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In recent years, very significant progress has been made in single-molecule magnets (SMMs), and one of the major milestone works is the hysteresis blocking temperature beyond the boiling point of...

The dimetallic fulvalene-bridged dysprosium complex [{Dy(Cp*)(μ-BH4)}2(Fvtttt)] (1, Cp* = C5Me5) is converted into the trimetallic borohydride-bridged species [{Dy(Cp*)(Fvtttt)}2Dy(μ-BH4)3] (2). In turn, 2 is reacted with a silylium electrophile to give [{Dy(Cp*)(μ-BH4)(Fvtttt)}2Dy][B(C6F5)4] ([3][B(C6F5)3]), the first trimetallic dysprosocenium cation. Compound [3][B(C6F5)3] can also be formed directly from 1 by adding two equivalents of the electrophile. A three-fold enhancement in the effective energy barrier from 2 to 3 is observed and interpreted with the aid of ab initio calculations., The first trimetallic dysprosocenium single-molecule magnet is described. This material signposts a polycationic dysprosium metallocene SMM with properties that could surpass those of leading systems.

Magnetic bistability in single-molecule magnets (SMMs) is a potential basis for new types of nanoscale information storage material. The standard model for thermally activated relaxation of the magnetization in SMMs is based on the occurrence of a single Orbach process. Here, we show that incorporating a phosphorus atom into the framework of the dysprosium metallocene [(CpiPr5)Dy(CpPEt4)]+[B(C6F5)4]− (CpiPr5 is penta-isopropylcyclopentadienyl, CpPEt4 is tetraethylphospholyl) leads to the occurrence of two distinct high-temperature Orbach processes, with energy barriers of 1410(10) and 747(7) cm–1, respectively. These barriers provide experimental evidence for two different spin–phonon coupling regimes, which we explain with the aid of ab initio calculations. The strong and highly axial crystal field in this SMM also allows magnetic hysteresis to be observed up to 70 K, using a scan rate of 25 Oe s–1. In characterizing this SMM, we show that a conventional Debye model and consideration of rotational contributions to the spin–phonon interaction are insufficient to explain the observed phenomena.

Carbonate concretions within tuffaceous mudstones in the Upper Cretaceous Cariblanco Formation of south-central Puerto Rico that contain solid and liquid hydrocarbons were affected by: 1) Three distinct events of vein/fracture formation accompanied or followed by sediment infilling; 2) pyrite formation throughout the concretion matrix, in foraminiferal chambers, and sediment vein fills; 3) four events of larger vein and fracture formation infilled by distinct calcite cements that postdate sediment infilled veins; 4) a late quartz void filling cement; and 5) formation of calcite-filled veinlets that crosscut all components. Petrographic and isotopic data suggest early concretion formation and septarian vein fills, close to the sediment-water interface, prior to any significant dewatering of infilling sediments. The δ13C values of the matrix and sediment infills (-15 to -30‰ PDB), their brightly luminescent character, and the sequestering of Fe into pyrite indicate formation in a sulfate-reducing environment with influx of diffusing methane. Fluid inclusion data, isotopic composition of carbonate cements (13C enrichments from − 18 to -8‰ and 18O depletion from − 4 to -12‰), and organic matter maturation suggest maximum burial temperatures of 150 to 200°C. Calcite cements and microspars were formed by the circulation of progressively warmer fluids, with warming induced by the gradual emplacement of the nearby Los Panes intrusion. The intrusion probably caused intense normal faulting, induced extensive warm fluid circulation, and resulted in a high geothermal gradient responsible for early hydrocarbon generation.

Innovative synthetic coordination and, increasingly, organometallic chemistry are at the heart of advances in molecular magnetism. Smart ligand design is essential for implementing controlled modifications to the electronic structure and magnetic properties of transition metal and f-element compounds, and many important recent developments use nontraditional ligands based on low-coordinate main group elements to drive the field forward. This review charts progress in molecular magnetism from the perspective of ligands in which the donor atoms range from low-coordinate 2p elements-particularly carbon but also boron and nitrogen-to the heavier p-block elements such as phosphorus, arsenic, antimony, and even bismuth. Emphasis is placed on the role played by novel main group ligands in addressing magnetic anisotropy of transition metal and f-element compounds, which underpins the development of single-molecule magnets (SMMs), a family of magnetic materials that can retain magnetization in the absence of a magnetic field below a blocking temperature. Nontraditional p-block donor atoms, with their relatively diffuse valence orbitals and more diverse bonding characteristics, also introduce scope for tuning the spin-orbit coupling properties and metal-ligand covalency in molecular magnets, which has implications in areas such as magnetic exchange coupling and spin crossover phenomena. The chemistry encompasses transition metals, lanthanides, and actinides and describes recently discovered molecular magnets that can be regarded, currently, as defining the state of the art. This review identifies that main group chemistry at the interface molecular magnetism is an area with huge potential to deliver new types of molecular magnets with previously unseen properties and applications.

