Events Archive

 

Speaker: Dr. Marc Kuchner, NASA

 

Abstract: Most scientists know all too well that they must market themselves. These days, only 15% of new investigators win NSF grants, only 25% of postdocs find permanent jobs in academia, and anti-science sentiments seem to have become mainstream. But the usual education of a scientist does little to teach us about the powerful tools business professionals use to win support for their ideas. Even the word “marketing” is often seen as taboo.
The Marketing for Scientists workshop aims to break the taboos and introduce scientists to the fundamental techniques from the business world that matter most to them, like sales, branding and relationship building. It uses the examples of Steve Jobs, George Lucas, and Barack Obama to show that marketing can be a positive, even healing force. It teaches scientists how to get their ideas across vividly while maintaining their integrity and building the outstanding reputations they need.

 

Host: SPS and PSGA

 

Abstract: A paraphrase of Tolstoy that has become popular in the field of nonlinear dynamics is that while all linear systems are linear in the same way, all nonlinear systems are nonlinear in their own ways. Despite this being quite true, one can find a number of  universal features in nonlinear systems which unify them in ways that enhance our understanding of their behavior.

There still remains a large number of unanswered questions about chaotic systems. Two such questions are the primary focus of this thesis.

The first question we will address is regarding the general shape of the strange attractor. Specifically what can we learn about the shape of strange attractor from the dynamical equations without numerically integrating them? Previously, we only had the fixed points to act as general guides as to the shape of the attractor, but these point sets are not exceedingly descriptive. We will outline work done to find more interesting sets of points from the dynamical equations themselves, sets of points which provide a sort of skeletal-structure for the strange attractors.

The second question is one which has been treated by only a small number of researchers, and not as descriptively as we do here. When viewed in co-dimension-2 space (that is, two control parameters of the attractor varied, all others kept constant), one finds some remarkable regular patterns in the mapping of the intensity of Lyapunov exponents. While progress has been made in addressing the origin of these shapes, there has not yet been a satisfactory explanation to the simple question: where do these patterns come from, and what do they tell us about the dynamical system? We will examine these patterns in detail and provide a broad explanatory mechanism for them, with a particular focus on the Rossler attractor.

 

Advisor: Dr. Robert Gilmore

 

Abstract: Abnormal protein aggregation has been suggested to be associated with a growing number of diseases. A better understanding of the biophysics and biochemistry of protein aggregation process will be essential to understanding the role of such aggregates in diseases, and critical to preventing or slowing down the aggregation process. The intensity of scattered light from protein solutions is dominated by the concentration fluctuations of the solution. This intensity will increase while aggregates are forming in the solution.  We have used light scattering to probe the initial stages of sickle hemoglobin assembly. We employed a novel micro-method for measuring light scattering in a rectangular glass capillary tube that is filled with 24 µL of hemoglobin solution. The solution was illuminated by a laser coming out of an optical fiber that is sealed into the glass tube. Scattered light was collected by a microscope objective at 90° to the incident light, and detected via Photomultiplier tube. Temperature is controlled by a thermoelectric stage. We studied the scattered intensities of five hemoglobin derivatives solution with various concentrations. We found that the intensity of scattered light kept relatively constant at low temperatures but increased after the temperature of the solution exceeded some particular value. Deoxygenated sickle hemoglobin, which forms polymers above solubility, scatters more light than HbSCO (which does not form polymers and differs from deoxygenated HbS by quaternary structural differences), HbACO, deoxygenated HbA, and deoxygenated cross-linked HbA (which do not form polymers and differ from deoxygenated HbS by an amino acid). We interpreted this by using two different theories, liquid-liquid demixing and the appearance of oligomers. We found that monomer and some large oligomer coexisting in the solution, which implies that there might be metastable states in the free energy landscape of hemoglobin aggregation. We obtained the enthalpy changes and entropy changes in the formation of oligomers and found that the enthalpy changes do not show concentration dependence. The axial contact and the lateral contact are found to have different strengths. We found that the data of HbSCO shows surprisingly similar behavior to the data of HbA rather than to that of deoxygenated HbS, which suggest that there are no lateral contacts between the HbSCO monomers. Aggregates concentration is not diagnostic for polymerization because of that although deoxygenated HbS creates more aggregates at the same concentration and temperature than other hemoglobin derivatives, all derivatives can create equal concentration of aggregates with varied temperature and monomer concentration.

