bluuebunny/crossref_metadata_2025_split huggingface dataset:
Volume entropy, weighted girths and stable balls on graphs
Authors: Balacheff Florent 
Published: February 2007

AbstractWe prove new isoperimetric inequalities on graphs involving quantities linked with concepts from differential geometry. First, we bound from above the product of the volume entropy (defined as the log of the exponential growth rate of the universal cover) and the girth of weighted graphs in terms of their cyclomatic number. In a second part, we study a natural polyhedron associated to a weighted graph: the stable ball. In particular, we relate the volume of this polyhedron, the weight of the graph and its cyclomatic number. © 2007 Wiley Periodicals, Inc. J Graph Theory 55: 291–305, 2007
Packing k‐edge trees in graphs of restricted vertex degrees
Authors: Kelmans A.K. 
Published: February 2007

AbstractLet ${\cal G}^{s}_{r}$ denote the set of graphs with each vertex of degree at least r and at most s, v(G) the number of vertices, and τk (G) the maximum number of disjoint k‐edge trees in G. In this paper we show that

if G ∈ ${\cal G}^{s}_{2}$ and s ≥ 4, then τ2(G) ≥ v(G)/(s + 1),
if G ∈ ${\cal G}^{3}_{2}$ and G has no 5‐vertex components, then τ2(G) ≥ v(G)4,
if G ∈ ${\cal G}^{s}_{1}$ and G has no k‐vertex component, where k ≥ 2 and s ≥ 3, then τk(G) ≥ (v(G) ‐k)/(sk ‐ k + 1), and
the above bounds are attained for infinitely many connected graphs.

Our proofs provide polynomial time algorithms for finding the corresponding packings in a graph. © 2007 Wiley Periodicals, Inc. J Graph Theory 55: 306–324, 2007
A field experiment on the influence of the postulated global climatic change on coastal marshland soils
Authors: Blume Hans‐Peter , Müller‐Thomsen Udo 
Published: February 2007

AbstractA climatic scenario postulates an increase of atmospheric CO2, 55 cm water‐level rise combined with a 30 cm higher tidal amplitude for the North Sea. Further, more frequent and stronger west storms, a 2.5°C mean‐annual‐temperature increase together with 15% more rainfall during winter time are to be expected until 2050 due to recent human impact.The possible consequences of the postulated changes in temperature and flooding dynamics were studied for soil formation as well as for soil‐ecological attributes and processes of two sites at Hedwigenkoog foreshore in N Germany: aHypersali‐tidalic Fluvisol(protothionic, calcaric) (1.5 m asl with >500 annual floods) and aGleyi‐sali‐tidalic Fluvisol(calcaric) under a salt meadow (2.2 m asl with 70 annual floods). Temperature, water, redox, nutrient and gas dynamics were measured at different soil depths for a period of 2 y. The topsoil of theGleyi‐sali‐tidalic Fluvisolwas permanently heated over an area of 14 m2to simulate a temperature rise of 1.5–2.5°C. The results are discussed in relation to two realistic scenarios. If the ground level of theGleyi‐sali‐tidalic Fluvisolis heaved up (due to sedimentation) as intensively as the sea level rises, it may be assumed that the soil unit including vegetation cover in principle will not noticeably change. Then, the temperature increase will intensify the activity of soil organisms, bioturbation, and formation of a crumb structure, however, there will be no further accumulation of soil humus. If there was no sedimentation during the next 50 y, the salt meadow itself together with the upper part of theGleyi‐sali‐tidalic Fluvisolwould be destroyed by erosion, and aHypersali‐tidalic Fluvisolwould be formed similar to the studied one.
Productivity increase in Northern Austria Norway spruce forests due to changes in nitrogen cycling and climate
Authors: Jandl Robert , Neumann Markus , Eckmüllner Otto 
Published: February 2007

