bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural Correlates of Probabilistic Category Learning in Patients with Schizophrenia
Authors: Weickert Thomas W. , Goldberg Terry E. , Callicott Joseph H. , Chen Qiang , Apud Jose A. , Das Sumitra , Zoltick Brad J. , Egan Michael F. , Meeter Martijn , Myers Catherine , Gluck Mark A. , Weinberger Daniel R. , Mattay Venkata S.
Published: January 2009

Functional neuroimaging studies of probabilistic category learning in healthy adults report activation of cortical-striatal circuitry. Based on previous findings of normal learning rate concurrent with an overall performance deficit in patients with schizophrenia, we hypothesized that relative to healthy adults, patients with schizophrenia would display preserved caudate nucleus and abnormal prefrontal cortex activation during probabilistic category learning. Forty patients with schizophrenia receiving antipsychotic medication and 25 healthy participants were assessed on interleaved blocks of probabilistic category learning and control tasks while undergoing blood oxygenation level-dependent functional magnetic resonance imaging. In addition to the whole sample of patients with schizophrenia and healthy adults, a subset of patients and healthy adults matched for good learning was also compared. In the whole sample analysis, patients with schizophrenia displayed impaired performance in conjunction with normal learning rate relative to healthy adults. The matched comparison of patients and healthy adults classified as good learners revealed greater caudate and dorsolateral prefrontal cortex activity in the healthy adults and greater activation in a more rostral region of the dorsolateral prefrontal, cingulate, parahippocampal and parietal cortex in patients. These results demonstrate that successful probabilistic category learning can occur in the absence of normal frontal-striatal function. Based on analyses of the patients and healthy adults matched on learning and performance, a minority of patients with schizophrenia achieve successful probabilistic category learning and performance levels through differential activation of a circumscribed neural network which suggests a compensatory mechanism in patients showing successful learning.
Fgfr1Is Required for Cortical Regeneration and Repair after Perinatal Hypoxia
Authors: Fagel Devon M. , Ganat Yosif , Cheng Elise , Silbereis John , Ohkubo Yasushi , Ment Laura R. , Vaccarino Flora M.
Published: January 2009

Chronic postnatal hypoxia causes an apparent loss of cortical neurons that is reversed during recovery (Fagel et al., 2006). The cellular and molecular mechanisms underlying this plasticity are not understood. Here, we show that chronic hypoxia from postnatal days 3 (P3) to 10 causes a 30% decrease in cortical neurons and a 24% decrease in cortical volume. T-brain-1 (Tbr1)+and SMI-32+excitatory neuron numbers were completely recovered 1 month after the insult, but the mice showed a residual deficit in Parvalbumin+and Calretinin+GABAergic interneurons. In contrast, hypoxic mice carrying a disrupted fibroblast growth factor receptor-1 (Fgfr1) gene in GFAP+ cells [Fgfr1conditional knock-out (cKO)], demonstrated a persistent loss of excitatory cortical neurons and a worsening of the interneuron defect. Labeling proliferating progenitors at P17 revealed increased generation of cortical NeuN+and Tbr1+excitatory neurons in wild-type mice subjected to hypoxic insult, whereasFgfr1 cKOfailed to mount a cortical neurogenetic response. Hypoxic wild-type mice also demonstrated a twofold increase in cell proliferation in the subventricular zone (SVZ) at P17 and a threefold increase in neurogenesis in the olfactory bulb (OB) at P48, compared with normoxic mice. In contrast,Fgfr1 cKOmice had decreased SVZ cell proliferation and curtailed reactive neurogenesis in the OB. Thus, the activation of FGFR-1 in GFAP+ cells is required for neuronal recovery after neonatal hypoxic injury, which is attributable in part to enhanced cortical and OB neurogenesis. In contrast, there is incomplete recovery of inhibitory neurons after injury, which may account for persistent behavioral deficits.
Rapid Activation of Plasticity-Associated Gene Transcription in Hippocampal Neurons Provides a Mechanism for Encoding of One-Trial Experience
Authors: Miyashita Teiko , Kubik Stepan , Haghighi Nahideh , Steward Oswald , Guzowski John F.
Published: January 2009

The hippocampus is hypothesized to support rapid encoding of ongoing experience. A critical prerequisite for such function is the ability to readily recruit enduring synaptic plasticity in hippocampal neurons. Hippocampal long-term potentiation (LTP) and memory consolidation require expression of the immediate-early gene (IEG)Arc. To determine whetherArctranscription could be driven by limited and controlled behavioral experience, we used a rectangular track paradigm. In past electrophysiological studies, pyramidal neurons recorded from rats running in one direction on similar tracks typically exhibited a single firing field. Using fluorescencein situhybridization, we show that the behavioral activity associated with a single lap around the track was sufficient to triggerArctranscription in complete CA3 neuronal ensembles, as predicted given the role of CA3 in one-trial learning. In contrast,Arctranscription in CA1 ensembles was recruited incrementally, with maximal activation achieved after four laps a day for 4 consecutive days. To test whetherArctranscription is linked to learning and plasticity, or merely elicited by location-specific firing, we inactivated the medial septum, a treatment that compromises hippocampus-dependent learning and LTP but spares location-specific firing in CA1 neurons. Septal inactivation abolished track training-inducedArctranscription in CA1 and CA3 neurons, showing thatArctranscription requires plasticity-inducing stimuli. Accordingly, LTP induction activatedArctranscription in CA1 neuronsin vivo. These findings demonstrate for the first time that a single brief experience, equivalent to a single crossing of a firing field, can trigger IEG expression required for long-term plasticity in the hippocampus.
Early-Stage Waves in the Retinal Network Emerge Close to a Critical State Transition between Local and Global Functional Connectivity
Authors: Hennig Matthias H. , Adams Christopher , Willshaw David , Sernagor Evelyne
Published: January 2009