Breaking through the nitrogen ceiling Single-molecule magnets could prove useful in miniaturizing a wide variety of devices. However, their application has been severely hindered by the need to cool them to extremely low temperature using liquid helium. Guo et al. now report a dysprosium compound that manifests magnetic hysteresis at temperatures up to 80 kelvin. The principles applied to tuning the ligands in this complex could point the way toward future architectures with even higher temperature performance. Science , this issue p. 1400

The five new Ni(II) coordination polymers (CPs) {[Ni(bitp)(bpe)0.5(H2O)2]·0.5bpe}n (1), {[Ni(bitp)(bpa)0.5(H2O)2]·0.5bpa}n (2), {[Ni(bitp)(4,4′-bpy)0.5(H2O)]·H2O}n (3), {[Ni1.5(bitp)(Hbitp)(2,2′-bp...

A series of fulvalene-supported dimetallic dysprosium metallocene SMMs provides a roadmap to poly-cationic dysprosocenium single-molecule magnets., The dinucleating fulvalenyl ligand [1,1′,3,3′-(C5tBu2H2)2]2– (Fvtttt) was used to synthesize the dimetallic dysprosocenium cation [{Dy(η5-Cp*)}2(μ-BH4)(η5:η5-Fvtttt)]+ (3) as the salt of [B(C6F5)4]– (Cp* = C5Me5). Compound [3][B(C6F5)4] was obtained using a method in which the double half-sandwich complex [{Dy(BH4)2(THF)}2(Fvtttt)] (1) was reacted with KCp* to give the double metallocene [{Dy(Cp*)(μ-BH4)}2(Fvtttt)] (2), followed by removal of a bridging borohydride ligand upon addition of [(Et3Si)2(μ-H)][B(C6F5)4]. The dimetallic fulvalenyl complexes 1–3 give rise to single-molecule magnet (SMM) behaviour in zero applied field, with the effective energy barriers of 154(15) cm–1, 252(4) cm–1 and 384(18) cm–1, respectively, revealing a significant improvement in performance across the series. The magnetic properties are interpreted with the aid of ab initio calculations, which show substantial increases in the axiality of the crystal field from 1 to 2 to 3 as a consequence of the increasingly dominant role of the Fvtttt and Cp* ligands, with the barrier height and hysteresis properties being attenuated by the equatorial borohydride ligands. The experimental and theoretical results described in this study furnish a blueprint for the design and synthesis of poly-cationic dysprosocenium SMMs with properties that may surpass those of benchmark systems.

Multiturn coils is an effective transmitter for transient electromagnetic method (TEM) used in narrow space and complex terrain at presently. However, its high mutual inductance coupling and long turn-off time affect the quality of later data processing and interpretation. Compared with multiturn coils, the new conical source has low mutual inductance and short turn-off time. Based on the superposition principle, we use Hankel transform and numerical filtering method for forward modelling of the conical source field in the layered-media and explore TEM characteristics excited by this source. We apply improved damped least square inversion to integrated transient electromagnetic (TEM) data. We first invert the induced voltage into similar resistivity and apparent depth, and then use the inverted results as input parameters in the initial model and transform the apparent resistivity data into the frequency domain. Then, damped least square inversion is performed in the frequency domain using the initial model. Subsequently, we use automated model building to search for the extremes and inflection points in the resistivity–depth data that are treated as critical layer parameters. The inversion of theoretical and observed data suggests that the method modifies the resistivity and depth and yields a model of the underground layers.

ion of a chloride ligand from the dysprosium metallocene [(Cpttt)2DyCl] (1Dy Cpttt=1,2,4‐tri(tert‐butyl)cyclopentadienide) by the triethylsilylium cation produces the first base‐free rare‐earth metallocenium cation [(Cpttt)2Dy]+ (2Dy) as a salt of the non‐coordinating [B(C6F5)4]− anion. Magnetic measurements reveal that [2Dy][B(C6F5)4] is an SMM with a record anisotropy barrier up to 1277 cm−1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low‐lying Kramers doublets correspond to a well‐defined MJ value, with no significant mixing even in the higher doublets. peerReviewed

