Steep Change Research Articles

A statistical framework to quantify spatial variation in channel gradients using the integral method of channel profile analysis

AbstractWe present a statistical technique for analyzing longitudinal channel profiles. Our technique is based on the integral approach to channel analysis: Drainage area is integrated over flow distance to produce a transformed coordinate, χ, which has dimensions of length. Assuming that profile geometry is conditioned by the stream power law, defined as E = KAmSn where E is erosion rate, K is erodibility, A is drainage area, S is channel gradient, and m and n are constants, the slope of a transformed profile in χ‐elevation space should reflect the ratio of erosion rate to channel erodibility raised to a power 1/n; this quantity is often referred to as the channel steepness and represents channel slope normalized for drainage area. Our technique tests all possible contiguous segments in the channel network to identify the most likely locations where channel steepness changes and also identifies the most likely m/n ratio. The technique identifies locations where either erodibility or erosion rates are most likely to be changing. Tests on a simulated landscape demonstrate that the technique can accurately retrieve both the m/n ratio and the correct number and location of segments eroding at different rates where model assumptions apply. Tests on natural landscapes illustrate how the method can distinguish between spurious channel convexities due to incorrect selection of the m/n ratio from those which are candidates for changing erodibility or erosion rates. We also show how, given erosion or uplift rate constraints, the method can be used to constrain the slope exponent, n.

The Behavior of Zeta Potential of Silica Suspensions

Zeta potential is one of the most relevant parameters controlling the rheological behavior of ceramic suspensions. In this work, it was observed that for pH values below the isoelectric point (IEP), the positive value of zeta potential of water suspensions of α-quartz and α-cristobalite, experiences a sudden steep increase with the increase in specific surface area of the powders. For pH values above the IEP, the zeta potential values of crystalline forms of silica (α-quartz and α-cristobalite), get gradually more negative with the increase in pH. Conversely in the case of vitreous silica, for pH values above 6, there occurs a steep change towards more negative values of zeta potential than those presented by quartz and cristobalite. These findings have not yet been accounted for in the DLVO theory but may provide subsidies for better understanding of how to stabilize and destabilize crystalline and vitreous silica water suspensions.

Stochastic Modeling of Polyethylene Glycol as a Suppressor in Copper Electroplating

The desorption / adsorption of suppressor additive during Cu electroplating plays a critical role in the void-free filling of recessed features such as through-silicon vias (TSVs) used in 3-dimensional integration. A stochastic model was proposed for Polyethylene Glycol (PEG) as a suppressor additive in Cu electroplating. Using the proposed model, a program capable of simulating transient processes such as cyclic voltammograms (CVs) was developed. The steep change of current density due to suppressor desorption, as well as the characteristic hysteresis, observed in the CVs was shown in simulation. The dependency of PEG desorption / adsorption on various factors, including the bath composition, scan rate and molecular weight, was simulated. The simulation results were confronted side-by-side with the corresponding experimental measurements. An overall good qualitative match was shown.

Two-Dimensional Variable Property Conjugate Heat Transfer Simulation of Nanofluids in Microchannels

Laminar two-dimensional forced convective heat transfer of CuO-water and Al2O3-water nanofluids in a horizontal microchannel has been studied numerically, considering axial conduction effects in both solid and liquid regions and variable thermal conductivity and dynamic viscosity. The results show that using nanoparticles with higher thermal conductivities will intensify enhancement of heat transfer characteristics and slightly increases shear stress on the wall. The obtained results show more steep changes in Nusselt number for lower diameters and also higher values of Nusselt number by decreasing the diameter of nanoparticles. Also, by utilizing conduction number as the criterion, it was concluded from the results that adding nanoparticles will intensify the axial conduction effect in the geometry considered.

