Effect of Short-range Repulsive Interactions on the Dynamics of the Methane Molecule

Using a computer simulation technique, an attempt has been made to explain the A-type transition in the specific heat of solid methane at around 20 K in terms of the changes in the dynamical behaviour of the methane molecule under the influence of its nearest neighbours. Different exponents of the short-range repulsive interaction occurring in the expression for the potential energy have been tried in order to select the appropriate value. The well known Lennard-Jones (6-12) and (6-15) potentials are found to reveal a phase transition in a well defined region. From an analysis of the direction cosine data, the three-dimensional motion of the central methane molecule has been visualised before and after the transition. Pertaining to the Lennard-Jones potential, the period of the torsional oscillation (libration) of the methane molecule comes out to be of the order of 0�3xlO-12 s. From the computed critical rotational kinetic. energy, the transition temperature is found to be 20�2 K which agrees well with experimental observations.

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Molecular Dynamics of the Phase Transition in Solid Deuterated Methane

Australian Journal of Physics ◽

10.1071/ph930523 ◽

1993 ◽

Vol 46 (4) ◽

pp. 523 ◽

Cited By ~ 2

Author(s):

MK Kansal ◽

SK Trikha

Keyword(s):

Transition Temperature ◽

Three Dimensional ◽

Direction Cosine ◽

Dynamical Behaviour ◽

Methane Molecule ◽

Lennard Jones Potential ◽

Jones Potential ◽

Lennard Jones ◽

Central Molecule ◽

Tetrahedral Molecule

The rotational dynamics of a single deuterated methane molecule in the presence of its twelve nearest neighbours has been studied by using a computer simulation technique. The three-dimensional motion of the tetrahedral molecule is described by the appropriate algorithm equations, as well as by the well known Lennard-Jones potential. The importance of the inverse-twelfth-power repulsive potential for the dynamics of the deuterated methane molecule is also highlighted. The second-nearest neighbour interactions contribute only 7% to the potential energy of the whole system and this hardly affects the dynamics of the central molecule. A detailed analysis of the direction cosine data reveals a change in the dynamical behaviour of the molecule around the transition temperature, which could be attributed to the singularity observed in the specific heat data. Corresponding to the Lennard-Jones potential, the period of oscillation of the central molecule comes out to be 0�38xlO-12 s. Making use of the (dimensionless) average rotational kinetic energy at the transition, (ERK)critical = 6�3, and the period, the transition temperature is found to be 27�7 K, which is in quite good agreement with one of the ..\-type transition temperatures reported by Clusius et al.

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Computer Simulation Studies of the Phase Transition in Compressible Deuteroammonium Chloride

Australian Journal of Physics ◽

10.1071/ph850733 ◽

1985 ◽

Vol 38 (5) ◽

pp. 733

Author(s):

Sadhana Pandey ◽

SK Trikha

Keyword(s):

Phase Transition ◽

Computer Simulation ◽

Dynamical Behaviour ◽

Simulation Technique ◽

Simulation Studies ◽

Lennard Jones ◽

Nearest Neighbours ◽

Computer Simulation Technique ◽

Computer Simulation Studies

The effects of pressure on the dynamical behaviour of an ND t ion near the A transition under the influence of its nearest neighbours in deuteroammonium chloride have been studied by using the computer simulation technique. The well-known Lennard Jones (6-12) potential is used as the representative interaction between ND t and CI-. The libration frequency of the ND t ion is estimated to be approximately 130 and 145 cm -1 at pressures of 1 atm and 3 kbar respectively.

