bluuebunny/crossref_metadata_2025 huggingface dataset:
Distance Hereditary Graphs and the Interlace Polynomial
Authors: ELLIS-MONAGHAN JOANNA A. , SARMIENTO IRASEMA
Published: August 2007

The vertex-nullity interlace polynomial of a graph, described by Arratia, Bollobás and Sorkin in [3] as evolving from questions of DNA sequencing, and extended to a two-variable interlace polynomial by the same authors in [5], evokes many open questions. These include relations between the interlace polynomial and the Tutte polynomial and the computational complexity of the vertex-nullity interlace polynomial. Here, using the medial graph of a planar graph, we relate the one-variable vertex-nullity interlace polynomial to the classical Tutte polynomial when x=y, and conclude that, like the Tutte polynomial, it is in general #P-hard to compute. We also show a relation between the two-variable interlace polynomial and the topological Tutte polynomial of Bollobás and Riordan in [13].

We define the γ invariant as the coefficient of x1in the vertex-nullity interlace polynomial, analogously to the β invariant, which is the coefficientof x1in the Tutte polynomial. We then turn to distance hereditary graphs, characterized by Bandelt and Mulder in [9] as being constructed by a sequence ofadding pendant and twin vertices, and show that graphs in this class have γ invariant of 2n+1whenntrue twins are added intheir construction. We furthermore show that bipartite distance hereditary graphs are exactly the class of graphs with γ invariant 2, just as the series-parallel graphs are exactly the class of graphs with β invariant 1. In addition, we show that a bipartite distance hereditary graph arises precisely as the circle graph of an Euler circuitin the oriented medial graph of a series-parallel graph. From this we conclude that the vertex-nullity interlace polynomial is polynomial time to compute for bipartite distancehereditary graphs, just as the Tutte polynomial is polynomial time to compute for series-parallel graphs.
A ten-year review of commercial vaccine performance for control of tick infestations on cattle
Authors: Fuente José de la , Almazán Consuelo , Canales Mario , Pérez de la Lastra José Manuel , Kocan Katherine M. , Willadsen Peter
Published: August 2007

Ticks are important ectoparasites of domestic and wild animals, and tick infestations economically impact cattle production worldwide. Control of cattle tick infestations has been primarily by application of acaricides which has resulted in selection of resistant ticks and environmental pollution. Herein we discuss data from tick vaccine application in Australia, Cuba, Mexico and other Latin American countries. Commercial tick vaccines for cattle based on theBoophilus microplusBm86 gut antigen have proven to be a feasible tick control method that offers a cost-effective, environmentally friendly alternative to the use of acaricides. Commercial tick vaccines reduced tick infestations on cattle and the intensity of acaricide usage, as well as increasing animal production and reducing transmission of some tick-borne pathogens. Although commercialization of tick vaccines has been difficult owing to previous constraints of antigen discovery, the expense of testing vaccines in cattle, and company restructuring, the success of these vaccines over the past decade has clearly demonstrated their potential as an improved method of tick control for cattle. Development of improved vaccines in the future will be greatly enhanced by new and efficient molecular technologies for antigen discovery and the urgent need for a tick control method to reduce or replace the use of acaricides, especially in regions where extensive tick resistance has occurred.
Directed exospermia: II. VUV-UV spectroscopy of specialized UV screens, including plant flavonoids, suggests using metabolic engineering to improve survival in space
Authors: Zalar Andreja , Tepfer David , Hoffmann Søren V. , Kollmann Albert , Leach Sydney
Published: August 2007

We used synchrotron light to determine VUV-UV absorption spectra (125–340 nm) of thin films of substances associated with UV resistance in specific groups of organisms or across limited phylogenetic boundaries: scytonemin, mycosporine-like amino acids, dipicolinic acid, β-carotene, melanin and flavonoids (quercitrin, isoquercitrin, robinin and catechin). The objective was to extend known UV absorption spectra into the vacuum UV, and to evaluate the likely effectiveness of these molecules in shielding DNA from the unfiltered solar UV found in space, using similarity with DNA absorption spectra as the primary criterion. The spectroscopy indicated that plant flavonoids would be ideal UV screens in space. We suggest that flavonoids represent primitive UV screens, and offer explanations (including horizontal gene transfer) for their presence in plants. We also discuss the possibility of improving UV resistance by increasing flavonoid accumulation through metabolic engineering, in the hope of better adapting life for space travel, i.e. for its dissemination away from the Earth (exospermia). Finally, we propose using plant seeds as exospermia vehicles for sending life (including artificial life) into space.
Two distinct mechanisms segregate Prospero in the longitudinal glia underlying the timing of interactions with axons
Authors: Griffiths Rachel C. , Benito-Sipos Jonathan , Fenton Janine C. , Torroja Laura , Hidalgo Alicia
Published: August 2007

