bluuebunny/crossref_metadata_2025 huggingface dataset:
Local Control of Murine Subglottis Development
Authors: Mankarious Leila A. , Pires Valerie L. , Rudnick Jennifer A.
Published: May 2006

OBJECTIVE

To determine if subglottic development is at least partially under local control and to determine which tissue layer(s) is predominantly responsible.

DESIGN

The suglottises of 12 day‐3 CD1 mice were grown in whole organ culture. The 12 subglottises were divided into 3 individual groups: + + +, − + +, and − − −. Group + + + had all tissue layers of the subglottis intact: luminal epithelium, cricoid cartilage, inner and outer perichondrium. Group ‐ + + had all layers intact with the exception of luminal epithelium. Group − − − had all layers removed (luminal epithelium, inner and outer perichondrium) resulting in cricoid cartilage‐only rings. All rings were grown in basic medium without the use of growth factors or serum for 15 days. Measurements of the rings were taken before and after organ culture growth.

RESULTS

Group +++ was the only group that experienced growth. Only luminal growth was statistically significant although all rings experienced growth in both the luminal and external diameter. Group ‐ + + did not experience any growth. Group — lost structural integrity with collapse of the ring and did not experience growth of any dimension of the cartilage.

CONCLUSIONS

Growth of the subglottis is under local control but may have additional influences from the outside that were not investigated here. Removal of just the epithelium stunts growth of the entire ring, but preferentially the lumen more so than the external diameter. Removal of all tissue layers around the cricoid cartilage results in a structural collapse of the ring, suggesting that the cartilage in this age group is dependent on surrounding tissues for structural integrity.
Histopathologic Parameters as Predictors of Response to Endoscopic Sinus Surgery in Nonallergic Patients with Chronic Rhinosinusitis
Authors: Baudoin Tomislav , Čupić Hrvoje , Geber Goran , Vagić Davor , Grgić Marko , Kalogjera Livije
Published: May 2006

OBJECTIVE

To estimate the predictable value of histopathologic parameters in chronic rhinosinusitis (CRS) for response to endoscopic sinus surgery (ESS).

STUDY DESIGN

Symptomatology was rated in 100 patients prior to as well as 12 and 24 months after surgery. Specimens taken during the procedure were examined and scored for goblet cells, subepithelial thickening, mast cells, and eosinophils. Multiple regression analysis was performed to predict the total score of subjective symptoms before treatment by histopathologic parameters. The correlation between histopathologic parameters and postoperative symptoms was then evaluated.

RESULTS

Goblet cells were the best predictor correlating with 5 symptoms. Subepithelial thickening correlated with 4 symptoms. Mast cell infiltration correlated with 3 symptoms. Eosinophilic infiltration correlated with only one symptom (P < 0.05).

CONCLUSION

Certain histopathologic parameters in CRS are predictive of favorable response to ESS.

SIGNIFICANCE

Pathologic evaluation may help the ENT surgeon to predict the persistence of certain CRS symptoms after ESS, even in patients at low risk for surgical failure.

EBM rating: C‐4
Improvements in Quality of Life in Children After Surgical Therapy for Sinonasal Disease
Authors: Rudnick Emily F. , Mitchell Ron B.
Published: May 2006

OBJECTIVES

To study changes in quality of life in children with chronic sinonasal disease after surgical therapy.

STUDY DESIGN AND SETTING

Prospective, nonrandomized quality of life study of children with sinonasal disease who undergo adenoidectomy or functional endoscopic sinus surgery (FESS) at an academic institution. Caregivers completed a preoperative SN‐5 quality of life survey and a second survey within 6 months after surgery.

RESULTS

Twenty‐two children were enrolled in the study (mean, 6.5 years; range, 1.4 to 15.9). The majority (59%) of children underwent adenoidectomy. The mean total score was 25.8 at initial presentation and 12.0 at follow‐up (P > 0.001). Postoperative scores for all domains were significantly different from preoperative scores. The domains with the greatest change in mean score were nasal obstruction and emotional distress. There were no significant differences in outcome between children who underwent adenoidectomy and those who underwent FESS.

CONCLUSIONS

After either adenoidectomy or FESS, caregivers report a dramatic improvement in the quality of life of children with sinonasal disease.

EBM rating: B‐3b
Modulation of Immune Mediators with MQT‐based Immunotherapy
Authors: Krouse John H. , Krouse Helene J.
Published: May 2006

OBJECTIVE

Assess immune and clinical changes with immunotherapy based on modified quantitative testing (MQT).

BACKGROUND

Immunotherapy promotes immunomodulation that occurs over several years. Quantitative testing offers the advantage of initiating immunotherapy with robust antigen concentrations. This study assessed whether changes in immune mediators and allergy symptoms occur rapidly using quantitative techniques.

METHODS

Sixteen allergic adults were tested using MQT. Subjects had serum drawn for immunoglobulins E and G4 (IgE, IgG4) to 3 antigens, Der p1, Der f1, and Fel d1, and for interleukins IL‐1β, IL‐2, IL‐4, IL‐5, IL‐10, IL‐12, and IL‐13, and IL‐1 receptor antagonist (IL‐1RA). Subjects also completed the Sino‐Nasal Outcome Test‐20 (SNOT‐20), the Allergy Outcome Scale (AOS), and the Rhinosinusitis Disability Index (RSDI). They underwent MQT‐based immunotherapy and completed outcome measures again at 6 and 12 weeks.

