Murre's conjecture for rational homogeneous bundles over a variety
microbial nutrition
Alcaligens and Pseudomonas sp. Nitrobacter Nitrosomonas Desulfovibrio
Thiobacillus denitrificans Thiobacillus ferrooxidans
Electron donor H2 NO2NH4+ H2 S0. H2S Fe2+
Facilitated diffusion
The rate of diffusion across selectively permeable membranes is greatly increased by the use of carrier proteins, sometimes called permeases, which are embedded in the plasina membrane. Since the diffusion process is aided by a carrier, it is called facilitated diffusion. The rate of facilitated diffusion increases with the concentratioti gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion.
Light energy, inorganic Algae, Purple and hydrogen/electron(H/e-) donor, green bacteria, CO2 carbon source Cyanobacteria Light energy, inorganic H/edonor, Organic carbon source Chemical energy source (inorganic), Inorganic H/edonor, CO2 carbon source Chemical energy source (organic), Organic H/e- donor, Organic carbon source Purple nonsulfur bacteria, Green sulfur bacteria SulfurSulfur-oxdizing bacteria, Hydrogen bacteria, Nitrifying bacteria Most bacteria, fungi, protozoa
兴安升麻醇提物成分分析及基于网络药理学探讨其促进皮肤伤口愈合的作用机制
李艳娜，张富源，程伟峰，等. 兴安升麻醇提物成分分析及基于网络药理学探讨其促进皮肤伤口愈合的作用机制[J]. 食品工业科技，2023，44（24）：12−22. doi: 10.13386/j.issn1002-0306.2023050247LI Yanna, ZHANG Fuyuan, CHENG Weifeng, et al. Analysis of the Components of Cimicifuga dahurica (Turcz.) Maxim. Alcohol Extract and Exploration of Its Mechanism of Promoting Skin Wound Healing Based on Network Pharmacology[J]. Science and Technology of Food Industry, 2023, 44(24): 12−22. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2023050247· 特邀主编专栏—枸杞、红枣、沙棘等食药同源健康食品研究与开发（客座主编：方海田、田金虎、龚桂萍） ·兴安升麻醇提物成分分析及基于网络药理学探讨其促进皮肤伤口愈合的作用机制李艳娜1，张富源1，程伟峰2，桑亚新1，王向红1,*（1.河北农业大学食品科技学院，河北保定 071000；2.河北雅果食品有限公司，河北保定 071000）摘 要：为了深入挖掘兴安升麻生理功能，本研究采用醇提法提取活性成分，通过HPLC-MS 分析兴安升麻的化学成分并基于网络药理学探讨其对皮肤伤口的促愈机制。
结果表明，兴安升麻中鉴定出125种化学成分，其中萜类、苯丙素类及酮类化合物含量较多，主要包括隐绿原酸、绿原酸、白术内脂III 等活性成分，可作用于一个或多个靶点， EGFR 、KDR 、F2可能为促愈过程中发挥作用的重要靶点，且橘皮素、山姜素、5-去甲川陈皮素等活性成分可能在此过程中发挥重要作用，说明兴安升麻具有多成分、多靶点作用于促进皮肤伤口愈合的特性；兴安升麻可能通过VEGF 、EGFR 和TNF 信号通路调控相关因子和蛋白的表达，发挥对皮肤伤口的促愈作用。
【精品】翻译综合
一个抑制肿瘤的连续模型-------艾丽斯H伯杰，阿尔弗雷德G. Knudson 与皮埃尔保罗潘多尔菲今年，也就是2011 年，标志着视网膜母细胞瘤的统计分析的第四十周年，首次提供了证据表明，肿瘤的发生，可以由两个突变发起。
这项工作提供了“二次打击”的假说，为解释隐性抑癌基因（TSGs）在显性遗传的癌症易感性综合征中的作用奠定了基础。
然而，四十年后，我们已经知道，即使是部分失活的肿瘤抑制基因也可以致使肿瘤的发生。
在这里，我们分析这方面的证据，并提出了一个关于肿瘤抑制基因功能的连续模型来全方位的解释肿瘤抑制基因在癌症过程中的突变。
虽然在1900 年之前癌症的遗传倾向已经被人认知，但是，是在19 世纪曾一度被忽视的孟德尔的遗传规律被重新发现之后，癌症的遗传倾向才更趋于合理化。
到那时，人们也知道，肿瘤细胞中的染色体模式是不正常的。
接下来对癌症遗传学的理解做出贡献的人是波威利，他提出，一些染色体可能刺激细胞分裂，其他的一些染色体 a 可能会抑制细胞分裂，但他的想法长期被忽视。
现在我们知道，这两种类型的基因，都是存在的。
在这次研究中，我们总结了后一种类型基因的研究历史，抑癌基因（TSGs），以及能够支持完全和部分失活的肿瘤抑制基因在癌症的发病中的作用的证据。
我们将抑制肿瘤的连续模型与经典的“二次打击”假说相结合，用来说明肿瘤抑制基因微妙的剂量效应，同时我们也讨论的“二次打击”假说的例外，如“专性的单倍剂量不足”，指出部分损失的抑癌基因比完全损失的更具致癌性。
这个连续模型突出了微妙的调控肿瘤抑制基因表达或活动的重要性，如微RNA（miRNA）的监管和调控。
最后，我们讨论了这种模式在┲⒌恼锒虾椭瘟乒 讨械挠跋臁！岸 未蚧鳌奔偎?第一个能够表明基因的异常可以导致癌症的发生的证据源自1960 年费城慢性粒细胞白血病细胞的染色体的发现。
后来，在1973 年，人们发现这个染色体是是第9 号和第22 号染色体异位的结果，并在1977 年，在急性早幼粒细胞白血病患者中第15 号和第17 号染色体易位被识别出来。
藻类水热反应与慢速热解
Thermochemical conversion of raw and defatted algal biomass via hydrothermal liquefaction and slow pyrolysisDerek R.Vardon a ,⇑,Brajendra K.Sharma b ,Grant V.Blazina a ,Kishore Rajagopalan b ,Timothy J.Strathmann aa Dept.of Civil and Environmental Engineering,University of Illinois at Urbana-Champaign,205N.Mathews Ave.,Urbana,IL 61801,United States bIllinois Sustainable Technology Center,University of Illinois at Urbana Champaign,1Hazelwood Dr.,Champaign,IL 61820,United Statesa r t i c l e i n f o Article history:Received 1November 2011Received in revised form 2January 2012Accepted 4January 2012Available online 10January 2012Keywords:AlgaeHydrothermal liquefaction Pyrolysis Scenedesmus Spirulinaa b s t r a c tThermochemical conversion is a promising route for recovering energy from algal biomass.Two thermo-chemical processes,hydrothermal liquefaction (HTL:300°C and 10–12MPa)and slow pyrolysis (heated to 450°C at a rate of 50°C/min),were used to produce bio-oils from Scenedesmus (raw and defatted)and Spirulina biomass that were compared against Illinois shale oil.Although both thermochemical conver-sion routes produced energy dense bio-oil (35–37MJ/kg)that approached shale oil (41MJ/kg),bio-oil yields (24–45%)and physico-chemical characteristics were highly influenced by conversion route and feedstock selection.Sharp differences were observed in the mean bio-oil molecular weight (pyrolysis 280–360Da;HTL 700–1330Da)and the percentage of low boiling compounds (bp <400°C)(pyrolysis 62–66%;HTL 45–54%).Analysis of the energy consumption ratio (ECR)also revealed that for wet algal biomass (80%moisture content),HTL is more favorable (ECR 0.44–0.63)than pyrolysis (ECR 0.92–1.24)due to required water volatilization in the latter technique.Ó2012Elsevier Ltd.All rights reserved.1.IntroductionAlgae are a diverse group of microorganisms that have garnered increased attention as a feedstock for renewable energy production and pollution remediation.Algae hold promise as a bioenergy feed-stock due to their prolific growth rate and lipid productivity,ability to grow in saline and degraded waterbodies,utilization of waste carbon dioxide,and production of fuel precursors and high-value biochemicals (Mata et al.,2009).Furthermore,integration of algal cultivation into wastewater treatment may be advantageous (Pitt-man et al.,2010)for nutrient capture to support algal growth and mitigate eutrophication in effluent-receiving water bodies.How-ever,despite these benefits,effective dewatering of harvested algal biomass for lipid extraction presents a current limitation to eco-nomical and sustainable biofuel production due to the high energy,operating,and capital costs (U.S.Department of Energy,2010).Many commercial efforts are underway to maximize economic return and improve energy balances in algal cultivation.Currently,much work is focused on extracting high value chemicals (e.g.,nutraceuticals)and energy-dense lipids (e.g.,for