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To obtain accurate resonance peaks from surface plasmon resonance (SPR) spectra, a denoising approach based on generalized S-transform optimized by a new iterative algorithm of bald eagle search (BES) is reported and applied. First, a fiber SPR sensing system is used to collect the original noisy spectra, and the generalized S-transform is performed to obtain the corresponding S-domain spectrum. Next, the denoising threshold ( λ n ) is optimized by the BES algorithm to denoise and reconstruct the SPR reflection spectrum. Finally, the original SPR reflection and the denoised reflection spectra are used to evaluate the fitness function until the optimal denoising threshold ( λ n ) and denoising effect are obtained. The experimental results show that the developed method maintains a relatively stable denoising for SPR reflection spectra as the average values of root mean square error ( RMSE ) and signal to noise ratio ( SNR ) are 0.27 and 23.6, respectively. This method overcomes the problem of arbitrary selection of basic functions or thresholds in conventional denoising methods, improves the accuracy of SPR sensor, and provides a new approach for spectral denoising. [ABSTRACT FROM AUTHOR]

We analyzed the characteristics of main karstic/non-karst reaches of the Lijiang River to uncover the causes behind different flood behaviors by providing a better understanding of the flood formation. Having 63 years of rainfall-runoff data and applying the HEC-HMS model, geo/hydrological features were investigated. The available reservoir capacity of karts (ARCK) was included through soil moisture accounting loss data to assess its impact. In particular, the expected instantaneous peak discharge rates/times were found largely imbalanced with generated unit hydrographs. Moreover, significant gaps among the floods' features for different subbasins in terms of required peak modifications (2-4 times larger for mid-upstream, respectively) were mainly associated with the unique karst structure and initial condition due to various ARCK in rainy/dry seasons. Besides, notable dissimilarities between the wedge/prism storage volumes and the hydrograph's wave traveling/receding time were observed owing to the geomorphological conditions. Although the contribution rates of drivers in karst flood formation cannot be quantitively modeled, based on our results the ARCK emerged to play a substantial role on the forecasted results, comparatively. Our results suggest that since ARCK varies, taking it into account (as initial abstraction) results in a more reliable estimation. This was underpinned by the results in which the unmodified simulations had a qualified rate of 52% accuracy on average and increased to 67.5% after the ARCK inclusion. This work adds to the body of evidence illustrating that in karst hydrology, ignoring the situational circumstances in modeling might lead to inaccuracies in flood forecasting for such dynamic watersheds. [ABSTRACT FROM AUTHOR]

The objective of this work was to modify the HEC-HMS flood prediction for the karstic watershed of the Lijiang River, South China, through the quantitative inclusion into the model of the available reservoir capacity of karst (ARCK) as a case study. Due to the complexities caused by hidden drainage networks in karst hydrology, as a new approach, soil moisture accounting loss was used to reflect the ARCK in flood forecasting. The soil moisture loss was analyzed against daily rainfall runoff data across 1.5 years by using an artificial neural network via phyton programming. Through the correlations found among the amounts of soil moisture and river flow fluctuations in response to precipitation and its intervals, coefficients were introduced to the model for output modifications. ARCK analysis revealed that while heavy rainfalls with longer intervals (i.e., 174 mm/2d after 112 days of the dry season) may not cause considerable changes in the river flow magnitude (0.1–0.64 higher owing to high ARCK), relatively small rainfalls with higher frequency (i.e., 83 mm/4d during the wet season) can cause drastic raise of river flow (10–20 times greater at different stations) due to lower ARCK. Soil moisture accounting loss coefficients did enhance the model's simulated hydrographs accuracy (NSE) up to 16% on average as compared to the initial forecasting via real data. However, the modifications were valid for flood events within a few years from the soil moisture observation period. Our result suggested that the inclusion of ARCK in modeling through soil moisture accounting loss can lead to increased prediction accuracy through consistent monitoring. [ABSTRACT FROM AUTHOR]

In view of the premature convergence of particle swarm optimization (PSO) that is often caused by the loss of diversity, an improved cooperative PSO (ICPSO) is proposed. The method can dynamically combine the optimum values of the particles themselves, the global particles and the optimum values in groups, use the current optimization stage to dynamically adjust the shared proportion of information and effectively fuse various reference information, which can obtain superior global and local optimization performance. Additionally, to improve the diversity of the algorithm, a dynamic adjustment method using the grouping coefficient r for the convergence rate is put forward. This method makes the algorithm have a more appropriate convergence rate while improving the convergence precision and enhancing the performance of the algorithm. Finally, the algorithm is used to optimize a neural network. The convergence condition and convergence rate of the algorithm are assessed by theoretical analysis and simulation experiments. The results show that ICPSO has more advantages in its diversity and the adjustment of the convergence rate compared to other related algorithms. Regarding neural network optimization, the training speed and optimization precision of the ICPSO-BP neural network are the highest, which has reached the best and average level of classification accuracy 98.5%, 96.3% for 20 iterations in Iris, and 98.7%, 95.1% in Wine. Its average iteration times score the best in five problems out of six. [ABSTRACT FROM AUTHOR]

Wind energy forecasting is significantly affected by the strong volatility, intermittency and variability of the wind speed sequence itself. Therefore, to improve forecast accuracy and stability, based on nonlinear auto-regressive model with exogenous inputs (NARX) and the hybrid chaos-cloud salp swarm algorithm (CC-SSA), a short-term wind speed prediction method is proposed. Firstly, to reduce the complexity of the original wind speed data and generate subcomponents with different patterns and low complexity, a mixed modal decomposition method is carried out by combining variational modal decomposition (VMD) based on Pearson correlation coefficient and generalized S-transform (GST) based on adaptive sample entropy. Therefore, the complementary advantages of different mode decompositions are obtained by combining the two different subcomponents into a mixed component. Secondly, by using cloud model and chaotic map, the improved CC-SSA algorithm is proposed to improve the convergence performance of salp swarm algorithm (SSA). Finally, by using CC-SSA algorithm to optimize the weights of NARX, the CC-SSA-NARX forecasting model is established to predict wind speed. The experimental results show that for the 1-Step, 2-Step, and 3-Step datasets of the actual wind speed in the studied region, the MAE, MAPE, RMSE, and R 2 of the CC-SSA-NARX model are 0.23, 6 %, 0.27, and 0.97 respectively. The proposed model present the highest prediction index among the other 7 comparative models, showing high accuracy and generalization ability in short-term wind speed prediction, it can provide a certain reference for enhancing the stability of wind power generation and promoting the sustainable development of the wind power industry to some extent. • A mixed decomposition method using VMD and generalized S-transform is proposed. • An improved SSA algorithm based on chaotic cloud (CC-SSA) is proposed. • The proposed CC-SSA is applied to optimize the parameter of NARX. • A short-term wind speed prediction model of CC-SSA-NARX is constructed. [ABSTRACT FROM AUTHOR]

Ferroelectric materials have been a key research topic owing to their wide variety of modern electronic and photonic applications. For the quick exploration of higher operating speed, smaller size, and superior efficiencies of novel ferroelectric devices, the ultrafast dynamics of ferroelectrics that directly reflect their respond time and lifetimes have drawn considerable attention. Driven by time‐resolved pump‐probe spectroscopy that allows for probing, controlling, and modulating dynamic processes of ferroelectrics in real‐time, much research efforts have been made to understand and exploit the ultrafast dynamics of ferroelectric. Herein, the current state of ultrafast dynamic features of ferroelectrics tracked by time‐resolved pump‐probe spectroscopy is reviewed, which includes ferroelectrics order parameters of polarization, lattice, spin, electronic excitation, and their coupling. Several potential perspectives and possible further applications combining ultrafast pump‐probe spectroscopy and ferroelectrics are also presented. This review offers a clear guidance of ultrafast dynamics of ferroelectric orders, which may promote the rapid development of next‐generation devices. [ABSTRACT FROM AUTHOR]

Aimed at the numerous parameters that affect the performance of fiber Surface Plasmon Resonance (SPR) sensor, which make it difficult to determine the optimal parameters by traditional mathematical modeling, on the one hand, a tapered fiber SPR sensor model is proposed to improve the detection sensitivity of sensor. On the other hand, a new intelligence algorithm with fast search speed and high search accuracy, Bald Eagle Search Algorithm (BES), is adopted to optimize the structural parameters of tapered fiber SPR sensor, including the metal film thickness (d 2), sensing area length (L), taper ratio (TR), and measured refractive index (n 3). At the same time, a comprehensive fitness function is defined to improve the optimization effect, which take the sensitivity, resolution and linearity of the proposed sensor model into account. In the verification process, establish three different optimization experiments, including one partition optimization, two partition optimizations and three partition optimizations. The experimental results indicate that the optimization effect of the three partition optimizations is the best, for three different optimization intervals, the obtained fitness function values are 80%, 81% and 78%, respectively. In addition, the performance of BES is compared with other five optimization algorithms, the results indicate that the best shape of SPR reflection spectrum can be obtained by BES, its average sensitivities is 2218.85 nm/RIU, which ranks first. Therefore, by three partition optimizations and BES algorithm, the optimized parameters are more representative, which make the obtained reflection spectrum based on the optimized parameters has smallest degradation. The proposed method can provide an efficient and intelligent design idea for SPR sensor, it can greatly increase the flexibility of SPR sensor design. • A tapered fiber SPR sensor is designed and the BES algorithm is used to optimize the structural parameters of the sensor. • A novel fitness function is proposed, which involved full-width-at-half-maximum (FWHM), figure of merit (FOM) and linearity. • Three experiments are established by dividing the measured refractive index range into some smaller intervals. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights: • The Arqiale deposit is a distal skarn Zn-Pb deposit. • Regional magmatism and mineralization age are consistent at ca. 340 Ma. • S-Pb isotope compositions suggests the ore-forming materials were derived from a magmatic source. • There is significant potential for skarn Zn-Pb deposits associated with Late Paleozoic magmatic intrusions in Western Tianshan. Abstract The Arqiale deposit, located in the southern Yili Block of Western Tianshan, Xinjiang, China, is a newly discovered large Zn-Pb deposit with a resource of approximately 10 million tons ore grading 9.65% Zn+Pb, and a certain amount of Cu and Ag. The Zn-Pb orebodies are tabular and lentoid in shape, developed along SW-striking and NW-dipping interlayer structures between the Lower Carboniferous Akeshake (mainly carbonate rocks) and Dahalajunshan (mainly volcanic rocks) formations. Garnet and pyroxene-rich skarn, formed in the early (prograde) stage of skarnization, occurs only locally as lenses within skarn bodies enriched in actinolite, tremolite, ilvaite, biotite, epidote, chlorite, calcite, quartz and fluorite, which were formed in the retrograde stage. Metallic minerals comprise sphalerite, galena, chalcopyrite, pyrite, and hematite. They mainly occur as disseminations, patches and massive ores, replacing retrograde skarn minerals and crosscut by later stage quartz and calcite veinlets. There is a general trend of increasing Cu contents and decreasing Zn/Pb ratios from the upper and south portion to the lower and north portion of the orebody. Rb-Sr dating of seven sphalerite samples yielded an isochron age of 339.5 ± 2.7 Ma, which is almost identical to the 341.8 ± 2.5 Ma age obtained from Sm-Nd dating of eight actinolite samples. Furthermore, zircon U-Pb dating yielded an age of 343 ± 6 Ma for a gabbro-diorite stock that is located about 600 m south of the Zn-Pb orebody. The age data indicate that the mineralization and retrograde skarnization were contemporaneous, and they are likely related to a magmatic intrusion of similar age which may be linked to the gabbro-diorite stock. Thus, although the direct causative intrusion has not been identified, the Arqiale deposit can be classified as a distal skarn deposit. The δ34S V-CDT values of 26 ore sulfide samples range from −7.1‰ to +1.3‰ with an average of −1.5‰. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 25 ore sulfide samples range from 18.266 to 18.880, 15.577 to 15.668 and 38.068 to 38.720, respectively, which are similar to the Early Carboniferous intrusions of the Wusun Range and partly overlap with the volcanic rocks of the Dahalajunshan Formation, and are different from the carbonate rocks of the Akeshake Formation. Based on these data, we propose that the Arqiale deposit formed from magmatic-hydrothermal fluids emanated from a concealed magmatic intrusion which may be located beneath the northern and deep part of the deposit. Much of the metals and sulfur may have been derived from the magmatic intrusions, although some of them may have also been extracted from the volcanic rocks underlying the deposit. The results of this study indicate that there is a great potential of finding more skarn Zn-Pb mineralization in Western Tianshan, where numerous Early Carboniferous arc-related intrusions with similar ages as the Arqiale deposit, in relation to the subduction of the Southern Tianshan Oceanic plate underneath the Yili-Central Tianshan Block, were emplaced into or beneath carbonate rocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Skarn Zn-Pb metallogeny in the Tianshan is related to the Late Paleozoic subduction of the Paleo-Asian Ocean. • The ore-forming materials were mainly derived from magmatic source, and partly from country rocks. • A genetic model of skarn Zn-Pb metallogenesis related to the Paleozoic oceanic slab subduction in the Tianshan is established. The Tianshan orogenesis was initiated as a dynamic response to the subduction of several branches of the Paleo-Asian Ocean (PAO) and formed a significant polymetallic metallogenic belt in the western Central Asia. Skarn-related Zn-Pb deposits occupies an essential position in Zn-Pb mineral resources of the Tianshan, but its genesis remains ambiguous, and its economic importance is substantially undervalued. Here, we present a comprehensive overview of the spatiotemporal distribution, geological characteristics, geochemical characteristics of causative intrusions, fluid inclusion geochemistry, H-O-C-S-Pb isotopic systematics to constrain the tectonic setting, source and metallogenic mechanism of skarn Zn-Pb deposits in the Tianshan. Our study suggests that the 380–320 Ma and 350–300 Ma skarn type Zn-Pb mineralization occurred in the Tianshan is temporally and genetically related to the Late Paleozoic subduction of the PAO. The skarn type Zn-Pb resources are primarily hosted by distal skarns, with causative intrusions characterized by calc-alkaline to high-K calc-alkaline, peraluminous, and oxidized rock series that originated from partial melting of depleted mantle wedge and metasomatized by subducted sediment or sediment-derived melts. The hydrothermal fluids that enriched with ore-forming elements were mainly released from the causative intrusions and channeled along interlayer fracture structures within the host rocks, where Zn-Pb mineralization took place due to fluid-rock interaction and fluid mixing. Finally, the mineralization model established in this study may be used to evaluate similar skarn Zn-Pb mineralization systems elsewhere in the Tianshan. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Woxi deposit is featured by coenriched Au-Sb-W elemental association. • The Au, Sb, and W occurred mainly as invisible gold, stibnite, and scheelite. • Transition of fluid-rock interaction to phase separation caused ore precipitation. • Dissolution-reprecipitation process facilitate coenriched Au-Sb-W metallogenesis. It is well-known that tungsten and antimony are commonly enriched in the gold deposit and occur as Au-Sb or Au-W deposits. However, the Woxi deposit, located in the West Jiangnan Orogen of South China, is remarkably co-enriched in the Au-Sb-W elemental association. This deposit is characterized by multistage Au mineralization and reactivation of structures developed in the Neoproterozoic metamorphic rocks, but the detailed mechanism of its co-enriched Au-Sb-W metallogeny is still unclear. Here, we perform detailed petrographic observations and ore mineral textural and pyrite compositional analyses by using SEM and LA-ICP-MS to constrain ore-forming physiochemical conditions and to decipher the Au-Sb-W metallogenic mechanism in the Woxi deposit. The Woxi deposit consists of nine auriferous quartz lodes in the shape of stratiform, tabular, and lenticular, which are surrounded by alteration halos in the Neoproterozoic slate. These orebodies are distributed along the bedding-parallel fracture zones of the EW-striking and N -dipping in the purplish red slate of the Madiyi Formation, below the regional EW-striking Woxi fault. Four stages of hydrothermal mineralization and alteration processes could be recognized in the Woxi. Stage 1 occurs in bleached slate, and consists of euhedral, porous, and coarse auriferous pyrite (Py1), with slight arsenopyrite, siderite, and rutile. Stage 2 mainly consists of subhedral to euhedral and compositional zoning auriferous pyrite (Py2) and scheelite (Sch1), with slight wolframite and apatite hosted in quartz veinlets and native gold enclaved in Sch1. Stage 3 is characterized by scheelite (Sch2) and stibnite, with slight native gold and dendritic-shaped anhedral auriferous pyrite (Py3) hosted in quartz veins. Stage 4 features a quartz-calcite-barite-chlorite mineral assemblage that occurred as veinlets, or in the pressure shadows of Py1. Gold is mainly incorporated in the three stages (S1 to S3) of arsenian pyrite (Py1to Py3) as invisible gold and, to a lesser extent, formed visible native gold at late S2 and S3, tungsten mineralization occurs mainly as scheelite (Sch1) and wolframite at S2, with a minor amount of scheelite (Sch2) at S3, and antimony mineralization is mainly occurred as stibnite at S3. Furthermore, invisible gold most likely occurs as nanoscale particles of Au-Bi-Pb-bearing tellurides in Py1, and may be hosted in the structurally bounded lattice of Py2 and Py3.The SEM study presents highly developed dissolution-reprecipitation microstructures in hydrothermal minerals, such as pyrite, arsenopyrite, wolframite, scheelite, and apatite. Mineral paragenesis and pyrite trace element signatures suggest the ore fluid is characterized by elevated f O2 , low pH and high temperature in S1, decreased f O2 , medium pH and medium temperature in S2, and elevated f O2 , high pH and low temperature in S3. The evolution of the physicochemical condition may be induced by penetration of multipulse ore-forming fluids and the transition of the ore-forming mechanism from fluid-rock interaction in S1 and early S2 to phase separation in late S2 and S3, as suggested by textural and LA-ICP-MS analyses. This study highlighted that coupled dissolution-reprecipitation reactions might facilitate the association of the Au-Sb-W elemental that successively mineralized and co-enriched in the Woxi deposit. [ABSTRACT FROM AUTHOR]

Based on the hydrological characteristics of a rice-based irrigation system in Southern China, the SWAT (Soil and Water Assessment Tool) model was modified in order to develop the Rice Irrigation System-Soil and Water Assessment Tool (RIS-SWAT). The irrigation water movement, water balance module, and rice yield calculations of the paddy field were improved within the SWAT model. In addition, the seepage of the irrigation canal and the pond’s effect on the irrigation modules were added to the RIS-SWAT. The impact of water management on the water cycle of the small watershed irrigation system (SWIS) was evaluated by conducting a scenario analysis with RIS-SWAT. The results indicated that an increase in the maximum water ponding depth of a paddy field could decrease irrigation water and rainfall loss. The canal water supply was reduced by 20%, resulting in an increase in irrigation water productivity without a reduction in the rice yield. The temporal and spatial distributions of the irrigation water in different subbasins did not significantly affect the water cycle within the SWIS. Furthermore, when the canal water supply was reduced by 20–40% and the pond water supply was increased, the rice yield was not affected. Thus, the water productivity of irrigation systems could be improved through the implementation of water management policies and practices that reduce field outflows and reuse the return flows captured by ponds. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Woxi deposit is an orogenic Au-Sb-W deposit. • U-Pb dating on apatite and wolframite yielded a robust gold mineralization age of ca. 141 Ma. • Pyrite in situ S-Pb isotopic signatures suggest the ore-forming metals and fluids mainly derived from a metasomatized lithospheric mantle. • This study provides a new example of orogenic gold deposit that was controlled by translithospheric processes in a back-arc environment far from the plate subduction zone. The majority of gold mineralization in the Jiangnan Orogenic Belt (JOB) of South China share similarities with the orogenic type, but the nature of mineralization remains controversial, especially in terms of intracrustal versus subcrustal origin of ore fluids and metals and their relationships with the subduction of the Paleo-Pacific plate. This paper reports results of in situ analyses of minerals closely related to gold mineralization, including U-Pb ages of apatite and wolframite, and S-Pb isotopes of pyrite, from the Woxi Au-Sb-W deposit in the western Jiangnan Orogen, and use them to address the above problems. The Woxi deposit, which consists of several auriferous quartz lodes hosted by ductile–brittle shear zones in the Neoproterozoic slate. The hydrothermal mineralization and alteration processes are divided into four stages. Early-ore stage (S1) is characterized by disseminated, euhedral, porous, coarse auriferous pyrite (Py1) with minor amounts of arsenopyrite, siderite, and rutile in the bleached slate. Main-ore stage (S2) is characterized by subhedral to euhedral, auriferous pyrite (Py2) with compositional zoning, with small amounts of wolframite and apatite in quartz veinlets. Late-ore stage (S3) is represented by scheelite and stibnite with minor amounts of native gold and anhedral, dendritic auriferous pyrite (Py3) in quartz veinlets. Post-ore stage (S4) features a quartz-calcite-barite-chlorite mineral assemblage that occurs as veinlets or in pressure shadows of Py1. Apatite and wolframite associated with Py2 yield a consistent U-Pb age of ca. 141 Ma, which is corresponded to a time when the Paleo-Pacific plate started to roll back, and a Basin-and-Range style tectonic regime began to developing in South China. The different stages of pyrite have variable S isotopes, with the δ34S CDT values (mainly between −6‰ and +1 ‰) largely overlapping with those of the metasomatized mantle (−5‰ ∼ + 5 ‰), and Pb isotope ratios between crustal and mantle values. Taking these results together, we proposed that the Woxi deposit and many other gold deposits in the JOB formed from subcrustal processes involving the metasomatized upper mantle above the subduction zone. Given the extended distance from JOB to the Paleo-Pacific plate boundary, the metasomatized mantle underneath the JOB is likely initially formed during the plate subduction leading to the formation of the JOB during the Neoproterozoic, which is further fertilized by upwelling asthenosphere due to rollback of the Paleo-Pacific plate in the Mesozoic. [ABSTRACT FROM AUTHOR]

Most electronic devices exploit the electric charge of electrons, but it is also possible to build devices that rely on other properties of electrons. Spintronic devices, for example, make use of the spin of electrons. Valleytronics is a more recent development that relies on the fact that the conduction bands of some materials have two or more minima at equal energies but at different positions in momentum space. To make a valleytronic device it is necessary to control the number of electrons in these valleys, thereby producing a valley polarization. Single-layer MoS2 is a promising material for valleytronics because both the conduction and valence band edges have two energy-degenerate valleys at the corners of the first Brillouin zone. Here, we demonstrate that optical pumping with circularly polarized light can achieve a valley polarization of 30% in pristine monolayer MoS2. Our results, and similar results by Mak et al., demonstrate the viability of optical valley control and valley-based electronic and optoelectronic applications in MoS2 monolayers. [ABSTRACT FROM AUTHOR]

Abstract: Polycarbonate films were irradiated by MeV ions, including carbon clusters (n =1–5) with the same atomic dose and energy, Cl+, Ti+, and Ni+. UV–VIS–NIR spectrophotometer was employed to detect the optical absorption of irradiated samples. From the absorption spectrum, it is found that the damage cross-section of samples irradiated by carbon clusters increases non-linearly with the increase in cluster size. It should be induced by the collective effect and the non-linear effect of cluster ions. Attenuated total reflectance was employed to analyze the change of chemical bonds on the surface of samples. Some new bonds such as –OH are formed. [Copyright &y& Elsevier]

The Uragen giant sandstone-hosted Zn–Pb deposit has a proven reserve of 5.90 Mt metals in the southern ore zone and potentially 10 Mt metals for the whole deposit, and orebodies are strictly confined to the bleached clastic rocks of the Lower Cretaceous red beds. The bleaching has been used to guide lead–zinc exploration; however, its nature and origin, as well as the relationship with Zn–Pb mineralization, remains unclear, although it is closely related to regional oil–gas infillings. Detailed field investigation and petrographic observation, TESCAN-integrated mineral analyzer (TIMA), and X-ray fluorescence (μ-XRF) analysis of the red and bleached sandstone at the same sedimentary layer demonstrate that the bleaching is mainly caused by the reductive dissolution of hematite pigment, which probably resulted from the interaction with H2S formed by in situ sulfate reduction during hydrocarbon migration. The calcite cements in the bleached sandstones show δ13C and δ18O values of −5.36~−5.94‰ and 20.94~27.91‰, respectively, and these samples fall close to the evolution line of decarboxylation of organic matter in δ13C-δ18O diagram, also suggesting a genetic relationship between the bleaching and hydrocarbon-bearing fluids. Petrol–mineral composition changes and sulfide characteristics of red, bleached, mineralized zones, as well as pyrite locally replaced by coarse-grained galena in the mineralized zone, imply that the bleaching may occurred before Zn–Pb mineralization. Mass balance calculation and μ-XRF analysis indicate that large amounts of Fe and minor Zn were extracted from red beds with little or no sulfates; however, the red beds with abundant sulfates may be a sink for leached ore metals during the bleaching process. We therefore propose that the former accumulations of iron sulfides and reduced sulfur in the bleached zones may provide an ideal chemical trap for later Zn–Pb mineralization, and the bleached zones with high ∑S contents are the favorable prospective targets of the Uragen-style sandstone-hosted Zn–Pb deposits. [ABSTRACT FROM AUTHOR]

• The Aqishan deposit is a distal skarn Zn-Pb mineralization system. • Re-Os dating of pyrite and zircon U-Pb dating of granodiorite porphyry are consistent at ca. 306 Ma. • Ore-forming materials are mainly derived from magmatic source, some sulfur is sourced from country rocks. • There is significant potential for skarn Zn-Pb mineralization associated with Late Paleozoic magmatism in the Eastern Tianshan. The Aqishan deposit, located in the Eastern Tianshan, Xinjiang, China, is a newly discovered large-scale Zn-Pb deposit with a proven reserve of 1.94 Mt Pb and Zn metal at an average grade of 1.05%. The Zn-Pb orebodies are tabular and lentoid in shape, developed within skarnized carbonates and calcareous volcanoclastic rocks of the Yamansu Formation. The skarn mineral assemblages are characterized by abundant garnet, epidote, chlorite, actinolite, calcite and quartz, with minor amounts of pyroxene. Metallic minerals, comprising sphalerite, galena, chalcopyrite, pyrite, pyrrhotite and arsenopyrite, mainly occur as disseminations and irregular patches within the skarn. Re-Os dating of five syn-ore stage pyrite samples yielded an isochron age of 301 ± 13 Ma, which is in agreement with the 306 ± 2.8 Ma age obtained from the granodiorite porphyry occurring at southeast part of the Aqishan Zn-Pb deposit. The ε Hf (t) values of zircon from the granodiorite porphyry vary from + 9.62 to + 14.69, suggesting a juvenile crust source. The δ 34 S V-CDT values of 22 sulfide samples range from −11.6‰ to −2.76‰, with an average of −5.08‰. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 9 sulfide samples range from 18.102 to 18.336, 15.539 to 15.655, and 37.929 to 38.479, respectively, which are similar to the Carboniferous grantoids of the Aqishan area and partly overlap with the volcanoclastic rocks of the Yamansu Formation. Based on these data, we propose that the Aqishan deposit formed from magmatic-hydrothermal fluids that emanated from the granodiorite porphyry. Much of the metals were derived from the magmatic intrusions with minor contributions from the volcanoclastic rocks, whereas the sulfur may have been mainly extracted from the country rocks with slight contributions from a magmatic source. The close genetic relationships between the Carboniferous magmatism and skarn type Zn-Pb mineralization in the Aqishan area as well as other deposits in the region suggests a great potential of finding more analogous deposits in the Eastern Tianshan, where carbonates or calcareous volcanoclastic rocks and plutons that related to the subduction of the Northern Tianshan Oceanic slab beneath the Yili-Central Tianshan Terrane during Late Paleozoic are well-developed. [ABSTRACT FROM AUTHOR]

Textile-reinforced concrete (TRC), a new composite material commonly used for repair and reinforcement of engineered structural surfaces, is easily affected by high temperatures in the event of fire. Therefore, when investigating the fire resistance of this material, it is important to evaluate and improve its high-temperature mechanical properties. In this study, ordinary portland cement and high-alumina cement TRC were prepared, with various proportions of metakaolin used to replace the cement, to investigate the changes in the mechanical properties of TRC and its deterioration mechanism. The experimental results showed that metakaolin improved the mechanical properties of ordinary portland cement sheets at low temperatures, with optimum substitutions of 15% and 20% in ordinary portland cement and high-alumina cement, respectively. Moreover, basalt fiber woven mesh was shown to significantly improve the ductility and flexural properties of TRC sheets, and high-alumina cement-based TRC exhibited superior bending properties at 800°C with 216.4% ultimate improvement over ordinary portland cement. The results of microscopic analysis and X-ray diffraction (XRD) experiments revealed that the decrease in the high-temperature mechanical performance of the TRC sheets was caused by a combination of high-temperature damage to the matrix concrete, deterioration or oxidative deterioration of the fibers themselves, and damage to the bonding surface of both the concrete and the fibers. At high temperatures, the microstructure of the high-alumina cement TRC was tighter and bonded more effectively to the basalt fiber grid. [ABSTRACT FROM AUTHOR]

The formation of many hydrothermal gold deposits is closely related to iron-rich rocks. The host rocks of the Madiyi Formation of the Mid- to Late Neoproterozoic Banxi Group for the Woxi Au (-Sb-W) deposit, which is located in western Hunan Province of the western Jiangnan Orogen, South China, is rich in hematite, which provides a good example for studying the relationship between the formation of gold deposit and iron-rich rocks. Field investigation and petrographic observation on the unaltered, weakly altered and strongly altered rocks demonstrate that the bleaching is caused by a combination of carbonatization, sulfidation and sericitization. Mass balance calculation suggests that, during decolourization there is no change in TFe2O3, while FeO is gained and Fe2O3 is lost. Geochemical modeling found that Au was mainly present as AuHS(aq) and Au(HS)2−, and that the water-rock interactions decreased the sulfur fugacity which destroyed the stability of such aqueous complexes. Combined with the locally occurred native gold in quartz veins, it is concluded that the major gold precipitation mechanisms are sulfidation and fluid boiling. Based on previous geochronological and geochemical research further gold mineralization is proposed to be generated by deep sourced magmatic or metamorphic fluid migrated upward along the Woxi fault, and the iron-rich Madiyi Formation is the idea chemical trap for gold deposition. The decrease of sulfur contents caused by fluid-rock interactions and fluid boiling are the major mechanisms for gold mineralization. [ABSTRACT FROM AUTHOR]

Nitride perovskite LaWN3 has been predicted to be a promising ferroelectric material with unique properties for diverse applications. However, due to the challenging sample preparation at ambient pressure, the crystal structure of this nitride remains unsolved, which results in many ambiguities in its properties. Here, the authors report a comprehensive study of LaWN3 based on high‐quality samples synthesized by a high‐pressure method, leading to a definitive resolution of its crystal structure involving nitrogen deficiency. Combined with theoretical calculations, these results show that LaWN3 adopts an orthorhombic Pna21 structure with a polar symmetry, possessing a unique atomic polarization along the c‐axis. The associated atomic polar distortions in LaWN3 are driven by covalent hybridization of W: 5d and N: 2p orbitals, opening a direct bandgap that explains its semiconducting behaviors. The structural stability and electronic properties of this nitride are also revealed to be closely associated with its nitrogen deficiency. The success in unraveling the structural and electronic ambiguities of LaWN3 would provide important insights into the structures and properties of the family of nitride perovskites. [ABSTRACT FROM AUTHOR]

The remobilization, migration, precipitation, and enrichment of ore-forming elements are closely related to structures. Therefore, detailed regional and ore-field structural analyses are critical for determining the genesis of a mineral deposit. The Jiangnan Orogenic Belt (JOB) is an important gold polymetallic metallogenic belt in South China, which is characterized by multiple periods of gold mineralization in the Paleozoic and Mesozoic. However, the genesis of these gold polymetallic deposits is still not well understood due to a lack of systematic research on the regional geology, ore-controlling structures and metallogenic mechanism. In this study, a detailed structural survey at the surface and in the subsurface tunnels was conducted on the Woxi Au-Sb-W deposit, the genesis of which is relatively controversial among the gold polymetallic deposits in the JOB due to poor structural constraints. In addition, a wolframite U-Pb dating was carried out to further constrain the relationship between structures and mineralization. Based on the results of these studies, together with those from previous studies, it is proposed that the Woxi deposit and surrounding areas likely underwent six periods of regional deformation, which are constrained in time and geodynamic setting. Furthermore, we present a systematic discussion on the roles of ore-controlling structures in the transportation, distribution, and deposition of ore-forming elements and localization of orebodies. According to the wolframite dating results, structural analyses, and previous data, we propose that the Woxi Au-Sb-W deposit was formed in two stages during the Yanshanian: a W (wolframite)-Au mineralization stage at ca. 140 Ma and an Au-Sb-W (scheelite) mineralization stage at <130 Ma. These mineralizing events are interpreted to have a tight relationship with tectonic reactivation, and the ore-forming fluids were derived from deep sources, including those of magmatic or metamorphic origins. The Woxi deposit can therefore be classified as an "intracontinental reactivation-type", and the mineralization is related to lithospheric extension caused by plate retreat, retention, and delamination following the cessation of westward subduction of the Paleo-Pacific Plate beneath the East Asian continent. [ABSTRACT FROM AUTHOR]

Metal halide perovskites have gained huge research interest within few decades due to their optoelectronic applications. Recently, inorganic metal halide perovskites CsPbX3 (X = Cl, Br, I) has shown the improved stability with promising optical and electrical properties. We report the enhancement of PL intensity and the extension of carrier lifetime from strained CsPbBr3 microwires in air environment. PL intensity is enhanced more than fivefold for all the studied microwires under strain than the original. Maximum enhancement in PL intensity of more than 25-fold has been observed from a wire with lateral width of 630 nm. Based on the experiment and simulation results, we conclude that tensile strain can improve the oxygen adsorption by the defects on the surface of CsPbBr3 microwires, which will suppress the non-radiative transitions and enhance the light emission efficiency. These findings demonstrate that the strain engineering is an effective way to improve the performance of CsPbBr3 microstructures for optoelectronic applications. [ABSTRACT FROM AUTHOR]

OASIS, an irrigation diagnosis model, is applied to the Zhanghe Irrigation System in central China to investigate the contribution of smaller local storages (in “melons on the vine” configuration) as compared with the main reservoir. Results show that local storages are more important in normal-to-wet years, while the main reservoir is critical in dry years, which implies a strong policy correction relevant to many parts of the world. Balanced investment in various storage infrastructures with associated management practices is a cost-effective strategy for irrigation development. [ABSTRACT FROM AUTHOR]

Abstract: Super-hydrophobic PTFE surfaces were obtained by irradiation of 200keV Xe+ ion with the fluence of ions/cm2. The contact angle of water on such surface is as large as . SEM and XPS were used to investigate how the topological and chemical changes affect the wettability of the irradiated surface. Needle like structures at nanometer scale caused by irradiation are considered to be the reason of the super-hydrophobicity. The formation of oxygen containing group and defluorination effect on the treated surface are inferred to have negative contribution to the hydrophobic optimization of PTFE surface. [Copyright &y& Elsevier]

Abstract: Carbon cluster ions (n =1–5) and Cl+, Ti+, Ni+ ions were used to bombard polycarbonate (PC) films. By comparing the electronic energy loss and the number of chromophores at a fixed wavelength, we obtained the electronic energy loss S e of carbon cluster ions in PC. [Copyright &y& Elsevier]

On‐chip coherent light source has always been fascinating and intriguing due to its various potential applications. In the past decades, there has been some progress in the development of chip coherent light (e.g., nanolaser, Bose‐Einstein condensation and nonlinear optical effects). However, these methods strictly depend on materials and extreme experimental conditions, and are usually not tunable. Here, a hybrid structure is designed which combines a chirped surface plasmon metasurface with a monolayer transition metal dichalcogenide (TMDC) to achieve a coherent second harmonic generation (SHG) covering the entire visible light spectrum. Using only finite number of metallic grooves, a continuous resonance tuning is obtained. By translating the metasurface in space, a space‐frequency locking SHG is demonstrated. Although the Q factor of the surface plasmon cavity is low, its near‐field enhancements of both fundamental and SH waves are still obvious. Significantly, the broad linewidth of plasmonic cavity leads to a large degree of overlap between adjacent localized modes, that enables the tuning of the output wavelength continuously at room temperature. Meanwhile, the exciton resonance also plays an important role. This monolithic tunable device demonstrates the potentials of 2D material‐plasmon hybrid metasurface and to construct an efficient broadband tunable on‐chip coherent light source. [ABSTRACT FROM AUTHOR]

On‐chip coherent light source has always been fascinating and intriguing due to its various potential applications. In the past decades, there has been some progress in the development of chip coherent light (e.g., nanolaser, Bose‐Einstein condensation and nonlinear optical effects). However, these methods strictly depend on materials and extreme experimental conditions, and are usually not tunable. Here, a hybrid structure is designed which combines a chirped surface plasmon metasurface with a monolayer transition metal dichalcogenide (TMDC) to achieve a coherent second harmonic generation (SHG) covering the entire visible light spectrum. Using only finite number of metallic grooves, a continuous resonance tuning is obtained. By translating the metasurface in space, a space‐frequency locking SHG is demonstrated. Although the Q factor of the surface plasmon cavity is low, its near‐field enhancements of both fundamental and SH waves are still obvious. Significantly, the broad linewidth of plasmonic cavity leads to a large degree of overlap between adjacent localized modes, that enables the tuning of the output wavelength continuously at room temperature. Meanwhile, the exciton resonance also plays an important role. This monolithic tunable device demonstrates the potentials of 2D material‐plasmon hybrid metasurface and to construct an efficient broadband tunable on‐chip coherent light source. [ABSTRACT FROM AUTHOR]

Abstract Copper and Fe are redox-sensitive metals, and their isotopic compositions may potentially record changes of oxidation conditions in high-temperature magmatic Ni–Cu mineralization systems. High-precision Cu and Fe isotope data for sulfides (chalcopyrite) and whole-rock samples of the Tulaergen magmatic Ni–Cu system (NW China) were analyzed to evaluate redox-induced fractionation during segregation of sulfide melt from silicate melt and internal fractionation within segregated sulfide melt. Sulfide mineralization includes disseminated and massive types, with massive sulfides being further divided into Cu- and Fe-rich ores. Numerical modeling using mass-balance and Rayleigh equations indicate that disseminated sulfide mineralization was generated from a common parental magma, and massive sulfides were formed by monosulfide solid-solution (MSS)–residual sulfide liquid fractionation. During segregation of sulfide melt from silicate melt, crystallization of olivine and pyroxenes with sulfide segregation, in an Fe2+-dominated phase, led to the incorporation of lighter Fe isotopes in these minerals. The residual silicate melt became progressively more oxidized, with δ56Fe whole-rock values increasing as melts evolved. The disseminated chalcopyrite formed in early stages has lighter Cu and heavier Fe isotopic compositions than the disseminated sulfides formed in later stages due to charge-balance effects. Minor accumulated Ni–Cu sulfide melt was fractionated into an Fe-rich MSS cumulate and a Cu-rich sulfide liquid. MSS crystallization caused the oxygen fugacity of the evolved sulfide liquid to increase, which was accompanied by increasing δ65Cu and decreasing δ56Fe values in chalcopyrite. Iron isotopic compositions of the whole system were shifted towards heavier values from MSS cumulate to the evolved sulfide melt. Numerical modeling using the Rayleigh equation indicates that the fractionation factors α65Cu residual sulfide melt–MSS and α56Fe residual sulfide melt–MSS are ∼1.0011 and ∼1.0005, respectively, during internal fractionation within segregated sulfide melt. This study demonstrates that redox reactions play a key role in Cu and Fe isotope fractionation in high-temperature magmatic Ni–Cu mineralization systems. Furthermore, Cu and Fe isotopes can be used to trace concealed orebodies. Elevated δ65Cu and δ56Fe whole-rock values may indicate Cu-rich mineralization potential, while light Cu and Fe isotopic compositions imply favorable hosts for disseminated and Fe-rich orebodies in mafic–ultramafic intrusions. [ABSTRACT FROM AUTHOR]

Highlights • Four types of wind speed data were used in reduced set Penman-Monteith model for ETo forecasting. • Three modified reduced set Penman-Monteith models were proposed. • ETo forecast performance can be significantly improved through considering wind speed. • Wind speed data type was recommended for each station in different climate zone. Abstract Farm irrigation management and real-time irrigation decisions are based on a series of parameters including irrigation water demand predictions which estimated by the short-term daily reference evapotranspiration (ETo). Based on the temperature data, a simplest empirical model called the temperature-based method, was developed to forecast near-future ETo. Although temperature is one of the most influential weather variables in ETo forecasting, wind velocity also has non-ignorable impact on the forecast performance of ETo. Therefore, we employed the Reduced-set Penman-Monteith (RPM) model for short-term ETo forecasting using temperature data derived from public weather forecasts and wind speed data. Four different types of wind speed data were adopted as model inputs, including wind speed assumed as a default value, i.e., u 2 = 2.0 m s−1 (W1), forecasted wind speed (W2), long-term daily average wind speed (W3) and annual average wind speed (W4). Based on the above-mentioned wind speed inputs, we presented four types of RPM models (RC, RF, RD and RM models respectively corresponding to W1, W2, W3 and W4) to forecast daily ETo for lead times up to 7 days for eight weather stations in China. The results confirmed that the highest precision wind speed input was W3, followed by W4, W1 and W2, and the most accurate ETo forecasts of four RPM models was provided by RC, followed with RD, RM and RF. By comparing with one of the most common used temperature-based models, the Hargreaves-Samani (HS), it was found that the performance of RPM approaches were better than that of HS model for arid and sub-arid regions whereas opposite results were found in sub-tropical area, suggesting inclusion of wind speed parameter makes positive impact on ETo forecast for arid and semi-arid regions. Further, it was found that the greatest type of RPM model, the RC model, was superior to HS method for most climate regions, including arid, humid, sub-arid and sub-humid areas, thus, the W1 wind speed type could be highly recommended for ETo forecasting for most climate regions. [ABSTRACT FROM AUTHOR]

Sulfoxides and cyclic ureas are photochemically deoxygenating solvents in which the oxidative stress could be released and efficient triplet–triplet annihilation photon upconversion (TTA-UC) can operate in air. Such solvents can be practically screened out by harnessing the property of photo-activated phosphorescence. [ABSTRACT FROM AUTHOR]

Two new bithiophene imide (BTI)-based n-type polymers were synthesized. f-BTI2-FT based on a fused BTI dimer showed a smaller band gap, a lower LUMO, and higher crystallinity than s-BTI2-FT containing a BTI dimer connected through a single bond. s-BTI2-FT exhibited a remarkable electron mobility of 0.82 cm2 V−1 s−1, and f-BTI2-FT showed a further improved mobility of 1.13 cm2 V−1 s−1 in transistors. When blended with the polymer donor PTB7-Th, f-BTI2-FT-based all-polymer solar cells (all-PSCs) attained a PCE of 6.85 %, the highest value for an all-PSC not based on naphthalene (or perylene) diimide polymer acceptors. However, s-BTI2-FT all-PSCs showed nearly no photovoltaic effect. The results demonstrate that f-BTI2-FT is one of most promising n-type polymers and that ring fusion offers an effective approach for designing polymers with improved electrical properties. [ABSTRACT FROM AUTHOR]

