bluuebunny/crossref_metadata_2025 huggingface dataset:
ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation
Authors: Boutté Yohann , Jonsson Kristoffer , McFarlane Heather E. , Johnson Errin , Gendre Delphine , Swarup Ranjan , Friml Jiří , Samuels Lacey , Robert Stéphanie , Bhalerao Rishikesh P.
Published: September 2013

Significance

Unlike in animals, postembryonic development in plants is highly flexible and allows them to modulate their growth patterns in response to external signals or as part of endogenous developmental programs. Differential cell elongation is a widely used developmental program used in plants to respond to external and endogenous signals. Asymmetric distribution of the plant hormone indole-acetic acid (auxin) mediated by plasma membrane localized auxin carriers is crucial for differential cell elongation. Our results identify distinct mechanisms for trafficking of auxin influx and efflux carriers from the post-Golgi compartment
trans
-Golgi network to the plasma membrane during differential cell elongation in which the
trans
-Golgi network–localized ECHIDNA protein plays a key role by acting at the level of secretory vesicles genesis.
Implementation of cell-free biological networks at steady state
Authors: Niederholtmeyer Henrike , Stepanova Viktoria , Maerkl Sebastian J.
Published: September 2013

Significance

Transcription and translation can be performed in vitro, outside of cells, allowing the assembly of artificial genetic networks. This bottom-up approach to engineering biological networks in a completely defined and minimal environment is instructive to define the rules and limitations of network construction. It is, however, still challenging to implement complex genetic networks in vitro because the reactions are usually performed in a batch format, where reaction products accumulate and synthesis rates decline over time. Here, we addressed this problem by developing a microfluidic device to perform in vitro transcription and translation reactions in continuous mode, where synthesis rates stay constant. This allowed us to build and implement a genetic oscillator that showed sustained oscillations for extended periods of times.
Dendritic growth gated by a steroid hormone receptor underlies increases in activity in the developing
Drosophila
locomotor system
Authors: Zwart Maarten F. , Randlett Owen , Evers Jan Felix , Landgraf Matthias
Published: September 2013

Significance

Why do bigger animals have bigger brains, and how do they get them? We find in
Drosophila
larvae that motoneuron dendrites, the branched structures receiving information from other neurons, grow as the animal gets bigger, and that this is regulated on a cell-by-cell basis by a specific isoform of a steroid hormone receptor, whose functions were unknown. As these dendrites enlarge, they form more connections with presynaptic partners, leading to greater levels of neuronal activity. We propose that these nerve cells increase their activity to compensate for the demands of a bigger body.
Distortional binding of transition state analogs to human purine nucleoside phosphorylase probed by magic angle spinning solid-state NMR
Authors: Vetticatt Mathew J. , Itin Boris , Evans Gary B. , Schramm Vern L.
Published: September 2013

Significance

Enzymes are efficient at bringing reactants to the transition state. Transition state analogs mimic the transition state but are chemically stable. What forces do enzymes apply to transition state analogs? Solid-state NMR is used to answer this question for human purine nucleoside phosphorylase. When imperfect and near-perfect transition state analogs are analysed on and off the enzyme, greater distortions are observed for the imperfect transition state analog. The distortion is energetically large and is toward the transition state geometry. In contrast, the near-perfect analog experiences almost no distortion, stabilizing the enzyme in a favored conformation near the transition state. Both inhibitors bind with picomolar dissociation constants, but the enzyme expends more energy distorting the imperfect inhibitor toward the transition state.
Observation of the controlled assembly of preclick components in the in situ click chemistry generation of a chitinase inhibitor
Authors: Hirose Tomoyasu , Maita Nobuo , Gouda Hiroaki , Koseki Jun , Yamamoto Tsuyoshi , Sugawara Akihiro , Nakano Hirofumi , Hirono Shuichi , Shiomi Kazuro , Watanabe Takeshi , Taniguchi Hisaaki , Sharpless K. Barry , Ōmura Satoshi , Sunazuka Toshiaki
Published: September 2013

Significance

Several in situ click chemistry studies have been reported. To date, there is evidence to indicate that proteins act as mold between azide and alkyne fragments by X-ray analysis of protein–ligand complexes. However, only “postclick” structural evidence has been available. We succeeded in obtaining crystal structures of a chitinase complexed with an azide inhibitor and an
O
-allyl oxime fragment as a mimic of a click partner, revealing a mechanism for accelerating triazole formation in chitinase. This is an example to express the “preclick” state of in situ click chemistry and a demonstration to show that the in situ click chemistry approach will benefit from this analysis for future plans. We also performed density functional theory calculations to explore the chitinase-contributed Huisgen cycloaddition.
Evidence for at least six Hox clusters in the Japanese lamprey (
Lethenteron japonicum
)
Authors: Mehta Tarang K. , Ravi Vydianathan , Yamasaki Shinichi , Lee Alison P. , Lian Michelle M. , Tay Boon-Hui , Tohari Sumanty , Yanai Seiji , Tay Alice , Brenner Sydney , Venkatesh Byrappa
Published: September 2013

