Free Masses Research Articles

Acetone variability in the upper troposphere: analysis of CARIBIC observations and LMDz-INCA chemistry-climate model simulations

Abstract. This paper investigates the acetone variability in the upper troposphere (UT) as sampled during the CARIBIC airborne experiment and simulated by the LMDz-INCA global chemistry climate model. The aim is to (1) describe spatial distribution and temporal variability of acetone; (2) propose benchmarks deduced from the observed data set; and (3) investigate the representativeness of the observational data set. According to the model results, South Asia (including part of the Indian Ocean, all of India, China, and the Indochinese peninsula) and Europe (including Mediterranean Sea) are net source regions of acetone, where nearly 25 % of North Hemispheric (NH) primary emissions and nearly 40 % of the NH chemical production of acetone take place. The impact of these net source regions on continental upper tropospheric acetone is studied by analysing CARIBIC observations of 2006 and 2007 when most flight routes stretched between Frankfurt (Germany) and Manila (Philippines), and by focussing over 3 sub-regions where acetone variability is strong: Europe-Mediterranean, Central South China and South China Sea. Important spatial variability was observed over different scales: (1) east-west positive gradient of annually averaged acetone vmr in UT over the Eurasian continent, namely a factor two increase from east to west; (2) ocean/continent contrast with 50 % enhancement over the continents; (3) the acetone volume mixing ration (vmr) may vary in summer by more than 1000 pptv within only 5 latitude-longitude degrees; (4) the standard deviation for measurements acquired during a short flight sequence over a sub-region may reach 40 %. Temporal variability is also important: (1) the acetone volume mixing ratio (vmr) in the UT varies with the season, increasing from winter to summer by a factor 2 to 4; (2) a difference as large as 200 pptv may be observed between successive inbound and outbound flights over the same sub-region due to different flight specifications (trajectory in relation to the plume, time of day). A satisfactory agreement for the abundance of acetone is found between model results and observations, with e.g. only 30 % overestimation of the annual average over Central-South China and the South China Sea (between 450 and 600 pptv), and an underestimation by less than 20 % over Europe-Mediterranean (around 800 pptv). Consequently, annual budget terms could be computed with LMDz-INCA, yielding a global atmospheric burden of 7.2 Tg acetone, a 127 Tg yr−1 global source/sink strength, and a 21-day mean residence time. Moreover the study shows that LMDz-INCA can reproduce the impact of summer convection over China when boundary layer compounds are lifted to cruise altitude of 10–11 km and higher. The consequent enhancement of acetone vmr during summer is reproduced by LMDz-INCA, to reach agreement on an observed maximum of 970 ± 400 pptv (average during each flight sequence over the defined zone ± standard deviation). The summer enhancement of acetone is characterized by a high spatial and temporal heterogeneity, showing the necessity to increase the airborne measurement frequency over Central-South China and the South China Sea in August and September, when the annual maximum is expected (daily average model values reaching potentially 3000 pptv). In contrast, the annual cycle in the UT over Europe-Mediterranean is not reproduced by LMDz-INCA, in particular the observed summer enhancement of acetone to 1400 ± 400 pptv after long-range transport of free tropospheric air masses over North Atlantic Ocean is not reproduced. In view of the agreement on the acetone annual cycle at surface level, this disagreement in UT over Europe indicates misrepresentation of simulated transport of primary acetone or biased spatial distribution of acetone chemical sinks and secondary sources. The sink and source budget in long-range transported free tropospheric air masses may be studied by analysing atmospheric chemical composition observed by CARIBIC in summer flights between North America and Europe.

