797 research outputs found
Manual for starch gel electrophoresis: A method for the detection of genetic variation
The procedure to conduct horizontal starch gel electrophoresis on enzymes is described in detail. Areas covered are (I) collection and storage of specimens, (2)
preparation of tissues, (3) preparation of a starch gel, (4) application of enzyme extracts to a gel, (5) setting up a gel for electrophoresis, (6) slicing a gel, and (7)
staining a gel. Recipes are also included for 47 enzyme stains and 3 selected gel buffers. (PDF file contains 26 pages.
The Behavior of Granular Materials under Cyclic Shear
The design and development of a parallel plate shear cell for the study of
large scale shear flows in granular materials is presented. The parallel plate
geometry allows for shear studies without the effects of curvature found in the
more common Couette experiments. A system of independently movable slats
creates a well with side walls that deform in response to the motions of grains
within the pack. This allows for true parallel plate shear with minimal
interference from the containing geometry. The motions of the side walls also
allow for a direct measurement of the velocity profile across the granular
pack. Results are presented for applying this system to the study of transients
in granular shear and for shear-induced crystallization. Initial shear profiles
are found to vary from packing to packing, ranging from a linear profile across
the entire system to an exponential decay with a width of approximately 6 bead
diameters. As the system is sheared, the velocity profile becomes much sharper,
resembling an exponential decay with a width of roughly 3 bead diameters.
Further shearing produces velocity profiles which can no longer be fit to an
exponential decay, but are better represented as a Gaussian decay or error
function profile. Cyclic shear is found to produce large scale ordering of the
granular pack, which has a profound impact on the shear profile. There exist
periods of time in which there is slipping between layers as well as periods of
time in which the layered particles lock together resulting in very little
relative motion.Comment: 10 pages including 12 figure
Memory of the Unjamming Transition during Cyclic Tiltings of a Granular Pile
Discrete numerical simulations are performed to study the evolution of the
micro-structure and the response of a granular packing during successive
loading-unloading cycles, consisting of quasi-static rotations in the gravity
field between opposite inclination angles. We show that internal variables,
e.g., stress and fabric of the pile, exhibit hysteresis during these cycles due
to the exploration of different metastable configurations. Interestingly, the
hysteretic behaviour of the pile strongly depends on the maximal inclination of
the cycles, giving evidence of the irreversible modifications of the pile state
occurring close to the unjamming transition. More specifically, we show that
for cycles with maximal inclination larger than the repose angle, the weak
contact network carries the memory of the unjamming transition. These results
demonstrate the relevance of a two-phases description -strong and weak contact
networks- for a granular system, as soon as it has approached the unjamming
transition.Comment: 13 pages, 15 figures, soumis \`{a} Phys. Rev.
Role of a cdk5-associated protein, p35, in herpes simplex virus type 1 replication in vivo
Previous studies have shown that herpes simplex virus type 1 (HSV-1) replication is inhibited by the cyclin-dependent kinase (cdk) inhibitor roscovitine. One roscovitine-sensitive cdk that functions in neurons is cdk5, which is activated in part by its binding partner, p35. Because HSV establishes latent infections in sensory neurons, we sought to determine the role p35 plays in HSV-1 replication in vivo. For these studies, wild-type (wt) and p35-/- mice were infected with HSV-1 using the mouse ocular model of HSV latency and reactivation. The current results indicate that p35 is an important determinant of viral replication in vivo
Specific food intake, fat and fiber intake, and behavioral correlates of BMI among overweight and obese members of a managed care organization
BACKGROUND: The study examined correlates of body mass index (BMI) in overweight and obese members of a managed care organization seeking treatment for obesity. It assessed intake of specific foods, dietary fat or fiber, and behaviors attempted to control weight. METHODS: Participants were 508 men and 1293 women who were > 18 years and had a self-reported BMI > 27.0. This paper reports analyses of baseline and 24-month follow-up data from a randomized weight-loss trial. Cross-sectional and prospective relationships between BMI and behaviors were examined with regression analyses controlling for age and education. RESULTS: At baseline, hamburger and beef consumption were associated with higher BMI for men; for women, hamburger, fried chicken, hot dog, bacon or sausage, egg, French fry, and overall fat consumption were associated with higher BMI, while eating high fiber cereal, fruit, and overall fiber intake were associated with lower BMI. Virtually all forms of weight control behavior were reported more often in heavier people. Subscribing to exercise magazines, however, was associated with lower BMI. Decreased fat intake and increased fruit/vegetable/fiber intake over the course of the study were associated with reductions in BMI at 24 months. CONCLUSION: The same behaviors that differentiate individuals with different body weight in the general population also differentiate between individuals of different body weights at the high end of the weight distribution. Educational efforts aimed at preventing weight gain and reducing obesity might benefit from focusing on specific foods known to be associated empirically with body weight and weight change over time
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Improved electron-beam ion-trap lifetime measurement of the Ne8+ 1s2s3S1 level
An earlier electron-beam ion-trap (EBIT) lifetime measurement of the Ne8+ 1s2s3S1 level has been improved upon, reducing the uncertainties to less than the scatter in the existing theoretical calculations. The new result, 91.7±0.4 μs, agrees with the previous value, but is more precise by a factor of 4. The new value distinguishes among theoretical values, as agreement is obtained only with those calculations that employ "exact" nonrelativistic or relativistic wave functions. Routes to measurements with even higher accuracy are discussed
Dynamics of tongue microbial communities with single-nucleotide resolution using oligotyping
.© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 5 (2014): 568, doi:10.3389/fmicb.2014.00568.The human mouth is an excellent system to study the dynamics of microbial communities and their interactions with their host. We employed oligotyping to analyze, with single-nucleotide resolution, oral microbial 16S ribosomal RNA (rRNA) gene sequence data from a time course sampled from the tongue of two individuals, and we interpret our results in the context of oligotypes that we previously identified in the oral data from the Human Microbiome Project. Our previous work established that many of these oligotypes had dramatically different distributions between individuals and across oral habitats, suggesting that they represented functionally different organisms. Here we demonstrate the presence of a consistent tongue microbiome but with rapidly fluctuating proportions of the characteristic taxa. In some cases closely related oligotypes representing strains or variants within a single species displayed fluctuating relative abundances over time, while in other cases an initially dominant oligotype was replaced by another oligotype of the same species. We use this high temporal and taxonomic level of resolution to detect correlated changes in oligotype abundance that could indicate which taxa likely interact synergistically or occupy similar habitats, and which likely interact antagonistically or prefer distinct habitats. For example, we found a strong correlation in abundance over time between two oligotypes from different families of Gamma Proteobacteria, suggesting a close functional or ecological relationship between them. In summary, the tongue is colonized by a microbial community of moderate complexity whose proportional abundance fluctuates widely on time scales of days. The drivers and functional consequences of these community dynamics are not known, but we expect they will prove tractable to future, targeted studies employing taxonomically resolved analysis of high-throughput sequencing data sampled at appropriate temporal intervals and spatial scales.Supported by National Institutes of Health (NIH) National Institute of Dental and Craniofacial Research Grant DE022586 (to Gary G. Borisy). Daniel R. Utter was supported by the Woods Hole Partnership Education Program; A. Murat Eren was supported by a G. Unger Vetlesen Foundation grant to the Marine Biological Laboratory; David B. Mark Welch was supported by NSF DBI-126259
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Experimental M1 Transition Rates of Coronal Lines from Ar X, Ar XIV, and Ar XV
Transition probabilities of three magnetic dipole (M1) transitions in multiply charged ions of Ar have been measured using the Livermore electron-beam ion trap. Two of the transitions are in the ground configurations of Ar XIV (B-like) and Ar IX (F-like), and are associated with the coronal lines at 4412.4
and 5533.4 ÅŽ , respectively. The third is in the excited 2s2p configuration of Be-like Ar XV and produces the coronal line at 5943.73 Å. Our results for the three atomic level lifetimes are 9.32^0.12 ms for the Ar X 2s22p5 2P1/2 level, 9.70^0.15 ms for the Ar XIV 2s22p level, and 15.0^0.8 ms for the Ar XVo 2P3/2o 2s2p level. These results diff†er significantly from earlier measurements and are the most accurate ones to date
X-Ray Spectroscopic Laboratory Experiments In Support of the NASA X-Ray Astronomy Flight Program
During the 1997 performance period, our work focused on the L-shell X-ray emission from highly charged iron ions in the 10-18 A region. Details of our accomplishments in 1997 are presented in the following. We start by describing the laboratory measurements made and their impact on the X-ray flight program and conclude by an overview of new instrumental capabilities developed for uses in the coming year
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