Clinical characteristics of patients with early-and late-onset optic neuromyelitis optica spectrum disease

Objective:To analyze the different clinical features of patients with early-onset(EO-NMOSDs)and late-onset neuromyelitis optica spectrum diseases(LO-NMOSDs).Methods:A total of 51patients with neuromyelitis optica spectrum disease who were diagnosed in our hospital for the first time from January 2015 to December 2022 were included in the First Affiliated Hospital of Hainan Medical College and divided into 22 cases in the EO-NMOSDs group and 29 cases in the LO-NMOSDs group according to whether the age of onset was 50 years old.The basic data,Extended Disability Status Scale(EDSS)score,blood and cerebrospinal fluid test indicators of the two groups were statistically analyzed.Results:There were no significant differences in demographic characteristics,clinical features and serum AQP-4 antibody positivity rate between the two groups(all P>0.05),and there were significant differences in triglycerides(TG),low-density lipoprotein(LDL),apolipoprotein A(APOA),apolipoprotein B(APOB)and lipoprotein a(P=0.010,P=0.048,P=0.014,P=0.061,P=0.001,respectively),and cerebrospinal fluid LDH,There were significant differences between microprotein quantification and EDSS score(P=0.018,P=0.034,P=0.025,respectively),and the level of microprotein quantification in cerebrospinal fluid of LO-NMOSDs had a certain correlation with the degree of disability(r=0.52,P<0.03).Conclusion:LO-NMOSDs and EO-NMOSDs group patients have similar demographic characteristics,serum AQP-4 antibody positive rate and clinical features,but compared with EO-NMOSDs,patients in LO-NMOSDs group are prone to abnormal lipid metabolism,higher trace proteins in cerebrospinal fluid and more likely to be disabled,and among LO-NMOSDs,the higher the trace protein in the cerebrospinal fluid,the more severe the disability status of patients.

An optical method for wavelength fine-selection in optical spectrum analysers

This letter describes a novel optical method for wavelength fine-selection in the optical spectrum analysers (OSAs) for dense wavelength division multiplexing (DWDM) applications. The proposed new method employs a 'refractive optical lever' system consisting of a rotating optical wedge prism. A new OSA system based on Littman-type monochromator is proposed and the wavelength selection accuracy and resolution of OSA that has included such an optical lever system have been improved by a factor of 20 to 100 depending on the wedge angle and offset orientation angle of the optical wedge prism. This proposed 'refractive optical lever' may also simplify the rotation mechanism of the mirror in the commercially available OSAs.

Theoretical study of broadband near-field optical spectrum of twisted bilayer graphene

We theoretically study the broadband near-field optical spectrum of twisted bilayer graphene(TBG)at various twist angles near the magic angle using two different models.The spectrum at low Fermi energy is characterized by a series of peaks that are almost at the same energies as the peaks in the far-field optical conductivity of TBG.When the Fermi energy is near a van Hove singularity,an additional strong peak appears at finite energy in the near-field spectrum,which has no counterpart in the optical conductivity.Based on a detailed calculation of the plasmon dispersion,we show that these spectroscopic features are associated with interband and intraband plasmons,which can provide critical information about the local band structure and plasmonic excitations in TBG.The near-field peaks evolve systematically with the twist angle,so they can serve as fingerprints for identifying the spatial dependent twist angle in TBG samples.Our findings pave the way for future experimental studies of the novel optical properties of TBG in the nanoscale.

First-principles study of the bandgap renormalization and optical property ofβ-LiGaO_(2)

Theβ-LiGaO_(2)with an orthorhombic wurtzite-derived structure is a candidate ultrawide direct-bandgap semiconductor.In this work,using the non-adiabatic Allen-Heine-Cardona approach,we investigate the bandgap renormalization arising from electron-phonon coupling.We find a sizable zero-point motion correction of-0.362 eV to the gap atΓ,which is dominated by the contributions of long-wavelength longitudinal optical phonons.The bandgap ofβ-LiGaO_(2)decreases monotonically with increasing temperature.We investigate the optical spectra by comparing the model Bethe-Salpether equation method with the independent-particle approximation.The calculated optical spectra including electron-hole interactions exhibit strong excitonic effects,in qualitative agreement with the experiment.The contributing interband transitions and the binding energy for the excitonic states are analyzed.

