On the relevance of iron adsorption to container materials in small-volume experiments on iron marine chemistry: Fe-aided assessment of capacity, affinity and kinetics

Iron chemistry in seawater has been extensively studied in the laboratory, mostly in small-volume sample bottles. However, little has been reported about iron wall sorption in these bottles. In this paper, radio-iron ⁵⁵Fe was used to assess iron wall adsorption, both in terms of capacity, affinity and kinetics. Various bottle materials were tested. Iron sorption increased from polyethylene/polycarbonate to polymethylmetacrylate (PMMA)/high-density polyethylene/polytetrafluoroethylene to glass/quartz, reaching equilibrium in a 25–70 h period. PMMA was studied in more detail: ferric iron (Fe(III)) adsorbed on the walls of the bottles, whereas ferrous iron (Fe(II)) did not. Considering that in seawater the inorganic iron pool mostly consists of ferric iron, the wall will be a factor that needs to be considered in bottle experiments.The present data indicate that for PMMA with specific surface (S)-to-volume (V) ratio S/V, both iron capacity (42 ± 16 × 10^− 9 mol/m² or 1.7 × 10^− 9 mol/L recalculated for the S/V-specific PMMA bottles used) and affinity (log K_Fe'W = 11.0 ± 0.3 m²/mol or 12.4 ± 0.3 L/mol, recalculated for the S/V-specific PMMA bottles used) are of similar magnitude as the iron capacity and -affinity of the natural ligands in the presently used seawater and thus cannot be ignored.Calculation of rate constants for association and dissociation of both Fe'L (iron bound to natural occurring organic ligands) and Fe'W (iron adsorbed on the wall of vessels) suggests that the two iron complexes are also of rather similar kinetics, with rate constants for dissociation in the order of 10 ⁻⁴–10^− 5 L/s and rate constants for association in the order of 10⁸ L/(mol s). This makes that iron wall sorption should be seriously considered in small-volume experiments, both in assessments of shorter-term dynamics and in end-point observations in equilibrium conditions. Therefore, the present data strongly advocate making use of iron mass balances throughout in experiments in smaller volume set-ups on marine iron (bio) chemistry.     

单层正三角锯齿型石墨烯量子点的电子结构和磁性

采用基于密度泛函理论的广义梯度近似(GGA),对不同尺寸(N=2—11)的单层正三角锯齿型石墨烯量子点(Z _{N -GNDs)的结构进行优化,得到与实验数据较好符合的晶格常数,进一步计算得到不同尺寸下体系的自旋多重度、磁矩、电子态密度以及自旋电子密度.结果表明:所有体系都呈现金属性,在尺寸较小的体系中量子尺寸效应对电子结构的影响比较明显;与单层石墨烯片一样,sp²杂化作用和非键态电子在量子点中仍起到非常重要的作用;费米能级上有自旋向上的电子分布,体系的自旋多重度}     

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.     

Marine bacterioneuston

A specific community of heterotrophic microorganisms—bacterioneuston—was detected in the near surface microlayers of the sea (microhorizons 150, 1–2 cm) by means of original methods and sampling devices. Investigation of bacterioneuston in the different seas (the Black Sea, the Sea of Azov, the north-eastern part of the Pacific Ocean) revealed its peculiar features which are high content of microorganisms, its flourishing during the period of wind and wave action increase, a rich specific composition with a bright pigmentation of strains and somewhat specific biochemical properties.The ways and sources of bacterioneuston formation as well as its part in the life of water ecosystems are discussed in this paper.     

The complex band structure for armchair graphene nanoribbons

Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well with the bulk band structure calculated by a Hermitian matrix. The complex band structure gives extra information on carrier's decay behaviour. The imaginary loop connects the conduction and valence band, and can profoundly affect the characteristics of nanoscale electronic device made with graphene nanoribbons. In this work, the complex band structure calculation includes not only the first nearest neighbour interaction, but also the effects of edge bond relaxation and the third nearest neighbour interaction. The band gap is classified into three classes. Due to the edge bond relaxation and the third nearest neighbour interaction term, it opens a band gap for N=3M-1. The band gap is almost unchanged for N=3M+1, but decreased for N=3M. The maximum imaginary wave vector length provides additional information about the electrical characteristics of graphene nanoribbons, and is also classified into three classes.     

