bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonothermal Synthesis of Novel Nitrides: Case Study on CaGaSiN3
Authors: Häusler Jonas , Neudert Lukas , Mallmann Mathias , Niklaus Robin , Kimmel Anna‐Carina L. , Alt Nicolas S. A. , Schlücker Eberhard , Oeckler Oliver , Schnick Wolfgang
Published: December 2016

The first gallium‐containing nitridosilicate CaGaSiN3 was synthesized in newly developed high‐pressure autoclaves using supercritical ammonia as solvent and nitriding agent. The reaction was conducted in an ammonobasic environment starting from intermetallic CaGaSi with NaN3 as a mineralizer. At 770 K, intermediate compounds were obtained, which were subsequently converted to the crystalline nitride at temperatures up to 1070 K (70–150 MPa). The impact of other mineralizers (e.g., LiN3, KN3, and CsN3) on the product formation was investigated as well. The crystal structure of CaGaSiN3 was analyzed by powder X‐ray diffraction and refined by the Rietveld method. The structural results were further corroborated by transmission electron microscopy, 29Si MAS‐NMR, and first‐principle DFT calculations. CaGaSiN3 crystallizes in the orthorhombic space group Cmc21 (no. 36) with lattice parameters a=9.8855(11), b=5.6595(1), c=5.0810(1) Å, (Z=4, Rwp=0.0326), and is isostructural with CaAlSiN3 (CASN). Eu2+ doped samples exhibit red luminescence with an emission maximum of 620 nm and FWHM of 90 nm. Thus, CaGaSiN3:Eu2+ also represents an interesting candidate as a red‐emitting material in phosphor‐converted light‐emitting diodes (pc‐LEDs). In addition to the already known substitution of alkaline‐earth metals in (Ca,Sr)AlSiN3:Eu2+, inclusion of Ga is a further and promising perspective for luminescence tuning of widely used red‐emitting CASN type materials.
Nanosized NIR‐Luminescent Ln Metal–Organic Cage for Picric Acid Sensing
Authors: Yin Shao‐Yun , Zhu Yi‐Xuan , Pan Mei , Wei Zhang‐Wen , Wang Hai‐Ping , Fan Ya‐Nan , Su Cheng‐Yong
Published: December 2016

Near‐infrared (NIR) luminescence detection of picric acid (PA) was achieved sensitively and selectively by using a nanosized NdIII metal–organic cage (MOC) for the first time.
Transient immunological and clinical effectiveness of treating mice bearing premalignant oral lesions with PD‐1 antibodies
Authors: Levingston Corinne A. , Young M. Rita I.
Published: December 2016

A carcinogen‐induced premalignant oral lesion model that progresses to oral cancer was used to examine the impact of blocking PD‐1 on cytokine expression and on progression of lesions to cancer. The results of this study show increased production of IL‐2 and the inflammatory cytokines IL‐6, IL‐17 and TNF‐α by spleen cells of lesion‐bearing mice that were treated with PD‐1 antibody for 1 week compared to cytokine production by spleen cells of lesion‐bearing mice treated with control antibody. Production of IFN‐γ increased at 3 weeks of PD‐1 antibody treatment, although production of the other Th1 and inflammatory mediators declined. By 5 weeks, levels of these cytokines declined for both control and PD‐1 antibody‐treated mice. Flow cytometric analysis for IFN‐γ‐expressing cells showed shifts in CD4+ cells expressing IFN‐γ consistent with the changes in cytokine secretion. Whether or not treatment generated reactivity to lesions or HNSCC was determined. Spleen cells from PD‐1 antibody‐treated mice were stimulated by lysates of premalignant lesion and HNSCC tongue tissues to produce increased levels of Th1 and select inflammatory cytokines early in the course of PD‐1 antibody treatment. However, with continued treatment, reactivity to lesion and HNSCC lysates declined. Analysis of clinical response to treatment suggested an early delay in lesion progression but, with continued treatment, lesions in PD‐1 antibody‐treated mice progressed to the same degree as in control antibody‐treated mice. Overall, these results show an early beneficial response to PD‐1 antibody treatment, which then fails with continued treatment and lesion progression.
How do two specialist butterflies determine growth and biomass of a shared host plant?
Authors: Hashimoto Koya , Ohgushi Takayuki
Published: December 2016

Although insect herbivory can modify subsequent quantity and quality of their host plants, change in plant quantity following herbivory has received less attention than plant quality. In particular, little is known about how previous herbivore damage determines plant growth and biomass in an insect species‐specific manner. We explored whether herbivore species‐specific food demand influences plant growth and biomass. To do this, we conducted a series of experiments and field survey using two specialist butterflies, Sericinus montela and Atrophaneura alcinous, and their host plant, Aristolochia debilis. It is known that A. alcinous larva requires four times more food resources to fulfill its development than S. montela larva. Despite that A. alcinous larvae imposed greater damage on plants than S. montela larvae, plant growth did not differ due to herbivory by these species both in single and multiple herbivory events. On the other hand, total aboveground biomass of the plants was reduced more by A. alcinous than S. montela feeding regardless of the number of herbivory events. Feeding on plants with a history of previous herbivory neither decreased nor increased larval growth. Our results suggest that food demand of the two butterfly species determined subsequent plant biomass, although the plant response may depend on tolerance of the host plant (i.e., ability to compensate for herbivore damage). Such difference in the effects of different herbivore species on host plant biomass is more likely to occur than previously thought, because food demand differs in most herbivore species sharing a host plant.
Genetic Counselor Practices Involving Pediatric Patients with FAP: an Investigation of their Self‐Reported Strategies for Genetic Testing and Hepatoblastoma Screening
Authors: Lawson Caitlin E. , Attard Thomas M. , Dai Hongying , Septer Seth
Published: December 2016

