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The central engine that powers gamma-ray bursts (GRBs), the most powerful explosions in the universe, is still not identified. Besides hyper-accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisecond magnetars, have been suggested to power both long and short GRBs. The presence of a magnetar engine following compact star mergers is of particular interest as it would provide essential constraints on the poorly understood equation of state for neutron stars. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau features present in the X-ray afterglow light curves of some short GRBs. Additionally, some X-ray transients lacking gamma-ray bursts (GRB-less) have been identified as potential magnetar candidates originating from compact star mergers. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs, and the associated theoretical challenges have been addressed. Here we present a comprehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties point toward a compact star merger origin, being consistent with its association with a kilonova. More intriguingly, an extended X-ray emission component emerges as the $\gamma$-ray emission dies out, signifying the emergence of a magnetar central engine. We also identify an achromatic temporal break in the high-energy band during the prompt emission phase, which was never observed in previous bursts and reveals a narrow jet with half opening angle of approximately $3.4^\circ$., Comment: 44 pages, 10 figures, 5 tables

The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available., Comment: Accepted by RAA

Integrated approaches for managing natural resources are needed to meet the increasing demand for freshwater, energy and food, while, in parallel, mitigating and adapting to climate change, maintaining the integrity of ecosystems, and ensuring equitable access to resources. The Water-Energy-Food (WEF) Nexus has been proposed as a cross-sectoral approach to understand, analyse, and manage the complex trade-offs and exploit synergies that arise among these resource sectors. Although not initially included as a component of the Nexus, the importance of ecosystems in supporting water, energy and food security is increasingly recognised by the Nexus community of researchers and practitioners. However, attempts to conceptually integrate Ecosystems into the Nexus have yet to converge into a common framework. A group of natural resources management researchers, system thinkers and ecosystem services experts from the European network COST Action CA20138 NEXUSNET have compiled and investigated the various approaches for integrating ecosystems in the WEF Nexus. By combining literature analysis with interdisciplinary workshops – one of which was held in a hybrid format (in person and online) at the University of Oulu, Finland, in September 2022 – we reveal a multiplicity of concepts utilised to represent, partially or fully, ecosystems in the Nexus, namely “natural environment”, “ecosystem services” and “biodiversity”. Disparity was also found in the role attributed to ecosystems in the Nexus framework, being it an underlying layer from which resources for Nexus sectors are extracted or the pillar of an expanded Nexus system – i.e., the WEF-Ecosystems Nexus. Through this collaborative effort, we present possible advantages and disadvantages of adopting differential WEF-Ecosystems Nexus approaches, highlighting their potential complementarity and integration to support future advancement of Nexus research. In the oral presentation, we will show our preliminary findings and encou

The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available., Comment: Accepted by RAA

As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy ($LEIA$), a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in July 2022, has a mostly un-vignetted field of view of $18.6^\circ \times 18.6^\circ $. Its spatial resolution is in the range of 4$-$7 arcmin in FWHM and the focal spot effective area is 2$-$3 cm$^2$, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1 and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5$-$4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster eye MPO., Comment: 11 pages, 4 figures. Accepted for publication in Astrophysical Journal Letter

The three-dimensional and temperature-dependent electronic structures of the heavy-fermion superconductor CePt2In7 are investigated. Angle-resolved photoemission spectroscopy using variable photon energy establishes the existence of quasi-two- and three-dimensional Fermi surface topologies. Temperature-dependent 4d-4f on-resonance photoemission spectroscopies data reveal that heavy quasiparticle bands begin to form at a temperature well above the characteristic (coherence) temperature T+. The emergence of low-lying crystal electric field excitation may be responsible for the "relocalization" or the precursor to the establishment of heavy electrons coherence in heavy-fermion compounds. These findings provide critical insight into understanding the hybridization in heavy-fermion systems.

