bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of UT-A1-mediated transepithelial urea flux in MDCK cells
Authors: Fröhlich Otto , Klein Janet D. , Smith Pauline M. , Sands Jeff M. , Gunn Robert B.
Published: April 2006

Transepithelial [14C]urea fluxes were measured across cultured Madin-Darby canine kidney (MDCK) cells permanently transfected to express the urea transport protein UT-A1. The urea fluxes were typically increased from a basal rate of 2 to 10 and 25 nmol·cm−2·min−1 in the presence of vasopressin and forskolin, respectively. Flux activation consisted of a rapid-onset component of small amplitude that leveled off within ∼10 min and at times even decreased again, followed by a delayed, strong increase over the next 30–40 min. Forskolin activated urea transport through activation of adenylyl cyclase; dideoxyforskolin was inactive. Vasopressin activated urea transport only from the basolateral side and was blocked by OPC-31260, indicating that its action was mediated by basolateral V2 receptors. In the presence of the phosphodiesterase inhibitor IBMX, vasopressin activated as strongly as forskolin. By itself, IBMX caused a slow increase over 50 min to ∼5 nmol·cm−2·min−1. 8-Bromoadenosine 3′,5′-cyclic monophosphate (8-BrcAMP; 300 μM) activated urea flux only when added basolaterally. IBMX augmented the activation by basolateral 8-BrcAMP. Urea flux activation by vasopressin and forskolin were only partially blocked by the protein kinase A inhibitor H-89. Even at concentrations >10 μM, urea flux after 60 min of stimulation was reduced by <50%. The rapid-onset component appeared unaffected by the presence of H-89. These data suggest that activation of transepithelial urea transport across MDCK-UT-A1 cells by forskolin and vasopressin involves cAMP as a second messenger and that it is mediated by one or more signaling pathways separate from and in addition to protein kinase A.
Distinct K+ conductive pathways are required for Cl− and K+ secretion across distal colonic epithelium
Authors: Halm Susan Troutman , Liao Tianjiang , Halm Dan R.
Published: April 2006

Secretion of Cl− and K+ in the colonic epithelium operates through a cellular mechanism requiring K+ channels in the basolateral and apical membranes. Transepithelial current [short-circuit current ( Isc)] and conductance ( Gt) were measured for isolated distal colonic mucosa during secretory activation by epinephrine (Epi) or PGE2 and synergistically by PGE2 and carbachol (PGE2 + CCh). TRAM-34 at 0.5 μM, an inhibitor of KCa3.1 (IK, Kcnn4) K+ channels (H. Wulff, M. J. Miller, W. Hänsel, S. Grissmer, M. D. Cahalan, and K. G. Chandy. Proc Natl Acad Sci USA 97: 8151–8156, 2000), did not alter secretory Isc or Gt in guinea pig or rat colon. The presence of KCa3.1 in the mucosa was confirmed by immunoblot and immunofluorescence detection. At 100 μM, TRAM-34 inhibited Isc and Gt activated by Epi (∼4%), PGE2 (∼30%) and PGE2 + CCh (∼60%). The IC50 of 4.0 μM implicated involvement of K+ channels other than KCa3.1. The secretory responses augmented by the K+ channel opener 1-EBIO were inhibited only at a high concentration of TRAM-34, suggesting further that KCa3.1 was not involved. Sensitivity of the synergistic response (PGE2 + CCh) to a high concentration TRAM-34 supported a requirement for multiple K+ conductive pathways in secretion. Clofilium (100 μM), a quaternary ammonium, inhibited Cl− secretory Isc and Gt activated by PGE2 (∼20%) but not K+ secretion activated by Epi. Thus Cl− secretion activated by physiological secretagogues occurred without apparent activity of KCa3.1 channels but was dependent on other types of K+ channels sensitive to high concentrations of TRAM-34 and/or clofilium.
Activation of adenosine A2A receptors alters postsynaptic currents and depolarizes neurons of the supraoptic nucleus
Authors: Ponzio Todd A. , Wang Yu-Feng , Hatton Glenn I.
Published: April 2006

Supraoptic nucleus (SON) neurons secrete oxytocin or vasopressin in response to various physiological stimuli (e.g., lactation/suckling, dehydration). Released near fenestrated capillaries of the neurohypophysis, these peptides enter the blood and travel to peripheral target organs. The pervasive neuromodulator adenosine, acting at A1 receptors, is an important inhibitory regulator of magnocellular neuroendocrine cell activity. Another high-affinity adenosine receptor exists in this system, however. We examined the physiological effects of adenosine A2A receptor activation and determined its localization among various cell types within the SON. In whole cell patch-clamp recordings from rat brain slices, application of the selective adenosine A2A receptor agonist CGS-21680 caused membrane depolarizations in SON neurons, often leading to increased firing activity. Membrane potential changes were persistent (>10 min) and could be blocked by the selective A2A receptor antagonist ZM-241385, or GDP-β-S, the latter suggesting postsynaptic sites of action. However, ±-α-methyl-(4-carboxyphenyl)glycine or TTX also blocked CGS-21680 effects, indicating secondary actions on postsynaptic neurons. In voltage-clamp mode, application of CGS-21680 caused a slight increase (∼8%) in high-frequency clusters of excitatory postsynaptic currents. With the use of specific antibodies, adenosine A2A receptors were immunocytochemically localized to both the magnocellular neurons and astrocytes of the SON. Ecto-5′nucleotidase, an enzyme involved in the metabolism of ATP to adenosine, was also localized to astrocytes of the SON. These results demonstrate that adenosine acting at A2A receptors can enhance the excitability of SON neurons and modulate transmitter release from glutamatergic afferents projecting to the nucleus. We suggest that adenosine A2A receptors may function in neuroendocrine regulation through both direct neuronal mechanisms and via actions involving glia.
Plethysmographic estimation of thoracic gas volume in apneic mice
Authors: Jánosi Tibor Z. , Adamicza Ágnes , Zosky Graeme R. , Asztalos Tibor , Sly Peter D. , Hantos Zoltán
Published: April 2006

