bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain-induced electronic properties of van der Waals heterostructures based on tin dichalcogenides
Authors: Tong Xianyu , Fang Liang , Liu Rulin
Published: May 2019

As a newly emerged form of two-dimensional material, tin dichalcogenides have attracted considerable interest, and building van der Waals (vdW) heterostructures based on them could open up new applications. Here, six vdW heterostructures based on SnS2 and SnSe2 are investigated via first-principle calculations. Except for graphene/SnS2(SnSe2), which behaves as a metal, the other heterostructures including HfS2/SnS2(SnSe2) and ZrS2/SnS2(SnSe2) all behave as a semiconductor. Furthermore, particular attention is paid to the tunable electronic properties of the semiconductor heterolayers under differing in-plane biaxial strain. It is found that both tensile and compressive strain can effectively modulate the band structures and carrier effective mass. The strain changes the band gaps of the semiconductor heterostructures considerably, ultimately causing either a semiconductor-to-metal transition or a variation in the band edge. Analyzing the projected density of states and charge density difference shows that these changes are due mainly to the shifts in energy states and interlayer charge transfer of the vdW heterostructures. The present study suggests that vdW heterostructures based on tin dichalcogenides are viable candidates for nanoscale electronic and optoelectronic applications.
Recent progress of study on optical solitons in fiber lasers
Authors: Song Yufeng , Shi Xujie , Wu Chengfa , Tang Dingyuan , Zhang Han
Published: May 2019

Solitons are stable localized wave packets that can propagate long distance in dispersive media without changing their shapes. As particle-like nonlinear localized waves, solitons have been investigated in different physical systems. Owing to potential applications in optical communication and optical signal processing systems, optical solitons have attracted intense interest in the past three decades. To experimentally study the formation and dynamics of temporal optical solitons, fiber lasers are considered as a wonderful nonlinear system. During the last decade, several kinds of theoretically predicted solitons were observed experimentally in fiber lasers. In this review, we present a detailed overview of the experimentally verified optical solitons in fiber lasers, including bright solitons, dark solitons, vector solitons, dissipative solitons, dispersion-managed solitons, polarization domain wall solitons, and so on. An outlook for the development on the solitons in fiber lasers is also provided and discussed.
On the transport of particles/cells in high-throughput deterministic lateral displacement devices: Implications for circulating tumor cell separation
Authors: Aghilinejad Arian , Aghaamoo Mohammad , Chen Xiaolin
Published: May 2019

Deterministic lateral displacement (DLD), which takes advantage of the asymmetric bifurcation of laminar flow around the embedded microposts, has shown promising capabilities in separating cells and particles of different sizes. Growing interest in utilizing high-throughput DLD devices for practical applications, such as circulating tumor cell separation, necessitates employing higher flow rates in these devices, leading to operating in moderate to high Reynolds number (Re) regimes. Despite extensive research on DLD devices in the creeping regime, limited research has focused on the physics of flow, critical size of the device, and deformable cell behavior in DLD devices at moderate to high Re. In this study, the transport behavior of particles/cells is investigated in realistic high-throughput DLD devices with hundreds of microposts by utilizing multiphysics modeling. A practical formula is proposed for the prediction of the device critical size, which could serve as a design guideline for high-throughput DLD devices. Then, the complex hydrodynamic interactions between a deformable cell and DLD post arrays are investigated. A dimensionless index is utilized for comparing different post designs to quantify the cell–post interaction. It is shown that the separation performances in high-throughput devices are highly affected by Re as well as the micropost shapes. These findings can be utilized for the design and optimization of high-throughput DLD microfluidic devices.
Fabrication and non-destructive characterization of tapered single-ring hollow-core photonic crystal fiber
Authors: Pennetta Riccardo , Enders Michael T. , Frosz Michael H. , Tani Francesco , Russell Philip St.J.
Published: May 2019

We report on the properties of tapered single-ring hollow-core photonic-crystal fibers, with a particular emphasis on applications in nonlinear optics. The simplicity of these structures allows the use of non-invasive side-illumination to assess the quality of the tapering process, by observing the scattered far-field spectrum originating from excitation of whispering-gallery modes in the cladding capillaries. We investigate the conditions that ensure adiabatic propagation in the up- and down-tapers, and the scaling of loss-bands (created by anti-crossings between the core mode and modes in the capillary walls) with taper ratio. We also present an analytical model for the pressure profile along a tapered hollow fiber under differential pumping.
Using Pauli energy to appraise the quality of approximate semilocal non-interacting kinetic energy density functionals
Authors: Liu Siyuan , Zhao Dongbo , Rong Chunying , Lu Tian , Liu Shubin
Published: May 2019

It is well-known that the kinetic energy density (KED) functional is the most difficult to approximate in density functional theory (DFT), yet to take full advantage of DFT with its density-based descriptive capability of molecular properties, an accurate account of KED is a must. To have a better idea of how an approximate KED formula behaves and where we should focus in the future development of better approximate KEDs, in this work we propose to employ the Pauli energy to assess their quality. We tested the performance of a total of 22 approximate semilocal noninteracting KED functionals from the literature for 18 neutral atoms and 20 small molecules. We found that generalized gradient approximation formulas of the KED functional can often reasonably accurately predict the total kinetic energy value for atoms and molecules but failed miserably to forecast the integrated values for Pauli energy related properties. The reason behind this is that presently available approximate KED functionals are unable to accurately account for the kinetic energy distribution in the medium range away from nuclei, where the Pauli energy plays a crucial role. Our results strongly suggest that the key information missing in approximate KED functionals comes from the medium regions, not nuclear cusps nor asymptotic areas, and the Pauli energy is a reliable measure of the quality of approximate KED functionals. Future efforts in developing better KED approximations should be invested in the regions of molecules where chemical bonds are formed in order to accurately account for the Pauli energy.
Detailed description of pulse isotopic exchange method for analyzing oxygen surface exchange behavior on oxide ion conductors
Authors: Song Chun-lin , Yi Jian-xin , Yan Yan
Published: May 2019

A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an 18O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of 18O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate 18O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues 18O2, 16O18O, and 16O2 in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350-900 ° C. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La2NiO4+δ the reaction is limited by the apparent rate of dissociative adsorption of O2 molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ~800 ° C to rate-limitations by O2 dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.
Numerical convergence of the Sinc discrete variable representation for solving molecular vibrational states with a conical intersection in adiabatic representation
Authors: Shi Hai-mei , Guo Guang-hai , Sun Zhi-gang
Published: May 2019

Within the Born-Oppenheimer (BO) approximation, nuclear motions of a molecule are often envisioned to occur on an adiabatic potential energy surface (PES). However, this single PES picture should be reconsidered if a conical intersection (CI) is present, although the energy is well below the CI. The presence of the CI results in two additional terms in the nuclear Hamiltonian in the adiabatic presentation, i.e., the diagonal BO correction (DBOC) and the geometric phase (GP), which are divergent at the CI. At the same time, there are cusps in the adiabatic PESs. Thus usually it is regarded that there is numerical difficulty in a quantum dynamics calculation for treating CI in the adiabatic representation. A popular numerical method in nuclear quantum dynamics calculations is the Sinc discrete variable representation (DVR) method. We examine the numerical accuracy of the Sinc DVR method for solving the Schrödinger equation of a two dimensional model of two electronic states with a CI in both the adiabatic and diabatic representation. The results suggest that the Sinc DVR method is capable of giving reliable results in the adiabatic representation with usual density of the grid points, without special treatment of the divergence of the DBOC and the GP. The numerical uncertainty is not worse than that after the introduction of an arbitrary vector potential for accounting the GP, whose accurate form usually is not easy to obtain.
Effects of fish kills on fish consumers and other water-dependent fauna: exploring the potential effect of mass mortality of carp in Australia
Authors: McGinness Heather M. , Paton Alexandra , Gawne Ben , King Alison J. , Kopf R. Keller , Mac Nally Ralph , McInerney Paul J.
Published: May 2019

Although the effects of mass fish mortality (MFM) events on fish populations and water quality are frequently reported, the effects on consumers of fish and other water-dependent fauna are relatively poorly understood. Managing the effects of MFM events on other fauna is important when they occur in ecologically or culturally sensitive locations, or involve protected or significant species or ecosystems. Better understanding of the effects of such events on fish consumers and other water-dependent fauna would aid proactive management of predictable events, such as pest-fish biocontrol releases. We conducted a global literature review to synthesise the effects of unexpected MFM events on fish consumers and other water-dependent fauna in freshwater, estuarine and marine ecosystems. We then constructed two conceptual models distinguishing between the short-term (hours to weeks) and long-term (months to years) effects of such events, highlighting the importance of key factors in determining the magnitude of the response. Last, we used these models and relevant literature to explore the potential implications of the proposed release of cyprinid herpes virus 3 as a biological control agent for the invasive common carp (Cyprinus carpio) in Australia and develop recommendations to minimise adverse effects of carp mass mortality on food webs.
Genomic divergence and adaptive convergence in
Drosophila simulans
from Evolution Canyon, Israel
Authors: Kang Lin , Rashkovetsky Eugenia , Michalak Katarzyna , Garner Harold R. , Mahaney James E. , Rzigalinski Beverly A. , Korol Abraham , Nevo Eviatar , Michalak Pawel
Published: May 2019

