Low RH Research Articles

Current-carrying property and damage mechanism of rolling contact pairs in different water conditions: From vapor to liquid

The tribological and conductive properties of current-carrying rolling pairs were investigated in humid air and water drops. As the environment changes from a very low RH atmosphere (10% relative humidity) to liquid water, current-carrying friction coefficient increased from 0.14 to 1.03. It is speculated that current-induced adhesion, meniscus force and current-induced meniscus force can provide additional friction force. With the increasing of the friction coefficient, the wear mechanism current-carrying pairs transforms from adhesive and abrasive wear to severe fatigue wear. When water changes from a gaseous state to a liquid state, the form of fatigue changes from scale to spalling because of pressurization effect. X-ray photoelectron spectroscopy (XPS) analysis shows that water is advantageous to tribo-oxidation and electrochemical oxidation, resulting in the formation of CuO. The weakening effect of oxidation on the electrical conductivity can be illustrated by contact resistance and conductive atomic force microscopy (CAFM) map. The paper reported the mechanical and chemical effects on the current-carrying contact pairs in wet conditions, which could be very helpful in understanding on water-involved surface damage and oxidation.

Fabrication of low cost and low impact RH and temperature sensors for the internet of environmental-friendly things

Given the increasing number of connected devices as a consequence of the Internet of Things (IoT) revolution, the issue of the removal and recycling of electronics is becoming more and more urgent. In this context, biodegradable electronics is expected to be one of the biggest technological revolutions to tackle this problem. Following this direction, in this work we present the fabrication and characterization of temperature and humidity sensors based on biodegradable materials with the goal of making their removal easier as well as reducing their environmental impact. In particular, these multi-sensing devices were fabricated following a screen-printing process using a carbon-based paste and a conjugated polymer, both on paper and on a water soluble substrate. The results are more than promising and show how with our biodegradable sensors it is possible to obtain a sensitivity of 1 dec/20%RH to moisture content and around 0.04%/°C sensitivity to temperature. It is demonstrated that the simplicity and flexibility of the fabrication approach followed in this work paves the way to a set of new “green” IoT nodes that could be extended to wide range of sensing applications.

Water Vapor Sorption and Diffusivity in Bio-Based Poly(Ethylene Vanillate)-PEV.

The dynamic and equilibrium water vapor sorption properties of amorphous and highly crystalline poly(ethylene vanillate) (PEV) films were determined via gravimetric analysis, at 20 °C, over a wide range of relative humidity (0–95% RH). At low RH%, the dynamic of the sorption process obeys Fick’s law while at higher relative humidity it is characterized by a drift ascribable to non-Fickian relaxations. The non-Fickian relaxations, which are responsible for the incorporation of additional water, are correlated with the upturn of the sorption isotherms and simultaneously the hysteresis recorded between sorption and desorption cycles. The sorption isotherms of amorphous and highly crystalline PEV are arranged in the same concentration range of that of PET proving the similarity of the two polyesters. Water diffusion coefficients, whose determination from individual kinetic sorption/desorption curves required treatment with the Barens–Hopfenberg model, were demonstrated to be ≈10× higher for amorphous PEV compared to amorphous PET. Such a difference originates from the enhanced segmental flexibility of PEV chains.

Improving the strength of recycled liner for corrugated packaging by adding virgin fibres: Effect of refrigerated storage on paper properties

The high humidity produced by the ripening of fruit and vegetables during refrigerated storage and transport leads to a noticeable loss of strength of corrugated board packaging. Increasing use of recycled fibres in the manufacture of corrugated board further reduces box compression strength. Adding virgin fibres to the furnish composition of liner paper could solve this problem.Various proportions of unbleached virgin eucalyptus and pine fibres were added to a recycled furnish used to manufacture liner paper for corrugated board. Laboratory sheets of each fibre blend were characterised by tensile, bursting and compressive strength. The change in the strength properties and moisture content of the sheets during refrigerated storage at 6°C and high relative humidity (90% RH) was also studied.The results showed that paper strength improved with the proportion of virgin fibres added. Pine fibres yielded higher increments than eucalyptus fibres in tensile and burst indices, whereas both fibres improved compression strength at a similar rate. After 4 h of exposure at refrigerated storage, the paper strength properties decreased considerably, in particular compression strength, which showed a loss of about 70% compared to the reference value. The percentage of strength lost compared to the value in standard conditions was influenced only by exposure time at low temperature and high RH. However, an increase in the amount of pine fibres added enhanced the remaining tensile and burst indices.

