On the use of weather data in ecological studies along altitudinal and latitudinal gradients

Global warming has created a need for studies along climatic gradients to assess the effects of temperature on ecological processes. Altitudinal and latitudinal gradients are often used as such, usually in combination with air temperature data from the closest weather station recorded at 1.5–2 m above the ground. However, many ecological processes occur in, at, or right above the soil surface. To evaluate how representative the commonly used weather station data are for the microclimate relevant for soil surface biota, we compared weather station temperatures for an altitudinal (500–900 m a.s.l.) and a latitudinal gradient (49–68°N) with data obtained by temperature sensors placed right below the soil surface at five sites along these gradients. The mean annual temperatures obtained from weather stations and adjusted using a lapse rate of ?5.5°C km^?1 were between 3.8°C lower and 1.6°C higher than those recorded by the temperature sensors at the soil surface, depending on the position along the gradients. The monthly mean temperatures were up to 10°C warmer or 5°C colder at the soil surface. The within‐site variation in accumulated temperature was as high as would be expected from a 300 m change in altitude or from a 4° change in latitude or a climate change scenario corresponding to warming of 1.6–3.8°C. Thus, these differences introduced by the decoupling are significant from a climate change perspective, and the results demonstrate the need for incorporating microclimatic variation when conducting studies along altitudinal or latitudinal gradients. We emphasize the need for using relevant temperature data in climate impact studies and further call for more studies describing the soil surface microclimate, which is crucial for much of the biota.     

Superhydrophobicity of Bionic Alumina Surfaces Fabricated by Hard Anodizing

Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique.The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa.The water contact angles of the as-anodized bionic samples were measured using a contact angle meter (JC2000A) with the 3 μL water drop at room temperature.The measurement of the wetting property showed that the water contact angle of the unmodified as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time.The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure.The structure is composed of the micro-scaled alumina columns and pores.The height of columns and the depth of pores depend on the anodizing time.The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol (ODT),showing a change in the wettability from hydrophobicity to super-hydrophobicity.This improvement in the wetting property is attributed to the decrease in the surface energy caused by the chemical modification.     

Biomimetic Hydrophobic Surfaces with Low or High Adhesion Based on Poly(vinyl alcohol) and SiO2 Nanoparticles

Superhydrophobic surfaces are often found in nature,such as plant leaves and insect wings.Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves,biomimetic hydrophobic surfaces with high or low adhesion were prepared with a facile drop-coating approach in this paper.Poly(vinyl alcohol) (PVA) was used as adhesive and SiO2 nanoparticles were used to fabricate surface micro-structure.Stearic acid or dodecafluoroheptyl-propyl-trimethoxysilane (DFTMS) were used as low surface energy materials to modify the prepared PVA/SiO2 coating surfaces.The effects of size of SiO2 nanoparticles,concentration of SiO2 nanoparticle suspensions and the modifications on the wettability of the surface were investigated.The morphology of the PVA/SiO2 coating surfaces was observed by using scanning electron microscope.Water contact angle of the obtained superhydrophilic surface could reach to 3°.Stearic acid modified PVA/SiO2 coating surfaces showed hydrophobicity with high adhesion.By mixing the SiO2 nanoparticles with sizes of 40 nm and 200 nm and modifying with DFTMS,water contact angle of the obtained coating surface could be up to 155° and slide angle was only 5°.This work provides a facile and useful method to control surface wettability through changing the roughness and chemical composition of a surface.     

Self-organized Polymer Aggregates with a Biomimetic Hierarchical Structure and its Superhydrophobic Effect

Nature always gives us inspirations to fabricate functional materials by mimicking the structure design of biomaterials. In this article, we report that polymeric aggregates with morphology similar to the papilla on lotus leaf can be self-organized in the polymer solution by adding 16 wt% water into 5 mg/ml polycarbonate solution in N, N′-dimethylformamide. The hierarchically structured aggregates at micro- and nano-scale alone show superhydrophobic effect without the need of modification with low surface energy compound. Small amount of liquid can be wrapped by the aggregates to form the so-called liquid marble. Influence of the amount of water added into the solution on the morphology of resultant polymer aggregates was investigated. By using the hierarchical aggregates as the surface building blocks, superhydrophobic coating with a static water contact angle larger than 160° and sliding angle less than 5° (for a water drop of 5 μl) was formed. Other solutions, like acid, basic and blood plasma are also repelled on the coating.     

