The cross section for the radiative capture of protons by C12 near 100 Kev

A low voltage accelerator and high current ion source has been used to determine the cross section of the reaction C12(pγ)N13 over the energy range from 88 to 128 kev. A counter arrangement is described which detects 26 percent of all the positrons from the decay of the N13 produced in the reaction and which has a low background rate of 5.5 counts per minute. With this accelerator and detector, yields of the order of 10^-16 positron per proton and cross sections as low as 10^-10 barn or 10^-34 cm^2 can be measured with errors of the order of ±20 percent. The cross section for the C12(pγ)N13 reaction has been found to fit the semi-empirical expression σ=0.0024E^-1exp[-6E^-1/2] barn with E in Mev over the energy range measured. This is in satisfactory agreement with the Breit-Wigner one-level dispersion formula using constants determined at the 456-kev resonance. The astrophysical implications of these results in connection with the carbon-nitrogen cycle of nuclear reactions in stellar interiors are discussed

A hierarchical statistical framework for emergent constraints: application to snow-albedo feedback

Emergent constraints use relationships between future and current climate states to constrain projections of climate response. Here, we introduce a statistical, hierarchical emergent constraint (HEC) framework in order to link future and current climate with observations. Under Gaussian assumptions, the mean and variance of the future state is shown analytically to be a function of the signal-to-noise (SNR) ratio between data-model error and current-climate uncertainty, and the correlation between future and current climate states. We apply the HEC to the climate-change, snow-albedo feedback, which is related to the seasonal cycle in the Northern Hemisphere. We obtain a snow-albedo-feedback prediction interval of $(-1.25, -0.58)$ \%$K^{-1}$. The critical dependence on SNR and correlation shows that neglecting these terms can lead to bias and under-estimated uncertainty in constrained projections. The flexibility of using HEC under general assumptions throughout the Earth System is discussed.Comment: 19 pages, 5 Figure

Incubation period of typhoidal salmonellosis : a systematic review and meta-analysis of outbreaks and experimental studies occurring over the last century

Background Salmonella Typhi is a human pathogen that causes typhoid fever. It is a major cause of morbidity and mortality in developing countries and is responsible for several outbreaks in developed countries. Studying certain parameters of the pathogen, such as the incubation period, provides a better understanding of its pathophysiology and its characteristics within a population. Outbreak investigations and human experimental studies provide an avenue to study these relevant parameters. Methods In this study, the authors have undertaken a systematic review of outbreak investigation reports and experimental studies, extracted reported data, tested for heterogeneity, identified subgroups of studies with limited evidence of heterogeneity between them and identified factors that may contribute to the distribution of incubation period. Following identification of relevant studies, we extracted both raw and summary incubation data. We tested for heterogeneity by deriving the value of I2 and conducting a KS-test to compare the distribution between studies. We performed a linear regression analysis to identify the factors associated with incubation period and using the resulting p-values from the KS-test, we conducted a hierarchical cluster analysis to classify studies with limited evidence of heterogeneity into subgroups. Results We identified thirteen studies to be included in the review and extracted raw incubation period data from eleven. The value of I2 was 84% and the proportion of KS test p-values that were less than 0.05 was 63.6% indicating high heterogeneity not due to chance. We identified vaccine history and attack rates as factors that may be associated with incubation period, although these were not significant in the multivariable analysis (p-value: 0.1). From the hierarchical clustering analysis, we classified the studies into five subgroups. The mean incubation period of the subgroups ranged from 9.7 days to 21.2 days. Outbreaks reporting cases with previous vaccination history were clustered in a single subgroup and reported the longest incubation period. Conclusions We identified attack rate and previous vaccination as possible associating factors, however further work involving analyses of individual patient data and developing mathematical models is needed to confirm these as well as examine additional factors that have not been included in our study

