Shift In Depth Research Articles

Behavioral responses of two deep-sea fish species to red, far-red, and white light

The relatively unobtrusive deep-sea camera system Eye-in-the-Sea (EITS) was deployed in Monterey Bay Canyon, California, USA, to assess the relative photosensitivity of 2 deep- sea fishes, Coryphaenoides acrolepis and Anoplopoma fimbria. Previous studies addressing the in situ response of deep-sea fishes to red and white light were done in the presence of ROV-induced stimuli. Here, we report on the behavioral response of C. acrolepis and A. fimbria in a vehicle-free environment when subjected to white (full visible spectrum), red (685 nm), and far-red (695 nm) illu- mination in situ. Under far-red light conditions, A. fimbria spent significantly more time in the field- of-view and demonstrated an increase in entrances/exits when compared to the situation under red-light and white-light conditions. No significant difference in the average time C. acrolepis spent in the field-of-view was found between any of the test wavelengths; however, the entrances-to-exits ratio for C. acrolepis decreased during white-light conditions. While A. fimbria often displayed a flight response at the onset of white and sometimes red (685 nm) illumination, C. acrolepis did not demonstrate a similar behavioral response when exposed to light within its range of visual sensitiv- ity. A. fimbria undergo a dramatic ontogenic shift in depth, inhabiting well-lit, near-shore waters as juveniles and moving into deeper waters as adults. It is thought that C. acrolepis spend part of their early life history in the light-limited mesopelagic, below the permanent thermocline, and move into deeper waters as they mature. Based on the results of the present study, we hypothesize that systematic differences in the phototactic responses of deep-sea fishes are a function of life history as well as spectral sensitivity.

Testing the predictive power of seagrass depth limit models

The power of equations predicting seagrass depth limit (Zc) from light extinction (K z) was tested on data on seagrass depth limits collected from the literature. The test data set comprised 424 reports of seagrass colonization depth and water transparency, including data for 10 seagrass species. This data set confirmed the strong negative relationship betweenZ c andK z. The regression equation in Duarte (1991) overestimated the realized seagrass colonization depths at colonization depths < 5 m, while there was no prediction bias above this threshold. These results indicated that seagrass colonizing turbid waters (K z 0.27 m-1) have higher apparent light requirements than those growing in clearer waters. The relationship between seagrass colonization depth and light attenuation shifts at a threshold of light attenuation of 0.27 m-1, requiring separate equations to predictZ c for seagrass growing in more turbid waters and clearer waters, and to set targets for seagrass restoration and conservation efforts.

SU‐FF‐T‐262: Indications of Effective Depth Reversal for Cylindrical Ion Chambers in Electron Beams

Purpose: Cylindrical ionization chamber measurements of electron beam depth dose are corrected for the effective depth of measurement and water/air stopping power ratio. The purpose of this presentation is to examine whether a unidirectional upstream shift from physical to effective depth of measurement as often used in data acquisition systems makes sense. Method and Materials: Ionization chamber measurements of depth dose corrected for effective depth by a unidirectional shift and water/air stopping power ratio at depth are compared with diode and EBT film measurements for standard electron beam cone sizes over the nominal energy range of 6 MeV to 20 MeV. The diode results are obtained with a NIST traceable electrometer and are used without correction for any change in water/silicon stopping power ratio vs depth. The EBT film density is converted to dose based on a characteristic curve from films exposed in plastic water at the nominal depth of dose maximum. EBT film results are used without additional corrections for any change in water/EBT film stopping power ratio vs depth. The EBT film density is evaluated with a pin‐hole densitometer as well as a VIDAR film scanner. Results: Good agreement of all measurements at depth from 80 to 10 percent suggest ignoring variation in stopping power ratio for both diode and EBT film has little impact on the results. Both diode and film suggest a slightly deeper depth of dose maximum and a more rapid drop in dose from Dmax towards the surface. Conclusion: Agreement between ionization chamber results and the high resolution solid detector results would improve if the shift in the effective depth of measurement of the ionization chamber is based on dose gradient and reverses as the gradient reverses with perhaps no shift at the zero gradient position. This may impact on calibration protocols.

