scholarly journals Local probing of relaxation time distributions in ferroelectric polymer nanomesas: Time-resolved piezoresponse force spectroscopy and spectroscopic imaging

2008 ◽  
Vol 92 (23) ◽  
pp. 232903 ◽  
Author(s):  
Brian J. Rodriguez ◽  
Stephen Jesse ◽  
Jihee Kim ◽  
Stephen Ducharme ◽  
Sergei V. Kalinin
Keyword(s):  
Relaxation Time ◽  
Force Spectroscopy ◽  
Spectroscopic Imaging ◽  
Time Resolved ◽  
Ferroelectric Polymer

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging

2003 ◽  
Vol 57 (4) ◽  
pp. 357-366 ◽  
Author(s):  
Rohit Bhargava ◽  
Ira W. Levin
Keyword(s):  
Fourier Transform ◽  
Imaging Modality ◽  
Spectroscopic Imaging ◽  
Fourier Transform Infrared ◽  
Dynamic Processes ◽  
Time Resolved ◽  
Ir Imaging ◽  
Infrared Spectroscopic ◽  
Infrared Spectroscopic Imaging ◽  
Ft Ir

Fourier transform infrared (FT-IR) imaging allows simultaneous spectral characterization of large spatial areas due to its multichannel detection advantage. The acquisition of large amounts of data in the multichannel configuration results, however, in a poor temporal resolution of sequentially acquired data sets, which limits the examination of dynamic processes to processes that have characteristic time scales of the order of minutes. Here, we introduce the concept and instrumental details of a time-resolved infrared spectroscopic imaging modality that permits the examination of repetitive dynamic processes whose half-lives are of the order of milliseconds. As an illustration of this implementation of step-scan FT-IR imaging, we examine the molecular responses to external electric-field perturbations of a microscopically heterogeneous polymer–liquid crystal composite. Analysis of the spectroscopic data using conventional univariate and generalized two-dimensional (2D) correlation methods emphasizes an additional capability for accessing of simultaneous spatial and temporal chemical measurements of molecular dynamic processes.

Time-resolved nano-Newton force spectroscopy in air and vacuum using a load cell of ultra micro-balance

2019 ◽  
Vol 90 (4) ◽  
pp. 043117 ◽  
Author(s):  
Biswajit Panda ◽  
Mehra S. Sidhu ◽  
Pooja Munjal ◽  
Shivali Sokhi ◽  
Kamal P. Singh
Keyword(s):  
Force Spectroscopy ◽  
Load Cell ◽  
Time Resolved ◽  
Micro Balance

Time-resolved spectroscopic imaging reveals the fundamentals of cellular NADH fluorescence

2008 ◽  
Vol 33 (20) ◽  
pp. 2365 ◽  
Author(s):  
Dong Li ◽  
Wei Zheng ◽  
Jianan Y. Qu
Keyword(s):  
Spectroscopic Imaging ◽  
Time Resolved ◽  
Nadh Fluorescence

scholarly journals Virtual Breast Quasi-static Elastography (VBQE)

2016 ◽  
Vol 39 (2) ◽  
pp. 108-125 ◽  
Author(s):  
David Rosen ◽  
Yu Wang ◽  
Jingfeng Jiang
Keyword(s):  
Relaxation Time ◽  
Three Dimensional ◽  
Primary Objective ◽  
Transfer Efficiency ◽  
External Compression ◽  
Time Resolved ◽  
Time Constants ◽  
Strain Measurements ◽  
Relaxation Time Constants

Viscoelasticity Imaging (VEI) has been proposed to measure relaxation time constants for characterization of in vivo breast lesions. In this technique, an external compression force on the tissue being imaged is maintained for a fixed period of time to induce strain creep. A sequence of ultrasound echo signals is then utilized to generate time-resolved strain measurements. Relaxation time constants can be obtained by fitting local time-resolved strain measurements to a viscoelastic tissue model (e.g., a modified Kevin-Voigt model). In this study, our primary objective is to quantitatively evaluate the contrast transfer efficiency (CTE) of VEI, which contains useful information regarding image interpretations. Using an open-source simulator for virtual breast quasi-static elastography (VBQE), we conducted a case study of contrast transfer efficiency of VEI. In multiple three-dimensional (3D) numerical breast phantoms containing various degrees of heterogeneity, finite element (FE) simulations in conjunction with quasi-linear viscoelastic constitutive tissue models were performed to mimic data acquisition of VEI under freehand scanning. Our results suggested that there were losses in CTE, and the losses could be as high as −18 dB. FE results also qualitatively corroborated clinical observations, for example, artifacts around tissue interfaces.

