The importance of northern peatlands in global carbon systems during the Holocene

We applied an inverse model to simulate global carbon (C) cycle dynamics during the Holocene period using atmospheric carbon dioxide (CO2) concentrations reconstructed from Antarctic ice cores and prescribed C accumulation rates of Northern Peatlands (NP) as inputs. Previous studies indicated that different sources could contribute to the 20 parts per million by volume (ppmv) atmospheric CO2 increase over the past 8000 years. These sources of C include terrestrial release of 40–200 petagram C (PgC, 1 petagram=1015 gram), deep oceanic adjustment to a 500 PgC terrestrial biomass buildup early in this interglacial period, and anthropogenic land-use and land-cover changes of unknown magnitudes. Our study shows that the prescribed peatland C accumulation significantly modifies our previous understanding of Holocene C cycle dynamics. If the buildup of the NP is considered, the terrestrial pool becomes the C sink of about 160–280 PgC over the past 8000 years, and the only C source for the terrestrial and atmospheric C increases is presumably from the deep ocean due to calcium carbonate compensation. Future studies need to be conducted to constrain the basal times and growth rates of the NP C accumulation in the Holocene. These research endeavors are challenging because they need a dynamically-coupled peatland simulator to be constrained with the initiation time and reconstructed C reservoir of the NP. Our results also suggest that the huge reservoir of deep ocean C explains the major variability of the glacial-interglacial C cycle dynamics without considering the anthropogenic C perturbation

Comment on "On the Origin of the Highest Energy Cosmic Rays"

We show that the photodisintegration of heavy cosmic ray nuclei with energies above 10^20 eV is dominated by interactions with photons from the cosmic microwave background radiation, rather than from infrared ones. This implies that the observed air shower events with energies 2-3 10^20 eV cannot originate from Fe nuclei coming from distances beyond 10 MpcComment: 1 page, 2 figure

On Higgs and sphaleron effects during the leptogenesis era

We discuss the effects of various processes that can be active during the leptogenesis era, and present the Boltzmann equations that take them into account appropriately. A non-vanishing Higgs number asymmetry is always present, enhancing the washout of the lepton asymmetry. This is the main new effect when leptogenesis takes place at $T>10^{12}$ GeV, reducing the final baryon asymmetry and tightening the leptogenesis bound on the neutrino masses. If leptogenesis occurs at lower temperatures, electroweak sphalerons partially transfer the lepton asymmetry to a baryonic one, while Yukawa interactions and QCD sphalerons partially transfer the asymmetries of the left-handed fields to the right-handed ones, suppressing the washout processes. Depending on the specific temperature range in which leptogenesis occurs, the final baryon asymmetry can be enhanced or suppressed by factors of order 20%--40% with respect to the case when these effects are altogether ignored.Comment: one reference adde

A new model of Holocene peatland net primary production, decomposition, water balance, and peat accumulation

Peatland carbon and water cycling are tightly coupled, so dynamic modeling of peat accumulation over decades to millennia should account for carbon-water feedbacks. We present initial results from a new simulation model of long-term peat accumulation, evaluated at a wellstudied temperate bog in Ontario, Canada. The Holocene Peat Model (HPM) determines vegetation community composition dynamics and annual net primary productivity based on peat depth (as a proxy for nutrients and acidity) and water table depth. Annual peat (carbon) accumulation is the net balance above- and below-ground productivity and litter/peat decomposition – a function of peat hydrology (controlling depth to and degree of anoxia). Peat bulk density is simulated as a function of degree of humification, and affects the water balance through its influence on both the growth rate of the peat column and on peat hydraulic conductivity and the capacity to shed water. HPM output includes both time series of annual carbon and water fluxes, peat height, and water table depth, as well as a final peat profile that can be “cored” and compared to field observations of peat age and macrofossil composition. A stochastic 8500-yr, annual precipitation time series was constrained by a published Holocene climate reconstruction for southern Quebec. HPM simulated 5.4 m of ´ peat accumulation (310 kg C m−2 ) over 8500 years, 6.5% of total NPP over the period. Vascular plant functional types accounted for 65% of total NPP over 8500 years but only 35% of the final (contemporary) peat mass. Simulated age-depth and carbon accumulation profiles were compared to a radiocarbon dated 5.8 m, c.9000-yr core. The simulated core was younger than observations at most depths, but had a similar overall trajectory; carbon accumulation rates were generally higher in the simulation and were somewhat more variable than observations. HPM results were sensitive to centuryscale anomalies in precipitation, with extended drier periods (precipitation reduced ∼10%) causing the peat profile to lose carbon (and height), despite relatively small changes in NP

