Formation energies of low-indexed surfaces of tin dioxide terminated by nonmetals

The surface formation energies of four low-indexed surfaces, including (001), (100), (110) and (011), of tin dioxide (SnO2) terminated by nonmetals (H, N, O, F, Cl, Br, and I) have been studied with the frameworks of density functional theory. A strong dependence of relative surface stabilities on surface atoms has been presented based on the calculations. Several instructions, in particular the selection of specific precursors and morphology controlling agents, have been further illustrated as a guideline for experimentalists.

Bond dissociation energies of organic molecules

In this Account we have compiled a list of reliable bond energies that are based on a set of critically evaluated experiments. A brief description of the three most important experimental techniques for measuring bond energies is provided. We demonstrate how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.

Correlations and volatility spillovers across commodity and stock markets: Linking energies, food, and gold

This paper employs a VAR-GARCH model to investigate the return links and volatility transmission between the S&P 500 and commodity price indices for energy, food, gold and beverages over the turbulent period from 2000 to 2011. Understanding the price behavior of commodity prices and the volatility transmission mechanism between these markets and the stock exchanges are crucial for each participant, including governments, traders, portfolio managers, consumers, and producers. For return and volatility spillover, the results show significant transmission among the S&P 500 and commodity markets. The past shocks and volatility of the S&P 500 strongly influenced the oil and gold markets. This study finds that the highest conditional correlations are between the S&P 500 and gold index and the S&P 500 and WTI index. We also analyze the optimal weights and hedge ratios for commodities/S&P 500 portfolio holdings using the estimates for each index. Overall, our findings illustrate several important implications for portfolio hedgers for making optimal portfolio allocations, engaging in risk management and forecasting future volatility in equity and commodity markets. © 2013 Elsevier B.V.

Cultural safety and diversity: Refocusing our energies in mental health nursing practice, education and research

INTRODUCTION AND BACKGROUND: This presentation draws on a body of work assessing cultural safety's potential to generate change in mental health nursing research (Cox and Simpson 2015), in education and in clinical practice (Cox and Taua 2013, 2016; Happell, Cowin, Roper, Lakeman & Cox 2013). It presents evidence to suggest that cultural safety could resolve the conceptual confusion surrounding culture and diversity in nursing curricular, in clinical and in research practice. The history and nature of mental health work recommend cultural safety to focus attention on diversity, power imbalance, racism, cultural dominance, and structural inequality, identified as barriers and tensions in clinical practice and in service user participation. Cultural safety gives mental health nursing a well theorized and articulated model, which is evolving to improve practice into the future. DESCRIPTION: This work involved an immersion in the literature on cultural safety and the Service User Research movement. It draws on 5 months' work with a service users' research group in the UK and reflections on 9 years of cultural safety teaching. POLICY/PRACTICE CHANGE: This work provokes a crucial change of emphasis from locating the source of issues in the diversity of people to locating it in how society responds to diversity: a change from individualistic to systemic concerns. IMPLICATIONS FOR MENTAL HEALTH NURSING: Cultural safety in clinical practice, education, and research is specifically concerned with awareness of the impact of systemic workplace cultures and with staff cultural self-awareness to bring about cultural change and person-centred care of individuals' unique needs and aspirations within their life context.

Time-Dependent Density Functional Molecular Orbital and Excited State Calculations on Bis(porphyrinyl)butadiynes in the Monocationic, Neutral, Monoanionic, and Dianionic Oxidation States

We report a theoretical study of the multiple oxidation states (1+, 0, 1−, and 2−) of a meso,meso-linked diporphyrin, namely bis[10,15,20-triphenylporphyrinatozinc(II)-5-yl]butadiyne (4), using Time-Dependent Density Functional Theory (TDDFT). The origin of electronic transitions of singlet excited states is discussed in comparison to experimental spectra for the corresponding oxidation states of the close analogue bis{10,15,20-tris[3‘,5‘-di-tert-butylphenyl]porphyrinatozinc(II)-5-yl}butadiyne (3). The latter were measured in previous work under in situ spectroelectrochemical conditions. Excitation energies and orbital compositions of the excited states were obtained for these large delocalized aromatic radicals, which are unique examples of organic mixed-valence systems. The radical cations and anions of butadiyne-bridged diporphyrins such as 3 display characteristic electronic absorption bands in the near-IR region, which have been successfully predicted with use of these computational methods. The radicals are clearly of the “fully delocalized” or Class III type. The key spectral features of the neutral and dianionic states were also reproduced, although due to the large size of these molecules, quantitative agreement of energies with observations is not as good in the blue end of the visible region. The TDDFT calculations are largely in accord with a previous empirical model for the spectra, which was based simplistically on one-electron transitions among the eight key frontier orbitals of the C4 (1,4-butadiyne) linked diporphyrins.

Electronic states of trans-polyacetylene, poly(p-phenylene vinylene) and sp-hybridised carbon species in amorphous hydrogenated carbon probed by resonant Raman scattering

Inclusions of sp-hybridised, trans-polyacetylene [trans-(CH)x] and poly(p-phenylene vinylene) (PPV) chains are revealed using resonant Raman scattering (RRS) investigation of amorphous hydrogenated carbon (a-C:H) films in the near IR – UV range. The RRS spectra of trans-(CH)x core Ag modes and the PPV CC-H phenylene mode are found to transform and disperse as the laser excitation energy ћωL is increased from near IR through visible to UV, whereas sp-bonded inclusions only become evident in UV. This is attributed to ћωL probing of trans-(CH)x chain inhomogeneity and the distribution of chains with varying conjugation length; for PPV to the resonant probing of phelynene ring disorder; and for sp segments, to ћωL probing of a local band gap of end-terminated polyynes. The IR spectra analysis confirmed the presence of sp, trans-(CH)x and PPV inclusions. The obtained RRS results for a-C:H denote differentiation between the core Ag trans-(CH)x modes and the PPV phenylene mode. Furthermore, it was found that at various laser excitation energies the changes in Raman spectra features for trans-(CH)x segments included in an amorphous carbon matrix are the same as in bulk trans-polyacetylene. The latter finding can be used to facilitate identification of trans-(CH)x in the spectra of complex carbonaceous materials.

The way forward : report on the preparatory phase of prefabricated building design and construction methodology: identifying critical issues and recommending the way forward

This is an initial report of the PolyU SD part of the team to study Pre-fabricated Building Design and Construction Methodology and marks the completion of Phase 1. It follows our first notes prepared for the meeting on 2 February that identified some critical issues including future lifestyles, life expectancy of buildings, sustainability, size, flexibility and planning considerations. It is also an expansion of our presentation in Dongguan on 23 February. It is not a comprehensive survey of existing approaches or possible ways forward, but it has homed in on certain specific issues and does give specific examples to make the suggestions concrete. It is recommended that more comprehensive research be done to establish previous work and experience internationally. It is also recommended that more research be done on lifestyles as a preliminary to developing at least three concepts for evaluation before proceeding to the detailed design of one concept for full prototyping and market testing. The goal at this point is not to define a single direction but to suggest several future trajectories for further consideration. By the same token, this report is not intended as an exhaustive description of the considerable base of knowledge and ideas brought by the PolyU team to this exciting task. Before taking on an issue of this magnitude and importance in the definition of Hong Kong's future, one must carry out a thoughtful analysis of the issues at hand and an informed definition of paradigms, directions, goals and methods whereby our energies can be best used in the next steps. This report is the result of this analysis

Compliance in peritoneal dialysis : a qualitative study of renal nurses

End-stage renal failure is a life-threatening condition, often treated with home-based peritoneal dialysis (PD). PD is a demanding regimen, and the patients who practise it must make numerous lifestyle changes and learn complicated biomedical techniques. In our experience, the renal nurses who provide mostPDeducation frequently express concerns that patient compliance with their teaching is poor. These concerns are mirrored in the renal literature. It has been argued that the perceived failure of health professionals to improve compliance rates with PD regimens is because ‘compliance’ itself has never been adequately conceptualized or defined; thus, it is difficult to operationalize and quantify. This paper examines how a group of Australian renal nurses construct patient compliance with PD therapy. These empirical data illuminate how PD compliance operates in one practice setting; how it is characterized by multiple and often competing energies; and how ultimately it might be pointless to try to tame ‘compliance’ through rigid definitions and measurement, or to rigidly enforce it in PD patients. The energies involved are too fractious and might be better spent, as many of the more experienced nurses in this study argue, in augmenting the energies that do work well together to improve patient outcomes.

Estimating total cross sections from neutron-nucleus collisions using a simple functional form

Total cross sections for neutron scattering from nuclei, with energies ranging from 10 to 600 MeV and from many nuclei spanning the mass range 6Li to 238U, have been analyzed using a simple, three-parameter, functional form. The calculated cross sections are compared with results obtained by using microscopic (g-folding) optical potentials as well as with experimental data. The functional form reproduces those total cross sections very well. When allowance is made for Ramsauer-like effects in the scattering, the parameters of the functional form required vary smoothly with energy and target mass. They too can be represented by functions of energy and mass.

Optical absorption and EPR studies on tenorite mineral

Optical absorption and EPR studies of the mineral tenorite, a cupric oxide, which originated from Mexico and contains 54.40 wt% of CuO. EPR spectral results indicate two Cu(II) closely interacting ions to give a d2 type structure. The calculated spin Hamiltonian at Rt and LNT are g = 2.160 and D = 125 G . The intensity of resonance line is not the same in low and high field regions. The optical absorption spectrum is due to Cu(II) which three sets of energies indicating Cu(II) in two independent tetragonal C4v symmetry, in addition to d2 structure of octahedral coordination. The octahedral and tetragonal field parameters are compared with those reported for several other copper containing minerals.

Effects of collimator backscatter in an Elekta linac by Monte Carlo simulation

The effects of radiation backscattered from the secondary collimators into the monitor chamber in an Elekta linac (producing 6 and 10 MV photon beams) are investigated using BEAMnrc Monte Carlo simulations. The degree and effects of this backscattered radiation are assessed by evaluating the changes to the calculated dose in the monitor chamber, and by determining a correction factor for those changes. Additionally, the fluency and energy characteristics of particles entering the monitor chamber from the downstream direction are evaluated by examining BEAMnrc phase-space data. It is shown that the proportion of particles backscattered into the monitor chamber is small (<0.35 %), for all field sizes studied. However, when the backscatter plate is removed from the model linac, these backscattered particles generate a noticeable increase in dose to the monitor chamber (up to approximate to 2.4 % for the 6 MV beam and up to 4.4 % for the 10 MV beam). With its backscatter plate in place, the Elekta linac (operating at 6 and 10 MV) is subject to negligible variation of monitor chamber dose with field size. At these energies, output variations in photon beams produced by the clinical Elekta linear accelerator can be attributed to head scatter alone. Corrections for field-size-dependence of monitor chamber dose are not necessary when running Monte Carlo simulations of the Elekta linac operating at 6 and 10 MV.

Thermal tweezers for manipulation of adatoms and nanoparticles on surfaces heated by interfering laser pulses

We conduct the detailed numerical investigation of a nanomanipulation and nanofabrication technique—thermal tweezers with dynamic evolution of surface temperature, caused by absorption of interfering laser pulses in a thin metalfilm or any other absorbing surface. This technique uses random Brownian forces in the presence of strong temperature modulation (surfacethermophoresis) for effective manipulation of particles/adatoms with nanoscale resolution. Substantial redistribution of particles on the surface is shown to occur with the typical size of the obtained pattern elements of ∼100 nm, which is significantly smaller than the wavelength of the incident pulses used (532 nm). It is also demonstrated that thermal tweezers based on surfacethermophoresis of particles/adatoms are much more effective in achieving permanent high maximum-to-minimum concentration ratios than bulk thermophoresis, which is explained by the interaction of diffusing particles with the periodic lattice potential on the surface. Typically required pulse regimes including pulse lengths and energies are also determined. The approach is applicable for reproducing any holographically achievable surfacepatterns, and can thus be used for engineering properties of surfaces including nanopatterning and design of surface metamaterials.

Thin film deposition and characterization of pure and iron-doped electron-beam evaporated tungsten oxide for gas sensors

Pure Tungsten Oxide (WO3) and Iron-doped (10 at%) Tungsten Oxide (WO3:Fe) nanostructured thin films were prepared using a dual crucible Electron Beam Evaporation techniques. The films were deposited at room temperature in high vacuum condition on glass substrate and post-heat treated at 300 oC for 1 hour. From the study of X-ray diffraction and Raman the characteristics of the as-deposited WO3 and WO3:Fe films indicated non-crystalline nature. The surface roughness of all the films showed in the order of 2.5 nm as observed using Atomic Force Microscopy (AFM). X-Ray Photoelectron Spectroscopy (XPS) analysis revealed tungsten oxide films with stoichiometry close to WO3. The addition of Fe to WO3 produced a smaller particle size and lower porosity as observed using Transmission Electron Microscopy (TEM). A slight difference in optical band gap energies of 3.22 eV and 3.12 eV were found between the as-deposited WO3 and WO3:Fe films, respectively. However, the difference in the band gap energies of the annealed films were significantly higher having values of 3.12 eV and 2.61 eV for the WO3 and WO3:Fe films, respectively. The heat treated samples were investigated for gas sensing applications using noise spectroscopy and doping of Fe to WO3 reduced the sensitivity to certain gasses. Detailed study of the WO3 and WO3:Fe films gas sensing properties is the subject of another paper.

Adiabatic compression testing - part II : background and approach to estimating severity of test methodology

Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies; however, a thorough evaluation of the test parameters and test system influences on the thermal energy produced during the test has not yet been performed. This paper presents a background for adiabatic compression testing and discusses an approach to estimating potential differences in the thermal profiles produced by different test laboratories. A “Thermal Profile Test Fixture” (TPTF) is described that is capable of measuring and characterizing the thermal energy for a typical pressure shock by any test system. The test systems at Wendell Hull & Associates, Inc. (WHA) in the USA and at the BAM Federal Institute for Materials Research and Testing in Germany are compared in this manner and some of the data obtained is presented. The paper also introduces a new way of comparing the test method to idealized processes to perform system-by-system comparisons. Thus, the paper introduces an “Idealized Severity Index” (ISI) of the thermal energy to characterize a rapid pressure surge. From the TPTF data a “Test Severity Index” (TSI) can also be calculated so that the thermal energies developed by different test systems can be compared to each other and to the ISI for the equivalent isentropic process. Finally, a “Service Severity Index” (SSI) is introduced to characterizing the thermal energy of actual service conditions. This paper is the second in a series of publications planned on the subject of adiabatic compression testing.