Black Layer Research Articles

The Influence of Humid Atmosphere during the MAPbI3 Perovskite Layer Preparation on the Characteristics of Its Solar Cells

Organometal halide perovskite (hybrid perovskite) materials have emerged as a promising material for high power conversion efficiency and low-cost solar cells. The formation of organo-metal halide perovskite layer, however, is very sensitive to some process parameters such as concentration, temperature, and humidity. In this study, we report the preparation of CH3NH3PbI3 (MAPbI3) perovskite crystal layers under a relatively humid air atmosphere and investigated the characteristics of their solar cells with both mesoporous cell structure and planar cell structure. Due to high humidity, we found that the formed layer tends to form a shiny grey to black color layer on the top of the dark brown color perovskite layer. This layer showed poor x-ray diffraction (XRD) pattern and caused poor solar cell performance. The formation of this layer, however, can be prevented by anti-solvent treatment during the preparation of perovskite layer.

First Report of Neoscytalidium dimidiatum Causing Black Canker and Root Rot of Walnut in Turkey

Walnut (Juglans regia L.) is a commercially important crop with about 87,670 ha grown in Turkey, the fourth largest producer worldwide. During summer 2018, unfamiliar and serious decline symptoms associated with stem and branch cankers were observed in walnut trees in two orchards in Sanliurfa Province, Southeastern Anatolia Region. In a 3-year-old orchard of 450 trees (cv. Chandler) in Kayseri, Siverek District, about 62% of trees had deep, large, and black cankers in the trunks and on main branches, drastically reduced tree vigor, and yellowing, wilting, and browning of the leaves, followed by leaf drop. In a 12-year-old orchard with 30 trees (cv. Kaman), in Yaylak, Bozova District, 40% of trees had similar symptoms. Symptoms were first noticed in trunks. Bark cracks, cankers in trunks, and dark discoloration or a black sooty, dusty mass of fungal spores under peeling bark on the trunk and main branches were the most striking symptoms. Deep cankers expanded longitudinally, extending along trunks and into the phloem of the trees, which consequently died, and occasionally laterally extending into the sapwood. Declining trees had dry root rot symptoms, with black necrosis on the surface, and under the cracked and coarse bark extending from the taproot and some large roots to the crown, and black rot and loss of fine roots. Samples were taken from under the bark of trunk cankers, crown tissues, and root tissues of five trees per orchard. The sections of samples were surface sterilized in 2% NaOCl for 2 min and rinsed twice in sterile distilled water, blotted dry with sterilized filter paper, placed on PDA, and incubated at 28°C. A fungus with identical cultural characteristics was consistently isolated. On PDA, the mycelium growth was white and then turned black with age. Rapidly growing colonies (average, 40 mm/day) produced mycelia that disarticulated into 0- to 1-septate, cylindrical-truncate or rod-shaped, thick-walled, hyaline to brown arthroconidia occurring singly or in arthric chains and averaged 9.6 ± 3.7 × 5.5 ± 1.6 μm with a length/width ratio of 1.79. These characteristics were consistent with the description of the arthric synanamorph of Neoscytalidium dimidiatum (Penz.) Crous & Slippers (Crous et al. 2006). The rDNA internal transcribed spacer (ITS) and large subunit (LSU) genes of two single conidial isolates (one from under bark tissues; one from root tissues) were amplified with ITS6/ITS4 and NL1/NL4 primer pairs, respectively, and the amplicons sequenced. The ITS and LSU sequences deposited in GenBank (ITS, MK430050 and MK430051; LSU, MK430056 and MK430057) had 100% identity with many sequences of N. dimidiatum, including recently available ones (Turkolmez et al. 2019; ITS, MH114591; LSU, MH114592), in line with the morphological features. Pathogenicity tests were performed on 20 replicates of 1-year-old container-grown J. regia ‘Chandler’ seedlings with a N. dimidiatum isolate by removing a 5-mm-diameter bark plug from the stem with a cork borer and placing an equivalent-sized 7-day-old culture disc of N. dimidiatum onto the exposed vascular cambium. The wound was covered with wet, autoclaved cotton wool and sealed with Parafilm. Treated plants were maintained in a growth chamber with a 16/8-h light/dark photoperiod at 26°C and 55% RH and watered on demand. Within 3 weeks, average lesion lengths under the bark of all inoculated stems were >150 mm, and the lesions were covered with a black sooty layer. Leaf blight was also observed, similar to naturally affected trees. Control plants remained healthy. N. dimidiatum was reisolated only from lesions of inoculated stems, fulfilling Koch’s postulates. In Turkey, N. dimidiatum has been reported as a destructive new blight of tomato (Turkolmez et al. 2019) and canker, shoot blight, and root rot of pistachio (Dervis et al. 2019). This is the first report of N. dimidiatum infection of walnuts in Turkey. By the end of 2018, all symptomatic trees had died. Recent occurrence of this severe disease suggests it could have a significant potential for limiting walnut production.

Preparation of aluminum nitride by combustion of a Mg-Al alloy

Abstract Aluminum nitride (AlN) was synthesized by combustion of spherical Mg–Al alloy particles in air. Alloy powder was freely poured on a sample table, which formed a cone with a diameter of 1-2 cm. A commercial electro-thermal furnace was used to ignite the cone to start the synthesis. During the combustion, the temperature was measured and the actual burning process was recorded by a video camera. The morphology and phase makeup of the raw powders and the synthesized AlN powders were analyzed by scanning electron microscopy and X-ray diffraction. The thermodynamic properties and ignition temperatures were studied using differential scanning calorimetry and thermogravimetric analysis. Moreover, the effects of the Mg–Al alloy particle size (212.8 μm, 124.1 μm, 61.1 μm, and 29.5 μm) on the morphology of AlN were investigated. The results show that the combustion of Mg greatly promoted the nitridation of Al and that Al in both large and small alloy particles could be completely converted into AlN. The combustion products of the alloy consisted of two different layers: an upper white layer containing MgO and a lower black layer containing AlN. More AlN whiskers formed when small particles were used. However, very small Mg–Al alloy particles hindered the formation of AlN whiskers.

Descending Infrared Transmission Spectra of CdZnTe Substrates Due to Surface Roughness

The (111)B-oriented Cd0.96Zn0.04Te substrates with rough surfaces have been found to have infrared (IR) transmission spectra which decrease rapidly in intensity as the photon energy increases. The rough surfaces were produced by Everson etching or rough polishing. The descending spectra could be qualitatively described by an equation found in the literature. Flat low intensity IR transmission spectra were found to be due to a combination of free carrier absorption and rough surfaces. The B-side of the substrate is the growth side. By etching the A-side of the substrate only we found that the black layer formed by the Everson etch on this side introduces two features in the IR transmission spectra: a dip at approx. 625 cm−1 and a special kind of ascending IR transmission spectrum: The ascending spectrum increases from approx. 65% at 500 cm−1 up to 72.5% at the highest wavenumbers around 4000 cm−1. There is a correlation between the dip and the ascending spectrum: six out of the seven spectra with largest dip have the highest transmission at 4000 cm−1 suggesting a common origin.

Space-time ph variability in the Black Sea

Based on the archival data for the period from 1956 to 2010, space-time pH changes in the Black Sea upper layer are analyzed. In the surface layer, a statistically significant decreasing in the pH value (at a level of -0.06 pH units per 50 years) was found. It is mostly due to the growing concentrations of carbon dioxide in the atmosphere. Intermediate layers are characterized by a negative pH trend which absolute value more than fivefold exceeds the surface pH trend. Likely reason of the pH decreases here is a long-term upward moving of acidic waters with a typical velocity of ~1 m per year.

