bluuebunny/crossref_metadata_2025 huggingface dataset:
On the spectrum of critical sets in latin squares of order 2n
Authors: Donovan Diane , LeFevre James , van Rees G. H. John
Published: February 2007

Suppose that L is a latin square of order m and P ⊑ L is a partial latin square. If L is the only latin square of order m which contains P, and no proper subset of P has this property, then P is a critical set of L. The critical set spectrum problem is to determine, for a given m, the set of integers t for which there exists a latin square of order m with a critical set of size t. We outline a partial solution to the critical set spectrum problem for latin squares of order 2n. The back circulant latin square of even order m has a well‐known critical set of size m2/4, and this is the smallest known critical set for a latin square of order m. The abelian 2‐group of order 2n has a critical set of size 4n‐3n, and this is the largest known critical set for a latin square of order 2n. We construct a set of latin squares with associated critical sets which are intermediate between the back circulant latin square of order 2n and the abelian 2‐group of order 2n. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 25–43, 2008
List circular coloring of trees and cycles
Authors: Raspaud André , Zhu Xuding
Published: February 2007

Suppose G=(V, E) is a graph and p ≥ 2q are positive integers. A (p, q)‐coloring of G is a mapping ϕ: V → {0, 1, …, p‐1} such that for any edge xy of G, q ≤ |ϕ(x)‐ϕ(y)| ≤ p‐q. A color‐list is a mapping L: V → $\cal P$({0, 1, …, p‐1}) which assigns to each vertex v a set L(v) of permissible colors. An L‐(p, q)‐coloring of G is a (p, q)‐coloring ϕ of G such that for each vertex v, ϕ(v) ∈ L(v). We say G is L‐(p, q)‐colorable if there exists an L‐(p, q)‐coloring of G. A color‐size‐list is a mapping ℓ which assigns to each vertex v a non‐negative integer ℓ(v). We say G is ℓ‐(p, q)‐colorable if for every color‐list L with |L(v)| = ℓ(v), G is L‐(p, q)‐colorable. In this article, we consider list circular coloring of trees and cycles. For any tree T and for any p ≥ 2q, we present a necessary and sufficient condition for T to be ℓ‐(p, q)‐colorable. For each cycle C and for each positive integer k, we present a condition on ℓ which is sufficient for C to be ℓ‐(2k+1, k)‐colorable, and the condition is sharp. © 2007 Wiley Periodicals, Inc. J Graph Theory 55: 249–265, 2007
Volume entropy, weighted girths and stable balls on graphs
Authors: Balacheff Florent
Published: February 2007

We 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

Let ${\cal G}^{s}_{r}$ 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

A 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

We 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

The 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

The 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

Ammonium (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

Sole 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

Changes 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

Two 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

Nuclear 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

Nitrogen 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

The 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

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.
Recurrence of Hepatitis B is Associated with Cumulative Corticosteroid Dose and Chemotherapy Against Hepatocellular Carcinoma Recurrence After Liver Transplantation
Authors: Yi Nam-Joon , Suh Kyung-Suk , Cho Jai Young , Kwon Choon Hyuck , Lee Kwang-Woong , Joh Jae Won , Lee Suk-Koo , Kim Soon Il , Lee Kuhn Uk
Published: February 2007