Orbital tuning of a lower Cretaceous composite record (Maiolica Formation, central Italy)

A high‐resolution pelagic bulk carbonate stable isotope record from a central Tethyan lower Cretaceous composite section is presented. Three well‐exposed sedimentary sequences (Chiaserna Monte Acuto, Bosso, and Gorgo a Cerbara sections, central Italy) cropping out throughout the Maiolica Formation were correlated by a detailed magnetostratigraphy, lithostratigraphy, and calcareous plankton biostratigraphy in order to reconstruct a continuous composite record from the middle Berriasian to the lower Aptian. The integrated stratigraphy of the three sequences provided an accurate time framework for the new high‐resolution C isotope curve which is presented in this study. The composite δ13C signal, recorded in the depth domain, was analyzed by combined Lomb‐Scargle periodogram and weighted wavelet Z transform (WWZ) – weighted wavelet amplitudes (WWA) Foster wavelet spectral methodologies, both appropriate for unevenly sampled curves. These tools allowed us to unravel the main frequencies modulating the record and their hypothetical shift in depth, respectively. The long‐term, ∼400,000 and ∼2,400,000 years, eccentricity cycles were consistently recorded throughout all the composite record. Once band‐pass filtered in these two periodicity bands and compared to the lithologic pattern cycles identified throughout the composite sequence, the δ13C signal was used as a valuable proxy record for a reliable construction of an orbital tuning of the early Cretaceous. An estimated age for all the different stratigraphic events recognized throughout the composite record was reported. In particular, the reestimated ages of the paleomagnetic chrons, documented in the upper part of the record, show differences with those reported by Gradstein et al. (2004) up to ∼2 m.y. The Valanginian carbon shift, present in the middle part of the composite sequence was estimated to be ∼2.3 m.y. long. The good agreement between the estimated age of the base of this positive carbon isotope excursion (∼136.34 m.y.) and the predominant volcanic phase associated to the Paranà‐Etendeka large igneous province intrusion confirmed a possible cause‐effect link between the two events.

Flattening without picking

We present an efficient full-volume automatic dense-picking method for flattening seismic data. First local dips (stepouts) are calculated over the entire seismic volume. The dips are then resolved into time shifts (or depth shifts) using a nonlinear Gauss-Newton iterative approach that exploits fast Fourier transforms to minimize computation time. To handle faults (discontinuous reflections), we apply a weighted inversion scheme. The weight identifies locations of faults, allowing dips to be summed around the faults to reduce the influence of erroneous dip estimates near the fault. If a fault model is not provided, we can estimate a suitable weight (essentially a fault indicator) within our inversion using an iteratively reweighted least squares (IRLS) method. The method is tested successfully on both synthetic and field data sets of varying degrees of complexity, including salt piercements, angular unconformities, and laterally limited faults.

SU-FF-T-221: Evaluation of An Electron Monte Carlo Dose Calculation Algorithm for Electron Beam Radiotherapy

Purpose: To systematically evaluate the electron Monte Carlo (eMC) dose calculation algorithm of the Eclipse treatment planning system and to identify factors that affect its calculation accuracy. Method and Materials: Percent depth dose (PDD) and profiles for each electron energy/applicator/depth combination were measured for four Varian Clinac 21EX Linacs. Cutout factors for various cutout sizes down to 3×3 cm2 were also measured. Statistical comparison between eMC calculation and measurement was performed for parameters such as shift in depth of PDD curves, field size, penumbra width, average dose difference within 80% of field size, beam symmetry, Bremsstrahlung dose, and cutout factor. Analysis of variance was used to identify factors that have significant influence on the observed discrepancies. Results: The agreement between measured and calculated 50% PDD depth was within ±2 mm for nearly all machine/energy/applicator combinations except the 6×6 6 MeV beams on three machines where maximum difference was 3.8 mm. The calculated field width was larger than that of measured in most of the cases but within 3%. The differences between calculated and measured penumbra were also within 3%. The calculated Bremsstrahlung doses were smaller than measurements, with a few exceptions. Analysis of variance identified machine as a significant variable for the observed discrepancies in PDD, field width, and penumbra, suggesting possible variations among linacs or the quality of measured data. Calculation grid size was found to have significant effect on calculation accuracy. Using grid size of 5 mm resulted in approximate 10% discrepancies. Reducing grid size yielded significant improvement on the calculated cutout factor: from 5% discrepancy to less than 3% when grid size of 1 mm was used. Conclusion: The overall agreement between the eMC calculation and measurements was acceptable. Calculation grid size of 2.5 mm or smaller is recommended for all field sizes for eMC algorithm.

