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Physical Chemistry

2016

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Articles 1 - 30 of 33

Full-Text Articles in Physics

125te Nmr And Seebeck Effect In Bi2te3 Synthesized From Stoichiometric And Te-Rich Melts, E. M. Levin, Trevor M. Riedemann, A. Howard, Na Hyun Jo, Sergey L. Bud’Ko, Paul C. Canfield, Thomas A. Lograsso Nov 2016

125te Nmr And Seebeck Effect In Bi2te3 Synthesized From Stoichiometric And Te-Rich Melts, E. M. Levin, Trevor M. Riedemann, A. Howard, Na Hyun Jo, Sergey L. Bud’Ko, Paul C. Canfield, Thomas A. Lograsso

Materials Science and Engineering Publications

Bi2Te3 is a well-known thermoelectric material and, as a new form of quantum matter, a topological insulator. Variation of local chemical composition in Bi2Te3 results in formation of several types of atomic defects, including Bi and Te vacancies and Bi and Te antisite defects; these defects can strongly affect material functionality via generation of free electrons and/or holes. Nonuniform distribution of atomic defects produces electronic inhomogeneity, which can be detected by 125Te nuclear magnetic resonance (NMR). Here we report on 125Te NMR and Seebeck effect (heat to electrical energy conversion) for two single crystalline samples: (#1) grown from stoichiometric ...


Comparison Of S-Adsorption On (111) And (100) Facets Of Cu Nanoclusters, Jeffrey S. Boschen, Jiyoung Lee, Theresa L. Windus, James W. Evans, Patricia A. Thiel, Da-Jiang Liu Oct 2016

Comparison Of S-Adsorption On (111) And (100) Facets Of Cu Nanoclusters, Jeffrey S. Boschen, Jiyoung Lee, Theresa L. Windus, James W. Evans, Patricia A. Thiel, Da-Jiang Liu

Physics and Astronomy Publications

In order to gain insight into the nature of chemical bonding of sulfur atoms on coinage metal surfaces, we compare the adsorption energy and structural parameters for sulfur at four-fold hollow (4fh) sites on (100) facets and at three-fold hollow (3fh) sites on (111) facets of Cu nanoclusters. Consistent results are obtained from localized atomic orbital and plane-wave based density functional theory using the same functionals. PBE and its hybrid counterpart (PBE0 or HSE06) also give similar results. 4fh sites are preferred over 3fh sites with stronger bonding by ∼0.6 eV for nanocluster sizes above ∼280 atoms. However, for ...


Koh Etching Of (100) Si Wafer, No 2, Inayat Bajwa Sep 2016

Koh Etching Of (100) Si Wafer, No 2, Inayat Bajwa

Protocols and Reports

This report describes KOH etching of (100) Si wafer through a hard mask of silicon oxide, and reveals that the scattered etch rate is ascribed to the etch rates of the different crystal planes exposed during the etching.


Alamethicin In Lipid Bilayers: Combined Use Of X-Ray Scattering And Md Simulations, Jianjun Pan, D. Peter Tieleman, John F. Nagle, Norbert Kučerka, Prof. Stephanie Tristram-Nagle Ph.D. Aug 2016

Alamethicin In Lipid Bilayers: Combined Use Of X-Ray Scattering And Md Simulations, Jianjun Pan, D. Peter Tieleman, John F. Nagle, Norbert Kučerka, Prof. Stephanie Tristram-Nagle Ph.D.

John Copeland Nagle

We study fully hydrated bilayers of two di-monounsaturated phospholipids diC18:1PC (DOPC) and diC22:1PC with varying amounts of alamethicin (Alm). We combine the use of X-ray diffuse scattering and molecular dynamics simulations to determine the orientation of alamethicin in model lipids. Comparison of the experimental and simulated form factors shows that Alm helices are inserted transmembrane at high humidity and high concentrations, in agreement with earlier results. The X-ray scattering data and the MD simulations agree that membrane thickness changes very little up to 1/10 Alm/ DOPC. In contrast, the X-ray data indicate that the thicker diC22:1PC ...


Fractional Charge Methods For Correcting Approximate Kohn-Sham Potentials, Darya N. Komsa Aug 2016

Fractional Charge Methods For Correcting Approximate Kohn-Sham Potentials, Darya N. Komsa

Electronic Thesis and Dissertation Repository

The Kohn-Sham density functional theory relies on approximating the exchange-correlation energy functional or the corresponding potential. The behavior of the exchange-correlation potential as a function of position in a system can be used to detect and correct deficiencies of the parent functional. The too-fast decay of the potentials derived from common density functionals is a major problem, because it causes inaccurate Rydberg excitation energies and erroneous fractional charges in dissociating molecules. An efficient method to correct the shape of the exchange-correlation potential was proposed by Gaiduk et al. [A. P. Gaiduk, D. S. Firaha, and V. N. Staroverov, Phys. Rev ...


Developing Hyperpolarized Silicon Particles For In Vivo Mri Targeting Of Ovarian Cancer, Nicholas Whiting, Jingzhe Hu, Niki M. Zacharias, Ganesh L. R. Lokesh, David E. Volk, David G. Menter, Rajesha Rupaimoole, Rebecca Previs, Anil K. Sood, Pratip Bhattacharya Aug 2016

Developing Hyperpolarized Silicon Particles For In Vivo Mri Targeting Of Ovarian Cancer, Nicholas Whiting, Jingzhe Hu, Niki M. Zacharias, Ganesh L. R. Lokesh, David E. Volk, David G. Menter, Rajesha Rupaimoole, Rebecca Previs, Anil K. Sood, Pratip Bhattacharya

Nicholas Whiting

Silicon-based nanoparticles are ideally suited for use as biomedical imaging agents due to their biocompatibility, biodegradability, and simple surface chemistry that facilitates drug loading and targeting. A method of hyperpolarizing silicon particles using dynamic nuclear polarization, which increases magnetic resonance imaging signals by several orders-of-magnitude through enhanced nuclear spin alignment, has recently been developed to allow silicon particles to function as contrast agents for in vivo magnetic resonance imaging. The enhanced spin polarization of silicon lasts significantly longer than other hyperpolarized agents (tens of minutes, whereas <1  min for other species at room temperature), allowing a wide range of potential ...


Structural Behavior Of Nbsexte2-X Superconductors Under High Pressure, Vahe Mkrtchyan Aug 2016

Structural Behavior Of Nbsexte2-X Superconductors Under High Pressure, Vahe Mkrtchyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Niobium chalcogenide compounds have recently gained a great deal of interest due to the fact that a superconducting phase coexists with the charge density wave state (CDW), as well as their potential for numerous applications. Two superconducting compositions, NbSexTe2-x (x=2, 1.5) were prepared by solid state route using high purity Nb, Se, and Te powders. Powder X-ray diffraction patterns collected at ambient conditions for NbSe2 and NbSe1.5Te0.5 showed a single phase with hexagonal crystal structure, with space group P63mmc. High-pressure X-ray diffraction measurements were performed at the Advanced Photon Source at Argonne National Laboratory to investigate ...


Directed Self-Assembly Of Block Copolymer, No1, Hiromichi Yamamoto Aug 2016

Directed Self-Assembly Of Block Copolymer, No1, Hiromichi Yamamoto

Protocols and Reports

The PS-rich and neutral PS-b-PMMA block copolymer (BCP) films were spin coated on the neutral random copolymer hydroxyl-terminated PS-r-PMMA layers grafted on the native oxide and 50 nm thick PECVD amorphous silicon oxide layers. Relationship between the grafting density of BCP and surface density of hydroxyl moiety on silicon oxide is discussed. Furthermore, optimization of annealing BCP films is reported, and wetted and de-wetted BCP films are shown in optical microscope images. In addition, finger print and nanopore structures of BCP films are also indicated in SEM images.


Statistical Biophysics Blog: So You Want To Learn Biology? Required Reading, Part 1, Daniel M. Zuckerman Jun 2016

Statistical Biophysics Blog: So You Want To Learn Biology? Required Reading, Part 1, Daniel M. Zuckerman

Scholar Archive

Franklin Harold's The Way of the Cell provides a particularly readable and useful introduction to cell biology for physical scientists and other quantiative folks.


The Treatment Of Exchange In Path Integral Simulations Via An Approximate Pseudopotential, Randall W. Hall Jun 2016

The Treatment Of Exchange In Path Integral Simulations Via An Approximate Pseudopotential, Randall W. Hall

Randall W. Hall

An approximate form that includes the effects of exchange is suggested for the short time propagator used in path integral simulations. The form is inspired physically by the approximation made in Hartree–Fock treatments of atoms and molecules. The approximate propagator is used with q u a n t i t a t i v e accuracy in two systems: an ideal gas of fermions localized in a three‐dimensional harmonic well and the triplet state of the sodium dimer.


