bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct microRNA profiles are associated with the severity of hepatitis C virus recurrence and acute cellular rejection after liver transplantation
Authors: Joshi Deepak , Salehi Siamak , Brereton Helen , Arno Matthew , Quaglia Alberto , Heaton Nigel , O'Grady John , Agarwal Kosh , Aluvihare Varuna
Published: February 2013

Recurrent hepatitis C virus (HCV) infection is associated with accelerated fibrosis rates after liver transplantation (LT) and is the leading cause of graft failure. Furthermore, distinguishing recurrent HCV from acute cellular rejection (ACR) can be problematic, and this can lead to inappropriate treatments and adverse outcomes. We hypothesized that intragraft microRNA (miRNA) expression profiles could distinguish the severity of recurrent HCV and differentiate recurrent HCV from ACR. We established meticulously matched post-LT patient cohorts in order to derive robust global miRNA expression profiles and minimize the impact of variables known to influence HCV recurrence. These cohorts consisted of patients with slow HCV fibrosis progression (Ishak stage < F2), fast HCV fibrosis progression (Ishak stage ≥ F2), ACR, and nonviral etiologies. We found increased intragraft expression of miRNA-146a, miRNA-19a, miRNA-20a, and miRNA-let7e in slow progressors versus fast progressors, and we validated these findings with quantitative PCR. This miRNA network regulates the expression of cardinal genes implicated in promoting antifibrogenic, antiangiogenic, and anti-inflammatory pathways. miRNA-19a and miRNA-20a were also specifically detected in the serum of slow progressors. Furthermore, intragraft miRNA expression distinguished fast HCV progression from ACR. Here, changes in the expression of key miRNAs regulating fibrogenic and angiogenic pathways were associated with fast HCV progression. We demonstrate specific miRNA expression signatures that discriminate the rates of fibrosis progression in patients with recurrent HCV, and we distinguish recurrent HCV from ACR after LT. A pathway analysis indicates that specific miRNAs may play a regulatory role in these processes. Selected miRNAs may serve as intragraft and serum biomarkers for recurrent HCV after LT and help to distinguish between ACR and recurrent HCV. Liver Transpl 19:383–394, 2013. © 2013 AASLD.
Cerebrospinal fluid Aβ levels correlate with structural brain changes in Parkinson's disease
Authors: Beyer Mona K. , Alves Guido , Hwang Kristy S. , Babakchanian Sona , Bronnick Kolbjorn S. , Chou Yi‐Yu , Dalaker Turi O. , Kurz Martin W. , Larsen Jan P. , Somme Johanne H. , Thompson Paul M. , Tysnes Ole‐Bjørn , Apostolova Liana G.
Published: February 2013

ParkWest is a large Norwegian multicenter study of newly diagnosed drug‐naïve subjects with Parkinson's disease (PD). Cognitively normal PD subjects (PDCN) and PD subjects with mild cognitive impairment (PDMCI) from this cohort have significant hippocampal atrophy and ventricular enlargement, compared to normal controls. Here, we aimed to investigate whether the same structural changes are associated with cerebrospinal fluid (CSF) levels of amyloid beta (Aβ)38, Aβ40, Aβ42, total tau (t‐tau), and phosphorylated tau (p‐tau). We performed three‐dimensional radial distance analyses of the hippocampi and lateral ventricles using the MRI data from ParkWest subjects who provided CSF at baseline. Our sample consisted of 73 PDCN and 18 PDMCI subjects. We found significant associations between levels of all three CSF Aβ analytes and t‐tau and lateral ventricular enlargement in the pooled sample. In the PDCN sample, all three amyloid analytes showed significant associations with the radial distance of the occipital and frontal horns of the lateral ventricles. CSF Aβ38 and Aβ42 showed negative associations, with enlargement in occipital and frontal horns of the lateral ventricles in the pooled sample, and a negative association with the occipital horns in PDMCI. CSF Aβ levels in early PD correlate with ventricular enlargement, previously associated with PD dementia. Therefore, CSF and MRI markers may help identify PD patients at high risk for developing cognitive decline and dementia in the course of their illness. Contrary to Alzheimer's disease, we found no associations between CSF t‐tau and p‐tau and hippocampal atrophy. © 2013 Movement Disorder Society
Effects of deep brain stimulation in dyskinetic cerebral palsy: A meta‐analysis
Authors: Koy Anne , Hellmich Martin , Pauls K. Amande M. , Marks Warren , Lin Jean‐Pierre , Fricke Oliver , Timmermann Lars
Published: February 2013