The incidence of hepatitis B (HB) recurrence after a liver transplantation has been reduced by prophylaxis with hepatitis B immunoglobulin (HBIG) and lamivudine. However, the long-term incidence of recurrence is <10%, and the factors associated with HB recurrence are unclear. This study analyzed the factors associated with HB recurrence in 203 recipients who underwent liver transplantation for HB in 3 major centers in Korea over 4 years. Eighty-five patients (41.9%) had a hepatocellular carcinoma (HCC). Preoperative active virus replicators with the HBeAg(+) (46.8%) and/or hepatitis B virus DNA(+) (39.4%) were observed in 136 patients (67.0%). The HB prophylaxis consisted of either HBIG monotherapy (n = 95, HBIG group) or combination therapy with lamivudine (n = 108, combination group). HB recurrence was defined as the appearance of the HBsAg. The follow-up period was 28.3 ± 13.1 months (mean ± SD). HB recurred in 21 patients (10.3%) after transplantation. The time from transplantation to recurrence was 16.3 ± 9.4 months. Pre-LT DNA positivity was more prevalent in HBIG group (55.8%) than in the combination group (39.8%) (P = 0.015). However, the incidence of HB recurrence was similar in the HBIG (6.3%) and combination group (13.8%), as well as between the active replicators (12.5%) and nonreplicators (4.1%) (P < 0.05). There was a far higher incidence of HB recurrence in patients receiving corticosteroid pulse therapy (21.0% vs. 7.9%), patients who experienced HCC recurrence (31.3% vs. 8.6%), and patients receiving chemotherapy to prevent HCC recurrence (25.0% vs. 4.4%) (P < 0.05). The cumulative corticosteroid dose was higher in patients who experienced recurrence of HB (P = 0.002). Multivariable analysis confirmed the effect of the cumulative corticosteroid dose and chemotherapy to be risk factors. Liver transplantation for HB is safe, with low recurrence rates if adequate prophylaxis is used. However, the cumulative corticosteroid dose and the chemotherapy used for HCC were risk factors for HB recurrence, so careful monitoring for HB recurrence is needed in these patients. Liver Transpl 13:451–458, 2007. © 2007 AASLD.
Inflammation is An Important Determinant of Levels of the Endogenous Nitric Oxide Synthase Inhibitor Asymmetric Dimethylarginine (ADMA) in Acute Liver Failure
Authors: Mookerjee Rajeshwar P. , Dalton Neil R. , Davies Nathan A. , Hodges Stephen J. , Turner Charles , Williams Roger , Jalan Rajiv
Published: February 2007

Acute liver failure (ALF) is characterized by rapid progressive organ failure and poor outcome. The pathophysiology of multiorgan dysfunction in ALF remains unclear but increased systemic inflammatory response is believed to be an important determining factor. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, results from proteolysis and the liver is a major site for its metabolism. ADMA has been shown to independently predict outcome in multiorgan failure associated with severe liver dysfunction. In this study, we tested the hypothesis that proinflammatory cytokine driven responses are important in modulating ADMA levels in patients with acetaminophen-induced ALF. Blood samples were collected from 10 ALF patients (grade IV encephalopathy) from admission until the time of transplantation or death, and assayed for cytokines and ADMA. A total of 8 patients required treatment for raised intracranial pressure and all patients were managed with standard of care, including full mechanical ventilation and veno-venous hemofiltration. ADMA levels were markedly higher in ALF patients compared to age-matched controls (P < 0.001) and correlated with the levels of proinflammatory cytokines. In pretransplantation patients undergoing hepatic venous catheterization, we demonstrated no significant uptake of ADMA across the failing liver. However, following liver transplantation, ADMA levels reduced acutely. A timed study of ADMA levels during transplantation demonstrated a slight increase during the anhepatic phase but a marked and sustained reduction in ADMA following liver reperfusion. In conclusion, our data show a significant correlation between ADMA levels and proinflammatory cytokines, supporting a hypothesis that proinflammatory cytokines may regulate ADMA metabolism in ALF. Liver Transpl 13:400–405, 2007. © 2007 AASLD.
Orthotopic Liver or Multivisceral Transplantation As Treatment of Metastatic Neuroendocrine Tumors
Authors: Olausson Michael , Friman Styrbjörn , Herlenius Gustaf , Cahlin Christian , Nilsson Ola , Jansson Svante , Wängberg Bo , Ahlman Håkan
Published: February 2007

