bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly efficient, polymerizable, sulfur‐containing photoinitiator comprising a structure of planar N‐phenylmaleimide and benzophenone for photopolymerization
Authors: Wang Hongyu , Wei Jun , Jiang Xuesong , Yin Jie
Published: April 2006

In a continuation of research on chemically bonded photoinitiators comprising a structure of planar N‐phenylmaleimide (NPMI) and benzophenone (BP), a novel, highly efficient, polymerizable, sulfur‐containing photoinitiator, 4‐[(4‐maleimido)thiophenyl]benzophenone (MTPBP), was synthesized by the introduction of an NPMI group into BP. Another chemically bonded photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), was selected to evaluate its photoefficiency. The results showed that MTPBP possessed a greatly redshifted UV maximal absorption and a very weak fluorescence emission. Electron spin resonance spectra indicated that the CS bond in its molecule underwent photolysis reactions to generate radicals to initiate the polymerization. Three representative types of different functionality monomers—methyl methacrylate, 1,6‐hexanediol diacrylate, and trimethylolpropane triacrylate—were chosen to be initiated through dilatometry and differential scanning photocalorimetry with unsaturated tertiary amine N,N‐dimethylaminoethyl methacrylate as the coinitiator. The results showed surprisingly high efficiency of MTPBP due to the mutual influence between NPMI and BP as in their physical mixtures and photolysis reactions at the CS bond. Both MPBP and MTPBP behaved with similar regularity toward different monomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3738–3750, 2006
Hybrid Comminution with High‐Pressure Roller and Stirred Bead Milling
Authors: Wang Yanmin , Forssberg Eric , Lin Peng
Published: April 2006

This paper presents the experimental results on the wet grinding of a moist calcium carbonate material in a hybrid comminution system, which consists of a high pressure roller mill (HPRM) and a subsequent stirred bead mill. The results show that the pre‐treatment of the material with the HPRM could result in energy saving and efficient size reduction during the subsequent wet ultra‐fine grinding in the stirred bead mill. It was found that the level of fineness of the ground product is dramatically influenced by the number of repeat passes of pre‐grinding in the HRPM. The formation of micro‐cracks in the particles under compressive loads was discussed in order to elucidate the role of the HRPM as a pre‐grinder in the hybrid comminution system. The simulated breakage behaviors of various irregular shaped particles indicate that the tortuous micro‐crack propagation paths and the crack branching behavior are related to the heterogeneity of the particle and the stress distributions.
Multiple molecular dynamics simulations of human p450 monooxygenase CYP2C9: The molecular basis of substrate binding and regioselectivity toward warfarin
Authors: Seifert Alexander , Tatzel Stephan , Schmid Rolf D. , Pleiss Jürgen
Published: April 2006

To examine the molecular basis of activity and regioselectivity of the clinically important human microsomal cytochrome P450 (CYP) monooxygenase 2C9 toward its substrate warfarin, 22 molecular dynamics simulations (3–5 ns each) were performed in the presence and absence of warfarin. The resulting trajectories revealed a stable protein core and mobile surface elements. This mobility leads to the formation of two surface channels in the region between F‐G loop, B′ helix/B‐B′ loop, β1‐sheet, and between helices F and I and the turn in the C‐terminal antiparallel β‐sheet in the presence of warfarin. Besides the nonproductive state of the CYP2C9 warfarin complex captured in the crystal structure, three additional states were observed. These states differ in the shape of the substrate binding cavity and the position of the warfarin molecule relative to heme. In one of these states, the 7‐ and 6‐positions of warfarin contact the heme with a marked geometrical preference for position 7 over position 6. This modeling result is consistent with experimentally determined regioselectivity (71 and 22% hydroxylation in positions 7 and 6, respectively). Access to the heme group is limited by the core amino acids Ala297, Leu362, Leu366, and Thr301, which therefore are expected to have a major impact on regioselectivity. In addition, modeling predicts that autoactivation of warfarin is sterically hindered. Our study demonstrates how the combination of mobile surface and rigid core leads to interesting properties: a broad substrate profile and simultaneously a high regioselectivity. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Adverse Effects of Citrate/Gold Nanoparticles on Human Dermal Fibroblasts
Authors: Pernodet Nadine , Fang Xiaohua , Sun Yuan , Bakhtina Asya , Ramakrishnan Aditi , Sokolov Jonathan , Ulman Abraham , Rafailovich Miriam
Published: April 2006

Nanoscale engineering is one of the most dynamically growing areas at the interface between electronics, physics, biology, and medicine. As there are no safety regulations yet, concerns about future health problems are rising. We investigated the effects of citrate/gold nanoparticles at different concentrations and exposure times on human dermal fibroblasts. We found that, as a result of intracellular nanoparticle presence, actin stress fibers disappeared, thereby inducing major adverse effects on cell viability. Thus, properties such as cell spreading and adhesion, cell growth, and protein synthesis to form the extracellular matrix were altered dramatically. These results suggest that the internal cell activities have been damaged.
Total Parathyroidectomy Without Autotransplantation for Renal Hyperparathyroidism: Experience with a qPTH‐controlled Protocol
Authors: Lorenz Kerstin , Ukkat Jörg , Sekulla Carsten , Gimm Oliver , Brauckhoff Michael , Dralle Henning
Published: April 2006

Background

Controversy regarding the optimal surgical treatment for secondary hyperparathyroidism (sHPT) continues. Subtotal parathyroidectomy (PTX) with a small remnant and total parathyroidectomy with autotransplantation prevail, although impaired by considerable recurrence rates. Concerns about postoperative management and long‐term supplementation prevent broader acceptance of total parathyroidectomy without autotransplantation.

