bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrient management in a Pinusradiata plantation after thinning: the effect of nitrogen fertilizer on soil nitrogen fluxes and tree growth
Authors: Carlyle J.C.
Published: February 2008

The influence of N fertilizer on soil mineral N fluxes, canopy development, and tree growth was studied in a thinned 11-year-old Pinusradiata D. Don plantation. Ammonium sulphate and single superphosphate were applied in an incomplete factorial design, but only the main effects of N application at 0 (control) or 200 kg N•ha−1 are considered here. Spring application of fertilizer increased the quantity of mineral N in the forest floor plus surface soil (0–0.30 m) from 1.2 to 194 kg•ha−1. Within 51 weeks this had fallen to 8.3 kg•ha−1, and after 89 weeks had returned to prefertilizer levels. In the unfertilized soil, rates of net mineralization were low with little seasonal variation. Nitrogen fertilizer increased N mineralization; over the 2 years of measurement fertilized and unfertilized soils mineralized 155 and 77 kg N•ha−1, respectively. There was no net immobilization of fertilizer N. There was no leaching of mineral N from the unfertilized soil whereas 149 kg N•ha−1 was leached below 0.30 m during the 2 years after fertilizer application. Nitrogen uptake increased from 71 kg•ha−1 in the control to 203 kg•ha−1 in the fertilized treatment. Fifty-one percent (103 kg•ha−1) of N uptake by trees in the fertilized treatment occurred within 20 weeks of fertilizer application. Fertilized trees took up 58% of the available N (N added as fertilizer plus N mineralized), while 42% was leached. Ammonium dominated the soil mineral N pool and mineral N fluxes, with nitrate generally accounting for less than 10% of mineral N in both fertilized and unfertilized soils. Leaching of mineral N from the fertilized soil (Nleach, kg•ha−1•week−1) was highly correlated (r2 = 0.92) with soil mineral N content (Nstart, kg•ha−1) and effective rainfall (rainfall minus evaporation, Reff, mm•week−1) according to the relationship Nleach = aNstart + bReff, while N uptake (kg•ha−1•week−1) was highly correlated (r2 = 0.91) with soil mineral N content and N mineralization (Nmin, kg•ha−1•week−1) according to the relationship Nuptake = aNstart + bNmin. Fertilizer increased needle N concentrations and content by 52 and 87%, respectively, after 58 weeks, and resulted in a 17% increase in leaf area index after 71 weeks. These differences were reflected by an increase in basal area increment of 23% during the 2 years since fertilizer application. The rapid uptake of N fertilizer was associated with storage in existing biomass. Uptake of fertilizer N should, therefore, increase with plantation biomass. Consequently, it should be possible to increase the uptake of N fertilizer, and minimize leaching, by applying fertilizer before, rather than after, thinning. Such a strategy may be particularly appropriate for soils that have a low capacity to retain applied N.
Tectonic influences on tree growth in northern Patagonia, Argentina: the roles of substrate stability and climatic variation
Authors: Kitzberger Thomas , Veblen Thomas T. , Villalba Ricardo
Published: February 2008

In northern Patagonia, Argentina, we examined the influences of climatic variation and inter-site variation in substrate stability on the dendroecological effects of earthquakes. In association with the great earthquake in 1960 centered off the coast of nearby Valdivia, Chile, extensive tree mortality occurred in northern Patagonia in Nothofagusdombeyi–Austrocedruschilensis stands on unstable debris fans. To examine the effects of the 1960 and earlier earthquakes on tree growth, we developed tree-ring chronologies from samples of the surviving A. chilensis on unstable debris fan sites and at adjacent nonfan sites of more stable substrates. For controlling the effects of regional climatic variation, we also produced a tree-ring chronology from this species in a more distant and undisturbed stand. Strong variations in tree-growth patterns on fan sites were associated with the historically documented major seismic events of south central Chile that occurred in 1737, 1751, 1837, and 1960. Tree-ring chronologies from nonfan sites (i.e., sites of greater substrate stability) showed much less response to these earthquakes. On the fan sites, strong growth suppressions were associated with the former three earthquakes, whereas strong releases followed the 1960 earthquake. The difference in response is explained by the occurrence of the 1960 earthquake during a period of drought, which in combination with the violent shaking of the ground, resulted in extensive tree mortality followed by growth releases of the survivors. However, severe droughts in the absence of earthquakes also can produce tree mortality and subsequent release of the survivors. Consequently, the synergistic effects of climatic variation and earthquake events must be carefully considered in developing records of both climatic variation and earthquakes.
Mating system in natural populations of eastern white pine in Quebec
Authors: Beaulieu J. , Simon J.-P.
Published: February 2008

The mating system in two natural eastern white pine (Pinusstrobus L.) populations in Quebec was investigated. These populations contrasted in density and age. The single-locus as well as multilocus outcrossing rate estimates were obtained from four polymorphic enzyme loci using open-pollinated progeny data. The single-locus outcrossing rates ranged from 0.934 to 1.110 with a mean of 1.026 in one population and varied from 0.862 to 1.186 with a mean of 1.007 in the other population. Multilocus estimates exceeded 1.0 in both populations, suggesting the possible absence of self-fertilization. Pollen pool gene frequencies were homogeneous in one population and heterogeneous in the other. The positive or less negative F-values found in the filial populations compared with those observed in the parental populations suggest the presence of a family structure favouring consanguineous matings.
Effect of N supply upon the seasonal partitioning of N and P uptake in young Sitka spruce (Piceasitchensis)
Authors: Proe M.F. , Millard P.
Published: February 2008