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Molecular Dynamics of the Phase Transition in Compressible Ammonium Chloride

Australian Journal of Physics ◽

10.1071/ph840667 ◽

1984 ◽

Vol 37 (6) ◽

pp. 667

Author(s):

Sadhana Pandey ◽

SK Trikha

Keyword(s):

Phase Transition ◽

Molecular Dynamics ◽

Computer Simulation ◽

High Pressure ◽

Raman Spectrum ◽

Ammonium Chloride ◽

Dynamical Behaviour ◽

Lennard Jones ◽

Nearest Neighbours ◽

Computer Simulation Technique

The effects of pressure on the dynamical behaviour of an NH: ion near the A transition under the influence of its nearest neighbours in ammonium chloride have been studied by using the computer simulation technique. The Lennard Jones (6-12) potential is used as the representative interaction between NH: and Cl-. The present calculations reveal a decrease in entropy of the system with increasing pressure. The libration frequency of the NH: ion is estimated to be approximately 170, 182 and 210 cm -1 at pressures of 1 atm, 3 and 10 kbar respectively, in agreement with the Raman spectrum study of NH4CI at high pressure (Ebisuzaki and Nicol 1969).

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Rotational Motion of the NH+4 Ion in Ammonium Chloride

Australian Journal of Physics ◽

10.1071/ph840197 ◽

1984 ◽

Vol 37 (2) ◽

pp. 197

Author(s):

Sadhana Pandey ◽

SK Trikha

Keyword(s):

Computer Simulation ◽

Rotational Motion ◽

Three Dimensional ◽

Rotational Dynamics ◽

Ammonium Ion ◽

Lennard Jones Potential ◽

Jones Potential ◽

Lennard Jones ◽

Nearest Neighbours ◽

Computer Simulation Technique

The rotational motion of the ammonium ion in NH4CI at low temperature under the influence of its nearest neighbours has been studied using a computer simulation technique. The Lennard Jones potential is used as the representative interaction between NHt and CI-. Three values of the time increment At occurring in the algorithm equation are taken to illustrate the three-dimensional effect on the rotational dynamics of the NH: ion. In each case we notice a well defined transition gap around = 1�25 separating phases II and III which are known from the literature. The libration frequency of the ammonium ion is found to be 1"0; 170 em-1, corresponding to the transition temperature of 242 K, which is in agreement with the Raman spectra study by Couzi et af. (1973).

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Three dimensional and Doppler ultrasound examination before and after procedures of the biliary system

Zeitschrift für Gastroenterologie ◽

10.1055/s-2008-1079705 ◽

2008 ◽

Vol 46 (05) ◽

Author(s):

G Székely ◽

Á Szilvás ◽

F Siket

Keyword(s):

Doppler Ultrasound ◽

Ultrasound Examination ◽

Three Dimensional ◽

Biliary System ◽

Before And After

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Three-dimensional analysis of the root canal preparation with Reciproc Blue®, WaveOne Gold® and XP EndoShaper®: a new method in vivo

BMC Oral Health ◽

10.1186/s12903-021-01450-1 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Javier Caviedes-Bucheli ◽

Nestor Rios-Osorio ◽

Diana Usme ◽

Cristian Jimenez ◽

Adriana Pinzon ◽

...

Keyword(s):

3D Reconstruction ◽

Root Canal ◽

Paired Comparison ◽

Three Dimensional ◽

New Method ◽

Root Canal Preparation ◽

Paired Data ◽

Before And After ◽

Student’S T

Abstract Background The purpose of this study was to evaluate the changes in canal volume after root canal preparation in vivo with 3 different single-file techniques (Reciproc-Blue®, WaveOne-Gold® and XP-EndoShaper®), with a new method using CBCT and 3D reconstruction. Methods In this prospective study, thirty human lower premolars from healthy patients were used, in which extraction was indicated for orthodontic reasons. All the teeth used were caries- and restoration-free with complete root development, without signs of periodontal disease or traumatic occlusion, and with only one straight canal (up to 25º curvature). Teeth were randomly divided into three different groups: Reciproc-Blue, WaveOne-Gold and XP-EndoShaper. CBCT scans before root canal preparation were used to create a 3D reconstruction with RHINOCEROS 5.0 software to assess the initial canal volume, and then compared with 3D reconstructions after canal preparation to measure the increase in canal volume. Student’s t test for paired data were used to determine statistically significant differences between the before and after canal volumes. Anova test was used to determine statistically significant differences in the percentage of canal volume increase between the groups and Tukey's post-hoc test were used to paired comparison. Results Reciproc-Blue showed the higher increase in canal volume, followed by WaveOne-Gold and XP-EndoShaper (p = 0.003). XP-EndoShaper did not show a statistically significant increase in canal volume after root canal preparation (p = 0.06). Conclusion With this model, Reciproc-Blue showed higher increase in root canal volume, followed by WaveOne-Gold, while XP-EndoShaper did not significantly increase root canal volume during preparation.

