Hard X-ray Emission from Cassiopeia A SNR

We report the results of extracting the hard X-ray continuum spectrum of Cas A SNR from RXTE/PCA Target of Opportunity observations (TOO) and CGRO/OSSE observations. The data can rule out the single thermal bremsstrahlung model for Cas A continuum between 2 and 150 keV. The single power law model gives a mediocre fit (∼5%) to the data with a power-law index, Γ = 2.94±0.02. A model with two component (bremsstrahlung + bremsstrahlung or bremsstrahlung + power law) gives a good fit. The power law index is quite constrained suggesting that this continuum might not be the X-ray thermal bremmstrahlung from accelerated MeV electrons at shock fronts [1] which would have Γ ≃2.26. With several SNRs detected by ASCA showing a hard power-law nonthermal X-ray continuum, we expect a similar situation for Cas A SNR which has Γ=2.98±0.09. We discuss the implication of the hardest nonthermal X-rays detected from Cas A to the synchrotron radiation model

Endothelial Cells Promote the Colorectal Cancer Stem Cell Phenotype through a Soluble Form of Jagged-1

SummaryWe report a paracrine effect whereby endothelial cells (ECs) promote the cancer stem cell (CSC) phenotype of human colorectal cancer (CRC) cells. We showed that, without direct cell-cell contact, ECs secrete factors that promoted the CSC phenotype in CRC cells via Notch activation. In human CRC specimens, CD133 and Notch intracellular domain-positive CRC cells colocalized in perivascular regions. An EC-derived, soluble form of Jagged-1, via ADAM17 proteolytic activity, led to Notch activation in CRC cells in a paracrine manner; these effects were blocked by immunodepletion of Jagged-1 in EC-conditioned medium or blockade of ADAM17 activity. Collectively, ECs play an active role in promoting Notch signaling and the CSC phenotype by secreting soluble Jagged-1

Stimuli-Sensitive Pyrenylated Hydrogels as Optical Sensing Platform for Multiple Metal Ions

In the present work, we report a thermoresponsive hydrogel formed by the self-assembly of compounds 1 and 2 Milli Q water. Both hydrogels showed thixotropic behavior. Atomic force microscopy (AFM) studies confirm the fiber-like microstructure of compounds 1 and 2, but denser fibers were observed in the case of compound 1. The hydrogel formed by compound 1 detected Cu2+, Fe3+, and Hg2+, whereas the hydrogel of 2 showed a change in the optical signal, specifically upon adding Cu2+ and Hg2+. Mechanistically, adding metal ions to the hydrogel resulted in the formation of a (1:1) complex with Fe3+ and Hg2+ and (2:1) with Cu2+. The detection of metal ions has also been achieved in real-life samples, such as in tap water. Low-cost portable gel-coated paper strips have also been developed for the onsite detection of these metal ions

Microenvironment Sensitive Charge-Transfer Dye for Tandem Sensing of Multiple Analytes at Mesoscopic Interfaces

An easy to synthesize amphiphilic dye is developed whose sensing behavior in surfactant assemblies can be modulated through surface-charge, micropolarity, and local pH, etc. Thus, the micelle-bound probe shows remarkable ion dependent bathochromic shifts in the charge-transfer band, enabling simultaneous ratiometric detection of four different metal ions, such as Cu2+, Ni2+, Hg2+, and Zn2+, at parts per billion (ppb) level in water. This is indeed a striking observation since naked-eye sensing of multiple metal ions at the mesoscopic interface is not known to date. Moreover, the probe even shows distinct color response against copper ion in different oxidation states, which is also unheard of. Further, the in situ formed metal complexes can be employed for naked-eye screening of three different amino acids, such as histidine, cysteine, and aspartic acid, in aqueous medium. Probes of this class, which are capable of multiplexing, offer new ways of efficiently screening multiple analytes in complex, real-life samples (e.g., wastewater management, analysis of pharmaceutical drugs, etc.). Further, low-cost reusable dye-coated paper discs were also developed as an ecofriendly method for on-site sensing of metal ions

Gelation of novel pyrene-cored chiral dendrimers: dendritic effect in gelation and shear thinning behavior

Synthesis and gelation property of novel pyrene-cored chiral dendrimers PyFG1 and PyFG2 have been studied. Dendritic effect was found to play a crucial role in the self-assembly pattern, solvents for gelation and the shear thinning behavior of the gels as well

Gelation of novel pyrene-cored chiral dendrimers:dendritic effect in gelation and shear thinning behavior

\u3cp\u3eSynthesis and gelation property of novel pyrene-cored chiral dendrimers PyFG1 and PyFG2 have been studied. Dendritic effect was found to play a crucial role in the self-assembly pattern, solvents for gelation and the shear thinning behavior of the gels as well.\u3c/p\u3

Multimodal Ion Sensing by Structurally Simple Pyridine-End Oligo p-Phenylenevinylenes for Sustainable Detection of Toxic Industrial Waste

Environmental pollution induced by toxic metal ions and harmful chemicals mainly from industrial waste poses a significant threat which urges for their rapid detection before release into the ecosystem above the permissible level. Optical sensors are inexpensive, simple, yet efficient in sensing such toxicants. Herein, we show that structurally simple pi-conjugated pyridine-end p-phenylenevinylene oligomers can selectively sense toxic metal ions and anions in solution, supramolecular gels, as well as in solid support. Interaction of Hg2+ at nanomolar concentrations with the linear pyridine-ends via two-site coordination was clearly seen from ``naked eye'' color changes and fluorometric investigations. The sensitivity as well as selectivity of the oligomers toward Hg2+ was found to be greatly affected by the extent of aromatic conjugation and pK(a) of the end-pyridine functionalities. Interestingly, one of the oligomers (3) containing an isoniazid moiety renders visual color changes with both Hg2+ and CN- ions through two different binding sites involving two nonidentical sensing pathways which enable this probe for the detection of multiple analytes at the same time. Moreover, these ions (Hg2+/CM-) showed remarkable tuning of the supramolecular assembly (molecular gels) of 3, depicting reversible sol gel transformation on complementary addition of Hg2+/CN- in proper stoichiometry which could be useful in scavenging toxic ions from industrial wastes. In addition, the low-cost, reusable paper discs coated with the probe molecules show rapid, onsite detection of toxic ions even from the contaminated water samples. Therefore, this highly efficient multimodal sensing of toxic ions by easy-to-synthesize molecular probes could inspire the design of new sensors with varying chromophores for the color-tunable sensing of toxic ions