Biodiversity refugia formed by unique features of the Mediterranean arid landscape, such as the dramatic ecological contrast of “Evolution Canyon,” provide a natural laboratory in which local adaptations to divergent microclimate conditions can be investigated. Significant insights have been provided by studies of
Drosophila melanogaster
diversifying along the thermal gradient in Evolution Canyon, but a comparative framework to survey adaptive convergence across sister species at the site has been lacking. To fill this void, we present an analysis of genomic polymorphism and evolutionary divergence of
Drosophila simulans
, a close relative of
Drosophila melanogaster
with which it co-occurs on both slopes of the canyon. Our results show even deeper interslope divergence in
D. simulans
than in
D. melanogaster
, with extensive signatures of selective sweeps present in flies from both slopes but enhanced in the population from the hotter and drier south-facing slope. Interslope divergence was enriched for genes related to electrochemical balance and transmembrane transport, likely in response to increased selection for dehydration resistance on the hotter slope. Both species shared genomic regions that underwent major selective sweeps, but the overall level of adaptive convergence was low, demonstrating no shortage of alternative genomic solutions to cope with the challenges of the microclimate contrast. Mobile elements were a major source of genetic polymorphism and divergence, affecting all parts of the genome, including coding sequences of mating behavior-related genes.
Coupling of COPII vesicle trafficking to nutrient availability by the IRE1α-XBP1s axis
Authors: Liu Lin , Cai Jie , Wang Huimin , Liang Xijun , Zhou Qian , Ding Chenyun , Zhu Yuangang , Fu Tingting , Guo Qiqi , Xu Zhisheng , Xiao Liwei , Liu Jing , Yin Yujing , Fang Lei , Xue Bin , Wang Yan , Meng Zhuo-Xian , He Aibin , Li Jian-Liang , Liu Yong , Chen Xiao-Wei , Gan Zhenji
Published: May 2019

The cytoplasmic coat protein complex-II (COPII) is evolutionarily conserved machinery that is essential for efficient trafficking of protein and lipid cargos. How the COPII machinery is regulated to meet the metabolic demand in response to alterations of the nutritional state remains largely unexplored, however. Here, we show that dynamic changes of COPII vesicle trafficking parallel the activation of transcription factor X-box binding protein 1 (XBP1s), a critical transcription factor in handling cellular endoplasmic reticulum (ER) stress in both live cells and mouse livers upon physiological fluctuations of nutrient availability. Using live-cell imaging approaches, we demonstrate that XBP1s is sufficient to promote COPII-dependent trafficking, mediating the nutrient stimulatory effects. Chromatin immunoprecipitation (ChIP) coupled with high-throughput DNA sequencing (ChIP-seq) and RNA-sequencing analyses reveal that nutritional signals induce dynamic XBP1s occupancy of promoters of COPII traffic-related genes, thereby driving the COPII-mediated trafficking process. Liver-specific disruption of the inositol-requiring enzyme 1α (IRE1α)–XBP1s signaling branch results in diminished COPII vesicle trafficking. Reactivation of XBP1s in mice lacking hepatic IRE1α restores COPII-mediated lipoprotein secretion and reverses the fatty liver and hypolipidemia phenotypes. Thus, our results demonstrate a previously unappreciated mechanism in the metabolic control of liver protein and lipid trafficking: The IRE1α-XBP1s axis functions as a nutrient-sensing regulatory nexus that integrates nutritional states and the COPII vesicle trafficking.
An activatable PET imaging radioprobe is a dynamic reporter of myeloperoxidase activity in vivo
Authors: Wang Cuihua , Keliher Edmund , Zeller Matthias W. G. , Wojtkiewicz Gregory R. , Aguirre Aaron D. , Buckbinder Leonard , Kim Hye-Yeong , Chen Jianqing , Maresca Kevin , Ahmed Maaz S. , Motlagh Negin Jalali , Nahrendorf Matthias , Chen John W.
Published: May 2019

Significance

The innate immune response mediates tissue damage in many diseases, but available clinical imaging technologies do not distinguish between damaging and beneficial immune responses. We developed and validated a positron emission tomography radioprobe to noninvasively report on the activity of the damaging enzyme myeloperoxidase secreted by proinflammatory innate immune cells. The high sensitivity and specificity of the radioprobe enable the detection of damaging inflammation at an earlier stage than currently possible. Such early detection could lead to early treatment before irreversible damage occurs. With its properties characterized and synthesis automated, this radioprobe is a promising imaging biomarker ready for translation to track many diseases, including cardiovascular, neurological, and rheumatological diseases.
A scarcity mindset alters neural processing underlying consumer decision making
Authors: Huijsmans Inge , Ma Ili , Micheli Leticia , Civai Claudia , Stallen Mirre , Sanfey Alan G.
Published: May 2019

Significance

How poverty impacts decision making is a vitally important societal question. Recent influential theories proposed that altered decision making by the poor might be explained by a “scarcity” mindset. Here, we created an experimental manipulation which allowed us to investigate how consumer decisions and their neural processes are affected by scarcity, while circumventing potential confounds associated with comparing individuals with high and low income. Neuroimaging results suggest that a scarcity mindset affects neural mechanisms underlying goal-directed decision making, and that the effects of scarcity are largest when they are compared with previous situations when resources were abundant. The current findings contribute to a greater understanding of the mechanisms by which limited resources affect decision making.
Reverse engineering field-derived vertical distribution profiles to infer larval swimming behaviors
Authors: James M. K. , Polton J. A. , Brereton A. R. , Howell K. L. , Nimmo-Smith W. A. M. , Knights A. M.
Published: May 2019

