Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain

A (10x10) single-walled carbon nanotube consisting of 400 atoms with 20 layers is simulated under tensile loading using our developed O(N) parallel tight-binding molecular-dynamics algorithms. It is observed that the simulated carbon nanotube is able to carry the strain up to 122% of the relaxed tube length in elongation and up to 93% for compression. Young s modulus, tensile strength, and the Poisson ratio are calculated and the values found are 0.311 TPa, 4.92 GPa, and 0.287, respectively. The stress-strain curve is obtained. The elastic limit is observed at a strain rate of 0.09 while the breaking point is at 0.23. The frequency of vibration for the pristine (10x10) carbon nanotube in the radial direction is 4.71x10^3 GHz and it is sensitive to the strain rate.Comment: 11 pages, 8 figure

Continuous oral contraceptives versus long-term pituitary desensitization prior to IVF/ICSI in moderate to severe endometriosis:study protocol of a non-inferiority randomized controlled trial

STUDY QUESTIONS: The primary objective is to investigate if continuous use of oral contraceptives is non-inferior compared to long-term pituitary desensitization with a GnRH agonist prior to IVF/ICSI in patients with moderate to severe endometriosis with regard to treatment efficacy. Secondary objectives concern treatment safety and cost-effectiveness. WHAT IS KNOWN ALREADY: Long-term pituitary desensitization with a GnRH agonist for 3-6 months prior to IVF/ICSI improves clinical pregnancy rates in women suffering from endometriosis. However, discussion about this treatment strategy exists because of its uncomfortable side effects. Alternatively, IVF/ICSI pre-treatment with continuously administered oral contraceptives may offer fewer side-effects and lower (in)direct costs, as well as encouraging IVF outcomes in women with endometriosis. To date, these two different IVF/ICSI pre-treatment strategies in women with endometriosis have not been directly compared. STUDY DESIGN SIZE DURATION: An open-label, parallel two-arm randomized controlled multicenter trial is planned, including patients with moderate to severe endometriosis. To demonstrate an absolute difference of 13% (delta of 10% with non-inferiority margin of 3%) with a power of 80% 137 patients per group are sufficient. Taking into account a withdrawal of patients of 10% and a cancelation rate of embryo transfer after ovarian pick up of 10% (for instance due to fertilization failure), the sample size calculation is rounded off to 165 patients per group; 330 patients in total will be included. After informed consent, eligible patients will be randomly allocated to the intervention or reference group by using web based block randomization stratified per centre. Study inclusion is expected to be complete in 3-5 years. PARTICIPANTS/MATERIALS SETTING METHODS: The research population consists of patients with moderate to severe endometriosis (ASRM III/IV) who are scheduled for their first, second or third IVF/ICSI treatment attempt. Women aged over 41 years, younger than 18 years, with a known contraindication for the use of oral contraceptives and/or GnRH agonists or with severe male factor infertility will be excluded from participation. After informed consent patients are allocated to the intervention group (one-phase oral contraceptive continuously during three subsequent months) or the reference group (three Leuprorelin 3.75 mg i.m./s.c. depot injections during three subsequent months). Tibolon 2.5 mg can be given daily as add-back therapy in the reference group. After 3 months of pre-treatment the IVF/ICSI stimulation phase will be started. The primary outcome is live birth rate after fresh embryo transfer. Secondary outcomes are cumulative live birth rate after one IVF/ICSI treatment cycle (including fresh and frozen embryo transfers up to 15 months after randomization), ongoing pregnancy rate and time to pregnancy. In addition, treatment outcome parameters, adverse events, side-effects during the first 3 months, complications, recurrence of endometriosis (complaints), quality of life, patient preferences, safety and costs effectiveness will be reported. Measurements will be performed at baseline and at 3, 6, 9, 12 and 15 months after randomization. STUDY FUNDING/COMPETING INTERESTs: All authors have no conflict of interest related to this manuscript. The department of reproductive medicine of the Amsterdam UMC location VUmc has received several research and educational grants from Guerbet, Merck and Ferring not related to the submitted work. TRIAL REGISTRATION NUMBER: The trial is registered as the COPIE trial (Continuous use of Oral contraceptives as an alternative for long-term Pituitary desensitization with a GnRH agonist prior to IVF/ICSI in Endometriosis patients) in the Dutch Trial Register (Ref. No. NTR6357, http://www.trialregister.nl). TRIAL REGISTRATION DATE: 16 March 2017. DATE OF FIRST PATIENT’S ENROLMENT: Enrollment is planned for November 2018

Language motivation in a reconfigured Europe: access, identity, autonomy

In this paper, I propose that we need to develop an appropriate set of conceptual tools for examining motivational issues pertaining to linguistic diversity, mobility and social integration in a rapidly changing and expanding Europe. I begin by drawing on research that has begun to reframe the concept of integrative motivation in the context of theories of self and identity. Expanding the notion of identity, I discuss the contribution of the Council of Europe's European Language Portfolio in promoting a view of motivation as the development of a plurilingual European identity and the enabling of access and mobility across a multilingual Europe. Next, I critically examine the assumption that the individual pursuit of a plurilingual identity is unproblematic, by highlighting the social context in which motivation and identity are constructed and embedded. To illuminate the role of this social context, I explore three inter-related theoretical frameworks: poststructuralist perspectives on language motivation as 'investment'; sociocultural theory; and theories of autonomy in language education. I conclude with the key message that, as with autonomy, language motivation today has an inescapably political dimension of which we need to take greater account in our research and pedagogical practice

