We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate as a rheometer at the molecular level. Two systems are studied: "brush/wall" and "brush/brush". A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rat...

OBJECTIVE A low-viscosity resin (infiltrant) was used to inhibit the progression of white spot lesions (WSLs) and resolve associated esthetic issues. An alternative pretreatment was explored to increase the pore volume of the surface layer of the WSLs. Also, the penetration effects of the infiltrant were evaluated for various pretreatments. METHODS Sixty two artificial lesions were fabricated...

Nacrtak Forest biomass from timber harvesting residues is often used during mechanized forest opera­ tions to improve trafficability of strip roads (machine operating trails). In particular, during cut-to-length operations brush mats from harvesting residues are created on operating trails to reduce rutting. However, forest biomass is becoming increasingly important as a source of renewable ene...

The rheology of confined polymer layers is of great fundamental importance because of its numerous industrial applications, e.g. the use of polymer as an additive to enhance the lubrication effect of two shearing surfaces separated by a very small distance. In the present study, we focus on one specific type of confined polymer system, the so-called polymer brush. A brush consists of many polym...

In this article, we consolidate several literature reports in an attempt to provide a structural definition of a polymer brush as a tethered polymer layer with a high grafting density of polymer chains. We will try to distinguish a brush from grafted polymer layers and coated layers and provide a reasonable approach to the description of the brush regime with a single parameter S—reduced grafti...

There are four key messages from health for climate negotiations. Two positive ones include (i) health as a motivator for action and policy and (ii) huge health co-benefits to be included in the cost-benefit trade-offs of climate negotiations. Two warning messages: (iii) there are health-based absolute limits of adaptations and (iv) hotter average temperatures will cut work productivity of farm...

We study the wetting by water of complex "hydrophobic-hydrophilic" surfaces made of a hydrophobic substrate covered by a hydrophilic polymer brush. Polystyrene (PS) substrates covered with polystyrene- block-poly(acrylic acid) PS- b-PAA diblock copolymer layers were fabricated by Langmuir-Schaefer depositions and analyzed by atomic force microscopy (AFM) and ellipsometry. On bare PS substrate, ...

Introduction The conformation of a polymer chain is very sensitive to changes in the surrounding environment. When polymer chains are chemically tethered at one end to a stiff solid substrate or interface with a sufficiently high grafting density, the chains avoid overlapping and stretch along the surface normal to form a polymer brush layer. Thus, substrates and interfaces can be modified with...

foreign body ingestion especially in large sizes is seen in children and people with mental illness like mental retardation. the patient is a 19-year-old woman without mental illness. she swallowed one tooth-brush during tooth- brushing, which passed through the esophagus and went in to the stomach and stuck there. after primary endoscopy, was determined that tooth-brush was adult size and its ...