In situ tests for ice strength measurements

Ice effects have caused extensive damage. Enormous forces have been recorded. On the other hand, ice has been used as a structural material under various situations. To use ice beneficially and to assess the danger of ice forces, it is necessary to know the mechanical properties of ice.Results from the large number of ice tests carried out in laboratories show the difficulties of sampling and testing procedures. Most of the tests have not reproduced faithfully enough the conditions existing in nature. To obtain adequate results, laborious and slow samplings and preparations of test specimens have been necessary. Recently, extensive use has been made of in situ tests in order to reduce the number of factors whixh can induce errors in measurements. Large scale tests have simulated actual structures. General ice properties have become available from small-scale in situ tests. Since these tests give rapid results, a large number are already available with a good coverage of field conditions.A theoretical basis has been devised for these in situ tests which measure essentially the unconfined and confined compressive strengths of ice, and practical devices have been developed to execute these tests. A correlation of measurements from laboratory tests and in situ tests has established a link between natural and artificial environments. Brittle elastic and clastic theories have been applied, to find the best correlations for ice tests. Test results have been related to the mechanical properties as used in engineering practice.A very summary conclusion of results is that cold sea ice and cold fresh water ice are both very strong. However, depending on the load rate, ice can be quite brittle, which mitigates dangerous effects from ice action against massive structures.     

Geometrical properties of perfect breaking waves on composite breakwaters

The experimental results have so far shown that when a wave breaks on a vertical wall with an almost vertical front face at the instant of impact that is called perfect breaking or perfect impact, the greatest impact forces are produced on the wall. Therefore, the configuration of breaking waves is important in the design considerations of coastal structures. The present study is concerned with determining the geometrical properties of oscillatory waves that break perfectly on the vertical wall of composite-type breakwaters. The laboratory tests for perfect breaking waves on composite breakwaters are conducted with base slopes of 1/2, 1/4 and 1/6, and with berm widths of 0.00, 0.10, 0.20, 0.30 and 0.40 m. The shape and the dimensions of waves at the instant of perfect breaking on the wall are determined using a video camera. The experimental results for the geometrical properties of the breakers are presented non-dimensionally. Within the range of present experimental conditions, it is found that the dimensionless breaker crest height, h_b/d_w, and dimensionless breaker height, H_b/d_w, decrease; and, dimensionless breaker depth, d_w/H₀, increases with increasing relative berm width, B/D. The breaker height index, H_b/H₀, is almost unaffected by B/D. The deep-water wave steepness and the base slope of the breakwater do not seem to influence the geometrical properties of the breakers at wall systematically.     

附着基粗糙度等因素与海藻密度的相关性研究

海藻附着基表面粗糙度与孢子附着密度有密切的相关性;已经由许多研究证实。但是海藻苗的密度是否仍然受到附着基粗糙度的影响;还缺乏明确的结论。本文以尼龙和亚克力两种材料作为海藻附着基;悬挂于自然海区中使海藻孢子附着并萌发生长;用以研究附着基表面粗糙度对4种海藻密度的影响。结果显示;多管藻、尾孢藻、点叶藻、硬毛藻这4种海藻;在不具沟槽的光滑面;密度显著低于任何有沟槽的粗糙面;但粗糙度不同的附着基之间比较;对海藻密度的影响并不显著。室内培育的海带苗;在尼龙上的密度与粗糙度成正相关;但是将海带苗移至海上培育后;不再与粗糙度有相关性;可能与其假根状固着器下海后的发育有关。本文还试验了海泥、灭活海泥和低栖硅藻3种沉积物与附着基粗糙度对海藻密度的影响;结果表明;沉积物和附着基粗糙度;以及它们的交互作用对海藻密度的影响;因附着基的材料和海藻种类而有差别。     

In situ experimentation at the water/sediment interface in the deep sea: 1. Submersible experimental instrumentation developed for sampling and incubation

In order to make progress in the study of processes in deep-sea ecosystems, we have developed a strategy for the use of submersibles in conjunction with free vehicles. The BIOCYAN programme, which was conducted by French oceanographers at a permanent station in the Bay of Biscay, involved the use of submersibles for benthic ecological studies. It lead to the development of a variety of equipment for sampling and experimental studies. The submersible Cyana has a limited equipment workload, so the initial step was to develop a free vehicle which could function as a shuttle to act as an independent transport for equipment to be used from the submersible. Two other devices have been developed for sampling with precision the surficial layers of the sediment, one of which can be used in conjunction with an injection module to measure rates of processes in situ by incubations, following injection with labelled substrates. These devices, the free-lift shuttle, tube corers, a blade box corer and the associated injection module are described.     

