bluuebunny/crossref_metadata_2025 huggingface dataset:
From Marvelous Antidote to the Poison of Idolatry: The Transatlantic Role of Andean Bezoar Stones During the Late Sixteenth and Early Seventeenth Centuries
Authors: Stephenson Marcia
Published: January 2010

Introducing intertwined themes of profit, the hunt for treasure, and the excavation of camelid bodies; and drawing from the analysis of Renaissance medical books, bilingual Aymara–Spanish and Quechua–Spanish dictionaries, inquisition records, and inventories of curiosity cabinets, this essay considers how Peruvian bezoar stones acquired transatlantic importance following their discovery in 1568 by a Spanish soldier. In spite of its less-than-glamorous physiological genesis as a calcinated concretion formed in the digestive tract of ruminants, including the four species of Andean camelids, the bezoar stone played a significant yet academically overlooked role in the social and economic history of modern Europe and Spanish America for its use as an antidote to poisons, and the stones constituted one of the most sought-after objects for the fashionable cabinets of curiosities belonging to Europe’s powerful elites. However, for indigenous pastoral peoples, bezoars were central to the reproduction of native cultural practices and directly linked to the foundational myths of Andean cosmology. The stones were believed to protect the herds and the shepherds, for whom the camelids represented the primary source of wealth. Consequently, the bezoar stone takes on unforeseen significance as a neglected site where the colonial drama of competing epistemologies was enacted.
Undressing the Coya and Dressing the Indian Woman: Market Economy, Clothing, and Identities in the Colonial Andes, La Plata (Charcas), Late Sixteenth and Early Seventeenth Centuries
Authors: Presta Ana María
Published: January 2010

This essay addresses the specific indigenous identity of Indian women resettled in colonial La Plata, particularly those associated with mercantile trades and consequently involved in the creation of colonial markets. The search for Indian women’s urban identities rests upon the material culture associated with labor activities and social standing among those recently settled in the Spanish urban milieu. Objects and places, goods and spaces can be manipulated, reappropriated, and reinterpreted by new social actors on their road to history. Things have meaning and are bound to culture and identity. In this way, indigenous women’s dress and adornment are associated with the dramatic changes brought about by the new mercantile economy introduced by the Spaniards. Indian women who resettled in the city and gained economic success pursuing mercantile trades adopted distinctive components of female dress. These styles evoked both the recent Inca past and certain elements of Spanish attire and adornment that forged a specific identity associated with a specific trade, asserting a newly acquired status in the emerging colonial society
Premodern Shakespeare
Authors: Beckwith Sarah , Simpson James
Published: January 2010

The deepest periodic division in English literary history is between the “medieval” and the “early modern,” not least because the cultural investments in maintaining that division are exceptionally powerful. Narratives of national and religious identity and freedom; of individual liberties; of the history of education and scholarship; of reading or the history of the book; of a national drama; of the very possibility of persuasive historical consciousness itself–each of these narratives (and many more) is motivated by positing a powerful break around 1530. Late medieval English studies are rapidly transforming in many directions, but one especially vigorous transformation well underway seeks to speak across that entrenched divide. A wide range of scholars, mostly medievalists but also early modernists, have begun to set late medieval textual and dramatic cultures into dialogue with their early modern counterparts. This special issue focuses the conversation at an especially rich point, that of Shakespearean theater. These essays explore “premodern Shakespeare”: how Shakespeare's drama addresses and expresses the cultural revolution of the relatively recent past, and how Shakespeare looks as seen from the perspective of late medieval texts.
Who's Afraid of Darwin? Revisiting Chambers and Hardison... and Nietzsche
Authors: Parker John
Published: January 2010

This essay contends that medieval drama would be much better served, particularly in connection to Shakespeare, if the field were to drop its resentment of “evolution.” The standard critique, as first launched by O. B. Hardison, Jr. against E. K. Chambers, is almost completely bogus, owing to Hardison's symptomatic and crypto-religious misconception of Darwin. Chambers's evolutionary framework derives equally from Nietzsche (in particular, his concept of genealogy), and this nineteenth-century inheritance is something to embrace rather than piously castigate. A truly “Darwinian” perspective in the tradition of Nietzsche would help liberate the field from the tyranny of positivist historicism, for one thing, while offering a crucial account of the drama's role in an ongoing series of challenges to the coherence and legitimacy of Christianity.
Good King Henry and the Genealogy of Shakespeare's First History Plays
Authors: Sanok Catherine
Published: January 2010

