bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of the Painting Methods of Mural Paintings in Ancient Tombs of Goguryeo Using Scanning Electron Microscope
Authors: Han Kyeongsoon , Lee Sangjin , Lee Hwasoo
Published: August 2013

Disputes on the painting methods of Goguryeo murals can mainly be categorized into whether the murals adapted eastern secco or western fresco; however, the murals have their own unique methods as well. There are different viewpoints among experts on interpreting the painting methods. This study involved the creation of research samples to discover the painting methods under dispute and may help discover the methods based on scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX) studies. Goguryeo murals introduced pseudo-fresco rather than buon fresco methods. Unlike fresco techniques in the West, Goguryeo painters mixed traditional soft binders and adapted typical secco painting techniques for paintings, borders, and corrections after drying. The disputed issues may be resolved by these techniques, and samples may be produced based on the analyzed data. Therefore, many questions can finally be answered through SEM-EDX elemental mapping.
Adaptive Phenotypic Plasticity of Siberian Elm in Response to Drought Stress: Increased Stomatal Pore Depth
Authors: Park Go Eun , Kim Ki Woo , Lee Don Koo , Hyun Jung Oh
Published: August 2013

Leaf stomatal characteristics of Siberian elm (Ulmus pumila) were investigated by electron microscopy and white light scanning interferometry. On the basis of average annual precipitations, two types of tree specimens were collected from Korea, China, and Mongolia: (1) trees under normal environmental conditions and (2) trees under arid conditions. Field emission scanning electron microscopy revealed oval-shaped stomata on the lower surface, and they were ca. 20 μm in width. In-lens secondary electron imaging showed differences in electron density and stomatal pore depth between the two types. According to the line profile analysis by white light scanning interferometry, stomata under arid conditions appeared to have higher levels of the stomatal pore depth than ones under normal conditions. Focused ion beam–field emission electron microscopy supported the increased stomatal pore depth with the increasing drought stress gradient. These results suggest that complementary microscopy can be employed to unravel the adaptive phenotypic plasticity of Siberian elm in response to drought stress.
Rapid Method for Electron Tomographic Reconstruction and Three-Dimensional Modeling of the Murine Synapse Using an Automated Fiducial Marker-Free System
Authors: Kim Hyun-wook , Oh Seung Hak , Kim Namkug , Nakazawa Eiko , Rhyu Im Joo
Published: August 2013

Electron tomography (ET) has recently afforded new insights into neuronal architecture. However, the tedious process of sample preparation, image acquisition, alignment, back projection, and additional segmentation process of ET repels beginners. We have tried Hitachi's commercial packages integrated with a Hitachi H-7650 TEM to examine the potential of using an automated fiducial-less approach for our own neuroscience research. Semi-thick sections (200–300 nm) were cut from blocks of fixed mouse (C57BL) cerebellum and prepared for ET. Sets of images were collected automatically as each section was tilted by 2° increments (±60°). “Virtual” image volumes were computationally reconstructed in three dimension (3D) with the EMIP software using either the commonly used “weighted back-projection” (WBP) method or “topography-based reconstruction” (TBR) algorithm for comparison. Computed tomograms using the TBR were more precisely reconstructed compared with the WBP method. Following reconstruction, the image volumes were imported into the 3D editing software A-View and segmented according to synaptic organization. The detailed synaptic components were revealed by very thin virtual image slices; 3D models of synapse structure could be constructed efficiently. Overall, this simplified system provided us with a graspable tool for pursuing ET studies in neuroscience.
Three-Dimensional Structure ofDrosophilaTestis Tip: The Spatial Relation Between Dividing Cells
Authors: Lee Kyung Eun , Han Sung Sik , Jeon Hyesung
Published: August 2013

At the apical tip ofDrosophilatestis, there is a stem cell niche known as the proliferation center, where the stem cells are maintained by hub cell cluster for the regulation of differentiation and proliferation. Germline stem cells go through mitosis four times from one primary spermatogonial cell to the 16-cell stage before the maturation. The cells derived from the same germline stem cell are located within one cyst, an enclosed system by two cyst cells, and they are connected by the intercellular bridges called ring canals. In this study, the three-dimensional (3D) structure ofDrosophilatestis tip was reconstructed from serial sections. The size of cells at each stage was compared in volume from the 3D structure. The stages of cells in a cyst could be distinguishable exactly by counting the cells linked with intercellular bridges in 3D-reconstructed structure. The cysts containing the same stage cells appeared in the horizontal plane. Both the germline stem cell directly attached to the hub cell and the spermatogonial cells detached from the hub cell were divided at the almost perpendicular direction to the spermatogonial cell layers. The dividing phase in one cyst was delayed gradually through the cytoplasmic region of intercellular bridge.
Oxidation Mechanism of Nickel Oxide/Carbon Nanotube Composite
Authors: Kim Tae-Hoon , Park Min-Ho , Ryu Jiho , Yang Cheol-Woong
Published: August 2013

