621 research outputs found
Trapping of 27 bp - 8 kbp DNA and immobilization of thiol-modified DNA using dielectrophoresis
Dielectrophoretic trapping of six different DNA fragments, sizes varying from
the 27 to 8416 bp, has been studied using confocal microscopy. The effect of
the DNA length and the size of the constriction between nanoscale fingertip
electrodes on the trapping efficiency have been investigated. Using finite
element method simulations in conjunction with the analysis of the experimental
data, the polarizabilities of the different size DNA fragments have been
calculated for different frequencies. Also the immobilization of trapped
hexanethiol- and DTPA-modified 140 nm long DNA to the end of gold
nanoelectrodes was experimentally quantified and the observations were
supported by density functional theory calculations.Comment: 17 pages (1 column version), 8 figure
Para to Ortho transition of metallic dimers on Si(001)
Extensive electronic structure calculations are performed to obtain the
stable geometries of metals like Al, Ga and In on the Si(001) surface at 0.5 ML
and 1 ML coverages. Our results coupled with previous theoretical findings
explain the recent experimental data in a comprehensive fashion. At low
coverages, as shown by previous works, `Para' dimers give the lowest energy
structure. With increasing coverage beyond 0.5 ML, `Ortho' dimers become part
of low energy configurations leading toward a `Para' to `Ortho' transition at 1
ML coverage. For In mixed staggered dimers (`Ortho' and `Para') give the lowest
energy configuration. For Ga, mixed dimers are non-staggered, while for Al
`Para' to `Ortho' transition of dimers is complete. Thus at intermediate
coverages between 0.5 and 1 ML, the `Ortho' and `Para' dimers may coexist on
the surface. Consequently, this may be an explanation of the fact that the
experimental observations can be successfully interpreted using either
orientation. A supported zigzag structure at 0.5 ML, which resembles , does not undergo a dimerization transition, and hence stays
semi-metallic. Also, unlike the soliton formation is ruled out
for this structure.Comment: 8 pages, 6 figure
The neuromuscular, biochemical, and endocrine responses to a single-session vs. double-session training day in elite athletes
Purpose:
The aim of this study was to compare the acute neuromuscular, biochemical, and endocrine responses of a
training day consisting of a speed session only to performing a speed and weight training session on the same day.
Methods:
Fifteen male academy level rugby players completed two
protocols in a randomized order. The speed only protocol
involved performing 6 maximal effort repetitions of 50m running sprints with 5 minutes recovery between each sprint, while the speed and weights protocol involved the same
sprinting session but was followed 2h post by a lower body weights session consisting of 4 sets of 5 back squat and Romanian deadlift at 85% 1RM. Testosterone, cortisol, creatine kinase, lactate, and perceived muscle soreness were
determined immediately before, immediately after, 2h post,
and 24h post both protocols. Peak power, relative peak power, jump height, and average rate of force development
were determined from a counter movement jump (CMJ) at
the same time points.
Results:
At 24h post, muscle soreness was significantly higher
following the speed and weights protocol compared to speed only protocol (effect size eta2= .253, F=4.750, p < 0.05).
There was no significant difference between any of the CMJ variables at any of the post training time points. Likewise creatine kinase, testosterone, and cortisol were unaffected by the addition of a weight training session.
Conclusion:
These data indicate that the addition of a weight training
session 2h post a speed session, while increasing the perception of fatigue the following day, does not result in a difference in endocrine response or in neuromuscular capability
Molecular dynamics study of melting of a bcc metal-vanadium II : thermodynamic melting
We present molecular dynamics simulations of the thermodynamic melting
transition of a bcc metal, vanadium using the Finnis-Sinclair potential. We
studied the structural, transport and energetic properties of slabs made of 27
atomic layers with a free surface. We investigated premelting phenomena at the
low-index surfaces of vanadium; V(111), V(001), and V(011), finding that as the
temperature increases, the V(111) surface disorders first, then the V(100)
surface, while the V(110) surface remains stable up to the melting temperature.