Low surface roughness, low residual stress, and(002) textured aluminum nitride(AlN) thin films are favored for applications in microelectronic and optoelectronic devices. In this paper, AlN thin films were deposited by reactive high power pulsed magnetron sputtering(HPPMS). The effect of aluminum target sputtering mode and sputtering power on thin film residual stress, crystalline structure, surface roughness, and morphology of AlN thin films was studied. The results indicate that, with Al target sputtering mode transfer from metallic mode to transitional and compound modes, respectively, the number of Al species decrease, and ion-to-neutral ratio of Al species increase. Comparing the AIN thin film deposited in compound mode with that deposited in transitional mode, the latter exhibited lower surface roughness and residual stress. In addition, AlN thin film with (002) texture and lower residual stress is obtained by increasing sputtering power in transitional mode. For fabricating AIN film via reactive HPPMS with a particular (002) texture, low surface roughness, and residual stress, sputtering the target in the transitional mode with high sputtering power is optimal.

Based on the 850 $\mu$m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the $\lambda$ Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well known active star-forming regions, while the $\lambda$ Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant Hii region. PGCCs in the $\lambda$ Orionis cloud have higher dust temperatures ($Td=16.13\pm0.15$ K) and lower values of dust emissivity spectral index ($ \beta=1.65\pm0.02$) than PGCCs in the Orion A (Td=13.79$\pm 0.21$K, $\beta=2.07\pm0.03$) and Orion B ($Td=13.82\pm0.19$K, $\beta=1.96\pm0.02$) clouds. We find 119 sub-structures within the 40 detected PGCCs and identify them as cores. Of total 119 cores, 15 cores are discovered in the $\lambda$ Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the $\lambda$ Orionis cloud show much lower mean values of size R=0.08 pc, column density N(H2)=$(9.5\pm1.2) \times 10^{22}$ cm$^{-2}$, number density n(H2)=$(2.9 \pm 0.4)\times10^{5}$ cm$^{-3}$, and mass $M_{core}$=$1.0\pm0.3$ M$_{\odot}$ compared to the cores in the Orion A (R=0.11pc, $N(H2)=(2.3\pm0.3) \times 10^{23}$ cm$^{-2}$, n(H2)=$(3.8\pm0.5) \times 10^{5}$cm$^{-3}$, and $M_{core}$=$2.4 \pm 0.3$ M$_{\odot}$) and Orion B (R=0.16pc, N(H2)=$(3.8 \pm 0.4) \times 10^{23}$cm$^{-2}$, n(H2)=$(15.6\pm1.8)\times10^{5}$ cm$^{-3}$, and $M_{core}$= $2.7\pm0.3$ M$_{\odot}$) clouds. These core properties in the $\lambda$ Orionis cloud can be attributed to the photodissociation and external heating by the nearby Hii region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.

Based on the 850 $\mu$m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the $\lambda$ Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well known active star-forming regions, while the $\lambda$ Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant Hii region. PGCCs in the $\lambda$ Orionis cloud have higher dust temperatures ($Td=16.13\pm0.15$ K) and lower values of dust emissivity spectral index ($ \beta=1.65\pm0.02$) than PGCCs in the Orion A (Td=13.79$\pm 0.21$K, $\beta=2.07\pm0.03$) and Orion B ($Td=13.82\pm0.19$K, $\beta=1.96\pm0.02$) clouds. We find 119 sub-structures within the 40 detected PGCCs and identify them as cores. Of total 119 cores, 15 cores are discovered in the $\lambda$ Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the $\lambda$ Orionis cloud show much lower mean values of size R=0.08 pc, column density N(H2)=$(9.5\pm1.2) \times 10^{22}$ cm$^{-2}$, number density n(H2)=$(2.9 \pm 0.4)\times10^{5}$ cm$^{-3}$, and mass $M_{core}$=$1.0\pm0.3$ M$_{\odot}$ compared to the cores in the Orion A (R=0.11pc, $N(H2)=(2.3\pm0.3) \times 10^{23}$ cm$^{-2}$, n(H2)=$(3.8\pm0.5) \times 10^{5}$cm$^{-3}$, and $M_{core}$=$2.4 \pm 0.3$ M$_{\odot}$) and Orion B (R=0.16pc, N(H2)=$(3.8 \pm 0.4) \times 10^{23}$cm$^{-2}$, n(H2)=$(15.6\pm1.8)\times10^{5}$ cm$^{-3}$, and $M_{core}$= $2.7\pm0.3$ M$_{\odot}$) clouds. These core properties in the $\lambda$ Orionis cloud can be attributed to the photodissociation and external heating by the nearby Hii region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.

