8,517 research outputs found
Grass Control in Corn with Accent and Beacon
The traditional method for grass control in corn is based on using herbicides applied to soil and incorporated before planting or to the soil surface after planting. This approach has been successful in controlling crabgrass, fall panicum and foxtails, but johnsongrass and shattercane control was sometimes inadequate
Global marine bacterial diversity peaks at high latitudes in winter.
Genomic approaches to characterizing bacterial communities are revealing significant differences in diversity and composition between environments. But bacterial distributions have not been mapped at a global scale. Although current community surveys are way too sparse to map global diversity patterns directly, there is now sufficient data to fit accurate models of how bacterial distributions vary across different environments and to make global scale maps from these models. We apply this approach to map the global distributions of bacteria in marine surface waters. Our spatially and temporally explicit predictions suggest that bacterial diversity peaks in temperate latitudes across the world's oceans. These global peaks are seasonal, occurring 6 months apart in the two hemispheres, in the boreal and austral winters. This pattern is quite different from the tropical, seasonally consistent diversity patterns observed for most macroorganisms. However, like other marine organisms, surface water bacteria are particularly diverse in regions of high human environmental impacts on the oceans. Our maps provide the first picture of bacterial distributions at a global scale and suggest important differences between the diversity patterns of bacteria compared with other organisms
The magnetic field environment of active region 12673 that produced the energetic particle events of September 2017
Forecasting solar energetic particles (SEPs), and identifying flare/CMEs from
active regions (ARs) that will produce SEP events in advance is extremely
challenging. We investigate the magnetic field environment of AR 12673,
including the AR's magnetic configuration, the surrounding field configuration
in the vicinity of the AR, the decay index profile, and the footpoints of
Earth-connected magnetic field, around the time of four eruptive events. Two of
the eruptive events are SEP-productive (2017 September 4 at 20:00~UT and
September 6 at 11:56~UT), while two are not (September 4 at 18:05~UT and
September 7 at 14:33~UT). We analysed a range of EUV and white-light
coronagraph observations along with potential field extrapolations and find
that the CMEs associated with the SEP-productive events either trigger null
point reconnection that redirects flare-accelerated particles from the flare
site to the Earth-connected field and/or have a significant expansion (and
shock formation) into the open Earth-connected field. The rate of change of the
decay index with height indicates that the region could produce a fast CME ( 1500~km~s), which it did during events two and three. The AR's
magnetic field environment, including sites of open magnetic field and null
points along with the magnetic field connectivity and propagation direction of
the CMEs play an important role in the escape and arrival of SEPs at Earth.
Other SEP-productive ARs should be investigated to determine whether their
magnetic field environment and CME propagation direction are significant in the
escape and arrival of SEPs at Earth.Comment: Accepted in ApJ, 18 pages, 8 Figures, 2 Table
Transitional disks and their origins: an infrared spectroscopic survey of Orion A
Transitional disks are protoplanetary disks around young stars, with inner
holes or gaps which are surrounded by optically thick outer, and often inner,
disks. Here we present observations of 62 new transitional disks in the Orion A
star-forming region. These were identified using the \textit{Spitzer Space
Telescope}'s Infrared Spectrograph and followed up with determinations of
stellar and accretion parameters using the Infrared Telescope Facility's SpeX.
We combine these new observations with our previous results on transitional
disks in Taurus, Chamaeleon I, Ophiuchus and Perseus, and with archival X-ray
observations. This produces a sample of 105 transitional disks of "cluster" age
3 Myr or less, by far the largest hitherto assembled. We use this sample to
search for trends between the radial structure in the disks and many other
system properties, in order to place constraints on the possible origins of
transitional disks. We see a clear progression of host star accretion rate and
the different disk morphologies. We confirm that transitional disks with
complete central clearings have median accretion rates an order of magnitude
smaller than radially continuous disks of the same population. Pre-transitional
disks --- those objects with gaps that separate inner and outer disks --- have
median accretion rates intermediate between the two. Our results from the
search for statistically significant trends, especially related to ,
strongly support that in both cases the gaps are far more likely to be due to
the gravitational influence of Jovian planets or brown dwarfs orbiting within
the gaps, than to any of the photoevaporative, turbulent or grain-growth
processes that can lead to disk dissipation. We also find that the fraction of
Class II YSOs which are transitional disks is large, 0.1-0.2, especially in the
youngest associations.Comment: 96 pages, 25 figures, resubmitted to Ap
The Merging of a Coronal Dimming and the Southern Polar Coronal Hole
We report on the merging between the southern polar coronal hole and an adjacent coronal dimming induced by a coronal mass ejection on 2022 March 18, resulting in the merged region persisting for at least 72 hr. We use remote sensing data from multiple co-observing spacecraft to understand the physical processes during this merging event. The evolution of the merger is examined using Extreme-UltraViolet (EUV) images obtained from the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory and Extreme Ultraviolet Imager, which is on board the Solar Orbiter spacecraft. The plasma dynamics are quantified using spectroscopic data obtained from the EUV Imaging Spectrometer on board Hinode. The photospheric magnetograms from the Helioseismic and Magnetic Imager are used to derive the magnetic field properties. To our knowledge, this work is the first spectroscopical analysis of the merging of two open-field structures. We find that the coronal hole and the coronal dimming become indistinguishable after the merging. The upflow speeds inside the coronal dimming become more similar to that of a coronal hole, with a mixture of plasma upflows and downflows observable after the merging. The brightening of the bright points and the appearance of coronal jets inside the merged region further imply ongoing reconnection processes. We propose that component reconnection between the coronal hole and coronal dimming fields plays an important role during this merging event because the footpoint switching resulting from the reconnection allows the coronal dimming to intrude onto the boundary of the southern polar coronal hole
Excitation of Kaluza-Klein gravitational mode
We investigate excitation of Kaluza-Klein modes due to the parametric
resonance caused by oscillation of radius of compactification. We consider a
gravitational perturbation around a D-dimensional spacetime, which we
compactify on a (D-4)-sphere to obtain a 4-dimensional theory. The perturbation
includes the so-called Kaluza-Klein modes, which are massive in 4-dimension, as
well as zero modes, which is massless in 4-dimension. These modes appear as
scalar, vector and second-rank symmetric tensor fields in the 4-dimensional
theory. Since Kaluza-Klein modes are troublesome in cosmology, quanta of these
Kaluza-Klein modes should not be excited abundantly. However, if radius of
compactification oscillates, then masses of Kaluza-Klein modes also oscillate
and, thus, parametric resonance of Kaluza-Klein modes may occur to excite their
quanta. In this paper we consider part of Kaluza-Klein modes which correspond
to massive scalar fields in 4-dimension and investigate whether quanta of these
modes are excited or not in the so called narrow resonance regime of the
parametric resonance. We conclude that at least in the narrow resonance regime
quanta of these modes are not excited so catastrophically.Comment: 15 pages LaTeX, submitted to Phys.Rev.
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The characteristics of cognitive neuroscience tests in a schizophrenia cognition clinical trial: Psychometric properties and correlations with standard measures.
In comparison to batteries of standard neuropsychological tests, cognitive neuroscience tests may offer a more specific assessment of discrete neurobiological processes that may be aberrant in schizophrenia. However, more information regarding psychometric properties and correlations with standard neuropsychological tests and functional measures is warranted to establish their validity as treatment outcome measures. The N-back and AX-Continuous Performance Task (AX-CPT) are two promising cognitive neuroscience tests designed to measure specific components of working memory and contextual processing respectively. In the current study, we report the psychometric properties of multiple outcome measures from these two tests as well as their correlations with standard neuropsychological measures and functional capacity measures. The results suggest that while the AX-CPT and N-back display favorable psychometric properties, they do not exhibit greater sensitivity or specificity with functional measures than standard neurocognitive tests
Model-As-A-Service (MaaS) Using the Cloud Services Innovation Platform (CSIP)
Cloud infrastructures for modelling activities such as data processing, performing environmental simulations, or conducting model calibrations/optimizations provide a cost effective alternative to traditional high performance computing approaches. Cloud - based modelling examples emerged into the m ore formal notion: \u27Model - as - a - Service\u27 (MaaS). This paper presents the Cloud Services Innovation Platform (CSIP) as a software framework offering MaaS. It describes both the internal CSIP infrastructure and software architecture that manages cloud resources for typical modelling tasks, and the use of CSIP\u27s \u27 ModelServices API \u27 for a modelling application . CSIP\u27s architecture supports fast and resource aware auto - scaling of computational resources. An example model service is presented: the USDA hydrograph model EFH2 used in the desktop - based \u27engineering field tools\u27 is deployed as a CSIP service. This and other MaaS CSIP examples benefit from the use of cloud resources to enable straightforward scalable model deployment into cloud environments
Three Week Hypergravity Training Intervention Decreases Ground Contact Time During Repeated Jumping and Improves Sprinting and Shuttle Running Performance
International Journal of Exercise Science 9(2): 149-158, 2016. This study examined the effects of a non-traditional training method, hypergravity training (HT), on anaerobic performance. Highly active men (n = 9) completed a 3 week HT protocol in which weighted vests were worn 8 h/day, 4+ days/week separate from training. Vest loads were 11.2 ± 0.6% of body mass during week one, and increased to 13.2 ± 0.7% (week 2), and 16.1 ± 0.4% (week 3). Performance testing included power clean 1-RM (PC), counter movement jumps, 4 continuous jumps, 36.6 m sprints (SP), a 137.2 m short shuttle run (SSR), and a 274.3 m long shuttle run (LSR). A 3 week non-hypergravity training period (NHT) proceeded HT. Baseline SP improved from 4.69 ± 0.29 s to 4.58 ± 0.22 s post-treatment, and regressed after NHT (4.69 ± 0.24 s) (p = 0.006, ES = 1.80). Improvements in SSR (p = 0.012, ES = 1.71) occurred from baseline (26.7 ± 1.5 s) to post-treatment (26.2 ± 1.4 s), followed by a return to near-baseline values (26.9 ± 1.8 s). Jumping tasks displayed similar trends, but no statistical differences and modest effect sizes (0.51 - 0.62) were found except for improved ground contact time during repeated jumps post-HT (ES = 2.26). PC and LSR performances did not improve. Three weeks of HT significantly enhanced short running task performances and decreased ground contact time between 4 continuous jumps. HT may be incorporated into training programs prior to key points in an athletic season without hindering the quality of regular training session activities
Bostonia. Volume 4
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
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