425 research outputs found
Unambiguous interpretation of atomically resolved force microscopy images of an insulator
The (111) surface of CaF 2 was imaged with dynamic mode scanning force microscopy and modeled using atomistic simulation. Both experiment and theory showed a clear triangular contrast pattern in images, and theory demonstrated that the contrast pattern is due to the interaction of a positive electrostatic potential tip with fluorine ions in the two topmost surface layers. We find a good agreement of position and relative height of scan line features between theory and experiment and thus establish for the first time an unambiguous identification of sublattices of an insulator imaged by force microscopy
Investigating Atomic Details of the CaF(111) Surface with a qPlus Sensor
The (111) surface of CaF has been intensively studied with
large-amplitude frequency-modulation atomic force microscopy and atomic
contrast formation is now well understood. It has been shown that the apparent
contrast patterns obtained with a polar tip strongly depend on the tip
terminating ion and three sub-lattices of anions and cations can be imaged.
Here, we study the details of atomic contrast formation on CaF(111) with
small-amplitude force microscopy utilizing the qPlus sensor that has been shown
to provide utmost resolution at high scanning stability. Step edges resulting
from cleaving crystals in-situ in the ultra-high vacuum appear as very sharp
structures and on flat terraces, the atomic corrugation is seen in high clarity
even for large area scans. The atomic structure is also not lost when scanning
across triple layer step edges. High resolution scans of small surface areas
yield contrast features of anion- and cation sub-lattices with unprecedented
resolution. These contrast patterns are related to previously reported
theoretical results.Comment: 18 pages, 9 Figures, presented at 7th Int Conf Noncontact AFM
Seattle, USA Sep 12-15 2004, accepted for publication in Nanotechnology,
http://www.iop.or
Unambiguous Interpretation of Atomically Resolved Force Microscopy Images of an Insulator
The (111) surface of CaF2 was imaged with dynamic mode scanning force microscopy and modeledusing atomistic simulation. Both experiment and theory showed a clear triangular contrast pattern in images, and theory demonstrated that the contrast pattern is due to the interaction of a positive electrostatic potential tip with fluorine ions in the two topmost surface layers. We find a good agreement of position and relative height of scan line features between theory and experiment and thus establish for the first time an unambiguous identification of sublattices of an insulator imaged by force microscopy.Peer reviewe
Role of tip structure and surface relaxation in atomic resolution dynamic force microscopy: CaF2(111) as a reference surface
By combining experimental dynamic scanning force microscope (SFM) images of the CaF2(111) surface with an extensive theoretical modeling, we demonstrate that the two different contrast patterns obtained reproducibly on this surface can be clearly explained in terms of the change of the sign of the electrostatic potential at the tip end. We also present direct theoretical simulations of experimental dynamic SFM images of an ionic surface at different tip-surface distances. Experimental results demonstrate a qualitative transformation of the image pattern, which is fully reproduced by the theoretical modeling and is related to the character of tip-induced displacements of the surface atoms. The modeling of the image transformation upon a systematic reduction of the tip-surface distance with ionic tips allows an estimate of the tip-surface distance present in experiment, where 0.28â0.40 nm is found to be optimal for stable imaging with well-defined atomic contrast. We also compare the modeling with ionic tips to results for a pure silicon tip. This comparison demonstrates that a silicon tip can yield only one type of image contrast and that the tip-surface interaction is not strong enough to explain the image contrast observed experimentally. The proposed interpretation of two types of images for the CaF2(111) surface can also be used to determine the chemical identity of imaged features on other surfaces with similar structure.Peer reviewe
Atomic resolution force microscopy imaging on a strongly ionic surface with differently functionalized tips
éæȹ性ćŠçć·„ç 究ćæ°ç©ç§ćŠçł»Three types of tips for noncontact atomic force microscopy imaging, namely, a silicon nanopillar tip, a carbon nanopillar tip, and a fluoride cluster tip, are prepared for atomic resolution imaging on the CaF2 (111) surface. The most enhanced atomic corrugation is obtained with the fluoride cluster tip prepared by gently touching the fluorite surface. Atom resolved images are much harder to obtain with the other tips. This demonstrates the importance of having a polar tip for atomic resolution imaging of an ionic surface and supports the general notion that a surface is best imaged with a tip of the same material. © 2010 American Vacuum Society
A project to assist Family Actions's Building Bridges practitioners with the use of the Index of Family Relations as an outcome measurement: final report
With support from DCSFâs Parenting Fund, Family Action commissioned a team of researchers from the University of East London to evaluate the utility of the Index of Family Relations (IFR) for continued use as an outcome measure to evaluate its work
A project to assist Family Actionâs Building Bridges practitioners with the use of the Index of Family Relations as an outcome measurement (Final Report).
