Applications of Floquet-Magnus and Fer Expansion Approaches during Cross Polarization Radiation in Solid State NMR

This paper investigates the concept of Cross Polarization (CP) experiment in addition to revisiting the two potential expansion schemes recently developed in the field of solid-state nuclear magnetic resonance (SSNMR): namely, the Floquet-Magnus expansion and the Fer expansion. We use the aforementioned expansion schemes for the calculation of effective Hamiltonians and propagators when the spin system undergoes Cross Polarization radiation. CP is the gateway experiment into SSNMR. An in-depth comprehension of the underlying mechanics of spin dynamics during the cross-polarization experiment is pivotal for further experimental developments and optimization of more complex solid-state NMR experiments. The main contribution of this work is a prospect related to spin physics;particularly regarding to generalization of the calculation. This work reports original yet interesting novel ideas and developments that include calculations performed on the CP experiment. In fact, the approach presented could play a major role in the interpretation of several fine NMR experiments in solids, which would in turn provide significant new insights in spin physics. The generality of the work points towards potential applications in problems related in solid-state NMR and theoretical developments of spectroscopy as well as interdisciplinary research areas as long as they include spin dynamics concepts.

On the use of cross polarization in solid-state NMR:1 H spinlock versus adiabatic demagnetization in the rotating frame

Cross polarization(CP)is a widely used solid-state nuclear magnetic resonance(NMR)technique for enhancing the polarization of dilute S spins from much larger polarization of abundant I spins such as 1 H.To achieve such a polarization transfer,the I spin should either be spin-locked or be converted to the dipolar ordered state through adiabatic demagnetization in the rotating frame.In this work,we analyze the spin dynamics of the Hartmann-Hahn CP(HHCP)utilizing the 1 H spin-locking,and the dipolar-order CP(DOCP)having the 1 H adiabatic demagnetization.We further propose an adiabatic demagnetization CP(ADCP)where a constant radio-frequency pulse is applied on the S spin while 1 H is adiabatically demagnetized.Our analyses indicate that ADCP utilizes the adiabatic passage to effectively achieve the polarization transfer from the 1 H to S spins.In addition,the dipolar ordered state generated during the 1 H demagnetization process could also be converted into the observable S polarization through DOCP,further enhancing the polarized signals.It is shown by both static and magic-angle-spinning(MAS)NMR experiments that ADCP has dramatically broadened the CP matching condition over the other CP schemes.Various samples have been used to demonstrate the polarization transfer efficiency of this newly proposed ADCP scheme.

Polarization Reconfigurable Patch Antenna for Wireless Power Transfer Related Applications

A polarized reconfigurable patch antenna is proposed in this paper.The proposed antenna is a dual cross-polarized patch antenna with a programmable power divider.The programmable power divider consists of two branch line couplers(BLC)and a digital phase shifter.By adjusting the phase of the phase shifter,the power ratio of the power divider can be changed,and thus the feed power to the antenna input port can be changed to reconfigure the antenna polarization.The phase-controlled power divider and the cross dual-polarized antenna are designed,fabricated and tested,and then they are combined to realize the polarized reconfigurable antenna.By moving the phase of the phase shifter,the antenna polarization is reconfigured into vertical polarization(VP),horizontal polarization(HP),and circular polarization(CP).The test is conducted at the frequency of 915 MHz,which is widely used for simultaneous wireless information and power transfer(SWIPT)in radio-frequency identification(RFID)applications.The results demonstrate that when the antenna is configured as CP,the axial ratio of the antenna is less than 3 dB,and when the antenna is configured as HP or VP,the axial ratio of the antenna exceeds 20 dB.Finally,experiments are conducted to verify the influence of antenna polarization changes on wireless power transmitting.As expected,the reconfigured antenna polarization can help improve the power transmitting efficiency.

