bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Contributing to Variation in Seed Production among Remnant Populations of the Endangered Daisy Gerbera aurantiaca1
Authors: Johnson Steven D. , Collin Carine L. , Wissman H. Jörgen , Halvarsson Erika , Ågren Jon
Published: March 2006

The species‐rich mist‐belt grasslands of southern Africa have been severely reduced in extent as a result of commercial afforestation, thus confining many endemic plants and animals to small populations in habitat fragments. We investigated the influence of various environmental factors on seed production and seedling recruitment in remnant populations of the endangered grassland herb Gerbera aurantiaca (Asteraceae). Experiments with color traps showed that Eriesthis beetles, which appear to be the primary pollinators of G. aurantiaca, were most abundant in the two largest y extant populations. Seeds are produced in a very small proportion (typically <10%) of the ca 80 female florets in a capitulum. The mean number of seeds produced in undamaged capitula was found to be significantly lower in small than in large populations. Pollen limitation was evident from a significant overall increase in seed set after supplementalpollination in three populations over two seasons. The proportion of capitula containing seed predators did not differ markedly among populations or years, but lepidopteran larvae, which destroy all of the seeds in a capitulum, weremost abundant in the two largest populations in 2003. The presence of juvenile plants varied markedly amongpopulations, but this could not be linked firmly to estimates of seed production. Clonal growth is likely to contribute to the persistence of small isolated populations of G. aurantiaca, even when seed production is severely compromised by pollen limitation and predation.
Sex in Space: A Synthesis
Authors: Ghazoul Jaboury , Shaanker R. Uma
Published: March 2006

The five papers in this Special Section illustrate that pollination processes are often disrupted by changing plant distributions. They further demonstrate that plant pollination and seed production outcomes are highly complex due to multidimensional spatial effects and numerous interactive biological responses of both plants and pollinators at individual and population scales. Nevertheless, these studies also lend support to some emerging generalities that (through modeling) begin to provide a coherent framework by which further research, and ultimately management planning, could proceed.
Termite Mounds as Nutrient–Rich Food Patches for Elephants
Authors: Holdo Ricardo M. , McDowell Lee R.
Published: March 2006

This study compared elephant use of woody vegetation on termite mounds with surrounding woodlands in western Zimbabwe. Twelve sites consisting of paired plots on termite mounds and in woodlands were selected. At each site, soil and vegetation samples (leaf and stem) were collected for chemical analysis. Both soil and plant samples were analyzed for calcium, magnesium, potassium, sodium, and phosphorus, and plant samples were also analyzed for crude protein concentration. Two indices of elephant feeding damage were computed: the median number of stems and branches removed per plant, and the mass of stems and branches removed by elephants per unit area. Termite mound soils had higher concentrations of all elements tested than soils from woodlands, and termite mounds differed from woodland plots in terms of plant species composition. Trees growing on termite mounds had higher concentrations of all nutrients except sodium and crude protein, and were subjected to more intense feeding by elephants than trees from the surrounding vegetation matrix. Termite mounds may play an important role in determining food availability and spatial feeding patterns by elephants and other herbivores.
Lack of Genetic Structuring among Tropical Brazilian Wood Stork Populations and Low Genetic Differentiation from North American Populations
Authors: Rocha Cristiano Dosualdo , Del Lama Silvia Nassif , Regitano Luciana Correia de Almeida
Published: March 2006

The Wood Stork (Mycteria americana) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, and PEP‐A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations (Fst= 0.012) and low differentiation was detected between Pantanal and North American populations (Fst= 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations.

O Cabeça‐seca (Mycteria americana) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando‐se em dados de oito locos alozímicos (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, e PEP‐A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal (Fst= 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (.Fst= 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul.
Aquatic Insect Assemblages in Shrimp‐dominated Tropical Streams, Puerto Rico
Authors: Ramirez Alonso , Hernandez‐Cruz Luz Raquel
Published: March 2006

We examined the effects of shrimp on insects in Puerto Rico by assessing insect assemblages in streams relative to varying shrimp densities and also by manipulating shrimp presence. Insect assemblages were typical of tropical island streams and insects were found in all stream habitats. Shrimp impacted insects directly via predation and competition and indirectly through removing particles from the water column. Variation in shrimp distribution is likely to be an important factor determining insect‐assemblage structure in tropical streams.

