Measuring dielectric properties at the nanoscale using Electrostatic Force Microscopy

Several electrostatic force microscopy (EFM) - based methods have been recently developed to study the nanoscale dielectric properties of thin insulating layers. Some methods allow measuring quantitatively the static dielectric permittivity whereas some others provide qualitative information about the temperature-frequency dependence of dielectric properties. In this chapter, all these methods are described and illustrated by experiments on pure and nanostructured polymer films. A section is dedicated to EFM probe - sample models and especially to the Equivalent Charge Method (ECM)

Could an endoneurial endothelial crosstalk between Wnt/β-catenin and Sonic Hedgehog pathways underlie the early disruption of the infra-orbital blood-nerve barrier following chronic constriction injury?

BackgroundBlood–nerve barrier disruption is pivotal in the development of neuroinflammation, peripheral sensitization, and neuropathic pain after peripheral nerve injury. Activation of toll-like receptor 4 and inactivation of Sonic Hedgehog signaling pathways within the endoneurial endothelial cells are key events, resulting in the infiltration of harmful molecules and immunocytes within the nerve parenchyma. However, we showed in a previous study that preemptive inactivation of toll-like receptor 4 signaling or sustained activation of Sonic Hedgehog signaling did not prevent the local alterations observed following peripheral nerve injury, suggesting the implication of another signaling pathway.MethodsUsing a classical neuropathic pain model, the infraorbital nerve chronic constriction injury (IoN-CCI), we investigated the role of the Wnt/β-catenin pathway in chronic constriction injury-mediated blood–nerve barrier disruption and in its interactions with the toll-like receptor 4 and Sonic Hedgehog pathways. In the IoN-CCI model versus control, mRNA expression levels and/or immunochemical detection of major Wnt/Sonic Hedgehog pathway (Frizzled-7, vascular endothelial-cadherin, Patched-1 and Gli-1) and/or tight junction proteins (Claudin-1, Claudin-5, and Occludin) readouts were assessed. Vascular permeability was assessed by sodium fluorescein extravasation.ResultsIoN-CCI induced early alterations in the vascular endothelial-cadherin/β-catenin/Frizzled-7 complex, shown to participate in local blood–nerve barrier disruption via a β-catenin-dependent tight junction protein downregulation. Wnt pathway also mediated a crosstalk between toll-like receptor 4 and Sonic Hedgehog signaling within endoneurial endothelial cells. Nevertheless, preemptive inhibition of Wnt/β-catenin signaling before IoN-CCI could not prevent the downregulation of key Sonic Hedgehog pathway readouts or the disruption of the infraorbital blood–nerve barrier, suggesting that Sonic Hedgehog pathway inhibition observed following IoN-CCI is an independent event responsible for blood–nerve barrier disruption.ConclusionA crosstalk between Wnt/β-catenin- and Sonic Hedgehog-mediated signaling pathways within endoneurial endothelial cells could mediate the chronic disruption of the blood–nerve barrier following IoN-CCI, resulting in increased irreversible endoneurial vascular permeability and neuropathic pain development

Mortality, violence and access to care in two districts of Port-au-Prince, Haiti

ABSTRACT: BACKGROUND: Towards the end of 2006 open conflict broke out between United Nations forces and armed militia in Port-au-Prince, Haiti. Fighting was most intense in the district of Cité Soleil. METHODS: A cross-sectional, random-sample survey among the conflict-affected populations living in Cité Soleil and Martissant was carried out over a 4-week period in 2006 using a semi-structured questionnaire to assess exposure to violence and access to health care. Household heads from 945 households (corresponding to 4,763 people) in Cité Soleil and 1,800 household (9,539 people) in Martissant provided information on household members. The average recall period was 579 days for Cité Soleil and 601 days for Martissant. RESULTS: In Cité Soleil 120 deaths (21 children) were reported (CMR 0.4 deaths/10,000 people/day; <5 MR 0.5 deaths/10,000/day) while in Martissant 165 deaths (8 children) were reported (CMR 0.3/10,000 people/day; <5 MR 0.2/10,000 people/day). Violence was reported as the main cause of adult mortality in both locations (mainly gunshot wounds) accounting for 29.2% of deaths in Cité Soleil and 23% of deaths in Martissant. 22.9% of families in Cité Soleil and 18.6% in Martissant reported at least one victim of violence. Destruction of property and belongings was common in both Cité Soleil (52.4% of families) and Martissant (14.9%). Access to health services was limited, with 11% (22/196) of victims of violence in Cité Soleil and 23% (49/212) in Martissant unable to access care due to insecurity or lack of money. DISCUSSION: Extrapolating to the total population of these two districts some 2,000 violent deaths occurred over the recall period. Among the survivors, violence had lasting effects in terms of physical and mental health and loss of property and possessions

