On the Origin of Tibetans and Their Genetic Basis in Adapting High-Altitude Environments

Since their arrival in the Tibetan Plateau during the Neolithic Age, Tibetans have been well-adapted to extreme environmental conditions and possess genetic variation that reflect their living environment and migratory history. To investigate the origin of Tibetans and the genetic basis of adaptation in a rigorous environment, we genotyped 30 Tibetan individuals with more than one million SNP markers. Our findings suggested that Tibetans, together with the Yi people, were descendants of Tibeto-Burmans who diverged from ancient settlers of East Asia. The valleys of the Hengduan Mountain range may be a major migration route. We also identified a set of positively-selected genes that belong to functional classes of the embryonic, female gonad, and blood vessel developments, as well as response to hypoxia. Most of these genes were highly correlated with population-specific and beneficial phenotypes, such as high infant survival rate and the absence of chronic mountain sickness

Kinetics of Uranium(VI) Desorption from Contaminated Sediments: Effect of Geochemical Conditions and Model Evaluation

Stirred-flow cell experiments were performed to investigate the kinetics of uranyl [U(VI)] desorption from a contaminated sediment collected from the Hanford 300 Area at the U.S. Department of Energy Hanford Site, Washington. Three influent solutions of variable pH, Ca and carbonate concentrations that affected U(VI) aqueous and surface speciation were used under dynamic flow conditions to evaluate the effect of geochemical conditions on the rate of U(VI) desorption. The measured rate of U(VI) desorption varied with solution chemical composition that evolved as a result of thermodynamic and kinetic interactions between the solutions and sediment. The solution chemical composition that led to a larger disequilibrium between adsorbed U(VI) and equilibrium adsorption state yielded a faster desorption rate. The experimental results were used to evaluate a multirate, surface complexation model (SCM) that has been proposed to describe U(VI) desorption kinetics in the Hanford sediment that contained complex adsorbed U(VI) in mass transfer limited domains (Lui et al. Water Resour. Res. 2008, 44, W08413). The model was modified and supplemented by including multirate, ion exchange reactions to describe the geochemical interactions between the solutions and sediment. With the same set of model parameters, the modified model reasonably well described the evolution of major ions and the rates of U(VI) desorption under variable geochemical and flow conditions, implying that the multirate SCM is an effective way to describe U(VI) desorption kinetics in subsurface sediments

Nutrient leaching and copper speciation in compost-amended bioretention systems

Bioretention systems are designed to remove contaminants from stormwater; however, studies have shown that bioretention systems can export excess nitrogen, phosphorus, and copper when amended with compost. The objectives of this study were (1) to quantify removal of nitrates, phosphorus, copper, and dissolved organic matter (DOM) from compost-amended bioretention systems, and (2) to investigate the role of DOM on the leaching of copper. Simulated bioretention systems were irrigated with stormwater for seven storms in two-weeks intervals. Leachates were analyzed for nutrients, copper, and DOM. Visual MINTEQ was used to determine the speciation of copper and to quantify interactions of copper with DOM. Results showed that compost-amended bioretention systems were a source of nitrates, phosphorus, and DOM. Nitrate and phosphorus amounts were elevated up to three orders of magnitude in the leachate compared to the stormwater itself. Bioretention systems were a source for copper during the first 3–5 storms, but during later storms, they were a sink for copper. Copper speciation modeling indicated that the majority of dissolved copper was complexed with DOM. Dissolved organic matter thus helps to mobilize copper from the compost, particularly in the first few storms after compost application. However, since copper-DOM complexes are usually much less toxic than free copper ions, we expect that compost amendments may reduce harmful effects of copper on aquatic organisms. [Display omitted] •Rainstorms release N, P, and Cu from compost-amended bioretention systems.•Successive rainstorms cause new peaks in outflow concentrations.•Chemical speciation modeling indicates that copper in leachate forms organic bidentate complexes

Receptivity of Boundary Layer over a Blunt Wedge due to Freestream Pulse Disturbances at Mach 6

Direct numerical simulation (DNS) of a hypersonic compressible flow over a blunt wedge with fast acoustic disturbances in freestream is performed. The receptivity characteristics of boundary layer to freestream pulse acoustic disturbances are numerically investigated at Mach 6, and the frequency effects of freestream pulse wave on boundary layer receptivity are discussed. Results show that there are several main disturbance mode clusters in boundary layer under acoustic pulse wave, and the number of main disturbance clusters decreases along the streamwise. As disturbance wave propagates from upstream to downstream direction, the component of the modes below fundamental frequency decreases, and the component of the modes above second harmonic components increases quickly in general. There are competition and disturbance energy transfer between different boundary layer modes. The nose boundary layer is dominated by the nearby mode of fundamental frequency. The number of the main disturbance mode clusters decreases as the freestream disturbance frequency increases. The frequency range with larger growth narrows along the streamwise. In general, the amplitudes of both fundamental mode and harmonics become larger with the decreasing of freestream disturbance frequency. High frequency freestream disturbance accelerates the decay of disturbance wave in downstream boundary layer

a real-time key recovery attack on the lightweight stream cipher a2u2

The stream cipher A2U2 proposed by David et al. [7] is one of lightweight cipher primitives. In this paper we present a real-time key recovery attack on A2U2 under the known-plaintext-attack model, which only needs at most 210 consecutive ciphertext bits and its corresponding plaintext with the time complexity about 224.7. Our result is much better than that of the attack proposed by M. Abdelraheem et al. in [9] whose complexity is O(2 49 x C), where C is the complexity of solving a sparse quadratic equation system on 56 unknown key bits. Furthermore we provide a new approach to solving the above sparse quadratic equation system, which reduces the complexity C to a very small constant. Finally we do an entire experiment on a PC and recover all bits of a random key in a few seconds. © Springer-Verlag 2012.The stream cipher A2U2 proposed by David et al. [7] is one of lightweight cipher primitives. In this paper we present a real-time key recovery attack on A2U2 under the known-plaintext-attack model, which only needs at most 210 consecutive ciphertext bits and its corresponding plaintext with the time complexity about 224.7. Our result is much better than that of the attack proposed by M. Abdelraheem et al. in [9] whose complexity is O(2 49 x C), where C is the complexity of solving a sparse quadratic equation system on 56 unknown key bits. Furthermore we provide a new approach to solving the above sparse quadratic equation system, which reduces the complexity C to a very small constant. Finally we do an entire experiment on a PC and recover all bits of a random key in a few seconds. © Springer-Verlag 2012

on guess and determine analysis of rabbit

Rabbit is a stream cipher proposed by M. Boesgaard et al., and has been selected into the final portfolio after three evaluation phases of the ECRYPT Stream Cipher Project (eSTREAM). So far only a few papers studied its security besides a series of white papers by the designers of Rabbit. Recently we presented a new idea to evaluate the security of a word-oriented stream cipher algorithm from a smaller data granularity instead of its original data granularity and applied it successfully to the stream cipher SOSEMANUK. In this work we apply the same idea to the Rabbit algorithm and analyze its security in resistance against the guess and determine attack from the view point of byte units. As a result, we present two new approaches of solving all x(j,t)+1's and g(j,t)'s from the next-state function and the extraction scheme of Rabbit, whose complexities are 2(166) and 2(140.68) respectively, which are dramatically lower than those proposed by Lu et al. (2(192) and 2(174) resp.) at ISC 2008. Finally based on the above new results we propose a byte-based guess and determine attack on Rabbit, which only needs a small segment of known key stream to recover the whole internal state of Rabbit with time complexity 2(242). Though the complexity of our attack is far higher than that of a brute force (2(128)), we believe that some new techniques adopted in this paper are of interest for future work on Rabbit.Natural Science Foundation of China60833008, 60902024; National 973 Program2007CB807902Rabbit is a stream cipher proposed by M. Boesgaard et al., and has been selected into the final portfolio after three evaluation phases of the ECRYPT Stream Cipher Project (eSTREAM). So far only a few papers studied its security besides a series of white papers by the designers of Rabbit. Recently we presented a new idea to evaluate the security of a word-oriented stream cipher algorithm from a smaller data granularity instead of its original data granularity and applied it successfully to the stream cipher SOSEMANUK. In this work we apply the same idea to the Rabbit algorithm and analyze its security in resistance against the guess and determine attack from the view point of byte units. As a result, we present two new approaches of solving all x(j,t)+1's and g(j,t)'s from the next-state function and the extraction scheme of Rabbit, whose complexities are 2(166) and 2(140.68) respectively, which are dramatically lower than those proposed by Lu et al. (2(192) and 2(174) resp.) at ISC 2008. Finally based on the above new results we propose a byte-based guess and determine attack on Rabbit, which only needs a small segment of known key stream to recover the whole internal state of Rabbit with time complexity 2(242). Though the complexity of our attack is far higher than that of a brute force (2(128)), we believe that some new techniques adopted in this paper are of interest for future work on Rabbit

Effect of a Roughness Element on the Hypersonic Boundary Layer Receptivity Due to Different Types of Free-Stream Disturbance with a Single Frequency

The hypersonic flow field around a blunt cone was simulated using a high-order finite difference method. Fast acoustic waves, slow acoustic waves, entropy waves, and vortical waves were introduced into the free-stream to determine the influence of a free-stream with disturbances on the hypersonic flow field and boundary layer. The effect of disturbance type on the evolution of perturbations in the hypersonic boundary layer was analyzed. Fast Fourier Transform was adopted to analyze the effect of the disturbance type on the evolution of different modes in the boundary layer. A roughness element was introduced into the flow field to reveal the impact of the roughness element on hypersonic boundary layer receptivity. The results showed that a free-stream with disturbances affected the hypersonic flow field and boundary layer; acoustic waves had the greatest influence. The impact of slow acoustic waves on the flow field was mainly concentrated in the region between the shock and the boundary layer, whereas the influence of fast acoustic waves was mainly concentrated in the boundary layer. Multi-mode perturbations formed in the boundary layer were caused by the free-stream with disturbances, wherein the fundamental mode was the dominant mode of the perturbations in the boundary layer caused by fast acoustic waves, entropy waves, and vortical waves. The dominant modes of the perturbations in the boundary layer caused by slow acoustic waves were both the fundamental mode and the second harmonic mode. The roughness element changed the propagation process of different modes of perturbations in the boundary layer. In the downstream region of the roughness element, perturbations in the boundary layer caused by the slow acoustic waves had the greatest influence. The second harmonic mode in the boundary layer was significantly suppressed, and the fundamental mode became the dominant mode. The effects of fast acoustic waves and entropy waves on the boundary layer receptivity were similar, except the amplitude of the perturbations in the boundary layer caused by the fast acoustic waves was larger