Xiqiang Zhao

A microwave reactor for characterization of pyrolyzed biomass

A microwave reactor (MWR) was designed to investigate microwave-induced pyrolysis of biomass. Condensation of tars on the quartz reactor and the pipelines was prevented by an electric heating device, and a temperature control function allowed determination of product characteristics at constant temperatures. Temperature had an important influence on microwave pyrolysis; the yields of gas products increased from 17.69 wt.% to 22.27 wt.% and the ratio of combustible gas to total gas products increased from 67.21 vol.% to 77.14 vol.% as the temperature increased from 400 °C to 600 °C. A large number of volatiles was released as temperature increased, resulting in an increase in the number of pores of the coke and a uniform pore structure was obtained. The specific surface area of coke increased from 0.89 m(2)/g (400 °C) to 9.81m(2)/g (600 °C) and the pore volume increased from 0.006 cm(3)/g (400 °C) to 0.012 cm(3)/g (600 °C), but the average pore size decreased from 282.16 nm (400 °C) to 46.64 nm (600 °C).

Molecular cloning and characterization of the cathepsin B-like proteinase from the cotton boll worm, Helicoverpa armigera

An enzyme purified from the ovaries of Helicoverpa armigera, as an active form with molecular mass of 30 kDa on SDS‐PAGE, was identified as a cysteine proteinase because it could be inhibited by E‐64, a specific inhibitor of cysteine proteinase, and required reducing conditions for activity. This enzyme was further identified as a cathepsin B‐like cysteine proteinase by partial amino acid sequencing. A cDNA encoding this proteinase was cloned from H. armigera, using degenerate primers and RACE techniques. Results of Northern blots indicated that the mRNA encoding the proteinase was transcribed in the ovaries, the fat bodies of female and male adults, pupae and in the larvae. No mRNA was detected from the larval epidermis or from the midgut. Hence, transcription of the cathepsin B‐like cysteine proteinase from H. armigera was tissue‐specific, but not gender‐ or developmental stage‐specific. However, proteolytic activities were only detected from ovaries, and adult female and male fat bodies. No activity was observed from pupal and larval fat bodies, from the larval epidermis or from the midgut. Only one form of mRNA of ≈ 1100 bases was detected, and in situ hybridization showed that the transcripts were distributed in the adult female fat bodies, follicular cells and the oocytes. Since the proteinase expressed in ovaries was able to degrade vitellin in vitro, it may be involved in the degradation of vitellin during embryonic development.

A cathepsin L-like proteinase is involved in moulting and metamorphosis in Helicoverpa armigera.

Holometabolous insects undergo larval moulting and metamorphosis within their life cycle. A cDNA encoding the cathepsin L‐like proteinase Ha‐cathL has been cloned from Helicoverpa armigera. It has a sequence of 1826 bp and encodes a 550‐residue protein with a molecular mass of 63 kDa. Northern blot analysis indicated that Ha‐cathL is specifically expressed in haemocytes, with increased expression during larval moulting and metamorphosis. In vivo experimentation revealed that Ha‐cathL is up‐regulated by 20‐hydroxyecdysone. Meanwhile, in situ hybridization and immunocytochemistry revealed that Ha‐cathL mRNA is mainly expressed in granulocytes and plasmatocytes. Knock down of cathepsin L by RNA interference results in larvae death before pupation or the formation of a chimeric pupa containing a larval head and thorax, abnormal wings and the pupal abdomen. The reason for this is that the affected haemocytes cannot become granulated, and therefore cannot participate in fat body remodelling and wing development. These facts suggest that Ha‐cathL is involved in larval moulting and metamorphosis by participating in the functioning of haemocytes.

Microwave pyrolysis of wheat straw: Product distribution and generation mechanism

Microwave pyrolysis of wheat straw is studied, combined with analysis of products, the distribution and generation pathway of products are investigated. Only a small amount of volatiles released when microwave pyrolysis of pure straw. Mixtures of adding CuO and Fe3O4 can pyrolyze, and the majority in pyrolysis products is in liquid-phase. Severe pyrolysis occur after adding carbon residue, the CO content in pyrolysis gas products is high, and the maximum volume content of H2 can exceed 35 vol.%. The high-temperature is helpful for increasing the yield of combustible gas in gaseous products, in particular the H2 production, but also helpful for improving the conversion of sample. Pyrolysis is carried out layer by layer from the inside to outside. As the internal material firstly pyrolyze and pyrolysis products released pass through the low temperature zone, the chance of occurrence of secondary reactions is reduced.

Molecular cloning and expression patterns of the molt-regulating transcription factor HHR3 from Helicoverpa armigera.

Molt‐regulating transcription factors, hormone receptor 3 (HR3), play important roles in regulating expression of tissue‐specific genes involved in insect molting and metamorphosis. A 1668 bp cDNA encoding a molt‐regulating transcription factor (HHR3) was cloned from Helicoverpa armigera, which encodes a protein made up of 556 amino acids. This 62 kDa protein was found to have an isoelectric point (pI) of 6.52. There was no signal peptide or N‐glycosylation site found in this cDNA. A DNA‐binding region signature of nuclear hormone receptor was found from amino acids 107–133. A possible outside to inside transmembrane helice was found from amino acids 72–90. Northern blots of the larvae revealed five bands of HHR3 named as band 0, 1, 2, 3 and 4 with molecular masses determined as 2.1, 2.6, 3.6, 4.5 and 5.5 kb, respectively. The expression patterns of HHR3 in vivo were variable with developmental stages and tissues. Results showed that band 1–4 of HHR3 was only briefly expressed during molting, which suggested these bands are involved in the regulation of molting cascade, whereas band 0 was expressed in both molting and feeding larvae. Band 1 and 2 of HHR3 could be induced from epidermis of newly molted 6th instar larvae by non‐steroidal ecdysone agonist, RH‐2485.