Seasonal relationships between N supply, tree growth, and partitioning of both N and P have been studied in young trees using 15N and 32P isotopes. Three-year-old clonal cuttings of Sitka spruce (Piceasitchensis (Bong.) Carr.) were grown for 2 years in sand irrigated with a nutrient solution containing either 1.0 mol N•m−3 (low N) or 6.0 mol N•m−3 (high N). In the first year, trees received 2-week pulses of 15N and 32P to label current nutrient uptake during either a period of rapid spring growth or shortly after bud set in summer. In the second year, trees that had been preconditioned to a low-N supply received 3-week pulses of 15N at either the low rate of application or at the high rate to simulate a single application of N fertilizer. In spring of the first year, N treatment had no effect upon tree growth. Low-N trees increased the partition of 15N uptake to roots, but the partition of 32P was not affected by N supply and was similar to the partition of 15N in the high-N treatment. At the time of the later pulse, however, growth was affected by N supply and 32P partitioning to roots increased to match the partition of 15N in the low-N treatment. During the second year, the additional 15N given to Low-N trees to simulate fertilizer application was partitioned predominantly to current shoots and roots. Results are discussed in relation to the processes of internal cycling and the partition of nutrients taken up by larger trees.
Genetic variation and productivity of Populustrichocarpa and its hybrids. VIII. Leaf and crown morphology of native P. trichocarpa clones from four river valleys in Washington
Authors: Dunlap J.M. , Stettler R.F. , Heilman P.E.
Published: February 2008

A common-garden study of Populustrichocarpa Torr. & Gray was initiated in 1985, when clonal material from 128 trees was collected from sites distributed along two mesic (Hoh, Nisqually) and two xeric (Dungeness, Yakima) river valleys. This material was grown for 1 year at Puyallup, Wash. In spring 1986, cuttings from this material were used to establish two replicate plantations, one at Puyallup and the other at Wenatchee, Wash. Data were collected from a subset of 80 clones on 8 single-leaf and 14 crown traits after two growing seasons. Analyses of variance revealed significant (p ≤ 0.10) differences among rivers in nearly all single-leaf traits by the second year at both plantations. Two-year leaf sizes at Puyallup significantly declined in this order: Hoh (388 cm2) > Nisqually > Dungeness > Yakima (194 cm2). At Wenatchee, a similar mesic > xeric pattern was found among river sources, but leaves were smaller there. When grown at Puyallup, leaves of clones from lower elevations in the Yakima valley were significantly (p ≤ 0.10) smaller, lighter, thinner, and weighed less per unit area than upper elevation clones. Chi-square tests showed that abaxial leaf surfaces were greener in Yakima trees than in trees from other locations, especially in those from the the lower Yakima valley. In the crown traits of trees grown in Puyallup, river and clone-within-site-within-river effects were significant for all traits, whereas site-within-river effects were significant for only 8 traits. Mesic-origin trees were significantly larger in size traits, e.g., branch length, than xeric-origin trees. Trees from the Yakima drainage system were leafier and branchier (p ≤ 0.10) than both Nisqually and Hoh trees. Values for most crown traits were greater (p ≤ 0.10) in the xeric, lower Yakima clones than in the mesic, upper Yakima clones. These mesic-xeric differences were similar for Dungeness trees, although there were few significant differences between the lower and upper elevational groups. Single-leaf and crown traits of trees from the four river valleys seem to be adapted to the respective mesic and xeric conditions of the source environments. Within the Yakima river valley, a sharp change in leaf and crown traits and in atmospheric moisture levels coincide midway along the transect, suggesting the presence of a steep selection gradient in the Bristol Canyon area.
An induced defense reaction in white spruce to attack by the white pine weevil, Pissodesstrobi
Authors: Alfaro René I.
Published: February 2008

An induced defense reaction in the leaders of white spruce, Piceaglauca (Moench) Voss, occurs in response to attack by the white pine weevil, Pissodesstrobi Peck. The response was initiated shortly after feeding and oviposition in the attacked shoot and consisted of the cambium switching from producing normal tracheids and parenchyma ray cells to producing traumatic resin canals, arranged in a ring fashion in the developing xylem. In sectioned leaders, these traumatic resin canals could be seen emptying their contents into feeding and oviposition cavities dug by the adults, and into the larval galleries. This defense reaction killed eggs and larvae. When the leader survived the attack, the cambium reverted to producing normal xylem tissue, leaving one or more rings of traumatic resin canals embedded in the xylem annual ring.
CHAOTIC PHENOMENON IN NONLINEAR GYROTROPIC MEDIUM
Authors: UGULAVA A. , CHOTORLISHVILI L. , NICKOLADZE K. , MCHEDLISHVILI G.
Published: February 2008

