bluuebunny/crossref_metadata_2025 huggingface dataset:
Baerveldt glaucoma implants in the management of refractory glaucoma after vitreous surgery
Authors: Van Aken Elisabeth , Lemij Hans , Vander Haeghen Yves , De Waard Peter
Published: December 2008

Purpose:  To examine the effectiveness and safety of Baerveldt glaucoma implants in eyes with refractory glaucoma following vitrectomy.

Methods:  We performed a retrospective study of a non‐comparative case series of 30 eyes of 30 patients who had undergone the implantation of a Baerveldt glaucoma device. All eyes (30/30) had a minimum follow‐up of 6 months, and 16/30 (53%) had a follow‐up of 24 months. Surgical success was defined as intraocular pressure (IOP) < 22 mmHg on the last two follow‐up visits with or without glaucoma medication and a decrease in IOP of at least 20% compared to preoperative values with or without glaucoma medication.

Results:  The mean IOP before implantation of a Baerveldt glaucoma device was 30 mmHg [± 11.4 mmHg standard deviation (SD)] with maximally tolerated medical therapy. Six months after implantation of the Baerveldt glaucoma device, the mean IOP was 17.3 mmHg (± 6.7 mmHg SD) and the mean number of glaucoma medications had gone down from 3.0 (± 0.4 SD) to 0.3 (± 0.3 SD). Successful outcomes were found in 24 eyes (80%). Small complications occurred in six eyes (20%): transient postoperative hypotony (17%) and tube retraction (3%). Larger complications occurred in another six eyes (20%): corneal decompensation requiring keratoplasty (7%), suprachoroidal haemorrhage (3%) and persistently high IOP (10%).

Conclusion:  Baerveldt glaucoma devices are a valid treatment option in eyes with refractory glaucoma after vitreous surgery, although failure occurred in 20% of our patients. Transient complications occurred in 20% and severe complications in another 20%.
Comparison of Kinematics, Kinetics, and EMG Throughout Wheelchair Propulsion in Able-Bodied and Persons With Paraplegia: An Integrative Approach
Authors: Dubowsky Sarah R. , Sisto Sue Ann , Langrana Noshir A.
Published: December 2008

A systematic integrated data collection and analysis of kinematic, kinetic, and electromyography (EMG) data allow for the comparison of differences in wheelchair propulsion between able-bodied individuals and persons with paraplegia. Kinematic data from a motion analysis system, kinetic data from force-sensing push rims, and electromyography data from four upper-limb muscles were collected for ten push strokes. Results are as follows: Individuals with paraplegia use a greater percentage of their posterior deltoids, biceps, and triceps in relation to maximal voluntary contraction. These persons also reached peak anterior deltoid firing nearly 10 deg earlier on the push rim, while reaching peak posterior deltoid nearly 10 deg later on the push rim. Able-bodied individuals had no triceps activity in the initial stages of propulsion while their paraplegic groups had activity throughout. Able-bodied participants also had, on average, peak resultant, tangential, and radial forces occurring later on the push rim (in degrees). There are two main conclusions that can be drawn from this integrative investigation: (1) A greater “muscle energy,” as measured by the area under the curve of the percentage of EMG throughout propulsion, results in a greater resultant joint force in the shoulder and elbow, thus potentially resulting in shoulder pathology. (2) Similarly, a greater muscle energy may result in fatigue and play a factor in the development of shoulder pain and pathology over time; fatigue may compromise an effective propulsive stroke placing undue stresses on the joint capsule. Muscle activity differences may be responsible for the observed kinematic and kinetic differences between the two groups. The high incidence of shoulder pain in manual wheelchair users as compared to the general population may be the result of such differences, although the results from this biomedical investigation should be examined with caution. Future research into joint forces may shed light on this. Further investigation needs to focus on whether the pattern of kinematics, kinetics, and muscle activity during wheelchair propulsion is compensatory or evolutionary by tracking individuals longitudinally.
Elastic Anisotropy of Human Cortical Bone Secondary Osteons Measured by Nanoindentation
Authors: Franzoso Giampaolo , Zysset Philippe K.
Published: December 2008

The identification of anisotropic elastic properties of lamellar bone based on nanoindentation data is an open problem. Therefore, the purpose of this study was to develop a method to estimate the orthotropic elastic constants of human cortical bone secondary osteons using nanoindentation in two orthogonal directions. Since the indentation modulus depends on all elastic constants and, for anisotropic materials, also on the indentation direction, a theoretical model quantifying the indentation modulus from the stiffness tensor of a given material was implemented numerically (Swadener and Pharr, 2001, “Indentation of Elastically Anisotropic Half-Spaces by Cones and Parabolae of Revolution,” Philos. Mag. A, 81(2), pp. 447–466). Nanoindentation was performed on 22 osteons of the distal femoral shaft: A new holding system was designed in order to indent the same osteon in two orthogonal directions. To interpret the experimental results and identify orthotropic elastic constants, an inverse procedure was developed by using a fabric-based elastic model for lamellar bone. The experimental indentation moduli were found to vary with the indentation direction and showed a marked anisotropy. The estimated elastic constants showed different degrees of anisotropy among secondary osteons of the same bone and these degrees of anisotropy were also found to be different than the one of cortical bone at the macroscopic level. Using the log-Euclidean norm, the relative distance between the compliance tensors of the estimated mean osteon and of cortical bone at the macroscopic level was 9.69%: Secondary osteons appeared stiffer in their axial and circumferential material directions, and with a greater bulk modulus than cortical bone, which is attributed to the absence of vascular porosity in osteonal properties. The proposed method is suitable for identification of elastic constants from nanoindentation experiments and could be adapted to other (bio)materials, for which it is possible to describe elastic properties using a fabric-based model.
A Nonintrusive Method of Measuring the Local Mechanical Properties of Soft Hydrogels Using Magnetic Microneedles
Authors: Chippada Uday , Yurke Bernard , Georges Penelope C. , Langrana Noshir A.
Published: December 2008