Prospero is required in dividing longitudinal glia (LG) during axon guidance; initially to enable glial division in response to neuronal contact, and subsequently to maintain glial precursors in a quiescent state with mitotic potential. Only Prospero-positive LG respond to neuronal ablation by over-proliferating, mimicking a glial-repair response. Prospero is distributed unequally through the progeny cells of the longitudinal glioblast lineage. Just before axon contact the concentration of Prospero is higher in two of the four progeny cells, and after axon guidance Prospero is present only in six out of ten progeny LG. Here we ask how Prospero is distributed unequally in these two distinct phases. We show that before neuronal contact, longitudinal glioblasts undergo invaginating divisions, perpendicular to the ectodermal layer. Miranda is required to segregate Prospero asymmetrically up to the four glial-progeny stage. After neuronal contact, Prospero is present in only the LG that activate Notch signalling in response to Serrate provided by commissural axons, and Numb is restricted to the glia that do not contain Prospero. As a result of this dual regulation of Prospero deployment, glia are coupled to the formation and maintenance of axonal trajectories.
Integrating laboratory creep compaction data with numerical fault models: A Bayesian framework
Authors: Fitzenz Delphine D. , Jalobeanu André , Hickman Stephen H.
Published: August 2007

We developed a robust Bayesian inversion scheme to plan and analyze laboratory creep compaction experiments. We chose a simple creep law that features the main parameters of interest when trying to identify rate‐controlling mechanisms from experimental data. By integrating the chosen creep law or an approximation thereof, one can use all the data, either simultaneously or in overlapping subsets, thus making more complete use of the experiment data and propagating statistical variations in the data through to the final rate constants. Despite the nonlinearity of the problem, with this technique one can retrieve accurate estimates of both the stress exponent and the activation energy, even when the porosity time series data are noisy. Whereas adding observation points and/or experiments reduces the uncertainty on all parameters, enlarging the range of temperature or effective stress significantly reduces the covariance between stress exponent and activation energy. We apply this methodology to hydrothermal creep compaction data on quartz to obtain a quantitative, semiempirical law for fault zone compaction in the interseismic period. Incorporating this law into a simple direct rupture model, we find marginal distributions of the time to failure that are robust with respect to errors in the initial fault zone porosity.
Sorted bed forms as self‐organized patterns: 1. Model development
Authors: Coco Giovanni , Murray A. Brad , Green Malcolm O.
Published: August 2007

Here we present a modified version of the exploratory numerical model originally presented by Murray and Thieler (2004) and use it to further investigate the development of sorted bed forms on the inner continental shelf. The new version of the model is based on widely accepted parameterizations for hydrodynamics and sediment transport that are more detailed and empirically tested than the parameterizations used in the original model. The shallow water wave equations are replaced by the general equations, and changes in water depth related to morphological development are accounted for. This model reproduces the main results of the previous one, supporting the hypothesis that sorted bed forms are a self‐organized pattern and develop as a result of a coupling between bed composition and sediment flux. The sensitivity of the model predictions, evaluated in terms of the geometry of the sorted bed forms and their growth rate, with respect to external forcing variables and internal model parameterizations, shows increasing (decreasing) sorted bed form spacing (height) with increasing wave height and period. The opposite occurs for increasing water depths. More complicated behavior is observed when the ratio fine‐to‐coarse sediment diameter (or the percentage of fine and coarse material) is varied. The shape of the suspended sediment and current profiles and the formulation used to predict the geometry of wave‐generated ripples can significantly affect (or even inhibit) growth rates of sorted bed forms. Results from a sensitivity analysis show that there are deficiencies in the description of small‐scale processes that limit the ability to quantitatively predict sorted bed form evolution, highlighting gaps in our knowledge of sediment transport over mixed grain beds that need to be filled.
Sorted bed forms as self‐organized patterns: 2. Complex forcing scenarios
Authors: Coco Giovanni , Murray A. Brad , Green Malcolm O. , Thieler E. Robert , Hume T. M.
Published: August 2007

We employ a numerical model to study the development of sorted bed forms under a variety of hydrodynamic and sedimentary conditions. Results indicate that increased variability in wave height decreases the growth rate of the features and can potentially give rise to complicated, a priori unpredictable, behavior. This happens because the system responds to a change in wave characteristics by attempting to self‐organize into a patterned seabed of different geometry and spacing. The new wavelength might not have enough time to emerge before a new change in wave characteristics occurs, leading to less regular seabed configurations. The new seabed configuration is also highly dependent on the preexisting morphology, which further limits the possibility of predicting future behavior. For the same reasons, variability in the mean current magnitude and direction slows down the growth of features and causes patterns to develop that differ from classical sorted bed forms. Spatial variability in grain size distribution and different types of net sediment aggradation/degradation can also result in the development of sorted bed forms characterized by a less regular shape. Numerical simulations qualitatively agree with observed geometry (spacing and height) of sorted bed forms. Also in agreement with observations is that at shallower depths, sorted bed forms are more likely to be affected by changes in the forcing conditions, which might also explain why, in shallow waters, sorted bed forms are described as ephemeral features. Finally, simulations indicate that the different sorted bed form shapes and patterns observed in the field might not necessarily be related to diverse physical mechanisms. Instead, variations in sorted bed form characteristics may result from variations in local hydrodynamic and/or sedimentary conditions.
Scale‐dependence of natural variability of flow regimes in a forested landscape
Authors: Sanford S. E. , Creed I. F. , Tague C. L. , Beall F. D. , Buttle J. M.
Published: August 2007

