Amphiphilic anthanthrene trimers that exfoliate graphite and individualize single wall carbon nanotubes

A phosphodiester-linked dialkynyl substituted anthanthrene trimer (1) has been designed and synthesized. Its graphene ribbon like structure is expected to facilitate interactions with nanographene (NG) and single wall carbon nanotubes (SWCNT) to yield novel and stable carbon-based nanomaterials. Interactions with trimer 1 leads to exfoliation of NG and to the individualization of SWCNTs. Phosphate groups, in general, and their negative charges, in particular, render the resulting nanomaterials soluble in ethanol, which is ecologically favourable over DMF required for the processing of pristine NG or SWCNTs. The newly formed nanomaterials were probed by complementary spectroscopic and microscopic techniques. Of particular importance were transient absorption fluorescence excitation measurements, which revealed an efficient energy transfer within the carbon-based nanomaterials

Electric and magnetic signatures of dust devils from the 2000–2001 MATADOR desert tests

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94763/1/jgre1728.pd

Theoretical Study of the Effect of Ionospheric Return Currents on the Electron Temperature

An electron heat flow can occur in a partially ionized plasma in response to either an electron temperature gradient (thermal conduction) or an electron current (thermoelectric heat flow). The former process has been extensively studied, while the latter process has received relatively little attention. Therefore a time-dependent three-dimensional model of the high-latitude ionosphere was used to study the effect of field-aligned ionospheric return currents on auroral electron temperatures for different seasonal and solar cycle conditions as well as for different upper boundary heat fluxes. The results of this study lead to the following conclusions: (1) The average, large-scale, return current densities, which are a few microamps per square meter, are too small to affect auroral electron temperatures. (2) Current densities greater than about 10−5 A m−2 are needed for thermoelectric heat flow to be important. (3) The thermoelectric effect displays a marked solar cycle and seasonal dependence. (4) Thermoelectric heat transport corresponds to an upward flow of electron energy. (5) This energy flow can be either a source or sink of electron energy, depending on the altitude and geophysical conditions. (6) Thermoelectric heat transport is typically a sink above 300 km and acts to lower ambient electron temperatures by as much as 2000 K for field-aligned return current densities of the order of 5 × 10−5 A m−2. For this case, the electron temperature decreases with altitude above 300 km with a gradient that can exceed 1 K km−1. Also, the electron temperature can drop below both the ion and neutral temperatures in the upper F region owing to thermoelectric cooling. (7) A downward magnetospheric heat flux in combinations with an upward thermoelectric heat flux can produce steep positive electron temperature gradients in the topside ionosphere

Characterization of Botulinum Neurotoxin Type A Neutralizing Monoclonal Antibodies and Influence of Their Half-Lives on Therapeutic Activity

Botulinum toxins, i.e. BoNT/A to/G, include the most toxic substances known. Since botulism is a potentially fatal neuroparalytic disease with possible use as a biowarfare weapon (Centers for Disease Control and Prevention category A bioterrorism agent), intensive efforts are being made to develop vaccines or neutralizing antibodies. The use of active fragments from non-human immunoglobulins (F(ab')2, Fab', scFv), chemically modified or not, may avoid side effects, but also largely modify the in vivo half-life and effectiveness of these reagents. We evaluated the neutralizing activity of several monoclonal anti-BoNT/A antibodies (mAbs). F(ab')2 fragments, native or treated with polyethyleneglycol (PEG), were prepared from selected mAbs to determine their half-life and neutralizing activity as compared with the initial mAbs. We compared the protective efficiency of the different biochemical forms of anti-toxin mAbs providing the same neutralizing activity. Among fourteen tested mAbs, twelve exhibited neutralizing activity. Fragments from two of the best mAbs (TA12 and TA17), recognizing different epitopes, were produced. These two mAbs neutralized the A1 subtype of the toxin more efficiently than the A2 or A3 subtypes. Since mAb TA12 and its fragments both exhibited the greatest neutralizing activity, they were further evaluated in the therapeutic experiments. These showed that, in a mouse model, a 2- to 4-h interval between toxin and antitoxin injection allows the treatment to remain effective, but also suggested an absence of correlation between the half-life of the antitoxins and the length of time before treatment after botulinum toxin A contamination. These experiments demonstrate that PEG treatment has a strong impact on the half-life of the fragments, without affecting the effectiveness of neutralization, which was maintained after preparation of the fragments. These reagents may be useful for rapid treatment after botulinum toxin A contamination