biodiesel)from al-gae,but this still leaves behind a large residual of ‘‘defatted’’bio-mass.Effective utilization of defatted algal biomass will be necessary to achieve favorable energy balances and productioncosts (Pan et al.,2010).Several downstream uses have been consid-ered for defatted algal biomass,including animal feed and fertil-izer,or as a feedstock for energy production through direct burning,ethanol fermentation,or anaerobic digestion (Mata et al.,2009).Here,we focus on examining the potential of different thermochemical conversion routes for recovering energy dense bio-oil products from raw and defatted algal biomass.Thermochemical conversion technologies are a promising op-tion for transforming diverse biomass feedstocks into energy dense,transportable liquid fuels that can combusted directly or upgraded into petroleum replacements (Bridgwater,2011;Duan and Savage,2011;Brown and Stevens,2011;Elliott,2007).Two thermochemical routes,hydrothermal liquefaction (HTL)and slow pyrolysis,were examined in this study to compare the chemical characteristics of bio-oils that can be produced from algal biomass,including defatted biomass.HTL is ideal for processing high-moisture (i.e.,wet)biomass since water is used as the reaction medium under high tempera-ture (250–350°C)and pressure (5–15MPa).These conditions pro-duce a highly reactive solvation environment and avoid an energetically costly phase change associated with biomass plex biomolecules decompose and reform into a variety of compounds that partition into a self-separating bio-oil phase when conditions return to ambient temperature and pressure.HTL has been tested with a wide range of biomass feedstocks including agricultural and forest residues (Minowa et al.,1998),manure,sewage sludge (Suzuki et al.,1988;Vardon et al.,2011),and several0960-8524/$-see front matter Ó2012Elsevier Ltd.All rights reserved.doi:10.1016/j.biortech.2012.01.008Corresponding author.Tel.:+12177663916.E-mail address:dvardon2@ (D.R.Vardon).algal species,including Spirulina(Jena et al.,2011;Vardon et al., 2011),Nannochloropsis(Biller and Ross,2011;Brown et al., 2010),and Chlorella(Biller and Ross,2011).Alternatively,pyrolysis technologies are best suited for the con-version of dry feedstocks(<5%moisture)since moisture must be removed before biomass is heated to high temperatures(400–600°C)under ambient pressure.The dried biomass is heated in the absence of oxygen to cleave and volatilize biomolecules,which re-condense into an aqueous and bio-oil phase;a carbon-rich solid phase,typically referred to as biochar,is also obtained.Pyrolysis technologies are often classified by their heating rate,with rates of0.1–1°C/s referred to as slow pyrolysis,10–200°C/s as fast pyro-lysis,and>1000°C/s asflash pyrolysis(Demirbas and Arin,2002). This study focused on slow pyrolysis due to its potential for pro-ducing more energy dense bio-oils that approach petroleum crude oils(Duman et al.,2010;Maggi and Delmon,1994).Pyrolysis has been studied extensively with lignocellulosic feedstocks and has been scaled to pilot and commercial production levels(Bridgwater, 2011;Brown and Stevens,2011).Non-traditional feedstocks have also been examined,such as hazelnut shells(Pütün et al.,1999), chicken litter,switch grass(Mullen et al.,2009),and cherry seed (Duman et al.,2010).Pyrolysis of several algal species have also been tested,including Chlorella(Demirbasß,2006;Miao et al., 2004;Peng et al.,2000;Grierson et al.,2009),heterotrophically en-hanced Chlorella(Miao and Wu,2004),Microcystis(Miao et al., 2004),salt-water Tetraselmis(Grierson et al.,2011,2009),and Nan-nochloropsis residue(Pan et al.,2010).Bio-oils produced from HTL and slow pyrolysis display diverse chemical properties that are heavily influenced by the source feed-stock composition.Algae of varying biochemical composition have been shown to produce bio-oils with distinct chemical characteris-tics(Grierson et al.,2009;Biller and Ross,2011;Jena et al.,2011), but to our knowledge no studies have examined how the chemistry of thermochemical bio-oils derived from defatted algal biomass compare to those produced from the parent algae(non-defatted) or other low-lipid algal species with composition similar to defatted algae biomass.This study examined thermochemical bio-oils pro-duced from raw and defatted Scenedesmus,a species with a range of lipid contents(10–55%)suitable for biodiesel production(Mata et al.,2009)and amenable for wastewater treatment(Pittman et al.,2010).These bio-oils were also compared with bio-oils pro-duced from thermochemical conversions of Spirulina,which has a nutritional profile similar to defatted algal biomass(i.e.,high pro-tein,low-lipid)that has been used as a feedstock in recent studies examining HTL(Biller and Ross,2011;Jena et al.,2011;Vardon et al.,2011).To our knowledge,this is thefirst study to examine ther-mochemical conversion of Scenedesmus biomass,in raw or defatted form,as well as thefirst study to directly compare the chemical properties of bio-oils produced from the different algal feedstocks via HTL and slow pyrolysis.The thermochemically-derived bio-oils were also compared with Illinois shale oil,a low-grade petroleum crude.Bio-oils and shale oil were analyzed for bulk properties (e.g.,elemental analysis and higher heating value)and physico-chemical characteristics(e.g.,molecular constituents,functional group allocation,proton speciation,molecular weight distribution, and boiling point distribution).Results were used to determine the influence of feedstock and thermochemical conversion method on bio-oil yield and chemistry and to evaluate the energy balances for algal biomass thermochemical conversions.2.Methods2.1.Algal feedstocks and shale oilScenedesmus biomass was provided by Stellarwind Bio Energy LLC(Indianapolis,IN)and Spirulina biomass was obtained from Cyanotech located in(Kailua-Kona,HI).Algal samples were used in dry powder form(moisture content<5%)and stored at5°C prior to processing.Scenedesmus biomass was defatted by using hexane in a Soxhlet extraction apparatus.Crude lipids were extracted until the recirculated solvent ran clear($24h).Illinois shale oil was ob-tained from the Illinois State Geological Survey(Champaign,IL).2.2.Thermochemical conversionAlgal biomass conversions with HTL and pyrolysis were con-ducted in triplicate batch reactions.Hydrothermal liquefaction was performed in a Parr4575500-ml reactor using approximately 250g of biomass slurry(80wt.