Significance

Estimating the dispersal of propagules in terrestrial, freshwater, and marine ecosystems has been of primary research interest for many years, yet efforts to accurately predict dispersal, especially in marine ecosystems, have remained a significant and unresolved challenge. A common approach is to use a biophysical model, but field studies and genetic tools reveal that these models can overestimate dispersal range, often attributed to inaccurate behavioral parameterization. This study reverse engineers a biophysical model in an effort to describe larval behavior. The approach demonstrated, which can be applied to any species with a larval phase, provides a method for assessing in situ larval behavior that negates the need for a mechanistic understanding of behavioral responses to cues.
Improving mechanical properties for pure irons by local surface mechanical attrition treatment
Authors: Wei Yinghui , Cui Huiqi , Wei Huan , Liu Baosheng , Du Huayun , Hou Lifeng
Published: May 2019

After a short-time surface mechanical attrition treatment process, a planar uneven structure was obtained on the surface of irons. The yield strength of the sample subjected to surface mechanical attrition treatment for 60 s is almost twice than that of the annealed sample, but the ductility is still well retained. The good combination of strength and ductility is mainly due to the extra strain hardening and the coexistence of soft and hard phases. The extra strain hardening delays the annihilation of dislocations and reduces the plastic instability, while the hard phase in the planar uneven structure suppresses the crack initiation, and the soft phase delays the crack propagation.
Resistance to change. The problem of high non-take up in implementing policy innovations in the Italian long-term care system
Authors: Ranci Costanzo , Arlotti Marco
Published: May 2019

This article illustrates how the implementation of ‘interstitial’ innovation in welfare policy can be hampered by resistance to change on the part of its intended beneficiaries by means of a case study of a policy innovation in long-term care in Italy: the Home Care Premium (HCP) programme. In a policy area characterised by long-standing institutional inertia, HCP represents an innovative programme which provides a generous, conditional cash-for-care benefit to encourage the regular employment of in-house care assistants. However, the implementation of the scheme was hampered by high non-take up (NTU) rates, i.e. the percentage of beneficiaries who did not claim the cash-for-care benefit for which they were eligible.

The article uses a ‘mixed method’ approach to show how high NTU rates can be explained by individually ‘situated’ decisions taken by the intended beneficiaries based on cost-benefit evaluations that are deeply rooted in social attitudes and adaptive practices shaped by the existing institutional context. The study also shows how the policy design of the programme partially failed to manage the institutional complementarity of different welfare programs effectively, thus weakening the capacity of this ‘interstitial’ policy to bring about policy innovation. The results of the case study may therefore be of interest to scholars interested in policy change and the role played by beneficiaries in policy implementation.

Abbreviations: non-take up (NTU); long-term care (LTC)
Placental extracellular vesicles express active dipeptidyl peptidase IV; levels are increased in gestational diabetes mellitus
Authors: Kandzija Neva , Zhang Wei , Motta‐Mejia Carolina , Mhlomi Vuyane , McGowan‐Downey Jennifer , James Tim , Cerdeira Ana Sofia , Tannetta Dionne , Sargent Ian , Redman Christopher W. , Bastie Claire C. , Vatish Manu
Published: May 2019

Gestational diabetes mellitus (GDM) is the most common metabolic disorder in pregnancy and is characterized by insulin resistance and decreased circulating glucagon‐like peptide‐1 (GLP‐1). GDM resolves rapidly after delivery implicating the placenta in the disease. This study examines the biological functions that cause this pathology. The placenta releases syncytiotrophoblast‐derived extracellular vesicles (STB‐EVs) into the maternal circulation, which is enhanced in GDM. Dipeptidyl peptidase IV (DPPIV) is known to play a role in type 2 diabetes by breaking down GLP‐1, which in turn regulates glucose‐dependent insulin secretion. STB‐EVs from control and GDM women were analysed. We show that normal human placenta releases DPPIV‐positive STB‐EVs and that they are higher in uterine than paired peripheral blood, confirming placental origin. DPPIV‐bound STB‐EVs from normal perfused placentae are dose dependently inhibited with vildagliptin. DPPIV‐bound STB‐EVs from perfused placentae are able to breakdown GLP‐1 in vitro. STB‐EVs from GDM perfused placentae show greater DPPIV activity. Importantly, DPPIV‐bound STB‐EVs increase eightfold in the circulation of women with GDM. This is the first report of STB‐EVs carrying a biologically active molecule that has the potential to regulate maternal insulin secretion.
Molecular determinants for agonist recognition and discrimination in P2X2 receptors
Authors: Gasparri Federica , Wengel Jesper , Grutter Thomas , Pless Stephan A.
Published: May 2019

P2X receptors (P2XRs) are trimeric ligand-gated ion channels that open a cation-selective pore in response to ATP binding. P2XRs contribute to synaptic transmission and are involved in pain and inflammation, thus representing valuable drug targets. Recent crystal structures have confirmed the findings of previous studies with regards to the amino acid chains involved in ligand recognition, but they have also suggested that backbone carbonyl atoms contribute to ATP recognition and discrimination. Here we use a combination of site-directed mutagenesis, amide-to-ester substitutions, and a range of ATP analogues with subtle alterations to either base or sugar component to investigate the contributions of backbone carbonyl atoms toward ligand recognition and discrimination in rat P2X2Rs. Our findings demonstrate that while the Lys69 backbone carbonyl makes an important contribution to ligand recognition, the discrimination between different ligands is mediated by both the side chain and the backbone carbonyl oxygen of Thr184. Together, our data demonstrate how conserved elements in P2X2Rs recognize and discriminate agonists.
Deterministic multi-mode nonlinear coupling for quantum circuits
Authors: Sefi Seckin , Marek Petr , Filip Radim
Published: May 2019

We present a general technique for deterministically implementing a multi-mode nonlinear coupling between several propagating microwave or optical modes in quantum circuits. The measurement induced technique combines specifically prepared resource states together with feasible feed-forward operations. We explore several ways of generating the suitable resource states and discuss their difference on an illustrative example of cubic coupling between two modes. We also show that the required entangled states with requisite nonlinear properties can be already generated in the present day experiments.
Level attraction and level repulsion of magnon coupled with a cavity anti-resonance
Authors: Rao J W , Yu C H , Zhao Y T , Gui Y S , Fan X L , Xue D S , Hu C-M
Published: May 2019

We report on coherent and dissipative coupling between a magnon mode and an anti-resonance of transmission in a cylindrical microwave cavity. By effectively suppressing coherent coupling, we observe the hybridized dispersion to change from level repulsion to level attraction. A careful examination reveals distinct differences in the line shape and phase evolution of transmission spectra between these coupling behaviors. For a quantitative understanding of the interactions between the magnon mode and the cavity anti-resonance, we develop a model which precisely describes our experimental observations, particularly, the signature in the line shape and phase of the microwave transmission. Our work sets a foundation for understanding strong coupling between magnon modes and cavity anti-resonances. In addition, it also confirms the ubiquity of level attraction in coupled magnon-photon systems, which may be helpful to develop future magnon-based hybrid quantum systems.
Biochemical Szilard engines for memory-limited inference
Authors: Brittain Rory A , Jones Nick S , Ouldridge Thomas E
Published: May 2019

By designing and leveraging an explicit molecular realisation of a measurement-and-feedback-powered Szilard engine, we investigate the extraction of work from complex environments by minimal machines with finite capacity for memory and decision-making. Living systems perform inference to exploit complex structure, or correlations, in their environment, but the physical limits and underlying cost/benefit trade-offs involved in doing so remain unclear. To probe these questions, we consider a minimal model for a structured environment—a correlated sequence of molecules—and explore mechanisms based on extended Szilard engines for extracting the work stored in these non-equilibrium correlations. We consider systems limited to a single bit of memory making binary ‘choices’ at each step. We demonstrate that increasingly complex environments allow increasingly sophisticated inference strategies to extract more free energy than simpler alternatives, and argue that optimal design of such machines should also consider the free energy reserves required to ensure robustness against fluctuations due to mistakes.
A New Class of All-Inorganic Perovskite Microplate for Lasing
Authors: Du Juan , Liu Zhengzheng , Leng Yuxin , Hu Zhiping , Tang Xiaosheng , Zhou Miao , Kobayashi Takayoshi
Published: May 2019

We report a stable low-threshold amplified spontaneous emission performance from a new type of all-inorganic perovskite CsPb2Br5 microplate with superior crystallization, enhanced stability, and tunability under both one- and two-photon excitation for the first time.
Dynamics analysis of nanoparticles optically driven by a Laguerre-Gaussian beam with optical spin
Authors: Tamura Mamoru , Omatsu Takashige , Iida Takuya
Published: May 2019

We theoretically discover that the spin angular momentum (SAM) enables to modulate the orbital torque through the inter-particle light-induced force (IP-LIF). Laguerre - Gaussian beam with the orbital angular momentum (OAM) can induce the orbital motion for the optically trapped objects. In addition, the SAM can also accelerate or decelerate the orbital motion due to the IP-LIF. Our discovery provides a new physical aspect, i.e. the IP-LIF plays an important role in the many-body dynamics of nanoparticles via the SAM-OAM coupling.
Photocarrier injection by two-photon excitation in rubrene single crystal
Authors: Goto K , Takayama T , Ohata K , Matsushita K , Akimoto I
Published: May 2019

We performed photocarrier injection by two-photon excitation in rubrene crystal using laser pulses of nanosecond-duration at various wavelengths under an external electric field. Based on the excitation spectra, it is revealed that photocarriers are injected at excitation energies corresponding to the intrinsic absorption by two-photon process, in contrast to the midgap-states-mediated injection by one-photon process. This result means that the two-photon excitation method is useful to inject photocarriers free from the surface traps.
Excitation energy dependence for electron traps in CaTiO3:Pr, Al single crystals
Authors: Nanai Y , Igarashi A , Kamioka H
Published: May 2019

We investigated the red afterglow process of CaTiO3:Pr, Al through photoluminescence and thermoluminescence measurements by using fabricated single crystals. The crystals with several cubic millimeter in size were obtained through a flux method. We found that the afterglow properties varied with the excitation energy. At room temperature, the red afterglow was observed for the charge transfer from Pr3+ to Ti4+ excitation and the direct excitation of Pr3+, while not observed for the interband excitation of CaTiO3 due to the relaxation process going through 4d15d1 state of Pr3+. For the direct excitation of Pr3+ at 80 K, the excited electrons did not reached to trap states for afterglow due to a potential barrier, which can overcome with thermal assistance at room temperature. For the charge transfer excitation at 80 K, the excited electrons could reach the traps with excess energy.
Electronic state of nitrogen in doped titanium dioxide
Authors: Funabiki H , Ozawa K , Sekiya T
Published: May 2019

A yellow N-doped TiO2 powder was prepared by the sol-gel method using titanium tetra-isopropoxide and hydrazine monohydrate. An EPR signal was induced by the irradiation of light with hv ≥ 2.2 eV to the yellow TiO2 powder and the signal intensity gradually decreased in the dark. The EPR signal was due to thermally trapped carriers interacting with the doped N. The thermal activation energy of the trapped carriers was estimated to be 0.22 eV. XPS measurement was performed on the yellow powder as well as colorless and blue N-doped powders obtained by oxidation and reduction, respectively. The N1s bands at 399.5 eV can be assigned to nitrogen adsorbed on the surface. The atomic valence of nitrogen in the colorless, yellow and blue powders was positive, neutral and negative, respectively. The atomic valence of nitrogen in doped TiO2 depends on the oxidation-reduction procedure.
Dynamics of the electric-field induced magnetization in antiferromagnetic chromium oxide observed by Faraday rotation
Authors: Hikita R , Taniguchi H , Shinkai T , Kohmoto T
Published: May 2019

We observed the dynamics of the electric-field induced magnetization in antiferromagnetic chromium oxide (Cr2O3) by the Faraday-rotation measurement using a continuous-wave probe light in the millisecond region and a pulse probe light in the nanosecond region. It was found that the Faraday-rotation amplitude linearly depends on the electric field, decreases with increasing temperature, and disappears above the Néel temperature. In the nanosecond region, nanosecond rise of the electric-field induced Faraday-rotation signal was observed.
Generation processes of superfluorescence of biexcitons in CuCl quantum dots by one- and two-photon resonant excitation
Authors: Kawamura K , Yoshida T , Nasu M , Ishihara J , Ishikawa A , Miyajima K
Published: May 2019

We investigated the influence of excitation processes of a biexciton on the generation of superfluorescence, which is pulsed radiation from coherently coupled two-level systems, from biexcitons in CuCl quantum dots. Two excitation processes of biexcitons were examined: resonant two-photon excitation of biexcitons, and resonant one-photon excitation of excitons. The excitation density dependence of the time-resolved photoluminescence was measured. The results showed that for one-photon excitation, a stronger peak intensity, longer delay time and wider pulse width were observed compared to resonant two-photon excitation. The high density of the excited dots in the one-photon excitation process results in the strong pulse, while an initial population of excitons results in a suppression of coherent coupling.
Temperature-dependent carrier injection routes under optical excitation in high-purity diamond crystals
Authors: Hamabata S , Akimoto I , Naka N
Published: May 2019

We have investigated carrier injection routes in high-purity diamond crystals in a wide temperature range using the time-resolved cyclotron resonance method. By analysing the excitation spectra, we find that carriers are injected under optical excitation above the energy threshold for exciton generation with emission of a transverse acoustic phonon at 10 K and 80 K, whereas with absorption of a transverse optical phonon at 300 K. The excitation power dependence clearly shows that the carriers are generated by thermal dissociation of excitons at 300 K.
Preparation of ZnSe-ZnS alloy quantum dots by a hydrothermal method and their optical properties
Authors: Nishimura Hisaaki , Lin Yuxin , Kunimasa Yuki , Kim DaeGwi
Published: May 2019

We prepared colloidal ZnSe
x
S1−x
alloy quantum dots (QDs) and investigated their optical properties. ZnSe
x
S1−x
QDs were successfully prepared by a hydrothermal method, which was confirmed by the results of X-ray structural analysis. When the alloy composition was decreased from x = 1 to 0, the absorption energy continuously shifted to the high energy side. Band-edge photoluminescence (PL) was the main PL band in ZnSe QDs, whereas only defect - related PL band was observed in ZnS QDs. The band-edge PL was clearly observed as the main PL band for x = 0.52 to 1, which shifted to the high energy side by decreasing x.
Energy relaxation from STE to In+ centers in NaI:In+ crystals
Authors: Watanabe S , Kawai T , Mizoguchi K
Published: May 2019

