bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity in the Lateral Intraparietal Area Predicts the Goal and Latency of Saccades in a Free-Viewing Visual Search Task
Authors: Ipata Anna E. , Gee Angela L. , Goldberg Michael E. , Bisley James W.
Published: April 2006

The purpose of saccadic eye movements is to facilitate vision, by placing the fovea on interesting objects in the environment. Eye movements are not made for reward, and they are rarely restricted. Despite this, most of our knowledge about the neural genesis of eye movements comes from experiments in which specific eye movements are rewarded or restricted. Such experiments have demonstrated that activity in the lateral intraparietal (LIP) area of the monkey correlates with the monkey's planning of a memory-guided saccade or deciding where, on the basis of motion information, to make a saccade. However, other experiments have shown that neural activity in LIP can easily be dissociated from the generation of saccadic eye movements, especially when sophisticated behavioral paradigms dissociate the monkey's locus of attention from the goal of an intended saccade. In this study, we trained monkeys to report the results of a visual search task by making a nontargeting hand movement. Once the task began, the monkeys were entirely free to move their eyes, and rewards were not contingent on the monkeys making specific eye movements. We found that neural activity in LIP predicted not only the goal of the monkey's saccades but also their saccadic latencies.
A Biophysically Based Neural Model of Matching Law Behavior: Melioration by Stochastic Synapses
Authors: Soltani Alireza , Wang Xiao-Jing
Published: April 2006

In experiments designed to uncover the neural basis of adaptive decision making in a foraging environment, neuroscientists have reported single-cell activities in the lateral intraparietal cortex (LIP) that are correlated with choice options and their subjective values. To investigate the underlying synaptic mechanism, we considered a spiking neuron model of decision making endowed with synaptic plasticity that follows a reward-dependent stochastic Hebbian learning rule. This general model is tested in a matching task in which rewards on two targets are scheduled randomly with different rates. Our main results are threefold. First, we show that plastic synapses provide a natural way to integrate past rewards and estimate the local (in time) “return” of a choice. Second, our model reproduces the matching behavior (i.e., the proportional allocation of choices matches the relative reinforcement obtained on those choices, which is achieved through melioration in individual trials). Our model also explains the observed “undermatching” phenomenon and points to biophysical constraints (such as finite learning rate and stochastic neuronal firing) that set the limits to matching behavior. Third, although our decision model is an attractor network exhibiting winner-take-all competition, it captures graded neural spiking activities observed in LIP, when the latter were sorted according to the choices and the difference in the returns for the two targets. These results suggest that neurons in LIP are involved in selecting the oculomotor responses, whereas rewards are integrated and stored elsewhere, possibly by plastic synapses and in the form of the return rather than income of choice options.
Sympathetic Sprouting Drives Hippocampal Cholinergic Reinnervation That Prevents Loss of a Muscarinic Receptor-Dependent Long-Term Depression at CA3–CA1 Synapses
Authors: Scheiderer Cary L. , McCutchen Eve , Thacker Erin E. , Kolasa Krystyna , Ward Matthew K. , Parsons Dee , Harrell Lindy E. , Dobrunz Lynn E. , McMahon Lori L.
Published: April 2006

Degeneration of septohippocampal cholinergic neurons results in memory deficits attributable to loss of cholinergic modulation of hippocampal synaptic circuits. A remarkable consequence of cholinergic degeneration is the sprouting of noradrenergic sympathetic fibers from the superior cervical ganglia into hippocampus. The functional impact of sympathetic ingrowth on synaptic physiology has never been investigated. Here, we report that, at CA3–CA1 synapses, a Hebbian form of long-term depression (LTD) induced by muscarinic M1receptor activation (mLTD) is lost after medial septal lesion. Unexpectedly, expression of mLTD is rescued by sympathetic sprouting. These effects are specific because LTP and other forms of LTD are unaffected. The rescue of mLTD expression is coupled temporally with the reappearance of cholinergic fibers in hippocampus, as assessed by the immunostaining of fibers for VAChT (vesicular acetylcholine transporter). Both the cholinergic reinnervation and mLTD rescue are prevented by bilateral superior cervical ganglionectomy, which also prevents the noradrenergic sympathetic sprouting. The new cholinergic fibers likely originate from the superior cervical ganglia because unilateral ganglionectomy, performed when cholinergic reinnervation is well established, removes the reinnervation on the ipsilateral side. Thus, the temporal coupling of the cholinergic reinnervation with mLTD rescue, together with the absence of reinnervation and mLTD expression after ganglionectomy, demonstrate that the autonomic-driven cholinergic reinnervation is essential for maintaining mLTD after central cholinergic cell death. We have discovered a novel phenomenon whereby the autonomic and central nervous systems experience structural rearrangement to replace lost cholinergic innervation in hippocampus, with the consequence of preserving a form of LTD that would otherwise be lost as a result of cholinergic degeneration.
“Don't Step on My Groove!”: Gender and the Social Experience of Rock
Authors: Bessett Danielle
Published: April 2006

This article utilizes a symbolic interactionist framework to examine how gender is, and is not, salient in “depth‐listening” practices. Based on qualitative interviews with male and female fans of contemporary “angry” rock music by female performers, the author shows that men and women engage in similar processes of cultivation (especially with regard to emotion) in depth listening, but that they also employ gender as a socio‐semiotic resource to interpret their relationships to the music and artists differently and to evaluate what this music could mean in their daily lives. Gender identity is influential in how the music is constructed as personally transformative for informants and as having implications for social change.
Growing Up Punk: Negotiating Aging Identity in a Local Music Scene
Authors: Davis Joanna R.
Published: April 2006