Electrical stimulation of intercostal muscles was employed to measure thoracic gas volume (TGV) during airway occlusion in the absence of respiratory effort at different levels of lung inflation. In 15 tracheostomized and mechanically ventilated CBA/Ca mice, the value of TGV obtained from the spontaneous breathing effort available in the early phase of the experiments (TGVsp) was compared with those resulting from muscle stimulation (TGVst) at transrespiratory pressures of 0, 10, and 20 cmH2O. A very strong correlation ( r2 = 0.97) was found, although with a systematically (∼16%) higher estimation of TGVst relative to TGVsp, attributable to the different durations of the stimulated (∼50 ms) and spontaneous (∼200 ms) contractions. Measurements of TGVst before and after injections of 0.2, 0.4, and 0.6 ml of nitrogen into the lungs in six mice resulted in good agreement between the change in TGVst and the injected volume ( r2 = 0.98). In four mice, TGVsp and TGVst were compared at end expiration with air or a helium-oxygen mixture to confirm the validity of isothermal compression in the alveolar gas. The TGVst values measured at zero transrespiratory pressure in all CBA/Ca mice [0.29 ± 0.05 (SD) ml] and in C57BL/6 ( N = 6; 0.34 ± 0.08 ml) and BALB/c ( N = 6; 0.28 ± 0.06 ml) mice were in agreement with functional residual capacity values from previous studies in which different techniques were used. This method is particularly useful when TGV is to be determined in the absence of breathing activity, when it must be known at any level of lung inflation or under non-steady-state conditions, such as during pharmaceutical interventions.
Stochastic behavior of atrial and ventricular intrinsic cardiac neurons
Authors: Waldmann M. , Thompson G. W. , Kember G. C. , Ardell J. L. , Armour J. A.
Published: April 2006

To quantify the concurrent transduction capabilities of spatially distributed intrinsic cardiac neurons, the activities generated by atrial vs. ventricular intrinsic cardiac neurons were recorded simultaneously in 12 anesthetized dogs at baseline and during alterations in the cardiac milieu. Few (3%) identified atrial and ventricular neurons (2 of 72 characterized neurons) responded solely to regional mechanical deformation, doing so in a tightly coupled fashion (cross-correlation coefficient r = 0.63). The remaining (97%) atrial and ventricular neurons transduced multimodal stimuli to display stochastic behavior. Specifically, ventricular chemosensory inputs modified these populations such that they generated no short-term coherence among their activities (cross-correlation coefficient r = 0.21 ± 0.07). Regional ventricular ischemia activated most atrial and ventricular neurons in a noncoupled fashion. Nicotinic activation of atrial neurons enhanced ventricular neuronal activity. Acute decentralization of the intrinsic cardiac nervous system obtunded its neuron responsiveness to cardiac sensory stimuli. Most atrial and ventricular intrinsic cardiac neurons generate concurrent stochastic activity that is predicated primarily upon their cardiac chemotransduction. As a consequence, they display relative independent short-term (beat-to-beat) control over regional cardiac indexes. Over longer time scales, their functional interdependence is manifest as the result of interganglionic interconnections and descending inputs.
Serotonin-Immunoreactive CPT Interneurons inHermissenda: Identification of Sensory Input and Motor Projections
Authors: Tian Lian-Ming , Kawai Ryo , Crow Terry
Published: April 2006