Familial adenomatous polyposis (FAP) is a cancer predisposition syndrome that causes early‐onset polyposis and is associated with an increased risk for hepatoblastoma. There is currently a lack of consensus on when to order APC (adenomatous polyposis coli) gene testing or implement surveillance for hepatoblastoma. An online questionnaire was completed by 62 genetic counselors to capture their current practices regarding these questions. Extracolonic findings associated with FAP that were most likely to prompt APC testing in an otherwise asymptomatic 10 year‐old child with a negative family history were multiple desmoid tumors, congenital hypertrophy of the retinal pigment epithelium (CHRPE), jaw osteomas, and hepatoblastoma. For hepatoblastoma screening, the majority did recommend this in children less than age five years with known APC mutations. An interval of every 3–6 months was most commonly suggested; however, responses extended to screening on a less than annual basis. These results highlight the need for further investigation into why some genetic counselors do not recommend APC testing in young at‐risk children and what factors influence views about the ideal age and indication for APC testing. Studies of these issues would help to define the best clinical practice model for genetic testing and hepatoblastoma screening in pediatric patients with FAP.
Modification of Nonionic Vesicles by Adding Decanol and Functional Lanthanide Ions
Authors: Selivanova Natalia M. , Gubaidullin Aidar T. , Romanova Ksenia A. , Galyametdinov Yuriy G.
Published: December 2016

Colloid systems modified by luminescent ions in situ are highly attractive for the design of new molecular architectures and adaptable for monitoring and visualizing soft drug delivery systems. This paper presents original results on the characterization of the self‐organization process and the structure of vesicles formed by tetraethylene glycol monodecyl ether (C12EO4) in the presence of lanthanide ions and decanol additives. Detailed characterization of surface activity, aggregation properties and microstructure of individual and mixed aggregates has been carried out based on surface tension, electron microscopy, small‐angle X‐ray scattering, dynamic light scattering analysis and fluorescence spectroscopy. The small‐angle scattering results in combination with quantum‐chemical calculations assume the multishell vesicle formation in C12EO4/C10H21OH/H2O media. In the C12EO4 solution the presence of Ln(III) ions and decanol initiate the formation of multilamellar vesicles with a size of about 100 nm. The luminescence analysis of the Eu(III) and Tb(III) complexes has shown the efficient solubilization in the C12EO4/C10H21OH/H2O vesicles, which leads to increase in the lifetime. The resulting outcome is the possibility to control micro and macro properties of a molecular organized system to give it the desired functionality.
Characteristics and clinical use of ocular and cervical vestibular evoked myogenic potentials for evaluating paediatric candidates for cochlear implants
Authors: Xu X-D , Hu J , Zhang Q , Zhang Y , Zhang X-T , Chen Y-F , Xu M
Published: December 2016

Objective:

This study aimed to define the characteristics and use of ocular and cervical vestibular evoked myogenic potentials for evaluating paediatric cochlear implant candidates.

Methods:

Ocular and cervical vestibular evoked myogenic potentials of 34 paediatric cochlear implant candidates were analysed. All patients also underwent a routine audiological examination, including computed tomography.

Results:

In all, 27 patients with normal inner-ear structures had absent or impaired vestibular evoked myogenic potential responses. In paediatric candidates with inner-ear malformations, ocular and cervical vestibular evoked myogenic potentials had lower thresholds and higher amplitudes. Vestibular evoked myogenic potential responses in this cohort were classified into three groups. There was significant concordance between vestibular evoked myogenic potentials and temporal bone computed tomography findings.

Conclusion:

Ocular and cervical vestibular evoked myogenic potential waveforms were different in paediatric candidates with normal and abnormal inner-ear structures. Therefore, vestibular evoked myogenic potential responses can indicate temporal bone structure.
The role of symptomatic presentation in influenza A transmission risk
Authors: WARDELL R. , PREM K. , COWLING B. J. , COOK A. R.
Published: December 2016

Computer models can be useful in planning interventions against novel strains of influenza. However such models sometimes make unsubstantiated assumptions about the relative infectivity of asymptomatic and symptomatic cases, or conversely assume there is no impact at all. Using household-level data from known-index studies of virologically confirmed influenza A infection, the relationship between an individual's infectiousness and their symptoms was quantified using a discrete-generation transmission model and Bayesian Markov chain Monte Carlo methods. It was found that the presence of particular respiratory symptoms in an index case does not influence transmission probabilities, with the exception of child-to-child transmission where the donor has phlegm or a phlegmy cough.
Impact of changes in multi-pillar pension systems in CEE countries on individual pension wealth
Authors: CHŁOŃ-DOMIŃCZAK AGNIESZKA
Published: December 2016

