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Bio- heat transfer model of human eye

Laser surgery is used in several eye related treatment including retinal detachment and macular degeneration. During laser irradiation, pigmented retinal and adjacent choroidal region absorb most of the energy. Overheating of these tissues above photocoagulation (~ 60 degree C) could lead to thermal damage disrupting cellular mechanisms. We formulated a bio-heat transfer model for the human eye, incorporating several parameters of interest including the choroidal blood perfusion. Using the retinal irradiation specifications during an actual surgery, the simulation results suggested over-heating of certain retinal regions. Pulsation of laser irradiation with specific parameters is proposed as a method to reduce thermal damage in these regions.

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Posted by Dr. Arunn Narasimhan.

A new molecular cluster of silver

A new molecular cluster of silver composed of 152 atoms, protected with molecular linkers called ligands, having a mass of 25 kDa was isolated. This is the smallest cluster at which spectroscopic properties suggest the emergence of metallicity. Clusters are aggregates of atoms and molecules whose properties are distinctly different from the two extremes - atomic/molecular regime and the bulk. Atomically precise clusters of noble metals with novel properties have been chased by several research groups. These clusters have been studied often by mass spectrometry as their mass spectral signatures are unique. The overall composition of the new cluster isolated is Ag152(SCH2CH2Ph)60 where SCH2CH2Ph is the ligand. Computed structure of the cluster is unique in the sense that it has a 60 atom core and 92 atom shell covered with thiolate ligands. The clusters form crystals in which organised cluster assemblies are seen. This was published recently in Nano Letters.

Coherent structures in turbulent convection

Figure (a) shows the complex turbulent velocity field near a heated horizontal surface obtained by particle image velocimetry. This random velocity field contains organised motion of coherent structures, which could be extracted from the velocity field as shown in figure (b). The coherent structures, shown as blue lines in the view from above in figure (b), are rising sheets of fluid that transport the heat away from the surface. The red arrows show the cold fluid impinging on to the hot surface in between these structures. The rising sheets move around laterally and merge, with new sheets being formed in the vacant regions. Understanding these complex dynamics is essential whereever turbulent heat transfer from horizontal surfaces occur; the applications range from heating a pale of water to our climate.

Autonomous Motility of Active Filaments due to Spontaneous Flow-Symmetry Breaking

A cytoskeletal filament, with molecular motors walking on it, can be modeled as an elastic filament with a permanent distribution of stresslets along its contour. We show that an initially straight filament is unstable and can lead to autonomous filament motion which, depending on conformational symmetry, can be translational or rotational. Our results can be tested also on synthetic chains of autocatalytic particles or other linearly connected systems where chemical energy is converted to mechanical energy in a fluid environment.

Synthesis of Nanotubes

Carbon nanotube (CNT), a fascinating form of carbon in the ‘nano’ dimension, has captivated the interest of scientific community for over two decades. However, the unavailability of large quantities of this material and cost factors have proved to be a real ‘bottleneck’ with regards to the practical applications of CNTs. Using novel catalysts, we have indigenously developed automated chemical vapor deposition system, which can produce up to 10 g CNTs in a single process. The screen shots of the video during the growth of CNTs at different time intervals are shown. High quality of these nanotubes can be discerned from the electron micrographs.