When giving some away makes sense to jump-start the diffusion process.

This paper uses an analytical model to examine when it makes sense to provide incentives to innovators to adopt a new product. The model allows for separate segments of innovators and imitators, each of which follows a Bass-type diffusion process. Interestingly “seeding” the market is optimal for a limited range of situations and these do not appear to include those where there is a downturn in sales (chasm) as sales move from the first to the second segment. Research has frequently identified different segments of adopters of new products. Categorizations include innovators vs imitators (Bass, 1969; Rogers, 1995; Mahahan et al., 1990; Im et al., 2003), technophiles vs “normal” people, and business vs consumer users. Further, considerable effort has gone into studying the influence of members of the first group on the second. This paper focuses on when, if ever, it makes sense for a manufacture of a new product to “seed” the market by subsidizing a few early adopters to speed the adoption process. The paper builds on earlier work by Kalish and Lilien (1983) which focused on the impact of widely available government subsidies on the adoption of socially desirable innovations (i.e. alternative energy sources) as well as the work of Jain et al. (1995). Unlike that work, we concentrate on providing subsidies (here free goods) to selective individuals in the context of a model which allows for separate segments of innovators and imitators and nests the standard Bass (1969) model.

Chandra Observations of Six QSOs at z ≈\approx 3

We report the results of our Chandra observations of six QSOs at $z\sim 3$ from the Palomer Transit Grism Survey. Our primary goal is to investigate the possible systematic change of $\alpha_{ox}$ between $z>4$ and $z\sim 3$, between which a rapid rise of luminous QSO number density with cosmic time is observed. The summed spectrum showed a power-law spectrum with photon index of $\Gamma \approx 1.9$, which is similar to other unabsorbed AGNs. Combining our $z\sim 3$ QSOs with X-ray observations of QSOs at $z>4$ from literaure/archive, we find a correlation of $\alpha_{\rm ox}$ with optical luminosity. This is consistent with the fact that the luminosity function slope of the luminous end of the X-ray selected QSOs is steeper than that of optically-selected QSOs. We discuss an upper limit to the redshift dependence of $\alpha_{ox}$ using a Monte-Carlo simulation. Within the current statistical errors including the derived limits on the redshift dependence of $\alpha_{\rm ox}$, we found that the behaviors of the X-ray and optically-selected QSO number densities are consistent with each other.Comment: 13 Pages, 3 Figures, Astronomical Journal in press, An entry in Table 2 corrected--Log Lx for PC 1000+4751 from 44.0 (incorrect) to 45.0 (correct). A few minor errors correcte

Trypanosoma barbari, a new species from the newt Triturus torosus

Whlle making studies of the parasites of fishes and amphibians at the Pacific Marine Station, Dillon Beach, California, during August, 1949, the writer encountered a hitherto unreported trypanasome from a female Triturus torosua. From the information obtained from the one smear, which was stained, the animal was presumed to be monomorphic, However, during February, 1950, a search was made expressly for the purpose of\u27 obtaining specimens of this Pacific Coast newt, and of the eight animals examined six were parasitized. Contrary to the primary observations, evidence was accumulated which proved beyond any doubt that the flagellate is polymorphic and that, evidently, it has not been reported or described. The name Trypanasoma barbari is proposed for this species

Modeling Choice Among Assortments

In this paper we propose a model for describing consumer decision making among assortments or menus of options from which a single option will be chosen at a later time. Central to the derivation of the model is an assumption that consumers are uncertain about their future preferences. The model captures both the utility of the items within the assortments as well as the flexibility the items offer as a group. We support our model empirically with two laboratory experiments. In the first experiment we test the underlying assumptions. In the second, we compare the predictive validity of our model to that provided by other models suggested in the literature

Many Paths to Alzheimer's Disease: A Unifying Hypothesis Integrating Biological, Chemical, and Physical Risk Factors

Sporadic Alzheimer's disease (AD) is a complex, multifactorial disease. We should therefore expect to find many factors involved in its causation. The known neuropathology seen at autopsy in patients dying with AD is not consistently seen in all patients with AD and is sometimes seen in patients without dementia. This suggests that patients follow different paths to AD, with different people having slightly different combinations of predisposing physical, chemical and biologic risk factors, and varying neuropathology. This review summarizes what is known of the biologic and chemical predisposing factors and features in AD. We postulate that, underlying the neuropathology of AD is a progressive failure of neurons, with advancing age or other morbidity, to rid themselves of entropy, i.e., the disordered state resulting from brain metabolism. Understanding the diverse causes of AD may allow the development of new therapies targeted at blocking the paths that lead to dementia in each subset of patients

Making Choices While Smelling, Tasting, and Listening: The Role of Sensory (Dis)similarity When Sequentially Sampling Products

Marketers are increasingly allowing consumers to sample sensory-rich experiential products before making purchase decisions. The results of seven experimental studies (two conducted in field settings, three conducted in a laboratory, and two conducted online) demonstrate that the order in which consumers sample products and the level of (dis)similarity between the sensory cues of the products influence choices. In the absence of any moderators, when sampling a sequence of sensory-rich experiential products (e.g., fragrances, chocolates, flavored beverages, music) with similar sensory cues (e.g., smell, taste, color, sound), consumers prefer the first product in the sequence. However, when sampling a sequence of products with dissimilar sensory cues, consumers prefer the last product. These findings (1) contribute to a better understanding of the role of sequential sensory cues on consumer choice formation, (2) have implications for effects related to sensory habituation and sensory trace fading, and (3) help resolve apparent inconsistencies in prior research on order effects in the context of choices for sequentially sampled experiential products

State-Dependence Effects in Surveys

In recent years academic research has focused on understanding and modeling the survey response process. This paper examines an understudied systematic response tendency in surveys: the extent to which observed responses are subject to state dependence, i.e., response carryover from one item to another independent of specific item content. We develop a statistical model that simultaneously accounts for state dependence, item content, and scale usage heterogeneity. The paper explores how state dependence varies by response category, item characteristics, item sequence, respondent characteristics, and whether it becomes stronger as the survey progresses. Two empirical applications provide evidence of substantial and significant state dependence. We find that the degree of state dependence depends on item characteristics and item sequence, and it varies across individuals and countries. The article demonstrates that ignoring state dependence may affect reliability and predictive validity, and it provides recommendations for survey researchers