Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 75
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Phys Rev Lett ; 124(13): 131301, 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32302154

RESUMO

Using only cosmic microwave background polarization data from the polarbear experiment, we measure B-mode polarization delensing on subdegree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments.

2.
Mol Psychiatry ; 23(10): 2078-2089, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29112191

RESUMO

Functional imaging and gene expression studies both implicate the medial prefrontal cortex (mPFC), particularly deep-layer projection neurons, as a potential locus for autism pathology. Here, we explored how specific deep-layer prefrontal neurons contribute to abnormal physiology and behavior in mouse models of autism. First, we find that across three etiologically distinct models-in utero valproic acid (VPA) exposure, CNTNAP2 knockout and FMR1 knockout-layer 5 subcortically projecting (SC) neurons consistently exhibit reduced input resistance and action potential firing. To explore how altered SC neuron physiology might impact behavior, we took advantage of the fact that in deep layers of the mPFC, dopamine D2 receptors (D2Rs) are mainly expressed by SC neurons, and used D2-Cre mice to label D2R+ neurons for calcium imaging or optogenetics. We found that social exploration preferentially recruits mPFC D2R+ cells, but that this recruitment is attenuated in VPA-exposed mice. Stimulating mPFC D2R+ neurons disrupts normal social interaction. Conversely, inhibiting these cells enhances social behavior in VPA-exposed mice. Importantly, this effect was not reproduced by nonspecifically inhibiting mPFC neurons in VPA-exposed mice, or by inhibiting D2R+ neurons in wild-type mice. These findings suggest that multiple forms of autism may alter the physiology of specific deep-layer prefrontal neurons that project to subcortical targets. Furthermore, a highly overlapping population-prefrontal D2R+ neurons-plays an important role in both normal and abnormal social behavior, such that targeting these cells can elicit potentially therapeutic effects.


Assuntos
Transtorno do Espectro Autista/metabolismo , Transtorno do Espectro Autista/patologia , Córtex Pré-Frontal/patologia , Potenciais de Ação/efeitos dos fármacos , Animais , Transtorno Autístico/metabolismo , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Feminino , Proteína do X Frágil da Deficiência Intelectual/genética , Relações Interpessoais , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Neurônios/fisiologia , Optogenética , Córtex Pré-Frontal/fisiologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Receptores de Dopamina D2/metabolismo , Comportamento Social , Ácido Valproico/farmacologia
3.
Nature ; 495(7441): 344-7, 2013 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-23485967

RESUMO

In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.

4.
Nature ; 488(7411): 349-52, 2012 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-22895340

RESUMO

In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.

6.
Br J Cancer ; 110(4): 976-83, 2014 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-24366298

RESUMO

BACKGROUND: Securing a diagnosis of ovarian cancer and establishing means to predict outcomes to therapeutics remain formidable clinical challenges. Early diagnosis is particularly important since survival rates are markedly improved if tumour is detected early. METHODS: Comprehensive miRNA profiles were generated on presurgical plasma samples from 42 women with confirmed serous epithelial ovarian cancer, 36 women diagnosed with a benign neoplasm, and 23 comparably age-matched women with no known pelvic mass. RESULTS: Twenty-two miRNAs were differentially expressed between healthy controls and the ovarian cancer group (P<0.05), while a six miRNA profile subset distinguished presurgical plasma from benign and ovarian cancer patients. There were also significant differences in miRNA profiles in presurgical plasma from women diagnosed with ovarian cancer who had short overall survival when compared to women with long overall survival (P<0.05). CONCLUSION: Our preliminary data support the utility of circulating plasma miRNAs to distinguish women with ovarian cancer from those with a benign mass and identify women likely to benefit from currently available treatment for serous epithelial ovarian cancer from those who may not.