Secondary dystonia encompasses a heterogeneous group with different etiologies. Cerebral palsy is the most common cause. Pharmacological treatment is often unsatisfactory. There are only limited data on the therapeutic outcomes of deep brain stimulation in dyskinetic cerebral palsy. The published literature regarding deep brain stimulation and secondary dystonia was reviewed in a meta‐analysis to reevaluate the effect on cerebral palsy. The Burke‐Fahn‐Marsden Dystonia Rating Scale movement score was chosen as the primary outcome measure. Outcome over time was evaluated and summarized by mixed‐model repeated‐measures analysis, paired Student t test, and Pearson's correlation coefficient. Twenty articles comprising 68 patients with cerebral palsy undergoing deep brain stimulation assessed by the Burke‐Fahn‐Marsden Dystonia Rating Scale were identified. Most articles were case reports reflecting great variability in the score and duration of follow‐up. The mean Burke‐Fahn‐Marsden Dystonia Rating Scale movement score was 64.94 ± 25.40 preoperatively and dropped to 50.5 ± 26.77 postoperatively, with a mean improvement of 23.6% (P < .001) at a median follow‐up of 12 months. The mean Burke‐Fahn‐Marsden Dystonia Rating Scale disability score was 18.54 ± 6.15 preoperatively and 16.83 ± 6.42 postoperatively, with a mean improvement of 9.2% (P < .001). There was a significant negative correlation between severity of dystonia and clinical outcome (P < .05). Deep brain stimulation can be an effective treatment option for dyskinetic cerebral palsy. In view of the heterogeneous data, a prospective study with a large cohort of patients in a standardized setting with a multidisciplinary approach would be helpful in further evaluating the role of deep brain stimulation in cerebral palsy. © 2013 Movement Disorder Society
The role of SCARB2 as susceptibility factor in Parkinson's disease
Authors: Hopfner Franziska , Schulte Eva C. , Mollenhauer Brit , Bereznai Benjamin , Knauf Franziska , Lichtner Peter , Zimprich Alexander , Haubenberger Dietrich , Pirker Walter , Brücke Thomas , Peters Annette , Gieger Christian , Kuhlenbäumer Gregor , Trenkwalder Claudia , Winkelmann Juliane
Published: February 2013

Background

Genetic variation in the glucocerebrosidase (GBA) gene is strongly associated with Parkinson's disease (PD). Transport of glucocerebrosidase to the lysosome involves the protein encoded by the SCARB2 gene. An association between the common SNP rs6812193, upstream of SCARB2, and PD has been reported previously. The role of exonic variants in the SCARB2 gene in PD has not been examined.

Methods

We studied the role of exonic variants in SCARB2 and tried to replicate the association between the SNP rs6812193 and PD in a German and Austrian sample. Screening of all SCARB2 exons by high‐resolution melting curve analysis was performed in 376 German PD patients. The SNP rs6812193 was analyzed in 984 PD patients and 1014 general population controls.

Results

We identified no novel exonic variants in SCARB2 but confirmed the association between SNP rs6812193 and PD (OR, 0.86; P=.02). © 2013 Movement Disorder Society
Robust reconstruction of B1+ maps by projection into a spherical functions space
Authors: Sbrizzi Alessandro , Hoogduin Hans , Lagendijk Jan J. , Luijten Peter , van den Berg Cornelis A. T.
Published: February 2013

Purpose

Several parallel transmit MRI techniques require knowledge of the transmit radiofrequency field profiles (B1+). During the past years, various methods have been developed to acquire this information. Often, these methods suffer from long measurement times and produce maps exhibiting regions with poor signal‐to‐noise ratio and artifacts. In this article, a model‐based reconstruction procedure is introduced that improves the robustness of B1+ mapping.

Theory and Methods

The missing information from undersampled B1+ maps and the regions of poor signal to noise ratio are reconstructed through projection into the space of spherical functions that arise naturally from the solution of the Helmholtz equations in the spherical coordinate system.

Results

As a result, B1+ data over a limited range of the field of view/volume is sufficient to reconstruct the B1+ over the full spatial domain in a fast and robust way. The same model is exploited to filter the noise of the measured maps. Results from simulations and in vivo measurements confirm the validity of the proposed method.

Conclusion

A spherical functions model can well approximate the magnetic fields inside the body with few basis terms. Exploiting this compression capability, B1+ maps are reconstructed in regions of unknown or corrupted values. Magn Reson Med 71:394–401, 2014. © 2013 Wiley Periodicals, Inc.
Optical limiting materials: Synthesis, electrochemical and optical studies of new thiophene based conjugated polymers carrying 1,3,4‐oxadiazole units
Authors: Shivashankar Sunitha M. , Anantapadmanabha Vishnumurthy K. , Adhikari Airody Vasudeva
Published: February 2013

In this communication we report synthesis of three new donor‐acceptor (D–A) type conjugated polymers carrying 1,3,4‐oxadiazole moiety and thiophene unit with different side groups at its 3,4 positions (4‐methoxybenzyl:P1, 3‐methylbenzyl:P2 and 4‐nitrobenzyl:P3) through polycondensation route using a series of newly synthesized monomers. The structures of new monomers and polymers were confirmed by NMR, FTIR spectroscopic methods followed by elemental analysis. Further, molecular weight and thermal stability were determined using gel permeation chromatography and thermogravimetric analysis. The linear optical and electrochemical properties of polymers were investigated by UV–vis absorption, fluorescence spectroscopic, and cyclic voltammetric studies. The polymers P1–P3 were found to be thermally stable and their electrochemical band gaps were determined to be 1.98, 2.14, and 2.18 eV respectively. Further their nonlinear optical properties were investigated by Z‐scan method using 532 nm, 7 ns laser pulses. The results reveal that they possess good optical limiting behavior due to effective three‐photon absorption (3PA) with absorption coefficient 2.5 × 10−24 m−3W2, 1.6 × 10−24 m−3W2, and 1.0 × 10−24 m−3W2. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
Lewis acid–base properties of cellulose acetate phthalate‐polycaprolactonediol blend by inverse gas chromatography
Authors: Sudharshan Reddy Annem , Reddi Rani Papulareddy , Subramanyam Reddy Kalluru
Published: February 2013

