Melanoidin and aldocyanoin microspheres: Implications for chemical evolution and early precambrian micropaleontology

Summary Two new classes of organic microspheres are described. One of them (melanoidin) is synthesized from amino acids and sugars in heated aqueous solutions. The other (aldocyanoin) is formed in aqueous solutions of ammonium cyanide and formaldehyde at room temperature.The general properties of these microspheres, including conditions of synthesis, size and shape, mechanical and pH stability, and solubility, are compared with corresponding properties of other –protocell– model systems. It is concluded that melanoidin and aldocyanoin microspheres are plausible candidates for precellular units in the primitive hydrosphere.Since the bulk of the organic carbon in early Precambrian sediments is insoluble kerogen-melanoidin, it is suggested that some Precambrian –microfossils– may be abiotic melanoidin microspheres of the type described herein.     

海洋生物质的热解特性与动力学研究

以定生浒苔、漂浮浒苔、石莼、大叶藻、海带、龙须菜和裙带菜7种海洋生物质为研究对象,以1种草类生物质玉米秸秆、1种木质类生物质锯末为对照,用热重分析法对其热解过程及其动力学规律进行了研究。利用TG-DTG-DTA曲线分析了它们的基本热解特性。结果表明,整个热解过程主要为干燥失水、剧烈失重和缓慢失重3个阶段,海洋生物质的Tmax明显低于2类陆生生物质,而且大叶藻的热解稳定性相对较高,而漂浮浒苔的热解稳定性较低,燃烧特性较好。同时,用Coats-Redfern法求得相应的活化能E和频率因子A,发现3类生物质的热解反应机理函数不同。     

Pyrolysis of olive residue and sugar cane bagasse: non-isothermal thermogravimetric kinetic analysis

Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2-50 K min(-1) providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538-543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600-607 K). The two biomass mainly devolatilized around 473-673 K, with total volatile yield of about 70-75%. The char in final residue was about 19-26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa-Flynn-Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10-40% conversion range have a value of 153-162 kJ mol(-1) and 168-180 kJ mol(-1) for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50-80% conversion range, this value is 204-215 kJ mol(-1) and 231-240 kJ mol(-1) for the cellulose degradation of olive residue and sugar cane bagasse, respectively.     

Design,Construction, and Operation of a Fast Pyrolysis Plant for Biomass

A continuous fluidized‐bed plant (PDU‐scale) for fast pyrolysis of lingnocellulosic biomass gives rise to bio‐oil yields of 65 wt.‐%. The average reactor gas residence time was 1.2 s only. The gas and charcoal yields were 15–20 wt.‐%, respectively. The bio oils were chemically characterized. The main monomeric products of the thermal degradation of carbohydrates are acetic acid, hydroxyacetaldehyde, hydroxypropanone, and levoglucosan. The process described in this paper can also be used for disposal of inorganic‐, metal‐organic‐, and chlorine‐organic contaminated waste‐wood. Inorganic compounds of wood preservatives are concentrated in the charcoal fraction and can be separated easily. Chlorine‐organic wood preservatives are mostly degraded. The process has been positively tested as a technique for disposal, recycling, and exploitation of industrial biomass waste (wood waste, grinding grit, fibre sludge, cocoa shell and modern composites like HPL). Bio oil from fast pyrolysis can be used for the production of energy and chemical feedstock. Research for these purposes is ongoing.     

Pyrolysis of grape bagasse: effect of pyrolysis conditions on the product yields and characterization of the liquid product

In this study, pyrolysis of grape bagasse was investigated with the aim to study the product distribution and their chemical compositions and to identify optimum process conditions for maximizing the bio-oil yield. Particular investigated process variables were temperature (350-600 °C), heating rate (10-50 °C/min) and nitrogen gas flow rate (50-200 cm³/min). The maximum oil yield of 27.60% was obtained at the final pyrolysis temperature of 550 °C, sweeping gas flow rate of 100 cm³/min and heating rate of 50 °C/min in a fixed-bed reactor. The elemental analysis and heating value of the bio-oils were determined, and then the chemical composition of the bio-oil was investigated using chromatographic and spectroscopic techniques such as column chromatography, ¹H NMR and FTIR. The fuel properties of the bio-oil such as flash point, viscosity and density were also determined. The bio-oils obtained from grape bagasse were presented as an environmentally friendly feedstock candidate for bio-fuels.     

