A new and improved setup of the SF6 retrieval together with a newly calibrated version of MIPAS-ENVISAT level 1b spectra (version 5, ESA data version 5.02/5.06) was used to obtain a new global SF6 ...data set, covering the total observational period of MIPAS from July 2002 to April 2012 for the first time. Monthly and zonally averaged SF6 profiles were converted into mean age of air using a tropospheric SF6-reference curve. The obtained data set of age of air was compared to airborne age of air measurements. The temporal evolution of the mean age of air was then investigated in 10° latitude and 1–2 km altitude bins. A regression model consisting of a constant and a linear trend term, two proxies for the quasi-biennial oscillation variation, sinusoidal terms for the seasonal and semiannual variation and overtones was fitted to the age of air time series. The annual cycle for particular regions in the stratosphere was investigated and compared to other studies. The age of air trend over the total MIPAS period consisting of the linear term was assessed and compared to previous findings of Stiller et al. (2012). While the linear increase of mean age is confirmed to be positive for the northern midlatitudes and southern polar middle stratosphere, differences are found in the northern polar upper stratosphere, where the mean age is now found to increase as well. The magnitude of trends in the northern midlatitude middle stratosphere is slightly lower compared to the previous version and the trends fit remarkably well to the trend derived by Engel et al. (2009). Negative age of air trends found by Stiller et al. (2012) are confirmed for the lowermost tropical stratosphere and lowermost southern midlatitudinal stratosphere. Differences to the previous data versions occur in the middle tropical stratosphere around 25 km, where the trends are now negative. Overall, the new latitude–altitude distribution of trends appears to be less patchy and more coherent than the previous one. The new data provide evidence of an accelerating shallow branch of the Brewer–Dobson circulation, at least in the Southern Hemisphere. Finally the age of air decadal trends are compared to trends calculated with simulated SF6 values by the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and good agreement is found. The hemispheric asymmetry in the trends found in the MIPAS data is also indicated in the trends calculated with simulated SF6 values by the KASIMA model.
Ratification of the Minamata Convention on Mercury has led to the establishment of Peruvian regulations limiting mercury concentrations in air to 2000 ng/m3over a 24-hr measurement period. As a ...result, three communities in Madre de Dios, Peru were mapped during October 2017 to determine Hg0 vapor concentrations in the air. The town of Tres Islas exhibited Hg0 concentrations less than 200 ng/m3: the minimum risk level defined by the Agency for Toxic Substances and Disease Registry. These low concentrations were reflective of a town in the region with limited exposure to artisanal and small-scale gold mining (ASGM). However, the ASGM communities of Laberinto and Delta One exhibited concentrations of Hg0 vapor that exceeded 2,000,000 ng/m3 surrounding active gold shops, where amalgams and processed amalgams were heated with open flames. Laberinto was reevaluated in May 2018 during which time Hg0 levels on the sidewalks in front of gold shops again exceeded 2,000,000 ng/m3. Within the scope of this paper a rapid mapping technique allows for the detection of sources of Hg0 pollution and identifies neighborhoods that require intervention to decrease Hg0 emissions. In addition, this work highlights the difficulties of measuring total gaseous mercury in ASGM communities with gold shops according to the Peruvian law.
•Hg0 concentrations were measured and mapped in three towns in Madre de Dios, Peru•Hg0 concentrations exceeding 2,000,000 ng/m3 were measured in and around gold shops•Air Concentrations of Hg0 from ASGM activities greatly exceed Peruvian standards•Existing ventilation and mercury capture systems in gold shops are ineffective•Gold shops in mining communities are a threat to human and environmental health
A new first-order asymptotic theory for
heteroskedasticity-autocorrelation (HAC) robust tests based on
nonparametric covariance matrix estimators is developed. The bandwidth of
the covariance matrix ...estimator is modeled as a fixed proportion of the
sample size. This leads to a distribution theory for HAC robust tests that
explicitly captures the choice of bandwidth and kernel. This contrasts
with the traditional asymptotics (where the bandwidth increases more
slowly than the sample size) where the asymptotic distributions of HAC
robust tests do not depend on the bandwidth or kernel. Finite-sample
simulations show that the new approach is more accurate than the
traditional asymptotics. The impact of bandwidth and kernel choice on size
and power of t-tests is analyzed. Smaller bandwidths lead to
tests with higher power but greater size distortions, and large bandwidths
lead to tests with lower power but smaller size distortions. Size
distortions across bandwidths increase as the serial correlation in the
data becomes stronger. Overall, the results clearly indicate that for
bandwidth and kernel choice there is a trade-off between size distortions
and power. Finite-sample performance using the new asymptotics is
comparable to the bootstrap, which suggests that the asymptotic theory in
this paper could be useful in understanding the theoretical properties of
the bootstrap when applied to HAC robust tests.We thank an editor and a referee for constructive comments on
a previous version of the paper. Helpful comments provided by Cliff
Hurvich, Andy Levin, Jeff Simonoff, and seminar participants at NYU
(Statistics), U. Texas Austin, Yale, U. Montreal, UCSD, UC Riverside, UC
Berkeley, U. of Pittsburgh, SUNY Albany, U. Aarhus, Brown U., NBER/NSF
Time Series Conference, and 2003 Winter Meetings of the Econometrics
Society are gratefully acknowledged. We gratefully acknowledge financial
support from the National Science Foundation through grant SES-0095211. We
thank the Center for Analytic Economics at Cornell
University.
