Condensed Matter Physics Seminars

Condensed Matter and Biophysics Seminars and Nano@Wayne Seminars.

Condensed Matter seminars are held Fridays at 2:30 PM in Room 245 of the Physics Research Building.

Nano@Wayne seminars are held Tuesdays at 2:30 PM in the Welcome Center Auditorium unless otherwise noted.

Consult the schedule below to see which seminar is being held on a particular day.

Fall 2017 ; organizer Prof. Alex Matos Abiague, amatos@wayne.edu


November 3 

Speaker: Prof. Andrei Slavin, Oakland University

Title: Current-induced THz-frequency dynamics in dielectric antiferromagnets

Abstract:

Antiferromagnetic (AFM) materials have natural resonance frequencies in the sub-THz to THz  frequency range. Thus, it is tempting to use antiferromagnets as active layers in THz-frequency spin-torque nano-oscillators (STNOs) [1]. However, a familiar mechanism of spin-transfer torque (STT) damping compensation used in ferromagnetic (FM) STNOs [2] does not work for the AFM materials. In the AFM two magnetic sublattices are aligned anti-parallel to each other, so, when the STT compensates damping in one of the sublattices,  it increases the damping in the other sublattice, resulting in a zero net effect.  At the same time, the STT can cause a lattice instability in an AFM. For example, it has been shown in [3], that the STT can lead to the reorientation of the order vector l in the AFM with cubic anisotropy.

In this work we propose a novel approach to the excitation of oscillations in AFM materials. In the framework of this approach the STT is used to change the effective energy landscape of the AFM. We show theoretically, that in a bi-axial AFM (such as NiO [4]) the magnetic lattice can lose its stability under the action of STT, which results in a self-sustained precession of the order vector l of the AFM. We found that for NiO the lowest threshold of the self-sustained oscillations occurs for the STT directed along the hard axis of a single crystal NiO. The threshold of generation in this case is determined by the weak easy plane anisotropy (Ha1≈ 380 Oe in NiO) of the bi-axial AFM, and not by the Gilbert damping of the AFM. Above the generation threshold the AFM order vector l starts to precess in the AFM easy plane with the frequency defined by the magnitude of the STT and by the Gilbert damping in the AFM, see Fig. 2. The threshold of the self-sustained oscillations for the case of the STT directed  along  the easy axis of the AFM  in several orders of magnitude higher, than in the case when the STT is directed along the AFM hard axis.

[1] R. Khymyn, I. Lisenkov, V. S. Tiberkevich, B. A. Ivanov and A. N. Slavin,  Sci. Rep. 7, 43705 (2017).

[2] A. Slavin and V. Tiberkevich, IEEE Trans. on Magnetics  45, 1875 (2009).

[3] E. V. Gomonai and V. M. Loktev,  Low Temp. Phys. 34, 198 (2008).

[4] A.J. Sievers and M. Tinkham, Phys. Rev. 129, 1566 (1963).

 

October 13 

Speaker: Prof. Johannes Pollanen, Michigan State University

Title: Creating and controlling electronic quantum matter … one electron at a time

Abstract:

Creating and controlling novel quantum states of matter is at the forefront of modern condensed matter physics. Our research group, the Laboratory for Hybrid Quantum Systems (LHQS), is focused on creating and discovering electronic quantum states of matter in low-dimensional electron systems and controlling tailor-made quantum circuits. In our experiments we put together quantum materials and devices with fundamentally different, but complementary, properties to create hybrid systems that exhibit altogether new physical phenomena or capabilities.

I will discuss our recent invention of hybrid devices coupling high frequency microwaves to two-dimensional electron systems and superconducting quantum bits (qubits). I will also describe our work on a unique low-dimensional hybrid system composed of an ensemble of electrons trapped in two-dimensions above the free surface of a thin film of superfluid helium and coupled to nano-fabricated electric lattices on the substrate underneath the helium.

 

September 22 

Speaker: Prof. Boris I. Yakobson, Rice University

Title: Defects in 2D materials: dislocations, grain boundaries, physical properties

Abstract:

It is of great interest and importance for materials design to uncover, through computational and theoretical modeling, the following relationships: {basic atomic interactions à structure/morphology (including defects) à functionality (including electronics)}. We will discuss recent examples from low-dimensional materials, where we seem to achieve satisfactory degree of understanding, mostly focusing on nucleation and islands shapes of graphene, h-BN, metal dichalcogenides MX2 [1], grain boundaries and dislocations [2] including the nanoscale electromagnetism of the latter, heterojunctions [3], if time permits—catalysis [4].

[1] V. Artyukhov et al. Phys. Rev. Lett. 114, 115502 (2015); Artyukhov - Z. Hu et al. Nano Lett. 16, 3696 (2016).

[2] X. Zou et al. Nano Lett. 15, 3495 (2015); A. Aziz et al. Nature Comm. 5, 4867 (2014); Zou et al. Small, 11, 4503 (2015); F. Xu et al. Nano Lett. 16, 3439 (2016).

[3] Y. Gong et al. Nature Mater. 13, 1135 (2014); H. Yu, A. Kutana, et al. Nano Lett. 16, 5032 (2016).

[4] Y. Liu et al. Phys. Rev. Lett. 113, 028304 (2014); X. Zou et al. Acc. Chem. Res. 48, 73 (2015); Nature Energy, 6, 17132 (2017).

