A Novel A Priori Simulation Algorithm for Absorbing Receivers in Diffusion-Based Molecular Communication Systems

A novel a priori Monte Carlo (APMC) algorithm is proposed to accurately simulate the molecules absorbed at spherical receiver(s) with low computational complexity in diffusion-based molecular communication (MC) systems. It is demonstrated that the APMC algorithm achieves high simulation efficiency since by using this algorithm, the fraction of molecules absorbed for a relatively large time step length precisely matches the analytical result. Therefore, the APMC algorithm overcomes the shortcoming of the existing refined Monte Carlo (RMC) algorithm which enables accurate simulation for a relatively small time step length only. Moreover, for the RMC algorithm, an expression is proposed to quickly predict the simulation accuracy as a function of the time step length and system parameters, which facilitates the choice of simulation time step for a given system. Furthermore, a rejection threshold is proposed for both the RMC and APMC algorithms to significantly save computational complexity while causing an extremely small loss in accuracy.Comment: 11 pages, 14 figures, submitted to IEEE Transactions on NanoBioscience. arXiv admin note: text overlap with arXiv:1803.0463

Studying the Voice of Mo Yan and Howard Goldblatt: Zhang Kou in the Garlic Ballads

In 2012, a Chinese, Mo Yan 莫言, became the laureate of the Nobel Prize in Literature. It was the first time in China’s history; this is not because Mo Yan is better than other Chinese writers, or that he follows some Western writers like Gabriel García Márquez, but because he works with better translators, who make his stories captivating for Western readers, than whom his precursors work with. Even though Mo Yan sticks closely to dialect and culture in rural areas in northern China, his translators adjust his writings to an accessible form in another language. In order to understand why these translations make Mo Yan’s works popular in the Western world, this thesis focuses onMo Yan’s English translator, Howard Goldblatt, and studies his translation techniques. This thesis aims at a minor character, Zhang Kou 张扣, in one of Mo Yan’s understudied novels, The Garlic Ballads Tiantang suantai zhi ge 天堂蒜薹之歌. The novel received not as much scholarly attention as his Red Sorghum Clan Hong gaoliang jiazu 红高粱家 族, so scholarship of Zhang Kou is limited. By analogizing the Chinese and English version of the standby of the garlic riot Zhang Kou, both the writing style of Mo Yan and the translating features of Goldblatt are part of this discussion. With the analyses of Zhang Kou’s representation of the voice of both the author and the translator, Mo Yan’s original depictions of Zhang Kou contrast with Goldblatt’s rewriting of the counterparts; it reveals how the two voices, though articulated by the same character, are different. In this thesis, the introduction to Goldblatt’s translating techniques focuses on how he overcomes the barriers between the two languages and unites his own voice with that of Mo Yan. By concentrating on the transformation of Zhang Kou’s voice, this thesis argues that Goldblatt adapts Mo Yan’s voice to the English-speaking world rhetorically, culturally and ideologically, and that this is the reason why he makes Mo Yan’s writing popular in the West

The Phase Behavior of Ubqln Proteins and Implications for Protein Quality Control

