221 research outputs found
RESULTS OF TWO DECADES OF RESEARCH WORK ON STABILISATION AND AGRICULTURAL REVALUATION OF AN APPROPRIATED LANDSLIDE
Starting with 1976, a totally unproductive piece of land located in the Chinteni Valley, Cluj County, severely degraded by landslides, was used as an experimental field in order to study the actual possibilities of agricultural reinstatement of these lands. Out of a large range of problems studied since then, the present paper shows the most important experimental results concerning the gradual stabilisation and agricultural revaluation of landslides by means of hydro- and
agroappropriative works applied. The presented results emphasise the fact that as a consequence of appropriation works applied to this landslide (drainage and levellment) as well as by using crop technologies specific for slopes, the horizontal and vertical
displacements of ground have been significantly reduced. Gradually, there has been noted an obvious tendency of a long term land stabilisation followed by a natural incorporation of this land into the equilibrium condition of the slope to which it belongs
Hundredfold Enhancement of Light Emission via Defect Control in Monolayer Transition-Metal Dichalcogenides
Two dimensional (2D) transition-metal dichalcogenide (TMD) based
semiconductors have generated intense recent interest due to their novel
optical and electronic properties, and potential for applications. In this
work, we characterize the atomic and electronic nature of intrinsic point
defects found in single crystals of these materials synthesized by two
different methods - chemical vapor transport and self-flux growth. Using a
combination of scanning tunneling microscopy (STM) and scanning transmission
electron microscopy (STEM), we show that the two major intrinsic defects in
these materials are metal vacancies and chalcogen antisites. We show that by
control of the synthetic conditions, we can reduce the defect concentration
from above to below . Because these point
defects act as centers for non-radiative recombination of excitons, this
improvement in material quality leads to a hundred-fold increase in the
radiative recombination efficiency
Compiler-aided systematic construction of large-scale DNA strand displacement circuits using unpurified components
Biochemical circuits made of rationally designed DNA molecules are proofs of concept for embedding control within complex molecular environments. They hold promise for transforming the current technologies in chemistry, biology, medicine and material science by introducing programmable and responsive behaviour to diverse molecular systems. As the transformative power of a technology depends on its accessibility, two main challenges are an automated design process and simple experimental procedures. Here we demonstrate the use of circuit design software, combined with the use of unpurified strands and simplified experimental procedures, for creating a complex DNA strand displacement circuit that consists of 78 distinct species. We develop a systematic procedure for overcoming the challenges involved in using unpurified DNA strands. We also develop a model that takes synthesis errors into consideration and semi-quantitatively reproduces the experimental data. Our methods now enable even novice researchers to successfully design and construct complex DNA strand displacement circuits
Identifying conditions for inducible protein production in E. coli: combining a fed-batch and multiple induction approach
BACKGROUND: In the interest of generating large amounts of recombinant protein, inducible systems have been studied to maximize both the growth of the culture and the production of foreign proteins. Even though thermo-inducible systems were developed in the late 1970's, the number of studies that focus on strategies for the implementation at bioreactor scale is limited. In this work, the bacteriophage lambda P(L )promoter is once again investigated as an inducible element but for the production of green fluorescent protein (GFP). Culture temperature, induction point, induction duration and number of inductions were considered as factors to maximize GFP production in a 20-L bioreactor. RESULTS: It was found that cultures carried out at 37°C resulted in a growth-associated production of GFP without the need of an induction at 42°C. Specific production was similar to what was achieved when separating the growth and production phases. Shake flask cultures were used to screen for desirable operating conditions. It was found that multiple inductions increased the production of GFP. Induction decreased the growth rate and substrate yield coefficients; therefore, two time domains (before and after induction) having different kinetic parameters were created to fit a model to the data collected. CONCLUSION: Based on two batch runs and the simulation of culture dynamics, a pre-defined feeding and induction strategy was developed to increase the volumetric yield of a temperature regulated expression system and was successfully implemented in a 20-L bioreactor. An overall cell density of 5.95 g DW l(-1 )was achieved without detriment to the cell specific production of GFP; however, the production of GFP was underestimated in the simulations due to a significant contribution of non-growth associated product formation under limiting nutrient conditions
Enhanced tunable second harmonic generation from twistable interfaces and vertical superlattices in boron nitride homostructures
Broken symmetries induce strong even-order nonlinear optical responses in materials and at interfaces. Unlike conventional covalently bonded nonlinear crystals, van der Waals (vdW) heterostructures feature layers that can be stacked at arbitrary angles, giving complete control over the presence or lack of inversion symmetry at a crystal interface. Here, we report highly tunable second harmonic generation (SHG) from nanomechanically rotatable stacks of bulk hexagonal boron nitride (BN) crystals and introduce the term twistoptics to describe studies of optical properties in twistable vdW systems. By suppressing residual bulk effects, we observe SHG intensity modulated by a factor of more than 50, and polarization patterns determined by moiré interface symmetry. Last, we demonstrate greatly enhanced conversion efficiency in vdW vertical superlattice structures with multiple symmetry-broken interfaces. Our study paves the way for compact twistoptics architectures aimed at efficient tunable frequency conversion and demonstrates SHG as a robust probe of buried vdW interfaces
Compiler-aided systematic construction of large-scale DNA strand displacement circuits using unpurified components
Biochemical circuits made of rationally designed DNA molecules are proofs of concept for embedding control within complex molecular environments. They hold promise for transforming the current technologies in chemistry, biology, medicine and material science by introducing programmable and responsive behaviour to diverse molecular systems. As the transformative power of a technology depends on its accessibility, two main challenges are an automated design process and simple experimental procedures. Here we demonstrate the use of circuit design software, combined with the use of unpurified strands and simplified experimental procedures, for creating a complex DNA strand displacement circuit that consists of 78 distinct species. We develop a systematic procedure for overcoming the challenges involved in using unpurified DNA strands. We also develop a model that takes synthesis errors into consideration and semi-quantitatively reproduces the experimental data. Our methods now enable even novice researchers to successfully design and construct complex DNA strand displacement circuits
Does the gross motor development of romanian and hungarian 6 â 7-year-old children depend on the degree of obesity? (First phase of a longitudinal study)
Approximate Solutions to Fractional Subdiffusion Equations: The heat-balance integral method
The work presents integral solutions of the fractional subdiffusion equation
by an integral method, as an alternative approach to the solutions employing
hypergeometric functions. The integral solution suggests a preliminary defined
profile with unknown coefficients and the concept of penetration (boundary
layer). The prescribed profile satisfies the boundary conditions imposed by the
boundary layer that allows its coefficients to be expressed through its depth
as unique parameter. The integral approach to the fractional subdiffusion
equation suggests a replacement of the real distribution function by the
approximate profile. The solution was performed with Riemann -Liouville
time-fractional derivative since the integral approach avoids the definition of
the initial value of the time-derivative required by the Laplace transformed
equations and leading to a transition to Caputo derivatives. The method is
demonstrated by solutions to two simple fractional subdiffusion equations
(Dirichlet problems): 1) Time-Fractional Diffusion Equation, and 2)
Time-Fractional Drift Equation, both of them having fundamental solutions
expressed through the M-Write function. The solutions demonstrate some basic
issues of the suggested integral approach, among them: a) Choice of the
profile, b) Integration problem emerging when the distribution (profile) is
replaced by a prescribed one with unknown coefficients; c) Optimization of the
profile in view to minimize the average error of approximations; d) Numerical
results allowing comparisons to the known solutions expressed to the M-Write
function and error estimations.Comment: 15 pages, 7 figures, 3 table
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