2,154 research outputs found
Diversity of Orchidaceae from Murum Dam, Belaga, Sarawak, Borneo
Murum Dam in Sarawak is located about 70 km upstream of Bakun Dam, on the rivers Murum, Danum and Plieran, forming a reservoir over an area of 245 km2. The area consists of mainly lowland to hilly mixed dipterocarp forests, with riparian and alluvial forests along the main rivers and streams, as well as patches of mossy and heath forests. Most of these forests are logged over and some areas have been converted into oil palm plantations. A flora rescue project was carried out to collect selected plant species including orchids from the areas affected by the dam. Most epiphytic orchids were collected from partially submerged trees. Over 2,000 specimens of orchids from 80 genera and c. 276 species were collected from May 2013 to December 2014. The most abundant genus recorded is Bulbophyllum Thouars (c. 44 species). Of these, 37 species are endemic to Borneo, two (Bulbophyllum upupops J.J.Verm., P.O’Byrne & A.L.Lamb and Thrixspermum lingiae P.O’Byrne & Gokusing) are newly described and ten species are new records for Sarawak. The collection of species from this work has provided valuable material for the research and conservation of orchids from vulnerable areas around dams
Ubiquitin Ligases of the N-End Rule Pathway: Assessment of Mutations in UBR1 That Cause the Johanson-Blizzard Syndrome
Background: Johanson-Blizzard syndrome (JBS; OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, facial dysmorphism with the characteristic nasal wing hypoplasia, multiple malformations, and frequent mental retardation. Our previous work has shown that JBS is caused by mutations in human UBR1, which encodes one of the E3 ubiquitin ligases of the N-end rule pathway. The N-end rule relates the regulation of the in vivo half-life of a protein to the identity of its N-terminal residue. One class of degradation signals (degrons) recognized by UBR1 are destabilizing N-terminal residues of protein substrates.
Methodology/Principal Findings: Most JBS-causing alterations of UBR1 are nonsense, frameshift or splice-site mutations that abolish UBR1 activity. We report here missense mutations of human UBR1 in patients with milder variants of JBS. These single-residue changes, including a previously reported missense mutation, involve positions in the RING-H2 and UBR domains of UBR1 that are conserved among eukaryotes. Taking advantage of this conservation, we constructed alleles of the yeast Saccharomyces cerevisiae UBR1 that were counterparts of missense JBS-UBR1 alleles. Among these yeast Ubr1 mutants, one of them (H160R) was inactive in yeast-based activity assays, the other one (Q1224E) had a detectable but weak activity, and the third one (V146L) exhibited a decreased but significant activity, in agreement with manifestations of JBS in the corresponding JBS patients.
Conclusions/Significance: These results, made possible by modeling defects of a human ubiquitin ligase in its yeast counterpart, verified and confirmed the relevance of specific missense UBR1 alleles to JBS, and suggested that a residual activity of a missense allele is causally associated with milder variants of JBS
Global Engineering Competency in Context: Situations and Behaviors
Engineering graduates encounter worlds of professional practice that are increasingly global in character. This new reality poses challenges for engineering educators and employers, who are faced with the formidable task of preparing engineers to be more effective in diverse national and cultural contexts. In response, many commentators have proposed lists of attributes or competencies deemed important or even essential for global engineering work. However, such lists have tended to lack explicit grounding in empirical studies of engineering practice, including typical kinds of work situations and related behavioral requirements. As a step toward establishing a more robust definition and developmental theory of global engineering competency, this paper reports results from a wide-ranging literature review on engineering practice in global context. The findings are organized around three main contextual dimensions of global engineering competency: technical coordination; engineering cultures; and ethics, standards, and regulations. Particular efforts are made to relate our findings to prior discussions of what it means to be a globally competent engineer, while further illustrating each dimension by giving examples drawn from interviews with practicing engineers. The paper concludes with a review of ongoing and future work, including how our findings are inspiring creation of situational prompts and activities for both assessment and instructional uses
A commensal strain of Staphylococcus epidermidis protects against skin neoplasia.
We report the discovery that strains of Staphylococcus epidermidis produce 6-N-hydroxyaminopurine (6-HAP), a molecule that inhibits DNA polymerase activity. In culture, 6-HAP selectively inhibited proliferation of tumor lines but did not inhibit primary keratinocytes. Resistance to 6-HAP was associated with the expression of mitochondrial amidoxime reducing components, enzymes that were not observed in cells sensitive to this compound. Intravenous injection of 6-HAP in mice suppressed the growth of B16F10 melanoma without evidence of systemic toxicity. Colonization of mice with an S. epidermidis strain producing 6-HAP reduced the incidence of ultraviolet-induced tumors compared to mice colonized by a control strain that did not produce 6-HAP. S. epidermidis strains producing 6-HAP were found in the metagenome from multiple healthy human subjects, suggesting that the microbiome of some individuals may confer protection against skin cancer. These findings show a new role for skin commensal bacteria in host defense. Sci Adv 2018 Feb 28; 4(2):eaao450
OXYGEN REACTIVE POLYMERS FOR TREATMENT OF TRAUMATIC BRAIN INJURY
Methods and compositions for treating traumatic brain injury . The methods and compositions utilize a multi - functional oxygen reactive polymer ( ORP ) that includes repeating units that include a reactive oxygen species ( ROS ) scavenging group and a polyalkylene oxide group . For theranostic applications , the oxygen reactive polymer fur ther includes a diagnostic group
Bridging the rodent to human translational gap: Marmosets as model systems for the study of Alzheimer\u27s disease.
INTRODUCTION: Our limited understanding of the mechanisms that trigger the emergence of Alzheimer\u27s disease (AD) has contributed to the lack of interventions that stop, prevent, or fully treat this disease. We believe that the development of a non-human primate model of AD will be an essential step toward overcoming limitations of other model systems and is crucial for investigating primate-specific mechanisms underlying the cellular and molecular root causes of the pathogenesis and progression of AD.
METHODS: A new consortium has been established with funding support from the National Institute on Aging aimed at the generation, characterization, and validation of Marmosets As Research Models of AD (MARMO-AD). This consortium will study gene-edited marmoset models carrying genetic risk for AD and wild-type genetically diverse aging marmosets from birth throughout their lifespan, using non-invasive longitudinal assessments. These include characterizing the genetic, molecular, functional, behavioral, cognitive, and pathological features of aging and AD.
RESULTS: The consortium successfully generated viable founders carrying
DISCUSSION: By establishing marmoset models of AD, we will be able to investigate primate-specific cellular and molecular root causes that underlie the pathogenesis and progression of AD, overcome limitations of other model organisms, and support future translational studies to accelerate the pace of bringing therapies to patients
Engineering Anomalously Large Electron Transport in Topological Semimetals
Anomalous transport of topological semimetals has generated significant
interest for applications in optoelectronics, nanoscale devices, and
interconnects. Understanding the origin of novel transport is crucial to
engineering the desired material properties, yet their orders of magnitude
higher transport than single-particle mobilities remain unexplained. This work
demonstrates the dramatic mobility enhancements result from phonons primarily
returning momentum to electrons due to phonon-electron dominating over
phonon-phonon scattering. Proving this idea, proposed by Peierls in 1932,
requires tuning electron and phonon dispersions without changing symmetry,
topology, or disorder. This is achieved by combining de Haas - van Alphen
(dHvA), electron transport, Raman scattering, and first-principles calculations
in the topological semimetals MX (M=Nb, Ta and X=Ge, Si). Replacing Ge with
Si brings the transport mobilities from an order magnitude larger than single
particle ones to nearly balanced. This occurs without changing the crystal
structure or topology and with small differences in disorder or Fermi surface.
Simultaneously, Raman scattering and first-principles calculations establish
phonon-electron dominated scattering only in the MGe compounds. Thus, this
study proves that phonon-drag is crucial to the transport properties of
topological semimetals and provides insight to further engineer these
materials.Comment: 12 pages, 5 figure
Magnetic field-induced non-trivial electronic topology in Fe3−xGeTe2
The anomalous Hall, Nernst and thermal Hall coefficients of
FeGeTe display several features upon cooling, like a reversal in
the Nernst signal below K pointing to a topological transition (TT)
associated to the development of magnetic spin textures. Since the anomalous
transport variables are related to the Berry curvature, a possible TT might
imply deviations from the Wiedemann-Franz (WF) law. However, the anomalous Hall
and thermal Hall coefficients of FeGeTe are found, within our
experimental accuracy, to satisfy the WF law for magnetic-fields
applied along its inter-layer direction. Surprisingly, large anomalous
transport coefficients are also observed for applied along the planar
\emph{a}-axis as well as along the gradient of the chemical potential, a
configuration that should not lead to their observation due to the absence of
Lorentz force. However, as \emph{a}-axis is increased,
magnetization and neutron scattering indicate just the progressive canting of
the magnetic moments towards the planes followed by their saturation. These
anomalous planar quantities are found to not scale with the component of the
planar magnetization (), showing instead a sharp decrease beyond 4 T which is the field required to align the magnetic moments
along . We argue that locally chiral spin structures, such as
skyrmions, and possibly skyrmion tubes, lead to a field dependent
spin-chirality and hence to a novel type of topological anomalous transport.
Locally chiral spin-structures are captured by our Monte-Carlo simulations
incorporating small Dzyaloshinskii-Moriya and biquadratic exchange
interactions.Comment: 34 pages, 10 figures, submitted to Applied Physics Review
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