Punk music, in its thirty‐odd‐year history, is traditionally conceived of as a youth subcultural phenomenon. As one of many ways to rebel, kids might choose or find in punk rock an anti‐authoritarian, destructive, or anarchistic ideology that helps them manage the tumult of adolescence. But what happens next? In this conceptual article, the author is interested in how punks negotiate their identity as punks, as they age. She examines this by looking at people's experiences in a local punk scene. Based on these observations, she argues that “aging identity” and “the scene” are theoretical tools in a dialectic relationship with one another, which highlights the fluidity of both. This theory helps promote “the scene” as a more useful concept than subculture. Furthermore, looking at the local punk rock music scene as a scene—rather than a subculture—illustrates how identity forms over time as a cumulative process, synthesized in the relationship between changing self and other. From her research on a punk scene, the author argues that to construct a long‐term conception of scene involvement, punk scene members look to real and idealized others to demonstrate what they see as successful and unsuccessful ways of aging in connection with the music scene.
Postmodern Swing Dance and Secondary Adjustment: Identity as Process
Authors: Renshaw Scott W.
Published: April 2006

In this article, the author describes activities of strategic consumption that members of a postmodern swing dance scene utilized to construct identity. He deploys Goffman's category of “contained secondary adjustment” for describing social interactions that are moments of purposeful resistance designed to usurp (while also being lodged within) organizational and/or institutional claims and constraints for identity and self. Specifically, the article describes swing dancers' presentations of unique selves, thrift store shopping, tavern socializing, and swing dancing. Swing dancers utilized these secondary adjustments to resist the dictates of corporate‐driven and mass‐mediated claims and constraints for “mainstream” consumer identities. These secondary adjustments add up to an “identity distancing,” which is the individual's and/or group's purposeful distancing and separation from other identities or groups associated with popular culture. Describing the swing dancers' secondary adjustments reaffirms the symbolic interactionist stance that identity construction is a durable social interactional process.
Musicians' Worlds: Music‐Making as a Collaborative Activity
Authors: Martin Peter J.
Published: April 2006

The term “popular music” encompasses a huge range and variety of styles. This article reasons that the adoption of a sociological approach, and in particular Becker's “art worlds” perspective, brings some analytic clarity and methodological rigor to studies of musicians' work in an otherwise diverse array of styles and contexts. An empirical focus on “musicians' worlds” can produce not only systematic descriptions of their organizational features but, by examining occupational problems and responses to them, can generate explanations of salient aspects of musicians' cultures. These points are developed in a brief consideration of three studies of musicians active in different styles, times, and places. It is concluded that, despite their apparent contrasts, an art worlds perspective can reveal the “generic social processes” underlying musicians' practices in these diverse settings.
When Art Loses its Sting: The Evolution of Protest Art in Authoritarian Contexts
Authors: Adams Jacqueline
Published: April 2006

Change in art is an understudied topic in sociological research. This article examines protest artworks ( arpilleras) produced by shantytown women during and shortly after the dictatorship in Chile, to explore the question why political art that is for sale changes over time. This research is based on 136 semi-structured and in-depth interviews with various members of the art world in Chile, Europe, and the United States, a year's worth of participant observation of art groups in Santiago and over five hundred photographs of arpilleras, taken by the author and analyzed thematically. Political art that is for sale can change because the intermediary (the organization connecting producers and buyers) becomes less or more politically conservative, develops a precarious financial situation, grows more afraid of repression, and has the power to enforce the changes it desires; because the original buyers are replaced with new buyers with different motivations; and because new artists with new ideas begin making the art, one artist in the group produces something different and the idea spreads, artists censor themselves, and artists have new experiences or learn about new events. Through these sources of change, international social movements, local and international political and economic developments, and global institutions impact the art. Meanings attached to the art by the different parties (intermediaries, buyers, and artists) and class differences between artists and intermediaries are also important in facilitating change. These findings, based as they are on political art made in a repressive context, not only contribute to our understanding of artistic evolution but they help correct the bias in the sociology of art toward “art” made in democratic countries of the “First World.” They are not just applicable to authoritarian regimes but also to art by politicized minority groups in democratic contexts, and to other cultural products such as newspapers, magazines, documentaries, and books.
Structural evolution of WO3 nanoclusters on ZrO2
Authors: Angeles-Chavez C. , Cortes-Jácome M.A. , Torres-Garcia E. , Toledo-Antonio J.A.
Published: April 2006

Direct evidence of the transformation of WOx species in WO3 nanoclusters on WOx–ZrO2 system was achieved by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy on samples obtained by a conventional precipitation method and annealed from 560 to 800 °C. WO3 Nanoclusters with 2-nm crystal size orthorhombic structure were identified on the ZrO2 surface after annealing at 800 °C.
Long-term phase instability in a water-quenched uranium alloy
Authors: Zhou J. , Hsiung L.M.
Published: April 2006

