bluuebunny/crossref_metadata_2025 huggingface dataset:
Tuning of in-plane optical anisotropy by inserting ultra-thin InAs layer at interfaces in (001)-grown GaAs/AlGaAs quantum wells
Authors: Yu J. L. , Cheng S. Y. , Lai Y. F. , Zheng Q. , Chen Y. H. , Tang C. G.
Published: January 2015

The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness of the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.
Guided vortex motion and ratchet effect in an anisotropic superconductor with a periodic pinning potential
Authors: Shklovskij V. A. , Seo Jin-Taek
Published: January 2015

Two-dimensional adiabatic ratchet dynamics of Abrikosov vortices in a symmetric periodic pinning potential is considered in the presence of dc and ac transport currents and anisotropy of the viscous vortex motion at zero temperature. Exact analytical expressions for two anisotropic nonlinear current-voltage responses along and across the transport current direction are derived and analyzed within the framework of the washboard model of pinning potential. The physical origin of these voltages, which are odd with respect to the current direction reversal, is the interplay between the vortex guiding effect, which is even with respect to the magnetic field reversal, and the asymmetry of the pinning potential due to its tilt induced by the dc component of the transport current.
Structural study of growth, orientation and defects characteristics in the functional microelectromechanical system material aluminium nitride
Authors: Hrkac Viktor , Kobler Aaron , Marauska Stephan , Petraru Adrian , Schürmann Ulrich , Kiran Chakravadhanula Venkata Sai , Duppel Viola , Kohlstedt Hermann , Wagner Bernhard , Lotsch Bettina Valeska , Kübel Christian , Kienle Lorenz
Published: January 2015

The real structure and morphology of piezoelectric aluminum nitride (AlN) thin films as essential components of magnetoelectric sensors are investigated via advanced transmission electron microscopy methods. State of the art electron diffraction techniques, including precession electron diffraction and automated crystal orientation mapping (ACOM), indicate a columnar growth of the AlN grains optimized for piezoelectric application with a {0 0 0 1} texture. Comparing ACOM with piezoresponse force microscopy measurements, a visual correlation of the structure and the piezoelectric properties is enabled. With a quantitative analysis of the ACOM measurements, a statistical evaluation of grain rotations is performed, indicating the presence of coincidence site lattices with Σ7, Σ13a, Σ13b, Σ25. Using a geometric phase analysis on high resolution micrographs, the occurrence of strain is detected almost exclusively at the grain boundaries. Moreover, high resolution imaging was applied for solving the atomic structure at stacking mismatch boundaries with a displacement vector of 1/2 ⟨1 0 -1 1⟩. All real structural features can be interpreted via simulations based on crystallographic computing in terms of a supercell approach.
Influence of a gold substrate on the optical properties of graphene
Authors: Matković Aleksandar , Chhikara Manisha , Milićević Marijana , Ralević Uroš , Vasić Borislav , Jovanović Djordje , Belić Milivoj R. , Bratina Gvido , Gajić Radoš
Published: January 2015

Spectroscopic ellipsometry combined with measurements of electrical characteristics and Kelvin probe force microscopy have been employed to investigate the interaction between graphene and a gold substrate, and the consequent changes of graphene's complex refractive index on gold. A strong blue shift, as much as 350 meV, of the prominent absorption peak (exciton-shifted M-point Van Hove singularity in the ultraviolet range) of graphene has been observed, with respect to the peak position for the sample on an insulating substrate where this peak was observed at about 4.55 eV. The results show that an interaction between graphene and a gold substrate can be characterized through the change of graphene's optical properties. In addition, the effects that a water layer trapped between graphene and gold during the transfer process has on the charge transfer between graphene and the gold substrate have been investigated.
Coupling and single-photon purity of a quantum dot-cavity system studied using hydrostatic pressure
Authors: Zhou P. Y. , Wu X. F. , Ding K. , Dou X. M. , Zha G. W. , Ni H. Q. , Niu Z. C. , Zhu H. J. , Jiang D. S. , Zhao C. L. , Sun B. Q.
Published: January 2015

We propose an approach to tune the emission of a single semiconductor quantum dot (QD) to couple with a planar cavity using hydrostatic pressure without inducing temperature variation during the process of measurement. Based on this approach, we studied the influence of cavity mode on the single-photon purity of an InAs/GaAs QD. Our measurement demonstrates that the single-photon purity degrades when the QD emission resonates with the cavity mode. This negative influence of the planar cavity is mainly caused by the cavity feeding effect.
Distinguishing the laser-induced spin precession excitation mechanism in Fe/MgO(001) through field orientation dependent measurements
Authors: Ma T. P. , Zhang S. F. , Yang Y. , Chen Z. H. , Zhao H. B. , Wu Y. Z.
Published: January 2015

