bluuebunny/crossref_metadata_2025 huggingface dataset:
Closing the dementia care gap: Can referral to Alzheimer's Association chapters help?
Authors: Reuben David , Levin Jennifer , Frank Janet , Hirsch Susan , McCreath Heather , Roth Carol , Wenger Neil
Published: November 2009

The quality of care provided by primary‐care physicians for patients with dementia remains poor, in part because physicians do not provide counseling and education. Local Alzheimer's Association chapters have the potential to improve the quality of care provided for dementia, but are hampered by a lack of referrals from primary‐care physicians. Many physicians remain unaware of the services available through Alzheimer's Association chapters, but recognize the need to provide support to families, ensure patient safety, and manage behavioral problems. At present, systems to promote referrals and communication with local chapters are lacking. Practice redesign may facilitate linkages between practices and Alzheimer's Association chapters. However, if these linkages are to be adopted and sustained, they must demonstrate a relative advantage to physicians beyond the care they currently provide, and must be compatible with how care is currently delivered in their practices.
Cerebral blood flow in ischemic vascular dementia and Alzheimer's disease, measured by arterial spin‐labeling magnetic resonance imaging
Authors: Schuff Norbert , Matsumoto Shinji , Kmiecik Joseph , Studholme Colin , Du Antao , Ezekiel Frank , Miller Bruce L. , Kramer Joel H. , Jagust William J. , Chui Helen C. , Weiner Michael W.
Published: November 2009

Background

Our objectives were to compare the effects of subcortical ischemic vascular dementia (SIVD) and Alzheimer's disease (AD) on cerebral blood flow (CBF), and then to analyze the relationship between CBF and subcortical vascular disease, measured as volume of white‐matter lesions (WMLs).

Methods

Eight mildly demented patients with SIVD (mean ± SD; aged 77 ± 8 years; Mini‐Mental State Examination score 26 ± 3 years) and 14 patients with AD were compared with 18 cognitively normal elderly subjects. All subjects had CBF measured using arterial spin‐labeling magnetic resonance imaging, and brain volumes were assessed using structural magnetic resonance imaging.

Results

AD and SIVD showed marked CBF reductions in the frontal (P = 0.001) and parietal (P = 0.001) cortices. In SIVD, increased subcortical WMLs were associated with reduced CBF in the frontal cortex (P = 0.04), in addition to cortical atrophy (frontal, P = 0.05; parietal, P = 0.03).

Conclusions

Subcortical vascular disease is associated with reduced CBF in the cortex, irrespective of brain atrophy.
Cognitive performance and informant reports in the diagnosis of cognitive impairment and dementia in African Americans and whites
Authors: Potter Guy G. , Plassman Brenda L. , Burke James R. , Kabeto Mohammed U. , Langa Kenneth M. , Llewellyn David J. , Rogers Mary A.M. , Steffens David C.
Published: November 2009

Background

The diagnosis of cognitive impairment and dementia must reflect an increasingly diverse and aging United States population. This study compared direct testing and informant reports of cognition with clinical diagnoses of cognitive impairment and dementia between African Americans and whites.

Methods

Participants in the Aging, Demographics, and Memory Study completed in‐person dementia evaluations, and were assigned clinical diagnoses (by a consensus panel of dementia experts) of normal; cognitive impairment, not demented (CIND); and dementia. The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) total score and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) were used to assess cognitive performance and reported cognitive decline.

Results

A higher CERAD total score was associated with lower odds of CIND and dementia, at comparable ratios between African Americans and whites. Higher IQCODE scores were associated with increased odds of dementia in both African Americans and whites. Higher IQCODE scores were associated with increased odds of CIND among whites, but not among African Americans.

Conclusions

Cultural differences may influence informant reports of prevalent CIND and dementia. Our findings also highlight the need for more comparative research to establish the cultural validity of measures used to diagnose these conditions.
The existence of cognitive plateaus in Alzheimer's disease
Authors: Bozoki Andrea C. , An Hyonggin , Bozoki Eva S. , Little Roderick J.
Published: November 2009

Background

The objective of this study was to evaluate the existence of cognitive plateaus in some individuals during the course of Alzheimer's disease (AD).

Methods

Data came from the historical patient group collected via the Consortium to Establish a Registry for Alzheimer's Disease (CERAD, Duke University, 1988–1996). Data reduction was performed by using principal components analysis to derive a single cognitive measure (F1), followed by application of a novel plateau‐searching algorithm to individual patient data, looking for stable periods of 3 years or longer. To evaluate the time dependence of F1, we fitted a linear mixed model to the group and to individual data points.

Results

Twenty‐two percent of AD subjects (54/243) and 98% of healthy control subjects (253/258) exhibited a plateau. Within the AD plateau group, the most common pattern was a single plateau (mean, 3.6 years; range, 3 to 7 years) that extended for the entire measurement period (28/54 subjects). Briefer plateau durations were seen at the beginning or end of the measurement period. Initial cognitive function (F1) was slightly higher in the plateau group, which was also slightly older and less well‐educated. Men and women were equally represented.

