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Articles 1 - 30 of 39
Full-Text Articles in Physical Sciences and Mathematics
Differential Nitrogen Uptake By Aquatic Communities In A Chesapeake Bay Tributary And In The Coastal Alaskan Arctic, Brianna Stanley
Differential Nitrogen Uptake By Aquatic Communities In A Chesapeake Bay Tributary And In The Coastal Alaskan Arctic, Brianna Stanley
Dissertations, Theses, and Masters Projects
Nitrogen (N) is one of the essential building blocks for all life and is available in the form of dissolved N in aquatic ecosystems. It is important to understand how this N can support primary and secondary production mediated by phytoplankton and bacteria, respectively, as it can affect both microbial loop biogeochemistry and the higher trophic levels of food webs. Nitrogen studies have traditionally focused on dissolved inorganic N (DIN) as a labile N source. Dissolved organic N (DON), while still often considered refractory, has been increasingly recognized as an important N source supporting primary and secondary production. However, the …
Polyaromatic-Terminated Iron Polypyridyl Complexes For The Functionalization Of Carbon Surfaces And Electrocatalytic Hydrogen Generation, Caroline Marie Margonis
Polyaromatic-Terminated Iron Polypyridyl Complexes For The Functionalization Of Carbon Surfaces And Electrocatalytic Hydrogen Generation, Caroline Marie Margonis
Dissertations, Theses, and Masters Projects
Artificial Photosynthesis (AP) focuses on developing methods for the conversion of solar energy into chemical fuel in the form of H2 and O2. Heterogeneous photocatalytic systems incorporating carbon nanotubes (CNTs) have shown much promise but are currently limited and expensive due to their reliance on noble metals. To that end, this work focuses on the development and synthesis of cheaper naphthalene- and pyrene-terminated iron polypyridyl complexes for use in the simultaneous functionalization of carbon surfaces, electrocatalytic proton reduction, and eventual incorporation in photocatalytic systems. Cyclic voltammetry was used to characterize the adsorption behavior of each complex on the surface of …
Water Clarity And Suspended Particle Dynamics In The Chesapeake Bay: Local Effects Of Oyster Aquaculture, Regional Effects Of Reduced Shoreline Erosion, And Long-Term Trends In Remotely Sensed Reflectance, Jessica Turner
Dissertations, Theses, and Masters Projects
Water clarity is a key indicator of the ecosystem health in the Chesapeake Bay. Estuarine water clarity fluctuates due to external inputs from the watershed as well as processes occurring within the estuary itself, such as sediment resuspension and organic matter production. Therefore, water clarity requires study at multiple spatial and temporal scales and with multiple metrics. One local-scale process potentially influencing water clarity is shellfish aquaculture. One part of this dissertation examined how water quality and hydrodynamics varied among oyster farms as well as inside versus outside the extent of caged areas located in southern Chesapeake Bay. Current speed …
Sediment Transport And Trapping On The Ayeyarwady-Martaban Continental Shelf, Matthew Joshua Fair
Sediment Transport And Trapping On The Ayeyarwady-Martaban Continental Shelf, Matthew Joshua Fair
Dissertations, Theses, and Masters Projects
The Ayeyarwady and Thanlwin Rivers, which primarily drain Myanmar, are together one of the largest point sources of freshwater and sediment to the global ocean. Much of the estimated 600 Mt of river sediment annually carried by the combined Ayeyarwady and Thanlwin River system is delivered to a wide continental shelf in the northern Andaman Sea. Called here the Ayeyarwady-Martaban continental shelf, this area is influenced by strong tides, monsoon conditions, and periodic cyclones; however, the processes that dominate dispersal of fluvial material in the coastal ocean of this system remain poorly understood. The shelf exhibits a dramatic asymmetry of …
Estuarine Microbiomes And Biogeochemistry: Impacts Of Spatiotemporal Variation, Algal Blooms, And Microplastics, Samantha Grace Fortin
Estuarine Microbiomes And Biogeochemistry: Impacts Of Spatiotemporal Variation, Algal Blooms, And Microplastics, Samantha Grace Fortin
Dissertations, Theses, and Masters Projects
Estuaries are biogeochemical hotspots connecting terrestrial and coastal ecosystems. Anthropogenic disturbances, including increased nitrogen loading and plastic pollution, may have significant impacts on estuarine carbon and nitrogen cycling by altering microbiome structure and functions. The overarching goal of this dissertation was to examine how microbiomes and their associated biogeochemical processes are influenced by natural variation and anthropogenic disturbances in the York River Estuary (YRE). In chapter 2, spatial and temporal variation in benthic microbiomes and the rates of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were examined to determine biotic and abiotic drivers of nitrogen …
Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility, Kayla Copeman
Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility, Kayla Copeman
Dissertations, Theses, and Masters Projects
Commonly used in aerospace, automotive, marine, defense, electronic, and manufacturing industries, epoxy adhesives offer advantages over mechanical joints by providing stronger and/or more flexible bonds, more uniform stress distribution, low shrinkage, and lightweight connections between materials. Determination of curing kinetics and properties of interfaces between epoxy and inorganic substrates provides insight that is useful for quality control and defect detection for such applications. Single-sided NMR provides a nondestructive and inexpensive method for probing epoxy materials and spatially resolving the decay of spin-lattice and spin-spin relaxation times (T1 and T2) during and after curing of epoxy resins onto substrates. In this …
Low-Overhead Techniques For Secure And Reliable Gpu Computing, Gurunath Kadam
Low-Overhead Techniques For Secure And Reliable Gpu Computing, Gurunath Kadam
Dissertations, Theses, and Masters Projects
In recent years, Graphics Processing Units (GPUs) have become a de facto choice to accelerate the computations in various domains such as machine learning, security, financial and scientific computing. GPUs leverage the inherent data parallelism in the target applications to provide high throughput at superior energy efficiency. Due to the rising usage of GPUs for a large number of applications, they are facing new challenges, especially in the security and reliability domains. From the security side, recently several microarchitectural attacks targeting GPUs have been demonstrated. These attacks leak the secret information stored on GPUs, for example, the parameters of a …
Ultrafast Optical Control And Characterization Of Carrier And Spin Dynamics In Novel Magnetic Topological Insulator Systems, Peiwen Liu
Dissertations, Theses, and Masters Projects
Magnetic topological insulators (MTIs) are of considerable interest in developing novel spintronics and quantum computing applications. Under the topological protection by time-reversal Z2 invariant number, magnetic topological insulators are provided with robust electronic and magnetic properties against local perturbations. The quantum anomalous Hall effect (QAHE), which harbors dissipationless chiral edge states in MTIs, provides a competitive platform for future low-power consumption and high-speed spintronic devices. Although the present studies on both bulk and surface magnetic properties in MTIs have made significant progress, the in-depth understanding of the exchange couplings and the interaction between the two magnetization sources is far from …
Performance Optimization With An Integrated View Of Compiler And Application Knowledge, Ruiqin Tian
Performance Optimization With An Integrated View Of Compiler And Application Knowledge, Ruiqin Tian
Dissertations, Theses, and Masters Projects
Compiler optimization is a long-standing research field that enhances program performance with a set of rigorous code analyses and transformations. Traditional compiler optimization focuses on general programs or program structures without considering too much high-level application operations or data structure knowledge. In this thesis, we claim that an integrated view of the application and compiler is helpful to further improve program performance. Particularly, we study integrated optimization opportunities for three kinds of applications: irregular tree-based query processing systems such as B+ tree, security enhancement such as buffer overflow protection, and tensor/matrix-based linear algebra computation. The performance of B+ tree query …
Data-Driven Reflectance Estimation Under Natural Lighting, Victoria Cooper
Data-Driven Reflectance Estimation Under Natural Lighting, Victoria Cooper
Dissertations, Theses, and Masters Projects
Bidirectional Reflectance Distribution Functions, (BRDFs), describe how light is reflected off of a material. BRDFs are captured so that the materials can be re-lit under new while maintaining accuracy. BRDF models can approximate the reflectance of a material, but are unable to accurately represent the full BRDF of the material. Acquisition setups for BRDFs trade accuracy for speed with the most accurate methods, gonioreflectometers, being the slowest. Image-based BRDF acquisition approaches range from using complicated controlled lighting setups to uncontrolled known lighting to assuming the lighting is unknown. We propose a data-driven method for recovering BRDFs under known, but uncontrolled …