A novel, biophysically realistic model for early-stage, acetylcholine-mediated retinal waves is presented. In this model, neural excitability is regulated through a slow after-hyperpolarization (sAHP) operating on two different temporal scales. As a result, the simulated network exhibits competition between a desynchronizing effect of spontaneous, cell-intrinsic bursts, and the synchronizing effect of synaptic transmission during retinal waves. Cell-intrinsic bursts decouple the retinal network through activation of the sAHP current, and we show that the network is capable of operating at a transition point between purely local and global functional connectedness, which corresponds to a percolation phase transition. Multielectrode array recordings show that, at this point, the properties of retinal waves are reliably predicted by the model. These results indicate that early spontaneous activity in the developing retina is regulated according to a very specific principle, which maximizes randomness and variability in the resulting activity patterns.
Deafness and Permanently Reduced Potassium Channel Gene Expression and Function in HypothyroidPit1dwMutants
Authors: Mustapha Mirna , Fang Qing , Gong Tzy-Wen , Dolan David F. , Raphael Yehoash , Camper Sally A. , Duncan R. Keith
Published: January 2009

The absence of thyroid hormone (TH) during late gestation and early infancy can cause irreparable deafness in both humans and rodents. A variety of rodent models have been used in an effort to identify the underlying molecular mechanism. Here, we characterize a mouse model of secondary hypothyroidism, pituitary transcription factor 1 (Pit1dw), which has profound, congenital deafness that is rescued by oral TH replacement. These mutants have tectorial membrane abnormalities, including a prominent Hensen's stripe, elevated β-tectorin composition, and disrupted striated-sheet matrix. They lack distortion product otoacoustic emissions and cochlear microphonic responses, and exhibit reduced endocochlear potentials, suggesting defects in outer hair cell function and potassium recycling. Auditory system and hair cell physiology, histology, and anatomy studies reveal novel defects of hormone deficiency related to deafness: (1) permanently impaired expression of KCNJ10 in the stria vascularis ofPit1dwmice, which likely contributes to the reduced endocochlear potential, (2) significant outer hair cell loss in the mutants, which may result from cellular stress induced by the lower KCNQ4 expression and current levels inPit1dwmutant outer hair cells, and (3) sensory and strial cell deterioration, which may have implications for thyroid hormone dysregulation in age-related hearing impairment. In summary, we suggest that these defects in outer hair cell and strial cell function are important contributors to the hearing impairment inPit1dwmice.
Working Memory-Related Hippocampal Deactivation Interferes with Long-Term Memory Formation
Authors: Axmacher Nikolai , Elger Christian E. , Fell Juergen
Published: January 2009

Previous findings indicate that the hippocampus does not only play a role in long-term memory (LTM) encoding, but is important for working memory (WM) as well, in particular when multiple items are being processed. A recent study showed that maintenance of multiple items was associated with hippocampal activation (hippocampus-dependent WM), while maintenance of individual items induced hippocampal deactivations (hippocampus-independent WM). Here, we used two complimentary approaches to investigate whether WM-related activity patterns occur also during LTM encoding of sequentially presented items and whether they are related to the primacy effect, i.e., improved LTM encoding of items presented at the beginning of the list. Intracranial electroencephalogram in epilepsy patients and functional MRI in healthy subjects were recorded during a word-list learning task. As expected, the proportion of successfully encoded items was higher at the beginning of the list than at later list positions. Items at the beginning of the list which were subsequently forgotten were associated with negative blood oxygen level dependent responses and positive direct current slopes, corresponding to hippocampal deactivations, suggesting that they were not processed in hippocampus-dependent WM. These deactivations were absent for items later in the list and for subsequently remembered items. These data show that if processing of items at the beginning of the list is accompanied by hippocampal activity patterns previously observed during hippocampus-dependent WM, these items are subsequently remembered. However, deactivations of the hippocampus as previously observed during WM maintenance of individual items predicts failure of LTM encoding.
Genetic Influences on Sociability: Heightened Amygdala Reactivity and Event-Related Responses to Positive Social Stimuli in Williams Syndrome
Authors: Haas Brian W. , Mills Debra , Yam Anna , Hoeft Fumiko , Bellugi Ursula , Reiss Allan
Published: January 2009

Williams syndrome (WS) is a genetic disorder caused by a hemizygous microdeletion on chromosome 7q11.23. WS is associated with a compelling neurocognitive profile characterized by relative deficits in visuospatial function, relative strengths in face and language processing, and enhanced drive toward social engagement. We used a combined functional magnetic resonance imaging (fMRI) and event-related potential (ERP) approach to examine the neural basis of social responsiveness in WS participants to two types of social stimuli, negative (fearful) and positive (happy) emotional facial expressions. Here, we report a double dissociation consistent across both methods such that WS participants exhibited heightened amygdala reactivity to positive (happy) social stimuli and absent or attenuated amygdala reactivity to negative (fearful) social stimuli, compared with controls. The fMRI findings indicate that atypical social processing in WS may be rooted in altered development of disparate amygdalar nuclei that subserve different social functions. The ERP findings suggest that abnormal amygdala reactivity in WS may possibly function to increase attention to and encoding of happy expressions and to decrease arousal to fearful expressions. This study provides the first evidence that the genetic deletion associated with WS influences the function of the amygdala to be particularly responsive to socially appetitive stimuli.
Sharing Musical Expression Through Embodied Listening: A Case Study Based on Chinese Guqin Music
Authors: Leman Marc , Desmet Frank , Styns Frederik , Van Noorden Leon , Moelants Dirk
Published: January 2009