Signal and contrast effects due to T2 decay during k-space readout of UTE (ultrashort TE) sequences

In ultrashort TE (UTE) imaging, the short T2 values of the tissues of interest are comparable to the k-space readout duration, which result in significant T2 decay during k-space readout. This decay consequently causes significant effects on signal and contrast in UTE sequences, which we evaluate in this paper using models that incorporate the gradient slew rate slew and maximal constant gradient strength gmax, in conjunction with objects of diameter L. The resulting signal and contrast relationships demonstrate steep signal changes between T2 values of ~50–500μs, corresponding to high T2 weighted contrast in this range. When γ⋅gmax2/(4π⋅slew)>1/(2L), termed the “ramp only” regime, gmax has no significant effect whereas decreasing slew leads to decreases in signal amplitude and shifts the contrast peak to higher T2 values. When γ⋅gmax2/(4π⋅slew)<1/(2L), termed the “mixed gradient” regime, both gmax and slew have significant effects, where decreases in either gmax or slew lead to lower signal amplitudes and shifts the contrast peak to higher T2 values. Under typical scan settings, the “ramp only” regime is usually dominant. Further, we demonstrate an unusual dependence of T2 weighted signal and contrast on object size, whereby objects with smaller values of L demonstrate lower signal amplitudes and peak contrast at higher T2 values, compared to otherwise identical objects with larger L. These results improve understanding of T2 weighted signal and contrast properties in short T2 tissue imaging with UTE.

Seismic Affection Analysis of Weir Dam Based on 3-D FEM

The vibrant-type-disintegration method is applied to calculate structure seismic action of a weir dam. Based on calculation and analysis of the weir dam, special attention is paid to the stress state of key parts. The results show that the displacement and stress of weir dam are affected by earthquake excitation direction. Since large principal tensile stress appears in the joint of girder and pier, and the zone of principal tensile stress is large because of the thrust of radial gate and steep changes of geometry shape, we should pay special attention when calculating anti-seismic checking and reinforcement arrangement.

Seismic Behavior Analysis of Spillway Weir Section Based on ANSYS

The response spectrum method was applied to calculate the seismic behavior analysis of a spillway weir gate. Based on the analysis of the structure performance, special attentions were paid to the stress state of the key parts on the surface and root of the pier. The results showed that the displacement and stress of the whole structure were related to the direction of earthquake excitation; large principal tensile stress and principal tensile stress area appeared in steep change points of geometry shape, special attention should be paid when calculating anti-seismic checking and reinforcement arrangement; the displacement and stress of the weir section met the standard requirements.

Difficult diagnosis of malignant hyperthermia during laparoscopic surgery

Difficult diagnosis of malignant hyperthermia during laparoscopic surgery

Theory of Gradient Elution Liquid Chromatography with Linear Solvent Strength: Part 1. Migration and Elution Parameters of a Solute Band

Based on the previous theoretical developments most notably by Snyder, this report offers the most complete theoretical framework of gradient elution LC with linear solvent strength (LSS). All statements of the theory are formulated as explicit mathematical expressions. The physics of chromatography in general and of the LSS model in particular were used only to justify the most basic mathematical expressions of the framework. Everything else was obtained by means of verifiable mathematical transformations. The framework was used for derivation of the largest systematic collection of mathematical expressions describing migration and elution parameters of a solute band. Majority of these expressions are new. They include not only the elution parameters of a band, but also previously unknown migration parameters as functions of distance and time traveled by the band. The set of the band parameters in this report was chosen on the basis of the needs for the study of the peak width formation (part 2 of this series) and for detailed study of performance of gradient LC similar to that recently published for temperature-programed GC. As an illustration of the utility of several parameters considered here, a simple way of prediction of a possibility of the reversal of a solute elution order due to the change in the gradient steepness has been found.

Synthesis and properties of novel chiral side-chain liquid crystalline polysiloxanes containing different chiral pendant groups