Impact Of Canyon Upwelling And Downwelling In The Mid-Atlantic Bight, Haixing Wang
Impact Of Canyon Upwelling And Downwelling In The Mid-Atlantic Bight, Haixing Wang
Dissertations, Theses, and Masters Projects
Submarine canyons can impact regional oceanography and provide a conduit for shelf-slope exchanges via topographically induced processes such as canyon upwelling and downwelling. Between Virginia and New York in the Mid-Atlantic Bight (MAB), there are five major shelf-incising canyons (Norfolk, Washington, Baltimore, Wilmington, and Hudson canyons) and four sizable slope-confined canyons (Accomac, Spencer, Lindenkhol, and Toms canyons). Canyon upwelling and downwelling at these canyons have not been well studied. Consequently, the associated hydrographic variability and dynamics inside the canyons and on the adjacent shelf are largely unknown, and the integrated impact of submarine canyons on MAB shelf hydrography and shelf-slope …
Excited J-- Resonances In Meson-Meson Scattering From Lattice Qcd, Christopher Johnson
Excited J-- Resonances In Meson-Meson Scattering From Lattice Qcd, Christopher Johnson
Dissertations, Theses, and Masters Projects
Understanding the excited light meson spectrum is vital to our understanding of how quarks and gluons bind to become hadrons. This sector is home to a plethora of states including hadrons laying outside the quark model. Distinguishing the from the rest of the spectrum would be made easier if we first had a handle on the light quark anti-quark spectrum. I present the first determination of excited light JPC=1--,2--,3-- resonances in meson-meson scattering at the SU(3) flavor point from lattice QCD. This system can be described in the context of pseudoscalar-vector elastic scattering and I determine two 1-- resonances; a …
Improving Observation, Assessment, And Management Of Atlantic Coastal Sharks, Cassidy Dawn Peterson
Improving Observation, Assessment, And Management Of Atlantic Coastal Sharks, Cassidy Dawn Peterson
Dissertations, Theses, and Masters Projects
Coastal sharks represent a group of stocks for which observation, assessment, and management are particularly challenging. Large distributional ranges, complex migratory behavior, low economic value, and relatively few observations in fishery independent surveys hinder relative abundance estimation. Assessing stock status of coastal sharks is encumbered by limited data availability, data quality, and knowledge of life history strategy. Further, coastal sharks are challenging to manage due to their slow intrinsic population growth rates, competing stakeholder interests, history of overexploitation, and in some cases, subjection to international exploitation. This dissertation aimed to improve the capacity to observe relative abundance of coastal sharks. …
Revisiting Isolation For System Security And Efficiency In The Era Of Internet Of Things, Lele Ma
Revisiting Isolation For System Security And Efficiency In The Era Of Internet Of Things, Lele Ma
Dissertations, Theses, and Masters Projects
Isolation is a fundamental paradigm for secure and efficient resource sharing on a computer system. However, isolation mechanisms in traditional cloud computing platforms are heavy-weight or just not feasible to be applied onto the computing environment for Internet of Things(IoT). Most IoT devices have limited resources and their servers are less powerful than cloud servers but are widely distributed over the edge of the Internet. Revisions to the traditional isolation mechanisms are needed in order to improve the system security and efficiency in these computing environments. The first project explores container-based isolation for the emerging edge computing platforms. We show …
Quantifying The Increased Resiliency Of Chesapeake Bay Hypoxia To Environmental Conditions: A Benefit Of Nutrient Reductions, Luke Thomas Frankel
Quantifying The Increased Resiliency Of Chesapeake Bay Hypoxia To Environmental Conditions: A Benefit Of Nutrient Reductions, Luke Thomas Frankel
Dissertations, Theses, and Masters Projects
Seasonal hypoxia is a characteristic feature of the Chesapeake Bay as a result of anthropogenic eutrophication from agriculture and urban development throughout the watershed. Although in recent years coordinated management efforts have successfully reduced the flux of nutrients into the Bay, the overall goal of sufficient oxygen concentrations below the pycnocline for living resources remains unfulfilled. This was particularly apparent in 2018 and 2019 when the volume of hypoxic water exceeded the long-term (35-year) average due to anomalously high riverine discharge. To quantify the impact of watershed nutrient reductions, conventional statistical methods were employed in concert with a 3-D numerical …
