Search

Previous studies showed that metal preconcentration in fluids and/or magma is critical to the formation of gold deposit in arcs and is closely related to the segregation of sulfide phases. However, the depth range and the magnitude of and associated mechanism by which the deep crust controls the metal preconcentration of arc mineralization remain enigmatic. Here we present geophysical observations of the medium-scale Baogutu porphyry copper–gold deposit and the large-scale Hatu epithermal gold deposit from the late Paleozoic arc in the western Junggar, NW China. During the closure of Paleo-Asian Ocean, Baogutu deposit formed at ∼313 Ma relating to the adakitic intrusions driven by the ridge-related subduction, and Hatu deposit formed at ∼300 Ma just before the subduction termination. The transcrustal structures of resistivity and shear-wave velocity would show the signatures of metal preconcentration by reasoning the cause of low-resistivity anomaly to the persisting sulfide phases and the change of shear-wave velocity to the garnet proportion, respectively. Our results showed that the sulfide phases persisted in the entire deep crust and thus the metal preconcentration could occur in the base cumulates and mush reservoir beneath Hatu deposit, but the signatures were not fully reflected beneath the Baogutu deposit. These observations suggest that the reduced permeability of brittle-ductile transition and the water flux associated with magma likely affect the rising rate of melt, resulting in different efficiency of the metal preconcentration. Thus, the endowments of mineralization in arcs are controlled by crustal structures and contemporaneous arc magmatism during subduction.

In this study, an activated porous graphite oxide (PG) with a superior surface area of ~ 3010 m2 g− 1 was applied as electrode component for discrimination of dopamine (DA) and uric acid (UA) via cyclic voltammetry (CV), in the presence of high content of ascorbic acid (AA). Contributable to microwave exfoliation and KOH assisted activation, the as-prepared PG remarkably improves the signal at glassy carbon electrode (GCE) for analyte. The electrochemical performance of PG/GCE was studied with CV and electrochemical impedance spectroscopy (EIS) measurements. The CV data implied that the PG film effectively enlarges the electro-active area of the working electrode while the EIS data revealed that the PG modification enhances the electron transfer kinetics between analyte and electrode. The peak separations between DA, UA and AA were remarkably enlarged and their redox peak currents were enhanced. This makes the proposed sensor feasible for simultaneous determination of DA and UA in the presence of AA. Under optimum conditions, the oxidation peak currents for DA and UA increased linearly over concentration ranges of 0.5–60 μM and of 0.5–100 μM, with detection limits of 0.04 μM and 0.02 μM (at a signal-to-noise ratio of 3, S/N = 3), respectively. Applications of the PG/GCE for urine and serum analyses were investigated. The results with good recoveries indicate the feasibility of the developed electrode in clinic sensing application.

Chronic wounds are difficult to heal spontaneously largely due to the corrupted extracellular matrix (ECM) where cell ingrowth is obstructed. Thus, the objective of this study was to develop a three-dimensional (3D) biodegradable scaffold mimicking native ECM to replace the missing or dysfunctional ECM, which may be an essential strategy for wound healing. The 3D fibrous scaffolds of poly(lactic acid-co-glycolic acid) (PLGA) were successfully fabricated by liquid-collecting electrospinning, with 5~20 µm interconnected pores. Surface modification with the native ECM component aims at providing biological recognition for cell growth. Human dermal fibroblasts (HDFs) successfully infiltrated into scaffolds at a depth of ~1400 µm after seven days of culturing, and showed significant progressive proliferation on scaffolds immobilized with collagen type I. In vivo models showed that chronic wounds treated with scaffolds had a faster healing rate. These results indicate that the 3D fibrous scaffolds may be a potential wound dressing for chronic wound repair. MOE (Min. of Education, S’pore) Published version

Atomic force microscopic observations on an isothermally crystallized poly(ethylene naphthalate) (PEN)/clay nanocomposite suggest that the presence of nanoclay alters the lamellar organization in PEN mainly in three ways: 1) physically blocking the crystal growth front and creating wide amorphous regions within the spherulites, which may then be filled by secondary lamellae branching out from the primary lamellae of the same spherulite, or primary lamellae developed from other nearby nucleating centers; 2) inducing random twisting of lamellae; and 3) causing irregular crystallite growth fronts, with the protrusion of some leading lamellae. In particular, the physical hindrance imposed by clay tends to be more prevalent for lamellae that grow roughly perpendicular to the clay long axes. This may give rise to an anisotropic crystalline morphology if the clay layers exhibit a preferred orientation induced by flow.

Thermally stable organically modified clays based on 1,3-didecyl-2-methylimidazolium (IM2C10) and 1-hexadecyl-2,3-dimethyl-imidazolium (IMC16) were used to prepare poly(ethylene naphthalate) (PEN)/montmorillonite (MMT) nanocomposites via a melt intercalation process. Examination by X-ray diffraction and transmission electron microscopy indicates that an intercalated nanocomposite was formed with IMC16-MMT, while unmodified MMT (Na-MMT) and IM2C10-MMT are generally incompatible with PEN. Thermogravimetric analysis reveals that the peak derivative weight loss temperature of the intercalated PEN/IMC16-MMT was more than 10 °C higher compared to neat PEN, PEN/Na-MMT, or PEN/IM2C10-MMT. Dynamic mechanical analysis also showed that a more significant improvement of the storage modulus was achieved in the better dispersed PEN/IMC16-MMT. The effect of annealing on the dynamic storage modulus of the hybrids is also investigated.

In this paper the growth and laser properties of Nd, Ce and Cr ions-co-doped yttrium aluminum garnet (Nd:Ce:Cr:YAG) crystals were reported. Nd:Ce:Cr:YAG single crystals were grown in DJL-40D model crystal growth furnace with medium frequency induction heating by Czochralski technique from iridium crucible. The influence of the doping concentration of Nd, Ce and Cr ions on the optical quality and the pulse laser performance of the crystal and the technology conditions for growing high quality crystal were also investigated. The dimension of Nd:Ce:Cr:YAG crystal boules grown is up to (Phi) 40 multiplied by 150 mm. The interference fringe of the laser rods with the dimension (Phi) 5 multiplied by 80 mm is less than 0.5/25 mm and the extinction ratio is more than 26 dB. The pulse laser properties of Nd:Ce:Cr:YAG and ND:YAG laser rods were tested comparatively. The typical pulse laser characteristics of Nd:Ce:Cr:YAG crystal are relatively lower, threshold, higher laser efficiency, and relatively higher output power, better thermal stability and smaller nature divergence angle at Q- switching operation. At the same time, the UV radiation of pump flashlamp will not lead to the reduction of laser output.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.