bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy metals in wetland plants and soil of Lake Taihu, China
Authors: Yang Hongjun , Shen Zhemin , Zhu Songhe , Wang Wenhua 
Published: December 2007

Abstract
Properties of vertical distribution of soil near water bodies are vary considerably from those of land and may greatly affect the transportation of heavy metals in wetlands. Vertical distributions of heavy metals (Cr, Cd, Cu, Pb, and Zn) in the soil of aquatic-terrestrial ecotone (ATE) of Lake Taihu, China, and in wetland plant tissues were studied. Generally, concentrations of heavy metals decreased with increasing depth in the top 40-cm cores and then increased slightly with increasing depth. This investigation indicated that concentrations of Cd, Cr, Pb, and Zn exceeded the geochemical background values in the Taihu Lake area. Concentrations of Cd at all depth soil columns exceeded the Environment Quality Standard for Soils of China. Correlation analysis showed that concentrations of Zn, Cr, Cd, and Pb correlated significantly with one another, suggesting that they had the same origin. The concentration of Cu was negatively correlated with root biomass, which may explain the lower concentration of copper in the soil cores. The dominant plants of the wetland were Phragmites australis and Ludwigia prostrata, and heavy metal accumulated primarily in the root tissue. The general order was root &gt; rhizome &gt; stem &gt; leaf, whereas in L. prostrata, leaf was the main tissue for Cr accumulation. Both P. australis and L. prostrata had the highest concentration factor (CF) to Cu, and CF was 20.3 and 15.8, respectively. Aquatic-terrestrial ecotone plants are more effective in controlling Cu pollution than other heavy metals. This will be very significant for ATE reestablishment near Cu-polluted sites.
Evaluation of estrogenicity of sewage effluent and reclaimed water using vitellogenin as a biomarker
Authors: An Lihui , Hu Jianying , Yang Min 
Published: December 2007

Abstract
To evaluate the quality of reclaimed water, the estrogenicity of effluent from a sewage treatment plant and of reclaimed water treated with coagulation–sedimentation–filtration using the effluent as raw water was assessed using vitellogenin (VTG) as a biomarker. After a three-week exposure, significant (p &lt; 0.05) induction of VTG occurred in female crucian carp (Carassius carassius) exposed continuously to the secondary effluent and reclaimed water with different dilutions (12.5, 25, 50, and 100% for secondary effluent; 50 and 100% for reclaimed water); no induction of VTG was detected when exposed to 12.5 and 25% reclaimed water. For male fish, however, only 100% secondary effluent induced the production of VTG (mean ± standard deviation, 38.6 ± 9.8 μg/ml). When the exposure time was prolonged to three months, VTG was induced significantly in both females and males at all gradient concentrations of secondary effluent and at 50 and 100% reclaimed water. The results indicated that no obvious VTG was detected in fish exposed to reclaimed water diluted more than fourfold. Ozonation of the secondary effluent under an ozone consumption dose of 8.5 mg/L resulted in a VTG level equal to that of 12.5% secondary effluent or 50% reclaimed water. Furthermore, VTG induction reflects the cumulative effects of estrogenic activity in the secondary effluent and reclaimed water compared with the in vitro assays, in which estrogenic activities in effluent changed markedly during the experiment.
Tissue-dependent distribution and bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in vegetation samples collected from Dongting Lake, China
Authors: Fang Liping , Zheng Minghui , Xiao Ke , Yang Yongbin 
Published: December 2007

Abstract
The concentration of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soils and different species of vegetation collected from the Dongting Lake region, China. Use of sodium pentachlorophenate (Na-PCP) was the main contamination source of PCDD/Fs for soil/sediment and vegetation in the Dongting Lake region. Reed (Phragmitas communis Trin), Polygonum orientale L., and Artemisia selengensis Turcz ex Bess were selected as model plants to explore the pathway of PCDD/Fs transfer from contaminated soil to vegetation. In the vegetation tissue samples, the total international toxic equivalency values ranged from 0.14 to 1.64 pg international toxic equivalency/g dry weight with a mean value of 0.67 pg international toxic equivalency/g dry weight. Polychlorinated dibenzo-p-dioxins and dibenzofurans congener distribution and bio accumulation varied among vegetation species. Polychlorinated dibenzo-p-dioxins and dibenzofuran levels in the leaves were found to be higher than those in the root and stem, which were affected considerably by volatilization from contaminated soil. Volatilization from polluted soil and subsequent sorption to leaves may be a significant pathway for contamination of vegetation in Dongting Lake region.
Semipermeable membrane device–assisted desorption of pyrene from soils and its relationship to bioavailability
Authors: Sun Hongwen , Wang Cuiping , Huo Chong , Zhou Zunlong 
Published: December 2007

