Near-field reflection backscattering apertureless optical microscopy: application to spectroscopy experiments on opaque samples, comparison between lock-in and digital photon counting detection techniques

An apertureless scanning near-field optical microscope (ASNOM) in reflection backscattering configuration is designed to conduct spectroscopic experiments on opaque samples constituted of latex beads. The ASNOM proposed takes advantage of the depth-discrimination properties of confocal microscopes to efficiently extract the near-field optical signal. Given their importance in a spectroscopic experiment, we systematically compare the lock-in and synchronous photon counting detection methods. Some results of Rayleigh's scattering in the near field of the test samples are used to illustrate the possibilities of this technique for reflection backscattering spectroscopy.     

Two Algorithms in Search of a Type-System

The authors’ programming formalism is a version of call-by-value under a complexity-theoretically motivated type system. programs run in type-2 polynomial-time and all standard type-2 basic feasible functionals are -definable ( types are confined to levels 0, 1, and 2). A limitation of the original version of is that the only directly expressible recursions are tail-recursions. Here we extend so that a broad range of affine recursions are directly expressible. In particular, the revised can fairly naturally express the classic insertion- and selection-sort algorithms, thus overcoming a sticking point of most prior implicit-complexity-based formalisms. The paper’s main work is in refining the original time-complexity semantics for to show that these new recursion schemes do not lead out of the realm of feasibility.     

Inhibition of biological reductive dissolution of hematite by ferrous iron

Bacterial dissimilatory iron reduction is self-inhibited by the production of ferrous [Fe(II)] iron resulting in diminished iron reduction as Fe(II) accumulates. Experiments were conducted to investigate the mechanisms of Fe(II) inhibition employing the dissimilatory metal-reducing bacterium Shewanella putrefaciens strain CN32 under nongrowth conditions in a system designed to minimize precipitation of ferrous iron minerals. After an initial period (ca. 1 day) of relatively rapid iron reduction, hematite reduction rates were controlled by mass transfer of Fe(II). Experiments in which hematite was equilibrated with Mn(II) prior to inoculation indicated that the observed inhibition was not due to Fe(II) sorption. At longer times, soluble Fe(II) accumulated such that the reaction was slowed due to a decreased thermodynamic driving force. The thermodynamic evaluation also supported the prior conclusion that hydrated hematite surface sites may yield substantially more energy during bioreduction than "bulk" hematite. For well-mixed conditions, the rates of hematite reduction were directly proportional to the biologically available reaction potential.     

Dynamic Measurements in Combustible and Detonable Aerosols

We present all the methods used at the ISL for determining the principal parameters of rapid fuel air aerosol dispersions and of their reactions, i.e. combustion and detonation. In a shock tube or in the free atmosphere. we measure the velocity of the dispersed fuel, the breaking of the droplets, their size distribution and their velocities. The investigation of the thermal variations due to the fuel evaporation allows to obtain the composition of the two-phase mixture air/combustible gaz – fuel.     

Computing the polyadic decomposition of nonnegative third order tensors

Computing the minimal polyadic decomposition (also often referred to as canonical decomposition or sometimes Parafac) amounts to finding the global minimum of a coercive polynomial in many variables. In the case of arrays with nonnegative entries, the low-rank approximation problem is well posed. In addition, due to the large dimension of the problem, the decomposition can be rather efficiently calculated with the help of preconditioned nonlinear conjugate gradient algorithms, as subsequently shown, if equipped with an algebraic calculation of the globally optimal stepsize in low dimension. Other algorithms are also studied (gradient and quasi-Newton approaches) for comparisons. Two versions of each algorithm are considered: the enhanced line search version (ELS), and the backtracking version alternating with ELS. Computer simulations are provided and demonstrate the good behavior of these algorithms dedicated to nonnegative arrays, compared to others put forward in the literature. Finally, applications in the context of data analysis illustrate various algorithms. The main advantage of the suggested approach is to explicitly take into account the nonnegative nature of the loading matrices in the problem parameterization, instead of enforcing positive entries by projection. According to the experiments we have run, such an approach also happens to be more robust with respect to possible modeling errors.     

Characterization of impact of process options in Germanium-On-Insulator (GeOI) high-k & metal gate pMOSFETs by low-frequency noise

The impact of technological processes on Germanium-On-Insulator (GeOI) noise performance is studied. We present an experimental investigation of low-frequency noise (LFN) measurements carried out on (GeOI) PMOS transistors with different process splits. The front gate is composed of a SiO₂/HfO₂ stack with a TiN metal gate electrode. The result is an aggressively reduced equivalent oxide thickness (EOT) of 1.8 nm. The buried oxide is used as a back gate for experimental purposes. Front and back gate interfaces are characterized and the slow oxide trap densities are extracted. The obtained values are comprised between 5 × 10¹⁷ and 8 × 10¹⁸ cm⁻³eV⁻¹. No correlation between front interface trap density and front interface mobility is observed. We underline a strong correlation between rear interface trap density and rear interface mobility degradation. The impact of Ge film thickness is equally studied. For thin films, the measured drain-current noise spectral density shows that LFN can be described by the carrier fluctuation model from weak to strong inversion. For thicker film devices, in weak inversion the LFN can be described by the mobility fluctuation model and in strong inversion the LFN is described by the carrier fluctuation model. The α_H parameter for these devices is 1.2 × 10⁻³. These results are significant for the future development of GeOI technologies.     

A Wide-Range Mixed-Mode DLL for a Combination 512 Mb 2.0 Gb/s/pin GDDR3 and 2.5 Gb/s/pin GDDR4 SDRAM

A mixed-mode delay-locked loop (MDLL) for a 512 Mb graphics SDRAM is presented in this paper. The MDLL extends its lock range into the gigahertz realm by applying clock division and analog phase generation (APG). The divided clock from the MDLL is used for clocking logic and tracking deterministic access latency in the SDRAM. A short discussion of some of the side effects and advantages of using a divided, multi-phase clock for logic operation is presented. A low-power clock distribution network (CDN) based on the presented MDLL is also disclosed. Fabricated in a 1.5 V 95 nm triple-metal CMOS process, the MDLL achieves a measured RMS jitter of 4.6 ps and peak-to-peak jitter of 38 ps at GDDR4 mode with a 1 GHz clock. Power consumption for the entire MDLL-based CDN is 107 mW at 800 MHz and 1.5 V.