bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying microbubble clustering in turbulent flow from single-point measurements
Authors: Calzavarini Enrico , van den Berg Thomas H. , Toschi Federico , Lohse Detlef
Published: April 2008

Single-point hot-wire measurements in the bulk of a turbulent channel have been performed in order to detect and quantify the phenomenon of preferential bubble accumulation. We show that statistical analysis of the bubble-probe colliding-time series can give a robust method for investigation of clustering in the bulk regions of a turbulent flow where, due to the opacity of the flow, no imaging technique can be employed. We demonstrate that microbubbles (R0≃100μm) in a developed turbulent flow, where the Kolmogorov-length scale is η≃R0, display preferential concentration in small scale structures with a typical statistical signature ranging from the dissipative range, O(η), up to the low inertial range O(100η). A comparison to Eulerian–Lagrangian numerical simulations is also presented to further support our proposed way to characterize clustering from temporal time series at a fixed position.
The mechanism of surfactant effects on drop coalescence
Authors: Dai Bing , Leal L. Gary
Published: April 2008

We utilize numerical solutions, based on a boundary-integral scheme, to investigate the mechanisms by which surfactant influences the coalescence of a pair of equal size drops that undergo a head-on collision in a biaxial linear flow. It is known that the addition of surfactant inhibits coalescence in the sense that the time required for film drainage to the point of film rupture is significantly increased. Although there is a direct effect on the rate of film drainage due to Marangoni effects within the thin film, we find that an equally important effect is due to the fact that the hydrodynamic force pushing the drops together is increased, hence causing the film to be more strongly deformed into a dimpled configuration that slows the film drainage process.
Angle-resolving time-of-flight electron spectrometer for near-threshold precision measurements of differential cross sections of electron-impact excitation of atoms and molecules
Authors: Lange M. , Matsumoto J. , Setiawan A. , Panajotović R. , Harrison J. , Lower J. C. A. , Newman D. S. , Mondal S. , Buckman S. J.
Published: April 2008

This article presents a new type of low-energy crossed-beam electron spectrometer for measuring angular differential cross sections of electron-impact excitation of atomic and molecular targets. Designed for investigations at energies close to excitation thresholds, the spectrometer combines a pulsed electron beam with the time-of-flight technique to distinguish between scattering channels. A large-area, position-sensitive detector is used to offset the low average scattering rate resulting from the pulsing duty cycle, without sacrificing angular resolution. A total energy resolution better than 150meV (full width at half maximum) at scattered energies of 0.5–3eV is achieved by monochromating the electron beam prior to pulsing it. The results of a precision measurement of the differential cross section for electron-impact excitation of helium, at an energy of 22eV, are used to assess the sensitivity and resolution of the spectrometer.
High-throughput analysis of thin-film stresses using arrays of micromachined cantilever beams
Authors: Kim Hyun-Jong , Han Jun-Hyun , Kaiser Roy , Oh Kyu Hwan , Vlassak Joost J.
Published: April 2008

We report on a technique for making high-throughput residual stress measurements on thin films by means of micromachined cantilever beams and an array of parallel laser beams. In this technique, the film of interest is deposited onto a silicon substrate with micromachined cantilever beams. The residual stress in the film causes the beams to bend. The curvature of the beams, which is proportional to the residual stress in the film, is measured by scanning an array of parallel laser beams generated with a diffraction grating along the length of the beams. The reflections of the laser beams are captured using a digital camera. A heating stage enables measurement of the residual stress as a function of temperature. As the curvature of each beam is determined by the local stress in the film, the film stress can be mapped across the substrate. This feature makes the technique a useful tool for the combinatorial analysis of phase transformations in thin films, especially when combined with the use of films with lateral composition gradients. As an illustration, we apply the technique to evaluate the thermomechanical behavior of Fe–Pd binary alloys as a function of composition.
Single mode high-contrast subwavelength grating vertical cavity surface emitting lasers
Authors: Huang Michael C. Y. , Zhou Ye , Chang-Hasnain Connie J.
Published: April 2008

We present a single mode vertical-cavity surface-emitting laser (VCSEL) utilizing a single-layer, high-contrast subwavelength grating (HCG) based top mirror, which provides both the ultrahigh reflectivity and lateral transverse modes control. Experimentally, we demonstrate that merely 11 HCG stripes with a thickness of 230nm are required to achieve lasing operation. The finite area of HCG, in combination with an oxide aperture of 2–6μm, effectively discriminates the higher-order transverse modes in VCSELs with a side mode suppression ratio of ⩾40dB. Furthermore, a single (first high-order transverse) mode, high output power of 2.3mW laser was achieved from a VCSEL with a 10μm oxide aperture.
Potential barriers to electron carriers in C60 field-effect transistors
Authors: Konishi Atsushi , Shikoh Eiji , Kubozono Yoshihiro , Fujiwara Akihiko
Published: April 2008

Transport properties of C60 field-effect transistors (FETs) have been investigated in the temperature range between 160 and 300K. Activation energy was estimated from temperature dependence of resistance at the linear region and of current at the saturation region for various channel lengths. Variation of activation energy values is attributed to carrier injection barrier at contact between source electrode and C60 channel, and barriers to carrier hopping between trap states in the channel of C60.
Evidence of field induced nucleation in phase change memory
Authors: Karpov I. V. , Mitra M. , Kau D. , Spadini G. , Kryukov Y. A. , Karpov V. G.
Published: April 2008