AbstractDesorption of pyrene from three different soils was studied using a semipermeable membrane device (SPMD)–assisted method to develop a new approach to predict bioavailability of hydrophobic organic compounds (HOCs) in soils. The results showed that pyrene desorption increased with reduction of soil organic matter content and elevation of pyrene concentration in unaged soils, and the 50-d desorption percentage was 52.2 ± 3.6%, 76.3 ± 1.5%, and 99.4 ± 3.3% for soils 1, 2, and 3, respectively, at an initial pyrene concentration of 10 mg/kg and 73.6 ± 4.9%, 94.1 ± 4.1%, and 98.3 ± 4.9%, respectively, at an initial pyrene concentration of 100 mg/kg. Aging led to a reduction in SPMD–assisted desorption because of movement of pyrene molecules from easy-desorbing to difficult-desorbing sites. The pyrene 50-d desorption percentage from 180-d–aged soils reduced to 5.8 ± 0.6%, 18.8 ± 0.9%, and 34.2 ± 3.1% in soils 1, 2, and 3, respectively, at an initial pyrene concentration of 10 mg/kg and 43.9 ± 2.9%, 54.3 ± 4.7%, and 86.3 ± 3.5%, respectively, at an initial pyrene concentration of 100 mg/kg. Dry and wet conditions during aging had different effects on aging-derived reduction of pyrene desorption, which was found, to our knowledge for the first time, to depend on pollutant concentration. The water to soil ratio during desorption had a significant effect on SPMD–assisted desorption dynamics. When this ratio changed from 10:1 to 1:1, desorption dynamics became more linear and slower, because when the ratio was low, the SPMD could not contact with soil particles well and the diffusion of pyrene from pore water into the SPMD might become the limiting step for SPMD accumulation of pyrene from soils. Good correlations were found between SPMD–assisted desorption and the biota–soil accumulation factor for both unaged and aged soils. The SPMD–assisted desorption is considered to be a reliable approach to predict the bioavailability of HOCs in soils.
Residues of DDTs and their spatial distribution characteristics in soils from the Yangtze River Delta, China
Authors: Li Qingbo , Zhang Haibo , Luo Yongming , Song Jing , Wu Longhua , Ma Jianmin 
Published: December 2007

Abstract
Organochlorine pesticides were used extensively in the Yangtze River Delta, China. However, knowledge about their residual levels and environmental fates in soils of this area is limited. This paper presents the residue isomers and spatial pattern of dichlorodiphenyltrichloroethane (DDT) in soils across 17 main cities in the Yangtze River Delta. Forty-three soil surface (0–15 cm) samples were collected during a field campaign conducted in October 2003 in the Delta. Six DDT isomers (1-[2-chlorophenyl]-1-[4-chlorophenyl]-2,2-dichloroethane [o,p′-DDD], 1-[2-chlorophenyl]-1-[4-chlorophenyl]-2,2-dichloroethylene [o,p-′DDE], 1,1,1-trichloro-2-[p-chlorophenyl]-2-[o-chlorophenyl]ethane [o,p′-DDT], p,p′-dichlorodiphenyldichloroethane [p,p′-DDD], p,p′-dichlo-rodiphenyldichloroethylene [p,p-DDE], p,p-dichlorodiphenyltrichloroethane [p,p-DDT]) were detected using gas chromatography. The results show that p,p′-DDE was the dominant isomer in the soil samples. The levels of DDT are generally low in soils of this area and are comparable to DDT levels in other cities in China and in soils from developed countries such as the United States and Germany. The isomer ratios of o,p′-DDT to p,p′-DDT and DDT to (DDD + DDE) were employed to identify the source of DDT. The computed ratios implied that the source of DDT might be related to the application of dicofol, an acaricide manufactured from technical DDTs and mainly used on cotton fields to treat mites.
Inhibitory effects of atrazine on Chlorella vulgaris as assessed by real-time polymerase chain reaction
Authors: Qian Haifeng , Sheng G. Daniel , Liu Weiping , Lu Yingcong , Liu Zhenghai , Fu Zhengwei 
Published: December 2007

