Improvement of tea leaves fermentation with Aspergillus spp. pectinase

The pectinase enzymes isolated from Aspergillus spp., A. indicus, A. flavus and A. niveus were used for fermentation of tea leaves. The enzymes were purified and characterized. The effect of both crude enzyme preparation and purified pectinase enzymes on the improvement of tea leaf fermentation were determined in terms of theaflavin, thearubigin, high polymerized substances, total liquor colour, dry matter content and total soluble solids of the tea produced. The crude enzyme preparations obtained from ethanol precipitation were found to be more effective in improving tea leaf fermentation than the purified pectinase enzymes.     

Long‐term impact of nitrogen and potassium fertilizers on yield,soil nutrients and biochemical parameters of tea

A field experiment was conducted with tea cultivar UPASI‐9 over a period of 9 years to evaluate the long‐term effects of nitrogen (N) and potassium (K) fertilizers on yield, biochemical parameters, soil and leaf nutrient status. The yield increase was as high as 66% over the control for N application of 450 kg ha^?1 year^?1. Polyphenol and amino acid contents increased with increase in K application rate. Positive and significant correlation was found between nitrate reductase activity and the amino acid content of the tea shoots. While ammoniacal nitrogen in the soil was not affected by the application of fertilizer, ammonium acetate extractable K increased. The failure to apply fertilizer resulted in depletion of the organic matter status of the soil. Although increased rate of nitrogen application increased the overall yield of made tea (kg ha^?1 year^?1), the specific yield (kg kg^?1 N) declined. The soil tended to become acidic from frequent application of high doses of nitrogenous fertilizer. The leaf NK status was significantly influenced by the various treatments. Copyright © 2004 Society of Chemical Industry     

Characterization of palladium supported on sulfated zirconia catalysts by DRIFTS, XAS and n-butane isomerization reaction in the presence of hydrogen

Palladium supported on sulfated zirconia (PdSZ) has been characterized by the n-butane isomerization reaction in the presence of hydrogen, X-ray absorption spectroscopy (XAS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) of adsorbed carbon monoxide. Catalyst calcination at 873 K followed by hydrogen reduction at 513 K results in the formation of 30–40 Å Pd metal clusters, but the surface can only weakly adsorb CO, though stronger than Pd-free, sulfated zirconia catalysts. In the presence of hydrogen, PdSZ has a lower n-butane isomerization activity than SZ, and the Pd function cannot stabilize the reaction at low H₂/n-butane ratios.     

Structural and electrical properties of (Bi0.9Dy0.1)(Fe0.975TM0.025)O3±δ (TM=Ni,Cr and Ti) thin films

Pure BiFeO₃ and rare earth and transition metal ions co-doped (Bi_0.9Dy_0.1)(Fe_0.975TM_0.025)O_3±δ (TM=Ni²⁺, Cr³⁺ and Ti⁴⁺) thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. The changes in the microstructure and the electrical properties with doping elements were investigated. The thin films were well crystallized and randomly oriented, with no detectable impurity and secondary phases. The leakage current densities were reduced and the ferroelectric properties were improved in the co-doped thin films. Among the thin films, the (Bi_0.9Dy_0.1)(Fe_0.975Cr_0.025)O₃ thin film exhibited well saturated hysteresis loops with remnant polarization (2P_r) of 36 μC/cm² and coercive electric field (2E_c) of 954 kV/cm at 1000 kV/cm and low leakage current density of 1.91×10⁻⁵ A/cm² at 100 kV/cm. The enhanced properties observed in the co-doped thin films could be considered as being the result of the suppression of oxygen vacancies and of the modified microstructure.     

Ta2O5/Nb2O5 and Y2O3 Co-doped Zirconias for Thermal Barrier Coatings

Zirconia doped with 3.2–4.2 mol% (6–8 wt%) yttria (3–4YSZ) is currently the material of choice for thermal barrier coating topcoats. The present study examines the ZrO₂-Y₂O₃-Ta₂O₅/Nb₂O₅ systems for potential alternative chemistries that would overcome the limitations of the 3–4YSZ. A rationale for choosing specific compositions based on the effect of defect chemistry on the thermal conductivity and phase stability in zirconia-based systems is presented. The results show that it is possible to produce stable (for up to 200 h at 1000°–1500°C), single (tetragonal) or dual (tetragonal + cubic) phase chemistries that have thermal conductivity that is as low (1.8–2.8W/m K) as the 3–4YSZ, a wide range of elastic moduli (150–232 GPa), and a similar mean coefficient of thermal expansion at 1000°C. The chemistries can be plasma sprayed without change in composition or deleterious effects to phase stability. Preliminary burner rig testing results on one of the compositions are also presented.     

Superhigh selective capture of volatile organic compounds exploiting cigarette butts-derived engineering carbonaceous adsorbent

Herein, we develop cost-efficient superhigh-performance of engineering carbonaceous adsorbent from cigarette butts using combined wet-impregnated and re-dispersed method of KOH, which optimizes the implant approach of activator, breaking the restriction of selective capture of toluene using traditional activated carbon. The Brunauer-Emmett-Teller (BET) surface area and pore volume of targeted adsorbent can attain 3088 m²·g^-1 and 1.61 cm³·g^-1, respectively, by optimizing the temperature-dependent synthetic factor effect of the adsorbent. The adsorption capacity of resultant adsorbent for presenting volatile benzene and toluene shows a positive correlation with increasing carbonization temperature of carbon precursor. Besides, we demonstrated the unsmoked and smoked butts derived adsorbents afford feeble difference in saturated adsorbed capacity of volatile organic compounds (VOCs). The highest adsorption capacity of sample CF-800 for benzene and toluene in CF group is as high as 1268.1 and 1181.6 mg·g^-1 respectively, slightly higher than that of sample UF-800, but far outperforming reported other adsorbents. The predicted adsorption selectivity of CF-800 and UF-800 for C₇H₈/H₂O (g) using the DIH (difference of isosteric heats) equation reach up to ca. 3800 and 7500 respectively, indicating the weak adsorbability of water vapor on the developed adsorbent and greater superiority of the smoked butts derived adsorbents in selective capture of VOCs at low relative humidity in the competitive adsorption process for practical mixed VOCs.     