Characterization of the Topography and Wettability of English Weed Leaves and Biomimetic Replicas

The topography and wettability of the underside of English weed （Oxalis pes-caprae） leaves and of their biomimetic replicas are investigated. Polyvinyl siloxane molds were cast from the leaves and then filled with an epoxy pre-polymer to produce replicas. The particular topographical structures of leaves and replicas were evaluated by optical microscopy and Scanning Electron Microscopy （SEM） analysis. The static wettability of leaves and replicas was assessed by contact angle measurements, while the dynamic wettability was characterized by estimating contact angle hysteresis and studying the dynamic behavior of impacting water droplets. A smooth glass slip and its replica were used as control surfaces. The replica moulding method used was able to transfer the characteristic pattern of irregular 100 μm - 200 μm × 60 μm convex papillae interspersed with stomata of the original leaf to the epoxy replicas. The static contact angle of 143°± 3° and the contact angle hysteresis of 2~ indicate that the underside of the English weed leaf is close to superhydrophobic. The lower contact angles （130° ± 4°） and higher hysteresis （31°） observed for the replica when compared with the original leaves were associated to an inaccurate replication of the chemistry and structures of the three-dimensional wax projections covering the plant surface. Also, trichomes in the original leaves could not be accurately reproduced due to their flexibility and fragility. Differences in wetting behavior were also evident from droplet impact experiments, with rebound regimes prevailing in the original leaves and regimes characterized by higher adhesion and larger dissipation predominating in the replicas. Nevertheless, the morphological features of the leaf transferred to the replica were sufficient to promote a clear hydrophobic behavior of the replica when compared with the smooth epoxy reference surface.     

水分梯度下荒漠植物多样性与稳定性对土壤因子的响应

荒漠生态系统多样性的研究对维持荒漠区群落稳定性有着重要意义。以艾比湖流域荒漠植物群落为研究对象,基于野外样方调查数据及实验分析,探讨不同水分梯度下植物多样性与稳定性的变化规律及土壤因子对二者的影响。结果表明:(1)随土壤水分含量下降,Shannon-Wiener多样性指数(H)、Simpson多样性指数(D)、Pielou均匀度指数(J)、Margalef丰富度指数(R)和种群密度稳定性(ICV)指数均呈下降趋势,且当土壤含水量低于4.65%时,荒漠植物多样性与群落稳定性总体显著降低(P<0.05);(2)不同水分梯度下影响艾比湖流域植物多样性的土壤因子具有差异性,高水梯度为硝态氮与有机质,中水梯度下影响植物多样性的因子为pH,低水梯度为全氮和有机质;(3)仅在环境适宜的情况下,土壤因子(土壤含盐量与有机质)才能对群落稳定性产生显著影响(P<0.01);(4)三种梯度下,物种多样性均对群落稳定性有显著性影响(P<0.001),植物多样性与群落稳定性存在正相关关系。     

Wetting control through topography and surface hydrophilic/hydrophobic property changes by coarse grained simulation

Abstract

The changes of wetting state of water droplet on the solid surface featuring pillared structures are quantitatively studied by Coarse Grained simulation. Our results demonstrate that wetting state changes with the different topography (surface roughness), and it depends on the intrinsic hydrophilic/hydrophobic property of surface as well. Only if the contact angle of water droplet on the smooth surface is larger than 93.13°, the wetting state translates from the Wenzel state to the Cassie state on the rough surface with certain pillar height and width, and the contact angle climb up to the highest point and then remain almost unchanged with the increasing of pillar height and the same pillar distance. However, the wetting state does not change if the contact angle on the smooth surface is 85.1° or less, no matter what pillar structure the surface has. Additionally, the contact angles will remain almost unchanged if the pillar height is higher than a certain value. Our simulation results provide a quantitative understanding about the wetting state of water droplet on solid rough surfaces, and the results show the wetting state can be controlled by combining rough structure design and hydrophilic/hydrophobic property change of surfaces.     

Bacterial attachment on optical fibre surfaces

Optical fibres have received considerable attention as high-density sensor arrays suitable for both in vitro and in vivo measurements of biomolecules and biological processes in living organisms and/or nano-environments. The fibre surface was chemically modified by exposure to a selective etchant that preferentially erodes the fibre cores relative to the surrounding cladding material, thus producing a regular pattern of cylindrical wells of approximately 2.5 μm in diameter and 2.5 μm deep. The surface hydrophobicity of the etched and non-etched optical fibres was analysed using the sessile pico-drop method. The surface topography was characterised by atomic force microscopy (AFM), while the surface chemistry was probed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Six taxonomically different bacterial strains showed a consistent preference for attachment to the nano-scale smoother (R _q = 273 nm), non-etched fibre surfaces (water contact angle, θ = 106° ± 4°). In comparison, the surfaces of the etched optical fibres (water contact angle, θ = 96° ± 10°) were not found to be amenable to bacterial attachment. Bacterial attachment on the non-etched optical fibre substrata varied among different strains.     

Synthesis and hemocompatibity evaluation of segmented polyurethane end-capped with both a fluorine tail and phosphatidylcholine polar headgroups

To improve the hemocompatibility of polyurethanes, an amine monomer containing a long fluorine tail and phosphatidylcholine polar headgroups, 2-amino-3-oxo-3-(2-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctan amido) ethyl amino) propyl phosphorylcholine (FASPC) was firstly synthesized and characterized. Then four kinds of fluorinated phosphatidylcholine end-capped polyurethanes with different chemical structures were prepared. The surface properties of these prepared polyurethanes were characterized using X-ray photoelectron spectroscopic analysis (XPS) and water contact angle measurements. The results indicated that the phosphatidylcholine (PC) polar headgroups along with the fluorine tail could be easily enriched on the top surfaces, and the PC groups could be highly oriented on the outmost surface when the polymer film was in contact with water for only 30 s at room temperature. The evaluation of hemocompatibity was carried out via fibrinogen adsorption and platelet adhesion. Fibrinogen adsorption (37°C for 90 min) decreased by 98% to 87% compared to that on ordinary polyurethane surfaces, and almost no platelet adhesion and activation was observed at 37°C for 2 h.     

A superhydrophilic nitinol shape memory alloy with enhanced anti-biofouling and anti-corrosion properties

This work reports on a nitinol (NiTi) surface modification scheme based on a chemical oxidation method, and characterizes its effects on wetting, biofouling and corrosion. The scheme developed is also compared with selected previous oxidation methods. The proposed method turns NiTi into superhydrophilic in ~5 min, and the static contact angle and contact angle hysteresis were measured to be ~7° and ~12°, respectively. In the PRP (platelet rich plasma) test, platelet adhesion was reduced by ~89% and ~77% respectively, compared with the original NiTi and the NiTi treated with the previous chemical oxidation scheme. The method developed provides a high (~1.1 V) breakdown voltage, which surpasses the ASTM standard for intervascular medical devices. It also provides higher superhydrophilicity, hemo-compatibility and anti-corrosion resistance than previous oxidation schemes, with a significantly reduced process time (~5 min), and will help the development of high performance NiTi devices.     

Do Variations in Local Leaf Irradiance Explain Changes to Leaf Nitrogen within Row Maize Canopies?