Examinamos los efectos de los camarones sobre los insectos en Puerto Rico, para ello estudiamos quebradas con densidades contrastantes de camarones y manipulamos su presencia. Los ensamblajes de insectos fueron tipicos de quebradas de islas tropicales y usaron todos los hábitats. Los camarones impactaron directamente a los insectos via depredacion y competencia e indirectamente al remover particulas del agua. Variacion en la distribución de camarones es un factor importante en determinar la estructura de los ensamblajes de insectos en las quebradas tropicales.
Placing an Omnivore in a Complex Food Web: Dietary Contributions to Adult Biomass of an Ant
Authors: Tillberg Chadwick V. , Breed Michael D.
Published: March 2006

Workers of Paraponera clavata, a common Neotropical ant, collect both nectar and insect prey. Previous reports show that nectar accounts for up to 90 percent of the ants’ food loads, while calculations suggest that nectar contributes only 10 percent of colonies’ energy supply. We assessed the trophic source of carbon and nitrogen in adult workers using stable isotope analysis. Carbon in adult workers was largely derived from plant sources. Worker nitrogen isotopic ratios varied significantly among colonies and were enriched compared to prey. Prey nitrogen isotope ratios suggest considerable intercolonial variation in diet, with some colonies collecting prey from lower trophic levels than other colonies. The importance of nectar as a source of metabolic carbon in adult worker biomass, coupled with the high frequency of nectar collection, supports the conclusion that omnivory is a key to supporting this species’ biomass in Neotropical wet forests.
Beyond Paradise—Meeting the Challenges in Tropical Biology in the 21st Century
Authors: Bawa Kamaljit S. , Kress W. John , Nadkarni Nalini M.
Published: March 2006

Tropical ecosystems support a diversity of species and ecological processes that are unparalleled anywhere else on Earth. Despite their tremendous social and scientific importance, tropical ecosystems are rapidly disappearing. To usher tropical ecosystems and the human communities dependent upon them through the environmental transformations of the 21st century, tropical biologists must provide critical knowledge in three areas: 1) the structure and function of tropical ecosystems; 2) the nature and magnitude of anthropogenic effects on tropical ecosystems; and 3) the socio‐economic drivers of these anthropogenic effects. To develop effective strategies for conservation, restoration, and sustainable management of tropical ecosystems, scientific perspectives must be integrated with social necessities. A new set of principles built on a framework for pursuing relevant tropical biological research will facilitate interdisciplinary approaches, integrate biological knowledge with the social sciences, and link science with policy. We propose four broad recommendations for immediate action in tropical biology and conservation that are fundamental to all biological and social disciplines in the tropics: 1) assemble and disseminate information on life's diversity in the tropics; 2) enhance tropical field stations and build a worldwide network to link them with tropical field biologists at their field sites; 3) bring the field of tropical biology to the tropics by strengthening institutions in tropical countries through novel partnerships between tropical and temperate zone institutions and scientists; and 4) create concrete mechanisms to increase interactions between tropical biologists, social scientists, and policy makers.
Physical Damage in Relation to Carbon Allocation Strategies of Tropical Forest Tree Saplings
Authors: Pauw Anton , Van Bael Sunshine A. , Peters Halton A. , Allison Steven D. , Camargo José L. C. , Cifuentes‐Jara Miguel , Conserva Aurlstela , Restom Teresa Garcia , Heartsill‐Scalley Tamara , Mangan Scott A. , Nunez‐lturri Gabriela , Rivera‐Ocasio Elsie , Rountree Mark , Vetter Susanne , de Castllho Carolina Volkmer
Published: March 2006

We show that tropical forest tree saplings with greater belowground carbon allocation have more breakage scars along their stems. We suggest the existence of alternative carbon allocation strategies in relation to physical damage in the forest understorey. “Tolerators” allocate more belowground, have enhanced resprouting ability and slower aboveground growth, whereas “escapers” allocate less belowground, are not well prepared for recovering from damage, but grow fast enough to escape from the damage‐susceptible size class.

Brinzales de árboles tropicales que asignan mayor cantidad de carbono bajo el suelo muestran más cicatrices de fractura en sus tallos. Sugerimos la existencia de estrategias alternativas de asignación de carbono en respuesta a daño fisico en el sotobosque: los “tolerantes” asignan mayor cantidad de carbono bajo el suelo, tienen mayor capacidad para rebrotar y su crecimiento aéreo es lento; los “escapistas” asignan menor cantidad de carbono bajo el suelo y no están bien preparados para recuperarse después de ocurrido un daño, pero crecen lo suficientemente rápido para escapar de la clase diamétrica más susceptible a daños.
The Flexible Breeding System of Werauhia sintenisii, a Cloud Forest Bromeliad from Puerto Rico
Authors: Lasso Eloisa , Ackerman James D.
Published: March 2006

The tropical mountain cloud forest bromeliads studied thus far have been reported as self compatible; however, whether or not autogamy and apomixis occur is not known. We characterized the breeding system of Werauchia sintenisii using a series of treatments to detect self‐compatibility, autogamy, and apomixes. The natural fruit set of this population was 97 percent. Pollen origin (self vs. cross) did not affect fruit and seed set. Werauhia sintenisii is autogamous but not apomictic. All pollinator‐excluded flowers produced fruits, but flowers that were emasculated and caged did not produce any fruit. Factors affecting the evolution of autogamy in this system are discussed.