Abstract
Atrazine, a highly toxic herbicide, is frequently detected in surface water because of its heavy application. Algae are among the aquatic organisms most susceptible to atrazine pollution in water. In the present study, the aquatic alga Chlorella vulgaris Beijerinck was chosen to assess the acute toxicity of atrazine (48–96 h) in terms of gene transcription and physiological changes. A real-time polymerase chain reaction (PCR) assay was used to quantify transcript levels of three photosystem genes in C. vulgaris. The diel patterns for regulation of the psaB (photosystem I reaction center protein subunit B), psbC (an integral membrane protein component of photosystem II), and rbcL (large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase) gene transcripts were successfully quantified. Results showed that atrazine reduced the transcript abundances of three target genes and that the abundances decreased with increasing atrazine concentration. The determined smallest transcript levels of psaB, psbC, and rbcL, which occurred at the highest atrazine concentration tested (400 μg/L), were only 34.6, 34.6, and 8.1%, respectively, of the control sample value. Exposure to atrazine increased the level of malondialdehyde by 1.74-fold (the highest value) in C. vulgaris, suggesting potential oxidative damage to the alga. The activities of antioxidation enzymes (e.g., superoxide dismutase, peroxidase, and catalase) also increased markedly in the presence of atrazine, with maximum increases of 1.82-, 1.59-, and 2.31-fold, respectively. These elevated activities may help to alleviate the oxidative damage. Our results demonstrate that atrazine is highly toxic to this alga and that real-time PCR is an efficient technique for assessing the toxicity of xenobiotic compounds in algae.
Reverse Mathematics and Π12 Comprehension
Authors: Mummert Carl , Simpson Stephen G. 
Published: December 2007

AbstractWe initiate the reverse mathematics of general topology. We show that a certain metrization theorem is equivalent to Π12 comprehension. An MF space is defined to be a topological space of the form MF(P) with the topology generated by {Np ∣ p ϵ P}. Here P is a poset, MF(P) is the set of maximal filters on P, and Np = {F ϵ MF(P) ∣ p ϵ F }. If the poset P is countable, the space MF(P) is said to be countably based. The class of countably based MF spaces can be defined and discussed within the subsystem ACA0 of second order arithmetic. One can prove within ACA0 that every complete separable metric space is homeomorphic to a countably based MF space which is regular. We show that the converse statement, “every countably based MF space which is regular is homeomorphic to a complete separable metric space,” is equivalent to . The equivalence is proved in the weaker system . This is the first example of a theorem of core mathematics which is provable in second order arithmetic and implies Π12 comprehension.
Weak Distributivity, A Problem of Von Neumann and the Mystery of Measurability
Authors: Balcar Bohuslav , Jech Thomas 
Published: December 2007

This article investigates the weak distributivity of Boolean σ-algebras satisfying the countable chain condition. It addresses primarily the question when such algebras carry a σ-additive measure. We use as a starting point the problem of John von Neumann stated in 1937 in the Scottish Book. He asked if the countable chain condition and weak distributivity are sufficient for the existence of such a measure.Subsequent research has shown that the problem has two aspects: one set theoretic and one combinatorial. Recent results provide a complete solution of both the set theoretic and the combinatorial problems. We shall survey the history of von Neumann's Problem and outline the solution of the set theoretic problem. The technique that we describe owes much to the early work of Dorothy Maharam to whom we dedicate this article.§1. Complete Boolean algebras and weak distributivity. ABoolean algebrais a setBwith Boolean operationsa˅b(join),a˄b(meet) and −a(complement), partial orderinga≤bdefined bya˄b=aand the smallest and greatest element,0and1. By Stone's Representation Theorem, every Boolean algebra is isomorphic to an algebra of subsets of some nonempty setS, under operationsa∪b,a∩b,S−a, ordered by inclusion, with0= ∅ and1=S.Complete Boolean algebras and weak distributivity.A Boolean algebrais a setBwith Boolean operationsa˅b(join),a˄b(meet) and -a(complement), partial orderinga≤bdefined bya˄b=aand the smallest and greatest element.0and1. By Stone's Representation Theorem, every Boolean algebra is isomorphic to an algebra of subsets of some nonempty setS, under operationsa∪b,a∩b,S-a, ordered by inclusion, with0= ϕ and1=S.
A new “feasible” arithmetic
Authors: Bellantoni Stephen , Hofmann Martin 
Published: December 2007

