bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanodot to nanowire: A strain-driven shape transition in self-organized endotaxial CoSi2 on Si(100)
Authors: Mahato J. C. , Das Debolina , Juluri R. R. , Batabyal R. , Roy Anupam , Satyam P. V. , Dev B. N.
Published: July 2012

We report a phenomenon of strain-driven shape transition in the growth of nanoscale self-organized endotaxial CoSi2 islands on Si(100) substrates. Nanodots of CoSi2 grow in the square shape following the four fold symmetry of the Si(100) substrate, up to a critical size of 67 × 67 nm2, where a shape transition takes place. Larger islands grow as nanowires with ever increasing length and the width decreasing to an asymptotic value of ∼25 nm. This produces long nanowires of nearly constant width. The endotaxial nanostructures grow into the Si substrate with a small extension above the surface.
Radially dependent effective piezoelectric coefficient and enhanced piezoelectric potential due to geometrical stress confinement in ZnO nanowires/nanotubes
Authors: Kim S. M. , Sohn J. I. , Kim H. J. , Ku J. , Park Y. J. , Cha S. N. , Kim J. M.
Published: July 2012

A theoretical model for the radially dependent effective piezoelectric coefficient and corresponding piezoelectric potential in intrinsic ZnO nanowires (NWs)/nanotubes (NTs) is presented. Substrate-bound ZnO structures oriented along the c-axis with diameters of 100–5000 nm (NWs) and inner diameters of 100–900 nm (NTs; fixed outer diameter, 1000 nm) were examined using finite element method analysis. The piezoelectric potential depended nonlinearly on the NT/NW size, which we explain using the effective piezoelectric coefficient and peak piezoelectric potentials. We propose that this coefficient can be used to judge the degree of enhancement of the piezoelectric potential in ZnO NWs/NTs.
Epitaxial relationship of semipolar s-plane (11¯01) InN grown on r-plane sapphire
Authors: Dimitrakopulos G. P.
Published: July 2012

The heteroepitaxy of semipolar s-plane (11¯01) InN grown directly on r-plane sapphire by plasma-assisted molecular beam epitaxy is studied using transmission electron microscopy techniques. The epitaxial relationship is determined to be (11¯01)InN ∥ (11¯02)Al2O3, [1¯1¯20]InN ∥ [202¯1¯]Al2O3, [11¯02¯]InN ∼∥ [022¯1]Al2O3, which ensures a 0.7% misfit along [1¯1¯20]InN. Two orientation variants are identified. Proposed geometrical factors contributing to the high density of basal stacking faults, partial dislocations, and sphalerite cubic pockets include the misfit accommodation and reduction, as well as the accommodation of lattice twist.
Quantitative study of the interfacial intermixing and segregation effects across the wetting layer of Ga(As,Sb)-capped InAs quantum dots
Authors: Luna Esperanza , Beltrán Ana M. , Sánchez Ana M. , Molina Sergio I.
Published: July 2012

Quantitative chemical information from semiconductor nanostructures is of primary importance, in particular at interfaces. Using a combination of analytical transmission electron microscopy techniques, we are able to quantify the interfacial intermixing and surface segregation across the intricate non-common-atom wetting layer (WL) of Ga(As,Sb)-capped InAs quantum dots. We find: (i) the WL-on-GaAs(buffer) interface is abrupt and perfectly defined by sigmoidal functions, in analogy with two-dimensional epitaxial layers, suggesting that the interface formation process is similar in both cases; (ii) indium segregation is the prevailing mechanism (e.g., over antimony segregation), which eventually determines the composition profile across the GaAs(cap)-on-WL interface.
Monolithic high-temperature superconducting heterodyne Josephson frequency down-converter
Authors: Du J. , Zhang T. , Macfarlane J. C. , Guo Y. J. , Sun X. W.
Published: July 2012

A monolithic microwave integrated circuit (MMIC) frequency down-converter based on a compact high-Tc superconducting (HTS) device is demonstrated. The on-chip integrated HTS down-converter consists of a 7–9 GHz bandpass filter for RF input, a lowpass filter for intermediate frequency output, and a self-pumped Josephson heterodyne mixer. All the above passive and active components are fabricated on a single 10 mm × 20 mm chip of YBa2Cu3O7−x film on MgO substrate. Characterization of this MMIC HTS down-converter in terms of frequency response, conversion gain, frequency-tuneability, bias dependence, dynamic range, linearity, and intrinsic noise are presented in this paper.
Correlation between reflectivity and resistivity in multi-component metallic systems
Authors: Hu T. T. , Hsu J. H. , Huang J. C. , Kuan S. Y. , Lee C. J. , Nieh T. G.
Published: July 2012

Optical reflectivity and electrical resistivity of multi-component AgMgAl alloys, both crystalline and amorphous, were measured. The crystalline alloys exhibit high reflection in infrared region but a steeper drop in visible and ultraviolet regions. By contrast, amorphous alloys show a lower but relatively uniform reflectivity in the visible and infrared regions. In both cases, the reflectivity was observed to scale with the square root of electrical resistivity. The scaling law was explained based on classical reflection theory. The different scaling factors for crystalline and amorphous alloys could be rationalized by the difference in the mean free time of charge carriers.
Magnetostriction in the vicinity of structural transitions in Ni2MnGa
Authors: Barandiarán J. M. , Chernenko V. A. , Gutiérrez J. , Orúe I. , Lázpita P.
Published: July 2012