Path Integral Study Of The Correlated Electronic States Of Na4–Na6, Randall W. Hall Jun 2016

Path Integral Study Of The Correlated Electronic States Of Na4–Na6, Randall W. Hall

Randall W. Hall

Feynman’s path integral formulation of quantum mechanics is used to study the correlated electronic states of Na4–Na6. Two types of simulations are performed: in the first, the nuclei are allowed to move at finite temperature in order to find the most stable geometries. In agreement with previous calculations, we find that planar structures are the most stable and that there is significant vibrational amplitude at finite temperatures, indicating that the Born–Oppenheimer surface is relatively flat. In the second type of simulation, the nuclei are held fixed at symmetric and asymmetric geometries and the correlated electron density is ...


Rotational And Hyperfine Analysis Of Aus, Ian A. Wyse May 2016

Rotational And Hyperfine Analysis Of Aus, Ian A. Wyse

Macalester Journal of Physics and Astronomy

Gas phase diatomic gold sulfide, AuS, was analyzed using optical spectroscopy. High-resolution spectra were collected and characterized and a global fit of the A2+-X23/2 (0,0), B2-X23/2 (0,0), and C2Δ3/2-X21/2 (0,0) transitions at 15570 cm-1, 16290 cm-1, and 17670 cm-1 was compiled and resulted in rotational constant determinations for the A2+((2σ)1(4π)4), B2((2σ)2(4π)2(2σ*)1), and C2Δ3/2((2σ)2(4π)2(2σ*)1) upper ...


Variable Pathlength Cavity Spectroscopy Development Of An Automated Prototype, Ryan Schmeling May 2016

Variable Pathlength Cavity Spectroscopy Development Of An Automated Prototype, Ryan Schmeling

Theses and Dissertations

ABSTRACT

VARIABLE PATHLENGTH CAVITY SPECTROSCOPY

DEVELOPMENT OF AN AUTOMATED PROTOTYPE

by

Ryan Andrew Schmeling

The University of Wisconsin-Milwaukee, 2016

Under the Supervision of Professor Joseph H. Aldstadt III

Spectroscopy is the study of the interaction of electromagnetic radiation (EMR) with matter to probe the chemical and physical properties of atoms and molecules. The primary types of analytical spectroscopy are absorption, emission, and scattering methods. Absorption spectroscopy can quantitatively determine the chemical concentration of a given species in a sample by the relationship described by Beer’s Law. Upon inspection of Beer’s Law, it becomes apparent that for a given ...


Energy Transfer And Localization In Molecular Crystals, Mitchell A. Wood May 2016

Energy Transfer And Localization In Molecular Crystals, Mitchell A. Wood

Open Access Dissertations

With the aim of developing new technologies for the detection and defeat of energetic materials, this collection of work was focused on using simulations to characterize materials at extremes of temperature, pressure and radiation. Each branch of the work here is collected by which material response is potentially used as the detectable signal.

Where the chemical response is of interest, this work will explore the possibility of non-statistical chemical reactions in condensed-phase energetic materials via reactive molecular dynamics (MD) simulations. We characterize the response of three unique high energy density molecular crystals to different means of energy input: electric fields ...


Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl Mar 2016

Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl

Faculty Publications

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends on ...


Koh Etching Of (100) Si Wafer, No 1, Inayat Bajwa Mar 2016

Koh Etching Of (100) Si Wafer, No 1, Inayat Bajwa

Protocols and Reports

No abstract provided.


What Is The Best Method To Fit Time-Resolved Data? A Comparison Of The Residual Minimization And The Maximum Likelihood Techniques As Applied To Experimental Time-Correlated, Single-Photon Counting Data, Kalyan Santra, Jinchun Zhan, Xueyu Song, Emily A. Smith, Namrata Vaswani, Jacob W. Petrich Feb 2016

What Is The Best Method To Fit Time-Resolved Data? A Comparison Of The Residual Minimization And The Maximum Likelihood Techniques As Applied To Experimental Time-Correlated, Single-Photon Counting Data, Kalyan Santra, Jinchun Zhan, Xueyu Song, Emily A. Smith, Namrata Vaswani, Jacob W. Petrich

Chemistry Publications

The need for measuring fluorescence lifetimes of species in subdiffraction-limited volumes in, for example, stimulated emission depletion (STED) microscopy, entails the dual challenge of probing a small number of fluorophores and fitting the concomitant sparse data set to the appropriate excited-state decay function. This need has stimulated a further investigation into the relative merits of two fitting techniques commonly referred to as “residual minimization” (RM) and “maximum likelihood” (ML). Fluorescence decays of the well-characterized standard, rose bengal in methanol at room temperature (530 ± 10 ps), were acquired in a set of five experiments in which the total number of “photon ...