The U–6 wt% Nb (U6Nb) alloy in the water-quenched (WQ) state has been in service for a number of years. Its long-term reliability is affected by the changes of the alloy microstructure and mechanical properties during service. In this paper, the water quenched U–6 wt% Nb (WQ-U6Nb) alloy in service for 15 years at ambient temperatures was studied using an analytical transmission electron microscopy (TEM) analysis. We found that the long-term natural aging resulted in a disorder–order phase transformation, leading to the formation of anti-phase boundaries (APBs). The newly found ordered phase was then identified by proposing two phase transform schemes, which were also discussed with regards to the potential subsequence of the microstructural evolution for the alloy in further service. The initial study also provides convincing evidence for the disorder–order transformation, which has been predicted by numerous studies to be a transient thermodynamic event before spinodal decomposition. This suggests that the long-term naturally aged WQ–U6Nb is a good model alloy to study thermodynamic and kinetic phenomena requiring chronic processes.
Sintered compacts of nano and micron-sized BaTiO3: Dramatic influence on the microstructure and dielectric properties
Authors: Shanker Vishnu , Ahmad Tokeer , Ip Henry , Ganguli Ashok K.
Published: April 2006

Sintered compacts of nano-sized and micron-sized BaTiO3 show sharp ferroelectric transition and high dielectric constant at specific compositions. The sintered compacts with 1 wt% nano-BaTiO3 show a maximum dielectric constant of 1680. At the transition temperature (Tc) there are two maxima at 0.5 and 2 wt%. The variation in the dielectric constant at Tc is also reflected in the behavior of the ferroelectric transition as studied by differential scanning calorimetry. This interesting oscillatory variation of the dielectric constant and dielectric loss with increase in the amount of nanoparticles in the sintered compacts is observed for the first time. The variation of the dielectric properties and the ferroelectric transition of the sintered compacts could be related to subtle changes in the microstructure.
Enhanced thermal stability of the devitrified nanoscale icosahedral phase in novel multicomponent amorphous alloys
Authors: Kim K.B. , Warren P.J. , Cantor B. , Eckert J.
Published: April 2006

In this paper, details are given for the structural evolution of (Ti33Zr33Hf33)70(Ni50Cu50)20Al10, (Ti25Zr25Hf25Nb25)70(Ni50Cu50)20Al10, and (Ti33Zr33Hf33)70(Ni33Cu33Ag33)20Al10 amorphous alloys, part of wider program of alloy development by equiatomic substitution. All three alloys initially crystallize by forming a nanoscale icosahedral phase. However, at higher temperatures, their decomposition sequences differ significantly. The nanoscale icosahedral phase in the (Ti33Zr33Hf33)70(Ni50Cu50)20Al10 alloy decomposes into a mixture of Zr2Cu-type and icosahedral phases. This icosahedral phase still exists after heating up to 970 K, indicating a high thermal stability of this phase. The nanoscale icosahedral phase in the (Ti33Zr33Hf33)70(Ni33Cu33Ag33)20Al10 alloy also transforms into a mixture of Zr2Cu-type and icosahedral phase during the second exothermic reaction but then transforms into a mixture of Zr2Cu-type and Ti2Ni-type phases. The nanoscale icosahedral phase in the (Ti25Zr25Hf25Nb25)70(Ni50Cu50)20Al10 alloy decomposes into a mixture of Ti2Ni-type and MgZn2-type phases during the second exothermic reaction. It is concluded that the formation of the Zr2Cu-type phase retards the decomposition of the nanoscale icosahedral phase, which increases the thermal stability. In contrast, formation of Ti2Ni-type and MgZn2-type phases accelerates the decomposition of the nanoscale icosahedral phase, which decreases its thermal stability.
Low friction and severe wear of alumina in cryogenic environment: A first report
Authors: Khanna Rohit , Basu Bikramjit
Published: April 2006

Structural ceramics are considered as potential candidate materials for use in hybrid bearings in rocket turbopumps, operated under high stress in cryogenic environment. The friction and wear-related surface failure is considered as one of the critical factors in selecting the materials for cryo-turbopumps of Space Shuttle Main Engine (SSME). To obtain fundamental understanding of the tribological properties of ceramics in cryogenic environment, a very first set of sliding wear tests were carried out on self-mated Al2O3, a model brittle ceramic material, in liquid nitrogen (LN2) under varying load (2–10 N) and high rotational speed of 2550 rpm, using a newly designed cryogenic tribometer. The present research attempts to answer some important questions: (i) What would be the influence of LN2 on frictional and fracture behavior at sliding contacts? (ii) How does the material removal process occur in LN2 environment? Our experimental results reveal that self-mated alumina exhibits low steady-state coefficient of friction ∼0.13–0.18 and suffers from high wear rate (10−5 mm3/Nm) under the selected testing conditions. The novelty of the present work also lies in presenting some interesting results, for the first time, concerning the deformation and fracture of alumina at cryogenic temperature under high speed sliding conditions. Detailed scanning electronic microscope observation of the worn surfaces indicates that severe damage of both ball and flat occurs in cryogenic environment by transgranular and intergranular fracture. The observed wear behavior is explained in terms of thermal heat dissipation and brittle fracture of alumina in LN2.
Cellulose micro/nanocrystals reinforced polyurethane
Authors: Marcovich N.E. , Auad M.L. , Bellesi N.E. , Nutt S.R. , Aranguren M.I.
Published: April 2006