Serotonin immunoreactive (5-HT-IR) neurons identified as cerebropleural ganglion triplets (CPTs) in Hermissenda may be homologues of 5-HT-IR neurons identified in other opisthobranch molluscs. In studies of isolated nervous systems and semi-intact preparations we used a combination of immunohistochemical techniques and fluorescent labeling with Lucifer yellow to identify 5-HT-IR CPT neurons after investigating sensory inputs and motor neuron projections. Here we show that identified 5-HT-IR CPT interneurons receive sensory input from mechanoreceptors and photoreceptors. In semi-intact preparations with intact pedal nerves P1 and P2, cutaneous stimulation of the middle or tail regions of the foot with calibrated von Frey hairs elicited spikes recorded from identified CPT interneurons. Illumination of the eyes evoked a small complex excitatory postsynaptic potential (EPSP) and resulted in a modest increase in the spike discharge of CPT interneurons. Immunostaining of Lucifer yellow–labeled neurons revealed that CPT interneurons projected an axonal process to the contralateral pedal ganglion. Depolarization of CPT interneurons with extrinsic current evoked EPSPs and spikes recorded from identified VP2 pedal neurons, motor neurons previously shown to elicit movement of the anterior foot. Extrinsic current stimulation of CPT interneurons in semi-intact preparations evoked movement of the anterior foot but did not facilitate ciliary activity or evoke PSPs recorded in identified VP1 ciliary motor neurons. Our results show that CPT neurons are polysensory interneurons that contribute to reflexive foot contractions in Hermissenda.
Cortical Control of a Whisking Central Pattern Generator
Authors: Cramer Nathan P. , Keller Asaf
Published: April 2006

Whether the motor cortex regulates voluntary movements by generating the motor pattern directly or by acting through subcortical central pattern generators (CPGs) remains a central question in motor control. Using the rat whisker system, an important model system of mammalian motor control, we develop an anesthetized preparation to investigate the interaction between the motor cortex and a whisking CPG. Using this model we investigate the involvement of a serotonergic component of the whisking CPG in determining whisking kinematics and the mechanisms through which drive from the CPG is converted into movements by vibrissa motor units. Consistent with an action of the vibrissa motor cortex (vMCx) on a subcortical CPG, the frequency of whisking evoked by intracortical microstimulation (ICMS) of vMCx differed significantly from the stimulation frequency, whereas whisking onset latencies correlated negatively with stimulation intensity. Further, ICMS-evoked whisking was suppressed by a serotonin receptor antagonist, supporting previous findings that the whisking CPG contains a significant serotonergic component. The amplitude of ICMS-evoked whisking was correlated with the number of active motor units—isolated from vibrissal EMGs or recorded directly from vibrissa motoneurons—and their activity level. In addition, whisking frequency was correlated with the firing rate of these motoneurons. These findings support the hypothesis that vMCx regulates whisking through its actions on a subcortical CPG.
Discharge Properties of Monkey Tectoreticular Neurons
Authors: Rodgers C. Kip , Munoz Douglas P. , Scott Stephen H. , Paré Martin
Published: April 2006

The intermediate layers of the superior colliculus (SC) contain neurons that clearly play a major role in regulating the production of saccadic eye movements: a burst of activity from saccade neurons (SNs) is thought to provide a drive signal to set the eyes in motion, whereas the tonic activity of fixation neurons (FNs) is thought to suppress saccades during fixation. The exact contribution of these neurons to saccade control is, however, unclear because the nature of the signals sent by the SC to the brain stem saccade generation circuit has not been studied in detail. Here we tested the hypothesis that the SC output signal is sufficient to control saccades by examining whether antidromically identified tectoreticular neurons (TRNs: 33 SNs and 13 FNs) determine the end of saccades. First, TRNs had discharge properties similar to those of nonidentified SC neurons and a proportion of output SNs had visually evoked responses, which signify that the saccade generator must receive and process visual information. Second, only a minority of TRNs possessed the temporal patterns of activity sufficient to terminate saccades: Output SNs did not cease discharging at the time of saccade end, possibly continuing to drive the brain stem during postsaccadic fixations, and output FNs did not resume their activity before saccade end. These results argue against a role for SC in regulating the timing of saccade termination by a temporal code and suggest that other saccade centers act to thwart the extraneous SC drive signal, unless it controls saccade termination by a spatial code.
The Strengthening Relationship between ENSO and Northeast Monsoon Rainfall over Sri Lanka and Southern India
Authors: Zubair Lareef , Ropelewski C. F.
Published: April 2006

Recently, it was reported that the relationship of the Indian southwest monsoon rainfall with El Niño–Southern Oscillation (ENSO) has weakened since around 1980. Here, it is reported that in contrast, the relationship between ENSO and the northeast monsoon (NEM) in south peninsular India and Sri Lanka from October to December has not weakened. The mean circulation associated with ENSO over this region during October to December does not show the weakening evident in the summer and indeed is modestly intensified so as to augment convection. The intensification of the ENSO–NEM rainfall relationship is modest and within the historical record but stands in contrast to the weakening relationship in summer. The intensification of the circulation is consistent with the warming of surface temperatures over the tropical Indian Ocean in recent decades. There is modestly intensified convection over the Indian Ocean, strengthening of the circulation associated with ENSO (Walker circulation), and enhanced rainfall during El Niño episodes in a manner consistent with an augmented ENSO–NEM relationship.
Investigating the Causes of the Response of the Thermohaline Circulation to Past and Future Climate Changes
Authors: Stouffer R. J. , Yin J. , Gregory J. M. , Dixon K. W. , Spelman M. J. , Hurlin W. , Weaver A. J. , Eby M. , Flato G. M. , Hasumi H. , Hu A. , Jungclaus J. H. , Kamenkovich I. V. , Levermann A. , Montoya M. , Murakami S. , Nawrath S. , Oka A. , Peltier W. R. , Robitaille D. Y. , Sokolov A. , Vettoretti G. , Weber S. L.
Published: April 2006

