Cresols - An investigation into their electronic structure and spectra

The three isomeric cresols were subjected to the all-valence-electron CNDO/2 andPPP-CI calculations. Results from this study were used: (i) to compare the electronic structures of these isomers vis-Ã-vis parent compounds-phenol and toluene, (ii) to obtain a quantitative picture of their chemical reactivities and electronic absorption spectra. Using the sgr-core charges derived from CNDO/2 calculations and subsequently revising the valence-state ionisation potential and one-center-two-electron repulsion integrals, thePPP-CI calculations were performed on the title compounds according toNishimoto andForster scheme. In these calculations the pseudo-unsaturated nature of the methyl group has been given due consideration. In spectral assignment, compared to the conventionalPPP approach, the CNDO/2-basedPPP-CI method gave a better agreement with the experimental data.

An auger spectroscopic study of the surface oxidation of zinc

An Auger study of the oxidation of zinc has been carried out to confirm that the relative intensities of the metal lines in election-beam induced Auger spectra are directly proportional to the number of valence electrons and therefore of direct use in investigating surface oxidation of metals.

Resistance Noise in Graphene Based Field Effect Devices

We present a low-frequency electrical noise measurement in graphene based field effect transistors. For single layer graphene (SLG), the resistance fluctuations is governed by the screening of the charge impurities by the mobile charges. However, in case of Bilayer graphene (BLG), the electrical noise is strongly connected to its band structure, and unlike single layer graphene, displays a minimum when the gap between the conduction and valence band is zero. Using double gated BLG devices we have tuned the zero gap and charge neutrality points independently, which offers a versatile mechanism to investigate the low-energy band structure, charge localization and screening properties of bilayer graphene

Vibrational spectra of imidazoline-2-thione and imidazoline-2-one

Raman and infrared spectra of imidazoline-2-thione (IMZT) and imidazoline-2-one (IMZO) have been recorded. Normal coordinate analyses have been performed for all the fundamental vibrations of IMZT, IMZT-d2 and IMZO employing a Urey—Bradley potential function supplemented with valence type force constants for the out of plane modes. The results of the vibrational analyses are discussed in relation to the assignments in related molecules. The vibrational assignments for IMZT and IMZO have been compared with those in structurally similar molecules and the need to obtain more reliable band assignments for some of the molecules considered is emphasised.

Mikä yliopisto-opiskelijaa kiihdyttää? : Opiskeluympäristöjen tutkimusta CASS-kokemusotantamenetelmällä flow-teoriaa ja ydintunneteorioita soveltaen

Flow experience is often defined either as an experience of high concentration and enjoyment or as a situation, where high challenges are matched with high skills. According to core-emotion theories, the experience of any emotion contains two core emotions: valence and arousal. Through an accurate mathematical model, the present study investigated, whether the experience of concentration and enjoyment is related to situations where both challenge and skills are high and in balance. Further, it was investigated what sort of core emotions are related to differing relationships between challenge and skills. Finally, university students’ experiences of their natural study environments were described in terms of core emotions and in terms of relationships between challenge and skills. Participants were 55 university students who participated two weeks research period. Altogether 3367 questionnaire answers were collected with the CASS experience-sampling method, operating in 3G-mobile phones. The relationship between challenge and skills (competence) was defined in an exact way in polar coordinates. An enjoyable and concentrated flow experience was defined as a sum variable of absorption, interest and enthusiasm. Core emotions were calculated with factor analysis from nine emotion variables. As expected, an experience of concentration and enjoyment was, on average, related to the situations where both challenge and skills were high and in balance. This was not, however, the case in every situation. Thus, it should be taken into consideration how flow experience is operationalised in experience sampling studies. When flow experience was defined as a situation of high challenge and high skills, it was often related to high valence and arousal emotions such as excitement or enthusiasm. A happier or a more tranquil enjoyment was related to situations of moderate challenge and high skills. Experiences differed clearly between various natural study environments. At lectures students were often bored or mentally absent, and did not experience challenges. In a small group students were often excited or enthusiastic, and showed optimal balance between challenge and skills. At library students felt satisfied and were engaged in highly challenging work.