Nano- and micron-sized cellulose crystals were prepared and utilized as reinforcements for polyurethane composites. The cellulose crystals obtained from microcrystalline cellulose (MCC) were incorporated into a polar organic solvent, dimethylformamide (DMF), and ultrasonicated to obtain a stable suspension. The suspension was an effective means for incorporating the cellulose crystals into the polyol-isocyanate mixture, utilized to produce polyurethane composite films. The use of DMF presents an interesting alternative for the use of cellulose crystals as reinforcement of a broad new range of polymers. Moreover, the rheology of the uncured liquid suspensions was investigated, and analysis of the results indicated the formation of a filler structure pervading the liquid suspension. Besides, films were prepared by casting and thermal curing of the stable suspensions. Thermomechanical and mechanical testing of the films were carried out to analyze the performance of the composites. The results indicated that a strong filler-matrix interaction was developed during curing as a result of a chemical reaction occurring between the crystals and the isocyanate component.
Fracture of nanoporous methyl silsesquioxane thin-film glasses
Authors: Guyer Eric P. , Patz Matthias , Dauskardt Reinhold H.
Published: April 2006

The fracture of nanoporous methylsilsesquioxane thin-film glasses in moist air and aqueous solutions was investigated. We demonstrate the effects of controlled volume fractions of nanometer sized pores on the films resistance to fracture. Subcritical cracking accelerated by the presence of moisture, controlled pH, and hydrogen peroxide solutions is reported. Surprising changes in the near threshold growth rate behavior were observed for buffered solutions. We demonstrate that these changes are related to the unexpected diffusion of the aqueous solutions into the highly hydrophobic films. The presence of the solution changes the surface stress of the internal pore surfaces, which changes the stress state of the film. The change in film stress surrounding the crack alters the crack driving force and has profound effects on the resulting crack-growth threshold behavior.
Limit analysis-based approach to determine the material plastic properties with conical indentation
Authors: Ogasawara Nagahisa , Chiba Norimasa , Chen Xi
Published: April 2006

Representative strain plays an important role in indentation analysis; by using the representative strain and stress, the normalized indentation load becomes a function of one variable, which facilitates the reverse analysis of obtaining the material plastic properties. The accuracy of such function is critical to indentation analysis. Traditionally, polynomial functions are used to fit the function, which does not incorporate correct elastic/plastic limits and has no physical basis. In this paper, we have proposed a new limit analysis-based functional formulation based on the theoretical solutions of conical/wedge indentation on elastic and rigid plastic solids. It is found that both limits agree well with numerical results, and the new approach involves no—or at most one—fitting parameter, which can be obtained with much less effort compare with the traditional polynomial approach. Reverse analyses on five different materials have shown that the new and simple limit analysis-based formulation works better than the traditional polynomial fit. The new technique may be used to quickly and effectively measure material plastic properties for any conical indenter if the elastic modulus is known a priori.
Effects of loading rate on the deformation and cracking of dental multilayers: Experiments and models
Authors: Niu Xinrui , Soboyejo Wole
Published: April 2006

The paper presents the results of combined experimental, analytical, and computational studies of contact-induced deformation and cracking in dental multilayers. These include studies of individual layers and composite structures that consist of tri-layers of glass bonded to ceramic-filled polymer foundation with an acrylate-based join material. Loading-rate-dependent Young's moduli of the join and foundation materials were obtained from monotonic compression tests. Critical loads were also determined for the tri-layers from Hertzian contact tests at different loading rates. The fracture onset (sub-surface radial cracking) was detected using an in situ telescope. The measured rate-dependent Young's moduli were then incorporated into a finite element model that was used to predict the rate-dependent critical loads in the tri-layer system. Finally, the paper shows that the observed loading rate-dependence of the critical load (for radial cracking) is due to the combined effects of slow crack growth in glass and rate-dependent Young's moduli in the join and foundation layers.
Hot pressing and characterizations of mechanically alloyed Zr52Al6Ni8Cu14W20 glassy powders.
Authors: El-Eskandarany M. Sherif , Inoue A.
Published: April 2006

Low-energy ball milling technique was successfully used to synthesis new glassy Zr52Al6Ni8Cu14W20 multicomponent alloy powders using mechanical alloying method. During the intermediate stage of milling the atoms of Zr, Al, Ni, and Cu migrated and diffused into the W lattice to form a body-centered cubic solid solution phase. As the milling time increases, the obtained metastable powders are subsequently subjected to continuous defects and lattice imperfections that lead to a gradual change in the free energy so that solid solution phase transformed to another metastable phase (glassy). The glassy powders that were obtained after 720 ks milling are fully amorphous and have spherical-like morphology with an average particle size of 0.60 μm in diameter. The synthetic glassy Zr52Al6Ni8Cu14W20 alloy powder, which exhibits a glass transition temperature of 811 K, crystallizes at a high temperature (884 K) through a single sharp exothermic peak with an enthalpy change of crystallization of −5.48 kJ/mol. Whereas the supercooled liquid region before crystallization of the obtained glassy powders is 73 K, the reduced glass transition temperature (ratio between Tg and liquidus temperatures) was found to be 0.46. The fabricated glassy powders were consequently hot-pressed into bulk samples in an argon gas atmosphere at several temperatures with a pressure of 936 MPa. The samples that were consolidated within the temperature of the supercooled liquid region are fully dense, with relative density above ∼99.82%, and maintain their original homogeneous glassy structure. They have high Vickers microhardness values in the range between 8.46 and 8.62 GPa. They also show very high fracture strength (2.13 GPa) with an extraordinary high Young's modulus of 138 GPa. Neither yielding stress, nor plastic strain could be detected for this glassy alloy, the elastic strain of which is 1.47%.
Fabrication of rutile TiO2 thin films by low-temperature, bias-assisted cathodic arc deposition and their dielectric properties
Authors: Huang A.P. , Chu Paul K. , Wang L. , Cheung W.Y. , Xu J.B. , Wong S.P.
Published: April 2006