Numerous studies have dealt with the relationship between leafnitrogen content and leaf irradiance. However, most of themrefer to dense stands presenting reduced horizontal heterogeneityof foliage distribution. Both gradients of leaf nitrogen andleaf irradiance related to canopy depth are significant undersuch conditions, and modelling radiative exchange using a turbid-mediumanalogy and dividing the canopy into vegetation layers is sufficient.Conversely, row crops such as maize are characterized by stronghorizontal heterogeneity of foliage distribution and the one-dimensional(1D) approach may be unsuitable. We thus modelled the three-dimensional(3D) geometry of maize canopies with varying densities and atdifferent developmental stages using plant digitizing underfield conditions. The nitrogen content per unit area of eachleaf part was obtained subsequently by nitrogen analysis. Wenext calculated radiative exchange using a 3D volume-based approachwithin the canopies in order to estimate local leaf irradianceon a daily integration scale. Vertical gradients in leaf nitrogencontent per unit area observed in dense stands during the vegetativephase corresponded largely to those reported in the literature.We also identified significant gradients in nitrogen contentalong the leaves, which had not before been clearly demonstrated.Our study shows that local light climate during plant developmentplays a major role in leaf nitrogen distribution and remobilization.Moreover, brutal plant thinning involves rapid changes in leafnitrogen partitioning. It is concluded that taking account ofthe 3D heterogeneity of nitrogen and irradiance distributionmay have implications for modelling crop photosynthesis andproduction. Copyright 1999 Annals of Botany Company 3D plant architecture, horizontal gradients in leaf nitrogen, leaf irradiance, leaf nitrogen content per unit area, maize, nitrogen partitioning, nitrogen remobilization, virtual plant, Zea mays L.     

The effects of superficial wax on leaf wettability

Experiments are described which provide more information on the role played by superficial waxes in the natural water-repellency of leaf surfaces. Contact angles of water were measured on a variety of leaf surfaces, before and after removal of wax, and on smooth films of the isolated superficial waxes. The differences in wettability of leaf surfaces are not wholly accounted for by differences which occur in the chemical and hydrophobic properties of their superficial waxes. Waxes isolated from leaves exhibiting contact angles less than 90° are usually more hydrophobic than the leaf surface itself. On most leaves exhibiting angles greater than 90° wax is the dominant factor governing water-repellency, the isolated wax normally making at least a 60 % contribution to the contact angle measured on the leaf surface. Additional factors, such as roughness, responsible for the occurrence of contact angles greater than 110° on certain leaf surfaces, reside in the wax layer. The hydrophobic properties of some leaves are unaffected by chloroform washing, revealing that superficial waxes play little part in their wettability.     

A geometric approach to study the contact mechanisms in the patellofemoral joint of normal versus patellofemoral pain syndrome subjects

The biomechanics of the patellofemoral (PF) joint is complex in nature, and the aetiology of such manifestations of PF instability as patellofemoral pain syndrome (PFPS) is still unclear. At this point, the particular factors affecting PFPS have not yet been determined. This study has two objectives: (1) The first is to develop an alternative geometric method using a three-dimensional (3D) registration technique and linear mapping to investigate the PF joint contact stress using an indirect measure: the depth of virtual penetration (PD) of the patellar cartilage surface into the femoral cartilage surface. (2) The second is to develop 3D PF joint models using the finite element analysis (FEA) to quantify in vivo cartilage contact stress and to compare the peak contact stress location obtained from the FE models with the location of the maximum PD. Magnetic resonance images of healthy and PFPS subjects at knee flexion angles of 15°, 30° and 45° during isometric loading have been used to develop the geometric models. The results obtained from both approaches demonstrated that the subjects with PFPS show higher PD and contact stresses than the normal subjects. Maximum stress and PD increase with flexion angle, and occur on the lateral side in healthy and on the medial side in PFPS subjects. It has been concluded that the alternative geometric method is reliable in addition to being computationally efficient compared with FEA, and has the potential to assess the mechanics of PFPS with an accuracy similar to the FEA.     

The impact of recombinant fusion-hydrophobin coated surfaces on E. coli and natural mixed culture biofilm formation

The impact of increased surface hydrophobicity on biofilms regarding retardation, repulsion, or attraction was studied with hydrophobin modified glass substrata. Recombinantly produced fungal hydrophobins forming self-assembled monolayers were used as the surface coating. The adsorption dynamics of hydrophobins were analysed with a quartz crystal microbalance which showed the surface coating to be rapid and stable. The change of surface wettability was determined by water contact angle measurements and demonstrated an increase in hydrophobicity in range of 60–62°. The homogeneity of the monolayers was demonstrated by immunofluorescence microscopy. Atomic force microscopy was applied to visualise the uniform texture of the coated materials. The hydrophobin coatings had no impact on different biofilms in terms of spatial distribution, cell numbers, and population composition. In consequence, hydrophobicity might not represent an important parameter for biofilm formation. Nevertheless, recombinant hydrophobins are suitable for large scale surface modification and functionalization with bioactive molecules.     

A Preliminary Study of the Surface Properties of Earthworms and Their Relations to Non-Stain Behaviour

The surface properties of earthworms were studied using nitrogen adsorption/desorption isotherm and dynamic contact angle measurement with the aim to understand their non-stain behaviour. The results obtained by applying dynamic contact angle technique using water, glycerol, cooking oil and dimethylsilicone show that the surface properties of earthworms are a function of time. The critical surface energy, calculated using advancing angle, is as low as 11 × 10~(-3) J·m~(-2). However this hydrophobic behaviour at the initial contact moment changes progressively into hydrophilic as time goes by. This behaviour together with the creeping movement of corrugated surface is believed to be responsible for the non-stain behaviour of earthworms. The nitrogen adsorption isotherm of dried skin of earthworms at 77.3 K exhibits more or less Type V isotherm with surface area of 13 m~2·g~(-1) calculated using the α_s plot. The Type V isotherm is the indication of weak interaction between nitrogen and the worm surface.     

The Effect of Dissolved Organic Carbon on Bacterial Adhesion to Conditioning Films Adsorbed on Glass from Natural Seawater Collected during Different Seasons

Adhesion of three marine bacterial strains, i.e. Marinobacter hydrocarbonoclasticus, Psychrobacter sp. and Halomonas pacifica with different cell surface hydrophobicities was measured on glass in a stagnation point flow chamber. Prior to bacterial adhesion, the glass surface was conditioned for 1?h with natural seawater collected at different seasons in order to determine the effect of seawater composition on the conditioning film and bacterial adhesion to it. The presence of a conditioning film was demonstrated by an increase in water contact angle from 15° on bare glass to 50° on the conditioned glass, concurrent with an increase in the amount of adsorbed organic carbon and nitrogen, as measured by X-ray photoelectron spectroscopy. Multiple linear regression analysis on initial deposition rates, with as explanatory variables the temperature, salinity, pH and concentration of dissolved organic carbon (DOC) of the seawater at the time of collection, showed that the concentration of DOC was most strongly associated with the initial deposition rates of the three strains. Initial deposition rates of the two most hydrophilic strains to a conditioning film, increased with the concentration of DOC in the seawater, whereas the initial deposition rate of the most hydrophobic strain decreased with an increasing concentration of DOC.     

Optimization of procedures for separation of motile and nonmotile bull and rabbit spermatozoa with bovine serum albumin gradients

The effect of equipment design, separatory media, and time and temperature of separation were studied. Discontinuous 4%/10% bovine serum albumin (BSA) gradients were used to isolate highly motile spermatozoa in rabbit and bull semen. For all conditions tested, motility of spermatozoa collected from the 4% BSA gradient layer (top) was less than or equal to the motility of the unseparated controls. Fractions collected from the 10% BSA gradient layer contained highly motile spermatozoa. In experiment 1, washed bull spermatozoa were diluted with phosphate-buffered saline (PBS) containing 2% BSA or 4% BSA before being fractionated on BSA columns contained in test tubes. Inclusion of BSA in PBS tended to reduce loss of motility during washing, but the proportion of sperm recovered was highest in PBS. In experiment 2, motility and recovery of buck spermatozoa collected from the 10% BSA gradient region tended to be higher when fractionation temperature was 30°C as compared to 35°C, and motility was significantly higher when incubation time was 30 min as compared to 1 hr. The proportion of sperm recovered was unaffected by incubation time. In experiments 1 and 2, 41 of 48 separations resulted in at least one fraction containing spermatozoa with motility greater than or equal to 90%. In the third experiment, the surface area on which bull and buck spermatozoa were layered was increased by forming the 4%/10% BSA gradients in conical supports. Separation of sperm on conically shaped columns was not as effective as on cylinders. The use of cylinders to support the BSA gradients and a separation time of 30 min at 30°C is recommended.     

类金刚石薄膜的制备及其血液相容性的初步研究

本文以单晶硅为基体,Ar等离子体对基体进行清洗,用法制备类金刚石(DLC)膜和掺氮的DLC膜。沉积DLC膜所用的气体是乙炔和氩气,沉积掺氮的DLC膜用乙炔和氮气。利用衰减全反射红外光谱(ATR-FTIR)和扫描电子显徽镜(SEM)对沉积的DLC膜和掺氮的DLC膜进行结构分析和观察表面形貌。考察了乙炔比例、放电功率等沉积参数对DLC膜的影响。通过接触角和血小板黏附实验,进行了DLC膜的抗凝血性能分析,效果较好。     

Fabrication of Bioinspired Structured Superhydrophobic and Superoleophilic Copper Mesh for Efficient Oil-water Separation

Oily water treatment has attracted the attention of many researchers.The development of effective and cheap oil/water separation materials is urgent for treating this problem.Herein,inspired by superhydrophobic typical plant leaves such as lotus,red rose and marigold,superhydrophobic and superoleophilic copper mesh was fabricated by etching and then surface modification with 1-dodecanethiol (HS(CH2)11CH3).A rough silver layer is formed on the mesh surface after immersion.The obtained mesh surface exhibits superhydrophobicity and superoleophilicity and the static water contact angle was 153° ± 3°.In addition,the as-prepared copper mesh shows self-cleaning character with water and chemical stability.The as-prepared copper foam can easily remove the organic solvents either on water or underwater.We demonstrate that by using the as-prepared mesh,oils can be absorbed and separated,and that high separation efficiencies of larger than 92％ are retained for various oils.Thus,such superhydrophobic and superoleophilic copper mesh is a very promising material for the application of oil spill cleanup and industrial oily wastewater treatment.     

Temperature and the hygropreference of the Arctic Collembolan Onychiurus arcticus and mite Lauroppia translamellata

The hygropreference of adult Onychiurus arcticus (Tullberg) was investigated over 2 h at 0, 10 and 20°C, along humidity gradients (12–98% RH) established using different salt solutions. At all temperatures O. arcticus preferred the highest humidity (98% RH). At 0 and 20°C, saturated conditions were preferred to 98% RH. The hygropreference of the mite Lauroppia translamellata (Willmann) was also assessed at 20°C, and no clear RH preference was observed. This species survived the loss of 24.9 ± 2.1% of its initial water content when held for 24 h at 20°C and 12% RH. A range of assays designed to eliminate the influence of thigmotactic behaviour and population clumping permit exclusion of these factors as being responsible for the observed results. The mean initial water content of O. arcticus samples (71.7 ± 10.9, 73.4 ± 4.0 and 73.8 ± 23.5% at 0, 10 and 20°C, respectively) did not differ significantly between temperatures, indicating that the results were not influenced by differences in initial hydrated state. The percentage water loss of individuals within the gradient increased with temperature, and differed significantly between regimes. The ecological significance of the observed humidity preferences are discussed.