AbstractA classical quantified modal logic is used to define a “feasible” arithmetic whose provably total functions are exactly the polynomial-time computable functions. Informally, one understands ⃞∝ as “∝ is feasibly demonstrable”. differs from a system that is as powerful as Peano Arithmetic only by the restriction of induction to ontic (i.e., ⃞-free) formulas. Thus, is defined without any reference to bounding terms, and admitting induction over formulas having arbitrarily many alternations of unbounded quantifiers. The system also uses only a very small set of initial functions.To obtain the characterization, one extends the Curry-Howard isomorphism to include modal operations. This leads to a realizability translation based on recent results in higher-type ramified recursion. The fact that induction formulas are not restricted in their logical complexity, allows one to use the Friedman A translation directly.The development also leads us to propose a new Frege rule, the “Modal Extension” rule: if ⊢ ∝ a then ⊢ A ↔ ∝ for new symbol A.
Wellordering proofs for metapredicative Mahlo
Authors: Strahm Thomas 
Published: December 2007

AbstractIn this article we provide wellordering proofs for metapredicative systems of explicit mathematics and admissible set theory featuring suitable axioms about the Mahloness of the underlying universe of discourse. In particular, it is shown that in the corresponding theories EMA of explicit mathematics and KPm0 of admissible set theory, transfinite induction along initial segments of the ordinal φω00, for φ being a ternary Veblen function, is derivable. This reveals that the upper bounds given for these two systems in the paper Jäger and Strahm [11] are indeed sharp.
Proving consistency of equational theories in bounded arithmetic
Authors: Beckmann† Arnold 
Published: December 2007

AbstractWe consider equational theories for functions denned via recursion involving equations between closed terms with natural rules based on recursive definitions of the function symbols. We show that consistency of such equational theories can be proved in the weak fragment of arithmetic S21. In particular this solves an open problem formulated by Takeuti (c.f. [5, p.5 problem 9.]).
Open questions in the theory of spaces of orderings
Authors: Marshall Murray A. 
Published: December 2007

Spaces of orderings provide an abstract framework in which to study spaces of orderings of formally real fields. Spaces of orderings of finite chain length are well understood [9, 11]. The Isotropy Theorem [11] and the extension of the Isotropy Theorem given in [13] are the main tools for reducing questions to the finite case, and these are quite effective. At the same time, there are many questions which do not appear to reduce in this way. In this paper we consider four such questions, for a space of orderings (X, G).1. Is it true that every positive primitive formula P(a) with parameters a in G which holds in every finite subspace of (X, G) necessarily holds in (X, G)?2. If f: X → ℤ is continuous and Σx∈Vf(x) ≡ 0 mod ∣V∣ holds for all fans V in X with ∣V∣ ≤ 2n, does there exist a form ϕ with entries in G such that mod Cont(X, 2nℤ)?3. Is it true that Cont(X, 2nℤ) ∩ Witt(X, G) = In(X, G), where I(X, G) denotes the fundamental ideal?4. Is the separating depth of a constructible set C in X necessarily bounded by the stability index of (X, G)?The unexplained terminology and notation is explained later in the main body of the paper. In a certain sense Question 1 is the main question. At the same time, Questions 2, 3 and 4 are of considerable interest, both from the point of view of quadratic form theory and from the point of view of real algebraic geometry.
Maximal contiguous degrees
Authors: Cholak Peter , Downey Rod , Walk Stephen 
Published: December 2007

AbstractA computably enumerable (c.e.) degree is a maximal contiguous degree if it is contiguous and no c.e. degree strictly above it is contiguous. We show that there are infinitely many maximal contiguous degrees. Since the contiguous degrees are definable, the class of maximal contiguous degrees provides the first example of a definable infinite anti-chain in the c.e. degrees. In addition, we show that the class of maximal contiguous degrees forms an automorphism base for the c.e. degrees and therefore for the Turing degrees in general. Finally we note that the construction of a maximal contiguous degree can be modified to answer a question of Walk about the array computable degrees and a question of Li about isolated formulas.
How to extend the semantic tableaux and cut-free versions of the second incompleteness theorem almost to Robinson's arithmetic q
Authors: Willard Dan E. 
Published: December 2007

