Scalable production of magnetic fluorescent cellulose microparticles

Cellulose - Fluorescent and magnetic nano- and microparticles have already been used for wide range of (bio)applications. Multimodal imaging as well as simultaneous control and monitoring of...     

Magnetic nano- and microparticles in biotechnology

Both synthetic and biologically produced magnetic nano- and microparticles exhibit several types of responses to external magnetic field which have been already employed in various areas of biosciences, biotechnology, medicine, environmental technology, etc. This short review shows selected important biotechnological applications of magnetic particles, and the biological processes leading to biogenic magnetic particles formation. Presented at the 1st Nanomaterials and Nanotechnology Meeting, Nano Ostrava, Ostrava, Czech Republic, 1–4 September 2008.     

Multiplicities in highp t hadron-nucleus interactions

We present results obtained in π^? A (A=C, Cu, Pb) — collisions at 38 GeV/c. A single particle trigger selects events with one charged particle in the central region and large transverse momentum. The effect of this trigger on the multiplicities of all charged particles and of protons is shown.     

Dichlorosilylene: Rate constant for the gas-phase reaction with nitric oxide

Using the recently detected intense UV absorption spectrum of it has been established that SiCl₂ reacts with nitric oxide in the gas phase with a bimolecular rate constant, k(SiCl₂+NO), of (1.6±0.1)×10⁹ M⁻¹s⁻¹ at 25°C.     

Preconcentration of middle oxyethylated nonylphenols from water samples on magnetic solid phase

Magnetic solid phase extraction (MSPE) is proposed as a simple and fast method for the preconcentration of free middle oxyethylated nonylphenols (NPs) from water. Middle oxyethylated NPs were extracted by MSPE from different water samples (10 and 500 ml samples of distilled, potable, well, river and pond water in concentrations of 30 and 0.6 μg ml⁻¹) using magnetically modified polyphenyleneoxide, Tenax TA and Tenax GR as magnetic adsorbents. Recoveries were 80–100% and relative standard deviations were less than 10%.     

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.     

Reaction of hydrogen atoms with diethyldisulfide and ethylmethyldisulfide

H atoms react with C₂H₅SSC₂H₅ to give C₂H₅SH as the sole retrievable product with ? = 2.32 at 25°C and 2.84 at 145°C. The primary reaction is postulated to be H + C₂H₅SSC₂H₅ ← C₂H₅SH + C₂H₅S with k₁ = (4.73 ± 0.64) × 10¹³ exp [?(1710 ± 69)/RT] cm³/mol·s relative to the rate constant of the H + C₂H₄ ← C₂H₅ reaction. The high value of the entropy of activation suggests the presence of partial hydrogen bonding in diethyldisulfide which is broken in the transition state. Ethylmethyldisulfide reacts similarly: H + C₂H₅SSCH₃ ← C₂H₅SH + CH₃S or CH₃SH + C₂H₅S. The thiyl radicals propagate a chain of radical exchange reactions forming the symmetrical disulfides with exposure-time-dependent quantum yields. The overall kinetics conform to a 16-step mechanism from which the rate constants of the elementary reactions could be established by computer modeling. Thiyl radicals react considerably more slowly with disulfides than H atoms.     

The reactions of hydrogen atoms with bis(trifluoromethyl)disulfide

The reactions of hydrogen atoms produced by the mercury-photosensitized decomposition of H₂ with bis(trifluoromethyl)disulfide has been studied. The rate coefficient for the primary reaction, H + CF₃SSCF₃ → CF₃SH + CF₃S, was determined in competition with the reaction H + C₂H₄S → SH + C₂H₄ to have the value k = (3.0 ± 0.18) × 10¹⁴ exp[-(4560 ± 140)/RT] cm³ mol^?1 S^?1. The high A factor can be partially accounted for by assuming free rotation for the two CF₃ groups and the SCF₃ groups about the S—S bond in the transition state. The relatively high activation energy is attributed to inductive and orbital overlap effects. CH₃SH, H₂S, and CF₃SH all react with CF₃SSCF₃ to yield solid complexes which were not explored further.