Conclusions

In a patient sample predating the widespread use of cholinesterase inhibitors, we found that approximately one fifth of individuals with AD demonstrated periods of prolonged cognitive stability. This significant interindividual variability must be considered when providing prognostic information to families and when assessing individual patient responses to pharmacotherapy. We advise caution when assessing results of potentially disease‐modifying agents at the individual patient level.
Can we do better in developing new drugs for Alzheimer's disease?
Authors: Gauthier Serge , Scheltens Philip
Published: November 2009

The past 30 years have seen multiple attempts at demonstrating the safety and efficacy of drugs for Alzheimer's disease (AD), predominantly to improve symptoms. Only five drugs (tacrine, donepezil, rivastigmine, galantamine, memantine) have obtained regulatory approval in most countries. Their cost‐effectiveness from a societal perspective has not been universally recognized, and anybody who thinks these drugs are useful for individual patients will have to agree that the improvement above the starting point of treatment is moderate. Most of the benefit has been in slowing down progression of symptoms rather than a readily detectable improvement above baseline. There have also been attempts at arresting progression of AD, but all have failed until now. Should we change our approach to developing new drugs for AD so as to move forward? This review will highlight some options to consider in the development of future drugs for AD, with emphasis on strategies to prevent AD or arrest its progression.
Everyday technologies for Alzheimer's disease care: Research findings, directions, and challenges
Authors: Carrillo Maria C. , Dishman Eric , Plowman Tim
Published: November 2009

The Everyday Technologies for Alzheimer's Care initiative was launched by the Alzheimer's Association and Intel Corporation in 2003 to identify and fund promising research in the use of technology—especially information and communication technologies—for monitoring, diagnosing, and treating Alzheimer's disease. At the last two progress meetings, scientific leaders of the two partners, together with aging health technology academic scientists, met to review the most recent research and discuss how current and developing technologies can address growing needs in Alzheimer care.
Differential CXCR4 expression and function in subpopulations of the feline lymphoma cell line 3201 susceptible to feline immunodeficiency virus
Authors: Tochikura Tadafumi S. , Motokawa Kenji , Naito Yuko , Kozutsumi Yasunori , Tanabe-Tochikura Akiko , Hohdatsu Tsutomu
Published: November 2009

The infection of feline thymic lymphoma 3201 cells with a cell culture-adapted Petaluma strain of feline immunodeficiency virus (FIV) led to the establishment of survivor cells designated as 3201-S after a productive infection associated with extensive cell killing. 3201-S cells were free of FIV DNA, and were found to express CXCR4, a coreceptor for infection but not CD134, a primary receptor. When 3201-S cells were reinfected with FIV, viral DNA was transiently detectable for 5 days postinfection, indicating that 3201-S cells cannot support the FIV replicative cycle. Furthermore, comparative studies found that in contrast to SDF-1α-responsive 3201 cells, 3201-S cells did not show a flux of Ca2+ in response to SDF-1α, implying that CXCR4 is not functionally active on 3201-S cells. These results suggest that 3201 cells can be heterogeneous in the phenotype of the CXCR4 expressed, and this heterogeneity may account for the differences in susceptibility to FIV. Determining the mechanism(s) within 3201-S cells that restrict FIV could result in therapeutic strategies against FIV infection.
A Case of Carbon tetrachloride Poisoning in Southern Rhodesia
Authors: Blackie W. K.
Published: November 2009

Since the introduction of carbon tetrachloride for the treatment of the hookworm infestations of man it has been ascertained that in certain conditions fatal poisoning may follow oral administration of the drug. If carbon tetrachloride is given in cases of alcoholic cirrhosis of the liver, or if alcohol is taken immediately after the drug, severe gastro-intestinal symptoms are to be anticipated with death in two or three days. Davis (1924) showed that in dogs the toxicity of the drug was intimately associated with certain dietetic factors. He found that a high carbohydrate diet enabled the liver to withstand relatively large doses of the drug. High protein diets also protected the liver against injury (although less efficiently than carbohydrate) but an “all-fat” diet was invariably associated with extensive damage to the hepatic parenchyma. Lambert (1923) while carrying out hookworm treatment on a large scale in Fiji found that where a patient was heavily infested with Ascaris lumbricoides as well as with hookworm it was unwise to exhibit carbon tetrachloride without first getting rid of the ascarids.
Masked Translation Priming Effects With Highly Proficient Simultaneous Bilinguals
Authors: Duñabeitia Jon Andoni , Perea Manuel , Carreiras Manuel
Published: November 2009

One essential issue for models of bilingual memory organization is to what degree the representation from one of the languages is shared with the other language. In this study, we examine whether there is a symmetrical translation priming effect with highly proficient, simultaneous bilinguals. We conducted a masked priming lexical decision experiment with cognate and noncognate translation equivalents. Results showed a significant masked translation priming effect for both cognates and noncognates, with a greater priming effect for cognates. Furthermore, the magnitude of the translation priming was similar in the two directions. Thus, highly fluent bilinguals do develop symmetrical between-language links, as predicted by the Revised Hierarchical model and the BIA+ model. We examine the implications of these results for models of bilingual memory.
Feature Bindings Are Maintained in Visual Short-Term Memory Without Sustained Focused Attention
Authors: Delvenne Jean-François , Cleeremans Axel , Laloyaux Cédric
Published: November 2009

