Parks & Trails Partnership

UNLV is committed to demonstrating how the traditional values of higher education can be adapted to the conditions and needs of individuals and communities in the 21st century. Key macrothemes of the university’s strategic plan include Economic Development, Preservation of History & Culture, and Community Outreach & Collaboration. In keeping with these macrothemes, UNLV is embarking on several partnerships with the BLM and related agencies to provide a wide array of research, technical assistance, education, and service support on projects funded through the SNPLMA. UNLV is a research extensive university with academic departments and research centers and institutes that embrace a broad scope of interests and expertise

A time-varying subsidence parameterization for the atmospheric boundary layer

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005.Includes bibliographical references (p. 46-49).This study examines the effect of a time-varying parameterization for subsidence in the atmospheric boundary layer (ABL) on a one-dimensional coupled land-atmosphere model. Measurements of large-scale divergence in the ABL are scarce and often marred by error, providing the motivation to model this important physical process and estimate its values from indirect but related observations. Constant parameterizations of-large- scale divergence and/or subsidence velocity are adequate for periods within a characteristic synoptic time scale, but longer studies require a parameterization that yields to local atmospheric change. After confirming the potential significance of subsidence in the ABL, this experiment investigates two key areas: (1) the ability to model subsidence change as a response to estimated time-varying model error and (2) the net improvement and potential benefits of this enhancement. This study indicates a consistent reduction of root-mean-square error scores for the time-varying subsidence (divergence) parameter scheme versus a constant parameterization for the 2 m specific humidity measurement, with negligible change to the 2 m temperature measurement.(cont.) Model error does not improve explicitly, in spite of the presumed improvement to model physics. However, the unknown nature of the model error precludes an accurate diagnose of change, thus leaving the root-mean-square-error scores as the principal tool of evaluation and hence the justifying the potential usefulness of the time-varying parameterization.by David D. Flagg.S.M

AXIS—an Autonomous Expendable Instrument System

Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 34 (2017): 2673-2682, doi:10.1175/JTECH-D-17-0054.1.Expendable bathythermographs (XBT) to profile upper-ocean temperatures from vessels in motion have been in use for some 50 years now. Developed originally for navy use, they were soon adapted by oceanographers to map out upper-ocean thermal structure and its space–-time variability from both research vessels and merchant marine vessels in regular traffic. These activities continue today. This paper describes a new technology—the Autonomous Expendable Instrument System (AXIS)—that has been developed to provide the capability to deploy XBT probes on a predefined schedule, or adaptively in response to specific events without the presence of an observer on board. AXIS is a completely self-contained system that can hold up to 12 expendable probes [XBTs, XCTDs, expendable sound velocimeter (XSV)] in any combination. A single-board Linux computer keeps track of what probes are available, takes commands from ashore via Iridium satellite on what deployment schedule to follow, and records and forwards the probe data immediately with a time stamp and the GPS position. This paper provides a brief overview of its operation, capabilities, and some examples of how it is improving coverage along two lines in the Atlantic.Initial development of AXIS mechanical design elements wasmade possible by awards from the Cecil H. and Ida M. Green Technology Innovation Fund and the Sealark Foundation to the team of Dave Fratantoni, Keith von der Heydt (WHOI), and Terry Hammar (WHOI). Construction of the first full AXIS prototype was supported by a technology grant from the National Science Foundation (OCE-0926853) and the second one through an NSF-funded (OCE-1061185) subcontract from the University of Rhode Island.2018-06-2

Hydration of a side-chain-free n-type semiconducting ladder polymer driven by electrochemical doping

