Now showing items 6029-6048 of 13757

    • Localization and Invigoration of Mei-yu Front Rainfall due to Aerosol-Cloud Interactions: A Preliminary Assessment Based on WRF Simulations and IMFRE 2018 Field Observations

      Liu, Lin; Cui, Chunguang; Deng, Yi; Zhou, Zhimin; Hu, Yang; Wang, Bin; Ren, Jing; Cai, Zhaoxin; Bai, Yongqing; Yang, Junmei; et al. (AMER GEOPHYSICAL UNION, 2020-07)
      Aerosol-cloud interactions remain a major source of uncertainty in our understanding and modeling of the Earth's hydrological cycle. Based upon a diagnostic and modeling analysis utilizing the latest field measurements from the Integrative Monsoon Frontal Rainfall Experiment (IMFRE) 2018, this paper reports the effects of aerosols on the cloud properties along the Mei-yu front over the Middle Reaches of Yangtze River in China. Numerical experiments with the Weather Research and Forecasting (WRF) model suggest that increasing aerosol number concentration reduces surface precipitation by similar to 8.8% and delays the onset of rainfall by similar to 30 min. Furthermore, warm clouds are suppressed but the convective cores are slightly intensified. This corresponds to an overall aerosol effect of "localization and invigoration" of the Mei-yu rainfall and thus an elevated probability of short-term heavy rainfall. The signals of "convective invigoration" with a bulk scheme in this study are relatively weak compared to those simulated by bin microphysics. The increased aerosol concentration strengthens Mei-yu front and changes local morphology of the front, consistent with earlier studies demonstrating positive effects of convective heating on the genesis and maintenance of Mei-yu front via conditional instability of the second kind (CISK) and diabatic generation of potential vorticity. Also discussed are the uncertainties of bulk microphysics in simulating aerosol-cloud interactions, which may shed light on the design of future field campaigns to further understand the impact of aerosol-cloud interactions on weather and climate over China in boreal summer.
    • Localization of ZIP14 and ZIP8 in HIBCPP Cells

      Morgan, Shannon E.; Schroten, Horst; Ishikawa, Hiroshi; Zhao, Ningning; Univ Arizona, Dept Nutr Sci (MDPI, 2020-08)
      The blood-cerebrospinal fluid barrier (BCB) is important in maintaining brain manganese (Mn) homeostasis. This barrier consists of a single layer of epithelial cells, connected by tight junctions, that restrict the passage of nutrients to only allow molecules to be carried through the membrane by a transporter. These epithelial cells are polarized with asymmetrical blood-facing and cerebrospinal fluid-facing sides. Here, we have established a polarized model of a human choroid plexus papilloma cell line, HIBCPP. For the first time, Mn importers ZIP14 and ZIP8 were identified in HIBCPP cells and were found to be enriched at the basolateral and apical sides of the cell monolayer, respectively. The localization of each ZIP protein adds to the understanding of Mn transport across the HIBCPP BCB model to help understand the mechanism of Mn homeostasis within the brain.
    • Localized Radial Roll Patterns in Higher Space Dimensions

      Bramburger, Jason J.; Altschuler, Dylan; Avery, Chloe I.; Sangsawang, Tharathep; Beck, Margaret; Carter, Paul; Sandstede, Björn; Univ Arizona, Dept Math (SIAM PUBLICATIONS, 2019-08-01)
      Localized roll patterns are structures that exhibit a spatially periodic profile in their center. When following such patterns in a system parameter in one space dimension, the length of the spatial interval over which these patterns resemble a periodic profile stays either bounded, in which case branches form closed bounded curves ("isolas"), or the length increases to infinity so that branches are unbounded in function space ("snaking"). In two space dimensions, numerical computations show that branches of localized rolls exhibit a more complicated structure in which both isolas and snaking occur. In this paper, we analyze the structure of branches of localized radial roll solutions in dimension 1+epsilon, with 0 < epsilon << 1, through a perturbation analysis. Our analysis sheds light on some of the features visible in the planar case.
    • Localizing Transformations of the Galaxy-Galaxy Lensing Observable

