Complete Polarization Control in Multimode Fibers with Polarization and Mode Coupling

Multimode optical fibers have seen increasing applications in communication, imaging, high-power lasers and amplifiers. However, inherent imperfections and environmental perturbations cause random polarization and mode mixing, making the output polarization states very different from the input one. This poses a serious issue for employing polarization sensitive techniques to control light-matter interactions or nonlinear optical processes at the distal end of a fiber probe. Here we demonstrate a complete control of polarization states for all output channels by only manipulating the spatial wavefront of a laser beam into the fiber. Arbitrary polarization states for individual output channels are generated by wavefront shaping without constraint on input polarizations. The strong coupling between spatial and polarization degrees of freedom in a multimode fiber enables full polarization control with spatial degrees of freedom alone, transforming a multimode fiber to a highly-efficient reconfigurable matrix of waveplates

A New Seamless Bitstream Switching Scheme for H.264 Video Adaptation with Enhanced Coding Performance

[[abstract]]In this paper, we propose a new seamless bitstream switching scheme to improve the coding performance of H.264 SP-frames for rate adaptation. Our method removes one of the two re-quantization blocks in the SP-frame encoders so as to significantly improve coding performance. The seamless switching property of SP-frames is retained by properly restructuring the primary and secondary switching frame codecs. Experimental results show that our proposed scheme achieves close coding performance to that of regular H.264 P-frames and significantly better performance than that of SP-frames. The proposed method also provides the advantage of using a single secondary switching bitstream for both switching-up and switching-down processes[[fileno]]2030144030014[[department]]電機工程學

Bear with me : signs are tricksters, and reality is invisible to the naked eye: a one-person play

The creation of a one-person play is required in order to complete the Master of Fine Arts degree in acting. There are no official guidelines, only twenty to forty minutes in length is required. Although I was very excited about receiving the challenge, I did not breathe a sigh of relief until I found the topic I wanted to explore－Signs and Reality, and the one-person play that followed: Bear With Me. Since I am not a native English speaker, I have been frustrated by miscommunication through words in the English-speaking world, which gave me the eagerness to talk about the problem. Later on, I found out signs and words as well as the meaning of them change based on time and place, in other words, signs and words in themselves are unreliable, and also efficient and effective communication does not need to depend on them. These two thoughts wove into the spine of my play. Ironically, it is impossible to create a play without using words, so using words precisely became a big challenge, especially for the person who tried to create an English play and whose native tongue is not English. I believe theatre can take place anywhere, and either traditional theatre or experimental theatre has been a comfortable, convenient space for theatre creators. I think theatre should not be confined to a small box, but it should try to reach its extremes instead, so I challenged myself to have my play in a forest as the location and the atmosphere of my play. Except for the challenges mentioned above, I needed to figure out the journey of my central character and what I wanted my audience to get from the play. These both are essential questions for the play; if I did not solve the problems, my play would be just making a fuss about nothing. Fortunately, bear with me to say that my performances turned out to be a bare success

THE EFFECT OF INSULIN AND CARBOHYDRATE SUPPLEMENTATION ON GLYCOGEN REPLENISHMENT AMONG DIFFERENT HINDLIMB MUSCLES IN RATS FOLLOWING PROLONGED SWIMMING

In the present study we investigated the interactive effects of insulin and carbohydrate on glycogen replenishment in different rat hindlimb muscles. Forty male Sprague Dawley rats were assigned to 5 groups, including 1) sedentary control with carbohydrate supplement (2 g glucose · kg body wt-1), 2) sedentary rats with 16 hours recovery, carbohydrate and insulin (0.5 U · kg body wt-1), 3) swimming without recovery, 4) swimming with 16 hours recovery and carbohydrate supplement, and 5) swimming with 16 hours recovery, carbohydrate and insulin. The swimming protocol consisted of two 3 h swimming sections, which were separated by a 45 min rest. The insulin and carbohydrate were administered to the rats immediately after exercise. At the end of the experiment, the soleus (S), plantaris (P), quadriceps (Q) and gastrocnemius (G) were surgically excised to evaluate glycogen utilization and replenishment. We observed that glycogen utilization was significantly lower in G and Q than S and P during swimming (p <0.05), and S showed the greatest capacity of glycogen resynthesis after post-exercise recovery (p <0.05). In the sedentary state, the glycogen synthesis did not differ among hindlimb muscles during insulin and carbohydrate treatments. Interestingly, with insulin and carbohydrate, the glycogen resynthesis in S and P were significantly greater than in Q and G following post-exercise recovery (p <0.05). We therefore concluded that the soleus and plantaris are the primary working muscles during swimming, and the greatest glycogen replenishment capacity of the soleus during post-exercise recovery is likely due to its highest insulin sensitivity

Comparison of diffusion-weighted imaging and contrast-enhanced T1-weighted imaging on a single baseline MRI for demonstrating dissemination in time in multiple sclerosis

BACKGROUND: The 2010 Revisions to the McDonald Criteria have established that dissemination in time (DIT) of multiple sclerosis (MS) can be demonstrated by simultaneous presence of asymptomatic gadolinium-enhancing and nonenhancing lesions on a single magnetic resonance imaging (MRI). However, gadolinium-based contrast agents (GBCAs) have contraindications. Diffusion-weighted imaging (DWI) can detect diffusion alterations in active inflammatory lesions. The purpose of this study was to investigate if DWI can be an alternative to contrast-enhanced T1-weighted imaging (CE T1WI) for demonstrating DIT in MS. METHODS: We selected patients with clinically definite MS and evaluated their baseline brain MRI. Asymptomatic lesions were identified as either hyperintense or nonhyperintense on DWI and enhancing or nonenhancing on CE T1WI. Fisher’s exact test was performed to determine whether the hyperintensity on DWI was related to the enhancement on CE T1WI (P < 0.05). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the DWI to predict lesion enhancement were calculated. RESULTS: Twenty-two patients with 384 demyelinating lesions that were hyperintense on T2-weighted imaging and more than 3 mm in size were recruited. The diffusion hyperintensity and lesion enhancement were significantly correlated (P <0.001). The sensitivity, specificity, PPV, NPV and accuracy were 100%, 67.9%, 32.3%, 100% and 72.1%, respectively. CONCLUSIONS: A hyperintense DWI finding does not necessarily overlap with contrast enhancement. There are many false positives, possibly representing other stages of lesion development. Although DWI may not replace CE T1WI imaging to demonstrate DIT due to the low PPV, it may serve as a screening MRI sequence where the use of GBCAs is a concern

Development of Multiplexable Biosensors to Quantify the Spatiotemporal Dynamics of Rho GTPases and Protein Kinases in the Same Living Cell

Cell motility is a highly dynamic and heterogenous cellular process regulated by the coordination of multiple Rho GTPases, Src family kinases, and the mitogen-activated protein kinase (MAPK) cascades. However, it has been difficult to monitor more than two protein activities in the same cell due to the overlapping spectra of current biosensors and biological perturbations at high biosensor concentrations. Dye-based biosensors, which rely on an affinity scaffold that binds only to the activated conformation of the endogenous targets and an environment-sensing dye that changes its fluorescence properties to report the specific binder-target interactions, possess great potential to monitor multiple endogenous targets in the same cell. Here, I created novel environment-sensing dyes and exploited novel affinity scaffolds to develop multiplexable dye-based biosensors capable of quantifying the spatiotemporal dynamics of multiple Rho GTPases and protein kinases in the same cell. Src protein kinase is an upstream regulator of the Cdc42 GTPase. The coordination of Cdc42 and Src at the leading edge has not been well characterized due to lack of multiplexable biosensors to monitor Cdc42 and Src activities in the same living cell. Therefore, I developed novel near infrared merocyanine dyes and a red ratiometric merocyanine dye with an intrinsic ratiometric response that can be used to construct multiplexible biosensors. The relative timing and the subcellular localization of active Cdc42 and Src during leading edge dynamics and during pinocytosis were revealed using the new dyes. Src also plays an important role in the MAPK-mediated cell motility. However, the precise roles of MAPKKs and MAPKs at the leading edge remain poorly characterized due to the lack of sensitive biosensors for each target. By taking advantage of the specific interactions between MAPKKs and MAPKs, I developed the first substrate-based biosensor designs to report the activity of endogenous MEK1/2 and MKK3/6. I also developed a sensitive ERK1/2 biosensor based on artificial binders through collaborations with the Plűckthun group. This work will provide a foundation to study the crosstalk between Rho GTPases, Src family kinases and the MAPK cascades via multiplexed live cell imaging.Doctor of Philosoph