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作者： david andreea 浙江师范大学

学位级别：硕士

香根草油是从香根草(Vetiveria zizanioides(L.)Nash)的根中提取的一种植物精油,在香料工业中常被大量用作主要的调香成分,而且在食品工业中也可用作调味剂。由于香根草油用途广泛,且具有抗氧化、抗菌、消炎等生物活性,近年来有大量有... 详细信息

香根草油是从香根草(Vetiveria zizanioides(L.)Nash)的根中提取的一种植物精油,在香料工业中常被大量用作主要的调香成分,而且在食品工业中也可用作调味剂。由于香根草油用途广泛,且具有抗氧化、抗菌、消炎等生物活性,近年来有大量有关其提取技术和成分分析的研究报道,研究热点围绕如何降低生产成本及环境污染,以满足日益增长的市场需求。二氧化碳膨胀乙醇(CO expanded ethanol,CXE)是一种环境友好的新型绿色溶剂,提取的效率及成本与传统蒸馏法相当,并高于超临界二氧化碳萃取。本研究经优化得到最优的工艺操作条件,与水蒸汽蒸馏工艺和超临界流体萃取工艺进行比较,评估新工艺的特点及可行性。由于香根草的化学成分复杂,香气及功效成分含量低,传统方法很难进行分离鉴定。本研究对香根草油进行了二级分子蒸馏,去除了大部分非挥发成分,显著增强色谱峰分离度,对有效成分进行了富集,结合GC-MS精油的组成分析,鉴定主要的特征性香气成分、抗菌成分及抗氧化成分,为制定产品质量标准提供理论依据,同时考察分子蒸馏用于精制香根油的可行性。CXE是一种混合流体,由主体的极性溶剂乙醇和压缩的超临界或亚临界二氧化碳组成,二氧化碳会导致溶剂的体积膨胀,对其溶解能力和传质效率等性能产生了显著影响。CXE流体对各种溶质均具有很强的溶解能力,其低温和隔氧的操作条件尤其适用于易氧化和不耐热的组分的提取。通过与水蒸汽蒸馏(HD)、间接蒸气蒸馏(IVD)及超临界流体萃取(SFE)等传统方法进行对比,综合评测了CXE萃取获得的香根草油的化学组成、抗菌及抗氧化活性。由于根系材料提取油的化学组成比植物的其他部位提取物更为复杂,因此需要进一步的精炼过程。分子蒸馏是一种在真空和低温条件下进行的分离富集技术,比较适用于热敏性的精油组分。两级分子蒸馏是一种有效的预处理方法,能使各组分有效分离,提供更可靠的成分鉴定,并对各馏分的抗氧化活性进行了测定。主要研究内容如下:(1)水蒸汽蒸馏、间接蒸气蒸馏和超临界流体萃取等传统方法提取香根草油的研究。结果表明提取时间、物料粒径及浸泡时间对香根草精油的得率有显着影响。水蒸汽蒸馏和间接蒸汽蒸馏法的提取时间为12-18小时,而超临界流体萃取的提取时间仅为2小时。HD和IVD的油得率为0.6%(w/w),SFE油得率约为0.5%(w/w)。(2)采用由极性溶剂(乙醇)和压缩的CO形成的CXE进行了香精油的绿色提取,并与纯乙醇提取进行了对比。采用基于中心组合设计(CCD)响应面法(RSM),优化了萃取工艺,得到了最佳操作条件:温度50oC,压力8.4 MPa,CO摩尔分数0.22及乙醇流速5 m L/min。CXE萃取的油得率为5.12-7.42%,显著高于常规方法。气相色谱-质谱(GC-MS)分析了CXE方法得到的香根草精油样品。结果表明,CXE油主要成分为烃、醇、羰基化合物及羧酸,其中22种成分与传统香根草精油的成分相同或相似。CXE油中的三种主要成分分别为valerenol(18.48%)、valerenal(10.21%)和β-cadinene(6.23%)。(3)结合GC-MS分析,对香根草油进行了两阶段的分子蒸馏,进一步精制分离。通过调节压力、进料温度、蒸发温度、进料速度和刮板转速进行第一阶段分子蒸馏,在低压(0-2 Pa)、进料温度80oC的条件下,可以确保精油样品的流动性,其密度约为0.878g/m L,粘度为4.764 mPa·s。在蒸发温度80oC的条件下可得到相对较高的总回收率(79.81%),并得到三个馏分:1R含量为28.61%,1D为51.01%和1D为0.19%。刮板转速设定为300 rpm,进料速度为2 m L/min,可形成约5 mm完整的蒸发膜,停留时间约为15 s。第二阶段的分子蒸馏将一级冷凝器温度降为5oC,其他条件与第一阶段相同。GC-MS分析表明,在第一阶段分子蒸馏中,可以去除大部分相对分子量较高的非挥发组分,在第二次分子蒸馏中,轻馏分(2D)中,一些特定组分出现了富集,如khusimene(1.79%),β–vatirenene(5.86%)和humulane-1,6-dien-3ol(10.74%)等。此外,两阶段的分子蒸馏总共发现了74种成分,第一阶段发现了38种成分,第二阶段发现了43种成分。经分子蒸馏后,GC色谱峰的分离度显著改善,因而分子蒸馏可用作色谱法鉴定香精油总组成的预处理方法。(4)通过DPPH和ABTS自由基清除试验检测了传统提取和绿色提取的香根草精油的抗氧化活性,结果表明香根草精油的抗氧化能力按降序排列依次为:IVD>HD>CXE>SFE。此外,DPPH自由基清除试验表明,新方法得到的香根草精油及分子蒸馏馏分的抗氧化活性与传统精油相近。(5)通过微量稀释法测定了香根草精油对革

