Effect of Thermomechanical Fatigue on Precipitation Microstructure in Two Precipitation-Hardened Cast Aluminum Alloys

Thermal loading induces modifications of the precipitation microstructure of Al–Si–Cu–Mg alloys. This study focuses on the effect of deformation on precipitation microstructure during thermomechanical loadings. Several specimens were thermomechanically cycled while others were exposed to the same thermal cycles without any mechanical loading. The nature and morphological characteristics of the precipitation microstructure of the thermomechanically cycled specimens are compared to those of the thermally aged ones, using transmission electron microscopy (TEM), in order to assess the effect of deformation on the precipitation microstructure and especially on the kinetics of precipitate growth. The absence of any significant effect of superimposed straining during thermal cycling is discussed. Implications for the prevision of yield strength degradation during service operation are briefly presented.

     

Spatial statistical analysis and geographic information systems

In this paper, we discuss a number of general issues that pertain to the interface between GIS and spatial analysis. In particular, we focus on the various paradigms for spatial data analysis that follow from the existence of this interface. We outline a series of questions that need to be confronted in the analysis of spatial data, and the extent to which a GIS can facilitate their resolution. We also review a number of exploratory and confirmatory techniques that we feel should form the core of a spatial analysis module for a GIS.     

In-situ diagnostic of femtosecond laser probe pulses for high resolution ultrafast imaging

Ultrafast imaging is essential in physics and chemistry to investigate the femtosecond dynamics of nonuniform samples or of phenomena with strong spatial variat...     

Opposing Roles of DCs and iNKT Cells in the Induction of Foxp3 Expression by MLN CD25+CD4+ T Cells during IFNγ-Driven Colitis

We have previously shown that a deficiency of CD1d-restricted invariant natural killer T (iNKT) cells exacerbates dextran sulfate sodium (DSS)-induced colitis in Yeti mice that exhibit IFNγ-mediated hyper-inflammation. Although iNKT cell-deficiency resulted in reduced Foxp3 expression by mesenteric lymph node (MLN) CD4⁺ T cells in DSS-treated Yeti mice, the cellular mechanisms that regulate Foxp3 expression by CD25⁺CD4⁺ T cells during intestinal inflammation remain unclear. We found that Foxp3⁻CD25⁺CD4⁺ T cells expressing Th1 and Th17 phenotypic hallmarks preferentially expanded in the MLNs of DSS-treated Yeti/CD1d knockout (KO) mice. Moreover, adoptive transfer of Yeti iNKT cells into iNKT cell-deficient Jα18 KO mice effectively suppressed the expansion of MLN Foxp3⁻CD25⁺CD4⁺ T cells during DSS-induced colitis. Interestingly, MLN dendritic cells (DCs) purified from DSS-treated Yeti/CD1d KO mice promoted the differentiation of naive CD4⁺ T cells into Foxp3⁻CD25⁺CD4⁺ T cells rather than regulatory T (Treg) cells, indicating that MLN DCs might mediate Foxp3⁺CD25⁺CD4⁺ T cell expansion in iNKT cell-sufficient Yeti mice. Furthermore, we showed that Foxp3⁻CD25⁺CD4⁺ T cells were pathogenic in DSS-treated Yeti/CD1d KO mice. Our result suggests that pro-inflammatory DCs and CD1d-restricted iNKT cells play opposing roles in Foxp3 expression by MLN CD25⁺CD4⁺ T cells during IFNγ-mediated intestinal inflammation, with potential therapeutic implications.     

Effect of pre rigor stretching on beef tenderness development

The objective of this study was to determine effects of pre rigor stretching on beef tenderness development. Beef loins (M. longissimus dorsi; n=24) were assigned to either stretching or non-stretching treatments and aged for 14days at -1.5°C. Sarcomere length, shear force, water-holding capacity and proteolysis were determined for the loins at 1, 7 and 14days of ageing. Stretching increased the length of the loins by 33% resulting in a trend of increasing sarcomere length (P=0.19). However, no significant differences for shear force values, purge, drip and cooking losses between treatments were found. Shear force values decreased with ageing times (P<0.05). Western blot assay found that stretching did not affect the extent of desmin degradation. The findings from the present study suggest that pre rigor stretching with the current increase in length will not contribute to tenderness improvement of the beef loins.     

Experimental method based on wavelength-modulation spectroscopy for the characterization of semiconductor lasers under direct modulation

An experimental method is presented for characterization of the combined intensity and frequency modulation produced when the injection current of a laser diode is modulated. The reported technique is based on the analysis of the harmonic signals produced when a modulated laser is used to probe a gas absorption line by the so-called wavelength-modulation spectroscopy method. Based on a theoretical model of this technique, we present two methods that facilitate the determination of (i) the deviation in laser frequency and (ii) the phase shift between intensity and frequency modulation. These methods are illustrated experimentally by measurement of the modulation parameters of a 2-microm distributed-feedback laser by use of a CO2 absorption line. The experimental results have been compared with those obtained with another traditional method and have shown full agreement in the frequency range (400 Hz-30 kHz) considered.     

A Multi-Disciplinary Contribution to the Provenance Determination of Ancient Greek and Roman Marble Artifacts

The problem of determining the provenance of the white marble used for antique artifacts has been tackled in different ways. During the past decade it became clear that a multimethod approach is required to solve the problem. In addition, reliable reference material, i.e., samples collected at the ancient quarry sites in an archaeologically and geologically justified manner, turned out to be a prerequisite for reliable provenance determination. A multimethod approach based on petrography, stable isotope analysis of O and C, and trace element analysis yields complementary information. These methods were applied to the same set of 225 quarry samples. When processed with powerful statistical methods, the data thus obtained allowed all major types of marble used in antiquity to be distinguished. Thus, most problems concerning the provenance of artifacts can be solved. This approach was successfully applied to the provenance determination of about 75 artifacts from different museums in Europe and the USA.     

Digital neighborhoods

With the advent of ‘big data’ there is an increased interest in using social media to describe city dynamics. This paper employs geo-located social media data to identify ‘digital neighborhoods’ – those areas in the city where social media is used more often. Starting with geo-located Twitter and Foursquare data for the New York City region in 2014, we applied spatial clustering techniques to detect significant groupings or ‘neighborhoods’ where social media use is high or low. The results show that beyond the business districts, digital neighborhoods occur in communities undergoing shifting socio-demographics. Neighborhoods that are not digitally oriented tend to have higher proportion of minorities and lower incomes, highlighting a social–economic divide in how social media is used in the city. Understanding the differences in these neighborhoods can help city planners interested in generating economic development proposals, civic engagement strategies, and urban design ideas that target these areas.     

Finite sample properties of Moran's I test for spatial autocorrelation in tobit models

In this note, we investigate the finite‐sample properties of Moran's I test statistic for spatial autocorrelation in tobit models suggested by Kelejian and Prucha. We fill a void in the theoretical literature by investigating the finite sample properties of this test statistic in a series of Monte Carlo simulations, using data sets ranging from 49 to 15,625 observations. We find that the test is unbiased, has considerable power and approximates the asymptotic normal distribution even for medium‐sized sample sizes, empirically confirming the theoretical results of Kelejian and Prucha. However, some caution is needed, since the statistic turns out to be sensitive to misspecification in the form of heteroscedasticity. In such instances the test over‐rejects the null hypothesis, mistaking heteroscedasticity for spatial autocorrelation.