Assuntos
Biomarcadores Tumorais/sangue , MicroRNAs/sangue , Neoplasias Epiteliais e Glandulares/sangue , Neoplasias Epiteliais e Glandulares/mortalidade , Neoplasias Ovarianas/sangue , Neoplasias Ovarianas/mortalidade , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores Tumorais/genética , Carcinoma Epitelial do Ovário , Feminino , Humanos , Pessoa de Meia-Idade , Neoplasias Epiteliais e Glandulares/genética , Neoplasias Ovarianas/genética , Sobrevida , Resultado do Tratamento , Adulto Jovem
7.
Phys Rev Lett ; 113(2): 021301, 2014 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-25062161

RESUMO

Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ∼30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat+sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.

8.
Phys Rev Lett ; 112(13): 131302, 2014 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-24745402

RESUMO

We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.

9.
Rev Sci Instrum ; 95(2)2024 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-38385955

RESUMO

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀0.42 m) and large (⌀6 m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8 Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505 mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50 K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2 Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 µrad s. During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance.

10.
Phys Rev Lett ; 111(14): 141301, 2013 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-24138230

RESUMO

Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This "B-mode" signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals. In this Letter we present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the South Pole Telescope (SPTpol). We construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel-SPIRE map of the cosmic infrared background. We compare this template to the B modes measured directly by SPTpol, finding a nonzero correlation at 7.7σ significance. The correlation has an amplitude and scale dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable.

11.
East Asian Arch Psychiatry ; 33(1): 15-20, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36991551

RESUMO

OBJECTIVE: To determine whether meaning in life (MIL) was associated with a lower risk of depression in people from low-income families during the COVID-19 pandemic. METHODS: Individuals from low-income families were recruited at a community centre during the fourth wave of the COVID-19 pandemic in Hong Kong. Levels of MIL were assessed using the Meaning in Life Questionnaire (MLQ). Severity of depressive symptoms was assessed using the Patient Health Questionnaire-9 (PHQ-9). Scores of ≥24 on the Presence of Meaning subscale (MLQ-P) and Search for Meaning subscale (MLQ-S) were considered high. A score of ≥10 on the PHQ-9 was indicative of clinical depression. Correlations between MLQ and PHQ-9 scores were examined, along with associations between presence of/search for meaning and risk of clinical depression. RESULTS: Among 102 participants, 64 (62.7%) had clinical depression; 14 (13.7%) had both high presence of meaning and high search for meaning. The MLQ score was correlated with the PHQ-9 score (r = -0.56, p < 0.001). The adjusted risk ratio for depression was 0.31 (p = 0.006) in participants with both high presence of meaning and high search for meaning. CONCLUSION: Among people with lower socioeconomic status, MIL may be important for protecting against depression during the COVID-19 pandemic.


Assuntos
COVID-19 , Humanos , COVID-19/epidemiologia , Hong Kong/epidemiologia , Depressão/epidemiologia , Depressão/diagnóstico , Pandemias , Inquéritos e Questionários
12.
Rev Sci Instrum ; 94(6)2023 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-37862532

RESUMO

A half-wave plate (HWP) is often used as a modulator to suppress systematic error in the measurements of cosmic microwave background (CMB) polarization. A HWP can also be used to measure circular polarization (CP) through its optical leakage from CP to linear polarization. The CP of the CMB is predicted from various sources, such as interactions in the Universe and extension of the standard model. Interaction with supernova remnants of population III stars is one of the brightest CP sources. Thus, the observation of the CP of CMB is a new tool for searching for population III stars. In this paper, we demonstrate the improved measurement of the leakage coefficient using the transmission measurement of an actual HWP in the laboratory. We measured the transmittance of linearly polarized light through the HWP used in Polarbear in the frequency range of 120-160 GHz. We evaluate the properties of the HWP by fitting the data with a physical model using the Markov Chain Monte Carlo method. We then estimate the band-averaged CP leakage coefficient using the physical model. We find that the leakage coefficient strongly depends on the spectra of CP sources. We thus calculate the maximum fractional leakage coefficient from CP to linear polarization as 0.133 ± 0.009 in the Rayleigh-Jeans spectrum. The nonzero value shows that Polarbear has a sensitivity to CP. Additionally, because we use the bandpass of detectors installed in the telescope to calculate the band-averaged values, we also consider systematic effects in the experiment.