We study the organic electrochemical transistors (OECTs) performance of the ladder polymer, poly(benzimidazobenzophenanthroline) (BBL) in an attempt to better understand how an apparently hydrophobic side-chain-free polymer is able to operate as an OECT with favorable redox kinetics in an aqueous environment. We examine two BBLs of different molecular masses from different sources. Both BBLs show significant film swelling during the initial reduction step. By combining electrochemical quartz crystal microbalance (eQCM) gravimetry, in-operando atomic force microscopy (AFM), and both ex-situ and in-operando grazing incidence wide-angle x-ray scattering (GIWAXS), we provide a detailed structural picture of the electrochemical charge injection process in BBL in the absence of any hydrophilic side-chains. Compared with ex-situ measurements, in-operando GIWAXS shows both more swelling upon electrochemical doping than has previously been recognized, and less contraction upon dedoping. The data show that BBL films undergo an irreversible hydration driven by the initial electrochemical doping cycle with significant water retention and lamellar expansion that persists across subsequent oxidation/reduction cycles. This swelling creates a hydrophilic environment that facilitates the subsequent fast hydrated ion transport in the absence of the hydrophilic side-chains used in many other polymer systems. Due to its rigid ladder backbone and absence of hydrophilic side-chains, the primary BBL water uptake does not significantly degrade the crystalline order, and the original dehydrated, unswelled state can be recovered after drying. The combination of doping induced hydrophilicity and robust crystalline order leads to efficient ionic transport and good stability.Comment: 24 pages, 5 figure

Tunable Indistinguishable Photons From Remote Quantum Dots

Single semiconductor quantum dots have been widely studied within devices that can apply an electric field. In the most common system, the low energy offset between the InGaAs quantum dot and the surrounding GaAs material limits the magnitude of field that can be applied to tens of kVcm^-1, before carriers tunnel out of the dot. The Stark shift experienced by the emission line is typically 1 meV. We report that by embedding the quantum dots in a quantum well heterostructure the vertical field that can be applied is increased by over an order of magnitude whilst preserving the narrow linewidths, high internal quantum efficiencies and familiar emission spectra. Individual dots can then be continuously tuned to the same energy allowing for two-photon interference between remote, independent, quantum dots

The Role of Side Chains and Hydration on Mixed Charge Transport in <i>n</i> ‐Type Polymer Films

Introducing ethylene glycol (EG) side chains to a conjugated polymer backbone is a well‐established synthetic strategy for designing organic mixed ion‐electron conductors (OMIECs). However, the impact that film swelling has on mixed conduction properties has yet to be scoped, particularly for electron‐transporting (n‐type) OMIECs. Here, the authors investigate the effect of the length of branched EG chains on mixed charge transport of n‐type OMIECs based on a naphthalene‐1,4,5,8‐tetracarboxylic‐diimide‐bithiophene backbone. Atomic force microscopy (AFM), grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), and scanning tunneling microscopy (STM) are used to establish the similarities between the common‐backbone films in dry conditions. Electrochemical quartz crystal microbalance with dissipation monitoring (EQCM‐D) and in situ GIWAXS measurements reveal stark changes in film swelling properties and microstructure during electrochemical doping, depending on the side chain length. It is found that even in the loss of the crystallite content upon contact with the aqueous electrolyte, the films can effectively transport charges and that it is rather the high water content that harms the electronic interconnectivity within the OMIEC films. These results highlight the importance of controlling water uptake in the films to impede charge transport in n‐type electrochemical devices

Characterizing the Near-infrared Spectra of Flares from TRAPPIST-1 During JWST Transit Spectroscopy Observations

We present the first analysis of JWST near-infrared spectroscopy of stellar flares from TRAPPIST-1 during transits of rocky exoplanets. Four flares were observed from 0.6--2.8 $\mu$m with NIRISS and 0.6--3.5 $\mu$m with NIRSpec during transits of TRAPPIST-1b, f, and g. We discover P$\alpha$ and Br$\beta$ line emission and characterize flare continuum at wavelengths from 1--3.5 $\mu$m for the first time. Observed lines include H$\alpha$, P$\alpha$-P$\epsilon$, Br$\beta$, He I $\lambda$0.7062$\mu$m, two Ca II infrared triplet (IRT) lines, and the He I IRT. We observe a reversed Paschen decrement from P$\alpha$-P$\gamma$ alongside changes in the light curve shapes of these lines. The continuum of all four flares is well-described by blackbody emission with an effective temperature below 5300 K, lower than temperatures typically observed at optical wavelengths. The 0.6--1 $\mu$m spectra were convolved with the TESS response, enabling us to measure the flare rate of TRAPPIST-1 in the TESS bandpass. We find flares of 10$^{30}$ erg large enough to impact transit spectra occur at a rate of 3.6$\substack{+2.1 \\ -1.3}$ flare d$^{-1}$, $\sim$10$\times$ higher than previous predictions from K2. We measure the amount of flare contamination at 2 $\mu$m for the TRAPPIST-1b and f transits to be 500$\pm$450 and 2100$\pm$400 ppm, respectively. We find up to 80% of flare contamination can be removed, with mitigation most effective from 1.0--2.4 $\mu$m. These results suggest transits affected by flares may still be useful for atmospheric characterization efforts.Comment: 29 pages, 17 figures, 3 tables, accepted to The Astrophysical Journa