Pinecone biomass-derived activated carbon: the potential electrode material for the development of symmetric and asymmetric supercapacitors

Activated carbon, from biomass (pinecone), was synthesized by conventional pyrolysis/chemical activation process and utilized for the fabrication of supercapacitor electrodes. The pinecone-activated carbon synthesized with 1:4 ratio of KOH (PAC4) showed an increase in surface area and pore density with a considerable amount of oxygen functionalities on the surface. Moreover, PAC4, as supercapacitor electrode, exhibited excellent electrochemical performances with specific capacitance value ∼185 Fg⁻¹ in 1 M H₂SO₄, which is higher than that of nonactivated pinecone carbon and 1:2 ratio KOH-based activated carbon (PAC2) (∼144 Fg⁻¹). The systematic studies were performed to design various forms of devices (symmetric and asymmetric) to investigate the effect of device architecture and operating voltage on the performance and stability of the supercapacitors. The symmetric supercapacitor, designed utilizing PAC4 in H₂SO₄ electrolyte, exhibited a maximum device-specific capacitance of 43 Fg⁻¹ with comparable specific energy/power and excellent stability (∼96% after 10 000 cycles). Moreover, a symmetric supercapacitor was specially designed using PAC4, as a positive electrode, and PAC2, as a negative electrode, under their electrolytic ion affinity, and which operates in aqueous Na₂SO₄ electrolyte for a wide cell voltage (1.8 V) and showed excellent supercapacitance performances. Also, a device was assembled with poly(3,4-ethylene dioxythiophene) (PEDOT) nanostructure, as positive electrode, and PAC4, as a negative electrode, to evaluate the feasibility of designing a hybrid supercapacitor, using polymeric nanostructure, as an electrode material along with biomass-activated carbon electrode.     

Structural modification by different pretreatment methods to enhance microwave-assisted extraction of β-carotene from carrots

Since the structure of a material is a key factor influencing the extraction efficiency, any means to modify the structure to enhance extraction is attractive. As limited information is available on the effect of sample pretreatment prior to extraction on the extractability of a bioactive compound, the effects of selected pretreatment methods, i.e., soaking in citric acid, blanching in water as well as in citric acid, on the sample structure and subsequent microwave-assisted extraction (MAE) were investigated; carrots and β-carotene (as well as carotenoids) were selected as the test material and bioactive compound, respectively. A suitable condition to extract β-carotene in terms of the microwave power and extraction time was determined. Comparison between MAE and Soxhlet extraction was also made. At the optimized condition the contents of β-carotene and total carotenoids extractable from carrots blanched in water (29.74 and 58.04 mg/100 g dry basis) and in citric acid (32.08 and 61.62 mg/100 g dry basis) were significantly higher than those from the untreated carrots (23.26 and 51.79 mg/100 g dry basis). The antioxidant activities of the extracts obtained from carrots blanched in water and in citric acid were also higher than that from carrots with no pretreatment. Comparison between MAE and Soxhlet extraction revealed that the extract from MAE contained lower amounts of β-carotene and total carotenoids and exhibited lower antioxidant activity; the required MAE time was significantly shorter, however.     

Photocatalytic degradation of carbofuran using semiconductor oxides

The photocatalytic degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) was investigated in an aqueous solution using Degussa P-25 TiO2 and ZnO as photocatalysts. The progress of degradation was monitored using TOC analyzer, HPLC, GC-MS and UV-vis spectrophotometer. The effects of various experimental parameters such as initial concentration of carbofuran, pH of the solution, catalyst loading and light intensity were systematically studied in order to achieve maximum degradation efficiency. The complete mineralization of carbofuran was confirmed by TOC analyzer. The degradation with ZnO showed less efficiency than TiO2. The formation of NO(3)(-) was identified and quantified using HPLC. In addition, four different intermediates formed during the degradation process were also identified and characterized by GC-MS. The mineralization rate was compared with lamps of wavelength 254 and 365 nm under similar conditions. The rate with 254 nm was observed to be very close to that of 365 nm.     

GTD analysis of near-field and far-field patterns of a parabolic subreflector illuminated by a plane wave

A geometrical theory of diffraction (GTD) analysis of the principal plane far-field and near-field patterns of a near-field Cassegrainian subreflector is presented. The uniform geometrical theory of diffraction (UGTD) [1] that drastically reduces the computation time has been utilized to analyze the subreflector in the form of a paraboloid illuminated by a plane wave. The numerical computations of the far-field amplitude and phase patterns of a typical paraboloidal subreflector based on the above technique correlate well with the results obtained by physical optics current integration, justifying the validity of the analysis presented. The GTD near-field analysis presented here is an improvement over that published earlier [2] and removes some of its limitations.