      Park, Y.; Rozo, E.; Krause, E.; Department of Physics, University of Arizona; Department of Astronomy and Steward Observatory, University of Arizona (American Physical Society, 2021)
      Modern cosmological analyses of galaxy-galaxy lensing face a theoretical systematic effect arising from the nonlocality of the observed galaxy-galaxy lensing signal. Because the predicted tangential shear signal at a given separation depends on the physical modeling on all scales internal to that separation, systematic uncertainties in the modeling of nonlinear small scales are propagated outward to larger scales. Even in the absence of other limiting factors, this systematic effect alone can necessitate conservative small-scale cuts, resulting in significant losses of information in the tangential shear data vector. We construct a simple linear transformation of the standard galaxy-galaxy observable that removes this nonlocality, which ensures that the cosmological signal contained within the transformed observable is exclusively drawn from well-understood physical scales. This new observable, through its robustness against nonlocality, also enables a significant extension in the range of usable scales in galaxy-galaxy lensing compared to the standard approach in current cosmological analyses. © 2021 American Physical Society.
    • Locally defined quantum emission from epitaxial few-layer tungsten diselenide

      Wu, Wei; Dass, Chandriker K.; Hendrickson, Joshua R.; Montaño, Raul D.; Fischer, Robert E.; Zhang, Xiaotian; Choudhury, Tanushree H.; Redwing, Joan M.; Wang, Yongqiang; Pettes, Michael T.; et al. (AMER INST PHYSICS, 2019-05-29)
      Recently, single photons have been observed emanating from point defects in two-dimensional (2D) materials including WSe2, WS2, hexagonal-BN, and GaSe, with their energy residing in the direct electronic bandgap. Here, we report single photon emission from a nominal weakly emitting indirect bandgap 2D material through deterministic strain induced localization. A method is demonstrated to create highly spatially localized and spectrally well-separated defect emission sites in the 750-800nm regime in a continuous epitaxial film of few-layer WSe2 synthesized by a multistep diffusion-mediated gas source chemical vapor deposition technique. To separate the effects of mechanical strain from the substrate or dielectric-environment induced changes in the electronic structure, we created arrays of large isotropically etched ultrasharp silicon dioxide tips with spatial dimensions on the order of 10 mu m. We use bending based on the small radius of these tips-on the order of 4nm-to impart electronic localization effects through morphology alone, as the WSe2 film experiences a uniform SiO2 dielectric environment in the device geometry chosen for this investigation. When the continuous WSe2 film was transferred onto an array of SiO2 tips, an similar to 87% yield of localized emission sites on the tips was observed. The outcomes of this report provide fundamental guidelines for the integration of beyond-lab-scale quantum materials into photonic device architectures for all-optical quantum information applications.
    • Locating line and node disturbances in networks of diffusively coupled dynamical agents

      Delabays, R.; Pagnier, L.; Tyloo, M.; Department of Mathematics, University of Arizona (IOP Publishing Ltd, 2021)
      A wide variety of natural and human-made systems consist of a large set of dynamical units coupled into a complex structure. Breakdown of such systems can have a dramatic impact, as in the case of neurons in the brain or lines in an electric grid, to name but a few. Preventing such catastrophic events requires in particular to be able to detect and locate the source of disturbances as fast as possible. We propose a simple method to identify and locate disturbances in networks of coupled dynamical agents, relying only on time series measurements and on the knowledge of the (possibly Kron-reduced) network structure. The strength and the appeal of the present approach lies in its simplicity paired with the ability to precisely locate disturbances and even to differentiate between line and node disturbances. If we have access to measurement at only a subset of nodes, our method is still able to identify the location of the disturbance if the disturbed nodes are measured. If not, we manage to identify the region of the network where the disturbance occurs. © 2021 The Author(s).
    • Locating the intense interstellar scattering towards the inner Galaxy