The paper shows the impact of changes in multi-pillar pension systems in six Central and Eastern European countries for individual pension wealth. It demonstrates that the post-crisis changes in pension system reduced pension wealth of workers in Poland and increased in Lithuania and Slovakia. The change did not have significant impact on pension wealth in Estonia and Romania. The magnitude of this effect is highest in those countries where the reduction of the fully-funded pension contribution was permanent. Loss or gain in pension wealth varies with age of participants – it is higher for younger people, who will accumulate their pension wealth to a larger extent after the change. The level of the change in pension wealth depends also on the wage level – higher earners lose more relative to the average wage level. The difference in pension wealth depends also on the difference between rates of return in fully funded and pay-as-you-go (PAYG) components of the pension system. The net outcome of post-crisis pension system modifications depends both on the magnitude of fully-funded contribution reduction, but also on the design of PAYG component and the way individual pension rights are accrued. These results indicate the rise in implicit liability of pension system in Slovakia to be higher than the reduction of the explicit liability caused by the pension system change and the lower rise of implicit liability in Poland and Latvia.
Understanding Tectonic Processes Following Great Earthquakes
Authors: Witman Sarah
Published: December 2016

Scientists parse out the processes underlying tectonic signals detected by GPS networks.
Climate Efforts Will Continue Despite Rhetoric, Officials Say
Authors: Showstack Randy
Published: December 2016

Secretary of the Interior says that citizens can help hold the Trump administration accountable for what they want to see happen in terms of action on climate change.
Expression and bioactivity of human α-fetoprotein in a Bac-to-Bac system
Authors: Lin Bo , Liu Kun , Wang Wenting , Li Wei , Dong Xu , Chen Yi , Lu Yan , Guo Junli , Zhu Mingyue , Li Mengsen
Published: December 2016

α-fetoprotein (AFP) is an early serum growth factor in foetal embryonic development and hepatic oncogenesis. A growing number of investigations of AFP as a tumour-specific biomarker have concluded that AFP is an important target for cancer treatment. AFP also plays an immunomodulatory role in the treatment of several autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, myasthenia gravis and thyroiditis. In an effort to support biochemical screening and drug design and discovery, we attempted to express and purify human AFP in a Bac-to-Bac system. Two key factors affecting the expression of recombinant human AFP (R-AFP), namely the infectious baculovirus inoculum volume and the culturing time post-infection, were optimized to maximize the yield. We achieved a high yield of approximately 1.5 mg/l of harvested medium with a 72–96 h incubation period after infection and an inoculum volume ratio of 1:100. We also assessed the role of R-AFP in the proliferation of the human liver cancer cell line Bel 7402, and the results indicated that R-AFP promoted the growth of hepatoma cells. We concluded that this method can produce high yields of R-AFP, which can be used for studies related to AFP.
Neutrophil-derived microparticles are released into the coronary circulation following percutaneous coronary intervention in acute coronary syndrome patients
Authors: Martínez Gonzalo J. , Barraclough Jennifer Y. , Nakhla Shirley , Kienzle Vivian , Robertson Stacy , Mallat Ziad , Celermajer David S. , Patel Sanjay
Published: December 2016

To evaluate (i) local coronary and systemic levels of microparticles (MP) in acute coronary syndrome (ACS) and stable angina pectoris (SAP) patients and (ii) their release after plaque disruption with percutaneous coronary intervention (PCI). MP are small vesicles originating from plasma membranes of cells after activation or apoptosis and are implicated in the pathogenesis of atherosclerosis. Neutrophils play a role in plaque destabilization and shed neutrophil-derived MP that have the potential to drive significant proinflammatory and thrombotic downstream effects. Eight ACS and eight SAP patients were included. Coronary sinus (CS) samples pre-intervention (CS1), 45 s following balloon angioplasty (CS2) and at 45 s intervals following stent deployment (CS3, CS4 and CS5), together with peripheral vein samples, pre- and post-PCI were analysed for neutrophil-derived (CD66b+), endothelial-derived (CD144+), platelet-derived (CD41a+), monocyte-derived (CD14+) and apoptotic (Annexin V+) MP. ELISA for interleukin (IL)-6, myeloperoxidase (MPO) and P-selectin was also performed. CD66b+ MP levels were similar in both groups pre-intervention. Post-PCI, CS levels rose significantly in ACS but not SAP patients (ACS area under the curve (AUC): 549 ± 83, SAP AUC: 24 ± 29, P<0.01). CS CD41a+, CD144+, CD14+ and Annexin V+ MP levels did not differ between groups. Acute neutrophil-derived MP release post-PCI occurs in ACS compared with stable patients, likely to be reflective of plaque MP content in vulnerable lesions.
New fungal defensin-like peptides provide evidence for fold change of proteins in evolution
Authors: Wu Yucheng , Gao Bin , Zhu Shunyi
Published: December 2016

Defensins containing a consensus cystine framework, Cys[1]…Cys[2]X3Cys[3]…Cys[4]… Cys[5]X1Cys[6] (X, any amino acid except Cys; …, variable residue numbers), are extensively distributed in a variety of multicellular organisms (plants, fungi and invertebrates) and essentially involved in immunity as microbicidal agents. This framework is a prerequisite for forming the cysteine-stabilized α-helix and β-sheet (CSαβ) fold, in which the two invariant motifs, Cys[2]X3Cys[3]/Cys[5]X1Cys[6], are key determinants of fold formation. By using a computational genomics approach, we identified a large superfamily of fungal defensin-like peptides (fDLPs) in the phytopathogenic fungal genus – Zymoseptoria, which includes 132 structurally typical and 63 atypical members. These atypical fDLPs exhibit an altered cystine framework and accompanying fold change associated with their secondary structure elements and disulfide bridge patterns, as identified by protein structure modelling. Despite this, they definitely are homologous with the typical fDLPs in view of their precise gene structure conservation and identical precursor organization. Sequence and structural analyses combined with functional data suggest that most of Zymoseptoria fDLPs might have lost their antimicrobial activity. The present study provides a clear example of fold change in the evolution of proteins and is valuable in establishing remote homology among peptide superfamily members with different folds.
Further resolution enhancement of high-sensitivity laser scanning photothermal microscopy applied to mouse endogenous
Authors: Nakata Kazuaki , Tsurui Hiromichi , Kobayashi Takayoshi
Published: December 2016

