Rock-eating mycorrhizas: their role in plant nutrition and biogeochemical cycles

A decade ago, tunnels inside mineral grains were found that were likely formed by hyphae of ectomycorrhizal (EcM) fungi. This observation implied that EcM fungi can dissolve mineral grains. The observation raised several questions on the ecology of these ¿rock-eating¿ fungi. This review addresses the roles of these rock-eating EcM associations in plant nutrition, biogeochemical cycles and pedogenesis. Research approaches ranged from molecular to ecosystem level scales. Nutrient deficiencies change EcM seedling exudation patterns of organic anions and thus their potential to mobilise base cations from minerals. This response was fungal species-specific. Some EcM fungi accelerated mineral weathering. While mineral weathering could also increase the concentrations of phytotoxic aluminium in the soil solution, some EcM fungi increase Al tolerance through an enhanced exudation of oxalate. Through their contribution to Al transport, EcM hyphae could be agents in pedogenesis, especially podzolisation. A modelling study indicated that mineral tunnelling is less important than surface weathering by EcM fungi. With both processes taken together, the contribution of EcM fungi to weathering may be significant. In the field vertical niche differentiation of EcM fungi was shown for EcM root tips and extraradical mycelium. In the field EcM fungi and tunnel densities were correlated. Our results support a role of rock-eating EcM fungi in plant nutrition and biogeochemical cycles. EcM fungal species-specific differences indicate the need for further research with regard to this variation in functional traits

All-Electrical Quantum Computation with Mobile Spin Qubits

We describe and discuss a solid state proposal for quantum computation with mobile spin qubits in one-dimensional systems, based on recent advances in spintronics. Static electric fields are used to implement a universal set of quantum gates, via the spin-orbit and exchange couplings. Initialization and measurement can be performed either by spin injection from/to ferromagnets, or by using spin filters and mesoscopic spin polarizing beam-splitters. The vulnerability of this proposal to various sources of error is estimated by numerical simulations. We also assess the suitability of various materials currently used in nanotechnology for an actual implementation of our model.Comment: 10 pages, 6 figs, RevTeX

mspire: mass spectrometry proteomics in Ruby

Summary: Mass spectrometry-based proteomics stands to gain from additional analysis of its data, but its large, complex datasets make demands on speed and memory usage requiring special consideration from scripting languages. The software library ‘mspire’—developed in the Ruby programming language—offers quick and memory-efficient readers for standard xml proteomics formats, converters for intermediate file types in typical proteomics spectral-identification work flows (including the Bioworks .srf format), and modules for the calculation of peptide false identification rates

Observation of room temperature gate tunable quantum confinement effect in photodoped junctionless MOSFET

In the pursuit of room temperature quantum hardware, our study introduces a gate voltage tunable quantum wire within a tri-gated n-type junctionless MOSFET. The application of gate voltage alters the parabolic potential well of the tri-gated junctionless MOSFET, enabling modification of the nanowire's potential well profile. In the presence of light, photogenerated electrons accumulate at the center of the junctionless nanowire, aligning with the modified potential well profile influenced by gate bias. These carriers at the center are far from interfaces and experience less interfacial noise. Therefore, such clean photo-doping shows clear, repeatable peaks in current for specific gate biases compared to the dark condition, considering different operating drain-to-source voltages at room temperature. We propose that photodoping-induced subband occupation of gate tunable potential well of the nanowire is the underlying phenomenon responsible for this kind of observation. This study reveals experimental findings demonstrating gate-induced switching from semi-classical to the quantum domain, followed by the optical occupancy of electronic sub-bands at room temperature. We developed a compact model based on the Nonequilibrium Green's function formalism to understand this phenomenon in our illuminated device better. This work reveals the survival of the quantum confinement effect at room temperature in such semi-classical transport.Comment: 12 pages, 6 figure

A nanomechanical resonator shuttling single electrons at radio frequencies

We observe transport of electrons through a metallic island on the tip of a nanomechanical pendulum. The resulting tunneling current shows distinct features corresponding to the discrete mechanical eigenfrequencies of the pendulum. We report on measurements covering the temperature range from 300 K down to 4.2 K. We explain the I-V curve, which differs from previous theoretical predictions, with model calculations based on a Master equation approach.Comment: 5 pages, 4 jpeg-figure

Accurate Characterization of Silicon-On-Insulator MOSFETs for the Design of Low-Voltage, Low-Power RF Integrated Circuits

The maturation of low cost Silicon-on-Insulator (SOI) MOSFET technology in the microwave domain has brought about a need to develop specific characterization techniques. An original scheme is presented, which, by combining careful design of probing and calibration structures, rigorous in-situ calibration, and a new powerful direct extraction method, allows reliable identification of the parameters of the non-quasi-static small-signal model and the high-frequency noise parameters for MOSFETs. The extracted model is shown to be valid up to 40 GHz.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44055/1/10470_2004_Article_271487.pd

Determining the electronic performance limitations in top-down fabricated Si nanowires with mean widths down to 4 nm

Silicon nanowires have been patterned with mean widths down to 4 nm using top-down lithography and dry etching. Performance-limiting scattering processes have been measured directly which provide new insight into the electronic conduction mechanisms within the nanowires. Results demonstrate a transition from 3-dimensional (3D) to 2D and then 1D as the nanowire mean widths are reduced from 12 to 4 nm. The importance of high quality surface passivation is demonstrated by a lack of significant donor deactivation, resulting in neutral impurity scattering ultimately limiting the electronic performance. The results indicate the important parameters requiring optimization when fabricating nanowires with atomic dimensions

The curious case of thin-body Ge crystallization

The authors investigate the templated crystallization of thin-body Ge fin structures with high aspect ratios. Experimental variables include fin thickness and thermal treatments, with fin structures oriented in the direction. Transmission electron microscopy determined that various crystal defects form during crystallization of amorphous Ge regions, most notably (111) stacking faults, twin boundaries, and small crystallites. In all cases, the nature of the defects is dependent on the fin thickness and thermal treatments applied. Using a standard 600 degrees C rapid-thermal-anneal, Ge structures with high aspect ratios crystallize with better crystal quality and fewer uncured defects than the equivalent Si case, which is a cause for optimism for thin-film Ge devices. (C) 2011 American Institute of Physics. (doi:10.1063/1.3643160