Digital Commons Network^™

Medical Physics Workforce In The United States, Wayne D. Newhauser, Dustin A. Gress, Michael D. Mills, David W. Jordan, Steven G. Sutlief, Melissa C. Martin, Edward Jackson

Faculty Publications

No abstract provided.

Greater Evolutionary Divergence Of Thermal Limits Within Marine Than Terrestrial Species, Matthew Sasaki, Jordanna M. Barley, Sarah Gignoux-Wolfsohn, Cynthia G. Hays, Morgan W. Kelly, Alysha B. Putnam, Seema N. Sheth, Andrew R. Villeneuve, Brian S. Cheng

Faculty Publications

There is considerable uncertainty regarding which ecosystems are most vulnerable to warming. Current understanding of organismal sensitivity is largely centred on species-level assessments that do not consider variation across populations. Here we used meta-analysis to quantify upper thermal tolerance variation across 305 populations from 61 terrestrial, freshwater, marine and intertidal taxa. We found strong differentiation in heat tolerance across populations in marine and intertidal taxa but not terrestrial or freshwater taxa. This is counter to the expectation that increased connectivity in the ocean should reduce intraspecific variation. Such adaptive differentiation in the ocean suggests there may be standing genetic variation …

Epidemic Time Series Similarity Is Related To Geographic Distance And Age Structure, Tad Dallas, Grant Foster, Robert L. Richards, Bret D. Elderd

Faculty Publications

Objective

More similar locations may have similar infectious disease dynamics. There is clear overlap in putative causes for epidemic similarity, such as geographic distance, age structure, and population size. We compare the effects of these potential drivers on epidemic similarity compared to a baseline assumption that differences in the basic reproductive number (R₀) will translate to differences in epidemic trajectories.

Methods

Using COVID-19 case counts from United States counties, we explore the importance of geographic distance, population size differences, and age structure dissimilarity on resulting epidemic similarity.

Results

We find clear effects of geographic space, age structure, …

Highlighting Excellence In Small Schools, Anneris Coria-Navia, Aimee Leukert, Jerome Thayer, Maria Bastien Valenca, Elissa Kido

Faculty Publications

No abstract provided.

Potential Use Of Engineered Nanoparticles In Ocean Fertilization For Large-Scale Atmospheric Carbon Dioxide Removal, Peyman Babakhani, Tanapon Phenrat, Mohammed Baalousha M.Sc, Ph.D., Kullapa Soratana, Caroline L. Peacock, Benjamin S. Twining, Michael F. Hochella Jr.

Faculty Publications

Artificial ocean fertilization (AOF) aims to safely stimulate phytoplankton growth in the ocean and enhance carbon sequestration. AOF carbon sequestration efficiency appears lower than natural ocean fertilization processes due mainly to the low bioavailability of added nutrients, along with low export rates of AOF-produced biomass to the deep ocean. Here we explore the potential application of engineered nanoparticles (ENPs) to overcome these issues. Data from 123 studies show that some ENPs may enhance phytoplankton growth at concentrations below those likely to be toxic in marine ecosystems. ENPs may also increase bloom lifetime, boost phytoplankton aggregation and carbon export, and address …

Insectdisease: Programmatic Access To The Ecological Database Of The World’S Insect Pathogens, Tad Dallas, Colin J. Carlson, Patrick R. Stephens, Sadie J. Ryan, David W. Onstad

Faculty Publications

Curated databases of species interactions are instrumental to exploring and understanding the spatial distribution of species and their biotic interactions. In the process of conducting such projects, data development and curation efforts may give rise to a data product with utility beyond the scope of the original work, but which becomes inaccessible over time. Data describing insect host–pathogen interactions are fairly rare, and should thus be preserved and curated with appropriate metadata. Here, we introduce the insectDisease R package, a mechanism for curating, updating and distributing data from the Ecological Database of the World's Insect Pathogens, a database of insect …

