Lack Of Decay Research Articles

3775-year-old wood burial supports "wood vaulting" as a durable carbon removal method.

Six-times more carbon dioxide (CO2) is removed each year by terrestrial photosynthesis than fossil fuel emissions. However, the carbon is mostly returned to the atmosphere by decomposition. We found a 3775-year-old ancient wood log buried 2 meters belowground that was preserved far beyond its expected lifetime. The wood had near-perfect preservation, with carbon loss less than 5% compared to a modern sample. The lack of decay is likely due to the low permeability of the compact clay soil at the burial site. Our observation suggests a hybrid nature-engineering approach for carbon removal by burying woody biomass in similar anoxic environments. We estimate a global sequestration potential of up to 10 gigatonnes CO2 per year with existing technology at a low cost of $30 to $100 per tonne after optimization.

The Screened Poisson–Vlasov System with Infinite Charge and Vanishing Screening

The Vlasov equation may be used to model the dynamics of a collisionless plasma. We consider a situation where the plasma has unbounded support and the charge density does not decay as |x|→ ∞. The electric field is computed from the screened Poisson equation, whose fundamental solution decays exponentially as |x|→ ∞ and hence gives a convergent integral despite the lack of decay of the charge density. The limit as the screening is removed is studied in one space dimension. It is shown that if some assumptions on the initial conditions hold, then the limit in question exists (but is not uniform) and the problem satisfied by the limit is identified.

Polyharmonic smoothing splines and the multidimensional Wiener filtering of fractal-like signals

Motivated by the fractal-like behavior of natural images, we develop a smoothing technique that uses a regularization functional which is a fractional iterate of the Laplacian. This type of functional was initially introduced by Duchon for the approximation of nonuniformily sampled, multidimensional data. He proved that the general solution is a smoothing spline that is represented by a linear combination of radial basis functions (RBFs). Unfortunately, this is tedious to implement for images because of the poor conditioning of RBFs and their lack of decay. Here, we present a much more efficient method for the special case of a uniform grid. The key idea is to express Duchon's solution in a fractional polyharmonic B-spline basis that spans the same space as the RBFs. This allows us to derive an algorithm where the smoothing is performed by filtering in the Fourier domain. Next, we prove that the above smoothing spline can be optimally tuned to provide the MMSE estimation of a fractional Brownian field corrupted by white noise. This is a strong result that not only yields the best linear filter (Wiener solution), but also the optimal interpolation space, which is not bandlimited. It also suggests a way of using the noisy data to identify the optimal parameters (order of the spline and smoothing strength), which yields a fully automatic smoothing procedure. We evaluate the performance of our algorithm by comparing it against an oracle Wiener filter, which requires the knowledge of the true noiseless power spectrum of the signal. We find that our approach performs almost as well as the oracle solution over a wide range of conditions.

The Population Structure of African Cultivated Rice Oryza glaberrima (Steud.)

Abstract Genome-wide linkage disequilibrium (LD) was investigated for 198 accessions of Oryza glaberrima using 93 nuclear microsatellite markers. Significantly elevated levels of LD were detected, even among distantly located markers. Free recombination among loci at the population genetic level was shown (1) by a lack of decay in LD among markers on the same chromosome and (2) by a strictly increasing composite likelihood function for the recombination parameter. This suggested that the elevation in LD was due not to physical linkage but to other factors, such as population structure. A Bayesian clustering analysis confirmed this hypothesis, indicating that the sample of O. glaberrima in this study was subdivided into at least five cryptic subpopulations. Two of these subpopulations clustered with control samples of O. sativa, subspecies indica and japonica, indicating that some O. glaberrima accessions represent admixtures. The remaining three O. glaberrima subpopulations were significantly associated with specific combinations of phenotypic traits—possibly reflecting ecological adaptation to different growing environments.

DECAY AND REINDUCTION OF HEAT ACCLIMATION 561

The effects of heat acclimation, its decay and subsequent reacclimation were investigated. Acclimation (A) comprised 6 d, 70% ˙VO2 max cycling, 50 min, 34°C, 70% RH. This was followed by 21 d decay and 6 d reacclimation (R). Heart rate (HR), rectal temperature (Trec) and sweat rate (SR) were monitored in 8 cyclists (˙VO2 max = 61.8 ml.kg-1.min-1 ± 5.6 SD). Tests were conducted during winter. All variables changed over time (p<0.05). During A, final exercise HR decreased from 182 bpm on day one to 164 bpm on day six. Trec decreased from 39.33 °C to 38.82 °C and SR increased from 1.30 L.hr-1 to 1.64 L.hr-1 with acclimation. As a result of 21 d with no heat exposure there was decay in HR and SR (p<0.05). However, Trec showed no decay at all. During R, there was a decreased(p<0.05) HR (174 bpm to 163 bpm) and increased SR (1.34 L.hr-1 to 1.60 L.hr-1). Trec showed no change throughout R (38.74 °C to 38.64 °C). There were no differences between final A and R values for any variable. It was concluded that the high humidity and high exercise intensity produced full acclimation in 6 d and that during R the subjects could not achieve a greater level of heat tolerance. The lack of decay in Trec indicates some retention of the adaptations even after 21 d without heat exposure.

Sufficient Conditions for Ackerberg–O’Malley Resonance

An investigation is made of the asymptotic nature of the solution of the boundary-value problem \[\varepsilon y'' + 2xA(\varepsilon ,x)y' - A(\varepsilon ,x)B(\varepsilon ,x)y = 0;\quad y(a) = l,\quad y(b) = m,\] as $\varepsilon \to 0$, where $A(\varepsilon ,x)$ and $B(\varepsilon ,x)$ are continuous real functions of $\varepsilon $ and x, $a 0$, and $A(\varepsilon ,x)$ is nonzero in $[a,b]$. Particular attention is paid to the problem of resonance, which arises when the limiting form of the solution exhibits an unusual lack of decay (in the case $A(\varepsilon ,x) 0$). By application of a recent theory of differential equations with coalescing turning points sufficient conditions for resonance are established, both with and without the assumption that $A(\varepsilon ,x)$ and $B(\varepsilon ,x)$ are analytic functions of $\varepsilon $ and x. Illustrative examples are also included.