The Atlantic thermohaline circulation (THC) is an important part of the earth's climate system. Previous research has shown large uncertainties in simulating future changes in this critical system. The simulated THC response to idealized freshwater perturbations and the associated climate changes have been intercompared as an activity of World Climate Research Program (WCRP) Coupled Model Intercomparison Project/Paleo-Modeling Intercomparison Project (CMIP/PMIP) committees. This intercomparison among models ranging from the earth system models of intermediate complexity (EMICs) to the fully coupled atmosphere–ocean general circulation models (AOGCMs) seeks to document and improve understanding of the causes of the wide variations in the modeled THC response. The robustness of particular simulation features has been evaluated across the model results. In response to 0.1-Sv (1 Sv ≡ 106 m3 s−1) freshwater input in the northern North Atlantic, the multimodel ensemble mean THC weakens by 30% after 100 yr. All models simulate some weakening of the THC, but no model simulates a complete shutdown of the THC. The multimodel ensemble indicates that the surface air temperature could present a complex anomaly pattern with cooling south of Greenland and warming over the Barents and Nordic Seas. The Atlantic ITCZ tends to shift southward. In response to 1.0-Sv freshwater input, the THC switches off rapidly in all model simulations. A large cooling occurs over the North Atlantic. The annual mean Atlantic ITCZ moves into the Southern Hemisphere. Models disagree in terms of the reversibility of the THC after its shutdown. In general, the EMICs and AOGCMs obtain similar THC responses and climate changes with more pronounced and sharper patterns in the AOGCMs.
Impact of Atmospheric Moisture Storage on Precipitation Recycling
Authors: Dominguez Francina , Kumar Praveen , Liang Xin-Zhong , Ting Mingfang
Published: April 2006

Computations of precipitation recycling using analytical models are generally performed under the assumption of negligible change in moisture storage in the atmospheric column. Because the moisture storage term is nonnegligible at smaller time scales, most recycling studies using analytical models are done at monthly or longer time scales. A dynamic precipitation recycling model, which incorporates the change in moisture storage, is developed. It is derived formally from the conservation of mass equation and is presented in a simple and computationally efficient form. This model allows for recycling analysis at a range of temporal scales, from daily to monthly and longer. In comparison to the traditional models that do not include the storage term, the new model presents almost identical spatial and temporal variability, but predicts recycling ratios that are 12%–33% larger at a monthly level.

The dynamic model is used to study the variability of monthly precipitation recycling over the conterminous United States using Reanalysis-II data from 1979 to 2000. On average, the southeastern and southwestern parts of the country exhibit high summer recycling ratios, contrasting with the low values in the northeastern and northwestern United States. The Colorado region also presents high recycling ratios. Dominant modes of spatiotemporal variability in recycling are identified using EOF analysis. The first mode captures strong recycling ratios over the western United States during the summers of 1986, 1992, and 1998. The second mode captures anomalous high recycling ratios during 1988 and 1989 over the central part of the country, and anomalous low ratios during 1980 and 1993.
Dynamical Processes Related to the Appearance of Quasi-Stationary Waves on the Subtropical Jet in the Midsummer Northern Hemisphere
Authors: Sato Naoki , Takahashi Masaaki
Published: April 2006

Statistical features of quasi-stationary planetary waves were examined on the subtropical jet in the midsummer Northern Hemisphere by using objectively analyzed data and satellite data. As a result, a quasi-stationary wave train that is highly correlated with the midsummer climate over Japan was identified. A clear phase dependency of the appearance of waves was also confirmed. An analysis of temporal evolution and wave activity flux revealed that the eastward propagation of the wave packet starts in the Middle East, passes over East Asia, and reaches North America. The anomaly pattern is strengthened through kinetic energy conversion near the entrance of the Asian jet over the Middle East. The interaction between the anomaly pattern and the basic field contributes to the appearance of the anomalous wavelike pattern. Although the wave train is correlated with the anomaly of convective activity over the western North Pacific and the Indian Ocean, it is implied that internal dynamics are important in determining the statistical features of the appearance of anomalous quasi-stationary waves on the subtropical jet.
Variability in the Characteristics of Precipitation Systems in the Tropical Pacific. Part II: Implications for Atmospheric Heating
Authors: L'Ecuyer Tristan S. , Masunaga Hirohiko , Kummerow Christian D.
Published: April 2006