Does the maintenance of feature bindings in visual short-term memory (VSTM) require sustained focused attention? This issue was investigated in three experiments, in which memory for single features (i.e., colors or shapes) was compared with memory for feature bindings (i.e., the link between the color and shape of an object). Attention was manipulated during the memory retention interval with a retro-cue, which allows attention to be directed and focused on a subset of memory items. The retro-cue was presented 700 ms after the offset of the memory display and 700 ms before the onset of the test display. If the maintenance of feature bindings – but not of individual features – in memory requires sustained focused attention, the retro-cue should not affect memory performance. Contrary to this prediction, we found that both memory for feature bindings and memory for individual features were equally improved by the retro-cue. Therefore, this finding does not support the view that the sustained focused attention is needed to properly maintain feature bindings in VSTM.
Activating Gender Stereotypes During Online Spoken Language Processing
Authors: Pyykkönen Pirita , Hyönä Jukka , van Gompel Roger P. G.
Published: November 2009

This study used the visual world eye-tracking method to investigate activation of general world knowledge related to gender-stereotypical role names in online spoken language comprehension in Finnish. The results showed that listeners activated gender stereotypes elaboratively in story contexts where this information was not needed to build coherence. Furthermore, listeners made additional inferences based on gender stereotypes to revise an already established coherence relation. Both results are consistent with mental models theory (e.g., Garnham, 2001 ). They are harder to explain by the minimalist account ( McKoon & Ratcliff, 1992 ), which suggests that people limit inferences to those needed to establish coherence in discourse.
Processing of Global and Selective Stop Signals
Authors: van de Laar Maria C. , van den Wildenberg Wery P. M. , van Boxtel Geert J. M. , van der Molen Maurits W.
Published: November 2009

This paper applied Donders’ subtraction method to examine the processing of global and selective stop signals in the stop-signal paradigm. Participants performed on three different versions of the stop task: a global task and two selective tasks. A global task required participants to inhibit their response to a go signal whenever a stop signal was presented (Stop-a task). A selective stop task required participants to inhibit to one stop signal but not to the other (Stop-c task). Another selective stop task required them to inhibit when the response indicated by go and stop signals was the same but not when they were different (Stop-b task). Stop-signal reaction time (SSRT) was shortest for Stop-a and longest for Stop-b, with intermediate values for the Stop-c task. Additional control experiments that manipulated stop probability confirmed the robustness of global and selective stopping latencies even when the stop-signal probability varied. The current findings contribute to the conclusion that Donders’ subtraction method provides a useful tool for estimating the durations of subprocesses that together comprise SSRT.
Bidirectionality in Synesthesia
Authors: Gevers Wim , Imbo Ineke , Cohen Kadosh Roi , Fias Wim , Hartsuiker Robert J.
Published: November 2009

Color-grapheme synesthetes automatically perceive achromatic numbers as colored (e.g., 7 is turquoise). Up until recently, synesthesia was believed to be unidirectional. For instance, the number 7 gives rise to the percept of turquoise but the perception of turquoise does not trigger the number 7. However, some recent studies argue for bidirectional connections ( Cohen Kadosh et al., 2005 ; Johnson et al., 2007 ; Knoch et al., 2005 ). In this study, a multiplication verification task (e.g., 7 × 2 = 14, true/false?) was used to test bidirectionality. In agreement with previous studies we observed that the presentation of colors evokes numerical magnitudes. The current findings add two important notions to previous studies: (a) The influence of color on the processing of numerical information can be extended to multiplication verification tasks and (b) The perception of color can both facilitate and interfere with the processing of digit-related information.
Taxing Executive Processes Does Not Necessarily Increase Impulsive Decision Making
Authors: Franco-Watkins Ana M. , Rickard Timothy C. , Pashler Hal
Published: November 2009

A link has been established between impulsivity in real-world situations and impulsive decision making in laboratory tasks in brain-damaged patients and individuals with substance abuse. Whether or not this link exists for all individuals is less clear. We conducted an experiment to determine whether taxing central executive processes with a demanding cognitive load task results in impulsive decision making in a normal sample. Participants (n = 53) completed a delay discounting task under the presence (load condition) and absence (control condition) of a demanding generation task. Results indicated that taxing working memory is neither necessary nor sufficient to produce impulsive decision making; instead, the demanding generation task resulted in an increase in the number of inconsistent choices.
Absence of Low-Level Visual Difference Between Canonical and Noncanonical Finger-Numeral Configurations
Authors: Di Luca Samuel , Pesenti Mauro
Published: November 2009

