Mass inflation in f(R) gravity: A conjecture on the resolution of the mass inflation singularity

We study gravitational collapse of a charged black hole in f(R) gravity using double-null formalism. We require cosmological stability to f(R) models; we used the Starobinsky model and the R + (1/2)cR^2 model. Charged black holes in f(R) gravity can have a new type of singularity due to higher curvature corrections, the so-called f(R)-induced singularity, although it is highly model-dependent. As the advanced time increases, the internal structure will approach the Cauchy horizon, which may not be an inner apparent horizon. There is mass inflation as one approaches the Cauchy horizon and hence the Cauchy horizon may be a curvature singularity with nonzero area. However, the Ricci scalar is finite for an out-going null observer. This can be integrated as follows: Cosmologically stable higher curvature corrections of the Ricci scalar made it bounded even in the presence of mass inflation. Finally, we conjecture that if there is a general action including general higher curvature corrections with cosmological stability, then the corrections can make all curvature components finite even in the presence of mass inflation. This might help us to resolve the problem of inner horizon instability of regular black hole models.Comment: 31 pages, 15 figure

The Significance of Calcium-sensing Receptor in Sustaining Photosynthesis and Ameliorating Stress Responses in Plants

Calcium ions (Ca2+) regulate plant growth and development during exposure to multiple biotic and abiotic stresses as the second signaling messenger in cells. The extracellular calcium-sensing receptor (CAS) is a specific protein spatially located on the thylakoid membrane. It regulates the intracellular Ca2+ responses by sensing changes in extracellular Ca2+ concentration, thereby affecting a series of downstream signal transduction processes and making plants more resilient to respond to stresses. Here, we summarized the discovery process, structure, and location of CAS in plants and the effects of Ca2+ and CAS on stomatal functionality, photosynthesis, and various environmental adaptations. Under changing environmental conditions and global climate, our study enhances the mechanistic understanding of calcium-sensing receptors in sustaining photosynthesis and mediating abiotic stress responses in plants. A better understanding of the fundamental mechanisms of Ca2+ and CAS in regulating stress responses in plants may provide novel mitigation strategies for improving crop yield in a world facing more extreme climate-changed linked weather events with multiple stresses during cultivation

Managing Linguistic Data Summaries in Advanced P2P Applications

chapitre... à corrigerAs the amount of stored data increases, data localization techniques become no longer sufficient in P2P systems. A practical approach is to rely on compact database summaries rather than raw database records, whose access is costly in large P2P systems. In this chapter, we describe a solution for managing linguistic data summaries in advanced P2P applications which are dealing with semantically rich data. The produced summaries are synthetic, multidimensional views over relational tables. The novelty of this proposal relies on the double summary exploitation in distributed P2P systems. First, as semantic indexes, they support locating relevant nodes based on their data descriptions. Second, due to their intelligibility, these summaries can be directly queried and thus approximately answer a query without the need for exploring original data. The proposed solution consists first in defining a summary model for hierarchical P2P systems. Second, appropriate algorithms for summary creation and maintenance are presented. A query processing mechanism, which relies on summary querying, is then proposed to demonstrate the benefits that might be obtained from summary exploitation

Surgical excision promotes tumor growth and metastasis by promoting expression of MMP-9 and VEGF in a breast cancer model

Surgery is still the main curative therapeutic modality for breast cancer. Although surgery often results in the successful removal of the primary tumor, its process could increase the risk of metastases of residual cancer cells. Understanding of the connection between breast cancer metastasis and surgical wound will lead to the establishment of a proper treatment strategy for postoperative cancer patient. Aim: To study the influence of surgical procedure on the metastasis of primary breast cancer. Methods: We established MDA-MB-435 human breast cancer xenograft model. Levels of Pro-matrix metalloproteinase 9 (Pro-MMP-9) and vascular endothelial growth factor (VEGF) in host serum and tumors were tested at different time points with ELISA and zymography and correlated to tumor growth and postoperative metastasis. Results: Our study demonstrated surgical wound had promoting effect on tumor growth and pulmonary metastasis of human breast cells, if tumor cells remain in bodies. This effect might be related to the postoperative interaction of cancer and host cells, which resulted in expression of Pro-MMP-9. Surgical process could also increase the VEGF expression in tumor tissues. Conclusions: Surgical wound-produced host Pro-MMP-9 and tumor cell VEGF might be important mediators leading to metastasis of residual breast cancer after surgery.Хирургическое лечение до сих пор остается главным терапевтическим подходом при лечении больных раком молочной железы. Хотя хирургическое удаление опухоли в большинстве случаев достаточно эффективно, в то же время оно может увеличить риск метастазирования остаточных опухолевых клеток. Понимание связи между метастазированием при раке молочной железы и операционной раной позволит выбрать наилучшую стратегию постоперационного лечения. Цель: определить влияние хирургического вмешательства на метастазирование опухоли. Методы: была создана модель рака молочной железы человека в виде ксенотрансплантата MDA-MB-435. Уровень Pro-матричной металлопротеиназы 9 (Pro-MMP-9) и фактора роста эндотелия сосудов (VEGF) в сыворотке реципиента и опухолях оценивались в разные временные промежутки методом ELISA и зимографии. При этом определяли наличие корелляции между этими показа- и зимографии. При этом определяли наличие корелляции между этими показа и зимографии. При этом определяли наличие корелляции между этими показателями, ростом опухоли и постоперационными метастазами. Результаты: было показано, что операционная рана способствует росту опухоли молочной железы и ее метастазированию в легкие в случае, когда при удалении опухоли в ране остаются опухолевые клетки. Это может быть связано с постоперационным взаимодействием опухолевых и окружающих их нормальных клеток, которое приводит к экспрессии Pro-MMP-9. Удаление опухоли может также способствовать увеличению экспрессии VEGF опухолевыми клетками. Выводы: Pro-MMP-9, экспрессируемый нормальными клетками, окружающими постоперационную рану, а также VEGF, продуцируемый опухолевыми клетками, могут быть важными медиаторами метастазирования остаточных опухолевых клеток после хирургического вмешательства

Manipulation of magnetization reversal of Ni81Fe19 nanoellipse arrays by tuning the shape anisotropy and the magnetostatic interactions

Two series of highly ordered two-dimensional arrays of Ni81Fe19 nanoellipses were nanofabaricated with different aspect ratios, R, and element separations, S, to investigate the influence of the self-demagnetization and the magnetostatic interaction upon the magnetization reversal. For nanostructures with low shape anisotropy, an additional magnetic easy axis was induced orthogonal to the shape-induced easy axis by reducing the separations along both axes. For the structures with larger shape anisotropy, the switching field distribution/coercivity (SFD/Hc ) was reduced, and for the array with the smallest separations (20 nm and 35 nm along the long and short axes, respectively), coherent rotation of the whole array occurred. The magnitude of both the shape anisotropy and a configurational anisotropy induced by the magnetostatic interactions have been estimated. These results provide some useful information for the design of potential magnetic nanodot logic and for high-density magnetic random access memory

Dynamics near the Surface Reconstruction of W(100)

Using Brownian molecular dynamics simulation, we study the surface dynamics near the reconstruction transition of W(100) via a model Hamiltonian. Results for the softening and broadening of the surface phonon spectrum near the transition are compared with previous calculations and with He atom scattering data. From the critical behavior of the central peak in the dynamical structure factor, we also estimate the exponent of the power law anomaly for adatom diffusion near the transition temperature.Comment: 8 pages, 8 figures, to appear in Phys. Rev.

