1,073 research outputs found
MYB10 and MYB72 are Required for Growth under Iron-Limiting Conditions
Iron is essential for photosynthesis and is often a limiting nutrient for plant productivity. Plants respond to conditions of iron deficiency by increasing transcript abundance of key genes involved in iron homeostasis, but only a few regulators of these genes have been identified. Using genome-wide expression analysis, we searched for transcription factors that are induced within 24 hours after transferring plants to iron-deficient growth conditions. Out of nearly 100 transcription factors shown to be up-regulated, we identified MYB10 and MYB72 as the most highly induced transcription factors. Here, we show that MYB10 and MYB72 are functionally redundant and are required for plant survival in alkaline soil where iron availability is greatly restricted. myb10myb72 double mutants fail to induce transcript accumulation of the nicotianamine synthase gene NAS4. Both myb10myb72 mutants and nas4-1 mutants have reduced iron concentrations, chlorophyll levels, and shoot mass under iron-limiting conditions, indicating that these genes are essential for proper plant growth. The double myb10myb72 mutant also showed nickel and zinc sensitivity, similar to the nas4 mutant. Ectopic expression of NAS4 rescues myb10myb72 plants, suggesting that loss of NAS4 is the primary defect in these plants and emphasizes the importance of nicotianamine, an iron chelator, in iron homeostasis. Overall, our results provide evidence that MYB10 and MYB72 act early in the iron-deficiency regulatory cascade to drive gene expression of NAS4 and are essential for plant survival under iron deficiency
Magnetized massive stars as magnetar progenitors
The origin of ultra-intense magnetic fields on magnetars is a mystery in
modern astrophysics. We model the core collapse dynamics of massive progenitor
stars with high surface magnetic fields in the theoretical framework of a
self-similar general polytropic magnetofluid under the self-gravity with a
quasi-spherical symmetry. With the specification of physical parameters such as
mass density, temperature, magnetic field and wind mass loss rate on the
progenitor stellar surface and the consideration of a rebound shock breaking
through the stellar interior and envelope, we find a remnant compact object
(i.e. neutron star) left behind at the centre with a radius of cm
and a mass range of solar masses. Moreover, we find that surface
magnetic fields of such kind of compact objects can be
G, consistent with those inferred for magnetars which include soft gamma-ray
repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The magnetic field
enhancement factor critically depends on the self-similar scaling index ,
which also determines the initial density distribution of the massive
progenitor. We propose that magnetized massive stars as magnetar progenitors
based on the magnetohydrodynamic evolution of the gravitational core collapse
and rebound shock. Our physical mechanism, which does not necessarily require
ad hoc dynamo amplification within a fast spinning neutron star, favours the
`fossil field' scenario of forming magnetars from the strongly magnetized core
collapse inside massive progenitor stars. With a range of surface magnetic
field strengths over massive progenitor stars, our scenario allows a continuum
of magnetic field strengths from pulsars to magnetars.Comment: 10 pages, 4 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Active cooling control of the CLEO detector using a hydrocarbon coolant farm
We describe a novel approach to particle-detector cooling in which a modular
farm of active coolant-control platforms provides independent and regulated
heat removal from four recently upgraded subsystems of the CLEO detector: the
ring-imaging Cherenkov detector, the drift chamber, the silicon vertex
detector, and the beryllium beam pipe. We report on several aspects of the
system: the suitability of using the aliphatic-hydrocarbon solvent PF(TM)-200IG
as a heat-transfer fluid, the sensor elements and the mechanical design of the
farm platforms, a control system that is founded upon a commercial programmable
logic controller employed in industrial process-control applications, and a
diagnostic system based on virtual instrumentation. We summarize the system's
performance and point out the potential application of the design to future
high-energy physics apparatus.Comment: 21 pages, LaTeX, 5 PostScript figures; version accepted for
publication in Nuclear Instruments and Methods in Physics Research
Sodium atoms and clusters on graphite: a density functional study
Sodium atoms and clusters (N<5) on graphite (0001) are studied using density
functional theory, pseudopotentials and periodic boundary conditions. A single
Na atom is observed to bind at a hollow site 2.45 A above the surface with an
adsorption energy of 0.51 eV. The small diffusion barrier of 0.06 eV indicates
a flat potential energy surface. Increased Na coverage results in a weak
adsorbate-substrate interaction, which is evident in the larger separation from
the surface in the cases of Na_3, Na_4, Na_5, and the (2x2) Na overlayer. The
binding is weak for Na_2, which has a full valence electron shell. The presence
of substrate modifies the structures of Na_3, Na_4, and Na_5 significantly, and
both Na_4 and Na_5 are distorted from planarity. The calculated formation
energies suggest that clustering of atoms is energetically favorable, and that
the open shell clusters (e.g. Na_3 and Na_5) can be more abundant on graphite
than in the gas phase. Analysis of the lateral charge density distributions of
Na and Na_3 shows a charge transfer of about 0.5 electrons in both cases.Comment: 20 pages, 6 figure
The Grizzly, October 29, 1997
Pennsylvania German Art Featured at Berman Art Museum • Pfahler Workers Dismissed • New Chaplain Introduced to Community • Commonwealth Brawl Raises Student Concern • Opinion: Award Winning My Ass; A Sweet Suite; Kudos to the College; Hail to the Queen; Leaving Home for Homecoming • Ghost Stories • Bears to Clash with Muhlenberg Mules • Men\u27s B-ball Gearing Up • Player Profiles: Lieberman, Steigerwalt Lead by Example; Mahoney a Constant Force for Young Women\u27s Teamhttps://digitalcommons.ursinus.edu/grizzlynews/1408/thumbnail.jp
Concept for a Future Super Proton-Proton Collider
Following the discovery of the Higgs boson at LHC, new large colliders are
being studied by the international high-energy community to explore Higgs
physics in detail and new physics beyond the Standard Model. In China, a
two-stage circular collider project CEPC-SPPC is proposed, with the first stage
CEPC (Circular Electron Positron Collier, a so-called Higgs factory) focused on
Higgs physics, and the second stage SPPC (Super Proton-Proton Collider) focused
on new physics beyond the Standard Model. This paper discusses this second
stage.Comment: 34 pages, 8 figures, 5 table
The Grizzly, November 5, 1997
Distinguished Alumni Return for Symposium • Ursinus Students and Faculty Attend Million Woman March • More Grants Received by Ursinus • Student\u27s Perseverance Rewarded • Test the Waters this Spring • Opinion: Faculty Responds to Curriculum Questions; Tired of Falling Asleep? • Stress Management • November Stress • Oedipus! Lives • There\u27s Something Brewing in The Java Trench • What\u27s with The Giant Green Gymnasium Anyway? • Ursinus: The Pseudo Liberal Arts College • Bears\u27 Swimmers Kick Back at Dickinson Relay Carnival • Men\u27s Soccer Continues to Struggle • Player Profiles: Jill Grau; Megan Larkinhttps://digitalcommons.ursinus.edu/grizzlynews/1409/thumbnail.jp
Associations of vitamin D pathway genes with circulating 25-hydroxyvitamin-D, 1,25-dihydroxyvitamin-D, and prostate cancer:a nested case-control study
Vitamin D pathway single nucleotide polymorphisms (SNPs) are potentially useful proxies for investigating whether circulating vitamin D metabolites [total 25-hydroxyvitamin-D, 25(OH)D; 1,25-dihydroxyvitamin, 1,25(OH)2D] are causally related to prostate cancer. We investigated associations of sixteen SNPs across seven genes with prostate-specific antigen-detected prostate cancer
Subtle variation in sepsis-III definitions markedly influences predictive performance within and across methods
Early detection of sepsis is key to ensure timely clinical intervention. Since very few end-to-end pipelines are publicly available, fair comparisons between methodologies are difficult if not impossible. Progress is further limited by discrepancies in the reconstruction of sepsis onset time. This retrospective cohort study highlights the variation in performance of predictive models under three subtly different interpretations of sepsis onset from the sepsis-III definition and compares this against inter-model differences. The models are chosen to cover tree-based, deep learning, and survival analysis methods. Using the MIMIC-III database, between 867 and 2178 intensive care unit admissions with sepsis were identified, depending on the onset definition. We show that model performance can be more sensitive to differences in the definition of sepsis onset than to the model itself. Given a fixed sepsis definition, the best performing method had a gain of 1–5% in the area under the receiver operating characteristic (AUROC). However, the choice of onset time can cause a greater effect, with variation of 0–6% in AUROC. We illustrate that misleading conclusions can be drawn if models are compared without consideration of the sepsis definition used which emphasizes the need for a standardized definition for sepsis onset
Cross-Sectional Study of Sleep Quantity and Quality and Amnestic and Non-Amnestic Cognitive Function in an Ageing Population: The English Longitudinal Study of Ageing (ELSA)
Background
The aim was to investigate the association between sleep disturbances and cognitive function in younger and older individuals from an ageing population.
Methods
3,968 male and 4,821 female white participants, aged 50 years and over, from the English Longitudinal Study of Ageing (ELSA) were studied. Information on sleep quality and quantity as well as both amnestic (memory, ACF) and non-amnestic (non-memory, nACF) function was available at Wave 4 (2008). Analysis of covariance was used to evaluate the relationship between sleep and cognitive function.
Results
After adjustment for multiple confounders in the younger group (50–64 years) duration of sleep explained 15.2% of the variance in ACF (p = 0.003) and 20.6% of nACF (p = 0.010). In the older group (65+ years) the estimates were 21.3% (p<0.001) and 25.6% (p<0.001), respectively. For sleep quality, there was a statistically significant association between sleep quality and both ACF (p<0.001) and nACF (p<0.001) in the older age group, but not in the younger age group (p = 0.586 and p = 0.373, respectively; interaction between age and sleep quality in the study sample including both age groups: p<0.001 for ACF and p = 0.018 for nACF). Sleep quality explained between 15.1% and 25.5% of the variance in cognition. The interaction with age was independent of duration of sleep. At any level of sleep duration there was a steeper association between sleep quality and ACF in the older than the younger group.
Conclusions
The associations between sleep disturbances and cognitive function vary between younger and older adults. Prospective studies will determine the temporal relationships between sleep disturbances and changes in cognition in different age groups
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