Fission decay of N = Z nuclei at high angular momentum: 60^{60}Zn

Using a unique two-arm detector system for heavy ions (the BRS, binary reaction spectrometer) coincident fission events have been measured from the decay of $^{60}$Zn compound nuclei formed at 88MeV excitation energy in the reactions with $^{36}$Ar beams on a $^{24}$Mg target at $E_{lab}(^{36}$Ar) = 195 MeV. The detectors consisted of two large area position sensitive (x,y) gas telescopes with Bragg-ionization chambers. From the binary coincidences in the two detectors inclusive and exclusive cross sections for fission channels with differing losses of charge were obtained. Narrow out-of-plane correlations corresponding to coplanar decay are observed for two fragments emitted in binary events, and in the data for ternary decay with missing charges from 4 up to 8. After subtraction of broad components these narrow correlations are interpreted as a ternary fission process at high angular momentum through an elongated shape. The lighter mass in the neck region consists dominantly of two or three-particles. Differential cross sections for the different mass splits for binary and ternary fission are presented. The relative yields of the binary and ternary events are explained using the statistical model based on the extended Hauser-Feshbach formalism for compound nucleus decay. The ternary fission process can be described by the decay of hyper-deformed states with angular momentum around 45-52 $hbar$.Comment: 23 pages, 25 figure

Ecohydrology effects of an invasive grass (Phalaris arundinacea) on semi-arid riparian zones

Riparian areas (floodplains) provide key ecological functions that are linked to the ecohydrology however; they are particularly susceptible to invasion by alien species. In much of the western United States, riparian zones are shifting from native woody and herbaceous species to invasive grass dominated ecosystems that may alter hydrology, including changes to stream flow. Compared to the woody species they often replace, dense grass stands may have higher rates of growth (productivity) and water loss through leaves (transpiration), yet may access shallower water sources and thus reduce stream flow. In eastern Washington, many streams experience low flow that degrades water quality, concentrates pollutants, and reduces habitat. Most of these streams\u27 riparian zones have extensive stands of reed canary grass (Phalaris arundinacea). Reed canary grass was historically planted for erosion control and as a forage crop, but its ability to invade and create monotypic stands has allowed it to out compete native vegetation in riparian areas throughout much of the temperate United States. My goal is to determine the effect of reed canary grass on the ecohydrology of riparian zones along low order streams in a semi-arid region. I conducted vegetation, groundwater, and stream flow surveys at nine sites along four watersheds to determine community composition and hydrologic regime measured the length of the growing season for nine riparian species. I measured the amount of biomass and calculated the amount of photosynthetic surface for dense stands of nine riparian species. The amount of water used by different species was determined by measuring transpiration rates of reed canary grass and other riparian species throughout the growing season. Hydrogen and oxygen isotopes from different water sources (stream water and deep groundwater) were used to determine the proportion of water sources use by different plants species. Reed canary grass was found with greater cover than other riparian species on low elevation geomorphic positions in the riparian zone. It had the longest growing season by two weeks. Although its transpiration rates per unit leaf area are not exceptional compared to other species, its high specific leaf area and ability to produce dense stands of photosynthetic biomass results in more photosynthetic surface through which to transpire water than any other riparian species. Reed canary grass was found to rely heavily on surface water sources along different elevations in the riparian zone. My results implicate reed canary grass as a major factor in the regional low stream flow during the growing season. Although the presence of reed canary grass can add some benefits to a riparia buffer, I present strong evidence that it is altering the ecohydrology of these ecosystems. The management of this grass, particularly in a semi-arid region, could improve water quality and quantity --Document

An Exact Algorithm for TSP in Degree-3 Graphs via Circuit Procedure and Amortization on Connectivity Structure

The paper presents an O^*(1.2312^n)-time and polynomial-space algorithm for the traveling salesman problem in an n-vertex graph with maximum degree 3. This improves the previous time bounds of O^*(1.251^n) by Iwama and Nakashima and O^*(1.260^n) by Eppstein. Our algorithm is a simple branch-and-search algorithm. The only branch rule is designed on a cut-circuit structure of a graph induced by unprocessed edges. To improve a time bound by a simple analysis on measure and conquer, we introduce an amortization scheme over the cut-circuit structure by defining the measure of an instance to be the sum of not only weights of vertices but also weights of connected components of the induced graph.Comment: 24 pages and 4 figure

RoofKIT - Circular Construction and Solar Energy Use in Practice at the Solar Decathlon Europe 21/22

he contribution of the RoofKIT team to the SDE 21/22 competition is the extension for an existing café in Wuppertal, Germany, to create new functions and living space for the building with simultaneous energetic upgrading. The energy concept targets all renewable resources available on and in the building for energy supply: mainly solar energy which is used via PVT collectors, as well as waste heat from ventilation and grey water which is recovered for pre-heating. As part of the competition, a demonstration unit will be built representing a small cut-out of the extension. An integral building and energy concept combines physical properties of the building with adapted building services technologies to achieve maximum indoor comfort – particularly considering possible overheating of the lightweight construction during summer – and minimum CO2 emissions. The latter extends to the whole lifecycle of the building unit and one of the major goals of the project is to realize an almost completely mono-fraction and circular building construction as a contribution to the urban mining concept

The extrasolar planet Gliese 581 d: a potentially habitable planet? (Corrigendum to arXiv:1009.5814)

We report here that the equation for H2O Rayleigh scattering was incorrectly stated in the original paper [arXiv:1009.5814]. Instead of a quadratic dependence on refractivity r, we accidentally quoted an r^4 dependence. Since the correct form of the equation was implemented into the model, scientific results are not affected.Comment: accepted to Astronomy&Astrophysic

The population of deformed bands in 48^{48}Cr by emission of 8^{8}Be from the 32^{32}S + 24^{24}Mg reaction

Using particle-$\gamma$ coincidences we have studied the population of final states after the emission of 2 $\alpha$-particles and of $^{8}$Be in nuclei formed in $^{32}$S+$^{24}$Mg reactions at an energy of $\textrm{E}_{\rm L}(^{32}\textrm{S}) = 130 {\rm MeV}$. The data were obtained in a setup consisting of the GASP $\gamma$-ray detection array and the multidetector array ISIS. Particle identification is obtained from the $\Delta$E and E signals of the ISIS silicon detector telescopes, the $^{8}$Be being identified by the instantaneous pile up of the $\Delta$E and E pulses. $\gamma$-ray decays of the $^{48}$Cr nucleus are identified with coincidences set on 2 $\alpha$-particles and on $^{8}$Be. Some transitions of the side-band with $K^\pi=4^{-}$ show stronger population for $^{8}$Be emission relative to that of 2 $\alpha$-particles (by a factor $1.5-1.8$). This observation is interpreted as due to an enhanced emission of $^{8}$Be into a more deformed nucleus. Calculations based on the extended Hauser-Feshbach compound decay formalism confirm this observation quantitatively.Comment: 17 pages, 9 figures accepted for publication in J. Phys.

Redefined ion association constants have consequences for calcium phosphate nucleation and biomineralization

Calcium orthophosphates (CaPs), as hydroxyapatite (HAP) in bones and teeth are the most important biomineral for humankind. While clusters in CaP nucleation have long been known, their speciation and mechanistic pathways to HAP remain debated. Evidently, mineral nucleation begins with two ions interacting in solution, fundamentally underlying solute clustering. Here, we explore CaP ion association using potentiometric methods and computer simulations. Our results agree with literature association constants for Ca2+ and H2PO4−, and Ca2+ and HPO42-, but not for Ca2+ and PO43− ions, which previously has been strongly overestimated by two orders of magnitude. Our data suggests that the discrepancy is due to a subtle, premature phase separation that can occur at low ion activity products, especially at higher pH. We provide an important revision of long used literature constants, where association of Ca2+ and PO43− actually becomes negligible below pH 9.0, in contrast to previous values. Instead, [CaHPO4]0 dominates the aqueous CaP speciation between pH ~6–10. Consequently, calcium hydrogen phosphate association is critical in cluster-based precipitation in the near-neutral pH regime, e.g., in biomineralization. The revised thermodynamics reveal significant and thus far unexplored multi-anion association in computer simulations, constituting a kinetic trap that further complicates aqueous calcium phosphate speciation

Entropy Drives Calcium Carbonate Ion Association

The understanding of the molecular mechanisms underlying the early stages of crystallisation is still incomplete. In the case of calcium carbonate, experimental and computational evidence suggests that phase separation relies on so-called pre-nucleation clusters (PNCs). A thorough thermodynamic analysis of the enthalpic and entropic contributions to the overall free energy of PNC formation derived from three independent methods demonstrates that solute clustering is driven by entropy. This can be quantitatively rationalised by the release of water molecules from ion hydration layers, explaining why ion association is not limited to simple ion pairing. The key role of water release in this process suggests that PNC formation should be a common phenomenon in aqueous solutions

Determination of the charge carrier compensation mechanism in Te-doped GaAs by scanning tunneling microscopy.

We identified the charge carrier compensation mechanism in Te-doped GaAs with atomically resolved scanning tunneling microscopy. Three types of defects were found: tellurium donors (Te-As), Ga vacancies (V-Ga), and Ga vacancy-donor complexes (V-Ga-Te-As). We show quantitatively that the compensation in Te-doped bulk GaAs is exclusively caused by vacancy-donor complexes in contrast to Si-doped GaAs. This is explained with the Fermi-level effect as the universal mechanism leading to Ga vacancy formation in n-doped GaAs, and a Coulomb interaction leading to the formation of the complexes. The quantification of the carrier compensation yields a -3e charge state of V-Ga in bulk GaAs. (C) 2003 American Institute of Physics