The role of citizens in mapping has evolved considerably over the last decade. This chapter outlines the background to citizen sensing in mapping and sets the scene for the chapters that follow, which highlight some of the main outcomes of a collaborative programme of work to enhance the role of citizens in mapping.

The role of citizens in mapping has evolved considerably over the last decade. This chapter outlines the background to citizen sensing in mapping and sets the scene for the chapters that follow, which highlight some of the main outcomes of a collaborative programme of work to enhance the role of citizens in mapping.

The role of citizens in mapping has evolved considerably over the last decade. This chapter outlines the background to citizen sensing in mapping and sets the scene for the chapters that follow, which highlight some of the main outcomes of a collaborative programme of work to enhance the role of citizens in mapping.

Citizens are increasingly becoming an important source of geographic information, sometimes entering domains that had until recently been the exclusive realm of authoritative agencies. This activity has a very diverse character as it can, amongst other things, be active or passive, involve spatial or aspatial data and the data provided can be variable in terms of key attributes such as format, description and quality. Unsurprisingly, therefore, there are a variety of terms used to describe data arising from citizens. In this article, the expressions used to describe citizen sensing of geographic information are reviewed and their use over time explored, prior to categorizing them and highlighting key issues in the current state of the subject. The latter involved a review of ~100 Internet sites with particular focus on their thematic topic, the nature of the data and issues such as incentives for contributors. This review suggests that most sites involve active rather than passive contribution, with citizens typically motivated by the desire to aid a worthy cause, often receiving little training. As such, this article provides a snapshot of the role of citizens in crowdsourcing geographic information and a guide to the current status of this rapidly emerging and evolving subject.

Citizens are increasingly becoming an important source of geographic information, sometimes entering domains that had until recently been the exclusive realm of authoritative agencies. This activity has a very diverse character as it can, amongst other things, be active or passive, involve spatial or aspatial data and the data provided can be variable in terms of key attributes such as format, description and quality. Unsurprisingly, therefore, there are a variety of terms used to describe data arising from citizens. In this article, the expressions used to describe citizen sensing of geographic information are reviewed and their use over time explored, prior to categorizing them and highlighting key issues in the current state of the subject. The latter involved a review of ~100 Internet sites with particular focus on their thematic topic, the nature of the data and issues such as incentives for contributors. This review suggests that most sites involve active rather than passive contribution, with citizens typically motivated by the desire to aid a worthy cause, often receiving little training. As such, this article provides a snapshot of the role of citizens in crowdsourcing geographic information and a guide to the current status of this rapidly emerging and evolving subject.

Citizens are increasingly becoming an important source of geographic information, sometimes entering domains that had until recently been the exclusive realm of authoritative agencies. This activity has a very diverse character as it can, amongst other things, be active or passive, involve spatial or aspatial data and the data provided can be variable in terms of key attributes such as format, description and quality. Unsurprisingly, therefore, there are a variety of terms used to describe data arising from citizens. In this article, the expressions used to describe citizen sensing of geographic information are reviewed and their use over time explored, prior to categorizing them and highlighting key issues in the current state of the subject. The latter involved a review of ~100 Internet sites with particular focus on their thematic topic, the nature of the data and issues such as incentives for contributors. This review suggests that most sites involve active rather than passive contribution, with citizens typically motivated by the desire to aid a worthy cause, often receiving little training. As such, this article provides a snapshot of the role of citizens in crowdsourcing geographic information and a guide to the current status of this rapidly emerging and evolving subject.