We report parallel and perpendicular magnetostriction measurements performed in polycrystalline Ni2MnGa to shed light on the magnetoelastic coupling, responsible for the ordinary magnetostriction, and giant magnetic field-induced strains (MFIS). Parallel magnetostriction is negative while its perpendicular component switches from positive to negative at the martensitic transformation. The saturation magnetostriction is negative, takes moderate values and has a large increase in absolute value at both pre- and martensitic temperatures, arising from the lattice softening at the transitions. The reported values are those of the true magnetostriction and can be a starting point for further studies of MFIS.
Efficiency enhancement utilizing hybrid charge generation layer in tandem organic light-emitting diodes
Authors: Xiao J. , Wang X. X. , Zhu H. , Gao X. , Yang Z. H. , Zhang X. H. , Wang S. D.
Published: July 2012

We report the incorporation of lithium fluoride doped 4,7-diphenyl-1,10-phenanthroline, Al, and molybdenum trioxide which is utilized to form the charge generation layer in tandem organic light-emitting diodes. Both the fluorescent and phosphorescent tandem devices based on this hybrid charge generation layer show the enhanced luminous efficiency and reduced operating voltage compared with the devices using conventional charge generation layer. The mechanism of the efficiency enhancement is ascribed to the improvement of charge balance due to the efficient charge separation in the hybrid charge generation layer. The hybrid layer can act as the effective charge injection buffer layer as well.
Gain measurements of scattering-assisted terahertz quantum cascade lasers
Authors: Burghoff David , Wang Ivan Chan Chun , Hu Qing , Reno John L.
Published: July 2012

Using terahertz time-domain spectroscopy, the gain of scattering-assisted terahertz quantum cascade lasers is measured. By examining the intersubband gain and absorption over a wide range of bias voltages, we experimentally detect energy anticrossings—revealing information about the mechanism of laser action—and compare the resonant-tunneling injection scheme to the scattering-assisted injection scheme. The temperature performance of the gain medium is also measured and discussed, and an additional intersubband transition is identified that contributes to scattering-assisted lasing action at high temperatures.
Enhanced piezoelectric properties of (Na0.5+y+zK0.5−y)(Nb1−xTa
x
)O3 ceramics
Authors: Sung Y. S. , Baik S. , Lee J. H. , Ryu G. H. , Do D. , Song T. K. , Kim M. H. , Kim W. J.
Published: July 2012

A- and B-site ratios in (Na0.5+y+zK0.5−y)(Nb1−xTax)O3 ceramics with ABO3 structure were investigated to differentiate the effects of polymorphic phase transition (PPT), morphotropic phase boundary (MPB), and Na nonstoichiometry on piezoelectric coefficient (d33). MPB was intrinsically determined by the ratio between Na and K, whereas PPT was extrinsically controlled by Ta substitution. PPT temperature between orthorhombic and tetragonal phases (TO−T) was reduced to room temperature at x = 0.45. d33 was increased to 310 pC/N at y = 0.03 and z = 0 by the combined effects of PPT and MPB and was further enhanced to 333 pC/N by the Na nonstoichiometry at z = 0.015 with improved density.
Magnetic and dielectric properties of Aurivillius phase Bi6Fe2Ti3O18 and the doped compounds
Authors: Yang J. , Yin L. H. , Liu Z. , Zhu X. B. , Song W. H. , Dai J. M. , Yang Z. R. , Sun Y. P.
Published: July 2012

The magnetic and dielectric properties of Bi6Fe2Ti3O18, Bi6FeCoTi3O18, and Bi5LaFeCoTi3O18 are investigated. The room-temperature ferromagnetism is observed in the samples Bi6FeCoTi3O18 and Bi5LaFeCoTi3O18 compared with the paramagnetic behavior in Bi6Fe2Ti3O18 at room temperature. The ferromagnetism in Bi6FeCoTi3O18 and Bi5LaFeCoTi3O18 can be ascribed to spin canting of the Fe-based and Co-based sublattices via the antisymmetric Dzyaloshinskii-Moriya interaction. The frequency-dependent behavior of the dielectric loss peak in Bi6FeCoTi3O18 and Bi5LaFeCoTi3O18 manifests itself a thermally activated relaxation process. The rather large activation energy (2.62 ± 0.11 eV for Bi6FeCoTi3O18 and 1.97 ± 0.07 eV for Bi5LaFeCoTi3O18) implies that the relaxation process is not due to the thermal motion of oxygen vacancies inside ceramics.
Sampled grating, distributed feedback quantum cascade lasers with broad tunability and continuous operation at room temperature
Authors: Slivken S. , Bandyopadhyay N. , Tsao S. , Nida S. , Bai Y. , Lu Q. Y. , Razeghi M.
Published: July 2012

A dual-section, single-mode quantum cascade laser is demonstrated in continuous wave at room temperature with up to 114 nm (50 cm−1) of tuning near a wavelength of 4.8 μm. Power above 100 mW is demonstrated, with a mean side mode suppression ratio of 24 dB. By changing the grating period, 270 nm (120 cm−1) of gap-free electrical tuning for a single gain medium has been realized.
Rydberg excitations power a new single-photon source
Authors: Miller Johanna L.
Published: July 2012

A long-range interaction prevents two atoms from simultaneously being driven to highly excited states.
Artificial materials manipulate heat flow
Authors: Miller Johanna L.
Published: July 2012