AbstractWe investigated the long‐term temporal trend in growth rate, soil chemical status, and nutrient content of needles of two Norway spruce (Picea abies) stands in the Bohemian Massif, Austria. The aim was to quantify changes in the site productivity over the last four decades as a consequence of the enriching effect of N deposition, rising CO2 levels in the atmosphere, and changes in forest‐management practices. We used the data records of control plots from forest‐amelioration experiments that have been monitored for more than four decades. Both stands showed increased growth rates and a large deviation from the growth pattern of earlier applicable yield tables. The nutrient levels in the foliage remained unchanged and neither suggested luxury consumption nor nutrient imbalances. Results from soil chemistry analysis were inconclusive in respect of changes in soil conditions: an enrichment of the mineral soil with N and a decrease in the C : N ratio. Changes were confined to the uppermost part of the soil profile. Our data support the hypothesis that the sites are in a steady process of aggradation and that site productivity is rising.
Photosynthetic water‐use efficiency of irrigated winter and summer crops in a typical mountain oasis of northern Oman
Authors: Golombek Sabine D. , Gebauer Jens , Buerkert Andreas 
Published: February 2007

AbstractThe millenia‐old existence of traditional, surface‐irrigated Omani mountain oases implies a remarkable sustainability of such systems in a hyperarid environment. This study was conducted in the mountain oasis of Balad Seet, situated in the Al‐Jabal‐al‐Akhdar mountains of northern Oman, to investigate the water‐use efficiency (WUE) of these oases and how farmers regulate it. In 2005, gas exchange of single leaves of 9–16 plants was measured for the most important perennial field crop alfalfa in both February and August, for the typical winter crop oat in February, and the dominating summer crop sorghum in August. The measurements were conducted five times a day in subplots irrigated the evening before and in the surrounding control plots, where plants had been withheld from irrigation for 14–16 d.Water deficit at the end of the irrigation interval reduced the stomatal conductance (gs) strongly in summer alfalfa, oat, and sorghum, but only slightly in winter alfalfa. In oat, the reduction of net photosynthetic rate (PN) at the end of the irrigation cycle was caused mainly by stomatal closure, in sorghum by nonstomatal factors and in summer alfalfa by both, whereas PN in winter alfalfa remained unaffected. The ratio of net photosynthetic rate to stomatal conductance (PN/gs), the “intrinsic water‐use efficiency”, increased in all investigated crops in response to drought because of a stronger reduction of gs than of PN. This increase was small in winter alfalfa, but much stronger in oat, sorghum, and summer alfalfa.The data indicate that alfalfa maintains a relatively high CO2 assimilation rate year‐round, contributing to a relatively high annual dry‐matter production. The decrease of the light intensity in the late afternoon caused by the shading effect of the surrounding mountains diminishes the crop evapotranspiration in the oasis.
Effects of wastewater irrigation on soil and cabbage‐plant (brassica olerecea var. capitate cv. yalova‐1) chemical properties
Authors: M. Kiziloglu Fatih , Turan Metin , Sahin Ustun , Angin Ilker , Anapali Omer , Okuroglu Mustafa 
Published: February 2007

AbstractThe use of wastewater for irrigation is increasingly being considered as a technical solution to minimize soil degradation and to restore nutrient contents of soils. The aim of this study is to increase fertility and minimize degradation of soils irrigated with wastewater exposed to different purification treatments. A field experiment was conducted to investigate the effects of control and irrigation with wastewater, which had undergone different purification treatments, on macro‐ and micronutrient distribution within the soil profile and nutrient contents of cabbage (Brassica olerecea var. Capitate cv. Yalova‐1) in Erzurum, Turkey. Wastewater irrigation and preliminary treatment–wastewater irrigation significantly affected soil chemical properties especially at 0–30 cm soil depth and plant nutrient contents after one year. Application of wastewater increased soil salinity, organic matter, exchangeable Na, K, Ca, Mg, plant‐available P, and micro‐elements and decreased soil pH. Wastewater increased also yield and N, P, K, Fe, Mn, Zn, Cu, B, and Mo contents of cabbage plants. Undesirable side effects were not observed in plant heavy‐metal contents, due to salinity and toxic concentrations of metals from the application of wastewater to soil.
N form–dependent growth retardation of Arabidopsis thaliana seedlings as revealed from physiological and microarray studies
Authors: Hoffmann Anne , Milde Sabine , Desel Christine , Hümpel Anja , Kaiser Hartmut , Hammes Enno , Piippo Mirva , Soitamo Arto , Aro Eva‐Mari , Gerendás Jóska , Sattelmacher Burkhard , Hansen Ulf‐Peter 
Published: February 2007