The energy relaxation from host crystals to impurity centers has been investigated by measuring the absorption and excitation spectra and the temperature dependence of the luminescence spectrum of NaI:In+. In the absorption spectrum, the A, B, and C bands due to the In+ centers are confirmed at 3.8, 4.0, and 4.5 eV, respectively. The excitation spectrum for the AT luminescence due to the In+ centers responds to the energy position of the A, B, and C bands and also the energy region above the exciton transition of NaI. The fact suggests the existence of the energy relaxation from host crystals to the In+ centers. The total intensity of the AT and AX luminescence due to the In+ centers exhibits different temperature dependence between the excitations at the C band and host crystals. Under excitation at the C band, the total intensity of the AT and AX luminescence monotonously declines with increasing temperature from 10 to 300 K. On the other hand, under excitation at host crystals, the total intensity of the AT and AX luminescence exhibits an increase with increasing temperature from 10 to 50 K, and a decrease with increasing temperature from 50 to 100 K. We discuss the temperature dependence of the total intensity of the luminescence under excitation at host crystals in relation to free excitons and self-trapped excitons.
Intermediate band formation by InGaAs/GaAs multistacked quantum dots without strain compensation
Authors: Goshima Keishiro , Inukai Keisuke , Tsuda Norio , Sugaya Takeyoshi
Published: May 2019

Quantum dots (QDs) are widely used for enhancing the performance of optical devices. Intermediate-band solar cells that use multistacked QDs can surpass the conversion efficiency of conventional silicon cells. We performed the optical characterization of In0.4Ga0.6As/GaAs multistacked QDs without strain compensation. We used the theoretical and experimental techniques prescribed for intermediate-band solar cells, i.e., photoluminescence (PL) spectroscopy and two-color excitations spectroscopy. The interdot spacings were not uniform and were found to be 15 nm and 7 nm. The results verify the formation of intermediate bands by the multistacked QDs. Using the theoretical studies and experimental results, we performed an in-depth study on the mechanism underlying the formation of intermediate bands by the multistacked QDs and the effect of different interdot spacings.
Proposed scheme of realization of artificial nano-heterostructures by optical force under double resonance
Authors: Yamada Yuto , Hoshina Masayuki , Yokoyama Tomohiro , Ishihara Hajime
Published: May 2019

We theoretically study a new configuration control of nanoparticles based on an optical force, which enables to trap two kinds of nanoparticles simultaneously in two-dimensional hetero-arrangement. Our proposed scheme utilizes two resonance effects on a localized surface plasmon and an electronic transition of nanoparticles. These resonances change the optical force behavior significantly. We propose periodic rhomboid metallic nanostructures with two linear polarized laser beams, the directions of which polarization are parallel to the two diagonals of rhomboid. The polarization direction fractionates the trapped nanoparticles when the two laser frequencies correspond to the electronic transition energies of two kinds of particles, respectively. We evaluate the feasibility of our proposed scheme numerically. The map of the optical force shows a clear spatial separation of trapping position for the two kinds of particles. Our results demonstrate an essential advantage of the optical manipulation that enables creating novel nanostructures unrealizable by conventional nanofabrication techniques.
Complex-angle analysis of electromagnetic waves on interfaces
Authors: Oue Daigo
Published: May 2019

Electromagnetic wave is reflected and refracted at interfaces, satisfying Fresnel-Snell law which is required by conservations of energy and momentum. If the incident angle is lower than the critical angle, we can use this Fresnel-Snell law, but the Fresnel-Snell law is modified in the case of existence of dissipation (ñ = n + ik,k > 0) or in the condition of total internal reflection. In the cases, we have to extend the angle of refraction from real number to complex number (

θ
→

θ
˜

=
θ
+
i
ψ
,
ψ
≠
0

). In this paper, by using complex-angle approach, we analyse the behaviour of electromagnetic waves in various kind of interfaces: dielectric - dielectric system, dissipative dielectric - dielectric system, and metal - dielectric system. We show that iso-frequency curves in wavenumber space is opened in the case where n, k > 0, and closed either when n → 0 or when k → 0 (’Lifshitz transition’ of electromagnetic waves). Excess momentum (wavevector) and anomalous circular polarisation emerging with the transition are also discussed.
Greenness trends and carbon stocks of mangroves across Mexico
Authors: Vázquez-Lule Alma , Colditz Rene , Herrera-Silveira Jorge , Guevara Mario , Rodríguez-Zúñiga María Teresa , Cruz Isabel , Ressl Rainer , Vargas Rodrigo
Published: May 2019

