Validation of the New Mix Design Process for Cold In-Place Rehabilitation Using Foamed Asphalt, 2007

Asphalt pavement recycling has grown dramatically over the last few years as a viable technology to rehabilitate existing asphalt pavements. Iowa's current Cold In-place Recycling (CIR) practice utilizes a generic recipe specification to define the characteristics of the CIR mixture. As CIR continues to evolve, the desire to place CIR mixture with specific engineering properties requires the use of a mix design process. A new mix design procedure was developed for Cold In-place Recycling using foamed asphalt (CIR-foam) in consideration of its predicted field performance. The new laboratory mix design process was validated against various Reclaimed Asphalt Pavement (RAP) materials to determine its consistency over a wide range of RAP materials available throughout Iowa. The performance tests, which include dynamic modulus test, dynamic creep test and raveling test, were conducted to evaluate the consistency of a new CIR-foam mix design process to ensure reliable mixture performance over a wide range of traffic and climatic conditions. The “lab designed” CIR will allow the pavement designer to take the properties of the CIR into account when determining the overlay thickness.

A gated single-photon avalanche diode array fabricated in a conventional CMOS process for triggered systems

A bidimensional array based on single-photon avalanche diodes for triggered imaging systems is presented. The diodes are operated in the gated mode of acquisition to reduce the probability to detect noise counts interfering with photon arrival events. In addition, low reverse bias overvoltages are used to lessen the dark count rate. Experimental results demonstrate that the prototype fabricated with a standard HV-CMOS process gets rid of afterpulses and offers a reduced dark count probability by applying the proposed modes of operation. The detector exhibits a dynamic range of 15 bits with short gated"on" periods of 10ns and a reverse bias overvoltage of 1.0V.

Condensation of helium in nanoscopic alkali wedges at zero temperature

We present a complete calculation of the structure of liquid 4He confined to a concave nanoscopic wedge, as a function of the opening angle of the walls. This is achieved within a finite-range density functional formalism. The results here presented, restricted to alkali metal substrates, illustrate the change in meniscus shape from rather broad to narrow wedges on weak and strong alkali adsorbers, and we relate this change to the wetting behavior of helium on the corresponding planar substrate. As the wedge angle is varied, we find a sequence of stable states that, in the case of cesium, undergo one filling and one emptying transition at large and small openings, respectively. A computationally unambiguous criterion to determine the contact angle of 4He on cesium is also proposed.

Helium in polygonal nanopores at zero temperature: Density functional theory calculations

We investigate adsorption of helium in nanoscopic polygonal pores at zero temperature using a finite-range density functional theory. The adsorption potential is computed by means of a technique denoted as the elementary source method. We analyze a rhombic pore with Cs walls, where we show the existence of multiple interfacial configurations at some linear densities, which correspond to metastable states. Shape transitions and hysterectic loops appear in patterns which are richer and more complex than in a cylindrical tube with the same transverse area.

Natural selection in a postglacial range expansion: the case of the colour cline in the European barn owl.

Gradients of variation-or clines-have always intrigued biologists. Classically, they have been interpreted as the outcomes of antagonistic interactions between selection and gene flow. Alternatively, clines may also establish neutrally with isolation by distance (IBD) or secondary contact between previously isolated populations. The relative importance of natural selection and these two neutral processes in the establishment of clinal variation can be tested by comparing genetic differentiation at neutral genetic markers and at the studied trait. A third neutral process, surfing of a newly arisen mutation during the colonization of a new habitat, is more difficult to test. Here, we designed a spatially explicit approximate Bayesian computation (ABC) simulation framework to evaluate whether the strong cline in the genetically based reddish coloration observed in the European barn owl (Tyto alba) arose as a by-product of a range expansion or whether selection has to be invoked to explain this colour cline, for which we have previously ruled out the actions of IBD or secondary contact. Using ABC simulations and genetic data on 390 individuals from 20 locations genotyped at 22 microsatellites loci, we first determined how barn owls colonized Europe after the last glaciation. Using these results in new simulations on the evolution of the colour phenotype, and assuming various genetic architectures for the colour trait, we demonstrate that the observed colour cline cannot be due to the surfing of a neutral mutation. Taking advantage of spatially explicit ABC, which proved to be a powerful method to disentangle the respective roles of selection and drift in range expansions, we conclude that the formation of the colour cline observed in the barn owl must be due to natural selection.