Us Scientific Leadership Addressing Energy, Ecosystems, Climate, And Sustainable Prosperity: Report In Brief From The Berac Subcommittee On International Benchmarking, Maureen Mccann, Patrick Reed, Ana Alonso, Ludmilla Aristilde, Massie S. Ballon, Crysten Blaby, Allison A. Campbell, Kenneth James Davis, Brian H. Davison, Ben Evans, Robert F. Fischetti, Serita D. Frey, Ann M. Fridlind, Efi Foufoula-Georgiou, Ramon Gonzalez, Michael N. Gooseff, Nathan Hillson, Janet Jansson, Klaus Keller, Markus Kleber, Costas Maranas, Gerald A. Meehl, Himadri Pakrasi, Jennifer Pett-Ridge, Kristala Prather, Johannes Quaas, G. Philip Robertson, Alistair Rogers, Tim Scheibe, Thomas R. Schneider, Gary Stacey, Margaret S. Torn, Kerstin Kleese Van Dam, Detlef Vuuren, John Weyant, Stan Wullschleger, Shaocheng Xie, Seung Yon (Sue) Rhee, Huimin Zhao

Faculty Publications

This document presents the subcommittee’s overarching and domain-specific findings and recommendations for the next decade, identified by consensus across the full BERAC subcommittee and experts interviewed for this assessment.

A New Feudalism: Selfish Genes, Great Wealth, And The Rise Of The Dynastic Family Trust (Dft), Eric Kades

Faculty Publications

Today’s record levels of economic inequality are infecting our future as the top 0.01% bequeath vast wealth to their descendants. With the death of the Rule Against Perpetuities (RAP), this inequality has the potential to harden social class lines—not just for a generation or two, but forever. Although it may sound implausible, interviews with estate lawyers serving very high-net-worth clients reveal that some members of the wealthiest tier of testators are already exploiting the RAP’s elimination, along with a tax loophole, to establish dynasty trusts that will financially empower their bloodline as long as it continues. Recent work in evolutionary …

What Does It Mean To Take Online Classes As An International Student During Covid-19?, Katie K. Koo, Mei Jiang

Faculty Publications

Using the Theory of Social Support and the Community of Inquiry as theoretical frameworks, this qualitative study explored international students’ experiences, challenges, and perceptions of online learning environments during the COVID-19 pandemic in the United States. By conducting three virtual focus group interviews with 18 international students, we identified four key themes that encapsulate participants’ challenges and experiences of online learning: social isolation in online learning spaces, difficulties with engaging in online class discussions and activities, limited opportunities for improving English proficiency in the online setting and limited academic support from faculty and advisors. Implications for research and practice to …

Profile Of A Comparative And International Education Leader: Marco Aurelio Navarro-Leal, Gus Gregorutti

Faculty Publications

This article is a biographical sketch of Professor Marco Aurelio Navarro-Leal, and includes reflections from his upbringing, education, and contributions in comparative and international education (CIE). Marco has been a key player in establishing the Mexican Comparative Education Society (SOMEC), advancing the CIE field with the involvement of local and international scholars dedicated to improving not only Mexican education, but also education within the entire Latin American region. He has also been actively involved in the global expansion of CIE through his leadership in such organizations as the World Council of Comparative Education Societies (WCCES). This article is based on …

A Nationwide Study Of Maternal Exposure To Ambient Ozone And Term Birth Weight In The United States, Shengzhi Sun, Jiajia Wang, Wangnan Cao, Lizhi Wu, Yu Tian, Feng Sun, Zhenyu Zhang, Yang Ge, Jianqiang Du, Xiaobo Li, Rui Chen

Faculty Publications

Background: Maternal exposure to ozone (O₃) may cause systemic inflammation and oxidative stress and contribute to fetal growth restriction. We sought to estimate the association between maternal exposure to O₃ and term birth weight and term small for gestational age (SGA) in the United States (US).

Methods: We conducted a nationwide study including 2,179,040 live term singleton births that occurred across 453 populous counties in the contiguous US in 2002. Daily county-level concentrations of O₃ data were estimated using a Bayesian fusion model. We used linear regression to estimate the association between O_{3 …}

White Matter Hyperintensity Load Is Associated With Premature Brain Aging, Natalie Busby, Sarah Newman-Norlund, Sara Sayers, Roger Newman-Norlund, Sarah Wilson, Samaneh Nemati, Chris Rorden, Janina Wilmskoetter, Nicholas Riccardi, Rebecca Roth, Julius Fridriksson, Leonardo Bonilha

Faculty Publications

Background: Brain age is an MRI-derived estimate of brain tissue loss that has a similar pattern to aging-related atrophy. White matter hyperintensities (WMHs) are neuroimaging markers of small vessel disease and may represent subtle signs of brain compromise. We tested the hypothesis that WMHs are independently associated with premature brain age in an original aging cohort.

