1,959 research outputs found
Lattice Knots in a Slab
In this paper the number and lengths of minimal length lattice knots confined
to slabs of width , is determined. Our data on minimal length verify the
results by Sharein et.al. (2011) for the similar problem, expect in a single
case, where an improvement is found. From our data we construct two models of
grafted knotted ring polymers squeezed between hard walls, or by an external
force. In each model, we determine the entropic forces arising when the lattice
polygon is squeezed by externally applied forces. The profile of forces and
compressibility of several knot types are presented and compared, and in
addition, the total work done on the lattice knots when it is squeezed to a
minimal state is determined
BFACF-style algorithms for polygons in the body-centered and face-centered cubic lattices
In this paper the elementary moves of the BFACF-algorithm for lattice
polygons are generalised to elementary moves of BFACF-style algorithms for
lattice polygons in the body-centred (BCC) and face-centred (FCC) cubic
lattices. We prove that the ergodicity classes of these new elementary moves
coincide with the knot types of unrooted polygons in the BCC and FCC lattices
and so expand a similar result for the cubic lattice. Implementations of these
algorithms for knotted polygons using the GAS algorithm produce estimates of
the minimal length of knotted polygons in the BCC and FCC lattices
Minimal knotted polygons in cubic lattices
An implementation of BFACF-style algorithms on knotted polygons in the simple
cubic, face centered cubic and body centered cubic lattice is used to estimate
the statistics and writhe of minimal length knotted polygons in each of the
lattices. Data are collected and analysed on minimal length knotted polygons,
their entropy, and their lattice curvature and writhe
Acute mental health care according to recent mental health legislation. Part III. Structuring space for acute mental health care
Objective: This is the third of three reports on the follow-up review of mental health care at Helen Joseph Hospital (HJH). The study reviewed existing South African standards for mental health care facilities. Architectural principles and implications for the use of space were deducted from recent legislation. Objectives were to evaluate the use of space in the existing physical facilities, to identify appropriate architectural solutions considering identified human rights requirements and to provide provisional cost estimates to align the unit towards its designated functions. Method: Personal interviews were conducted. An on-site assessment and survey was made of existing and potential new spaces. Results: Spatial requirements for implementing the Mental Health Act, No. 17 of 2002 (MHCA) were explored. Principles for spatial design of acute facilities include that: - spaces should communicate clear individual identity; - space should be segregated into zones according to user functionality and privacy; - communal leisure spaces should open into safe contained outdoor spaces; - circulation routes should preferably be circular; - sufficient visual connection should exist between circulation space and group activities; and - open lines of sight should be provided to all access points. The potential options for extension included: - an extensive unused single storey structural shell for a potential office wing on the same floor; - a huge vacant double volume space which could be accessed across the existing flat roof for potential occupational therapy activities; and - the existing roof area could be altered and secured to become an adequate outside leisure and garden area. A proposed concept design in two phases – based on these principles - was submitted to hospital and provincial management. Conclusion: To implement the MHCA without violating the human rights of mental health care users at HJH will require specific adjustment and extension of the current use of space at HJH.Key words: Architecture; Hospitals; Mental health services; Human right
The Compressibility of Minimal Lattice Knots
The (isothermic) compressibility of lattice knots can be examined as a model
of the effects of topology and geometry on the compressibility of ring
polymers. In this paper, the compressibility of minimal length lattice knots in
the simple cubic, face centered cubic and body centered cubic lattices are
determined. Our results show that the compressibility is generally not
monotonic, but in some cases increases with pressure. Differences of the
compressibility for different knot types show that topology is a factor
determining the compressibility of a lattice knot, and differences between the
three lattices show that compressibility is also a function of geometry.Comment: Submitted to J. Stat. Mec
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