UAV-Based 3D Spectrum Sensing in Spectrum-Heterogeneous Networks

In cognitive radio networks, collaborative spectrum sensing has been recognized as a key technology to enable secondary users (SUs) to detect spectrum holes and opportunistically access primary licensed spectrum band without harmful interference. Most of the existing studies focus on 1D or 2D spectrum opportunity detection and explicitly or implicitly assume that all SUs share the same spectrum opportunity. In this paper, we first investigate the issue of joint spatial-temporal spectrum sensing in 3D spectrum-heterogeneous space by leveraging the location flexibility of flying unmanned aerial vehicle (UAV) spectrum sensors. We divide the sensing space into three layers: black layer, grey layer, and white layer, which represent different spatial spectrum access opportunities. Then, we formulate the 3D spatial-temporal opportunity sensing model and derive the spatial-temporal false alarm and detection probabilities at both single UAV level and whole network level. Afterwards, we design a temporal fusion window and a spatial fusion sphere to address the composite spatial-temporal data fusion, called 3D spatial-temporal sensing (3DSTS). A comparison among 3DSTS, the benchmark 3D non-cooperative sensing (3DNCS) and 3D cooperative sensing (3DCS) shows the inefficiency of the traditional sensing schemes in the 3D spectrum-heterogeneous networks. Furthermore, we develop three improved versions of 3DSTS, which show much better detection performance. To maximize the utilization of spectrum resource and minimize the interference to the PU, a sensing-based power control scheme is also proposed. Finally, numerical simulations corresponding to the theoretical analysis are demonstrated.

Dynamics of the Black Sea Upper Layer Based on Satellite Data: Gridded Altimetry versus High Resolution IR Images

Dynamics of the Black Sea Upper Layer Based on Satellite Data: Gridded Altimetry versus High Resolution IR Images

Study of the Process of the Black Sea Upper Layer Mixing in the Zone of the Rim Current Activity in Winter Based on the Drifters Data

Study of the Process of the Black Sea Upper Layer Mixing in the Zone of the Rim Current Activity in Winter Based on the Drifters Data

Issledovanie protsessa peremeshivaniya verkhnego sloya CHernogo morya v zone deystviya Osnovnogo Chernomorskogo techeniya v zimniy period po dannym drifterov

Issledovanie protsessa peremeshivaniya verkhnego sloya CHernogo morya v zone deystviya Osnovnogo Chernomorskogo techeniya v zimniy period po dannym drifterov

Putnikovye dannye dlya issledovaniya dinamiki poverkhnostnogo sloya Chernogo morya: al'timetriya na regulyarnoy setke i IK-izobrazheniya vysokogo razresheniya

Purpose. During more than 20 years, very detailed notions of the sea level variability in the World Ocean and its particular parts have been obtained based on satellite altimetry observations. Their advantage consists in possibility of a fairly rapid assessment of the surface currents’ velocities at synoptic scales. The alternative method for studying surface dynamics is estimation of the motions using a sequence of visible/infrared (IR) satellite images of the sea surface. The purpose of the present study is to compare the results obtained from application of two described methods used to analyze general circulation of the Black Sea surface layer. Methods and Results. The structure of the current fields in the northwestern Black Sea in winter, 1999 is investigated using the results of analysis of the IR image sequence from the NOAA/AVHRR sensors, as well as the gridded sea level anomaly data (processing level L4) and the along-track measurements (level processing L3) from the Copernicus Marine Environment Monitoring Service. The surface currents’ velocities are estimated based on the sea level field, which is calculated using two versions of mean dynamic topography. To compare the gridded altimetry and the results of the image sequence processing, a simple procedure is proposed for reconstructing the sea level using the current velocities’ components. The results of reconstructing the surface circulation features by two methods were compared and demonstrated, in particular, the anticyclonic eddy locations in the northwestern part of the Black Sea. It is noted that the locations of the eddy center in the sea level fields reconstructed from the altimetry data and by processing of the IR image sequence are different. Evolution of the eddy is investigated using the sea level anomaly data. It is shown that its motion is rather intermittent in time that can be a result of applying the procedure of optimal interpolation. Conclusions. It is noted that the gridded satellite altimetry product from the CMEMS, being applied to the Black Sea basin, should be used with due regard for the provided information on the mapping errors.

PGM-Free Electrode Development and Optimization Using H2 Limiting Current

PEMFCs with platinum group metal (PGM) catalysts can meet performance targets, but the main obstacle for widespread commercialization is the high cost. Alternatively, precious group metal-free (PGM-free) catalyst can meet cost targets and have the potential to reach DOE performance goals. However, successful PGM-free PEMFC development must include device-level studies and microstructure optimization, especially for minimizing the concentration overpotential in the thick PGM-free electrode layers. To date, limited work has been done to decouple the gas phase transport losses from those associated with stability1, active-site density2 and ion transport at the MEA level. Elucidating the voltage loss contributions or resistances stemming from gas transport and proton conduction at the MEA level along with subsequent correlation to MEA performance will help identify phenomena currently limiting the inception of PGM-free electrode performance and identify paths to improved electrode optimization. Baker et al. and Beuscher first suggested the use of limiting current for mass transport characterization in 2006.3,4 The technique has been developed over the past decade for operando measurement, deconvolution, and quantification of the discrete contributions to the concentration overpotential, often expressed as a mass transport resistance, arising from constituent materials and cell components.5,6 However, this method can be difficult to apply to PGM-free based electrodes, where ohmic contributions may dominate over transport phenomena. In this condition, hydrogen could be used as the molecular probe for mass transport resistance instead of oxygen. Spingler et al. first attempted the use of hydrogen as a probe molecule for PGM based electrodes.7 In this work, we integrated a platinum black (PtB) sensor layer into the MEA., enabling in situ determination of mass transport resistance throughout the entire PGM-free catalyst layer. These experiments were performed using a 5 cm2 differential cell, operated at differential conditions in all experiments such that the reactant concentration gradient down the channel was negligible. The total transport resistance ( ) is written in Equation 1 and was measured for various PGM-free electrodes with different ionomer loadings. Rtotal = nFCH2, channel / id Here, we will present 1) a limiting current measurement approach to characterize in situ mass transport resistances in fuel cell materials through bulk catalyst layer at an MEA device level; 2) PGM-free catalyst performance with different ionomer loading in the cathode; 3) how to balance mass transport and ionomer loading to achieve the best FC performance. The results from this experimental approach not only offer the guidance of transport properties and the role of ionomer loading played in the PGM-free electrodes but also increase our understanding of achieving an optimized performance for a PGM-free catalyst at an MEA level. Improved device-level understanding of mass transport limitations in the catalyst coated layer can help accelerate deployment of low cost, PGM-free PEMFCs and be useful to guide ongoing research and development in both catalyst synthesis and membrane electrode assembly fabrication.

Durability and weatherability of a styrene-ethylene-butylene-styrene (SEBS) block copolymer-based sensing skin for civil infrastructure applications

Structural health monitoring of civil infrastructure requires low-cost, scalable, long-term, and robust sensing technologies due to the size and complexity of the geometries under consideration. This paper investigates the durability and weatherability of a large area sensing skin engineered for civil infrastructure applications. This sensing skin is based on a soft elastomeric capacitor made of three thin layers based on an SEBS block co-polymer matrix. The inner layer is filled with titania and acts as the dielectric, while the external layers are doped with carbon black and work as the conductive plates. In this work, a variety of specimens, including the dielectric layer without the conductive plates, were fabricated and tested within an accelerated weathering chamber by simulating thermal, humidity, and UV radiation cycles. Beyond the accelerated weathering tests, a sensor deployed on a bridge in Iowa for six and a half years was removed from the field and analyzed in the laboratory. A variety of other tests were performed in order to characterize the specimens’ mechanical, thermal, optical, and electrical performance. Additionally, strain sensitivity analyses were performed on specimens of interest. Results showed that titania inclusions improved the sensor dielectric's durability against weathering, while the carbon black doped conductive layers provided the skin sensor with a high level of durability and weatherability protection. The results in this work contribute to a better understanding of the degradation of SEBS-based matrices as well as the behavior of these skin sensors when deployed for the monitoring of civil infrastructure.

Use of THM-PY-GC/MS technique to characterize complex, multilayered Chinese lacquer

Use of micro-destructive analytical techniques to explore the complex matrix composition, structure and lacquering techniques of multilayer lacquered objects has been the focus of many researchers. This work presents the results of a comprehensive investigation of the “Tixi” carved lacquer micro-sample excavated from Zhejiang province in China (Song Dynasty, A.D. 960-A.D. 1279). Stereomicroscopy, EPMA-EDS, FTIR, μ-RS and THM-Py-GC/MS were used in a comprehensive study of the object. The results show that the structure of the lacquer body consists of one wooden body layer, one lacquer ash layer, one ground lacquer layer and four lacquer film pigment layers, which indicates that it has been lacquered for several times. The chemical composition analysis results show that the lacquer stucco layer was made from the ashes by“Wan lacquering” craft. The lacquer film was made up of pigment (soot (black layer), orpiment (yellow layer), cinnabar (red layer)), lacquer sap, heat-bodied tung oil and tannins (partial layer); the presence of the series of catechols, acid catechols, phenols, alkyl benzenes, and hydrocarbons in which each has a maximum side chain length of 17 carbons and the most abundant member has nine carbons clearly indicate the species of the lacquer tree was Rhus succedanea that produces laccol. “Tixi” carved craft was used to make different lacquer film pigment veins layers appear simultaneously to emerge its unique characteristics like “drifting clouds and flowing water”.

The nature and origin of pigments in black opal from Lightning Ridge, New South Wales, Australia

Black opal (opal-AG) owes its dark coloration to a fine-grained pigment commonly inferred to be mainly carbon, yet chemical compositions for black opals suggest there may be additional components. Here we search for such components in pigment concentrates prepared by dissolving black opal nodules (nobbies) from Lightning Ridge (NSW) in hydrofluoric acid, using electron microscopy (scanning electron microscopy, transmission electron microscopy), X-ray diffraction and laser-ablation ICP-MS. The results demonstrate the presence of sulfides—predominantly pyrite and chalcopyrite, with minor galena and Ti-oxide phases, as additional components of the pigment. ATR-FTIR analysis indicates the presence of C=O and C–H groups, consistent with an organic origin. Transmission electron microscopy images of pigment show variously deformed, originally spherical ∼100 nm particles rich in sulfide and carbon, which are interpreted as thin coatings of pigment on now dissolved opaline silica spheres. Laser-ablation ICP-MS analysis identifies remnant silica in pigment concentrates, which may be interpreted as opaline silica surviving HF treatment protected as inclusions in sulfides. When examined within the context of petrographic observations from more than 1000 opal nodules (nobbies) at Lightning Ridge, these new results suggest that pigment carbon and sulfides in the nodules formed microbially under initially anoxic groundwater conditions, within pre-existing cavities concurrently being filled with silica sol ultimately derived from chemical weathering of feldspar-rich volcaniclastic sediment. Intensely black pigment layers observed at the floor of many nodules indicate settling of dark, high-density (sulfide–Ti-oxide-rich) pigment within cavities, with the implication that sulfate-reducing bacterial (SRB) activity commences early during the silica sol-gel ripening process. Microbial activity may persist until after the cavity has completely filled with the silica sol, as illustrated by abundant black opals with uniformly distributed pigment. Pigment formed at this stage may no longer be able to settle out within the ripening and increasingly viscous silica gel, thus forming pigmentation throughout the opal cavity. The existence of ‘amber’, pigment-poor opal with intensely black basal pigment layers is interpreted as signalling a lack of sulfate to sustain further SRB activity, or a change to more oxidising conditions, possibly related to interaction with surface waters within a downward-penetrating weathering front. A change in redox conditions would shut off activity of SRB and thus sulfide pigment production and allow development of aerobic microbial activity as described by others.

Use of remote sensing to predict the optimal harvest date of corn

Accurate prediction of optimal harvest date (OHD) is important to maximize the yield of corn as it approaches maturity. Yield loss occurs if harvest occurs in advance of, or is delayed past, OHD; both scenarios are undesirable. If corn is harvested prematurely, high residual moisture makes it prone to mildew during storage, which produces aflatoxin. The grain quality then deteriorates, leading to a serious decrease in yield. If corn is harvested too late, the crop quality declines severely. Previous studies have demonstrated the utility of three corn kernel indicators (kernel moisture, milk line, black layer) in predicting corn harvest date; however, these indicators do not satisfy the demand of modern agriculture. Therefore, in this study, remote sensing techniques, which have proven useful in the application of Precision Agriculture, were used for timely estimation of OHD for large-area crops. We proposed a new method for predicting corn OHD in fields using remote sensing by assessing corn kernel moisture (CKM) and identifying an effective biochemical indicator to relate OHD and remote sensing data. We estimated CKM using canopy chlorophyll content (CCC), a significant biochemical parameter that can be estimated from remote sensing images using PROSAIL, a popular used radiative transfer model. Since CKM decreases at a regular rate after entering the maturity period, OHD can be predicted based on the estimated CKM using a baseline assumption that OHD occurs when CKM drops to 30%. The prediction method was evaluated by analyzing measured CKM, and the temporal variation in one hundred-grain weight and yield. The results of this study enabled us to successfully and accurately estimate CKM using a non-linear model (R2 = 0.92) and predict CKM (R2 = 0.64) and corn OHD. This study provides new avenues for predicting crop OHD using remote sensing multispectral imagery and suggests that remote sensing techniques are effective for accurately predicting corn OHD across large areas.

Sulfuric acid speleogenesis in the Majella Massif (Abruzzo, Central Apennines, Italy)

Many active and inactive hypogene sulfuric acid cave systems are known along the Apennines, Italy. The Cavallone-Bove cave system is located in the external part of the central Apennine Chain, in the Majella Massif, and opens at 1470 m asl along the Taranta Gorge (South of Chieti). The presence in these caves of peculiar geomorphological features, such as feeders, rising channels, megacusps, cupolas, and replacement pockets, offers evidence of rising acidic fluids. The secondary mineral deposits, including meter-size white gypsum deposits, alunite, jarosite, black layers of iron‑manganese oxides and hydroxides, along with a rare association of authigenic rutile-ilmenite minerals indicate a sulfuric acid origin. Stable isotope analyses of sulfates further confirm a sulfuric acid speleogenetic (SAS) origin of these minerals and, in general, of the whole cave system, with H2S coming from the bacterial sulfate reduction of deep-seated Triassic evaporites interacting with hydrocarbons. Alunite dating demonstrates this water table SAS cave to have been active at least until 1.52 ± 0.28 Ma. All the evidence suggests that Cavallone-Bove is an ancient sulfuric acid karst system that was uplifted <1 km above pre-existing base level. The age of speleogenesis further suggests that tectonic uplift of this area was as high as 670 m My−1 over the last 1.5 Ma.

Experimentally Derived Sedimentary, Molecular, and Isotopic Characteristics of Bone-Fueled Hearths

Molecular and isotopic analysis of sediments from archaeological combustion features is a relatively new area of study. Applications can inform us about ancient pyro-technologies and patterns of animal exploitation in a wide range of human contexts, but may be particularly informative with regard to ancient hunter-gatherers. Our analyses of sediments from experimental bone and wood fires, and from controlled laboratory heating sequences, provide fine-grained data on the formation and location of biomarkers from pyrolyzed animal fats in hearths. Integrating microstratigraphic, molecular, and isotopic data can improve recognition of bone fires in archaeological contexts, perhaps even where bone preservation is poor. Experimental bone fires produced an upper layer of calcined bone above a thin layer of tarry black amorphous material coating mineral sediments. Mineral sediments beneath the black layer showed little alteration but high lipid content. Sampling for molecular and isotopic analysis should target the black layer as the bulk of pyrolyzed biomarkers are located here and stable isotope values are less affected than in the overlying layer of ash or calcined bone. The combined presence of certain symmetric and slightly asymmetric saturated long-chain ketones (14-nonacosanone, 16-hentriacontanone 16-tritriacontanone, and 18-pentatriacontanone), especially together with heptadecane (C17n-alkane), are molecular indicators of the thermal degradation of terrestrial animal fat. Formation and relative dominance of these molecules in hearth sediments relates to the initial prevalence of specific precursor fatty acids and can provide broad separations between sources. We suggest that separations could be further supported and expanded by combining stable isotope analysis of the same compounds.

