bluuebunny/crossref_metadata_2025 huggingface dataset:
In defense of the tenure system
Authors: Greenberg Gary , Billings Dorothy K.
Published: February 2007

We do not dispute the findings of Ceci et al.'s study, though they are based on survey research which does not always reflect real-life experiences. We report on cases we have defended on the basis of the tenure system, few of which mirror the situations reported in the target article. We end with a strong defense of the tenure system in the modern university.
Tenure is a necessary – not a sufficient – condition for controversial research
Authors: MacDonald Kevin
Published: February 2007

The Ceci et al. article is consistent with tenure being a necessary condition for controversial research. In the absence of tenure, as in the United Kingdom, professors have been fired and suspended for politically controversial issues. There are a variety of reasons why tenure does not ensure that professors will engage in controversial research, including career interests and the desire to be liked.
Why ritualized behavior? Precaution Systems and action parsing in developmental, pathological and cultural rituals
Authors: Boyer Pascal , Liénard Pierre
Published: February 2007

Ritualized behavior, intuitively recognizable by its stereotypy, rigidity, repetition, and apparent lack of rational motivation, is found in a variety of life conditions, customs, and everyday practices: in cultural rituals, whether religious or non-religious; in many children's complicated routines; in the pathology of obsessive-compulsive disorders (OCD); in normal adults around certain stages of the life-cycle, birthing in particular. Combining evidence from evolutionary anthropology, neuropsychology and neuroimaging, we propose an explanation of ritualized behavior in terms of an evolved Precaution System geared to the detection of and reaction to inferred threats to fitness. This system, distinct from fear-systems geared to respond to manifest danger, includes a repertoire of clues for potential danger as well as a repertoire of species-typical precautions. In OCD pathology, this system does not supply a negative feedback to the appraisal of potential threats, resulting in doubts about the proper performance of precautions, and repetition of action. Also, anxiety levels focus the attention on low-level gestural units of behavior rather than on the goal-related higher-level units normally used in parsing the action-flow. Normally automatized actions are submitted to cognitive control. This “swamps” working memory, an effect of which is a temporary relief from intrusions but also their long-term strengthening. Normal activation of this Precaution System explains intrusions and ritual behaviors in normal adults. Gradual calibration of the system occurs through childhood rituals. Cultural mimicry of this system's normal input makes cultural rituals attention-grabbing and compelling. A number of empirical predictions follow from this synthetic model.
Why ritual works: A rejection of the by-product hypothesis
Authors: Alcorta Candace Storey , Sosis Richard
Published: February 2007

We argue that ritual is not a by-product as Boyer & Lienard (B&L) claim, but rather an evolved adaptation for social communication that facilitates non-agonistic social interactions among non-kin. We review the neurophysiological effects of ritual and propose neural structures and networks beyond the cortical-striato-pallidal-thalamic circuit (CSPT) likely to be implicated in ritual. The adaptationist approach to ritual offers a more parsimonious model for understanding these effects as well as the findings B&L present.
Habit formation in Tourette Syndrome with associated obsessive-compulsive behavior: At the crossroads of neurobiological modelling
Authors: Rothenberger Aribert , Roessner Veit , Banaschewski Tobias
Published: February 2007

Tourette Syndrome (TS) and Obsessive-Compulsive Disorder (OCD) are highly associated and often it is difficult to differentiate their symptomatology. In TS, habit forming neuronal systems may form habits of their own – sometimes similar to ritualized behavior. However, whereas in OCD merely the “affect-loop” is touched, in TS the “sensorimotor-loop” plays the major role, although some overlap can be seen in the clinical spectrum between TS and OCD. The latter is mainly related to the “just-right” phenomenon which shows a clear developmental course. An analogous behavioral model for TS and OCD with reference to “just-right” is suggested.
Ritualized behavior as a domain-general choice of actions
Authors: Wang Hongbin , Bello Paul
Published: February 2007

Although we agree that ritualized behavior is a mystery that calls out for an explanation, we do not think that the proposed domain-specific two-component system offers an empirically well-justified and theoretically parsimonious description of the phenomena. Instead, we believe that the deployment of domain-general mechanisms based on choice of actions could also explain the essential features of ritualized behavior.
Precaution systems and ritualized behavior
Authors: Boyer Pascal , Liénard Pierre
Published: February 2007

In reply to commentary on our target article, we supply further evidence and hypotheses in the description of ritualized behaviors in humans. Reactions to indirect fitness threats probably activate specialized precaution systems rather than a unified form of danger-avoidance or causal reasoning. Impairment of precaution systems may be present in pathologies other than obsessive-compulsive disorder (OCD), autism in particular. Ritualized behavior is attention-grabbing enough to be culturally transmitted whether or not it is associated with group identity, cohesion, or with any other social aspect of collective ceremonies.
Separate estimates of portion size were not essential for energy and nutrient estimation: results from the Southern Community Cohort food-frequency questionnaire pilot study
Authors: Schlundt David G , Buchowski Maciej S , Hargreaves Margaret K , Hankin Jean H , Signorello Lisa B , Blot William J
Published: February 2007

Objective

A food-frequency questionnaire (FFQ) was developed to assess habitual dietary intake in the Southern Community Cohort Study (SCCS), a prospective epidemiological study to analyse disparities in cancer and other chronic diseases between African-Americans and Whites.