%moisture).Conversion conditions were identical to those previously reported(Vardon et al.,2011), with30-min HTL reactions taking place at300°C,and pressure ranging from10to12MPa.Slow pyrolysis was conducted using a Thermolyne79400tube furnace.Approximately100g of dry bio-mass was loaded into the furnace chamber and heated to450°C at a rate of50°C/min,with a nitrogen sweep gasflow rate of $100ml/min and a reaction time of2h.Volatile products were condensed in an ice-chilled collection vessel while the remaining biomass solid(biochar)was collected and weighed separately.The liquid products obtained from HTL and slow pyrolysis con-tained a water-insoluble organic phase,suspended solids,and an aqueous phase with dissolved constituents.The combined liquid products were rinsed with dichloromethane(DCM)to separate the aqueous and DCM-soluble organics(Pütün et al.,1999;Peng et al.,2000;Grierson et al.,2011;Biller and Ross,2011;Brown et al.,2010;Duan and Savage,2011).A Teflon-coated stainless steel pressurizedfiltration assembly(Millipore)was then used to re-move suspended solids from the DCM and aqueous phases.Thefil-ter(Satorious0.45-l m cellulose membranes)and retained solids were recovered and dried to determine the mass of residual solids. Thefiltered DCM-soluble organics were then recovered using a separatory funnel and DCM was evaporated under reduced pres-sure to recover the bio-oil phase.For slow pyrolysis,the aqueous-phase included water-soluble constituents as well as water formed from biomass decomposition. For HTL,aqueous phase constituents consisted of total dissolved solids that were measured gravimetrically afterfiltration and evap-oration of the aqueous phase at65°C for$12h to remove water since it served as the reaction medium.The mass balance yields were calculated as the ratio of the cor-responding product phase to the initial dry feedstock mass,includ-ing ash.The bio-oil yield accounted for the mass of DCM-soluble organics recovered afterfiltration and DCM evaporation.For HTL, the aqueous phase yields accounted for the mass of dissolved aqueous constituents remaining after DCM extraction,filtration and water evaporation.For pyrolysis,the aqueous phase yields also accounted for re-condensed water evolved during the conversion process.The solid phase yields accounted for the mass of dried par-ticulates retained after DCM extraction andfiltration,plus the pyrolysis biochar residual remaining in the tube stly, the gas-phase yields were calculated based on the resulting mass difference.2.3.Feedstock and oil analysesForage analysis of the algal biomass was performed by Midwest Labs(Omaha,Nebraska)to determine crude protein,neutral deter-gentfiber(hemicellulose,cellulose,and lignin),acid detergentfiber (cellulose and lignin),lignin and ash content.Elemental analysis of the dried algal feedstocks,bio-oils,and shale oil was conducted by the University of Illinois Microanalysis Laboratory(Urbana,IL). Samples were processed for total carbon/hydrogen/nitrogen using an Exeter Analytical CE-440Elemental Analyzer.Sulfur wasD.R.Vardon et al./Bioresource Technology109(2012)178–187179measured by ICP-OES in axial mode(PerkinElmer Optima2000DV) after sample digestion(PerkinElmer Multiwave3000Digester).Bio-oils and shale oil were extensively characterized to obtain bulk and molecular characteristics using a variety of physico-chemical methods.Gas chromatography–mass spectroscopy(GC–MS)identified low-boiling point molecular constituents in the bio-oil and shale oil,attenuated total reflectance-Fourier Trans-form infrared(ATR-FTIR)and1H and13C nuclear magnetic reso-nance spectroscopy(NMR)provided information regarding ‘‘whole’’oil chemical functionality,size exclusion chromatography (SEC)evaluated the oil molecular weight distribution,and simu-lated distillation(Sim-Dist)determined the boiling point distribu-tion to provide insight into the composition of bio-oils in terms of equivalent petroleum products.These methods were described in detail previously(Vardon et al.,2011).Replicate bio-oils obtained from triplicate conversion reactions were analyzed separately by each method,with the exception of13C NMR analysis,which was only performed for a single replicate due to the high cost of analy-sis.Average values and standard deviations were reported.Since the focus of this study was on the influence of algal biomass com-position and conversion method on thermochemical bio-oil chem-istry,detailed analyses were not conducted on the aqueous,solid, or gas phase products.3.Results and discussion3.1.Feedstock compositionForage analysis revealed that crude protein was the predomi-nant fraction for all algal feedstocks(56–72%),with defatted Scene-desmus displaying the highest percentage(72%)(Table1).The high protein content is typical for many algal species investigated for biofuel production such as Nannochloropsis(52–57%)(Biller and Ross,2011;Brown et al.,2010)and Chlorella(51–55%)(Miao et al.,2004;Biller and Ross,2011;Peng et al.,2000).Total carbohy-drates ranged from20–25%,with raw and defatted Scenedesmus containing a significantly higher fraction of acid detergentfiber (ADF),comprised of cellulose and lignin.These recalcitrant fractions,particularly lignin,are less desirable components for thermochemical conversion.Their presence in biomass has been associated with lower HTL and pyrolysis bio-oil yields and bio-oil energetic contents compared to lipid,protein,and simple carbohy-drate