bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulse‐width modulation control strategy for high efficiency LLC resonant converter with light load applications
Authors: Pan Haiyan , He Chao , Ajmal Farooq , Chen Henglin , Chen Guozhu
Published: October 2014

LLC resonant converters, generally adopting frequency modulation control, can hardly achieve high efficiency under both heavy and light load conditions. Especially under light load conditions, the high‐switching frequency seriously degrades converter's efficiency. This study propose a new pulse‐width modulation (PWM) control strategy for LLC resonant converters under light load applications on the premise of no change in the main circuit structure. The voltage gain of the converter is regulated by varying duty ratio instead of increasing switching frequency and therefore zero‐current switching for rectifier diodes can be realised under light load conditions. With the proposed PWM control strategy, the gain is not affected by the load variations and an optimal design of the magnetic components is possible, therefore the efficiency is further improved by reducing both the switching losses and the losses in magnetic components. Experimental results demonstrate the effectiveness of the proposed PWM strategy by increasing the efficiency of LCC resonant converter, especially under light load conditions.
Sensorless power factor control for mixed conduction mode boost converter using passivity‐based control
Authors: Cimini Gionata , Ippoliti Gianluca , Orlando Giuseppe , Pirro Matteo
Published: October 2014

In this study, a power factor (PF) control for an AC–DC boost converter operating in light load condition has been presented. A passivity‐based current control able to operate in either continuous conduction mode (CCM) and in discontinuous conduction mode has been implemented. A voltage proportional integral‐based control with input feed‐forward has been implemented in order to increase PF and regulate the DC output. A current observer, suitable for both operating modes has been adopted in order to eliminate the need for expensive current sensor. The proposed mixed conduction mode control scheme has been numerically tested using a powerful software simulation platform and compared with classical CCM control scheme. Experimental tests have been finally performed on a real boost converter controlled by a Texas Instruments microcontroller in order to validate the results and to prove the feasibility of the algorithm.
3‐Phase 4‐wire matrix converter‐based voltage sag/swell generator to test low‐voltage ride through in wind energy conversion systems
Authors: Díaz Matías , Cárdenas Roberto , Rojas Félix , Clare Jon
Published: October 2014

The high penetration of energy from wind energy conversion systems (WECSs) can have a significant influence on the stability, power quality and reliability of power systems. Therefore several countries have developed stringent grid codes in recent years in order to enhance the overall stability of power systems. In these grid codes, the capacity to fulfil low‐voltage ride through (LVRT) requirements is considered an important issue for the control of WECSs. Therefore in this study, a novel voltage sag/swell generator (VSG) based on a 4‐leg matrix converter is presented. This VSG can be used to generate the symmetrical and asymmetrical faults required to test LVRT algorithms in a laboratory environment. The performance of the VSG is experimentally demonstrated and compared with the operation of other VSGs conventionally used for LVRT studies.
Active‐clamping forward converter with non‐linear step‐down conversion
Authors: Lin Jing‐Yuan , Tzeng Weng‐Zeng , Lin Chien‐Yu , Wang Chao‐Fu , Liu Pang‐Jung
Published: October 2014

This study proposes a forward converter with non‐linear step‐down conversion ratio. In comparison with traditional forward converters, it has a higher duty utilisation ratio. Furthermore, the two output inductors can equally divide the load current, and therefore the current stress of inductors and output diodes can be reduced. Thus, the proposed converter is suitable for high step‐down applications. On the primary side, active‐clamp control can nullify the voltage spike of main switch while also achieving zero voltage switching operation of the main switch and auxiliary switch, hence the switching loss can be reduced. Detailed analysis and design of the proposed converter are described. Experimental results are recorded for a prototype converter with an AC input voltage ranging from 90 to 264 V, an output voltage of 12 V, and an output power of 240 W.
Comparing Artistic and Geometrical Perspective Depictions of Space in the Visual Field
Authors: Baldwin Joseph , Burleigh Alistair , Pepperell Robert
Published: October 2014

Which is the most accurate way to depict space in our visual field? Linear perspective, a form of geometrical perspective, has traditionally been regarded as the correct method of depicting visual space. But artists have often found it is limited in the angle of view it can depict; wide-angle scenes require uncomfortably close picture viewing distances or impractical degrees of enlargement to be seen properly. Other forms of geometrical perspective, such as fisheye projections, can represent wider views but typically produce pictures in which objects appear distorted. In this study we created an artistic rendering of a hemispherical visual space that encompassed the full visual field. We compared it to a number of geometrical perspective projections of the same space by asking participants to rate which best matched their visual experience. We found the artistic rendering performed significantly better than the geometrically generated projections.
Evaluation of factors associated with dynamics of Cichla ocellaris invasion of the Upper Paraná River floodplain system, Brazil
Authors: Espínola Luis A. , Minte-Vera Carolina V. , Junior Horacio F. Júlio , Santos Luciano N. , Winemiller Kirk O.
Published: October 2014

