Effects of tissue surface curvature and incident light angle on diffuse correlation spectroscopy

Diffuse correlation spectroscopy is an emerging technique for the continuous, non-invasive monitoring of blood flow in biological tissues. However, the influence of oblique incidence and surface curvature has not been fully discussed. In this paper, we study the effects of the incident angle and surface curvature on diffuse correlation spectroscopy measurement and the blood flow index (BFI). For semi-infinite plane with lower absorption, oblique incidence angle has slightly stronger influence. Larger incident angles lead to high values and a reduced decay rate of the normalized electric field temporal autocorrelation. When the radius of curvature is more than 10?cm, the BFI estimation error reduced to less than 5% and very close to semi-infinite plane case. Besides, for the surface with small radius of curvature, larger incident angles sometimes may cause smaller estimated errors of the BFI. This work may help improve BFI estimation accuracy from diffuse correlation spectroscopy.     

Atomic force microscopy of the morphology and mechanical behaviour of barnacle cyprid footprint proteins at the nanoscale

Barnacles are a major biofouler of man-made underwater structures. Prior to settlement, cypris larvae explore surfaces by reversible attachment effected by a ‘temporary adhesive’. During this exploratory behaviour, cyprids deposit proteinaceous ‘footprints’ of a putatively adhesive material. In this study, footprints deposited by Balanus amphitrite cyprids were probed by atomic force microscopy (AFM) in artificial sea water (ASW) on silane-modified glass surfaces. AFM images obtained in air yielded better resolution than in ASW and revealed the fibrillar nature of the secretion, suggesting that the deposits were composed of single proteinaceous nanofibrils, or bundles of fibrils. The force curves generated in pull-off force experiments in sea water consisted of regions of gradually increasing force, separated by sharp drops in extension force manifesting a characteristic saw-tooth appearance. Following the relaxation of fibrils stretched to high strains, force–distance curves in reverse stretching experiments could be described by the entropic elasticity model of a polymer chain. When subjected to relaxation exceeding 500 ms, extended footprint proteins refolded, and again showed saw-tooth unfolding peaks in subsequent force cycles. Observed rupture and hysteresis behaviour were explained by the ‘sacrificial bond’ model. Longer durations of relaxation (>5 s) allowed more sacrificial bond reformation and contributed to enhanced energy dissipation (higher toughness). The persistence length for the protein chains (L_P) was obtained. At high elongation, following repeated stretching up to increasing upper strain limits, footprint proteins detached at total stretched length of 10 µm.     

Contributions of chemical and mechanical surface properties and temperature effect on the adhesion at the nanoscale

The atomic force microscope (AFM) is a powerful tool to investigate surface properties of model systems at the nanoscale. However, to get semi-quantitative and reproducible data with the AFM, it is necessary to establish a rigorous experimental procedure. In particular, a systematic calibration procedure of AFM measurements is necessary before producing reliable semi-quantitative data. In this paper, we study the contributions of the chemical and mechanical surface properties or the temperature influence on the adhesion energy at a local scale. To reach this objective, two types of model systems were considered. The first one is composed of rigid substrates (silicon wafers or AFM tips covered with gold) which were chemically modified by molecular self-assembling monolayers to display different surface properties (methyl and hydroxyl functional groups). The second one consists of model polymer networks (cross-linked polydimethylsiloxane) of variable mechanical properties. The comparison of the force curves obtained from the two model systems shows that the viscoelastic contributions dominate for the adhesion with polymer substrates, whereas, chemical contributions dominate for the rigid substrates. The temperature effect on the adhesion energy is also reported. Finally, we propose a relation for the adhesion energy at the nanoscale. This relation relates the energy measured during the separation of the contact to the three parameters: the surface properties of the polymer, the energy dissipated within the contact zone and the temperature.     

Assessment of the curvature effect on the stability and postbuckling behavior of ribbed panels

The article discusses the effect of curvature on the buckling of square-in-plan spherical panels stiffened with two pairs of cross ribs. The efficiency of two variants of ribbing has been studied. __________ Translated from Problemy Prochnosti, No. 6, pp. 128–133, November–December, 2007.     

