Chiral structured illumination microscopy: a microscopy modality for imaging fluorescent chiral domains at sub-wavelength resolution

This thesis covers the development of chiral structured illumination microscopy (chiral SIM), a novel wide-field super-resolution microscopy that is able to address the shortcomings restricting the capability of conventional chiral imaging techniques. Ac- cordingly, the research background and fundamentals in regards to this new microscopy method are introduced at the beginning. The subsequent chapters illustrate the de- velopment of chiral SIM in both theoretical and experimental aspects. In particular, we establish the theoretical framework of chiral SIM and investigate possible far-field illumination schemes for its experimental realization. The proof-of-principle numerical simulations demonstrate its ability to image and discriminate chiral domains at super- resolution. The signal-to-noise ratio of the chiral SIM images simulated under different experimental conditions is analyzed to inspect the performance of chiral SIM. Meanwhile, we study the near-field illumination schemes that exploit the superchiral near fields generated by plasmonic or dielectric nanostructures to reinforce the chiroptical responses and elaborate on the main difficulty of applying them in the proposed chiral SIM method. After a series of theoretical work, we present our experimental attempts at the chiral SIM method. The fabrication and inspection of the selected chiral sample and the optical setups are specifically discussed. Although the experimental results are unsatisfactory, based on the following investigation, we further propose a new optical setup to solve the potential issues of the original chiral SIM setup. Finally, we summarize this thesis and provide suggestions that should be beneficial to the subsequent research in chiral SIM and may also open up new research fields

Detection of Circulating Tumor Cells and Circulating Tumor Stem Cells in Breast Cancer by Using Flow Cytometry

We demonstrated the value of multiparameter flowcytometry in detecting human tumor cells of breast cancer in peripheral blood, which had a sensitivity limit of 10-5 and higher specificity compares with real‐time polymerase chain reaction (RT‐PCR). It was also found that circulating tumor cell (CTC) number was related with TNM stage, metastasis and the overall survival of patients. CTC level was one of the important factors for patients’ prognosis. At the same time, we also verified the circulating tumor stem cell (CTSC) was connected with TNM stage by multiparameter cytometry. The detection of CTC and CTSC by multiparameter flowcytometry may be used to diagnose disease at early stage to guide clinical therapy or to predict prognosis. Multiparameter flowcytometry has the potential to be a valuable tool for prognosis assessment among patients with breast cancer in clinical situation in China

Signal and noise analysis for chiral structured illumination microscopy

Recently, chiral structured illumination microscopy has been proposed to image fluorescent chiral domains at sub-wavelength resolution. Chiral structured illumination microscopy is based on the combination of structured illumination microscopy, fluorescence-detected circular dichroism, and optical chirality engineering. Since circular dichroism of natural chiral molecules is typically weak, the differential fluorescence is also weak and can be easily buried by the noise, hampering the fidelity of the reconstructed images. In this work, we systematically study the impact of the noise on the quality and resolution of chiral domain images obtained by chiral SIM. We analytically describe the signal-to-noise ratio of the reconstructed chiral SIM image in the Fourier domain and verify our theoretical calculations with numerical demonstrations. Accordingly, we discuss the feasibility of chiral SIM in different experimental scenarios and propose possible strategies to enhance the signal-to-noise ratio for samples with weak circular dichroism

Signal and Noise Analysis for Chiral Structured Illumination Microscopy

Recently, chiral structured illumination microscopy has been proposed to image fluorescent chiral domains at sub-wavelength resolution. Chiral structured illumination microscopy is based on the combination of structured illumination microscopy, fluorescence-detected circular dichroism, and optical chirality engineering. Since circular dichroism of natural chiral molecules is typically weak, the differential fluorescence is also weak and can be easily buried by the noise, hampering the fidelity of the reconstructed images. In this work, we systematically study the impact of the noise on the quality and resolution of chiral domain images obtained by chiral SIM. We analytically describe the signal-to-noise ratio of the reconstructed chiral SIM image in the Fourier domain and verify our theoretical calculations with numerical demonstrations. Accordingly, we discuss the feasibility of chiral SIM in different experimental scenarios and propose possible strategies to enhance the signal-to-noise ratio for samples with weak circular dichroism.Comment: 18 page

The catalytic domain of human hepatitis delta virus RNA A proton nuclear magnetic resonance study