Las bromelias de Bosques Montanos estudiadas hasta la fecha han sido reportadas como auto‐compatibles. Sin embargo, se desconoce si las mismas son autógamas o apomfcticas. Caracterizamos el sistema de apareamiento de Werauchia sintenisii por medio de una serie de tratamientos diseñados para detectar auto‐compatibilidad, autogamia, y apomixes. En la población estudiada 97 por ciento de las flores producen frutos. El origen del pollen (propio vs foráneo) no affectó el número de semillas y fructos producidos. Werauhia sintenisii es autogama pero no apomictica. Todas las flores que fueron excluidas a los polinizadores produjeron frutos, sin embargo aqudlas que fueron emasculadas y excluidas a los polinizadores no produjeron frutos. Se discuten los factores que han podido afectar la evolución de autogamia en este sistema.
Population Dynamics of Pterocereus gaumeri, a Rare and Endemic Columnar Cactus of Mexico
Authors: Méndez Martha , Durán Rafael , Olmsted Ingrid , Oyama Ken
Published: March 2006

We conducted a demographic examination of Pterocereus gaumeri, a rare and endemic columnar cactus of the Yucatan peninsula, Mexico. Growth, survival, and fecundity of individuals were recorded in two populations from 1997 to 1999. Size‐based population projection matrices were constructed to document the population dynamics. Seed germination and seedling establishment experiments were conducted in the field to estimate the rate of seed and seedling survival. Our results show that P. gaumeri did not reproduce by asexual means or vegetative growth and thus relies wholly on sexual reproduction for population growth. Low reproductive success, seed predation, and low seedling survival appear to be important factors that contribute to the rarity of this species. The population growth rate (X) varied between 0.9545 and 1.0316. According to the matrix elasticity values, population dynamics of this species depend mainly on adult survival, with low values in fecundity and survival for the lowest size categories. Our results did not indicate that the population size of P. gaumeri was decreasing; however, increasing pressure on land use transformation is one of the most important factors that may threaten the persistence of this species.

Se presenta un estudio demográfico de Pterocereus gaumeri, un cactus raro, y endémico columnar de la Peninsula de Yucatán, México. Desde 1997 a 1999, se registró el crecimiento, la sobrevivencia y la fecundidad de individuos en dos poblaciones. Se construyeron marrices de proyección basadas en tamano poblacional para documentar la dinámica de las poblaciones. Se realizaron experimentos de germinación de semillas y establecimiento de plántulas en condiciones naturales, para estimar la tasa de sobrevivencia de semillas y plántulas. Nuestros resultados sugieren que P. gaumeri no se reproduce asexualmente o por crecimiento vegetative, por lo tan to el crecimiento poblacional depende completamente de la reproducción sexual. El bajo éxito reproductivo, la depredación de semillas y la baja tasa de sobrevivencia parecen ser factores importantes que contribuyen a la rareza de esta especie. La tasa de crecimiento poblacional (λ) varia entre 0.9545 y 1.0316. De acuerdo con los valores de las matriz de elasticidad, la dinámica poblacional de esta especie depende principalmente de la sobrevivencia de los adultos, con valores bajos en fecundidad y sobrevivencia de las categorias de tamanos menores. Nuestros resultados no indican que el tamano poblacional de P. gaumeri esté decreciendo, sin embargo, el incremento de presion por el cambio de uso de la tierra es uno de los factores más significativos que puede amenazar la continuidad de esta especie.
Forest Tree Persistence, Elephants, and Stem Scars
Authors: Sheil Douglas , Salim Agus
Published: March 2006

Sixteen percent of tree stems 10 cm diameter or greater recorded in seven 1 ha plots in Rabongo Forest, Uganda had stem damage attributable to elephants (Loxodonta africana). We propose four strategies that may help tree species persist under these conditions: repellence, resistance, tolerance and avoidance. We sought and found evidence for each strategy. Large, shade‐tolerant Cynometra alexandri dominated basal area (often >50%) and showed severe scarring. Nearly 80 percent of stems were small pioneer species. Scarring frequency and intensity increased with stem size. Stem‐size distributions declined steeply, implying a high mortality to growth rate ratio. Tree species with spiny stems or with known toxic bark defenses were unscarred. Epiphytic figs escaped damage while at small sizes. Mid‐successional tree species were scarce and appeared sensitive to elephants. Savanna species were seldom scarred. Taking stem size‐effects into account by using a per‐stem logistic modeling approach, scarring became more probable with slower growth and with increasing species abundance, and also varied with location. Pioneer and shade‐bearer guilds showed a deficit of intermediate‐sized stems. Evidence that selective elephant damage is responsible for monodominant C. alexandri forests remains equivocal; however, elephants do influence tree diversity, forest structure, and the wider landscape.
Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest
Authors: Hodgkison Robert , Balding Sharon T. , Zubaid Akbar , Kunz Thomas H.
Published: March 2006