Laser-induced forward transfer of liquids: Study of the droplet ejection process

Laser-induced forward transfer (LIFT) is a laser direct-write technique that offers the possibility of printing patterns with a high spatial resolution from a wide range of materials in a solid or liquid state, such as conductors, dielectrics, and biomolecules in solution. This versatility has made LIFT a very promising alternative to lithography-based processes for the rapid prototyping of biomolecule microarrays. Here, we study the transfer process through the LIFT of droplets of a solution suitable for microarray preparation. The laser pulse energy and beam size were systematically varied, and the effect on the transferred droplets was evaluated. Controlled transfers in which the deposited droplets displayed optimal features could be obtained by varying these parameters. In addition, the transferred droplet volume displayed a linear dependence on the laser pulse energy. This dependence allowed determining a threshold energy density value, independent of the laser focusing conditions, which acted as necessary conditions for the transfer to occur. The corresponding sufficient condition was given by a different total energy threshold for each laser beam dimension. The threshold energy density was found to be the dimensional parameter that determined the amount of the transferred liquid per laser pulse, and there was no substantial loss of material due to liquid vaporization during the transfer.

Optimization of Soil Stabilization with Class C Fly Ash, January 1987

Previous Iowa DOT sponsored research has shown that some Class C fly ashes are ementitious (because calcium is combined as calcium aluminates) while other Class C ashes containing similar amounts of elemental calcium are not (1). Fly ashes from modern power plants in Iowa contain significant amounts of calcium in their glassy phases, regardless of their cementitious properties. The present research was based on these findings and on the hyphothesis that: attack of the amorphous phase of high calcium fly ash could be initiated with trace additives, thus making calcium available for formation of useful calcium-silicate cements. Phase I research was devoted to finding potential additives through a screening process; the likely chemicals were tested with fly ashes representative of the cementitious and non-cementitious ashes available in the state. Ammonium phosphate, a fertilizer, was found to produce 3,600 psi cement with cementitious Neal #4 fly ash; this strength is roughly equivalent to that of portland cement, but at about one-third the cost. Neal #2 fly ash, a slightly cementitious Class C, was found to respond best with ammonium nitrate; through the additive, a near-zero strength material was transformed into a 1,200 psi cement. The second research phase was directed to optimimizing trace additive concentrations, defining the behavior of the resulting cements, evaluating more comprehensively the fly ashes available in Iowa, and explaining the cement formation mechanisms of the most promising trace additives. X-ray diffraction data demonstrate that both amorphous and crystalline hydrates of chemically enhanced fly ash differ from those of unaltered fly ash hydrates. Calciumaluminum- silicate hydrates were formed, rather than the expected (and hypothesized) calcium-silicate hydrates. These new reaction products explain the observed strength enhancement. The final phase concentrated on laboratory application of the chemically-enhanced fly ash cements to road base stabilization. Emphasis was placed on use of marginal aggregates, such as limestone crusher fines and unprocessed blow sand. The nature of the chemically modified fly ash cements led to an evaluation of fine grained soil stabilization where a wide range of materials, defined by plasticity index, could be stabilized. Parameters used for evaluation included strength, compaction requirements, set time, and frost resistance.

Objective assessment of image quality in conventional and digital mammography taking into account dynamic range.

The goal of this work is to develop a method to objectively compare the performance of a digital and a screen-film mammography system in terms of image quality. The method takes into account the dynamic range of the image detector, the detection of high and low contrast structures, the visualisation of the images and the observer response. A test object, designed to represent a compressed breast, was constructed from various tissue equivalent materials ranging from purely adipose to purely glandular composition. Different areas within the test object permitted the evaluation of low and high contrast detection, spatial resolution and image noise. All the images (digital and conventional) were captured using a CCD camera to include the visualisation process in the image quality assessment. A mathematical model observer (non-prewhitening matched filter), that calculates the detectability of high and low contrast structures using spatial resolution, noise and contrast, was used to compare the two technologies. Our results show that for a given patient dose, the detection of high and low contrast structures is significantly better for the digital system than for the conventional screen-film system studied. The method of using a test object with a large tissue composition range combined with a camera to compare conventional and digital imaging modalities can be applied to other radiological imaging techniques. In particular it could be used to optimise the process of radiographic reading of soft copy images.

Assessing small non-zero perceptions of chance: The case of H1N1 (swine) flu risks

Feelings of invulnerability, seen in judgments of 0% risk, can reflect misunderstandings of risk and risk behaviors, suggesting increased need for risk communication. However, judgments of 0% risk may be given by individuals who feel invulnerable, and by individuals who are rounding from small non-zero probabilities. We examined the effect of allowing participants to give more precise responses in the 0-1% range on the validity of reported probability judgments. Participants assessed probabilities for getting H1N1 influenza and dying from it conditional on infection, using a 0-100% visual linear scale. Those responding in the 0-1% range received a follow-up question with more options in that range. This two-step procedure reduced the use of 0% and increased the resolution of responses in the 0-1% range. Moreover, revised probability responses improved predictions of attitudes and self-reported behaviors. Hence, our two-step procedure allows for more precise and more valid measurement of perceived invulnerability. [Authors]

Assessment of skinfold thickness equations in estimating body composition in children with inflammatory bowel

