Calcium isotope fractionation during microbially induced carbonate mineral precipitation

We report the calcium isotope fractionation during the microbially-induced precipitation of calcium carbonate minerals in pure cultures of the marine sulfate-reducing bacterium Desulfovibrio bizertensis. These data are used to explore how the calcium isotope fractionation factor during microbially-induced carbonate mineral precipitation differs from the better-constrained calcium isotope fractionation factors during biogenic or abiotic carbonate mineral precipitation. Bacterial growth was then modulated with antibiotics, and the evolution of δ44Ca in solution was monitored under different microbial growth rates. The faster the microbial growth rate, the larger the calcium isotope fractionation during carbonate mineral precipitation, ranging from Δ44Ca(s-f) between -1.07‰ and -0.48‰. The reported calcium isotope fractionation can help us understand the link between calcium isotope fractionation and microbial metabolism in carbonate minerals precipitated during sedimentary diagenesis.The work was supported by ERC 307582 StG (CARBONSINK) to AVT and NERC 700 NE/R013519/1 to HJ

Topological Quantum Phase Transition in Synthetic Non-Abelian Gauge Potential

The method of synthetic gauge potentials opens up a new avenue for our understanding and discovering novel quantum states of matter. We investigate the topological quantum phase transition of Fermi gases trapped in a honeycomb lattice in the presence of a synthetic non- Abelian gauge potential. We develop a systematic fermionic effective field theory to describe a topological quantum phase transition tuned by the non-Abelian gauge potential and ex- plore its various important experimental consequences. Numerical calculations on lattice scales are performed to compare with the results achieved by the fermionic effective field theory. Several possible experimental detection methods of topological quantum phase tran- sition are proposed. In contrast to condensed matter experiments where only gauge invariant quantities can be measured, both gauge invariant and non-gauge invariant quantities can be measured by experimentally generating various non-Abelian gauges corresponding to the same set of Wilson loops

The hidden perils of read mapping as a quality assessment tool in genome sequencing

This article provides a comparative analysis of the various methods of genome sequencing focusing on verification of the assembly quality. The results of a comparative assessment of various de novo assembly tools, as well as sequencing technologies, are presented using a recently completed sequence of the genome of Lactobacillus fermentum 3872. In particular, quality of assemblies is assessed by using CLC Genomics Workbench read mapping and Optical mapping developed by OpGen. Over-extension of contigs without prior knowledge of contig location can lead to misassembled contigs, even when commonly used quality indicators such as read mapping suggest that a contig is well assembled. Precautions must also be undertaken when using long read sequencing technology, which may also lead to misassembled contigs

Optimal Network QoS over the Internet of Vehicles for E-Health Applications

Wireless technologies are pervasive to support ubiquitous healthcare applications. However, a critical issue of using wireless communications under a healthcare scenario is the electromagnetic interference (EMI) caused by RF transmission, and a high level of EMI may lead to a critical malfunction of medical sensors. In consideration of EMI on medical sensors, we study the optimization of quality of service (QoS) within the whole Internet of vehicles for E-health and propose a novel model to optimize the QoS by allocating the transmit power of each user. Our results show that the optimal power control policy depends on the objective of optimization problems: a greedy policy is optimal to maximize the summation of QoS of each user, whereas a fair policy is optimal to maximize the product of QoS of each user. Algorithms are taken to derive the optimal policies, and numerical results of optimizing QoS are presented for both objectives and QoS constraints

All-linear time reversal by a dynamic artificial crystal

The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance. Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing. In this paper, we report the experimental realization of all-linear time reversal. The time-reversal mechanism we propose is based on the dynamic control of an artificial crystal structure, and is demonstrated in a spin-wave system using a dynamic magnonic crystal. The crystal is switched from an homogeneous state to one in which its properties vary with spatial period a, while a propagating wave packet is inside. As a result, a linear coupling between wave components with wave vectors k≈π/a and k′=k−2ππ/a≈−π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet. The reversal mechanism is entirely general and so applicable to artificial crystal systems of any physical nature

Effective Field Theories

Effective field theories encode the predictions of a quantum field theory at low energy. The effective theory has a fairly low ultraviolet cutoff. As a result, loop corrections are small, at least if the effective action contains a term which is quadratic in the fields, and physical predictions can be read straight from the effective Lagrangean. Methods will be discussed how to compute an effective low energy action from a given fundamental action, either analytically or numerically, or by a combination of both methods. Basically,the idea is to integrate out the high frequency components of fields. This requires the choice of a "blockspin",i.e. the specification of a low frequency field as a function of the fundamental fields. These blockspins will be the fields of the effective field theory. The blockspin need not be a field of the same type as one of the fundamental fields, and it may be composite. Special features of blockspins in nonabelian gauge theories will be discussed in some detail. In analytical work and in multigrid updating schemes one needs interpolation kernels \A from coarse to fine grid in addition to the averaging kernels $C$ which determines the blockspin. A neural net strategy for finding optimal kernels is presented. Numerical methods are applicable to obtain actions of effective theories on lattices of finite volume. The constraint effective potential) is of particular interest. In a Higgs model it yields the free energy, considered as a function of a gauge covariant magnetization. Its shape determines the phase structure of the theory. Its loop expansion with and without gauge fields can be used to determine finite size corrections to numerical data.Comment: 45 pages, 9 figs., preprint DESY 92-070 (figs. 3-9 added in ps format

CLort: High Throughput and Low Energy Network Intrusion Detection on IoT Devices with Embedded GPUs

While IoT is becoming widespread, cyber security of its devices is still a limiting factor where recent attacks (e.g., the Mirai bot-net) underline the need for countermeasures. One commonly-used security mechanism is a Network Intrusion Detection System (NIDS), but the processing need of NIDS has been a significant bottleneck for large dedicated machines, and a show-stopper for resource-constrained IoT devices. However, the topologies of IoT are evolving, adding intermediate nodes between the weak devices on the edges and the powerful cloud in the center. Also, the hardware of the devices is maturing, with new CPU instruction sets, caches as well as co-processors. As an example, modern single board computers, such as the Odroid XU4, come with integrated Graphics Processing Units (GPUs) that support general purpose computing. Even though using all available hardware efficiently is still an open issue, it has the promise to run NIDS more efficiently.In this work we introduce CLort, an extension to the well-known NIDS Snort that a) is designed for IoT devices b) alleviates the burden of pattern matching for intrusion detection by offloading it to the GPU. We thoroughly explain how our design is used as part of the latest release of Snort and suggest various optimizations to enable processing on the GPU. We evaluate CLort in regards to throughput, packet drops in Snort, and power consumption using publicly available traffic traces.\ua0CLort achieves up to 52% faster processing throughput than its CPU counterpart. CLort can also analyze up to 12% more packets than its CPU counterpart when sniffing a network.\ua0Finally, the experimental evaluation shows that CLort consumes up to 32% less energy than the CPU counterpart, an important consideration for IoT devices

The role of microbial sulfate reduction in calcium carbonate polymorph selection

Microbial sulfate reduction is a dominant metabolism in many marine sedimentary environments. The influence of this metabolism on the kinetics of CaCO3 growth, as well as the dominant polymorphs precipitated, is poorly understood. To investigate the role of microbial metabolism on CaCO3 precipitation and polymorph selection, we conducted growth experiments with the sulfate reducing bacteria (D. bizertensis) in media with varying Mg/Ca and different seeding materials (calcite and kaolinite). Our results suggest that sulfate reducing bacteria both induce carbonate mineral precipitation through an increase in alkalinity and serve as a nucleation sites for the growing carbonate mineral; the majority of the carbonate minerals produced were on cell material rather than mineral seeds. We also find the Mg/Ca and presence of phosphate in the media play a key role in controlling the rates of carbonate mineral precipitation and calcium carbonate polymorph selection. In media where the Mg/Ca is greater than 2, crystalline monohydrocalcite (MHC) is the primary carbonate mineral produced. Although phosphate concentrations have a lesser effect on which polymorph initially precipitates, a series of transformation experiments suggests that the presence of phosphate stabilizes MHC crystals and prevents its transformation to more stable calcium carbonate polymorphs. Collectively, these results suggest that the polymorph of microbially-mediated calcium carbonate cements is determined by the solution chemistry upon nucleation.Ministry of Education Malaysia, SLAI (Skim Latihan Akademik IPTA) scholarship to CY