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This study investigated indium tin oxide (ITO) films that were deposited on fluororesin-46 (F46) and polyimide (PI) transparent flexible substrates by a DC magnetron sputtering system. The optical properties of ITO films on F46 and PI including transmittance and reflectance in visible, near-infrared, and infrared spectral regions were obtained, and the surface morphology, and optical and electrical properties of ITO/F46 and ITO/PI after vacuum ultraviolet irradiation were investigated. The results showed that the mean transmittances of ITO/F46 and ITO/PI decreased and the sheet resistance increased after the irradiation, and these effects were mainly attributed to the greater surface roughness and crystal defects caused by the irradiation.

Two kinds of high absorber were designed based on sub-wavelength grating structure for aluminum substrate. The absorption and electric field distribution of these two structures were calculated by using the finite difference time domain method. One absorber was obtained by using Al2O3/SiO2 double layers and Al rectangular sub-wavelength layer which has high absorption peaks both in TE polarization and TM polarization in infrared spectrum. Another absorber was a single layer structure with a triangular sub-wavelength grating structure which had a broadband absorption in TE polarization at spectral range of 300-1000nm.Simulation results showed that the absorption of this absorber increase and then decreases with the increasing of the height of sub-wavelength grating. The average absorption reached the maximum when the height of grating was 800nm.

This study was designed to explore the effect and mechanism of miR-206/miR-613 on the expression of OATP1B1 gene. Bioinformatic analysis was used to predict the potential miRNAs target sites in 3’-untranslated region (3’-UTR) of OATP1B1 mRNA. The expression level of miR-206/miR-613 and OATP1B1 mRNA and protein was determined with RT-qPCR and Western blot, respectively. Luciferase assay was used to explore the exact mechanism of the effect of miR-206/miR-613 on the expression of OATP1B1 mRNA and protein. The results showed that the seed sequences of miR-206/miR-613 has perfect complementary with 3’-UTR of OATP1B1 mRNA in terms of sequence specificity. The secondary structure between miR-206/ miR-613 and 3’-UTR of OATP1B1 mRNA was rather stable. The OATP1B1 protein level was down-regulated by 24.7%, 38.8% by overexpression of miR-206/miR-613. The expression was up-regulated by 25%, 38.2% by inhibition of miR-206/miR-613. However, overexpression or inhibition of miR-206/miR-613 had no effect on the expression of OATP1B1 mRNA. The luciferase activity of p MIR/OATP1B1-WT luciferase reporter gene was decreased by 35% and 30% through overexpression of miR-206/miR-613. The expression was increased by 33.1% and 32.5% through inhibition of miR-206/miR-613. When the binding sites in the 3’-UTR of OATP1B1 mRNA complementary with miR-206/miR-613 was mutated, overexpression or inhibition of miR-206/miR-613 had no effect on the luciferase activity. Collectively, miR-206/miR-613 post-transcriptionally regulates the expression of OATP1B1 protein by directly targeting the 3’-UTR of OATP1B1 mRNA.

Using H2 and Al (CH3)3(TMA) as precursor, we investigated the atomic layer deposition mechanism of the metal Al on Si (100) surface by density functional theory. The reaction process comprises two half-reaction depositions: TMA "half-reaction" includes I and II on the H blunt reaction surface; H2 "half-reaction" includes the subsequent reaction Ⅲ and Ⅳ. In the TMA half reaction process, trimethyl aluminum first molecularly adsorbed in the active site of H*-Si9H12-H* to form a stable complex in the form of chemical adsorption state. Potential curves show that at 298 K, adsorption energy is -2.26kJ/mol, with respect to the chemical adsorption state, the activation barrier energy is 124.72kJ/mol, and finally the whole exothermic reaction energy is 41.4kJ/mol. After H2 half reaction, the bond length between Al-Si can be considered equal; two Al-C bonds become relatively stable molecular structure. The adsorption energy is -0.10kJ/mol at 298 K, and the activation barrier energy 189.15kJ/mol. The results show that two half-reaction process mechanism is similar, TMA endothermic reaction needs more energy to be carried out under heating conditions ; endothermic and exothermic reaction energy is basic balance, the activation energy is large, so the reaction is the best using ionized gas to be carried out.