The ecological integrity of riverine ecosystems is dependent upon the natural flow regime of the river system. Maintaining natural variability in the flow regime is critical for conserving the structure and function of riverine ecosystems. This research seeks to determine relations between natural variability in the flow regime and basin scale. A distributed hydrologic model was used to characterize the natural flow regime of basins from first to fifth order within tributaries of the Batchawana River in the Algoma Highlands of central Ontario using the range of variability approach (RVA). A 30‐year simulated flow record was used to calculate natural variability in the flow regime, defined by the S80 [(90th percentile – 10th percentile)/median]. Flow variability under wetter conditions was similar across all basins, regardless of scale. Conversely, flow variability under drier conditions was scale‐dependent, with smaller basins (<600 ha) showing a large range in variability and larger basins (>600 ha) showing a smaller range in variability that converged toward a constant with increasing area. The effect of basin area on flow variability suggested the existence of a representative elementary area (REA). Within the REA, morphometric sources of natural variability were determined through multivariate regression analyses. A combination of indices describing the near‐stream riparian area within a basin, median basin residence time, and basin curvature was significantly related to flow variability under drier conditions. These findings present a potential management template for establishing reference conditions against which impacts of disturbance on flows throughout a regional drainage basin may be measured.
Implications of present‐day abiogenic methane fluxes for the early Archean atmosphere
Authors: Emmanuel Simon , Ague Jay J.
Published: August 2007

During Earth's early history, greenhouse warming by atmospheric methane helped to maintain elevated surface temperatures. Here, we estimate the present‐day abiogenic CH4 flux generated by mineral alteration (serpentinization) at mid‐ocean ridges, volcanic emissions, and geothermal sources; in addition, we assess the impact that abiogenic methane may have had on greenhouse warming during the early prebiotic Archean. Based on estimates of the rate of seafloor spreading and the degree of serpentinization within the oceanic crust, the flux of methane generated by serpentinized lithosphere is calculated to be ∼1.35 Mt CH4 y−1, while volcanic and geothermal sources are estimated to contribute ∼0.1 and ∼0.9 Mt CH4 y−1, respectively. Furthermore, it is shown that if atmospheric CO2 partial pressures were above 0.01 bar, the present‐day level of abiogenic methane production could have been sufficient to maintain above‐freezing surface temperatures during the Archean. The very high temperatures (∼70°C) that have been suggested for the early Archean, however, would have required extremely high methane fluxes or, more likely, greatly elevated atmospheric CO2 levels.
EOSINOPHILIA AND ACQUISITION OF RESISTANCE TO NEMATOSPIROIDES DUBIUS IN MICE SENSITIZED WITH ADULT WORMS
Authors: Hurley James C , Vadas Mathew A
Published: August 2007

BALB/c mice develop resistance to challenge with N. dubius third stage infective larvae (L3) 2–3 weeks after the administration of N. dubius worms. In contrast, CBA/H mice fail to develop resistance. Experiments were performed to test the hyptothesis that the reason for the different behaviour of these mice was a difference in their eosinophil response. BALB/c mice and BALB/c → (BALB/c → CBA/H)F1 bone marrow chimaeras but not CBA/H mice or CBA/H → (BALB/c × CBA/H)F1 chimaeras mounted strong eosinophilia after N. dubius sensitization and the eosinophil response Was associated with resistance to L3 infection in these mice. Induction of a mild eosinophilia in CBA/H mice by non‐parasite antigen keyhole limpet haemocyanin (KLH) in complete Freund's adjuvant (CFA) following cyclophosphamide (CY) treatment was associated with the acquisition of a degree of resistance to L3 infection. In BALB/c mice, increase in eosinophilia induced by CY and KLH‐CFA was not associated with a further reduction in worm numbers. These experiments support the hypothesis that eosinophilia is an important component of host protective immunity in vivo, and suggest a new basis for the heterogeneity of the outcome of some parasite infestations.
FALLOPIAN TUBE MICROVASCULATURE IN THE RABBIT
Authors: Verco Christopher J , Ganon Brendan J , Jones Warren R
Published: August 2007

The microvascular architecture of rabbit Fallopian tube isthmic, ampullary and fimbrial regions was examined by the corrosion vascular cast‐scanning electron microscope method. The aorta and inferior vena cava of virgin adult female rabbits (2·5–3·5 kg) were cannulated; after blood wash out, methacrylate casting medium was infused via the aorta. After plastic hardening, Fallopian tubes were excised, tissues corroded and casts prepared for scanning electron microscopy. The isthmic myosalpinx is encircled subserosally by an interlocking venous plexus. We suggest that a rise in pelvic venous pressure could lead to a decrease in isthmic luminal diameter and thus act as a sphincter contributing to the known delay in ovum transport at the ampullary isthmic junction. Stereo pairs of photomicrographs showed that isthmic plicae are supplied by arterioles which change little in diameter passing through the tubal wall. Near the apex of a fold, these arterioles terminate in a subepithelial capillary plexus which drains to deep mucosal and plical core venules. In contrast, the ampulla is supplied by smaller and less frequent arterioles. Frequent large venules extending high into the plicae drain the subepithelial capillary plexus. Based on this microvascular architecture, we suggest that the subepithelial capillary plexus of the apical region of the plicae probably contains high pressure blood in the isthmus and lower pressure blood in the ampulla. Therefore, plicae in these regions may be specialised for net luminal fluid secretion and absorption respectively, implying a role for the microvasculature in tubal transport by initiation or modification of fluid flow along the lumen.
DETECTION OF SPECIFIC MURINE ANTI‐TUMOUR IMMUNITY AND SERUM FACTORS BY THE INDIRECT E‐ROSETTE AUGMENTATION ASSAY
Authors: Phillips RG , Halliday WJ
Published: August 2007