AbstractLet us recall that Raphael Robinson's Arithmetic Q is an axiom system that differs from Peano Arithmetic essentially by containing no Induction axioms [13], [18]. We will generalize the semantic-tableaux version of the Second Incompleteness Theorem almost to the level of System Q. We will prove that there exists a single rather long Π1 sentence, valid in the standard model of the Natural Numbers and denoted as V. such that if α is any finite consistent extension of Q + V then α will be unable to prove its Semantic Tableaux consistency. The same result will also apply to axiom systems α with infinite cardinality when these infinite-sized axiom systems satisfy a minor additional constraint, called the Conventional Encoding Property.Our formalism will also imply that the semantic-tableaux version of the Second Incompleteness Theorem generalizes for the axiom system IΣ0, as well as for all its natural extensions. (This answers an open question raised twenty years ago by Paris and Wilkie [15].)
Degree spectra of relations on computable structures in the presence of Δ20isomorphisms
Authors: Hirschfeldt Denis R. 
Published: December 2007

AbstractWe give some new examples of possible degree spectra of invariant relations on Δ20-categorical computable structures, which demonstrate that such spectra can be fairly complicated. On the other hand, we show that there are nontrivial restrictions on the sets of degrees that can be realized as degree spectra of such relations. In particular, we give a sufficient condition for a relation to have infinite degree spectrum that implies that every invariant computable relation on a Δ20-categorical computable structure is either intrinsically computable or has infinite degree spectrum. This condition also allows us to use the proof of a result of Moses [23] to establish the same result for computable relations on computable linear orderings.We also place our results in the context of the study of what types of degree-theoretic constructions can be carried out within the degree spectrum of a relation on a computable structure, given some restrictions on the relation or the structure. From this point of view we consider the cases of Δ20-categorical structures, linear orderings, and 1-decidable structures, in the last case using the proof of a result of Ash and Nerode [3] to extend results of Harizanov [14].
Compact complex manifolds with the DOP and other properties
Authors: Pillay Anand , Scanlon Thomas 
Published: December 2007

AbstractWe point out that a certain complex compact manifold constructed by Lieberman has the dimensional order property, and has U-rank different from Morley rank. We also give a sufficient condition for a Kähler manifold to be totally degenerate (that is, to be an indiscernible set, in its canonical language) and point out that there are K3 surfaces which satisfy these conditions.
Modules with few types over some finite-dimensional algebras
Authors: Prest Mike , Puninskaya Vera 
Published: December 2007

AbstractUsing the description of the Ziegler spectrum we characterise modules with various stability-theoretic properties (ω-stability, superstability, categoricity) over certain classes of finite-dimensional algebras. We also show that, for modules over the algebras we consider, having few types is equivalent to being ω-stable.
ℵ0-categorical structures with arbitrarily fast growth of algebraic closure
Authors: Evans David M. , Pantano M. E. 
Published: December 2007

Various results have been proved about growth rates of certain sequences of integers associated with infinite permutation groups. Most of these concern the number of orbits of the automorphism group of an ℵ0-categorical structure on the set of unordered n-subsets or on the set of n-tuples of elements of . (Recall that by the Ryll-Nardzewski Theorem, if is countable and ℵ0-categorical, the number of the orbits of its automorphism group Aut() on the set of n-tuples from is finite and equals the number of complete n-types consistent with the theory of .) The book [Ca90] is a convenient reference for these results. One of the oldest (in the realms of ‘folklore’) is that for any sequence (Kn)n∈ℕ of natural numbers there is a countable ℵ0-categorical structure such that the number of orbits of Aut() on the set of n-tuples from is greater than kn for all n.These investigations suggested the study of the growth rate of another sequence. Let be an ℵ0-categorical structure and X be a finite subset of . Let acl(X) be the algebraic closure of X, that is, the union of the finite X-definable subsets of . Equivalently, this is the union of the finite orbits on of Aut()(X), the pointwise stabiliser of X in Aut(). Define
0# and inner models
Authors: Friedman SY D. 
Published: December 2007

In this paper we examine the cardinal structure of inner models that satisfy GCH but do not contain 0#. We show, assuming that 0# exists, that such models necessarily contain Mahlo cardinals of high order, but without further assumptions need not contain a cardinal κ which is κ-Mahlo. The principal tools are the Covering Theorem for L and the technique of reverse Easton iteration.Let I denote the class of Silver indiscernibles for L and 〈iα ∣ α ϵ ORD〉 its increasing enumeration. Also fix an inner model M of GCH not containing 0# and let ωα denote the ωα of the model M[0#], the least inner model containing M as a submodel and 0# as an element.