Experimental data on switching in phase change memory testify in favor of its underlying nucleation mechanism with field dependent nucleation barrier. Similar to the standard nucleation, switching occurs after exponentially long delay time when the conditions are not favorable enough, e.g., the nucleation barrier not low or the temperature not high enough. The switching statistics is found to be consistent with the nucleation mechanism as well. A theoretical model of nucleation switching is outlined.
Particle enrichment employing grooved microfluidic channels
Authors: Chen Hsiu-Hung , Gao Dayong
Published: April 2008

The well-studied chaotic micromixer has found its application on the enrichment of microparticles. Here, we report the use of such patterning flows produced by a grooved surface integrated into a microfluidic device to continuously concentrate the flowing particles of comparable sizes to the depth of the channel. The particle distributions after passing through the grooves illustrate the enrichment profiles and the size-dependent patterns. We expect that the alignment of the concentrated particles can facilitate the visualization of sizing and counting in cell-based devices.
Theoretical determination of contact angle in quantum dot self-assembly
Authors: Li X. L. , Yang G. W.
Published: April 2008

We have established an analytic thermodynamic theory to elucidate the evolution of contact angle upon the quantum dot (QD) self-assembly. It is found that the balance between surface energy and elastic relaxation energy plays a crucial role in the determination of contact angle in the heteroepitaxial system. The size-dependent surface energy determines a low contact angle in the QDs with small volume at the initial stage of growth, while the elastic relaxation energy becomes more significant and induces a high contact angle in the QDs with large volume.
Real-time gap impedance monitoring of dielectrophoretic assembly of multiwalled carbon nanotubes
Authors: An Libao , Friedrich Craig R.
Published: April 2008

We report on a real-time monitoring method for the assembly of a small number of multiwalled carbon nanotubes (MWNTs) by dielectrophoresis (DEP). A time-varying impedance model was developed to estimate the number of MWNTs which span an electrode gap indicated by the instantaneous decrease of gap impedance during DEP. Sudden decreases in gap impedance signals corresponding to tube deposition were measured. The impedance values agreed with the impedance model. Experiments confirmed that DEP assembly and measurement of gap impedance changes due to tube deposition can be accomplished with a single instrument, also providing a feedback signal for DEP process control.
Highly efficient inverted polymer solar cell by low temperature annealing of Cs2CO3 interlayer
Authors: Liao Hua-Hsien , Chen Li-Min , Xu Zheng , Li Gang , Yang Yang
Published: April 2008

We demonstrate a highly efficient inverted bulk heterojunction polymer solar cell based on regioregular poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester with a low temperature annealed interfacial buffer layer, cesium carbonate (Cs2CO3). This approach improves the power conversion efficiency of the inverted cell from 2.3% to 4.2%, with short-circuit current of 11.17mA∕cm2, open-circuit voltage of 0.59V, and fill factor of 63% under AM1.5G 100mW∕cm2 irradiation. This result is comparable to the previous regular structure device on the same system. Ultraviolet photoelectron spectroscopy shows that the work function of annealed Cs2CO3 layer decreases from 3.45to3.06eV. Further x-ray photoelectron spectroscopy results reveal that Cs2CO3 can decompose into low work function, doped cesium oxide Cs2O upon annealing, which is accountable for the work-function reduction and device efficiency improvement.
Another Reason Why Adults Find it Hard to Draw Accurately
Authors: Matthews William J , Adams Amy
Published: April 2008

Misperception of objects is a major cause of inaccuracies in adults' drawing. It has previously been established that participants' drawings are biased by their knowledge of the drawn object. We hypothesised that additional inaccuracy arises because drawings are biased towards participants' idiosyncratic canonical representations of the object. We report that participants' free drawings of a cylinder are correlated with their observational drawings of the same shape, providing evidence that people's observational drawings are distorted by their individual schematic representations of the objects in question. It is unclear whether this reflects a perceptual distortion or a bias in drawing production; in either case, this result provides a further explanation why people are poor at drawing from observation.
Ibn Al-Haytham and Psychophysics
Authors: Aaen-Stockdale Craig
Published: April 2008

Persian scholar Ibn al-Haytham (‘Alhazen’) has rightly been credited with many advances in optics and vision science, but recent spurious claims that he is the ‘founder of psychophysics’ rest upon unsupported assertions, a conflation of psychophysics with the wider discipline of psychology, and semantic arguments over what it is to ‘found’ a school of thought.
Assessment of spatial variability of penetration resistance and hardpan characteristics in a cassava field
Authors: Mohawesh Osama , Ishida Tomoyasu , Fukumura Kazunari , Yoshino Kunihiko
Published: April 2008

