bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery of steady periodic wave profiles from pressure measurements at the bed
Authors: Clamond D. , Constantin A.
Published: January 2013

We derive an equation relating the pressure at the flat bed and the profile of an irrotational steady water wave, valid for all classical solutions of the governing equations for water waves. This permits the recovery of the surface wave from pressure measurements at the bed. Although we focus on periodic waves, the extension to solitary waves is straightforward. We illustrate the usefulness of the equation beyond the realm of linear theory by investigating the regime of shallow-water waves of small amplitude and by presenting a numerical example.
Available potential energy density for Boussinesq fluid flow
Authors: Winters Kraig B. , Barkan Roy
Published: January 2013

An exact expression ${\mathscr{E}}_{a} $ for available potential energy density in Boussinesq fluid flows (Roullet & Klein, J. Fluid Mech., vol. 624, 2009, pp. 45–55; Holliday & McIntyre, J. Fluid Mech., vol. 107, 1981, pp. 221–225) is shown explicitly to integrate to the available potential energy ${E}_{a} $ of Winters et al. (J. Fluid Mech., vol. 289, 1995, pp. 115–128). ${\mathscr{E}}_{a} $ is a positive definite function of position and time consisting of two terms. The first, which is simply the indefinitely signed integrand in the Winters et al. definition of ${E}_{a} $, quantifies the expenditure or release of potential energy in the relocation of individual fluid parcels to their equilibrium height. When integrated over all parcels, this term yields the total available potential energy ${E}_{a} $. The second term describes the energetic consequences of the compensatory displacements necessary under the Boussinesq approximation to conserve vertical volume flux with each parcel relocation. On a pointwise basis, this term adds to the first in such a way that a positive definite contribution to ${E}_{a} $ is guaranteed. Globally, however, the second term vanishes when integrated over all fluid parcels and therefore contributes nothing to ${E}_{a} $. In effect, it filters the components of the first term that cancel upon integration, isolating the positive definite residuals. ${\mathscr{E}}_{a} $ can be used to construct spatial maps of local contributions to ${E}_{a} $ for direct numerical simulations of density stratified flows. Because ${\mathscr{E}}_{a} $ integrates to ${E}_{a} $, these maps are explicitly connected to known, exact, temporal evolution equations for kinetic, available and background potential energies.
Energy harvesting efficiency of piezoelectric flags in axial flows
Authors: Michelin Sébastien , Doaré Olivier
Published: January 2013

Self-sustained oscillations resulting from fluid–solid instabilities, such as the flutter of a flexible flag in axial flow, can be used to harvest energy if one is able to convert the solid energy into electricity. Here, this is achieved using piezoelectric patches attached to the surface of the flag, which convert the solid deformation into an electric current powering purely resistive output circuits. Nonlinear numerical simulations in the slender-body limit, based on an explicit description of the coupling between the fluid–solid and electric systems, are used to determine the harvesting efficiency of the system, namely the fraction of the flow kinetic energy flux effectively used to power the output circuit, and its evolution with the system’s parameters. The role of the tuning between the characteristic frequencies of the fluid–solid and electric systems is emphasized, as well as the critical impact of the piezoelectric coupling intensity. High fluid loading, classically associated with destabilization by damping, leads to greater energy harvesting, but with a weaker robustness to flow velocity fluctuations due to the sensitivity of the flapping mode selection. This suggests that a control of this mode selection by a careful design of the output circuit could provide some opportunities to improve the efficiency and robustness of the energy harvesting process.
Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions
Authors: van Haren Hans
Published: January 2013

In the ocean, sloping bottom topography is important for the generation and dissipation of internal waves. Here, the transition of such waves to turbulence is demonstrated using an accurate bottom-pressure sensor that was moored with an acoustic Doppler current profiler and high-resolution thermistor string on the sloping side of the ocean guyot ‘Great Meteor Seamount’ (water depth 549 m). The site is dominated by the passage of strong frontal bores, moving upslope once or twice every tidal period, with a trail of high-frequency internal waves. The bore amplitude and precise timing of bore passage vary every tide. A bore induces mainly non-hydrostatic pressure, while the trailing waves induce mainly internal hydrostatic pressure. These separate (internal wave) pressure terms are independently estimated using current and temperature data, respectively. In the bottom-pressure time series, the passage of a bore is barely visible, but the trailing high-frequency internal waves are. A bore is obscured by higher-frequency pressure variations up to ${\sim} 4{\times} 1{0}^{3} ~\mathrm{cpd} \approx 80N$ (cpd, cycles per day; $N$, the large-scale buoyancy frequency). These motions dominate the turbulent state of internal tides above a sloping bottom. In contrast with previous bottom-pressure observations in other areas, infra-gravity surface waves contribute little to these pressure variations in the same frequency range. Here, such waves do not incur observed pressure. This is verified in a consistency test for large-Reynolds-number turbulence using high-resolution temperature data. The high-frequency quasi-turbulent internal motions are visible in detailed temperature and acoustic echo images, revealing a nearly permanently wave-turbulent tide going up and down the bottom slope. Over the entire observational period, the spectral slope and variance of bottom pressure are equivalent to internal hydrostatic pressure due to internal waves in the lower 100 m above the bottom, by non-hydrostatic pressure due to high-frequency internal waves and large-scale overturning. The observations suggest a transition between large-scale internal waves, small-scale internal tidal waves residing on thin (${{\sim} }1~\mathrm{m} $) stratified layers and turbulence.
Maximum power from a turbine farm in shallow water
Authors: Garrett Chris , Cummins Patrick
Published: January 2013

