Adoption of near-coincident-site lattice orientations by contacting monolayer rafts of metallic nanoparticles with different superlattice periodicities

A hexagonal raft of monodisperse alkane-thiol-stabilized Au nanoparticles has been self-assembled from solution on to an amorphous C substrate and then subsequently a second layer of monodisperse but differently sized gold nanoparticles deposited on top of the first. Detailed analysis of electron micrographs obtained from various regions of this bilayer revealed the presence of several distinct epitaxial interface structures. A simple near-coincident-site lattice model is used to rationalize the existence of the observed characteristic nanoparticle interface structures.     

Foam coarsening under forced drainage

A monodisperse liquid foam is allowed to coarsen while subject to a constant flow of liquid. The average bubble size is indirectly monitored by measurement of the velocity of forced drainage waves. After an initial period the average bubble diameter is found to increase with the square root of time. The rate of this increase is a function of the flow rate; coarsening is slower in wet foams. This rate is linked to the variation in the film area in a foam as a function of liquid fraction.     

Energy,compressibility and covalency in the carbon subgroup

It is shown that a scaling relation of the type K V ₀/ E ₀ constant, where K₀, V₀ and E₀ are the bulk modulus, volume and total energy respectively at normal pressure, holds for the C subgroup of the Mendeleev periodic table of elements, which consists of C itself, Si, Ge, Sn and Pb. This means that so-called covalency does not contribute significantly to the compressibility of the corresponding substances. The extreme high value of the bulk modulus of diamond is clearly the result of its highest known atomic density.     

On the macroscopic s- and d -wave symmetry in cuprate superconductors

The relevant recent experiments probing the surface and probing the bulk of cuprate superconductors are reviewed. The former yield without doubt d -wave symmetry, whereas the latter suggest a substantial s -symmetry component, at least. To reconcile these observations, it is proposed that the superconducting wavefunction varies as a function of the distance x from the surface. Its character is d on the surface and substantially s in the bulk. This is only possible by going beyond known classical solid-state theory, but it is borne out by the presence of supersymmetry.     

The order–dsorder transition at twin boundaries in Cu3Au as studied by TEM

Abstract

The order-disorder phase transition at ∑ = 3{111}- and {211}-type twin boundaries has been studied in the L1²-ordered alloy Cu³Au employing in situ heating in a transmission electron microscope. Evidence is presented for an order-disorder phase transition occurring in these boundaries prior to the bulk transition. The temperature difference ΔT between the transition temperature of both boundary types and the bulk is estimated as 0.5K <ΔT<2K. No difference in T _c for the twin boundaries can be established as yet. The nature of the order-disorder transition in both twin boundaries is presumably a second-order phase transition.     

The relative energy of fcc and hcp foams

The energies of face-centred cubic (fcc) and hexagonal close-packed (hcp) monodisperse foams, associated with their total surface area, are equal in the wet and dry limits, in the usual model. We prove that for all intermediate values of liquid fraction, hcp has lower energy. Energy considerations are thus not sufficient to explain the observed preference for crystallization into fcc over hcp in experiments using monodisperse bubbles.     

Observation of positron trapping in nickel vacancies in single-crystal nickel oxide

Abstract

Positron lifetime spectroscopy has been used to observe trapping of positrons in single-crystal NiO prepared with excess non-stoichiometry of oxygen. Two lifetime components are resolved; the longer lifetime and its intensity are interpreted as due to localisation of positrons in nickel vacancies. The positron bulk lifetime deduced from the results is 150ps and is in good agreement with theoretical calculations.     

Plastic behaviour of an AlAs/GaAs superlattice with a short period

Nanoindentation has been used to investigate the plastic behaviour of an AlAs/GaAs superlattice with a short period. The sample was grown on a (001) surface of a GaAs single crystal by metal-organic vapour-phase epitaxy. The mechanical response of the superlattice to nanoindentation testing was compared with that of a (001) surface of bulk GaAs. The indents formed were observed by transmission electron microscopy. The plastic zone size associated with each indent was measured as a function of the maximum load. Finally the arrangement of the dislocations generated by the indenter has been analysed and compared with the arrangement observed in deformed bulk GaAs.     

On the size dependence of the critical point of nanoscale interstitial solid solutions

It is shown that a size dependence of the critical temperature T_c of the miscibility gap in nanocrystalline and nanoscale particle interstitial solid solutions results from stress owing to elastic interaction of the bulk with layers of material at the grain boundaries or surfaces which have a small solute susceptibility (i.e. a weak dependence of the concentration on the chemical potential) at the phase transition. When the volume fraction occupied by the interfacial layers is not too large, then the changes in T_c and in the critical concentration x_c can be predicted on the basis of a series expansion of the solute chemical potential in the bulk about the critical point. The model can be extended to free-standing thin films and coherent multilayers. The dependence of the pressure on the hydrogen concentration in the crystal lattice of nanocrystalline palladium-hydrogen is measured on the basis of X-ray diffraction data. The result agrees with the predictions of the theory.     

Hot isostatic pressing of bulk magnesium diboride: Mechanical and superconducting properties

Hot isostatic pressing with glass encapsulation (pressure, 200MPa; temperature, 1000C over 200min; cooling under pressure) was used to synthesize bulk MgB 2 with diameters up to 20mm and thicknesses up to 10mm from MgB 2 powder. A sharp superconducting transition was measured at 38.5K. This method can be scaled to larger sample sizes and complex shapes. The data for density, microhardness, fracture toughness and sound speed for bulk magnesium diboride are presented. Ball milling the powder results in a more homogeneous final microstructure with a higher resistivity and with a similar superconducting transition.     

Tension and compression of bulk Al-7.5 wt% Mg alloy

The mechanical behaviour of bulk ultrafine-grained Al-7.5 wt% Mg alloy consolidated from cryomilled powders has been investigated. The experimental data show that the alloy exhibits high strength, low strain hardening, serrated flow and relatively high ductility. In addition, the data indicate that the yield strength in tension is essentially equal to that in compression. The yield and flow strengths of the alloy are discussed in terms of strengthening processes that are related to grain size, the Orowan mechanism and solid-solution hardening. The serrations in the stress-strain curve are discussed in terms of dynamic strain ageing and deformation twinning.     

'Nanotwin' networks connecting columnar defects in YBa2Cu3O7-delta and implications for magnetic vortex interactions

A unique structure, a network of nanotwins, is revealed for the first time in high-energy ion-irradiated YBa₂Cu₃O_7-delta. This structure is shown to form only at ion doses of 1011 cm-2 or greater and thus is not revealed in any earlier electron microscopy studies. In this higher-dose regime, the well known columnar defects are connected by the nanotwin structure, thus affecting bulk superconducting properties. Consequences for a number of published interpretations of such measurements related to pinning and dynamics of magnetic vortices are discussed.     

THE UNIVERSITY AND THE STATE IN A PLURAL SOCIETY

Abstract

I address what I call the ‘Number Issue’, which is raised by our ordinary talk and beliefs about certain social groups and institutions, and I take the Hallé orchestra as my example. The Number Issue is that of whether the Hallé is one individual or several individuals. I observe that if one holds that it is one individual, one faces an accusation of metaphysical extravagance. The bulk of the paper examines the difficulty of reconciling the view that the Hallé is several individuals with two prima facie plausible theses about the manner of its persistence through time. The paper is structured around some remarks made by Peter Simons about groups, and the Hallé in particular, in his Parts.     

Band-edge states in ultrasmall silicon quantum boxes: Calculations of electronic states and oscillator strengths

Band-edge states and oscillator strengths in four configurations of ultrasmall Si quantum boxes (QBs) with (100) planes saturated by H have been calculated using the extended Hückel-type non-orthogonal tight-binding method. It is found that, while the valence-band edge states are always bulk like, both bulk-like and surface-like states occur at the conduction-band (CB) edge, depending on the atom configuration of the QB studied. An analysis shows that the surface-like CB edge states are caused by an interhydride interaction between trihydride units on the hydrogenated QB surface and there is significant correlation of oscillator strength with the CB edge states.     