A Novel Polymer-Salt Complex Based on LiCl Doped SPEEK/Poly(Ether Ether Ketone)-Co-Poly(Ethylene Glycol) for Humidity Sensors

A novel humidity sensor based on polymer-salt complexes was developed in this research. Poly(ethylene glycol) (PEG) segmented poly(ether ether ketone) copolymers (PEEK-co-PEG) has been successfully synthesized via condensation polymerization and the structure of this copolymer was confirmed by <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> H NMR. Humidity sensors based on SPEEK/PEEK-co-PEG composites were prepared, and then humidity sensitive characteristics were systematically studied. Comparing with pure SPEEK, PEEK-co-PEG composites can significantly reduce the hysteresis effect of humidity sensors with the proportion of introduced PEG flexible segments increasing. Furthermore, different contents of LiCl were doped into polymer composites and their humidity sensing characteristics were also investigated. The humidity sensor based on SPEEK/PEEK-co-PEG/LiCl with [Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ]:[O] ratio of 1:2 had excellent sensitivity, linearity, negligible hysteresis and quick response. Moreover, we proposed that the humidity sensing mechanism of sensors based on polymer-salt complexes is related to the combination of both directional motion of Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> on PEG backbone under low RH and ionization (SPEEK polyelectrolyte, Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and Cl <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> ) under high RH. On the basis of these humidity sensing characteristics and mechanism, this work provides an approach to integrating polymeric and inorganic complexes as the promising materials for humidity sensors.

Impact of hurdle technologies and low temperatures during ripening on the production of nitrate-free pork salami: A microbiological and metabolomic comparison

In this work, cold-dry fermented nitrate-free sausages were produced by adopting hurdle technologies. The strategy consists of using lactic acid bacteria (LAB) growing at low temperatures, the addition of lactic and ascorbic acids, and low temperatures during the ripening-drying process (35 days at different RH values). Four experimental conditions (B and B1 with 0.2% ascorbic acid, R and R1 with 0.3% lactic acid – B1 and R1 with lower RH during ripening) were compared with a control (N; traditionally manufactured, 80 mg/kg of nitrates and nitrites). Overall, sample R underwent a pH change from 5.22 (t0) to 5.06 (t14). Besides, all samples displayed aw values ≤ 0.92 at t22, thus reaching values < 0.895 at t35. Interestingly, the lower RH values (65–80%) during ripening determined a case hardening, significantly affecting colour parameters. Metabolomics coupled with TBARS assay showed few differences when comparing B and R with the control, whereas lipid oxidation markers (18-hydroxyoleate, LogFC = 0.83–16-Hydroxy-hexadecanoic acid, LogFC = 0.77) and MDA increased in B1 and R1. Overall, RH values revealed to be critical parameters, to be accurately defined to avoid undesired phenomena when hurdle technologies are used. Nonetheless, our findings support the manufacturing of nitrate-free salami by unconventional technologies.

Exceptional ground motion during the shallow Mw 4.9 2019 Le Teil earthquake, France

An unusually damaging Mw 4.9 earthquake occurred on November 11, 2019 in the south east of France within the lower Rhône river valley, an industrial region that hosts several operating nuclear power plants. The hypocentre of this event occurred at an exceptionally shallow depth of about 1 km. Here we use far-field seismological observations to demonstrate that the rupture properties are consistent with those commonly observed for large deeper earthquakes. In the absence of strong motion sensors in the fault vicinity, we perform numerical predictions of the ground acceleration on a virtual array of near-fault stations. These predictions are in agreement with independent quantitative estimations of ground acceleration from in-situ observations of displaced objects. Both numerical and in-situ analyses converge toward estimates of an exceptional level of ground acceleration in the fault vicinity, that locally exceeded gravity, and explain the unexpectedly significant damage.

