bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical study of the anthropogenic greenhouse gas (SF5CF3) and analysis of the reaction of SF6 with CF
Authors: Morgon Nelson H. 
Published: July 2010

AbstractSF5CF3 was recently detected in the earth's atmosphere. This has lead to various experimental and theoretical studies aimed at establishing the properties of this molecule, from which to understand how it is formed, how it may impact on the atmosphere (it is a powerful greenhouse gas), and how it may be destroyed in the atmosphere. SF5CF3 is chemically very inert, and is not destroyed in the troposhere. Theoretical calculations using effective core potential (ECP) based on high‐level methods — QCISD(T), were performed for molecular systems related to SF5CF3. Existing values for the S–C bond dissociation energy in SF5CF3 span a wide range, from estimates of about 200 to 300 kJ mol−1, obtained from theoretical calculations on SF5CF3 using the DFT, G2, and G3 protocols, to 390 ± 45 kJ mol−1 derived from experimental studies of the photoionisation of SF5CF3. At the QCISD(T)/ECP + GCM (generator coordinate method) level, the dissociation energy ‐ Do (SF5 ‐CF3, 0 K), is 274.7 kJ mol−1. In addition to calculations on individual molecules, the reactions of SF6 with CF were studied. The first objective was to locate the reactant ion‐molecule complex, the transition state, and the product ion‐molecule complex for each of these systems. On the basis of literature thermochemistry, the reaction of SF6 with CF, in which the CF reactant anion abstracts F+ from SF6 to leave SF, is highly exothermic (−343 kJ mol−1). At the QCISD(T)/ECP + GCM level gives a value of −377.6 kJ mol−1. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Temperature dependence of the energetics and structure for the Ar dimer and trimer
Authors: Pérez De Tudela R. , Márquez‐Mijares M. , González‐Lezana T. , Roncero O. , Miret‐Artés S. , Delgado‐Barrio G. , Villarreal P. 
Published: July 2010

AbstractA path‐integral Monte Carlo (PIMC) method has been used to investigate the dynamics of the Ar dimer and trimer with temperature. Energy and radial distributions are compared with estimates obtained from alternative approaches based on the calculation of the discrete and continuum rovibrational spectra of the two systems. The analysis of the Ar2 case reveals that the system only evolves between the equilibrium configuration and the breaking of the ArAr bond. This feature thus differs from the situation observed for the trimer in a previous study where the existence of a collinear isomer between the equilateral arrangement and the predissociative ArAr2 structure was manifested. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Hydrogen surface passivation of Si and Ge nanowires: A semiempirical approach
Authors: Miranda A. , Serrano F. A. , Vázquez‐Medina R. , Cruz‐Irisson M. 
Published: July 2010

AbstractA semiempirical nearest‐neighbor tight‐binding approach, that reproduces the indirect band gaps of elemental semiconductors, has been applied to study the electronic and optical properties of Si and Ge nanowires (NWs). The calculations show that Si‐NWs keep the indirect bandgap whereas Ge‐NWs changes into the direct bandgap when the wire cross section becomes smaller. Also, the band gap enhancement of Si‐NWs showing to quantum confinement effects is generally larger than that of similar‐sized Ge‐NWs, confirming the larger quantum confinement effects in Si than in Ge when they are confined in two dimensions. Finally, the dependence of the imaginary part of the dielectric function on the quantum confinement within two different schemes: intra‐atomic and interatomic optical matrix elements are applied. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2448–2454, 2010
Multireference coupled‐cluster methods for ground and low‐lying excited states. A benchmark illustration on CH + potentials
Authors: Li Xiangzhu , Paldus Josef 
Published: July 2010