This paper explores changes in the principal components of observed energy budgets across the tropical Pacific in response to the strong 1998 El Niño event. Multisensor observations from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and precipitation radar (PR) instruments aboard TRMM are used to quantify changes in radiative and latent heating in the east and west Pacific in response to the different phases of the El Niño–Southern Oscillation. In periods of normal east–west SST gradients there is substantial heating in the west Pacific and cooling in the east, implying strong eastward atmospheric energy transport. During the active phase of the El Niño, both the east and west Pacific tend toward local radiative–convective equilibrium resulting in their temporary energetic decoupling. It is further demonstrated that the response of these regions to ENSO-induced SST variability is directly related to changes in the characteristics of clouds and precipitation in each region. Through quantitative analysis of the radiative and latent heating properties of shallow, midlevel, and deep precipitation events and an equivalent set of nonprecipitating cloud systems, times of reduced atmospheric heating are found to be associated with a shift toward shallow and midlevel precipitation systems and associated low-level cloudiness. The precipitation from such systems is typically less intense, and they do not trap outgoing longwave radiation as efficiently as their deeper counterparts, resulting in reduced radiative and latent heating of the atmosphere. The results also suggest that the net effect of precipitating systems on top-of-the-atmosphere (TOA) fluxes and the efficiency with which they heat the atmosphere and cool the surface exhibit strong dependence on their surroundings. The sensitivity of cloud radiative impacts to the atmospheric and surface properties they act to modify implies the existence of strong feedbacks whose representation may pose a significant challenge to the climate modeling community.
Estimating Large-Scale Precipitation Minus Evapotranspiration from GRACE Satellite Gravity Measurements
Authors: Swenson Sean , Wahr John
Published: April 2006

Currently, observations of key components of the earth's large-scale water and energy budgets are sparse or even nonexistent. One key component, precipitation minus evapotranspiration (P − ET), remains largely unmeasured due to the absence of observations of ET. Precipitation minus evapotranspiration describes the flux of water between the atmosphere and the earth's surface, and therefore provides important information regarding the interaction of the atmosphere with the land surface. In this paper, large-scale changes in continental water storage derived from satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) project are combined with river discharge data to obtain estimates of areally averaged P − ET.

After constructing an equation describing the large-scale terrestrial water balance reflecting the temporal sampling of GRACE water storage estimates, GRACE-derived P − ET estimates are compared to those obtained from a reanalysis dataset [NCEP/Department of Energy (DOE) reanalysis-2] and a land surface model driven with observation-based forcing [Global Land Data Assimilation System (GLDAS)/Noah] for two large U.S. river basins. GRACE-derived P − ET compares quite favorably with the reanalysis-2 output, while P − ET from the Noah model shows significant differences. Because the uncertainties in the GRACE results can be computed rigorously, this comparison may be considered as a validation of the models.

In addition to showing how GRACE P − ET estimates may be used to validate model output, the accuracy of GRACE estimates of both the seasonal cycle and the monthly averaged rate of P − ET is examined. Finally, the potential for estimating seasonal evapotranspiration is demonstrated by combining GRACE seasonal P − ET estimates with independent estimates of the seasonal cycle of precipitation.
The Interannual Variability and Trend of Precipitable Water over Southern Greece
Authors: Kassomenos P. A. , McGregor G. R.
Published: April 2006

The precipitable water (PW) content was estimated over southern Greece for three atmospheric layers, using 28-yr twice-daily radiosonde measurements of temperature, humidity, and atmospheric pressure. Precipitable water demonstrates considerable variation at the monthly and interannual time scales as well as statistically significant upward trends at the annual level and for June–August (JJA) and September–November (SON). The relationship between PW and surface climate was also found to vary by season and surface climate variable. Disaggregation of seasonal PW trends by synoptic type revealed that seasonal trends might be attributed to increases in moisture in a limited number of airmass types such that maritime air masses appear to be becoming moister while their continental counterparts are drying. Despite fundamental changes to the intrinsic PW properties of air masses for some synoptic categories, the significance of these for determining the overall trend in seasonal PW levels is related to their weighted contribution as determined by changing airmass frequency. Consequently, the climatological effects of a moistening or drying air mass may be offset by a declining frequency. It is also shown that increasing PW trends cannot be attributed unequivocally to airmass warming as significant increases in PW have occurred in conjunction with falling temperatures in some seasons and airmass types. Accordingly, factors other than the commonly assumed global-warming-related increase in atmospheric moisture via the link between temperature and saturation vapor pressure must be considered if the mechanisms responsible for PW trends over southern Greece are to be fully understood.
Examination of the Bouchet–Morton Complementary Relationship Using a Mesoscale Climate Model and Observations under a Progressive Irrigation Scenario
Authors: Ozdogan Mutlu , Salvucci Guido D. , Anderson Bruce T.
Published: April 2006

The complementary relationship between actual and potential evaporation over southeastern Turkey was examined using a mesoscale climate model and field data. Model simulations of both actual and potential evaporation produce realistic temporal patterns in comparison to those estimated from field data; as evaporation from the surface increases with increasing irrigation, potential evaporation decreases. This is in accordance with the Bouchet–Morton complementary relationship and suggests that actual evapotranspiration can be readily computed from routine meteorological observations. The driving mechanisms behind irrigation-related changes in actual and potential evaporation include reduced wind velocities, increased atmospheric stability, and depressed humidity deficits. The relative role of each in preserving the complementary relation is assessed by fitting a potential evaporation model to pan evaporation data. The importance of reduced wind velocity in maintaining complementarity was unexpected, and thus examined further using a set of perturbation simulation experiments with changing roughness parameters (reflecting growing cotton crops), changing moisture conditions (reflecting irrigation), and both. Three potential causes of wind velocity reduction associated with irrigation may be increased surface roughness, decreased thermal convection that influences momentum transfer, and the development of anomalous high pressure that counteracts the background wind field. All three are evident in the mesoscale model results, but the primary cause is the pressure-induced local wind system. The apparent necessity of capturing mesoscale dynamical feedbacks in maintaining complementarity between potential and actual evaporation suggests that a theory more complicated than current descriptions (which are based on feedbacks between actual evaporation and temperature and/or humidity gradients) is required to explain the complementary relationship.
Fractal Distribution of Snow Depth from Lidar Data
Authors: Deems Jeffrey S. , Fassnacht Steven R. , Elder Kelly J.
Published: April 2006