The aims of this study were to investigate the diet and relative abundance of fruit bats in a lowland Malaysian rain forest and to test the hypothesis that the local assemblage structure of fruit bats varies significantly over time in relation to the availability of food. In total, 352 fruit bats of eight species were captured during 72,306 m2 mist‐net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculita, Chironax melanocephalus, and Cynopterus brachyotis) that fed on a wide range of “steady state” and “big bang” food resources were captured continuously throughout the study period, with no significant variation in capture rates over time. In contrast, five species that fed exclusively or almost exclusively on “big bang” food resources were sampled intermittently, with significant temporal variation in the capture rates of two species (Cynopterus horsfieldi and Megaerops ecaudatus). Significant variation in the capture rates of the remaining three species (Dyacopterus spadiceus, Eonycteris spelaea, and Rousettus amplexicaudatus) could not be detected due to small sample sizes. Since ephemeral “big bang” food resources were only sporadically available within the study area and were associated with large canopy trees and strangler figs, these results suggest that food abundance, or the availability of specific food items, may be important factors limiting local fruit bat species diversity in old‐growth Paleotropical rain forest. Thus, only three fruit bat species were locally resident within the forest throughout the study period. Therefore, further studies on the ranging behavior and habitat requirements of Malaysian fruit bats are required to assess the adequacy of existing reserves and protected areas.
The Striped Squirrel (Tamiops swinhoei hainanus) as a Nectar Robber of Ginger (Alpinia kwangsiensisy)
Authors: Deng Xao‐Bao , Ren Pan‐Yu , Gao Jiang‐Yun , Li Qing‐Jun
Published: March 2006

Nectar robbing by squirrels is reported for the first time in the striped squirrel (Tamiops swinhoei hainanus), which was found robbing nectar from ginger plants (Alpinia kwangsiensis) in tropical forests of south Yunnan, China. We describe the behavior of squirrels visiting inflorescences, and we compare the fruit set of inflorescences visited by squirrels with that of inflorescences not subject to nectar robbing by squirrels. Most of the styles of robbed flowers were damaged and the affected plants exhibited reduced fruit set.
Logging Speeds Little Red Fire Ant Invasion of Africa
Authors: Walsh Peter D. , Henschel Phillipp , Abernethy Kate A. , Tutin Caroline E. G. , Telfer Paul , Lahm Sally A.
Published: March 2006

Here, we document the invasion of equatorial Africa by the little red fire ant (Wasmannia auropunctata). Commercial logging and other forms of natural resource extraction have catapulted W. auropunctata into the interior of Gabon at a rate 60 times faster than the unassisted rate we measured over 19 years at the Lope Reserve. We also present photographic evidence suggesting that W. auropunctata is negatively affecting the country's exceptionally rich and intact large mammal fauna.

Nous documentons l'invasion de l'Afrique Equatoriale par la fourmi électrique (Wasmannia auropunctata). L'exploitation forestière et les autres formes d'extraction des ressources naturelles ont catapultéWasmannia auropunctataá l'interieur du Gabon á un rythme 60 fois plus rapide que la progression non assistée que nous avons mesurée sur 19 ans á la Réserve de la Lopé. Nous présentons également des photographies suggérant que Wasmannia auropunctata a un impact négatif sur la faune de grands mammiféres exceptionnellement riche et intacte du pays.
Developments in Modeling Liquefaction of Granular Soils, Caused by Cyclic Loads
Authors: Sawicki Andrzej , Mierczyński Jecek
Published: March 2006

The aim of this review article is to present historical developments of mechanics of saturated granular soils in relation to the liquefaction phenomenon, as well as to analyze the present state of this subject in connection with practically important problems. The first part is an introduction to mechanics of liquefaction, in order to make this paper self-contained. Then, some basic empirical findings are described. In the third part, the development of theoretical approaches to liquefaction-related problems, such as cyclic loading compaction and pore pressure accumulation, or cyclic loading degradation of shearing resistance, is presented. The fourth part deals with the presentation of the methods applied for solving practically important problems and those that have not been solved satisfactorily. The last part of this paper presents some of the most important conclusions and suggestions regarding further research. There are 152 references cited in this review article, and a supplementary bibliography of 45 publications is also included.
Design of Sandwich Panels With Prismatic Cores
Authors: Wei Z. , Zok F. W. , Evans A. G.
Published: March 2006

The paper focuses on optimization of lightweight sandwich panels with prismatic cores subject to bending loads in the two principal in-plane directions. Comparisons are made with optimal designs of panels with corrugated cores: a limiting case. When optimized for loading transverse to the prism axis, prismatic panels outperform those with corrugated cores, especially at lower loads. In contrast, when optimized for longitudinal loading, the corrugated core panel is always superior. Both panels exhibit significant anisotropy: a deficiency mediated by optimizing jointly for both orientations. The designs emerging from joint optimizations have only slightly lower load capacity than those optimized singly, but with the benefit of equal strengths in the two principal directions. Moreover, jointly optimized corrugated and prismatic panels perform equally well. Both are competitive with honeycomb core panels, especially at high load capacities. With the additional potential for multifunctionality (notably active cooling), the corrugated panels appear to be particularly promising thermostructural elements.
Investigation into Tangential Force and Axial Stress Effects on Fretting Fatigue Behavior
Authors: Lee Hyukjae , Mall Shankar
Published: March 2006

