Origin of the Scaling Law in Human Mobility: Hierarchical Organization of Traffic Systems

Uncovering the mechanism leading to the scaling law in human trajectories is of fundamental importance in understanding many spatiotemporal phenomena. We propose a hierarchical geographical model to mimic the real traffic system, upon which a random walker will generate a power-law travel displacement distribution with exponent -2. When considering the inhomogeneities of cities' locations and attractions, this model reproduces a power-law displacement distribution with an exponential cutoff, as well as a scaling behavior in the probability density of having traveled a certain distance at a certain time. Our results agree very well with the empirical observations reported in [D. Brockmann et al., Nature 439, 462 (2006)].Comment: 6 figures, 4 page

Huge enhancement of electronmechanical responses in compositionally modulated PZT

Monte Carlo simulations based on a first-principles-derived Hamiltonian are conducted to study the properties of PZT alloys compositionally modulated along the [100] pseudocubic direction near the morphotropic phase boundary (MPB). It is shown that compositional modulation causes the polarization to continuously rotate away from the modulation direction, resulting in the unusual triclinic and C-type monoclinic ground states and huge enhancement of electromechanical responses (the peak of piezoelectric coefficient is as high as 30000 pC/N). The orientation dependence of dipole-dipole interaction in modulated structure is revealed as the microscopic mechanism to be responsible for these anomalies.Comment: 5 pages, 4 figure

Empirical study on clique-degree distribution of networks

The community structure and motif-modular-network hierarchy are of great importance for understanding the relationship between structures and functions. In this paper, we investigate the distribution of clique-degree, which is an extension of degree and can be used to measure the density of cliques in networks. The empirical studies indicate the extensive existence of power-law clique-degree distributions in various real networks, and the power-law exponent decreases with the increasing of clique size.Comment: 9 figures, 4 page

Asymmetric Synthesis of Chiral-at-P Alkenylphosphonamidates through Nickel-Catalyzed C-P Coupling of Phosphoramidites and Alkenyl Halides

P-stereogenic compounds are widely used as ligands in asymmetric catalysis and are present in a myriad of bioactive compounds and pharmaceuticals. Yet, their stereocontrolled preparation remains challenging. Herein, we report a novel strategy towards versatile chiral-at-P alkenylphosphonamidates through a one-pot Ni-catalyzed C-P coupling/diastereoselective hydrolysis of readily available phosphoramidites and alkenyl halides. Remarkably, a chemo- and diastereodivergent behavior was observed upon subtle changes in the reaction conditions. Additionally, selective derivatizations of chiral alkenylphosphonamidates demonstrate their versatility as building blocks for the synthesis of structurally diverse P-stereogenic compounds.</p

Effect of Seed Treatment and Foliar Fungicides on Soybean White Mold and Yield Response

Soybean white mold has been a production problem for soybean producers since early 1990. Sclerotia germinate and produce apothecia, and apothecia produce ascospores. These spores attack soybean plants at flowering. In addition, sclerotia can germinate and colonize soybean plants. Therefore, seed treatment and or foliar application may help reduce incidence and severities and yield loss due to white mold. In Iowa, for the first time in the 2009 growing season, we observed wide spread of both the soybean sudden death syndrome (SDS) and white mold (WM). Sporadically, the simultaneous occurrence of SDS and WM had only been observed once in 2007. Many growers experienced the occurrence of SDS and WM on the same farm, and some in the same field. This is complicating management strategies. Objectives of these studies were to assess effects of seed treatment and foliar spray on soybean white mold and yield response at the ISU Northeast Research Farm, Nashua, Iowa

Early-life experience reduces excitation to stress-responsive hypothalamic neurons and reprograms the expression of corticotropin-releasing hormone.

Increased sensory input from maternal care attenuates neuroendocrine and behavioral responses to stress long term and results in a lifelong phenotype of resilience to depression and improved cognitive function. Whereas the mechanisms of this clinically important effect remain unclear, the early, persistent suppression of the expression of the stress neurohormone corticotropin-releasing hormone (CRH) in hypothalamic neurons has been implicated as a key aspect of this experience-induced neuroplasticity. Here, we tested whether the innervation of hypothalamic CRH neurons of rat pups that received augmented maternal care was altered in a manner that might promote the suppression of CRH expression and studied the cellular mechanisms underlying this suppression. We found that the number of excitatory synapses and the frequency of miniature excitatory synaptic currents onto CRH neurons were reduced in "care-augmented" rats compared with controls, as were the levels of the glutamate vesicular transporter vGlut2. In contrast, analogous parameters of inhibitory synapses were unchanged. Levels of the transcriptional repressor neuron-restrictive silencer factor (NRSF), which negatively regulates Crh gene transcription, were markedly elevated in care-augmented rats, and chromatin immunoprecipitation demonstrated that this repressor was bound to a cognate element (neuron-restrictive silencing element) on the Crh gene. Whereas the reduced excitatory innervation of CRH-expressing neurons dissipated by adulthood, increased NRSF levels and repression of CRH expression persisted, suggesting that augmented early-life experience reprograms Crh gene expression via mechanisms involving transcriptional repression by NRSF

Revealing ‘plasmaron’ feature in DySb by optical spectroscopy study

We report magnetic susceptibility, resistivity and optical spectroscopy study on single crystal sample DySb. It exhibits extremely large magnetoresistance (XMR), and a magnetic phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state at about 10 K. A 'screened' plasma edge at about 4000 cm−1 is revealed by optical measurement, which suggests that the material has a low carrier density. With decreasing temperature, the 'screened' plasma edge shows a blue shift, possibly due to a decrease of the effective mass of carriers. Notably, an anomalous temperature dependent midinfrared absorption feature is observed in the vicinity of the 'screened' plasma edge. In addition, it can be connected to the inflection point in the real part of the dielectric function , the frequency of which exactly tracks the temperature dependent 'screened' plasma frequency. This phenomena can be explained by the appearance of a coupled electron–plasmon 'plasmaron' feature