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51.
  • Dahlin, Jakob, 1976- (författare)
  • Aerosols of Isocyanates, Amines and Anhydrides : Sampling and Analysis
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during thermal degradation of polymers such as polyurethane (PUR) or epoxy.Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the compounds are listed as human carcinogens. Many workers are exposed.Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates, aminoisocyanates and anhydrides using di-n-butylamine (DBA) as reagent to form stabile urea derivatives or amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled detection limits as low as 10 attomoles. A nitrogen-selective LC-detector enabled quantification of DBA-derivatives in reference solutions. A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (<1 µm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Aromatic isocyanates become associated to small particles (<1 µm). As a reference method, air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder-impactor sampler and the reference method.
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52.
  • de Jong, Roelof S., et al. (författare)
  • 4MOST-4-metre Multi-Object Spectroscopic Telescope
  • 2014
  • Ingår i: Ground-based and Airborne Instrumentation for Astronomy V. - : SPIE. - 1996-756X .- 0277-786X. ; 9147
  • Konferensbidrag (refereegranskat)abstract
    • 4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with similar to 2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; similar to 1600 fibres go to two spectrographs with resolution R> 5000 (lambda similar to 390-930 nm) and similar to 800 fibres to a spectrograph with R> 18,000 (lambda similar to 392-437 nm & 515-572 nm & 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020. This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more detailed descriptions of the instrument concept[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].
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53.
  • De Rezende, Susanna F., et al. (författare)
  • Automating algebraic proof systems is NP-hard
  • 2021
  • Ingår i: STOC 2021 - Proceedings of the 53rd Annual ACM SIGACT Symposium on Theory of Computing. - New York, NY, USA : ACM. - 0737-8017. - 9781450380539 ; , s. 209-222
  • Konferensbidrag (refereegranskat)abstract
    • We show that algebraic proofs are hard to find: Given an unsatisfiable CNF formula F, it is NP-hard to find a refutation of F in the Nullstellensatz, Polynomial Calculus, or Sherali-Adams proof systems in time polynomial in the size of the shortest such refutation. Our work extends, and gives a simplified proof of, the recent breakthrough of Atserias and Müller (JACM 2020) that established an analogous result for Resolution.
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54.
  • De Rezende, Susanna F., et al. (författare)
  • KRW composition theorems via lifting
  • 2020
  • Ingår i: Proceedings - 2020 IEEE 61st Annual Symposium on Foundations of Computer Science, FOCS 2020. - 0272-5428. - 9781728196213 - 9781728196220 ; 2020-November, s. 43-49
  • Konferensbidrag (refereegranskat)abstract
    • One of the major open problems in complexity theory is proving super-logarithmic lower bounds on the depth of circuits (i.e., mathrm{P} nsubseteq text{NC}{1}). Karchmer, Raz, and Wigderson [13] suggested to approach this problem by proving that depth complexity behaves'as expected' with respect to the composition of functions f diamond g. They showed that the validity of this conjecture would imply that mathrm{P} nsubseteq text{NC}{1}. Several works have made progress toward resolving this conjecture by proving special cases. In particular, these works proved the KRW conjecture for every outer function, but only for few inner functions. Thus, it is an important challenge to prove the KRW conjecture for a wider range of inner functions. In this work, we extend significantly the range of inner functions that can be handled. First, we consider the monotone version of the KRW conjecture. We prove it for every monotone inner function whose depth complexity can be lower bounded via a query-to-communication lifting theorem. This allows us to handle several new and well-studied functions such as the s-t-connectivity, clique, and generation functions. In order to carry this progress back to the non-monotone setting, we introduce a new notion of semi-monotone composition, which combines the non-monotone complexity of the outer function with the monotone complexity of the inner function. In this setting, we prove the KRW conjecture for a similar selection of inner functions, but only for a specific choice of the outer function f.
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55.
  • de Rezende, Susanna F., 1989-, et al. (författare)
  • Lifting with Simple Gadgets and Applications to Circuit and Proof Complexity
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • We significantly strengthen and generalize the theorem lifting Nullstellensatz degree to monotone span program size by Pitassi and Robere (2018) so that it works for any gadget with high enough rank, in particular, for useful gadgets such as equality and greater-than. We apply our generalized theorem to solve two open problems:We present the first result that demonstrates a separation in proof power for cutting planes with unbounded versus polynomially bounded coefficients. Specifically, we exhibit CNF formulas that can be refuted in quadratic length and constant line space in cutting planes with unbounded coefficients, but for which there are no refutations in subexponential length and subpolynomialline space if coefficients are restricted to be of polynomial magnitude.We give the first explicit separation between monotone Boolean formulas and monotone real formulas. Specifically, we give an explicit family of functions that can be computed with monotone real formulas of nearly linear size but require monotone Boolean formulas of exponential size. Previously only a non-explicit separation was known.An important technical ingredient, which may be of independent interest, is that we show that the Nullstellensatz degree of refuting the pebbling formula over a DAG G over any field coincides exactly with the reversible pebbling price of G. In particular, this implies that the standard decision tree complexity and the parity decision tree complexity of the corresponding falsified clause search problem are equal.
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56.
  • de Rezende, Susanna F., et al. (författare)
  • Nullstellensatz Size-Degree Trade-offs from Reversible Pebbling
  • 2019
  • Ingår i: Proceedings of the 34th Annual Computational Complexity Conference (CCC ’19). - : Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing. - 9783959771160 ; , s. 18:1-18:16
  • Konferensbidrag (refereegranskat)abstract
    • We establish an exactly tight relation between reversible pebblings of graphs and Nullstellensatz refutations of pebbling formulas, showing that a graph G can be reversibly pebbled in time t and space s if an only if there is a Nullstellensatz refutation of the pebbling formula over G in size t + 1 and degree s (independently of the field in which the Nullstellensatz refutation is made). We use this correspondence to prove a number of strong size-degree trade-offs for Nullstellensatz, which to the best of our knowledge are the first such results for this proof system.