      Dexter, J.; Deller, A.; Bower, G. C.; Demorest, P.; Kramer, M.; Stappers, B.W.; Lyne, A. G.; Kerr, M.; Spitler, L. G.; Psaltis, D.; et al. (OXFORD UNIV PRESS, 2017-11)
      We use VLBA+VLA observations to measure the sizes of the scatter-broadened images of six of the most heavily scattered known pulsars: three within the Galactic Centre (GC) and three elsewhere in the inner Galactic plane (Delta l < 20 degrees). By combining the measured sizes with temporal pulse broadening data from the literature and using the thin-screen approximation, we locate the scattering medium along the line of sight to these six pulsars. At least two scattering screens are needed to explain the observations of the GC sample. We show that the screen inferred by previous observations of SGR J1745-2900 and Sgr A*, which must be located far from the GC, falls off in strength on scales less than or similar to 0 degrees.2. A second scattering component closer to (Delta < 2 kpc) or even (tentatively) within (Delta < 700 pc) the GC produces most or all of the temporal broadening observed in the other GC pulsars. Outside the GC, the scattering locations for all three pulsars are similar or equal to 2 kpc from Earth, consistent with the distance of the Carina-Sagittarius or Scutum spiral arm. For each object the 3D scattering origin coincides with a known H II region (and in one case also a supernova remnant), suggesting that such objects preferentially cause the intense interstellar scattering seen towards the Galactic plane. We show that the H II regions should contribute greater than or similar to 25 per cent of the total dispersion measure (DM) towards these pulsars, and calculate reduced DM distances. Those distances for other pulsars lying behind H II regions may be similarly overestimated.
    • Location and Setting of the Mars InSight Lander, Instruments, and Landing Site

      Golombek, M; Williams, N; Warner, N H; Parker, T; Williams, M G; Daubar, I; Calef, F; Grant, J; Bailey, P; Abarca, H; et al. (AMER GEOPHYSICAL UNION, 2020-09-21)
      Knowing precisely where a spacecraft lands on Mars is important for understanding the regional and local context, setting, and the offset between the inertial and cartographic frames. For the InSight spacecraft, the payload of geophysical and environmental sensors also particularly benefits from knowing exactly where the instruments are located. A similar to 30 cm/pixel image acquired from orbit after landing clearly resolves the lander and the large circular solar panels. This image was carefully georeferenced to a hierarchically generated and coregistered set of decreasing resolution orthoimages and digital elevation models to the established positive east, planetocentric coordinate system. The lander is located at 4.502384 degrees N, 135.623447 degrees E at an elevation of -2,613.426 m with respect to the geoid in Elysium Planitia. Instrument locations (and the magnetometer orientation) are derived by transforming from Instrument Deployment Arm, spacecraft mechanical, and site frames into the cartographic frame. A viewshed created from 1.5 m above the lander and the high-resolution orbital digital elevation model shows the lander is on a shallow regional slope down to the east that reveals crater rims on the east horizon similar to 400 m and 2.4 km away. A slope up to the north limits the horizon to about 50 m away where three rocks and an eolian bedform are visible on the rim of a degraded crater rim. Azimuths to rocks and craters identified in both surface panoramas and high-resolution orbital images reveal that north in the site frame and the cartographic frame are the same (within 1 degrees).
    • Location-grouping algorithm based on limited actuators deformable mirror for high precision wavefront aberration correction in adaptive optics system

      Yan, Meng; Huang, Lei; Bian, Qi; Zhou, Chenlu; Ma, Xingkun; Gong, Mali; Univ Arizona, Coll Opt Sci; Tsinghua Univ. (China); Tsinghua Univ. (China); Tsinghua Univ. (China); et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2016-07-27)
      The aberration in the center position of wavefront can be corrected well when the deformable mirrors (DM) used in high-resolution adaptive optics system of telescope. However, for the defocus and spherical aberration of telescope, the four corners of the wavefront cannot be corrected well. A novel correction method with different levels and regions of deformable mirror is proposed to solve this problem. The control elements of wavefront in four corners are divided. And every four or five DM units in one corner is in a group. Compared with conventional correction method, the location-grouping method showed significant advantages in correction of different order aberrations.
    • Location‐Routing with Conflicting Objectives: Coordinating eBeam Phytosanitary Treatment and Distribution of Mexican Import Commodities