Soil compaction is generally defined as an increase of the natural density of soil at a particular depth. This compacted soil layer spatially varies over the field. Describing within-field variability is a fundamental first step towards determining the size of management zones. The purpose of the study was to explain the spatial variability of penetration resistance (PR) and hardpan characteristics. Soil PR, dry bulk density (BD), and water content (WC) were measured on the nodes of a mesh. Statistical and geostatistical analysis were used to analyse the spatial variability of PR at 5 depths: 0.0–0.1, 0.1–0.2, 0.2–0.3, 0.3–0.4, and 0.4–0.5 m, and hardpan characteristics. PR had the maximum variability among the measured properties. Hardpan lower edge depth varied from 0.297 to 0.714 m, having a mean and CV of 0.411 m and 20.43, respectively. PR was inversely related to WC. Correlation between BD and WC and PR for the same layer was relatively high. PR and hardpan characteristics showed spatial variability across the field, except PR at depth 0.1–0.2 m. Spherical isotropic models fitted all the measured properties. The range of values of the spatial structure was greater than 7.6 m. The results showed that hardpan and PR spatially varied across the field. These results are important in determining the necessary tillage technique as well as the tillage depth and the target compacted area for a suitable land management. These results also have important implications for how site-specific management information should be collected and explained.
Release of hydrophobic molecules from polymer micelles into cell membranes revealed by Förster resonance energy transfer imaging
Authors: Chen Hongtao , Kim Sungwon , Li Li , Wang Shuyi , Park Kinam , Cheng Ji-Xin
Published: April 2008

It is generally assumed that polymeric micelles, upon administration into the blood stream, carry drug molecules until they are taken up into cells followed by intracellular release. The current work revisits this conventional wisdom. The study using dual-labeled micelles containing fluorescently labeled copolymers and hydrophobic fluorescent probes entrapped in the polymeric micelle core showed that cellular uptake of hydrophobic probes was much faster than that of labeled copolymers. This result implies that the hydrophobic probes in the core are released from micelles in the extracellular space. Förster resonance energy transfer (FRET) imaging and spectroscopy were used to monitor this process in real time. A FRET pair, DiIC18(3)and DiOC18(3), was loaded into monomethoxy poly(ethylene glycol)-block-poly(d,l-lactic acid) micelles. By monitoring the FRET efficiency, release of the core-loaded probes to model membranes was demonstrated. During administration of polymeric micelles to tumor cells, a decrease of FRET was observed both on the cell membrane and inside of cells, indicating the release of core-loaded probes to the cell membrane before internalization. The decrease of FRET on the plasma membrane was also observed during administration of paclitaxel-loaded micelles. Taken together, our results suggest a membrane-mediated pathway for cellular uptake of hydrophobic molecules preloaded in polymeric micelles. The plasma membrane provides a temporal residence for micelle-released hydrophobic molecules before their delivery to target intracellular destinations. A putative role of the PEG shell in the molecular transport from micelle to membrane is discussed.
Extreme polyploidy in a large bacterium
Authors: Mendell Jennifer E. , Clements Kendall D. , Choat J. Howard , Angert Esther R.
Published: April 2008

Cells rely on diffusion to move metabolites and biomolecules. Diffusion is highly efficient but only over short distances. Although eukaryotic cells have broken free of diffusion-dictated constraints on cell size, most bacteria and archaea are forced to remain small. Exceptions to this rule are found among the bacterial symbionts of surgeonfish;
Epulopiscium
spp. are cigar-shaped cells that reach lengths in excess of 600 μm. A large
Epulopiscium
contains thousands of times more DNA than a bacterium such as
Escherichia coli
, but the composition of this DNA is not well understood. Here, we present evidence that
Epulopiscium
contains tens of thousands of copies of its genome. Using quantitative, single-cell PCR assays targeting single-copy genes, we have determined that copy number is positively correlated with
Epulopiscium
cell size. Although other bacteria are known to possess multiple genomes, polyploidy of the magnitude observed in
Epulopiscium
is unprecedented. The arrangement of genomes around the cell periphery may permit regional responses to local stimuli, thus allowing
Epulopiscium
to maintain its unusually large size. Surveys of the sequences of single-copy genes (
dnaA
,
recA
, and
ftsZ
) revealed genetic homogeneity within a cell consistent with only a small amount (≈1%) of the parental DNA being transferred to the next generation. The results also suggest that the abundance of genome copies in
Epulopiscium
may allow for an unstable genetic feature, a long mononucleotide tract, in an essential gene. With the evolution of extreme polyploidy and large cell size,
Epulopiscium
has acquired some of the advantages of eukaryotic cells.
Pink1 regulates mitochondrial dynamics through interaction with the fission/fusion machinery
Authors: Yang Yufeng , Ouyang Yingshi , Yang Lichuan , Beal M. Flint , McQuibban Angus , Vogel Hannes , Lu Bingwei
Published: April 2008

Mitochondria form dynamic tubular networks that undergo frequent morphological changes through fission and fusion, the imbalance of which can affect cell survival in general and impact synaptic transmission and plasticity in neurons in particular. Some core components of the mitochondrial fission/fusion machinery, including the dynamin-like GTPases Drp1, Mitofusin, Opa1, and the Drp1-interacting protein Fis1, have been identified. How the fission and fusion processes are regulated under normal conditions and the extent to which defects in mitochondrial fission/fusion are involved in various disease conditions are poorly understood. Mitochondrial malfunction tends to cause diseases with brain and skeletal muscle manifestations and has been implicated in neurodegenerative diseases such as Parkinson's disease (PD). Whether abnormal mitochondrial fission or fusion plays a role in PD pathogenesis has not been shown. Here, we show that Pink1, a mitochondria-targeted Ser/Thr kinase linked to familial PD, genetically interacts with the mitochondrial fission/fusion machinery and modulates mitochondrial dynamics. Genetic manipulations that promote mitochondrial fission suppress
Drosophila Pink1
mutant phenotypes in indirect flight muscle and dopamine neurons, whereas decreased fission has opposite effects. In
Drosophila
and mammalian cells, overexpression of Pink1 promotes mitochondrial fission, whereas inhibition of Pink1 leads to excessive fusion. Our genetic interaction results suggest that Fis1 may act in-between Pink1 and Drp1 in controlling mitochondrial fission. These results reveal a cell biological role for Pink1 and establish mitochondrial fission/fusion as a paradigm for PD research. Compounds that modulate mitochondrial fission/fusion could have therapeutic value in PD intervention.
The fetal liver is a niche for maturation of primitive erythroid cells
Authors: Isern Joan , Fraser Stuart T. , He Zhiyong , Baron Margaret H.
Published: April 2008