Methods: Brain age was calculated using machine-learning on whole-brain tissue estimates from T1-weighted images using the BrainAgeR analysis pipeline in 166 healthy adult participants. WMHs were manually delineated on FLAIR images. WMH load was defined as the cumulative volume of WMHs. A positive difference …

Substrate Availability And Not Thermal Acclimation Controls Microbial Temperature Sensitivity Response To Long-Term Warming, Luiz A. Domeignoz-Horta, Grace Pold, Hailey Erb, David Sebag, Eric Verrecchia, Trent Northen, Katherine Louie, Emiley Eloe-Fadrosh, Christa Pennacchio, Melissa A. Knorr, Serita D. Frey, Jerry M. Melillo, Kristen M. Deangelis

Faculty Publications

Microbes are responsible for cycling carbon (C) through soils, and predicted changes in soil C stocks under climate change are highly sensitive to shifts in the mechanisms assumed to control the microbial physiological response to warming. Two mechanisms have been suggested to explain the long-term warming impact on microbial physiology: microbial thermal acclimation and changes in the quantity and quality of substrates available for microbial metabolism. Yet studies disentangling these two mechanisms are lacking. To resolve the drivers of changes in microbial physiology in response to long-term warming, we sampled soils from 13- and 28-year-old soil warming experiments in different …

Variation In Human Water Turnover Associated With Environmental And Lifestyle Factors, Yosuke Yamada, Xueying Zhang, Mary E.T. Henderson, Hiroyuki Sagayama, Herman Pontzer, Daiki Watanabe, Tsukasa Yoshida, Misaka Kimura, Philip N. Ainslie, Lene F. Andersen, Liam J. Anderson, Lenore Arab, Issad Baddou, Kweku Bedu-Addo, Ellen E. Blaak, Stephane Blanc, Alberto G. Bonomi, Carlijn V.C. Bouten, Pascal Bovet, Maciej S. Buchowski, Nancy F. Butte, Stefan G. Camps, Graeme L. Close, Jamie A. Cooper, Richard Cooper, Sai Krupa Das, Lara R. Dugas, Simon Eaton, Ulf Ekelund, Sonja Entringer, Terrence Forrester, Barry W. Fudge, Annelies H. Goris

Faculty Publications

Water is essential for survival, but one in three individuals worldwide (2.2 billion people) lacks access to safe drinking water. Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using isotope-tracking (2H) methods. Age, body size, and composition were significantly associated with WT, as were physical activity, athletic status, pregnancy, socioeconomic status, and environmental characteristics (latitude, altitude, air temperature, and humidity). People who lived in countries with a low human development …

An Assessment Of Future Tidal Marsh Resilience In The San Francisco Estuary Through Modeling And Quantifiable Metrics Of Sustainability, James T. Morris, Judith Z. Drexler, Lydia J.S. Vaughn, April H. Robinson

Faculty Publications

Quantitative, broadly applicable metrics of resilience are needed to effectively manage tidal marshes into the future. Here we quantified three metrics of temporal marsh resilience: time to marsh drowning, time to marsh tipping point, and the probability of a regime shift, defined as the conditional probability of a transition to an alternative super-optimal, suboptimal, or drowned state. We used organic matter content (loss on ignition, LOI) and peat age combined with the Coastal Wetland Equilibrium Model (CWEM) to track wetland development and resilience under different sea-level rise scenarios in the Sacramento-San Joaquin Delta (Delta) of California. A 100-year hindcast of …

Hematophagy And Tick-Borne Rickettsial Pathogen Shape The Microbial Community Structure And Predicted Functions Within The Tick Vector, Amblyomma Maculatum., Abdulsalam Adegoke, Deepak Kumar, Khemraj Budachetri, Shahid Karim

Faculty Publications

Background: Ticks are the primary vectors of emerging and resurging pathogens of public health significance worldwide. Analyzing tick bacterial composition, diversity, and functionality across developmental stages and tissues is crucial for designing new strategies to control ticks and prevent tick-borne diseases.