Small multi-turn coil devices are used with the transient electromagnetic method (TEM) in areas with limited space, particularly in underground environments such as coal mines roadways and engineering tunnels, and for detecting shallow geological targets in environmental and engineering fields. However, the equipment involved has strong mutual inductance coupling, which causes a lengthy turn-offtime and a deep “blind zone”. This study proposes a new transmitter device with a conical-shape source and derives the radius formula of each coil and the mutual inductance coefficient of the cone. According to primary field characteristics, results of the two fields created, calculation of the conical-shaped source in a uniform medium using theoretical analysis, and a comparison of the inductance of the new device with that of the multi-turn coil, show that inductance of the multi-turn coil is nine times greater than that of the conical source with the same equivalent magnetic moment of 926.1 A·m2. This indicates that the new source leads to a much shallower “blind zone.” Furthermore, increasing the bottom radius and turn of the cone creates a larger mutual inductance but increasing the cone height results in a lower mutual inductance. Using the superposition principle, the primary and secondary magnetic fields for a conical source in a homogeneous medium are calculated; results indicate that the magnetic behavior of the cone is the same as that of the multi-turn coils, but the transient responses of the secondary field and the total field are more stronger than those of the multi-turn coils. To study the transient response characteristics using a cone-shaped source in a layered earth, a numerical filtering algorithm is then developed using the fast Hankel transform and the improved cosine transform, again using the superposition principle. During development, an average apparent resistivity inverted from the induced electromotive force using each coil is defined to represent the comprehensive resistivity of the conical source. To verify the forward calculation method, the transient responses of H type models and KH type models are calculated, and data are inverted using a “smoke ring” inversion. The results of inversion have good agreement with original models and show that the forward calculation method is effective. The results of this study provide an option for solving the problem of a deep “blind zone” and also provide a theoretical indicator for further research.

To seek novel dysprosium based single-molecule magnets, a dinuclear dysprosium complex, namely [Dy2(L)2(DBM)2(DMF)2]·2DMF (1) was successfully obtained by employing tridentate Schiff base ligand (where H2L = 2-hydroxy-N′’-(2-hydroxy-3-methoxybenzylidene) benzohydrazide), HDBM = dibenzoylmethane, DMF = dimethylformamide). Single-crystal X-ray structural analysis reveals that the key feature of 1 is neutral dinuclear complex, in which two Dy(III) ions with eight-coordinated environment are bridged by two phenoxido oxygen atoms from two Schiff base ligands. Interestingly, complex 1 could be regarded as the structurally related derivatives to our previous reported complex of [Dy2(L)2(DBM)2(DMF)2] (1a) but adding two guest DMF solvents. More importantly, the energy barrier to magnetic relaxation of 1 is slightly higher, with a value of 33 K, when compared to the corresponding complex 1a of 24 K, which provides a good example towards regulating magnetization dynamics in dinuclear dysprosium (III) single-molecule magnets by guest solvent molecules.

Reduction of the uranium(III) metallocene [(eta(5)-(C5Pr5)-Pr-i)(2)UI] (1) with potassium graphite produces the "second-generation" uranocene [(eta(5)-(C5Pr5)-Pr-i)(2)U] (2), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground-state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f(3) 6d(1). Appreciable covalent contributions to the metal-ligand bonds were determined from a computational study of 2, including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s-6dz2 mixing. peerReviewed

ion of iodide from [(η5 -C5 i Pr5 )2 UI] (1) produced the cationic uranium(III) metallocene [(η5 -C5 i Pr5 )2 U]+ (2) as a salt of [B(C6 F5 )4 ]- . The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82° at uranium. Analysis of the bonding in 2 showed that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, thus leading to non-negligible covalent contributions to the bonding. Investigation of the dynamic magnetic properties of 2 revealed that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation by a Raman process.

We report a high-resolution three-dimensional (3D) Magnetotelluric (MT) study to define the mineralizing system of the Xiangshan (XS) volcanic Basin, which hosts the largest volcanic-related uranium deposits in China. MT data from 81 stations were collected and inverted, using a 3D Truncated Newton (TRN) inversion algorithm. The generated electrical resistivity model reveals a high resistivity layer in the shallow, followed by a conductivity layer, and they were formed respectively by the Cretaceous Ehuling Formation and Daguding Formation. Under these Cretaceous formations, a series of high resistivity features delineate the Precambrian metamorphic basement. The contact zone between the high resistivity and conductivity layer corresponds to the inter-formational surface in the Cretaceous volcanic cover, whereas the contact zone between the volcanic cover and metamorphic basement represents the unconformity surface which was supported by gravity data. The identified faults in the 3D resistivity model coincide with the NE- and NS-trending faults observed on the surface. These faults are the crucial ore-controlling structures with high permeability allowing the ore-forming fluids to migrate upwards. We reveal a possible genetic model for the uranium mineralization in the XS volcanic Basin. The mixture of the descending meteoric water and ascending magmatic fluids along the deep faults formed the ore-forming fluids. The precipitation and enrichment of uranium were prone to occur in the ring faults, interfaces, unconformity surfaces and those geologic contacts intersecting with faults, where the physical and chemical properties of the ore-forming fluids were changed. Given that the mafic magmatism generally was coeval with the uranium mineralization, the deep-seated magmatism is supposed to be the force that drove the fluids upwards and governed the circulative convection of ore-forming fluids in the XS volcanic Basin.

Two new three-dimensional isostructural lanthanide metal–organic frameworks (Ln(III)-MOFs), [LnL(H2O)3]·3H2O·0.75DMF (1-Ln; Ln = Dy(III) and Eu(III) ions, H3L = biphenyl-3′-nitro-3,4′,5-tricarboxylic acid, DMF = N,N′-dimethylformamide), were synthesized and characterized. The appearance of temperature-dependent out-of-phase (χ″M) signal reveals that complex 1-Dy displays slow magnetic relaxation behavior with the energy barrier (ΔUeff) of 57 K and a pre-exponential factor (τ0) of 3.89 × 10–8 s at 1200 Oe direct current field. The luminescence explorations demonstrated that 1-Eu exhibits high quenching efficiency and low detection limit for sensing nitrobenzene and Cr2O72–. Meanwhile, the fluorescence intensity of the quenched 1-Eu samples will be resumed after washing with DMF or water, indicating that 1-Eu may be used as a highly selective and recyclable luminescence sensing material for sensing nitrobenzene and Cr2O72– anion.

Two 3D isostructural metal-organic frameworks with 1D ferrimagnetic chains, formulated as [M3(L)(μ3-OH)2(H2O)4] [H4L = (1,1':4',1″-terphenyl)-2',3,3″,5'-tetracarboxylic acid, where M = Mn for 1 and Co for 2], have been successfully synthesized by employing different center metal ions and a multicarboxylate ligand under identical reaction conditions in this work. The single-crystal X-ray diffraction data of 1 and 2 reveal that the complexes are two 3D isostructural frameworks based on 1D [M3(OH)2]n chains composed of triangular subunits as rod-shaped secondary building units, which are classified as binodal 4,6-connected fry nets with the point symbol (5(10)·6(3)·7(8))(5(4)·6(2)). The magnetic properties revealed that complexes 1 and 2 exhibit ferrimagnetic behavior. Also, the alternating-current susceptibility of 2 displays slow magnetic relaxation, showing interesting magnetic behavior of a single-chain magnet with an effective energy barrier of 32 K.

The Gan-Hang Belt in Southeast China is characterized by several igneous and siliciclastic basins associated with crustal extension during Late Mesozoic. The sedimentary evolution of the red basins is still poorly understood. In this study, sedimentary facies analysis and pebble counting were performed on outcrop sections of the Late Cretaceous Guifeng Group inthe Yongfeng-Chongren Basin in central Jiangxi Province. Thirty-five conglomerate outcrops were chosen to measure pebble lithology, size, roundness, weathering degree and preferred orientation. Results show that gravels are mostly fine to coarse pebbles and comprise dominantly quartzites, metamorphic rocks, granitoids and sandstones. Rose diagrams based on imbricated pebbles indicate variable paleocurrent directions. Combining with typical sedimentary structures and vertical successions, we suggest that the Guifeng Group were deposited in alluvial fan, river and playa lake depositional systems. The proposed depositional model indicates that the Hekou Formation represents the start-up stage of the faulted basin, accompanied by sedimentation in alluvial fan and braided river environments. Then this basin turned into a stable expansion stage during the deposition of the Tangbian Formation. Except for minor coarse sediments at the basin margin, the other area is covered with fine-grained sediments of lake and river environments. The Lianhe Formation, however, is once again featured by conglomerates, suggesting a probable tectonic event. Therefore, the study region possibly suffered two tectonic events represented by the conglomerates of the Hekou and Lianhe formations in the context of the crustal extension in Southeast China.

The Xiangshan Basin hosts the largest volcanic-related uranium deposits in China. Despite several decades of extensive research, the key factors controlling volcanic-related uranium mineralization in the Xiangshan Basin remain unclear. In this paper, we present a review of previous studies and highlight the critical features that are closely related to the uranium mineralization in the Xiangshan Basin, with focus on the geological feathers, host rocks, ore-controlling structures, alterations, mineralization, fluid inclusions, and geochronological and geochemical data of the uranium deposits. Based on these reviews, a comprehensive genetic model is proposed to better explain the uranium mineralization mechanism. The uranium mineralization at Xiangshan is mainly hosted in felsic volcanic and sub-volcanic rocks, and spatially close to the Cretaceous–Tertiary redbeds. The mineralization mainly took place from ~125 to ~70 Ma, which is much younger than the ages of host volcanic rocks (~135 Ma) and broadly contemporaneous with the development of the redbed basins and mafic magmatism. The uranium mineralization occurs mainly as veins controlled by brittle structures such as fractures, faults and volcanic structures. The extensional reactivation of preexisting structures and development of new fractures created permeability for the circulation of the ore-forming fluids and provided spaces for uranium precipitation. The ore-forming fluids are characterized by basinal brines with a meteoric water origin, possibly mixed with mantle-derived fluids. The uranium was mostly contributed by the host volcanic and sub-volcanic rocks. The precipitation of uranium is related to redox reactions with reductants such as Fe2+, H2S and CH4 as well as other mechanisms related to change of physical and chemical conditions due to fluid boiling. The comprehensive review of the geological characteristics related to uranium mineralization reveals that the key factors controlling the uranium mineralization in the Xiangshan volcanic basin are related to the coupling of shallow (development of oxidizing fluids in the redbeds and brittle structures in the volcanic rocks) and deep-seated (thermal activities related to mafic magmatism) geological processes. It is proposed that meteoric water infiltrated into the high-permeability redbed basins, and evolved to oxidizing basinal fluids. The oxidizing fluids further circulated into the volcanic basin along brittle structures and extracted uranium from the volcanic rocks. The heat provided by mafic magmatic activities accompanying upward-flowing deep-source hot fluids promoted the uranium extraction and transportation.