The net retention volumes, VN, of n‐alkanes and five polar probes are determined on cellulose acetate phthalate–polycaprolactonediol blend column by inverse gas chromatography in the temperature range 323.15–363.15 K. The dispersive surface energy,
$\gamma _{\bf S}^{\bf d}$, of the blend has been calculated using the VN values of n‐alkanes and the
$\gamma _{\bf S}^{\bf d}$
at 333.15 K is 12.6 mJ/m2. The
$\gamma _{\bf S}^{\bf d}$
values are decreasing linearly with increase of temperature. The VN values of the five polar solutes are used to calculate the specific component of the enthalpy of adsorption,
${\Delta }{H}_{\bf a}^{\bf S}$. The Lewis acid–base parameters, Ka and Kb, are derived using
${\bf \Delta }{H}_{\bf a}^{\bf S}$
values and are found to be 0.019 and 0.403, respectively. The Ka and Kb values indicate that the blend surface contain more basic sites and interact strongly with the acidic probes. The acid–base parameters have been used to analyze the preferential interaction of the solid surface with acidic and basic probes. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
Effect of phase morphology and interfacial strength on barrier properties of high density polyethylene/polyamide 6 membranes
Authors: Lei Fan , Du Qin , Li Ting , Li Jiang , Guo Shaoyun
Published: February 2013

A barrier and resistance membrane consisting of alternating layers of high‐density polyethylene (HDPE) and polyamide 6 (PA6) was prepared by microlayered coextrusion. The influence of phase morphology, number of layers, and compatibilizer (CP) content of HDPE/PA6‐microlayered membranes on their gas barrier and water resistance properties were characterized using a scanning electron microscopy, gas in permeability, and water absorption tests. The results suggest that this special‐layered structure led to significant improvement of gas barrier and water resistance properties, compared with conventional membranes. In addition, the barrier and resistance properties of microlayered membranes were obviously enhanced with increased number of layers and CP content. An optimal number of layers and CP content were determined for the improved barrier and resistance properties. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
Rheological and electrical properties of carbon black‐based poly(vinylidene fluoride) composites
Authors: Wang Jianghong , Wu Defeng , Li Xiang , Zhang Ming
Published: February 2013

Carbon black (CB)–filled poly(vinylidene fluoride) composites (PCBp) were prepared by melt compounding. The linear rheology was then studied in detail. The composites show typical solid‐like response in the low‐frequency region, which is attributed to the percolation of CB particles. However, the transient percolated CB network is temperature dependent during the small amplitude oscillatory shear flow. Therefore, the principle of time–temperature superposition is invalid on the dynamic rheological responses of those percolated PCBp. A two‐phase viscoelastic model was then used to further describe the linear responses of PCBp to relate hierarchical structures of CB particles to flow responses of composites. In addition, the electrical and dielectric properties of PCBp were also investigated, aiming at further exploring the percolation behavior of CB. POLYM. ENG. SCI., 53:2541–2548, 2013. © 2013 Society of Plastics Engineers
Directing convection to pattern thin polymer films
Authors: Janes Dustin W. , Katzenstein Joshua M. , Shanmuganathan Kadhiravan , Ellison Christopher J.
Published: February 2013

Convection can be harnessed in elegant ways to pattern surfaces, often using uncomplicated equipment and materials, providing an interesting platform for future technological developments in thin film topographic assemblies. This manuscript contains a brief review of thin polymer film patterning methods that rely on directing convection, such as “coffee ring” patterning, lithographically induced self‐assembly, and electrohydrodynamic patterning. These techniques are described in the context of a recent approach explored in our group for generating topographic patterns by photochemically directing Marangoni flow in thin polymer films with subtle gradients in surface energy. Aspects unique to this process are highlighted so that they may facilitate new developments in manufacturing technologically impactful patterned surfaces. For example, the features produced by photochemically directed Marangoni‐driven flow are preprogrammed in the solid state, thermally developed and can be formed in multilayer films. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
Substrate interaction effects on order to disorder transition behavior in block copolymer films
Authors: Ahn Hyungju , Lee Yonghoon , Lee Hoyeon , Kim Yoonkeun , Ryu Du Yeol , Lee Byeongdu
Published: February 2013

We present an overview of the recent progress on the phase transition in the block copolymer (BCP) films in terms of the interfacial interactions effects of the substrates and the χ (Flory‐Huggins segmental interaction parameter) effects between the two blocks. For the BCP films thinner than a critical thickness (Lc) above which the transition is independent of film thickness, the order‐to‐disorder transition (ODT) increased or decreased with decreasing film thickness depending on the interfacial interaction types. The rapid and slow changes in the ODT were attributed to the relative magnitude of enthalpic contribution to χ between two blocks. Interestingly, a periodic amplification in the block composition for the BCP films suppressed the compositional fluctuation in the film geometry, resulting in the ODT shifts from the bulk ODTs above Lc. This effect of the BCP films was more illustrated by the ODT shift effects depending on the strength of the preferential interactions on the substrates. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
PKCδ Is Required for Jagged-1 Induction of Human Mesenchymal Stem Cell Osteogenic Differentiation
Authors: Zhu Fengchang , Sweetwyne Mariya T. , Hankenson Kurt D.
Published: February 2013