Exogenous Ca2+ priming can improve peanut photosynthetic carbon fixation and pod yield under early sowing scenarios in the field

Harnessing cold-resilient and calcium-enriched peanut production technology are crucial for high-yielding peanut cultivation in high-latitude areas. However, there is limited field data about how exogenous calcium (Ca2+) application would improve peanut growth resilience during exposure to chilling stress at early sowing (ES). To help address this problem, a two-year field study was conducted to assess the effects of exogenous foliar Ca2+ application on photosynthetic carbon fixation and pod yield in peanuts under different sowing scenarios. We measured plant growth indexes, leaf photosynthetic gas exchange, photosystems activities, and yield in peanuts. It was indicated that ES chilling stress at the peanut seedling stage led to the reduction of Pn, gs, Tr, Ls, WUE, respectively, and the excessive accumulation of non-structural carbohydrates in leaves, which eventually induced a chilling-dependent feedback inhibition of photosynthesis due mainly to weaken growth/sink demand. While exogenous Ca2+ foliar application improved the export of nonstructural carbohydrates, and photosynthetic capacity, meanwhile activated cyclic electron flow, thereby enhancing growth and biomass accumulation in peanut seedlings undergoing ES chilling stress. Furthermore, ES combined with exogenous Ca2+ application can significantly enhance plant chilling resistance and peanut yield ultimately in the field. In summary, the above results demonstrated that exogenous foliar Ca2+ application restored the ES-linked feedback inhibition of photosynthesis, enhancing the growth/sink demand and the yield of peanuts

Dynamics of false vacuum bubbles: beyond the thin shell approximation

We numerically study the dynamics of false vacuum bubbles which are inside an almost flat background; we assumed spherical symmetry and the size of the bubble is smaller than the size of the background horizon. According to the thin shell approximation and the null energy condition, if the bubble is outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven tunneling, expanding and inflating solutions are impossible. In this paper, we extend our method to beyond the thin shell approximation: we include the dynamics of fields and assume that the transition layer between a true vacuum and a false vacuum has non-zero thickness. If a shell has sufficiently low energy, as expected from the thin shell approximation, it collapses (Type 1). However, if the shell has sufficiently large energy, it tends to expand. Here, via the field dynamics, field values of inside of the shell slowly roll down to the true vacuum and hence the shell does not inflate (Type 2). If we add sufficient exotic matters to regularize the curvature near the shell, inflation may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a wormhole is dynamically generated around the shell (Type 3). By tuning our simulation parameters, we could find transitions between Type 1 and Type 2, as well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find another class of solutions (Type 4). Finally, we discuss the generation of a bubble universe and the violation of unitarity. We conclude that the existence of a certain combination of exotic matter fields violates unitarity.Comment: 40 pages, 41 figure

Turbulent diffusion and drift in galactic magnetic fields and the explanation of the knee in the cosmic ray spectrum

We reconsider the scenario in which the knee in the cosmic ray spectrum is explained as due to a change in the escape mechanism of cosmic rays from the Galaxy from one dominated by transverse diffusion to one dominated by drifts. We solve the diffusion equations adopting realistic galactic field models and using diffusion coefficients appropriate for strong turbulence (with a Kolmogorov spectrum of fluctuations) and consistent with the assumed magnetic fields. We show that properly taking into account these effects leads to a natural explanation of the knee in the spectrum, and a transition towards a heavier composition above the knee is predicted.Comment: 17 pp., 6 figures; revised version with minor changes. To appear in JHE

Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity

Recent application of ultrafast pump/probe optical techniques to superconductors has renewed interest in nonequilibrium superconductivity and the predictions that would be available for novel superconductors, such as the high-Tc cuprates. We have reexamined two of the classical models which have been used in the past to interpret nonequilibrium experiments with some success: the mu* model of Owen and Scalapino and the T* model of Parker. Predictions depend on pairing symmetry. For instance, the gap suppression due to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave as opposed to n for s-wave. Finally, we consider these models in the context of S-I-N tunneling and optical excitation experiments. While we confirm that recent pump/probe experiments in YBCO, as presently interpreted, are in conflict with d-wave pairing, we refute the further claim that they agree with s-wave.Comment: 14 pages, 11 figure