Theoretical Study of the Si_<i>n</i>Mg_<i>m</i> Clusters and Their Cations: Toward Silicon Nanowires with Magnesium Linkers

We investigated the structures of the singly and doubly magnesium-doped silicon clusters in both neutral and cationic states, Si_<i>n</i>Mg_<i>m</i>^0/+, with <i>n</i> = 1–10 and <i>m</i> = 1 and 2. Total atomization energies (TAEs), heats of formation (Δ<i>H</i>_f), and binding energies (<i>E</i>_bs) were determined using the composite G4 method. The <i>E</i>_bs of the Mg-doped clusters are decreased with respect to those of the pure Si counterparts, irrespective of the charge state. As no experimental values are actually available for these systems, the predicted thermochemical values can be used with an expected error margin of ±3 kcal/mol (±0.15 eV or ±12 kJ/mol), due to the uncertainty on the experimental heat of formation of the silicon atom and of the method used. The growth sequence of the singly doped neutral Si_<i>n</i>Mg is similar to that of the singly doped neutral Si_<i>n</i>Li clusters. In Si_<i>n</i>Mg structures, the Mg atom tends to favor addition on either an edge or a face of the anionic ground-state structure Si_<i>n</i>^– framework. Only in Si₈Mg, Mg substitutes a Si atom in the Si₉ framework. For the cations Si_<i>n</i>Mg⁺, the behavior of Mg differs from that of Li. The Mg atom seems to cap one edge or face of the cationic Si_<i>n</i>⁺ instead of the neutral bare Si_<i>n</i> as in the case of Li. The doubly Mg-doped neutral Si_<i>n</i>Mg₂ clusters grow basically following a method comparable to that of the doubly doped neutral Si_<i>n</i>X₂ with X = Li and Al reported in previous studies. In their growth pattern, one Mg atom substitutes into a position of Si_<i>n</i>+1, whereas the other Mg atom is usually added on an edge, or a face, of the existing cluster. There are however a few exceptions to this observation, such as Si₁₀Mg₂. In this size, the cyclic framework Si₅–Mg–Si₅–Mg turns out to be more stable than the cage-type Si₁₀–Mg₂. The Si_<i>n</i>Mg₂⁺ cations contain the cationic Si_<i>n</i>+1⁺ frameworks in which one Mg atom actually substitutes into a Si position and the remaining Mg atom caps on an edge, or a face. Again, Si₁₀Mg₂⁺ appears as an exception to this trend. The most interesting result of this study is that the Mg dopant, due to its large electron transfer capacity, behaves as a cation, Mg^δ+, and thereby induces an ionic entity with the Si_<i>n</i>^δ− anionic partner. The resulting Mg cation can serve as a linker between Si<i>_k</i>^δ− blocks, leading to stabilized linear and cyclic [(Si_<i>k</i>)­Mg]_<i>l</i> structures. In the systems with <i>k</i> = 3, 5, 7, 8, and 10, the linear frameworks can be regarded as possible starting blocks for silicon assemblies, giving rise to potential 1D nanowire materials

Structure, Thermochemical Properties, and Growth Sequence of Aluminum-Doped Silicon Clusters Si_<i>n</i>Al_<i>m</i> (<i>n</i> = 1–11, <i>m</i> = 1–2) and Their Anions

A systematic examination of the aluminum doped silicon clusters, Si_<i>n</i>Al_<i>m</i> with <i>n</i> = 1–11 and <i>m</i> = 1–2, in both neutral and anionic states, is carried out using quantum chemical calculations. Lowest-energy equilibrium structures of the clusters considered are identified on the basis of G4 energies. High accuracy total atomization energies and thermochemical properties are determined for the first time using the G4 and CCSD­(T)/CBS (coupled-cluster theory with complete basis set up to <i>n</i> = 3) methods. In each size, substitution of Si atoms at different positions of a corresponding pure silicon clusters by Al dopants invariably leads to a spectrum of distinct binary structures but having similar shape and comparable energy content. Such an energetic degeneracy persists in the larger cluster sizes, in particular for the anions. The equilibrium growth sequences for Al-doped Si clusters emerge as follows: (i) neutral <i>singly doped</i> Si_<i>n</i>Al clusters favor Al atom substitution into a Si position in the structure of the corresponding cation Si_<i>n</i>+1⁺, whereas the anionic Si_<i>n</i>Al^– has one Si atom of the isoelectronic neutral Si_<i>n</i>+1 being substituted by the Al impurity; and (ii) for <i>doubly doped</i> Si_<i>n</i>Al₂^0/– clusters, the neutrals have the shape of Si_<i>n</i>+1 counterparts in which one Al atom substitutes a Si atom and the other Al adds on an edge or a face of it, whereas the anions have both Al atoms substitute two Si atoms in the Si_<i>n</i>+2⁺ frameworks. The Al dopant also tends to avoid high coordination position

Development and validation of the Vietnamese primary care assessment tool

<div><p>Objective</p><p>To adapt the consumer version of the Primary Care Assessment Tool (PCAT) for Vietnam and determine its internal consistency and validity.</p><p>Design</p><p>A quantitative cross sectional study.</p><p>Setting</p><p>56 communes in 3 representative provinces of central Vietnam.</p><p>Participants</p><p>Total of 3289 people who used health care services at health facility at least once over the past two years.</p><p>Results</p><p>The Vietnamese adult expanded consumer version of the PCAT (VN PCAT-AE) is an instrument for evaluation of primary care in Vietnam with 70 items comprising six scales representing four core primary care domains, and three additional scales representing three derivative domains. Sixteen other items from the original tool were not included in the final instrument, due to problems with missing values, floor or ceiling effects, and item-total correlations. All the retained scales have a Cronbach’s alpha above 0.70 except for the subscale of Family Centeredness.</p><p>Conclusions</p><p>The VN PCAT-AE demonstrates adequate internal consistency and validity to be used as an effective tool for measuring the quality of primary care in Vietnam from the consumer perspective. Additional work in the future to optimize valid measurement in all domains consistent with the original version of the tool may be helpful as the primary care system in Vietnam further develops.</p></div

PCAT translation and validation process.

<p>PCAT translation and validation process.</p

Characteristics of the participants (n = 3289).

<p>Characteristics of the participants (n = 3289).</p

Changes in the final translated questionnaires from the original PCAT.

<p>Changes in the final translated questionnaires from the original PCAT.</p

Ultimate Manipulation of Magnetic Moments in the Golden Tetrahedron Au₂₀ with a Substitutional 3d Impurity

Nanocluster systems that are electronically stable and highly magnetic have been of intense research interest due to their potential as magnetic superatoms. In this study, we consider a more intriguing case of the unique golden pyramid with a substitutional 3<i>d</i> impurity. In particular, we investigate the geometry, stability, and magnetic properties of Au₁₉M clusters (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) by means of density functional theory calculations. It is found that the structural patterns of doped species evolve from endohedrally doped cages to exohedrally doped tetrahedrons when M goes from Sc to Cu. The robustness of the Au₂₀ unit tends to be retained in its tetrahedral doped counterparts. Remarkably, the quenched magnetic moment of Au₂₀ increases in a systematic manner with the appearance of 3<i>d</i> impurities. We demonstrate that not only the interaction between the magnetic impurity and valence electrons of the Au host but also the itinerant behavior of the impurity valence states have been taken into account to understand the magnetism of Au₁₉M clusters

Structure Dependent Magnetic Coupling in Cobalt-Doped Silicon Clusters

The structure of cobalt-doped silicon clusters, Si_<i>n</i>Co⁺ (<i>n</i> = 5–8) and Si_<i>n</i>Co₂⁺ (<i>n</i> = 8–12), is investigated in a combined infrared multiple photon dissociation spectroscopy and density functional theory study. The singly doped clusters have exohedral structures in which the Co atom substitutes an atom of bare Si_<i>n</i>+1⁺ clusters. In the doubly doped Si_<i>n</i>Co₂⁺ clusters, the second Co atom is adsorbed to the singly doped counterparts and, for <i>n</i> ≥ 9, one of the Co atoms is encapsulated by a silicon cage. Computational analysis of the electronic and magnetic properties of the identified isomers indicates a distance dependent magnetic coupling between the Co atoms in the Si_<i>n</i>Co₂⁺ clusters

Genotype file for Canine HD semi custom array (bed)

Genotype file for Canine HD semi custom array (bed

Y haplotype calls for indviduals

Y haplotype calls for indvidual