Nonlinear gyrotropic medium is a medium whose natural optical activity depends on the intensity of the incident light wave. The Kuhn's model is used to study nonlinear gyrotropic medium with great success. The Kuhn's model presents itself as a model of nonlinear coupled oscillators. In the study of the Kuhn's nonlinear model, classical dynamics in the case of weak as well as strong nonlinearity is analysed. In the case of weak nonlinearity, analytical solutions which are in good agreement with the numerical solutions are obtained. In the case of strong nonlinearity, the values of those parameters for which chaos is formed in the system under study have been determined. The subject of interest is also the question of the Kuhn's model integrability. It is seen that at certain values of the interaction potential, this model is exactly integrable and under certain conditions, it is reduced to the so-called universal Hamiltonian. In the case of quantum-mechanical consideration, the possibility of stochastic absorption of external field energy by nonlinear gyrotropic medium is shown. Finally, further generalization of the Kuhn's model for an infinite chain of interacting oscillators is offered.
AGING EFFECT ON THE PHOTOSYNTHESIZED POROUS SILICON
Authors: ALWAN ALWAN M. , ABDULRAZAQ OMAR A.
Published: February 2008

The photoluminescence spectrum of the freshly photosynthesized porous silicon (PS) has been investigated. This measurement was repeated after three and six months for the same sample after storage under ambient condition (open air at room temperature). Photoluminescence (PL) measurements of the stored PS show different peak positions and intensity width as compared with the results of the fresh PS. A blue shift in PL peak positions with aging time was observed. PL relative intensity is strongly diminished after 6 months of aging. Dark I-V characteristics of Al/PS/n - Si/Al structure shows a behavior of PS/n - Si isotype heterojunction for fresh device and a MIS (metal-insulator-semiconductor) device due to contribution of Al/PS Schottky barrier after aging, essentially after 6 months.
THE FORM EFFECTS OF MAGNETORESISTIVITY IN p-TYPE DIAMOND FILMS
Authors: KONG CHUN-YANG , XU JIE , CUI YU-TING , WANG WAN , QING GUO-PING , LAN MAO-PING , RUAN HAI-BO
Published: February 2008

The geometric form effects of magnetoresistivity (MR) from chemical vapor deposited p-type diamond films were investigated. The MR patterns (width/length ratio = 1, 2, 3, 4, 5, 6) were produced on p-type diamond films by photolithography and ion etching in oxygen plasma. The experimental results showed that the MR in diamond films with the strip structure changed with width–length ratio at magnetic field intensity of 3 T. The changes of MR strongly depended on the geometric form of the samples. With the width–length ratio increasing from 1 to 6, the MR increases from 0.08 to 1.0. It was almost changing linearly with the increase of width-to-length ratio. The geometric form effect is closely related to the Hall effect. A calculation formula of form effect of MR was presented.
INFLUENCE OF ELECTRON–PHONON INTERACTION ON EFFECTIVE MASS IN SOME HEAVY FERMION (HF) SYSTEMS
Authors: MOHANTY S. , KALTA B. K. , NAYAK P.
Published: February 2008

It is a fact that for ordinary metals, the electron–phonon interaction increases the quasi-particle mass, which is in contrast to the finding by Fulde et al. that, for some heavy Fermion (HF) systems, it decreases. Some experiments on HF systems suggest that there exists a strong coupling of the elastic degrees of freedom with these at the electronic and magnetic ones. To understand the effect of electron–phonon interaction on effective mass, the electron–phonon coupling mechanism in the framework of the periodic Anderson model is considered, and a simple expression is derived. This involves various model parameters namely, the position of the 4f level; the effective coupling strength, g, temperature, b; and the electron–phonon coupling strength, r. The influence of these parameters on the value of effective mass is studied, and interesting results were found. For simplicity, the numerical calculation is performed in the long wavelength limit.
CONSENSUS PROBLEMS IN SCALE-FREE NETWORK
Authors: WU ZHENGPING , GUAN ZHI-HONG
Published: February 2008

Recent advances in complex network research have stimulated increasing interest in understanding the relationship between the topology and dynamics of complex networks. In this paper, we investigate the consensus problem in a class of scale-free network with a heterogeneity parameter. It is found that, for a scale-free network, the time to reach a consensus is hundreds of times shorter than that of the nearest-neighbor coupled network with the same average degree and network size, and its robustness to the node-failure and edge-failure is increased at the same time. Furthermore, as the scale-free network becomes more homogenous, or its average degree becomes larger, the time to reach a consensus will become shorter, but not notably shorter. Therefore, the scale-free network with a larger exponent r and average degree k is a better choice to obtain a faster convergence speed in the consensus problem.
ENERGY RELEASE RATE OF INTERFACE DELAMINATION BETWEEN A THIN COATING AND AN ELASTIC SUBSTRATE
Authors: DUAN X.-Y. , LI X.-F.
Published: February 2008

The mechanical properties of materials such as elastic modulus, hardness, and fracture toughness, can be measured by nanoindentation. For a thin film coated on an elastic substrate, the cross-sectional nanoindentation technique can decrease the influence of plastic deformation around the nanoindenter apex on fracture toughness for interface delamination. Considering the effect of the elastic substrate, the theory of an elastic beam bonded to an elastic foundation is further developed to obtain the energy release rate of interfacial debonding. Explicit closed-form solutions are determined, and the influence of the substrate on the energy release rate is shown graphically.
INSTANTON SOLUTION OF A NONLINEAR POTENTIAL IN FINITE SIZE
Authors: ZOLI MARCO
Published: February 2008