Air Quality, Atmospheric Variables and Spread of COVID-19 in Delhi (India): An Analysis

Based on a time series analysis of the criteria pollutants, meteorological parameters, and COVID-19 positive cases, this paper explores the impact of epidemic prevention and control actions on air quality for five different periods of COVID-19 outbreak in Delhi, India. The study found that under the epidemic control measure during 11 May-19 June 2020, the average concentrations of atmospheric air pollutants PM2.5, PM10, NO2, and CO were reduced to 42.15 µg m-3, 128.68 µg m-3, 27.31 ppb, and 0.83 ppm respectively, and were 73.85%, 46.48%, 63.43%, and 50.18% lower than the pre-COVID-19 level of January 2020, respectively. The steep fall of PM2.5, NO2, and CO was due to a drastic reduction in vehicular emission, but PM10 did not fall below the National Ambient Air Quality Standard. Between January 2020 to 11 May -19 June 2020 period, the pollutants O3 and SO2 increased significantly by 217.33% and 57.58 % respectively. The rise of SO2 in Delhi was due to long-distance transfer, power plant emissions, and biomass burning. The sharp increase of O3 happened due to accumulation in the atmosphere. During the peak COVID-19 phase (9 April –10 May 2020) Delhi had unprecedented improved AQI classes of II and III only. However, the pivotal pollutants in terms of their cumulative contribution to the AQI classes were PM10 and O3. Low RH and low-temperature situations exhibited positive correlations with the new COVID-19 infection cases in Delhi. Comparatively lower NO2 level in the air demonstrated a significant negative correlation with new COVID-19 cases while average SO2 concentration in the air, when increased to 24.05 ppb, showed a negative correlation with new COVID-19 cases in Delhi. This study indicated a possibility of O3 exhibiting a positive correlation with new COVID-19 cases under the condition of comparatively low temperature and low humidity.

Characterization of hysteresis free, low-temperature hydrothermally synthesized zinc oxide for enhanced humidity sensing

The hygroscopic properties of a material allow water retention and release of water vapor from surface of a nanostructure. Most nanostructure exhibit morphological change due to swelling or directional expansion upon water intake. The study focuses on characterizing the hygroscopic properties of additive enhanced zinc oxide via weighing method and testing of its hysteresis free sensing potential. Zinc oxide (ZnO) was prepared along with added additive via modified low temperature hydrothermal synthesis. The growth solution was coated on to glass slides before characterization of hygroscopicity and water adsorption hysteresis. The sample was placed in a sealed chamber with sensitive microbalance to measure mass gain and loss of the sample. The humidity within the chamber was manipulated chemically and temperature was left at constant ambient temperature. Relative humidity range from 40 to 80 % RH was exposed to the samples. The additive enhanced zinc oxide (ZnO-HMT) film has shown superior water retention and release capabilities by having steeper gradient compared to its initial version. ZnO-HMT could maintain its mass at low RH% of 37.5 % and high RH% of 80 % at closely similar value upon exposed to several cycles of incremental and decremental RH%. The mass intake and release of ZnO-HMT was also greater at 1.5 mg per 10 % increment and decrement of RH within 40 RH% - 80 RH% compared to ZnO which only have 0.9 mg mass change at each increment. Microscopic observation has shown apparent morphology change to ZnO-HMT nanostructure upon exposed to increased humidity from lower humidity. ZnO-HMT shown potent candidate as a humidity sensor material to be implemented into optical sensors that requires strain as the sensing mechanism to take advantage of the hygroscopic nature of the material.

Deleterious Effects of Storage Environmental Conditions on The Seed Quality of Two Varieties of Tomato (Solanum lycopersicum L.) Stored in Triple Laminated Aluminum Packing in Sri Lanka

Tomato is one of the most commonly growing vegetable crops among the farmers in Sri Lanka. Standard laboratory germination of tomato seeds fulfills the regulatory requirements of seed marketing. However, poor field performance is an overwhelming problem to farmers. Present study was focused on the longevity of two varieties of tomato seeds as affected by their quality characters (percentage germination, moisture, field emergence and vigour index, seed protein and carbohydrate contents) including seed health (exposure of Clavibacter michiganensis subsp. Michiganensis (CMMV), Spotted wilt virus (TSWV) and Leaf curly top virus (LCTV)) under four different storage environmental conditions during a one-year long storage study. Seeds were packed in triple-laminated aluminum packets (TLA) and stored in low temperature storage conditions (17±1 °C and 65% RH) and in ambient conditions in Gannoruwa, Kundasale, and MahaIlluppallama that represent the three agro-ecologically zones; Mid Country Wet Zone (MCWZ), Mid Country Intermediate Zone (MCIZ) and Low Country Dry Zone (LCDZ) respectively. Seed quality parameters displayed varied responses depending on the variety. Physiological changes that occur in seeds due to temperature, RH, changes in proteins and carbohydrate content, CMMV and TSWV during storage were manifested as reduction in seed germination, field emergence and vigour index. However, none of the seedling carried LCTV and therefore its effect on seed quality parameters could not be assessed. The seeds could be stored for ca. 29 months at low and constant temperatures and RH conditions without compromising local seed germination standards compared to ambient storage in the three environments. CMMV and TSWV detected in all seed samples indicated potential threats to tomato farmers in Sri Lanka.&#x0D;