      Geismar, H. Neil; Huang, Yiwei; Pillai, Suresh D.; Sriskandarajah, Chelliah; Youn, Seokjun; Univ Arizona, Eller Coll Management, Dept Management Informat Syst (WILEY, 2020-02-10)
      We study a generalized location-routing problem in which the key decisions are made by supply chain partners with conflicting objectives. The context of our problem is the irradiation by electron beam (eBeam) of fresh produce imported from Mexico to reduce the threat of insects and pests to the U.S. agriculture. Because too few irradiation facilities exist to serve the current demand, we focus on two parties to be coordinated: the eBeam Services Provider, who will choose the facilities' locations and capacities, and the Distributor, who will determine routes for transporting fruits from Mexico to commercial hubs in the United States via these facilities. We demonstrate the value of cooperation and how that cooperation can be achieved and enforced for a supply chain that must coordinate the independent companies by the strategic decisions of facility location and capacity construction, as opposed to the more common coordination by capacity allocation or pricing. The parties' interactions are modeled as a sequential game with perfect information. Specifically, we formulate the sequential and cooperative decision-making problems as mixed-integer programs, analyze the computational complexity of the problems, and conduct extensive computational experiments. Additionally, we detail three schemes by which the parties can engage in profitable and enforceable cooperation. These methods progressively increase each party's commitment as trust is built and profits rise. Total cooperation increases overall profit by an average of 8.6%. Further, a stochastic program that uses sample average approximation is applied to demonstrate the results' robustness to nature's supply variations while maximizing the supply chain's overall profit.
    • Lochos and Ariston

      Bauschatz, John; Univ Arizona, Dept Hist (HOLZHAUSEN VERLAG GMBH, 2017-03)
      Nine documents from the Duke Papyrus Archive reveal much about the careers of two high-ranking officials and their activities in the Herakleopolite nome during the late second century B.C.: Ariston, ton proton philon, strategos, nomarches and epi ton prosodon, and Lochos, ton proton philon and possibly the well-known strategos of the Thebaid.
    • LoCuSS: exploring the connection between local environment, star formation, and dust mass in Abell 1758

      Bianconi, M; Smith, G P; Haines, C P; McGee, S L; Finoguenov, A; Egami, E; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2020-01-14)
      We explore the connection between dust and star formation, in the context of environmental effects on galaxy evolution. In particular, we exploit the susceptibility of dust to external processes to assess the influence of dense environment on star-forming galaxies. We have selected cluster Abell 1758 from the Local Cluster Substructure Survey (LoCuSS). Its complex dynamical state is an ideal test-bench to track dust removal and destruction in galaxies due to merger and accretion shocks. We present a systematic panchromatic study (from 0.15 mu m with GALEX to 500 mu m with Herschel) of spectroscopically confirmed star-forming cluster galaxies at intermediate redshift. We observe that the main subclusters (A1758N and A1758S) belong to two separate large-scale structures, with no overlapping galaxy members. Star forming cluster members are found preferentially outside cluster central regions, and are not isotropically distributed. Rather, these galaxies appear being funneled towards the main subclusters along separate accretion paths. Additionally, we present the first study of dust-to-stellar (DTS) mass ratio used as an indicator for local environmental influence on galaxy evolution. Star-forming cluster members show lower mean values (32 per cent at 2.4 sigma) of DTS mass ratio and lower levels of infrared emission from birth clouds with respect to coeval star-forming field galaxies. This picture is consistent with the majority of star-forming cluster members infalling in isolation. Upon accretion, star formation is observed to decrease and warm dust is destroyed due to heating from the intracluster medium radiation, ram-pressure stripping, and merger shocks.
    • LoCuSS: exploring the selection of faint blue background galaxies for cluster weak-lensing

      Ziparo, Felicia; Smith, Graham P.; Okabe, Nobuhiro; Haines, Chris P.; Pereira, Maria J.; Egami, Eiichi; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2016-12-21)
      Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogues derived from the Cosmological Evolution Survey (COSMOS) and our own observations of massive galaxy clusters at z similar or equal to 0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to identify safely faint blue background galaxies with the same 1 per cent contamination level that we have achieved with red galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. Nevertheless, our least contaminated blue galaxy sample yields stacked weak-lensing results consistent with our previously published results based on red galaxies, and we show that the stacked clustercentric number density profile of these faint blue galaxies is consistent with expectations from consideration of the lens magnification signal of the clusters. Indeed, the observed number density of blue background galaxies changes by similar to 10-30 per cent across the radial range over which other surveys assume it to be flat.
    • LoCuSS: pre-processing in galaxy groups falling into massive galaxy clusters at z = 0.2