The spontaneous interaction of sheep erythrocytes and human lymphocytes results in the formation of aggregates known as E‐rosettes. The antigen reactivity of murine T‐lymphocytes can be detected indirectly by the production of a lymphokine that augments the E‐rosette‐forming ability of human lymphocytes. An indirect E‐rosette augmentation (ERA) assay was used to study cellular reactivity and tumour‐related serum reactions in mice bearing methylcholanthrene (MCA)‐induced tumours. The assay was used to demonstrate the antigenic specificity of two tumours and to detect blocking factors in tumour‐bearer serum. Blocking factors were shown to be tumour‐specific and to act on lymphocytes at an early stage before exposure to antigen.
LEISHMANIA TROPICA MAJOR IN MICE: VACCINATION AGAINST CUTANEOUS LEISHMANIASIS IN MICE OF HIGH GENETIC SUSCEPTIBILITY
Authors: Mitchell Graham F , Handman Emanuela
Published: August 2007

BALB/c and BALB/c.H‐2b mice are genetically susceptible to development of persistent and severe disease following cutaneous injection of promastigotes of the protozoan parasite, Leishmania tropica major, whereas C57BL/6 are relatively resistant. Resistance in C57BL/6 can be further increased by intraperitoneal injection of living, but not killed, promastigotes prior to cutaneous challenge. Severely diseased BALB/c mice can show resistance to development of a second cutaneous lesion but apparently only in the advanced stages of systemic life‐threatening disease. A striking level of resistance to persistent disease has been demonstrated in BALB/c.H‐2b mice pre‐injected with frozen and thawed L. t. major‐infected macrophages of the continuous macrophage cell line IC‐21 (H‐2b) together with Corynebacterium parvum. No resistance is seen in recipients of either C. parvum or the crude antigen mixture alone. Protection is afforded by intraperitoneal and not subcutaneous injection of crude antigen plus adjuvant. In these vaccination studies all evidence points to the infected macrophage as the most appropriate source of ‘host‐protective’ antigens as well as being the most likely target of host‐protective immunity. Resistance is expressed in vaccinated mice as minimal signs of cutaneous disease and rapid resolution of any small lesions which do develop. Frozen and thawed promastigotes plus C. parvum will not induce resistance to persistent disease in BALB/c H‐2b mice and preincubation of promastigotes with sera from resistant vaccinated mice does not influence their capacity to cause cutaneous disease. The results provide baseline data for vaccination attempts in genetically susceptible hosts using isolated L. t major antigens (and, in particular, infected macrophage antigens) and highlight the utility of the intraperitoneal route of injection and the use of the therapeutic biological, C. parvum, as an adjuvant in such studies.
SALIVA AND BREAST MILK COMPOSITION DURING THE MENSTRUAL CYCLE OF WOMEN
Authors: Prosser CG , Hartmann PE
Published: August 2007

Two acute changes in breast milk composition occur during the ovulatory menstrual cycle of women. To determine whether these changes were peculiar to the mammary gland, the composition of unstimulated whole saliva was followed during the menstrual cycle of women. This investigation showed acute, 3–9‐fold increases in the concentration of glucose in saliva during the ovulatory menstrual cycle of lactating women. These changes were synchronous with changes in the concentrations of Na and K in breast milk. In contrast to salivary glucose, milk glucose decreased at these times. Milk glucose values were 1·3‐fold lower on these days than on the days preceding and following the decrease. Similar acute increases were observed in salivary glucose of non‐lactating women. The total duration of the changes in milk and saliva composition was 12–32 h. No cyclic changes in the concentration of glucose were observed in the saliva from women taking oral contraceptives.

Since two different epithelial glands are affected simultaneously during the menstrual cycle, it is likely that a hormonal mechanism is involved. Moreover, since the acute increases in salivary glucose also occurred in non‐lactating women, we suggest that the factors causing the changes in milk composition are not just a consequence of lactation and are probably closely associated with the hormones controlling the menstrual cycle in all women.
PLASMA CLEARANCE AND DISTRIBUTION OF 125I‐OVINE PLACENTAL LACTOGEN IN SHEEP
Authors: Reddy S , Watkins WB
Published: August 2007

The plasma clearance of 125I‐ovine placental lactogen (125I‐oPL) in pregnant, non‐pregnant and foetal sheep followed a biphasic exponential curve. The initial half‐life (t1(½)) of the hormone ranged from 5·7–12·7 min. The molecular identity of 125I‐oPL in plasma samples was examined by gel filtration chromatography. At the end of blood sampling, the high concentrations of radioactivity in the thyroid, kidney and urine were largely non‐protein‐bound. A similar pattern was obtained for the low concentration of radioactivity in amniotic fluid. The maternal‐foetal compartments showed negligible bi‐directional transfer of radioactivity.