The Euclidean path integral method is applied to a quantum tunneling model which accounts for finite size (L) effects. The general solution of the Euler Lagrange equation for the double well potential is found in terms of Jacobi elliptic functions. The antiperiodic instanton interpolates between the potential minima at any finite L inside the quantum regime, and generalizes the well-known (anti)kink solution of the infinite size case. The derivation of the functional determinant, stemming from the quantum fluctuation contribution, is given in detail. The explicit formula for the finite size semiclassical path integral is presented.
GALOIS GROUPS IN RATIONAL CONFORMAL FIELD THEORY
Authors: GEPNER DORON
Published: February 2008

It was established before that fusion rings in a rational conformal field theory (RCFT) can be described as rings of polynomials, with integer coefficients, modulo some relations. We use the Galois group of these relations to obtain a local set of equations for the points of the fusion variety. These equations are sufficient to classify all the RCFT, Galois group by Galois group. It is shown that the Galois group is equivalent to the pseudo RCFT group. We prove that the Galois groups encountered in RCFT are all Abelian, implying solvability by radicals of the modular matrix.
RECENT DEVELOPMENT IN DIAMOND SYNTHESIS
Authors: CHEN CHANGLE , CHEN QIANWANG
Published: February 2008

The high pressure-high temperature (HPHT) method led to wide applications of artificial diamonds in industry. Low temperature coating of diamonds has been studied for some time, and chemical vapor deposition has been developed. In this contribution, we will focus on the most recent developments in diamond synthesis, and especially the important progress upon hydrothermal synthesis and the reduction of carbide (HSRC), which has attracted more and more attention due to its great commercial potential. Especially, we will discuss the synthesis of colorless, large diamond crystals from the reduction of carbon dioxide or carbonates. In addition, some recent progress on the theoretical studies of the metastable nucleation and growth of diamonds will also be reviewed. Finally, theories about the genesis of natural diamond were briefly reviewed, and a new theory based on our experimental results was proposed, which suggests that diamond within the Earth could be produced from carbon dioxide wherever carbon dioxide existed and the conditions (e.g., temperature, pressure, and reducing environment) are satisfied.
ON AUTOMORPHISMS OF SURFACE BRAID GROUPS
Authors: BELLINGERI PAOLO
Published: February 2008

We study automorphisms of surface braid groups and we compute the corresponding outer automorphism groups.
DIRECTED GRAPHS AND KRONECKER INVARIANTS OF PAIRS OF MATRICES
Authors: TOWBER JACOB
Published: February 2008

Call two pairs (M,N) and (M′,N′) of m × n matrices over a field K, simultaneously K-equivalent if there exist square invertible matrices S,T over K, with M′ = SMT and N′ = SNT. Kronecker [2] has given a complete set of invariants for simultaneous equivalence of pairs of matrices.

Associate in the natural way to a finite directed graph Γ, with v vertices and e edges, an ordered pair (M,N) of e × v matrices of zeros and ones. It is natural to try to compute the Kronecker invariants of such a pair (M,N), particularly since they clearly furnish isomorphism-invariants of Γ. Let us call two graphs "linearly equivalent" when their two corresponding pairs are simultaneously equivalent.

There have existed, since 1890, highly effective algorithms for computing the Kronecker invariants of pairs of matrices of the same size over a given field [1,2,5,6] and in particular for those arising in the manner just described from finite directed graphs.

The purpose of the present paper, is to compute directly these Kronecker invariants of finite directed graphs, from elementary combinatorial properties of the graphs. A pleasant surprise is that these new invariants are purely rational — indeed, integral, in the sense that the computation needed to decide if two directed graphs are linearly equivalent only involves counting vertices in various finite graphs constructed from each of the given graphs — and does not involve finding the irreducible factorization of a polynomial over K (in apparent contrast both to the familiar invariant-computations of graphs furnished by the eigenvalues of the connection matrix, and to the isomorphism problem for general pairs of matrices).
RIBBONLENGTH OF TORUS KNOTS
Authors: KENNEDY BROOKE , MATTMAN THOMAS W. , RAYA ROBERTO , TATING DAN
Published: February 2008

Using Kauffman's model of flat knotted ribbons, we demonstrate how all regular polygons of at least seven sides can be realized by ribbon constructions of torus knots. We calculate length to width ratios for these constructions thereby bounding the Ribbonlength of the knots. In particular, we give evidence that the closed (respectively, truncation) Ribbonlength of a (q + 1,q) torus knot is (2q + 1) cot (π/(2q + 1)) (respectively, 2q cot (π/(2q + 1))). Using these calculations, we provide the bounds c1 ≤ 2/π and c2 ≥ 5/3 cot π/5 for the constants c1 and c2 that relate Ribbonlength R(K) and crossing number C(K) in a conjecture of Kusner: c1 C(K) ≤ R(K) ≤ c2 C(K).
AUTOMORPHISMS OF BRAID GROUPS ON S2, T2, P2 AND THE KLEIN BOTTLE K
Authors: ZHANG PING
Published: February 2008