Significance

Lampreys and hagfishes (cyclostomes) are the only living group of jawless vertebrates and therefore are important for the study of vertebrate evolution. We have characterized Hox clusters in the Japanese lamprey (
Lethenteron japonicum
), and shown that it contains at least six Hox clusters as compared with four Hox clusters in tetrapods. This suggests that the lamprey lineage has undergone an additional round of genome duplication compared with tetrapods. Several conserved noncoding elements (CNEs) were predicted in the Hox clusters of lamprey, elephant shark, and human. Transgenic assay of CNEs demonstrated their potential to function as
cis
-regulatory elements. Thus, these CNEs may represent part of the core set of
cis
-regulatory elements that were present in the common ancestor of vertebrates.
Long-term legacy of massive carbon input to the Earth system: Anthropocene versus Eocene
Authors: Zeebe Richard E. , Zachos James C.
Published: September 2013

Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO
2
), a total of 5000 Pg C may enter the atmosphere, causing CO
2
concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8
°
C and surface ocean pH to decline by approximately 0.7 units. A carbon release of this magnitude is unprecedented during the past 56 million years—and the outcome accordingly difficult to predict. In this regard, the geological record may provide foresight to how the Earth system will respond in the future. Here, we discuss the long-term legacy of massive carbon release into the Earth's surface reservoirs, comparing the Anthropocene with a past analogue, the Palaeocene–Eocene Thermal Maximum (PETM, approx. 56 Ma). We examine the natural processes and time scales of CO
2
neutralization that determine the atmospheric lifetime of CO
2
in response to carbon release. We compare the duration of carbon release during the Anthropocene versus PETM and the ensuing effects on ocean acidification and marine calcifying organisms. We also discuss the conundrum that the observed duration of the PETM appears to be much longer than predicted by models that use first-order assumptions. Finally, we comment on past and future mass extinctions and recovery times of biotic diversity.
On the identification of a Pliocene time slice for data–model comparison
Authors: Haywood Alan M. , Dolan Aisling M. , Pickering Steven J. , Dowsett Harry J. , McClymont Erin L. , Prescott Caroline L. , Salzmann Ulrich , Hill Daniel J. , Hunter Stephen J. , Lunt Daniel J. , Pope James O. , Valdes Paul J.
Published: September 2013

The characteristics of the mid-Pliocene warm period (mPWP: 3.264–3.025 Ma BP) have been examined using geological proxies and climate models. While there is agreement between models and data, details of regional climate differ. Uncertainties in prescribed forcings and in proxy data limit the utility of the interval to understand the dynamics of a warmer than present climate or evaluate models. This uncertainty comes, in part, from the reconstruction of atime slabrather than atime slice, where forcings required by climate models can be more adequately constrained. Here, we describe the rationale and approach for identifying a time slice(s) for Pliocene environmental reconstruction. A time slice centred on 3.205 Ma BP (3.204–3.207 Ma BP) has been identified as a priority for investigation. It is a warm interval characterized by a negative benthic oxygen isotope excursion (0.21–0.23‰) centred on marine isotope stage KM5c (KM5.3). It occurred during a period of orbital forcing that was very similar to present day. Climate model simulations indicate that proxy temperature estimates are unlikely to be significantly affected by orbital forcing for at least a precession cycle centred on the time slice, with the North Atlantic potentially being an important exception.
Warm ocean processes and carbon cycling in the Eocene
Authors: John Eleanor H. , Pearson Paul N. , Coxall Helen K. , Birch Heather , Wade Bridget S. , Foster Gavin L.
Published: September 2013

Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5–33.7 Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.
New methods for understanding systems consolidation
Authors: Tayler Kaycie K. , Wiltgen Brian J.
Published: September 2013

According to the standard model of systems consolidation (SMC), neocortical circuits are reactivated during the retrieval of declarative memories. This process initially requires the hippocampus. However, with the passage of time, neocortical circuits become strengthened and can eventually retrieve memory without input from the hippocampus. Although consistent with lesion data, these assumptions have been difficult to confirm experimentally. In the current review, we discuss recent methodological advances in behavioral neuroscience that are making it possible to test the basic assumptions of SMC for the first time. For example, new transgenic mice can be used to monitor the activity of individual neurons across the entire brain while optogenetic approaches provide precise control over the activity of these cells using light stimulation. These tools can be used to examine the reactivation of neocortical neurons during recent and remote memory retrieval and determine if this process requires the hippocampus.
Niphargus–Thiothrix associations may be widespread in sulphidic groundwater ecosystems: evidence from southeastern Romania
Authors: Flot Jean‐François , Bauermeister Jan , Brad Traian , Hillebrand‐Voiculescu Alexandra , Sarbu Serban M. , Dattagupta Sharmishtha
Published: September 2013