Photothermal microscopy has intrinsically super resolution capability due to the bilinear dependence of signal intensity of pump and probe. In the present paper, we have made further resolution improvement of high-sensitivity laser scanning photothermal microscopy by applying non-linear detection. By this, the new method has the following advantages: (1) super resolution with 61% and 42% enhancement from the diffraction limit values of the probe and pump wavelengths, respectively, by a second-order non-linear scheme, (2) compact light source using inexpensive conventional diode lasers, (3) wide applicability to nonfluorescent materials such as gold nanoparticles (GNPs) and hematoxylin-eosin stained biological samples, (4) relative robustness to optical damage, and (5) a high-frame rate using a Galvano mirror. The maximum resolution is determined to be 160 nm in the second-order non-linear detection mode and 270 nm in the linear detection mode by the PT signal of GNPs. The pixel rate and frame rate for 300 × 300 pixel image are 50 μs and 4.5 s, respectively. The pixel and frame rate are shorter than the rates, which are 1 ms and 100 s, respectively, using the piezo-driven stage system.
Comparison of liquid-state anomalies in Stillinger-Weber models of water, silicon, and germanium
Authors: Dhabal Debdas , Chakravarty Charusita , Molinero Valeria , Kashyap Hemant K.
Published: December 2016

We use molecular dynamics simulations to compare and contrast the liquid-state anomalies in the Stillinger-Weber models of monatomic water (mW), silicon (Si), and germanium (Ge) over a fairly wide range of temperatures and densities. The relationships between structure, entropy, and mobility, as well as the extent of the regions of anomalous behavior, are discussed as a function of the degree of tetrahedrality. We map out the cascade of density, structural, pair entropy, excess entropy, viscosity, and diffusivity anomalies for these three liquids. Among the three liquids studied here, only mW displays anomalies in the thermal conductivity, and this anomaly is evident only at very low temperatures. Diffusivity and viscosity, on the other hand, show pronounced anomalous regions for the three liquids. The temperature of maximum density of the three liquids shows re-entrant behavior consistent with either singularity-free or liquid-liquid critical point scenarios proposed to explain thermodynamic anomalies. The order-map, which shows the evolution of translational versus tetrahedral order in liquids, is different for Ge than for Si and mW. We find that although the monatomic water reproduces several thermodynamic and dynamic properties of rigid-body water models (e.g., SPC/E, TIP4P/2005), its sequence of anomalies follows, the same as Si and Ge, the silica-like hierarchy: the region of dynamic (diffusivity and viscosity) anomalies encloses the region of structural anomalies, which in turn encloses the region of density anomaly. The hierarchy of the anomalies based on excess entropy and Rosenfeld scaling, on the other hand, reverses the order of the structural and dynamic anomalies, i.e., predicts that the three Stillinger-Weber liquids follow a water-like hierarchy of anomalies. We investigate the scaling of diffusivity, viscosity, and thermal conductivity with the excess entropy of the liquid and find that for dynamical properties that present anomalies there is no universal scaling of the reduced property with excess entropy for the whole range of temperatures and densities. Instead, Rosenfeld’s scaling holds for all the three liquids at high densities and high temperatures, although deviations from simple exponential dependence are observed for diffusivity and viscosity at lower temperatures and intermediate densities. The slope of the scaling of transport properties obtained for Ge is comparable to that obtained for simple liquids, suggesting that this low tetrahedrality liquid, although it stabilizes a diamond crystal, is already close to simple liquid behavior for certain properties.
Theoretical study of the buffer-gas cooling and trapping of CrH(X6Σ+) by 3He atoms
Authors: Kłos Jacek , Hapka Michał , Chałasiński Grzegorz , Halvick Philippe , Stoecklin Thierry
Published: December 2016

We present a theoretical study of the Zeeman relaxation of the magnetically trappable lowest field seeking state of CrH(X6Σ+) in collisions with 3He. A two dimensional potential energy surface (PES) was calculated with the partially spin-restricted coupled cluster singles, doubles, and non-iterative triples [RCCSD(T)] method. The global minimum was found for the collinear He⋯Cr–H geometry with the well depth of 1143.84 cm−1 at Re = 4.15 a0. Since the RCCSD(T) calculations revealed a multireference character in the region of the global minimum, we performed additional calculations with the internally contracted multireference configuration interaction with the Davidson correction (ic-MRCISD+Q) method. The resulting PES is similar to the RCCSD(T) PES except for the region of the global minimum, where the well depth is 3032 cm−1 at Re = 3.8 a0. An insight into the character of the complex was gained by means of symmetry-adapted perturbation theory based on unrestricted Kohn-Sham description of the monomers. Close coupling calculations of the Zeeman relaxation show that although the ΔMJ=MJ′−MJ = −1 and −2 transitions are the dominant contributions to the collisional Zeeman relaxation, ΔMJ<−2 transitions cannot be neglected due to the large value of CrH spin-spin constant. The calculated elastic to inelastic cross section ratio is 1600 for the RCCSD(T) PES and 500 for the MRCISD+Q PES, while the estimate from the buffer-gas cooling and magnetic trapping experiment is 9000.
Vibrational spectroscopy and dynamics of W(CO)6 in solid methane as a probe of lattice properties
Authors: Thon Raphael , Chin Wutharath , Chamma Didier , Galaup Jean-Pierre , Ouvrard Aimeric , Bourguignon Bernard , Crépin Claudine
Published: December 2016

