21,190 research outputs found
Topological mechanochemistry of graphene
In view of a formal topology, two common terms, namely, connectivity and
adjacency, determine the quality of C-C bonds of sp2 nanocarbons. The feature
is the most sensitive point of the inherent topology of the species so that
such external action as mechanical deformation should obviously change it and
result in particular topological effects. The current paper describes the
effects caused by uniaxial tension of a graphene molecule in due course of a
mechanochemical reaction. Basing on the molecular theory of graphene, the
effects are attributed to both mechanical loading and chemical modification of
edge atoms of the molecule. The mechanical behavior is shown to be not only
highly anisotropic with respect to the direction of the load application, but
greatly dependent on the chemical modification of the molecule edge atoms thus
revealing topological character of the graphene deformation.Comment: 9 pages, 10 figures, 1 table. arXiv admin note: text overlap with
arXiv:1301.094
Mathematical modelling of the pathogenesis of multiple myeloma-induced bone disease
Multiple myeloma (MM) is the second most common haematological malignancy and results in destructive bone lesions. The interaction between MM cells and the bone microenvironment plays an important role in the development of the tumour cells and MM-induced bone disease and forms a 'vicious cycle' of tumour development and bone destruction, intensified by suppression of osteoblast activity and promotion of osteoclast activity. In this paper, a mathematical model is proposed to simulate how the interaction between MM cells and the bone microenvironment facilitates the development of the tumour cells and the resultant bone destruction. It includes both the roles of inhibited osteoblast activity and stimulated osteoclast activity. The model is able to mimic the temporal variation of bone cell concentrations and resultant bone volume after the invasion and then removal of the tumour cells and explains why MM-induced bone lesions rarely heal even after the complete removal of MM cells. The behaviour of the model compares well with published experimental data. The model serves as a first step to understand the development of MM-induced bone disease and could be applied further to evaluate the current therapies against MM-induced bone disease and even suggests new potential therapeutic targets
Monochorionic twins discordant for trisomy 13: A case report, systematic literature search and synthesis of available evidence
This article presents the tenth reported case of monochorionic twins discordant for
trisomy 13. Discordant aneuploidies in monochorionic twins are rare. Aetiologies
include mitotic error in early cell division and ārescueā chromosome loss in an initially trisomic zygote. Clinicians should offer early amniocentesis of both sacs and
consider selective termination
Treatment of esophageal achalasia in children: Today and tomorrow
Esophageal achalasia (EA) is a rare esophageal motility disorder in children. Laparoscopic Heller myotomy (LHM) represents the treatment of choice in young patients. Peroral endoscopic myotomy (POEM) is becoming an alternative to LHM. The aim of this study is to evaluate the effectiveness, safety, and outcomes of POEM vs LHM in treatment of children with EA.
Data of pediatric patients with EA, who underwent LHM and POEM from February 2009 to December 2013 in two centers, were collected.
Eighteen patients (9 male, mean age: 11.6 years; range: 2-17 years) were included. Nine patients (6 male, mean age: 10.7 years; range: 2-16 years) underwent LHM, and the other 9 (3 males, mean age: 12.2 years; range: 6-17 years) underwent POEM procedure. Mean operation time was shorter in POEM group compared with LHM group (62/149 minutes). Myotomy was longer in POEM group than in LHM group (11/7 cm). One major complication occurred after LHM (esophageal perforation). No clinical and manometric differences were observed between LHM and POEM in follow-up. The incidence of iatrogenic gastroesophageal reflux disease was low (1 patient in both groups).
Results of a midterm follow-up show that LHM and POEM are safe and effective treatments also in children. Besides, POEM is a mini-invasive technique with an inferior execution timing compared to LHM. A skilled endoscopic team is mandatory to perform this procedur
Full-mouth disinfection versus one-stage mechanical debridement in the management of adult periodontitis - microbiological morphotype monitoring
published_or_final_versio
Full-mouth disinfection versus one-stage full-mouth mechanical debridement in the management of adult periodontitis - clinical results
published_or_final_versio
Inflation and the cosmic microwave background
I give a status report and outlook concerning the use of the cosmic microwave
background anisotropies to constrain the inflationary cosmology, and stress its
crucial role as an underlying paradigm for the estimation of cosmological
parameters.Comment: 8 pages LaTeX file, with two figures incorporated using epsf. To
appear, proceedings of `The non-sleeping universe', Porto (Astrophysics and
Space Science
Intrinsic foot muscles act to stabilise the foot when greater fluctuations in centre of pressure movement result from increased postural balance challenge
Ā© 2020 The Author(s) Background: Increased postural balance challenge is associated with more fluctuations in centre of pressure movement, indicating increased interference from the postural control system. The role of intrinsic foot muscles in balance control is relatively understudied and whether such control system interference occurs at the level of these muscles is unknown. Research Question: Do fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge? Methods: Surface EMGs were recorded using a grid of 13 Ć 5 channels from the plantar surface of the foot of 17 participants, who completed three balance tasks: bipedal stance; single leg stance and bipedal tip-toe. Centre of pressure (CoP) movement was calculated from simultaneously recorded force plate signals. Fluctuations in CoP and EMGs for each task were quantified using a sample entropy based metric, Entropy Halflife (EnHL). Longer EnHL indicates fewer signal fluctuations. Results: The shortest EMG EnHL, 9.27 Ā± 3.34 ms (median Ā± interquartile range), occurred during bipedal stance and the longest during bipedal tip-toe 15.46 Ā± 11.16 ms, with 18.80 Ā± 8.00 ms recorded for single leg stance. Differences were statistically significant between bipedal stance and both bipedal tip-toe (p < 0.001) and single leg stance (p < 0.001). CoP EnHL for both anterior-posterior and medial-lateral movements also differed significantly between tasks (p < 0.001, both cases). However, anterior-posterior CoP EnHL was longest for bipedal stance 259.84Ā±230.22 ms and shortest for bipedal tip-toe 146.25Ā±73.35 ms. Medial-lateral CoP EnHL was also longest during bipedal stance 215.73Ā±187.58 ms, but shortest for single leg stance 113.48Ā±83.01 ms. Significance: Fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge. Fluctuations in CoP movement during balance must be predominantly driven by excitation of muscles extrinsic to the foot. Intrinsic foot muscles therefore likely play a greater role in stabilisation of the foot than balance control during the postural tasks studied
Quadratic optimal functional quantization of stochastic processes and numerical applications
In this paper, we present an overview of the recent developments of
functional quantization of stochastic processes, with an emphasis on the
quadratic case. Functional quantization is a way to approximate a process,
viewed as a Hilbert-valued random variable, using a nearest neighbour
projection on a finite codebook. A special emphasis is made on the
computational aspects and the numerical applications, in particular the pricing
of some path-dependent European options.Comment: 41 page
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