A Market Basket Analysis Conducted with a Multivariate Logit Model

The following research is guided by the hypothesis that products chosen on a shopping trip in a supermarket can indicate the preference interdependencies between different products or brands. The bundle chosen on the trip can be regarded as the result of a global utility function. More specifically: the existence of such a function implies a cross-category dependence of brand choice behavior. It is hypothesized that the global utility function related to a product bundle results from the marketing-mix of the underlying brands. Several approaches exist to describe the choice of specific categories from a set of many alternatives. The models are discussed in brief; the multivariate logit approach is used to estimate a model with a German data set.market basket analysis, multivariate logit model, brand choice behavior, marketing-mix

An empirical test of theories of price valuation using a semiparametric approach, reference prices, and accounting for heterogeneity

In this paper we estimate and empirically test different behavioral theories of consumer reference price formation. Two major theories are proposed to model the reference price reaction: assimilation contrast theory and prospect theory. We assume that different consumer segments will use different reference prices. The study builds on earlier research by Kalyanaram and Little (1994); however, in contrast to their work, we use parametric and semiparametric approaches to detect the structure of the underlying data sets. The different models are tested using a program module in GAUSS that was able to account for heterogeneity. The model types were calibrated by a simulation study. The calibrated modules were then used to analyze real market data.price valuation, semiparametric approach, reference prices, heterogeneity

Estimation with the Nested Logit Model: Specifications and Software Particularities

The paper discusses the nested logit model for choices between a set of mutually exclusive alternatives (e.g. brand choice, strategy decisions, modes of transportation, etc.). Due to the ability of the nested logit model to allow and account for similarities between pairs of alternatives, the model has become very popular for the empirical analysis of choice decisions. However the fact that there are two different specifications of the nested logit model (with different outcomes) has not received adequate attention. The utility maximization nested logit (UMNL) model and the non-normalized nested logit (NNNL) model have different properties, influencing the estimation results in a different manner. This paper introduces distinct specifications of the nested logit model and indicates particularities arising from model estimation. The effects of using various software packages on the estimation results of a nested logit model are shown using simulated data sets for an artificial decision situation.nested logit model, utility maximization nested logit, nonnormalized nested logit, simulation study

Estimation with the Nested Logit Model: Specifications and Software Particularities

Due to its ability to allow and account for similarities betweenpairs of alternatives, the nested logit model is increasingly used in practical applications. However the fact that there are two different specifications of the nested logit model has not received adequate attention. The utility maximization nested logit (UMNL) model and the non-normalized nested logit (NNNL) model have different properties, influencing the estimation results in a different manner. As the NNNL specification is not consistent with random utility theory (RUT), the UMNL form is preferred. This article introduces distinct specifications of the nested logit model and indicates particularities arising from model estimation. Additionally, it demonstrates the performance ofsimulation studies with the nested logit model. In simulation studies with the nested logit model using NNNL software (e. g. PROC MDC in SAS(c) ), it must be pointed out that the simulation of the utility function´s error terms needs to assume RUT-conformity. But as the NNNL specification is not consistent with RUT, the input parameters cannot be reproduced without imposing restrictions. The effects of using various software packages on the estimation results of a nested logit model are shown on the basis of a simulation study.nested logit model, utility maximization nested logit, non-normalized nested logit, simulation study

"Investigating the Competitive Assumption of Multinomial Logit Models of Brand Choice by Nonparametric Modeling"

The Multinomial Logit (MNL) model is still the only viable option to study nonlinear responsiveness of utility to covariates nonparametrically. This research investigates whether MNL structure of inter-brand competition is a reasonable assumption, so that when the utility function is estimated nonparametrically, the IIA assumption does not bias the result. For this purpose, the authors compare the performance of two comparable nonpara-metric choice models that differ in one aspect: one assumes MNL com-petitive structure and the other infers the pattern of brands' competition nonparametrically from data.