Invasion by Cichla ocellaris was studied in the Upper Paraná River floodplain. Generalised linear models and the Akaike Information Criterion (AIC) were applied to standardised gill-net catch data (CPUE), with years, rivers, secchi depth, and their respective interactions. Generalised additive models and AIC were used to evaluate relationships of CPUE for C. ocellaris with standard length, sampling year and secchi depth. C. ocellaris was first recorded in 1992 in the Paraná and Ivinheima Rivers. Nevertheless, the CPUE of individuals was very low in the latter until 2000, and the species was not recorded from the Baía River until 2000. In 2001, CPUE of C. ocellaris greatly increased (from 20 to 140) in all three rivers, and this coincided with changes in hydrology and suspended sediment. Greater secchi depth is thought to benefit foraging by these visually oriented, diurnal piscivores. The estimated annual growth rate for local populations was 21% for the Paraná, 42% for the Ivinheima, and 73% for the Baía Rivers. Consequently, relative to other populations, C. ocellaris of the Baía River and, to a lesser degree, the Ivinheima River, appear to be less influenced by density-dependent factors given their more recent invasions of those areas.
The influence of concrete on the geochemical qualities of urban streams
Authors: Tippler Carl , Wright Ian A. , Davies Peter J. , Hanlon Alison
Published: October 2014

The geochemical signature of freshwater streams can be used to determine the extent and nature of modification to stream water geochemistry due to urban development. This approach used the Gibbs (1970) diagram as a model for evaluation of changes to ionic composition linked to urban development. In this multi-year study, the geochemistry of 21 waterways in the Georges River catchment, Sydney, were monitored and compared with the level of urban development as measured by sub-catchment imperviousness and directly connected imperviousness. The results reflect a strong relationship between the intensity of sub-catchment urban development and stream geochemistry. All major geochemical attributes increased with escalating levels of urban development. The largest increase was for bicarbonate, which increased 18 times from a mean of 6.4 mg L–1 at non-urban streams to a mean of 118 mg L–1 at urban streams. Similarly, mean concentrations of calcium increased by 14 times (from 2 to 27.9 mg L–1). Mean salinity was enriched in the most urban streams, compared with non-urban streams, by more than 6 times. We attribute this, in part, to the influence of urban geology, notably concrete stormwater infrastructure. Changes in stream geochemistry due to urban development are an important element of the urban stream syndrome.
Filming and snorkelling as visual techniques to survey fauna in difficult to access tropical rainforest streams
Authors: Ebner Brendan C. , Fulton Christopher J. , Cousins Stephen , Donaldson James A. , Kennard Mark J. , Meynecke Jan-Olaf , Schaffer Jason
Published: October 2014

Dense tropical rainforest, waterfalls and shallow riffle-run-pool sequences pose challenges for researcher access to remote reaches of streams for surveying aquatic fauna, particularly when using capture-based collecting techniques (e.g. trapping, backpack and boat electrofishing). We compared the detection of aquatic species (vertebrates and invertebrates >1cm in body length) within pool habitats of a rainforest stream obtained by two visual techniques during both the wet and dry season: active visual survey by snorkelling and baited remote underwater video stations (BRUVSs). Snorkelling detected more species than a single BRUVS at each site, both within and among seasons. Snorkelling was most effective for recording the presence and abundance of diurnally active small-bodied species (adult size <150mm total length), although both techniques were comparable in detecting large-bodied taxa (turtles, fish and eels). On the current evidence, snorkelling provides the most sensitive and rapid visual technique for detecting rainforest stream fauna. However, in stream sections dangerous to human observers (e.g. inhabited by crocodiles, entanglement, extreme flows), we recommend a stratified deployment of multiple BRUVSs across a range of stream microhabitats within each site.
Tolerance of young seedlings of different tree species and a cereal to poor soil aeration
Authors: Azam Gausul , Murray Robert S. , Grant Cameron D. , Nuberg Ian K.
Published: October 2014

Poor soil aeration restricts the establishment of plants, yet some species used in revegetation programs are more tolerant of waterlogging than others. This study evaluated the sensitivity to poor soil aeration of young seedlings of Acacia salicina, Eucalyptus camaldulensis, E. leucoxylon, and E. kochii. A reference cereal crop, barley (Hordeum vulgare var. Keel), was also included. Seedlings were grown for 21 days in a loamy sand under a range of controlled volumetric air contents of the soil (εair, 0.000–0.200 m3 m–3), then the diameter and total length of roots, plus the dry masses of shoots and roots, were measured, and water use and water-use efficiency (WUE) calculated. All plant species had some sensitivity to poor soil aeration but their tolerance varied widely. Seedlings of E. camaldulensis were highly tolerant of waterlogging, whereas seedlings of E. kochii were highly sensitive. Seedlings of barley and A. salicina showed moderate tolerance and had significantly greater WUE than any of the eucalypts. Among the more sensitive species, no single aeration state caused a consistent reduction in all plant parameters; some species responded to any restriction in aeration by reducing WUE; others showed declining WUE only when aeration fell below 0.15 m3 m–3. No single early-growth parameter adequately described a species’ sensitivity to waterlogging; some were simple (e.g. shoot mass) and others more integrated (e.g. WUE). Differences in growth rate and water use by the different species under low εair suggest that land managers and revegetation agencies have scope to select superior species for improving the establishment of trees on waterlogged soils. Furthermore, the wide variation in tolerance to poor soil aeration among the tree seedlings compared with barley suggests considerable scope for genetic improvement of cereals by using material from native trees.
Dynamic architecture of a protein kinase
Authors: McClendon Christopher L. , Kornev Alexandr P. , Gilson Michael K. , Taylor Susan S.
Published: October 2014