The maximum power that can be obtained from a confined array of turbines in steady or tidal flows is considered using the two-dimensional shallow-water equations and representing the turbine farm by a uniform local increase in friction within a circle. Analytical results supported by dimensional reasoning and numerical solutions show that the maximum power depends on the dominant term in the momentum equation for flows perturbed on the scale of the farm. If friction dominates in the basic flow, the maximum power is a fraction (half for linear friction and 0.75 for quadratic friction) of the dissipation within the circle in the undisturbed state; if the advective terms dominate, the maximum power is a fraction of the undisturbed kinetic energy flux into the front of the turbine farm; if the acceleration dominates, the maximum power is similar to that for the linear frictional case, but with the friction coefficient replaced by twice the tidal frequency.
Use of narrow-band imaging in detection of nasopharyngeal carcinoma
Authors: Thong J F , Loke D , Karumathil Sivasankarannair R , Mok P
Published: January 2013

Aim:

To compare narrow-band images of nasopharyngeal carcinoma with those of normal adenoidal tissue.

Method:

Patients with a nasopharyngeal mass were evaluated using both conventional white light and narrow-band light. Biopsies were performed and Epstein–Barr viral serology was tested for all patients.

Results:

Thirty consecutive patients were recruited. Twenty-one patients had normal adenoidal tissue and seven had nasopharyngeal carcinoma. One patient with papillary adenocarcinoma was excluded. The features of narrow-band imaging in normal adenoidal tissue were: (1) a regularly arranged follicular pattern, and (2) each ‘follicle’ comprising a pale centre with surrounding dark periphery. The features of narrow-band imaging in nasopharyngeal carcinoma were: (1) absence of surface patterns (n = 7), and/or (2) ‘reverse’, haphazard follicular pattern comprising a dark brown centre and pale periphery (n = 3).

Conclusion:

Narrow-band imaging of the surface of adenoidal tissue and nasopharyngeal carcinoma appears to identify distinct, characteristic features as described. Narrow-band imaging may be a useful adjunct in differentiating normal adenoidal tissue from malignancy. Further studies are needed to evaluate its diagnostic accuracy.
Parasitic infections in mixed system-based heliciculture farms: dynamics and key epidemiological factors
Authors: SEGADE P. , GARCÍA-ESTÉVEZ J. , ARIAS C. , IGLESIAS R.
Published: January 2013

Heliciculture is an excellent alternative to obtain edible snails but its viability is seriously threatened by pathogens. A parasitological survey was conducted in 3 mixed system-based heliciculture farms in Galicia (NW Spain), with the species Tetrahymena rostrata, Tetrahymena limacis, Tetratrichomonas limacis, Cryptobia helicogenae, Brachylaima aspersae (metacercariae and sporocysts), Alloionema appendiculatum, Nemhelix bakeri, and Riccardoella limacum being commonly found infecting Helix aspersa aspersa (petit-gris) snails. With the exception of C. helicogenae, N. bakeri, and B. aspersae sporocysts, all species were also detected in Helix aspersa maxima (gros-gris) snails, although generally with lower parameters. Most monoxenous infections, and consequently multiple parasitism, exhibited a rising trend during the first 2 months of intensive mating, with tendencies being slowed down or even reversed during the third month as a result of accumulated mortality and a sampling-derived reduction in host density. No parasites were vertically transmitted and infections were initially acquired from invading gastropod and micromammal reservoirs during fattening. Finally, artificial hibernation reduced significantly the prevalence of most species. These results confirm the importance of parasites in heliciculture and emphasize the need to prevent the entry of wild reservoirs into the farms and to rapidly remove the carcasses of dead snails from the reproduction units and fattening pens.
Gene expression analysis of ABC transporters in a resistant Cooperia oncophora isolate following in vivo and in vitro exposure to macrocyclic lactones
Authors: DE GRAEF J. , DEMELER J. , SKUCE P. , MITREVA M. , VON SAMSON-HIMMELSTJERNA G. , VERCRUYSSE J. , CLAEREBOUT E. , GELDHOF P.
Published: January 2013

Members of the ATP-binding cassette (ABC) transporter family (P-glycoproteins, Half-transporters and Multidrug Resistant Proteins) potentially play a role in the development of anthelmintic resistance. The aim of this study was to investigate the possible involvement of ABC transporters in anthelmintic resistance in the bovine parasite, Cooperia oncophora. Partial sequences of 15 members of the ABC transporter protein family were identified, by mining a transcriptome dataset combined with a degenerate PCR approach. Reverse transcriptase PCR showed that most of the ABC transporters identified were constitutively transcribed throughout the life cycle of C. oncophora. Constitutive differences in gene transcript levels between a susceptible and resistant isolate were only observed for Con-haf-9 and Con-mrp-1 in eggs of the resistant isolate, while no differences were observed in L3 or the adult life stage. Analysis of resistant adult worms, collected from calves 14 days after treatment with either ivermectin or moxidectin, showed a significant 3- to 5-fold increase in the transcript levels of Con-pgp-11 compared to non-exposed worms. Interestingly, a 4-fold transcriptional up-regulation of Con-pgp-11 was also observed in L3 of the resistant isolate, after in vitro exposure to different concentrations of ivermectin, whereas this effect was not observed in exposed L3 of the susceptible isolate. The results suggest that the worms of this particular resistant isolate have acquired the ability to up-regulate Con-pgp-11 upon exposure to macrocyclic lactones. Further work is needed to understand the genetic basis underpinning this process and the functional role of PGP-11.
Alcohol consumption in men is influenced by qualitatively different genetic factors in adolescence and adulthood
Authors: Edwards A. C. , Kendler K. S.
Published: January 2013

Background

Alcohol consumption is influenced by genetic factors. Previous studies have examined the heritability of alcohol consumption, or related phenotypes, from adolescence into adulthood, frequently finding that total heritability changes over time. However, it remains unclear whether the same genes underlie liability to alcohol consumption across development versus whether novel risk genes become important over time.

Method

A population-based study of adult male twins (n=1790) born in Virginia, USA, retrospectively reported on their average monthly alcohol consumption from early adolescence through adulthood. We used twin modeling methods to explore genetic and environmental influences on alcohol consumption over time.

Results

One latent genetic factor accounted for the majority of the heritability in alcohol consumption during mid- to late adolescence, but its influence declined thereafter; from young adulthood forward, heritability was largely attributable to a second genetic factor. The total heritability of alcohol consumption increased from 0 at ages 12–14 years to 0.40 by ages 18–21 years. Shared environmental factors declined in influence over time.

Conclusions

The heritability of alcohol consumption over time is dynamic both quantitatively and qualitatively. These results have important implications for gene identification endeavors. Furthermore, these findings could inform efforts to elucidate developmentally dynamic behaviors, such as antisocial behavior.
Postsecularist discourse in an ‘age of transition’
Authors: CAMILLERI JOSEPH A.
Published: January 2013

The last twenty years have seen the emergence of an intriguing postsecular discourse which seeks to remedy the limitations of the secular interpretation of politics. The resurgence of religion in the public sphere, the vociferous articulation of fundamentalist worldviews, and the intensification of conflict within and between religious traditions as well as between religious and secularist dispositions are evidence enough of the need to rethink standard secularist formulations. However, this article argues that postsecularity as a concept raises as many questions as it answers. While it rightly draws our attention to the profound discontinuities of our age, post-secularist thought is too preoccupied with certain specificities of contemporary Western discourse and practice to be able to make sense of the wider challenge-response dynamic that is integral to the current period of transition. This article examines the lacunae of post-secularity and avenues for further development of its insights by reference to four closely interlinked features of a rapidly transforming world order: (a) the transnational character of much religious discourse and practice; (b) the decline of the West and the corresponding shift in the economic and geopolitical centre of gravity; (c) the complex relationship between the resurgence of religion and the wider phenomenon of identity politics; and (d) the emerging dialectic between conflictual and dialogical approaches to cultural and geopolitical pluralism.
Islam and the postsecular
Authors: PASHA MUSTAPHA KAMAL
Published: January 2013

The language of the ‘postsecular’ acknowledges the enduring presence of faith in politics, repudiating secularisation theses claiming diminution or privatisation of religion in social and political life. In cognitive and experiential worlds, those presumably unfettered by these conceptions (for example, the Islamic Cultural Zones or ICZs), the postsecular presents a different order of challenge and possibility. The term ICZs refers to Muslim majority areas informed by transnational subjectivities loosely connecting varied Islamic societies around symbolic commonality, memory, and historical experience. The term stresses the plurality of Islamic cultural experience, albeit distinguished by recognisable semiotic markers, without essentialising Islamic identity. This article questions the hegemonic view pervasive in both secular and postsecular theorising of the fiction of immutability of faith in the ICZs and recognises its rupture and displacement under conditions of late modernity. The ontological dislocation in the character of religion itself under conditions of late modernity opens up the possibility to account for the assumed resistance of Islam to secular modernity, but also to explain Islam's imbrications in politics read under the sign of Political Islam. Paradoxically, under the condition of late modernity, a more homogenised Islam appears to crystallise in the ICZs at odds with an ‘open’ Islam.
Postsecular resistance, the body, and the 2011 Egyptian Revolution
Authors: MAVELLI LUCA
Published: January 2013

At the heart of the notion of the postsecular is an implied and largely under-theorised idea of resistance against the pathologies of modern secular formations. This is most notably exemplified by Jürgen Habermas's highly influential approach which argues that these pathologies can be resisted through a cooperative cognitive effort of secular and religious consciousnesses. This article contends that this understanding overlooks moreembodiedforms of resistance to the effect that it curtails our capacity to conceptualise postsecular resistance in international relations. Following a contextualisation of Habermas's approach in the broader Kantian tradition to which it belongs, the article develops a contending Foucauldian reading of the body as a locus of resistance and uses this framework to analyse some of the events leading to the 2011 Egyptian revolution. The focus is on the publication of images and videos of police abuses by Egyptian bloggers and independent media as a practice of resistance to the widespread and systematic use of torture. The emotional response to these images, it will be argued, contributed to unite Egyptians despite longstanding fractures, most notably that between secularists and Islamists, thus turning the body from an ‘inscribed surface of events’ into a postsecular locus of resistance. The article concludes by highlighting the main implications of this analysis for future research agendas on the postsecular in international relations.
Distribution of tree species along a gallery forest–savanna gradient: patterns, overlaps and ecological thresholds
Authors: Azihou Akomian Fortuné , Kakaï Romain Glèlè , Bellefontaine Ronald , Sinsin Brice
Published: January 2013

Savannas intermingled with gallery forests are dynamic habitats typical in Africa. This study aims to determine if differences in species traits lead to non-overlapping distribution of gallery-forest and savanna species and abrupt transition between gallery forest and savanna. Tree species densities were measured in 375 plots of 1500 m2 covering a total sample area of 56.25 ha along forty 3-km transects located at right angles to a riverbed with gallery forest into surrounding savanna. Location, vegetation type, soil physical properties, erosion and fire occurrence were recorded as site factors. Data analysis included the quantification of co-occurrence patterns, threshold indicator taxa analysis and fuzzy set ordination. The gallery forest–savanna gradient predicted floristic composition of plots with a correlation of 0.595 but its accuracy was locally modified by the occurrence of fire and the physical properties of soil that covered more than 30% of the range of residuals. The distribution of gallery-forest and savanna tree species did not overlap. Along the gallery forest–savanna gradient, savanna species gradually increased in density while gallery-forest species showed a community threshold at 120 m from the river beyond the width of gallery forest. The forest species driving this trend should play an important role in the dynamics of gallery forest–savanna boundaries.
Germination patterns and ecological characteristics of Vellozia seeds from high-altitude sites in south-eastern Brazil
Authors: Soares da Mota Letícia A. , Garcia Queila S.
Published: January 2013

The present work aims to determine whether there are patterns of seed and germination characteristics in Vellozia due to the phylogenetic proximity among the species examined and if these characteristics explain their restricted geographical distributions. We evaluated the germination characteristics of freshly collected seeds from 13 species of the genus Vellozia (Velloziaceae) that show different degrees of endemism, collected at various locations in the Espinhaço Mountain Range in Minas Gerais State, south-eastern Brazil. The size and mass of the seeds, as well as the influence of light and temperature on their germination, were measured. Experiments were performed in germination chambers under constant temperatures of 10–40°C (intervals of 5°C), with a 12-h photoperiod, as well as in continuous darkness. All species studied had small seeds with mass varying from 0.06 to 1.21 mg. Most species required light for germination, displaying high germinability in the range of 15–40°C; some species, however, germinated in the absence of light at the highest temperatures (35 and 40°C). The sizes and masses of the seeds showed significant linear correlations, but light sensitivity was not related to these seed characteristics. The responses observed suggest that light requirement for germination, associated with the small sizes of Vellozia spp. seeds, contribute to the formation of persistent seed banks. The observed tolerance of these seeds to a wide range of germination temperatures is consistent with the large daily temperature fluctuations experienced in campos rupestres sites, although these seed characteristics cannot by themselves explain the high degree of endemism or the restricted distributions observed among the species examined.
Adult Ageing and Social Policy: New Risks to Identity
Authors: Biggs Simon , Kimberley Helen
Published: January 2013

This article considers changing perceptions of adult ageing and their interpretation in social policy. Once wider international trends are outlined, Australian policy is used as a case example. It is argued that a mismatch between policy initiatives and personal change is a new social risk associated with demographic and socio-cultural development, having implications for the way in which social ageism and age discrimination should be considered. The article concludes with a consideration of new directions that a critical, life course sensitised approach to social policy might take.
Pregnancy Causes Diminished Myogenic Tone and Outward Hypotrophic Remodeling of the Cerebral Vein of Galen
Authors: van der Wijk Anne-Eva , Schreurs Malou PH , Cipolla Marilyn J
Published: January 2013

Pregnancy increases the risk of several complications associated with the cerebral veins, including thrombosis and hemorrhage. In contrast to the cerebral arteries and arterioles, few studies have focused on the effect of pregnancy on the cerebral venous side. Here, we investigated for the first time the effect of pregnancy on the function and structure of the cerebral vein of Galen in rats. Our major finding was that cerebral veins from late-pregnant (LP, n = 11) rats had larger lumen diameters and thinner walls than veins from nonpregnant (NP, n = 13) rats, indicating that pregnancy caused outward hypotrophic remodeling of the vein of Galen. Moreover, veins from NP animals had a small amount of myogenic tone at 10 mm Hg (3.9 ± 1.0%) that was diminished in veins during pregnancy (0.8 ± 0.3%; P < 0.01). However, endothelium-dependent and -independent vasodilation of the veins was unchanged during pregnancy. Using immunohistochemistry, we show that the vein of Galen receives perivascular innervation, and that serotonergic innervation of cerebral veins is significantly higher in veins from LP animals. Outward hypotrophic remodeling and diminished tone of cerebral veins during pregnancy may contribute to the development of venous pathology through elevated wall tension and wall stress, and possibly by promoting venous blood stasis.
Impairment in Long-Term Memory Formation and Learning-Dependent Synaptic Plasticity in Mice Lacking Glycogen Synthase in the Brain
Authors: Duran Jordi , Saez Isabel , Gruart Agnes , Guinovart Joan J , Delgado-García José M
Published: January 2013

Glycogen is the only carbohydrate reserve of the brain, but its overall contribution to brain functions remains unclear. Although it has traditionally been considered as an emergency energetic reservoir, increasing evidence points to a role of glycogen in the normal activity of the brain. To address this long-standing question, we generated a brain-specific Glycogen Synthase knockout (GYS1Nestin-KO) mouse and studied the functional consequences of the lack of glycogen in the brain under alert behaving conditions. These animals showed a significant deficiency in the acquisition of an associative learning task and in the concomitant activity-dependent changes in hippocampal synaptic strength. Long-term potentiation (LTP) evoked in the hippocampal CA3-CA1 synapse was also decreased in behaving GYS1Nestin-KO mice. These results unequivocally show a key role of brain glycogen in the proper acquisition of new motor and cognitive abilities and in the underlying changes in synaptic strength.
Effect of Ritonavir on 99mTechnetium–Mebrofenin Disposition in Humans: A Semi‐PBPK Modeling and In Vitro Approach to Predict Transporter‐Mediated DDIs
Authors: Pfeifer ND , Goss SL , Swift B , Ghibellini G , Ivanovic M , Heizer WD , Gangarosa LM , Brouwer KLR
Published: January 2013

A semiphysiologically based pharmacokinetic (semi‐PBPK) model was developed to describe a unique blood, liver, and bile clinical data set for the hepatobiliary imaging agent 99mTechnetium–mebrofenin (99mTc–mebrofenin), and to simulate sites/mechanisms of a 99mTc–mebrofenin–ritonavir drug–drug interaction (DDI). The transport inhibitor ritonavir (multiple‐dose: 2 × 300 mg) significantly increased systemic 99mTc–mebrofenin exposure as compared with control (4,464 ± 1,861 vs. 1,970 ± 311 nCi min/ml; mean ± SD), without affecting overall hepatic exposure or biliary recovery. A novel extrahepatic distribution compartment was required to characterize 99mTc–mebrofenin disposition. Ritonavir inhibited 99mTc–mebrofenin accumulation in human sandwich‐cultured hepatocytes (SCH) (half maximal inhibitory concentration (IC50) = 3.46 ± 1.53 µmol/l). Despite ritonavir accumulation in hepatocytes, intracellular binding was extensive (97. 6%), which limited interactions with multidrug resistance protein 2 (MRP2)‐mediated biliary excretion. These in vitro data supported conclusions from modeling/simulation that ritonavir inhibited 99mTc–mebrofenin hepatic uptake, but not biliary excretion, at clinically relevant concentrations. This integrated approach, utilizing modeling, clinical, and in vitro data, emphasizes the importance of hepatic and extrahepatic distribution, assessment of inhibitory potential in relevant in vitro systems, and intracellular unbound concentrations to assess transporter‐mediated hepatic DDIs.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e20; doi:10.1038/psp.2012.21; advance online publication 2 January 2013
Introduction and review of the years 2010–2011
Authors: Albini Angelo
Published: January 2013

After a short introduction on the changes adopted in the format of this series, some representative findings on photochemistry and applications published in 2010–11 are reviewed.
Photoprotection of human skin
Authors: Herzog Bernd
Published: January 2013

UV radiation can cause damage to human skin. The ambient UV radiation which humans are exposed to is largely controlled by the amount of stratospheric ozone, which absorbs the UVC and short-wave UVB radiation of the sun. There has been a certain depletion of the ozone layer due to emission of chlorofluorocarbons in the last century. As these substances have been banned, the ozone layer is already slowly recovering. In the epidermis of human skin melanin can be produced as an own protection system against UV radiation. The amount of this protection depends strongly on skin type. Sunscreens can help to increase the protection against the damaging effects of solar irradiation in the UVB and UVA range. The active ingredients of sunscreens are UV filters, which have to be specifically approved for this application. Quite high concentrations of these filters have to be incorporated into the sunscreen formulations to achieve good protection, and in most cases a cocktail of filters is used, which also allows various designs of the UV protection spectra. The most important quantity for the assessment of a sunscreen is the sun protection factor (SPF), which is measured in vivo on human volunteers. As the same sun protection factor can be obtained with different shapes of the absorbance curve, the protection in the UVA range has to be assessed with another method. Great progress has been achieved in the development of in vitro methodology for the assessment of UVA protection in the last decade. Not all of the available UV filters are photostable, and therefore irradiation steps are included in most of these methods. The performance of sunscreens can be simulated with model calculations. For the calculation the quantitative UV spectra of all UV absorbers must be known as well as the kinetics of a possible photodegradation. In addition, action spectra, irradiance profiles, and the irregularity of the sunscreen film forming on the skin have to be taken into consideration. With that realistic simulations are possible only with the input of the filter amounts to be used. The simulations can help to understand specific properties of sunscreens such as the dependence of the protection at different application amounts or variations of the solar spectrum.
Photo-induced water oxidation: New photocatalytic processes and materials
Authors: Berardi Serena , La Ganga Giuseppina , Puntoriero Fausto , Sartorel Andrea , Campagna Sebastiano , Bonchio Marcella
Published: January 2013

New progress towards artificial photosynthetic methods and solar fuels will depend on the discovery of highly robust multi-electron catalysts and materials enabling light-activated water splitting with high quantum efficiency and low overpotential, thus mimicking the natural process.
Impurity distribution and microstructure of Ga-doped ZnO films grown by molecular beam epitaxy
Authors: Kvit A. V. , Yankovich A. B. , Avrutin V. , Liu H. , Izyumskaya N. , Özgür Ü. , Morkoç H. , Voyles P. M.
Published: January 2013

We report microstructural characterization of heavily Ga-doped ZnO (GZO) thin films on GaN and sapphire by aberration-corrected scanning transmission electron microscopy. Growth under oxygen-rich and metal-rich growth conditions leads to changes in the GZO polarity and different extended defects. For GZO layers on sapphire, the primary extended defects are voids, inversion domain boundaries, and low-angle grain boundaries. Ga doping of ZnO grown under metal-rich conditions causes a switch from pure oxygen polarity to mixed oxygen and zinc polarity in small domains. Electron energy loss spectroscopy and energy dispersive spectroscopy spectrum imaging show that Ga is homogeneous, but other residual impurities tend to accumulate at the GZO surface and at extended defects. GZO grown on GaN on c-plane sapphire has Zn polarity and no voids. There are misfit dislocations at the interfaces between GZO and an undoped ZnO buffer layer and at the buffer/GaN interface. Low-angle grain boundaries are the only threading microstructural defects. The potential effects of different extended defects and impurity distributions on free carrier scattering are discussed.
Threshold gate voltage and subthreshold swing of the ultrathin silicon-on-insulator field effect transistor: Analytical model
Authors: Dobrovolsky V. , Sizov F.
Published: January 2013

Threshold gate voltage vth and subthreshold swing s are both the key characteristics of a field effect transistor (FET) operating in the ON/OFF mode. In this mode, the electron concentration in the transistor channel is low. Therefore, in an ultrathin silicon-on-insulator FET, where the electron energy is quantized, electrons occupy only the lowest quantum subband and become two-dimensional (2D). This electron property allowed to derive analytical expressions for such single/double gate FET characteristics. The developed model relates the vth rise at the Si-film thinning with the increasing of electron energy in the channel by quantization. The limit of swing s is identical to that in bulk FETs, but its origin is different: the gate voltage drop entirely across the source-channel barrier with the electron Boltzmann distribution is the cause of the s limit. By contrast, in the bulk FET, the gate voltage drop across the surface barrier is a reason for this limit. The obtained expressions are also valid above the threshold gate voltage, if electrons remain 2D.
Theoretical photo-thermo-hydrodynamic approach to the laser ablation of metals
Authors: Stafe Mihai
Published: January 2013

Here, we employ theory and experiments to investigate the laser ablation process of a metal (Al) using nanosecond laser-pulses at 532 nm wavelength in atmospheric air. We analyze experimentally the dependence of the ablation rate of Al on laser fluence which is varied over a wide range (from ∼4 to 500 J/cm2) by changing the laser pulses energy. The experimental data indicate that the ablation rate increases approximately linearly to ∼1.5 μm/pulse when increasing the fluence to ∼50 J/cm2, whereas further increase of the laser fluence leads to a much slower, non-linear increase of the ablation rate. By extrapolating towards zero the linear fitting curve, we find the ablation threshold fluence of Al to be ∼1.9 J/cm2. To understand and control the underlying phenomena involved in laser ablation, we propose a robust and efficient theoretical model for reliable yet fast calculation of the ablation rate of metals. We use a one-dimensional photo-thermo-hydrodynamic model that accounts for the material heating, melting, evaporation, melt ejection, and ablation plasma shielding during nanosecond laser irradiation. The model considers that the reflectivity of the target surface, the heat capacity, thermal conductivity, and the mass density of the metallic material depend on the aggregation state. The non-linear heat equation of the model is solved numerically in a multi-step iterative method. The solution of the heat equation gives the time evolution of the temperature within the target, leading further to the evaporation and melt ejection velocities, and to the ablation rate. There is a good agreement between the numerical and the experimental results on the ablation rate for a very wide fluence range, i.e., up to 150 J/cm2 when phase separation occurs in the ablating layer whose average temperature during the laser pulse reaches the Al critical temperature. The validity fluence range of the present model is approximately one order of magnitude wider than in previous theoretical works on nanosecond laser ablation of metals.
On the absolute thermodynamics of water from computer simulations: A comparison of first-principles molecular dynamics, reactive and empirical force fields
Authors: Pascal Tod A. , Schärf Daniel , Jung Yousung , Kühne Thomas D.
Published: January 2013

