California Institute of Technology

About: California Institute of Technology is a education organization based out in Pasadena, California, United States. It is known for research contribution in the topics: Galaxy & Redshift. The organization has 57649 authors who have published 146691 publications receiving 8620287 citations. The organization is also known as: Caltech & Cal Tech.

Path-integral derivation of black-hole radiance

Abstract: The Feynman path-integral method is applied to the quantum mechanics of a scalar particle moving in the background geometry of a Schwarzschild black hole. The amplitude for the black hole to emit a scalar particle in a particular mode is expressed as a sum over paths connecting the future singularity and infinity. By analytic continuation in the complexified Schwarzschild space this amplitude is related to that for a particle to propagate from the past singularity to infinity and hence by time reversal to the amplitude for the black hole to absorb a particle in the same mode. The form of the connection between the emission and absorption probabilities shows that a Schwarzschild black hole will emit scalar particles with a thermal spectrum characterized by a temperature which is related to its mass, $M$, by $T=\frac{\ensuremath{\hbar}{c}^{3}}{8\ensuremath{\pi}}\mathrm{GMk}$. Thereby a conceptually simple derivation of black-hole radiance is obtained. The extension of this result to other spin fields and other black-hole geometries is discussed.

The Dynamics of Cavitation Bubbles

Abstract: Three regimes of liquid flow over a body are defined, namely: (a) noncavitating flow; (b) cavitating flow with a relatively small number of cavitation bubbles in the field of flow; and (c) cavitating flow with a single large cavity about the body. The assumption is made that, for the second regime of flow, the pressure coefficient in the flow field is no different from that in the noncavitating flow. On this basis, the equation of motion for the growth and collapse of a cavitation bubble containing vapor is derived and applied to experimental observations on such bubbles. The limitations of this equation of motion are pointed out, and include the effect of the finite rate of evaporation and condensation, and compressibility of vapor and liquid. A brief discussion of the role of "nuclei" in the liquid in the rate of formation of cavitation bubbles is also given.

The First Targeted Delivery of siRNA in Humans via a Self-Assembling, Cyclodextrin Polymer-Based Nanoparticle: From Concept to Clinic

Abstract: Experimental therapeutics developed to exploit RNA interference (RNAi) are now in clinical studies. Here, the translation from concept to clinic for the first experimental therapeutic to provide targeted delivery of synthetic, small interfering RNA (siRNA) in humans is described. This targeted, nanoparticle formulation of siRNA, denoted as CALAA-01, consists of a cyclodextrin-containing polymer (CDP), a polythethylene glycol (PEG) steric stabilization agent, and human transferrin (Tf) as a targeting ligand for binding to transferrin receptors (TfR) that are typically upregulated on cancer cells. The four component formulation is self-assembled into nanoparticles in the pharmacy and administered intravenously (iv) to patients. The designed features of this experimental therapeutic are described, and their functions illustrated.

Fusion and Fission: Interlinked Processes Critical for Mitochondrial Health

Abstract: Mitochondria are dynamic organelles that continually undergo fusion and fission. These opposing processes work in concert to maintain the shape, size, and number of mitochondria and their physiological function. Some of the major molecules mediating mitochondrial fusion and fission in mammals have been discovered, but the underlying molecular mechanisms are only partially unraveled. In particular, the cast of characters involved in mitochondrial fission needs to be clarified. By enabling content mixing between mitochondria, fusion and fission serve to maintain a homogeneous and healthy mitochondrial population. Mitochondrial dynamics has been linked to multiple mitochondrial functions, including mitochondrial DNA stability, respiratory capacity, apoptosis, response to cellular stress, and mitophagy. Because of these important functions, mitochondrial fusion and fission are essential in mammals, and even mild defects in mitochondrial dynamics are associated with disease. A better understanding of these processes likely will ultimately lead to improvements in human health.