Methane solids present more than one accessible crystalline phase at low temperature at zero pressure. We trap W(CO)6 in CH4 and CD4 matrices between 8 and 35 K to probe the interaction between an impurity and its surrounding molecular solid under various physical conditions. Linear and nonlinear vibrational spectroscopies of W(CO)6 highlight different kinds of interaction and reveal new and remarkable signatures of the phase transition of methane. The structures in the absorption band of the antisymmetric CO stretching mode exhibit a clear modification at the transition between phase II and phase I in CH4 and motional narrowing is observed upon temperature increase. The vibrational dynamics of this mode is probed in stimulated photon echo experiments performed with a femtosecond IR laser. A short component around 10 ps is detected in the population relaxation lifetime in the high temperature phase of solid CH4 (phase I) and disappears at lower temperatures (phase II) where the vibrational lifetime is in the hundreds of ps. The analysis of the nonlinear time-resolved results suggests that the short component comes from a fast energy transfer between the vibrational excitation of the guest and the lattice in specific families of sites. Such fast transfers are observed in the case of W(CO)6 trapped in CD4 because of an energy overlap of the excitation of W(CO)6 and a lattice vibron. In solid CH4, even when these V-V transfers are not efficient, pure dephasing processes due to the molecular nature of the host occur: they are temperature dependent without a clear modification at the phase transition.
In search of discrete symmetry violations beyond the standard model: Thorium monoxide reloaded
Authors: Denis Malika , Fleig Timo
Published: December 2016

We present an updated electron electric dipole moment (EDM) effective electric field of Eeff= 75.2 GV/cm and 229Th magnetic hyperfine interaction constant A|| = −1266 MHz, the nucleon-electron scalar-pseudoscalar interaction constant WS = 106.0 kHz, and the molecule-frame static electric dipole moment D = −4.41 D for the Δ13 science state of ThO. The criticisms of the results from Fleig and Nayak [J. Mol. Spectrosc. 300, 16 (2014)] made in Skripnikov and Titov [J. Chem. Phys. 142, 024301 (2015)] are addressed and largely found to be unsubstantiated within the framework of the present approach. The present findings confirm the slightly relaxed constraints on relevant beyond-standard-model parameters, in particular the electron EDM, de, and the nucleon-electron scalar-pseudoscalar coupling constant, CS.
Boundary homogenization for a sphere with an absorbing cap of arbitrary size
Authors: Dagdug Leonardo , Vázquez Marco-Vinicio , Berezhkovskii Alexander M. , Zitserman Vladimir Yu.
Published: December 2016

This paper focuses on trapping of diffusing particles by a sphere with an absorbing cap of arbitrary size on the otherwise reflecting surface. We approach the problem using boundary homogenization which is an approximate replacement of non-uniform boundary conditions on the surface of the sphere by an effective uniform boundary condition with appropriately chosen effective trapping rate. One of the main results of our analysis is an expression for the effective trapping rate as a function of the surface fraction occupied by the absorbing cap. As the cap surface fraction increases from zero to unity, the effective trapping rate increases from that for a small absorbing disk on the otherwise reflecting sphere to infinity which corresponds to a perfectly absorbing sphere. The obtained expression for the effective trapping rate is applied to find the rate constant describing trapping of diffusing particles by an absorbing cap on the surface of the sphere. Finally, we find the capacitance of a metal cap of arbitrary size on a dielectric sphere using the relation between the capacitance and the rate constant of the corresponding diffusion-limited reaction. The relative error of our approximate expressions for the rate constant and the capacitance is less than 5% over the entire range of the cap surface fraction from zero to unity.
A surface interaction model for self-assembly of block copolymers under soft confinement
Authors: Song Jun-Qing , Liu Yi-Xin , Zhang Hong-Dong
Published: December 2016

The surface interaction between substrates and block copolymers is one of the most important factors that control the alignment of self-assembled domains under thin film confinement. Most previous studies simply modeled substrates modified by grafting polymers as a hard wall with a specified surface energy, leading to an incomplete understanding of the role of grafted polymers. In this study, we propose a general model of surface interactions where the role of grafted polymers is decomposed into two independent contributions: the surface preference and the surface softness. Based on this model, we perform a numerical analysis of the stability competition between perpendicular and parallel lamellae of symmetric diblock copolymers on substrates modified by homopolymers using self-consistent field theory. The effects of the surface preference and the surface softness on the alignment of lamellar domains are carefully examined. A phase diagram of the alignment in the plane of the surface preference parameter and the surface softness parameter is constructed, which reveals a considerable parameter window for preparing stable perpendicular lamellae even on highly preferential substrates.
Bond dissociation energies of diatomic transition metal selenides: TiSe, ZrSe, HfSe, VSe, NbSe, and TaSe
Authors: Sorensen Jason J. , Persinger Thomas D. , Sevy Andrew , Franchina Jordan A. , Johnson Eric L. , Morse Michael D.
Published: December 2016

