Modified Landscapes

Modified Landscapes is a body of work that reflects serious thought regarding Nature and its future. My personal experience and beliefs are at the core of why I believe this subject to be of great importance and why it will sustain many artists’ investigations for the time to come. The influences that informed this process are explored through experiences I had traveling, reading and exploring the photograph as a material object. The manipulation of the photograph is meant to question the beautiful, untouched scene and break the Romantic gaze that is historically tied to representations of Nature and insist upon contemporary reflection on the neglected state of our environment

High-Resolution Seafloor Absolute Pressure Gauge Measurements Using a Better Counting Method

Vibrating quartz force transducers are the critical component of most deep-sea pressure and depth gauges in use in oceanography, producing a frequency output that varies with pressure. Accurate and low drift pressure measurements can be obtained by precisely measuring this frequency. In most imple- mentations, the frequency is determined by counting the number of cycles of a high-frequency standard oscillator occurring during a large number of cycles of the lower-frequency quartz force oscillator. Res- olution is limited by the sampling interval (length of counting) and the frequency of the frequency stan- dard. Alternative counting methods can provide significant (20–40 dB) improvements in resolution at sampling rates above 1 Hz. Each counting method can be described as a different filter applied to the output of a counter of the frequency standard gated at each transition of the transducer quartz oscillator. Improvements in resolution can be understood as the result of minimizing the aliasing of higher-frequency counting noise into the spectrum below the Nyquist frequency. A simple multipole infinite impulse re- sponse (IIR) filter designed to limit spectral leakage of high-frequency noise minimizes the noise spectrum and thereby optimizes the resolution of the pressure output. The resultant noise spectrum rises as fre- quency squared above 1 Hz, independent of the sampling rate. At frequencies below 1 Hz, it is limited by noise in the electronics driving the force transducer quartz oscillator. Resolution increases with frequency of the frequency standard up to about 200 MHz, plateauing for higher frequencies due to other noise sources (likely electronic)

A SEA FLOOR GRAVITY SURVEY OF THE SLEIPNER FIELD TO MONITOR CO2 MIGRATION

Since 1996, excess CO{sub 2} from the Sleipner natural gas field has been sequestered and injected underground into a porous saline aquifer 1000 m below the seafloor. In 2002, we carried out a high precision micro-gravity survey on the seafloor in order to monitor the injected CO{sub 2}. A repeatability of 5 {micro}Gal in the station averages was observed. This is considerably better than pre-survey expectations. These data will serve as the baseline for time-lapse gravity monitoring of the Sleipner CO{sub 2} injection site. A repeat survey has been scheduled for the summer of 2005. This report covers 9/19/04 to 3/18/05. During this time, gravity and pressure modeling were completed and work graduate student Scott Nooner began writing his Ph.D. dissertation, of which this work is a the major part. Improvements to the gravimeters are also underway that will hopefully increase the measurement precision

Post Eruption inflation of the East Pacific Rise at 9°50′ N

In June 2008, we installed a geodetic network at 9°50′ N on the East Pacific Rise to track the long‐term movement of magma following the 2005/6 eruption. This network consists of 10 concrete benchmarks stretching from the ridge to 9 km off‐axis. During three campaign‐style surveys, measurements of vertical seafloor motions were made at each of these benchmarks by precisely recording ambient seawater pressure as a proxy for seafloor depth with a mobile pressure recorder (MPR). The MPR was deployed using the manned submersible Alvin in 2008 and 2009 and the remotely operated vehicle Jason in 2011. The MPR observations are supplemented with data from a multiyear deployment of continuously recording bottom pressure recorders (BPRs) extending along this segment of the ridge that can record rapid changes in seafloor depth from seafloor eruptions and/or dike intrusions. These measurements show no diking events and up to 12 cm of volcanic inflation that occurred from December 2009 to October 2011 in the area of the 2005/6 eruption. These observations are fit with an inflating point source at a depth of 2.7 km and volume change of 2.3 × 106 m3/yr located on the ridge axis at approximately 9°51.166′ N, 407 m from our northernmost benchmark, suggesting that the magma chamber underlying this segment of the ridge is being recharged from a deeper source at a rate that is about half the long‐term inflation rate observed at Axial Seamount on the Juan de Fuca Ridge. These data represent the second location that active volcanic uplift has been measured on a mid‐ocean ridge segment, and the first on a nonhotspot influenced segment

Chemical Properties of the Leinamycin-Guanine Adduct in DNA

The reaction of the antitumor agent leinamycin with thiols converts this natural product into an episulfonium ion that alkylates the N7-position of guanine residues in double-stranded DNA. It is reported here that depurination of this adduct is unusually facile, occurring with a half-life of about 3.5 h at pH 7 and 37°C in duplex DNA. This is one of the most rapid depurination reactions ever observed for an N7-alkylguanine residue. The rate constant for the depurination reaction was measured at several temperatures, and the activation parameters were calculated from the data. The energy of activation (E a ) for this reaction is 24.6 kcal/mol, and the Arrhenius A value is 1.2 × 10 13 s -1 . These values correspond to a ∆H ‡ ) 24.0 kcal/mol and ∆S ‡ ) -0.78 eu and are consistent with the expected unimolecular (D N + A N ) mechanism for the depurination reaction. Changes in ionic strength (0-500 mM NaCl) or pH (3-8) do not significantly alter the rate of depurination, and the base excision repair protein Aag, which removes a variety of N7-alkylguanine residues from duplex DNA, does not excise the leinamycin-guanine adduct. Possible biological implications of this rapid depurination process are considered. Finally, during the course of these studies, the release of hydrolyzed leinamycin (4; Scheme 1) from leinamycin-modified DNA was observed. This result suggests that leinamycin may be a reversible DNA alkylating agent

Axial Seamount

Author Posting. © Oceanography Society, 2010. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 23, 1 (2010): 38-39.Axial Seamount is a hotspot volcano superimposed on the Juan de Fuca Ridge (JdFR) in the Northeast Pacific Ocean. Due to its robust magma supply, it rises ~ 800 m above the rest of JdFR and has a large elongate summit caldera with two rift zones that parallel and overlap with adjacent segments of the spreading center

Retaining Adolescent and Young Adult Participants in Research During a Pandemic: Best Practices From Two Large-Scale Developmental Neuroimaging Studies (NCANDA and ABCD)

The novel coronavirus pandemic that emerged in late 2019 (COVID-19) has created challenges not previously experienced in human research. This paper discusses two large-scale NIH-funded multi-site longitudinal studies of adolescents and young adults – the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA) and the Adolescent Brain Cognitive Development (ABCD) Study – and valuable approaches to learn about adaptive processes for conducting developmentally sensitive research with neuroimaging and neurocognitive testing across consortia during a global pandemic. We focus on challenges experienced during the pandemic and modifications that may guide other projects, such as implementing adapted protocols that protect the safety of participants and research staff, and addressing assessment challenges through the use of strategies such as remote and mobile assessments. Given the pandemic’s disproportionate impacts on participants typically underrepresented in research, we describe efforts to retain these individuals. The pandemic provides an opportunity to develop adaptive processes that can facilitate future studies’ ability to mobilize effectively and rapidly

Retaining Adolescent and Young Adult Participants in Research During a Pandemic: Best Practices From Two Large-Scale Developmental Neuroimaging Studies (NCANDA and ABCD)

The novel coronavirus pandemic that emerged in late 2019 (COVID-19) has created challenges not previously experienced in human research. This paper discusses two large-scale NIH-funded multi-site longitudinal studies of adolescents and young adults – the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA) and the Adolescent Brain Cognitive Development (ABCD) Study – and valuable approaches to learn about adaptive processes for conducting developmentally sensitive research with neuroimaging and neurocognitive testing across consortia during a global pandemic. We focus on challenges experienced during the pandemic and modifications that may guide other projects, such as implementing adapted protocols that protect the safety of participants and research staff, and addressing assessment challenges through the use of strategies such as remote and mobile assessments. Given the pandemic’s disproportionate impacts on participants typically underrepresented in research, we describe efforts to retain these individuals. The pandemic provides an opportunity to develop adaptive processes that can facilitate future studies’ ability to mobilize effectively and rapidly

Structural subnetwork evolution across the life-span: rich-club, feeder, seeder

The impact of developmental and aging processes on brain connectivity and the connectome has been widely studied. Network theoretical measures and certain topological principles are computed from the entire brain, however there is a need to separate and understand the underlying subnetworks which contribute towards these observed holistic connectomic alterations. One organizational principle is the rich-club - a core subnetwork of brain regions that are strongly connected, forming a high-cost, high-capacity backbone that is critical for effective communication in the network. Investigations primarily focus on its alterations with disease and age. Here, we present a systematic analysis of not only the rich-club, but also other subnetworks derived from this backbone - namely feeder and seeder subnetworks. Our analysis is applied to structural connectomes in a normal cohort from a large, publicly available lifespan study. We demonstrate changes in rich-club membership with age alongside a shift in importance from 'peripheral' seeder to feeder subnetworks. Our results show a refinement within the rich-club structure (increase in transitivity and betweenness centrality), as well as increased efficiency in the feeder subnetwork and decreased measures of network integration and segregation in the seeder subnetwork. These results demonstrate the different developmental patterns when analyzing the connectome stratified according to its rich-club and the potential of utilizing this subnetwork analysis to reveal the evolution of brain architectural alterations across the life-span