JAG1, the gene for the Jagged-1 ligand (Jag1) in the Notch signaling pathway, is variably mutated in Alagille Syndrome (ALGS). ALGS patients have skeletal defects, and additionally JAG1 has been shown to be associated with low bone mass through genome-wide association studies. Plating human osteoblast precursors (human mesenchymal stem cells—hMSCs) on Jag1 is sufficient to induce osteoblast differentiation; however, exposure of mouse MSC (mMSC) to Jag1 actually inhibits osteoblastogenesis. Overexpression of the notch-2 intracellular domain (NICD2) is sufficient to mimic the effect of Jag1 on hMSC osteoblastogenesis, while blocking Notch signaling with a γ-secretase inhibitor or with dominant-negative mastermind inhibits Jag1-induced hMSC osteoblastogenesis. In pursuit of interacting signaling pathways, we discovered that treatment with a protein kinase C δ (PKCδ) inhibitor abrogates Jag1-induced hMSC osteoblastogenesis. Jag1 results in rapid PKCδ nuclear translocation and kinase activation. Furthermore, Jag1 stimulates the physical interaction of PKCδ with NICD. Collectively, these results suggest that Jag1 induces hMSC osteoblast differentiation through canonical Notch signaling and requires concomitant PKCδ signaling. This research also demonstrates potential deficiencies in using mouse models to study ALGS bone abnormalities.
Bioimage informatics for understanding spatiotemporal dynamics of cellular processes
Authors: Yang Ge
Published: February 2013

The inner environment of the cell is highly dynamic and heterogeneous yet exquisitely organized. Successful completion of cellular processes within this environment depends on the right molecules or molecular complexes to function at the right place at the right time. Understanding spatiotemporal behaviors of cellular processes is therefore essential to understanding their molecular mechanisms at the systems level. These behaviors are usually visualized and recorded using imaging techniques. However, to infer from them systems‐level molecular mechanisms, computational analysis and understanding of recorded image data is crucial, not only for acquiring quantitative behavior measurements but also for comprehending complex interactions among the molecules or molecular complexes involved. The technology of computational analysis and understanding of biological images is often referred to simply as bioimage informatics. This article introduces fundamentals of bioimage informatics for understanding spatiotemporal dynamics of cellular processes and reviews recent advances on this topic. Basic bioimage informatics concepts and techniques for characterizing spatiotemporal cell dynamics are introduced first. Studies on specific cellular processes such as cell migration and signal transduction are then used as examples to analyze and summarize recent advances, with the focus on transforming quantitative measurements of spatiotemporal cellular behaviors into knowledge of underlying molecular mechanisms. Despite the advances made, substantial technological challenges remain, especially in representation of spatiotemporal cellular behaviors and inference of systems‐level molecular mechanisms. These challenges are briefly discussed. Overall, understanding spatiotemporal cell dynamics will provide critical insights into how specific cellular processes as well as the entire inner cellular environment are dynamically organized and regulated. WIREs Syst Biol Med 2013, 5:367–380. doi: 10.1002/wsbm.1214

This article is categorized under:

Analytical and Computational Methods > Analytical Methods

Analytical and Computational Methods > Computational Methods

Laboratory Methods and Technologies > Imaging
Null-polygonal minimal surfaces in AdS4 from perturbed W minimal models
Authors: Hatsuda Yasuyuki , Ito Katsushi , Satoh Yuji
Published: February 2013

Abstract

We study the null-polygonal minimal surfaces in AdS4, which correspond to the gluon scattering amplitudes/Wilson loops in$ \mathcal{N} $= 4 super Yang-Mills theory at strong coupling. The area of the minimal surfaces withncusps is characterized by the thermodynamic Bethe ansatz (TBA) integral equations or the Y-system of the homogeneous sine-Gordon model, which is regarded as the SU(n− 4)4/U(1)n−5generalized parafermion theory perturbed by the weight-zero adjoint operators. Based on the relation to the TBA systems of the perturbedWminimal models, we solve the TBA equations by using the conformal perturbation theory, and obtain the analytic expansion of the remainder function around the UV/regular-polygonal limit forn= 6 and 7. We compare the rescaled remainder function forn= 6 with the two-loop one, to observe that they are close to each other similarly to the AdS3case.
Assessing Parameter Invariance in the BLIM: Bipartition Models
Authors: de Chiusole Debora , Stefanutti Luca , Anselmi Pasquale , Robusto Egidio
Published: February 2013

In knowledge space theory, the knowledge state of a student is the set of all problems he is capable of solving in a specific knowledge domain and a knowledge structure is the collection of knowledge states. The basic local independence model (BLIM) is a probabilistic model for knowledge structures. The BLIM assumes a probability distribution on the knowledge states and a lucky guess and a careless error probability for each problem. A key assumption of the BLIM is that the lucky guess and careless error probabilities do not depend on knowledge states (invariance assumption). This article proposes a method for testing the violations of this specific assumption. The proposed method was assessed in a simulation study and in an empirical application. The results show that (1) the invariance assumption might be violated by the empirical data even when the model’s fit is very good, and (2) the proposed method may prove to be a promising tool to detect invariance violations of the BLIM.
Update on Pharmaceutical Intervention for Disorders of Consciousness and Agitation After Traumatic Brain Injury in Children
Authors: Suskauer Stacy J. , Trovato Melissa K.
Published: February 2013