European source and sink areas of CO<sub>2</sub> retrieved from Lagrangian transport model interpretation of combined O<sub>2</sub> and CO<sub>2</sub> measurements at the high alpine research station Jungfraujoch

Abstract. The University of Bern monitors carbon dioxide (CO2) and oxygen (O2) at the High Altitude Research Station Jungfraujoch since the year 2000 by means of flasks sampling and since 2005 using a continuous in situ measurement system. This study investigates the transport of CO2 and O2 towards Jungfraujoch using backward Lagrangian Particle Dispersion Model (LPDM) simulations and utilizes CO2 and O2 signatures to classify air masses. By investigating the simulated transport patterns associated with distinct CO2 concentrations it is possible to decipher different source and sink areas over Europe. The highest CO2 concentrations, for example, were observed in winter during pollution episodes when air was transported from Northeastern Europe towards the Alps, or during south Foehn events with rapid uplift of polluted air from Northern Italy, as demonstrated in two case studies. To study the importance of air-sea exchange for variations in O2 concentrations at Jungfraujoch the correlation between CO2 and APO (Atmospheric Potential Oxygen) deviations from a seasonally varying background was analyzed. Anomalously high APO concentrations were clearly associated with air masses originating from the Atlantic Ocean, whereas low APO concentrations were found in air masses advected either from the east from the Eurasian continent in summer, or from the Eastern Mediterranean in winter. Those air masses with low APO in summer were also strongly depleted in CO2 suggesting a combination of CO2 uptake by vegetation and O2 uptake by dry summer soils. Other subsets of points in the APO-CO2 scatter plot investigated with respect to air mass origin included CO2 and APO background values and points with regular APO but anomalous CO2 concentrations. Background values were associated with free tropospheric air masses with little contact with the boundary layer during the last few days, while high or low CO2 concentrations reflect the various levels of influence of anthropogenic emissions and the biosphere. The pronounced cycles of CO2 and O2 exchanges with the biosphere and the ocean cause clusters of points and lead to a seasonal pattern.

Aerosol climatology and planetary boundary influence at the Jungfraujoch analyzed by synoptic weather types

Abstract. Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coefficients, aerosol number concentration) and trace gases (CO, NOx, SO2) measured at the Jungfraujoch (JFJ, 3580 m a.s.l.) have been analyzed as a function of different synoptic weather types. The Schüepp synoptic weather type of the Alps (SYNALP) classification from the Alpine Weather Statistics (AWS) was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL) influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO2 and NOx concentrations were used as precursor tracers for new particle formation and growth, respectively. The aerosol optical parameters and number concentration show elevated loadings during advective weather types during the December–March period and for the convective anticyclonic and convective indifferent weather types during the April–September period. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in winter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The fraction of PBL air transported to the JFJ was estimated by the relative increase of the specific humidity and CO.

Temperature dependences of YBa2Cu3Ox and La2 − xSrxCuO4 resistivity interms of the negative-U centers model

The temperature dependence of the normal-phase resistivityρ(T) ofYBa2Cu3Ox (YBCO)and La2 − xSrxCuO4 (LSCO) is analyzed by using the Boltzmann equation for holes in theτ-approximation, in which the dependence of the relaxation time on energy and temperatureτ(ε, T) is due to acoustic phonons. The temperature dependence of the chemical potentialμ(T) and effectivecarrier mass m* ∼ 10–100 free electron masses, obtained by fitting to the temperaturedependence of the Hall coefficient in terms of the negative-U centers model, areused to calculate ρ(T). The results obtained are compared with experimental data. It isshown that they are consistent over a wide range of doping levelsx and coincide inabsolute magnitude, ρ ∼ 10 − 4–10 − 3 Ω cm. In addition, the slope ratio of the dependence of the normal-phaseρ(T) on thesize of the x-ray coherent-scattering region and on the oxygen content is calculated for a set of epitaxialYBa2Cu3Ox films.

Characterizing summertime chemical boundary conditions for airmasses entering the US West Coast

Abstract. The objective of this study is to analyze the pollution inflow into California during summertime and how it impacts surface air quality through combined analysis of a suite of observations and global and regional models. The focus is on the transpacific pollution transport investigated by the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission in June 2008. Additional observations include satellite retrievals of carbon monoxide and ozone by the EOS Aura Tropospheric Emissions Spectrometer (TES), aircraft measurements from the MOZAIC program and ozonesondes. We compare chemical boundary conditions (BC) from the MOZART-4 global model, which are commonly used in regional simulations, with measured concentrations to quantify both the accuracy of the model results and the variability in pollution inflow. Both observations and model reflect a large variability in pollution inflow on temporal and spatial scales, but the global model captures only about half of the observed free tropospheric variability. Model tracer contributions show a large contribution from Asian emissions in the inflow. Recirculation of local US pollution can impact chemical BC, emphasizing the importance of consistency between the global model simulations used for BC and the regional model in terms of emissions, chemistry and transport. Aircraft measurements in the free troposphere over California show similar concentration ranges, variability and source contributions as free tropospheric air masses over ocean, but caution has to be taken that local pollution aloft is not misinterpreted as inflow. A flight route specifically designed to sample boundary conditions during ARCTAS-CARB showed a prevalence of plumes transported from Asia and thus may not be fully representative for average inflow conditions. Sensitivity simulations with a regional model with altered BCs show that the temporal variability in the pollution inflow does impact modeled surface concentrations in California. We suggest that time and space varying chemical boundary conditions from global models provide useful input to regional models, but likely still lead to an underestimate of peak surface concentrations and the variability associated with long-range pollution transport.

Coetzee and Late Style: Exile within the Form

Let us trace a theme, but more than a theme, an enactment, of exile as it has come to inform recent work of J. M. Coetzee. Exile I mean not simply in political sense-the final decision to shake dust of [South Africa] off [his] feet, to seek a place where it is not yet properly shameful to be alive, in Australia (1)--but more intrinsically than that, insofar as it affects substance of his art, and very frame of his writing body. This is exile from one's body about which Paul Rayment thinks in Slow Man: is running down (53-54), unstrung in Homeric language. So it is with characters of Elizabeth Costello and JC, in their respective books, Elizabeth Costello and Diary of a Bad Year persons taking regretful leave of their bodies. This sequence is a literature of leave- taking, a trilogy of novels in flight from homeland, from body, and from very comforts of novelistic form. Novels against novel. This is a kind of aesthetic exile that implies a deliberate self-distancing from necessity of formal finishing, given that what had characterized Coetzee's art up to Nobel ceremony was just this quality of laborious finishedness: spare prose and a spare, thrifty (Coetzee, Doubling 20), chiseled gauntness without any trace of flaccidity or unassimilated matter. Not so with this last trilogy, which suddenly, as with a weary shrug of shoulders, shows all seams and fissures, failures of integration, which would hitherto have been smoothed over in a determinate movement of formal resolution. It is a literature touched by death, and intimately so. Its style is, to be clear, a late style, as Adorno memorably described it apropos of Beethoven: The power of subjectivity in works of art is irascible gesture with which it takes leave of works themselves. It breaks their bonds, not in order to express itself, but in order, expressionless, to cast off appearance of art. Of works themselves it leaves only fragments behind, and communicates itself, like a cipher, only through blank spaces from which it has disengaged itself. Touched by death, hand of master sets free masses of material that he used to form; its tears and fissures, witnesses to finite powerlessness of I confronted with Being, are its final work. (566) We read at start of Elizabeth Costello, after a brief description of eponymous character's attire and appearance: the blue costume, greasy hair, are details, signs of a moderate realism. Supply particulars, allow significations to emerge of themselves. A procedure pioneered by Daniel Defoe (4). That is an irascible gesture. You cannot simply call it metafiction and leave it at that. Characteristic of opening movements of this book, such discourse is more aggressively disenchanting and disappointing than that term allows. There is a scene in restaurant, mainly dialogue, which we will skip (7) we read. It is not a good idea to interrupt narrative too often, since storytelling works by lulling reader or listener into a dreamlike state in which time and space of real world fade away, superseded by time and space of fiction. Breaking into dream draws attention to constructedness of story, and plays havoc with realist illusion. However, unless certain scenes are skipped over we will be here all afternoon. (16) This passage is doing something more interesting than pacing track of postmodern metafiction; after all, as Coetzee has written, Anti-illusionism-displaying tricks you are using instead of hiding them-is a common ploy of postmodernism. But in end there is only so much mileage to be got out of ploy. Anti-illusionism is, I suspect, only a marking of time, a phase of recuperation, in history of novel. The question is, what's next? …

Strong Coupling Series for QCD at Finite Temperature and Density

We discuss the use of strong coupling expansions for Yang-Mills theory and QCD at finite temperature and density. In particular we consider the onset of temperature effects for the free energy and screening masses, derive the hadron resonance gas model from first principles and compute the weakening of the deconfinement transition with chemical potential.

Collision-Geometry-Based Pulsed Guidance Law for Exoatmospheric Interception

I N THE absence of aerodynamic control forces, divert thrusters are used to generate lateral acceleration required by interceptors in exoatmospheric engagements. The thrusters can be fired as pulses of constant lateral acceleration magnitude. The pulse width or duration is determined by the guidance law used. Several guidance laws based on the zero-effort miss (ZEM) have been proposed in the literature for exoatmospheric engagements. A ZEM-based midcourse guidance law for intercepting strategic targets and spacecraft is proposed by Newman [1,2]. Later, Hablani [3] proposed a ZEM-based pulsed guidance law with image processing delays for the endgame phase. Hablani [4] also demonstrated that zero-effort-miss guidance is superior to proportional navigation guidance in the endgame phase of an exoatmospheric interception using divert thrusters. Miss distance analysis of ZEM guidance with respect to various measurement errors is carried out by Hablani and Pearson [5]. Zarchan [6] has derived the ZEM-based pulsed guidance implemented with equally spaced pulses. ZEMcan be calculated from the instantaneous line-ofsight rate, the closing velocity, and the time to go. Lateral distance traveled by the interceptor depends on the width of the divert thruster pulse, which can be evaluated by equating the lateral distance to the ZEM. Because of the assumptions involved, interception cannot be guaranteed by firing a single pulse even for exact ZEM calculations. Subsequent pulses are fired to achieve a satisfactory miss distance. In this Note, an interceptor endgame pulsed guidance law is derived by attempting to attain the collision heading rather than negating ZEM. It is shown that this strategy is more effective than ZEM-based guidance for intercepting targets with higher heading angles off the nominal head-on case. The interceptor and the target are assumed to be constant speed lag free point masses. A planar engagement scenario is considered, assuming that the interceptor can perform uncoupled guidance commands in two perpendicular planes. The proposed guidance law, to determine the pulse width, is derived in steps by 1) obtaining the collision heading based on the collision triangle engagement geometry and parameters, and 2) computing the width of the pulse fired by the divert thruster to attain the collision heading. In the existing pulsed guidance laws, the pulses are fired either at fixed intervals [6] or every time the line-of-sight rate (or zero-effort miss) crosses a predefined threshold value [3]. In the present work, it is shown that firing pulses in quick succession results in minimum pulse widths and hence minimum control effort for interception. For comparative study, the derivation of pulsed guidance [6], based on ZEM steering, is described briefly in Sec. II. The proposed guidance law is derived in Sec. III, followed by some results on pulse firing sequence in Sec. IV. Simulation studies are carried out in Sec. V.

Radiative impact of mixing state of black carbon aerosol in Asian outflow

The radiative impact of the mixing state of black carbon (BC) aerosol is investigated in Asian outflow. The mixing state and size distribution of BC aerosol were measured with a ground‐based single‐particle soot photometer at a remote island (Fukue) in Japan in spring 2007. The mass concentration of BC in Asian continental air masses reached 0.5 μg m−3, with a mass median diameter of 200–220 nm. The median value of the shell/core diameter ratio increased to ∼1.6 in Asian continental and maritime air masses with a core diameter of 200 nm, while in free tropospheric and Japanese air masses it was 1.3–1.4. On the basis of theoretical calculations using the size distribution and mixing state of BC aerosol, scattering and absorption properties of PM1 aerosols were calculated under both dry and ambient conditions, considering the hygroscopic growth of aerosols. It was estimated that internal mixing enhanced the BC absorption by a factor of 1.5–1.6 compared to external mixing. The calculated absorption coefficient was 2–3 times higher in Asian continental air masses than in clean air. Coatings reduced the single‐scattering albedo (SSA) of PM1 aerosol by 0.01–0.02, which indicates the importance of the mixing state of BC aerosol in evaluating its radiative influence. The SSA was sensitive to changes in air mass type, with a value of ∼0.98 in Asian continental air masses and ∼0.95 in Japanese and free tropospheric air masses under ambient conditions.

Mount Kenya Global Atmosphere Watch Station (MKN): Installation and Meteorological Characterization

Abstract The meteorological conditions at the Mount Kenya (station identifier MKN) tropical Global Atmosphere Watch Programme station are described. Like other stations in mountainous terrain, the site experiences thermally induced wind systems that disturb free tropospheric conditions. Therefore, the adequacy of the site for long-term background atmospheric composition measurements needs to be evaluated. Meteorological parameters for the period June 2002–June 2006 were analyzed, focusing on the development of thermally induced wind systems and boundary layer influence. Filters based on the local wind and day–night differences in specific humidity were developed for selection of times representative of undisturbed free tropospheric conditions. In addition, the convective boundary layer depth was evaluated. Throughout the whole year the station is influenced by thermally induced wind systems and the atmospheric boundary layer. The filters distinguished between thermally and synoptically influenced days. Thermally influenced days (86%) dominated. However, maxima in specific humidity were also reached in the afternoon on synoptically influenced days and were attributed to mixing in the convective boundary layer. During nighttime, downslope wind dominated that carries undisturbed free tropospheric air masses. Nevertheless, during 24% of all nights the specific humidity was also elevated, possibly indicating the presence of residual layers. It is recommended that nighttime data only (2100–0400 UTC) be used for analysis of long-term trends of the free tropospheric background while the remaining data can be used to characterize composition and trends of the regional atmospheric boundary layer. Further exclusion of apparent pollution events and residual layer influence should be considered. With these constraints, the Mount Kenya Global Atmosphere Watch site is adequate for the study of trends and budgets of background atmospheric composition.

In situ determination of atmospheric aerosol composition as a function of hygroscopic growth

An in situ measurement setup to determine the chemical composition of aerosols as a function of hygroscopicity is presented. This has been done by connecting a custom‐built Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) and an Aerosol Time‐of‐Flight Mass Spectrometer (ATOFMS), commercially available from TSI (Model 3800). Single particle bipolar mass spectra from aerosols leaving the HTDMA could thus be obtained as a function of the hygroscopic growth factor. For these studies the HTDMA was set at a relative humidity of 82% and particles with a dry diameter of 260 nm were selected. The setup was first laboratory tested, after which field experiments were performed. Two data sets were obtained during wintertime 2007 in Switzerland: the first in the urban Zurich environment and the other at the remote high alpine research station Jungfraujoch (JFJ). In Zurich, several thousand mass spectra were obtained in less than 2 days of sampling due to a high aerosol loading. At the JFJ, due to low particle concentrations in free tropospheric air masses, a longer sampling period was required. Both in Zurich and at the JFJ, two different growth factor modes were observed. Results from these two locations show that most aerosol particles were a mixture of several compounds. A large contribution of organics and combustion species was found in the less hygroscopic growth mode for both locations. Noncombustion refractory material (e.g., metals, mineral dust, and fly ash) was also highly enhanced in the nonhygroscopic particles. Sulfate, normally considered highly soluble, was found to be a constituent in almost all particles independent of their hygroscopic growth factor.

From Moon-fall to motions under inverse square laws

The motion of two bodies, along a straight line, under the inverse square law of gravity is considered in detail, progressing from simpler cases to more complex ones: (a) one body fixed and one free, (b) both bodies free and identical mass, (c) both bodies free and different masses and (d) the inclusion of electrostatic forces for both bodies free and different masses. The equations of motion (EOM) are derived starting from Newton's second law or from conservation of energy. They are then reduced to dimensionless EOM using appropriate scales for time and distance. Solutions of the dimensionless EOM as well as the original EOM are given. The time interval for the bodies to fall is expressed as a function of the distance fallen. Formulae for the inverse were obtained. The coalescence times for the different cases are (a) where L is the initial separation of the two bodies and m1 is the mass of the fixed body, (b) and (c) where mT is the total mass of the two bodies and (d) where and is a measure of the ratio of the electrostatic force to gravity. The last formula may also be used when with the interpretation that there is no collision if t is infinity or imaginary. We also discuss this motion along the straight line as a special case of the general elliptic motion of two bodies. I believe that this paper will be useful to university tutors as well as undergraduate and even graduate students who prefer to consider the special case before the general case, and their relationship.

Collective pinning model of the mixed state inYBa2Cu3O7−δ: Critical currents and flux creep

Magnetic hysteresis and flux creep measurements in single crystal samples of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (YBCO) are presented for a wide range of $B$,$T$ phase space. Some of these samples can be described as weakly or collectively pinned. For these, over a large portion of this phase space, the flux creep can be described in terms of thermally activated single-fluxoid motion. A simple model based on maximizing the pinning energy of a fluxoid segment provides a good, semiquantitative picture of the low-temperature data, where the experimentally measured critical current density $j$ is proportional to $1∕T$ and the activation barrier height is proportional to ${j}^{\ensuremath{-}\ensuremath{\mu}}$, where $\ensuremath{\mu}=1$. In this model individual fluxoids are pinned by stochastic fluctuations in defect concentration, and are driven over the pinning barriers by critical currents and thermal activation. Incorporating flux lattice elasticity into this simple model leads to new predictions for the low-temperature data and allows the simple model to be extended to higher temperature. There are two distinct effects, both of which can be put in the form of effective current densities. One effective current density ${j}_{s}$ arises from direct fluxoid-fluxoid repulsion, and the second effective current density ${j}_{r}$ arises from fluxoid relaxation. In YBCO at $7\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $2\phantom{\rule{0.3em}{0ex}}\mathrm{T}$, where the measured critical current density is $j=8.9\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{m}}^{2}$, we find ${j}_{s}=0.57\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{m}}^{2}\phantom{\rule{0.3em}{0ex}}(6%)$ and ${j}_{r}=\ensuremath{-}2.1\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{m}}^{2}$ $(\ensuremath{-}20%)$. We present a discussion of their origin that leads to plausible temperature and field dependences. The model accounts for the rapid drop of $j(T)$ with increasing temperature, the peak effect in $j(B)$ at high temperature, and the temperature and field dependence of the ``critical exponent'' $\ensuremath{\mu}$. Thermal fluxoid vibrations play an important role in the pinning, and we find effects consistent with calculations in the literature. The model postulates that fluxoid motion takes place by hopping in segments on a characteristic length scale ${l}_{\mathrm{model}}$. In the model we find ${l}_{\mathrm{model}}=104\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ at $7\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $2\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. A completely independent measurement from the creep-derived four-volume $VX$ yields a length ${l}_{VX}=102\ifmmode\pm\else\textpm\fi{}5\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ at the same temperature and field. Excellent agreement between the two independently determined lengths persists over a wide range of temperatures. A failure of these two lengths to agree marks the boundary for single-fluxoid hopping, and we present a diagram of the pinning regimes in $B$,$T$ phase space. From the measured prefactor of thermally activated creep at $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ we infer a value for the attempt frequency ${f}_{a}=8.5\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. This value is in reasonable agreement with a published theoretical calculation of the relaxation frequency for overdamped fluxoids in an Abrikosov lattice. Finally, based on these data we estimate the mass per unit length of a YBCO fluxoid segment, and compare our result with Suhl's theory to obtain a quasiparticle effective mass of 30 free electron masses.

Impact of ice supersaturated regions and thin cirrus on radiation in the midlatitudes

In this study we investigate the radiative impact of ice supersaturated regions (ISSRs, i.e., cloud free air masses in the upper troposphere that are supersaturated with respect to ice) and thin cirrus. For this purpose we use corrected radiosonde data obtained from routine measurements over the meteorological observatory in Lindenberg, Germany. The radiative effect of the measured ice supersaturation is determined. By constructing an idealized profile from the measurement data the radiative properties of ISSRs and thin cirrus containing ice supersaturation were studied. The impact of ISSRs on the surface forcing is negligible but locally, within the vertical profile, changes in the heating rates up to 1 K d−1 for typical values of 130% relative humidity with respect to ice compared to the saturated profiles are found. This is also important for the local dynamics within the supersaturated layers. The outgoing longwave radiation due to the enhanced water vapor content inside ISSRs decreases up to 0.8 W m−2. The radiative impact of thin cirrus is much stronger. Thin cirrus influence the surface budget, the top of the atmosphere radiation and the vertical profile of the heating rates. Changes in the outgoing longwave radiation and in the reflected shortwave flux at top of the atmosphere up to 64 W m−2 and 79 W m−2, respectively, are possible. Changes in the surface flux (downward) up to 89 W m−2 are found. The maximal heating rate differences between thin cirrus and ISSR amount to 15 K d−1. The radiative impact of thin cirrus clouds depends strongly on cloud ice content and the size of the ice crystals. Additionally, the radiative impact of cirrus formed by parameterizations not allowing ice supersaturations in large‐scale models is estimated. The errors due to artificially formed cirrus are quite large; differences up to 3 K d−1 in the vertical heating profiles and up to 38 and 40 W m−2 in the outgoing longwave radiation and the surface flux, respectively, are found. Thus we recommend using physically based parameterizations in GCMs which allow ice supersaturation.

Hypernuclear Magnetic Moments and Λ–N Interactionin 17ΛO

Hypernuclear magnetic moment andΛ–N interaction in 17ΛO has been studied withinrelativistic mean field theory. Without core polarization, therelativistic results are found to fit the Schmidt value well and notbe sensitive to Λ–N interaction. The relativistic magneticmoment is enhanced with nearly equal contributions of therelativistic and free masses. When Λ hyperon occupies the l = 0or l = 1 orbit, the effect of Λ–N interaction on themagnetic moment of valence proton is different.

In Vitro Validation of Right Ventricular Volume and Mass Measurement by Real‐Time Three‐Dimensional Echocardiography

To evaluate initially the feasibility and accuracy of real-time three-dimensional echocardiography (RT-3DE) for quantifying right ventricular (RV) volume and wall mass in an in vitro experimental study. In ten excised porcine hearts, measurements of RV volume and free wall mass with RT-3DE were outlined and calculated by 2-, 4-, 8- and 16-plane methods with Tom Tec 4D Cardio-View RT 1.0. The results were compared with those of 2D length method and 2D biplane Simpson method. The values of RV silicone latex cast and free wall mass measured by water displacement were served as reference values. RV shapes of excised porcine hearts with RT-3DE were similar to those of the actual anatomic RVs and RV silicone latex casts. From the findings of analysis of variance and Student-Newman-Keuls test, there was no significant difference between measurements of RV volume with RT-3DE 16-plane (mean 64.05 ml), 8-plane (61.83 ml) and the reference values of RV silicone latex casts (62.94 ml). No significant difference was found between measurements of RV free wall mass with 16-plane (72.81 g), 8-plane (71.05 g) and the reference values of RV free wall masses (76.21 g). However, there was significant difference between measurements of RV volume and free wall mass with 2-plane, 2D biplane Simpson method and the reference values. Furthermore, the measurements of RV volume and free wall mass with 16-plane and 8-plane were better correlated with the reference values than those with 4-plane and 2D length method. RT-3DE will be a valuable technique for quantifying irregular crescentic RV volume and wall mass.

Low-Frequency Gravitational Wave Searches Using Spacecraft Doppler Tracking.

This paper discusses spacecraft Doppler tracking, the current-generation detector technology used in the low-frequency (∼millihertz) gravitational wave band. In the Doppler method the earth and a distant spacecraft act as free test masses with a ground-based precision Doppler tracking system continuously monitoring the earth-spacecraft relative dimensionless velocity 2Δv/c = Δν/ν0, where Δν is the Doppler shift and ν0 is the radio link carrier frequency. A gravitational wave having strain amplitude h incident on the earth-spacecraft system causes perturbations of order h in the time series of Δν/ν0. Unlike other detectors, the ∼ 1–10 AU earth-spacecraft separation makes the detector large compared with millihertz-band gravitational wavelengths, and thus times-of-flight of signals and radio waves through the apparatus are important. A burst signal, for example, is time-resolved into a characteristic signature: three discrete events in the Doppler time series. I discuss here the principles of operation of this detector (emphasizing transfer functions of gravitational wave signals and the principal noises to the Doppler time series), some data analysis techniques, experiments to date, and illustrations of sensitivity and current detector performance. I conclude with a discussion of how gravitational wave sensitivity can be improved in the low-frequency band.

