Seasonal and spatial variation in the chemical character of dissolved organic matter within a small boreal forest watershed

Dissolved organic matter (DOM) is a significant carbon reservoir and component of the terrestrial-to-aquatic flux (Qualls et al., 1991). The terrestrial-to-aquatic carbon flux, a relatively new addition to global carbon models, is currently estimated to transfer a total of 1.7 petagrams (Pg) carbon (C) yr⁻¹ globally (IPCC, 2013). Terrestrially derived DOM has been identified as a significant pool of organic matter in the aquatic environment. However, the quantity and chemical composition of DOM transferred, as well as the mechanisms driving its transfer, are less understood. This thesis focuses on expanding our knowledge of the processing DOM undergoes as it is transferred from terrestrial-to-aquatic environments by: 1) developing a standardized extraction methodology that can yield representative eluates when applied to sourced samples from throughout the terrestrial-to-aquatic interface and 2) applying the designed methodology to conduct a year long study of DOM quantity and composition in the terrestrial-to-aquatic interface in a boreal forest watershed. Experimental results suggest that although solid phase extraction with a divinyl benzene sorbent (SPE-PPL) yields high extraction efficiencies when applied to DOM, it is subject to selectivity. Extractions performed at high loading volumes were found to select against O-alkyl DOM hydrogen constituents, additionally all SPE-PPL experiments were found to select against nitrogenous DOM components. However, by considering proper extraction parameters, SPE-PPL can produce bulk representative eluates for nuclear magnetic resonance (NMR) analysis from land positions spanning the terrestrial-to-aquatic interface. Results from the field study revealed that DOM transferred from terrestrial-to-aquatic land positions in a boreal forest watershed is both temporally and regionally variable, however, proximity immediately downstream of ponds appeared to be a major hydrologic control, while seasonal variation in hydrologic flow paths may represent another control in boreal forest watersheds. Dissolved organic matter chemical composition and quantity in traditional boreal forest streams related to shifts in the hydraulic flow path of the watershed, indicated by changes in riverine DOM chemical composition that correlated to seasonal wet and dry periods. Increases in both dissolved organic carbon (DOC) concentration and the presence of O-alkyl DOM hydrogen functionalities in the stream indicated a shift from groundwater sources during the dry period to soil water sources during the wet period. Conversely streams downslope of ponds seemed to be buffered against shifts in DOM chemical composition associated with changes in hydrologic flow paths. Dissolved organic matter chemical composition of streams downslope of ponds were relatively constant throughout the year resembling the characterization of pond outflows, even during periods of high hydraulic conductivity, via additions of autochthonous DOM produced in the pond. These additions of autochthonous DOM are negligible in streams not downslope of ponds. Further application of this approach during key periods of DOM export, such as spring snowmelt and fall rain periods may prove help to reveal the processes controlling the terrestrial-to-aquatic carbon flux in boreal forest landscapes

Netons: Vibrations of Complex Networks

We consider atoms interacting each other through the topological structure of a complex network and investigate lattice vibrations of the system, the quanta of which we call {\em netons} for convenience. The density of neton levels, obtained numerically, reveals that unlike a local regular lattice, the system develops a gap of a finite width, manifesting extreme rigidity of the network structure at low energies. Two different network models, the small-world network and the scale-free network, are compared: The characteristic structure of the former is described by an additional peak in the level density whereas a power-law tail is observed in the latter, indicating excitability of netons at arbitrarily high energies. The gap width is also found to vanish in the small-world network when the connection range $r = 1$.Comment: 9 pages, 6 figures, to appear in JP

CryoEM structure of the human SLC4A4 sodium-coupled acid-base transporter NBCe1.

Na+-coupled acid-base transporters play essential roles in human biology. Their dysfunction has been linked to cancer, heart, and brain disease. High-resolution structures of mammalian Na+-coupled acid-base transporters are not available. The sodium-bicarbonate cotransporter NBCe1 functions in multiple organs and its mutations cause blindness, abnormal growth and blood chemistry, migraines, and impaired cognitive function. Here, we have determined the structure of the membrane domain dimer of human NBCe1 at 3.9 Å resolution by cryo electron microscopy. Our atomic model and functional mutagenesis revealed the ion accessibility pathway and the ion coordination site, the latter containing residues involved in human disease-causing mutations. We identified a small number of residues within the ion coordination site whose modification transformed NBCe1 into an anion exchanger. Our data suggest that symporters and exchangers utilize comparable transport machinery and that subtle differences in their substrate-binding regions have very significant effects on their transport mode