Citizens are increasingly becoming an important source of geographic information, sometimes entering domains that had until recently been the exclusive realm of authoritative agencies. This activity has a very diverse character as it can, amongst other things, be active or passive, involve spatial or aspatial data and the data provided can be variable in terms of key attributes such as format, description and quality. Unsurprisingly, therefore, there are a variety of terms used to describe data arising from citizens. In this article, the expressions used to describe citizen sensing of geographic information are reviewed and their use over time explored, prior to categorizing them and highlighting key issues in the current state of the subject. The latter involved a review of ~100 Internet sites with particular focus on their thematic topic, the nature of the data and issues such as incentives for contributors. This review suggests that most sites involve active rather than passive contribution, with citizens typically motivated by the desire to aid a worthy cause, often receiving little training. As such, this article provides a snapshot of the role of citizens in crowdsourcing geographic information and a guide to the current status of this rapidly emerging and evolving subject.

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($\alpha$), which ranges from $\alpha\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km/s consistent with Keplerian motion around a ~1.3 solar mass star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHa358 at 2.9 mm., Comment: 11 pages, 5 figures, 2 tables, accepted for publication in the Astrophysical Journal Letters

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($\alpha$), which ranges from $\alpha\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km/s consistent with Keplerian motion around a ~1.3 solar mass star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHa358 at 2.9 mm., Comment: 11 pages, 5 figures, 2 tables, accepted for publication in the Astrophysical Journal Letters

Context. To further understand the processes involved in the formation of massive stars, we have undertaken a study of the gas dynamics surrounding three massive star forming regions. By observing the large scale structures at high resolution, we are able to determine properties such as driving source, and spatially resolve the bulk dynamical properties of the gas such as infall and outflow. Aims. With high resolution observations, we are able to determine which of the cores in a cluster forming massive stars is responsible for the large scale structures. Methods. We present CO observations of three massive star forming regions with known HII regions and show how the CO traces both infall and outflow. By combining data taken in two SMA configurations with JCMT observations, we are able to see large scale structures at high resolution. Results. We find large (0.26-0.40 pc), massive (2-3 M_sun) and energetic (13-17 \times 10^44 erg) outflows emanating from the edges of two HII regions suggesting they are being powered by the protostar(s) within. We find infall signatures in two of our sources with mass infall rates of order 10-4 M_sun/yr. Conclusions. We suggest that star formation is ongoing in these sources despite the presence of HII regions. We further conclude that the source(s) within a single HII region are responsible for the observed large scale structures; that these large structures are not the net effect of multiple outflows from multiple HII regions and hot cores., Comment: 8 pages,2 figures, accepted for publication in A&A

We have investigated the photoluminescence (PL) of two carefully selected dilute nitride Ga1−xInxNyAs1−y multiple quantum well structures in magnetic fields up to 50 T as a function of temperature and excitation power. The observation of a nonmonotonic dependence of the PL energy on temperature indicates that localized states dominate the luminescence at low temperature, while magneto-PL experiments give new insights into the nature of the localization. We find that the low-temperature spatial distribution of carriers in the quantum well is different for electrons and holes because they are captured by different disorder-induced complexes that are spatially separated. A study of the thermalization of the carriers toward free states leads to the determination of the free-exciton wave-function extent in these systems and enables an assessment of the localization potentials induced by inhomogeneity in the quantum well.

