Experimental comparison of coherent polarization-switched QPSK to polarization-multiplexed QPSK for 10 x 100 km WDM transmission

Polarization-switched quadrature phase-shift keying has been demonstrated experimentally at 40.5Gb/s with a coherent receiver and digital signal processing. Compared to polarization-multiplexed QPSK at the same bit rate, its back-to-back sensitivity at 10-3 bit-error-ratio shows 0.9dB improvement, and it tolerates about 1.6dB higher launch power for 10 × 100km, 50GHz-spaced WDM transmission allowing 1dB penalty in required optical-signal-to-noise ratio relative to back-to-back

Examining environmental drivers of spatial variability in aflatoxin accumulation in Kenyan maize: potential utility in risk prediction models

Maize, a staple food in most African countries, is prone to contamination by aflatoxins, toxic secondary metabolites mainly produced by Aspergillus flavus and A. parasiticus. Aflatoxins are known to cause liver cancer, and chronic exposure has been linked to other adverse health outcomes including growth faltering in children. To mitigate exposure in maize-dependent populations, there is need to identify the factors associated with aflatoxin contamination. This is difficult, however, because of high sampling cost and lack of affordable and accurate analytical methods. Publicly available, remotely-sensed data on vegetation, precipitation, and soil properties could be useful in predicting locations at risk for aflatoxin contamination in maize. This study investigates the utility of publicly available remotely-sensed data on rainfall, vegetation cover (indicated by normalized difference vegetation index or NDVI), and soil characteristics as potential predictors of aflatoxin contamination in Kenyan maize. Aflatoxin was analyzed in maize samples (n=2466) that were collected in 2009 and 2010 at 243 local hammer mills in eastern and western Kenya. Overall, 60% of maize samples had detectable aflatoxin. Global positioning system coordinates of each mill location were linked to remotely-sensed, spatially explicit indicators of average monthly NDVI, total monthly rainfall, and soil properties. Higher rainfall and vegetation cover during the maize pre-flowering period were significantly associated with higher prevalence of aflatoxin contamination. Conversely, higher rainfall and vegetation cover during the maize flowering and post-flowering periods (not including harvest) were associated with lower prevalence of aflatoxin contamination. Water stress throughout the growing season may cause increased plant susceptibility to fungal colonization and aflatoxin accumulation. Soil organic carbon content, pH, total exchangeable bases, salinity, texture, and soil type were significantly associated with aflatoxin. In conclusion, this study shows that remotely-sensed data can be regressed on available aflatoxin data highlighting important potential predictors that could reduce the cost of data collection and the cost of aflatoxin risk forecasting models.Keywords: Aflatoxin, GIS, NDVI, soil characteristics, rainfall, mycotoxins, East Africa, Keny

On the Erasure and Regeneration of the Primordial Baryon Asymmetry by Sphalerons

We show that a cosmological baryon asymmetry generated at the GUT scale, which would be destroyed at lower temperatures by sphalerons and possible new B- or L-violating effects, can naturally be preserved by an asymmetry in the number of right-handed electrons. This results in a significant softening of previously derived baryogenesis-based constraints on the strength of exotic B- or L-violating interactions.Comment: 10 pp. LaTex (2 figures, included) UMN-TH-1201/9

Suppressing the μ\mu and neutrino masses by a superconformal force

The idea of Nelson and Strassler to obtain a power law suppression of parameters by a superconformal force is applied to understand the smallness of the $\mu$ parameter and neutrino masses in R-parity violating supersymmetric standard models. We find that the low-energy sector should contain at least another pair of Higgs doublets, and that a suppression of \lsim O(10^{-13}) for the $\mu$ parameter and neutrino masses can be achieved generically. The superpotential of the low-energy sector happens to possess an anomaly-free discrete R-symmetry, either $R_3$ or $R_6$, which naturally suppresses certain lepton-flavor violating processes, the neutrinoless double beta decays and also the electron electric dipole moment. We expect that the escape energy of the superconformal sector is \lsim O(10) TeV so that this sector will be observable at LHC. Our models can accommodate to a large mixing among neutrinos and give the same upper bound of the lightest Higgs mass as the minimal supersymmetric standard model.Comment: 24 page

Constraints on Baryon-Nonconserving Yukawa Couplings in a Supersymmetric Theory

The 1-loop evolution of couplings in the minimal supersymmetric standard model, extended to include baryon nonconserving $(B\!\!\!/)$ operators through explicit $R$-parity violation, is considered keeping only $B\!\!\!/$ superpotential terms involving the maximum possible number of third generation superfields. If all retained Yukawa couplings $Y_i$ are required to remain in the perturbative domain $(Y_i < 1)$ upto the scale of gauge group unification, upper bounds ensue on the magnitudes of the $B\!\!\!/$ coupling strengths at the supersymmetry breaking scale, independent of the model of unification. They turn out to be similar to the corresponding fixed point values reached from a wide range of $Y_i$ (including all $Y_i$ greater than unity) at the unification scale. The coupled evolution of the top and $B\!\!\!/$ Yukawa couplings results in a reduction of the fixed point value of the former.Comment: PRL-TH-94/8 and TIFR/TH/94-7, 15 pages, LaTe