Materials and Methods

The standardized surgical procedure with intraoperative PTH assessment (qPTH) included cervical thymectomy, histological proof of four parathyroid specimens and obligatory cryopreservation of parathyroid tissue in all 23 patients undergoing total PTX without autotransplantation. Whenever qPTH did not normalize, complete cervical exploration of ectopic sites was performed. Another 64 patients with subtotal PTX for sHPT served as comparison for the postoperative course.

Results

There were 13 primary and 10 completion (5 persistent, 5 recurrent sHPT) total PTX with 14 concurrent thyroid resections performed. Mean preoperative PTH was 1.351 pg/ml (12–72 pg/ml) and serum calcium was 2.5 mmol/l (2.25–2.5 mmol/l). PTH showed intraoperative normalization in 15 patients and a 50% PTH reduction from preoperative values in all. Postoperative course was not significantly different from the subtotal PTX group and showed PTH within the normal range for 5 patients (4 < 35 pg/ml), 7 with PTH < 12 pg/ml, and 4 without measurable PTH. In 4 patients PTH did not normalize postoperatively. Serum calcium levels were below normal in all patients: < 2.25 mmol/l in 9, < 2.00 mmol/l in 7, and <1.8 mmol/l in 6 patients. Only 1 patient required intermittent early postoperative i.v. calcium supplementation, 6 patients received oral calcium and vitamin D supplement for low calcium levels, but no severe hypocalcemic symptoms were encountered. Mean postoperative hospital stay was 5 days. No recurrent laryngeal nerve palsies were encountered. Complications were two cervical bleedings following postoperative hemodialysis requiring evacuation.

Conclusions

Total PTX without autotransplantation proves to be an equally safe and successful procedure for sHPT as subtotal PTX or total PTX with autotransplantation. Measurable PTH after total PTX as demonstrated in this study, supports the idea of uncontrollable isolated cell nests that are inevitably prone to stimulated growth with time. Therefore, total PTX is superior with regard to prevention of recurrence. Adequate supplementation with calcium and vitamin D, often necessary after subtotal PTX to suppress inadequate PTH and protect from recurrence, will prevent severe hypocalcemia and with the modern aluminium‐diminishing dialysis regimen, development of adynamic bone disease appears less likely than feared. If necessary, cryopreserved parathyroid tissue can be autotransplanted on demand.
The role of molecular modelling in biomedical research
Authors: Tramontano Anna
Published: April 2006

The synergy between experimental and computational biology has greatly benefited both fields, providing invaluable information in many different areas of the life sciences. This minireview will focus on one specific aspect of computational biology, molecular modelling, and describe a few examples highlighting the effectiveness of protein structural analysis and modelling in providing relevant information about systems of biomedical interest.
Leader sequence of a plant ribosomal protein gene with complementarity to the 18S rRNA triggers in vitro cap‐independent translation
Authors: Vanderhaeghen Rudy , De Clercq Rebecca , Karimi Mansour , Van Montagu Marc , Hilson Pierre , Van Lijsebettens Mieke
Published: April 2006

Cap‐independent translation (CIT) occurs at the leader sequences of uncapped plant viral RNAs, but also at a number of normally capped cellular mRNAs and has been correlated with sequence complementarity to 18S rRNA. The ribosomal protein S18 (RPS18) is a component of the small ribosomal subunit and is encoded by three gene copies (A, B, and C) in the Arabidopsis thaliana genome. The RPS18C mRNA was most abundant and contained a short 5′ untranslated region of 84 bp that is complementary to a novel putative interaction site at the 3′ end of the 18S rRNA. The RPS18C leader mediated CIT as demonstrated by dicistronic constructs consisting of luciferase and chloramphenicol acetyl transferase reporter genes in an in vitro wheat germ extract system. CIT was rapidly inhibited upon addition of an oligonucleotide that competed for the 18S rRNA site complementary to the RPS18C leader and interfered with polysome assembly at the transcript.
Differential expression of HR38 in the mushroom bodies of the honeybee brain depends on the caste and division of labor
Authors: Yamazaki Yurika , Shirai Kenichi , Paul Rajib Kumar , Fujiyuki Tomoko , Wakamoto Akiko , Takeuchi Hideaki , Kubo Takeo
Published: April 2006

