Thermal decomposition of specifically phosphorylated D-glucoses and their role in the control of the Maillard reaction

One of the main shortcomings of the information available on the Maillard reaction is the lack of knowledge to control the different pathways, especially when it is desired to direct the reaction away from the formation of carcinogenic and other toxic substances to more aroma and color generation. The use of specifically phosphorylated sugars may impart some elements of control over the aroma profile generated by the Maillard reaction. Thermal decomposition of 1- and 6-phosphorylated glucoses was studied in the presence and absence of ammonia and selected amino acids through pyrolysis/gas chromatography/mass spectrometry using nonpolar PLOT and medium polar DB-1 columns. The analysis of the data has indicated that glucose-1-phosphate relative to glucose undergoes more extensive phosphate-catalyzed ring opening followed by formation of sugar-derived reactive intermediates as was indicated by a 9-fold increase in the amount of trimethylpyrazine and a 5-fold increase in the amount of 2,3-dimethylpyrazine, when pyrolyzed in the presence of glycine. In addition, glucose-1-phosphate alone generated a 6-fold excess of acetol as compared to glucose. On the other hand, glucose-6-phosphate enhanced retro-aldol reactions initiated from a C-6 hydroxyl group and increased the subsequent formation of furfural and 4-cyclopentene-1,3-dione. Furthermore, it also stabilized 1- and 3-deoxyglucosone intermediates and enhanced the formation of six carbon atom-containing Maillard products derived directly from them through elimination reactions such as 1,6-dimethyl-2,4-dihydroxy-3-(2H)-furanone (acetylformoin), 2-acetylpyrrole, 5-methylfurfural, 5-hydroxymethylfurfural, and 4-hydroxy-2,5-dimethyl-3-(2H)-furanone (Furaneol), due to the enhanced leaving group ability of the phosphate moiety at the C-6 carbon. However, Maillard products generated through the nucleophilic action of the C-6 hydroxyl group such as 2-acetylfuran and 2,3-dihydro-3,5-dihydroxy-4H-pyran-4-one were retarded, due to the blocked nucleophilic atom at C-6.     

Anisotropic violation of the Wiedemann-Franz law at a quantum critical point

A quantum critical point transforms the behavior of electrons so strongly that new phases of matter can emerge. The interactions at play are known to fall outside the scope of the standard model of metals, but a fundamental question remains: Is the basic concept of a quasiparticle-a fermion with renormalized mass-still valid in such systems? The Wiedemann-Franz law, which states that the ratio of heat and charge conductivities in a metal is a universal constant in the limit of zero temperature, is a robust consequence of Fermi-Dirac statistics. We report a violation of this law in the heavy-fermion metal CeCoIn5 when tuned to its quantum critical point, depending on the direction of electron motion relative to the crystal lattice, which points to an anisotropic destruction of the Fermi surface.     

Improved learning in a large-enrollment physics class

We compared the amounts of learning achieved using two different instructional approaches under controlled conditions. We measured the learning of a specific set of topics and objectives when taught by 3 hours of traditional lecture given by an experienced highly rated instructor and 3 hours of instruction given by a trained but inexperienced instructor using instruction based on research in cognitive psychology and physics education. The comparison was made between two large sections (N = 267 and N = 271) of an introductory undergraduate physics course. We found increased student attendance, higher engagement, and more than twice the learning in the section taught using research-based instruction.     

Hybrid speciation in experimental populations of yeast

Most models of speciation require gradual change and geographic or ecological isolation for new species to arise. Homoploid hybrid speciation occurred readily between Saccharomyces cerevisiae and Saccharomyces paradoxus. Hybrids had high self-fertility (about 82%), low fertility when backcrossed to either parental species (about 7.5%), and vigorous growth under different thermal environments that favored one or the other of the parental species. Extensive karyotypic changes (tetrasomy) were observed in the hybrids, although genic incompatibilities accounted for 50% of the variation in self-fertility.     