Fretting fatigue behavior of a titanium alloy was investigated using a dual actuator test setup which was capable to apply the pad displacement independent of the applied cyclic load on specimen. Fretting fatigue tests were conducted using this setup with a phase difference between cyclic load on the specimen and tangential force on the fretting pad with cylinder-on-flat contact configuration under partial slip condition. Two axial stress ratios were used. The relative slip range and tangential force range were related to each other and this relationship was not influenced by phase difference, axial stress ratio, and contact load under the partial slip condition. Change in the phase difference caused the change in relative slip as well as tangential force for a given applied pad displacement and axial load. However, there was no effect of phase difference on fretting fatigue life at a given relative slip level. Fretting fatigue tests with a fully reversed axial stress showed longer fatigue life than tension-tension counterparts at a given relative slip, tangential force range, and axial stress range. Finite element analysis was conducted by including the complete load history effects, which showed that stress distribution on the contact surface stabilized after the first fatigue cycle. Unlike relative slip and∕or tangential force range, a critical plane-based parameter appears to take into account the stress ratio effects to characterize fretting fatigue behavior.
Analysis of Shadow Mask Tension Subjected to Thermal and Mechanical Loads
Authors: Moon Y. H. , Hyun D. I. , Van Tyne C. J.
Published: March 2006

In cathode ray tubes, a tension is imposed into the shadow mask during manufacturing to avoid slight variations in the position due to in service temperatures or deformation. Initially, tension is imparted to the shadow mask after it is welded to the compressed mask frame and the frame is allowed to retract. Subsequently, during further processing of the cathode ray tube, the tensioned shadow mask is subjected to heating. The heating causes some of the tension to decrease due to stress relaxation phenomenon associated with heating and creep. In the present study, the tension variation during manufacturing has been analyzed and the appropriate material characteristics and processing conditions to assure a more stable shadow mask for final service are suggested.
Creep-Induced Microstructural Change in 304-Type Austenitic Stainless Steel
Authors: Ohtani Toshihiro , Ogi Hirotsugu , Hirao Masahiko
Published: March 2006

We studied microstructure changes of 304-type austenitic stainless steel subjected to a tensile stress at 973K. We monitored the shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). The attenuation peaks at 40% to 50% and a minimum value at 70% of the creep life, being independent of the applied stress. A drastic change in dislocation mobility and arrangement interrupted this novel attenuation phenomenon, as supported by SEM and TEM observations. The relationship between attenuation change and microstructure evolution can be explained with the string’s model. EMAR demonstrates a potential for assessing damage advance and predicting the remaining creep life of metals.
How an antenna launches its input power into radiation: The pattern of the Poynting vector at and near an antenna
Authors: Jackson J. D.
Published: March 2006

I address the question of whether the seat of the power radiated by an antenna made of conducting members is distributed over the arms of the antenna according to −J∙E, where J is the current density and E is the electric field produced by the source. Poynting’s theorem permits only a global identification of the total input power, usually from a localized generator, with the total power radiated to infinity, not a local correspondence of −J∙Ed3x with a specific radiated power, r2S∙r̂dΩ. I describe a model antenna consisting of two perfectly conducting hemispheres of radius a separated by a small equatorial gap across which occurs the driving oscillatory electric field. The fields and surface current are determined by solution of the boundary value problem. In contrast to the first approach (not a boundary value problem), the tangential electric field vanishes on the metallic surface. There is no radial Poynting vector at the surface. Numerical examples are shown to illustrate how the energy flows from the input region at the gap and is guided near the antenna by its arms until it is launched at larger r∕a into the radiation pattern determined by the value of ka.
Restructuring the introductory electricity and magnetism course
Authors: Chabay Ruth , Sherwood Bruce
Published: March 2006

In the electricity and magnetism (E&M) segment of the traditional introductory calculus-based physics course, many new and increasingly abstract concepts, embodied in complex formal relations, are introduced at a rapid pace. As a result, many students find E&M significantly more difficult than classical mechanics. We describe a different intellectual structure for the E&M course that stresses conceptual coherence, connects the abstract field concept to concrete microscopic models of matter, and follows a clear story line, culminating in the classical model of the interaction of electromagnetic radiation and matter. This sequence has proven to be effective in teaching the basic concepts of E&M.
Time in classical electrodynamics
Authors: Rohrlich Fritz
Published: March 2006

There is considerable misunderstanding in the literature concerning time in classical electrodynamics. The following conceptual exposition focuses on three points: advanced radiation exists mathematically but not physically; there exists an asymmetry of time due to radiation; and the equations of motion of charged particles are invariant under time reversal. These three points are mutually consistent.
HBV, HCV, and TTV detection by in situ polymerase chain reaction could reveal occult infection in hepatocellular carcinoma: comparison with blood markers
Authors: Comar M , Dal Molin G , D’Agaro P , Crocè S L , Tiribelli C , Campello C
Published: March 2006

Objective:To report a retrospective analysis on the presence of hepatitis B virus (HBV), hepatitis C virus (HCV), and transfusion transmitted virus (TTV) sequences in formalin fixed, paraffin embedded liver biopsies from eight patients with hepatocellular carcinoma, in comparison with blood markers.

