Magnetic properties of highroad-side pine tree leaves in Beijing and their environmental significance

This is a report on magnetic properties of highroad-side tree (Pinus pumila Regel) leaves collected along an expressway linking Beijing City and the Capital International Airport and further focus on their environmental contributions. A series of rock magnetic experiments show that the primary mag-netic mineral of leaf samples was identified to be magnetite,in the pseudo-single domain (PSD) grain size range 0.2―5.0 μm. On the other hand,magnet-ite concentration and grain size in leaves are ascer-tained to decrease with increasing of sampling dis-tance to highroad asphalt surface,suggesting that high magnetic response to traffic pollution is localized within a distance of some two meters away from highroad asphalt surface. Although magnetic suscep-tibility is ordinarily regarded as a simple,rapid and low-cost method for monitoring traffic pollution,saturation isothermal remanent magnetization (SIRM) can be treated as a valid proxy for monitoring air par-ticulate matter (PM) when samples are magnetically weak. It is believed that a synthetic rock magnetic study is an effective method for determining concen-tration and grain size of ferromagnets in the atmos-pheric PM,and then it should be a rapid and feasible technique for monitoring atmospheric pollution.     

Magnetic properties of street dust and topsoil in Beijing and its environmental implications

Environmental magnetic measurements were carried out on the sanrhples of street dust and topsoil, which were collected along the roadway in the urban and suburb of Beijing, including magnetic susceptibility （X）, anhysteretic remanent magnetization （ARM）, isothermal remanent magnetization （IRM） of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representative samples. Obvious differences exist between the samples of street dust and those of topsoil. Compared with topsoil samples, the concentration of magnetic particles and high-coercivity components in street dust samples are higher, and the magnetic grains are coarser. Both dust and topsoil samples are dominated by ferrimagnetic minerals, and iron particles are only detected in some dust samples. These results suggest that street dust samples reflect the characteris- tic of particles produced by industrial and traffic activities, and the magnetic property of topsoil sam- ples represents the characteristic of particles from both anthropogenic and natural sources. The distribution of magnetic parameters is influenced by the environment where the samples are collected, like industry, traffic density and other road conditions. Hard isothermal remanent magnetization （HIRM） may be used as an indicator of particles produced by traffic activity. Dust storm samples collected on 17 and 18 April, 2006 have different magnetic properties from street dust and natural particles, like loess and paleosol, which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.     

Spatial and temporal variation in magnetic properties of street dust in Lanzhou City, China

Urban environmental problems are of increasing concern. Lanzhou is a large industrial city in Northwest China. Street dust samples representing different temporal and spatial scales were collected for magnetic properties study. Magnetic measurements indicate a high concentration of magnetic minerals in Lanzhou street dust, dominated by pseudo-single domain （PSD） magnetite. The concentration of magnetic materials is distinctly high in winter and spring, low in autumn. Similarly, higher concentrations associated with heavy industry, concentrated residential development, and vehicular traffic suggest mixed contributions of magnetic material from both anthropogenic and natural sources. XIf and SOFT% are effective magnetic parameters that denote seasonal differences among magnetic properties in street dust, convenient and economical methods for monitoring street dust pollution.     

Iron reduction in tidal flat sediment indicated by magnetic measurements and its significance in the study of heavy metal pollution

Magnetic measurements and chemical analysis were conducted on the anoxic core sediment from the tidal flat along the southern bank of Yangtze Estuary. The synchronous increase in magnetite and heavy metal concentration at a depth of 54 cm is revealed, which reflects the anthropogenic input due to the near shore sewage discharge. However, the heavy metal concentration declines at the top of sediment column (4–20 cm) with the reduction of fine magnetite grains, as indicated by the magnetic measurements. It is inferred that selective dissolution of finer magnetite happens under the reduced environment. Such a phenomenon is significant for the heavy metal pollution study in the tidal flat sediments.     

