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Journal articles on the topic 'Molecules and Processes'

Author: Grafiati

Published: 7 September 2023

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1

ZACHARIAS, H. "LASER SPECTROSCOPY OF DYNAMICAL SURFACE PROCESSES." International Journal of Modern Physics B 04, no. 01 (January 1990): 45–91. http://dx.doi.org/10.1142/s0217979290000036.

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Physical phenomena associated with energy deposition into adsorbed molecules will be discussed. This energy may be provided to the adsorbate either thermally, by a catalytic surface reaction or by laser radiation. When enough energy is supplied adsorbed molecules eventually desorb from the substrate. Observation of the desorption flux with internal state selection provides detailed information about the molecular dynamics in this process, because the internal excitations are associated with the dynamics on the potential energy hypersurface. The rotational cooling effect previously observed in molecular beam scattering has also been found for desorption. In several systems strong vibrational excitation has been observed. Recent developments permit in addition the velocity distributions of molecules to be determined with internal quantum state resolution. The complete energetics of desorbing molecules can thus be determined. Finally, making use of the polarized nature of the laser radiation, alignment effects in the desorption can be observed, permitting to analyze the vector properties of the rotational angular momentum.

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2

Robson, Alex, Kevin Burrage, and Mark C. Leake. "Inferring diffusion in single live cells at the single-molecule level." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1611 (February 5, 2013): 20120029. http://dx.doi.org/10.1098/rstb.2012.0029.

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The movement of molecules inside living cells is a fundamental feature of biological processes. The ability to both observe and analyse the details of molecular diffusion in vivo at the single-molecule and single-cell level can add significant insight into understanding molecular architectures of diffusing molecules and the nanoscale environment in which the molecules diffuse. The tool of choice for monitoring dynamic molecular localization in live cells is fluorescence microscopy, especially so combining total internal reflection fluorescence with the use of fluorescent protein (FP) reporters in offering exceptional imaging contrast for dynamic processes in the cell membrane under relatively physiological conditions compared with competing single-molecule techniques. There exist several different complex modes of diffusion, and discriminating these from each other is challenging at the molecular level owing to underlying stochastic behaviour. Analysis is traditionally performed using mean square displacements of tracked particles; however, this generally requires more data points than is typical for single FP tracks owing to photophysical instability. Presented here is a novel approach allowing robust Bayesian ranking of diffusion processes to discriminate multiple complex modes probabilistically. It is a computational approach that biologists can use to understand single-molecule features in live cells.

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3

Bogdan, Diana, and Valer Tosa. "Processes in Isotopes and Molecules." Journal of Physics: Conference Series 182 (July 1, 2009): 011001. http://dx.doi.org/10.1088/1742-6596/182/1/011001.

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4

van Dishoeck, Ewine F. "Photodissociation Processes of Astrophysical Molecules." Symposium - International Astronomical Union 120 (1987): 51–65. http://dx.doi.org/10.1017/s0074180900153793.

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5

Letokhov, V. S. "Infrared multiphoton processes in molecules." Applied Physics B Photophysics and Laser Chemistry 47, no. 3 (November 1988): 207. http://dx.doi.org/10.1007/bf00697338.

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6

Jiang, Chen-Wei, Xiang Zhou, Rui-Hua Xie, and Fu-Li Li. "Semiclassical Molecular Dynamics Simulations for Ultrafast Processes in Molecules." Quantum Matter 2, no. 5 (October 1, 2013): 353–63. http://dx.doi.org/10.1166/qm.2013.1067.

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7

Hashemi, Reza, Alexander Kühn, and Eugen Illenberger. "Electron capture induced processes in molecules and molecular aggregates." International Journal of Mass Spectrometry and Ion Processes 100 (October 1990): 753–84. http://dx.doi.org/10.1016/0168-1176(90)85107-d.

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8

Byassee, Tyler A., Warren C. W. Chan, and Shuming Nie. "Probing Single Molecules in Single Living Cells." Microscopy and Microanalysis 7, S2 (August 2001): 28–29. http://dx.doi.org/10.1017/s1431927600026210.

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Direct observation of single molecules and single molecular events inside living cells could dramatically improve our understanding of basic cellular processes (e.g., signal transduction and gene transcription) as well as improving our knowledge on the intracellular transport and fate of therapeutic agents (e.g., antisense RNA and gene therapy vectors). However, a key remaining question is whether single-molecule methodologies could be developed to study complex molecular processes in living cells. in contrast to clean and well-controlled conditions in-vitro, the intracellular environment contains a broad collection of biological macromolecules and fluorescent materials such as porphyrins and flavins. This complex environment is known to produce intense background fluorescence, commonly known as autofluorescence. Thus, a major concern is that this intracellular background could overwhelm the relatively weak signals arising from single molecules.We demonstrate that fluorescence detection of single molecules can be achieved by tightly focusing a laser beam into a living cell (see Figure 1). The observed background fluorescence is indeed higher than that in-vitro (e.g., pure biological buffer), but this background is continuous and stable, and does not significantly interfere with the measurement of single-molecule photon bursts. Specifically, we report single-molecule results on three types of extrinsic fluorescent molecules in cultured human HeLa cells (a cervical cancer cell line).