Significance

Protein kinases represent a critically important family of regulatory enzymes. Their activity can be altered by mutations and binding events distant from the active site. To understand the nature of these long-distance effects, we used microsecond-timescale molecular dynamic simulation to subdivide a prototypical kinase, protein kinase A, into contiguous communities that exhibit internally correlated motions. Surprisingly, most of these unconventional structural entities were centered around known protein kinase functions. We thus propose a new framework for analysis of protein kinase structure and function that differs from traditional representations based simply on sequence motifs and secondary structure elements. These results extend our view on the dynamic nature of protein kinases and open a door to understanding of allosteric signaling in these enzymes.
Foraging and Growth Potential of Juvenile Chinook Salmon after Tidal Restoration of a Large River Delta
Authors: David Aaron T. , Ellings Christopher S. , Woo Isa , Simenstad Charles A. , Takekawa John Y. , Turner Kelley L. , Smith Ashley L. , Takekawa Jean E.
Published: October 2014

We evaluated whether restoring tidal flow to previously diked estuarine wetlands also restores foraging and growth opportunities for juvenile Chinook Salmon Oncorhynchus tshawytscha. Several studies have assessed the value of restored tidal wetlands for juvenile Pacific salmon Oncorhynchus spp., but few have used integrative measures of salmon performance, such as habitat‐specific growth potential, to evaluate restoration. Our study took place in the Nisqually River delta, Washington, where recent dike removals restored tidal flow to 364 ha of marsh—the largest tidal marsh restoration project in the northwestern contiguous United States. We sampled fish assemblages, water temperatures, and juvenile Chinook Salmon diet composition and consumption rates in two restored and two reference tidal channels during a 3‐year period after restoration; these data were used as inputs to a bioenergetics model to compare Chinook Salmon foraging performance and growth potential between the restored and reference channels. We found that foraging performance and growth potential of juvenile Chinook Salmon were similar between restored and reference tidal channels. However, Chinook Salmon densities were significantly lower in the restored channels than in the reference channels, and growth potential was more variable in the restored channels due to their more variable and warmer (2°C) water temperatures. These results indicate that some—but not all—ecosystem attributes that are important for juvenile Pacific salmon can recover rapidly after large‐scale tidal marsh restoration.

Received April 23, 2014; accepted July 9, 2014
A Market Model of Eastern Bering Sea Alaska Pollock: Sensitivity to Fluctuations in Catch and Some Consequences of the American Fisheries Act
Authors: Strong James W. , Criddle Keith R.
Published: October 2014

A simultaneous-equation equilibrium model of domestic and international markets for fillets, surimi, and roe of Alaska pollock (i.e., Walleye Pollock Gadus chalcogrammus) is used to examine the combined effect of variability in landings and changes in product mix on first wholesale prices and revenues. From the commencement of Americanization in the mid-1970s through the joint venture era of the 1980s and following full Americanization in early 1990s, U.S. producers of Alaska pollock focused mainly on selling surimi and roe to Japan. Passage of the American Fisheries Act of 1998 (AFA) unleashed an economic transformation that more than doubled fishery revenues without increasing exploitation rates or catches. The increased value came about because freedom from the race for fish allowed fishers and processors to increase product quality, improve product recovery rates, diversify their mix of product forms, and develop new markets in the USA and Europe. Despite the size and importance of the Alaska pollock fishery—among U.S. fisheries, it consistently ranks number one by volume and in the top five by value—little attention has been given to the development of a formal model of Alaska pollock markets or the market impacts of the AFA. The results of the model indicate that first wholesale revenues are maximized when harvests are maximized, but the value of the harvest is particularly sensitive to changes in the demand for Alaska pollock harvested in Russian waters, price differentials between fillet and surimi, and Japanese inventories of Alaska pollock products. Comparative static simulations comparing pre- and post-AFA fishery product recovery rates and product mix indicate revenues would have increased by 62% from 1998 to 2007.