Responsiveness and agitation are common targets for pharmaceutical intervention after traumatic brain injury (TBI) in children. This focused review presents a critical discussion of the limited literature available on the use of medications for disorders of consciousness and agitation in children with TBI. For disorders of consciousness, evidence from several small studies supports a potential benefit of dopaminergic agents for improving responsiveness in some children with lower levels of function after TBI. Larger studies, likely requiring multicenter collaborations, are needed to more definitively address questions regarding the use of medications for responsiveness in children with TBI. The literature regarding use of pharmaceutical agents for agitation in children with TBI is even more limited. The dearth of literature regarding the effects of medications used for agitation in children with TBI highlights the need for additional basic and clinical science contributions in this area.
Manipulability analysis of human thumb, index and middle fingers in cooperative 3D rotational movements of a small object
Authors: Orlando M. Felix , Dutta Ashish , Saxena Anupam , Behera Laxmidhar , Tamei Tomoya , Shibata Tomohiro
Published: February 2013

The combined motion of the human thumb, index and middle fingers while rotating a small object across the extended, intermediate and flexed planes with respect to the fingers was analyzed. Auto reflective markers were attached on the fingers to track their motion across three postures and planes via a 3D motion capture system. Central, right and left rotation postures were considered in each plane for investigation and the rotation experiments were performed with 30 healthy subjects. The obtained data were used to compute the finger joint angles. Based on the three criteria of (i) manipulability measure, (ii) major axis direction angle of the manipulability ellipsoid and (iii) ratio of the minor over major axis lengths, the collective behavior of the fingers was studied. It has been found after analysis that the thumb and middle finger were active, while the index finger operated passively when manipulating small objects in cooperative rotational motion across the three planes. Activeness refers to the independence of a digit in controlling the motion of an object whereas passiveness denotes its dependence on other digits. An active finger governs the motion of an object whereas a passive finger simply supports it. The results of this investigation are of great importance in planning treatment for rehabilitation and for designing controllers for robotic therapists, finger exoskeletons and prostheses.
Molecular typing ofLeptospiraspp. strains isolated from field mice confirms a link to human leptospirosis
Authors: LI S. J. , WANG D. M. , ZHANG C. C. , LI X. W. , YANG H. M. , TIAN K. C. , WEI X. Y. , LIU Y. , TANG G. P. , JIANG X. G. , YAN J.
Published: February 2013

In recent years, human leptospirosis has been reported in Jinping and Liping counties, Guizhou province, but the leptospires have never been isolated. To track the source of infection and understand the aetiological characteristics, we performed surveillance for field mice carriage of leptospirosis in 2011. Four strains of leptospire were isolated fromApodemus agrarius. PCR confirmed the four isolates as pathogenic. Multiple-locus variable-number tandem repeat analysis (MLVA) showed that the four strains were closely related to serovar Lai strain 56601 belonging to serogroup Icterohaemorrhagiae, which is consistent with the antibody detection results from local patients. Furthermore, the diversity of leptospiral isolates from different hosts and regions was demonstrated with MLVA. Our results suggest thatA. agrariusmay be the main carrier ofLeptospirain Jinping and Liping counties, and the serogroup Icterohaemorrhagiae serovar may be the epidemic serogroup ofLeptospira. This will contribute to the control and prevention of leptospirosis in these localities.
Multimodal language learner interactions via desktop videoconferencing within a framework of social presence: Gaze
Authors: Satar H. Müge
Published: February 2013

Desktop videoconferencing (DVC) offers many opportunities for language learning through its multimodal features. However, it also brings some challenges such as gaze and mutual gaze, that is, eye-contact. This paper reports some of the findings of a PhD study investigating social presence in DVC interactions of English as a Foreign Language (EFL) teacher trainees. The case study approach involved the exploration of online interactions of five cases (pairs) within an interpretivist paradigm. Data collection included interviews, questionnaires and analysis of DVC recordings. The study emphasizes the importance of eye-contact in online multimodal communication to facilitate the establishment of social presence. Five types of gaze that were observed in learner interactions and participants’ perspectives on eye-contact are reported. The conclusions include technical suggestions for the use of a webcam as well as pedagogical implications of online video interaction.
Neurochemical Profile of Patients with Type 1 Diabetes Measured by 1H-MRS at 4 T
Authors: Mangia Silvia , Kumar Anjali F , Moheet Amir A , Roberts Rachel J , Eberly Lynn E , Seaquist Elizabeth R , Tkáč Ivan
Published: February 2013