AbstractAmmonium (NH$ _4^+ $) nutrition causes retardation of growth in many plant species. In Arabidopsis grown with NH$ _4^+ $ as the sole N source, growth retardation occurs already at early stages before photosynthesis has come to its full power. In order to describe the peculiarities of these retarded plants, they were compared with nitrate (NO$ _3^- $)‐grown plants of the same age of 15 d. Photosynthetic activity as measured by CO2 uptake per unit chlorophyll is half as high in NH$ _4^+ $‐grown seedlings as in NO$ _3^- $‐grown ones. This finding is confirmed by the analysis of chlorophyll fluorescence. Chloroplasts of NO$ _3^- $‐grown, but not of NH$ _4^+ $‐grown, seedlings show starch deposits after 5 h of illumination with 40 μmol m–2 s–1. Gene‐expression analysis based on cDNA microarray and on Northern blots provide a clue about the biochemical background. After the first 2 weeks of growth, it seems that NO$ _3^- $‐grown seedlings subsist mainly on normal photosynthesis, whereas NH$ _4^+ $‐grown seedlings still use lipids from the seeds stored in oleosomes. Corresponding to this observation, the mRNAs for enzymes of β‐oxidation are more strongly expressed in NH$ _4^+ $‐grown seedlings. Different carbohydrate sources for sucrose synthesis are indicated by different gene expression. Higher gene expression of fructose bisphosphate aldolase (cytosolic isoform) in NO$ _3^- $‐grown seedlings indicates the dependence on photosynthesis, whereas a higher gene expression of PEP carboxykinase in NH$ _4^+ $‐grown seedlings points to a prominent role of β‐oxidation of storage lipids still present.
Relationship between water and nitrogen uptake in nitrate‐ and ammonium‐supplied Phaseolus vulgaris L. plants
Authors: Guo Shiwei , Kaldenhoff Ralf , Uehlein Norbert , Sattelmacher Burkhard , Brueck Holger 
Published: February 2007

AbstractSole ammonium supply provokes negative effects on dry‐mass formation, leaf growth, and water uptake of ammonium‐sensitive plants. To study the effects of N form on nutrient and water uptake and aquaporin expression, French bean plants were grown in a split‐root system. Five treatments were compared: homogeneous nitrate (NN) and ammonium (AA) supply; spatially separated supply of nitrate and ammonium (NA); and half of the root system supplied with N‐free nutrient solution, the other half with either nitrate (N0) or ammonium (A0). Ten days after onset of treatments, root dry mass (DM) and water‐uptake rate (WUR) were significantly reduced under ammonium compared to nitrate supply. WUR from nitrate‐supplied vessels was 80% higher than that from N‐free nutrient solution, while WUR from N‐free nutrient solution was 130% higher than that from ammonium‐supplied vessels. Potassium uptake was lower under ammonium supply and the ratio of N : K uptake of treatment AA was significantly higher compared to others. High K uptake from N‐free nutrient solution of A0 plants resulted in a ratio of N : K uptake comparable to nitrate‐supplied plants, but shoot growth resembled that to plants under sole ammonium supply. Within 24 h after onset of treatments, expression of aquaporin was lower under ammonium compared to nitrate supply. From these data, it can be concluded that reduced root water transport under ammonium supply is directly related to aquaporin activity.
Nitrogen turnover in bare soil planted subsequently with grass as investigated by electro‐ultrafiltration (EUF)
Authors: Maci Ardian , Rroço Evan , Kosegarten Harald , Mengel Konrad 
Published: February 2007

AbstractChanges of EUF‐extractable nitrogen (N) (nitrate, ammonium, organic N) in 20 arable bare soils, subsequently planted with ryegrass (Lolium multiflorum L.) and cutting three times were investigated in pot experiments. All 20 soils responded qualitatively in the same way. During the period of bare soil, there was a significant increase of EUF‐extractable nitrate (EUF NO$ _3^- $), while extractable ammonium (EUF NH$ _4^+ $) remained on the same level and organic N (EUF Norg) decreased. This decrease, however, was not significant. From sowing until the first cutting of the grass, EUF‐NO$ _3^- $ concentration decreased to almost zero. This low EUF‐NO$ _3^- $ level was maintained throughout the subsequent experimental period (three cuttings of grass). During the growth of the first cutting, EUF Norg decreased while EUF NH$ _4^+ $ remained constant, however, on a low level. EUF NH$ _4^+ $ fell during the growth of the second and third cutting. In this period, however, the N supply of the grass was insufficient. EUF Norg decreased during the growth of the second cutting, but increased during the growth of the third cutting. This shows that the EUF‐Norg fraction represents a transient pool, which gains and loses N. EUF NO$ _3^- $, EUF NH$ _4^+ $, and EUF Norg correlated with the N uptake of the grass. Strongest correlation for EUF NO$ _3^- $ was found for the first cutting (p < 0.001), and for EUF NH$ _4^+ $ and EUF Norg for the second and third cutting (p < 0.001). Total soil N was not correlated with the N uptake of the grass. EUF Norg was only about 2% of the total N. This relatively small EUF‐Norg fraction, however, is relevant for the mineralization of organic soil N, and the N quantity indicated by EUF Norg is in the range of the N amount mineralized in arable soils within a growing season.
Defoliation, nitrogen, and competition: effects on plant growth and resource allocation of Cleistogenes squarrosa and Artemisia frigida
Authors: Gao Ying Zhi , Wang Shi Ping , Han Xing Guo , Chen Quan Sheng , Zhou Zhi Yong , Patton Bob Dale 
Published: February 2007