Soft hydrogels serving as substrates for cell attachment are used to culture many types of cells. The mechanical properties of these gels influence cell morphology, growth, and differentiation. For studies of cell growth on inhomogeneous gels, techniques by which the mechanical properties of the substrate can be measured within the proximity of a given cell are of interest. We describe an apparatus that allows the determination of local gel elasticity by measuring the response of embedded micron-sized magnetic needles to applied magnetic fields. This microscope-based four-magnet apparatus can apply both force and torque on the microneedles. The force and the torque are manipulated by changing the values of the magnetic field at the four poles of the magnet using a feedback circuit driven by LABVIEW. Using Hall probes, we have mapped out the magnetic field and field gradients produced by each pole when all the other poles are held at zero magnetic field. We have verified that superposition of these field maps allows one to obtain field maps for the case when the poles are held at arbitrary field values. This allows one to apply known fields and field gradients to a given microneedle. An imaging system is employed to measure the displacement and rotation of the needles. Polyacrylamide hydrogels of known elasticity were used to determine the relationship between the field gradient at the location of the needles and the force acting on the needles. This relationship allows the force on the microneedle to be determined from a known field gradient. This together with a measurement of the displacement of the needle in a given gel allows one to determine the stiffness (F∕δ) of the gel and the elastic modulus, provided Poison’s ratio is known. Using this method, the stiffness and the modulus of elasticity of type-I collagen gels were found to be 2.64±0.05nN∕μm and 284.6±5.9Pa, respectively. This apparatus is presently being employed to track the mechanical stiffness of the DNA-cross-linked hydrogels, developed by our group, whose mechanical properties can be varied on demand by adding or removing cross-linker strands. Thus a system that can be utilized to track the local properties of soft media as a function of time with minimum mechanical disturbance in the presence of cells is presented.
A Conserved Molecular Framework for Compound Leaf Development
Authors: Blein Thomas , Pulido Amada , Vialette-Guiraud Aurélie , Nikovics Krisztina , Morin Halima , Hay Angela , Johansen Ida Elisabeth , Tsiantis Miltos , Laufs Patrick
Published: December 2008

Diversity in leaf shape is produced by alterations of the margin: for example, deep dissection leads to leaflet formation and less-pronounced incision results in serrations or lobes. By combining gene silencing and mutant analyses in four distantly related eudicot species, we show that reducing the function of
NAM
/
CUC
boundary genes (
NO APICAL MERISTEM
and
CUP-SHAPED COTYLEDON
) leads to a suppression of all marginal outgrowths and to fewer and fused leaflets. We propose that
NAM/CUC
genes promote formation of a boundary domain that delimits leaflets. This domain has a dual role promoting leaflet separation locally and leaflet formation at distance. In this manner, boundaries of compound leaves resemble boundaries functioning during animal development.
B:2a:P1.5 Meningococcal Strains Likely Arisen from Capsular Switching Event Still Spreading in Spain
Authors: Castilla Jesús , Vázquez Julio A. , Salcedo Celia , García Cenoz Manuel , García Irure José Javier , Torroba Luis , Beristain Xabier , Abad Raquel , Barricarte Aurelio
Published: December 2008

Eighteen clustered cases of meningococcal disease associated with B:2a:P1.5 strains doubled the annual incidence up to 4.3 × 10
5
in Navarra, Spain, in 2007. Eleven percent of cases were fatalities, and 74% of cases were individuals 10 to 24 years old. This is the third cluster associated with this strain in northern Spain since 2001.
Utility of Pyrosequencing in Identifying Bacteria Directly from Positive Blood Culture Bottles
Authors: Jordan J. A. , Jones-Laughner J. , Durso M. B.
Published: December 2008

Growth in liquid media is the gold standard for detecting microorganisms associated with bloodstream infections. The Gram stain provides the first clue as to the etiology of infection, with phenotypic identification completed 1 or 2 days later. Providing more detailed information than the Gram stain can impart, and in less time than subculturing, would allow the use of more directed empirical therapy and, thus, reduce the patient's exposure to unnecessary or ineffective antibiotics sooner. The study had two objectives, as follows: (i) to identify new targets to improve our ability to differentiate among certain enteric gram-negative rods or among certain
Streptococcus
species and (ii) to determine whether real-time PCR and pyrosequencing could as accurately identify organisms directly from positive blood culture bottles as culture-based methods. Two hundred and fifty-five consecutive positive blood culture bottles were included. The results showed a high level of agreement between the two approaches; of the 270 bacteria isolated from the 255 blood culture bottles, results for pyrosequencing and culture-based identifications were concordant for 264/270 (97.8%) bacteria with three failed sequences, and three sequences without match. Additionally, compared to the universal 16S rRNA gene target, the new 23S rRNA gene targets greatly improved our ability to differentiate among certain enteric gram-negative rods or among certain
Streptococcus
species. In conclusion, combining real-time PCR and pyrosequencing provided valuable information beyond that derived from the initial Gram stain and in less time than phenotypic culture-based identification. This strategy, if implemented, could result in a more directed empirical therapy in patients and would promote responsible antibiotic stewardship.
Transmission Networks and Population Turnover of Echovirus 30
Authors: Leitch E. C. McWilliam , Bendig J. , Cabrerizo M. , Cardosa J. , Hyypiä T. , Ivanova O. E. , Kelly A. , Kroes A. C. M. , Lukashev A. , MacAdam A. , McMinn P. , Roivainen M. , Trallero G. , Evans D. J. , Simmonds P.
Published: December 2008

Globally, echovirus 30 (E30) is one of the most frequently identified enteroviruses and a major cause of meningitis. Despite its wide distribution, little is known about its transmission networks or the dynamics of its recombination and geographical spread. To address this, we have conducted an extensive molecular epidemiology and evolutionary study of E30 isolates collected over 8 years from a geographically wide sample base (11 European countries, Asia, and Australia). 3Dpol sequences fell into several distinct phylogenetic groups, interspersed with other species B serotypes, enabling E30 isolates to be classified into 38 recombinant forms (RFs). Substitutions in VP1 and 3Dpol regions occurred predominantly at synonymous sites (ratio of nonsynonymous to synonymous substitutions, 0.05) with VP1 showing a rapid substitution rate of 8.3 × 10−3substitutions per site per year. Recombination frequency was tightly correlated with VP1 divergence; viruses differing by evolutionary distances of >0.1 (or 6 years divergent evolution) almost invariably (>97%) had different 3Dpol groups. Frequencies of shared 3Dpol groups additionally correlated with geographical distances, with Europe and South Asia showing turnover of entirely distinct virus populations. Population turnover of E30 was characterized by repeated cycles of emergence, dominance, and disappearance of individual RFs over periods of 3 to 5 years, although the existence and nature of evolutionary selection underlying these population replacements remain unclear. The occurrence of frequent “sporadic” recombinants embedded within VP1 groupings of other RFs and the much greater number of 3Dpol groups than separately identifiable VP1 lineages suggest frequent recombination with an external diverse reservoir of non-E30 viruses.
Level of Herpes Simplex Virus Type 1 Latency Correlates with Severity of Corneal Scarring and Exhaustion of CD8+T Cells in Trigeminal Ganglia of Latently Infected Mice
Authors: Mott Kevin R. , Bresee Catherine J. , Allen Sariah J. , BenMohamed Lbachir , Wechsler Steven L. , Ghiasi Homayon
Published: December 2008

A hallmark of infection with herpes simplex virus type 1 (HSV-1) is the establishment of latency in ganglia of the infected individual. During the life of the latently infected individual, the virus can occasionally reactivate, travel back to the eye, and cause recurrent disease. Indeed, a major cause of corneal scarring (CS) is the scarring induced by HSV-1 following reactivation from latency. In this study, we evaluated the relationship between the amount of CS and the level of the HSV-1 latency-associated transcript (LAT) in trigeminal ganglia (TG) of latently infected mice. Our results suggested that the amount of CS was not related to the amount of virus replication following primary ocular HSV-1 infection, since replication in the eyes was similar in mice that did not develop CS, mice that developed CS in just one eye, and mice that developed CS in both eyes. In contrast, mice with no CS had significantly less LAT, and thus presumably less latency, in their TG than mice that had CS in both eyes. Higher CS also correlated with higher levels of mRNAs for PD-1, CD4, CD8, F4/80, interleukin-4, gamma interferon, granzyme A, and granzyme B in both cornea and TG. These results suggest that (i) the immunopathology induced by HSV-1 infection does not correlate with primary virus replication in the eye; (ii) increased CS appears to correlate with increased latency in the TG, although the possible cause-and-effect relationship is not known; and (iii) increased latency in mouse TG correlates with higher levels of PD-1 mRNA, suggesting exhaustion of CD8+T cells.
Geochemistry of the Lower Cretaceous Chaswood Formation, Nova Scotia, Canada: provenance and diagenesisGeological Survey of Canada Contribution 20080004.
Authors: Piper David J.W. , Pe-Piper Georgia , Ledger-Piercey Shannon
Published: December 2008

