bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Volatile Flavor Constituents of the Peel (Flavedo) from Five Greek Citrus Varieties Cultivated in the Area of Arta
Authors: Demertzis P. G. , Passa A. I. , Akrida-Demertzi K.
Published: February 2013

Citrus is one of the world's most important fruit crops with a total world production of approximately 105 million metric tons. The citrus fruit consists of the following fundamental parts: the flavedo (external colored part of the peel), the albedo (white internal part of the peel), the pericarp which contains the above mentioned parts, and the pulp containing the juices and the seeds, called endocarp. The flavedo is composed mainly of cellulosic material and contains other components such as essential oils, non-volatile fraction of the essential oil (paraffin waxes, steroids, fatty acids, flavones etc.), and additional components such as pigments, bitter compounds (limonin) and enzymes.

In the present study the volatile flavor constituents of the peel (flavedo) from five Greek citrus varieties cultivated in the area of Arta (Zambetakis lemon variety, Navelina oranges, Valencia oranges, Common orange variety and bitter oranges) have been characterized by headspace solid-phase microextraction (HS-SPME) in conjunction with gas chromatography - mass spectrometry (GC-MS). For HS-SPME method a 100-μm PDMS fiber coating was utilized. GC-MS separations of volatile compounds were made using a 60 m×320 μm I.D.×1 μm film thickness DB5 (non polar) column. Eighty two (82) compounds were totally identified in citrus peel samples. More specifically, a total of 52, 57, 54, 53 and 36 compounds were found in Zambetakis lemon variety, Navelina oranges, Valencia oranges, common orange variety and bitter oranges, respectively. The identified compounds belong to the group of esters, alcohols, aldehydes and mainly sesquiterpene hydrocarbons. Limonene was the most abundant component in all samples, followed by sabinene, β-pinene, β-myrcene and linalool.
Flavor and Sensory Characteristics of Yogurt Derived from Milk Treated by High Intensity Ultrasound
Authors: Sfakianakis Panagiotis , Tzia Constantina
Published: February 2013

High intensity ultrasound (US) treatment has been proven to homogenize milk and reduce its microbial load while simultaneously assist in the formation of volatiles that affect its flavor and aroma. Additionally, high intensity US treatment has positive effect on the formation of yogurt curd and improve some of its quality and sensory characteristics. The current work aims to the study the sensory characteristics of yogurt produced from milk treated by high intensity US, furthermore to characterize the volatile components produced during fermentation process. Yogurt samples were produced by bovine milk (3,5% fat content and 3,3% protein content) that was previously ultrasonicated (frequency of 20 kHz and intensity range 150–750 W) for 10 min, using industrial starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus). After the end of fermentation process (pH = 4,7) samples were stored at 4 °C overnight. Volatile components were analyzed by using solid phase microextraction headspace analysis in combination with gas chromatography/mass spectrometry. The compounds that were identified belonged mostly to three categories carboxylic acids (hexanoic acid, octanoic acid), ketones (2,3 butadienone, 2-heptanone, 2-nonanone) and aliphatic hydrocarbons. Sensory evaluation was conducted on the yogurt samples for flavor, texture and overall acceptance. Results proved that milk treated by high intensity US led to acceptable yogurt with superior texture characteristics (cohesiveness, hardness, firmness) and inferior taste and flavor (off flavors). The volatile compounds that affect aroma and flavor are formed during the US treatments of the milk, due to high localized temperature and cavitation phenomena as well as during fermentation.
Effects of Naturally Occurring Phenolic Compounds in Coffee on the Formation of Maillard Aromas
Authors: Wang Yongmin , Tang Ho Chi
Published: February 2013

The major naturally occurring phenolic compound in coffee is chlorogenic acid, or 5-caffeoylquinic acid. During coffee roasting, chlorogenic acid undergoes different thermal reactions and has significant impacts on the sensory properties of roasted coffee. It was hypothesized that caffeic, ferulic, and chlorogenic acids as antioxidants could affect formation of nitrogen-containing and sulfur-containing heterocyclic compounds and Strecker degradation products under roasting conditions. The objective of this study was to investigate effects of naturally occurring phenolic compounds in coffee on the formation of Maillard aromas and explore the mechanisms. The results from study on the roast model systems of D-glucose with L-lysine and D-glucose with L-leucine indicated that naturally occurring phenolic compounds in coffee like caffeic, ferulic, and chlorogenic acids could inhibit alkylpyrazine formation under the coffee roast conditions. Moreover, the results suggested that the three phenolic compounds were strong inhibitors of the Strecker degradation of leucine. In addition, caffeic and chlorogenic acids greatly reduced the formation of thiazoles, thiophenes, 5,6-dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine, and 3, 5-dimethyl-1,2,4-trithiolane in the roast model systems of L-cysteine and D-glucose.
Effect of Laurus Nobilis (Bay Leaf) Essential Oil on the Formulation, Oxidative Stability and Sensory Characteristics of O/W/O Olive Oil Microemulsions
Authors: Polychniatou Vasiliki , Tzia Constantina
Published: February 2013

The aim of the present work was the preparation and characterization of o/w/o co-surfactant free olive oil microemulsions with Laurus nobilis (bay leaf) essential oil, in order to obtain a system that could provide a controlled, sustained product with desirable sensory characteristics and prolonged oxidative stability.
Omega-3 Oils, Their Food and Non-food Application and Beneficial Health Effects
Authors: Shahidi Fereidoon , Al-Khalifa Abdulrhman S.
Published: February 2013

