6,111 research outputs found
The invertebrate Caenorhabditis elegans biosynthesizes ascorbate.
l-Ascorbate, commonly known as vitamin C, serves as an antioxidant and cofactor essential for many biological processes. Distinct ascorbate biosynthetic pathways have been established for animals and plants, but little is known about the presence or synthesis of this molecule in invertebrate species. We have investigated ascorbate metabolism in the nematode Caenorhabditis elegans, where this molecule would be expected to play roles in oxidative stress resistance and as cofactor in collagen and neurotransmitter synthesis. Using high-performance liquid chromatography and gas-chromatography mass spectrometry, we determined that ascorbate is present at low amounts in the egg stage, L1 larvae, and mixed animal populations, with the egg stage containing the highest concentrations. Incubating C. elegans with precursor molecules necessary for ascorbate synthesis in plants and animals did not significantly alter ascorbate levels. Furthermore, bioinformatic analyses did not support the presence in C. elegans of either the plant or the animal biosynthetic pathway. However, we observed the complete (13)C-labeling of ascorbate when C. elegans was grown with (13)C-labeled Escherichia coli as a food source. These results support the hypothesis that ascorbate biosynthesis in invertebrates may proceed by a novel pathway and lay the foundation for a broader understanding of its biological role
Molecular ion trap-depletion spectroscopy of BaCl
We demonstrate a simple technique for molecular ion spectroscopy. BaCl
molecular ions are trapped in a linear Paul trap in the presence of a
room-temperature He buffer gas and photodissociated by driving an electronic
transition from the ground X state to the repulsive wall of the
A state. The photodissociation spectrum is recorded by monitoring the
induced trap loss of BaCl ions as a function of excitation wavelength.
Accurate molecular potentials and spectroscopic constants are determined.
Comparison of the theoretical photodissociation cross-sections with the
measurement shows excellent agreement. This study represents the first
spectroscopic data for BaCl and an important step towards the production of
ultracold ground-state molecular ions.Comment: 5 pages, 5 figure
Reflowable documents composed from pre-rendered atomic components
Mobile eBook readers are now commonplace in today’s society, but their document layout algorithms remain basic, largely due to constraints imposed by short battery life. At present, with any eBook file format not based on PDF, the layout of the document, as it appears to the end user, is at the mercy of hidden reformatting and reflow algorithms interacting with the screen parameters of the device on which the document is rendered. Very little control is provided to the publisher or author, beyond some basic formatting options.
This paper describes a method of producing well-typeset, scalable, document layouts by embedding several pre-rendered versions of a document within one file, thus enabling many computationally expensive steps (e.g. hyphenation and line-breaking) to be carried out at document compilation time, rather than at ‘view time’. This system has the advantage that end users are not constrained to a single, arbitrarily chosen view of the document, nor are they subjected to reading a poorly typeset version rendered on the fly. Instead, the device can choose a layout appropriate to its screen size and the end user’s choice of zoom level, and the author and publisher can have fine-grained control over all layouts
Analisis Kinerja Coolant Pada Radiator
This research learn about characteristic of radiator coolant effectiveness, which are influenced by flow rate, density, and fluid viscosity. Experimental method is used to get parameters: such as coolant temperature, air temperature and flow rate. This study use É›-NTU method to analyze the data. The results of coolant A, B, and water have effectiveness of 40%, 37%, and 36% respectively, it is caused by coolant A have the biggest Universal coefficient number and convection coefficient number are compared with coolant B and water
Phase Conjugation and Negative Refraction Using Nonlinear Active Metamaterials
We present experimental demonstration of phase conjugation using nonlinear
metamaterial elements. Active split-ring resonators loaded with varactor diodes
are demonstrated theoretically to act as phase-conjugating or time-reversing
discrete elements when parametrically pumped and illuminated with appropriate
frequencies. The metamaterial elements were fabricated and shown experimentally
to produce a time reversed signal. Measurements confirm that a discrete array
of phase-conjugating elements act as a negatively-refracting time reversal RF
lens only 0.12 thick
Microscopic examination of hot spots giving rise to nonlinearity in superconducting resonators
We investigate the microscopic origins of nonlinear rf response in
superconducting electromagnetic resonators. Strong nonlinearity appearing in
the transmission spectra at high input powers manifests itself through the
emergence of jumplike features near the resonant frequency that evolve toward
lower quality factor with higher insertion loss as the rf input power is
increased. We directly relate these characteristics to the dynamics of
localized normal regions (hot spots) caused by microscopic features in the
superconducting material making up the resonator. A clear observation of
hot-spot formation inside a Nb thin film self-resonant structure is presented
by employing the microwave laser scanning microscope, and a direct link between
microscopic and macroscopic manifestations of nonlinearity is established.Comment: 5 pages, 4 figure
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