Studies of Charge Exchange in a High‐Pressure Pulsed Electron Impact Source

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/56/3/10.1063/1.1677327.A high pressure pulsed ion source has been used in a time‐of‐flight mass spectrometer in order to study the charge exchangereactions in Ar–H2 and Ar–D2 systems using the ion source in the Čermák mode of operation. As the source was used in a pulsed mode, it was possible to identify the various secondary ions arising from the charge exchangereactions in these systems. Very good agreement has been shown to exist between the experimental results and simple theoretical deductions. Calculations have been made to determine the cross sections for the charge exchangereactions between the various species from the experimental data

Well-Typed Programs Can’t Be Blamed

We introduce the blame calculus, which adds the notion of blame from Findler and Felleisen’s contracts to a system similar to Siek and Taha’s gradual types and Flanagan’s hybrid types. We characterise where positive and negative blame can arise by decomposing the usual notion of subtype into positive and negative subtypes, and show that these recombine to yield naive subtypes. Naive subtypes previously appeared in type systems that are unsound, but we believe this is the first time naive subtypes play a role in establishing type soundness

Synthesis of CdS and CdSe nanocrystallites using a novel single-molecule precursors approach

The synthesis of CdS and CdSe nanocrystallites using the thermolysis of several dithioor diselenocarbamato complexes of cadmium in trioctylphosphine oxide (TOPO) is reported. The nanodispersed materials obtained show quantum size effects in their optical spectra and exhibit near band-edge luminescence. The influence of experimental parameters on the properties of the nanocrystallites is discussed. HRTEM images of these materials show well-defined, crystalline nanosized particles. Standard size fractionation procedures can be performed in order to narrow the size dispersion of the samples. The TOPO-capped CdS and CdSe nanocrystallites and simple organic bridging ligands, such as 2,2¢-bipyrimidine, are used as the starting materials for the preparation of novel nanocomposites. The optical properties shown by these new nanocomposites are compared with those of the starting nanodispersed materials

Role of Temperature in the Growth of Silver Nanoparticles Through a Synergetic Reduction Approach

This study presents the role of reaction temperature in the formation and growth of silver nanoparticles through a synergetic reduction approach using two or three reducing agents simultaneously. By this approach, the shape-/size-controlled silver nanoparticles (plates and spheres) can be generated under mild conditions. It was found that the reaction temperature could play a key role in particle growth and shape/size control, especially for silver nanoplates. These nanoplates could exhibit an intensive surface plasmon resonance in the wavelength range of 700–1,400 nm in the UV–vis spectrum depending upon their shapes and sizes, which make them useful for optical applications, such as optical probes, ionic sensing, and biochemical sensors. A detailed analysis conducted in this study clearly shows that the reaction temperature can greatly influence reaction rate, and hence the particle characteristics. The findings would be useful for optimization of experimental parameters for shape-controlled synthesis of other metallic nanoparticles (e.g., Au, Cu, Pt, and Pd) with desirable functional properties

Potent Anti-Tumor Effect Generated by a Novel Human Papillomavirus (HPV) Antagonist Peptide Reactivating the pRb/E2F Pathway

Human papillomavirus type 16 (HPV16) E7 is a viral oncoprotein believed to play a major role in cervical cancer. In this study, an antagonist peptide against HPV16E7 protein was first identified from screening the c7c phage display peptide library. The binding specificity and affinity of the selected peptide to HPV16E7 were tested by competitive enzyme-linked immunosorbent assay (ELISA). The antagonist peptide showed obvious anti-tumor efficacy both in cell lines and animal tumor models. Significant cell proliferation inhibition with high specificity was noted when HPV16-positive cells were treated with the peptide. This anti-tumor efficacy was resulted from overriding the activities of HPV16E7 and reactivating the pRb/E2F pathway, as shown by a series of experiments. Flow cytometry analysis revealed that the selected peptide induced G1 arrest in a dose-dependent manner. Competitive ELISA, pull down, and Co-IP experiments indicated that the selected peptide disrupted the interaction between HPV16E7 and pRb proteins both in vitro and in vivo. Luciferase reporter assay verified that transcription activities of E2F were suppressed by the peptide through restoration of pRb. RT-PCR and Western blot revealed that it reduced cyclins A, D1, and E1 expression, and led to HPV16E7 protein degradation, but pRb protein stabilization. The current study suggests that this specific peptide may serve as a potential therapeutic agent for HPV16-positive cervical cancer

The big problem of small particles : a comparison of methods for determination of particle size in nanocrystalline anatase powders

We compare different methods for particle size determination in nanocrystalline anatase (TiO2) powders: transmission electron microscopy (TEM), nitrogen adsorption measurements, mercury porosimetry, and X-ray diffraction(XRD). The main source of errors in TEM is the sampling of the powder population, whereas in XRD the deconvolution of peak broadening due to instrument, microstrains, and crystalline domain size is delicate and can lead to unreliable results. Different approaches including Scherrer and Williamson-Hall equations are discussed. The presence of mesopores due to agglomerate formation is clearly revealed in adsorption measurements and porosimetry