The formation of various fullerenyl radicals during the polymerization of methyl methacrylate (MMA) and styrene in the presence of C
60
fullerene is studied using the density functional method. It is ...shown that the interaction of an initiating radical with the fullerene molecule, yielding fullerenyl radical, is less favorable in energy terms than the initiation of the chain, i.e., the interaction of the same radical with a monomer. For radical polymerization of styrene, the termination of polystyrene chains on the fullerene is thermodynamically more probable than the growth of polystyrene chains, with the reactions being equiprobable in the case of MMA polymerization. The addition of monomer molecules to fullerenyl radicals is characterized by an enthalpy of activation exceeding that for conventional free radical chain growth by no more than 1.4 to 2.3 times; the thus formed growth radicals with fullerene molecules incorporated into the backbone polymer feature a reactivity not inferior to conventional polymer growth radicals.
Strain plays a critical role in the properties of materials. In silicon and silicon-germanium, strain provides a mechanism for control of both carrier mobility and band offsets. In materials ...integration, strain is typically tuned through the use of dislocations and elemental composition. We demonstrate a versatile method to control strain by fabricating membranes in which the final strain state is controlled by elastic strain sharing, that is, without the formation of defects. We grow Si/SiGe layers on a substrate from which they can be released, forming nanomembranes. X-ray-diffraction measurements confirm a final strain predicted by elasticity theory. The effectiveness of elastic strain to alter electronic properties is demonstrated by low-temperature longitudinal Hall-effect measurements on a strained-silicon quantum well before and after release. Elastic strain sharing and film transfer offer an intriguing path towards complex, multiple-layer structures in which each layer's properties are controlled elastically, without the introduction of undesirable defects.
Although the neuronal circuits that generate leech movements have been studied for over 30 years, the list of interneurons (INs) in these circuits remains incomplete. Previous studies showed that ...some motor neurons (MNs) are electrically coupled to swim-related INs, e.g., rectifying junctions connect IN 28 to MN DI-1 (dorsal inhibitor), so we searched for additional neurons in these behavioral circuits by co-injecting Neurobiotin and Alexa Fluor 488 into segmental MNs DI-1, VI-2, DE-3 and VE-4. The high molecular weight Alexa dye is confined to the injected cell, whereas the smaller Neurobiotin molecules diffuse through gap junctions to reveal electrical coupling. We found that MNs were each dye-coupled to approximately 25 neurons, about half of which are likely to be INs. We also found that (1) dye-coupling was reliably correlated with physiologically confirmed electrical connections, (2) dye-coupling is unidirectional between MNs that are linked by rectifying connections, and (3) there are novel electrical connections between excitatory and inhibitory MNs, e.g. between excitatory MN VE-4 and inhibitory MN DI-1. The INs found in this study provide a pool of novel candidate neurons for future studies of behavioral circuits, including those underlying swimming, crawling, shortening, and bending movements.
The pharmacokinetics of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF), induction of anti-GM-CSF antibodies, and clinical effects related to the induction of the ...antibodies were analyzed in patients with metastatic colorectal carcinoma (CRC) who were not on chemotherapy (n = 20, nonimmunocompromised patients). rhGM-CSF (250 micrograms/m2/d; Escherichia coli-derived) was administered subcutaneously for 10 days every month for 4 months. Eight patients with multiple myeloma (MM) on intensive chemotherapy followed by rhGM-CSF treatment were also included (immunocompromised patients). After a single injection of GM-CSF at the first cycle in CRC patients, the maximum calculated concentration (Cmax) was 5.24 +/- 0.56 ng/mL; the half life (T1/2) was 2.91 +/- 0.8 hours; and the area under the concentration curve (AUC) was 30.86 +/- 6.03 hours x ng/mL (mean +/- SE). No anti-GM-CSF antibodies were detected. During the subsequent cycles, 95% of the CRC patients developed anti-GM-CSF IgG antibodies, which significantly altered the pharmacokinetics of rhGM-CSF at the third and fourth cycles with decreased Cmax (2.87 +/- 0.57 ng/mL; P < .05), T1/2 (1.57 +/- 0.2 hours; P < .05), and AUC (14.90 +/- 4.10 hours x ng/mL; P < .005). The presence of anti-GM-CSF antibodies significantly reduced the GM-CSF-induced enhancement of granulocytes, and there was a clear tendency for a decreased increment of monocytes. Antibodies diminished systemic side effects of rhGM-CSF. Only 1 of 8 MM patients showed a very low anti-GM-CSF antibody titer after GM-CSF therapy, as shown by enzyme-linked immunosorbent assay and Western blot. Therefore, in nonimmunocompromised patients, exogenous nonglycosylated GM-CSF induced an anti-GM-CSF IgG antibody response in practically all patients, which seemed to be of clinical significance. In immunocompromised patients, virtually no significant antibody response was shown.
