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At least 1,063 records · Page 59

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NASA NTRS2016

The Focal Plane Assembly for the Athena X-Ray Integral Field Unit Instrument

This paper summarizes a preliminary design concept for the focal plane assembly of the X-ray Integral Field Unit on the Athena spacecraft, an imaging microcalorimeter that will enable high spectral resolution imaging and point-source spectroscopy. The instrument's sensor array will be a 3840-pixel transition edge sensor (TES) microcalorimeter array, with a frequency domain multiplexed SQUID readout system allowing this large-format sensor array to be operated within the thermal constraints of the instrument's cryogenic system. A second TES detector will be operated in close proximity to the sensor array to detect cosmic rays and secondary particles passing through the sensor array for off-line coincidence detection to identify and reject events caused by the in-orbit high-energy particle background. The detectors, operating at 55 mK, or less, will be thermally isolated from the instrument cryostat's 2 K stage, while shielding and filtering within the FPA will allow the instrument's sensitive sensor array to be operated in the expected environment during both on-ground testing and in-flight operation, including stray light from the cryostat environment, low-energy photons entering through the X-ray aperture, low-frequency magnetic fields, and high-frequency electric fields.

SQUID amplifier↗

NASA NTRSDate not supplied

Recent Mineralogical Discoveries in Gale Crater, Mars from the CheMin XRD Instrument, Demonstrating a Watery Past

Curiosity landed in Gale crater August 2012 and has traversed (~27 km) sedimentary rocks that comprise a ~5 km-high mound, informally known as Mount Sharp, to investigate depositional/diagenetic environments and potential habitability. VSWIR spectra revealed the lowermost slopes of Mount Sharp contain mineral assemblages that are indicative of water-rock interactions (1-3), with sulfate-bearing units overlying phyllosilicate-bearing units. This mineralogical succession may mark the beginning of the transition from a relatively wet/warm to a very dry/cold Mars (e.g., 1, 4). Thirty-four powdered rock samples have been analyzed by the CheMin XRD instrument and mineralogical results from the first 6 years of the mission are reviewed in [5]. Here we describe the mineralogical diversity observed over the most recent 4 years. Sediments in the Vera Rubin Ridge (VRR) and Glen Torridon (GT) region were deposited in a lacustrine-fluvial environment and are syndepositional. The mineralogy suggests post-depositional fluid-rock interaction. Differences in mineralogy could have been the result of silica-poor, briny groundwater that destabilized smectite and precipitated hematite in VRR [6]. Other hypotheses include lake water-groundwater mixing or diagenesis driven by deeply sourced fluids altering smectite to precipitate hematite and amorphous silica. Preserved bedforms in the clay-sulfate transition region indicate a change from lacustrine-fluvial to aeolian depositional environments. Mineralogical changes include the identification of goethite along with the disappearance of phyllosilicate. The absence of crystalline Mg-sulfate in drilled samples from this transition region may mean that: 1) Sulfates are concentrated in secondary concretions not sampled by Curiosity’s drill, or 2) Sulfate components are either X-ray amorphous or if crystalline, became amorphous in the relatively low-humidity environment of the rover. Continued exploration of sulfate-rich rocks will elucidate this environmental transition above the phyllosilicate-rich sediments.

V M Tu↗

NASA NTRS1986

Further evidence for lightning on Venus

Impulsive electrical signals at all frequencies recorded by the plasma wave instrument on Pioneer Venus are found to cluster around periapsis. The signals are strongest at 100 Hz and have a secondary peak at 5.4 kHz. These characteristics are consistent with generation by lightning in the Venus atmosphere and the direct propagation of whistler mode signals below the electron gyro frequency and the partial transmission of electromagnetic waves in the presence of electron density inhomogeneities above the electron gyro frequency. The scattering by electron density inhomogeneities may also weaken any correlation with surface topographical features. Thus, the source of these signals may either be intercloud lightning at high altitudes or lightning in volcanic plumes near the ground, despite the large scatter in inferred source locations.

