Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 174
Filtrar
Mais filtros

Intervalo de ano de publicação
1.
Cell ; 186(14): 3013-3032.e22, 2023 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-37352855

RESUMO

Mitochondrial DNA (mtDNA) is a potent agonist of the innate immune system; however, the exact immunostimulatory features of mtDNA and the kinetics of detection by cytosolic nucleic acid sensors remain poorly defined. Here, we show that mitochondrial genome instability promotes Z-form DNA accumulation. Z-DNA binding protein 1 (ZBP1) stabilizes Z-form mtDNA and nucleates a cytosolic complex containing cGAS, RIPK1, and RIPK3 to sustain STAT1 phosphorylation and type I interferon (IFN-I) signaling. Elevated Z-form mtDNA, ZBP1 expression, and IFN-I signaling are observed in cardiomyocytes after exposure to Doxorubicin, a first-line chemotherapeutic agent that induces frequent cardiotoxicity in cancer patients. Strikingly, mice lacking ZBP1 or IFN-I signaling are protected from Doxorubicin-induced cardiotoxicity. Our findings reveal ZBP1 as a cooperative partner for cGAS that sustains IFN-I responses to mitochondrial genome instability and highlight ZBP1 as a potential target in heart failure and other disorders where mtDNA stress contributes to interferon-related pathology.


Assuntos
Cardiotoxicidade , DNA Mitocondrial , Animais , Camundongos , DNA Mitocondrial/metabolismo , Imunidade Inata , Interferons/metabolismo , Nucleotidiltransferases/genética , Nucleotidiltransferases/metabolismo , Fosforilação
2.
J Med Internet Res ; 26: e42140, 2024 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-38319701

RESUMO

BACKGROUND: Health care providers worldwide are rapidly adopting electronic medical record (EMR) systems, replacing paper record-keeping systems. Despite numerous benefits to EMRs, the environmental emissions associated with medical record-keeping are unknown. Given the need for urgent climate action, understanding the carbon footprint of EMRs will assist in decarbonizing their adoption and use. OBJECTIVE: We aimed to estimate and compare the environmental emissions associated with paper medical record-keeping and its replacement EMR system at a high-volume eye care facility in southern India. METHODS: We conducted the life cycle assessment methodology per the ISO (International Organization for Standardization) 14040 standard, with primary data supplied by the eye care facility. Data on the paper record-keeping system include the production, use, and disposal of paper and writing utensils in 2016. The EMR system was adopted at this location in 2018. Data on the EMR system include the allocated production and disposal of capital equipment (such as computers and routers); the production, use, and disposal of consumable goods like paper and writing utensils; and the electricity required to run the EMR system. We excluded built infrastructure and cooling loads (eg. buildings and ventilation) from both systems. We used sensitivity analyses to model the effects of practice variation and data uncertainty and Monte Carlo assessments to statistically compare the 2 systems, with and without renewable electricity sources. RESULTS: This location's EMR system was found to emit substantially more greenhouse gases (GHGs) than their paper medical record system (195,000 kg carbon dioxide equivalents [CO2e] per year or 0.361 kg CO2e per patient visit compared with 20,800 kg CO2e per year or 0.037 kg CO2e per patient). However, sensitivity analyses show that the effect of electricity sources is a major factor in determining which record-keeping system emits fewer GHGs. If the study hospital sourced all electricity from renewable sources such as solar or wind power rather than the Indian electric grid, their EMR emissions would drop to 24,900 kg CO2e (0.046 kg CO2e per patient), a level comparable to the paper record-keeping system. Energy-efficient EMR equipment (such as computers and monitors) is the next largest factor impacting emissions, followed by equipment life spans. Multimedia Appendix 1 includes other emissions impact categories. CONCLUSIONS: The climate-changing emissions associated with an EMR system are heavily dependent on the sources of electricity. With a decarbonized electricity source, the EMR system's GHG emissions are on par with paper medical record-keeping, and decarbonized grids would likely have a much broader benefit to society. Though we found that the EMR system produced more emissions than a paper record-keeping system, this study does not account for potential expanded environmental gains from EMRs, including expanding access to care while reducing patient travel and operational efficiencies that can reduce unnecessary or redundant care.