Methods:A direct in situ polymerase chain reaction (PCR) technique was developed for the detection and localisation of genomic signals in the liver tissue. Conventional serological and molecular methods were used for blood evaluation.

Results:In situ PCR showed the presence of one of the three viruses (four HCV, two HBV, and one TTV) in seven of the eight patients. In addition, a co-infection with HBV and HCV was detected in one patient. HCV and HBV sequences were located in the cytoplasm and the nucleus, respectively. When compared with blood markers, these findings were compatible with one occult HBV and two occult HCV infections.

Conclusions:These findings provide further evidence for occult HBV and HCV infections in cancerous tissues from patients with hepatocellular carcinomas. In situ PCR could be an additional tool for evaluating the viral aetiology of hepatocellular carcinoma alongside conventional diagnostic procedures.
Down-regulated nucleoside diphosphate kinasenm23-H1expression is unrelated to high-risk human papillomavirus but associated with progression of cervical intraepithelial neoplasia and unfavourable prognosis in cervical cancer
Authors: Branca M , Giorgi C , Ciotti M , Santini D , Di Bonito L , Costa S , Benedetto A , Bonifacio D , Di Bonito P , Paba P , Accardi L , Mariani L , Ruutu M , Favalli C , Syrjänen K
Published: March 2006

Objective:One of the factors leading to an invasive phenotype is thenm23family of metastases-associated genes. Of the six known members,nm23-H1is the most frequently studied potential anti-metastatic gene in cervical cancer. However, the possible molecular links to oncogenic human papillomavirus (HPV) are completely unexplored as yet.

Materials and methods:As a part of the HPV-Pathogen Istituto Superiore di Sanità study, a series of 150 squamous cell carcinomas (SCCs) and 152 cervical intraepithelial neoplasia (CIN) lesions were examined by immunohistochemical staining fornm23-H1, and tested for HPV by polymerase chain reaction (PCR) with three sets of primers (MY09/11, GP5+/GP6+and short PCR fragment). Follow-up data were available on all patients with SCC, and 67 CIN lesions were monitored by serial PCR for clearance or persistence of HPV after cone treatment.

Results:A linear decrease (p = 0.001) was observed innm23-H1expression, starting from CIN1 (85% with normal expression), with the most dramatic down regulation on transition from CIN2 (70% normal) to CIN3 (39%) and further to SCC (25%). Reduced expression was associated with CIN3 or cancer at an odds ratio 8.72 (95% confidence interval 4.13 to 18.41).Nm23-H1was of no use as a marker of the high-risk human papillomavirus (HR-HPV) type, and it did not predict clearance or persistence of HR-HPV after treatment of CIN. Importantly,nm23-H1expression was a significant prognostic factor in cervical cancer, reduced expression being associated with lower survival (p = 0.022) in univariate analysis. In the multivariate (Cox) regression model, however, only the International Federation of Gynecology and Obstetrics stage (p = 0.001) and age (p = 0.011) remained independent prognostic predictors.

Conclusions:Down-regulatednm23-H1expression is markedly associated with progression from CIN2 to CIN3, and predicts poor prognosis in cervical cancer.Nm23-H1down regulation is probably orchestrated by mechanisms independent of HR-HPV oncoproteins and is possibly related to the emergence of a proteolytic phenotype.
Crystalline plasma cell inclusions in helicobacter-associated gastritis
Authors: Stewart C J R , Spagnolo D V
Published: March 2006

Background:Crystalline cytoplasmic inclusions are well documented in B cell lymphomas but have rarely been described in reactive plasmacytic infiltrates.

Aim:Three cases of Lelicobacter-associated gastritis are described in which plasma cells focally contained rhomboid and needle-shaped crystalline inclusions.

Methods:Crystalline inclusions were identified in the gastric biopsy specimens from three patients undergoing routine upper gastrointestinal endoscopy. The cells were characterised immunohistochemically using the following antisera: cytokeratin, leucocyte common antigen, desmin, CD20, CD68, CD79a, CD138, immunoglobulin (Ig)G, IgA and IgM heavy chains, and κ and λ Ig light chains. Clinical follow-up data were obtained.

Results:All biopsies showed a Lelicobacter-associated active chronic gastritis. Variable numbers of plasma cells with intracytoplasmic crystalline inclusions in the superficial lamina propria were seen. The crystals were not stained with any of the antisera tested, but the cells containing the crystals expressed CD79a and CD138 and, in the two assessable cases, showed IgA and λ light chain immunoreactivity. The more numerous morphologically normal plasma cells in each patient were polytypic, and there were no histological features to suggest lymphoma. Crystals were not identified in the plasma cells in mucosal biopsy specimens from other sites in any of the patients.

