scholarly journals Nanopatterning Gold by Templated Solid State Dewetting on the Silica Warp and Weft of Diatoms

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Jon Hiltz ◽  
Ahmadreza Hajiaboli ◽  
Gursimranbir Singh ◽  
R. Bruce Lennox ◽  
Gregor F. Fussmann ◽  
...  
Keyword(s):  
Lattice Points ◽  
Particle Sizes ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Nitzschia Palea ◽  
Periodic Distribution ◽  
Multiple Particles ◽  
Faceted Particles ◽  
Rhombic Lattice ◽  
Selective Accumulation

The diatom,Nitzschia palea, exhibits complex silica shell (frustule) topography that resembles the warp and weft pattern of woven glass. The surface is perforated with a rhombic lattice of roughly oblong pores between periodically undulating transverse weft costae. Exfoliated frustules can be used to template gold nanoparticles by thermally induced dewetting of thin gold films. Acting as templates for the process, the frustules give rise to two coexisting hierarchies of particle sizes and patterned distributions of nanoparticles. By examining temperature dependent dewetting of 5, 10, and 15 nm Au films for various annealing times, we establish conditions for particle formation and patterning. The 5 nm film gives distributions of small particles randomly distributed over the surface and multiple particles at the rhombic lattice points in the pores. Thicker films yield larger faceted particles on the surface and particles that exhibit shapes that are roughly conformal with the shape of the pore container. The pores and costae are sources of curvature instabilities in the film that lead to mass transport of gold and selective accumulation in the weft valleys and pores. We suggest that, with respect to dewetting, the frustule comprises 2-dimensional sublattices of trapping sites. The pattern of dewetting is radically altered by interposing a self-assembled molecular adhesive of mercaptopropyltrimethoxysilane between the Au film overlayer and the frustule. By adjusting the interfacial energy in this manner, a fractal-like overlay of Au islands coexists with a periodic distribution of nanoparticles in the pores.

scholarly journals Temperature-dependent nanomechanics and topography of bacteriophage T7

2018 ◽  
Author(s):  
Zsuzsanna Vörös ◽  
Gabriella Csík ◽  
Levente Herényi ◽  
Miklós Kellermayer
Keyword(s):  
Structural Changes ◽  
Mechanical Stability ◽  
Genetic Material ◽  
Heat Inactivation ◽  
Infectious Agents ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Partial Denaturation ◽  
Induced Changes ◽  
T7 Bacteriophage

AbstractViruses are nanoscale infectious agents which may be inactivated by heat treatment. Although heat inactivation is thought to be caused by the release of genetic material from the capsid, the thermally-induced structural changes in viruses are little known. Here we measured the heat-induced changes in the properties of T7 bacteriophage particles exposed to two-stage (65 °C and 80 °C) thermal effect by using AFM-based nanomechanical and topographical measurements. We found that exposure to 65 °C caused the release of genomic DNA due to the loss of the capsid tail which leads to a destabilization of the T7 particles. Further heating to 80 °C surprisingly led to an increase in mechanical stability due to partial denaturation of the capsomeric proteins kept within the global capsid arrangement.

Thermally Induced Activation Energy of Crystalline Silicon in Alkaline Solution

1970 ◽  
Vol 11 ◽  
pp. 215-222
Author(s):  
SK Lamichhane
Keyword(s):  
Activation Energy ◽  
Potassium Hydroxide ◽  
Etch Rate ◽  
Crystalline Silicon ◽  
Lattice Parameter ◽  
Device Fabrication ◽  
Strong Anisotropy ◽  
Temperature Dependent ◽  
Thermal Agitation ◽  
Thermally Induced

Etching of crystalline silicon by potassium hydroxide (KOH) etchant with temperature variation has been studied. Results presented here are temperature dependent ER (etch rate) along the crystallographic orientations. Etching and activation energy are found to be consistently favorable with the thermal agitation for a given crystal plane. Study demonstrates that the contribution of microscopic activation energy effectively controls the etching process. Such a strong anisotropy in ER on KOH allows us a precious control of lateral dimensions of the silicon microstructure as well as surface growth of the crystal during micro device fabrication. Key words: anisotropy; activation energy; etch rate; lattice parameter; micromachining DOI: 10.3126/njst.v11i0.4148Nepal Journal of Science and Technology 11 (2010) 215-222

The singlet-quintet transition in Tris[2-(pyridin-2-yl)benzothiazole]iron(II) Bis(tetraphenylborate)

1984 ◽  
Vol 37 (6) ◽  
pp. 1157 ◽  
Author(s):  
AT Baker ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Spectral Data ◽  
Magnetic Moment ◽  
Spin Transition ◽  
Empirical Treatment ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Thiazole Derivative

The tris[2-(pyridin-2-yl)benzothiazole]iron(II) ion has been isolated as the tetraphenylborate salt which is stable in the atmosphere for short periods. The deep red complex displays a temperature-dependent magnetic moment and thermochroism which are associated with a thermally induced singlet (1A1) ↔ quintet (5T2) spin transition. An empirical treatment of the transition, which is continuous, yields ∆H and ∆S values of 22.7 kJ mol-1 and 91 JK-1 mol-1 over the range 275-364 K. Spectral data for the corresponding nickel(11) complex confirm the intermediate nature of the field strength of the benzothiazole and indicate that it is a weaker ligand than the corresponding thiazole derivative.

scholarly journals Semiempirical Atom-centered Density Matrix Propagation Approach to Temperature-dependent Vibrational Spectroscopy of Irinotecan