13.
East Asian Arch Psychiatry ; 32(1): 17-21, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35332106

RESUMO

OBJECTIVE: This study aimed to determine the prevalence of depression and the level of perceived social support among occupational therapists during the pandemic, and to identify any associations between depression and perceived social support. METHODS: Using convenience and snowball sampling, occupational therapists aged ≥18 years who were working in Hong Kong and able to read and understand Chinese were invited to participate in a survey between January 2021 and April 2021 (during the fourth wave of COVID-19 pandemic). Data collected included age, sex, education level, employment status, marital status, living status, level of perceived social support (measured by the Multidimensional Scale of Perceived Social Support [MSPSS-C]) and level of depression (measured by the Patient Health Questionnaire-9 [PHQ-9]). RESULTS: 87 occupational therapists completed the survey. The mean MSPSS-C score was 67.87; 88.5% of participants had a high level of perceived social support. The mean PHQ-9 score was 4.67; 59.8% of participants had no or minimal depression and 11.5% of participants had clinical depression. The MSPSS-C score negatively correlated with the PHQ-9 score (rs = -0.401, p < 0.001). In regression analysis, the MSPSS-C score was associated with the PHQ-9 score (F(1, 85) = 44.846, r = 0.588, p < 0.001). About 34.5% of the variance of the PHQ-9 score was accounted for by the MSPSS-C score. CONCLUSION: Higher level of perceived social support is associated with lower level of depression. Social support might serve as a protective factor for depression among occupational therapists in Hong Kong during the pandemic.


Assuntos
COVID-19 , Transtorno Depressivo Maior , Adolescente , Adulto , COVID-19/epidemiologia , Depressão/epidemiologia , Transtorno Depressivo Maior/epidemiologia , Hong Kong/epidemiologia , Humanos , Terapeutas Ocupacionais , Pandemias , Apoio Social
14.
J Low Temp Phys ; 209(5-6): 1232-1241, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36467122

RESUMO

Lenslet-coupled antenna arrays have been used in CMB experiments and are the baseline technology for the next-generation satellite missions such as LiteBIRD and PICO. Lenslets are small hemispherical lenses mounted on the focal plane that couple light to the detectors and are typically made of silicon or alumina due to their high focusing power and low absorption loss. To minimize reflection at the vacuum-dielectric interface, lenslets require anti-reflection (AR) coatings. Metamaterials have been used in large microwave optical components because they avoid any mismatch on the thermal expansion between the lens and its coating, but so far they have only been machined on surfaces of comparatively large radius of curvature. As a first step to understand the feasibility of machining metamaterial AR layers in lenslets through laser-etching for the LiteBIRD mission, a model in ANSYS HFSS was developed. The goal of the simulation was to optimize transmission in three frequency bands while meeting assumed laser machinability constraints and optical requirements. Simulation results from flat silicon show that an AR metamaterial coating made under the assumed conditions is feasible, and the baseline parameters for further curved-surface studies are provided.

15.
Ann Rheum Dis ; 70(5): 864-7, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21177295

RESUMO

OBJECTIVES: The genetic aetiology of osteoarthritis has not yet been elucidated. To enable a well-powered genome-wide association study (GWAS) for osteoarthritis, the authors have formed the arcOGEN Consortium, a UK-wide collaborative effort aiming to scan genome-wide over 7500 osteoarthritis cases in a two-stage genome-wide association scan. Here the authors report the findings of the stage 1 interim analysis. METHODS: The authors have performed a genome-wide association scan for knee and hip osteoarthritis in 3177 cases and 4894 population-based controls from the UK. Replication of promising signals was carried out in silico in five further scans (44,449 individuals), and de novo in 14 534 independent samples, all of European descent. RESULTS: None of the association signals the authors identified reach genome-wide levels of statistical significance, therefore stressing the need for corroboration in sample sets of a larger size. Application of analytical approaches to examine the allelic architecture of disease to the stage 1 genome-wide association scan data suggests that osteoarthritis is a highly polygenic disease with multiple risk variants conferring small effects. CONCLUSIONS: Identifying loci conferring susceptibility to osteoarthritis will require large-scale sample sizes and well-defined phenotypes to minimise heterogeneity.