It is shown that for the braid group Bn(M) on a closed surface M of nonnegative Euler characteristic, Out (Bn(M)) is isomorphic to a group extension of the group of central automorphisms of Bn(M) by the extended mapping class group of M, with an explicit and complete description of Aut (Bn(S2)), Aut (Bn(P2)), Out (Bn(S2)) and Out (Bn(P2)).
LUNE-FREE KNOT GRAPHS
Authors: ELIAHOU SHALOM , HARARY FRANK , KAUFFMAN LOUIS H.
Published: February 2008

This paper is an exploration of simple four-regular graphs in the plane (i.e. loop-free and with no more than one edge between any two nodes). Such graphs are fundamental to the theory of knots and links in three dimensional space, and their planar diagrams. We dedicate this paper to Frank Harary (1921–2005), whose fascination with graphs of knots inspired this work, and with whom we had the pleasure of developing this paper.
CATEGORIFICATION OF THE DICHROMATIC POLYNOMIAL FOR GRAPHS
Authors: STOŠIĆ MARKO
Published: February 2008

For each graph and each positive integer n, we define a chain complex whose graded Euler characteristic is equal to an appropriate n-specialization of the dichromatic polynomial. This also gives a categorification of n-specializations of the Tutte polynomial of graphs. Also, for each graph and integer n ≤ 2, we define the different one-variable n-specializations of the dichromatic polynomial, and for each polynomial, we define graded chain complex whose graded Euler characteristic is equal to that polynomial. Furthermore, we explicitly categorify the specialization of the Tutte polynomial for graphs which corresponds to the Jones polynomial of the appropriate alternating link.
RESTRICTING GLOBALLY-DEFINED MACKEY FUNCTORS TO NILPOTENT FINITE GROUPS
Authors: BOURIZK ISMAÏL
Published: February 2008

Let B be the Burnside ring considered as a globally-defined Mackey functor, and k be a field of positive characteristic q. We prove that, when k ⊗ℤ B is restricted to nilpotent groups of order prime to q, the only simple Mackey functors that can appear as subquotients of it are of the form SE,k, where E is the direct product of elementary abelian p-groups. In the special case k = 𝔽2, the simple Mackey functor SE,𝔽2 must appear as a filtration factor in 𝔽2 ⊗ℤ B for every direct product of elementary abelian p-groups E of odd order.
MAX MODULES RELATIVE TO A TORSION THEORY
Authors: CHARALAMBIDES STELIOS , CLARK JOHN
Published: February 2008

We introduce the concepts of τ-Max modules and left τ-Max rings which are torsion-theoretic analogues of Max modules and left Max rings. A generalization is obtained of an important theorem by Shock and used to characterize τ-Noetherian rings using τ-Max modules. We then characterize left τ-Max rings and obtain a torsion-theoretic version of a result by Hirano. We conclude with results on τ-short modules, introduced as a torsion analogue of a concept recently defined by Bilhan and Smith.
AN AFFIRMATIVE ANSWER TO A QUESTION ON NOETHERIAN RINGS
Authors: HUYNH DINH VAN , RIZVI S. TARIQ
Published: February 2008

It is shown that a ring R is right noetherian if and only if every cyclic right R-module is a direct sum of a projective module and a module Q, where Q is either injective or noetherian. This provides an affirmative answer to a question raised by P. F. Smith.
A DOMAIN TEST FOR LIE COLOR ALGEBRAS
Authors: PRICE KENNETH L.
Published: February 2008

Lie color algebras are generalizations of Lie superalgebras and graded Lie algebras. The properties of a Lie color algebra can often be related directly to the ring structure of its universal enveloping algebra. We study the effects of torsion elements and torsion subspaces.

Let [Formula: see text] denote a Lie color algebra. If [Formula: see text] is homogeneous and torsion then x2 = 0 in [Formula: see text]. If no homogeneous element of [Formula: see text] is torsion, then [Formula: see text] so [Formula: see text] is semiprime. In this case we can give a test which uses Gröbner basis methods to determine when [Formula: see text] is a domain. This is applied in an example to show [Formula: see text] may be a domain even if [Formula: see text] contains torsion elements and torsion subspaces.
EXTENDING TORSION RADICALS
Authors: KOSLER KARL A.
Published: February 2008

Over an arbitrary ring R, a symmetric radical is shown to be strongly normalizing. For a fully semiprimary Noetherian ring R, a symmetric radical is normalizing if and only if the class of torsion factor rings of R is closed under ring isomorphisms. In case S is a strongly normalizing or normalizing extension ring of R, a symmetric radical for S is constructed as an extension of a symmetric radical for R. Applications address questions concerning the behavior of Krull dimension and linked prime ideals of S.
ON THE COHEN–MACAULAYNESS OF SOME GRADED RINGS
Authors: PATIL D. P. , TAMONE G.
Published: February 2008

