Laterite Fe–Mn deposits are widespread in South China, with the majority of Fe–Mn ore being present in residual quaternary clay beds. However, detailed geological data on the lateritization of low-iron-content carbonate rocks are rare. In this study, we present new results on the mineralogy and geochemistry, as well as a genetic model, of the Maojun laterite Fe–Mn deposit in the Lanshan area, Hunan Province, South China. The profile sequence of laterite consists of an eroded bedrock horizon at its base, an intermediate black–brown clay layer containing earthy Fe–Mn ore, and a reddish-brown clay layer with nodular ferromanganese ore in contact with reddish-brown or yellowish-brown clay on top. Field evidence and chemical analysis indicated that during lateritization, the Mn-Fe-containing carbonate rocks of the Huanggongtang (D2h) and Shetianqiao formations (D3s) saw a more significant removal of mobile elements (Mg, Ca, and Na) whilst insoluble elements (Fe, Mn, Si, Al, Pb, and Zn) exhibited persistent enrichment in situ. Discriminative diagrams of Fe–Mn mineralization, as well as the assemblage-related enrichment of Y, U, Mo, Pb, and Zn and depletion of high-field-strength elements Zr, Nb, and Th, imply that subsequent hydrothermal circulation overprinted on the previously formed hydrogenous deposit. Mineralogical studies conducted using XRD, EPMA, HR-TEM, and TIMA indicated the predominance of iron and manganese oxides; hematite, goethite, limonite, and hollandite were identified as major oxide phases and cryptomelane, pyrolusite, and coronadite were present in minute quantities. Similar minerals constitute the upper ferromanganese nodule horizons, although they possess distinct textures and concentrations. The mineralogy, geochemical associations, and Ti mass balance show a continuous vertical evolution from top to bottom in the lateritic profile. Ferromanganese concretions from the drenching zone with poorly crystallized Al–goethite, Al–hematite, limonite, Fe–kaolinite, Fe–Mn oxides and hollandite predominate in shallow parts, and microcrystalline hematite, goethite and hollandite were found in deeper layers. Mn2+ can be rapidly oxidized and precipitated on the surface of hematite and limonite as high-valence-state (Mn4+) manganese oxides and binds strongly with mobile elements (Ba, K, Pb, Zn, Ca, and Ni). Petrographical, mineralogical, and geochemical studies show that three stages comprised the formation of the Maojun laterite Fe–Mn deposit.
We present systematic characterization of a photoacoustic imaging system optimized for rapid, high-resolution tomographic imaging of small animals. The system is based on a 128-element ultrasonic transducer array with a 5-MHz center frequency and 80% bandwidth shaped to a quarter circle of 25 mm radius. A 16-channel data-acquisition module and dedicated channel detection electronics enable capture of a 90-deg field-of-view image in less than 1 s and a complete 360-deg scan using sample rotation within 15 s. Measurements on cylindrical phantom targets demonstrate a resolution of better than 200 microm and high-sensitivity detection of 580-microm blood tubing to depths greater than 3 cm in a turbid medium with reduced scattering coefficient mu(s) (')=7.8 cm(-1). The system is used to systematically investigate the effects of target size, orientation, and geometry on tomographic imaging. As a demonstration of these effects and the system imaging capabilities, we present tomographic photoacoustic images of the brain vasculature of an ex vivo mouse with varying measurement aperture. For the first time, according to our knowledge, resolution of sub-200-microm vessels with an overlying turbid medium of greater than 2 cm depth is demonstrated using only intrinsic biological contrast.