The initiation of radical polymerization of methyl methacrylate in the presence of benzoyl peroxide-metallocene (Cp
2
Fe, Cp
2
ZrCl
2
, and Cp
2
TiCl
2
; (C
5
Me
5
)
2
Fe, (C
5
Me
5
)
2
ZrC
l2
, and ...(AcC
5
H
4
)(C
5
H
5
)Fe) systems is studied. It is shown that a metallocene affects the rate of initiation and the initial rate of polymerization. On the basis of quantum-chemical calculations, a new mechanism of the initiation reaction may be advanced: Namely, the decomposition of benzoyl peroxide proceeds via the stage of complexation with a metallocene, while the nature of a metallocene determines the probability of complexation and decomposition.
Abstract Most stars form in clusters and groups rather than in isolation. We present ≲5″ angular resolution (∼2000 au, or 0.01 pc) Very Large Array NH 3 (1,1), (2,2), and (3,3) and 1.3 cm continuum ...emission observations of the dense gas within the Serpens South protocluster and extended filaments to the north and south. We identify 94 dense cores using a dendrogram analysis of the NH 3 (1,1) integrated intensity. Gas temperatures T K and nonthermal line widths σ NT both increase toward the center of the young stellar cluster, in the dense gas generally and in the cores specifically. We find that most cores (54%) are supervirial, with gravitationally bound cores located primarily in the filaments. Cores in the protocluster have higher virial parameters by a factor of ∼1.7, driven primarily by the increased core σ NT values. These cores cannot collapse to form stars unless they accrete additional mass or their core internal motions are reduced. The southern filament shows a significant velocity gradient previously interpreted as mass flow toward the cluster. We find more complex kinematics in the northern filament. We find a strong correlation between σ NT and T K , and argue that the enhanced temperatures and nonthermal motions are due to mechanical heating and interaction between the protocluster-driven outflows and the dense gas. Filament-led accretion may also contribute to the increased σ NT values. Assuming a constant fraction of core mass ends up in the young stars, future star formation in the Serpens South protocluster will shift to higher masses by a factor of ∼2.
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•Arctic sea ice releases sequestered anthropogenic microlitter upon summer melting.•The release coincides with the ice-edge bloom, suggesting high bioavailability.•Microlitter likely ...originating from a wastewater outlet is detected in a fjord.•Local point- and diffuse sources of microlitter are not negligible in the Arctic.•A multivariate analytical approach is suggested beneficial in microlitter research.
Human activities leave traces of marine litter around the globe. The Arctic is, despite its remoteness, emerging as an area of no exception to this environmental issue. Arctic sea ice has previously been found to constitute a temporal sink of microplastics, but the potential release and subsequent fate of microplastics in the marine environment are yet unknown. Furthermore, the relative importance of local sources of microplastics in the Arctic marine environment is under discussion. In this study, the concentration and distribution of anthropogenic microparticles (AMPs, <5 mm, including microplastics) have been investigated in marine waters and sea ice of Svalbard. Seawater samples throughout the water column and floating sea ice samples were collected along a transect originating in Rijpfjorden, reaching northwards to the sea ice-edge. Seawater samples were also collected along a transect extending westwards from head to mouth of Kongsfjorden. Samples were collected throughout the water column with stations positioned to enable detection of potential AMP emissions from the wastewater outlet in Ny-Ålesund. Along both transects, environmental parameters were measured to explore potential correlations with AMP distribution. High concentrations of AMPs were detected in sea ice (158 ± 155 AMPs L−1). Based on both AMP concentrations and characteristics, AMPs identified in seawater of the marginal ice zone are to a large extent likely released during the melting of sea ice. The release of AMPs during summer melting of sea ice was concomitantly taking place with the ice-edge bloom, suggesting increased bioavailability to Arctic marine biota. Concentrations of AMPs were up to an order of magnitude higher in Kongsfjorden (up to 48.0 AMPs L−1) than in Rijpfjorden (up to 7.4 AMPs L−1). The distribution and composition of AMPs in Kongsfjorden suggest the wastewater outlet in Ny-Ålesund to be a likely source. Our results emphasize the importance of local point- and diffuse sources of AMPs in the Arctic and stress the urgency of considering their associated environmental impact. Implementation of regulatory policy is of importance, particularly since human activities and environmental pressures are increasing in the Arctic.
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