Search

The photocatalytic degradation of tetracycline has been improved using H2O2-assisted Z-scheme-type heterojunction Bi3NbO7/Bi2Sn2O7 system under visible light irradiation. A possible photocatalytic degradation mechanism has been proposed.

Crystal structure modification was introduced into CdWO4 via La doping strategy and the characterization results of SEM, XRD, TEM and EDS confirmed the morphology, crystal phase structure and composition of the CdWO4 and La-doped CdWO4 nanorods. Meanwhile, the partial substitution of Cd by La ions in CdWO4 nanocrystal was confirmed via some classic formulas. Excellent electrocatalytic performance was obtained on the electrochemical sensing interface when the La ions were doped into the CdWO4 lattice. The exquisite and regular rod-like 1.0% La-doped CdWO4 nanorods modified electrochemical sensor was established and applied to detect BPA with a highly sensitive detection limit (2.0 × 10−8 M). The more excellent electrocatalytic activity of 1.0% La-doped CdWO4 than other doping ratio nanomaterials was verified. The possible mechanism of the electrochemical catalysis of BPA was proposed based on the effective electrochemical analysis methods (EIS, CV and I-t) and the deductions from various physicochemical characterizations. More electron transmission channels were formed in the crystal due to the moderate amount of La ions in CdWO4 nanorods. Unprecedently, electrocatalytic performance of nanomaterials can be more efficiently promoted through regulating the doping atmosphere of crystal within the materials. This novel strategy will potentially provide a significant reference for solving the related electrocatalysis and electrochemical sensing interface's problems.

To treat typical organic wastewater efficiently, a novel Fenton-like processes based on ZnO/CuO composite cathode induced by oxygen reduction reaction (ORR) electrocatalysis with enhanced electrocatalytic performance was established successfully. Electrochemical testing investigation indicated that the ZnO/CuO cathode possessed conspicuous redox peak and better conductivity than uncompounded electrodes. Additionally, the removal efficiency of methylene blue and its chemical oxygen demand (COD) reached 96.4% and 70.8% after 120 min, respectively. Next, the feasibility of the material in practical application was also discussed. Subsequently, electrocatalytic principle based on valence state changes of metal elements on the electrode surface were also studied by x-ray photoelectron spectroscopy (XPS). Redox reactions between the active species H2O2 and the species Cu+ promoting Fenton-like processes were deduced. Namely, the conversion of Cu(I) and Cu(II) on the electrode surface was accompanied by OH generation. The combination of ZnO and CuO improved the surface morphology, increasing the active site of ORR and the yield of H2O2, thus greatly enhanced the Fenton-like activity. Finally, the main intermediates were identified by Gas chromatography-mass spectrometer (GC-MS), and possible pathways for dye degradation were proposed. In short, the research of ZnO/CuO cathode provided great significance for heterogeneous Fenton-like degradation and also showed its application potential in water treatment and remediation.

TiO2 nanosheet based flowerlike architectures with a surface area as high as 171 m2 g−1 were prepared through a solvothermal method. The sensing performance of TiO2 nanosheet based flowerlike architectures is enhanced by increasing density of surface unsaturated Ti atoms with dangling bonds through hydrogenation. We proposed a concept of the unsaturated Ti atoms serving as the sensing reaction active sites, and described in detail the sensing mechanism at the atomic and molecular level. The unsaturated Ti atoms not only generate non-contributing (free) electrons and adsorb oxygen molecules, but also catalyze the sensing reaction. In principle, the hydrogenation strategy may be used to improve sensing performances and catalytic activities of other metal oxides. The concept of the unsaturated metal Ti atoms serving as active sites can deepen understanding of the sensing and other catalytic reaction mechanisms, and provides a new insight to the design and fabrication of advanced sensing materials, catalysts and electronic devices.

The search for active semiconductor photocatalysts that can utilize adequately solar-energy remains to be an open issue. CdTe nanoflakes and nanowires with a range of texture coefficients of (111) have been synthesized. Photocatalytic activities of the CdTe nanocrystals in degradation of malachite green, methyl orange, acid red 88 and ciprofloxacin can be enhanced by increasing the texture coefficients of (111) and reducing texture coefficient of (220). The exposed polar {111} facets were found to be the active facets, and a charge separation model between polar Cd-CdTe (111) and Te-CdTe ( 1 ¯ 1 ¯ 1 ¯ ) surfaces is proposed. An internal electric field is created between polar Cd-CdTe (111) and Te-CdTe ( 1 ¯ 1 ¯ 1 ¯ ) surfaces by the spontaneous polarization, and the internal electric field drives separation of the photoinduced electrons and holes. Therefore, the CdTe nanoflakes with exposed polar {111} facets synthesized by using oleylamine as a morphology controlling agent show superior photocatalytic activity, compared with CdTe nanowires, nanocrystals with irregular shapes and commercial powders as well as CdS branched nanostructures. The charge separation model provides a clear opinion into charge transfer in the semiconductor nanocrystals with exposed active facets, and affords guidance to design more effective photocatalysts, solar cells and other photoelectronic devices.

Novel Ti/Sb2O3–SnO2/Er–PbO2 anodes were fabricated based on doping Er ions into the PbO2 crystal and enhanced electrocatalytic degradation efficiency for organic pollutants was achieved successfully. The doping principle, possible degradation pathway of methylene blue and electrocatalytic mechanism have been discussed in depth. Based on the comprehensive analysis of crystal parameters by X-ray diffraction (XRD) results and typical formulas, the doping principle was confirmed to be the partial substitution of Pb ions by Er ions in PbO2 nanocrystal and might form point defects. Additionally, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) investigation indicated that the Ti/Sb2O3–SnO2/Er–PbO2 anodes possessed higher oxygen overpotential and better conductivity than undoped electrodes. The optimum conditions for the degradation of methylene blue were obtained via studying the effects of different parameters, such as electrolyte concentration (0.01–0.4 M Na2SO4), current density (20–60 mA cm−2), initial methylene blue concentration (10–70 mg L−1) and initial pH (3–11). At the optimum conditions, the total organic carbon (TOC), the decolorization rate constant (kdec) and the energy consumption (EC) reached up to 65.34%, 0.036 min−1 and 0.08 (kWh(gTOC))−1, respectively. Moreover, the electrocatalytic degradation mechanism of the Ti/Sb2O3–SnO2/Er–PbO2 anodes to methylene blue was proposed to be that, the presence of point defects induced an increase of electron transport tunnels, and promoted the production of more hydroxyl radicals ( OH) and SO4 -. The possible electrocatalytic mineralization pathway of methylene blue at Ti/Sb2O3–SnO2/Er–PbO2 anodes was also speculated by UV–visible absorption spectroscopy, gas chromatography combined with mass spectrometry (GC-MS) and liquid chromatography combined with mass spectrometer (LC-MS). This work will provide significant references for exploring the mechanism between doped electrodes materials and electrocatalytic degradation performance.

NiSe ultralong nanobelts were synthesized by a solvothermal reaction of Ni with Se and KBH4 in ethylenediamine and subsequent annealing in Ar. The aspect ratios of NiSe ultralong nanobelts can be tuned by altering the reaction time. The adsorption performance of NiSe nanostructures with different aspect ratios was investigated, and the as-obtained NiSe ultralong nanobelts exhibited excellent adsorption capability of malachite green in wastewater, which could be attributed to their unique honeycomb-like assembly and high surface area. The adsorption process agreed well with the pseudo-second-order kinetics and the Langmuir isotherm equation. Thermodynamic parameters indicated that the adsorbent processes were spontaneous. Electrostatic attraction between malachite green and NiSe ultralong nanobelts was considered as the adsorption mechanism. The NiSe ultralong nanobelts could be regarded as a promising adsorbent for the removal of MG in wastewaters.

Crystal facet engineering of semiconductors has been proven to be an effective strategy to increase photocatalytic performances. However, the mechanism involved in the photocatalysis is not yet known. Herein, we report our success in that photocatalytic performances of the Cl(-) ion capped CoO octahedrons with exposed {111} facets were activated by a treatment using AgNO3 and NH3·H2O solutions. The clean CoO {111} facets were found to be highly reactivity faces. On the basis of the polar structure of the exposed {111} surfaces, a charge separation model between polar {111} surfaces is proposed. There is an internal electric field between polar {111} surfaces due to the spontaneous polarization. The internal electric field provides a driving force for charge separation. The reduction and oxidation reactions selectively take place on the positive and negative polar {111} surfaces. The charge separation model provides a clear insight into charge transfer in the semiconductor nanocrystals with high photocatalytic activities and offer guidance to design more effective photocatalysts, solar cells, photoelectrodes, and other photoelectronic devices.

