Dissipation due to tunneling two-level systems in gold nanomechanical resonators

We present measurements of the dissipation and frequency shift in nanomechanical gold resonators at temperatures down to 10 mK. The resonators were fabricated as doubly-clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as $T^{0.5}$, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems

Strong electronic correlation and strain effects at the interfaces between polar and nonpolar complex oxides

The interface between the polar LaAlO$_3$ and nonpolar SrTiO$_3$ layers has been shown to exhibit various electronic and magnetic phases such as two dimensional electron gas, superconductivity, magnetism and electronic phase separation. These rich phases are expected due to the strong interplay between charge, spin and orbital degree of freedom at the interface between these complex oxides, leading to the electronic reconstruction in this system. However, until now all of these new properties have been studied extensively based on the interfaces which involve a polar LaAlO$_3$ layer. To investigate the role of the A and B cationic sites of the ABO$_3$ polar layer, here we study various combinations of polar/nonpolar oxide (NdAlO$_3$/SrTiO$_3$, PrAlO$_3$/SrTiO$_3$ and NdGaO$_3$/SrTiO$_3$) interfaces which are similar in nature to LaAlO$_3$/SrTiO$_3$ interface. Our results show that all of these new interfaces can also produce 2DEG at their interfaces, supporting the idea that the electronic reconstruction is the driving mechanism for the creation of the 2DEG at these oxide interfaces. Furthermore, the electrical properties of these interfaces are shown to be strongly governed by the interface strain and strong correlation effects provided by the polar layers. Our observations may provide a novel approach to further tune the properties of the 2DEG at the selected polar/nonpolar oxide interfaces.Comment: 5 pages, 4 figure

Atomically flat interface between a single-terminated LaAlO3 substrate and SrTiO3 thin film is insulating

The surface termination of (100)-oriented LaAlO3 (LAO) single crystals was examined by atomic force microscopy and optimized to produce a single-terminated atomically flat surface by annealing. Then the atomically flat STO film was achieved on a single-terminated LAO substrate, which is expected to be similar to the n-type interface of two-dimensional electron gas (2DEG), i.e., (LaO)-(TiO2). Particularly, that can serve as a mirror structure for the typical 2DEG heterostructure to further clarify the origin of 2DEG. This newly developed interface was determined to be highly insulating. Additionally, this study demonstrates an approach to achieve atomically flat film growth based on LAO substrates.Comment: 4 pages, 3 figure

Phytochemical profile and toxicity of thyme-derived (Thymus vulgaris) essential oil against the exotic rugose spiraling whitefly (Aleurodicus rugioperculatus Martin) infesting coconut

Microwave-assisted heat extraction of thyme (Thymus vulgaris) yielded 1.64 per cent w/v of yellow to amber coloured and less viscous oil with a peculiar aroma. GC-MS analysis revealed the presence of 20 compounds, out of which thymol (51.94%), p-cymene (14.5%), γ-terpinene (10.09%), linalool (3.48%), and endo-borneol (3.95%) were the major compounds. Eggs, second instar nymphs and pupae of rugose spiraling whitefly (RSW) were subjected to contact toxicity assessment by complete immersion (dip method) in various concentrations of thyme oil. The results showed that essential oils at 0.35 per cent concentration exhibited 100 per cent mortality in the second instar nymphs. Thyme oil (0.5%) inhibited egg hatching and adult emergence to the tune of 100 per cent when the eggs and pupal stages were treated. Probit analysis indicated that the median lethal concentration (LC50) of thyme oil to eggs, second instar nymph sand pupal stages were 0.19, 0.13 and 0.21 per cent, respectively. Thyme oil proved to be an excellent toxicant to different developmental life stages of RSW; hence it can be successfully incorporated into the integrated pest management (IPM) programme for whitefly management in the coconut ecosystem

Chemistry of chromium bis-acetylide complexes

Stable paramagnetic Cr(II) and Cr(III) bis(alkynyl) complexes of the type [trans(RC≡C)2Cr(dmpe)2] n+ (R=Ph, SiMe3, SiEt3, C≡C-SiMe3 n=0, 1) were prepared and characterised by NMR, cyclic voltammetry, EPR, magnetic measurements, and X-ray single-crystal diffraction studies. Graphical Abstrac