EPIQR-TOBUS: a new generation of refurbishment decision aid methods

In a large majority of European countries, the amount of maintenance and refurbishment works represents nearly 50% of the total amount spent in the building sector. New requirements are being added to the necessity of maintaining or re-establishing the building stock's usage value. They are linked to the determination to reduce energy consumption, pollutant emissions, work site wastes, to improve the Indoor Environment Quality (IEQ) and all the modern conveniences inside buildings. Two European projects, EPIQR (réf. nr.: JOR3-CT96-0044) and TOBUS (réf. nr.: JOR3-CT98-Û235), developed in the IIIrd and IVth framework programs put the foundations of a new generation of refurbishment decision aid tools. A structured diagnosis scheme covering the state of deterioration of the building elements, energy performance, indoor environment quality, functional obsolescence offer a new concept which helps architects and engineers to approach the building refurbishment with a global view of the whole process, to take informed decisions, to construct coherent refurbishment scenarii and calculate a reasonable investment budget in the very first stage of the refurbishment project. EPIQR project addresses residential buildings and it has been finished in 1998, TOBUS addresses office buildings and it is still in course. The support of these methods is a multimedia computer program. Several modules help the users to treat the data collected during a diagnosis survey, to set up refurbishment scenarii and calculate their cost or energy performance, and finally to visualise the results in a comprehensive way and to prepare quality reports. This paper presents the structure and the main features of the method and softwar

Pulling a polymer out of a potential well and the mechanical unzipping of DNA

Motivated by the experiments on DNA under torsion, we consider the problem of pulling a polymer out of a potential well by a force applied to one of its ends. If the force is less than a critical value, then the process is activated and has an activation energy proportinal to the length of the chain. Above this critical value, the process is barrierless and will occur spontaneously. We use the Rouse model for the description of the dynamics of the peeling out and study the average behaviour of the chain, by replacing the random noise by its mean. The resultant mean-field equation is a nonlinear diffusion equation and hence rather difficult to analyze. We use physical arguments to convert this in to a moving boundary value problem, which can then be solved exactly. The result is that the time $t_{po}$ required to pull out a polymer of $N$ segments scales like $N^2$. For models other than the Rouse, we argue that $t_{po}\sim N^{1+\nu}$Comment: 11 pages, 6 figures. To appear in PhysicalReview

The importance of flavor in leptogenesis

We study leptogenesis from the out-of-equilibrium decays of the lightest heavy neutrino $N_1$ in the medium (low) temperature regime, T\lsim 10^{12} GeV ($10^{10}$ GeV), where the rates of processes mediated by the $\tau$ (and $\mu$) Yukawa coupling are non negligible, implying that the effects of lepton flavors must be taken into account. We find important quantitative and qualitative differences with respect to the case where flavor effects are ignored: (i) The cosmic baryon asymmetry can be enhanced by up to one order of magnitude; (ii) The sign of the asymmetry can be opposite to what one would predict from the sign of the total lepton asymmetry $\epsilon_1$; (iii) Successful leptogenesis is possible even with $\epsilon_1=0$.Comment: 27 pages, 2 figures. Added 3 reference

`Natural Masslessness Conservation' for neutrinos in two Higgs-doublet models

We present a model which supplements the Standard Electroweak Model with three right-handed neutrinos and one extra scalar doublet which does not develop a vacuum expectation value. With the aid of a discrete symmetry the neutrinos are kept strictly massless. This model has several interesting features. It has unsuppressed lepton flavour violating processes, in particular $\mu \rightarrow e \gamma$, hinting at the possibility that these may soon be within experimental reach. The $Z$ and $W$ interactions become non-diagonal at one loop level. In particular, a non-trivial leptonic mixing matrix is seen to arise from the clash between the charged gauge boson and the charged scalar interactions.Comment: (Latex file, 12 pages. Two figures available upon request). CMU-preprin