Design

Frequency and portion size estimates were obtained for each of 104 foods. Daily intakes of 13 food groups, energy and 18 nutrients were computed. Each participant's rank and quintile classification of nutrient intakes was determined with and without the use of the subject's reported portion size.

Subjects

The sample was obtained from the SCCS pilot study conducted in Tennessee, Mississippi and Florida, and consisted of 209 adults, 54% African-American, with a mean (standard deviation) age of 57.1 (12.5) years.

Results

Correlations between the ranks from the two methods of estimation were high, ranging from 0.66 to 0.94 for food groups and 0.81 to 0.94 for nutrients. Pearson correlations were similarly high for food groups and nutrients. Concordance in exact quintile rank across the nutrient indices ranged from 52 to 70%, rising to 90–99% for concordance within adjacent quintiles.

Conclusions

To reduce the respondents' burden and to increase data completeness, the assignment of a uniform portion size when scoring the SCCS FFQ was considered acceptable.
Trends in fruit, vegetable and salad intakes in 9–10-year-old schoolchildren living in Liverpool, 2000–2005
Authors: Johnson B , Hackett AF
Published: February 2007

Objective

To report on the fruit, vegetable and salad intakes of Liverpool schoolchildren aged 9–10 years over a 5-year period (2000–2005).

Design

Cross-sectional observational study.

Setting

Between 75 and 100 Liverpool primary schools took part in each survey year.

Subjects

Subjects consisted of five separate cohorts of 9–10-year-old children from all areas of the city.

Main outcome measures

Number and proportion of boys and girls who reported eating fruit, vegetables and salad on the previous day.

Results

There was an upward trend in the reported intake of fruit between 2002 and 2005. Girls were more likely than boys to report eating fruit (P < 0.001). The trend in salad intake was positive. Between 2000 and 2005 there were significant increases in the number of boys (χ2 = 17.57, P = 0.001) and girls (χ2 = 80.56, P = 0.001) eating salad. Girls were significantly more likely to eat salad than boys in all years (χ2 = 58.75, P = 0.001). Trends in vegetable intake were similar to those for salad, with both sexes reporting yearly increases over the 5-year period. The increase in the number of boys who reported eating vegetables between 2000 and 2005 was 23.5% (χ2 = 32.9, P = 0.000). In girls there was a 44.8% increase over the same period (χ2 = 110.3, P < 0.000).

Conclusions

The data reveal positive trends in the fruit, vegetable and salad intakes of Liverpool schoolchildren between 2000 and 2005. Further research is needed to elucidate the specific factors that have enabled the changes to take place.
Utilization of Restaurant Waste Oil as a Precursor for Sophorolipid Production
Authors: Shah Vishal , Jurjevic Mia , Badia Daniel
Published: February 2007

Approximately 100 billion liters of oil is generated per week as waste from restaurants around the country. Because of health, environmental, and economic factors, current methods of disposal are ineffective for disposal of the restaurant oil wastes. In this study we have investigated the ability of Candida bombicola to fermentatively transform the restaurant oil waste into glycolipids called sophorolipids. Batch and fed‐batch studies were carried out using oil waste as the lipid feedstock in Erlenmeyer flasks and in a fermentor. Batch fermentation in a fermentor gave the highest yield of sophorolipids of 34 g L−1. Fermentation using oleic acid as control feedstock were also carried out. Batch fermentation in the fermentor using this pure fatty acid gave a highest yield of 42 g L−1. The difference in the sophorolipid yield was attributed to the fatty acid composition of restaurant oil waste.
Slip rates on the Chelungpu and Chushiang thrust faults inferred from a deformed strath terrace along the Dungpuna river, west central Taiwan
Authors: Simoes Martine , Avouac Jean Philippe , Chen Yue‐Gau
Published: February 2007

The Chelungpu fault produced the September 1999 Mw = 7.6 Chi‐Chi earthquake, central Taiwan. The shortening rate accommodated by this structure, integrated over several seismic cycles, and its contribution to crustal shortening across the Taiwanese range have remained unresolved. To address the issues, we focus our study on the Chelungpu and Chushiang thrust faults within the southernmost portion of the Chi‐Chi rupture area. Structural measurements and available seismic profiles are used to infer the subsurface geometry of structures. The Chushiang and Chelungpu faults appear as two splay faults branching onto a common ramp that further north connects only to the Chelungpu surface trace. We survey a deformed strath terrace along the Dungpuna river, buried under a 11,540 ± 309 years old fill deposit. Given this age, the dip angles of the faults, and the vertical throw determined from the offset of the strath terrace across the surface fault traces, we estimate slip rates of 12.9 ± 4.8 and 2.9 ± 1.6 mm/yr on the Chelungpu and Chushiang faults, respectively. These yield a total shortening rate of 15.8 ± 5.1 mm/yr to be absorbed on their common decollement at depth. This total value is an upper bound for the slip rate on the Chelungpu fault further north, where the Chushiang fault disappears and transfers shortening to adjacent faults. Combining these results with the recently constrained shortening rate on the Changhua blind thrust reveals that all these frontal faults presently absorb most of the long‐term horizontal shortening across the Taiwanese range. They thus stand as the major sources of seismic hazards in this heavily populated area. The return period of earthquakes similar to the Chi‐Chi event over a ∼80 km long stretch of the Western Foothills is estimated to be ∼64 years. This value is an underestimate because it assumes that all the faults locked during the interseismic period slip only during such large events. Comparison with historical seismicity suggests that episodic aseismic deformation might also play a major role in accommodating shortening.
Modeling and analysis of aerosol processes in an interactive chemistry general circulation model
Authors: Verma Sunita , Boucher O. , Reddy M. S. , Upadhyaya H. C. , Le Van P. , Binkowski F. S. , Sharma O. P.
Published: February 2007

An “online” aerosol dynamics and chemistry module is included in the Laboratoire de Météorologie Dynamique general circulation model (LMDZ), so that the chemical species are advected at each dynamical time step and evolve through chemical and physical processes that have been parameterized consistently with the meteorology. These processes include anthropogenic and biogenic emissions, over 50 gas/aqueous phase chemical reactions, transport due to advection, vertical diffusion and convection, dry deposition and wet scavenging. We have introduced a size‐resolved representation of aerosols which undergo various processes such as coagulation, nucleation and dry and wet scavenging. The model considers 16 prognostic tracers: water vapor, liquid water, dimethyl sulfide (DMS), hydrogen sulfide (H2S), dimethyl sulphoxide (DMSO), methanesulphonic acid (MSA), sulfur dioxide (SO2), nitrogen oxides (NOX), carbon monoxide (CO), nitric acid (HNO3), ozone (O3), hydrogen peroxide (H2O2), sulfate mass and number for Aitken and accumulation modes. The scheme accounts for two‐way interactions between tropospheric chemistry and aerosols. The oxidants and chemical species fields that represent the sulfate aerosol formation are evolved interactively with the model dynamics. A detailed description on the coupled climate‐chemistry interactive module is presented with the evaluation of chemical species in winter and summer seasons. Aqueous phase reactions in cloud accounted for 71% of sulfate production rate, while only 45% of the sulfate burden in the troposphere is derived from in‐cloud oxidation.
Southern Hemisphere Additional Ozonesondes (SHADOZ) 1998–2004 tropical ozone climatology: 3. Instrumentation, station‐to‐station variability, and evaluation with simulated flight profiles
Authors: Thompson Anne M. , Witte Jacquelyn C. , Smit Herman G. J. , Oltmans Samuel J. , Johnson Bryan J. , Kirchhoff Volker W. J. H. , Schmidlin F. J.
Published: February 2007

The Southern Hemisphere Additional Ozonesondes (SHADOZ) project has collected more than 3000 ozone profiles from 14 tropical and subtropical sites using balloon‐borne electrochemical concentration cell (ECC) ozonesondes flown with standard radiosondes. Published analysis of ozonesonde precision from SHADOZ profiles measured in 1998–2000 revealed that variations in ozonesonde technique might cause small station‐to‐station biases in the total ozone measurement. We present further evaluation of imprecisions and accuracy based on 1998–2004 SHADOZ data, results from laboratory simulations of ozonesonde flights, and a revised back‐scattered ultraviolet algorithm, the TOMS version 8, 2004 release. The laboratory studies used standard ECC ozonesondes in a flight simulation chamber to evaluate techniques used at SHADOZ stations. Ozone deviations from a standard ozone instrument in the chamber tests resemble those of SHADOZ station data relative to a SHADOZ‐defined climatological reference. Certain systematic variations in SHADOZ ozone profiles are accounted for by differences in solution composition, data processing, and instrument manufacturer. When SHADOZ total ozone column amounts are compared to the new TOMS algorithm, discrepancies between sonde and satellite decline 1–2 percentage points on average, compared to version 7 TOMS.
Anthropogenic CO2 accumulation rates in the North Atlantic Ocean from changes in the 13C/12C of dissolved inorganic carbon
Authors: Quay P. , Sonnerup R. , Stutsman J. , Maurer J. , Körtzinger A. , Padin X. A. , Robinson C.
Published: February 2007

The anthropogenic CO2 accumulation rate for the North Atlantic Ocean was estimated on the basis of the decrease in the δ13C of the dissolved inorganic carbon measured between cruises in 1981 (Transient Tracers in the North Atlantic), 1993 (OACES) and 2003 (Repeat Hydrography). A mean depth‐integrated δ13C change of −15.0 ± 3.8‰ m yr−1 was estimated by applying a multiple linear regression approach to determine the anthropogenic δ13C decrease at 22 stations where δ13C depth profiles were compared. The largest and deepest anthropogenic δ13C decreases occurred in the subpolar ocean and, in contrast, the smallest and shallowest decreases occurred in the tropical ocean. A mean anthropogenic CO2 accumulation rate of 0.63 ± 0.16 mol C m−2 yr−1 (0.32 ± 0.08 Pg C yr−1) in the North Atlantic Ocean over the last 20 years was determined from the mean depth‐integrated δ13C change and a ratio of anthropogenic δ13C to DIC change of −0.024‰ (μmol kg−1)−1. Only half of the accumulated anthropogenic CO2 in the North Atlantic during the last 20 years was the result of air‐sea CO2 uptake, based on a comparison of the air‐sea 13CO2 flux to the DIC13 inventory change, with the other half likely a result of northward advective transport.
GCM simulations of the Indian Ocean dipole influence on East African rainfall: Present and future
Authors: Conway D. , Hanson C. E. , Doherty R. , Persechino A.
Published: February 2007

Six coupled GCMs are assessed in terms of their ability to simulate observed characteristics of East African rainfall, the Indian Ocean dipole and their temporal correlation. Model results are then used to analyze the future behaviour of rainfall and the DMI. All models simulate reasonably well the spatial distribution and variability of annual and seasonal rainfall over the 1961–1990 period. Model simulation of observed DMI characteristics is less consistent with observations, however, five models reproduce similar correlations to those observed between the DMI and East African short rains (SON). In the future, there are no clear inter‐model patterns of rainfall or DMI behaviour. In this sample of models four (two) out of six simulate modest increases (decreases) in annual rainfall by the 2080s. For SON, three of the six models indicate a trend towards increasingly positive phase of the DMI, two indicate a decrease and one shows no substantial change.
Location of the reconnection line at the magnetopause during southward IMF conditions
Authors: Trattner K. J. , Mulcock J. S. , Petrinec S. M. , Fuselier S. A.
Published: February 2007

Magnetic reconnection transfers energy from magnetic fields to particles in space, but the conditions under which reconnection is initiated are not well understood. Indirect evidence confirms the existence of reconnection where merging fields are anti‐parallel, but also confirms the existence of another type of reconnection, called component reconnection. This ambiguity has resulted in considerable debate over which of these types of reconnection dominates. Here we report on a method using 3D plasma observations from the TIMAS instrument on Polar as it passes through the northern cusp to calculate the distance to the reconnection line, and subsequently trace this distance to the magnetopause. Results from 130 events reveal that in general, magnetic reconnection occurs along an extended line across the dayside magnetopause, consistent with the component reconnection scenario. These results indicate that reconnection in other regions of space (e.g., solar flares, Earth's magnetotail) should not be limited to anti‐parallel magnetic field geometries.
Effects of interplanetary magnetic clouds, interaction regions, and high‐speed streams on the transient modulation of galactic cosmic rays
Authors: Singh Y. P. , Badruddin
Published: February 2007

Interplanetary manifestations of coronal mass ejections (CMEs) with specific plasma and field properties, called “interplanetary magnetic clouds,” have been observed in the heliosphere since the mid‐1960s. Depending on their associated features, a set of observed magnetic clouds identified at 1 AU were grouped in four different classes using data over 4 decades: (1) interplanetary magnetic clouds moving with the ambient solar wind (MC structure), (2) magnetic clouds moving faster than the ambient solar wind and forming a shock/sheath structure of compressed plasma and field ahead of it (SMC structure), (3) magnetic clouds “pushed” by the high‐speed streams from behind, forming an interaction region between the two (MIH structure), and (4) shock‐associated magnetic clouds followed by high‐speed streams (SMH structure). This classification into different groups led us to study the role, effect, and the relative importance of (1) closed field magnetic cloud structure with low field variance, (2) interplanetary shock and magnetically turbulent sheath region, (3) interaction region with large field variance, and (4) the high‐speed solar wind stream coming from the open field regions, in modulating the galactic cosmic rays (GCRs). MC structures are responsible for transient decrease with fast recovery. SMC structures are responsible for fast decrease and slow recovery, MIH structures produce depression with slow decrease and slow recovery, and SMH structures are responsible for fast decrease with very slow recovery. Simultaneous variations of GCR intensity, solar plasma velocity, interplanetary magnetic field strength, and its variance led us to study the relative effectiveness of different structures as well as interplanetary plasma/field parameters. Possible role of the magnetic field, its topology, field turbulence, and the high‐speed streams in influencing the amplitude and time profile of resulting decreases in GCR intensity have also been discussed.
Effect of moisture on leaf litter decomposition and its contribution to soil respiration in a temperate forest
Authors: Cisneros‐Dozal Luz Maria , Trumbore Susan E. , Hanson Paul J.
Published: February 2007

The degree to which increased soil respiration rates following wetting is caused by plant (autotrophic) versus microbial (heterotrophic) processes, is still largely uninvestigated. Incubation studies suggest microbial processes play a role but it remains unclear whether there is a stimulation of the microbial population as a whole or an increase in the importance of specific substrates that become available with wetting of the soil. We took advantage of an ongoing manipulation of leaf litter 14C contents at the Oak Ridge Reservation, Oak Ridge, Tennessee, to (1) determine the degree to which an increase in soil respiration rates that accompanied wetting of litter and soil, following a short period of drought, could be explained by heterotrophic contributions; and (2) investigate the potential causes of increased heterotrophic respiration in incubated litter and 0–5 cm mineral soil. The contribution of leaf litter decomposition increased from 6 ± 3 mg C m−2 hr−1 during a transient drought, to 63 ± 18 mg C m−2 hr−1 immediately after water addition, corresponding to an increase in the contribution to soil respiration from 5 ± 2% to 37 ± 8%. The increased relative contribution was sufficient to explain all of the observed increase in soil respiration for this one wetting event in the late growing season. Temperature (13°C versus 25°C) and moisture (dry versus field capacity) conditions did not change the relative contributions of different decomposition substrates in incubations, suggesting that more slowly cycling C has at least the same sensitivity to decomposition as faster cycling organic C at the temperature and moisture conditions studied.
Isentropic loading experiments of a plastic bonded explosive and constituents
Authors: Baer M. R. , Hall C. A. , Gustavsen R. L. , Hooks D. E. , Sheffield S. A.
Published: February 2007

The plastic bonded explosive PBX 9501 and its constituents [cyclotetramethylene tetranitramine (HMX) crystals, nitroplasticized Estane ®5703 and a fine-crystallite HMX laden binder mixture] were subjected to a ramped quasi-isentropic compression load using the Z machine at Sandia National Laboratories to determine equation of state and constitutive property data. Various sample thicknesses of these materials were subjected to an identical ramp loading history up to 4.5 GPa over 350 ns and particle velocities were measured using a velocity interferometry technique to assess material response. Upon defining appropriate constitutive relationships for the individual constituents, a topologically disordered model of the composite material was numerically simulated and details of the mesoscale simulation indicate that much of the plastic deformation first occurs locally at the large HMX crystal contacts points and subsequently by the deformation of the interstitial fine-crystallite/binder material.
Molecular level approaches for investigation of electron transfer in nonpolar solvents
Authors: Leontyev I. V. , Tachiya M.
Published: February 2007

The authors extend their previous work published in Leontyev and TachiyaJ. Chem. Phys. 123, 224502 (2005) and study not only forward but also reverse electron transfer between pyrene and dimethylaniline in a nonpolar solvent, n-hexane. The distribution function methodology and molecular dynamics technique adopted in their previous work are used. Two algorithms (I and II) are formulated for obtaining the reorganization energy and the solvation free energy difference in the linear response approximation. The two algorithms are combined with different cutoff schemes and tested for polarizable and nonpolarizable solvent models. Agreement between the results obtained by the two algorithms was achieved only for simulations employing the particle mesh Ewald treatment. It is concluded that algorithm I provides a reliable scheme for evaluation of the reorganization energy and the solvation free energy difference. Moreover, a new algorithm referred to as the G-function algorithm is formulated which does not assume the linear response approximation, and is tested on evaluation of the solvation free energy difference. Agreement between the results from the G-function algorithm and those from algorithms I and II is fairly good, although it depends on the degree of statistical consistency of the simulations. In the case of nonpolar solvents the G-function method has practical importance because, unlike the conventional thermodynamic integration approach, it requires equilibrium molecular configuration ensembles only for the initial and final states of the system.
Temperature sensitivity of Cu Kα imaging efficiency using a spherical Bragg reflecting crystal
Authors: Akli K. U. , Key M. H. , Chung H. K. , Hansen S. B. , Freeman R. R. , Chen M. H. , Gregori G. , Hatchett S. , Hey D. , Izumi N. , King J. , Kuba J. , Norreys P. , Mackinnon A. J. , Murphy C. D. , Snavely R. , Stephens R. B. , Stoeckel C. , Theobald W. , Zhang B.
Published: February 2007

The interaction of a 75J 10ps, high intensity laser beam with low-mass, solid Cu targets is investigated. Two instruments were fielded as diagnostics of Cu K-shell emission from the targets: a single photon counting spectrometer provided the absolute Kα yield [C. Stoeckl et al., Rev. Sci. Instrum. 75, 3705 (2004)] and a spherically bent Bragg crystal recorded 2D monochromatic images with a spatial resolution of 10μm [J. A. Koch et al., Rev. Sci. Instrum. 74, 2130 (2003)]. Due to the shifting and broadening of the Kα spectral lines with increasing temperature, there is a temperature dependence of the crystal collection efficiency. This affects measurements of the spatial pattern of electron transport, and it provides a temperature diagnostic when cross calibrated against the single photon counting spectrometer. The experimental data showing changing collection efficiency are presented. The results are discussed in light of modeling of the temperature-dependent spectrum of Cu K-shell emission.
Microhydration of cytosine and its radical anion: Cytosine∙(H2O)n (n=1–5)
Authors: Kim Sunghwan , Schaefer Henry F.
Published: February 2007

Microhydration effects on cytosine and its radical anion have been investigated theoretically, by explicitly considering various structures of cytosine complexes with up to five water molecules. Each successive water molecule (through n=5) is bound by 7–10kcalmol−1 to the relevant cytosine complex. The hydration energies are uniformly higher for the analogous anion systems. While the predicted vertical detachment energy (VDE) of the isolated cytosine is only 0.48eV, it is predicted to increase to 1.27eV for the lowest-lying pentahydrate of cytosine. The adiabatic electron affinity (AEA) of cytosine was also found to increase from 0.03to0.61eV for the pentahydrate, implying that the cytosine anion, while questionable in the gas phase, is bound in aqueous solution. Both the VDE and AEA values for cytosine are smaller than those of uracil and thymine for a given hydration number. These results are in qualitative agreement with available experimental results from photodetachment-photoelectron spectroscopy studies of Schiedt et al. [Chem. Phys. 239, 511 (1998)].
Image processing for resonance frequency mapping in atomic force modulation microscopy
Authors: Arinéro R. , Lévêque G. , Girard P. , Ferrandis J. Y.
Published: February 2007

It has been demonstrated that the resonance frequency of the cantilever in atomic force modulation microscopy can be used to study local mechanical properties. We developed a numerical method to achieve mapping of the resonance frequency without significant modification of the device. By making the assumption that the resonance spectrum can be approximated by a Lorentzian curve, we established analytical expressions of the resonance frequency and the width of the curve (damping) depending on the real and imaginary parts of the vibration at a single frequency. Then, resonance frequency and damping images were produced from the recording of both the real and imaginary part images of the complex amplitude. The results on a standard high-impact polystyrene sample are shown.
Simultaneous measurement of Young’s and shear moduli of multiwalled carbon nanotubes using atomic force microscopy
Authors: Guhados Ganesh , Wan Wankei , Sun Xueliang , Hutter Jeffrey L.
Published: February 2007

Carbon nanotubes (CNTs) are widely hailed as the strongest material known to mankind. However, experimental measurements—and even theoretical estimates—of their mechanical properties span a wide range. We present an atomic force microscopy study of multiwalled CNTs, which, unlike previous such studies, measures the tube compliance as a function of position along suspended tubes. This permits a simultaneous determination of the effective Young’s and shear moduli of CNTs: 350±110 and 1.4±0.3GPa, respectively.
Photoelectron spectrum from a thin organic layer exposed to intense x rays
Authors: Jung M. C. , Shin H. J. , Chung J.
Published: February 2007

When an organic layer on a conducting substrate is exposed to intense x rays, such as in scanning photoelectron microscopy (SPEM), the photoelectron spectrum for the exposed area shows a kinetic energy shift towards higher binding energy due to the accumulation of local charges. We present experimental evidence that in the thin organic layer of approximately 100nm thickness in organic light-emitting devices, there exists an unshifted spectral component besides the local-charging-shifted spectral component. This finding enabled us to reliably investigate the chemical structures of organic layers using SPEM, which was shown to be advantageous in obtaining the space-resolved chemical structural information of a specimen.
Scintillation characteristics of Lu3Al5O12:Ce optical ceramics
Authors: Nikl Martin , Mares Jiri A. , Solovieva Natasha , Li Hui-Li , Liu Xue-Jian , Huang Li-Ping , Fontana Ilaria , Fasoli Mauro , Vedda Anna , D’Ambrosio Carmelo
Published: February 2007

Optical absorption, luminescence, and scintillation characteristics of Lu3Al5O12:Ce optical ceramics were measured and compared with an analogous high quality single crystal. Optical absorption of the former shows an additional light scattering loss due to nanovoids and/or refraction index inhomogeneities. Even though radioluminescence intensity of the optical ceramics prepared by a coprecipitation route exceeds that of single crystal, its scintillation light yield is lower due to the charge carrier retrapping in the process of energy transfer towards the Ce3+ emission centers. Retrapping processes are evidenced by thermoluminescence measurements below room temperature. Lu3Al5O12:Ce optical ceramics does not show the presence of the LuAl antisite defects which decreases the scintillation figure of merit in single crystals grown from the melt [M. Nikl, Phys. Status Solidi A 202, 201 (2005)]. Furthermore, using the ceramic technology, one can achieve both the homogeneous doping and higher Ce concentration. Similar to Y3Al5O12:Ce, the optical ceramics may therefore become competitive to the Lu3Al5O12:Ce single crystals, if trapping phenomena at other defects can be further reduced.
Fabry-Perot effects in InGaN∕GaN heterostructures on Si-substrate
Authors: Hums C. , Finger T. , Hempel T. , Christen J. , Dadgar A. , Hoffmann A. , Krost A.
Published: February 2007

A strong intensity modulation is found in spatially and angular resolved photoluminescence spectra of InGaN∕GaN heterostructures and quantum wells epitaxially grown on Si(111) substrates. This Fabry-Perot effect results from the high refractive index contrasts at the GaN∕Si and the Air/InGaN interfaces. It can be used for a wavelength stabilization of the sample upon temperature change and, e.g., in the case of light emitting diodes, to additionally reduce the blueshift at increasing injection currents. A simple geometric approach has been chosen to calculate the influence of layer thickness, absorption and refractive indices, as well as detection angle. The cavity can be described quantitatively by a simple three layer Fabry-Perot model. An analytical expression is derived for the external luminescence line shape. Microphotoluminescence measurements at samples with the silicon substrate locally removed corroborate the model.
High photoluminescence quantum efficiency InGaN multiple quantum well structures emitting at 380nm
Authors: Graham D. M. , Dawson P. , Chabrol G. R. , Hylton N. P. , Zhu D. , Kappers M. J. , McAleese C. , Humphreys C. J.
Published: February 2007

In this paper we report the design of high room temperature photoluminescence internal efficiency InGaN-based quantum well structures emitting in the near ultraviolet at 380nm. To counter the effects of nonradiative recombination the quantum wells were designed to have a large indium fraction, high barriers, and a small quantum well thickness. To minimize the interwell and interbarrier thickness fluctuations we used Al0.2In0.005Ga0.795N barriers, where the inclusion of the small fraction of indium was found to lead to fewer structural defects and a reduction in the layer thickness fluctuations. This approach has led us to achieve, for an In0.08Ga0.92N∕Al0.2In0.005Ga0.795N multiple quantum well structure with a well width of 1.5nm, a photoluminescence internal efficiency of 67% for peak emission at 382nm at room temperature.
Mechanical design and force calibration of dual-axis micromechanical probe for friction force microscopy
Authors: Fukuzawa Kenji , Terada Satoshi , Shikida Mitsuhiro , Amakawa Hiroaki , Zhang Hedong , Mitsuya Yasunaga
Published: February 2007

A dual-axis micromechanical probe that combines a double cantilever and torsion beams is presented. This probe can reduce the mechanical cross-talk between the lateral and vertical force detections. In addition, dual-axis forces can be detected by measuring the dual-axis displacement of the probe end using the optical lever-based method used in conventional friction force microscopes (FFMs). In this paper, the mechanical design of the probe, the details of the fabrication method, FFM performance, and calibration of the friction force are discussed. The mechanical design and the microfabrication method for probes that can provide a force resolution of the order of 1nN without mechanical cross-talk are presented. Calibration of the lateral force signal is possible by using the relationship between the lateral force and the piezodisplacement at the onset of the probe scanning. The micromechanical probe enables simultaneous and independent detection of atomic and friction forces. This leads to accurate investigation of nanotribological phenomena and visualization of the distribution of the friction properties, which helps the identification of the material properties.
Red luminescence of Cr in β-Ga2O3 nanowires
Authors: Nogales Emilio , García José A. , Méndez Bianchi , Piqueras Javier
Published: February 2007

Red luminescence emission from chromium doped β-Ga2O3 nanowires has been studied by means of photoluminescence (PL) techniques. PL excitation shows several bands in the ultraviolet-visible region. Time decay values, obtained by time resolved PL, at different temperatures fit a three level model with thermal population of the upper level from the middle one. From the results, the origin of the emission is assigned to Cr3+ ions in the β-Ga2O3 host, and values for the energy level separation and Huang-Rhys factor of the broad T24-A24 emission are estimated.
Relaxation-allowed nuclear magnetic resonance transitions by interference between the quadrupolar coupling and the paramagnetic interaction
Authors: Ling Wen , Jerschow Alexej
Published: February 2007

Of the various ways in which nuclear spin systems can relax to their ground states, the processes involving an interference between different relaxation mechanisms, such as dipole-dipole coupling and chemical shift anisotropy, have become of great interest lately. The authors show here that the interference between the quadrupolar coupling and the paramagnetic interaction (cross-correlated relaxation) gives rise to nuclear spin transitions that would remain forbidden otherwise. In addition, frequency shifts arise. These would be reminiscent of residual anisotropic interactions when there are none. While interesting from a fundamental point of view, these processes may become relevant in magnetic resonance imaging experiments which involve quadrupolar spins, such as Na23, in the presence of contrast agents. Geometrical constraints in paramagnetic molecule structures may likewise be derived from these interference effects.
Structural properties of epitaxial γ-Al2O3 (111) thin films on 4H-SiC (0001)
Authors: Tanner Carey M. , Sawkar-Mathur Monica , Lu Jun , Blom Hans-Olof , Toney Michael F. , Chang Jane P.
Published: February 2007

Al 2 O 3 thin films were grown on 4H-SiC (0001) by thermal atomic layer deposition and were crystallized to the γ-Al2O3 phase by rapid thermal annealing in N2 at 1100°C. The films were found to be chemically stable during processing based on x-ray photoelectron spectroscopy. The change in film structure was initially confirmed by reflection high-energy electron diffraction. As shown by high-resolution transmission electron microscopy images, the abrupt interface of the as-deposited films with the 4H-SiC substrate was preserved during crystallization, indicating no interfacial reaction. Selected area electron diffraction and synchrotron-based x-ray diffraction established an epitaxial relationship of γ-Al2O3 (111) ‖ 4H-SiC (0001) and in-plane orientation of γ-Al2O3 (11¯0) ‖ 4H-SiC (112¯0). No other alumina phases or orientations were observed and no in-plane misorientation was observed in the 27Å Al2O3 films. The full width at half maximum of the γ-Al2O3 (222) rocking curve is 0.056°, indicating a lack of mosaic spread and a high-quality crystalline film. Twinning around the γ-Al2O3 [111] axis was the only defect observed in these films.
Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres
Authors: Sheridan T. E. , Katschke M. R. , Wells K. D.
Published: February 2007

A method for measuring the time-averaged vertical electric field and its gradient in the plasma sheath using clusters with n=2 or 3 floating microspheres of known mass is described. The particle charge q is found by determining the ratio of the breathing frequency to the center-of-mass frequency for horizontal (in-plane) oscillations. The electric field at the position of the particles is then calculated using the measured charge-to-mass ratio, and the electric-field gradient is determined from the vertical resonance frequency. The Debye length is also found. Experimental results are in agreement with a simple sheath model.
Thermal beam of metastable krypton atoms produced by optical excitation
Authors: Ding Y. , Hu S.-M. , Bailey K. , Davis A. M. , Dunford R. W. , Lu Z.-T. , O’Connor T. P. , Young L.
Published: February 2007

A room-temperature beam of krypton atoms in the metastable 5s[3∕2]2 level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124nm for the first-step excitation from the ground level 4p6S01 to the 5s[3∕2]1 level. An 819nm Ti:sapphire laser is used for the second-step excitation from 5s[3∕2]1 to 5s[3∕2]2 followed by a spontaneous decay to the 5s[3∕2]2 metastable level. A metastable atomic beam with an angular flux density of 3×1014s−1sr−1 is achieved at the total gas flow rate of 0.01cm3∕s at STP (or 3×1017at.∕s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.
Enhanced visible-light absorption from PdO nanoparticles in nitrogen-doped titanium oxide thin films
Authors: Li Qi , Liang Wei , Ku Shang Jian
Published: February 2007

Composite films were made by embedding nanoparticles of p-type PdO semiconductor in a n-type titanium oxide matrix. With the assistance of nitrogen ion beam, these PdO nanoparticles were confined to less than a couple of nanometers. The resulting nanocomposite films demonstrated an unusual “redshift” in the optical absorption spectrum, contrary to the well-known quantum size effect from semiconductor nanoparticles. The absorption in the visible-light range is shown to result from absorption by metallic-like nanoparticles as palladium changed its valence state from Pd2+ to Pd in nitrogen-doped titanium oxide matrix under visible-light illumination.
Work function tuning of the TixTayN metal gate electrode for advanced metal-oxide-semiconductor devices applications
Authors: Cheng Chin-Lung , Liu Chien-Wei , Jeng Jin-Tsong
Published: February 2007

A work function (WF) tuning of the TixTayN metal gate ranging from 4.1to4.8eV has been observed using a post-metal-annealing (PMA). The mechanism related to the effective tunable WF can be explained using the creation of the extrinsic states, which is usually associated with the bonding defects that formed at the TixTayN∕SiO2 interface. The results display that the electron trapping is generated in the gate dielectric during the PMA treatments. The reduction on equivalent-oxide thickness with increasing the PMA temperature can be attributed to the combination of the densification of the SiO2 and the high-k layer that formed at the TixTayN∕SiO2 interface.
Significant dependence of morphology and charge carrier mobility on substrate surface chemistry in high performance polythiophene semiconductor films
Authors: Kline R. Joseph , DeLongchamp Dean M. , Fischer Daniel A. , Lin Eric K. , Heeney Martin , McCulloch Iain , Toney Michael F.
Published: February 2007

The authors report a significant dependence of the morphology and charge carrier mobility of poly(2,5-bis(3-dodecylthiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT) films on the substrate surface chemistry upon heating into its liquid crystal phase. In contrast with films on bare silicon oxide surfaces, pBTTT films on oxide functionalized with octyltrichlorosilane exhibit substantial increases in the lateral dimensions of molecular terraces from nanometers to micrometers, increased orientational order, and higher charge carrier mobility. The large-scale crystallinity of this polymer plays an important role in the high carrier mobility observed in devices, but renders it more sensitive to substrate surface chemistry than other conjugated polymers.
Retrolinkin, a membrane protein, plays an important role in retrograde axonal transport
Authors: Liu Jia-Jia , Ding Jianqing , Wu Chengbiao , Bhagavatula Prasanthi , Cui Bianxiao , Chu Steve , Mobley William C. , Yang Yanmin
Published: February 2007

Retrograde axonal transport plays an important role in the maintenance of neuronal functions, but the mechanism is poorly defined partly because the constituents of the retrograde transport system and their interactions have yet to be elucidated. Of special interest is how dynein/dynactin motor proteins interact with membrane cargoes. Here, we report that an endosomal vesicle protein, termed retrolinkin, functions as a receptor tethering vesicles to dynein/dynactin through BPAG1n4. Retrolinkin, a membrane protein highly enriched in neuronal endosomes, binds directly to BPAG1n4. Deletion of retrolinkin membrane-association domains disrupts retrograde vesicular transport, recapitulating the BPAG1 null phenotype. We propose that retrolinkin acts with BPAG1n4 to specifically regulate retrograde axonal transport. Our work lays the foundation for understanding fundamental issues of axonal transport and provides insights into the molecular mechanisms underlying human neurodegenerative disorders.
Lifelong accumulation of bone in mice lacking
Pten
in osteoblasts
Authors: Liu Ximeng , Bruxvoort Katia J. , Zylstra Cassandra R. , Liu Jiarong , Cichowski Rachel , Faugere Marie-Claude , Bouxsein Mary L. , Wan Chao , Williams Bart O. , Clemens Thomas L.
Published: February 2007

Bone formation is carried out by the osteoblast, a mesenchymal cell whose lifespan and activity are regulated by growth factor signaling networks. Growth factors activate phosphatidylinositol 3-kinase (PI3K), which enhances cell survival and antagonizes apoptosis through activation of Akt/PKB. This process is negatively regulated by the Pten phosphatase, which inhibits the activity of PI3K. In this study, we investigated the effects of Akt activation in bone
in vivo
by conditionally disrupting the
Pten
gene in osteoblasts by using Cre-mediated recombination. Mice deficient in
Pten
in osteoblasts were of normal size but demonstrated a dramatic and progressively increasing bone mineral density throughout life.
In vitro
osteoblasts lacking
Pten
differentiated more rapidly than controls and exhibited greatly reduced apoptosis in association with markedly increased levels of phosphorylated Akt and activation of signaling pathways downstream of activated Akt. These findings support a critical role for this tumor-suppressor gene in regulating osteoblast lifespan and likely explain the skeletal abnormalities in patients carrying germ-line mutations of
PTEN
.
Cocaine-induced brain activation detected by dynamic manganese-enhanced magnetic resonance imaging (MEMRI)
Authors: Lu Hanbing , Xi Zheng-Xiong , Gitajn Leah , Rea William , Yang Yihong , Stein Elliot A.
Published: February 2007

Dynamic manganese-enhanced magnetic resonance imaging (MEMRI) detects neuronal activity based on the passage of Mn
2+
into active neurons. Because this mechanism is independent of any hemodynamic response, it is potentially ideal for pharmacological studies and was applied to investigate the acute CNS effects of cocaine in the rat. Dose-dependent, region-specific MEMRI signals were seen mostly in cortical and subcortical mesocorticolimbic structures. To verify the spatial accuracy and physiological mechanisms of MEMRI, neuronal activation following electrical forepaw stimulation revealed somatotopic signal enhancement in the primary and secondary somatosensory cortices, which was blocked by diltiazem, a Ca
2+
channel antagonist. These data suggest that MEMRI may serve as a tool for investigating the effects of pharmacological agents and opens an application of MRI to study CNS drug effects at a systems level.