Pyrolysis of groundnut de-oiled cake and characterization of the liquid product

Renewable biomass is considered as an important energy resource all over the world and for an agriculture based economy like that of India, the future prospects of being able to convert widely available biomass materials into various forms of fuel is most attractive. In this study, pyrolysis of groundnut de-oiled cake was investigated with an aim of studying the physical and chemical characteristics of the bio-fuel produced and to determine its feasibility as a commercial fuel. Thermal pyrolysis of groundnut de-oiled cake was done in a semi-batch reactor at a temperature range of 200-500 °C and at a heating rate of 20 °C/min. The chemical analysis of the bio-fuel showed the presence of functional groups such as alkanes, alkenes, alkynes, aldehydes, ketones, carboxylic acids, esters, amines, nitriles, nitro compounds and aromatics rings. The physical properties of the bio-fuel obtained were close to that of diesel and petrol.     

流感病毒的裂解气相色谱分析

裂解气相色谱法(Pyrolysis Gas Chromatography,PGC)在微生物学的应用中曾多侧重于细菌的鉴定,Mayer最早用PGC做植物病毒的快速鉴定,80年代国内开始开展了病毒的PGC研究。本文报道用PGC分析流感病毒和新城疫病毒的初步结果。     

Pyrolysis of Mixed Date Stones and Pistachio Shells: Identification of Bio-Oil and Utilization of Bio-Char as Activated Carbon Precursor

Thermal pyrolysis of mixed date stones and pistachio shells in a semi-batch reactor was addressed in this study. The highest yield of liquids (51.20 %) was produced at 500 °C, 90 min, 20 °C/min heating rate, and 50 mesh particle size. Under these conditions, yield of liquid from date stones and pistachio shells separately was 49.12 % and 47.67 %, respectively. The FT-IR results confirmed the presence of multiple oxygen-containing compounds in the bio-oil. Results from GC–MS declared that it was predominately composed of acids (57.57 %), esters (21.35 %), phenols (4.63 5), and alcohols (3.49 5). The obtained biochar was transformed into activated carbon (AC) by the optimized ZnCl₂ activation method. The ideal AC was synthesized at 600 °C for 60 min using a 2 : 1 ZnCl₂: biochar impregnation ratio. FESEM and XRD measurements showed that the AC was amorphous. The prepared AC was effective in eliminating dibenzothiophene (DBT) from model fuel (200 ppm DBT/hexane) with a maximum performance 95.26 % at 40 °C for 1h using 0.35 g of the AC. The exhausted AC was regenerated and reutilized 4 times, and removal efficiency reached 88.23 % in the 4^th cycle under ideal working conditions.     

大型海藻浒苔热解特性与动力学研究

以2005年10月采自江苏如东海区的条浒苔(Enteromorpha clathrata)为研究材料,用热重分析法对其热解过程及其动力学规律进行了研究。采用10、20、30℃/min等升温速率分别对0.18、0.28、0.45mm等粒径样品进行热解,结果表明样品非等温失重过程主要为脱水、保持、剧烈失重和缓慢失重4个阶段,且热解失重区为190～520℃之间范围;通过对最大失重率Dmax、失重率峰值温度θmax、挥发等参数分析,可以得出温度Ts和r值都随升温速率的增加而增加,升温速率越高,反应时间越短,热解特性指数增加;当样品粒径为0.28mm以上时,颗粒粒径越大对热解过程影响较大。用Coats-Redfern方法计算出样品的热解动力学参数,发现其热解反应机理函数不同于木质类生物质,求得的活化能E与频率因子A之间存在动力学补偿效应。     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Pyrolysis of safflower (Charthamus tinctorius L.) seed press cake: part 1. The effects of pyrolysis parameters on the product yields

Safflower (Charthamus tinctorius L.) seed press cake was pyrolysed in a fixed-bed reactor. The effects of pyrolysis temperature, heating rate and sweep gas flow rates on the yields of the products were investigated. Pyrolysis runs were performed using pyrolysis temperatures between 400 and 600 °C with heating rates of 10, 30 and 50 °C min⁻¹. The obtained bio-char, gas and bio-oil yields ranged between 25 and 34 wt%, 19 and 25 wt%, and 28 and 36 wt%, respectively, at different pyrolysis conditions. The highest liquid yield was obtained at 500 °C pyrolysis temperature with a heating rate of 50 °C min⁻¹ under the sweep gas of N₂ with a flow rate of 100 cm³ min⁻¹. Employing the higher heating rate of 50 °C min⁻¹ results in maximum bio-oil yield, probably due to the decrease in mass transfer limitations. According to the results obtained under the conditions of this study, the effects of pyrolysis temperature and sweep gas flow rate are more significant than the effect of heating rate on the yields.     