We used a cDNA microarray to identify genes expressed in a caste (worker)‐ and division of labor (nurse bees or foragers)‐dependent manner in the honeybee brain. Among the identified genes, one encoded a putative orphan receptor (HR38) homologue that mediates ecdysteroid‐signaling. Real‐time reverse transcription‐polymerase chain reaction indicated that expression of this gene is higher in forager brains, as compared to nurse bees and queens. In the forager brain, expression was concentrated in a subset of the mushroom body neurons, suggesting that ecdysteroid‐signaling in the mushroom bodies might be involved in the division of labor of the workers.
Substrate‐induced double sided H‐bond network as a means of domain closure in 3‐phosphoglycerate kinase
Authors: Varga Andrea , Flachner Beáta , Konarev Peter , Gráczer Éva , Szabó Judit , Svergun Dmitri , Závodszky Péter , Vas Mária
Published: April 2006

Closure of the two domains of 3‐phosphoglycerate kinase, upon substrate binding, is essential for the enzyme function. The available crystal structures cannot provide sufficient information about the mechanism of substrate assisted domain closure and about the requirement of only one or both substrates, since lattice forces may hinder the large scale domain movements. In this study the known X‐ray data, obtained for the open and closed conformations, were probed by solution small‐angle X‐ray scattering experiments. The results prove that binding of both substrates is essential for domain closure. Molecular graphical analysis, indeed, reveals formation of a double‐sided H‐bond network, which affects substantially the shape of the main molecular hinge at β‐strand L, under the concerted action of both substrates.
JOHN DEWEY AND THE SOVIET UNION: PRAGMATISM MEETS REVOLUTION
Authors: ENGERMAN DAVID C.
Published: April 2006

John Dewey, like many other American intellectuals between the world wars, was fascinated by Soviet events. After visiting Russia in 1928 he wrote excitedly about the “Soviet experiment” and especially about Soviet educational theorists. In his early enthusiasm Dewey hoped that the US and the USSR could learn from each other, especially among the cosmopolitan group of progressive pedagogues he met on his trip. Observing the rise of Stalinism in the 1930s, though, his optimism dissipated; at the same time he came to emphasize historical and cultural differences between the US and the USSR. The result is apparent in Dewey's writings in the late 1930s (especially Freedom and Culture, 1939), as he began to evaluate the Soviet Union in terms that would have been anathema to him a decade earlier. He increasingly blamed Russia's cultural heritage for inhibiting Soviet development along the lines he had envisioned. Dewey's transformation suggests the importance of a cultural reading of American ideas about the USSR. Many American observers joined Dewey in seeing the USSR as the product of Russian culture, with its historical traditions and its own national character—and not just as the instantiation or betrayal of a political doctrine.
WHY THE MARGINS MATTER: OCCULTISM AND THE MAKING OF MODERNITY
Authors: LAQUEUR THOMAS
Published: April 2006

“Occult,” a 1902 international encyclopedia of religion tells us, is derived “from Latin occultus—Hidden,” and
is applied to the assumption that insight into and control over nature is to be obtained by mysterious or magical procedures and by long apprenticeship in secret lore. The physical science of the middle ages, alchemy and astrology, and in modern times spiritualism, theosophy, and palmistry contain various factors of occult lore. Such doctrines, known as occultism, fall outside the realm of modern science. See MAGIC.
Characterization of excess pore pressures at the toe of the Nankai accretionary complex, Ocean Drilling Program sites 1173, 1174, and 808: Results of one‐dimensional modeling
Authors: Gamage K. , Screaton E.
Published: April 2006

Elevated fluid pore pressures play a critical role in the development of accretionary complexes, including the development of the décollement zone. In this study, we used measured permeabilities of core samples from Ocean Drilling Program (ODP) Leg 190 to develop a permeability‐porosity relationship for hemipelagic sediments at the toe of the Nankai accretionary complex. This permeability‐porosity relationship was used in a one‐dimensional loading and fluid flow model to simulate excess pore pressures and porosities. Simulated excess pore pressure ratios (as a fraction of lithostatic pressure‐hydrostatic pressure) using the best fit permeability‐porosity relationship were lower than predicted from previous studies. We then tested sensitivity of excess pore pressure ratios in the underthrust sediments to bulk permeability, lateral stress in the prism, and a hypothetical low‐permeability barrier at the décollement. Our results demonstrated significant increase in pore pressures below the décollement with lower bulk permeability, such as obtained by using the lower boundary of permeability‐porosity data, or when a low‐permeability barrier is added at the décollement. In contrast, pore pressures in the underthrust sediments demonstrated less sensitivity to added lateral stresses in the prism, although the profile of the excess pore pressure ratio is affected. Both simulations with lateral stress and a low‐permeability barrier at the décollement resulted in sharp increases in porosity at the décollement, similar to that observed in measured porosities. Furthermore, in both scenarios, maximum excess pore pressure ratios were found at the décollement, suggesting that either of these factors would contribute to stable sliding along the décollement.
Spatial organization in the step‐pool structure of a steep mountain stream (Vogelbach, Switzerland)
Authors: Milzow Christian , Molnar Peter , McArdell Brian W. , Burlando Paolo
Published: April 2006