Singh, R. N.↗

NASA NTRS1990

Free-field propagation of high intensity noise

Observed spectral data from supersonic jet aircraft are known to contain much more high frequency energy than can be explained by linear acoustic propagation theory. It is believed that the high frequency energy is an effect of nonlinear distortion due to the extremely high acoustic levels generated by the jet engines. The objective, to measure acoustic waveform distortion for spherically diverging high intensity noise, was reached by using an electropneumatic acoustic source capable of generating sound pressure levels in the range of 140 to 160 decibels (re 20 micro Pa). The noise spectrum was shaped to represent the spectra generated by jet engines. Two microphones were used to capture the acoustic pressure waveform at different points along the propagation path in order to provide a direct measure of the waveform distortion as well as spectral distortion. A secondary objective was to determine that the observed distortion is an acoustic effect. To do this an existing computer prediction code that deals with nonlinear acoustic propagation was used on data representative of the measured data. The results clearly demonstrate that high intensity jet noise does shift the energy in the spectrum to the higher frequencies along the propagation path. In addition, the data from the computer model are in good agreement with the measurements, thus demonstrating that the waveform distortion can be accounted for with nonlinear acoustic theory.

Welz, Joseph P.↗

DOE OSTI2024

Novel principal component analysis tool based on python for analysis of complex spectra of time-of-flight secondary ion mass spectrometry

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful surface analysis tool, which can simultaneously provide elemental, isotopic, and molecular information with part per million (ppm) sensitivity. However, each spectrum may be composed of hundreds of ion signals, which makes the spectra data complex. Principal component analysis (PCA) is a multivariate analysis technique that has been widely used to figure out the variances among samples in ToF-SIMS spectra data analysis and is showing great success in the explanation of complex ToF-SIMS spectra. So far, several software tools have been developed for PCA of ToF-SIMS spectra; however, none of them are freely available. Such a situation leads to some difficulties in extending applications of PCA to various research fields. More importantly, it has long been challenging for common researchers to understand PCA plots and extract chemical differences among samples. In this work, we developed a new and flexible software tool (named “advanced spectra pca toolbox”) based on python for PCA of complex ToF-SIMS spectra along with an easy-to-read manual. It can generate data analysis reports automatically to explain chemical differences among samples, allowing less experienced researchers to easily understand tricky PCA results. Moreover, it is expandable and compatible with artificial intelligence/machine learning functions. Pure goethite and different lignin adsorbed goethite samples were used as a model system to demonstrate our new software tool, proving that our software tool can be readily used in complex spectra data processing. Our new software tool is open-source, convenient, flexible, and expandable. We expect this open-source tool will benefit the ToF-SIMS community.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Safety and effectiveness of a non-electric infant warmer for hypothermia in Rwanda: A cluster-randomized stepped-wedge trial

Background: Neonatal hypothermia is a common source of morbidity and mortality in low resource settings. We developed the Dream Warmer, a low cost, re-usable non-electric infant warmer to prevent and treat hypothermia. Methods: We conducted a cluster-randomized stepped-wedge trial. The primary aim was to assess the effect on overall euthermia rates of introducing the warmer compared to standard of care in rural Rwandan hospitals. The secondary aims were to assess effects of warmer introduction on mortality, as well as the safety and feasibility of the warmer. Ten district hospitals participated in the study from November 19th 2019 to July 15th 2020. Patients were eligible to use the warmer if they were 1) hypothermic (temp < 36·5 °C) or 2) or at risk of hypothermia (weight < 2·5 kg or estimated post menstrual age < 35 weeks) when Kangaroo Mother Care was not available. An encounter was defined as the data from an individual infant on a single day. Trial of a Non Electric Infant Warmer for Prevention and Treatment of Hypothermia in Rwanda [NCT03890211]. Findings: Over the study period, 3179 patients were enrolled across the ten neonatal wards, yielding 12,748 encounters; 464 unique infants used the warmer 892 times, 79% eligible due to hypothermia. Because of limited study nurse resources, the warmer was used in only 18% of eligible encounters. Despite this low rate of warmer use, the rate of euthermia rose from 51% (95% CI 50–52%) of encounters pre-intervention to 67% (66–68%) post-intervention; p < 0·0001. Among the encounters in which the warmer was used, only 11% (9–13%) remained hypothermic. While mortality rates pre- and post-intervention did not change, mortality rate among those who used the warmer was significantly lower than among those who did not (0·9% vs 2·8%, p = 0·01). Use of the warmer did not affect hyperthermia rates. There were no safety concerns or instances of incorrect warmer use. Interpretation: Introduction of the warmer increased rates of euthermia with no associated safety concerns.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2022