Experimental Investigation of a Direct Evaporative Cooling System for Year-Round Thermal Management with Solar-Assisted Dryer

Building cooling is achieved by the extensive use of air conditioners. These mechanically driven devices provide thermal comfort by deteriorating the environment with increased energy consumption. To alleviate environmental degradation, the need for energy-efficient and eco-friendly systems for building cooling becomes essential. Evaporative cooling, a typical passive cooling technique, could meet the energy demand and global climatic issues. In conventional direct evaporative cooling, the sensible cooling of air is achieved by continuous water circulation over the cooling pad. Despite its simple operation, the problem of the pad material and water stagnation in the sump limits its usage. Moreover, the continuous pump operation increases the electrical energy consumption. In the present work, a porous material is used as the water storage medium eliminating the pump and sump. An experimental investigation is performed on the developed setup, and experiments are conducted for three different RH conditions (low, medium, and high) to assess the porous material’s ability as a cooling medium. Cooling capacity, effectiveness, and water evaporation rate are determined to evaluate the direct evaporative cooling system’s performance. The material that replaces the pump and sump is vermicompost due to its excellent water retention characteristics. There is no necessity to change material each time. However, the vermicompost is regenerated at the end of the experiment using a solar dryer. The passing of hot air over the vermicompost also avoids mould spores’ transmission, if any, present through the air. The results show that vermicompost produces an average temperature drop of 9.5°C during low RH conditions. Besides, vermicompost helps with the energy savings of 21.7% by eliminating the pump. Hence, vermicompost could be an alternate energy-efficient material to replace the pad-pump-sump of the conventional evaporative cooling system. Further, if this direct evaporative cooling system is integrated with solar-assisted drying of vermicompost, it is possible to provide a clean and sustainable indoor environment. This system could pave the way for year-round thermal management of building cooling applications with environmental safety.

The dynamic competition in adsorption between gaseous benzene and moisture on metal-organic frameworks across their varying concentration levels

Metal-organic frameworks (MOFs) have opened a new path for the construction of air/gas purification systems through a number of technological routes (e.g., adsorption and/or catalysis). To develop MOFs with upgraded adsorption performance, the breakthrough (BT) behavior of two MOF sorbents (e.g., MOF-199 and UiO-66-NH 2 ) was investigated using gaseous benzene under the interactive conditions between the two key variables: (i) the inlet benzene vapor concentration (10 to 200 ppm) and (ii) relative humidity (RH = 0 to 100%). According to the comparison of adsorption performance derived using gaseous benzene, MOF-199 outperformed UiO-66-NH 2 by 2 to 16-fold when assessed at 10% BT and zero RH. This observation thus reflects the high reactivity of Cu-metal sites for interaction with benzene ring compared with Zr sites. The dynamic adsorption data for the two MOFs at various RH conditions also indicated the competitive inhibition effect of water vapor on benzene adsorption mechanism, especially at low benzene concentrations (< 100 ppm) and high RH level of > 50%. Adsorption kinetics of benzene onto the two MOFs showed good fitting with both pseudo-first and -second-order kinetics at low RH (0–20%) conditions, whereas the results at high RH (> 50%) failed to fit with both kinetics (e.g., R 2 ≤ 0.87) because of the high roll-up effect. The water vapor acted as a competitive component, reducing the performance of the MOF adsorbents in purifying humidified gaseous streams. That effect became more prominent as the benzene concentration decreased (≤ 50 ppm), reflecting the dynamic interaction between multiple adsorbates (water and benzene) and the adsorbent. In addition, the exothermic adsorption property was evident for both MOFs under the dry conditions, while the patterns were reversed under humid conditions (e.g., 100% RH). Overall, the adsorption properties of VOCs onto MOFs and their uptake mechanisms are affected sensitively by an interplay between the key variables (e.g., concentration levels of competing adsorbates) along with the structural stabilities of sorbents against water vapor. • The adsorption of VOCs is compared at varying RH levels for MOF-199 and UiO-66-NH 2. • The performance of MOFs is assessed w.r.t. competition between benzene and water vapor. • Their performance was evaluated using key metrics like breakthrough volumes. • MOF-199 displayed the better performance at all benzene concentration levels under dry condition. • Moisture had negative effects on benzene adsorption, especially MOF-199 at low benzene levels.

