Smooth Outer Surface Research Articles

Arthropod eyes: The early Cambrian fossil record and divergent evolution of visual systems

Four types of eyes serve the visual neuropils of extant arthropods: compound retinas composed of adjacent facets; a visual surface populated by spaced eyelets; a smooth transparent cuticle providing inwardly directed lens cylinders; and single-lens eyes. The first type is a characteristic of pancrustaceans, the eyes of which comprise lenses arranged as hexagonal or rectilinear arrays, each lens crowning 8–9 photoreceptor neurons. Except for Scutigeromorpha, the second type typifies Myriapoda whose relatively large eyelets surmount numerous photoreceptive rhabdoms stacked together as tiers. Scutigeromorph eyes are facetted, each lens crowning some dozen photoreceptor neurons of a modified apposition-type eye. Extant chelicerate eyes are single-lensed except in xiphosurans, whose lateral eyes comprise a cuticle with a smooth outer surface and an inner one providing regular arrays of lens cylinders. This account discusses whether these disparate eye types speak for or against divergence from one ancestral eye type. Previous considerations of eye evolution, focusing on the eyes of trilobites and on facet proliferation in xiphosurans and myriapods, have proposed that the mode of development of eyes in those taxa is distinct from that of pancrustaceans and is the plesiomorphic condition from which facetted eyes have evolved. But the recent discovery of enormous regularly facetted compound eyes belonging to early Cambrian radiodontans suggests that high-resolution facetted eyes with superior optics may be the ground pattern organization for arthropods, predating the evolution of arthrodization and jointed post-protocerebral appendages. Here we provide evidence that compound eye organization in stem-group euarthropods of the Cambrian can be understood in terms of eye morphologies diverging from this ancestral radiodontan-type ground pattern. We show that in certain Cambrian groups apposition eyes relate to fixed or mobile eyestalks, whereas other groups reveal concomitant evolution of sessile eyes equipped with optics typical of extant xiphosurans. Observations of fossil material, including that of trilobites and eurypterids, support the proposition that the ancestral compound eye was the apposition type. Cambrian arthropods include possible precursors of mandibulate eyes. The latter are the modified compound eyes, now sessile, and their underlying optic lobes exemplified by scutigeromorph chilopods, and the mobile stalked compound eyes and more elaborate optic lobes typifying Pancrustacea. Radical divergence from an ancestral apposition type is demonstrated by the evolution of chelicerate eyes, from doublet sessile-eyed stem-group taxa to special apposition eyes of xiphosurans, the compound eyes of eurypterids, and single-lens eyes of arachnids. Different eye types are discussed with respect to possible modes of life of the extinct species that possessed them, comparing these to extant counterparts and the types of visual centers the eyes might have served.

Study on interface structure and performance of homogeneous-reinforced polyvinyl chloride hollow fiber membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating and matrix layers were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influence of various pre-wetting solutions on interface structure and performance of HR membranes were investigated. The results showed that the HRPVC membranes had a dense and smooth outer surface with no obvious pores. A dense interface was formed in the HR membrane between the coating layer and the matrix membrane without pre-wetting process. Due to the filling of the pores of the outer edge of the matrix membrane by pre-wet solutions, the HRPVC hollow fiber membranes formed porous interface in the coating process. The pure water flux of the pre-wet HR membranes was higher than that of the un-pre-wet HR membrane, but lower than that of the matrix membrane. The optimum properties of HRPVC membranes were obtained as the ethanol weight fraction reached 60 wt% in the pre-wet solutions. In the optimum pre-wetting conditions, the tensile strength of HRPVC hollow fiber membranes was 9.5 MPa, while the elongation-at-break value was 97.4 %.

