bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the optimum form of an aperture for a confinement of the optically excited electric near field
Authors: BORTCHAGOVSKY E. , COLAS DES FRANCS G. , NABER A. , FISCHER U.C. 
Published: February 2008

SummaryA triangular nanoaperture in an aluminium film was used previously as a probe in a scanning near‐field optical microscope to image single fluorescent molecules with an optical resolution down to 30 nm. The high‐resolution capability of the triangular aperture probe is because of a highly confined spot of the electric near field which emerges at an edge of the aperture, when the incident light is polarized perpendicular to this edge. Previous numerical calculations of the near‐field distribution of a triangular aperture in a planar metal film using the field susceptibility technique yielded a nearly quantitative agreement with the experimental results. Using the same numerical technique we now explored the possibility for a further confinement of the electric near field and an increase in its intensity by modifications of the form of a triangular aperture. By introducing a kink on an edge pointing into the aperture, an arrow‐shaped aperture is formed with one convex and three concave metal corners. It turns out that this form leads to a substantial further confinement of the near‐field intensity at the convex corner. By extending the wings of this arrow‐shaped aperture a further 5‐fold increase of the intensity can be obtained without a deterioration of the confined spot.
Real‐time monitoring of the surface relief formation on azo‐polymer films upon near‐field excitation
Authors: AMBROSIO A. , CAMPOSEO A. , MADDALENA P. , PATANÈ S. , ALLEGRINI M. 
Published: February 2008

SummaryWe use near‐field optical microscopy to investigate the early state formation of photo‐induced topographical structures on the free surface of azobenzene‐containing polymers. The near‐field technique is employed to monitor in real time the mass migration during the embossing of the surface of 50/50 copolymer films of polymethacrylate and polymethacrylate containing 3‐methyl‐4′‐pentyloxy‐azobenzene units. The dynamic of surface relief formation induced by light have been investigated as a function of the sample temperature. Furthermore, a formula derived from Navier–Stokes equations for classical laminar flow has been used to fit the mass displacement data during the embossing process. Excellent agreements between the experimental data and the fitting formula have been found for all the temperature considered.
Evanescent field enhancement due to plasmonic resonances of a metamaterial slab
Authors: CHIU K. P. , KAO T. S. , TSAI D. P. 
Published: February 2008

SummaryThe characteristics of plasmonic resonance in a dielectric‐sandwiched metamaterial film at visible wavelengths of 650 and 568 nm have been investigated (for both p‐ and s‐polarized light). Our calculated results demonstrate that each mode of plasmonic resonance has maximum resonance strength at a particular film thickness of the metamaterial. We also demonstrated that the effect of evanescent field enhancement is due to plasmonic resonances of the sandwiched metamaterial system. And the stronger the plasmonic resonance strength the larger the evanescent field is enhanced at the interfaces of the metamaterial film. Also we see that the plasmonic resonances in a sandwiched metamaterial are influenced not only by the materials that constitute the interfaces but also by the thickness of surrounding dielectrics or distance between evanescent light source and metamaterial film. Finally, our results show that there might be an effective light propagation length that will let the coupling efficiency between evanescent light source and SPs resonance become a maximum. These properties of plasmonic resonances to structure parameters of metamaterial film and its surrounding dielectrics provide a useful way to control the optical responses of an optoelectronic device when the wavelength of light source is fixed. That is, by suitably choosing light polarizations, thickness of the metamaterial thin film or the surrounding dielectrics and the position of evanescent light source, it is possible to modulate the plasmonic resonance wavenumber or resonance strength of the system. Therefore, the optical responses of the system can be modulated. Our results will be helpful for the structure design to control the behaviours of coupled plasmonic resonances and consequently the optical properties of the dielectric‐sandwiched metamaterial film.
Polarization‐maintaining near‐field optical probes
Authors: PATANÈ S. , CEFALÌ E. , SPADARO S. , GARDELLI R. , ALBANI M. , ALLEGRINI M. 
Published: February 2008