Niphargus is a speciose amphipod genus found in groundwater habitats across Europe. Three Niphargus species living in the sulphidic Frasassi caves in Italy harbour sulphur‐oxidizing Thiothrix bacterial ectosymbionts. These three species are distantly related, implying that the ability to form ectosymbioses with Thiothrix may be common among Niphargus. Therefore, Niphargus–Thiothrix associations may also be found in sulphidic aquifers other than Frasassi. In this study, we examined this possibility by analysing niphargids of the genera Niphargus and Pontoniphargus collected from the partly sulphidic aquifers of the Southern Dobrogea region of Romania, which are accessible through springs, wells and Movile Cave. Molecular and morphological analyses revealed seven niphargid species in this region. Five of these species occurred occasionally or exclusively in sulphidic locations, whereas the remaining two were restricted to nonsulphidic areas. Thiothrix were detected by PCR on all seven Dobrogean niphargid species and observed using microscopy to be predominantly attached to their hosts' appendages. 16S rRNA gene sequences of the Thiothrix epibionts fell into two main clades, one of which (herein named T4) occurred solely on niphargids collected in sulphidic locations. The other Thiothrix clade was present on niphargids from both sulphidic and nonsulphidic areas and indistinguishable from the T3 ectosymbiont clade previously identified on Frasassi‐dwelling Niphargus. Although niphargids from Frasassi and Southern Dobrogea are not closely related, the patterns of their association with Thiothrix are remarkably alike. The finding of similar Niphargus–Thiothrix associations in aquifers located 1200 km apart suggests that they may be widespread in European groundwater ecosystems.
Impact of Left Anterior Line on Left Atrial Appendage Contractility in Patients Who Underwent Catheter Ablation for Chronic Atrial Fibrillation
Authors: JANG SUNG‐WON , OH YONG‐SEOG , SHIN WOO‐SEUNG , UHM JAE SUN , KIM SUNG‐HWAN , KIM JI‐HOON , LEE MAN‐YOUNG , RHO TAI‐HO
Published: September 2013

Background

Left anterior line (LAL) has been used as a substitute for mitral isthmus line for catheter ablation of chronic atrial fibrillation (AF). However, it results in left anterolateral conduction delay and might affect left atrial (LA) contractility. We aimed to investigate whether LAL decreases LA appendage function.

Methods

This study included 46 patients (30 men, mean age 58 ± 9 years, group 1) with persistent AF who underwent catheter ablation including LAL. Thirty patients with paroxysmal AF who received no additional LA ablation were compared as control group (21 males, mean age 56 ± 8 years, group 2). Transthoracic and transesophageal echocardiography with Doppler tissue imaging was performed in sinus rhythm before and after the ablation. We compared the following variables: (1) E/A ratio of the mitral flow velocity, (2) ratio of early mitral inflow and mitral septal annulus velocity (E/Em), (3) peak velocity of appendage outflow (ApVmax), and (4) time delay from QRS onset to appendage outflow (TDqa).

Results

LA diameter was significantly reduced after ablation in both groups. In group 1, parameters for diastolic function (E/A ratio, 1.7 ± 0.5 vs 2.0 ± 0.6, P = 0.197; E/Em, 11.7 ± 4.8 vs 11.6 ± 5.1, P = 0.883) and appendage flow (ApVmax, 55.2 ± 19.9 cm/s vs 50.3 ± 19.3 cm/s, P = 0.203; TDqa, –77.3 ± 30.1 ms vs –66.1 ± 60.8 ms, P = 0.265) did not change significantly after ablation. Changes of ApVmax and TDqa after ablation were not significantly different between two groups (P = 0.409 and P = 0.195, respectively).

Conclusions

LAL ablation did not aggravate mitral flow pattern or change appendage outflow. LAL could be used without concern over worsening LA diastolic and appendage function.
A new ammonoid fauna from the Carnian (Upper Triassic) Kasimlar Formation of the Taurus Mountains (Anatolia, Turkey)
Authors: Lukeneder Susanne , Lukeneder Alexander
Published: September 2013

We describe a new ammonoid fauna from the Taurus Mountains of southern Turkey. The Carnian ammonoid fauna from Aşağiyaylabel is presented for the first time. Ammonoids were obtained from limestone to marl beds of an approximately 35‐m‐thick section, which presents the rare opportunity to investigate ammonoid faunas across the Lower–Upper Carnian boundary. Intense sampling near the village of Aşağiyaylabel led to the recognition of a new Lower Carnian (Julian 2) to Upper Carnian (Tuvalian 1) ammonoid fauna from the Kasimlar Formation. The genus Kasimlarceltites gen. nov. is reported for the first time from the Taurus Mountains, which represents the main faunal element and occurs as huge mass occurrence (n ≫ 1 million). Kasimlarceltites krystyni gen. et sp. nov., Klipsteinia disciformis sp. nov. and Anasirenites crassicrenulatus sp. nov. occur within the Lower Carnian Carbonate member (Units A–B) of the Kasimlar Formation from the Taurus Platform Units. Ammonoids described from the marls of the Tuvalian Marlstone member were deposited during a major, Tethyan‐wide climate crisis – the so‐called Carnian crisis – characterized by a demise of carbonate platforms. Based on the biostratigraphic relevance of certain ammonoid taxa described herein, the age of the analysed parts of the Kasimlar Formation is Julian 2 to Tuvalian 1. The discovery of the new ammonoid assemblages from Aşağiyaylabel substantiates the significance of Upper Triassic faunas within the Taurus Mountains and facilitates the correlation with faunal assemblages from other regions in the Tethyan Realm. The ammonoid fauna and facies indicate a general deepening from open‐platform margins, over deeper shelf settings down to an open marine‐influenced basinal environment. The tentative habitat for Kasimlarceltites gen. nov. is a shallow platform environment to upper mid‐ramp.
Modulation of the autonomic nervous system and behaviour by acute glial cell Gq protein‐coupled receptor activation in vivo
Authors: Agulhon Cendra , Boyt Kristen M. , Xie Alison Xiaoqiao , Friocourt Francois , Roth Bryan L. , McCarthy Ken D.
Published: September 2013

Key points

The activation of glial Gq protein‐coupled receptor (Gq‐GPCR) signalling cascades broadly activates the autonomic nervous system

The activation of glial Gq‐GPCR signalling cascades affects activity‐related behaviour.