IN THIS STUDY WE REPORT ON THE RESULT OF AN experiment in which a guqin music performance was recorded and individual listeners were asked to move their arm along with the music that they heard. Movement velocity patterns were extracted from both the musician and the listeners. The analysis reveals that the listeners' movement velocity patterns tend to correlate with each other, and with the movement velocity patterns of the player's shoulders. The findings support the hypothesis that listeners and player share, to a certain degree, a sensitivity for musical expression and its associated corporeal intentionality.
What do Music Training and Musical Experience Teach Us About Brain Plasticity?
Authors: Habib Michel , Besson Mireille
Published: January 2009

THIS ARTICLE SUMMARIZES THE MAIN EVIDENCE TO date regarding links between the brain and music. Musical expertise, often linked to early and intensive learning, is associated with neuroanatomical distinctive features that have been demonstrated through modern neuroimaging techniques, especially magnetic resonance imaging (MRI). These distinctive features are present in several brain regions, all more or less involved either in gestural motor skill (therefore probably related to the use of an instrument) or auditory perception. There also is growing evidence that learning music has more general effects on brain plasticity. One important notion, related to this topic, is that of a probable "sensitive period," around 7 years of age, beyond which music-induced structural changes and learning effects are less pronounced. These data are discussed in the perspective of using music training for remediation in children with specific language and reading disorders.
Enchantment in Times of War: Aby Warburg, Walter Benjamin, and the Secularization Thesis
Authors: Newman Jane O.
Published: January 2009

This article reads Aby Warburg's and Walter Benjamin's work on the astrological movements of the Reformation era in dialogue with the theory of relations between the spiritual and the temporal developed in Protestant "war theology" during World War I. War theology developed themes already present in historical Protestant doctrine, notably Luther's Two Kingdoms theory (Zwei Reiche Lehre). Warburg and Benjamin were wrestling with the challenge of living at a time of great conflict in a highly sacralized—rather than secularized—world with deep roots in early modern Lutheranism. Max Weber was working out his ideas about magic, Calvinism, and secularization at the same time. The article thus also suggests the need to reassess his theses about the emergence of a secular world purged of irrationalism in dialogue with Warburg's and Benjamin's work.
Mysticism, Modernity, and the Invention of Aesthetic Experience
Authors: Largier Niklaus
Published: January 2009

In this article I argue that Luther's critique of the radical reformers establishes a specific distinction between the spiritual and the secular. It excludes the use of inspired speech and mystical tropes from legitimate readings of the Bible and from the political sphere. In doing so, Luther's intervention not only neutralizes certain mystical traditions but also prepares the grounds for the use of mystical tropes in a new epistemological space, the realm of aesthetic experience and self-fashioning, and for the discussions about aesthetics in modernity.
The Public Person and the Play of Fact
Authors: Picciotto Joanna
Published: January 2009

This essay explores seventeenth-century English constructions of the public as a sacred corporate person engaged in the production of facts.
Atherosclerotic risk factors and complications in patients with non-functioning adrenal adenomas treated with or without adrenalectomy: a long-term follow-up study
Authors: Sereg Márta , Szappanos Ágnes , Tőke Judit , Karlinger Kinga , Feldman Karolina , Kaszper Éva , Varga Ibolya , Gláz Edit , Rácz Károly , Tóth Miklós
Published: January 2009

Objective

Despite the increased prevalences of hypertension, type 2 diabetes mellitus (T2DM), hyperlipidemy, and obesity in patients with non-functioning adrenal adenomas (NFAAs), there is a paucity of data on long-term atherosclerotic morbidity as well as the long-term cardiovascular effects of adrenalectomy in these patients.

Design, patients, and methods

This retrospective study includes the results of baseline and follow-up investigations of 125 patients (29 males and 96 females; mean age 60.1 years) with NFAAs referred for endocrine evaluation between 1990 and 2001. Of the 125 patients, 47 underwent unilateral adrenalectomy, while 78 patients were followed conservatively. These patients were reinvestigated after a mean follow-up time of 9.1 (5–16) years in 2006, with special emphasis on laboratory and other atherosclerotic risk factors (ARF), vascular events, and interventions.

Results

The prevalences of hypertension, impaired glucose tolerance or T2DM, hyperlipidemy, and obesity were 82, 43, 58, and 50%, and 89, 58, 82, and 50% at baseline and follow-up, respectively. None of the investigated ARF prevalences were different between patients treated and not treated with adrenalectomy, and between patients with and without subclinical Cushing's syndrome. The prevalences of angina pectoris, acute myocardial infarction, coronary, and peripheral arterial interventions or cerebrovascular stroke did not differ significantly between patients treated and not treated with adrenalectomy.

