A monolithic MQW InP/InGaAsP-based comb generator

We report a monolithic optical frequency comb generator using quaternary/quaternary multiple quantum well InV/InGaAsP material as phase modulator and gain medium in a Frequency Modulated (FM) laser design. The modulation was generated by quantum confined Stark effect to achieve a comb-line spacing of 24.4 GHz. The laser was fabricated using a single epitaxial growth step and quantum well intermixing to realize low loss phase and modulation sections. The resulting comb generator produces lines with a spacing exactly given by the modulation frequency, differential phase noise between adjacent lines of -82 dBc/Hz at 1 kHz offset and a comb spectrum width of up to 2 THz

Shape of Deconstruction

We construct a six-dimensional Maxwell theory using a latticized extra space, the continuum limit of which is a shifted torus recently discussed by Dienes. This toy model exhibits the correspondence between continuum theory and discrete theory, and give a geometrical insight to theory-space model building.Comment: 10 pages, 2 figures, RevTeX4. a citation adde

A monolithic MQW InP-InGaAsP-Based optical comb generator

We report the first demonstration of a monolithic optical-frequency comb generator. The device is based on multi-section quaternary/quaternary eight-quantum-well InP-InGaAsP material in a frequency-modulated (FM) laser design. The modulation is generated using quantum-confined Stark-effect phase-induced refractive index modulation to achieve fast modulation up to 24.4 GHz. The laser was fabricated using a single epitaxial growth step and quantum-well intermixing to realize low-loss phase adjustment and modulation sections. The output was quasicontinuous wave with intensity modulation at less than 20% for a total output power of 2 mW. The linewidth of each line was limited by the linewidth of the free running laser at an optimum of 25 MHz full-width at half-maximum. The comb generator produces a number of lines with a spacing exactly equal to the modulation frequency (or a multiple of it), differential phase noise between adjacent lines of -82 dBc/Hz at 1-kHz offset (modulation source-limited), and a potential comb spectrum width of up to 2 THz (15 nm), though the comb spectrum was not continuous across the full span

Study of the physicochemical quality of water in the Sebi-Ponty basin at Diamniadio (Senegal)

The Sebi-Ponty dam has a basin that is widely used by the population for agro-pastoral activities (animal watering, agriculture, etc.). This basin covers an average area of 106,000 m2 and an average depth of 7 m or about a volume of 435,000 m3. The origin of the water is rainfall (runoff and direct descent). The availability of water is estimated to eight months taking into account the water being drawn, infiltration and evaporation. A qualitative knowledge of the contents of this pool will be a great benefit to those activities of the population. Itrsquos in this context that this study was carried out by this group of researchers, following physic-chemical compositions were targeted: turbidity, color, temperature, conductivity, pH, hardness alkalinity, nitrite, iron, phosphate, boron, and chlorine concentrations. The physico-chemical results obtained on samples taken in the basin between October and December showed that the concentrations of boron, iron and nitrite exceeded the levels recommended by the standard for agro pastoral needs. While turbidity, color, temperature, conductivity, pH, hardness, alkalinity, phosphate and chlorine are at acceptable levels

What Precision Electroweak Physics Says About the SU(6)/Sp(6) Little Higgs

We study precision electroweak constraints on the close cousin of the Littlest Higgs, the SU(6)/Sp(6) model. We identify a near-oblique limit in which the heavy W' and B' decouple from the light fermions, and then calculate oblique corrections, including one-loop contributions from the extended top sector and the two Higgs doublets. We find regions of parameter space that give acceptably small precision electroweak corrections and only mild fine tuning in the Higgs potential, and also find that the mass of the lightest Higgs boson is relatively unconstrained by precision electroweak data. The fermions from the extended top sector can be as light as 1 TeV, and the W' can be as light as 1.8 TeV. We include an independent breaking scale for the B', which can still have a mass as low as a few hundred GeV.Comment: 52 pages, 16 figure

Massive Supergravity and Deconstruction

We present a simple superfield Lagrangian for massive supergravity. It comprises the minimal supergravity Lagrangian with interactions as well as mass terms for the metric superfield and the chiral compensator. This is the natural generalization of the Fierz-Pauli Lagrangian for massive gravity which comprises mass terms for the metric and its trace. We show that the on-shell bosonic and fermionic fields are degenerate and have the appropriate spins: 2, 3/2, 3/2 and 1. We then study this interacting Lagrangian using goldstone superfields. We find that a chiral multiplet of goldstones gets a kinetic term through mixing, just as the scalar goldstone does in the non-supersymmetric case. This produces Planck scale (Mpl) interactions with matter and all the discontinuities and unitarity bounds associated with massive gravity. In particular, the scale of strong coupling is (Mpl m^4)^1/5, where m is the multiplet's mass. Next, we consider applications of massive supergravity to deconstruction. We estimate various quantum effects which generate non-local operators in theory space. As an example, we show that the single massive supergravity multiplet in a 2-site model can serve the function of an extra dimension in anomaly mediation.Comment: 24 pages, 2 figures, some color. Typos fixed and refs added in v

Little Hierarchy, Little Higgses, and a Little Symmetry

Little Higgs theories are an attempt to address the little hierarchy problem, i.e., the tension between the naturalness of the electroweak scale and the precision measurements showing no evidence for new physics up to 5-10 TeV. In little Higgs theories, the Higgs mass-squareds are protected to the one-loop order from the quadratic divergence. This allows the cutoff to be raised up to \~10 TeV, beyond the scales probed by the precision data. However, strong constraints can still arise from the contributions of the new TeV scale particles and hence re-introduces the fine-tuning problem. In this paper we show that a new symmetry, denoted as T-parity, under which all heavy gauge bosons and scalar triplets are odd, can remove all the tree-level contributions to the electroweak observables and therefore makes the little Higgs theories completely natural. The T-parity can be manifestly implemented in a majority of little Higgs models by following the most general construction of the low energy effective theory a la Callan, Coleman, Wess and Zumino. In particular, we discuss in detail how to implement the T-parity in the littlest Higgs model based on SU(5)/SO(5). The symmetry breaking scale f can be even lower than 500 GeV if the contributions from the unknown UV physics at the cutoff are somewhat small. The existence of $T$-parity has drastic impacts on the phenomenology of the little Higgs theories. The T-odd particles need to be pair-produced and will cascade down to the lightest T-odd particle (LTP) which is stable. A neutral LTP gives rise to missing energy signals at the colliders which can mimic supersymmetry. It can also serve as a good dark matter candidate.Comment: 20 pages, 2 figures, RevTeX; v2: Yukawa sector in the SU(5)/SO(5) model slightly modified. Also added comments on the Dirac mass term for the fermionic doublet partner; v3: clarifying comments on the modified Yukawa sector. version to appear on JHE

Influences of naturally occurring agents in combination with fluoride on gene expression and structural organization of Streptococcus mutans in biofilms

<p>Abstract</p> <p>Background</p> <p>The association of specific bioactive flavonoids and terpenoids with fluoride can modulate the development of cariogenic biofilms by simultaneously affecting the synthesis of exopolysaccharides (EPS) and acid production by <it>Streptococcus mutans</it>, which enhanced the cariostatic effectiveness of fluoride <it>in vivo</it>. In the present study, we further investigated whether the biological actions of combinations of myricetin (flavonoid), <it>tt</it>-farnesol (terpenoid) and fluoride can influence the expression of specific genes of <it>S. mutans </it>within biofilms and their structural organization using real-time PCR and confocal fluorescence microscopy.</p> <p>Results</p> <p>Twice-daily treatment (one-minute exposure) during biofilm formation affected the gene expression by <it>S. mutans </it>both at early (49-h) and later (97-h) stages of biofilm development. Biofilms treated with combination of agents displayed lower mRNA levels for <it>gtfB </it>and <it>gtfD </it>(associated with exopolysaccharides synthesis) and <it>aguD </it>(associated with <it>S. mutans </it>acid tolerance) than those treated with vehicle-control (<it>p </it>< 0.05). Furthermore, treatment with combination of agents markedly affected the structure-architecture of <it>S. mutans </it>biofilms by reducing the biovolume (biomass) and proportions of both EPS and bacterial cells across the biofilm depth, especially in the middle and outer layers (vs. vehicle-control, <it>p </it>< 0.05). The biofilms treated with combination of agents were also less acidogenic, and had reduced amounts of extracellular insoluble glucans and intracellular polysaccharides than vehicle-treated biofilms (<it>p </it>< 0.05).</p> <p>Conclusion</p> <p>The data show that the combination of naturally-occurring agents with fluoride effectively disrupted the expression of specific virulence genes, structural organization and accumulation of <it>S. mutans </it>biofilms, which may explain the enhanced cariostatic effect of our chemotherapeutic approach.</p

New massive supergravity multiplets

We present new off-shell formulations for the massive superspin-3/2 multiplet. In the massless limit, they reduce respectively to the old minimal (n=-1/3) and non-minimal ($n\neq -1/3, 0$) linearized formulations for 4D N=1 supergravity. Duality transformations, which relate the models constructed, are derived.Comment: 18 pages, LaTeX; v2: minor changes, references adde