Cell-specific measurements show nitrogen fixation by particle-attached putative non-cyanobacterial diazotrophs in the North Pacific Subtropical Gyre

Abstract Biological nitrogen fixation is a major important source of nitrogen for low-nutrient surface oceanic waters. Nitrogen-fixing (diazotrophic) cyanobacteria are believed to be the primary contributors to this process, but the contribution of non-cyanobacterial diazotrophic organisms in oxygenated surface water, while hypothesized to be important, has yet to be demonstrated. In this study, we used simultaneous 15 N-dinitrogen and 13 C-bicarbonate incubations combined with nanoscale secondary ion mass spectrometry analysis to screen tens of thousands of mostly particle-associated, cell-like regions of interest collected from the North Pacific Subtropical Gyre. These dual isotope incubations allow us to distinguish between non-cyanobacterial and cyanobacterial nitrogen-fixing microorganisms and to measure putative cell-specific nitrogen fixation rates. With this approach, we detect nitrogen fixation by putative non-cyanobacterial diazotrophs in the oxygenated surface ocean, which are associated with organic-rich particles (<210 µm size fraction) at two out of seven locations sampled. When present, up to 4.1% of the analyzed particles contain at least one active putative non-cyanobacterial diazotroph. The putative non-cyanobacterial diazotroph nitrogen fixation rates (0.76 ± 1.60 fmol N cell −1 d −1 ) suggest that these organisms are capable of fixing dinitrogen in oxygenated surface water, at least when attached to particles, and may contribute to oceanic nitrogen fixation.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1990

Heavy Nucleus Collector (HNC) project for the NASA Long Duration Exposure Facility (LDEF)

The primary goal of the heavy nucleus collector (HNC) experiment was to obtain high resolution composition measurements for cosmic ray nuclei in the platinum-lead and actinide region of the periodic table. Secondary objectives include studies of selected groups of elements of lower charge. These goals were to be realized by orbiting a large area array of dielectric nuclear track detectors in space for several years. In this time sufficient actinide nuclei would be collected to determine the nucleosynthetic age of the cosmic radiation and the relative mix of r- and s-process elements in the cosmic ray source. The detector consists of approximately 50 trays assembled in pressurized canisters. Each tray would contain 8 half-stacks (4 stacks total) and an event thermometer which would record the temperature of each event at the time of exposure. Each stack would contain 7 layers of Rodyne-P, CR-39 and Cronar plastic track detectors interleaved with copper stripping foils. Upon return to Earth, detectors would be removed for analysis. Ultraheavy nuclei would have left tracks through the detector sheets that would be made visible after etching in a hot sodium hydroxide solution.

Tarle, Gregory↗

NASA NTRS1994

A new measurement of the flux of the light cosmic-ray nuclei at high energies

A new cosmic-ray detector utilizing a ring-imaging Cerenkov counter to determine the energy of light cosmic-ray nuclei was flown on high-altitude balloon from Fort Sumner, NM, in 1991 September. We describe the design and performance of this instrument and discuss the data analysis procedures. The measurement provides a new determination of the absolute flux and differential energy spectrum of the primary cosmic-ray species helium between 40 and 320 GeV/nucleon. The experiment also yields the spectra of carbon and oxygen and some information on the intensities of the secondary nuclei Li, Be, and B. A comparison between our results and previous measurements of heavier nuclei (Z greater than or equal to 4) from HEAO 3 and Spacelab 2 indicates good consistency between these measurements. The data set is compared with the results of a leaky box propagation model. We find good agreement with this model if the abundance of helium relative to oxygen at the source is taken to be 25 +/- 6 and if the source spectrum is given by a power law in energy proportional to E(exp -2.15).

Buckley, J.↗

NASA NTRS2004

On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions

Although abundance gradients in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in G333.6-0.2 with the Kuiper Airborne Observatory and reobserved the central position with the Infrared Space Observatory's Long Wavelength Spectrometer in far-infrared lines of S++, N++, N+, and O++. We also added the N+ lines at 122 and 205 microns to the suite of lines measured in W43 by Simpson et al.. The measured electron densities range from approx. 40 to over 4000 per cu cm in a single HII region, indicating that abundance analyses must consider density variations, since the critical densities of the observed lines range from 40 to 9000 per cu cm. We propose a method to handle density variations and make new estimates of the S/H and N/H abundance ratios. We find that our sulfur abundance estimates for G333.6-0.2 and W43 agree with the S/H abundance ratios expected for the gradient previously reported by Simpson et al., with the S/H values revised to be smaller owing to changes in collisional excitation cross sections. The estimated N/H, S/H, and N/S ratios are the most reliable because of their small corrections for unseen ionization states (< or approx. 10%). The estimated N/S ratios for the two sources are smaller than what would be calculated from the N/H and S/H ratios in our previous paper. If all low excitation H II regions had similar changes to their N/S ratios as a result of adding measurements of N+ to previous measurements of N++, there would be no or only a very small gradient in N/S. This is interesting because nitrogen is considered to be a secondary element and sulfur is a primary element in galactic chemical evolution calculations. We compute models of the two H II regions to estimate corrections for the other unseen ionization states. We find, with large uncertainties, that oxygen does not, have a high abundance, with the result that the N/O ratio is as high (approx. 0.35) as previously reported. The reasons for the uncertainty in the ionization corrections for oxygen are both the non-uniqueness of the H II region models and the sensitivity of these models to different input atomic data and stellar atmosphere models. We discuss these predictions and conclude that only a few of the latest models adequately reproduce H II region observations, including the well-known, relatively-large observed Ne++/O++ ratios in low- and moderate-excitation H II regions.

Simpson, Janet P.↗

NASA NTRS2024

Accurate Assessment of Land-Atmosphere Coupling in Climate Models Requires High Frequency Data Output

Land-atmosphere (L-A) interactions are important for understanding convective processes, climate feedbacks, the development and perpetuation of droughts, heatwaves, pluvials, and other land-centred climate anomalies. Local L-A coupling (LoCo) metrics capture relevant L-A processes, highlighting the impact of soil and vegetation states on surface flux partitioning, and the impact of surface fluxes on boundary layer (BL) growth, development, and entrainment of air above the BL. A primary goal of the Climate Process Team on Coupling Land and Atmospheric Subgrid Parameterizations (CLASP) is parameterizing and characterizing the impact of subgrid heterogeneity in global and regional earth system models (ESMs) to improve the connection between land and atmospheric states and processes. A critical step in achieving that aim is the incorporation of L-A metrics, especially LoCo metrics, into climate model diagnostic process streams. However, because land-atmosphere interactions span time scales of minutes (e.g., turbulent fluxes), hours (e.g., BL growth and decay), days (e.g., soil moisture memory), and seasons (e.g., variability of behavioural regimes between soil moisture and latent heat flux), with multiple processes of interest happening in different geographic regions at different times of year, there is not a single metric that captures all the modes, means, and methods of interaction between the land and the atmosphere. And while monthly means of most of the LoCo-relevant variables are routinely saved from ESM simulations, data storage constraints typically preclude routine archival of the hourly data that would enable the calculation of all LoCo metrics. Here we outline a reasonable data request that would allow for adequate characterization of sub-daily coupling processes between the land and the atmosphere, preserving enough sub-daily output to describe, analyse, and better understand L-A coupling in modern climate models. A secondary request involves embedding calculations within the models to determine mean properties in and above the BL to further improve characterization of model behaviour. Higher-frequency model output will (i) allow for more direct comparison with observational field campaigns on process-relevant time scales, (ii) enable demonstration of inter-model spread in L-A coupling processes, and (iii) aid in targeted identification of sources of deficiencies and opportunities for improvement of the models.

Kirsten L. Findell↗

NASA NTRS1993

A photoautotrophic source for lycopane in marine water columns

Suspended particulate matter and recent sediments from diverse oceanic sites have been investigated for their contents of lycopane. Lycopane was present in all samples, including both oxic and anoxic water column and sediments. The highest concentrations in the water column were found in surface waters of the central Pacific gyre (1.5 ng/L) and in the anoxic waters of the Cariaco Trench (1.1 ng/L) and the Black Sea (0.3 ng/L). Vertical concentration profiles suggest that lycopane is probably algal in origin. Moreover, biogeochemical conditions in anoxic zones apparently result in a secondary production of lycopane from an as yet unidentified precursor. Compound-specific carbon isotopic analyses have been carried out on lycopane from water column and sediment samples. Isotopic compositions of lycopane range between -23.6 and -32.9 percent and are consistent with a photoautotrophic origin. We postulate that some lycopane is produced in surface waters of the ocean, while additional lycopane is produced in anoxic zones by anaerobic microbial action on an algal precursor.

Wakeham, Stuart G.↗

NASA NTRS1974

Application of remote sensing techniques in land-use planning: Flood-plain delineation

The delineation of areas subject to inundation by means of remotely-sensed data acquisition represents a considerable saving in personnel time. Repeated input from aerial sensor sources provides the planner with a potent tool for the formation of a data base and for the monitoring of land use patterns over a period of time. The primary output of this project was a set of base map overlays at a scale of 1:62,500 delineating areas which require special regulations when proposed for land use involving human habitation or certain classes of storage. A secondary product of the study was county-wide maps of watershed configurations and of soil hydrologic groups. Further research is anticipated to extend the mapping of watershed areas outside the political boundaries of Cochise County, which will provide data for subsequent rainfall-runoff relationship studies in the area. All of the data provided will be incorporated into the Cochise County composite computer mapping project now operational. Results of this project have improved the pool of information available to the planning staff of Cochise County.

Altenstadter, J.↗

NASA NTRS1985

AY Ceti - A flaring, spotted star with a hot companion

AY Ceti is a late-type single-line spectroscopic binary, a bright X-ray source (L/x/ equal to about 1.5 x 10 to the 31st ergs/s), and a spotted star, as evidenced by its prominent photometric wave. In this paper, observations made with the IUE satellite and the VLA radio interferometer are reported. The 1200-2000 A UV spectrum of AY Cet shows a hot stellar continuum and a very broad Ly-alpha absorption line from a previously unobserved white dwarf secondary. The UV spectrum can be matched to the energy distribution of a (T/eff/ = 18,000 K, log g = 8) model atmosphere. Superposed on this hot continuum are high-excitation emission lines typical of chromospheres and transition regions of active late-type stars, e.g., the spotted RS CVn binaries. It is concluded that the bright lines and soft X-ray emission of AY Cet arise from the cool primary star, rather than from mass transfer and accretion onto the secondary as has recently been proposed for the similar system 56 Peg. Two strong radio flares on AY Cet were observed. The second was rapidly variable and left-hand circularly polarized at levels up to pi(c) = 86 + or - 5 percent at 20 cm wavelength. The most likely emission mechanism is an electron-cyclotron maser.

Simon, T.↗

NASA NTRS1992

Facilities and capabilities catalog for landing and escape systems

This catalog serves as a single source reference for designers of landing and escape systems for spacecraft, aircraft, weapons, and airdrop system. It includes those facilities which may be required by a system designer in planning a development test program for many applications. The primary objective of this catalog is to provide a means for identifying critical facilities with the U.S. which can be used for the development of landing and escape systems. A secondary objective is to provide a useful tool to the system designer for picking and choosing facilities and capabilities. The six chapters in this volume include wind tunnels, drop zones, test aircraft, fabrication facilities, design tools, and other miscellaneous facilities. A different data sheet format is used for each of the chapters which provides information on performance, location, special capabilities, and a local point of contact. All inputs were solicited from the individual facilities and have not been independently verified for accuracy.