Introduction: Growth is a central process in paediatrics. Weight and height evaluation are therefore routine exams for every child but in some situation, particularly inflammatory bowel disease (IBD), a wider evaluation of nutritional status needs to be performed. The assessment of body composition is essential in order to maintain acceptable growth using the following techniques: Dual-energy X-ray absorptiometry (DEXA), bio-impedance-analysis (BIA) and anthropometric measurements (skinfold thickness skin), the latter being most easily available and most cost effective. Objectives: To assess the accuracy of skinfold equations in estimating percentage body fat (%BF) in children with inflammatory bowel disease (IBD), compared with assessment of body fat dual energy X-ray absorptiometry (DEXA). Methods: Twenty-one patients (11 females, 10 males; mean age: 14.3 years, range 12 - 16 years) with IBD (Crohn's disease n = 15, ulcerative colitis n = 6)). Estimated%BF was computed using 6 established equations based on the triceps, biceps, subscapular and suprailiac skinfolds (Deurenberg, Weststrate, Slaughter, Durnin & Rahaman, Johnston, Brook) and compared to DEXA. Concordance analysis was performed using Lin's concordance correlation and the Bland-Altman limits of agreement method. Results: Durnin & Rahaman's equation shows a higher Lin's concordance coefficient with a small difference amongst raw values for skinfolds and DEXA compared to the other equations. Correlation coefficient between mean and difference is close to zero with a non-significant Bradley-Blackwood test. Conclusion: Body composition in paediatric IBD patients using the Durnin & Rahaman skinfold-equation adequately reflects values obtained by DEXA.

Space Competition and Time Delays in Human Range Expansions. Application to the Neolithic Transition

Space competition effects are well-known in many microbiological and ecological systems. Here we analyze such an effectin human populations. The Neolithic transition (change from foraging to farming) was mainly the outcome of a demographic process that spread gradually throughout Europe from the Near East. In Northern Europe, archaeological data show a slowdown on the Neolithic rate of spread that can be related to a high indigenous (Mesolithic) population density hindering the advance as a result of the space competition between the two populations. We measure this slowdown from a database of 902 Early Neolithic sites and develop a time-delayed reaction-diffusion model with space competition between Neolithic and Mesolithic populations, to predict the observed speeds. The comparison of the predicted speed with the observations and with a previous non-delayed model show that both effects, the time delay effect due to the generation lag and the space competition between populations, are crucial in order to understand the observations

Multiple introductions boosted genetic diversity in the invasive range of black cherry (Prunus serotina; Rosaceae).

BACKGROUND AND AIMS: Black cherry (Prunus serotina) is a North American tree that is rapidly invading European forests. This species was introduced first as an ornamental plant, then it was massively planted by foresters in many countries, but its origins and the process of invasion remain poorly documented. Based on a genetic survey of both native and invasive ranges, the invasion history of black cherry was investigated by identifying putative source populations and then assessing the importance of multiple introductions on the maintenance of gene diversity. METHODS: Genetic variability and structure of 23 populations from the invasive range and 22 populations from the native range were analysed using eight nuclear microsatellite loci and five chloroplast DNA regions. KEY RESULTS: Chloroplast DNA diversity suggests there were multiple introductions from a single geographic region (the north-eastern United States). A low reduction of genetic diversity was observed in the invasive range for both nuclear and plastid genomes. High propagule pressure including both the size and number of introductions shaped the genetic structure in Europe and boosted genetic diversity. Populations from Denmark, The Netherlands, Belgium and Germany showed high genetic diversity and low differentiation among populations, supporting the hypothesis that numerous introduction events, including multiple individuals and exchanges between sites, have taken place during two centuries of plantation. CONCLUSIONS: This study postulates that the invasive black cherry has originated from east of the Appalachian Mountains (mainly the Allegheny plateau) and its invasiveness in north-western Europe is mainly due to multiple introductions containing high numbers of individuals.

Variation of grain nitrogen content in relation with grain yield in old and modern Spanish wheats grown under a wide range of agronomic conditions in a Mediterranean region

Wheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/ 07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0.75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content ; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0.13 to 0.40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0.22 (mean of the four manipulative experiments) in the oldest cultivar to 0.51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

Breaking up the writing process: how wikis can support understanding the composition and revision strategies of young writers

Understanding how best to support immature writers in the development of their understanding of the writing process is an important concern for researchers and teachers. Social technologies have become key features of leisure and work place writing, yet knowledge about how to design educational settings that take full advantage of the affordances of web 2.0 technologies to support early writing is scarce. This paper presents a small scale study that investigated how writing in a wiki environment might facilitate and support students’ use of composition and revision strategies. Our findings show that wiki can enlarge young writers’ experience of the process of composition and revision both through their own efforts and by observing the process in others. In this study students employed a wide range of types of revisions both surface and text based changes. These revisions took place during the process of composition as well as at the end. It is argued here that writing in a wiki not only provides young writers with experience of a mode of composition prevalent in the contemporary work environment, but breaks up the process of writing in a way that may support students’ understanding of the processes of composition and revision.