      Bianconi, M; Smith, G P; Haines, C P; McGee, S L; Finoguenov, A; Egami, E; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2018-01)
      We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via theirX-ray emission in the infall regions of 23 massive (< M-200 > = 10(15) M-circle dot) clusters at 0.15 < z < 0.3. Highly complete spectroscopic coverage combined with 24 mu m imaging from Spitzer allows us to make a consistent and robust selection of cluster and group members including star-forming galaxies down to a stellar mass limit of M* = 2 x 10(10) M-circle dot. The fraction f(SF) of star-forming galaxies in infalling groups is lower and with a flatter trend with respect to clustercentric radius when compared to the rest of the cluster galaxy population. At R approximate to 1.3 r(200), the fraction of star-forming galaxies in infalling groups is half that in the cluster galaxy population. This is direct evidence that star-formation quenching is effective in galaxies already prior to them settling in the cluster potential, and that groups are favourable locations for this process.
    • LoCuSS: scaling relations between galaxy cluster mass, gas, and stellar content

      Mulroy, Sarah L; Farahi, Arya; Evrard, August E; Smith, Graham P; Finoguenov, Alexis; O’Donnell, Christine; Marrone, Daniel P; Abdulla, Zubair; Bourdin, Hervé; Carlstrom, John E; et al. (OXFORD UNIV PRESS, 2019-03)
      We present a simultaneous analysis of galaxy cluster scaling relations between weak-lensing mass and multiple cluster observables, across a wide range of wavelengths, that probe both gas and stellar content. Our new hierarchical Bayesian model simultaneously considers the selection variable alongside all other observables in order to explicitly model intrinsic property covariance and account for selection effects. We apply this method to a sample of 41 clusters at 0.15 < z < 0.30, with a well-defined selection criteria based on RASS X-ray luminosity, and observations from Chandra/XMM, SZA, Planck, UKIRT, SUSS, and Subaru. These clusters have well-constrained weak-lensing mass measurements based on Subaru/SuprimeCam observations, which serve as the reference masses in our model. We present 30 scaling relation parameters for 10 properties. All relations probing the intracluster gas are slightly shallower than self-similar predictions, in moderate tension with prior measurements, and the stellar fraction decreases with mass. K-band luminosity has the lowest intrinsic scatter with a 95th percentile of 0.16, while the lowest scatter gas probe is gas mass with a fractional intrinsic scatter of 0.16 +/- 0.03. We find no distinction between the core-excised X-ray or high-resolution Sunyaev-Zel'dovich relations of clusters of different central entropy, but find with modest significance that higher entropy clusters have higher stellar fractions than their lower entropy counterparts. We also report posterior mass estimates from our likelihood model.
    • LoCuSS: The infall of X-ray groups on to massive clusters

      Haines, C P; Finoguenov, A; Smith, G P; Babul, A; Egami, E; Mazzotta, P; Okabe, N; Pereira, M J; Bianconi, M; McGee, S L; et al. (OXFORD UNIV PRESS, 2018-07)
      Galaxy clusters are expected to form hierarchically in a Lambda cold dark matter (Lambda CDM) universe, growing primarily through mergers with lower mass clusters and the continual accretion of group-mass haloes. Galaxy clusters assemble late, doubling their masses since z similar to 0.5, and so the outer regions of clusters should be replete with accreting group-mass systems. We present an XMM-Newton survey to search for X-ray groups in the infall regions of 23 massive galaxy clusters (< M-200 > similar to 10(15)M(circle dot)) at z similar to 0.2, identifying 39 X-ray groups that have been spectroscopically confirmed to lie at the cluster redshift. These groups have mass estimates in the range 2 x 10(13)-7 x 10(14)M(circle dot), and group-to-cluster mass ratios as low as 0.02. The comoving number density of X-ray groups in the infall regions is similar to 25x higher than that seen for isolated X-ray groups from the XXL survey. The average mass per cluster contained within these X-ray groups is 2.2 x 10(14)M(circle dot), or 19 +/- 5 per cent of the mass within the primary cluster itself. We estimate that similar to 10(15)M(circle dot) clusters increase their masses by 16 +/- 4 per cent between z = 0.223 and the present day due to the accretion of groups with M-200 >= 10(13.2)M(circle dot). This represents about half of the expected mass growth rate of clusters at these late epochs. The other half is likely to come from smooth accretion of matter not bound within haloes. The mass function of the infalling X-ray groups appears significantly top heavy with respect to that of 'field' X-ray systems, consistent with expectations from numerical simulations, and the basic consequences of collapsed massive dark matter haloes being biased tracers of the underlying large-scale density distribution.
    • The LOFT mission concept: a status update