Models for light dark matter particles with masses below 1 GeV/c Formula omitted are a natural and well-motivated alternative to so-far unobserved weakly interacting massive particles. Gram-scale ...cryogenic calorimeters provide the required detector performance to detect these particles and extend the direct dark matter search program of CRESST. A prototype 0.5 g sapphire detector developed for the Formula omitted-cleus experiment has achieved an energy threshold of Formula omitted eV. This is one order of magnitude lower than for previous devices and independent of the type of particle interaction. The result presented here is obtained in a setup above ground without significant shielding against ambient and cosmogenic radiation. Although operated in a high-background environment, the detector probes a new range of light-mass dark matter particles previously not accessible by direct searches. We report the first limit on the spin-independent dark matter particle-nucleon cross section for masses between 140 and 500 MeV/c Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Neural fingerprinting is the identification of individuals in a cohort based on neuroimaging recordings of brain activity. In magneto- and electroencephalography (M/EEG), it is common practice to use ...second-order statistical measures, such as correlation or connectivity matrices, when neural fingerprinting is performed. These measures or features typically require coupling between signal channels and often ignore the individual temporal dynamics. In this study, we show that, following recent advances in multivariate time series classification, such as the development of the RandOm Convolutional KErnel Transformation (ROCKET) classifier, it is possible to perform classification directly on short time segments from MEG resting-state recordings with remarkably high classification accuracies. In a cohort of 124 subjects, it was possible to assign windows of time series of 1 s in duration to the correct subject with above 99% accuracy. The achieved accuracies are vastly superior to those of previous methods while simultaneously requiring considerably shorter time segments.
The CRESST-II cryogenic dark matter search aims for the detection of WIMPs via elastic scattering off nuclei in CaWO
4
crystals. We present results from a low-threshold analysis of a single upgraded ...detector module. This module efficiently vetoes low energy backgrounds induced by
α
-decays on inner surfaces of the detector. With an exposure of 29.35 kg live days collected in 2013 we set a limit on spin-independent WIMP-nucleon scattering which probes a new region of parameter space for WIMP masses below 3 GeV/c
2
, previously not covered in direct detection searches. A possible excess over background discussed for the previous CRESST-II phase 1 (from 2009 to 2011) is not confirmed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Two-dimensional infrared (2D-IR) spectroscopy is a powerful technique capable of accessing structure and dynamics with ultrafast time resolution in a wide range of chemical contexts. Since the early ...development of 2D-IR and related nonlinear IR spectroscopy methods, coordination complexes have been used primarily due to their well-defined structures and large transition intensities. As research interests have broadened to include catalysis and photocatalysis, however, 2D-IR spectroscopy has found great success in characterizing structural dynamics in a wide range of coordination complexes.
The formation of the proper number of functional nephrons requires a delicate balance between renal progenitor cell self-renewal and differentiation. The molecular factors that regulate the dramatic ...expansion of the progenitor cell pool and differentiation of these cells into nephron precursor structures (renal vesicles) are not well understood. Here we show that Sall1, a nuclear transcription factor, is required to maintain the stemness of nephron progenitor cells. Transcriptional profiling of Sall1 mutant cells revealed a striking pattern, marked by the reduction of progenitor genes and amplified expression of renal vesicle differentiation genes. These global changes in gene expression were accompanied by ectopic differentiation at E12.5 and depletion of Six2+Cited1+ cap mesenchyme progenitor cells. These findings highlight a novel role for Sall1 in maintaining the stemness of the progenitor cell pool by restraining their differentiation into renal vesicles.
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