Demonstrating the Mechanics of Principal Component Analysis via Spreadsheets

Principal component analysis (PCA) is a popular multivariate statistical method that is used for dimensionality reduction. When teaching PCA in a marketing research or business analytics course, the mechanics of the analysis are often not communicated to the students. Students observe computer output that contains information pertaining to eigenvalues, component loadings, and rotated loadings, yet an understanding of how these numbers were obtained is lacking. This paper presents an Excel workbook that demonstrates the mechanics of PCA, which include (1) the construction of the correlation matrix from the raw data, (2) the extraction of eigenvalues and eigenvectors from the correlation matrix and the computation of the component loadings, and (3) the rotation of the component loadings to improve interpretability

A Morph-Based Simulated Annealing Heuristic for a Modified Bin-Packing Problem

This paper presents a local-search heuristic, based on the simulated annealing (SA) algorithm for a modified bin- packing problem (MBPP). The objective of the MBPP is to assign items of various sizes to a fixed number of bins, such that the sum-of-squared deviation (across all bins) from the target bin workload is minimized. This problem has a number of practical applications which include the assignment of computer jobs to processors, the assignment of projects to work teams, and infinite loading machine scheduling problems. The SA-based heuristic we developed uses a morph-based search procedure when looking for better allocations. In a large computational study we evaluated 12 versions of this new heuristic, as well as two versions of a previously published SA-based heuristic that used a completely random search. The primary performance measure for this evaluation was the mean percent above the best known objective value (MPABKOV). Since the MPABKOV associated with the best version of the random-search SA heuristic was more than 290 times larger than that of the best version of the morph-based SA heuristic, we conclude that the morphing process is a significant enhancement to SA algorithms for these problems

“Money worlds” and Well-Being: An Empirical Test of Tatzel’s Model of Consumer Styles Based on Money Dispositions and Materialism with Extension to other Consumer Behavior Variables

Miriam Tatzel (2002) has proposed a comprehensive theory of “money worlds and well-being” comprised of four prototypes of consumer behaviors based on whether consumers are high or low on materialism and simultaneously tight or loose with money. These four prototypes (Value Seekers, Non-Spenders, Big Spenders, and Experiencers) are proposed to differ strikingly along a variety of values, attitudes, and behaviors. Three earlier studies have reported tests or the model, but none specifically tried to confirm empirically the four types of consumers. The present study uses data from 1016 U.S. student consumers to test empirically the proposed typology and the proposed differences across the prototypes. A cluster analysis confirmed that a four-cluster solution best represented the data, confirming Tatzel’s fundamental proposal. Subsequent ANOVAs showed that two of the four groups differed predictably in the hypothesized directions. Significant differences between Big Spenders and Non-spenders were found in levels of price sensitivity, status consumption, generosity, brand engagement, worry about debt, and spending. The other two groups, Value Seekers and Experiencers, fell between them. These findings provide partial confirmation for Tatzel’s theory and suggest several applications for decision makers

Rhodium catalyzed hydrogenation reactions in aqueous micellar systems as green solvents

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The hydrogenation of itaconic acid and dimethyl itaconate is transferred from methanol to aqueous micellar solutions of several surfactants, e.g., SDS and Triton X-100, in order to facilitate the recovery of the catalyst. The reaction rate and selectivity strongly depends on the chosen surfactant and in some cases also on the surfactant concentration. In the best case the selectivity is the same as in methanol but the reaction rate is still lower because of a lower hydrogen solubility in water. Repetitive semi-batch experiments are chosen to demonstrate that high turn-over-numbers (>1000) can be reached in aqueous micellar solutions. No notable catalyst deactivation is observed in these experiments. The performance of micellar reaction systems is controlled by the partition coefficient of the substrates between the micelles and the continuous aqueous phase which can be predicted using the Conductor-like Screening Model for Real Solvents (COSMO-RS).DFG, EXC 314, Unifying Concepts in Catalysi

Identification of the DNA methylation signature of Mowat-Wilson syndrome

Mowat-Wilson syndrome (MOWS) is a rare congenital disease caused by haploinsufficiency of ZEB2, encoding a transcription factor required for neurodevelopment. MOWS is characterized by intellectual disability, epilepsy, typical facial phenotype and other anomalies, such as short stature, Hirschsprung disease, brain and heart defects. Despite some recognizable features, MOWS rarity and phenotypic variability may complicate its diagnosis, particularly in the neonatal period. In order to define a novel diagnostic biomarker for MOWS, we determined the genome-wide DNA methylation profile of DNA samples from 29 individuals with confirmed clinical and molecular diagnosis. Through multidimensional scaling and hierarchical clustering analysis, we identified and validated a DNA methylation signature involving 296 differentially methylated probes as part of the broader MOWS DNA methylation profile. The prevalence of hypomethylated CpG sites agrees with the main role of ZEB2 as a transcriptional repressor, while differential methylation within the ZEB2 locus supports the previously proposed autoregulation ability. Correlation studies compared the MOWS cohort with 56 previously described DNA methylation profiles of other neurodevelopmental disorders, further validating the specificity of this biomarker. In conclusion, MOWS DNA methylation signature is highly sensitive and reproducible, providing a useful tool to facilitate diagnosis

Blepharophimosis with intellectual disability and Helsmoortel‐Van Der Aa Syndrome share episignature and phenotype

Blepharophimosis with intellectual disability (BIS) is a recently recognized disorder distinct from Nicolaides‐Baraister syndrome that presents with distinct facial features of blepharophimosis, developmental delay, and intellectual disability. BIS is caused by pathogenic variants in SMARCA2, that encodes the catalytic subunit of the superfamily II helicase group of the BRG1 and BRM‐associated factors (BAF) forming the BAF complex, a chromatin remodeling complex involved in transcriptional regulation. Individuals bearing variants within the bipartite nuclear localization (BNL) signal domain of ADNP present with the neurodevelopmental disorder known as Helsmoortel‐Van Der Aa Syndrome (HVDAS). Distinct DNA methylation profiles referred to as episignatures have been reported in HVDAS and BAF complex disorders. Due to molecular interactions between ADNP and BAF complex, and an overlapping craniofacial phenotype with narrowing of the palpebral fissures in a subset of patients with HVDAS and BIS, we hypothesized the possibility of a common phenotype‐specific episignature. A distinct episignature was shared by 15 individuals with BIS‐causing SMARCA2 pathogenic variants and 12 individuals with class II HVDAS caused by truncating pathogenic ADNP variants. This represents first evidence of a sensitive phenotype‐specific episignature biomarker shared across distinct genetic conditions that also exhibit unique gene‐specific episignatures

ISL1 is a major susceptibility gene for classic bladder exstrophy and a regulator of urinary tract development.

Previously genome-wide association methods in patients with classic bladder exstrophy (CBE) found association with ISL1, a master control gene expressed in pericloacal mesenchyme. This study sought to further explore the genetics in a larger set of patients following-up on the most promising genomic regions previously reported. Genotypes of 12 markers obtained from 268 CBE patients of Australian, British, German Italian, Spanish and Swedish origin and 1,354 ethnically matched controls and from 92 CBE case-parent trios from North America were analysed. Only marker rs6874700 at the ISL1 locus showed association (p = 2.22 × 10-08). A meta-analysis of rs6874700 of our previous and present study showed a p value of 9.2 × 10-19. Developmental biology models were used to clarify the location of ISL1 activity in the forming urinary tract. Genetic lineage analysis of Isl1-expressing cells by the lineage tracer mouse model showed Isl1-expressing cells in the urinary tract of mouse embryos at E10.5 and distributed in the bladder at E15.5. Expression of isl1 in zebrafish larvae staged 48 hpf was detected in a small region of the developing pronephros. Our study supports ISL1 as a major susceptibility gene for CBE and as a regulator of urinary tract development

Complexity of the Genetics and Clinical Presentation of Spinocerebellar Ataxia 17

Spinocerebellar ataxia type 17 (SCA17) is a rare autosomal dominant neurodegenerative disease caused by a CAG repeat expansion in the TATA-box binding protein gene (TBP). The disease has a varied age at onset and clinical presentation. It is distinct from other SCAs for its association with dementia, psychiatric symptoms, and some patients presenting with chorea. For this reason, it is also called Huntington’s disease-like 4 (HDL-4). Here we examine the distribution of SCA17 allele repeat sizes in a United Kingdom-based cohort with ataxia and find that fully penetrant pathogenic alleles are very rare (5 in 1,316 chromosomes; 0.38%). Phenotype-genotype correlation was performed on 30 individuals and the repeat structure of their TBP genes was examined. We found a negative linear correlation between total CAG repeat length and age at disease onset and, unlike SCA1, there was no correlation between the longest contiguous CAG tract and age at disease onset. We were unable to identify any particular phenotypic trait that segregated with particular CAG/CAA repeat tract structures or repeat lengths. One individual within the cohort was homozygous for variable penetrance range SCA17 alleles. This patient had a similar age at onset to heterozygotes with the same repeat sizes, but also presented with a rapidly progressive dementia. A pair of monozygotic twins within the cohort presented 3 years apart with the sibling with the earlier onset having a more severe phenotype with dementia and chorea in addition to the ataxia observed in their twin. This appears to be a case of variable expressivity, possibly influenced by other environmental or epigenetic factors. Finally, there was an asymptomatic father with a severely affected child with an age at onset in their twenties. Despite this, they share the same expanded allele repeat sizes and sequences, which would suggest that there is marked difference in the penetrance of this 51-repeat allele. We therefore propose that the variable penetrance range extend from 48 repeats to incorporate this allele. This study shows that there is variability in the presentation and penetrance of the SCA17 phenotype and highlights the complexity of this disorder