116 research outputs found
Is Primary Fixation with the Sliding Hip Screw Introduced into the Non-ideal Position Sufficient for Stable Pertrochanteric Fracture Stabilisation? A Biomechanical Evaluation and Experimental Study
Purpose: Proximal femoral fractures are most commonly sustained fractures in the elderly. The one of the current treatment option of stable pertrochanteric fracture is Sliding Hip Screw. The necessity of a repeat surgery, due to the failure of the first osteosynthesis, may jeopardize the patient's life. Common causes of a failure include: fracture pattern, implant position, implant's properties and the bone quality. Each screw position variant results in damage to various load-bearing bone structures during healing. The aim of this study was analysis of different screw positions with focuse on the risky position with the need of the intra-operative implant reintroduction.Methods: With the use of a numerical computational model and finite element methods, the authors analyzed five positions of Sliding Hip Screw in the proximal femur, with the objective of determining positions with an increased risk of failure. The ideal position was in the middle third of the femoral neck anchored subchondrally.Results: In model situations, it has been shown that in stable fractures the screw position in proximal third of the femoral neck significantly increased the strain of the plate and screw and may lead to the osteosynthesis failure. The other analysed positions do not significantly increase the risk of failure for entire fixation. Conclusions: It is not necessary to re-introduce Sliding Hip Screw into the ideal position (except placening in the proximal third of the neck) during the surgery. Damage to load-bearing structures relative to various implant placements does not impact the resultant overall fixation stability
Diffusion of Mn interstitials in (Ga,Mn)As epitaxial layers
Magnetic properties of thin (Ga,Mn)As layers improve during annealing by
out-diffusion of interstitial Mn ions to a free surface. Out-diffused Mn atoms
participate in the growth of a Mn-rich surface layer and a saturation of this
layer causes an inhibition of the out-diffusion. We combine high-resolution
x-ray diffraction with x-ray absorption spectroscopy and a numerical solution
of the diffusion problem for the study of the out-diffusion of Mn interstitials
during a sequence of annealing steps. Our data demonstrate that the
out-diffusion of the interstitials is substantially affected by the internal
electric field caused by an inhomogeneous distribution of charges in the
(Ga,Mn)As layer.Comment: 11 pages, 5 figure
Disc-oscillation resonance and neutron star QPOs: 3:2 epicyclic orbital model
The high-frequency quasi-periodic oscillations (HF QPOs) that appear in the
X-ray fluxes of low-mass X-ray binaries remain an unexplained phenomenon. Among
other ideas, it has been suggested that a non-linear resonance between two
oscillation modes in an accretion disc orbiting either a black hole or a
neutron star plays a role in exciting the observed modulation. Several possible
resonances have been discussed. A particular model assumes resonances in which
the disc-oscillation modes have the eigenfrequencies equal to the radial and
vertical epicyclic frequencies of geodesic orbital motion. This model has been
discussed for black hole microquasar sources as well as for a group of neutron
star sources. Assuming several neutron (strange) star equations of state and
Hartle-Thorne geometry of rotating stars, we briefly compare the frequencies
expected from the model to those observed. Our comparison implies that the
inferred neutron star radius "RNS" is larger than the related radius of the
marginally stable circular orbit "rms" for nuclear matter equations of state
and spin frequencies up to 800Hz. For the same range of spin and a strange star
(MIT) equation of state, the inferrred radius RNS is roughly equal to rms. The
Paczynski modulation mechanism considered within the model requires that RNS <
rms. However, we find this condition to be fulfilled only for the strange
matter equation of state, masses below one solar mass, and spin frequencies
above 800Hz. This result most likely falsifies the postulation of the neutron
star 3:2 resonant eigenfrequencies being equal to the frequencies of geodesic
radial and vertical epicyclic modes. We suggest that the 3:2 epicyclic modes
could stay among the possible choices only if a fairly non-geodesic accretion
