Search

Ag/BiOI and Ag/AgI/BiOI composites were successfully in-situ synthesized via the same facile photoreduction strategy through adjusting the Ag + amount. The scanning electron microscopy shows that Ag and Ag/AgI nanoparticles were loaded on the surface of BiOI microplates. The formation of Ag originated from the surface adsorbed Ag + for Ag/BiOI while from the first-step cation-exchange generated AgI for Ag/AgI/BiOI. Under visible light ( λ >420 nm), both Ag/BiOI and Ag/AgI/BiOI displayed higher photocatalytic activities than pure BiOI for degradation of rhodamine B. It provides a universal way to obtain Ag/BiOX and Ag/AgX/BiOX photocatalysts using photoreduction strategy for their potential application in water purification.

Three kinds of crystal phase BiPO4(HP, LTBP, and HTBP) were selectively synthesized by controlling the preparation conditions. Structures of the three samples are all constructed by PO4 and BiO8 polyhedra but with different geometric structures. Detailed characterization was carried out by X-ray diffraction(XRD), scanning eletron microscopy(SEM) and Raman, UV-Vis, and luminescence spectrometries. Three samples exhibit huge distinctions in their photoluminescence(PL) lifetime: 0.68, 162 and 160 μs for HP, LTBP, and HTBP, respectively. More interesting, an outstanding photocatalytic activity is observed for as-prepared LTBP nanorod, which shows even higher activity for the degradation of MB solution than P25. In addition, experiments were carried out to clarify the role of hydroxyl (·OH) and superoxide radicals(O2 ·) played in photocatalytic process and it was found O2 · was the main active species in BiPO4 photocatalysts. Further comparison of structural and photocatalytic properties of the three samples finds that structure distortion is contributed to their property difference. A correlation was found between photocatalytic performance and the distortion of BiO8 dodecahedra. The internal field generated by the distortion of BiO8 dodecahedra was believed advantageous for the separation of electron and hole, which was in favor of the improvement of photocatalytic activity. This correlation may help to design other photocatalysts with high activity.

This paper deals with the issues of both robust state estimation and actuator fault detection for a class of uncertain switched linear systems under average dwell time (ADT). A robust switched observer is proposed to estimate the states of switched system even if it is subject to simultaneous disturbance inputs and actuator faults, where the disturbance inputs are decoupled and the actuator faults are suppressed by designing a switching sliding-mode control law. The observer gain matrices are also obtained by solving an optimization problem with linear matrix inequality constraints, and a switching signal is designed to guarantee the exponential stability of error dynamics. Next, a fault detection observer is developed as fault detector to not only estimate the states of switched system under the case of no actuator faults but also detect the occurrence of actuator faults. Finally, a numerical simulation is given to illustrate the effectiveness of the proposed methods.

The axial strain sensitivity of long period fiber grating (LPFG) is analyzed by new transfer matrix method. The new transfer matrix method can be used to analyze the modes coupling between the core mode and multiple cladding modes. Compared with the previous method used, such as solving the coupled mode equation by the fourth order adaptive step size Runge-Kutta algorithm, the new transfer matrix method (TMM) has a faster calculation speed. Theoretical results are excellent agreement with the method of solving the coupled mode equation (SCME).

This paper studies the preview control problem for continuous-time control systems. A design method for an optimal preview controller is presented, when the desired tracking and disturbance are piecewise-continuously differentiable functions. Applying the same techniques as for optimal control in linear quadratic optimal control, we derive a type-one servomechanism with both desired tracking preview and disturbance preview compensation. A proof is presented that if the original system is stabilizable and detectable, the closed-loop system is asymptotically stable. We also design a full-dimensional state observer for the considered system. Finally, numerical simulations show the efficiency of the controller.

