bluuebunny/crossref_metadata_2025 huggingface dataset:
Ein Michelson‐Interferometer in der Schule
Authors: Hütz Benjamin , Wallkötter Sebastian , Heizenreder Martin
Published: March 2012

Im Rahmen eines Physikprojekts haben wir am Hohenstaufen‐Gymnasium in Kaiserslautern mit geringem Kostenaufwand ein Michelson‐Interferometer gebaut. Der Einsatz in Schulversuchen eröffnet den Zugang zu einem vertieften Verständnis von Licht und dessen Eigenschaften.
A three‐dimensional monotone and conservative semi‐Lagrangian scheme (SLICE‐3D) for transport problems
Authors: Zerroukat M. , Allen T.
Published: March 2012

The Semi‐Lagrangian Inherently Conserving and Efficient (SLICE) scheme is extended to three‐dimensional transport on the sphere (SLICE‐3D). This paper presents details of the scheme for a longitude–latitude C‐type staggering grid. The scheme is applied to a passive transport with an analytically defined wind field that can be considered as an ‘idealized climate circulation’. The performance of SLICE‐3D is assessed against the widely used standard non‐conservative Semi‐Lagrangian (SL) scheme. The computational performance of the scheme for multiple species transport on parallel machines is also examined. Copyright © 2012 British Crown copyright, the Met Office. Published by JohnWiley & Sons Ltd.
Identification of free radicals in oxidized and glycoxidized phosphatidylethanolamines by spin trapping combined with tandem mass spectrometry
Authors: Simões Cláudia , Domingues Pedro , Domingues Maria Rosario M.
Published: March 2012

RATIONALE

Nonenzymatic glycation of phosphatidylethanolamines (PEs) seems to a have a role in angiogenesis and atherosclerosis. Glycated PEs are more easily oxidized, enhancing oxidative stress. This study aims to evaluate the influence of glycation on the formation of intermediate radical species during oxidation of glycated PEs.

METHODS

In the present study, the radical intermediaries formed during the oxidation of palmitoyl‐lineoyl phosphatidylethanolamine (PLPE) and glycated PLPE (gPLPE) were trapped using a spin trap (DMPO) and the radical adducts were analyzed by electrospray ionization mass spectrometry (ESI‐MS) and tandem mass spectrometry (ESI‐MS/MS). Mass spectra were acquired using a electrospray Q‐TOF 2 mass spectrometer.

RESULTS

Several spin adducts of PLPE and gPLPE were identified, corresponding to carbon‐ and oxygen‐centered radicals. Interpretation of the MS/MS spectra showed the existence of different sites where radical formation occurred, at the sn‐2 acyl chain, ethanolamine moiety (particularly in C‐1) and, in the case of glycated derivatives, also in the glucose moiety (particularly in C‐3, C‐4 and C‐5).

CONCLUSIONS

These results suggested the presence of more sites susceptible to oxidation in glycated PLPE, which may be responsible for the increase in the oxidative reaction rate occurring in glycated compounds. Copyright © 2012 John Wiley & Sons, Ltd.
The effect of localized lateral growth of multiwalled carbon nanotubes with ammonia plasma post‐treatment
Authors: Yau Wei‐Hung , Tsai Chien‐Huang
Published: March 2012

We present horizontally‐oriented multiwalled carbon nanotubes (CNTs) grown by means of thermal chemical vapor deposition. The CNT is across the trenches of the catalytic metals on predefined Ti electrodes. The properties of the lateral multiwalled CNT, following post‐ammonia plasma treatment, are reported. Information about the ammonia plasma treated on the interface structure of CNT is obtained using X‐ray photoelectron spectroscopy. The experimental results show that upon exposure to ammonia, the electrical property of the CNT is found to increase. Copyright © 2012 John Wiley & Sons, Ltd.
Effect of field emission property of carbon‐like nanofiber treated by using a fluorocarbon/oxygen plasma
Authors: Tsai Chien‐Huang
Published: March 2012

Carbon‐like nanofiber (CNF) is synthesized using microwave plasma‐enhanced chemical vapor deposition. We present the effects of fluorocarbon and oxygen (CF4/O2) plasma‐treated on the microstructural, crystal, and field emission (FE) characteristics of CNF by SEM, transmission electron microscopy, micro‐Raman, and FE system. Results showed that the presence of the damaged CNF occurs at 2 min CF4/O2 plasma treatment and some amorphous carbon particles after 10 min CF4/O2 plasma treatment. One can also observe that turn‐on fields were enhanced (2.75 uA/cm2) at 2 min CF4/O2 plasma treatment; this indicates a remarkable FE enhancement of the local emission region in CNFs. Complementary information was obtained by thermal desorption atmospheric pressure ionization mass spectrometry and XPS. It can be found that the broken surface morphologies could be attributed to the chemical reaction exchanged via plasma excitation; a large number of bonding (C–F and C–O) in the CNF was detected. In addition, it is observed that the CNF has higher fluorine desorbed at 277.5 and 427 °C after CF4/O2 plasma treatment. Copyright © 2012 John Wiley & Sons, Ltd.
Damage profiles of Si (001) surface via Ar cluster beam sputtering
Authors: Kyoung Yong Koo , Lee Hyung Ik , Chung Jae Gwan , Heo Sung , Lee Jae Cheol , Cho Young Joon , Kang Hee Jae
Published: March 2012