The layered composites conduct heat anisotropically, to counterintuitive effect.
NASA receives spy telescopes
Authors: Kramer David
Published: July 2012

Surplus instruments could mean big savings for future astrophysics missions, but not anytime soon.
Kinetics and mechanism of copper release from selected agricultural calcareous soils of northern Iran
Authors: Motlagh M. Barani
Published: July 2012

Availability of soil copper (Cu) to plants is dependent on the release into the soil solution of Cu from the solid phases. To ascertain the pattern of Cu release and the soil characteristics affecting it, the kinetics of Cu release by diethylenetriaminepentaacetic acid (DTPA) from 14 calcareous soils of northern Iran was investigated using six kinetic models. The release pattern was generally characterised by an initial fast reaction followed by a slower reaction that continued up to 192 h. The kinetic data were best described by the power function equation as evidenced by relatively high values of the coefficient of determination (R2) and relatively low values of the standard error of the estimate. The Cu release pattern based on the parabolic diffusion equation suggested the possible involvement of two different mechanisms. Conformity of the shell progressive particle diffusion equation to kinetic data may indicate that the release rate is controlled by diffusion of Cu and/or DTPA molecules through a reacted soil particle or aggregate rather than diffusion through the film surrounding soil particles. Rate constants for the power function equation (a and b), the parabolic diffusion equation (k′p), and the initial release rate (ab) were closely associated with cation exchange capacity (CEC). From results reported herein, CEC seems to be the most important influencing factor in controlling Cu release from calcareous soils of northern Iran.
How discourse context shapes the lexicon
Authors: Brown Esther L. , Raymond William D.
Published: July 2012

Using a corpus of Medieval Spanish text, we examine factors affecting the Modern Standard Spanish outcome of the initial /f/ in Latin FV‑ words. Regression analyses reveal that the frequency of a word’s use in extralexical phonetic reducing environments and lexical stress patterns significantly predict the modern distribution of f‑ ([f]) and h‑ (Ø) in the Spanish lexicon of FV‑ words. Quantification of extralexical phonetic context of use has not previously been incorporated in studies of diachronic phonology. We find no effect of word frequency, lexical phonology, word class, or word transmission history. The results suggest that rather than frequency of use, it is more specifically a word’s likelihood of use in contexts favoring reduction that promotes phonological change. The failure to find a significant effect of transmission history highlights the relative importance of language internal sources of change. Results are consistent with usage-based approaches; contextual variation creates differential articulatory pressures among words, yielding variable pronunciations that, when registered in memory, promote diachronic change.
Localizing the component processes of lexical access using modern neuroimaging techniques
Authors: Meltzer Jed A.
Published: July 2012

Neuroimaging plays an increasingly important role in the investigation of all aspects of human cognition, including language. Historically, experimental psychology and neuroimaging relied on very different techniques, as neuroimaging studies required comparisons between different tasks rather than manipulation of conditions within a single task, as is standard in behavioural experiments. However, methodology has advanced in the past decade such that many classic behavioural paradigms can now be employed in studies that measure brain activity. We review the technical foundations of conducting studies on single-trial brain responses, using event-related fMRI and electrophysiological recordings. We focus in particular on studies of picture naming, illustrating how the same techniques that were originally used to define temporal processing stages in reaction time studies can now be applied to brain imaging studies to reveal the neural localization of those stages.
Quantity, Structure, and Habitat Selection of Natural Spawning Reefs by Walleyes in a North Temperate Lake: A Multiscale Analysis
Authors: Raabe Joshua K. , Bozek Michael A.
Published: July 2012

Spawning habitat, the cornerstone of self‐sustaining, naturally reproducing walleye Sander vitreus populations, has received limited quantitative research. Our goal was to quantitatively describe the structure and quantity of natural walleye spawning habitat and evaluate potential selection of habitat in Big Crooked Lake, Wisconsin. In 2004 and 2005, we located and delineated walleye egg deposition polygons through visual snorkel and scuba surveys. We also delineated recently deposited, adhesive egg patches daily along one spawning reef in 2005. To determine habitat selection, we quantified and compared spawning and lakewide available habitat at different scales. In both years, walleyes used similar spawning habitat, including three geomorphic types: linear shorelines, a point bar, and an island. Walleyes used only 14% of the entire lake shoreline and 39% of the shoreline comprised of gravel (6.4–76.0 mm), cobble (76.1–149.9 mm), or coarser substrates for spawning in 2005, indicating selection of specific spawning habitat. Lakewide, walleyes spawned close to shore (outer egg deposition polygon boundary mean distance = 2.7 m), in shallow water (outer egg deposition polygon boundary mean depth = 0.3 m), and over gravel substrate (percent coverage mean = 64.3) having low embeddedness (mean = 1.30). Our best nearshore (0–13‐m) resource selection function predicted an increase in the relative probability of egg deposition with the increasing abundance of gravel, cobble, and rubble (150.0–303.9‐mm) substrates and a decrease with increasing distance from shore and water depth (89.9% overall correct classification). Adhesive egg patches confirmed that walleyes actively chose nearshore, shallow‐water, and coarse‐substrate spawning habitat. The quantitative habitat information and predictive models will assist biologists in developing walleye spawning reef protection strategies and potentially aid in designing and evaluating artificial spawning reefs.
The Economic Value of Catching and Keeping or Releasing Saltwater Sport Fish in the Southeast USA
Authors: Carter David W. , Liese Christopher
Published: July 2012

To evaluate the economic effects of bag limit and minimum size regulations, it is important to understand how anglers’ valuation of catch varies. Using a sportfishing demand model, we estimated angler willingness to pay (WTP) for groupers Epinephelus spp. and Mycteroperca spp., red snapper Lutjanus campechanus, dolphinfish Coryphaena hippurus, and king mackerel Scomberomorus cavalla by using data from a choice experiment survey with questions about fishing trips in the southeast USA. Beyond differentiating by species and the number of fish caught (second through sixth), our catch disposition model separately estimated angler WTP for one additional fish caught and kept, caught and released due to a minimum size limit, and caught and released due to a bag limit. Angler valuations of groupers, red snapper, and king mackerel were similar and more than five times the angler valuation of dolphinfish. For all species, the angler valuation decreased with each successive fish. For red snapper and groupers, anglers indicated that keeping a fish was worth more than eight times the value of releasing the fish due to a bag limit. For all species except king mackerel, angler WTP did not differ much between a fish released due to a bag limit and a fish released due to a size limit. For king mackerel, the value of a fish caught and released due to a bag limit was more than 2.5 times the value of a fish released due to a size limit and was nearly half the value of a fish that was caught and kept. We compared our angler WTP values with those in the literature, and we provide a policy application example. Results suggest that measures of the economic effects of sportfishing regulations can be seriously misstated if the species, number, and disposition of the catch are not considered.

Received January 3, 2011; accepted February 9, 2012
Backwaters in the Upper Reaches of Reservoirs Produce High Densities of Age-0 Crappies
Authors: Dagel Jonah D. , Miranda L. E.
Published: July 2012

Reservoir backwaters are aquatic habitats in floodplains of reservoir tributaries that are permanently or periodically flooded by the reservoir. Like many reservoir arms, backwaters are commonly shallow, littoral habitats, but they differ from arms in various respects, including their support of primarily wetland plant assemblages that are tolerant to flooding. Elsewhere, the reservoir floods mainly upland plants that are less tolerant to flooding, producing a band of barren shoreline along the fluctuation zone. We investigated differences in relative abundance of age-0 crappies Pomoxis spp. in backwaters and arms of widely fluctuating flood control reservoirs, examined the effect of water level, and estimated the likelihood and timing with which these habitats are flooded annually. Higher catch rates of age-0 crappies were obtained in backwater habitats than in arm habitats. When inundated during the crappie spawning season, backwaters provided vegetated habitat at lower water levels than arms. Backwaters flooded earlier than arms and remained flooded longer to provide prolonged nursery habitat. Whereas vegetated habitat was inundated almost yearly in backwaters and arms, inundation that was timed to the onset of spawning occurred less regularly. Because of differences in water elevation, vegetated habitats were flooded in time for crappie spawning about every other year in backwaters but only every third year in arms. Recruitment of age-0 crappies was inversely correlated with high water levels during the months preceding the spawning period, perhaps because early flooding degraded the vegetation. Our results suggest that water levels may be managed during late winter and spring to regularly flood wetland vegetation communities in backwaters; however, water levels should be maintained at or below normal pool and should only irregularly flood upland vegetation in reservoir arms to promote the preservation of such vegetation. Furthermore, management efforts to enhance crappie recruitment should consider the enhancement and preservation of backwaters.

Received June 15, 2011; accepted February 7, 2012
Observations of Hatchery-Reared Rio Grande Silvery Minnow Using a Fishway
Authors: Archdeacon Thomas P. , Remshardt W. Jason
Published: July 2012

We designed a study to determine if Rio Grande silvery minnow Hybognathus amarus, an endangered species, would use an instream, rock channel fishway on the Rio Grande near Albuquerque, New Mexico. We implanted 6,657 Rio Grande silvery minnow with passive integrated transponders and used a passive scanning station with two antennas located within the fishway to document movements from seven release locations, up to 19.7 km upstream and 13.5 km downstream of the diversion dam. Between 11 March and 21 August 2011, 243 individuals were detected (3.7% of all fish released), with 74.1% fish being detected from upstream release sites and 25.9% from downstream release sites. We determined 14 Rio Grande silvery minnow successfully ascended the fishway, and an additional 20 fish from downstream release locations were detected on the upstream antenna only, inferring passage. We conclude Rio Grande silvery minnow can use appropriately constructed fishways.

Received October 17, 2011; accepted March 21, 2012
A force for good? Markets, cellars and labour in the South African wine industry after apartheid
Authors: Ewert Joachim
                      Winfried
Published: July 2012

This paper argues that on balance, deregulation and the exposure to overseas markets has been beneficial to the South African wine industry, resulting in strong growth, increased employment and much improved international competitiveness. However, the paper also draws attention to the fact that not everybody has benefited in equal measure from the process of upgrading, modernisation and internationalisation. Since the start of the transition in the mid 1990s, a number of growers have left the industry and for many workers employment has become less secure.