The ubiquitin-proteasome system (UPS) and autophagy are essential pathways for maintaining protein quality control (PQC) in cells. Misfolded proteins and large aggregates are cleared by UPS and autophagy signaled by ubiquitin (Ub) or polyubiquitin (polyUb) chains. Shuttle proteins facilitate cargo transporting by interacting with both ubiquitin and degradation machineries. Previously, our lab discovered that the shuttle protein Ubiquilin-2 (UBQLN2) is recruited to stress granules in cells and undergoes liquid-liquid phase separation (LLPS) in vitro. LLPS is a biophysical process by which proteins separate themselves from the surrounding aqueous solution by forming protein-rich droplets. The overarching goals of this work are to understand how the UBQLN family of proteins form droplets via phase separation, as well as how UBQLN2 LLPS is regulated by interactions with protein quality control (PQC) proteins, specifically Ub and polyUb chains.Chapter two focused on studying the molecular driving forces of UBQLN2 LLPS. Previously, our lab identified residues of UBQLN2 that promote self-interactions and phase separation, which are called stickers and the sequences separating stickers are called spacers . Here, I systematically introduced all 19 single amino acid substitutions at three stickers and two spacers , leading to a UBQLN2 library of 95 point mutants. By screening for the phase transitions of these proteins and mapping out phase diagrams, we discovered that the LLPS of UBQLN2 is largely driven by hydrophobic amino acids in the sticker positions but not spacers. Amino acid substitutions in the sticker positions significantly changed the shape of the phase diagram as well as the characteristics of the dense phase, which is the protein-rich phase inside the condensates. PolyUb chains of different linkages have different functions in cells. Preliminary data from our lab suggest that K48-linked and K63-linked polyubiquitin chains differentially modulate UBQLN2 LLPS. Chapter three revealed how interactions between UBQLN2 and polyUb chains affect UBQLN2 functionality and its ability to phase separate. The data suggest that polyUb chains of different linkages differentially modulate UBQLN2 LLPS. I found that the compact Ub4 chains (K11 and K48) largely drive disassembly of UBQLN2 condensates, while extended and more flexible Ub4 chains (K63 and M1) promote multi-component LLPS via heterotypic interactions with UBQLN2. The UBQLN family consists of 5 protein members (UBQLN1-4 and UBQLNL), with highly conserved sequences and structures. Besides UBQLN2, UBQLN4 also plays a role in PQC. However, the phase behavior of UBQLN4 is largely unknown, as well as the sequence and structural basis for the phase behavior of the protein. In chapter four, I characterize the LLPS properties of UBQLN4 for the first time and compare its behavior with UBQLN2. I successfully designed, cloned, expressed, and purified various UBQLN4 C-terminal deletion constructs. Turbidity assay data suggest that the LLPS behavior of UBQLN4 constructs is concentration- and temperature-dependent, like UBQLN2, but in a different manner than UBQLN2 equivalent constructs. More stringent studies are needed to unravel the differences in LLPS behavior of different UBQLNs

Simplified Cooperative Detection for Multi-Receiver Molecular Communication

Diffusion-based molecular communication (MC) systems experience significant reliability losses. To boost the reliability, an MC scheme where multiple receivers (RXs) work cooperatively to decide the signal of a transmitter (TX) by sending the same type of molecules to a fusion center (FC) is proposed in this paper. The FC observes the total number of molecules received and compares this number with a threshold to determine the TX's signal. The proposed scheme is more bio-realistic and requires relatively low computational complexity compared to existing cooperative schemes where the RXs send and the FC recognizes different types of molecules. Asymmetric and symmetric topologies are considered, and closed-form expressions are derived for the global error probability for both topologies. Results show that the trade-off for simplified computations leads to a slight reduction in error performance, compared to the existing cooperative schemes.Comment: 5 pages, 4 figures, Will be presented as an invited paper at the 2017 IEEE Information Theory Workshop in November 2017 in Kaohsiung, Taiwa

Tuition fees and student mobility

The upsurge in the popularity of studying abroad continues across the globe. By adopting the context of human capital migration theory, our paper aims to examine how tuition fees influences international student mobility. We focus on the international student inflow in five Nordic countries and Germany from 26 non EU/EAA and 31 EU/EEA countries, covering 3206 observations in total. During the period between 2003-2012 we employed a modified gravity model to empirically test the relationship between tuition fees and student inflow. The results reveal that, compared to providing free higher education, charging tuition fees has negative effects on student inflow

Photoacoustic computed tomography guided microrobots for targeted navigation in intestines in vivo

Tremendous progress in synthetic micro/nanomotors has been made for potential biomedical applications. However, existing micro/nanomotor platforms are inefficient for deep tissue imaging and motion control in vivo. Here, we present a photoacoustic computed tomography (PACT) guided investigation of micromotors in intestines in vivo. The micromotors enveloped in microcapsules exhibit efficient propulsion in various biofluids once released. PACT has visualized the migration of micromotor capsules toward the targeted regions in real time in vivo. The integration of the developed microrobotic system and PACT enables deep imaging and precise control of the micromotors in vivo