Participation of haemocytes in fat body degradation via cathepsin L expression.

Insect haemocytes are known to participate in innate immunity via the phagocytosis of pathogens. However, the function of haemocytes in tissue remodelling is less understood. We report here that haemocytes play roles in fat body degradation by expressing a cysteine proteinase cathepsin L in the lepidopteran Helicoverpa armigera. During metamorphosis, haemocytes undergo morphological changes by increasing their cell size and transforming their granulocytes into macrogranulocytes. The population of haemocytes also changes with increased number of granulocytes and decreased plasmatocytes. The expression level of cathepsin L in haemocytes, mainly in granulocytes and plasmatocytes, increases. The steroid hormone 20‐hydroxyecdysone is able to promote the transformation of granulocytes into macrogranulocytes, and up‐regulate the expression level of cathepsin L. The knock‐down of the cathepsin L gene by RNA interference in haemocytes in vitro results in deficient granulocytes transforming into macrogranulocytes. Haemocytes are able to enter the decomposed fat body during metamorphosis. The over‐expression of the proteinase domain C1A of cathepsin L results in cell apoptosis. Haemocytes, especially macrogranulocytes, undergo apoptosis and cathepsin L is released into haemolymph and the fat body during metamorphosis for fat body decomposition and degradation. These results suggest that cathepsin L is related to the transformation of granulocytes to macrogranulocytes to enter the fat body, and induce haemocyte apoptosis for further tissue degradation.

β-thymosin is upregulated by the steroid hormone 20-hydroxyecdysone and microorganisms

Thymosins have diverse biological activities including actin‐sequestering and tissue repair in vertebrates, however, there is little information about the function of thymosins in invertebrates. We isolated a β‐thymosin gene in Helicoverpa armigera. It has two transcript variants, HaTHY1 and HaTHY2, encoding 19.0 kDa and 14.5 kDa peptides, respectively. HaTHY1 was mainly transcribed in the integument and midgut, while HaTHY2 was principally presented in the fat body and haemocytes. The transcript levels of HaTHY2 showed some fluctuation; there was an obvious increase at the metamorphic stage in the integument or fat body. HaTHY was able to be upregulated by 20‐hydroxyecdysone or by bacterial and viral challenge. These data suggest that HaTHY is upregulated by the steroid hormone and by responses to microorganism infection.

Drying behavior of lignite under microwave heating

ABSTRACT Because of lignite’s high moisture content, it must be dried before most applications. Microwave radiation may be suitable for efficient drying because of its special heating properties. This study investigated the drying behavior of lignite samples from eastern Inner Mongolia by microwave thermogravimetric analysis. Three stages of microwave drying were observed: preheating, fast weight loss, and falling rate drying periods. Samples’ surface temperatures increased dramatically during preheating, dropped slightly in the second period, and rose again in the final period. The measured surface temperature was <95°C during microwave heating. The overall moisture content decreased more rapidly under higher microwave power. Fine lignite particles (diameter <0.2 mm) and lump samples (particle size 10 mm) dried better than granular lignite (particle size 1–2 mm). The samples also underwent slight natural drying (1–2% point reduction in moisture content) after microwave treatment. The critical moisture content of lignite (11–15% under experimental conditions) was redefined. Energy consumption was analyzed to evaluate the feasibility of the proposed drying process.

Numerical simulation of hot-spot effects in microwave heating due to the existence of strong microwave-absorbing media

Hot spots can occur in microwave heating when the heated materials have different microwave absorbing properties, resulting in non-uniform temperature distribution. Understanding the features and extent of hot-spot effects can be essential in microwave-assisted processes, but little has been reported quantitatively due to the difficulty in direct determination. The issues are measured experimentally and numerically simulated using silicon carbide (SiC) particles dispersed in paraffin oil as a representative case here. Hot spots are definitively shown to exist and may trigger temperature gaps between surrounding substances at the magnitude of several hundred degrees Celsius or even higher in certain cases. The temperature gaps are enhanced for larger sized SiC particles, with a higher heat generation rate and increasing heating time. The extent of hot-spot effects substantially depends on how much and how quickly heat generated by the strong microwave absorbing media can be transferred to the weak ones. The findings have great practical value. By choosing materials with strong microwave absorption, or where discharges occur due to microwave–metal interactions, prominent hot spots can be intentionally forged and the temperature gradient may be tailored to enhance chemical reactions and catalytic processes for specific scientific and engineering applications.

Pyrolysis of tyre powder using microwave thermogravimetric analysis: Effect of microwave power.

The pyrolytic characteristics of tyre powder treated under different microwave powers (300, 500, and 700 W) were studied via microwave thermogravimetric analysis. The product yields at different power levels were studied, along with comparative analysis of microwave pyrolysis and conventional pyrolysis. The feedstock underwent preheating, intense pyrolysis, and final pyrolysis in sequence. The main and secondary weight loss peaks observed during the intense pyrolysis stage were attributed to the decomposition of natural rubbers and synthetic rubbers, respectively. The total mass loss rates, bulk temperatures, and maximum temperatures were distinctively higher at higher powers. However, the maximum mass loss rate (0.005 s-1), the highest yields of liquid product (53%), and the minimum yields of residual solid samples (43.83%) were obtained at 500 W. Compared with conventional pyrolysis, microwave pyrolysis exhibited significantly different behaviour with faster reaction rates, which can decrease the decomposition temperatures of both natural and synthetic rubber by approximately 110 °C–140 °C.