The use of rutile-type titanium dioxide (TiO2) thin films as advanced gate dielectrics has been hampered by thermodynamic instability during the high deposition or annealing temperature of 800 °C. In this work, we demonstrate that rutile-type TiO2 thin films can be produced on p-type Si (100) at lower substrate temperature by means of bias-assisted cathodic arc deposition. The influence of the substrate bias on the microstructural and dielectric characteristics of the TiO2 thin films is investigated in detail. Our results show that by applying a suitable bias to the Si substrate, as-deposited rutile-type TiO2 thin films can be obtained at 450 °C. The permittivity of the materials increases significantly from 21 up to 76. The interfacial and electrical properties of TiO2/Si (100) are also improved. The effects and mechanism of the bias on the microstructural and dielectric characteristics are described.
Formation, and mechanical and magnetic properties of bulk ferromagnetic Fe-Nb-B-Y-(Zr, Co) alloys
Authors: Park J.M. , Park J.S. , Kim D.H. , Kim J-H. , Fleury E.
Published: April 2006

Fe element was partially substituted by Zr and Co in an attempt to enhance the glass-forming ability, and mechanical and soft magnetic properties of Fe74-xNb6B17Y3(Zr, Co)x (x = 3, 5, 8) amorphous alloys. Both partial replacements resulted in the enhancement of the glass-forming ability, and 3-mm diameter rods with a fully amorphous structure were prepared by a copper mold casting method. Zr and Co containing Fe-based bulk amorphous alloys exhibited high compressive fracture strength of about 4 and 3.5 GPa, respectively. However, Zr and Co induced different effects on the magnetic properties. Whereas the partial replacement of Fe by Zr was found to decrease dramatically the saturation magnetization, the partial replacement of Fe by Co provided an increase of about 25% of the saturation magnetization.
On determination of material parameters from loading and unloading responses in nanoindentation with a single sharp indenter
Authors: Wang Lugen , Rokhlin S.I.
Published: April 2006

This paper quantitatively describes the loading-unloading response in nanoindentation with sharp indenters using scaling analyses and finite element simulations. Explicit forward and inverse scaling functions for an indentation unloading have been obtained and related to those functions for the loading response [L. Wang et al., J. Material Res.20(4), 987–1001 (2005)]. The scaling functions have been obtained by fitting the large deformation finite element simulations and are valid from the elastic to the full plastic indentation regimes. Using the explicit forward functions for loading and unloading, full indentation responses for a wide range of materials can be obtained without use of finite element calculations. The corresponding inverse scaling functions allow one to obtain material properties from the indentation measurements. The relation between the work of indentation and the ratio between hardness and modulus has also been studied. Using these scaling functions, the issue of nonuniqueness of the determination of material modulus, yield stress, and strain-hardening exponent from nanoindentation measurements with a single sharp indenter has been further investigated. It is shown that a limited material parameter range in the elastoplastic regime can be defined where the material modulus, yield stress, and strain-hardening exponent may be determined from only one full indentation response. The error of such property determination from scattering in experimental measurements is determined.
Formation and processing of mesoporous barium titanate powders via the micelle template method
Authors: Wang Hong-Wen , Kuo Chien-Hung , Liao Tsai-Huei , Lin Ren-Jay , Cheng Syh-Yuh
Published: April 2006

Mesoporous barium titanate powders having a 100- to 300-nm size were prepared by hydration and condensation of titanium tetra-isopropoxide and barium precursors in the presence of an organic surfactant, tetradecylamine, which was used as a self-assembly micelle. The processing and sintering of these mesoporous barium titanate powders has been investigated. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to identify the structural characteristics and morphologies of the powders. Mesoporous wormhole-like powders with surface areas around 53 ∼ 108 m2/g could be obtained after removing the micelle organics by calcination at 400 °C for 3 h. Powders derived using barium hydroxide were found to form a larger pore size and a higher surface area. The addition of acetic acid was also effective in increasing the surface area. A formation mechanism for the mesoporous structure is depicted. Heat treatment caused the mesoporous spheres to shrink, and 155- ∼ 330-nm grain sizes were readily obtained after pressureless sintering at 900 ∼ 1000 °C for 1 h in air.
Clinical trials with retinoids for breast cancer chemoprevention
Authors: Zanardi S , Serrano D , Argusti A , Barile M , Puntoni M , Decensi A
Published: April 2006

Retinoids have been studied as chemopreventive agents in clinical trials due to their established role in regulating cell growth, differentiation and apoptosis in preclinical models. Experimental evidence suggests that retinoids affect gene expression both directly, by activating and/or repressing specific genes, and indirectly, by interfering with different signal transduction pathways. Induction of apoptosis is a unique feature of fenretinide, the most widely studied retinoid in clinical trials on breast cancer chemoprevention due to its selective accumulation in breast tissue and to its favourable toxicological profile. In a phase III breast cancer prevention trial, fenretinide showed a durable trend to a reduction of second breast malignancies in premenopausal women. This pattern was associated with a favourable modulation of circulating IGF-I and its main binding protein (IGF-binding protein-3, IGFBP-3), which have been associated with breast cancer risk in premenopausal women in different prospective studies. In a subsequent biomarker study on premenopausal women who had participated in the phase III trial, high IGF-I and low IGFBP-3 baseline levels were found to predict second breast cancer risk, although the magnitude of their changes during treatment did not fulfil the requirements for suitable surrogate end-point biomarkers. In postmenopausal women, fenretinide did not reduce second breast cancer incidence, nor did it induce significant modulation of the IGF system. Similarly, fenretinide was not found to affect risk biomarkers significantly in early postmenopausal women on hormone replacement therapy, who are at increased risk of developing breast cancer. Biomarker studies of fenretinide alone or in combination with different nuclear receptor ligands are being conducted. In particular, clinical trials of fenretinide and tamoxifen have proved to be feasible, and this combination appears to be safe and well tolerated in high-risk women, especially when low-dose tamoxifen is employed. Novel retinoid X receptor-selective retinoids, or rexinoids, have been shown to suppress the development of breast cancer in several animal models with minimal toxicity, and are being intensively studied either alone or in combination with selective oestrogen receptor modulators, both in vitro and in vivo. The rexinoid, bexarotene, has recently been approved for the treatment of patients with cutaneous T-cell lymphoma, and a biomarker trial with bexarotene in women with high breast cancer risk is currently underway.
Somatostatin receptor subtype 5 (SSTR5) mRNA expression is related to histopathological features of cell proliferation in insulinomas
Authors: de Sá Sandra Valéria , Corrêa-Giannella Maria Lúcia , Machado Márcio Carlos , de Souza Jean Jorge S , Pereira Maria Adelaide Albergaria , Patzina Rosely Antunes , Siqueira Sheila Aparecida Coelho , Machado Marcel Cerqueira César , Giannella-Neto Daniel
Published: April 2006

Insulinomas are rare endocrine neoplasias that constitute the most frequent islet cell tumours. Somatostatin (SST) analogs are tentatively used to inhibit insulin secretion and control tumour growth in patients with local invasion or inoperative metastasis, but variable responses have been reported. Data regarding somatostatin receptor (SSTR) subtypes expression in insulinomas are conflicting. In this study, we evaluated 16 cases of primary insulinomas (including four primary plurihormonal tumours) and two hepatic metastases. Histopathological and immunohistochemical analysis for some features associated with tumour aggressiveness and semi-quantitative RT-PCR for SSTR1-5 and real-time qPCR for SSTR5 were performed. SSTR subtypes 1, 3, and 5 were expressed in 100%, SSTR2 in 89%, and SSTR4 only in 22% of the insulinomas. SSTR5 mRNA was positively correlated with histopathological features related to tumour aggressiveness (large tumour diameter, well-differentiated endocrine tumour with uncertain behaviour and higher number of cells with nuclear atypia). SSTR5 mRNA expression in primary insulinomas was lower than in primary plurihormonal tumours (P < 0.05). The observed positive correlation between SSTR5 expression and tumour size suggests that the use of SST analogues more specific to SSTR5 in the treatment of insulinomas deserves attention.
Mechanism of gonadotropin-releasing hormone (GnRH)-I and -II-induced cell growth inhibition in ovarian cancer cells: role of the GnRH-I receptor and protein kinase C pathway
Authors: Kim Ki-Yon , Choi Kyung-Chul , Auersperg Nelly , Leung Peter C K
Published: April 2006

In our previous studies, we demonstrated that ERK1/2 (extracellular signal-regulated protein kinase) and p38 MAPK (mitogen-activated protein kinase) are required for gonadotropin-releasing hormone (GnRH)-II-induced anti-proliferation of ovarian cancer cells. In the present study, we examined the role of the GnRH-I receptor, as well as the activation of protein kinase C (PKC), in the anti-proliferative effect induced by GnRH-I or II in ovarian cancer cells. Our results demonstrated that Antide, a GnRH-I antagonist, reversed the activation of ERK1/2 induced by GnRH-I or II and abolished the anti-proliferative effect of GnRH-I and II in ovarian cancer cells. Transfection of short-interfering RNA to abrogate the gene expression of the GnRH-I receptor reversed GnRH-I and II-induced anti-proliferation. These results indicate that GnRH-I or II induce anti-proliferation through the GnRH-I receptor in ovarian cancer cells. In addition, the activation of ERK1/2 by GnRH-I or II was mimicked by phorbol-12-myristate 13-acetate, a PKC activator. Pretreatment with GF109203X, an inhibitor of PKC, blocked GnRH-induced ERK1/2 activation and anti-proliferation. These results suggest that the activation of PKC is responsible for GnRH-induced ERK1/2 activation and anti-proliferation in ovarian cancer cells. Taken together, these results indicate that binding of GnRH-I and II to the GnRH-I receptor activates ERK1/2 through a PKC-dependent pathway and is essential for GnRH-induced anti-proliferation of ovarian cancer cells.
Role of exon-16-deleted HER2 in breast carcinomas
Authors: Castiglioni F , Tagliabue E , Campiglio M , Pupa S M , Balsari A , Ménard S
Published: April 2006