Predissociation thresholds have been observed in the resonant two-photon ionization spectra of TiSe, ZrSe, HfSe, VSe, NbSe, and TaSe. It is argued that the sharp onset of predissociation corresponds to the bond dissociation energy in each of these molecules due to their high density of states as the ground separated atom limit is approached. The bond dissociation energies obtained are D0(TiSe) = 3.998(6) eV, D0(ZrSe) = 4.902(3) eV, D0(HfSe) = 5.154(4) eV, D0(VSe) = 3.884(3) eV, D0(NbSe) = 4.834(3) eV, and D0(TaSe) = 4.705(3) eV. Using these dissociation energies, the enthalpies of formation were found to be Δf,0KHo(TiSe(g)) = 320.6 ± 16.8 kJ mol−1, Δf,0KHo(ZrSe(g)) = 371.1 ± 8.5 kJ mol−1, Δf,0KHo(HfSe(g)) = 356.1 ± 6.5 kJ mol−1, Δf,0KHo(VSe(g)) = 372.9 ± 8.1 kJ mol−1, Δf,0KHo(NbSe(g)) = 498.9 ± 8.1 kJ mol−1, and Δf,0KHo(TaSe(g)) = 562.9 ± 1.5 kJ mol−1. Comparisons are made to previous work, when available. Also reported are calculated ground state electronic configurations and terms, dipole moments, vibrational frequencies, bond lengths, and bond dissociation energies for each molecule. A strong correlation of the measured bond dissociation energy with the radial expectation value, ⟨r⟩nd, for the metal atom is found.
Ice formation on kaolinite: Insights from molecular dynamics simulations
Authors: Sosso Gabriele C. , Tribello Gareth A. , Zen Andrea , Pedevilla Philipp , Michaelides Angelos
Published: December 2016

The formation of ice affects many aspects of our everyday life as well as important technologies such as cryotherapy and cryopreservation. Foreign substances almost always aid water freezing through heterogeneous ice nucleation, but the molecular details of this process remain largely unknown. In fact, insight into the microscopic mechanism of ice formation on different substrates is difficult to obtain even if state-of-the-art experimental techniques are used. At the same time, atomistic simulations of heterogeneous ice nucleation frequently face extraordinary challenges due to the complexity of the water-substrate interaction and the long time scales that characterize nucleation events. Here, we have investigated several aspects of molecular dynamics simulations of heterogeneous ice nucleation considering as a prototypical ice nucleating material the clay mineral kaolinite, which is of relevance in atmospheric science. We show via seeded molecular dynamics simulations that ice nucleation on the hydroxylated (001) face of kaolinite proceeds exclusively via the formation of the hexagonal ice polytype. The critical nucleus size is two times smaller than that obtained for homogeneous nucleation at the same supercooling. Previous findings suggested that the flexibility of the kaolinite surface can alter the time scale for ice nucleation within molecular dynamics simulations. However, we here demonstrate that equally flexible (or non flexible) kaolinite surfaces can lead to very different outcomes in terms of ice formation, according to whether or not the surface relaxation of the clay is taken into account. We show that very small structural changes upon relaxation dramatically alter the ability of kaolinite to provide a template for the formation of a hexagonal overlayer of water molecules at the water-kaolinite interface, and that this relaxation therefore determines the nucleation ability of this mineral.
Limits for the graphene on ferroelectric domain wall p-n-junction rectifier for different regimes of current
Authors: Strikha Maksym V. , Morozovska Anna N.
Published: December 2016

Here, we present the theory of the conductivity of a pn junction (pnJ) in a graphene channel, placed on a ferroelectric substrate, caused by the ferroelectric domain wall for the case of the arbitrary current regime: from ballistic to diffusive one. We calculated the ratio of the pnJ conductions for opposite polarities of voltages, applied to source and drain electrodes of the channel, G+total/G−total, as a function of graphene channel length L, electron mean free path λ, and ferroelectric substrate permittivity ε33f. We have demonstrated that the small values of G+total/G−total (0.1 and smaller), which correspond to the efficient graphene pnJ based rectifier, can be obtained for the ferroelectrics with high ε33f≫100 and for the ratios of L/λ ∼ 1 or smaller. However, for ferroelectrics with extremely high ε33f (relaxor or PbZrxTi1−xO3 with the composition x near the morphotropic phase boundary x = 0.52), the ratio G+total/G−total can be essentially smaller than unity for the case of a pronounced diffusive regime of current as well. This makes the ferroelectric substrates with high permittivity excellent candidates for the fabrication of new generation of rectifiers based on the graphene pnJ. The temperature effect on the G+total/G−total ratio was studied within the Landau-Ginzburg-Devonshire approach. We have demonstrated that the rectifying properties of the graphene pnJ become better in the vicinity of Curie temperature. However, for the temperatures higher than the Curie temperature, the rectifying effect vanishes due to the ferroelectric polarization disappearance.
Terahertz radiation generation and shape control by interaction of array Gaussian laser beams with plasma
Authors: Bakhtiari Farhad , Golmohammady Shole , Yousefi Masoud , Ghafary Bijan
Published: December 2016

In the present paper, a scheme for generation of terahertz (THz) radiation in electron-neutral collisional plasma based on beating of two Gaussian laser array beams has been proposed. It is shown that the efficiency of THz radiation based on the Gaussian laser array beams can be enhanced drastically in comparison with the efficiency of THz radiation based on the Gaussian one. Furthermore, the producing THz radiation by the Gaussian laser array beams, which has an exclusive field profile, is affected by some array structure parameters. It can also be used to overcome the negative consequences of electron neutral collisions in plasma, which may be occurring in the THz radiation generation process. Optimizing the collisional plasma, laser beams and array structure parameters, THz radiation efficiency up to 0.07% can be obtained in our scheme which is about three times greater than the maximum efficiency obtained for standard (single) Gaussian laser beam. Also, considering the electrostatic energy channel in solving the THz wave equation, and reduction of THz radiation efficiency to 0.054%, in this assumption, the ratio between the efficiency of Gaussian laser array beams and standard Gaussian laser beam remained unchanged.
Charge transfer at organic-inorganic interfaces—Indoline layers on semiconductor substrates
Authors: Meyenburg I. , Falgenhauer J. , Rosemann N. W. , Chatterjee S. , Schlettwein D. , Heimbrodt W.
Published: December 2016

We studied the electron transfer from excitons in adsorbed indoline dye layers across the organic-inorganic interface. The hybrids consist of indoline derivatives on the one hand and different inorganic substrates (TiO2, ZnO, SiO2(0001), fused silica) on the other. We reveal the electron transfer times from excitons in dye layers to the organic-inorganic interface by analyzing the photoluminescence transients of the dye layers after femtosecond excitation and applying kinetic model calculations. A correlation between the transfer times and four parameters have been found: (i) the number of anchoring groups, (ii) the distance between the dye and the organic-inorganic interface, which was varied by the alkyl-chain lengths between the carboxylate anchoring group and the dye, (iii) the thickness of the adsorbed dye layer, and (iv) the level alignment between the excited dye (π*-level) and the conduction band minimum of the inorganic semiconductor.
Crystal structure and phase transition behavior in (K1−xNax)NbO3-based lead-free piezoelectric ceramic over a wide range of temperatures
Authors: Yamada H. , Matsuoka T. , Kozuka H. , Yamazaki M. , Ohbayashi K. , Ida T.
Published: December 2016

The phase transition temperature in a (K, Na)NbO3 (KNN) phase of a KNN-based composite lead-free piezoelectric ceramic with a KTiNbO5 system ((K1−xNax)0.86Ca0.04Li0.02Nb0.85O3−δ–K0.85Ti0.85Nb1.15O5–BaZrO3–Co3O4–Fe2O3–ZnO) is lower than that in an undoped KNN ceramic by approximately 200 °C. We have studied the structural changes around the phase transition by using synchrotron powder X-ray diffraction and transmission electron microscopy. The crystal system of the main KNN phase is assigned to tetragonal as a stable structure at room temperature and does not change to orthorhombic on lowering the temperature all at once. The crystal structure changes from tetragonal to orthorhombic through the successive transition state. The curve of the phase transition temperature from x = 0.33 to 0.75 has a V shape and reaches its lowest value of approximately 0 °C in the vicinity of x = 0.56. From selected-area electron diffraction patterns of the KNN phase, weak superlattice spots owing to the tilt-ordered NbO6 octahedra are observed for x ≥ 0.56. This tilt-ordered NbO6 octahedral phase is formed at the nanometer-scale (nanodomains) in the tetragonal and orthorhombic KNN matrices, regardless of the phase transition. The minimum x to generate the nanodomains is substantially equal to the Na fraction at which the starting temperature of the successive phase transition shifts to the lowest.
Polarization states and dielectric responses of elastically clamped ferroelectric nanocrystals
Authors: Azovtsev A. V. , Pertsev N. A.
Published: December 2016

Polarization states and physical properties of ferroelectrics depend on the mechanical boundary conditions due to electrostrictive coupling between electric polarization and lattice strains. Here, we describe theoretically both equilibrium thermodynamic states and electric permittivities of ferroelectric nanocrystals subjected to the elastic three-dimensional (3D) clamping by a surrounding dielectric material. The problem is solved by the minimization of a special thermodynamic potential that describes the case of an ellipsoidal ferroelectric inclusion embedded into a linear elastic matrix. Numerical calculations are performed for BaTiO3, PbTiO3, and Pb(Zr0.5Ti0.5)O3 nanoparticles surrounded by silica glass. It is shown that, in the case of BaTiO3 and PbTiO3, elastic 3D clamping may change the order of a ferroelectric phase transition from first to second. Furthermore, the mechanical inclusion–matrix interaction shifts the temperatures of structural transitions between different ferroelectric states and even eliminates some ferroelectric phases existing in stress-free BaTiO3 and Pb(Zr0.5Ti0.5)O3 crystals. Another important effect of elastic clamping is the lowering of the symmetry of ferroelectric states in ellipsoidal inclusions, where orthorhombic and monoclinic phases may form instead of the tetragonal and rhombohedral bulk counterparts. Finally, our thermodynamic calculations show that the dielectric responses of studied perovskite ferroelectrics are sensitive to matrix-induced clamping as well. For instance, dielectric peaks occurring at structural transitions between different ferroelectric phases in BaTiO3 appear to be much higher in spherical inclusions than in the freestanding crystal. Predicted clamping-induced enhancement of certain dielectric responses at room temperature indicates that composite materials comprising nanocrystals of perovskite ferroelectrics are promising for device applications requiring the use of high-permittivity dielectrics.
Interaction of xenon clusters with intense sub-cycle laser pulses
Authors: Venkat Prachi , Holkundkar Amol R.
Published: December 2016

In this work, we have studied the interaction dynamics of the intense sub-cycle laser with the Xe2600 (Xenon) cluster by using a molecular dynamic code. The code is benchmarked against a couple of experimental works on Xe clusters. In the sub-cycle regime, the plane wave prescription of the laser pulse is not adequate, giving unrealistic field profiles, and hence in this study, we have relied on complex-source based sub-cycle pulsed beam model, which is an exact solution of Maxwell's equations. In order to see the effect of the sub-cycle pulses, the laser pulse duration is varied from 0.2 to 1 laser cycle while keeping the pulse energy conserved (by varying the peak amplitude with pulse duration). It has been observed that for the same laser energy the more energetic ions are obtained for sub-cycle pulses. Although the cluster explosion is symmetric, higher charge states are observed along the direction of laser polarization. The conversion efficiency of the energy absorbed per atom to average kinetic energy is found to be maximum for the shortest pulse duration of 0.2 laser cycle. The scaling law for maximum ion energy, total energy absorbed, and average kinetic energy of the ions with laser pulse duration is also deduced.
The study of ambipolar behavior in phosphorene field-effect transistors
Authors: Guo Cheng , Wang Lin , Xing Huaizhong , Chen Xiaoshuang
Published: December 2016

The electrical characteristics of phosphorene field effect transistors (FETs) were investigated with the two-dimensional (2D) numerical simulation. In this study, it is found that the Schottky barrier plays an important role in the ambipolar transfer characteristics of phosphorene-based FETs. It is demonstrated that when the barrier heights are equal between electron and hole doping, the ambipolar current output dominates across the whole bias range. In the meantime, the saturation leakage current output of the transfer characteristic is only determined by the number of phosphorene layers or the bandgap rather than the Schottky barrier height between phosphorene and metal contact. The ambipolar behaviors become more pronounced as the channel lengths of transistors are decreased, all the geometric and material parameters are taken into account to improve the ambipolar output and understanding its underlying mechanisms. The presented results open the path to design phosphorene-based logic device, photo detector with low dark current for both electronic and optoelectronic applications.
Wavelength and composition dependence of the thermo-optic coefficient for InGaAsP-based integrated waveguides
Authors: Melati Daniele , Waqas Abi , Alippi Andrea , Melloni Andrea
Published: December 2016

A method to take into account the wavelength, composition, and temperature dependencies in the calculation of the refractive index and linear thermo-optic coefficient of In1−xGaxAsyP1−y alloys is presented. The method, based on the modified single oscillator model, shows a good agreement with experimental data for InP reported in literature at different wavelength and temperature ranges. Further, we exploit this approach with a Film-Mode Matching solver to calculate the linear thermo-optic coefficients of both phase and group effective indices of an InGaAsP-based waveguide. The same waveguide structure is also experimentally investigated through a reflectometric technique and results are found to be in accordance with the simulations performed exploiting the proposed method. In both cases, a dependence of the group index on temperature, almost twice that of the phase index, is observed. These results provide a deeper understanding on the influence of the temperature on the behaviour of optical waveguides and devices, making possible an accurate and realistic modelling of integrated circuits.
Probing the effect of point defects on the leakage blocking capability of Al0.1Ga0.9N/Si structures using a monoenergetic positron beam
Authors: Uedono Akira , Zhao Ming , Simoen Eddy
Published: December 2016

Vacancy-type defects in Al0.1Ga0.9N were probed using a monoenergetic positron beam. Al0.1Ga0.9N layers with different carbon doping concentrations ([C] = 5 × 1017−8 × 1019 cm−3) were grown on Si substrates by metalorganic vapor phase epitaxy. The major defect species in Al0.1Ga0.9N was determined to be a cation vacancy (or cation vacancies) coupled with nitrogen vacancies and/or with carbon atoms at nitrogen sites (CNs). The charge state of the vacancies was positive because of the electron transfer from the defects to CN-related acceptors. The defect charge state was changed from positive to neutral when the sample was illuminated with photon energy above 1.8 eV, and this energy range agreed with the yellow and blue luminescence. For the sample with high [C], the charge transition of the vacancies under illumination was found to be suppressed, which was attributed to the trapping of emitted electrons by CN-related acceptors. With increasing [C], the breakdown voltage under the reverse bias condition increased. This was explained by the trapping of the injected electrons by the positively charged vacancies and CN-related acceptors.
Mechanism of stabilization and magnetization of impurity-doped zigzag graphene nanoribbons
Authors: Uchida Yuuki , Gomi Shun-ichi , Matsuyama Haruyuki , Akaishi Akira , Nakamura Jun
Published: December 2016

Doping is an efficient way to modify the electronic structure of graphene. Although there have been a considerable number of studies on the electronic structure of impurity-doped graphene, every study has suggested a different interpretation of the appearance of impurity levels of dopants located near the so-called zigzag edge of graphene nanoribbons (GNRs). Here, we propose a charge transfer model that satisfactorily explains the change in electronic structure upon N(B) doping of zigzag GNR (ZGNR). The structural stability and electronic structure of the doped ZGNR have been investigated using first-principles calculations based on the density functional theory. The formation energy of doping increases as a function of the distance between the N(B) atom and the zigzag edge, and two tendencies are observed depending on whether the dopant is an odd or even number of sites away from the zigzag edge. Such peculiar behavior of the formation energy can be successfully explained by charge transfer between the so-called edge state localized at the edge and the 2p-state of the dopant. Such an electron (hole) transfer leads to the compensation (disappearance) of the local spin-magnetic moment at one side of the ZGNR, manifesting in the ferromagnetic ground state of ZGNR.