The oxidation mechanism and thermal stability of nickel oxide (NiO)/carbon nanotube (CNT) composites were investigated by examining composites with different NiO contents by thermogravimetric analysis and transmission electron microscopy (TEM). NiO acts as a catalyst in the oxidation of CNT in the composite. CNTs can be oxidized, even in a vacuum, by reducing NiO to nickel at temperatures lower than the normal oxidation temperature of CNTs. This phase transition was confirmed directly by in situ heating TEM observations. In air, reduction by CNT occurs simultaneously with reoxidation by gaseous O2 molecules, and NiO maintains its phase. The thermal stability decreased with increasing NiO content because of defects in the CNT generated by the NiO loading.
Prepubertal chronic stress and ketamine administration to rats as a neurodevelopmental model of schizophrenia symptomatology
Authors: Ram Edward , Raphaeli Shani , Avital Avi
Published: August 2013

Increased vulnerability to psychiatric disorders, such as schizophrenia, has been associated with higher levels of stress. In the early development of the central nervous system, changes in function of glutamatergic N-Methyl-D-aspartate (NMDA) receptors can possibly result in the development of psychosis, cognitive impairment and emotional dysfunction in adulthood. Thus, in this study we examined the behavioural consequences of the exposure of male rats to chronic stress (postnatal days 30–60) and ketamine administration (postnatal days 41–45); both during a sensitive developmental time window. We found that the locomotor activity of both ketamine and ketamine+chronic stress groups was significantly higher compared with that of the control rats. In contrast, the locomotor activity of the chronic stress group was significantly lower compared with all other groups. Examining anhedonia in the sucrose preference test we found a significantly decreased sucrose intake in both ketamine+chronic stress and the chronic stress groups compared with the control rats. No significant differences were observed in sucrose intake between the control and the ketamine group. The object recognition test revealed that the attention to the novel object was significantly impaired in the ketamine+chronic stress group. Similarly, the ketamine+chronic stress group showed the poorest learning ability in the eight-arm radial maze, starting on the 8th day. Finally, throughout the different pre-pulse intensities, the ketamine+chronic stress group showed impaired PPI compared with all other groups. The results indicate that the combination of prepubertal onset of chronic stress and ketamine may serve as a valid novel animal model for schizophrenia-like symptoms.
Do spiritual patients want spiritual interventions?: A qualitative exploration of underserved cancer patients' perspectives on religion and spirituality
Authors: Stein Emma M. , Kolidas Evelyn , Moadel Alyson
Published: August 2013

Objective:

This study examines religion and spirituality among advanced cancer patients from an underserved, ethnically-diverse population by exploring patient conceptualizations of religion and spirituality, the role of religion and spirituality in coping with cancer, and patient interest in spiritual support.

Method:

Qualitative semi-structured interviews were conducted with patients who had participated in a study of a “mind-body” support group for patients with all cancer types. Analysis based on grounded theory was utilized to identify themes and theoretical constructs.

Results:

With regard to patient conceptualizations of religion and spirituality, three categories emerged: (1) Spirituality is intertwined with organized religion; (2) Religion is one manifestation of the broader construct of spirituality; (3) Religion and spirituality are completely independent, with spirituality being desirable and religion not. Religion and spirituality played a central role in patients' coping with cancer, providing comfort, hope, and meaning. Patients diverged when it came to spiritual support, with some enthusiastic about interventions incorporating their spiritual values and others stating that they already get this support through religious communities.

Significance of results:

Spirituality plays a central role in the cancer experience of this underserved ethnically-diverse population. While spirituality seems to be a universal concern in advanced cancer patients, the meaning of spirituality differs across individuals, with some equating it with organized religion and others taking a more individualized approach. It is important that psychosocial interventions are developed to address this concern. Future research is needed to further explore the different ways that patients conceptualize spirituality and to develop spiritually-based treatments that are not “one size fits all.”
“How I kept track of it of course was my business”: Cancer patient self-monitoring as self-stylized work
Authors: Hermansen-Kobulnicky Carol J. , Purtzer Mary Anne
Published: August 2013

Objectives:

Self-monitoring behaviors of cancer patients benefit patients, caregivers, and providers, and yet the phenomenon of self-monitoring from the cancer-patient perspective has not been studied. We examined cancer patients' self-monitoring preferences and practices, focusing on the meaning of self-monitoring within the cancer experience.

Methods:

Semi-structured interviews were conducted among adult cancer patients who had been seen at least once at a rural United States cancer center. Questions sought out the meaning of self-monitoring and its practical aspects. Qualitative data were analyzed by adapting the four-stepped method by Giorgi for empirical phenomenological analysis.

Results:

Twenty participants were interviewed (11 women and 9 men). Transcribed interviews revealed that cancer patient self-monitoring is self-stylized work that ranges from simple to complex, while being both idiosyncratic and routine. Participants reported using tools with systems for use that fit their distinctive lives for the purpose of understanding and using information they deemed to be important in their cancer care. Three conceptual categories were discerned from the data that help to elucidate this self-stylized work as fitting their individual priorities and preferences, reflecting their identities, and being born of their work lives.

Significance of results:

Findings highlight patients' unique self-monitoring preferences and practices, calling into question the assumption that the sole use of standardized tools are the most effective approach to engaging patients in this practice. Self-monitoring efforts can be validated when providers welcome or adapt to patients' self-stylized tools and systems. Doing so may present opportunity for improved communications and patient-centered care.
Sleep in family caregivers of patients admitted to hospice: A pilot study
Authors: Lerdal Anners , Gay Caryl L. , Saghaug Elisabeth , Gautvik Kaare , Grov Ellen Karine , Normann Are , Slaaen Joran , Slåtten Kari , Tallang Oddveig Utheim , Lee Kathryn A.
Published: August 2013

Objectives:

Caring for a dying family member is known to interfere with sleep, yet little is known about caregiver sleep once the patient is admitted to hospice. The aim of this pilot study was to describe the sleep of partners and other family caregivers of patients in hospice.

Methods:

The pilot study used a cross-sectional, descriptive, and comparative design. Participants included the primary family caregivers of patients recently admitted to a hospice in Norway. Caregiver sleep during the prior month was measured with the Pittsburgh Sleep Quality Index (PSQI). During the patient's hospice stay, caregiver sleep was measured using wrist actigraphy for four nights and three days.

Results:

Twenty family caregivers (12 partners and 8 other relatives) completed the study protocol without difficulty. On the PSQI, most caregivers (n = 13) reported clinically significant sleep problems during the prior month. Once the patient was admitted to hospice, actigraphy indicated that 10 caregivers had clinically significant sleep disruption (≥15% wake after sleep onset) and six averaged <7 hours of sleep per night. Partner caregivers reported more trouble falling asleep, and less sleep medication use, in the prior month than other types of family caregivers. However, once the patient was admitted to hospice, and after adjusting for caregiver age, partner caregivers experienced less sleep disruption than other caregivers.

Significance of results:

Findings demonstrate feasibility of the study protocol and indicate that sleep problems are common for caregivers of dying patients, even after the patient is admitted to hospice. The caregiver's relationship to the patient may be an important factor to consider in future studies.
Phenotypic characterization of indigenous rice (Oryza sativa L.) germplasm collected from the state of Nagaland, India
Authors: Roy Somnath , Rathi R. S. , Misra A. K. , Bhatt B. P. , Bhandari D. C.
Published: August 2013

Nagaland is one of the eight states in the north-eastern region of India, where a considerable diversity exists in cultivated rice. Recent exploration in this tribal-dominated state has resulted in a collection of 130 rice accessions growing under diverse agroecological conditions. The agromorphological characterization data of 124 rice landraces revealed a significant variability in plant architecture and grain morphological and quality traits. Multivariate analyses including principal component analysis (PCA) and cluster analysis were performed to assess the patterns of morphological variation. The PCA extracted 12 components, which explained 75.4% of the total variation for 38 quantitative and qualitative traits. The cluster analysis grouped 124 rice landraces into five clusters, and the number of landraces in each cluster ranged from 1 to 59. The correlations among the traits are discussed, which will be useful in considering traits for genetic improvement in grain yield and quality. The landraces have been conserved in the national genebank for further utilization.
How to Beat Procrastination
Authors: Krause Kathrin , Freund Alexandra M.
Published: August 2013

Procrastination, defined as the subjectively aversive inability to initiate or complete the pursuit of a given goal, is a common phenomenon in academic contexts. This theoretical paper presents a dynamic model that centers on the role of goal focus in influencing procrastination during goal pursuit. Our central hypothesis is that focusing on the means of goal pursuit (i.e., adopting a process focus) reduces procrastination, particularly when fear of failure is high. Focusing on the means should decrease the salience of performance outcomes and thereby reduce fear of failure. This, in turn, should facilitate the initiation and maintenance of goal pursuit. In contrast, when means are perceived as unpleasant (high task aversiveness), focusing more on the outcome of goal pursuit (i.e., adopting an outcome focus) should reduce procrastination by directing attention away from the means while highlighting the importance of goal achievement. Furthermore, the model takes account of dynamic contextual factors, particularly the distance to a given deadline.
The myotubularin–amphiphysin 2 complex in membrane tubulation and centronuclear myopathies
Authors: Royer Barbara , Hnia Karim , Gavriilidis Christos , Tronchère Hélène , Tosch Valérie , Laporte Jocelyn
Published: August 2013

Myotubularin (MTM1) and amphiphysin 2 (BIN1) are two proteins mutated in different forms of centronuclear myopathy, but the functional and pathological relationship between these two proteins was unknown. Here, we identified MTM1 as a novel binding partner of BIN1, both in vitro and endogenously in skeletal muscle. Moreover, MTM1 enhances BIN1‐mediated membrane tubulation, depending on binding and phosphoinositide phosphatase activity. BIN1 patient mutations induce a conformational change in BIN1 and alter its binding and regulation by MTM1. In conclusion, we identified the first molecular and functional link between MTM1 and BIN1, supporting a common pathological mechanism in different forms of centronuclear myopathy.
Nitrogen fixation in distinct microbial niches within a chemoautotrophy-driven cave ecosystem
Authors: Desai Mahesh S , Assig Karoline , Dattagupta Sharmishtha
Published: August 2013

Microbial sulfur and carbon cycles in ecosystems driven by chemoautotrophy—present at deep-sea hydrothermal vents, cold seeps and sulfidic caves—have been studied to some extent, yet little is known about nitrogen fixation in these systems. Using a comprehensive approach comprising of 15N2 isotope labeling, acetylene reduction assay and nitrogenase gene expression analyses, we investigated nitrogen fixation in the sulfide-rich, chemoautotrophy-based Frasassi cave ecosystem (Italy). Nitrogen fixation was examined in three different microbial niches within the cave waters: (1) symbiotic bacterial community of Niphargus amphipods, (2) Beggiatoa-dominated biofilms, which occur at the sulfide–oxygen interface, and (3) sulfidic sediment. We found evidence for nitrogen fixation in all the three niches, and the nitrogenase gene (homologs of nifH) expression data clearly show niche differentiation of diazotrophic Proteobacteria within the water streams. The nifH transcript originated from the symbiotic community of Niphargus amphipods might belong to the Thiothrix ectosymbionts. Two abundantly expressed nifH genes in the Beggiatoa-dominated biofilms are closely related to those from Beggiatoa- and Desulfovibrio-related bacteria. These two diazotrophs were consistently found in Beggiatoa-dominated biofilms collected at various time points, thus illustrating species-specific associations of the diazotrophs in biofilm formation, and micron-scale niche partitioning of sulfur-oxidizing and sulfate-reducing bacteria driven by steep redox gradients within the biofilm. Finally, putative heterotrophs (Geobacter, Azoarcus and Desulfovibrio related) were the active diazotrophs in the sulfidic sediment. Our study is the first to shed light on nitrogen fixation in permanently dark caves and suggests that diazotrophy may be widespread in chemosynthetic communities.
A yeast one‐hybrid and microfluidics‐based pipeline to map mammalian gene regulatory networks
Authors: Gubelmann Carine , Waszak Sebastian M , Isakova Alina , Holcombe Wiebke , Hens Korneel , Iagovitina Antonina , Feuz Jean‐Daniel , Raghav Sunil K , Simicevic Jovan , Deplancke Bart
Published: August 2013

The comprehensive mapping of gene promoters and enhancers has significantly improved our understanding of how the mammalian regulatory genome is organized. An important challenge is to elucidate how these regulatory elements contribute to gene expression by identifying their trans‐regulatory inputs. Here, we present the generation of a mouse‐specific transcription factor (TF) open‐reading frame clone library and its implementation in yeast one‐hybrid assays to enable large‐scale protein–DNA interaction detection with mouse regulatory elements. Once specific interactions are identified, we then use a microfluidics‐based method to validate and precisely map them within the respective DNA sequences. Using well‐described regulatory elements as well as orphan enhancers, we show that this cross‐platform pipeline characterizes known and uncovers many novel TF–DNA interactions. In addition, we provide evidence that several of these novel interactions are relevant in vivo and aid in elucidating the regulatory architecture of enhancers.
A chiral-based magnetic memory device without a permanent magnet
Authors: Dor Oren Ben , Yochelis Shira , Mathew Shinto P. , Naaman Ron , Paltiel Yossi
Published: August 2013

Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices.
Prelamin A causes progeria through cell-extrinsic mechanisms and prevents cancer invasion
Authors: de la Rosa Jorge , Freije José M.P. , Cabanillas Rubén , Osorio Fernando G. , Fraga Mario F. , Fernández-García M. Soledad , Rad Roland , Fanjul Víctor , Ugalde Alejandro P. , Liang Qi , Prosser Haydn M. , Bradley Allan , Cadiñanos Juan , López-Otín Carlos
Published: August 2013

Defining the relationship between ageing and cancer is a crucial but challenging task. Mice deficient in Zmpste24, a metalloproteinase mutated in human progeria and involved in nuclear prelamin A maturation, recapitulate multiple features of ageing. However, their short lifespan and serious cell-intrinsic and cell-extrinsic alterations restrict the application and interpretation of carcinogenesis protocols. Here we present Zmpste24 mosaic mice that lack these limitations. Zmpste24 mosaic mice develop normally and keep similar proportions of Zmpste24-deficient (prelamin A-accumulating) and Zmpste24-proficient (mature lamin A-containing) cells throughout life, revealing that cell-extrinsic mechanisms are preeminent for progeria development. Moreover, prelamin A accumulation does not impair tumour initiation and growth, but it decreases the incidence of infiltrating oral carcinomas. Accordingly, silencing of ZMPSTE24 reduces human cancer cell invasiveness. Our results support the potential of cell-based and systemic therapies for progeria and highlight ZMPSTE24 as a new anticancer target.
Quantum Transport Enhancement by Time-Reversal Symmetry Breaking
Authors: Zimborás Zoltán , Faccin Mauro , Kádár Zoltán , Whitfield James D. , Lanyon Ben P. , Biamonte Jacob
Published: August 2013

Quantum mechanics still provides new unexpected effects when considering the transport of energy and information. Models of continuous time quantum walks, which implicitly use time-reversal symmetric Hamiltonians, have been intensely used to investigate the effectiveness of transport. Here we show how breaking time-reversal symmetry of the unitary dynamics in this model can enable directional control, enhancement and suppression of quantum transport. Examples ranging from exciton transport to complex networks are presented. This opens new prospects for more efficient methods to transport energy and information.
Metabolic profiling of Alzheimer's disease brains
Authors: Inoue Koichi , Tsutsui Haruhito , Akatsu Hiroyasu , Hashizume Yoshio , Matsukawa Noriyuki , Yamamoto Takayuki , Toyo'oka Toshimasa
Published: August 2013

Alzheimer's disease (AD) is an irreversible, progressive brain disease and can be definitively diagnosed after death through an examination of senile plaques and neurofibrillary tangles in several brain regions. It is to be expected that changes in the concentration and/or localization of low-molecular-weight molecules are linked to the pathological changes that occur in AD and determining their identity would provide valuable information regarding AD processes. Here, we propose definitive brain metabolic profiling using ultra-performance liquid chromatography coupled with electrospray time-of-flight mass spectrometry analysis. The acquired data were subjected to principal components analysis to differentiate the frontal and parietal lobes of the AD/Control groups. Significant differences in the levels of spermine and spermidine were identified using S-plot, mass spectra, databases and standards. Based on the investigation of the polyamine metabolite pathway, these data establish that the downstream metabolites of ornithine are increased, potentially implicating ornithine decarboxylase activity in AD pathology.
Multiscale distribution of oxygen puddles in 1/8 doped YBa2Cu3O6.67
Authors: Ricci Alessandro , Poccia Nicola , Campi Gaetano , Coneri Francesco , Caporale Alessandra Stella , Innocenti Davide , Burghammer Manfred , Zimmermann Martin v. , Bianconi Antonio
Published: August 2013

Despite intensive research a physical explanation of high Tc superconductors remains elusive. One reason for this is that these materials have generally a very complex structure making useless theoretical models for a homogeneous system. Little is known on the control of the critical temperature by the space disposition of defects because of lack of suitable experimental probes. X-ray diffraction and neutron scattering experiments used to investigate y oxygen dopants in YBa2Cu3O6+y lack of spatial resolution. Here we report the spatial imaging of dopants distribution inhomogeneity in YBa2Cu3O6.67 using scanning nano X-ray diffraction. By changing the X-ray beam size from 1 micron to 300 nm of diameter, the lattice inhomogeneity increases. The ordered oxygen puddles size distribution vary between 6–8 nm using 1 × 1 μm2 beam, while it is between 5–12 nm with a fat tail using the 300 × 300 nm2 beam. The increased inhomogeneity at the nanoscale points toward a network of superconducting puddles made of ordered oxygen interstitials.
A Model for Coaching Parents to Implement Teaching Strategies With Their Young Children With Language Delay or Developmental Disabilities
Authors: Stoner Julia , Meadan Hedda , Angell Maureen
Published: August 2013

This article focuses on the coaching model used in the Parent-Implemented Communication Strategies (PiCS) Project. The PiCS model was used to train and coach parents to deliver naturalistic and visual teaching strategies in their homes with their young children with developmental disabilities. The foundational concepts and rationale for training and coaching parents to implement intervention are discussed. The PiCS coaching model was developed using best practices of early intervention and includes five steps that prepare parents to implement intervention with high quality.
More Than Words—The Hanen Program for Parents of Children with Autism Spectrum Disorder: A Teaching Model for Parent-implemented Language Intervention
Authors: Weitzman Elaine
Published: August 2013

There has been an increased emphasis on caregiver-implemented intervention in the field of early intervention. However, this form of intervention can be effective only if the provider has the skills to teach, scaffold and coach the caregiver within a supportive, collaborative partnership. This article describes More Than Words—The Hanen Program for Parents of Children With Autism Spectrum Disorder, a manualized parent-implemented intervention for groups of parents and caregivers. In this program, the speech-pathologist assumes the role of mediator, utilizing specific techniques and activities based on adult education principles, providing a multifaceted, collaborative learning experience that enables parents to become effective language facilitators for their child.
Performance evaluation of Welch's periodogram‐based energy detection for spectrum sensing
Authors: Martínez Daniela M. , Andrade Ángel G.
Published: August 2013

In this work, the authors present the evaluation of energy detection (ED) based on the Welch's periodogram for spectrum sensing applied to cognitive radio networks. The authors analyse the impact of the number of points in the discrete Fourier transform and the number of averaged periodograms for power density spectrum estimation on the performance of ED. The authors identify that the inclusion of these parameters in the distribution of the test statistic used to detect the presence of primary users, improves the probability of detection. However, in the presence of noise uncertainty, the improvement on the probability of detection will come at the expense of an increased probability of false alarm. With the approach considered in this work is possible to increment the probability of detection for a given and low signal‐to‐noise ratio, without increasing the number of samples collected from primary signal. However, to maintain a constant probability of false alarm, accurate techniques for noise variance estimation are needed, because detection‐threshold value is highly dependent on the noise power present at each sensing interval.
Degrees of freedom of SIMO X channel
Authors: Wang Xianfeng , Xiao Limin , Zhao Yifei , Xu Xibin , Wang Jing
Published: August 2013

In this study, the authors mainly study the degrees of freedom (DoFs) of M × N user single input multiple output (SIMO) (or multiple input single output (MISO)) X channels, in which the channel coefficients are drawn from a continuous distribution and data‐sharing among users are unavailable. First, the authors establish an outer bound of DoFs for multiple‐in multiple‐out (MIMO) X channel, which is tighter than those in previous work. For SIMO X channel with R antennas at each user, the authors prove that the DoFs is [MNR/(M + NR − R)], which is achieved by symbol extension and interference alignment. As the transmitters and receivers are interchangeable in the network considered, the authors obtain corresponding results for MISO X channel. Finally, the authors generalise our result to MIMO X channel with R antennas at each user, and show that its DoFs is [MNR/(M + N − 1)].
Spectrum sharing and power allocation in multi‐input–multi‐output multi‐band underlay cognitive radio networks
Authors: Ghamari Adian Mehdi , Aghaeinia Hassan , Norouzi Yaser
Published: August 2013

Maximisation of the sum‐rate of secondary users (SUs), equipped with multi‐antenna transmitters and receivers, is considered in the context of multi‐input–multi‐output antenna multi‐band cognitive radio networks (MIMO‐MB‐CRNs) with coexisting primary users (PUs). The total interference power introduced to the PUs is constrained to maintain reliable communication for them. An interference channel configuration is considered for ad hoc networking, where the receivers treat the interference from undesired transmitters as noise. Using game theory approach, the strong duality in convex optimisation and the primal decomposition method, a low complexity semi‐distributed algorithm is proposed for spectrum sharing and power allocation for MIMO‐MB‐CRNs. The key idea behind the algorithm is the introduction of a diagonal block pricing factor matrix for each SU link. This matrix regulates network interference by encouraging SU links to work in a more altruistic manner. The proposed algorithm is configured in two iterative algorithms, Jacobi and Gauss–Seidel algorithms, and their performance is investigated through simulations. The simulation results showed that the proposed algorithm dramatically improves sum‐rate and achieves higher energy efficiency, compared with other algorithms.
Simple and low‐cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications
Authors: Yusoff Zubaida , Lees Jonathan , Chaudhary Muhammad Akmal , Carrubba Vincenzo , Choi Heungjae , Tasker Paul , Cripps Steve C.
Published: August 2013

A simple analogue technique called auxiliary envelope tracking, or AET, is presented, which is shown to be capable of improving the efficiency of a radio frequency power amplifier (RFPA). This AET signal is an amplified envelope signal that supplies the drain port of the RFPA. The concept of AET is explained and a theoretical background for the technique is presented. The main feature of this technique lies in the separation of the DC and AC components of the tracking signal. This allows for a very simple and low‐cost tracking generator design that consists of a simple source follower amplifier and an RF broadband transformer. A practical system has been implemented and the measured results are obtained for WCDMA signals. A measurement on the realised system shows a 50% improvement in the drain efficiency at average output power of 33 dBm of a 25 W GaN. This substantial improvement is achieved at a competitive WCDMA signal with peak‐to‐average envelope power ratio of 9.17 dB.
Frequency‐selectable dual‐band Wilkinson divider/combiner
Authors: Chongcheawchamnan Mitchai , Julrat Sakol , Shafique Mohammad Farhan , Robertson Ian D.
Published: August 2013

A technique for realising a compact frequency‐selectable dual‐band Wilkinson divider/combiner is presented in this study. To provide a frequency‐selection function, the band‐pass transmission‐line transformer (TLT) in a dual‐band device is replaced with a tuneable band‐reject TLT. To realise this tuneable device, a variable capacitively loaded spur‐line filter is proposed for its compact size. The theory based on an ideal transmission‐line circuit is developed to provide a design procedure. The proposed circuits are demonstrated with simulated and measured results of a Wilkinson divider/combiner fabricated on FR4 substrate.
Substrate integrated waveguide filters with broadside‐coupled complementary split ring resonators
Authors: Huang Liwen , Robertson Ian D. , Wu Weiwei , Yuan Naichang
Published: August 2013

Four designs of substrate integrated waveguide (SIW) filter employing integrated broadside‐coupled complementary split‐ring resonators are compared. By changing the orientation of the rings, four types of SIW unit cell are proposed and investigated and it is shown that, for one particular topology, two poles and two zeros can be realised with a single unit cell. Bandpass filters based on the proposed resonators coupled by evanescent‐mode SIW sections have been fabricated and tested. The proposed filters have the advantages of compact size, high selectivity and ease of integration.
Method for automatization of the alignment of a laboratory based x-ray phase contrast edge illumination system
Authors: Millard T. P. , Endrizzi M. , Ignatyev K. , Hagen C. K. , Munro P. R. T. , Speller R. D. , Olivo A.
Published: August 2013

Here we present a general alignment algorithm for an edge illumination x-ray phase contrast imaging system, which is used with the laboratory systems developed at UCL. It has the flexibility to be used with all current mask designs, and could also be applied to future synchrotron based systems. The algorithm has proved to be robust experimentally, and can be used for the automatization of future commercial systems through automatic alignment and alignment correction.
Photoacoustic monitoring of sedimentation of micro-particles in low viscosity fluids
Authors: Pech-May Nelson W. , Alvarado-Gil Juan J.
Published: August 2013

In this work, the potential of photoacoustic technique in the study of the sedimentation process of particles in liquids is explored. Experiments were performed using zirconia particles of 50 and 100 μm in three different low viscosity liquids, water, citronella, and ethylene glycol. It is shown that the evolution of the PA signal depends not only on the kind of liquids used but also on the size of the particles. An effective thermal model is developed in order to study the process and to infer the evolution of the thermal conductivity of the sedimented layer when it behaves as thermally thin, or the thermal effusivity if it behaves as thermally thick. It is shown that based on these results, the time evolution of the volume fraction of particles, in the region in which the sediment is deposited, can be obtained. These results can be useful in establishing a methodology for the photoacoustic monitoring of the process of sedimentation in more complex systems.
Polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co2Mn(Ga0.25Ge0.75) Heusler alloy
Authors: Du Ye , Nakatani T. M. , Takahashi Y. K. , Hase N. , Furubayashi T. , Hono K.
Published: August 2013

We have studied the structure and magnetoresistive properties of polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves (PSVs) with Co2Mn(Ga0.25Ge0.75) (CMGG) ferromagnetic layers and a Ag spacer. With (110) textured CMGG thin films and (111) textured Ag spacer, the PSVs annealed at 350 °C with 2 nm CoFe buffer layers showed ΔRA of 3.7 mΩ μm2 and MR ratio of 12.2%, while the PSVs without the buffer layer showed ΔRA of only 1.3 mΩ μm2. High angle angular dark field images showed that the drop of ΔRA by annealing was due to the deterioration of the multi-layer CMGG/Ag/CMGG structure. Energy-dispersive X-ray spectroscopy images further confirmed the interdiffusion between CMGG layer and the Ag layer outside the CMGG/Ag/CMGG trilayer. In addition, we discuss the difference in the magnetoresistive properties of polycrystalline and epitaxial PSVs.
High dielectric tunability of KTa0.60Nb0.40O3 single crystal
Authors: Li Huan , Tian Hao , Gong Dewei , Meng Qingxin , Zhou Zhongxiang
Published: August 2013

The dielectric nonlinear behavior of KTa0.60Nb0.40O3 single crystal grown by the top-seeded solution growth method was studied. High dielectric tunability (77%) and low loss (2.3%) was obtained at 1 kHz and room temperature, indicating that the KTa0.60Nb0.40O3 crystal is an attractive candidate for tunable device applications. The dielectric nonlinear behavior was further studied in terms with the Landau-Ginzburg-Devonshire thermodynamic theory completed with the Langevin term. It is found that the “extrinsic” polarization plays a remarkable role in the dielectric nonlinear behavior and it gives an amount of 42.1% contribution to the dielectric tunability with E = 1 kV/mm.
An analysis method for transmission measurements of superconducting resonators with applications to quantum-regime dielectric-loss measurements
Authors: Deng Chunqing , Otto Martin , Lupascu Adrian
Published: August 2013

Superconducting resonators provide a convenient way to measure loss tangents of various dielectrics at low temperature. For the purpose of examining the microscopic loss mechanisms in dielectrics, precise measurements of the internal quality factor at different values of energy stored in the resonators are required. Here, we present a consistent method to analyze a LC superconducting resonator coupled to a transmission line. We first derive an approximate expression for the transmission S-parameter S21(ω), with ω the excitation frequency, based on a complete circuit model. In the weak coupling limit, we show that the internal quality factor is reliably determined by fitting the approximate form of S21(ω). Since the voltage V of the capacitor of the LC circuit is required to determine the energy stored in the resonator, we next calculate the relation between V and the forward propagating wave voltage Vin+, with the latter being the parameter controlled in experiments. Due to the dependence of the quality factor on voltage, V is not simply proportional to Vin+. We find a self-consistent way to determine the relation between V and Vin+, which employs only the fitting parameters for S21(ω) and a linear scaling factor. We then examine the resonator transmission in the cases of port reflection and impedance mismatch. We find that resonator transmission asymmetry is primarily due to the reflection from discontinuity in transmission lines. We show that our analysis method to extract the internal quality factor is robust in the non-ideal cases above. Finally, we show that the analysis method used for the LC resonator can be generalized to arbitrary weakly coupled lumped and distributed resonators. The generalization uses a systematic approximation on the response function based on the pole and zero which are closest to the resonance frequency. This Closest Pole and Zero Method is a valuable tool for analyzing physical measurements of high-Q resonators.
Role of joule heating effect and bulk-surface phases in voltage-driven metal-insulator transition in VO2 crystal
Authors: Simon Mun Bongjin , Yoon Joonseok , Mo Sung-Kwan , Chen Kai , Tamura Nobumichi , Dejoie Catherine , Kunz Martin , Liu Zhi , Park Changwoo , Moon Kyungsun , Ju Honglyoul
Published: August 2013

We report the characteristics of a voltage-induced metal-insulator transition (MIT) in macro-sized VO2 crystals. The square of MIT onset voltage (VCMIT2) value shows a linear dependence with the ambient temperature, suggesting that the Joule heating effect is the likely cause to the voltage-induced MIT. The combination of optical microscope images and Laue microdiffraction patterns show the simultaneous presence of a metallic phase in the bulk of the crystal with partially insulating surface layers even after the MIT occurs. A large asymmetry in the heating power just before and after the MIT reflects the sudden exchange of Joule heat to its environment.
Study of electron acceleration and x-ray radiation as a function of plasma density in capillary-guided laser wakefield accelerators
Authors: Ju J. , Svensson K. , Ferrari H. , Döpp A. , Genoud G. , Wojda F. , Burza M. , Persson A. , Lundh O. , Wahlström C.-G. , Cros B.
Published: August 2013

Laser wakefield electron acceleration in the blow-out regime and the associated betatron X-ray radiation were investigated experimentally as a function of the plasma density in a configuration where the laser is guided. Dielectric capillary tubes were employed to assist the laser keeping self-focused over a long distance by collecting the laser energy around its central focal spot. With a 40 fs, 16 TW pulsed laser, electron bunches with tens of pC charge were measured to be accelerated to an energy up to 300 MeV, accompanied by X-ray emission with a peak brightness of the order of 1021 ph/s/mm2/mrad2/0.1%BW. Electron trapping and acceleration were studied using the emitted X-ray beam distribution to map the acceleration process; the number of betatron oscillations performed by the electrons was inferred from the correlation between measured X-ray fluence and beam charge. A study of the stability of electron and X-ray generation suggests that the fluctuation of X-ray emission can be reduced by stabilizing the beam charge. The experimental results are in good agreement with 3D particle-in-cell (PIC) simulation.
Magnetization dynamics in permalloy films with stripe domains
Authors: Tee Soh Wee , Phuoc Nguyen N. , Tan C. Y. , Ong C. K.
Published: August 2013

Through a systematic investigation of the field-dependent dynamic magnetization of a series of NiFe films with and without stripe domains in conjunction with the static magnetization process, we demonstrate that the experimental rotatable anisotropy field is not a fixed value but strongly varied with the external in-plane magnetic field, being qualitatively associated with the emergence of stripe domains. Moreover, the frequency linewidth spectra of the films with stripe domains show an abnormal behavior with three distinct regimes which are strongly correlated with both the static magnetization process and the competition between external magnetic field and dynamic anisotropy field. The results are discussed in terms of the effect of inhomogeneous magnetization associated with the formation of stripe domains and the field-dependent dynamic anisotropy that cause the broadening of frequency linewidth.
Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube
Authors: Mondal Sourav , De Sirshendu
Published: August 2013

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.
Label-free electronic probing of nucleic acids and proteins at the nanoscale using the nanoneedle biosensor
Authors: Esfandyarpour Rahim , Javanmard Mehdi , Koochak Zahra , Esfandyarpour Hesaam , Harris James S. , Davis Ronald W.
Published: August 2013

Detection of proteins and nucleic acids is dominantly performed using optical fluorescence based techniques, which are more costly and timely than electrical detection due to the need for expensive and bulky optical equipment and the process of fluorescent tagging. In this paper, we discuss our study of the electrical properties of nucleic acids and proteins at the nanoscale using a nanoelectronic probe we have developed, which we refer to as the Nanoneedle biosensor. The nanoneedle consists of four thin film layers: a conductive layer at the bottom acting as an electrode, an oxide layer on top, and another conductive layer on top of that, with a protective oxide above. The presence of proteins and nucleic acids near the tip results in a decrease in impedance across the sensing electrodes. There are three basic mechanisms behind the electrical response of DNA and protein molecules in solution under an applied alternating electrical field. The first change stems from modulation of the relative permittivity at the interface. The second mechanism is the formation and relaxation of the induced dipole moment. The third mechanism is the tunneling of electrons through the biomolecules. The results presented in this paper can be extended to develop low cost point-of-care diagnostic assays for the clinical setting.
The doping of the polyimide alignment layer by semiconductor quantum dots
Authors: Konshina E. A. , Galin I. F. , Gavrish E. O. , Vakulin D. A.
Published: August 2013

We investigated the electro-optic properties of nematic liquid crystal cells oriented by polyimide (PI) layer doped with 3.5 nm semiconductor quantum dots (QDs) CdSe/ZnS at concentrations of 0.05 and 0.1 wt. %. It is shown that doping PI orienting layer by QDs reduces the permittivity and the phase delay, as well as increases the electrical resistance of the cells. Also we observed deceleration of liquid crystal (LC) optical response caused by the screening effect of the orienting layer.