关键词：香根草油 CO2膨胀乙醇分子蒸馏 GC-MS 生物活性

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结合GC-MS的分子蒸馏富集柚皮精油抗氧化成分的研究

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中国粮油学报 2018年第7期33卷 65-71页

作者：王芳岳朝敏 andreea david 林洁茹何宇城邓刚浙江师范大学化学与生命科学学院金华321004 浙江师范大学行知学院金华321004

分子蒸馏技术富集柚皮精油的抗氧化成分,经两次分子蒸馏后,得到两种重馏分(1RH、2RH)、两种中间馏分(1DM、2DM)和一种轻馏分(1DL)。分子蒸馏过程中,采用气相色谱-质谱联用技术(GC-MS)实时分析了各馏分的化学组成,确定了33种化合物。通... 详细信息

分子蒸馏技术富集柚皮精油的抗氧化成分,经两次分子蒸馏后,得到两种重馏分(1RH、2RH)、两种中间馏分(1DM、2DM)和一种轻馏分(1DL)。分子蒸馏过程中,采用气相色谱-质谱联用技术(GC-MS)实时分析了各馏分的化学组成,确定了33种化合物。通过测定各馏分清除DPPH·和ABTS+·的能力得知,香叶醇和β-石竹烯是主要的抗氧化物质,被富集到重馏分(2RH)中,浓缩比分别为3.7和4.3,同时D-柠檬烯在轻馏分(1DL)中得到明显富集,浓缩比达4.9。抗氧化实验表明重馏分(2RH)的抗氧化能力较原油得到了明显提升,清除DPPH·和ABTS+·的能力分别比原油提高了60%和75%。分子蒸馏技术不仅用于分离脂肪和脂肪酸,而且在植物精油精制及提高附加值方向也具有广阔的应用前景。

关键词：分子蒸馏抗氧化活性精油

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超临界CO2夹带乙醇萃取裂殖壶藻油脂的工艺研究

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中国粮油学报 2019年第11期34卷 45-50,56页

作者：李佩雷李红娜敬科举林洁茹 andreea david 邓刚浙江师范大学化学与生命科学院金华321004 厦门大学化学化工学院厦门361005

研究了超临界CO2夹带乙醇流体从裂殖壶藻Schizochytrium sp.中提取富含DHA油脂的新工艺。基于气液相平衡性质,确定了夹带剂乙醇的添加范围,并对提取过程进行动力学分析,确定了二氧化碳的使用量。通过中心组合设计的响应面优化试验,获得... 详细信息

研究了超临界CO2夹带乙醇流体从裂殖壶藻Schizochytrium sp.中提取富含DHA油脂的新工艺。基于气液相平衡性质,确定了夹带剂乙醇的添加范围,并对提取过程进行动力学分析,确定了二氧化碳的使用量。通过中心组合设计的响应面优化试验,获得了最佳提取工艺条件:温度52℃、压力38 MPa、乙醇摩尔比0.04。该条件下,微藻油脂的回收率约为88.2%,显著高于纯超临界CO 2萃取的回收率(71.9%)。根据Peng-Robinson方程考察了混合流体的密度变化对油脂溶解度的影响,部分解释了操作条件对油脂回收率的影响。脂肪酸组成分析显示,新工艺得到的油脂中的DHA质量分数约为39.9%,略高于传统工艺。由此可知,超临界CO 2夹带乙醇流体是一种极性范围广、溶解能力强的绿色提取介质,非常适用于中性微藻油脂的提取。

关键词：油脂提取超临界CO 2 夹带剂裂殖壶藻

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Late Ordovician Mass Extinction: Earth, fire and ice