Transformation of ZnO nanorods into nanotubes and their field emission studies

Synthesis of vertically well-aligned ZnO nanorods on Au coated silicon substrate by a facile electrochemical route has been carried out. The transformation of as-deposited ZnO nanorods into nanotubes was achieved via simple, single step, chemical etching process using KOH as etchant. The influence of various parameters of the etching, such as concentration of the etchant, bath temperature and duration on morphological features of the ZnO nanotubes has been investigated. It is observed that formation of ZnO nanotubes with smooth inner and outer surfaces is achieved when the etching was performed at 65°C for 1 h duration, and at higher bath temperatures and longer durations, over etching of nanorods takes place. Field emission investigations of the ZnO nanorods and nanotubes were carried out at base pressure of 1 × 10-8 mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 7.2 V/μm and 8.4 V/μm, corresponding to ZnO nanorods and nanotubes emitter respectively, and emission current density of ~ 352.5 μA/cm2 has been drawn from the ZnO nanotubes emitter at an applied field of 13.77 V/μm. The ZnO nanotubes emitter exhibits excellent emission current stability at the preset value of 1 μA over duration of 3 h, indicating its potential as electron source for practical applications.

Denitrifying sulfide removal process on high-salinity wastewaters.

Denitrifying sulfide removal (DSR) process comprising both heterotrophic and autotrophic denitrifiers can simultaneously convert nitrate, sulfide, and acetate into nitrogen gas, elemental sulfur (S(0)), and carbon dioxide, respectively. Sulfide- and nitrate-laden wastewaters at 2-35g/L NaCl were treated by DSR process. A C/N ratio of 3:1 was proposed to maintain high S(0) conversion rate. The granular sludge with a compact structure and smooth outer surface was formed. The microbial communities of DSR consortium via high-throughput sequencing method suggested that salinity shifts the predominating heterotrophic denitrifiers at <10g/L NaCl to autotrophic denitrifiers at >10g/L NaCl.

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

Nodular chromite is a characteristic feature of ophiolitic podiform chromitite and there has been much debate about how it forms. Nodular chromite from the Troodos ophiolite in Cyprus is unusual in that it contains skeletal crystals enclosed within the centres of the nodules and interstitial to them. 3D imaging and electron backscatter diffraction have shown that the skeletal crystals within the nodules are single crystals that are surrounded by a rim of polycrystalline chromite. 3D analysis reveals that the skeletal crystals are partially or completely formed cage or hopper structures elongated along the <111> axis. The rim is composed of a patchwork of chromite grains that are truncated on the outer edge of the rim. The skeletal crystals formed first from a magma supersaturated in chromite and silicate minerals crystallised from melt trapped between the chromite skeletal crystal blades as they grew. The formation of skeletal crystals was followed by a crystallisation event which formed a silicate-poor rim of chromite grains around the skeletal crystals. These crystals show a weak preferred orientation related to the orientation of the core skeletal crystal implying that they formed by nucleation and growth on this core, and did not form by random mechanical aggregation. Patches of equilibrium adcumulate textures within the rim attest to in situ development of such textures. The nodules were subsequently exposed to chromite undersaturated magma resulting in dissolution, recorded by truncated grain boundaries in the rim and a smooth outer surface to the nodule. None of these stages of formation require a turbulent magma. Lastly the nodules impinged on each other causing local deformation at points of contact.

Preparation and performance of homogeneous braid reinforced cellulose acetate hollow fiber membranes

Homogeneous braid reinforced (HBR) cellulose acetate (CA) hollow fiber membranes were fabricated through dry–wet spinning process which consisted of CA separation layer and CA hollow tubular braids. The performance of various CA concentration membranes were characterized in terms of pore size distribution, pure water flux (PWF), protein solution flux (PSF), mechanical strength, and membrane morphologies were observed by a scanning electron microscope. The results showed that the HBR CA hollow fiber membranes, especially with high CA concentration in the dope solutions, possessed dense and smooth outer surface. The tensile strength of HBR CA hollow fiber membranes which exceeded 11 MPa mainly depended on the tubular braids. With the increase of CA concentration, the tensile strength and bursting strength of the membranes increased. In addition, there was effective interfacial bonding state between the separation layer and the tubular braid when the CA concentration was higher than 10 wt%. The increase of CA concentration brought about the decrease of membrane pore size and the increase of protein rejection. Considering the PWF, rejection and stable PSF, the best CA concentration in the dope solutions was 10 wt%. Then the membrane fouling and cleaning processes for the activated sludge solution were studied by comparing with reinforced polyvinylidene fluoride (PVDF) hollow fiber membrane. The lower flux decline in the filtration of activated sludge solution and higher recovery in the flux indicated that the HBR CA hollow fiber membrane had better anti-fouling properties than the PVDF membrane.

Preparation and interface structure study on dual-layer polyvinyl chloride matrix reinforced hollow fiber membranes

Polyvinyl chloride (PVC) matrix reinforced hollow fiber membranes including separation layer and porous supported matrix were fabricated via dry–wet spinning process. The mixtures of PVC or polyvinylidene fluoride (PVDF) polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by a melt-spinning method. The influences of pre-wetting solutions and polymer concentration on structure and performance of homogenous-reinforced (HMR) PVC hollow fiber membranes were investigated. Furthermore, the interfacial bonding state of HMR PVC hollow fiber membranes was characterized by an indirect method and comparative analysis. The results showed that a dense interface formed in the HMR PVC hollow fiber membrane between these two layers without pre-wetting process. Compared with the matrix membrane which had a rougher outer surface with obvious big pores, the prepared HMR PVC hollow fiber membrane possessed a dense and smooth outer surface with no obvious big pores. Due to the filling of the pre-wet solutions into the pores in the outer edge of the matrix membrane, the HMR PVC hollow fiber membranes formed porous interface in the coating process which improved its permeability. The HMR PVC hollow fiber membranes had a more favorable interfacial bonding than the heterogeneous-reinforced (HTR) PVDF hollow fiber membranes. The tensile strength of prepared PVC matrix reinforced hollow fiber membranes was higher than 12MPa but lower than the original PVC hollow fiber matrix membrane.

Wind Tunnel Study of Vortex Shedding behind Cooling Tower Models

Wind tunnel measurements of vortex shedding behind cooling tower models were performed in VZLU. Two variants of cooling tower models were used, i.e. model with smooth wall outer surface and model with rough wall surface. Measurements were conducted using hot-wire anemometer. Time signal from the anemometer was transformed using Fast-Fourier routine into frequency spectrum. Measurements have shown significant differences between smooth and rough variant of model surface and dependency of vortex shedding frequency on Reynolds number.

Preparation and Properties of 3D Chitosan Microtubes

The preparation of 3D chitosan microtubes from polymer solutions in citric and lactic acids by the wet and dry molding methods is described. The mechanism of formation of the insoluble polymeric layer constructing the walls of these microtubes is characterized. The microtubes obtained from chitosan solutions in citric acid are found to have a fragile porous inner layer. For those obtained from chitosan solutions in lactic acid the morphology, elastic-deformation properties, physicomechanical properties, and biocompatibility were assessed. These samples have smooth outer and inner surfaces with no visible defects and high values of elongation at break. The strength of the microtubes obtained by the dry method is much higher than in the case of the wet one. A high adhesion and high proliferative activity of the epithelial-like MA-104 cellular culture on the surface of our microtubular substrates in model in vitro experiments were revealed. Prospects of using chitosan microtubes as vascular prostheses are suggested.

Durable and Water-Floatable Ionic Polymer Actuator with Hydrophobic and Asymmetrically Laser-Scribed Reduced Graphene Oxide Paper Electrodes

Ionic polymer actuators driven by electrical stimuli have been widely investigated for use in practical applications such as bioinspired robots, sensors, and biomedical devices. However, conventional ionic polymer-metal composite actuators have a serious drawback of poor durability under long-term actuation in open air, mainly because of the leakage of the inner electrolyte and hydrated cations through cracks in the metallic electrodes. Here, we developed a highly durable and water-floatable ionic polymer artificial muscle by employing hydrophobic and asymmetrically laser-scribed reduced graphene oxide paper electrodes (HLrGOP). The highly conductive, flexible, and cost-effective HLrGOP electrodes have asymmetrically smooth hydrophobic outer and rough inner surfaces, resulting in liquid-impermeable and water-floatable functionalities and strong bonding between an ionic polymer and the electrodes. More interestingly, the HLrGOP electrode, which has a unique functionality to prevent the leakage of the vaporized or liquid electrolyte and mobile ions during electrical stimuli, greatly contributes to an exceptionally durable ionic polymer-graphene composite actuator that is a prerequisite for practical applications in active biomedical devices, biomimetic robots, touch-feedback haptic systems, and flexible soft electronics.

Construction and application of α-Fe2O3 nanocubes dominated by the composite interaction between polyvinyl chloride and potassium ferrocyanide

The present work provides a novel route for the preparation of hematite (α-Fe2O3) nanocubes by a facile, one-step procedure through a noncovalent composite interaction between polyvinyl chloride (PVC, a polymer) and potassium ferrocyanide (PF, a coordination compound) with an initial molar ratio of 20 : 1. Field-emission scanning electron microscopy analysis reveals the formation of well-ordered α-Fe2O3 nanocube granules featuring a uniform and smooth outer surface. Control experiments show that the composite ratios of PVC to PF played a crucial role in generating the nanocubic structure. Temperature-dependent sintering experiments proved that the α-Fe2O3 nanocubes were derived from a structural transformation from nanoplates emerging at lower temperatures, suggesting a condition optimization process of the 2D plate structure to the 3D cubic structure. The one-step synthesis of the nanoplates at lower temperatures is considered to be related to the composite interaction between PVC and PF. A series of independent experiments including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and conductivity were performed to explain the presence of the composite interaction. Interestingly, we found that the composite interaction has improved considerably the physical properties of the polymer (e.g., crystallization degree and glass transition temperature) and the coordination compound (e.g., conductivity and microwave absorption ability). Finally, our data indicate that the as-prepared α-Fe2O3 nanocubes exhibited a higher lithium storage capacity and better cycling performance than the α-Fe2O3 nanoparticles with irregular shapes. We believe that the present results open up many opportunities in nanostructural materials of metal oxides associated with the composite interaction between a polymer and a coordination compound.

22pm1-G5 消化管内走行カプセル

We have developed a traveling small capsule, which has a smooth outer surface and is driven by inertia force and friction force. Measuring only 11 mm in diameter and 24 mm in length, it is sufficiently small to be placed in the human gullet or intestines. The capsule contains a small magnet, a coil, batteries and a circuit, and an electric pulse drives the magnet to move the capsule. Our capsule may be useful for medical treatments such as inspection and drug delivery.

Structure design and performance study on homogeneous-reinforced polyvinyl chloride hollow fiber membranes

Homogeneous-reinforced (HR) polyvinyl chloride (PVC) hollow fiber membranes consisting of coating layer and matrix layer were fabricated via coating process. The mixtures of polymer solutions were uniformly coated on the homogeneous PVC matrix membrane which was prepared by melt-spinning method. The influences of PVC concentration and poly(ethylene glycol) (PEG) molecular weight in polymer solutions on structure and performance of HR membranes were investigated. The results showed that the HR PVC membranes had a dense and smooth outer surface compared with matrix membrane. The maximum pure water flux and protein permeation flux of HR PVC membranes were obtained as the PVC concentration reached to 10wt.% and PEG molecular weight was 2000. The increase of PVC concentration and PEG molecular weight brought about the increase of protein rejection rate and the decrease of membrane porosity. The high flux recovery rate (>85.00%) indicated that the HR membranes had excellent anti-fouling property. Moreover, the HR PVC membranes had a favorable interfacial bonding force between the coating layer and matrix membrane. The tensile strength of HR membranes decreased slightly compared with matrix membrane and was nearly 19MPa, but the elongation at break was opposite which was nearly 102%.

Chemical, mineralogical and morphological changes in weathered coal fly ash: A case study of a brine impacted wet ash dump

The mobility of species in coal fly ash (FA), co-disposed with brine using a wet ash handling system, from a coal fired power generating utility has been investigated. The study was conducted in order to establish if the wet ash dump could act as a salt sink. The ash was dumped as a slurry with 5:1 brine/ash ratio and the dam was in operation for 20 years. Weathered FA samples were collected along three cores at a South African power station's wet ash dump by drilling and sampling the ash at 1.5 m depth intervals. A fresh FA sample was collected from the hoppers in the ash collection system at the power station. Characterization of both fresh FA and weathered FA obtained from the drilled cores S1, S2 and S3 was done using X-ray diffraction (XRD) for mineralogy, X-ray fluorescence (XRF) for chemical composition and scanning electron microscopy (SEM) for morphology. Analysis of extracted pore water and moisture content determination of the fresh FA and the weathered FA obtained from the drilled cores S1, S2 and S3 was done in order to evaluate the physico-chemical properties of the FA. The XRD analysis revealed changes in mineralogy along cores S1, S2 and S3 in comparison with the fresh FA. The SEM analysis revealed spherical particles with smooth outer surfaces for the fresh FA while the weathered ash samples obtained from cores S1, S2 and S3 consisted of agglomerated, irregular particles appearing to be encrusted, etched and corroded showing that weathering and leaching had occurred in the ash dump. The moisture content (MC) analysis carried out on the fresh FA (1.8%) and the weathered FA obtained from the drilled cores S1 (41.4–73.2%), S2 (30.3–94%) and S3 (21.7–76.2%)indicated that the ash dump was water logged hence creating favourable conditions for leaching of species. The fresh fly ash (n = 3) had a pH of 12.38 ± 0.15, EC value of 4.98 ± 0.03 mS/cm and TDS value of 2.68 ± 0.03 g/L, the pH of the drilled core S1 (n = 45) was 10.04 ± 0.50, the EC value was 1.08 ± 0.14 mS/cm and the TDS value was 0.64 ± 0.08 g/L. Core S2 (n = 105) had pH of 10.04 ± 0.23; EC was 1.08 ± 0.06 mS/cm and TDS was 0.64 ± 0.04 g/L, while core S3 (n = 66) had pH of 11.04 ± 0.09; EC was 0.99 ± 0.03 mS/cm and TDS was 0.57 ± 0.01 g/L. The changes in pH values can be attributed to the dissolution and flushing out of alkaline oxides like CaO and MgO from the dumped ash. The variations in pH values shows that the fly ash is acidifying over time and metal mobility can be expected under these conditions. The large decrease of EC in the drilled ash cores S1, S2 and S3 compared to the fresh ash indicated a major loss of ionic species over time in the ash dump. The XRF analysis showed the progressive dissolution of the major aluminosilicate ash matrix which influenced the release of minor and trace elements into the pore water enhancing their mobility as the ash dam acidified over time. Brine co-disposal on the ash may have been responsible for the slight enrichment of some species such as Na (0.27–0.56%), SO42− (0.06–0.08%), Mg (0.57–0.96 %) and K (0.02–0.34%) in the disposed weathered FA. However, there was no significant accumulation of these species in the disposed FA despite continuous addition of large volumes of highly saline brine over the 20 year period that the dump existed, indicating that the ash dam was incapable of holding salts and continually released elements to the environment over the lifetime of the dam.

Avian eggs from the Eocene Willwood and Chadron formations of Wyoming and Nebraska

ABSTRACT Partial eggs from the Eocene Willwood Formation of Wyoming contain unidentifiable embryonic remains; the eggs are referable to a theropod on the basis of their structural layering of calcite and to an avian theropod because of their Eocene age. We assign the specimens to the oofamily Medioolithidae as Microolithus wilsoni, oogen. et oosp. nov., on the basis of the following unique combination of characters: 600-μm-thick eggshell composed of three structural layers; abrupt and undulating contact between the mammillary and continuous layers; smooth and glossy outer egg surface; faint or obscure prisms of the continuous layer; non-branching pores; and mammillary-to-total shell thickness ratio of 1:4. The eggshell microstructure resembles that of some extant neognath bird eggs. We refer a single egg from Chadron Formation of eastern Nebraska to incertae sedis as Metoolithus nebraskensis, oogen. et oosp. nov. A combination of characters distinguishes the egg from other fossil and modern avian eggs, namely, thicker eggshell, prominent ornamentation, flared upper portion of the prisms, variable mammillary thickness, and irregular squamatic texture in the continuous layer. These characteristics more closely resemble Mesozoic non-avian theropod eggs and likely reflect mosaic evolution in the non-avian to avian-theropod transition. Finally, an external layer occurs in a wide range of Paleogene and Cretaceous eggs of variable size and taxonomic affinities, indicating that this feature may not represent an apomorphic character for the avian crown group with respect to non-avian theropod eggshell. Therefore, an external layer cannot be used to identify neognath birds in the Mesozoic.

Ultrastructural Analysis of the Rugose Cell Envelope of a Member of the Pasteurellaceae Family

Bacterial membranes serve as selective environmental barriers and contain determinants required for bacterial colonization and survival. Cell envelopes of Gram-negative bacteria consist of an outer and an inner membrane separated by a periplasmic space. Most Gram-negative bacteria display a smooth outer surface (e.g., Enterobacteriaceae), whereas members of the Pasteurellaceae and Moraxellaceae families show convoluted surfaces. Aggregatibacter actinomycetemcomitans, an oral pathogen representative of the Pasteurellaceae family, displays a convoluted membrane morphology. This phenotype is associated with the presence of morphogenesis protein C (MorC). Inactivation of the morC gene results in a smooth membrane appearance when visualized by two-dimensional (2D) electron microscopy. In this study, 3D electron microscopy and atomic force microscopy of whole-mount bacterial preparations as well as 3D electron microscopy of ultrathin sections of high-pressure frozen and freeze-substituted specimens were used to characterize the membranes of both wild-type and morC mutant strains of A. actinomycetemcomitans. Our results show that the mutant strain contains fewer convolutions than the wild-type bacterium, which exhibits a higher curvature of the outer membrane and a periplasmic space with 2-fold larger volume/area ratio than the mutant bacterium. The inner membrane of both strains has a smooth appearance and shows connections with the outer membrane, as revealed by visualization and segmentation of 3D tomograms. The present studies and the availability of genetically modified organisms with altered outer membrane morphology make A. actinomycetemcomitans a model organism for examining membrane remodeling and its implications in antibiotic resistance and virulence in the Pasteurellaceae and Moraxellaceae bacterial families.

Post-treatment effect on morphology and performance of polyurethane-based hollow fiber membranes through melt-spinning method

Polyurethane-based (PU-based) hollow fiber membranes were fabricated by melt-spinning method. The influence of hot-air treatment conditions including theoretical draw ratio, temperature and time on morphology and performance of membranes were investigated. The results showed that the maximum mean pore size and pure water flux were obtained as the theoretical draw ratio and treatment temperature reached to 2 and 70°C, respectively. The deformation-recovery was mainly governed by the treatment temperature in comparison with theoretical draw ratio when the membrane was treated in hot air. The least treatment time that obtained the best pure water flux was 30min. However, when the membrane treated in stress free conditions, the pore sizes on membrane outer surface were shrunk and the pure water flux decreased with the increment of heat treatment temperature. Moreover, a dense and smooth outer surface with thick skin layer formed as treatment temperature reached at 150°C. The PU-based hollow fiber membranes which treated at the optimum treatment conditions were used to the microfiltration test of the Direct Sky Blue 5B dye wastewater and the removal rate of Direct Sky Blue 5B particles was higher than 94.57%.

A Comparative Study of an Aircraft Radome Closed Mold through Vacuum Infusion Technique

In this paper, manufacturing process of aircraft radome via closed mold with vacuum infusion process is presented. Closed mold is needed to get smooth inner and outer surface. The radome mold was formed from the original part of the aircraft Duke 60 Beachcraft. The closed mold is made from fiber glass/polyester composite via hand lay-up technique. Tooling grade vinyl ester gel coat is applied on the mold to produce fine smooth surface and protection. Later, the radome part is fabricated with vacuum infusion and the consistency of thickness is achieved.

Towards a more representative in vitro method for fish ecotoxicology: morphological and biochemical characterisation of three-dimensional spheroidal hepatocytes

The use of fish primary cells and cell lines offer an in vitro alternative for assessment of chemical toxicity and the evaluation of environmental samples in ecotoxicology. However, their uses are not without limitations such as short culture periods and loss of functionality, particularly with primary tissue. While three-dimensional (spheroid) technology is now established for in vitro mammalian toxicity studies, to date it has not been considered for environmental applications in a model aquatic species. In this study we report development of a reproducible six-well plate, gyratory-mediated method for rainbow trout (Oncorhynchus mykiss) hepatocyte spheroid culture and compare their functional and biochemical status with two-dimensional (2D) monolayer hepatocytes. Primary liver spheroid formation was divided into two stages, immature (1-5 days) and mature (≥6 days) according to size, shape and changes in functional and biochemical parameters (protein, glucose, albumin and lactate dehydrogenase). Mature spheroids retained the morphological characteristics (smooth outer surface, tight cell-cell contacts) previously described for mammalian spheroids as demonstrated by light and scanning electron microscopy. Glucose production and albumin synthesis were significantly higher in mature spheroids when compared to conventional 2D monolayer cultures (P < 0.01) and increased as spheroids matured (P < 0.01). Basal lactate dehydrogenase (LDH) leakage significantly decreased during spheroid formation and was significantly lower than 2D cultures (P < 0.01). It is therefore suggested that mature spheroids can maintain a high degree of functional, biochemical and morphological status over-time in culture that is superior to conventional 2D models and can provide realistic organotypic responses in vitro. Trout spheroids that take ~6-8 days to reach maturity would be suitable for use in acute toxicological tests and since it is possible to culture individual spheroids for over a month, there is potential for this work to lead towards in vitro bioaccumulation alternatives and to conduct high throughput screens of chronic exposure. This is an important step forward for developing alternative in vitro tools in future fish ecotoxicological studies.

Solar thermally driven cooling systems: Some investigation results and perspectives

A big increase in the number of solar thermal cooling installations and research efforts could be seen over the last years worldwide. Especially the producers of solar thermal collectors and systems have been looking for thermal chillers in the small capacity range to provide air conditioning for one or two family houses. Furthermore, many developments aim to increase the efficiency of the system and to decrease the specific costs of the produced refrigeration capacity. The growth in the use of solar thermal cooling systems amounted about 860% from 52 units in 2004 to 450 units in 2009 [1]. This tendency is expected to be continuously in the next years.The practical examinations on solar thermally driven absorption machines with refrigeration capacity of 15, 10 and 5kW have shown that this technology has a good chance to be standardized and to replace partly the conventional one. These systems can save more primary energy at high fraction of solar thermally driving by suitable control and regulation of the system. The investing costs still higher as the conventional one, however, the operating costs are less than the conventional one. The Coefficient of Performance (COP) depends on the kind of the system, work temperatures and conditions as well as the refrigeration capacity of the systems. It lies between 0.4 and 1.2.In the framework of the research on this field, we built, tested and measured two prototypes. After measuring the first prototype, the chillers were redesigned to reduce internal heat losses and make the heat and mass transfer over the surfaces of heat exchangers more effective. Thus, many investigations have been done on some types of heat exchangers for optimization of heat and mass transfer in the system.In this contribution we will show some investigation results on solar thermally driven system in small capacity range. Moreover, we will illustrate an experimental setup for investigation of heat transfer by shell tube heat exchanger consisting of two kinds of tubes. The first one has a smooth outer surface and the other one has a ribbed outer surface. The aim of these investigations is to optimize the whole system.