Received June 21, 2013; accepted July 1, 2014
Gujarati Asians in East Africa, 1880–2000: Colonization, de-colonization and complex citizenship issues
Authors: Oonk Gijsbert
Published: October 2014

In this paper, I argue that despite the general belief to the contrary, there is a great deal of continuity in the history of the colonial and post-colonial practice of citizenship in the Indian Ocean region. This debate is usually described from the perspective of the state and its representatives. Indeed, more often than not, the position of the migrants themselves is not discussed. This paper aims to fill this gap. In the case of the South Asians in East Africa, I will demonstrate that migrants were able to negotiate their own space for identity formation and accepting and changing formal citizenship options. Indeed, they were also able to negotiate with colonial officials and, after the 1960s, Britain, Canada, India and even the United Nations about defending their rights as citizens or agreeing new regulations for international migration and citizenship. The debate on citizenship and belonging has become the centre of academic and public debate since the 1990s in Europe and the USA. However, historical cases in colonial contexts might shed some light on long-term continuity in such discussions.
The Effects of Rearing Density on Growth, Fin Erosion, Survival, and Migration Behavior of Hatchery Winter Steelhead
Authors: Kavanagh Maureen , Olson Douglas E
Published: October 2014

Juvenile winter steelhead Oncorhynchus mykiss at Eagle Creek National Fish Hatchery in Estacada, Oregon, were reared for three brood years (2004–2006) at raceway densities of 7,500 (214 fish/m3), 15,000 (429 fish/m3), and 22,500 fish (643 fish/m3) to determine the effects of rearing density on growth, fin erosion, survival, adult yield, and migration behavior. Coded wire tags were used to evaluate adult survival, and fish were radio-tagged to monitor migration times from the hatchery to the mouth of Eagle Creek following volitional release from the hatchery. We found rearing density had a significant effect (P < 0.05) on steelhead growth, fin erosion, and adult survival. Winter steelhead reared in low-density raceways (13.6 kg/m3 at release) were significantly larger at release, larger at return, had significantly better dorsal fin condition, and had significantly greater smolt-to-adult survival rates than did those reared in medium (23.4 kg/m3) and high (35.2 kg/m3) density raceways. No significant relationship between smolt size at release and migration timing was detected; however, the effect of rearing density on fish migration was noticeable in brood year 2004. In that year (2004), smolts from the medium- and high-density groups took from 6 to15 d longer to out-migrate than those from the low-density group.
Rainbow Trout Rearing Performance, Intestinal Morphology, and Immune Response after Long-term Feeding of High Levels of Fermented Soybean Meal
Authors: Barnes Michael E , Brown Michael L , Bruce Timothy , Sindelar Scott , Neiger Regg
Published: October 2014

The incorporation of PepSoyGen (PSG), a commercially produced fermented soybean meal product, was evaluated in a 205-d feeding trial. Three isonitrogenous and isocaloric experimental diets containing 0, 35, or 50% PSG and 40, 15, and 0% fish meal, respectively, were fed to Rainbow Trout Oncorhynchus mykiss. The diets containing either 0% or 35% PSG produced similar total tank weight gains, percent gains, and feed conversion ratios and were significantly different from the diets containing 50% PSG at the end of the trial. Mean individual fish lengths and weights were significantly greater in the fish receiving 35% PSG than either of the other two diets. Specific growth rate (SGR) was significantly lower in the 50% PSG treatment, but there was no significant difference in SGR between the other two diets. Viscerosomatic index was significantly lower in the fish fed 35% PSG. Hepatosomatic index was not significantly different among the diets, but fish receiving 50% PSG had a significantly poorer liver condition scores. No other significant differences were observed in health assessments of fat, fin condition, gills, pseudobranchs, opercles, eyes, guts, kidneys, or spleens. Significant differences were observed in distal intestine morphology among the diets at day 94, but no differences were observed at the end of the trial on day 205. Splenosomatic index, macrophage activity, and respiratory burst activity were not significantly different among the dietary treatments. Based on these results, PSG can safely constitute 35% of Rainbow Trout diets without any decrease in rearing performance compared with a reference blend containing fish meal.
Evaluation of Porous, Geotextile Liners for Erosion Control in Small Aquaculture Ponds
Authors: Saengrungruang Puttitorn , Boyd Claude E
Published: October 2014

Two geotextile liners, one with 0.090-mm openings and the other with 0.355-mm openings, were each installed in three 0.04-ha earthen ponds at the E. W. Shell Fisheries Center, Auburn, Alabama. Geotextile liners did not tear or decay during the 2-year study, and they prevented erosion of pond bottoms compared with three unlined ponds. However, the liners with 0.090-mm openings floated up into the water column in all three ponds, while the other liner floated up in one pond. Production, survival, and feed conversion ratio for hybrid catfish (♀ Channel Catfish Ictalurus punctatus×♂ Blue Catfish I. furcatus) did not differ (P > 0.05) among control and lined ponds. Phytoplankton abundance as estimated by chlorophyll a concentration was greater in lined ponds—especially in those lined with the less permeable geotextile—than in control ponds. This difference was attributed to differences in phosphorus uptake by bottom soil among lined and control ponds. Control ponds had higher turbidity than lined ponds in spite of greater chlorophyll a concentration in the lined ponds. This was the result of sediment resuspension by aeration in the unlined ponds. In laboratory tests, geotextiles with openings of 0.090–0.840 mm did not allow normal exchange of phosphorus between soil and water. Nevertheless, if the floating problem could be solved, porous geotextiles should be given further consideration for erosion control in small ponds and possibly in intensive, heterotrophic floc systems for commercial culture of marine shrimp and a few other species. They probably are too expensive for use in large ponds for green-water culture of fish and shrimp.
Performance of Two Egg Collector Designs for Use with Mummichogs
Authors: Janiak Courtnay R , McIntosh Dennis
Published: October 2014

The Mummichog Fundulus heteroclitus is a popular marine baitfish in the species’ natural range along the east coast of North America from Florida to the Gulf of St. Lawrence. Interest in commercial culture of Mummichogs has grown over the last two decades, but little research has been conducted to examine species-specific culture techniques; thus, Mummichog culture has not advanced. Our objectives were to evaluate the performance of two egg collectors designed to mimic the structures of natural substrates and to maximize labor efficiency. A tray-style collector (TSC) and a disk-style collector (DSC) were both placed in each of six 5,000-L tanks stocked with approximately 700 adult Mummichogs of both sexes. The numbers of eggs collected, fertilized eggs, and viable larvae that hatched as well as the time required to rinse collectors during each biweekly collection were compared between the two designs. Over the 8-week study, there was no significant difference between designs in terms of the number of eggs collected or the total rinse time. However, the percentage of unfertilized eggs collected was twice as high for TSCs (mean ± SD = 8.53 ± 0.59%) than for DSCs (4.42 ± 0.36%). Additionally, larval yield was significantly higher for DSCs (79.10 ± 12.93%) than for TSCs (72.63 ± 13.95%). Based on these results, we conclude that both designs are efficient at collecting Mummichog eggs and that the DSC is the more advantageous design for maximizing fertilization rate and larval yield.
A Portable Freshwater Closed-System Fish Egg Incubation System
Authors: Sutherland Jenny L , Manny Bruce A , Kennedy Gregory , Roseman Edward F , Allen Jeffrey , Black M Glen
Published: October 2014

To identify fish eggs collected in the field to species, a portable closed-system fish egg incubation system was designed and used to incubate and hatch the eggs in the laboratory. The system is portable, small in scale (2.54 × 1.52 × 2.03 m), and affordable, with the approximate cost of the system being US$8,300 (2012). The main tank is 678 L and holds a battery of up to 21 (egg) incubation jars. The system includes three independent water pumping systems to (1) provide aerated water to hatching jars, (2) filter and sterilize incubation water, and (3) provide temperature-controlled water in the main tank bath and the incubation jars. The system was successfully used to incubate freshwater fish eggs to raise resulting larvae to the post-yolk-sac stage for three seasons (spring 2012, spring 2013, and fall 2013) over two consecutive years, at two different locations, enabling us to identify fish eggs to species by providing identifiable fish larvae from incubated fish eggs.
Leucine Affects Growth and Hepatic Growth-Related Factor Gene Expression in Japanese Amberjack Seriola quinqueradiata
Authors: Kawanago M , Takemura S , Ishizuka R , Kousaka T , Shioya I
Published: October 2014

We examined the effect of dietary supplementation of leucine on body weight and hepatic insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) gene expression in juvenile Japanese Amberjack Seriola quinqueradiata. Crystalline leucine was dissolved in deionized water and added to the basal diet. Deionized water only was added to the basal diet as a control. The dietary concentration of free leucine was 0.03, 0.85, and 2.43 g/100 g diet for the control, 1% leucine-supplemented, and 3% leucine-supplemented diets, respectively. A growth trial was conducted for 77 d, after which the body weight was measured and the fish were then fasted for 3 d and refed. At 3, 9, and 24 h after refeeding, the liver and muscle were dissected for gene expression analysis. The mean body weight significantly increased in the 1% leucine-supplemented group during the growth trial. The expression of hepatic IGBFP-1 significantly increased at 3 and 9 h after refeeding in the leucine-supplemented groups. The expression of hepatic IGF1 significantly decreased at 9 h and that of IGF2 significantly decreased at 9 and 24 h after refeeding in the 3% leucine-supplemented group. The expression of hepatic IGFBP-2, IGFBP-3, and IGFBP-5 were similar among the groups and were only affected by feeding time. In conclusion, we demonstrated for the first time that leucine supplementation increases body weight and influences the hepatic growth factor system in Japanese Amberjack.
Let's dance – feel better! Mood changes following dancing in different situations
Authors: Zajenkowski Marcin , Jankowski Konrad S. , Kołata Daria
Published: October 2014

In the present study, we examined mood changes following dancing. Previous works suggested that contextual factors may influence affective states; it has been shown that changes in mood following competition differ from those following recreational exercise. The study has been conducted in Warsaw, Poland. Mood was assessed before and after dance activity in three groups of ballroom dancers: recreational (n = 32) and competitive (n = 38) dancers doing ordinary training and competitive dancers taking part in a dance competition (n = 35). We observed a moderately positive change in recreational dancers doing ordinary training; they reported higher energetic arousal (EA) and hedonic tone (HT) and lower tense arousal (TA) after dance activity. In comparison dancers taking part in a competition were higher on TA before dancing and felt less pleasure after dancing than recreational and competitive dancers doing ordinary training; HT, TA and EA moderately decreased during competition. In general, the current study suggests that dance can elicit changes in mood; however, situational context has to be taken into consideration when explaining the influence of dance on mood.
A discrete pathway for the transfer of intermembrane space proteins across the outer membrane of mitochondria
Authors: Gornicka Agnieszka , Bragoszewski Piotr , Chroscicki Piotr , Wenz Lena-Sophie , Schulz Christian , Rehling Peter , Chacinska Agnieszka
Published: October 2014

Mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria with the help of protein translocases. For the majority of precursor proteins, the role of the translocase of the outer membrane (TOM) and mechanisms of their transport across the outer mitochondrial membrane are well recognized. However, little is known about the mode of membrane translocation for proteins that are targeted to the intermembrane space via the redox-driven mitochondrial intermembrane space import and assembly (MIA) pathway. On the basis of the results obtained from an in organello competition import assay, we hypothesized that MIA-dependent precursor proteins use an alternative pathway to cross the outer mitochondrial membrane. Here we demonstrate that this alternative pathway involves the protein channel formed by Tom40. We sought a translocation intermediate by expressing tagged versions of MIA-dependent proteins in vivo. We identified a transient interaction between our model substrates and Tom40. Of interest, outer membrane translocation did not directly involve other core components of the TOM complex, including Tom22. Thus MIA-dependent proteins take another route across the outer mitochondrial membrane that involves Tom40 in a form that is different from the canonical TOM complex.
Optimal Sequential Plantings of Corn and Soybeans Under Price Uncertainty
Authors: Livingston Michael , Roberts Michael J. , Zhang Yue
Published: October 2014

Optimal crop choice and fertilizer applications depend on the stochastic dynamics of commodity prices, fertilizer prices, and the agronomic effects of rotation versus monoculture. The efficient decision rule accounts for real option values associated with maintaining land disposition in an environment with highly uncertain future prices and irreversible past planting decisions. We parameterize a baseline model for a representative acre in Iowa and compare the model's predictions and profits to relatively naive, shorter horizon decision rules, and a field managed with optimal fertilizer applications conditional on corn and soybeans always being rotated. We also examine the effects of a permanently larger premium on corn prices relative to soybean prices, which has been observed in locations near recently established ethanol plants. We then compare the various decision rules to actual crop choices in a panel of over 6,500 Iowa plots during 1979–2007. As compared to less forward‐looking objectives, we find the agronomic benefits of rotations coupled with real option values can lead to a more inelastic response of planting decisions to both transitory and permanent price changes. Always rotating, regardless of prices, is close to optimal, but so are shorter‐horizon objectives. One implication is that reduced corn monoculture and fertilizer application rates might be implemented with modest incentive payments of $4 per acre or less.
Seismic attenuation: effects of interfacial impedance on wave-induced pressure diffusion
Authors: Qi Qiaomu , Müller Tobias M. , Rubino J. Germán
Published: October 2014

Seismic attenuation and dispersion in layered sedimentary structures are often interpreted in terms of the classical White model for wave-induced pressure diffusion across the layers. However, this interlayer flow is severely dependent on the properties of the interface separating two layers. This interface behaviour can be described by a pressure jump boundary condition involving a non-vanishing interfacial impedance. In this paper, we incorporate the interfacial impedance into the White model by solving a boundary value problem in the framework of quasi-static poroelasticity. We show that the White model predictions for attenuation and dispersion substantially change. These changes can be attributed to petrophysically plausible scenarios such as imperfect hydraulic contacts or the presence of capillarity.
Testing primordial non-Gaussianities on galactic scales at high redshift
Authors: Habouzit Mélanie , Nishimichi Takahiro , Peirani Sébastien , Mamon Gary A. , Silk Joseph , Chevallard Jacopo
Published: October 2014

Primordial non-Gaussianities provide an important test of inflationary models. Although the Planck cosmic microwave background experiment has produced strong limits on non-Gaussianity on scales of clusters, there is still room for considerable non-Gaussianity on galactic scales. We have tested the effect of local non-Gaussianity on the high-redshift galaxy population by running five cosmological N-body simulations down to z = 6.5. For these simulations, we adopt the same initial phases, and either Gaussian or scale-dependent non-Gaussian primordial fluctuations, all consistent with the constraints set by Planck on cluster scales. We then assign stellar masses to each halo using the halo–stellar mass empirical relation of Behroozi et al. Our simulations with non-Gaussian initial conditions produce halo mass functions that show clear departures from those obtained from the analogous simulations with Gaussian initial conditions at z ≳ 10. We observe a >0.3 dex enhancement of the low end of the halo mass function, which leads to a similar effect on the galaxy stellar mass function, which should be testable with future galaxy surveys at z > 10. As cosmic reionization is thought to be driven by dwarf galaxies at high redshift, our findings may have implications for the reionization history of the Universe.
Orbital period of Swift J1816.7–1613 revealed by the Swift Burst Alert Telescope
Authors: La Parola V. , Segreto A. , Cusumano G. , Masetti N. , D'Aì A. , Melandri A.
Published: October 2014

We have analysed the Swift data relevant to the high-mass X-ray binary Swift J1816.7–1613. The timing analysis of the Burst Alert Telescope survey data unveiled a modulation at a period of P0 = 118.5 ± 0.8 d, which we interpret as the orbital period of the X-ray binary system. The modulation is the result of a sequence of bright flares, lasting ∼30 d, separated by long quiescence intervals. This behaviour is suggestive of a Be binary system, where periodic or quasi-periodic outbursts are the consequence of an enhancement of the accretion flow from the companion star at the periastron passage. The position of Swift J1816.7–1613 on the Corbet diagram strengthens this hypothesis. The broad-band 0.2–150 keV spectrum is well modelled with a strongly absorbed power law with a flat photon index Γ ∼ 0.2 and a cut-off at ∼10 keV.
Functional Significance of Single Nucleotide Polymorphisms in the Lactase Gene in Diverse US Patients and Evidence for a Novel Lactase Persistence Allele at −13909 in Those of European Ancestry
Authors: Baffour‐Awuah Nana Yaa , Fleet Sarah , Montgomery Robert K. , Baker Susan S. , Butler Johannah L. , Campbell Catarina , Tischfield Samuel , Mitchell Paul D. , Allende‐Richter Sophie , Moon Jennifer E. , Fishman Laurie , Bousvaros Athos , Fox Victor , Kuokkanen Mikko , Grand Richard J. , Hirschhorn Joel N.
Published: October 2014

Objectives:

Recent data from mainly homogeneous European and African populations implicate a 140‐bp region 5′ to the transcriptional start site of LCT (the lactase gene) as a regulatory site for lactase persistence and nonpersistence. Because there are no studies of US nonhomogeneous populations, we performed genotype/phenotype analysis of the −13910 and −22018 LCT single nucleotide polymorphisms (SNPs) in New England children, mostly of European ancestry.

Methods:

Duodenal biopsies were processed for disaccharidase activities, RNA quantification by reverse transcription polymerase chain reaction (RT‐PCR), allelic expression ratios by PCR, and genotyping and SNP analysis. Results were compared with clinical information.

Results:

Lactase activity and mRNA levels, and sucrase‐to‐lactase ratios of enzyme activity and mRNA, showed robust correlations with genotype. None of the other LCT SNPs showed as strong a correlation with enzyme or mRNA levels as did −13910. Data were consistent, with the −13910 being the causal sequence variant instead of −22018. Four individuals heterozygous for −13910T/C had allelic expression patterns similar to individuals with −13910C/C genotypes; of these, 2 showed equal LCT expression from the 2 alleles and a novel variant (−13909C>A) associated with lactase persistence.

Conclusions:

The identification of −13910C/C genotype is likely to predict lactase nonpersistence, consistent with prior published studies. A −13910T/T genotype will frequently, but not perfectly, predict lactase persistence in this mixed European‐ancestry population; a −13910T/C genotype will not predict the phenotype. A long, rare haplotype in 2 individuals with −13910T/C genotype but equal allele‐specific expression contains a novel lactase persistence allele present at −13909.
Relation Between Vitamin D Status and Nonalcoholic Fatty Liver Disease in Children
Authors: Hourigan Suchitra K. , Abrams Stephanie , Yates Katherine , Pfeifer Kim , Torbenson Michael , Murray Karen , Roth Christian L. , Kowdley Kris , Scheimann Ann O. ,   NASH CRN
Published: October 2014

Objectives:

In adults, vitamin D deficiency is common in patients with nonalcoholic fatty liver disease (NAFLD) and has been associated with the severity of histology. There are known differences between adult and pediatric NAFLD, with little data regarding the relation between vitamin D and pediatric NAFLD. The aim of the present study was to examine the relation between vitamin D levels and NAFLD in children.

Methods:

Clinical and histological data were used from children ages 2 to 18 years with biopsy‐proven NAFLD enrolled in the Nonalcoholic Steatohepatitis Clinical Research Network studies. 25(OH) vitamin D levels were measured from serum. Data examined included demographics, anthropometrics, laboratory markers, and liver histology. Data were analyzed using 3 categories of vitamin D level: deficient (≤20 ng/mL), insufficient (21–29 ng/mL), and sufficient (≥30 ng/mL).

Results:

A total of 102 children were studied. There was a high prevalence (80/102, 78%) of vitamin D deficiency or insufficiency; however, there were no significant associations between vitamin D level and the histological characteristics or severity of NAFLD. Significantly higher levels of triglycerides were found in those with vitamin D deficiency (P = 0.004), but there was no association with other features of the metabolic syndrome.

Conclusions:

There is a high prevalence of vitamin D deficiency and insufficiency in children with biopsy‐proven NAFLD; however, no association was found between vitamin D deficiency and the severity of disease on biopsies. This differs from adult NAFLD studies in which vitamin D deficiency correlates with histological severity, suggesting differences in the risk factors for or consequences of pediatric NAFLD.
Rate of Celiac Disease in Children
Authors: Preston Deborah L. , Elitsur Yoram
Published: October 2014

Objectives:

The low rate of celiac disease diagnosed in children from the United States may be limited by the practice of “serology‐led” diagnosis. The frequency of seronegative celiac disease is unknown, but is underestimated in children and may result in misdiagnosis of celiac disease. The aim of the present study was to investigate the rate of celiac disease after upper endoscopy (esophagogastroduodenescopy [EGD]) with no prior positive celiac serology compared with the rate of celiac disease followed by positive serology.

Methods:

Charts of all of the first diagnostic EGDs in children (2009–2013) were retrospectively reviewed. Patients with confirmed celiac disease were divided into 4 groups: group A, positive EGD/positive serology (histology‐led diagnosis); group B, positive serology/positive histology (serology‐led diagnosis); group C, positive histology followed by negative serology (control 1); and group D, positive serology followed by negative histology (control 2).

Results:

A total of 761 upper endoscopic charts were reviewed. Of these, 15 children were confirmed with celiac disease (1.97%). There was no significant difference in the demographic data or clinical symptoms between group A and group B. No significant difference was observed in the rate of celiac disease between histology‐led celiac diagnosis (group A) and serology‐led celiac diagnosis (group B) (1.18% vs 0.79%, P = 0.273).

Conclusions:

The rate of celiac disease in endoscopy‐led diagnosis was comparable to that in the serology‐led diagnosis, suggesting that to increase the detection of celiac disease in children, an adequate number of intestinal biopsies should be performed in every diagnostic upper endoscopic procedure.
Preservation of Biochemical Liver Function With Low‐Dose Soy‐Based Lipids in Children With Intestinal Failure–Associated Liver Disease
Authors: Khan Faraz A. , Fisher Jeremy G. , Sparks Eric A. , Potemkin Alexis , Duggan Christopher , Raphael Bram P. , Modi Biren P. , Jaksic Tom
Published: October 2014

Objectives:

Intestinal failure–associated liver disease (IFALD) contributes to significant morbidity in pediatric patients with intestinal failure (IF); however, the use of parenteral nutrition (PN) with a fish oil–based intravenous (IV) emulsion (FO) has been associated with biochemical reversal of cholestasis and improved outcomes. Unfortunately, FO increases the complexity of care: because it can be administered only under Food and Drug Administration compassionate use protocols requiring special monitoring, it is not available as a 3‐in‐1 solution and is more expensive than comparable soy‐based IV lipid emulsion (SO). Because of these pragmatic constraints, a series of patient families were switched to low‐dose (1 g kg−1 day−1) SO following biochemical resolution of cholestasis. The present study examines whether reversal of cholestasis and somatic growth are maintained following this transition.

Methods:

The present study is a chart review of all children with IFALD who switched from FO to SO following resolution of cholestasis. Variables are presented as medians (interquartile ranges). Comparisons were performed using the Wilcoxon signed‐rank test.

Results:

Seven patients ages 25.9 (16.2–43.2) months were transitioned to SO following reversal of cholestasis using FO. At a median follow‐up of 13.9 (4.3–50.1) months, there were no significant differences between pretransition and post‐transition serum alanine and aspartate aminotransferases, direct bilirubin, and weight‐for‐age z scores. Because of recurrence of cholestasis, 1 patient was restarted on FO after 4 months on SO.

Conclusions:

Biochemical reversal of IFALD and growth were preserved after transition from FO to SO in 6 of 7 (86%) patients. Given the challenges associated with the use of FO, SO may be a viable alternative in select patients with home PN.
Potassium availability triggers
Mycobacterium tuberculosis
transition to, and resuscitation from, non-culturable (dormant) states
Authors: Salina Elena G. , Waddell Simon J. , Hoffmann Nadine , Rosenkrands Ida , Butcher Philip D. , Kaprelyants Arseny S.
Published: October 2014

Dormancy in non-sporulating bacteria is an interesting and underexplored phenomenon with significant medical implications. In particular, latent tuberculosis may result from the maintenance of
Mycobacterium tuberculosis
bacilli in non-replicating states in infected individuals. Uniquely, growth of
M. tuberculosis
in aerobic conditions in potassium-deficient media resulted in the generation of bacilli that were non-culturable (NC) on solid media but detectable in liquid media. These bacilli were morphologically distinct and tolerant to cell-wall-targeting antimicrobials. Bacterial counts on solid media quickly recovered after washing and incubating bacilli in fresh resuscitation media containing potassium. This resuscitation of growth occurred too quickly to be attributed to
M. tuberculosis
replication. Transcriptomic and proteomic profiling through adaptation to, and resuscitation from, this NC state revealed a switch to anaerobic respiration and a shift to lipid and amino acid metabolism. High concordance with mRNA signatures derived from
M. tuberculosis
infection models suggests that analogous NC mycobacterial phenotypes may exist during disease and may represent unrecognized populations
in vivo
. Resuscitation of NC bacilli in potassium-sufficient media was characterized by time-dependent activation of metabolic pathways in a programmed series of processes that probably transit bacilli through challenging microenvironments during infection.
Study of dynamic underwater implosion mechanics using digital image correlation
Authors: Gupta Sachin , Parameswaran Venkitanarayanan , Sutton Michael A. , Shukla Arun
Published: October 2014

The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid–structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.