Conclusion

Our study confirms previous investigations reporting markedly increased prevalences of various ARF in patients with NFAAs. Adrenalectomy performed in these patients failed to decrease the prevalence of ARF and atherosclerotic morbidity.
Presence of pituitary adenylate cyclase activating polypeptide-38 in human plasma and milk
Authors: Borzsei Rita , Mark Laszlo , Tamas Andrea , Bagoly Terez , Bay Csaba , Csanaky Katalin , Banki Eszter , Kiss Peter , Vaczy Alexandra , Horvath Gabriella , Nemeth Jozsef , Szauer Edit , Helyes Zsuzsanna , Reglodi Dora
Published: January 2009

Objective

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide widely distributed throughout the body. It is involved in the regulation of various physiological and pathophysiological processes, such as reproduction, thermoregulation, motor activity, brain development, neuronal survival, inflammation and pain. Since little is known about its distribution in humans, our aim was to examine PACAP-38 in human plasma. Furthermore, based on the presence of vasoactive intestinal peptide, structurally the closest to PACAP, in milk and PACAP and its receptors in the mammary gland, our aim was to study PACAP-38 in human milk.

Design and methods

The presence of PACAP-38 was determined by mass spectrometry in plasma samples from healthy male and female volunteers (age: 20–40), as well as in plasma and milk samples from lactating women (age: 20–35). PACAP concentration was measured with a specific and sensitive RIA.

Results

Our results revealed that PACAP-38 is present in human plasma, its concentration is relatively stable in healthy volunteers and it is not significantly altered by gender, age, food intake or hormonal cycle in females. However, PACAP-38 plasma levels significantly increased in lactating women having 1–6 month-old babies. Moreover, this study is the first which provides evidence for the presence of PACAP-38 in the human milk with levels 5–20-fold greater in the milk whey than in the respective plasma samples.

Conclusions

We found PACAP-38 in human plasma and its increase during the first 6 months of the lactation period. A prominent, nearly 10-fold higher concentration of this peptide was detected in human milk. Based on the literature, several important actions of milk-derived PACAP-38 can be suggested such as mammary gland proliferation, nutrient transfer as well as regulation of growth/differentiation of certain tissues of the neonates. The novelty of the present descriptive data provides a basis for further investigations on the mechanism of PACAP-38 secretion in human milk and its functional significance.
Effect of testosterone replacement therapy on arterial stiffness in older hypogonadal men
Authors: Yaron Marianna , Greenman Yona , Rosenfeld Joseph B , Izkhakov Elena , Limor Rona , Osher Etty , Shenkerman Galina , Tordjman Karen , Stern Naftali
Published: January 2009

Objective

To assess arterial stiffness in a cohort of hypogonadal males and to investigate the effect of testosterone replacement therapy on arterial properties in this specific group.

Design

Eighteen male patients with untreated acquired hypogonadism due to either adult-onset idiopathic hypogonadotropic hypogonadism (n=9) or pituitary tumor (n=9) and 12 age-, sex, and weight-matched eugonadal healthy controls were recruited for the study. Arterial properties, plasma glucose, lipid profile, total, and bioavailable testosterone (BT) levels were measured in fasting state. In the hypogonadal subjects, the effect of transdermal testosterone replacement therapy on arterial properties was studied by repeat noninvasive measurements at baseline, as well as 48 h and 90 days following the initiation of treatment.

Methods

Arterial stiffness was evaluated using applanation tonometry and pulse wave analysis by three different standard devices that assess various measures of arterial stiffness: pulse wave velocity (PWV), augmentation index (AIx), and large/small artery compliance (C1 and C2).

Results

Age- and blood pressure-adjusted PWV was significantly higher in hypogonadal men (8.90±2.29 vs 6.78±1.16 m/s in the control group;P=0.025). Testosterone therapy increased BT level from 2.01±1.04 to 4.68±2.43 and 7.83±6.2 nmol/l after 48 h and 3 months respectively (P=0.001). PWV decreased from 8.9±2.29 to 8.24±1.39 and 8.25±1.82 m/s after 48 h and 3 months of treatment respectively (P=0.03).

Conclusions

Male hypogonadism is associated with increased PWV, which is rapidly but incompletely ameliorated by normalization of circulating testosterone levels.
Multiple mechanisms of germ cell loss in the perinatal mouse ovary
Authors: Rodrigues Patricia , Limback Darlene , McGinnis Lynda K , Plancha Carlos E , Albertini David F
Published: January 2009

In the perinatal ovary of most mammals, external and internal factors establish a primordial follicle reserve that specifies the duration of the reproductive lifespan of a given species. We analyzed the mechanism of follicle loss and survival in C57BI/6 mice using static and dynamic assays of apoptosis, autophagy, and ovarian morphogenesis. We confirm an initial loss soon after birth, when about 44% of the germ cells detectable at the end of the fetal period abruptly disappear. The observations that (1) few germ or somatic cells were apoptotic in newborn ovaries, (2) vitally stained organ cultures exhibit active extrusion of non-apoptotic germ cells and (3) germ-cell lysosome amplification occurs at birth suggested that additional mechanisms are involved in perinatal germ cell loss. Newborn mouse ovaries cultured in the pH sensitive dye lysotracker red exhibit an increased incidence of acidified non-apoptotic germ cells when maintained in the absence but not in the presence of serum, implying a role for autophagy in germ cell attrition. Inhibitors of autophagy, but not apoptosis, reduce germ cell acidification induced by serum starvation in ovary organ cultures and protein mediators of both autophagy and apoptosis are expressed at birth. From these findings we suggest that multiple perinatal mechanisms establish the primordial follicle reserve in mice.
Relationship of vascular perfusion of the wall of the preovulatory follicle to in vitro fertilisation and embryo development in heifers
Authors: Siddiqui M A R , Gastal E L , Gastal M O , Almamun M , Beg M A , Ginther O J
Published: January 2009