Two novel chiral liquid crystalline monomers, and a series of their corresponding chiral side-chain polymers (P1–P7) based on poly(methylhydrogeno)siloxane have been prepared. The chemical structures and liquid crystalline properties of the synthesized monomers and polymers have been investigated using various experimental techniques. Thermal analysis shows that all polymers have wide mesophase temperature ranges with a high thermal stability. With the increase of M2 molar ratio in the polymer systems, the isotropic phase transition and glass transition temperatures of all polymers increase, and the temperature ranges of N* phase and mesophase become broad. The effect of cholesteryl mesogens on mesophase behaviors, optical properties, and molecular arrangement of LC polysiloxanes and their advanced applications have also been discussed. For homopolymer P1, it shows a single SA phase. With increasing the content of M2 in the polymer systems, P2 and P3 reveal a SA–N* phase transition when they are heated, and P4–P7 reveal a N* phase. For N* phase polymers P4–P7, the reflection wavelengths exhibit blue shift, suggesting that the pitch decreases with a decrease in the amount of the smectic domains induced by the M1. The reflection wavelengths of P4–P7 are almost across the entire visible region when they are heated, which offer stremendous potential for various optical applications. For P2 and P3, the reflection wavelengths show a very steep change around the temperature of the SA–N* phase transition, which can be used as thermally sensitive liquid crystal devices requiring fast response, such as sensors, and thermally induced tuning.

Flow variability and longitudinal patterns in parafluvial water chemistry, aquatic invertebrates and microbial activity

Summary Parafluvial zones occur in emergent gravel bars and other river sediment structures where exchange with surface water is limited to horizontal inflow and outflow. Within parafluvial zones, interstitial water flows down longitudinal flowpaths in response to hydraulic-head gradients. Changes in physical and biogeochemical conditions along these flowpaths lead to the formation of longitudinal gradients in solute concentrations, biota and microbial activity. The influence of river-flow variability on interstitial residence times, flowpath sizes and solute influx suggests that flow variability also affects longitudinal gradients in parafluvial zones. We studied associations between longitudinal gradients and flow variation in the forms of flow fluctuations and variable water sources. We used data from parafluvial zones in a New Zealand river to test four predictions: (i) longitudinal gradients in solutes, invertebrates and microbial activity are steeper in runoff-dominated losing and neutral reaches compared with groundwater-dominated gaining reaches; (ii) moderate-to-large floods eliminate longitudinal gradients, which reform during recessions; (iii) between floods, gradients in parafluvial chemistry change in steepness and direction in response to changes in river-flow levels; and (iv) between floods, invertebrate abundance and diversity are positively related to river flow. In Study 1, we measured solute concentrations, invertebrate composition and microbial activity over a range of flow levels in vegetated gravel bars with contrasting water sources (alluvial groundwater in a gaining reach, and hillslope runoff in losing and neutral reaches). In Study 2, we made repeated measurements in unvegetated gravel bars before and after a one-in-2-year flood to assess its effects on longitudinal gradients in nutrients and invertebrate communities. In Study 1, we detected gradients along parafluvial flowpaths in , dissolved reactive phosphorus and major ion concentrations and in pH, electrical conductivity and invertebrate density. There was little congruence between bars in different reaches, or among variables; some gradients became steeper as flow increased, and others shifted from negative to positive or vice versa or approached zero. Parafluvial chemistry was strongly affected by water source; median concentrations of most solutes were 2–20 times higher in the groundwater-dominated parafluvial zone than in the runoff-dominated parafluvial zones. Prior to the flood during Study 2, the parafluvial zones were characterised by negative longitudinal gradients in dissolved organic carbon (DOC) and dissolved organic N (DON) and positive gradients in . These gradients were eliminated by the flood, but and DOC gradients redeveloped during the post-flood period. Differences between the steepness and direction of gradients in Study 1 and the pre-flood period in Study 2 may be related to differences in terrestrial vegetation, as well as differences in flow regimes. Associations between river-flow levels and parafluvial invertebrate communities differed in the two studies, which corresponded to different flow ranges. Invertebrate density and taxon richness were positively correlated with flow over a range of low flows in Study 1, but there was no detectable correlation over a range of high flows in Study 2. These results suggest that beneficial effects of flow fluctuations on invertebrate communities peak at moderate flow levels, beyond which invertebrate–flow relationships become unstable.

Measuring the forces generated by erosive debris flows

Like water flows, debris flows can carve out steep valleys and change landscapes. By studying the mechanics of bedrock incision caused by flowing debris, scientists are better able to understand patterns and rates of landscape evolution. Laboratory studies and models have shown how flowing granular materials can cut into rock, but field measurements are needed to confirm the findings and provide information about the more complex natural environment.