We have investigated the photoluminescence (PL) of two carefully selected dilute nitride Ga1−xInxNyAs1−y multiple quantum well structures in magnetic fields up to 50 T as a function of temperature and excitation power. The observation of a nonmonotonic dependence of the PL energy on temperature indicates that localized states dominate the luminescence at low temperature, while magneto-PL experiments give new insights into the nature of the localization. We find that the low-temperature spatial distribution of carriers in the quantum well is different for electrons and holes because they are captured by different disorder-induced complexes that are spatially separated. A study of the thermalization of the carriers toward free states leads to the determination of the free-exciton wave-function extent in these systems and enables an assessment of the localization potentials induced by inhomogeneity in the quantum well.

Context. To further understand the processes involved in the formation of massive stars, we have undertaken a study of the gas dynamics surrounding three massive star forming regions. By observing the large scale structures at high resolution, we are able to determine properties such as driving source, and spatially resolve the bulk dynamical properties of the gas such as infall and outflow. Aims. With high resolution observations, we are able to determine which of the cores in a cluster forming massive stars is responsible for the large scale structures. Methods. We present CO observations of three massive star forming regions with known HII regions and show how the CO traces both infall and outflow. By combining data taken in two SMA configurations with JCMT observations, we are able to see large scale structures at high resolution. Results. We find large (0.26-0.40 pc), massive (2-3 M_sun) and energetic (13-17 \times 10^44 erg) outflows emanating from the edges of two HII regions suggesting they are being powered by the protostar(s) within. We find infall signatures in two of our sources with mass infall rates of order 10-4 M_sun/yr. Conclusions. We suggest that star formation is ongoing in these sources despite the presence of HII regions. We further conclude that the source(s) within a single HII region are responsible for the observed large scale structures; that these large structures are not the net effect of multiple outflows from multiple HII regions and hot cores., Comment: 8 pages,2 figures, accepted for publication in A&A

We report a magneto-optical study of InAs-InGaAs-GaAs self-assembled quantum dots (QDs) subjected to post-growth thermal annealing at different temperatures. At low temperatures annealing strongly affects the bimodal distribution of QDs; at higher temperatures a strong blueshift of the emission occurs. Magnetophotoluminescence reveals that the annealing increases the QD size, with a larger effect occurring along the growth axis, and decreases the carrier effective masses. The main contribution to the blueshift is deduced to be an increase in the average Ga composition of the QDs. The inadvertent annealing which occurs during the growth of the upper AlGaAs cladding layer in laser structures is also studied.

Ceriops zippeliana, a member of the mangrove Rhizophoraceae, was first reported in 1849. It was considered to be a synonym of C. decandra, which is still widely accepted. We present morphological and molecular evidence to show that C. zippeliana is significantly distinct from C. decandra, and illustrations and an identification key to both spe

Carrier relaxation is a key issue in determining the efficiency of semiconductor optoelectronic device operation. Devices incorporating semiconductor quantum dots have the potential to overcome many of the limitations of quantum-well-based devices because of the predicted long quantum-dot excited-state lifetimes. For example, the population inversion required for terahertz laser operation in quantum-well-based devices (quantum-cascade lasers1, 2) is fundamentally limited by efficient scattering between the laser levels, which form a continuum in the plane of the quantum well. In this context, semiconductor quantum dots are a highly attractive alternative for terahertz devices, because of their intrinsic discrete energy levels. Here, we present the first measurements, and theoretical description, of the intersublevel carrier relaxation in quantum dots for transition energies in the few terahertz range. Long intradot relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. Our studies pave the way for quantum-dot terahertz device development, providing the fundamental knowledge of carrier relaxation times required for optimum device design.

Ceriops zippeliana, a member of the mangrove Rhizophoraceae, was first reported in 1849. It was considered to be a synonym of C. decandra, which is still widely accepted. We present morphological and molecular evidence to show that C. zippeliana is significantly distinct from C. decandra, and illustrations and an identification key to both species.