Materials and methods: Here, we explored the microbial communities across the developmental timeline and in different tissues of the Gulf-Coast ticks (Amblyomma maculatum). Using a high-throughput sequencing approach, the influence of blood meal and Rickettsia parkeri, a spotted fever group rickettsiae infection in driving changes in microbiome composition, diversity, and functionality was determined.

Results: This study …

Laboratory Evaluation And Field Feasibility Of Micro-Encapsulated Insecticide Effect On Rhodnius Prolixus And Triatoma Dimidiata Mortality In Rural Households In Boyaca, Colombia, Lidia Gual-Gonzalez, Manuel Medina, Cesar Valverde-Castro, Virgilio Beltran, Rodrigo Caro, Omar Triana-Chavez, Melissa Nolan Ph.D., Mph, Omar Cantillo-Barraza

Faculty Publications

Chagas disease is a neglected vector-borne zoonosis caused by the parasite Trypanosoma cruzi that is primarily transmitted by insects of the subfamily Triatominae. Although control efforts targeting domestic infestations of Rhodnius prolixus have been largely successful, with several regions in Boyacá department certified free of T. cruzi transmission by intradomicile R. prolixus, novel native species are emerging, increasing the risk of disease. Triatoma dimidiata is the second most important species in Colombia, and conventional control methods seem to be less effective. In this study we evaluated the efficacy and usefulness of micro-encapsulated insecticide paints in laboratory conditions and its …

Soil Microbial Communities Vary In Composition And Functional Strategy Across Soil Aggregate Size Class Regardless Of Tillage, Lukas T. Bernhardt, Richard G. Smith, Andrew S. Grandy, Jessica E. Mackay, Nicholas D. Warren, Kevin M. Geyer, Jessica G. Ernakovich

Faculty Publications

The physicochemical environment within aggregates controls the distribution of carbon and microbial communities in soils. Agricultural management, such as tillage, can disrupt aggregates and the microscale habitat provided to microorganisms, thus altering microbial community dynamics. Categorizing microbial communities into life history strategies with shared functional traits—as has been done to understand plant community structure for decades—can illuminate how the soil physicochemical environment constrains the membership and activity of microbial communities. We conducted an aggregate scale survey of microbial community composition and function through the lens of the yield–acquisition–stress (Y–A–S) tolerator life history framework. Soils collected from a 7-year tillage experiment …

Christ In The Covenant Curses? Deuteronomy 28 And The Gospel, A. Rahel Wells

Faculty Publications

No abstract provided.

A Molecular Chemodosimeter To Probe “Closed Shell” Ions In Kidney Cells, Rashid Mia

Faculty Publications

Two quinidine-functionalized coumarin molecular probes have been synthesized and have been found to bind metal cations (Cd2+, Co2+, Cu2+, Fe2+, Hg2+, Ni2+, and Zn2+) with high affinity in organic–aqueous media (DMSO–HEPES). The chemodosimeters coordinate with the Zn2+ ions in a two-to-one ratio (molecular probe : Zn2+) with a log β of 10.0 M−2. Upon the addition of the closed-shell metal ions studied, a fluorescence turn-on via an excimer formation is seen at 542 nm due to the quinaldine moiety adopting a syn arrangement when coordinated to the metal Zn2+ ions. Confocal microscopy monitored free Zn2+ ions in the Human Embryonic …

High School Course-Completion Trajectories And College Pathways For All: A Transcript Analysis Study On Elective Computer Science Courses, Hsun-Yu Chan, Ting-Lan Ma, Guan K. Saw, Yen-Ming Huang

Faculty Publications

Abstract: Whereas researchers regard high school math and science coursework as the best indicator of college readiness for students in the United States, computer science coursework and its relationship to college attendance, particularly for minoritized students, have not received due attention despite its root in the mathematical and scientific reasoning ability. We examined students’ high school course completion patterns across subjects and grade levels with a special focus on elective computer science courses and whether the coursework pattern transitions worked differently for minoritized students in Texas, USA. Latent profile analysis and latent transition analysis revealed multiple patterns of coursework, including …

Machine Learning With Gradient-Based Optimization Of Nuclear Waste Vitrification With Uncertainties And Constraints, Lagrande Gunnell, Kyle Manwaring, Xiaonan Lu, Jacob Reynolds, John Vienna, John Hedengren

