We study resistance sparsification of graphs, in which the goal is to find a sparse subgraph (with reweighted edges) that approximately preserves the effective resistances between every pair of nodes. We show that every dense regular expander admits a (1 + ε)-resistance sparsifier of size Õ(n/ε), and conjecture this bound holds for all graphs on n nodes. In comparison, spectral sparsification i...

We show that r pseudo-random bits can be obtained by concatenating t blocks of r=t pseudo-random bits, where the blocks are generated in parallel. This can be considered as a parallel version of 8] { recycling random bits by doing a random walk on an expander. The proof is based on the fact that t simultaneous independent random walks on an expander graph is equivalent to a random walk on a muc...

INTRODUCTION In plastic and reconstructive surgery, self-activating hydrogel expanders are used to augment soft-tissue space. The purpose of this study was to investigate the morphological response of underlying bone to the constant pressure exerted by a hydrogel expander. METHODS Eighteen Lewis rats were randomly divided into three groups. In group 1, a hydrogel expander was placed subperios...

Background. Tissue expansion has been a major advance in reconstructive burn surgery. The conventional tissue expander requires serial filling with the possibility of painful procedures, which can be a major challenge and source of anxiety in children. The osmotic self-inflating tissue expander, on the other hand, is a device that does not require external filling, offering apparent benefits pa...

BACKGROUND Percutaneous kyphoplasty using a bone expander polymer device, such as percutaneous vertebroplasty and balloon kyphoplasty, is a therapeutic intervention for painful osteoporotic vertebral body compression fractures. Typically the procedure involves placement of bilateral Sky Bone Expanders in the fractured vertebral body via a transpedicular approach. We describe performance of "SKy...

BACKGROUND Botulinum toxin A has been successfully used in a variety of areas to temporarily obliterate muscle mobility for either functional or aesthetic gain. Tissue expander-based breast reconstruction has been plagued with pain and discomfort. OBJECTIVE The purpose of this pilot study was to evaluate the role of a neurotoxin (Botulinum toxin A) in expander-based breast reconstruction. M...

Background When tissue expansion is necessary in breast reconstruction, a single-stage approach is possible using adjustable expander/implants, with or without the use of acellular dermal matrix. We aimed to present the senior author's single-stage experience over a period of 12 years using combined expander/implants in breast reconstruction. Methods This is a Single-institution, retrospectiv...

OBJECTIVE To preserve the mastectomy skin envelope in select patients destined to receive radiation following mastectomy, we performed immediate tissue expander-implant reconstruction with a subpectoral tissue expander and an inferolateral AlloDerm hammock for complete implant coverage. We hypothesized that the AlloDerm hammock may allow greater intraoperative volume expansion and potentially a...

Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optim...

BACKGROUND In 2008, the authors' institution adopted a policy requiring that all patients, regardless of preoperative risk, receive both sequential compression devices and a single preoperative subcutaneous 5000 unit injection of heparin. A previously published 12-year review at this same institution before this policy demonstrated a 1.5% 30-day postoperative incidence of hematoma in primary au...