Damage profiles on Si (001) surface via argon gas cluster ion beam sputtering and mono‐atomic argon ion beam sputtering were investigated using medium energy ion scattering. The surface thickness damaged by Ar cluster ion beam sputtering was approximately 10 nm for 20 keV, 6.4 nm for 10 keV, and 4.2 nm for 5 keV and the composition of the implanted Ar atoms was 0.2 at% for 20 keV and 0.1 at% for both 10 and 5 keV. The surface thickness damaged by Ar ion beam sputtering was approximately 5.3 nm for 1 keV, 8.5 nm for 2 keV, and 12 nm for 3 keV and the maximum Ar concentration of the implanted Ar atoms in the Si substrate was 5.5 at% for 1 keV, 5.8 at% for 2 keV, and 7.8 at% for 3 keV. The depth of the damaged layers after Ar ion sputtering on Si (001) is proportional to the in‐depth distribution of the implanted primary Ar ions. The depth of the damaged layer after the Ar cluster ion beam sputtering did not depend on the implanted Ar atoms because the implanted Ar atoms are negligible. Understanding the details about the damage process via Ar cluster ion beam sputtering can be useful for the practical surface analysis. Copyright © 2012 John Wiley & Sons, Ltd.
Der Bau eiserner Brücken im Südwesten Deutschlands 1844 bis 1889 – Vom Gitterträger zum Fachwerk (Teil 3)
Authors: Trautz Martin , Voormann Friedmar
Published: March 2012

Zwischen 1856 und 1858 hatte die Pforzheimer Firma Gebrüder Benckiser mehrere große Gitterträgerbrücken für die Schweizer Eisenbahngesellschaften ausgeführt. Entgegen den Entwicklungen in Preußen handelte es sich dabei um gelenklose Durchlaufträger über drei oder vier Felder. Für diesen Brückentyp optimierte Benckiser den Bauvorgang: der Kastenträger, gebildet aus den Gitterträgern und den Querträgern, wurde auf einer Widerlagerseite vorgefertigt, dann mittels Walzen und einem Hebelmechanismus frei auskragend auf die Pfeiler und schließlich bis auf das jenseitige Widerlager hinübergeschoben.

In diesem Bauverfahren, das heute als Taktschiebeverfahren vor allem im Betonbrückenbau Anwendung findet, errichteten die Gebrüder Benckiser zwischen 1859 und 1860 zwei grenzüberschreitende Eisenbahnbrücken: die Rheinbrücke Waldshut–Koblenz und die Rheinbrücke Kehl–Straßburg. Erst nach 1860 ging man im Südwesten zum Bau mehrgliedriger Streben‐ und Ständerfachwerkträger mit parallelen oder gekrümmten Gurten über.

The construction of iron bridges in the southwest of Germany from 1844 to 1889 – from lattice girders to truss girders (part 3). Between 1856 and 1858, Bros. Benckiser, a company from Pforzheim in Germany, had built several lattice girder bridges for Switzerland’s railway companies. In contrast to developments in Prussia, they were built as continuous beams without joints, spanning three to four bays. Benckiser used this structural feature for the construction process of the bridges and optimized it that way. The box girder was prefabricated as lattice girder at one abutment side and pushed on rollers and lifting mechanisms, cantilevering at the intermediate supports, into its final position.

With this construction process, which is known today as Incremental Launching Method and used primarily in concrete bridge building, Benckiser Bros. constructed two cross‐boundary railway bridges between 1859 and 1860: the Rhine bridges Waldshut–Koblenz and Kehl–Strassburg. It was not until 1860 that the company adopted truss girders with single or multiple bracing for steel bridges with parallel or curved chords.
Prüfungen im großen Maßstab
Authors: Weich Imke , Lorenz Jan , Fischl Andreas , Rodic Slobodan , Buschner Josef
Published: March 2012

Wissenschaftliche und anwendungsorientierte versuchstechnische Untersuchungen werden größtenteils an skalierten Kleinproben durchgeführt, um diese im Labor mit akzeptablem Aufwand umsetzen zu können. Allerdings ist bei der Bewertung der Ergebnisse zu berücksichtigen, dass aufgrund der Skalierung der Versuchskörper im Vergleich zum realen Bauteil Maßstabseffekte auftreten können. Dabei sind geometrische, statistische und technologische Größeneinflüsse zu berücksichtigen, die sich im Stahlbau insbesondere auf die Ermüdungsfestigkeit von Bauteilen auswirken.

An der Hochschule München, Labor für Stahl und Leichtmetallbau, wurden aus diesem Grund von Professor Bucak in den letzten Jahren vielfältige Großbauteilversuche durchgeführt. Im vorliegenden Beitrag werden Untersuchungsergebnisse vorgestellt, anhand derer die Bedeutung von Großbauteilversuchen deutlich wird sowie der auftretende Maßstabseffekt bewertet werden kann.

Large‐scale testing. Most scientific laboratory testing for practical construction applications is carried out using small, scaled‐down models in order to keep expenses to an acceptable level. However, in the evaluation of results it is important to remember that size effects may occur due to the scaled‐down size of the test specimen compared to the real component. Geometric, statistical and technological factors have to be considered which may have an effect on the fatigue strength, in particular, of components in steel constructions.