Let (R,𝔪) be a 1-dimensional Cohen–Macaulay local ring of multiplicity e and embedding dimension ν ≥ 2. Let B denote the blowing-up of R along 𝔪 and let I be the conductor of R in B. Let x ∈ 𝔪 be a superficial element in 𝔪 of degree 1 and [Formula: see text], [Formula: see text]. We assume that the length [Formula: see text]. This class of local rings contains the class of 1-dimensional Gorenstein local rings (see 1.5). In Sec. 1, we prove that (see 1.6) if the associated graded ring G = gr 𝔪(R) is Cohen–Macaulay, then I ⊆ 𝔪s + xR, where s is the degree of the h-polynomial h R of R. In Sec. 2, we give necessary and sufficient conditions (see Corollaries 2.4, 2.5, 2.9 and Theorem 2.11) for the Cohen–Macaulayness of G. These conditions are numerical conditions on the h-polynomial h R, particularly on its coefficients and the degree in comparison with the difference e - ν. In Sec. 3, we give some conditions (see Propositions 3.2, 3.3 and Corollary 3.4) for the Gorensteinness of G. In Sec. 4, we give a characterization (see Proposition 4.3) of numerical semigroup rings which satisfy the condition [Formula: see text].
ON THE COMMUTING GRAPH ASSOCIATED WITH THE SYMMETRIC AND ALTERNATING GROUPS
Authors: IRANMANESH A. , JAFARZADEH A.
Published: February 2008

The commuting graph of a group G, denoted by Γ(G), is a simple undirected graph whose vertices are all non-central elements of G and two distinct vertices x, y are adjacent if xy = yx. The commuting graph of a subset of a group is defined similarly. In this paper we investigate the properties of the commuting graph of the symmetric and alternating and subsets of transpositions and involutions in the symmetric groups.
FINITE CYCLIC TAME EXTENSIONS OF kp((t))
Authors: WILSON ULRICA
Published: February 2008

Let p be a prime number and let ℚ/ℤ′ be the elements in ℚ/ℤ of order prime to p. Let [Formula: see text], where c is a prime power of p. We use characters and valuation theory to prove that Δ is a parameter space for the cyclic tame extensions of the formal Laurent series field kp((t)) of degree prime to p. Furthermore, we construct the cyclic tame extension corresponding to a given triple in Δ. The structure of finite cyclic tame extensions of the p-adic number fields was thoroughly investigated by A. A. Albert in 1935. Here we get the same result as consequence of our main theorem.
Climate change and groundwater: a short review
Authors: Dragoni W. , Sukhija B. S.
Published: February 2008

There is a general consensus that climate change is an ongoing phenomenon. This will inevitably bring about numerous environmental problems, including alterations to the hydrological cycle, which is already heavily influenced by anthropogenic activity. The available climate scenarios indicate areas where rainfall may increase or diminish, but the final outcome with respect to man and environment will, generally, be detrimental. Groundwater will be vital to alleviate some of the worst drought situations. The paper analyses the main methods for studying the relationships between climate change and groundwater, and presents the main areas in which hydrogeological research should focus in order to mitigate the likely impacts.
Application of isotope techniques in groundwater recharge studies in arid western Rajasthan, India: some case studies
Authors: Sinha U. K. , Navada S. V.
Published: February 2008

Environmental isotope studies of groundwaters carried out in the arid region of Rajasthan, India, suggest that recharge to shallow groundwater occurs as a result of direct infiltration of precipitation and/or through river channels during episodic floods. In many parts of Rajasthan deep fresh groundwater is available, which was recharged in the past when the climatic conditions were more favorable than at present. However, negligible modern recharge and over-exploitation of groundwater resources have led to the deterioration of groundwater quality in the Bhadka–Bheemda area of Barmer district. Buried river courses (palaeochannels) could be potential sources of groundwater since radiocarbon measurements of groundwater along palaeochannels in Jaisalmer district revealed that it was old water recharged a few thousand years ago.
A tale of two cities in ancient Canaan: how the groundwater storage capacity of Arad and Jericho decided their history
Authors: Issar A. S.
Published: February 2008

The history of two ancient cities, Arad and Jericho, sheds light on the role of groundwater storage in deciding the survival of settlements in arid and semi-arid regions when climate changes take place. Arad, which was dependent on a local perched horizon, was deserted during the global warm periods, which spelled dryness in the Middle East. This was in spite of one of the earliest systems of artificial recharge to groundwater developed by its inhabitants. On the other hand Jericho, which depended on the supply from a perennial spring, fed by a regional aquifer, was almost continuously settled from prehistoric times to the present.
Impacts of climatic change on water resources: the future of groundwater recharge with reclaimed water in the south of Europe
Authors: Salgot M. , Torrens A.
Published: February 2008

In an era of increasing contest for limited water resources, the wise joint management of conventional and non-conventional water resources must be considered. Water scarcity is aggravated in coastal zones which are often characterized by high population densities and intense economic activities making heavy seasonal water demands. In this context, the use of non-conventional water increases the availability of water supplies. Non-conventional water resources of lower quality could be directed to meet additional needs. As a consequence, significantly more potable water would be available to meet human demand for safe water.

Non-conventional water resources are described: waste water reclamation and reuse, and its potential application for increasing groundwater resources, as well as several practical applications.
Adaptation to climate change: strategies for sustaining groundwater resources during droughts
Authors: Sukhija B. S.
Published: February 2008

Extreme climate conditions are expected in the twenty-first century in the form of higher maximum temperature (with more hot days) resulting in frequent droughts. The continents of Africa and Asia are anticipated to be extremely vulnerable to droughts. In the impending extreme climate conditions, humanity's sustenance hinges on groundwater as it forms the world's largest freshwater resource. Adaptive and mitigation measures entail well planned strategies for sustained groundwater through extreme climate conditions including droughts. In this paper two such strategies are discussed to overcome the problem of droughts: (i) artificial groundwater recharge using percolation ponds; and (ii) identifying and characterizing deep aquifers resilient to droughts through detailed geophysical, hydrogeological and isotopic studies.

