Departmental Seminars

Fall 2017

 

Aug 21, 2017
10:30 AM
Room 1011, EB1
Dr. Marc Lavine
Science Magazine

There is a strong desire, often driven by real or perceived pressures, to publish research in a top tier journal like Science.  However, with a rejection rate above 90%, it is a difficult process.  When a paper gets rejected without referee comments, it is hard to know why the paper failed to get past the initial screening process.  In this talk, I will describe the publication process at Science, within the broader context of developing skills for more effective scientific communication.  Aside from publishing in high impact journals, good communication tools are essential for forming scientific collaborations, bypassing research obstacles, avoiding conflicts during scientific presentations and explaining scientific research to funding bodies and the public at large, who are the primary source of financial support for scientific research.

Aug 28, 2017
10:30 AM
Room 1011, EB1
Dr. Moti Herskowitz
Ben-Gurion University of the Negev, Israel

Among critical challenges facing modern society, conversion of waste liquids and gases to renewable, eco-friendly, socially-acceptable, economically-competitive, sustainable and fungible liquid fuels for transportation to replace fuels produced from crude oil is one of the most urgent tasks. In spite of major investment in R&D and significant scientific progress in this field, the current progress is very limited. Sustainable and renewable fuels account for <10% of the total transportation fuels.The Blechner Center (http://www.bgu.ac.il/indcat/) has developed, over the past two decades, a wide variety of technologies in the area of alternative fuels and chemicals. Integrated catalytic technologies for conversion of CO2/CO/H2 mixtures to fuels and chemicals are ready for demonstration and commercialization.The seminar will focus on existing and foreseeing catalytic processes for converting waste liquids and gases to liquid fuels and chemicals.

Sep 11, 2017
10:30 AM
Room 1011, EB1

Dr. Roe-Hoan Yoon
Virginia Tech

The stability of colloids, foams, and wetting films is controlled by the surface forces in the thin liquid films (TLFs) of water confined between macroscopic surfaces. The classical DLVO theory uses the van der Waals and double-layer forces to predict the stability of mildly hydrophobic colloids with contact angles (θ) of up to ~60o. For colloids of stronger hydrophobicity, it is necessary to extend the theory by considering contributions from hydrophobic forces.1 Many investigators actually measured the hydrophobic forces directly using the surface force apparatus (SFA) and atomic force microscope (AFM), while others showed evidences that they are artifacts resulting from Nano-bubbles, drying effect, charge correlation, etc. The debate on hydrophobic forces has been ongoing for more than a generation now, but its origin is still unknown.

At Virginia Tech, we have been measuring the hydrophobic forces that may be present in three different types of TLFs, i.e., colloid, foam, and wetting films, and have obtained thermodynamically consistent results. It has been shown that hydrophobic interactions at macroscopic length scale are enthalpic involving enthalpy-entropy compensation.2,3 This finding is contrary to what is known for the hydrophobic interactions at molecular scale, e.g., self-assembly of hydrocarbon chains, but is consistent with predictions from the molecular dynamic simulations reported in the literature. More recently, we have developed a method which measures both hydrodynamic and surface forces present in wetting films using an air bubble effectively as a sensor and confirms the results by direct force measurement using a cantilever spring.4,5 The results have been used to determine the free energies (DG) of film thinning and rupture using the Frumkin-Derjaguin isotherm. If time permits, thermodynamic evidences for the hydrophobic forces of molecular origin will also be discussed briefly.

  1. Xu, Z. and Yoon, R.-H., J. Colloid and Interface Sci., 134, 427 (1990)
  2. Wang, J., Eriksson, J.C., and Yoon, R.-H., J. Colloid and Interface Sci., 364, 257 (2011)
  3. Li, Z. and Yoon, R-H., Langmir, 30, 13312 (2014)
  4. Pan, L., Jung, S., Yoon, R.-H., J. Colloid and Interface Sci. 361, 321 (2011)
  5. Pan, L. and Yoon, R.-H., Minerals Engineering 98, 240 (2016) 
Sep 18, 2017
10:30 AM
Room 1011, EB1