Conclusions:Crystalline inclusions in plasma cells can occur in association with Lelicobacter gastritis. Although light chain restriction was shown in two patients, the overall histological and clinical findings indicated a reactive process. The presence of plasma cell crystals in isolation should not be considered to be diagnostic of lymphoma.
DAMAGE SPREADING AND THE BLOCK DISTRIBUTION FUNCTION IN THE TWO-DIMENSIONAL LATTICE GAS MODEL
Authors: KWAK WOOSEOP , LANDAU D. P.
Published: March 2006

Monte Carlo simulations have been used to carry out a comparative study of the block distribution function and damage spreading characteristics of a half-filled lattice gas model (conserved order parameter) and a simple Ising model (non-conserved order parameter). Spin-exchange heat-bath dynamics were used to check the validity of equilibrium predictions for the lattice gas model using a histogram ratio analysis. Histogram reweighting was used to extract the interface energy for the lattice gas model, and the critical exponent β =1/8 was successfully estimated by using sub-block scaling and sub-block damage scaling.
TEMPERATURE ESTIMATION IN THE TWO-DIMENSIONAL ISING MODEL
Authors: CAIAFA C. F. , PROTO A. N.
Published: March 2006

We present two new algorithms for the estimation of the temperature from a realization of a 2-D Ising model. The methods here introduced are based in the maximization of pseudo likelihood and on the minimum mean squared error (MSE) fit of the conditional probability function. We derive the analytical expressions of these estimators and also we include computational results comparing these new techniques with the traditional method. A very good performance in terms of the average absolute error and the average standard deviation is demonstrated through simulations in a 100 × 100 lattice in the ferromagnetic and antiferromagnetic cases. Summarizing, we have provided two new useful computational tools that allow us to measure the "virtual" temperature of an Ising like system.
EPIDEMIC CONTROL IN A HIERARCHICAL SOCIAL NETWORK
Authors: GRABOWSKI ANDRZEJ , KOSIŃSKI ROBERT A.
Published: March 2006

The phenomenon of epidemic spreading in a population with a hierarchical structure of interpersonal interactions is described and investigated numerically. The SIR model with incubation time is used. In our model the localization of individuals in different social groups, the effectiveness of different interpersonal interactions and the mobility of a contemporary community are taken into account. The influence of different control methods on the spreading process is investigated as a function of different initial conditions. The cost-effectiveness of mass preventive random vaccinations, target vaccinations and sick leaves are compared. A critical range of vaccinations, sufficient for suppressing of an epidemic is calculated. The results of numerical calculations are similar to the solutions of the master equation for the spreading process.
TIME DEPENDENCE OF THE SURVIVAL PROBABILITY OF AN OPINION IN A CLOSED COMMUNITY
Authors: AYDINER EKREM , GÖNÜLOL MELTEM
Published: March 2006

The time dependence of the survival probability of an opinion in a closed community has been investigated in accordance with social temperature by using the Kawasaki-exchange dynamics based on previous study in Ref. 1. It is shown that the survival probability of opinion decays with stretched exponential law consistent with previous static model. However, the crossover regime in the decay of the survival probability has been observed in this dynamic model unlike previous model. The decay characteristics of both regimes obey to stretched exponential.
A NOTE ON THE INTEGRABILITY OF NON-HERMITIAN EXTENSIONS OF CALOGERO–MOSER–SUTHERLAND MODELS
Authors: FRING ANDREAS
Published: March 2006

We consider non-Hermitian but PT-symmetric extensions of Calogero models, which have been proposed by Basu-Mallick and Kundu for two types of Lie algebras. We address the question of whether these extensions are meaningful for all remaining Lie algebras (Coxeter groups) and if in addition one may extend the models beyond the rational case to trigonometric, hyperbolic and elliptic models. We find that all these new models remain integrable, albeit for the non-rational potentials one requires additional terms in the extension in order to compensate for the breaking of integrability.
TESTABLE AND UNTESTABLE ASPECTS OF DARK ENERGY
Authors: FRAMPTON PAUL H.
Published: March 2006

It has been suggested that dark energy will lead to a frequency cutoff in an experiment involving a Josephson junction. Here we show that were such a cutoff detected, it would have dramatic consequences including the possible demise of the string landscape.
ALLEVIATION OF AN INDETERMINACY PROBLEM AFFECTING TWO CLASSICAL ITERATIVE IMAGE THRESHOLDING ALGORITHMS
Authors: BOAST CHARLES W. , BAVEYE PHILIPPE
Published: March 2006

