bluuebunny/crossref_metadata_2025 huggingface dataset:
On data-independent multicomponent interpolators and the use of priors for optimal reconstruction and 3D up/down separation of pressure wavefields
Authors: Özdemir Kemal , Özbek Ali , van Manen Dirk-Jan , Vassallo Massimiliano
Published: December 2010

In marine acquisition, the interference between the upgoing and downgoing wavefields introduces a receiver ghost which reduces the effective bandwidth of the seismic wavefield. A two-component streamer provides means for removing the receiver ghost by measuring pressure and vertical particle velocity. However, due to nonuniform and relatively sparse sampling in the crossline direction, the seismic data are usually severely aliased in the crossline direction and the deghosting may not be feasible in a true 3D sense. A true multicomponent streamer measures all components of the particle motion wavefield in addition to the pressure wavefield. This enables solving the 3D deghosting and crossline reconstruction problems simultaneously, without making assumptions on the wavefield or the subsurface. We havedeveloped two data-independent algorithms suited for multicomponent acquisition. The first algorithm reconstructs the total pressure wavefield in the crossline direction by using the pressure and the crossline component of particle motion simultaneously. The second algorithm reconstructs the upgoing pressure wavefield by using the pressure, the crossline, and the vertical components of particle motion simultaneously. Both algorithms are optimal in the minimum-mean-squares-error sense and are ideally suited for a small number of irregularly spaced samples, as is common in towed marine acquisition. We find that by using the spectrum of the wavefield as a priori information, these algorithms have the potential to overcome higher-order aliasing than what is predicted by multichannel sampling theorems. Such a priori information can be extracted from an unaliased portion of the seismic data in novel and robust manners.
Antialiasing condition and filter for the reciprocity equation of correlation type
Authors: Cao Weiping , Schuster Gerard T.
Published: December 2010

An antialiasing formula has been derived for interferometric redatuming of seismic data. More generally, this formula is valid for numerical implementation of the reciprocity equation of correlation type, which is used for redatuming, extrapolation, interpolation, and migration. The antialiasing condition can be, surprisingly, more tolerant of a coarser trace sampling compared to the standard antialiasing condition. Numerical results with synthetic vertical seismic profile (VSP) data show that interferometry artifacts are effectively reduced when the antialiasing condition is used as a constraint with interferometric redatuming.
Curvelet-based multiple prediction
Authors: Donno Daniela , Chauris Hervé , Noble Mark
Published: December 2010

The suppression of multiples is a crucial task when processing seismic reflection data. Using the curvelet transform for surface-related multiple prediction is investigated. From a geophysical point of view, a curvelet can be seen as the representation of a local plane wave and is particularly well suited for seismic data decomposition. For the prediction of multiples in the curvelet domain, first it is proposed to decompose the input data into curvelet coefficients. These coefficients are then convolved together to predict the coefficients associated with multiples, and the final result is obtained by applying the inverse curvelet transform. The curvelet transform offers two advantages. The directional characteristic of curvelets allows for exploitation of Snell’s law at the sea surface. Moreover, the possible aliasing in the predicted multiple is better managed by using the curvelet multiscale property to weight the prediction according to the low-frequency part of the data. 2D synthetic and field data examples show that some artifacts and aliasing effects are indeed reduced in the multiple prediction with the use of curvelets, thus allowing for an improved multiple subtraction result.
On sampling functions and Fourier reconstruction methods
Authors: Naghizadeh Mostafa , Sacchi Mauricio D.
Published: December 2010

Random sampling can lead to algorithms in which the Fourier reconstruction is almost perfect when the underlying spectrum of the signal is sparse or band-limited. Conversely, regular sampling often hampers the Fourier data recovery methods. However, 2D signals that are band-limited in one spatial dimension can be recovered by designing a regular acquisition grid that minimizes the mixing between the unknown spectrum of the well-sampled signal and aliasing artifacts. This concept can be easily extended to higher dimensions and used to define potential strategies for acquisition-guided Fourier reconstruction. The wavenumber response of various sampling operators is derived and sampling conditions for optimal Fourier reconstruction are investigated using synthetic and real data examples.
Multicomponent ocean bottom and vertical cable seismic acquisition for wavefield reconstruction
Authors: Amundsen Lasse , Westerdahl Harald , Thompson Mark , Haugen Jon Andre , Reitan Arne , Landrø Martin , Ursin Bjørn
Published: December 2010

In ocean-bottom seismic and vertical-cable surveying, receiver stations are stationary on the sea floor while a source vessel shoots on a predetermined [Formula: see text] grid on the sea surface. To reduce exploration cost, the shot point interval often is so coarse that the data recorded at a given receiver station are undersampled and thus irrecoverably aliased. However, when the pressure field and its [Formula: see text]- and [Formula: see text]-derivatives are measured in the water column, the nonaliased pressure field can be reconstructed by interpolation. Likewise, if the vertical component of the particle velocity (or acceleration) and its [Formula: see text]- and [Formula: see text]-derivatives are measured, then this component can also be reconstructed by interpolation. The interpolation scheme can be any scheme that reconstructs the field from its sampled values and sampled derivatives. In the case that the two fields’ first-order derivatives are recorded, the total number of components is six. When also their second-order derivatives are measured, the number of components is 10. The properly interpolated measurements of pressure and vertical component of particle velocity from the multicomponent measurements allow true 3D up/down wavefield decomposition (deghosting) and wave-equation demultiple before wave-equation migration.
Antileakage Fourier transform for seismic data regularization in higher dimensions
Authors: Xu Sheng , Zhang Yu , Lambaré Gilles
Published: December 2010

Wide-azimuth seismic data sets are generally acquired more sparsely than narrow-azimuth seismic data sets. This brings new challenges to seismic data regularization algorithms, which aim to reconstruct seismic data for regularly sampled acquisition geometries from seismic data recorded from irregularly sampled acquisition geometries. The Fourier-based seismic data regularization algorithm first estimates the spatial frequency content on an irregularly sampled input grid. Then, it reconstructs the seismic data on any desired grid. Three main difficulties arise in this process: the “spectral leakage” problem, the accurate estimation of Fourier components, and the effective antialiasing scheme used inside the algorithm. The antileakage Fourier transform algorithm can overcome the spectral leakage problem and handles aliased data. To generalize it to higher dimensions, we propose an area weighting scheme to accurately estimate the Fourier components. However, the computational cost dramatically increases with the sampling dimensions. A windowed Fourier transform reduces the computational cost in high-dimension applications but causes undersampling in wavenumber domain and introduces some artifacts, known as Gibbs phenomena. As a solution, we propose a wavenumber domain oversampling inversion scheme. The robustness and effectiveness of the proposed algorithm are demonstrated with some applications to both synthetic and real data examples.
Efficient seismic forward modeling using simultaneous random sources and sparsity
Authors: Neelamani Ramesh (Neelsh) , Krohn Christine E. , Krebs Jerry R. , Romberg Justin K. , Deffenbaugh Max , Anderson John E.
Published: December 2010

The high cost of simulating densely sampled seismic forward modeling data arises from activating sources one at a time in sequence. To increase efficiency, one could leverage recent innovations in seismic field-data acquisition and activate several (e.g., 2–6) sources simultaneously during modeling. However, such approaches would suffer from degraded data quality because of the interference between the model’s responses to the simultaneous sources. Two new efficient simultaneous-source modeling approaches are proposed that rely on the novel tandem use of randomness and sparsity to construct almost noise-free model response to individual sources. In each approach, the first step is to measure the model’s cumulative response with all sources activated simultaneously using randomly scaled band-limited impulses or continuous band-limited random-noise waveforms. In the second step, the model response to each individual sourceis estimated from the cumulative receiver measurement by exploiting knowledge of the random source waveforms and the sparsity of the model response to individual sources in a known transform domain (e.g., curvelet domain). The efficiency achievable by the approaches is primarily governed by the sparsity of the model response. By invoking results from the field of compressive sensing, theoretical bounds are provided that assert that the approaches would need less modeling time for sparser (i.e., simpler or more structured) model responses. A simulated modeling example is illustrated that shows that data collected with as many as 8192 sources activated simultaneously can be separated into the 8192 individual source gathers with data quality comparable to that obtained when the sources were activated sequentially. The proposed approaches could also dramatically improve seismic field-data acquisition efficiency if the source signatures actually probing the earth can be measured accurately.
Reversal of Endogenous Dopamine Receptor Silencing in Pituitary Cells Augments Receptor-Mediated Apoptosis
Authors: Al-Azzawi Haneen , Yacqub-Usman Kiren , Richardson Alan , Hofland Leo J. , Clayton Richard N. , Farrell William E.
Published: December 2010

Dopamine (DA)-agonist targeting of the DA D2 receptor (D2R) in prolactinomas is the first-line treatment choice for suppression of prolactin and induction of tumor shrinkage. Resistance to DA agonists seems to be related to receptor number. Using the MMQ and GH3 pituitary cell lines, that either do or do not express D2R, respectively, we explored the epigenetic profile associated with the presence or absence of D2R in these cells lines. These studies led us to explore pharmacological strategies designed to restore receptor expression and thereby potentially augment DA agonist-mediated apoptosis. We show in GH3 cells that the D2R harbors increased CpG island-associated methylation and enrichment for histone H3K27me3. Conversely, MMQ cells and normal pituitaries show enrichment for H3K9Ac and barely detectable H3K27me3. Coculture of GH3 cells with the demethylating agent zebularine and the histone deacetylase inhibitor trichostatin A was responsible for a decrease in CpG island methylation and enrichment for the histone H3K9Ac mark. In addition, challenge of GH3 cells with zebularine alone or coculture with both agents led to expression of endogenous D2R in these cells. Induced expression D2R in GH3 cells was associated with a significant increase in apoptosis indices to challenge with either DA or bromocriptine. Specificity of a receptor-mediated response was established in coincubations with specific D2R antagonist and siRNA approaches in GH3 cell and D2R expressing MMQ cell lines. These studies point to the potential efficacy of combined treatment with epigenetic drugs and DA agonists for the medical management of different pituitary tumor subtypes, resistant to conventional therapies.
Bioluminescence Resonance Energy Transfer Reveals the Adrenocorticotropin (ACTH)-Induced Conformational Change of the Activated ACTH Receptor Complex in Living Cells
Authors: Cooray Sadani N. , Chung Teng-Teng , Mazhar Khansa , Szidonya Laszlo , Clark Adrian J. L.
Published: December 2010

The melanocortin 2 receptor (MC2R) accessory protein (MRAP) is a small single-transmembrane domain protein that plays a pivotal role in the function of the MC2R. The pituitary hormone, ACTH, acts via this receptor complex to stimulate adrenal steroidogenesis. Using both coimmunoprecipitation and bioluminescence resonance energy transfer (BRET), we show that the MC2R is constitutively homodimerized in cells. Furthermore, consistent with previous data, we also show that MRAP exists as an antiparallel homodimer. ACTH enhanced the BRET signal between MC2R homodimers as well as MC2R-MRAP heterodimers. However, ACTH did not enhance the physical interaction between these dimers as determined by coimmunoprecipitation. Real-time BRET analysis of the MRAP-MC2R interaction revealed two distinct phases of the ACTH-dependent BRET increase, an initial complex series of changes occurring over the first 2 min and a later persistent increase in BRET signal. The slower ACTH-dependent phase was inhibited by the protein kinase A inhibitor KT5720, suggesting that signal transduction was a prerequisite for this later conformational change. The MRAP-MC2R BRET approach provides a unique tool with which to analyze the activation of this receptor.
Regulation of Sertoli-Germ Cell Adhesion and Sperm Release by FSH and Nonclassical Testosterone Signaling
Authors: Shupe John , Cheng Jing , Puri Pawan , Kostereva Nataliya , Walker William H.
Published: December 2010

Testosterone and FSH act in synergy to produce the factors required to maximize the production of spermatozoa and male fertility. However, the molecular mechanisms by which these hormones support spermatogenesis are not well established. Recently, we identified a nonclassical mechanism of testosterone signaling in cultured rat Sertoli cells. We found that testosterone binding to the androgen receptor recruits and activates Src tyrosine kinase. Src then causes the activation of the epidermal growth factor receptor, which results in the phosphorylation and activation of the ERK MAPK and the cAMP response element-binding protein transcription factor. In this report, we find that FSH inhibits testosterone-mediated activation of ERK and the MAPK pathway in Sertoli cells via the protein kinase A-mediated inhibition of Raf kinase. In addition, FSH, as well as inhibitors of Src and ERK kinase activity, reduced germ cell attachment to Sertoli cells in culture. Using pathway-specific androgen receptor mutants we found that the nonclassical pathway is required for testosterone-mediated increases in germ cell attachment to Sertoli cells. Studies of seminiferous tubule explants determined that Src kinase, but not ERK kinase, activity is required for the release of sperm from seminiferous tubule explants. These findings suggest the nonclassical testosterone-signaling pathway acts via Src and ERK kinases to facilitate the adhesion of immature germ cells to Sertoli cells and through Src to permit the release of mature spermatozoa. In contrast, FSH acts to limit testosterone-mediated ERK kinase activity and germ cell attachment.
Toward a Synthesized History of Photography: A Conceptual Genealogy of Shashin
Authors: Fukuoka Maki
Published: December 2010

By the 1870s photography in Japan came to be called shashin, a term introduced from China and used in Japan since the eighteenth century. This article approaches the history of photography through the conceptual framework that surrounded shashin in the decades before its pairing with photography. What did shashin indicate in the context of the prephotographic production of images? What kinds of meanings were attached to the term that would later resonate with photographic technology? This article considers the study of materia medica in nineteenth-century Japan to explore these questions. It examines various pictorial representations characterized as shashin in nineteenth-century Owari domain to suggest that the term shashin was deployed to articulate, negotiate, and concretize a particular relationship between plants and their illustrations. Shifting focus from the technological history to the conceptual history of photography, this article aims to demonstrate the interrelatedness of methods of picture making and historically situated epistemologies through the concept of shashin.
Portable Monuments: Architectural Photography and the “Forms” of Empire in Modern China
Authors: Jones Andrew F.
Published: December 2010

The prominent architectural historian Liang Sicheng devoted much of his career to the photographic, graphic, and textual documentation of old Chinese buildings. This project was grounded in his efforts to (re)construct a Chinese architectural “Order,” and in so doing to posit a functional equivalence between Chinese civilization and that of the West.

This essay examines the genealogy of this claim by situating Liang's work in relation to nineteenth- and early-twentieth-century practices of architectural photography. It argues that colonial photographs of Chinese architectural monuments and surrounding urban spaces serve not only to “document” these buildings as signifiers of civilizational difference but also to transform them into a form of currency (both real and symbolic) in the unequal economy of colonial exchange. At the same time that these buildings begin to circulate as images in the global marketplace, in other words, they also serve to reify and fix in place the lived spaces and historical processes that they pictorially represent.

This reification takes place in collusion with the distinctive characteristics and constraints of nineteenth-century photographic technologies. This essay compares the work of two war photographers, Felix Beato and James Ricalton, who documented Beijing in conjunction with imperialist military campaigns against the Qing dynasty, first in 1860 and later in the wake of the Boxer uprising in 1900. An understanding of the divergent imaging technologies these two men employed (wet-collodion photography and stereography, respectively) is crucial to decoding not only how these images look to us now but also the way they suggested and perpetuated imperial ways of seeing, evaluating, and profiting from technologically reproduced visions of “China” and Chinese architecture, particularly the walls and monuments of Beijing.
A Thousand Words: The Powers and Dangers of Text and Image
Authors: Cather Kirsten
Published: December 2010

This article discusses the obscenity trial of director Oshima Nagisa's 1976 book In the Realm of the Senses, which includes a series of still photographs and the screenplay from his notorious film of the same name. The case illustrates how obscenity convictions in postwar Japan often hinged on an understanding of the affective power of still images versus moving ones and of images versus text. Central to the censor's charges of obscenity against both the still photos and the screenplay was the contention that they were actually moving images. The essay explores why the censors employed this rhetoric and why films nonetheless were consistently exonerated while literature was consistently found guilty of obscenity in the landmark postwar trials.
Novels to See/Movies to Read: Photographic Fiction in Japanese Women's Magazines
Authors: Frederick Sarah
Published: December 2010

This article analyzes interactions between text and photographic image in works of photographic fiction (shashin shôsetsu) printed in Japanese women's magazines from the 1930s to the 1950s, including their interaction with cinema and print culture. The essay considers the complex effects of shifting technologies of visual reproduction on national and gendered identities, with particular attention to the significance of the “fictional” status of such photographic images during this era of intense historical reality.
Second-order properties and central limit theory for the vertex process of iteration infinitely divisible and iteration stable random tessellations in the plane
Authors: Schreiber Tomasz , Thäle Christoph
Published: December 2010

The point process of vertices of an iteration infinitely divisible or, more specifically, of an iteration stable random tessellation in the Euclidean plane is considered. We explicitly determine its covariance measure and its pair-correlation function, as well as the cross-covariance measure and the cross-correlation function of the vertex point process and the random length measure in the general nonstationary regime. We also give special formulae in the stationary and isotropic setting. Exact formulae are given for vertex count variances in compact and convex sampling windows, and asymptotic relations are derived. Our results are then compared with those for a Poisson line tessellation having the same length density parameter. Moreover, a functional central limit theorem for the joint process of suitably rescaled total edge counts and edge lengths is established with the process (ξ, tξ), t > 0, arising in the limit, where ξ is a centered Gaussian variable with explicitly known variance.
Scaling limits for shortest path lengths along the edges of stationary tessellations
Authors: Voss Florian , Gloaguen Catherine , Schmidt Volker
Published: December 2010

We consider spatial stochastic models, which can be applied to, e.g. telecommunication networks with two hierarchy levels. In particular, we consider Cox processes XL and XH concentrated on the edge set T(1) of a random tessellation T, where the points XL,n and XH,n of XL and XH can describe the locations of low-level and high-level network components, respectively, and T(1) the underlying infrastructure of the network, such as road systems, railways, etc. Furthermore, each point XL,n of XL is marked with the shortest path along the edges of T to the nearest (in the Euclidean sense) point of XH. We investigate the typical shortest path length C* of the resulting marked point process, which is an important characteristic in, e.g. performance analysis and planning of telecommunication networks. In particular, we show that the distribution of C* converges to simple parametric limit distributions if a scaling factor κ converges to 0 or ∞. This can be used to approximate the density of C* by analytical formulae for a wide range of κ.
New discount and average optimality conditions for continuous-time Markov decision processes
Authors: Guo Xianping , Ye Liuer
Published: December 2010

This paper deals with continuous-time Markov decision processes in Polish spaces, under the discounted and average cost criteria. All underlying Markov processes are determined by given transition rates which are allowed to be unbounded, and the costs are assumed to be bounded below. By introducing an occupation measure of a randomized Markov policy and analyzing properties of occupation measures, we first show that the family of all randomized stationary policies is ‘sufficient’ within the class of all randomized Markov policies. Then, under the semicontinuity and compactness conditions, we prove the existence of a discounted cost optimal stationary policy by providing a value iteration technique. Moreover, by developing a new average cost, minimum nonnegative solution method, we prove the existence of an average cost optimal stationary policy under some reasonably mild conditions. Finally, we use some examples to illustrate applications of our results. Except that the costs are assumed to be bounded below, the conditions for the existence of discounted cost (or average cost) optimal policies are much weaker than those in the previous literature, and the minimum nonnegative solution approach is new.
The stationary probability density of a class of bounded Markov processes
Authors: Ramli Muhamad Azfar , Leng Gerard
Published: December 2010

In this paper we generalize a bounded Markov process, described by Stoyanov and Pacheco-González for a class of transition probability functions. A recursive integral equation for the probability density of these bounded Markov processes is derived and the stationary probability density is obtained by solving an equivalent differential equation. Examples of stationary densities for different transition probability functions are given and an application for designing a robotic coverage algorithm with specific emphasis on particular regions is discussed.
On zero-truncating and mixing Poisson distributions
Authors: Valero J. , Pérez-Casany M. , Ginebra J.
Published: December 2010

The distributions that result from zero-truncating mixed Poisson (ZTMP) distributions and those obtained from mixing zero-truncated Poisson (MZTP) distributions are characterised based on their probability generating functions. One consequence is that every ZTMP distribution is an MZTP distribution, but not vice versa. These characterisations also indicate that the size-biased version of a Poisson mixture and, under certain regularity conditions, the shifted version of a Poisson mixture are neither ZTMP distributions nor MZTP distributions.
Stochastic velocity motions and processes with random time
Authors: De Gregorio Alessandro
Published: December 2010

The aim of this paper is to analyze a class of random processes which models the motion of a particle on the real line with random velocity and subject to the action of friction. The speed randomly changes when a Poissonian event occurs. We study the characteristic and moment generating functions of the position reached by the particle at time t > 0. We are able to derive the explicit probability distributions in a few cases. The moments are also widely analyzed. For the random motions having an explicit density law, further interesting probabilistic interpretations emerge if we consider randomly varying time. Essentially, we consider two different types of random time, namely Bessel and gamma times, which contain, as particular cases, some important probability distributions (e.g. Gaussian, exponential). For the random processes built by means of these compositions, we derive the probability distributions for a fixed number of Poisson events. Some remarks on possible extensions to random motions in higher spaces are proposed. We focus our attention on the persistent planar random motion.
Information ranking and power laws on trees
Authors: Jelenković Predrag R. , Olvera-Cravioto Mariana
Published: December 2010

In this paper we consider the stochastic analysis of information ranking algorithms of large interconnected data sets, e.g. Google's PageRank algorithm for ranking pages on the World Wide Web. The stochastic formulation of the problem results in an equation of the form where N, Q, {Ri}i≥1, and {C, Ci}i≥1 are independent nonnegative random variables, the {C, Ci}i≥1 are identically distributed, and the {Ri}i≥1 are independent copies of stands for equality in distribution. We study the asymptotic properties of the distribution of R that, in the context of PageRank, represents the frequencies of highly ranked pages. The preceding equation is interesting in its own right since it belongs to a more general class of weighted branching processes that have been found to be useful in the analysis of many other algorithms. Our first main result shows that if ENE[Cα] = 1, α > 0, and Q, N satisfy additional moment conditions, then R has a power law distribution of index α. This result is obtained using a new approach based on an extension of Goldie's (1991) implicit renewal theorem. Furthermore, when N is regularly varying of index α > 1, ENE[Cα] < 1, and Q, C have higher moments than α, then the distributions of R and N are tail equivalent. The latter result is derived via a novel sample path large deviation method for recursive random sums. Similarly, we characterize the situation when the distribution of R is determined by the tail of Q. The preceding approaches may be of independent interest, as they can be used for analyzing other functionals on trees. We also briefly discuss the engineering implications of our results.
On customer flows in jackson queueing networks
Authors: Tan Sen , Xia Aihua
Published: December 2010

Melamed's theorem states that, for a Jackson queueing network, the equilibrium flow along a link follows a Poisson distribution if and only if no customers can travel along the link more than once. Barbour and Brown (1996) considered the Poisson approximate version of Melamed's theorem by allowing the customers a small probabilitypof travelling along the link more than once. In this note, we prove that the customer flow process is a Poisson cluster process and then establish a general approximate version of Melamed's theorem that accommodates all possible cases of 0 ≤p< 1.
Approximations to quasi-birth-and-death processes with infinite blocks
Authors: Bean Nigel , Latouche Guy
Published: December 2010

The numerical analysis of quasi-birth-and-death processes rests on the resolution of a matrix-quadratic equation for which efficient algorithms are known when the matrices have finite order, that is, when the number of phases is finite. In this paper we consider the case of infinitely many phases from the point of view of theoretical convergence of truncation and augmentation schemes, and we develop four different methods. Two methods rely on forced transitions to the boundary. In one of these methods, the transitions occur as a result of the truncation itself, while in the other method, they are artificially introduced so that the augmentation may be chosen to be as natural as possible. Two other methods rely on forced transitions within the same level. We conclude with a brief numerical illustration.
Subexponential tails of discounted aggregate claims in a time-dependent renewal risk model
Authors: Li Jinzhu , Tang Qihe , Wu Rong
Published: December 2010

Consider a continuous-time renewal risk model with a constant force of interest. We assume that claim sizes and interarrival times correspondingly form a sequence of independent and identically distributed random pairs and that each pair obeys a dependence structure described via the conditional tail probability of a claim size given the interarrival time before the claim. We focus on determining the impact of this dependence structure on the asymptotic tail probability of discounted aggregate claims. Assuming that the claim size distribution is subexponential, we derive an exact locally uniform asymptotic formula, which quantitatively captures the impact of the dependence structure. When the claim size distribution is extended regularly varying tailed, we show that this asymptotic formula is globally uniform.
Time reversal of some stationary jump diffusion processes from population genetics
Authors: Hutzenthaler Martin , Taylor Jesse Earl
Published: December 2010

We describe the processes obtained by time reversal of a class of stationary jump diffusion processes that model the dynamics of genetic variation in populations subject to repeated bottlenecks. Assuming that only one lineage survives each bottleneck, the forward process is a diffusion on [0,1] that jumps to the boundary before diffusing back into the interior. We show that the behavior of the time-reversed process depends on whether the boundaries are accessible to the diffusive motion of the forward process. If a boundary point is inaccessible to the forward diffusion then time reversal leads to a jump diffusion that jumps immediately into the interior whenever it arrives at that point. If, instead, a boundary point is accessible then the jumps off of that point are governed by a weighted local time of the time-reversed process.
Drosophila melanogaster as a model for human intestinal infection and pathology
Authors: Apidianakis Yiorgos , Rahme Laurence G.
Published: December 2010

Recent findings concerning Drosophila melanogaster intestinal pathology suggest that this model is well suited for the study of intestinal stem cell physiology during aging, stress and infection. Despite the physiological divergence between vertebrates and insects, the modeling of human intestinal diseases is possible in Drosophila because of the high degree of conservation between Drosophila and mammals with respect to the signaling pathways that control intestinal development, regeneration and disease. Furthermore, the genetic amenability of Drosophila makes it an advantageous model species. The well-studied intestinal stem cell lineage, as well as the tools available for its manipulation in vivo, provide a promising framework that can be used to elucidate many aspects of human intestinal pathology. In this Perspective, we discuss recent advances in the study of Drosophila intestinal infection and pathology, and briefly review the parallels and differences between human and Drosophila intestinal regeneration and disease.
Widespread regulatory activity of vertebrate microRNA* species
Authors: Yang Jr-Shiuan , Phillips Michael D. , Betel Doron , Mu Ping , Ventura Andrea , Siepel Adam C. , Chen Kevin C. , Lai Eric C.
Published: December 2010

An obligate intermediate during microRNA (miRNA) biogenesis is an ∼22-nucleotide RNA duplex, from which the mature miRNA is preferentially incorporated into a silencing complex. Its partner miRNA* species is generally regarded as a passenger RNA, whose regulatory capacity has not been systematically examined in vertebrates. Our bioinformatic analyses demonstrate that a substantial fraction of miRNA* species are stringently conserved over vertebrate evolution, collectively exhibit greatest conservation in their seed regions, and define complementary motifs whose conservation across vertebrate 3′-UTR evolution is statistically significant. Functional tests of 22 miRNA expression constructs revealed that a majority could repress both miRNA and miRNA* perfect match reporters, and the ratio of miRNA:miRNA* sensor repression was correlated with the endogenous ratio of miRNA:miRNA* reads. Analysis of microarray data provided transcriptome-wide evidence for the regulation of seed-matched targets for both mature and star strand species of several miRNAs relevant to oncogenesis, including mir-17, mir-34a, and mir-19. Finally, 3′-UTR sensor assays and mutagenesis tests confirmed direct repression of five miR-19* targets via star seed sites. Overall, our data demonstrate that miRNA* species have demonstrable impact on vertebrate regulatory networks and should be taken into account in studies of miRNA functions and their contribution to disease states.
Inflammatory and structural biomarkers in acute traumatic spinal cord injury
Authors: Kwon Brian K. , Casha Steve , Hurlbert R. John , Yong V. Wee
Published: December 2010

The paralysis of an acute spinal cord injury (SCI) remains a catastrophic condition for which there are currently no effective treatments. While the diagnosis of acute traumatic SCI is typically quite easy to make, distinguishing the exact degree of severity and prognosticating the extent of neurologic recovery are challenging. Functional neurologic measures are currently used to stratify injury severity and predict neurologic outcome. However, these measures are often impossible to determine in acutely injured patients. Additionally, for patients deemed to be of a specific injury severity, the variability in spontaneous neurologic recovery is high. Both of these issues severely impair the ability to perform clinical trials in novel therapies for SCI. Biomarkers that could more precisely define the severity of injury and better predict neurologic outcome would be extremely valu-able. Furthermore, biological surrogate outcomes measures would be very useful in small preliminary clinical trials of novel therapies if they could inform decisions around the therapeutic regimen for subsequent larger clinical trials. This review highlights our ongoing work in establishing biomark-ers for SCI using cerebrospinal fluid samples from acutely injured patients.
Platelet function testing in hirudin and BAPA anticoagulated blood
Authors: Mani Helen , Hellis Mirna , Lindhoff-Last Edelgard
Published: December 2010

Background: Sodium citrate is the most commonly used anticoagulant for platelet function testing. However, the use of citrated blood for platelet function analysis has been criticized due to creation of a non-physiological milieu. Moreover, platelet function measurements performed with citrated blood need to be completed within 4 h after blood collection. Alternatively, hirudin and recently, a dual thrombin/factor Xa inhibitor benzylsulfonyl-d-Arg-Pro-4-amidinobenzylamide (BAPA), can be used to improve the reactivity after prolonged storage of platelets. The present study investigated platelet function tests using hirudin and BAPA anticoagulated blood.

Methods: Blood was obtained from 30 healthy individuals and 20 patients on aspirin or clopidogrel therapy, and stored for 2, 12, 24 or 48 h. Light transmission aggregometry and impedance platelet aggregometry were performed using adenosine 5-diphosphate (ADP) and arachidonic acid as agonists. The vasodilator stimulated phosphoprotein (VASP) phosphorylation assay was evaluated.

Results: Platelet aggregation measurements of healthy individuals and patients showed stable platelet aggregation values induced by arachidonic acid, after 24 h, when hirudin or BAPA anticoagulated blood was used. However, citrated blood resulted in significantly reduced platelet response after 12 h. ADP-induced light transmission aggregation of healthy individuals and patients exhibited unchanged platelet aggregation after 12 h using hirudin or BAPA anticoagulated blood, while significantly reduced platelet response was observed after 12 h when using citrated blood. In contrast, measurement of ADP-induced aggregation by use of impedance aggregometry resulted in reduced stability over 12 h using hirudin or BAPA anticoagulated blood. The VASP assay exhibited no significant changes in results over a storage period of 48 h, independent of the anticoagulants used.

Conclusions: Use of hirudin or BAPA anticoagulated blood resulted in improvement of stability of platelet function measurements.
Serum cholesterol measured by isotope dilution liquid chromatography tandem mass spectrometry
Authors: Zhou Weiyan , Li Hongxia , Dong Jun , Wang Shu , Yang Ruiyue , Zhang Chuanbao , Chen Wenxiang
Published: December 2010

Background: Accurate cholesterol measurements are essential for the prevention and management of cardiovascular diseases. Quality assurance of cholesterol measurements requires reference methods.

Methods: An isotope dilution liquid chromatography mass spectrometric (ID/LC/MS) method was developed. Serum samples were sampled volumetrically using automated dilutors, treated with potassium hydroxide and equilibrated with 3,4-13C2 cholesterol. The natural cholesterol and the internal standard were extracted with hexane and oxidized to cholest-4-en-3,6-diones with chromic acid. The oxidation products were separated on reversed phase LC and detected by tandem MS. The method was calibrated using aqueous cholesterol calibrators and the calibration function was established with a polynomial regression.

Results: The correlation coefficients of the calibration curves were always >0.9999. The coefficients of variation (CV) of the volumetric sampling and the LC/MS analysis averaged 0.22% and 0.50%, respectively, and the total measurement CV was 0.60%. Other sources of measurement uncertainty were minor. Results on certified reference materials agreed within 1% of the certified values.

Conclusions: An ID/LC/MS method for serum cholesterol has been developed. The method is simple and accurate and may be used as a candidate reference method.
Performance Characteristics of a Dual Fuel Engine Operated with Mahua Biodiesel and Liquefied Petroleum Gas
Authors: Kapilan N. , Babu T. P. Ashok , Reddy R. P.
Published: December 2010

Fuel crisis because of dramatic increase in vehicular population and environmental concerns have renewed the interest of the scientific community to look for alternative fuels of bio-origin such as vegetable oils and ethanol. India is looking at biodiesel derived from Mahua oil (MO), as one of the renewable alternative fuels for compression ignition (CI) engine. Although MO biodiesel (MOB) has several advantages over fossil diesel, in the present scenario, the use of biodiesel is restricted due to its high cost. In India, liquefied petroleum gas (LPG) is easily available and is one of the cheapest gaseous fuels. Hence, use of LPG to fuel a CI engine along with MOB seems to be an option for substitution of fossil diesel. In the present work, LPG, which was fumigated along with the air and biodiesel was admitted into the engine cylinder through conventional fueling device as an igniter. A single cylinder CI engine was modified to work in dual fuel mode and engine tests were carried out at rated speed under variable load conditions. The performance of the engine in dual fuel mode was compared with the diesel. The dual fuel operation results in thermal efficiency close to the diesel and also reduces the NOx and smoke emissions significantly. From the experimental results, we concluded that biodiesel in dual fuel mode with cheaper gaseous fuel induction is an option for reducing the operating cost of the biodiesel fuelled CI engine.
Overlap of quantitative trait loci for early growth rate, and for body weight and age at onset of sexual maturity in chickens
Authors: Podisi B K , Knott S A , Dunn I C , Law A S , Burt D W , Hocking P M
Published: December 2010

Critical age, weight and body composition have been suggested as necessary correlates of sexual maturity. A genome scan to identify quantitative trait loci (QTL) for age and body weight at first egg (AFE and WFE) was conducted on 912 birds from an F2broiler–layer cross using 106 microsatellite markers. Without a covariate, QTL for body WFE were detected on chromosomes 2, 4, 8, 27 and Z and a single QTL for AFE was detected on chromosome 2. With AFE as a covariate, additional QTL for body WFE were found on chromosomes 1 and 13, with abdominal fat pad as covariate a QTL for body WFE was found on chromosome 1. With body WFE as covariate, additional QTL for AFE were found on chromosomes 1, 3, 4, 13 and 27. The QTL generally acted additively and there was no evidence for epistasis. Consistent with the original line differences, broiler alleles had positive effects on body WFE and negative effects on AFE, whereas the phenotypic correlation between the two traits was positive. The mapped QTL for body WFE cumulatively accounted for almost half the body weight difference between the chicken lines at puberty. Overlapping QTL for body WFE and body weight to 9 weeks of age indicate that most QTL affecting growth rate also affect body WFE. The co-localisation of QTL for body weight, growth and sexual maturity suggests that body weight and growth rate are closely related to the attainment of sexual maturity and that the genetic determination of growth rate has correlated effects on puberty.
Reduced progesterone concentration during growth of the first follicular wave affects embryo quality but has no effect on embryo survival post transfer in lactating dairy cows
Authors: Rivera Fernando A , Mendonça Luís G D , Lopes Gláucio , Santos José E P , Perez Rolando V , Amstalden Marcel , Correa-Calderón Abelardo , Chebel Ricardo C
Published: December 2010

Fertility of lactating dairy cows is associated with reduced progesterone (P4) concentration compared with nonlactating animals. The objective of the current study was to determine whether P4 during growth of the first follicular wave (FFW) affects embryo quality. Lactating Holstein cows at 33±3 days post partum were allocated to one of three treatments. Cows in the FFW and FFW with P4 (FFWP) treatments started the superstimulation protocol on day 1 of the estrous cycle and second follicular wave (SFW) cows started the superstimulation protocol on estrous cycle day 7. Cows were superstimulated with 400 mg of NIH-FSH-P1 (FSH) given twice daily for 5 days, two prostaglandin F2α (PGF2α) injections given with the ninth and tenth injections of FSH, GNRH given 48 h after the first PGF2α injection, and timed insemination 12 and 24 h after the GNRH injection. Cows in the FFWP treatment received two intravaginal P4 inserts during the superstimulation. Embryos were recovered 6.5 days after artificial insemination and excellent/good and fair embryos were frozen and transferred. Blood was sampled daily from estrous cycle day 0 until insemination from donor cows. During the superstimulation protocol, P4 was (P<0.01) greatest for SFW cows followed by FFWP and FFW cows respectively. The percentage of embryos–oocytes from SFW and FFWP cows classified as excellent/good and fair embryos was (P=0.02) greater than those of FFW cows. Pregnancy per embryo transfer was not (P≥0.73) affected by embryo donor treatment. Reduced embryo quality of cows induced to ovulate the follicles from the first follicular wave is a consequence of reduced P4 during follicle growth.
Characterization and biological activity of relaxin in porcine milk
Authors: Frankshun Amy-Lynn , Ho Teh-Yuan , Reimer David C , Chen Joseph , Lasano Salamia , Steinetz Bernard G , Bartol Frank F , Bagnell Carol A
Published: December 2010

A lactocrine mechanism for delivery of maternally derived relaxin (RLX) into the neonatal circulation as a consequence of nursing was proposed for the pig. Immunoreactive RLX was detected in colostrum and in the serum of newborn pigs only if they were allowed to nurse. Milk-borne RLX concentrations are highest during early lactation (9–19 ng/ml), declining to <2 ng/ml by postnatal day 14. Whether milk-borne RLX is bioactive is unknown. Evidence that RLX concentrations in milk are higher than in maternal circulation in several species suggests the mammary gland as a site of local RLX production. It is unknown whether the porcine mammary gland is a source of RLX. Therefore, objectives were to evaluate RLX bioactivity in porcine milk during the first 2 weeks of lactation, identify the form of RLX in porcine milk, and determine whether mammary tissue from early lactation is a source of milk-borne RLX. Milk RLX bioactivity was determined using anin vitrobioassay in which cAMP production by human embryonic kidney (HEK293T) cells transfected with the human RLX receptor (RXFP1) was measured. RLX bioactivity was highest at lactation day (LD) 0, decreasing to undetectable levels by LD 4. Immunoblot analysis of milk proteins revealed an 18 kDa band, indicating proRLX as the primary form of RLX in porcine milk. ProRLX protein and transcripts were detected in porcine mammary tissue on LD 0 and 7. Results support the lactocrine hypothesis by defining the nature and a potential source for bioactive proRLX in porcine colostrum/milk.