8,741 research outputs found
Evaluating the Competitive Yardstick Effect of Cooperatives on Imperfect Markets: A Simulation Analysis
Agribusiness,
Eight new state records of aleyrodine whiteflies found in Clark County, Nevada and three newly described taxa (Hemiptera: Aleyrodidae, Aleyrodinae)
Eight new state records and the three newly described species are the subject of this publication. Whiteflies (Hemiptera: Sternorrhyncha: Aleyrodidae: Aleyrodinae) were collected from 2003 through 2009 within the Las Vegas area of Clark County, Nevada to determine the occurrence of newly established species and host range and distribution. Prior to 2003 the following ten whiteflies were known to be established in Nevada: Aleuroglandulus subtilis Bondar, Aleuroplatus berbericolus Quaintance and Baker, Aleyrodes spiraeoides Quaintance, Bemisia tabaci (Gennadius), Dialeurodes citri (Ashmead), Siphoninus phillyreae (Haliday), Tetraleurodes mori (Quaintance), Trialeurodes abutiloneus (Haldeman), Trialeurodes packardi (Morrill), and Trialeurodes vaporariorum (Westwood). Based on collections made after 2003, eleven additional whitefly species were found in Nevada. Of these the following eight were described species from California and other western U.S. states: Aleuroparadoxus arctostaphyli Russell, Aleuroplatus gelatinosus (Cockerell), Aleuropleurocelus ceanothi (Sampson), Aleuropleurocelus nigrans (Bemis), Tetraleurodes quercicola Nakahara, Trialeurodes corollis (Penny), Trialeurodes eriodictyonis Russell, and Trialeurodes glacialis (Bemis). Three new species are described and illustrated: Aleuropleurocelus nevadensis Dooley sp. nov., Tetraleurodes quercophyllae Dooley sp. nov., and Trialeurodes pseudoblongifoliae Dooley sp. nov
When Should You Adjust Standard Errors for Clustering?
In empirical work in economics it is common to report standard errors that
account for clustering of units. Typically, the motivation given for the
clustering adjustments is that unobserved components in outcomes for units
within clusters are correlated. However, because correlation may occur across
more than one dimension, this motivation makes it difficult to justify why
researchers use clustering in some dimensions, such as geographic, but not
others, such as age cohorts or gender. It also makes it difficult to explain
why one should not cluster with data from a randomized experiment. In this
paper, we argue that clustering is in essence a design problem, either a
sampling design or an experimental design issue. It is a sampling design issue
if sampling follows a two stage process where in the first stage, a subset of
clusters were sampled randomly from a population of clusters, while in the
second stage, units were sampled randomly from the sampled clusters. In this
case the clustering adjustment is justified by the fact that there are clusters
in the population that we do not see in the sample. Clustering is an
experimental design issue if the assignment is correlated within the clusters.
We take the view that this second perspective best fits the typical setting in
economics where clustering adjustments are used. This perspective allows us to
shed new light on three questions: (i) when should one adjust the standard
errors for clustering, (ii) when is the conventional adjustment for clustering
appropriate, and (iii) when does the conventional adjustment of the standard
errors matter
Scottish Archaeological Research Framework: Future Thinking on Carved Stones
No abstract available
Untangling the Genetic Basis of Fibrolytic Specialization by Lachnospiraceae and Ruminococcaceae in Diverse Gut Communities
The Lachnospiraceae and Ruminococcaceae are two of the most abundant families from the order Clostridiales found in the mammalian gut environment, and have been associated with the maintenance of gut health. While they are both diverse groups, they share a common role as active plant degraders. By comparing the genomes of the Lachnospiraceae and Ruminococcaceae with the Clostridiaceae, a more commonly free-living group, we identify key carbohydrate-active enzymes, sugar transport mechanisms, and metabolic pathways that distinguish these two commensal groups as specialists for the degradation of complex plant material
Zintl phases for thermoelectric devices
By converting waste heat into electricity and improving the efficiency of refrigeration systems, thermoelectric devices could play a significant role in solving today's energy problems. Increasing the thermoelectric efficiency (as measured by the thermoelectric material's figure-of-merit, zT) is critical to the development of this technology. Complex Zintl phases, in particular, make ideal candidates for thermoelectric materials because the necessary electron–crystal, phonon–glass properties can be engineered with an understanding of the Zintl chemistry. A recent example is the discovery that Yb14MnSb11, a transition metal Zintl compound, has twice the zT as the material currently in use at NASA. This perspective outlines a strategy to discover new high zT materials in Zintl phases, and presents results pointing towards the success of this approach
The metabolomic profile of gamma-irradiated human hepatoma and muscle cells reveals metabolic changes consistent with the Warburg effect
The two human cell lines HepG2 from hepatoma and HMCL-7304 from striated muscle were γ-irradiated with doses between 0 and 4 Gy. Abundant γH2AX foci were observed at 4 Gy after 4 h of culture post-irradiation. Sham-irradiated cells showed no γH2AX foci and therefore no signs of radiation-induced double-strand DNA breaks. Flow cytometry indicated that 41.5% of HepG2 cells were in G2/M and this rose statistically significantly with increasing radiation dose reaching a plateau at ∼47%. Cell lysates from both cell lines were subjected to metabolomic analysis using Gas Chromatography-Mass Spectrometry (GCMS). A total of 46 metabolites could be identified by GCMS in HepG2 cell lysates and 29 in HMCL-7304 lysates, most of which occurred in HepG2 cells. Principal Components Analysis (PCA) showed a clear separation of sham, 1, 2 and 4 Gy doses. Orthogonal Projection to Latent Structures-Discriminant Analysis (OPLS-DA) revealed elevations in intracellular lactate, alanine, glucose, glucose 6-phosphate, fructose and 5-oxoproline, which were found by univariate statistics to be highly statistically significantly elevated at both 2 and 4 Gy compared with sham irradiated cells. These findings suggested upregulation of cytosolic aerobic glycolysis (the Warburg effect), with potential shunting of glucose through aldose reductase in the polyol pathway, and consumption of reduced Glutathione (GSH) due to γ-irradiation. In HMCL-7304 myotubes, a putative Warburg effect was also observed only at 2 Gy, albeit a lesser magnitude than in HepG2 cells. It is anticipated that these novel metabolic perturbations following γ-irradiation of cultured cells will lead to a fuller understanding of the mechanisms of tissue damage following ionizing radiation exposure
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