molecular weight measurements, FT-IR, and NMR ( 1 H and 13 C). PdO nanoparticles ( b ) were obtained when unmodified PdCl 2 ( 2 ) was used as precursor. XRD studies were done to determine crystal structure and phases of synthesized powders which was found to be cubic, tetragonal (Pd@PdO) and tetragonal (PdO), respectively. TEM studies were done to confirm the results obtained from XRD. HRTEM and SAED patterns confirmed the formation of core–shell nanoparticles. Crystallite size of both the samples as approximated by XRD and TEM were found to be in nanometer range. Raman spectroscopy confirmed the presence of PdO in both the samples. Surface morphologies of both the samples were evaluated by SEM. The absorption spectra of samples, (a) and (b) show the energy band gap of 1.43 and 1.89 eV, respectively.

Methane in the form of natural gas is increasingly used as a transportation fuel, but the treatment of methane in the exhaust is a challenge since methane is a potent greenhouse gas. Pd is one of the most active catalysts for methane oxidation. Previous work has shown that transformation of Pd into the oxide, and decomposition of the oxide to metallic Pd can occur as temperature is raised in an oxidizing atmosphere, causing profound changes in catalytic reactivity. Equilibrium thermodynamics predict that the phases Pd and PdO must be in equilibrium at a well-defined temperature and oxygen pressure, since the two phases are immiscible and do not form solid solutions. But catalytic data suggests the existence of metallic Pd under conditions where only PdO should be thermodynamically stable. In this study we have explored the Pd ↔ PdO transition at high temperature using in situ XRD, TGA and from TEM examination of Pd catalysts that were quenched in liquid nitrogen or in a heating TEM holder to prevent any changes in microstructure during cooling. Corresponding data was obtained during methane oxidation, helping shed light on the nature of the working catalyst. The results show that the oxidation of metallic Pd to PdO is kinetically-controlled at high temperatures, allowing Pd to co-exist along with PdO. We refer to these as metastable Pd ↔ PdO structures. TEM shows that Pd and PdO domains can co-exist within a single particle, forming a phase boundary but allowing both Pd and PdO to be exposed to the gas phase. This kinetically controlled oxidation of Pd explains why we do not see core–shell PdO–Pd structures at elevated temperatures. Graphical Abstract

The Interdecadal Pacific Oscillation (IPO) is a 40–60 year quasi-oscillation seen mostly in the Pacific basin, but its impacts on surface temperature (T) and precipitation (P) have been found over Australia, the Southwest U.S. and other regions. Here, a global analysis of IPO’s impacts on T and P and its modulation of ENSO’s influence on T and P over the globe is performed using observational and reanalysis data and model simulations. Since 1920, there are two warm (1924–1944 and 1977–1998) and two cold (1945–1976 and 1999–present) IPO phases, whose change is associated with abrupt shifts in North Pacific sea level pressure (SLP) and contrasting anomaly patterns in T and P and atmospheric circulation over the eastern and western Pacific. The IPO explains more than half of the interdecadal variations in T and P over many regions, such as northeastern Australia, western Canada and northern India. Significant correlations between the IPO and local P are observed over eastern Australia, southern Africa and the Southwest U.S. The IPO also modulates ENSO’s influence on local T and P over most of these regions. T over northern India is positively correlated with Niño3.4 ENSO index during cold IPO phases but the correlation turns negative or insignificant during IPO warm phases. Over northeastern Australia, the T versus ENSO and P versus ENSO correlations are stronger during the IPO cold phases than during the warm phases. The P versus ENSO correlation over southern Africa tends to be negative during IPO warm phases but becomes weaker or insignificant during IPO cold phases. The IPO-induced P anomalies can be explained by the associated anomaly circulation, which is characterized by a high SLP center and anti-cyclonic flows over the North Pacific, and negative SLP anomalies and increased wind convergence over the Indonesia and western Pacific region during IPO cold phases. These observed influences of the IPO on regional T and P are generally reproduced by an atmospheric model forced by observed sea surface temperatures.