Nuclear polarization dynamics are measured in the nuclear spin bistability regime in a single optically pumped InGaAs/GaAs quantum dot. The controlling role of nuclear spin diffusion from the dot into the surrounding material is revealed in pump-probe measurements of the nonlinear nuclear spin dynamics. We measure nuclear spin polarization decay times in the range of 0.2-5 s, strongly dependent on the optical pumping time. The long nuclear spin decay arises from polarization of the material surrounding the dot by spin diffusion for long (>5s) pumping times. The time-resolved methods allow the detection of the unstable nuclear polarization state in the bistability regime otherwise undetectable in cw experiments.

Nuclear polarization dynamics are measured in the nuclear spin bistability regime in a single optically pumped InGaAs/GaAs quantum dot. The controlling role of nuclear spin diffusion from the dot into the surrounding material is revealed in pump-probe measurements of the nonlinear nuclear spin dynamics. We measure nuclear spin polarization decay times in the range of 0.2-5 s, strongly dependent on the optical pumping time. The long nuclear spin decay arises from polarization of the material surrounding the dot by spin diffusion for long (>5s) pumping times. The time-resolved methods allow the detection of the unstable nuclear polarization state in the bistability regime otherwise undetectable in cw experiments.

It is demonstrated that capping InAs self-assembled quantum dots with a thin GaAsSb layer allows the emission to be extended beyond 1.5 um at room temperature. This behaviour is attributed to the formation of a type-II system for Sb composition above -15%. Magneto-optical spectroscopy suggests that the type-II excitons remain compact and it is postulated that strain modulation of the GaAsSb layer results in hole localization immediately above the quantum dots.

We show that by illuminating an InGaAs/GaAs self-assembled quantum dot with circularly polarized light, the nuclei of atoms constituting the dot can be driven into a bistable regime, in which either a thresholdlike enhancement or reduction of the local nuclear field by up to 3 T can be generated by varying the pumping intensity. The excitation power threshold for such a nuclear spin “switch” is found to depend on both the external magnetic and electric fields. The switch is shown to arise from the strong feedback of the nuclear spin polarization on the dynamics of the spin transfer from electrons to the nuclei of the dot.

It is demonstrated that capping InAs self-assembled quantum dots with a thin GaAsSb layer allows the emission to be extended beyond 1.5 um at room temperature. This behaviour is attributed to the formation of a type-II system for Sb composition above -15%. Magneto-optical spectroscopy suggests that the type-II excitons remain compact and it is postulated that strain modulation of the GaAsSb layer results in hole localization immediately above the quantum dots.

We show that by illuminating an InGaAs/GaAs self-assembled quantum dot with circularly polarized light, the nuclei of atoms constituting the dot can be driven into a bistable regime, in which either a thresholdlike enhancement or reduction of the local nuclear field by up to 3 T can be generated by varying the pumping intensity. The excitation power threshold for such a nuclear spin “switch” is found to depend on both the external magnetic and electric fields. The switch is shown to arise from the strong feedback of the nuclear spin polarization on the dynamics of the spin transfer from electrons to the nuclei of the dot.

Objective: To examine E1AF mRNA expression and to determine whether it is correlated with tumor progression and matrilysin in human rectal cancer. Methods: Real-time RT-PCR was used to determine E1AF and matrilysin expression in 100 matched rectal cancers and normal tissues. Results: Among the 100 rectal cancers, 69 cases of E1AF mRNA overexpression were observed. E1AF mRNA overexpression correlated well with matrilysin. In carcinomas, E1AF mRNA overexpression correlated significantly with depth of invasion, lymph node metastasis, venous involvement and advanced pTNM stage. Conclusions: E1AF was correlated significantly with tumor progression of human rectal cancer and may be an important factor in rectal cancer progression. Copyright © 2008 S. Karger AG.