Spatial organization in the step‐pool structure of a 1.58 km long section of the Vogelbach, a steep mountain stream (average channel bed slope 0.17 m/m) in the Alpthal basin, Switzerland, is analyzed to evaluate the extent of randomness in the occurrence of steps and to isolate the potential hydraulic and topographic controls on step placement. Statistics of the observed step sequence are compared with those of random sequences generated by permutation from the observed step height distribution. Hydraulic and topographic controls on step placement are analyzed from step length and steepness distributions and relations between mean step properties and step height and channel gradient for both observed and random sequences. Results show that (1) observed step length distributions are statistically significantly different from randomly generated sequences, (2) step steepness is significantly different in observed data because of a positive correlation between mean step length and height and it remains fairly constant for all step sizes, (3) spatial organization in steps does not extend far beyond the nearest step, and (4) the influence of channel gradient on step properties is insignificant and highly variable, indicating that hydraulic rather than topographic controls are dominant for step placement in this stream. Although the Vogelbach is a steep stream on the boundary between a cascading and step‐pool morphology where we would expect randomness to dominate, spatial organization was nevertheless detected in many important aspects of the step‐pool geometry.
Rectification of the heading and tilting of sediment trap arrays due to strong tidal currents in a submarine canyon
Authors: Lee I‐Huan , Liu James T.
Published: April 2006

Two taut‐line sediment trap moorings deployed in Kao‐ping Submarine Canyon were subjected to tidal flows, resulting in significant vertical movements and tilt of the mounted instruments. Based on simple trigonometric relations, the true heading and tilt angles were derived from the raw readings of heading, pitch, and roll of the two Nortek Aquadopp Doppler current meters (NADCM). The true tilt and heading angles of the NADCMs were highly correlated with depth and reflected the orientation of the axis of the canyon, respectively. The precluded data points of tilt and heading angles therefore can be reconstructed. Our study suggests a systematic way to rectify the heading and tilting of a sediment trap array of the mounted NADCM from raw readings of the heading, pitch and roll meters.
An exact particle tracking algorithm for advective‐dispersive transport in networks with complete mixing at nodes
Authors: Rhodes Matthew E. , Blunt Martin J.
Published: April 2006

We present an exact particle tracking algorithm for advective‐dispersive transport in a network of one‐dimensional bonds connected at volume‐less nodes. We derive an analytical solution for the transit probability of a particle that has just arrived at a node to first arrive at a nearest‐neighbor node. This solution is compared to traditional random walk simulations in a network where particle motion is simulated in small time steps with empirical mixing rules at nodes. We demonstrate that this latter approach gives a good representation of the cumulative arrival time probability distribution, but that the fraction of the total flux arriving at each node is in error by more than 1% when compared to the analytical probability unless 105 or more time steps are used to simulate transport between nodes. Finally, we show how to obtain semianalytical solutions for tracer transport in a network and discuss how these results can be used for more complex settings where there is incomplete mixing at nodes, or where the bonds are no longer one‐dimensional.
Evidence for anthropogenic 14C‐enrichment in estuarine waters adjacent to the North Sea
Authors: Ahad Jason M. E. , Ganeshram Raja S. , Spencer Robert G. M. , Uher Günther , Gulliver Pauline , Bryant Charlotte L.
Published: April 2006

The isotopic composition (δ13C and Δ14C) of high molecular weight dissolved organic carbon (HMW DOC) was studied in the Tyne and Tweed estuaries, NE England. Despite significant removal of terrigenous HMW DOC in the low salinity regions (S < 15), Δ14C remained modern with little variation around 115‰. This lack of apparent age discrimination was attributed to either non‐oxidative removal or the absence of a significant proportion of old refractory C in the HMW DOC pool. At S > 15, we observed seaward increases in δ13C and Δ14C. With no documented local 14C inputs, we attributed non‐bomb related 14C‐enrichment at S > 15 to a possible ‘lingering effect’ of distal anthropogenic sources in near‐coastal North Sea HMW DOC. Given the global distribution of potential sources, we propose that anthropogenic 14C should be considered in assigning ages of DOC pools in near‐coastal waters and suggest its possible use as a tracer for DOC transformations.
Growth of Co clusters on thin films Al2O3∕NiAl(100)
Authors: Luo M. F. , Chiang C. I. , Shiu H. W. , Sartale S. D. , Wang T. Y. , Chen P. L. , Kuo C. C.
Published: April 2006

We present a scanning tunnel microscopy study of Co clusters grown through vapor deposition on Al2O3 thin films over NiAl(100) at different coverages and temperatures. Formation of Co clusters was observed at 90, 300, 450, and 570K. At the three lower temperatures, we find narrow cluster size distributions and the mean sizes (with a diameter of 2.6nm and a height of 0.7nm) do not change significantly with the coverage and temperature, until the clusters start to coalesce. Even on 3–4-nm-wide crystalline Al2O3 strips where the deposited Co atoms are confined, the same features sustain. Only at 570K the normal growth mode where the cluster size increases with the deposition coverage is observed, although the data are less conclusive. A simple modeling of kinetic surface processes on a strip confirms the normal growth mode, but fails to show a favored size unless additional energetic constraints are applied on the cluster sizes. Increasing Co coverages to cluster coalescence, a larger preferable size (mean diameter of 3.5nm and height of 1.4nm) appears for growth at 450K. These two sizes are corroborated by morphology evolution of high Co coverages deposited at 300K and annealed to 750K, in which the coalescence is eliminated and the two preferable geometries appear and coexist.
Dynamics of glass-forming liquids. XI. Fluctuating environments by dielectric spectroscopy
Authors: Huang Wei , Richert Ranko
Published: April 2006