Pyrolysis mass spectra,sulfhydryl and tryptophan content of the embryonic nuclei from adult human normal and nuclear-cataractous lenses

Cataractous state-related alterations were studied by Curie-point pyrolysis low voltage mass spectrometry performed on the embryonic nuclei from adult normal and nuclear-cataractous human lenses. It was shown that the relative intensities of ion signals assigned to sulfur dioxide and, tentatively, to other sulfur oxidation products correlate with the increase in lens nuclear color. Since these ion signals may represent pyrolysis fragments from methionine sulfoxide, methionine sulfone, cysteic acid and disulfide compounds present in the parent material, it is concluded that progressive oxidation of sulfur compounds appears to take place during nuclear cataractogenesis. Automated pyrolysis mass spectrometry coupled with multivariate analysis of the spectral data by computer turned out to be a rapid method of characterizing submilligram samples of lens material.The results were supported by data obtained by conventional determination of sulfhydryl and tryptophan groups.     

Problems in the interpretation of Ramapithecus: with special reference to anterior tooth reduction

The dental proportions of Ramapithecus specimen FT 1271-2 (from Fort Ternan, Kenya) have been compared with undoubted fossil pongids from the Miocene of East Africa. Compared to its Miocene pongid contemporaries, Ramapithecus exhibits distinct anterior tooth reduction both in its incisor and canine dimensions. This distinction is most clearly seen in comparisons of Ramapithecus with pongids of similar cheek tooth size, i.e., Dryopithecus africanus and Pan paniscus. The differences in dental proportions between the phylogenetic lines of D. africanus to Pan and Ramapithecus to Homo are discussed in terms of various dietary hypotheses. The similarities in dental proportions of Gorilla and Ramapithecus illustrate their non-frugivorous dietary preferences, but have little or no value as far as the taxonomic assessment of Ramapithecus is concerned.     

Assessing the affinities of fossils using canonical variates and generalized distances

Canonical variate analysis and generalized distances are commonly used multivariate statistical techniques for assessing the comparative morphology of living and fossil primates. Some common pitfalls of these methods when used to analyze fossil specimens are: (1) ignoring the possibility that a fossil belongs to a group other than one of the predefined reference samples (i.e., restricted versus unrestricted approaches to classification), (2) misinterpreting probabilities of group membership (i.e., posterior versus typicality probabilities), and (3) failing to understand how sample sizes influence multivariate ordinations in trying to effectively illustrate the morphometric affinities of a fossil (i.e., weighted versus unweighted analyses with fossils entered indirectly or directly into the analysis). To better understand canonincal variate analysis and generalized distances, the workings of these methods are portrayed graphically as a series of rotations and rescaling of data plotted in a multivariate data space. The influence of sample sizes and the importance of higher-numberer canonical variates are emphasized. Simple examples taken from the literature illustrate how the different approaches to including a fosil in canonical variate analysis may affect the multivariate results upon which physical anthropologists base their interpretations of the fossil's morphology.     

Constraints on the evolution of biochemical pathways

The considerable constraints that can be imposed on the evolution of primary metabolic pathways are apparent in the carbon pathway of photosynthesis in plants. Here, the unfortunate dual nature of the key enzyme, rubisco, to act as both a carboxylase and an oxygenase has led to a variety of adaptations in higher plants to maintain the efficiency of photosynthesis as a response to climatic stress.
Constraints on secondary metabolism are less apparent, although evolution can proceed by both loss of enzymic ability (as in the shikimate pathway) and by gain (as in the mevalonate pathway). One evolutionary trend in angiosperms is towards more highly toxic allelochemicals to provide protection from herbivory or microbial attack. One constraint on alkaloid evolution is the concomitant need to develop a metabolic pathway to recycle the nitrogen for other purposes. In the terpenoid series of compounds, there is a correlation between increasing oxygenation of a carbon skeleton and increasing toxicity. However, increasing oxygenation, especially peroxide formation, may produce a compound too unstable to act effectively against predators. In the evolution of blue flower colour, the synthesis of delphinidin 3-glucoside is only the first step in the production of a stable pigment complex capable of providing intense in vivo colouration. In the coevolution of plants and animals, some insects (e.g. the Monarch butterfly) have developed the ability to sequester and store plant toxins to avoid the cost of synthesis but here again there are clear constraints on the processes involved.     

