Electronic band structure and Fermi surface of Ag5_5Pb2_2O6_6

We present electronic band structure of Ag$_5$Pb$_2$O$_6$ with layered hexagonal structure containing one-dimensional chains and two-dimensional Kagom\'{e} layers of silver. A half-filled conduction band shows extremely simple, single nearly-free-electron-like Fermi surface. The conduction band is composed of an antibonding state of Pb-$6s$ and O-$2p$ mixing with Ag-4d and $5s$. Mass enhancement in the state density at the Fermi energy is expected to be negligibly small by comparing with the specific-heat data. Calculated Fermi velocity is consistent with small anisotropy observed in transport properties. Doping effects on the electronic structure are also discussed.Comment: 6 pages, 9 figures; fig7 replaced, reference 6 adde

Microscopic Evidence for Evolution of Superconductivity by Effective Carrier Doping in Boron-doped Diamond:11B-NMR study

We have investigated the superconductivity discovered in boron (B)-doped diamonds by means of 11B-NMR on heteroepitaxially grown (111) and (100) films. 11B-NMR spectra for all of the films are identified to arise from the substitutional B(1) site as single occupation and lower symmetric B(2) site substituted as boron+hydrogen(B+H) complex, respectively. A clear evidence is presented that the effective carriers introduced by B(1) substitution are responsible for the superconductivity, whereas the charge neutral B(2) sites does not offer the carriers effectively. The result is also corroborated by the density of states deduced by 1/T1T measurement, indicating that the evolution of superconductivity is driven by the effective carrier introduced by substitution at B(1) site.Comment: 4 pages, 6 figures, to be published in Phys. Rev. B (Brief report

Workplace fraud and theft in SMEs: evidence from the mobile telephone sector in Nigeria

Purpose - This study investigates employee fraud within small enterprises in the Nigerian mobile phone sector. It also seeks to understand the key factors that motivate employees to engage in fraudulent behaviours against their employers, and the consequences of these fraudulent behaviours on small businesses (SMEs) in Nigeria. Design/methodology/approach - The empirical study involves the use of quantitative research. Data was collected through structured questionnaires from 159 business owners, sales representatives, cashiers and suppliers. Frequency distribution, Percentages, Pearson correlation, and multiple regression analysis were used to analyse the collected data. Findings - The findings from this research shows a significant relationship between personal and organisational factors and employee theft. Particularly, organisational factors made the strongest positive contribution to employee theft. The research also revealed that employee theft had significant effects on employers but less significance on employees. In addition, the research revealed that many businesses did not have preventive measures against employee theft in their firms. Originality/Value – This study shows the relationship between different factors that could cause an employee to engage in fraudulent behaviours, particularly in SMEs in Nigeria

Consumers' expectations for product lifetimes of consumer durables

Product lifetimes are a relevant topic of discussion towards establishing a circular economy, particularly in terms of the reduction of environmental impacts by improving product longevity. Various researchers have developed models to estimate actual lifetimes and have reported case studies for some product categories (e.g. electrical and electronic equipment, and vehicles). However, actual lifetimes may not necessarily meet consumers' expectations. Therefore, an integration of the two perspectives—actual and expected product lifetimes—should prove helpful in optimizing product lifetimes. We proposed different definitions of expected product lifetimes from the consumer perspective and then investigated consumer expectations of the product lifetimes of consumer durables according to these definitions. Several types of EEE were examined as case studies, and questionnaire surveys were conducted. We found that exp ected lifetimes varied according to the definition used. Expected product life-times should be measured by using clearly defined terms to analyse the gaps between actual product lifetimes and consumer expectations

J1−J2J_1-J_2 Quantum Heisenberg Antiferromagnet: Improved Spin-Wave Theories Versus Exact-Diagonalization Data

We reconsider the results cocerning the extreme-quantum $S=1/2$ square-lattice Heisenberg antiferromagnet with frustrating diagonal couplings ($J_1-J_2$ model) drawn from a comparison with exact-diagonalization data. A combined approach using also some intrinsic features of the self-consistent spin-wave theory leads to the conclusion that the theory strongly overestimates the stabilizing role of quantum flutcuations in respect to the N\'{e}el phase in the extreme-quantum case $S=1/2$. On the other hand, the analysis implies that the N\'{e}el phase remains stable at least up to the limit $J_{2}/J_{1} = 0.49$ which is pretty larger than some previous estimates. In addition, it is argued that the spin-wave ansatz predicts the existence of a finite range ($J_{2}/J_{1}<0.323$ in the linear spin-wave theory) where the Marshall-Peierls sigh rule survives the frustrations.Comment: 13 pages, LaTex, 7 figures on reques

An Infrared Imaging Method for High-Throughput Combinatorial Investigation of Hydrogenation-Dehydrogenation and New Phase Formation of Thin Films

We have developed an infrared imaging setup enabling in situ infrared images to be acquired, and expanded on capabilities of an infrared imaging as a high-throughput screening technique, determination of a critical thickness of a Pd capping layer which significantly blocks infrared emission from below, enhancement of sensitivity to hydrogenation and dehydrogenation by normalizing raw infrared intensity of a Mg thin film to an inert reference, rapid and systematic screening of hydrogenation and dehydrogenation properties of a Mg–Ni composition spread covered by a thickness gradient Pd capping layer, and detection of formation of a Mg2Si phase in a Mg thin film on a thermally oxidized Si substrate during annealing

Vortex lattice structures of Sr2_2RuO4_4

The vortex lattice structures of Sr$_2$RuO$_4$ for the odd parity representations of the superconducting state are examined for the magnetic field along the crystallographic directions. Particular emphasis is placed upon the two dimensional representation which is believed to be relevant to this material. It is shown that when the zero-field state breaks time reversal symmetry, there must exist two superconducting transitions when there is a finite field along a high symmetry direction in the basal plane. Also it is shown that a square vortex lattice is expected when the field is along the $c$-axis. The orientation of the square lattice with respect to the underlying ionic lattice yields information as to which Ru 4d orbitals are relevant to the superconducting state.Comment: 5 pages, 2 figure

Instability of antiferromagnetic magnons in strong fields

We predict that spin-waves in an ordered quantum antiferromagnet (AFM) in a strong magnetic field become unstable with respect to spontaneous two-magnon decays. At zero temperature, the instability occurs between the threshold field $H^*$ and the saturation field $H_c$. As an example, we investigate the high-field dynamics of a Heisenberg antiferromagnet on a square lattice and show that the single-magnon branch of the spectrum disappears in the most part of the Brillouin zone.Comment: RevTeX, 4 pages, 3 figures, accepted to PR