PH variation and influence in an autotrophic nitrogen removing biofilm system using an efficient numerical solution strategy

A pH simulator consisting of an efficient numerical solver of a system of nine nonlinear equations was constructed and implemented in the modeling software MATLAB. The pH simulator was integrated in a granular biofilm model and used to simulate the pH profiles within granules performing the nitritation-anammox process for a range of operating points. The simulation results showed that pH profiles were consistently increasing with increasing depth into the granule, since the proton-producing aerobic ammonium-oxidizing bacteria (AOB) were located close to the granule surface. Despite this pH profile, more NH3 was available for AOB than for anaerobic ammonium oxidizers, located in the center of the granules. However, operating at a higher oxygen loading resulted in steeper changes in pH over the depth of the granule and caused the NH3 concentration profile to increase from the granule surface towards the center. The initial value of the background charge and influent bicarbonate concentration were found to greatly influence the simulation result and should be accurately measured. Since the change in pH over the depth of the biofilm was relatively small, the activity potential of the microbial groups affected by the pH did not change more than 5% over the depth of the granules.

Sex-biased parasitism is not universal: evidence from rodent–flea associations from three biomes

The distribution of parasites among individual hosts is characterised by high variability that is believed to be a result of variations in host traits. To find general patterns of host traits affecting parasite abundance, we studied flea infestation of nine rodent species from three different biomes (temperate zone of central Europe, desert of Middle East and tropics of East Africa). We tested for independent and interactive effects of host sex and body mass on the number of fleas harboured by an individual host while accounting for spatial clustering of host and parasite sampling and temporal variation. We found no consistent patterns of the effect of host sex and body mass on flea abundance either among species within a biome or among biomes. We found evidence for sex-biased flea infestation in just five host species (Apodemus agrarius, Myodes glareolus, Microtus arvalis, Gerbillus andersoni, Mastomys natalensis). In six rodent species, we found an effect of body mass on flea abundance (all species mentioned above and Meriones crassus). This effect was positive in five species and negative in one species (Microtus arvalis). In M. glareolus, G. andersoni, M. natalensis, and M. arvalis, the relationship between body mass and flea abundance was mediated by host sex. This was manifested in steeper change in flea abundance with increasing body mass in male than female individuals (M. glareolus, G. andersoni, M. natalensis), whereas the opposite pattern was found in M. arvalis. Our findings suggest that sex and body mass are common determinants of parasite infestation in mammalian hosts, but neither of them follows universal rules. This implies that the effect of host individual characteristics on mechanisms responsible for flea acquisition may be manifested differently in different host species.

Abstract 4802: Gender disparity in esophageal cancer incidence.

Abstract Introduction: Over the past thirty years, esophageal cancer (EC) incidence has been increasing more rapidly than any other solid neoplasm in the Western world. Globally, there is a large male predominance in both esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). The reasons for this gender difference and the possible role of estrogen remains unclear. We conducted an analytical epidemiological study to determine if estrogen exposure explains the male predominance in observed esophageal cancer incidence. Materials/Methods: We evaluated the Surveillance Epidemiology and End Results (SEER) cancer incidence trends from 1975 to 2008 using SEER Stat to calculate the annual percentage change (APC) in each five year age group and in EAC and ESCC by gender. Results: Male predominance in incidence rates of EC was most evident in the younger population and those with EAC histology as previously demonstrated. EAC and ESCC incidence rates both increases with aging, consistent with cancer being an age-related disease, but the male: female incidence ratio of EAC significantly decreased with aging. The rate of increase for EAC incidence in post menopausal females is greater than in any other demographic category. This increasing incidence rate in the post menopausal female was also observed in the ESCC, but to a lesser extent. The APC was negative (-1.5) between 1975-2008 only in the 50-64 age female cohort. Interestingly, the APC doubled in the last two age groupings of older females (age 65-74 = + 0.3 and age 75 and greater = + 0.7). APC rates for the males increased gradually in all their age groups (age 50-64 = +1.2, age 65-74 = +1.4, age 75+ = +1.9). Conclusions: The males’ incidence of EAC increases at a steep rate with aging and females’ incidence rates are not as steep except after age 60-64 where their incidence rate of change steeply increases. The steeper change in EAC incidence rates in the post menopausal female may explain why the male: female EAC incidence ratio decreases with age as seen nationally (SEER). The negative APC in the female 50-64 years age group may be explained by their peri-menopausal state and by the increased use of post-menopausal hormonal therapy since 1975 for this age group. Using age as a proxy for estrogen exposure, our findings suggest a hormonal component for the observed age-related, declining male to female EAC incidence rate ratios. It also confirms gender differences in incidence long observed in EC and suggests that the pre-menopausal estrogen milieu in females may serve as a protective factor against EAC. Moreover, this protective state dissipates with time in the post menopausal females where the effect of estrogen exposure dissipates. Implications: Our initial epidemiological observation of gender-age differences warrants translation into a molecular epidemiology study with the use of sophisticated biomarkers to establish the seemingly protective role of estrogen exposure in esophageal adenocarcinoma. Citation Format: Luckson N. Mathieu, Norma Kanarek, Craig Hooker, Malcolm Brock. Gender disparity in esophageal cancer incidence. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4802. doi:10.1158/1538-7445.AM2013-4802

