A Multi-Drive Beam Scheme for Two-Beam Acceleration in a TeV Linear Collider

The Compact Linear Collider (CLIC) study of an e+/e- linear collider in the TeV energy range is based on Two-Beam Acceleration (TBA) in which the overall RF power needed to accelerate the beam is extracted from high intensity relativistic electron beams, the so-called drive beams. Due to the high beam power, acceleration and transport of the drive beams in an efficient and reliable way is specially challenging. An overview of a potentially effective scheme is presented. It is based on the generation of trains of short bunches, accelerated in low frequency c.w. superconducting cavities, stored in an isochronous ring and combined at high energy by funneling before injection by sectors into the drive linac. The various systems of the complex are discussed as well as the beam dynamics all along the process. An original method has been specially developed to stabilize such an intense beam during deceleration and RF power production in the drive lina

MicroRNAs in colorectal cancer stem cells: new regulators of cancer stemness?

Recently, the hypothesis that colorectal tumors originate from a subpopulation of cells called 'cancer stem cells' (CSCs) or tumor-initiating cells, which exhibit stem-like features, has been confirmed experimentally in various human cancers. Several studies have confirmed the existence of colorectal CSCs (CRCSCs) and have demonstrated that this rare cell population can be isolated by the expression of specific cell surface biomarkers. MicroRNAs (miRNAs) are a class of small non-coding RNAs, which are crucial for post-transcriptional regulation of gene expression and participate in a wide variety of biological functions, including development, cell proliferation, differentiation, metabolism and signal transduction. Moreover, new evidences suggest that miRNAs could contribute to preserve stemness of embryonic stem cells and could be involved in maintaining stemness of CSCs. Recent studies have begun to outline the role of miRNAs in regulation of CRCSCs. This review aims to summarize the recent advancement about the roles of miRNAs in CRCSCs that may represent a step forward in understanding the molecular mechanisms and the possible approaches for colorectal cancer therapy

Effects of PPARγ agonists on the expression of leptin and vascular endothelial growth factor in breast cancer cells.

The obesity hormone leptin has been implicated in breast cancer development. Breast cancer cells express the leptin receptor and are able to synthesize leptin in response to obesity-related stimuli. Furthermore, leptin is a positive regulator of vascular endothelial growth factor (VEGF) and high levels of both proteins are associated with worse prognosis in breast cancer patients. Peroxisome proliferator-activated receptor (PPAR) ligands are therapeutic agents used in patient with Type 2 diabetes and obesity which have recently been studied for their potential anti-tumor effect. Here, we studied if these compounds, ciglitazone and GW1929, can affect the expression of leptin and VEGF in breast cancer cells. In MDA-MB-231 and MCF-7 breast cancer cells, treatment with submolar concentrations of ciglitazone and GW1929 elevated the expression of leptin and VEGF mRNA and protein, and increased cell viability and migration. These effects coincided with increased recruitment of PPAR to the proximal leptin promoter and decreased association of a transcriptional factor Sp1 with this DNA region

A new method of RF power generation for two-beam linear colliders

In this paper we discuss a new approach to two-beam acceleration. The energy for RF production is initially stored in a long-pulse electron beam which is efficiently accelerated to about 1.2 GeV by a fully loaded, conventional, low frequency (~1 GHz) linac. The beam pulse length is twice the length of the high-gradient linac. Segments of this long pulse beam are compressed using combiner rings to create a sequence of higher peak power drive beams with gaps in between. This train of drive beams is distributed from the end of the linac against the main beam direction down a common transport line so that each drive beam can power a section of the main linac. After a 180-degree turn, each high-current, low-energy drive beam is decelerated in low-impedance decelerator structures, and the resulti ng power is used to accelerate the low-current, high-energy beam in the main linac. The method discussed here seems relatively inexpensive is very flexible and can be used to accelerate beams for lin ear colliders over the entire frequency and energy range