Undermining and Strengthening Social Networks through Network Modification

Social networks have well documented effects at the individual and aggregate level. Consequently it is often useful to understand how an attempt to influence a network will change its structure and consequently achieve other goals. We develop a framework for network modification that allows for arbitrary objective functions, types of modification (e.g. edge weight addition, edge weight removal, node removal, and covariate value change), and recovery mechanisms (i.e. how a network responds to interventions). The framework outlined in this paper helps both to situate the existing work on network interventions but also opens up many new possibilities for intervening in networks. In particular use two case studies to highlight the potential impact of empirically calibrating the objective function and network recovery mechanisms as well as showing how interventions beyond node removal can be optimised. First, we simulate an optimal removal of nodes from the Noordin terrorist network in order to reduce the expected number of attacks (based on empirically predicting the terrorist collaboration network from multiple types of network ties). Second, we simulate optimally strengthening ties within entrepreneurial ecosystems in six developing countries. In both cases we estimate ERGM models to simulate how a network will endogenously evolve after intervention

Symposium Review: \u3cem\u3eAmish and Old Order Mennonite Schools: A Concise History\u3c/em\u3e—Joseph Stoll; and The School by the Cornfield—Samuel Coon

Joseph Stoll, in Amish and Old Order Mennonite Schools: A Concise History, and Samuel Coon, in The School by the Cornfield, provide two very different perspectives on the struggle to establish Anabaptist schools. The books contrast primarily in their geographic and chronological scope. However, both write about parochial schools with a voice sympathetic to the vision of Amish and Mennonite school founders. They use similar sources, drawing on newspaper accounts, published Amish schools’ histories, and Amish and Mennonite periodicals, as well as personal recollections from individuals involved in school conflicts. [First paragraph.

Analysis of Galvanic Skin Response: Potential Relationships to Stimulus Responsivity and Brain Dopamine Signal

Fibromyalgia is a chronic pain disorder that presents itself with no apparent medical explanation for the pain. Functional alterations of neurotransmitters such as dopamine (DA) have been implicated in fibromyalgia neuropathology. It is not known how central dopamine function in pain is associated with objective peripheral measurements that are thought to be associated with the presence of pain and stress. Galvanic skin response (GSR), is a physiological measure of nervous system activation. GSR could potentially give insight to novel aspects of DA function. In this study, GSR was recorded from fibromyalgia patients (FM) and healthy controls (HC) while they underwent scanning with [18F]-fallypride (FAL) Positron Emission Tomography (PET). FAL is a D2/D3 DA receptor antagonist that is sensitive to changes in DA levels in the brain. Given the involvement of DA in cognitive processes, FAL PET can be used to examine baseline DA activity as well as changes from baseline during cognitive load tasks. Relationships between GSR and working memory load, acute pain, and DA function were studied and compared between FM and HC

Correlation Between Chromatid Deletion Production and Progression of the DNA Replication Fork in UV-Irradiated S Phase Xenopus Cells

Experimentation was performed primarily to determine whether progression of the DNA replication fork along segments of S phase Xenopus chromosomes, which contain UV-induced pre-aberrational lesions, plays a significant role in conversion of these lesions into chromatid deletions. Specifically, a Xenopus chromosome that was both easy to identify and that possessed a single DNA replication fork in one arm was found and used to conduct the experimentation. This chromosome was exposed to UV in early S phase and a Bromodeoxyuridine/Giemsa differential staining technique was applied in conjunction with conventional aberrational techniques to correlate progression of the DNA replication fork through segments of this arm with chromatid deletion production in these segments. The results point to direct evidence for the role of the DNA replication fork in converting some UV-induced pre-aberrational DNA damage into chromosomal deletions

CRISPR/Cas9-mediated mutagenesis of CAROTENOID CLEAVAGE DIOXYGENASE 8 in tomato provides resistance against the parasitic weed Phelipanche aegyptiaca.

Broomrapes (Phelipanche aegyptiaca and Orobanche spp.) are obligate plant parasites that cause extreme damage to crop plants. The parasite seeds have strict requirements for germination, involving preconditioning and exposure to specific chemicals strigolactones [SLs] exuded by the host roots. SLs are plant hormones derived from plant carotenoids via a pathway involving the Carotenoid Cleavage Dioxygenase 8 (CCD8). Having no effective means to control parasitic weeds in most crops, and with CRISPR/Cas9 being an effective gene-editing tool, here we demonstrate that CRISPR/Cas9-mediated mutagenesis of the CCD8 gene can be used to develop host resistance to the parasitic weed P. aegyptiaca. Cas9/single guide (sg) RNA constructs were targeted to the second exon of CCD8 in tomato (Solanum lycopersicum L.) plants. Several CCD8Cas9 mutated tomato lines with variable insertions or deletions in CCD8 were obtained with no identified off-targets. Genotype analysis of T1 plants showed that the introduced CCD8 mutations are inherited. Compared to control tomato plants, the CCD8Cas9 mutant had morphological changes that included dwarfing, excessive shoot branching and adventitious root formation. In addition, SL-deficient CCD8Cas9 mutants showed a significant reduction in parasite infestation compared to non-mutated tomato plants. In the CCD8Cas9 mutated lines, orobanchol (SL) content was significantly reduced but total carotenoids level and expression of genes related to carotenoid biosynthesis were increased, as compared to control plants. Taking into account, the impact of plant parasitic weeds on agriculture and difficulty to constitute efficient control methods, the current study offers insights into the development of a new, efficient method that could be combined with various collections of resistant tomato rootstocks

Modeling Agricultural Sheet, Rill and Ephemeral Gully Erosion

Mini-Symposium: Modeling Methodology for Agricultural Researc

Monetary discounting and ventral striatal dopamine receptor availability in nontreatment-seeking alcoholics and social drinkers

RATIONALE: Dopamine (DA) in the ventral striatum (VST) has long been implicated in addiction pathologies, yet its role in temporal decision-making is not well-understood. OBJECTIVES: To determine if VST DA D2 receptor availability corresponds with greater impulsive choice in both nontreatment-seeking alcoholics (NTS) and social drinkers (SD). METHODS: NTS subjects (n = 10) and SD (n = 13) received PET scans at baseline with the D2/D3 radioligand [(11)C]raclopride (RAC). Outside the scanner, subjects performed a delay discounting procedure with monetary rewards. RAC binding potential (BPND) was estimated voxelwise, and correlations were performed to test for relationships between VST BPND and delay discounting performance. Self-reported impulsivity was also tested for correlations with BPND. RESULTS: Across all subjects, greater impulsive choice for $20 correlated with lower BPND in the right VST. NTS showed greater impulsive choice than SD and were more impulsive by self-report. Across all subjects, the capacity of larger rewards to reduce impulsive choice (the magnitude effect) correlated negatively (p = 0.028) with problematic alcohol use (AUDIT) scores. Self-reported impulsivity did not correlate with BPND in VST. CONCLUSIONS: Preference for immediate reinforcement may reflect greater endogenous striatal DA or lower D2 number, or both. Alcoholic status did not mediate significant effects on VST BPND, suggesting minimal effects from alcohol exposure. The apparent lack of BPND correlation with self-reported impulsivity highlights the need for objective behavioral assays in the study of the neurochemical substrates of behavior. Finally, our results suggest that the magnitude effect may be more sensitive to alcohol-induced problems than single discounting measures