Inductive reasoning, domain specific and complex problem solving: Relations and development

This paper focuses on three different types of reasoning: domain-specific problem solving, complex (general) problem solving, and inductive reasoning. The objective of the study is to examine the differences in the developmental levels of inductive reasoning, domain-specific problem solving, and complex problem solving between three age groups and to describe the relations between the three constructs. The sample was drawn from 3rd to 11th grade students (aged 9–17) in Hungarian primary and secondary schools. There were 300–400 students in each cohort. The internal consistencies of the tests were good: Chronbach α varied between .72 and .95. Each of the skills showed a developmental tendency that could be identified with a logistic curve. In every area the pace of development proved to be relatively slow and the steepest change took place in Grade 7. The bivariate correlations between the three constructs were moderate ranging from .35 to .44 signalling that they do not constitute the same construct. The strength of the relationships between inductive reasoning and complex problem solving proved to be the most stable over time. The correlations between domain-specific and complex problem solving showed an increasing trend over time indicating that the strategies used in different problem solving situations become more similar with age. This study provides evidence that inductive reasoning, domain-specific problem solving and complex problem solving are related but distinct constructs and these skills can be fostered most efficiently between Grades 6 and 8.

Monitoring data requirements for shoreline prediction: How much, how long, and how often?

Splinter, K.D., Davidson, M.A., and Turner, I.L. Monitoring data requirements for shoreline prediction: How much, how long, and how often?Predicting future shoreline position and the subsequent vulnerability of coastal communities is of great interest to coastal managers and engineers. A number of empirically-based equilibrium shoreline models have been proposed, but all have been formulated on unique and relatively short-term datasets. As such, the transferability and calibration sensitivity of these models is unknown. Here we use a newly developed shoreline model, ShoreFor, driven by changes in offshore wave steepness and wave power, to determine model calibration coefficient sensitivity based on two key constraints in any monitoring program: 1) the duration of data collection of necessary shoreline and wave data (N); and, 2) the shoreline sampling interval (dt). The analysis was undertaken at two distinct sites: a 5-year data set from Gold Coast, QLD, Australia, a long, straight, open coast comprising medium grain sand with a strong annual cycle in the shoreline; and a 6-year data set from Narrabeen-Collaroy, NSW, Australia, which is a coarser, swash-aligned embayed beach whose shoreline variability is driven predominately by storms. In both cases, shoreline data were extracted weekly from video imagery and hourly offshore wave data were obtained from buoy measurements. Shoreline calibration datasets were then sub-sampled in both time (N) and frequency (dt). Results presented in this paper suggest calibration dataset requirements are beach-type dependent and linked to the rates of sediment exchange between the nearshore and shoreline. The storm-dominated site, Narrabeen-Collaroy, required more frequently sampled shoreline data to converge on model free parameters and maintain model hindcast normalized mean square error (NMSE) below 0.5. As a general ‘rule of thumb' a minimum of two years, sampled at dt ≤30 days was required to consistently resolve model coefficients at both sites, while calibration datasets longer than three years (roughly 50% of the data set) resulted in minimal improvement in model hindcast skill at the two sites examined.

