Search results for "shell"

Bulky Surface Ligands Promote Surface Reactivities of [Ag141X12(S-Adm)40]3+ (X = Cl, Br, I) Nanoclusters: Models for Multiple-Twinned Nanoparticles

2017

Surface ligands play important roles in controlling the size and shape of metal nanoparticles and their surface properties. In this work, we demonstrate that the use of bulky thiolate ligands, along with halides, as the surface capping agent promotes the formation of plasmonic multiple-twinned Ag nanoparticles with high surface reactivities. The title nanocluster [Ag141X12(S-Adm)40]3+ (where X = Cl, Br, I; S-Adm = 1-adamantanethiolate) has a multiple-shell structure with an Ag71 core protected by a shell of Ag70X12(S-Adm)40. The Ag71 core can be considered as 20 frequency-two Ag10 tetrahedra fused together with a dislocation that resembles multiple-twinning in nanoparticles. The nanocluster…

A Density Functional Study of Open-Shell Cyclopentadienyl−Molybdenum(II) Complexes. A Comparison of Stabilizing Factors: Spin-Pairing, Mo−X π Bonding…

2000

International audience; The dissociation of PH3 from the 18-electron system CpMoX(PH3)3 to afford the corresponding 16-electron CpMoX(PH3)2 fragment has been investigated theoretically by density functional theory for X = H, CH3, F, Cl, Br, I, OH, and PH2. The product is found to prefer a triplet spin state for all X ligands except PH2, the singlet−triplet gap varying between 1.7 kcal/mol for OH to 8.7 kcal/mol for F. The Mo−PH3 bond dissociation energy to the 16-electron ground state varies dramatically across the series, from 4.5 kcal/mol for OH to 23.5 kcal/mol for H, and correlates with experimental observations on trisubstituted phosphine derivatives. Geometry-optimized spin doublet Cp…

The Generation Effect: Cavity Accessibility in Dense‐Shell Polyphenylene Dendrimers

2014

Size exclusion is a widespread phenomenon in supra- and macromolecular chemistry. Herein, the size exclusion properties of polyphenylene dendrimers on the surface of high fundamental frequency quartz crystal microbalances are reported. For this purpose, a new dense fifth-generation polyphenylene dendrimer, which was previously not possible owing to the high steric demand of the dendron arms, was synthesized. By increasing the volume and size of subjected analytes an affinity shift from smaller to larger dendrimers can be obtained.

Tiedemiehiä ja tiedon rajoja : fantastisen merkitys Frankensteinissa ja Draculassa

2005

INVESTIGATIONS OF STRAIN AND STRESS STATE AND CAPACITY IN SHORT CYLINDRICAL SHELLS UNDER INTERNAL PRESSURE

1989

In the paper it has been assumed that a triaxial stress and strain state occurs in a shell. The finite element method was used and owing to that digitization of the problem was possible. Such digitization was necessary for a numerical analysis of the moment stress state in the shell. On the ground of physical relations of the Prandtl-Reuss plastic flow theory an algorithm was formulated. The algorithm was a basis of calculating strains and stresses and determining capacity in a short cylindrical shell with rigid bottoms. The shell was subject to internal pressure. Experiments were carried out, as well. The results obtained with: equations of the membraneous shell theory, using plastic flow …

First observation of excited states in 108Sb

1995

A spectroscopic study of Sb-108 has been carried out as a part of a larger experiment where in total twenty-nine different residual nuclei were identified. This study gives the first information on excited levels in this nucleus. A low-lying two-quasi-particle multiplet together with some of the higher lying levels are discussed within the framework of the nuclear shell model. A rotational, strongly coupled, band is identified as, most likely, being built on the deformed pig9/2(-1) nuh11/2 configuration in accordance with total routhian surface calculations. Tentative spins and parities are presented as well as B(M1)/B(E2) ratios for some of the transitions in the strongly coupled band.

Minute co-variations of Sr/Ca ratios and microstructures in the aragonitic shell of Cerastoderma edule (Bivalvia) – Are geochemical variations at the…

2017

Abstract It remains a challenging task to reconstruct water temperatures from Sr/Ca ratios of bivalve shells. Although in many aragonitic species, Sr/Ca is negatively correlated to temperature – which is expected based on abiogenic precipitation experiments, the incorporation of Sr into the shell of bivalves is strongly controlled by physiological processes and occurs away from the predicted thermodynamic equilibrium. Strontium-to-calcium ratios of aragonitic shells remain far below that of the ambient water. Moreover, Sr concentrations vary considerably among shell portions consisting of different microstructures and/or organic content. Values observed at annual growth lines and within the…

HyperShell: An expert system shell in a hypermedia environment—application in medical audiology

1990

HyperShell is an expert system shell developed in a hypermedia environment. Several artificial intelligence techniques such as frames and semantic networks are used in an original interpretation to enhance the interaction between the user and the program. The typical navigation tools of hypermedia such as clickable buttons and text search are extended to the semantic structure of HyperShell, creating a set of new tools. Examples from a medical expert system (Audex HM) developed in HyperShell are described.

Growth patterns of the topshell Phorcus lineatus (da Costa, 1778) in northern Iberia deduced from shell sclerochronology

2019

Combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns, respectively. Recent investigations have shown that the gastropod Phorcus lineatus (da Costa, 1778) forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment, demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies. In contrast, the shell growth patterns of this species have received virtually no attention despite providing infor…

Atomistic simulation of SrTiO3 and BaTiO3 (110) surface relaxations

2000

Abstract The (110) surface relaxations were calculated for SrTiO 3 and BaTiO 3 perovskites in a cubic phase. Using a shell model, the positions of atoms in 16 near- surface layers placed atop a slab of rigid ions are calculated. The strong surface rumpling and induced surface dipole moments perpendicular to the surface are predicted for both the O-terminated and TiO-terminated surfaces.