flow is assumed, or if a different modulation mechanism operates.Comment: 7 pages, 4 figures (in colour), accepted for publication in Astronomy
& Astrophysic
Quasiperiodic oscillations in a strong gravitational field around neutron stars testing braneworld models
The strong gravitational field of neutron stars in the brany universe could
be described by spherically symmetric solutions with a metric in the exterior
to the brany stars being of the Reissner-Nordstrom type containing a brany
tidal charge representing the tidal effect of the bulk spacetime onto the star
structure. We investigate the role of the tidal charge in orbital models of
high-frequency quasiperiodic oscillations (QPOs) observed in neutron star
binary systems. We focus on the relativistic precession model. We give the
radial profiles of frequencies of the Keplerian (vertical) and radial epicyclic
oscillations. We show how the standard relativistic precession model modified
by the tidal charge fits the observational data, giving estimates of the
allowed values of the tidal charge and the brane tension based on the processes
going in the vicinity of neutron stars. We compare the strong field regime
restrictions with those given in the weak-field limit of solar system
experiments.Comment: 26 pages, 6 figure
Anomalous Magnetoresistance by Breaking Ice Rule in Bi2Ir2O7/Dy2Ti2O7 Heterostructure
While geometrically frustrated quantum magnets are known for a variety of
exotic spin states that are of great interests of understanding emergent
phenomena as well as enabling revolutionary quantum technologies, most of them
are necessarily good insulators which are difficult to be integrated with
modern electrical circuit that relies on moving charge carriers. The grand
challenge of converting fluctuations and excitations of frustrated moments into
electronic responses is finding ways to introduce charge carriers that interact
with the localized spins without destroying the spin states. Here, we show
that, by designing a Bi2Ir2O7/Dy2Ti2O7 heterostructure, the breaking of the
spin ice rule in insulating Dy2Ti2O7 can lead to a charge response in the
Bi2Ir2O7 conducting layer that can be detected as anomalous magnetoresistance.
These results demonstrate a novel and feasible interfacial approach for
electronically probing exotic spin states in insulating magnets, laying out a
blueprint for the metallization of frustrated quantum magnets
Farsighted Risk Mitigation of Lateral Movement Using Dynamic Cognitive Honeypots
Lateral movement of advanced persistent threats has posed a severe security
challenge. Due to the stealthy and persistent nature of the lateral movement,
defenders need to consider time and spatial locations holistically to discover
latent attack paths across a large time-scale and achieve long-term security
for the target assets. In this work, we propose a time-expanded random network
to model the stochastic service links in the user-host enterprise network and
the adversarial lateral movement. We design cognitive honeypots at idle
production nodes and disguise honey links as service links to detect and deter
the adversarial lateral movement. The location of the honeypot changes randomly
at different times and increases the honeypots' stealthiness. Since the
defender does not know whether, when, and where the initial intrusion and the
lateral movement occur, the honeypot policy aims to reduce the target assets'
Long-Term Vulnerability (LTV) for proactive and persistent protection. We
further characterize three tradeoffs, i.e., the probability of interference,
the stealthiness level, and the roaming cost. To counter the curse of multiple
attack paths, we propose an iterative algorithm and approximate the LTV with
the union bound for computationally efficient deployment of cognitive
honeypots. The results of the vulnerability analysis illustrate the bounds,
trends, and a residue of LTV when the adversarial lateral movement has infinite
duration. Besides honeypot policies, we obtain a critical threshold of
compromisability to guide the design and modification of the current system
parameters for a higher level of long-term security. We show that the target
node can achieve zero vulnerability under infinite stages of lateral movement
if the probability of movement deterrence is not less than the threshold
Updating algal evolutionary relationships through plastid genome sequencing: did alveolate plastids emerge through endosymbiosis of an ochrophyte?