Based on the 1979–2018 datasets of Climate Prediction Center (CPC) daily maximum air temperature, HadISST, and NCEP-DOE II reanalysis, the impact of Pacific decadal oscillation (PDO) and Atlantic multidecadal oscillation (AMO) on the interdecadal variability in extreme high temperature (EHT) in North China (NC) is investigated through observational analysis and National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 5.3 (CAM5.3) numerical simulations. The observational results show an interdecadal shift in NC’s EHT in approximately 1996 with a cold period from 1983 to 1996 and a warm period from 1997 to 2014. The summer PDO and AMO are both closely related to NC’s EHT, of which AMO dominates. From the cold to warm period, the combination of PDO and AMO changed from a positive PDO (+ PDO) phase and a negative AMO (− AMO) phase to a negative PDO (− PDO) phase and a positive AMO (+ AMO) phase. The shift in the antiphase combination of PDO and AMO plays an important role in the interdecadal transition of NC’s EHT in 1996. PDO could impact NC’s EHT through the Pacific-East Asia teleconnection pattern, and AMO could influence the NC’s EHT through an atmospheric wave train in the midlatitudes of the Northern Hemisphere. During the warm period (− PDO and + AMO), warmer sea surface temperature anomalies (SSTA) in the northern North Pacific (NP) and North Atlantic (NA) could cause anticyclonic circulation anomalies over these two basins. The anticyclonic circulations anomalies over the NP could enhance the anticyclone over NC through the Pacific-East Asian (PEA) teleconnection pattern. It could also cause an easterly wind from the NP to NC which would weaken the upper westerly over NC. The anticyclonic anomalies over the NA, which were parts of the wave train, could affect other sectors of the wave train, resulting in anticyclonic anomalies over NC. The anticyclonic anomalies over NC could strengthen the continental high and weaken the upper zonal westerly, resulting in favorable EHT conditions. During the cold period (+ PDO and − AMO), because of the same atmospheric response mechanism, a westerly wind from NC to NP and a wave train with reversed anomaly centers could be found, causing a cyclonic anomaly over NC that is not conducive to the EHT. A series of numerical simulations using CAM5.3 confirm the above observational results and show that the combination of + PDO and − AMO changing to − PDO and + AMO has a great impact on the interdecadal shift in EHT in NC in 1996. The simulations also show that both + AMO and − PDO can lead the EHT in NC individually, and the impact of AMO on the EHT in NC is dominant.

PdO/γ-Al2O3 catalysts are one of the most active catalytic components for the complete oxidation of methane. Under reaction conditions, especially in a wet feed, the catalysts suffer severe performance degradation. This study establishes a series of testing protocols to systematically investigate the causes of catalyst deactivation under methane oxidation reaction conditions. Four distinct catalyst deactivation modes are identified. Two of the deactivation modes are directly related to H2O, either from the feed gas or as a part of the reaction products, with one (Mode 2) being attributed to the formation of surface hydroxyl groups and the other (Mode 3) to the competitive adsorption of H2O on the catalysts. The impact of the two deactivation modes is acute and severe but reversible. In contrast, the other two deactivation modes are gradual and persistent but irreversible. Both modes are induced by CH4 oxidation reaction, with the impact of a wet feed (Mode 4) being substantially more severe than that of a dry feed (Mode 1). The major cause of the irreversible catalyst deactivation is attributed to surface reconstruction of PdO nanoparticles, which behaves as a passivation layer lowering the number of coordinately unsaturated Pd sites for CH4 activation. Although the passivation layer is relatively stable against thermal or hydrothermal treatment, it is not completely inert. Formation and partial regeneration of the passivation layer is a highly dynamic process and heavily depends on the reaction temperature: a lower reaction temperature (≤ 450 ℃) can lead to quicker catalyst deactivation; but a higher reaction temperature (between 500 – 550 ℃) can result in a greater extent of catalyst deactivation.

The paper examined the potential demand for a food specialty dairy product, cheese, with alternative multiple labels. A random-parameter logit model was applied to interpret the results of online discrete choice experiments (DCE) for the elicitation of the preference of the cheese consumers surveyed in two European countries, France (n = 400) and Italy (n = 408). We analyzed consumers’ choices of quality-labeled cheeses, i.e., protected-designation-of-origin (PDO)-labeled Parmigiano Reggiano and Comté. Other features were tested, such as organic (Comté) and Mountain Product (Parmigiano Reggiano) labels, companies’ brands and price. The paper contributes to the literature on credence attributes by examining consumers’ willingness to pay (WTP) for differentiated cheese products in two EU countries, and by identifying the effects of personal characteristics, in terms of socio-demographics and level of product involvement, on the differences in preferences. The results show that price was the most important attribute in both countries, followed by the PDO quality label, particularly when paired with the second quality feature. Two cheese consumer segments were identified via latent class models in each country, helping producers to improve their marketing of agri-food products with a high gastronomic value and differentiation potential.

Food, agriculture, and labeling, affecting the environment are well connected concepts, the balance between them being determined not only by pedological and climatic factors or the development level of agricultural techniques, but also by national governments and international organizations’ food processing, trade policies and regulations. In this context, the European Union (EU) encourages the use of different food quality schemes: “Protected Designation of Origin” (PDO), “Protected Geographical Indication” (PGI), and “Traditional Specialty Guaranteed” (TSG) to protect producers of special-quality foods and assist consumers in their purchasing decisions. This review examines existing studies on the impact of these labels on customers behavior. A total of 32 studies were found and systematized. The papers were selected if they featured unique empirical research on consumer perceptions of any of PDO, PGI and TSG labels. Using the search strategy, a literature analysis was performed based on papers extracted from Web of Science, Springer Link, Emerald Insights, and Science Direct. Although these papers highlight quite diversified findings, the internationally used labels play an increasing role in contemporary society and pandemic conditions caused by COVID-19, thus making the quality schemes relevant in consumer decision-making processes.