The plasma t1(½) of 125I‐oPL determined here provides evidence that the hormone has a short biological half‐life in sheep. The virtual tack of placental passage of the hormone implies discrete mechanisms for unidirectional secretion of oPL into the two circulatory systems. Our data also suggest the importance of the kidneys in the metabolism of the hormone.
EFFECTS OF COBALT‐CHROME ALLOY WEAR PARTICLES ON THE MORPHOLOGY, VIABILITY AND PHAGOCYTIC ACTIVITY OF MURINE MACROPHAGES IN VITRO
Authors: Garrett R , Wilksch J , Vernon‐Roberts B
Published: August 2007

Metallic wear particles were prepared from orthopaedic cobalt‐chrome alloy by milling in medium supplemented with 20% foetal calf serum to maintain particle dispersion. The size distribution of particles was determined by sedimentation and centrifugation and particle concentration was assessed using light extinction. Monolayers of mouse peritoneal macrophages were exposed to metal particles at different concentrations for varying periods. After 4 h of exposure to particle concentrations exceeding 30 μg/ml there was a progressive decline in cell viability, and light and electron microscopy showed that surviving cells had assumed remarkably smooth profiles and contained abundant endocytosed metal. Phagocytic uptake of polystyrene spherules was inhibited markedly by exposure to metal particles even at concentrations at which macrophages remained 100% viable, and preceded the reduction of viability at higher concentrations.

The findings are consistent with a pathological role for the metallic wear particles observed frequently within macrophages in the synovial tissues around loose artificial joints in humans.
SPECIFICITY OF PASSIVE SERUM PROTECTION AGAINST NIPPOSTRONGYLUS BRASILIENSIS AND NEMATOSPIROIDES DUBIUS IN MICE
Authors: Brindley Paul J , Dobson Colin
Published: August 2007

Fewer and smaller worms were recovered from, and significantly fewer parasite eggs were voided by, mice injected with mouse antiserum raised against Nippostrongylus brasiliensis or Nematospiroides dubius after infection with the homologous nematode species compared with the control mice. The passive transfer of protective immunity was specific for the species which induced the antibody response in the donor mice. Passively immunized mice infected with the heterologous nematode species harboured the same number of worms, with the same epg output, as parasites in the control mice, but were stunted. Serological cross‐reactions were observed between the two donor antiserum pools and N. dubius and N. brasiliensis antigens.
THE ENHANCEMENT OF CULTURED SPONTANEOUS CYTOTOXIC T CELLS FROM NORMAL AND ATHYMIC (nu/nu) MICE
Authors: Skinner Margot , Marbrook John
Published: August 2007

Subsets of natural killer cells may be characterised by the target cell profile, cell surface markers and the effect of growth factors on the production of effector cells. The subset which appears in primary cultures (spontaneous or natural T killer cells) is enhanced by the supernatants of Con A‐stimulated rat spleen cultures. The enhancement can be attributed to an increased number of clones rather than an expansion of clone size in 5‐day cultures. With semi‐purified IL‐2 preparations, clones of spontaneous cytotoxic cells are also detectable in nu/nu spleen cultures. These results suggest such spontaneous cytotoxicity is a general phenomenon within cytotoxic responses.
RAT POST‐IMPLANTATION EMBRYO CULTURE USING HETEROLOGOUS SERUM
Authors: Priscott PK
Published: August 2007

In the present study sera from twelve species have been compared to rat serum and ascitic fluid for their ability to support the growth of post‐implantation rat embryos. No alternative to rat serum or rat ascitic fluid was found. The basis for this apparent species specificity was further analysed. A marked improvement in embryonic growth was seen when rat serum was added to the heterologous serum prior to culture, whereas replenishment of a heterologous serum several times during culture had no effect. The experiments suggested that heterologous sera were nutritionally inadequate but not simply in energy source. Possible mechanisms for the specificity arc discussed.
STARVATION IN THE RAT: EFFECT ON PEPTIDES OF THE GUT AND BRAIN
Authors: Shulkes A , Caussignac Y , Lamers CB , Solomon TE , Yamada T , Walsh JH
Published: August 2007