This work explored the selective synthesis of polymorphs of CdWO{sub 4} in either tetragonal or monoclinic phase by optimizing the experimental parameters. Systematic characterization indicated that both polymorphs possessed similar spherical morphologies but different structural building blocks. Electronic structures calculations for both polymorphs demonstrated the same constructions of conduction band or valence band, while the conduction band widths of both polymorphs were quite different. Both CdWO{sub 4} polymorphs exhibited good photocatalytic activity for degradation of methyl orange under UV light irradiation. When comparing to some other well-known tungstate oxide materials, the photocatalytic activity was found to follow such a consequence, monoclinic CdWO{sub 4{approx}}monoclinic ZnWO{sub 4}>tetragonal CdWO{sub 4}>tetragonal CaWO{sub 4}. The specific photocatalytic activity of monoclinic CdWO{sub 4} was even higher than that of commercial TiO{sub 2} photocatalyst (Degussa P25). The increased activity from the tetragonal CdWO{sub 4} to the monoclinic was consistent with the trend of the decreased symmetry, and this could be explained in terms of the geometric structures and electronic structures for both polymorphs. -- Graphical abstract: Monoclinic CdWO{sub 4} exhibited a much higher photocatalytic activity than the tetragonal form owing to the lower symmetry, more distorted geometric structure, and the dispersive band configuration. Display Omitted Research highlights:more » > Polymorphs of CdWO{sub 4} in either tetragonal or monoclinic phase were selectively synthesized. > Both polymorphs possessed similar spherical morphologies, while the relevant structural building blocks were different. > Photocatalytic activities of CdWO{sub 4} polymorphs depended strongly on the symmetry, geometric structure, as well as band configuration.« less

In this work, water-soluble and blue-emitting carbon nanodots (CDs) were synthesized from apple peels for the first time via one-step hydrothermal method. The synthetic route is facile, green, economical and viable. The as-prepared CDs were characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), fluorescence and UV–Vis absorption spectroscopy in terms of their morphology, surface functional groups and optical properties. The results show that these CDs possessed ultrasmall size, good dispersivity, and high tolerance to pH, ionic strength and continuous UV irradiation. Significantly, the CDs had fast and reversible response towards temperature, and the accurate linear relationship between fluorescence intensity and temperature was used to design a novel nanothermometer in a broad temperature range from 5 to 65[Formula: see text]C facilely. In addition, the fluorescence intensity of CDs was observed to be quenched immediately by Cr(VI) ions based on the inner filter effect. A low-cost Cr(VI) ions sensor was proposed employing CDs as fluorescent probe, and it displayed a wide linear range from 0.5 to 200[Formula: see text][Formula: see text]M with a detection limit of 0.73[Formula: see text][Formula: see text]M. The practicability of the developed Cr(VI) sensor for real water sample assay was also validated with satisfactory recoveries.

Targeted brain hypothermia has the potential to prevent cerebral ischemia injury during open heart and neck surgeries or after traumatic head injury. In this study, in vivo experiments were performed to test the performance of a newly developed cooling device in an inexpensive animal model. Rat brain hypothermia was induced by inserting an interstitial cooling device in the rat neck muscle and placing the device on the common carotid artery to cool the arterial blood supplied to the brain. Coolant was circulating inside the cooling device to achieve either mild or moderate temperature reductions at the surface of the device. Temperatures were measured inside the rat brain tissue, as well as on the head skin surface. For the mild cooling (cooling device surface temperature was 18.7 ± 4.5 °C), the temperature reductions were 2.2 ± 0.6 °C, 2.1 ± 0.6 °C, 1.9 ± 0.6 °C and 1.6 ± 0.9 °C at sites of brain-5 mm, brain-2 mm, skull, and scalp, respectively. After the surface temperature was further decreased to 12.8 ± 2.8 °C (moderate cooling), the temperature reduction in the head increased more than 85% to 3.7 ± 3.2 °C, 3.7 ± 3.0 °C, 3.3 ± 2.5 °C and 2.5 ± 1.0 °C, respectively. The experimental data were also used to validate a previously developed theoretical model for humans. Experimentally measured geometrical and physiological parameters of the rat neck and brain were substituted into the scaled-down theoretical model to simulate the temperature distribution in the rat neck and brain. The theoretically predicted brain temperatures showed a good agreement with the experiment data. We believe that this study is the first step in developing a reliable cooling device to achieve fast cooling and to control rewarming in future clinical studies and to benefit a large patient population.

