Vibrational absorption spectra are presented for isolated molecules of some common polyfluorides, present in food and pharmaceutical production, which are calculated using density function theory (DFT). This study further demonstrates using DFT for characterizing IR-spectral features of substances within the environment. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for calculating the infrared (IR) spectra presented here. DFT calculated spectra can be used to construct templates, which are for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.
This study examines estimation of dielectric functions, based on the ability of pseudo-broadened DFT-calculated IR spectra to have very high correlation with measured IR-spectra, on the macroscale. For the case of dielectric-function estimation, one seeks by means of pseudo broadening, a best or most reasonable approximation of macroscale absorbance spectra using DFT spectra. Specifically, this study examines scalability of DFT-calculated IR spectra with respect to meso and macro scales, characteristic of dielectric response as measured using different IR spectroscopies. A case study analysis concerning scalability of IR spectra for caffeine is described.
Extraction of spectrum features for target molecules from measured spectra, for purpose of their detection, can be achieved by comparison to template spectra within a spectrum database, which are sufficient approximations of dominant spectral features. This study continues presentation of the concept of using Density Functional Theory (DFT) to calculate template spectra for practical detection of target substances, by comparison with spectra within databases. DFT-calculated spectra are well posed for comparison to measured spectra, as template spectra, to the extent of their scalability to larger space-time scales.
Identification of target molecules can be achieved by comparison of measured spectra to signal templates having patterns associated with known materials. This report describes the concept of using IR spectra calculated using density functional theory (DFT) as signal templates. Specifically, aspects of using DFT calculated IR spectra as templates for comparison with IR spectral measurements associated with different types of detector schemes and complex spectral-signature backgrounds. Comparison of DFT calculated and measured IR spectra, in practice, must consider that there exist artifacts due to computational errors and model assumptions in the case of DFT calculated spectra, and artifacts due to measurement errors and experimental-design assumptions in the case of spectral measurements. This paper examines aspects of combining, as complementary information within a database, DFT-calculated and measured IR spectra for spectrum feature extraction, which is for identification of target molecules.
Calculations are presented of vibrational absorption spectra for isolated molecules of some common pesticides using density function theory (DFT). This study further demonstrates using DFT for characterizing IR-spectral features of substances within the environment. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for calculating the infrared (IR) spectra presented here. DFT calculated spectra can be used to construct templates, which are for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.
Identification of target molecules, based on spectrum-feature extraction by comparison of spectra, can be accomplished using signal templates having patterns associated with known materials. This study examines the concept of using IR spectra calculated using density functional theory (DFT) as signal templates. In principle, DFT calculated IR spectra should provide reasonable templates for comparison with IR spectral measurements associated with different types of detector schemes and complex spectral-signature backgrounds. In practice, however, there exists artifacts due to computational errors and model assumptions in the case of DFT calculated spectra, and artifacts due to measurement errors and experimental-design assumptions in the case of spectral measurements. Accordingly, the use of DFT calculated spectra as signal templates must consider these artifacts. In this study, case-study analysis of IR absorption spectra for a water contaminant of interest is presented, which demonstrates aspects of using DFT calculated IR spectra to determine the presence of target molecules.
Calculations are presented of vibrational absorption spectra for isolated PFAS molecules using density function theory (DFT). These contaminants are among widely spread carcinogens in the environment of industrial countries. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for calculating the infrared (IR) spectra presented here. DFT calculated spectra can be used to construct templates, which are for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.
Calculations are presented of vibrational absorption spectra for isolated molecules of nitorsamines using density function theory (DFT). These contaminants are among widely spread carcinogens in the environment of industrial countries. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for calculating the infrared (IR) spectra presented here. DFT calculated spectra can be used to construct templates, which are for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.
Comparisons of IR absorption spectra calculated using density functional theory (DFT) and measured IR transmission spectra for three nitrosamines are presented. These nitrosamines are major environmental contaminants. In general, identification of target molecules by cross correlation of spectra can be accomplished using signal templates having patterns associated with known materials. DFT calculated IR spectra can provide reasonable templates for filtering of IR spectral measurements associated with different types of detector schemes and complex spectral-signature backgrounds. The comparisons of spectra presented here demonstrate that DFT calculated IR spectra can be cross correlated with measured spectra to determine the presence of target molecules.
Calculations are presented of vibrational absorption spectra for PCE, TCE, DCE and VC molecules using density function theory (DFT). These ground water contaminants are among the most widely spread carcinogens in the environment of industrial countries. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The chlorohydrocarbons, whose spectra are calculated, are characterized by an interconnected equilibrium network. The simultaneous knowledge of the spectrum of each molecule within this network will be useful for detection and monitoring of the water contaminants. The DFT software GAUSSIAN was used for the calculations of the infrared (IR) spectra presented here.