A comparative study of magnetic properties between whole cells and isolated magnetosomes of <Emphasis Type="Italic">Magnetospirillum magneticum</Emphasis> AMB-1

The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials in biotechnological and biomedical applications. We carried out magnetic and electron transmission microscopy analyses of fresh Magnetospirillum magneticum AMB-1 whole cells and isolated magnetosomes. Results revealed that AMB-1 synthesized single-domain magnetite magneto-somes, which are arra...     

New Early Triassic paleomagnetic data from Huangben section, Guangdong and its tectonic implications

Continent China is composed of several blocks of variable sizes during different geological times, inwhich South China Block is composed of three tectonic units: Yangtze Block, Jiangnan Fold Belt and Southeast China Coastal Fold Belt (Fig. 1(a)), the last…     

Magnetic records of Core MD77-181 in the Bay of Bengal and their paleoenvironmental implications

Located in the low latitude region of the northeastern Indian Ocean, the Bay of Bengal represents one of the largest marginal seas in the world. The Bengal Fan hosts erosional products mostly from Himalayas and is under the influence of the Indian monsoon system. The Bengal Fan has thus been one of the ideal places for studying the uplift of the Tibet Plateau and the history of the Indian monsoon[1―8]. The intensity of the Indian monsoon is controlled by secular variations in insola- ti…     

Magnetic granulometry of recent sediments from the Huguang Maar and its implication for provenience

To understand the origin and its climatic implications of the Huguang Maar sediments, we conducted laser grain size analysis and rock mangtic measurement for the recent deposits from the Huguang Maar and for the volcanic rocks of the caldera for comparison. The grain size distributions are dominated by clayey silts for both the bulk sediments and magnetic separates. Acquisition of isothermal remanent magnetization (IRM) and thermal demagnetization of IRM suggest (titano) magnetite as the dominating magnetic mineral in the sediments; high coercivity minerals are not detected. Therefore, the ratio of the susceptibility of anhysteretic remanent magnetization (k _ARM) to the weak field magnetic susceptibility (k), k _ARM/k can be used to estimate the grain size of magnetite. The sediments and volcanic rocks yield values of 13.7 and 11.8 for the k _ARM/_k, respectively, corresponding to grain size values of ～0.03 µm and ～0.05 µm. The magnetic granulometry of lake sediments is distinctive from one of the Chinese loess, in which published data suggest a value of 6.0 for k _ARM/_k, and grain size of ～0.1 µm, but is akin to the nearby volcanic rocks. Although a Loess Plateau source of the lake sediments cannot be fully ruled out, the catchment is most probably the main source. We explain the slightly finer magnetite grain size in sediments than in the volcanic rocks as being disintegrated of particles during erosion and transportation. We conclude that there is no evidence for aeolian input of the Loess Plateau dusts into the Huguang Maar, and the relationship between magnetic parameters of the lake sediments and winter monsoon intensity is probably more complicated than previously thought.     

Preparation and characterization of Ni-P hollow material based on the shape of <Emphasis Type="Italic">Nocadia</Emphasis>

A new type Ni-P hollow material with rod-shape is prepared by electroless deposition method and heat treatment based on the shape of Nocadia, a kind of bacteria. The material is characterized and its magnetic, electromagnetic and mechanical properties are measured. It is found that the Ni-P coating transforms from a disordered structure before hollowing to an ordered arrangement of face centered cubic （FCC） Ni after hollowing at 673 K and body centered tetragonal Ni3P occurs. After hollowing no change of the surface morphology has been found. But the cytoplasm disappears and the Ni-P layer becomes more compact. A new type hollow material with shell thickness of 150-200 nm is obtained. The saturation magnetization （Ms）, remanent magnetization （Mr） and coercivity （Hc） are enhanced to 20 emu/g, 2.7 emu/g and 117.5Oe, respectively. The dielectric and magnetic loss are improved to 14 and 0.4, respectively. The hardness and the elastic modulus are raised to 1.80 GPa and 23.79 GPa, respectively. All show great improvement compared with those before hollowing.     