Pore-Filled PEMs from Poly(Phenylene Sulfonic Acid)s and Electrospun Poly(Phenylene Sulfone) Fiber Mats

Novel, composite, non-PFSA-based fuel cell membranes have been fabricated using a pore filling technique. The membranes consist of a mechanically stabilizing skeleton from an electrospun poly(phenylene sulfone) (PPSU) fiber mat and a thermally crosslinkable poly(phenylene sulfonic acid) (cPPSA) proton conducting ionomer that fills the interfiber voids. The work builds on two prior studies carried out in the labs of Prof. M. Litt and Prof. P.N. Pintauro demonstrating: (1) Exceptionally high proton conductivity, even at very low RH (down to 20% RH), of cPPSA solution cast films, and (2) Excellent durability of electrospun perfluorosulfonic acid (PFSA) ionomers/PPSU composite membranes, exceeding that of the pristine PFSA. Unfortunately, the high proton conductivity of cPPSA films, especially at low relative humidity, was offset by their significant brittleness, which made handling of those materials, including fabrication of membrane-electrode-assemblies, extremely difficult. The proposed pore-filling strategy should alleviate the brittleness problem leading to a robust, low RH-conductive PEM that is a true competitor to PFSA membranes and suitable for commercial applications.Experiments focused on optimizing the cPPSA/PPSU ratio to achieve the desired balance of tensile strength and proton conductivity, and on minimizing membrane thickness to obtain area specific resistance (ASR) lower than 0.02 S/cm in the 40-90% RH range at 80oC. cPPSA copolymer was synthesized using Ullmann coupling copolymerization of 4,4′-dibromobiphenyl 3,3′-disulfonic acid with 1,4-dibromobenzene-2,5-disulfonic, followed by grafting certain fraction of backbone sulfonic acid groups with biphenyl linker [1]. The PPSU fiber mat was electrospun from NMP/acetone solution. Pore-filling was carried out by pouring a solution of cPPSA in methanol over the framed mat, followed by heating at 70oC to evaporate solvent. The cPPSA was crosslinked by an additional heating step, in a vacuum oven at 210oC for 1-2 hours. The resultant membranes had excellent proton conductivity, 5-10 times greater than that of Nafion® 211 in the 40-90% RH range at 80oC. Details of the membrane fabrication and characterization work will be presented in this talk.[1] M. Litt and R. Wycisk, Poly(Arylenesulfonic Acids) with Frozen-In Free Volume as Hydrogen Fuel Cell Membrane Materials, Polymer Reviews, 55, 307 (2015).

Phosphoric Acid-Doped Biphenyl-Backbone Ion-Pair Coordinated Pems with Broad Relative Humidity Tolerance

Fuel cell has been recognized as a promising electrochemical device attributed to its high energy efficiency and zero CO2 emission. As an essential component of fuel cell, currently the most widely used proton exchange membrane (PEM), Nafion®, operates only at low temperature (<100 ˚C) and high relative humidity (>80% RH). Although phosphoric acid (PA)-doped polybenzimidazole membranes have been reported to offer good proton conductivity at temperatures 140–180 ˚C, they suffer from severe performance degradation due to acid leaching when moisture is present. For wider adoption of PEM fuel cell technology, the development of PEM that is capable of working over a broad operating condition window is highly desirable. In this presentation, three PA-doped biphenyl-backbone ion-pair coordinated PEMs with different quaternary ammonium structures (alkyltrimethylammonium, piperidinium, and 1,2-dimethylimidazolium) were reported. The resulting PA-doped PEMs were comprehensively characterized in terms of PA doping level, proton conductivity, RH tolerance, thermal stability, and mechanical properties. Acid titration result indicates the PA doping levels of three membrane samples were between six and eight, and the size and structure of cation groups of the ion-pair polymers were found to affect their PA doping levels. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity was observed up to 70% RH at 80 ˚C for 10 h. A combination of high proton conductivity at low RH conditions and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as PEM fuel cell and electrochemical hydrogen compressor.

Penicillium rubens germination on desiccated and nutrient-depleted conditions depends on the water activity during sporogenesis

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected.This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour.The lag time, tl, and initial growth rate, μfp, of the germ tubes were monitored.The effect of aw history on germination and initial growth depends on the RH of the environment. Only at low RH do spores produced at low aw have a smaller tl and higher μfp compared to those grown at high aw. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low aw and placed in high RH.Spores grown on lowered aw attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high RH and lowered aw history.We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment.

Atmospheric humidity is unlikely to serve as an important water source for crustose soil lichens in the Tabernas Desert

Abstract Dew is commonly regarded as an important water source for lichens. This is also the case for crustose lichens that are attached to the substrate, whether rocks or soil. While being verified during ample research on rock-dwelling lichens in the Negev, the findings from soil-dwelling lichens (lichen biocrusts) are not conclusive. In the Tabernas Desert, the soil surface is characterized by a lush cover of crustose lichens. These soil biocrusts (biological soil crusts) were reported to use dew for photosynthesis while, at the same time, it was also observed that these crustose chlorolichens are relatively non-wettable. In an attempt to explore the apparent controversy, two year-long meteorological data (minimum air temperature and relative humidity, RH), during which chlorolichens were thought to utilize dew for photosynthesis (2006–2007) were analyzed. The analysis includes a comparison to the meteorological conditions that prevailed in the Negev during 135 days of manual dew measurements. As found for the Negev, net photosynthesis by the chlorolichens is expected once the RH, as measured at the meteorological station, is ≥90% while vapor condensation (dew) is expected once RH is ≥95%. RH in the Negev was substantially higher than the average RH of 75.0–87.2% registered during the rainless days of 2006–2007 in the Tabernas, implying that RH in the Tabernas is too low to facilitate frequent dew formation and net photosynthesis by the lichens. Photosynthesis in the Tabernas is mainly confined to rainy periods, taking place either due to direct wetting by rain, or following vapor condensation from the subsurface (distillation). Our findings do not support the view that dew is an important water source for the establishment and growth of crustose soil lichens in the Tabernas. Moreover, the low RH in the Tabernas may also imply that dew may only have a very limited role in providing water to lithobionts in this ecosystem.

An overview of chalcophile element contents of pyrrhotite, pentlandite, chalcopyrite, and pyrite from magmatic Ni-Cu-PGE sulfide deposits

We have compiled the trace element concentrations in pyrrhotite, pentlandite, chalcopyrite, and pyrite from magmatic Ni-Cu-PGE ore deposits with the aim of understanding their petrogenesis and whether these minerals can be used as indicator minerals. Among the samples, there are some of the most studied world-class Ni-Cu- (Aguablanca, Duluth, Jinchuan, Noril’sk-Talnakh-Kharaelakh, Sudbury, Voisey’s Bay, and others) and PGE-dominated (Bushveld, Lac des Iles, Stillwater, Great Dyke, and Penikat) deposits. Crustal assimilation may be constrained using As/Se and Sb/Se ratios in pentlandite. The degree of interaction between the silicate and sulfide liquids (R-factor) can be estimated by the content of highly chalcophile elements (Dsulf liq/sil liq above 1000) in sulfide minerals. The fractional crystallization of the sulfide liquid can be traced using Se/Te ratios of pentlandite. Pyrite formed by exsolution from MSS has higher Rh, Ru, Ir, and Os than co-existing pyrrhotite, whereas pyrite formed by hydrothermal alteration of pyrrhotite inherits the Rh, Ru, Ir, and Os contents of the pyrrhotite it replaced. Sulfide minerals are preserved in transported glacial cover and their trace element chemistry can be used to discriminate their source. Pentlandite from Ni-Cu deposits has much lower Rh and Pd concentrations than those from PGE-dominated deposits, pyrite from magmatic deposits has higher Co/Sb and Se/As ratios relative to pyrite from hydrothermal deposits, and chalcopyrite from magmatic deposits has much higher Ni and lower Cd concentrations than those from hydrothermal deposits.