 

Advisor: Dr. Frank Ferrone

 

Abstract: Strange attractors in R3 are remarkably well understood because they may be classified through a topological analysis. This involves determining the organization of the unstable periodic orbits in the attractor by computing linking numbers for pairs of these orbits. This topological invariant can be calculated by a four dimensional dynamical system and show the first steps in extending the current topological analysis program to higher dimensions. The linking numbers for pairs of unstable periodic orbits are computed in three different ways. Firstly, through projections of the attractor to three dimensional subspaces. Secondly, using a recently proposed higher dimensional linking integral to compute linking numbers in R4 for the first time. Thirdly, with a dimensionality reduction technique, Locally Linear Embedding, that successfully represents pairs of orbits in three dimensions allowing the organization within the strange attractor to be determined.

 

Advisor: Dr. Robert Gilmore

The Department of Physics is hosting a public observing night on November 2, 2011 from 6:30 p.m. to 8:30 p.m. at the Joseph R. Lynch Observatory, atop the Main Building (32nd and Chestnut Streets).

 

All members of the Drexel community (and friends) are invited to come to view celestial objects through the observatory's telescope. For directions, talk details, and cancellation status, visit http://www.physics.drexel.edu/observatory.

 

For more information, contact the Director of the Lynch Observatory, Dr. Gordon T. Richards at gtr@physics.drexel.edu.

The Society of Physics Students and Steinbright Career Development Center will host a Physics Co-op Student Panel. This event will take the place of the freshmen UNIV101 class scheduled at that time. All students and faculty are invited to attend. Drexel University's Co-op Coordinator Nicole Napoleon will be leading the panel. This is a great opportunity for freshman and sophomores to hear directly from students who have done co-op in the past and for veteran co-op students  to network with each other and learn from their peers.  Additionally, faculty can become more familiar with co-op experiences and to offer their advice.

 

Abstract: A protein's ultimate function and activity is determined by the unique three-dimensional structure taken by the folding process. Protein malfunction due to misfolding is the culprit of many clinical disorders, such as abnormal protein aggregations. This leads to neurodegenerative disorders like Huntington's and Alzheimer's disease. We focus on a subset of the folding problem, exploring the role and effects of entropy on the process of protein folding. Four major concepts and models are developed each pertains to a specific aspect of the folding process: entropic forces, conformational states under crowding, aggregation, and macrostate kinetics from microstate trajectories.
The exclusive focus on entropy is well-suited for crowding studies, as many interactions are non-specific. We show how a stabilizing entropic force can arise purely from the motion of crowders in solution. In addition we are able to make a quantitative prediction of the crowding effect with an implicit crowding approximation using an aspherical scaled-particle theory.
In order to investigate the effects of aggregation, we derive a new operator expansion method to solve the Ising/Potts model with external fields over an arbitrary graph. Here the external fields are representative of the entropic forces. We show that this method reduces the problem of calculating the partition function to the solution of recursion relations.
Many of the methods employed are coarse-grained approximations. As such, it is useful to have a viable method for extracting macrostate information from time series data. We develop a method to cluster the microstates into physically meaningful macrostates by grouping similar relaxation times from a transition matrix. 
Overall, the studied topics allow us to understand deeper the complicated process involving proteins.

 

Advisor: Dr. Jiam-Min Yuan

Title: "Exploring Nature Moments after the Big Bang:
The LHC Accelerator and the CMS Experiment"

 

Speaker: Dr. Tejinder S. Virdee, Imperial College, London and CERN

 

Abstract: The LHC project, comprising the accelerator and the experiments, aims to tackle some of the most fundamental questions about the origin, evolution and composition of our universe.  Potential discoveries include new forms of matter, new forces of nature, new dimensions of space and time.  Particular questions to be addressed include: what is the origin of mass, what constitutes dark matter, why is the universe composed of matter, not antimatter, and more. The discoveries have the potential to alter our perception of how Nature operates at the fundamental level.