The effects of starvation on the tissue concehtrations of some peptides common to the gastrointestinal tract and the central nervous system have been examined. Groups of 6 rats were either fed ad libitum or starved for up to 4 days and killed by decapitation. Antrum, fundus, duodenum, jejunum, ileum, colon, pancreas and brain were dissected, weighed and then frozen on dry ice. The tissues were extracted sequentially in boiling water and 3% acetic acid, centrifuged and the supernatants radioimmunoassayed for gastrin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP), gastric inhibitory peptide (GIP) and soma‐tostatin. Each peptide was not assayed in each tissue. Starvation had no effect on the concentrations of peptides measured in the fundus (somatostatin and VIP), ileum (somatostatin, GIP, VIP) and colon (somatostatin, GIP, VIP). VIP concentration was increased in the jejunum and GIP was increased in both the duodenum and jejunum. Antral gastrin was the only peptide in the gastrointestinal tract to be decreased by food deprivation. Somatostatin concentration was approximately doubled in the antrum, duodenum, jejunum and pancreas. Brain VIP was unchanged. Brain somatostatin and CCK were significantly reduced by starvation. We conclude that starvation results in organ‐specific and hormone‐specific alterations in tissue concentrations of peptides of the gastrointestinal tract and the central nervous system.
PRIMARY VIRAEMIA RESPONSES OF HERONS TO EXPERIMENTAL INFECTION WITH MURRAY VALLEY ENCEPHALITIS, KUNJIN AND JAPANESE ENCEPHALITIS VIRUSES
Authors: Boyle David B , Dickerman Robert W , Marshall Ian D
Published: August 2007

Rufous night herons, Pacific herons, little egrets and intermediate egrets were experimentally infected with Murray Valley encephalitis, Kunjin or Japanese encephalitis viruses. Viraemias of at least one day's duration were detected in all birds except two intermediate egrets inoculated with a very low dose of Kunjin virus and one rufous night heron inoculated with Japanese encephalitis virus. There was usually a viraemia of 3 to 5 days' duration commencing on the first or second day and continuing until day 5 or 6 and rarely until day 7. Maximum titres tended to be higher in young birds, up to 2–5 months of age (104–105 mouse LD50/ml), than in older birds more than 8 months of age (103–104 mouse LD50/ml). Significant differences in maximum viraemia titres were not observed in the different species or between Murray Valley encephalitis and Kunjin viruses. Japanese encephalitis viraemias were significantly lower, but this was probably due to the high mouse brain passage level of the strain used. The onset of viraemia was earlier in intermediate egrets than in rufous night herons inoculated with similar doses of Murray Valley encephalitis virus, but no difference in the susceptibility to infection was observed. With Kunjin virus there was a significant difference in the susceptibility of intermediate egrets and rufous night herons, with rufous night herons being more susceptible to infection with low doses of virus. This difference in threshold of infection, if it extends to other species with both Kunjin and Murray Valley encephalitis viruses, may, in part, be an explanation for the greater incidence of natural infections observed in rufous night herons compared with other species and orders of water birds.
MECHANICAL EFFECTS OF RIGHT ATRIAL PRESSURE ON HEART RATE IN THE CONSCIOUS RABBIT
Authors: Ludbrook J , Graham WF
Published: August 2007

We attempted to delect and quantify the mechanical effects of change in right atrial pressure on the chronotropic properties of the cardiac pacemaker, when blood volume was altered in an isohaemic fashion by ± 27% in 8 conscious rabbits. Under control conditions there was a strong negative association between heart rate and right atrial pressure, attributable to the baroreceptor‐heart rate reflex. After deletion of the main afferent sources of reflex effects on heart rate, by denervating the arterial baroreceptors and chemoreceptors, there was an insignificant association between heart rate and right atrial pressure or arterial pressure. Then, in addition, the main neurohumoral effects on the cardiac pacemaker were eliminated by three different pharmacologic treatments: (1) the cardiac nerves were blocked by instilling 2% procaine into the pericardial sac, (2) cardiac β‐adrenoceptors and cholinergic receptors were blocked with intravenous propranolol and hyoscine methyl bromide, (3) the above treatments were combined with autonomic ganglion‐blockade by intravenous pentolinium. The combination of cardiac afferent and efferent blockade (1 and 3) revealed a small but consistent positive association between heart rate and right atrial pressure of 1·3 and 0·7 beats/min/mmHg, respectively. With efferent blockade alone (2), there was a steeper positive association of 2·3 beats/min/mmHg. We conclude that in the conscious rabbit there may be a mechanical effect of right atrial pressure on the cardiac pacemaker, but that it is so small as to be of little importance under physiological conditions.
Suppression of the Rayleigh-Taylor instability of thin liquid films by the Marangoni effect
Authors: Alexeev Alexander , Oron Alexander
Published: August 2007

Stabilization of the Rayleigh-Taylor instability of a thin liquid film by the Marangoni effect arising from heating of the liquid at the gas-liquid interface in a bilayer setting is investigated. Solution of time-dependent Navier-Stokes and long-wave evolution equations in both two and three dimensions shows the emergence of nontrivial nonruptured steady states in the system when the applied temperature gradient exceeds a certain critical value.
Modeling of polyethylene and poly (L-lactide) polymer blends and diblock copolymer: Chain length and volume fraction effects on structural arrangement
Authors: Lee Wen-Jay , Ju Shin-Pon , Wang Yao-Chun , Chang Jee-Gong
Published: August 2007

Dissipative particle dynamics (DPD), a mesoscopic simulation approach, has been used to investigate the chain length effect on the structural property of the immiscible polyethylene (PE)/poly(L-lactide) (PLLA) polymer in a polymer blend and in a system with their diblock copolymer. In this work, the interaction parameter in DPD simulation, related to the Flory-Huggins interaction parameter χ, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics simulation. The immiscibility property of PE and PLLA polymers induces the phase separation and exhibits different architectures at different volume fractions. In order to observe the structural property, the radius of gyration is used to observe the detailed arrangement of the polymer chains. It shows that the structure arrangement of a polymer chain is dependent on the phase structure and has a significantly different structural arrangement character for the very short chains in the homopolymer and copolymers. The chain length effect on the degree of stretching or extension of polymers has also been observed. As the chain length increases, the chain exhibits more stretching behavior at lamellae, perforated lamellae, and cylindrical configurations, whereas the chain exhibits a similar degree of stretching or extension at the cluster configuration.
Synchrotron x-ray studies of molecular liquid SnI4
Authors: Fuchizaki Kazuhiro , Kohara Shinji , Ohishi Yasuo , Hamaya Nozomu
Published: August 2007

Synchrotron x-ray diffraction measurements were performed on liquid SnI4 up to a scattering vector of 25A−1, utilizing a horizontal two-axis diffractometer installed at the SPring-8 bending magnet beam line BL04B2 in Japan. An effective method based on the maximum entropy method was devised to transform the measured total structure factor to the reduced radial distribution function. The reliability of the density estimation is discussed.
Effects of noncircular collars on an axisymmetric jet
Authors: New T. H. , Tan K. S. , Tsai H. M.
Published: August 2007

An experimental investigation was carried out to study the effects of noncircular collars on an axisymmetric jet using surface flow visualization and hot-wire anemometry. Circular, square, and triangular collars with expansion ratios of 1.20, 1.35, and 1.54, respectively, with collar lengths of up to two jet diameters were used. Flow visualization shows that circular collars led to equidistant flow reattachments along the collar wall, while square and triangular collars resulted in the formation of a pair of counter-rotating vortex-pairs on each side of the collar wall. These vortex-pairs are caused by the presence of the three-dimensional velocity gradients between locations of minimum and maximum step-heights, which drove fluid from the collar wall centerlines towards the corners. Time-averaged velocity measurements show that the circular collar required the shortest collar length to achieve maximum centerline velocity decay, followed by square and triangular collars. Centerline turbulence intensity and velocity spectra results reveal that all three collars were able to suppress vortex-pairing events when they were sufficiently long with the triangular collar being the most effective. Furthermore, the triangular collar also produces the widest overall jet-spread, ahead of square and circular collars, respectively, even though it demonstrates significantly different jet-spreads along planes of minimum and maximum step-height. Self-excitation frequencies from all three collars could be distinguished into distinct frequency bands with changes in the collar lengths. Within each band, the circular collar results in the largest variation of excitation frequency over the square and triangular collars, respectively. Lastly, square and triangular collars require wider ranges of collar lengths for each of the frequency bands, as compared to the circular collar.
Dynamics of tapping mode atomic force microscopy in liquids: Theory and experiments
Authors: Basak Sudipta , Raman Arvind
Published: August 2007

A mathematical model is presented to predict the oscillating dynamics of atomic force microscope cantilevers with nanoscale tips tapping on elastic samples in liquid environments. Theoretical simulations and experiments performed in liquids using low stiffness probes on hard and soft samples reveal that, unlike in air, the second flexural mode of the probe is momentarily excited near times of tip-sample contact. The model also predicts closely the tip amplitude and phase of the tip at different set points.
Evolution of spin coherence dynamics and g factor with electron excess energy in bulk intrinsic GaAs
Authors: Lai Tianshu , Teng Lihua , Jiao Zhongxing , Xu Haihong , Lei Liang , Wen Jinhui , Lin Weizhu
Published: August 2007

Circularly polarized absorption quantum-beat spectroscopy is used to study excess-energy dependence of electron-spin coherence dynamics in intrinsic GaAs. Absorption quantum beats are observed. The quantum-beat oscillatory frequency is used as a high precision measure of electron g factor. Double linear energy dependence of g factor is obtained and disagrees with the prediction of k∙p theory. A theoretical calculation reveals the double linear energy dependence reflects the energy dependence of g factor of electrons measured through light-hole- and heavy-hole-electron transitions, respectively. The phase of the quantum beats provides the key information to distinguish the two transitions experimentally.
Dynamic process of dendrite fragmentation in solidification from undercooled Si melt using time-resolved x-ray diffraction
Authors: Nagashio K. , Nozaki K. , Kuribayashi K. , Katayama Y.
Published: August 2007

The spontaneous dendrite fragmentation in solidification from undercooled Si melt was analyzed by time-resolved two-dimensional x-ray diffractometry. For the sample solidified at ΔT=261K, several spots appeared at 1ms after recalescence and the subsequent transition from spots to rings occurred within ∼25ms, which suggests that the fragmentation occurred after recalescence but just at the initial stage of the plateau period. Although the present experiment supported that the driving force for the fragmentation is a capillarity effect at the plateau period, the time scale for the fragmentation differed from the current quantitative prediction.
Strain relaxation and stress-driven interdiffusion in InAs∕InGaAs∕InP nanowires
Authors: Nieto L. , Bortoleto J. R. R. , Cotta M. A. , Magalhães-Paniago R. , Gutiérrez H. R.
Published: August 2007

