News & Press Releases

Are you getting ready for exams in the library? Could you use a few moments to stretch your legs and decompress? Then head over to Library Room 135 on the first floor for some Kahoot trivia! Bring your phone to participate in this interactive game of pop culture topics like music, movies, and sports. Snacks will be provided. Questions? Contact emma.wood@umassd.edu

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EAS Doctoral Dissertation Defense by Soolmaz Khoshkalam Date: Friday,December 13, 2024 Time: 9:00 a.m. Topic: Potential of Mean Force-Based Lattice Element: Extension to Dynamic and Nonlinear Analysis of Structures Location: LIB 314 Abstract: The potential-of-mean-force (PMF) approach to the lattice element method (LEM) has recently been adapted to model the response of structural systems. LEM relies on lattice discretization of the domain via a set of particles that interact through prescribed potential functions, representing the mechanical properties of members. The approach offers unique advantages, including robustness to discontinuity and failure without the need for mesh refinement. The overall goal of this research is two-fold: (i) extend the quasi-static PMF-based LEM to model the dynamic behavior of structures (ii) blend the quasi-static PMF-based LEM with Force Analogy method for nonlinear analysis. Such developments provide a means for simulating nonlinear response and failure under dynamic loading that is the nature of most natural hazards and extreme conditions. To accomplish the first goal, integration methods from Molecular Dynamics (MD) are used to estimate of the trajectory of particles in the Lattice Element Method (LEM) and to simulate the dynamic response with a focus on structural (or building) systems. More specifically Verlet-Velocity method is used to estimate the location and momentum of each particle at every time step. To assure accuracy and the numerical stability, we also explore implicit integration techniques such as Hilber-Hughes-Taylor method and midpoint method. Noting that the rotational degrees of freedom have minimal contribution to the kinetic energy of the system we develop an energy-based approach for condensation to reduce the computational cost. Our approach relies on the Euler-Lagrange equations and manifests itself in the form of minimum potential energy theorem for mass-less degrees of freedom. To address another critical aspect of dynamic simulation, the mass matrix, we adopt an energy-based approach and utilize the kinetic energy of the lattice elements to maintain consistency with the kinetic energy of their continuous counterparts. To achieve the second goal, we incorporate the nonlinear behavior of materials under various actions, including bending, torsion, and axial forces, through the introduction of novel potential functions inspired by the Force Analogy Method. These potential functions are calibrated using section properties that represent the nonlinear stress-strain responses of materials, such as nonlinear moment-curvature relationships. The utility of the proposed framework and its and accuracy are validated through its application in quasi-static linear and nonlinear simulations of large-scale buildings subjected to different loading conditions. ADVISOR(S): Dr. Mazdak Tootkaboni, Dept of Civil and Environmental Engineering (Advisor) (mtootkaboni@umassd.edu) Dr. Arghavan Louhghalam, Dept. of Civil and Environmental Engineering (Co-Advisor) (Arghavan_Louhghalam@uml.edu) COMMITTEE MEMBERS: Dr. Alfa Heryudono, Department of Mathematics and Dr. Zheng Chen, Department of Mathematics NOTE: All EAS Students are ENCOURAGED to attend.

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This intermediate to advanced workshop explores the use of formulas and functions in Excel. Topics covered include text functions, named cell ranges, conditional formatting, conditional statements, absolute cell references, as well as the VLOOKUP function. The Introduction to Excel workshop or equivalent previous experience is required. This workshop will take place in Library-128. Contact Rich Legault for more information at 508-999-8799, or email RLegault@umassd.edu. Seating is limited, so please register today!

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The Psychology Department will be hosting our annual Fall Psychology Research Conference on Friday, December 13th, from 4pm-7pm, to be held at the UMass Dartmouth Marketplace. We have two excellent presentations scheduled, followed by student poster presentations, and then awards. In addition, student poster presentations will also be available for viewing on the Psychology Department's Research Conference YouTube page, beginning Tuesday - please feel free to check these out and vote for your favorites! The conference schedule is provided below: 4:00-4:10: Welcome and opening remarks 4:10-4:40: Patrick Rich, PhD (Assistant Professor of Psychology, Stonehill College): "Does Implying Information Make it More Difficult to Correct?" 4:45-5:15: Natalie Sabik (Associate Professor of Public Health, Univ. of Rhode Island): "Using gender as a lens to explore how social influences shape stress, health, and well-being" 5:20-6:30: Poster presentations 6:30-6:45: Closing remarks For more information about the conference, please contact Dr. Elizabeth Richardson at erichardson@umassd.edu Sponsored by the College of Arts and Sciences, Psi Chi, Psychology Club, and the Psychology Department.