Assuntos
Pegada de Carbono , Registros Eletrônicos de Saúde , Hospitais Especializados , Prontuários Médicos , Papel , Clima , Software , Meio Ambiente , Índia , Oftalmologia , Setor de Assistência à Saúde , Mudança Climática
3.
Environ Res ; 239(Pt 1): 117378, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37832768

RESUMO

2,4,6-triamino-1,3,5-trinitrobenzene (TATB) is an Insensitive High Explosive (IHE) that is increasingly being used as a safer alternative to traditional energetic materials. However, the high thermal stability of TATB poses challenges for its disposal, particularly through existing open burning methods and its ability to remain in the environment for long period of time. Therefore, this study investigated the persistence of TATB in the environment by conducting small-scale experiments which were designed to examine the resistance of TATB to open burning and to assess unburnt residues. To evaluate the fate and transport of the unburnt materials in soil, laboratory-scale soil column transport studies were conducted to gauge the movement of TATB through soil. The results indicate that TATB exhibits a high resistance to burning, leaving unburnt materials that can persist in soil. The study emphasizes the importance of efficient disposal methods for explosives and highlights the need for further research to understand the environmental impact and toxicity of TATB.


Assuntos
Substâncias Explosivas , Solo , Trinitrobenzenos
4.
Nature ; 531(7592): 83-7, 2016 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-26878237

RESUMO

Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable--and hence little known and largely ignored--georgeite. The first three of these minerals are widely used as catalyst precursors for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient formation of georgeite; with few exceptions it uses sodium carbonate as the carbonate source, but this also introduces sodium ions--a potential catalyst poison. Here we show that supercritical antisolvent (SAS) precipitation using carbon dioxide (refs 13, 14), a process that exploits the high diffusion rates and solvation power of supercritical carbon dioxide to rapidly expand and supersaturate solutions, can be used to prepare copper/zinc hydroxycarbonate precursors with low sodium content. These include stable georgeite, which we find to be a precursor to highly active methanol-synthesis and superior LTS catalysts. Our findings highlight the value of advanced synthesis methods in accessing unusual mineral phases, and show that there is room for exploring improvements to established industrial catalysts.

5.
Cereb Cortex ; 31(7): 3338-3352, 2021 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-33693614

RESUMO

Autism spectrum disorder (ASD) is associated with atypical brain development. However, the phenotype of regionally specific increased cortical thickness observed in ASD may be driven by several independent biological processes that influence the gray/white matter boundary, such as synaptic pruning, myelination, or atypical migration. Here, we propose to use the boundary sharpness coefficient (BSC), a proxy for alterations in microstructure at the cortical gray/white matter boundary, to investigate brain differences in individuals with ASD, including factors that may influence ASD-related heterogeneity (age, sex, and intelligence quotient). Using a vertex-based meta-analysis and a large multicenter structural magnetic resonance imaging (MRI) dataset, with a total of 1136 individuals, 415 with ASD (112 female; 303 male), and 721 controls (283 female; 438 male), we observed that individuals with ASD had significantly greater BSC in the bilateral superior temporal gyrus and left inferior frontal gyrus indicating an abrupt transition (high contrast) between white matter and cortical intensities. Individuals with ASD under 18 had significantly greater BSC in the bilateral superior temporal gyrus and right postcentral gyrus; individuals with ASD over 18 had significantly increased BSC in the bilateral precuneus and superior temporal gyrus. Increases were observed in different brain regions in males and females, with larger effect sizes in females. BSC correlated with ADOS-2 Calibrated Severity Score in individuals with ASD in the right medial temporal pole. Importantly, there was a significant spatial overlap between maps of the effect of diagnosis on BSC when compared with cortical thickness. These results invite studies to use BSC as a possible new measure of cortical development in ASD and to further examine the microstructural underpinnings of BSC-related differences and their impact on measures of cortical morphology.


Assuntos
Transtorno do Espectro Autista/diagnóstico por imagem , Mapeamento Encefálico/métodos , Córtex Cerebral/diagnóstico por imagem , Substância Cinzenta/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Substância Branca/diagnóstico por imagem , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Bases de Dados Factuais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
6.
J Chem Phys ; 156(6): 064704, 2022 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-35168339

RESUMO

The development of new electrocatalysts for the hydrogen evolution reaction (HER) could reduce the dependence on Pt and other rare metals and enable large-scale production of hydrogen with near-zero carbon emissions. Mechanistic insight into the electrocatalytic activity of a material helps to accelerate the development of new electrocatalysts. Alternative electrocatalyst materials such as transition metal oxides and sulfides can undergo insertion reactions that change their properties. Recent reports indicate that the presence of inserted ions can influence the electrocatalytic activity. Here, we utilized a materials chemistry approach to understand the role of proton insertion in the HER activity of the layered tungsten oxide hydrates (WO3·xH2O, x = 1, 2). We synthesized a series of tungsten oxide hydrates along with an octylamine-pillared tungsten oxide (OA-WO3). We used cyclic voltammetry to study the electrochemical reactivity of each material and performed ex situ x-ray diffraction and Raman spectroscopy to understand bulk and surface structural changes during electrochemical cycling. We show an inverse relationship between the degree of proton insertion and HER overpotential in tungsten oxides: the lack of proton insertion leads to a high overpotential for the HER. We discuss three hypotheses for how proton insertion leads to the HER activity in WO3·xH2O: (1) proton insertion changes the electronic band structure of WO3·xH2O, (2) the presence of bulk protons can influence ΔGH,ads at the surface sites, and (3) the inserted protons may participate in the HER mechanism on WO3·xH2O. Overall, this work shows the critical role of proton insertion in enabling the high HER activity in tungsten oxides.

7.
Mol Psychiatry ; 25(3): 614-628, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31028290

RESUMO

Significant heterogeneity across aetiologies, neurobiology and clinical phenotypes have been observed in individuals with autism spectrum disorder (ASD). Neuroimaging-based neuroanatomical studies of ASD have often reported inconsistent findings which may, in part, be attributable to an insufficient understanding of the relationship between factors influencing clinical heterogeneity and their relationship to brain anatomy. To this end, we performed a large-scale examination of cortical morphometry in ASD, with a specific focus on the impact of three potential sources of heterogeneity: sex, age and full-scale intelligence (FIQ). To examine these potentially subtle relationships, we amassed a large multi-site dataset that was carefully quality controlled (yielding a final sample of 1327 from the initial dataset of 3145 magnetic resonance images; 491 individuals with ASD). Using a meta-analytic technique to account for inter-site differences, we identified greater cortical thickness in individuals with ASD relative to controls, in regions previously implicated in ASD, including the superior temporal gyrus and inferior frontal sulcus. Greater cortical thickness was observed in sex specific regions; further, cortical thickness differences were observed to be greater in younger individuals and in those with lower FIQ, and to be related to overall clinical severity. This work serves as an important step towards parsing factors that influence neuroanatomical heterogeneity in ASD and is a potential step towards establishing individual-specific biomarkers.


Assuntos
Transtorno do Espectro Autista/patologia , Encéfalo/anatomia & histologia , Encéfalo/patologia , Adolescente , Adulto , Fatores Etários , Córtex Cerebral/patologia , Criança , Pré-Escolar , Bases de Dados Factuais , Feminino , Humanos , Inteligência/fisiologia , Testes de Inteligência , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Neuroimagem , Caracteres Sexuais
8.
Proc Biol Sci ; 287(1941): 20201786, 2020 12 23.
Artigo em Inglês | MEDLINE | ID: mdl-33323093

RESUMO

Understanding whether organisms will be able to adapt to human-induced stressors currently endangering their existence is an urgent priority. Globally, multiple species moult from a dark summer to white winter coat to maintain camouflage against snowy landscapes. Decreasing snow cover duration owing to climate change is increasing mismatch in seasonal camouflage. To directly test for adaptive responses to recent changes in snow cover, we repeated historical (1950s) field studies of moult phenology in mountain hares (Lepus timidus) in Scotland. We found little evidence that population moult phenology has shifted to align seasonal coat colour with shorter snow seasons, or that phenotypic plasticity prevented increases in camouflage mismatch. The lack of responses resulted in 35 additional days of mismatch between 1950 and 2016. We emphasize the potential role of weak directional selection pressure and low genetic variability in shaping the scope for adaptive responses to anthropogenic stressors.


Assuntos
Adaptação Fisiológica , Lebres , Fenótipo , Pigmentos Biológicos , Animais , Mudança Climática , Cor , Humanos , Muda , Estações do Ano , Neve
9.
Acc Chem Res ; 52(10): 2950-2959, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31571486

RESUMO

Lead halide perovskites (LHPs) are attractive material systems for light emission, thanks to the ease and diverse routes of synthesis, the broad tunability in color, the high emission quantum efficiencies, and the strong light-matter coupling which may potentially lead to exciton-polariton condensation. This account contrasts the laser-like coherent light emission from highly lossy Fabry-Perot cavities, formed naturally from LHP nanowires (NWs) and nanoplates (NPs), with highly reflective cavities made of LHP gain media, sandwiched between two distributed Bragg reflector (DBR) mirrors. The mechanism responsible for the operation of conventional semiconductor lasers involves stimulated emission of electron and hole pairs bound by the Coulomb potential, i.e., excitons or, at excitation density above the so-called Mott threshold, an electron-hole plasma (EHP). We discuss how lasing from LHP NWs or NPs likely originates from stimulated emission of an EHP, not excitons or exciton-polaritons. A character central to this kind of lasing is the dynamically changing photonic properties in the naturally formed cavity. In contrast to the more static conditions of a DBR cavity, lasing modes and gain profiles are extremely sensitive to material properties and excitation conditions in an NW/NP cavity. While such unstable photonic cavities pose engineering challenges in the application of NW/NP lasers, they provide excellent probes of many-body physics in the LHP material. For sufficiently strong light-matter coupling expected for LHPs in DBR cavities, an exciton-polariton, i.e., the superposition state between the exciton and the cavity photon, can form. An exciting prospect of strong light-matter coupling is the potential formation of an exciton polariton condensate, which possesses many interesting quantum and nonlinear effects, such as superfluidity, long-range coherence, and laserlike light emission. However, it is difficult to distinguish coherent light from an exciton-polariton condensate and that from conventional stimulated laser emission. Several reports have established the condition of strong coupling for LHPs in DBR cavities. We stress, however, that these studies have not included necessary experiments to unambiguously establish the formation of exciton-polariton condensation, and several experiments and routes of analysis are needed to make a more convincing case for exciton-polariton condensation in LHP based systems. The potential of exciton-polariton condensation expands the horizon of LHP materials from conventional optoelectronics to quantum devices.

10.
Hum Biol ; 92(1): 45-57, 2020 11 17.
Artigo em Inglês | MEDLINE | ID: mdl-33231026

RESUMO

Native Hawaiian and other Pacific Islanders, and the environment they are in relationship with, have been the targets of exploitation, extraction, and destruction. Environmental atrocities throughout the Pacific have demonstrated how imperialism, capitalism, and white supremacy drive destruction through efforts to dominate and exploit for material gain. The relationship between Pacific people and the environment, which defines who they are socially, spiritually, and ancestrally, continues to be damaged and even severed by these injustices. The purpose of this article is to provide examples of major environmental injustices in the Pacific and to develop a deeper understanding of the relationship between settler colonialism and environmental injustices. Indigenous knowledge, with a focus on traditional ecological knowledge, is incorporated not just to demonstrate the deep impact of injustices on Pacific people's cultures but also to highlight how this way of knowing cultivates a path to revitalization and community resilience. Cultural practices rooted in traditional ecological knowledge, such as the preservation of food systems, promote reciprocity between living beings and self-determination, necessary for community flourishing. With this understanding, Pacific peoples' relationship with their land offers further evidence of the critical role culture and Indigenous knowledge can play in environmental justice policies and practices.