Mineral magnetism of quaternary red earth in Eastern China and Its paleoenvironmental significance

Mineral magnetic measurements have been made on Quaternary Red Earth profiles from Zhejiang Province, Eastern China. Three distinctive magnetic stratigraphic horizons have been identified on the basis of magnetic susceptibility, anhysteretic remanent magnetization, saturation isothermal remanent magnetization and magnetization parameters measurements. Magnetic measurements revealed that there were great variations in ferrimagnetic mineral concentration, mineralogy assemblages and grain size in Quaternary Red Earth profiles, suggesting that these variations reflect pedogenic processes fluctuation and environmental changes. The preliminary results indicate that mineral magnetic measurement of Quaternary Red Earth is useful for studying the Quaternary environmental changes recorded in paleosols.     

Rock magnetic studies on the hominoid-bearing sediments at Zhupeng, Yuanmou Basin, southwestern China and its paleoclimatic significance

It has been proposed that paleoclimatic changes and tectonic events strongly affect hominoid evolution. The Zhupeng section at Yuanmou Basin, southwestern China, with the hominoid-bearing fluvial-lacustrine sediments, is an ideal natural laboratory to test this hypothesis. This study provided an integrated magnetic study, including low-frequency susceptibility, the anisotropy of magnetic susceptibility, temperature-dependent susceptibility, hysteresis loops, isothermal remanent magnetization, and anhysteretic remanent magnetization, on samples from the Baozidongqing section at Zhupeng. Results show that the dominant mag- netic carrier is hematite, with minor amount of magnetite. Both the composition and concentration of magnetic miner- als strongly correlate with the lithostratigraphy. At least eight short-term events defined by higher concentrations of magnetite were identified. These short events reflect that the subtropical dry-hot climate is similar to today＇s climate. Basing on the lithostratigraphic and rock magnetic results, we suggest that Yuanmou Basin was in a steady deposition environment from about 11 to 7 Ma, which is characterized by alternating of long-term torrid-humid climate and short-term dry-hot climate. Our study provides invaluable environment information for understanding the climate shift and the relationship between paleoenvironment and hominoid evolution in southwestern China during late Miocene.     

Paleomagnetism of early Paleozoic volcanic rocks from the Beishan area,Gansu of northwest China: Preliminary insight into early Paleozoic kinemics of the Beishan terrane

We report rock magnetic and paleomagnetic results for Middle Silurian Gongpoquan and Middle Ordovician Huaniushan volcanic samples collected from the Mazongshan and Hongliuyuan areas of Gansu Province, northwest China. The resultsindicate that the main magnetic mineral of the Gongpoquan and Huaniushan volcanic rock is magnetite, and it may remain characteristic remanent magnetization acquired at the time of formation of the rocks. However, with the exception of samples from site go20, most of Middle Ordovician Huaniushan volcanic samples have a very weak nature remanent magnetization, and generally show an erratic demagnetization behavior, which does not allow isolation of characteristic remanent magnetizations from these samples. Comparison of paleomagnetic results obtained from the Beishan area of Gansu with Paleozoic apparent polar wander paths for Tarimand Siberia suggests that the Beishan tarrane, the southern part of the Beishanarea of Gansu beyond the Mingshui-Shipanjin-Xiaohuang- shan zone, and adjacent Tarim block and Siberia plate could not have been connected in their present configuration by the Middle Silurian time. On the other hand, we infer that the early Paleozoic Mingshui-Shipanjin-Xiaohuangshan oceanic basin may open from west to east during period from the Ordovician to Silurian, and the post-Middle Silurian closing of this oceanic basin may result from a progressed eastward scissor-like rotation.     

