Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays

Here we present a study on the presence of physisorbed water on the surface of aligned carbon nanotubes (CNTs) in ambient conditions, where the wet CNT array mass can be more than 200% larger than that of dry CNTs, and modeling indicates that a water layer >5 nm thick can be present on the outer CNT surface. The experimentally observed nonlinear and non-monotonic dependence of the mass of adsorbed water on the CNT packing (volume fraction) originates from two competing modes. Physisorbed water cannot be neglected in the design and fabrication of materials and devices using nanowires/nanofibers, especially CNTs, and further experimental and ab initio studies on the influence of defects on the surface energies of CNTs, and nanowires/nanofibers in general, are necessary to understand the underlying physics and chemistry that govern this system.National Science Foundation (U.S.) (NSF Grant No. CMMI-1130437)National Science Foundation (U.S.) (NSF Award Number ECS-0335765)United States. Army Research Office (contract W911NF-07-D-0004

Emergence of super-Poissonian light from indistinguishable single-photon emitters

The optical interference constitutes a paramount resource in modern physics. At the scale of individual atoms and photons, it is a diverse concept that causes different coherent phenomena. We present the experimental characterization of both coherent and statistical properties of light emitted from ensembles of trapped ions increasing with a number of contributing phase-incoherent independent atomic particles ranging from a single to up to several hundreds. It conclusively demonstrates how super-Poissonian quantum statistics non-trivially arises purely from the finite number of indistinguishable single-photon emitters in the limit of a single detection mode. The achieved new optical emission regime in which these independent atoms contribute coherently to the super-Poissonian statistics provides a new perspective on the emergence of optical coherence at the atomic scale and constitutes a unique toolbox for its generation and control at the most microscopic level

Randomized Controlled Trial of a Parenting Program to Reduce the Risk of Child Maltreatment in South Africa

Parenting programs in high-income countries have been shown to reduce the risk of child maltreatment. However, there is limited evidence of their effectiveness in low- and middle-income countries. The objective of this study was to examine the initial effects of a parenting program in reducing the risk of child maltreatment in highly-deprived and vulnerable communities in Cape Town, South Africa. Low-income parents (N = 68) with children aged three to eight years were randomly assigned to either a group-based parenting program or a wait-list control group. Observational and parent-report assessments were taken at baseline and at immediate post-test after the intervention was delivered. Primary outcomes were parent-report and observational assessments of harsh parenting, positive parenting, and child behavior problems. Secondary outcomes were parent-report assessments of parental depression, parenting stress, and social support. Results indicated moderate treatment effects for increased frequency of parent-report of positive parenting (d = 0.63) and observational assessments of parent-child play (d = 0.57). Observational assessments also found moderate negative treatment effects for less frequent positive child behavior (d = −0.56). This study is the first randomized controlled trial design to rigorously test the effectiveness of a parenting program on reducing the risk of child maltreatment in sub-Saharan Africa using both observational and self-report assessments. Results provide preliminary evidence of effectiveness of reducing the risk of child maltreatment by improving positive parenting behavior. Further development is required to strengthen program components regarding child behavior management and nonviolent discipline strategies. Future research would benefit from a larger trial with sufficient power to determine program effectiveness

Co-occurrence of intimate partner violence against mothers and maltreatment of their children with behavioral problems in Eastern Europe

This study investigates the co-occurrence of intimate partner violence (IPV) against mothers and their risk of perpetrating child maltreatment (CM) in North Macedonia, the Republic of Moldova, and Romania. Risk factors for IPV, CM, and their co-occurrence were identified. Two samples (N1 = 112, N2 = 701) of mothers with children with behavioral problems were assessed. IPV was reported by 64% of mothers, CM by 96%, and their co-occurrence by 63%. Mothers exposed to emotional IPV reported more physical and emotional CM. Mothers exposed to physical IPV reported more physical CM. Motheŕs own history of CM and offspring's behavior problems were associated with IPV and CM co-occurrence

Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.United States. Army Research Office (contract W911NF-07-D-0004)United States. Army Research Office (contract W911NF-13-D-0001)United States. Air Force Office of Scientific Research (AFRL/RX contract FA8650-11-D-5800, Task Order 0003)National Science Foundation (U.S.) (NSF Award No. ECS-0335765)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship