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In families with febrile seizures and temporal lobe epilepsy, mutations affecting different GABAergic mechanisms suggest that failure of chloride conductance to limit depolarization may be directly epileptogenic. This “GABAergic disinhibition” hypothesis has been discounted historically for two reasons. First, early attempts to produce hippocampal sclerosis and epilepsy simply by eliminating hippocampal GABA neurons consistently failed to do so. Second, the notion persists that because clinical epilepsy diagnosis is typically delayed for years or decades after brain injury, temporal lobe epileptogenesis should be presumed to involve a complex pathological transformation process that reaches completion during this “latent period.” Recent advances clarify both issues. Although spatially limited hippocampal GABA neuron ablation causes only submaximal granule cell hyperexcitability, more spatially extensive ablation maximizes granule cell hyperexcitability and triggers nonconvulsive granule cell status epilepticus, hippocampal sclerosis, and epilepsy. Recent studies also show that disinhibited granule cells begin to generate clinically subtle seizures immediately post-injury, and these seizures then gradually increase in duration to become clinically obvious. Therefore, rather than being a seizure-free “gestational” state of potentially interruptible epileptogenesis, the “latent period” is more likely an active epileptic state when barriers to seizure spread and clinical expression are gradually overcome by a kindling process. The likelihood that an epileptic brain state exists long before clinical diagnosis has significant implications for anti-epileptogenesis studies. The location, magnitude, and spatial extent of inherited, autoimmune, and injury-induced disinhibition may determine the latency to clinical diagnosis and establish the continuum between the benign, treatable, and refractory forms of temporal lobe epilepsy.

The impact of anthropogenic aerosols on clouds is a leading source of uncertainty in estimating the effect of human activity on the climate system. The challenge lies in the scale difference between clouds (~1-10 km) and general circulation and climate (~1000 km). To address this, we utilize three different novel sets of simulations that allow to resolve convection while also including a epresentation of large-scale processes. Our findings demonstrate that aerosol-cloud interaction intensifies tropical overturning circulation. Employing a weak temperature gradient approximation, we attribute variations in circulation to clear-sky humidity changes driven by warm rain suppression by aerosols. In two sets of simulations accounting for sub-tropical-tropical coupling, we show that aerosol-driven sub-tropical rain suppression leads to increased advection of cold and moist air from the sub-tropics to the tropics, thus enhancing tropical cloudiness. The increased tropical cloudiness has a strong cooling effect by reflecting more of the incoming solar radiation. The classical “aerosol-cloud lifetime effect” is shown here to have a strong remote effect (sub-tropical aerosols increase cloudiness in the tropics), thus widening the concept of cloud adjustments to aerosol perturbation with important implications for marine cloud brightening.

Aging and neurodegeneration are associated with changes in brain tissue at the molecular level, affecting its organization, density, and composition. These changes can be detected using quantitative MRI (qMRI), which provides physical measures that are sensitive to structural alterations. However, a major challenge in brain research is to relate physical estimates to their underlying biological sources. In this talk, I will discuss the community's efforts to use qMRI to identify biological processes that underlie changes in brain tissue. Specifically, I will highlight approaches for differentiating between changes in the concentration and composition of myelin and iron during aging. By exploring the molecular landscape of the aging and neurodegenerative brain using qMRI, we aim to gain a better understanding of these processes and potentially provide new metrics for evaluating them.

Draw an arbitrary open curve on the plane and copy it multiple times to form a translationally invariant infinite trajectory. Then, incline the plane slightly and ask yourself: can one chisel a stone that will roll exactly down this infinite trajectory?
We will examine this question in practice and theory. Intriguing links to optics and quantum systems will be discussed. Bringing a tennis ball or a baseball is always recommended.

Eckmann et al. Tumbling downhill along a given curve. Am Math Soc Notices - in press.
Sobolev et al. Solid-body trajectoids shaped to roll along desired pathways. Nature 2023.

The sediment – bottom-water interface is suggested as a key control on
the chemical composition of the ocean by studies of trace elements in the
ocean water-column, yet data regarding trace element fluxes and
interactions taking place in the top ten cm of abyssal sediments are
scarce. To bridge this gap, I analysed the trace and major element
composition of porewater and sediment of red-clay sediment from the
abyssal North Pacific, and hydrothermally influenced sediment from the
Mid-Atlantic Ridge. The top sediment at both study regions is aerobic,
nevertheless, there is large variability in the porewater concentrations of
many elements at the top five cm. The North Pacific red-clay sediment is
a source of cobalt, nickel, copper, arsenic, vanadium and barium to the
deep-ocean, the magnitude of these fluxes is consistent with fluxes
calculated based on the water-column distribution of most elements, and
are equivalent to the global supply of these elements by rivers. The
hydrothermally influenced sediment is a strong source of copper, zinc
and cobalt up to three km from the vent due to oxidation of sulfide
minerals. Close to the vents, the sediment is high in iron oxyhydroxides
that adsorb the oxyanions vanadate, arsenate and phosphate, acting as
a sink for these elements. The results of this study highlight the
importance of red-clay sediment in shaping the chemical composition of
the ocean, and suggest an important role for hydrothermally influenced
sediment in modulating the contributions of hydrothermal vents to ocean
biogeochemistry.

Let
u be a Bernoulli measure on a fractal in R^d generated by a finite collection of contracting similarities with no rotations and with rational coefficients