The Marketplace

Investigating the Molecular Bases of the HIV-1 Nef-Mediated Hijacking of ALIX and PTPN23 by Priya Sridharan Date: Tuesday, December 17, 2024 Time: 9:00AM Place: SENG 311 Abstract: HIV-1 Nef is a multifunctional accessory protein with a molecular mass of 27 kDa that plays a central role in lentiviral pathogenesis by manipulating the host cell's immune response to enhance viral replication. Nef influences a wide range of host cell processes, including signal transduction and vesicular transport pathways. One of its key functions is the downregulation of cell surface receptors, particularly CD4 and MHC class I (MHCI). Nef downregulates CD4 by accelerating its endocytosis via the clathrin/AP-2 pathway. Subsequently, Nef targets CD4 to the multivesicular body (MVB) pathway for eventual delivery to lysosomes, a process involving the endosomal sorting complex required for transport (ESCRT) machinery. While the structural details of Nef-mediated AP2-dependent endocytosis of CD4 have been revealed previously, the process leading to CD4 retention in late endosomes and its CD4 degradation in lysosomes remain mechanistically unknown. Research led by Dr. Luis L. P. da Silva at the University of Sao Paulo discovered that Nef directly interacts with Alix (apoptosis-linked gene 2-interacting protein X), a critical component of the ESCRT machinery, to enable lysosomal delivery of CD4. In this dissertation project, the Alix-Nef interaction was investigated using biochemical assays, revealing new insights into this interaction as well as Nef biology. PTPN23, a putative protein tyrosine phosphatase and paralog of Alix, contains a protein tyrosine phosphatase (PTP) domain and a PEST motif, along with regions shared with Alix, namely the Bro1 domain, the coiled-coil (CC) domains, and a proline-rich region (PRR). Like Alix, PTPN23 supports ESCRT function and is a key regulator in endosomal sorting and vesicular trafficking. Unlike Alix, PTPN23 adopts an open, extended conformation that allows for simultaneous interactions with multiple ESCRT components. Preliminary data from our collaborator, Dr. John Guatelli's lab, suggests that PTPN23 is hijacked by HIV-1 Nef to facilitate receptor mistrafficking, presumably leading to the lysosomal degradation of cell surface receptors. Consequently, this mechanism could enhance viral immune evasion and pathogenesis. The potential binding interaction between Nef and PTPN23 was also investigated in this dissertation. PhD Dissertation Committee: Dr. Xiaofei Jia (Advisor), Associate Professor (Chemistry/Biochemistry) Dr. Tracie Ferreira, Associate Professor/Chair (Bioengineering) Dr. Shuowei Cai, Professor (Chemistry/Biochemistry) Dr. Christopher J Brigham, Associate Professor (Department of Bioengineering)

Science and Engineering Building

EAS Doctoral Proposal Defense by Zhuoyuan Leng Date: Tuesday, December 17, 2024 Time: 10:00am Topic: Experimental and Numerical Studies on Mixed-mode Fracture of Additively Manufactured Polymer Nanocomposites Location: LIB 314 Zoom Link: https://umassd.zoom.us/j/92967323046?pwd=ppH0sI5z79H46F0rQhSkb2S4Y16mlA.1 Abstract: This study investigates the mixed-mode fracture behavior of ABS nanocomposites fabricated using fused deposition modeling (FDM) for automotive and aerospace applications. The scope includes quasi-static and dynamic mixed-mode fracture scenarios, and cyclic mixed-mode fatigue fracture properties, using experimental and numerical methods, focusing on understanding crack dynamics and enhancing the fracture toughness of ABS composites. It explores fracture criteria under mixed mode loading conditions and assesses the influence of printing direction, loading type, and nanoparticle weight percentage. The experimental methodology is divided into three parts: (1) quasi-static mixed-mode loading of ABS nanocomposites with different printing directions, (2) dynamic mixed-mode loading using a modified Hopkinson pressure bar setup, and (3) cyclic fatigue loading to assess fatigue fracture performance. Scanning electron microscopy (SEM) will be used to analyze fracture surfaces and correlate them to fracture mechanisms under various mode-mixities and loading conditions. Simulation studies focus on crack dynamics using the phase-field method (PF) implemented in COMSOL, with anisotropic material formulations to model different printing directions and dynamic loading scenarios. Comparisons between simulations and experiments will enhance the understanding of fracture mechanisms. The outcome can be used to optimize ABS nanocomposite performance and provide insights for structural applications. ADVISOR(S): Dr. Vijaya Chalivendra, Department of Mechanical Engineering (vchalivendra@umassd.edu) COMMITTEE MEMBERS: Dr. Caiwei Shen, Department of Mechanical Engineering Dr. Jay Wang, Department of Physics Dr. Jun Li, Research Associate Professor, ERAU NOTE: All EAS Students are ENCOURAGED to attend.

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