Liver transplantation can be a therapeutic option for individual patients with neuroendocrine tumors metastatic only to the liver. In this consecutive series of 15 patients (5 multivisceral and 10 orthotopic liver transplantations) with well-differentiated carcinoids, or endocrine pancreatic tumors, we allowed higher proliferation rate (Ki67 <10%), large tumor burden, and higher age than previous studies. Liver transplantation offered good relief of symptoms, long disease-free intervals, and potential cure in individual patients. The survival of grafts and patients compared well with transplantation for benign disease. The overall 5-year survival was 90%. The recurrence-free survival of both multivisceral and liver transplantation related to the time after transplantation (about 20% at 5 years) despite inclusion of patients with higher risk. In conclusion, the critical prognosticators for long-term outcome still remain to be defined. The experience with multivisceral transplantation for patients with endocrine tumors of the pancreatic head is still limited. Liver Transpl 13:327–333, 2007. © 2007 AASLD.
Addition of Adenosine Monophosphate-Activated Protein Kinase Activators to University of Wisconsin Solution
Authors: Ben Mosbah Ismail , Massip-Salcedo Marta , Fernández-Monteiro Izabel , Xaus Carme , Bartrons Ramon , Boillot Olivier , Roselló-Catafau Joan , Peralta Carmen
Published: February 2007

This study investigates how the addition of trimetazidine (TMZ) and aminoimidazole-4-carboxamide ribonucleoside (AICAR) to University of Wisconsin (UW) solution protects steatotic livers. Steatotic and nonsteatotic livers were preserved for 24 hours at 4°C in UW and UW with TMZ and AICAR (separately or in combination) and then perfused ex vivo for 2 hours at 37°C. Adenosine monophosphate-activated protein kinase (AMPK) or nitric oxide (NO) synthesis inhibition in livers preserved in UW with TMZ was also investigated. Hepatic injury and function (transaminases, bile production, and sulfobromophthalein clearance) and factors potentially involved in the susceptibility of steatotic livers to ischemia-reperfusion (I/R), including vascular resistance, mitochondrial damage, adenosine triphosphate depletion, and oxidative stress were evaluated. AMPK, NO synthase (NOS), nitrate, and nitrite levels were also determined. The addition of TMZ and AICAR (separately or in combination) to UW reduced hepatic injury, improved functionality, and protected against the mechanisms responsible for the vulnerability of steatotic livers to I/R. Like AICAR, TMZ increased AMPK, constitutive NOS, and nitrates and nitrites, and conversely, AMPK or NO synthesis inhibition abolished the benefits of TMZ. In conclusion, TMZ, by means of AMPK, increased NO, thus protecting steatotic livers against their vulnerability to I/R injury. TMZ and AICAR may constitute new additives to UW solution in steatotic liver preservation, whereas a combination of both seems unnecessary. Liver Transpl 13:410–425, 2007. © 2007 AASLD.
Vaccination Against Hepatitis B in Liver Transplant Recipients
Authors: Bauer Tanja , Günther Matthias , Bienzle Ulrich , Neuhaus Ruth , Jilg Wolfgang
Published: February 2007