 

 


Winter 2017 ; organizer Prof. Takeshi Sakamoto, Sakamoto@wayne.edu


March 24  Prof. Dawen Cai; Cell & Developmental Bioloogy, The University of Michigan

                 Title: Mapping neural circuits at the single cell and single synapse resolution in the mouse brain

Abstract: Neural circuits, composed of intercellular connected neurons with distinct properties lay the physical foundation of any brain function. Identifying subtype and connections of individual neurons in a circuit is the key to understand how information is processed and propagated in the brain. In order to obtain a detailed wiring diagram between neurons, we optimized and developed a series of multispectral labeling, super-resolution imaging and computational tools to allow neuronal morphology and connectivity features being directly measured at the single cell and single synapse resolution in a densely labeled mouse brain. We developed the second generation Brainbow reagents to densely label specific subtypes of neurons in rich colors and developed processing protocols to allow super-resolution 3D imaging at tens of nanometer spatial resolution by Expansion Microscopy. Using our user-guided tracing software, nTracer, we obtained the wiring diagram and quantified the divergent or convergent connection patterns of VIP+ neurons in the suprachiasmatic nucleus (SCN) or PV+ neurons in the hippocampal CA1, respectively. Designed to be carried out with standard surgical, imaging and computational instrumentations, our comprehensive circuit mapping tool set will allow high-resolution, high-throughput neural circuit mapping in a regular neuroscience laboratory.

 

March 31  Prof. Colin Wu; Department of Chemistry, Oakland University

                Title: DNA Helicases: Machines on Genes

Abstract: Guanine rich nucleic acid sequences can form G-quadruplex (G4) structures that impede DNA metabolic pathways.  The FANCJ helicase plays a crucial role in safeguarding the integrity of the human genome by promoting DNA replication through G4-forming regions.  Here, we show that FANCJ is targeted to G-quadruplexes although direct interaction with a G4 alone does not support its unfolding.  Instead, this reaction requires ssDNA binding and ATP hydrolysis.  The unfolded G-quadruplex can quickly reform, and FANCJ undergoes repeated rounds of G4 processing while bound to the DNA.  This action would allow FANCJ to clear the substrate for a DNA polymerase to bypass replication-stalling G4s. Our findings suggest the mechanism by which FANCJ recognizes G4-containing DNA, mediates stepwise G4 unfolding, and partitions its role between supporting DNA repair as well as facilitating the progression of the replication fork through G-rich sequences.

 

April 7      Prof. Yaoyun Shi; Department of Electrical Engineering and Computer Science,

                                               The University of Michigan.

                 Title: General Randomness Amplification with Non-signaling Security

Abstract: Highly unpredictable events appear to be abundant in life. However, when modeled rigorously, their existence in nature is far from evident. In fact, the world can be deterministic while at the same time the predictions of quantum mechanics are consistent with observations. Assuming that randomness does exist but only in a weak form, could highly random events be possible? This fundamental question was first raised by Colbeck and Renner (Nature Physics, 8:450{453, 2012). In this work, we answer this question positively, without the various restrictions assumed in the previous works. More precisely, our protocol uses quantum devices, a single weak randomness source quantified by a general notion of non-signaling min-entropy, tolerates a constant amount of device imperfection, and the security is against an all-powerful non-signaling adversary. Unlike the previous works proving non-signaling security, our result does not rely on any structural restrictions or independence assumptions. Thus it implies a stronger interpretation of the dichotomy statement put forward by Gallego et al. (Nature Communications, 4:2654, 2013):either our world is fully deterministic or there exist in nature events that are fully random."

 

April 14    Prof. Wei Zhang; Department of Physics, Oakland University

                Title: Energy-efficient electronics concepts enabled by spin-orbital effects

Abstract: New concepts for low-power, high-capability electronic devices are urgently required due to the rapid-reaching fundamental limits of conventional charge-based electronic devices. Spin-orbitronics and spin-caloritronics, aiming at harnessing spin-orbit coupling in condensed matter for electronic computing, offer promising approach towards future energy-efficient electronics. The spin-Hall effect, existing in most d-orbital metals, is one of the most important enabling phenomena in spin-orbitronics, and has attracted increasing research interests in both fundamentals and applications. I will introduce the concept of spin-Hall effect, followed by microwave electric approaches that allow for precise quantification of such an effect. I will then talk about relevant materials and articulate how such an effect can be influenced by introducing magnetic ordering and by studying series of antiferromagnetic materials. Finally, I will demonstrate how such an effect could serve as a useful technology in enabling other spintronic applications such as driving insulating nanomagnets, transforming spin current in antiferromagnets, and manipulating magnetic skyrmions.  

 

April 21    Prof. Kevin Wood; Department of Physics, The University of Michigan

Title:  Population density modulates antibiotic efficacy, treatment bistability, and the evolution of resistance in bacteria

Abstract:  The inoculum effect (IE) is an increase in the minimum inhibitory concentration (MIC) of an antibiotic as a function of the initial size of a microbial population. However, classical measurements of the IE involve growing populations, and population density changes by many orders of magnitude on the timescale of the experiment. Therefore, the functional relationship between population density and antibiotic inhibition is generally not known, leaving many questions about the impact of the IE on different treatment strategies unanswered. In this talk, I will discuss our recent work to address these questions by measuring real-time per capita growth of Enterococcus faecalis populations at fixed population densities using multiplexed computer-automated culture devices. We show that density-dependent growth inhibition is pervasive for commonly used antibiotics, with some drugs showing increased inhibition and others decreased inhibition at high densities. For several drugs, the density dependence is mediated by changes in extracellular pH, a community-level phenomenon not previously linked with the IE. Using a simple mathematical model, we demonstrate how this density dependence can modulate population dynamics in constant drug environments and lead to bistable treatment outcomes in a pharmacological model of antibiotic treatment.  Finally, I will discuss our ongoing work to understand the effects of density fluctuations on the evolution of drug resistance.

 


 

Fall 2015

     Organizer: Prof. Kelly, cvkelly@wayne.edu


September 11

      Barber Interdisplinary Summer Research Program Final Presentations

September 18

      Speaker: Pavithra Pathirathna, Department of Chemistry, Wayne State University

Title: Fast scan cyclic voltammetry of metals at carbon-fiber microelectrodes

Abstract: The behavior of trace metals is the environment is controlled by speciation. For example, metal complexation with organic/inorganic ligands reduces the impact of trace metals. On the flip side, trace metals are mobilized during dynamic environmental events such as storms, which increases their toxicity.  Rapid, real-time characterization of metal complexation would allow a better understanding of metals in the environment. We recently described an ultrafast, Hg-free method to detect copper and lead at carbon fiber microlectrodes (CFMs) using fast scan cyclic voltammetry (FSCV). Moreover, we explored the surface adsorption as the underlying mechanism of our fast FSCV signal. We study copper binding with a model set of ligands illustrating a wide spectrum of thermodynamic equilibrium constants expected to be found in natural waters. We identify mathematical relationships between thermodynamic equilibrium constants (K) for copper complexation and the FSCV signal. We utilize fast scan controlled adsorption voltammetry (FSCAV) to quantify ambient Cu2+ levels in real environmental samples and develop a model that relates the FSCV signal to free copper in solution to the solution K. We, hence, showcase the power of FSCV as a speciation sensor.

