bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density functional crystal orbital study of cyano‐substituted poly(para‐phenylene‐vinylene) and poly(quinoxaline‐vinylene)
Authors: Bartha F. , Howard I. A. , Geerlings P. , Van Alsenoy C. , Vanderzande D. , Cleij T. J. , Bogár F. 
Published: January 2006

AbstractWe have calculated the optical and electronic properties of several conjugated organic polymers: poly(p‐phenylene‐vinylene) (PPV) and its derivatives. Cyano substitutions on the phenylene ring: poly(2,5‐dicyano‐p‐phenylene‐vinylene) (2,5‐DCN‐PPV) and on the vinylene linkage: poly(p‐phenylene‐7(,8)‐(di)cyano‐vinylene) are considered. In addition, poly(quinoxaline‐vinylene) (PQV) is studied. The infinite isolated quasi‐1D chains are treated with periodic boundary conditions, using atomic basis sets. In a comparative study of PPV, some issues regarding the selection of the functionals and basis sets are discussed and excitation energies derived from time‐dependent and from ordinary methods are compared. It is concluded that for these polymers the calculations are informative at the B3LYP/6‐31G** density functional theory (DFT) level. The absolute values might change with improved methods, but the similarity of the polymers suggests that the relative characterization is adequate. Band structures are communicated along with characteristics of the highest occupied and the lowest unoccupied crystal orbitals (HOCO and LUCO). Electron affinities, ionization potentials, valence and conduction bandwidths, and effective masses at the bandgap are given. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Investigation of several unique tandem mass spectrometric fragmentation patterns of NFDEIDR, an orcokinin analog, and its N‐terminal dimethylated form
Authors: Fu Qiang , Li Lingjun 
Published: January 2006

AbstractOrcokinins are a family of myotropic neuropeptides widely present in various decapod crustaceans and insect species. The majority of the orcokinins identified to date share a conserved sequence of NFDEIDR at their N‐termini. Electrospray ionization quadrupole time‐of‐flight tandem mass spectrometric (ESI‐QTOF‐MS/MS) analysis of doubly charged orcokinin precursor ions reveals the presence of a y(n − 1) + 10 peak, which is more intense than that for the y(n − 1) ion. To elucidate the identity of this novel fragment ion and understand the mechanism underlying this fragmentation, we employed a combined approach involving the use of isotopic N‐terminal dimethylation, methyl esterification, and isotope‐encoded NFDEIDR. Comparison of the fragmentation patterns of these chemically modified orcokinin analogs allowed the determination of the structure of the y(n − 1) + 10 ion as y(n − 1) + COH2O. The yx + COH2O ions, along with the yx + CO and yx + CONH3 ions, are also present in the MS/MS spectra of NFDEIDR and several other peptides. Additionally, we report two other unusual fragmentation ions in the MS/MS spectra of N‐terminal dimethyl NFDEIDR (2+), which yields the novel fragment ions of the y(n − 1) + 38 ion and the [M+2H–59]2+ ion. These two ion series involve the neutral loss of the asparagine side chain. The same sets of ions are also present in other peptides with dimethyl‐modified asparagines at the N‐terminus. The competition between the side‐chain loss and loss of dimethylamine is described. The loss of the side chain of N‐terminal dimethyl Asp1 is reported as well. We also report for the first time the neutral loss of ammonia from the N‐terminal amino group of Asn1 and the loss of CO2 from the side chain of aspartic acid. Copyright © 2006 John Wiley & Sons, Ltd.
Combined use of gas chromatography and selected ion flow tube mass spectrometry for absolute trace gas quantification
Authors: Kubišta Jiří , Španěl Patrik , Dryahina Kseniya , Workman Clive , Smith David 
Published: January 2006

AbstractThe value of the gas chromatography (GC) and selected ion flow tube mass spectrometry (SIFT‐MS) combination for the analysis of trace gases is demonstrated by the quantification of acetone in air samples using the three precursor ions available to SIFT‐MS, viz. H3O+, NO+ and O, and by the separation of the isomers 1‐propanol and 2‐propanol, and their analysis using H3O+ precursor ions. It is shown that the GC/SIFT‐MS combination allows for accurate trace gas quantification obviating the regular, time‐consuming calibrations that are usually required for the more commonly used detectors of GC systems, and the positive identification of isomers in mixtures that is often challenging using SIFT‐MS alone. Thus, the GC/SIFT‐MS combination paves the way to more confident analyses of complex mixtures such as exhaled breath. Copyright © 2006 John Wiley & Sons, Ltd.
Nuclear signalling through phospholipase C and phosphatidyl 4,5‐bisphosphate
Authors: Ho Ka Kei , Mann David J. 
Published: January 2006