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Inferring Single-Cell 3D Chromosomal Structures Based on the Lennard-Jones Potential

International Journal of Molecular Sciences ◽

10.3390/ijms22115914 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5914

Author(s):

Mengsheng Zha ◽

Nan Wang ◽

Chaoyang Zhang ◽

Zheng Wang

Keyword(s):

Single Cell ◽

Loss Function ◽

Gaussian Function ◽

Three Dimensional ◽

Lennard Jones Potential ◽

Jones Potential ◽

Cubic Lattice ◽

Lennard Jones ◽

3D Fish ◽

Well Depth

Reconstructing three-dimensional (3D) chromosomal structures based on single-cell Hi-C data is a challenging scientific problem due to the extreme sparseness of the single-cell Hi-C data. In this research, we used the Lennard-Jones potential to reconstruct both 500 kb and high-resolution 50 kb chromosomal structures based on single-cell Hi-C data. A chromosome was represented by a string of 500 kb or 50 kb DNA beads and put into a 3D cubic lattice for simulations. A 2D Gaussian function was used to impute the sparse single-cell Hi-C contact matrices. We designed a novel loss function based on the Lennard-Jones potential, in which the ε value, i.e., the well depth, was used to indicate how stable the binding of every pair of beads is. For the bead pairs that have single-cell Hi-C contacts and their neighboring bead pairs, the loss function assigns them stronger binding stability. The Metropolis–Hastings algorithm was used to try different locations for the DNA beads, and simulated annealing was used to optimize the loss function. We proved the correctness and validness of the reconstructed 3D structures by evaluating the models according to multiple criteria and comparing the models with 3D-FISH data.

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Scientific validation of three-dimensional stereophotogrammetry compared to the IGAIS clinical scale for assessing wrinkles and scars after laser treatment

Scientific Reports ◽

10.1038/s41598-021-91922-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Barbara Helena Barcaro Machado ◽

Ivy Dantas De Melo E. Silva ◽

Walter Marou Pautrat ◽

James Frame ◽

Mohammad Najlah

Keyword(s):

Laser Treatment ◽

Three Dimensional ◽

Skin Surface ◽

Clinical Scale ◽

3D Images ◽

Laser Resurfacing ◽

Before And After ◽

Measuring Outcomes ◽

Skin Scar ◽

Scientific Validation

AbstractMeasuring outcomes from treatments to the skin is either reliant upon patient’s subjective feedback or scale-based peer assessments. Three-Dimensional stereophotogrammetry intend to accurately quantify skin microtopography before and after treatments. The objective of this study is comparing the accuracy of stereophotogrammetry with a scale-based peer evaluation in assessing topographical changes to skin surface following laser treatment. A 3D stereophotogrammetry system photographed skin surface of 48 patients with facial wrinkles or scars before and three months after laser resurfacing, followed immediately by topical application of vitamin C. The software measured changes in skin roughness, wrinkle depth and scar volume. Images were presented to three observers, each independently scoring cutaneous improvement according to Investigator Global Aesthetic Improvement Scale (IGAIS). As for the results, a trend reflecting skin/scar improvement was reported by 3D SPM measurements and raters. The percentage of topographical change given by the raters matched 3D SPM findings. Agreement was highest when observers analysed 3D images. However, observers overestimated skin improvement in a nontreatment control whilst 3D SPM was precise in detecting absence of intervention. This study confirmed a direct correlation between the IGAIS clinical scale and 3D SPM and confirmed the efficacy and accuracy of the latter when assessing cutaneous microtopography alterations as a response to laser treatment.

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