A splice variant of the human gene HER2, lacking exon-16 (ΔHER2) which encodes a small extracellular region, has been described. This altered receptor forms disulfide bond-stabilized homodimers. We report here that the ΔHER2 splice variant represents about 9% of the HER2 mRNA obtained from most of the 46 breast carcinoma samples with HER2 expression levels ranging from 3+ to 0 by HercepTest. Analysis of human cells transfected with ΔHER2 or wild-type (WT) cDNA revealed no growth of WT cells in nude mice, whereas clones expressing 10-fold less ΔHER2 were tumorigenic. Unlike WT transfectants, ΔHER2-expressing cells showed low sensitivity to two new therapeutic drugs targeting receptors of the HER family (ZD1839 and Trastuzumab), whereas an inhibitor of the HER2 tyrosine kinase domain (Emodin) blocked activation of both ΔHER2 and WT transfectants. Taken together, our findings indicate that the ΔHER2 transcript encodes the transforming form of the oncoprotein. It is plausible that malignant transformation arises when a critical threshold of ΔHER2 is reached in HER2-overexpressing tumors. Specific inhibitors of HER2 catalytic activity represent a promising approach to therapy of HER2-overexpressing tumors.
Increased expression of type 2 3α-hydroxysteroid dehydrogenase/type 5 17β-hydroxysteroid dehydrogenase (AKR1C3) and its relationship with androgen receptor in prostate carcinoma
Authors: Fung K-M , Samara E N S , Wong C , Metwalli A , Krlin R , Bane B , Liu C Z , Yang J T , Pitha J V , Culkin D J , Kropp B P , Penning T M , Lin Hsueh-Kung
Published: April 2006

Type 2 3α-hydroxysteroid dehydrogenase (3α-HSD) is a multi-functional enzyme that possesses 3α-, 17β- and 20α-HSD, as well as prostaglandin (PG) F synthase activities and catalyzes androgen, estrogen, progestin and PG metabolism. Type 2 3α-HSD was cloned from human prostate, is a member of the aldo-keto reductase (AKR) superfamily and was named AKR1C3. In androgen target tissues such as the prostate, AKR1C3 catalyzes the conversion of Δ4-androstene-3,17-dione to testosterone, 5α-dihydrotestosterone to 5α-androstane-3α,17β-diol (3α-diol), and 3α-diol to androsterone. Thus AKR1C3 may regulate the balance of androgens and hence trans-activation of the androgen receptor in these tissues. Tissue distribution studies indicate that AKR1C3 transcripts are highly expressed in human prostate. To measure AKR1C3 protein expression and its distribution in the prostate, we raised a monoclonal antibody specifically recognizing AKR1C3. This antibody allowed us to distinguish AKR1C3 from other AKR1C family members in human tissues. Immunoblot analysis showed that this monoclonal antibody binds to one species of protein in primary cultures of prostate epithelial cells and in LNCaP prostate cancer cells. Immunohistochemistry with this antibody on human prostate detected strong nuclear immunoreactivity in normal stromal and smooth muscle cells, perineurial cells, urothelial (transitional) cells, and endothelial cells. Normal prostate epithelial cells were only faintly immunoreactive or negative. Positive immunoreactivity was demonstrated in primary prostatic adenocarcinoma in 9 of 11 cases. Variable increases in immunoreactivity for AKR1C3 was also demonstrated in non-neoplastic changes in the prostate including chronic inflammation, atrophy and urothelial (transitional) cell metaplasia. We conclude that elevated expression of AKR1C3 is highly associated with prostate carcinoma. Although the biological significance of elevated AKR1C3 in prostatic carcinoma is uncertain, AKR1C3 may be responsible for the trophic effects of androgens and/or PGs on prostatic epithelial cells.
A molecular mimic demonstrates that phosphorylated human prolactin is a potent anti-angiogenic hormone
Authors: Ueda Eric , Ozerdem Ugur , Chen Yen-Hao , Yao Min , Huang Kuang Tzu , Sun Huiqin , Martins-Green Manuela , Bartolini Paolo , Walker Ameae M
Published: April 2006

S179D prolactin (PRL) is an experimentally useful mimic of naturally phosphorylated human prolactin. S179D PRL, but not unmodified PRL, was found to be anti-angiogenic in both the chorioallantoic membrane and corneal assays. Further investigation using human endothelial in vitro models showed reduced cell number, reduced tubule formation in Matrigel, and reduced migration and invasion, as a function of treatment with S179D PRL. Analysis of growth factors in human endothelial cells in response to S179D PRL showed: a decreased expression or release of endogenous PRL, heme-oxygenase-1, basic fibroblast growth factor (bFGF), angiogenin, epidermal growth factor and vascular endothelial growth factor; and an increased expression of inhibitors of matrix metalloproteases. S179D PRL also blocked signaling from bFGF in these cells. We conclude that this molecular mimic of a pituitary hormone is a potent anti-angiogenic protein, partly as a result of its ability to reduce utilization of several well-established endothelial autocrine growth loops, partly by its ability to block signaling from bFGF and partly because of its ability to decrease endothelial migration. These findings suggest that circulating levels of phosphorylated PRL may influence the progression of cancer and, furthermore, that S179D PRL may be a useful anti-angiogenic therapeutic.
Epidermal growth factor-induced neuroendocrine differentiation and apoptotic resistance of androgen-independent human prostate cancer cells
Authors: Humez S , Monet M , Legrand G , Lepage G , Delcourt P , Prevarskaya N
Published: April 2006