A conceptual model for anticipating the impact of landscape evolution on groundwater recharge in degrading permafrost environments

Temperatures in the arctic and subarctic are rising at more than twice the rate of the global average, driving the accelerated thawing of permafrost across the region. The impacts of permafrost degradation have been studied in the discontinuous permafrost zone at Umiujaq, in northern Quebec, Canada, for over 30 years, but the effects of changing land cover on groundwater recharge is not well understood. The water table fluctuation method was used to compute groundwater recharge using four years of water level data and soil moisture readings from five field sites characteristic of different stages of permafrost degradation and vegetation invasion. Results indicate that as vegetation grows taller, groundwater recharge increases, likely due to increased snow thickness. Results were then combined with a preexisting conceptual model that describes the evolution from tundra to shrubland and forests to create a new model for describing how groundwater recharge is affected by landscape evolution

Paralyzing Action from a Distance in an Arboreal African Ant Species

Due to their prowess in interspecific competition and ability to catch a wide range of arthropod prey (mostly termites with which they are engaged in an evolutionary arms race), ants are recognized as a good model for studying the chemicals involved in defensive and predatory behaviors. Ants' wide diversity of nesting habits and relationships with plants and prey types implies that these chemicals are also very diverse. Using the African myrmicine ant Crematogaster striatula as our focal species, we adopted a three-pronged research approach. We studied the aggressive and predatory behaviors of the ant workers, conducted bioassays on the effect of their Dufour gland contents on termites, and analyzed these contents. (1) The workers defend themselves or eliminate termites by orienting their abdominal tip toward the opponent, stinger protruded. The chemicals emitted, apparently volatile, trigger the recruitment of nestmates situated in the vicinity and act without the stinger having to come into direct contact with the opponent. Whereas alien ants competing with C. striatula for sugary food sources are repelled by this behavior and retreat further and further away, termites defend their nest whatever the danger. They face down C. striatula workers and end up by rolling onto their backs, their legs batting the air. (2) The bioassays showed that the toxicity of the Dufour gland contents acts in a time-dependent manner, leading to the irreversible paralysis, and, ultimately, death of the termites. (3) Gas chromatography-mass spectrometry analyses showed that the Dufour gland contains a mixture of mono- or polyunsaturated long-chain derivatives, bearing functional groups like oxo-alcohols or oxo-acetates. Electrospray ionization-mass spectrometry showed the presence of a molecule of 1584 Da that might be a large, acetylated alkaloid capable of splitting into smaller molecules that could be responsible for the final degree of venom toxicity

Does ratification of human-rights treaties have effects on population health?

Human-rights treaties indicate a country's commitment to human rights. Here, we assess whether ratification of human-rights treaties is associated with improved health and social indicators. Data for health (including HIV prevalence, and maternal, infant, and child [<5 years] mortalities) and social indicators (child labour, human development index, sex gap, and corruption index), gathered from 170 countries, showed no consistent associations between ratification of human-rights treaties and health or social outcomes. Established market economy states had consistently improved health compared with less wealthy settings, but this was not associated with treaty ratification. The status of treaty ratification alone is not a good indicator of the realisation of the right to health. We suggest the need for stringent requirements for ratification of treaties, improved accountability mechanisms to monitor compliance of states with treaty obligations, and financial assistance to support the realisation of the right to health