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A mandatory requirement for the concept of intelligent systems and of digital or cyber-physical twins is the availability of high-quality data. Therefore, the authors investigate the possibility to integrate sensors, actuators and information technologies in standardized machine elements such as screws, bearings and couplings. In this paper, the focus is on sensing machine elements, which are a sub-category of mechatronic machine elements. To gain insights about those in development as well as to verify and validate their functionality, prototypes are needed. Those prototypes should help the designer to gain knowledge about the product in development and they should preferably be developed with low efforts. Therefore, a method is proposed to analyse concepts of mechatronic machine elements, especially sensing machine elements, regarding critical aspects that may interfere with the functionality of the product. The method is based on analysing the flow of the signal that is used for the measurement, starting from its mechanical origin and ending at the analysis unit. Different examples of sensing machine elements are given in this article and the respective flow of the usable signal is analysed, leading to the identification of subsystems that can be tested individually. Based on this, prototypes for the subsystems are developed and introduced.

Upscaling motor protein activity to perform work in man-made devices has long been an ambitious goal in bio-nanotechnology. The use of hierarchical motor assemblies, as realized in sarcomeres, has so far been complicated by the challenges of arranging sufficiently high numbers of motor proteins with nanoscopic precision. Here we suggest an alternative approach based on actomyosin cortex-like force production, allowing low complexity motor arrangements in a contractile meshwork that can be locally activated by ATP. The design is reminiscent of a motorized exoskeleton coating and thereby actuating soft protein-based polymer structures from the outside. This readily supports the connection and assembly of micro-3D printed modules into larger structures, thereby scaling up mechanical work. We provide an analytical model of force production in these systems and demonstrate the design flexibility by 3D printed units performing complex mechanical tasks, such as micro-arms and hands that perform sign language and wave.

Due to increasing global competition, the demand for more individualization and constantly changing requirements, the importance of time to market and a high degree of flexibility in product development is increasing. New manufacturing technologies as well as improved methodical approaches in product development can be used for this purpose. The additive manufacturing industry has developed strongly in recent years and the possibilities of using this technology for final components are constantly increasing. At the same time, there are many efforts that contribute to identifying and implementing the potential of this manufacturing technology during product development. Other approaches, such as agile product development from software industry, are applied at the organizational level and also try to tackle the aforementioned challenges. This contribution therefore presents an approach using agile product development methods to develop components for additive manufacturing. The potentials of additive manufacturing are specifically used (e.g. tool-free manufacturing) to enable the principles of agile development also for physical products. The Design Pattern Matrix as an opportunistic approach is applied to systematically link the potentials of additive manufacturing with the functions of the product. Therefore, design elements are conducted from additive manufacturing case studies and provided to design engineers during the development. Furthermore, already known methods of design for additive manufacturing are classified into the procedure of the agile framework scrum.

The digitalization of the Industry is one of the megatrends taking place, but many companies struggle to follow this trend. The main reason is the absence of simple solutions for the integration of sensory functions, which are applicable to the existing system. Therefore, this paper discusses the aspects of simplicity in the context of integrating sensory functions into existing systems, to support the development of digitalized products.Two general requirements can be formulated for a solution to be applicable simple: The first requirement is affected by the product structure. The solution must affect the least possible amount of modules and must not interfere with the interfaces of the modular platform. The second requirement is affected by the effort to model the behaviour of the desired information and the possible data a sensory function is delivering. The effort to develop a reliable solution has to be compared with the commercial potential of the solution.To consider the mentioned requirements, the paper explains three approaches to assess the simplicity of solutions on an example of the desired monitoring of the functions of a rotary plug valve.

One of the grand challenges of bottom-up synthetic biology is the development of minimal machineries for cell division. The mechanical transformation of large-scale compartments, such as Giant Unilamellar Vesicles (GUVs), requires the geometry-specific coordination of active elements, several orders of magnitude larger than the molecular scale. Of all cytoskeletal structures, large-scale actomyosin rings appear to be the most promising cellular elements to accomplish this task. Here, we have adopted advanced encapsulation methods to study bundled actin filaments in GUVs and compare our results with theoretical modeling. By changing few key parameters, actin polymerization can be differentiated to resemble various types of networks in living cells. Importantly, we find membrane binding to be crucial for the robust condensation into a single actin ring in spherical vesicles, as predicted by theoretical considerations. Upon force generation by ATP-driven myosin motors, these ring-like actin structures contract and locally constrict the vesicle, forming furrow-like deformations. On the other hand, cortex-like actin networks are shown to induce and stabilize deformations from spherical shapes., Cytoskeletal networks support and direct cell shape and guide intercellular transport, but relatively little is understood about the self-organization of cytoskeletal components on the scale of an entire cell. Here, authors use an in vitro system and observe the assembly of different types of actin networks and the condensation of membrane-bound actin into single rings.

