Breaking the optical efficiency limit of virtual reality with a nonreciprocal polarization rotator

A catadioptric lens structure,also known as pancake lens,has been widely used in virtual reality(VR)displays to reduce the formfactor.However,the utilization of a half mirror(HM)to fold the optical path thrice leads to a significant optical loss.The theoretical maximum optical efficiency is merely 25%.To transcend this optical efficiency constraint while retaining the foldable characteristic inherent to traditional pancake optics,in this paper,we propose a theoretically lossless folded optical system to replace the HM with a nonreciprocal polarization rotator.In our feasibility demonstration experiment,we used a commercial Faraday rotator(FR)and reflective polarizers to replace the lossy HM.The theoretically predicted 100%efficiency can be achieved approximately by using two high-extinction-ratio reflective polarizers.In addition,we evaluated the ghost images using a micro-OLED panel in our imaging system.Indeed,the ghost images can be suppressed to undetectable level if the optics are with antireflection coating.Our novel pancake optical system holds great potential for revolutionizing next-generation VR displays with lightweight,compact formfactor,and low power consumption.

The Relationships among Perception of Body Image, a Desire for Thinness, and Dieting Behavior in Young Females in Japan

The aim of this study was to investigate the relationship among body image perceptions, a desire for thinness, and dieting behavior in young females in Japan. The subjects were 302 Japanese female university students (age 19.9 ± 1.4 years). An anonymous, self-administered questionnaire survey was conducted between July and August 2011. The questionnaire clarified the subjects’ physical status, perception about personal body shape, desired body shape, the time frame when they first thought about body shape dieting, exercise habits, and eating behaviors. The results revealed that many of the underweight or normal weight subjects perceived themselves as obese, and often the reasons for the perception of obesity were comparisons with others or with themselves in the past. The scores of EAT-26 in those who perceived themselves as obese were higher than the scores in those who did not. Those who perceived themselves as obese had a desire to become slim, were concerned about body shape at an early age, were concerned about dieting, had dieting experience, and were willing to increase daily exercise. These results indicated that incorrect perceptions about body shape have connection to a desire for thinness and dieting behavior.

The Efficacy of Microcurrent Therapy on Eccentric Contraction-Induced Muscle Damage in Rat Fast-Twitch Skeletal Muscle

Microcurrent (MC) therapy, in which a very small electric current is applied to the body, has widely been used to promote tissue healing and relieve symptoms. The aim of this study was to examine the effect of MC treatment on eccentric contraction (ECC)-induced muscle damage in rat fast-twitch skeletal muscles. Tibialis anterior muscles underwent 200 repeated ECCs in situ and were then stimulated (25 μA, 0.3 Hz) for 20 min (MC treatment). MC treatment was performed immediately after ECC and during a recovery period of 3 days (a total of 4 times). Three days after ECC, the muscles were excised and used for measure of force output and for biochemical analyses. In MC-treated muscles, tetanic forces at 20 Hz and 100 Hz were partially and fully restored, respectively, whereas in non-treated muscles, both forces remained depressed. Biochemical analyses revealed that MC treatment partially or completely inhibited ECC-induced reductions: in 1) the Ca2+-release function of sarcoplasmic reticulum (SR), 2) proteolysis of ryanodine receptor, a Ca2+ release channel of SR, and 3) myosin ATPase activity. On the other hand, MC treatment was unable to lessen increases in the activity of calpain, a cytosolic, Ca2+-activated neutral protease. These results indicate that MC treatment results in beneficial effects, such as restoration of muscle performance following ECC, although the precise mechanisms are still unknown at this time.

Retinal ganglion cell protection by hop-flower extract as a novel neuroprotective strategy for glaucoma

In glaucoma,a leading cause of blindness,retinal ganglion cells are progressively damaged.Intraocular pressure reduction is the only established treatment for glaucoma(Collaborative Normal-Tension Glaucoma Study Group,1998;Vass et al.,2007).However,in some cases,visual field loss progresses despite sufficiently reduced intraocular pressure(Collaborative Normal-Tension Glaucoma Study Group,1998;Killer and Pircher,2018).While intraocular pressure and age are known risk factors for glaucoma(Ernest et al.,2013),the underlying mechanisms of glaucoma progression are not fully understood.

Heterogeneous Round-Trip Trading and the Emergence of Volatility Clustering in Speculation Game

This study is a detailed analysis of Speculation Game,a simple agent-based model of financial markets,in which the round-trip trading and the dynamic wealth evolution with variable trading volumes are implemented.Instead of herding behavior,the authors find that the heterogeneous holding periods in round-trip trades can contribute to the emergence of volatility clustering.In particular,the spontaneous redistribution of market wealth through repetitions of round-trip trades with non-uniform horizons can widen the wealth disparity and establish the Pareto distribution of the capital size.As a result,the intermittent placements of relatively big orders from endogenously emerged rich traders can bring on large fluctuations in price return.Empirical data are used to support the scenario derived from the model.

Extension and Comparative Study of AUSM-Family Schemes for Compressible Multiphase Flow Simulations

Several recently developed AUSM-family numerical flux functions(SLAU,SLAU2,AUSM+-up2,and AUSMPW+)have been successfully extended to compute compressible multiphase flows,based on the stratified flow model concept,by following two previous works:one by M.-S.Liou,C.-H.Chang,L.Nguyen,and T.G.Theofanous[AIAA J.46:2345-2356,2008],in which AUSM+-up was used entirely,and the other by C.-H.Chang,and M.-S.Liou[J.Comput.Phys.225:840-873,2007],in which the exact Riemann solver was combined into AUSM+-up at the phase interface.Through an extensive survey by comparing flux functions,the following are found:(1)AUSM+-up with dissipation parameters of Kp and Ku equal to 0.5 or greater,AUSMPW+,SLAU2,AUSM+-up2,and SLAU can be used to solve benchmark problems,including a shock/water-droplet interaction;(2)SLAU shows oscillatory behaviors[though not as catastrophic as those of AUSM+(a special case of AUSM+-up with Kp=Ku=0)]due to insufficient dissipation arising from its ideal-gas-based dissipation term;and(3)when combined with the exact Riemann solver,AUSM+-up(Kp=Ku=1),SLAU2,and AUSMPW+are applicable to more challenging problems with high pressure ratios.

Negative refraction of deep water waves through water channel network

A design method of a negative refractive index for free surface water waves in deep water is presented. To obtain a condition of a negative index, an analogy between water waves in a water channel and electric waves in an electric circuit is employed. An analytical solution of waves around a periodic array of rectangular columns is obtained by a circuit analysis. Attention is not focused on columns but a space among columns, and then the space is regarded as the water channel. Therefore, the circuit analysis can be applied to water waves. One channel is treated as a unit structure and a number of channels are periodically cascaded as a network. The negative refraction and backward waves by a network of the water channels are shown. Since the negative refraction might occur even around simple periodic structures, it is meaningful to understand wave phenomenon around offshore structures and develop innovative technology.