Faculty Publications

Gekko is an optimization suite in Python that solves optimization problems involving mixed-integer, nonlinear, and differential equations. The purpose of this study is to integrate common Machine Learning (ML) algorithms such as Gaussian Process Regression (GPR), support vector regression (SVR), and artificial neural network (ANN) models into Gekko to solve data based optimization problems. Uncertainty quantification (UQ) is used alongside ML for better decision making. These methods include ensemble methods, model-specific methods, conformal predictions, and the delta method. An optimization problem involving nuclear waste vitrification is presented to demonstrate the benefit of ML in this field. ML models are compared …

Salinity And Hydraulic Retention Time Induce Membrane Phospholipid Acyl Chain Remodeling In Halanaerobium Congolense Wg10 And Mixed Cultures From Hydraulically Fractured Shale Wells, Chika Jude Ugwuodo, Fabrizio Colosimo, Jishnu Adhikari, Yuxiang Shen, Appala Raju Badireddy, Paula J. Mouser

Faculty Publications

Bacteria remodel their plasma membrane lipidome to maintain key biophysical attributes in response to ecological disturbances. ForHalanaerobiumand other anaerobic halotolerant taxa that persist in hydraulically fractured deep subsurface shale reservoirs, salinity, and hydraulic retention time (HRT) are important perturbants of cell membrane structure, yet their effects remain poorly understood. Membrane-linked activities underliein situmicrobial growth kinetics and physiologies which drive biogeochemical reactions in engineered subsurface systems. Hence, we used gas chromatography–mass spectrometry (GC–MS) to investigate the effects of salinity and HRT on the phospholipid fatty acid composition ofH. congolenseWG10 and mixed enrichment cultures from hydraulically fractured shale wells. We also coupled …

Rickettsia Parkeri Infection Modulates The Sialome And Ovariome Of The Gulf Coast Tick, Amblyomma Maculatum, Melina Garcia Guizzo, Khemraj Budachetri, Abdulsalam Adegoke, Jose M.C. Ribeiro, Shahid Karim

Faculty Publications

The Gulf Coast tick, Amblyomma maculatum, is a vector of several tick-borne pathogens, including Rickettsia parkeri. The ability of R. parkeri to persist within the tick population through transovarial and transstadial transmission, without apparently harming the ticks, contributes to the pathogen’s perpetuation in the tick population. Previous studies have shown that the R. parkeri load in A. maculatum is regulated by the tick tissues’ oxidant/antioxidant balance and the non-pathogenic tick microbiome. To obtain further insights into the interaction between tick and pathogen, we performed a bulk RNA-Seq for differential transcriptomic analysis of ovaries and salivary …

Dynamics Of Bottlebrush Polymers In Solution By Neutron Spin Echo Spectroscopy, Karin J. Bichler, Bruno Jakobi, Dirk Honecker, Laura R. Stingaciu, Thomas K. Weldeghiorghis, James H.P. Collins, Gerald J. Schneider

Faculty Publications

We present dynamical and morphological studies on poly(dimethylsiloxane) (PDMS)-based bottlebrush polymers in solution. A combination of small-angle neutron scattering (SANS), pulsed field gradient nuclear magnetic resonance (PFG NMR), and neutron spin echo (NSE) spectroscopy was used to identify structural changes inherent in changing the side-chain length while keeping the backbone constant. These morphological changes are mirrored in the diffusion coefficient determined by PFG NMR, resulting in two coefficients for the elongated and one for the more spherical sample. Faster motions are tracked by NSE using the advantage of time- and length-scale resolutions with the diffusion coefficient predetermined by PFG NMR. …

Resilience Resources And Coping Strategies Of Covid-19 Female Long Haulers: A Qualitative Study, Atefeh Aghaei, Abhishek Aggarwal, Ran Zhang, Xiaoming Li Ph.D., Shan Qiao Ph.D.