While recent arguments for the saint play as a formal influence on the Shakespearean history play rely on a teleological notion of “secularization,” they may encourage us to rethink the genealogy of Shakespeare's earliest history plays, plays about the reign of Henry VI, who was venerated as a saint. In contrast to Tudor promotion of Henry as a saintly king, the popular cult–which preceded and outlived its political appropriation–celebrated Henry VI for his likeness to ordinary English men and women. This essay explores the resonance between the cult and the plays, especially how the physical and affective lives of English citizens attend the king's failure to symbolize the body politic. Religion can thus be understood as a mediating rather than a rejected term when studying the development of the history plays as a form for thinking about English community.
Shakespeare's Theater Games
Authors: Bishop Tom
Published: January 2010

In Shakespearean drama, the conception of acting as “play” was shaped by an inheritance of medieval “player” routines and strategies and by the environment of the professional Elizabethan theater. Arguing from a theoretical and practical discussion of the role of “play” in medieval drama, using the example of Mankind, this essay examines how the actor, seen as engaged in both collaborative and competitive play, can illuminate certain strategies in Shakespeare's work. Examples drawn from Richard III, Twelfth Night, Much Ado about Nothing, and King Lear illustrate how different kinds of playerly routines register the actor's dramatic situation on stage and how these scenes are deployed for the poetic and dramatic ends of the works. These deployments register a distinctly premodern approach to the energies of the theatrical occasion, an approach that is submerged by later developments.
“Many Zitas”: The Young Catholic Worker and Household Workers in Cold War Chile
Authors: Hutchison Elizabeth Quay
Published: January 2010

This article reconstructs the origins and effects of radical Catholic activism on the expansion of household workers' associations in Chile during the Cold War. Joining the efforts of local priests affiliated with the Juventud Obrera Católica (JOC) in the 1950s, a generation of live-in household workers in Santiago and other urban centers nurtured a sizable movement for empleadas domésticas that was unique in the Americas—the JOC de Empleadas—which joined housing and vocational services with a lay Catholic movement to advance empleadas' labor rights. Impacted by both the radicalization of their religious leadership and the revolutionary politics of the period, the Catholic household workers' movement of the 1960s turned increasingly to union organizing and legislative reform to advance its agenda, pressing for greater recognition and regulation of domestic service as a matter of labor rights. Through its focus on the Catholic Church as a transnational and hegemonic actor in the mobilization of household workers, and on the changing discourse of domestic service as “labor,” this article challenges the persistent stereotype of Latin American Catholicism in relation to workers' movements prior to Vatican II.
Nuclear-localized subtype of end-binding 1 protein regulates spindle organization in Arabidopsis
Authors: Komaki Shinichiro , Abe Tatsuya , Coutuer Silvie , Inzé Dirk , Russinova Eugenia , Hashimoto Takashi
Published: January 2010

End-binding 1 (EB1) proteins are evolutionarily conserved plus-end-tracking proteins that localize to growing microtubule plus ends where they regulate microtubule dynamics and interactions with intracellular targets. Animal EB1 proteins have acidic C-terminal tails that might induce an autoinhibitory conformation. Although EB1 proteins with the same structural features occur in plants (EB1a and EB1b in Arabidopsis thaliana), a variant form (EB1c) is present that lacks the characteristic tail. We show that in Arabidopsis the tail region of EB1b, but not of EB1c, inhibits microtubule assembly in vitro. EB1a and EB1b form heterodimers with each other, but not with EB1c. Furthermore, the EB1 genes are expressed in various cell types of Arabidopsis, but the expression of EB1c is particularly strong in the meristematic cells where it is targeted to the nucleus by a nuclear localization signal in the C-terminal tail. Reduced expression of EB1c compromised the alignment of spindle and phragmoplast microtubules and caused frequent lagging of separating chromosomes at anaphase. Roots of the eb1c mutant were hypersensitive to a microtubule-disrupting drug and complete rescue of the mutant phenotype required the tail region of EB1c. These results suggest that a plant-specific EB1 subtype has evolved to function preferentially on the spindle microtubules by accumulating in the prophase nucleus.
On the interpretation of results from small punch creep tests
Authors: Hyde T H , Stoyanov M , Sun W , Hyde C J
Published: January 2010

The small punch creep testing method is highly complex and involves interactions between a number of non-linear processes. The deformed shapes that are produced from such tests are related to the punch and specimen dimensions and to the elastic, plastic, and creep behaviour of the test material, under contact and large deformation conditions, at elevated temperature. Owing to its complex nature, it is difficult to interpret the small punch test creep data in relation to the corresponding uniaxial creep behaviour of the material. One of the aims of this paper is to identify the important characteristics of the creep deformation resulting from ‘localized’ deformations and from the ‘overall’ deformation of the specimen. Following this, the results of approximate analytical and detailed finite element analyses of small punch tests are investigated. It is shown that the regions of the uniaxial creep test curves dominated by primary, secondary, and tertiary creep are not those that are immediately apparent from the displacement versus time records produced during a small punch test. On the basis of the interpretation of the finite element results presented, a method based on a reference stress approach is proposed for interpreting the results of small punch test experimental data. Future work planned for the interpretation of small punch tests data is briefly addressed.
Recast and oxide formation in laser-drilled acute holes in CMSX-4 nickel single-crystal superalloy
Authors: Leigh S , Sezer K , Li L , Grafton-Reed C , Cuttell M
Published: January 2010

The present study investigates the effects of four controllable variables on the metallurgy and geometry of acute (30° to surface) laser percussion drilled holes in 2 mm thick flat pieces of nickel superalloy: CMSX-4. Design of experiment (DOE) and statistical modelling were used in the experimental study to understand parameter interactions. Assist gas pressure, nozzle stand-off distance, focal plane position (FPP), and number of pulses were chosen as the independent process variables. A central composite design (CCD) was chosen as it offered the most economical number of experiments for the required information. The response surface method (RSM) was used to develop three models. The significant factors in each model were identified based on the analysis of variance (ANOVA), and the models were checked by complete residual analysis. It was found that a high FPP and high nozzle stand off gave the minimum entrance oxide layer thickness whereas the recast layer was minimized for a zero FPP and high pulse number.
Shielding gas influence on the ferritic stainless steel weldability
Authors: Filho D F , Ferraresi V A , Scotti A
Published: January 2010

Ferritic stainless steels are not characterized by good weldability. Wires made of austenitic stainless steels are usually applied to join ferritic materials because of the good mechanical resistance, tenacity, and ductility reached by austenitic weld metal. However, novel ferritic stainless steel wires, stabilized with niobium and titanium, have been developed to tackle the target of matching the required mechanical properties and keeping the costs lower by using ferritic stainless steels. The characterization of these wires concerning weldability aspects (operational and metallurgical) has not been accomplished yet. The aim of the present study was to investigate the influence of the shielding gas composition (pure argon and mixtures with O2 or CO2) on the chemical composition and microstructure of weld deposits obtained with gas metal arc welding using stabilized ferritic wires (ER430Ti and ER430LNb). The study was made comparatively to a non-stabilized wire (ER430). For each combination gas/wire, three layers of beads were deposited. To prevent interference from base metal dilution, a UNS 43932 was used as support for the layers and only the last layer was analysed. A special experimental approach was applied to permit more reliable comparison among different combinations of wire-shielding gas. Predicted equations for the demanded level of stabilizers in the wire were successfully applied. The results showed that the shielding gas composition played an important role in determining the final chemical composition and microstructure of the deposits, but its effect was dependent on the chemical composition of the deposit as a rule. In general, it was confirmed that the increase in CO2 in the shielding gas augmented the carbon content (and martensite formation) in the weld metal, but wire stabilized with niobium could prevent this detrimental effect but was not able to arrest grain coarsening. There were always losses of alloying elements due to the presence of O2/CO2, but the intensity depended on the amount of titanium/niobium.
Finite element method simulation of internal defects in billet-to-billet extrusion
Authors: Hatzenbichler T , Buchmayr B
Published: January 2010

During billet-to-billet extrusion of aluminium alloys, internal defects occur at the location where the billets are welded together. These defects are unacceptable and must be cut out from the extruded section. Hence, the efficiency of this process significantly depends on the length of these internal defects. The defects that arise inside the extruded section are the so-called back-end defect, which occurs as a result of inflow of the lateral billet surface contaminated with oxide into the extrudate, and transverse welds, which occur as a result of inflow of the face surfaces of the billets pressed together. The length of these defects depends on different process parameters such as friction, billet temperature, geometry of the tools, geometry of the extrudate, etc. In this study, finite element method (FEM) simulation is done to quantify the main parameters influencing the back-end defect and transverse weld formation. The first part of this work deals with modelling techniques that have to be developed to obtain information about the length of internal defects in extruded products from FEM simulation. Comparison is done between the simulation results and experimental studies to verify the results obtained from finite element analysis. In the second part of this work, the model is used to determine the main parameters influencing the back-end defect and the length of transverse welds in a computational investigation.
Experimental investigation of the effect of the circumferential loading of a rotary striking action cropping system
Authors: Tang Y , Zhao S D , Lin J
Published: January 2010

The current paper reports the results of an experimental investigation into the effect of the circumferential loading on the quality of the billet cross-section and cropping time during a novel bar-cropping process. The new precision bar-cropping process technique uses a continuous circumferential strike on a metal bar with a pre-machined V-shaped notch. According to the relationship between loading mode and crack propagation, several different control curves of strike frequency versus time and stroke versus time were designed and applied in order to analyse how to improve the quality of the cropped billets and decrease the cropping time. The experimental results indicate that the ideal control mode is the combination of a linear decrement in the strike frequency—time curve and a linear increment in the stroke—time curve during the rotary strike cropping, by which higher cross-section quality and shorter cropping time may be achieved. Moreover, a new assessment method is proposed for the purpose of evaluating the cross-section of the cropped billet.
Stress distribution and contact status analysis of a bolted rotor with curvic couplings
Authors: Yuan S-X , Zhang Y-Y , Zhang Y-C , Jiang X-J
Published: January 2010