The potassium cyclobutadienyl [K2{η4‐C4(SiMe3)4}] (1) reacts with MCl3(THF)3.5 (M=Y, Dy) to give the first rare‐earth cyclobutadienyl complexes, that is, the complex anions [M{η4‐C4(SiMe3)4}{η4‐C4(SiMe3)3‐κ‐(CH2SiMe2}]2−, (2M), as their dipotassium salts. The tuck‐in alkyl ligand in 2M is thought to form through deprotonation of the “squarocene” complexes [M{η4‐C4(SiMe3)4}2]− by 1. Complex 2Dy is a single‐molecule magnet, but with prominent quantum tunneling. An anisotropy barrier of 323(22) cm−1 was determined for 2Dy in an applied field of 1 kOe, and magnetic hysteresis loops were observed up to 7 K. nonPeerReviewed

Two isostructural lanthanide-based MOFs [Ln(HL)L]·H2O (1-Ln, Ln = Eu, Dy, H2L = 5-((pyridin-4-ylthio)methyl)isophthalic acid) were successfully obtained via the solvothermal reaction. 1-Eu exhibits high fluorescence quenching efficiency for C2O72- and Fe3+, which can be potentially used as a luminescent probe; 1-Dy behaves as a typical single-molecule magnet with an energy barrier (ΔUeff) of 54(2) K.

CONSPECTUS: The discovery of materials capable of storing magnetic information at the level of single molecules and even single atoms has fueled renewed interest in the slow magnetic relaxation properties of single-molecule magnets (SMMs). The lanthanide elements, especially dysprosium, continue to play a pivotal role in the development of potential nanoscale applications of SMMs, including, for example, in molecular spintronics and quantum computing. Aside from their fundamentally fascinating physics, the realization of functional materials based on SMMs requires significant scientific and technical challenges to be overcome. In particular, extremely low temperatures are needed to observe slow magnetic relaxation, and while many SMMs possess a measurable energy barrier to reversal of the magnetization (Ueff), very few such materials display the important properties of magnetic hysteresis with remanence and coercivity. Werner-type coordination chemistry has been the dominant method used in the synthesis of lanthanide SMMs, and most of our knowledge and understanding of these materials is built on the many important contributions based on this approach. In contrast, lanthanide organometallic chemistry and lanthanide magnetochemistry have effectively evolved along separate lines, hence our goal was to promote a new direction in single-molecule magnetism by uniting the nonclassical organometallic synthetic approach with the traditionally distinct field of molecular magnetism. Over the last several years, our work on SMMs has focused on obtaining a detailed understanding of why magnetic materials based on the dysprosium metallocene cation building block {Cp2Dy}+ display slow magnetic relaxation. Specifically, we aspired to control the SMM properties using novel coordination chemistry in a way that hinges on key considerations, such as the strength and the symmetry of the crystal field. In establishing that the two cyclopentadienyl ligands combine to provide a strongly axial crystal field, we were able to propose a robust magneto-structural correlation for understanding the properties of dysprosium metallocene SMMs. In doing so, a blueprint was established that allows Ueff and the magnetic blocking temperature (TB) to be improved in a well-defined way. Although experimental discoveries with SMMs occur more rapidly than quantitative theory can (currently) process and explain, a clear message emanating from the literature is that a combination of the two approaches is most effective. In this Account, we summarize the main findings from our own work on dysprosium metallocene SMMs, and consider them in the light of related experimental studies and theoretical interpretations of related materials reported by other protagonists. In doing so, we aim to contribute to the nascent and healthy debate on the nature of spin dynamics in SMMs and allied molecular nanomagnets, which will be crucial for the further advancement of this vibrant research field.

A submicron pixel’s light and dark performance were studied by experiment and simulation. An advanced node technology incorporated with a stacked CMOS image sensor (CIS) is promising in that it may enhance performance. In this work, we demonstrated a low dark current of 3.2 e−/s at 60 °C, an ultra-low read noise of 0.90 e−·rms, a high full well capacity (FWC) of 4100 e−, and blooming of 0.5% in 0.9 μm pixels with a pixel supply voltage of 2.8 V. In addition, the simulation study result of 0.8 μm pixels is discussed.

The effect of altitude on thermal conduction, surface temperature, and thermal radiation of partial arc was investigated on the basis of molecular gas dynamics to facilitate a deep understanding of the pollution surface discharge mechanism. The DC flashover model was consequently modified at high altitude. The validity of the modified DC flashover model proposed in this paper was proven through a comparison with the results of high-altitude simulation experiments and earlier models. Moreover, the modified model was found to be better than the earlier modified models in terms of forecasting the flashover voltage. Findings indicated that both the thermal conduction coefficient and the surface thermodynamics temperature of partial arc had a linear decrease tendency with the altitude increasing from 0 m to 3000 m, both of which dropped by approximately 30% and 3.6%, respectively. Meanwhile, the heat conduction and the heat radiation of partial arc both had a similar linear decrease of approximately 15%. The maximum error of DC pollution flashover voltage between the calculation value according to the modified model and the experimental value was within 6.6%, and the pollution flashover voltage exhibited a parabola downtrend with increasing of pollution.

Employing an uninvestigated eight N-donor bitriazole ligand, 5′-(pyrazin-2-yl)-2H,4′H-3,3′-bi(1,2,4-triazole) (H2pzbtz), five complexes, {[Zn2(pzbtz)(SO4)(H2O)2]·2H2O}n (1), {[Cd(pzbtz)]·3H2O}n (2), [Zn3(Hpzbtz)2(SO4)2(H2O)6] (3), [Co(Hpzbtz)2(H2O)2] (4) and {[Co2(pzbtz)2(H2O)2]·4H2O}n (5), have been solvothermally synthesised by altering the reaction solvents and temperatures. Complex 1 shows a three-dimensional (3D) framework with a very rare (3,5)-connected fsc-3,5-Cmce-2 topology. Complex 2 exhibits a (4,4)-connected 3D pts framework with 1D channels. Complexes 3 and 4 are discrete trinuclear and mononuclear molecules, respectively. Complex 5 presents a chiral 3D framework based on a novel trinuclear Co3(tr)4 cluster and features an unusual six-connected lcy topology. In the five complexes, H2pzbtz show a very variety of geometrical configurations and coordination modes. Due to the planarity of H2pzbtz, complexes 1–3 display strong photoluminescence; in particular, 1 features highly selective luminescent sensing for the Cu2+ ion and nitrobenzene molecule. In addition, 2 shows highly selective adsorption for CO2 over CH4, and 5 exhibits antiferromagnetic exchange interactions among the Co2+ ions.

This review outlines recent advances in the design of 3d-, 4f-, and 3d–4f type magnetic molecules for use as excellent cryogenic magnetic coolants based on the magnetocaloric effect (MCE), and the structure-magnetocaloric correlations of reported molecular coolants. Further improvements in the MCE values of molecular magnetic materials are also proposed based on assembly strategies from molecular chemistry and crystal engineering.

The synthesis and structural characterization of two benzoquinone-bridged dinuclear rare-earth complexes [BQ(MCl2·THF3)2] (BQ = 2,5-bisoxide-1,4-benzoquinone; M = Y (1), Dy (2)) are described. Of these reported metal complexes, the dysprosium analogue 2 is the first discrete bridged dinuclear lanthanide complex in which both metal centres reside in pentagonal bipyramidal environments. Interestingly, both complexes undergo significant thermal expansion upon heating from 120 K to 293 K as illustrated by single-crystal X-ray and powder diffraction experiments. AC magnetic susceptibility measurements reveal that 2 does not show the slow relation of magnetization in zero dc field. The absent of single-molecule behaviour in 2 arises from the rotation of the principal magnetic axis as compared to the pseudo-C5 axis of the pentagonal bipyramidal environment as suggested by ab initio calculations. The cyclic voltammetry and chemical reduction experiments demonstrated that complexes 1 and 2 can be reduced to radical species containing [BQ3˙−]. This study establishes efficient synthetic strategy to make bridged redox-active multinuclear lanthanide complexes with a pentagonal bipyramidal coordination environment that are potential precursors for single-molecule magnets. peerReviewed

The synthesis, structure and magnetic properties of the indigo-bridged dilanthanide complexes [{(η5-Cp*)2Ln}2(μ-ind)]n- with Ln = Gd or Dy and n = 0, 1 or 2 are described. The gadolinium complexes with n = 0 and 2 show typically weak exchange coupling, whereas the complex bridged by the radical [ind]3- ligand shows an unusually large coupling constant of J = -11 cm-1 (-2J formalism). The dysprosium complexes with n = 0 and 1 are single-molecule magnets in zero applied field, whereas the complex with n = 2 does not show slow magnetic relaxation.