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National Science Review 2024年第1期11卷 51-65页

作者： david A.T.Harper Palaeoecosystems Group Department of Earth SciencesDurham University

The Late Ordovician Mass Extinction was the earliest of the ‘big’ five extinction events and the earliest to affect the trajectory of metazoan life. Two phases have been identified near the start of the Hirnantian period and in the middle. It was a massive taxonomic extinction, a weak phylogenetic extinction and a relatively benign ecological extinction. A rapid cooling, triggering a major ice age that reduced the temperature of surface waters, prompted a drop in sea level of some 100 m and introduced toxic bottom waters onto the shelves. These symptoms of more fundamental planetary processes have been associated with a range of factors with an underlying driver identified as volcanicity. Volcanic eruptions, and other products, may have extended back in time to at least the Sandbian and early Katian, suggesting the extinctions were more protracted and influential than hitherto documented.

关键词： Ordovician LOME paleoecology palaeobiogeography biotas

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One-dimensional monotone nonautonomous dynamical systems

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Science China Mathematics 2024年第2期67卷 281-314页

作者： david Cheban Faculty of Mathematics and Computer Science Laboratory of Fundamental and Applied MathematicsMoldova State UniversityChisinau 2009Moldova

This work is devoted to the study of the dynamics of one-dimensional monotone nonautonomous(cocycle) dynamical systems. A description of the structures of their invariant sets, omega limit sets,Bohr/Levitan almost periodic and almost automorphic motions, global attractors, and pinched and minimalsets is given. An application of our general results is given to scalar differential and difference equations.

关键词： one-dimensional dynamics pinched and minimal sets global attractors monotone nonautonomous cocycle almost periodic solutions scalar differential/difference equations

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Kerogen Kinetic Distributions and Simulations Provide Insights into Petroleum Transformation Fraction (TF) Profiles of Organic-Rich Shales

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Journal of Earth Science 2024年第3期35卷 747-757页

作者： david A.Wood DWA Energy Limited Lincoln LN59JPUnited Kingdom

Two hundred and fifty single first-order Arrhenius reactions are simulated to generate S2 pyrograms at three heating rates 25,15,and 5°C·*** activation energy(E)and pre-exponential factor(A)of the reactions simulated follow a long-established trend of those variable values displayed by shales and *** characteristics of the transformation fraction(TF)profiles(product generation window temperatures)of the simulated single reactions are compared to the TF profiles of recorded shale pyrograms generated by multiple reactions with different E-A values lying near the defined E-A *** similarities and differences are observed between the TF profile values of the two *** similarities support the spread of E-A values involved in shale pyrogram best *** differences are most likely explained by the complexity of the multiple kerogen first-order and second-order reactions contributing to the recorded shale pyrograms versus the simplicity and crispness of the single first-order reactions *** results also justify the validity of using the previously described“variable E-A pyrogram-fitting method”of multi-heating-rate shale pyrograms enabling optimizers to choose multiple reactions from an unlimited range of E-A *** contrast,further doubt is cast on the validity of the constant-A pyrogram-fitting method used by the Easy%Ro technique,in that a distribution of reactions with a single A value is unlikely to represent the complex variety of kerogen macerals observed in shale *** profiles generated by the variable E-A pyrogram-fitting method lie close to the established E-A trend and are likely to provide more realistic TF generation window temperatures than TF profiles generated by the constant-A pyrogram-fitting method.

关键词： transformation fraction profiles simulated S2 pyrograms multiple heating rates kerogen/shale kinetics S2 pyrogram fitting techniques kerogen petroleum research.

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Analysis of ancient mass extinction recoveries in marine environments: generating strategies for managing outcomes of the current mass extinction

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National Science Review 2024年第1期11卷 8-10页

作者： david J.Bottjer Department of Earth Sciences University of Southern California

The defining feature of a mass extinction and its associated recovery is the global amount of extinction that occurred[1]. However, there is finer-scale detail to the story, as seen in the ongoing modern mass extinction(the sixth mass extinction), which exhibits variable effects among marine ecosystems and environments, and hence geographic areas [1].

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Gastroesophageal reflux following peroral endoscopic myotomy for achalasia:Bumps in the road to success

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World Journal of Gastroenterology 2024年第29期30卷 3461-3464页

作者： david Itskoviz Stephen david Howard Malnick Kaplan Medical Center Institute of Gastroenterology and HepatologyHebrew University Medical School of JerusalemRehovot 76100Israel Kaplan Medical Center Department of Internal Medicine CHebrew University Medical School of JerusalemRehovot 76100Israel

Achalasia can significantly impair the quality of *** clinical presentation typically includes dysphagia to both solids and liquids,chest pain,and *** can be delayed in patients with atypical presentations,and they might receive a wrong diagnosis,such as gastroesophageal reflux disease(GERD),owing to overlapping symptoms of both *** the cause of achalasia is poorly understood,its impact on the motility of the esophagus and gastroesophageal junction is well *** treatment modalities have been utilized,with the most common being surgical Heller myotomy with concomitant fundoplication and pneumatic balloon ***,peroral endoscopic myotomy(POEM)has gained popularity as an effective treatment for achalasia,despite a relatively high incidence of GERD occurring after treatment compared to other *** magnitude of post-POEM GERD depends on its definition and is influenced by patient and procedure-related *** longterm sequelae of post-POEM GERD are yet to be determined,but it appears to have a benign course and is usually manageable with clinically available *** risk factors for post-POEM GERD and modifying the POEM procedure in selected patients may improve the overall success of this technique.

关键词： Achalasia Per-oral endoscopic myotomy Gastroesophageal reflux Pneumatic dilatation Heller myotomy Proton pump inhibitor Acidic fermentation

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Discovery of strong bulk Dzyaloshinskii-Moriya interaction in composition-uniform centrosymmetric magnetic single layers

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 174-180页

作者： Lijun Zhu david Lujan Xiaoqin Li State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China Department of Physics Center for Complex Quantum SystemsUniversity of Texas at AustinAustin 78712USA

Dzyaloshinskii-Moriya interaction(DMI)is the key ingredient of chiral spintronic phenomena and the emerging technologies based on such phenomena.A nonzero DMI usually occurs at magnetic interfaces or within non-centrosymmetric single ***,we report the observation of a strong unexpected DMI within a centrosymmetric polycrystalline ferromagnet that has neither a crystal inversion symmetry breaking nor a composition *** DMI is a bulk effect,increases with the thickness of the magnetic layer,and is insensitive to the symmetry of the interfaces or the neighboring *** observe a total DMI strength that is a factor of>2 greater than the highest interfacial DMI in the *** DMI most likely arises from the strong spin-orbit coupling,strong orbital hybrization,and a“hidden”long-range asymmetry in the *** discovery of the strong unconventional bulk DMI in centrosymmetric,composition-uniform magnetic single layers provides fundamental building blocks for the emerging field of spintronics and will stimulate the exploitation of unconventional spin-orbit phenomena in a wide range of materials.

关键词： Brillouin light scattering Dzyaloshinskii-Moriya interaction spin wave

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Evaluation of hand infections in the emergency department using point-of-care ultrasound

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World Journal of Emergency Medicine 2024年第4期15卷 283-288页

作者： david Ahmad Haidar david Mintz Brandon M Wubben Omar Rizvi Srikar Adhikari Department of Emergency Medicine Michigan MedicineAnn Arbor 48109-1382USA University of Arizona College of Medicine Tucson 85724USA Department of Emergency Medicine University of IowaIowa City 52242-1009USA Department of Surgery University of Arizona College of MedicineTucson 85724USA Department of Emergency Medicine University of Arizona College of MedicineTucson 85724USA

BACKGROUND:We aimed to evaluate the utility of point-of-care ultrasound(POCUS)in the assessment of hand infections that present to the emergency department(ED)and its impact on medical decision making and patient ***:We conducted a retrospective review of patients who presented to two urban academic EDs with clinical presentations concerning for skin and soft tissue infections(SSTI)of the hand between December 2015 and December *** trained POCUS fellowship physicians reviewed an ED POCUS database for POCUS examinations of the *** then reviewed patients’electronic health records(EHR)for demographic characteristics,history,physical examination findings,ED course,additional imaging studies,consultations,impact of POCUS on patient care and final ***:We included a total of 50 cases(28 male,22 female)in the final *** most common presenting symptoms and exam findings were pain(100%),swelling(90%),and erythema(74%).The most common sonographic findings were edema(76%),soft tissue swelling(78%),and fluid surrounding the tendon(57%).POCUS was used in medical decision making 68%of the time(n=34),with the use of POCUS leading to changes in management 38%of the time(n=19).POCUS use led to early antibiotic use(11/19),early consultation(10/19),and led to the performance of a required procedure(8/19).The POCUS diagnosis was consistent with the discharge diagnosis of flexor tenosynovitis 8/12 times,abscess 12/16 times,and cellulitis 14/20 ***:POCUS is beneficial for evaluating of hand infections that present to the ED and can be used as an important part of medical decision making to expedite patient care.

关键词： Ultrasound Point-of-care ultrasound Cellulitis Abscess Flexor tenosynovitis

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