Learned Vocal Variation Is Associated with Abrupt Cryptic Genetic Change in a Parrot Species Complex

Contact zones between subspecies or closely related species offer valuable insights into speciation processes. A typical feature of such zones is the presence of clinal variation in multiple traits. The nature of these traits and the concordance among clines are expected to influence whether and how quickly speciation will proceed. Learned signals, such as vocalizations in species having vocal learning (e.g. humans, many birds, bats and cetaceans), can exhibit rapid change and may accelerate reproductive isolation between populations. Therefore, particularly strong concordance among clines in learned signals and population genetic structure may be expected, even among continuous populations in the early stages of speciation. However, empirical evidence for this pattern is often limited because differences in vocalisations between populations are driven by habitat differences or have evolved in allopatry. We tested for this pattern in a unique system where we may be able to separate effects of habitat and evolutionary history. We studied geographic variation in the vocalizations of the crimson rosella (Platycercus elegans) parrot species complex. Parrots are well known for their life-long vocal learning and cognitive abilities. We analysed contact calls across a ca 1300 km transect encompassing populations that differed in neutral genetic markers and plumage colour. We found steep clinal changes in two acoustic variables (fundamental frequency and peak frequency position). The positions of the two clines in vocal traits were concordant with a steep cline in microsatellite-based genetic variation, but were discordant with the steep clines in mtDNA, plumage and habitat. Our study provides new evidence that vocal variation, in a species with vocal learning, can coincide with areas of restricted gene flow across geographically continuous populations. Our results suggest that traits that evolve culturally can be strongly associated with reduced gene flow between populations, and therefore may promote speciation, even in the absence of other barriers.

An Overview of Strut-and-Tie Model and its Common Challenges

B-Regions are parts of the structure in which Bernoulli's principle of straight-line strain is used. D-Regions are parts of the structure with a complicated variation in strain. In essence, D-Regions contain the parts of structure which are near to the concentrated forces or steep changes in geometry which are so-called geometrical discontinuities or static discontinuities. Strut-and-Tie Model (STM) is one of the best models to analyse the D-regions. Nevertheless, according to the existing literature, there are still some challenges about STM which are addressed in this paper. STM and its details are investigated to show its common challenges presents some recommendations to overcome these challenges. According to this review, the major challenges in STM are related to the strut effectiveness factor, static uncertainties of STM, strain compatibility, and anchorage requirements in STM. The scope of this research is confined to the two dimensional STM.

Microstructure transformation of PDMS-E grafted gelatin polymers induced by SDS and SDBS

Inorganic–organic hybrid materials with tunable chemical and physical properties were prepared from mono epoxy terminated polydimethylsiloxane (PDMS) macromonomer and gelatin for improving their flexibility and hydrophobicity. Sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) were used to enhance the compatibility of two polymers phases. Measurement of grafting density indicated that anionic surfactants played a crucial role in deciding the detailed microstructure of PDMS-E grafted gelatin (PGG) polymers in alkaline solution. The interaction between gelatin and SDS/SDBS was investigated by viscosity and SEM. Viscosity analysis showed a regular increase in SDS system and a steeper change in the case of SDBS. SEM micrographs displayed a series of structural transitions (spherical, spindle, irregular granular and spherical aggregates) with the increase of SDS concentration, but spindle and granular aggregates appeared alternately as varying SDBS concentrations. The results demonstrated that both the electrostatic and hydrophobic interactions between anionic surfactant and gelatin controlled the aggregate structure of gelatin–SDS/SDBS, which affected the compatibility between gelatin and PDMS. Thermal properties of PGG polymers had changed with the modification of polymer microstructure. The results above revealed that microstructure transformation of PGG polymers was determined by the compatibility of two polymers in anionic surfactant aqueous solution and the chemical nature of their monomers.