Under ambient conditions, CO

Three one-dimensional (1D) hetereobimetallic coordination polymers [Fe(II)(L)2(AgCN)2]·Solv (L = bpt(-), 1; L = Mebpt(-), Solv = 1.75EtOH, 2; L = bpzt(-), 3) with in situ generated AgCN species were synthesized by solvothermal reactions of Fe(II) salt, K[Ag(CN)2], and the corresponding ligands [bptH = 3,5-bis(pyridin-2-yl)-1,2,4-triazole, MebptH = 3-(3-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole, and bpztH = 3,5-bis(pyrazin-2-yl)-1,2,4-triazole]. They were further characterized by X-ray crystallography, magnetic and photomagnetic measurements, and differential scanning calorimetry. Single-crystal X-ray analyses show that they are isostructural with 1D zigzag chain structures with rhombus {Fe2Ag2} units, in which the substituted bpt(-) ligand connects the Fe(II) ion and AgCN species in a cis bridging mode. Then the zigzag chains are packed into three-dimensional supramolecular structures by π···π interactions. Most importantly, weak Ag···N interactions (2.750 Å at 150 K) between the π-stacked neighboring chains present in complex 3. Magnetic susceptibility measurements exhibit that complex 1 displays characteristic paramagnetic behavior in the temperature range investigated. Complex 2 undergoes a gradual spin-crossover (SCO) with critical temperatures T(1/2)↓ = 232 K and T(1/2)↑ = 235 K, whereas 3 exhibits an abrupt SCO with critical temperatures T(1/2)↓ = 286 K and T(1/2)↑ = 292 K. The magnetostructural relationships suggest that the magnetic behaviors can be modulated from paramagnetic behavior to abrupt and hysteretic SCO near room temperature through adjustment of the electronic substituent effect and intermolecular interactions.

A flat plate model are employed to investigate the development mechanism of the initial electrons along the insulation surface in this paper, and the field emission properties of pollutant (NaCl) and water (H2O) adsorbed on the copper electrode are studied. The voltage when partial arc occurs is computed and a flat plate experiment is carried out to validate the computing results. Results indicate that pollutant and water have an important impact on the field emission, where pollutant is more significant than water. Meanwhile, the pollutant and water can increase the probability to form the partial arc.

As a significant technological means of collecting global statistics and its changing information, remote sensing technology plays a critically important role in the investigation of territorial resources. Therefore, using remote sensing technology to interpret the tourism resources of Danxia landform can make up for many shortages of traditional methods so as to do less for more. In this article, the tourism resources of Danxia landform in Jiangxi province are extracted by remote sensing technology and its average area error is reduced to 11% through the statistics data. It can be concluded that it is feasible to investigate the tourism resources of Danxia landform by means of computer automatic identification and classification.

The transformation of Mn(II) glycolates (glc) between the three-dimensional coordination polymer [Mn(glc)2]n (1) and discrete mononuclear phase [Mn(glc)2 (H2O)2] (2) can be reversibly switched by water molecules, which dramatically change the magnetocaloric effect (MCE) of Mn(II) glycolates from the maximum of 6.9 J kg(-1) K(-1) in 1 to 60.3 J kg(-1) K(-1) in 2. This case example reveals that the effect of magnetic coupling on MCE plays a dominant role over that of other factors such as magnetic density for 3d-type magnetic refrigerants.

Herein we explored the transitions of two magnetic interaction states (antiferromagnetic or ferromagnetic) upon structural variations in two dinuclear Dy(iii) complexes.

In search of simple approaches to rationally enhance the energy barriers in polynuclear dysprosium single-molecule magnets, a new system containing two structurally closely related dinuclear dysprosium complexes, namely [Dy2(L)2(DBM)2(DMF)2] (1) and [Dy2(L)2(DBM)2(DMA)2]·2DMA (2) (HDBM = dibenzoylmethane, H2L = 2-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide), is introduced and the structure-dependent magnetic properties are investigated. The two complexes display only slight variations in the coordination geometries of the Dy(III) ion but display remarkably different magnetic behaviors. By replacing the DMF (dimethylformamide) ligand in complex 1 with DMA (dimethylacetamide) in 2 while retaining the same coordination atoms, we were able to create a 3-fold enhancement in the energy barrier, from 24 K for complex 1 to 77 K for complex 2. Complete-active-space self-consistent field (CASSCF) calculations revealed that the charge distribution surrounding the Dy(III) centers in 1 and 2 is the key factor in determining the relaxation properties of the SMMs. The introduction of an electron-donating CH3 group in DMA to replace the hydrogen in DMF resulted in a larger average charge along the magnetic axes of complex 2 compared to complex 1, which resulted in a stronger easy-axis ligand field, thus increasing the energy difference between the ground and the first excited states of complex 2. This work presents a simple method to rationally enhance the energy barrier in polynuclear lanthanide SMMs through fine-tuning of the electrostatic potential of the atoms along the magnetic axis.

Two spin-crossover (SCO) supramolecular isomers formulated as [Fe(Mebpt){Au(CN)2}]n·xH2O (1, x = 0, and 2·H2O, x = n, MebptH = 3-(5-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole) have been successfully isolated and characterized by single-crystal X-ray crystallography, thermogravimetric analysis, differential scanning calorimetry, variable-temperature powder X-ray diffraction, and magnetic measurements. Structural analysis reveals that 1 is a two-dimensional coordination layer and 2·H2O is a one-dimensional coordination ladder structure, in which the Mebpt(-) ligands are coordinated in trans and cis bridging mode in 1 and 2·H2O, respectively. Dramatically, their SCO properties are further influenced by the octahedral coordination configuration of Fe(II). In 1, only the Fe(II) centers in trans configuration exhibit spin transition (Tc = 303 K), while in 2·H2O and the dehydrated 2, gradual two-step SCO (Tc1 = 235 K, Tc2 = 313 K) and one-step SCO behaviors (Tc = 315 K) occur, respectively.