Population-level impact and herd effects following the introduction of human papillomavirus vaccination programmes: updated systematic review and meta-analysis

Background More than 10 years have elapsed since human papillomavirus (HPV) vaccination was implemented. We did a systematic review and meta-analysis of the population-level impact of vaccinating girls and women against human papillomavirus on HPV infections, anogenital wart diagnoses, and cervical intraepithelial neoplasia grade 2+ (CIN2+)to summarise the most recent evidence about the effectiveness of HPV vaccines in real-world settings and to quantify the impact of multiple age-cohort vaccination.Methods In this updated systematic review and meta-analysis, we used the same search strategy as in our previous paper. We searched MEDLINE and Embase for studies published between Feb 1, 2014, and Oct 11, 2018. Studies were eligible if they compared the frequency (prevalence or incidence) of at least one HPV-related endpoint (genital HPV infections, anogenital wart diagnoses, or histologically confirmed CIN2+) between pre-vaccination and post-vaccination periods among the general population and if they used the same population sources and recruitment methods before and after vaccination. Our primary assessment was the relative risk (RR) comparing the frequency (prevalence or incidence) of HPV-related endpoints between the pre-vaccination and post-vaccination periods. We stratified all analyses by sex, age, and years since introduction of HPV vaccination. We used random-effects models to estimate pooled relative risks.Findings We identified 1702 potentially eligible articles for this systematic review and meta-analysis, and included 65 articles in 14 high-income countries: 23 for HPV infection, 29 for anogenital warts, and 13 for CIN2+.After 5\u20138 years of vaccination, the prevalence of HPV 16 and 18 decreased significantly by 83% (RR 0\ub717, 95% CI 0\ub711\u20130\ub725) among girls aged 13\u201319 years, and decreased significantly by 66% (RR 0\ub734, 95% CI 0\ub723\u20130\ub749) among women aged 20\u201324 years. The prevalence of HPV 31, 33, and 45 decreased significantly by 54% (RR 0\ub746, 95% CI 0\ub733\u20130\ub766) among girls aged 13\u201319 years. Anogenital wart diagnoses decreased significantly by 67% (RR 0\ub733, 95% CI 0\ub724\u20130\ub746) among girls aged 15\u201319 years, decreased significantly by 54% (RR 0\ub746, 95% CI 0.36\u20130.60) among women aged 20\u201324 years, and decreased significantly by 31% (RR 0\ub769, 95% CI 0\ub753\u20130\ub789) among women aged 25\u201329 years. Among boys aged 15\u201319 years anogenital wart diagnoses decreased significantly by 48% (RR 0\ub752, 95% CI 0\ub737\u20130\ub775) and among men aged 20\u201324 years they decreased significantly by 32% (RR 0\ub768, 95% CI 0\ub747\u20130\ub798). After 5\u20139 years of vaccination, CIN2+ decreased significantly by 51% (RR 0\ub749, 95% CI 0\ub742\u20130\ub758) among screened girls aged 15\u201319 years and decreased significantly by 31% (RR 0\ub769, 95% CI 0\ub757\u20130\ub784) among women aged 20\u201324 years.Interpretation This updated systematic review and meta-analysis includes data from 60 million individuals and up to 8 years of post-vaccination follow-up. Our results show compelling evidence of the substantial impact of HPV vaccination programmes on HPV infections and CIN2+ among girls and women, and on anogenital warts diagnoses among girls, women, boys, and men. Additionally, programmes with multi-cohort vaccination and high vaccination coverage had a greater direct impact and herd effects