Dr. Nikhil Nair
Tufts University

Efforts in synthetic biology and metabolic engineering have largely focused on improving biosynthetic productivity and yields of biological processes under the assumption that that nutrient uptake rates and assimilation into central metabolism are not limiting. These assumptions are not valid in biological systems engineered to utilize non-native nutrients. For example, non-native C5 sugar (viz. xylose, arabinose) metabolism in the yeast S. cerevisiae and C1 (viz. CO2, methanol) utilization in E. coli are non-optimal, even after extensive engineering efforts, compared to that of native C6 sugar substrates like glucose and galactose. Thus, there is significant need to answer the following questions:

  • Why have current designs implementations of non-native nutrient assimilation pathways not been more successful?
  • How do we engineer biological systems to better assimilate nutrients they did not natural evolve to utilize?
  • What are the merits of success when evaluating the designs?

In this talk, I will present our recent advances in answering these questions using pentose assimilation by S. cerevisiae as a test case. Insights from these work will significantly advance future efforts in synthetic biological focused on valorizing low value feedstocks into high-value products.

In addition, I will briefly discuss our recent efforts in developing a united platform to treat a large family of orphan diseases called inborn errors of metabolism (IEM). IEMs are a family of >500 disorders that individually affect less than 1 in 10,000 newborns but cumulatively affect nearly 1 in 1000 infants. Most of these disorders have no current treatment options and our goal is to leverage the gut microbiota as a modulator of metabolism to alleviate chronic and acute pathologies associated with these disorders. I will discuss results from our work in developing engineered gut bacteria and synthetic enzymes as novel therapeutics to treat 9 distinct disorders within this family.

Sep 25, 2017
10:30 AM
Room 1011, EB1

Dr. Benjamin McCool
ExxonMobil

Highlights

  1. Overview of ExxonMobil Research and Engineering and Corporate Strategic Research
  2. Highlights from ExxonMobil’s 25+ years or research in inorganic membranes technology
  3. Focus on current research in NF and RO separations of complex hydrocarbon feeds

3. Provide perspectives for future membrane use in refining and petrochemical industryExxonMobil has been interested in the use of membranes for both gas and liquid separations for at least the last 25 years.  In that time we have investigated numerous applications and worked with membranes of all types. That work resulted in over 150 granted US patents and over 50 publications in the peer reviewed literature. This presentation will provide an overview of the work from the past 25 years – including key findings in our continued progression toward understanding molecular transport and materials engineering aspects of membrane separations. Specific examples will be presented on zeolite membranes for the separations of CO2/CH4 and xylenes as well as hybrid systems for aromatics/non-aromatics pervaporation.

The second half of the presentation will focus on our on-going work in the separation of complex liquid hydrocarbon mixtures using inorganic membranes.  We will cover our efforts in novel materials development, compositional modeling for separation products in complex mixtures, and process concept development for nano-filtration and hydrocarbon reverse osmosis applications.

Oct 2, 2017
10:30 AM
Room 1011, EB1

Dr. Jianhua “Joshua” Tong
Clemson University

It is believed that protonic ceramic fuel cells (PCFCs) and other protonic ceramic based energy conversion/storage devices operating at intermediate temperature of 200-600oC will be able to avoid both high-temperature and low-temperature challenges for the counterpart devices, which will allow the production of the reliable and cost-effective electricity and the effective activation of C-H bond for gas-to-liquid conversion and N≡N bond for ammonia synthesis. Although the “Norby gap” at 300-600oC was identified because of the poor ionic conductivities, the new proton conducting oxides have been proved to have high proton conductivities at 200-600oC for promising fuel cells, catalytic or electrocatalytic membrane reactors, hydrogen or steam permeation membranes, electrolyzers, and sensors. However, commercial viability of solid state energy conversion devices based on proton conducting oxides crucially hinges on overcoming several significant challenges: 1) proton conducting ceramic materials/structures with high total proton conductivity, 2) stable, compatible, and active electrodes, 3) cost-effective fabrication technique for cells, and 4) new fabrication technique for highly compacted stacks.