AbstractPhosphoinositides are key signalling intermediates with well established roles in transducing ligand mediated signals from the cell surface to the cytosol. Over recent years, strong evidence has accumulated for a role for phosphoinositides within the nucleus. Here we discuss recent advances in our understanding of a key phosphoinositide species phosphatidylinositol 4,5‐bisphosphate (PtdIns(4,5)P2) in the nucleus. The activation/nuclear translocation mechanisms of phospholipase C family members are reviewed and the roles of nuclear PtdIns(4,5)P2, from the generation of the second messenger molecules inositol 1,4,5‐trisphosphate and diacylglycerol to putative functions in the co‐ordination of multiprotein complexes involved in transcription will be discussed.
X-ray diffraction single-crystal structure characterization of iron ludwigite from room temperature to 15 K
Authors: Mir M. , Janczak Jan , Mascarenhas Y. P. 
Published: January 2006

Iron ludwigite exhibits a superstructure between 283 and 144 K. Anomalies in its transport properties are due to a structural transition related to a charge-ordering phenomenon in the low-dimensional structure. This ordering produces a commensurate transversal charge density wave in the system. To understand these structural characteristics, an X-ray single-crystal diffraction study has been performed at 300 and 15 K. No changes were found in the crystalline structure, except for contraction of the cell volume. The bond-valence sum for each cation shows that at room temperature each Fe4—Fe2—Fe4 triad is composed of three Fe3+ions with one extra electron per triad, and at 15 K in each Fe4a—Fe2—Fe4btriad the extra electron is accommodated in the Fe4a—Fe2 pair of each triad.
Increased laser Doppler flow in skin tumors corresponds to elevated vessel density and reactive hyperemia
Authors: Stücker Markus , Springer Christian , Paech Volker , Hermes Nico , Hoffmann Matthias , Altmeyer Peter 
Published: January 2006

Background/purpose: Tumor angiogenesis plays a key role in tumor growth and formation of metastasis. Quantitative analysis of tumor blood flow is a prerequisite for developing novel treatment strategies such as antiangiogenic and antivascular treatment options. Laser Doppler flow in malignant melanomas has been shown to be increased compared with normal skin and melanocytic nevi. This study investigated whether this phenomenon is originated by elevated blood vessel density or by reactive hyperemia.Methods: Laser Doppler flow was studied in 35 melanocytic nevi, 22 malignant melanomas and three basal cell carcinomas. After excision digital imaging analysis was performed in microtome sections (factor VIII‐associated antigen and CD 31 labelled). The ratio of vessel area in histological sections from tumor tissue and in non‐lesional skin was calculated and related to Doppler flow values.Results: Malignant melanomas demonstrated an enlargement of vessel cross‐sectional area by factor 3.7±1.9 and of Doppler flow by factor 10.56±10.7, and melanocytic nevi accomplished increase of vessel cross‐sectional area by factor 1.7±0.9 and of Doppler flow by factor 2.7±3.5.Conclusion: The laser Doppler flow is influenced by the number and the velocity of erythrocytes in the tissue. The greater increase of laser Doppler flow than of vessel density in histological sections demonstrates that the flow signal in skin tumors is caused by neovascularization as well as by functional hyperemia. Laser Doppler perfusion imaging is a useful method for non‐invasive, repeated and quantitative assessment of tumor vascular network and effects of antiangiogenic treatment directed vs. tumor vasculature in vivo, but it cannot distinguish between increased vessel density and reactive hyperemia.
Sensitive skin: correlation with skin surface microrelief appearance
Authors: Sparavigna Adele , Di Pietro Antonino , Setaro Michele 
Published: January 2006