Assuntos
Osteoartrite do Quadril/genética , Osteoartrite do Joelho/genética , Estudos de Casos e Controles , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Humanos , Herança Multifatorial , Polimorfismo de Nucleotídeo Único
16.
Genes Immun ; 11(6): 515-21, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19847193

RESUMO

Previous work has demonstrated that Northern and Southern European ancestries are associated with specific systemic lupus erythematosus (SLE) manifestations. In this study, 1855 SLE cases of European descent were genotyped for 4965 single-nucleotide polymorphisms and principal components analysis of genotype information was used to define population substructure. The first principal component (PC1) distinguished Northern from Southern European ancestry, PC2 differentiated Eastern from Western European ancestry and PC3 delineated Ashkenazi Jewish ancestry. Compared with Northern European ancestry, Southern European ancestry was associated with autoantibody production (odds ratio (OR)=1.40, 95% confidence interval (CI) 1.07-1.83) and renal involvement (OR 1.41, 95% CI 1.06-1.87), and was protective for discoid rash (OR=0.51, 95% CI 0.32-0.82) and photosensitivity (OR=0.74, 95% CI 0.56-0.97). Both serositis (OR=1.46, 95% CI 1.12-1.89) and autoantibody production (OR=1.38, 95% CI 1.06-1.80) were associated with Western compared to Eastern European ancestry. Ashkenazi Jewish ancestry was protective against neurologic manifestations of SLE (OR=0.62, 95% CI 0.40-0.94). Homogeneous clusters of cases defined by multiple PCs demonstrated stronger phenotypic associations. Genetic ancestry may contribute to the development of SLE endophenotypes and should be accounted for in genetic studies of disease characteristics.


Assuntos
Endofenótipos , Predisposição Genética para Doença/genética , Lúpus Eritematoso Sistêmico/genética , População Branca/genética , Adulto , Estudos de Coortes , Feminino , Predisposição Genética para Doença/epidemiologia , Humanos , Lúpus Eritematoso Sistêmico/epidemiologia , Masculino , América do Norte/epidemiologia , Polimorfismo de Nucleotídeo Único/genética
17.
J Exp Med ; 170(5): 1627-33, 1989 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-2809510

RESUMO

Cytokines secreted in response to invading micro-organisms are important mediators of detrimental hemodynamic and metabolic changes in the host. To test whether cachectin/TNF plays a role in triggering release of other cytokines in the setting of infection, anesthetized baboons were passively immunized against systemic cachectin/TNF before infusion of a LD100 dose of live Escherichia coli. Bacteremia led to significant increases in circulating levels of cachectin/TNF, IL-1 beta, and IL-6. Although bacterial endotoxin/lipopolysaccharide is a potent stimulus for the synthesis and release of IL-1 and IL-6 in vitro, specific neutralization of cachectin/TNF in vivo with mAb pretreatment significantly attenuated both the IL-1 beta and the IL-6 responses despite fulminant overwhelming bacteremia. These data suggest that cachectin/TNF is essential for the initiation or amplification of IL-1 and IL-6 release during lethal gram-negative septic shock syndrome.