After liver transplantation for hepatitis-B-related diseases, patients currently receive lifelong treatment with hepatitis B immunoglobulin to prevent endogenous reinfection with hepatitis B virus (HBV). Active immunization with hepatitis B vaccine would be a preferable alternative; however, most attempts to immunize these patients with standard vaccine have failed. A recent study with a new adjuvanted hepatitis B vaccine was exceptionally successful, leading to a high-titered long-lasting antibody response in 80% of all vaccinees. To identify the immunological mechanisms behind these unexpected results, the successfully vaccinated participants were tested for hepatitis B surface antigen (HBsAg)-specific T and B cells, and their cellular responses to revaccination with conventional vaccine were studied. HBsAg-specific CD4+ T lymphocytes could be detected in 13 of 16 patients after immunization with the new vaccine. Unexpectedly, these T cells produced almost exclusively interleukin (IL)-10 and had a CD4+/CD25+ phenotype. They were functionally active, suppressing cytokine secretion in HBsAg-specific (Th1) cells, thus representing antigen-specific regulatory T cells (TReg). Following a booster dose with conventional vaccine 22-31 months after completion of the initial vaccination series, the T-cell pattern in the revaccinated individuals changed substantially: 7 days after revaccination 9 of 11 individuals showed a switch to a Th1-type immune response with HBsAg-specific T cells secreting IL-2, interferon gamma and tumor necrosis factor alpha as observed in healthy controls. Four weeks after the booster, 4 patients still showed a Th1-type cytokine pattern, whereas in 5 patients only IL-10-secreting cells were detectable. After 1 year, in 3 of 4 revaccinated individuals only IL-10-secreting cells could be found, whereas the specific T cells of the fourth patient still showed a Th1-type of response. HBsAg-specific TReg cells could be demonstrated in HBV-positive liver transplant recipients successfully immunized with a new adjuvanted vaccine. Revaccination led to immediate disappearance of the these cells and the appearance of HBsAg-specific T cells with a Th1-type cytokine profile, which in most cases were replaced by the IL-10-secreting regulatory cells during the following months. The specific induction of TReg cells could contribute to the poor response of liver transplant recipients to conventional vaccine. In conclusion,, for successful vaccination of these patients, a vaccine with a strong inhibitory effect on TReg cells would be desirable. Liver Transpl 13:434–442, 2007. © 2007 AASLD.
Increased Ischemic Injury in Old Mouse Liver
Authors: Selzner Markus , Selzner Nazia , Jochum Wolfram , Graf Rolf , Clavien Pierre-Alain
Published: February 2007

Although livers exhibit only minimal morphologic changes with age, how older livers tolerate pathologic conditions such as normothermic ischemia is unknown. Young 6-week-old mice and old 60-week-old mice underwent 60 minutes of hepatic ischemia and various periods of reperfusion. Markers of hepatocyte injury, hepatic energy content, and mitochondrial function were determined. Ischemic preconditioning and glucose injection were evaluated as protective strategies against reperfusion injury in old mice. Reperfusion injury was far worse in old mice compared with mice in the young control group. Ischemic preconditioning was highly protective against reperfusion injury in young but not in old mice. Older livers had dramatically reduced adenosine triphosphate (ATP) levels and glycogen contents. The low intrahepatic energy level in old mice was associated with a reduced mitochondrial ATP production. Preoperative injection of glucose restored the intrahepatic ATP content and protected against reperfusion injury. Furthermore, glucose injection restored the protective effect of ischemic preconditioning, resulting in additive protection when both strategies were combined. Aging of the liver is associated with mitochondrial dysfunction and decreased intrahepatic energy content, resulting in poorer tolerance against ischemic injury. Improving intrahepatic ATP levels in old livers by glucose injection protects the old liver against ischemic injury and restores the protective effects of ischemic preconditioning. Liver Transpl 13:382–390, 2007. © 2007 AASLD.
Electrical Properties of a Composite Film of Poly(acrylonitrile) Nanoparticles Coated with Carbon Nanotubes
Authors: Han Seung‐Jin , Kim Bumsu , Suh Kyung‐Do
Published: February 2007

A novel time‐ and cost‐saving technique to fabricate a CNT composite film was suggested by using poly(acrylonitrile) nanoparticles coated with functionalized carbon nanotubes. Composite films were formed with fCNTs attached to nanoparticles by hot pressing onto PMMA films. The electrical properties (conductivity and electromagnetic interference shielding effectiveness) of the films were investigated. It was observed that CNT/polymer composite films with PAN nanoparticles coated with fCNTs showed good electrical properties because of enhanced dispersity of CNTs in the polymer matrix.

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Atom Transfer Radical Polymerization and Third‐Order Nonlinear Optical Properties of New Azobenzene‐Containing Side‐Chain Polymers
Authors: Li Najun , Xu Qingfeng , Lu Jianmei , Xia Xuewei , Wang Lihua
Published: February 2007

The atom transfer radical polymerization (ATRP) technique has been successfully applied to synthesize a series of nonlinear optically (NLO) active homopolymers, 4‐(4‐nitrophenyl‐diazenyl) phenyl acrylate (P‐NPAPA) and 4‐(4‐methoxyphenyl‐diazenyl) phenyl acrylate (P‐MPAPA), containing azobenzene groups on the side chain. The third‐order NLO properties of the polymer films were measured by the degenerated four‐wave mixing (DFWM) technique. A dependence of the χ(3) values and response times of polymers on their number‐average molecular weight and the electronic effect of the substituent (nitro‐ or methoxy‐) on the azobenzene group have been evidenced. The increasing χ(3) value of the polymer films at the magnitude of about 10−10 was displayed with increasing molecular weight and the presence of the push‐pull electronic system contributes much in enhancing the third‐order NLO susceptibility of polymers.