The effect of the extent of vascular perfusion of the wall of the preovulatory follicle on in vitro cleavage rate of the recovered oocyte and embryo development to >8 cells was studied in 52 heifers. Heifers received a luteolytic dose of prostaglandin F2α (PGF2α) when the largest follicle was ≥11 mm. An ovulation-inducing injection of GnRH was given 36 h later (hour 0), and collection of follicular fluid and the oocyte was done at hour 26. Vascular perfusion of the follicular wall was assessed by colour Doppler ultrasonography at hours 0 and 26. Each of the recovered oocytes (41/52; 79%) was mature (extruded polar body). Cleavage and embryo development were assessed at 48 h and 120 h respectively, after in vitro fertilisation (IVF). The percentage of cleaved oocytes and >8 cell embryos was 80% (31/39) and 55% (17/31) respectively. Vascular perfusion of the follicular wall was greater (lower pulsatility index; P<0.001) for follicles that produced cleaved versus non-cleaved oocytes and greater (P<0.04) for follicles that produced >8 cell versus ≤8 cell embryos. Percentage of follicular wall with Doppler signals of blood flow was greater (P<0.001) for >8 cell versus ≤8 cell embryos. Follicular-fluid concentration of free IGF1 was lower for cleaved oocytes (P<0.001) and >8 cell embryos (P<0.05), and oestradiol was lower (P<0.05) for >8 cell embryos. Results supported the hypothesis that greater vascular perfusion of the wall of the preovulatory follicle was positively associated with IVF and embryo development.
Expression of ovarian tumour suppressor OPCML in the female CD-1 mouse reproductive tract
Authors: Fleming Jean S , McQuillan H James , Millier Melanie J , Sellar Grant C
Published: January 2009

Opioid binding protein/cell adhesion molecule-like gene (OPCML) is frequently inactivated in epithelial ovarian cancer, but the role of this membrane protein in normal reproductive function is unclear. The ovarian surface epithelium (OSE) is thought to be the cell of origin of most epithelial ovarian cancers, some of which arise after transformation of OSE cells lining ovarian inclusion cysts, formed during ovulation. We used immunohistochemistry, immunoblotting and quantitative RT-PCR (qRT-PCR) to investigate OPCML expression in the uteri and ovaries of cycling 3-month CD-1 mice, as well as in ovaries from older mice containing inclusion cysts derived from rete ovarii tubules. Immunoblotting showed OPCML bands in uterine, but not whole ovarian or muscle extracts. Strong OPCML immunoreactivity was observed in oviduct, rete ovarii and uterus, whereas in ovary more immunoreactivity was seen in granulosa cells than OSE. No staining was observed in OSE around ovulation sites, where OSE cells divide to cover the site. OPCML immunoreactivity was also weaker in more dysplastic cells lining large ovarian inclusion cysts, compared with normal rete ovarii. No significant changes inOpcmlmRNA expression were observed in whole ovarian and uterine extracts at different stages of the cycle. We conclude that murine OPCML is more consistently expressed in cells lining the uterus, oviduct and rete ovarii than in ovary and is not expressed in OSE associated with ovulation sites. This observation supports the hypothesis that a proportion of epithelial ovarian cancers arise from ductal cells and other epithelia of the secondary Mullerian system, rather than the OSE.
Thermal coarsening of nanoporous gold: Melting or recrystallization
Authors: Hakamada Masataka , Mabuchi Mamoru
Published: January 2009

The thermal coarsening of nanoporous Au was examined and compared with the thermal instability of Au nanoparticles. The nanoporous Au was coarsened at temperatures far below the melting temperature of Au nanoparticles, which possess sizes similar to the nanoligaments. Differential scanning calorimetry characterization of nanoporous Au exhibited an exothermal peak around 470 K. These results suggest that solid-state process like recrystallization, rather than melting, is responsible for the thermal coarsening of nanoporous Au.
Nanostructural characterizations of hydrogen-permselective Si–Co–O membranes by transmission electron microscopy
Authors: Fujisaki Shinji , Hataya Koji , Saito Tomohiro , Arai Shigeo , Iwamoto Yuji , Kuroda Kotaro
Published: January 2009

Nanostructural characterizations of liquid metal–organic precursors-derived cobalt-doped amorphous silica (Si–Co–O) membranes supported on a mesoporous anodic alumina capillary (MAAC) tube were performed to study their unique high-temperature hydrogen gas permeation properties. Cross-sectional scanning transmission electron microscopy images and selected-area electron diffraction patterns indicated that the metal cobalt and the different oxidation states of cobalt oxides (CoO and Co3O4) nanocrystallites having a size range of 5–20 nm were in situ formed in the mesopore channels of the MAAC tube. In addition, high-resolution transmission electron microscopy micrographs and electron energy loss spectroscopy elemental mapping images indicated that the highly dense Co-doped amorphous Si–O formed within the mesopore channels of the MAAC tube. These nanostructural features could contribute to the hydrogen-selective permeation properties observed for the membranes.
The role of Cu addition in the coercivity enhancement of sintered Nd-Fe-B permanent magnets
Authors: Li W.F. , Ohkubo T. , Akiya T. , Kato H. , Hono K.
Published: January 2009