Study Of Infrared Emission Spectroscopy For The B 1Δg- A 1Πu And B ′1Σg +- A 1Πu Systems Of C2, Wang Chen, Kentarou Kawaguchi, Peter F. Bernath, Jian Tang Feb 2016

Study Of Infrared Emission Spectroscopy For The B 1Δg- A 1Πu And B ′1Σg +- A 1Πu Systems Of C2, Wang Chen, Kentarou Kawaguchi, Peter F. Bernath, Jian Tang

Chemistry & Biochemistry Faculty Publications

Thirteen bands for the B1Δg-A1Πu system and eleven bands for the B′1Σg +-A1Πu system of C2 were identified in the Fourier transform infrared emission spectra of hydrocarbon discharges. The B′1Σg + v = 4 and the B1Δg v = 6, 7, and 8 vibrational levels involved in nine bands were studied for the first time. A direct global analysis with Dunham parameters was carried out satisfactorily for the B1Δg-A1Πu system except for a small perturbation in the ...


Procesy Cieplne I Aparaty (Lab), Wojciech M. Budzianowski Jan 2016

Procesy Cieplne I Aparaty (Lab), Wojciech M. Budzianowski

Wojciech Budzianowski

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Inżynieria Chemiczna Lab., Wojciech M. Budzianowski Jan 2016

Inżynieria Chemiczna Lab., Wojciech M. Budzianowski

Wojciech Budzianowski

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Transport Signatures Of Quantum Phase Transitions And The Interplay Of Geometry And Topology In Nodal Materials, Benjamin Josef Wieder Jan 2016

Transport Signatures Of Quantum Phase Transitions And The Interplay Of Geometry And Topology In Nodal Materials, Benjamin Josef Wieder

Publicly Accessible Penn Dissertations

The research presented in this thesis is divided into two parts. In the first part, we propose response signatures for quantum phase transitions in superconducting and bilayer graphene systems. In superconducting systems, there is the promise for realizing a Majorana quasiparticle: a fermion that is its own antiparticle and possesses some of the non-Abelian braiding statistics required to form a topological quantum computer. We propose conductance and noise signatures showing the presence of Majorana fermions in topological insulator-superconductor heterostructure Josephson Junctions. We then move on to address the possibility of realizing the physics of quantum point contacts in graphene bilayers ...


First Principles Studies Of Magnetic Oxides, Spin-Driven Ferroelectricity, And The Effect Of Polarization In The Chemistry Of Functional Heterointerfaces, Diomedes Saldana-Greco Jan 2016

First Principles Studies Of Magnetic Oxides, Spin-Driven Ferroelectricity, And The Effect Of Polarization In The Chemistry Of Functional Heterointerfaces, Diomedes Saldana-Greco

Publicly Accessible Penn Dissertations

Achieving accurate description and understanding of the chemical and physical properties of complex materials enables the further development of their technological applications. Employing density functional theory (DFT) with rotationally invariant Hubbard corrections, we present an extensive study of binary manganese oxides modeling their noncollinear spin patterns and computing their electronic structures in agreement with experimental results. Leveraging on our success in predicting accurately magnetic properties, we explore the noncollinear cycloidal magnetic order in CaMn$_{7}$O$_{12}$, which breaks inversion symmetry generating one of the largest spin-driven ferroelectric polarizations measured to date. Based on a generalized spin-current model ...


Pyrolysis And Spectroscopy Of Cyclic Aromatic Combustion Intermediates, Grant Thornton Buckingham Jan 2016

Pyrolysis And Spectroscopy Of Cyclic Aromatic Combustion Intermediates, Grant Thornton Buckingham

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

We have studied the pyrolysis of aromatic combustion intermediates using an array of detection techniques. The molecules investigated include cyclic aromatic molecules with hydrocarbon substituents (ethylbenzene, n-propylbenzene, isopropylbenzene, and styrene), oxygen-containing substituents (anisole and phenol), triply substituted systems (vanillin), resonance stabilized radicals (benzyl radical and tropyl radical) and phenyl radical. At the exit of a resistively heated micro-reactor (1 mm inner diameter, 3 cm long), the pyrolysis fragments are detected using photoionization mass spectrometry (PIMS), matrix isolation vibrational spectroscopy, microwave spectroscopy, tunable VUV synchrotron-based PIMS, and table-top VUV PIMS with photoelectron photoion coincidence spectroscopy (PEPICO). This array of detection methods ...