components of biomass(Biller and Ross,2011;Minowa et al., 1998;Peng et al.,2000).Crude lipids were found to be a minor component of all three algal feedstocks,in decreasing order of raw Scenedesmus(13%),Spirulina(5%),and defatted Scenedesmus (<1%).While algal lipids are desirable for increasing thermochem-ical conversion bio-oil yields and energetic contents(Biller and Ross,2011;Miao and Wu,2004),greater economic return may be realized by extracting and processing lipids to obtain specialty biochemicals such as polyunsaturated fatty acids,carotenoids, and b-carotene(Mata et al.,2009).Due to the independent nature of forage assays,total carbohydrates,calculated by subtraction, were less than neutral detergentfiber(NDF)values for raw and defatted Scenedesmus biomass.Elemental analysis of the algal biomass revealed comparable car-bon(C),hydrogen(H),and nitrogen(N)values,with high N contents (8–10%)due to protein(Table1).The high N content greatly distin-guishes algal biomass from lignocellulosic feedstocks,which typi-cally contain<1%N(Mohan et al.,2006;Minowa et al.,1998). Interestingly,despite the significantly higher protein content of defatted Scenedesmus compared to raw Scenedesmus(72%and56% protein,respectively),the N content determined from elemental analysis was only$1%greater.Feedstock N is an important consid-eration because a significant portion can be carried over into the bio-oil products(Pan et al.,2010;Biller and Ross,2011;Brown et al., 2010;Jena et al.,2011;Miao et al.,2004),leading to problems with direct combustion(i.e.,NO x emissions)and creating additional tech-nical challenges when upgrading bio-oils.However,protein rich bio-mass may still be desirable because of the higher thermochemical bio-oil conversion efficiencies compared to those obtained with bio-mass that is richer in more recalcitrant carbohydrates and lignin. Furthermore,depending on its chemical form,N that partitions into the liquid or solid phase may also be useful as a fertilizer.Higher heating values(HHVs)of the dried algal feedstocks were calculated based on the elemental composition using Dulong’s for-mula and ranged from18to23MJ/kg.Raw Scenedesmus biomass had the highest energy content(23MJ/kg)due to its crude lipid content,with values similar to the moderate lipid species Chlorella (23–24MJ/kg)(Biller and Ross,2011;Demirbasß,2006).The HHV of defatted Scenedesmus biomass was lower as expected(21MJ/kg), and equivalent to past reports for defatted Nannochloropsis residue (Pan et al.,2010).Lastly,Spirulina biomass had the lowest HHV (18MJ/kg)due to high O content.3.2.Thermochemical conversion3.2.1.Mass balanceMass balances were highly dependent on the conversion process(i.e.,HTL or slow pyrolysis)and feedstock composition (Table2).HTL produced greater bio-oil yields for all feedstocks (7–14%higher than pyrolysis),calculated as a percentage of the dry biomass including ash,compared to slow pyrolysis under the conditions studied.Raw Scenedesmus resulted in the highest yield of HTL bio-oil(45%),followed by defatted Scenedesmus(36%),and Spirulina(31%).The range of HTL bio-oil yields was consistent with past reports for microalgae that vary based on nutritional profiles and conversion conditions(Brown et al.,2010;Biller and Ross, 2011;Jena et al.,2011;Vardon et al.,2011).The highest bio-oil conversion efficiency for raw Scenedesmus is likely due to the feed-stock’s high crude lipid and protein content,with previous studies identifying HTL conversion efficiencies in the order of lipid>pro-tein>carbohydrate(Biller and Ross,2011).Likewise,the greater bio-oil conversion efficiency of defatted Scenedesmus compared to Spirulina may be the result of higher crude protein of the former (Biller and Ross,2011);the high protein content of defatted Scene-desmus may offset the lower crude lipid content.Recalcitrant car-bohydrates and lignin can lead to reduced bio-oil yields(Minowa et al.,1998),possibly due to the condensation of phenolic com-pounds derived from lignin that result in the formation of residual solids(Toor et al.,2011).Table1Algal biomass nutritional profile,elemental analysis,and higher heating value(drybasis as wt.%).Feedstock Scenedesmus Defatted Scene.SpirulinaBiomass nutritional profileCrude Protein567264Crude Lipid13<15Total Carbohydrates252120Neutral Detergent Fiber32312Acid Detergent Fiber17161Lignin1113<1Organics949389Ash6711Biomass elemental analysis and HHVC52.149.945.2H7.47.1 6.4N8.89.99.8O*31.132.137.8S0.480.960.80HHV(MJ/kg)22.621.317.7*Oxygen content determined by difference for total mass.180 D.R.Vardon et al./Bioresource Technology109(2012)178–187Apart from the bio-oil fraction,the remaining feedstock was converted under HTL conditions into residual solid(6–11%),dis-solved aqueous constituents(17–23%),and gas phase products (30–41%).HTL solid yields were consistent with past reports for Spirulina(Jena et al.,2011);however,the dissolved aqueous con-stituents measured here were lower,which may be a byproduct of different approaches used to determine aqueous phase product yields.Aqueous phase organics can be derived from the decompo-sition of carbohydrates into polar,low molecular weight com-pounds such as formic,acetic,lactic,and acrylic acid(Biller and Ross,2011).The high volatility of these compounds may result in losses to the gas phase when measuring the yield of dissolved aqueous constituents by gravimetric analysis of total dissolved sol-ids remaining after water evaporation.Bio-oil yields obtained for slow pyrolysis were lower than for HTL,ranging from24%to31%,in the order of raw Scenedesmus> defatted Scenedesmus$Spirulina feedstocks.Similar to HTL,bio-oil conversion efficiencies were linked to feedstock composition. Previous pyrolysis studies with model biological compounds have shown that n-alkane liquid yields follow the order of lipids>pro-tein>cellulose>lignin(Evans and Felbeck,1983).Additionally, Miao and Wu(2004)demonstrated the beneficial effect of elevated lipid content