Neuroendocrine differentiation (NED) has been implicated in prostate cancer progression and hormone-therapy failure. Neuroendocrine cells are non-proliferating and escape apoptotic cell death, although their origin and the causes of their apoptotic resistance have as yet been poorly elucidated. This study demonstrates a new mechanism involved in controlling NED. We report that epidermal growth factor (5–50 ng/ml) promotes neuroendocrine-like differentiation of androgen-independent DU145 prostate cancer cells. This differentiation is associated with an increase in the expression of Neuron Specific Enolase (NSE) and a reduction in cell proliferation and is blocked by inhibiting tyrosine kinase activity with genistein and with compound 56 (C56). An increase in the cAMP level, using dibutryl cAMP (db-cAMP) (1 mM) and isobutylmethylxanthine (100 μM), does not promote NED by itself, but does increase the effect of EGF on NED. In addition, EGF-induced NED protects cells from apoptosis induced with thapsigargin (1 μM) by reducing the thapsigargin-induced cytosolic calcium overload. In order to describe how EGF-induced NED protects cells against thapigargin-induced calcium overload we investigated the spatiotemporal calcium signalling linked to apoptosis. By using thapsigargin in various conditions on DU145 cells and using micro-fluorimetric calcium measurements, we show that depletion of intracellular calcium store induces apoptosis and that the amplitude and duration of the capacitive calcium entry are two apoptosis-modulating parameters. We show that protection against thapsigargin-induced apoptosis conferred by NED is achieved by reducing the amount and the speed of calcium that can be released from calcium pools, as well as modulating the amplitude of the subsequent calcium entry.
Gender difference in the activity but not expression of estrogen receptors α and β in human lung adenocarcinoma cells
Authors: Dougherty Susan M , Mazhawidza Williard , Bohn Aimee R , Robinson Krista A , Mattingly Kathleen A , Blankenship Kristy A , Huff Mary O , McGregor William G , Klinge Carolyn M
Published: April 2006

The higher frequency of lung adenocarcinoma in women smokers than in men smokers suggests a role for gender-dependent factors in the etiology of lung cancer. We evaluated estrogen receptor (ER) α and β expression and activity in human lung adenocarcinoma cell lines and normal lung fibroblasts. Full-length ERα and ERβ proteins were expressed in all cell lines with higher ERβ than ERα. Although estradiol (E2) binding was similar, E2 stimulated proliferation only in cells from females, and this response was inhibited by anti-estrogens 4-hydroxytamoxifen (4-OHT) and ICI 182,780. In contrast, E2 did not stimulate replication of lung adenocarcinoma cells from males and 4-OHT or ICI did not block cell proliferation. Similarly, transcription of an estrogen response element-driven reporter gene was stimulated by E2 in lung adenocarcinoma cells from females, but not males. Progesterone receptor (PR) expression was increased by E2 in two out of five adenocarcinoma cell lines from females, but none from males. E2 decreased E-cadherin protein expression in some of the cell lines from females, as it did in MCF-7 breast cancer cells, but not in the cell lines from males. Thus, ERα and ERβ expression does not correlate with the effect of ER ligands on cellular activities in lung adenocarcinoma cells. On the other hand, coactivator DRIP205 expression was higher in lung adenocarcinoma cells from females versus males and higher in adenocarcinoma cells than in normal human bronchial epithelial cells. DRIP205 and other ER coregulators may contribute to differences in estrogen responsiveness between lung adenocarcinoma cells in females and males.
Activation of multiple cancer-associated genes at the ERBB2 amplicon in breast cancer
Authors: Kauraniemi P , Kallioniemi A
Published: April 2006

During the past decade the role of the ERBB2 (neu/HER2) oncogene as an important predictor of patient outcome and response to various therapies in breast cancer has been clearly established. This association of ERBB2 aberrations with more aggressive disease and poor clinical outcome, together with the high prevalence of such alterations in breast cancer, has also made ERBB2 an attractive target for therapy. A specific antibody-based therapy, Herceptin, directed against the extracellular domain of the ERBB2 receptor tyrosine kinase, was recently developed and several clinical trials have shown the therapeutic efficacy of this drug against ERBB2-positive breast cancer. However, a relatively large fraction of patients does not benefit from Herceptin treatment, indicating that other factors beyond ERBB2 itself must influence therapy response in ERBB2-positive tumors. It is well known that amplification of the 17q12–q21 region is the most common mechanism for ERBB2 activation in breast cancer and that it leads to simultaneous activation of several other genes. These co-amplified and co-activated genes may have an impact on disease progression and the clinical behavior of ERBB2-positive tumors and thus represent important targets of research. In this paper we discuss the current knowledge on the structure of the ERBB2 amplicon, the genes involved, and their possible contribution to breast cancer pathogenesis.
Stainless Steels for Implants
Authors: Zardiackas Lyle D.
Published: April 2006

Stainless steel has been and continues to be among the most widely used metals for implant applications. Along with Co‐Cr alloys, CP titanium and titanium alloys, and expanding use of Ni‐Ti alloy (Nitinol), implant‐quality austenitic steels find a variety of uses for implants. These alloys are used for orthopedic, dental, and cardiovascular applications.