For this reason, over recent years Professor Bucak has carried out a variety of large‐scale component tests at the Munich University Steel and Light Metal Construction Laboratory. The article below presents research results which highlight the importance of large‐scale component testing and evaluate any occurring size effects.
Effect of gap width on stability of non‐Newtonian Taylor‐Couette flow
Authors: Ashrafi N. , Karimi Haghighi H.
Published: March 2012

The effect of gap width on the stability of non‐Newtonian Taylor‐Couette flow is studied. The fluid is assumed to follow the pseudo plastic Carreau‐Bird model and mixed boundary conditions are imposed. The dynamical system, resulted from Galerkin projection of the conservation of mass and momentum equations, includes additional nonlinear terms in the velocity components originated from the shear‐dependent viscosity. It is observed that, depending on the gap width for certain fluid, the base flow loses its radial flow stability to the vortex structure known as Taylor vortices. The emergence of theses vortices corresponds to the onset of a supercritical bifurcation also seen in the flow of a linear fluid. A range of parameters is found in which the combination of shear thinning and gap effect leads to destabilizing the vortex structure indicated as the point of Hopf bifurcation. This is not observed in the Newtonian flow, in which the vortices remain stable regardless of the inertia. Furthermore, upon increase of gap width both the critical Taylor and Hopf bifurcation numbers also increase. The obtained results are in good agreement with the available studies carried out only for certain cases.
Crack on the boundary of a thin elastic inclusion inside an elastic body
Authors: Khludnev A. , Negri M.
Published: March 2012

We propose a model for a 2D elastic body with a thin elastic inclusion in which delamination of the inclusion may take place, thus forming a crack. Non‐linear boundary conditions at the crack faces are imposed to prevent mutual penetration. We prove existence and uniqueness of the equilibrium configuration, considering both the variational and the differential formulations. Moreover, we study the dependence of solutions on the rigidity of the beam and we prove that in the limit corresponding to infinite and zero rigidity, we recover the case of a semi‐rigid inclusion and the case of a crack with non‐penetration conditions, respectively. The convergence of solutions is proved both using variational inequalities and Γ‐convergence.
Preoperative Assessment of the Pancreas in Multiple Endocrine Neoplasia Type 1
Authors: Lewis Mark A. , Thompson Geoffrey B. , Young William F.
Published: March 2012

Background

Many serologic and radiographic modalities are used for monitoring multiple endocrine neoplasia type 1 (MEN 1) patients for pancreaticoduodenal neuroendocrine tumors (PNETs). We compared serum markers and imaging studies obtained preoperatively with the gross pathology and immunohistochemical findings and correlated preoperative testing with postoperative outcome.

Methods

From 2000 to 2008, 52 MEN 1 patients [32 (62%) female; median age = 43 years, range 19–74 years] underwent 56 pancreatic operations [49 (88%) distal pancreatectomies] for suspected PNETs. Preoperative serum markers [human pancreatic polypeptide (HPP), gastrin, and glucagon] and imaging [CT, 111In pentetreotide scintigraphy, and endoscopic ultrasound (EUS)] were compared to the pathologic findings. Postoperative serum markers and survival were followed.

Results

Human pancreatic polypeptide had the highest agreement between an elevated serum level and positive tumor immunostaining (83% vs. 50% agreement for gastrin vs. 67% agreement for glucagon). Preoperative CT had 81% sensitivity and positive predictive value (PPV) of 97% for PNETs. 111In pentetreotide scintigraphy had 84% sensitivity and PPV of 96%. Preoperative endoscopic ultrasonography (EUS) had 100% sensitivity and PPV, with close correlation (rs = 0.93) between the largest lesion seen on EUS and pathology. Median follow‐up was 4.3 years (range = 0.1–10.9 years). Overall survival was 89% at 5‐year follow‐up.

Conclusions

Our study substantiates EUS as providing the highest preoperative sensitivity and PPV in assessing the presence of PNETs in MEN 1 patients. CT and octreotide scintigraphy can yield both false‐positive and false‐negative results. HPP, gastrin, and glucagon were the most commonly measured tumor markers in our series but did not always correlate with immunostaining. With an aggressive surgical approach, satisfactory rates of biochemical improvement and long‐term survival were observed.
Integrated organic–aqueous biocatalysis and product recovery for quinaldine hydroxylation catalyzed by living recombinant Pseudomonas putida
Authors: Ütkür F Özde , Thanh Tran Tan , Collins Jonathan , Brandenbusch Christoph , Sadowski Gabriele , Schmid Andreas , Bühler Bruno
Published: March 2012