Primitive erythroid cells (EryP) are the earliest differentiated cell type of the mammalian embryo. They appear in the yolk sac by embryonic day 7.5, begin to enter the embryonic circulation 2 days later and continue to mature in a stepwise and synchronous fashion. Like their adult counterparts, EryP enucleate. However, EryP circulate throughout the embryo for several days before the first enucleated forms can be identified in the blood. We have used transgenic mouse lines in which GFP marks EryP to investigate this seemingly long lag and have identified a previously unrecognized developmental niche for EryP maturation. After exiting the yolk sac, EryP begin to express cell adhesion proteins, including α4, α5, and β1 integrins, on their surface and migrate into the fetal liver (FL), where they interact with macrophages within erythroblastic islands. Binding of EryP to FL macrophages
in vitro
is stage-specific and partly depends on VCAM-1. The ability to tag and track EryP nuclei using a transgenic mouse line expressing an H2B-EGFP fusion allowed us to identify and characterize extruded EryP nuclei and to demonstrate that molecules such as α4, α5, and β1 integrins are redistributed onto the plasma membrane surrounding the extruding nucleus. FL macrophages engulf extruded EryP nuclei in cocultures and in the native FL
in vivo
. We conclude that EryP home to, complete their maturation, and enucleate within the FL, a tissue that is just developing as EryP begin to circulate. Our observations suggest a simple solution for a puzzling aspect of the development of the primitive erythroid lineage.
An acoustic comparison of English monophthongs and diphthongs produced by Australian and Thai speakers
Authors: Tsukada Kimiko
Published: April 2008

This study investigated acoustic-phonetic characteristics of English vowels (four monophthongs /I æ ~ %/ and two diphthongs /eI o~/) spoken by native speakers of Australian English (AusE, n = 6) and Thai (T, n = 15). The Thai speakers had lived in Australia for an average of 3.2 years. While the Thai speakers did not differ significantly from the AusE speakers in their vowel quality for monophthongs, they were more dissimilar in their production of diphthongs. Specifically, the Thai speakers produced English diphthongs with less formant movement, a phenomenon widely reported for speakers of various other Southeast Asian languages. Differences between the Thai and AusE groups reached statistical significance for the female speakers. As for temporal characteristics, the Thai speakers produced significantly shorter monophthongs, but not diphthongs, than did AusE speakers. As a result, the ratio of monophthongs to diphthongs was much smaller for the Thai (0.53) than for the AusE group (0.72). It appeared that the Thai speakers equated the English diphthongs /eI/ and /o~/ with the long vowels /e˜/ and /o˜/, respectively, in their first language (L1) Thai. Further, their production of the diphthongs may be related to a large number of diphthongs in the Thai vowel inventory, which may encourage its speakers to substitute existing L1 categories for English diphthongs rather than forming authentic, new phonetic categories.
Comparison of Endothelial Cell Proliferation in Normal Liver and Adipose Tissue in B6C3F1 Mice, F344 Rats, and Humans
Authors: Ohnishi Takamasa , Arnold Lora L. , Clark Nicol M. , Wisecarver James L. , Cohen Samuel M.
Published: April 2008

Peroxisome proliferator-activated receptor gamma (PPARγ) and dual PPARα and γ agonists have been developed for use in the treatment of diabetes and hyperlipidemias. Vascular tumors were increased in mice treated with some PPAR agonists, but not in rats. Spontaneous hemangiosarcomas are common in several strains of mice, uncommon in rats, and rarely occur in humans. The objective of this study was to determine the endothelial cell proliferation rate in liver and adipose tissue of B6C3F1 mice, F344 rats, and humans to aid in investigations of the genesis and development of hemangiosarcoma formation, and to determine the relevance of the increased endothelial cell proliferation rate in drug-treated rodents in assessing the risk of these drugs in humans. We determined the endothelial cell labeling index (LI) in untreated mice, rats, and humans, in normal liver, brown fat (rats and mice only) and white fat by dual immunohistochemistry of CD31 and Ki-67. The LI, highest in mice and lowest in humans, was statistically significantly greater in the mouse compared to the human and rat. The increased rate of spontaneous or PPAR agonist-induced hemangiosarcoma formation in mice may be related to the higher background endothelial cell proliferation rate compared to rats and humans.
Excess Mortality in Two-Year Rodent Carcinogenicity Studies
Authors: Roth A. , Kadyszewski E. , Geffray B. , Paulissen J. , Weaver R. J.
Published: April 2008

This paper considers the impacts of various patterns of differential or excess mortality on the biological and statistical interpretation of 2-year rodent carcinogenicity studies. It provides suggestions on experimental design that are intended to maximize the value of such studies for carcinogenic risk assessment. Specifically, it recommends dose reduction, possibly to the level of dose cessation, when biologically feasible and considers the merits of termination of the entire study as alternatives to the commonly employed strategy of terminating particular dose groups. It then recommends statistical analysis modifications that are appropriate when these suggestions on experimental design are adopted. One of the recommended modifications is a new statistical test to determine whether a dose group exceeds the maximum tolerated dose (MTD) on the basis of mortality. While the authors provide recommendations for the most commonly occurring exigencies, they acknowledge the need for and strongly support the practice of active engagement of the appropriate regulatory agency, e.g., the FDA, prior to any action.
Cytoscape ESP: simple search of complex biological networks
Authors: Ashkenazi Maital , Bader Gary D. , Kuchinsky Allan , Moshelion Menachem , States David J.
Published: April 2008

Summary: Cytoscape enhanced search plugin (ESP) enables searching complex biological networks on multiple attribute fields using logical operators and wildcards. Queries use an intuitive syntax and simple search line interface. ESP is implemented as a Cytoscape plugin and complements existing search functions in the Cytoscape network visualization and analysis software, allowing users to easily identify nodes, edges and subgraphs of interest, even for very large networks.

Availabiity:  http://chianti.ucsd.edu/cyto_web/plugins/

Contact:  ashkenaz@agri.huji.ac.il
Pheromones enhance somatosensory processing in newt brains through a vasotocin-dependent mechanism
Authors: Thompson R.R , Dickinson P.S , Rose J.D , Dakin K.A , Civiello G.M , Segerdahl A , Bartlett R
Published: April 2008

We tested whether the sex pheromones that stimulate courtship clasping in male roughskin newts do so, at least in part, by amplifying the somatosensory signals that directly trigger the motor pattern associated with clasping and, if so, whether that amplification is dependent on endogenous vasotocin (VT). Female olfactory stimuli increased the number of action potentials recorded in the medulla of males in response to tactile stimulation of the cloaca, which triggers the clasp motor reflex, as well as to tactile stimulation of the snout and hindlimb. That enhancement was blocked by exposing the medulla to a V1a receptor antagonist before pheromone exposure. However, the antagonist did not affect medullary responses to tactile stimuli in the absence of pheromone exposure, suggesting that pheromones amplify somatosensory signals by inducing endogenous VT release. The ability of VT to couple sensory systems together in response to social stimulation could allow this peptide to induce variable behavioural outcomes, depending on the immediate context of the social interaction and thus on the nature of the associated stimuli that are amplified. If widespread in vertebrates, this mechanism could account for some of the behavioural variability associated with this and related peptides both within and across species.
Global patterns in marine dispersal estimates: the influence of geography, taxonomic category and life history
Authors: Bradbury Ian R , Laurel Benjamin , Snelgrove Paul V.R , Bentzen Paul , Campana Steven E
Published: April 2008

We examine estimates of dispersal in a broad range of marine species through an analysis of published values, and evaluate how well these values represent global patterns through a comparison with correlates of dispersal. Our analysis indicates a historical focus in dispersal studies on low-dispersal/low-latitude species, and we hypothesize that these studies are not generally applicable and representative of global patterns. Large-scale patterns in dispersal were examined using a database of correlates of dispersal such as planktonic larval duration (PLD, 318 species) and genetic differentiation (
F
ST
, 246 species). We observed significant differences in
F
ST
(
p
<0.001) and PLD (
p
<0.001) between taxonomic groups (e.g. fishes, cnidarians, etc.). Within marine fishes (more than 50% of datasets), the prevalence of demersal eggs was negatively associated with PLD (
R
2
=0.80,
p
<0.001) and positively associated with genetic structure (
R
2
=0.74,
p
<0.001). Furthermore, dispersal within marine fishes (i.e. PLD and
F
ST
) increased with latitude, adult body size and water depth. Of these variables, multiple regression identified latitude and body size as persistent predictors across taxonomic levels. These global patterns of dispersal represent a first step towards understanding and predicting species-level and regional differences in dispersal, and will be improved as more comprehensive data become available.
Variation in contributions to teaching by meerkats
Authors: Thornton Alex
Published: April 2008

Recent evidence from cooperative insect, bird and mammal societies has challenged the assumption that teaching is restricted to humans. However, little is known about the factors affecting the degree to which individuals in such societies contribute to teaching. Here, I examine variation in contributions to teaching in meerkats, where older group members teach pups to handle difficult prey. I show that investment in teaching varies with characteristics of pups, helpers, groups and ecological conditions. Although prior experience in caring for pups did not significantly influence teaching behaviour, younger helpers, which were still investing in growth, contributed less to teaching than older individuals. This suggests that, in common with other cooperative activities, contributions to teaching vary with the costs experienced by individual group members. However, in contrast to other forms of helping in meerkats, I detected no effects of nutritional state on teaching, suggesting that it carries relatively low costs. In species where individuals can potentially gain direct or indirect fitness benefits from facilitating learning in others, low costs divided among multiple group members may help tip the balance towards selection for teaching.
Phylogeny and geography predict pathogen community similarity in wild primates and humans
Authors: Davies T. Jonathan , Pedersen Amy B
Published: April 2008