Background/purpose: Sensitive skin is a condition associated with reduced tolerance to environmental factors and/or the application of topical products, such as cosmetics. Its pathophysiology has not been fully elucidated and few data are available on its prevalence. The aim of this study was to investigate possible correlation between objective sensitivity and skin surface microrelief.Methods: During an epidemiological survey conducted for a campaign promoted by International Society of Plastic Dermatology in Italy, 243 adult healthy subjects of both sexes with no evident dermatological disorder but positive to the lactic acid stinging test, were submitted to cyanoacrylate stratum corneum stripping from the volar forearm for the determination of the irregularity of the skin surface microrelief (irregularity skin index (ISI)).Results: A significant correlation was found between intensity of symptoms in stingers and ISI (rs=−0.47; P<0.001).Conclusion: Sensitive skin is common in the healthy population. ISI can contribute towards the identification of subjects with sensitive skin and the development of more specific skin treatments for this prevalent condition.
The incidence and pathophysiology of hyponatraemia after subarachnoid haemorrhage
Authors: Sherlock Mark , O'Sullivan Eoin , Agha Amar , Behan Lucy Ann , Rawluk Danny , Brennan Paul , Tormey William , Thompson Christopher J. 
Published: January 2006

SummaryBackground  Hyponatraemia is common following subarachnoid haemorrhage (SAH) but the pathogenesis is unclear.Objective  To establish the incidence, pathophysiology and consequences of hyponatraemia following SAH.Methods  A retrospective case‐note analysis of all patients with SAH admitted to Beaumont Hospital between January 2002 and September 2003. Three hundred and sixteen cases of SAH were substantiated by computed tomography (CT) scan and angiogram findings. Hyponatraemia was defined as plasma sodium < 135 mmol/l.Results  One hundred and seventy‐nine patients (56·6%) developed hyponatraemia and 62 (19·6%) developed significant hyponatraemia (plasma sodium < 130 mmol/l). The incidence of severe hyponatraemia following hypophysectomy was lower in the period of analysis (5/81, 6·2%, P < 0·01). Hyponatraemia was more common in patients with identified aneurysms (anterior circulation 102/168, 60·7%, posterior circulation 56/95, 60·8%) than in those with no radiological aneurysm (21/54, 38·8%, P < 0·001). Hyponatraemia was more common after aneurysmal clipping (68/103, 66%) or coiling (82/132, 62%) than after conservative treatment (29/81, 36%, P < 0·001). The aetiology of significant hyponatraemia was the syndrome of inappropriate antidiuretic hormone secretion (SIADH) 39/62 (69·2%), cerebral salt‐wasting syndrome (CSWS) 4/62 (6·5%), hypovolaemic hyponatraemia 13/62 (21%), hypervolaemic hyponatraemia 3/62 (4·8%) and mixed CSW/SIADH 3/62 (4·8%). Hyponatraemia was associated with longer hospital stay (24·0 ± 2·6 vs. 11·8 ± 0·8 days, P < 0·001) but did not affect mortality (P = 0·07). Hyponatraemia developed more than 7 days following SAH in 21·4% and more then 7 days following intervention in 31·8%.Conclusions  Hyponatraemia is common following SAH and is associated with longer hospital stay. Clipping and coiling of aneurysms are associated with higher rates of hyponatraemia. SIADH is the commonest cause of hyponatraemia after SAH. Delayed hyponatraemia is common, and has implications for early discharge strategies.
Pond canopy cover: a resource gradient for anuran larvae
Authors: SCHIESARI LUIS 
Published: January 2006

Summary1. The gradient in pond canopy cover strongly influences freshwater species distributions. This study tested the effects of canopy cover on the performance of two species of larval anurans, a canopy cover generalist (Rana sylvatica, the wood frog) and an open‐canopy specialist (R. pipiens, the leopard frog), and tested which factors co‐varying with canopy cover mediate these effects.2. A field transplant experiment demonstrated that canopy cover had negative performance effects on both species. However, leopard frogs, which grow faster than wood frogs in open‐canopy ponds, were more strongly affected by closed‐canopy pond conditions.3. Closed‐canopy ponds had lower temperature, dissolved oxygen (DO), and food nutritional quality as indicated by carbon‐to‐nitrogen ratio (C : N) analysis of field‐sampled food types, and of gut contents of transplanted larvae.4. Laboratory experiments demonstrated that higher temperature and food quality but not DO substantially increased larval growth. However, only food quality increased growth rates of leopard frogs more than wood frogs.5. The strong correlation of growth rates to gut content C : N in the field, and the similarity of growth curves as a function of resource quality in the field and laboratory, strongly suggest that resources are of primary importance in mediating intraspecific, and especially interspecific differences in performance across the canopy cover gradient.
Changing habitat associations of a thermally constrained species, the silver‐spotted skipper butterfly, in response to climate warming
Authors: DAVIES ZOE G. , WILSON ROBERT J. , COLES SOPHIE , THOMAS CHRIS D. 
Published: January 2006

