Modes of Growth in Dynamic Systems

Regardless of a system's complexity or scale, its growth can be considered to be a spontaneous thermodynamic response to a local convergence of down-gradient material flows. Here it is shown how growth can be constrained to a few distinct modes that depend on the availability of material and energetic resources. These modes include a law of diminishing returns, logistic behavior and, if resources are expanding very rapidly, super-exponential growth. For a case where a system has a resolved sink as well as a source, growth and decay can be characterized in terms of a slightly modified form of the predator-prey equations commonly employed in ecology, where the perturbation formulation of these equations is equivalent to a damped simple harmonic oscillator. Thus, the framework presented here suggests a common theoretical under-pinning for emergent behaviors in the physical and life sciences. Specific examples are described for phenomena as seemingly dissimilar as the development of rain and the evolution of fish stocks.Comment: 16 pages, 6 figures, including appendi

Influence of Hydrodynamic Interactions on the Kinetics of Colloidal Particle's Adsorption

The kinetics of irreversible adsorption of spherical particles onto a flat surface is theoretically studied. Previous models, in which hydrodynamic interactions were disregarded, predicted a power-law behavior $t^{-2/3}$ for the time dependence of the coverage of the surface near saturation. Experiments, however, are in agreement with a power-law behavior of the form $t^{-1/2}$. We outline that, when hydrodynamic interactions are considered, the assymptotic behavior is found to be compatible with the experimental results in a wide region near saturation.Comment: 4 pages, 1 figures, Phys. Rev. Lett. (in press

Dynamic Scaling of an Adsorption-Diffusion Process on Fractals

A dynamic scaling of a diffusion process involving the Langmuir type adsorption is studied. We find dynamic scaling functions in one and two dimensions and compare them with direct numerical simulations, and we further study the dynamic scaling law on fractal surfaces. The adsorption-diffusion process obeys the fracton dynamics on the fractal surfaces.Comment: 9 pages, 7 figure

Development of a thermal ionizer as ion catcher

An effective ion catcher is an important part of a radioactive beam facility that is based on in-flight production. The catcher stops fast radioactive products and emits them as singly charged slow ions. Current ion catchers are based on stopping in He and H$_2$ gas. However, with increasing intensity of the secondary beam the amount of ion-electron pairs created eventually prevents the electromagnetic extraction of the radioactive ions from the gas cell. In contrast, such limitations are not present in thermal ionizers used with the ISOL production technique. Therefore, at least for alkaline and alkaline earth elements, a thermal ionizer should then be preferred. An important use of the TRI$\mu$P facility will be for precision measurements using atom traps. Atom trapping is particularly possible for alkaline and alkaline earth isotopes. The facility can produce up to 10$^9$ s$^{-1}$ of various Na isotopes with the in-flight method. Therefore, we have built and tested a thermal ionizer. An overview of the operation, design, construction, and commissioning of the thermal ionizer for TRI$\mu$P will be presented along with first results for $^{20}$Na and $^{21}$Na.Comment: 10 pages, 4 figures, XVth International Conference on Electromagnetic Isotope Separators and Techniques Related to their Applications (EMIS 2007

Links from mantle to microbe at the Lau Integrated Study Site : insights from a back-arc spreading center

Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 62–77, doi:10.5670/oceanog.2012.04.The Lau Integrated Study Site (ISS) has provided unique opportunities for study of ridge processes because of its back-arc setting in the southwestern Pacific. Its location allows study of a biogeographical province distinct from those of eastern Pacific and mid-Atlantic ridges, and crustal compositions along the ridge lie outside the range of mid-ocean ridge crustal compositions. The Lau ISS is located above a subduction zone, at an oblique angle. The underlying mantle receives water and other elements derived from the downgoing lithospheric slab, with an increase in slab influence from north to south. Water lowers the mantle melting temperature and leads to greater melt production where the water flux is greater, and to distinctive regional-scale gradients along the ridge. There are deeper faulted axial valleys with basaltic volcanism in the north and inflated axial highs with andesites in the south. Differences in igneous rock composition and release of magmatic volatiles affect compositions of vent fluids and deposits. Differences in vent fluid compositions and small-scale diffuse-flow regimes correlate with regional-scale patterns in microbial and megafaunal distributions. The interdisciplinary research effort at the Lau ISS has successfully identified linkages between subsurface processes and deep-sea biological communities, from mantle to microbe to megafauna.Support was provided by National Science Foundation grants OCE-1038135 to MKT, OCE-0732369 and OCE-0240985 to CRF, OCE-0732369 and OCE-0838107 to PRG, OCE-0242618 to CHL, OCE-0242902 and OCE-0752256 to PJM, OCE-0728391 and OCE-0937404 to A-LR, and a GRFP to RB