Faculty Publications

Background: Female long haulers deal with persistent post-acute COVID-19 symptoms that have serious health implications. This study aimed to identify resilience resources at multiple socio-ecological levels for female long haulers and describe how resilience resources affect their responses to long COVID. Methods: Purposive sampling was adopted to recruit participants through social media from April to June 2021 followed by 15 semi-structured interviews. An inductive analytical approach was adopted to categorize themes by open and axial coding that were verified by peer review. Results: Female long haulers relied on resources at various socio-ecological levels to foster their resilience in response to …

An Autoencoder-Based Deep Learning Method For Genotype Imputation, Meng Song, Jonathan Greenbaum, Joseph Luttrell Iv, Weihua Zhou, Chong Wu, Zhe Luo, Chuan Qiu, Lan Juan Zhao, Kuan-Jui Su, Qing Tian, Hui Shen, Huixiao Hong, Ping Gong, Xinghua Shi, Hong-Wen Deng, Chaoyang Zhang

Faculty Publications

Genotype imputation has a wide range of applications in genome-wide association study (GWAS), including increasing the statistical power of association tests, discovering trait-associated loci in meta-analyses, and prioritizing causal variants with fine-mapping. In recent years, deep learning (DL) based methods, such as sparse convolutional denoising autoencoder (SCDA), have been developed for genotype imputation. However, it remains a challenging task to optimize the learning process in DL-based methods to achieve high imputation accuracy. To address this challenge, we have developed a convolutional autoencoder (AE) model for genotype imputation and implemented a customized training loop by modifying the training process with a …

Assessment And Constraint Of Mesozooplankton In Cmip6 Earth System Models, C. M. Petrik, J. Y. Luo, R. F. Heneghan, J. D. Everett, C. S. Harrison, A. J. Richardson

Faculty Publications

Although zooplankton play a substantial role in the biological carbon pump and serve as a crucial link between primary producers and higher trophic level consumers, the skillful representation of zooplankton is not often a focus of ocean biogeochemical models. Systematic evaluations of zooplankton in models could improve their representation, but so far, ocean biogeochemical skill assessment of Earth system model (ESM) ensembles have not included zooplankton. Here we use a recently developed global, observationally based map of mesozooplankton biomass to assess the skill of mesozooplankton in six CMIP6 ESMs. We also employ a biome-based assessment of the ability of these …

Divergent Effects Of Biological And Physical Processes On Dissolved Oxygen And Dissolved Inorganic Carbon Dynamics On A Eutrophied And Hypoxic Continental Shelf, Zoraida J. Quiñones-Rivera, Björn Wissel, R. Eugene Turner, Nancy N. Rabalais, Dubravko Justić, Kerri P. Finlay, Charles S. Milan

Faculty Publications

Dissolved oxygen (DO) and dissolved inorganic carbon (DIC) represent reciprocal sides of aquatic metabolism. In closed systems, absolute DO and DIC changes follow a ~ 1 : 1 ratio, but in open systems coupling depends on mixing, air–sea gas exchange, and anaerobic respiration. To quantify DO–DIC controls in coastal waters, we evaluated their concentrations and stable isotopes together with water quality and physical conditions across the hypoxic zone off the Louisiana continental shelf in July 2002 and July 2003. This area is characterized by high yet variable productivity and strong seasonal changes in vertical stratification and river discharge. Prior to …

Development Of The Mentalizing Network Structures And Theory Of Mind In Extremely Preterm Youth, Xiaoxue Fu Ph.D., Andy Hung, Aryanne D. De Silva, Tyler Busch, Whitney I. Mattson, Kristen R. Hoskinson, Hudson Gerry, Eric E. Nelson

Faculty Publications

Adolescents born preterm (<37 weeks of gestation) are at elevated risk for deficits in social cognition and peer relationships. Theory of Mind (ToM) is a complex form of social cognition important for regulating social interactions. ToM and the underlying mentalizing network continue to develop across adolescence. The present study recruited 48 adolescents (12–17 years old) who were either born extremely preterm (EPT; <28 weeks of gestation) or full-term (FT) at birth. Cortical thickness, gray matter volume and surface area were measured in four regions of the mentalizing network: the temporoparietal junction, anterior temporal cortex, posterior superior temporal sulcus and frontal pole (mBA10). We also assessed the adolescents’ performance on a ToM task. Findings revealed both group differences and group-by-age interaction effects in the gray matter indices within the temporal lobe regions of the mentalizing network. The EPT group also performed significantly worse than the FT group on the ToM task. The cortical structural measures that discriminated the EPT and FT groups were not related to ToM performance. These results highlight altered developmental changes in brain regions underlying mentalizing functions in EPT adolescents relative to FT controls.