CdSe hexagonal nanoflakes have been synthesized via a reaction of CdCl 2 -oleylamine with Se-tri-n-octylphosphine at 300 °C for 30 min. The CdSe hexagonal nanoflakes with the typical side lengths of 9.5–12.3 nm are single-crystalline wurtzite structure and are enclosed by {0 0 1} top and down surfaces. Size control of the CdSe nanoflakes from 3.3 to 18.6 nm is achieved by adjusting reaction temperature and time, and the size-dependent absorption and photoluminescence properties are observed. The formation of CdSe hexagonal nanoflakes results from the selective adsorption of oleylamine on the (0 0 1) prismatic facet. The as-obtained CdSe nanoflakes with exposed {0 0 1} facets show higher photocatalytic activity than CdSe commercial powders for degradation of malachite green. The present study motivates us to further explore new synthetic methods for the preparation of other II–VI semiconductor with a high percentage of reactive facets.

Genes coding for proteins involved in steroid hormone signaling have been identified as ovarian cancer risk-modifier candidates. AIB1 gene (amplified in breast cancer-1), an androgen receptor (AR) coactivator, expresses a polyglutamine (poly-Q) sequence within the carboxyl-terminal coding region. We hypothesized that genotypic variations in the androgen-signaling pathway promote aggressive epithelial ovarian cancer biology and sought to examine the effect of AIB1 poly-Q repeat length on ovarian cancer risk with a case–control study. The genotype analysis of the AIB1 poly-Q repeat was conducted in 3,000 epithelial ovarian cancer (EOC) cases and 3,000 healthy controls. When analyzed as a categorical variable with cutoff of

The 3-dimensional hierarchical ZnO flower-like architectures have been synthesized in a Zn(Ac)2·2H2O-Na2SeO3-KBH4-pyridine solvothermal system at 100°C for 24h. The flower-like architecture is assembled from ZnO nanosheets with a thickness of ∼1.5nm, and the flower-like architecture specific surface area is 132m(2)/g. When the ZnO flower-like architecture is used as the adsorbent for acid fuschin (AF), malachite green (MG), basic fuchsin (BF), congo red (CR) and acid red (AR) in water, the adsorption capacities for AF, MG, BF, CR and AR are 7154.9, 2587.0, 1377.9, 85.0 and 38.0mg/g, respectively. Evidently, the as-obtained ZnO flower-like architectures show excellent adsorption performances for triphenylmethane dyes, and the adsorption capacity of 7154.9mg/g for AF is the highest of all adsorbents for dyes. The adsorption mechanism can be attributed to the electrostatic attraction and the formation of ion-association complex between triphenylmethane dyes and ZnO hierarchical flower-like architectures.

We investigated the efficacy and safety of a new second-line chemotherapy of combining folinic acid, 5-fluorouracil and irinotecan (FOLFIRI) with both panitumumab and bevacizumab to treat patients with metastatic colorectal cancer (mCRC). Patients with mCRC and unsuccessful previous oxaliplatin-based chemotherapy were included in the study. The FOLFIRI arm was given FOLFIRI only. The FOLFIRI+PB arm was given panitumumab (3 mg/kg) and bevacizumab (3 mg/kg) plus FOLFIRI every other week. Between 2009 and 2013, 155 and 137 patients were included in the FOLFIRI arm and FOLFIRI+PB arm, respectively. The response rate was 40.1 % for FOLFIRI+PB arm versus 30.1 % for FOLFIRI arm. The disease-controlled rate in FOLFIRI+PB arm was improved to 62.2 from 50.2 % in FOLFIRI arm. The median overall survival was 13.9 months in FOLFIRI+PB arm as compared to 10.7 months in FOLFIRI arm. A series of adverse events were comparable between two arms, whereas some of the antibody therapy-associated toxicities were observed in FOLFIRI+PB arm. The new strategy of combining panitumumab and bevacizumab with FOLFIRI as second-line chemotherapy for patients with mCRC is safe and feasible.

In this paper, we present a new hardware acceleration method to speedup the ordered-subsets expectation-maximization (OS-EM) algorithm for quantitative single photon emission computed tomography (SPECT) image reconstruction with varying focal-length fan-beam (VFF) collimation. By utilizing the geometrical symmetry of VFF point-spread function (PSF), compensation for object-specific attenuation and system-specific PSF are accelerated using currently available PC video/graphics card technologies. A tenfold acceleration of quantitative SPECT reconstruction is achieved.