for fast pyrolysis of microalgae,resulting in higher bio-oil yields and energetic contents.During pyrolysis,the remaining feedstock was converted into residual solid(30–33%),water and dissolved aqueous constituents (15–27%),and gas phase(12–21%),with the overall product distri-butions falling within the range of values previously reported for slow pyrolysis of microalgae(Grierson et al.,2009).The product phase distribution for slow pyrolysis of microalgae is influenced by the relative proportion of proteins,lipids,and carbohydrates (Grierson et al.,2009),which are known to decompose at lower temperatures compared to lignocellulose(Peng et al.,2000).The yield of dissolved aqueous constituents partially results from the degradation of cellulose and hemicellulose into water-soluble organics(Duman et al.,2010),while the gas phase yield has been shown to be highly dependent on process temperature due to sec-ondary cracking reactions(Peng et al.,2000).Lastly,the yield of so-lid biochar remaining after volatilization is of particular interest due to its soil amendment properties and carbon storage capacity (Grierson et al.,2011).3.2.2.Bulk propertiesElemental analysis of the bio-oils(Table3)demonstrated that HTL and slow pyrolysis produced bio-oils with a significantly high-er percentage of C(71–74%)and lower percentage of O(8–11%) compared to the initial feedstocks(45–52%C;31–38%O).How-ever,the nitrogen contents of the bio-oils(7–10%)remained nearly unchanged from the feedstocks(9–10%).The S content was minor for all bio-oils(0.4–1.4%),consistent with the low S content of the feedstocks(0.5–1.0%).In comparison,shale oil displayed a higher percentage of C(83%)and significantly lower percentages of O (6%)and N(0.7%)compared to the bio-oils.The total heteroatom content of the shale oil(8%N,O,and S)was less than half the val-ues measured for the bio-oils(17–20%N,O,and S).The large differ-ence in heteroatom contents represents a major distinction between bio-oils and petroleum crude oils,with the former requir-ing further processing for heteroatom reduction.The HHVs of the bio-oils(35–37MJ/kg)were significantly in-creased from the initial feedstocks(18–23MJ/kg),consistent with the large reductions in oxygen content.These values are slightly lower than the HHV estimated for the Illinois shale oil examined here(41MJ/kg)and petroleum crudes in general(41–48MJ/kg; (Speight,2001).HHVs of the HTL-derived bio-oils were consistent with previous reports for microalgae(33–40MJ/kg)(Biller and Ross,2011;Brown et al.,2010;Jena et al.,2011).For slow pyrolysis, the HHV of bio-oil produced from Spirulina(35MJ/kg)in this study was higher compared to past reports for bio-oil derived from the low-lipid microalgae Tetraselmis(28MJ/kg).Likewise,the bio-oil produced from defatted Scenedesmus(36MJ/kg)was greater than past reports for Nannochloropsis residue(24MJ/kg non-catalytic; 33MJ/kg catalytic)(Pan et al.,2010).Comparison of the HHV of pyrolysis bio-oils reported in different studies is complicated by differing conversion,recovery and aqueous phase separation meth-ods.For example,in this study DCM was used to recover the pyro-lysis bio-oil(Peng et al.,2000;Grierson et al.,2011;Pütün et al., 1999),resulting in negligible bio-oil moisture content.Residual water in the bio-oil can appear to increase the overall yield,but lower its HHV,as shown for wood-derived pyrolysis oils which typically range from15to25MJ/kg and contain15–30%water con-tent(Mohan et al.,2006).3.3.Bio-oil physico-chemical characterization3.3.1.Gas chromatography–mass spectroscopyAnalysis of low-boiling compounds(bp<350°C)in the bio-oil by GC–MS revealed distinct chemical class distributions for the major compounds comprising>1%of the total ion chromatogram (TIC)as shown in Table4(see Table S1in the Supplemental infor-mation for a full listing of major compounds).The bio-oils con-tained a much greater percentage of heteroatom compounds compared to Illinois shale oil,with the latter dominated by straight,branched,and cyclic hydrocarbons(56%).The remaining major compounds in Illinois shale oil were oxygenated,consistent with the oil’s5.9%O content and comparatively low N and S con-tents(<1%).In general,the major compounds in the HTL bio-oil identified by GC–MS consisted of cyclic nitrogenates(e.g.,pyrolle,indole,pyra-zine,and pyrimidine compounds),cyclic oxygenates(e.g.,phenols and phenol derivatives with aliphatic side-chains),and cyclic nitro-gen and oxygen compounds(e.g.,pyrrolidinedione,piperidinedi-one,and pyrrolizinedione compounds),similar with past reports of HTL bio-oils obtained from microalgae(Brown et al.,2010;Biller and Ross,2011;Jena et al.,2011).These compounds are likely de-rived from proteins,carbohydrates,and lignin in the feedstocks, which undergo a complex series of depolymerization,decomposi-tion,and reformation reactions,including Malliard reactions be-tween amino acids and sugars(Toor et al.,2011).As expected, HTL of defatted Scenedesmus produced bio-oil with the lowest frac-tion of hydrocarbons due to the negligible lipid content.The minor amount of fatty acids,esters,and hydrocarbons is likely due to the lower feedstock crude lipid content,since these compounds are known triglyceride decomposition products during thermochemi-cal conversion(Biller and Ross,2011;Miao and Wu,2004;Peterson et al.,2008).Triglycerides readily breakdown under HTL conditions to produce glycerol and fatty acids,the latter which can undergoTable2Mass balance of HTL and pyrolysis of algae(ash included)a.Feedstock Biocrude(%)Solids(%)Aqueous(%)Gaseous(%)bHydrothermal liquefactionScenedesmus45±47±217±230±3Defatted Scene.36±56±217±441±9Spirulina31±211±123±435±4Slow pyrolysisScenedesmus31±230±227±312±3Defatted Scene.24±333±121±221±2Spirulina24±130±215±315±3a Uncertainties represent standard deviations determined from triplicate ther-mochemical conversions.b Gaseous phase determined by difference for total recovery.D.R.Vardon et al./Bioresource