Assuntos
Interleucina-1/metabolismo , Interleucina-6/metabolismo , Sepse/fisiopatologia , Choque Séptico/fisiopatologia , Fator de Necrose Tumoral alfa/fisiologia , Animais , Imunização Passiva , Papio , Sepse/sangue , Choque Séptico/sangue , Fator de Necrose Tumoral alfa/imunologia
18.
East Asian Arch Psychiatry ; 30(3): 67-72, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32994373

RESUMO

OBJECTIVE: To determine associations between mindfulness meditation and mental health and health-related quality of life among Buddhist monastics. METHODS: This is a cross-sectional study of Chinese Buddhist monastics aged ≥18 years who practised mindfulness meditation daily. Mental health was assessed by the 12-item General Health Questionnaire (GHQ-12), whereas health-related quality of life was assessed by the 12-item Short Form Health Survey (SF-12). The number of years and the average daily amount of time spent in mindfulness meditation were collected. RESULTS: 47 monastics completed the interview. They practised mindfulness meditation for a mean of 7.3 years, 1.1 hours per day. Both the number of years (ß = -0.48, p = 0.03) and amount of daily practice (ß = -0.53, p < 0.001) of mindfulness meditation were associated with the GHQ-12 score, after adjusting for age, sex, education, and years of being a monastic. Only the amount of daily practice (ß = 0.44, p = 0.004) was associated with the mental component summary of SF-12. Neither was associated with the physical component summary of SF-12. CONCLUSIONS: Among Chinese Buddhist monastics who practise daily mindfulness meditation, spending more time each day and having longer years of practice were associated with better mental health.


Assuntos
Budismo/psicologia , Meditação , Saúde Mental , Atenção Plena , Monges/psicologia , Qualidade de Vida , Adulto , Povo Asiático/psicologia , Estudos Transversais , Feminino , Humanos , Masculino , Meditação/psicologia , Fatores de Tempo
19.
Sci Adv ; 6(36)2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32917614

RESUMO

Global strategies to halt the dual crises of biodiversity loss and climate change are often formulated separately, even though they are interdependent and risk failure if pursued in isolation. The Global Safety Net maps how expanded nature conservation addresses both overarching threats. We identify 50% of the terrestrial realm that, if conserved, would reverse further biodiversity loss, prevent CO2 emissions from land conversion, and enhance natural carbon removal. This framework shows that, beyond the 15.1% land area currently protected, 35.3% of land area is needed to conserve additional sites of particular importance for biodiversity and stabilize the climate. Fifty ecoregions and 20 countries contribute disproportionately to proposed targets. Indigenous lands overlap extensively with the Global Safety Net. Conserving the Global Safety Net could support public health by reducing the potential for zoonotic diseases like COVID-19 from emerging in the future.


Assuntos
Biodiversidade , Mudança Climática , Conservação dos Recursos Naturais/métodos , Clima , Planeta Terra , Ecossistema , Humanos , Saúde Pública
20.
Rev Sci Instrum ; 91(12): 124503, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-33380005

RESUMO

We present the design and laboratory evaluation of a cryogenic continuously rotating half-wave plate (CHWP) for the POLARBEAR-2b (PB-2b) cosmic microwave background receiver, the second installment of the Simons Array. PB-2b will observe at 5200 m elevation in the Atacama Desert of Chile in two frequency bands centered at 90 GHz and 150 GHz. In order to suppress atmospheric 1/f noise and mitigate systematic effects that arise when differencing orthogonal detectors, PB-2b modulates linear sky polarization using a CHWP rotating at 2 Hz. The CHWP has a 440 mm clear aperture diameter and is cooled to ≈50 K in the PB-2b receiver cryostat. It consists of a low-friction superconducting magnetic bearing and a low-torque synchronous electromagnetic motor, which together dissipate <2 W. During cooldown, a grip-and-release mechanism centers the rotor to <0.5 mm, and during continuous rotation, an incremental optical encoder measures the rotor angle with a noise level of 0.1 µrad/Hz. We discuss the experimental requirements for the PB-2b CHWP, the designs of its various subsystems, and the results of its evaluation in the laboratory. The presented CHWP has been deployed to Chile and is expected to see first light on PB-2b in 2020 or 2021.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA