High-order harmonic generation from Rydberg states at fixed Keldysh parameter

Because the commonly adopted viewpoint that the Keldysh parameter $\gamma$ determines the dynamical regime in strong field physics has long been demonstrated to be misleading, one can ask what happens as relevant physical parameters, such as laser intensity and frequency, are varied while $\gamma$ is kept fixed. We present results from our one- and fully three-dimensional quantum simulations of high-order harmonic generation (HHG) from various bound states of hydrogen with $n$ up to 40, where the laser intensities and the frequencies are scaled from those for $n=1$ in order to maintain a fixed Keldysh parameter $\gamma$$< 1$ for all $n$. We find that as we increase $n$ while keeping $\gamma$ fixed, the position of the cut-off scales in well defined manner. Moreover, a secondary plateau forms with a new cut-off, splitting the HHG plateau into two regions. First of these sub-plateaus is composed of lower harmonics, and has a higher yield than the second one. The latter extends up to the semiclassical $I_p+3.17U_p$ cut-off. We find that this structure is universal, and the HHG spectra look the same for all $n\gtrsim 10$ when plotted as a function of the scaled harmonic order. We investigate the $n$-, $l$- and momentum distributions to elucidate the physical mechanism leading to this universal structure

Phase-dependent interference fringes in the wavelength scaling of harmonic efficiency

We describe phase-dependent wavelength scaling of high-order harmonic generation efficiency driven by ultra-short laser fields in the mid-infrared. We employ both numerical solution of the time-dependent Schr\"{o}dinger equation and the Strong Field Approximation to analyze the fine-scale oscillations in the harmonic yield in the context of channel-closing effects. We show, by varying the carrier-envelope phase, that the amplitude of these oscillations depend strongly on the number of returning electron trajectories. Furthermore, the peak positions of the oscillations vary significantly as a function of the carrier-envelope phase. Owing to its practical applications, we also study the wavelength dependence of harmonic yield in the "single-cycle" limit, and observe a smooth variation in the wavelength scaling originating from the vanishing fine-scale oscillations.Comment: 5 pages, 4 figure

Halka açılan şirketlerin kısa ve uzun dönem fiyat performansları:Türkiye örneği 1990-1993

Ankara : The Graduate School of Business Administration of Bilkent Univ., 1996.Thesis (Master's) -- İhsan Doğramacı Bilkent University, 1996.Includes bibliographical references (leaves 45-48).The purpose of this study is to examine both the initial and medium-long term price performance of initial public offerings in Istanbul Stock Exchange during the continuous 1990-1993 period. In the light of the findings, initial public offerings are found to be underpriced meaning that investors in initial public offering market can exercise significant short-term returns relative to the market. In addition, in the whole period, the effect of this initial underpricing continues up to the second month. However, when we look at the long-term results, it is seen that IPOs underperformed the market although the results are not significant. As a result, investors in the IPO merket can exercise initial abnormal returns but in the long-run they produce a negative return although not significant.Yavuz, Z. NurşinM.S

Antiproliferative Activity of Some Medicinal Plants on Human Breast and Hepatocellular Carcinoma Cell Lines and their Phenolic Contents

Purpose: To determine the phenolic composition and antiproliferative activity of 16 different extracts (hexane, dichloromethane, methanol and water) obtained from Bellis perennis, Convolvulus galaticus, Trifolium pannonicum and Lysimachia vulgaris on human breast cancer (MCF-7) and human hepatocellular carcinoma (HepG2/C3A) cell lines.Methods: The aerial parts of the plants were successively extracted with hexane, dichloromethane, methanol and water using a Soxhlet apparatus. The phenolic content of the plants were determined by plants by high performance liquid chromatography (HPLC) while their antiproliferative activity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, a yellow tetrazole (MTT) assay.Results: Among the tested extracts, the methanol extract of B. perennis showed the best antiproliferative activity against MCF-7 cell line with IC50 (inhibiting 50 % of cell growth) value of 71.6 μg/mL. Furthermore, the dichloromethane extract of C. galaticus showed the best anti-proliferative activity against HepG2/C3A cell line with IC50 of 57.3 μg/mL. The HPLC data for the plant extracts showed the presence of the following phenolic compounds: gallic acid monohydrate, caffeic acid, rutin hydrate, luteolin-7-O-β-D glucoside, kaempferol, myricetin, quercetin, coumarin and apigenin.Conclusion: The findings of this study indicate that there is some justification for the use of B. perennis and C. galaticus as traditional anticancer medicinal herbs.Keywords: Bellis perennis, Convolvulus galaticus, Trifolium pannonicum subsp. elongatum, Lysimachia vulgaris, MCF-7, HepG2/C3A, Phenolics, Breast cancer, Antiproliferativ

Zoledronic acid induces apoptosis via stimulating the expressions of ERN1, TLR2, and IRF5 genes in glioma cells

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor that affects older people. Although the current therapeutic approaches for GBM include surgical resection, radiotherapy, and chemotherapeutic agent temozolomide, the median survival of patients is 14.6 months because of its aggressiveness. Zoledronic acid (ZA) is a nitrogen-containing bisphosphonate that exhibited anticancer activity in different cancers. The purpose of this study was to assess the potential effect of ZA in distinct signal transduction pathways in U87-MG cells. In this study, experiments performed on U87-MG cell line (Human glioblastoma-astrocytoma, epithelial-like cell line) which is an in vitro model of human glioblastoma cells to examine the cytotoxic and apoptotic effects of ZA. IC50 dose of ZA, 25 μM, applied on U87-MG cells during 72 h. ApoDIRECT In Situ DNA Fragmentation Assay was used to investigate apoptosis of U87MG cells. The quantitative reverse transcription polymerase chain reaction (qRT-PCR) (LightCycler480 System) was carried out for 48 gene expression like NF-κB, Toll-like receptors, cytokines, and inteferons. Our results indicated that ZA (IC50 dose) increased apoptosis 1.27-fold in U87MG cells according to control cells. According to qRT-PCR data, expression levels of the endoplasmic reticulum-nuclei-1 (ERN1), Toll-like receptor 2 (TLR2), and human IFN regulatory factor 5 (IRF5) tumor suppressor genes elevated 2.05-, 2.08-, and 2.3-fold by ZA, respectively, in U87MG cells. Our recent results indicated that ZA have a key role in GBM progression and might be considered as a potential agent in glioma treatment. © 2015, International Society of Oncology and BioMarkers (ISOBM)

Classification of Spherically Symmetric Static Spacetimes according to their Matter Collineations

The spherically symmetric static spacetimes are classified according to their matter collineations. These are studied when the energy-momentum tensor is degenerate and also when it is non-degenerate. We have found a case where the energy-momentum tensor is degenerate but the group of matter collineations is finite. For the non-degenerate case, we obtain either {\it four}, {\it five}, {\it six} or {\it ten} independent matter collineations in which four are isometries and the rest are proper. We conclude that the matter collineations coincide with the Ricci collineations but the constraint equations are different which on solving can provide physically interesting cosmological solutions.Comment: 15 pages, no figure, Late

Matter collineations of Spacetime Homogeneous G\"odel-type Metrics

The spacetime homogeneous G\"odel-type spacetimes which have four classes of metrics are studied according to their matter collineations. The obtained results are compared with Killing vectors and Ricci collineations. It is found that these spacetimes have infinite number of matter collineations in degenerate case, i.e. det$(T_{ab}) = 0$, and do not admit proper matter collineations in non-degenerate case, i.e. det$(T_{ab}) \ne 0$. The degenerate case has the new constraints on the parameters $m$ and $w$ which characterize the causality features of the G\"odel-type spacetimes.Comment: 12 pages, LaTex, no figures, Class. Quantum.Grav.20 (2003) 216