Purpose: Evidence suggests that the majority of colorectal carcinomas arise from adenomas, and l-arginine suppresses colorectal tumorigenesis. We suppose that l-arginine may inhibit the process of carcinogenesis from colorectal adenoma to adenocarcinoma. The aim of this study was to investigate the effects of l-arginine on the formation and development of colorectal tumors. Experimental Design: We selected 60 patients with colorectal cancer and 60 patients with colorectal adenoma (CRA) and divided them into four groups of 30 patients each. We gave 30 g (120 mL) of l-arginine everyday for 3 days to the test groups, whereas l-arginine was substituted by 5% glucose in the control groups. The expression of the proliferating cell nuclear antigen, survivin, and nitric oxide synthase was examined immunohistochemically, and ornithine decarboxylase (ODC) activity was examined spectrophotometrically. Serum nitric oxide (NO) was detected by the Griess assay. Results: In patients with CRA, the proliferating cell nuclear antigen and survivin labeling indexes and ODC activity of the tumor and paratumor mucosa in the l-arginine–treated group after l-arginine treatment were significantly lower as compared with the corresponding pretreatment values (P < 0.01). Moreover, inducible nitric oxide synthase expression in the tumor markedly increased after l-arginine treatment (P < 0.05). Serum NO levels in the patients with colorectal cancer were markedly higher than those in the patients with CRA, and l-arginine treatment was responsible for this increase (P < 0.05). Conclusions: Our results show that l-arginine can restrain crypt cell hyperproliferation and the expression of survivin, an inhibitor of apoptosis protein. This suggests that l-arginine can block the formation and development of colorectal tumors, and this effect might be related to the increased serum NO concentration and decreased ODC activity.

This paper deals with the problem of robust state estimation for a class of switched linear systems with unknown inputs under average dwell time (ADT) switching, where the switching of the observers is synchronous with that of the estimated system. First, based on the feasibility of an optimization problem with linear matrix inequality (LMI) constraint, a robust sliding-mode switched observer is developed such that the asymptotic state reconstruction is guaranteed even if the switched system is with unknown inputs. Second, a reduced-order switched system which avoids the influence of unknown inputs is constructed by the technique of state transformation, and a reduced-order switched observer is proposed to estimate the continuous states of the original switched system. Next, the conditions under which a full-order switched observer exists also guarantee the existence of a reduced-order switched observer. The convergence of the state estimate is proved to be exponential by appropriate Lyapunov analysis. Finally, the simulation results confirm the predicted performance and applicability by a simplified three-tank system.

The refractive index sensitivity of long period fiber grating is analyzed by new transfer matrix method. Compared to traditional transfer matrix method, The new transfer matrix method can be used to analyze the modes coupling between the core mode and multiple cladding modes through only one time calculation. Compared with the previous method used, such as solving the coupled mode equation by the fourth order adaptive step size Runge-Kutta algorithm, the new transfer matrix method has a faster calculation speed. Theoretical results are excellent agreement with the method of solving the coupled mode equation.

A new transfer matrix method for long-period fiber gratings with coupled multiple cladding modes is proposed and numerically characterized. The transmission spectra of uniform and non-uniform longperiod fiber gratings are numerically characterized. The theoretical results excellently agree with the experimental measurements. Compared with commonly used methods, such as using the fourth-order adaptive step size control of the Runge-Kutta algorithm in solving the coupled mode equation, the new transfer matrix method exhibits a faster calculation speed.

