Symbolic Maximum Likelihood Estimation with Mathematica

Mathematica is a symbolic programming language that empowers the user to undertake complicated algebraic tasks. One such task is the derivation of maximum likelihood estimators, demonstrably an important topic in statistics at both the research and expository level. In this paper, a Mathematica package is provided that contains a function entitled SuperLog. This function utilises pattern-matching code that enhances Mathematica's ability to simplify expressions involving the natural logarithm of a product of algebraic terms. This enhancement to Mathematica's functionality can be of particular benefit for maximum likelihood estimation

Controlling the second-harmonic in a phase matched negative-index metamaterial

Nonlinear metamaterials (NLMMs) have been predicted to support new and exciting domains in the manipulation of light, including novel phase matching schemes for wave mixing. Most notable is the so-called nonlinear-optical mirror, in which a nonlinear negative-index medium emits the generated frequency towards the source of the pump. For the first time, we experimentally demonstrate the nonlinear-optical mirror effect in a bulk negative-index NLMM, along with two other novel phase matching configurations, utilizing periodic poling to switch between the three phase matching domains.Comment: 5 pages, 7 figure

Use of legacy data in geomorphological research

This paper considers legacy data and data rescue within the context of geomorphology. Data rescue may be necessary dependent upon the storage medium (is it physically accessible) and the data format (e.g. digital file type); where either of these is not functional, intervention will be required in order to retrieve the stored data. Within geomorphological research, there are three scenarios that may utilize legacy data: to reinvestigate phenomena, to access information about a landform/process that no longer exists, and to investigate temporal change. Here, we present three case studies with discussion that illustrate these scenarios: striae records of Ireland were used to produce a palaeoglacial reconstruction, geomorphological mapping was used to compile a map of glacial landforms, and aerial photographs were used to analyze temporal change in river channel form and catchment land cover

Universal binding energy relations in metallic adhesion

Scaling relations which map metallic adhesive binding energy onto a single universal binding energy curve are discussed in relation to adhesion, friction, and wear in metals. The scaling involved normalizing the energy to the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. The universal curve was found to be accurately represented by E*(A*)= -(1+beta A) exp (-Beta A*) where E* is the normalized binding energy, A* is the normalized separation, and beta is the normalized decay constant. The calculated cohesive energies of potassium, barium, copper, molybdenum, and samarium were also found to scale by similar relations, suggesting that the universal relation may be more general than for the simple free electron metals

Universal binding energy relations in metallic adhesion

Rose, Smith, and Ferrante have discovered scaling relations which map the adhesive binding energy calculated by Ferrante and Smith onto a single universal binding energy curve. These binding energies are calculated for all combinations of Al(111), Zn(0001), Mg(0001), and Na(110) in contact. The scaling involves normalizing the energy by the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. Rose et al. have also found that the calculated cohesive energies of K, Ba, Cu, Mo, and Sm scale by similar simple relations, suggesting the universal relation may be more general than for the simple free electron metals for which it was derived. In addition, the scaling length was defined more generally in order to relate it to measurable physical properties. Further this universality can be extended to chemisorption. A simple and yet quite accurate prediction of a zero temperature equation of state (volume as a function of pressure for metals and alloys) is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions, and results compare favorably with experiment for a broad range of metals

Feminism and bluebeard

The story of Bluebeard (AT 312) has had an especially lively history in written literature since it was first published in 1697. One reason for the attraction may be that it is hard to decide whether Bluebeard is about a woman or a man: each sex reads, and therefore retells, Bluebeard very differently. Out of the extensive field of literary rewritings of Bluebeard this paper selects a number of stories by women writers whose response to the tale has been, by and large, a feminist response. The first of them is Victorian, and dates from 1874

Peter, Potter, Rabbits, Robbers

Critical discourses about realism and fantasy in children's literature have in the past included discussion of the merits, and demerits, of these conventions as they differently engage child readers. Beatrix Potter's works, situated at an intersection of the two literary conventions, seem to me rather to invite a useful complication of the distinction commonly made between them. Potter is clearly a fantasist. Yet aspects of her work support a scholarly tendency to claim her for realism, and this is often done by connecting Potter's life and works. In this essay I join those who have turned Potter studies towards investigating the cultural and literary contexts within which she worked

Identification of bile salt hydrolase inhibitors, the promising alternative to antibiotic growth promoters to enhance animal production

Currently there is a global trend to eliminate the use of antibiotic growth promoters (AGP) in animal production due to the risk of creating reservoirs of antibiotic resistant bacteria. Previous studies have shown that the ability of AGP to promote growth is highly correlated with a decrease in the activity of bile salt hydrolase (BSH), an enzyme produced by commensal bacteria and whose actions may compromise host lipid metabolism; thus, BSH inhibitors could be a novel AGP alternative. In this study, a recombinant bile salt hydrolase (rBSH) from Lactobacillus salivarius was produced in an E. coli expression system, purified, and enzymatically characterized. Purification by nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography consistently yielded approximately 15 mg of rBSH per liter of induced culture. A standard 2-step BSH activity assay which estimates the amount of amino acids liberated from conjugated bile acids was used to determine substrate specificity of the BSH and the effect of pH, temperature, and dietary compounds on BSH activity. The rBSH displayed its highest hydrolysis activity for glycochenodeoxycholic acid although there was no preference among other substrates tested. Optimal activity was observed between pH of 5.0 and 6.0 and between temperatures of 35°C to 55°C. Preliminary assays identified different dietary compounds that were potent inhibitors, including copper and zinc compounds which have previously been shown to boost feed efficiency and promote growth of poultry and swine. Furthermore, a high-throughput screening system (HTS) was developed for fast and efficient identification of potent BSH inhibitors. This HTS system was utilized to screen a compound library comprised of 2,240 biologically active and structurally diverse compounds. The pilot screen led to 107 hits and a preliminary review of biochemical information of the corresponding compounds further narrowed down those of interest. Several lead compounds have been validated by the standard 2-step BSH activity assay and will be subjected to future in vivo analysis in a large-scale animal study. Overall, this study characterized a BSH with broad substrate specificity and developed and validated different strategies for identification of BSH inhibitors, the promising alternatives to AGP for enhancing the productivity and sustainability of food animals

Flow cytometric analysis of phytoplankton viability in Elkhorn Slough, California.

The phytoplankton community structure of Elkhorn Slough was characterized flow cytometrically and found to be dominated in the upper reaches by small cryptophytes (\u3c 5 microm) and picoeukaryotic phytoplankton (\u3c 3 microm). Cell-specific viability of the small cryptophyte population was quantified along a 5 km transect from the mouth to the shallow upper reaches of Elkhorn Slough using fluorescein diacetate (FDA). Corroborative viability techniques, including SYTOX Green stain and cell digestion assay, were determined to be inappropriate for use in Elkhorn Slough due to indiscriminate staining of suspended particulates and incompatibility with cell target material. Viability analysis with FDA revealed a higher fraction of active cryptophyte cells in the upper reaches, the area of their dominance, and a lower fraction of active cells in the lower slough. It was concluded that cell death (as defined by a lack of FDA-linked esterase enzyme activity) is an important force structuring the phytoplankton community of Elkhorn Slough

Mothers as Career Leaders: Do Maternity Leave Laws Make a Difference?

On a national level, the Family and Medical Leave Act (FMLA) of 1993 is the only law that provides certain qualifying individuals with 12 weeks of unpaid, job protected maternity leave, although some states and private firms have implemented forms of paid maternity leave. Previous research indicates that female employees, regardless of their parental status, receive fewer promotions due to information asymmetry after the FMLA (Thomas 2015). In addition, some research finds that particular industries are more family friendly due to access to flexible work schedules for mothers (Goldin 2014). This thesis expands on both findings using data from the National Longitudinal Surveys beginning in 1979 to capture the effects of maternity leave type and length on promotions. Results from differences-in-differences models show that having a child after the passage of the FMLA results in decreased unpaid leave and increased paid leave. Contrary to prior literature, we find no evidence that employers are promoting female employees less frequently after passage of the FMLA. Other models suggest there are negative effects on promotion when having a child, regardless of industry. However, there is no statistically significant evidence to suggest the negative effects of motherhood differ after passage of the FMLA. Our findings differ from prior literature in that the negative effects of the FMLA on career advancement appear to be confined only to the sub-sample of mothers working jobs for which maternity leave benefits were not previously available. Taken together, these results suggest that the FMLA may have been largely reactive to family friendly changes already occurring in the workplace structure, thus having little effect on the majority of firms and working women