The authors have investigated strain relaxation in InAs∕InGaAs∕InP nanowires (NW’s). Transmission electron microscopy images show an additional stress field attributed to compositional modulation in the ternary layer, which disrupts NW formation and drives Ga interdiffusion into InAs, according to grazing incidence x-Ray diffraction under anomalous scattering conditions. The strain profile along the NW, however, is not significantly affected when interdiffusion is considered. Results show that the InAs NW energetic stability is preserved with the introduction of ternary buffer layer in the structure.
New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering
Authors: Saint-Lager M.-C. , Bailly A. , Dolle P. , Baudoing-Savois R. , Taunier P. , Garaudée S. , Cuccaro S. , Douillet S. , Geaymond O. , Perroux G. , Tissot O. , Micha J.-S. , Ulrich O. , Rieutord F.
Published: August 2007

A new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100K in UHV and 600K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1–1000mbars and as a continuous flow cell for pressure lower than 10−3mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd8Ni92(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules.
Influence of the liquid carbazole concentration on charge trapping in C60 sensitized photorefractive polymers
Authors: Ribierre J. C. , Aoyama T. , Kobayashi T. , Sassa T. , Muto T. , Wada T.
Published: August 2007

We study by two-beam coupling experiments the photorefractive properties of a poly(Nvinylcarbazole) (PVK) matrix plasticized with different concentrations of 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, and doped with the photosensitizer C60 and the electro-optic push-pull chromophore 4-piperidinobenzylidene malonitrile. The steady state and dynamic photorefractive performances of these materials are optimized by tuning the concentration ratio between PVK and EHCz. In parallel, the trap density values are determined by a spectroscopic method based on the strong absorption of the C60− anion in the near infrared region and are compared with those obtained from the photorefractive measurements. The results obtained from both techniques are in good agreement and show the important role played by the liquid carbazole in the charge trapping processes and the photorefractive properties of C60 sensitized photorefractive polymers.
Measurement of Poisson’s ratio with contact-resonance atomic force microscopy
Authors: Hurley D. C. , Turner J. A.
Published: August 2007

We describe contact-resonance atomic force microscopy (AFM) methods to quantitatively measure Poisson’s ratio ν or shear modulus G at the same time as Young’s modulus E. In contact-resonance AFM, the frequencies of the cantilever’s resonant vibrations are measured while the tip is in contact with the sample. Simultaneous measurement of flexural and torsional vibrational modes enables E and ν to be determined separately. Analysis methods are presented to relate the contact-resonance frequencies to the tip-sample contact stiffness, which in turn determines the sample’s nanoscale elastic properties. Experimental results are presented for a glass specimen with fused silica used as a reference material. The agreement between our contact-resonance AFM measurements and values obtained from other means demonstrates the validity of the basic method.
An approximate solution of Dirac-Hulthén problem with pseudospin and spin symmetry for any κ state
Authors: Soylu A. , Bayrak O. , Boztosun I.
Published: August 2007

For any spin-orbit quantum number κ, the analytical solutions of the Dirac equation are presented for the Hulthén potential by applying an approximation to spin-orbit coupling potential for the case of spin symmetry, Δ(r)=C=const, and pseudospin symmetry Σ(r)=C=const. The bound state energy eigenvalues and the corresponding spinors are obtained in the closed forms.
Visibility of graphene flakes on a dielectric substrate
Authors: Abergel D. S. L. , Russell A. , Fal’ko Vladimir I.
Published: August 2007

The authors model the optical visibility of monolayer and bilayer graphene deposited on a SiO2∕Si substrate or thermally annealed on the surface of SiC. Visibility is much stonger in reflection than in transmission, reaching the optimum conditions when the bare substrate transmits light resonantly. In the optical range of frequencies a bilayer is approximately twice as visible as a monolayer thereby making the two types of graphene distinguishable from each other.
Method to analyze electromechanical stability of dielectric elastomers
Authors: Zhao Xuanhe , Suo Zhigang
Published: August 2007

Subject to an electric voltage, a layer of a dielectric elastomer reduces its thickness, so that the voltage induces a high electric field. The positive feedback may cause the elastomer to thin down drastically, resulting in an electrical breakdown. The authors show that the electromechanical instability occurs when the Hessian of the free-energy function ceases to be positive definite. Their calculation shows that the stability of the actuator is markedly enhanced by prestresses, agreeing with existing experimental observations.
Coupling nanowire chemiresistors with MEMS microhotplate gas sensing platforms
Authors: Meier Douglas C. , Semancik Steve , Button Bradley , Strelcov Evgheni , Kolmakov Andrei
Published: August 2007

Recent advances in nanotechnology have yielded materials and structures that offer great potential for improving the sensitivity, selectivity, stability, and speed of next-generation chemical gas sensors. To fabricate practical devices, the “bottom-up” approach of producing nanoscale sensing elements must be integrated with the “top-down” methodology currently dominating microtechnology. In this letter, the authors illustrate this approach by coupling a single-crystal SnO2 nanowire sensing element with a microhotplate gas sensor platform. The sensing results obtained using this prototype sensor demonstrate encouraging performance aspects including reduced operating temperature, reduced power consumption, good stability, and enhanced sensitivity.