Direct measurement of the reaction front in chemically amplified photoresists

The continuing drive by the semiconductor industry to fabricate smaller structures using photolithography will soon require dimensional control at length scales comparable to the size of the polymeric molecules in the materials used to pattern them. The current technology, chemically amplified photoresists, uses a complex reaction-diffusion process to delineate patterned areas with high spatial resolution. However, nanometer-level control of this critical process is limited by the lack of direct measurements of the reaction front. We demonstrate the use of x-ray and neutron reflectometry as a general method to measure the spatial evolution of the reaction-diffusion process with nanometer resolution. Measuring compositional profiles, provided by deuterium-labeled reactant groups for neutron scattering contrast, we show that the reaction front within the material is broad rather than sharply defined and the compositional profile is altered during development. Measuring the density profile, we directly correlate the developed film structure with that of the reaction front.     

Pyroclastic activity at Home Plate in Gusev Crater, Mars

Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.     

Declines in abundance and distribution of the ivory gull (Pagophila eburnea) in Arctic Canada

The ivory gull (Pagophila eburnea) is a seabird that inhabits Arctic oceans throughout the year, often in association with polar pack ice. It is rare (<14,000 breeding pairs globally) and remains one of the most poorly known seabird species in the world. Canada supports breeding populations of international significance, and residents of communities in the Canadian High Arctic currently observe fewer ivory gulls than they did in the 1980s. However, no population trend data existed for this species in Canada prior to this study. We initiated aerial surveys in July 2002 and 2003 of most known ivory gull colonies in Canada to assess current population levels. Forty two colonies were visited, 14 of which were new discoveries. We recorded an 80% decline in numbers of nesting ivory gulls. Several of the largest known colonies were completely extirpated and those that remained supported significantly fewer nesting birds than previously observed. Results were similar in both years despite some differences in local sea ice conditions, suggesting a numerical decline in the population and not simply annual fluctuations in colony occupation. Declines have occurred in all habitat types and across the known Canadian breeding range, suggesting that causes of the decline may be related to factors occurring during migration or on wintering grounds. We recommend that international efforts now be directed at assessing population status and trends of this species in other circumpolar countries.     

Comparison of MALDI-TOF mass spectrometric to enzyme colorimetric quantification of glucose from enzyme-hydrolyzed starch

Successful quantification of the glucose produced by enzyme hydrolysis of starch was achieved by a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) protocol, using sorbitol as an internal standard. The starch contents measured by MALDI-TOF MS of corn starch, fiber-enriched oat flour derivatives, oat and barley flours, and barley flour/corn starch composites were evaluated in comparison to a widely accepted and validated method of starch determination, which relies on enzyme colorimetry (EC). The average starch content measured in a series of corn starch samples of different masses was 93 and 101% for EC and MALDI-TOF MS, respectively, values that represent the estimated purity of the sample. There was an agreement of 99% between the starch contents determined by the two analytical methods for complex flour-derived samples. Starch values estimated by MALDI-TOF MS consistently showed a greater degree of variability than those determined by EC, but this limitation was readily compensated by rapid acquisition of multiple mass spectra. This study is the first to report the quantification of glucose by MALDI-TOF MS, and it offers new perspectives into the potential utility of MALDI-TOF MS as a definitive tool for monosaccharide analysis and rapid starch determination in complex samples.     

The origin of the A genome donor of wheats (Triticum: Poaceae) – a perspective based on the sequence variation of the 5S DNA gene units

In a prior study on the haplomes of wheat using the 5S rRNA gene we assigned the long A1 and short A1 unit classes to the A haplome in the diploid T. monococcum. The short A1 unit class is absent in the tetraploids T. turgidum and T. timopheevii and in the hexaploid T. aestivum, although present in the hexaploid T. zhukovskyi. Both T. turgidum and T. aestivum contained a different 5S DNA unit class labeled the short A2.The purpose of this paper was to study the short A2 units in the two diploid species to shed light on the theory that the A haplome donor of T. turgidum and T. aestivum was T. urartu. Fifty eight clones were obtained from 12 accessions, sequenced and analyzed. As expected T. baeoticum, which is often classified as a subspecies of T. monococcum, contained the long A1 and the short A1 5S DNA units. Unexpectedly, T. urartu had the long A1 and the short G1 unit classes instead and other units not found so far in Triticum. These findings support the hypothesis that the donor of the A genome in T. zhukovskyi was T. monococcum, as identified by the short A1 units. However, the short A1 units are absent in T. timopheevii, also a carrier of the A genome. The short G1 units found in T. urartu also identify it as a possible donor of the G genome to T. timopheevii. The short G1 units were also found in T. aestivum in our prior study. The long G1 unit class was not found in T. urartu but reported from T. timopheevii and T. zhukovskyi. The implications of these and related findings on the evolution of wheats are discussed.     