 

October 23

      Speaker: Dr. Mai Lam, Department of Biomedical Engineering, Wayne State University


Title: Creating translatable techniques for repairing tissues using stem cells and biomaterials

Abstract: Disease, injury and aging create a need for methods for repair or replacement of damaged tissues as donor tissue sources are perpetually lacking. Tissue engineering and regenerative medicine have great potential to fill this need, though present techniques result in little if any functional recovery. Our lab aims to meet this need by modeling our reparative techniques in the lab after physiological cues already optimized for tissue creation in the body. We use tools such stem cells and biomaterials to repair damaged tissues and for engineering new tissue replacements. Our current work includes developing new treatments for cardiac tissue repair following heart attack and creating engineered knee meniscus tissue. Our main goal is to improve translation of tissue engineering and regenerative medicine techniques to the patient.

Bio: Dr. Lam specializes in tissue engineering, regenerative medicine, biomaterials, and stem cell therapy. She received her bachelor's degree in Materials Science & Engineering, and master's and doctorate degrees in Biomedical Engineering from the University of Michigan- Ann Arbor. She completed her postdoctoral training at Stanford University in the Stem Cell and Cardiovascular Institutes where she used her engineering background to help improve stem cell therapy using biomaterials

 

October 30

      Speaker: Dr. Greg van Anders, Department of Chemical Engineering, University of Michigan

      http://dazzy.engin.umich.edu/~grva/

Title: Engineering Emergence in Soft Matter with Digital Alchemy

Abstract: Colloids are a broad class of soft materials that every person, starting with the milk we receive as newborns, has a long history of experience with. Despite their familiarity, colloids exhibit a number of interesting and unexpected phenomena that we are still working to understand, and touch on basic questions in condensed matter physics, statistical mechanics, and emergence. First, I will discuss how emergent "shape entropy" effects order colloidal matter. Then, I will discuss how we can rationally engineer colloid shape to get target structures that emerge from the collective properties of dense colloidal suspensions, using first principles of statistical mechanics with "digital alchemy".

 

November 6

      Speakers: Anwesha Sarkar and Bhim ChamlagainDepartment of Physics, Wayne State University

Speaker: Bhim Chamlagain

Title: Substrate and dielectric engineering in 2D electronics Abstract: Substrate plays an important role in the performance of field-effect transistors (FETs) with two-dimensional transition metal dichalcogenide (TMD) channels. In this work, we systematically study the transport properties of few-layer MoS2 FETs consistently fabricated on substrates SiO2, Al2O3, SiO2 modified by octadecyltrimethoxysilane (OTMS) self-assembled monolayers (SAMs) and hexagonal boron nitride (hBN). Hall bar devices were designed on SiO2 and hBN to measure carrier density. Standard four-probe electrical transport measurement and hall bar measurement were carried out at temperatures ranging from 77 K to room temperature to understand the scattering mechanism and estimate the drift mobility. By comparing field-effect and Hall mobilities, we demonstrate that the intrinsic drift mobility of multiplayer MoS2 in the high carrier density metallic region is limited to ~ 40 cm2/Vs at room temperature, independent of substrate and sample thickness. While the optical-phonon scattering remains dominant down to below ~ 100 K in MoS2 devices on h-BN, extrinsic scattering mechanisms from SiO2 start to degrade the carrier mobility of MoS2 below ~ 200 K. We also introduce engineering of 2D dielectric to enhance the performance of TMDs based FET. Brief discussion of engineering of 2D dielectric and fabrication of MoS2 FET will discuss.

Speaker: Anwesha Sarkar

Title: Interaction Forces and Reaction Kinetics of Ligand-Cell Receptors Systems Using Atomic Force Microscopy Abstract: Atomic Force Microscopy (AFM) provides superior imaging resolution and the ability to measure forces at the nanoscale. It is an important tool for studying a wide range of bio-molecular samples from proteins, DNA to living cells. We developed AFM measurement procedures to measure protein interactions on live cells at the single molecular level. These measurements can be interpreted by using proper statistical approaches and can yield important parameters about ligand-receptor interactions on live cells. However, the standard theory for analyzing rupture force data does not fit the experimental rupture force histograms. Most of the experimental measurements of rupture force data generate a probability distribution function (pdf) with a high force tail. We show that this unexpected high force tail can be attributed to multiple attachments and heterogeneous bonding by studying a model system, biotin-avidin. We have applied our methodology to the medically relevant system of discoidin domain receptors (DDR) on live cells and their interaction with their ligand, collagen.

