The spectrum of the Liouville-von Neumann operator in the Hilbert-Schmidt space

The singular continuous spectrum of the Liouville operator of quantum statistical physics is, in general, properly included in the difference of the spectral values of the singular continuous spectrum of the associated Hamiltonian. The absolutely continuous spectrum of the Liouvillian may arise from a purely singular continuous Hamiltonian. We provide the correct formulas for the spectrum of the Liouville operator and show that the decaying states of the singular continuous subspace of the Hamiltonian do not necessarily contribute to the absolutely continuous subspace of the Liouvillian.

Inter-phyla studies on neuropeptides: the potential for broad-spectrum anthelmintic and/or endectocide discovery

Flatworm, nematode and arthropod parasites have proven their ability to develop resistance to currently available chemotherapeutics. The heavy reliance on chemotherapy and the ability of target species to develop resistance has prompted the search for novel drug targets. In view of its importance to parasite/pest survival, the neuromusculature of parasitic helminths and pest arthropod species remains an attractive target for the discovery Of novel endectocide targets. Exploitation of the neuropeptidergic system in helminths and arthropods has been hampered by a limited Understanding of the functional roles of individual peptides and the structure of endogenous targets, such as receptors. Basic research into these systems has the potential to facilitate target characterization and its offshoots (screen development and drug identification). Of particular interest to parasitologists is the fact that selected neuropeptide families are common to metazoan pest species (nematodes, platyhelminths and arthropods) and fulfil specific roles in the modulation of muscle function in each of the three phyla. This article reviews the inter-phyla activity of two peptide families, the FMRFamide-like peptides and allatostatins, on motor function in helminths and arthropods and discusses the potential of neuropeptide signalling as a target system that could uncover novel endectocidal agents.

The effect of H-2 and the presence of hot-O-(ads) during the decomposition of N2O on platinum

The decomposition of N2O was studied using a silica-supported Pt catalyst. The catalyst was found to exhibit short-lived activity at low temperatures to yield N-2 and O-(ads), the latter remained adsorbed on the surface and poisoned the active sites. Creation of hot-O-(ads) atoms during N2O decomposition is proposed to allow O-2 desorption at intermediate temperatures. Inclusion of H-2 as a reducing agent greatly enhanced the activity and suppressed low temperature deactivation. Simultaneous and sequential pulsing of N2O and H-2 showed that H-2 inclusion with the N2O gas stream produced the greatest activity. A mechanism involving H-(ads) addition to

Low-temperature catalytic decomposition of N2O on platinum and bismuth-modified platinum: identification of active sites

Classification of the active surface sites of platinum catalysts responsible for low temperature N2O decomposition, in terms of steps, kinks and terraces, has been achieved by controlled addition of bismuth to as-received platinum/graphite catalysts.

A first principles study of methanol decomposition on Pd(111): Mechanisms for O-H bond scission and C-O bond scission

There is some dispute as to whether methanol decomposition occurs by O-H bond scission or C-O bond scission. By carrying out density functional theory calculations, we investigate both scenario of the reaction pathways of methanol decomposition on a Pd(111) surface. It is shown that the O-H bond scission pathway is much more energetically favorable than the C-O bond scission pathway. The high reaction barrier in the latter case is found to be due to the poor bonding abilities of CH3 and OH with the surface at the reaction sites. (C) 2001 American Institute of Physics.

Phase transition and decomposition temperatures, heat capacities and viscosities of pyridinium ionic liquids

Ionic liquids are organic salts with low melting points. Many of these compounds are liquid at room temperature in their pure state. Since they have negligible vapor pressure and would not contribute to air pollution, they are being intensively investigated for a variety of applications, including as solvents for reactions and separations, as non-volatile electrolytes, and as heat transfer fluids. We present melting temperatures, glass transition temperatures, decomposition temperatures, heat capacities, and viscosities for a large series of pyridinium-based ionic liquids. For comparison, we include data for several imidazolium and quaternary ammonium salts. Many of the compounds do not crystallize, but form glasses at temperatures between 188 K and 223 K. The thermal stability is largely determined by the coordinating ability of the anion, with ionic liquids made with the least coordinating anions, like bis(trifluoromethylsulfonyl)imide, having the best thermal stability. In particular, dimethylaminopyridinium bis(trifluoromethylsulfonyl)imide salts have some of the best thermal stabilities of any ionic liquid compounds investigated to date. Heat capacities increase approximately linearly with increasing molar mass, which corresponds with increasing numbers of translational, vibrational, and rotational modes. Viscosities generally increase with increasing number and length of alkyl substituents on the cation, with the pyridinium salts typically being slightly more viscous than the equivalent imidazolium compounds. (c) 2005 Elsevier Ltd. All rights reserved.

Family functioning during the diagnosis process in families with children on the autism spectrum,

While the causes of autism spectrum disorder (ASD) still are not fully understood, increasingly research focuses on interventions and treatment of children diagnosed with ASD. Considerably less attention is paid to family systems, family functioning, and family needs. This paper takes a family system perspective exploring how families with children on the autism spectrum function during the particularly stressful period of the diagnosis process and thereafter. Recommendations made in this paper include the need for empirical studies that address in detail family systems, family needs, the assessment and diagnostic process, service provision, social support networks, and additional stressful life events. Furthermore, the development of a family functioning assessment tools is called for in order to promote child-family-centred assessment and intervention. Details of an ongoing comparative study are outlined that will make a contribution to family studies and autism research field with a specific focus on the diagnosis

Experiences of parents during diagnosis and forward planning for children with Autism Spectrum Disorder.

Background For families of children diagnosed with autism spectrum disorder (ASD) getting a diagnosis is a traumatic experience on which future care and education plans for the child depend. In this paper parental experiences of diagnosis and forward planning for children with ASD are reported. Method This paper is part of a large cross-sectional study conducted in Northern Ireland and the Republic of Ireland that assessed the needs and experiences of parents of children diagnosed with ASD. Questionnaires were designed and completed by 95 parents, reporting on 100 children, as well as 67 multi-disciplinary professionals. Results Findings confirm that diagnostic and planning processes are extremely stressful for parents, that statutory diagnosis takes a long time, that care and education plans do not include full parental participation, and that reviews of plans do not consistently include intervention data. Conclusion Policy and practice implications of these findings are important for future revisions of diagnostic tools and manuals.

Living with children diagnosed with Autism Spectrum Disorder: Parental and professional views

The number of children diagnosed with an autistic spectrum disorder (ASD) is rising and is now thought to be as high as 1:100. While the debate about best treatment continues, the effects of having a child diagnosed with ASD on family life remain relatively unexplored. This article, by Karola Dillenburger of Queens University Belfast, Mickey Keenan of the University of Ulster, Alvin Doherty from the Health Service Executive Western Region, Tony Byrne of Parents’ Education as Autism Therapists (PEAT) and Stephen Gallagher of the University of Ulster, sets out to adjust that balance. Drawing upon data from a comprehensive study of parental needs, these authors argue that parental and professional views do not always concur; that families make extraordinary sacrifices; that siblings are affected; and that parents are under tremendous stress. Parents argue that educational and social service supports are not efficient and that they are forced to rely largely on support from within the family or from friends. In particular, some important differences between parental and professional perceptions became apparent in relation to interventions based on Applied Behaviour Analysis (ABA). The authors of this article propose that these differences need to be taken seriously by teachers and other professionals as well as by policy-makers.

Phylloseptin-1 (PSN-1) from Phyllomedusa sauvagei skin secretion: a novel broad-spectrum antimicrobial peptide with antibiofilm activity

Amphibian skin secretions have proven to be rich sources of antimicrobial peptides that are proposed to be fundamental components of the innate immune system. As amphibian skin is a multi-functional organ playing, among other things, a crucial role in respiration, it has been deemed that a core biological role for such peptides is control of microbial flora on this surface. To date, however, antimicrobial efficacy has been universally determined by means of establishing minimum inhibitory concentrations (MICs) using planktonic organisms rather than those within a biofilm such as would occur on this exposed surface. Here we describe the identification and structural characterisation of a novel 19 amino acid residue antimicrobial peptide of the phylloseptin family, named PSN-1, from the skin secretion of the waxy monkey frog, Phyllomedusa sauvagei. PSN-1 displayed broad-spectrum activity against a range of planktonic organisms with a high potency (MIC 5 µM) against Staphylococcus aureus. In a specific bioassay with the same organism grown as a biofilm, the minimal biofilm eradication concentration (MBEC) was found to be of the same high potency (5 µM). The present data would suggest that evaluation of actions and potency of amphibian skin secretion antimicrobial peptides might best be achieved by evaluating MBEC rather than MIC using planktonic organisms and that data arising from such studies may have more biological relevance in reflecting the purpose for which they have evolved through natural selection.