Determination of chromosomal ploidy in Agave ssp.

Chromosome observation is necessary to elucidate the structure, function and organization of Agave plants’ genes and genomes. However, few researches about chromosome observation of Agave ssp. were done, not only because their chromosome numbers are large, but also because their ploidies are complicated. The root tips of 19 Agave ssp. germplasms were used as materials for determining their chromosomal ploidies. Through normal pre-treatment, fixation, digesting and Giemsa staining, the glass slides with expelled cells on them were obtained. Observed with a light microscope, the results showed that 10 germplasms are diploids, including 4 wild species and a local variety which are good parents for cross-breeding. The main cultivar in China A.hybrid cv NO 11648 is also a diploid. A. cantala Roxb used as parent for disease-resistant breeding is a triploid. A. hybrid cv nanya NO.1 and A. hybrid cv nanya NO.2 are tetraploids. The other germplasms belong to polyploids. Although three germplasms’ ploidies were reported before, the other 16 germplasms’ were first reported in this paper. These results will provide theoretical basis for cross-breeding

Reconciling conflicting evidence for the cause of the observed early 21st century Eurasian cooling

It is now well established that the Arctic is warming at a faster rate than the global average. This warming, which has been accompanied by a dramatic decline in sea ice, has been linked to cooling over the Eurasian subcontinent over recent decades, most dramatically during the period 1998–2012. This is a counter-intuitive impact under global warming given that land regions should warm more than ocean (and the global average). Some studies have proposed a causal teleconnection from Arctic sea-ice retreat to Eurasian wintertime cooling; other studies argue that Eurasian cooling is mainly driven by internal variability. Overall, there is an impression of strong disagreement between those holding the “ice-driven” versus “internal variability” viewpoints. Here, we offer an alternative framing showing that the sea ice and internal variability views can be compatible. Key to this is viewing Eurasian cooling through the lens of dynamics (linked primarily to internal variability with some potential contribution from sea ice; cools Eurasia) and thermodynamics (linked to sea-ice retreat; warms Eurasia). This approach, combined with recognition that there is uncertainty in the hypothesized mechanisms themselves, allows both viewpoints (and others) to co-exist and contribute to our understanding of Eurasian cooling. A simple autoregressive model shows that Eurasian cooling of this magnitude is consistent with internal variability, with some periods exhibiting stronger cooling than others, either by chance or by forced changes. Rather than posit a “yes-or-no” causal relationship between sea ice and Eurasian cooling, a more constructive way forward is to consider whether the cooling trend was more likely given the observed sea-ice loss, as well as other sources of low-frequency variability. Taken in this way both sea ice and internal variability are factors that affect the likelihood of strong regional cooling in the presence of ongoing global warming.</p

Intellectual property enclosure and economic discourse in the 2012 London Olympic Games.

Special legislation associated with mega sporting events has enabled new forms of cultural enclosure, effectively commoditising aspects of cultural expression that previously remained in the public domain. In this article, the authors examine the tension between economic and political justifications for hosting the Olympics and the intellectual property enclosures that are imposed upon host nations. These enclosures extend beyond what is traditionally protected under trade mark law, to include ‘generic’ terms. Enabling market competitors to freely use generic, descriptive language is a core doctrine of trade mark law, seeking to balance monopoly IP rights with free market competition. The authors evaluate the impact of special legislative enclosures on the public interest, and argue that collective access to expression should be more carefully considered in political and economic calculations of the value of the Olympics

A Room-Temperature Ferroelectric Resonant Tunneling Diode

Resonant tunneling is a quantum-mechanical effect in which electron transport is controlled by the discrete energy levels within a quantum-well (QW) structure. A ferroelectric resonant tunneling diode (RTD) exploits the switchable electric polarization state of the QW barrier to tune the device resistance. Here, the discovery of robust room-temperature ferroelectric-modulated resonant tunneling and negative differential resistance (NDR) behaviors in all-perovskite-oxide BaTiO3/SrRuO3/BaTiO3 QW structures is reported. The resonant current amplitude and voltage are tunable by the switchable polarization of the BaTiO3 ferroelectric with the NDR ratio modulated by ≈3 orders of magnitude and an OFF/ON resistance ratio exceeding a factor of 2 × 104. The observed NDR effect is explained an energy bandgap between Ru-t2g and Ru-eg orbitals driven by electron–electron correlations, as follows from density functional theory calculations. This study paves the way for ferroelectric-based quantum-tunneling devices in future oxide electronics