In an earlier study, biocatalytic carbon oxyfunctionalization with water serving as oxygen donor, e.g., the bioconversion of quinaldine to 4-hydroxyquinaldine, was successfully achieved using resting cells of recombinant Pseudomonas putida, containing the molybdenum-enzyme quinaldine 4-oxidase, in a two-liquid phase (2LP) system (Ütkür et al. J Ind Microbiol Biotechnol 38:1067–1077, 2011). In the study reported here, key parameters determining process performance were investigated and an efficient and easy method for product recovery was established. The performance of the whole-cell biocatalyst was shown not to be limited by the availability of the inducer benzoate (also serving as growth substrate) during the growth of recombinant P. putida cells. Furthermore, catalyst performance during 2LP biotransformations was not limited by the availability of glucose, the energy source to maintain metabolic activity in resting cells, and molecular oxygen, a possible final electron acceptor during quinaldine oxidation. The product and the organic solvent (1-dodecanol) were identified as the most critical factors affecting biocatalyst performance, to a large extent on the enzyme level (inhibition), whereas substrate effects were negligible. However, none of the 13 alternative solvents tested surpassed 1-dodecanol in terms of toxicity, substrate/product solubility, and partitioning. The use of supercritical carbon dioxide for phase separation and an easy and efficient liquid–liquid extraction step enabled 4-hydroxyquinaldine to be isolated at a purity of >99.9% with recoveries of 57 and 84%, respectively. This study constitutes the first proof of concept on an integrated process for the oxyfunctionalization of toxic substrates with a water-incorporating hydroxylase.
Lipid Structure of Lallemantia Seed Oil: A Potential Source of Omega‐3 and Omega‐6 Fatty Acids for Nutritional Supplements
Authors: Zlatanov Magdalen , Antova Ginka , Angelova‐Romova Maria , Momchilova Svetlana , Taneva Sabina , Nikolova‐Damyanova Boryana
Published: March 2012

The lipid composition of the seed oil of three varieties (L‐74, VIR‐11 and BGR‐455) of Lallemantia iberica Fisch. & Mey. (Lamiaceae) harvested in Bulgaria was examined in detail. Triacylglycerols (TAG >90%), phospholipids (<3%), sterol esters (~0.2%), and accompanying compounds—sterols (~0.3%) and tocopherols (336–499 mg/kg)—were determined for the first time. In addition, the specific distribution of fatty acids between the lipid classes was elucidated. Nineteen TAG species were unambiguously identified and quantified and of these the highly unsaturated trilinolenin, dilinolenyl linoleate and dilinolenyl palmitate comprised 59% of the total TAG. Phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine were the main phospholipids. Beta‐sitosterol was the main sterol component, followed by campesterol and stigmasterol. Gamma‐tocopherol predominated (>90%) in the tocopherol fraction. Palmitic acid (16:0) was the major fatty acid of the phospholipids and oleic acid (cis 9‐18:1) dominated in the sterol ester fraction. The three varieties have similar lipid compositions with BGR‐455 being slightly more saturated. Due to its composition, Lallemantia oil might compete successfully with flax and other plant oils as a source of linolenic fatty acid in industrial and dietary applications.
Communicating Phylogeny: Evolutionary Tree Diagrams in Museums
Authors: MacDonald Teresa , Wiley E. O.
Published: March 2012

Tree of life diagrams are graphic representations of phylogeny—the evolutionary history and relationships of lineages—and as such these graphics have the potential to convey key evolutionary ideas and principles to a variety of audiences. Museums play a significant role in teaching about evolution to the public, and tree graphics form a common element in many exhibits even though little is known about their impact on visitor understanding. How phylogenies are depicted and used in informal science settings impacts their accessibility and effectiveness in communicating about evolution to visitors. In this paper, we summarize the analysis of 185 tree of life graphics collected from museum exhibits at 52 institutions and highlight some potential implications of how trees are presented that may support or hinder visitors’ understanding about evolution. While further work is needed, existing learning research suggests that common elements among the diversity of museum trees such as the inclusion of anagenesis and absence of time and shared characters might represent potential barriers to visitor understanding.
Proteomic analysis of plasma from a Tau transgenic mouse
Authors: Kim Yoon‐Ha , Lee Eun‐Kyung , Park Seung‐Ah , Kim Nam‐Hee , Kim Chan‐Wha
Published: March 2012

The neurofibrillary tangles (NFTs) formed by the accumulation of abnormal tau filaments have been shown to be involved in Alzheimer's disease (AD) brain degeneration. In this study, a tau transgenic mouse (pNSE/htau23) model was used to monitor changes in protein levels and to search for novel biomarker candidates suitable for the early diagnosis of AD before onset of clinical symptoms. Plasma samples from 2‐month (n = 13, asymptomatic) and 4‐month (n = 7, symptomatic) tau transgenic mice were compared to the control group (n = 8) by 2‐dimensional gel electrophoresis (2‐DE) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Three proteins, ATP synthase, Adenosine kinase and Regucalcin showed significantly decreased levels in the plasma of tau transgenic mouse, which was further confirmed by Western blotting. This study suggests that these proteins could be used as candidate biomarkers for early diagnosis of AD in combination with previously discovered protein biomarkers.
Origin of climbing fiber neurons and the definition of rhombic lip
Authors: Dun Xin‐peng
Published: March 2012

Wilhelm His identified the rhombic lip in human embryos a century ago and thought that all mossy and climbing fiber neurons are derived from it. This has been accepted for more than one hundred years. However, recent genetic fate mapping studies have demonstrated that mossy fiber and climbing fiber neurons have distinct progenitor pools and originate from different subdomains in the ventricular zone of the caudal hindbrain. The majority of climbing fiber neurons has been found to derive from more medial parts of the caudal hindbrain although its dorsal boundary is unclear currently. Subsequently, several new definitions for the rhombic lip have been made according to the expression domain of different transcription factors, such as Math1, Wnt1 and Olig3, which have different ventral boundaries and make the area of rhombic lip confused. Therefore, a precise definition for rhombic lip is still lacking for the main reason that the origin of the entire inferior olivary nuclei is still unclear. Further genetic fate mapping is needed to determine the origin of all climbing fiber neurons which will help to give the rhombic lip an unambiguous definition.
A re-analysis of the iron content of plant-based foods in the United Kingdom
Authors: Bruggraber Sylvaine F. A. , Chapman Thomas P. E. , Thane Christopher W. , Olson Ashley , Jugdaohsingh Ravin , Powell Jonathan J.
Published: March 2012

