bluuebunny/crossref_metadata_2025 huggingface dataset:
Second-harmonic generation in quantum cascade lasers with electric field and current dependent nonlinear susceptibility
Authors: Qu Dongxia , Xie Feng , Shu Gary , Momen Safiyy , Narimanov Evgenii , Gmachl Claire F. , Sivco Deborah L.
Published: January 2007

The authors demonstrate a quantum cascade laser design with an integrated resonant nonlinearity for second-harmonic generation. Its nonlinear power conversion efficiency is strongly dependent on the injected current density due to an electric field and current dependent nonlinear susceptibility. This dependence produces an observed tenfold increase of the conversion efficiency over the current density range of 2.7–7.5kA∕cm2. Furthermore, bidirectional lasing at widely different wavelengths is a side effect for this active region design.
Room-temperature ferromagnetism of Cu-implanted GaN
Authors: Lee Jong-Han , Choi In-Hoon , Shin Sangwon , Lee Sunggoo , Lee J. , Whang Chungnam , Lee Seung-Cheol , Lee Kwang-Ryeol , Baek Jong-Hyeob , Chae Keun Hwa , Song Jonghan
Published: January 2007

1 MeV  Cu2+ ion was implanted into GaN with a dose of 1×1017cm−2 at room temperature. After implantation, the samples were subsequently performed by rapid thermal annealing at 700, 800, and 900°C for 5min. Both nonmagnetic Cu ion implanted samples annealed at 700 and 800°C exhibit the ferromagnetism at room temperature, and the saturation magnetization of these samples is estimated to be 0.057μB and 0.27μB per Cu atom from M-H curve, respectively. However, the sample annealed at 900°C does not show ferromagnetism due to clustering of Cu during the annealing process.
Redox properties of CeO2–MO2 (M=Ti, Zr, Hf, or Th) solid solutions from first principles calculations
Authors: Andersson D. A. , Simak S. I. , Skorodumova N. V. , Abrikosov I. A. , Johansson B.
Published: January 2007

The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.
Capacitance spectroscopy of amorphous/crystalline silicon heterojunction solar cells at forward bias and under illumination
Authors: Gudovskikh A. S. , Kleider J. P.
Published: January 2007

An original method of characterization of interface properties of hydrogenated amorphous silicon/crystalline silicon heterojunction solar cells is proposed. This is based on the measurement of the capacitance under AM1.5 illumination at forward bias close to the open-circuit voltage. The capacitance is very sensitive to the quality of both the front heterojunction and the back contact. The authors show that the comparison of the low-frequency capacitance with the open-circuit voltage can be used to deduce both the back surface recombination velocity of minority carriers and the front interface defect density. The technique can be applied to other types of solar cells.
Practical and simple circuitry for the measurement of small capacitance
Authors: Lin D. Y. , Wu J. D. , Chang Y. J. , Wu J. S.
Published: January 2007

Practical and cost-effective circuitry with high sensitivity has been developed to measure a small capacitance using current compensation method. The circuitry uses an electronic switch to periodically connect or separate the capacitor under test (Cx) from a reference capacitor (Cr). When Cx is connected in parallel with Cr the total capacitance becomes Cx+Cr. On the other hand, as Cx is separated from Cr, the total capacitance is only Cr. This periodic change of the capacitance generates a periodic square-wave output with an amplitude in proportion to the capacitance of Cx. A high sensitivity of ΔV∕ΔC=202.2mV∕pF has been achieved, making the circuitry a powerful tool in measuring small capacitances. Three applications have been performed to present its capability: (a) displacement, (b) height of liquid, and (c) angle of tilt. The experimental results demonstrate the performance of the circuitry.
Complete ground state gain recovery after ultrashort double pulses in quantum dot based semiconductor optical amplifier
Authors: Dommers Sabine , Temnov Vasily V. , Woggon Ulrike , Gomis Jordi , Martinez-Pastor Juan , Laemmlin Matthias , Bimberg Dieter
Published: January 2007

Gain recovery dynamics are studied in electrically pumped quantum dot (QD) based semiconductor optical amplifiers (SOAs) after amplification of double femtosecond laser pulses using ultrafast pump-probe spectroscopy with heterodyne detection. The authors observe a distinct change in gain recovery in the ground state when a significant excited state population is achieved. A complete gain recovery is found when two 150fs pulses with 5ps time delay pass through the SOA in resonance to the ground state under high injection currents of 80–100mA. The obtained results open the way for ultrafast (>200GHz) operation in p-doped QD based SOAs at 1.3μm telecommunications wavelengths.
Dynamic wetting of shear thinning fluids
Authors: Seevaratnam G. K. , Suo Y. , Ramé E. , Walker L. M. , Garoff S.
Published: January 2007

The impact of non-Newtonian behavior on dynamic wetting is critical since many fluids exhibit such behavior somewhere in the high-shear environment inherent in the wedge flow near a moving contact line. This impact will be different for two broad categories of non-Newtonian behavior, shear thinning, and elasticity. In this paper, we discuss the steady-state wetting of a fluid, aqueous solutions of xanthan gum, dominated by shear thinning but with negligible elasticity. In the shear thinning fluid, viscous bending near the contact line is greatly reduced compared to a Newtonian fluid having the same zero-shear viscosity. Concomitant with this reduction in viscous bending, the effective dynamic contact angle has a much weaker dependence on capillary number, Ca, than is observed in, or predicted for, Newtonian fluids. A simple lubrication model using a constitutive relation with power-law shear thinning at high shear rates and a Newtonian plateau at low shear rates mimics the trends seen in our data and elucidates the origins of the reduced viscous bending.
Large-scale structure visualization and convection velocity in supersonic blunt-base cylinder wakes
Authors: Kastengren Alan L. , Dutton J. Craig , Elliott Gregory S.
Published: January 2007

Time-correlated imaging has been used to study supersonic blunt-base cylinder wakes at 0° and 10° angle-of-attack to an M=2.46 flow. Most of the temporal evolution of the large-scale structures consists of swelling, shrinking, or rollover, with interactions between structures seeming to play a small role. While structures occasionally merge, rotational pairing events are not observed in the visualizations. The position of the recompression shock in the windward part of the angle-of-attack wake appears to fluctuate on rapid time scales, with disturbances in the shock position tending to follow the convection of large-scale structures in the adjoining shear layer. A consistent difference in the structure convection velocity seems to exist between the high-speed and low-speed sides of the shear layers in this study. The stream selection rule is followed for both the axisymmetric and angle-of-attack wakes before reattachment, but the recompression and reattachment processes greatly influence the structure convection velocity in the axisymmetric wake. Convection velocity measurements in the end-view visualizations show that the large-scale structures have a significant circumferential velocity component in the angle-of-attack wake during and after reattachment, while the large-scale structures in the axisymmetric wake do not, as expected.
Convection in a supercritical fluid: A reduced model for geophysical flows
Authors: Accary Gilbert , Bontoux Patrick , Zappoli Bernard
Published: January 2007

Convection in a fluid, slightly above its gas-liquid critical point, is numerically investigated in two configurations where the strong stratification of the fluid—induced by its high compressibility—controls the development and/or the onset of convection: (i) the evolution of a thermal plume in a stable environment where the penetrative convection is found to be blocked by the fluid stratification, and (ii) the convection onset and outset in a supercritical fluid layer according to the Schwarzschild criterion, which usually occurs in the atmosphere when the local temperature gradient exceeds the adiabatic temperature one. Hence, two situations, commonly encountered in large-scale geophysical flows, are reproduced in a centimetric cell containing a supercritical fluid.
Investigation of effective internal field in congruent lithium niobate crystal by digital holographic interferometry
Authors: Zhi Ya’nan , Liu De’an , Qu Weijuan , Luan Zhu , Liu Liren
Published: January 2007

The phase contrast across the crystal thickness induced by the internal field is measured by the digital holographic interferometry just after the congruent lithium niobate crystal is partially poled. The direction of applied external field is antiparallel to that of internal field, and the measured phase contrast varies linearly with the applied external field. A new internal field is obtained by this method and named effective internal field. The distinct discrepancy between effective and equivalent internal fields is observed. The authors attribute this effect to the new macroscopic representation of elastic dipole components of defect complex in the crystal.
Through-wafer electroplated copper interconnect with ultrafine grains and high density of nanotwins
Authors: Xu Luhua , Dixit Pradeep , Miao Jianmin , Pang John H. L. , Zhang Xi , Tu K. N. , Preisser Robert
Published: January 2007

High aspect ratio (∼15) and ultrafine pitch (∼35μm) through-wafer copper interconnection columns were fabricated by aspect-ratio-dependent electroplating. By controlling the process parameters, ultrafine copper grains with nanoscale twins (twin lamellar width ∼20nm) were obtained in the copper columns. Transmission electron microscope reveals that the density of these nanotwins depends on the location along the length of the columns. The highest twin density was achieved at the bottom of the column where the electroplating starts. The presence of higher density of the nanotwins yields significant higher hardness (∼2.4GPa) than that with lower twin density (∼1.8GPa). The electrical conductivity of the electroplated copper (2.2μΩcm) is retained comparable to the pure copper.
Spontaneous liquifaction of isomerizable molecular crystals
Authors: Tombari E. , Ferrari C. , Salvetti G. , Johari G. P.
Published: January 2007

A lattice vacancy raises the energy of the neighboring (flexible) molecule in a crystal, which may be enough to isomerize it to a tautomer that does not fit the lattice site, thus creating a liquidlike local region embedding the vacancy. Similar regions may appear elsewhere in the lattice and the regions may ultimately merge. Thus a crystal may spontaneously liquefy over a period of hours to years at a temperature below its normal melting point. Simultaneous heat capacity and heat absorption measurements of several such molecular crystals show that they spontaneously liquefy at a temperature far below their reputed melting point, according to a non-exponential rate kinetics and a temperature dependent rate constant, and do not crystallize on cooling.
Corrigendum to: Estimating the internal conductance to CO2 movement
Authors: Warren Charles
Published: January 2007

The concentration of CO2 in the chloroplast is less than atmospheric owing to a series of gas-phase and liquid-phase resistances. For a long time it was assumed that the concentration of CO2 in the chloroplasts is the same as in the intercellular spaces (e.g. as measured by gas exchange). There is mounting evidence that this assumption is invalid and that CO2 concentrations in the chloroplasts are significantly less than intercellular CO2. It is now generally accepted that internal conductance (gi) is a significant limitation to photosynthesis, often as large as that due to stomata. Internal conductance describes this decrease in CO2 concentration between the intercellular spaces and chloroplasts as a function of net photosynthesis [gi = A�/�(Ci – Cc)]. Internal conductance is commonly estimated by simultaneous measurements of gas exchange and chlorophyll a fluorescence or instantaneous discrimination against 13CO2. These common methods are complemented by three alternative methods based on (a) the difference between intercellular and chloroplastic CO2 photocompensation points, (b) the curvature of an A�/�Ci curve, and (c) the initial slope of an A�/�Ci curve v. the estimated initial slope of an A�/�Cc curve. The theoretical basis and protocols for estimating internal conductance are described. The common methods have poor precision with relative standard deviations commonly > 10%; much less is known of the precision of the three alternative methods. Accuracy of the methods is largely unknown because all methods share some common assumptions and no truly independent and assumption-free method exists. Some assumptions can and should be tested (e.g. the relationship of fluorescence with electron transport). Methods generally require knowledge of either the kinetic parameters of Rubisco, or isotopic fractionation by Rubisco. These parameters are difficult to measure, and thus are generally assumed a priori. For parameters such as these a sensitivity analysis is recommended. One means of improving confidence in gi estimates is by using two or more methods, but it is essential that the methods chosen share as few common assumptions as possible. All methods require accurate and precise measurements of A and Ci — these are best achieved by minimising leaks, maximising the signal-to-noise ratio by using a large leaf area and moderate flow rate, and by taking into account cuticular and boundary layer conductances.
Manganese toxicity in two varieties of Douglas fir (Pseudotsuga menziesii var. viridis and glauca) seedlings as affected by phosphorus supply
Authors: Dučić Tanja , Polle Andrea
Published: January 2007

Manganese (Mn) is an essential micronutrient in all organisms but may become toxic when present in excess. To investigate whether interior and coastal varieties of Douglas fir [Pseudotsuga menziesii (Mirbel) Franco, var. glauca (DFG) and var. viridis (DFV)] differed in Mn tolerance, seedlings were exposed to excess Mn in hydroponic solutions. Root growth, biomass production, Mn concentrations in different tissues and Mn subcellular localisation were determined. Both varieties showed similar whole-plant Mn accumulation and biomass reduction in response to increases in Mn in the nutrient solution. Since excess Mn inhibited root elongation growth more strongly in DFG than in DFV, biomass allocation in DFV was shifted towards a relative increase in root biomass and a relative decrease in DFG. X-ray microanalysis showed that Mn enrichment in cell walls and vacuoles of DFV root cortex and epidermis cells was higher than in DFG. In roots, precipitates were observed in which Mn concentrations correlated with phosphorus (P) and to a minor extent with calcium. We suggest that the higher persistence of root growth under Mn stress in DFV was caused by greater entrapment in the vacuole and in the apoplast and by more efficient Mn detoxification in insoluble complexes with P than in DFG. To investigate whether P supply affected Mn uptake and toxicity, Douglas fir seedlings were exposed to excess Mn under P deficiency. In P-limited seedlings of both varieties, roots growth was less sensitive to excess Mn than under sufficient P-supply, although in planta Mn concentrations were not diminished. In DFG, which maintained P homeostasis under limited P supply, the negative effect of Mn stress was partially reversed, showing that Mn susceptibility is affected by P metabolism.
A proposal for robust temperature compensation of circadian rhythms
Authors: Hong Christian I. , Conrad Emery D. , Tyson John J.
Published: January 2007

The internal circadian rhythms of cells and organisms coordinate their physiological properties to the prevailing 24-h cycle of light and dark on earth. The mechanisms generating circadian rhythms have four defining characteristics: they oscillate endogenously with period close to 24 h, entrain to external signals, suffer phase shifts by aberrant pulses of light or temperature, and compensate for changes in temperature over a range of 10°C or more. Most theoretical descriptions of circadian rhythms propose that the underlying mechanism generates a stable limit cycle oscillation (in constant darkness or dim light), because limit cycles quite naturally possess the first three defining properties of circadian rhythms. On the other hand, the period of a limit cycle oscillator is typically very sensitive to kinetic rate constants, which increase markedly with temperature. Temperature compensation is therefore not a general property of limit cycle oscillations but must be imposed by some delicate balance of temperature dependent effects. However, “delicate balances” are unlikely to be robust to mutations. On the other hand, if circadian rhythms arise from a mechanism that concentrates sensitivity into a few rate constants, then the “balancing act” is likely to be more robust and evolvable. We propose a switch-like mechanism for circadian rhythms that concentrates period sensitivity in just two parameters, by forcing the system to alternate between a stable steady state and a stable limit cycle.
Continuous polyelectrolyte adsorption under an applied electric potential
Authors: Ngankam A. Pascal , Van Tassel Paul R.
Published: January 2007

Interactions between charged macromolecules (e.g., proteins, nucleic acids, polyelectrolytes) and charged surfaces govern many natural and industrial processes. We investigate here the influence of an applied electric potential on the adsorption of charged polymers, and report the following significant result: the adsorption of certain amine side chain-containing polycations may become continuous, i.e., asymptotically linear (or nearly linear) in time over hours, upon the application of a modest anodic potential. Employing optical waveguide lightmode spectroscopy (OWLS) and an indium tin oxide (ITO) substrate, we show that asymptotic kinetics, and the adsorbed mass at the onset of the asymptotic regime, depend sensitively on polymer chemistry (in particular, side chain volume and charge location), increase with applied potential and ionic strength (conditions favoring a thicker initial layer), and are independent of bulk polymer concentration (suggesting postadsorption events to be rate limiting). X-ray photoelectron spectra reveal a suppressed polymer charge within layers formed via continuous adsorption, but no evidence of electrochemical reactions. We propose a mechanism based on polymer–polymer binding within the adsorbed layer, enabled by suppressed electrostatic repulsion and/or enhanced ionic correlations near the conducting surface, and stabilized by short-range attractive interactions. Continuous adsorption under an applied electric potential offers the possibility of nanoscale films of tailored polymer content realized in a single step.
β Cells cannot directly prime diabetogenic CD8 T cells in nonobese diabetic mice
Authors: de Jersey James , Snelgrove Sarah L. , Palmer Stephanie E. , Teteris Simon A. , Mullbacher Arno , Miller Jacques F. A. P. , Slattery Robyn M.
Published: January 2007

Type 1 diabetes (T1D) is caused by the destruction of insulin-producing islet β cells. CD8 T cells are prevalent in the islets of T1D patients and are the major effectors of β cell destruction in nonobese diabetic (NOD) mice. In addition to their critical involvement in the late stages of diabetes, CD8 T cells are implicated in the initiation of disease. NOD mice, in which the β2-microglobulin gene has been inactivated by gene targeting (NOD.β2M−/−), have a deficiency in CD8 T cells and do not develop insulitis, which suggests that CD8 T cells are required for the initiation of T1D. However, neither in humans nor in NOD mice have the immunological requirements for diabetogenic CD8 T cells been precisely defined. In particular, it is not known in which cell type MHC class I expression is required for recruitment and activation of CD8 T cells. Here we have generated transgenic NOD mice, which lack MHC class I on mature professional antigen-presenting cells (pAPCs). These “class I APC-bald” mice developed periislet insulitis but not invasive intraislet insulitis, and they never became diabetic. Recruitment to the islet milieu does not therefore require cognate interaction between CD8 T cells and MHC class I on mature pAPCs. Conversely, such an interaction is critically essential to allow the crucial shift from periislet insulitis to invasive insulitis. Importantly, our findings demonstrate unequivocally that CD8 T cells cannot be primed to become diabetogenic by islet β cells alone.
Color naming reflects optimal partitions of color space
Authors: Regier Terry , Kay Paul , Khetarpal Naveen
Published: January 2007

The nature of color categories in the world's languages is contested. One major view holds that color categories are organized around universal focal colors, whereas an opposing view holds instead that categories are defined at their boundaries by linguistic convention. Both of these standardly opposed views are challenged by existing data. Here, we argue for a third view based on a proposal by Jameson and D'Andrade [Jameson KA, D'Andrade RG (1997) in
Color Categories in Thought and Language
, eds Hardin CL, Maffi L (Cambridge Univ Press, Cambridge, U.K.), pp 295–319]: that color naming across languages reflects optimal or near-optimal divisions of an irregularly shaped perceptual color space. We formalize this idea, test it against color-naming data from a broad range of languages and show that it accounts for universal tendencies in color naming while also accommodating some observed cross-language variation.
Childhood maltreatment predicts adult inflammation in a life-course study
Authors: Danese Andrea , Pariante Carmine M. , Caspi Avshalom , Taylor Alan , Poulton Richie
Published: January 2007

Stress in early life has been associated with insufficient glucocorticoid signaling in adulthood, possibly affecting inflammation processes. Childhood maltreatment has been linked to increased risk of adult disease with potential inflammatory origin. However, the impact of early life stress on adult inflammation is not known in humans. We tested the life-course association between childhood maltreatment and adult inflammation in a birth cohort followed to age 32 years as part of the Dunedin Multidisciplinary Health and Development Study. Regression models were used to estimate the effect of maltreatment on inflammation, adjusting for co-occurring risk factors and potential mediating variables. Maltreated children showed a significant and graded increase in the risk for clinically relevant C-reactive protein levels 20 years later, in adulthood [risk ratio (RR) = 1.80, 95% confidence interval (CI) = 1.26–2.58]. The effect of childhood maltreatment on adult inflammation was independent of the influence of co-occurring early life risks (RR = 1.58, 95% CI = 1.08–2.31), stress in adulthood (RR = 1.64, 95% CI = 1.12–2.39), and adult health and health behavior (RR = 1.76, 95% CI = 1.23–2.51). More than 10% of cases of low-grade inflammation in the population, as indexed by high C-reactive protein, may be attributable to childhood maltreatment. The association between maltreatment and adult inflammation also generalizes to fibrinogen and white blood cell count. Childhood maltreatment is a previously undescribed, independent, and preventable risk factor for inflammation in adulthood. Inflammation may be an important developmental mediator linking adverse experiences in early life to poor adult health.
Identification of Rab11 as a small GTPase binding protein for the Evi5 oncogene
Authors: Westlake Christopher J. , Junutula Jagath R. , Simon Glenn C. , Pilli Manohar , Prekeris Rytis , Scheller Richard H. , Jackson Peter K. , Eldridge Adam G.
Published: January 2007

The Evi5 oncogene has recently been shown to regulate the stability and accumulation of critical G
1
cell cycle factors including Emi1, an inhibitor of the anaphase-promoting complex/cyclosome, and cyclin A. Sequence analysis of the amino terminus of Evi5 reveals a Tre-2, Bub2, Cdc16 domain, which has been shown to be a binding partner and GTPase-activating protein domain for the Rab family of small Ras-like GTPases. Here we describe the identification of Evi5 as a candidate binding protein for Rab11, a GTPase that regulates intracellular transport and has specific roles in endosome recycling and cytokinesis. By yeast two-hybrid analysis, immunoprecipitation, and Biacore analysis, we demonstrate that Evi5 binds Rab11a and Rab11b in a GTP-dependent manner. However, Evi5 displays no activation of Rab11 GTPase activity
in vitro
. Evi5 colocalizes with Rab11
in vivo
, and overexpression of Rab11 perturbs the localization of Evi5, redistributing it into Rab11-positive recycling endosomes. Interestingly,
in vitro
binding studies show that Rab11 effector proteins including FIP3 compete with Evi5 for binding to Rab11, suggesting a partitioning between Rab11–Evi5 and Rab11 effector complexes. Indeed, ablation of Evi5 by RNA interference causes a mislocalization of FIP3 at the abscission site during cytokinesis. These data demonstrate that Evi5 is a Rab11 binding protein and that Evi5 may cooperate with Rab11 to coordinate vesicular trafficking, cytokinesis, and cell cycle control independent of GTPase-activating protein function.
New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates
Authors: Bloch Jonathan I. , Silcox Mary T. , Boyer Doug M. , Sargis Eric J.
Published: January 2007

Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchontan mammals (tree shrews and flying lemurs). We report results from a comprehensive cladistic analysis using cranial, postcranial, and dental evidence including data from recently discovered Paleocene plesiadapiform skeletons (Ignacius clarkforkensissp. nov.;Dryomomys szalayi, gen. et sp. nov.), and the most plesiomorphic extant tree shrew,Ptilocercus lowii. Our results, based on the fossil record, unambiguously place plesiadapiforms with Euprimates and indicate that the divergence of Primates (sensu lato) from other euarchontans likely occurred before or just after the Cretaceous/Tertiary boundary (65 Mya), notably later than logistical model and molecular estimates. Anatomical features associated with specialized pedal grasping (including a nail on the hallux) and a petrosal bulla likely evolved in the common ancestor of Plesiadapoidea and Euprimates (Euprimateformes) by 62 Mya in either Asia or North America. Our results are consistent with those from recent molecular analyses that group Dermoptera with Scandentia. We find no evidence to support the hypothesis that any plesiadapiforms were mitten-gliders or closely related to Dermoptera.
Recent Advances in the Calculation of Oscillator Strengths
Authors: A Hibbert
Published: January 2007

A review of work published since the last beam-foil spectroscopy conference in Gatlinburg (1975) is presented. For allowed transitions whereLScoupling is valid, the NCMET and FOTOS schemes are compared and an extension of the application of FOTOS is proposed. Where relativistic effects are important–for medium to heavy atoms and for forbidden transitions–the stability of coefficients in configuration interaction expansions, and the way in which the Breit or Breit-Pauli terms are introduced, are discussed.
f-Value Measurements for 3d-Elements
Authors: Martin C E Huber
Published: January 2007

We give a survey of data on transition probabilities of allowed lines that belong to the spectra of neutral and singly-ionized iron-group elements. The classical methods used to determine oscillator strengths of weak lines (usually on a relative scale) are reviewed and some of the difficulties arising in investigating the spectra of 3d-elements are pointed out. The quality of experimental lifetimes andf-values of strong lines, i.e., of data which are frequently used to establish absolute scales, are discussed in the context of the methods employed. The results on weak lines are then assessed, element by element, and some applications are mentioned. It is concluded that further, more precise measurements are needed, since a given oscillator strength of a weak line is, in most cases, known within a factor of 1.5 or 2 only. The importance of confirming existing data is stressed. An urgent need is found to exist for better data on singly-ionized 3d-elements.
The Solar Chemical Composition
Authors: O Engvold
Published: January 2007

A brief review is given of recent solar abundance results. The relative abundance of 68 chemical elements is known for the sun.
Measurements of Lifetimes and Corresponding Branching Ratios for Excited States in Simple Molecules and Molecular Ions
Authors: G R Möhlmann  , F J de Heer
Published: January 2007

A description will be given of lifetime measurements for excited levels and molecular ions using the delayed coincidence technique. The excited levels are produced by electrons incident on gaseous targets. The effects of space charge, which may distort lifetime measurements for molecular ions in the case of relatively long-lived excited states, are analyzed. The lifetime determinations are combined with branching-ratio studies whereby absolute transition probabilities can be obtained. Together with theoretical Franck-Condon factors such data provide information about the variation of the electronic transition moment as a function of ther-centroid.
Recent Advances in Studies of Molecular Transition Probabilities
Authors: Peter Erman
Published: January 2007

The development of high power electron excitation applied in the High Frequency Deflection technique has enabled time resolved precision spectroscopy to be performed with a resolving power as high as 1:105. This is typically a two orders of magnitude higher resolution than what is commonly achieved using other approaches and this has created new possibilities of studying hitherto unknown properties of fundamental molecules. Thus a great number of time resolved studies of individual rotational levels including resolved spin-orbit and Λ components show that radiationless destructions of molecules are much more common in nature than earlier believed implying a violation of the Born Oppenheimer approximation which demands new theoretical treatments of molecular structure. Among important applications of the radiationless processes should be mentioned determinations of dissociation energies with superior accuracy and molecular formation rates. An extensive programme for theoretical studies of the obtained results is in progress in collaboration with the quantum chemistry groups in Århus and Uppsala. This programme also includes precision estimates of oscillator strengths with applications to molecular abundance estimates and to laser physics.
Energy Levels and Transition Probabilities in Mo XIV
Authors: L J Curtis  , A Lindgård  , B Edlén  , I Martinson  , S E Nielsen
Published: January 2007

An investigation is made of the energy levels in Mo XIV (Cu I isoelectronic sequence). Published material is combined with previously unreported measurements to obtain reasonably accurate energies for terms withn= 4, 5, 6, 7 and 8. For the ionization limit we find the value 2 441 ± 2 kK. These data are used to calculate transition probabilities, oscillator strengths and radiative lifetimes for a large number of transitions by means of a numerical Coulomb approximation procedure.
An Effective Hamiltonian for the ABC Effect
Authors: Arne Reitan
Published: January 2007

The reaction np→d(ππ)° is studied in a Hamiltonian formalism, in the momentum region from threshold to 3 GeV/c. We are able to reproduce the enhancement in the deuteron recoil-momentum spectrum at ππ missing-mass values near 300 MeV (the ABC effect).
Analysis of the 2p43s, 2p43p and 2p43d Configurations of Five-times Ionized Silicon (Si VI)
Authors: Marie-Christine Artru  , Wan-Ü Lydia Brillet
Published: January 2007

The Si VI spectrum has been investigated in the vacuum UV. About seventy new lines (690-1 344 Å) have been identified as transitions between the 2p43s, 2p43pand 2p43dconfigurations, leading to the determination of energy levels belonging to these configurations. Intercombination lines between terms of different multiplicities or different parentages are observed. The ground-term transitions from the 2s2p6level (246-249 Å) and from the 2p43sconfiguration (91-101 Å) have been remeasured. The level identifications are supported by parametric calculations and isoelectronic comparison.
On the Hologram Recording Based on the F→Z1 Colour Centre Conversion in KCl:Ca and KBr:Ca Crystals
Authors: J Ruuskanen
Published: January 2007

Use of the F → Z
1 colour centre conversion for hologram recording in KCl and KBr single crystals doped with Ca has been studied. A new technique for measurement of the H-D curve (optical density versus exposure energy) has been described. Further, measured diffraction efficiency values for holograms by taking advantage of the H-D curves are presented. The readout of the hologram was observed to be destructive, and experimental data describing this property are also given.
Parametric Instabilities in Laser Heating of Magnetically Confined Plasmas
Authors: S J Karttunen  , R R E Salomaa
Published: January 2007

This paper discusses the generation of parametric instabilities in laser heating of plasmas confined in a linear magnetic device. The nonlinearities are taken into account by the inclusion of a ponderomotive force. We derive a generalized dielectric tensor and the corresponding dispersion relation which enables us to determine the instability thresholds and linearized growth rates. The cases where the parametrically excited low frequency wave propagates either parallel or perpendicular to the magnetic field are analyzed in detail. Propagation in an oblique direction is briefly described. As regards the laser heating schemes, the low frequency filamentation and the stimulated Brillouin scattering seem to pose a possible difficulty. Fortunately, several of the potential instabilities cannot be excited in the configuration considered.
Particle Aspect Analysis of E×B Drift Instability in the Presence of Non-Uniform Electric Field
Authors: K D Misra  , M S Tiwari
Published: January 2007

A physical mechanism and the dynamical details of the drift wave instability have been studied by investigating the trajectories of the charge particles in the presence of ambient magnetic field and non-uniform electric field. The effect of finite gyro-radius corrections have also been accounted. The general dispersion relation for the electrostatic drift wave has been obtained. The expression for the growth rate have been derived from an energy balance approach. Our expression reduces to well known results under limiting conditions. The finite gyroradius correction due to inhomogeneous electric field is found to have a destabilising effect. The important geophysical situations for the existence of inhomogeneous electric field have been outlined and potential application of this result have been indicated.
Basic Features of EXTRAP Concept
Authors: B Lehnert
Published: January 2007

The potentialities and properties are discussed of a recently suggested axially symmetric, quasi-steady, closed, high-beta magnetic confinement system. A toroidal pinch of non-circular cross section is immersed in the strong, inhomogeneous polodial vacuum field from a set of ring-shaped conductors, all carrying currents in the opposite direction of the plasma current. This "EXTRAP" concept is expected to have some important advantages, as compared to magnetic bottles based on a main torodial field component. Concerning plasma equilibrium, there are closed local and average guiding centre orbits, beta values of order unity should become available, there is no magnetic surface splitting limit, cyclotron radiation should be kept at a comparatively low level, and bootstrap operation may become possible. Concerning plasma stability, the system should not become sensitive to magnetic island formation and asymmetries, and the short magnetic connection lengths as well as the strong vacuum field gradients should favour stabilization of flute-type, kink, and other magnetohydrodynamic modes. Concerning reactor technology, high power densities are expected to be reached, superconducting coils should not become necessary, the coil stresses are moderate, and repair and replacement are facilitated by the coil geometry. Before a final judgement can be made on this concept, however, extensive experiments and further theoretical analysis are needed.
The Ionicity of CdO by X-ray Powder Diffraction at 80 K
Authors: E Rantavuori  , M Linkoaho  , R Kuoppala
Published: January 2007

The X-ray structure factors of CdO powder have measured with CuKα radiation at 80 K for ten reflections. The Debye-Waller coefficients were 1 400 ± 500 pm2 and 5 700 ± 1 000 pm2, and the ionic radii 124 ± 5 pm and 125 ± 5 pm for cadmium and oxygen, respectively. The degree of ionization obtained here was 1.7 ± 0.2 e, in fair agreement with the ideal value 2.0 for Cd+2O-2.
Coatings of Ultrafine Chromium Particles: Efficient Selective Absorbers of Solar Energy
Authors: C G Granqvist
Published: January 2007

Calculations of the optical and infrared absorption in coatings comprised of ultrafine chromium particles show that these exhibit the desired properties of an efficient selective absorber of solar energy.
Quantitative Surface Analysis Using ESCA
Authors: David M Hercules
Published: January 2007

Quantitative surface analysis using ESCA is considered from three perspectives: 1) some limitations on its use for quantitative surface measurements, 2) use with depth profiling to study SnF2 treated dental enamel and 3) utility of ESCA for studying surface species on catalysts. Enhancement of the surface sensitivity of ESCA by making measurements at low angles is restricted to very thin films. Optimum is a film thickness of ca. one-half the photoelectron escape depth. The utility of a quantitative measurement is influenced by both the distribution of the measured species in the photoelectron escape depth. ESCA is valuable for trace-metal analysis, although calibration curves are non-linear. Dental enamel treated with SnF2 shows three distinct zones of composition. The outermost layer consists almost entirely of Sn(OH)2, produced by hydrolysis. The next layer is composed of a mixture of species produced by several reactions. The bulk of the tooth consists primarily of a mixture of apatite and fluoroapatite. The nature of the nickel species on a catalyst surface varies with treatment and with support. On silica, the dominant species is NiO. On γ-alumina two species are present. One is a pseudoaluminate, Ni(+2) ions occupying tetrahedral sites in the alumina lattice. The second is an oxide which is reducible in hydrogen at 450°C.
Photoelectron Spectroscopy in a Strong Magnetic Field
Authors: G Beamson  , S J Pearce  , D W Turner
Published: January 2007

A new photoelectron spectroscopic method is described directed towards the measurement of the photoelectron spectroscopy of trapped ions. An electrostatic retarding field electron velocity analyser incorporating a channel plate multiplier is included with an ion trap in a strong magnetic field. A method is described for combining photoelectron spectroscopic with ion cyclotron resonance experiments to give positive identification of those features in the photoemission associated with double ionization processes of particular mass selected ions. The theoretical form of the retarding field photoelectron curve and its dependence upon β is discussed and preliminary experiments reported which show an abnormality in the angular distribution for argon and xenon.
Valence Electron Spectrum of C6H6Excited by Linearly Polarized HeI Radiation
Authors: L Mattsson  , L Karlsson  , R Jadrny  , K Siegbahn
Published: January 2007

Angular distributions of photoelectrons are conveniently studied with the application of a fourfold mirror polarizer on a conventional UV-source. This technique provides plane polarized radiation which promotes maximum sensitivity in the determination of the asymmetry parameter β. As an example polarized HeI radiation has been used to induce the electron spectrum of benzene.
Vibrational and Vibronic Structure in the Valence Electron Spectra of CH3X Molecules (X=F, Cl, Br, I, OH)
Authors: Leif Karlsson  , Reinhard Jadrny  , Lars Mattsson  , Foo Tim Chau  , Kai Siegbahn
Published: January 2007

Valence electron spectra of the methyl halides and of methyl alcohol have been induced by means of the HeI resonance radiation at 21.22 eV. A large number of new vibrational bands are reported. The observation of these was facilitated by a high instrumental resolving power and fast data acquisition. In most cases the new bands are observed in1A1→2Etransitions but also the electron band of the1A1→2A1transition of CH3I exhibits extensive progressions of closely spaced vibrational bands not previously reported. The vibrational structure of the1A1→2Etransitions is affected by vibronic coupling. The structure of the 2eelectron band of CH3Cl probably reflects the operation of the Ham effect. Calculations of the band structure including spin-orbit coupling are performed according to a model which is briefly described.
Valence Electron Spectra of the Chlorofluoromethanes CF3Cl, CF2Cl2and CFCl3
Authors: R Jadrny  , L Karlsson  , L Mattsson  , K Siegbahn
Published: January 2007

He I induced valence electron spectra are presented from CF3Cl, CF2Cl2and CFCl3. A high resolution electron spectrometer with a computerized multichannel detector system is used for detailed data recordings. Several new electronic and vibrational bands are reported.
Vibronic Interaction in Molecules and Ions. II. The first order Jahn-Teller interaction and spin-orbit coupling in doubly degenerate electronic states of C3vtype molecules
Authors: F T Chau  , L Karlsson
Published: January 2007