The aim of this article is to provide some basis for the design and assembly of a bolted rotor with curvic couplings. It is well known that the key difference between a bolted rotor with curvic couplings and an integrated one is the contact interface. According to the characteristics of curvic couplings and spindle bolts, the model of a bolted rotor with curvic couplings of the turbine end of a heavy duty gas turbine was built. A method of accurately applying the preload force has been studied in this article. The three-dimensional finite-element contact method was used, non-linear behaviours such as friction and contact were also taken into account, and the dynamic contact between the spindle bolts and the sidewall of turbine wheels was included. The tendency of stress, which involved the rotor, curvic couplings, and the spindle bolts, was determined and the radial slippage trend of curvic teeth was also determined, by investigating the stress distribution and contact behaviour of the bolted rotor with curvic couplings during the course of preload, warm-up, speed-up, and running. It can be seen from the results that the contact stress of curvic couplings is dominant during the course of preload, and the bent stress is dominant when the rotating speed increased to 3000 r/min; the stress inequality on two sides of a tooth is caused by torque, so the stress proportion induced by torque should be restricted to an appropriate level to avoid anisotropy of the rotor.
A comparative numerical study of four turbulence models for the prediction of horizontal axis wind turbine flow
Authors: Tachos N S , Filios A E , Margaris D P
Published: January 2010

The analysis of the near and far flow fields of an experimental National Renewable Energy Laboratory (NREL) rotor, which has been used as the reference rotor for the Viscous and Aeroelastic Effects on Wind Turbine Blades (VISCEL) research program of the European Union, is described. The horizontal axis wind turbine (HAWT) flow is obtained by solving the steady-state Reynolds-averaged Navier—Stokes (RANS) equations, which are combined with one of four turbulence models (Spalart—Allmaras, k—∊, k—∊ renormalization group, and k—ω shear stress transport (SST)) aiming at validation of these models through a comparison of the predictions and the free field experimental measurements for the selected rotor. The computational domain is composed of 4.2×106 cells merged in a structured way, taking care of refinement of the grid near the rotor blade in order to enclose the boundary layer approach. The constant wind condition 7.2 m/s, which is the velocity of the selected experimental data, is considered in all calculations, and only the turbulence model is altered. It is confirmed that it is possible to analyse a HAWT rotor flow field with the RANS equations and that there is good agreement with experimental results, especially when they are combined with the k—ω SST turbulence model.
A theoretical analysis of billiard ball dynamics under cushion impacts
Authors: Mathavan S , Jackson M R , Parkin R M
Published: January 2010

The last two decades have seen a growing interest in research related to billiards. There have been a number of projects aimed at developing training systems, robots, and computer simulations for billiards. Determination of billiard ball trajectories is important for all of these systems. The ball's collision with a cushion is often encountered in billiards and it drastically changes the ball trajectory, especially when the ball has spin. This work predicts ball bounce angles and bounce speeds for the ball's collision with a cushion, under the assumption of insignifi-cant cushion deformation. Differential equations are derived for the ball dynamics during the impact and these equations are solved numerically. The numerical solutions together with previous experimental work by the authors predict that for the ball—cushion collision, the values of the coefficient of restitution and the sliding coefficient of friction are 0.98 and 0.14, respectively. A comparison of the numerical and experimental results indicates that the limiting normal velo-city under which the rigid cushion assumption is valid is 2.5 m/s. A number of plots that show the rebound characteristics for given ball velocity—spin conditions are also provided. The plots quantify various phenomena that have hitherto only been described in the billiards literature.
A calculation of cricket ball trajectories
Authors: Baker C J
Published: January 2010

While a number of past investigations have measured the aerodynamic forces on cricket balls, in general these forces have not been used to calculate the trajectories of balls between bowler and batsman. This article presents such a calculation. It begins with the full trajectory equations as developed for the study of debris flight in extreme windstorms, which are adapted for the cricket ball case. A collation of earlier experimental data is then presented for drag and side force coefficients on cricket balls. From these data, which show considerable scatter, a small number of generic force characteristics are derived for use in the trajectory equations. These characteristics have constant force coefficients in the subcritical and supercritical Reynolds number regions, and a transition between these two regions with a variable gradient. An approximate analysis of the trajectory equations results in very simple forms for the trajectories in the sub- and supercritical Reynolds number regimes, which reveal the governing dimensionless parameters of the problem, and enable the effect of crosswinds to be quantified. The predicted parabolic profiles are in agreement with some very simple calculations carried out by earlier investigators, revealing the limited range of validity of such calculations, and with the limited real bowling trajectories that have been observed. A full solution of the trajectory equations is then presented for the generic force coefficient characteristics, and a study of trajectories through the Reynolds number range is carried out. In the transition region between sub- and supercritical flows, complex ball trajectories are shown to be possible.
Mechanical buckling of cylindrical shells with varying material properties
Authors: Khazaeinejad P , Najafizadeh M M
Published: January 2010