Structure-Sensitive Mechanism of Nanographene Failure

The response of a nanographene sheet to external stresses is considered in terms of a mechanochemical reaction. The quantum chemical realization of the approach is based on a coordinate-of-reaction concept for the purpose of introducing a mechanochemical internal coordinate (MIC) that specifies a deformational mode. The related force of response is calculated as the energy gradient along the MIC, while the atomic configuration is optimized over all of the other coordinates under the MIC constant-pitch elongation. The approach is applied to the benzene molecule and (5, 5) nanographene. A drastic anisotropy in the microscopic behavior of both objects under elongation along a MIC has been observed when the MIC is oriented either along or normally to the C-C bonds chain. Both the anisotropy and high stiffness of the nanographene originate at the response of the benzenoid unit to stress.Comment: 19 pages, 7 figures 1 tabl

Atomistic Simulations of Nanotube Fracture

The fracture of carbon nanotubes is studied by atomistic simulations. The fracture behavior is found to be almost independent of the separation energy and to depend primarily on the inflection point in the interatomic potential. The rangle of fracture strians compares well with experimental results, but predicted range of fracture stresses is marketly higher than observed. Various plausible small-scale defects do not suffice to bring the failure stresses into agreement with available experimental results. As in the experiments, the fracture of carbon nanotubes is predicted to be brittle. The results show moderate dependence of fracture strength on chirality.Comment: 12 pages, PDF, submitted to Phy. Rev.

Combinatorial nuclear level density by a Monte Carlo method

We present a new combinatorial method for the calculation of the nuclear level density. It is based on a Monte Carlo technique, in order to avoid a direct counting procedure which is generally impracticable for high-A nuclei. The Monte Carlo simulation, making use of the Metropolis sampling scheme, allows a computationally fast estimate of the level density for many fermion systems in large shell model spaces. We emphasize the advantages of this Monte Carlo approach, particularly concerning the prediction of the spin and parity distributions of the excited states, and compare our results with those derived from a traditional combinatorial or a statistical method. Such a Monte Carlo technique seems very promising to determine accurate level densities in a large energy range for nuclear reaction calculations.Comment: 30 pages, LaTex, 7 figures (6 Postscript figures included). Fig. 6 upon request to the autho

Universal Equilibrium Currents in the Quantum Hall Fluid

The equilibrium current distribution in a quantum Hall fluid that is subjected to a slowly varying confining potential is shown to generally consist of strips or channels of current, which alternate in direction, and which have universal integrated strengths. A measurement of these currents would yield direct independent measurements of the proper quasiparticle and quasihole energies in the fractional quantum Hall states.Comment: 4 pages, Revte

Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields

The magnetoresistivity tensor of an interacting two-dimensional electron system with a lateral and unidirectional electric or magnetic modulation, in a perpendicular quantizing magnetic field, is calculated within the Kubo formalism. The influence of the spin splitting of the Landau bands and of the density of states (DOS) on the internal structure of the Shubnikov-de Haas oscillations is analyzed. The Coulomb electron - electron interaction is responsible for strong screening and exchange effects and is taken into account in a screened Hartree-Fock approximation, in which the exchange contribution is calculated self-consistently with the DOS at the Fermi level. This approximation describes both the exchange enhancement of the spin splitting and the formation of compressible edge strips, unlike the simpler Hartree and Hartree-Fock approximations, which yield either the one or the other.Comment: 20 pages, revtex, 7 ps figures, to appear in Phys. Rev.

Variação diária da temperatura do solo em um sistema agroflorestal de cafeeiro (Coffea arabica L.) com seringueiras (Hevea brasiliensis Müell. Arg.).

A temperatura afeta praticamente todos os processos fisiológicos das plantas. A germinação, respiração, transpiração, atividade fotossintética, e demais processos fisiológicos são afetados e, em certa extensão, controlados pela temperatura. Em solo nu ocorre grande amplitude de variação, podendo atingir altas temperaturas, inadequadas ao desenvolvimento radicular. Com o intuito de observar a variação da temperatura do solo em um Sistema Agroflorestal (SAF) foi realizado em Piracicaba, SP um experimento do consórcio de seringueiras e cafeeiros

Identification of DNA methylation changes at cis-regulatory elements during early steps of HSC differentiation using tagmentation-based whole genome bisulfite sequencing

Epigenetic alterations during cellular differentiation are a key molecular mechanism which both instructs and reinforces the process of lineage commitment. Within the haematopoietic system, progressive changes in the DNA methylome of haematopoietic stem cells (HSCs) are essential for the effective production of mature blood cells. Inhibition or loss of function of the cellular DNA methylation machinery has been shown to lead to a severe perturbation in blood production and is also an important driver of malignant transformation. HSCs constitute a very rare cell population in the bone marrow, capable of life-long self-renewal and multi-lineage differentiation. The low abundance of HSCs has been a major technological barrier to the global analysis of the CpG methylation status within both HSCs and their immediate progeny, the multipotent progenitors (MPPs). Within this Extra View article, we review the current understanding of how the DNA methylome regulates normal and malignant hematopoiesis. We also discuss the current methodologies that are available for interrogating the DNA methylation status of HSCs and MPPs and describe a new data set that was generated using tagmentation-based whole genome bisulfite sequencing (TWGBS) in order to comprehensively map methylated cytosines using the limited amount of genomic DNA that can be harvested from rare cell populations. Extended analysis of this data set clearly demonstrates the added value of genome-wide sequencing of methylated cytosines and identifies novel important cis-acting regulatory regions that are dynamically remodeled during the first steps of haematopoietic differentiation