Lignin was obtained from black liquor of papermaking by the acid to separation, and carbonized after loading various amounts of nickel and calcium or nickel alone. The influences of the temperature, amount of nickel and amount of calcium on the crystallized size (Lc) and the electromagnetic shielding (EMS) capacities in the range of 50~800 MHz for the chars from lignin were investigated. The results showed that Lc and EMS capacities in the entire of frequency of the chars with 6wt% calcium increased with increasing amount of the nickel loaded and also increased with increasing carbonization temperature from 700 to 900°C. Some amounts of calcium significantly enhanced the formation of crystallized carbon. Lc and EMS capacities of the chars with loaded 8wt% nickel increased with increasing amount of calcium and then decreased. It was founded that chars of lignin with co-loading of 8wt% nickel and 6wt% calcium were suitable as EMS materials with exceeding a practical standard of EMS capacity (30dB) in the range of 50~800 MHz.

The study was designed to explore the drug-drug interactions mechanisms mediated by OATP1B1 between traditional Chinese medicine Danshensu and rosuvastatin. First, the changes of rosuvastatin pharmacokinetics were investigated in presence of Danshensu in rats. Then, the primary rat hepatocytes model was established to explore the effects of Danshensu on the uptake of rosuvastatin by hepatocytes. Finally, HEK293T cells with overexpression of OATP1B1*a and OATP1B1*5 were established using a lentiviral delivery system to explore the effects of Danshensu on the uptake of rosuvastatin. Rosuvastatin pharmacokinetic parameters of C(max0, AUCO(0-t), AUC(0-∞) were increased about 123%, 194% and 195%, by Danshensu in rats, while the CL z/F value was decreased by 60%. Uptake of rosuvastatin in the primary rat hepatocytes was decreased by 3.13%, 41.15% and 74.62%, respectively in the presence of 20, 40 and 80 μmol x L(-1) Danshensu. The IC50 parameters was (53.04 ± 2.43) μmol x L(-1). The inhibitory effect of Danshensu on OATP1B1 mediated transport of rosuvastatin was related to the OATP1B1 gene type. In OATP1B1*5-HEK293T mutant cells, transport of rosuvastatin were reduced by (39.11 ± 4.94)% and (63.61 ± 3.94)%, respectively, by Danshensu at 1 and 10 μmol x L(-1). While transport of rosuvastatin was reduced by (8.22 ± 2.40)% and (11.56 ± 3.04)% and in OATP1B1*1a cells, respectively. Danshensu significantly altered the pharmacokinetics of rosuvastatin in rats, which was related to competitive inhibition of transport by OATPJBI. Danshensu exhibited a significant activity in the inhibition of rosuvastatin transport by OATP1B1*5-HEK293T, but not by OATP1B1*1a, suggesting a dependence on OATP1B1 sequence.

In this paper, feasibility of aluminium deposition on inner wall of pipes by atomic layer deposition was studied. Firstly, by solving kinetics equation of gas adsorption on the pipe inner wall, the time for the reactant to reach saturated adsorption on the wall was calculated. Secondly, according to the aluminium crystal structure, the thickness of each deposition cycle was obtained. Finally, the minimum aluminium thickness and number of atomic layer deposition cycles that can meet electromagnetic requirement of wave guide was calculated.

The dual-step dual-team holographic method to fabricate square lattices is proposed. The effect of intensity threshold was analyzed by calculating the intensity spatial distribution. The photonic band gap properties of two-dimensional square lattice fabricated by holographic lithography are investigated numerically. The influences of intensity threshold and dielectric contrast on photonic gap are comprehensively studied by plane wave expansion method. Calculations of band structure as a function of the intensity threshold show that the full photonic band gap does not increase monotonically with dielectric contrast ratio, but has a peak value instead by studying the relation between the complete PBG and the dielectric contrast.

The effect of intensity threshold on the filling ratio was analyzed by calculating the intensity spatial distribution. The photonic band gap properties of two-dimensional triangular lattice fabricated by holographic lithography are investigated numerically. The influences of intensity threshold and dielectric contrast, on photonic gap are comprehensively studied by plane wave expansion method. Calculations of band structure as a function of the intensity threshold show that the PBG of positive structure opens for TM and TE polarization separate, and the negative structure has the complete PBG. The complete PBG does not increase monotonically with dielectric contrast ratio, but has a peak value instead by studying the relation between the complete PBG and the dielectric contrast ratio. The optimal dielectric contrast is 22 when intensity threshold is 0.2.