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New Carbazole‐Based Copolymers as Amorphous Hole‐Transporting Materials for Multilayer Light‐Emitting Diodes
Authors: Grigalevicius Saulius , Ma Liang , Qian Gang , Xie Zhiyuan , Forster Michael , Scherf Ullrich
Published: February 2007

New carbazole‐based copolymers, which contain various concentrations of 9‐alkyl‐3,6‐carbazole fragments in the main chain connected via alkylene spacers, have been synthesized by Ni(0)‐catalyzed Yamamoto‐type aryl‐aryl coupling reactions. Full characterization of the copolymer structure by NMR spectroscopy and elemental analysis is presented. These compounds represent amorphous materials of high thermal stability with glass transition temperatures of 151–162 °C and thermal decomposition starting at temperatures >390 °C. UV‐Vis absorption and photoluminescence emission of the copolymers confirmed that the effectively conjugated segment in the 3,6‐linked carbazole‐type copolymers is limited to dyads (dimeric units). However, copolymers with varying concentrations of the oligocarbazole chromophores demonstrate different charge injection and transport properties in multilayer light‐emitting diodes with the copolymers as the hole transport and Alq3 as the electroluminescent/electron transport layer. The device based on a copolymer composed of oligocarbazole blocks with an average length of around four carbazoles exhibited the best overall performance with a turn‐on voltage of 3.5 V, a maximal photometric efficiency of 4.1 cd · A−1 and maximum brightness of about 4 200 cd · m−2.

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Recent advances in the treatment of thromboembolic diseases: Venous thromboembolism
Authors: Agrawal Y.K. , Vaidya Hitesh , Bhatt Hardik , Manna Kuntal , Brahmkshatriya Pathik
Published: February 2007

Venous thromboembolic diseases are the major concern of rising cost of healthcare and are commonest health problem across the globe. Both genetic and acquired risk factors are believed to be strongly linked with these diseases. Commonly encountered problems to the therapy include dose fixing and routine monitoring, yet some serious problems of bleeding also necessitate the immediate need to develop new agents. The review is primarily concerned with the new developments in the treatment of thromboembolic diseases. Therapeutic applications of anticoagulants, antiplatelets, and thrombolytics have been discussed in enough detail. © 2007 Wiley Periodicals, Inc. Med Res Rev, 27, No. 6, 891–914, 2007
Controlling the photoluminescence of water‐soluble conjugated poly[2‐(3‐thienyl)ethyloxy‐4‐butylsulfonate)] for biosensor applications
Authors: López‐Cabarcos Enrique , Retama Jorge Rubio , Sholin Veronica , Carter Sue Ann
Published: February 2007

The photoluminescence of poly[2‐(3‐thienyl)ethyloxy‐4‐butylsulfonate)] (PTE‐BS) in aqueous solution increases threefold on addition of the surfactant tetrabutylammonium perchlorate (TBA). Furthermore, the luminescence of the PTE‐BS/TBA system is reduced by more than five times by the addition of small amounts of the cationic electron acceptor methyl viologen (MV2+). The Stern–Volmer constant KSV = 1.4 × 104 L mol−1 for the quenching of the polymer–surfactant complex by MV2+ is approximately 60 times smaller than the KSV = 8.4 × 105 L mol−1 obtained in water polymer solutions without surfactant. Thus, the luminescence of PTE‐BS in aqueous solution can be modulated by complexing the polymer either with a surfactant or with a quencher. In this contribution we show that the surfactant/quencher tuning effect found in polymers of the phenylenevinylene family, such as poly(2,5‐methoxy‐propyloxysulfonate phenylenevinylene), also appears in polymers of the thiophene family such as PTE‐BS. Copyright © 2007 Society of Chemical Industry
Light trapping effect of submicron surface textures in crystalline Si solar cells
Authors: Sai Hitoshi , Kanamori Yoshiaki , Arafune Koji , Ohshita Yoshio , Yamaguchi Masafumi
Published: February 2007