Sampling diverse characters improves phylogenies: Craniodental and postcranial characters of vertebrates often imply different trees

Morphological cladograms of vertebrates are often inferred from greater numbers of characters describing the skull and teeth than from postcranial characters. This is either because the skull is believed to yield characters with a stronger phylogenetic signal (i.e., contain less homoplasy), because morphological variation therein is more readily atomized, or because craniodental material is more widely available (particularly in the palaeontological case). An analysis of 85 vertebrate datasets published between 2000 and 2013 confirms that craniodental characters are significantly more numerous than postcranial characters, but finds no evidence that levels of homoplasy differ in the two partitions. However, a new partition test, based on tree‐to‐tree distances (as measured by the Robinson Foulds metric) rather than tree length, reveals that relationships inferred from the partitions are significantly different about one time in three, much more often than expected. Such differences may reflect divergent selective pressures in different body regions, resulting in different localized patterns of homoplasy. Most systematists attempt to sample characters broadly across body regions, but this is not always possible. We conclude that trees inferred largely from either craniodental or postcranial characters in isolation may differ significantly from those that would result from a more holistic approach. We urge the latter.     

Linear measurements of cortical bone and dental enamel by computed tomography: Applications and problems

This paper explores the potential of high-resolution computed tomography (CT) as a morphometric tool in paleoanthropology. The accuracy of linear measurements of enamel thickness and cortical bone thickness taken from CT scans is evaluated by making comparison with measurements taken directly from physical sections. The measurements of cortical bone are taken on extant and fossil specimens with and without attached matrix, and the dental specimens studied include a sample of 12 extant human molars. Local CT numbers (representing X-ray, attenuation) are used to determine the exact position of the boundaries of a structure. Using this technique most studied dimensions, including four of human molar enamel thickness, could be obtained from CT scans with a maximum error range of ±0.1 mm. The limitations of the method are discussed with special reference to problems associated with highly mineralized fossils. © 1993 Wiley-Liss, Inc.     

Variations in the Properties of Extractable “Humic Matter” and Associated Kerogen in Sediments through Geologic Time: Their Significance for Precambrian Biological Evolution and Paleoecology

Chemical properties and δ¹³C values of benzene/methanol-extractable “humic matter” and associated kerogen in a large, diverse collection of Precambrian and Phanerozoic sediments from different parts of the world showed complex systematic variations through geologic time, reflecting major developments in the history of Precambrian life, and different kinds of sediment yielded similar patterns of variation. Moreover, certain data differentiate clearly between glacial and nonglacial detrital sediments, or between lacustrine and marine sediments, and some data suggest the occurrence of Precambrian land life. The abundance of aromatic groups and the proportion of aliphatic to aromatic groups in the extracts showed little variation from the early Archean (ca. 3.3 Ga) to the mid-Proterozoic (ca. 1.6-1.3 or 1.3-1.1 Ga), whereupon they increased sharply, peaked ca. 1.1-0.900 Ga, and then plunged to a minimum in the late Proterozoic (ca. 0.800 Ga) or early Phanerozoic. This is interpreted as indicating that cyanobacteria were the dominant photoautotrophs until the mid-Proterozoic, when algae evolved, proliferating until the late Proterozoic, whereupon their populations were depleted by herbivorous metazoans. Nitrogenous aromatic material increased to a maximum ca. 3.4–3.3 Ga and then decreased steadily to ca. 1.3 Ga, suggesting that early Precambrian cyanobacteria were enriched in photoprotective as well as photosynthetic tetrapyrrole pigments owing to the lack of ultraviolet radiation-shielding atmospheric O₂ and O₃. The concentration increased again starting ca. 1.3–0.800 Ga, reflecting the rise of algae, peaked ca. 0.680 Ga, and dropped catastrophically to a much lower value in the Cambrian (ca. 0.510 Ga), suggesting mass mortality at the Precambrian-Cambrian boundary.