Also, as the temperature increases, the disorder spreads from the surface layer
into the bulk, establishing a thin quasiliquid film in the surface region. We
conclude that the hierarchy of premelting phenomena is inversely proportional
to the surface atomic density, being most pronounced for the V(111) surface
which has the lowest surface density
PCV170 The Association of Hosptial Type and Stroke Centre With Mortality, Length of Stay and Hospital Cost of Ischemic Stroke Patients in Alberta
A review of recent perspectives on biomechanical risk factors associated with anterior cruciate ligament injury
There is considerable evidence to support a number of biomechanical risk factors associated with non-contact anterior cruciate ligament (ACL) injury. This paper aimed to review these biomechanical risk factors and highlight future directions relating to them. Current perspectives investigating trunk position and relationships between strength, muscle activity and biomechanics during landing/cutting highlight the importance of increasing hamstring muscle force during dynamic movements through altering strength, muscle activity, muscle length and contraction velocity. In particular, increased trunk flexion during landing/cutting and greater hamstring strength are likely to increase hamstring muscle force during landing and cutting which have been associated with reduced ACL injury risk. Decision making has also been shown to influence landing biomechanics and should be considered when designing tasks to assess landing/cutting biomechanics. Coaches should therefore promote hamstring strength training and active trunk flexion during landing and cutting in an attempt to reduce ACL injury risk.Peer reviewe
Mechanical properties and formation mechanisms of a wire of single gold atoms
A scanning tunneling microscope (STM) supplemented with a force sensor is
used to study the mechanical properties of a novel metallic nanostructure: a
freely suspended chain of single gold atoms. We find that the bond strength of
the nanowire is about twice that of a bulk metallic bond. We perform ab initio
calculations of the force at chain fracture and compare quantitatively with
experimental measurements. The observed mechanical failure and nanoelastic
processes involved during atomic wire fabrication are investigated using
molecular dynamics (MD) simulations, and we find that the total effective
stiffness of the nanostructure is strongly affected by the detailed local
atomic arrangement at the chain bases.Comment: To be published in Phys. Rev. Lett. 4 pages with 3 figure
Uncertainty in maritime risk analysis: Extended case study on chemical tanker collisions
Uncertainty is inherent to risk analysis. Therefore, it is extremely important to properly address the issue of uncertainty. In the field of risk analysis for maritime transportation systems, the effect of uncertainty is rarely discussed or quantified. For this reason, this article discusses a case study dealing with risk analysis for a chemical spill in the Gulf of Finland and analyses the related uncertainties by adopting a systematic framework. Risk is assessed in terms of the expected spill frequency and spill volumes caused by collisions between ships and chemical tankers in the Gulf of Finland. This is done by applying a collision consequence with a novel approach-to-collision-speed linkage model and Gulf of Finland-specific causation factors, which are based on reanalysing accident data. This article also presents a metamodel for assessing collision probability with initial vessel speeds for any given scenario where a chemical tanker is about to be struck by another vessel. Even when conducting a risk analysis using state-of-the-art methods, there is still a medium-high degree of uncertainty in the model presented in this article, which only becomes apparent when conducting a systematic uncertainty assessment analysis. However, an uncertainty assessment is an important part of quantitative maritime risk analysis. For this purpose, a qualitative framework for uncertainty assessment analysis is introduced for general use in the field of maritime risk analysis.</p
Effect of combined uphill-downhill sprint training on kinematics and maximum running speed in experienced sprinters
This study examined the effects of sprint running training on sloping surfaces (3°) in experienced sprinters using selected kinematic variables. Twelve experienced sprinters were randomly allocated to two training groups (combined uphill–downhill and horizontal). Pre- and post-training tests were performed to examine the effects of six weeks of training on maximum running speed, step rate, step length, step time, contact time, braking and propulsive phase of contact time, flight time and selected postural characteristics during a step cycle in the final steps of a 35m sprint test. In the combined uphill–downhill training group, maximum running speed was substantially greater (from 9.08 ± 0.90 m s-1 to 9.51 ± 0.62 m s-1; p <0.05) after training by 4.8%; step rate, contact time, step time and concentric phase was not modified. There were no significant changes in maximal speed or sprint kinematics in the horizontal training group. Overall, the posture characteristics did not change with training. The combined uphill–downhill training method was substantially more effective in improving the maximum running speed in experienced sprinters than a traditional horizontal training method
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