Canonical finger numeral configurations are named faster than less familiar finger configurations and activate a semantic place-coding representation as symbolic stimuli. However, this does not exclude categorically the possibility that mere visuo-perceptual differences between canonical and noncanonical finger configurations may induce differences in processing speed. This study capitalizes on the fact that, in typical visual-detection tasks, participants focus on low-level visuo-perceptual features to detect a target among distractors sharing the same high-level semantic features, producing the so-called pop-out effect. Participants had to decide whether a canonical finger configuration was present among a set of distractors expressing the same numerosity in a noncanonical way. The results showed that the time needed to detect the presence of the target grew linearly with the number of distractors. This indicates that the canonical target enjoyed no perceptual saliency among the noncanonical configurations (i.e., no pop-out effect) excluding visuo-perceptual differences as the source of the better identification of and semantic access of canonical configurations.
Effects of Intentional Motor Actions on Embodied Language Processing
Authors: Rueschemeyer Shirley-Ann , Lindemann Oliver , van Rooij Daan , van Dam Wessel , Bekkering Harold
Published: November 2009

Embodied theories of language processing suggest that this motor simulation is an automatic and necessary component of meaning representation. If this is the case, then language and action systems should be mutually dependent (i.e., motor activity should selectively modulate processing of words with an action-semantic component). In this paper, we investigate in two experiments whether evidence for mutual dependence can be found using a motor priming paradigm. Specifically, participants performed either an intentional or a passive motor task while processing words denoting manipulable and nonmanipulable objects. The performance rates (Experiment 1) and response latencies (Experiment 2) in a lexical-decision task reveal that participants performing an intentional action were positively affected in the processing of words denoting manipulable objects as compared to nonmanipulable objects. This was not the case if participants performed a secondary passive motor action (Experiment 1) or did not perform a secondary motor task (Experiment 2). The results go beyond previous research showing that language processes involve motor systems to demonstrate that the execution of motor actions has a selective effect on the semantic processing of words. We suggest that intentional actions activate specific parts of the neural motor system, which are also engaged for lexical-semantic processing of action-related words and discuss the beneficial versus inhibitory nature of this relationship. The results provide new insights into the embodiment of language and the bidirectionality of effects between language and action processing.
Irrelevant Words Trigger an Attentional Blink
Authors: Stein Timo , Zwickel Jan , Kitzmantel Maria , Ritter Johanna , Schneider Werner X.
Published: November 2009

It has been argued that salient distractor items displayed during rapid serial visual presentation (RSVP) trigger an attentional blink (AB) when they share features with the target item. Here we demonstrate that salient distractor words induce an AB independently of feature overlap with the target. In two experiments a color-highlighted irrelevant word preceded a target by a variable lag in an RSVP series of false font strings. Target identification was reduced at short relative to long temporal lags between the distractor word and the target, irrespective of feature sharing with the distractor word. When the target shared features with the distractor word, target accuracy was reduced across all lags. Accordingly, feature sharing between the distractor word and the target did not amplify the AB, but had an additive effect on attentional capture by the distractor word.
On the Semantic Content of Grammatical Gender and Its Impact on the Representation of Human Referents
Authors: Irmen Lisa , Kurovskaja Julia
Published: November 2009

Grammatical gender has been shown to provide natural gender information about human referents. However, due to formal and conceptual differences between masculine and feminine forms, it remains an open question whether these gender categories influence the processing of person information to the same degree. Experiment 1 compared the semantic content of masculine and feminine grammatical gender by combining masculine and feminine role names with either gender congruent or incongruent referents (e.g., Dieser Lehrer [masc.]/Diese Lehrerin [fem.] ist mein Mann/meine Frau; This teacher is my husband/my wife). Participants rated sentences in terms of correctness and customariness. In Experiment 2, in addition to ratings reading times were recorded to assess processing more directly. Both experiments were run in German. Sentences with grammatically feminine role names and gender incongruent referents were rated as less correct and less customary than those with masculine forms and incongruent referents. Combining a masculine role name with an incongruent referent slowed down reading to a greater extent than combining a feminine role name with an incongruent referent. Results thus specify the differential effects of masculine and feminine grammatical gender in denoting human referents.
Comprehensive study of sodium, copper, and silver clusters over a wide range of sizes 2≤N≤75
Authors: Itoh Masahiro , Kumar Vijay , Adschiri Tadafumi , Kawazoe Yoshiyuki
Published: November 2009

The geometric and electronic structures of NaN, CuN, and AgN metal clusters are systematically studied based on the density functional theory over a wide range of cluster sizes 2≤N≤75. A remarkable similarity is observed between the optimized geometric structures of alkali and noble metal clusters over all of the calculated cluster sizes N. The most stable structures are the same for the three different metal clusters for approximately half the cluster sizes N considered in this study. Even if the most stable structures are different, the same types of structures are obtained when the metastable structures are also considered. For all of the three different metal clusters, the cluster shapes change in the order of linear, planar, opened, and closed structures with increasing N. This structural-type transition leads to a deviation from the monotonic increase in the specific volume with N. A remarkable similarity is also observed for the N dependence of the cluster energy E(N) for the most stable geometric structures. The amplitude of this energy difference is larger in the two noble metal clusters than in the alkali metal cluster. This is attributed to the contribution of d electrons to the bonds. The magic number is explicitly defined with a new criterion in the framework of total energy calculations. In the case of NaN, a semiquantitative comparison between the experimental abundance spectra [Knight et al., Phys. Rev. Lett. 52, 2141 (1984)] and the total energy calculations is carried out. The changing aspect of the Kohn–Sham eigenvalues from N=2 to N=75 is presented for the three different metal clusters. The feature of the bulk density of states already appears at N=75 for all of three clusters. With increasing N, the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap clearly exhibits an odd-even alternation and converges to 0. Although there is a similarity in the N dependence of the HOMO-LUMO gap between the three metal clusters, it is much stronger between the two noble metal clusters. The growth aspect of the d band below the Fermi level of the noble metal clusters with increasing N is presented. A good correspondence is observed in the d characteristic of the electronic states between the cluster composed of 75 atoms and the bulk metal. The similarities observed in the N dependence of the geometric structures and E(N)s originate from the similarity in that of the electronic structures.
On the shock response of cubic metals
Authors: Bourne N. K. , Gray G. T. , Millett J. C. F.
Published: November 2009