The fluvial Chaswood Formation records a complex history of tectonic reactivation of basement horsts and shedding of clastic sediment. Previous mineralogical studies indicate sources from both local and more distant basement rocks of the Appalachians. Because such mineralogical studies identify only particular source rocks, the geochemistry of 60 samples from a complete section through the Chaswood Formation in borehole RR-97-23 was investigated to determine the character of bulk sediment supply. The detrital signature is partially obscured by diagenetic processes that caused concentration of K, P, Sr, and U at three regional unconformities. The elements Ti (in ilmenite and its alteration products), Zr (in zircon), Th, and Y are largely controlled by the abundance of heavy minerals in the rocks. Ilmenite is the dominant first-cycle heavy mineral, whereas much of the zircon is of polycyclic origin; therefore, the Ti/Zr ratio is a guide to the proportion of first-cycle sediment supply from crystalline basement. High Cr, Sr, and Ni/Co ratio in mudstones appear related to supply from weathered mafic crystalline basement. Three cycles of sediment supply are recognized, each overlying a regional unconformity. These reflect uplift of horsts that resulted first in shedding of readily eroded Carboniferous sandstones, then rapid erosion of crystalline basement and, finally, greater supply of deeply weathered regolith. This study provides a template for interpreting more distal sediments in the Scotian Basin, where the direct effects of source-area tectonics are not recorded in the stratigraphic succession.
Basin architecture and syndepositional fault activity during deposition of the Neoproterozoic Mackenzie Mountains supergroup, Northwest Territories, CanadaNorthwest Territories Geoscience Office Contribution 0040.
Authors: Turner Elizabeth C. , Long Darrel G.F.
Published: December 2008

The early Neoproterozoic Mackenzie Mountains supergroup (MMSG; ∼4 km thick, <1083 Ma, >779 Ma) was deposited in a large but poorly understood basin. Analysis of new and existing stratigraphic data reveals unexpected, abrupt changes in thickness and lithofacies patterns in formation scale and smaller units over short distances parallel and perpendicular to depositional strike. These isopach and lithofacies patterns depict irregularly subsiding syndepositional sub-basins. These basins may have developed during basin extension in a lower-plate segment of an evolving passive margin, as the result of episodic, excessive subsidence along growth faults parallel to the basin margin, and crustal-scale (transfer) faults at a high angle to the margin. The extent of the lower-plate area is inferred to correspond to the distribution of the MMSG (∼500 km strike length); upper-plate segments are inferred to flank the MMSG embayment to the northwest and southeast. A lower-plate model for the arcuate MMSG embayment has important implications for the Mackenzie Mountains zinc district. The present-day regional distribution of known carbonate-hosted base-metal showings suggests that the configuration of the thinned, faulted Neoproterozoic lower-plate segment, together with later reactivation of basement-rooted transfer faults during Neoproterozoic–Paleozoic rifting or Laramide compression, may have been important in focussing metalliferous fluids into overlying units.
Sinusoidal magnetic field stimulates magnetosome formation and affects mamA, mms13, mms6, and magA expression in Magnetospirillum magneticum AMB-1
Authors: Wang Xiaoke , Liang Likun , Song Tao , Wu Longfei
Published: December 2008

Magnetic particles are currently one of the most important materials in the industrial sector, where they have been widely used for biotechnological and biomedical applications. To investigate the effects of the imposed magnetic field on biomineralization in Magnetospirillum magneticum AMB-1 and to suggest a new approach that enhances formation of magnetosomes, cultures inoculated with either magnetic or nonmagnetic precultures were incubated under a sinusoidal magnetic field or geomagnetic field. The results showed that the sinusoidal magnetic field up-regulated mms6 expression in the cultures inoculated with magnetic cells, and magA, mms6, and mamA expression in the cultures inoculated with nonmagnetic cells. The applied sinusoidal magnetic field could block cell division, which could contribute to a decrease in the OD600 values and an increase in the coefficient of magnetism values of the cultures, which could mean that the percentage of mature magnetosome-containing bacteria was increased. The linearity of magnetosome chains was affected, but the number of magnetic particles in cells was increased when a sinusoidal magnetic field was applied to the cultures. The results imply that the variable intensity and orientation of the sinusoidal magnetic field resulted in magnetic pole conversion in the newly forming magnetic particles, which could affect the formation of magnetic crystals and the arrangement of the adjacent magnetosome.
Removal of the lichen mat by reindeer enhances tree growth in a northern Scots pine forest
Authors: Macias Fauria Marc , Helle Timo , Niva Aarno , Posio Heikki , Timonen Mauri
Published: December 2008

Reindeer ( Rangifer tarandus L.) lichen grazing enhanced Scots pine ( Pinus sylvestris L.) growth in a northeastern Fennoscandian forest. Lichen mat removal by grazing in a previously ungrazed area increased soil versus air temperature coupling. This caused faster soil spring warming and higher soil temperatures during late spring and summer, which are related to an earlier start of and better growth conditions during the trees’ growing season. Tree growth was related to spring and summer climate during the study period, 1896–2001. Snowmelt date, and ultimately soil warming and start of the growing season, may have caused the relationships between tree growth and spring climate. A drop in July temperature and an increase in the spring signals were found and attributed to the “divergence problem,” a widespread weakening in the relationships between tree growth and summer temperature in northern latitudes observed in the late 20th century. Differences in the relationships between tree growth and climate were found between trees growing in grazed and ungrazed parts of the stand. Tree growth differences were detected ∼10 years after the removal of the lichen mat. The fertilizing effect of reindeers on tree growth was considered minimal in this study, but its influence cannot be completely ruled out. Grazing intensity may thus be an important component of boreal forest carbon uptake.
Landscape-level variation in forest response to hurricane disturbance across a storm track
Authors: Busby Posy E. , Motzkin Glenn , Boose Emery R.
Published: December 2008

Hurricane wind speeds at a given site are related to the intensity of the storm and the distance and direction from the storm center. As a result, forest damage is expected to vary predictably with respect to location relative to the storm track. To determine whether patterns of forest response along the track of a major hurricane in coastal New England were consistent with the expected patterns of wind damage, we investigated tree growth responses to the storm in several study sites that are similar with respect to site conditions, vegetation, and disturbance history. Growth responses to a severe hurricane in 1944 varied predictably among study sites with respect to distance from the storm track. Sites closest to the storm track experienced lesser wind damage and exhibited minimal growth responses, whereas sites farther east of the storm track and closer to the area of maximum estimated wind speed were characterized by greater wind damage and growth changes. Variation in estimated wind speed among our study sites (5–10 m/s) is not much greater than anticipated increases in hurricane intensity predicted under future climate scenarios (3–7 m/s). Thus, our results suggest that the magnitude of anticipated increases in wind speeds associated with Atlantic hurricanes may be sufficient to cause changes in forest response.
Standardized approaches in effectiveness monitoring programs and regional relevance: lessons from the Bowron River Watershed Riparian Evaluation Project
Authors: Nordin L. J. , Rex J. F. , Maloney D. A. , Tschaplinski P. J.
Published: December 2008

Streams and riparian areas in the Bowron River watershed were assessed using the riparian management routine effectiveness evaluation, a protocol developed for postharvest operational monitoring in British Columbia. Located in the British Columbia interior, the study watershed has had several decades to recover since a period of intensive salvage logging from 1977 to 1987 in response to a spruce beetle ( Dendroctonus rufipennis ) outbreak. Correlations were found with site-specific watershed characteristics and attributes that are used to answer the protocol indicator questions. Channel width was the strongest covariate, exhibiting the most significant relationships with the stream and riparian attributes. Suggestions on how to adjust standard protocols for stream size and landscape heterogeneity are discussed and include the use of appropriate reference sites for baseline data. We used correlations with watershed characteristics and multiple regressions based on regional reference sites to predict upper and lower threshold values by which attribute measurements could be compared. Sites that were assessed above or below threshold values for an attribute were considered to be outside the range of natural variation and were given a failing score. Attributes with the most failures 20–30 years postharvest were disturbed ground, bare soil, undercut banks, and shade.
Is there a middle way between permanent plots and chronosequences?
Authors: Myster Randall W. , Malahy Michael P.
Published: December 2008

Although permanent plots have proven critical to studies of vegetation dynamics, their logistic limitations have led to the wide use of chronosequences as an alternative. Here, we test whether or not an approach combining permanent plots and chronosequences could be used successfully to accurately predict the vegetation changes that one would see in permanent plots in the same area. We used plot data from five pastures in the Luquillo Mountains of Puerto Rico, USA, and found that (i) for species composition and abundance, the five pastures did not form a single trajectory or show any convergence, (ii) for successional rate, there was a general decrease with time since abandonment for most pastures, but that decrease was not monotonic and one pasture of the five had no decrease at all, and (iii) total species richness and total plant cover showed pastures that lined up well by age, forming almost a single trajectory with little variation. We conclude that the utility of using chronosequences either alone or with permanent plots depends largely on the parameter under study with broad structural parameters, such as total species richness and total plant cover, performing best.
Recruitment patterns following a severe drought: long-term compositional shifts in Patagonian forests
Authors: Suarez María L. , Kitzberger Thomas
Published: December 2008

Severe droughts have the potential of inducing transient shifts in forest canopy composition by altering species-specific adult tree mortality patterns. However, permanent vegetation change will occur only if tree recruitment patterns are also affected. Here, we analyze how a massive mortality event triggered by the 1998–1999 drought affected adult and sapling mortality and recruitment in a mixed Nothofagus dombeyi (Mirb.) Blume – Austrocedrus chilensis (D. Don) Flor. et Boult. forests of northern Patagonia. Comparing drought-induced and tree-fall gaps, we assessed changes in forest composition, microenvironments, and seedling density and survival of both species. Drought-kill disturbance shifted species composition of both canopy and sapling cohorts in favour of A. chilensis. Drought gaps were characterized by a shadier and more xeric environment, affecting the recruitment pattern of N. dombeyi seedlings. The seedling cohort was composed mostly of A. chilensis, and its survival was always higher than that of N. dombeyi. Additionally, A. chilensis seedlings showed higher plasticity than N. dombeyi seedlings, increasing its root to shoot ratios in drought gaps. The results suggest that extreme drought itself is a strong driving force in forest dynamics, with important imprints on forest landscapes. Future climate-change scenarios, projecting an increased in frequency and severity of droughts, alert us about expected long-term compositional shifts in many forest ecosystems.
Belowground competition influences growth of natural regeneration in thinned Douglas-fir stands
Authors: Devine Warren D. , Harrington Timothy B.
Published: December 2008

Using a factorial combination of understory removal and trenching treatments, we examined the influences of belowground competition from understory and overstory vegetation on growth of naturally established Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii) saplings in thinned stands of Douglas-fir on moderately productive, glacially derived soils near Tacoma, Washington. Under limited light (26% ± 16% of full sun), sapling height and diameter growth were significantly reduced by belowground competition from overstory trees. Regardless of presence or absence of belowground competition from trees, understory vegetation did not have a detectable effect on sapling growth. Nitrogen deficiency in saplings was not detected in the presence of belowground competition: where tree roots were excluded, foliar nitrogen concentration and content increased without an increase in foliar mass. Belowground competition from overstory trees had a greater negative effect on growing season soil water content than did understory vegetation. Under the conditions of restricted light availability in this study, limitations in soil water content from competition had a strong growth-limiting effect on Douglas-fir regeneration. As potential canopy trees in a future uneven-aged stand, this sapling cohort would benefit from root gaps created during harvests.
IMPACT PARAMETER MODEL FOR GPD
Authors: TROSHIN S. M. , TYURIN N. E.
Published: December 2008

We propose a dynamical model for the unpolarized generalized parton distribution function (GPD) based on impact parameter representation and discuss its x and t dependencies at large and small values of these variables.
DARK ENERGY WITH POLYTROPIC EQUATION-OF-STATE
Authors: MUKHOPADHYAY UTPAL , RAY SAIBAL , DUTTA CHOUDHURY S. B.
Published: December 2008

Equation-of-state parameter plays a significant role for guessing the real nature of dark energy. Here polytropic equation-of-state p = ωρnis chosen for some of the kinematical Λ-models viz., [Formula: see text], [Formula: see text] and Λ ~ ρ. Although in dust cases (ω = 0) closed form solutions show no dependency on the polytropic index n, but in non-dust situations some new possibilities are opened up including phantom energy with supernegative (ω < -1) equation-of-state parameter.
IMPLICATIONS OF THE CRYSTAL BARREL DATA FOR MESON–BARYON SYMMETRIES
Authors: AFONIN S. S.
Published: December 2008

Making use of numerous resonances discovered by the Crystal Barrel collaboration, we discuss some possible relations between the baryon and meson spectra of resonances composed of the light non-strange quarks. Our goal is to indicate new features that should be reproduced by the realistic dynamical models describing the hadron spectrum in the sector of light quarks.
THE CURRENT CHARACTERISTICS OF TWO-STATE FLASHING RATCHETS COMPOSED OF TWO ASYMMETRIC POTENTIALS
Authors: GAO TIANFU , ZHANG YUE , CHEN JINCAN
Published: December 2008

The transport of Brownian particles in two-state flashing ratchets composed of two asymmetric potentials with the same period is investigated. The analytic expression of a probability current is derived by using the power series expansion method and used to generate the curve characteristics of the current varying with other parameters. The effects of the asymmetric parameters and heights of two potentials and the transition rates between two states on the probability current are discussed in detail. The influence of other parameters on the behaviors of the current is also analyzed. It is found that the current is affected by not only the asymmetric parameters and heights of two potentials but also the transition rates between two states. It is also found that the heights of two potentials may change the magnitude as well as the direction of the current when the transition rates between two states are not the same. It is expected that the results obtained here may be observed in some physical and biological systems.
THE PREDICATES FOR THE EXACT VORONOI DIAGRAM OF ELLIPSES UNDER THE EUCLIDIEAN METRIC
Authors: EMIRIS IOANNIS Z. , TSIGARIDAS ELIAS P. , TZOUMAS GEORGE M.
Published: December 2008

This article examines the computation of the Delaunay graph and its dual Voronoi diagram of a set of ellipses in the Euclidean plane. We propose the first complete methods, under the exact computation paradigm, for the predicates of an incremental algorithm: κ1 decides which one of two given ellipses is closest to a given exterior point; κ2 decides the position of a query ellipse relative to an external bitangent line of two given ellipses; κ3 decides the position of a query ellipse relative to a Voronoi circle of three given ellipses; κ4 determines the type of conflict between a Voronoi edge, defined by four given ellipses, and a query ellipse. The article is restricted to non-intersecting ellipses, but the extension to arbitrary ones is possible.

The ellipses are input in parametric representation, i.e., constructively in terms of their axes, center and rotation. For κ1 and κ2 we derive algebraic conditions optimal in terms of the degree of the algebraic numbers involved, and provide efficient implementations in C++ . For κ3 we compute a tight bound on the number of complex tritangent circles and design an exact symbolic-numeric algorithm, which is implemented in MAPLE. This essentially answers κ4 as well. We conclude with further work on lifting the condition of non-intersecting ellipses.
A SPANNING TREE MODEL FOR KHOVANOV HOMOLOGY
Authors: WEHRLI S.
Published: December 2008

We show that the Khovanov complex of a connected link diagram D retracts to a subcomplex whose generators are in 2:1 correspondence with the spanning trees of the "black graph" of D. Using this result, we give a new proof of Lee's theorem on the support of Khovanov homology of alternating knots.
AN APPLICATION OF TQFT: DETERMINING THE GIRTH OF A KNOT
Authors: HERNÁNDEZ LISA , LIN XIAO-SONG
Published: December 2008

A knot diagram can be divided by a circle into two parts, such that each part can be coded by a planar tree with integer weights on its edges. A half of the number of intersection points of this circle with the knot diagram is called the girth. The girth of a knot is the minimal girth of all diagrams of this knot. The girth of a knot minus one is an upper bound of the Heegaard genus of the 2-fold branched covering of that knot. We will use Topological Quantum Field Theory (TQFT) coming from the Kauffman bracket to determine the girth of some knots. Consequently, our method can be used to determine the Heegaard genus of the 2-fold branched covering of some knots.
Synthesis and Characterization of PdSn Oxygen Reduction Electrocatalyst
Authors: Salvador-Pascual José J. , Chavéz-Carbayar José , Solorza-Feria Omar
Published: December 2008

PdSn synthesized by a NaBH4 reduction of PdCl2 and SnCl2 in a THF solution, was examined as electrocatalyst for the oxygen reduction reaction (ORR) in acid media by rotating disk electrode (RDE). The structure, morphology and composition of the catalyst were characterized by using XRD, SEM, TEM and AFM techniques. Nanocrystalline particles with less than 10 nm in size were observed. The PdSn catalysts exhibited high current densities for the ORR compared to that of pure Pd catalysts. The effect of temperature on the kinetics was analyzed with an apparent activation energy of 53.18 {plus minus} 0.08 kJ mol-1.
Voltammetric Formation of Polyaniline on Gold and Platinum under Static and Forced Convection Conditions
Authors: Zafra-Roldan Alejandrina , Garfias-García Elizabeth , Romero-Romo Mario A. , Ramírez-Silva Maria T. , Palomar-Pardavé Manuel E.
Published: December 2008

The present research work studied the formation of conducting polyaniline (PANI) films in acid media. Cyclic voltammetry, under static and forced convection conditions were used for the polymer electrodeposition onto different working electrodes: gold and platinum. It was observed that during the first voltammetric cycle, under static conditions, the aniline oxidation potential is independent of the substrate; although after the first cycle, it was observed that PANI than oxidation process occurs at a smaller potential on the gold electrode, compared to that taking place on platinum, which suggests that different aniline oligomeric species had been deposited on the electrodes surfaces. So far, the results obtained under forced convection conditions indicate a current density increment associated to the first oxidation branch, although subsequently, as the rotation rate increased the polyaniline growth did not occur.
Neutralizing Amines Effect on Corrosion Process of Carbon Steel Exposed in Acid Sour Media
Authors: Quej-Aké L. , Sierra Román C. , Arce Elsa M. , Marín Jesús
Published: December 2008

To control the corrosion process in primary distillation towers by the influence of acid sour media (HCl+H2S), neutralizing compounds are widely used in oilfield. Amines typically used are Monoethanol Amine (MEA), Ethylenediamine (E), Ethylenediamine at 60% (E60) and 2-ethylhexillamine (2-EH), being the first one the most used. In this work Electrochemical Impedance Spectroscopy (EIS) technique is used to study the amines concentration effect on carbon steel corrosion process in sour solution (0.5 M HCl + 500 ppm of H2S at 40 oC, pH 2). The quantitative analysis of EIS diagrams showed an active behavior of the interface without amine. Furthermore, metal activity increases in presence of MEA and E. However, at different dosages (5, 15 and 30 ppm) both E60 and 2-EH amines, exhibit a positive effect to control corrosion. Finally, EIS analysis is supported by scanning electron microscopy (SEM) characterization.
Analysis of Copper Diffusion Processes Using Impedance Data
Authors: Bastidas David M. , Cano Emilio , Fajardo Santiago , Bastidas Jose M.
Published: December 2008

The corrosion of a copper electrode in a 5% HCl solution is analyzed using impedance data recorded at the corrosion potential. A straight line is observed at high frequencies, attributed to a diffusion process in the film covering the copper surface. This line curls down towards the real axis at intermediate frequencies, drawing a depressed quarter lemmiscate. The impedance plot is completed by a second straight line at very low frequencies.
Electrochemical Corrosion Behavior of UNS S30403 Weldments in Seawater
Authors: Santillan Nestor , Valdez Benjamin , Schorr Miguel , Carrillo Monica , Martinez Alejandro
Published: December 2008

The results of electrochemical measurements performed on austenitic stainless steel weldments exposed to synthetic seawater and polluted seawater are presented. The test zones were classified as stainless steel base metal (UNS S30403 annealed), welding zone and heat affected zone (HAZ), in order to analyze the effect of different microstructures on the corrosion behavior. The HAZ showed high corrosion susceptibility in the synthetic seawater test. Welded specimens immersed in polluted seawater display a large biofouling deposit and localized corrosion induced by organisms adhered to the surface.
Effect of Flow on the Electrochemical Behavior of Zn Galvanic Anodes in Artificial Seawater Media
Authors: Garcia-Roldan Vicente , Genesca Juan
Published: December 2008

The effect of hydrodynamics on the corrosion of a commercial Zn galvanic anode in artificial seawater media at room temperature was studied in a RCE system under turbulent flow conditions. Five different rotation rates were studied: 0, 1000, 3000, 5000 and 7000 rpm. The corrosion rates were measured by Linear Polarization Resistance Technique. For the system studied, the steady-state corrosion potential increased with increasing RCE rotation rate. The effect of increasing the rotation rate is to increase the availability of oxygen at the surface, which in turn will polarize the corrosion reaction in the more noble direction. The corrosion rate increases with increasing velocity over the range of rotational rates studied. This reflects the fact that the rate of corrosion is controlled, at least in part, by the rate of mass transfer. In this case, the effect of increasing RCE rotation rate on the corrosion rate is to increase the interfacial concentration of the reactant (oxygen).
Electrochemical Response of Carbon Electrodes Modified with Zeolites
Authors: Davila Martin M. , Pérez María A. , De la Paz Elizalde María
Published: December 2008

In this work we studied the electrochemical behavior of a glassy carbon electrode modified with natural and synthetic zeolites. Iron exchanged zeolites were set up for the detection of arsenic species. The electrochemical response both in KCl and HCl 0.1 M of the electrodes after modification was investigated by cyclic and differential pulse voltammetry. The electrochemical parameters of the redox pairs Fe3+/Fe2+ and Fe2+/Fe0 were determined for the iron containing electrode and the effect of repetitive potential cycling on the formation of iron oxides was studied. The reactivity of the exchanged iron species in the zeolite and the reduction of the complex As(V)-iron generated in-situ could be demonstrated.
Structural, gene expression, and functional analysis of the fugu (Takifugu rubripes) insulin-like growth factor binding protein-4 gene
Authors: Li Mingyu , Li Yun , Lu Ling , Wang Xianlei , Gong Qingli , Duan Cunming
Published: December 2008

The insulin-like growth factor (IGF) signaling pathway is a conserved pathway that regulates animal development, growth, metabolism, reproduction, and aging. The biological actions of IGFs are modulated by IGF-binding proteins (IGFBPs). Although the structure and function of fish IGFBP-1, -2, -3, and -5 have been elucidated, there is currently no report on the full-length structure of a fish IGFBP-4 nor its biological action. In this study, we cloned and characterized the IGFBP-4 gene from fugu. Sequence comparison, phylogenetic, and synteny analyses indicate that its chromosomal location, gene, and protein structure are similar to its mammalian orthologs. Fugu IGFBP-4 mRNA was easily detectable in all adult tissues examined with the exception of spleen. Older animals tended to have higher levels of IGFBP-4 mRNA in the muscle and eyes compared with younger animals. Starvation resulted in significant increases in IGFBP-4 mRNA abundance in the muscle, liver, gallbladder, and brain. Overexpression of fugu and human IGFBP-4 in zebrafish embryos caused a significant decrease in body size and somite number, suggesting that fugu IGFBP-4 inhibits growth and development, possibly by binding to IGFs and inhibiting their binding to the IGF receptors. These results provide new information about the structural and functional conservation, expression patterns, and physiological regulation of the IGFBP-4 gene in a teleost fish.
Hypocapnia increases the prevalence of hypoxia-induced augmented breaths
Authors: Bell Harold J. , Ferguson Carrie , Kehoe Valerie , Haouzi Philippe
Published: December 2008

Augmented breaths promote respiratory instability and have been implicated in triggering periods of sleep-disordered breathing. Since respiratory instability is well known to be exacerbated by hypocapnia, we asked whether one of the destabilizing effects of hypocapnia might be related to an increased prevalence of augmented breaths. With this question in mind, we first sought to determine whether hypoxia-induced augmented breaths are more prevalent when hypocapnia is also present. To do this, we studied the breath-by-breath ventilatory responses of a group of freely behaving adult rats in a variety of different respiratory background conditions. We found that the prevalence of augmented breaths was dramatically increased during hypocapnic-hypoxia compared with room air conditions. When hypocapnia was prevented during exposure to hypoxia by adding 5% CO2 to the inspired air, the rate of occurrence of augmented breaths was no greater than that observed in room air. The addition of CO2 alone to room air had no effect on the prevalence of augmented breaths. We conclude that in spontaneously breathing rats, hypoxia promotes the generation of augmented breaths, but only in poikilocapnic conditions, where hypocapnia develops. Our results, therefore, reveal a means by which CO2 exerts a stabilizing influence on breathing, which may be of particular relevance during sleep in conditions commonly associated with respiratory instability.
Dual simulated childbirth injury delays anatomic recovery
Authors: Pan Hui Q. , Kerns James M. , Lin Dan L. , Sypert David , Steward James , Hoover Christopher R. V. , Zaszczurynski Paul , Butler Robert S. , Damaser Margot S.
Published: December 2008

A dual childbirth injury model, including vaginal distension (VD) and pudendal nerve crush (PNC), may best represent the injuries seen clinically. The objective of this study was to investigate urethral function, anatomy, and neurotrophin expression after several simulated childbirth injuries. Groups of 140 rats underwent PNC, VD, PNC+VD, or neither (C). Four days after injury, all injury groups had significantly decreased leak-point pressure (LPP) compared with C rats. Ten days after injury, LPP in PNC and PNC+VD rats remained significantly lower than C rats. Three weeks after injury, LPP in all injury groups had recovered to C values. Histological evidence of injury was still evident in the external urethral sphincter (EUS) after VD and PNC+VD 10 days after injury. Three weeks after injury, the EUS of PNC+VD rats remained disrupted. One day after VD, brain-derived neurotrophic factor (BDNF) expression in the EUS was reduced, while neurotrophin-4 (NT-4) and nerve growth factor (NGF) expression was unchanged. BDNF, NT-4, and NGF expression was dramatically upregulated in the EUS after PNC. After PNC+VD, NGF expression was upregulated, and BDNF and NT-4 expression was upregulated somewhat but not to the same extent as after PNC. Ten days after injury, PNC+VD had the least number of normal nerve fascicles near the EUS, followed by PNC and VD. Twenty-one days after injury, all injury groups had fewer normal nerve fascicles, but without significant differences compared with C rats. PNC+VD therefore provides a more severe injury than PNC or VD alone.