Percolation ponds act as artificial recharge structures which are constructed across monsoon streams with the purpose of harvesting surface runoff caused by monsoon streams. Conventional and tracer methods were developed in India to determine how effective these artificial recharge structures could be. From studies carried out on percolation ponds located in diverse geological formations such as granites, basalts and sandstones, it was concluded that these structures are quite useful for overcoming droughts in semi-arid and arid regions, and it was demonstrated that the role of geology outweighs the effect of climate on such structures. It has been shown that in a similar climatic environment, the percolation ponds in sandstones were far more efficient (efficiency 60%) than those in basalts (efficiency 20–30%).

Recently it has been realized that certain deep aquifers can yield a good quantity and quality of water even during extreme climate events. The Neyveli aquifer in southern India has been demonstrated to be such a representative aquifer for mitigation of droughts. Very extensive and intensive hydrogeological and isotopic studies on the aquifer revealed that the aquifer has distinct characteristics, namely: (i) distinct recharge area; (ii) extensive groundwater regime with high degree of recharge rate; (iii) wide span of radiocarbon ages from Modern to >30 000 years
bp
indicating modern as well as palaeorecharge; and (iv) minimal changes in groundwater quality despite very heavy and continuous withdrawal during the last four decades. All these criteria provide the necessary ingredients for drought resilient aquifers which can be used to identify similar aquifers elsewhere in the world.
Some aspects of groundwater regime in Bulgaria with respect to climate variability
Authors: Benderev A. D. , Orehova T. V. , Bojilova E. K.
Published: February 2008

Groundwater regime in Bulgaria is influenced by climate variability. The impact is evident especially for karst water. A time series analysis of spring discharge for selected karst basins was performed. The impact of the 1982–1994 drought period on groundwater regime was detected. For springs that drain open and mountainous karst, the impact of climate variability is similar to that on surface waters. In fact, the difference in degree of influence of the drought period is related to the specific geological structure of the karst massifs and recharge conditions. Furthermore, the porous waters are characterized by a weaker reaction to such an effect. In general, groundwater use during the 1982–1994 drought period was impacted by climate variability due to limited resource availability.
Effects of climate change on groundwater resources in Campania (southern Italy)
Authors: Ducci D. , Tranfaglia G.
Published: February 2008

In order to estimate the influence of global climate change upon the hydrological regime, variations in the water budget prompted by precipitation and temperature changes were evaluated in the region of Campania (southern Italy). In many parts of the region, precipitation distribution in the last 20 years shows a marked reduction. During the same period, Campania also experienced a regional temperature increase of about 0.3°C. Water budgets, calculated in a geographical information system environment for the region's hydrogeological structures, show a mean decrease of 30% of average infiltration within the present climate scenario. The structures most affected are carbonate aquifers, with the flow of springs being significantly reduced (about 70 m
3
/s). The most severely affected zones are the mountainous areas in the southern and northern parts of Campania.
Climate change, drought and groundwater availability in southern Italy
Authors: Polemio M. , Casarano D.
Published: February 2008

Data for the period 1821 to 2003 from 126 rain gauges, 41 temperature gauges, eight river discharge gauges and 239 wells, located in southern Italy, have been analysed to characterize the effect of recent climate change on availability of water resources, focusing on groundwater resources. Regular data are available from 1921 to 2001. Many analysis methods are used: principal component analysis, to divide the study area into homogenous portions; trend analysis, considering the Mann–Kendall, Student-
t
and Craddock tests, autocorrelation and cross-correlation analyses, and seasonal, annual and moving-average variables, applying the spatial analysis to each variable with a geographical information system approach.

A widespread decreasing trend of annual rainfall is observed over 97% of the whole area. The decreasing trend of rainfall worsens or decreases as mean annual rainfall increases; the spatial mean of trend ranges from −0.8 mm/a in Apulia to −2.9 mm/a in Calabria. The decrease in rainfall is notable after 1980: the recent droughts of 1988–1992 and 1999–2001 appear to be exceptional. On a seasonal basis, the decreasing trend is concentrated in winter; a slight positive trend is observed in summer, the arid season in which the increase is useless as it is transformed into actual evapotranspiration. The temperature trend is not significant and homogeneous everywhere if the temperature increase seems to prevail, especially from about 1980. Net rainfall, calculated as a function of monthly rainfall and temperature, shows a huge and generalized negative trend.