The response of four cubic metals to shock loading is reviewed in order to understand the effects of microstructure on continuum response. Experiments are described that link defect generation and storage mechanisms at the mesoscale to observations in the bulk. Four materials were reviewed; these were fcc nickel, the ordered fcc intermetallic Ni3Al, the bcc metal tantalum, and two alloys based on the intermetallic phase TiAl; Ti–46.5Al–2Cr–2Nb and Ti–48Al–2Cr–2Nb–1B. The experiments described are in two groups: first, equation of state and shear strength measurements using Manganin stress gauges and, second, postshock microstructural examinations and measurement of changes in mechanical properties. The behaviors described are linked through the description of time dependent plasticity mechanisms to the final states achieved. Recovered targets displayed dislocation microstructures illustrating processes active during the shock-loading process. Reloading of previously shock-prestrained samples illustrated shock strengthening for the fcc metals Ni and Ni3Al while showing no such effect for bcc Ta and for the intermetallic TiAl. This difference in effective shock hardening has been related, on the one hand, to the fact that bcc metals have fewer available slip systems that can operate than fcc crystals and to the observation that the lower symmetry materials (Ta and TiAl) both possess high Peierls stress and thus have higher resistances to defect motion in the lattice under shock-loading conditions. These behaviors, compared between these four materials, illustrate the role of defect generation, transport, storage, and interaction in determining the response of materials to shock prestraining.
Improving a high-resolution fiber-optic interferometer through deposition of a TiO2 reflective coating by simple dip-coating
Authors: Subba-Rao Venkatesh , Sudakar Chandran , Esmacher Jason , Pantea Mircea , Naik Ratna , Hoffmann Peter M.
Published: November 2009

Fiber-optic based interferometers are used to detect small displacements, down to the subnanometer range. Coating the end of the optical fiber with a partially reflecting thin film greatly improves the resolution of interferometers by increasing the multiple reflections between the fiber end and the measured object. In this work, we present a quick and easy thin film deposition technique to coat the end of a single optical fiber by dip-coating a metal-organic precursor, which is then decomposed in a propane flame. The coated fiber was tested for morphology and usefulness for interferometric application. We found that this coating technique is much faster and easier than conventional thin coating techniques, and yields results that are comparable or better than can be achieved with sputtering or thermal evaporation.
Chemical engineering of prehydrogenated C and BN-sheets by Li: Application in hydrogen storage
Authors: Khazaei Mohammad , Bahramy Mohammad Saeed , Venkataramanan Natarajan Sathiyamoorthy , Mizuseki Hiroshi , Kawazoe Yoshiyuki
Published: November 2009

Our first-principles calculations show that if the hydrogen atoms on one of the faces of a graphane sheet (prehydrogenated graphene) are substituted with Li atoms, the resulting monolayer attains a good hydrogen storage capacity of around 3.8 wt % close to the revised Department of Energy (DOE) target. It is observed that Li atoms are strongly hybridized with the monolayer and donate their electrons to the substrate such that their binding energy to the surface becomes around −3.27 eV, which is far larger than the cohesive energy of Li in its metal bulk structure. It indicates that Li atoms on the monolayer are not aggregated or clusterized at high doping concentration and high temperature. Our calculation shows that the binding energy of H2 molecules with the monolayer surface is around −0.1 eV resulting from the electrostatic interaction of the polarized charge of hydrogen molecules with the induced electric field by positively charged Li atoms. Similarly, we have examined the hydrogen storage capacity of Li-substituted prehydrogenated boron nitride (BN) sheet; it is observed that it also has a very good hydrogen storage capability similar to Li-substituted graphane sheet.
How to measure quantum yields in scattering media: Application to the quantum yield measurement of fluorescein molecules encapsulated in sub-100 nm silica particles
Authors: Martini M. , Montagna M. , Ou M. , Tillement O. , Roux S. , Perriat P.
Published: November 2009

Dye quantum yield is generally measured using the method of Williams, which consists in comparing the absorbance and the emission of the dye to test with those of a reference. Unfortunately, this method is no more applicable when the sample presents some significant scattering which is, for instance, the case when the dyes are encapsulated in silica particles with a size below 100 nm. Indeed the photons scattered by the particles are further absorbed by the dyes and generate an additional light emission leading to an overestimation of the quantum yield. Nevertheless, the paper shows that the Williams’s method can be still applied if the sample is compared with a reference that has exactly the same scattering properties than those of the sample. In the case of a test sample consisting of dyes encapsulated within particles, such a reference can be easily realized by incorporating in a solution of reference dyes, an adequate proportion of particles with the same size than those of the test sample. We prove theoretically and experimentally that relevant values of quantum yield are then obtained.
The role of the exchange in the embedding electrostatic potential for the fragment molecular orbital method
Authors: Fedorov Dmitri G. , Kitaura Kazuo
Published: November 2009

We have examined the role of the exchange in describing the electrostatic potential in the fragment molecular orbital method and showed that it should be included in the total Fock matrix to obtain an accurate one-electron spectrum; however, adding it to the Fock matrices of individual fragments and pairs leads to very large errors. For the error analysis we have used the virial theorem; numerical tests have been performed for solvated phenol at the Hartree–Fock level with the 6-31G∗ and 6-311G∗∗ basis sets.
A portable high-field pulsed-magnet system for single-crystal x-ray scattering studies
Authors: Islam Zahirul , Ruff Jacob P. C. , Nojiri Hiroyuki , Matsuda Yasuhiro H. , Ross Kathryn A. , Gaulin Bruce D. , Qu Zhe , Lang Jonathan C.
Published: November 2009

We present a portable pulsed-magnet system for x-ray studies of materials in high magnetic fields (up to 30 T). The apparatus consists of a split-pair of minicoils cooled on a closed-cycle cryostat, which is used for x-ray diffraction studies with applied field normal to the scattering plane. A second independent closed-cycle cryostat is used for cooling the sample to near liquid helium temperatures. Pulsed magnetic fields (∼1 ms in total duration) are generated by discharging a configurable capacitor bank into the magnet coils. Time-resolved scattering data are collected using a combination of a fast single-photon counting detector, a multichannel scaler, and a high-resolution digital storage oscilloscope. The capabilities of this instrument are used to study a geometrically frustrated system revealing strong magnetostrictive effects in the spin-liquid state.
Soluble state high resolution atomic force microscopy study of Alzheimer’s β-amyloid oligomers
Authors: Shekhawat Gajendra S. , Lambert Mary P. , Sharma Saurabh , Velasco Pauline T. , Viola Kirsten L. , Klein William L. , Dravid Vinayak P.
Published: November 2009

We report here the direct observation of high resolution structures of assemblies of Alzheimer β-amyloid oligomers and monomers using liquid atomic force microscopy (AFM). Visualization of nanoscale features of Aβ oligomers (also known as ADDLs) was carried out in tapping mode AFM in F12 solution. Our results indicate that ADDL preparations exist in solution primarily as a mixture of monomeric peptides and higher molecular mass oligomers. Our study clearly reveals that the size and shape of these oligomer aggregates exhibit a pronounced dependence on concentration. These studies show that wet AFM enables direct assessment of oligomers in physiological fluids and suggests that this method may be developed to visualize Aβ oligomers from human fluids.
Extended Kalman filter estimates the contour length of a protein in single molecule atomic force microscopy experiments
Authors: Fernandez Vicente I. , Kosuri Pallav , Parot Vicente , Fernandez Julio M.
Published: November 2009

Atomic force microscopy force spectroscopy has become a powerful biophysical technique for probing the dynamics of proteins at the single molecule level. Extending a polyprotein at constant velocity produces the now familiar sawtooth pattern force-length relationship. Customarily, manual fits of the wormlike chain (WLC) model of polymer elasticity to sawtooth pattern data have been used to measure the contour length Lc of the protein as it unfolds one module at a time. The change in the value of Lc measures the number of amino acids released by an unfolding protein and can be used as a precise locator of the unfolding transition state. However, manual WLC fits are slow and introduce inevitable operator-driven errors which reduce the accuracy of the Lc estimates. Here we demonstrate an extended Kalman filter that provides operator-free real time estimates of Lc from sawtooth pattern data. The filter design is based on a cantilever-protein arrangement modeled by a simple linear time-invariant cantilever model and by a nonlinear force-length relationship function for the protein. The resulting Kalman filter applied to sawtooth pattern data demonstrates its real time, operator-free ability to accurately measure Lc. These results are a marked improvement over the earlier techniques and the procedure is easily extended or modified to accommodate further quantities of interest in force spectroscopy.
Two-dimensional GaAs/AlGaAs superlattice structures for solar cell applications: Ultimate efficiency estimation
Authors: Kłos Jarosław W. , Krawczyk Maciej
Published: November 2009

We calculate the band structure of a two-dimensional GaAs/AlGaAs superlattice and estimate the ultimate efficiency of solar cells using this type of structure for solar energy conversion. The superlattice under consideration consists of gallium arsenide rods forming a square lattice and embedded in aluminum gallium arsenide. The ultimate efficiency is determined versus structural parameters including the filling fraction, the superlattice constant, the rod geometry, and the concentration of Al in the matrix material. The calculated efficiency of the superlattice proves to exceed the efficiency of each component material in the monolithic state in a wide range of parameter values.
Numerical model and study of cascaded third harmonic generation in two-sectioned a periodically poled Mg-doped LiTaO3 structure
Authors: Louchev Oleg A. , Wada Satoshi
Published: November 2009

The feasibility of cascaded second harmonic generation (SHG) and third harmonic generation (THG) in a monolithic two-sectioned periodically poled lithium tantalate crystal is analyzed. Simulation using a computational nonlinear optical model rigorously coupled with a thermal model suggests that 25%–30% THG efficiency can be achieved for a 3 W 20 ns pulsed 1.064 μm laser operating at 10 kHz if the crystal is composed of two sections: (i) ≈8.0 μm period first-order SHG structure and (ii) ≈6.6 μm period third-order THG structure. Significant inhibition of THG efficiency arises due to absorption of SH and TH, the heat release along the crystal, and associated thermal dephasing and lensing which can be effectively compensated by decreasing the temperature of the operating crystal below the quasiphase matching temperature. Corrections for the energy exchange lengths for optimal SHG and THG section design are suggested.
Optically active Er3+ ions in SiO2 codoped with Si nanoclusters
Authors: Navarro-Urrios D. , Lebour Y. , Jambois O. , Garrido B. , Pitanti A. , Daldosso N. , Pavesi L. , Cardin J. , Hijazi K. , Khomenkova L. , Gourbilleau F. , Rizk R.
Published: November 2009

Optical properties of directly excited erbium (Er3+) ions have been studied in silicon rich silicon oxide materials codoped with Er3+. The spectral dependence of the direct excitation cross section (σdir) of the Er3+ atomic I415/2→I411/2 transition (around 0.98 μm) has been measured by time resolved μ-photoluminescence measurements. We have determined that σdir is 9.0±1.5×10−21 cm2 at 983 nm, at least twice larger than the value determined on a stoichiometric SiO2 matrix. This result, in combination with a measurement of the population of excited Er3+ as a function of the pumping flux, has allowed quantifying accurately the amount of optically active Er3+. This concentration is, in the best of the cases, 26% of the total Er population measured by secondary ion mass spectrometry, which means that only this percentage could provide optical gain in an eventual optical amplifier based on this material.
Effect of ultraviolet irradiation on luminescence properties of undoped ZnS and ZnS:Ag nanoparticles
Authors: Qu Hua , Cao Lixin , Su Ge , Liu Wei , Sun Yuanguang , Dong Bohua
Published: November 2009

Undoped ZnS and ZnS:Ag nanoparticles have been prepared through hydrothemal synthesis. The changes of luminescence properties induced by ultraviolet irradiation have been investigated. For both samples, the initial slight increase in luminescence is ascribed to the fast electron filling, while the succedent decrease is supposed to be caused by nonradiative pathways originating from some unknown photochemical products. The more remarkable decrease in ZnS:Ag is put down to the segregation of Ag on the surfaces of ZnS:Ag nanoparticles. Multipeaks Gaussian fitting is applied to the emission spectra. The fitting peaks around 490 nm in both samples are related with the surface states emission and the fitting peaks around 456 nm in ZnS nanoparticles and 443 nm in ZnS:Ag nanoparticles are attributed to the type of donor-acceptor pair luminescence, which corresponds to the transition between different donor levels and acceptor levels in different samples. A model of stretched exponential function is used to fit the fluorescence decay spectra. Result shows that the introduction of Ag+ ions causes a spectacular lifetime shortening of ZnS. Experiment result also verifies the model as that the lifetimes of both samples are notably shortened after irradiation for 2 h.
The combined influence of connectivity and disorder on Jc and Tc performances in MgxB2+10wt %SiC
Authors: Li W. X. , Zeng R. , Lu L. , Li Y. , Dou S. X.
Published: November 2009

The influences of connectivity and disorder on the critical current density Jc are discussed to clarify the different mechanisms of Jc(H) enhancement in different magnetic field ranges. Excess Mg in MgxB2+10 wt % SiC composites effectively improves the connectivity, as evidenced by both the resistivity properties and the Raman scattering. The promising Jc(H) of Mg1.15B2+10 wt % SiC is attributed to both the high connectivity and the improved irreversibility field, Hirr, which is in agreement with the Raman fitting analysis. Raman scattering measurements suggest a strengthened electron-E2g coupling and weakened disorder with Mg addition.
Global existence and stability for a von Karman equations with memory in noncylindrical domains
Authors: Park Jong Yeoul , Kang Jum Ran
Published: November 2009

In this paper, we study the initial-boundary value problem for the von Karman equations inside domains with moving ends. Global existence, uniqueness of solutions, and the exponential decay to the energy are established provided the initial data are bounded.
Mechanism of Na-doped p-type ZnO films: Suppressing Na interstitials by codoping with H and Na of appropriate concentrations
Authors: Lin S. S. , He H. P. , Lu Y. F. , Ye Z. Z.
Published: November 2009