Assuntos
Colonialismo , Havaiano Nativo ou Outro Ilhéu do Pacífico , Havaí , Humanos , População Branca
11.
J Ethn Cult Divers Soc Work ; 30(1-2): 1-12, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-34135696

RESUMO

This special issue and introduction focuses on promoting health equity and addressing health disparities among Indigenous peoples of the United States (U.S.) and associated Territories in the Pacific Islands and Caribbean. We provide an overview of the current state of health equity across social, physical, and mental health domains. In Part 1 of the special issue, we trace promotive, protective, and risk factors related to Indigenous health equity. Part 2 of the special issue describes interventions that address and promote wellness, providing promising pathways to achieving and transcending health equity.

12.
J Am Chem Soc ; 141(33): 13143-13147, 2019 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-31357860

RESUMO

Singlet fission, the generation of two triplet excited states from the absorption of a single photon, may potentially increase solar energy conversion efficiency. A major roadblock in realizing this potential is the limited number of molecules available with high singlet fission yields and sufficient chemical stability. Here, we demonstrate a strategy for developing singlet fission materials in which we start with a stable molecular platform and use strain to tune the singlet and triplet energies. Using perylene diimide as a model system, we tune the singlet fission energetics from endoergic to exoergic or iso-energetic by straining the molecular backbone. The result is an increase in the singlet fission rate by 2 orders of magnitude. This demonstration opens a door to greatly expanding the molecular toolbox for singlet fission.

13.
Am J Community Psychol ; 64(1-2): 107-117, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31322733

RESUMO

Although Hawai'i is often portrayed as an idyllic paradise and is recognized as one of the healthiest States in the United States, pervasive health disparities exist among Native Hawaiians. Similar to other indigenous populations across the globe, these disparities are linked to unjust social and economic policies rooted in colonization and historical trauma. Western-centric efforts to address these disparities have yielded limited results. Consequently, indigenous frameworks to decolonize western-centric research processes have emerged. The Waimanalo Pono Research Hui is an example of a community-academic partnership that uses indigenous methodologies and principles of community-based participatory research as the foundation to engage Native Hawaiian community members in research. Monthly gatherings are held where community members and academic researchers share a meal and discuss community priorities with the goal of shaping research and programming that are rooted in Native Hawaiian values. A mission for the group has been created as well as protocols for community engagement to ensure all projects that work with the Waimanalo Pono Research Hui are ethically sound and grounded in the community's preferences, cultural knowledge, and lived experiences. Our community members continually report that the Waimanalo Pono Research Hui has positively transformed their perception of and willingness to engage in research. Similarly, university students and academic researchers express how much their knowledge about working with communities has grown and inspired them. Creating spaces for communities and researchers to build authentic relationships and engage in ongoing conversations can promote culturally grounded and community-driven research and programming.


Assuntos
Pesquisa Participativa Baseada na Comunidade/métodos , Relações Comunidade-Instituição , Competência Cultural , Promoção da Saúde/métodos , Povos Indígenas , Pesquisa Participativa Baseada na Comunidade/organização & administração , Cultura , Havaí , Promoção da Saúde/organização & administração , Humanos
14.
Opt Lett ; 43(9): 2177-2180, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29714783

RESUMO

Phonon polaritons (PhPs) are long-lived electromagnetic modes that originate from the coupling of infrared (IR) photons with the bound ionic lattice of a polar crystal. Cubic-boron nitride (cBN) is such a polar, semiconductor material which, due to the light atomic masses, can support high-frequency optical phonons. Here we report on random arrays of cBN nanostructures fabricated via an unpatterned reactive ion etching process. Fourier-transform infrared reflection spectra suggest the presence of localized surface PhPs within the reststrahlen band, with quality factors in excess of 38 observed. These can provide the basis of next-generation IR optical components such as antennas for communication, improved chemical spectroscopies, and enhanced emitters, sources, and detectors.

