12,066 research outputs found
Sugar Maple Borer (Coleoptera: Cerambycidae) Activity Associated With Periods of Severe Defoliation
A perusal of previous research on sugar maple borer, Glycobius speciosus, in northern New York State strongly associates severe early and late season defoliation with increased borer damage. This re-examination of earlier work suggests foliage protection may be necessary when forest management objectives are concerned with wood volume and quality
Characterization of aluminum/RP-1 gel propellant properties
Research efforts are being conducted by the NASA Lewis Research Center to formulate and characterize the properties of Al/RP-1 and RP-1 gelled propellants for rocket propulsion systems. Twenty four different compositions of gelled fuels were formulated with 5 and 16 micron, atomized aluminum powder in RP-1. The total solids concentration in the propellant varied from 5 to 60 wt percent. Tests were conducted to evaluate the stability and rheological characteristics of the fuels. Physical separation of the solids occurred in fuels with less than 50 wt percent solids concentration. The rheological characteristics of the Al/RP-1 fuels varied with solids concentration. Both thixotropic and rheopectic gel behavior were observed. The unmetallized RP-1 gels, which were formulated by a different technique than the Al/RP-1 gels, were highly viscoelastic. A history of research efforts which were conducted to formulate and characterize the properties of metallized propellants for various applications is also given
Crystallographic Analyses of Ion Channels: Lessons and Challenges
Membrane proteins fascinate at many levels, from their central functional roles in transport, energy transduction, and signal transduction processes to structural questions concerning how they fold and operate in the exotic environments of the membrane bilayer and the water-bilayer interface and to methodological issues associated with studying membrane proteins either in situ or extracted from the membrane. This interplay is beautifully exemplified by ion channels, a collection of integral membrane proteins that mediate the transmembrane passage of ions down their electrochemical potential gradient (for general reviews, see Refs. 1 and 2). Ion channels are key elements of signaling and sensing pathways, including nerve cell conduction, hormone response, and mechanosensation. The characteristic properties of ion channels reflect their conductance, ion selectivity, and gating. Ion channels are often specific for a particular type of ion (such as potassium or chloride) or a class of ions (such as anions) and are typically regulated by conformational switching of the protein structure between "open" and "closed" states. This conformational switching may be gated in response to changes in membrane potential, ligand binding, or application of mechanical forces. Detailed functional characterizations of channels and their gating mechanisms have been achieved, reflecting exquisite methodological advances such as patch clamp methods that can monitor the activities of individual channels (3). Until recently, corresponding information about the three-dimensional structures of channels was not available, reflecting difficulties in obtaining sufficient quantities of membrane proteins for crystallization trials. Happily, this situation has started to change with the structure determinations of the Streptomyces lividans K+ channel (KcsA (4)) and the Mycobacterium tuberculosis mechanosensitive channel (MscL (5)).
A variety of reviews (6-12) have appeared recently that discuss functional implications of these channel structures. This review discusses these developments from a complementary perspective, by considering the implications of these structures from within the larger framework of membrane protein structure and function. Because of space restrictions, this review necessarily emphasizes membrane proteins that are composed primarily of alpha-helical bundles, such as KcsA and MscL, rather than beta-barrel proteins, such as porins, typically found in bacterial outer membranes
Average motion of emerging solar active region polarities I: Two phases of emergence
Our goal is to constrain models of active region formation by tracking the
average motion of active region polarity pairs as they emerge onto the surface.
We measured the motion of the two main opposite polarities in 153 emerging
active regions (EARs) using line-of-sight magnetic field observations from the
Solar Dynamics Observatory Helioseismic Emerging Active Region (SDO/HEAR)
survey (Schunker et al. 2016). We first measured the position of each of the
polarities eight hours after emergence and tracked their location forwards and
backwards in time. We find that, on average, the polarities emerge with an
east-west orientation and the separation speed between the polarities
increases. At about 0.1 days after emergence, the average separation speed
reaches a peak value of 229 +/- 11 m/s, and then starts to decrease, and about
2.5 days after emergence the polarities stop separating. We also find that the
separation and the separation speed in the east-west direction are
systematically larger for active regions with higher flux. Our results reveal
two phases of the emergence process defined by the rate of change of the
separation speed as the polarities move apart. Phase 1 begins when the opposite
polarity pairs first appear at the surface, with an east-west alignment and an
increasing separation speed. We define Phase 2 to begin when the separation
speed starts to decrease, and ends when the polarities have stopped separating.
This is consistent with the picture of Chen, Rempel, & Fan (2017): the peak of
a flux tube breaks through the surface during Phase 1. During Phase 2 the
magnetic field lines are straightened by magnetic tension, so that the
polarities continue to move apart, until they eventually lie directly above
their anchored subsurface footpoints.Comment: accepted A&
Has climate change taken prominence over biodiversity conservation?
The growing prominence of climate change has led to concerns that other important environmental issues, such as biodiversity loss, are being overshadowed. We investigate this assertion by examining trends in biodiversity and climate change coverage within the scientific and newspaper press, as well as the relative distribution of funding through the World Bank and the National Science Foundation, since the late 1980s. Our indicators substantiate some of these fears. To prevent biodiversity from becoming a declining priority, conservationists need to analyze the discourse surrounding climate change and determine how it has become the predominant environmental topic. In addition, given the common drivers of biodiversity loss and climate change, we argue that win–win solutions must be sought wherever possible. Conservationists need to be proactive and take this opportunity to use the mounting interest in climate change as a flagship to leverage more support and action to prevent further biodiversity loss
Interactions of Applied Hormones in the Germination of Lepidium Virginicum Seeds
Author Institution: Department of Botany, The Ohio State UniversityTests of the germination response of light sensitive Lepidium virginicum seeds to applied gibberellic acid confirmed earlier reports that gibberellic acid can substitute for red light. Further tests indicated that promotion of germination by either red light or gibberellic acid can be nullified by abscisic acid. Dark incubation of the seeds in kinetin alone resulted in only slight promotion of germination. Combinations of suboptimal gibberellic acid plus kinetin did not enhance germination to a level greater than that for kinetin alone. Optimal concentrations of gibberellic acid plus kinetin can reverse inhibition of certain abscisic acid concentrations. A comparison of these responses with those of Grand Rapids variety of lettuce seed was made
Optimized imaging using non-rigid registration
The extraordinary improvements of modern imaging devices offer access to data
with unprecedented information content. However, widely used image processing
methodologies fall far short of exploiting the full breadth of information
offered by numerous types of scanning probe, optical, and electron
microscopies. In many applications, it is necessary to keep measurement
intensities below a desired threshold. We propose a methodology for extracting
an increased level of information by processing a series of data sets
suffering, in particular, from high degree of spatial uncertainty caused by
complex multiscale motion during the acquisition process. An important role is
played by a nonrigid pixel-wise registration method that can cope with low
signal-to-noise ratios. This is accompanied by formulating objective quality
measures which replace human intervention and visual inspection in the
processing chain. Scanning transmission electron microscopy of siliceous
zeolite material exhibits the above-mentioned obstructions and therefore serves
as orientation and a test of our procedures
Retention of Administrators in Nursing Homes: What Can Management Do?
Annual turnover among nursing home administrators may be 40% or higher. To investigate the factors that could lead to greater administrator retention, responses to a survey (53% response rate) were analyzed using factor analysis and multiple regression models. Results show that higher retention is observed when administrators are allowed to function independently, are involved in decision making, are treated fairly, and are given reasonable goals to achieve. Organizations must hire administrators whose values match theirs. Multifacility chain organizations and for-profit facilities appear to have a greater need to embrace organizational principles that lead to greater job satisfaction
Predicting Turnover and Retention in Nursing Home Administrators: Management and Policy Implications
Administrator turnover and its impact on the quality of patient care are important concerns in the nursing home industry. This study evaluates a model to determine which factors, attitudes, and personal characteristics can predict tenure. Responses to a survey from 290 nursing home administrators (NHAs) who furnished data on their previous positions were analyzed using logistic regression methods. The extracted model correlates tenure with the administrator\u27s past patterns of stability, community attachment, organizational commitment, and facility performance. The model is particularly effective (85% accuracy) in flagging NHAs who are likely to depart within their first 3 years of employment. Implications of these findings for recruitment, retention, and licensure policy are discussed
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