The impact of type 1 diabetes mellitus (T1DM) on a comprehensive neurochemical profile of the human brain has not been reported yet. Our previous proton magnetic resonance spectroscopy (1H-MRS) studies on T1DM were focused exclusively on the assessment of brain glucose levels. In this study, we reexamined our previously acquired data to investigate concentration differences of a broad range of neurochemicals in T1DM subjects relative to nondiabetic controls. We selected MRS data from 13 subjects (4 F/9 M, age = 41 ± 11 years, body mass index = 26 ± 3 kg/m2) with well-controlled T1DM (disease duration = 22 ± 12 years, A1C = 7.5% ± 2.0%) and 32 nondiabetic controls (14 F/18 M, age = 36 ± 10 years, body mass index = 27 ± 6 kg/m2) acquired during a hyperglycemic clamp (target [Glc]plasma = 300 ± 15 mg/dL). The 1H-MR spectra were collected from two 15.6-mL voxels localized in gray-matter-rich occipital lobe and in white-matter-rich parieto-occipital region using ultra-short echo-time STEAM at 4 T. LCModel analysis allowed reliable quantification of 17 brain metabolites. Lower levels of N-acetylaspartate (by 6%, P = 0.007) and glutamate (by 6%, P = 0.045) were observed in the gray matter of T1DM patients as compared with controls, which might indicate a partial neuronal loss or dysfunction as a consequence of long-term T1DM. No other differences in metabolites were observed between subjects with T1DM and controls.
The non-random walk of chiral magnetic charge carriers in artificial spin ice
Authors: Zeissler K. , Walton S. K. , Ladak S. , Read D. E. , Tyliszczak T. , Cohen L. F. , Branford W. R.
Published: February 2013

The flow of magnetic charge carriers (dubbed magnetic monopoles) through frustrated spin ice lattices, governed simply by Coulombic forces, represents a new direction in electromagnetism. Artificial spin ice nanoarrays realise this effect at room temperature, where the magnetic charge is carried by domain walls. Control of domain wall path is one important element of utilizing this new medium. By imaging the transit of domain walls across different connected 2D honeycomb structures we contribute an important aspect which will enable that control to be realized. Although apparently equivalent paths are presented to a domain wall as it approaches a Y-shaped vertex from a bar parallel to the field, we observe a stark non-random path distribution, which we attribute to the chirality of the magnetic charges. These observations are supported by detailed statistical modelling and micromagnetic simulations. The identification of chiral control to magnetic charge path selectivity invites analogy with spintronics.
Practical guide for validated memristance measurements
Authors: Du Nan , Shuai Yao , Luo Wenbo , Mayr Christian , Schüffny René , Schmidt Oliver G. , Schmidt Heidemarie
Published: February 2013

Chua [IEEE Trans. Circuit Theory 18, 507–519 (1971)10.1109/TCT.1971.1083337] predicted rather simple charge-flux curves for active and passive memristors (short for memory resistors) and presented active memristor circuit realizations already in the 1970 s. The first passive memristor has been presented in 2008 [D. B. Strukov, G. S. Snider, and D. R. Williams, Nature (London) 453, 80–83 (2008)10.1038/nature06932]. Typically, memristors are traced in complicated hysteretic current-voltage curves. Therefore, the true essence of many new memristive devices has not been discovered so far. Here, we give a practical guide on how to use normalized charge-flux curves for the prediction of hysteretic current-voltage characteristics of memristors. In the case of memristive BiFeO3 thin film capacitor structures, the normalized charge-flux curves superimpose for different numbers of measurement points Ns and a different measurement time per measurement point Ts. Such normalized charge-flux curves can be used for the prediction of current-voltage characteristics for input signals with arbitrarily chosen Ns and Ts.
Evaluation of the sensitivity limits of water vapor transmission rate measurements using electrical calcium test
Authors: Kempe Michael D. , Reese Matthew O. , Dameron Arrelaine A.
Published: February 2013

The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and/or oxygen. It is estimated that this will require high barriers with water vapor transmission rates (WVTR) between 10−4 and 10−6 g/m2/day. Thus, there is a need to develop a relatively fast, low cost, and quantitative method to evaluate such low permeation rates. Prior works have demonstrated that Ca films, because they change optically and electrically upon reaction with moisture, can be used as a sensor, enabling one to calculate a WVTR between 10 and 10−6 g/m2/day or better. In this work, we analyze the accuracy of an electrical Ca test method. We focus on the effects of the addition of a diffusion spacer and the effects of interactions of edge-seal material with changes to the spacer contacting surface on the overall accuracy. Furthermore, we examine a series of factors that can lead to different errors resulting in qualitative rather than quantitative Ca test behavior. We demonstrate that accurate, relatively high throughput, and reproducible measurements are possible for very low WVTR films in the 10−6 g/m2/day range.
Critique of charge collection efficiencies calculated through small perturbation measurements of dye sensitized solar cells
Authors: Sivaram Varun , Kirkpatrick James , Snaith Henry
Published: February 2013

Through experiment and simulation, we critically examine the conventional method of extracting the charge collection efficiency, ηc, of dye-sensitized solar cells (DSSCs). We demonstrate that the collection efficiency extracted by measuring transient decay rates at short circuit deviates considerably from the true value as ηc decreases. This discrepancy arises from two sources of error: first, transient voltage decay rates are especially sensitive to perturbation size near short circuit, and second, the decay rates are influenced by transient equilibration between trapped and free charge during the measurement. Only if the collection efficiency is high (>90%) do the true and measured values coincide well. This finding finally elucidates the disparity between steady-state and transient measurements of the collection efficiency; the former is more accurate for devices with a low ηc, and the latter for devices with a high ηc. For the first time, we present a fully nondimensional model of the DSSC, allowing us to fit device parameters without extensive material knowledge. The resulting simulations and fitting of solid-state dye sensitized solar cells additionally enable us to quantify the inaccuracy of small perturbation measurements of the collection efficiency when ηc is below 90%.
Defect dynamics in polycrystalline zirconium alloy probed in situ by primary extinction of neutron diffraction
Authors: Kabra Saurabh , Yan Kun , Carr David G. , Harrison Robert P. , Dippenaar Rian J. , Reid Mark , Liss Klaus-Dieter
Published: February 2013