Two new bithiophene imide (BTI)-based n-type polymers were synthesized. f-BTI2-FT based on a fused BTI dimer showed a smaller band gap, a lower LUMO, and higher crystallinity than s-BTI2-FT containing a BTI dimer connected through a single bond. s-BTI2-FT exhibited a remarkable electron mobility of 0.82 cm2 V−1 s−1, and f-BTI2-FT showed a further improved mobility of 1.13 cm2 V−1 s−1 in transistors. When blended with the polymer donor PTB7-Th, f-BTI2-FT-based all-polymer solar cells (all-PSCs) attained a PCE of 6.85 %, the highest value for an all-PSC not based on naphthalene (or perylene) diimide polymer acceptors. However, s-BTI2-FT all-PSCs showed nearly no photovoltaic effect. The results demonstrate that f-BTI2-FT is one of most promising n-type polymers and that ring fusion offers an effective approach for designing polymers with improved electrical properties. [ABSTRACT FROM AUTHOR]

Unreacted lead iodide is commonly believed to be beneficial to the efficiency of methylammonium lead iodide perovskite based solar cells, since it has been proposed to passivate the defects in perovskite grain boundaries. However, it is shown here that the presence of unreacted PbI2 results in an intrinsic instability of the film under illumination, leading to the film degradation under inert atmosphere and faster degradation upon exposure to illumination and humidity. The perovskite films without lead iodide have improved stability, but lower efficiency due to inferior film morphology (smaller grain size, the presence of pinholes). Optimization of the deposition process resulted in PbI2 -free perovskite films giving comparable efficiency to those with excess PbI2 (14.2 ± 1.3% compared to 15.1 ± 0.9%) Thus, optimization of the deposition process for PbI2 -free films leads to dense, pinhole-free, large grain size perovskite films which result in cells with high efficiency without detrimental effects on the film photostability caused by excess PbI2 . However, it should be noted that for encapsulated devices illuminated through the substrate (fluorine-doped tin oxide glass, TiO2 film), film photostability is not a key factor in the device degradation. [ABSTRACT FROM AUTHOR]

Abstract: Multicharged ions (, , , ) at constant speed (Bohr velocity) were used to irradiate PC (polycarbonate) foils which were subsequently chemically etched. Because of the low ion dose of , pores on the surface were discrete. The diameters of the pores were measured by means of scanning electron microscopy (SEM). From the linear dependence of the pore diameter on the etching time, the transversal etching rate can be obtained. It was found that the transversal etching rate decreased with ion charge. These results can mainly be explained by the variation of the charge exchange process for ions with a different charge state. [Copyright &y& Elsevier]

• The Zn-Pb mineralization age of the Caixiashan deposit is 337.2 ± 5.7 Ma. • Reduced sulfur of multiple sources may involve a possible input of magmatic sulfur. • Ore metals are mainly sourced from wall rocks and Carboniferous felsic intrusions. • It is a distal high-temperature carbonate replacement deposit related to intrusions. The Caixiashan Zn-Pb deposit is the largest carbonate-hosted Zn-Pb deposit in Eastern Tianshan, NW China. The deposit comprises the No. Ⅰ, Ⅱ, III and IV ore zones with a proven reserve of 131 Mt ore at 3.95% Pb + Zn. The orebodies generally occur as irregular lenses and pods in altered carbonate rocks of the Mesoproterozoic Kawabulake Group near faults. The mineralization is characterized by massive, disseminated and vein/veinlet sulfides including pyrite, pyrrhotite, sphalerite and galena with minor arsenopyrite and chalcopyrite, as well as sulfosalt minerals of Ag, As, Sb and Pb. The mineralization is associated with tremolite, chlorite, silica and carbonate alterations. Rb-Sr isotopic dating of sphalerite and pyrrhotite yields an isochron age of 337.2 ± 5.7 Ma, which is interpreted as the mineralization age. Zircon U-Pb dating reveals that stocks of diorite, quartz diorite, K-feldspar granite and monzonitic granite that occur in the deposit area were emplaced at 348.2 ± 3.7 Ma, 351.9 ± 3.5 Ma, 333.6 ± 3.6 Ma and 330.0 ± 3.6 Ma, respectively. These age data suggest that the mineralization is coeval with Carboniferous granitic magmatism. The δ34S V-CDT values of sulfides (excluding the syn-sedimentary pyrite) range from −2.42‰ to 19.1‰, suggesting that the reduced sulfur was mainly derived from thermal sulfate reduction (TSR) of seawater-derived sulfates in the marine sedimentary basement rocks and minor contribution by replacement of syn-sedimentary pyrite, as well as a possible input of magmatic sulfur. The Pb isotopic compositions of sulfides, with 206Pb/204Pb ranging from 17.074 to 17.361, 207Pb/204Pb from 15.422 to 15.614, and 208Pb/204Pb from 36.685 to 37.303, partly overlap with those of basement rocks of the Mesoproterozoic Kawabulake Group and the Carboniferous intrusions, suggesting that the ore metals were derived from both the basement and Carboniferous magmatism. On the basis of the spatio-temporal relations between hydrothermal alterations/mineralization and Carboniferous magmatism, we conclude that the Caixiashan Zn-Pb deposit is a high-temperature carbonate replacement deposit related to concealed granitic intrusions, which were formed in an arc environment related to the subduction of the South Tianshan Ocean plate beneath the Central Tianshan massif during the Carboniferous time. The results of this study indicate that there is a great potential of finding more large-scale Zn-Pb deposits similar to Caixiashan in Eastern Tianshan. [ABSTRACT FROM AUTHOR]

Abstract: The size of alpha-particle tracks on electrochemically etched ultraviolet-irradiated polyallyldiglycol carbonate (PADC) films were studied. PADC films were first irradiated with 3MeV alpha particles and then pre-etched chemically using aqueous 6.25N NaOH solution for 2h. The films were then exposed to incoherent broad-band ultraviolet (UV) radiation provided by a mercury lamp for different durations up to 2h. The films were then electrochemically etched in a 6.25N NaOH solution, with an a.c. voltage of about 1200 and a frequency of 5kHz, for 2h at room temperature. The mean sizes of the tracks (or trees) were measured and were found to increase for short UV exposures and decrease for prolonged UV exposures. The results can be explained by the dominance of chain scission at the beginning of UV exposure and the dominance of cross linking for prolonged UV exposure. This explanation is further supported by results from X-ray photo-electron spectroscopy (XPS). Here, the C–O–C bonds decrease for short UV exposures, which is explained by scission of the polymer chains, and increase again for prolonged UV exposure, which indicates cross linking. From nano-indentation measurements, the hardness and the reduced modulus increase monotonically with the UV irradiation. Apparently, these quantities only characterize the amount of cross linking, and do not give information on the initial scission process. [Copyright &y& Elsevier]