Chiral and herringbone symmetry breaking in water-surface monolayers

We report the observation from monolayers of eicosanoic acid in the L′2 phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of their nearest neighbors. In this region we find a structural transition, which we tentatively identify as the rotator-herringbone transition L2d−L2h

Behaviour of uranium along Jucar River (Eastern Spain) Determination of 234U/238U and 235U/238U ratios

The uranium concentration and the U-234/U-238, U-235/U-238 activity ratios were studied in water samples from Jucar River, using low-level alpha-spectrometry. The effects of pH, temperature and salinity were considered and more detailed sampling was done in the neighbourhood of Cofrentes Nuclear plant (Valencia, Spain). Changes were observed in the uranium concentration with the salinity and the U-234/U-238 activity ratio was found to vary with pH. Leaching and dilution, which depend on pH and salinity, are the probable mechanisms for these changes in the concentration of uranium and the activity ratios.Rodríguez Álvarez, MJ.; Sanchez, F. (1995). Behaviour of uranium along Jucar River (Eastern Spain) Determination of 234U/238U and 235U/238U ratios. Journal of Radioanalytical and Nuclear Chemistry. 190(1):113-120. doi:10.1007/BF02035642S1131201901M. J. RORDÍGUEZ-AALVAREZ, F. SÁNCHEZ, E. NAVARRO, Proc. 3nd Intern. Summer School, Huelva Spain, M. GARCÍA-LEÓN, G. MADURGA (Eds), World Scientific, Singapore, 1994.M. IVANOVICH, R. S. HARMON (Eds), Uranium Disequilibrium Series: Applications to Environmental Problems, Clarendon Press, Oxford, 1982.K. OSMOND, J. B. COWART, At. Energy Rev., 14 (1976) 621.B. L. DICKSON, R. L. MEAKINS, Nucl. Instrum. Methods Phys. Res., 223 (1983) 593.J. L. GASCÓN, MURILLO, PhD Thesis, University of Zaragoza, Spain, 1990.M. C. MORÓN, A. MARTINEZ-AGUIRRE, M. GARCÍA-LEÓN, Intern. Conf. on Environmental Radioactivity in the Mediterranean Area, Barcelona 10–13 May 1988, SNE-ENS, Barcelona, 1988, p. 111.R. BOJANOWSKI, R. FUKAI, S. BALLESTRA, H. ASARI, Determination of natural radioactive elements in marine environmental materials by ion-exchange and α-spectrometry. Proc. 4th Symp. on the Determination of Radionuclides in Environmental and Biological Materials, April 1983, London, Ed-Rd Press.R. GARCÍA-TENORIO, M. GARCÍA-LEÓN, G. PIAZZA, Anal. Física B, 82 (1986) 238.L. HALLSTADIUS, Nucl. Instrum. Methods Phys. Res., 223 (1984) 266.F. VERA, A. MARTIN, Nucl. Instrum. Methods Phys. Res., A276 (1989) 289.A. MARTINEZ-AGUIRRE, M. GARCÍA-LEÓN, J. Radioanal. Nucl. Chem., 155 (1991) 97.J. R. DOOLEY, H. C. ROSHOLT, Econ. Geol., 61 (1996) 326.A. MARTINEZ-AGUIRRE, M. GARCÍA-LEÓN, Radiat. Prot. Dosim., 45 (1992) 249.J. TOOLE, M. S. BAXTER, J. THOMSON, Estuarine, Coastal and Shelf Sci., 25 (1987) 283.S. G. BHAT, S. KRISHANASWAMI, Proc. Indian Acad. Sci., A LXX, (1969).K. K. TUREKIAN, J. K. COCHRAN, in: Chemical Oceanography, Vol. 7, J. P. RILEY and R. CHESTER (Eds), 2nd ed., Academic Press, New York, 1978.D. LANGMUIR, Geochim. Cosmochim. Acta, 42 (1978) 547.J. M. MARTIN, M. MEYBECK, Mar. Chem., 7 (1979) 173.Radionuclide Transformations, Annals of the ICRP, ICRP Publication 38, Vol. 11–13, Pergamon Press, 1983.A. MANGINI, G. SONNTAG, G. BERTSCH, E. MÜLLER, Nature, 278 (1979) 337.M. R. SCOTT, in: M. IVANOVICH, R. S. HARMON (Eds), Uranium Disequilibrium Series: Applications to Environmental Problems, Clarendon Press, Oxford, 1982.J. K. OSMOND, J. B. COWART, in: M. IVANOVICH, R. S. HARMON (Eds), Uranium Disequilibrium Series: Applications to Environmental Problems, Clarendon Press, Oxford, 1982.R. BOWEN (Eds), Isotopes in the Earth Sciences, Elsevier Applied Science, 1988.F. VERA, PhD Thesis, University Extremadura, Spain, 1988.F. VERA, A. MARTIN, J. Radioanal. Nucl. Chem., 134 (1988) 73

Central role of detachment faults in accretion of slow-spreading oceanic lithosphere

Author Posting. © Macmillan Publishers, 2008. This is the author's version of the work. It is posted here by permission of Macmillan Publishers for personal use, not for redistribution. The definitive version was published in Nature 455 (2008): 790-794, doi:10.1038/nature07333.The formation of oceanic detachment faults is well established from inactive, corrugated fault planes exposed on seafloor formed along ridges spreading at less than 80 km/My1-4. These faults can accommodate extension for up to 1-3 Myrs5, and are associated with one of two contrasting modes of accretion operating along the northern Mid-Atlantic Ridge (MAR). The first is symmetrical accretion, dominated by magmatic processes with subsidiary high-angle faulting and formation of abyssal hills on both flanks. The second is asymmetrical accretion involving an active detachment fault6 along one ridge flank. An examination of ~2500 km of the MAR between 12.5 and 35°N reveals asymmetrical accretion along almost half of the ridge. Hydrothermal activity identified to date in the study region is closely associated with asymmetrical accretion, which also exhibits high-levels of near continuous hydroacoustically and teleseismically recorded seismicity. Enhanced seismicity is probably generated along detachment faults accommodating a sizeable proportion of the total plate separation. In contrast, symmetrical segments have lower levels of seismicity, which concentrates primarily at their ends. Basalts erupted along asymmetrical segments have compositions that are consistent with crystallization at higher pressures than basalts from symmetrical segments, and with lower extents of partial melting of the mantle. Both seismic and geochemical evidence indicate that the axial lithosphere is thicker and colder at asymmetrical sections of the ridge, either because associated hydrothermal circulation efficiently penetrates to greater depths, or because the rising mantle is cooler. We suggest that much of the variability in seafloor morphology, seismicity and basalt chemistry found along slow-spreading ridges can be thus attributed to the frequent involvement of detachments in oceanic lithospheric accretion.Supported by CNRS (JE), NSF (DKS, HS, JC, CL and SE), WHOI (JE, DKS, HS and JC), Harvard University (JE, CL and SE), Univ. of Leeds (JC), and MIT (JE)

A xenon gas purity monitor for EXO

We discuss the design, operation, and calibration of two versions of a xenon gas purity monitor (GPM) developed for the EXO double beta decay program. The devices are sensitive to concentrations of oxygen well below 1 ppb at an ambient gas pressure of one atmosphere or more. The theory of operation of the GPM is discussed along with the interactions of oxygen and other impurities with the GPM's tungsten filament. Lab tests and experiences in commissioning the EXO-200 double beta decay experiment are described. These devices can also be used on other noble gases.Comment: 41 pages, 26 figure