Mangroves cover less than 0.1% of Earth’s surface, store large amounts of carbon per unit area, but are threatened by global environmental change. The capacity of mangroves productivity could be characterized by their canopy greenness, but this property has not been systematically tested across gradients of mangrove forests and national scales. Here, we analyzed time series of Normalized Difference Vegetation Index (NDVI), mean air temperature and total precipitation between 2001 and 2015 (14 years) to quantify greenness and climate variability trends for mangroves not directly influenced by land use/land cover change across Mexico. Between 2001 and 2015 persistent mangrove forests covered 432 800 ha, representing 57% of the total current mangrove area for Mexico. We found a temporal greenness increase between 0.003[0.001–0.004] and 0.004[0.002–0.005] yr−1 (NDVI values ± 95%CI) for mangroves located over the Gulf of California and the Pacific Coast, with many mangrove areas dominated by Avicennia germinans. Mangroves developed along the Gulf of Mexico and Caribbean Sea did not show significant greenness trends, but site-specific areas showed significant negative greenness trends. Mangroves with surface water input have above ground carbon stocks (AGC) between 37.7 and 221.9 Mg C ha−1 and soil organic carbon density at 30 cm depth (SOCD) between 92.4 and 127.3 Mg C ha−1. Mangroves with groundwater water input have AGC of 12.7 Mg C ha−1 and SOCD of 219 Mg C ha−1. Greenness and climate variability trends could not explain the spatial variability in carbon stocks for most mangrove forests across Mexico. Site-specific characteristics, including mangrove species dominance could have a major influence on greenness trends. Our findings provide a baseline for national-level monitoring programs, carbon accounting models, and insights for greenness trends that could be tested around the world.
Variation in seed longevity among diverse Indica rice varieties
Authors: Lee Jae-Sung , Velasco-Punzalan Marlina , Pacleb Myrish , Valdez Rocel , Kretzschmar Tobias , McNally Kenneth L , Ismail Abdel M , Cruz Pompe C Sta , Sackville Hamilton N Ruaraidh , Hay Fiona R
Published: May 2019

Background and Aims

Understanding variation in seed longevity, especially within closely related germplasm, will lead to better understanding of the molecular basis of this trait, which is particularly important for seed genebanks, but is also relevant to anyone handling seeds. We therefore set out to determine the relative seed longevity of diverse Indica rice accessions through storage experiments. Since antioxidants are purported to play a role in seed storability, the antioxidant activity and phenolic content of caryopses were determined.

Methods

Seeds of 299 Indica rice accessions harvested at 31, 38 and 45 d after heading (DAH) between March and May 2015 and differing in harvest moisture content (MC) were subsequently stored at 10.9 % MC and 45 °C. Samples were taken at regular intervals and sown for germination. Germination data were subjected to probit analysis and the resulting parameters that describe the loss of viability during storage were used for genome-wide association (GWA) analysis.

Key Results

The seed longevity parameters, Ki [initial viability in normal equivalent deviates (NED)], −σ−1 (σ is the time for viability to fall by 1 NED in experimental storage) and p50 [time for viability to fall to 50 % (0 NED)], varied considerably across the 299 Indica accessions. Seed longevity tended to increase as harvest MC decreased and to decrease as harvest MC increased. Eight major loci associated with seed longevity parameters were identified through GWA analysis. The favourable haplotypes on chromosomes 1, 3, 4, 9 and 11 enhanced p50 by ratios of 0.22–1.86.

Conclusions

This is the first study to describe the extent of variation in σ within a species’ variety group. A priori candidate genes selected based on rice genome annotation and gene network ontology databases suggested that the mechanisms conferring high seed longevity might be related to DNA repair and transcription, sugar metabolism, reactive oxygen species scavenging and embryonic/root development.
Are model organisms representative for climate change research? Testing thermal tolerance in wild and laboratory zebrafish populations
Authors: Morgan Rachael , Sundin Josefin , Finnøen Mette H , Dresler Gunnar , Vendrell Marc Martínez , Dey Arpita , Sarkar Kripan , Jutfelt Fredrik
Published: May 2019

Model organisms can be useful for studying climate change impacts, but it is unclear whether domestication to laboratory conditions has altered their thermal tolerance and therefore how representative of wild populations they are. Zebrafish in the wild live in fluctuating thermal environments that potentially reach harmful temperatures. In the laboratory, zebrafish have gone through four decades of domestication and adaptation to stable optimal temperatures with few thermal extremes. If maintaining thermal tolerance is costly or if genetic traits promoting laboratory fitness at optimal temperature differ from genetic traits for high thermal tolerance, the thermal tolerance of laboratory zebrafish could be hypothesized to be lower than that of wild zebrafish. Furthermore, very little is known about the thermal environment of wild zebrafish and how close to their thermal limits they live. Here, we compared the acute upper thermal tolerance (critical thermal maxima; CTmax) of wild zebrafish measured on-site in West Bengal, India, to zebrafish at three laboratory acclimation/domestication levels: wild-caught, F1 generation wild-caught and domesticated laboratory AB-WT line. We found that in the wild, CTmax increased with increasing site temperature. Yet at the warmest site, zebrafish lived very close to their thermal limit, suggesting that they may currently encounter lethal temperatures. In the laboratory, acclimation temperature appeared to have a stronger effect on CTmax than it did in the wild. The fish in the wild also had a 0.85–1.01°C lower CTmax compared to all laboratory populations. This difference between laboratory-held and wild populations shows that environmental conditions can affect zebrafish’s thermal tolerance. However, there was no difference in CTmax between the laboratory-held populations regardless of the domestication duration. This suggests that thermal tolerance is maintained during domestication and highlights that experiments using domesticated laboratory-reared model species can be appropriate for addressing certain questions on thermal tolerance and global warming impacts.