Rotational field dependence of laser-induced magnetization precession in a single-crystal Fe/MgO(001) sample was studied by the time resolved magneto-optical Kerr effect. Polar and longitudinal magnetization components were separated by measuring precession dynamics under opposite fields. When the applied field is weaker than the anisotropy field of an Fe film, the precession amplitude is small for the field direction near the easy axis and becomes larger as the field rotates towards the hard axis, showing a four-fold symmetry in agreement with the in-plane magnetic anisotropy; whereas at higher fields, the amplitude displays a drop near the hard axis. Such precession behavior can be well reproduced using an excitation model with rapidly modified but slowly recovered magnetic anisotropy and considering the elliptical precession trajectory. Our results indicate that the dominant mechanism for triggering Fe spin precession is the anisotropy modulation correlating with the lattice thermalization, rather than the transient anisotropy modulation due to the high electron temperature within 1 ps.
Photoluminescence of a quantum-dot molecule
Authors: Kruchinin Stanislav Yu. , Rukhlenko Ivan D. , Baimuratov Anvar S. , Leonov Mikhail Yu. , Turkov Vadim K. , Gun'ko Yurii K. , Baranov Alexander V. , Fedorov Anatoly V.
Published: January 2015

The coherent coupling of quantum dots is a sensitive indicator of the energy and phase relaxation processes taking place in the nanostructure components. We formulate a theory of low-temperature, stationary photoluminescence from a quantum-dot molecule composed of two spherical quantum dots whose electronic subsystems are resonantly coupled via the Coulomb interaction. We show that the coupling leads to the hybridization of the first excited states of the quantum dots, manifesting itself as a pair of photoluminescence peaks with intensities and spectral positions strongly dependent on the geometric, material, and relaxation parameters of the quantum-dot molecule. These parameters are explicitly contained in the analytical expression for the photoluminescence differential cross section derived in the paper. The developed theory and expression obtained are essential in interpreting and analyzing spectroscopic data on the secondary emission of coherently coupled quantum systems.
Magnetization dynamics in La0.67Ca0.33MnO3 epitaxial films probed with resonant and non-resonant microwave absorption
Authors: Porwal Rajni , Pant R. P. , Budhani R. C.
Published: January 2015

Temperature (T) dependent microwave absorption measurements are performed on La0.67Ca0.33MnO3 (LCMO) epitaxial thin films of thickness 100 and 200 nm in an electron paramagnetic resonance spectrometer operating in X-band. The resonant absorption peak is monitored for out-of-plane (H⊥) and in-plane (H∥) dc magnetic field (H) as the system goes through magnetic ordering. These data suggest a resilient transformation to the ferromagnetic (FM) phase in the vicinity of the Curie temperature (TC), indicative of a phase separation, which is dominant in the thinner film. The saturation magnetization is calculated from SQUID magnetometry on the same film. A pronounced zero-field absorption is seen in H∥ geometry displaying anomalous growth in 100 nm film at T < TC. This feature is correlated with the magneto-conductivity of the manganite which is colossal in the vicinity of TC in the well-ordered film of thickness 200 nm. Signature of standing spin wave modes is seen in H⊥ measurements which are analyzed to calculate the spin wave stiffness constant D(T) in the limit of zero temperature. The same is also inferred from the decay of equilibrium magnetization in the framework of Bloch law. These studies reveal that a bulk like LCMO is obtained in the fully relaxed thicker films.
Dual-wavelength excited photoluminescence spectroscopy of deep-level hole traps in Ga(In)NP
Authors: Dagnelund D. , Huang Y. Q. , Tu C. W. , Yonezu H. , Buyanova I. A. , Chen W. M.
Published: January 2015

By employing photoluminescence (PL) spectroscopy under dual-wavelength optical excitation, we uncover the presence of deep-level hole traps in Ga(In)NP alloys grown by molecular beam epitaxy (MBE). The energy level positions of the traps are determined to be at 0.56 eV and 0.78 eV above the top of the valance band. We show that photo-excitation of the holes from the traps, by a secondary light source with a photon energy below the bandgap energy, can lead to a strong enhancement (up to 25%) of the PL emissions from the alloys under a primary optical excitation above the bandgap energy. We further demonstrate that the same hole traps can be found in various MBE-grown Ga(In)NP alloys, regardless of their growth temperatures, chemical compositions, and strain. The extent of the PL enhancement induced by the hole de-trapping is shown to vary between different alloys, however, likely reflecting their different trap concentrations. The absence of theses traps in the GaNP alloy grown by vapor phase epitaxy suggests that their incorporation could be associated with a contaminant accompanied by the N plasma source employed in the MBE growth, possibly a Cu impurity.
Solid-immersion fluorescence microscopy with increased emission and super resolution
Authors: Liau Z. L. , Liau A. A. , Porter J. M. , Salmon W. C. , Sheu S. S. , Chen J. J.
Published: January 2015

