Commercially pure titanium (CP-Ti) has received a great deal of attention in medical applications. Improvement of its mechanical properties plays a key role in enhancing the biomechanical ...compatibility of Ti implants, leading to avoid revision surgeries. Emerging advanced manufacturing technologies such as selective laser melting (SLM) is providing an ideal platform for producing components with almost no geometric constraints and is economically feasible down to a batch size of one. This study presents the results of using SLM to produce CP-Ti parts starting from powder with a wide grain size range up to 100μm. Accurate manipulation of SLM manufacturing parameters were applied to produce nearly full dense (>99.5%) CP-Ti parts without any post-treatments. Compared with the properties of those manufactured by traditional processing technologies, the microhardness, compressive, and tensile strengths of SLM-processed CP-Ti parts have been improved to 261Hv, 1136MPa, and 757MPa, respectively, due to the formation of refined martensitic α′ grains during SLM. The optimal manufacturing parameters could enhance the strength and hardness of CP-Ti and yet maintaining the ductility of titanium. Fractography study of the tensile-failed SLM-processed specimens showed that incompletely melted particles and porosities caused early fracture in porous sample. Mixture of dimples and minor quasi-cleavage facets covered most fracture surface of full dense sample.
Ti and Ti-TiB composite materials were produced by selective laser melting (SLM). Ti showed an α΄ microstructure, whereas the Ti-TiB composite revealed a distribution of needle-like TiB particles ...across an α-Ti matrix. Hardness (H) and reduced elastic modulus (Er) were investigated by nanoindentation using loads of 2, 5 and 10 mN. The results showed higher H and Er values for the Ti-TiB than Ti due to the hardening and stiffening effects of the TiB reinforcements. On increasing the nanoindentation load, H and Er were decreased. Comparison of the nanoindentation results with those derived from conventional hardness and compression tests indicated that 5 mN is the most suitable nanoindentation load to assess the elastic modulus and hardness properties. The wear resistance of the samples was related to their corresponding H/Er and H3/Er2 ratios obtained by nanoindentation. These investigations showed that there is a high degree of consistency between the characterization using nanoindentation and the wear evaluation from conventional wear tests.
The large-scale distribution of neutral hydrogen in the Universe will be luminous through its 21 cm emission. Here, for the first time, we use the auto-power spectrum of 21 cm intensity fluctuations ...to constrain neutral hydrogen fluctuations at z ∼ 0.8. Our data were acquired with the Green Bank Telescope and span the redshift range 0.6 < z < 1 over two fields totalling 41 deg2 and 190 h of radio integration time. The dominant synchrotron foregrounds exceed the signal by ∼103, but have fewer degrees of freedom and can be removed efficiently. Even in the presence of residual foregrounds, the auto-power can still be interpreted as an upper bound on the 21 cm signal. Our previous measurements of the cross-correlation of 21 cm intensity and the WiggleZ galaxy survey provide a lower bound. Through a Bayesian treatment of signal and foregrounds, we can combine both fields in auto- and cross-power into a measurement of ΩHI
bHI
= 0.62+0.23
−0.15 × 10−3 at 68 per cent confidence with 9 per cent systematic calibration uncertainty, where ΩHI
is the neutral hydrogen (H i) fraction and bHI
is the H i bias parameter. We describe observational challenges with the present data set and plans to overcome them.
Commercially pure titanium (CP-Ti) and Ti–TiB composite parts with three different porosity levels (i.e. 10%, 17% and 37%) were produced by selective laser melting (SLM). Scanning electron microscopy ...(SEM) investigations show that martensitic (α′) microstructure exists in SLM-processed CP-Ti parts, whilst SLM-processed Ti–TiB composites present needle-shape TiB particles distributed in α-Ti matrix. Mechanical properties of these porous samples decrease with porosity level increasing. The yield strength and elastic modulus of porous CP-Ti parts range 113–350MPa and 13–68GPa respectively, which are much lower than those for porous Ti–TiB counterparts (234–767MPa and 25–84GPa respectively) mainly due to the strengthening effect induced by TiB particles in Ti–TiB samples. Compression stress–strain curves of 37% porous CP-Ti parts show a typical three-stage behavior of ductile porous metals. Also, the elastic moduli of both 37% porous CP-Ti and Ti–TiB samples are similar to that of human bone. SEM investigations of the porous CP-Ti samples after compression testing show that no crack presents until 50% compressive strain and most of deformation is absorbed by porous areas. In contrast, μ-CT investigations indicate that all porous Ti–TiB samples fail at early stages of compression testing due to cracks resulting from insufficient ductility of struts of porous areas, because they are not able to accommodate high strains of the deformation at high strengths.
The present work is directed to characterize the phosphogypsum (PG) wastes by means of in situ atmospheric radon measurements, gross-alpha and gamma-ray spectrometry measurements. The average radon ...concentrations in three locations: Valea Calugareasca, Navodari and Turnu Magurele are 21.88 ± 3.19, 26.56 ± 2.90 and 33.43 ± 3.64 (Bq × m
−3
), respectively. The γ-ray measurements showed that the total activities are 1510.62 ± 148.08, 1838.77 ± 165.04, 1363.83 ± 147.96 (Bq × kg
−1
). The results shows in all cases elevated levels of radon and
226
Ra for PG samples, indicating the necessity to find suitable routes to reduce its radiation impact on the surrounding environment.
The present study investigates the wear properties of commercially pure titanium (CP-Ti) parts produced using selective laser melting (SLM) and casting. Scanning electron microscopy (SEM) ...investigations show that SLM-produced CP-Ti parts have martensitic (α΄) microstructure, whereas cast-produced CP-Ti samples exhibit plate-like (α) microstructure. SEM studies on the wear surfaces at moderate loads (15N) show shallow ploughing grooves at certain regions and some delamination cracks for both SLM and cast CP-Ti samples. On increasing the load to 30N, deeper ploughing grooves were observed in both samples along with delamination of material at certain regions. However, ploughing grooves were found to be very shallow in SLM samples compared with the cast parts. Although both SLM and cast CP-Ti exhibited similar wear mechanisms, SLM CP-Ti showed better wear resistance due to its martensitic microstructure, finer grain size and superior microhardness.
•Wear-properties of commercially pure-Ti prepared by SLM and casting processes.•Both samples show similar wear mechanisms.•SLM-processed sample show superior wear performance than cast specimens.•The superior wear properties are attributed to the martensitic microstructure.
Coronary atherosclerosis complicated by plaque disruption and thrombosis is a critical event in myocardial infarction and stroke, the major causes of cardiovascular death. In atherogenesis, ...macrophages (MAC) and smooth muscle cells (SMC) are key actors; they synthesize matrix components and numerous factors involved in the process. Here, we design experiments to investigate whether SMC–MAC communication induces changes in ECM protein composition and/or neo-angiogenesis. Cell to cell communication was achieved using trans-well chambers, where SMCs were grown in the upper chamber and differentiated MAC in the bottom chamber for 24 or 72h. We found that cross-talk between MAC and SMC during co-culture: (i) significantly decreased the expression of ECM proteins (collagen I, III, elastin) in SMC; (ii) increased the expression and activity of metalloprotease MMP-9 and expression of collagenase MMP-1, in both MAC and SMC; (iii) augmented the secretion of soluble VEGF in the conditioned media of cell co-culture and VEGF gene expression in both cell types, compared with control cells. Moreover, the conditioned media collected from MAC–SMC co-culture promoted endothelial cell tube formation in Matrigel, signifying an increased angiogenic effect. In addition, the MAC–SMC communication led to an increase in inflammatory IL-1β and TLR-2, which could be responsible for cellular signaling. In conclusion, MAC–SMC communication affects factors and molecules that could alter ECM composition and neo-angiogenesis, features that could directly dictate the progression of atheroma towards the vulnerable plaque. Targeting the MAC–SMC cross-talk may represent a novel therapeutic strategy to slow-down or retard the plaque progression.
•MAC and SMC cross-talk decreases the expression of extracellular matrix proteins.•MMP-1 and MMP-9 are increased by cell-to-cell cross-talk.•Soluble factors released by cell-to-cell cross-talk have angiogenic properties.•IL-1β and TLR-2 mediate endothelial tube-like formation.
The effect of chemical composition on microstructure and tensile properties of a series of low modulus Ti-Nb-Cu-Ni-Al alloys was studied. These alloys consist of primary micrometer-sized β-Ti ...dendrites surrounded by intermetallic phases. The morphology of the intermetallic phases is strongly affected by composition. Due to the composite microstructure, the alloys exhibit a low Young's modulus (77–84GPa) together with a high yield strength of about 1000MPa as well as moderate tensile ductility. The results demonstrate that complete substitution of Al by Ti reduces the Young's modulus by 5%. Increasing Nb content at the expense of Ti causes a significant improvement of tensile ductility.
In this Letter, 21 cm intensity maps acquired at the Green Bank Telescope are cross-correlated with large-scale structure traced by galaxies in the WiggleZ Dark Energy Survey. The data span the ...redshift range 0.6 < z < 1 over two fields totaling ~41 deg. sq. and 190 hr of radio integration time. The cross-correlation constrains Omega sub(H I)b sub(H I)r = 0.43 + or - 0.07(stat.) + or - 0.04(sys.) x 10 super(?3), where Omega sub(H I) is the neutral hydrogen (H I) fraction, r is the galaxy-hydrogen correlation coefficient, and b sub(H I) is the H I bias parameter. This is the most precise constraint on neutral hydrogen density fluctuations in a challenging redshift range. Our measurement improves the previous 21 cm cross-correlation at z ~ 0.8 both in its precision and in the range of scales probed.
Immunotherapy is regarded as one of the major breakthroughs in cancer treatment. Despite its success, only a subset of patients responds—urging the quest for predictive biomarkers. We hypothesize ...that artificial intelligence (AI) algorithms can automatically quantify radiographic characteristics that are related to and may therefore act as noninvasive radiomic biomarkers for immunotherapy response.
In this study, we analyzed 1055 primary and metastatic lesions from 203 patients with advanced melanoma and non-small-cell lung cancer (NSCLC) undergoing anti-PD1 therapy. We carried out an AI-based characterization of each lesion on the pretreatment contrast-enhanced CT imaging data to develop and validate a noninvasive machine learning biomarker capable of distinguishing between immunotherapy responding and nonresponding. To define the biological basis of the radiographic biomarker, we carried out gene set enrichment analysis in an independent dataset of 262 NSCLC patients.
The biomarker reached significant performance on NSCLC lesions (up to 0.83 AUC, P<0.001) and borderline significant for melanoma lymph nodes (0.64 AUC, P=0.05). Combining these lesion-wide predictions on a patient level, immunotherapy response could be predicted with an AUC of up to 0.76 for both cancer types (P<0.001), resulting in a 1-year survival difference of 24% (P=0.02). We found highly significant associations with pathways involved in mitosis, indicating a relationship between increased proliferative potential and preferential response to immunotherapy.
These results indicate that radiographic characteristics of lesions on standard-of-care imaging may function as noninvasive biomarkers for response to immunotherapy, and may show utility for improved patient stratification in both neoadjuvant and palliative settings.
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