[Une dynamique pour le bien? Les marchès, les caves et la main-d'œuvre dans l'industrie du vin sud-africain aprés l'apartheid]. Cet article soutient que dans l'ensemble, la déréglementation et l'ouverture aux marchés d'outre-mer ont été bénéfiques pour l'industrie du vin sud africain, ce qui a entrainé une forte croissance, favorisé l'augmentation de l'emploi et une compétitivité internationale bien améliorée. Toutefois, le document attire également l'attention sur le fait que tout le monde n'a pas à part égale profité de ce processus d'amélioration, de modernisation et d'internationalisation. Depuis le début de la transition au milieu des années 1990, un certain nombre de producteurs ont quitté l'industrie car pour de nombreux actifs, le monde du travail était devenu moins certain.

Mots-clés : les marchès ; le vin ; l'Afrique du Sud
Weber meets Godzilla: social networks and the spirit of capitalism in East Asia and Africa
Authors: Meagher Kate
Published: July 2012

This paper explores the cultural foundations of contemporary network capitalism in East Asia, and its implications for African enterprise development. It considers how neo-Weberian perspectives on the cultural determinants of East Asian network success have served to validate intensified processes of labour exploitation while glossing over the role of the state in making networks work for development. It is argued that the ideology of the Confucian ethic draws on notions of social solidarity to normalise the use of unfree labour in capitalist accumulation strategies, while concealing the critical role of the state in mobilising society around cultural values and socialising risk to diffuse potentially disruptive social tensions. The obfuscation of these processes in cultural analyses of Asian network success has cast the poor performance of African enterprise networks as a product of cultural dysfunction, obscuring underlying processes of state withdrawal and policy failure. The problems arising from Chinese business networks in Africa bring out the contradictions of cultural interpretations of network dynamism.

[Weber rencontre Godzilla : les réseaux sociaux et l'esprit du capitalisme en Asie de l'Est et en Afrique]. Cet article explore les fondements culturels du réseau du capitalisme contemporain en Asie de l'Est et ses implications pour le développement des entreprises en Afrique. Il considère la manière dont les perspectives néo-wébériennes sur les déterminants culturels de la réussite du réseau de l'Asie de l'Est ont servi à valider les processus intensifiés de l'exploitation du marché du travail tout en passant sous silence le rôle de l'État en faisant en sorte que les réseaux puissent œuvrer pour le développement. Il est soutenu que l'idéologie de l'étique confucéenne s'appuie sur les notions de solidarité sociale afin de normaliser l'utilisation du travail non libre dans les stratégies de l'accumulation capitaliste, tout en dissimulant le rôle déterminant de l'État dans la mobilisation de la société autour des valeurs culturelles et la banalisation du risque susceptible de provoquer des tensions sociales potentielles et perturbatrices. L'occultation de ces processus dans les analyses culturelles de la réussite du réseau asiatique a mis en lumière la mauvaise performance des réseaux d'entreprises africaines en tant que produit d'un dysfonctionnement culturel, occultant les processus souterrains de désengagement de l'État et l'échec des dispositions. Les problèmes émergeant des réseaux d'entreprises chinoises en Afrique mettent en évidence les contradictions d'interprétations culturelles de la dynamique de réseau.

Mots-clés: les réseaux sociaux; le capitalisme; l'Asie de l'Est; l'Afrique
Worker agency in colonial, apartheid and post-apartheid gold mining workplace regimes
Authors: Phakathi Timothy
                      Sizwe
Published: July 2012

This paper locates the understanding of the organisation of work and worker agency on South African gold mines within the context of the racialisation and deracialisation of the economic and labour market strategies of the colonial, apartheid and post-apartheid mining regimes. It argues that as much as racial and coercive labour practices profited the gold mining companies, they were not sustainable. The mineworkers were not passive acceptors of racial and coercive forms of labour control. The post-apartheid work order led to the restructuring of the gold mining workplace towards efficiency, productivity and equity. This signalled a shift from worker coercion to consent in the day-to-day running of the production process inside the pit. The paper calls attention to workers' subjective orientation, agency and resilience to repressive and contemporary work structures – not just as recipients but also as shapers of such work structures within the politics, limits and contradictions of capitalist production systems.

[Agence de travailleur sous la période coloniale, dans le cadre des activités aurifères pendant et après l'apartheid]. Ce document éclaire sur la compréhension de l'organisation du travail et de l'agence du travailleur des mines d'or sud-africaines dans le contexte de la ségrégation raciale et celui de la non-ségrégation raciale des stratégies économiques et du marché du travail des époques coloniale, d'apartheid et des régimes miniers après l'ère de l'apartheid. Il fait valoir que, au temps où la race et les pratiques de travail forcé profitaient aux compagnies minières d'or, elles n'étaient pas durables. Les mineurs n'étaient pas des accepteurs passifs face aux aspects liés à la race et à la contrainte en rapport au contrôle de la main d'œuvre. L'ordre sur le travail qui intervint après la période de l'apartheid a conduit à la restructuration du travail des mines d'or vers l'efficacité, la productivité et l'équité. Ce fut un signal pour un changement partant de la coercition des travailleurs à consentir dans la foulée et au jour le jour, à un processus de production à l'intérieur même de la fosse. Le document attire l'attention des travailleurs sur l'orientation subjective, l'agence et la flexibilité par rapport aux structures de travail contemporaines et répressives – et pas seulement en tant que bénéficiaires mais aussi comme innovateurs de telles structures au sein de la sphère politique, les limites et les contradictions des systèmes de production capitaliste.

