7 research outputs found
Scaled tree fractals do not strictly self-assemble
In this paper, we show that any scaled-up version of any discrete
self-similar {\it tree} fractal does not strictly self-assemble, at any
temperature, in Winfree's abstract Tile Assembly Model.Comment: 13 pages, 3 figures, Appeared in the Proceedings of UCNC-2014, pp
27-39; Unconventional Computation and Natural Computation - 13th
International Conference, UCNC 2014, London, ON, Canada, July 14-18, 2014,
Springer Lecture Notes in Computer Science ISBN 978-3-319-08122-
Doubles and Negatives are Positive (in Self-Assembly)
In the abstract Tile Assembly Model (aTAM), the phenomenon of cooperation
occurs when the attachment of a new tile to a growing assembly requires it to
bind to more than one tile already in the assembly. Often referred to as
``temperature-2'' systems, those which employ cooperation are known to be quite
powerful (i.e. they are computationally universal and can build an enormous
variety of shapes and structures). Conversely, aTAM systems which do not
enforce cooperative behavior, a.k.a. ``temperature-1'' systems, are conjectured
to be relatively very weak, likely to be unable to perform complex computations
or algorithmically direct the process of self-assembly. Nonetheless, a variety
of models based on slight modifications to the aTAM have been developed in
which temperature-1 systems are in fact capable of Turing universal computation
through a restricted notion of cooperation. Despite that power, though, several
of those models have previously been proven to be unable to perform or simulate
the stronger form of cooperation exhibited by temperature-2 aTAM systems.
In this paper, we first prove that another model in which temperature-1
systems are computationally universal, namely the restricted glue TAM (rgTAM)
in which tiles are allowed to have edges which exhibit repulsive forces, is
also unable to simulate the strongly cooperative behavior of the temperature-2
aTAM. We then show that by combining the properties of two such models, the
Dupled Tile Assembly Model (DTAM) and the rgTAM into the DrgTAM, we derive a
model which is actually more powerful at temperature-1 than the aTAM at
temperature-2. Specifically, the DrgTAM, at temperature-1, can simulate any
aTAM system of any temperature, and it also contains systems which cannot be
simulated by any system in the aTAM
The Power of Duples (in Self-Assembly): It's Not So Hip To Be Square
In this paper we define the Dupled abstract Tile Assembly Model (DaTAM),
which is a slight extension to the abstract Tile Assembly Model (aTAM) that
allows for not only the standard square tiles, but also "duple" tiles which are
rectangles pre-formed by the joining of two square tiles. We show that the
addition of duples allows for powerful behaviors of self-assembling systems at
temperature 1, meaning systems which exclude the requirement of cooperative
binding by tiles (i.e., the requirement that a tile must be able to bind to at
least 2 tiles in an existing assembly if it is to attach). Cooperative binding
is conjectured to be required in the standard aTAM for Turing universal
computation and the efficient self-assembly of shapes, but we show that in the
DaTAM these behaviors can in fact be exhibited at temperature 1. We then show
that the DaTAM doesn't provide asymptotic improvements over the aTAM in its
ability to efficiently build thin rectangles. Finally, we present a series of
results which prove that the temperature-2 aTAM and temperature-1 DaTAM have
mutually exclusive powers. That is, each is able to self-assemble shapes that
the other can't, and each has systems which cannot be simulated by the other.
Beyond being of purely theoretical interest, these results have practical
motivation as duples have already proven to be useful in laboratory
implementations of DNA-based tiles
Producibility in Hierarchical Self-assembly
Three results are shown on producibility in the hierarchical model of tile self-assembly. It is shown that a simple greedy polynomial-time strategy decides whether an assembly α is producible. The algorithm can be optimized to use O(|α | log2 |α|) time. Cannon, Demaine, Demaine, Eisenstat, Patitz, Schweller, Summers, and Winslow [5] showed that the problem of deciding if an assembly α is the unique producible terminal assembly of a tile system T can be solved in O(|α|2|T | + |α||T |2) time for the special case of noncooperative “temperature 1” systems. It is shown that this can be improved to O(|α||T | log |T |) time. Finally, it is shown that if two assemblies are producible, and if they can be overlapped consistently – i.e., if the positions that they share have the same tile type in each assembly – then their union is also producible.
Resiliency to multiple nucleation in temperature-1 self-assembly
We consider problems in variations of the two-handed abstract Tile Assembly Model (2HAM), a generalization of Erik Winfree’s abstract Tile Assembly Model (aTAM).In the latter, tiles attach one-at-a-time to a seed-containing assembly.In the former, tiles aggregate into supertiles that then further combine to form larger supertiles; hence, constructions must be robust to the choice of seed (nucleation) tiles.We obtain three distinct results in two 2HAM variants whose aTAM siblings are well-studied.In the first variant, called the restricted glue 2HAM (rg2HAM), glue strengths are restricted to −1, 0, or 1.We prove this model is Turing universal, overcoming undesired growth by breaking apart undesired computation assembly via repulsive forces.In the second 2HAM variant, the 3D 2HAM (3D2HAM), tiles are (three-dimensional) cubes.We prove that assembling a (roughly twolayer) n × n square in this model is possible with O(log2 n) tile types.The construction uses “cyclic, colliding” binary counters, and assembles the shape non-deterministically.Finally, we prove that there exist 3D2HAM systems that only assemble infinite aperiodic shapes.SCOPUS: cp.kinfo:eu-repo/semantics/publishe
Random Number Selection in Self-Assembly
Abstract. We investigate methods for exploiting nondeterminism inherent within the Tile Assembly Model in order to generate uniform random numbers. Namely, given an integer range {0,..., n − 1}, we exhibit methods for randomly selecting a number within that range. We present three constructions exhibiting a trade-off between space requirements and closeness to uniformity. The first selector selects a random number with probability Θ ( 1 n) using O(log 2 n) tiles. The second selector takes a user-specified parameter that guarantees the probabilities are arbitrarily close to uniform, at the cost of additional space. The third selector selects a random number with probability exactly 1 n, and uses no more space than the first selector with high probability, but uses potentially unbounded space
PERSEPSI PERAWAT MENGENAI KEBUTUHAN SPIRITUAL DAN PEMENUHAN KEBUTUHAN SPIRITUAL PASIEN DI INSTALASI GAWAT DARURAT
Patient overcrowding and rapid patient turnover in emergency department cause nurses to be less than optimal in providing patients spiritual needs. This condition can affect the emergency nurses' perceptions of spirituality and fulfill the patient's spiritual needs. The unmet of emergency patients spiritual needs can results a poor treatment. With a good perception of spirituality, nurses will have the ability to meet the patients spiritual needs. The aim of this study is to describe nurses’ perception of spiritual needs and fulfill the spiritual needs of patients in the emergency department. This study was used descriptive survey research. Samples were taken using total sampling technique and obtained 75 participants. Data were taken using the Spiritual Care Giving Scale (SCGS) questionnaire and analyzed by univariate analysis. The results showed that more than a half of emergency nurses considered spiritual needs and fulfilled the patient’s spiritual needs as very important (57,3%). Every aspect of fulfilling spiritual needs is also perceived to be very important by emergency nurses. An aspect that need to be improved are values in fulfilling spiritual needs. The value of spirituality is interpreted as a very important part of holistic nursing. Consequently, emergency nurses need to improve their understanding of spirituality so that the implementation of fulfilling patients spiritual needs in emergency department can be positively reinforced.
Keywords : emergency nurse, perception, spiritua