 

November 13

      Speaker: Dr. Mohammad Mehrmohammadi, Department of Biomedical Engineering, Wayne State University

       https://engineering.wayne.edu/profile/mohammad.mehrmohammadi/

Title: New Developments in Medical Ultrasound: From Cellular and Molecular Theranostics to Tissue Elastography

 

November 20

      Undergraduate Research Fair (all day)

      Details to be posted here when available: https://waynestatesps.wordpress.com/

 

December 4

      Speaker: Dr. Jeff Potoff, Department of Chemical Engineering and Materials Science, Wayne State University

      http://potoff1.eng.wayne.edu/

Title: "Understanding Membrane Fusion at the Atomic Level: Insights from Molecular Dynamics Simulations"

Abstract: Membrane fusion is a critical step in a variety of cellular functions, including exocytosis, hormone secretion, drug delivery and neurotransmitter release.  Ca2+ has by hypothesized to play a key role in triggering membrane fusion, but the specific mechanism is still unclear. In this talk, I discuss the development and validation of molecular mechanics models also known as "force fields" for phospholipids.  These models are used in molecular dynamics simulations to show how the influx of Ca2+ enhances fusion between apposed membranes.  Simulations reveal the formation of a Ca2+-phospholipid "anhydrous complex" between apposed bilayers, whereas similar calculations performed with Na+ display only complexation between neighboring lipids within the same bilayer. The binding of Ca2+ to apposed phospholipids brings large regions of the bilayers into close contact (<4 Å), displacing water from phospholipid head groups in the process and creating regions of local dehydration.  The effect of bilayer spacing, lipid head group, and Na+ and Ca2+ on water structure is discussed.  Simulations are also used to elucidate how Ca2+ binding to the membrane fusion protein snaptotagamin (SYT) lowers free energy barriers, allowing SYT to insert into the lipid bilayer.

 

December 11

      Speakers: Abir Maarouf and Utsab ShresthaDepartment of Physics, Wayne State University

Speaker: Abir Maarouf
Title: Polarized Localization Microscopy Detects Nanoscale Membrane Curvature and Reveal Protein and Lipid Dynamics
Abstract: The dynamical lateral sorting of membrane lipids and proteins in conjunction with membrane curvature, are postulated to provide a physical basis to initiate and regulate many complex cellular processes such as endocytosis/exocytosis. However, many hypotheses concerning these processes are unanswered because of the diffraction-limited resolution of most optical techniques (~200 nm), and the inability to observe nanoscale curvature with super-resolution microscopy. To overcome these experimental limitations, we developed Polarized Localization Microscopy (PLM). PLM is a super-resolution optical imaging technique that enables the detection of nanoscale membrane curvature and correlating membrane topology to single-molecule dynamics and molecular sorting. PLM combines the advantages of polarized total internal reflection fluorescence microscopy and fluorescence localization microscopy to reveal single-fluorophore locations and membrane orientation without reducing localization precision by point spread function manipulation. PLM was used to resolve nanoscale membrane curvature in lipid bilayers with continuous planar and curved regions with radii of curvature as small as 20 nm. Further, time-dependent curvature generation and bud growth induced by cholera toxin subunit B was detected, revealing a possible mechanism of cholera immobilization and cellular internalization. PLM will provide fundamental insights of curvature sensitive biological mechanisms that have been previously intractable, including neuronal communication, immunological signaling, and viral infections.

Speaker: Utsab Shrestha 
Title: Dynamics of Protein from Deep-sea Hyperthermophile Detected by Quasi-elastic Neutron Scattering
Abstract: Deep-sea microorganisms can adapt to extreme conditions such as high temperature and pressure. What makes these organisms survive and reproduce in such critical conditions remains an open question. In this work, we use quasi-elastic neutron scattering (QENS) to investigate the dynamic behavior of inorganic pyrophosphatase (IPPase) from Thermococcus thioreducens that is found near the hydrothermal vents deep under the sea, where the pressure is ~1000 bar (100 MPa) . Two spectrometers were used to investigate the β-relaxation dynamics of IPPase over a wide temperature range in time ranges from 2 to 25 ps, and from 100 ps to 2 ns within protein secondary structure. Our results reveal that, under a pressure of 100 MPa, close to that of the native environment deep under the sea, IPPase displays much faster relaxation dynamics than a mesophilic model protein, hen egg white lysozyme (HEWL) [1], opposite to what we observed previously under ambient pressure [2]. This contradictory observation implies that high pressure affects the dynamical properties of proteins by distorting their energy landscapes. Accordingly, we derived a schematic denaturation phase diagram that can be used as a general picture to understand the effects of pressure on protein dynamics and activities.
[1] Shrestha et al (2015). Proc Natl Acad Sci USA 112(45):13886-13891 
[2] Chu et al (2012), J Phys Chem B 116(33): 9917-9921.
 

Winter 2015


February 6

Speaker: Dr. Loren Schwiebert, Department of Computer Science, Wayne State University

Title: Implementing and Optimizing Algorithms for GPUs

Abstract: In this talk, I will describe some of the features of the Graphics Processing Unit (GPU), also known as a graphics card or gaming card, that make it an attractive option for parallelizing some programs. As part of this talk, I will review the features of the GPU. In addition, I will present some of the challenges that must be overcome to get good performance from the GPU. Although GPU programming is typically done in C or C++, it is possible to write GPU programs in Fortran. Some simple programming examples will be given to illustrate these concepts. Basic knowledge of programming in a high level language is sufficient to follow the examples in the talk. Finally, I will present some results of our research on porting a 2D Phase-Field Crystal model to the GPU.

 

February 20

Speaker: Dr. Mohammad R.N. Avanaki, Department of Biomedical Engineering, Wayne State University

Title: High-Resolution Imaging Modalities in Biomedical Research

Abstract: Optical imaging is becoming the method of choice for applications where high-resolution images are required non-invasively. Optical imaging technologies are capable of representing the internal structure of a sample across a range of spatial scales, and that has made them favored tools in biomedical research studies.

I will divide my talk into two parts:

In the first part of this talk, I will explain the principle of one of the high-resolution optical imaging modalities, optical coherence tomography (OCT), and how it can help in biomedical studies. Just like every other imaging system, OCT systems have limitations. I will discuss three separate limitations. First, there is speckle noise due to the use of a broadband illumination source. Second, there is intensity decay due to tissue absorption. And finally, there are aberrations and blurriness due to point spread function (PSF) distortion. I will then discuss a number of algorithms devised to reduce the impact of these limitations. Moreover, I will explain how by using the enhanced Huygens-Fresnel (eHF) light propagation theorem, we can extract optical properties from a specific region in an OCT image. This ability is important in automating disease diagnostics and adding more data to the morphological information that the OCT has already provided. As concrete evidence, the results of using this method to differentiate basaloid and healthy tissues will also be demonstrated.