15.
Nanotechnology ; 29(3): 035605, 2018 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-29176049

RESUMO

We present a liquid phase post synthesis self-assemble protocol that transforms trillions of carbon nanotubes (CNTs) in powder form into densely packed flexible, robust and binder-free macroscopic membranes with a hierarchical pore structure. We employ charge transfer engineering to spontaneously disperse the CNTs in a liquid medium. The processing protocol has limited or no impact on the intrinsic properties of the CNTs. As the thickness of the CNT membrane is increased, we observed a gradual transition from high flexibility to buckling and brittleness in the flexural properties of the membranes. The binder-free CNT membranes have bulk mass density greater than that of water (1.0 g cm-3). We correlate the mass of the CNTs in the membrane to the thickness of the membrane and obtained a bulk mass density of ∼1.11 g cm-3 ± 0.03 g cm-3. We demonstrate the use of the CNT membranes as electrode in a pristine and oxidized single/stacked solid-state capacitor as well as pristine interdigitated microcapacitor that show time constant of ∼32 ms with no degradation in performance even after 10 000 cycles. The capacitors show very good temperature dependence over a wide range of temperatures with good cycling performance up to 90 °C. The specific capacitance of the pseudocapacitive CNT electrode at room temperature was 72 F g-1 and increased to 100 F g-1 at 70 °C. The leakage current of bipolar stacked solid state capacitor was ∼100 nA cm-2 at 2.5 V when held for 72 h.

16.
J Environ Manage ; 220: 126-135, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-29777995

RESUMO

In the West, limited government capacity to solve environmental problems has triggered the rise of a variety of "nonstate actors" to supplement government efforts or provide alternative mechanisms for addressing environmental issues. How does this development - along with our efforts to understand it - map onto environmental governance processes in China? China's efforts to address environmental issues reflect institutionalized governance processes that differ from parallel western processes in ways that have major consequences for domestic environmental governance practices and the governance of China "going abroad." China's governance processes blur the distinction between the state and other actors; the "shadow of the state" is a major factor in all efforts to address environmental issues. The space occupied by nonstate actors in western systems is occupied by shiye danwei ("public service units"), she hui tuanti ("social associations") and e-platforms, all of which have close links to the state. Meanwhile, international NGOs and multinational corporations are also significant players in China. As a result, the mechanisms of influence that produce effects in China differ in important ways from mechanisms familiar from the western experience. This conclusion has far-reaching implications for those seeking to address global environmental concerns, given the importance of China's growing economy and burgeoning network of trade relationships.


Assuntos
Política Ambiental , Programas Governamentais , China , Governo , Humanos
17.
Faraday Discuss ; 197: 287-307, 2017 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-28197597

RESUMO

The effect of sodium species on the physical and catalytic properties of Cu/ZnO catalysts derived from zincian georgeite has been investigated. Catalysts prepared with <100 ppm to 2.1 wt% Na+, using a supercritical CO2 antisolvent technique, were characterised and tested for the low temperature water-gas shift reaction and also CO2 hydrogenation to methanol. It was found that zincian georgeite catalyst precursor stability was dependent on the Na+ concentration, with the 2.1 wt% Na+-containing sample uncontrollably ageing to malachite and sodium zinc carbonate. Samples with lower Na+ contents (<100-2500 ppm) remained as the amorphous zincian georgeite phase, which on calcination and reduction resulted in similar CuO/Cu particle sizes and Cu surface areas. The aged 2.1 wt% Na+ containing sample, after calcination and reduction, was found to comprise of larger CuO crystallites and a lower Cu surface area. However, calcination of the high Na+ sample immediately after precipitation (before ageing) resulted in a comparable CuO/Cu particle size to the lower (<100-2500 ppm) Na+ containing samples, but with a lower Cu surface area, which indicates that Na+ species block Cu sites. Activity of the catalysts for the water-gas shift reaction and methanol yields in the methanol synthesis reaction correlated with Na+ content, suggesting that Na+ directly poisons the catalyst. In situ XRD analysis showed that the ZnO crystallite size and consequently Cu crystallite size increased dramatically in the presence of water in a syn-gas reaction mixture, showing that stabilisation of nanocrystalline ZnO is required. Sodium species have a moderate effect on ZnO and Cu crystallite growth rate, with lower Na+ content resulting in slightly reduced rates of growth under reaction conditions.