We investigate solid-immersion fluorescence microscopy suitable for super-resolution nanotechnology and biological imaging, and have observed limit of resolution as small as 15 nm with microspheres, mitochondria, and chromatin fibers. We have further observed that fluorescence efficiency increases with excitation power density, implicating appreciable stimulated emission and increased resolution. We discuss potential advantages of the solid-immersion microscopy, including combined use with previously established super-resolution techniques for reaching deeper beyond the conventional diffraction limit.
Dielectric functions of Cu2ZnSnSe4 and Cu2SnSe3 semiconductors
Authors: Hirate Yoshiki , Tampo Hitoshi , Minoura Shota , Kadowaki Hideyuki , Nakane Akihiro , Kim Kang Min , Shibata Hajime , Niki Shigeru , Fujiwara Hiroyuki
Published: January 2015

The dielectric functions of co-evaporated Cu2ZnSnSe4 (CZTSe) and Cu2SnSe3 (CTSe) polycrystalline layers are determined accurately from self-consistent spectroscopic ellipsometry analyses. To minimize the effects of the compositional modulation and light scattering induced by rough surfaces, quite thin CZTSe and CTSe layers (<50 nm) having the single-phase stoichiometric compositions are characterized. The dielectric functions of CZTSe and CTSe show rather similar spectral features with almost identical critical point energies for the transition peaks at 2.4 and 3.9 eV. The CTSe dielectric function, however, indicates strong free carrier absorption, expressed by the Drude model, due to high p-type conductivity in the layer. We find that CZTSe and CTSe show quite large absorption coefficients exceeding 105 cm−1 at 2.0 eV with band gap values of 0.91 ± 0.02 eV and 0.68 ± 0.05 eV, respectively. To characterize the optical transition in CZTSe in more detail, the dielectric response of each interband transition is calculated by applying density functional theory. The calculation result reveals that the strong visible light absorption in CZTSe is induced by the high joint density of states at the P point in the Brillouin zone. The optical constants of CZTSe and CTSe deduced in this study are further parameterized in an energy range up to 6.0 eV by expressing the transition peaks using the Tauc-Lorentz model. From the above results, we discuss the fundamental optical properties of (Cu,Se)-based compound semiconductors.
Effects of humidity and depurination on the charge transport in DNA films
Authors: Lee E. , Han J. H. , Kim D. , Jeon G. W. , Lee Cheol Eui , Park Y. J. , Kim H. D. , Kim J.
Published: January 2015

We have investigated the humidity and depurination (creating apurinic sites) effects on the electrical conduction in the λ-DNA films at different relative humidities and depurination times. The DNA films were found to follow the polaron hopping model, and the polaron hopping distance turned out to decrease at the higher relative humidity, more water molecules supposedly being adsorbed on the film. The activation energy showed little dependence on the depurination time at the higher relative humidity, whereas at the lower humidity it increased sharply with increasing depurination time.
Mechanics and optics of stretchable elastomeric microlens array for artificial compound eye camera
Authors: Li Zhengwei , Xiao Jianliang
Published: January 2015

Compound eye-inspired imaging devices can find vast applications due to their remarkable imaging characteristics, such as extremely large field of view angle, low aberrations, high acuity to motion, and infinite depth of field. Recently, researchers have successfully developed a digital camera that resembles the structure and functions of apposition compound eyes of arthropod, by combining an elastic array of microlenses with a stretchable array of photodetectors in their planar form and then transforming into a hemispherical shape. Designing an elastomeric microlens array that can be mechanically stretched to very large extent without deteriorating the optical performance is critical to this development. In this study, mechanics and optics of the stretchable microlens array, in which each hemispherical microlens sits on top of a supporting post connected to a base membrane, are studied. The results show that proper designs of the microlenses, supporting posts and base membrane are critically important to meet both mechanical and optical requirements simultaneously. This study can have important implications in not only the design of artificial compound eye cameras, but also other developments that require stretchable optical elements.
Ab initio study of shallow acceptors in bixbyite V2O3
Authors: Sarmadian N. , Saniz R. , Partoens B. , Lamoen D.
Published: January 2015

We present the results of our study on p-type dopability of bixbyite V2O3 using the Heyd, Scuseria, and Ernzerhof hybrid functional (HSE06) within the density functional theory (DFT) formalism. We study vanadium and oxygen vacancies as intrinsic defects and substitutional Mg, Sc, and Y as extrinsic defects. We find that Mg substituting V acts as a shallow acceptor, and that oxygen vacancies are electrically neutral. Hence, we predict Mg-doped V2O3 to be a p-type conductor. Our results also show that vanadium vacancies are relatively shallow, with a binding energy of 0.14 eV, so that they might also lead to p-type conductivity.
Elasticity dominates strength and failure in metallic glasses
Authors: Liu Z. Q. , Qu R. T. , Zhang Z. F.
Published: January 2015