Remanence acquisition and its alteration on sediments

Previous palaeomagnetic work shows that the mechanism of remanence acquisition on sediments is very complicated. Different magnetizing processes under different conditions may produce some anomalous magnetic signals which have nothing to do with the changes of the geomagnetic field and are difficult to explain. The depositional remanent magnetization (DRM) may produce an inclination error and a bedding error, while postdepositional remanent magnetization (PDRM) may result in a time delay between the magnetic and sedimentary ages. When there are some different magnetic phases with different lock-in depths in the sediments, it is difficult to judge the depth of the reversal or excursion, or even the artificial magnetic signal may be produced. Even if there is only one magnetic phase in the sediment, the recorded magnetic signals may also be different if the lock-in depth is changed comparative to the lasting period of one reversal or excursion. Demagnetization may also change the primary magnetic records and the changes of water content may result in the displacement of magnetic boundary. The so-called “unstable core”, representing subtle changes in mineralogy into and out of a self-reversal region or a viscous magnetization region, gives a complicated palaeornagnetic record with many apparent changes in the palaeomagnetic direction. Moreover, some physical disturbances, such as biodisturbance, deformation, drilling processes and drying effects, may result in the remanence alteration. Some palaeomagnetic investigations demonstrate that good magnetic signals are invariably achieved on homogenous mud or clay sediments, but the worse signals on inhomogeneous profiles, especially on sandy layers.     

Composition dependence of viscosity for Al（1-x）Mgx（0≤x≤0. 10） alloys

Viscosities of molten Al（1-x）Mgx（0≤x≤0. 10 alloys have been measured in the temperature range of 973 K--1173 K by a torsional oscillation cup method. The viscosity dependence on temperature for Al（1-x）Mgx（0≤x≤0. 10 melts obeys Arrhenius equation. The viscosity increases with increasing magnesium concentration in the investigated system. There is an important relationship between viscosity and its glass-forming ability for metallic melt.     

菱铁矿热处理后的异常等温剩磁与逆向磁化

菱铁矿经过适当温度热处理后的异常等温剩磁曲线的全部形态与初始剩磁态的３个集合相对应。根据ＩＲＭ曲线存在负微商线段这一事实，提出有逆磁相存在，并用正常磁相和逆磁相的耦合来解释这种异常等温剩磁行为，这种逆向剩磁是在室温下获得的，在弱化时没有任何热过程和化学过程发生，在本质上已与观察到的逆向热剩磁和逆向化学剩磁不同。     

Mineral magnetic properties of surface sediments at Bei’anhe, Beijing, and its environmental significance

A multiparameter investigation of surface sediments from the Bei＇anhe section （Beijing） has been conducted using environmental magnetic approaches. The studied sedimentary sequence consists of pluvial and lacustrine silts and clay of the Holocene age. Magnetite, hematite and pyrrhotite were identiffed as the dominant magnetic minerals. The mineral magnetic characteristics are considered to reflect the Holocene paleoenvironmental processes of the studied area, which are different from the mineral magnetic properties of typical polluted sections reported in the Beijing area. The low-field magnetic susceptibility and saturated isothermal remanence magnetization of the section decrease gradually with increasing depth. This indicates that the concentration of magnetic minerals in the strata decreases down the section. Values of interparametric ratios, such as ARM/SIRM, XARM/Xand SIRM/X, gradually increase with increasing depth, which indicates a down-section decreasing trend in the magnetic grain size of the sediments. Pyrrhotite occurs below the depth of 22 cm, suggesting the existence of redox interface. The magnetic variations of the Bei＇anhe surface sediments might be controlled by two geological processes： reductive diagenesis and pedogenesis. Our findings may have provided a reference point for magnetic investigation of polluted surface sediments in the Beijing area.     

华南地块中三叠统巴东组红层磁倾角浅化效应

对华南地块中三叠统巴东组红层样品进行系统的岩石磁学和古地磁学研究, 采用高场等温剩磁各向异性(hf-AIR)方法, 识别出巴东组红层的磁倾角浅化因子f = 0.63。岩石磁学研究结果显示, 巴东组红层的主要载磁矿物为赤铁矿和少量磁铁矿; 磁化率和高场等温剩磁各向异性组构均指示其具有典型沉积组构特征, 表明未遭受后期构造应力改造。高温特征剩磁分量为碎屑赤铁矿所携带, 具有单一负极性, 并在95%置信水平上通过褶皱检验, 与前人在同一剖面不同位置获得的以正极性为主的古地磁方向一致。该特征剩磁方向在地层校正后的平均方向为D_s = 222.1°, I_s = ?27.2° (α₉₅ = 8.7°), 对应古地磁极为48.1°N, 215.5°E (A₉₅ = 8.4°)。对包括本文数据在内的华南中三叠世红层高质量古地磁极数据(Q≥5)用f = 0.63 进行统一校正后, 获得平均古地磁极为48.5°N, 207.6°E (A₉₅ = 10.7°)。对比华北地块同样经hf-AIR方法浅化校正后的早三叠世古地磁极, 两者在其东部参考点上的古纬度完全一致, 验证了前人提出的华南华北中生代剪刀式旋转拼合模型。     

垂直磁记录薄膜交换耦合作用及开关场分布的测量

采用Lakeshore7407型振动样品磁强计,以Co-Pt垂直磁记录薄膜为例,详细介绍了垂直薄膜等温剩磁(isothermalremanentmagnetization,IRM)曲线、直流退磁剩磁(directcurrentdemagnetizationremanence,DCD)曲线的测量方法和退磁因子的计算方法,并给出根据退磁场修正后的IRM和DCD曲线计算垂直磁记录薄膜曲线和开关场分布(SFD)的方法.最后详细讨论了薄膜的微观组织和易磁化轴取向分布对退磁场、交换耦合作用和SFD的影响.结果表明:退磁场的存在使得直接测量得到的晶粒间交换耦合作用偏小,开关场分布宽化;影响晶粒间交换耦合作用的内在原因是介质的微观组织和易磁化轴的取向分布.     

Restricted allowable generalized quantum gates

An allowable generalized quantum gate (introduced by Long, Liu and Wang) has the form of U = Σ _k=0 ^d−1 c _k U _k , where U _k’s are unitary operators on a Hilbert space H and |Σ _k=0 ^d−1 c _k |⩽1 and |c _k |⩽1 (0⩽k⩽d−1). In this work we consider a kind of AGQGs, called restricted allowable generalized quantum gates (RAGQGs), satisfying 0 < Σ _k=0 ^d−1|c _k |⩽1. Some properties of the set RAGQG(H) of all RAGQGs on H are established. Especially, we prove that the extreme points of RAGQG(H) are exactly unitary operators on H and that B(H)=R ⁺ RAGQG(H).     

Magnetic properties of surface soils across the southern Tarim Basin and their relationship with climate and source materials

The magnetic susceptibility (χ) of surface soils on the Chinese Loess Plateau (CLP) has strong positive correlation with mean annual precipitation.It is widely accepted that ultrafine magnetite/maghemite grains produced during pedogenesis are responsible for the enhancement of χ,and loess χ on the CLP has been widely used as a proxy for the intensity of the East Asian summer monsoon.However,few works have investigated mechanisms for the enhancement of χ in the case of surface aeolian sediments in westerly-dominated inland China,north of the Tibetan Plateau.Here detailed rock magnetism and grain size studies of 49 surface samples taken across the southern Tarim Basin for different rainfall/temperature/altitude conditions are presented.The results show that samples taken from desert have the lowest χ values and that χ of loessic sand and loess samples decreases with increasing altitude.In addition,the rock magnetism studies suggest that the magnetic properties of surface soils across the southern Tarim Basin are mainly controlled by the concentration of coarse aeolian ferrimagnetic minerals.The contribution of ultrafine pedogenically produced magnetic grains to χ is very limited.