Nonparametric modeling of buying behavior in fast moving consumer goods markets

"From the statistical point of view a nonparametric formulation of a brand choice model (NDE) is a powerful alternative to the logit model. But in the marketing context, researchers in general want to have parameter values to make predictions or to estimate market shares. This leads to a semiparametric model (GAM) formulation with two possible ways of using the results. One is to perform estimation of choice probabilities, but there one is confronted with the same problem as in the nonparametric approach, because no parameters are estimated for the nonparametric part of the model. The second possibility of a semiparametric model formulation overcomes this problem. In addition, with the estimation results a modified parametric model formulation can be estimated. This also gives the possibility to work with the parameter values to estimate market shares or make predictions. Especially for this use of modeling, the underlying data structure should be detected correctly. Therefore, two different estimation algorithms for a GAM were presented and the application of the semiparametric model to a real data set was reported. The estimations were made by the two common algorithms, backfitting and marginal integration, and are compared to each other. An interaction effect in the variable price in the data set was discovered, which leads to the need of additional studies of the data set." (author's abstract

Tensilely strained germanium nanomembranes for infrared light emitting devices

Thesis (Ph.D.)--Boston Universitydevelopment of group-IV semiconductor lasers has attracted significant attention in recent years, since it represents the key missing ingredient for the large-scale monolithic integration of electronics and photonics in a CMOS-compatible fashion. The main challenge is to convert the indirect-bandgap group-IV materials into efficient light emitters. Many researchers have focused on improving the light emission efficiency of these materials in the near-infrared (NIR) spectral region, to replace the existing chip-to- chip communication technology with optical links. At the same time, group-IV lasers operating at mid-infrared (MIR) wavelengths also possess many important applications, mainly in the area of chemical and biological sensing, such as trace-gas detection, environmental monitoring, medical diagnostics, and industrial process control. Motivated by these applications, here I focus on improving the light emission efficiency of germanium (Ge). The small energy difference between its direct and indirect bandgaps can be further decreased with the introduction of tensile strain, leading to significantly improved radiative efficiency. At the same time, the bandgap energy shifts into the technologically important 2.1-2.5 µm MIR atmospheric transmission window. At 1.9% tensile strain, Ge even becomes a direct-bandgap semiconductor. In this work, tensile strain is introduced in Ge nanomembranes (NMs), i.e., single-crystal sheets with nanoscale thicknesses, through the application of mechanical stress. Our strain-resolved photoluminescence (PL) measurements performed on these NMs demonstrate a significant red-shift and enhancement in the emission spectra with increasing strain. PL measurement results obtained with a 24-nm-thick NM also reveal that the membrane is converted into direct-bandgap Ge with the application of 2% tensile strain. Furthermore, theoretical analysis of the high-strain PL spectra shows that population inversion can be achieved in these ultrathin NMs with gain values as high as 300 cm−1. Two-dimensional periodic structures fabricated on the top surface of such membranes result in further enhanced light collection through first-order diffraction of the in-plane emitted luminescence. Furthermore, the cavity modes of these periodic structures are also resolved in the strain-dependent PL spectra. These results are promising for the demonstration of Ge NM lasers operating in the technologically important 2.1-2.5 µm spectral region for potential applications in biochemical sensing and spectroscopy

Long-term outcome after a treosulfan-based conditioning regimen for patients with acute myeloid leukemia: A report from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

BACKGROUND: Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for patients with acute myeloid leukemia (AML). However, post-HCT relapse and regimen-related toxicity remain significant barriers to long-term survival. In recent years, new conditioning regimens have been explored to improve transplantation outcomes in patients with AML. Treosulfan combines a potent immunosuppressive and antileukemic effect with a low toxicity profile. METHODS: To investigate the role of treosulfan-based conditioning, the European Society for Blood and Marrow Transplantation Acute Leukemia Working Party performed a registry analysis of 520 adult patients with AML who received treosulfan-based conditioning and underwent HCT between 2000 and 2012, including 225 patients in first complete remission, 107 in second or later complete remission, and 188 with active/advanced disease 188 (88 with primary refractory disease). The median patient age was 57 years (range, 20-73 years). Donors were human leukocyte antigen-identical siblings (n = 187), unrelated donors (n = 235), or mismatched related donors (n = 98). Conditioning regimens included treosulfan (42 g/m2 [n = 396], 36 g/m2 [n = 109], or 30 g/ m2 [n = 15]) with fludarabine or alkylating agents followed by infusion of hematopoietic stem cells (bone marrow, n = 52; peripheral blood, n = 468). RESULTS: At a median follow-up of 61 months, the 5-year overall survival, leukemia-free survival, relapse incidence, and nonrelapse mortality rates were 38%, 33%, 42%, and 25%, respectively. The incidence of grade II-IV acute and chronic graft-versus-host disease was 24% (grade III-V, 11%) and 38%, respectively. Only 11 patients (2%) developed veno-occlusive disease, with two deaths (0.4%) from veno-occlusive disease. CONCLUSIONS: Treosulfan-based conditioning regimens provide an acceptable long-term survival with favorable nonrelapse mortality and a very low risk of veno-occlusive disease. Further studies are needed to optimize the treosulfan-based conditioning regimen for patients with AML

Protein Kinase C δ: a Gatekeeper of Immune Homeostasis

Human autoimmune disorders present in various forms and are associated with a life-long burden of high morbidity and mortality. Many different circumstances lead to the loss of immune tolerance and often the origin is suspected to be multifactorial. Recently, patients with autosomal recessive mutations in PRKCD encoding protein kinase c delta (PKC) have been identified, representing a monogenic prototype for one of the most prominent forms of humoral systemic autoimmune diseases, systemic lupus erythematosus (SLE). PKC is a signaling kinase with multiple downstream target proteins and with functions in various signaling pathways. Interestingly, mouse models have indicated a special role of the ubiquitously expressed protein in the control of B-cell tolerance revealed by the severe autoimmunity in Prkcd / knockout mice as the major phenotype. As such, the study of PKC deficiency in humans has tremendous potential in enhancing our knowledge on the mechanisms of B-cell tolerance.(VLID)347918

The Phenotype and Treatment of WIP Deficiency: Literature Synopsis and Review of a Patient With Pre-transplant Serial Donor Lymphocyte Infusions to Eliminate CMV

Early diagnosis of primary immunodeficiency disorders (PID) is vital and allows directed treatment, especially in syndromes with severe or profound combined immunodeficiency. In PID patients with perinatal CMV or other opportunistic, invasive infections (e.g., Pneumocystis or Aspergillus), multi-organ morbidity may already arise within the first months of life, before hematopoietic stem cell transplantation (HSCT) or gene therapy can be undertaken, compromising the definitive treatment and outcome. Deficiency of Wiskott-Aldrich syndrome (WAS) protein-interacting protein (WIP deficiency) causes an autosomal recessive, WAS-like syndrome with early-onset combined immunodeficiency that has been described in three pedigrees to date. While WAS typically includes combined immunodeficiency, microthrombocytopenia, and eczema, the clinical and laboratory phenotypes of WIP-deficient patients–including lymphocyte subsets, platelets, lymphocyte proliferation in vitro, and IgE—varied widely and did not entirely recapitulate WAS, impeding early diagnosis in the reported patients. To elucidate the phenotype of WIP deficiency, we provide a comprehensive synopsis of clinical and laboratory features of all hitherto-described patients (n = 6) and WIP negative mice. Furthermore, we summarize the treatment modalities and outcomes of these patients and review in detail the course of one of them who was successfully treated with serial, unconditioned, maternal, HLA-identical donor lymphocyte infusions (DLI) against life-threatening, invasive CMV infection, followed by a TCRαβ/CD19-depleted, treosulfan/melphalan-conditioned, peripheral blood HSCT and repetitive, secondary-prophylactic, CMV-specific DLI with 1-year post-HSCT follow-up. This strategy could be useful in other patients with substantial premorbidity, considered “too bad to transplant,” who have an HLA-identical family donor, to eliminate infections and bridge until definitive treatment