Abstract:  Glial fibrillary acidic protein (GFAP)‐expressing cells (GFAP+ glial cells) are the predominant cell type in the central and peripheral nervous systems. Our understanding of the role of GFAP+ glial cells and their signalling systems in vivo is limited due to our inability to manipulate these cells and their receptors in a cell type‐specific and non‐invasive manner. To circumvent this limitation, we developed a transgenic mouse line (GFAP‐hM3Dq mice) that expresses an engineered Gq protein‐coupled receptor (Gq‐GPCR) known as hM3Dq DREADD (designer receptor exclusively activated by designer drug) selectively in GFAP+ glial cells. The hM3Dq receptor is activated solely by a pharmacologically inert, but bioavailable, ligand (clozapine‐N‐oxide; CNO), while being non‐responsive to endogenous GPCR ligands. In GFAP‐hM3Dq mice, CNO administration increased heart rate, blood pressure and saliva formation, as well as decreased body temperature, parameters that are controlled by the autonomic nervous system (ANS). Additionally, changes in activity‐related behaviour and motor coordination were observed following CNO administration. Genetically blocking inositol 1,4,5‐trisphosphate (IP3)‐dependent Ca2+ increases in astrocytes failed to interfere with CNO‐mediated changes in ANS function, locomotor activity or motor coordination. Our findings reveal an unexpectedly broad role of GFAP+ glial cells in modulating complex physiology and behaviour in vivo and suggest that these effects are not dependent on IP3‐dependent increases in astrocytic Ca2+.
Analytical Modeling of the Strength of Tubesheets for Steam Surface Condensers
Authors: Peng Wengen , Hu Yanwei , Liu Yuanchun , Jin Guangri , He Yurong
Published: September 2013

A tubesheet is one of the most important components in the design of a steam surface condenser. In this work, an analytical method to determine the strength of a tubesheet is established based on a beam-strip model. The validation of this beam-strip model is confirmed through a finite-element method (FEM) with the same boundary conditions and mechanical properties of the tubesheet. Effects of various parameters that affect the strength of the tubesheet are analyzed, including the tubesheet thickness, applied loading, fixity type, and length of the unperforated zone. The modeling results show that the most significant factor influencing the maximum stress that the tubesheet can bear is the tubesheet thickness, while other parameters have a weaker impact. From an engineering point of view, the beam-strip model is a useful method for the design of tubesheet.
An Infinite Sequence of Collinear Cracks Subjected to Concentrated Loads
Authors: Yan Xiangqiao , Wei Yintao
Published: September 2013

A numerical approach to an infinite sequence of collinear cracks is presented in this paper. Numerical examples are included to illustrate the accuracy of the numerical approach. Specifically, an infinite sequence of collinear cracks subjected to concentrated loads is analyzed using the numerical approach. Many numerical results of the stress intensity factors (SIFs) are given. In addition, an experiential formula to calculate the SIFs of the infinite sequence of collinear cracks is presented. Numerical examples show that the experiential formula has very high accuracy.
Energetic and Dynamic Analysis of Multifrequency Legged Robot Locomotion With an Elastically Suspended Load
Authors: Da Xingye , Ackerman Jeffrey , Seipel Justin
Published: September 2013

Elastically suspended loads can reduce the energetic cost and peak forces of legged robot locomotion. However, legged locomotion frequently exhibits multiple frequency modes due to variable leg contact times, body pitch and roll, and transient locomotion dynamics. We used a simple hexapod robot to investigate the effect of multiple frequency components on the energetic cost, dynamics, and peak forces of legged robot locomotion using a high-speed motion tracking system and the fast Fourier transform (FFT). The trajectories of the robot body and the suspended load revealed that the robot was excited by both a body pitching frequency and the primary locomotion frequency. Both frequency modes affected the dynamics of the legged robot as the natural frequency of the elastic load suspension was varied. When the natural frequency of the load suspension was reduced below the primary locomotion and body pitching frequencies, the robot consumed less average power with an elastically suspended load versus a rigidly attached load. To generalize the experimental results more broadly, a modified double-mass coupled-oscillator model with experimental parameters was shown to qualitatively predict the energetic cost and dynamics of legged robot locomotion with an elastically suspended load. The experimental results and the theoretical model could help researchers better understand locomotion with elastically suspended loads and design load suspension systems that are optimized to reduce the energetic cost and peak forces of legged locomotion.
The Effects of a Parametric Variation of the Rim Seal Geometry on the Interaction Between Hub Leakage and Mainstream Flows in High Pressure Turbines
Authors: Popović Ivan , Hodson Howard P.
Published: September 2013