A phenomenological model for the relative biological effectiveness in therapeutic proton beams

To study the effects of a variable relative biological effectiveness (RBE) in inverse treatment planning for proton therapy, fast methods for three-dimensional RBE calculations are required. We therefore propose a simple phenomenological model for the RBE in therapeutic proton beams. It describes the RBE as a function of the dose, the linear energy transfer (LET) and tissue specific parameters. Published experimental results for the dependence of the parameters alpha and beta from the linear-quadratic model on the dose averaged LET were evaluated. Using a linear function for alpha(LET) in the relevant LET region below 30 keV per micrometre and a constant beta, a simple formula for the RBE could be derived. The new model was able to reproduce the basic dependences of RBE on dose and LET, and the RBE values agreed well with experimental results. The model was also applied to spread-out Bragg peaks (SOBP), where the main effects of a variable RBE are an increase of the RBE along the SOBP plateau, and a shift in depth of the distal falloff. The new method allows fast RBE estimations and has therefore potential applications in iterative treatment planning for proton therapy.

Dynamics of gas hydrate: case of the Congo continental slope

A numerical model is developed to study the temperature effect on stability and phase transformation of gas-hydrate. The model uses a mathematical formulation based on the enthalpy form of the conservation law of energy. The use of the enthalpy form instead of the temperature form as often done in the literature has made the problem numerically simpler. The model is then applied to describe the effect of sea bottom temperature variations on the stability of gas hydrate occurrences and on the seafloor reflectivity in sediments of the Congo continental slope. Indeed, a migrating seafloor reflectivity front is observed on 3D seimic images from two surveys performed 6 months apart and interpreted as a migrating gas hydrate stability zone. Seawater temperature variations were recorded over a 230-day period. At the seafloor, the amplitude of these variations could explain a 75-m shift in water depth of the upper limit of the gas hydrate stability zone. However, the response of the sediment to a perturbation applied at the seafloor is not immediate because of the effects of thermal diffusion and of latent heat of hydrate dissociation. Thermal modelling shows that the depth of penetration of these perturbations is around 2 m for the saturated sediment and around 6 m for hydrate-bearing sediments (hydrate fraction of 0.1). The switch between gas and gas hydrate generated by these temperature fluctuations concern only the first meter of sediment. These appear too small to explain the migration of the seafloor reflectivity, considering that the wavelength of the seismic signal is significantly larger (around 10 m). However, for temperature fluctuations with larger wavelength the switch between gas and gas hydrate will be more important and consequently could explain the reflectivity contrast as a possible migrating gas or gas hydrate front.

Micromechanical analysis on residual stress-induced nanoindentation depth shifts in DLC films

A depth change in nanoindentation curve by an influence of elastic residual stress was modeled as a reversible surface deformation by adopting an elastic contact mechanics for a flat punch. The model, however, yielded overestimated stresses for two diamond-like carbon films. The discrepancy was discussed from a viewpoint of irreversible deformation around the punch.

308 インデンテーション法による加工表面の残留応力の評価手法([2]計測システムと応用技術)(OS10 加工計測・評価)

Depth-sensing indentation system was used to measure the residual stress in the engineered surface of stainless steel. Different with other measurement methods, such as X-ray diffraction_techniques, depthsensing indentation provides a way of accurately measuring residual stresses even with unknown material properties. Comparing the load-depth curves of residual stress existing and stress-free samples, the closed form of expression correlating the level of residual stress with load and depth shifts in the load-depth curves is given. Based on theoretical analysis, a new experimental scheme for determination of the residual stress by indentation is suggested.