An ab initio theoretical study of the optical spectrum of CF_2

The ab initio calculation methods have been used to calculate the spectral and electronic characteristics of difluorocarbene in the ground electronic state(~1A_1),the lowest-lying singlet(~1B_1)and triplet(~3B_1)states,The optimized equilibrium geometries,rotational constants,harmonic vibrational frequencies and energy gaps,electronic charges,dipole moments of these states have been computed with different basis sets.The calculated vibrational frequency of ~3B_1 state(v_2=522 cm^(-1))and the energy separation(2.26eV)between ~3B_1 and ~1A_1 states are in good agreement with the experimental re- sults(519 cm^(-1),2.46 eV respectively).According to the calculations the previous assignment of vibrational symmetries of ~1B_1 state was corrected,and some experimentally undetermined vibrational frequencies were predicted.

Interrogation of optical Ramsey spectrum and stability study of an ^(87)Sr optical lattice clock

The optical Ramsey spectrum is experimentally realized in an ^(87)Sr optical lattice clock, and the measured linewidth agrees well with theoretical expectation. The coherence time between the clock laser and the atoms, which indicates the maximum free evolution period of using Ramsey detection to measure the atom-laser phase information, is determined as 340(23) ms by measuring the fringe contrasts of the Ramsey spectrum as a function of the free evolution period. Furthermore, with the same clock duty cycle of about 0.1, the clock stability is measured by using the Ramsey and Rabi spectra,respectively. The experimental and theoretical results show approximately the same stability as the two detection methods, which indicates that Ramsey detection cannot obviously improve the clock stability until the clock duty cycle is large enough. Thus, it is of great significance to choose the detection method of a specific clock.

Petahertz communication:Harmonizing optical spectra for wireless communications

With the rapid deployment of Next-Generation Networks(NGN),the research community has initiated discussions on an entirely new suite of optical enabling techniques.To pave the way for the development of future wireless networks,this article aims to unify the existing infrared,visible light,and ultraviolet subbands while also exploring the potential of the Petahertz(PHz)band to support extremely bandwidth-thirsfy telepresence style applications.Our focus is on the emerging Petahertz Communication(PetaCom)framework,scenario-dependent propagation channels,modulation schemes,system performance,multiple access techniques,and networking.We conclude with a range of PetaCom challenges and open research issues.

Optical absorption and electromagnetically induced transparency in semiconductor quantum well driven by intense terahertz field

An approach for solving the excitonic absorption in a semiconductor quantum well driven by an intense terahertz field is presented.The formalism relies on the stationary single-photon Schro¨dinger equation in the full quantum mechanical framework.The optical absorption dynamics in both weak and strong couplings are discussed and compared.The excitonic absorption spectra show the Autler-Townes doublets for the resonance terahertz field,a replica peak for the non-resonance terahertz field,and the electromagnetically induced transparency phenomenon for modulating the decay rate of the second electron state in the weak coupling.In particular,the electromagnetically induced transparency phenomenon window range is discussed.In the strong coupling region,the multi-order energy level resonance splitting due to the strong optical field is found.There are three（non-resonance terahertz field） or four（resonance terahertz field） peaks in the optical absorption spectra.This work provides a simple and convenient approach to deal with the optical absorption in the exciton system.

Tunable edge bands and optical properties in black phosphorus nanoribbons under electric field

For several types of the applied electric field configuration on the normal-zigzag black phosphorus nanoribbon(nZZ-BPNR)we investigate the band structure and the linear optical absorption spectrum,especially for the edge states and the corresponding low-energy absorption peaks.The obtained results show that the applied electric field can not only open another band gap at k=0.5 point,but also can change completely the spacial probabilities of edge states in the two edge bands.The strength of electric field can tune the two band gaps at the Γ point and 0.5 point.Further,one remarkable feature is that the forbidden transitionallowed.The lowest-excited-energy linear absorption peakfrom the transition between two edge bands at the Γ point.Finally,in comparison with the lowest-excited-energy peaks among various configurations,the second type of electric field configuration can move this peak blue-shift larger than other configurations.

Spectral Target-Detecting System Using Sine-Wave Modulation

Target detection is one of the key technology of precision chemical application.Previously the digital coding modulation technique was commonly used to emit and receive the optical signal in the target detection systems previously in China.It was difficult to adjust the output power,and the anti-interference ability was weak in these systems.In order to resolve these problems,the target detection method based on analog sine-wave modulation was studied.The spectral detecting system was set up in the aspects of working principle,electric circuit,and optical path.Lab testing was performed.The results showed that the reflected signal from the target varied inversely with detection distances.It indicated that it was feasible to establish the target detection system using analog sine-wave modulation technology.Furthermore,quantitative measurement of the reflected optical signal for near-infrared and visible light could be achieved by using this system.The research laid the foundation for the future development of the corresponding instrument.

Spatial and Excitation Variations for Different Applied Voltages in an Atmospheric Neon Plasma Jet

A neon plasma jet was generated in air, driven by a 9 kHz sinusoidal power supply. The characteristics of the plasma plume and the optical spectra with plasma propagation for different applied voltages were investigated. By increasing the applied voltage, the plasma plume first increases and then retracts to become short and bulky. The shortened effect of Ne plasma plume （about 10 mm） for the further voltage increasing is more apparent than that of He （about 3 mm） and Ar （about 1 mm）. Emission intensity of the N2 （337 am） increases with the applied voltage, gradually substituting the emission intensity of Ne （702 nm and 585 am） as the noticeable radiation. At the nozzle opening, the Ne （702 am） emission dominates, while the Ne （585 nm） emission is most noticeable around the tip of the plasma plume. The spatial distribution of the three spectral lines indicates that Ne （702 nm） emission decreases dramatically with plasma propagation while Ne （585 am） and N2 （337 nm） emissions reach their maxima at the middle of the plasma plume. The results indicate that the Ne （702 nm） emission is much more sensitive to the average electron temperature and the density of the high-energy electrons, so it changes greatly at the tube nozzle and little at the tip region as the voltage increases. The population of high-energy electrons, the average electron temperature, the collision with air molecules and the Penning effect between Ne metastables and air molecules may explain their different variations with plasma propagating and voltage increasing.

Characteristics of a large gap uniform discharge excited by DC voltage at atmospheric pressure

A large-gap uniform discharge is ignited by a coaxial dielectric barrier discharge and burns between a needle anode and a plate cathode under a low sustaining voltage by feeding with flowing argon. The basic aspects of the large-gap uniform discharge are investigated by optical and spectroscopic methods. From the discharge images, it can be found that this discharge has similar regions with glow discharge at low pressure except a plasma plume region. Light emission signals from the discharge indicate that the plasma column is invariant with time, while there are some stochastic pulses in the plasma plume region. The optical emission spectra scanning from 300 nm to 800 nm are used to calculate the excited electron temperature and vibrational temperature of the large-gap uniform discharge. It has been found that the excited electron temperature almost keeps constant and the vibrational temperature increases with increasing discharge current. Both of them decreases with increasing gas flow rate.

A full numerical calculation of the Franz-Keldysh effect on magnetoexcitons in a bulk semiconductor

We have performed a full numerical calculation of the Franz-Keldysh （FK） effect on magnetoexcitons in a bulk GaAs semiconductor. By employing an initial wlue method in combination with the application of a perfect matched layer, the numerical effort and storage size are dramatically reduced due to a significant reduction in both computed domain and number of base functions. In the absence of an electric field, the higher magnetoexcitonic peaks show distinct Fano lineshape due to the degeneracy with continuum states of the lower Landau levels. The magnetoexcitons that belong to the zeroth Landau level remain in bound states and lead to Lorentzian lineshape, because they are not degenerated with continuum states. In the presence of an electric field, the FK effect on each magnetoexcitonic resonance can be identified for high magnetic fields. However, for low magnetic fields, the FK oscillations dominate the spectrum structure in the vicinity of the bandgap edge and the magnetoexcitonic resonances dominate the spectrum structure of higher energies. In the moderate electric fields, the interplay of FK effect and magnetoexcitonic resonance leads to a complex and rich structure in the absorption spectrum.

Electric and plasma characteristics of RF discharge plasma actuation under varying pressures

The electric and plasma characteristics of RF discharge plasma actuation under varying pressure have been inves- tigated experimentally. As the pressure increases, the shapes of charge-voltage Lissajous curves vary, and the discharge energy increases. The emission spectra show significant difference as the pressure varies. When the pressure is 1000 Pa, the electron temperature is estimated to be 4.139 eV, the electron density and the vibrational temperature of plasma are /peak /lPeak which describes the electron temper- 4.71 x 10^11 cm-3 and 1.27 eV, respectively. The ratio of spectral lines ＂391.4/＇380.5 ature hardly changes when the pressure varies between 5000-30000 Pa, while it increases remarkably with the pressure below 5000 Pa, indicating a transition from filamentary discharge to glow discharge. The characteristics of emission spec- trum are obviously influenced by the loading power. With more loading power, both of the illumination and emission spectrum intensity increase at 10000 Pa. The pin-pin electrode RF discharge is arc-like at power higher than 33 W, which results in a macroscopic air temperature increase.

Long dynamic range spread spectrum optical domain reflectometer

The performance of an optical time domain reflectometer(OTDR) is significantly improved using spread spectrum technology. The concept of spread spectrum OTDR(SSOTDR) is proposed, the theoretical basis and simulation results of the new method are given, and the problem of direct application of bipolar spread spectrum codes to OTDR and despreading in the optical domain are solved. The simulation results show the feasibility of the SSOTDR, which exhibits better dynamic range reported to date for a practical long-haul OTDR system without using conventional average technique.

Design of a broad spectrum multichannel optical filter based on FBG

To increase the channel number in the optic filter, the multiple-phase-shift (MPS) technology is adoped based on the multiple-reflection-spectrum-envelopes-concatenation (MRSEC) model which has a broadband flatness. The reflection spectra of the MPS digital concatenated sample gratings are simulated with transfer matrix method, the results show that wave band of the reflection spectrum is widened and the channel number is multiplied. What’s more, the spectrum flatness is improved with the increasing of refraction index change. Moreover, to improve the extinction ratio and peak value when MPS is adopted in concatenated SFBG, an available designing method based on the cascaded unit is put forward and the optimized results are obtained.

Polymeric Iodoplumbate Incorporating Copper Iodide Complex Cation Layer:Structure and Theoretical Study of a New Semi-conductive Hybrid:{[Cu(Ⅱ)(bipy)_2I][PbI_3](H_2O)_2}_n

A new iodoplumbate polymer incorporating copper iodide complex cation {[Cu（Ⅱ）（bipy）2I][PbI3]（H2O）2}n 1（bipy = 2,2＇-bipyridine） has been synthesized and structurally determined.It crystallizes in the triclinic system,space group P1 with a = 7.979（4）,b = 14.538（11）,c = 15.853（8）,α = 110.77（2）,β = 97.955（18）,γ = 104.88（2）°,V = 1607.3（17）3,Z = 2,C20H16CuI4N4O2Pb,Mr = 1122.72,Dc = 2.320 g/cm3,F（000） = 1006,μ（MoKα） = 9.753,the final R = 0.0627 and wR = 0.1741 for 4846 observed reflections with Ⅰ 〉 2σ（Ⅰ）.Structural analysis indicates that 1 consists of 2-D {[Cu（Ⅱ）（bipy）2I]}nn＋ cation layers（based on π-π interaction and hydrogen bonds） and [PbI3]nn-polyanions.The C-H···I hydrogen bonds between {[Cu（Ⅱ）（bipy）2I]}nn＋ cation layers and [PbI3]nn-polyanions lead to the formation of an interesting 3-D network.Optical absorp-tion spectrum indicates that 1 is a semiconductor,which is further validated by DFT calculation.Its electronic structure is also discussed.

A new method of calculating the orbital angular momentum spectra of Laguerre-Gaussian beams in channels with atmospheric turbulence

Studying orbital angular momentum（OAM） spectra is important for analyzing crosstalk in free-space optical（FSO）communication systems. This work offers a new method of simplifying the expressions for the OAM spectra of Laguerre-Gaussian（LG） beams under both weak/medium and strong atmospheric turbulences. We propose fixing the radius to the extreme point of the intensity distribution, review the expression for the OAM spectrum under weak/medium turbulence,derive the OAM spectrum expression for an LG beam under strong turbulence, and simplify both of them to concise forms.Then, we investigate the accuracy of the simplified expressions through simulations. We find that the simplified expressions permit accurate calculation of the OAM spectrum for large transmitted OAM numbers under any type of turbulence. Finally,we use the simplified expressions to analytically address the broadening of the OAM spectrum caused by atmospheric turbulence. This work should contribute to the concise theoretical derivation of analytical expressions for OAM channel matrices for FSO-OAM communications and the analytical study of the laws governing OAM spectra.

Polysilicon Prepared from SiCl_4 by Atmospheric-Pressure Non-Thermal Plasma

Non-thermal plasma at atmospheric pressure was explored for the preparation of polysilicon from SiCl4. The power supply sources of positive pulse and alternating current （8 kHz and 100 kHz） were compared for polysilicon preparation. The samples prepared by using the 100 kHz power source were crystalline silicon. The effects of H2 and SiCl4 volume fractions were investigated. The optical emission spectra showed that silicon species played an important role in polysilicon deposition

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites.In order to understand the physical mechanism of APPTs,high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes.The plume images and spectra at different times and positions are experimentally recorded,and the spatial distribution,composition,and trajectory of plasmas can be concluded through analyzing them.With the increase of the distance from the ablation surface,two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.