20GHz picosecond pulse generation by 1300nm mode-locked quantum dot master oscillator power amplifier

An integrated 1300 nm QD mode-locked narrow stripe MOPA is shown to generate 10.5 ps Fourier transform limited pulses at 20 GHz. The pulse train has an average power of 46.4 mW and peak powers exceeding 0.31 W

Non-critical waveguide alignment for vertically coupled microring using a mode-expanded bus architecture

Vertically coupled microrings in an all-pass filter configuration are fabricated with a range of waveguide misalignments deliberately introduced into the lithography masks to demonstrate noncritical fabrication requirements. The microrings have a mode-expanded bus design which allows a greatly reduced variation in power coupling coefficient-only 6% for fabrication misalignments as high as 1 mum. This represents a five-fold improvement in fabrication tolerance when compared with conventional design

Demonstration of a lossless monolithic 16x16 QW SOA switch

10Gb/s error-free operation of the first monolithic 16×16 quantum well semiconductor optical amplifier switch is demonstrated. The switch has a 2dB facet-to-facet gain and a minimum power penalty of 2.5dB

40 Gb/s data transmission over a 1 m long multimode polymer spiral waveguide

We report record error-free data transmission of 40Gb/s over a 1m-long multimode polymer spiral waveguide. The waveguide imposes no significant transmission impairments in the link despite its highly-multimoded nature and long length, demonstrating its potential in high-speed board-level optical interconnections

Non-Critical Waveguide Alignment for Vertically-Coupled Microring using a Mode-Expanded Bus Architecture

Vertically coupled microrings in an all-pass filter configuration are fabricated with a range of waveguide misalignments deliberately introduced into the lithography masks to demonstrate noncritical fabrication requirements. The microrings have a mode-expanded bus design which allows a greatly reduced variation in power coupling coefficient-only 6% for fabrication misalignments as high as 1 µm. This represents a five-fold improvement in fabrication tolerance when compared with conventional designs

One particle spectral weight of the three dimensional single band Hubbard model

Dynamic properties of the three-dimensional single-band Hubbard model are studied using Quantum Monte Carlo combined with the maximum entropy technique. At half-filling, there is a clear gap in the density of states and well-defined quasiparticle peaks at the top (bottom) of the lower (upper) Hubbard band. We find an antiferromagnetically induced weight above the naive Fermi momentum. Upon hole doping, the chemical potential moves to the top of the lower band where a robust peak is observed. Results are compared with spin-density-wave (SDW) mean-field and self consistent Born approximation results, and also with the infinite dimensional Hubbard model, and experimental photoemission (PES) for three dimensional transition-metal oxides.Comment: 11 pages, REVTeX, 16 figures included using psfig.sty. Ref.30 correcte

Stripes, Pseudogaps, and Van Hove Nesting in the Three-band tJ Model

Slave boson calculations have been carried out in the three-band tJ model for the high-T_c cuprates, with the inclusion of coupling to oxygen breathing mode phonons. Phonon-induced Van Hove nesting leads to a phase separation between a hole-doped domain and a (magnetic) domain near half filling, with long-range Coulomb forces limiting the separation to a nanoscopic scale. Strong correlation effects pin the Fermi level close to, but not precisely at the Van Hove singularity (VHS), which can enhance the tendency to phase separation. The resulting dispersions have been calculated, both in the uniform phases and in the phase separated regime. In the latter case, distinctly different dispersions are found for large, random domains and for regular (static) striped arrays, and a hypothetical form is presented for dynamic striped arrays. The doping dependence of the latter is found to provide an excellent description of photoemission and thermodynamic experiments on pseudogap formation in underdoped cuprates. In particular, the multiplicity of observed gaps is explained as a combination of flux phase plus charge density wave (CDW) gaps along with a superconducting gap. The largest gap is associated with VHS nesting. The apparent smooth evolution of this gap with doping masks a crossover from CDW-like effects near optimal doping to magnetic effects (flux phase) near half filling. A crossover from large Fermi surface to hole pockets with increased underdoping is found. In the weakly overdoped regime, the CDW undergoes a quantum phase transition ($T_{CDW}\to 0$), which could be obscured by phase separation.Comment: 15 pages, Latex, 18 PS figures Corrects a sign error: major changes, esp. in Sect. 3, Figs 1-4,6 replace

Non-neoclassical up/down asymmetry of impurity emission on Alcator C-Mod

We demonstrate that existing theories are insufficient to explain up/down asymmetries of argon x-ray emission in Alcator C-Mod ohmic plasmas. Instead of the poloidal variation, ñ[subscript z]/〈n[subscript z]〉, being of order the inverse aspect ratio, ϵ, and scaling linearly with B[subscript t][superscript _ over n][subscript e]/I[2 over p], it is observed over 0.8 < r/a < 1.0 to be of order unity and exhibits a threshold behaviour between 3.5 <B[subscript t][superscript _ over n][subscript e]/I[subscript p] < 4.0 (T10[superscript 20] m[superscript −3] MA[superscript −1]). The transition from a poloidally symmetric to asymmetric impurity distribution is shown to occur at densities just below those that trigger a reversal of the core toroidal rotation direction, thought to be linked to the transition between the linear and saturated ohmic confinement regimes. A possible drive is discussed by which anomalous radial transport might sustain the impurity density asymmetry as the ratio of the perpendicular to parallel equilibration times, τ[subscript ⊥,z]/τ[subscript ∥,z], approaches unity. This explanation requires a strong up/down asymmetry in radial flux which, while not observable on C-Mod, has been measured in TEXT and Tore Supra ohmic plasmas.United States. Dept. of Energy (Contract DE-FC02-99ER54512)United States. Dept. of Energy (Fusion Research Postdoctoral Research Program

Comparative study of classification algorithms using molecular descriptors in toxicological databases

The rational development of new drugs is a complex and expensive process, comprising several steps. Typically, it starts by screening databases of small organic molecules for chemical structures with potential of binding to a target receptor and prioritizing the most promising ones. Only a few of these will be selected for biological evaluation and further refinement through chemical synthesis. Despite the accumulated knowledge by pharmaceutical companies that continually improve the process of finding new drugs, a myriad of factors affect the activity of putative candidate molecules in vivo and the propensity for causing adverse and toxic effects is recognized as the major hurdle behind the current "target-rich, lead-poor" scenario. In this study we evaluate the use of several Machine Learning algorithms to find useful rules to the elucidation and prediction of toxicity using ID and 2D molecular descriptors. The results indicate that: i) Machine Learning algorithms can effectively use ID molecular descriptors to construct accurate and simple models; ii) extending the set of descriptors to include 2D descriptors improve the accuracy of the models