RESULTS

Nine subjects completed the study. Analysis demonstrated significant increases in IgG4 levels to all antigens, significant decreases in serum levels of IL‐1β and IL‐5, and significant increases in levels of IL‐1RA. Improvement was also noted in AOS and RSDI subscales.

CONCLUSION

Immunotherapy based on MQT demonstrates significant changes in immunoglobulin and cytokine levels by 12 weeks following initiation. In addition, improvement in symptom and quality‐of‐life measures occurs by 12 weeks. These findings support the rapid onset of clinical effects with MQT‐based treatment of inhalant allergy.

EBM rating: C‐4
Upper respiratory tract involvement of sarcoidosis in the Turkish population
Authors: Yanardağ Halil , Enoz Murat , Papila Irfan , Uygun Sedat , Caner Metin , Karayel Tuncer
Published: May 2006

PRINCIPLES AND METHODS

Upper respiratory tract (URT) involvement is rare in sarcoidosis. In this descriptive study, we retrospectively evaluated the clinical and demographic features of 12 (2.19%) patients with URT involvement out of the 546 sarcoidosis patients with follow‐up visits at our center within the last 40‐year period.

RESULTS

Out of the 546 patients, 12 (2.19%) had upper respiratory tract involvement, 5 (0.91%) had laryngeal involvement, 4 (0.73%) had sinonasal tract involvement, 2 (0.36) patients had salivary gland involvement, and 1 patient had tonsillary involvement. The number of stage 0 subjects among other sarcoidosis patients was significantly lower than that among those with URT involvement.

CONCLUSIONS

URT involvement is rarely diagnosed in patients with systemic sarcoidosis. The most common site for URT involvement among the Turkish population is the larynx, followed by the sinonasal tract.

EBM rating: C‐4
Streaming flows due to g-jitter-induced natural convection
Authors: Farooq A. , Homsy G. M.
Published: May 2006

We investigate streaming in a square cavity where a lateral temperature gradient interacts with a constant gravity field modulated by small harmonic oscillations of order ε. The Boussinesq equations are expanded by regular perturbation in powers of ε, and the O(ε2) equations contain Reynolds-stress-type terms that cause streaming. The resulting hierarchy of equations is solved by finite differences to investigate the O(ε1) and O(ε2) fields and their parametric dependence on the Rayleigh number Ra, Prandtl number Pr, and forcing frequency ω. It has been found that the streaming flow is quite small at small values of Ra, but becomes appreciable at high Ra and starts to influence such flow properties as the strength of the circulation and the overall heat transfer. Under suitable parametric conditions of finite frequency and moderate Pr the periodic forcing motion interacts with the instabilities associated with the O(εo) base flow leading to resonances that become stronger as Ra increases. It is argued that these resonances will have their greatest effect on streaming for Pr ≈ 1. At low frequencies the streaming flow shows marked structural changes as Ra is increased leading to an interesting change in the sign of the O(ε2) contribution to the Nusselt number. Also, as the frequency is changed the O(ε2) Nusselt number again changes sign at approximately the resonant frequency.
The propagation of weak shocks in non-uniform flows
Authors: Kevlahan N. K.-R.
Published: May 2006

A new theory of the propagation of weak shocks into non-uniform, two-dimensional flows is introduced. The theory is based on a description of shock propagation in terms of a manifold equation together with compatibility conditions for shock strength and its normal derivatives behind the shock. This approach was developed by Ravindran & Prasad (1993) for shocks of arbitrary strength propagating into a medium at rest and is extended here to non-uniform media and restricted to moderately weak shocks. The theory is tested against known analytical solutions for cylindrical and plane shocks, and against a full direct numerical simulation (DNS) of a shock propagating into a sinusoidal shear flow. The test against DNS shows that the present theory accurately predicts the evolution of a moderately weak shock front, including the formation of shock-shocks due to shock focusing. The theory is then applied to the focusing of an initially parabolic shock, and to the propagation of an initially straight shock into a variety of simple flows (sinusoidal shear, vortex array, point-vortex array) exhibiting some fundamental properties of turbulent flows. A number of relations are deduced for the variation of shock quantities with initial shock strength MS0 and the Mach number of the flow ahead of the shock MU (e.g. separation of shock-shocks and maximum shock strength at a focus). It is found that shock-shocks are likely to form in turbulent flows with Mt/M1N > 0.14–0.25, where Mt is the average Mach number of the turbulence and M1N is the Mach number of the shock in a flow at rest. The shock moves up to 1.5% faster in a two-dimensional vortex array than in uniform flow.
Submarine radial vents on Mauna Loa Volcano, Hawai'i
Authors: Wanless V. Dorsey , Garcia M. O. , Trusdell F. A. , Rhodes J. M. , Norman M. D. , Weis Dominique , Fornari D. J. , Kurz M. D. , Guillou Hervé
Published: May 2006

A 2002 multibeam sonar survey of Mauna Loa's western flank revealed ten submarine radial vents and three submarine lava flows. Only one submarine radial vent was known previously. The ages of these vents are constrained by eyewitness accounts, geologic relationships, Mn‐Fe coatings, and geochemical stratigraphy; they range from 128 years B.P. to possibly 47 ka. Eight of the radial vents produced degassed lavas despite eruption in water depths sufficient to inhibit sulfur degassing. These vents formed truncated cones and short lava flows. Two vents produced undegassed lavas that created “irregular” cones and longer lava flows. Compositionally and isotopically, the submarine radial vent lavas are typical of Mauna Loa lavas, except two cones that erupted alkalic lavas. He‐Sr isotopes for the radial vent lavas follow Mauna Loa's evolutionary trend. The compositional and isotopic heterogeneity of these lavas indicates most had distinct parental magmas. Bathymetry and acoustic backscatter results, along with photography and sampling during four JASON2 dives, are used to produce a detailed geologic map to evaluate Mauna Loa's submarine geologic history. The new map shows that the 1877 submarine eruption was much larger than previously thought, resulting in a 10% increase for recent volcanism. Furthermore, although alkalic lavas were found at two radial vents, there is no systematic increase in alkalinity among these or other Mauna Loa lavas as expected for a dying volcano. These results refute an interpretation that Mauna Loa's volcanism is waning. The submarine radial vents and flows cover 29 km2 of seafloor and comprise a total volume of ∼2 × 109 m3 of lava, reinforcing the idea that submarine lava eruptions are important in the growth of oceanic island volcanoes even after they emerged above sea level.
Interseismic strain accumulation: Spin‐up, cycle invariance, and irregular rupture sequences
Authors: Hetland E. A. , Hager B. H.
Published: May 2006

Using models of infinite length strike‐slip faults in an elastic layer above linear viscoelastic regions, we investigate interseismic deformation. In the models we investigate, interseismic strain accumulation on mature faults is the result of the cumulative effects of all previous ruptures and is independent of the fault loading conditions. The time for a fault to spin‐up to a mature state depends on the rheologies and the fault loading conditions. After the model has spun‐up, the temporal variation of shear stresses is determined by the fault slip rate and model rheologies. The change in stress during spin‐up depends on the slip rate, rheologies, and fault loading conditions but is independent of the magnitude of the initial stress. Over enough cycles such that the cumulative deformation is block‐like, the average mature interseismic velocities are equal to the interseismic velocities of an elastic model with the same geometry and distribution of shear moduli. In a model that has spun‐up with the fault rupturing periodically, the cumulative deformation is block‐like at the end of each seismic cycle, and the interseismic deformation is cycle‐invariant (i.e., the same in all cycles). When the fault ruptures nonperiodically, the fault spins up to a mature state that is the same as if the fault had ruptured periodically with the mean slip rate. When the fault slip rate within each cycle varies, the interseismic deformation evolves toward the cycle‐invariant deformation determined by the most recent fault slip rate. Around a fault whose slip rate has been faster (slower) than average, interseismic velocities are larger (smaller) than the cycle‐invariant velocities and increase (decrease) from cycle to cycle.
The 1996 equatorial Atlantic warm event: Origin and mechanisms
Authors: Illig S. , Gushchina D. , Dewitte B. , Ayoub N. , du Penhoat Y.
Published: May 2006

We investigate the interannual warm event that occurred in the equatorial Atlantic in boreal spring‐summer 1996. The role of local coupled air‐sea interactions versus Tropical Pacific remote forcing is analysed using observations and ensemble experiments of an intermediate coupled model of the Tropical Atlantic. Results show that the persistent anomalous cold conditions in the Tropical Pacific over 1995–96 were favorable to the growth of the local air‐sea interactions that led to the 1996 warming in the equatorial Atlantic. Based on the estimation of the changes in the Walker circulation over the Pacific and Atlantic for the meteorological reanalyses and the coupled model, a mechanism of Pacific‐Atlantic equatorial connection is proposed to explain this particular warm episode.
Dependence of flux transfer events on solar wind conditions from 3 years of Cluster observations
Authors: Wang Y. L. , Elphic R. C. , Lavraud B. , Taylor M. G. G. T. , Birn J. , Russell C. T. , Raeder J. , Kawano H. , Zhang X. X.
Published: May 2006

We investigate the dependence of Cluster high‐latitude magnetopause and low‐latitude flank flux transfer events (FTEs) on solar wind conditions using measurements from Cluster FGM and CIS and ACE MFI and SWEPAM between February 2001 and June 2003. We find that there are strong dependences of Cluster FTE occurrence on the IMF Bxgsm, Bygsm, and Bzgsm components but not on the IMF magnitude. There are strong dependences of Cluster FTE occurrence on the IMF clock, tilt, spiral, and cone angles. However, some patterns are significantly different from previous results. The solar wind density, speed, Beta, VxBz, dynamic pressure, and magnetosonic Mach number have different degrees of control on FTE occurrence. FTE separation time is found to be clearly controlled by IMF Bygsm, Bzgsm, and magnitude, and the IMF clock, tilt, spiral, and cone angles, and weakly controlled by the solar wind VxBz and magnetosonic Mach number. There is no obvious control of it by other IMF and solar wind parameters. FTE peak‐peak magnitude is found to be controlled by IMF Bygsm, Bzgsm, and magnitude and by the solar wind density and dynamic pressure but not by other IMF and solar wind parameters. The FTE dawn‐dusk asymmetry is not likely caused by the Parker spiral IMF. Some FTE statistical patterns are strongly dependent on FTE locations. Finally, we see ∼4% of the FTEs corresponding to a single change in IMF Bzgsm from positive to negative, ∼4% corresponding to a single change from negative to positive, and ∼43% corresponding to multiple changes in the sign of IMF Bzgsm, all within the 10‐min interval preceding the FTEs. There is still no evidence for a direct correlation between IMF Bzgsm changing sign and FTEs.
Oblique propagation and nonlinear wave particle processes
Authors: Hamza A. M. , Meziane K. , Mazelle C.
Published: May 2006

The wave‐particle interaction plays a fundamental role in plasma physics; it is an energy momentum exchange mechanism between particles and waves. The most fundamental examples treated in the literature address the interaction of a single wave propagating along a background magnetic field with a single ion or electron. In the present paper we propose to investigate this specific problem, but this time we take into account the fact that the electromagnetic wave propagates obliquely with respect to the background field. The obliqueness manifests itself in the appearance of a parallel component in the electric field which in turn impacts the dynamics of the charged particle it interacts with and provides a mechanism of acceleration. This parallel component of the electric field can trap or untrap particles. The parallel propagation case is recovered automatically by setting the angle of propagation with respect to the background magnetic field to zero. A simple, yet complex, dynamical system is derived and limiting cases are treated analytically while numerical integration is used to investigate the general cases. We find that physical trapping occurs for a class of initial conditions and that phase space trapping (pitch angle versus gyrophase for example) remains in some cases a signature of the dynamical system.
Dynamic simulation of a dipping fault using a three‐dimensional finite difference method with nonuniform grid spacing
Authors: Zhang Wenbo , Iwata Tomotaka , Irikura Kojiro
Published: May 2006

We propose a method to analyze dynamic rupture processes of earthquakes with a dipping fault, using a three‐dimensional finite difference (FD) method with nonuniform grid spacing. This approach does not require aligning the fault plane to the FD grid for implementation of the FD method. It can be used to deal with a realistically complex fault geometry model. We validate our method by studying two dynamic source problems that have been analyzed by Madariaga et al. One is the instantaneous rupture of a circular fault embedded in a homogeneous elastic medium; the other is the spontaneous rupture of a rectangular fault which starts from a local circular asperity on the fault plane. Our numerical results for different dipping faults are similar with those obtained by Madariaga et al. using a horizontal fault plane model in full space, thus validating our method for dipping fault models.
A thermal pressurization model for the spontaneous dynamic rupture propagation on a three‐dimensional fault: 1. Methodological approach
Authors: Bizzarri A. , Cocco M.
Published: May 2006

We investigate the role of frictional heating and thermal pressurization on earthquake ruptures by modeling the spontaneous propagation of a three‐dimensional (3‐D) crack on a planar fault governed by assigned constitutive laws and allowing the evolution of effective normal stress. We use both slip‐weakening and rate‐ and state‐dependent constitutive laws; in this latter case we employ the Linker and Dieterich evolution law for the state variable, and we couple the temporal variations of friction coefficient with those of effective normal stress. In the companion paper we investigate the effects of thermal pressurization on the dynamic traction evolution. We solve the 1‐D heat conduction equation coupled with Darcy's law for fluid flow in porous media. We obtain a relation that couples pore fluid pressure to the temperature evolution on the fault plane. We analytically solve the thermal pressurization problem by considering an appropriate heat source for a fault of finite thickness. Our modeling results show that thermal pressurization reduces the temperature increase caused by frictional heating. However, the effect of the slipping zone thickness on temperature changes is stronger than that of thermal pressurization, at least for a constant porosity model. Pore pressure and effective normal stress evolution affect the dynamic propagation of the earthquake rupture producing a shorter breakdown time and larger breakdown stress drop and rupture velocity. The evolution of the state variable in the framework of rate‐ and state‐dependent friction laws is very different when thermal pressurization is active. In this case the evolution of the friction coefficient differs substantially from that inferred from a slip‐weakening law. This implies that the traction evolution and the dynamic parameters are strongly affected by thermal pressurization.
Southern tropical upper tropospheric zonal ozone wave‐1 from SAGE II observations (1985–2002)
Authors: Wang Pi‐Huan , Fishman Jack , Harvey V. Lynn , Hitchman Matthew H.
Published: May 2006

Using multiyear data (1985–2002) derived from the second Stratospheric Aerosol and Gas Experiment (SAGE II) and meteorological information (1992–2004) from the United Kingdom Meteorological Office, the present study investigates the seasonal structure of the southern tropical zonal ozone wave‐1 in the upper troposphere. By using multiyear near‐global ozone profile measurements from the SAGE II satellite instrument, the present study complements the analyses based on data from tropical ozonesonde networks, such as the Southern Hemisphere Additional Ozonesondes (SHADOZ), and from satellite total tropospheric ozone. The seasonal variations in the meridional ozone distributions in the high‐ozone longitudinal sector (40°W–60°E) and the low‐ozone longitudinal sector (60°E–320°E) are investigated in detail. The results indicate that the southern tropical zonal ozone wave‐1 is a year‐round feature, with the strongest amplitude occurring in austral spring and weakest in autumn. The influence of the meridional (Hadley) and equatorial (Walker) circulations on the ozone wave‐1 is also examined. The analysis suggests that both Hadley and Walker circulations can contribute to the formulation of the ozone wave‐1 climatological structure.
Chemical ozone loss and related processes in the Antarctic winter 2003 based on Improved Limb Atmospheric Spectrometer (ILAS)–II observations
Authors: Tilmes Simone , Müller Rolf , Grooß Jens‐Uwe , Spang Reinhold , Sugita Takafumi , Nakajima Hideaki , Sasano Yasuhiro
Published: May 2006

In this study, ILAS‐II (Improved Limb Atmospheric Spectrometer) measurements were used to analyze chemical ozone loss during the entire Antarctic winter 2003, using the tracer‐tracer correlation technique. The temporal evolution of both the accumulated local chemical ozone loss and the loss in column ozone in the lower stratosphere is in step with increasing solar illumination. Half of the entire loss in column ozone of 157 DU occurred during September 2003. By the end of September 2003, almost the total amount of ozone was destroyed between 380 and 470 K. Further, ozone loss rates increased strongly during September for the entire lower stratosphere. The values of accumulated ozone loss and ozone loss rates are strongly dependent on altitude. Once ozone loss is saturated during September, especially at latitudes between 380 and 420 K, ozone loss rates decrease, and accumulated ozone loss can no longer increase. Moreover, at altitudes above 470 K, accumulated ozone loss depends on the amount of PSCs occurring during winter and spring. During September, ozone mixing ratios show a large day to day variation. Box model simulations by the Chemical Lagrangian Model of the Stratosphere (CLaMS) show that this is a result of the different histories of the observed air masses. Further, the box model supports the general evolution of ozone loss values during September as a result of the strong increase of halogen catalyzed ozone destruction.
Isotopic exchange between snow and atmospheric water vapor: Estimation of the snowmelt component of groundwater recharge in the southwestern United States
Authors: Earman Sam , Campbell Andrew R. , Phillips Fred M. , Newman Brent D.
Published: May 2006

The contribution of snowmelt to groundwater recharge at four sites in the southwestern United States was evaluated using stable isotopes of O and H. Paired precipitation collectors were installed at the study sites; data show that (1) there is often a significant difference between the stable isotope composition of fresh snow and the bulk meltwater derived from it (this suggests that using the isotope composition of high‐elevation springs as a proxy for precipitation may not be sound if snow is a recharge source) and (2) collector design can significantly influence the stable isotope composition of collected snow. Because the isotope composition of snow from a given location becomes heavier (i.e., more rain‐like) with increased exposure, using bulk snowmelt compositions to calculate input to groundwater recharge results in significantly increased estimates of snowmelt contributions to recharge (compared to estimates derived from fresh snow signatures). Snowmelt provides at least 40–70% of groundwater recharge at the study sites, although only 25–50% of average annual precipitation falls as snow. On the basis of these results and presently accepted scenarios for alterations in precipitation in the western United States over the next 50 years (significantly decreased snowpack due to increased atmospheric CO2), investigations of how climate change may affect groundwater resources are needed. We also investigated the potential for snow/atmospheric water vapor isotope exchange to influence the isotope signature of snow (which has been a subject of debate); the results of a laboratory experiment suggest that it can drive significant shifts in the isotope signature of snow, even at temperatures below 0°C.
A role for newly forming sea ice in springtime polar tropospheric ozone loss? Observational evidence from Halley station, Antarctica
Authors: Jones A. E. , Anderson P. S. , Wolff E. W. , Turner J. , Rankin A. M. , Colwell S. R.
Published: May 2006

Since March 2003, measurements of surface ozone have been made at the British Antarctic Survey Clean Air Sector Laboratory (CASLab) at Halley station in coastal Antarctica. Detailed measurements of boundary layer meteorology, as well as standard meteorological parameters, are also measured at the CASLab. Combining these data allows us to probe the transport pathway of air masses during ozone depletion events (ODEs). ODEs were observed at Halley on several occasions during Antarctic spring 2003. On some occasions, extremely rapid loss of ozone was observed (loss of 16 ppbv in 1 min on one occasion), which was associated with regional‐scale transport. For each such event during 2003, the air mass originated in the southern Weddell Sea, an area of vigorous sea‐ice production. On other occasions the development of the event and its recovery were strongly associated with the build‐up and decline of a stable boundary layer. In these cases, air masses had had recent contact with a nearby open water lead where sea‐ice production is known to occur. The data presented here are entirely consistent with the idea that halogens responsible for ozone loss are derived during new sea‐ice formation from an associated surface such as brine slush or frost flowers.
Relative humidity over Antarctica from radiosondes, satellites, and a general circulation model
Authors: Gettelman A. , Walden V. P. , Miloshevich L. M. , Roth W. L. , Halter B.
Published: May 2006

Radiosonde measurements are used to validate measurements of relative humidity (RH) over Antarctica from the Atmospheric Infrared Sounder (AIRS) satellite instrument. Radiosonde observations are corrected for most known biases but still have a solar heating dry bias of up to 8% relative to other instruments. AIRS reproduces the observations of temperature and relative humidity with good fidelity. There is a ∼20% moist bias to the data in the upper troposphere relative to radiosonde measurements, but it is within the standard deviation of the measurements. Probability distribution functions of RH from radiosondes and AIRS are similar, suggesting that variability over Antarctica is well reproduced by the satellite. AIRS data are also compared to simulations from the Community Atmosphere Model version 3 (CAM3) and are found to be significantly moister than the model, although the model does not allow supersaturation with respect to ice or liquid water. A climatology from AIRS indicates that it has a repeatable annual cycle over Antarctica. Supersaturation with respect to ice is very common over the continent, particularly in winter, where it might occur almost half the time in the troposphere. This may affect the quantity and isotopic composition of ice over Antarctica.
Relaxing the well‐mixed greenhouse gas approximation in climate simulations: Consequences for stratospheric climate
Authors: Curry C. L. , McFarlane N. A. , Scinocca J. F.
Published: May 2006

The climatic consequences of relaxing the uniform greenhouse gas (GHG) assumption in the Canadian Centre for Climate Modelling and Analysis atmospheric general circulation model are examined. A simple chemical loss parameterization for nitrous oxide, methane, CFC‐11, and CFC‐12 is employed that includes stratospheric water vapor production from methane oxidation. Multidecadal mean distributions of these species are obtained that compare reasonably well with UARS satellite observations of the stratosphere. The radiative impact of these changes is a widespread cooling of the stratosphere (with a spatially averaged, annual mean value of 0.6 K), compared to the model with specified uniform GHG distributions. This cooling results from an approximate doubling of the amount of middle to upper stratospheric moisture (as a result of methane oxidation) and exceeds the radiatively induced warming due to decreases in the other GHGs. Annual mean temperature changes of up to +8 K in the upper winter polar stratosphere, by contrast, are dynamically induced because of increases in the residual mean circulation and associated heating.
Scenarios regarding the lead of equatorial sea surface temperature over global ice volume
Authors: Ashkenazy Yosef , Tziperman Eli
Published: May 2006

Recent proxy evidences indicate that the equatorial sea surface temperature (SST) may have led global ice volume by ∼3 kyr during the late Pleistocene glacial cycles. Given the short timescales of equatorial dynamics, equatorial climate variability is characterized by a timescale of no more than a few years. It would seem somewhat surprising therefore that the equatorial ocean and atmosphere can determine and lead the long‐timescale 100 kyr glacial cycles. Two scenarios are presented according to which such a lead may be observed even when the equatorial ocean and atmosphere are not necessarily responsible for leading the glacial cycles (they may still act as a strong amplifier). First, it is shown that if the plankton‐based proxy reflects the warm season temperature rather than an annual temperature, it may lead the global temperature, although the dynamics of the glacial cycles may still be dominated by the Northern Hemisphere ice sheets. It is noted that a present‐day seasonal bias of the equatorial proxy record is still inconclusive, and the possibility of a proxy bias only during glacial times is considered as well. A second scenario is suggested in which global sea level rises before equatorial SST, yet the later evolution of factors such as the atmospheric CO2 and equatorial SST is faster and takes the lead over global ice volume. If the initial rise of sea level is masked by a sufficiently large proxy noise (because of instrumental and natural noise), it may not be seen and the lead may be attributed to the equatorial SST and CO2.
Late Cenozoic partitioning of oblique plate convergence in the Zagros fold‐and‐thrust belt (Iran)
Authors: Authemayou Christine , Chardon Dominique , Bellier Olivier , Malekzadeh Zaman , Shabanian Esmaeil , Abbassi Mohammad Reza
Published: May 2006

The NW trending Zagros fold‐and‐thrust belt is affected by two major dextral faults: (1) the NW trending Main Recent Fault that accommodates partitioning of oblique convergence at the rear of the western Zagros and (2) the north trending Kazerun Fault located in the central Zagros. Combined structural and fault kinematics studies and SPOT images analysis have shown a Pliocene kinematic change accompanied by a fault pattern reorganization, which has led to a modification in the accommodation of oblique convergence. Since the late Pliocene, the distributed transpressional deformation operating at the rear of the belt has become partitioned along the newly formed Main Recent Fault. This fault cuts through early Pliocene nappes and transpressional structures by right‐laterally reactivating high‐angle thrusts. The southeastern termination of the Main Recent Fault connects to the northern termination of Kazerun Fault that consists of three fault zones that end in bent, orogen‐parallel splay thrust faults. The Kazerun Fault, together with a series of north to NNW trending inherited basement strike‐slip faults, define an orogen‐scale fan‐shaped fault pattern pointing toward the Main Recent Fault–Kazerun Fault junction. This structural pattern allows slip from along the Main Recent Fault to become distributed by transfer to the longitudinal thrust faults and folds of the Zagros belt, with the fan‐shaped fault pattern acting as a horse‐tail termination of the Main Recent Fault.
Effects of sodium chloride on constitutive relations in variably saturated porous media
Authors: Burns Erick R. , Selker John S. , Parlange Jean‐Yves , Guenther Ronald B.
Published: May 2006

