Conformational Entropy as a Means to Control the Behavior of Poly(diketoenamine) Vitrimers In and Out of Equilibrium.

Control of equilibrium and non-equilibrium thermomechanical behavior of poly(diketoenamine) vitrimers is shown by incorporating linear polymer segments varying in molecular weight (MW) and conformational degrees of freedom into the dynamic covalent network. While increasing MW of linear segments yields a lower storage modulus at the rubbery plateau after softening above the glass transition (Tg ), both Tg and the characteristic time of stress relaxation are independently governed by the conformational entropy of the embodied linear segments. Activation energies for bond exchange in the solid state are lower for networks incorporating flexible chains; the network topology freezing temperature decreases with increasing MW of flexible linear segments but increases with increasing MW of stiff segments. Vitrimer reconfigurability is therefore influenced not only by the energetics of bond exchange for a given network density, but also the entropy of polymer chains within the network

Characterizing response types and revealing noun ambiguity in German association norms

This paper presents an analysis of semantic association norms for German nouns. In contrast to prior studies, we not only collected associations elicited by written representations of target objects but also by their pictorial representations. In a first analysis, we identified systematic differences in the type and distribution of associate responses for the two presentation forms. In a second analysis, we applied a soft cluster analysis to the collected target-response pairs. We subsequently used the clustering to predict noun ambiguity and to discriminate senses in our target nouns

Magnetic resonance imaging analysis of the bioabsorbable Milagro™ interference screw for graft fixation in anterior cruciate ligament reconstruction

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months

Non-Compositional Term Dependence for Information Retrieval

Modelling term dependence in IR aims to identify co-occurring terms that are too heavily dependent on each other to be treated as a bag of words, and to adapt the indexing and ranking accordingly. Dependent terms are predominantly identified using lexical frequency statistics, assuming that (a) if terms co-occur often enough in some corpus, they are semantically dependent; (b) the more often they co-occur, the more semantically dependent they are. This assumption is not always correct: the frequency of co-occurring terms can be separate from the strength of their semantic dependence. E.g. "red tape" might be overall less frequent than "tape measure" in some corpus, but this does not mean that "red"+"tape" are less dependent than "tape"+"measure". This is especially the case for non-compositional phrases, i.e. phrases whose meaning cannot be composed from the individual meanings of their terms (such as the phrase "red tape" meaning bureaucracy). Motivated by this lack of distinction between the frequency and strength of term dependence in IR, we present a principled approach for handling term dependence in queries, using both lexical frequency and semantic evidence. We focus on non-compositional phrases, extending a recent unsupervised model for their detection [21] to IR. Our approach, integrated into ranking using Markov Random Fields [31], yields effectiveness gains over competitive TREC baselines, showing that there is still room for improvement in the very well-studied area of term dependence in IR

Single synapse glutamate imaging reveals multiple levels of release mode regulation in mammalian synapses

Mammalian central synapses exhibit vast heterogeneity in signaling strength. In order to understand the extent of this diversity, how it is achieved, and its functional implications, characterization of a large number of individual synapses is required. Using glutamate imaging, we characterized the evoked release probability and spontaneous release frequency of over 24,000 individual synapses. We found striking variability and no correlation between action potential-evoked and spontaneous synaptic release strength, suggesting distinct regulatory mechanisms. Subpixel localization of individual evoked and spontaneous release events reveals tight spatial regulation of evoked release and enhanced spontaneous release outside of evoked release region. Using on-stage post hoc immune-labeling of vesicle-associated proteins, Ca(2+)-sensing proteins, and soluble presynaptic proteins we were able to show that distinct molecular ensembles are associated with evoked and spontaneous modes of synaptic release