This report describes the methods and findings of a partnership project between Family Action
practitioners and managers, and a research team led by Angela Harden and Eva Lloyd of the
University of East London. Since 1999, Family Action has been providing services in a number of
locations across England under the Building Bridges name, working with families affected by
parental mental health problems and other complex needs. Since 2004, Building Bridges projects
have been using four separate validated psychometric tools to measure family functioning,
parental satisfaction, selfâesteem and depression in order to evaluate the impact of its services
on outcomes for parents and their children: the Index of Family Relations (IFR); the Kansas
Parental Satisfaction Scale; the Rosenberg SelfâEsteem Scale; and the Depression Rating Scale.
Some years ago, the Building Bridges service model was independently evaluated (Morris, 2007).
In the light of Family Actionâs commitment to ongoing monitoring and evaluation of its work, a
decision was taken to build on the findings of the 2007 evaluation. The focus selected for further
research was an important cultural issue identified by Morris (2007: 25) regarding the
appropriateness of the Index of Family Relations for black and minority ethnic (BME)
communities, in particular Bangladeshi and Somali families. With support from DCSFâs Parenting
Fund, Family Action commissioned a team of researchers from the University of East London to
evaluate the utility of the IFR for continued use as an outcome measure to evaluate its work
The Effects of Contingent Convertible (CoCo) Bonds on Insurers' Capital Requirements Under Solvency II
Formulacija i evaluacija monolitnih matriksnih polimernih filmova za transdermalnu isporuku nitrendipina
The objective of the present work was to develop a suitable transdermal drug delivery system for nitrendipine. Polymeric films of nitrendipine were prepared by the film casting technique (glass ring) on mercury substrate. They were evaluated for physicochemical parameters, in vitro release and ex vivo permeation (heat separated human epidermis). Release of the drug from the films followed anomalous transport (0.5 < n < 1).
Polymeric combination containing Eudragit RL 100:PVP K 30 in 4:6 ratio showed the best results. Maximum drug release and skin permeability coefficient in 48 h were 85.8 % and 0.0142 cm h-1, respectively, in formulation C3 (Eudragit RL 100: Plasdone S 630; 4:6) and 88.0 % and 0.0155 cm h-1, respectively, in formulation D3 (Eudragit RL 100: PVP K 30; 4:6). FTIR and TLC studies indicated no drug and polymer interaction.Cilj rada bio je razvoj transdermalnog sustava nitrendipina. Polimerni filmovi nitrendipina pripravljeni su metodom lijevanja (stakleni prsten) na podlozi od ĆŸive. Ispitivani su fiziÄkokemijski parametri, in vitro oslobaÄanje i ex vivo permeacija (toplinom odvojena humana epiderma). OslobaÄanje lijeka iz filmova slijedilo je anomalni transport (0,5 < n < 1). Najbolji rezultati postignuti su kombinacijom polimera Eudragit RL 100 i PVP K 30 u omjeru 4:6. Maksimalno oslobaÄanje ljekovite tvari i najbolji koeficijent permeacije kroz koĆŸu tijekom 48 h bio je 85,8 %, odnosno 0,0142 cm h1 za formulaciju C3 (Eudragit RL 100 : Plasdone S 630; 4:6) i 88,0 %, odnosno 0,0155 cm h1 za formulaciju D3 (Eudragit RL 100 : PVP K 30; 4:6). FTIR i TLC ukazuju na to da nema interakcije izmeÄu ljekovite tvari i polimera
Transition Radiation Spectroscopy with Prototypes of the ALICE TRD
We present measurements of the transition radiation (TR) spectrum produced in
an irregular radiator at different electron momenta. The data are compared to
simulations of TR from a regular radiator.Comment: 4 pages, 5 Figures, Proceedings for "TRDs for the 3rd millennium"
(Sept. 4-7, 2003, Bari, Italy
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