On Supporting Android Software Developers And Testers, Carlos Eduardo Bernal Cardenas
On Supporting Android Software Developers And Testers, Carlos Eduardo Bernal Cardenas
Dissertations, Theses, and Masters Projects
Users entrust mobile applications (apps) to help them with different tasks in their daily lives. However, for each app that helps to finish a given task, there are a plethora of other apps in popular marketplaces that offer similar or nearly identical functionality. This makes for a competitive market where users will tend to favor the highest quality apps in most cases. Given that users can easily get frustrated by apps which repeatedly exhibit bugs, failures, and crashes, it is imperative that developers promptly fix problems both before and after the release. However, implementing and maintaining high quality apps is …
Recruitment And Post-Settlement Mortality Of The Soft-Shell Clam, Mya Arenaria, Shantelle Landry
Recruitment And Post-Settlement Mortality Of The Soft-Shell Clam, Mya Arenaria, Shantelle Landry
Dissertations, Theses, and Masters Projects
The soft-shell clam, Mya arenaria, is a benthic, filter-feeding, infaunal clam typically found in intertidal and shallow subtidal waters. Chesapeake Bay stocks of M. arenaria have been depleted since the 1960s due to various factors including predation, temperature, low recruitment, habitat loss, disease mortalities, and commercial harvest. As an important prey item for many commercial species, low abundances of these clams are mostly the result of the voracious appetite of the blue crab, Callinectes sapidus. In addition to predation, summer water temperatures in the Chesapeake Bay are likely driving the low abundances of M. arenaria, as water temperatures commonly surpass …
Controls On Estuarine Sediment Bed Erodibility: Insights From The York River Estuary, Cristin Lee Wright
Controls On Estuarine Sediment Bed Erodibility: Insights From The York River Estuary, Cristin Lee Wright
Dissertations, Theses, and Masters Projects
The erodibility of estuarine sediment beds has a number of ecological and societal implications, including alteration of benthic habitats, light-limitation of primary production, and reintroduction of pollutants to the water column, as well as impacts on dredging operations and on the fate of potentially dangerous objects on the seafloor. The objectives of this study are to better understand controls on bed erodibility in estuarine environments, including the roles of sediment grain size, water content, percent organics, and bed fabric, as well as effects of tides, storms, salinity distribution, river discharge, and location within the estuary. An extensive set of erosion …
Uncovering Information Operations On Twitter Using Natural Language Processing And The Dynamic Wavelet Fingerprint, Spencer Lee Kirn
Uncovering Information Operations On Twitter Using Natural Language Processing And The Dynamic Wavelet Fingerprint, Spencer Lee Kirn
Dissertations, Theses, and Masters Projects
Information Operations (IO) are campaigns waged by covert, powerful entities to distort public discourse in a direction that is advantageous for them. It is the behaviors of the underlying networks that signal these campaigns in action, not the specific content they are posting. In this dissertation we introduce a social media analysis system that uncovers these behaviors by analyzing the specific post timings of underlying accounts and networks. The presented method first clusters tweets based on content using Natural Language Processing (NLP). Each of these clusters - referred to as topics - are plotted in time using the attached metadata …
Sediment And Terrestrial Organic Carbon Budgets For The Offshore Ayeyarwady Delta: Establishing A Baseline For Future Change, Evan Rose Flynn
Sediment And Terrestrial Organic Carbon Budgets For The Offshore Ayeyarwady Delta: Establishing A Baseline For Future Change, Evan Rose Flynn
Dissertations, Theses, and Masters Projects
Large river deltas serve as globally important archives of terrestrial and shallow marine biogeochemical signatures because of rapid sediment burial, and have the potential to impact global biogeochemical cycling on modern and geologic timescales. This study investigates modern sediment and terrestrial organic carbon (TerrOC) accumulation within the offshore Ayeyarwady Delta in order to determine sediment and TerrOC budgets for this largely understudied mega-delta. The Ayeyarwady is the world’s third largest delta in terms of sediment supply, and remains one of the last long free-flowing rivers in Asia. However, recent increases in regional anthropogenic impacts risk severe alterations to sediment and …
Investigating The Electron Transfer Dynamics Of Eosin Y Photosensitizers Using Single Molecule Spectroscopy, Kelly Margaret Kopera
Investigating The Electron Transfer Dynamics Of Eosin Y Photosensitizers Using Single Molecule Spectroscopy, Kelly Margaret Kopera
Dissertations, Theses, and Masters Projects
Growing global energy demands have necessitated the search for alternative sources of renewable fuels. Dye-sensitized photocatalysis (DSP) is a promising low cost, sustainable method that directly converts solar energy to readily usable forms of energy such as hydrogen fuel. While DSP is a promising technology, its efficiency is limited by back electron transfer and kinetic redundancy. In order to fully understand these processes, single-molecule spectroscopy (SMS) is used to probe the electron transfer (ET) dynamics of photosensitizers. In particular, eosin Y (EY), a brominated fluorescein derivative that undergoes intersystem crossing prior to injection, is investigated using SMS. In this approach, …
High-Dimensional Machine Learning Models In Fintech, Qiong Wu
High-Dimensional Machine Learning Models In Fintech, Qiong Wu
Dissertations, Theses, and Masters Projects
This thesis develops several forecasting models for simultaneously predicting the prices of d assets traded in financial markets, a most fundamental problem in the emerging area of ``FinTech''. The models are optimized to address three critical challenges, C1. High-dimensional interactions between assets. Assets could interact (e.g., Amazon's disclosure of its revenue change in cloud services could indicate that revenues also could change in other cloud providers). The number of possible interactions is quadratic in d, and is often much larger than the number of observations. C2. Non-linearity of the hypothesis class. Linear models are usually insufficient to characterize the relationship …
Distributed Byzantine Tolerant Machine Learning, Qi Xia
Distributed Byzantine Tolerant Machine Learning, Qi Xia
Dissertations, Theses, and Masters Projects
Oftentimes, training a large-scale deep learning neural network on a single machine becomes more difficult in a complex network model. Distributed training provides an efficient solution, but opens up participating workers to Byzantine attacks. This problem emerges when some workers cheat during uploading gradients or weights to the central server, e.g., the information received by the server is not always the true result computed by workers. In order to address this problem, we investigate Byzantine problems in distributed machine learning and respectively defend against these kinds of attacks in three scenarios: i) classic distributed machine learning; ii) federated learning; and …
Evaluating The Use Of Acoustic Warning Signals To Reduce Avian Collision Risk, Robin Grace Thady
Evaluating The Use Of Acoustic Warning Signals To Reduce Avian Collision Risk, Robin Grace Thady
Dissertations, Theses, and Masters Projects
Collisions with human-made structures are responsible for billions of bird deaths each year, resulting in ecological damage as well as regulatory and financial burdens to many industries. Acoustic warning signals can alert birds to obstacles in their flight paths in order to mitigate collisions, but these signals should be tailored to the sensory ecology of birds in flight. The effectiveness of various acoustic warning signals likely depends on the influence of background noise and the relative ability of various sound types to propagate within a landscape. I evaluated the ability of four sound signals to elicit collision-avoidant flight behaviors from …
Light-Matter Interactions In Quasi-Two-Dimensional Geometries, David James Lahneman
Light-Matter Interactions In Quasi-Two-Dimensional Geometries, David James Lahneman
Dissertations, Theses, and Masters Projects
Emergent phenomena that occur at length scales smaller than approximately half the wavelength of light cannot be resolved by conventional optical techniques due to the Abbe diffraction limit. Scattering-type scanning near-field infrared microscopy (S-SNIM) can circumvent this diffraction limit allowing infrared spectroscopy at nano-scale dimensions independent of the wavelength. Additionally, there is enhanced surface sensitivity resulting from this nanoconfinement of infrared light. S-SNIM is uniquely suitable to study a diverse range of material properties inaccessible by far-field optics in the infrared such as the optical properties of ultrathin films as well as hybrid light matter surface waves called polaritons. Initially, …
Electronic Effects In A Cyclization Cascade To Diversified, Polycyclic, Helical Molecules, Caleb Lee Burns
Electronic Effects In A Cyclization Cascade To Diversified, Polycyclic, Helical Molecules, Caleb Lee Burns
Dissertations, Theses, and Masters Projects
Heterocyclic aromatic compounds and their derivatives are ubiquitous in the pharmaceutical and photochemical industries. Naphthochromene derivatives in particular have garnered great interest for their photochemical properties and biological activity. Herein, the effects of electronics on a three-step cascade reaction between aryl substituted 2-(4-aryl-3-((triethylsilyl)oxy)but-1-yn-1-yl)phenols and structurally diverse aldehydes is explored. The cascade is initiated by alkynyl substrate addition to BF3-activated aldehydes. The aldehyde undergoes condensation with the substrate phenol moiety forming an oxocarbenium ion, this initiates the alkynyl-Prins cyclization forming a new six-membered heterocyclic ring with an internal alkenyl cation. The cation is subsequently trapped by a Friedel-Crafts (FC) reaction by …
Ac & Dc Zeeman Interferometric Sensing With Ultracold Trapped Atoms On A Chip, Shuangli Du
Ac & Dc Zeeman Interferometric Sensing With Ultracold Trapped Atoms On A Chip, Shuangli Du
Dissertations, Theses, and Masters Projects
This thesis presents progress in developing a trapped atom interferometer on a chip, based on AC Zeeman potentials. An atom interferometer is a high-precision measuring tool that can detect various types of forces and potentials. The trapped atom interferometer introduced in this thesis targets the shortcomings of traditional ballistic atom interferometers, which are typically meter-scale in height. Notably, a trapped atom interferometer has a localized atomic sample, a potentially longer interferometric phase accumulation time, and the prospect of being the basis for a more compact instrument. This thesis presents multiple projects in the development of a trapped atom interferometer based …
Calculation Of Gluon Pdf In The Nucleon Using Pseudo-Pdf Formalism With Wilson Flow Technique In Lqcd, Md Tanjib Atique Khan
Calculation Of Gluon Pdf In The Nucleon Using Pseudo-Pdf Formalism With Wilson Flow Technique In Lqcd, Md Tanjib Atique Khan
Dissertations, Theses, and Masters Projects
A comprehensive study of the gluonic content in the nucleon from a first principles lattice quantum chromodynamics calculation is presented. The unpolarized gluonic distribution in the nucleon is calculated using the pseudo-PDF framework on the lattice. First, the spectral analyses of the low-lying states in the nucleon, as well as in the delta are performed on the lattice, identifying baryons states with hybrid characteristics, in which the gluons play a manifestly structural role, and determining a set of operators which have significant overlaps onto the ground state of the nucleon. Techniques such as distillation for smearing the quark fields, momentum …
Rethinking Cache Hierarchy And Interconnect Design For Next-Generation Gpus, Mohamed Assem Abd Elmohsen Ibrahim
Rethinking Cache Hierarchy And Interconnect Design For Next-Generation Gpus, Mohamed Assem Abd Elmohsen Ibrahim
Dissertations, Theses, and Masters Projects
To match the increasing computational demands of GPGPU applications and to improve peak compute throughput, the core counts in GPUs have been increasing with every generation. However, the famous memory wall is a major performance determinant in GPUs. In other words, in most cases, peak throughput in GPUs is ultimately dictated by memory bandwidth. Therefore, to serve the memory demands of thousands of concurrently executing threads, GPUs are equipped with several sources of bandwidth such as on-chip private/shared caching resources and off-chip high bandwidth memories. However, the existing sources of bandwidth are often not sufficient for achieving optimal GPU performance. …
Radiofrequency Ac Zeeman Trapping For Neutral Atoms, Andrew Peter Rotunno
Radiofrequency Ac Zeeman Trapping For Neutral Atoms, Andrew Peter Rotunno
Dissertations, Theses, and Masters Projects
This thesis presents the first experimental demonstration of a two-wire AC Zeeman trap on an atom chip. The AC Zeeman energy is a resonant, bipolar, state-dependent atomic energy shift produced by alternating magnetic fields with frequencies near hyperfine transitions. We demonstrate that high gradients in this energy, as near an atom chip, can produce a spin-state selective force greater than gravity for ultracold rubidium atoms. Our novel trap is generated by a local minimum in AC Zeeman energy. Using less than one watt of power, we demonstrate trap frequency on the order of a few hundred Hz, trap depth about …