In the UK contemporary estimates of dietary Fe intakes rely upon food Fe content data from the 1980s or before. Moreover, there has been speculation that the natural Fe content of foods has fallen over time, predominantly due to changes in agricultural practices. Therefore, we re-analysed common plant-based foods of the UK diet for their Fe content (the ‘2000s analyses’) and compared the values with the most recent published values (the ‘1980s analyses’) and the much older published values (the ‘1930s analyses’), the latter two being from different editions of the McCance and Widdowson food tables. Overall, there was remarkable consistency between analytical data for foods spanning the 70 years. There was a marginal, but significant, apparent decrease in natural food Fe content from the 1930s to 1980s/2000s. Whether this represents a true difference or is analytical error between the eras is unclear and how it could translate into differences in intake requires clarification. However, fortificant Fe levels (and fortificant Fe intake based upon linked national data) did appear to have increased between the 1980s and 2000s, and deserve further attention in light of recent potential concerns over the long-term safety and effectiveness of fortificant Fe. In conclusion, the overall Fe content of plant-based foods is largely consistent between the 1930s and 2000s, with a fall in natural dietary Fe content negated or even surpassed by a rise in fortificant Fe but for which the long-term effects are uncertain.
A new problem of evil: authority and the duty of interference
Authors: MARING LUKE
Published: March 2012

The traditional problem of evil sets theists the task of reconciling two things: God and evil. I argue that theists face the more difficult task of reconciling God and evils that God is specially obligated to prevent. Because of His authority, God's obligation to curtail evil goes far beyond our Samaritan duty to prevent evil when doing so isn't overly hard. Authorities owe their subjects a positive obligation to prevent certain evils; we have a right against our authorities that they protect us. God's apparent mistake is not merely the impersonal wrong of failing to do enough good – though it is that too. It is the highly personal wrong of failing to live up to a moral requirement that comes bundled with authority over persons. To make my argument, I use the resources of political philosophy and defend a novel change to the orthodox account of authority.
Dendritic morphology and tracer-coupling pattern of physiologically identified transient uniformity detector ganglion cells in rabbit retina
Authors: SIVYER BENJAMIN , VANEY DAVID I.
Published: March 2012

Transient uniformity detectors (UDs) are a unique type of retinal ganglion cell (RGC) whose maintained firing is transiently suppressed by all types of visual stimuli. In this study, we have characterized the dendritic morphology and tracer-coupling pattern of UDs that were labeled by loose-seal electroporation of Neurobiotin following functional identification in the isolated rabbit retina. The UDs have a bistratified dendritic tree, branching near the margins of the inner plexiform layer in stratum 1 (part of the OFF sublamina) and stratum 4/5 (part of the ON sublamina). Characteristically, many of the distal dendrites in the OFF arbor do not terminate there but dive recurrently back to the ON arbor. As a consequence, the ON dendritic arbor is usually twice as large as the OFF dendritic arbor in area. The UDs sometimes show homologous tracer coupling to neighboring RGCs with the same morphology, and from this material, we estimate that the UDs have a threefold dendritic field overlap and a maximum density of ~100 cells/mm2 on the peak visual streak, accounting for ~2% of RGCs in rabbit retina. The UDs also show strong heterologous tracer coupling to a novel type of amacrine cell that costratifies with the ON arbor of the UD. Consistent with their unistratified medium-field morphology, these St4/5 amacrine cells appear to be GABAergic: their somata are immunopositive for GABA but immunonegative for glycine and glycine transporter 1. We compare the dendritic morphology of the UDs to that of other types of bistratified RGCs described in rabbit retina and note that the stratification levels and distinctive recurrent dendrites closely resemble those of the “ON bistratified diving” RGCs. This raises the possibility that there are two types of RGCs with distinctive physiological properties that have almost identical bistratified dendritic morphologies.
Microglia and neuronal cell death
Authors: Marín-Teva José L. , Cuadros Miguel A. , Martín-Oliva David , Navascués Julio
Published: March 2012

Microglia, the brain's innate immune cell type, are cells of mesodermal origin that populate the central nervous system (CNS) during development. Undifferentiated microglia, also called ameboid microglia, have the ability to proliferate, phagocytose apoptotic cells and migrate long distances toward their final destinations throughout all CNS regions, where they acquire a mature ramified morphological phenotype. Recent studies indicate that ameboid microglial cells not only have a scavenger role during development but can also promote the death of some neuronal populations. In the mature CNS, adult microglia have highly motile processes to scan their territorial domains, and they display a panoply of effects on neurons that range from sustaining their survival and differentiation contributing to their elimination. Hence, the fine tuning of these effects results in protection of the nervous tissue, whereas perturbations in the microglial response, such as the exacerbation of microglial activation or lack of microglial response, generate adverse situations for the organization and function of the CNS. This review discusses some aspects of the relationship between microglial cells and neuronal death/survival both during normal development and during the response to injury in adulthood.
The Effect of Followers’ Belongingness Needs on Leaders’ Procedural Fairness Enactment
Authors: Cornelis Ilse , Van Hiel Alain , De Cremer David
Published: March 2012

An important component of ethical leadership entails leaders’ enactment of procedural fairness. The present two studies examined the role of followers’ relational motives as antecedents of leaders’ adherence to procedural fairness rules and explored the mediating role of attraction. In an experimental study, we demonstrated that followers’ belongingness needs influenced leaders’ inclination to grant them voice. This finding was corroborated in a multisource field study of organizational supervisors. Furthermore, these two studies demonstrated that the effect of followers’ belongingness needs on the enactment of fair procedures was mediated through a process of interpersonal and group attraction. We discuss the relevance of these findings for theories of procedural rule adherence as a dependent variable and for the literature on ethical leadership.
Ethical Leadership, Employee Well-Being, and Helping
Authors: Kalshoven Karianne , Boon Corine T.
Published: March 2012

In this multi-source study, we examined the link between ethical leadership, human resource management (HRM), employee well-being, and helping. Based on the Conservation of Resources Theory, we proposed a mediated moderation model linking ethical leadership to helping, which includes well-being as an intermediary variable and HRM as a contextual moderator. Results from 221 leader-employee dyads revealed that the relationship between ethical leadership and helping occurs through well-being only when HRM was low, but not when HRM was high. Job-related well-being fully mediated the relationship of the interaction between ethical leadership with HRM and employee helping.
A Trust-Focused Model of Leaders’ Fairness Enactment
Authors: Seppälä Tuija , Lipponen Jukka , Pirttilä-Backman Anna-Maija , Lipsanen Jari
Published: March 2012

In this article, we present a trust-focused model for understanding leader’s fairness enactment. The model suggests that leaders are motivated to act fairly to gain subordinates’ trust, to show trust in their subordinates, to show that they are worth the subordinates’ trust in them, and because they are willing to be vulnerable to the actions of cooperative subordinates. The mediating role of the leader’s trust in the relationship between a subordinate’s cooperation and the leader’s fairness is also tested.
Iron speciation and mixing in single aerosol particles from the Asian continental outflow
Authors: Moffet Ryan C. , Furutani Hiroshi , Rödel Tobias C. , Henn Tobias R. , Sprau Peter O. , Laskin Alexander , Uematsu Mitsuo , Gilles Mary K.
Published: March 2012

Bioavailable iron from atmospheric aerosol is an essential nutrient that can control oceanic productivity, thereby impacting the global carbon budget and climate. Particles collected on Okinawa Island during an atmospheric pollution transport event from China were analyzed using complementary single particle techniques to determine the iron source and speciation. Comparing the chemical composition and spatial distribution of iron within ambient particles and standard Asian mineral dust, it was determined that field‐collected atmospheric Fe‐containing particles have numerous sources, especially anthropogenic sources such as coal combustion. Fe‐containing particles were found to be internally mixed with secondary species such as sulfate, soot, and organic carbon. The mass weighted average Fe(II) fraction (defined as Fe(II)/[Fe(II) + Fe(III)]) was determined to be 0.33 ± 0.08. Within the experimental uncertainty, this value lies close to the range of 0.26–0.30 determined for representative Asian mineral dust. Previous studies have indicated that the solubility of iron from combustion is much higher than that from mineral dust. Therefore, chemical and/or physical differences other than oxidation state may help explain the higher solubility of iron in atmospheric particles.
Toward disentangling the effect of hydrologic and nitrogen source changes from 1992 to 2001 on incremental nitrogen yield in the contiguous United States
Authors: Alam Md Jahangir , Goodall Jonathan L.
Published: March 2012

The goal of this research was to quantify the relative impact of hydrologic and nitrogen source changes on incremental nitrogen yield in the contiguous United States. Using nitrogen source estimates from various federal data bases, remotely sensed land use data from the National Land Cover Data program, and observed instream loadings from the United States Geological Survey National Stream Quality Accounting Network program, we calibrated and applied the spatially referenced regression model SPARROW to estimate incremental nitrogen yield for the contiguous United States. We ran different model scenarios to separate the effects of changes in source contributions from hydrologic changes for the years 1992 and 2001, assuming that only state conditions changed and that model coefficients describing the stream water‐quality response to changes in state conditions remained constant between 1992 and 2001. Model results show a decrease of 8.2% in the median incremental nitrogen yield over the period of analysis with the vast majority of this decrease due to changes in hydrologic conditions rather than decreases in nitrogen sources. For example, when we changed the 1992 version of the model to have nitrogen source data from 2001, the model results showed only a small increase in median incremental nitrogen yield (0.12%). However, when we changed the 1992 version of the model to have hydrologic conditions from 2001, model results showed a decrease of approximately 8.7% in median incremental nitrogen yield. We did, however, find notable differences in incremental yield estimates for different sources of nitrogen after controlling for hydrologic changes, particularly for population related sources. For example, the median incremental yield for population related sources increased by 8.4% after controlling for hydrologic changes. This is in contrast to a 2.8% decrease in population related sources when hydrologic changes are included in the analysis. Likewise we found that median incremental yield from urban watersheds increased by 6.8% after controlling for hydrologic changes—in contrast to the median incremental nitrogen yield from cropland watersheds, which decreased by 2.1% over the same time period. These results suggest that, after accounting for hydrologic changes, population related sources became a more significant contributor of nitrogen yield to streams in the contiguous United States over the period of analysis. However, this study was not able to account for the influence of human management practices such as improvements in wastewater treatment plants or Best Management Practices that likely improved water quality, due to a lack of data for quantifying the impact of these practices for the study area.
Resource quality affects carbon cycling in deep-sea sediments
Authors: Mayor Daniel J , Thornton Barry , Hay Steve , Zuur Alain F , Nicol Graeme W , McWilliam Jenna M , Witte Ursula F M
Published: March 2012

Deep-sea sediments cover ∼70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of 13C-labelled diatoms and faecal pellets to a cold water (−0.7 °C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized >300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource quality-limited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth.
Buffer layer-induced positive magnetoresistance in manganite-based heterojunctions
Authors: Gao W. W. , Lü W. M. , Wei A. D. , Wang J. , Shen J. , Shen B. G. , Sun J. R.
Published: March 2012

Effects of the LaMnO3 (LMO) buffer layer on the magnetoresistive behaviors of La0.67A0.33MnO3/LaMnO3/SrTiO3:0.05 wt% Nb (LAMO/LMO/STON, A = Ca, Sr) have been experimentally studied. In addition to an enhanced response to a magnetic field, the current-voltage relations show a downward shift in magnetic field, indicating an increase of the junction resistance. It is completely different from that observed in the junctions without buffer layer. The positive magnetoresistance (MR) is strongly dependent on the thickness of the LMO layer, increasing first then decreasing with the increase of layer thickness. Furthermore, it is significantly stronger in LCMO/LMO/STON than in LSMO/LMO/STON. The maximal MR at 50 K is ∼90% for LCMO/LMO/STON and ∼52% for LSMO/LMO/STON, occurring at the LMO thickness of 4 nm under the field of 5 T. The MR persists up to 350 K, and it is ∼30% and ∼24% for the LCMO and LSMO junctions, respectively. An analysis of the current-voltage characteristics indicates an increase in interfacial barrier in magnetic field, which is the origin for the positive MR.
The magnetocaloric effect and critical behavior in amorphous Gd60Co40−xMnx alloys
Authors: Zheng Z. G. , Zhong X. C. , Yu H. Y. , Franco V. , Liu Z. W. , Zeng D. C.
Published: March 2012

The amorphous alloys Gd60Co40−xMnx (x = 0, 5, 10, 15) were prepared by melt spinning. The Curie temperature, Tc, increases monotonously with Mn addition, ranging from 198 K for x = 0 to 205 K for x = 15, while the maximum values of −ΔSM under the applied field change from 0 to 5 T are 7.7, 7.1, 6.2 and 5.4 J·kg−1·K−1 for x = 0, 5, 10, and 15, respectively. All samples undergo a second order ferri-paramagnetic phase transition. The critical behavior around the transition temperature is investigated in detail, using both the standard Kouvel-Fisher procedure as well as the study of the field dependence of the magnetocaloric effect. Results indicate that the obtained critical exponents are reliable, and that the present alloys exhibit local magnetic interaction.
Multiferroic behavior of disordered bismuth-substituted zinc ferrite
Authors: Mito S. , Takagi H. , Baryshev A. V. , Inoue M.
Published: March 2012

In this study, we reported the multiferroic behavior of disordered bismuth-substituted zinc ferrite. Bi:ZnFe2O4 films were deposited by using the RF-magnetron sputtering method. As-deposited films exhibited a ferromagnetic hysteresis and a large Faraday rotation angle in the short wavelength range (∼400 nm): a saturation magnetization of 120 G and the Faraday rotation angle of −1.2 deg/μm were observed. Ferroelectric hysteresis was measured using the Sawyer-Tower method. Dielectric constant of Bi:ZnFe2O4 was measured with a LCR meter in a frequency range from 120 Hz to 100 kHz. For 120 Hz, the dielectric constant of 800 was observed at room temperature. By contrast, the dielectric constant of disordered zinc ferrite was 5.5 at 120 Hz. Our studies showed that bismuth substitution in ZnFe2O4 enhanced the dielectric constant drastically. Furthermore, in the films, voltage-induced alteration of the magneto-optic Kerr rotation angle was identified.
Observations of ferrofluid flow under a uniform rotating magnetic field in a spherical cavity
Authors: Torres-Díaz Isaac , Rinaldi Carlos , Khushrushahi Shahriar , Zahn Markus
Published: March 2012

Flow of a ferrofluid in spherical and cylindrical geometries were measured under the influence of a uniform rotating magnetic field produced by two perpendicular spherical coils, a so-called fluxball, excited by quadrature currents. Using an ultrasound velocity profile technique and a commercial oil based ferrofluid (EFH1, Ferrotec) we observed rotational flow around the z-axis. In comparison, the radial component of the flow was found to be negligible. Results show that the magnitude of the azimuthal velocity profile increases as the applied magnetic field amplitude increases. This behavior is also observed for ferrofluid in a cylindrical container placed inside the fluxball cavity and inside a two-pole stator winding. These results indicate that inhomogeneities in the magnetic field produced by slots and finite height of the stator winding used in prior experiments are not the source of previously observed flows produced by a two pole stator winding. The experiments reported here either point to the existence of non-uniform demagnetizing magnetic fields due to the finite height of the cylindrical container, the existence of couple stresses and spin viscosity in ferrofluids, or to the need to develop alternate governing and constitutive equations capable of describing the experimental observations.
Monte Carlo simulations of Landau-Lifshitz dynamics driven by a jump-noise process
Authors: Lee A. , Liu Z. , Serpico C. , Bertotti G. , Mayergoyz I.
Published: March 2012

A numerical technique for Monte Carlo simulations of Landau-Lifshitz dynamics driven by a jump-noise process is presented and illustrated by numerical examples. The two central elements of this technique are the “midpoint” finite-difference scheme for integration of deterministic precessions and “self-scattering” which results in time-homogenization of a jump-noise process.
Exciton transport in organic semiconductors: Förster resonance energy transfer compared with a simple random walk
Authors: Feron K. , Zhou X. , Belcher W. J. , Dastoor P. C.
Published: March 2012

Förster resonance energy transfer theory (FRET) and a simple random walk (RW) are both implemented in a dynamic Monte Carlo simulation with the aim of determining the exciton diffusion length from photoluminescence (PL) measurements. The calculated diffusion lengths obtained from both models are shown to be the same. As such, given that the computational time of a random walk is typically 2–3 orders of magnitude smaller than the FRET approach, this work shows that the RW methodology can be a preferable model for the determination of diffusion lengths. We also show that the RW approach may also be implemented in Monte Carlo simulations that describe organic solar cells. Despite the fact that (compared with FRET) RW does not account for non-nearest neighbor hopping or energy relaxation, we show that the resulting overestimation of the simulated current will not exceed 2% for typical OPV parameters. In addition, by taking advantage of the gain in speed we are able to investigate the impact of the exciton diffusion length on the optimal interface distance and show that materials with longer exciton diffusion lengths are less sensitive to variations in the morphology of the active layer of an organic solar cell.
Bunching characteristics of silicon nanowire arrays
Authors: Khorasaninejad Mohammadreza , Abedzadeh Navid , Singh Jawanda Ajayinder , O Nixon , Anantram M. P. , Singh Saini Simarjeet
Published: March 2012

Ordered arrays of silicon nanowires were fabricated by etching, and their bunching characteristics were parametrically studied by varying the diameter, the length, and the pitch. The diameter to length ratio was found to be critical for the nanowires to stand vertically without bunching. For a length of 650 nm, 40 nm and larger diameter nanowires were vertical, whereas for a length of 400 nm, 34 nm and larger diameter nanowires were vertical. Further, the phase change between the bunching and vertical nature of nanowires happens abruptly and was verified by finite element modeling of the deflections of the nanowire tips for different diameters. The detailed experimental study provides guidelines for silicon nanowire arrays being considered for different applications including solar cells, optical waveguides, and sensors.
Dynamical heterogeneity in a highly supercooled liquid under a sheared situation
Authors: Mizuno Hideyuki , Yamamoto Ryoichi
Published: March 2012

In the present study, we performed molecular dynamics simulations and investigated dynamical heterogeneity in a supercooled liquid under a steady shear flow. Dynamical heterogeneity can be characterized by three quantities: the correlation length ξ4(t), the intensity χ4(t), and the lifetime τhetero(t). We quantified all three quantities by means of the correlation functions of the particle dynamics, i.e., the four-point correlation functions, which are extended to the sheared condition. Here, to define the local dynamics, we used two time intervals t = τα and τngp; τα is the α-relaxation time, and τngp is the time at which the non-Gaussian parameter of the Van Hove self-correlation function is maximized. We discovered that all three quantities (ξ4(t), χ4(t), and τhetero(t)) decrease as the shear rate $\dot{\gamma }$γ̇ of the steady shear flow increases. For the time interval t = τα, the scalings $\xi _4(\tau _\alpha ) \sim \dot{\gamma }^{-0.08}$ξ4(τα)∼γ̇−0.08, $\chi _4(\tau _\alpha ) \sim \dot{\gamma }^{-0.26}$χ4(τα)∼γ̇−0.26, and $\tau _{\rm hetero}(\tau _\alpha ) \sim \dot{\gamma }^{-0.88}$τ hetero (τα)∼γ̇−0.88 were obtained. The steady shear flow suppresses the heterogeneous structure as well as the lifetime of the dynamical heterogeneity. In addition, we demonstrated that all three quantities in the sheared non-equilibrium state can be mapped onto those in the equilibrium state through the α-relaxation time τα. This finding means that the same relation between τα and three quantities holds in both the equilibrium state and the sheared non-equilibrium state and therefore proposes that the dynamical heterogeneity can play a similar role in the drastic change of τα due to not only the temperature but also the shear rate.
Natural polarizability and flexibility via explicit valency: The case of water
Authors: Kale Seyit , Herzfeld Judith
Published: March 2012

As the dominant physiological solvent, water drives the folding of biological macromolecules, influences conformational changes, determines the ionization states of surface groups, actively participates in catalytic events, and provides “wires” for long-range proton transfer. Elucidation of all these roles calls for atomistic simulations. However, currently available methods do not lend themselves to efficient simulation of proton transfer events, or even polarizability and flexibility. Here, we report that an explicit account of valency can provide a unified description for the polarizability, flexibility, and dissociability of water in one intuitive and efficient setting. We call this approach LEWIS, after the chemical theory that inspires the use of valence electron pairs. In this paper, we provide details of the method, the choice of the training set, and predictions for the neat ambient liquid, with emphasis on structure, dynamics, and polarization. LEWIS water provides a good description of bulk properties, and dipolar and quadrupolar responses.