SummaryWe demonstrate that tapered optical fibre probes can be easily modified in the taper cone to realize an electric dipole producing a well‐defined near‐field polarized light. This novel structure is made of a Short‐cut Double C–shaped probe design combined to the usual full metal coating near the tapered end of the fibre. Hence, the cone at the apex of the probe is excited by an equivalent dipole whose spatial orientation is dictated by the probe geometry, regardless the polarization state of the incoming light. Properties and performances of such a configuration are first predicted by a finite‐difference time domain simulation, showing that the near field coming out from the probe is linearly polarized. Following this novel design, a probe prototype is manufactured and tested. Its measured polar diagram confirms the polarization maintenance property in the near field.
Mutualism, market effects and partner control
Authors: JOHNSTONE R. A. , BSHARY R. 
Published: February 2008

AbstractIntraspecific cooperation and interspecific mutualism often feature a marked asymmetry in the scope for exploitation. Cooperation may nevertheless persist despite one‐sided opportunities for cheating, provided that the partner vulnerable to exploitation has sufficient control over the duration of interaction. The effectiveness of the threat of terminating an encounter, however, depends upon the ease with which both the potential victim and the potential exploiter can find replacement partners. Here, we extend a simple, game‐theoretical model of this form of partner control to incorporate variation in the relative abundance of potential victims and exploiters, which leads to variation in the time required for individuals of each type to find a new partner. We show that such market effects have a dramatic influence on the stable level of exploitation (and consequent duration of interaction). As the relative abundance of victims decreases, they become less tolerant to exploitation, terminating encounters earlier (for a given level of exploitation), whereas exploiters behave in a more cooperative manner. As a result, the stable duration of interaction actually increases, despite the decreasing tolerance of the victims. Below a critical level of relative victim abundance, the model suggests that the cost of finding a replacement partner becomes so great that it does not pay to exploit at all.
Radiation and divergence in the Rhagoletis Pomonella species complex: inferences from DNA sequence data
Authors: XIE X. , MICHEL A. P. , SCHWARZ D. , RULL J. , VELEZ S. , FORBES A. A. , ALUJA M. , FEDER J. L. 
Published: February 2008

AbstractHere, we investigate the evolutionary history and pattern of genetic divergence in the Rhagoletis pomonella (Diptera: Tephritidae) sibling species complex, a model for sympatric speciation via host plant shifting, using 11 anonymous nuclear genes and mtDNA. We report that DNA sequence results largely coincide with those of previous allozyme studies. Rhagoletis cornivora was basal in the complex, distinguished by fixed substitutions at all loci. Gene trees did not provide reciprocally monophyletic relationships among US populations of R. pomonella, R. mendax, R. zephyria and the undescribed flowering dogwood fly. However, private alleles were found for these taxa for certain loci. We discuss the implications of the results with respect to identifiable genetic signposts (stages) of speciation, the mosaic nature of genomic differentiation distinguishing formative species and a concept of speciation mode plurality involving a biogeographic contribution to sympatric speciation in the R. pomonella complex.
Genetic variation in pathogen‐induced early hatching of toad embryos
Authors: GOMEZ‐MESTRE I. , TOUCHON J. C. , SACCOCCIO V. L. , WARKENTIN K. M. 
Published: February 2008

AbstractAccelerated hatching is one of few defences available to embryos, and is effective against many egg‐stage risks. We present the first analysis of genetic variation in hatching plasticity, examining premature hatching of American toad embryos in response to pathogenic water moulds. We reared eggs from half‐ and full‐sib families in the presence and absence of water mould. Hatching age and hatchling size showed low cross‐environment genetic correlations, suggesting that early‐induced hatching can evolve largely independently of spontaneous hatching. We found less phenotypic and additive genetic variation for early‐induced hatching than spontaneous hatching, and a stronger correlation between egg and induced hatchling sizes. Directional selection by the pathogen may have eroded variation in early‐induced hatching, pushing it against the constraint of hatching gland development. Later hatching has a second, muscular component. This pattern of variation may characterize defences based on developmental transitions, although other inducible defences show more variation in induced phenotypes.
Evolution of bone microanatomy of the tetrapod tibia and its use in palaeobiological inference
Authors: KRILOFF A. , GERMAIN D. , CANOVILLE A. , VINCENT P. , SACHE M. , LAURIN M. 
Published: February 2008

AbstractBone microanatomy appears to track changes in various physiological or ecological properties of the individual or the taxon. Analyses of sections of the tibia of 99 taxa show a highly significant (P ≤ 0.005) relationship between long‐bone microanatomy and habitat. Randomization tests reveal a highly significant (P ≤ 0.005) phylogenetic signal on several compactness profile parameters and lifestyle. Discriminant analyses yield an inference model which has a success rate of 63% when lifestyle is coded into three states (aquatic, amphibious and terrestrial) or 83% for a binary model (aquatic vs. amphibious to terrestrial). Lifestyle is inferred to have been terrestrial for the stem‐tetrapodDiscosauriscus(Early Permian), the basal synapsidDimetrodon(Early Permian), the dicynodont therapsidDicynodon(Late Permian), an unindentified gorgonopsian (Late Permian); the parareptilePareiasaurus(Middle or Late Permian) is modelled as being aquatic, but was more likely amphibious.
Marine reserves: size and age do matter
Authors: Claudet Joachim , Osenberg Craig W. , Benedetti‐Cecchi Lisandro , Domenici Paolo , García‐Charton José‐Antonio , Pérez‐Ruzafa Ángel , Badalamenti Fabio , Bayle‐Sempere Just , Brito Alberto , Bulleri Fabio , Culioli Jean‐Michel , Dimech Mark , Falcón Jesús M. , Guala Ivan , Milazzo Marco , Sánchez‐Meca Julio , Somerfield Paul J. , Stobart Ben , Vandeperre Frédéric , Valle Carlos , Planes Serge 
Published: February 2008

AbstractMarine reserves are widely used throughout the world to prevent overfishing and conserve biodiversity, but uncertainties remain about their optimal design. The effects of marine reserves are heterogeneous. Despite theoretical findings, empirical studies have previously found no effect of size on the effectiveness of marine reserves in protecting commercial fish stocks. Using 58 datasets from 19 European marine reserves, we show that reserve size and age do matter: Increasing the size of the no‐take zone increases the density of commercial fishes within the reserve compared with outside; whereas the size of the buffer zone has the opposite effect. Moreover, positive effects of marine reserve on commercial fish species and species richness are linked to the time elapsed since the establishment of the protection scheme. The reserve size‐dependency of the response to protection has strong implications for the spatial management of coastal areas because marine reserves are used for spatial zoning.
Site‐specific microbial communities in three PCB‐impacted sediments are associated with different in situ dechlorinating activities
Authors: Kjellerup Birthe V. , Sun Xueli , Ghosh Upal , May Harold D. , Sowers Kevin R. 
Published: February 2008

SummaryCompetitive PCR and denaturing HPLC analyses together with an assay detecting potential polychlorinated biphenyl (PCB) dechlorinating activities were combined with physical‐chemical site characterizations to identify factors affecting the reductive dechlorination of PCBs in the three historically impacted sediments: Grasse and Buffalo Rivers, NY and Anacostia River, DC. In Grasse River sediment an in situ enriched population of Dehalococcoides phylotypes was abundant in high numbers together with a relatively high dechlorination activity and a high concentration of congeners containing unflanked chlorine substitutions. In contrast microbial communities in Anacostia and Buffalo Rivers sediments consisted of similar total numbers of putative dechlorinating bacteria, but the populations consisted of more diverse putative dechlorinating phylotypes and were associated with lower dechlorination activities and higher concentrations of flanked congeners. Differences observed in the PCB dechlorination activity were not influenced by the chemical PCB availability in spiked sediment or physical sediment characteristics, but were consistent with the concentration of PCBs and total organic carbon in the native sediment. Application of molecular methods for selective detection of indigenous microbial dechlorinating communities combined with assessment of the dechlorinating activity and analysis of the in situ congener profiles provided a comprehensive approach for characterization and identification of sites that are amenable to bioremediation, which is essential for the development of in situ treatment strategies.
Transcription and activities of NOx reductases in Agrobacterium tumefaciens: the influence of nitrate, nitrite and oxygen availability
Authors: Bergaust Linda , Shapleigh James , Frostegård Åsa , Bakken Lars 
Published: February 2008