We present the absolute enthalpy, entropy, heat capacity, and free energy of liquid water at ambient conditions calculated by the two-phase thermodynamic method applied to ab initio, reactive and classical molecular dynamics simulations. We find that the absolute entropy and heat capacity of liquid water from ab initio molecular dynamics (AIMD) is underestimated, but falls within the range of the flexible empirical as well as the reactive force fields. The origin of the low absolute entropy of liquid water from AIMD simulations is due to an underestimation of the translational entropy by 20% and the rotational entropy by 40% compared to the TIP3P classical water model, consistent with previous studies that reports low diffusivity and increased ordering of liquid water from AIMD simulations. Classical MD simulations with rigid water models tend to be in better agreement with experiment (in particular TIP3P yielding the best agreement), although the TIP4P-ice water model, the only empirical force field that reproduces the experimental melting temperature, has the lowest entropy, perhaps expectedly. This reiterates the limitations of existing empirical water models in simultaneously capturing the thermodynamics of solid and liquid phases. We find that the quantum corrections to heat capacity of water can be as large as 60%. Although certain water models are computed to yield good absolute free energies of water compared to experiments, they are often due to the fortuitous enthalpy-entropy cancellation, but not necessarily due to the correct descriptions of enthalpy and entropy separately.
Strong-field induced XUV transmission and multiplet splitting in 4d−16p core-excited Xe studied by femtosecond XUV transient absorption spectroscopy
Authors: Lin Ming-Fu , Pfeiffer Adrian N. , Neumark Daniel M. , Leone Stephen R. , Gessner Oliver
Published: January 2013

Light-induced coupling of core-excited states of Xe atoms is investigated by femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy with photon energies ranging from 50 eV to 72 eV. Coupling of the 4d−1(2D5/2)6p(2P3/2) (65.1 eV) and 4d−1(2D3/2)6p(2P1/2) (67.0 eV) core-excited states to nearby states by a strong infrared laser field leads to a threefold enhancement of XUV transmission. The transmission at 65.1 eV (67.0 eV) changes from 3.2 ± 0.4% (5.9 ± 0.5%) without the coupling laser to 9 ± 2% (22 ± 5%) at the maximum of the laser field. A strong-field induced broad XUV absorption feature between 60 eV and 65 eV is ascribed to splitting of the field-free absorption lines into multiple branches when the Rabi frequencies of the coupling transitions exceed the infrared laser frequency. This picture is supported by a comparison of the strong-field induced absorption spectrum with a numerical integration of the von Neumann equation for a few-level quantum system. The valence hole-alignment of strong-field ionized Xe is revisited, confirming the previously observed reduced alignment compared to theoretical predictions.
Enhanced phonon scattering by mass and strain field fluctuations in Nb substituted FeVSb half-Heusler thermoelectric materials
Authors: Fu Chenguang , Xie Hanhui , Zhu T. J. , Xie Jian , Zhao X. B.
Published: January 2013

The substitution of V by Nb in FeV1−xNbxSb (x = 0, 0.1, 0.2, 0.3, and 0.4) half-Heusler thermoelectric materials was introduced to lower the lattice thermal conductivity by the alloy scattering. A significantly reduced thermal conductivity of ∼5.5 W m−1 K−1 for the FeV0.6Nb0.4Sb was obtained at room temperature, a decrease of ∼55% compared with that of FeVSb. The disorder scattering parameters of mass fluctuation Γm and strain field fluctuation Γs were calculated to explore the dominant factors for the enhanced phonon scattering. The obtained Γm was comparable to the Γs. Therefore, the reduction of thermal conductivity in Nb substituted FeVSb compounds was attributed to both the mass and the strain field fluctuations.
Elastic, dielectric and piezoelectric characterization of single domain PIN-PMN-PT: Mn crystals
Authors: Huo Xiaoqing , Zhang Shujun , Liu Gang , Zhang Rui , Luo Jun , Sahul Raffi , Cao Wenwu , Shrout Thomas R.
Published: January 2013

Mn modified 0.26Pb(In1/2Nb1/2)O3−0.42Pb(Mg1/3Nb2/3)O3−0.32PbTiO3 (PIN-PMN-PT:Mn) single crystals with orthorhombic perovskite crystal structure were polarized along [011] direction, resulting in the single domain state “1O.” The complete set of material constants was determined using the combined resonance and ultrasonic methods. The thickness shear piezoelectric coefficient d15 and electromechanical coupling factor k15 were found to be on the order of 3100 pC/N and 94%, respectively, much higher than longitudinal d33 ∼ 270 pC/N and k33 ∼ 70%. Using the single domain data, the rotated value of d33* along [001] direction was found to be 1230 pC/N, in agreement with the experimentally determined d33 value of 1370 pC/N, conferring extrinsic contributions being about 10%, which was also confirmed using the Rayleigh analysis. In addition, the mechanical quality factors Qm were evaluated for different “1O” vibration modes, where the longitudinal Qm was found to be ∼1200, much higher than the value for “4O” crystals, ∼300.
Magnetic properties of ZnS doped with noble metals (X = Ru, Rh, Pd, and Ag)
Authors: Tan Zhiyun , Xiao Wenzhi , Wang Lingling , Yang Youchang
Published: January 2013