TiO2 films were fabricated on Si substrate by using electron-beam gun evaporation. Influence of deposition rate, deposition temperature and ion beam bombarding on stress in TiO2 films was studied by AFM and XRD. The results show that deposition temperature of 423K and deposition rate of 0.2nm/s, the average stress in titanium oxide thin films is less than 48.2MPa. The average stress decreases to compressive stress of 16.7MPa from tensile stress of 72.9MPa by the ion beam energy of 113eV and bombarding time of 300s. The microstructure change of TiO2 films is main factors of stress development.

A reflective electrochromic device is fabricated on a 10 cm×10 cm flexible PI/Al substrate using magnetron sputtering. The device has a complementary all-thin-film structure and consists of seven layers. Indium tin oxide (ITO) acts as a transparent electrode deposited on the top, meanwhile, an aluminum (Al) film is adopted as an inter-counter bottom electrode and provides high reflectance. Tungsten oxide (WO 3 ) is used as the main electrochromic layer and nickel oxide (NiO) acts as the complementary electrochromic layer. Lithium niobate (LiNbO 3 ) is applied as a Li+ ion conductor layer. Especially, in the seven-layer structure, two tantalum oxides (Ta 2 O 5 ) are added as transition layers to prevent Li+ escaping from LiNbO 3 when the potential is not applied on the device. When the device is in an electrochromic process, both Ta 2 O 5 provide excellent conductivity for Li + ions and act as the dielectric of electrons. The complementary device with structure Al/NiO/Ta 2 O 5 /LiNbO 3 /Ta 2 O 5 /WO 3 /ITO exhibits good optical properties, and the reflectance modulation reaches up to 55% measured by a spectrophotometer in the range of 400–1600 nm. The cyclic stability of the electrochromic device is investigated. The results indicate that the charge density involved in the electrochromic process decreases and the electrochromic response time increases with the cycle number because of the Li + insertion in WO 3.

In the paper, ion-assisted e-beam evaporation (IAEE) method was used to deposit SiO2 film on CBA(CaO-Al2O3-BaO) glass substrate, and the influence of processing parameters on the performance of the thin films was studied. The result shows that the ion energy, substrate temperature and evaporating rate are key factors that affect the abrasion resistance and transmission of the SiO2 film. Heat treatment was used to eliminate the absorption of H2O in spectrum range of 2.7~3.5μm. SiO2 film with good abrasion resistance and high transmission in spectrum range 3.0~5.0μm was deposited successfully on the special glass substrate.

Liquid chromatography–electrospray ionization mass spectrometry has been used for rapid, selective, and sensitive quantitative analysis of mitiglinide in human plasma. Sample pretreatment involved solid-phase extraction from plasma with gliclazide as internal standard. Separation was performed on a C18 column (150 × 2.0 mm) with 71:29 (v/v) acetonitrile–water (containing 0.1% formic acid and 0.2 mmol L−1 ammonium acetate) as mobile phase at a flow rate of 0.2 mL min−1. The method was validated then successfully applied to a clinical bioequivalence study of mitiglinide in 20 healthy volunteers after oral administration.

Highly ordered arrays consisting uniform fluorescent cadmium selenide ( CdSe ) quantum dots (QDs) ring or dot structures were obtained by self-assembly of QDs on chemically patterned substrates. In this method, Au substrates with alternating hydrophobic and hydrophilic square patterns are firstly fabricated by microcontact printing, which allows water droplets to condense on the hydrophilic regions to provide two-dimensional template arrays. The CdSe QDs are then assembled at the liquid/liquid interfaces to give uniform micro or nanostructures. The shape and size of the rings and dots can be tailored by controlling the relative evaporation speed of the water and the organic solvents. The obtained nanostructures have ideal topography to avoid substrate-induced fluorescence quenching.