Estimation of heavy and opaque mineral contents of beach and offshore placers using rock magnetic techniques

Exploration for placer deposits involves heavy and opaque mineral data that are conventionally obtained using toxic and expensive chemicals and time-consuming and tedious microscopic counting of a large number of grains. In this investigation, we have used rock magnetic properties to obtain estimates of heavy and opaque mineral contents of placers from the SW coast of India. Magnetic susceptibility and other magnetic properties show strong correlations with heavy and opaque (r > 0.87 andr > 0.94; significant at the 1% level) mineral contents. As one or more types of magnetic minerals are invariably present in placers, magnetic properties may be used as a proxy for heavy and opaque mineral contents. This simple, rapid, inexpensive, and nondestructive method may be adopted by those involved in placer exploration to rapidly scan a large number of samples and delineate economically important pockets for more detailed investigations. This method saves considerable time and tedium. Using magnetic properties, rather than radioactivity, as a proxy for heavy and opaque mineral contents is more advantageous because one or more magnetic minerals are always present, but a radioactive mineral may not always be present in placers. An important limitation is that the ratio of magnetic to heavy/opaque mineral contents should not vary widely.     

Multi-sensor satellite time series of optical properties and chlorophyll-a concentration in the Adriatic Sea

Advanced remote sensing techniques and regional algorithms are combined to produce and analyze a 12-year multi-sensor time series of bio-optical properties for the Adriatic Sea. First, a multi-sensor series of normalized water-leaving radiance L_WN is created with an optically-based merging technique applied to SeaWiFS and MODIS data, then distributions of inherent optical properties (IOPs) are obtained with a semi-analytical bio-optical model. Additionally, Chla is computed by two regional empirical algorithms associated with two classes of optical properties representative of open ocean waters and Adriatic coastal regions (Classes 1 and 2, respectively). The domain of applicability of each algorithm is dynamically determined on the basis of the L_WN input spectrum by a novelty detection approach. The various satellite products are validated using a comprehensive bio-optical time series collected in the northern Adriatic. At the basin level, the frequency of occurrence of Classes 1 and 2 are 61% and 10%, respectively, with Class 2 waters particularly located in the northern part and characterized by higher levels of Chla and IOPs. The annual cycle of Chla over the 12-year period exhibits significant variations in amplitude and phase; moreover, the annual cycle shows a reduced amplitude during a period centered on 2004 for a time interval that varies with the region. In the northern Adriatic, the overall level of Chla appears lower between 2003 and 2008 compared to the beginning of the series.     

一种制备单原子碳链的方案

考虑到迄今为止实验上尚不能制备含有上百个原子的自由单原子链,本文提出利用探针从graphene中拉伸较长单原子碳链的设想,并通过分子动力学计算发现,室温下可以利用C60探针以1 m/s的速度从graphene的zigzag边缘拉出较长的一维单原子碳链,为实验提供了一种制备单原子碳链的可能方案.     

Current methods for obtaining,logging and splitting marine sediment cores

The main types of deep-sea sediment coring devices are described and their relative merits and drawbacks are discussed. These devices include box corers, gravity corers, piston corers, giant piston corers and vibrocorers. Recent utilisations of kevlar and polyester coring warps are also discussed, since these are the only warps capable of handling the large weights associated with the larger devices. Recent developments in wholecore logging, including P wave, density and magnetic susceptibility, are described as are methods of subcoring and core splitting to obtain the maximum amount of detail on the split surfaces. The wholecore logs together with a good colour photograph of the recently split sediment surface provide a lasting unambiguous record of the core.     

Indirect evidence of deep flow east of a North Pacific seamount

East-west vertical sections centered on Kinmei Seamount (35N, 172E) of potential temperature, salinity, and oxygen, based on recent standard hydrographic measurements, and vertical profiles ofin situ temperature and density ( ₄) east of the seamount, based on STD data, show contrasting variability in the deep water characteristics east and west of the seamount. These data are consistent with horizontal variations in water mass properties (temperature-salinity and temperature-oxygen curves) east of the seamount between 2,600–3,900 m but not west of the seamount. East of the seamount on surfaces of constant potential temperature (or density) salinity and oxygen are higher at a station 200 km from the seamount than at stations on either side. From these relations and from known deep water properties of the North Pacific, it is suggested that east of the seamount, between 2,600–3,900 m, the observations are consistent with northward flow, which is interpreted to be a western boundary current with an east-west scale of about 300 km.     

Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model (GSM) beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope vert pvert and the smaller the off-axis distance vert dvert are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The GSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.     