Fermion Masses and Gauge Mediated Supersymmetry Breaking from a Single U(1)

We present a supersymmetric model of flavor. A single U(1) gauge group is responsible for both generating the flavor spectrum and communicating supersymmetry breaking to the visible sector. The problem of Flavor Changing Neutral Currents is overcome, in part using an `Effective Supersymmetry' spectrum among the squarks, with the first two generations very heavy. All masses are generated dynamically and the theory is completely renormalizable. The model contains a simple Froggatt-Nielsen sector and communicates supersymmetry breaking via gauge mediation without requiring a separate messenger sector. By forcing the theory to be consistent with SU(5) Grand Unification, the model predicts a large tan beta and a massless up quark. While respecting the experimental bounds on CP violation in the K-system, the model leads to a large enhancement of CP violation in B-(B bar) mixing as well as in B decay amplitudes.Comment: LaTeX, 25 pages, 8 figure

Adaptation of Autocatalytic Fluctuations to Diffusive Noise

Evolution of a system of diffusing and proliferating mortal reactants is analyzed in the presence of randomly moving catalysts. While the continuum description of the problem predicts reactant extinction as the average growth rate becomes negative, growth rate fluctuations induced by the discrete nature of the agents are shown to allow for an active phase, where reactants proliferate as their spatial configuration adapts to the fluctuations of the catalysts density. The model is explored by employing field theoretical techniques, numerical simulations and strong coupling analysis. For d<=2, the system is shown to exhibits an active phase at any growth rate, while for d>2 a kinetic phase transition is predicted. The applicability of this model as a prototype for a host of phenomena which exhibit self organization is discussed.Comment: 6 pages 6 figur

Einstein, incompleteness, and the epistemic view of quantum states

Does the quantum state represent reality or our knowledge of reality? In making this distinction precise, we are led to a novel classification of hidden variable models of quantum theory. Indeed, representatives of each class can be found among existing constructions for two-dimensional Hilbert spaces. Our approach also provides a fruitful new perspective on arguments for the nonlocality and incompleteness of quantum theory. Specifically, we show that for models wherein the quantum state has the status of something real, the failure of locality can be established through an argument considerably more straightforward than Bell's theorem. The historical significance of this result becomes evident when one recognizes that the same reasoning is present in Einstein's preferred argument for incompleteness, which dates back to 1935. This fact suggests that Einstein was seeking not just any completion of quantum theory, but one wherein quantum states are solely representative of our knowledge. Our hypothesis is supported by an analysis of Einstein's attempts to clarify his views on quantum theory and the circumstance of his otherwise puzzling abandonment of an even simpler argument for incompleteness from 1927.Comment: 18 pages, 8 figures, 1 recipe for cupcakes; comments welcom

Pliocene and pleistocene volcanic interaction with cordilleran ice sheets, damming of the Yukon River and vertebrate palaeontology, Fort Selkirk volcanic group, west-central Yukon, Canada

Romeo Sherpa green journal. Permission to archive accepted author manuscriptNeogene volcanism in the Fort Selkirk area began with eruptions in the Wolverine Creek basin ca. 4.3 Ma and persisted to ca. 3.0 Ma filling the ancestral Yukon River valley with at least 40 m of lava flows. Activity at the Ne Ch’e Ddhäwa eruptive center overlapped with the last stages of the Wolverine Creek eruptive centers. Hyaloclastic tuff was erupted between ca. 3.21 and 3.05 Ma. This eruption caused or was coincident with damming of Yukon River. The first demonstrable incursion of a Cordilleran ice sheet into the Fort Selkirk area was coincident with a second eruption of the Ne Ch’e Ddhäwa eruptive center ca. 2.1 Ma. The Ne Ch’e Ddhäwa subglacial mound was erupted beneath at least 300 m of glacial ice (Ne Ch’e Ddhäwa Glaciation). The Eruption of the Fort Selkirk center occurred between the last eruption of Ne Ch’e Ddhäwa and Fort Selkirk Glaciation (ca. 2.1e1.5 Ma). Till and outwash from Fort Selkirk Glaciation are conformably overlain by nonglacial sediments that contain the Fort Selkirk tephra (fission track dated at ca. 1.5 Ma). These nonglacial sediments also preserve a short magnetic reversal (reversed to normal) identified as the Gilsá polarity excursion. Temporal control and sedimentology constrain Fort Selkirk Glaciation and the Fort Selkirk Local Fauna to marine isotope stage 54. Rapid and extensive eruption of the Pelly eruptive center filled the Yukon River valley with 70 m of lava which buried these glacial and nonglacial sediments and dammed Yukon River. Local striations and erratic pebbles occur on the last of these lava flows. They document a subsequent incursion of glacial ice during the last 500 ka of the Matuyama Chron (Forks Glaciation). The last major eruption of mafic lava occurred in the middle Pleistocene west of (early Holocene) Volcano Mountain in basin of Black Creek: lava flowed down the valley presently occupied by Black Creek and dammed Yukon River in the area of the Black Creek confluence. This eruption predated the middle Pleistocene Reid Glaciation. Minor volcanism has continued in this area since the middle Pleistocene at Volcano Mountain.Ye