Fluorescence Anisotropy and Mobility of Dansyl Fluorophore in Labelled Homologous Alkanes

1999 ◽  
Vol 64 (9) ◽  
pp. 1369-1384 ◽  
Author(s):  
Drahomír Výprachtický ◽  
Veronika Pokorná ◽  
Jan Pecka ◽  
František Mikeš
Keyword(s):  
Relaxation Time ◽  
Steady State ◽  
Conformational Changes ◽  
Fluorescence Anisotropy ◽  
Relaxation Spectrum ◽  
Rotational Relaxation ◽  
Aliphatic Chain ◽  
Time Resolved ◽  
Methylene Groups ◽  
Rotational Relaxation Time

Using the steady-state and time-resolved fluorescence anisotropy, the mobility of 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore in homologous 1-[2-acetamido-3-(1H-indol-3-yl)propanamido]-n-[5-(dimethylamino)naphthalene-1-sulfonamido]alkanes 1 was studied in binary solvents glycerol-water. Steady-state fluorescence data were evaluated by the generalized Perrin equation and the micro-Brownian motion of dansyl fluorophore was described by means of average characteristics (rotational relaxation times) of the rotational relaxation spectrum. The rotational relaxation time of "fast" motions caused by torsional vibrations of single bonds within the rotational-isomeric states decreases with increasing number of methylene groups in homologous compounds. The rotational relaxation time of "slow" motions due to conformational changes of the chain between the tryptophane and dansyl fluorophore remains at first approximately constant with increasing number of methylene groups but increases considerably for long aliphatic chains. The observed decrease in the rate of conformational changes of a long aliphatic chain is probably due to intramolecular interaction of parts of the methylene chain in a medium with high water content. The values of activation enthalpy ∆H≠ and activation entropy ∆S≠ calculated from experimental data corroborate such interpretation. Time-resolved anisotropy of dansyl fluorophore at a particular binary solvent composition confirmed the shape of rotational relaxation spectrum and the measured rotational correlation times have been discussed. The time-dependent decays of anisotropy supported our previous interpretation in terms of intramolecular association of the long aliphatic chain in polar medium.

Pump-Probe Study of Bi1-xSbx Alloys

1992 ◽  
Vol 291 ◽  
Author(s):  
J. Vidal ◽  
T.K. Cheng ◽  
A.W. Fung ◽  
H.J. Zeiger ◽  
G. Dresselhaus ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Lattice Dynamics ◽  
Optical Response ◽  
Vibrational Frequencies ◽  
Oscillatory Behavior ◽  
Lattice Vibrations ◽  
Time Resolved ◽  
Pump Probe ◽  
Model Based ◽  
Reflectivity Signal

ABSTRACTBi1-xSbx alloys undergo a semimetal-semiconductor transition at x = 0.065 and 0.22 and are semiconducting between these limits. We investigate this system by means of femtosecond time-resolved experiments, and observe an optical response similar to those in Bi, Sb, Te and Ti2O3. A previously-reported model describes the mechanism of generation of coherent lattice vibrations via the optically excited carriers in this class of materials. As predicted by the model, the modulated reflectivity signal ΔR/R in Bi.88Sb.12 shows a beating oscillatory behavior with the Bi-Bi and Bi-Sb A1g vibrational frequencies. Model-based calculations of the ΔR background relaxation time at different Sb compositions provide understanding of the carrier and lattice dynamics throughout the transition.

Sign in / Sign up

Export Citation Format

Share Document