A quantitative treatment invoking first-order Jahn-Teller interaction together with spin-orbit coupling is employed to determine the energy levels of2Eelectronic states of C3vtype molecules. Both the static and dynamic nature of the interactions are discussed. The vibronic energies as well as vibrational transition probabilities of1A1→2Etransitions are presented from two sets of calculations corresponding to different magnitudes of the spin-orbit coupling. An application is made to explain the vibronic structure of the 2eelectron band of the high resolution electron spectra of CH3Cl, CH3Br and CH3I. The magnitude of the vibronic coupling is determined in terms of a Jahn-Teller coupling parameter. The result for CH3Cl+suggests that the spin-orbit splitting is quenched and the geometry of the ground ionic state is distorted to Csor C1symmetry.
Argon KLL and KLM Auger Electron Spectra
Authors: L Asplund  , P Kelfve  , B Blomster  , H Siegbahn  , K Siegbahn
Published: January 2007

The completeKLLandKLMAuger electron spectra of argon have been recorded at high resolution. The satellite lines in theKLLspectrum have been investigated and relativistic multiconfigurational Dirac-Fock calculations have been made to suggest assignments for these structures. Investigations of the neonKLLspectrum are employed to interpret part of the shake-off satellites.
Electron Spectroscopy and Ultra-soft X-ray Emission of Free Molecules
Authors: J Nordgren  , H Ågren  , L Selander  , C Nordling  , K Siegbahn
Published: January 2007

Recent developments of molecular X-ray emission spectroscopy and its interrelation with electron spectroscopy are discussed. Deep-lying level energies obtained by X-ray emission and ESCA are compared. Valence electron structure of small molecules is studied as well as multiply excited inner vacancy states of free atoms.
Comparison of Experimental and Theoretical Binding and Transition Energies in the Actinide Region
Authors: M O Krause  , C W Nestor Jr
Published: January 2007

The present status of experimental and theoretical binding and transition energy determinations is reviewed. Experimental data and the most recent theoretical predictions are compared for the energies ofKα1X-rays,Mseries X-rays,K-LLAuger electrons,K,L3,MandNlevels, and the 4fspin-orbit splitting. In addition, theKα1andLadata are fitted by Moseley-type diagrams, and data on the shallow levels and the valence bands of actinide oxides are discussed. Comparison shows that the single-particle Dirac-Fock theory and the inclusion of quantum-electrodynamic contributions predicts energies of the innermost levels generally within the accuracy of data, that is in the order of magnitude of 1 eV. However, in theN, O... shells large deviations do occur presumably due to strong many-electron interactions. The inclusion of many-electron effects in the relativistic theory remains a challenge, as do experimental investigations affording an accuracy of better than 1 eV for the various electronic levels.
Theoretical Calculation of Relative Intensities in ESCA
Authors: V I Nefedov  , V G Yarzhemsky
Published: January 2007

Calculations of the photoionization cross-sections of atomic and molecular levels for the A1Kα and MgKα lines depending on the wave function of the final and the initial states are analysed. Thens, npandndphotoionization cross-sections of atomic shells forZ⩽ 36 and the HF, NH3, H2O, CH4, CH3F, CH2F2, CHF3, CF4, N2, CO and C2H4molecular levels for the YMζ line and the photoionization cross-sections of atoms forZ⩽ 36 and the CH4, N2and H2O molecular levels for the ZrMζ line are calculated. The theoretical cross-sections of atoms forZ⩽ 10 for the FKα line are presented too. Photoionization cross-section calculations using Hartree-Fock-Slater potential are in better agreement with the experiment than those using orthogonalized plane waves for photo-electron wave functions.
On a Many-electron Description of Photoionization Processes: Application to the 5, 5 ESCA Spectrum in Xe
Authors: Göran Wendin
Published: January 2007

It is demonstrated that a 5score hole in Xe is strongly influenced by (mainly) 5⇌52mdsuper Coster-Kronig dipole fluctuations. This leads to a 5level shift of ∼ 3.1 eV to lower binding energy (monopole relaxation gives ∼ 0.8 eV) and to a prominent satellite spectrum.
Many-electron Effects in the 3p Core Hole Spectrum of Kr Application to the Elements Ge to Zr. Application to the Elements Ge to Zr
Authors: M Ohno  , G Wendin
Published: January 2007

The spectral function for a 3core hole (M2,3vacancy) in atomic Kr is calculated within the framework of many-body theory. The resulting position and width of the core level is in good agreement with experiment. In particular, we find that super Coster-Kronig dipole fluctuations give an additional relaxation energy shift of ∼ 3 eV, which is ∼ 30% of the shift due to monopole relaxation. We also study the variation of theM2,3width in free atoms as a function of atomic numberZ(for the elements Ge, Br, Kr, Rb and Zr) and we discuss the influence of solid state effects.
Scattered Wave Calculations of Monomers and Dimers of Tetraselenafulvalene (TSeF)
Authors: F Herman
Published: January 2007

The energy levels of the TSeF molecule have been calculated by the scattered wave method and compared with the experimental photoemission spectrum for TSeF vapor. There is good overall agreement between theory and experiment. Scattered wave calculations for model TSeF dimers lead to a value of 0.59 eV for the infinite stack bandwidth for the TSeF stack in crystalline TSeF-TCNQ (compare with our earlier values of 0.47 eV for TTF and 0.58 eV for TCNQ bandwidths in TTF-TCNQ). The dependence of the bandwidth on stacking distance is also reported for TTF-TCNQ and TSeF-TCNQ.