To understand the mechanism of the coercivity enhancement by a trace addition of Cu in Nd-Fe-B sintered magnets, we investigated the microstructure difference between Cu-doped and Cu-free alloys using high resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), and laser assisted three dimensional atom probe (LA-3DAP). From a serial sectioning back scattered electron (BSE) images of the Nd-rich phase obtained by an integration of the focused ion beam (FIB) and HRSEM technique, it was found that Cu addition leads to a continuous formation of Nd-rich thin layers along the grain boundaries. 3DAP analysis has shown that a thin Cu-rich layer with a thickness of approximately 2 nm is present at the interface between the Nd2Fe14B and Nd-rich phase grains.
Effect of film thickness on the structural and electrical properties of Ga-doped ZnO thin films prepared on glass and Al2O3 (0001) substrates by RF magnetron sputtering method
Authors: Shin Seung Wook , Pawar S.M. , Kim Tae-Won , Moon Jong-Ha , Kim Jin Hyeok
Published: January 2009

Thin films of Ga-doped ZnO (GZO) were prepared on glass and Al2O3 (0001) substrates by using RF magnetron sputtering at a substrate temperature of 350 °C, RF power of 175 W, and working pressure of 6 mTorr. The effect of film thickness and substrate type on the structural and electrical properties of the thin films was investigated. X-ray diffraction study showed that GZO thin films on glass substrates were grown as a polycrystalline hexagonal wurtzite phase with a c-axis preferred, out-of-plane orientation and random in-plane orientation. However, GZO thin films on Al2O3 (0001) substrates were epitaxially grown with an orientation relationship of . The structural images from scanning electron microscopy and atomic force microscopy showed that the GZO thin films on glass substrates had a rougher surface morphology than those on Al2O3 (0001) substrates. The electrical resistivity of 1000 nm-thick GZO thin films grown on glass and Al2O3 (0001) substrates was 3.04 × 10−4 Ωcm and 1.50 × 10−4 Ωcm, respectively. It was also found that the electrical resistivity difference between the films on the two substrates decreased from 9.48 × 10−4 Ωcm to 1.45 × 10−4 Ωcm with increasing the film thickness from 100 nm to 1000 nm.
Energy transfer and enhanced broadband near-infrared luminescence in Yb–Bi codoped phosphate glasses
Authors: Ruan Jian , Wu Botao , Chen Danping , Qiao Yanbo , Qiu Jianrong
Published: January 2009

In this article, we report on enhanced broadband near-infrared emission in Yb–Bi codoped phosphate glasses. The emission intensity of Yb–Bi codoped glass was ˜32 times larger than that of Bi-doped glass when excited with 980-nm laser diode. The highest 1/efluorescent lifetime of Yb–Bi codoped glass reached 1650 μs. The dependence of emission intensity and fluorescent lifetime on Yb2O3concentration was investigated. The enhancement of the near-infrared emission is due to energy transfer from Yb3+(2F5/2–2F7/2) transition to Bi ions, and the highest energy transfer efficiency reached 50%. Yb–Bi codoped phosphate glass should be a promising candidate for broadband optical amplification.
Piezoelectric, ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films with compositions around the morphotropic phase boundary prepared by a sol-gel process of reduced thermal budget
Authors: Calzada M.L. , Algueró M. , Santos A. , Stewart M. , Cain M.G. , Pardo L.
Published: January 2009

Single perovskite polycrystalline Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) thin films with PMN to PT ratios around the morphotropic phase boundary composition (070PMN-0.30PT, 0.65PMN-0.35PT, and 0.60PMN-0.40PT) have been prepared by chemical solution deposition (CSD). Air-stable and precipitate-free PMN and PT precursor sols were separately synthesized, and PMN-PT sols were obtained by the simple mixture in air of the former. The PMN-PT sols were deposited onto Pt-coated Si substrates and dried on a hot-plate. Crystallization of the films was carried out by rapid thermal processing (RTP) in oxygen, using different temperatures, soaking times, and heating rates. Single perovskite PMN-PT thin films were obtained at low temperatures (650 °C) with short soaking times (6s) and rapid heating rates (200 °C/s). The films show a columnar growth and a uniform thickness. Both the evolution of the perovskite distortion and the electrical properties with the PMN to PT ratio indicate the correct formation of the solid solution. The temperature and frequency dependences of the permittivity and the ferroelectric loops also indicate an increase of the relaxor characteristic of the films as compared with bulk materials. Piezoelectric coefficients were measured across the ferroelectric loop by optical interferometry, and an enhancement of piezoelectricity at the MPB composition was found. A piezoelectric d33 coefficient of ∼55 pC/N was measured in ∼300-nm-thick films of this composition with a saturation polarisation of Ps ∼25 μC/cm2.
Titanium nitride nanopowders produced via sodium reductionin liquid ammonia
Authors: Yuan Boyan , Yang Mei , Zhu Hongmin
Published: January 2009