Consequences of adult and juvenile movement for marine protected areas

Adult and juvenile mobility has a considerable influence on the functioning of marine protected areas. It is recognized that adult and juvenile movement reduces the core benefits of protected areas, namely protecting the full age–structure of marine populations, while at the same time perhaps improving fisheries yield over the no-reserve situation through export of individuals from protected areas. Nevertheless, the study of the consequences of movement on protected area functioning is unbalanced. Significant attention has been paid to the influence of certain movement patterns, such as diffusive movement and home ranges, while the impacts of others, such as density-dependent movements and ontogenetic migrations, have been relatively ignored. Here we review the diversity of density-independent and density-dependent movement patterns, as well as what is currently known about their consequences for the conservation and fisheries effects of marine protected areas. We highlight a number of ‘partially addressed’ issues in marine protected area research, such as the effects of reserves targeting specific life phases, and a number of essentially unstudied issues, such as density-dependent movements, nomadism, ontogenetic migrations, behavioral polymorphism and ‘dynamic’ reserves that adjust location as a realtime response to habitat changes. Assessing these issues will be essential to creating effective marine protected area networks for mobile species and accurately assessing reserve impacts on these species.     

Contrasting Observation and Transect-Based Models of Cattle Distribution on Lincoln National Forest,New Mexico

Perceptions of cattle distribution and resource conflicts are often based upon qualitative observations of cattle by managers or the general public. Such information on cattle presence and inferred habitat preferences may not reflect true habitat correlates of cattle because observations do not include any sampling design. We documented cattle presence and used presence data to model distribution of cattle with respect to landscape features on the Lincoln National Forest (LNF) of south-central New Mexico, an area of conflict with regard to cattle herbivory. We recorded cattle presence both from visual observations of cattle while conducting other research activities and from randomized pellet-group transects during the spring–autumn period when cattle grazed the high-elevation habitats. Distribution of cattle differed for several habitat variables between datasets, although distribution models from both datasets indicated that elevation, slope, distance to water and roads, and vegetation cover type most influenced cattle presence. Cattle presence was associated with a variety of cover types, and cattle were generally within 500 m of water and on slopes of < 15–20%. Observation-based models showed positive associations with open cover types, including the strongest positive association with montane meadows, the area of conflict in LNF. In contrast, transect-based models showed positive associations with more cover types (11) than did observation-based (6). Observation-based models also showed higher association with areas closer to roads. Inferred habitat preferences based on casual observations of cattle may not accurately reflect true distribution or use, as transect-based models predicted much broader distribution throughout LNF and higher overall probabilities of cattle presence. Because cattle distribution included many other vegetation cover types in addition to montane meadows, management to enhance positive correlates of cattle distribution on LNF may be useful to alter cattle distribution away from areas of perceived conflict.     

Predicted and observed finger diameters in field soils

Wetting front instability resulting in fingered flow has been found in both wettable and nonwettable soils. Understanding how and when this phenomenon occurs under field conditions is greatly limited. Laboratory research has resulted in a number of expressions for finger diameter. In this paper we test the applicability of one of these equations for three different soils in the Netherlands where detailed soil sampling of moisture content was done earlier. In addition, information needed for finger prediction, such as the main wetting and drying loops of the soil moisture characteristic curves and the unsaturated and saturated soil conductivities, were measured in the laboratory. Results show that predicted finger diameters for the two sandy soils agreed well with the observed moisture patterns, while for the loess soil the wetting front was flat as predicted. The finger diameters in dry soil were based on the main wetting loop and in the wet soils were dependent on the main drying loop.     

Stepwise thermal analysis technique for estimating mercury phases in soils and sediments

Traces of H4 phases in soils, sediments and mineral standards were determined by thermal analysis at successively higher temperature steps. Mercury was liberated at each step, concentrated on Au, then determined by flameless atomic absorption. Some Hq determinations were made by liberating the element by continuous heating at the rate of 20 and 100°C min^?1. Soil samples were collected from the vicinity of a Hg mine, a Cu deposit and fault zones. Sediment samples were collected near a H9 roasting plant, a chlor-alkali plant and a Cu smelter. The results show that, for all the samples, most of the Hg is liberated during the 200°C temperature step. Some samples show thermal release characteristics similar to those of a. cinnabar-quartz mixture. Other samples show characteristics possibly related to sorbed elemental Hg. The results show that stepwise compared to continuous heating gives more resolution and thus may prove to be easier in estimating traces of Hg phases in soils and sediments.