Density functional theory calculations are carried out to study the electronic structures and magnetic properties in zinc-blende structure ZnS doped with nonmagnetic noble metals (X = Ru, Rh, Pd, and Ag). Results show robust magnetic ground states for X-doped ZnS. The total magnetic moments are about 2.0, 3.0, and 2.0 μB per supercell for the Ru-, Rh-, and Pd-doped ZnS, respectively. As the atomic number of X element increases, the local magnetic moment tends toward delocalize and the hybridization between X-4d and S-3p states become stronger. This trend is strongly related to the difference in electronegativity between the substitutional X and the cation in the ZnS host. For Ag-doped ZnS, both non-spin- and spin-polarized calculations yield nearly equal total energy. The substitution of Zn in ZnS parent material by the nonmagnetic 4d transition-metals may lead to half-metallic ferromagnetism which stems from the hybridization between X-4d and S-3p states and could be attributed to a double-exchange mechanism. Curie temperature values are estimated using mean-field approximation.
Electron cyclotron resonance near the axis of a quadrupole linear trap
Authors: Kotelnikov I. A. , Romé M.
Published: January 2013

The quasi-longitudinal propagation of an extraordinary electromagnetic wave in the vicinity of the electron cyclotron resonance layer in an open linear trap with a quadrupole magnetic field is studied analytically, taking into account the inhomogeneity of the magnetic field in a paraxial approximation. The ray trajectories are derived from a simplified dispersion equation, that is, nonetheless able to accurately describe the transition from finite to zero perpendicular refractive index. A criterion for an on-axis resonance point to be an attractor for the ray trajectories is formulated, which generalizes a similar criterion for axisymmetric linear traps derived in a recent paper [D. S. Bagulov and I. A. Kotelnikov, Phys. Plasmas 19, 082502 (2012)].
Improvement and empirical research on chaos control by theory of “chaos + chaos = order”
Authors: Fulai Wang
Published: January 2013

This paper focuses on advancing the understanding of Parrondian effects and their paradoxical behavior in nonlinear dynamical systems. Some examples are given to show that a dynamics combined by more than two discrete chaotic dynamics in deterministic manners can give rise to order when combined. The chaotic maps in our study are more general than those in the current literatures as far as “chaos + chaos = order” is concerned. Some problems left over in the current literatures are solved. It is proved both theoretically and numerically that, given any m chaotic dynamics generated by the one-dimensional real Mandelbrot maps, it is no possible to get a periodic system when all the m chaotic dynamics are alternated in random manner, but for any integer m(m≥2) a dynamics combined in deterministic manner by m Mandelbrot chaotic dynamics can be found to give rise to a periodic dynamics of m periods. Numerical and mathematical analysis prove that the paradoxical phenomenon of “chaos + chaos = order” also exist in the dynamics generated by non-Mandelbrot maps.
Impact of connection delays on noise-induced spatiotemporal patterns in neuronal networks
Authors: Yang X. L. , Senthilkumar D. V. , Kurths J.
Published: January 2013

In the present work, we investigate the nontrivial roles of independent Gaussian noise and time-delayed coupling on the synchronous dynamics and coherence property of Fitz Hugh–Nagumo neurons on small-world networks by numerical simulations. First, it is shown that an intermediate level of noise in the neuronal networks can optimally induce a temporal coherence state when the delay in the coupling is absent. We find that this phenomenon is robust to changes of the coupling strength and the rewiring probability of small-world networks. Then, when appropriately tuned delays with moderate values are included in the coupling, the neurons on the networks can reach higher ordered spatiotemporal patterns which are the most coherent in time and almost synchronized in space. Moreover, the tuned delays are within a range, and the period of the firing activity is delay-dependent which equals nearly to the length of the coupling delay. This result implies that the higher ordered spatiotemporal dynamics induced by intermediate delays could be the result of a locking between the period-1 neuronal spiking activity and the delay. The performance of moderate delays in enhancing the ordered spatiotemporal patterns is also examined to be robust against variations of the network randomness.
An improved thermodynamic perturbation theory for square-well m-point model of the patchy colloids
Authors: Kalyuzhnyi Y. V. , Hlushak S. P. , Cummings P. T.
Published: January 2013

We propose an improved version of Wertheim's first order thermodynamic perturbation theory for the square-well m-point model of patchy colloids. Our version of the theory takes into account changes in the free volume of the system due to bond formation. The new theory is a significant improvement, giving good agreement with Monte Carlo simulations of the model.
Instability, collapse, and oscillation of sheaths caused by secondary electron emission
Authors: Campanell M. D. , Khrabrov A. V. , Kaganovich I. D.
Published: January 2013

The Debye sheath is shown to be unstable under general conditions. For surface materials with sufficient secondary electron emission (SEE) yields, the surface's current-voltage characteristic has an unstable branch when the bulk plasma temperature (Te) exceeds a critical value, or when there are fast electron populations present. The plasma-surface interaction becomes dynamic where the sheath may undergo spontaneous transitions or oscillations. Using particle-in-cell simulations, we analyze sheath instabilities occurring in a high Te plasma slab bounded by walls with SEE. As the plasma evolves, whenever the sheath enters an unstable state, its amplitude rapidly collapses, allowing a large flux of previously trapped electrons to hit the wall. These hot electrons induce more than one secondary on average, causing a net loss of electrons from the wall. The sheath collapse quenches when the surface charge becomes positive because the attractive field inhibits further electrons from escaping. Sheath instabilities influence the current balance, energy loss, cross-B-field transport and even the bulk plasma properties. Implications for discharges including Hall thrusters are discussed. More generally, the results show that common theories that treat emission as a fixed (time-independent) “coefficient” do not capture the full extent of SEE effects.