Technology109(2012)178–187181decarboxylation and decarbonylation reactions to produce stable hydrocarbons(Peterson et al.,2008;Toor et al.,2011).Pyrolysis bio-oils displayed a significantly higher percentage of cyclic oxygenates(16–24%)compared to HTL bio-oils(8–12%),pri-marily in the form of phenolic compounds.Interestingly,pyrolysis bio-oil derived from Spirulina contained a higher percentage of straight-branched oxygenates compared to the Scenedesmus-de-rived bio-oils,which may be due to the larger percentage of simple carbohydrates in the feedstock.In contrast,lignin and cellulose have been shown to form primarily cyclic oxygenates that include phenolics,guaiacols,pyrogallols,and syringols,(Mohan et al., 2006;Demirbas and Arin,2002).Cyclic nitrogen compounds were also present in large amounts(9–13%),similar to past reports on pyrolysis bio-oils derived from Nannochloropsis residue(Pan et al.,2010),and consistent with contributions from protein com-ponents in the algal feedstocks.Pyrolysis of defatted Scenedesmus produced bio-oils with the lowest percentage of total hydrocarbons(straight,branched,and cyclic),similar to HTL-derived bio-oils;however,minor amounts of hydrocarbons were observed in both HTL and pyrolysis bio-oils, indicating that trace lipids remained in the feedstock or that pro-tein and carbohydrates were converted into hydrocarbons.As an example of the latter,during HTL small molecules produced from the decomposition,decarboxylation,and deamination of proteins may re-polymerize through Fischer–Tropsch-type reactions into hydrocarbons(Biller and Ross,2011;Peterson et al.,2008).Simi-larly,proteins have been shown to generate n-alkanes during pyro-lysis(Evans and Felbeck,1983).It should be emphasized that the GC–MS method was only able to characterize the low boiling frac-tion of the oils(bp<350°C)due to instrument temperature constraints.3.3.2.ATR-FTIR spectroscopyATR-FTIR spectroscopic analysis is consistent with the elevated heteroatom functionality of thermochemical bio-oils compared to Illinois shale oil(Fig.S1,Supplemental information).Significant peaks assigned to heteroatom-containing functional groups(Jena et al.,2011;Duan and Savage,2011;Pütün et al.,1999;Grierson et al.,2011)were observed in all bio-oil samples(1800–600cmÀ1)(Fig.S2,Supplemental information)despite prominent C A H stretch(3000–2840cmÀ1),CH2bending(1465cmÀ1),and CH3bending(1375cmÀ1)peaks.Strong absorbance between 1680–1600cmÀ1and1575–1525cmÀ1is observed for all bio-oils, possibly due to C@O stretching and N A H bending modes associ-ated with amide and amine compounds(Grierson et al.,2011). Nitrogenous functionality is consistent with compounds observed by GC–MS and similar peaks observed in slow pyrolysis bio-oil pro-duced from the microalgae Tetraselmis were attributed to protein-derived compounds(Grierson et al.,2011).The C@O stretching mode for carboxylic acids(1730–1700cmÀ1)was minor in all bio-oils,consistent with the relatively low crude lipid content of the feedstocks;however,no significant differences were observed between the bio-oils obtained from raw versus defatted feedstocks. In comparison,heteroatom peaks(1750–1500cmÀ1)were much smaller in spectra of Illinois shale oil,consistent with the lower heteroatom content and higher percentage of aliphatic compounds identified in shale oil.3.3.3.NMR spectroscopy1H NMR and13C NMR spectra provided further information regarding the proton and carbon speciation in bio-oils and Illinois shale oil(Figs.S3and S4,Supplemental information).The bio-oils displayed high aliphatic functionality(1H NMR0.5–1.5ppm;13C NMR0–55ppm),with>50%of the spectral area located in these re-gions(Fig.1and Fig.2).The high aliphatic functionality is consis-tent with the high bio-oil HHVs(Mullen et al.,2009)and the strong C A H peaks observed by FTIR.In comparison,spectra of low en-ergy–density bio-oils are reported to exhibit much less aliphatic functionality(Mullen et al.,2009).Previous work by Mullen et al. (2009)examined the aliphatic functionality of pyrolysis bio-oils derived from switch-grass(10%of1H NMR spectral area;21%of 13C NMR spectral area)and corn stover(11%of1H NMR spectral area;24%of13C NMR spectral area)(Mullen et al.,2009),which were significantly less compared to the algae-derived bio-oils examined in this study(50–55%of1H NMR spectral area;57–64%of13C NMR spectral area).13C NMR provided additional information by subdividing the aliphatic region into short aliphatics(0–28ppm;terminal methyl carbon,methylene carbon adjacent to terminus)and long/ branched aliphatics(28–55ppm;methylene carbon downstream from terminus,methylene carbon adjacent to branch points).HTL bio-oil derived from Scenedesmus(raw and defatted)displayed the highest fraction of long/branched aliphatic carbon in addition to the highest bio-oil M w(see below).This may be due to large oli-gomer compounds that contain a high fraction of methylene car-bon.Illinois shale oil also contained a high percentage of long/ branched aliphatic carbons,consistent with the high percentage of paraffin compounds identified by GC–MS.A significant fraction of the remaining spectral area for all bio-oils was assigned to aromatic and unsaturated functionality.13C NMR revealed that27–39%of the distributed carbon in the bio-oil was aromatic or unsaturated in nature.Similarly,34–43%of the dis-tributed protons detected by1H NMR were in the a-position to an unsaturated bond/heteroatom(1.5–3.0ppm)or contained in an aromatic/hetero-aromatic ring(6.0–8.5ppm).The observed func-tionality encompasses the wide range of alkene,heteroatom,aro-matic,and hetero-aromatic structures identified by GC–MS and peaks detected by ATR-FTIR.Likewise,Illinois shale oil displayedTable3Elemental analysis,higher heating value,and energy consumption ratio of thermochemical bio-oils and Illinois shale oil.aFeedstock C(%)H(%)N(%)O(%)S(%)HHV b(MJ/kg)ECRHydrothermal liquefaction bio-oilScenedesmus72.6±2.69.0±0.3 6.5±0.110.5±2.7 1.35±0.3135.50.44 Defatted Scene.72.2±0.68.9±0.17.8±0.310.5±0.50.90±0.4335.30.55 Spirulina72.2±2.39.1±0.38.1±0.29.2±2.8 1.41±0.5635.80.63Slow pyrolysis bio-oilScenedesmus73.9±2.39.3±0.27.9±0.38.1±2.60.84±0.1336.70.92 Defatted Scene.72.6±0.48.9±0.210.0±0.48.2±0.20.40±0.2835.7 1.22 Spirulina71.2±0.19.0±0.19.6±0.09.2±0.2 1.07±0.1335.2 1.24Shale oilIllinois shale oil82.89.90.7 5.90.7841.0-a Uncertainties represent standard deviations of bio-oils produced from independent thermochemical conversions conducted in triplicate.b HHVs obtained for moisture-free bio-oil following DCM extraction.182 D.R.Vardon et al./Bioresource Technology109(2012)178–187。
