A polyethylene glycol enhanced ligation-triggered self-priming isothermal amplification for the detection of SARS-CoV-2 D614G mutation.

We presented a polyethylene glycol (PEG) enhanced ligation-triggered self-priming isothermal amplification (PEG-LSPA) for the detection D614G mutation in S-glycoprotein of SARS-CoV-2. PEG was employed to improve the ligation efficiency of this assay by constructing a molecular crowding environment. Two hairpin probes (H1 and H2) were designed to contain 18 nt and 20 nt target binding site at their 3' end and 5' end, respectively. In presence of target sequence, it complemented with H1 and H2 to trigger ligation by ligase under molecular crowding condition to form ligated H1-H2 duplex. Then 3' terminus of the H2 would be extended by DNA polymerase under isothermal conditions to form a longer extended hairpin (EHP1). 5' terminus of EHP1 with phosphorothioate (PS) modification could form hairpin structure due to the lower Tm value. The resulting 3' end overhang would also fold back as a new primer to initiate the next round of polymerization, resulting in the formation of a longer extended hairpin (EHP2) containing two target sequence domains. In the circle of LSPA, long extended hairpin (EHPx) containing numerous target sequence domains was produced. The resulting DNA products can be monitored in real-time fluorescence signaling. Our proposed assay owns an excellent linear range from 10 fM to 10 nM with a detection limit down to 4 fM. Thus, this work provides a potential isothermal amplification method for monitoring mutations in SARS-CoV-2 variants.

A distinctive Eocene Asian monsoon and modern biodiversity resulted from the rise of eastern Tibet.

The uplift of eastern Tibet, Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked, but in obscure ways. Sedimentology, geochronology, clumped isotope thermometry, and fossil leaf-derived numerical climate data from the Relu Basin, eastern Tibet, show at âˆ¼50-45 Ma the basin was a hot (mean annual air temperature, MAAT, ∼27 °C) dry desert at a low-elevation of 0.6 ± 0.6 km. Rapid basin rise to 2.0 ± 0.9 km at 45-42 Ma and to 2.9 ± 0.9 km at 42-40 Ma, with MAATs of âˆ¼20 and âˆ¼16 °C, respectively, accompanied seasonally varying increased annual precipitation to > 1500 mm. From âˆ¼39 to 34 Ma, the basin attained 3.5 ± 1.0 km, near its present-day elevation (∼3.7 km), and MAAT cooled to âˆ¼6 °C. Numerically-modelled Asian monsoon strength increased significantly when this Eocene uplift of eastern Tibet was incorporated. The simulation/proxy congruence points to a distinctive Eocene Asian monsoon, quite unlike that seen today, in that it featured bimodal precipitation and a winter-wet regime, and this enhanced biodiversity modernisation across eastern Asia. The Paleogene biodiversity of Asia evolved under a continually modifying monsoon influence, with the modern Asian monsoon system being unique to the present and a product of a long gradual development in the context of an ever-changing Earth system.

A lumped parameter model of the longitudinal NiMnGa transducer based on piezomagnetic equations.

The NiMnGa alloy is a typical magnetic shape memory alloy with up to 6% immense strain, high energy density, and low effective elastic modulus. These comprehensive characteristics make it possible to realize a low-frequency underwater acoustic transducer. To describe the field-induced dynamic strain, an equivalent circuit model (ECM) of a longitudinal NiMnGa transducer is presented as a lumped parameter model, which couples magnetics, mechanics, and acoustics. In this paper, we focus on the piezomagnetic equations as the constitutive relationship of the NiMnGa element with a dynamic magnetic field. Furthermore, combined with the dynamic kinetic equation, the equivalent circuit is derived, and it has the advantage of containing acoustical terminals. The proposed model can predict the resonance frequency, effective stiffness, and input impedance of the NiMnGa transducer. Finally, a finite element model (FEM) is developed to verify the lumped parameter model. The results indicate that the spring's stiffness increases the resonance frequency, while the mass load is on the contrary, and they both agree well with the results of ECM. In addition, the FEM and ECM can also predict the dynamic responses, which provide a guideline for the design of longitudinal NiMnGa transducers.

The rise and demise of the Paleogene Central Tibetan Valley.

Reconstructing the Paleogene topography and climate of central Tibet informs understanding of collisional tectonic mechanisms and their links to climate and biodiversity. Radiometric dates of volcanic/sedimentary rocks and paleotemperatures based on clumped isotopes within ancient soil carbonate nodules from the Lunpola Basin, part of an east-west trending band of basins in central Tibet and now at 4.7 km, suggest that the basin rose from <2.0 km at 50 to 38 million years (Ma) to >4.0 km by 29 Ma. The height change is quantified using the rates at which wet-bulb temperatures (Tw) decline at land surfaces as those surface rise. In this case, Tw fell from ~8°C at ~38 Ma to ~1°C at 29 Ma, suggesting at least ~2.0 km of surface uplift in ~10 Ma under warm Eocene to Oligocene conditions. These results confirm that a Paleogene Central Tibetan Valley transformed to a plateau before the Neogene.