In the second part of this talk, I will look into another high-resolution imaging modality, photoacoustic tomography. As opposed to OCT, where the attenuation of the backscattered light reaching the detector limits the penetration depth, photoacoustic tomography uses optical excitation and acoustic detection, and dramatically increases the penetration depth. I will explain how we developed a functional connectivity photoacoustic tomography (fcPAT) system, which allowed, for the first time, noninvasive imaging of resting-state functional connectivity (RSFC) in the mouse brain, with a large field of view and high spatial resolution. This neuroimaging technique can easily be applied to mice, the most widely used model species for human brain disease studies. I will demonstrate results that show fcPAT is a promising, noninvasive technique for functional imaging of the mouse brain. Due to the low cost of fcPAT compared with current functional imaging modalities such as functional Magnetic Resonance Imaging (fMRI), we expect that fcPAT will enable many laboratories that previously did not consider functional neuroimaging to contribute further to ongoing studies of brain disease.

At the end, I will give a brief overview about the ongoing projects in my lab and my future directions, pointing out the areas for collaboration.

 

March 27

Speaker: Laura Gunther, Department of Physics and Astronomy, Wayne State University

Title: The Regulation of Actomyosin ATPase in Cardiac Muscle by the N-Terminal Extension of Cardiac Troponin I and T

Abstract: Contraction of cardiac muscle is the basis of heart function. Heart failure, i.e., weakened contraction of cardiac muscle is the most common cause of morbidity and mortality of heart diseases. Cardiac muscle contraction is regulated by calcium via the function of troponin, a protein complex associated with the myofilaments in muscle cells. The cardiac troponin subunits T (cTnT) and I (cTnI) have unique N-terminal extensions that can be selectively removed by restrictive proteolysis during cardiac adaptation to physiological and pathological stresses, indicating a role of these proteins in modulating cardiac contraction. This study aims to understand the effects of the N-terminal extensions of cTnT and cTnI on the actomyosin ATPase kinetics in response to Ca2+ signal, which is the foundation of cardiac muscle power generation. The ATP binding and ADP dissociation rates of the actomyosin ATPase of cardiac myofibrils containing cTnI lacking the N-terminal extension (cTnI-ND) have been measured using stopped flowmetry with mant-dATP and mant-dADP, respectively. The results showed that the second order mant-dATP binding rate for cTnI-ND myofibrils was three-fold as fast as that of wild type myofibrils. Moreover, the ADP dissociation rate of cTnI-ND myofibrils was positively dependent on calcium concentrations, while the wild type controls were not significantly affected. We have also measured the ADP dissociation and Pi dissociation rates of the actomyosin ATPase of cardiac myofibrils containing cTnT lacking the N-terminal extension (cTnT-ND) using stopped flowmetry with mant-dADP and phosphate binding protein. The results showed that the rate of phosphate release from myofibrils is approximately that of the steady state ATPase rate suggesting that phosphate release is rate-limiting for cTnT-ND and WT myofibrils. ADP dissociation experiments showed that it is not rate limiting. cTnT-ND ADP release does not appear to be significantly different from that of WT, however it is consistently lower than that on WT. Further studies will be performed to determine the other steps of the ATPase cycle in cTnI-ND and cTnT- ND myofibrils. The anticipated results will determine the rate-limiting steps of actomyosin ATPase cycle that are regulated by the N-terminal extensions of cTnI and cTnT.

Completion of the proposed study will lead to new understanding of the function of the N-terminal segments of cTnI and cTnT as well as troponin-tropomyosin-mediated regulation of cardiac muscle contraction, which in turn, may provide useful information for the development of new treatment for heart failure.

 

April 10

Speaker: Dr. Eugene Kim, Department of Physics, University of Windsor

Title: Characterizing Entanglement in Superconductors

Abstract: Entanglement expresses the nonlocality inherent in quantum mechanics, in which states of a composite system cannot be written as a product of states of the individual subsystems; described by Einstein as 'spooky', this property was appreciated by Schrodinger to be 'the characteristic trait of quantum mechanics'. In many-body systems entanglement between the constituent particles gives rise to phases with highly nontrivial and, at times, even exotic properties.

The traditional way of characterizing many-body systems has been by the consequences of entanglement, namely with local order parameters and correlation functions of local operators. Recently, however, it has been appreciated that it pays to go back to the source, and study the entanglement directly; this is done by cutting the system into (typically) two pieces and seeing how the pieces 'talk to each other'. A variety of many-body systems have been studied in this way, shedding new light/insights on their properties.

In this talk, I will describe our recent work to characterize entanglement in superconductors; in particular, I will describe how this allows one to probe a subtle form of order in certain classes of superconductors, namely topological order. With time permitting, I will discuss possibilities of experimentally measuring entanglement in these systems.

 

April 17

Speaker: Dr. Kai Sun, Department of Physics, University of Michigan

Title: Topological Kondo insulators and Topological Crystalline Kondo Insulators

Abstract: In the study of strongly-correlated insulators, a long-standing puzzle remained open for over 40 years. Some Kondo insulators (or mixed-valent insulators) display strange electrical transport that cannot be understood if one assumes that it is governed by the three-dimensional bulk. In this talk, I show that some 3D Kondo insulators have the right ingredients to be topological insulators, which we called "topological Kondo insulators". For a topological Kondo insulator, the low-temperature transport is dominated by the 2D surface rather than the 3D bulk, because the bulk of this material is an insulator while its surface is a topologically-protected 2D metal. This theoretical picture offers a natural explanation for the long-standing puzzle mentioned above. In addition, we also find that Kondo insulators can support another type of nontrivial topological structure protected by lattice symmetries, which we called "topological crystalline Kondo insulators". In particular, we predict that SmB6 is both a topological Kondo insulator and a topological crystalline Kondo insulator and I will also discuss recent experiments, which reveal the surface states in SmB6.

