Impact of quasi-isotropic raster layup on the mechanical behaviour of fused filament fabrication parts

The development of fused filament fabrication has extended the range of application of additive manufacturing in various areas of research. However, the mechanical strength of the fused filament fabrication–printed parts were considerably lower than that of parts fabricated by other conventional methods, owing to the observed anisotropic behaviour and formation of voids by weak interlayer diffusion. Intense studies on the effect of design and process parameters of the printed parts on the mechanical properties have been done, whereas studies on the effect of build orientations and raster patterns needs special concern. The main aim of this work is to fabricate parts printed using quasi-isotropic laminate arrangement of rasters, achieved by a raster layup of [45/0/−45/90]s, and to compare their mechanical properties with those of the commonly used 0°/90° (cross) and 45°/−45° (crisscross) raster oriented parts. The quasi-isotropic–oriented samples were observed with improved mechanical behaviour in tensile, compressive, flexural and impact tests compared to the commonly employed raster orientations.

Atom Probe Study of 1-Octadecanethiol Self-Assembled Monolayers on Platinum (111) and (200) Surfaces

Atom probe tomography measurements of self-assembled monolayers of 1-octadecanethiol on platinum tips were performed and their fragmentation behavior under the influence of different laser powers was investigated. The carbon backbone evaporates in the form of small hydrocarbon fragments consisting of one to four carbon atoms, while sulfur evaporates exclusively as single ions. The carbon molecules evaporate at very low fields of 5.9 V/nm, while S requires a considerably higher evaporation field of 23.4 V/nm. With increasing laser power, a weak, but noticeable trend toward larger fragment sizes is observed. No hydrocarbon fragments containing S are detected, indicating that a strong S–Pt bond has formed. The observed surface coverage of S fits well with literature values and is higher for (111)-oriented samples than for (200).

Geological-structural mapping and geocronology of shear zones: A methodological proposal

The deformation registered in rocks in the field can be characterized based on the structures preserved in outcrops, which can related be to wide discontinuity zones named faults and shear zones. The geological-structural mapping and the geochronology of these tectonic structures are a topic of great interest not only for tectonic modeling but also for reconstruction of the geological evolution of the national territory. The methodology suggest for the analysis of faults and shear zones is based on eight steps, including: 1) definition of the geological context in which the structure was developed; 2) photointerpretation, image geoprocessing, and geological-structural mapping of the structural and lithological characteristics of the faults and shear zones; 3) petrographic analysis of field-oriented samples; 4) quantification of strain orientation and geometry through 3D finite strain analyses and quantification of non-coaxiliaty of deformation through vorticity analyses; 5) SEM-TEM-EBSD microanalysis; 6) quantification of the P-T conditions of deformation through phase-equilibria modeling or conventional geothermobarometry; 7) dating of syn-kinematic minerals phases and mylonitic rocks through Ar-Ar analyses, in order to determine the reactivation and deformation ages of the structure, respectively, as well as the implementation of the U-Pb technique in syn-kinematic calcite crystals developed in the fault planes; and 8) dating of geological elements adjacent to the structure, such as syn-kinematic intrusive bodies associated with the deformation event using zircon U-Pb dating, rocks hydrothermally altered through Ar-Ar method, and zircon and apatite fission-tracks dating of the blocks adjacent to the faults for determining exhumation ages.

Influences of Dispersions’ Shapes and Processing in Magnetic Field on Thermal Conductibility of PDMS–Fe3O4 Composites

Composites of magnetite (Fe3O4) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (α-FeOOH) and spherical hematite (α-Fe2O3), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe3O4 composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.

Repository scale classification and decomposition of tandem mass spectral data

Various studies have shown associations between molecular features and phenotypes of biological samples. These studies, however, focus on a single phenotype per study and are not applicable to repository scale metabolomics data. Here we report MetSummarizer, a method for predicting (i) the biological phenotypes of environmental and host-oriented samples, and (ii) the raw ingredient composition of complex mixtures. We show that the aggregation of various metabolomic datasets can improve the accuracy of predictions. Since these datasets have been collected using different standards at various laboratories, in order to get unbiased results it is crucial to detect and discard standard-specific features during the classification step. We further report high accuracy in prediction of the raw ingredient composition of complex foods from the Global Foodomics Project.

The southernmost occurrence of the volcanic-rich layer of 5.5 Main the Northern Apennines: clues on its deposition

<p>A volcanic-rich horizon crops along the Northern Apennines chain for about 200 km, in the post-evaporitic sedimentary sequence with an age of 5.5 Ma. Its thickness ranges between 30-200 cm and has been interpreted either as a primary fallout or a giant gravity flow in seawater (Aldinucci et al., 2005; Trua et al., 2010; Cosentino et al., 2013). Here, we focus on the two southernmost occurrences in the Abruzzo region (Central Italy): Castiglione a’ Casauria (CAC 42°14'10'' 13°53'29') and San Vittorino (SVT 42°12'10'' 13°53'29'') villages.</p><p>The SVT and CAC deposits are lithified with thickness of 80 and 220 cm, respectively, mildly fractured and greyish to light brown in colour. Four (SVT) and fifteen (CAC) oriented samples coaxial to the field, were cut and polished to expose about 470 and 700 cm<sup>2</sup>, respectively, of their vertical mesoscopic surfaces. The oriented thin sections and powders were prepared according to these mesoscopic attributes.</p><p>The XRPD (X-ray powder diffraction) spectra show the presence of a peculiar prominent large shoulder reflecting significative silicate non-crystalline phase, i.e. volcanic glass, plus faint Bragg reflections indicative of minor amounts of quartz, two feldspars (anorthite and sanidine), clinopyroxene, biotite and montmorillonite. The latter mineral results from post-emplacement and secondary crystallization. In addition, calcite and dolomite XRPD peaks occur with intensity inversely proportional to that of the silicate glass, reflecting the abundance or paucity of sedimentary versus volcanic fractions in sub-layers.</p><p>The microscopic 2D textures plus compositional features were investigated by SEM and EPMA. Both volcanic layers are very rich in fine-grained (averaging on 200 mm) and highly sorted glassy ashy clasts, while minerals are very poor (< 5 area%) in agreement with XRPD outcomes. Lithified ashes are mainly blocky in shape and un-broken. The ashes plot in the rhyolitic TAS field and overlap those already reported from other Northern Apennine sites. The amount of volatiles (H<sub>2</sub>O + CO<sub>2</sub>) estimated from EPMA average on about 6 wt.%, in agreement with the quantities of LOI determined on both bulk samples.</p><p>Field observations coupled with analysis on mesoscopic polished rock slices and thin sections do not shown any significant vertical size gradation and sorting, while fossils are almost absent. By contrast, both volcanic-rich deposits show: sedimentary- and volcanic-rich sub-layers, cm-sized volcanic clasts dispersed prevalently on the uppermost sedimentary sub-layers, cm-sized convolute laminations and slumped pseudo-beds. All these features demonstrate mass transport, soft-sediment deformation and fluid escape in seawater. Nonetheless, the absence of rounded ashy clasts, lithic sedimentary rock and classic Bouma sequence features (typical in coeval and adjacent deposits) mirror for local remobilization of poorly consolidated to loose carbonate and tephra deposits. In parallel, the high sorting of fine ashy clasts suggest a primary deposition from a distal fall-out eruptions. The location and features of both SVT and CAC volcanic-rich layers extend the previously inferred distribution of this ancient volcanic eruption.</p><p>References</p><p>Aldinucci et al., 2005. GeoActa, 4, 2005, pp. 67-82</p><p>Cosentino et al., 2013. Geology, 41, pp. 323-326</p><p>Trua et al., 2010. Italian Journal of Geosciences, 129, pp. 269-279</p>

Waffle method: A general and flexible approach for FIB-milling small and anisotropically oriented samples

Cryo-FIB/SEM has emerged from within the field of cryo-EM as the method for obtaining the highest resolution structural information of complex biological samples in-situ in native and non-native environments. However, challenges remain in conventional cryo-FIB/SEM workflows, including milling specimens with preferred orientation, low throughput when milling small specimens, cellular specimens that concentrate poorly in grid squares, and thick specimens that do not vitrify well. Here we present a general approach we call the ‘waffle method’ which leverages high-pressure freezing to address these challenges. We illustrate the mitigation of these challenges by applying the waffle method to reveal the macrostructure of the polar tube in microsporidian spores in multiple complementary orientations by cryo-ET, which was previously not possible due to preferred orientation of the spores on the grid. We also present a unique and critical stress-relief gap design specifically for waffled lamellae. Additionally, we describe applications of the waffle method which are currently being explored. We propose the waffle method as a way to achieve many of the advantages of cryo-liftout on the specimen grid while avoiding the long, technically-demanding process that cryo-liftout requires.

Assessment of Fiber Orientation on the Mechanical Properties of PA6/Cellulose Composite

Cellulose is being considered as a suitable renewable reinforcement for materials production. In particular, cellulose based composites are attracting global interest for their unique and intrinsic properties such as strength to weight ratio, dimensional stability and low thermal expansion and contraction. This article investigates the preparation of cellulose pulp fibers with polyamide-6 (PA6) polymer and the effect of fiber orientation within the matrix on the final properties of the biocomposite. Cellulose pulp fibers were melt compounded with PA6 using a thermo-kinetic mixer. Different formulations were prepared and the compounds were manufactured into test samples by injection molding. Mechanical characterization revealed that elastic modulus and the flexural properties increased linearly with the fiber composition. The effect of fiber orientation was examined from square samples out of which individual specimens were cut at different directions with respect to the flow direction. The contributions related to fiber content and effect of fiber orientation on the tensile properties assessed lent positively towards parallel oriented samples (0°) with respect to flow direction. Furthermore, the cellulose network within the biocomposite revealed the superior interfacial properties between the cellulose and PA6 matrix when observed under a scanning electron microscope.

Quantifying shortening across the central Appalachian fold-thrust belt, Virginia and West Virginia, USA: Reconciling grain-, outcrop-, and map-scale shortening

We present a kinematic model for the evolution of the central Appalachian fold-thrust belt (eastern United States) along a transect through the western flank of the Pennsylvania salient. New map and strain data are used to construct a balanced geologic cross section spanning 274 km from the western Great Valley of Virginia northwest across the Burning Spring anticline to the undeformed foreland of the Appalachian Plateau of West Virginia. Forty (40) oriented samples and measurements of >300 joint orientations were collected from the Appalachian Plateau and Valley and Ridge province for grain-scale bulk finite strain analysis and paleo-stress reconstruction, respectively. The central Appalachian fold-thrust belt is characterized by a passive-roof duplex, and as such, the total shortening accommodated by the sequence above the roof thrust must equal the shortening accommodated within duplexes. Earlier attempts at balancing geologic cross sections through the central Appalachians have relied upon unquantified layer-parallel shortening (LPS) to reconcile the discrepancy in restored line lengths of the imbricated carbonate sequence and mainly folded cover strata. Independent measurement of grain-scale bulk finite strain on 40 oriented samples obtained along the transect yield a transect-wide average of 10% LPS with province-wide mean values of 12% and 9% LPS for the Appalachian Plateau and Valley and Ridge, respectively. These values are used to evaluate a balanced cross section, which shows a total shortening of 56 km (18%). Measured magnitudes of LPS are highly variable, as high as 17% in the Valley and Ridge and 23% on the Appalachian Plateau. In the Valley and Ridge province, the structures that accommodate shortening vary through the stratigraphic package. In the lower Paleozoic carbonate sequences, shortening is accommodated by fault repetition (duplexing) of stratigraphic layers. In the interval between the duplex (which repeats Cambrian through Upper Ordovician strata) and Middle Devonian and younger (Permian) strata that shortened through folding and LPS, there is a zone that is both folded and faulted. Across the Appalachian Plateau, slip is transferred from the Valley and Ridge passive-roof duplex to the Appalachian Plateau along the Wills Mountain thrust. This shortening is accommodated through faulting of Upper Ordovician to Lower Devonian strata and LPS and folding within the overlying Middle Devonian through Permian rocks. The significant difference between LPS strain (10%–12%) and cross section shortening estimates (18% shortening) highlights that shortening from major subsurface faults within the central Appalachians of West Virginia is not easily linked to shortening in surface folds. Depending on length scale over which the variability in LPS can be applied, LPS can accommodate 50% to 90% of the observed shortening; other mechanisms, such as outcrop-scale shortening, are required to balance the proposed model.