The objective of this work was to assess and understand the effects of a parametric variation performed on a typical overlapping rim seal geometry. The datum geometry has been the focus of a detailed experimental investigation employing a large-scale linear cascade subjected to a range of the mass flow rates and swirl velocities of the leakage air. The parametric variations described in this paper were examined using validated computational fluid dynamics (CFD). As a part of the parametric studies, both the axial and the radial seal clearance between the rotor fin (angel wing) and stator platform were varied as well as the length of the overlap between stator and rotor platforms. In addition, the effects of forward and backward facing annulus steps were also investigated. It has been found that a backward-facing annulus step was detrimental for all conditions considered, while a forward-facing step offered improvements for smaller step heights and/or lower leakage fractions. Tightening of the seal clearances closer to the annulus line improved the sealing effectiveness but often at the expense of increased losses. On the other hand, increasing the overlap length led to improvements in the sealing effectiveness with very small effects on the overall losses. Moving the rim seal away from the blade-leading edges reduced the pressure asymmetry at the rim seal and increased the flow uniformity of the leakage air. However, this led to an increased cross-passage flow (more negative skew) and higher losses at all but lowest leakage fractions. The results presented in this paper highlight the fact that there may not be an optimum rim seal solution that would offer an improvement for the full range of leakage fractions and that, for different rim sealing flows, there may be a different optimum geometry. In addition, rotor disk movements in radial and axial directions at various off-design conditions should be considered as a part of the design process. Based on the presented results, it may be of a benefit to the turbine designer to consider rotor disk designs that would be more biased towards the upstream and outward disk movements, which would result in tightening of the seal clearances and avoidance of a backward-facing annulus step.
Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout
Authors: Marosky A. , Seidel V. , Sattelmayer T. , Magni F. , Geng W.
Published: September 2013

In most dry, low-NOx combustor designs of stationary gas turbines, the front panel impingement cooling air is directly injected into the combustor primary zone. This air partially mixes with the swirling flow of premixed reactants from the burner and reduces the effective equivalence ratio in the flame. However, local unmixedness and the lean equivalence ratio are supposed to have a major impact on combustion performance. The overall goal of this investigation is to answer the question of whether the cooling air injection into the primary combustor zone has a beneficial effect on combustion stability and NOx emissions or not. The flame stabilization of a typical swirl burner with and without front panel cooling air injection is studied in detail under atmospheric conditions close to the lean blowout limit (LBO) in a full-scale, single-burner combustion test rig. Based on previous isothermal investigations, a typical injection configuration is implemented for the combustion tests. Isothermal results of experimental studies in a water test rig adopting high-speed planar laser-induced fluorescence (HSPLIF) reveal the spatial and temporal mixing characteristics for the experimental setup studied under atmospheric combustion. This paper focuses on the effects of cooling air injection on both flame dynamics and emissions in the reacting case. To reveal dependencies of cooling air injection on combustion stability and NOx emissions, the amount of injected cooling air is varied. OH*-chemiluminescence measurements are applied to characterize the impact of cooling air injection on the flame front. Emissions are collected for different cooling air concentrations, both global measurements at the chamber exit, and local measurements in the region of the flame front close to the burner exit. The effect of cooling air injection on pulsation level is investigated by evaluating the dynamic pressure in the combustor. The flame stabilization at the burner exit changes with an increasing degree of dilution with cooling air. Depending on the amount of cooling, only a specific share of the additional air participates in the combustion process.
A Systematic Approach to Estimate the Impact of the Aerodynamic Force Induced by Rotating Stall in a Vaneless Diffuser on the Rotordynamic Behavior of Centrifugal Compressors
Authors: Bianchini Alessandro , Biliotti Davide , Ferrara Giovanni , Ferrari Lorenzo , Belardini Elisabetta , Giachi Marco , Tapinassi Libero , Vannini Giuseppe
Published: September 2013

One of the main challenges of the present industrial research on centrifugal compressors is the need for extending the left margin of the operating range of the machines. As a result, interest is being paid to accurately evaluating the amplitude of the pressure fluctuations caused by rotating stall, which usually occurs prior to surge. The related aerodynamic force acting on the rotor can produce subsynchronous vibrations, which can prevent the machine's further operation, in case their amplitude is too high. These vibrations are often contained due to the stiffness of the oil journals. Centrifugal compressor design is, however, going towards alternative journal solutions having lower stiffness levels (e.g., active magnetic bearings or squeeze film dampers), which will be more sensitive to this kind of excitation: consequently, a more accurate estimation of the expected forces in the presence of dynamic external forces such as those connected to an aerodynamically unstable condition is needed to predict the vibration level and the compressor operability in similar conditions. Within this scenario, experimental tests were carried out on industrial impellers operating at high peripheral Mach numbers. The dedicated test rig was equipped with several dynamic pressure probes that were inserted in the gas flow path; moreover, the rotor vibrations were constantly monitored with typical vibration probes located near the journal bearings. The pressure field induced by the rotating stall in the vaneless diffuser was reconstructed by means of an ensemble average approach, thus defining the amplitude and frequency of the external force acting on the impeller. The calculated force value was then included in the rotordynamic model of the test rig: the predicted vibrations on the bearings were compared with the measurements, showing satisfactory agreement. Moreover, the procedure was applied to two real multistage compressors, showing notable prediction capabilities in the description of rotating stall effects on the machine rotordynamics. Finally, the prospects of the proposed approach are discussed by investigating the response of a real machine in high-pressure functioning when different choices of journal bearings are made.
Unified Applicable Propulsion System Performance Metrics
Authors: Schmitz Oliver , Hornung Mirko
Published: September 2013

