Laser guiding of cold molecules in a hollow optical fiber and continuous-wave cold molecular beam generation

A novel scheme for guiding arbitrary buffer-gas cooled neutral molecules in a hollow optical fiber(HOF) using a red-detuned HE 11 mode is proposed and analysed theoretically.We give the electromagnetic field distribution of the HE 11 mode in the HOF and calculate the optical potential of an I 2 molecule,and study the molecule guiding mechanism using a classical Monte Carlo simulation.Using a 6 kW input laser,an S-shape HOF with a 2 cm curvature radius for both bends,and an input molecular beam with a transverse temperature of 0.5 K and longitudinal temperature of 5 K,we obtain a guiding efficiency of ～0.126% for the scheme,and the transverse and longitudinal temperatures of the guided molecular beam are 1.9 mK and 0.5 K,respectively.     

Highly sensitive giant magnetoimpedance in a solenoid containing FeCo-based ribbon

The highly sensitive giant magneto-impedance effect in a solenoid containing a magnetic core of Fe36Co36Nb4Si4.8B19.2(FeCo-based) ribbon under a weak magnetic field(WMF) is presented in this paper.The FeCo-based amorphous ribbon is prepared by single roller quenching and annealed with Joule heat in a flowing nitrogen atmosphere.The giant magnetoimpedance effect in solenoid(GMIES) profiles are measured with an HP4294A impedance analyzer.The result shows that the GMIES responds to the WMF sensitively(as high as 1580 %/A·m 1).The high sensitivity can be obtained in a moderate narrow range of annealing current density(30-34 A/mm 2) and closely depends on the driven current frequency.The highest sensitivity(1580 %/A·m 1) is obtained when the FeCobased amorphous ribbon is annealed at 32 A/mm 2 for 10 min and then driven with an alterning current(AC) at the frequency of 350 kHz.The highly sensitive GMIES under the WMF may result from the multiple magnetic-anisotropic structure,which is induced by the temperature gradient produced during Joule-heating the ribbon.     

An effective reflectance method for designing broadband antireflection films coupled with solar cells

The solar spectrum covers a broad wavelength range,which requires that antireflection coating(ARC) is effective over a relatively wide wavelength range for more incident light coming into the cell.In this paper,we present two methods to measure the composite reflection of SiO2/ZnS double-layer ARC in the wavelength ranges of 300-870 nm(dualjunction) and 300-1850 nm(triple-junction),under the solar spectrum AM0.In order to give sufficient consideration to the ARC coupled with the window layer and the dispersion effect of the refractive index of each layer,we use multidimensional matrix data for reliable simulation.A comparison between the results obtained from the weighted-average reflectance(WAR) method commonly used and that from the effective-average reflectance(EAR) method introduced here shows that the optimized ARC through minimizing the effective-average reflectance is convenient and available.     

Thermospin effects in parallel coupled double quantum dots in the presence of the Rashba spin-orbit interaction and Zeeman splitting

The thermoelectric and the thermospin transport properties,including electrical conductivity,Seebeck coefficient,thermal conductivity,and thermoelectric figure of merit,of a parallel coupled double-quantum-dot Aharonov-Bohm interferometer are investigated by means of the Green function technique.The periodic Anderson model is used to describe the quantum dot system,the Rashba spin-orbit interaction and the Zeeman splitting under a magnetic field are considered.The theoretical results show the constructive contribution of the Rashba effect and the influence of the magnetic field on the thermospin effects.We also show theoretically that material with a high figure of merit can be obtained by tuning the Zeeman splitting energy only.     

Propagation properties of stochastic electromagnetic double-vortex beams in a turbulent atmosphere

Based on the extended Huygens-Fresnel principle,we study the propagation properties of stochastic electromagnetic double-vortex beams in a turbulent atmosphere.The result shows that the spreading of partially coherent double-vortex beams can be smaller than that of fully coherent ones.The degree of polarization of this kind of beam will experience change,which is dependent on the degree of polarization of the source plane,the atmospheric turbulence,topological charge,and the spatial coherence.The results may have applications in space optical communication.     

Study on the relationships between Raman shifts and temperature range for α-plane GaN using temperature-dependent Raman scattering

In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition(LPMOCVD) are investigated.We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K.The temperature-dependences of GaN phonon modes(A1(TO),E2(high),and E1(TO)) and the linewidths of E2(high) phonon peak are studied.The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range,and the relationship can be fitted to the pseudo-Voigt function.From analytic results we find a critical temperature existing in the relationship,which can characterize the anharmonic effects of a-plane GaN in different temperature ranges.In the range of higher temperature,the relationship exhibits an approximately linear behavior,which is consistent with the analyzed results theoretically.     

Monitoring of ducting by using a ground-based GPS receiver

In this paper,we describe the estimation of low-altitude refractivity structure from simulation and real ground-based GPS delays.The vertical structure of the refractive environment is modeled using three parameters,i.e.,duct height,duct thickness,and duct slope.The refractivity model is implemented with a priori constraints on the duct height,thickness,and strength,which might be derived from soundings or numerical weather-prediction models.A ray propagation model maps the refractivity structure into a replica field.Replica fields are compared with the simulation observed data using a squarederror objective function.A global search for the three environmental parameters is performed using a genetic algorithm.The inversion is assessed by comparing the refractivity profiles from the radiosondes to those estimated.This technique could provide near-real-time estimation of the ducting effect.The results suggest that ground-based GPS provides significant atmospheric refractivity information,despite certain fundamental limitations of ground-based measurements.Radiosondes are typically launched just a few times daily.Consequently,estimates of temporally and spatially varying refractivity that assimilate GPS delays could substantially improve over-estimates caused by using radiosonde data alone.     

Total systematic error in redox titrations with visual indicators--I: basic principles

The following factors contribute to the total error in redox titrations with visual indicators: the end-point error (DeltaV(T)), which arises from the difference between the potential of the equivalence point and that of the actual end-point determined by a given indicator ; the indicator consumption error (DeltaV(T)), which arises from the amount of indicator oxidized (or reduced) by the titrant; the irreversibility error, which is in fact a part of the indicator consumption error, arising from the generally uncontrolled processes connected with the irreversibility of the redox processes, decomposition of the reaction products, etc. The first two factors can be evaluated on the basis of the physicochemical characteristics of all the systems involved. They contribute to the total systematic error. The third, being not strictly controlled, in general increases the positive indicator consumption error, depending on such parameters as rate of titrant addition, stirring, effect of decomposition products on the potential, etc.     

Acid–base interactions and swelling of cellulose fibers in organic liquids

Drago’s acid–base approach was used to quantify the hydrogen bonding interactions in solvent swelling of cellulose fibers. The fiber swelling was correlated with acid–base, dispersive interactions and solvent molar volume. The acid–base interaction potentials of solvents were expressed in terms of their electron pair donor and acceptor numbers. The acid–base interaction terms of cellulosic materials were determined by using: (1) Flory–Huggins; (2) multiple regression models. We have used the swelling data of Mantanis and coworkers, which were based on the equilibrium liquid holding capacities of various compressed fibers in water and series of organic solvents. According to our interpretations, acid–base interactions and molar volume parameters were the major contributors to the overall solubility parameter. Acid–base interaction terms were balanced in alpha-cellulose sample. However spruce wood and sulfite pulp samples were more acidic than basic and therefore swollen better in organic basic solvents. For a good swelling behavior solvent must have high electron pair donor number/acceptor number ratio and high electron pair donor number–acceptor number difference.     

Total systematic error in redox titrations with visual indicators--II. Experimental verification

The equations for calculating the transition potential of a redox indicator and the total titration error have been verified experimentally. Good agreement has been obtained for reversible indicators such as Variamine Blue, 4-methyl-4'-aminodiphenylamine and ferroin. In the latter case it was shown that at the usual concentrations the indicator acts as a one-colour indicator, whereas for higher concentrations its behaviour is typical of a two-colour indicator. In the case of a pseudoreversible indicator--diphenylaminosulphonic acid--the calculated values give only the minimum error. In real conditions the error is always more positive.