Though many arid and contaminated sites have high salinity, prediction of effects of salinity on water movement in soils has been based on dilute solution approximations. Here a sensitivity analysis compares predicted liquid and vapor pressure in variably saturated porous media found using both the dilute approximations and a more general formulation that is valid for salt concentrations from zero to saturation. Sodium chloride (NaCl) was selected as a representative salt of environmental importance. Salt‐mineral interactions are not included in the analysis. The dilute approximations neglect the salt‐related changes in specific volume, which translate into nonnegligible pressure effects (i.e., error >1%) under dry conditions, being more pronounced for finer media. The analysis shows that for silt textures, the dilute approximation to the vapor pressure constitutive relation is acceptable for water contents θ > 5%, for sand θ > 1%, and for loam θ > 2%. When computing gradients of vapor pressure resulting from gradients in salt concentration, volume correction is necessary for silt for θ < 10%. Gradients in vapor pressure with changes in water content require volume correction, except under dilute conditions (i.e., <0.5 molal). For concentrated solutions in silt, salt effect errors are not acceptable for prediction of liquid pressure, nor are the effects on gradients negligible. Errors for sand and loam are only marginally better, with acceptable errors generally occurring only for ionic strengths of less than 1 molal. An example of use of the constitutive relations to plot results from experiments is provided to illustrate how the theory may be used to determine which thermodynamic corrections must be incorporated into analyses of the experimental results. Here the volumetric effects of the salt on vapor depression were negligible, though volumetric effects may be nonnegligible for computation of gradients of both vapor and liquid pressures. The method of analysis of nonideal effects developed herein is general, and the resulting corrections to the dilute approximation may be easily implemented in numerical codes.
Developing portfolios of water supply transfers
Authors: Characklis Gregory W. , Kirsch Brian R. , Ramsey Jocelyn , Dillard Karen E. M. , Kelley C. T.
Published: May 2006

Most cities rely on firm water supply capacity to meet demand, but increasing scarcity and supply costs are encouraging greater use of temporary transfers (e.g., spot leases, options). This raises questions regarding how best to coordinate the use of these transfers in meeting cost and reliability objectives. This paper combines a hydrologic–water market simulation with an optimization approach to identify portfolios of permanent rights, options, and leases that minimize the expected costs of meeting a city's annual demand with a specified reliability. Spot market prices are linked to hydrologic conditions and described by monthly lease price distributions which are used to price options via a risk‐neutral approach. Monthly choices regarding when and how much water to acquire through temporary transfers are made on the basis of anticipatory decision rules related to the ratio of expected supply to expected demand. The simulation is linked with an algorithm that uses an implicit filtering search method designed for solution surfaces that exhibit high‐frequency, low‐amplitude noise. This simulation‐optimization approach is applied to a region that currently supports an active water market, with results suggesting that temporary transfers can reduce expected water supply costs substantially, while still maintaining high reliability. Also evaluated are trade‐offs between expected costs and cost variability that occur with variation in a portfolio's distribution of rights, options, and leases.
Interpretation and inversion of low‐frequency head observations
Authors: Vasco D. W. , Karasaki K.
Published: May 2006

An asymptotic expression for transient head variations, valid at low‐frequencies, forms the basis for an efficient scheme for estimating hydraulic conductivity. The critical computational step is equivalent to solving the governing equation for steady state head. Thus, model parameter sensitivities, relating changes in head to changes in hydraulic conductivity, of the fully transient problem can be computed with the equivalent of four steady state head computations. A comparison of model parameter sensitivities computed using the low‐frequency asymptotic approach and sensitivities computed using a purely numerical approach indicates good agreement. An inversion of synthetic hydraulic tomography data indicates that it is possible to estimate overall permeability variations using the technique. In an actual application to truncated crosswell pressure tests from the Raymond field site, we image two high permeability fracture zones, in agreement with a conceptual model of the region. The location of the two fracture zones correlates with the position of transmissive fractures, as measured by borehole conductivity logs.
On the spatial and temporal sampling of soil moisture fields
Authors: Manfreda Salvatore , Rodríguez‐Iturbe Ignacio
Published: May 2006

Recent work by Isham et al. and Rodrìguez‐Iturbe et al. has characterized the space‐time variability of soil moisture through its analytically derived covariance function which depends on soil properties, vegetation structure, and rainfall patterns typical of a region. This paper uses such characterization to address the strategies and methodologies for the sampling of soil moisture fields. The focus is on the estimation of the long‐term mean soil moisture and the daily soil moisture averaged over a given area as a function of the network geometry, number of stations, number of sampling days and landscape heterogeneity. It is found that the spatial geometry of the network has a significant impact on the sampling of the average soil moisture over an area in any particular day, while it is much less relevant for the sampling of the long‐term mean daily soil moisture over the region. In the latter case, the length of the record is a commanding factor in what concerns the variance of estimation, specially for soils with shallow rooted vegetation. Spatial vegetation heterogeneity plays an important role on the variance of estimation of the soil moisture, being particularly critical for the sampling of the average soil moisture over an area for a given day.
Automatic deployment of a 2‐D geophone array for efficient ultra‐shallow seismic imaging
Authors: Tsoflias Georgios P. , Steeples Don W. , Czarnecki Gerard P. , Sloan Steven D. , Eslick Robert C.
Published: May 2006

The cost of three‐dimensional seismic‐reflection surveys is approximately inversely proportional to the square of the target depth, which renders ultra‐shallow 3‐D surveys uneconomical when employing conventional acquisition methods. We developed instrumentation that automatically deploys an array of geophones for efficient acquisition of shallow 3‐D seismic reflection data. The components of the instrumentation are: a rigid‐steel platform used for positioning, planting, and transporting geophones; a hydraulically controlled mechanism for decoupling the geophones from the platform during seismic‐data recording; and a 2‐D array of 72 geophones. Tests of both automatically planted geophones and conventional hand‐planted geophones resulted in comparable ultra‐shallow seismic data. Field tests show automatic planting and moving of the geophone array is possible in three minutes by one or two field operators. Conceptually, the design could accommodate hundreds of geophones handled by a single operator. The instrumentation presented is a new approach to efficient ultra‐shallow 3‐D seismic acquisition.
Whisker Stimulation Enhances Angiogenesis in the Barrel Cortex following Focal Ischemia in Mice
Authors: Whitaker Vivian R , Cui Lin , Miller Scott , Yu Shan P , Wei Ling
Published: May 2006