Omega-3 oils from marine resources, including algal origin, serve as building blocks of organs with electrical activity such as the heart, retina of the eye and the brain. They also provide important benefits related to cardiovascular disease, type-2 diabetes, autoimmune disorders, inflammatory diseases and mental health. Hence their incorporation into food or use as supplement is of paramount importance. Inclusion of omega-3 oils in foods such as bread, cereals, orange juice, milk and other dairy products and nutrition bars may enhance their intake level. However, stability and stabilization of the oils must be considered in order to ensure healthfulness and integrity of products with acceptable sensory characteristics. This overview provides a cursory account of the relevant issues of importance to both manufacturer and consumers.
Metabolism of Dietary Phenolic Acids
Authors: Wang Yu , Shahidi Fereidoon , Ho Chi-Tang
Published: February 2013

Phenolic acids, one group of commonly occurring polyphenolic compounds in foods, are classified into hydroxybenzoic and hydroxycinnamic acids which include gallic, and protocatechuic as well as caffeic and ferulic acids, respectively. They have demonstrated strong antioxidant and health beneficial properties especially for various degenerative diseases such as cancers and cardiovascular diseases in in vitro and in vivo models. However, phenolic acids are shown to undergo methylation, sulfation and glucuronidation during metabolism, with consequent changes of their structures and biological activities. In order to reveal a relationship between parent phenolic acids and their metabolites, intestinal, hepatic and microbial metabolisms as well as metabolites are reviewed in both in-vitro and in-vivo models. The importance of metabolites of phenolic acids and their biological activities are discussed.
The Molecular Targets of Garcinol Confer Antitumor Effects
Authors: Ho Chi-Tang , Pan Min-Hsiung , Ho Yuan-Soon
Published: February 2013

Garcinol (Gar), a polyisoprenylated benzophenone derivative, is purified from the rind of the Garcinia indica fruit, and its antioxidative, antiglycation and free radical-scavenging activities have been studied previously. Although the fruit has been consumed traditionally for centuries, its biological activities, specifically its anticancer potential, were only determined in recent scientific investigations. Gar is also effective in blocking azoxymethane-induced colonic aberrant crypt focus formation and induces apoptosis in human HL60 cancer cells. Another study demonstrated that cigarette smoke extract-induced COX-2 expression is blocked by Gar pretreatment. In a previous study, we demonstrated that the α9-nicotinic receptor (α9-nAChR) was significantly induced by nicotine (Nic) in human breast cancer cells. We also found that Nic-induced α9-nAChR protein expression was blocked by Gar. Both in vitro and in vivo studies have demonstrated the potential of this compound against several cancer types, including breast cancer, colon cancer, pancreatic cancer, and leukemia. These findings suggest a possible chemopreventive and/or therapeutic potential of Gar through the inhibition of different types of hazard factor-induced protein expression, which is known to play a role in environmental factor-mediated tumorigenesis.
Total Phenolics, Antioxidant and Antibacterial Activity of Commercial Pomegranate Based Juices from Greece
Authors: Zografou E. Ch. , Kallimanis A. , Akrida-Demertzi K. , Demertzis P. G.
Published: February 2013

Pomegranate (Punica granatum L.) is a fruit that increasingly is becoming recognised for its health properties, prompting the development of derivate products that attempt to keep the main properties of the raw fruit. Pomegranate can be consumed as a fruit or is used for the production of juices, jams, jellies, flavorings for drinks etc. Pomegranate juices may also be combined with other fruit juices.

In the present study, five commercial pomegranate-based juices (natural pomegranate juice, natural pomegranate-strawberry juice and natural pomegranate-blackberry juice, pomegranate juice from concentrate and pomegranate-grape juice from concentrate) were analyzed for total phenolics, antioxidant and antibacterial activity. The amount of total phenolics was measured with the Folin-Ciocalteu reagent and the antioxidant capacity was determined by the scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH). The antibacterial activity of the juices was screened using two Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes) and one Gram-negative (Escherichia coli). Results showed that the juices from concentrate contained noticeably higher total phenolics than the other juices. Furthermore, the addition of other fruit juices (blackberry, strawberry) to the natural pomegranate juice increased the amount of the phenolics. The DPPH method revealed that higher concentration of phenolic content of the juices is associated with higher radical scavenging activity. In the microbiological assay, the most sensitive bacteria to the juices tested were S. aureus and E. coli. Little or no inhibitory effect was observed against L. monocytogenes.
Nuclear export factor 3 is involved in regulating the expression of TGF-β3 in an mRNA export activity-independent manner in mouse Sertoli cells
Authors: Yin Yimeng , Wang Guishuan , Liang Ning , Zhang Huijuan , Liu Zhimin , Li Wenqing , Sun Fei
Published: February 2013

The NXF (nuclear export factor) family members are implicated in the transport of mRNA from the nucleus to the cytoplasm. Recently, some members of the NXF family have been reported to play divergent functional roles, such as post-transcriptional regulation, translational control, regulation of mRNA stability and trafficking. However, little is known about the roles of NXF3 in spermatogenesis. In the present study, we found that mouse NXF3, specifically expressed in principal cells in segment II of the caput epididymis, as well as Sertoli cells in the mouse testis, was required to mediate TGF-β (transforming growth factor β)-induced down-regulation of Tgfb3/TGF-β3 mRNA expression and protein secretion in Sertoli cells. In addition, NXF3 was also involved in TGF-β-induced transcriptional regulation of other genes associated with Sertoli cell maturation and the restructuring of the Sertoli cell BTB (blood–testis barrier), such as Gata1 (GATA-binding protein 1), Wt1 (Wilms's tumour homologue 1), Cldn11 (claudin11) and Cdkn1a (cyclin-dependent kinase inhibitor 1A or p21Cip1). The transcriptional regulation of NXF3 was mediated through physical interaction with STRAP (serine/threonine kinase receptor-associated protein), where NXF3 inhibited the complex formation among Smad7, STRAP and activated type I TGF-β receptor. Taken together, our data provide mechanistic insights into the roles of NXF3 in TGF-β-mediated expression of Tgfb3 and other genes. NXF3 may be implicated in Sertoli cell maturation and the extensive restructuring of the Sertoli cell BTB.
The direct renin inhibitor aliskiren improves vascular remodelling in transgenic rats harbouring human renin and angiotensinogen genes
Authors: Savoia Carmine , Arrabito Emanuele , Parente Rosa , Sada Lidia , Madaro Luca , Nicoletti Carmine , Zezza Luigi , Alonzo Alessandro , Rubattu Speranza , Michelini Serena , Muller Dominik N. , Volpe Massimo
Published: February 2013

In the present study, we tested the hypothesis that chronic treatment with the direct rennin inhibitor aliskiren improves the remodelling of resistance arteries in dTGR (double-transgenic rats). dTGR (5 weeks) were treated with aliskiren (3 mg/kg of body mass per day) or ramipril (1 mg/kg of body mass per day) for 14 days and compared with age-matched vehicle-treated dTGR. BP (blood pressure) was similarly reduced in both aliskiren-treated and ramipril-treated rats compared with control dTGR (167±1 and 169±2 mmHg compared with 197±4 mmHg respectively; P<0.05). The M/L (media-to-lumen) ratio assessed on pressurized preparations was equally reduced in aliskiren-treated and ramipril-treated rats compared with controls (6.3±0.5 and 6.4±0.2% compared with 9.8±0.4% respectively; P<0.05). Endothelium-dependent and -independent relaxations were similar among the groups. L-NAME (NG-nitro-L-arginine methyl ester) significantly reduced acetylcholine-induced dilation in drug-treated dTGR. This effect was significantly more prominent in aliskiren-treated rats. eNOS (endothelial NO synthase) expression showed a 2-fold increase only in aliskiren-treated dTGR as compared with controls (P<0.01) and ramipril-treated dTGR (P<0.05). Plasma nitrite, as an index of NO production, was significantly increased in dTGR treated with either aliskiren or ramipril compared with controls. Only aliskiren induced a 2-fold increase in plasma nitrite, which was significantly greater than that induced by ramipril (P<0.05). gp91phox expression and ROS (reactive oxygen species) production in aorta were significantly and similarly reduced by both drugs. In conclusion, equieffective hypotensive doses of aliskiren or ramipril reduced the M/L ratio of mesenteric arteries and improved oxidative stress in dTGR. However, only aliskiren increased further NO production in the vasculature. Hence, in dTGR, direct renin inhibition induces favourable effects similar to that induced by ACE (angiotensin-converting enzyme) inhibition in improving vascular remodelling through different mechanisms.
Uniform depth region‐based registration between colour channels and its application to single camera‐based multifocusing
Authors: Lee Jinhee , Paik Joonki
Published: February 2013

This study presents a spatially varying image registration method based on regions of the same depth. The proposed registration method uses phase correlation matching to measure colour shifting vectors (CSVs) between colour channels in a pre‐specified region of the same distance to the camera, and aligns colour channels of the corresponding region according to the CSV. The authors also present the foreground region detection method by using binary edge labelling and analysis of histograms of channel‐shifting features. The major contribution of this study is 2‐fold: (i) the proposed method can be considered as a region‐wise approximated version of fully non‐rigid registration, which is widely used in the medical imaging area, and (ii) it can compensate misalignment between red (R), green (G) and blue (B) colour channels caused by refraction and chromatic aberration of a multiple colour‐filtered aperture (MCA) camera, which has been proposed as a single camera‐based multifocusing system. Among various applications of non‐rigid image registration, the proposed region‐based registration method is particularly suitable for multifocusing images acquired by an MCA camera. In depth analysis of each step of the proposed algorithm is provided with experimental results, and its application to the MCA camera is also provided to realise efficient depth estimation and highly accurate multifocusing functions using a single camera. Without using joint histogram or geometric transformation, the proposed region‐adaptive approach successfully approximates the fully non‐rigid registration with significantly reduced amount of computation.
Transmission of JPEG2000 images over frequency‐selective channels with unequal power allocation
Authors: Shayegannia Moein , Hajshirmohammadi Atousa , Muhaidat Sami , Torki Mahin
Published: February 2013

In this study, transmission of JPEG2000 images using an unequal power allocation (UPA) scheme and orthogonal frequency division multiplexing (OFDM) over block‐fading frequency‐selective channels is presented. A distortion model is provided to evaluate the contribution of each coding pass (CP) in the construction of the received image. The optimisation algorithm exploits the hierarchical structure of the JPEG2000 images and uses the distortion model along with the channel state information for allocating optimal values of power for each CP to minimise the end‐to‐end distortion. Furthermore, the actual total power consumed for transmission is measured and compared with the total power initially assigned. For the purpose of simulations, the authors set the number of OFDM subcarriers to be 16, the length of the cyclic prefixes equal to the channel memory length and analyse the quality of the received image in a 2‐tap and 3‐tap frequency‐selective channel, with and without our proposed UPA technique in an OFDM system. The results show an improvement of up to 10.5 dB in the decoded image quality when the UPA scheme is used. In addition, our system manages to maintain similar quality for the received image in a multi‐tap channel scenario.
Mechanical spectra of glass-forming liquids. I. Low-frequency bulk and shear moduli of DC704 and 5-PPE measured by piezoceramic transducers
Authors: Hecksher Tina , Olsen Niels Boye , Nelson Keith A. , Dyre Jeppe C. , Christensen Tage
Published: February 2013

We present dynamic shear and bulk modulus measurements of supercooled tetraphenyl-tetramethyl-trisiloxane (DC704) and 5-phenyl-4-ether over a range of temperatures close to their glass transition. The data are analyzed and compared in terms of time-temperature superposition (TTS), the relaxation time, and the spectral shape parameters. We conclude that TTS is obeyed to a good approximation for both the bulk and shear moduli. The loss-peak shapes are nearly identical, while the shear modulus relaxes faster than the bulk modulus. The temperature dependence of this decoupling of time scales is constant over the temperature range explored here. In addition, we demonstrate how one can measure reliably the DC shear viscosity over ten orders of magnitude by using the two measuring techniques in combination.
In-plane optical anisotropy induced by asymmetrically δ-doping in (001) GaAs/AlGaAs quantum wells studied by reflectance difference spectroscopy
Authors: Yu J. L. , Chen Y. H. , Bo X. , Jiang C. Y. , Ye X. L. , Wu S. J. , Gao H. S.
Published: February 2013

In-plane optical anisotropy (IPOA) in modulation-doped (001) GaAs/AlGaAs quantum wells (QWs) has been studied by reflectance difference spectroscopy (RDS). By changing the position of the δ-doping layer, we introduce an asymmetric potential into the quantum well system, which results in an additional IPOA. Compared to symmetrically doped and undoped structure, the asymmetrically doped QWs exhibit larger IPOA, which is clearly demonstrated both by the RDS results measured at 80 K and the linear extrapolation of the RDS signal under uniaxial strain measured at room temperature. Numerical calculations within the envelope function framework show that the asymmetric potential induced by asymmetrically doping will introduce additional hole-mixing coefficients. This work demonstrates that the IPOA of QWs can be tailored by changing the delta-doping position.
Hole injection-reduced hot carrier degradation in n-channel metal-oxide-semiconductor field-effect-transistors with high-k gate dielectric
Authors: Tsai Jyun-Yu , Chang Ting-Chang , Lo Wen-Hung , Chen Ching-En , Ho Szu-Han , Chen Hua-Mao , Tai Ya-Hsiang , Cheng Osbert , Huang Cheng-Tung
Published: February 2013

This work finds a significant difference in degradation under hot carrier stress (HCS) due to additional hole injection in n-channel metal-oxide-semiconductor field-effect-transistors with high-k gate dielectric. A comparison performed on degradation of input/output (I/O) and standard performance (SP) devices showed that performance degradation of the I/O device is worse than the SP device under HCS. For the SP device, both channel-electrons and hot holes can inject into gate dielectric, in which hole acts to diminish the stress field. However, I/O device shows only electron injection. The proposed model is confirmed by gate induced drain leakage current and simulation tool.
Higher dimensional abelian Chern-Simons theories and their link invariants
Authors: Gallot L. , Pilon E. , Thuillier F.
Published: February 2013

The role played by Deligne-Beilinson cohomology in establishing the relation between Chern-Simons theory and link invariants in dimensions higher than three is investigated. Deligne-Beilinson cohomology classes provide a natural abelian Chern-Simons action, non trivial only in dimensions 4l + 3, whose parameter k is quantized. The generalized Wilson (2l + 1)-loops are observables of the theory and their charges are quantized. The Chern-Simons action is then used to compute invariants for links of (2l + 1)-loops, first on closed (4l + 3)-manifolds through a novel geometric computation, then on \documentclass[12pt]{minimal}\begin{document}$\mathbb {R}^{4l+3}$\end{document}R4l+3 through an unconventional field theoretic computation.
Mechanical instability and ideal strengths of layered M2SC (M = Ti, Zr, and Hf) compounds
Authors: Cui Shouxin , Wei Dongqing , Hu Haiquan , Gong Zizheng
Published: February 2013

The behavior of M2SC (M = Ti, Zr, Hf) under tensile and shear deformations was investigated using the plane-wave pseudopotential density functional method. The microscopic mechanism that determines the structural stability is studied using the results of electronic structure calculations. It is shown that the structural failure of M2SC can be ascribed to the breakage of weak covalent M – S bond under uniaxial tensile tension, and the plasticity of these ternary materials can be triggered by electronic instabilities at finite shear deformations. Layered structural stability of M2SC is determined by the strength M – S bond under tensile tension, which is less resistive to shear deformation than to tensile strain. The stress-strain relationships of these ternary materials are presented and compared with corresponding binary carbides. Our study demonstrates that the ideal shear strength for M2SC is limited by the electronic instabilities which in turn lead to elastic instability. M2SC ceramics are predicted to be intrinsically brittleness in nature based on low bulk-modulus-to-shear-modulus ratios and negative Cauchy pressure (C12−C44). We propose that the brittleness of M2SC originates from larger movement of a dislocation in a glide plane and this can be quantized by larger Peierls stress, which is in turn initiated by novel layered structure for M2SC ceramics.
Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy
Authors: Malissa H. , Schuster D. I. , Tyryshkin A. M. , Houck A. A. , Lyon S. A.
Published: February 2013

We discuss the design and implementation of thin film superconducting coplanar waveguide micro-resonators for pulsed electron spin resonance experiments. The performance of the resonators with P doped Si epilayer samples is compared to waveguide resonators under equivalent conditions. The high achievable filling factor even for small sized samples and the relatively high Q-factor result in a sensitivity of 4.5 × 108 spins per shot, which is superior to that of conventional waveguide resonators, in particular to spins close to the sample surface. The peak microwave power is on the order of a few milliwatts, which is compatible with measurements at ultra-low temperatures. We also discuss the effect of the nonuniform microwave magnetic field on the Hahn echo power dependence.
Confinement and integration of magnetic impurities in silicon
Authors: Rueß Frank J. , El Kazzi Mario , Czornomaz Lukas , Mensch Philipp , Hopstaken Marinus , Fuhrer Andreas
Published: February 2013

Integration of magnetic impurities into semiconductor materials is an essential ingredient for the development of spintronic devices such as dilute magnetic semiconductors. While successful growth of ferromagnetic semiconductors was reported for III-V and II-VI compounds, efforts to build devices with silicon technology were hampered by segregation and clustering of magnetic impurities such as manganese (Mn). Here, we report on a surface-based integration of Mn atoms into a silicon host. Control of Mn diffusion and low-temperature silicon epitaxy lead to confined Mn δ-layers with low interface trap densities, potentially opening the door for a new class of spintronic devices in silicon.
Three-dimensional imaging of copper pillars using x-ray tomography within a scanning electron microscope: A simulation study based on synchrotron data
Authors: Martin N. , Bertheau J. , Bleuet P. , Charbonnier J. , Hugonnard P. , Laloum D. , Lorut F. , Tabary J.
Published: February 2013

While microelectronic devices are frequently characterized with surface-sensitive techniques having nanometer resolution, interconnections used in 3D integration require 3D imaging with high penetration depth and deep sub-micrometer spatial resolution. X-ray tomography is well adapted to this situation. In this context, the purpose of this study is to assess a versatile and turn-key tomographic system allowing for 3D x-ray nanotomography of copper pillars. The tomography tool uses the thin electron beam of a scanning electron microscope (SEM) to provoke x-ray emission from specific metallic targets. Then, radiographs are recorded while the sample rotates in a conventional cone beam tomography scheme that ends up with 3D reconstructions of the pillar. Starting from copper pillars data, collected at the European Synchrotron Radiation Facility, we build a 3D numerical model of a copper pillar, paying particular attention to intermetallics. This model is then used to simulate physical radiographs of the pillar using the geometry of the SEM-hosted x-ray tomography system. Eventually, data are reconstructed and it is shown that the system makes it possible the quantification of 3D intermetallics volume in copper pillars. The paper also includes a prospective discussion about resolution issues.
Atomic force microscope mediated chromatography
Authors: Anderson M. S.
Published: February 2013

An atomic force microscope (AFM) is presented as an instrument for rapid, miniaturized chromatography. The AFM is used to inject a sample, provide shear driven liquid flow over a functionalized substrate, and detect separated components. The components are then analyzed with surface enhanced Raman spectroscopy using AFM deposition of gold nanoparticles on the separated bands. This AFM mediated chromatography (AFM-MC) is demonstrated using lipophilic dyes and normal phase chemistry. A significant reduction in both size and separation time scales is achieved with 25 μm length scale and 1 s separation times. AFM-MC has general applications to trace chemical analysis and microfluidics.
Disintegration of rocks based on magnetically isolated high voltage discharge
Authors: He Mengbing , Jiang Jinbo , Huang Guoliang , Liu Jun , Li Chengzu
Published: February 2013

Recently, a method utilizing pulsed power technology for disintegration of rocks arouses great interest of many researchers. In this paper, an improved method based on magnetic switch and the results shown that the uniform dielectrics like plastic can be broken down in water is presented, and the feasible mechanism explaining the breakdown of solid is proposed and proved experimentally. A high voltage pulse of 120 kV, rise time 0.2 μs was used to ignite the discharging channel in solids. When the plasma channel is formed in the solid, the resistance of the channel is quiet small; even if a relatively low voltage is applied on the channel on this occasion, it will produce high current to heat the plasma channel rapidly, and eventually disintegrate the solids. The feasibility of promising industrial application in the drilling and demolition of natural and artificial solid materials by the method we presented is verified by the experiment result in the paper.
Fluid-solid equilibrium of carbon dioxide as obtained from computer simulations of several popular potential models: The role of the quadrupole
Authors: Pérez-Sánchez G. , González-Salgado D. , Piñeiro M. M. , Vega C.
Published: February 2013

In this work the solid-fluid equilibrium for carbon dioxide (CO2) has been evaluated using Monte Carlo simulations. In particular the melting curve of the solid phase denoted as I, or dry ice, was computed for pressures up to 1000 MPa. Four different models, widely used in computer simulations of CO2 were considered in the calculations. All of them are rigid non-polarizable models consisting of three Lennard-Jones interaction sites located on the positions of the atoms of the molecule, plus three partial charges. It will be shown that although these models predict similar vapor-liquid equilibria their predictions for the fluid-solid equilibria are quite different. Thus the prediction of the entire phase diagram is a severe test for any potential model. It has been found that the Transferable Potentials for Phase Equilibria (TraPPE) model yields the best description of the triple point properties and melting curve of carbon dioxide. It is shown that the ability of a certain model to predict the melting curve of carbon dioxide is related to the value of the quadrupole moment of the model. Models with low quadrupole moment tend to yield melting temperatures too low, whereas the model with the highest quadrupole moment yields the best predictions. That reinforces the idea that not only is the quadrupole needed to provide a reasonable description of the properties in the fluid phase, but also it is absolutely necessary to describe the properties of the solid phase.
Structural stability of hydrogenated amorphous carbon overcoats used in heat-assisted magnetic recording investigated by rapid thermal annealing
Authors: Wang N. , Komvopoulos K. , Rose F. , Marchon B.
Published: February 2013

Ultrathin amorphous carbon (a-C) films are extensively used as protective overcoats of magnetic recording media. Increasing demands for even higher storage densities have necessitated the development of new storage technologies, such as heat-assisted magnetic recording (HAMR), which uses laser-assisted heating to record data on high-stability media that can store single bits in extremely small areas (∼1 Tbit/in.2). Because HAMR relies on locally changing the coercivity of the magnetic medium by raising the temperature above the Curie temperature for data to be stored by the magnetic write field, it raises a concern about the structural stability of the ultrathin a-C film. In this study, rapid thermal annealing (RTA) experiments were performed to examine the thermal stability of ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition. Structural changes in the a-C:H films caused by RTA were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray reflectivity, and conductive atomic force microscopy. The results show that the films exhibit thermal stability up to a maximum temperature in the range of 400–450 °C. Heating above this critical temperature leads to hydrogen depletion and sp2 clustering. The critical temperature determined by the results of this study represents an upper bound of the temperature rise due to laser heating in HAMR hard-disk drives and the Curie temperature of magnetic materials used in HAMR hard disks.
Long-time dynamics for a class of Kirchhoff models with memory
Authors: Jorge Silva Marcio Antonio , Ma To Fu
Published: February 2013

This paper is concerned with a class of Kirchhoff models with memory effects \documentclass[12pt]{minimal}\begin{document}$u_{tt}\break + \alpha \Delta ^2 u - \mbox{div}(\vert \nabla u \vert ^{p-2}\nabla u) - \int _{0}^{\infty } \mu (s) \Delta ^{2}u(t-s)ds - \Delta u_t + f(u) = h,$\end{document}utt+αΔ2u−div(|∇u|p−2∇u)−∫0∞μ(s)Δ2u(t−s)ds−Δut+f(u)=h, defined in a bounded domain of \documentclass[12pt]{minimal}\begin{document}$\mathbb {R}^N$\end{document}RN. This non-autonomous equation corresponds to a viscoelastic version of Kirchhoff models arising in dynamics of elastoplastic flows and plate vibrations. Under assumptions that the exponent p and the growth of f(u) are up to the critical range, it turns out that the model corresponds to an autonomous dynamical system in a larger phase space, by adding a component which describes the relative displacement history. Then the existence of a global attractor is granted. Furthermore, in the subcritical case, this global attractor has finite Hausdorff and fractal dimensions.
Structural and magnetic properties of In1−xMnxSb: Effect of Mn complexes and MnSb nanoprecipitates
Authors: Kochura A. V. , Aronzon B. A. , Lisunov K. G. , Lashkul A. V. , Sidorenko A. A. , De Renzi R. , Marenkin S. F. , Alam M. , Kuzmenko A. P. , Lähderanta E.
Published: February 2013

Structural and magnetic properties of the group III-V diluted magnetic semiconductor In1−xMnxSb with x = 0.005–0.06, including the nuclear magnetic resonance (NMR) investigations, are reported. Polycrystalline In1−xMnxSb samples were prepared by direct alloying of indium antimonide, manganese and antimony, followed by a fast cooling of the melt with a rate of 10–12 K/s. According to the X-ray diffraction data, part of Mn is substituted for In, forming the In1−xMnxSb matrix. Atomic force microscopy and scanning tunneling microscopy investigations provide evidence for the presence of microcrystalline MnSb inclusions (precipitates), having a size of ∼100–600 nm, and the fine structure of nanosize grains with a Gaussian distribution around the diameter of ∼24 nm. According to the NMR spectra, the majority of Mn enters the MnSb inclusions. In addition to the single Mn ions, which contribute to the magnetization M (T) only in the low-temperature limit of T < 10–20 K, and MnSb nanoprecipitates responsible for the ferromagnetic (FM) properties of In1−xMnxSb, a superparamagnetic (SP) contribution of atomic-size magnetic Mn complexes (presumably dimers) has been established. The fraction of the MnSb phase, η ∼ 1–4%, as well as the concentration, nsp ∼ (0.8–3.2) × 1019 cm−3, and the magnetic moment of the Mn dimers, μ ∼ 8–9 μB, are determined. The solubility limit of Mn in the InSb matrix, NSL ∼ 1020 cm−3, is estimated. Hysteresis in low (H < 500 Oe) magnetic fields and saturation of the magnetization in high (H > 20 kOe) magnetic fields are observed, indicating a presence of the SP and FM contributions to the dependence of M (H) up to T ∼ 500 K. The hysteresis is characterized by the coercivity field, Hc, decreasing between ∼100 and 75 Oe when T is increased from 5 to 510 K. The values of Hc are in reasonable agreement with the effect of the largest MnSb inclusions. The maximum of M (T), measured in the zero-field-cooled and the field-cooled conditions in a weak field of 500 Oe, is observed at T ∼ 510 K and is attributable to the Hopkinson effect.
Self-doping and the role of oxygen vacancies in the magnetic properties of cubic BaFeO3−δ
Authors: Ribeiro B. , Godinho M. , Cardoso C. , Borges R. P. , Gasche T. P.
Published: February 2013

Although barium ferrate is known to accommodate a range of oxygen stoichiometries, which give rise to distinct magnetic properties, the mechanism underlying this coupling is not clearly understood. In order to address this issue, the electronic and magnetic properties of pseudocubic BaFeO3−δ with 0 ≤δ≤ 0.5 were studied using density functional theory. The present results attest the influence of the oxygen content on the magnetic order: for high oxygen content, the magnetic interactions are predominantly ferromagnetic whereas for oxygen deficient stoichiometries the antiferromagnetic interactions prevail. The threshold separating the two regimes is determined by the competition between double-exchange and super-exchange interactions which sensitively depend on the occupation of the oxygen band. Due to the high electronic affinity of the Fe ions in this compound, which results in a negative ligand to metal charge transfer energy, the system behaves as self-doped and the oxygen content has little effect on the 3d Fe band occupation, affecting instead the occupation of the anionic band.
Photocatalytic water splitting to hydrogen production of reduced graphene oxide/SiC under visible light
Authors: Yang Jingjing , Zeng Xiaopeng , Chen Lijuan , Yuan Wenxia
Published: February 2013

We report a method to realize the H2 production and graphene-oxide (GO) reduction simultaneously over GO/SiC composite under visible light irradiation with KI as sacrifice reagent. The weight content of GO is regulated in the reaction system. The rate of H2 production reaches to 95 μL/h with 1% GO content in GO/SiC composite system, which is 1.3 times larger compared to the case in pure SiC NPs under visible light. The reduced-GO sheet can serve as an electron collector and transporter to efficiently separate the photo-generated electron-hole pairs, lengthening the lifetime of the charge carriers effectively.
Density functional theory calculation of the optical properties and topological analysis of the electron density of MBi2B2O7 (M = Ca,Zn) compounds
Authors: Merad Boudia I. , Reshak A. H. , Ouahrani T. , Bentalha Z.
Published: February 2013

The topology of the electron density for congruent melting oxyborate Bi2ZnOB2O6 and CaBi2B2O7 is studied in light of the theory of atoms in molecules. All the electron density critical points in the unit cell are systematically calculated. What makes these compounds most interesting is a rich collection of B–O long-distance bond paths. We focus on the study of the asymmetric bonds and basins forming the anisotropic B2O5 groups in these compounds. B2O5 shows transferable contributions to the crystal, with long bond paths. We relate these observations to the strong behavior, which favorites its application to the second harmonic generation field. Wherefore, the analyses of bonding and related optical properties as well as the multipole moments of the CaBi2B2O7 compounds are predicted for the first time. CaBi2B2O7 exhibits some uniaxial dielectric anisotropy resulting in a strong birefringence. We also report calculations of the complex second-order optical susceptibility dispersion for the principal tensor components and evaluate their intra-and inter-band contributions.
A motion-capturing pressure-sensitive paint method
Authors: Sakaue Hirotaka , Miyamoto Kensuke , Miyazaki Takeshi
Published: February 2013

A motion-capturing pressure-sensitive paint (PSP) method is introduced to capture unsteady motions and flow fields of objects. Conventionally, the intensity-based method has been used to cancel the pressure-independent image of a PSP measurement to extract the pressure-dependent image. However, this method is not applicable if the pressure-independent image changes in time. The new motion-capturing method, namely imaging a two-color PSP-coated surface with a high-speed color camera, acquires both images simultaneously. This PSP has a reference luminescence in blue established using an appropriately tuned quantum dot, and a pressure-sensitive luminescence in red from bathophen ruthenium. The former has a luminescence spectrum from 400 to 550 nm, whereas the spectrum of the latter is around 620 nm. These are matched with the blue and red color ranges of the camera, which simultaneously acquires these images. By simply ratioing the blue and red images from each measurement, we can cancel the pressure-independent image, which are dependent on camera-PSP distance and illumination non-uniformity. The pressure sensitivity of the motion-capturing method is 1.12%/kPa which, due to the spectral overlap of the red and blue images, is slightly smaller than that of the intensity-based method by 0.01%/kPa. The response times are almost identical for both methods as both can respond to a step-pressure change within a time delay of 90 μs. A demonstration of this new method to sonic-jet impingement shows that the pressure-independent images can be used to cancel that component of the flow during unsteady motion and flows over a PSP-coated surface. The method can provide real-time pressure maps during unsteady motion created during a sonic jet impingement.
Concurrent improvement of magneto-optical and perpendicular magnetic properties in CoPt/Ag stacked structures with ZnO intermediate thin layers
Authors: Yamane H.
Published: February 2013

The magneto-optical properties of stacked-layer structures consisting of hcp-Co80Pt20 thin films and noble metal underlayers were investigated under polar Kerr measurement conditions. For CoPt/Ag stacked films, insertion of a 2-nm-thick ZnO layer into the interface resulted in the concurrent improvement of the magneto-optical enhancement at the plasma edge of Ag and perpendicular magnetic anisotropy. An ideal square out-of-plane hysteresis loop with a large Kerr rotation of approximately 1.25° was obtained in the CoPt/ZnO/Ag stacked structure. Moreover, heat treatment in a vacuum resulted in further improvement of the perpendicular magneto-optical properties in the stacked structures with thin CoPt layers.
Orientation dependence of electronic structure and optical gain of (11N)-oriented III-V-N quantum wells
Authors: Fan W. J.
Published: February 2013

A ten-band k·p Hamiltonian for III-V-N dilute nitride semiconductor quantum wells (QWs) grown on the (11N)-oriented substrates is presented. The energy dispersion curves, optical transition matrix elements, internal piezoelectric field, and optical gain of InGaAsN/GaAs on the (110), (111), (113), and (11∞)-oriented substrates are investigated including band-anti-crossing, strain, and piezoelectric field effects. The band structures and optical gain are sensitive to the substrate orientation. The fundamental transition energy is the largest for the (111)-oriented QW and the smallest for (11∞)-oriented QW. The absolute values of internal piezoelectric field in the well and barrier layers reach the maximum for the (111)-QW, and zero for the (110) and (11∞)-oriented QWs. There exists an injection current density turning point. When the injection current density is below the turning point, the (111)-oriented QW has the largest peak gain. At the larger injection current density, the (11∞)-oriented QW has the largest peak gain.
Negative differential photovoltage in a biased double heterojunction
Authors: Žukauskas A. , Meškauskas D. , Jakštas V. , Vitta P.
Published: February 2013

We report on negative differential photovoltage (DPV), which is observed under modulated photoexcitation of a double heterojunction, when the common positive photovoltage increment due to photocurrent modulation is suppressed by high bias current. The negative DPV was shown to be due to the effect of photoconductivity on the series resistance of the heterojunction and due to the modulation of junction temperature. In AlGaInP double heterojunction light-emitting diodes, the magnitudes of negative DPV in the range of −10 μV correspond to the estimated variation of series resistance and junction temperature as low as ∼10−3 Ω and ∼10−2 K, respectively.
Probing defect emissions in bulk, micro- and nano-sized α-Al2O3 via X-ray excited optical luminescence
Authors: Wang Zhiqiang , Li Chunlei , Liu Lijia , Sham Tsun-Kong
Published: February 2013

The electronic structure and optical properties of bulk, micro-sized, and nano-sized α-Al2O3 (wafer, microparticles (MPs), nanowires (NWs), and nanotubes (NTs)) have been investigated using X-ray absorption near-edge structures (XANES) and X-ray excited optical luminescence (XEOL). XANES results show that the wafer, MPs, and NTs have characteristic features of α-Al2O3. The NWs have a core/shell structure with a single crystalline α-Al2O3 core surrounded by an amorphous shell, which is consistent with transmission electron microscopy result. It is found that some Al3+ in the shell and core/shell interface of the NWs as well as the surface of the NTs were reduced to Al2+ or Al1+ during the growth process. XEOL results show that the wafer and MPs have a broad emission at 325 nm and a sharp emission at 694 nm, which are attributed to F+ center and Cr3+ impurities, respectively. The NWs exhibit an intense emission at 404 nm that comes from F center, while the NTs show relatively weak luminescence at 325, 433, and 694 nm, which are attributed to F+ center, F center, and Cr3+ impurities, respectively. The O K-edge XEOL confirms that the emissions of α-Al2O3 in the range of 250–550 nm are related to the oxygen site. Furthermore, on the basis of XEOL and photoluminescence yield, the strong luminescence of the NWs (404 nm) is related to the Al2+ or Al1+ in the shell and core/shell interface, while the luminescence of the NTs at 325 and 433 nm are related to the bulk and the Al2+ or Al1+ on the surface, respectively.
Graphene hydrogenation by molecular hydrogen in the process of graphene oxide thermal reduction
Authors: Mikoushkin V. M. , Nikonov S. Yu. , Dideykin A. T. , Vul' A. Ya. , Sakseev D. A. , Baidakova M. V. , Vilkov O. Yu. , Nelyubov A. V.
Published: February 2013

Thermal reduction in molecular hydrogen of the graphene oxide films has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. The restoration process was revealed to be accompanied by hydrogenation due to collisionally induced interaction of molecular hydrogen with carbon atoms. One side hydrogenated graphene films consisting of 20 μm one monolayer flakes were fabricated on SiO2/Si surface with hydrogen concentration as far as 40 at. %, at which the 0.3 eV bandgap opening was observed. It was shown that both H-coverage and bandgap width of the films can be controlled by varying the temperature of the heat treatment.
Conditions for a carrier multiplication in amorphous-selenium based photodetector
Authors: Masuzawa Tomoaki , Kuniyoshi Shingo , Onishi Masanori , Kato Richika , Saito Ichitaro , Yamada Takatoshi , Koh Angel T. T. , Chua Daniel H. C. , Shimosawa Tatsuo , Okano Ken
Published: February 2013

Amorphous selenium is a promising candidate for high sensitivity photodetector due to its unique carrier multiplication phenomenon. More than 10 carriers can be generated per incident photon, which leads to high photo-conversion efficiency of 1000% that allows real-time imaging in dark ambient. However, application of this effect has been limited to specific devices due to the lack in material characterization. In this article, mechanism of carrier multiplication has been clarified using time-of-flight secondary ion mass spectroscopy and Raman spectroscopy. A prototype photodetector achieved photo conversion efficiency of 4000%, which explains the signal enhancement mechanism in a-Se based photodetector.