After α + β-zirconium has fully transformed into β-phase upon heating, the intensities of all β-Zr Bragg reflections decrease simultaneously as a function of time. It is shown that this effect represents a transition from the kinematic to the dynamic theory of diffraction due to the ever increasing crystal perfection driven by thermal recovery of the system. The best fitting coherent crystallite size of 30 μm and other microstructural features are verified by in situ laser scanning confocal microscopy. This effect of primary extinction in neutron diffraction has been employed to further investigate the crystal perfection kinetics. Upon further heating, crystal recovery is identified as a process of dislocation annihilation, suffering from lattice friction. Upon cooling, precipitating α-Zr induces strain into the perfect β-crystallites, re-establishing the kinematic diffraction intensities. An Avrami analysis leads to the estimations of nucleation time, consumption of nucleation sites and lower-dimensional growth. Such technique bears great value for further investigation on all metal systems annealed close to the melting temperature.
Shrink-induced sorting using integrated nanoscale magnetic traps
Authors: Nawarathna Dharmakeerthi , Norouzi Nazila , McLane Jolie , Sharma Himanshu , Sharac Nicholas , Grant Ted , Chen Aaron , Strayer Scott , Ragan Regina , Khine Michelle
Published: February 2013

We present a plastic microfluidic device with integrated nanoscale magnetic traps (NSMTs) that separates magnetic from non-magnetic beads with high purity and throughput, and unprecedented enrichments. Numerical simulations indicate significantly higher localized magnetic field gradients than previously reported. We demonstrated >20 000-fold enrichment for 0.001% magnetic bead mixtures. Since we achieve high purity at all flow-rates tested, this is a robust, rapid, portable, and simple solution to sort target species from small volumes amenable for point-of-care applications. We used the NSMT in a 96 well format to extract DNA from small sample volumes for quantitative polymerase chain reaction (qPCR).
Electronic band structures of Ge1−xSnx semiconductors: A first-principles density functional theory study
Authors: Lee Ming-Hsien , Liu Po-Liang , Hong Yung-An , Chou Yen-Ting , Hong Jia-Yang , Siao Yu-Jin
Published: February 2013

We conduct first-principles total-energy density functional calculations to study the band structures in Ge1−xSnx infrared semiconductor alloys. The norm-conserving optimized pseudopotentials of Ge and Sn have been constructed for electronic structure calculations. The composition-bandgap relationships in Ge1−xSnx lattices are evaluated by a detailed comparison of structural models and their electronic band structures. The critical Sn composition related to the transition from indirect- to direct-gap in Ge1−xSnx alloys is estimated to be as low as x∼ 0.016 determined from the parametric fit. Our results show that the crossover Sn concentration occurs at a lower critical Sn concentration than the values predicted from the absorption measurements. However, early results indicate that the reliability of the critical Sn concentration from such measurements is hard to establish, since the indirect gap absorption is much weaker than the direct gap absorption. We find that the direct band gap decreases exponentially with the Sn composition over the range 0 <x<0.375 and the alloys become metallic for x> 0.375, in very good agreement with the theoretical observed behavior [D. W. Jenkins and J. D. Dow, Phys. Rev. B 36, 7994, 1987]. For homonuclear and heteronuclear complexes of Ge1−xSnx alloys, the indirect band gap at L-pointis is found to decrease homonuclear Ge-Ge bonds or increase homonuclear Sn-Sn bonds as a result of the reduced L valley. All findings agree with previously reported experimental and theoretical results. The analysis suggests that the top of valence band exhibits the localization of bond charge and the bottom of the conduction band is composed of the Ge 4s4p and/or Sn 5s5p atomic orbits.
Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene nanoribbon-silicon interfaces
Authors: Vallabhaneni Ajit K. , Qiu Bo , Hu Jiuning , Chen Yong P. , Roy Ajit K. , Ruan Xiulin
Published: February 2013

Various models were previously used to predict interfacial thermal conductance of vertical carbon nanotube (CNT)-silicon interfaces, but the predicted values were several orders of magnitude off the experimental data. In this work, we show that the CNT filling fraction (the ratio of contact area to the surface area of the substrate) is the key to remedy this discrepancy. Using molecular dynamics, we have identified an upper limit of thermal interface conductance for C-Si interface which is around 1.25 GW/m2K, corresponding to a 100% filling fraction of carbon nanotube or graphene nanoribbon on substrate. By extrapolating to low filling fraction (∼1%) that was measured in experiments, our predicted interfacial thermal conductance agrees with experimental data for vertical CNT arrays grown on silicon substrate (∼3 MW/m2 K). Meanwhile, thermal rectification of more than 20% has been found at these C-Si interfaces. We observed that this is strongly dependent on the interfacial temperature drop than the filling fraction. This new effect needs to be considered in future thermal interface materials design.
Trapping of diffusing particles by clusters of absorbing disks on a reflecting wall with disk centers on sites of a square lattice
Authors: Berezhkovskii Alexander M. , Dagdug Leonardo , Vazquez Marco-Vinicio , Lizunov Vladimir A. , Zimmerberg Joshua , Bezrukov Sergey M.
Published: February 2013