In natural systems, host species are often co-infected by multiple pathogen species, and recent work has suggested that many pathogens can infect a wide range of host species. An important question therefore is what determines the host range of a pathogen and the community of pathogens found within a given host species. Using primates as a model, we show that infectious diseases are more often shared between species that are closely related and inhabit the same geographical region. We find that host relatedness is the best overall predictor of whether two host species share the same pathogens. A higher frequency of pathogen host shifts between close relatives or inheritance of pathogens from a common ancestor may explain this result. For viruses, geographical overlap among neighbouring primate hosts is more important in determining host range. We suggest this is because rapid evolution within viral lineages allows host jumps across larger evolutionary distances. We also show that the phylogenetic pattern of pathogen sharing with humans is the same as that between wild primates. For humans, this means we share a higher proportion of pathogens with the great apes, including chimpanzees and gorillas, because these species are our closest relatives.
Can prey exhibit threat-sensitive generalization of predator recognition? Extending the Predator Recognition Continuum Hypothesis
Authors: Ferrari Maud C.O , Messier François , Chivers Douglas P
Published: April 2008

Despite the importance of predator recognition in mediating predator–prey interactions, we know little about the specific characteristics that prey use to distinguish predators from non-predators. Recent experiments indicate that some prey who do not innately recognize specific predators as threats have the ability to display antipredator responses upon their first encounter with those predators if they are similar to predators that the prey has recently learned to recognize. The purpose of our present experiment is to test whether this generalization of predator recognition is dependent on the level of risk associated with the known predator. We conditioned fathead minnows to chemically recognize brown trout either as a high or low threat and then tested the minnows for their responses to brown trout, rainbow trout (closely related predator) or yellow perch (distantly related predator). When the brown trout represents a high-risk predator, minnows show an antipredator response to the odour of brown trout and rainbow trout but not to yellow perch. However, when the brown trout represents a low-risk predator, minnows display antipredator responses to brown trout, but not to the rainbow trout or yellow perch. We discuss these results in the context of the Predator Recognition Continuum Hypothesis.
The impact of dietary restriction, intermittent feeding and compensatory growth on reproductive investment and lifespan in a short-lived fish
Authors: Inness Claire L.W , Metcalfe Neil B
Published: April 2008

While dietary restriction usually increases lifespan, an intermittent feeding regime, where periods of deprivation alternate with times when food is available, has been found to reduce lifespan in some studies but prolong it in others. We suggest that these disparities arise because in some situations lifespan is reduced by the costs of catch-up growth (following the deprivation) and reproductive investment, a factor that has rarely been measured in studies of lifespan. Using three-spined sticklebacks, we show for the first time that while animals subjected to an intermittent feeding regime can grow as large as continuously fed controls that receive the same total amount of food, and can maintain reproductive investment, they have a shorter lifespan. Furthermore, we show that this reduction in lifespan is linked to rapid skeletal growth rate and is due to an increase in the instantaneous risk of mortality rather than in the rate of senescence. By contrast, dietary restriction caused a reduction in reproductive investment in females but no corresponding increase in longevity. This suggests that in short-lived species where reproduction is size dependent, selection pressures may lead to an increase in intrinsic mortality risk when resources are diverted from somatic maintenance to both growth and reproductive investment.
Evolutionary dynamics of segmental duplications from human Y-chromosomal euchromatin/heterochromatin transition regions
Authors: Kirsch Stefan , Münch Claudia , Jiang Zhaoshi , Cheng Ze , Chen Lin , Batz Christiane , Eichler Evan E. , Schempp Werner
Published: April 2008

Human chromosomal regions enriched in segmental duplications are subject to extensive genomic reorganization. Such regions are particularly informative for illuminating the evolutionary history of a given chromosome. We have analyzed 866 kb of Y-chromosomal non-palindromic segmental duplications delineating four euchromatin/heterochromatin transition regions (Yp11.2/Yp11.1, Yq11.1/Yq11.21, Yq11.23/Yq12, and Yq12/PAR2). Several computational methods were applied to decipher the segmental duplication architecture and identify the ancestral origin of the 41 different duplicons. Combining computational and comparative FISH analysis, we reconstruct the evolutionary history of these regions. Our analysis indicates a continuous process of transposition of duplicated sequences onto the evolving higher primate Y chromosome, providing unique insights into the development of species-specific Y-chromosomal and autosomal duplicons. Phylogenetic sequence comparisons show that duplicons of the human Yp11.2/Yp11.1 region were already present in the macaque–human ancestor as multiple paralogs located predominantly in subtelomeric regions. In contrast, duplicons from the Yq11.1/Yq11.21, Yq11.23/Yq12, and Yq12/PAR2 regions show no evidence of duplication in rhesus macaque, but map to the pericentromeric regions in chimpanzee and human. This suggests an evolutionary shift in the direction of duplicative transposition events from subtelomeric in Old World monkeys to pericentromeric in the human/ape lineage. Extensive chromosomal relocation of autosomal-duplicated sequences from euchromatin/heterochromatin transition regions to interstitial regions as demonstrated on the pygmy chimpanzee Y chromosome support a model in which substantial reorganization and amplification of duplicated sequences may contribute to speciation.
Influence of grazing and fire frequency on small‐scale plant community structure and resource variability in native tallgrass prairie
Authors: (Ciska) Veen G. F. , Blair John M. , Smith Melinda D. , Collins Scott L.
Published: April 2008