The dielectric relaxation of a 1wt% mixture of di-n-butylether in 3-methylpentane has been measured across a range of eight decades, in which the characteristic relaxation time varies from 5sto50ns. Each loss spectrum is a superposition of the dispersive solvent peak and a Debye peak which is one decade slower and readily assigned to the larger and more dipolar solute molecules. Fluctuating environments or rate exchange is made responsible for the Debye nature of probe rotation, implying that the environmental relaxation times fluctuate on time scales which are faster than the rotational correlation decay of the probe molecule. Within the experimental range from 2.2sto42ns regarding the mean α-relaxation time, the results are consistent with the exchange time matching the upper limit of structural relaxation times or two to three times their average value. As Tg is approached, no indication for a variation in exchange behavior or for slower environmental fluctuations is found.
Atomistic simulation of a model liquid crystal
Authors: McDonald Andrew J. , Hanna Simon
Published: April 2006

We present atomistic molecular dynamics computer simulations of the bulk phases of a model liquid crystal system based on 8CB. The model differs from real 8CB because it employs a united-atom description to eliminate all hydrogen atoms, and neglects all long-range electrostatic interactions. Despite this simplification, the pressure-temperature phase diagram shows an order-disorder transition, in which isotropic, smectic, and nematiclike behaviors are observed. A detailed analysis of the inter- and intramolecular structures of the ordered phases is given, together with an examination of finite size effects and the equilibration times of the system. It is shown that, whereas a system may appear to be thermodynamically and mechanically equilibrated after a period of 10–15ns, it is possible for an imprint of the starting configuration to persist for much longer time scales. In the present case, however, such an imprint does not appear to affect the observed phase behavior.
Si (111) substrates as highly effective pseudomasks for selective growth of GaN material and devices by ammonia-molecular-beam epitaxy
Authors: Tang H. , Haffouz S. , Bardwell J. A.
Published: April 2006

The unique property of Si (111) as effective pseudomask substrate for selective growth of GaN by ammonia-molecular-beam epitaxy is reported. The critical nucleation temperature of GaN on Si (111) surface is found to be as low as 700°C, much lower than that on sapphire or AlN surface. As a result, selective growth of GaN is possible by ammonia-molecular-beam epitaxy on Si (111) substrates using a patterned AlN buffer layer. The wide range of growth temperatures (700–900°C) available for selective growth is a critical advantage for control and optimization of the facet characteristics of the selectively grown GaN patterns as required for potential fabrication of site-specific GaN or InGaN quantum dots. The demonstrated ease of selective growth of GaN on silicon has also implications in potential on-chip integration of GaN devices with silicon devices.
Highly conserved syntenic blocks at the vertebrate Hox loci and conserved regulatory elements within and outside Hox gene clusters
Authors: Lee Alison P. , Koh Esther G. L. , Tay Alice , Brenner Sydney , Venkatesh Byrappa
Published: April 2006

Hox genes in vertebrates are clustered, and the organization of the clusters has been highly conserved during evolution. The conservation of Hox clusters has been attributed to enhancers located within and outside the Hox clusters that are essential for the coordinated “temporal” and “spatial” expression patterns of Hox genes in developing embryos. To identify evolutionarily conserved regulatory elements within and outside the Hox clusters, we obtained contiguous sequences for the conserved syntenic blocks from the seven Hox loci in fugu and carried out a systematic search for conserved noncoding sequences (CNS) in the human, mouse, and fugu Hox loci. Our analysis has uncovered unusually large conserved syntenic blocks at the HoxA and HoxD loci. The conserved syntenic blocks at the human and mouse HoxA and HoxD loci span 5.4 Mb and 4 Mb and contain 21 and 19 genes, respectively. The corresponding regions in fugu are 16- and 12-fold smaller. A large number of CNS was identified within the Hox clusters and outside the Hox clusters spread over large regions. The CNS include previously characterized enhancers and overlap with the 5′ global control regions of HoxA and HoxD clusters. Most of the CNS are likely to be control regions involved in the regulation of Hox and other genes in these loci. We propose that the regulatory elements spread across large regions on either side of Hox clusters are a major evolutionary constraint that has maintained the exceptionally long syntenic blocks at the HoxA and HoxD loci.
Nuclear spin noise imaging
Authors: Müller Norbert , Jerschow Alexej
Published: April 2006

NMR images were obtained from the proton spin noise signals of a water-containing phantom, which was placed in the highly tuned, low-noise resonant circuit of a cryogenically cooled NMR probe in the presence of systematically varied magnetic field gradients. The spatially resolved proton spin density was obtained from the raw signal by a modified projection–reconstruction protocol. Although spin noise imaging is inherently less sensitive than conventional magnetic resonance imaging, it affords an entirely noninvasive visualization of the interior of opaque objects or subjects. Thus, tomography becomes possible even when neither x-ray nor radio frequency radiation can be applied for technical or safety reasons.
Disulfide cross-linked protein represents a significant fraction of ALS-associated Cu, Zn-superoxide dismutase aggregates in spinal cords of model mice
Authors: Furukawa Yoshiaki , Fu Ronggen , Deng Han-Xiang , Siddique Teepu , O'Halloran Thomas V.
Published: April 2006