 

April 24

Speaker: Sharmine Alam, Department of Physics and Astronomy, Wayne State University

Title: Dynamics of nanoparticles in semidilute solution of spheres/polymers

Abstract: We investigated the dynamics of gold nanospheres (AuNS) and nanorods (AuNR) in synthetic polymer (polyethylene glycol) and biopolymer (bovine serum albumin) solutions. The variables are particle size and shape, polymer volume fraction, etc. The fluctuation correlation spectroscopy (FCS) was used to measure the translational (DT) and rotational diffusion (DR) of gold nanoparticles. Comparison will be made for the nano-viscosities at different length scales. The systemic investigation of the rigid particles (AuNR and AuNS) in a semidilute concentration of other particles (ludox) with a geometrical model of 'caging' will be presented.

 

Fall 2014


October 3

Speaker: Dr. Hengguang Li, Department of Mathematics, Wayne State University

Title: Some mathematical aspects of the finite element method

Abstract: We will review the finite element formulation in a general mathematical setting. In particular, we will show how it can be improved to effectively approximate practical problems with singularities. Applications in physics and engineering will be discussed.

 

October 10

Speakers: Gursharan Sandhu and Hsun-Jen Chuang, Department of Physics and Astronomy, Wayne State University

1.
Title: High-resolution quantitative whole-breast ultrasound: In vivo application using frequency-domain waveform tomography (by Gursharan Sandhu)

Abstract: Ultrasound tomography is a promising modality for breast imaging. Many current ultrasound tomography imaging algorithms are based on ray theory and assume a homogeneous background which is inaccurate for complex heterogeneous regions. They fail when the size of lesions are about the same size or smaller than the wavelength of ultrasound used. Therefore, in order to accurately image small lesions, wave theory must be used in ultrasound imaging algorithms to properly handle the heterogeneous nature of breast tissue and the diffraction effects that it induces. Using frequency-domain ultrasound waveform tomography, we present sound speed reconstructions of both phantom and in vivo patient data sets. The improvements in contrast and resolution made upon the previous ray-based methods are dramatic. While it was difficult to differentiate a high sound speed tumor from bulk parenchyma using ray-based methods, waveform tomography improves the shape and margins of a tumor to easily differentiate it from the bulk breast tissue. Waveform tomography is capable of finding lesions in very dense tissues, a difficult environment for existing ultrasound algorithms as well as mammography. By comparing the sound speed images produced by waveform tomography to MRI, we see that the complex structures in waveform tomography are consistent with those in MRI.

2.
Title: High performane WSe2 p- and n-Type Field Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts (by Hsun-Jen Chuang)

Abstract: We report the fabrication of both n-type and p-type WSe2 field effect transistors with hexagonal boron nitride passivated channels and ionic-liquid (IL)-gated graphene contacts. Our transport measurements reveal intrinsic channel properties including a metal-insulator transition at a characteristic conductivity close to the quantum conductance e2/h, a high ON/OFF ratio of >107 at 170 K, and large electron and hole mobility of µ ≈ 200 cm2V-1s-1 at 160 K. Decreasing the temperature to 77 K increases mobility of electrons to ≈330 cm2V-1s-1 and that of holes to ≈270 cm2V-1s-1. We attribute our ability to observe the intrinsic, phonon limited conduction in both the electron and hole channels to the drastic reduction of the Schottky barriers between the channel and the graphene contact electrodes using IL gating. We elucidate this process by studying a Schottky diode consisting of a single graphene/WSe2 Schottky junction. Our results indicate the possibility to utilize chemically or electrostatically highly doped graphene for versatile, flexible and transparent low-resistance Ohmic contacts to a wide range of quasi-2D semiconductors.

 

November 14

Speaker: Dr. Vasyl Tyberkevych, Department of Physics, Oakland University

Title: Magnetic nano-dot arrays: Reconfigurable microwave meta-materials

Abstract: Two-dimensional arrays of magnetic nano-dots, mutually coupled by magnetodipolar interaction, represent a novel class of artificial meta-materials operating in the GHz frequency range. Microwave properties of collective magnetic excitations (spin waves) in such arrays depend both on the shape and material parameters of individual nano-dots and on the geometry of the array's lattice, and can be tailored to the order. An interesting property of magnetic arrays is existence of several stable magnetic configurations, characterized by different orientations of static magnetic moments of nano-dots. In this presentation I will demonstrate that (i) the properties of collective spin waves strongly depend on the array's magnetic configuration and (ii) it is possible to controllably switch an array from one magnetic configuration to another, thus creating dynamically reconfigurable microwave meta-material.

 

November 21

Speaker: Dr. Ronald Tackett, Department of Physics, Kettering University

Title: Magnetic fluid hyperthermia treatment of cancer using dextran-coated Fe3O4 nanoparticles

Abstract: Clinically applied in many forms (i.e. whole body, regional, or local) using many different methods (radiative, ultrasonic, magnetic) hyperthermia is reliant on the high heat-sensitivity of malignant neoplastic tissue when compared to that of normal human cells. Colloidal suspensions of magnetic nanoparticles (ferrofluids) have been proposed as mediators for magnetic fluid hyperthermia (MFH) in which the local heating of tumors is achieved through the application of small magnitude kHz-range alternating magnetic fields. These ferrofluids can be delivered to a tumor site via direct injection or targeted to the site through the use of tumor specific antibodies. Once inside the tumor, the nanoparticles are exposed to an alternating magnetic field causing heating via the relaxation of the particles via the Brownian and Néel mechanisms. In this presentation, the characterization of dextran-coated Fe3O4-based ferrofluids will be presented with respect to the frequency-dependence of their heating characteristics.