A simple approximate formula is derived for the rate constant that describes steady-state flux of diffusing particles through a cluster of perfectly absorbing disks on the otherwise reflecting flat wall, assuming that the disk centers occupy neighboring sites of a square lattice. A distinctive feature of trapping by a disk cluster is that disks located at the cluster periphery shield the disks in the center of the cluster. This competition of the disks for diffusing particles makes it impossible to find an exact analytical solution for the rate constant in the general case. To derive the approximate formula, we use a recently suggested approach [A. M. Berezhkovskii, L. Dagdug, V. A. Lizunov, J. Zimmerberg, and S. M. Bezrukov, J. Chem. Phys. 136, 211102 (2012)]10.1063/1.4726015, which is based on the replacement of the disk cluster by an effective uniform partially absorbing spot. The formula shows how the rate constant depends on the size and shape of the cluster. To check the accuracy of the formula, we compare its predictions with the values of the rate constant obtained from Brownian dynamics simulations. The comparison made for 18 clusters of various shapes and sizes shows good agreement between the theoretical predictions and numerical results.
Percolation transition of short-ranged square well fluids in bulk and confinement
Authors: Neitsch Helge , Klapp Sabine H. L.
Published: February 2013

Using grand canonical Monte Carlo simulations, we investigate the percolation behavior of a square-well fluid with an ultra-short range of attraction in three dimension (3D) and in confined geometry. The latter is defined through two parallel and structureless walls (slit-pore). We focus on temperatures above the critical temperature of the (metastable) condensation transition of the 3D system. Investigating a broad range of systems sizes, we first determine the percolation thresholds, i.e., the critical packing fraction for percolation ηc. For the slit-pore systems, ηc is found to vary with the wall separation Lz in a continuous but non-monotonic way, \documentclass[12pt]{minimal}\begin{document}$\eta _{c}(L_{z}\rightarrow \infty )=\eta _{c}^{{\rm 3D}}$\end{document}ηc(Lz→∞)=ηc3D. We also report results for critical exponents of the percolation transition, specifically, the exponent ν of the correlation length ξ and the two fisher exponents τ and σ of the cluster-size distribution. These exponents are obtained from a finite-size analysis involving the cluster-size distribution and the radii of gyration distribution at the percolation threshold. Within the accuracy of our simulations, the values of the critical exponents of our 3D system are comparable to those of 3D random percolation theory. For narrow slit-pores, the estimated exponents are found to be close to those obtained from the random percolation theory in two dimensions.
A polychromator-type near-infrared spectrometer with a high-sensitivity and high-resolution photodiode array detector for pharmaceutical process monitoring on the millisecond time scale
Authors: Murayama Kodai , Genkawa Takuma , Ishikawa Daitaro , Komiyama Makoto , Ozaki Yukihiro
Published: February 2013

In the fine chemicals industry, particularly in the pharmaceutical industry, advanced sensing technologies have recently begun being incorporated into the process line in order to improve safety and quality in accordance with process analytical technology. For estimating the quality of powders without preparation during drug formulation, near-infrared (NIR) spectroscopy has been considered the most promising sensing approach. In this study, we have developed a compact polychromator-type NIR spectrometer equipped with a photodiode (PD) array detector. This detector is consisting of 640 InGaAs-PD elements with 20-μm pitch. Some high-specification spectrometers, which use InGaAs-PD with 512 elements, have a wavelength resolution of about 1.56 nm when covering 900–1700 nm range. On the other hand, the newly developed detector, having the PD with one of the world's highest density, enables wavelength resolution of below 1.25 nm. Moreover, thanks to the combination with a highly integrated charge amplifier array circuit, measurement speed of the detector is higher by two orders than that of existing PD array detectors. The developed spectrometer is small (120 mm × 220 mm × 200 mm) and light (6 kg), and it contains various key devices including the high-density and high-sensitivity PD array detector, NIR technology, and spectroscopy technology for a spectroscopic analyzer that has the required detection mechanism and high sensitivity for powder measurement, as well as a high-speed measuring function for blenders. Moreover, we have evaluated the characteristics of the developed NIR spectrometer, and the measurement of powder samples confirmed that it has high functionality.
Photothermal model fitting in the complex plane for thermal properties determination in solids
Authors: Zambrano-Arjona M. A. , Peñuñuri F. , Acosta M. , Riech I. , Medina-Esquivel R. A. , Martínez-Torres P. , Alvarado-Gil J. J.
Published: February 2013

Thermal properties of solids are obtained by fitting the exact complex photothermal model to the normalized photoacoustic (PA) signal in the front configuration. Simple closed-form expressions for the amplitude and phase are presented in all frequency ranges. In photoacoustic it has been common practice to assume that all the absorptions of radiation take place in the sample. However, in order to obtain the accurate thermal properties it is necessary to consider the PA signal contributions produced at the cell walls. Such contributions were considered in our study. To demonstrate the usefulness of the proposed methodology, commercial stainless steel layers AISI 302 were analyzed. It is shown that using our approach the obtained thermal diffusivity and effusivity were in good agreement with those reported in the literature. Also, a detailed procedure for the calculation of the standard error in the thermal properties is discussed.