Summary

The impact of climate change on the distribution, abundance, phenology and ecophysiology of species is already well documented, whereas the influence of climate change on habitat choice and utilization has received little attention. Here we report the changing habitat associations of a thermally constrained grassland butterfly, Hesperia comma, over 20 years.
Between 1982 and 2001–2, the optimum percentage of bare ground within habitat used for egg‐laying shifted from 41% to 21%.
Egg‐laying rates are temperature‐dependent and females actively adjust microhabitat usage in response to temperature variations; relatively warmer host plants are chosen or oviposition at low ambient temperatures, and cooler host plants at high ambient temperatures.
Climate warming has increased the availability of thermally suitable habitat for H. comma at the cool, northern edge of the species’ distribution, therefore increasing: (a) egg‐laying rate and potentially the realized rate of population increase; (b) effective area of habitat patches as more microhabitats within a given vegetation fragment are now suitable for egg‐laying; (c) buffering of populations against environmental variation as eggs are laid within a wider range of microhabitats; and (d) the number of habitat patches in the landscape that are currently available for colonization (including the use of more northerly facing aspects; Thomas et al., Nature, 2001, 411, 577–581).
Conservationists often assume the habitat requirements of a species to be constant, and manage habitats to maintain these conditions. For many species, these requirements are likely to change in response to climate warming, and care must be taken not to manage habitats based on outdated prescriptions.
The relationship between pollen and extant vegetation across an arid urban ecosystem and surrounding desert in Southwest USA
Authors: Stuart Glenn , Gries Corinna , Hope Diane 
Published: January 2006

AbstractAim  In this paper, we explore the relationship between pollen concentration in surface soil and extant perennial vegetation across a rapidly urbanizing arid ecosystem along with its surrounding agricultural and native Sonoran Desert land. We also investigate whether taxa behave as expected from known pollination characteristics (e.g. anemophilous vs. zoophilous) and whether the pollen–plant relationship differs between the undeveloped desert and agro‐urban regions.Location  We used a probability‐based sampling scheme at 200, 900‐m2 sites across the Central Arizona–Phoenix region, a 6400‐km2 area of the south‐western USA.Methods  Pollen–plant abundances were mapped across the study area using interpolation techniques, summary bar charts and scatterplots, then two statistical approaches were applied to examine the data quantitatively. Firstly, we used regression analysis of paired pollen concentration and plant cover data; secondly, pc‐ord was used on a cross‐matrix (contingency table) containing the presence/absence scores of both pollen and plants for each taxon at each site.Results  Mapping and quantitative analysis revealed that pollen–plant relationships do vary both between anemophilous and zoophilous groupings and by individual taxon. They also revealed that distribution patterns of both pollen and plant abundance vary consistently across the three main landscape types (desert, urban, agricultural) and that pollen taxa groupings are consistent with pollination method and source plant distribution regardless of landscape type.Main conclusions  These findings provide a broad range of comparative data to facilitate palynological reconstruction of past vegetation and aid in assessing types of prehistoric impacts on this vegetation. They also document that significant variation can occur in pollen rain across a city, even for taxa with widely distributed pollen, leading to the conclusion that forecasting pollen distribution patterns for allergy‐related pollen types using only one or a few pollen traps is likely to entail substantial error.
Chromosome healing by de novo telomere addition in Saccharomyces cerevisiae
Authors: Pennaneach Vincent , Putnam Christopher D. , Kolodner Richard D. 
Published: January 2006

SummaryThe repair of spontaneous or induced DNA damage by homologous recombination (HR) in Saccharomyces cerevisiae will suppress chromosome rearrangements. Alternative chromosome healing pathways can result in chromosomal instability. One of these pathways is de novo telomere addition where the end of a broken chromosome is stabilized by telomerase‐dependent addition of telomeres at non‐telomeric sites. De novo telomere addition requires the recruitment of telomerase to chromosomal targets. Subsequently, annealing of the telomerase reverse transcriptase RNA‐template (guide RNA) at short regions of homology is followed by extension of the nascent 3′‐end of the broken chromosome to copy a short region of the telomerase guide RNA; multiple cycles of this process yield the new telomere. Proteins including Pif1 helicase, the single‐stranded DNA‐binding protein Cdc13 and the Ku heterocomplex are known to participate in native telomere functions and also regulate the de novo telomere addition reaction. Studies of the sequences added at de novo telomeres have lead to a detailed description of the annealing–extension–dissociation cycles that copy the telomerase guide RNA, which can explain the heterogeneity of telomeric repeats at de novo and native telomeres in S. cerevisiae.
Hfq‐dependent alterations of the transcriptome profile and effects on quorum sensing in Pseudomonas aeruginosa
Authors: Sonnleitner Elisabeth , Schuster Martin , Sorger‐Domenigg Theresa , Greenberg Everett Peter , Bläsi Udo 
Published: January 2006

SummaryThe Pseudomonas aeruginosa quorum‐sensing (QS) systems, Las and Rhl, control the production of several virulence factors and other proteins, which are important to sustain adverse conditions. A comparative transcriptome analysis of a rpoS – and a rpoS–hfq – strain indicated that the Sm‐like RNA‐binding protein Hfq affects approximately 5% of the P. aeruginosa O1 transcripts. Among these transcripts 72 were identified to be QS regulated. Expression studies revealed that Hfq does not control the master regulators of the Las system, LasR and LasI. Upon entry into stationary phase, Hfq exerted a moderate stimulatory effect on translation of the rhlR gene and on the qscR gene, encoding a LasR/RhlR homologue. However, Hfq considerably stimulated translation of the rhlI gene, encoding the synthetase of the autoinducer N‐Butyryl‐homoserine lactone (C4‐HSL). Correspondingly, the C4‐HSL levels were reduced in a hfq– strain. To elucidate the stimulatory effect of Hfq on rhlI expression we asked whether Hfq affects the stability of the regulatory RNAs RsmY and RsmZ, which have been implicated in sequestration of the translational repressor RsmA, which in turn is known to negatively regulate RhlI synthesis. We demonstrate that Hfq binds to and stabilizes the regulatory RNA RsmY, which is further shown to bind to the regulatory protein RsmA. A model for the Hfq regulatory network is presented, wherein an alleviation of the negative effect of RsmA accounts for the observed stimulation of rhlI expression by Hfq. The model is corroborated by the observation that a rsmY– mutant mimics the hfq – phenotype with regard to rhlI expression.
The role of proton motive force in expression of the Staphylococcus aureus cid and lrg operons
Authors: Patton Toni G. , Yang Soo‐Jin , Bayles Kenneth W. 
Published: January 2006

SummaryThe Staphylococcus aureus cidABC and lrgAB operons have been shown to play a key role in the regulation of murein hydrolase activity and cell death in a manner thought to be analogous to bacteriophage‐encoded holins and anti‐holins respectively. Because of these functions, it has been proposed that the regulation of these operons is tightly controlled and responsive to key metabolic signals. The current study revealed the presence of two overlapping regulatory pathways controlling cidABC and lrgAB expression, one dependent on acetic acid and the other dependent on proton motive force (PMF). The latter pathway was analysed using agents that affect various aspects of the PMF. Gramicidin and carbonyl cyanide m‐chlorophenylhydrazone (CCCP), antimicrobial agents that dissipate the ΔpH and membrane potential (ΔΨ), both enhanced lrgAB expression. Restoration of the PMF by incubation of the bacteria in the presence of glucose restored lrgAB expression back to the uninduced state. In addition, valinomycin, which specifically collapses the ΔΨ, also induced lrgAB expression. In contrast, nigericin, which dissipates the ΔpH component of the PMF, was found to have a minimal effect on ΔΨ and lrgAB transcription. Finally, the ΔΨ‐inducible expression of lrgAB was shown to be dependent on the previously characterized LytSR two‐component regulatory system that is involved in the regulation of autolysis. The results of this study support a model in which the LytSR regulatory system responds to a collapse in ΔΨ by inducing the transcription of the lrgAB operon.