Fan-beam collimators are designed to improve the system sensitivity and resolution for imaging small objects such as the human brain and breasts in single photon emission computed tomography (SPECT). Many reconstruction algorithms have been studied and applied to this geometry to deal with every kind of degradation factor. This paper presents a new reconstruction approach for SPECT with circular orbit, which demonstrated good performance in terms of both accuracy and efficiency. The new approach compensates for degradation factors including noise, scatter, attenuation, and spatially variant detector response. Its uniform attenuation approximation strategy avoids the additional transmission scan for the brain attenuation map, hence reducing the patient radiation dose and furthermore simplifying the imaging procedure. We evaluate and compare this new approach with the well-established ordered-subset expectation-maximization iterative method, using Monte Carlo simulations. We perform quantitative analysis with regional bias-variance, receiver operating characteristics, and Hotelling trace studies for both methods. The results demonstrate that our reconstruction strategy has comparable performance with a significant reduction of computing time.

Spatial resolution variation as a function of distance from collimator surface in single photon emission computed tomography (SPECT) is a major obstacle for quantitative imaging. This work investigated two analytical inversion methods for correcting the distance-dependent resolution variation. The first one derives accurately an inversion formula, but approximates the resolution variation kernel. The second one considers accurately the resolution variation kernel, but approximates the inversion formula. Reconstructed images using the first method showed a better resolution recovery at the central area of field-of-view (FOV), consistent with the approach that the resolution kernel is approximated for near-field regions. The second method restored resolution better at the FOV periphery, consistent with the theory that the formula is approximated for far-field regions. The first method is very sensitive to the approximation. The second one is robust and, therefore, is a better choice for quantitative SPECT imaging.

The non-stationary Poisson noise in single photon emission computed tomography (SPECT) sinogram is a major cause to compromise the quality of reconstructed images and challenge any compensation strategy for photon attenuation, scatter and collimator response. Research utilizing three-dimensional Wiener filter after Anscombe transformation, which converts Poisson distributed noise into Gaussian distributed one, has been conducted recently with noticeable success. However, the prerequisite of stationary random process for the Wiener approach is not exactly valid for the SPECT sinogram. In this paper, the non-stationary Poisson noise was first modulated by the Anscombe transformation and then the modulated noise model was analyzed. A Kalman filter for the modulated non-stationary noise model was designed to extract the means or signals from the Poisson noise sinogram. Monte Carlo program was used to generate projection data from the MCAT phantom, simulating SPECT data acquisition. The reconstructed results demonstrated a significant improvement with the Kalman filter, as compared to the Wiener approach. Dramatic improvement is seen, as compared to linear low-pass filters, at noisy levels of 100 thousand counts in a 128/spl times/128/spl times/128 sinogram size. The capability of Kalman filter for nonstationary noise model was theoretically proved and experimentally demonstrated.

In dynamic SPECT studies, the acquired sinograms have both spatial and temporal correlations among the time sequence, in addition to the spatial correlation within each time frame (i.e., a 3D sinogram). We propose a theoretically based multi-frame filtering algorithm, which considers both the spatial and temporal correlations, for restoring the gated sinograms degraded by the Poisson noise. This spatio-temporal filtering task is greatly simplified by first applying the Anscombe transformation to all the sinogram data, which converts Poisson distributed noise into Gaussian distributed one with constant variance (i.e., the noise is signal independent). By performing temporal Karhunen-Loeve (K-L) transformation on the Anscombe transformed data sequence, the filtering task is further simplified from a 4D problem to a 3D spatial process. In the K-L domain, the noise property of constant variance remains for all components, while the signal-to-noise ratio decreases monotonically for lower eigenvalue components. An accurate Wiener filter is then constructed for each component of a 3D data set. By this approach, the spatiotemporal filtering can be achieved at a reasonable computational cost. The computer simulations are very encouraging, by visual judgement, as compared to frame-by-frame 3D Wiener filtering along the time sequence.

A three-dimensional (3D) distance-weighted Wiener filtering, which takes the characteristics of Poisson noise into account as well as the frequency-distance relationship of projection data, is described and evaluated. The task of spatial filtering on Poisson noise can be greatly simplified without the estimation of noise-power spectrum by first applying the Anscombe transformation to the projection data, which converts Poisson distributed noise into Gaussian distributed one with constant variance. By extending the stationary-phase condition and frequency-distance relationship (derived from the noise-free 2D sinogram) into 3D situation, we obtain a weighting function in frequency domain which is only dependent on the distance of an interested point source from the object center. Since the Anscombe transformation only changes the distribution of projection data, not the pixel location, a distance-variant weighting window for the Anscombe transformed data is derived and incorporated into the Wiener filter. Considering the regions with higher signal-to-noise ratio (SNR) receive greater weight in the estimation of signal-power spectrum, the proposed filter optimizes the data used to estimate the power spectrum of observed data and thus produces a better spatial resolution. Simulation and experimental results show improved noise reduction, especially in the peripheral regions, as compared with conventional filtering methods.