SummaryThe ability of Agrobacetrium tumefaciens to perform balanced transitions from aerobic to anaerobic respiration was studied by monitoring oxygen depletion, transcription of nirK and norB, and the concentrations of nitrite, nitric oxide (NO) and nitrous oxide in stirred batch cultures with different initial oxygen, nitrate or nitrite concentrations. Nitrate concentrations (0.2–2 mM) did not affect oxygen depletion, nor the oxygen concentration at which denitrification was initiated (1–2 μM). Nitrite (0.2–2 mM), on the other hand, retarded the oxygen depletion as it reached ≈20 μM, and caused initiation of active denitrification as oxygen concentrations reached 10–17 μM. Unbalanced transitions occurred in treatments with high cell densities (i.e. with rapid transition from oxic to anoxic conditions), seen as NO accumulation to μM concentrations and impeded nitrous oxide production. This phenomenon was most severe in nitrite treatments, and reduced the cells' ability to respire oxygen during subsequent oxic conditions. Transcripts of norB were only detectable during the period with active denitrification. In contrast, nirK transcripts were detected at low levels both before and after this period. The results demonstrate that the transition from aerobic to anaerobic metabolism is a regulatory challenge, with implications for survival and emission of trace gases from denitrifying bacteria.
Isolation and cultivation of canine corneal cells for in vitro studies on the anti‐inflammatory effects of dexamethasone
Authors: Werner Anke , Braun Michael , Kietzmann Manfred 
Published: February 2008

AbstractObjective  This study was conducted to establish a protocol for the isolation and culture of canine corneal cells (i.e. endothelium, keratocytes, and epithelium) to be used for in vitro studies on the effects of dexamethasone in corneal inflammation.Animal material  Corneal endothelial cells, epithelial cells and keratocytes from enucleated eyes of dogs (euthanized not related to this study) were isolated and cultured.Procedure  Canine corneal cells were isolated using a combined enzymatic and mechanical technique and separately taken into culture. The three different cell types were verified by phase contrast microscopy, immunofluorescence, and Western blot using antivimentin and anticytokeratin antibodies. The mRNA for the glucocorticoid receptor (GR) was detected using reverse transcriptase polymerase chain reaction (RT‐PCR).To study dexamethasone effects, primary cells were stimulated with lipopolysaccharides (LPS) to induce production of inflammatory mediators, particularly prostaglandin E2 (PGE2). The concentration of PGE2 in cell culture supernatant was determined utilizing an ELISA assay. Results were compared between control, stimulated as well as stimulated and dexamethasone treated cells.Results  A protocol for the isolation and culture of canine corneal endothelium, keratocytes, and epithelium was successfully established. Using morphological criteria as well as immunocytochemistry and Western blotting the identity of the cells could be verified. RT‐PCR of the primary cells showed mRNA for the GR in all three cell types of the canine cornea. Furthermore, stimulation with LPS led to an increased PGE2‐production in epithelial cells and fibroblasts, which was significant for epithelial cells. The PGE2‐concentration was decreased in a dose dependent manner by the addition of dexamethasone.Conclusion  The three major cell types of the canine cornea (i.e. endothelium, keratocytes, and epithelium) can be isolated and cultured in vitro. The mRNA for the GR is shown in all three cell types, its functionality is demonstrated by the dose dependent reduction of PGE2‐production following dexamethasone treatment.
Congenital orbital cysts of neural tissue in two dogs
Authors: Regnier Alain , Raymond‐Letron Isabelle , Peiffer Robert L. 
Published: February 2008

AbstractA 3‐month‐old English Cocker Spaniel and a 6‐month‐old miniature poodle presented with clinical signs related to an abnormal right eye since birth. In both dogs, the right globe could not be identified and was replaced by a fluctuant intraorbital mass covered by a vascularized mucous membrane. Ultrasonography demonstrated that both masses were cystic structures markedly larger in size than the normal contralateral globes. In both cases, surgical excision revealed a multilobular cyst filling the whole orbital cavity. Histopathologic examination and immunostaining for glial fibrillary acid protein and S100 protein supported a diagnosis of neural cysts associated with ocular dysplasia. The definitive diagnosis was congenital cystic eye and microphthalmos with cyst for the Cocker Spaniel and miniature poodle, respectively. Karyotype was normal in both dogs. Congenital cystic eye and microphthalmos with cyst result from defects in early embryonic life that arise following formation of the optic vesicle and prior to closure of the optic fissure. To the authors’ knowledge neither has been reported in the canine species. They should be considered in the differential diagnosis of orbital cysts in dogs.
Isolation of obligate anaerobic bacteria from ulcerative keratitis in domestic animals
Authors: Ledbetter Eric C. , Scarlett Janet M. 
Published: February 2008

AbstractObjective To determine the frequency of obligate anaerobic bacterial isolation from corneal samples of domestic animals with ulcerative keratitis and to characterize the historical, clinical, cytological, and microbiological features of culture‐positive cases.Animals studied Three hundred and thirty domestic animals with ulcerative keratitis.Procedures Anaerobic bacteriologic culture and Gram stain were performed on corneal samples from consecutive animals examined with suspect septic ulcerative keratitis. Additional corneal diagnostics included: aerobic bacteriologic culture for all species; fungal culture for ungulates;Mycoplasmaculture and virus isolation or feline herpesvirus‐1 (FHV‐1) polymerase chain reaction (PCR) for cats. Historical, clinical, and cytological findings were correlated with microbiologic data.Results Anaerobic bacteria were isolated from 13.0% of corneal samples (dogs: 14.0%; horses: 12.9%; cats: 7.9%; alpacas: 18.8%). The most frequent isolates wereClostridium,Peptostreptococcus,Actinomyces,Fusobacterium, andBacteroidesspecies. The majority of these infections were mixed anaerobic and aerobic bacteria, unless antimicrobial therapy had been administered prior to presentation. The clinical appearance of anaerobic bacterial culture‐positive cases was highly variable. Ocular trauma, pre‐existing corneal disease, previous corneal surgery, and chronic dermatological disease were significantly (P ≤ 0.05) correlated with positive anaerobic cultures in one or more species.Conclusions The results of the present study demonstrate that obligate anaerobic bacteria are present within the intralesional flora of ulcerative keratitis in domestic animals. In most species evaluated, these bacteria were identified infrequently. Anaerobic bacterial infection of the cornea most frequently occurs in association with other ocular pathogens and previous corneal abnormalities.
A NOTE ON OPTIMUM STRATIFICATION FOR EQUAL ALLOCATION WITH RATIO AND REGRESSION METHODS OF ESTIMATION
Authors: Singh Ravindra 
Published: February 2008

SummaryWhen the information on a highly positively correlated auxiliary variable x is used to construct stratified regression (or ratio) estimates of the population mean of the study variable y, the paper considers the problem of determining approximately optimum strata boundaries (AOSB) on x when the sample size in each stratum is equal. The form of the conditional variance function V(y/x) is assumed to be known. A numerical investigation into the relative efficiency of equal allocation with respect to the Neyman and proportional allocations has also been made. The relative efficiency of equal allocation with respect to Neyman allocation is found to be nearly equal to one.
ESTIMATING THE MAXIMUM (MINIMUM) OF A QUADRATIC FUNCTION UNDER CERTAIN CORRELATION PATTERNS
Authors: Scariano Stephen M. 
Published: February 2008

SummaryMay nonidentity error correlation patterns encountered in regression theory allow computationally efficient techniques for modifying the usual procedures for constructing confidence intervals and performing F‐tests so that valid inferences can be drawn. Such techniques are explored in light of the general theme of this note.
CORRELATIONS AND CHARACTERIZATIONS OF THE UNIFORM DISTRIBUTION
Authors: Brown Timothy C. , Cartwright Donald I. , Eagleson G. K. 
Published: February 2008

SummaryTwo characterizations of the uniform distribution on a suitable compact space are proved. These characterizations are applied to a number of particular examples of which the most interesting is the following: if X, Y and Z are independent n‐vectors whose components are independent and identically distributed within a vector, then the pairwise independence of the product moment correlation coefficients between X, Y and Z implies that these vectors are normally distributed.
ROBUST COMPARISON OF DISPERSIONS FOR SAMPLES OF DIRECTIONAL DATA
Authors: Fisher N. I. 
Published: February 2008

SummaryRobust methods are proposed for testing whether several directional distributions on the unit p‐sphere have comparable dispersions. The families of distributions considered are the Langevin for random vectors, and the Generalised Scheidegger‐Watson for random axes, with specific interest in the Fisher and Watson distributions on the sphere. The methods are analogues of Levene's procedure for comparing variances of normal distributions.