Snowpack properties vary dramatically over a wide range of spatial scales, from crystal microstructure to regional snow climates. The driving forces of wind, energy balance, and precipitation interact with topography and vegetation to dominate snow depth variability at horizontal scales from 1 to 1000 m. This study uses land surface elevation, vegetation surface elevation, and snow depth data measured using airborne lidar at three sites in north-central Colorado. Fractal dimensions are estimated from the slope of a log-transformed variogram and demonstrate scale-invariant, fractal behavior in the elevation, vegetation, and snow depth datasets. Snow depth and vegetation topography each show two distinct fractal distributions over different scale ranges (multifractal behavior), with short-range fractal dimensions near 2.5 and long-range fractal dimensions around 2.9 at all locations. These fractal ranges are separated by a scale break at 15–40 m, depending on the site, which indicates a process change at that scale. Terrain has a fractal distribution over nearly the entire range of scales available in the data. Directional differences in the fractal dimensions for each parameter are also present at multiple scales, and are related to the wind direction frequency distributions at each site. The results indicate that different sampling resolutions may yield different results and allow rescaling in specific scale ranges. Resolutions of 10 m and finer are consistently self-similar, as are resolutions greater than 30 m, though the coarser resolutions show nearly random distributions.
Characterization and Evaluation of Hybrid Polarization Observation of Precipitation
Authors: Wang Yanting , Chandrasekar V. , Bringi V. N.
Published: April 2006

Transmitting an arbitrary state of polarization while receiving horizontal–vertical polarization states is termed the hybrid polarization mode of operation. A theoretical model is developed for hybrid mode dual-polarization measurements in terms of the covariance matrix under linear horizontal–vertical polarization basis. The cross polarization encountered introduces biases in the copolar parameters estimated in the hybrid mode. Such biases are investigated for different precipitation types and propagation effects resulting from hydrometeor orientation and antenna properties. Polarimetric data measured by the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar transmitting horizontal–vertical polarization states is alternately used to demonstrate the measurement accuracy that would be expected in different storm scenarios observed in the hybrid mode.
Maternal Employment
Authors: Riggio Heidi R. , Desrochers Stephan J.
Published: April 2006

Relations between maternal employment and young adults' work and family expectations, and self-efficacy were examined with 721 college students (mean age = 21 years). Young men expected more work hours per day and older retirement age, whereas women expected full-time work at a younger age and more time with spouse and children each week. Individuals with employed mothers reported less traditional family attitudes (e.g., fewer children planned, egalitarian division of household duties). Although women with employed mothers expected to spend less time per week with families than women with nonemployed mothers, men with employed mothers expected to spend more time with their families than men with nonemployed mothers. Women reported greater general, parenting, and work self-efficacy than men, and individuals with employed mothers reported greater parenting self-efficacy. Men with consistently non-employed mothers were particularly likely to report lower self-efficacy. Processes within dual-earner families are discussed as potential mechanisms underlying development of offspring self-efficacy.
Women, Work, and Family
Authors: Raskin Patricia M.
Published: April 2006

Three studies were conducted with partnered workingwomen with children younger than 18 years old living at home. The first two studies examine relationships among women's identity, career salience, attachment and coping styles, and work-family issues. The final study explores relations among individual differences, organizational variables, and turnover intent. Findings suggest that conflict as an identity element may be more a function of education and income than individual differences. Turnover intent was predicted only by organizational variables as perceived by the individual, not individual differences.
World Separation of Religion and State Into the 21st Century
Authors: Fox Jonathan
Published: April 2006

This study examines the extent of separation of religion and state (SRAS) between 1990 and 2002 in 152 states using the Religion and State database. The results show that when using a strict interpretation of SRAS—nostate support for religion and no state restrictions on religion–no state has full SRAS except the United States. Even when discounting moderate amounts of government involvement in religion (GIR), greater than three quarters of states do not have SRAS. The findings also show that GIR has increased slightly between 1990 and 2002, economic development is associated with higher levels of GIR, states with Muslim majorities have higher levels of government support for religion, and democracies have higher levels of SRAS than do autocratic states but rarely have full SRAS. This contradicts the idea that SRAS is an essential element of democracy and predictions that religion will cease to be an important political and social factor in modern times.
From Elysian Fields to the Guillotine?
Authors: Conley Richard S.
Published: April 2006