The adsorption of cytosine on graphene surface is studied using density functional theory with local density approximation. The cytosine is physisorbed onto graphene through π–π interaction, with a binding energy around -0.39 eV. Due to the weak interaction, the electronic properties of graphene show little change upon adsorption. The cytosine/graphene interaction can be strongly enhanced by introducing metal atoms. The binding energies increase to -0.60 and -2.31 eV in the presence of Li and Co atoms, respectively. The transport behavior of an electric sensor based on Co -doped graphene shows a sensitivity one order of magnitude higher than that of a similar device using pristine graphene. This work reveals that the sensitivity of graphene-based bio-sensors could be drastically improved by introducing appropriate metal atoms.

We report herein a simple method for attaching vinyl groups onto the sidewalls of carbon nanotubes (CNTs) and the application of vinyl-carbon nanotubes (CNT-C=C) in fabricating polymer composites. The synthesis of CNT-C=C was monitored with IR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The obtained CNT-C=C showed good compatibility with the in situ polymerization of poly(methyl methacrylate) (PMMA) and exhibited no tendency for phase separation in the final composite. A transmission electron microscopy study revealed a uniform coating on the CNT-C=C tubes, indicating good grafting efficiency of PMMA. The uniform dielectric PMMA coating was responsible for the lower electrical conductivity of the CNT-C=C/PMMA composites versus that of the CNTs without vinyl modification. (C) 2008 Wiley Periodicals, Inc.

With high diffractive efficiency, Continuous Relief Diffractive Optical Elements (CR-DOE) can be used to eliminate chromatic aberration, partial aberration and simplify optical system. The technology for CR-DOE with Laser Direct Writing method has advantages of simple process, short period and low cost. The paper studied on the characterization method of laser power for the technology. The principle of mask fabrication of CR-DOE by Laser Direct Writing is described in the paper. The relations between microstructure depth and laser power, exposing position radius and laser power were studied. The results showed that microstructure depth changes in direct ratio to laser power and laser power should change in direct to exposing position radius while several same depth microstructures were fabricated at different radius. At the end, the paper gave the charactering method and also fabricated the mask of a kind of centrosymmetric continuous relief diffractive focus lens with the method.

Rupatadine (RUP) is an oral antihistamine and platelet-activating factor antagonist and is shown as the substrate of CYP3A5 and P-gp. The significant interindividual differences of CYP3A5 and P-gp often cause bioavailability differences of some clinical drugs. The present study is aimed to evaluate the effect of genetic polymorphisms of CYP3A5 and MDR1 on RUP pharmacokinetics in healthy male Chinese volunteer subjects. Blood samples were collected from 36 subjects before and after a single, oral RUP 10 mg dose. A PCR–RFLP assay was used to genotype CYP3A5*3 and assess MDR1 C3435T variation. A validated LC–MS/MS method quantified plasma RUP concentration. The relationship between RUP plasma concentration, pharmacokinetic parameters, and polymorphic alleles (CYP3A5 and MDR1) were assessed. Plasma RUP concentrations were lower for CYP3A5*1/*1 carriers than for CYP3A5*3/*3 and CYP3A5*1/*3 carriers. Mean C max, AUC(0–t) and AUC(0–∞) were significantly lower, and the CLz and Vd were significantly higher in the CYP3A5 wild-type group, than in the CYP3A5 mutated group. MDR1 CT and MDR1 TT carriers had lower plasma RUP concentrations than MDR1 CC carriers. The mean C max, AUC0–t, AUC0–∞ and T max were significantly lower in the TT group than in the CC and CT groups. The mean CLz was higher in the TT group than in the CC and CT groups, but not significantly. These results suggest that CYP3A5 and MDR1 may play a key role in the variability of RUP metabolism and transport, respectively. CYP3A5 and MDR1 polymorphisms may be the main explanation for the differences observed in RUP pharmacokinetics, and therefore may provide a rationale for safe and effective clinical use of RUP. Our research lays down a solid theory foundation to guide the safe and effective clinical use of RUP and a route to achieve individualized therapy.