Thresholding algorithms are being increasingly used in a wide variety of disciplines to objectively discern patterns and objects in micrographs, still pictures or remotely-sensed images. Our experience has shown that three common thresholding algorithms exhibit indeterminacy, in that different operator inputs may lead to very different pattern characterizations. A grayscale image of a soil profile is used to illustrate this phenomemon in the case of the intermeans (IM), minimum error (ME), and Besag's iterated conditional modes (ICM) algorithms. For the illustrative example, the IM algorithm depends only weakly on the starting point of the iterative process — it converges to only two adjacent threshold values. In contrast, the ME algorithm converges to 14 different threshold values plus a segmentation that identifies the entire image as dye, and one that identifies none of it as dye. The ICM algorithm converges to an even wider variety of final segmentations, depending on its starting point. A noniterative modification of the IM and ME algorithms is proposed, providing a consistent method for choosing from among a set of apparently equally-valid segmentations.
A ROBUST BUYER–SELLER WATERMARKING SCHEME BASED ON DWT
Authors: LOU DER-CHYUAN , SHIEH JIEH-MING , TSO HAO-KUAN
Published: March 2006

In a buyer–seller watermarking protocol, a seller should embed a buyer's fingerprinting and seller's watermark into the work before the sale of a work to a buyer. If the work is violated, the fingerprinting and watermark can be extracted to correctly identify who holds the legal copyright of the work and trace the illegal reseller. In this paper, we propose a robust buyer–seller watermarking scheme based on discrete wavelet transformation (DWT) which embeds the buyer's fingerprinting and seller's watermark into an image. Besides, during the extraction phase, the extraction of the fingerprinting and watermark does not require the original image for more feasibility in real application. The proposed scheme has the following advantages. Firstly, the extraction of the fingerprinting and watermark does not require the original image. Secondly, the watermarked image maintains a good visual quality after the fingerprinting and watermark embedding. Thirdly, the proposed scheme is robust against several image processing attacks.
VOICE RETRIEVAL OF MANDARIN BROADCAST NEWS SPEECH
Authors: CHEN BERLIN
Published: March 2006

This paper presents an improved framework for voice retrieval of Mandarin broadcast news speech. First, several unsupervised and data-driven approaches for broadcast news transcription were proposed to improve the speech recognition accuracy and efficiency. Then, a multiscale indexing paradigm for broadcast news retrieval was exploited to alleviate the problems caused by the speech recognition errors and the flexible wording structure of the Chinese language. Finally, we used the PDA as the platform and broadcast radio programs collected in Taiwan as the document collection to establish a speech-based multimedia information retrieval prototype system. Very encouraging results were obtained.
OVERSEGMENTATION REDUCTION BY FLOODING REGIONS AND DIGGING WATERSHED LINES
Authors: FRUCCI MARIA
Published: March 2006

The watershed transformation is a primary tool for segmenting a grey-tone image into subsets that are of interest to a visual observer. The resulting image, however, may often appear oversegmented into a large number of tiny regions (basins), most of which are not significant to the problem of domain. In this paper, a method for removing these nonsignificant basins is presented. The notions of relative significance and intrinsic significance are introduced, which lead to the definition of three types of significance for a basin: strong, weak and partial. The merging of a basin with other basins only occurs when the significance of the basin is not strong, and is restricted to suitably selected adjacent basins. The merging is performed by using an iterated process consisting of two phases. The first involves the removal of certain regional minima, and is accomplished by following either a flooding or a digging scheme. The second identifies the basins corresponding to the regional minima remaining in the image and utilizes the watershed transformation. An appropriate selection of the basins to be merged produces a segmented image perceptually close to the original image. The performance of the proposed method is for the case of astronomic images.
THEORETICAL AND NUMERICAL STUDY OF AN IMPLICIT DISCRETIZATION OF A 1D INVISCID MODEL FOR RIVER FLOWS
Authors: BERMÚDEZ A. , MUÑOZ-SOLA R. , RODRÍGUEZ C. , VILAR M. A.
Published: March 2006

In this paper, we consider a 1D inviscid model to simulate river flows whose unknown are the water elevation, the flow rate and the wet area. We rewrite this model in terms of the wet area and the flow rate.

Next, by using a weak formulation and a discretization by characteristics, we derive an implicit semidiscretized scheme that involves a variational inequality. Under suitable hypothesis, we prove that this scheme has at least one solution. We present an algorithm for the numerical solution of the fully discretized problem and the numerical results obtained for channels with parabolic and rectangular sections and variable depth.

Finally, we perform a stability analysis for the semidiscretized scheme applied to a similar problem where the convection term has been omitted.
POWER-RATE ASYMPTOTIC EXPANSION FOR 1D VISCOUS HEAT-CONDUCTING GAS FLOWS
Authors: ZLOTNIK ALEXANDER
Published: March 2006

We consider the compressible Navier–Stokes system for 1D flows of a viscous heat-conducting gas. The zero velocity and stress together with the (positive) temperature or zero heat flux are prescribed on the boundaries. The large-time behavior of the solution is studied for the arbitrarily large initial data. Namely, the stabilization with the power rate of the specific volume divided by 1 + t and the temperature to constants as well as of the velocity to a linear function is proved in L2 and H1-norm by means of the Lyapunov functional method. The study is accomplished in the Lagrangian mass coordinates.