A new model for the soil-water retention curve that solves the problem of residual water contents

We present a new model for the soil‐water retention curve, θ(h_m), which, in contrast to earlier models, anchors the curve at zero water content and does away with the unspecified residual water content. The proposed equation covers the complete retention curve, with the pressure head, h_m, stretching over approximately seven orders of magnitude. We review the concept of pF from its origin in the papers of Schofield and discuss what Schofield meant by the ‘free energy, F ’. We deal with (historical) criticisms regarding the use of the log scale of the pressure head, which, unfortunately, led to the apparent demise of the pF. We espouse the advantages of using the log scale in a model for which the pF is the independent variable, and we present a method to deal with the problem of the saturated water content on the semi‐log graph being located at a pF of minus infinity. Where a smaller range of the water retention is being considered, the model also gives an excellent fit on a linear scale using the pressure head, h_m, itself as the independent variable. We applied the model to pF curves found in the literature for a great variety of soil textures ranging from dune‐sand to river‐basin clay. We found the equation for the model to be capable of fitting the pF curves with remarkable success over the complete range from saturation to oven dryness. However, because interest generally lies in the plant‐available water range (i.e. saturation, θ_s, to wilting point, θ_wp), the following relation, which can be plotted on a linear scale, is sufficient for most purposes: , where k₀, k₁ and n are adjustable fitting parameters.     

Nutritional utilization by the rat of diets based on lentil (Lens culinaris) seed meal or its fractions

The nutritional effects in the rat of raw lentil meal or its fractions have been evaluated in three feeding trials. Growth, gain/feed ratio, apparent N digestibility, and N retention were significantly (p < 0.05) reduced by the inclusion of whole lentil meal, dehulled lentil meal, or ethanol-extracted lentil meal as the sole source of protein in the diet. Pure lentil lectin and lectin-depleted albumin proteins had no significant negative effect on nutritional performance. In contrast, growth, gain/feed ratio, protein conversion efficiency, N digestibility, and N retention were significantly (p < 0.05) reduced by diets containing lentil globulins or lentil hulls. The poor nutritional quality of raw lentil meal for rats is therefore likely to be primarily due to the combined effects of these two components.     

Modeling First Break Milling of Debranned Wheat Using the Double Normalized Kumaraswamy Breakage Function

Debranning of wheat affects flour quality, initially by altering the breakage of wheat kernels during first break. The double normalized Kumaraswamy breakage function was applied to model the effect of debranning on wheat breakage during first break milling, in which type 1 breakage describes a relatively narrow distribution of midsized particles, whereas type 2 breakage describes a wide size range of predominantly small particles extending to very large particles. Mallacca (hard) and Consort (soft) wheats were debranned and milled at three roll gaps under sharp‐to‐sharp and dull‐to‐dull dispositions. Type 1 breakage increased at longer debranning times, whereas type 2 breakage decreased, for both wheat varieties under both dispositions. Sharp‐to‐sharp milling tended to produce more type 1 breakage than dull‐to‐dull. A mechanism of wheat breakage is proposed to explain the coproduction of very large and small particles via type 2 breakage and, hence, the effect of debranning. The proposed mechanism is that small particles of endosperm arise from scraping of large flat particles of wheat bran under the differential action of the rolls, such that removal of the bran reduces the production of the large bran particles and thus reduces the opportunity for the scraping mechanism that produces the very small particles.     

Standardized exercise test and daily heart rate responses of thoroughbreds undergoing conventional race training and detraining

Ten healthy sedentary male Thoroughbreds with previous race training experience were studied for 14 weeks. Horses were trained for 9 weeks, using a program designed after those used commonly in the United States. Horses were trained conventionally by slow trotting (250 m/min) for 2 weeks and galloping (390 to 450 m/min) for 4 weeks, followed by 3 weeks of galloping (440 to 480 m/min) and intermittent sprinting exercises (breezes) at distances between 600 and 1,000 m (900 to 950 m/min). The horses were then pasture rested for 5 weeks. A standardized exercise test (SET) involving an 800-m gallop at 800 m/min was administered before and after the 9-week training period and after the 5-week detraining period. Heart rate (HR) was monitored during exercise and at standardized intervals after exercise for 60 minutes. Venous blood for determination of plasma lactate concentration was obtained at 5 minutes after exercise. Heart rate was monitored daily at rest, during exercise, and through the first 60 minutes of recovery. Venous plasma samples (for lactate determination) were obtained 5 minutes after the sprinting exercises. Horses were observed daily before exercise for signs of lameness and were not allowed to train if lame. Differences after 9 weeks' training were seen in the SET recovery HR at 0.5 through 5 minutes after exercise (P less than 0.05 to P less than 0.01). Differences after detraining were seen in the SET recovery HR at 40 and 60 minutes after exercise (P less than 0.05 to P less than 0.01). Neither training nor detraining resulted in differences in plasma lactate concentration after the SET gallop.(ABSTRACT TRUNCATED AT 250 WORDS)