Algae with secondary plastids of a red algal origin, such as ochrophytes (photosynthetic stramenopiles), are diverse and ecologically important, yet their evolutionary history remains controversial. We sequenced plastid genomes of two ochrophytes, Ochromonas sp. CCMP1393 (Chrysophyceae) and Trachydiscus minutus (Eustigmatophyceae). A shared split of the clpC gene as well as phylogenomic analyses of concatenated protein sequences demonstrated that chrysophytes and eustigmatophytes form a clade, the Limnista, exhibiting an unexpectedly elevated rate of plastid gene evolution. Our analyses also indicate that the root of the ochrophyte phylogeny falls between the recently redefined Khakista and Phaeista assemblages. Taking advantage of the expanded sampling of plastid genome sequences, we revisited the phylogenetic position of the plastid of Vitrella brassicaformis, a member of Alveolata with the least derived plastid genome known for the whole group. The results varied depending on the dataset and phylogenetic method employed, but suggested that the Vitrella plastids emerged from a deep ochrophyte lineage rather than being derived vertically from a hypothetical plastid-bearing common ancestor of alveolates and stramenopiles. Thus, we hypothesize that the plastid in Vitrella, and potentially in other alveolates, may have been acquired by an endosymbiosis of an early ochrophyte
Divergence across mitochondrial genomes of sympatric members of the Schistosoma indicum group and clues into the evolution of Schistosoma spindale
Schistosoma spindale and Schistosoma indicum are ruminant-infecting trematodes of the Schistosoma indicum group that are widespread across Southeast Asia. Though neglected, these parasites can cause major pathology and mortality to livestock leading to significant welfare and socio-economic issues, predominantly amongst poor subsistence farmers and their families. Here we used mitogenomic analysis to determine the relationships between these two sympatric species of schistosome and to characterise S. spindale diversity in order to identify possible cryptic speciation. The mitochondrial genomes of S. spindale and S. indicum were assembled and genetic analyses revealed high levels of diversity within the S. indicum group. Evidence of functional changes in mitochondrial genes indicated adaptation to environmental change associated with speciation events in S. spindale around 2.5 million years ago. We discuss our results in terms of their theoretical and applied implications
Influence of 'Trichobilharzia regenti' (Digenea: Schistosomatidae) on the defence activity of 'Radix lagotis' (Lymnaeidae) haemocytes
Radix lagotis is an intermediate snail host of the nasal bird schistosome Trichobilharzia regenti. Changes in defence responses in infected snails that might be related to host-parasite compatibility are not known. This study therefore aimed to characterize R. lagotis haemocyte defence mechanisms and determine the extent to which they are modulated by T. regenti. Histological observations of R. lagotis infected with T. regenti revealed that early phases of infection were accompanied by haemocyte accumulation around the developing larvae 2â36 h post exposure (p.e.) to the parasite. At later time points, 44â92 h p.e., no haemocytes were observed around T. regenti. Additionally, microtubular aggregates likely corresponding to phagocytosed ciliary plates of T. regenti miracidia were observed within haemocytes by use of transmission electron microscopy. When the infection was in the patent phase, haemocyte phagocytic activity and hydrogen peroxide production were significantly reduced in infected R. lagotis when compared to uninfected counterparts, whereas haemocyte abundance increased in infected snails. At a molecular level, protein kinase C (PKC) and extracellular-signal regulated kinase (ERK) were found to play an important role in regulating these defence reactions in R. lagotis. Moreover, haemocytes from snails with patent infection displayed lower PKC and ERK activity in cell adhesion assays when compared to those from uninfected snails, which may therefore be related to the reduced defence activities of these cells. These data provide the first integrated insight into the immunobiology of R. lagotis and demonstrate modulation of haemocyte-mediated responses in patent T. regenti infected snails. Given that immunomodulation occurs during patency, interference of snail-host defence by T. regenti might be important for the sustained production and/or release of infective cercariae
Compatibilization of low-density polyethylene/polystyrene blends by segmented EB(PS-block-EB) n block copolymers
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