Oxidation induced restructuring of Rh-Ga SCALMS model catalyst systems.

Supported catalytically active liquid metal solutions have been receiving increasing attention recently. We investigated the oxidation behavior of macroscopic Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles supported on SiO2/Si(100) with low Rh content (<2.5 at. %) by x-ray photoelectron spectroscopy in ultra-high vacuum and under near-ambient pressure conditions using different photon energies and also using transmission electron microscopy. The experiments are accompanied by computational studies on the Ga oxide/Rh-Ga interface and Rh-Ga intermetallic compounds. For both Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles, exposure to molecular oxygen leads to the formation of an oxide shell in which Rh is enriched. Transmission electron microscopy on the Rh-Ga nanoparticles confirms the formation of an ∼4 nm thick gallium oxide film containing Rh. Based on ab initio molecular dynamics and computational studies on the Ga2O3/Ga interface, it is concluded that Rh incorporation into the Ga2O3 film occurs by substituting octahedrally coordinated Ga.

High relative humidity (HRH) storage alleviates chilling injury of zucchini fruit by promoting the accumulation of proline and ABA

Abstract In order to investigate the effect of water loss on the different physiological metabolism of zucchini fruit under cold stress after harvest, two cold rooms (4 ℃) with different relative humidities (RH: 74 ± 2 % and 98 ± 2 %) were used for cold storage. The result suggested that high relative humidity (HRH) storage slowed down the increase of weight loss, chilling injury index, malondialdehyde (MDA) content and cell death rate and maintained the postharvest quality such as firmness and flesh color in zucchini fruit. HRH storage promoted the accumulation of proline and induced higher ornithine δ-aminotransferase (OAT), Δ-1-pyrroline-5-carboxylate synthetase (P5CS) enzyme activities and lower proline dehydrogenase (PDH) enzyme activity as compared with low relative humidity (LRH) storage. The content of putrescine (Put) accumulated with the progress of cold damage, which could be delayed by HRH storage due to higher activities of polyamine oxidase (PAO), diamine oxidase (DAO) and ornithine decarboxylase (ODC). Besides, chilling stress induced the biosynthesis of abscisic acid (ABA) during storage and the zucchini fruit stored in high RH with less water loss showed more accumulation of ABA and higher activity of abscisic acid aldehyde oxidase (AAO) compared to zucchini fruit stored in low RH with severe dehydration during long-term cold storage. Taken together, our results suggested that the high RH storage could reduce water loss and alleviate chilling injury in zucchini fruit after harvest by promoting the accumulation of ABA and proline.

Intriguing behavior of UCo1−xRhxGe ferromagnets in magnetic field along the b axis

Single crystals of solid solutions of ferromagnetic superconductors UCoGe and URhGe were investigated by magnetization and specific-heat measurements. These compounds behave as anisotropic ferromagnets with the easy-magnetization direction along the orthorhombic $c$ axis. The maximum Curie temperature ${T}_{C}=\phantom{\rule{0.16em}{0ex}}20\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ has been observed in $\mathrm{UC}{\mathrm{o}}_{1\ensuremath{-}x}\mathrm{R}{\mathrm{h}}_{x}\mathrm{Ge}$ for $x=0.4$. The main interest of the study was the intriguing behavior in magnetic fields applied along the $b$ axis. The temperature dependence of the $b$-axis magnetic susceptibility exhibits a maximum at a characteristic temperature ${T}_{\mathrm{max}}$. For low Rh concentrations $(x&lt;0.4){T}_{\mathrm{max}}&gt;{T}_{C}$ and the magnetic entropy ${S}_{\mathrm{mag}}$ at ${T}_{C}$ is very low, whereas ${T}_{\mathrm{max}}={T}_{C}$ and the ${S}_{\mathrm{mag}}$ at ${T}_{C}$ is much higher for $x\ensuremath{\ge}0.4$. A metamagneticlike anomaly in magnetization is observed in all compounds, at a critical field which appears on a similar energy scale with the value of the corresponding ${T}_{\mathrm{max}}$. The character of three paramagnetic regimes which can be distinguished in the T-$x$ and H-$x$ phase diagrams, normal, correlated, and field polarized, is discussed in relation to the field-induced reentrant superconductivity in the parent compounds.