Formation of cluster crystals in an ultra-soft potential model on a spherical surface

We investigate the formation of cluster crystals with multiply occupied lattice sites on a spherical surface in systems of ultra-soft particles interacting via repulsive, bounded pair potentials. Not all interactions of this kind lead to clustering: we generalize the criterion devised in C. N. Likos et al., Phys. Rev. E, 2001, 63, 031206 to spherical systems in order to distinguish between cluster-forming systems and fluids which display reentrant melting. We use both DFT and Monte Carlo simulations to characterize the behavior of the system, and obtain semi-quantitative agreement between the two. We find that the number of clusters is determined by the ratio between the size s of the ultra-soft particles and the radius R of the sphere in such a way that each stable configuration spans a certain interval of s/R. Furthermore, we study the effect of topological frustration on the system due to the sphere curvature by comparing the properties of disclinations, i.e., clusters with fewer than six neighbors, and non-defective clusters. Disclinations are shown to be less stable, contain fewer particles, and be closer to their neighbors than other lattice points: these properties are explained on the basis of geometric and energetic considerations

A Catalogue of Digital Editions

Since the earliest days of hypertext, textual scholars have produced, discussed and theorised upon critical digital editions of manuscripts, in order to investigate how digital technologies can provide another means to present and enable the interpretative study of text. This work has generally been done by looking at particular case studies or examples of critical digital editions, and, as a result, there is no overarching understanding of how digital technologies have been employed across the full range of textual interpretations. This chapter will describe the creation of a catalogue of digital editions that could collect information about extant digital editions and, in so doing, contribute to research in related disciplines. The resulting catalogue will provide a means of answering, in the form of a quantitative survey, the following research questions: What makes a good digital edition? What features do digital editions share? What is the state of the art in the field of digital editions? Why are there so few electronic editions of ancient texts, and so many of texts from other periods? By collecting data regarding existing digital editions, and corresponding directly with the projects in question, we provide a unique record of extant digital critical editions of text across a range of subject areas, and show how this collaboratively edited catalogue can benefit the Digital Humanities community

Novel Details of Calsequestrin Gel Conformation in Situ

Calsequestrin (CASQ) is the major component of the sarcoplasmic reticulum (SR) lumen in skeletal and cardiac muscles. This calcium-binding protein localizes to the junctional SR (jSR) cisternae, where it is responsible for the storage of large amounts of Ca2+, whereas it is usually absent, at least in its polymerized form, in the free SR. The retention of CASQ inside the jSR is due partly to its association with other jSR proteins, such as junctin and triadin, and partly to its ability to polymerize, in a high Ca2+ environment, into an intricate gel that holds the protein in place. In this work, we shed some light on the still poorly described in situ structure of polymerized CASQ using detailed EM images from thin sections, with and without tilting, and from deep-etched rotary-shadowed replicas. The latter directly illustrate the fundamental network nature of polymerized CASQ, revealing repeated nodal points connecting short segments of the linear polymer. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A

Ablative brain surgery : an overview

Background: Ablative therapies have been used for the treatment of neurological disorders for many years. They have been used both for creating therapeutic lesions within dysfunctional brain circuits and to destroy intracranial tumors and space-occupying masses. Despite the introduction of new effective drugs and neuromodulative techniques, which became more popular and subsequently caused brain ablation techniques to fall out favor, recent technological advances have led to the resurgence of lesioning with an improved safety profile. Currently, the four main ablative techniques that are used for ablative brain surgery are radiofrequency thermoablation, stereotactic radiosurgery, laser interstitial thermal therapy and magnetic resonance-guided focused ultrasound thermal ablation. Object: To review the physical principles underlying brain ablative therapies and to describe their use for neurological disorders. Methods: The literature regarding the neurosurgical applications of brain ablative therapies has been reviewed. Results: Ablative treatments have been used for several neurological disorders, including movement disorders, psychiatric disorders, chronic pain, drug-resistant epilepsy and brain tumors. Conclusions: There are several ongoing efforts to use novel ablative therapies directed towards the brain. The recent development of techniques that allow for precise targeting, accurate delivery of thermal doses and real-time visualization of induced tissue damage during the procedure have resulted in novel techniques for cerebral ablation such as magnetic resonance-guided focused ultrasound or laser interstitial thermal therapy. However, older techniques such as radiofrequency thermal ablation or stereotactic radiosurgery still have a pivotal role in the management of a variety of neurological disorders

Highly extensible skeletal muscle in snakes

Many snakes swallow large prey whole, and this process requires large displacements of the unfused tips of the mandibles and passive stretching of the soft tissues connecting them. Under these conditions, the intermandibular muscles are highly stretched but subsequently recover normal function. In the highly stretched condition we observed in snakes, sarcomere length (SL) increased 210% its resting value (SL0), and actin and myosin filaments no longer overlapped. Myofibrils fell out of register and triad alignment was disrupted. Following passive recovery, SLs returned to 82% SL0, creating a region of double-overlapping actin filaments. Recovery required recoil of intracellular titin filaments, elastic cytoskeletal components for realigning myofibrils, and muscle activation. Stretch of whole muscles exceeded that of sarcomeres as a result of extension of folded terminal tendon fibrils, stretching of extracellular elastin and independent slippage of muscle fibers. Snake intermandibular muscles thus provide a unique model of how basic components of vertebrate skeletal muscle can be modified to permit extreme extensibility. © 2014. Published by The Company of Biologists Ltd

Structural and functional properties of ryanodine receptor type 3 in zebrafish tail muscle

The ryanodine receptor (RyR)1 isoform of the sarcoplasmic reticulum (SR) Ca2++ release channel is an essential component of all skeletal muscle fibers. RyR1s are detectable as "junctional feet" (JF) in the gap between the SR and the plasmalemma or T-tubules, and they are required for excitation-contraction (EC) coupling and differentiation. A second isoform, RyR3, does not sustain EC coupling and differentiation in the absence of RyR1 and is expressed at highly variable levels. Anatomically, RyR3 expression correlates with the presence of parajunctional feet (PJF), which are located on the sides of the SR junctional cisternae in an arrangement found only in fibers expressing RyR3. In frog muscle fibers, the presence of RyR3 and PJF correlates with the occurrence of Ca2++ sparks, which are elementary SR Ca2++ release events of the EC coupling machinery. Here, we explored the structural and functional roles of RyR3 by injecting zebrafish (Danio rerio) one-cell stage embryos with a morpholino designed to specifically silence RyR3 expression. In zebrafish larvae at 72 h postfertilization, fast-twitch fibers from wild-type (WT) tail muscles had abundant PJF. Silencing resulted in a drop of the PJF/JF ratio, from 0.79 in WT fibers to 0.03 in the morphants. The frequency with which Ca2++ sparks were detected dropped correspondingly, from 0.083 to 0.001 sarcomere-1 s-1. The few Ca2++ sparks detected in morphant fibers were smaller in amplitude, duration, and spatial extent compared with those in WT fibers. Despite the almost complete disappearance of PJF and Ca2++ sparks in morphant fibers, these fibers looked structurally normal and the swimming behavior of the larvae was not affected. This paper provides important evidence that RyR3 is the main constituent of the PJF and is the main contributor to the SR Ca2++ flux underlying Ca2++ sparks detected in fully differentiated frog and fish fibers. © 2015 Perni et al

Calagem e adubação fosfatada no desenvolvimento inicial de mudas de tucumã (Astrocaryum vulgare Mart.).

FertBio 2014

Chiral bis(benzo[1,2-b:4,3-b’]dithiophene)s: synthesis and stereochemical characterization

Thiophene-containing fused aromatic compounds are an interesting class of \uf070-conjugated systems in functional organic materials (1). Among them, benzo[1,2-b:4,3-b\u2019]dithiophene (BDT) and its derivatives are widely studied, for instance as units in mono and polydisperse oligomers in the field of the materials science (2), and as \uf070-spacers in push-pull organic chromophores for photovoltaic applications (3). Furthermore, BDT is a key intermediate for the synthesis of inherently chiral helical systems such as tetrathia[7]helicenes (4).Thus, BDT can be identified as a key starting molecule, which can allow access to more complex and interesting systems through a judicious functionalization of the \uf061-positions of the thiophene rings. In our ongoing studies on the synthesis and functionalization of BDTs (5,6), we have developed a novel synthesis to prepare bis(benzo[1,2-b:4,3-b\u2019]dithiophene) systems 2, starting from bromides 1 (Figure 1).Compounds 2 belong to an interesting class of chiral atropisomeric heterobiaryl derivatives with C2-symmetry, which can be selectively functionalized into bromides 3. The chiroptical properties of both systems 2 and 3 have been fully elucidated by experimental and theoretical studies. On the other hand, enantiopure bromides 3 represent useful intermediates for the enantioselective synthesis of the corresponding tetrathiahelicene derivatives

CHiral bis-benzo[1,2-b:4,3-b’]dithiophenes : synthesis and stereochemical properties

Thiophene-containing fused aromatic compounds are an interesting class of \u3c0-conjugated systems with applications in functional organic materials.1 Among them, benzo[1,2-b:4,3-b\u2019]dithiophene (BDT) and its derivatives are widely studied in the field of materials science,2 and for photovoltaic applications.3 Moreover, BDT is a key intermediate for the synthesis of inherently chiral helical systems such as tetrathia[7]helicenes.4 In our ongoing studies on the synthesis and functionalization of BDTs,5 we have developed a novel and convenient route to prepare an interesting class of chiral heterobiaryl bis(benzo[1,2-b:4,3-b\u2019]dithiophene) systems 2 and 3 (Figure 1). In this communication we will report the synthesis of compounds 2 and 3 along with the study of their chiroptical properties. Bromides 3 are also expected to have potential applications in asymmetric reactions, including the enantioselective synthesis of tetrathia[7]helicene derivatives