It is demonstrated that the emission of InAs quantum dots (QDs) capped with GaAsSb can be extended from 1.28 to 1.6 µm by increasing the Sb composition of the capping layer from 14% to 26%. Photoluminescence excitation spectroscopy is applied to investigate the nature of this large redshift. The dominant mechanism is shown to be the formation of a type-II transition between an electron state in the InAs QDs and a hole state in the GaAsSb capping layer. The prospects for using these structures to fabricate 1.55 µm injection lasers are discussed.

Four 10-ns molecular dynamics (MD) simulations of the human prion protein domain (HuPrP 125-228) in explicit water solution have been performed. Each of the simulations mimicked a different environment of the protein: the neutral pH environment was simulated with all histidine residues neutral and bearing a ND proton and with other titratable side chains charged, the weakly acidic environment was simulated with all titratable side chains charged, he strongly acidic environment was simulated with all titratable side chains protonated. The protein in neutral pH environment was simulated at both ambient (298 K) and higher (350 K) temperatures. The native fold is stable in he neutral pH/ambient temperature simulation. Through out all other simulations, a quite stable core consisted of 0-20 residues around the disulfide bond retain their initial conformations. However, the secondary structures of the Protein show changes of various degrees compared to the native fold, parts of the helices unfolded and the beta-sheets extended. Our simulations indicated that the heat-induced unfolding and acid-induced unfolding of HuPrP might follow different pathways: the initial stage of the acid-induced unfolding may include not only changes in secondary structures, but also changes in the tertiary structures. Under the strongly acidic condition, obvious tertiary structure changes take place after 10-ns simulation, the secondary structure elements and the loops becoming more parallel to each other, resulting in a compact state, which was stabilized by a large number of new, non-native side chain-side chain contacts. Such tertiary structure changes were not observed in the higher temperature simulation, and intuitively, they may favor the further extension of the beta-sheets and eventually the agglomeration of multiple protein molecules. The driving forces for this tertiary structure changes are discussed. Two additional 10-ns MD simulations, one with Asp202 protonated and the other wit

Four 10-ns molecular dynamics (MD) simulations of the human prion protein domain (HuPrP 125-228) in explicit water solution have been performed. Each of the simulations mimicked a different environment of the protein: the neutral pH environment was simulated with all histidine residues neutral and bearing a ND proton and with other titratable side chains charged, the weakly acidic environment was simulated with all titratable side chains charged, he strongly acidic environment was simulated with all titratable side chains protonated. The protein in neutral pH environment was simulated at both ambient (298 K) and higher (350 K) temperatures. The native fold is stable in he neutral pH/ambient temperature simulation. Through out all other simulations, a quite stable core consisted of 0-20 residues around the disulfide bond retain their initial conformations. However, the secondary structures of the Protein show changes of various degrees compared to the native fold, parts of the helices unfolded and the beta-sheets extended. Our simulations indicated that the heat-induced unfolding and acid-induced unfolding of HuPrP might follow different pathways: the initial stage of the acid-induced unfolding may include not only changes in secondary structures, but also changes in the tertiary structures. Under the strongly acidic condition, obvious tertiary structure changes take place after 10-ns simulation, the secondary structure elements and the loops becoming more parallel to each other, resulting in a compact state, which was stabilized by a large number of new, non-native side chain-side chain contacts. Such tertiary structure changes were not observed in the higher temperature simulation, and intuitively, they may favor the further extension of the beta-sheets and eventually the agglomeration of multiple protein molecules. The driving forces for this tertiary structure changes are discussed. Two additional 10-ns MD simulations, one with Asp202 protonated and the other wit

Electrochemical rate parameters for the outer-sphere reduction of several Cr(III) aquo and ammine complexes and also for vanadium and europium aquo complexes are compared at aqueous-metal interfaces formed with mercury, liquid gallium, lead, and underpotential deposited lead and thallium monolayers on silver. For reactants containing aquo ligands, substantial decreases in the rate constants, both before and after electrostatic double-layer corrections, were observed at a given electrode potential when substituting mercury by the other surfaces, especially lead and gallium. The rate alterations are accompanied by marked decreases in the apparent activation entropies, although offset by corresponding decreases in the measured activation enthalpies. These results are interpreted in terms of the varying influence of these metal surfaces on the interfacial solvent structure.

The application of current theoretical treatments of electron transfer to outer-sphere electrochemical reactions are considered with regard to the numerical prediction of rate parameters from thermodynamic and structural data. Formalisms based on a semiclassical treatment for the Frank-Condon barrier together with an encounter preequilibrium model for the preexponential factor are summarized and related to the more widely considered treatments for homogeneous redox reactions. Comparisons are made between the theoretical predictions and experimental rate parameters for representative inorganic outer-sphere reactions at electrode surfaces, and with related reactions in homogeneous solution. The effects of altering the electrode material and the outer-shell solvent are also considered. Although the measured rate parameters for several reactions at mercury electrodes are in reasonable agreement with the theoretical predictions, significant and even large discrepancies are seen for a number of cases. Likely reasons for these findings are discussed, including nonadiabaticity and specific solvation effects. (Author)

The electrochemistry of surface-bound couples is an area of considerable current interest. In addition to their potential applications in electrocatalysis, such couples that involve mechanistically uncomplicated one-electron transfer offer opportunities for studying several fundamental aspects of heterogeneous electron-transfer processes. For example, the interpretation of electrochemical rate parameters for surface-attached reactants is especially straightforward, since these provide direct information on the energetics of the elementary electron-transfer step. The comparison between redox thermodynamics of a given redox couple in solution and in the surface-bound state are expected to yield useful insights into the differences in the solvating environment between the interfacial region and the bulk solution. Bulk solution and surface thermodynamic behavior for two Co(III)/(II) redox couples adsorbed by different means is presented here in order to illustrate the virtues of such analyses for simple electrode reactions.

Unimolecular rate constants k sub et are presented for the one-electron electroreduction of various CoIII(NH3)5X complexes bound to mercury, platinum, and gold surfaces via either small inorganic or extended organic ligands X. These 'surface intramolecular' rate parameters are compared with estimates of k sub et for outer-sphere pathways obtained from homogeneous rate data in order to ascertain the consequences of reactant-surface binding upon the electron-transfer energetics. Only small or moderate decreases in the elementary reorganization barrier Delta G* sub et occur upon surface attachment, suggesting the occurrence of weak-overlap pathways. Aside from the dependence of k sub et upon the bridging ligand X at a given electrode potential due to differences in thermodynamic driving force, the observed variations in k sub et appear to be due in part to variations in the electronic transmission coefficient k sub el. Measurements of electrochemical frequency factors for reactants containing a series of thiophenecarboxylate bridges indicate that the substantial decreases in k sub et observed upon interruption of ligand conjugation arise predominantly from decreases in k sub el. (Author)

InAs quantum dot multi-mode-interference-reflector (MMIR) lasers, based on a 1-port MMIR and a single cleaved reflector, are designed, fabricated, and characterized to demonstrate capability for optoelectronic-integrated-circuits. Threshold current densities are less than 40% of those in cleaved-cleaved ridge waveguide lasers of the same cavity length.

Measurements of the confinement factor, internal loss, diffusion length and sidewall recombination, using special test structures and a new measurement method, explain the large differences in threshold current density of broad area and ridge lasers of different width.

We demonstrated 20 nm relative blue shifted III-V passive waveguides monolithically integrated with InAs QDs active laser diode emitting at 1290 nm through selective area proton implantation and post-annealing method. This work is promising for low-loss monolithic Photonic Integrated Circuits.

A SGC with 30% coupling efficiency is designed for a QD-GaAs-based optoelectronics integration platform using thin oxidized Al 0.98 Ga 0.02 As layers to overcome the otherwise poor refractive index contrast. coupling efficiency increased from 10% for the unoxidized equivalent and is suitable for outcoupling in active-passive integrated platforms.