Conversations about science across activities in Mexican-descent families

Parent-child 'everyday' conversations have been suggested as a source of children's early science learning (Ash, 2003; Callanan & Jipson, 2001). If such conversations are important then it would be pertinent to know whether children from different family backgrounds have different experiences talking about science in informal settings. We focus on the relation between parents' schooling and both their explanatory talk in science-related activities, and the styles of interaction they use with their children. Families from different schooling backgrounds within one underrepresented group in science education – Mexican-descent families – were included in this study. Forty families were observed in two science-related activities. In the sink-or-float task, families were asked to predict which of a variety of objects would sink and which would float, and then to test their predictions in a tub of water. The second activity was an open-ended visit to a local children's museum. Results showed similar patterns in scientific talk on the sink-or-float task across the two groups. However, interaction style varied with schooling across the two activities; parents with higher schooling were more directive than parents with basic schooling. Interaction style was also found to vary with task structure, with more open-ended tasks affording more collaborative interactions. Such research into parent-child conversations in science-related activities can help begin to guide us in bridging children's learning environments – home, school, and museum – and potentially fostering children's science learning, particularly in those groups underrepresented in the sciences

Effect of the size and shape of a red blood cell on elastic light scattering properties at the single-cell level

We demonstrate the use of a double-beam optical tweezers system to stabilize red blood cell (RBC) orientation in the optical tweezers during measurements of elastic light scattering from the trapped cells in an angle range of 5-30 degrees. Another laser (He-Ne) was used to illuminate the cell and elastic light scattering distribution from the single cell was measured with a goniometer and a photomultiplier tube. Moreover, CCD camera images of RBCs with and without laser illumination are presented as complementary information. Light scattering from a RBC was measured in different fixed orientations. Light scattering from cells was also measured when the length of the cell was changed in two different orientations. Light scattering measurements from spherical and crenate RBCs are described and the results are compared with other cell orientations. Analysis shows that the measured elastic light scattering distributions reveal changes in the RBC’s orientation and shape. The effect of stretching on the changes in scattering is larger in the case of face-on incidence of He-Ne laser light than in rim-on incidence. The scattering patterns from RBCs in different orientations as well as from a spherical RBC were compared with numerical results found in literature. Good correlation was found

Surface-enhanced Raman scattering measurement from a lipid bilayer encapsulating a single decahedral nanoparticle mediated by an optical trap

We present a new technique for the study of model membranes on the length-scale of a single nanosized liposome. Silver decahedral nanoparticles have been encapsulated by a model unilamellar lipid bilayer creating nano-sized lipid vesicles. The metal core has two roles (i) increasing the polarizability of vesicles, enabling a single vesicle to be isolated and confined in an optical trap, and (ii) enhancing Raman scattering from the bilayer, via the high surface-plasmon field at the sharp vertices of the decahedral particles. Combined this has allowed us to measure a Raman fingerprint from a single vesicle of 50 nmdiameter, containing just ∼104 lipid molecules in a bilayer membrane over a surface area of <0.01 µm2, equivalent to a volume of approximately 1 zepto-litre. Raman scattering is a weak and inefficient process and previous studies have required either a substantially larger bilayer area in order to obtain a detectable signal, or the tagging of lipid molecules with a chromophore to provide an indirect probe of the bilayer. Our approach is fully label-free and bio-compatible and, in the future, it will enable much more localized studies of the heterogeneous structure of lipid bilayers and of membrane-bound components than is currently possible

Quantum dot-based thermal spectroscopy and imaging of optically trapped microspheres and single cells

Laser‐induced thermal effects in optically trapped microspheres and single cells are investigated by quantum dot luminescence thermometry. Thermal spectroscopy has revealed a non‐localized temperature distribution around the trap that extends over tens of micrometers, in agreement with previous theoretical models besides identifying water absorption as the most important heating source. The experimental results of thermal loading at a variety of wavelengths reveal that an optimum trapping wavelength exists for biological applications close to 820 nm. This is corroborated by a simultaneous analysis of the spectral dependence of cellular heating and damage in human lymphocytes during optical trapping. This quantum dot luminescence thermometry demonstrates that optical trapping with 820 nm laser radiation produces minimum intracellular heating, well below the cytotoxic level (43 °C), thus, avoiding cell damage

Physiological and pathophysiological functions of different angiotensins in the brain

The renin–angiotensin system (RAS) is better known for its role in the control of blood pressure, but evidence obtained from animal experiments and clinical trials suggests that it is involved in complex brain functions. It is now well accepted that neuronal AT1 receptors mediate the stimulatory actions of angiotensin II regarding blood pressure and the intake of water and salt. In contrast, neuronal AT2 receptors have been implicated in the stimulation of apoptosis and as being antagonistic AT1 receptors. Angiotensin-(1-7) [Ang-(1-7)] mediates its antihypertensive effects by stimulating synthesis and release of vasodilator prostaglandins and nitric oxide. New data concerning the receptor types binding angiotensin IV or Ang-(1-7) also support the existence of complex site-specific interactions between multiple angiotensins and multiple receptors in the mediation of important central functions of the RAS. Different angiotensin receptors (AT1, AT2, AT4, Mas) are also present in memory-relevant structures. The effects of different angiotensins on cognition initiated the search for their mechanisms of action. Studies looking for a possible link between the RAS and brain disorders (stress, anxiety, depression, alcohol abuse, epilepsy, Alzheimer's disease) either inherited or acquired have been reviewed. The therapeutic potential of different angiotensins, as well as the potential use of agents known to influence the RAS, will be considered