Switching of Control Mechanisms during the Rapid Solidification of a Melt Pool

The Solidification of Alloys is Typically Controlled by Solute Diffusion Due to the Solute Partitioning Happening at the Solid-Liquid Interface. in This Study, We Show that the Switching from Solute Diffusion-Controlled Growth to Thermal Diffusion-Controlled Growth May Happen at the Solidification Front during Rapid Solidification Processes of Alloys Such as Additive Manufacturing using a Phase-Field Model. the Switching is Found to Be Triggered by the Cooling of the Solid-Liquid Interface When It Becomes Colder Than the Solidus Temperature. the Switching Introduces a Sudden Jump of Growth Velocity, an Increase in Solute Concentration, and the Refining of the Resulting Microstructures. All Those Changes Predicted by the Phase-Field Simulations Agree with Experimental Observations Quantitatively. the Switching of Control Mechanisms Can Be Exploited by Manipulating the Processing Conditions to Form Refined Microstructures or Layered Structures for Improved Mechanical Properties

Functional Analysis of Drosophila Integrator Complex in snRNA 3\u27 End Processing

Uridine-rich small nuclear RNAs (U snRNAs) play essential roles in eukaryotic gene expression by facilitating the removal of introns from mRNA precursors and the processing of the replication-dependent histone pre-mRNAs. Formation of the 3’ end of these snRNAs is carried out by a poorly characterized, twelve-membered protein complex named Integrator Complex. In the effort to understand Integrator Complex function in the formation of the snRNA 3’ end, we performed a functional RNAi screen in Drosophila S2 cells to identify protein factors required for snRNA 3’ end formation. This screen was conducted by using a fluorescence-based reporter that elicits GFP expression in response to a deficiency in snRNA processing. Besides scoring the known Integrator subunits, we identified Asunder and CG4785 as additional core members of the Integrator Complex. Additionally, we also found a conserved requirement for Cyclin C and Cdk8 in both fly and human snRNA 3’ end processing. We have further demonstrated that the kinase activity of Cdk8 is critical for snRNA 3’ end processing and is likely to function independent of its well-documented function within the Mediator Cdk8 module. Taken together, this work functionally defines the Drosophila Integrator Complex and demonstrates a novel function for Cyclin C/Cdk8 in snRNA 3’ end formation. This thesis work has also characterized an important functional interaction mediated by a microdomain within Integrator subunit 12 (IntS12) and IntS1 that is required for the activity of the Integrator Complex in processing the snRNA 3’ end. Through the development of a reporter-based functional RNAi-rescue assay in Drosophila S2 cells, we analyzed domains within IntS12 required for snRNA 3’ end formation. This analysis unexpectedly revealed that an N-terminal 30 amino acid region and not the highly conserved central PHD finger domain, is required for snRNA 3’ end cleavage. The IntS12 microdomain (1-45) functions autonomously, and is sufficient to interact and stabilize the putative scaffold protein IntS1. Our findings provide more details of the Integrator Complex for understanding the molecular mechanism of snRNA 3’ end processing. Moreover, these results lay the foundation for future studies of the complex through the identification of a novel functional domain within one subunit and the identification of additional subunits

Group Based Interference Alignment

In the $K$-user single-input single-output (SISO) frequency-selective fading interference channel, it is shown that the maximal achievable multiplexing gain is almost surely $K/2$ by using interference alignment (IA). However, when the signaling dimensions are limited, allocating all the resources to all users simultaneously is not optimal. So, a group based interference alignment (GIA) scheme is proposed, and it is formulated as an unbounded knapsack problem. Optimal and greedy search algorithms are proposed to obtain group patterns. Analysis and numerical results show that the GIA scheme can obtain a higher multiplexing gain when the resources are limited.Comment: 3 pages, 3 figures. resubmitted to IEEE Communications Letter

Preliminary analysis of PGRP-LC gene and structure characteristics in bumblebees

PGRP-LC is a significant pattern recognition receptor of the insect innate immune system that can recognize peptidoglycans and activate immune signaling pathways regulating the expression and release of antimicrobial peptides against infection. We for the first time analyzed the phylogenetic tree, purification and structure of bumblebee PGRP-LC. The results showed high conservation of bumblebee PGRP-LC among the 16 bumblebee species, and further phylogenetic analysis showed that the PGRP-LC phylogeny of different subgenera (Subterraneobombus, Megabombus, Melanobombus, Bombus) is consistent with that of the COI gene. Additionally, the phylogeny of PGRP-LCs among Bombus, Apis and the solitary bee Megachile rotundata coincides with the sociality evolution of bees. Moreover, bumblebee PGRP-LC (Bl-PGRP-LC) shares the Drosophila PGRP-LCx and PGRP-LCa topology, retaining conserved disulfide bonds and 80% binding residues involved in the interaction between TCT and PGRP-LCx. Therefore, Bl-PGRP-LC might share some similar binding characteristics with Drosophila PGRP-LCx. In addition, Bl-PGRP-LC has shorter β5 and β1 sheets, longer β2, β3, and β4 sheets and a shallow binding groove. To determine the characteristics of Bl-PGRP-LC, high-purity PGRP-LC inclusion bodies, soluble GST-tag Bl-PGRP-LC fusion protein and soluble pure Bl-PGRP-LC were obtained in vitro. The results will be helpful for further study of the function and structure of Bl-PGRP-LC