The discovery of a metallic glass in 1960 by Pol Duwez was serendipitous, as he quenched liquid melts of gold-silicon alloys at a rapid cooling rate of over one million degrees per second. The liquid ...froze as glass. The high cooling rates limited the product dimensions to microns. It was only in 1988 that Akihisa Inoue at the Tohoku University, Japan made a path-breaking discovery that by mixing many metals of different sizes together, it is possible to freeze the melt as glass at slow cooling rates of one degree per second. The specimen dimensions reached centimeters. One of the celebrated alloys has zirconium as the main element with addition of titanium, copper, nickel, aluminium and beryllium. Figure 1 displays some possible combinations. These glasses contained a minimum of three metals and occasionally reached giddy proportions of more 4. An example of the latter is Fe-Al, Ga-P, B, Si. In addition to the intrinsic interest of metallic glasses being produced at slow rates of cooling comparable to those of the millennia-old inorganic silicate glasses, these possess some unique properties. Figure 2 shows this 5. Their elasticity is comparable to that of polymers and higher than that of crystalline counterparts. Thus metallic glasses have found unusual applications as golf heads and cell phone shells.
Hybrid metal matrix composites are important class of engineering materials used in automotive, aerospace and other applications because of their lower density, higher specific strength, and better ...physical and mechanical properties compared to pure aluminium. The mechanical and wear properties of hybrid aluminium metal matrix composites were investigated. Mica and SiC ceramic particles were incorporated into Al 356 alloy by stir-casting route. Microstructures of the samples were studied using scanning electron microscope (SEM). The chemical composition was investigated through energy dispersive X-ray (EDX) detector. The results indicate that the better strength and hardness are achieved with Al/10SiC-3mica composites. The increase in mass fraction of mica improves the wear loss of the composites.
Metal matrix composites reinforced with graphite particles provide better machinability and tribological properties. The present study attempts to find the optimal level of machining parameters for ...multi-performance characteristics in turning of Al-SiC-Gr hybrid composites using grey-fuzzy algorithm. The hybrid composites with 5%, 7.5% and 10% combined equal mass fraction of SiC-Gr particles were used for the study and their corresponding tensile strength values are 170, 210, 204 MPa respectively. Al-10%(SiC-Gr) hybrid composite provides better machinability when compared with composites with 5% and 7.5% of SiC-Gr. Grey-fuzzy logic approach offers improved grey-fuzzy reasoning grade and has less uncertainties in the output when compared with grey relational technique. The confirmatory test reveals an increase in grey-fuzzy reasoning grade from 0.619 to 0.891, which substantiates the improvement in multi-performance characteristics at the optimal level of process parameters setting.
Protograph-based Raptor-like low-density parity-check codes (PBRL codes) are a family of easily encodable rate-compatible low-density parity-check (LDPC) codes. PBRL codes have an excellent ...performance across all design rates. Quasi-cyclic (QC) PBRL code families permit high-speed decoder implementations. PBRL codes designed thus far, for both long and short block-lengths, have been based on optimizing the iterative decoding threshold of the protograph of the PBRL family at various design rates. This paper introduces a design method to obtain better QC PBRL code families at short block-lengths (of a few hundred bits) for low frame error rate (FER) requirements. We first select a protomatrix for the highest design rate. To add a new row to lower the rate, we keep all the previously obtained rows of the PBRL protomatrix fixed and select the new row that maximizes an upper bound on the minimum distance of any QC-LDPC code that can be obtained from the protomatrix. The new QC PBRL code families outperform the original PBRL codes at short block-lengths by providing a significantly better low-FER performance. The standard approach to computing the aforementioned upper bounds requires complexity that grows exponentially with the size of the protomatrix. However, we show that the structure of the PBRL protomatrix lets us obtain the upper bounds with complexity that grows only linearly with the size of the PBRL protomatrix. Using the complexity reduction results, we also establish an equivalence between the exhaustive search to design a new row for the PBRL protomatrix according to the new design method and an integer linear program.
In the present investigation, a newly fabricated Al6061 reinforced with various quantity (0.4–1.6 wt%) of nano SiC in steps of 0.4 and fixed quantity (0.5 wt%) of micro graphite particle’s hybrid ...nanocomposites were prepared by ultrasonic assisted stir casting method. The influence of nano SiC and graphite content on the mechanical and tribological properties of Al6061 hybrid nanocomposites were studied. The pin-on-disc equipment was used to carry out experiment at 10–40 N applied load, 0.5 m/s sliding speed and 1000 m sliding distance. The Al/SiC/Gr hybrid nano-composite and matrix alloy wear surfaces were characterized by FESEM equipped with an EDS, 3D profilometer to understand the wear mechanisms. The results of Al/SiC/Gr self-lubricating hybrid nano-composites showed improved wear resistance than the Al6061 matrix alloy. The co-efficient of friction of Al/SiC/Gr hybrid nano-composites were lower than those of the unreinforced alloy at various applied load. Compared to matrix alloy, the surface roughness of Al/SiC/Gr hybrid nano-composites had significantly reduced to 66% at low load and 75% at high load. Self-lubricating Al/SiC/Gr hybrid nanocomposites showed superior surface smoothness compared to matrix alloy.
Background
Ecological evidence suggests vitamin D insufficiency (VDI) due to lower ambient ultraviolet radiation (UVR) exposure may be a risk factor for IgE‐mediated food allergy. However, there are ...no studies relating directly measured VDI during early infancy to subsequent challenge‐proven food allergy.
Objective
To prospectively investigate the association between VDI during infancy and challenge‐proven food allergy at 1 year.
Methods
In a birth cohort (n = 1074), we used a case‐cohort design to compare 25‐hydroxyvitamin D3 (25(OH)D3) levels among infants with food allergy vs a random subcohort (n = 274). The primary exposures were VDI (25(OH)D3 <50 nM) at birth and 6 months of age. Ambient UVR and time in the sun were combined to estimate UVR exposure dose. IgE‐mediated food allergy status at 1 year was determined by formal challenge. Binomial regression was used to examine associations between VDI, UVR exposure dose and food allergy and investigate potential confounding.
Results
Within the random subcohort, VDI was present in 45% (105/233) of newborns and 24% (55/227) of infants at 6 months. Food allergy prevalence at 1 year was 7.7% (61/786), and 6.5% (53/808) were egg‐allergic. There was no evidence of an association between VDI at either birth (aRR 1.25, 95% CI 0.70–2.22) or 6 months (aRR 0.93, 95% CI 0.41–2.14) and food allergy at 1 year.
Conclusions
There was no evidence that VDI during the first 6 months of infancy is a risk factor for food allergy at 1 year of age. These findings primarily relate to egg allergy, and larger studies are required.
Background: The diagnosis of latent Mycobacteriumtuberculosis (MTB) infection with a tuberculin skin test (TST) in children is complicated by the potential influence of prior exposure to Bacille ...Calmette Geurin (BCG) vaccination or environmental mycobacteria. A whole blood assay has recently been developed to quantitatively measure interferon gamma (IFN-γ) production by lymphocytes specific to the MTB antigens ESAT-6 and CFP-10, but its use and assessment in children has been limited. A study was undertaken to compare the performance of the whole blood IFN-γ assay with the TST in diagnosing latent tuberculosis (TB) infection or TB disease in children in routine clinical practice. Methods: One hundred and six children with a high risk of latent TB infection or TB disease were enrolled in the study. High risk was defined as contact with TB disease, clinical suspicion of TB disease, or recent arrival from an area of high TB prevalence. The whole blood IFN-γ assay was undertaken in 101 children. Results: Seventeen (17%) of the 101 assays yielded inconclusive results due to failure of positive or negative control assays. There was poor correlation between the whole blood IFN-γ assay and the TST (kappa statistic 0.3) with 26 (70%) of the 37 children defined as latent TB infection by TST having a negative whole blood IFN-γ assay. There were no instances of a positive whole blood IFN-γ assay with a negative TST. Mitogen (positive) control IFN-γ responses were significantly correlated with age (Spearman’s coefficient = 0.53, p<0.001) and, in children with latent TB infection identified by TST, those with a positive IFN-γ assay were older (median 12.9 v 6.92 years, respectively, p = 0.007). The whole blood IFN-γ assay was positive in all nine children with TB disease. Conclusion: There was poor agreement between the whole blood IFN-γ assay and TST for the diagnosis of latent TB. The whole blood IFN-γ assay may have lower sensitivity than the TST in diagnosing TB infection in children. A significant proportion of whole blood IFN-γ assays fail when used as a screening assay in routine practice.
Impaired CSF homeostasis and altered venous hemodynamics are proposed mechanisms for elevated pressure in IIH. However, the lack of ventricular expansion steered the focus away from CSF homeostasis ...in IIH. This study aims to measure intracranial CSF volumes and cerebral venous drainage with MR imaging to determine whether increased CSF volume from impaired CSF homeostasis and venous hemodynamics occur in obesity-related IIH.
Two homogeneous cohorts of 11 newly diagnosed pretreatment overweight women with IIH and 11 overweight healthy women were prospectively studied. 3D volumetric MR imaging of the brain was used to quantify CSF and brain tissue volumes, and dynamic phase contrast was used to measure relative cerebral drainage through the internal jugular veins.
Findings confirm normal ventricular volume in IIH. However, extraventricular CSF volume is significantly increased in IIH (290 ± 52 versus 220 ± 24 mL, P = .001). This is even more significant after normalization with intracranial volume (P = .0007). GM interstitial fluid volume is also increased in IIH (602 ± 57 versus 557 ± 31 mL, P = .037). Total arterial inflow is normal, but relative venous drainage through the IJV is significantly reduced in IIH (65 ± 7% versus 81 ± 10%, P = .001).
Increased intracranial CSF volume that accumulates in the extraventricular subarachnoid space provides direct evidence for impaired CSF homeostasis in obesity-associated IIH. The finding of larger GM interstitial fluid volume is consistent with increased overall resistance to cerebral venous drainage, as evident from reduced relative cerebral drainage through the IJV. The present study confirms that both impaired CSF homeostasis and venous hemodynamics coexist in obesity-associated IIH.
In cystic fibrosis (CF), pathophysiologic changes in the gastrointestinal tract lead to malnutrition and altered gut microbiome. Microbiome alterations have been linked to linear growth, gut ...inflammation and respiratory manifestations. Elucidating these gut microbiome alterations may provide insight into future nutritional management in CF.
Infants were followed for 12-months at four sites in the United States (US-CF) and Australia (AUS-CF). 16S rRNA gene sequencing was performed on longitudinal stool samples. Associations between microbial abundance and age, antibiotic prophylaxis, malnutrition, and breast feeding were evaluated using generalized linear mixed models. Taxonomic and predictive functional features were compared between groups.
Infants with CF (N = 78) were enrolled as part of a larger study. AUS-CF infants had higher mean weight-for-age z-scores than US-CF infants (p = 0.02). A subset of participants (CF N = 40, non-CF disease controls N = 10) provided stool samples for microbiome analysis. AUS-CF infants had lower stool alpha diversity compared to US-CF infants (p < 0.001). AUS-CF infants had higher relative abundance of stool Proteobacteria compared to US-CF infants which was associated with antibiotic prophylaxis (p < 0.001). Malnutrition (weight-for-age <10th percentile) was associated with depleted Lactococcus (p < 0.001). Antibiotic prophylaxis (p = 0.002) and malnutrition (p = 0.012) were linked with predicted decreased activity of metabolic pathways responsible for short chain fatty acid processing.
In infants with CF, gut microbiome composition and diversity differed between the two continents. Gut microbial diversity was not linked to growth. The relationship between malnutrition and antibiotic prophylaxis with reduced SCFA fermentation could have implications for gut health and function and warrants additional investigation.
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