Post-ischemia angiogenesis and vascular plasticity help to restore blood flow to ischemic tissue and likely benefit long-term functional recovery. Physical activity has been shown to cause morphologic and functional effects, including promoting angiogenesis in normal or injured animals. A therapeutic effect of peripheral activity on central angiogenesis after cerebral ischemia, however, has not been studied. In the present study of whisker-barrel cortex ischemia in the mouse model, we tested the hypothesis that enhancing whisker activity and sensory input to the ischemic barrel cortex might promote post-ischemia cerebral angiogenesis. Three days after focal ischemia in adult mice, the whiskers corresponding to the ischemic barrel cortex were stimulated by two methods: (1) whiskers on the right side of the mouse face were trimmed away, so the left whiskers were overused by the animals, (2) left whiskers were manually stimulated to enhance input signals to the ischemic barrel cortex. Western blot analysis showed that whisker stimulation increased expression of the angiogenic factors vascular endothelial growth factor, basic fibroblast growth factor, Tie-1, angiopoietin-2 (Ang-2), and possibly Ang-1. Co-immunostaining with markers for proliferation (5-bromo-2-deoxyuridine (BrdU)) and vascular endothelial cells (Glut-1/CD-31) identified vessel proliferation in the penumbra region. Whisker stimulation increased BrdU-positive endothelial cells and vessels in this region 7 and 14 days after ischemia. Whisker stimulation also attenuated endothelial cell death and increased local cerebral blood flow. Our data suggest that appropriately enhanced peripheral activity and afferent signals to the ischemic cortex can promote post-ischemic angiogenesis, which may imply beneficial effects of specific physical therapy on long-term recovery from ischemic stroke.
A Simple Method to Induce Focal Brain Hypothermia in Rats
Authors: Clark Darren L , Colbourne Frederick
Published: May 2006

Hypothermia reduces cell death and promotes recovery in models of cerebral ischemia, intracerebral hemorrhage and trauma. Clinical studies report significant benefit for treating cardiac arrest and studies are investigating hypothermia for stroke and related conditions. Both local (head) and generalized hypothermia have been used. However, selective brain cooling has fewer side effects than systemic cooling. In this study, we developed a method to induce local (hemispheric) brain hypothermia in rats. The method involves using a small metal coil implanted between the Temporalis muscle and adjacent skull. This coil is then cooled by flushing it with cold water. In our first experiment, we tested whether this method induces focal brain hypothermia in anesthetized rats. Brain temperature was assessed in the ipsilateral cortex and striatum, and contralateral striatum, while body temperature was kept normothermic. Focal, ipsilateral cooling was successfully produced, while the other locations remained normothermic. In the second experiment, we implanted the coil, and brain and body temperature telemetry probes. The coil was connected via overhead swivel to a cold-water source. Brain hypothermia was produced for 24 h, while body temperature remained normothermic. A third experiment measured brain and body temperature along with heart rate and blood pressure. Brain cooling was produced for 24 h without significant alterations in pressure, heart rate or body temperature. In summary, our simple method allows for focal brain hypothermia to be safely induced in anesthetized or conscious rats, and is, therefore, ideally suited to stroke and trauma studies.
Phosphonate self-assembled monolayers on aluminum surfaces
Authors: Hoque E. , DeRose J. A. , Hoffmann P. , Mathieu H. J. , Bhushan B. , Cichomski M.
Published: May 2006

Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDP∕Al∕Si), decylphosphonic acid (DP∕Al∕Si), and octadecylphosphonic acid (ODP∕Al∕Si) were studied by x-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), and friction force microscopy, a derivative of AFM, to characterize their surface chemical composition, roughness, and micro-/nanotribological properties. XPS analysis confirmed the presence of perfluorinated and nonperfluorinated alkylphosphonate molecules on the PFDP∕Al∕Si, DP∕Al∕Si, and ODP∕Al∕Si. The sessile drop static contact angle of pure water on PFDP∕Al∕Si was typically more than 130° and on DP∕Al∕Si and ODP∕Al∕Si typically more than 125° indicating that all phosphonic acid reacted Al∕Si samples were very hydrophobic. The surface roughness for PFDP∕Al∕Si, DP∕Al∕Si, ODP∕Al∕Si, and bare Al∕Si was approximately 35nm as determined by AFM. The surface energy for PFDP∕Al∕Si was determined to be approximately 11mN∕m by the Zisman plot method compared to 21 and 20mN∕m for DP∕Al∕Si and ODP∕Al∕Si, respectively. Tribology involves the measure of lateral forces due to friction and adhesion between two surfaces. Friction, adhesion, and wear play important roles in the performance of micro-/nanoelectromechanical systems. PFDP∕Al∕Si gave the lowest adhesion and coefficient of friction values while bare Al∕Si gave the highest. The adhesion and coefficient of friction values for DP∕Al∕Si and ODP∕Al∕Si were comparable.