2018 ◽  
Vol 19 (2) ◽  
pp. 149-159
Author(s):  
Bojana Koteska ◽  
Maja Simonoska Crcarevska ◽  
Marija Glavas Dodov ◽  
Jasmina Tonic Ribarska ◽  
Ljupco Pejov
Keyword(s):  
Molecular Dynamics ◽  
Density Matrix ◽  
Finite Temperature ◽  
Potential Energy Surfaces ◽  
Statistical Physics ◽  
Drug Carriers ◽  
Temperature Dependent ◽  
Autocorrelation Functions ◽  
Thermally Induced ◽  
Dynamics Simulations

In the present study, a molecular dynamics study of irinotecan molecule with the atom-centered density matrix propagation scheme was carried out at AM1 semiempirical level of theory, at series of different temperatures, ranging from 5 K to 300 K. Molecular dynamics simulations were performed within the NVE ensemble, initially injecting (and redistributing among the nuclei) various amounts of nuclear kinetic energies to achieve the desired target temperatures. Subsequently to initial equilibration phase of 2 ps, productive simulations were carried out for 8 ps. The accuracy of simulations and the closeness of the generated trajectory to those at the Born-Oppenheimer surface were carefully followed and analyzed. To compute the temperature-dependent rovibrational density of states spectra, the velocity-velocity autocorrelation functions were computed and Fourier-transformed. Fourier-transformed dipole moment autocorrelation functions were, on the other hand, used to calculate the temperature-dependent infrared absorption cross section spectra. The finite-temperature spectra were compared to those computed by a static approach, i.e. by diagonalization of mass-weighted Hessian matrices at the minima located on the potential energy surfaces. Thermally-induced spectral changes were analyzed and discussed. The advantages of finite-temperature statistical physics simulations based on semiempirical Hamiltonian over the static semiempirical ones in the case of complex, physiologically active molecular systems relevant to intermolecular interactions between drugs and drug carriers were pointed out and discussed.

Prediction of thermally induced postbuckling of clutch disks using the finite element method

2020 ◽  
pp. 135065012090197
Author(s):  
Zhuo Chen ◽  
Yun-Bo Yi ◽  
Ke Bao
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Temperature Fields ◽  
Frictional Heat ◽  
Temperature Dependent ◽  
Displacement Fields ◽  
Element Analysis ◽  
Nonlinear Buckling ◽  
Thermally Induced ◽  
Linear Buckling

Buckling and postbuckling of automotive clutch disks can be excited by the temperature fields caused by frictional heat generation during engagement of clutch systems. Linear and nonlinear buckling finite element analyses are performed to evaluate the thermal postbuckling of clutch metal disks. The dominant buckling modes are first obtained through performing linear buckling finite element analysis (FEA) analyses. The scaled displacement fields obtained from the linear buckling FEA analyses are added to the original geometries to generate the perturbed meshes. The postbuckling is then investigated by performing nonlinear buckling FEA analyses. The commercial FEA software ABAQUS is used in the current study. The effects of the temperature-dependent material properties are studied. It is concluded that the temperature dependence of material properties affects the postbuckling behaviors significantly.

Two-Dimensional Infrared and Near-Infrared Correlation Spectroscopy: Applications to Studies of Temperature-Dependent Spectral Variations of Self-Associated Molecules

1997 ◽  
Vol 51 (4) ◽  
pp. 526-535 ◽  
Author(s):  
Yukihiro Ozaki ◽  
Yongliang Liu ◽  
Isao Noda
Keyword(s):  
Near Infrared ◽  
Oleyl Alcohol ◽  
Correlation Spectroscopy ◽  
Intensity Change ◽  
Pure Liquid ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
2D Ir ◽  
Almost All

This paper demonstrates the potential of generalized two-dimensional (2D) Fourier transform (FT) infrared (IR) and near-infrared (NIR) correlation spectroscopy in the studies of temperature-dependent spectral variations of self-associated molecules. Three examples of the 2D correlation analysis are discussed in this paper. The first two are concerned with the temperature-dependent IR and NIR spectral changes of N-methylacetamide (NMA) in the pure liquid state. The 2D IR correlation approach revealed that almost all the peaks of NMA in the 3400–1100-cm−1 region consist of two to four separate bands. For example, the amide I band contains contributions from at least four distinct bands at 1685, 1665, 1650, and 1635 cm−1. The analysis of the asynchronous 2D IR spectrum in the amide I region showed that the sequence of spectral intensity change in the ascending order of temperature was given by 1635<1650<1665<1685 cm−1. These bands at 1635, 1650, 1665, and 1685 cm−1 were assigned to the amide I modes of chain oligomers of various sizes and dimer of NMA; the longer the chain, the lower the frequency. The closeup view of 2D NIR correlation spectra of NMA obtained at narrow spectral and temperature windows enabled us to propose not only band assignments in the 6800–6050-cm−1 region but also a detailed mechanistic picture of the thermally induced dissociation of NMA for each temperature range. We also applied the generalized 2D correlation approach to the analysis of a set of FT NIR spectra of oleyl alcohol under temperature variations. The 2D NIR analysis enhanced the spectral resolution and simplified the spectra with overlapped bands. For example, it was found that a band at 7090 cm−1 arising from the first overtone of an OH stretching mode of the monomeric alcohol consists of two bands due to the rotational isomerism of the free OH group. An intriguing possibility of correlating various overtone and fundamental bands to establish unambiguous assignments was also suggested from the 2D NIR study on oleyl alcohol.

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