This paper studies whether agents must agglomerate at a single location in a class of models of two-sided interaction. In these models there is an increasing returns effect that favors agglomeration, but also a crowding or market-impact effect that makes agents prefer to be in a market with fewer agents of their own type. We show that such models do not tip in the way the term is commonly used....

Miranda Holmes-Cerfon, Wei Zhou, Andrea L. Bertozzi, Michael P. Brenner, and Michael J. Aziz Harvard School of Engineering and Applied Sciences, 29 Oxford St., Cambridge, Massachusetts 02138, USA Kavli Institute for Bionano Science and Technology, 29 Oxford St., Cambridge, Massachusetts 02138, USA Department of Mathematics, University of California Los Angeles, Los Angeles, California 90095-155...

Background: Sachse cold knife is conventionally used for optical internal urethrotomy to manage urethral strictures. In this procedure, the complications and recurrence rates are relatively high. We suggest combined electro cutter and cold knife as a success alternative in the management of intractable anterior urethral strictures. Methods: In this prospective...

We have constructed an atomic force microscope enabling one to image the topography of a sample, and to monitor simultaneously ultrasonic surface vibrations in the MHz range. For detection of the distribution of the ultrasonic vibration amplitude, a part of the position-sensing light beam reflected from the cantilever is directed to an external knife-edge detector. Acoustic images taken on the ...

OI-RD microscopes scan focused Gaussian laser beams across a microarray to provide spatial maps of the reflectivity difference. I review some properties of Gaussian beams, with particular emphasis on the waist diameter, which governs the best resolution achievable with an OI-RD microscope. Data is presented demonstrating a scanning knife-edge method for measuring a Gaussian beam waist; this met...

gamma knife is a new noninvasive method for treatment of patient with brain tumors. ‎another name of this procedure is steriotatic radiosurgery.‎‏ ‏this computerized advanced ‎technique was implicated by a team including neurosurgeon, neuroradialogist, oncologist, and ‎a nurse. this method is used for treatment of certain brain tumors and lesions. the benefits are ‎low risk of postoperative com...

We consider the problem of multiple knife-edge diffraction estimation that is a fundamental task in many wireless communication applications. So far, one most accurate methods for this Vogler whose recursive implementation efficient to reduce high computational complexity direct one. However, original report, only presented final result algorithm without rigorous mathematical proof, thus making...

SEVERAL years ago a description was published of a new technique in performing the three-snip operation to relieve epiphora due to stenosis of the lacrimal punctum (Graves, 1926). The method was to dilate the punctum, insert a small grooved director, place the back of a large Ziegler knife in the groove, and then, by pushing it inwards towards the nose, to incise the upper edge of the canalicul...