Within-host mathematical modelling of the incubation period of Salmonella Typhi

Mechanistic mathematical models are often employed to understand the dynamics of infectious diseases within a population or within a host. They provide estimates that may not be otherwise available. We have developed a within-host mathematical model in order to understand how the pathophysiology of Salmonella Typhi contributes to its incubation period. The model describes the process of infection from ingestion to the onset of clinical illness using a set of ordinary differential equations. The model was parametrized using estimated values from human and mouse experimental studies and the incubation period was estimated as 9.6 days. A sensitivity analysis was also conducted to identify the parameters that most affect the derived incubation period. The migration of bacteria to the caecal lymph node was observed as a major bottle neck for infection. The sensitivity analysis indicated the growth rate of bacteria in late phase systemic infection and the net population of bacteria in the colon as parameters that most influence the incubation period. We have shown in this study how mathematical models aid in the understanding of biological processes and can be used in estimating parameters of infectious diseases

A Proof of a Conjecture of Ohba

We prove a conjecture of Ohba which says that every graph $G$ on at most $2\chi(G)+1$ vertices satisfies $\chi_\ell(G)=\chi(G)$.Comment: 21 page

Incidence and Growth of Patent Thickets - The Impact of Technological Opportunities and Complexity

We investigate incidence and evolution of patent thickets. Our empirical analysis is based on a theoretical model of patenting in complex and discrete technologies. The model cap- tures how competition for patent portfolios and complementarity of patents affect patent- ing incentives. We show that lower technological opportunities increase patenting in- centives in complex technologies while they decrease incentives in discrete technologies. Also, more competitors increase patenting incentives in complex technologies and reduce them in discrete technologies. To test these predictions a new measure of the density of patent thickets is introduced. European patent citations are used to construct measures of fragmentation and technological opportunity. Our empirical analysis is based on a panel capturing patenting behavior of 2074 firms in 30 technology areas over 15 years. GMM estimation results confirm the predictions of our theoretical model. The results show that patent thickets exist in 9 out of 30 technology areas. We find that decreased technological opportunities are a surprisingly strong driver of patent thicket growth

Social Interactions as a Source of Information about E-Cigarettes: A Study of U.S. Adult Smokers

The novelty of e-cigarettes and ambiguity about their effects may foster informal sharing of information, such as through social interactions. We aimed to describe smokers’ social interactions about e-cigarettes and their recommendations that others use e-cigarettes. Data were collected from 2149 adult smokers in North Carolina and California who participated in a study of the impact of pictorial cigarette pack warnings. In the previous month, almost half of participants (45%) reported talking to at least one person about e-cigarettes and nearly a third of participants (27%) recommended e-cigarettes to someone else. Smokers recommended e-cigarettes to cut back on smoking (57%), to quit smoking (48%), for health reasons (36%), and for fun (27%). In adjusted analyses, more frequent e-cigarette use, positive views about typical e-cigarette users, and attempting to quit smoking in the past month were associated with recommending e-cigarettes for health reasons (all p < 0.05). Social interactions appear to be a popular method of information-sharing about e-cigarettes among smokers. Health communication campaigns may help to fill in the gaps of smokers’ understanding of e-cigarettes and their long-term effects

A possible relation between dietary zinc and cAMP in the regulation of tumour cell proliferation in the rat

The possibility of an effect of zinc on the rate of tumour cell division, mediated through a regulation of cellular cAMP concentration, was investigated in the present study in rats. Dietary Zn deficiency (< 1·5 mg Zn/kg) but not Zn excess (500 mg Zn/kg) resulted in an increased cAMP concentration in transplanted hepatoma cells. Neither treatment had any effect on the cAMP concentration in regenerating liver or normal resting liver. Both the deficient and excess Zn diets resulted in a small reduction in tumour growth (not statistically significant). The results seem to indicate that the relation investigated in the present study does not apply in the cell line used

Messages to Motivate Human Papillomavirus Vaccination: National Studies of Parents and Physicians

Physician communication about human papillomavirus (HPV) vaccine is a key determinant of uptake. To support physician communication, we sought to identify messages that would motivate HPV vaccination