This article develops an integrative framework for explaining variation in monthly presidential and prime ministerial approval in Fifth Republic France. Melding theories of executive approval in the Anglo-American and French literatures, the empirical model closely examines macroeconomic indicators alongside contextual factors, such as cohabitation, temporal effects, and variables specific to French sociopolitical culture. The study refines prior models by utilizing the autoregressive integrated moving average technique to improve forecast estimates. The study also incorporates new archival data on unemployment to avoid measurement error. The results of the time-series analyses confirm that poor macroeconomic conditions yield larger drops in presidential approval. Similarly, short-term impacts of strikes and “rally effects” are consistently greater for changes in public confidence in the president. The import of time-decay effects and electoral factors varies dramatically for first and sub-sequent prime ministerial appointments.
Elongational Viscosity as a Tool to Predict the Foamability of Polyolefins
Authors: Ruinaard Henk
Published: April 2006

The foaming of polyolefins (POs) by direct gas injection is a delicate balance between the melt strength of the expanding polymer and the pressure of the blowing gas in the growing cells.

Important parameters in this process are: melting and crystallization temperature of the polyolefin grade, viscosity in the crystallization temperature range and elongational viscosity in the crystallization temperature range. In particular, the increase in elongational viscosity or so-called strain hardening is vital for a successful foam structure.

This study shows how the elongational viscosity is measured according to the rheological melt extension (RME) method. The experimental conditions for LDPE, LLDPE, HDPE, mPE plastomers, and PP are defined and used for a series of 25 PO grades.

These experiments show that the strain hardening ratio (SHR) is influenced by the average molecular length, molecular weight distribution (MWD) and the long chain branching (LCB).
Long-term Tensile and Compressive Behavior of Polymer Foams
Authors: Kraatz A. , Moneke M. , Kolupaev V.
Published: April 2006

Polymeric rigid foams are increasingly used for highly loaded mechanical applications, e.g., as core in foam sandwich constructions in aircraft or automotive parts. So far the mechanical behavior of rigid foams is not determined precisely. Therefore, the core of sandwich constructions is not taken into consideration for the mechanical design. This leads to oversizing and extended material consumption. This article presents experimental results of long-term tests and indicates a theory to take into account the difference of tensile and compressive behavior of foams. This theory is based on a strength hypothesis and can be implemented in commercial finite element programs. The proposed method leads to an improved mechanical design and, as a consequence, a reduction in mass of construction parts.
Fracture Toughness of High Density Polycarbonate Microcellular Foams
Authors: Bureau Martin N. , Kumar Vipin
Published: April 2006

Microcellular foams (MCFs) of polycarbonate (PC) with relative densities of 0.9 and 0.7 (MCF-0.9 and MCF-0.7) are produced by solid-state foaming. Microstructural characterization shows that they have bi-modal distribution of spherical cells, with median cell sizes of 3–4 mm and 6–9 mm for both cell populations. Tensile testing shows that ultimate tensile strength and Young’s modulus approximately ranked with relative density, although MCF-0.9 has a modulus similar to the unfoamed PC (uPC). Toughness measurements show that, when compared to uPC on a critical stress intensity factor basis, MCF-0.9 shows no reduction in toughness and MCF-0.7 shows a 35% reduction. When compared to uPC on strain energy basis, 12–15% increases in toughness are measured for both MCFs. Their fracture occurs by multiple initiation, growth, and coalescence of voids formed at cells acting as stress concentrators. A fine cell morphology results in prolonged growth and coalescence phases, and thus improves fracture toughness.
Description of the Foaming Process During the Extrusion of Foams Based on Renewable Resources
Authors: Potente Helmut , Ernst Wolfgang , Oblotzki Jörg
Published: April 2006

Some polymers based on renewable resources like starch can be plasticated by extrusion processing. Foams based on starch have an increasing importance in nonfood applications. Starch contains water, which works as a physical blowing agent for expansion of molten starch.

The aim of this work is to investigate how cell nucleation and foaming are affected by process parameters in the case of starch materials. Therefore, the cell nucleation has been investigated by a slit die with transparent inserts in the flow channel. It could be shown that a higher pressure gradient in the die leads to a later cell nucleation. Contrary to this, an earlier nucleation is supported by high shear rates. A later nucleation leads to a high cross-sectional expansion ratio.

Furthermore, the rheological properties also have an impact on the foaming behavior of molten starch. It was observed that, besides water content and temperature, the screw speed had a significant impact on the viscosity. In this case, the major effect is the specific mechanical energy input (SME) which increases with increasing screw speed.
The Neglected Dimension of Commercial Liberalism: Economic Cooperation and Transition to Peace
Authors: Press-Barnathan Galia
Published: April 2006