The analytical solutions of the first-order shear deformation theory are developed to study the buckling behaviour of functionally graded (FG) cylindrical shells under three types of mechanical loads. The Poisson's ratios of the FG cylindrical shells are assumed to be constant, while the Young's moduli vary continuously throughout the thickness direction according to the volume fraction of constituents given by power-law or exponential function. The stability equations are employed to obtain the closed-form solutions for critical buckling loads of each loading case. The dependence of the critical buckling loads on the variations of the material properties with a power-law or exponential function is studied. It is observed that these effects change appreciably the critical buckling loads. Results for critical loads are tabulated for thin and moderately thick shells. Although the critical buckling load of FG cylindrical shells decreases as the circumferential wave numbers increase, it rises for axially compressed long shells as the longitudinal wave numbers increase.
A three-dimensional vaneless diffuser stall model
Authors: Shen F , Chen H , Zhu X-C
Published: January 2010

A three-dimensional (3D) model is presented to study the occurrence of weak rotating waves in vaneless diffusers of centrifugal compressors. The model is an extension of the 2D one developed by Moore. 3D incompressible linearized Euler equations are cast on a rotating frame of reference travelling at the same circumferential speeds as the waves and the viscous effects are ignored. The diffuser is assumed to have two parallel walls and discharge into a large plenum. Solutions to the equations are obtained by a finite difference method and the singular value decomposition technique. Disturbances along the axial direction are found under zero undisturbed axial velocity. Resonant disturbances in the diffuser flow regardless of the compressor characteristics are also found as in the 2D cases found by Moore. Computational results show that both the critical flow angle and the propagation velocity of the wave are affected by the departure from the axial uniform distribution of the undisturbed radial velocity at the diffuser inlet, but the angle is less affected than the wave speed. The velocity distribution that satisfies Fj0rtoft's necessary conditions for flow instability is found slightly less stable and is more affected by the departure than those that do not. Shorter diffusers are affected more by the departure than the longer ones. The critical angle is shown to be increased non-linearly with the wave number and this helps to explain why wave numbers 2 to 4 are commonly observed in experiments. Finally, comparison with the experimental results in the open literature is made and a good agreement is shown.
Numerical analysis of a centrifugal fan for performance enhancement using boundary layer suction slots
Authors: Vasudeva Karanth K , Yagnesh Sharma N
Published: January 2010

Flow in centrifugal fans tends to be in a state of instability with flow separation zones on both the suction surface and the front shroud. The overall efficiency of the diffusion process in a centrifugal fan could be enhanced by judiciously introducing the boundary layer suction slots. With easy accessibility of computational fluid dynamics (CFD) as an analytical tool, an extensive numerical whole field analysis of the effect of boundary layer suction slots in discrete regions of suspected separation points is possible. This article attempts to explore the effect of boundary layer suction slots corresponding to various geometrical locations on the impeller as well as on the diffuser. The analysis shows that the suction slots located on the impeller blade near to its trailing edge appreciably improves the static pressure recovery across the fan. Slots provided at a radial distance of 30 per cent from the leading edge of the diffuser vane also significantly contribute to the static pressure recovery across the fan.
Prediction and suppression of inconsistent natural frequency and mode coupling of a cylindrical ultrasonic stator
Authors: Wang S , Xiu J , Gu J , Xu J , Liu J , Shen Z
Published: January 2010

Inconsistent frequency and mode coupling are primary concerns of ultrasonic motors. These modal properties are influenced by motor features, including piezoelectric ceramics, stator teeth, or other supports attached on a stator. While this influence is understood intuitively and has been studied numerically, they have not been clarified analytically. This work develops the analytical model of the example cylindrical stator and uses it to study the influence of the features on the modal properties. In this model, the stator is considered as a thin ring with equally spaced features. The analytical solution of the model is obtained by using the direct perturbation analysis, which connects the feature number and the wave number with the modal properties, and naturally provides an effective means to achieve the coincident frequency and suppress or even eliminate the predominant mode coupling only by optimizing the combination of the two numbers. Simulation results are well consistent with the analytical conclusions. The main feature of this work is that a quick and quantitative understanding of the effects of deviation from the perfect cylindrical stator is obtained. In addition, the derived analytical results contribute to the applications of common ultrasonic motor design choices. Furthermore, while the terminology of a cylindrical stator is used in this work, the analysis method applies for other stators, such as the disc-like or linear stator.
Cultured neural networks
Authors: Warwick K
Published: January 2010

This article looks at the use of cultured neural networks as the decision-making mechanism of a control system. In this case biological neurons are grown and trained to act as an artificial intelligence engine. Such research has immediate medical implications as well as enormous potential in computing and robotics. An experimental system involving closed-loop control of a mobile robot by a culture of neurons has been successfully created and is described here. This article gives a brief overview of the problem area and ongoing research. Questions are asked as to where this will lead in the future.
Disentangling the Impact of Multiple Innovations to Reduce Delayed Hospital Discharges
Authors: Manzano-Santaella Ana
Published: January 2010

Delayed hospital discharges are often blamed for interrupting the smooth operation of hospitals. In England, the Community Care Act in 2003 introduced fines to social services departments to resolve this issue. Evaluations of this policy reported success in the reduction of delays. However, this policy was an amalgam of several innovations, not just the introduction of fines. This simultaneity makes attribution of impact of fines a difficult task because of the potential impact of those other measures.

All the other designed organizational changes contain as much mechanisms of change as the more advertised fines. The exploration of how all these elements are connected unravels the inner workings of the programme as a whole, and by default, of the fines. This theoretical analysis also demonstrates how the reduction of some delays is based on the re-definition of key concepts for delayed discharges such as ‘safe to transfer’, team decisionmaking and causes for delays.
Predicting Utility Under Satiation and Habit Formation
Authors: Baucells Manel , Sarin Rakesh K.
Published: January 2010

We introduce a modification of the discounted utility model that accounts for both satiation and habit formation in intertemporal choice. Preferences depend on the satiation level and the habitual consumption level. These two state variables, together with the shape of the value function, drive the properties of the model. One unique feature of our model is that it addresses the trade-off between seeking variety and maintaining acquired habits. We examine several properties of our model, such as the nontrivial patterns of desirability (willingness to pay) for an additional unit of consumption, or the effect of abstaining from consumption (craving). We explore the shape of optimal consumption patterns in discrete and continuous choice settings. If subjects underestimate the changes in satiation and habituation levels, as occurs under projection bias, our model explains why people buy more when hungry, or prefer variety in advance of consumption but stay with the same consumption good in actual use.
How the Human Brain Recognizes Speech in the Context of Changing Speakers
Authors: von Kriegstein Katharina , Smith David R. R. , Patterson Roy D. , Kiebel Stefan J. , Griffiths Timothy D.
Published: January 2010

We understand speech from different speakers with ease, whereas artificial speech recognition systems struggle with this task. It is unclear how the human brain solves this problem. The conventional view is that speech message recognition and speaker identification are two separate functions and that message processing takes place predominantly in the left hemisphere, whereas processing of speaker-specific information is located in the right hemisphere. Here, we distinguish the contribution of specific cortical regions, to speech recognition and speaker information processing, by controlled manipulation of task and resynthesized speaker parameters. Two functional magnetic resonance imaging studies provide evidence for a dynamic speech-processing network that questions the conventional view. We found that speech recognition regions in left posterior superior temporal gyrus/superior temporal sulcus (STG/STS) also encode speaker-related vocal tract parameters, which are reflected in the amplitude peaks of the speech spectrum, along with the speech message. Right posterior STG/STS activated specifically more to a speaker-related vocal tract parameter change during a speech recognition task compared with a voice recognition task. Left and right posterior STG/STS were functionally connected. Additionally, we found that speaker-related glottal fold parameters (e.g., pitch), which are not reflected in the amplitude peaks of the speech spectrum, are processed in areas immediately adjacent to primary auditory cortex, i.e., in areas in the auditory hierarchy earlier than STG/STS. Our results point to a network account of speech recognition, in which information about the speech message and the speaker's vocal tract are combined to solve the difficult task of understanding speech from different speakers.
Sex Differences in Stress Response Circuitry Activation Dependent on Female Hormonal Cycle
Authors: Goldstein Jill M. , Jerram Matthew , Abbs Brandon , Whitfield-Gabrieli Susan , Makris Nikos
Published: January 2010

Understanding sex differences in stress regulation has important implications for understanding basic physiological differences in the male and female brain and their impact on vulnerability to sex differences in chronic medical disorders associated with stress response circuitry. In this functional magnetic resonance imaging study, we demonstrated that significant sex differences in brain activity in stress response circuitry were dependent on women's menstrual cycle phase. Twelve healthy Caucasian premenopausal women were compared to a group of healthy men from the same population, based on age, ethnicity, education, and right handedness. Subjects were scanned using negative valence/high arousal versus neutral visual stimuli that we demonstrated activated stress response circuitry [amygdala, hypothalamus, hippocampus, brainstem, orbitofrontal cortex (OFC), medial prefrontal cortex (mPFC), and anterior cingulate gyrus (ACG)]. Women were scanned twice based on normal variation in menstrual cycle hormones [i.e., early follicular (EF) compared with late follicular–midcycle (LF/MC) menstrual phases]. Using SPM8b, there were few significant differences in blood oxygenation level-dependent (BOLD) signal changes in men compared to EF women, except ventromedial nucleus (VMN), lateral hypothalamic area (LHA), left amygdala, and ACG. In contrast, men exhibited significantly greater BOLD signal changes compared to LF/MC women on bilateral ACG and OFC, mPFC, LHA, VMN, hippocampus, and periaqueductal gray, with largest effect sizes in mPFC and OFC. Findings suggest that sex differences in stress response circuitry are hormonally regulated via the impact of subcortical brain activity on the cortical control of arousal, and demonstrate that females have been endowed with a natural hormonal capacity to regulate the stress response that differs from males.
P2X7-Dependent Release of Interleukin-1β and Nociception in the Spinal Cord following Lipopolysaccharide
Authors: Clark Anna K. , Staniland Amelia A. , Marchand Fabien , Kaan Timothy K. Y. , McMahon Stephen B. , Malcangio Marzia
Published: January 2010

The cytokine interleukin-1β (IL-1β) released by spinal microglia in enhanced response states contributes significantly to neuronal mechanisms of chronic pain. Here we examine the involvement of the purinergic P2X7 receptor in the release of IL-1β following activation of Toll-like receptor-4 (TLR4) in the dorsal horn, which is associated with nociceptive behavior and microglial activation. We observed that lipopolysaccharide (LPS)-induced release of IL-1β was prevented by pharmacological inhibition of the P2X7 receptor with A-438079, and was absent in spinal cord slices taken fromP2X7knock-out mice. Application of ATP did not evoke release of IL-1β from the dorsal horn unless preceded by an LPS priming stimulus, and this release was dependent on P2X7 receptor activation. Extensive phosphorylation of p38 MAPK in microglial cells in the dorsal horn was found to correlate with IL-1β secretion following both LPS and ATP. In behavioral studies, intrathecal injection of LPS in the lumbar spinal cord produced mechanical hyperalgesia in rat hindpaws, which was attenuated by concomitant injections of either a nonspecific (oxidized ATP) or a specific (A-438079) P2X7 antagonist. In addition, LPS-induced hypersensitivity was observed in wild-type but notP2X7knock-out mice. These data suggest a critical role for the P2X7 receptor in the enhanced nociceptive transmission associated with microglial activation and secretion of IL-1β in the dorsal horn. We suggest that CNS-penetrant P2X7 receptor antagonists, by targeting microglia in pain-enhanced response states, may be beneficial for the treatment of persistent pain.
Functional Interaction of Medial Mediodorsal Thalamic Nucleus But Not Nucleus Accumbens with Amygdala and Orbital Prefrontal Cortex Is Essential for Adaptive Response Selection after Reinforcer Devaluation
Authors: Izquierdo Alicia , Murray Elisabeth A.
Published: January 2010

In nonhuman primates, reward-based decision making may be assessed through choices of objects overlying two different foods, one of which has been devalued by selective satiation. The most adaptive object choices yield the food of higher value. A large body of data identifies the amygdala and orbital prefrontal cortex (PFo) as neural mediators of adaptive responses to reinforcer devaluation. More recent work in nonhuman primates reveals the critical role of the medial, magnocellular portion of the mediodorsal nucleus of the thalamus (MDm) as well. Because both the nucleus accumbens (NA) and the MDm are anatomically related to the amygdala and PFo, and because both regions are implicated in reward processing, we tested whether either region necessarily interacts with the amygdala and PFo to mediate reinforcer devaluation effects. We used a crossed-disconnection design in which monkeys received amygdala and PFo lesions in one hemisphere combined with either NA or MDm lesions in the contralateral hemisphere. Monkeys that sustained NA disconnection, like controls, showed robust shifts in object choices in response to reinforcer devaluation. In contrast, monkeys that sustained MDm disconnection failed to adjust their object choices. Thus, MDm, but not NA, works together with the amygdala and PFo to support reward-based decision making.
Early-Life Experience Reduces Excitation to Stress-Responsive Hypothalamic Neurons and Reprograms the Expression of Corticotropin-Releasing Hormone
Authors: Korosi Aniko , Shanabrough Marya , McClelland Shawn , Liu Zhong-Wu , Borok Erzsebet , Gao Xiao-Bing , Horvath Tamas L. , Baram Tallie Z.
Published: January 2010