AbstractMultireference (MR), general‐model‐space (GMS), state‐universal (SU) coupled‐cluster (CC) method that considers singly (S) and doubly (D) excited cluster amplitudes relative to the reference configurations spanning the model space (GMS SU CCSD), as well as its externally corrected (ec) version (N,M)‐CCSD that uses N‐reference MR CISD as an external source of higher‐than‐pair cluster amplitudes in a M‐reference GMS CCSD, are used to investigate low‐lying states of the CH+ ion. Relying on a simple ab initio model that enables a comparison with the exact full configuration interaction energies, the performance of the GMS‐based methods is assessed in the whole relevant range of internuclear separations. It is shown that the ec (N,M)‐CCSD version provides best results for both the singlet and the triplet states considered. For triplets, the use of high‐spin (MS = 1) references is to be preferred. The GMS‐based MR SU CC results for the ten low‐lying states of CH+ clearly indicate the usefulness and reliability of these approaches. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Structural and electronic study of neutral, positive, and negative small rhodium clusters [Rhn, Rh, and Rh]
Authors: Mora M. A. , Mora‐Ramírez M. A. , Rubio‐Arroyo Manuel F. 
Published: July 2010

AbstractWe have carried out a systematic study for the determination of the structure and the fundamental state of neutral and ionic small rhodium clusters [Rhn, Rh, Rh (n = 5–10)] using ab initio Hartree‐Fock methods with a LANL2DZ basis set. A range of spin multiplicities is studied for each cluster. We present the bond lengths and angles and geometric configuration adopted for the clusters in its minimum energy conformation showing the differences when the clusters have different number of unpaired electrons. In addition, we report the vertical ionization potential and the adiabatic potential calculated by the Koopman's theorem. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2541–2547, 2010
The QM/MM‐ER studies for the origin of the antioxidative properties of MCI‐186 in aqueous solutions
Authors: Takahashi Hideaki , Iwata Yuichi , Kishi Ryohei , Nakano Masayoshi 
Published: July 2010

AbstractThe anionic derivative of the pharmaceutical compound 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one (MCI‐186) is known to deactivate the free radicals in biological systems by donating its excess electron. For the purpose to investigate the mechanism that the MCI‐186 anion exhibits the antioxidative activity in aqueous solutions, we have performed a series of quantum mechanical/molecular mechanical (QM/MM) simulations based on the density functional theory in combination with the theory of energy representation (QM/MM‐ER). For the computational convenience, MCI‐186 has been modeled by 1,3‐dimethyl‐2‐pyrazolin‐5‐one (DMP) by substituting the phenyl group in MCI‐186 by a methyl one. We have applied the QM/MM‐ER approach to compute free energy change δGaqassociated with the electron detachment from DMP anion in water. To make comparisons, we have also performed the simulations for a natural radical scavenger, ascorbic acid modeled by 3,4‐dihydroxy‐furan‐2‐one (DHF). In the QM/MM‐ER approach, the distribution functions of the solute–solvent interaction energy, which serve as fundamental variables to describe the free energy, are to be constructed with the QM/MM force field. The free energy changes δGaqwere computed as 99.1, 108.3 kcal/mol for DMP and DHF anions, respectively, whereas that for hydroxyl anion OH−taken as a reference system was evaluated as 138.9 kcal/mol. Thus, it was revealed that the free energies δGaqfor DMP and DHF anions are much smaller than that for hydroxyl anion, which directly indicates the high activities of the molecules as electron donors. We found that the small δGaqvalues can be mainly attributed to the small values in the absolutes of the solvation free energies. The fractional charge analyses provided the evidence that the delocalization of the excess charge on the solute gives rise to the destabilization of these radical scavengers in the solute–solvent interaction. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Ab initio electron propagator methods: Applications to nucleic acids fragments and metallophthalocyanines
Authors: Zakrzewski Viatcheslav G. , Dolgounitcheva Olga , Zakjevskii Alexander V. , Ortiz J. V. 
Published: July 2010

AbstractElectron propagator methods provide accurate and efficient determinations of electron binding energies and retain many interpretive advantages through their generation of associated Dyson orbitals. Methods that are based on the diagonal self‐energy approximation have been applied to nucleic acid fragments such as nucleotides and dinucleotides. These calculations can be made more feasible for larger systems through the introduction of quasiparticle virtual orbitals. Nondiagonal, renormalized self‐energies are needed for systems where correlation final states with low‐pole strengths are present. Applications to zinc phthalocyanine illustrate such capabilities. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Atomic radii in molecules for use in a polarizable force field
Authors: Swart Marcel , Van Duijnen Piet TH. 
Published: July 2010