This article examines the role of economic factors in facilitating the transition to peace between former enemies. It examines a less developed angle of the commercial liberalism approach, namely, when and how economic incentives can play a positive role in the process of building peace, rather than the standard focus on how economic interaction can reduce the likelihood of armed conflicts. It does so by distinguishing between two stages in the transition to peace: Stage I of a peace treaty (cold peace) and Stage II (normalization and movement toward warm peace), and by examining the role of economic factors in each of them. The article examines the impact of three factors: (1) the domestic balance of winners and losers from the process; (2) the economic power disparities between the two parties; and (3) the role of third-party (economic) involvement. There are different dynamics in the two stages in the transition to peace, and understanding them also has important practical implications for decisionmakers who want to promote peace. These arguments are examined in a qualitative comparative analysis of the transitions to peace between Egypt and Israel, Jordan and Israel, and Japan and the Philippines and Indonesia. The qualitative method provides a better understanding of the various causal mechanisms linking economic considerations, political considerations, and transition from conflict to peace.
How Peace Agreements Are Derailed: The Evolution of Values in Cyprus, 1959–74
Authors: Kanavou Angeliki Andrea
Published: April 2006

This article investigates the relationship between risk-taking behavior and value prioritization and develops an analytical framework that helps explain where groups stood over time on a high/low conflict continuum in the case of Cyprus (1959–74). It seeks to explain how peace agreements derail by focusing on the evolution of value-frames (the linguistic windows through which we see or interpret) held by agent/stakeholders representing ethnic groups in conflict. A value is an enduring belief that a specific mode of conduct is preferable to an opposite or converse mode of conduct or end-state of existence, and a value system is an enduring organization of beliefs concerning preferable modes of conduct or end-states of existence along a continuum of relative importance. With the use of smallest space analysis (SSA), the article creates a value-based model that could be applied to post-agreement processes to help assess psycho-political readiness to reach agreement or resort to force. The present study suggests monitoring the evolution of the value structures of groups in post-settlement processes to develop a better sense of how decisions to sign peace agreements are reassessed by the former signatories, how groups in conflict adapt to the demands of peace processes, and, as a consequence, how they establish the criteria to evaluate risks and gains.
Guerrilleras in Latin America: Domestic and International Roles
Authors: Gonzalez-Perez Margaret
Published: April 2006

This analysis identifies two different categories of guerrilla organizations and the roles of women within each. Guerrilla movements with ‘international’ agendas typically oppose US imperialism, capitalist expansion, or Western culture in general. ‘Domestic’ guerrilla organizations usually take action against perceived forces of oppression within their own nation. These different agendas have a direct impact on the role of women within them. Internationally oriented guerrilla groups assign traditional, limited gender roles to their female members, while domestic guerrilla organizations challenge domestic prohibitions, including those imposed on women, and encourage full and active participation of female members at all levels of guerrilla activity. This hypothesis is supported by comparative case studies of the groups in question. The study of women's roles within guerrilla movements provides insight into modern political issues, such as insurgencies and other non-traditional methods of warfare. The support of half a population can enable a guerrilla organization to further its objectives considerably, and as female participation increases, the group itself gains power. Thus, an in-depth understanding of women and their relationship to guerrilla movements contributes substantially to peace and conflict studies as well as studies of non-traditional warfare.
The New Rivalry Dataset: Procedures and Patterns
Authors: Klein James P. , Goertz Gary , Diehl Paul F.
Published: April 2006

The 1990s saw the emergence of a new research agenda focused on enduring rivalries, longstanding competitions between the same pair of states. The original Diehl & Goertz dataset on international rivalries has been perhaps the most widely used collection to study those rivalries. Here, that dataset is extended through 2001, and additional criteria beyond the time-density approach are used to define a population of rivalries. In the first half of the article, the conceptual and operational bases on which the original rivalry collection was based are described. The article explores each of the dimensions of the rivalry concept and the associated operational criteria. The ‘linked conflict’ dimension of the rivalry concept is made more explicit in the discussion of rivalry dimensions. The article then presents and discusses all the major changes made vis-‡-vis the earlier rivalry collection. In the second half of the article, empirical analyses highlight the conceptual dimensions of rivalry. Particular attention is devoted to the issue of rivalry symmetry, with an investigation of rival power capabilities. In an analysis on the linked conflict dimension, the article examines war occurrence and sequence in rivalry (most of which occurs at or near the outset of the rivalry) as well as the outcome and waiting times between disputes. The article concludes with a comparison of this dataset to another prominent rivalry collection.
Cue Convergence
Authors: Cho Jaeho , de Zuniga Homero Gil , Shah Dhavan V. , McLeod Douglas M.
Published: April 2006

Studies examining the effects of news cues (i.e., labels used to characterize issue domains and social groups) typically fail to consider the possibility that news stories may contain multiple cues that have interactive effects on audience processing and opinion expression. To test this possibility, the authors conduct a Web survey–embedded experiment that manipulates features of a news report about civil liberties restrictions targeted at Arabs portrayed as either immigrants or citizens and as either extremists or moderates. Hypotheses predict stronger intercorrelations and faster speed of response among a range of social intolerance evaluations when respondents encounter the combination of immigrant and extremist cues. Findings indicate the convergence of immigrant and extremist cues not only yield stronger associations between group evaluations, social intolerance, immigration opposition, and minority disempowerment but also reduce response latencies. The results across these two measures provide support for a theory of associative priming via cue convergence.