Measuring Extinction Curves of Lensing Galaxies

We critique the method of constructing extinction curves of lensing galaxies using multiply imaged QSOs. If one of the two QSO images is lightly reddened or if the dust along both sightlines has the same properties then the method works well and produces an extinction curve for the lensing galaxy. These cases are likely rare and hard to confirm. However, if the dust along each sightline has different properties then the resulting curve is no longer a measurement of extinction. Instead, it is a measurement of the difference between two extinction curves. This "lens difference curve'' does contain information about the dust properties, but extracting a meaningful extinction curve is not possible without additional, currently unknown information. As a quantitative example, we show that the combination of two Cardelli, Clayton, & Mathis (CCM) type extinction curves having different values of R(V) will produce a CCM extinction curve with a value of R(V) which is dependent on the individual R(V) values and the ratio of V band extinctions. The resulting lens difference curve is not an average of the dust along the two sightlines. We find that lens difference curves with any value of R(V), even negative values, can be produced by a combination of two reddened sightlines with different CCM extinction curves with R(V) values consistent with Milky Way dust (2.1 < R(V) < 5.6). This may explain extreme values of R(V) inferred by this method in previous studies. But lens difference curves with more normal values of R(V) are just as likely to be composed of two dust extinction curves with R(V) values different than that of the lens difference curve. While it is not possible to determine the individual extinction curves making up a lens difference curve, there is information about a galaxy's dust contained in the lens difference curves.Comment: 15 pages, 4 figues, ApJ in pres

Depoliticised ethnicity in Tanzania: a structural and historical Narrative

Much of the literature on ethnicity in Africa regards ethnicity as a central cleavage and associates its politicisation with civil war and deteriorating socio-economic conditions. Tanzanian society is not structured by this cleavage, making it an outlier among African states. Despite the negative impact of politicised ethnicity, little is known of the circumstances through which it germinates and comes to have negative consequences, or how it can be suppressed in Africa. The present article attempts a comprehensive analysis of the structural and historical factors that have made the move away from politicisation of ethnicity in Tanzania possible. It provides an eclectic structural and historical explanation that attributes lack of ethnic salience in Tanzanian politics to a particular ethnic structure, to certain colonial administrative and economic approaches, and to a sustained nation-building ethos. The argument results from a critical analysis of secondary material on ethnicity and the politics of Tanzania

Structural Modelling Under Challenge

Over the last two decades or so macroeconometric modelling which was in vogue over the sixties and the seventies has ceased to be high on the academic agenda. This has been for a number of developments in macroeconomic theory and in econometric methodology. At the same time it is by no means true that macroeconometric modelling in the Cowles Commission tradition has been given up. Like all healthy disciplines the subject has incorporated some of the new developments and rejected some. Structural models continue to be used for policy formulation and continue to be used for policy formulation and evaluation all over the world because no viable alternative has emerged so far. This paper is intended to take stock of the prevailing situation and to suggest the course that the subject is likely to take in the years to come.

Cross-species analysis traces adaptation of Rubisco towards optimality in a low dimensional landscape

Rubisco, probably the most abundant protein in the biosphere, performs an essential part in the process of carbon fixation through photosynthesis thus facilitating life on earth. Despite the significant effect that Rubisco has on the fitness of plants and other photosynthetic organisms, this enzyme is known to have a remarkably low catalytic rate and a tendency to confuse its substrate, carbon dioxide, with oxygen. This apparent inefficiency is puzzling and raises questions regarding the roles of evolution versus biochemical constraints in shaping Rubisco. Here we examine these questions by analyzing the measured kinetic parameters of Rubisco from various organisms in various environments. The analysis presented here suggests that the evolution of Rubisco is confined to an effectively one-dimensional landscape, which is manifested in simple power law correlations between its kinetic parameters. Within this one dimensional landscape, which may represent biochemical and structural constraints, Rubisco appears to be tuned to the intracellular environment in which it resides such that the net photosynthesis rate is nearly optimal. Our analysis indicates that the specificity of Rubisco is not the main determinant of its efficiency but rather the tradeoff between the carboxylation velocity and CO2 affinity. As a result, the presence of oxygen has only moderate effect on the optimal performance of Rubisco, which is determined mostly by the local CO2 concentration. Rubisco appears as an experimentally testable example for the evolution of proteins subject both to strong selection pressure and to biochemical constraints which strongly confine the evolutionary plasticity to a low dimensional landscape.Comment: http://www.pnas.org/content/107/8/3475.short http://www.ncbi.nlm.nih.gov/pubmed/20142476 http://www.weizmann.ac.il/complex/tlusty/papers/PNAS2010.pd

A comparison between correspondence analysis and categorical conjoint measurement

We show the equivalence of using correspondence analysis of concatenated tables and a particular algorithm of conjoint analysis named categorical conjoint measurement. The connection is made using canonical correlation. However, although we have proved that equivalence, the standard practice of conjoint analyses to focus in one dimension (the optimal solution) has some shortcomings once we introduce interaction effects. In that case, the use of visual techniques, like correspondence analysis, provides a faster and easier way to compile the preference structure. Finally, we provide an application of our setting making use of an experiment of perfumes where interaction effects between type of essences and strength of essences are shown

Climate Change Reporting: A Resource Based Perspective

Kajian ini dilakukan untuk mengkaji tahap serta faktor yang mengalakkan laporan pemanasan global di antara syarikat-syarikat yang tersenarai di Bursa Malaysia. This study investigates the extent of climate change disclosure among Malaysian public listed companies

Risk Mitigation Of Outsourcing Manufacturing Process: A Study On The Semiconductor Manufacturing Organizations In Malaysia

Penggunaan perkhidmatan pihak ketiga daripada proses pembuatan semikonduktor menjadi sebahagian daripada strategi korporat sebuah organisasi yang didorong oleh kelebihan kos dan fleksibiliti dalam ketidakpastian. Outsourcing of semiconductor manufacturing process is becoming integral part of the corporate strategy of an organization which is driven by cost advantage and flexibility during uncertainty

A COMPARISON BETWEEN CORRESPONDENCE ANALYSIS AND CATEGORICAL CONJOINT MEASUREMENT

We show the equivalence of using correspondence analysis of concatenated tables and a particular algorithm of conjoint analysis named categorical conjoint measurement. The connection is made using canonical correlation. However, although we have proved that equivalence, the standard practice of conjoint analyses to focus in one dimension (the optimal solution) has some shortcomings once we introduce interaction effects. In that case, the use of visual techniques, like correspondence analysis, provides a faster and easier way to compile the preference structure. Finally, we provide an application of our setting making use of an experiment of perfumes where interaction effects between type of essences and strength of essences are shown.