Recently, submicron textures have been researched and applied to multicrystalline silicon solar cells in order to improve their optical performance. In this study, the antireflection and light trapping effects of submicron surface textures in crystalline Si (c‐Si) solar cells were quantitatively investigated by numerical simulations based on Maxwell's equations with a simple two‐dimensional (2D) surface grating model. The calculated results showed that the surface reflection loss can be effectively reduced by using submicron Si surface gratings with appropriate aspect ratios. On the other hand, higher order diffractions that are caused by surface gratings that increase optical path lengths and light absorption near the band gap wavelength are dominant only for those with periods greater than 0·5 µm. From these results, it was inferred that submicron textures are effective for light trapping as well as for antireflection in thin c‐Si solar cells if appropriate dimensions are chosen. Copyright © 2007 John Wiley & Sons, Ltd.
Stability of the co‐continuous morphology during melt mixing for poly(ε‐caprolactone)/polystyrene blends
Authors: Sarazin Pierre , Favis Basil D.
Published: February 2007

Over the last 10 years, research into co‐continuous polymer blends has been intense. Despite these efforts, there are very few detailed studies on the stability of this complex morphology. In this work, blends of poly(ε‐caprolactone) and polystyrene were melt‐mixed in an internal mixer for time intervals of 0.5–120 min at set temperatures of 140 and 170 °C, and the effect of the mixing time on the co‐continuous morphology was studied. This blend system was chosen because each component could be selectively dissolved and this allowed for a complete study of the co‐continuous region. The phase continuity was measured with a solvent‐extraction gravimetric technique, and the concentration range for co‐continuity was determined. The phase size and phase size distribution were obtained with the mercury intrusion porosimetry technique. The results indicate that the co‐continuous morphology forms very early in the mixing process and achieves a stable morphology within the first 5 min of mixing for virtually all the co‐continuous compositions. For all cases studied, the co‐continuous morphology remains unchanged over mixing times as long as 1–2 h. These results support the notion of a stable steady‐state formation of co‐continuous morphologies during melt mixing similar to that observed for matrix/dispersed phase type blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 864–872, 2007
Spectroscopic studies of structural changes in irradiated LDPE and its blends
Authors: Ali Zakaria , Badr Yehia , Eisa Waiel
Published: February 2007

The low temperature glass transition occurring at low temperature in polyethylene samples was studied using Fourier transform infrared, FT‐Raman spectroscopic techniques, which are known to be sensitive to any structural changes in the investigated samples. Anomalous behavior was obtained in the temperature range (98 K → 383 K) indicating the existence of phase transition occurring at about 98 K and disappearing at about 323 K while heating for unirradiated virgin low density polyethylene (VPE) sample with or without crosslinking agent (trimethylol propane triacrylate, TMPTA). Addition of TMPTA monomer caused severe changes in the temperature dependence of both unirradiated and irradiated polyethylene samples. The results given indicated the occurrence of abnormal temperature dependence, which is thought to be related with low temperature structural change resulting from local crosslinking in scrapped polyethylene (SPE) sample already suffering from high degree of crosslinking. Differential scanning calorimetry (DSC) thermograms confirmed the observed new phase transition observed in both unirradiated and irradiated TMPTA loaded VPE/SPE (50/50 wt %) blend. Irradiation, addition of TMPTA as a crosslinking agent, and blending VPE with SPE were found to affect remarkably the variation of the vibration spectrum of LDPE and consequently the resulting structural changes. The experimental results obtained were discussed and correlated with reorientational disorders of the molecular segments (local crosslinking). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 850–859, 2007