This study is to report the effect of OATP1B1 gene mutation in the 521T --C in Chinese human on the pharmacokinetics of rosuvastatin and guide the reasonable clinical application of rosuvastatin by the feature of genetic polymorphism of OATP1B1. Plasma samples were determined with LC-MS: the analyte and internal standard pitavastatin were both analyzed by MS in the ESI, m/z was 480.0 for rosuvastatin and 420.0 for the IS, separately. Genotyping of OATP1B1 was determined with the method of polymerase chain reaction--amplification refractory mutation system targeted at 40 healthy volunteers and showed that there were 7 subjects with 521T --C mutant, accounting to 17.5% of total and wild type homozygote accounted to 82.5%. It was found that there were significant differences between OATP1B1 mutation in the 521T --C and wild type homozygote for rosuvastatin pharmacokinetic process in Chinese human. In contrast to OATP1B1 wild type group, OATP1B1 mutation group's absorption degree increased, elimination process decreased. The OATP1B1 mutation should be noted for guiding the reasonable application of rosuvastatin during its clinical use.

This study is to investigate the transportation of scutellarin in cell and live models and study on mechanism of absorption and transport of scutellarin in mouse liver. The concentration of scutellarin in plasma and liver from control and pretreated groups was determined by high performance liquid chromatography. The uptake of scutellarin was examined in control hepatocytes group, induced hepatocytes group and induced hepatocytes plus pravastatin group. Pravastatin can affect the pharmacokinetics of scutellarin in mouse: CL is decreased while AUC is increased. The scutellarin absorption of hepatocyte induced group was higher than that of control group, but was decreased in the group with pravastatin added. The research showed that there was potential drug interaction between pravastatin and scutellarin. The drugs may compete for oatp2 mediated transport pathway consisted in the uptake of scutellarin in liver.

A rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/ MS) method for quantification of pentoxyverine citrate in human plasma has been developed and applied for the bioequivalence and pharmacokinetics study. After extracted from plasma samples with ethyl acetate, analysis was performed in selected ion monitoring (SIM) mode with a positive electrospray ionization (ESI) interface with a mobile phase consisted of methanol and water (0.4% glacial acetic acid and 4 mmol x L(-1) ammonium acetate, 43 : 57, v/v). The linear concentration range of the calibration curves was 1.0-160.0 ng x mL(-1) for pentoxyverine citrate, inter- and intra-precision (RSD) was less than 12.5%, accuracy (RE) was in +/- 13.5% and absolute recovery was more than 80%. The method was proved simple, rapid, sensitive, specific and suitable for pharmacokinetic and bioequivalence study of Yufenweilin capsule containing pentoxyverine citrate.

The aim of this study was to explore potential herb–drug interaction between danshensu or ursolic acid and rosuvastatin. Compared to the control group given rosuvastatin alone, the concurrent use of danshensu (46 mg/kg) or ursolic acid (80 mg/kg) prior to the oral administration of rosuvastatin (100 mg/kg) increased the systemic exposure of rosuvastatin more than twofold. The plasma clearance of rosuvastatin was reduced to more than 57% in the presence of danshensu or ursolic acid. Rosuvastatin is minimally metabolized in the CYP2C9 isoenzyme pathway and to an even lesser extent in the CYP2C19 isoenzyme pathway. Rosuvastatin is a substrate of drug transporters such as human OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP. Therefore, the present results suggested that the potential drug interaction between danshensu or ursolic acid and rosuvastatin may be mediated by one or more transporters (OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP) and/or CYPs.

The metabolic character of tetramethylpyrazine (TMPz) in rat liver microsomes was studied in vitro and in vivo to identify which isoforms of cytochrome P450 were responsible for TMPz metabolism in rats, offer the theoretical foundation for the fact that it is rational to use medicine in clinic.Set up UV- HPLC method of TMPz, determine concentration of TMPz and its formation in rat plasma and liver microsomes incubation solution, analyze the correlation between TMPz's metabolic eliminate rate and each inducer. Erythromycin( ERY) N-demethylase activity of each sample in rat liver microsomes was measured using N-demethylation reaction of ERY as probe. The correlation between the rate of TMPz metabolite formation and the demethylase activity was analysed. After the SD rats who had been treated with inducer, inhibitor, or untreated, received administration of TMPz in vein, the plasma concentration of TMPz were determined by HPLC. Pharmacokinetic parameters of TMPz were computed and compared.The disppearing rate of TMPz in the incubation solutions of the rats liver microsomes, which treated with DEX, were markedly quicker than that of control group (P0. 01) , while no obvious difference between P-NF group or PB and control group was observed (P0. 05). The activity of ERY-N-demethylase in DEX-induced group was corespondingly enhanced, was much higer than that in control group. The correlation between the rate of TMPz metabolic product formation and the activity of N-demethylase was significant. After using Ket, the CYP3A inhibitor, the metabolism of TMPz could be significantly inhibited the metabolism of TMPz in rat liver microsomes. In vivo, CL( s) were larger than that of the control group,t,/2 were smaller than the control group in DEX group; By contrary, CL(s) was smaller than the control group,t1/2 was larger than the control group in Ket group.Results suggest that CYP3A plays a major role in TMPz metabolism in rats, TMPz lie in the possibility of Interaction among the medicines between TMPz and CYP3A inducers or inhibitors when they are used in clinic.