Reactions of 1,10-phenanthroline-2,9-dicarboxylic acid (H2phenda) with MnCl2·4H2O or MCl2·6H2O (M = Co, Ni) under solvothermal conditions yielded three octahedral clusters, (H3O)[MnII6(μ6-Cl)(phenda)6]·8MeOH (1·8MeOH), (H3O)[MII6(μ6-Cl)(phenda)6]·6H2O (M = Co, 2·6H2O; M = Ni, 3·6H2O). In the title compounds, the six metal centers are bridged by a μ6-Cl− and surrounded by six H2phenda ligands, forming an octahedral cluster. Magnetic studies show that the antiferromagnetic interactions are present in 1·8MeOH, 2·6H2O and 3·6H2O. Moreover, 3·6H2O clearly shows a nonzero out-of-phase χ″ signal with a peak at ca. 11 K, accompanied by a broad one for χ′.

With the rapid development of unmanned aerial vehicles (UAV) remote sensing technology, UAV nds its place in various applications where the large-scale orthoimage generation is a popular and important step. This paper is meant to apply hugely successful multi-view 3D reconstruction techniques in recent years in computer vision eld to UAV images, and presents a method of automatic generation of large scale true orthoimage based on structure from motion (SfM) and multi-view stereo (MVS) technologies. This paper includes the following key parts: First, an approach is proposed to build a Digital Surface Model (DSM), seemingly a necessary step for any good orthoimage generation, from the points cloud reconstructed by Patch-based Multi-view Stereo (PMVS).Then the key steps of our orthoimage generation method are presented, such as reference system de nition and transformation, the patch visibility computation, Markov Random Field(MRF) model based patch selection and seamless mosaicking. Finally, our orthimage generation method is tested with several sets of UAV images, and compared with some commercial software. The experiments show that our orthimage generation method performs satisfactorily for both terrain and urban area UAV images.

The comprehensive study reported herein provides compelling evidence that anion templates are the main driving force in the formation of two novel nanoscale lanthanide hydroxide clusters, {Gd38(ClO4)6} (1) and {Gd48Cl2(NO3)} (2), characterized by single-crystal X-ray crystallography, infrared spectroscopy, and magnetic measurements. {Gd38(ClO4)6}, encapsulating six ClO4(-) ions, features a cage core composed of twelve vertex-sharing {Gd4} tetrahedrons and one Gd⋅⋅⋅Gd pillar. When Cl(-) and NO3(-) were incorporated in the reaction instead of ClO4(-), {Gd48Cl2(NO3)} is obtained with a barrel shape constituted by twelve vertex-sharing {Gd4} tetrahedrons and six {Gd5} pyramids. What is more, the cage-like {Gd38} can be dynamically converted into the barrel-shaped {Gd48} upon Cl(-) and NO3(-) stimulus. To our knowledge, it is the first time that the linear M-O-M' fashion and the unique μ8-ClO4(-) mode have been crystallized in pure lanthanide complex, and complex 2 represents the largest gadolinium cluster. Both of the complexes display large magnetocaloric effect in units of J kg(-1) K(-1) and mJ cm(-3) K(-1) on account of the weak antiferromagnetic exchange, the high N(Gd)/M(W) ratio (magnetic density), and the relatively compact crystal lattice (mass density).

this article has analyzed the quality of water, air and soil in Mt. Longhushan Scenic Area in recent three years. It turns out that although the environmental quality is good and complies with the national standards, various indexes are increasing year by year. And meanwhile, the disordered development has affected the environment, hence, the cultural pollution cannot be neglected. According to the investigation results, the tourism development for scenic area has brought negative effect to the environment. Therefore, we must take the active actions, quicken the pace on completing the management system, make a reasonable plan so as to promote the sustainable development to the scenic area.

Supertetrahedral clusters: A family of lanthanide oxide supertetrahedral T3{Ln20} clusters (Ln = Tb, Dy, Ho, Er; see figure) were obtained from the solvothermal reaction of lanthanide(III) salts with polytriazolate ligands that could be methylated and oxidized in situ.

With the latest deregulation and opening-up policy of the Chinese government on low altitude airspace to private sectors, the applications of unmanned aerial vehicles (UAV) will be a huge potential market. Currently the automatic processing technology of UAV images is far behind the market demand, and has become the bottleneck of various applications. This work is meant to apply hugely successful scene reconstruction techniques in computer vision field to large scene reconstruction from UAV images. To this end, at first, specific problems of direct application of the Bundler, a popular increment reconstruction technique in computer vision, are investigated. Then a batch reconstruction method from UAV images is proposed by fully taking into account various pieces of prior information which are usually available in UAV images, such as those from GPS, IMU, DSM etc. Our method is tested with several sets of UAV images, and the experiments show that our method performs satisfactorily in terms of robustness, accuracy and scalability for UAV images.