Inhalt: Die Digitalisierung des Maschinenbaus erfordert die Integration zusätzlicher, möglichst prozessnaher Sensoren. Der vorliegende Artikel adressiert die Frage der Integration der Sensoren in Maschinenelemente als idealerweise standardisierte Bauteile und die Notwendigkeit zum Umdenken in der Konstruktion, um mit möglichst wenig Änderungen an Montagevorrichtungen und -prozessen die effiziente Integration der Sensoren zu ermöglichen. Eine Betrachtung der möglichen Vorteile von Bauteil-integrierten Sensoren und einer entsprechend ausgerichteten Konstruktion zeigt den Forschungsbedarf und das wirtschaftliche Potential des Ansatzes auf.

Der vorliegende Fachartikel thematisiert die Bewertung der Betriebsnotwendigkeit des Umlaufvermogens speziell von Verteilnetzbetreibern in Deutschland. Bedingt durch die Energiewende bedarf es in den nachsten Jahren enorme Investitionen in das Verteilnetz. Die Verzinsung fur das hierfur notwendige Kapital ergibt sich primar aus § 7 Strom/GasNEV. Dabei stellt die Bewertung des betriebsnotwendigen Umlaufvermogens, als Bestandteil der Vermogensbasis fur die kalkulatorische Eigenkapitalverzinsung, Regulierungsbehorden und Verteilnetzbetreiber vor Herausforderungen und fuhrt bisweilen zu unterschiedlichen Auffassungen in Hinblick auf die sachgerechte Hohe des anzusetzenden Umlaufvermogens. Diese Debatte erscheint umso dringlicher, als dass das Umlaufvermogen in einer Durchschnittsbetrachtung einen Anteil von 25 % am Gesamtvermogen darstellt. In diesem Zusammenhang stellt sich jedoch die Frage, ob Verteilnetzbetreiber uberhaupt Umlaufvermogen vorhalten mussen. Die Antwort hierauf ergibt sich mit Blick auf die branchentypischen Geschaftsprozesse (wie z. B. EEG-Prozess). Ferner kann festgestellt werden, dass das Vorhalten von Umlaufvermogen Kapitalkosten verursacht und in Folge den Unternehmenswert schmalert. Dies wirkt sich erschwerend bei der Beschaffung von Kapital aus. Die verschiedenen Zusammenhange von Umlaufvermogen und Unternehmenswert in regulierten Markten werden deshalb im Artikel genauer untersucht. Daruber hinaus wird festgestellt, dass die derzeitige Regulierungspraxis (pauschale Kurzungen) nicht uneingeschrankt nachvollziehbar erscheint. Vielmehr bedarf es eines positionsscharfen und mehrstufigen Prufschemas: Dient die Position der Leistungserbringung? Ist die Position nicht hoher als zum Zwecke der Leistungserbringung notwendig? Inwiefern ist die Position vergleichbar zu anderen Betrieben? Im Artikel werden hierzu geeignete Instrumente wie z. B. die Cashflow-Rechnung vertiefend untersucht. Zudem wird ein Benchmark erstellt welcher anhand der Liquiditat 3. Grades veranschaulicht, dass das Umlaufvermogen von Verteilnetzbetreibern im Vergleich zu wettbewerblichen Unternehmen vergleichsweise effizient erscheint. Die Forschungsergebnisse zeigen Handlungsbedarf bei der aktuellen Regulierungspraxis auf.

This paper discusses the challenges that arise from the need for additional sensory functions in existing systems. These additional functions lead to a wide variety of possible solutions for the sensor integration that must be reduced to the most promising ones. Therefore. models for the analysis of technical systems are outlined as a basis for a new model to analyze the sensor retrofit into existing system especially during early stages of the sensor integration. The new model is used exemplarily on a disk brake for the development of concepts for the measurement of the applied axial brake force. The results of the analysis lead to a qualitative evaluation of possible sensor locations that can be used to rank and evaluate the possible solutions before the development of concepts starts.

Cortical actomyosin flows, among other mechanisms, scale up spontaneous symmetry breaking and thus play pivotal roles in cell differentiation, division, and motility. According to many model systems, myosin motor-induced local contractions of initially isotropic actomyosin cortices are nucleation points for generating cortical flows. However, the positive feedback mechanisms by which spontaneous contractions can be amplified towards large-scale directed flows remain mostly speculative. To investigate such a process on spherical surfaces, we reconstituted and confined initially isotropic minimal actomyosin cortices to the interfaces of emulsion droplets. The presence of ATP leads to myosin-induced local contractions that self-organize and amplify into directed large-scale actomyosin flows. By combining our experiments with theory, we found that the feedback mechanism leading to a coordinated directional motion of actomyosin clusters can be described as asymmetric cluster vibrations, caused by intrinsic non-isotropic ATP consumption with spatial confinement. We identified fingerprints of vibrational states as the basis of directed motions by tracking individual actomyosin clusters. These vibrations may represent a generic key driver of directed actomyosin flows under spatial confinement in vitro and in living systems. (This article belongs to the Special Issue Symmetry Breaking in Cells and Tissues)