AbstractWe report here the results for an ab initio approach to obtain the parameters needed for molecular simulations using a polarizable force field. These parameters consist of the atomic charges, polarizabilities, and radii. The former two are readily obtained using methods reported previously (van Duijnen and Swart, J Phys Chem A 1998, 102, 2399; Swart et al. J Comput Chem 2001, 22, 79), whereas here we report a new approach for obtaining atomic second‐order radii (SOR), which is based on second‐order atomic moments in scaled Voronoi cells. These parameters are obtained from quantum‐chemistry calculations on the monomers, and used without further adaptation directly for intermolecular interactions. The approach works very well as shown here for four dimers, where high‐level coupled cluster with singles and doubles, and perturbative triples (CCSD(T)) and density functional theory (DFT) Swart‐Solà‐Bickelhaupt functional including Grimme's dispersion correction (SSB‐D) reference data are available for comparison. The energy surfaces for the three methods are very similar, which is also the case for the interaction between a water molecule with either a chloride anion or a sodium cation. These latter systems had previously been used to criticize Thole's damped point‐dipole method, but here we show that with the correct use of the method, it is perfectly able to describe the intermolecular interactions. This is most obvious for the induced dipole moment as function of the chloride–oxygen distance, where the direct (discrete) reaction field results are virtually indistinguishable from those obtained at CCSD(T)/aug‐cc‐pVTZ. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Effect of Zn doping on the sublimation rate of pentaerythritol tetranitrate using atomic force microscopy
Authors: Mridha Subrata , Weeks Brandon L. 
Published: July 2010

AbstractA series of Zn ion‐doped pentaerythritol tetranitrate (PETN) nanoislands in the form of thin films were prepared on Si substrates using spin coating. The effect of Zn concentrations on the sublimation energy was investigated by atomic force microscopy (AFM). The pure and Zn‐doped nanoislands are imaged by AFM in contact mode at room temperature after annealing isothermally for a given time. The volume of the islands starts to decrease after annealing at 45°C for pure PETN, whereas Zn‐doped nanoislands start to decrease in height and volume after annealing at 55–58°C. The minimum activation energy is found to be 29.7 Kcal/mol for 1,000 ppm Zn concentration. These studies are important for the long‐term stabilization of PETN. SCANNING 31: 181–187, 2009. © 2009 Wiley Periodicals, Inc.
Reflection confocal imaging of type I and type III isozymes of hexokinase in PC12 cells
Authors: Whallon Joanne H. , Preller Ana , Wilson John E. 
Published: July 2010

AbstractReflection confocal microscopy was used to determine the intracellular distribution of Type‐I and III isozymes of hexokinase (ATP:D‐hexose 6‐phosphotransferase, EC 2.7.1.1) in PC12 cells; detection was by staining with diaminobenzidine as a substrate for horseradish peroxidase‐conjugated antimouse immunoglobulins bound to isozyme‐specific monoclonal antibodies. With both isozymes, detection of the staining pattern was significantly enhanced by reflection confocal imaging compared with viewing with transmitted brightfield optics. For Type I, prominent staining of cytoplasmic organelles having a distribution consistent with that of mitochondria was noted. For Type III, intense staining at the nuclear periphery was observed. A distinct punctate pattern along the nuclear surface implied a nonuniform distribution of the Type III hexokinase and may represent preferential association with nuclear pore structures. A study of technical factors involved in optimizing the reflection image was conducted. We demonstrate that both the choice of objective and the thickness of the mounting medium are critical to successful imaging, and we describe a simple test for assessing the suitability of objectives in any system.
Electron microscopy of C. Sporogenes endospore attachment and germination
Authors: Panessa‐Warren Barbara J. , Tortora George T. , Warren John B. 
Published: July 2010