Complex Kerr Geometry and Nonstationary Kerr Solutions

In the frame of the Kerr-Schild approach, we consider the complex structure of Kerr geometry which is determined by a complex world line of a complex source. The real Kerr geometry is represented as a real slice of this complex structure. The Kerr geometry is generalized to the nonstationary case when the current geometry is determined by a retarded time and is defined by a retarded-time construction via a given complex world line of source. A general exact solution corresponding to arbitrary motion of a spinning source is obtained. The acceleration of the source is accompanied by a lightlike radiation along the principal null congruence. It generalizes to the rotating case the known Kinnersley class of "photon rocket" solutions.Comment: v.3, revtex, 16 pages, one eps-figure, final version (to appear in PRD), added the relation to twistors and algorithm of numerical computations, English is correcte

Ground State Structure in a Highly Disordered Spin Glass Model

We propose a new Ising spin glass model on $Z^d$ of Edwards-Anderson type, but with highly disordered coupling magnitudes, in which a greedy algorithm for producing ground states is exact. We find that the procedure for determining (infinite volume) ground states for this model can be related to invasion percolation with the number of ground states identified as $2^{\cal N}$, where ${\cal N} = {\cal N}(d)$ is the number of distinct global components in the ``invasion forest''. We prove that ${\cal N}(d) = \infty$ if the invasion connectivity function is square summable. We argue that the critical dimension separating ${\cal N} = 1$ and ${\cal N} = \infty$ is $d_c = 8$. When ${\cal N}(d) = \infty$, we consider free or periodic boundary conditions on cubes of side length $L$ and show that frustration leads to chaotic $L$ dependence with {\it all} pairs of ground states occuring as subsequence limits. We briefly discuss applications of our results to random walk problems on rugged landscapes.Comment: LaTex fil

Quasigroups, Asymptotic Symmetries and Conservation Laws in General Relativity

A new quasigroup approach to conservation laws in general relativity is applied to study asymptotically flat at future null infinity spacetime. The infinite-parametric Newman-Unti group of asymptotic symmetries is reduced to the Poincar\'e quasigroup and the Noether charge associated with any element of the Poincar\'e quasialgebra is defined. The integral conserved quantities of energy-momentum and angular momentum are linear on generators of Poincar\'e quasigroup, free of the supertranslation ambiguity, posess the flux and identically equal to zero in Minkowski spacetime.Comment: RevTeX4, 5 page

Kerr-Schild Approach to the Boosted Kerr Solution

Using a complex representation of the Debney-Kerr-Schild (DKS) solutions and the Kerr theorem we analyze the boosted Kerr geometries and give the exact and explicit expressions for the metrics, the principal null congruences, the coordinate systems and the location of the singularities for arbitrary value and orientation of the boost with respect to the angular momentum. In the limiting, ultrarelativistic case we obtain light-like solutions possessing diverging and twisting principal null congruences and having, contrary to the known pp-wave limiting solutions, a non-zero value of the total angular momentum. The implications of the above results in various related fields are discussed.Comment: 16 pages, LaTe

Rotating Black Hole, Twistor-String and Spinning Particle

We discuss basic features of the model of spinning particle based on the Kerr solution. It contains a very nontrivial {\it real} stringy structure consisting of the Kerr circular string and an axial stringy system. We consider also the complex and twistorial structures of the Kerr geometry and show that there is a {\it complex} twistor-string built of the complex N=2 chiral string with a twistorial $(x,\theta)$ structure. By imbedding into the real Minkowski $\bf M^4$, the N=2 supersymmetry is partially broken and string acquires the open ends. Orientifolding this string, we identify the chiral and antichiral structures. Target space of this string is equivalent to the Witten's `diagonal' of the $\bf CP^3\times CP^{*3}.$Comment: 19 p. 4 figures, extended version of hep-th/0412065, based on the talk given at the Conference `Symmetries and Spin'(SPIN-Praha-2004) July 200

Tri-critical behavior in rupture induced by disorder

We discover a qualitatively new behavior for systems where the load transfer has limiting stress amplification as in real fiber composites. We find that the disorder is a relevant field leading to tri--criticality, separating a first-order regime where rupture occurs without significant precursors from a second-order regime where the macroscopic elastic coefficient exhibit power law behavior. Our results are based on analytical analysis of fiber bundle models and numerical simulations of a two-dimensional tensorial spring-block system in which stick-slip motion and fracture compete.Comment: Revtex, 10 pages, 4 figures available upon reques