Polyurethanes synthetized with polyols of distinct molar masses: Use of the artificial neural network for prediction of degree of polymerization

The molar mass of the polyurethanes (PUs)' reagents directly influences their thermal response, affecting both the polymerization process and the enthalpy and the degree of reaction. This study reports applying an artificial neural network (ANN), associated with surface response methodology (SRM) models, to predict the calorimetric behavior of certain PU's bulk polymerizations. A noncatalyzed reaction between an aliphatic hexamethylene diisocyanate (HDI) and a polycarbonate diol (PCD) with distinct molar masses (500, 1000, and 2000 g/mol) was proposed. A high level of reliability of the predicted calorimetric curves was obtained due to an excellent agreement between theoretical and modeled results, enabling creating a 3D surface response to predict the reaction kinetics. Also, it was possible to observe that the polymerization kinetics is affected by the  OH group's association phenomena. The applied methodology can be extended for other materials or properties of interest.     

Electrochemical activity of sulfur networks synthesized through RAFT polymerization

Novel results concerning the inverse vulcanization of sulfur using reversible addition–fragmentation chain transfer (RAFT) polymerization are here reported. It is shown that RAFT polymerization can be used to carry out this crosslinking process, with the additional possibility to extend the reaction time from a few minutes as with classical free radical polymerization (FRP) to several hours. Higher control on viscosity and processability of the synthesized networks, as well as, the implementation of semibatch feed policies during crosslinking are important advantages of the RAFT process here explored comparatively to the FRP inverse vulcanization. Using cyclic voltammetry, it was assessed the electrochemical activity of the synthesized sulfur‐rich polymer networks. It is shown that the fundamental electrochemical activity of the elemental sulfur was preserved in the produced materials. Testing of electrochemical cells assembled with lithium in the anode and different sulfur based materials in the cathode, including the synthesized RAFT networks, is also shown. The results here presented highlight the new opportunities introduced by reversible‐deactivation radical polymerization mechanisms on the control of the synthesis process and in the design of such advanced materials and show also that many potential derivatizing possibilities can be achieved. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43993.     

Multicomponent Petasis‐borono Mannich Preparation of Alkylaminophenols and Antimicrobial Activity Studies

In this work we report the antibacterial activity of alkylaminophenols. A series of such compounds was prepared by a multicomponent Petasis‐borono Mannich reaction starting from salicylaldehyde and its derivatives. The obtained compounds were tested against a large panel of microorganisms, Gram‐positive and Gram‐negative bacteria, and a yeast. Among the several tertiary amine derivatives tested, indoline‐derived aminophenols containing a nitro group at the para‐phenol position showed considerable activity against bacteria tested with minimal inhibitory concentrations as low as 1.36 μm against Staphyloccocus aureus and Mycobacterium smegmatis. Cytotoxicity of the new para‐nitrophenol derivatives was observed only at concentrations much higher than those required for antibacterial activity.     

A New Folding Kinetic Mechanism for Human Transthyretin and the Influence of the Amyloidogenic V30M Mutation

Protein aggregation into insoluble amyloid fibrils is the hallmark of several neurodegenerative diseases, chief among them Alzheimer’s and Parkinson’s. Although caused by different proteins, these pathologies share some basic molecular mechanisms with familial amyloidotic polyneuropathy (FAP), a rare hereditary neuropathy caused by amyloid formation and deposition by transthyretin (TTR) in the peripheral and autonomic nervous systems. Among the amyloidogenic TTR mutations known, V30M-TTR is the most common in FAP. TTR amyloidogenesis (ATTR) is triggered by tetramer dissociation, followed by partial unfolding and aggregation of the low conformational stability monomers formed. Thus, tetramer dissociation kinetics, monomer conformational stability and competition between refolding and aggregation pathways do play a critical role in ATTR. Here, we propose a new model to analyze the refolding kinetics of WT-TTR and V30M-TTR, showing that at pH and protein concentrations close to physiological, a two-step mechanism with a unimolecular first step followed by a second-order second step adjusts well to the experimental data. Interestingly, although sharing the same kinetic mechanism, V30M-TTR refolds at a much slower rate than WT-TTR, a feature that may favor the formation of transient species leading to kinetic partition into amyloidogenic pathways and, thus, significantly increasing the probability of amyloid formation in vivo.     

Synthesis of poly(lactic acid) by heterogeneous acid catalysis from <Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid

Poly(lactic acid) (PLA) is an important polymer because of its significant biocompatibility and biodegradability. Supported H₃PW₁₂O₄₀ (H₃PW) on activated carbon was utilized for the catalytic polymerization of D,L-lactic acid, resulting in blends of PLA. The stability of the polymer was monitored by thermogravimetry (TGA), and the decomposition temperature (T_d) was used to determine the optimal production conditions (i.e., temperature of 180 °C for 15 h; 0.1 wt. % catalyst; 20 wt. % H₃PW/carbon calcined at 400 °C). The best catalyst was reused three times with good activity and recovery (95 %) and was analyzed to confirm the consistency of its Keggin structure, dispersion, and acidity, which are important parameters that affect the catalyst’s activity. The obtained polymer was characterized by gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FT-IR), ¹H/¹³C nuclear magnetic resonance (NMR) spectroscopy, specific optical rotation ([α]_D ²⁵), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The average molar mass of the polymer was 17,400 g mol^?1. Blends of poly(lactic acid) with 85 % poly(L-lactic acid) stereospecific isomer were obtained.

Open image in new window

Graphical Abstract Stereoselective synthesis of 85 % PLLA from polymerization of d,l-lactic acid using 12-tungstophosphoric acid supported on carbon as a catalyst

     

Angioarchitecture and morphology of temporomandibular joint of Monodelphis domestica

The opossum Monodelphis domestica presents movement of the temporomandibular joint (TMJ) reflecting adaptation to eating habits similar to movement in humans, but the structure of the TMJ is not yet known. Thus, nine young M. domestica, of both sexes were weighed, anesthetized with xylazine (10 mg kg^?1), and ketamine (70 mg kg^?1) and processed for: 1. The analyses of the macroscopic angioarchitecture after latex injection, as well as the topography of the TMJ; 2. The analysis of microvascularization after injection of Mercox resin and corrosion of soft tissue with NaOH using scanning electron microscopy and; 3. The histological evaluation of the TMJ with an optical microscope. Macroscopic analysis of the latex injected vessels revealed the distribution of the arteries from the common carotid artery, receiving branches of the superficial temporal and maxillary arteries. The mandibular condyle has the long axis in the lateral–lateral direction, and is convex in the anterior–posterior direction. Its topography was determined in relation to the eye and external acoustic meatus. With scanning electron microscopy, microvascularization consists of arterioles of varying diameter (85–15 µm) of the meandering capillary network in the retrodiscal region, and a network of straight capillaries in the TMJ anterior region. Via light microscopy the TMJ has similar histological features to those of humans. These macroscopic, microscopic and ultrastructural data from TMJ of the M. domestica could be a suitable model for TMJ physiology and pathophysiology studies for then speculate on possible human studies. Microsc. Res. Tech. 79:806–813, 2016. © 2016 Wiley Periodicals, Inc.     

Investigation of interfaces with analytical tools

This paper focuses on advancements in three areas of analyzing interfaces, namely, acoustic microscopy for detecting damage to closely spaced interfaces, thermal imaging to detect damage and degradation of thermal interface materials and laser spallation, a relatively new concept to understand the strength of interfaces. Acoustic microscopy has been used widely in the semiconductor assembly and package area to detect delamination, cracks and voids in the package, but the resolution in the axial direction has always been a limitation of the technique. Recent advancements in acoustic waveform analysis has now allowed for detection and resolution of closely spaced interfaces such as layers within the die. Thermal imaging using infrared (IR) thermography has long been used for detection of hot spots in the die or package. With recent advancements in very high-speed IR cameras, improved pixel resolution, and sophisticated software programming, the kinetics of heat flow can now be imaged and analyzed to reveal damage or degradation of interfaces that are critical to heat transfer. The technique has been demonstrated to be useful to understand defects and degradation of thermal interface materials used to conduct heat away from the device. Laser spallation is a method that uses a short duration laser pulse to cause fracture at the weakest interface and has the ability to measure the adhesion strength of the interface. The advantage of this technique is that it can be used for fully processed die or wafers and even on packaged devices. The technique has been used to understand interfaces in devices with copper metallization and low-k dielectrics.     

Vision and inertial sensor cooperation using gravity as a vertical reference

This paper explores the combination of inertial sensor data with vision. Visual and inertial sensing are two sensory modalities that can be explored to give robust solutions on image segmentation and recovery of 3D structure from images, increasing the capabilities of autonomous robots and enlarging the application potential of vision systems. In biological systems, the information provided by the vestibular system is fused at a very early processing stage with vision, playing a key role on the execution of visual movements such as gaze holding and tracking, and the visual cues aid the spatial orientation and body equilibrium. In this paper, we set a framework for using inertial sensor data in vision systems, and describe some results obtained. The unit sphere projection camera model is used, providing a simple model for inertial data integration. Using the vertical reference provided by the inertial sensors, the image horizon line can be determined. Using just one vanishing point and the vertical, we can recover the camera's focal distance and provide an external bearing for the system's navigation frame of reference. Knowing the geometry of a stereo rig and its pose from the inertial sensors, the collineations of level planes can be recovered, providing enough restrictions to segment and reconstruct vertical features and leveled planar patches.     

Microbial diversity during maturation and natural processing of coffee cherries of Coffea arabica in Brazil

The magnitude and diversity of the microbial population associated with dry (natural) processing of coffee (Coffea arabica) has been assessed during a 2-year period on 15 different farms in the Sul de Minas region of Brazil. Peptone water-washed samples were taken of maturing cherries on trees (cherries, raisins and dried cherries) and from ground fermentations. The microbial load varied from 3×10⁴ to 2.2×10⁹ cfu/cherry with a median value of 1.6×10⁷ cfu/cherry. The microbial load increased after heavy rainfall on cherries that were drying on the ground. At all stages, bacteria were usually the most abundant group, followed by filamentous fungi and finally yeasts. Counts of bacteria, yeasts and fungi varied considerably between farms and at different stages of maturation and processing and no consistent pattern could be seen. Yeasts showed an increase during the fermentation process. Median counts were not significantly different for fungi, yeasts and bacteria between the 2 years although Gram-negative bacteria dominated in the wet year and Gram-positive bacteria dominated in the dry year. Of a total of 754 isolates, 626 were identified to at least genus level comprising 44 genera and 64 different species. The 164 isolates of Gram-negative bacteria included 17 genera and 26 species, the most common of which were members of the genera Aeromonas, Pseudomonas, Enterobacter and Serratia. Of 191 isolates of Gram-positive bacteria, 23 were spore-forming and included six Bacillus species, and 118 were non-spore-formers of which over half were Cellulomonas with lesser numbers of Arthrobacter, Microbacterium, Brochothrix, Dermabacter and Lactobacillus. Of the 107 yeast isolates, 90 were identified into 12 genera and 24 different species and almost all were fermentative. The most common genera, in decreasing frequency, were Pichia, Candida, Arxula and Saccharomycopsis. There were many rarely described yeasts including Pichia lynferdii and Arxula adeninivorans. Almost all 292 fungal isolates were identified to genus level and 52 were identified to species level. Cladosporium, Fusarium and Penicillium each comprised about one third of the isolates and were found on all farms. Only 3% of the isolates were Aspergillus. Beauvaria, Monilia, Rhizoctonia and Arthrobotrys species were also occasionally found. The microbial flora is much more varied and complex than found in wet fermentations. The genera and species identified include members known to have all types of pectinase and cellulase activities.     

Stimuli-Responsive Multifunctional Nanomedicine for Enhanced Glioblastoma Chemotherapy Augments Multistage Blood-to-Brain Trafficking and Tumor Targeting

Minimal therapeutic advances have been achieved over the past two decades for glioblastoma (GBM), which remains an unmet clinical need. Here, hypothesis-driven stimuli-responsive nanoparticles (NPs) for docetaxel (DTX) delivery to GBM are reported, with multifunctional features that circumvent insufficient blood-brain barrier (BBB) trafficking and lack of GBM targeting—two major hurdles for anti-GBM therapies. NPs are dual-surface tailored with a i) brain-targeted acid-responsive Angiopep-2 moiety that triggers NP structural rearrangement within BBB endosomal vesicles, and ii) L-Histidine moiety that provides NP preferential accumulation into GBM cells post-BBB crossing. In tumor invasive margin patient cells, the stimuli-responsive multifunctional NPs target GBM cells, enhance cell uptake by 12-fold, and induce three times higher cytotoxicity in 2D and 3D cell models. Moreover, the in vitro BBB permeability is increased by threefold. A biodistribution in vivo trial confirms a threefold enhancement of NP accumulation into the brain. Last, the in vivo antitumor efficacy is validated in GBM orthotopic models following intratumoral and intravenous administration. Median survival and number of long-term survivors are increased by 50%. Altogether, a preclinical proof of concept supports these stimuli-responsive multifunctional NPs as an effective anti-GBM multistage chemotherapeutic strategy, with ability to respond to multiple fronts of the GBM microenvironment.