Active Pattern Formation In One And Two Dimensions, Hui-Shun Kuan Jan 2016

Active Pattern Formation In One And Two Dimensions, Hui-Shun Kuan

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

In this thesis, we studied active systems in one or two dimensions in which particles are self-propelled and repel each other. In one-dimensional models, we considered driven particles on single lanes or in anti-parallel overlaps with both binding/unbinding and switching between the lanes. These models are inspired by experiments on kinesin proteins walking on microtubules or anti-parallel overlaps. In the single-lane case, we focused on length regulation controlled by end concentration or flux. In the anti-parallel overlap case, we used a phase space flow method to determine the density profiles and compared the analytic results with kinetic Monte Carlo ...


Sulfur-Induced Structural Motifs On Copper And Gold Surfaces, Holly Walen Jan 2016

Sulfur-Induced Structural Motifs On Copper And Gold Surfaces, Holly Walen

Graduate Theses and Dissertations

The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur.

We choose very specific conditions: very low temperature (5 K), and very low sulfur coverage (≤ 0.1 monolayer). In this region of temperature-coverage ...


Understanding Electrical Conduction In Lithium Ion Batteries Through Multi-Scale Modeling, Jie Pan Jan 2016

Understanding Electrical Conduction In Lithium Ion Batteries Through Multi-Scale Modeling, Jie Pan

Theses and Dissertations--Chemical and Materials Engineering

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design ...


Sign Learning Kink-Based (Silk) Quantum Monte Carlo For Molecular Systems, Xiaoyao Ma, Randall W. Hall, Frank Loffler, Karol Kowalski, Kiran Bhaskaran-Nair, Mark Jarrell, Juana Moreno Jan 2016

Sign Learning Kink-Based (Silk) Quantum Monte Carlo For Molecular Systems, Xiaoyao Ma, Randall W. Hall, Frank Loffler, Karol Kowalski, Kiran Bhaskaran-Nair, Mark Jarrell, Juana Moreno

Collected Faculty and Staff Scholarship

The Sign Learning Kink (SiLK) based Quantum Monte Carlo (QMC) method is used to calculate the ab initioground state energies for multiple geometries of the H2O, N2, and F2 molecules. The method is based on Feynman’s path integral formulation of quantum mechanics and has two stages. The first stage is called the learning stage and reduces the well-known QMC minus sign problem by optimizing the linear combinations of Slater determinants which are used in the second stage, a conventional QMC simulation. The method is tested using different vector spaces and compared to the results of ...


The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves Jan 2016

The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves

Theses and Dissertations

Ge1-xSnx alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge1-xSnx thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in ...


Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch Jan 2016

Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch

Open Access Theses & Dissertations

Two-photon microscopy is a fluorescence imaging technique which provides distinct advantages in three-dimensional cellular and molecular imaging. The benefits of this technology may extend beyond imaging capabilities through exploitation of the quantum processes responsible for fluorescent events. This study utilized a two-photon microscope to investigate a synthetic photoreactive collagen peptidomimetic, which may serve as a potential material for tissue engineering using the techniques of two-photon photolysis and two-photon polymerization. The combination of these techniques could potentially be used to produce a scaffold for the vascularization of engineered three-dimensional tissues in vitro to address the current limitations of tissue engineering. Additionally ...


Excitonic States In Crystalline Organic Semiconductors: A Condensed Matter Approach, Lane Wright Manning Jan 2016

Excitonic States In Crystalline Organic Semiconductors: A Condensed Matter Approach, Lane Wright Manning

Graduate College Dissertations and Theses

In this work, a new condensed matter approach to the study of excitons based on crystalline thin films of the organic molecule phthalocyanine is introduced. The premise is inspired by a wealth of studies in inorganic semiconductor ternary alloys (such as AlGaN, InGaN, SiGe) where tuning compositional disorder can result in exciton localization by alloy potential fluctuations. Comprehensive absorption, luminescence, linear dichroism and electron radiative lifetime studies were performed on both pure and alloy samples of metal-free octabutoxy-phthalocyanine and transition metal octabutoxy-phthalocyanines, where the metal is Mn, Co, Ni, and Cu. Varying the ratios of the metal to metal-free phthalocyanines ...