18.
IEEE Trans Geosci Remote Sens ; 55(4): 1954-1966, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32661449

RESUMO

The Soil Moisture Active-Passive (SMAP) L-band microwave radiometer is a conical scanning instrument designed to measure soil moisture with 4% volumetric accuracy at 40-km spatial resolution. SMAP is NASA's first Earth Systematic Mission developed in response to its first Earth science decadal survey. Here, the design is reviewed and the results of its first year on orbit are presented. Unique features of the radiometer include a large 6-m rotating reflector, fully polarimetric radiometer receiver with internal calibration, and radio-frequency interference detection and filtering hardware. The radiometer electronics are thermally controlled to achieve good radiometric stability. Analyses of on-orbit results indicate that the electrical and thermal characteristics of the electronics and internal calibration sources are very stable and promote excellent gain stability. Radiometer NEDT < 1 K for 17-ms samples. The gain spectrum exhibits low noise at frequencies >1 MHz and 1/f noise rising at longer time scales fully captured by the internal calibration scheme. Results from sky observations and global swath imagery of all four Stokes antenna temperatures indicate that the instrument is operating as expected.

19.
Nano Lett ; 16(10): 6052-6057, 2016 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-27580074

RESUMO

We investigate the distribution and temperature-dependent optical properties of sharp, zero-phonon emission from defect-based single photon sources in multilayer hexagonal boron nitride (h-BN) flakes. We observe sharp emission lines from optically active defects distributed across an energy range that exceeds 500 meV. Spectrally resolved photon-correlation measurements verify single photon emission, even when multiple emission lines are simultaneously excited within the same h-BN flake. We also present a detailed study of the temperature-dependent line width, spectral energy shift, and intensity for two different zero-phonon lines centered at 575 and 682 nm, which reveals a nearly identical temperature dependence despite a large difference in transition energy. Our temperature-dependent results are well described by a lattice vibration model that considers piezoelectric coupling to in-plane phonons. Finally, polarization spectroscopy measurements suggest that whereas the 575 nm emission line is directly excited by 532 nm excitation, the 682 nm line is excited indirectly.

20.
J Biol Chem ; 290(18): 11547-56, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25784555

RESUMO

Lipid accumulation in liver and skeletal muscle contributes to co-morbidities associated with diabetes and obesity. We made a transgenic mouse in which the adiponectin (Adipoq) promoter drives expression of lipoprotein lipase (LPL) in adipocytes to potentially increase adipose tissue lipid storage. These mice (Adipoq-LPL) have improved glucose and insulin tolerance as well as increased energy expenditure when challenged with a high fat diet (HFD). To identify the mechanism(s) involved, we determined whether the Adipoq-LPL mice diverted dietary lipid to adipose tissue to reduce peripheral lipotoxicity, but we found no evidence for this. Instead, characterization of the adipose tissue of the male mice after HFD challenge revealed that the mRNA levels of peroxisome proliferator-activated receptor-γ (PPARγ) and a number of PPARγ-regulated genes were higher in the epididymal fat pads of Adipoq-LPL mice than control mice. This included adiponectin, whose mRNA levels were increased, leading to increased adiponectin serum levels in the Adipoq-LPL mice. In many respects, the adipose phenotype of these animals resembles thiazolidinedione treatment except for one important difference, the Adipoq-LPL mice did not gain more fat mass on HFD than control mice and did not have increased expression of genes in adipose such as glycerol kinase, which are induced by high affinity PPAR agonists. Rather, there was selective induction of PPARγ-regulated genes such as adiponectin in the adipose of the Adipoq-LPL mice, suggesting that increasing adipose tissue LPL improves glucose metabolism in diet-induced obesity by improving the adipose tissue phenotype. Adipoq-LPL mice also have increased energy expenditure.


Assuntos
Adipócitos/metabolismo , Dieta Hiperlipídica/efeitos adversos , Glucose/metabolismo , Lipase Lipoproteica/genética , Lipase Lipoproteica/metabolismo , Obesidade/metabolismo , Obesidade/patologia , Adipócitos/efeitos dos fármacos , Animais , Feminino , Humanos , Resistência à Insulina , Masculino , Camundongos , Camundongos Transgênicos , Obesidade/enzimologia , Obesidade/genética , Fenótipo , Tiazolidinedionas/farmacologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA