Quantum non-demolition measurements using cold atoms in an optical cavity

Abstract

In this paper we present a theoretical analysis of a recent quantum non-demolition experiment in optics using cold atoms in a magneto-optical trap as a nonlinear medium. A signal beam and a meter beam from two independent lasers are coupled within a A-type three-level scheme in the D1 line of ⁸⁷Rb atoms. The experimental results for the relevant quantum correlations of the fields represent up to now the best achievement for a single back-action evading measurement. Moreover, they are found to be in remarkably good agreement with the theoretical predictions from a fully quantum model for three-level atoms in a doubly resonant cavity.     

Estimating Bounds on Collisional Relaxation Rates of Spin-Polarized 87Rb Atoms at Ultracold Temperatures

We present quantum scattering calculations for the collisional relaxation rate coefficient of spin-polarized ⁸⁷Rb(f = 2,m = 2) atoms, which determines the loss rate of cold Rb atoms from a magnetic trap. Unlike the lighter alkali atoms, spin-polarized ⁸⁷Rb atoms can undergo dipolar relaxation due to both the normal spin-spin dipole interaction and a second-order spin-orbit interaction with distant electronic states of the dimer. We present ab initio calculations for the second-order spin-orbit terms for both Rb₂ and Cs₂. The corrections lead to a reduction in the relaxation rate for ⁸⁷Rb. Our primary concern is to analyze the sensitivity of the ⁸⁷Rb trap loss to the uncertainties in the ground state molecular potentials. Since the scattering length for the a³Σ⁺_u state is already known, the major uncertainties are associated with the X¹Σ⁺_g potential. After testing the effect of systematically modifying the short-range form of the molecular potentials over a reasonable range, and introducing our best estimate of the second-order spin-orbit interaction, we estimate that in the low temperature limit the rate coefficient for loss of Rb atoms from the f = 2,m = 2 state is between 0.4 × 10⁻¹⁵ cm³/s and 2.4 × 10⁻¹⁵ cm³/s (where this number counts two atoms lost per collision). In a pure condensate the rate coefficient would be reduced by 1/2.     

Serrated yielding in Nb–V dual phase steel

Abstract

The characteristics of serrated yielding (the Portevin–Le Chatelier effect) in a Nb–V dual phase steel have been studied in the temperature range 85–210°C at strain rates between 1·2 × 10^?5 and 1·2 × 10^?2 s^?1. Serrated yielding was found to initiate only after a critical strain ?_c was reached. The strain between two successive serrations ??_s increases almost linearly with strain, while the stress drop ?σ_c increases with strain up to ?σ_max, then decreases. The exponent β in the mobile dislocation density–plastic strain relationship (ρ_m= ?^β) is 1·09 in the temperature range 85–140°C and 1·34 in the temperature range 140–210°C. The results also indicate that in the same temperature ranges there are two values of activation energy for type A serrations, i.e. 79 and 119 kJ mol^?1 respectively. The results are discussed in terms of substitutional–interstitial solute atom interaction and changes of concentration of interstitial atoms.

MST/934     

Thermomechanical properties of iron: viscoplasticity of ferrite and of austenite—ferrite mixtures

The available data on secondary creep in creep tests and on maximum stress in hot deformation tests obtained for δ and α ferrite have been reviewed and expressed in the form of the equation ? = K(σ/E)^P_c sinh(Vσ/RT) exp(—Q_c/RT) with p_c = 2·5, V = 0·0013 m³ mol^?1, and K = 2·6 × 10¹⁷ s^?1, E and Q_c being temperature dependent functions. The approximate range of validity is Z = ? exp (Q_c/RT) ≈ 10¹—10¹¹ s^?1. Together with the corresponding equation for austenite the data can be used to predict the viscoplastic behaviour of austenite—ferrite mixtures.

MST/1538     

The effect of hydrostatic pressure on the Fermi surfaces of rubidium and cesium

The anisotropy and absolute values of the pressure coefficients for the Fermi surfaces of rubidium and cesium in the 25-bar pressure range at 1 K have been measured. In both cases the area pressure coefficient anisotropy is considerably greater than the dimensional anisotropy, about 4.7 times in Rb and 5.6 times in Cs. The mean values, at 2.13₃±0.005×10^?2 kbar^?1 for Rb and 2.87₄±0.01×10^?2 kbar^?1 for Cs, are in fair agreement with those derived from ultrasonic measurements of the bulk modulus, but are several percent lower than the corresponding piston-displacement figures.     

Electronic conduction in La-based perovskite-type oxides

Abstract

A systematic study of La-based perovskite-type oxides from the viewpoint of their electronic conduction properties was performed. LaCo_0.5Ni_0.5O_3±δ was found to be a promising candidate as a replacement for standard metals used in oxide electrodes and wiring that are operated at temperatures up to 1173 K in air because of its high electrical conductivity and stability at high temperatures. LaCo_0.5Ni_0.5O_3±δ exhibits a high conductivity of 1.9 × 10³ S cm^?1 at room temperature (R.T.) because of a high carrier concentration n of 2.2 × 10²² cm^?3 and a small effective mass m? of 0.10 m_e. Notably, LaCo_0.5Ni_0.5O_3±δ exhibits this high electrical conductivity from R.T. to 1173 K, and little change in the oxygen content occurs under these conditions. LaCo_0.5Ni_0.5O_3±δ is the most suitable for the fabrication of oxide electrodes and wiring, though La_1?xSr_xCoO_3±δ and La_1?xSr_xMnO_3±δ also exhibit high electronic conductivity at R.T., with maximum electrical conductivities of 4.4 × 10³ S cm^?1 for La_0.5Sr_0.5CoO_3±δ and 1.5 × 10³ S cm^?1 for La_0.6Sr_0.4MnO_3±δ because oxygen release occurs in La_1?xSr_xCoO_3±δ as elevating temperature and the electrical conductivity of La_0.6Sr_0.4MnO_3±δ slightly decreases at temperatures above 400 K.     

Space charge limited conduction and determination of density of localised states in semiconductor cobalt doped TiO2

Abstract

The space charge limited conduction (SCLC) mechanism in Co doped TiO₂ has been investigated at different temperatures. At lower electric fields, ohmic behaviour is observed while at higher electric fields nonohmic behaviour is observed. The results obtained confirm the presence of SCLC in Co doped TiO₂. The electronic parameters such as the position of the Fermi level above the valence band edge E _F, the density of states in valence band N _V and effective mass of holes m _h were found as 12·32 meV, 1·26 × 10¹⁵ m^?3 and 1·33 × 10^?7 m_e, respectively. The distribution of localised states in the forbidden band gap of the Co doped TiO₂ was characterised by current–voltage measurements and the density of localised states near the Fermi level N(E_F) was found to be 2·11 × 10¹⁷ eV^?1 m^?3.     

Superplastic behaviour of as received superplastic forming grade IN718 superalloy

Abstract

Tensile specimens of superplastic forming grade IN718 superalloy, containing banded microstructure in the as received state, were deformed at high temperatures T to investigate the stress σ versus strain rate ? · behaviour, the nature of the stress versus strain ? curves, ductility, and microstructure upon failure. The log σ–log ? · plot for the ? · range ～5 × 10^-6–3 × 10^-2 s^-1 at T = 1173–1248 K exhibited a strain rate sensitivity index m = 0·62 at low strain rates and m = 0·26 at high strain rates, representing region II and III behaviour, respectively. The activation energies were estimated to be 308 and 353 kJ mol^-1, respectively. All the σ–? curves, obtained at ? · = 1 × 10^-4 s^-1 for the temperature range 1173–1273 K, and at T = 1198 K for the strain rate range 1 × 10^-4–1 × 10^-2 s^-1, exhibited initial flow hardening, followed by flow softening. The microstructures revealed dynamic recrystallisation, grain growth, cavitation, and a variation in the amount of second phase particles. Grain growth and cavitation were found to increase with temperature in region II. Excessive grain growth at 1273 K led to the elimination of region II. Grain growth and cavitation were both found to be less pronounced as the strain rate increased in region III.     

Young's modulus of Fe-, Co-, Pd- and Pt-based amorphous wires produced by the in-rotating-water spinning method

This paper presents the Young's modulus of Fe_100?x?y Si _x B _y , Fe_100?x?y P _x C _y , Co_100?x?y Si _x B _y , Pd_77.5Cu₆Si_16.5, Pd₄₈Ni₃₂P₂₀ and Pt₆₀Ni₁₅P₂₅ amorphous wires determined from the Young's modulus sound velocity measurement. With increasing metalloid content, the Young's modulus increases from 1.58×10¹¹ to 1.87×10¹¹ N m^?2 for Fe-Si-B, from 1.40×10¹¹ to 1.52×10¹¹ N m^?2 for Fe-P-C and from 1.73×10¹¹ to 1.75×10¹¹ N m^?2 for Co-Si-B systems. The increase in Young's modulus with the amount of metalloid elements is the largest for B, followed by Si, C and then P. The Young's modulus of Fe- and Co-Si-B amorphous wires increases significantly with the replacement of iron or cobalt by IV–VII group transition metals. It was recognized that there existed a strong correlation between Young's modulus (E) and tensile fracture strength (σ _f); the ratio of σ _f to E is approximated to be 0.02 for all the amorphous wires investigated. These results imply that the Young's modulus is dominated mainly by the structural and compositional short-range orderings due to the strong interaction between metal and metalloid atoms which hinders the internal displacements. The existence of a constant ratio for σ _f/E was interpreted to originate from a common mechanism for plastic flow of the amorphous wires. Further, it was noted that the Young's modulus of the Fe- and Co-based amorphous wires with diameters of ? 100 to 120 Μm was slightly lower than that of the amorphous ribbons with thicknesses of ? 20 to 25 Μm. This difference was attributed to the difference in structural ordering due to the differences in the solidification processes.     

Disappearance of Trapped Yb+

Abstract

The storage time of Yb⁺ ions trapped in an r.f. trap was determined by the rf resonance absorption method in the presence of buffer gas, without and with laser radiation of a frequency equal to the transition from the S_1/2 ground state to the excited P_1/2 state. The storage time of the ions with the buffer gas (presure between 1 × 10^?4 and 4·2 × 10^?4 Pa) was several hours without the laser radiation; this period was shortened to several hundred seconds by irradiation with a 500 nW laser source. This phenomenon shows that the trapped Yb⁺ ions disappeared from the trap as a result of irradiation with the resonance laser light.     

Magnetic susceptibility measurement of single iron/cobalt carbonyl microcrystal by atmospheric magnetophoresis

Abstract

In this study, the use of an innovative atmospheric magnetophoresis, which enables us to measure the mass magnetic susceptibility and mass of a microparticle simultaneously, was demonstrated. Using this technique, we determined the magnetic susceptibility of a crystalline deposit of iron/cobalt carbonyl, mainly composed of Fe₂(CO)₉, which was prepared photochemically from a gaseous mixture of iron pentacarbonyl (Fe(CO)₅) and cobalt tricarbonyl nitrosyl (Co(CO)₃NO). The mass magnetic susceptibility and the characteristic relaxation time of the microcrystal were (7.0±1.9)×10^?9 m³ kg^?1 and (5.6±2.2)×10^?4 s, respectively. The observed magnetic susceptibility shows that the microparticle was paramagnetic. Assuming that the density was equal to that of Fe₂(CO)₉ (2.1×10³ kg m^?3) and that the shape of the particle was spherical, a hydrodynamic radius of 4.7 μm and a mass of 0.91 ng were observed. It was suggested that Co was incorporated in Fe₂(CO)₉.     

Electrical properties of iron phthalocyanine thin film device using gold and aluminium electrodes

The electrical conductivity of FePc thin film sandwich structures using gold and aluminium electrodes has been investigated for the freshly prepared devices and device after exposure to oxygen for 30 days. Current density-voltage characteristics of the devices in the forward bias showed an ohmic conduction in lower voltages and a space charge limited conduction (SCLC) controlled by a single and an exponential trapping levels at two different ranges of applied voltages. The hole concentrations are obtained as P _o = 3.92 × 10¹⁶ m⁻³ with a hole mobility μ = 5.81 × 10⁻⁶ m⁻¹ V⁻¹ s⁻¹. In the SCLC region a discrete trap level of 1.88 × 10²¹ m⁻³ is found at 0.66 eV followed by an exponential trap distribution of P _e = 4.63 × 10⁴⁶ J ⁻¹ m⁻³ at N _t(e) = 2.23 × 10²⁶ m⁻³. From the current limitations in the reverse bias, the conduction is identified as an electrode limited Schottky type of conduction. In the oxygen-doped samples, both in the forward and reverse bias the order of currents are much enhanced and a transition from the ohmic conduction to a space charged conduction is observed.     

Morphological and kinetic aspects of thermal oxidation of SiC whisker reinforced Al203

Abstract

The thermal oxidation susceptibility of a 30 vol.-%SiC whisker reinforced Al₂0₃ composite in air at 1300–1500°C has been investigated. It was found that the morphological changes associated with scale evolution lead to the formation of mullite and a glassy phase. In particular, the scale cross-section consisted of a porous external scale (white), and an internal black layer in contact with the unreacted matrix. The black scale region was relatively thin (0–6 μm), and contained partially oxidized SiC whiskers as well as glassy phases. In some .instances, the inner black scale/matrix interface exhibited intergranular cracking. The presence of these cracks was attributed to internal stresses induced by volume increases associated with the oxidation reaction. Additionally, the rates of scale thickening and of weight gain exhibited parabolic behaviour. At 1500°C parabolic rate constants K_p and K_m of 1·18 × 10^?14 m² S^?1 and 2·23 × 10^?9 kg² m^?4 S^?1, respectively werefound. From the rate constant data, activation energies of 577 and 542 kJ mol^?1 were determined on the basis of scale thickness and weight gain, respectively. Apparently, the oxidation rates in the black subzone were somewhat high to be rate limiting. Hence, the exhibited activation energies were ascribed to the diffusion of oxidant across the white scale region.

MST/2013     

In vitro and in vivo effects of morin on the intestinal absorption and pharmacokinetics of olmesartan medoxomil solid dispersions

Abstract

Purpose: In-situ evaluation to corroborate morin effects on the intestinal absorption and pharmacokinetic behavior of freeze-dried OLM-loaded solid dispersions with Caco-2 and in-vivo studies

Methods: Intestinal transport and absorption studies were examined by Caco-2 permeability, in-situ single pass perfusion and closed-loop models along with in-vivo pharmacokinetic studies to evaluate and confirm the effect of P-gp-mediated activity of morin. We evaluated the intestinal membrane damage in the presence of morin by measuring the release of protein and lactate dehydrogenase (LDH) followed by using qualitative and quantitative morphometric analysis to describe the surface characteristics of intestinal epithelium.

Results: Morin showed the highest P_eff value 13.8?±?0.34?×?10^?6?cm/s in jejunum than ileum (p?<?.01) at 100?µM with absorption enhancement of 1.31-fold together with enhanced (p?<?.01) secretory transport of 6.27?±?0.27?×?10?^?6?cm/s in Caco-2 monolayer cells. Our findings noticed 2.37 (in-situ); 2.39 (in-vivo) and 1.43 (in-situ); 1.36 (in-vivo) fold increase in AUC_0–t with elevated C_max and shortened T_max for freeze-dried solid dispersion in the presence of morin as compared to pure OLM and freeze-dried solid dispersions without morin, respectively.

Conclusions: Our study demonstrated that increased solubilization through freeze-dried OLM-loaded solid dispersion together with efflux inhibition improved intestinal permeability to one system that might lead to novel solubilization and efflux pump inhibition as a novel alternative potential to increase oral absorption and bioavailability of OLM.     

Large third-order nonlinearity of nonpolar A-plane GaN film at 800 nm determined by Z-scan technology

We report an investigation on the optical third-order nonlinear property of the nonpolar A-plane GaN film. The film sample with a thickness of ~2?μm was grown on an r-plane sapphire substrate by metal-organic chemical vapor deposition system. By performing the Z-scan method combined with a mode-locked femtosecond Ti:sapphire laser (800?nm, 50?fs), the optical nonlinearity of the nonpolar A-plane GaN film was measured with the electric vector E of the laser beam being polarized parallel (//) and perpendicular (⊥) to the c axis of the film. The results show that both the third-order nonlinear absorption coefficient β and the nonlinear refractive index n₂ of the sample film possess negative and large values, i.e. β_//?=??135?±?29?cm/GW, n_2//?=??(4.0?±?0.3)?×?10^?3?cm²/GW and β_⊥?=??234?±?29?cm/GW, n_2⊥?=??(4.9?±?0.4)?×?10^?3?cm²/GW, which are much larger than those of conventional C-plane GaN film, GaN bulk, and even the other oxide semiconductors.     

Neutron transmission properties of perfect silicon crystals

Silicon crystals are of interest as filter material for thermal neutron beams. For this reason the total cross-section has been determined as a function of temperature for neutron energies ranging from 22 × 10^?4 eV to 50 eV. Whereas cooling the filter to 77 K considerably improves the transmittance for thermal neutrons a further decrease in temperature has only a minor effect. The observed cross-section is well described by a treatment of thermal diffuse scattering based on the Debye approximation. Precise values of σ_abs and σ_free are given and compared to literature.     

Assessment of Intestinal Absorption of Vitexin-2″-O-Rhamnoside in Hawthorn Leaves Flavonoids in Rat Using In Situ and In Vitro Absorption Models

The purpose of this study was to investigate the absorption mechanism of vitexin-2″-O-rhamnoside, the index component in hawthorn leaves flavonoids (HLF) in the rat intestine, using two different absorption models, the in situ single-pass intestinal perfusion and the in vitro everted gut sac model. The effective permeability coefficients (P_eff) in the in situ single-pass intestinal perfusion experiments and the apparent permeability coefficients (P_app) in the in vitro everted gut sac experiments were calculated. Furthermore, the influences of the P-glycoprotein inhibitors, verapamil and digoxin, on the intestinal absorption of vitexin-2″-O- rhamnoside in HLF were studied using the above-mentioned two models. Results showed that there were no significant differences in the absorption of vitexin-2″-O-rhamnoside in HLF in four segments of the rat intestine, duodenum, jejunum, ileum, and colon, and at different concentrations of HLF ranging from 0.05 mg/ml to 0.5 mg/ml (P > 0.05). The P_eff values for vitexin-2″-O-rhamnoside in the rat jejunal perfusion at the concentration of 0.05, 0.1, 0.25, and 0.5 mg/ml were (2.48 ± 0.33) × 10^?5; (2.23 ± 0.67) × 10^?5; (2.18 ± 0.48) × 10^?5; and (2.25 ± 0.17) × 10^?5 cm/s, respectively. But there was significant difference between absence and presence of verapamil or digoxin (P < 0.05). P_eff and P_app values of vitexin-2″-O-rhamnoside in HLF were increased in the presence of verapamil or digoxin. In conclusion, vitexin-2″-O-rhamnoside can be classified into high permeability class drug according to the biopharmaceutical classification system. Passive diffusion dominates the absorptive transport behavior of vitexin-2″-O-rhamnoside in HLF. The absorption and secretion are mediated by the efflux transport system, P-gp. The absorption of vitexin-2″-O-rhamnoside in HLF can be enhanced administered together with P-gp inhibitors.     

Tuning the mechanical properties of composites from elastomeric to rigid thermoplastic by controlled addition of carbon nanotubes

A commercial thermoplastic polyurethane is identified for which the addition of nanotubes dramatically improves its mechanical properties. Increasing the nanotube content from 0% to 40% results in an increase in modulus, Y, (0.4–2.2 GPa) and stress at 3% strain, σ_{? = 3%}, (10–50 MPa), no significant change in ultimate tensile strength, σ_B, (≈50 MPa) and decreases in strain at break, ?_B, (555–3%) and toughness, T, (177–1 MJ m^?3). This variation in properties spans the range from compliant and ductile, like an elastomer, at low mass fractions to stiff and brittle, like a rigid thermoplastic, at high nanotube content. For mid‐range nanotube contents (≈15%) the material behaves like a rigid thermoplastic with large ductility: Y = 1.5 GPa, σ_{? = 3%} = 36 MPa, σ_B = 55 MPa, ?_B = 100% and T = 50 MJ m^?3. Analysis suggests that soft polyurethane segments are immobilized by adsorption onto the nanotubes, resulting in large changes in mechanical properties.     

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.