Nonuniversal power law scaling in the probability distribution of scientific citations

We develop a model for the distribution of scientific citations. The model involves a dual mechanism: in the direct mechanism, the author of a new paper finds an old paper A and cites it. In the indirect mechanism, the author of a new paper finds an old paper A only via the reference list of a newer intermediary paper B, which has previously cited A. By comparison to citation databases, we find that papers having few citations are cited mainly by the direct mechanism. Papers already having many citations ('classics') are cited mainly by the indirect mechanism. The indirect mechanism gives a power-law tail. The 'tipping point' at which a paper becomes a classic is about 21 citations for papers published in the Institute for Scientific Information (ISI) Web of Science database in 1981, 29 for Physical Review D papers published from 1975-1994, and 39 for all publications from a list of high h-index chemists assembled in 2007. The power-law exponent is not universal. Individuals who are highly cited have a systematically smaller exponent than individuals who are less cited.Comment: 7 pages, 3 figures, 2 table

Adverse Consequences to Assisting Victims of Campus Violence: Initial Investigations Among College Students

Despite growing interest in the use of bystander education programs to address the problems of sexual and relationship violence on college campuses, little knowledge exists on adverse consequences experienced by students intervening as a bystander. The current study examined the prevalence and correlates of adverse consequences of bystander intervention in two samples of first-year college students. In Study 1, 281 students completed a measure of negative consequences experienced when acting as a bystander to help someone at risk of sexual assault, relationship abuse, or stalking. Efficacy for bystander behavior was also assessed. Approximately one third of the students (97/281) reported having tried to help someone who had been at risk of violence during the previous academic year. Of these, approximately 17% (16/97) reported experiencing a negative consequence from having tried to help. Experiencing negative consequences was associated with lower levels of bystander efficacy. In Study 2, conducted at a different university, 299 students completed measures of negative consequences resulting from intervening as a bystander and efficacy for bystander behavior. Students also participated in virtual-reality simulations that provided opportunities to intervene as a bystander. Again, approximately one third of the students (99/299) reported having tried to help someone at risk of violence. Of these, 20% (20/99) reported experiencing a negative consequence. Two of the adverse consequences (physically hurt, got into trouble) were negatively associated with bystander efficacy and observed effectiveness of bystander behavior in the virtual simulations. Results of exploratory analyses suggest that training in bystander intervention might reduce the likelihood of experiencing adverse consequences

Statistics of Lead Changes in Popularity-Driven Systems

We study statistical properties of the highest degree, or most popular, nodes in growing networks. We show that the number of lead changes increases logarithmically with network size N, independent of the details of the growth mechanism. The probability that the first node retains the lead approaches a finite constant for popularity-driven growth, and decays as N^{-phi}(ln N)^{-1/2}, with phi=0.08607..., for growth with no popularity bias.Comment: 4 pages, 4 figures, 2 column revtex format. Minor changes in response to referee comments. For publication in PR

The investigation of time dependent flame structure by ionization probes

Ionization probes were used to measure mean ionization current and frequency spectra, auto-correlations and cross-correlations in jet flames with variation in the initial Reynolds numbers and equivalence ratios. Special attention was paid to the transitional region between the burner exit plane and the plane of onset of turbulence

In situ tropical peatland ire emission factors and their variability, as determined by field measurements in peninsula Malaysia

Fires in tropical peatlands account for >25% of estimated total greenhouse gas emissions from deforestation and degradation. Despite significant global and regional impacts, our understanding of specific gaseous fire emission factors (EFs) from tropical peat burning is limited to a handful of studies. Furthermore, there is substantial variability in EFs between sampled fires and/or studies. For example, methane EFs vary by 91% between studies. Here we present new fire EFs for the tropical peatland ecosystem; the first EFs measured for Malaysian peatlands, and only the second comprehensive study of EFs in this crucial environment. During August 2015 (under El Niño conditions) and July 2016, we embarked on field campaigns to measure gaseous emissions at multiple peatland fires burning on deforested land in Southeast Pahang (2015) and oil palm plantations in North Selangor (2016), Peninsula Malaysia. Gaseous emissions were measured using open-path Fourier transform infrared spectroscopy. The IR spectra were used to retrieve mole fractions of 12 different gases present within the smoke (including carbon dioxide and methane), and these measurements used to calculate EFs. Peat samples were taken at each burn site for physicochemical analysis and to explore possible relationships between specific physicochemical properties and fire EFs. Here we present the first evidence to indicate that substrate bulk density affects methane fire EFs reported here. This novel explanation of interplume, within-biome variability, should be considered by those undertaking greenhouse gas accounting and haze forecasting in this region and is of importance to peatland management, particularly with respect to artificial compaction

Targeting the ATP-dependent formation of herpesvirus ribonucleoprotein particle assembly as an antiviral approach

Human herpesviruses are responsible for a range of debilitating acute and recurrent diseases, including a number of malignancies. Current treatments are limited to targeting the herpesvirus DNA polymerases, however with emerging viral resistance and little efficacy against the oncogenic herpesviruses, there is an urgent need for new antiviral strategies. Herein we describe a mechanism to inhibit the replication of the oncogenic herpesvirus Kaposi’s sarcoma associated herpesvirus (KSHV), by targeting the ATP-dependent formation of viral ribonucleoprotein particles (vRNPs). We demonstrate that small molecule inhibitors which selectively inhibit the ATPase activity of the cellular human transcription/export complex (hTREX) protein UAP56, result in effective inhibition of vRNP formation, viral lytic replication and infectious virion production. Strikingly, as all human herpesviruses utilize conserved mRNA processing pathways involving hTREX components, we demonstrate the feasibility of this approach for pan-herpesvirus inhibition

Pyridine-3-carboxamide-6-yl-ureas as novel inhibitors of bacterial DNA gyrase: Structure based design, synthesis, SAR and antimicrobial activity

The development of antibacterial drugs based on novel chemotypes is essential to the future management of serious drug resistant infections. We herein report the design, synthesis and SAR of a novel series of N-ethylurea inhibitors based on a pyridine-3-carboxamide scaffold targeting the ATPase sub-unit of DNA gyrase. Consideration of structural aspects of the GyrB ATPase site has aided the development of this series resulting in derivatives that demonstrate excellent enzyme inhibitory activity coupled to potent Gram positive antibacterial efficacy

Virus-induced gene silencing database for phenomics and functional genomics in Nicotiana benthamiana

Virus-induced gene silencing (VIGS) is an important forward and reverse genetics method for the study of gene function in many plant species, especially Nicotiana benthamiana. However, despite the widespread use of VIGS, a searchable database compiling the phenotypes observed with this method is lacking. Such a database would allow researchers to know the phenotype associated with the silencing of a large number of individual genes without experimentation. We have developed a VIGS phenomics and functional genomics database (VPGD) that has DNA sequence information derived from over 4,000 N. benthamiana VIGS clones along with the associated silencing phenotype for approximately 1,300 genes. The VPGD has a built-in BLAST search feature that provides silencing phenotype information of specific genes. In addition, a keyword-based search function could be used to find a specific phenotype of interest with the corresponding gene, including its Gene Ontology descriptions. Query gene sequences from other plant species that have not been used for VIGS can also be searched for their homologs and silencing phenotype in N. benthamiana. VPGD is useful for identifying gene function not only in N. benthamiana but also in related Solanaceae plants such as tomato and potato. The database is accessible at http://vigs.noble.org.Noble Research Institute and NSF IOS-102564

Rank Statistics in Biological Evolution

We present a statistical analysis of biological evolution processes. Specifically, we study the stochastic replication-mutation-death model where the population of a species may grow or shrink by birth or death, respectively, and additionally, mutations lead to the creation of new species. We rank the various species by the chronological order by which they originate. The average population N_k of the kth species decays algebraically with rank, N_k ~ M^{mu} k^{-mu}, where M is the average total population. The characteristic exponent mu=(alpha-gamma)/(alpha+beta-gamma)$ depends on alpha, beta, and gamma, the replication, mutation, and death rates. Furthermore, the average population P_k of all descendants of the kth species has a universal algebraic behavior, P_k ~ M/k.Comment: 4 pages, 3 figure