Titanium nitride nanopowders were synthesized through a chemical reduction of titanium tetrachloride by sodium in liquid ammonia. The products of the reaction were the mixture of sodium chloride and titanium nitride nanopowders. The mixture was then separated by ammonia extraction. The nanopowders were heated under vacuum up to 1200 °C and were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET) surface area measurement, and chemical analysis. The results show that the product is nanocrystalline cubic phase TiN with Ti/N atomic ratio performed 1:1, and the surface area is from 20 to 50 m2·g−1depending on the heating temperature. The particle sizes estimated by the TEM analysis correspond well with the results of the surface area measurements. The XRD pattern indicates that the crystal size grows with an increase in heating temperature.
Stressed solid-phase epitaxial growth of (011) Si
Authors: Rudawski N.G. , Jones K.S. , Gwilliam R.
Published: January 2009

The solid-phase epitaxial growth kinetics of amorphized (011) Si with application of in-plane uniaxial stress to magnitude of 0.9 ± 0.1 GPa were studied. Tensile stresses did not appreciably change the growth velocity compared with the stress-free case, whereas compression tended to retard the growth velocity to approximately one-half the stress-free value. The results are explained using a prior generalized atomistic model of stressed solid-solid phase transformations. In conjunction with prior observations of stressed solid-phase epitaxial growth of (001) Si, it is advanced that the activation volume tensor associated with ledge migration may be substrate orientation-dependent.
Magnetodielectric Ni ferrite ceramics with Bi2O3 additive for potential antenna miniaturizations
Authors: Liew X.T. , Chan K.C. , Kong L.B.
Published: January 2009

This paper reports on the preparation and characterization of nickel ferrite (NiFe1.98O4) ceramics doped with Bi2O3 as sintering aid. Focus has been on the effects of concentration of Bi2O3 and sintering temperature on the densification, grain growth, dielectric, and magnetic properties of the NiFe1.98O4 ceramics, with an aim at developing magnetodielectric properties, with almost equal real permeability and permittivity, as well as sufficiently low magnetic and dielectric loss tangents, over 3 to 30 MHz (high frequency or HF band). X-ray diffraction results indicated that there is no obvious reaction between NiFe1.98O4 and Bi2O3, at Bi2O3 levels of up to 7 wt% and temperatures up to 1150 °C. The addition of Bi2O3 facilitated a liquid phase sintering mechanism for the densification of NiFe1.98O4 ceramics. The addition of Bi2O3 not only improved the densification but also promoted the grain growth of NiFe1.98O4 ceramics. To achieve sufficiently low dielectric loss tangent, the concentration of Bi2O3 should not be less than 5 wt%. The low dielectric loss tangents of the samples doped with high concentrations of Bi2O3 can be attributed to the full densification of the ceramics. Magnetic properties of the NiFe1.98O4 ceramics, as a function of sintering temperature and Bi2O3 concentration, can be qualitatively explained by the Globus model. Promising magnetodielectric properties have been obtained in the sample doped with 5% Bi2O3 and sintered at 1050 °C for 2 h. The sample has almost equal values of permeability and permittivity of ∼12, together with low dielectric and magnetic loss tangents, over 3 to 30 MHz. This material might be useful for the miniaturization of HF (3 to 30 MHz) antennas.
Effects of Nb doping on thermoelectric properties of Zn4Sb3at high temperatures
Authors: Li D. , Hng H.H. , Ma J. , Qin X.Y.
Published: January 2009

The thermoelectric properties of Nb-doped Zn4Sb3compounds, (Zn1–xNbx)4Sb3(x= 0, 0.005, and 0.01), were investigated at temperatures ranging from 300 to 685 K. The results showed that by substituting Zn with Nb, the thermal conductivities of all the Nb-doped compounds were lower than that of the pristine β-Zn4Sb3. Among the compounds studied, the lightly substituted (Zn0.995Nb0.005)4Sb3compound exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity. Its figure of merit, ZT, was greater than the undoped Zn4Sb3compound for the temperature range investigated. In particular, the ZT of (Zn0.995Nb0.005)4Sb3reached a value of 1.1 at 680 K, which was 69% greater than that of the undoped Zn4Sb3obtained in this study.
A comparison of continuous SPD processes for improving the mechanical properties of aluminum alloy 6111
Authors: Lapovok R. , Tóth L.S. , Winkler M. , Semiatin S.L.
Published: January 2009

Microstructure evolution, mechanical properties, formability, and texture development were determined for AA6111 samples processed by asymmetric rolling (ASR) with different roll friction, velocity, or diameters, conventional rolling (CR), and equal-channel-angular pressing (ECAP). Highly elongated or sheared grain structures were developed during ASR/CR and ECAP, respectively. ASR led to improvedr-values and formability compared with CR primarily as a result of the development of moderate shear-texture components analogous to those developed during ECAP of billet material. ASR based on different roll diameters gave the best combination of strength, ductility, and formability.
Growth of nanotubes in sol-gel-derived V2O5 powders and films prepared under acidic conditions
Authors: Ceccato R. , Dirè S. , Barone T. , De Santo G. , Cazzanelli E.
Published: January 2009

The structural evolution with temperature of some V2O5 gels and thin films is presented, and the role of the hydrolysis conditions is investigated. Several techniques, i.e., x-ray diffraction, differential thermal analysis, infrared, and temperature-dependent Raman spectroscopy, have been used to follow the thermal behavior of the samples. When the bulk xerogels begin to change from a nanocrystalline phase to the orthorhombic α-V2O5, in the temperature range 280 to 300 °C, a growth of vanadium oxide nanotubes also occurs, while at higher temperatures the crystallization into the α phase prevails. A slightly different evolution is observed for heat treated thin films, which show a structure containing polyvanadate chains near room temperature. They also present a growth of nanotubes for intermediate temperatures and a complete crystallization into the α phase when the temperature is further increased.
Compositionally graded mullite-based chemical vapor deposited coatings
Authors: Kulkarni Tushar , Wang H.Z. , Basu S.N. , Sarin V.K.
Published: January 2009

Dense, crystalline mullite (3Al2O3ċ2SiO2) coatings have been deposited by chemical vapor deposition on Si-based substrates using the AlCl3–SiCl4–CO2–H2 system. A graded coating composition has been achieved in the coatings, with the Al/Si ratio being stoichiometric (∼3) at the coating/substrate interface, and increasing monotonically toward the outer coating surface. The highest reported Al-rich mullite has been deposited in the process. At high Al/Si ratios, the mullite structure breaks down and an aluminosilicate phase similar to the metastable δ* Al2O3 is nucleated. Experimental evidence is presented in this study that this phase has some Si-incorporation in it and has been called δ*(Si)Al2O3. Like the other known aluminosilicates, δ*(Si)Al2O3 converts to mullite on heating at elevated temperatures.
Synthesis and pressureless sintering of Ti3SiC2 powder
Authors: Panigrahi B.B. , Chu Min-Cheol , Balakrishnan A. , Cho Seong-Jai
Published: January 2009

Ti3SiC2 powder of about 96 wt% purity was produced using TiCx and Si powders. The synthesis process was characterized by an exothermic reaction at ∼985 °C and low activation energy (∼27 kJ/mol) of conversion. Almost complete conversion to Ti3SiC2 phase was observed during sintering. The onset temperature of sintering was found to be at about 1060 °C using dilatometer. The density of nearly 99% (theoretical) was achieved through the pressureless sintering of Ti3SiC2 powder by 1 and 2 wt% Si powder additions. The sample (without sintering aid) sintered at 1500 °C for 4 h showed uniformly distributed angular grains, whereas the bimodal nature of the microstructure was observed when Si was added as a sintering aid.
Digital image correlation shows localized deformation bands in inelastic loading of fibrolamellar bone
Authors: Benecke Gunthard , Kerschnitzki Michael , Fratzl Peter , Gupta Himadri S.
Published: January 2009

Irreversible or plastic deformation in bone is associated with both permanent plastic strain as well as localized microdamage. Whereas mechanisms at the molecular and mesoscopic level have been proposed to explain aspects of irreversible deformation, a quantitative correlation of mechanical yielding, microstructural deformation, and macroscopic plastic strain does not exist. To address this issue, we developed and applied a two-dimensional image correlation technique to the tensile deformation of bovine fibrolamellar bone, to determine the spatial distribution of strain fields at the length scale of 10 μm to 1 mm in bone during irreversible tensile deformation. We find that tensile deformation is relatively homogeneous in the elastic regime and starts at the yield point, showing regions of locally higher strain. Multiple regions of high deformation can exist at the same time over a length scale of 1 to 10 mm. Macroscopic fracture always occurs at one of the locally highly deformed regions, but the selection of which region cannot be predicted. Locally, strain rates can be enhanced by a factor of 3 to 10 over global strain rates in the highly deformed zones and are lower but always positive in all other regions. Light microscopic imaging shows the onset of structural “banding” in the regions of high deformation, which is most likely correlated to microstructural damage at the inter- and intrafibrillar level.
Influence of oxygen deficiency on the out-of-plane tilt of epitaxial Y2O3 films on Ni–5%W tapes
Authors: Cantoni C. , Specht E.D. , Goyal A. , Li X. , Rupich M.
Published: January 2009

We analyzed the crystallographic c-axis tilt of (001) Y2O3 films grown on biaxially textured Ni–5%W tapes under different oxygen flux conditions. Results show that different tilting mechanisms were effective in films with different oxygen stoichiometry. Moreover, the structure of the film/substrate interface investigated by transmission electron microscopy, and the residual strain of the film investigated by x-ray diffraction were also dependent on the film oxygen content. Although the oxygen stoichiometric Y2O3 sample exhibited a coherent film/substrate interface and the sharpest out-of-plane texture, the films grown under reduced oxygen pressure exhibited a smaller overall c-axis tilt due to formation of interface dislocations and regions in which the film oxygen vacancies ordered to form a lattice superstructure.
Chemical bonding and mechanical properties of M2AC (M = Ti, V, Cr, A = Al, Si, P, S) ceramics from first-principles investigations
Authors: Liao Ting , Wang Jingyang , Zhou Yanchun
Published: January 2009

MAX-phase carbides (M is an early transition metal, A is an A-group element) exhibit an interesting bonding characteristic of alternative stacking of strong M–C bonds and relatively weak M–A bonds in one direction. In the present first-principles total energy calculations, we establish the relationship between mechanical properties and electronic structure for ternary M2AC (M = Ti, V, Cr, A = Al, Si, P, S) carbides. By systematically tuning elements on the M and A sites, pronounced enhancements of bulk modulus, elastic stiffness, and ideal shear strength are achieved in V-containing V2AC (A = Al, Si, P, and S) carbides. It is suggested that tailoring on the A site is more efficient than on the M site in strengthening the mechanical properties of studied serial carbides. The results highlight a general trend for tailor-made mechanical properties of ternary M2AC carbides by control of chemical bonding.