Nanocellulose aerogel-based porous coaxial fibers for thermal insulation

Strong, continuous, and highly porous coaxial fibers with cellulose nanofibril (CNF) aerogel core and cellulose-rich sheath were fabricated by wet-spinning hollow fibers and infusing them with aerogel precursor for high-performance thermal insulators. The sheath contained multiscale pores, including microvoids (14.5 μm) and sub-micron pores (133 nm) in bulk, as well as ca. 25–26 nm surface nanopores, to function as a template and protective sheath for the microporous CNF aerogel core. The porous coaxial fibers had many desirable qualities, including low density (0.2 g cm3), high porosity (85%), high specific tensile strength (23.5 ± 2.5 MPa g cm−3), wide working temperatures (−20 to 150 °C), continuous and large-scale producibility, as well as biodegradability. The unique combination of multiscale porous sheath and ultra-low density aerogel core synergistically minimizes heat conductivity by all three mechanisms, i.e., restrain air circulation to limit convective heat transfer, while the poor conducting cellulose permitting little conductive heat transfer and the highly crystalline aerogel cellular walls prohibit infrared radiation, effectively suppresses radiative heat transfer under extreme temperatures

Misallocation and manufacturing TFP in China and India

Resource misallocation can lower aggregate total factor productivity (TFP).We use microdata on manufacturing establishments to quantify the potential extent of misallocation in China and India versus the United States. We measure sizable gaps in marginal products of labor and capital across plants within narrowly defined industries in China and India compared with the United States. When capital and labor are hypothetically reallocated to equalize marginal products to the extent observed in the United States, we calculate manufacturing TFP gains of 30%–50% in China and 40%–60% in India.India,China, Economy

High-speed measurement of rotational anisotropy nonlinear optical harmonic generation using position sensitive detection

We present a method of performing high-speed rotational anisotropy nonlinear optical harmonic generation experiments at rotational frequencies of several hertz by projecting the harmonic light reflected at different angles from a sample onto a stationary position sensitive detector. The high rotational speed of the technique, $10^3$ to $10^4$ times larger than existing methods, permits precise measurements of the crystallographic and electronic symmetries of samples by averaging over low frequency laser power, beam pointing, and pulse width fluctuations. We demonstrate the sensitivity of our technique by resolving the bulk four-fold rotational symmetry of GaAs about its [001] axis using second harmonic generation

Misallocation and Manufacturing TFP in China and India

Resource misallocation can lower aggregate total factor productivity (TFP). We use micro data on manufacturing establishments to quantify the potential extent of misallocation in China and India compared to the U.S. Compared to the U.S., we measure sizable gaps in marginal products of labor and capital across plants within narrowly-defined industries in China and India. When capital and labor are hypothetically reallocated to equalize marginal products to the extent observed in the U.S., we calculate manufacturing TFP gains of 30-50% in China and 40-60% in India.

Relative Prices and Relative Prosperity

The positive correlation between PPP investment rates and PPP income levels across countries is one of the most robust findings of the empirical growth literature. We show that this relationship is almost entirely driven by differences in the price of investment relative to output across countries. When measured at domestic prices rather than at international prices, investment rates are little correlated with PPP incomes. We find that the high relative price of investment in poor countries is solely due to the low price of consumption goods in poor countries. Investment prices are no higher in poor countries than in rich countries. These facts suggest that the low PPP investment rates in poor countries are not due to low savings rates or to high tax or tariff rates on investment. Poor countries instead appear to be plagued by low efficiency in producing investment goods and in producing exportables to trade for machinery and equipment.

Investigation of nonlinear interaction phenomena in the ionosphere

Ionospheric phenomena as thermal radiation noise, propagation of naturally occurring radio noise through ionosphere, and generation of very low frequency emission

Nonadiabatic Dynamics in Open Quantum-Classical Systems: Forward-Backward Trajectory Solution

A new approximate solution to the quantum-classical Liouville equation is derived starting from the formal solution of this equation in forward-backward form. The time evolution of a mixed quantum-classical system described by this equation is obtained in a coherent state basis using the mapping representation, which expresses $N$ quantum degrees of freedom in a 2N-dimensional phase space. The solution yields a simple non-Hamiltonian dynamics in which a set of $N$ coherent state coordinates evolve in forward and backward trajectories while the bath coordinates evolve under the influence of the mean potential that depends on these forward and backward trajectories. It is shown that the solution satisfies the differential form of the quantum-classical Liouville equation exactly. Relations to other mixed quantum-classical and semi-classical schemes are discussed.Comment: 28 pages, 1 figur