Anisotropic deformation for local shape control

Computational Visual Media - We present a novel approach to mesh deformation that enables simple context sensitive manipulation of 3D geometry. The method is based on locally anisotropic...     

On the convergence of 3D free discontinuity models in variational fracture

Free discontinuity problems arising in the variational theory for fracture mechanics are considered. A Γ -convergence proof for an r-adaptive 3D finite element discretization is given in the case of a brittle material. The optimal displacement field, crack pattern and mesh geometry are obtained through a variational procedure that encompasses both mechanical and configurational forces. Possible extensions to cohesive fracture and quasi-static evolutions are discussed.     

Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB<Subscript>2</Subscript> Composites Produced by Direct Metal Laser Sintering (DMLS)

Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB₂ composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB₂, 1% wt. of nanosize TiB₂. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB₂ reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.     

Where Are We with RPE Replacement Therapy? A Translational Review from the Ophthalmologist Perspective

The retinal pigmented epithelium (RPE) plays a pivotal role in retinal homeostasis. It is therefore an interesting target to fill the unmet medical need of different retinal diseases, including age-related macular degeneration and Stargardt disease. RPE replacement therapy may use different cellular sources: induced pluripotent stem cells or embryonic stem cells. Cells can be transferred as suspension on a patch with different surgical approaches. Results are promising although based on very limited samples. In this review, we summarize the current progress of RPE replacement and provide a comparative assessment of different published approaches which may become standard of care in the future.     

Novel Insights into Autophagy and Prostate Cancer: A Comprehensive Review

Autophagy is a complex process involved in several cell activities, including tissue growth, differentiation, metabolic modulation, and cancer development. In prostate cancer, autophagy has a pivotal role in the regulation of apoptosis and disease progression. Several molecular pathways are involved, including PI3K/AKT/mTOR. However, depending on the cellular context, autophagy may play either a detrimental or a protective role in prostate cancer. For this purpose, current evidence has investigated how autophagy interacts within these complex interactions. In this article, we discuss novel findings about autophagic machinery in order to better understand the therapeutic response and the chemotherapy resistance of prostate cancer. Autophagic-modulation drugs have been employed in clinical trials to regulate autophagy, aiming to improve the response to chemotherapy or to anti-cancer treatments. Furthermore, the genetic signature of autophagy has been found to have a potential means to stratify prostate cancer aggressiveness. Unfortunately, stronger evidence is needed to better understand this field, and the application of these findings in clinical practice still remains poorly feasible.     

PDGF/PDGFR: A Possible Molecular Target in Scleroderma Fibrosis

Systemic sclerosis (SSc) is a clinically heterogeneous disorder of the connective tissue characterized by vascular alterations, immune/inflammatory manifestations, and organ fibrosis. SSc pathogenesis is complex and still poorly understood. Therefore, effective therapies are lacking and remain nonspecific and limited to disease symptoms. In the last few years, many molecular and cellular mediators of SSc fibrosis have been described, providing new potential options for targeted therapies. In this review: (i) we focused on the PDGF/PDGFR pathway as key signaling molecules in the development of tissue fibrosis; (ii) we highlighted the possible role of stimulatory anti-PDGFRα autoantibodies in the pathogenesis of SSc; (iii) we reported the most promising PDGF/PDGFR targeting therapies.     

Oxidative and carbonaceous patterning of Si surface in an organic media by scanning probe lithography

A simple top-down fabrication technique that involves scanning probe lithography on Si is presented. The writing procedure consists of a chemically selective patterning in mesitylene. Operating in an organic media is possible to perform local oxidation or solvent decomposition during the same pass by tuning the applied bias. The layer deposited with a positively biased tip with sub-100-nm lateral resolution consists of nanocrystalline graphite, as verified by Raman spectroscopy. The oxide pattern obtained in opposite polarization is later used as a mask for dry etching, showing a remarkable selectivity in SF₆ plasma, to produce Si nanofeatured molds.     

Interspecific Cross-Attraction between the South American Cerambycid Beetles <Emphasis Type="Italic">Cotyclytus curvatus</Emphasis> and <Emphasis Type="Italic">Megacyllene acuta</Emphasis> is Averted by Minor Pheromone Components

During field screening trials conducted in Brazil in 2015, adults of both sexes of the cerambycid beetles Cotyclytus curvatus (Germar) and Megacyllene acuta (Germar) (subfamily Cerambycinae, tribe Clytini) were significantly attracted to racemic 3-hydroxyhexan-2-one and racemic 2-methylbutan-1-ol, chemicals which previously have been identified as male-produced aggregation-sex pheromones of a number of cerambycid species endemic to other continents. Subsequent analyses of samples of beetle-produced volatiles revealed that males of C. curvatus sex-specifically produce only (R)-3-hydroxyhexan-2-one, whereas males of M. acuta produce the same compound along with lesser amounts of (2S,3S)-2,3-hexanediol and (S)-2-methylbutan-1-ol. Follow-up field trials showed that both sexes of both species were attracted to synthetic reconstructions of their respective pheromones, confirming that males produce aggregation-sex pheromones. The minor pheromone components of M. acuta, (S)-2-methylbutan-1-ol and (2S,3S)-2,3-hexanediol, synergized attraction of that species, but antagonized attraction of C. curvatus to (R)-3-hydroxyhexan-2-one. Beetles of other cerambycine species also were attracted in significant numbers, including Chrysoprasis linearis Bates, Cotyclytus dorsalis (Laporte & Gory), and Megacyllene falsa (Chevrolat). Our results provide further evidence that 3-hydroxyhexan-2-one is a major component of attractant pheromones of numerous cerambycine species world-wide. Our results also highlight our increasing understanding of the crucial role of minor pheromone components in imparting species specificity to cerambycid pheromone blends, as is known to occur in numerous species in other insect families.     

Precursor gas chemistry determines the crystallinity of carbon nanotubes synthesized at low temperature

Despite significant progress in carbon nanotube (CNT) synthesis by thermal chemical vapor deposition (CVD), the factors determining the structure of the resulting carbon filaments and other graphitic nanocarbons are not well understood. Here, we demonstrate that gas chemistry influences the crystal structure of carbon filaments grown at low temperatures (500 °C). Using thermal CVD, we decoupled the thermal treatment of the gaseous precursors (C₂H₄/H₂/Ar) and the substrate-supported catalyst. Varying the preheating temperature of the feedstock gas, we observed a striking transition between amorphous carbon nanofibers (CNFs) and crystalline CNTs. These results were confirmed using both a hot-wall CVD system and a cold-wall CVD reactor. Analysis of the exhaust gases (by ex situ gas chromatography) showed increasing concentrations of specific volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) that correlated with the structural transition observed (characterized using high-resolution transmission electron microscopy). This suggests that the crystallinity of carbon filaments may be controlled by the presence of specific gas phase precursor molecules (e.g., VOCs and PAHs). Thus, direct delivery of these molecules in the CVD process may enable selective CNF or CNT formation at low substrate temperatures. The inherent scalability of this approach could impact many promising applications, especially in the electronics industry.