In recent several years, using protonic ceramic fuel cells (PCFCs) as a case study, we have successfully addressed these four challenges. A perovskite-type mixed conducting cathode material system of BaCo0.4Fe0.4Zr0.2-xYxO3-δ (x=0-0.15) has been discovered. Furthermore, a facile cost-effective solid state reactive sintering (SSRS) method has been developed for fabricating proton conducting ceramics with controllable grain sizes and relative densities from low-cost carbonates and simple binary oxides. After understanding the mechanism, the SSRS method has been successfully used to fabricate PCFCs by one-step firing at a moderate temperature (1400oC), which is ~300oC lower than the conventional firing temperatures. A power density as high as ~600mW/cm2 was obtained at 600oC under H2/Air gradient. Most recently, the progress of 3D printing and reactive laser sintering of protonic ceramics provides a great potential for the fabrication highly compacted PCFC stacks. 

Oct 9, 2017
10:30 AM
Room 1011, EB1

Dr. David Kofke
University at Buffalo

Among the three common phases of matter, the liquid is the most difficult to understand and predict, and accordingly has attracted much of the attention of the molecular modeling community. Nevertheless, crystals and gases are important too, and pose interesting problems of their own. The relative ease of their description opens up opportunities for first-principles calculations, with accuracy sometimes exceeding experiment. Such capabilities can support new high-throughput approaches to design of many engineered systems.

The virial equation of state provides the standard treatment for the gas phase, yet because of the difficulty in computing the virial coefficients its general utility is largely unexplored.  Can it, for example, provide a general location for the critical point?  What is its convergence behavior when applied to realistic systems? Mixtures are treated exactly in the virial equation, so what can we learn about mixture behavior from it? We show the considerable advances that have been made on these questions over the past decade.

The solid phase is described reasonably well with harmonic analysis, but when using conventional simulation methods this good starting point provides no assistance in making simulations faster or more efficient.  A new “mapped averaging” framework has remedied this problem by removing harmonic contributions to properties. Then, direct measurement of the remaining anharmonic contributions by molecular simulation can be accomplished without noise from the harmonic behavior, producing results of exquisite precision. This advance is demonstrated via first-principles calculation of the properties of metals, and iron in particular at the extreme conditions found at the Earth’s inner core.

Oct 16, 2017
10:30 AM
Room 1011, EB1

Dr. George Petekidis
University of Crete, Greece

I will present key microscopic mechanisms affecting the structure and particle dynamics when attractive interactions are added in a hard sphere glass.  Furthermore the effect of attractions in the macroscopic response of repulsive (hard-sphere) and attractive glasses during nonlinear rheology and yielding is studied by a combined experimental and computer simulation study [1, 2].

I mainly focus on the way such systems yield under the application of steady or oscillatory shear via start-up shear tests and large amplitude oscillatory shear, as well as on the mechanisms of structural reformation and related stress relaxation after shear cessation. I discuss the phenomenology of two-step yielding, widely observed experimentally, its relation with quiescent microscopic dynamics and the underlying mechanisms affecting the relevant length- and time-scales during shear.

Both experiments and Brownian Dynamics (BD) simulations show two peaks in stress versus strain during start-up shear tests with good qualitative agreement suggesting that Hydrodynamic Interactions are not crucially important at such highly concentrated systems. Structural analysis obtained from BD simulations confirms that the first yield is related to the breaking of the structure at the length scales smaller than attraction range while the second yield point is a consequence of cage deformation and breaking.

I will finally compare the internal relaxation and the linear viscoelastic properties of attractive glasses under shear with those of repulsive glasses [3], by Orthogonal Superposition Rheometry where a small amplitude oscillation probes a sheared attractive glass in the ortogonal direction.

[1] N. Koumakis, M. Laurati, S.U. Egelhaaf, J. F. Brady and G. Petekidis, Phys Rev. Lett. 108, 098303 (2012)

[2] N. Koumakis, J. F. Brady and G. Petekidis Phys. Rev. Lett. 110, 178301 (2013)

[3] A. R. Jacob, A. S. Poulos, S. Kim, J. Vermant and G. Petekidis Phys. Rev. Lett. 115, 218301, (2015)

Oct 23, 2017
10:30 AM
Duke Energy Hall
James B. Hunt Jr. Library

Undergraduate Student Award

Future Leaders in Chemical Engineering is a one and one-half day, all-expense paid research symposium at NC State University recognizing the top undergraduate researchers in chemical engineering in the United States. Chemical engineering researchers (and those in related fields) who are within two years of graduating are eligible to apply.