To compare the effects of coronal Z-type lengthening of transverse carpal ligament with conventional open approach for carpal tunnel syndrome.A double-blinded study was conducted from January 2005 to August 2008 on 68 patients with a mean age of 41 years (range 27-55 years) diagnosed as severe carpal tunnel syndrome. They were randomized into two groups(A and B). Patients in group A underwent coronal Z-type lengthening of transverse carpal ligament; and patients in group B had conventional open approach surgery. Postoperative evaluation was scheduled at 1, 3, 6 and 12 months after the surgery and incidence rate of bowstring of the flexor tendons, improvement of grip strength and ADL activities of daily living) score were recorded.Fifty-eight patients had been followed up successfully, 30 and 28 for group A and B respectively. The Scar Tissue Formation of the flexor tendons in group B was observed more than that in group A at 6 and 12 month after operation. Improvement of grip strength were observed in two groups, which was statistically different between 6 and 12 months after operation and no significant difference was seen between 1 and 3 months after operation. According to ADL, the satisfaction rates documented on form for patients were statistically different in the two groups at 6 and 12 months after operation and no difference was noted at 1 and 3 months after operation.Excellent improvement of function and satisfaction were achieved by Coronal Z-type reconstruction of the flexor retinaculum for severe carpal tunnel syndrome. Our method offers a more effective alternative method for conventional carpal tunnel open decompression surgery.
A series of 6FDA-DABA (6FD) polyimide and branched poly(phenylene) (PP) block copolymers and homopolymers were successfully synthesized using a Diels-Alder and polycondensation reaction. PP and 6FD homopolymer blends in tetrahydrofuran were immiscible. The result coincides with their large chemical dissimilarity and theoretical solubility parameter differences of 25.47 and 33.17 (MJ/m 3 ) 1/2 . However, 6FD-PP block copolymer solutions were clear and thin films were robust and creasable. Densities and fractional free volumes (0.162~0.346) largely obeyed the rule of mixing, suggesting a "blend-like" morphology. At moderate PP block lengths, two distinct glass transition temperatures (340°C and 420°C) were evident, while large PP block lengths suppressed first-order polyimide transitions entirely. A SAXS and AFM morphological analysis revealed two distinct domains, with separation lengths increasing with PP block length. Their gas permeation, diffusion, sorption and separation properties were thoroughly investigated and exhibited a strong correlation with polymer chemistry, block length and FFV. A block copolymer had an O 2 permeability roughly between 6FD and PP, resulting in a 30% increase in O 2 /N 2 selectivity. The N 2 /CH 4 selectivities ranged from 4.2 to 0.58, suggesting that this 6FD-PP system could be efficiently tuned from highly N 2 selective to CH 4 selective performance. Five structural models, rule-of-mixture, Maxwell, EBM, laminate, and blend, were used to predict gas transport properties. Compared with experimental data, the miscible blend model provided the best results for the 6FD-PP block copolymer system. Block copolymerization by combining highly selective polyimide and highly permeable branched poly(phenylene) provides an opportunity for gas separation tuneability and improvement in selected gas pairs.
Real-time photoacoustic imaging requires ultrasonic array receivers and parallel data acquisition systems for the simultaneous detection of weak photoacoustic signals. In this paper, we introduce a newly completed ultrasonic receiving array system and report preliminary results of our measured point spread function. The system employs a curved ultrasonic phased array consisting of 128-elements, which span a quarter of a complete circle. The center frequency of the array is 5 MHz and the bandwidth is greater than 60%. In order to maximize the signal-to-noise ratio for photoacoustic signal detection, we utilized special designs for the analog front-end electronics. First, the 128 transducer-element signals were routed out using a 50-Ohm impedance matching PCB board to sustain signal integrity. We also utilize 128 low-noise pre-amplifiers, connected directly to the ultrasonic transducer, to amplify the weak photoacoustic signals before they were multiplexed to a variable-gain multi-stage amplifier chain. All front-end circuits were placed close to the transducer array to minimize signal lose due to cables and therefore improve the signal-to-noise ratio. Sixteen analog-to-digital converters were used to sample signals at a rate of 40 mega-samples per second with a resolution of 10-bits per sample. This allows us to perform a complete electronic scan of all 128 elements using just eight laser pulses.
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