Gene duplication has been proposed as an accelerator of evolution. Ancient genome duplication events have been identified in diverse organisms, such as yeast, vertebrates, and Arabidopsis. Here, we have identified a whole genome duplication event (WGD) in the rice genome, which took place prior to the divergence of grasses about 70 million years ago (mya). A total of 117 duplicated blocks were detected, which are distributed on all 12 chromosomes and cover about 60% of the rice genome. About 20% genes on these duplicated segments are retained as duplicate pairs. In contrast, 60% of the transcription factor genes are retained as duplicates. The identification of a WGD in the ancestral grass genome will impact the study of grass genome evolution, and suggest that polyploidization and subsequent gene losses and chromosomal rearrangements have played an important role in the diversification of grasses.

To study the effect of neferine (Nef) on toxicodynamics of dichlorvos (DDVP) for inhibiting the rabbit cholinesterase (ChE) and search the relativity between in vivo and in vitro reactivating effect of Nef.Calorimetric method was used to determine the blood concentraiton of DDVP, and 3P97 software was used to calculate the parameters of toxicokinetics. Ellman's method was used to determine the ChE activity in plasma. The toxicodynamics curve in vivo and the concentration-effect curve in vitro were drawn to compare the effects of Nef on these two curves.In the rabbit poisoned by ig DDVP 12.5 mg/kg there was almost no effect of Nef on the toxicokinetics of DDVP. The slope of toxicodynamics curves for depressed ChE increased about 3 times after treatment with Nef 7.5 mg/kg and pyratoxime methylchloride (2-PAM Cl) 50 mg/kg, compared with the untreated group, there was a higher significant difference (P0.01). In vitro Nef shifted the cumulative concentration-effect curve of DDVP on ChE to the right and decreased the maximal inhibitory effect obviously. The shift tendency of concentration-effect curve for DDVP in vitro was similar to that of the curve in vivo, difference between their value b was not significant (P0.05).Nef reactivates the ChE depressed by DDVP. The experiment in vitro may be used as a preliminary index to observe the reactivation of ChE inhibited by anticholinesterases.

Metal aluminum (Al) thin films are prepared by 2450 MHz electron cyclotron resonance plasma-assisted atomic layer deposition on glass and p-Si substrates using trimethylaluminum as the precursor and hydrogen as the reductive gas. We focus our attention on the plasma source for the thin-film preparation and annealing of the as-deposited films relative to the surface square resistivity. The square resistivity of as-deposited Al films is greatly reduced after annealing and almost reaches the value of bulk metal. Through chemical and structural analysis, we conclude that the square resistivity is determined by neither the contaminant concentration nor the surface morphology, but by both the crystallinity and crystal size in this process.

The feasibility of employing azulene-like molecules as a new type of high performance substitution-free molecular rectifier has been explored using NEGF-DFT calculation. The electronic transport behaviors of metal-molecule-metal junctions consisting of various azulene-like dithiol molecules are investigated, which reveals that the azulene-like molecules exhibit high conductance and bias-dependent rectification effects. Among all the substitution-free azulene-like structures, cyclohepta[b]cyclopenta[g]naphthalene exhibits the highest rectification ratio, revealing that the all fused aromatic ring structure and an appropriate separation between the pentagon and heptagon rings are essential for achieving both high conductance and high rectification ratio. The rectification ratio can be increased by substituting the pentagon ring with electron-withdrawing group and/or the heptagon ring with electron donating groups. Further increase of the rectification ratio may also be obtained by lithium adsorption on the pentagon ring. This work reveals that azulene-like molecules may be used as a new class of highly conductive unimolecular rectifiers.