Bioadhesion of various proteins on random,diblock and triblock copolymer surfaces and the effect of pH conditions

The adhesive interactions of block copolymers composed of poly(methyl methacrylate) (PMMA)/poly(acrylic acid) (PAA) and poly(methyl methacrylate)/poly(2-hydroxyethyl methacrylate) (PHEMA) with the proteins fibronectin, bovine serum albumin and collagen were studied by atomic force microscopy. Adhesion experiments were performed both at physiological pH and at a slightly more acidic condition (pH 6.2) to model polymer–protein interactions under inflammatory or infectious conditions. The PMMA/PAA block copolymers were found to be more sensitive to the buffer environment than PMMA/PHEMA owing to electrostatic interactions between the ionized acrylate groups and the proteins. It was found that random, diblock and triblock copolymers exhibit distinct adhesion profiles although their chemical compositions are identical. This implies that biomaterial nanomorphology can be used to control protein–polymer interactions and potentially cell adhesion.     

New perspectives on the roles of nanoscale surface topography in modulating intracellular signaling

The physical properties of biomaterials, such as elasticity, stiffness, and surface nanotopography, are mechanical cues that regulate a broad spectrum of cell behaviors, including migration, differentiation, proliferation, and reprogramming. Among them, nanoscale surface topography, i.e., nanotopography, defines the nanoscale shape and spatial arrangement of surface elements, which directly interact with the cell membranes and stimulate changes in the cell signaling pathways. In biological systems, the effects of nanotopography are often entangled with those of other mechanical and biochemical factors. Precise engineering of 2D nanopatterns and 3D nanostructures with well-defined features has provided a powerful means to study the cellular responses to specific topographic features. In this Review, we discuss efforts in the last three years to understand how nanotopography affects membrane receptor activation, curvature-induced cell signaling, and stem cell differentiation.     

纳米粒子的表面聚合物接枝改性

综述了纳米粒子与高分子聚合物复合的优点及不足,分析引起不足的原因,指出纳米粒子表面改性的重要性。同时在比较纳米粒子几种表面改性方法的基础上指出化学接枝改性的优越性,分析各种化学接枝改性方法及其有关的修饰机理和几种常用的表征方法。     

The effect of surface modification on thermal stability of nanodiamonds

The paper addresses the influence of surface modification through alteration of the functional top surface layer on the thermal stability of nanodiamond. The modification of nanodiamond by a high-temperature activation of its surface, which is followed by chemical treatment, is found to reduce concentration of metal impurities and oxygen-containing surface groups that are desorbed at temperatures below 773 K. As a consequence, the rate of oxidation of the modified diamonds at temperatures up to 773 K is 1.7 times slower. The oxidation onset temperature is shifted by 100 degrees.     

The influence of road curvature on fatal crashes in New Zealand

Bends in roads can cause crashes but a recent study in the UK found that areas with mostly curved roads had lower crash rates than areas with straighter roads. This present study aimed to replicate the previous research in a different country. Variations in the number of fatal road crashes occurring between 1996 and 2005 in 73 territorial local authorities across New Zealand were modelled against possible predictors. The predictors were traffic flow, population counts and characteristics, car use, socio-economic deprivation, climate, altitude and road characteristics including four measures of average road curvature. The best predictors of the number of fatal crashes on urban roads, rural state highways and other rural roads were traffic flow, speed limitation and socio-economic deprivation. Holding significant factors constant, there was no evidence that TLAs with the most curved roads had more crashes than elsewhere. Fatal crashes on urban roads were significantly and negatively related to two measures of road curvature: the ratio of road length to straight distance and the cumulative angle turned per kilometre. Weaker negative associations on rural state highways could have occurred by chance. These results offer limited support to the suggestion that frequently occurring road bends might be protective.     

The surface chemistry and stability of gold nanoparticles prepared using methanol extract of Eucalyptus camaldulensis

The development of nontoxic, clean techniques for synthesising metal nanoparticles such as gold has attracted increasing attention in recent years. Many reports have been published about the synthesis of gold nanoparticles using plant extracts. However, the stability of these prepared gold nanoparticles has not been investigated. In this research, the stability of gold nanoparticles prepared by Eucalyptus camaldulensis was investigated at different temperatures (4°C, 25°C and 45°C) for 8 weeks. Transmission electron microscopy and visible absorption spectroscopy confirmed the stability of gold nanoparticles during the storage period at the mentioned condition. In addition, Fourier transform–infrared spectroscopy was used to investigate the surface chemistry of gold nanoparticles prepared by the methanol extract of E. camaldulsis. The carboxyl group was characterised on the surface of the gold nanoparticles, and this functional group may have a critical role in the stability of gold nanoparticles prepared by the mentioned plant extract at different conditions. This functional group can be used for drug delivery of amino derivative drugs using gold nanoparticles.     

Photoinduced fabrication of complex surface relief structures on azobenzene functionalized polymers

Light induced fabrication of complex surface relief structures on azobenzene functionalized polymers is reported. Large class of side chain and main chain polymers can be utilized to record these relief structures. The recording and erasure process are strongly dependent on the polarization. Possible transport mechanism of polymer chains well below the glass transition temperature due to photoinduced effect is discussed.     

蛋白质超滤过程及超滤膜的表面改性研究现状

讨论了蛋白质溶液在超滤过程中造成蛋白质在膜面吸附的影响影响因素,对近10年来,人们在如何降低蛋白质在超滤膜表面的吸附,包括操作条件的选择以及膜的表面进行改性研究方面进行了综述。     

Cr-Si合金钢原始微观结构对表面纳米化过程的影响

利用表面机械加工法在经过调质处理的CrSi合金钢表面制备了纳米结构层,利用透射电镜(TEM)和X射线衍射(XRD)等分析技术对距表面不同深度的微观结构进行分析,研究原始微观结构对晶粒细化过程的影响.结果显示,在细化初期原始的小角度亚晶界被演化为高密度位错墙,长条形亚晶被演化为含有高密度位错的条形位错胞;一些原始的小角度...     

Modeling bacterial adhesion on the nanopatterned surface by varying contact area

Bacterial adhesion is a critical process in many fields,such as implant infections,microbiologically influ-enced corrosion and bioelectricity generation in microbial fuel cells.During bacterial adhesion,the con-tact area between the attached bacteria and the patterned surface plays an important role.In this study,different surface topographies and treatments were employed to simulate three circumstances with dif-ferent contact areas.A nanostripe structure with a period of 576.9 nm and a height of 203.5 nm was fabricated on pure titanium by femtosecond laser ablation.Bacteria in liquid attached to the peaks of the nanostripe structure and were stretched on the two adjacent nanostripes.Compared with the polished surface,the contact area between bacteria and the nanostripe surface was reduced to 50％,resulting in a reduction(about 50％)in the coverage rate of attached bacteria.In addition,the nanostripe surface was a hydrophobic surface with a water contact angle(WCA)of 112.1°,and the surface potential of the nanos-tripe surface was higher than that of the polished surface.However,the surface potential and wettability of the nanostripe surface played a minor role in the bacterial adhesion due to the reduced contact area.Upon drying,the attached bacteria on the nanostripe surface sank into the valley region and the contact area was about 40％larger than that on the polished surface.The lateral strength of bacterial adhe-sion on nanostripe surfaces was higher than that on polished surfaces,due to the larger contact area.Upon applying a lateral force of 10.0 nN,the percentage of bacteria remaining on the nanostripe sur-face(31.1％)was higher than that on the polished surface(11.9％).Hence,the bacterial adhesion on the nanopatterned surface was mainly determined by the contact area.The in-depth exploration of the rela-tion between bacterial adhesion on the nanopatterned surface and the contact area enables the rational surface designs of biomaterials to regulate bacterial adhesion.     

Tailoring the adhesion of optical films on polymethyl-methacrylate by plasma-induced surface stabilization

Adhesion of plasma-deposited optical and protective coatings, such as amorphous hydrogenated silicon nitride, SiN_1.3, on polymethyl-methacrylate (PMMA) substrates has been found to be limited by a cohesive failure inside the PMMA bulk. Using direct exposure to a low pressure plasma in helium or to vacuum ultraviolet (VUV) radiation generated from plasma, the adhesion of SiN_1.3 at high humidity and elevated temperature has been substantially increased. Using a multitechnique analytical approach, the enhanced adhesion was attributed to the initial etching of the weak boundary layer followed by formation of a crosslinked, graded, mechanically stabilized layer in the interfacial region (interphase), which possesses a physical thickness of 50 to 100 nm and a microhardness of about 2 GPa.     