AbstractThe bacterial endospores of C. sporogenes ATCC 3584 are quite small (approximately 0.7–1.0 μm in length) and are difficult to examine during the attachment and germination process by conventional light microscopy methods. Although transmission electron microscopy provides high magnification and resolution, it has not been possible to date to visualize the attachment process and surface changes of intact clostridial endospores. With the advent of higher resolution conventional scanning electron microscopes (SEM), it is now possible to study these small spores attached to their nutrient substrate in their intact state and readily obtain detailed morphologic information about the attachment, germination, and outgrowth process. Spores were examined in their dormant, dehydrated state and allowed to germinate. Samples were prepared for light, transmission, and SEM under anaerobic conditions for morphologic and histochemical examination. SEM revealed that the spores developed a distinct polarity at the beginning of the germination process and that the exosporial membrane at this time produced projections that attached the spore to a substrate. These projections were altered by calcium chelation with EDTA and the presence of barium. Following colchicine and cytochalasin B treatment, the exosporial membrane projections were morphologically altered and the germination sequence was modified. Histochemical examination of the spores suggested that calcium was predominantly located in the protoplast and spore coat.
Imaging of immunolabeled membrane receptors in uncoated sem specimens
Authors: Heinzmann U. , Reininger A. , Autrata R. , Höfler H. 
Published: July 2010

AbstractEpidermal growth factor receptors (EGFR) were labeled with 10 nm immunogold and examined on uncoated specimens of A431 human epidermoid carcinoma cells. A field emission gun and a high‐sensitivity YAG ring detector were used to demonstrate the affinity labeling simultaneously in the secondary‐electron (SE) and backscattered‐electron (BSE) modes with a low accelerating voltage (Vo). At Vo=2kV, the SE and BSE signals were too weak to identify all markers, while at Vo=3–7 kV labeling was observed unambiguously in both the SE and BSE modes with smaller and higher working distances. Increasing the Vo to above 7 kV sometimes provokes instability of the specimens. A Vo of ⩾ 10 kV produces charging artifacts in the SE image, but permits a BSE image of the gold markers providing additional topographic information. In conclusion, immunogold labeling can be used with good results for uncoated specimens.
Real‐time confocal microscopy of keratocyte activity in wound healing after cryoablation in rabbit corneas
Authors: Chew S. J. , Beuerman R. W. , Kaufman H. E. 
Published: July 2010

AbstractA modified tandem scanning confocal microscope was used for real‐time in vivo examination of the rabbit cornea following a cryogenic injury. The corneas of New Zealand white rabbits were frozen with a probe that had been cooled by immersion in liquid nitrogen, effectively destroying keratocytes in a central 5 mm diameter zone throughout the total thickness of the cornea. In these eyes, keratocyte repopulation and corneal stromal wound healing proceeded similarly to that which occurs after epikeratophakia, a refractive surgical procedure designed to change the curvature and optical power of the cornea. In epikeratophakia, a cryolathed donor corneal stroma lenticule is sutured onto the bare stroma of the recipient cornea. The collagen tissue lenticule is repopulated by keratocytes (corneal fibroblasts) that migrate in from the host cornea. In our study, the confocal microscope permitted sequential, noninvasive examination of the corneal stroma in the treated animals. Necrosis of the keratocytes, followed by activation of the remaining viable cells in the corneal periphery, was observed in the first 2 to 3 days after cryo injury. A fine stromal fibrous network was seen to develop; in three eyes, this network progressed to the development of a retrocorneal fibrous membrane and dense stromal fibrosis, both of which resulted in significant loss of corneal clarity. Our results suggest that the confocal microscope may be a valuable tool to provide much needed information on wound healing processes at the cellular level after corneal surgery and injury.
In vivo observation of the corneal epithelium
Authors: Tsubota Kazuo 
Published: July 2010

AbstractSpecular microscopy is an important addition to the ophthalmologist's diagnostic armamentarium. Using this technique, it has been found that normal corneal epithelial cells are polygonal, with no abnormal specular reflex. There are no spindle‐shaped, large or small cells, as may be observed in a variety of pathologic conditions. Spindle‐shaped cells are characteristic of the wound‐healing process with cell migration. Large cells were observed not only in wound healing, but also in aphakic diabetic patients, extended‐wear soft contact lens wearers, and individuals with keratoconus. These changes may result from depressed mitosis or inhibited sloughing of superficial cells. Morphometric analysis adds a quantitative dimension to epithelial cell analysis.
The use of confocal microscopy in evaluating corneal wound healing after excimer laser keratectomy
Authors: Essepian John P. , Rajpal Rajesh K. , Azar Dimitri T. , New Kent , Antonacci Robin , Shields William , Stark Walter J. 
Published: July 2010

AbstractCorneal wound healing following excimer laser keratectomy is the major cause of regression of treatment results. The amount of anterior strorhal haze that develops may be influenced by topical medications. Over a period of 6 months, we followed 15 New Zealand white rabbit eyes that underwent excimer laser keratectomy with the VISX 193‐nm ArF laser at a fluence of 150 mJ/cm2 for a depth of 130 μm. Eyes were randomized to treatment with prednisolone acetate, diclofenac sodium (Voltaren), a combination of both, and a control group. Drops were administered four times a day for 1 week, two times a day for 3 weeks, and the drops were then tapered. All eyes were reepithelialized by 5 to 7 days. The tandem scanning confocal microscope (TSCM) was used to evaluate the corneal wound in vivo weekly for a month and monthly for 6 months. During the early postoperative period, the TSCM revealed significant anterior stromal keratocyte activation with cell elongation and the spindle‐shaped appearance of fibroblasts in all groups. Collagenous stromal scarring was evident initially, then slowly decreased in all treatment groups. This study shows that TSCM is clinically useful for successive in vivo examinations of corneal wounds after excimer laser keratectomy and for comparing the effects of various topical medications.
Limitations in tandem scanning confocal microscopy as a diagnostic tool for microbial keratitis
Authors: Irvine John A. , Ariyasu Reginald 
Published: July 2010

AbstractOne potential application of tandem scanning confocal microscopy is the detection of in vivo pathogens. Our study of an experimental model of Acanthamoeba keratitis demonstrates that while this technology can successfully detect certain organisms, there are currently limitations. These limitations relate to instrument configuration, movement of either the tissue or the microscope, difficulty in reproducibly returning to the area of interest for serial examination, the lack of a distinctive morphology of some pathogens, and limited resolution of the microscope.
Surface plasmon and guided optical wave microscopies
Authors: Aust E. F. , Sawodny M. , Ito S. , Knoll W. 
Published: July 2010

AbstractThis article summarizes some recent developments in the field of surface plasmon and guided optical wave microscopies. It is shown that these imaging techniques based on evanescent light allow for a quantitative optical characterization of ultrathin films with a thickness sensitivity of a few Ångstroms and a lateral resolution of μm.
Evanescent‐field scanning microscope with fourier‐transform infrared spectrometer
Authors: Nakano T. , Kawata S. 
Published: July 2010

AbstractAn evanescent‐field scanning microscope for infrared microanalysis has been developed. This microscope uses an evanescent field produced by total internal reflection with a high refractive index prism to attain a high spatial resolution, better than the wavelength. This microscope was combined with a Fourier‐transform spectrometer. The principle of the method and experimental results for edge detection at different absorption wavelengths are described.
Contact angle analysis on polymethylmethacrylate and commercial wax by using an environmental scanning electron microscope
Authors: Brugnara Marco , Volpe Claudio Della , Siboni Stefano , Zeni Dario 
Published: July 2010

AbstractThe environmental scanning electron microscope (ESEM) represents one of the most exciting breakthroughs in electron microscopy since the invention of the electron microscope. Its ability to observe uncoated and hydrated samples enhances the possibility for investigating the wettability of surfaces at a microscopic level; by varying the relative vapour pressure or the temperature inside the chamber, it is possible to condense water drops on a micron scale. A large problem in measuring contact angles by ESEM is that the observation angle is not parallel or perpendicular to the surface; thus, the study of the droplets profile using the common algorithms such as spherical approximation or axisymmetric drop shape analysis (ADSA) is not possible, because only a spherical cap shape is commonly observed. In this paper we provide a useful mathematical model to calculate the real contact angle from the initial images. Initially, some simulated spherical caps with different contact and observation angles were created by an appropriate graphic package in order to test the mathematical model. Some real drops obtained by ESEM on wax and polymethylmethacrylate (PMMA) were then studied and the results compared with contact angles measured by common methods on the same materials.