In grasslands worldwide, grazing by ungulates and periodic fires are important forces affecting resource availability and plant community structure. It is not clear, however, whether changes in community structure are the direct effects of the disturbance (i.e. fire and grazing) or are mediated indirectly through changes in resource abundance and availability. In North American tallgrass prairies, fire and grazing often have disparate effects on plant resources and plant diversity, yet, little is known about the individual and interactive effects of fire and grazing on resource variability and how that variability relates to heterogeneity in plant community structure, particularly at small scales. We conducted a field study to determine the interactive effects of different long‐term fire regimes (annual vs four‐year fire frequency) and grazing by native ungulates (Bos bison) on small‐scale plant community structure and resource variability (N and light) in native tallgrass prairie. Grazing enhanced light and nitrogen availability, but did not affect small‐scale resource variability. In addition, grazing reduced the dominance of C4grasses which enhanced species richness, diversity and community heterogeneity. In contrast, annual fire increased community dominance and reduced species richness and diversity, particularly in the absence of grazing, but had no effect on community heterogeneity, resource availability and resource variability. Variability in the abundance of resources showed no relationship with community heterogeneity at the scale measured in this study, however we found a relationship between community dominance and heterogeneity. Therefore, we conclude that grazing generated small‐scale community heterogeneity in this mesic grassland by directly affecting plant community dominance, rather than indirectly through changes in resource variability.
Siblings as Providers of Support and Care during Middle Childhood: Children's Perceptions
Authors: Kosonen Marjut
Published: April 2008

This article describes some of the findings of a study undertaken to seek the views of 69 Scottish primary school children of their sisters and brothers. The study found that siblings were perceived to be a significant source of support and help to the children. Sibling support was particularly important to children with few other supportive relationships. Sibling caretaking which was viewed primarily positively both by the caretaking and looked after children, was found to be a common experience among the nine to 12–year‐old children. Negative consequences of sibling caretaking included annoying, domination and abuse by siblings. Although over a quarter of the children's siblings were not living in the Same household, the majority of children perceived siblings to hold a special importance in their lives. Issues raised for parents and professionals concern the maintenance of relationships between siblings who do not live together; how to enhance the supportive aspects of sibling relationships, while offering protection against the negative aspects of sibling dichotomy; and facing the reality of sibling caretaking. Much more needs to be known about children's everyday experiences of growing up with their sisters and brothers, if we are to understand more fully the complexities of sibling relationships.
Activation of Toll‐like receptor 2 by a novel preparation of cell wall skeleton from Mycobacterium bovis BCG Tokyo (SMP‐105) sufficiently enhances immune responses against tumors
Authors: Murata Masashi
Published: April 2008

The cell wall skeleton of Mycobacterium bovis BCG has been investigated as an immunopotentiating adjuvant for immuno‐therapy of malignant tumors via Toll‐like receptor (TLR) 2 and TLR4. However, due to its high molecular weight, highly complicated lipoglycan structure, and complicated purification and isolation procedure, its exact structure–activity relationship has not been well established. We have newly isolated the cell wall skeleton from M. bovis BCG Tokyo (SMP‐105) and examined the binding of SMP‐105 with TLR. It was revealed that highly purified SMP‐105 activates the nuclear factor‐kB promoter in a TLR2‐dependent manner, not a TLR4‐dependent manner, using a reporter gene assay system. Peritoneal exudated cells of TLR2 and MyD88 knockout mice severely reduced the induction of tumor necrosis factor‐a and interleukin‐6 in the presence of SMP‐105, whereas cells from TLR4 knockout mice produced similar levels of cytokines to wild‐type mice. Dendritic cells and macrophages accumulated in the draining lymph nodes of treated mice. When mice were administered both SMP‐105 and mitomycin C‐inactivated Lewis lung carcinoma cells simultaneously, interferon‐g‐producing cells reacting to the tumor were increased distinctly in draining lymph nodes. When C57BL/6 mice, into which splenocytes from OT‐I transgenic mice had been transferred, were administered with both SMP‐105 and E.G7‐OVA, OVA‐specific cytotoxic T lymphocytes (CTL) increased markedly. Mice treated with SMP‐105 and inactivated Lewis lung carcinoma cells suppressed the growth of implanted tumors. These results suggest that the activation of TLR2 by SMP‐105 sufficiently enhanced immune responses, such as the number of interferon‐g‐producing cells and CTL, and prevented the growth of tumors without the contribution of TLR4. (Cancer Sci 2008; 99: 1435–1440)
Tumor blood flow interruption after radiotherapy strongly inhibits tumor regrowth
Authors: Hori Katsuyoshi , Furumoto Shozo , Kubota Kazuo
Published: April 2008

To clarify the therapeutic significance of interrupting tumor blood flow after irradiation, we investigated X‐irradiation‐induced changes in hemodynamic parameters (blood flow, extravasation and washout of fluorescein isothiocyanate‐dextran, and interstitial fluid pressure) in a variant of Yoshida sarcoma, LY80. Tumors in anesthetized male Donryu rats received local irradiation (10 Gy). At 48 h after irradiation, tumor blood flow increased significantly; at 72–96 h after irradiation, a 2–2.5‐fold increase was observed. All parameters then consistently showed improved tumor microcirculation, which probably contributed to regrowth of cancer because certain cells survived irradiation. Rats received an intravenous dose (10 mg/kg) of a combretastatin derivative, AC7700 (AVE8062), which interrupts tumor blood flow and disrupts tumor vessels. At all times evaluated after irradiation, AC7700 completely stopped tumor blood flow. Radiotherapy efficacy was significantly enhanced when combined with AC7700: AC7700 given 48 h after irradiation, when tumor blood flow increased significantly, remarkably suppressed tumor regrowth compared with AC7700 given 48 h before irradiation. Also, postirradiation AC7700 completely inhibited not only primary tumor regrowth but also regional lymph node metastases in half of tumor‐bearing rats and led to a significant improvement in survival. These results strongly suggest that the combination effect was enhanced via interruption of increased tumor blood flow after irradiation. This therapeutic combination and timing may have important benefits, even in tumors with low sensitivity to either treatment alone, because the effect was considerably greater than additive. Our data thus show that destruction of tumor microcirculation after irradiation is quite effective for preventing cancer recurrence. (Cancer Sci 2008; 99: 1485–1491)
Evi‐1 promotes para‐aortic splanchnopleural hematopoiesis through up‐regulation of GATA‐2 and repression of TGF‐b signaling
Authors: Sato Tomohiko , Goyama Susumu , Nitta Eriko , Takeshita Masataka , Yoshimi Mayumi , Nakagawa Masahiro , Kawazu Masahito , Ichikawa Motoshi , Kurokawa Mineo
Published: April 2008

Evi‐1 is a zinc‐finger transcriptional factor whose inappropriate expression leads to leukemic transformation in mice and humans. Recently, it has been shown that Evi‐1 regulates proliferation of hematopoietic stem/progenitor cells at embryonic stage via GATA‐2 up‐regulation; however, detailed mechanisms underlying Evi‐1‐mediated early hematopoiesis are not fully understood. We therefore evaluated hematopoietic potential of Evi‐1 mutants using a cultivation system of murine para‐aortic splanchnopleural (P‐Sp) regions, and found that both the first zinc finger domain and the acidic domain were required for Evi‐1‐mediated hematopoiesis. The hematopoietic potential of Evi‐1 mutants was likely to be related to its ability to up‐regulate GATA‐2 expression. We also showed that the decreased colony forming capacity of Evi‐1‐deficient P‐Sp cells was successfully recovered by inhibition of TGF‐b signaling, using ALK5 inhibitor or retroviral transfer of dominant‐negative‐type Smad3. Our findings suggest that Evi‐1 promotes hematopoietic stem/progenitor expansion at the embryonic stage through up‐regulation of GATA‐2 and repression of TGF‐b signaling. (Cancer Sci 2008; 99: 1407–1413)
Detection of novel cancer‐testis antigen‐specific T‐cell responses in TIL, regional lymph nodes, and PBL in patients with esophageal squamous cell carcinoma
Authors: Mizukami Yoshiki , Kono Koji , Daigo Yataro , Takano Atsushi , Tsunoda Takuya , Kawaguchi Yoshihiko , Nakamura Yusuke , Fujii Hideki
Published: April 2008

We recently identified three HLA‐A2402‐restricted epitope peptides derived from cancer‐testis antigens (CTA), TTK protein kinase (TTK), lymphocyte antigen 6 complex locus K (LY6K), and insulin‐like growth factor (IGF)‐II mRNA binding protein 3 (IMP‐3) for the development of immunotherapies against esophageal squamous cell carcinoma (ESCC). In order to evaluate their immunotherapeutic potential in ESCC patients, we estimated by ELISPOT assay the TTK‐, LY6K‐, or IMP‐3‐specific T‐cell immune responses in tumor‐infiltrating lymphocytes (TIL), regional lymph node lymphocytes (RLNL), and peripheral blood lymphocytes (PBL) expanded from 20HLA‐A2402 (+) ESCC patients, and correlated their immune activity with the expression levels of TTK, LY6K, and IMP‐3, and MHC class I in the tumors. Induction of TTK‐antigen specific T‐cell response in TIL to the peptide‐pulsed target cells was detected in 14 out of 20 (70%) cases, while LY6K or IMP‐3 specific T‐cell activity was observed in 11 of 20 (55%) or in eight of 20 (40%) cases, respectively. Furthermore, T‐cell activity in RLNL and PBL was detectable in the similar proportion of the 20 ESCC patients. Interestingly, CTA‐specific T‐cell immune response was found in 13 of 14 (93%) TIL obtained from ESCC tumors with strong MHC class I expression, while it could be observed only in two of six (33%) TIL from ESCC tumors with weak MHC class I expression. These results strongly suggest the pre‐existence of specific T‐cell responses to HLA‐A24‐restricted epitope peptides from TTK, LY6K, and IMP‐3 in ESCC patients. Monitoring antigen‐specific T‐cell responses, as well as the expression levels of MHC class I and epitope CTA in tumors, should be a selection index for application of cancer vaccine therapies to the patients who are likely to show good immune response. (Cancer Sci 2008; 99: 1448–1454)