      Feroci, M.; Bozzo, E.; Brandt, S.; Hernanz, M.; van der Klis, M.; Liu, L.-P.; Orleanski, P.; Pohl, M.; Santangelo, A.; Schanne, S.; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2016-07-25)
      The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, > 8m(2) effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e. g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
    • A Log-Likelihood Ratio based Generalized Belief Propagation

      Amaricai, Alexandru; Bahrami, Mohsem; Vasic, Bane; Univ Arizona (IEEE, 2019-07)
      In this paper, we propose a reduced complexity Generalized Belief Propagation (GBP) that propagates messages in Log-Likelihood Ratio (LLR) domain. The key novelties of the proposed LLR-GBP are: (i) reduced fixed point precision for messages instead of computational complex floating point format, (ii) operations performed in logarithm domain, thus eliminating the need for multiplications and divisions, (iii) usage of message ratios that leads to simple hard decision mechanisms. We demonstrated the validity of LLR-GBP on reconstruction of images passed through binary-input two-dimensional Gaussian channels with memory and affected by additive white Gaussian noise.
    • Loneliness and social monitoring: A conceptual replication of Knowles et al.

      Floyd, Kory; Woo, Nathan T.; Univ Arizona, Dept Commun (WILEY, 2020-02-12)
      Contrary to the claim that loneliness routinely impairs the decoding of social cues such as emotion displays, Knowles, Lucas, Baumeister, and Gardner (2015) proposed that lonely adults "choke under pressure," experiencing impairments only when social monitoring is framed as diagnostic of general social skill. In four experiments, Knowles et al. showed that lonely individuals performed worse than nonlonely individuals at decoding social cues when the decoding task was framed as a test of social aptitude, but not when it was framed as a test of academic aptitude. The studies were small (N's ranging from 78 to 203), and all employed a convenience sample of mostly female undergraduate students, impairing both statistical power and external validity. In addition, the lack of a true control group precluded the studies from establishing whether loneliness inhibits social monitoring ability if no frame is offered. This study conceptually replicates the central hypothesis of Knowles et al. using a sample of adults that is substantially larger and more diverse demographically and geographically, and using a true control group in addition to the comparison group. Results revealed a significant main effect of loneliness on social monitoring ability but did not replicate the choking under pressure phenomenon.
    • A lonely dot on the map: Exploring the climate signal in tree-ring density and stable isotopes of clanwilliam cedar, South Africa

      De Mil, Tom; Meko, Matthew; Belmecheri, Soumaya; February, Edmund; Therrell, Matthew; Van den Bulcke, Jan; Trouet, Valerie; Laboratory of Tree-Ring Research, University of Arizona (Elsevier BV, 2021-10)
      Clanwilliam cedar (Widdringtonia cedarbergensis; WICE), a long-lived conifer with distinct tree rings in Cape Province, South Africa, has potential to provide a unique high-resolution climate proxy for southern Africa. However, the climate signal in WICE tree-ring width (TRW) is weak and the dendroclimatic potential of other WICE tree-ring parameters therefore needs to be explored. Here, we investigate the climatic signal in various tree-ring parameters, including TRW, Minimum Density (MND), Maximum Latewood Density (MXD), Maximum Latewood Blue Intensity (MXBI), and stable carbon and oxygen isotopes (δ18O and δ13C) measured in WICE samples collected in 1978. MND was negatively influenced by early spring (October-November) precipitation whereas TRW was positively influenced by spring November-December precipitation. MXD was negatively influenced by autumn (April-May) temperature whereas MXBI was not influenced by temperature. Both MXD and MXBI were negatively influenced by January-March and January-May precipitation respectively. We did not find a significant climate signal in either of the stable isotope time series, which were measured on a limited number of samples. WICE can live to be at least 356 years old and the current TRW chronology extends back to 1564 CE. The development of full-length chronologies of alternative tree-ring parameters, particularly MND, would allow for an annually resolved, multi-century spring precipitation reconstruction for this region in southern Africa, where vulnerability to future climate change is high.