AbstractWe have obtained and analyzed the 600 MHz proton NMR spectra of a 74-mer RNA derived from the catalytic domain of hepatitis delta virus genomic RNA (HDV RNA) to determine its secondary structure. Deconvolution of the NMR spectrum obtained at 32°C indicates that part of the 74-mer RNA molecule may exist in multiple conformations in equilibrium. The major conformer contains two A-U base pairs and 14 ± 2 G-C base pairs. It appears to contain no standard G-U base pairs. Our NMR melting study suggests that this conformer has at least two stem-loop regions. One of the regions has been identified to be a tetra-loop. We have assigned five imino proton resonances of the tetraloop stem. Our data is consistent with the pseudoknot model of Perrotta and Been

Absolute Entropy and Energy of Carbon Dioxide Using the Two-Phase Thermodynamic Model

The two-phase thermodynamic (2PT) model is used to determine the absolute entropy and energy of carbon dioxide over a wide range of conditions from molecular dynamics trajectories. The 2PT method determines the thermodynamic properties by applying the proper statistical mechanical partition function to the normal modes of a fluid. The vibrational density of state (DoS), obtained from the Fourier transform of the velocity autocorrelation function, converges quickly, allowing the free energy, entropy, and other thermodynamic properties to be determined from short 20-ps MD trajectories. The anharmonic effects in the vibrations are accounted for by the broadening of the normal modes into bands from sampling the velocities over the trajectory. The low frequency diffusive modes, which lead to finite DoS at zero frequency, are accounted for by considering the DoS as a superposition of gas-phase and solid-phase components (two phases). The analytical decomposition of the DoS allows for an evaluation of properties contributed by different types of molecular motions. We show that this 2PT analysis leads to accurate predictions of entropy and energy of CO_2 over a wide range of conditions (from the triple point to the critical point of both the vapor and the liquid phases along the saturation line). This allows the equation of state of CO_2 to be determined, which is limited only by the accuracy of the force field. We also validated that the 2PT entropy agrees with that determined from thermodynamic integration, but 2PT requires only a fraction of the time. A complication for CO_2 is that its equilibrium configuration is linear, which would have only two rotational modes, but during the dynamics it is never exactly linear, so that there is a third mode from rotational about the axis. In this work, we show how to treat such linear molecules in the 2PT framework

Generation of Optical Chirality Patterns with Plane Waves, Evanescent Waves and Surface Plasmon Waves

We systematically investigate the generation of optical chirality patterns by applying the superposition of two waves in three scenarios, namely plane waves in free space, evanescent waves of totally reflected light at dielectric interface and propagating surface plasmon waves on a metallic surface. In each scenario, the general analytical solution of the optical chirality pattern is derived for different polarization states and propagating directions of the two waves. The analytical solutions are verified by numerical simulations. Spatially structured optical chirality patterns can be generated in all scenarios if the incident polarization states and propagation directions are correctly chosen. Optical chirality enhancement can be obtained from the constructive interference of free-space circularly polarized light or enhanced evanescent waves of totally reflected light. Surface plasmon waves do not provide enhanced optical chirality unless the near-field intensity enhancement is sufficiently high. The structured optical chirality patterns may find applications in chirality sorting, chiral imaging and circular dichroism spectroscopy

A KINETIC ANALYSIS TO POWERISER (AN ENERGY STORAGE AND RETURN SPRING LEAF DEVICE)

The purpose of this study was to explore the efficiency of an Energy Storage and Return (ESAR) spring leaf walking device (Poweriser) during the walking. The result showed that the walking efficiency of poweriser was around 80% contrast to a normal walk during the mid-stance phase. In the meanwhile, the muscle activation mainly occurred in thigh muscle probably resulted from the ankle lock design of poweriser. On the other hand, the study also found that all the participants demonstrated a similar VGRF pattern and relative lower muscle loading on shank muscle during the continuous vertical jump with the poweriser. The present investigators doubted that the efficiency and performance of poweriser was influenced by the stiffness of leaf spring, the type of motion, and participant’s body mass

Revealing the Empty-State Electronic Structure of Single-Unit-Cell FeSe/SrTiO3_{3}

We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on SrTiO$_3$(001). We map the momentum-space band structure by combining quasiparticle interference imaging with decay length spectroscopy. In addition to quantifying the filled-state bands, we discover a $\Gamma$-centered electron pocket 75 meV above the Fermi energy. Our density functional theory calculations show the orbital nature of empty states at $\Gamma$ and suggest that the Se height is a key tuning parameter of their energies, with broad implications for electronic properties.Comment: 5 pages, 5 figure