Chemical profile of organic residues from ancient amphoras found in Pyrgi and Castrum Novum, Tyrrhenian Sea (Italy)

The organic residues in the form of black layer spots inside amphoras found on the sites of the former ancient ports of Pyrgi and Castrum Novum on the coast of the Tyrrhenian Sea were investigated using GC–MS and HPLC with fluorimetric detection. According to our hypothesis, the residues could be from waterproofing materials from pine trees, which ensured that amphoras could be used for transportation and the storage of liquids. Samples of the residues were removed, extracted with hexane and separated into three parts. The first part served directly for GC–MS analysis of hydrocarbons. The second part after the evaporation of hexane and silylation of the residue with MSTFA was used for the analysis of fatty and resin acids. Finally, the third part after evaporation of hexane and dilution of the residue with methanol was used for HPLC analysis of pinosylvin mono methyl ether and confirmation of retene presence using a fluorimetric detector. 18-Norabieta-8,11,13-triene, 19-norabieta-8,11,13-triene and 1,2,3,4-tetrahydroretene were found in the hexane extract, which are intermediates from the tar/pitch production process. The most abundant peak in the chromatogram of the hexane extract was dehydroabietic acid and retene. The latter is considered to be a marker for pine pitch. The most abundant compound in the derivatized hexane extract was also dehydroabietic acid, which occurs only as a minor component in fresh resins. This molecule is formed during the oxidative dehydrogenation of abietic acid, which predominates in original resins. Pinosylvin mono methyl ether was found in the methanolic extract using HPLC with fluorimetric detection and, to the best of our knowledge, it is the first finding of this substance in archaeological samples. Together with the abovementioned compounds, it supports the hypothesis of the resin's origin from trees of the Pinaceae family.

Study on the white layer in wire electrical discharge trim cutting of bearing steel GCr15

In wire electrical discharge machining (WEDM), a large amount of thermal energy is produced to remove workpiece material, and a certain thickness of white layer is also generated in this process. The white layer has a significantly negative effect on the reliability and service life of workpiece. Hence, predicting and decreasing white layer are important to evaluate and improve the performance of workpiece. In this paper, a multi-pulse thermal model is proposed to obtain the temperature distribution of workpiece during the trim cutting bearing steel GCr15. The temperature measurement experiment demonstrates that this thermal model is feasible and reliable. Additionally, a set of experiments are implemented to reveal the formation mechanism of white layer, such as microstructure observation, XRD measurement, and microhardness measurement. It can be found that the white layer has high microhardness due to high content of Fe3C. The black layer has low microhardness because of high content of retained austenite. In addition, the white layer thickness (WLT) of workpiece is predicted with high precision according to temperature distribution and the critical temperatures of metallographic transformation. Furthermore, the magnetic-assisted method is presented to reduce abnormal discharge status and WLT, and the WLT can be decreased as low as 5 μm.

Solar-driven high-temperature steam generation at ambient pressure

This paper demonstrates a facile solar steam generator for the generation of high-temperature steam at ambient pressure. The steam generator consists of a coiled copper tube (CCT) that serves as both solar collector and vapor heater. Both the inner and outer surfaces of the CCT are coated with black superhydrophobic copper oxide layer to improve the solar absorption, and such superhydrophobic layer prevents the condensation and clogging of water vapor during the heating process. Solar vapor is generated at the inlet of CCT through interfacial evaporation and subsequently heated inside the CCT as the vapor travels from the inlet to the outlet. By employing this approach, steam temperature that exceeds 100 °C under 1-sun illumination is demonstrated. Furthermore, steam temperature could reach as high as 250 °C under 10-sun illumination at ambient pressure. Successful sterilization experiment was also performed in this work to demonstrate the potential application of the high temperature steam generated. Such demonstrated approach helps open up the potential usage of solar-driven interfacial evaporation in applications that involve high-temperature steam, including medical sterilization, chemical manufacturing and food processing.