Two distinct deformation mechanisms of shearing and volume dilatation are quantitatively analyzed in metallic glasses (MGs) from the fundamental thermodynamics. Their competition is deduced to intrinsically dominate the strength and failure behaviors of MGs. Both the intrinsic shear and normal strengths give rise to the critical mechanical energies to activate destabilization of amorphous structures, under pure shearing and volume dilatation, respectively, and can be determined in terms of elastic constants. By adopting an ellipse failure criterion, the strength and failure behaviors of MGs can be precisely described just according to their shear modulus and Poisson's ratio without mechanical testing. Quantitative relations are established systematically and verified by experimental results. Accordingly, the real-sense non-destructive failure prediction can be achieved in various MGs. By highlighting the broad key significance of elasticity, a “composition-elasticity-property” scheme is further outlined for better understanding and controlling the mechanical properties of MGs and other glassy materials from the elastic perspectives.
Appearance of bulk superconductivity under hydrostatic pressure in Sr0.5RE0.5FBiS2 (RE = Ce, Nd, Pr, and Sm) compounds
Authors: Jha Rajveer , Tiwari Brajesh , Awana V. P. S.
Published: January 2015

We report the appearance of superconductivity under hydrostatic pressure (0–2.5 GPa) in Sr0.5RE0.5FBiS2 with RE = Ce, Nd, Pr, and Sm. The studied compounds, being synthesized by solid state reaction route, are crystallized in tetragonal P4/nmm space group. At ambient pressure, though the RE = Ce exhibits the onset of superconductivity below 2.7 K, the Nd, Pr, and Sm samples are not superconducting down to 2 K. With application of hydrostatic pressure (up to 2.5 GPa), superconducting transition temperature (Tc) is increased to around 10 K for all the studied samples. The magneto-resistivity measurements are carried out on all the samples under 2.5 GPa pressure and their upper critical fields (Hc2) are determined. The superconductivity of these compounds appears to be quite robust against magnetic field. Summarily, the Sr0.5RE0.5FBiS2 compounds with RE = Ce, Nd, Pr, and Sm are successfully synthesized and superconductivity is induced in them under hydrostatic pressure.
Cesium doping at C60/rubrene heterointerfaces for improving the performance of organic light- and current-generating devices
Authors: Cheng Chiu-Ping , Lu Meng-Han , Chu Yu-Ya , Wei Ching-Hsuan , Pi Tun-Wen
Published: January 2015

This study examined the effect of adding cesium (Cs) at C60/rubrene heterointerfaces by using synchrotron-radiation photoelectron spectroscopy. A C60/rubrene heterostructure is the basis of a novel organic dual device found to facilitate efficient integration of both electroluminescent and photovoltaic functions. With Cs doping, the interfacial dipole potential was considerably enlarged, as was the separation between the lowest unoccupied molecular orbital of C60 and the highest occupied molecular orbital of rubrene. However, the energy-level diagram indicated that a high Cs concentration prevents the formation of photoexcitons. By contrast, adding a small amount of Cs can effectively improve the efficiency of light- and current-generating devices. In particular, the deficiency of the dopants at the heterointerface may benefit the survival of photoexcitons.
Directed targeting of chromatin to the nuclear lamina is mediated by chromatin state and A-type lamins
Authors: Harr Jennifer C. , Luperchio Teresa Romeo , Wong Xianrong , Cohen Erez , Wheelan Sarah J. , Reddy Karen L.
Published: January 2015

Nuclear organization has been implicated in regulating gene activity. Recently, large developmentally regulated regions of the genome dynamically associated with the nuclear lamina have been identified. However, little is known about how these lamina-associated domains (LADs) are directed to the nuclear lamina. We use our tagged chromosomal insertion site system to identify small sequences from borders of fibroblast-specific variable LADs that are sufficient to target these ectopic sites to the nuclear periphery. We identify YY1 (Ying-Yang1) binding sites as enriched in relocating sequences. Knockdown of YY1 or lamin A/C, but not lamin A, led to a loss of lamina association. In addition, targeted recruitment of YY1 proteins facilitated ectopic LAD formation dependent on histone H3 lysine 27 trimethylation and histone H3 lysine di- and trimethylation. Our results also reveal that endogenous loci appear to be dependent on lamin A/C, YY1, H3K27me3, and H3K9me2/3 for maintenance of lamina-proximal positioning.
TUNEL vision spots apoptotic cells
Authors: Short Ben
Published: January 2015

In 1992, Gavrieli et al. described a new assay to detect cell death in vivo.
Effect of the Nixtamalization Process on the Dietary Fiber Content, Starch Digestibility, and Antioxidant Capacity of Blue Maize Tortilla
Authors: Bello‐Pérez Luis A. , Flores‐Silva Pamela C. , Camelo‐Méndez Gustavo A. , Paredes‐López Octavio , Figueroa‐Cárdenas Juan de Dios
Published: January 2015

Nixtamalization is an ancient process developed by the Mesoamerican cultures. Initially, volcanic ashes were used and then calcium hydroxide in commercial production, and more recently nixtamalization with calcium salts (NCS) has been proposed. The aim of this study was to evaluate the effect of NCS on carbohydrate digestibility and antioxidant capacity in the elaboration of blue maize tortillas. NCS in blue tortillas showed a high amount of total dietary fiber (14.27 g/100 g), the main fraction being insoluble dietary fiber. The contents of resistant starch and slowly digestible starch did not change with the nixtamalization process. The predicted glycemic index value was lower in blue tortillas with the NCS process (58) than with the traditional nixtamalization process (71). In general, NCS in blue tortillas presented a higher antioxidant capacity than traditional tortillas (ferric reducing antioxidant power method), indicating that phenolics present in blue maize maintain their activity after cooking. It can be concluded that the nutraceutical features (high dietary fiber content and antioxidant capacity) of blue maize tortillas are enhanced when they are elaborated with the NCS process.
Dough Strain Hardening Properties as Indicators of Baking Performance
Authors: Kindelspire Julie Y. , Glover Karl D. , Caffé‐Treml Melanie , Krishnan Padmanaban G.
Published: January 2015

Bread loaf volume is an important economic criterion. Breeders, millers, and bakers need measurements allowing them to evaluate dough performance during processing. Strain hardening is an important dough property. It describes the stability of the gas cell walls and the ability of cells to expand further; therefore, the higher the strain hardening index (n), the better the baking performance. Dough exhibits strain hardening during uniaxial extensibility tests. However, obtaining n from an extensibility test is time consuming. The objectives of this study were to identify the extensibility parameters that contribute to n. Three parameters were retained in the model (R2 = 0.90): dough strength (Rmax), extensional delay (EDiff), and initial slope of the curve (Ei). Rmax was the largest contributor and was proportional to the dough strain hardening properties. EDiff and Ei had a detrimental effect on n. The appropriateness of the model was validated with two sample sets (19 genotypes, 12 environments). Significant correlations were found between loaf volume and n (r = 0.52–0.64) for 7 of the 12 environments. The strain hardening index was found to be a good predictor for baking performance as judged by loaf volume.
Development of Molecular Assays for Detection of Stenocarpella maydis and Stenocarpella macrospora in Corn
Authors: Romero M. P. , Wise K. A.
Published: January 2015

The causal agents of Diplodia ear rot are two species of the Stenocarpella genus, S. macrospora and S. maydis. In addition to ears, both pathogens can infect leaves and stalks, and both are present in most corn-production regions around the world. It is difficult to visually distinguish between the two pathogens based on plant symptoms and fungal signs. To facilitate accurate and rapid pathogen identification, polymerase chain reaction (PCR) assays were developed for identification of each species. Species-specific primers of 18 to 20 nucleotides in length were designed, targeting a portion of the internal transcribed spacer (ITS) region of the fungal genome for conventional and real-time PCR assays. The conventional PCR method successfully amplified a single 1.7-kb and 800-bp fragment for each S. maydis and S. macrospora isolate, respectively. The real-time method was performed using SYBR green dye, and detection of each specific target pathogen was successfully obtained. In total, 82 S. maydis and 15 S. macrospora isolates were tested to evaluate the reproducibility of these primers. Both methods provide a rapid and specific tool for the detection of Stenocarpella spp.
When Less is More: “Slicing” Sequencing Data Improves Read Decoding Accuracy andDe NovoAssembly Quality
Authors: Lonardi Stefano , Mirebrahim Hamid , Wanamaker Steve , Alpert Matthew , Ciardo Gianfranco , Duma Denisa , Close Timothy J.
Published: January 2015

Since the invention of DNA sequencing in the seventies, computational biologists have had to deal with the problemde novogenome assembly with limited (or insufficient) depth of sequencing. In this work, for the first time we investigate the opposite problem, that is, the challenge of dealing with excessive depth of sequencing. Specifically, we explore the effect of ultra-deep sequencing data in two domains: (i) the problem of decoding reads to BAC clones (in the context of the combinatorial pooling design proposed in [1]), and (ii) the problem ofde novoassembly of BAC clones. Using real ultra-deep sequencing data, we show that when the depth of sequencing increases over a certain threshold, sequencing errors make these two problems harder and harder (instead of easier, as one would expect with error-free data), and as a consequence the quality of the solution degrades with more and more data. For the first problem, we propose an effective solution based on “divide and conquer”: we “slice” a large dataset into smaller samples of optimal size, decode each slice independently, then merge the results. Experimental results on over 15,000 barley BACs and over 4,000 cowpea BACs demonstrate a significant improvement in the quality of the decoding and the final assembly. For the second problem, we show for the first time that modernde novoassemblers cannot take advantage of ultra-deep sequencing data.
Isolation of Microtubules by Assembly/Disassembly Methods
Authors: Sloboda Roger D.
Published: January 2015

The microtubule-isolation procedures described here are based on the ability of the investigator to control the dimer-polymer distribution of tubulin by varying the temperature of the extract. In general, the extract is warmed to induce microtubule assembly, the polymer is collected by centrifugation, cooled to induce disassembly, clarified by centrifugation, and then warmed again to produce polymer. As long as the GTP supply is sufficient, the microtubules that result can be taken through numerous rounds of this in vitro assembly and disassembly reaction. Many microtubule-associated proteins (MAPs) associate with microtubules assembled in vitro. Some reagents can skew the equilibrium of assembly and disassembly toward formation of polymer. The inclusion of glycerol, for instance, promotes microtubule assembly by disrupting the hydration shell around the tubulin dimers. The result is a greater yield of tubulin per gram of starting material. However, the ratio of MAPs to tubulin is slightly lower, presumably because the glycerol also decreases the binding of MAPs to tubulin. Two methods are described here: The first uses buffer lacking assembly-promoting components, and the second uses buffer containing glycerol. These procedures are most efficient with vertebrate brain tissue, where the soluble protein can be up to 15%–20% tubulin. The first produces satisfactory yields when using chick or pig brain; the second is recommended for calf or cow brain. The second procedure may also be useful for studies of nonneuronal tissues where the relative concentration of tubulin per gram of wet weight is considerably lower than that of brain.
Measuring Caspase Activity by Förster Resonance Energy Transfer
Authors: Rehm Markus , Parsons Melissa J. , Bouchier-Hayes Lisa
Published: January 2015

Förster resonance energy transfer (FRET) occurs across very short distances (in the nanometer range) between donor and acceptor fluorophores that overlap in their emission and absorption spectra. FRET-compatible green fluorescent protein (GFP) variants that are fused to short peptide linkers containing caspase cleavage sites can be used to measure caspase activity. In the intact probes, the donor and acceptor fluorophores are in close proximity, and FRET is highly efficient. On caspase activation, proteolysis of the linker occurs, and the donor is separated from the acceptor. This results in a disruption of resonance energy transfer and an increase in donor fluorescence quantum yield; this event is typically referred to as sensitized emission or donor unquenching. A number of highly sensitive FRET probes based on the cyan fluorescent protein–yellow fluorescent protein (CFP-YFP) pair, or improved variants thereof, have been developed to detect intracellular caspase activities. In this protocol we describe how to use FRET-based caspase substrates and time-lapse imaging to measure caspase activity in cells undergoing apoptosis.
Imaging-Based Methods for Assessing Caspase Activity in Single Cells
Authors: Parsons Melissa J. , Rehm Markus , Bouchier-Hayes Lisa
Published: January 2015

Caspases, a family of proteases that are essential mediators of apoptosis, are divided into two groups: initiator caspases and executioner caspases. Each initiator caspase is activated at the apex of its respective pathway, which generally leads to the cleavage and activation of executioner caspases. Executioner caspases in turn cleave numerous substrates in the cell, leading to its demise. Initiator caspases are activated when inactive monomers undergo induced proximity to form an active caspase. In contrast, executioner caspases are activated by cleavage. Based on this key difference, different imaging techniques have been developed to measure caspase activation and activity on a single-cell basis. Bimolecular fluorescence complementation (BiFC) is used to measure induced proximity of initiator caspases, whereas Förster resonance energy transfer (FRET) permits the investigation of caspase-mediated substrate cleavage in real time. Because many of the events in apoptosis, including caspase activation, are asynchronous in nature, these single-cell imaging techniques have proven to be immensely powerful in ordering and dissecting caspase pathways. When coupled with parallel detection of additional hallmark events of apoptosis, they provide detailed and quantitative kinetic and positional insights into the signal transduction pathways that regulate cell death. Here we provide a brief introduction into BiFC- and FRET-based imaging of caspase activation and activity in single cells.
Identification and Computational Analysis of Gene Regulatory Elements
Authors: Taher Leila , Narlikar Leelavati , Ovcharenko Ivan
Published: January 2015

Over the last two decades, advances in experimental and computational technologies have greatly facilitated genomic research. Next-generation sequencing technologies have made de novo sequencing of large genomes affordable, and powerful computational approaches have enabled accurate annotations of genomic DNA sequences. Charting functional regions in genomes must account for not only the coding sequences, but also noncoding RNAs, repetitive elements, chromatin states, epigenetic modifications, and gene regulatory elements. A mix of comparative genomics, high-throughput biological experiments, and machine learning approaches has played a major role in this truly global effort. Here we describe some of these approaches and provide an account of our current understanding of the complex landscape of the human genome. We also present overviews of different publicly available, large-scale experimental data sets and computational tools, which we hope will prove beneficial for researchers working with large and complex genomes.
Date palm (Phoenix dactylifera) leaf extract as an eco-friendly corrosion inhibitor for carbon steel in 1M hydrochloric acid solution
Authors: Umoren S.A. , Gasem Z.M. , Obot I.B.
Published: January 2015

Purpose

– The purpose of the paper was to investigate the use of aqueous extract of date palm (Phoenix dactylifera) leaf as a green inhibitor for corrosion of carbon steel in 1M hydrochloric acid (HCl) solution.

Design/methodology/approach

– Extracts from the date palm were used as the main component of an environmentally friendly corrosion inhibitor for use in HCl pickling processes. Inhibition behavior on carbon steel in HCl was investigated using weight loss measurements, linear and potentiodynamic polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy.

Findings

– The results show that the extract exhibited good inhibition performance in 1M HCl. The inhibition efficiency increased with increase in the concentration of the inhibitor but decreased with increase in temperature. Inhibition efficiency also was found to increase as immersion time increased. The inhibitive action was due to adsorption of the date palm leaf components on the steel, which was consistent with the Langmuir isotherm.

Practical implications

– Date palm leaf extract (DPLE) is an effective inhibitor at room temperature and can be used to protect plain carbon steel from corrosion in HCl solution.

Originality/value

– This study provides new information on the inhibiting characteristics of DPLE under specified conditions. The environmentally friendly inhibitor could find possible applications in metal surface anodizing and acid pickling processes.
Treading the straight and righteous path: curbing corruption in the Philippines
Authors: Batalla Eric Vincent C.
Published: January 2015

Purpose

– The purpose of this paper is to examine the anti-corruption performance of the Philippine government, particularly under the leadership of President Benigno Aquino III.

Design/methodology/approach

– The paper evaluates the anti-corruption measures as represented by pertinent laws as well as anti-corruption agencies (ACAs) under the Aquino administration.

Findings

– The Aquino government has exercised remarkable political will in acting on high-profile cases involving former government officials, including former President Gloria Macapagal-Arroyo. However, the government’s overall anti-corruption performance is hampered by outdated and conflicting laws, lack of compliance with anti-corruption laws and regulations by public officials and employees, poor ACA operational capacities, judicial inefficiency, deficient organizational systems and change-resistant government agencies, and selective and partial enforcement of anti-corruption laws. These problems are characteristic of Philippine political administrations and are arguably rooted in a system long characterized by fragile state institutions, strong oligarchic control, and weak citizenship.

Originality/value

– The paper is intended to update scholars, policy makers, and anti-corruption practitioners interested in corruption, ACA performance, and political reform in the Philippines. It discusses corruption-related problems of public administration within the purview of political economy. Based on this perspective, it argues that the key to effective control of corruption is a change in the political system’s configuration rather than the mere change in leadership.
Anti-corruption measures in China: suggestions for reforms
Authors: Guo Yong , Li Songfeng
Published: January 2015

Purpose

– The purpose of this paper is to analyze several measures which the government of the People’s Republic of China (PRC) has adopted to curb corruption and to make recommendations to curb the spread of corruption.

Design/methodology/approach

– The study is based on the analysis of government policy documents and reports, and statistical data on anti-corruption measures in China.

Findings

– During the past ten years, the government of the PRC has adopted these anti-corruption measures: first, increasing the ability to handle cases for deterring corrupt officials; second, improving the work style of officials and prohibiting them from enjoying special privileges, and promoting moral behavior among them; third, reforming the economic and political system to reduce corruption opportunities; and fourth, reforming the Central Commission for Discipline Inspection (CCDI) to more effectively handle corruption cases. Nevertheless, in despite of these anti-corruption measures, there remain serious challenges for reducing corruption stemming from an irrational system of administrative reform and balancing the relationship between the CCDI and the judiciary departments to enhance the professionalism and efficiency of the anti-corruption agencies, which continue to constrain China’s current anti-corruption efforts. Therefore, the Chinese government should take a top-down approach, analyze the characteristics and trends of corruption in the new era, strengthen the institutional structures, and strive to suppress the spread of corruption.

Originality/value

– This paper will be useful for those scholars, policy-makers and anti-corruption practitioners who are interested in China’s anti-corruption measures.
Sibling rivalry among anti-corruption agencies in Taiwan
Authors: Ko Ernie , Su Yu-Chang , Yu Chilik
Published: January 2015

Purpose

– The purpose of this paper is to provide insights into the multiple anti-corruption agencies (ACAs) in Taiwan and their conflict resolution. The birth of the Agency Against Corruption (AAC) in 2011 created the unintended consequence of sibling rivalry with the elder Ministry of Justice Investigation Bureau (MJIB).

Design/methodology/approach

– A historical background of these agencies is discussed and followed by an analysis of the diversified conflicts among the prosecutor’s office, the AAC and the MJIB. The empirical sources of this study include 17 in-depth interviews with government officials both at ministerial level and field level, scholars and NGO representatives.

Findings

– The redundancy of ACAs in Taiwan is a fact, which is extremely difficult to change in the foreseeable future in the light of current political and fiscal constraints. This paper concludes that the conflicts among multiple ACAs and their operational weaknesses will not fade away after a mere directive from their superior, the Ministry of Justice, unless genuine cooperation is put into place in various individual cases.

Practical implications

– This paper provides a road-map for decision makers to improve collective anti-corruption performance. Taiwan’s AAC serves as the latest example testing the efficacy of the multiple specialized ACAs.

Originality/value

– This pioneering study provides insights into Taiwan’s anti-corruption policy and practices. More investigative studies should be conducted on the effectiveness of multiple ACAs in other countries.
Trust-building in international business ventures
Authors: Gerbasi Alexandra , Latusek Dominika
Published: January 2015

Purpose

– The purpose of this paper is to investigate collaboration and coordination practices in the organisation whose members come from two countries that differ dramatically in generalised trust: Poland and the USA.

Design/methodology/approach

– A qualitative field study conducted in Silicon Valley-based American-Polish start-up joint venture.

Findings

– There are three mechanisms can facilitate collaboration in organisations that differ in generalised trust: frequent interaction that may form a basis for knowledge-based trust, professional cultures that provide common platform for communication, and presence of intermediaries that possess understanding and ability to communicate of both cultures.

Practical implications

– The findings can be applied in the context of offshoring projects in knowledge intensive industries.

Originality/value

– Research presented in this paper investigates collaboration of parties from low-trust and high-trust cultures within one business venture.
Identifying mentors for student employees on campus
Authors: Frock David
Published: January 2015

Purpose

– This exploratory research project aims to seek an effective process for identifying supervisors of part-time student employees who also serve in a mentoring capacity.

Design/methodology/approach

– This paper is based on a review of literature and an evaluation process focused on established traits and functions of mentoring as applied to supervisors of student employees on a college campus.

Findings

– Supervisors of student employees may have the desire and capacity to engage students on a higher level but are not viewed and supported to meet this need based on their position within the organization. Untapped resources are being overlooked that would develop the supervisor and the student while advancing the overall institutional mission.

Research limitations/implications

– A study identifying mentors for part-time undergraduate student employees in higher education settings was necessary as a precursor to future research on the human resource development needs of professional staff in higher education.

Practical implications

– The results of this study confirmed that the approach utilized for identifying mentors through specific traits is effective and that common barriers exist across the institution that negatively impact supervisors from serving as mentors. These results will be used to address future research related to the value of training and educating the supervisors of undergraduate student employees on college campuses.

Originality/value

– Research exists on 360 evaluative processes, mentoring and the benefits of student development outside the classroom, but no research could be identified that addressed the opportunities of using this approach to potentially resolve organizational issues.
Sexuality education: implications for health, equity, and social justice in the United States
Authors: Elia John P. , Tokunaga Jessica
Published: January 2015

Purpose

– The purpose of this paper is to examine how school-based sexuality education has had a long and troubled history of exclusionary pedagogical practices that have negatively affected such populations as lesbian, gay, bisexual, trans, queer (LGBTQ) individuals, people of color, and the disabled. The social ecological model is introduced as a way of offering sexuality educators and school administrators a way of thinking more broadly about how to achieve sexual health through sexuality education efforts inside and outside of the school environment.

Design/methodology/approach

– This paper uses critical analysis of current and historical school-based sexuality education methods and curricula used in the USA. Authors use both academic journals and their own expertise/experience teaching sexuality education in the USA to analyze and critique the sources of sexuality education information and curricula used in schools.

Findings

– Historically, sexuality education in school settings in the USA has been biased and has generally not offered an educational experience fostering sexual health for all students. There are now welcome signs of reform and movement toward a more inclusive and progressive approach, but there is still some way to go. Sexuality education programs in schools need to be further and fundamentally reformed to do more to foster sexual health particularly for LGBTQ individuals, students of color, and people with disabilities.

Practical implications

– This paper offers sexuality educators ways of addressing structural issues within the sexuality education curriculum to better serve all students to increase the quality of their sexual health. Integrating critical pedagogy and anti-oppressive education can increase students’ sexual health along physical, social, emotional, intellectual, and spiritual dimensions.

Originality/value

– This paper provides historical analysis along with the identification of structural difficulties in the sexuality education curriculum and proposes both critical pedagogy and anti-oppressive education as ways of addressing sex and relationships education.
The sexuality education and attitudes of college students in China
Authors: Song Yu
Published: January 2015

Purpose

– The purpose of this paper is to examine the type and quality of sexuality education received by college students in Hangzhou, China. Their attitudes towards sex and sexuality were also explored. To set the broader context the regulations and laws governing the provision of sexuality education in China have also been examined.

Design/methodology/approach

– A cross-sectional survey of 132 college students was conducted in Hangzhou, China in 2013. The aim was to explore their experience of and attitudes towards their sexuality education.

Findings

– Most respondents lacked formal sexuality education. Neither schools nor parents were reported to be the major providers of sexuality education. The students reported that their main sources of knowledge and information relating to sex were their fellow schoolmates and the internet. Participants reported insufficient or inaccurate sexual knowledge as a key factor in their participation in unprotected sex. Attitudes towards premarital sex and cohabitation, and homosexual relationships were reported to be more open and tolerant than those of the older generation.

Originality/value

– The data from this study suggest that reluctance amongst parents and schools to provide formal and comprehensive sexuality education has resulted in unsatisfactory sexuality education in Hangzhou. The lack of sexuality education among college students may have had an influence on their unsafe sexual behaviours which is potentially damaging to both their physical and psychological health. Implications for improving the quality of sexuality education for young people in China are discussed.