Calculations are presented of vibrational absorption spectra for energy minimized structures of SixOy-nH2O molecular clusters using density function theory (DFT). DFT can provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the IR range. The absorption spectrum corresponding to excitation states of SixOy-nH2O molecular clusters consisting of relatively small numbers of atoms should be associated with response features that are intermediate between that of isolated molecules and that of a bulk system. DFT calculated absorption spectra represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for the calculations of excitation states presented here.
Calculations are presented of vibrational and electronic excited-state absorption spectra for As-H2O complexes using density function theory (DFT) and time-dependent density functional theory (TD-DFT). DFT and TD-DFT can provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the IR and UV-visible ranges. The absorption spectrum corresponding to excitation states of As-H2O complexes consisting of relatively small numbers of water molecules should be associated with response features that are intermediate between that of isolated molecules and that of a bulk system. DFT and TD-DFT calculated absorption spectra represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements and other types of theory based calculations. The DFT software GAUSSIAN was used for the calculations of excitation states presented here.
Calculations are presented of electronic-excited-state absorption spectra for molecular clusters of H2O using time-dependent density functional theory (TD-DFT). Calculation of excited state resonance structure using TD-DFT can provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the UV-visible range. The absorption spectrum corresponding to electronic excitation states of a molecular cluster consisting of a relatively small number of water molecules should be associated with response features that are intermediate between that of isolated molecules and that of a bulk lattice. TD-DFT calculated absorption spectra represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements and other types of theory based calculations. The DFT software GAUSSIAN was used for the calculations of electronic excitation states presented here.
Calculations are presented of vibrational resonance structure at THz frequencies for a 38 molecule cluster of H2O using density functional theory (DFT). This resonance structure is due to coupling of molecular vibrational modes. In particular, the coupling among resonance modes provides a reasonable molecular level interpretation of spectral features associated with THz excitation of molecular clusters. THz excitation is associated with frequencies that are characteristically perturbative to molecular electronic states, in contrast to frequencies that can induce appreciable electronic state transition. Owing to this characteristic of THz excitation, one is able to make a direct association between local oscillations about ground-state minima of molecules comprising a cluster and THz excitation spectra. The DFT software GAUSSIAN was used for the calculations of vibrational resonance structure presented here.
Experimental measurements conducted in the laboratory, involving hyperspectral analysis of water samples taken from public water resources in the New York City metro area, have motivated a reevaluation of issues concerning the potential application of this type of analysis for water monitoring, treatment and evaluation prior to filtration. One issue concerns hyperspectral monitoring of contaminants with respect to types and relative concentrations. This implies a need for better understanding the statistical profiles of water contaminants in terms of spatial-temporal distributions of electromagnetic absorption spectra ranging from the ultraviolet to infrared, which are associated with specific water resources. This issue also implies the need for establishing correlations between hyperspectral signatures and types of contaminants to be found within specific water resources. Another issue concerns the use of absorption spectra for determining changes in chemical and physical characteristics of contaminants after application of water treatments in order to determine levels of toxicity with respect to the environment.
Monitoring of water contaminants implies a need for determining their dielectric response properties with re-
spect to electromagnetic wave excitation at various frequencies. Iron is a naturally occurring water contaminant
resulting from decaying vegetation, which is at much higher concentrations than any other metal contaminant.
The present study uses density functional theory (DFT) for the calculation of ground state resonance struc-
ture and molecular stability analysis for Fe water complexes. The calculations presented are for excitation by
electromagnetic waves at frequencies within the THz range. Dielectric response functions calculated by DFT
can be used for the analysis of water contaminants. These functions provide quantitative initial estimates of
spectral response features for subsequent adjustment with respect to additional information such as laboratory
measurements and other types of theory based calculations. In addition, with respect to qualitative analysis,
DFT calculated absorption spectra provide for molecular level interpretation of response structure. The DFT
software GAUSSIAN was used for the calculations of ground state resonance structure presented here.
Calculations are presented of ground state resonance structure associated with molecular clusters of β-HMX
using density functional theory (DFT), which is for analysis using a model representation of the coupling between
resonance modes for ground state excitation. With respect to qualitative analysis, this model representation of
the coupling among resonance modes provides a reasonable molecular level interpretation of various features of
the excitation spectra associated with the ground state of molecular clusters. The DFT software GAUSSIAN
was used for the calculations of ground state resonance structure presented.
Calculations are presented of ground state resonance structure associated with water complexes of -HMX using
density functional theory (DFT), which is for subsequent construction of permittivity functions to be used for
simulations of explosives detection within a humid environment. The DFT software GAUSSIAN was used for
the calculations of ground state resonance structure presented.
In Shannon's information theory, noise is mathematically identical to entropy. The point
of this comment is to highlight the role of noise suppression in the ribosome transition state
(TS) reaction. When the rRNA of the ribosome peptidyl transfer center (PTC) is
considered along with the reactants which pass through it, enthalpy but also, noise
suppression, contributes to the catalysis of the TS reaction.
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