Alpha fetoprotein (AFP) is an oncoembryonal protein that is highly expressed in the majority of hepatocellular carcinomas. Previous studies have shown that AFP may be involved in multiple cell growth regulating, differentiating, and immunosuppressive activities. We investigated the effects of AFP gene silencing by siRNA on apoptosis and proliferation of hepatocellular carcinoma cell line EGHC-9901, which highly expresses AFP and may serve as an ideal model for investigation of AFP functions. siRNA expressing plasmid targeting the AFP gene was first established and subsequently transfected into hepatocellular carcinoma cell line EGHC-9901; cells were then divided into three groups: siRNA-afp, transfected with AFP-siRNA; siRNA-beta-actin, transfected with siRNA-beta-actin as the positive group; and vector control, transfected with empty vector as the blank control group. After G418 positive clone selection for a couple of weeks, Western blot and RT (reverse transcription)-PCR assay demonstrated that AFP expression was almost completely inhibited by siRNA-afp, which indicates that siRNA expressing plasmid targeting the AFP gene has been successfully established. Furthermore, MTT (methyl thiazolyl tetrazelium) assay showed that cells transfected with siRNA-afp proliferated at a significantly lower speed than the other two groups and flat plate clone formation assay also witnessed less clones with diameters of more than 75 μm in siRNA-afp immunofluorescence indicating that the apoptosis rate of cells transfected with siRNA-afp was significantly higher than the other two groups. Furthermore, flow cytometry manifested approximately 20% more cells of siRNA-afp within G1 phase than those of the negative group, indicating that inhibition of AFP expression may cause G1 phase arrest. Finally, Western blot and RT-PCR assay demonstrated that siRNA-afp induced a higher expression of caspase-3 than the other two groups whereas there was no difference in expression of caspase-8, caspase-9, and Bcl-2 between the three groups.

A new CAD software for the sensitivity properties of fiber gratings is reported, which takes the three-layers uniform wave guide as grating guide model. This software uses the transfer matrix method and the coupling mode equation to calculate the spectrum of Bragg grating and long period grating. Based on the Visual C++, the sensitivity properties about temperature, tension, refractive and other sensing quantity of grating can be analyzed. The software is useful for the optimal design of the sensitivity about fiber grating parameters.

To study the tracking problem for the uncertain nonlinear systems, a scheme, namely an improved indirect adaptive dynamic surface control, is proposed. The program used integral Lyapunov function can avoid the controller singularity, canceled the derivative of virtual input, and induced nonlinearity item which can make better use of nonlinear information to improve the performance of loop transition completely. The method is of characteristic with little calculation for unknown parameters to identify untidily. Finally theory is proved that the closed system is stable.

This paper focuses on the two aspects that are the analysis of the cable leakage capacitance and harmonic current amplified from the point where there is harmonic current heavily existing in the power cable transmission system. Firstly, the main parameters in the cable harmonic impedance model are estimated. Secondly, the equivalent circuit based on the cable power supplying is established as well as parameters included in the equivalent circuit are estimated. Finally, the harmonic leakage current is simulated by Matlab based on harmonic current and leakage capacitance. Results show that harmonic current through the cable leakage capacitor is amplified with the coincidence cases. It will cause the cable insulation medium theat and burning due to high harmonic current. It would provide a novel way to find the reason of the cable burning by suing analytical methods and results described in this paper.

The temperature sensitivity of long period fiber grating is analyzed by new transfer matrix method. The new transfer matrix method can analyze the modes coupled between the core mode and multiple cladding modes. Compared to the usual method used, such as solving the coupled mode equation by the fourth order adaptive step size Runge–Kutta algorithm, the new transfer matrix method has a faster calculation speed. The theoretical results are exactly in agreement with the method of solving the coupled mode equation.

The sensor sensitivity, such as axial strain sensitivity, temperature sensitivity and refractive index sensitivity, of long period fiber grating is analyzed by new transfer matrix method. The new transfer matrix method can be used to analyze the modes coupling between the core mode and multiple cladding modes. Compared with the previous method used, such as solving the coupled mode equation by the fourth order adaptive step size Runge-Kutta algorithm, the new transfer matrix method has a faster calculation speed. Theoretical results are excellent agreement with the method of solving the coupled mode equation.

CdWO4 polymorphs are solvothermally synthesized from mixtures of Cd2Cl2 and Na2WO4 using water as solvent to prepare monoclinic CdWO4, and propylene glycol for tetragonal CdWO4 (autoclave, 200 °C, 10 h).

