Topological phase transition and texture inversion in a tunable topological insulator

The recently discovered three-dimensional or bulk topological insulators are expected to exhibit exotic quantum phenomena. It is believed that a trivial insulator can be twisted into a topological state by modulating the spin-orbit interaction or the crystal lattice, driving the system through a topological quantum phase transition. By directly measuring the topological quantum numbers and invariants, we report the observation of a phase transition in a tunable spin-orbit system, BiTl(S(1-δ)Se(δ))(2), in which the topological state formation is visualized. In the topological state, vortex-like polarization states are observed to exhibit three-dimensional vectorial textures, which collectively feature a chirality transition as the spin momentum-locked electrons on the surface go through the zero carrier density point. Such phase transition and texture inversion can be the physical basis for observing fractional charge (±e/2) and other fractional topological phenomena.     

Genetic variation in germplasm accessions of Secale vavilovii Grossh

Summary The accurate identification and classification of wild species enhance the utilization of potential plant genetic resources. The wild rye species Secale vavilovii Grossh. may serve to broaden the genetic variation in cultivated rye, S. cereale. The combined analyses of cytological, isozymic and other genetic characteristics in the present study revealed that of the fourteen rye accessions designated as S. vavilovii, only three accessions were correctly classified. Thus it is essential to increase multidisciplinary, international research and collaboration to aid in the classification and utilization of the yet untapped plant germplasm.     

Regional chemical characteristics of lakes in North America Part II: Eastern United States

A survey of 1592 lakes ( >4 ha and ≤ 2,000 ha) was conducted in Fall, 1984. The study area was three regions of the eastern United States (Northeast, Upper Midwest, and Southeast) expected to contain the most lakes with acid neutralizing capacity (ANC) ≤400 μeq/L. The design of the survey provides statistically reliable estimates of the number, location and chemical characteristics of lakes in the study area. Frequency distribution statistics are presented for pH, ANC, sulfate and organic anion. The highest percentages and numbers of acidic lakes occurred in Florida, the Adirondaks, and the Upper Peninsula of Michigan. The highest percentages and numbers of lakes with high sulfate concentrations occurred in the Poconos/Catskills, Southern New England and Florida. The highest percentages and numbers of lakes with high organic anion concentrations occurred in Northeastern Minnesota, the Upper Great Lakes Area and Florida. The percentage of acidic lakes by sulfate concentration class revealed no discernable pattern across subregions. In contrast, the acidic lakes occur with the highest frequency in the lowest organic anion concentration class. The complex distribution of low ANC lakes cannot be explained simply by sulfate concentrations or organic acids.     

Aryldiones incorporating a [1,4,5]oxadiazepane ring. Part 2: chemistry and biology of the cereal herbicide pinoxaden

BACKGROUND: Pinoxaden is a new cereal herbicide that provides outstanding levels of post‐emergence activity against a broad spectrum of grass weed species for worldwide selective use in both wheat and barley. RESULTS: Factors influencing activity and tolerance to pinoxaden were in part linked to distinct structural parts of the active ingredient. Three complementary contributions that decisively impact upon the herbicidal potency against grasses were identified: a preferred 2,6‐diethyl‐4‐methyl aromatic substitution pattern, a dione area suitable for proherbicide formation and beneficial adjuvant effects. The uptake and translocation pattern of pinoxaden when coapplied with its tailored adjuvant were analysed by autoradiography, indicating extensive and rapid penetration, followed by effective distribution throughout the plant. Crop injury reduction on incorporation of the [1,4,5]oxadiazepane ring into the aryldione template was reinforced with safener technology. Comparative studies on the behaviour of pinoxaden applied either alone or in combination with the safener cloquintocet‐mexyl demonstrated that addition of the safener resulted in significant enhancement of metabolic degradation in wheat and barley, providing excellent crop tolerance and a substantial selectivity margin without adverse effects on weed control. CONCLUSION: The biological potential of pinoxaden and its active principle pinoxaden dione in terms of grass weed control and tolerance in cereals was fully exploited by inclusion of the safener cloquintocet‐mexyl in the formulation in combination with a specific and tailor‐made tank‐mix adjuvant based on methylated rape seed oil. Copyright © 2011 Society of Chemical Industry