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9

Басалаев, А. А., А. Г. Бузыкин, В. В. Кузьмичев, М. Н. Панов, А. В. Петров, and О. В. Смирнов. "Взаимодействие alpha-частиц keV-энергий с молекулами глицил-лейцина." Письма в журнал технической физики 47, no. 12 (2021): 23. http://dx.doi.org/10.21883/pjtf.2021.12.51062.18746.

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Radiation damage to isolated glycyl-leucine (C8H16N2O3) molecules caused by interaction with He2+ ions was studied. For the first time, the relative cross sections of the main processes of changes in the charge state of the collision partners and the relative cross sections of the fragmentation processes of singly and doubly charged molecular ions formed during single collisions of glycyl-leucine molecules with ions have been obtained. The optimized geometry of the molecule and singly charged glycyl-leucine ion was calculated using the density functional theory (DFT).

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10

Liu, Pingan, Junpeng Liu, and Mengjun Wang. "Adsorption of ethanol molecules on the Al (1 1 1) surface: a molecular dynamic study." Royal Society Open Science 6, no. 1 (January 2019): 181189. http://dx.doi.org/10.1098/rsos.181189.

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The adsorption process of ethanol molecules on Al slabs was investigated by molecular dynamic simulations with a ReaxFF force field. The force field used in this paper has been validated by comparing adsorption energy results with quantum mechanical (QM) calculations. All simulations were performed under the canonical (NVT) ensemble. The single-molecule adsorption simulation shows that the hydroxyl group plays a more important role in the whole progress than the ethyl group. Besides, decomposition of hydroxyl groups was also observed during multimolecule adsorption processes. Simulations of adsorption processes of Al slab by ethanol molecules at different temperatures and pressures (controlled by the number of ethanol molecules) was also performed. System energy and radial distribution function (RDF) plots were invoked to describe adsorption processes and centro-symmetry parameter (CSP) analysis was adopted to study the surface properties with coating layers. Our results indicate that the whole adsorption process can be divided into two periods and the greater the pressure, the more ethanol molecules diffuse into the Al slab. How raising the temperature helps the adsorption processes is related to the initial number of molecules. The crystal structure of the Al surface will become amorphous under the constant impact of ethanol molecules.

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11

Alegre-Requena, Juan V., César Saldías, Ricardo Inostroza-Rivera, and David Díaz Díaz. "Understanding hydrogelation processes through molecular dynamics." Journal of Materials Chemistry B 7, no. 10 (2019): 1652–73. http://dx.doi.org/10.1039/c8tb03036g.

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Molecular dynamics (MD) is currently one of the preferred techniques employed to understand hydrogelation processes for its ability to include large amounts of atoms in computational calculations, since substantial amounts of solvent molecules are involved in gel formation.

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12

Carlomusto, L., A. Cartelli, S. Solimeno, R. Velotta, and R. Bruzzese. "Experimental and Theoretical Analysis of Non-linear Vibrational Relaxation of Polyatomic Molecules Strongly Excited by Resonant Laser Radiation." Laser Chemistry 8, no. 2-4 (January 1, 1988): 315–34. http://dx.doi.org/10.1155/lc.8.315.

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We present a very simple theoretical model aimed at the analysis of non-linear relaxation processes in molecular gases in the presence of partial molecular dissociation induced by vibrational–vibrational exchange between highly excited molecules. The model has a phenomenological character, since it analyzes the behavior of a system of anharmonic diatomic molecules, which is a very rough approximation of a polyatomic molecule such as SF6. Nonetheless, it provides an interesting key for the interpretation of a number of peculiar features characterizing our experimental observation, with which a comparison is made. In particular, the model takes realistic account of the influence of dissociation processes on the relaxation time.

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13

Brumer, Paul, and Moshe Shapiro. "Quantum coherence in the control of molecular processes." Laser and Particle Beams 16, no. 4 (December 1998): 599–603. http://dx.doi.org/10.1017/s0263034600011423.

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Coherent control of molecular processes provides a means of controlling the dynamics of molecules, and of molecular processes, via laser-induced quantum interference. We briefly review this approach, provide relevant references, and highlight recent advances in the control of molecular processes.

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14

Reimers, Jeffrey R., Ante Bilić, Zheng-Li Cai, Mats Dahlbom, Nicholas A. Lambropoulos, Gemma C. Solomon, Maxwell J. Crossley, and Noel S. Hush. "Molecular Electronics: From Basic Chemical Principles to Photosynthesis to Steady-State Through-Molecule Conductivity to Computer Architectures." Australian Journal of Chemistry 57, no. 12 (2004): 1133. http://dx.doi.org/10.1071/ch04132.

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Molecular electronics offers many possibilities for the development of electronic devices beyond the limit of silicon technology. Its basic ideas and history are reviewed, and a central aspect of the delocalization of electrons across molecules and junctions is examined. Analogies between key processes affecting steady-state through-molecule conduction and equilibrium geometric and spectroscopic properties of paradigm molecules, such as hydrogen, ammonia, benzene, and the Creutz–Taube ion are drawn, and the mechanisms by which control can be exerted over molecular-electronic processes during biological photosynthesis are examined. Ab initio molecular dynamics and simulations of conductivity are then presented for carbon nanotube flanged to gold(111), and device characteristics are calculated for a molecular shift register clocked by two gold electrodes.

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15

HEINE, BARBARA. "Fast transfer processes in organic molecules†." International Journal of Electronics 70, no. 3 (March 1991): 505–8. http://dx.doi.org/10.1080/00207219108921301.

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16

BOHR, HENRIK, PER GREISEN, and BARRY MALIC. "EXCITED STATE PROCESSES IN PHOTOSYNTHESIS MOLECULES." International Journal of Modern Physics B 22, no. 25n26 (October 20, 2008): 4617–26. http://dx.doi.org/10.1142/s0217979208050371.

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A study of electronic processes in the chlorophyll and carothenoid molecules of the photo-reaction center II is presented with the focus on the electronic excitations and charge transfer in the photosynthetic process. Several novel ideas are mentioned especially concerning the electron replenishment and nuclear vibrational excitations. The study is build mainly on numerical quantum calculations of electronic structures of molecules in the photo-reaction center.

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17

Hill, S. M., P. J. Milla, T. Caseseca, and R. Mirakian. "Cell adhesion molecules in enteropathic processes." Pediatric Research 27, no. 5 (May 1990): 531. http://dx.doi.org/10.1203/00006450-199005000-00033.

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18

Ebeling, Werner, Victor Yu Podlipchuk, and Mikhail G. Sapeshinsky. "Microscopic Models and Simulations of Local Activation Processes." International Journal of Bifurcation and Chaos 08, no. 04 (April 1998): 755–65. http://dx.doi.org/10.1142/s0218127498000553.

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The classical reaction theory of Kramers describes transitions over a potential barrier (activation processes) by Fokker–Planck equations or the corresponding Langevin equations. Kramers model is based on the assumption of uncorrelated stochastic forces. In this work simple but more realistic microscopic models for transitions are developed. The physical forces leading to transitions are studied by means of molecular dynamics simulations. The investigation is restricted to two-dimensional systems. In particular we study local energy excitations of soft molecules solved in liquids. This investigation makes use of an analogy to Toda lattices. For Toda systems it was shown in earlier work that soliton excitations and soliton fusion at the soft sites may lead to local energy spots. The basic configuration studied here is a soft reacting site imbedded into a thermal bath of hard molecules. In the first part we develop a microscopic model for Kramers bistable potential well and calculate the transition rates by MD-simulations. In the following parts we study models for the dissociation of molecules and for the fusion of molecules.

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19

Spudich, James A. "Molecular motors: forty years of interdisciplinary research." Molecular Biology of the Cell 22, no. 21 (November 2011): 3936–39. http://dx.doi.org/10.1091/mbc.e11-05-0447.

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A mere forty years ago it was unclear what motor molecules exist in cells that could be responsible for the variety of nonmuscle cell movements, including the “saltatory cytoplasmic particle movements” apparent by light microscopy. One wondered whether nonmuscle cells might have a myosin-like molecule, well known to investigators of muscle. Now we know that there are more than a hundred different molecular motors in eukaryotic cells that drive numerous biological processes and organize the cell's dynamic city plan. Furthermore, in vitro motility assays, taken to the single-molecule level using techniques of physics, have allowed detailed characterization of the processes by which motor molecules transduce the chemical energy of ATP hydrolysis into mechanical movement. Molecular motor research is now at an exciting threshold of being able to enter into the realm of clinical applications.

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20

Lenn, Tchern, and Mark C. Leake. "Experimental approaches for addressing fundamental biological questions in living, functioning cells with single molecule precision." Open Biology 2, no. 6 (June 2012): 120090. http://dx.doi.org/10.1098/rsob.120090.

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In recent years, single molecule experimentation has allowed researchers to observe biological processes at the sensitivity level of single molecules in actual functioning, living cells, thereby allowing us to observe the molecular basis of the key mechanistic processes in question in a very direct way, rather than inferring these from ensemble average data gained from traditional molecular and biochemical techniques. In this short review, we demonstrate the impact that the application of single molecule bioscience experimentation has had on our understanding of various cellular systems and processes, and the potential that this approach has for the future to really address very challenging and fundamental questions in the life sciences.

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21

Rho, J., M. Andersen, A. Tappe, H. Gomez, M. Smith, J. P. Bernard, T. Onaka, and J. Cami. "Dust and Molecule Formation and Processing in Supernovae and their Remnants." Proceedings of the International Astronomical Union 10, H16 (August 2012): 583–85. http://dx.doi.org/10.1017/s1743921314012277.

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AbstractSupernovae (SNe) produce, fragment and destroy dust, molecules and nucleosynthetic elements, and reshape and modify the ISM. I will review recent infrared observations of supernova remnants (SNRs) and SNe which show that SNe are important sites of dust and molecule formation and are major dust creators in the Universe. Detection of carbon monoxide (CO) fundamental band from the young SNR Cas A indicates that astrochemical processes in SNRs interacting with molecular clouds provide astrophysical laboratories to study evolution of the ISM returning material from dense clouds into the more diffuse medium and galactic halo. Two dozen SNRs are known to be interacting with molecular clouds using H2 and millimeter observations. Recent Spitzer, Herschel and SOFIA observations along with ground-based observations have greatly advanced our understanding shock processing and astrochemistry of dust, H2, high J CO, and other neutral and ionized molecules and polycyclic aromatic hydrocarbon (PAH). Ionized molecules and warm layer of molecules that are excited by UV radiation, X-rays, or cosmic rays will be described. Finally I will discuss how astrochemical processes of dust and molecules in SNRs impact the large scale structures in the ISM.

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22

Mondal Roy, Sutapa, and Munna Sarkar. "Membrane Fusion Induced by Small Molecules and Ions." Journal of Lipids 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/528784.

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Membrane fusion is a key event in many biological processes. These processes are controlled by various fusogenic agents of which proteins and peptides from the principal group. The fusion process is characterized by three major steps, namely, inter membrane contact, lipid mixing forming the intermediate step, pore opening and finally mixing of inner contents of the cells/vesicles. These steps are governed by energy barriers, which need to be overcome to complete fusion. Structural reorganization of big molecules like proteins/peptides, supplies the required driving force to overcome the energy barrier of the different intermediate steps. Small molecules/ions do not share this advantage. Hence fusion induced by small molecules/ions is expected to be different from that induced by proteins/peptides. Although several reviews exist on membrane fusion, no recent review is devoted solely to small moleculs/ions induced membrane fusion. Here we intend to present, how a variety of small molecules/ions act as independent fusogens. The detailed mechanism of some are well understood but for many it is still an unanswered question. Clearer understanding of how a particular small molecule can control fusion will open up a vista to use these moleucles instead of proteins/peptides to induce fusion both in vivo and in vitro fusion processes.

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23

Ya Rudyak, V., and E. V. Lezhnev. "Direct stochastic molecular modelling of transport processes in gases." Journal of Physics: Conference Series 2056, no. 1 (October 1, 2021): 012003. http://dx.doi.org/10.1088/1742-6596/2056/1/012003.

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Abstract The stochastic molecular modeling method (SMM) of transport processes in rarefied gases developed by the authors is systematically discussed in this paper. It is shown that, it is possible to simulate the transport coefficients of rarefied gas with high accuracy, using a relatively small number of molecules. The data of modeling the thermal conductivity coefficient are presented for the first time. The second part of the paper is devoted to the generalization of the SMM method for modeling transport processes in confined conditions. To describe the dynamics of molecules in this case, the splitting of their evolution by processes is used: first, the movement of molecules in the configuration space is simulated, and then their dynamics in the velocity space is imitated. Anisotropy of viscosity and thermal conductivity in nanochannels has been established. The interaction of gas molecules with walls is described by specular or specular-diffuse reflection laws. Gas viscosity can be either greater than in the bulk or less, depending on the law of gas interaction with the channel walls.

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24

Castellani, Beatrice, and Andrea Nicolini. "Special Issue “Analysis and Experimental Study on Natural Gas Hydrate Exploitation Processes”." Processes 11, no. 3 (February 28, 2023): 727. http://dx.doi.org/10.3390/pr11030727.

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25

Balucani, Nadia. "Gas-phase prebiotic chemistry in extraterrestrial environments." Proceedings of the International Astronomical Union 5, H15 (November 2009): 682–83. http://dx.doi.org/10.1017/s1743921310010938.

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AbstractA variety of molecular species up to complex polyatomic molecules/radicals have been identified in many extraterrestrial gaseous environments, including interstellar clouds, cometary comae and planetary atmospheres. Amongst the identified molecules/radicals, a large percentage are organic in nature and encompass also prebiotic molecules. Different types of microscopic processes are believed to be involved in their formation, including surface processes, ion- and radical- molecule reactions. A thorough characterization of such a complex chemistry relies on a multi-disciplinary approach, where the observations are complemented by accurate chemical modeling. Unfortunately, a literature survey reveals that only a small percentage of the elementary reactions considered in the available models have been characterized in laboratory experiments. In this contribution, a brief overview will be given of recent experimental techniques that have allowed us to reach a better description of neutral-neutral gas-phase reactions, which might be responsible for the formation of simple prebiotic molecules.

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26

Popova, Anna M., Viacheslav V. Komarov, Lothar Schmidt, and Hartmut Jungclas. "Quantum Analysis of Dispersion and Induction Energies in Organic van der Waals Nanoclusters." Zeitschrift für Naturforschung A 72, no. 12 (November 27, 2017): 1127–30. http://dx.doi.org/10.1515/zna-2017-0223.

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AbstractA new analytical method is presented, which describes the interactions of three neutral organic molecules forming an isolated nanocluster. We assume that one of the three molecules has a permanent dipole moment. The induction processes and Coulomb interactions inside the nanocluster are considered taking into account molecular charges and structure properties. The functions of the dispersion and induction energies are obtained in analytical form without any phenomenological representations. The method was applied to a specific cluster consisting of two pyrene molecules and one pentene molecule with a dipole moment equal to 0.6 D. The values of the intermolecular interaction energies for these molecules are calculated and presented versus intermolecular distances.

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27

Avramenko, Aleksandr G. "Chemical applications of hybridized light-matter states (a review)." Voprosy Khimii i Khimicheskoi Tekhnologii, no. 4 (July 2023): 3–16. http://dx.doi.org/10.32434/0321-4095-2023-149-4-3-16.

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Interactions between light and matter are a fundamental part of chemical sciences responsible for basic photophysical processes such as phosphorescence and fluorescence. However, these photophysical phenomena occur in the "weak" limit of interaction between light and matter in which the photon and molecule interact with each other without the former fundamentally changing the physical properties of the latter. By constructing a Fabry-Perot cavity, which traps light of a certain frequency, then placing a molecule in a cavity that undergoes a molecular electron transition at the frequency of the trapped light, scientists can force strong light-matter interaction. This interaction occurs if the exchange between the light of the cavity mode and the molecule's excited state is faster than the decay rate of either state, forming a hybrid light-matter state known as a polariton. The photophysical properties of these polariton states have been of interest to scientists due to the possibility that they can allow for the modification of the reactivity of molecules without the addition of functional groups or modification of the surrounding environment. Of particular interest is the ability of polaritons to influence the potential energy surface of molecules, with polaritons showing the ability to both, suppress the photochemical reaction in molecules such as spiropyran and stilbene, while also enhancing the nonradiative relaxation rate of porphyrins. Due to their photonic nature, polaritons have also shown the ability to facilitate long range energy transfer processes in organic dye molecules. This review focuses on discussing these recent advances in a chemistry context as well as the optical design of cavities required to sustain polaritons.

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28

Solling, Theis I. "Nonstatistical Photoinduced Processes in Gaseous Organic Molecules." ACS Omega 6, no. 44 (October 26, 2021): 29325–44. http://dx.doi.org/10.1021/acsomega.1c04035.

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29

Tanaka, Yoshiya. "Signaling through adhesion molecules in inflammatory processes." Ensho 19, no. 4 (1999): 179–90. http://dx.doi.org/10.2492/jsir1981.19.179.

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30

Roth, Siegmar. "Switching Processes in Molecules and Conducting Polymers." Physica Scripta T29 (January 1, 1989): 206–8. http://dx.doi.org/10.1088/0031-8949/1989/t29/038.

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31

IWASAWA, Yasuhiro. "Catalytic Reaction Processes Promoted by Adsorbed Molecules." Hyomen Kagaku 17, no. 5 (1996): 254–61. http://dx.doi.org/10.1380/jsssj.17.254.

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32

Kovarskii, Viktor A. "Quantum processes in biological molecules. Enzyme catalysis." Physics-Uspekhi 42, no. 8 (August 31, 1999): 797–815. http://dx.doi.org/10.1070/pu1999v042n08abeh000480.

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Kovarskii, V. A. "Quantum processes in biological molecules. Enzyme catalysis." Uspekhi Fizicheskih Nauk 169, no. 8 (1999): 889. http://dx.doi.org/10.3367/ufnr.0169.199908c.0889.

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34

Kawai, Stephen H. "Mobiles, Molecules and the Coalescence of Processes." Leonardo 46, no. 1 (February 2013): 30–35. http://dx.doi.org/10.1162/leon_a_00481.

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The author provides an account of his development and experiences as both a visual (mobile) artist and a chemist. He describes the surprising similarities between the planning of the construction of a mobile and the execution of retrosynthetic analysis used to chemically create a particular molecule. The fusion of these two independently initiated mental processes into a common creative act can be referred to as a coalescence of processes. The present article discusses the consequences of this merging for both artistic and scientific practices, as well as its relevance to the artscience concept of idea translation.

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35

Weng, J., and E. Veje. "Absence of excited molecules in sputtering processes." Physical Review B 31, no. 3 (February 1, 1985): 1600–1602. http://dx.doi.org/10.1103/physrevb.31.1600.

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36

Steer, R. P. "Electronic energy-pooling processes in polyatomic molecules." Research on Chemical Intermediates 12, no. 1 (March 1989): 81–101. http://dx.doi.org/10.1163/156856789x00186.

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37

MATSUI, A. H., M. TAKESHIMA, K. MIZUNO, and T. AOKI-MATSUMOTO. "PHOTOPHYSICAL OVERVIEW OF EXCITATION ENERGY TRANSFER IN ORGANIC MOLECULAR ASSEMBLIES — A ROUTE TO STUDY BIO-MOLECULAR ARRAYS —." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3857–60. http://dx.doi.org/10.1142/s0217979201008846.

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Excitonic processes in organic molecular crystals are discussed in terms of two parameters, the crystal size and the constituent molecule size. From the luminescence and absorption spectra of a series of aromatic molecular crystals we find a systematic change in exciton energy transport as functions of the size of crystal and its constituent molecule size. Characteristic features of bulk crystals and microcrystallites are as follows. (1) In bulk crystals exciton energy transport depends on the constituent molecule size. When molecules are small, the exciton energy transport occurs by free excitons, but when molecules are large free exciton transport disappears because excitons get self-trapped. (2) In microcrystallites, exciton energy transport depends on the crystallite size. When the size is larger than a critical one, excitons travel as quantum mechanical waves but when the size is smaller than the critical one the exciton waves get confined within the crystallite. The results are independent of the chemical species of constituent molecules and thus applicable to novel molecular arrays such as biological molecular arrays.

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38

STANKIEWICZ, M., P. WINIARCZYK, J. RIUS I RIU, J. ÁLVAREZ, P. ERMAN, A. KARAWAJCZYK, E. RACHLEW, E. KUKK, M. HUTTULA, and P. HATHERLY. "SELECTIVE FRAGMENTATION OF VALENCE- AND CORE-ELECTRON-EXCITED CD4 and SF6 MOLECULES." Surface Review and Letters 09, no. 01 (February 2002): 117–23. http://dx.doi.org/10.1142/s0218625x02002105.

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Electron–ion coincidence measurements with energy-resolved electrons are a powerful tool in studies of molecular fragmentation processes, since fragmentation from a specific doorway state can be monitored while the remaining reactions are discriminated. Presently, we have applied this technique in measurements of coincidence spectra of the CD 4 and SF 6 molecules after valence and core electron excitation. The newly constructed energy-resolved electron–ion coincidence station developed for this project has been used. Our results on CD 4 are the first demonstration of a correlation between vibrations and molecular dissociation observed in this molecule. The SF 6 spectra reveal strong selectivity in dissociation following distinct electronic states of the molecule. This selectivity reflects the bonding properties of the potential surfaces involved in the studied processes. The obtained results exemplify the potential of the new multicoincidence station used in this work.

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McKoy, V., SN Dixit, RL Dubs, and DL Lynch. "Dynamics of Single and Multi-photon Ionisation Processes in Molecules." Australian Journal of Physics 39, no. 5 (1986): 761. http://dx.doi.org/10.1071/ph860761.

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Single-photon ionisation and resonant multiphoton ionisation studies, which can now be carried out using synchrotron radiation and pulsed dye lasers respectively, are providing important dynamical information on molecular photoionisation. In this paper we discuss some results of our recent studies of several, single- and multi-photon ionisation processes in molecules. The results will be taken from our studies of (i) single-photon ionisation of linear molecules with emphasis on the role of shape and autoionising resonances on these cross� sections, (ii) photoionisation from oriented NiCO as a simple but realistic model of photoemission in adsorbate-substrate systems, and (iii) resonant multiphoton ionisation of H2.

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40

Ito, Fuyuki. "Photochemical Methods for the Real-Time Observation of Phase Transition Processes upon Crystallization." Symmetry 12, no. 10 (October 19, 2020): 1726. http://dx.doi.org/10.3390/sym12101726.

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We have used the fluorescence detection of phase transformation dynamics of organic compounds by photochemical methods to observe a real-time symmetry breaking process. The organic fluorescent molecules vary the fluorescence spectra depending on molecular aggregated states, implying fluorescence spectroscopy can be applied to probe the evolution of the molecular-assembling process. As an example, the amorphous-to-crystal phase transformation and crystallization with symmetry breaking at droplet during the solvent evaporation of mechanofluorochromic molecules are represented in this review.

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41

Digel, I., P. Kayser, and G. M. Artmann. "Molecular Processes in Biological Thermosensation." Journal of Biophysics 2008 (May 12, 2008): 1–9. http://dx.doi.org/10.1155/2008/602870.

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Since thermal gradients are almost everywhere, thermosensation could represent one of the oldest sensory transduction processes that evolved in organisms. There are many examples of temperature changes affecting the physiology of living cells. Almost all classes of biological macromolecules in a cell (nucleic acids, lipids, proteins) can present a target of the temperature-related stimuli. This review discusses some features of different classes of temperature-sensing molecules as well as molecular and biological processes that involve thermosensation. Biochemical, structural, and thermodynamic approaches are applied in the paper to organize the existing knowledge on molecular mechanisms of thermosensation. Special attention is paid to the fact that thermosensitive function cannot be assigned to any particular functional group or spatial structure but is rather of universal nature. For instance, the complex of thermodynamic, structural, and functional features of hemoglobin family proteins suggests their possible accessory role as “molecular thermometers”.

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42

Liu, Jiang, Junchao Zhang, Xun Fu, Shu Yang, Yan Li, Jianmin Liu, Michael E. DiSanto, Ping Chen, and Xinhua Zhang. "The Emerging Role of Cell Adhesion Molecules on Benign Prostatic Hyperplasia." International Journal of Molecular Sciences 24, no. 3 (February 2, 2023): 2870. http://dx.doi.org/10.3390/ijms24032870.

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Benign prostatic hyperplasia (BPH) is a common disease in elderly men. It is characterized by prostatic enlargement and urethral compression and often causes lower urinary tract symptoms (LUTs) such as urinary frequency, urgency, and nocturia. Existing studies have shown that the pathological process of prostate hyperplasia is mainly related to the imbalance of cell proliferation and apoptosis, inflammation, epithelial–mesenchymal transition (EMT), and growth factors. However, the exact molecular mechanisms remain incompletely elucidated. Cell adhesion molecules (CAMs) are a group of cell surface proteins that mediate cell–cell adhesion and cell migration. Modulating adhesion molecule expression can regulate cell proliferation, apoptosis, EMT, and fibrotic processes, engaged in the development of prostatic hyperplasia. In this review, we went over the important roles and molecular mechanisms of cell adhesion molecules (mainly integrins and cadherins) in both physiological and pathological processes. We also analyzed the mechanisms of CAMs in prostate hyperplasia and explored the potential value of targeting CAMs as a therapeutic strategy for BPH.

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43

Goicoechea, Javier R., S. Cuadrado, J. Pety, A. Aguado, J. H. Black, E. Bron, J. Cernicharo, et al. "The ALMA view of UV-irradiated cloud edges: unexpected structures and processes." Proceedings of the International Astronomical Union 13, S332 (March 2017): 210–17. http://dx.doi.org/10.1017/s1743921317007761.

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AbstractFar-UV photons (FUV, E < 13.6 eV) from hot massive stars regulate, or at least influence, the heating, ionization, and chemistry of most of the neutral interstellar medium (H i and H2 clouds). Investigating the interaction between FUV radiation and interstellar matter (molecules, atoms and grains) thus plays an important role in astrochemistry.The Orion Bar, an interface region between the Orion A molecular cloud and the H ii region around the Trapezium cluster, is a textbook example of a strongly illuminated dense PDR (photodissociation region). The Bar is illuminated by a FUV field of a few 104 times the mean interstellar radiation field. Because of its proximity and nearly edge-on orientation, it provides a very good template to investigate the chemical content, structure, and dynamics of a strongly irradiated molecular cloud edge. We have used ALMA to mosaic a small field of the Bar where the critical transition from atomic to molecular gas takes place. These observations provide an unprecedented sharp view of this transition layer (≲ 1″ resolution or ≲ 414 AU). The resulting images (so far in the rotational emission of CO, HCO+, H13CO+, SO+, SO, and reactive ions SH+ and HOC+) show the small-scale structure in gas density and temperature, and the steep abundance gradients. The images reveal a pattern of high-density substructures, photo-ablative gas flows and instabilities at the edge of the molecular cloud. These first ALMA images thus show a more complex morphology than the classical clump/interclump static model of a PDR.In order to quantify the chemical content in strongly FUV-irradiated gas, we have also used the IRAM-30 m telescope to carry out a complete line-survey of the illuminated edge of the Bar in the millimeter domain. Our observations reveal the presence of complex organic molecules (and precursors) that were not expected in such a harsh environment. In particular, we have reported the first detection of the unstable cis conformer of formic acid (HCOOH) in the ISM. The energy barrier to internal rotation (the conversion from trans to cis) is approximately 4827 cm−1 (≈7000 K). Hence, this detection is surprising. The low inferred trans-to-cis abundance ratio of 2.8±1.0 supports a photoswitching mechanism: a given conformer absorbs a FUV stellar photon that radiatively excites the molecule to electronic states above the interconversion barrier. Subsequent fluorescent decay leaves the molecule in a different conformer form. This mechanism, which we have specifically studied with ab initio quantum calculations, was not considered so far in astrochemistry although it can affect the structure of a variety of molecules in PDRs.

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Kupka, Anna, Hermann Gies, and Klaus Merz. "Influence on Crystallisation Process of Amino Acids from Solution." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C546. http://dx.doi.org/10.1107/s2053273314094534.

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The famous Miller experiment to model the primordial soup demonstrated that amino acids can form spontaneously as the essential building blocks of life in solutions. It is, however, still an open question how self-recognition processes influence the transformation of these spontaneously formed amino acids in solvents into higher ordered structures in the solid state, thereby creating chiral materials and catalytically competent structures. The understanding of the first steps of molecular self-assembly processes in such environments will thus give important clues towards the understanding of biological evolution. Most of intermolecular interactions are not very strong and their formation is related to and affected by small changes in the molecular structure and the crystallisation conditions. Continuing our investigations on aggregation of substituted aromatic molecules in the solid state, we studied the influence and boundaries of weak directing substituents like deuterium on the aggregation of small molecules. Hydrogen/deuterium (H/D)-exchange, the smallest possible modification of a molecule, is generally seen as a non dominating parameter in the formation of crystal structures of chemical compounds. On the other hand, it could already be shown that the aggregation of molecules in the solid state of polymorphic N-heterocycle systems like pyridine-N-oxide or acridine can be very sensitive to small changes of the isotopic substitution pattern of the selected molecules. Within our project, the molecular aggregation of amino acids in solution with the formation of molecular aggregates and pre-nucleation clusters in deuterated and non-deuterated systems, and in particular the role of the solvent in these processes, will be studied in both experiment and theory.

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45

Fabryova, K., and M. Simon. "Function of the cell surface molecules (CD molecules) in the reproduction processes." General Physiology and Biophysics 28, no. 1 (2009): 1–7. http://dx.doi.org/10.4149/gpb_2009_01_1.

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Riso, Rosario R., Tor S. Haugland, Enrico Ronca, and Henrik Koch. "On the characteristic features of ionization in QED environments." Journal of Chemical Physics 156, no. 23 (June 21, 2022): 234103. http://dx.doi.org/10.1063/5.0091119.

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The ionization of molecular systems is important in many chemical processes, such as electron transfer and hot electron injection. Strong coupling between molecules and quantized fields (e.g., inside optical cavities) represents a new promising way to modify molecular properties in a non-invasive way. Recently, strong light–matter coupling has shown the potential to significantly improve the rates of hot electron driven processes, for instance, in water splitting. In this paper, we demonstrate that inside an optical cavity, the residual interaction between an outgoing free electron and the vacuum field is significant. We further show that since the quantized field is also interacting with the ionized molecule, the free electron and the molecular system are correlated. We develop a theoretical framework to account for the field induced correlation and show that the interaction between the free electron and the field, free electron–field interaction, has sizable effects on the ionization potential of typical organic molecules.

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Marinković, Bratislav, Vladimir Srećković, Veljko Vujčić, Stefan Ivanović, Nebojša Uskoković, Milutin Nešić, Ljubinko Ignjatović, Darko Jevremović, Milan Dimitrijević, and Nigel Mason. "BEAMDB and MOLD—Databases at the Serbian Virtual Observatory for Collisional and Radiative Processes." Atoms 7, no. 1 (January 14, 2019): 11. http://dx.doi.org/10.3390/atoms7010011.

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In this contribution we present a progress report on two atomic and molecular databases, BEAMDB and MolD, which are web services at the Serbian virtual observatory (SerVO) and nodes within the Virtual Atomic and Molecular Data Center (VAMDC). The Belgrade Electron/Atom (Molecule) DataBase (BEAMDB) provides collisional data for electron interactions with atoms and molecules. The Photodissociation (MolD) database contains photo-dissociation cross sections for individual rovibrational states of diatomic molecular ions and rate coefficients for the chemi-ionisation/recombination processes. We also present a progress report on the major upgrade of these databases and plans for the future. As an example of how the data from the BEAMDB may be used, a review of electron scattering from methane is described.

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Ortiz-Garcia, José J., and Rebecca C. Quardokus. "Influence of local chemical environment and external perturbations of porphyrins on surfaces." Journal of Vacuum Science & Technology A 41, no. 3 (May 2023): 030801. http://dx.doi.org/10.1116/6.0002401.

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Porphyrins and tetrapyrroles play crucial roles in biological processes such as photosynthesis and molecular transport. These nature-based molecules have found application in artificial systems, such as sensing, catalysis, and 2D/3D networks. They are ideal building blocks due to their chemical diversity, stability, and ability to self-assemble on surfaces. Derivatization of the peripheral positions allows for the rational design of magnetic, catalytic, and photochemical properties. Due to this, porphyrins have been used in a variety of natural and artificial systems such as photodynamic therapies and dye-sensitized solar cells. Recently, much work and attention have focused on using specific porphyrin and molecular relatives for molecular electronics due to their robust nature, functionality, and synthesis. The focus of this review is to summarize the mechanisms that affect the internal structure and properties of the molecules and how changes in the local chemical environment alter the electronic properties of the porphyrin. We review the current state of the literature concerning the intermolecular and surface-adsorbate interactions that dictate self-assembly. We will assess the effects that molecule-molecule and molecule-substrate interactions play on the molecule’s properties and the effects that external forces have on the molecular properties. The goal of this review is to dissect the mechanisms responsible for the unique properties that arise from porphyrinic systems adsorbed on surfaces.

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Schöier, Fredrik L., and Hans Olofsson. "Probing chemical processes in AGB stars." Proceedings of the International Astronomical Union 4, S251 (February 2008): 201–6. http://dx.doi.org/10.1017/s174392130802156x.

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AbstractWe are conducting multi-transition observations of circumstellar line emission from common molecules such as HCN, SiO, CS, SiS and CN for a large sample of AGB stars with varying photospheric C/O-ratios and mass-loss charachteristics. Our recently published results for SiO and SiS clearly show that major constraints on the relative roles of non-equilibrium chemistry, dust condensation, and photodissociation can be obtained from the study of circumstellar molecular line emission. Presented here are also preliminary results based on detailed radiative transfer modelling of HCN line emission.

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Siegmann, B., U. Werner, and H. O. Lutz. "Multiple Ionisation and Fragmentation of Molecules." Australian Journal of Physics 52, no. 3 (1999): 545. http://dx.doi.org/10.1071/ph98089.

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The multiple ionisation and dissociation of molecules, e.g. H2, N2, H2O, CH4 and C60, by fast ions was studied using a position- and time-sensitive multi-particle detector. The data obtained allow a clear separation of various reaction channels. Of special interest are the ‘Coulomb explosion’ processes like N2 → Nq+ +Nn+ or H2O → H+ + H+ +On+. For these reactions the coincident measurement of the momenta of correlated fragment ion yields a kinematically complete image of the molecular break-up process, and the fragmentation energy as well as angular correlations can be derived for each individual event. In the case of H2 as target molecule the CE model describes the fragmentation energy rather well, whereas in the case of more complex molecules, e.g. N2, CO and CH4, the simple CE model is insufficient to explain the measured energy and angular spectra. Better agreement was achieved with ab initio MCSCF calculations which take into account several molecular states of the fragmenting highly charged molecular ion.

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