Increased sensory input from maternal care attenuates neuroendocrine and behavioral responses to stress long term and results in a lifelong phenotype of resilience to depression and improved cognitive function. Whereas the mechanisms of this clinically important effect remain unclear, the early, persistent suppression of the expression of the stress neurohormone corticotropin-releasing hormone (CRH) in hypothalamic neurons has been implicated as a key aspect of this experience-induced neuroplasticity. Here, we tested whether the innervation of hypothalamic CRH neurons of rat pups that received augmented maternal care was altered in a manner that might promote the suppression of CRH expression and studied the cellular mechanisms underlying this suppression. We found that the number of excitatory synapses and the frequency of miniature excitatory synaptic currents onto CRH neurons were reduced in “care-augmented” rats compared with controls, as were the levels of the glutamate vesicular transporter vGlut2. In contrast, analogous parameters of inhibitory synapses were unchanged. Levels of the transcriptional repressor neuron-restrictive silencer factor (NRSF), which negatively regulatesCrhgene transcription, were markedly elevated in care-augmented rats, and chromatin immunoprecipitation demonstrated that this repressor was bound to a cognate element (neuron-restrictive silencing element) on theCrhgene. Whereas the reduced excitatory innervation of CRH-expressing neurons dissipated by adulthood, increased NRSF levels and repression of CRH expression persisted, suggesting that augmented early-life experience reprogramsCrhgene expression via mechanisms involving transcriptional repression by NRSF.
Sleep-Dependent Consolidation of Auditory Discrimination Learning in Adult Starlings
Authors: Brawn Timothy P. , Nusbaum Howard C. , Margoliash Daniel
Published: January 2010

Memory consolidation is widely believed to benefit from sleep. Sleep-dependent memory consolidation has been established broadly in humans, appearing in declarative and procedural tasks. Animal studies have indicated a variety of mechanisms that could potentially serve as the neural basis of sleep-dependent consolidation, such as the offline replay of waking neural activity and the modulation of specific sleep parameters or synaptic strength during sleep. Memory consolidation, however, cannot be inferred from neuronal events alone, and the behavioral demonstration of sleep-dependent consolidation has been limited in animals. Here we investigated whether adult animals undergo sleep-dependent memory consolidation comparable to that of humans. European starlings (Sturnus vulgaris) were trained to discriminate between segments of novel starling song and retested after retention periods that included a regular night of sleep or consisted only of wakefulness. Auditory discrimination performance improved significantly after retention periods that included sleep but not after time spent awake, and the performance changes following sleep were significantly greater than after comparable periods of wakefulness. Thus, sleep produces a pattern of memory benefits in adult starlings that is fundamentally similar to the patterns of sleep-dependent consolidation observed in humans, suggesting a common sleep-dependent mechanism works across many vertebrate species to consolidate memories and establishing a robust animal model for this phenomenon.
Olfactory Dysfunction Correlates with Amyloid-β Burden in an Alzheimer's Disease Mouse Model
Authors: Wesson Daniel W. , Levy Efrat , Nixon Ralph A. , Wilson Donald A.
Published: January 2010

Alzheimer's disease often results in impaired olfactory perceptual acuity—a potential biomarker of the disorder. However, the usefulness of olfactory screens to serve as informative indicators of Alzheimer's is precluded by a lack of knowledge regarding why the disease impacts olfaction. We addressed this question by assaying olfactory perception and amyloid-β (Aβ) deposition throughout the olfactory system in mice that overexpress a mutated form of the human amyloid-β precursor protein. Such mice displayed progressive olfactory deficits that mimic those observed clinically—some evident at 3 months of age. Also, at 3 months of age, we observed nonfibrillar Aβ deposition within the olfactory bulb—earlier than deposition within any other brain region. There was also a correlation between olfactory deficits and the spatial-temporal pattern of Aβ deposition. Therefore, nonfibrillar, versus fibrillar, Aβ-related mechanisms likely contribute to early olfactory perceptual loss in Alzheimer's disease. Furthermore, these results present the odor cross-habituation test as a powerful behavioral assay, which reflects Aβ deposition and thus may serve to monitor the efficacy of therapies aimed at reducing Aβ.
Blue-Yellow Opponency in Primate S Cone Photoreceptors
Authors: Packer Orin S. , Verweij Jan , Li Peter H. , Schnapf Julie L. , Dacey Dennis M.
Published: January 2010

The neural coding of human color vision begins in the retina. The outputs of long (L)-, middle (M)-, and short (S)-wavelength-sensitive cone photoreceptors combine antagonistically to produce “red-green” and “blue-yellow” spectrally opponent signals (Hering, 1878; Hurvich and Jameson, 1957). Spectral opponency is well established in primate retinal ganglion cells (Reid and Shapley, 1992; Dacey and Lee, 1994; Dacey et al., 1996), but the retinal circuitry creating the opponency remains uncertain. Here we find, from whole-cell recordings of photoreceptors in macaque monkey, that “blue-yellow” opponency is already present in the center-surround receptive fields of S cones. The inward current evoked by blue light derives from phototransduction within the outer segment of the S cone. The outward current evoked by yellow light is caused by feedback from horizontal cells that are driven by surrounding L and M cones. Stimulation of the surround modulates calcium conductance in the center S cone.