Exoplanet Atmosphere Measurements from Transmission Spectroscopy and other Planet-Star Combined Light Observations

It is possible to learn a great deal about exoplanet atmospheres even when we cannot spatially resolve the planets from their host stars. In this chapter, we overview the basic techniques used to characterize transiting exoplanets - transmission spectroscopy, emission and reflection spectroscopy, and full-orbit phase curve observations. We discuss practical considerations, including current and future observing facilities and best practices for measuring precise spectra. We also highlight major observational results on the chemistry, climate, and cloud properties of exoplanets.Comment: Accepted review chapter; Handbook of Exoplanets, eds. Hans J. Deeg and Juan Antonio Belmonte (Springer-Verlag). 22 pages, 6 figure

Localized induction of gene expression in embryonic stem cell aggregates using holographic optical tweezers to create biochemical gradients

Three-dimensional (3D) cell models that mimic the structure and function of native tissues are enabling more detailed study of physiological and pathological mechanisms in vitro. We have previously demonstrated the ability to build and manipulate 3D multicellular microscopic structures using holographic optical tweezers (HOTs). Here, we show the construction of a precisely patterned 3D microenvironment and biochemical gradient model consisting of mouse embryoid bodies (mEBs) and polymer microparticles loaded with retinoic acid (RA), embedded in a hydrogel. We demonstrate discrete, zonal expression of the RA-inducible protein Stra8 within mEBs in response to release of RA from polymer microparticles, corresponding directly to the defined 3D positioning of the microparticles using HOTs. These results demonstrate the ability of this technology to create chemical microgradients at definable length scales and to elicit, with fidelity and precision, specific biological responses. This technique can be used in the study of in vitro microenvironments to enable new insights on 3D cell models, their cellular assembly, and the delivery of drug or biochemical molecules for engineering and interrogation of functional and morphogenic responses

Neuromodulation for evaluating the pathophysiology of migraine

The two most frequently used techniques for the non-invasive modulation of brain activity are repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). These techniques have repeatedly been used to modulate the activity of a given area within a neuronal network to study pathophysiological changes in migraine. The most freqeuntly stimulated areas are visual and sensorimotor areas. We discuss here what kinds of paradoxical effects have been described in response to inhibitory and excitatory modulation in patients with episodic and chronic migraine and how neuromodulation can help distinguish patients with chronic migraine from those with medication overuse headache. Furthermore, we elaborate how these methods can normalize the habituation deficit in response to visual and somatosensory stimuli, frequently detected between migraine attacks. From the studies reviewed in this chapter, it emerges that the brain of the migraine patient is characterized by alterations of synaptic activity-dependent plasticity, i.e., the phenomena of long-term potentiation and depression