EELS analysis of vacuum arc-deposited diamond-like films

Abstract

Electron energy-loss spectroscopy measurements have been made on amorphous diamond-like carbon films produced by condensing the plasma stream from a filtered vacuum arc. The results are compared with spectra from diamond, graphitized carbon and amorphous carbon. Although the energy-loss spectra reveal the presence of a small quantity of sp²-bonded material in the diamond-like film, the high plasmon frequency and shape of the K-edge show that the material is essentially an amorphous form of diamond. The fraction of sp²- bonded carbon was quantified and found to be of the order of 15%. It was not possible to determine if the sp² carbon was on the surface or throughout the bulk.     

A thermodynamic model for nanocrystallization in bulk metallic glasses

The structural complexity of glass-forming alloys, which generally contain more than three components, can lead by partial crystallization during annealing to a dispersion of nanocrystals in an amorphous matrix, giving the material a very high mechanical strength. In the present study, the evolution of the driving force for crystallization is expressed as a function of the composition and the chemical potentials of the components. Application to Zr₆₀Al₁₀Cu₃₀ and Zr₆₀Al₁₀Cu₂₀Pd₁₀ bulk metallic glasses shows that the first crystallization step leads to a metastable equilibrium between nanocrystals of an intermetallic and a percolating amorphous phase. The effects of the number of components and of chemical bonding on the fraction crystallized is analysed and discussed.     

The (Neglected) role of the father in Children's mental health

BackgroundAlthough the bulk of the literature on child development, historically, has focused on the significant role of the mother, less attention has been given to that of the father. Therefore, more attention has been given to fathers’ roles in the last 20–30 years.AimThe aim of the current review was to explore the role of the father on a child's development.MethodsAn extensive literature search using 'Psycharticles', ‘PsychInfo’, and ‘Google Scholar’ databases using terms like 'father's role', 'child/children's', 'child development', and 'mental health' was conducted to achieve the objective of the study.ResultsFathers were found to play a significant role in nurturing their children. Fathers are considered to be important for the development of the child's autonomy, the shaping of gender identity, and the development of the moral system of the child. Usually, he is the one who establishes the feeling of security in the child's mind. He is considered to be the protector and defender of the family Freud's position is that the father is the symbol of security, power, and authority for the child.ConclusionAlthough the original aim of the research was to draw a line between parents' roles in the family and shed light on the father's role, the findings suggest that the fundamental concept in nurturing children depends on the complementary roles of parents as children need their parents equally.     

Mental Health Interventions in a General Hospital Following Terrorist Attacks

Abstract

Over three years of repeated terrorist attacks in Israel have shown that the victims suffering from acute stress syndromes constitute the bulk of the casualties. The large number of psychological victims presents an immediate problem of hospital surge capacity. The need for alleviating acute suffering and preventing chronic, disabling posttraumatic syndromes requires organizational and clinical skills. The article reviews deployment and intervention protocols for the treatment of victims and affected staff members in a general hospital setting.     

Three kinds of reliabilism

Abstract

The distinction between acting and suffering underlies any theory of agency. Among contemporary writers, Fred Dretske is one of the few who has attempted to explicate this distinction without restricting the notion of action to intentional action alone. Aristotle also developed a global account of agency, one which is deeper and more detailed than Dretske's, and it is to Aristotle's account (with some modifications) that the bulk of this paper is devoted. Dretske's sketchier theory faces at least two ground-level problems. It is shown in the course of the paper how these can be handled by the Aristotelian account, in a way which is friendly to Dretske's approach.     

Onset of plasticity in a Σ = 5 GaAs compliant structure

Compliant structures have been fabricated in which a thin GaAs layer (thickness between 10 and 20nm) was bonded on top of a GaAs substrate with a large twist angle (about 37). This twist angle value was chosen so that the energy of the boundary (coincident boundary of type =5 (001)) was minimized. The structure of the interface was characterized and the onset of plasticity in such a compliant substructure was investigated using nanoindentation that allowed the low-load deformation regime to be observed. The results are compared with those obtained under the same conditions on a GaAs bulk substrate alone. No plastic zone was observed by transmission electron microscopy in the compliant structure under loads below 0.25mN while, under the same loads, plastic deformation was observed in the bulk substrate. For higher loads (2mN), plastic-flow enhancement was observed in the compliant structure. The results are discussed in the light of the arrangement of dislocations observed in the plastic zones.