567 research outputs found
Identification of phenological stages and vegetative types for land use classification
There are no author-identified significant results in this report
EDUCATION AND PRODUCTION Effect of Differing Light Intensities on Abdominal Fat Deposition in Broilers
ABSTRACT Two trials were conducted in an attempt to determine if light intensity affected fat content of broilers as measured by the amount of abdominal fat. The light regimens used from 10 days of age had constant intensities of 2 or 52 lx. Results obtained showed that light intensity did not significantly influence the amount of abdominal fat produced by males or females at either 49 or 63 days of age. Light intensity had no significant effect on body weight, feed conversion (grams feed per gram body weight), or mortality at either 48 or 62 days of age for broilers of the same sex. The amount of light used was the amount produced from either 7.5 or 75-W incandescent bulbs in an enclosed house that was 11m wide with two strings of light bulbs 2.1 m high on 3-m centers equidistant from the ends and sidewalls of the house
Unzipping Kinetics of Double-Stranded DNA in a Nanopore
We studied the unzipping kinetics of single molecules of double-stranded DNA
by pulling one of their two strands through a narrow protein pore. PCR analysis
yielded the first direct proof of DNA unzipping in such a system. The time to
unzip each molecule was inferred from the ionic current signature of DNA
traversal. The distribution of times to unzip under various experimental
conditions fit a simple kinetic model. Using this model, we estimated the
enthalpy barriers to unzipping and the effective charge of a nucleotide in the
pore, which was considerably smaller than previously assumed.Comment: 10 pages, 5 figures, Accepted: Physics Review Letter
Graphene: A sub-nanometer trans-electrode membrane
Isolated, atomically thin conducting membranes of graphite, called graphene,
have recently been the subject of intense research with the hope that practical
applications in fields ranging from electronics to energy science will emerge.
Here, we show that when immersed in ionic solution, a layer of graphene takes
on new electrochemical properties that make it a trans-electrode. The
trans-electrode's properties are the consequence of the atomic scale proximity
of its two opposing liquid-solid interfaces together with graphene's well known
in-plane conductivity. We show that several trans-electrode properties are
revealed by ionic conductivity measurements on a CVD grown graphene membrane
that separates two aqueous ionic solutions. Despite this membrane being only
one to two atomic layers thick, we find it is a remarkable ionic insulator with
a very small stable conductivity that depends on the ion species in solution.
Electrical measurements on graphene membranes in which a single nanopore has
been drilled show that the membrane's effective insulating thickness is less
than one nanometer. This small effective thickness makes graphene an ideal
substrate for very high-resolution, high throughput nanopore based single
molecule detectors. Sensors based on modulation of graphene's in-plane
electronic conductivity in response to trans-electrode environments and voltage
biases will provide new insights into atomic processes at the electrode
surfaces.Comment: Submitted 12 April 2010 to Nature, where it is under revie
Chaperone-assisted translocation of a polymer through a nanopore
Using Langevin dynamics simulations, we investigate the dynamics of
chaperone-assisted translocation of a flexible polymer through a nanopore. We
find that increasing the binding energy between the chaperone and
the chain and the chaperone concentration can greatly improve the
translocation probability. Particularly, with increasing the chaperone
concentration a maximum translocation probability is observed for weak binding.
For a fixed chaperone concentration, the histogram of translocation time
has a transition from long-tailed distribution to Gaussian distribution with
increasing . rapidly decreases and then almost saturates with
increasing binding energy for short chain, however, it has a minimum for longer
chains at lower chaperone concentration. We also show that has a minimum
as a function of the chaperone concentration. For different , a
nonuniversal dependence of on the chain length is also observed.
These results can be interpreted by characteristic entropic effects for
flexible polymers induced by either crowding effect from high chaperone
concentration or the intersegmental binding for the high binding energy.Comment: 10 pages, to appear in J. Am. Chem. So
Fusion of secretory vesicles isolated from rat liver
Secretory vesicles isolated from rat liver were found to fuse after exposure to Ca2+. Vescle fusion is characterized by the occurrence of twinned vesicles with a continuous cleavage plane between two vesicles in freeze-fracture electron microscopy. The number of fused vesicles increases with increasing Ca2+-concentrations and is half maximal around 10–6 m. Other divalent cations (Ba2+, Sr2+, and Mg2+) were ineffective. Mg2+ inhibits Ca2+-induced fusion. Therefore, the fusion of secretory vesiclesin vitro is Ca2+ specific and exhibits properties similar to the exocytotic process of various secretory cells.
Various substances affecting secretionin vivo (microtubular inhibitors, local anethetics, ionophores) were tested for their effect on membrane fusion in our system.
The fusion of isolated secretory vesicles from liver was found to differ from that of pure phospholipid membranes in its temperature dependence, in its much lower requirement for Ca2+, and in its Ca2+-specificity. Chemical and enzymatic modifications of the vesicle membrane indicate that glycoproteins may account for these differences
Brain microbiota disruption within inflammatory demyelinating lesions in multiple sclerosis
Microbial communities reside in healthy tissues but are often disrupted during disease. Bacterial genomes and proteins are detected in brains from humans, nonhuman primates, rodents and other species in the absence of neurological disease. We investigated the composition and abundance of microbiota in frozen and fixed autopsied brain samples from patients with multiple sclerosis (MS) and age-and sex-matched nonMS patients as controls, using neuropathological, molecular and bioinformatics tools. 16s rRNA sequencing revealed Proteobacteria to be the dominant phylum with restricted diversity in cerebral white matter (WM) from MS compared to nonMS patients. Both clinical groups displayed 1,200-1,400 bacterial genomes/cm(3) and low bacterial rRNA: rDNA ratios in WM. RNAseq analyses showed a predominance of Proteobacteria in progressive MS patients' WM, associated with increased inflammatory gene expression, relative to a broader range of bacterial phyla in relapsing-remitting MS patients' WM. Although bacterial peptidoglycan (PGN) and RNA polymerase beta subunit immunoreactivities were observed in all patients, PGN immunodetection was correlated with demyelination and neuroinflammation in MS brains. Principal component analysis revealed that demyelination, PGN and inflammatory gene expression accounted for 86% of the observed variance. Thus, inflammatory demyelination is linked to an organ-specific dysbiosis in MS that could contribute to underlying disease mechanisms
Transverse Electronic Transport through DNA Nucleotides with Functionalized Graphene Electrodes
Graphene nanogaps and nanopores show potential for the purpose of electrical
DNA sequencing, in particular because single-base resolution appears to be
readily achievable. Here, we evaluated from first principles the advantages of
a nanogap setup with functionalized graphene edges. To this end, we employed
density functional theory and the non-equilibrium Green's function method to
investigate the transverse conductance properties of the four nucleotides
occurring in DNA when located between the opposing functionalized graphene
electrodes. In particular, we determined the electrical tunneling current
variation as a function of the applied bias and the associated differential
conductance at a voltage which appears suitable to distinguish between the four
nucleotides. Intriguingly, we observe for one of the nucleotides a negative
differential resistance effect.Comment: 19 pages, 7 figure
Self-Assembled Polymeric Membranes and Nanoassemblies on Surfaces: Preparation, Characterization, and Current Applications
Abstract Biomembranes play a crucial role in a multitude of biological processes, where high selectivity and efficiency are key points in the reaction course. The outstanding performance of biological membranes is based on the coupling between the membrane and biomolecules, such as membrane proteins. Polymer-based membranes and assemblies represent a great alternative to lipid ones, as their presence not only dramatically increases the mechanical stability of such systems, but also opens the scope to a broad range of chemical functionalities, which can be fine-tuned to selectively combine with a specific biomolecule. Tethering the membranes or nanoassemblies on a solid support opens the way to a class of functional surfaces finding application as sensors, biocomputing systems, molecular recognition, and filtration membranes. Herein, the design, physical assembly, and biomolecule attachment/insertion on/within solid-supported polymeric membranes and nanoassemblies are presented in detail with relevant examples. Furthermore, the models and applications for these materials are highlighted with the recent advances in each field
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