Meyerson, Robert E.↗

NASA NTRS1999

Streamwise Vorticity Generation in Laminar and Turbulent Jets

Complex streamwise vorticity fields are observed in the evolution of non-circular jets. Generation mechanisms are investigated via Reynolds-averaged (RANS), large-eddy (LES) and direct numerical (DNS) simulations of laminar and turbulent rectangular jets. Complex vortex interactions are found in DNS of laminar jets, but axis-switching is observed only when a single instability mode is present in the incoming mixing layer. With several modes present, the structures are not coherent and no axis-switching occurs, RANS computations also produce no axis-switching. On the other hand, LES of high Reynolds number turbulent jets produce axis-switching even for cases with several instability modes in the mixing layer. Analysis of the source terms of the mean streamwise vorticity equation through post-processing of the instantaneous results shows that, complex interactions of gradients of the normal and shear Reynolds stresses are responsible for the generation of streamwise vorticity which leads to axis-switching. RANS computations confirm these results. k - epsilon turbulence model computations fail to reproduce the phenomenon, whereas algebraic Reynolds stress model (ASM) computations, in which the secondary normal and shear stresses are computed explicitly, succeeded in reproducing the phenomenon accurately.

Demuren, Aodeji O.↗

DOE OSTI2020

CsI(Tl) pulse shape discrimination with the Belle II electromagnetic calorimeter as a novel method to improve particle identification at electron–positron colliders

Here we describe the implementation and performance of CsI(Tl) pulse shape discrimination for the Belle II electromagnetic calorimeter, representing the first application of CsI(Tl) pulse shape discrimination for particle identification at an electron–positron collider. The pulse shape characterization algorithms applied by the Belle II calorimeter are described. Control samples of $γ, μ^+, π^±, K^±$ and $ρ/ \bar{ρ}$ are used to demonstrate the significant insight into the secondary particle composition of calorimeter clusters that is provided by CsI(Tl) pulse shape discrimination. Comparisons with simulation are presented and provide further validation for newly developed CsI(Tl) scintillation response simulation techniques, which when incorporated with GEANT4 simulations allow the particle dependent scintillation response of CsI(Tl) to be modelled. Comparisons between data and simulation also demonstrate that pulse shape discrimination can be a new tool to identify sources of improvement in the simulation of hadronic interactions in materials. The $K^0_L$ efficiency and photon-as-hadron fake-rate of a multivariate classifier that is trained to use pulse shape discrimination is presented and comparisons are made to a shower-shape based approach. CsI(Tl) pulse shape discrimination is shown to reduce the photon-as-hadron fake-rate by over a factor of 3 at photon energies of 0.2 GeV and over a factor 10 at photon energies of 1 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Source apportionment of soot particles and aqueous-phase processing of black carbon coatings in an urban environment

Abstract. The impacts of soot particles on climate and human health depend on the concentration of black carbon (BC) as well as the thickness and composition of the coating material, i.e., organic and inorganic compounds internally mixed with BC. In this study, the size-resolved chemical composition of BC-containing aerosol was measured using a high-resolution soot particle aerosol mass spectrometer (SP-AMS) during wintertime in Fresno, California, a location influenced by abundant combustion emissions and frequent fog events. Concurrently, particle optical properties were measured to investigate the BC absorption enhancement. Positive matrix factorization (PMF) analysis was performed on the SP-AMS mass spectral measurements to explore the sources of soot particles and the atmospheric processes affecting the properties of BC coatings. The analysis revealed that residential woodburning and traffic are the dominant sources of soot particles. Alongside primary soot particles originating from biomass burning (BBOABC) and vehicles (HOABC) two distinct types of processed BC-containing aerosol were identified: fog-related oxidized organic aerosol (FOOABC) and winter-background OOABC (WOOABC). Both types of OOABC showed evidence of having undergone aqueous processing, albeit with differences. The concentration of FOOABC was substantially elevated during fog events, indicating the formation of aqueous secondary organic aerosol (aqSOA) within fog droplets. On the other hand, WOOABC was present at a relatively consistent concentration throughout the winter and was likely related to the formation of secondary organic aerosol (SOA) in both the gas phase and aerosol liquid water. By comparing the chemical properties and temporal variations in FOOABC and WOOABC, we gain insights into the key aging processes of BC aerosol. It was found that aqueous-phase reactions facilitated by fog droplets had a significant impact on the thickness and chemical composition of BC coatings, thereby affecting the light absorption and hygroscopic properties of soot particles. These findings underscore the important role of chemical reactions occurring within clouds and fogs and influencing the climate forcing of BC aerosol in the atmosphere.

54 ENVIRONMENTAL SCIENCES↗