AbstractTwo species, Artemisia frigida Willd. (C3, semishrub, and dominant on overgrazed sites) and Cleistogenes squarrosa (Trin.) Keng (C4, perennial bunchgrass, and dominant or codominant on moderately grazed sites) were studied to determine the effects of defoliation, nitrogen (N) availability, competition, and their interactions on growth, biomass, and N allocation in a greenhouse experiment. The main treatments were: two nitrogen levels (N0 = 0 mg N pot–1, N1 = 60 mg N pot–1), two defoliation intensities (removing 60% of total aboveground biomass and no defoliation), and three competitive replacement series (monocultures of each species and mixtures at 0.5:0.5). Our results were inconsistent with our hypothesis on the adaptive mechanisms of A. frigida regarding the interactive effects of herbivory, N, and competition in determining its dominant position on overgrazed sites. Cleistogenes squarrosa will be replaced by A. frigida on overgrazed sites, although C. squarrosa had higher tolerance to defoliation than did A. frigida. Total biomass and N yield and 15N recovery of C. squarrosa in mixed culture were consistently lower than in monocultures, whereas those of A. frigida grown in mixtures were consistently higher than in monocultures, suggesting higher competitive ability of A. frigida. Our results suggest that interspecific competitive ability may be of equal or greater importance than herbivory tolerance in determining herbivore‐induced species replacement in semi‐arid Inner Mongolian steppe. In addition, the dominance of A. frigida on overgrazed sites has been attributed to its ability to shift plant‐plant interactions through gap colonization, root niche differentiation, and higher resistance to water stress.
Comparing1H‐NMR imaging and relaxation mapping of German white asparagus from five different cultivation sites
Authors: Menzel Marion I. , Oros‐Peusquens Ana‐Maria , Pohlmeier Andreas , Shah N. Jon , Schurr Ulrich , Schneider Heike U. 
Published: February 2007

AbstractNuclear magnetic resonance imaging (MRI) and complementary analytical techniques were used to address the question whether white asparagus (Asparagus officinalisL.) from different cultivation sites in Germany can be distinguished on the basis of NMR relaxation times. Five locations with contrasting soil properties and composition within the two asparagus‐cultivation regions Rhineland and Lower Franconia were selected for this project. For the first time, entire asparagus plants in their authentic soil environment excavated directly from the original harvest site were imaged by the NMR technique. However, they could not be employed for determination of relaxation times of spearsin situ, because of artifacts arising from soil properties. Instead, market‐ready asparagus spears and freshly prepared spear saps from the five locations were used to acquire MRI data sets with different (slow and fast) imaging methods and to compute spatially resolved distributions (maps) of T1, T2, and T2* relaxation times. Comparison of the data for pith, vascular tissue, and peel of the spears yielded only marginal, if any, differences in T1, T2, and T2* between the specimens from the five locations, which were not sufficient for an unambiguous region‐related distinction. More pronounced differences in T1, T2, and T2* were visible for the spear saps, allowing a clear distinction between individual specimens for each of the two cultivation regions. The results are discussed in terms of an application potential for correlated NMR relaxation times of tissue saps for future geographic authentication of agricultural produces.
Leaf senescence induced by nitrogen deficiency as indicator of genotypic differences in nitrogen efficiency in tropical maize
Authors: Schulte auf'm Erley Gunda , Begum Nazma , Worku Mosisa , Bänziger Marianne , Horst Walter J. 
Published: February 2007

