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