Progress in the development of electrical storage and conversion technology progressively attains focus in aerospace motive power research. Novel propulsion system concepts based on hybrid or even entirely electrical energy sources are seriously considered for aircraft design. To this point, unified figures of merit are required in order to allow for consistent comparative investigations of existing combustion engines and future electrically-based propulsion systems. Firstly, this paper identifies the shortcomings of conventional performance metrics used for nonthermal electrical conversion processes and then approaches exergy-based loss methods as means of metrics extensions. Subsequently, energy source-independent figures of merit based on exergy analysis are derived and embedded into the well-known performance definitions. Finally, the unified metrics are demonstrated through application to a conventional turbofan, a parallel-hybrid turbofan, a novel integrated-hybrid turbofan concept, and an entirely electrical fan concept.
A Novel Methodology for Optimal Design of Compressor Plants Using Probabilistic Plant Design
Authors: Kurz Rainer , Thorp J. Michael , Zentmyer Erik G. , Brun Klaus
Published: September 2013

Equipment sizing decisions in the oil and gas industry often have to be made based on incomplete data. Often, the exact process conditions are based on numerous assumptions about well performance, market conditions, environmental conditions, and others. Since the ultimate goal is to meet production commitments, the traditional method of addressing this is to use worst case conditions and often adding margins onto these. This will invariably lead to plants that are oversized, in some instances, by large margins. In reality, the operating conditions are very rarely the assumed worst case conditions, however, they are usually more benign most of the time. Plants designed based on worst case conditions, once in operation, will, therefore, usually not operate under optimum conditions, have reduced flexibility, and therefore cause both higher capital and operating expenses.

The authors outline a new probabilistic methodology that provides a framework for more intelligent process-machine designs. A standardized framework using a Monte Carlo simulation and risk analysis is presented that more accurately defines process uncertainty and its impact on machine performance. Case studies are presented that highlight the methodology as applied to critical turbomachinery.
Two-Year Colleges, Physics Majors, and Diversity
Authors: White Susan C.
Published: September 2013

Two-Year Colleges, Physics Majors, and Diversity As noted last month, we're taking a look at physics in two-year colleges (TYCs). We expect to have the first reports from our 2012–13 Nationwide Survey of High School Physics Teachers in the spring of 2014. Last month we noted that the high school physics experience of undergraduate physics majors was quite different for students who started at a TYC and those who did not. That is not the only difference we saw. Nine percent of the physics undergraduate seniors in 2007 had started their college education at a TYC. These students are more racially diverse: about 20% of those who started at a TYC were Hispanic or a non-Asian minority. (African Americans are included in this group.) While about one physics major in 11 started at a TYC, the ratio for Hispanic and non-Asian minorities was about one in six. The Hispanics and non-Asian minority physics majors were almost twice as likely to have started at a TYC. In the November issue, we'll look at physics offerings in TYCs.
Vacuum Energy and Inflation: 2. A Vacuum Energy Universe
Authors: Huggins Elisha
Published: September 2013

In most of our undergraduate physics courses, we study what can happen in space, but space itself plays a passive role. In basic cosmology, the opposite is true. It is the behavior of space that plays the major role. In this, paper #2, we first discuss the nature of a simple expanding space, and then look at the consequence of applying Newton's law of gravity in this space. The calculations are particularly simple if most of the energy behaves like the vacuum energy discussed earlier in paper #1.1 The calculation is easy but the results are spectacular.
Mass, Speed, Direction: John Buridan's 14th-Century Concept of Momentum
Authors: Graney Christopher M.
Published: September 2013

“Modern science began in the Middle Ages,” a fact that has been forgotten thanks to the celebrated accomplishments of Copernicus and Galileo, who did not acknowledge their predecessors. So states James Hannam in a January 2010 article in History Today. Among the scientists of the Middle Ages that Hannam mentions is John Buridan, a French thinker who was the first to develop modern concepts of inertia and momentum.1 Buridan's work has been known to historians of science for decades2 and remains a topic of discussion among them today.3,4 However, it is not well-known in physics circles,5 although there was an American Journal of Physics discussion of Buridan 35 years ago as part of a history of inertia.6 Readers of The Physics Teacher may find Buridan of interest both as a matter of history and because Buridan presents important physics ideas in a different sort of way, which may be of value in the physics classroom.
What Is the Half-Life of Basketball Teams?
Authors: Hrepic Zdeslav
Published: September 2013

What do basketball teams have in common with radioactive nuclei? It turns out, there is more here than first meets the eye. The National Collegiate Athletic Association (NCAA) basketball tournaments feeds fans' craving when NBA competitions are not in swing, and the college tournament time has been referred to as “March Madness” or the “Big Dance”1 as many fans participate in “bracketing,” i.e., predicting winners.
Variations on the Zilch Cycle
Authors: Binder P.-M. , Tanoue C. K. S.
Published: September 2013

Thermo dynamic cycles in introductory physics courses are usually made up from a small number of permutations of isothermal, adiabatic, and constant-pressure and volume quasistatic strokes, with the working fluid usually being an ideal gas. Among them we find the Carnot, Stirling, Otto, Diesel, and Joule-Brayton cycles; in more advanced courses, steam cycles and refrigerators based on real working fluids are often introduced. Any additional cycles made up from the same simple strokes, and any extended analysis of known cycles, are welcome additions to the teaching repertory, as they provide more opportunities for practice and discussion.1–7 Our purpose in this note is to extend the analysis of the zilch cycle, introduced in Ref. 1, by presenting its TS diagram and by proposing several variations that do not contain adiabatic strokes, thus allowing a simpler mathematical treatment. As a bonus, we also provide results that make it possible to represent practically any elementary ideal-gas cycle in a TS diagram.
Color reproduction with a smartphone
Authors: Thoms Lars-Jochen , Colicchia Giuseppe , Girwidz Raimund
Published: September 2013

The world is full of colors. Most of the colors we see around us can be created on common digital displays simply by superposing light with three different wavelengths. However, no mixture of colors can produce a fully pure color identical to a spectral color. Using a smartphone, students can investigate the main features of primary color addition and understand how colors are made on digital displays.
Shallow-water acoustic tomography from angle measurements instead of travel-time measurements
Authors: Aulanier Florian , Nicolas Barbara , Mars Jérôme I. , Roux Philippe , Brossier Romain
Published: September 2013

For shallow-water waveguides and mid-frequency broadband acoustic signals, ocean acoustic tomography (OAT) is based on the multi-path aspect of wave propagation. Using arrays in emission and reception and advanced array processing, every acoustic arrival can be isolated and matched to an eigenray that is defined not only by its travel time but also by its launch and reception angles. Classically, OAT uses travel-time variations to retrieve sound-speed perturbations; this assumes very accurate source-to-receiver clock synchronization. This letter uses numerical simulations to demonstrate that launch-and-reception-angle tomography gives similar results to travel-time tomography without the same requirement for high-precision synchronization.
The Transcription Factor CREB Enhances Interleukin-17A Production and Inflammation in a Mouse Model of Atherosclerosis
Authors: Kotla Sivareddy , Singh Nikhlesh K. , Heckle Mark R. , Tigyi Gabor J. , Rao Gadiparthi N.
Published: September 2013

A lipoxygenase exacerbates atherosclerosis in mice by stimulating macrophages to produce a proinflammatory cytokine.
Arginine GlcNAcylation for Infection
Authors: Gough Nancy R.
Published: September 2013

Bacteria modify death domain proteins with GlcNAcylation to compromise apoptotic and inflammatory responses.
Mechanism of Action of the Novel Aminomethylcycline Antibiotic Omadacycline
Authors: Draper Michael P. , Weir S. , Macone A. , Donatelli J. , Trieber C. A. , Tanaka S. K. , Levy Stuart B.
Published: September 2013

Omadacycline is a novel first-in-class aminomethylcycline with potent activity against important skin and pneumonia pathogens, including community-acquired methicillin-resistant
Staphylococcus aureus
(MRSA), β-hemolytic streptococci, penicillin-resistant
Streptococcus pneumoniae
,
Haemophilus influenzae
, and
Legionella
. In this work, the mechanism of action for omadacycline was further elucidated using a variety of models. Functional assays demonstrated that omadacycline is active against strains expressing the two main forms of tetracycline resistance (efflux and ribosomal protection). Macromolecular synthesis experiments confirmed that the primary effect of omadacycline is on bacterial protein synthesis, inhibiting protein synthesis with a potency greater than that of tetracycline. Biophysical studies with isolated ribosomes confirmed that the binding site for omadacycline is similar to that for tetracycline. In addition, unlike tetracycline, omadacycline is active
in vitro
in the presence of the ribosomal protection protein Tet(O).
In Vivo
Efficacy of Humanized Ceftaroline Fosamil-Avibactam Exposures in a Polymicrobial Infection Model
Authors: Bhalodi Amira A. , Crandon Jared L. , Williams Gregory , Nicolau David P.
Published: September 2013

Although Gram-positive cocci are the most common pathogens in diabetic foot infections, these infections often are polymicrobial. The objective of this study was to assess the efficacy of a simulated human dose of 600 mg ceftaroline fosamil–600 mg avibactam every 8 h as a 1-h infusion in a polymicrobial
in vivo
murine model. Seven isolates were used (3 methicillin-resistant
Staphylococcus aureus
[MRSA] isolates, 1 methicillin-susceptible
S. aureus
[MSSA] isolate, 1
Escherichia coli
isolate, 1
Enterobacter cloacae
isolate, and 1
Bacteroides fragilis
isolate) in various combinations in an immunocompromised polymicrobial tissue infection to assess the efficacy of the simulated regimen. Each infection was comprised of at least one
S. aureus
isolate with a MIC of 0.25 to 1 μg/ml and one
Enterobacteriaceae
isolate with a MIC of 1 or 4 μg/ml. Eight of 16 infections also included
B. fragilis
, with a MIC of 0.5 μg/ml, as a third organism. Efficacy was evaluated after 24 h as the change in log
10
CFU from the level of 0-h controls. Efficacy was seen against all isolate combinations, with at least a 1-log kill against
Enterobacteriaceae
and a minimum of a 2-log kill against
S. aureus
and
B. fragilis
isolates. These bacterial reductions correlate with free drug concentration above the MIC (
f
T>MIC) produced by the humanized regimen of 100, 86, and 56% at MICs of 1, 2, and 4 μg/ml, respectively. The humanized regimen of 600 mg ceftaroline fosamil–600 mg avibactam every 8 h as a 1-h infusion showed predictable efficacy against all infections tested in this model. These data support further clinical investigation of ceftaroline fosamil-avibactam for the treatment of polymicrobial tissue infections.
Identification of Novel Genes Responsible for Overexpression of
ampC
in Pseudomonas aeruginosa PAO1
Authors: Tsutsumi Yuko , Tomita Haruyoshi , Tanimoto Koichi
Published: September 2013

The development of resistance to antipseudomonal penicillins and cephalosporins mediated by the chromosomal
ampC
gene in
Pseudomonas aeruginosa
is of clinical importance. We isolated piperacillin-resistant mutants derived from
P. aeruginosa
PAO1 and analyzed two mutants that had an insertion in
mpl
and
nuoN
. One mutant, YT1677, was resistant to piperacillin and ceftazidime and had an insertion in
mpl
, which encodes UDP-
N
-acetylmuramate:
l
-alanyl-γ-
d
-glutamyl-
meso
-diaminopimelate ligase. The other mutant, YT7988, showed increased MICs of piperacillin, ceftazidime, cefepime, and cefoperazone, and the insertion was mapped to
nuoN
, which encodes NADH dehydrogenase I chain N. Complementation experiments demonstrated that these mutations resulted in higher levels of resistance to β-lactams. The expression of genes reported to be involved in β-lactam resistance was examined by real-time PCR in YT1677 and YT7988 mutants. Overexpression was observed for only
ampC
, and other genes were expressed normally. Deletion of the
ampR
gene in YT1677 and YT7988 resulted in decreased expression of
ampC
, indicating that the mutations in YT1677 and YT7988 affected the expression of
ampC
through the function of AmpR.
Carbapenemase-Producing Enterobacteriaceae in Spain in 2012
Authors: Oteo Jesús , Saez David , Bautista Verónica , Fernández-Romero Sara , Hernández-Molina Juan Manuel , Pérez-Vázquez María , Aracil Belén , Campos José
Published: September 2013

We report the epidemiological impact of carbapenemase-producing
Enterobacteriaceae
(CPE) in Spain in 2012. Of the 237 carbapenemases detected, 163 were from the OXA-48 group, 60 were from VIM-1, 8 were from KPC-2, 5 were from IMP, and 1 was from NDM-1. Interhospital spread of carbapenemase-producing
Klebsiella pneumoniae
was due to a limited number of multilocus sequence types (MLST) and carbapenemase types, including ST15–VIM-1, ST11–OXA-48, ST405–OXA-48, ST101–KPC-2, and ST11–VIM-1. The number of CPE cases in Spain has increased sharply in recent years, due mainly to the emergence of OXA-48.
Predicting
In Vivo
Efficacy of Therapeutic Bacteriophages Used To Treat Pulmonary Infections
Authors: Henry Marine , Lavigne Rob , Debarbieux Laurent
Published: September 2013

The potential of bacteriophage therapy to treat infections caused by antibiotic-resistant bacteria has now been well established using various animal models. While numerous newly isolated bacteriophages have been claimed to be potential therapeutic candidates on the basis of
in vitro
observations, the parameters used to guide their choice among billions of available bacteriophages are still not clearly defined. We made use of a mouse lung infection model and a bioluminescent strain of
Pseudomonas aeruginosa
to compare the activities
in vitro
and
in vivo
of a set of nine different bacteriophages (PAK_P1, PAK_P2, PAK_P3, PAK_P4, PAK_P5, CHA_P1, LBL3, LUZ19, and PhiKZ). For seven bacteriophages, a good correlation was found between
in vitro
and
in vivo
activity. While the remaining two bacteriophages were active
in vitro
, they were not sufficiently active
in vivo
under similar conditions to rescue infected animals. Based on the bioluminescence recorded at 2 and 8 h postinfection, we also define for the first time a reliable index to predict treatment efficacy. Our results showed that the bacteriophages isolated directly on the targeted host were the most efficient
in vivo
, supporting a personalized approach favoring an optimal treatment.
Pharmacokinetic-Pharmacodynamic Analyses for Efficacy of Ceftaroline Fosamil in Patients with Community-Acquired Bacterial Pneumonia
Authors: Bhavnani Sujata M. , Hammel Jeffrey P. , Van Wart Scott A. , Rubino Christopher M. , Reynolds Daniel K. , Forrest Alan , Khariton Tatiana , Friedland H. David , Riccobene Todd A. , Ambrose Paul G.
Published: September 2013

Pharmacokinetic-pharmacodynamic (PK-PD) analyses for efficacy using phase III trial data from patients treated with a ceftaroline fosamil dosing regimen of 600 mg intravenously (i.v.) every 12 h (q12h) for 5 to 7 days for community-acquired bacterial pneumonia (CABP) were conducted. High clinical and microbiological success rates (84.7 and 86.3%, respectively) and percentages of time during the dosing interval that free-drug steady-state concentrations remained above the MIC (
f
%
T
>MIC) (98.4% had
f
%
T
>MIC values of ≥63.3) were observed among 124 microbiologically evaluable patients. As a result, significant PK-PD relationships could not be identified. These data provide support for the use of a ceftaroline fosamil dosing regimen of 600 mg i.v. q12h to treat patients with CABP.