We study subgroups of Z which possess group theoretic properties analogous to properties introduced by Menger (1924), Hurewicz (1925), Rothberger (1938), and Scheepers (1996). We obtain purely combinatorial characterizations of these properties, and combine them with other techniques to solve several questions of Babinkostova, Kočinac, and Scheepers. We also show that, while the Menger Conjectu...

In this paper propositions will be established concerning the collection of all the cut points of a given planef continuum. It will be shown that there does not exist an uncountable collection of mutually exclusive subcontinua of a given continuum M each of which contains at least one cut point of M. With the aid of this fundamental theorem it is shown, among other things, that the set of all t...

We establish a surprising connection between Menger’s classical covering property and Blass’s modern combinatorial notion of groupwise density. This connection implies a short proof of the groupwise density bound on the additivity number for Menger’s property.

The selection of a suitable scaffold matrix is critical for cell-based bone tissue engineering. This study aimed to identify and characterize natural marine sponges as potential bioscaffolds for osteogenesis. Callyspongiidae marine sponge samples were collected from the Fremantle coast of Western Australia. The sponge structure was assessed using scanning electron microscopy (SEM) and Hematoxyl...

Sponge diseases have been widely reported, yet the causal factors and major pathogenic microbes remain elusive. In this study, two individuals of the sponge Crella cyathophora in total that showed similar disease-like characteristics were collected from two different locations along the Red Sea coast separated by more than 30 kilometers. The disease-like parts of the two individuals were both c...

This study investigated the removal of micropollutants using polyurethane sponge as attached-growth carrier. Batch experiments demonstrated that micropollutants could adsorb to non-acclimatized sponge cubes to varying extents. Acclimatized sponge showed significantly enhanced removal of some less hydrophobic compounds (log D<2.5), such as ibuprofen, acetaminophen, naproxen, and estriol, as comp...

Mangrove roots in the well-protected channels and ponds among dense mangrove stands provide very similar habitats for sponges in the Twin Cays and Pelican Cays and harbor extraordinarily dense and diverse sponge communities in both locations. The species of sponges are very different, however, possibly because of an important difference in context: the Twin Cays mangrove roots are embedded in p...

The objective of this study is to develop an osteoinductive scaffold which enables the controlled release of bone morphogenetic protein (BMP)-2. A biodegradable gelatin sponge incorporating 50 wt% of btricalcium phosphate (β-TCP) was fabricated to investigate the osteoinduction activity. The sponge prepared had an interconnected pore structure with an average pore size of 200 mm. The in vivo re...

INTRODUCTION Medullary sponge kidney is a congenital anomaly characterized by diffuse ectasy of the collecting tubules of one or both kidneys. It is usually diagnosed in the second or third decade of life. CASE PRESENTATION Distal renal tubular acidosis is commonly observed in patients with medullary sponge kidney. We describe here a 50-day-old Egyptian Caucasian girl with medullary sponge ki...