 

 

Winter 2014


February 21

Title: Spin-polarized polariton lasers and condensates
Speaker: Chih-Wei Lai, Department of Physics and Astronomy, Michigan State University  

Abstract:
Lasing in semiconductors is generally independent of the spins of carriers in the gain medium. In a few spin-controlled lasers, charge carriers in the cavity drive the laser action, while the spins of the carriers determine the polarization state of the radiation. Such lasers are one of the most promising outcomes of research in spin-dependent optoelectronics. In the field of spin-controlled semiconductor lasers, massive effort has been focused upon materials with long spin relaxation times (~ns). Because the spin imbalance is generally lost quickly, these devices are typically operated at cryogenic temperatures. In contrast, we demonstrate room-temperature spin-polarized ultrafast pulsed lasing in InGaAs quantum wells (~10 ps) embedded within a GaAs microcavity. The microcavity, consisting of thousands of atomic layers of semiconductors grown one-by-one, is similar to vertical-cavity surface-emitting lasers (VCSEL) used in optical communication. Unlike a VCSEL, the polariton laser studied here has nonlinear output and energy shifts owing to the mixing of the free-carrier polarization and cavity light field. At room temperature, we observe features resembling those in exciton-polariton condensates at cryogenic temperatures, including the spontaneous build-up of spatial coherence, macroscopic occupation, spin polarization, and spin texture. Below T~40K, we observe additional long-lived coherent exciton-polariton emissions. In contrast to a conventional laser, the present polariton laser shows characteristics that are affected by spin-dependent and Coulomb many-body interactions. Our results should stimulate activities to exploit spin-orbit interaction and many-body effects for fundamental studies of quantum light-matter fluids and developments of spin-dependent optoelectronic devices.

 

March 21

Xiaogang Liang, University of Michigan

Title: Nanomanufacturing of Emerging 2D Materials for Nanoelectronic Applications

   

 

Winter 2013



March 29, Condensed Matter/Biophysics Seminar This seminar will take place at 2:00 pm in Room 312.

Speaker: Dr. Arun Annatharam, Department of Biology, Wayne State University

Title: The molecular regulation of membrane curvature during vesicle fusion and content release

Abstract: Assays for real-time investigation of exocytosis typically measure what is released from the secretory vesicle.  From this inferences are made about the dynamics of membrane remodeling as fusion progresses from start to finish.  I have recently undertaken a different approach to investigate the fusion process, by focusing not primarily on the vesicle, but rather its partner in exocytosis – the plasma membrane.  We have been guided by the idea that biochemical interactions between the vesicle and plasma membranes before and during fusion, cause changes in membrane conformation.  To enable study of membrane conformation, a novel imaging technique was developed combining polarized excitation of an oriented membrane probe (diI) with Total Internal Reflection Fluorescence Microscopy (pTIRFM).  Because this technique measures changes in membrane conformation (or deformations) directly, its usefulness persists even after vesicle cargo reporter (catecholamine, or protein), is no longer present.  In this seminar, I will first describe how pTIRFM works.  I will then discuss how the technique might be applied to study deformations in the membrane occurring with fusion pore dilation, and how dilation may be regulated by the GTPase activity of a major protein for endocytosis -- dynamin.
 


Date: March 22, APS MEETING - NO SEMINAR


Date: March 15, SPRING BREAK - NO SEMINAR


Date: March 8, Condensed Matter/Biophysics Seminar

Speaker: Dr. Jianjun Bao, Department of Physics, Wayne State University

Title: The structure and function of TRIOBP: an actin-bundling protein implicated in cancer biology

Abstract: In this talk, I will discuss the work from our laboratory on the novel role of the guanine nucleotide exchange factor (GEF) trio binding protein (TRIOBP) in pancreatic cancer progression. In the first portion of the talk, I will focus on identifying the actin-binding domains in TRIOBP isoform 4 (TRIOBP-4). Previous in vitro study reveals that TRIOBP-4 forms uniquely dense actin bundles distinct from any other known actin cross-linkers. As the first step to define the actin-bundling mechanism by TRIOBP-4, I will present our work on how we identify its actin-binding domain by biochemical assays, biophysical and cell biological methods. In the second portion of my talk, I will discuss the potential role of TRIOBP in pancreatic cancer progression that has not been reported yet. I will cover our findings on TRIOBP expression in cancer cell lines, and how TRIOBP isoforms 4 and 5 affect cancer cell cytoskeleton structure and directed migration. Finally, I will discuss the possibility that TRIOBP regulates genomic stability in cancer cells.
 


Date: March 1, Condensed Matter/Biophysics Seminar

Speaker: Dr. Anish Tuteja, Department of Materials Science & Engineering, University of Michigan

Title: Designing Surfaces with Extreme Wettabilities

Abstract: In this talk I will discuss the theoretical and experimental work in my group on developing surfaces with extreme wettabilities, i.e. surfaces that are either completely wet by, or completely repel, polar and/or non-polar liquids. The first portion of the talk will cover the design of so called "superomniphobic surfaces" i.e. surfaces which repel all liquids. Designing and producing textured surfaces that can resist wetting by low surface tension liquids such as various oils or alcohols has been a significant challenge in materials science, and no examples of such surfaces exist in nature. As part of this work, I explain how re-entrant surface curvature,in addition to surface chemistry and roughness, can be used to design one of the first ever surfaces that causes virtually all liquids, including concentrated organic and inorganic acids, bases and solvents, as well as, viscoelastic polymer solutions to roll-off and bounce.

The second portion of my talk will cover the design of the first-ever reconfigurable membranes that, counter-intuitively, are both superhydrophilic (i.e., water contact angles  ~ 0 degree)and superoleophobic (i.e., oil contact angles > 150 degrees). This makes these porous surfaces ideal for gravity-based separation of oil and water as they allow the higher density liquid (water) to flow through while retaining the lower density liquid (oil). These fouling-resistant membranes can separate, for the first time, a range of different oil–water mixtures, including emulsions, in a single-unit operation, with > 99.9% separation efficiency, by using the difference in capillary forces acting on the oil and water phases. As the separation methodology is solely gravity-driven, it is expected to be one of the most energy-efficient technologies for oil-water separation.

Finally I will discuss some other areas of current and future research, including the development of ice-phobic coatings that offer one of the lowest adhesion strengths with ice that have ever been reported.
 

 

Date: February 22, Condensed Matter/Biophysics Seminar

Speaker: Dr. Yuejian Wang, Oakland University

Title: The application of high-pressure technique in condensed matter physics

Abstract: Pressure along with temperature and chemical composition defines the state of matter. High pressure could decrease the distance among atoms, shorten the chemical bonds, and distort the electron orbitals. Beyond a certain pressure point, materials may reach a new state of equilibrium and transit into a phase with distinctive atomic arrangement and crystal structure exhibiting properties quite different from that stable phase at ambient conditions. For example, under high pressure soft and black graphite transforms into a superhard and light-transparent diamond. With the rapid development of technology (high pressure generation apparatus, synchrotron X-ray, Raman), high-pressure technique has become a prevalent and important tool for exploring the unique nature of matter in solid, liquid, or gaseous state under extreme conditions. In the talk, I will briefly go over the basicsof the high-pressure technology, its advantages, and its application in condensed matter physics as well as the new progressin the study of graphite under high pressure.
 


Date: January 25th, Condensed Matter Seminar

Speaker: Dr. Igor Berkutov,  WSU Department of Physics & Astronomy Postdoctoral fellow

Title: Quantum effects in the Silicon and Germanium based p-type quantum wells

Abstract
 


Date: January 8

Speaker: Dr. Gang-yu Liu

Title: Engineered Nanostructures for Investigation and Regulation of Cellular Signaling Processes

Nano@Wayne
 


Fall 2012

 

Date: September 11

Speaker: Dr. Vinod Labhasetwar

Title: Epigentic Modulation of the Biophysical Properties of Drug-Resistant Cell Lipids to Restore Drug Transport and Endocytic Functions

Nano@Wayne

 

Date: September 25

Speaker: Dr. Stephanie Brock

Title: The Role of Synthetic Levers for Control of Phase, Size and Morphology in Nanoscale Transition Metal Pnictides:  Consequences for Catalytic and Magnetic Properties,

Nano@Wayne

 

Date: October  9

Speaker: Dr. Valerica Raicu, Ph.D.

Title: "Probing Stoichiometry and Quaternary Structure of Membrane Protein Complexes in Live Cells"

Nano@Wayne

 

Date: October 12

Speaker: Dr. Harini G. Sundararaghavan (Department of Biomedical Engineering, WSU)

Title: Three dimensional gradient scaffolds for neural tissue engineering

Abstract:

Condensed Matter

 

Date: October 26

Speaker: Dr. Sarah Veatch (University of Michigan)

Title: Probing plasma membrane heterogeneity using super-resolution microscopy

Abstract: 

Condensed Matter

 

Date: November 9

Place: Room 245 in Physics building

Speaker: Dr. Xiaoming Mao (Department of Physics, University of Michigan)

Title: Isostaticity and a unified view of soft elasticity

Abstract

Condensed Matter

 

Date: November 16

Speaker: Dr. Barry Grant (Department of Computational Medicine & Bioinformatics, University of Michigan)

Title: Biomolecular Motors and Switches: From Machines to Drugs

Condensed Matter

 

Date: November 30

Place: Room 245 in Physics building 

Speaker: Dr. Julie Biteen (Department of Chemistry, University of Michigan)

Title: Peering into Cells One Molecule at a Time: Single-molecule and plasmon-enhanced fluorescence for
super-resolution imaging of living bacteria

Abstract

Condensed Matter

 

Date: December 7

Speaker: Dr. Lisa Lapidus (Department of Physics & Astronomy, Michigan State University)

Title: Understanding Aggregation Diseases from Physical Principles

Abstract

Condensed Matter

 

Winter 2012

 

Date: April 10

Speaker: Dr. Barry Dunietz , Department of Chemistry, University of Michigan

Title: Control of electron transport in nanostructured bridges: Insight and design by ab-initio modeling

Condensed Matter

 

Date: March 22

Speaker: Peter Hoffmann, Wayne State University, Physics

Title: Water in tight spaces - a nanoscale exploration of a familiar liquid

Nano@Wayne

 

Fall 2011

 

Date: September 20

Speaker: Gavin Lawes, Wayne State University, Physics

Nano@Wayne

 

Date: September 27

Speaker: Balaji Mandal, Wayne State University, Physics

Condensed Matter

 

Date: October 4

Speaker: Symposium

Nano@Wayne

 

Date: October 11

Speaker: Abbas

Nano@Wayne

 

Date: October 18

Speaker: Kabanov, Nebraska

Nano@Wayne

 

Date: October 25

Event: 3:30 PM, Physics Get Together, in Room 245 of the Physics Research Building

 

Date: November 1

Speaker: Rolinson, NRL

Nano@Wayne

 

Date: November 8

Speaker: Mahendra Kavdia, BME

Condensed Matter

 

Date: November 15

Speaker: Feng, UC Riverside

Nano@Wayne

 

Date: November 22

Thanksgiving Break - No seminar

 

Date: November 29

Speaker: David Rueda, Wayne State University, Chemistry

Condensed Matter

 

Date: December 6

Speaker: Lee, OSU

Nano@Wayne

 

 

Fall 2010

 

September 14

Debabrata Misha, Wayne State University.
Title: Microstructure and magnetic properties of Fe(Co, Mn)-Zr-B alloys and some oxide nanoparticles and their applications

September 21

Nano@Wayne http://research.wayne.edu/nano/seminars-and-events.php

September 28

Tom Kaplam, Michigan State University.
Title: TBA

October 5

Giovanni Fanchini, University of Western Ontario.
Title: Transparent and Conducting Films for Optoelectronic and Solar Applications from Carbon Nanotubes and Graphene.

October 12

Open

October 19

Nano@Wayne http://research.wayne.edu/nano/seminars-and-events.php

October 26

Vaness Sih, University of Michigan.
Title: Mapping Spin-Orbit
Splitting in Strained Semiconductors

November 2

Nano@Wayne http://research.wayne.edu/nano/seminars-and-events.php

November 9

Mary Rodgers, Wayne State University.
Title: Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Electronic Structure Theory:
Tools for Elucidating Structures and Intra/Intermolecular Interactions in Ionic Complexes

November 16

Nano@Wayne http://research.wayne.edu/nano/seminars-and-events.php

November 23

Thanksgiving Break