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57.
  • De Rezende, Susanna F., et al. (författare)
  • Nullstellensatz Size-Degree Trade-offs from Reversible Pebbling
  • 2021
  • Ingår i: Computational Complexity. - : Springer Science and Business Media LLC. - 1016-3328 .- 1420-8954. ; 30:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We establish an exactly tight relation between reversiblepebblings of graphs and Nullstellensatz refutations of pebbling formulas,showing that a graph G can be reversibly pebbled in time t and space s if and only if there is a Nullstellensatz refutation of the pebbling formulaover G in size t + 1 and degree s (independently of the field in whichthe Nullstellensatz refutation is made). We use this correspondenceto prove a number of strong size-degree trade-offs for Nullstellensatz,which to the best of our knowledge are the first such results for thisproof system.
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58.
  • De Rezende, Susanna, et al. (författare)
  • Lifting with simple gadgets and applications to circuit and proof complexity
  • 2020
  • Ingår i: Proceedings - 2020 IEEE 61st Annual Symposium on Foundations of Computer Science, FOCS 2020. - 0272-5428. - 9781728196213 - 9781728196220 ; 2020-November, s. 24-30
  • Konferensbidrag (refereegranskat)abstract
    • We significantly strengthen and generalize the theorem lifting Nullstellensatz degree to monotone span program size by Pitassi and Robere (2018) so that it works for any gadget with high enough rank, in particular, for useful gadgets such as equality and greater-than. We apply our generalized theorem to solve three open problems: •We present the first result that demonstrates a separation in proof power for cutting planes with unbounded versus polynomially bounded coefficients. Specifically, we exhibit CNF formulas that can be refuted in quadratic length and constant line space in cutting planes with unbounded coefficients, but for which there are no refutations in subexponential length and subpolynomial line space if coefficients are restricted to be of polynomial magnitude. •We give the first explicit separation between monotone Boolean formulas and monotone real formulas. Specifically, we give an explicit family of functions that can be computed with monotone real formulas of nearly linear size but require monotone Boolean formulas of exponential size. Previously only a non-explicit separation was known. •We give the strongest separation to-date between monotone Boolean formulas and monotone Boolean circuits. Namely, we show that the classical GEN problem, which has polynomial-size monotone Boolean circuits, requires monotone Boolean formulas of size 2{Omega(n text{polylog}(n))}. An important technical ingredient, which may be of independent interest, is that we show that the Nullstellensatz degree of refuting the pebbling formula over a DAG G over any field coincides exactly with the reversible pebbling price of G. In particular, this implies that the standard decision tree complexity and the parity decision tree complexity of the corresponding falsified clause search problem are equal. This is an extended abstract. The full version of the paper is available at https://arxiv.org/abs/2001.02144.
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59.
  • de Savigny, Don, et al. (författare)
  • Integrating community-based verbal autopsy into civil registration and vital statistics (CRVS) : system-level considerations
  • 2017
  • Ingår i: Global Health Action. - : Informa UK Limited. - 1654-9716 .- 1654-9880. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Reliable and representative cause of death (COD) statistics are essential to inform public health policy, respond to emerging health needs, and document progress towards Sustainable Development Goals. However, less than one-third of deaths worldwide are assigned a cause. Civil registration and vital statistics (CRVS) systems in low-and lowermiddle-income countries are failing to provide timely, complete and accurate vital statistics, and it will still be some time before they can provide physician-certified COD for every death.Proposals: Verbal autopsy (VA) is a method to ascertain the probable COD and, although imperfect, it is the best alternative in the absence of medical certification. There is extensive experience with VA in research settings but only a few examples of its use on a large scale. Data collection using electronic questionnaires on mobile devices and computer algorithms to analyse responses and estimate probable COD have increased the potential for VA to be routinely applied in CRVS systems. However, a number of CRVS and health system integration issues should be considered in planning, piloting and implementing a system-wide intervention such as VA. These include addressing the multiplicity of stakeholders and sub-systems involved, integration with existing CRVS work processes and information flows, linking VA results to civil registration records, information technology requirements and data quality assurance.Conclusions: Integrating VA within CRVS systems is not simply a technical undertaking. It will have profound system-wide effects that should be carefully considered when planning for an effective implementation. This paper identifies and discusses the major system-level issues and emerging practices, provides a planning checklist of system-level considerations and proposes an overview for how VA can be integrated into routine CRVS systems.
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60.
  • Dilday, Benjamin, et al. (författare)
  • A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey
  • 2010
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 715, s. 1021-1035
  • Tidskriftsartikel (refereegranskat)abstract
    • We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <= 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 <= z <= 0.3. We find values for the cluster SN Ia rate of (0.37+0.17+0.01 -0.12-0.01) SNur h 2 and (0.55+0.13+0.02 -0.11-0.01) SNur h 2 (SNux = 10-12 L -1 xsun yr-1) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31+0.18+0.01 -0.12-0.01) SNur h 2 and (0.49+0.15+0.02 -0.11-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04+1.99+0.07 -1.11-0.04) SNur h 2 and (0.36+0.84+0.01 -0.30-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94+1.31+0.043 -0.91-0.015 and 3.02+1.31+0.062 -1.03-0.048, for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find rL = [(0.49+0.15 -0.14)+(0.91+0.85 -0.81) × z] SNuB h 2. A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most three hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are hostless to be (9.4+8.3 -5.1)%.
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