复合型乳杆菌对肉鸡生产性能的影响

为探究肉鸡日粮中添加布氏乳杆菌、干酪乳杆菌和发酵乳杆菌组成的复合微生物饲料添加剂(microbial feed additives)对肉鸡生长性能、屠宰性能、肉品质及血液指标的影响。该试验选取了200只日龄相同、健康状态良好、体重无明显差别的肉鸡雏,品种为AA鸡。分为对照组(饲喂肉鸡基础饲粮)和试验组(饲喂添加复合微生物添加剂日粮,其中添加量为6 g·kg^(-1)),试验分两组进行,每组设置5个重复,每个重复20只。结果表明:与对照组相比试验组AA鸡日增重、全净膛率、半净膛率、生长激素(growth hormone,GH)含量有极显著提高(P<0.01),屠宰率显著提高(P<0.05),同时显著降低了料重比(P<0.05),试验组血清中总蛋白(TP)、血清白蛋白(ALB)、IgA、IgG显著增加(P<0.05),试验组肉鸡蒸煮损失、滴水损失极显著低于对照组(P<0.01),肉鸡剪切力极显著低于对照组(P<0.01),其他指标无显著差异。综上所述,在AA鸡日粮中添加微生物饲料添加剂可有效提高肉鸡的生产性能和屠宰性能,同时可提高肉鸡免疫功能。

基于深度特征字典学习和Largevis的遥感图像检索

提出了一种基于深度特征字典学习和Largevis的遥感图像检索方法。该方法以Inception v4为骨干网络,提取了第一个Reduction Block输出的特征图,并对其进行重组。然后利用K均值聚类算法对重组后的特征进行训练,构造深度特征字典。基于深度特征字典,对卷积特征图进行量化,得到紧凑的特征表示向量,将其与全连接层特征相结合,形成图像特征表示向量。为了避免“维度灾难”的问题,采用Largevis降维方法对图像特征表示向量进行降维。采用L2距离度量方法对降维后的特征进行相似性比对,实现了遥感图像的检索。在RS19、UCM和RSSCN7数据集上的实验结果表明,与现有的方法相比,该方法能获得更好的检索性能。

Magnetic field and performance analysis of a tubular permanent magnet linear synchronous motor applied in elevator door system

A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless structure of the forcer to improve the stability of the thrust. The influence of two major dimensions, the pitch and radius of the permanent magnet (PM), on magnetic field was studied and the best values were given by the finite element analysis (FEA). The magnetic field, back EMF and thrust of the motor were analyzed and the PM size was optimized to reduce the harmonic components of the magnetic field and improve the performance of the motor. Predicted results are validated by the experiment. It is shown that the performance of the motor and the novel elevator door system is satisfying.

Synthesis of Novel Monophosphoramidite Ligands Derived from L-Proline for Rh-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Acid Esters

Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand （Sc,Rα）-1b showed good enantioselectivity and up to 91% e.e. was obtained.

An Efficient Synthesis of Dicyclohexylmethyl Diazoacetate

Dicyclohexylmethyl diazoacetate was synthesized in excellent yield from the corresponding glycinate. which was derived in high yield from dicyclohexylmethyl chloroacetate via azide substitutuion, and reduction.

Theoretical and experimental study on the rheological properties of WIS grout and the dispersion and sealing mechanism

Recently a new grout material called water inflow sealing(WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter grouting(ICG) was proposed to investigate the influence of water dispersion on the rheological properties of the grout during the grouting process, and to testify the sealing performance of the grout,such as instant gelling ability(IGA) and anti-dispersion ability(ADA). In the experiment, dispersion was restricted in the downstream of the channel with a high turbulence intensity. The influences of ADA and IGA were therefore decoupled and evaluated separately. Experimental results revealed two distinctive sealing mechanisms of WIS. For a low initial velocity of water, WIS turned the shear flow of water into an overall movement of a plug by absorbing water into the particles. For a high initial velocity and the situation that the particles reached the outlet before sufficiently expanding, WIS modified the rheology of the water in the channel and reduced its velocity till the static state. The distinctive feature of WIS brings a reformation on the sealing mechanism and provides an effective way to control water inflow with high pressure and velocity.

Study on Synthesis of Azo-Coupling Products of 3-Aminotropolone

3-Acetamidotropolone 1 reacted with p-substitutedbenzenediazonium chloride in pyridine to afford 3-acetamido-5-(4-substitutedphenylazo)tropolones 2a~f. Hydrolysis of compounds 2a~f gave 3-amino-5-(4-substitutedphenylazo)tropolones 3a~f which could not be obtained directly from reactions of 3-aminotropolone with p-substitutedbenzenediazonium chloride. The structures of these new compounds 2a, 2c~f, 3a, 3c~f were confirmed from the elemental analysis and spectral data.

Synthesis of Chiral 3-Acylcamphors

3-Acylcamphors were synthesized in moderate yields by the condensation of camphor with esters using sodium hydride as a base.

Cyclopropanation of 1, 1-Dichloro-4-methyl-1,3-pentadiene with Diazoacetate

Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.

Synthesis and Potential Application of Novel C_(2)-Symmetrical Bis(ferrocenyl)P2N Ligand

A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.

Synthesis of novel chiral phosphine-triazine ligand derived fromα-phenylethylamine for Pd-catalyzed asymmetric allylic alkylation

A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-y1 pivalate with dimethyl malonate, good enantioselectivity （90% e.e.） was obtained by using this ligand.

Synthesis of Novel C_(2)-Symmetrical Bidentate Phosphoramidite Ligands for Rh-catalyzed Asymmetric Hydrogenation of β-(Acylamino)acrylates

Two new C2-symmetrical bidentate phosphoramidite ligands were synthesized and employed in the Rh-catalyzed asymmetric hydrogenation of β-（acylamino）acrylates, up to 89% ee with full conversions was obtained.

Selective Reduction of gem-Dichlorocyclopropane Derivatives

gem-Dichlorocyclopropanes were effectively reduced by lithium aluminum hydride, and monocylopropanes were obtained in good yields.

华南至东南亚沿海全新世环境演变与史前农业

华南至东南亚沿海地区新石器时期稻作农业的出现并成为主要经济形态显著滞后于长江下游.然而,对于制约华南沿海早期农业扩张的原因存在争议,而且一直以来缺少将考古证据与海岸带沉积与地貌演变的自然过程进行对比.本研究利用全新世孢粉记录集成,结合沿海地区钻孔古环境数据集,探讨了华南至东南亚地区沿海平原的全新世沉积过程与时空演变特征,并对沉积孢粉记录进行了集成.研究区的时空对比表明,以丘陵海岸为主的华南沿海地区在中全新世因海平面上升和海侵作用,海岸线深入陆地丘陵边缘.从6~5 ka BP之后,沉积体系开始从海相为主过渡到陆相的沉积环境,但该时期的海岸带平原土地仍较狭窄,有限的可耕种土地限制了稻作农业的发展空间.虽然在一些南方的考古遗址中发现了5~4 ka BP的水稻相关遗存,但总体揭示的经济形态仍停留在采集、渔猎为主的范畴.三角洲的演变从4 ka BP开始,进入陆地扩张和湿地面积显著增加的阶段,大部分河口湿地和沿海陆地平原逐渐形成一定的规模.尤其在2.5 ka BP之后,三角洲进积作用使平原面积加速扩大,其快速变化与花粉记录指示的稻作农业发展阶段呈现高度的耦合.特别是秦汉前后大规模的农业人口南迁,新的移民带来了先进的集约化水稻种植农业技术,进一步促进了该地区水稻农业的快速发展,并加大了刀耕火种对森林的破坏和引发严重的水土流失.此外,从沿海平原到丘陵山地的早期农业发展也存在滞后现象.本研究揭示了华南和东南亚沿海地区海岸带平原的形成阶段与农业发展过程是基本同步的,印证了人类文明发展与自然环境变化相互制约与依存的人-地关系.

Study on hydrodynamic diffusion law of the swelling particle slurry in karst pipeline

The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines.Currently,current research on the rheolog-ical model,flow computation theory,and plugging mechanism of this material is lacking.The conven-tional grouting slurry diffusion process,using the liquid-liquid two-phase flow method,fails to accurately simulate high solubility slurry and particle swelling.To address these limitations,this study established a precise constitutive model to describe the swelling particle slurry diffusion process in dynamic water.Additionally,a coupling calculation method was proposed to analyze the spatiotemporal heterogeneity of viscosity during slurry diffusion by considering the migration of slurry and the changes in viscosity.To investigate the interaction between particle swelling and flow field changes,a Compu-tational Fluid Dynamics-Discrete Element Method(CFD-DEM)coupling model was developed for the diffusion of swelling particle slurry.It is demonstrated that slurry viscosity increases exponentially within the diffusion front as the particle swelling rate rises,and the drag force exhibits an intriguing behavior of initially increasing and then decreasing as the slurry flows through the pipeline.Further-more,the CFD-DEM coupling model proved to be more accurate in describing viscosity distribution and diffusion distance compared to the finite element solution.The primary objective of this paper is to reveal the plugging mechanism and provide theoretical support for the engineering application of the swelling particle grouting material.

Challenges and opportunities in Quaternary palynology

Quaternary palynology plays a pivotal role in investigating global climate change and various other research fields,serving as an essential tool for the quantitative analysis of paleoenvironment changes.However,due to the vast diversity of terrestrial ecosystems and intricate interactions between vegetation,climate,and human activities,further advancements are required in the following aspects within this discipline.(1)The accuracy of classification in pollen morphology and fossil pollen identification needs improvement,particularly at the species level.This represents a significant challenge in present Quaternary palynology.Computer-aided intelligent recognition holds promise as a solution for species identification based on more detail pollen morphology.(2)Most pollen-based vegetation and climate reconstructions overlook the significance of bare ground.Neglecting bare ground can lead to substantial inaccuracies when quantitatively reconstructing past vegetation and climate.(3)While pollen records provide reliable information on paleoclimate changes,current quantitative climate reconstruction models heavily rely on modern pollen datasets derived from present-day vegetation disturbed more or less by human activities.This introduces bias and uncertainties into paleoclimate reconstruction.(4)Although pollen can serve as an indicator of human activities,accurately quantifying the intensity of human influence remains challenging.Improving accurate identification of crop pollen,reconstructing reliable land cover/use data,and integrating multidisciplinary data may enhance the identification and quantification of signals related to human activity in pollen records.

基于孢粉记录的亚洲季风湿润区6.8万年古气候变化定量重建

东亚季风降水的冰期-间冰期变率及其驱动机制一直备受关注和争议,然而在东亚季风湿润区内,具有完整的末次冰期以来古气候定量重建记录十分缺乏.本研究利用亚洲季风湿润区内的3个孢粉记录进行了古气候定量重建.结果表明6.8万年以来区域内的气候变化显著,年降雨量与年平均温度在末次冰盛期与全新世大暖期之间的差别可分别达到35%~51%与5~7℃.定量重建的降水记录揭示了H1与YD等快速气候变化期间东亚季风降水存在区域差异性,即印度季风影响下的中国西南部较为干燥的同时,中国中东部则表现为相对湿润.冰期-间冰期尺度下的降水记录综合变化趋势总体上与中国西南部和南亚地区的石笋δ^(18)O记录基本一致.气候重建结果还显示出MIS3降水变化对轨道太阳辐射的敏感性,尤其是南北半球间温度梯度对亚洲季风变率具有显著的影响.定量降水记录与瞬态模拟结果及主要气候强迫对比显示,在末次冰盛期过渡到全新世期间,降水的变化模式除了受控于太阳辐射变化外,还明显受到大西洋经向翻转环流事件的叠加影响.

Holocene millennial-scale megaflood events point to ENSO-driven extreme climate changes

Reconstructing the Holocene megaflood history is a key component of understanding the mechanism of past climate change and assessing the potential impact of future catastrophic events.The Pearl River is the longest watercourse in southern China,and its lower reach has been identified as one of the world's most vulnerable regions for flood exposure.However,there is a complete lack of millennial-scale geological records of paleomegafloods for the future prediction of once-in-a-hundred(even once-in-a-thousand)year floods in southern China.Here,we identified a series of paleomegaflood deposits interbedded with wood-rich peat layers in the lower West Pearl River area.All paleoflood layers have been well dated using AMS~(14)C dating method.According to the regional correlation of the flood sequence,sediment characteristics and provenance analysis,there have been at least 7 megafloods corresponding to once-in-a-thousand-year events in the lower reaches of the West Pearl River during the past 6000 years,with an average return period of approximately 855 years.The identified paleomegafloods were coeval with periods of strong El Ni?o-Southern Oscillation(ENSO),indicating that weakening of the Asian summer monsoon,associated with enhanced ENSO variability,may have triggered abnormally high precipitation leading to flooding of exceptional magnitude in southern China.In addition,the most prominent paleomegafloods identified in the lower Pearl River coincided with intervals of lower precipitation and fewer storms in central-eastern China,indicating the intensification of the meridional“tripole”pattern of precipitation across eastern China during the latter half of the Holocene.Increased land use and deforestation over the last 2000 years have resulted in soil loss and rapid degradation of local primeval forest ecosystems,leading to more catastrophic flooding.Large amounts of rice pollen in the uppermost flood layer during the Song Dynasty indicate that this megaflood may have inundated a large area of cultivated land.The periodic occurrence of Holocene megafloods not only caused damage to human existence,but also affected the evolution of local civilization.This study reveals for the first time a series of Holocene millennial-scale megafloods and sheds new light on the importance of atmosphere-ocean interactions in the tropical Pacific and monsoon subtropical climate dynamics for precipitation anomalies in East Asia.Our data yield valuable information for future research into climate extremes and hazard prevention.

Pollen-based Holocene quantitative temperature reconstruction on the eastern Tibetan Plateau using a comprehensive method framework

Quantitative climate reconstruction on long timescales can provide important insights for understanding the climate variability and providing valuable data for simulations. Unfortunately, the credibility of some attempts was hampered by incomplete reconstruction procedures. We here establish a comprehensive framework resting on high-quality Chinese modern pollen database, including modern pollen data screening, calibration set selection, major climate factor analysis, appropriate model selection, strict statistical assessment of results and ecological interpretation. The application of this framework to three high-resolution pollen records from the eastern Tibetan Plateau allows accurate quantitative inferences of Holocene temperature changes, which is the major control of regional vegetation. The results show that the mean warmest month temperature(MTwa)during the early Holocene was ca. 10.4℃ and reached the highest value at 8.5–6 ka BP(ca. 11℃). The early and mid-Holocene(11–5 ka BP) warmth was followed by 1.2℃ temperature decrease, culminating in the coolest temperatures of the Holocene during the Neoglacial cooling. Superimposing on the general cooling trend, MTwareveals a significant 500-yr periodicity with varying intensities through time, showing that warm(cold) intervals are in phase with solar maxima(minima) periods. This spectral similarity indicates a possible connection of multi-century scale climate fluctuations with solar forcing.

A combined geophysical and lithological study on eruptive history and Quaternary lacustrine stratigraphy of a maar in Leizhou Peninsula, China

As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number of maar-type volcanoes have been found in Leizhou Peninsula, South China, but little is known about their eruption processes and detailed stratigraphy of the post-eruptive sediments. We present a combined geophysical and geological analysis to study the eruptive history and post-eruptive sediment stratigraphy of a large maar, the elliptical(1.8 × 3.0 km^(2)) Jiudouyang(JDY) maar. The lacustrine stratigraphy revealed by drilling cores shows that the JDY maar lake has three major stages of evolution:(i) deep-lake sedimentary environment characterized by high autochthonous diatom productivity;(ii) shallow lake to swamp with very low water levels, characterized by a high total organic carbon(TOC) and abundant wood fragments;and,(iii) intermittent shallow lake and alluvial deposits composed of clay minerals and sand. The electrical resistivity tomography(ERT) values and lithological features are highly consistent, which clearly reveal the presence of ca. 50 m thick lacustrine sediments, directly underlain by a ca. 70 m thick basaltic lava rather than diatreme breccia in the crater. This infill sequence implies an alternation of eruption style from phreatomagmatic to Strombolian and/or lava flow, due to high magma flux and ascent rate of the Hainan Plume during the middle Pleistocene. The ERT data also reveal the initial phreatomagmatic crater floor at ca. 120 m depth. The initial crater had a large diameter/depth ratio(ca. 17), with an elongated shape(major axis to minor axis = 0.6), implying possible lateral vent migration during the eruption. A significant erosion under tropical weathering condition during the last few hundred thousand years, accounted for the large size of the maar crater. The study provides insights into the eruptive history and post-eruptive evolution of a large maar, as well as the spatial distribution of the lacustrine sediments.