Electrostatically gated membrane permeability in inorganic protocells

Although several strategies are now available to produce functional microcompartments analogous to primitive cell-like structures, little progress has been made in generating protocell constructs with self-controlled membrane permeability. Here we describe the preparation of water-dispersible colloidosomes based on silica nanoparticles and delineated by a continuous semipermeable inorganic membrane capable of self-activated, electrostatically gated permeability. We use crosslinking and covalent grafting of a pH-responsive copolymer to generate an ultrathin elastic membrane that exhibits selective release and uptake of small molecules. This behaviour, which depends on the charge of the copolymer coronal layer, serves to trigger enzymatic dephosphorylation reactions specifically within the protocell aqueous interior. This system represents a step towards the design and construction of alternative types of artificial chemical cells and protocell models based on spontaneous processes of inorganic self-organization

Primera cita de Cloudina carinata Cortijo et al., 2010 en Sudamérica, Formación de Tamengo, Grupo de Corumbá, Brasil Brazil

It is herein presented the unprecedented occurrence of Cloudina carinata Cortijo et al., 2010 in the American continent. This new occurrence expanded the geographic distribution of this species, until now reported from sections in Spain and Siberia. The assembled biomineralizing metazoans Cloudina carinata, Cloudina lucianoi (Beurlen & Sommer, 1957) and Corumbella werneri Hahn et al., 1982 are presented for the first time from the Tamengo Formation, Corumbá Group, Porto Figueiras section, Corumbá Municipality, Mato Grosso do Sul State, Brazil. This new occurrence could be employed as an additional biostratigraphic tool for international correlation of the terminal Ediacaran, as well as for palaeobiogeographic and palaeoecologic reconstructions.Se documenta en este resumen la primera aparición de Cloudina carinata Cortijo et al., 2010 en el continente americano. Esta nueva aparición extiende la distribución geográfica de esta especie, hasta ahora restringida a España y Siberia. Se presenta por primera vez en la Formación de Tamengo (Corumbá, Estado de Mato Grosso do Sul, Brasil) la asociación de metazoos mineralizados compuesta por Cloudina carinata, Cloudina lucianoi (Beurlen & Sommer, 1957) y Corumbella werneri Hahn et al., 1982. Esta asociación podría ser útil como marcador bioestratigráfico en las correlaciones internacionales del Ediacárico terminal, así como para futuras reconstrucciones paleobiogeográficas y paleoecológicas

Pure silica nanoparticles for liposome/lipase system encapsulation: Application in biodiesel production

In this work we report the synthesis of organic inorganic solid with spherical morphology where enzyme, as active compounds, is encapsulated. The organic phase of nanospheres is composed of l-phosphatidylcholine, as liposome, and lipase from Rhizomucor miehei, as enzyme. The organic phase is covered with porous inorganic silica shell that could stabilize the internal liposomal phase and, consequently, isolate and protect the bioactive molecules. The liposome and silica amount used during the immobilization procedure have been optimized in order to obtain active and stable heterogeneous biocatalyst. Hybrid-nanospheres containing the enzyme were used to catalyze the transesterification reaction of triolein with methanol to methyl esters, typical biodiesel mixture compounds. The encapsulated enzyme retains its activity after 5 reaction cycles. The total productivity of the best catalyst obtained is higher than that of the free enzyme.The authors, A.C. and U.D., thank the Spanish MICINN (Consolider Ingenio 2010-MULTICAT (CSD2009-00050) and MAT2011-29020-C02-01) for their financial support.Macario, A.; Verri, F.; Díaz Morales, UM.; Corma Canós, A.; Giordano, G. (2013). Pure silica nanoparticles for liposome/lipase system encapsulation: Application in biodiesel production. Catalysis Today. 204:148-155. doi:10.1016/j.cattod.2012.07.014S14815520

The Private Life of Environmental Treaties

The gravitational pull of environmental treaties is felt not only by states. Yet international lawyers almost exclusively focus on states to explain treaty compliance, measure treaty implementation, and assess treaty effectiveness. This essay draws attention to a phenomenon that falls outside traditional boundaries of treaty analysis: the efforts of private corporations that aim at complying with environmental treaties. Existing models of treaty implementation are inadequate to explain these direct interactions between corporations and treaties. The dominant grammar of treaty “compliance” equally fails to fit. Using a little-studied example - the UNESCO World Heritage Convention - this essay highlights the phenomenon of corporations’ aspiring to conform their behavior to environmental treaty requirements