Adsorption of amino acids by fullerenes and fullerene nanowhiskers

We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C₆₀) and fullerene nanowhiskers (FNWs). C₆₀ and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C₆₀ or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C₆₀ did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C₆₀ and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C₆₀ and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C₆₀ and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C₆₀. The theoretical simulations showed the bonding distance between C₆₀ and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C₆₀ showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C₆₀. In our study Try and Tyr were hardly adsorbed by C₆₀ and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.     

The influence of annealing twinning on microstructure evolution

This paper reports an experimental investigation on the effect of multiple twinning on the interface population in two low stacking-fault alloys. This is an important topic for grain boundary engineering because annealing twinning is the indirect cause of improved intergranular corrosion resistance in this class of materials. Proportions of Σ 3ⁿ (n = 1–5) boundaries were analysed in both a brass specimen and a superalloy specimen where the boundaries had been processed so as to be very mobile and less mobile respectively. When Σ 3 twin boundaries (as distinct from Σ 3 grain boundaries) are discounted, the Σ 3ⁿ distribution for both specimens had a peak at Σ 9, because Σ 3 + Σ 9 → Σ 3 occurs more frequently than Σ 3+Σ 9 → Σ 27. The distributions and reactions between various Σ 3ⁿ values are described and discussed in detail. A novel trace analysis procedure is used to extract information from Σ 3 boundaries to decide whether or not they are annealing twins, and so provide a convenient means to assess proportions of twin and non-twin Σ 3s. The data show unambiguously that a significant proportion of Σ 3s are not on 111, and these boundaries have on average higher angular deviations from the exact Σ 3 reference misorientation than do other Σ 3s. A population of Σ 3s which were vicinal to annealing twins were also recorded. These data support the contention that profuse annealing twinning produces concurrently many not-twin Σ 3s, which are pivotal in grain boundary engineering.     

GEOMETRY INDEPENDENT R-CURVES IN A TITANIUM ALLOY USING A NORMALISED AXIS FOR CRACK GROWTH

Data from a study of the effect of geometric variation on J-R curves for a titanium alloy in three-point bending are presented up to large amounts of growth. Four series are reported, various widths, various a/W ratios, various thicknesses and various absolute sizes, all failing in the limit load regime by stable tearing. Analysis is made in terms of J_m-R curves, adjusted to a common initiation toughness, J₁, to clarify the effects of geometry. Strong trends are then found with absolute size over a four fold range and with width over a two fold range; a weaker trend with a/W over a four fold range but practically none with thickness over a nine fold range. Many of these trends are different from those reported for other more ductile materials but consistent in some cases with those reported for another high strength material, HY130. All the deep notch cases (14 tests) reduce to a single group when plotted as J_m against a normalised abscissa, Δa/b_o, with a very slight trend to a higher curve for the thinner pieces.     

Observation of NMR Signals from a Thin 3He Slab

NMR free precession signals from a slab of normal ³ He of thickness comparable to the superfluid coherence length have been observed using a SQUID NMR spectrometer at a frequency of 880 kHz. This spectrometer is based on a SQUID with Additional Positive Feedback, directly coupled to a low noise room temperature amplifier, and operated in flux locked loop mode using the direct offset integration technique, with a bandwidth of several MHz. The sensitivity is such that the signal from a 100 nm slab on a 1 cm ² surface, corresponding to 2×10 ¹⁷ spins, is clearly resolved.     

A direct estimate of JIc from the load versus load-line displacement record

The purpose of this study is to examine the current standard fracture toughness test procedure to determine if there could be an easier method to get a J_Ic value from the test record. The current method for determining J_Ic involves a detailed computational and construction procedure. The objective in this study is to simplify the analysis for the determination of J_Ic. The results of this study show that the load and displacement record for a fracture toughness test can be used to directly estimate a J_Q value, a provisional value for fracture toughness, J_Ic. The J value taken at the maximum load point can be used along with an adjustment factor to estimate a J_Q value. This J_Q estimate is close to the one obtained from the construction procedure of ASTM Standard E 1820. When a unit‐sized specimen is tested, that is, a specimen with a width of 50 mm and a thickness of 25 mm the maximum load point provides a direct estimate of J_Q. Other sizes require a size adjustment factor, which is simply a square root relationship between the width of the test specimen and a unit width. The proposed new method of estimating J_Q is simple in concept and requires a minimum number of calculations. It appears to produce values of J_Q which are comparable to those obtained from the ASTM E1820 construction procedure and may produce less scatter.     

Vacuum seal for a rectangular flange

A new vacuum seal for a rectangular flange used in r.f. equipments, was developed. The vacuum seal consists of a recess with a flat surface, machined into a rectangular flange, a rectangular metal gasket with a raised projection on one face, and a mating flange with a recess and raised projection. No leak greater than 1 × 10⁻¹⁰ Pa m³/s was found in leak tests, before and after baking cycles (100 °C, 12 h).     

Low temperature preparation of TiO2 nanodot film on substrates

Herein, we report a photoinduced transition of hydrophobicity to high hydrophilicity of TiO₂ nanodot films in applications of cell sheet engineering. A phase-separation-induced self-assembly process was adopted to prepare a TiO₂ nanodot gel film on a substrate. Subsequently, a hydrothermal treatment (with ethanol/water at 140 °C for 2 h) was used to convert the nanodot gel film to TiO₂ nanodot solid film. The resulting TiO₂ dots were amorphous with adjustable size and density. The amorphous TiO₂ nanodot film showed a conversion from a good hydrophobic surface, with a water contact angle (WCA) of 67.6 ± 2.0°, to a highly hydrophilic one, with a WCA of 5.3 ± 2.0° (i.e. almost superhydrophilic) after UV irradiation. A good reversibility was also observed.     

Biosynthesis of eco‐friendly and recyclable Pd/LDHs catalyst using the withered leaves extract for Suzuki coupling reaction

The hydrotalcite‐supported palladium (Pd) catalyst is prepared with a green and environmentally friendly route, introducing the extract of withered leaves as a dispersant and reducing agent (Pd/LDHs‐B). Compared with the as‐prepared catalyst (Pd/LDHs‐P with the average diameter of 4.3 nm) using a chemical synthesis method with polyvinylpyrrolidone as a dispersant and ascorbic acid (Vc) as a reductant, the results indicate that the size of Pd nanoparticles in Pd/LDHs‐B is smaller (ca. 3.6 nm). The Pd‐LHDs‐B (0.5 mmol‰) exhibits higher activity (98.66%) than Pd/LDHs‐P (98.19%) in the Suzuki reaction of 4‐bromotoluene and phenylboronic acid at 60°C for 30 min. Also, the reusability of Pd/LDHs‐B is confirmed by recycling tests without a significant decrease in activity.Inspec keywords: nanoparticles, reduction (chemical), chemical engineering, catalysts, X‐ray diffraction, recycling, catalysis, organic compounds, palladium, particle sizeOther keywords: Suzuki reaction, reducing agent, hydrotalcite‐supported palladium catalyst biosynthesis process, environmentally friendly material, withered leaves extract, dispersant agent, chemical synthesis method, polyvinylpyrrolidone, ascorbic acid, nanoparticle size, 4‐bromotoluene, phenylboronic acid, recycling test, temperature 60.0 degC, size 4.3 nm, size 3.6 nm, time 30.0 min, Pd     

Capacitance-voltage and leakage-current characteristics of sol-gel-derived crystalline and amorphous SrTa2O6 thin films

SrTa₂O₆ (STA) is a promising high-dielectric-constant (ε) material. In this study, STA thin films were fabricated using the sol-gel method. The capacitance-voltage and leakage-current characteristics of crystalline and amorphous STA thin-film capacitors were investigated. STA thin films crystallized at an annealing temperature of 800 °C. Crystalline STA thin films exhibited a high ε of about 110, whereas amorphous STA thin films showed a much lower ε of about 26-41. However, amorphous STA thin films had a much more constant capacitance as a function of voltage. Of the amorphous thin films, the one annealed at 700 °C had the highest ε of about 41, the lowest leakage current of 10^− 8 A/cm², and a very constant capacitance as a function of voltage with a quadratic voltage-capacitance coefficient (α) of 27 ppm/V². The crystalline STA thin film had a negative α that was independent of frequency, which suggests that dipolar relaxation occurs and is responsible for the large change in the capacitance. The amorphous thin films had a positive α that decreased with increasing frequency, which implies that electrode polarization occurs.     

T-stress near the tips of a cruciform crack with unequal arms

The T-stress near the tips of a crack of cross shape embedded in an isotropic elastic solid is analyzed. The integral transform technique is employed to convert the associated boundary value problem to a system of singular integral equations. According to the stress difference method, T-stresses can be expressed as a sum of an integral involving crack opening displacement (COD) and applied loading at infinity. Obtained results indicate that, in addition to applied loading, T-stresses at the horizontal (vertical) crack tips depend on the COD of the vertical (horizontal) crack surface. COD plays a leading role in determining T-stresses, in particular for a cruciform crack of two crack-arm lengths of the same order. Moreover, T-stresses for a single-crack limiting case can be recovered from the present results as the length of one arm approaches zero. For a biaxial tension of the same magnitude, T-stresses are present for a cruciform crack, but absent for a single crack. Finally, for several cases of interest, T-stresses for a cruciform crack are evaluated and compared with those for a single crack, and the influence of the ratio of two crack-arm lengths b/a and the COD on the T-stress of a cruciform crack is examined.     

On the use of the theory of v-fluids for the construction of models of turbulence

The class of $\text{v-}\text{fluids}$, defined by Proudman[1] to be non-Newtonian fluids all of whose properties depend on a single dimensional constant whose dimensions are those of viscosity, is examined further as a source of possible models of turbulence at high Reynolds number. It is found that, while the general definition is valuable, certain aspects of Proudman's associated concept of a regular $\text{v-}\text{fluids}$ have a number of features that bring its value as a source of models of inhomogeneous turbulence into question. The nature of these problems suggests a suitable modification to the definition of a regular $\text{v-}\text{fluids}$. A number of constraints on the form and solution of the equations of a model of turbulence are proposed with the intention of improving the generality of models of a given degree of complexity, and their justification and significance discussed. In the light of these proposals the simplest modified regular $\text{v-}\text{fluids}$ that can be used to model homogeneous turbulence at infinite Reynolds number is described, and it is seen to include all the most desirable features of earlier models of this type, and is in addition capable of extension in a natural way to describe inhomogeneous turbulence.     

A Note on Moments of Gamma Order Statistics

Previously quadrature approximations were developed to determine the moments of a distribution of the response of a multivariable function when each of the variables is a random variable from a normal distribution. The error was shown to be of the order of the sixth power of the standard deviations of the random variables, but a more useful bound is desired in applied work. Only limited success has been achieved in this direction. It is shown that the best approximating distribution is a Beta distribution of the first kind with β₂ equal to 3 and mean, variance, and β₁ obtained by quadrature, where β₁ and β₂ are standard measures of skewness and kurtosis, respectively. A parametric study of the function X = C_o (a _o, ± y ₁ ± y ₂ ± … ±y_n ) ^m + b _o where the y_i all have the same standard deviation, σ, is conducted both analytically and by quadrature. The mean and variance obtained by quadrature are essentially exact in the range of interest. It is shown that for a large range of σ the above distribution is both a good approximation and a much better approximation than either a normal approximation with the same mean and variance or a linear approximation. The example also shows that the β₂ obtained by quadrature is a poor indicator of the precision of the quadrature approximation.     

Ln2Mo3O12 (Ln = La, Nd): A novel group of low loss microwave dielectric ceramics with low sintering temperature

Ln₂Mo₃O₁₂ (Ln = La, Nd) ceramics with a defect scheelite related structure were prepared via a solid state reaction method. The La₂Mo₃O₁₂ ceramics sintered at 930 °C for 2 h exhibited a low dielectric permittivity of 10.1, a high quality factor (Qf value) of 60,000 GHz and a temperature coefficient of −80 ppm/°C at 12.7 GHz. The Nd₂Mo₃O₁₂ ceramics sintered at 945 °C for 2 h possessed a dielectric permittivity of 8.2, a Qf value of 80,000 GHz, and a temperature coefficient of −60 ppm/°C at 15.8 GHz. This group of ceramics could be good candidates for microwave substrate applications.     

AC loss in YBCO coated conductors at high dB/dt measured using a spinning magnet calorimeter (stator testbed environment)

A new facility for the measurement of AC loss in superconductors at high dB/dt has been developed. The test device has a spinning rotor consisting of permanent magnets arranged in a Halbach array; the sample, positioned outside of this, is exposed to a time varying AC field with a peak radial field of 0.566 T. At a rotor speed of 3600 RPM the frequency of the AC field is 240 Hz, the radial dB/dt is 543 T/s and the tangential dB/dt is 249 T/s. Loss is measured using nitrogen boiloff from a double wall calorimeter feeding a gas flow meter. The system is calibrated using power from a known resistor. YBCO tape losses were measured in the new device and compared to the results from a solenoidal magnet AC loss system measurement of the same samples (in this latter case measurements were limited to a field of amplitude 0.1 T and a dB/dt of 100 T/s). Solenoidal magnet system AC loss measurements taken on a YBCO sample agreed with the Brandt loss expression associated with a 0–0.1 T I_c of 128 A. Subsequently, losses for two more YBCO tapes nominally identical to the first were individually measured in this spinning magnet calorimeter (SMC) machine with a B_max of 0.566 T and dB/dt of up to 272 T/s. The losses, compared to a simplified version of the Brandt expression, were consistent with the average I_c expected for the tape in the 0–0.5 T range at 77 K. The eddy current contribution was consistent with a 77 K residual resistance ratio, RR, of 4.0. The SMC results for these samples agreed to within 5%. Good agreement was also obtained between the results of the SMC AC loss measurement and the solenoidal magnet AC loss measurement on the same samples.     

Enhancement of in vitro antitumour activity of epirubicin in HER2+ breast cancer cells using immunoliposome formulation

Epirubicin (EPI) is one of the potent breast cancer (BC) chemotherapeutic agents, but its adverse effects limit its efficacy. Herein, EPI was selected to be loaded in liposomal carrier, which has been targeted by a monoclonal antibody, Herceptin. The preparation process of liposomes was a modified ethanol injection method followed by Herceptin conjugation. The in vitro cell toxicity and cellular uptake of optimum formulation against HER2+ and HER2− cancer cell lines were evaluated. The results showed that the drug loading (DL%) and encapsulation efficiency (EE%) of liposome preparation method yielded 30.62% ± 0.49% and 62.39% ± 8.75%, respectively. The average size of naked liposomes (EPI‐Lipo) and immunoliposomes (EPI‐Lipo‐mAb) was 234 ± 9.86 and 257.26 ± 6.25 nm, with a relatively monodisperse distribution, which was confirmed by SEM micrographs. The release kinetic followed Higuchi model for both naked and immunoliposomes. In vitro cytotoxicity study on three different BC cell lines including BT‐20, MDA‐MB‐453 and MCF‐7 demonstrated higher toxicity of EPI in the Herceptin conjugated form (EPI‐Lipo‐mAb) in comparison with the free EPI and EPI‐Lipo in HER2 overexpressing cell line. In addition, the cellular uptake study showed a higher uptake of immunoliposomes by MCF‐7 cells in comparison with naked liposomes. In conclusion, these data show that the targeted delivery of EPI to breast cancer cells can be achieved by EPI‐Lipo‐mAb in vitro, and this strategy could be used for breast cancer therapy with further studies.     

Magnetocaloric Effect of Perovskite Eu0.5Sr0.5CoO3

Magnetocaloric properties of the Eu_0.5Sr_0.5CoO₃ system near a phase transition from a ferromagnetic to a paramagnetic state are investigated. It is shown that the magnetic entropy change (ΔS _M ) peak spanning over a broad range of temperature leads to a remarkably wide working temperature region, yielding a significant performance in terms of refrigerant efficiency. Moreover, ΔS _M distribution is very uniform, which is desirable for Ericsson-cycle magnetic refrigerator. Eu_0.5Sr_0.5CoO₃ can be used as a working material of an apparatus based on the active magnetic regenerator cycle that cools hydrogen gas.     

Time-of-Flight Measurements of Vortices Emitted from Quantum Turbulence in Superfluid 4He

An oscillating obstacle generates quantum turbulence in superfluids, when vortices remained attached to obstacle surfaces or vortex rings collided with it during oscillation. Turbulence provides a source of vortices; however, the characteristics of these vortices are not clear. In the present work, we report the flight of vortices emitted from quantum turbulence in superfluid ⁴He at low temperatures, using vibrating wires as a generator and a detector of vortices. A vortex-free vibrating wire can detect only the first colliding vortex ring, though it will be refreshed after low vibration and be able to detect a vortex ring again. By measuring a period from the start of turbulence generation to the vortex detection repeatedly, we find an exponential distribution of time-of-flights with a non-detection period t ₀ and a mean detection period t ₁, suggesting a Poisson process. Both periods t ₀ and t ₁ increase with increasing distance between a generator and a detector. A vortex flight velocity estimated from period t ₀ suggests that the sizes of the emitted vortex rings distribute to a range smaller than a generator thickness or a generator vibration amplitude. Vortices are emitted radially from a turbulence region, at least in the direction of oscillator vibration.     

Limitations of employing undirected information flow graphs for the maintenance of rigid formations for heterogeneous vehicles

In this paper, we consider the problem of decentralized control of a collection of heterogeneous vehicles trying to maintain a rigid formation. In a rigid formation of vehicles, the separation distance between any pair of vehicles does not change throughout their motion and equals a pre-specified value that defines the formation. In each formation, there is a set of reference vehicles and a set of following vehicles. A reference vehicle may not be influenced by the motion of the following vehicle, but the motion of the following vehicle is influenced by the motion of the reference vehicle. Since we will be primarily dealing with translational maneuvers of the formation, we will consider formations where there is only one reference vehicle whose motion specifies the desired motion for all the vehicles in the formation. Each following vehicle attempts to maintain a specified constant safe distance from its adjacent vehicles in the collection. We call a vehicle B adjacent to a vehicle A if the relative position of vehicle B is known to vehicle A either by communication or by sensing. We only consider information flow graphs that are undirected when restricted to the set of following vehicles, i.e., graphs where a following vehicle A is adjacent to a following vehicle B if and only if the following vehicle B is adjacent to the following vehicle A. We model each vehicle as a point mass of one unit with two types of forces act on each vehicle - a controlled force, which is the output of an actuation system and a disturbing force over which there is no control. The actuation system is assumed to be linear and time invariant, and may be representable by a rational and strictly proper transfer function. The input to the control system of a vehicle in the formation is based on the error in maintaining the desired separation from its adjacent vehicles and the output of the control system is a command to the actuator.An earlier result showed that spacing errors due to disturbances amplify in a collection of identical vehicles with identically structured linear controllers if the reference vehicle information is not available to Ω(n) (A function f(n) is Ω(g(n)) if there is a constant c > 0 and a N > 0 such that ∣f(n)∣ > c∣g(n)∣ for all n > N.) vehicles, n being the size of the collection [1]. From the viewpoint of tolerance to communication failures, it is therefore necessary that there be at least two vehicles in the formation that are adjacent to Ω(n) vehicles in the formation. In this paper, we consider a broad class of heterogeneously structured controllers defined by a pre-specified bound, say B_c > 0 as follows: the allowable controller in conjunction with the actuation systems on-board any vehicle will produce a force no greater than B_c in response to a constant input to the control system. If this class of controllers were to be employed with the aforesaid undirected information flow graphs, we show that there is a critical size of the formation beyond which the motion of the vehicles in the formation will be unstable. This result shows the inability to scale such controllers for maintenance of rigid formations in conjunction with undirected information flow graphs.     

A microscopic calculation of the force on a wire moving through superfluid3He-B in the ballistic regime

When a macroscopic object moves through superfluid³He, it experiences a force arising from the effect of quasiparticle scattering. We develop a three-dimensional microscopic model to calculate the force on a smooth cylinder moving at constant velocityv as a model of a vibrating wire. At large (subcritical) wire velocity, the force tends to an asymptotic value as 1/v ², rather than exponentially as in a one-dimensional calculation. At lowv the force is linear inv. We briefly discuss the agreement of our calculations with experimental measurements on a vibrating wire below 0.2T _c, where the quasiparticle trajectories are ballistic.     

Study of the velocity distribution in an intense pulsed hydrogen beam

We present the results of measurements of the velocity distributions of particles in a pulsed hydrogen beam obtained from a dissociator with a radio frequency discharge (duration 1.0 ms, repetition rate 1 Hz). It is shown that the hydrogen inside the dissociator is heated up to ～2800 K, so the thermal dissociation of hydrogen molecules is essential. In order to cool the atoms, the gas was let through a pyrex channel 5 mm in diameter. The cooling channel walls being at room temperature and the channel having a length of 50 mm, we have obtained a supersonic beam of hydrogen atoms with a Mach number M_| = 2.7±0.25. When the channel walls were cooled by the flowing liquid nitrogen and the channel was 70 mm long we obtained a beam of cooled atoms with a Mach number M_| = 4.14±0.35. The velocity distribution of atoms depends on the power of the rf discharge inside the dissociator and on the gas consumption per pulse, and varies during the discharge pulse. For a temperature of the cooling channel walls T_ch = 77 K, a gas consumption N = 3.3×10¹⁷ molecules per pulse and a discharge power of 0.23 kW cm^?3, we have obtained an atomic beam with intensity I(0) = (2.8±0.8)×10²⁰ atoms sr^?1 s^?1 and a most probable velocity ν_MP = (1.97±0.07)×10⁵ cm s^?1.