A dynamic surface controller (DSC) is designed for a class of MIMO nonlinear systems. Firstly, the nonlinear system is transformed into a new system, which is viewed as a Parallel system composed of nominal system and its disturb system in induced by coupling, secondly, DSC are designed according to each system in ordered to synthesize the expectation control law, finally, ultimate control law is induced by the principle of least squares and Taylor series. Theoretical analysis gives the whole system stability.

In this study, the feasibility of a newly developed interstitial cooling device inserted into the neck muscle and placed on the surface of the common carotid artery is evaluated. A combination of vascular model and continuum model is developed to simulate the temperature fields in both the neck and brain regions. Parametric studies are conducted to test the sensitivity of various factors on the temperature distribution. It has been shown that the length of the device, temperature of the device, and the tissue gap between the device and the blood vessel are the dominant factors that determine the effectiveness of this cooling approach. Under the current design parameters, the device is capable of inducing a temperature drop of 2.8 degrees C along the common carotid artery and it results in a total of 90 W of heat carried away from the arterial blood. Although the degree of the cooling in the arterial blood is inversely proportional to the blood flow rate of the arteries, the total heat loss from the arterial blood does not vary significantly if the blood flow rate changes during the cooling. After the cold arterial blood is supplied to the brain hemisphere, temperature reduction in the brain tissue is almost uniform and up to 3.1 degrees C temperature drop is achieved within 1 hour. In addition to the possible benefits of brain hypothermia for stroke or head injury patients, the device has the potential to control fever as well as to improve patients' outcome during open neck and head surgery.

Understanding of formation mechanism of inorganic solids by solution chemistry is always disturbed by the interference effect of the impurities from starting materials. Herein, we exploited a new two-step route to the selective synthesis of BiPO4 of different polymorphs with an aim to eliminate the impurity interference effect. The first step is the room-temperature solution synthesis of a hexagonal phase (HP), and the second step involves sufficient washing of HP and a subsequent hydrothermal treatment of HP under given conditions. The formation mechanism of BiPO4 nanocrystals of different polymorphs was studied by monitoring the reaction parameters like pH, reaction temperature, time, and impurity ions as well as by sample characterizations using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. It is found that the pH of the solution is the determinant parameter for the selective synthesis of BiPO4 polymorphs. Namely, at 240 °C and under strong acidic conditions (pH 750 °C. Based on these observations, two kinds of phase transition mechanisms were discussed.

Developing new approaches to polymorphic control is significantly important for function and property design of inorganic materials. In this paper, we proposed a novel solvothermal (hydrothermal) approach for polymorphic control of CdWO4 nanocrystals. By tuning the synthetic parameters such as solvent, reaction temperature, and reaction time, both phase structure and crystallite size of CdWO4 nanocrystals were effectively controlled. As a result, two different crystalline phases of CdWO4 in monoclinic and tetragonal structures were successfully obtained. The photocatalytic performances of CdWO4 polymorphs were investigated by both degradation of MO under UV light irradiation and water splitting under visible light, which clearly demonstrates that the monoclinic structured CdWO4 nanocrystals exhibited a catalytic activity higher than that of tetragonal structured counterpart.

High purity SbPO4 hollow spheres assembled by nanoparticles were successfully fabricated by a template-free solvothermal reaction in a mixed solvent of water, ethanol, and oleic acid. The synthetic conditions for the hollow sphere SbPO4 were monitored by a series of time-resolved experiments and further optimized by adjusting the solvent ratio and pH value in the reaction system. Based on XRD and SEM characterization, it is interesting to reveal a phase conversion process from Sb4O5Cl2 to SbPO4 as well as morphology evolution. The phase and morphology transition mechanism was discussed from the chemical equilibrium perspective. Size distributions of Sb4O5Cl2 and SbPO4 samples were in a narrow range of 7 to 13 μm. The Sb4O5Cl2 spheres were constructed in situ by nanosheets, which act as self-sacrificed templates for the SbPO4 hollow spheres. Room-temperature alternative current impedance measurements indicate that the permittivity for the SbPO4 hollow spheres is as high as 130 at 40 Hz, which obviously originates from the interfacial effects with numerous carriers blocked. The synthetic methodology reported in this work can be applied to a broad class of assembled nanostructures for optimization of dielectric performance.