Mots-clés: l'apartheid; la démocratie; l'exploitation des mines d'or; le marché du travail; les travailleurs; l'Afrique du Sud
The challenges and promises of new therapies for cystic fibrosis
Authors: Pier Gerald B.
Published: July 2012

Therapeutic intervention in cystic fibrosis (CF) remains a challenge, partly because of the number of organs and tissues affected by the lack of a functional cystic fibrosis transmembrane conductance regulator (CFTR) protein. CF was originally regarded primarily as a gastrointestinal (GI) disease because of the failure to thrive and early death from malnutrition in infants with CF. However, successful interventions for the GI manifestations of CF have left chronic lung infections as the primary cause of morbidity and mortality. Despite a complex microbiology within the CF lung, one pathogen, Pseudomonas aeruginosa, remains the critical determinant of pulmonary pathology. Treatment and management of this infection and its associated symptoms are the major targets of extant and developing CF therapies. Understanding the multitude of effects of CFTR on mucosal physiology and susceptibility and progression of chronic lung disease, and how host immune responses fail to adequately control lung infection, will be essential for the development of improved therapies for CF.
Atomic interface structure of bixbyite rare-earth sesquioxides grown epitaxially on Si(1 1 1)
Authors: Niehle Michael , Trampert Achim
Published: July 2012

High-resolution transmission electron microscopy (HRTEM) is applied to thin crystalline films of (Gd1−x
Lu
x
)2O3 and (La1−x
Lu
x
)2O3 on Si(1 1 1). Electron micrographs confirm that an atomically smooth and chemically abrupt interface of epitaxially grown rare-earth thin films is feasible. This work demonstrates an unambiguous recognition of cubic bixbyite, which is the common cubic phase of rare-earth sesquioxides at room temperature except for the light lanthanoids. This serves as prerequisite to analyse the atomic configuration of the cubic oxide lattice at the interface to the Si(1 1 1) surface. Two new configurations which have not been considered yet, are proposed and proved by comparison of experimental HRTEM images and contrast simulations.
Criteria for Toeplitz operators on the sphere
Authors: Xia Jingbo
Published: July 2012

Let

H

2

(
S
)

H^{2}(S)

be the Hardy space on the unit sphere

S
S

in

C

n

\mathbf {C}^{n}

. We show that a set of inner functions

Λ
\Lambda

is sufficient for the purpose of determining which

A
∈

B

(

H

2

(
S
)
)

A\in {\mathcal {B}}(H^{2}(S))

is a Toeplitz operator if and only if the multiplication operators

{

M

u

:
u
∈
Λ
}

\{M_{u} : u \in \Lambda \}

on

L

2

(
S
,
d
σ
)

L^{2}(S,d\sigma )

generate the von Neumann algebra

{

M

f

:
f
∈

L

∞

(
S
,
d
σ
)
}

\{M_{f} : f \in L^{\infty }(S,d\sigma )\}

.
The Witten deformation for even dimensional conformally conic manifolds
Authors: Ludwig Ursula
Published: July 2012

The goal of this article is to generalise the Witten deformation to even dimensional conformally conic manifolds

X
X

and a class of functions

f
:
X
→

R

f: X \to \mathbb R

called admissible Morse functions. We get Morse inequalities relating the

L

2

\mathrm {L}^2

-Betti numbers of

X
X

with the number of critical points of the function

f
f

. Hereby the contribution of a singular point

p
p

of

X
X

to the Morse inequalities can be expressed in terms of the intersection cohomology of the local Morse data of

f
f

at

p
p

. The definition of an admissible Morse function is inspired by stratified Morse theory as developed by Goresky and MacPherson.
Rhizobial Plasmids That Cause Impaired Symbiotic Nitrogen Fixation and Enhanced Host Invasion
Authors: Crook Matthew B. , Lindsay Daniel P. , Biggs Matthew B. , Bentley Joshua S. , Price Jared C. , Clement Spencer C. , Clement Mark J. , Long Sharon R. , Griffitts Joel S.
Published: July 2012

The genetic rules that dictate legume-rhizobium compatibility have been investigated for decades, but the causes of incompatibility occurring at late stages of the nodulation process are not well understood. An evaluation of naturally diverse legume (genus Medicago) and rhizobium (genus Sinorhizobium) isolates has revealed numerous instances in which Sinorhizobium strains induce and occupy nodules that are only minimally beneficial to certain Medicago hosts. Using these ineffective strain-host pairs, we identified gain-of-compatibility (GOC) rhizobial variants. We show that GOC variants arise by loss of specific large accessory plasmids, which we call HR plasmids due to their effect on symbiotic host range. Transfer of HR plasmids to a symbiotically effective rhizobium strain can convert it to incompatibility, indicating that HR plasmids can act autonomously in diverse strain backgrounds. We provide evidence that HR plasmids may encode machinery for their horizontal transfer. On hosts in which HR plasmids impair N fixation, the plasmids also enhance competitiveness for nodule occupancy, showing that naturally occurring, transferrable accessory genes can convert beneficial rhizobia to a more exploitative lifestyle. This observation raises important questions about agricultural management, the ecological stability of mutualisms, and the genetic factors that distinguish beneficial symbionts from parasites.
Energy transfer processes along a supramolecular chain of π-conjugated molecules
Authors: Schmid S. A. , Abbel R. , Schenning A. P. H. J. , Meijer E. W. , Herz L. M.
Published: July 2012

We have investigated the energy transfer dynamics in a supramolecular linear polymer chain comprising oligofluorene (OF) energy donor units linked by quadruple hydrogen-bonding groups, and oligophenylene (OPV) chain ends that act as energy acceptors. Using femtosecond spectroscopy, we followed the dynamics of energy transfer from the main chain of OF units to the OPV chain ends and simulated these data taking a Monte Carlo approach that included different extents of electronic wave function delocalization for the energy donor and acceptor. Best correlations between experimental and theoretical results were obtained for the assumption of electronic coupling occurring between a localized donor dipole moment and a delocalized acceptor moment. These findings emphasize that geometric relaxation following initial excitation of the donor needs to be taken into account, as it leads to a localization of the donor's excited state wave function prior to energy transfer. In addition, our simulations show that the energy transfer from the main chain to the ends is dominated by an interplay between slow and spatially limited exciton migration along the OF segments comprising the main chain and the comparatively faster hetero-transfer to the end-cap acceptors from directly adjoining OF segments. These results clearly support the description of host–guest energy transfer in linear polymer chains as a two-step mechanism with exciton diffusion in the host being a prerequisite to energy transfer to the guest.
Coherence and decoherence in biological systems: principles of noise-assisted transport and the origin of long-lived coherences
Authors: Chin A. W. , Huelga S. F. , Plenio M. B.
Published: July 2012

The quantum dynamics of transport networks in the presence of noisy environments has recently received renewed attention with the discovery of long-lived coherences in different photosynthetic complexes. This experimental evidence has raised two fundamental questions: firstly, what are the mechanisms supporting long-lived coherences; and, secondly, how can we assess the possible functional role that the interplay of noise and quantum coherence might play in the seemingly optimal operation of biological systems under natural conditions? Here, we review recent results, illuminate them by means of two paradigmatic systems (the Fenna–Matthew–Olson complex and the light-harvesting complex LHII) and present new progress on both questions.
Measures and implications of electronic coherence in photosynthetic light-harvesting
Authors: Smyth Cathal , Fassioli Francesca , Scholes Gregory D.
Published: July 2012

We review various methods for measuring delocalization in light-harvesting complexes. Direct relations between inverse participation ratios (IPRs) and entanglement measures are derived. The B850 ring from the LH2 complex in
Rhodopseudomonas acidophila
is studied. By analysing electronic energy transfer dynamics in the B850 ring using different metrics for quantifying excitonic delocalization, we conclude that measures of entanglement are far more robust (in terms of time scale, temperature and level of decoherence) than IPRs, and are therefore more appropriate for the purpose of studying the time evolution of coherence in a system.
STAR RNA-binding protein Quaking suppresses cancer via stabilization of specific miRNA
Authors: Chen An-Jou , Paik Ji-Hye , Zhang Hailei , Shukla Sachet A. , Mortensen Richard , Hu Jian , Ying Haoqiang , Hu Baoli , Hurt Jessica , Farny Natalie , Dong Caroline , Xiao Yonghong , Wang Y. Alan , Silver Pamela A. , Chin Lynda , Vasudevan Shobha , DePinho Ronald A.
Published: July 2012

Multidimensional cancer genome analysis and validation has defined Quaking (QKI), a member of the signal transduction and activation of RNA (STAR) family of RNA-binding proteins, as a novel glioblastoma multiforme (GBM) tumor suppressor. Here, we establish that p53 directly regulates QKI gene expression, and QKI protein associates with and leads to the stabilization of miR-20a; miR-20a, in turn, regulates TGFβR2 and the TGFβ signaling network. This pathway circuitry is substantiated by in silico epistasis analysis of its components in the human GBM TCGA (The Cancer Genome Atlas Project) collection and by their gain- and loss-of-function interactions in in vitro and in vivo complementation studies. This p53–QKI–miR-20a–TGFβ pathway expands our understanding of the p53 tumor suppression network in cancer and reveals a novel tumor suppression mechanism involving regulation of specific cancer-relevant microRNAs.
Synthetic memory circuits for tracking human cell fate
Authors: Burrill Devin R. , Inniss Mara C. , Boyle Patrick M. , Silver Pamela A.
Published: July 2012

A variety of biological phenomena, from disease progression to stem cell differentiation, are typified by a prolonged cellular response to a transient environmental cue. While biologically relevant, heterogeneity in these long-term responses is difficult to assess at the population level, necessitating the development of biological tools to track cell fate within subpopulations. Here we present a novel synthetic biology approach for identifying and tracking mammalian cell subpopulations. We constructed three genomically integrated circuits that use bistable autoregulatory transcriptional feedback to retain memory of exposure to brief stimuli. These “memory devices” are used to isolate and track the progeny of cells that responded differentially to doxycycline, hypoxia, or DNA-damaging agents. Following hypoxic or ultraviolet radiation exposure, strongly responding cells activate the memory device and exhibit changes in gene expression, growth rates, and viability for multiple generations after the initial stimulus. Taken together, these results indicate that a heritable memory of hypoxia and DNA damage exists in subpopulations that differ in long-term cell behavior.
Growth phase-dependent control of transcription start site selection and gene expression by nanoRNAs
Authors: Vvedenskaya Irina O. , Sharp Josh S. , Goldman Seth R. , Kanabar Pinal N. , Livny Jonathan , Dove Simon L. , Nickels Bryce E.
Published: July 2012

Prokaryotic and eukaryotic RNA polymerases can use 2- to ∼4-nt RNAs, “nanoRNAs,” to prime transcription initiation in vitro. It has been proposed that nanoRNA-mediated priming of transcription can likewise occur under physiological conditions in vivo and influence transcription start site selection and gene expression. However, no direct evidence of such regulation has been presented. Here we demonstrate in Escherichia coli that nanoRNAs prime transcription in a growth phase-dependent manner, resulting in alterations in transcription start site selection and changes in gene expression. We further define a sequence element that determines, in part, whether a promoter will be targeted by nanoRNA-mediated priming. By establishing that a significant fraction of transcription initiation is primed in living cells, our findings contradict the conventional model that all cellular transcription is initiated using nucleoside triphosphates (NTPs) only. In addition, our findings identify nanoRNAs as a previously undocumented class of regulatory small RNAs that function by being directly incorporated into a target transcript.
Scc1 sumoylation by Mms21 promotes sister chromatid recombination through counteracting Wapl
Authors: Wu Nan , Kong Xiangduo , Ji Zhejian , Zeng Weihua , Potts Patrick Ryan , Yokomori Kyoko , Yu Hongtao
Published: July 2012

DNA double-strand breaks (DSBs) fuel cancer-driving chromosome translocations. Two related structural maintenance of chromosomes (Smc) complexes, cohesin and Smc5/6, promote DSB repair through sister chromatid homologous recombination (SCR). Here we show that the Smc5/6 subunit Mms21 sumoylates multiple lysines of the cohesin subunit Scc1. Mms21 promotes cohesin-dependent small ubiquitin-like modifier (SUMO) accumulation at laser-induced DNA damage sites in S/G2 human cells. Cells expressing the nonsumoylatable Scc1 mutant (15KR) maintain sister chromatid cohesion during mitosis but are defective in SCR and sensitive to ionizing radiation (IR). Scc1 15KR is recruited to DNA damage sites. Depletion of Wapl, a negative cohesin regulator, rescues SCR defects of Mms21-deficient or Scc1 15KR-expressing cells. Expression of the acetylation-mimicking Smc3 mutant does not bypass the requirement for Mms21 in SCR. We propose that Scc1 sumoylation by Mms21 promotes SCR by antagonizing Wapl at a step after cohesin loading at DSBs and in a way not solely dependent on Smc3 acetylation.
The retinoblastoma tumor suppressor and stem cell biology
Authors: Sage Julien
Published: July 2012

Stem cells play a critical role during embryonic development and in the maintenance of homeostasis in adult individuals. A better understanding of stem cell biology, including embryonic and adult stem cells, will allow the scientific community to better comprehend a number of pathologies and possibly design novel approaches to treat patients with a variety of diseases. The retinoblastoma tumor suppressor RB controls the proliferation, differentiation, and survival of cells, and accumulating evidence points to a central role for RB activity in the biology of stem and progenitor cells. In some contexts, loss of RB function in stem or progenitor cells is a key event in the initiation of cancer and determines the subtype of cancer arising from these pluripotent cells by altering their fate. In other cases, RB inactivation is often not sufficient to initiate cancer but may still lead to some stem cell expansion, raising the possibility that strategies aimed at transiently inactivating RB might provide a novel way to expand functional stem cell populations. Future experiments dedicated to better understanding how RB and the RB pathway control a stem cell's decisions to divide, self-renew, or give rise to differentiated progeny may eventually increase our capacity to control these decisions to enhance regeneration or help prevent cancer development.
Immunolabeling of Thin Sections of Drosophila Tissues for Transmission Electron Microscopy: Figure 1.
Authors: McDonald Kent L. , Sharp David J. , Rickoll Wayne
Published: July 2012

The main advantage of electron microscopy (EM) for immunolabeling is resolution, but there is also another aspect that is often overlooked. For many investigators, the definitive image of an organelle is the one generated by EM. This is especially true for membranous organelles, with the possible exception of the nucleus and plant vacuoles. For example, references to the Golgi apparatus, smooth and rough endoplasmic reticulum, centriole, kinetochore, or mitochondrion typically bring to mind the images in an electron micrograph. The components of the cytoskeleton also have characteristic structural features that are associated with their EM image. Thus, it can be more effective for investigators to view gold particles superimposed over the image of a microtubule (MT) or mitochondrion using EM than to see bright dots or lines in the light microscope. This is especially true if the immunofluorescence image is of fixed cells. Here, we provide an overview of methods of EM immunolabeling used for localizing specific antigens on thin sections of Drosophila tissues.
Postembedding Immunolabeling of Thin Sections of Drosophila Tissues for Transmission Electron Microscopy
Authors: McDonald Kent L. , Sharp David J. , Rickoll Wayne
Published: July 2012

Postembedding immunolabeling using resin sections is the recommended method for beginners carrying out electron microscopy (EM) immunolabeling. Postembedding labeling refers to labeling on sections, which is a method of gaining access to the interior of the cell without the harshness of detergent or ionic extraction as is performed with preembed labeling. Investigators already familiar with routine EM-sectioning techniques find EM immunolabeling using resin sections easiest to do, as procedures are similar to those used when performing light microscopy (LM) immunolabeling, but using a different resin. In addition, the overall preservation of structure is best in resin compared to use of cryosections or preembed labeling. The most critical component of immunoEM (iEM) is what primary antibody to use. This protocol descibes antibody labeling procedures for postembedding iEM using thin sections of Drosophila tissues.