中得抗生素处方Antibioticprescribingat
ABX do not influence subsequent OM or deafness at 1 month
May reduce no of children still in pain 2-7 days but for each 1 improved 3 will develop ABX related side effects
Typical features only present in 15% of patients with strep throat
Recent studies do not support antibiotics as preventative of non-suppurative complications which are rare anyway
Repeated courses may make recurrent infection more likely
UTI in children
BMJ 1996;312:961-964 (13 April)
Education and debate: ABC of Urology: URINARY INCONTINENCE AND URINARY INFECTION
The adult with ‘sinusitis – like symptoms’ in primary care does not need immediate antibiotics
Any effects may be minimal/modest
The guidelines say
Many cases are viral Reserve Rx for severe
生命哲学专业术语(3)
绵延：(法durée)法国柏格森用语。
指在内心深处连绵不断地变化着的心理流。
最初在《时间与自由意志》一书中提出。
柏格森认为，由思想上清晰地存在着的感觉、表象、概念等等组成的表层心理只是意识的外壳，有如河面上结成的冰，意识的真正本质是潜伏于冰层之下的心理绵延，唯有绵延才是“基本的自我”。
绵延与表层心理不同，它不是清晰的、固定的，而是没有间断性的质的连续变化，是一种没有确定流向的，不可预测的流动。
它是既无方向也无阶段可分的生成、变化过程。
它是真正的自我，也是真实的时间。
人的记忆可分为习惯记忆和真正记忆，前者全凭大脑的功能，后者则是精神的活动，它不凭大脑而能通过形象把过去的全部经验保存下来。
绵延的概念不仅表达柏格森的意识理论，而且表达了他的时间观、运动观，并以此为基础论证其本体论和认识论。
在时间观上，强调只有绵延才是“真实的时间”,其中过去、现在、将来相互渗透、浑然一体，没有截然分明的界限，它是不可度量的意识活动；物理学上的可以计量的时间，尤其是牛顿力学的绝对时间，是人为的；时间不是物质存在的形式，只是内在的心理的东西。
在运动观上，认为运动不是事物存在的形式，只是纯粹的流变，即心理绵延；这一变化是没有相对稳定性的，没有量变作准备的连续的质变，没有方向和规律可循的纯变化即“生成”。
柏格森把绵延视为真正的实在，断言“实在就是可动性，没有已造成的事物，只有正在创造的事物，没有自我保存的状态，只有正在变化的状态”,又用绵延描述作为宇宙本体的生命和生命进化的特征，提出了创造进化论和唯心主义的生命哲学。
在认识论上，柏格森把绵延视为认识所要把握的真正实在，认为理性和科学用静止的分析的方法无法把握绵延的运动，只有诉诸于直觉，以此论证其反理性主义的直觉主义。
理智的交融：(英immersion in the indivisible flow of consciousness)法国柏格森用语。
用以说明直觉的特征。
法布里珀罗基模共振英文
法布里珀罗基模共振英文The Fabryperot ResonanceOptics, the study of light and its properties, has been a subject of fascination for scientists and researchers for centuries. One of the fundamental phenomena in optics is the Fabry-Perot resonance, named after the French physicists Charles Fabry and Alfred Perot, who first described it in the late 19th century. This resonance effect has numerous applications in various fields, ranging from telecommunications to quantum physics, and its understanding is crucial in the development of advanced optical technologies.The Fabry-Perot resonance occurs when light is reflected multiple times between two parallel, partially reflective surfaces, known as mirrors. This creates a standing wave pattern within the cavity formed by the mirrors, where the light waves interfere constructively and destructively to produce a series of sharp peaks and valleys in the transmitted and reflected light intensity. The specific wavelengths at which the constructive interference occurs are known as the resonant wavelengths of the Fabry-Perot cavity.The resonant wavelengths of a Fabry-Perot cavity are determined bythe distance between the mirrors, the refractive index of the material within the cavity, and the wavelength of the incident light. When the optical path length, which is the product of the refractive index and the physical distance between the mirrors, is an integer multiple of the wavelength of the incident light, the light waves interfere constructively, resulting in a high-intensity transmission through the cavity. Conversely, when the optical path length is not an integer multiple of the wavelength, the light waves interfere destructively, leading to a low-intensity transmission.The sharpness of the resonant peaks in a Fabry-Perot cavity is determined by the reflectivity of the mirrors. Highly reflective mirrors result in a higher finesse, which is a measure of the ratio of the spacing between the resonant peaks to their width. This high finesse allows for the creation of narrow-linewidth, high-resolution optical filters and laser cavities, which are essential components in various optical systems.One of the key applications of the Fabry-Perot resonance is in the field of optical telecommunications. Fiber-optic communication systems often utilize Fabry-Perot filters to select specific wavelength channels for data transmission, enabling the efficient use of the available bandwidth in fiber-optic networks. These filters can be tuned by adjusting the mirror separation or the refractive index of the cavity, allowing for dynamic wavelength selection andreconfiguration of the communication system.Another important application of the Fabry-Perot resonance is in the field of laser technology. Fabry-Perot cavities are commonly used as the optical resonator in various types of lasers, providing the necessary feedback to sustain the lasing process. The high finesse of the Fabry-Perot cavity allows for the generation of highly monochromatic and coherent light, which is crucial for applications such as spectroscopy, interferometry, and precision metrology.In the realm of quantum physics, the Fabry-Perot resonance plays a crucial role in the study of cavity quantum electrodynamics (cQED). In cQED, atoms or other quantum systems are placed inside a Fabry-Perot cavity, where the strong interaction between the atoms and the confined electromagnetic field can lead to the observation of fascinating quantum phenomena, such as the Purcell effect, vacuum Rabi oscillations, and the generation of nonclassical states of light.Furthermore, the Fabry-Perot resonance has found applications in the field of optical sensing, where it is used to detect small changes in physical parameters, such as displacement, pressure, or temperature. The high sensitivity and stability of Fabry-Perot interferometers make them valuable tools in various sensing and measurement applications, ranging from seismic monitoring to the detection of gravitational waves.The Fabry-Perot resonance is a fundamental concept in optics that has enabled the development of numerous advanced optical technologies. Its versatility and importance in various fields of science and engineering have made it a subject of continuous research and innovation. As the field of optics continues to advance, the Fabry-Perot resonance will undoubtedly play an increasingly crucial role in shaping the future of optical systems and applications.。