The polarization effect of a laser in multiphoton Compton scattering

The multiphoton Compton scattering in a high-intensity laser beam is studied by using the laser-dressed quantum electrodynamics （QED） method, which is a non-perturbative theory for the interaction between a plane electromagnetic field and a charged particle. In order to analyze in the real experimental condition, a Lorentz transformation for the cross section of this process is derived between the laboratory frame and the initial rest frame of electrons. The energy of the scattered photon is analyzed, as well as the cross sections for different laser intensities and polarizations and different electron velocities. The angular distribution of the emitted photon is investigated in a special velocity of the electron, in which for a fixed number of absorbed photons, the electron energy will not change after the scattering in the lab frame. We obtain the conclusion that higher laser intensifies suppress few-laser-photon absorption and enhance more-laser-photon absorption. A comparison between different polarizations is also made, and we find that the linearly polarized laser is more suitable to generate nonlinear Compton scattering.

Research on novel multi-layer and multi-polarized slot-coupling planar antenna array

A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent elements in the radiation field is analyzed when adjacent elements are fed in opposite phase. Return loss and radiation pattern are measured for a 16-element antenna array at 12.5 GHz. The radiation pattern shows a good agreement with the calculated one in the shape of the main beam. The return-loss of the proposed antenna array is less than -20 dB in the 12.5 GHz frequency band （12.25-12.75 GHz）. Because of two feed ports the antenna can transmit arbitrary elliptic polarized waves if the two feed ports have different amplitude and phase. The main factors such as element spacing, substrate medium and manufacturing imperfection are analyzed and the corresponding conclusions are presented.

Radiation characteristics of ring patch antennas with capacitive feed patch

Ring patch antennas have the characteristics of electrically small size as decreasing the width of the conducting portion compared to those of conventional patch antennas.In the ring patch antenna,using capacitive feed method is suitable for impedance matching.The effect of the size of the feed patch on the input impedance of the square ring patch antennas are analyzed and radiation patterns of the square ring patch antennas are compared to that of a square conventional patch antenna by the simulated results.

Influence of the reagent vibration on the stereodynamics of the reactions D^-+H_2 and H^-+D_2

Employing the quasi-classical trajectory method and the potential energy surface of Panda and Sathyamurhy [Panda A N and Sathyamurthy N 2004 J. Chem. Phys. 121 9343], the effect of the reagent vibration on vector correlation of the ion-molecule reactions D- ＋ H2 and H- ＋ D2 is studied at a collision energy of 35.7 kcal/mol. Four generalized polarization-dependent differential cross sections （2π/σ） （dσ00/dωt）, （2π/σ） （dσ20/dσ20）, （27π/σ） （dσ22＋/dwt）, and （2π/σ）（dπ/σ） are presented in the centre-of-mass reference frame, separately. At the same time, the effects on the product angular distributions P（θr）, P（~r） and P（Oφ） of the title reactions are also analysed. The calculated results show that the scattering tendencies of the product HD, the alignment and the orientation of j^1 sensitively depend on reagent molecule vibration.

Detection and localization of the hemoglobin and collagen distribution of the uterine cervix

Changes of the blood vessels and collagen are associated with the development of abnormal cervical cells.Recently,optical coberence tomography and Mueller polarization images were 1used to provide information regarding the presence of collagen fibers in the cervical tissue.However,most of these methods need a lot of time for image recording and are expensive.In addition,the general survey on the absorption and distribution characteristics of collagen and blood in the cervical is still lacking.In this study,we developed a colposcopy combining cross-polarized inage and image procssing algorithm with an fficient analytical model to map the distribution of blood and collagen in the uterine.For this system's proof of concept,we captured and processed the case of cervical ectopy and Nabothian cyst.The results show that the distribution of blood and collagen maps matched with anatomical and physiological when compared with Lugol's iodline images.This technology has some advantages,such as low cost,real time,and can replace the 11se of acetic acid or Lugol's iodine in the future.

Design of broadband dual-polarized antenna with integrated Marchand balun

A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced （within 0.5 dB） power splitting and consistent （±5°） phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios （SWRs） of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation （〉 45 dB） and cross polarization （〉 30 dB） over the entire operating frequency band. Moreover, the gain （-8.6 dB） of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system （DCS）, personal communications service （PCS） and 3rd generation （3G） applications.