Effects of the biliopancreatic diversion on energy balance in the rat

This study was carried out to determine the effects of the biliopancreatic diversion (BPD), a bariatric surgery applied to the treatment of morbidly obese humans, on energy balance in rats. BPD was performed on a group of male Wistar rats. Body weight and food intake were measured daily throughout the study. Feces were also collected to assess energy losses and the determination of digestible energy. Energy expenditure and body composition were also determined for the 50-day length of the protocol. On the day of killing, the brain, the entire intestinal tract and white and brown adipose tissues were collected and weighed. Expression of neuropeptide Y (NPY) and agouti-related protein (AgRP) in the ARC nucleus were assessed by in situ hybridization. Marked changes in the regulation of energy balance were observed in the BPD-operated rats. A decrease in digestible energy and food intake coupled with an increase in the fecal energy density and protein fecal energy led to an important weight loss in the BPD-operated rats. This weight loss was observed in the loss of fat mass (specifically the white epididymal, inguinal, retroperitoneal and brown adipose tissues). The rats modified their food intake pattern to be able to potentially eat more during the entire day. An increase in the surfaces of all intestinal structures (muscular and mucosal layers) was observed in the BPD-operated rats. The NPY and AgRP expression in the brain were both shown to be greater in the BPD-operated rats than in the control animals. At the beginning of the study, the surgery led to an energy expenditure decrease, which, however, did not persist throughout the study despite the fact that BPD-operated rats exhibited persistent lower fat free masses. BPD led to a noticeable reduction in weight and fat gains in rats, which was in large part owing to a decrease in digestible energy intake led to by the gastrectomy, the intestinal malabsorption inherent to the surgery and to potentially a thermogenesis stimulation that occurred in the second end of the study. The reduction in energy gain occurs despite adaptations to thwart the intestinal malabsorption and the hunger signals from the central nervous system.

Bifurcation analysis of an automatic dynamic balancing mechanism for eccentric rotors

We present a nonlinear bifurcation analysis of the dynamics of an automatic dynamic balancing mechanism for rotating machines. The principle of operation is to deploy two or more masses that are free to travel around a race at a fixed distance from the hub and, subsequently, balance any eccentricity in the rotor. Mathematically, we start from a Lagrangian description of the system. It is then shown how under isotropic conditions a change of coordinates into a rotating frame turns the problem into a regular autonomous dynamical system, amenable to a full nonlinear bifurcation analysis. Using numerical continuation techniques, curves are traced of steady states, limit cycles and their bifurcations as parameters are varied. These results are augmented by simulations of the system trajectories in phase space. Taking the case of a balancer with two free masses, broad trends are revealed on the existence of a stable, dynamically balanced steady-state solution for specific rotation speeds and eccentricities. However, the analysis also reveals other potentially attracting states—non-trivial steady states, limit cycles, and chaotic motion—which are not in balance. The transient effects which lead to these competing states, which in some cases coexist, are investigated.

Exciton spectra, valence band splitting, and energy band structure of CuGa XIn 1−XS 2 and CuGa XIn 1−XSe 2 crystals

Exciton spectra are studied in CuGa X In 1− X S 2 solid solutions by means of photoreflectivity and wavelength modulation spectroscopy at liquid nitrogen temperature. The exciton parameters, dielectric constants, and free carrier effective masses are deduced from experimental spectra by calculations in the framework of a model taking into account the spatial dispersion and the presence of a dead-layer. The crystal field and spin orbit valence band splitting is calculated as a function of X taking into account the energy position of excitonic lines. The energy band structure of CuGa X In 1− X S 2 and CuGa X In 1− X Se 2 compounds is derived from optical spectra at photon energies higher than the fundamental band gap. The energies of optical transitions are tabulated for X values from 0 to 1.