Point mutations in Cu, Zn-superoxide dismutase (SOD1) cause a familial form of the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Aggregates of mutant SOD1 proteins are observed in histopathology and are invoked in several proposed mechanisms for motor neuronal death; however, the significant stability and activity of the mature mutant proteins are not readily explained in such models. Recent biochemical studies suggest that it is the immature disulfide-reduced forms of the familial ALS mutant SOD1 proteins that play a critical role; these forms tend to misfold, oligomerize, and readily undergo incorrect disulfide formation upon mild oxidative stress
in vitro
. Here we provide physiological support for this mechanism of aggregate formation and show that a significant fraction of the insoluble SOD1 aggregates in spinal cord of the ALS-model transgenic mice contain multimers cross-linked via intermolecular disulfide bonds. These insoluble disulfide-linked SOD1 multimers are found only in the spinal cord of symptomatic transgenic animals, are not observed in unafflicted tissue such as brain cortex and liver, and can incorporate WT SOD1 protein. The findings provide a biochemical basis for a pathological hallmark of this disease; namely, incorrect disulfide cross-linking of the immature, misfolded mutant proteins leads to insoluble aggregates.
Acoustic detection and satellite-tracking leads to discovery of rare concentration of endangered North Pacific right whales
Authors: Wade Paul , Heide-Jørgensen Mads Peter , Shelden Kim , Barlow Jay , Carretta James , Durban John , LeDuc Rick , Munger Lisa , Rankin Shannon , Sauter Allan , Stinchcomb Charles
Published: April 2006

The North Pacific right whale,Eubalaena japonica, is one of the most endangered species of whale in the world. On 10 August 2004, two right whales were located in the Bering Sea using headings to right whale calls provided by directional sonobuoys. A satellite-monitored radio tag attached to one of these whales functioned for 40 days. Over the 40-day period, this whale moved throughout a large part of the southeast Bering Sea shelf, including areas of the outer-shelf where right whales have not been seen in decades. In September, multiple right whales were acoustically located and subsequently sighted by another survey vessel approaching a near-real-time position from the tag. An analysis of photographs confirmed at least 17 individual whales (not including the tagged whales). Genetic analysis of biopsy samples identified 17 individuals: 10 males and 7 females. The discovery of seven females was significant, as only one female had been identified in the past. Genetics also confirmed the presence of at least two calves. Although the future of this population is highly uncertain, the discovery of additional females and calves gives some hope that this most critically endangered of all whale populations may still possess the capacity to recover.
Self-similar patterns of nature: insect diversity at local to global scales
Authors: Finlay Bland J , Thomas Jeremy A , McGavin George C , Fenchel Tom , Clarke Ralph T
Published: April 2006

The insects are probably the most hyperdiverse and economically important metazoans on the planet, but there is no consensus on the best way to model the dimensions of their diversity at multiple spatial scales, and the huge amount of information involved hinders data synthesis and the revelation of ‘patterns of nature’. Using a sample of more than 600k insect species in the size range 1–100 mm, we analysed insect body sizes and revealed self-similar patterns persisting across spatial scales from several hectares to the World. The same patterns were found in both Northern and Southern Hemispheres. The patterns include: parallel rank-abundance distributions; flatter species–area curves in smaller insects—indicating their wider geographical distribution; the recurrence of the same species-rich family in the same body-size class at all spatial scales—which generates self-similar size-frequency distributions (SFDs)—and the discovery that with decreasing mean body size, local species richness represents an increasing fraction of global species richness. We describe how these ‘rationalizing’ patterns can be translated into methods for monitoring and predicting species diversity and community structure at all spatial scales.
Continuum versus discrete model: a comparison for multicellular tumour spheroids
Authors: Schaller Gernot , Meyer-Hermann Michael
Published: April 2006

We study multicellular tumour spheroids with a continuum model based on partial differential equations (PDEs). The model includes viable and necrotic cell densities, as well as oxygen and glucose concentrations. Viable cells consume nutrients and become necrotic below critical nutrient concentrations. Proliferation of viable cells is contact-inhibited if the total cellular density locally exceeds volume carrying capacity. The model is discussed under the assumption of spherical symmetry. Unknown model parameters are determined by simultaneously fitting the cell number to several experimental growth curves for different nutrient concentrations. The outcome of the PDE model is compared with an analogous off-lattice agent-based model for tumour growth. It turns out that the numerically more efficient PDE model suffices to explain the macroscopic growth data. As in the agent-based model, we find that the experimental growth curves are only reproduced when a necrotic core develops. However, evaluation of morphometric properties yields differences between the models and the experiment.
A new multi-scale simulation model of the circulation: from cells to system
Authors: Bo Shim Eun , Hun Leem Chae , Abe Yasuyuki , Noma Akinori
Published: April 2006

We developed a comprehensive cell model that simulates the sequential cellular events from membrane excitation to contraction in the human ventricle. By combining this ventricular cell model with a lumped circulation model, we examined how blood pressure dynamics in the ventricle and aorta are related to the cellular processes. To convert cell contraction into ventricular pressure using Laplace's law, we introduced a simple geometric model of a ventricle: one shaped like a thin-walled hemisphere. The force of contraction of a single cell induces tension in the hemispheric ventricular wall, which generates the ventricular and aortic pressures in the lumped circulation model. The time courses of the hemodynamic properties, as well as the volume–pressure trajectory of the left ventricle, were well reproduced. Our multi-scale cardiovascular model, which covers from cardiac cells to the circulatory system, simulates the typical characteristics of heart mechanics, such as the pressure–volume relationship, stroke volume and the effect of the increased maximum free calcium concentration on cardiovascular hemodynamics. To test the cell-circulation coupling characteristics of the model, we simulated the effects of a decrease in
L
-type calcium channel conductance (cell level) on left ventricular pressure (system level). The variation due to different pacing frequencies for myocyte excitation was also investigated to assess the effects of heart rate on cardiac cells and the circulatory system.
Post-genomic science: cross-disciplinary and large-scale collaborative research and its organizational and technological challenges for the scientific research process
Authors: Welsh Elaine , Jirotka Marina , Gavaghan David
Published: April 2006

We examine recent developments in cross-disciplinary science and contend that a ‘Big Science’ approach is increasingly evident in the life sciences—facilitated by a breakdown of the traditional barriers between academic disciplines and the application of technologies across these disciplines. The first fruits of ‘Big Biology’ are beginning to be seen in, for example, genomics, (bio)-nanotechnology and systems biology. We suggest that this has profound implications for the research process and presents challenges both in technological design, in the provision of infrastructure and training, in the organization of research groups, and in providing suitable research funding mechanisms and reward systems. These challenges need to be addressed if the promise of this approach is to be fully realized. In this paper, we will draw on the work of social scientists to understand how these developments in science and technology relate to organizational culture, organizational change and the context of scientific work. We seek to learn from previous technological developments that seemed to offer similar potential for organizational and social change.
Ectopic hamartomatous thymoma: a case report with immunohistochemical study and review of the literature
Authors: Kushida Yoshio , Haba Reiji , Kobayashi Shoji , Ishikawa Masashi , Doi Takashi , Kadota Kyuichi
Published: April 2006

Abstract:  Ectopic hamartomatous thymoma (EHT) is a rare benign tumor. We present a case of EHT, which was seen as subcutaneous mass on the left supraclavicular area in a 19‐year‐old man. The tumor consisted of spindle cells, epithelial cells, adipose cells, and a small amount of lymphocytes, as described previously. Immunohistochemically, spindle cells were positive for keratin, a‐smooth muscle actin, CD34 and vimentin, but negative for desmin and S‐100 protein. Lymphocytes were positive for CD45RO but negative for CD20, CD1a, and CD99. Approximately, 5% of cells were positive for MIB‐1 and no cells stained for p53 and bcl‐2. Recognition of EHT is important and needs to be differentiated from high‐grade sarcomas such as synovial sarcoma or glandular malignant peripheral nerve sheath tumor.
Clear cell atypical fibroxanthoma – report of a case with review of the literature
Authors: Murali Rajmohan , Palfreeman Simon
Published: April 2006

Clear cell atypical fibroxanthoma (CCAFX) is a rare variant of atypical fibroxanthoma (AFX), a pleomorphic dermal tumour associated with a good prognosis. A 67‐year‐old man presented with a rapidly growing nodule on the ear, which had appeared over a 2‐week period. Sections showed an ulcerated nodule composed of pleomorphic spindled and polygonal cells with clear cytoplasm, invested by a delicate vascular stroma, reminiscent of clear cell renal cell carcinoma. Numerous mitotic figures were seen. The tumour cells stained with vimentin, CD68 and CD99 and were cytokeratin‐negative. The immunohistochemical and ultrastructural features supported a diagnosis of CCAFX. The diagnosis of CCAFX requires the exclusion of other pleomorphic clear cell tumours that can occur in the skin by using a combination of morphology, immunohistochemistry and electronmicroscopy.
Lipomatous mixed tumor with follicular differentiation of the skin
Authors: Kasashima Satomi , Hiroshi Minato , Toshinori Mori , Yoshio Oda
Published: April 2006

A very rare case of cutaneous mixed tumor with numerous adipose tissue and hair follicular structures in a 67‐year‐old Japanese male was reported. A well‐circumscribed tumor was in the subcutaneous tissue of the cheek and far from the parotid gland. Histologically, the tumor consisted of an admixture of the adipose tissue, fibromyxoid tissue with spindle cells, and branching tubular structures. Outer layers of ductal epithelial cells and single spindle cells were often in a transition, likely as typical mixed tumor. Branching ducts connected with keratinous cysts, strands of trichoblastic basophilic cells and clear cell nests. There was a gradual transition, between small‐sized adipocytes and vacuolated spindle cells. No chondroid stroma was seen. To our knowledge, this tumor is the first case of a lipomatous mixed tumor with hair follicular differentiation. The case indicates an additional wide spectrum of histologic appearances of cutaneous mixed tumor.
Associations of motor co‐ordination and attention with motor‐perceptual development in 3‐year‐old preterm and full‐term children who needed neonatal intensive care
Authors: Hemgren E. , Persson K.
Published: April 2006

Background  Children who have needed neonatal intensive care (NIC) are considered to be at risk for deficits such as developmental co‐ordination disorder and attention‐deficit/hyperactivity disorder. By assessing motor‐perceptual development, motor co‐ordination and attention already at 3 years of age, it might be possible to identify such deficits earlier than they are today.

Aim  To investigate the motor‐perceptual development in a group of 202 NIC children but had no major impairments, to describe associations of deficits in co‐ordination and attention with motor‐perceptual delays, and to estimate the prevalence of NIC children with combined deficits together with a motor‐perceptual delay.

Method  Co‐ordination and attention in children born very preterm (n = 57), moderately preterm (n = 75) and full‐term (n = 70) were observed according to a model for Combined Assessment of Motor Performance and Behaviour while they were assessed using a developmental scale, Motor‐Perceptual Development, 0–7 years, MPU.

Results  In two out of 14 MPU areas, a larger proportion of very preterm than of moderately preterm and full‐term children had marked developmental delay. Overall, the proportion of NIC children having a motor‐perceptual delay increased with increasing incoordination and especially increasing lack of attention. Twenty‐one (11%) of the NIC children had different motor‐perceptual delays combined with pronounced incoordination and pronounced lack of attention.

Conclusion  Deficits in co‐ordination and attention were associated with motor‐perceptual delays in areas important for daily living and development of academic skills. Therefore, to find children at risk for developmental co‐ordination disorder and attention‐deficit/hyperactivity disorder, assessments of co‐ordination and attention should be added to assessments of motor‐perceptual development in 3‐year‐old NIC children.
Fish assemblages in temporary ponds adjacent to ‘terra‐firme’ streams in Central Amazonia
Authors: PAZIN VICTOR F. V. , MAGNUSSON WILLIAM E. , ZUANON JANSEN , MENDONÇA FERNANDO P.
Published: April 2006

1. The effect of habitat structural features and physicochemical characteristics of the water on the composition and richness of fish assemblages in temporary ponds near streams were examined at three spatial scales: among ponds, among streams and between drainage basins, in a ‘terra‐firme’ (not subject to long‐term flooding) forest reserve in Central Amazonia.

2. The fish assemblage in temporary ponds was composed of subsets of 18 small‐bodied species widely distributed in the reserve. The assemblages had a nested subset structure, where smaller ponds contained subgroups of the species found in larger ponds.

3. Species composition and richness in temporary ponds were similar between drainage basins, although the fish assemblages in streams differed between basins.

4. Fish assemblage structure was influenced by local factors related to habitat structure, such as pond area and depth, canopy cover and hydroperiod. Physicochemical characteristics of the water in the ponds were similar between drainage basins and had little detectable effect on the structure of pond fish assemblages.

5. No correspondence was found between the composition, richness or abundance of fishes in the ponds and in stretches of the streams adjacent to the ponds. Therefore, it is not possible to predict the composition of these temporary pond fish assemblages from the fish assemblages found in adjacent streams.
Within‐lake variability in carbon and nitrogen stable isotope signatures
Authors: SYVÄRANTA JARI , HÄMÄLÄINEN HEIKKI , JONES ROGER I.
Published: April 2006

1. We assessed spatial and temporal variation in carbon and nitrogen isotopic signatures in different compartments of a single lake ecosystem. Stable isotope analyses were made on samples of particulate organic matter (POM), zooplankton, periphyton, macrophytes, macroinvertebrates and fish collected from several locations throughout the ice‐free period.

2. No spatial variation in δ13C or δ15N values was found for pelagic samples of POM and zooplankton. However, pelagic δ15N signatures increased steadily through the summer resulting in an almost 6‰ average increase in POM and zooplankton. A concurrent decrease in epilimnetic nitrate concentrations suggested that the increase in δ15N of POM and zooplankton could have resulted from a progressive 15N‐enrichment of the available inorganic nitrogen pool as the size of this pool was reduced.

3. Significant spatial variation in isotopic ratios was observed within littoral and profundal communities. Some spatial differences were likely related to lake‐specific characteristics, such as a major inlet and a small harbour area and some were interconnected with temporal events.

4. Marked differences between spring and autumn δ15N and δ13C values of fish at one site probably reflected a spring spawning immigration from a larger downstream lake and also indicated limited dispersal of these immigrants.

5. Our results indicate that restricted sampling of ecosystem components from lakes may provide misleading single values for the isotope end members needed for quantitative uses of stable isotopes in mixing models and for estimating trophic position. Hence we strongly advise that studies of individual lakes, or multiple lake comparisons, that utilise stable isotope analyses should pay more attention to potential within lake spatial and temporal variability of isotope ratios.