The ecophysiology of Phaeocystis globosa: A review

A straightforward ecophysiological characterization of Phaeocystis globosa is hampered by its complex polymorphic life cycle in whic flagellates and colonial cells express different physiological and morphological properties. There is also increasing evidence that, besides the existence of different species, the most widespread species Phaeocystis globosa (Scherffel) has to be subdivided into at least five different ecotypes which again differ in their ecophysiological properties. Most research has been performed on the P. globosa ecotype North European (English Channel/ North Sea isolates). From the available literature it must be concluded that flagellate cells are better competitors for light and phosphate than colonial cells, due to their superior uptake characteristics. To a limited extent this phenomenon is compensated in colonial cells by their ability to continue growth and cell division in the dark at the same rate as in the light, at the expense of extracellular colonial mucus. In contrast with other algal species, colonial cells of P. globosa are better competitors for nitrogen than for phosphorus.Flagellates transform into vegetative cells and form colonies in environments with irradiance levels of about 50 μE·m⁻²·s⁻¹ or more and an optimum phosphate concentration of 1 μM. A solid substrate and the presence of calcium are prerequisites for colony formation. In environments where phosphorus is limiting no new colonies are formed. There is some evidence that nitrate stimulates colony formation, whereas high ammonium values (above 1 μM) tend to suppress colony formation. Massive blooms of P. globosa colonies can be attributed to a combination of environmental conditions that induce colony formation and smaller grazing losses of colonial cells than of flagellates, rather than to superior ecophysiological characteristics of colonial cells.     

The hydrophobic fraction of organic matter in the Krka River Estuary

Surface active substances have been studied in the Krka River Estuary using an a.c. polarography method and various fractionation procedures. Total surface substances (SA_T) were separated into (particulate) heterodispersed and dissolved fractions by filtration. The dissolved fraction was separated into hydrophobic basic and neutral components, hydrophobic acid and hydrophilic components by sorption on to XAD-8 resin.The content and the composition of SA_T varied seasonally, depending on the biological activities taking place in the Krka River Estuary. The accumulation of SA_T, with hydrophobic properties, occurred at the fresh/saline water interface along the vertical profile. Daily changes in the form of the surface active substances along the vertical profile were observed. The formation of the heterodispersed fraction, especially observable in the upper freshwater layer and at the halocline, resulted in the change of physico-chemical properties of surface active substances. Organic matter appeared mainly in a dissolved form in the deeper saline water layer, showing negligible oscillations.The electrochemical characterization of the fractionated SA_T indicated that strong hydrophobicity of the surface active substances under natural pH conditions could be attributed to the significant contribution of the heterodispersed fraction of the organic material, which is the most reactive part of the surface active substances in the Krka River Estuary.The dissolved fraction of the surface active substances, prevailing in the deeper saline water layer, exhibited either hydrophilic or conditionally hydrophobic properties, depending on pH and ionic strength of the medium.     

浒苔多糖的分级纯化及保湿活性研究

用DEAE-Sepharose FF离子交换凝胶层析柱对浒苔(Enteromorpha)多糖进行分级纯化,利用HPLC色谱分析了单糖组成,并以甘油和透明质酸为对照,研究其吸湿和保湿活性。结果表明,浒苔多糖主要为葡萄糖醛酸-鼠李糖-木糖-甘露糖聚合物;浒苔多糖主要由两种组分组成,其一组分木糖和鼠李糖含量摩尔比为1.11:1,另一组分木糖和鼠李糖含量比为1:3.28;浒苔多糖具有与透明质酸相似的吸湿和保湿能力。     

Nonlinear properties of laboratory wind waves at energy containing frequencies

Nonlinear properties of wind waves in a wind-wave tunnel are investigated by measuring the probability density distribution of surface elevation. The surface elevation distribution of raw records are found to have a positive skewness (K ₃=0.21 to 0.43) and a negative kurtosis (K ₄=–0.74 to –0.41) with magnitude depending of fetch and wind speed. The values of skewness are in qualitative agreement with a prediction of the weak interaction theory for a random wave field incorporating the effects of second harmonics (Tayfun, 1980), but the values of kurtosis are different in sign from the prediction.To examine the nonlinear properties of energy containing components, higher harmonic components are excluded from the wave records by using a kind of a band-pass filter. The surface elevation distributions of the filtered waves show a sharp decrease in skewness , but the distributions remain highly non-Gaussian with a large negative kurtosis almost independent of the fetch and wind speed . It is concluded that the negative kurtosis is due to the non-random character of the phase and amplitude among the energy containing components, and that nonlinear interactions occur amongst the energy containing frequencies.     

Disorder-induced enhancement of conductance in doped nanowires

A new mechanism is proposed to explain the enhancement of conductance in doped nanowires. It is shown that the anomalous enhancement of conductance is due to surface doping. The conductance in doped nanowires increases with dopant concentration, which is qualitatively consistent with the existing experimental results. In addition, the I-V curves are linear and thus suggest that the metal electrodes make ohmic contacts to the shell-doped nanowires. The electric current increases with wire diameter (D) and decreases exponentially with wire length (L). Therefore, the doped nanowires have potential application in nanoscale electronic and optoelectronic devices.