Strains and pseudo-magnetic fields in circular graphene rings

We demonstrate that circular graphene ring under a shear stress displays strong pseudo-magnetic fields. We calculate the pseudo-magnetic field both from continuum elasticity theory as well as molecular dynamics simulations. Stable wrinkles are induced by shear deformations and lead to enhancement of the pseudo-magnetic field. The strong pseudo-magnetic field found here can be observed by imaging graphene flake at the atomic level e.g. through scanning tunneling microscope.Comment: 11 pages, 8 figures. (Appendixes A and B are added) To appear in Phys. Rev.

The Effect of Vitrification on Mouse Oocyte Apoptosis by Cryotop Method

Background: Oocyte cryopreservation is one of the most important topics in the field of assisted reproductive technology to preserve women fertility, but relationship between cryopreservation and apoptosis is still a matter of debate. The present study was aimed to investigate the effects of vitrification on apoptosis in mouse oocytes by Cryotop method. Method: A total of 200 germinal vesicle (GV) and 200 metaphase II (MII) oocytes were obtained from ovaries and fallopian tubes of NMRI mice, respectively and divided into control and experimental groups. Oocytes in experimental group were vitrified by Cryotop using vitrification medium and were kept in liquid nitrogen for one month. The survival rate of oocytes was evaluated after 2 hour incubation time. Then, the oocyte apoptosis was evaluated by TUNEL technique and compared with those in control group. The data was compared statistically using SPSS software and chi-square test. Results: The survival rates of vitrified GV (93%) and MII oocytes (88%) showed a significant decrease compared with the control group (P<0.05), but there was no significant difference in survival rate of both vitrified oocyte groups. The incidence of apoptosis in vitrified and control GV oocytes showed no significant difference (13% vs. 7%), but the rate of apoptosis in vitrified MII oocytes increased significantly not only in comparison with MII control group (25% vs. 5%) but also with vitrified GV oocytes (P<0.05). Conclusion: The results indicate that vitrification increases apoptosis in mouse MII oocytes and apoptosis may play a role in MII oocyte injury after vitrification

Topological electric current from time-dependent elastic deformations in graphene

We show the possibility of inducing an edge charge current by applying time-dependent strain in gapped graphene samples preserving time reversal symmetry. We demonstrate that this edge current has the same origin as the valley Hall response known to exist in the system.Comment: 5 pages, 3 figures, Accepted for publication in Phys. Rev.

Irreversibility in response to forces acting on graphene sheets

The amount of rippling in graphene sheets is related to the interactions with the substrate or with the suspending structure. Here, we report on an irreversibility in the response to forces that act on suspended graphene sheets. This may explain why one always observes a ripple structure on suspended graphene. We show that a compression-relaxation mechanism produces static ripples on graphene sheets and determine a peculiar temperature $T_c$, such that for $T<T_c$ the free-energy of the rippled graphene is smaller than that of roughened graphene. We also show that $T_c$ depends on the structural parameters and increases with increasing sample size.Comment: 4 pages, 4 Figure

Conductance of bilayer graphene in the presence of a magnetic field: Effects of disorder

We investigate the electronic transport properties of unbiased and biased bilayer graphene nanoribbon in n-p and n-n junctions subject to a perpendicular magnetic field. Using the non-equilibrium Green's function method and the Landauer-B\"{u}ttiker formalism, the conductance is studied for the cases of clean, on-site, and edge disordered bilayer graphene. We show that the lowest Hall plateau remains unchanged in the presence of disorder, whereas asymmetry destroys both the plateaus and conductance quantization. In addition, we show that disorder induces an enhancement of the conductance in the n-p region in the presence of magnetic fields. Finally, we show that the equilibration of quantum Hall edge states between distinctively doped regions causes Hall plateaus to appear in the regime of complete mode mixing.Comment: 8 pages, 7 figures. Accepted to Phys. Rev.

Effect of CRP on Some of the in vitro Physicochemical Properties of LDL

Abstract &nbsp;&nbsp; BACKGROUND: Atherosclerosis is the most important underlying cause of cardiovascular diseases (CVD) which recently has been classified as an inflammatory disorder. Accumulation of large amounts of oxidized LDL in the intima during local inflammation reaction led to increase several factors such as C -reactive protein (CRP). It has also been reported that CRP is able to bind with modified forms of LDL as well as oxidized LDL. These findings suggest possible positive or negative involvement of this protein in atherogenesis. The main objective of the present study was to assess the influence of CRP on LDL oxidation and the possible physical \changes of LDL in the presence of CRP in vitro. &nbsp;&nbsp; METHODS: In this study, the susceptibility of purified LDL to oxidation was assayed by monitoring of formation of conjugated dienes in different physiological concentrations of CRP (0 - 0.5 -2&nbsp; &micro;g/ml) using a shimadzu spectrophotometer. Electrophoresis was used to determine the electrophoretic mobility of LDL in those conditions. &nbsp;&nbsp; RESULTS: CRP significantly reduced the susceptibility of Cu++ -induced LDL oxidation through increasing the lag timeand there was positive relationship between these findings and CRP concentration (P &lt; 0.05). CRP caused a significant reduction in the electrophotretic mobility of LDL compared to native LDL (n-LDL) (P&lt;0.05).&nbsp; &nbsp;&nbsp; CONCLUSION: A considerable reduction was shown in LDL oxidation, in higher concentration of CRP, via an unknown mechanism. The electrophoretic mobility of LDL, in the oxidative condition, decreases in the presence of CRP compared to n-LDL, which can be indicative of the effect of this protein on the physical and chemical properties of LDL. It seems that, other pathway than LDL oxidation is responsible for the effect of CRP on the atherogenesis processes. &nbsp; &nbsp;&nbsp; Keywords: Atherosclerosis, Creactive protein, Low-density lipoprotein, Inflammation. &nbsp;</p

Stochastic ϕ4−\phi^4-Theory in the Strong Coupling Limit

The stochastic $\phi^4$-theory in $d-$dimensions dynamically develops domain wall structures within which the order parameter is not continuous. We develop a statistical theory for the $\phi^4$-theory driven with a random forcing which is white in time and Gaussian-correlated in space. A master equation is derived for the probability density function (PDF) of the order parameter, when the forcing correlation length is much smaller than the system size, but much larger than the typical width of the domain walls. Moreover, exact expressions for the one-point PDF and all the moments $$ are given. We then investigate the intermittency issue in the strong coupling limit, and derive the tail of the PDF of the increments $\phi(x_2) - \phi(x_1)$. The scaling laws for the structure functions of the increments are obtained through numerical simulations. It is shown that the moments of field increments defined by, $C_b=$, behave as $|x_1-x_2|^{\xi_b}$, where $\xi_b=b$ for $b\leq 1$, and $\xi_b=1$ for $b\geq1$Comment: 22 pages, 6 figures. to appear in Nuclear. Phys.

The Aharonov-Bohm effect in graphene rings

This is a review of electronic quantum interference in mesoscopic ring structures based on graphene, with a focus on the interplay between the Aharonov-Bohm effect and the peculiar electronic and transport properties of this material. We first present an overview on recent developments of this topic, both from the experimental as well as the theoretical side. We then review our recent work on signatures of two prominent graphene-specific features in the Aharonov-Bohm conductance oscillations, namely Klein tunneling and specular Andreev reflection. We close with an assessment of experimental and theoretical development in the field and highlight open questions as well as potential directions of the developments in future work.Comment: review article for "Special Issue on Graphene", to appear in "Solid State Communications

Effect of a gap opening on the conductance of graphene superlattices

The electronic transmission and conductance of a gapped graphene superlattice were calculated by means of the transfer-matrix method. The system that we study consists of a sequence of electron-doped graphene as wells and hole-doped graphene as barriers. We show that the transmission probability approaches unity at some critical value of the gap. We also find that there is a domain around the critical gap value for which the conductance of the system attains its maximum value.Comment: 14 pages, 5 figures. To appear in Solid State Communication