Permian-Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath

Other| April 01, 2003 Permian–Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath DANIEL J. LEHRMANN; DANIEL J. LEHRMANN 1Department of Geology, University of Wisconsin-Oshkosh, Oshkosh, WI 54901, lehrmann@uwosh.edu Search for other works by this author on: GSW Google Scholar JONATHAN L. PAYNE; JONATHAN L. PAYNE 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 Search for other works by this author on: GSW Google Scholar SHARON V. FELIX; SHARON V. FELIX 3The RETEC Group, Inc. RETEC, 5000 E. Spring St., Ste 250, Long Beach, CA 90815 Search for other works by this author on: GSW Google Scholar PETER M. DILLETT; PETER M. DILLETT 4Department of Geology, University of Kansas, Lawrence, KS 66045 Search for other works by this author on: GSW Google Scholar HONGMEI WANG; HONGMEI WANG 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar YOUYI YU; YOUYI YU 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar JIAYONG WEI JIAYONG WEI 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar PALAIOS (2003) 18 (2): 138–152. https://doi.org/10.1669/0883-1351(2003)18<138:PBSFSC>2.0.CO;2 Article history accepted: 22 Aug 2002 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DANIEL J. LEHRMANN, JONATHAN L. PAYNE, SHARON V. FELIX, PETER M. DILLETT, HONGMEI WANG, YOUYI YU, JIAYONG WEI; Permian–Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath. PALAIOS 2003;; 18 (2): 138–152. doi: https://doi.org/10.1669/0883-1351(2003)18<138:PBSFSC>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Permian-Triassic boundary (PTB) sections from isolated carbonate platforms in the Nanpanjiang Basin of south China contain Upper Permian skeletal packstones with diverse open-marine fossils overlain by a 7–15 m thick boundary horizon composed of calcimicrobial framestone constructed by globular to tufted, calcified cyanobacteria similar to Renalcis. The framestone contains interbeds of lime-grainstone with abundant thin-shelled bivalves and brachiopods. The overlying Lower Triassic strata contain microgastropod lime-packstones followed by a thick succession of thin-bedded lime-mudstones.The PTB event horizon is interpreted to occur at the top of the packstone containing diverse, open-marine fauna and Palaeofusulina and coincident with the abrupt change to calcimicrobial framestone lacking Permian macrofossils. The conformable biostratigraphic boundary occurs at the first appearance of Hindeodus parvus within the basal meter of the calcimicrobial framestone.Intensively studied PTB sections in south China, such as the GSSP at Meishan, primarily are condensed sections from deep-water, basin environments that contain a thin (< 30 cm) boundary horizon of claystone and lime-mudstone or marl. The sections reported herein are fundamentally different in that they consist of shallow-marine carbonate facies, contain a thick boundary horizon composed of calcimicrobial framestone, and lack evidence of an abrupt shift in depositional environment or water depth. The calcimicrobial framestone boundary horizon occurs in all of the isolated carbonate platforms in the Nanpanjiang Basin. A similar microbial facies has been found in the basal Triassic H. parvus zone in the Sichuan Basin and in Japan. Distribution of the calcimicrobial framestone suggests that it may represent an anomalous oceanic event that affected a vast area of the equatorial eastern Tethys and Panthalassa during and/or immediately following the end-Permian mass extinction. The persistence of similar calcimicrobial framestone horizons into the Upper Scythian suggests that detrimental environmental conditions associated with the extinction persisted until the end of the Scythian. Further study of these sections promises to provide constraints on causes of the extinction and the environments in the aftermath. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Seasonal oxygen and carbon isotope variability in euthecosomatous pteropods from the Sargasso Sea

We examine seasonal variations in the stable carbon and oxygen isotopic composition of individual shells of the pteropods Limacina inflata and Styliola subula, collected from Oceanic Flux Program sediment traps (at 500 m depth) near Bermuda in the western Sargasso Sea. Calcification depths estimated from L. inflata δ 18O vary between 200 and 650 m in late winter and spring, and between 50 and 250 m in late summer and fall. S. subula shows similar seasonal variability with calcification depths between 250 and 600 m in late winter and spring and 50–400 m in late summer and fall. These results suggest that both species calcify across a greater range of depths than indicated by previous geochemical studies. Furthermore, the data indicate that these species change their calcification depth in conjunction with changes in thermal stratification of the water column. Pteropod shell δ 13C values vary inversely with δ 13C DIC but show a positive correlation with seawater [CO 3 2−] and temperature after depth differences in δ 13C DIC are accounted for. We hypothesize that either the influence of temperature on metabolic CO 2 incorporation during shell growth and/or the influence of ambient [CO 3 2−] on shell geochemistry can explain these relationships. Taken together, the individual shell δ 18O and δ 13C data suggest that shell calcification, and by inference the life cycle, of these pteropods is several months or less. Individual pteropod shell analyses have potential for contributing to our understanding of the environmental parameters that play a role in seasonal calcification depth shifts, as well as to our knowledge of past upper ocean thermal structure.

Stochastic Modelling of 1-D Shallow Water Flows over Uncertain Topography

A second-order perturbation approach is used to investigate the effects of topographic uncertainty on a numerical model of shallow water flow. The governing equation is discretised using finite differences, the resulting nonlinear system expanded as a Taylor series about the unperturbed water depth to first and second-order, and the resulting matrix equation solved to derive second-order moments for the model solution. A Fourier technique is used to estimate the accuracy of the first- and second-order approximations and indicates that for even small perturbations, second-order terms are significant. Results are compared to those from Monte Carlo simulations, showing that significant nonlinear effects are well represented by the second-order stochastic model, predicting correctly the shift in the mean depth and an increase in the depth variance. The statistics of the solution are however still well represented by a Gaussian distribution, and therefore moments greater than order 2 need not be calculated.

New Evidence for Segmentation of the Alaska Subduction Zone

The purpose of this article is to provide additional evidence for segmentation of the subducted plate in Alaska and to introduce a catalog of the relocated earthquakes for future studies. We used the Joint Hypocenter Determination method to relocate 14,099 subduction-zone earthquakes that occurred from July 1988 to July 1998 and were located between 58° N and 65° N latitude. The earthquake data were taken from the Alaska Earthquake Information Center catalog. The selected earthquakes were divided into 16 blocks on the basis of their hypocentral locations, and each block was relocated separately. Average epicenter shift was 3.8 km and average upward and downward depth shifts were 4.1 and 4.4 km, respectively (roughly the same number of earthquakes shifted upward [47%] and downward [53%]). The overall change with respect to the initial locations is that the seismicity became more compact, revealing details about the fine structure of the Wadati-Benioff zone. In particular, we were able to identify more precisely the boundary between the Kenai and McKinley blocks of the subducting plate. In addition, there is evidence for plate segmentation within the McKinley block. Manuscript received 15 November 2000.

Optical recognition of organic vapours through ultrathin calix[4]pyrrole films

Thin films of meso-octaethylporphyrinogen were deposited on suitable surface by Langmuir–Blodgett technique in order to obtain optical sensors using Surface Plasmon Resonance (SPR)technique. In particular such coatings were tested in the molecular recognition of alcohol vapours such as ethanol and methanol. This resulted in a reversible shift in the resonance depth and position of the SPR curves. Different sensitivity and rate of response for different alcohol molecules were found.

Taphonomy of larger foraminifera: Relationships between living individuals and empty tests on flat reef slopes (Sesoko Island, Japan)

The depth distributions of larger foraminifera (27 species) were investigated along two transects in the fore reef areas of a NW Pacific fringing reef. One transect is distinguished by a strong flattening below the steep reef slope (−30 m), whereas further steepening characterizes the equivalent part in the other transect. According to the different taphonomic processes affecting foraminiferal tests before final sedimentation, empty tests were classified into the three categories ‘optimally’, ‘well’ and ‘poorly’ preserved. The depth distribution of each preservation state was compared with living individuals. While distributions of optimally preserved tests almost coincide with living individuals, well-preserved tests are characterized by significant depth shifts that are stronger at the upper-most slope compared with the deeper parts. Since the time-averaged traction forces are similar in both investigated transects, differences between the distributions of living individuals and well-preserved tests are more intensive on steep versus flat slopes. Poorly preserved tests signalize allochthonous origin or reworking of relict sediments.

Fibre-optic sensing applications of a pair of long-period fibregratings

We will discuss fibre-optic sensing applications withhigh resolution and sensitivity that are based on a pair oflong-period fibre gratings (LPFGs) characterized by a fineinterference fringe pattern and a narrow bandwidth. Thedependence of the shift in resonance wavelength and change ofpeak depth of a pair of LPFGs pair on changes in the externalenvironment such as the bending curvature, transverse load andsurrounding index are investigated experimentally. Thetemperature sensitivity of the LPFGs was suppressed to0.002 nm °C-1 in order to reduce the effect oftemperature on the performance of the sensor.

Shifts in Depth Distributions of Alewives, Rainbow Smelt, and Age-2 Lake Trout in Southern Lake Ontario following Establishment of Dreissenids

Abstract In the mid-1990s, biologists conducting assessments of fish stocks in Lake Ontario reported finding alewives Alosa pseudoharengus, rainbow smelt Osmerus mordax, and juvenile lake trout Salvelinus namaycush at greater depths than in the mid-1980s. To determine if depth distributions shifted coincident with the early 1990s colonization of Lake Ontario by exotic Dreissena mussels, we calculated mean depth of capture for each of the three species during trawl surveys conducted annually during 1978–1997 and examined the means for significant deviations from established patterns. We found that mean capture depth of alewives, rainbow smelt, and age-2 lake trout shifted deeper during the build up of the dreissenid population in Lake Ontario but that timing of the shift varied among seasons and species. Depth shifts occurred first for rainbow smelt and age-2 lake trout in June 1991. In 1992, alewives shifted deeper in June followed by age-2 lake trout in July–August. Finally, in 1993 and 1994, the distrib...

Two types of depth shifts in the wallpaper illusion: their spatial and temporal characteristics and the relationship to stereo capture

Two types of depth shifts in the wallpaper illusion: their spatial and temporal characteristics and the relationship to stereo capture

Diel vertical migration of myctophid fishes (Family Myctophidae) in the transitional waters of the western North Pacific

The diel vertical migration patterns of adult myctophid fishes were determined in the transitional waters of the western North Pacific off Japan, using day–night sampling from 20 to 700 m depths with a commercial otter trawl in the summer of 1995. A total of 12 species belonging to 9 genera were collected. Four patterns were recognized in the diel vertical migration of 11 of the 12 species. (1) Migrants showing clear day–night habitat separation with peak abundance above 200 m at night: Symbolophorus californiensis, Tarletonbeania taylori, Notoscopelus japonicus, Diaphus theta, Ceratoscopelus warmingi, and Diaphus gigas. (2) Semi‐migrants, in which part of the population often remains in the daytime habitat at night. The distribution depths of migratory and nonmigratory individuals do not overlap: Stenobrachius leucopsarus. (3) Passive‐migrants, in which there is no separation of day–night habitats, but the upper limit of daytime distribution depth shifts to a shallower layer at night, probably as the fish follow migratory prey: Lampanyctus jordani. (4) Nonmigrants: Stenobrachius nannochir, Lampanyctus regalis (&gt; 140 mm SL), and Protomyctophum thompsoni. The day–night habitat temperature ranges are also given for the 11 species. No remarkable east–west differences were seen in the vertical migration patterns compared with previous knowledge of eight of these species in the eastern Pacific. The diel migration patterns are newly described for three other species endemic to the western Pacific. The standing stock of myctophids in the study area was conservatively estimated at 18.5 ± 4.7 g m−2 (avg. ± SD).