Vibrational and 1H NMR spectra of N-(2-pyridyl)-thioformamide and N-(2-pyridyl)thioacetamide

The Raman and infrared spectra of N-(2-pyridyl) thioformamide and N-(2-pyridyl)-thioacetamide have been measured. The assignment of the bands is aided by the complete normal coordinate treatment for all the vibrations of N-(2-pyridyl)thioformamide and its N-deuterated molecule using a Urey—Bradley force function for the in-plane vibrations and a valence force function for the out of plane vibrations. Variable temperature 1H NMR study of the two pyridylthionamides has also been performed. It is inferred that while N-(2-pyridyl)thioformamide favours a cis —CSNH— group, the other compound favours a trans —CSNH— grouping at ambient temperature.

Metal Auger Intensity Ratios in Transition Metals and Their Compounds

Metal Auger intensity ratios of the type Z(CVV)/I(CC'V) and Z(CVV)/Z(CC'C"), where C, C' and C" denote core levels and V stands for a valence level, are shown to increase progressively with the number of valence electrons in the metal in the case of second-row transition metals and their oxides. Metal Auger intensity ratios in chalcogenides of transition metals can be correlated by taking the effective atomic charge on the metal into consideration. The possible use of metal Auger intensity ratios in the study of surface oxidation of second-row transition metals is illustrated in the case of zirconium.

Study of strontium compounds and minerals by X-ray absorption spectroscopy. I. K-edge shifts

The chemical shifts in the X-ray K-absorption edge of strontium in various compounds and in six minerals are measured using a single crystal X-ray spectrometer. Besides valence, the shifts are found to be governed by ionic charges on the absorbing ions, which are calculated employing Pauling's method. For the minerals the plot of chemical shift against the theoretically calculated ionic charges is used to determine the charges on the strontium ions.

Psychophysiology of flow experience : An explorative study

This study explored the possibilities the psychophysiological methodology offer to flow research. Facial electromyography has often been used to index valence, and electrodermal activity to index arousal, the two basic dimensions of emotion. It was hypothesized that these measures can also be used to examine enjoyment, a basic component of flow experiment. A digital game was used to induce flow, and physiological activity of 32 subjects was measured continuously. Flow State Scale was used to assess flow. Activity of corrugator supercilii muscle, an index of negative valence, was negatively correlated with flow reports, as hypothesized. Contrary to hypothesis, skin conductance level, an index of arousal, was unrelated to self-reported flow. The results for association between flow and zygomaticus major and orbicularis oculi muscle activities, indices of positive valence, were inconclusive, possibly due to experimental design where only tonic measures were available. Psychophysiological methods are recommended for future studies of flow. Specifically, the time series approach may be particularly viable in examining the temporal aspects of flow, an area currently unexplored. Furthermore, it is suggested that digital game research would benefit from psychophysiological study of game-related flow.

DFT study of electronic and optical properties of anatase titanium dioxide tuned by nitrogen and lithium co-doping

The electronic and optical properties of anatase titanium dioxide (TiO2), co-doped by nitrogen (N) and lithium (Li), have been investigated by density functional theory plus Hubbard correction term U, namely DFT+U. It is found that Li-dopants can effectively balance the net charges brought by N-dopants and shift the local state to the top of valence band. Depending on the distribution of dopants, the adsorption edges of TiO2 may be red- or blue-shifted, being consistent with recent experimental observations.