表面活性剂对NTC纳米粉体及热敏材料性能的影响

采用液相共沉淀法制备了CoMnNiO热敏电阻粉体材料，重点研究了表面活性剂在合成过程中对CoMnNiO粉体性能的影响，并采用XRD、TEM对制备的粉体进行了表征，同时探讨了表面活性剂对粉体的烧结性能和电学性能的影响。结果表明添加合适的表面活性剂能够较好地控制粉体材料的大小、形状，改善粉体材料的表面性能；通过研究粉体的烧灶性能以及电性能发现，加入一定量的表面活性剂可以提高粉体的烧结活性，并且使得材料的日值、R值一致性较好。     

The synergistic effect of 3D-printed microscale roughness surface and nanoscale feature on enhancing osteogenic differentiation and rapid osseointegration

Personalized precision therapy and rapid osseointegration are the main development directions of dental implants.3 D printing is a vital advanced manufacturing technology for personalized precision therapy.However,the osteogenesis of the 3 D printed Ti6 Al4 V implants is unsatisfactory.From the bionic perspective,the hierarchical micro/nano-topography can mimic the microenvironment of the multilevel structure of natural bone tissue and may endow the implant surface with superior bioactivity.In the present study,the hierarchical micro/nano-topography was successfully fabricated by construction the nanoscale feature on 3 D printed microscale roughness surface of 3 D-printed Ti6 Al4 V implants by alkali-heat treatment and hydrothermal treatment.Then the cell biological responses in vitro and osseointegration performance in vivo were systematically evaluated.The hierarchical micro/nano-topography evidently increased the roughness,improved the hydrophilicity and accelerated the hydroxyapatite deposition and mineralization,which significantly enhanced the adhesion,differentiation and extracellular matrix mineralization of bone marrow derived mesenchymal stromal cells(BMSCs).Most importantly,the hierarchical micro/nano-topography on 3 D-printed implants facilitated the new bone formation and rapid osseointegration in vivo.Our study suggested that 3 D-printed implant with micro/nano-topography may be a promising candidate to be applied in orthopedic field to meet the need of customized therapy and rapid osseointegration.     

Dissolution kinetics of Si into Ge (111) substrate on the nanoscale

In this paper we present experiments and simulations on the dissolution of Si into single crystalline Ge(111) substrates. The interface shift during the dissolution was tracked by X-ray Photoelectron Spectroscopy. It was obtained that the interface remained sharp and shifted according to anomalous kinetics similarly to our previous measurement in the Si/amorphous-Ge system. The interface shift, x, can be described by a power function of time x ∝ t^k_c with a kinetic exponent, k_c, of 0.85 ± 0.1, larger than the one measured for the amorphous system (0.7 ± 0.1). Both exponents, however, are different from the k_c = 0.5 Fickian (parabolic) value and it is interpreted as a nanoscale diffusional anomaly caused by the strong composition dependence of the diffusion coefficients.     

Viscoelastic nanoscale properties of cuticle contribute to the high-pass properties of spider vibration receptor (Cupiennius salei Keys).

Atomic force microscopy (AFM) and surface force spectroscopy were applied in live spiders to their joint pad material located distal of the metatarsal lyriform organs, which are highly sensitive vibration sensors. The surface topography of the material is sufficiently smooth to probe the local nanomechanical properties with nanometre elastic deflections. Nanoscale loads were applied in the proximad direction on the distal joint region simulating the natural stimulus situation. The force curves obtained indicate the presence of a soft, liquid-like epicuticular layer (20-40 nm thick) above the pad material, which has much higher stiffness. The Young modulus of the pad material is close to 15 MPa at low frequencies, but increases rapidly with increasing frequencies approximately above 30 Hz to approximately 70 MPa at 112 Hz. The adhesive forces drop sharply by about 40% in the same frequency range. The strong frequency dependence of the elastic modulus indicates the viscoelastic nature of the pad material, its glass transition temperature being close to room temperature (25 +/- 2 degrees C) and, therefore, to its maximized energy absorption from low-frequency mechanical stimuli. These viscoelastic properties of the cuticular pad are suggested to be at least partly responsible for the high-pass characteristics of the vibration sensor's physiological properties demonstrated earlier.