The trend of groundwater availability is so negative everywhere that the situation can be termed dramatic for water users, due not only to the natural drop in recharge but also to the increase of discharge by wells to compensate the non-availability of surface water tapped by dams, as a direct effect of droughts.
Climatological cycles in groundwater levels in a detritic aquifer
Authors: Luque-Espinar J. A. , Chica-Olmo M. , Pardo-Igúzquiza E.
Published: February 2008

The spectral analysis of waterhead measurements on a network of piezometers has allowed the analysis of the spatio-temporal variability of data in the Vega de Granada aquifer (southern Spain). This analysis has detected several long-term cycles in the piezometric time series for the period 1966–2001. A complete analysis, using different spectral methods of those time series, has detected four different cycles: a decadal period (11 years), a 3.2-year period, an annual period and a semi-annual period. The annual cycle is ubiquitous, as a reflection of the annual hydrological cycle. The decadal cycle can be traced to hydrological variations involving a climatological regime induced by sunspot activity (11-year cycle). The piezometers located close to streamflows reaching the aquifer or along the main river, in areas where the main river recharges the aquifer, present a statistically significant decadal cycle. The explanation for the presence and spatial distribution of the 3.2-year cycle is similar to the decadal cycle, though it is identified in fewer piezometers.
Yperia Krini spring (central Greece): inferences on climatic changes from its 2000 years of history
Authors: Rapti-Caputo D. , Helly B.
Published: February 2008

The development of past civilizations and the foundation of towns have always been strictly linked to the availability of water. In this paper, we analyse more than 2000 years of evolution of Yperia Krini spring in Thessaly (Greece), by investigating possible variations in terms of water discharge. In particular, the integrated analysis of geological, hydrological, hydrogeological and historical data relative to the spring, called by Sophocles a ‘gift of God and source of life’, allowed us to understand the role played by both climatic variations and anthropogenic activities on the behaviour and the characteristics of the local underground water resources within the Thessalian plain.
Origin of a fresh groundwater body in Cholistan, Thar Desert, Pakistan
Authors: Geyh M. A. , Ploethner D.
Published: February 2008

The Thar Desert of Pakistan stretches along the border to India and is one of the most densely populated deserts in the world. Brackish to saline groundwater prevails. A locally restricted fresh groundwater resource was discovered by a comprehensive hydrogeological, geophysical, and isotope hydrological survey conducted from 1986 to 1991. The origin, recharge mechanism and age of the fresh groundwater resource were assessed. There is only fossil groundwater and this must be mined. Sodium is the predominant cation. Present groundwater recharge is absent or extremely low as the annual precipitation rate and the potential evapotranspiration rate amount to less than 200 mm/a and about 2700 mm/a, respectively. The investigations comprised a hydrogeological well inventory, electrical resistivity transects on the ground and an air-borne electromagnetic survey, followed by a test-hole drilling programme combined with geophysical borehole logging, aquifer testing, and groundwater sampling for both chemical and environmental isotope analyses. The results of this study delivered a hydrogeological concept on the origin and recharge of the fresh groundwater body. We found that the fresh groundwater was indirectly recharged during flash floods in low lands during the last pluvial period rather than directly replenished in the high mountain areas far in the east.
Transient response of groundwater systems to climate changes
Authors: Seiler K.-P. , Gu W.-Z. , Stichler W.
Published: February 2008

Groundwater flow is steered by both the groundwater recharge rate and by discharge altitudes above or below sea level; it is further controlled by the hydraulic properties of the aquifer system and often contains a transient flow component affected by natural hydrologic processes. All present groundwater discharges have both recent (<100 years) and past groundwater recharge components (>100 years). The ratio of the present to the past groundwater recharge depends on the climate zone: it is large in humid and small in arid areas, hence at low recharge rates transient, and at high groundwater recharge rates steady-state conditions prevail. Developing groundwater management strategies while neglecting any transient response of groundwater resources, and conducted in sensitive recharge/discharge areas like dry lands, results in either over-estimates or under-estimates of safe yields of groundwater resources, and thus may lead to non-sustainable resource development. The consequence of this would be groundwater depletion and often also a deterioration of the hydraulic properties of the aquifer system by subsidence, which both take place only after a long period of time.
Role of Biologics and Other Therapies in Stricturing Crohn’s Disease: What Have We Learnt So Far?
Authors: Sorrentino D.
Published: February 2008

Background: Therapy of strictures, one of the most common complications of Crohn’s disease (CD), remains a challenging task in gastroenterology. While infliximab is widely recognized as being very effective in active CD, it has been reported to cause strictures in some patients. As a consequence, essentially by inference, many clinicians have chosen not to use it in the presence of strictures. Aims: To find evidence in the available data that infliximab does not cause strictures and that there is no rational basis to avoid its a priori use when a stricture is already present. In addition, to review what is currently known on the general management of strictures in CD. Methods: Discussion of the data that led to the hypothesis of a causal association between infliximab and strictures. Review of the mechanisms and the risk factors for stricture development in CD; of the different types of CD-related strictures; of the available means to distinguish them, and of the literature related to the efficacy and safety of infliximab as well as other biologics and other therapies in different stricturing scenarios. Results and Conclusions: Although larger controlled studies are due in the near future, current evidence indicates that infliximab does not cause strictures in CD. The drug appears safe and effective in the presence of an inflammatory stenosis while being predictably ineffective, but not harmful, in the presence of fibrosis. Different stricturing scenarios in CD must be clearly distinguished for proper management of this complication.
Do Stem Cells Exist in the Adult Kidney?
Authors: Gupta Sandeep , Rosenberg Mark E.
Published: February 2008

Adult stem cells exist in many organs and play a critical role in normal cell turnover and the response to injury. The existence of adult stem cells in the mammalian kidney remains controversial. Kidney stem cells have been isolated and characterized by many groups, often with discrepant results. This article will review the current state of knowledge regarding adult kidney stem cells and discuss future directions for kidney stem cell research.