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International audience; For the first time, a Zn1.1Ga1.8Ge0.1O4 transparent spinel ceramic has been fully densified by spark plasma sintering. XRD measurements show that this ceramic is composed of a pure cubic spinel phase. SEM analysis revealed a homogeneous and dense microstructure with the average grain size being 200 ± 100 nm. The transmittance of these fine-grained ceramics reached 70 % in the visible range and is very close to 80 % at 2 µm, thus close to the Tmax value deduced from the measurement of the refractive index. The ceramics exhibit excellent mechanical properties with a Young modulus of 222 GPa, a Vickers hardness of 14.25 GPa and a thermal conductivity of 7.3 W.m−1. K−1. By doping with Cr3+ ions, transparent Zn1.1Ga1.8Ge0.1O4 ceramics present both a red luminescence and a long-lasting afterglow during several minutes. Moreover, a near infrared broadband emission at 1.3 µm is also achieved with Ni2+ ions.

In order to investigate drying mechanisms at different stages, the distribution of water within the ceramic green bodies at different scales has been examined. The experimental measurements, using a simple weighing technique and Magnetic Resonance Imaging (MRI), show that during the first stage of drying involving shrinkage the material is constituted of uniquely solid and water with no gradient in water content within the sample. Then, during the second stage of drying, significant differences of water content as a function of position appear. As a complement, at the grain scale, observations using environmental scanning electron microscopy were made giving useful information on the solid–liquid–gas interfaces in the near surface part of the green body. Finally, the gradients in the water distribution were exploited to make a simple estimate of the diffusion coefficient of water with its dependence on the moisture content.

Design of high performance materials for thermal insulation or heat sinking requires understanding of the mechanisms controlling heat flow. The effect of grain size on the effective thermal conductivity of porous alumina ceramics has been investigated. After uniaxial pressing of a fine α-alumina powder, control of firing temperature and duration yielded ceramics with variations in grain size. Values of thermal conductivity corresponding to equivalent 100% dense ceramics were determined from laser flash measurements using Landauer’s relation to take porosity into account. These exhibited a strong decrease from 33 W m−1 K−1, for grain sizes larger than 2 μm, down to 8 W m−1 K−1 for an average grain size of 0.25 μm. A method to separate the contributions of localized thermal resistance (Kapitza resistance) at grain boundaries and grain conductivity for each sample is presented. The larger grain size samples (>0.5 μm) yield values for the effective grain boundary thermal resistance in the range 0.6–0.8 × 10−8 m2 K W−1 and a grain conductivity close to 35 W m−1 K−1. For smaller grain samples (

Alloy 709 (UNS S31025) has shown enhanced performance, particularly in creep strength, over current generation high temperature structural materials, specifically Type 316 stainless steel and Grade 91. Accurate knowledge of the thermal properties of the material is important to design efficient systems and to allow calculation of thermally induced stresses and stress gradients. Thermal diffusivity, thermal conductivity, specific heat capacity, and coefficients of thermal expansion have been determined for Alloy 709 as a function of temperature in the range of 20–850 °C. The results do not vary significantly for the three heats of Alloy 709 tested, and compare well with those reported for other high Cr, high Ni austenitic stainless steels. Deviations from monotonic behavior have been observed for the specific heat capacity and to a lesser degree for the thermal conductivity, while the thermal expansion and thermal diffusivity increase nearly linearly with increasing temperature.

In order to provide a thermal barrier in an arid environment, highly reflective coatings were deposited on porous substrates made of natural raw materials from Saudi Arabia. Although highly reflective coatings inhibit heat absorption from the incoming sunlight, the body of conventional ceramic tiles warms up to environmental temperature through conduction, convection and radiation. A strategy to reduce the penetration of this heat into the building is to use a highly porous substrate, which reduces the thermal conductivity of the tile, coupled with a highly reflective glaze. The approach leads to the concept of “cool” tiles, aimed at improving the thermal efficiency of buildings. The present paper provides a first example, based on layered wollastonite-hardystonite glass-ceramics developed by double pressing of glass powders and additives followed by sinter-crystallization.

Purpose To describe a case series of enlarged extraocular muscles in young patients. Design Retrospective interventional case series. Methods Study involves 6 young patients who presented with atypical restrictive strabismus and reduced eye movements. Examination, neuroimaging, biochemistry results, and biopsy results are presented. The surgeries are described, and the follow-up over 1-20 years is presented. Results All 6 patients had enlarged extraocular muscles that caused restrictive strabismus. The patients had no significant medical history. There was no identifiable underlying pathology on biochemistry tests or muscle biopsy. Three of the patients required multiple surgeries. Conclusion Atypical presentations of strabismus should be investigated for systemic conditions. Neuroimaging of the orbit and brain and a biopsy of the affected muscles should be considered. The patients should be counseled that multiple surgeries may be necessary to improve the strabismus, and it is unlikely that orthotropia will be attained.

Kaolinite and muscovite are major clay mineral phases found in the raw materials used for tile and brick production. As phyllosilicates, the crystal structures are layered yielding anisotropic properties. The thermo-physical properties of an extruded clay material, essentially composed of kaolinite, quartz and muscovite have been investigated in the parallel and perpendicular directions to the extrusion axis. Texture is characterized by scanning electron microscopy observations and X-ray diffraction measurements. Values of effective thermal conductivity measured by the laser flash technique and Young's modulus measured with an ultrasonic pulse-echo method reveal an anisotropy factor of 2 for the material in the green body at the macroscopic scale. The thermal conductivity of the solid phases of the material without the quartz fraction was then estimated using an analysis based on the Maxwell–Eucken and Landauer relations. This yields an anisotropy ratio = 3.5 for the clay phase, explained by the alignment of kaolinite and muscovite particles with the extrusion process. The elastic and thermal properties evolve as a function of the heat treatment temperature for the clay, resulting in isotropic behavior after treatment at 1300 °C. These evolutions are concomitant with mineralogical transformations of kaolinite including the formation of mullite above 1000 °C.

The effectiveness of two amorphous silica based wastes, rice husk ash and volcanic ash powders, used to act as structural reinforcement and partial replacement of metakaolin in porous matrices for thermal isolation was assessed. Both wastes produced colloidal phase that contributed to improve the reactivity and homogeneity of the matrices enhancing the mechanical strength. Rounded pores were obtained in relation with significant reduction of the interpore partitions under controlled addition of the blowing agent. The bulk thermal conductivity decreased from 0.6 to less than 0.15 W m −1 K −1 with the increase of the concentration of blowing agent. The final matrix presented pore size distribution and pore connectivity that allows analytical description and prediction of their effective thermal conductivity.Results demonstrated that clear relations can be established among the viscosity of the pastes, chemical composition, amount of blowing agent and the volume expansion/pore size distribution.

The use of cultigens and wild plants by pre-contact populations is well established in all regions of the circum-Caribbean and Greater Antilles except for Cuba, the largest island in the Caribbean. We examine a population traditionally understood by Cuban archaeologists as “fisher–gatherers” from the shell-matrix site of Canimar Abajo, Cuba to examine subsistence practices using a combination of starch evidence from dental calculus, aided by human bone collagen carbon and nitrogen isotope based probability analyses (Stable Isotope Analysis in R; SIAR). This dual analysis suggests that two chronologically distinct “fisher–gatherer” Cuban populations (11 adult skeletons from the older cemetery component, 1380–800 BCE; 23 adult skeletons from the younger cemetery component, 360–950 CE) from Canimar Abajo used at least two species of cultigens (beans and maize and/or sweet potatoes) along with wild plant species and various readily available estuarine, marine and terrestrial animal resources.

Purpose To evaluate the accuracy of the anterior segment optical coherence tomography (AS-OCT) in measuring the distance from the limbus to the insertion of primary and previously operated rectus muscles in children. Methods In this prospective, double masked, observational study the distance of the extraocular muscle insertion from the limbus measured by AS-OCT preoperatively was compared to intraoperative measurement using the surgical calipers. Consecutive patients 4-18 years of age undergoing primary or repeat strabismus surgery on horizontal or vertical rectus muscles between September 2013 and May 2014 were included. Patients with any condition that interfered with imaging were excluded. Participants were asked to look in the direction opposite to the muscle to ensure that the middle third of the muscle was being imaged and measured. Results A total of 65 muscles were evaluated, including 9 muscles undergoing reoperation and 10 vertical rectus muscles. Of these, 62 muscles were successfully imaged. In all reoperated eyes, the AS-OCT measurements were within 1 mm of the intraoperative measurements. Overall, 89.7% (95% CI, 78.8%-96.1%) of the measurements were within the 1 mm difference considered “clinically acceptable.” The intraclass correlation coefficient comparing the reliability of the AS-OCT measurements with intraoperative measurements was 0.73 (95% CI, 0.53-0.85), or “good” agreement. Conclusions AS-OCT can accurately detect rectus muscle insertions in primary or previously operated cases in children as young as 4 years of age.

Candidate materials for thermal insulation combine a solid phase of low thermal conductivity with porosity. Very porous ceramics based on a commercial clay containing 79% kaolinite were made by a direct foaming method using methylcellulose, drying at 70 °C before a consolidation at 1100 °C. The pore volume fraction ( v p ) was varied in the kaolin-based foam by modifying the amount of clay incorporated in the starting mixture. Measurements of the thermal conductivity with the hot disk method revealed a decrease from 0.23 W m−1 K−1 at v p = 0.57 to 0.054 W m−1 K−1 at v p = 0.95 in close agreement to predictions by the Hashin–Shtrikman upper bound, a cubic pore model and numerical simulation of an artificial microstructure representing the polyhedral pore shape with Voronoi mosaics. The effective Young's modulus, obtained from mechanical compression tests, also decreases with pore volume fraction as described by Ashby's relation. However the mechanical strength was sufficient for handling even the more porous kaolin-based foams.

International audience; Experimental results and theoretical models are used to assess the effective thermal conductivity of porous inorganic polymer cements, often indicated as geopolymers, with porosity between 30 and 70. vol.%. It is shown that the bulk chemical composition affects the microstructure (grains size, pores size, spatial arrangement of pores, homogeneity, micro cracks, bleeding channels) with consequently the heat flow behaviour through the porous matrix. In particular, introduction of controlled fine pores in a homogeneous matrix of inorganic polymer cements results in an increase of pore volume and improvement of the thermal insulation. The variation of the effective thermal conductivity with the total porosity was found to be consistent with analytical models described by Maxwell-Eucken and Landauer.

Sexually dimorphic characteristics in men may act as cues, advertising long-term health, dominance, and reproductive potential to prospective mates. Evolution has accordingly adapted human cognition so that women perceive sexually dimorphic facial features as important when judging the attractiveness and suitability of potential mates. Here we provide evidence showing, for the first time, that women's memory for details encountered in recently experienced episodes is also systematically biased by the presence of men's facial cues signaling enhanced or reduced sexual dimorphism. Importantly, the direction and strength of this bias are predicted by individual differences in women's preferences for masculine versus feminine facial features in men and are triggered specifically while viewing images of male but not female faces. No analogous effects were observed in male participants viewing images of feminized and masculinized women's faces despite the fact that male participants showed strong preferences for feminized facial features. These findings reveal a preference-dependent memory enhancement in women that would promote retention of information from encounters with preferred potential mates. We propose that women's memory for recently experienced episodes may therefore be functionally specialized for mate choice and in particular for the comparative evaluation of alternative potential mates. This also raises the possibility that similar specialization may be present in other species where it has been established that precursor, ‘episodic-like’ forms of memory exist.

International audience; Two sets of soils of volcanic origin, denoted LM1 and LM2, stabilised with variable OPC content and compacted at different pressures were studied. Optimal parameters, namely, compaction pressure, moisture and OPC contents have been defined for each sample in relation with their characteristic compressive strengths at the age of 7 days. Results show a compaction pressure of 8 MPa is adequate for both soils (LM1 and LM2) to yield maximum dry compressive strength of 9.0 ± 0.1 MPa. Furthermore, 20 wt% of coarse sand as sand replacement increases these values by about 50%. These results are acceptable values for building and civil engineering purposes.

The value of critical current density at 77 K in “zero” applied field ( J c ) characterizing the superconducting state for YBa 2 Cu 3 O 7− δ ceramics is closely related to the microstructure. The interrelationships between the microstructural factors such as pore volume fraction, oxygen content, average grain size, are complex. However, these factors also influence the normal state resistivity measured at room temperature ( ρ 300 ). We demonstrate how the current carrying cross section influences Jc and ρ 300 in a similar way. Data, reported for two classes of YBa 2 Cu 3 O 7− δ : small grain porous ceramics and larger-grain denser ceramics, reveal an approximate linear relation between ρ 300 K and J c . Extrapolation of this relation to a fully dense small grain YBa 2 Cu 3 O 7− δ ceramic yields values of ρ 300 = 0.4 mΩ cm and J c = 10 3 A cm −2 .

International audience; Specific heats of four clays (standard reference kaolins, commercial kaolin and montmorillonite) before and after dehydroxylation have been measured. The results were compared with handbook data for the thermal chemical properties of solids. Good agreement has been obtained for the reference kaolin before any thermal treatment. Then, following thermal treatments at 500 °C, 600 °C and 700 °C, dehydroxylation leads to a progressive decrease of heat capacity per unit mass. After dehydroxylation, heat capacity values for all the studied materials are rather similar and agree closely with those estimated by the rule of mixtures. Finally, an empirical relation describing the specific heat capacity (C) in J kg−1 K−1 of dehydroxylated kaolin from 40 °C to 1100 °C is proposed: C = 1128 + 0.102T − 36 × 106T−2 where T is in K.

Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments.

We describe a spectral element solution strategy for simulation of weakly turbulent vascular flows. Novel approaches for treatment of outflow boundary conditions and flow division are presented. We demonstrate that several million gridpoints are required to obtain converged rms statistics when uniform refinement is used and discuss possible approaches to cost reduction.

The thermal conductivity of a two-phase material, based on a glass matrix containing mm sized spherical alumina inclusions, has been studied as a function of the alumina phase volume fraction. The glass matrix and the alumina phase were chosen with almost identical coefficients of thermal expansion to ensure good thermal contact at the interface between the two phases. The thermal conductivity of the alumina phase was determined by local measurements on the inclusions using the mirage technique. For the glass phase and the two-phase samples, the thermal conductivity values were evaluated with the laser flash technique and compared to predictions by analytical models. The Maxwell–Eucken model gives a close agreement to these experimental values for alumina volume fractions up to 55%. In fact, we show that for large mm sized alumina inclusions, Hasselman's correction for the interface thermal resistance is not necessary.

Three aspects, which significantly reduce heat transfer through a polycrystalline material, are considered in this paper: porosity, grain boundary thermal resistance and the state of the grain–grain contacts. Tin oxide and alumina were chosen as model systems. Tin oxide, without a sintering additive, does not densify during thermal treatment but grain growth is not inhibited and consequently the microstructure can be varied. In alumina, variation of the thermal treatment conditions varies both grain size and porosity. Thermal conductivity measurements, using the laser-flash technique, reveal that the thermal resistance of a pressed powder compact is almost independent of temperature and at least a factor of 2.5 greater than a consolidated material with similar pore volume fraction and grain size. The reduced contact area of the grain–grain interfaces in the green body can explain this as demonstrated by numerical simulation. We also show that larger grain size increases the thermal conductivity of the porous ceramic.

Two sets of highly porous materials with different intrinsic thermal conductivity values for the solid skeleton were prepared: zirconia and alumina. Microstructural characterisation was performed, including the determination of the pore size distribution (PSD). The pore volume fraction was varied from 40 to 75%. Zirconia samples exhibit heterogeneous microstructures with a bimodal PSD. Alumina samples seems to be more organised with a monomodal PSD. The effective thermal conductivity was evaluated using the laser-flash technique. The experimental values were compared with predictions made with analytical models as a function of porosity. In particular, effective medium percolation theory (EMPT) for a two-phase system gives calculated values which are close to the experimental results for zirconia samples when the bimodal PSD was taken into account. Measurements on alumina samples have shown that EMPT is of limited use for an organised microstructure with porosity exceeding 65%. Complementary studies by computer simulation were also used to support some of the deductions which were made concerning the influence of the microstructure organisation on the effective thermal conductivity.

Highly porous zirconia ceramic with nanometric sized grains was prepared from an 8 mol% yttria stabilised zirconia suspension mixed with a commercial latex. The pore volume fraction was varied from 45 to 75% by adjusting the thermal treatment between 750 and 1100 °C. Observations of the microstructure reveal variation in pore shape and size. Mean grain sizes are less than 70 nm. Mercury porosimetry measurements reveal a bimodal pore size distribution. Thermal diffusivity measurements were made with the laser flash technique in order to determine the thermal conductivity at room temperature. The thermal conductivity approaches a lower limit of 0.1 W m −1 K −1 . Experimental results were shown to agree closely with predictions made with Landauer's effective medium expression for a two-phase system. The agreement was improved even further by taking into account the interfacial thermal resistance of the grain boundaries and the pore size distribution.

The overall thermal conductivity of a porous material is strongly sensitive to the volume fraction and spatial distribution of the pores. For this second aspect analytical models predicting thermal conductivity as a function of pore volume fraction are obliged to make a simplifying assumption concerning the pore shape. In order to describe the effects of the microstructure on heat transfer in greater detail, we have developed a method involving 2D finite element calculations based on real micrographs of the porous solid. The approach was tested on micrographs of tin oxide samples with pore contents from 10% to 50%. Quantitative results obtained for pore contents up to 20% give very good agreement to Rayleigh's model. Higher pore contents lead to a number of difficulties but the qualitative results are used to support the choice of Landauer's effective medium expression as an appropriate general analytical model for the thermal conductivity of a porous ceramic material.

The preparation of porous SiC ceramics from stoechiometric mixtures of silicon and graphite has been studied. Products with very high pore contents (≈80%) were obtained using a process which consisted of heating the reactive pellets in purified argon, at 15 °C min −1 , up to 1430 °C and applying a weak d.c. voltage across the sample for 20 s. The resulting electrical current was necessary for the ignition of an SHS reaction simultaneously in the whole sample. The analysis of the sample microstructure evolution all along the process has enabled the identification of the different mechanisms involved in the SiC formation. Before the SHS stage, the formation of silicon carbide, during heating from about 1325 up to 1430 °C, is associated with a large sample expansion, which mainly determined the final pore volume fraction. The pore transfer mechanisms, which occur during the SHS stage at 1430 °C, have a specific influence on the pore development. Since the final pore size distribution is strongly related to silicon grain granulometry, the porosity of the porous SiC ceramic, obtained by this process, can be easily modulated.

TODAM is a theory of distributed associative memory based on the convolution-correlation formalism of A. Borsellino and T. Poggio (1973, Kybernetik, 122, 113-122), and TODAM2 is a revised version which includes context, auto-associations for binding, a dual basis for item information, and mediators for associative information. It can explain some complex interactions (differential forgetting and differential attention) between item and associative information. In this paper we derive the basic expressions for the memory-probe dot product for the 2x2 cases (item and pair study crossed with item and pair probe), and then we apply these expressions to judgments of frequency (JOF) and judgments of recency (JOR). We report an experiment which tests both JOF and JOR for single items with post-cuing to control for encoding strategies and suggest an attenuation factor for repetition to improve the fits. With attenuation, TODAM2 can fit the JOR data, but the JOF fits, while not too bad, consistently predict too much dependence between item and associative information. Copyright 2001 Academic Press.

This paper describes a method to assess the electromagnetic characteristics of a superconducting ceramic material. YBa 2 Cu 3 O 7– δ ceramic samples have been made in the form of hollow cylinders with the standard 4 terminal configuration for measurement of the critical current ( I c ) attached to the outer surface. An additional wire carries a second internal current ( I int ) along the central axis. I c can thus be modulated by I int . In particular, an increase in I c can be achieved by directing I int in the opposite direction to the cylinder current in order to compensate the self-generated magnetic field. The I c – I int characteristic can be described by a critical state model where we assume a linear dependence between the local critical current density ( j c ) and the local magnetic field ( H ) for the superconducting polycrystalline material. Based on this linear model the experimental data for a given sample can be analysed to extract two parameters: the maximum local critical current density ( j 0 ) and the local magnetic field ( H 0 ) for which j c should vanish. The best sample yielded j 0 =1023 A cm –2 and H 0 =4450 A m –1 .

Measurement of the thermal diffusivity by the laser flash technique has been used to evaluate thermal conductivity values between 20°C and 900°C for tin oxide ceramics. By using MnO 2 as a sintering additive, strong variation of the microstructure in terms of porosity and average grain size was achieved in the samples. For dense ceramics, larger average grain size yielded a significant increase in the room temperature thermal conductivity. This could be attributed to a reduction of the number of grain boundaries in the heat flow path. The grain boundary interfacial resistance was consequently estimated at 4.1×10 −8 m 2 KW −1 . Data concerning the effects of additive amount, pore content, and temperature are also reported.

Emerging biomedical technologies present a new order of magnitude of complexity in their interactions with human patients. As such, they challenge established processes for protecting patients and the public health, while testing the capacity of those processes to ensure timely access to beneficial therapies—especially those representing significant advances over existing therapies. This article reviews the Food and Drug Administration (FDA) regulatory process—including the classification of medical products, the marketing review and approval pathways, and the 1997 FDA Modernization Act—and discusses other legal and policy considerations relevant to engineered tissues.

In order to prepare tin dioxide (SnO 2 ) based films by the pyrosol technique, different mixtures of tin precursors (chlorinated and nonchlorinated salts) and solvents (methanol, butanol and acetylacetone) have been tested. Depending on the surface aspect, the obtained deposits have been classified into three categories; there are smooth, slightly faceted and faceted surfaces. Smooth surfaces are obtained when the solvent has a high nebulization rate or when the salt has a high molecular weight. The development of facets occurs when the salt is light or when gaseous HCl is present in the pyrolysis region. The optical and electrical characteristics of the corresponding films are also discussed.

A thermal model is used to calculate the temperature distribution along YBa2Cu3O7−δ bars in liquid nitrogen for the case of heat sources situated at the ends. The predictions allow an appropriate choice of experimental conditions which avoid thermal effects influencing transport critical current measurements at 77 K. The zero field critical current density Jc is then shown to depend on the cross sectional area because of limitation by the self-induced magnetic field. Consistent with predictions from a critical state model based on the notion of a local magnetic field in the ceramic; this effect is shown to be strongly attenuated for porous or microcracked samples where the local current carrying capacity is reduced. Finally a correlation between the critical current density and the room temperature conductivity as a function of relative density is reported and discussed in terms of current distribution within YBa2Cu3O7−δ ceramics.

Tin oxide based thin films were deposited by the pyrosol process from methanol solutions of dibutyltindiacetate (DBTDA) and variable quantities of ammonium fluoride (NH4F). The optical and electrical characteristics of these films are closely linked to the film morphology (surface aspect and preferred orientation), which is strongly influenced by the chemical nature of the tin precursors. DBTDA precursor was chosen because of easy handling. The film crystallites do not present sharp edges which is an advantage for application as a transparent and conducting electrode in a device. When the ratio F/Sn is equal to 25at.% in the starting solution, the optical transmittance is between 78 and 95%, even for the thicker deposits (1.45μm) which exhibit a corresponding sheet resistance of 8.3 Ω/□.

The insulin resistance syndrome has recently been implicated in the etiology of coronary heart disease, with a possible metabolic defect at the level of the adipocyte. We report the effects of a low- versus high-glycemic-index (LGI and HGI, respectively) diet on insulin and glucose response as assessed by oral glucose tolerance test (OGTT) and insulin-stimulated glucose uptake in isolated adipocytes in a group of 32 patients with advanced coronary heart disease. The area under the insulin curve following OGTT was significantly reduced after 4 weeks in the LGI group (P < .03), but not in the HGI group. Insulin-stimulated glucose uptake in isolated adipocytes harvested from a presternal fat biopsy was significantly greater following the LGI diet (P < .05). This study demonstrates that simple short-term dietary measures can improve insulin sensitivity in patients with coronary heart disease.

The chemical nature of precursors and morphology (surface aspect and preferred orientations) for SnO2 films deposited by a pyrosol process are examined for starting solutions containing either SnCl4 or SnCl2 · 2H2O dissolved in methanol. A study by comparison shows that molecules formed from SnCl4 deposit more easily than polymer molecules produced from SnCl2 · 2H2O. The addition of HC1 in this last solution modifies significantly the chemical nature of the molecule participating in film development as well as the growth rate. Electrical measurements of the solution resistivity as a function of HC1 concentration show a minimum in the equivalent conductivity which is directly correlated with a maximum in the growth rate. This is explained by the association of SnCl2 and HC1 to form neutral HSnCl3 molecules. A geometrical approach is then developed to describe the growth form of the film crystallites. For thin films deposited from SnCl2 · 2H2O, the crystallite faces consist of (101) corresponding to (110) preferred orientation. For SnCl4, the crystallites consist of 111 faces corresponding to a (200) preferred orientation. The presence of (101) and (301) twin planes is used to explain the observation of (301) (211) and (101) preferred orientations respectively. Lastly, the electrical and optical characteristics of the corresponding films are also reported.

Pharmacokinetic (PK) modelling of dynamic contrast enhanced (DCE) MRI data has shown considerable promise in the detection of many cancers, including prostate. However, the clinical implementation of DCE-MRI acquisition protocols suitable for PK modelling has been greatly hindered by the lack of consistency with published PK parameter values, such as the volume-transfer constant ( K trans ), with widely varying acquisition protocols and PK modelling approaches adding to the confusion. A novel anthropomorphic dynamic prostate phantom has been developed to address this shortcoming. The device is capable of simultaneously producing two distinct contrast time-intensity curves (CTCs), representative of those observed in DCE-MRI data from healthy and tumorous prostate tissue, in an environment which closely mimics the male pelvic region. CTCs were measured using a custom-built optical scanner, and ‘ground truth’ PK parameter values derived from the data. DCE-MRI data were acquired using a 3T scanner (Achieva, Philips, Netherlands) and a 16-channel phased array detector coil (3D-SPGR, TR/TE = 3.6/1.75 ms, flip = 10°, voxel size = 1.1 × 1.1 × 4 mm 3 , FOV = 224 × 224 × 72 mm 3 , slices = 18). The parallel imaging factor and number of signal averages were varied to give temporal resolutions from 2.3 s to 20.3 s. K trans values derived from MR data from the phantom were compared with the ground truth values and were found to differ by −8.1% to −44.6%, with the lowest variance from ground truth values achieved at a temporal resolution of 6.8 s. The phantom provides a model system on which the quantitative validation of new prostate DCE-MRI protocols can be performed, and could contribute to the standardisation of clinical prostate DCE-MRI acquisition protocols.

The addition of 0.1 at% Bi to ZnO yields a ceramic with nonlinear current-voltage behaviour (I=KVα) characterized by a maximum α value of 5. The effect of further addition of 0.1 at% of a 3d transition element was tested through the series Sc, Ti, V, Cr, Mn, Fe, Co, Ni or Cu. This low level of doping does not provoke any marked variation in the microstructure. Mn followed by Cu gave the most significant enhancement to nonlinearity achieving α=50 and α=30 respectively. The strong performances due to Mn doping are counterbalanced by degradation of the electrical behaviour under repeated high-voltage cycles whereas the samples doped with other 3d elements were much stable. This is related to the capability of Mn to adopt several oxidation states.

1. The articular capsule or ligament, of the primary spines of the sea-urchin Eucidaris tribuloides behaves as a classical excitable tissue, responding with a shortening or contracture to a variety of stimuli including the cholinergic agonists acetylcholine (ACh), methacholine (MeACh), carbamylcholine (CCh) and nicotine. 2. d-Tubocurarine failed to decrease the amplitude of the acetylcholine-induced contractures, while the contractures elicited by methacholine were blocked by atropine. Neostigmine, but not eserine, increased the amplitude of ACh-induced contractures, suggesting the presence of AChE in the preparation. 3. The cholinergic agonists induced contracture of the ligament, but had quite different kinetics, the rate of rise of the contracture being fastest for ACh and decreasing in the following order: CCh, MeACh and nicotine. 4. Tyramine and octopamine exert an inhibitory action on "catch" and a relaxing effect on the contracting ligament. 5. The time courses of the contractures elicited in the same preparation were virtually identical to those of "catch". Therefore, we propose that "catch" and contracture are only two different aspects of the same phenomenon; namely the contracture of the muscle fibers present in the ligament.

1. This paper describes the effects of several cholinergic agonists and antagonists, and of β-phenylethylamine (PEA) and some of its derivatives, on the articular capsule, or ligament, of the primary spines of Eucidaris tribuloides. 2. Carbamylcholine (CCh), methacholine (MeACh), nicotine, and muscarine exert a stiffening effect similar to that of acetylcholine (ACh), although the time course of their actions varies widely. 3. Atropine induced stiffening and blocked and responses to muscarine and MeACh. The responses to MeACh were blocked also by 4-diphenylacetoxy-N-methylpiperidine, suggesting the presence in the ligament of type M3 muscarinic receptors, in addition to nicotinic ones. d-Tubocurarine induced stiffness of the ligament and failed to block the responses to ACh and nicotine. 4. While ACh induced only a slight desensitization, CCh caused a long-lasting blockade of the stiffening effects of the cholinergic agonists. This shows that the receptors for ACh have a site or sites that recognize the ester moieties of these molecules. 5. Eserine and neostigmine potentiate the responses to acetylcholine, indicating the presence of aeetyl-cholinesterase in the ligament. 6. β-Phenylethy lamine, epinephrine, norepinephrine, and dopamine induce diphasic responses; usually a brief softening followed by a slow and irreversible stiffening of the ligament. 7. In contrast to the above, tyramine and octopamine elicit a simple softening of ligaments which are stiff as a result of handling or by exposure to cholinergic agonists. However, tyramine and octopamine do not soften ligaments which become stiff as a result of exposure to adrenergic agonists.

The properties of a YBa2Cu3O(7−δ) ceramic superconductor are strongly influenced by the method of synthesis. A typical preparation of the ceramic involves calcination of a stoichiometric mixture of Y2O3, BaCO3 and CuO. The authors show that the method of mixing has a significant effect on the decomposition of BaCO3 and hence formation of the 123 phase. Furthermore, the reaction is promoted by lower oxygen partial pressure and a gas flow which removes the CO2. This aspect of carbon dioxide removal was found to be a serious problem for the preparation of a larger amount of material.

The similar proximal and distal attachments to the stereom of primary spine ligament in the echinoid Eucidaris tribuloides are described, from thin sections and SEM studies on frozen and fractured spine articulations and ligaments from decalcified material. The orthogonal structure of the general stereom is modified on the attachment zones where bundles of collagen cylinders enter approximately hexagonally arranged channels. Straps of collagen extend in parallel series between adjacent bundles via regularly placed ports and collagen loops rather than non-striated 'tendons' pass over skeletal trabeculae. The regular pattern of collagen straps is most evident on the proximal and distal attachment zones. Mechanical features of the non-adhesive mode of attachment are considered, together with similarities and differences between insertion of muscle cells and mutable collagenous tissue (ligament) in echinoderms.

Freeze-fracture replicas have been prepared from two fast-acting vertebrate muscles (frog sartorius and rabbit sacrospinalis) and are described with particular reference to the distribution of intercalated particles in the plasma membrane, T-tubule and SR cisternae. Orthogonal assemblies of small particles are present on the A face plasma membrane in each instance, and their distribution (in sartorius) is found to be random with respect to the underlying myofibrillar sarcomere repeat. Such assemblies are not present on A or B faces of T-tubule or SR cisternae. Asymmetric particle distribution is described for fracture faces of the T-tubules and SR: the profuse particle packing of the SR A face is uniform from terminal cisternae to medial fenestrated collar. Intercalated particles are present on A and B faces of T-tubule fractures: more commonly on the latter. These results are compared with studies on insect muscles, and a comparative approach to further studies on the correlation between membrane structure and function is discussed.

The ventral, postsynaptic membranes of the electroplaques of Narcine were examined for structures corresponding in location, numbers, position and form with nicotinic acetylcholine receptor-channel molecules. Electron micrographs of conventionally fixed material showed that the thickened outer lamina of these membranes contained about 6100 stained structures/μm 2 ; and calculations from this packing density and the estimated area of postsynaptic membranes/g tissue yielded a total number of structures within a factor of two of the number of receptor molecules/g determined from the binding of alpha-bungarotoxin. Examination of tissue prepared with a tannic acid/glutaraldehyde fixative revealed that the structures were uniform in character, cylindrical in shape, transmembrane in position, and that each contained a central core. Their diameter matched that of isolated receptor molecules, and their size can account for most of the receptor protein. We conclude that these receptor molecules are largely intramembranous, cylindrical and exhibit transmembrane pores.

It has previously been demonstrated that peripheral blood leucocytes of the nurse shark (Ginglymostoma cirrhatum) are capable of in vitro chemotaxis. In the present study we have identified the chemotactic cells as the shark granulocyte and monocyte-macrophage. Chemotaxis assays were set up in blind well chambers. Cells migrating into the filter in a chemotaxis assay were identified morphologically by transmission electron microscopy. Migration, in response to LPS-activated rat serum, was accompanied by change in cell shape and reorganization of the cytoskeleton. Ultrastructural changes included formation of lamellipodia with cell polarization, submembranous accumulation of microfilaments at points of plasma membrane contact with filter surfaces, densification of the membrane at these points of engagement, appearance of bundles of intermediate filaments extending into the protruded lamellipodia, and presence of oriented microtubules in the cytoplasma (cellular cortex). The phagocytic and chemotactic properties of the shark granulocyte and monocyte-macrophage points to their being structural and functional equivalents of the mammalian neutrophil and macrophage.