Control of InGaAs facets using metal modulation epitaxy (MME)

Control of faceting during epitaxy is critical for nanoscale devices. This work identifies the origins of gaps and different facets during regrowth of InGaAs adjacent to patterned features. Molecular beam epitaxy (MBE) near SiO2 or SiNx led to gaps, roughness, or polycrystalline growth, but metal modulated epitaxy (MME) produced smooth and gap-free "rising tide" (001) growth filling up to the mask. The resulting self-aligned FETs were dominated by FET channel resistance rather than source-drain access resistance. Higher As fluxes led first to conformal growth, then pronounced {111} facets sloping up away from the mask.Comment: 18 pages, 7 figure

Invariant NKT Cell Lines Derived from the NOD·H2h4 Mouse Enhance Autoimmune Thyroiditis

To study the role of invariant Natural Killer T cell ( iNKT) cells in autoimmune thyroiditis, we derived two iNKT cell lines from the spleens of NOD· H2h4 mice, a strain that develops spontaneous autoimmune thyroiditis exacerbated by excess dietary iodine. The two lines were CD1d-restricted and expressed CD4+, DX5+, and the Vα4Jα281 gene segment, of the T-cell receptor α locus. Upon stimulation with α-galactosyl-ceramide (α-GalCer), both lines rapidly produced IL-2, IL-4, IFN-γ, IL-10, and TNF-α. Strikingly, a similar cytokine response was also induced by thyroglobulin, one of the most abundant protein in the thyroid gland and a major autoantigen in human autoimmune thyroiditis. Transfer of the iNKT cell lines to syngeneic hosts enhanced autoimmune thyroiditis. Intraperitoneal injections of α-GalCer in iodine primed mice also induced thyroid disease. This paper reports for the first time that iNKT cells respond to thyroglobulin and enhance autoimmune thyroiditis in iodine fed NOD·H2h4 mice

Investigation of Heavy Metals in a Large Mortality Event in Caribou of Northern Alaska

We measured element concentrations (As, Cd, Cu, Pb, Zn, Fe) and body condition (gross and histologic endpoints) of animals from a caribou (Rangifer tarandus) mortality event that occurred in Alaska, in the area of Point Hope and Cape Thompson (including the Chariot site), in 1995. These were compared to results from hunter-killed caribou from reference sites (Barrow and Teshekpuk Lake, Alaska) and from the area of a mine (Red Dog Mine) to determine whether heavy metals had played a role in the mortality event or whether any elements were at concentrations of concern for human consumers. Starvation and malnutrition were major factors leading to death or severe weakness, as very little or no fat (very low body condition scores) and serous atrophy of fat (observed as watery contents of the marrow cavity, with no apparent fat, and histologically) were more prevalent in caribou associated with the mortality event than in hunter-killed animals from reference sites. Accumulation of hepatic (liver) hemosiderin in Kupffer cells (macrophages) was noted as an indicator of cachexia. Concentrations of lead in feces and liver, copper in the rumen contents, and arsenic in muscle were higher in caribou harvested near Red Dog Mine, as might be expected in that mineral-rich area, but were not at levels of concern for toxicoses. Kidney concentrations of cadmium, which increased significantly with increasing age, present a potential concern for human consumers, and this is an expected finding. We concluded that caribou had starved and that heavy metals had played no role in the mortality event. Further investigation of regional mineral differences is required to understand the sources and transport mechanisms that explain these findings and to properly address mining activity. Mortality events on the north slope of Alaska are common and likely involve starvation as described here, but in most cases they are not investigated, even though recent industrial activities have heightened concern among some local residents and wildlife managers.On a mesuré la concentration en éléments (As, Cd, Cu, Pb, Zn, Fe) et l'état corporel (points limites bruts et histologiques) de caribous (Rangifer tarandus) prélevés lors d'un épisode de mortalité qui s'est produit en 1995 en Alaska, dans la région de Point Hope et de Cape Thompson (y compris le site Chariot). On a comparé ces résultats à ceux de caribous tués par des chasseurs à des emplacements témoins (Barrow et Teshekpuk Lake, en Alaska) et à proximité d'une mine (Red Dog Mine) pour trouver si les métaux lourds avaient joué un rôle dans l'épisode de mortalité ou si la concentration d'un ou plusieurs éléments pouvait constituer un risque pour la consommation humaine. La famine et la malnutrition étaient des facteurs majeurs ayant causé la mort ou une extrême faiblesse, vu que la présence minime ou l'absence de graisse (très basses notes d'état corporel) et une atrophie séreuse de la graisse (observée sous forme de contenu aqueux de la cavité médullaire, sans graisse visible, et à la suite de l'examen histologique) étaient plus courantes chez le caribou associé à l'épisode de mortalité que chez les animaux des emplacements témoins tués par les chasseurs. On a noté dans le foie une accumulation d'hémosidérine hépatique des cellules de Kupffer (cellules macrophages) témoignant d'une cachexie. La concentration de plomb dans les matières fécales et le foie, de cuivre dans le rumen et d'arsenic dans le tissu musculaire était plus élevée chez le caribou provenant de Red Dog Mine, comme on pouvait s'y attendre dans cette zone riche en minéraux, mais cette concentration n'atteignait pas un niveau pouvant provoquer des toxicoses. La concentration de cadmium dans le rein, qui augmentait de façon significative avec l'âge, pourrait constituer un risque pour la consommation humaine, ce qui n'est pas surprenant. On a conclu que les caribous étaient morts de faim et que les métaux lourds n'avaient joué aucun rôle dans l'épisode de mortalité. Il faudrait effectuer des recherches plus poussées sur les différences régionales en minéraux afin de comprendre les mécanismes d'origine et de transport qui expliquent ces résultats et d'aborder comme il le faut les activités minières. Les épisodes de mortalité sont courants sur le versant Nord de l'Alaska et sont probablement liés à la famine, comme le décrit cet article, mais dans la plupart des cas ils ne font pas l'objet d'une enquête, même si l'activité industrielle récente est un sujet qui préoccupe de plus en plus certains résidents et gestionnaires locaux de la faune

Sources and export of nutrients in the Zambezi River basin: status and future trend

In the past decades, nutrient enrichment in African water bodies has been frequently reported and associated to long-term ecological and socio-economic consequences, such as species extinction, unsafe drinking water and compromised local livelihood. Meanwhile, rapid population growth and land-use change towards intensified food production are projected in Africa. As a result, substantial increases are expected in human-induced nutrient inputs (e.g. human waste and fertilizer) to the terrestrial and aquatic environments. This may potentially further deteriorate African water bodies. As part of the Integrated Solution for Water, Land and Energy (IS-WEL) project, this study aims to assess the status and projected changes of nutrient sources, inputs to rivers and export to seas, shading light on possible solutions to minimize further nutrient-induced deterioration of the water bodies and maximize the availability of water of suitable quality for different sectors. This study focuses on the Zambezi river basin, the fourth largest transboundary basin draining through eight southern African countries. Nutrient sources, inputs to rivers and export to sea are estimated using the MARINA model (Model to Assess River Inputs of Nutrients to seAs) under current conditions and future climate, land use and socio-economic projections up to 2050. Results show that for the current period (2005-2010), inputs of nutrients (nitrogen and phosphorus) to rivers and their export to sea are mainly attributed to natural sources. These sources include nitrogen fixation by the natural ecosystems, phosphorus weathering, and leaching of organic nitrogen and phosphorus from non-agricultural areas. By 2050, nutrient sources will be at least doubled due to anthropogenic inputs in the basin. Consequently, the fraction of human-induced nutrient export are projected to increase considerably, especially for dissolved inorganic phosphorus from domestic wastewater. Additionally, nutrient export to sea is strongly influenced by the intra- and inter-annual precipitation and discharge variabilities in the region. The study highlights the need to simultaneously consider source control, infrastructure development and climate adaptation to minimize further nutrient-induced deterioration of water bodies

Increasing future human-induced nitrogen exports to rivers and sea in the Zambezi river basin

In the past decades, nutrient enrichment in African water bodies has been frequently reported and lead to water security challenges, such as unsafe drinking water and compromised local livelihood. Meanwhile, rapid population growth and land-use change towards intensified food production are projected in Africa. Substantial increases in anthropogenic nutrient inputs (e.g. human waste and fertilizer) to the terrestrial and aquatic environments are therefore expected. This may further deteriorate African water bodies and threaten water security. As part of the Integrated Solution for Water, Land and Energy (IS-WEL) project funded by Global Environmental Facility and IIASA, this study aims to assess the status and projected changes of nitrogen (N) sources, associated inputs to rivers and export to sea. The study focuses on the Zambezi river basin, the 4th largest transboundary basin in Africa draining through 8 countries. N inputs to rivers and export to sea are estimated using the MARINA model (Model to Assess River Inputs of Nutrients to seAs) under current conditions and future climate, land use and socio-economic scenarios towards 2050. In addition to global climate (Representative Concentration Pathways) and socioeconomic (Shared Socioeconomic Pathways) scenarios, the study co-developed regional scenarios through stakeholder engagement in cooperation with the Zambezi Watercourse Commission. The regional scenarios, especially for sanitation and agricultural development, will later be incorporated in the model. Preliminary results show that for the current period (2010), N input to rivers and export to sea are mainly from natural sources, namely N fixation by the natural ecosystems and organic N leaching from non-agricultural areas. By 2050, N sources in the basin will be more than doubled due to anthropogenic inputs based on the global scenarios. Consequently, the fraction of human-induced N export is projected to increase considerably. Additionally, N export to sea is strongly influenced by the intra- and inter-annual climate variabilities in the region. The study highlights the need to simultaneously consider source control and climate adaptation in the regional contexts to minimize further N-induced deterioration of water bodies and ensure regional water security

Photon-mediated interactions between quantum emitters in a diamond nanocavity

Photon-mediated interactions between quantum systems are essential for realizing quantum networks and scalable quantum information processing. We demonstrate such interactions between pairs of silicon-vacancy (SiV) color centers coupled to a diamond nanophotonic cavity. When the optical transitions of the two color centers are tuned into resonance, the coupling to the common cavity mode results in a coherent interaction between them, leading to spectrally-resolved superradiant and subradiant states. We use the electronic spin degrees of freedom of the SiV centers to control these optically-mediated interactions. Such controlled interactions will be crucial in developing cavity-mediated quantum gates between spin qubits and for realizing scalable quantum network nodes

Bridging global, basin and local-scale water quality modeling towards enhancing water quality management worldwide

Global water quality (WQ) modeling is an emerging field. In this article, we identify the missing linkages between global and basin/local-scale WQ models, and discuss the possibilities to fill these gaps. We argue that WQ models need stronger linkages across spatial scales. This would help to identify effective scale-specific WQ management options and contribute to future development of global WQ models. Two directions are proposed to improve the linkages: nested multiscale WQ modeling towards enhanced water management, and development of next-generation global WQ models based-on basin/local-scale mechanistic understanding. We highlight the need for better collaboration among WQ modelers and policy-makers in order to deliver responsive water policies and management strategies across scales