Electron-electron interactions in polyacetylene

Experimental evidence for strong electron-electron interactions in polyacetylene is presented. These include (i) observation of a dipole forbidden state below the optical gap, (ii) observation of negative spin densities at sites at which noninteracting models predict zero spin density (iii) vanishing optical gap, in the infinite chain limit, in the closely related symmetrical linear cyanine dyes. To correctly explain these features it is necessary to solve correlated model Hamiltonians. Using diagrammatic valence bond method model exact solutions of correlated models of finite-size systems can be obtained and various physical properties of the low-lying states can be computed. These properties, when extrapolated to the infinite chain limit explain many of the experimental features observed in polyacetylene.

Surface oxidation of cadmium, indium, tin and antimony by photoelectron and Auger spectroscopy

Surface oxidation of Cd, In, Sn and Sb has been investigated by employing valence bands, metal 4d levels and plasmon bands in X-ray photoelectron spectra. O(KLL), metal M4N45N45, and plasmon transitions in electron-induced Auger spectra as well as Auger transitions due to the metal (metal oxide) and plasmons in X-ray-induced Auger spectra. The surface oxides are In2O4, CdO and a mixture of SnO and SnO2 in the case of In. Cd and Sn respectively. The facility of surface oxidation is found to vary as In>Cd>Sn>Sb. Inter-atomic Auger transitions involving oxygen valence bands have been identified on oxidized surfaces of Cd and In.

Ce1-xRuxO2-delta (x=0.05, 0.10): A New High Oxygen Storage Material and Pt, Pd-Free Three-Way Catalyst

Nanocrystalline Ce1-xRuxO2-delta (x = 0.05 and 0.10) of 8-10 nm sizes have been synthesized by hydrothermal method using melamine as complexing agent. Compounds have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray analysis (EDX) and their structures have been refined by the Rietveld method.The compounds crystallize in fluorite structure and the composition is Ce1-xRuxO2-x/2 where Ru is in +4 state and Ce is in mixed-valence (+3, +4) state. Substitution of Ru4+ ion in CeO2 activated the lattice oxygen. Ce1-xRuxO2-x/2 reversibly releases 0.22[O] and 0.42[O] for x = 0.05 and 0.10, respectively, which is higher than the maximumpossible OSC of 0.22 [O] observed for Ce0.50Zr0.50O2. Utilization of Higher OSC of Ce1-xRuxO2-delta (x = 0.05 and 0.10) is also reflected in terms of low-temperature CO oxidation with these catalysts, both in the presence and absence of feed oxygen. The Ru4+ ion acts as an active center for reducing molecules (CO, hydrocarbon ``HC'') and oxide ion vacancy acts as an active center for O-2 and NO, leading to low-temperature NO conversion to N-2. Thus due to Ru4+ ion, Ce1-xRuxO2-delta is not just a high oxygen storage material but also shows high activity toward CO, hydrocarbon ``HC'' oxidation, and NO reduction by CO at low temperature with high N-2 selectivity for three-way catalysis.

Infrared spectra of 1.3-dithiole-2-thione and its selenium analogues ând frequency assignment and molecular force constants

Infrared spectra of 1,3-dithiole-2-thione (DTT) and its four selenium analogues have been studied in the region 4000 to 20 cm�1. Assignment of all the fundamental frequencies was made by noting the band shifts on progressive selenation. Normal coordinate analysis procedures have been applied for both in-plane and out-of-plane vibrations to help the assignments. The Urey�Bradley force function supplemented with valence force constants for the out-of-plane vibrations was employed for coordinate calculations. A correlation of the infrared assignments of DTT with its different selenium analogues is accomplished. Further, the infrared assignments are compared with those of trithiocarbonate ion and its selenium analogues and other structurally related heterocyclic molecules.

X-ray photoelectron spectra and Auger studies of the surface oxidation of cobalt

Surface oxidation of Co has been investigated at different temperatures in the 300–600 K range at oxygen exposures upto 106 L by XPES and AES techniques. In the XPES, both the valence band and core level bands have been employed to monitor the oxidation while in the AES, metal Auger intensity ratios as well as O(KLL)/Co(L23M45M45) ratios have been examined. Only CoO is formed on the surface at high oxygen exposures at and above 500 K.