Integrated Calendar

The biological timekeeping system is composed of clocks that reside in nearly every cell in the body. The central clock in the brain keeps all clocks in synchrony with respect to each other and with the external environment. How these trillions of cellular clocks tick in harmony? We found that oxygen exhibit daily fluctuations in animals’ blood and tissue. These oxygen cycles can reset cellular circadian clocks in a manner that depends on the oxygen-sensing transcription factor HIF-1α. Exposing animals to a short change in oxygen levels accelerated their adaptation to a new time zone. Mice exposed to moderate hypoxia recovered faster from jet lag compare to mice that were exposed to constant atmospheric oxygen.

When faced with complex visual scene, observers inspect different parts of a scene sequentially, storing corresponding features in working memory for subsequent integration into a holistic perception. Yet models of perception rarely consider working memory explicitly. We probed processing hierarchy by comparing absolute judgements of single orientations and relative/ordinal judgements between two sequentially presented orientations. We found that lower-level, absolute judgements failed to account for higher-level, relative/ordinal judgements. However, when ordinal judgement was used to retrospectively decode memory representations of absolute orientations, striking aspects of absolute judgements, including their correlation and forward/backward aftereffects, were explained. We suggest that the brain prioritizes decoding of more useful, higher-level features, which are more invariant and categorical and thus easier to specify and maintain in noisy working memory, and that more-reliable higher-level decoding.

Today’s MRI receive coil arrays provide increased signal-to-noise-ratio (SNR) over standard single receivers. This excess SNR is often traded for either higher resolution or faster acquisitions. However, poor fit to patients can negate the array’s SNR gains. In fact, it is common, in clinical settings, to see coil elements offset from the anatomy to the point that the coils have poor fill-factor. This fit problem is exacerbated in pediatric imaging where patients come in different sizes.

In this work we present a new approach for designing and manufacturing MRI coils. We print coils using screen printing onto flexible plastic substrates. The resulting devices are extremely thin, light and flexible. In the first part of the presentation we will discuss the process and tradeoffs in using printing for making MRI coils as well as detailed analysis and characterization of the devices followed by demonstrating their use for pediatric MRI. In the second part, we will discuss a new application of these devices for minimally invasive interventional applications. Because our devices are extremely thin and made of plastic material and conductive inks, they are nearly transparent to ultrasound. This makes them ideal for use in MR Guided High Intensity Focused Ultrasound where the ultrasound transducers must have a clear acoustic path to the body, and therefore traditional coils are often displaced away from the body. We demonstrate feasibility for both head and body applications. This is a joint work with Prof. Ana Claudia Arias, Joseph Corea and Balthazar Lechene with collaborations with Stanford Radiology and GE Healthcare.

A combination of ideas originating from Condensed Matter physics, Supersymmetric Field Theory, and AdS/CFT has led to a detailed web of conjectured dualities. These relate the long distance behavior of different short distance theories. These dualities clarify a large number of confusing and controversial issues in Condensed Matter physics and in the study of 2+1 dimensional quantum field theory.