Hydrogen is codoped with sodium into ZnO films. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy indicate that the Na concentration decreases as the substrate temperature increases. Hall-effect tests reveal a transition from n-type to p-type conduction when the growth temperature increases, which is explained by the suppression of Na interstitials by codoping with H and Na of appropriate concentrations. An insulating intended Na–H codoped sample shows reduced resistivity and p-type conductivity after annealing at 550 °C, which may be due to dissociation of NaZn–H complexes. The realization of p-type ZnO by Na–H codoping may explain the discrepancies in behavior of Na in ZnO and suggests the potential of Na–H codoping method [E.-C. Lee and K. J. Chang, Phys. Rev. B 70, 115210 (2004)].
Wearable electronics self-powered by using human body heat: The state of the art and the perspective
Authors: Leonov Vladimir , Vullers Ruud J. M.
Published: November 2009

In this paper, we present our vision of what kind of wearable devices and how they can be powered by the heat of human beings and by using ambient light. The basic principles of designing body-powered devices and ways of their hybridizing with photovoltaic cells are discussed. The mechanisms of thermoregulation in humans and the laws of thermodynamics enable placing a distinct boarder between realistic targets and the science fiction. These allow prediction of application areas for wearable energy harvesters accounting for competitive batteries with long service life. The existing family of body-powered wearable devices and new technologies for thermopiles are discussed. The theory and practice point at the necessity of using microelectronic and microelectromechanical system technologies for the target application area. These technologies for thermopiles offer the possibility of reduced production cost. Therefore, autonomous systems powered thermoelectrically could be successfully marketed. The related aspects of design and fabrication are discussed.
Phase diagram and structural properties of a simple model for one-patch particles
Authors: Giacometti Achille , Lado Fred , Largo Julio , Pastore Giorgio , Sciortino Francesco
Published: November 2009

We study the thermodynamic and structural properties of a simple, one-patch fluid model using the reference hypernetted-chain (RHNC) integral equation and specialized Monte Carlo simulations. In this model, the interacting particles are hard spheres, each of which carries a single identical, arbitrarily oriented and attractive circular patch on its surface; two spheres attract via a simple square-well potential only if the two patches on the spheres face each other within a specific angular range dictated by the size of the patch. For a ratio of attractive to repulsive surface of 0.8, we construct the RHNC fluid-fluid separation curve and compare with that obtained by Gibbs ensemble and grand canonical Monte Carlo simulations. We find that RHNC provides a quick and highly reliable estimate for the position of the fluid-fluid critical line. In addition, it gives a detailed (though approximate) description of all structural properties and their dependence on patch size.
On the optical theorem and non-plane-wave scattering in quantum mechanics
Authors: Gouesbet G.
Published: November 2009

In quantum mechanics, the optical theorem states that the extinction cross section is equal (within a prefactor 4π∕k, in which k is a quantum wave number) to the imaginary part of the forward scattering angular function. This theorem is valid for plane wave scattering. We discuss modifications required for non-plane-wave scattering and establish a generalized expression for the extinction cross section in quantum mechanics. Examples are provided for two kinds of quantum shaped beams, namely, Gaussian and Bessel beams.
Observation of the zero-magnetic-field exciton spin splitting in high quality bulk GaAs and AlGaAs
Authors: Kozhemyakina E. V. , Zhuravlev K. S. , Amo A. , Ballarini D. , Viña L.
Published: November 2009

We present an experimental study of the zero-magnetic-field exciton spin splitting measured by time-resolved photoluminescence in high purity bulk GaAs and AlGaAs samples. The dynamics of the splitting differs from that observed in two dimensions. Initially, the splitting increases during 100–250 ps and then decays. This initial increase is attributed to the fast rise of the density of excitons formed from noncorrelated e-h pairs. The splitting dynamics is used to determine the exciton formation time, which is found to vary with excitation density from 70 to 360 ps.
Polarization entanglement with graded-index lenses
Authors: Vallone Giuseppe , Donati Gaia , De Martini Francesco , Mataloni Paolo
Published: November 2009

By using an optical device based on the integration of a graded-index (GRIN) rod lens and a single-mode optical fiber we efficiently collected photon pairs generated by spontaneous parametric down-conversion. We show that this system preserves the polarization entanglement of the two-photon states. Hence this device, characterized by a remarkable easiness of alignment and allowing for high coupling efficiency of single-mode radiation, can be used with photons entangled in various degrees of freedom, such as polarization and spatial momentum and to interconnect different sides of complex optical circuits.
Chemical changes on the green emitter tris(8-hydroxy-quinolinato)aluminum during device aging of p-i-n-structured organic light emitting diodes
Authors: Scholz Sebastian , Lüssem Björn , Leo Karl
Published: November 2009

Metal organic fluorescent and phosphorescent emitters are widely used in organic light emitting devices (OLEDs). Iridium-based triplet emitters are known to undergo chemical reactions with other materials during OLED aging. The material tris(8-hydroxy-quinolinato)aluminum (Alq3), which is widely used as electron transporting material and green fluorescent emitter, degrades mainly during hole transport. We investigate the chemical changes in Alq3 during device aging: using laser desorption ionization time-of-flight mass spectrometry, we study the reaction products found in degraded OLEDs. Similar to the reactions known from the phosphorescent iridium-based emitters, Alq3 undergoes a dissociation and further reaction with the hole blocking material 4,7-diphenyl-1,10-phenanthroline.