药学英语Unit 6 Text A 注释及译文
Drug Discovery and Natural Products It may be argued that drug discovery is a recent concept that evolved from modern science during the 20th century, but this concept in reality dates back many centuries, and has its origins in nature. On many occasions, humans have turned to Mother Nature for cures, and discovered unique drug molecules. Thus, the term natural product has become almost synonymous with the concept of drug discovery. In modem drug discovery and development processes, natural products play an important role at the early stage of "lead" discovery, i.e. discovery of the active (determined by various bioassays) natural molecule, which itself or its structural analogues could be an ideal drug candidate.1.origin ['ɔridʒin] n.起点，端点; 来源；出身, 血统.2.Synonymous [sɪ'nɔnəməs]adj.同义的，类义的.3.i.e. [,aɪ'i:] <拉> abbr. (=id est) 即，换言之.4.candidate ['kændidit] n.申请求职者, 候选人；报考者；候选物.有人可能认为药物发现是一个20世纪才出现的、来源于现代科学的新概念，但是事实上这个概念是源于自然界的，可以追溯到许多个世纪以前。
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2n
∆X = πi ∈ CHn(X × X) ⊗ Q
i=0
such that πi are orthogonal projectors (see §2.2). Some examples where this conjecture is verified are: curves, surfaces, a product of a
arXiv:0805.2048v1 [math.AG] 14 May 2008
MURRE’S CONJECTURE FOR A RATIONAL HOMOGENEOUS BUNDLE OVER A VARIETY
JAYA NN IYER
Abstract. In this paper, we investigate Murre’s conjectures on the structure of rational Chow groups for a rational homogeneous bundle Z → S over a smooth variety. Absolute Chow-Ku¨nneth projectors are exhibited for Z whenever S has a Chow–Ku¨nneth decomposition.
In this paper, we weaken the hypothesis on the cover X′ → A as above and obtain a Chow–Ku¨nneth decomposition whenever X′ → A is a rational homogeneous bundle over an abelian variety. This strengthens the results in [Iy] and if the open question [Ca-Pe, p.170] is answered positively then we will obtain a Chow–Ku¨nneth decomposition for all varieties which have a nef tangent bundle.
curve and surface [Mu1], [Mu3], abelian varieties and abelian schemes [Sh],[De-Mu], uniruled threefolds [dA-Mu¨1], elliptic modular varieties [Go-Mu], [GHM2]), universal families over Picard modular surfaces [MMWYK] and finite group quotients (maybe singular) of abelian varieties [Ak-Jo], some varieties with a nef tangent bundles [Iy], open moduli spaces of smooth curves, Simpsons’s Betti moduli spaces [Iy-Mu], universal families over some Shimura surfaces [Mi].
The new ingredient in the proof is to observe that a rational homogeneous bundle is ´etale locally a relative cellular variety, by applying a result of Colliot-Th´el`ene-Ojanguren [Co-Oj]. So relative Chow–Ku¨nneth projectors (in the sense of [De-Mu]) can be constructed over an ´etale cover. These projectors can be patched over the ´etale site, because the relative cohomology classes are all algebraic and the relative cohomology classes patch up. Hence, in this case, the relative Chow–Ku¨nneth projectors over the ´etale site descend to relative Chow–Ku¨nneth projectors for Z → S (see Corollary 3.4). The criterion of Gordon-Hanamura-Murre [GHM2], for obtaining absolute Chow–Ku¨nneth projectors from relative Chow–Ku¨nneth projectors can be directly applied.
In [Iy], we had looked at varieties which have a nef tangent bundle. Using the structure theorems of Campana and Peternell [Ca-Pe] and Demailly-Peternell-Schneider [DPS], we know that such a variety X admits a finite ´etale surjective cover X′ → X such that X′ → A is a bundle of smooth Fano varieties over an abelian variety. Furthermore, any fibre which is a smooth Fano variety necessarily has a nef tangent bundle. It is an open question [Ca-Pe, p.170] whether such a Fano variety is a rational homogeneous variety. We showed in [Iy] that whenever the ´etale cover is a relative cellular variety over A or if it
Moreover, the motive of the bundle Z → S is expressed as a sum of tensor products of summands of the motive of S with the twisted Tate motive (see Proposition 3.5).
0Mathematics Classification Number: 14C25, 14D05, 14D20, 14D21 0Keywords: Homogeneous spaces, ´etale site, Chow groups.
2
J. N. IYER
admits a relative Chow–Ku¨nneth decomposition, then X′ and X have a Chow–Ku¨nneth decomposition.
We state the result and proofs, in a slightly more general situation.
Theorem 1.1. Suppose Z is a rational homogeneous bundle over a smooth projective variety S. Assume that S has a Chow-Ku¨nneth decomposition. Then the motive of Z has an absolute Chow–Ku¨nneth decomposition.
We will use the standard framework of the category of Chow motives Mrat in this paper and refer to [Mu2] for details. We denote the category of motives M∼, where ∼ is any equivalence, for instance ∼ is homological or numerical equivalence. When S is a smooth variety, we also consider the category of relative Chow motives CHM(S) which was introduced in [De-Mu] and [GHM]. When S = SpecC then the category CHM(S) = Mrat.
1. Introduction
Suppose X is a nonsingular projective variety of dimension n defined over the complex numbers. Let CHi(X) ⊗ Q be the Chow group of codimension i algebraic cycles modulo rational equivalence, with rational coefficients. Jacob Murre [Mu2], [Mu3] has made the following conjecture which leads to a filtration on the rational Chow groups: