Nonplanar Chiral Metamaterials with Negative Index

We demonstrate experimentally and numerically that nonplanar chiral metamaterials give giant optical activity, circular dichroism, and negative refractive index. The transmission, reflection, and the retrieval results of the experiments agree pretty well with the simulations. This is an important step toward the design and fabrication of three-dimensional isotropic chiral metamaterials.Comment: 3 pages 4 figure

Marketing Channel and Technology Adoption: Chinese Villages in the Local Horticulture Market

China has been experiencing the substantial changes in agricultural sectors in the past decades. Interaction between diversified channels for marketing agricultural products and modern technology adoption are important for restructuring agriculture and improving productivity, but fewer researches have been done in this field in China. With the village - level data collected a round Beijing, the capital of China, this study attempts to find out the major market channel(s) in rural China and its (their) linkage with technology innovation in the horticulture sector. The study finds that small brokers still dominate horticultural product distribution in rural area because of their cheap labor costs; however, the modern supply chain components such as supermarkets are penetrating the rural area and competing with small brokers. Modern market channels stimulate the adoptions of new technology, whereas technology adoption had few effects on modern market channel selection. In addition, shares of crop such as vegetables and fruits are soaring; surprisingly villages farther away from Beijing experienced faster crop restructuring with higher specialization. In the future we try to incorporate wholesalers or supermarkets into the analysis, which can depict a more complete picture of rural market development.Crop Production/Industries,

Time-dependent versus static quantum transport simulations beyond linear response

To explore whether the density-functional theory non-equilibrium Green's function formalism (DFT-NEGF) provides a rigorous framework for quantum transport, we carried out time-dependent density functional theory (TDDFT) calculations of the transient current through two realistic molecular devices, a carbon chain and a benzenediol molecule inbetween two aluminum electrodes. The TDDFT simulations for the steady state current exactly reproduce the results of fully self-consistent DFT-NEGF calculations even beyond linear response. In contrast, sizable differences are found with respect to an equilibrium, non-self-consistent treatment which are related here to differences in the Kohn-Sham and fully interacting susceptibility of the device region. Moreover, earlier analytical conjectures on the equivalence of static and time-dependent approaches in the low bias regime are confirmed with high numerical precision.Comment: 4 pages, 4 figure

A frequency-response-based method of sound velocity measurement in an impedance tube

A stable and accurate new method for the measurement of the velocity of sound is proposed. The method is based on the characteristics of the frequency response measured at different positions in an impedance tube and it eliminates adverse effects caused by reflections from the transmitting transducer at the bottom of the impedance tube. A series of experiments is conducted, at different water temperatures, different positions in the impedance tube and under constant pressure, to validate the feasibility and stability of the new method. The new technique is also extended to hydrostatic pressure conditions with stable sound velocity. Our method generates an accurate measurement result in comparison to the estimated or average value obtained with currently existing methods. The novel method is suitable to be widely used in underwater acoustics

Production and state-selective detection of ultracold, ground state RbCs molecules

Using resonance-enhanced two-photon ionization, we detect ultracold, ground-state RbCs molecules formed via photoassociation in a laser-cooled mixture of 85Rb and 133Cs atoms. We obtain extensive bound-bound excitation spectra of these molecules, which provide detailed information about their vibrational distribution, as well as spectroscopic data on the RbCs ground a^3\Sigma^+ and excited (2)^3\Sigma^+, (1)^1\Pi states. Analysis of this data allows us to predict strong transitions from observed excited levels to the absolute vibronic ground state of RbCs, potentially allowing the production of stable, ultracold polar molecules at rates as large as 10^7 s^{-1}

Acoustic improvement of stator–rotor interaction with nonuniform trailing edge blowing

The results of unsteady-flow simulations and experiments are discussed to investigate active noise-reduction effects on the stator–rotor interaction in a single-stage low-speed compressor with nonuniform trailing edge blowing. It is found that for the investigated type of stator–rotor interaction noise, nonuniform trailing edge blowing has beneficial noise-reducing effects. The overall aim is to demonstrate that nonuniform trailing edge blowing can compensate momentum loss and reduce the axial thrust on rotor blades. The results illustrate how nonuniform trailing edge blowing influences the sound pressure level of the blade-passing frequencies and results in active noise reduction effects. The study was conducted using a trailing edge blowing system, a four-hole dynamic flow-field measurement system, and phase lock technology. The results obtained show that nonuniform trailing edge blowing leads to substantial noise-reduction effects, lowering sound levels by more than 10 dB with about 5‰ of inlet mass flow

Multidecadal drought cycles in the Great Basin recorded by the Great Salt Lake: modulation from a transition-phase teleconnection

pre-printThis study investigates the meteorological conditions associated with multidecadal drought cycles as revealed by lake level fluctuation of the Great Salt Lake (GSL). The analysis combined instrumental, proxy, and simulation datasets, including the Twentieth Century Reanalysis version 2, the North American Drought Atlas, and a 2000-yr control simulation of the GFDL Coupled Model, version 2.1 (CM2.1). Statistical evidence from the spectral coherence analysis points to a phase shift amounting to 6-9 yr between the wet-dry cycles in the Great Basin and the warm-cool phases of the interdecadal Pacific oscillation (IPO). Diagnoses of the sea surface temperature and atmospheric circulation anomalies attribute such a phase shift to a distinctive teleconnection wave train that develops during the transition points between the IPO's warm and cool phases. This teleconnection wave train forms recurrent circulation anomalies centered over the southeastern Gulf of Alaska; this directs moisture flux across the Great Basin and subsequently drives wet-dry conditions over the Great Basin and the GSL watershed. The IPO life cycle therefore modulates local droughts-pluvials in a quarter-phase manner

Absolute radiometric calibration of the EUNIS-06 170-205 A channel and calibration update for CDS/NIS

The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding-rocket payload was flown on 2006 April 12 (EUNIS-06), carrying two independent imaging spectrographs covering wave bands of 300-370 A in first order and 170-205 A in second order, respectively. The absolute radiometric response of the EUNIS-06 long-wavelength (LW) channel was directly measured in the same facility used to calibrate CDS prior to the SOHO launch. Because the absolute calibration of the short-wavelength (SW) channel could not be obtained from the same lab configuration, we here present a technique to derive it using a combination of solar LW spectra and density- and temperature-insensitive line intensity ratios. The first step in this procedure is to use the coordinated, cospatial EUNIS and SOHO/CDS spectra to carry out an intensity calibration update for the CDS NIS-1 waveband, which shows that its efficiency has decreased by a factor about 1.7 compared to that of the previously implemented calibration. Then, theoretical insensitive line ratios obtained from CHIANTI allow us to determine absolute intensities of emission lines within the EUNIS SW bandpass from those of cospatial CDS/NIS-1 spectra after the EUNIS LW calibration correction. A total of 12 ratios derived from intensities of 5 CDS and 12 SW emission lines from Fe Fe X - Fe XIII yield an instrumental response curve for the EUNIS-06 SW channel that matches well to a relative calibration which relied on combining measurements of individual optical components. Taking into account all potential sources of error, we estimate that the EUNIS-06 SW absolute calibration is accurate to about 20%.Comment: 11 pages, 10 figures, 4 tables. 2010, ApJ Suppl. In pres