Awardees will receive a plaque and present their research at a research symposium held October 23, 2017 on Centennial Campus at NC State University in Raleigh, NC. The symposium will also include information about applying to graduate school and fellowships. Students must be present to be eligible.

Nov 6, 2017
10:30 AM
Room 1011, EB1
Dr. Abraham Stroock
Cornell University

To begin, I will introduce two contexts to motivate fundamental physical questions about the thermodynamics and transport phenomena of water interacting with nanostructured materials: first, the evaporation-driven flow – transpiration – of water from the soil, through plants and into the atmosphere, and its connections to draught response; and, second, the nucleation of condensation and freezing by aerosol particles in the atmosphere, and its connections to cloud formation and atmospheric modeling.

Starting from the context of transpiration, I will use experiments in synthetic mimics of the vascular structure of plants to address questions about the breakdown of continuum behavior of liquids in nano-scale confinement, a much-debated topic over the past several decades. In particular, I will use a variety of measurements with a series of liquids to show that continuum thermodynamics and dynamics hold quantitatively in pores that are just 5-10 molecular diameters wide, if account is taken of a monolayer of immobilized molecules. In the context of aerosol-mediated nucleation ice from vapor, I will revisit a long history of measurements that have eluded theoretical explanation.

Using experiments with well-characterized synthetic substrates, I will provide strong evidence that freezing on insoluble aerosols proceeds in a two-step process – following the Ostwald step rule – with condensation of a supercooled liquid that subsequently freezes. Importantly, when we account for capillary condensation in nanoscale pore structure, our results provide a coherent structure-property relationship for aerosol-mediated freezing across an important range of conditions found in the atmosphere. I will conclude with perspectives on the translation of these insights and experimental methods toward tools for environmental measurements and for material design in applications for heat transfer and the management of freezing.

Nov 13, 2017
10:30 AM
Room 1011, EB1
Dr. Frank Gupton
Virginia Commonwealth University

Access to global public healthcare is impacted by many technical, economic, and social factors. It is widely recognized that the resources required to deliver and improve global public health are currently constrained.  A powerful way to increase access is to lower the cost of products and services that have already proven to be effective.  Currently, the cost of producing a wide range of pharmaceutical products is higher than it needs to be. The mission of Medicines for All (M4All) is to transform active pharmaceutical ingredient (API) processes in order to reduce medication cost and improve patient access.  To fulfil this objective, M4ALL has developed a set of core principles for API process development, which are derived from fundamental elements of process intensification that are commonly known but often neglected. These principles have been applied to several global health drugs yielding dramatic improvements in chemical efficiency. The development of novel heterogeneous cross- coupling that support this effort will also be presented.

Nov 27, 2017
10:30 AM
Room 1011, EB1
Dr. Aaron Anselmo
University of North Carolina, Chapel Hill

The clinical translation of therapeutics, both synthetic and biological, is often limited by their poor biological performance. While synthetic delivery systems (e.g. nanoparticles) are well-suited for therapeutic loading and controlled release, they struggle to navigate through the circulatory system, target specific tissues, and breach biological barriers as effectively as natural cells. Therapies utilizing natural cells benefit from the ability of cells to perform complex biological functions, however, these therapies lack the controlled release advantages of synthetic systems. Through understanding cell-material interactions, I have developed approaches to interface cells and synthetic materials that take advantage of the respective strengths of both the cells and the materials. First, I will discuss a strategy known as “cellular hitchhiking”, which involves the attachment of polymeric particles to the surface of circulatory cells so as to transfer innate circulatory (e.g. erythrocyte’s long circulation) and targeting abilities (e.g. leukocyte’s inflammation targeting) from cell to particle. The second part of my talk focuses on modifying therapeutic cells with synthetic polymers to improve the delivery of cell-therapeutics for enhanced host integration and function; specifically, improving the delivery of probiotics to the microbiome. The final part of my talk brings these two ideas together and leverages my fundamental findings of cell-material interactions to highlight the design, synthesis, and application of a synthetic cell, specifically a synthetic platelet capable of performing hemostasis.