AbstractNitrogen efficiency is a complex trait. Identification of secondary plant traits correlating with N efficiency would facilitate the breeding for N‐efficient cultivars. Sixteen tropical maize cultivars differing in grain yield at low N supply (N efficiency) under field conditions in Zimbabwe exhibited a significant negative correlation between N efficiency and leaf senescence during grain filling. The same cultivars were studied for leaf senescence under N deficiency in a short‐term nutrient‐solution experiment. Leaf chlorophyll contents as estimated by SPAD values and photosynthesis rates were used as measures for leaf senescence. Cultivars differed both in SPAD values and photosynthesis rates of the older leaves during N deprivation. Significant negative correlations were found between SPAD values, photosynthesis rates in the nutrient‐solution experiment, and leaf‐senescence scores in the field experiments, and positive correlations were found between photosynthesis rates and grain yield under low‐N conditions in the field. Relationships between physiological root parameters, which were also investigated in the nutrient‐solution experiment, and N uptake or grain yield of the cultivars in the field could not be established. It is concluded, that the assessment of the capacity of a genotype to maintain a higher photosynthetic capacity of older leaves during N deficiency–induced senescence at the seedling stage is a suitable selection parameter for the N efficiency of tropical maize cultivars.
Boron in plants and animals: Is there a role beyond cell‐wall structure?
Authors: Goldbach Heiner E. , Wimmer Monika A. 
Published: February 2007

AbstractThe role of boron (B) as a structural element of plant cell walls and its implications for plant growth have been well established. However, increasing evidence suggests one or more functions of boron beyond cell‐wall structure. This evidence arises from studies conducted with a large variety of organisms, such as plants, animals, and bacteria. In animals, embryogenic development seems to depend on adequate boron supply, and cell lines with a knockout of the Na+‐coupled boron transporter NaBC1, the mammalian homolog of Arabidopsis thaliana boron transporter AtBor1, stop to develop and proliferate. In bacteria, boron is an essential part of a signal molecule required for quorum sensing. This review aims to summarize some recent advances from plant, animal, and microbiological research related to the functions of boron and to highlight open questions for further research.
Failure of Hepatitis B Vaccination with Conventional HBsAg Vaccine in Patients with Continuous HBIG Prophylaxis After Liver Transplantation
Authors: Rosenau Jens , Hooman Nazanin , Hadem Johannes , Rifai Kinan , Bahr Matthias J. , Philipp Gunnar , Tillmann Hans L. , Klempnauer Juergen , Strassburg Christian P. , Manns Michael P. 
Published: February 2007

Abstract
Hepatitis B vaccination after liver transplantation for hepatitis B–related liver disease has been investigated as an alternative strategy to reinfection prophylaxis with hepatitis B immunoglobulin (HBIG) with conflicting results. In most studies, HBIG treatment was discontinued before vaccination. An outstanding good response was achieved with vaccination under continuous HBIG administration using hepatitis B surface antigen (HBsAg)-based vaccine containing special adjuvants. Both, adjuvants and continuous HBIG administration have been discussed as crucial factors for good response. Twenty-four patients were vaccinated with conventional double dose recombinant vaccine containing 40 μg HBsAg up to 12 times at weeks 0, 2, 4 (cycle 1), 12, 14, 16 (cycle 2), 24, 26, 28 (cycle 3), and 36, 38, 40 (cycle 4). All patients received 2,000 IU HBIG every 6 weeks (4 times intravenously and 4 times intramuscularly). A significant response was defined as reconfirmed increase of anti-HBs-antigen (anti-HBs) unexplained by HBIG administration or lack of anti-HBs decrease below 100 IU/L after discontinuation of HBIG treatment after week 48. Only 2 of 24 patients (8.3%) responded significantly. Anti-HBs started to increase after the seventh vaccination (cycle 3, during intramuscular HBIG administration) in 1 patient and after 12th vaccination (cycle 4, during intravenous HBIG administration) in the other. Maximum anti-HBs levels were >1,000 IU/L in both patients and decreased significantly slower as compared to passive prophylaxis during follow-up. In conclusion, the conventional HBsAg vaccine failed to induce a significant humoral immune response in most patients despite continued HBIG treatment. Further studies should address the question, of whether the use of potent adjuvant systems results in higher response rates. Liver Transpl 13: 367–373, 2007. © 2007 AASLD.