In 2010, the LHC accelerator collided protons and lead ions at unprecedented high energies. Outstanding progress was made in operating the accelerator with very good performance.

The Compact Muon Solenoid (CMS) experiment, one of the two large general-purpose experiments, also performed very well, close to the ambitious design performance set down some fifteen years ago. Physics measurements are confronting, more and more precisely, the predictions of the Standard Model of particle physics, whilst looking for new physics.

CMS is designed to operate in a very harsh environment created by hundreds of billions of particles produced every second, and to register with high accuracy the passage and energies of all these particles.  Thus, this demands huge data collection, transfer and processing rates on a scale greater than ever previously attempted. CMS comprises over 3500 scientists and engineers from over 180 institutions in 38 countries.

This talk will briefly recall the physics of the LHC, outline some of the challenges faced during the construction of the accelerator and CMS, their operation and performance, the first physics results, and the outlook.

 

The event is free and open to the public. For more information, please contact Jacqueline Sampson at kaczlectures@physics.drexel.edu, (215) 895-2708, or visit http://www.physics.drexel.edu/kacz.

Fundamental Studies of Sickle Hemoglobin Polymerization
 
Abstract: The key to the pathology of sickle cell disease is the polymerization of sickle hemoglobin (HbS), which is a point mutation of the normal hemoglobin (HbA). The polymerization of HbS occurs when the concentration of deoxy HbS exceeds the solubility. If inert molecules such as dextran are introduced to the solution, the solubility could be reduced significantly because of crowding. This makes the study of the solubility with limited amount of sample possible. By applying scaled particle theory, we have built the thermodynamic connection between the situation with and without dextran, which enable one to calculate the dextran-free solubility easily. The HbS polymerization could be modeled by the double nucleation mechanism. However, a fundamental element of this mechanism, the growth speed of individual polymer is still not precisely measured because the single polymer is 20nm diameter, thus below optical resolution. Our approach is based on the fact that a single fiber entering a region of concentrated deoxy HbS will generate large numbers of additional polymers by heterogeneous nucleation, allowing the presence of the first fiber to be inferred even if it is not directly observed directly. This idea is realized by projecting an optical pattern consisting of three parts: a large incubation circle, a small detection area, and a thin channel connecting the two areas to the sample. With increasing the channel on time, we can find the time just enough for the polymer reach the detection circle, and with the channel length measured, the polymer growth speed could be calculated. Our polymer growth rates obtained from pure HbS, HbS/HbA mixtures, and partial photolysis of HbS validate a simple linear growth rate equation including any non-polymerizing species in the activity coefficient calculation. This implies that monomer is adding to the end of the polymer one by one not by oligomers. Our approach also enables us to determine the monomer addition rates and release rates precisely, and their temperature dependence. These data are in agreement with previous DIC measurement. The ratio of these two rates is the solubility of individual polymer, which also agrees with the previously published centrifugation data.
 
Advisor: Dr. Frank Ferrone

Speaker: Cheryl Chao-Ping Hsu, Institute of Chemistry, Academia Sinica, Taipei

Abstract: I will try to talk about our work in two very different areas in this seminar.

The first part is about using characterizing transport rates for charge and excitation energy transfers using ab initio solutions of the Schrodinger’s equation. In particular, we have been focusing on the electronic coupling term, which is an off-diagonal Hamiltonian matrix element between the initial and final (diabatic) states in the transport processes. ET coupling is essentially the interaction of the two molecular orbitals (MOs) where the electron occupancy is changed. Singlet excitation energy transfer (SEET) contains a Förster dipole–dipole coupling term as its most important constituent. Triplet excitation energy transfer (TEET) involves an exchange of two electrons of different spin and energy; thus, it is like an overlap interaction of two pairs of MOs. I will briefly talk about our methodology development and some results that helped us better understand the phytophysics of the molecules.

The second part is a summary on our recent works in joining the emerging efforts in the field of systems biology and quantitative biology. I will talk about our recently developments in fundamental theory accounting for the fundamental statistical mechanics in the stochastic chemical kinetics, as well as some examples in our application projects where biologically relevant models were built.

See http://pubs.acs.org/doi/full/10.1021/ar800153f

 

Host: Dr. Jian-Min Yuan