Life implies motion. In cells, protein-based active molecular machines drive cell locomotion and intracellular transport, control cell shape, segregate genetic material, and split a cell in two parts. Key players among molecular machines driving these various cell functions are the cytoskeleton and motor proteins that convert chemical bound energy into mechanical work. Findings over the last decades in the field of in vitro reconstitutions of cytoskeletal and motor proteins have elucidated mechanistic details of these active protein systems. For example, a complex spatial and temporal interplay between the cytoskeleton and motor proteins is responsible for the translation of chemically bound energy into (directed) movement and force generation, which eventually governs the emergence of complex cellular functions. Understanding these mechanisms and the design principles of the cytoskeleton and motor proteins builds the basis for mimicking fundamental life processes. Here, a brief overview of actin, prokaryotic actin analogs, and motor proteins and their potential role in the design of a minimal cell from the bottom-up is provided.

Cortical actomyosin flows play pivotal roles in cell motility, cell division and animal morphogenesis. According to many model systems, myosin motor induced local contractions are key for generating cortical flows. However, the original mechanism how large-scale directed flows emerge from local motor activity in an apparently isotropic cortex is unknown. We reconstituted and confined minimal actomyosin cortices to the interfaces of emulsion droplets. The presence of ATP leads to myosin-induced cortical contractions that self-organize into directed flow-like actomyosin motions. By combining our experiments with theory, we found that the large-scale directional motion of actomyosin clusters emerges from individual asymmetric cluster vibrations, caused by intrinsic non-isotropic ATP consumption, in conjunction with spherical confinement. By tracking individual actomyosin clusters, we identified fingerprints of vibrational states as the basis of directed motions. These vibrations may represent a generic key driver of directed actomyosin flows under spatial confinementin vitroand in living systems.

The actomyosin cortex is involved in a range of many cellular processes like cell division, motility or shaping. To obtain this variety of functionalities the membrane-bound actin mesh has to be reconstituted by the motor protein myosin. But little is known about the underlying mechanism, which control the different tasks. An underlying in vitro study of a synthetic actomyosin cortex has shown that the cortex organizes into spatial clusters for certain ATP concentrations. Here we develop a curvilinear model that captures the viscoelastic material behavior and the kinetics of the myosin cross bridge. Further, we suggest a formulation for the active contractile stress produced by the motor protein myosin. We demonstrate that the spatial pattern generated by the curvilinear model is consistent with the experimental observations, including mesh clustering due to contractile forces and an absence of contraction for low and high ATP concentrations. Additionally we show that the cluster positioning can be tuned by the ATP-gradient.

Dynamic reorganization of the actomyosin cytoskeleton allows fast modulation of the cell surface, which is vital for many cellular functions. Myosin-II motors generate the forces required for this remodeling by imparting contractility to actin networks. However, myosin-II activity might also have a more indirect contribution to cytoskeletal dynamics; it has been proposed that myosin activity increases actin turnover in various cellular contexts, presumably by enhancing disassembly. In vitro reconstitution of actomyosin networks has confirmed the role of myosin in actin network disassembly, but the reassembly of actin in these assays was limited by factors such as diffusional constraints and the use of stabilized actin filaments. Here, we present the reconstitution of a minimal dynamic actin cortex, where actin polymerization is catalyzed on the membrane in the presence of myosin-II activity. We demonstrate that myosin activity leads to disassembly and redistribution in this simplified cortex. Consequently, a new dynamic steady state emerges in which the actin network undergoes constant turnover. Our findings suggest a multifaceted role of myosin-II in the dynamics of the eukaryotic actin cortex. This article has an associated First Person interview with the first author of the paper.

In modern machine architecture, complex mechanical components guarantee the function of the system. Specific maintenance rates reduce maintenance effort and cost. The combination of load and failure monitoring provide data to establish an individual maintenance rate depending on component specific remaining lifetime. In addition, algorithms can optimise the operation strategy to relieve the weakest components and extend the system lifetime. Adapted ball bearings contain a sensor mechanism depending on the relation of beating load and electric bearing impedance to measure load and failure data.

This paper discusses the difficulties caused by production precision for a widespread application of sensorial Mechatronic Machine Elements to expand existing machines or designs to Cyber-Physical-Systems. The production induced tolerances lead to an undetermined flow of forces in machine elements and prevent a reliable sensing of forces in Mechatronic Machine Elements. A promising approach to overcome these difficulties is Robust Design, which leads to determined mechanical functions that reduce uncertainty of force measurement in Mechatronic Machine Elements.

A thorough structure determination has been performed on Cu2ZnSnS4 nanoparticles, a popular photovoltaic material, using neutron diffraction—to characterize the long-range average crystal structure—and X-ray absorption fine structure (XAFS) spectroscopy at the Cu, Zn, and Sn K-edges to elucidate the element-specific local structure. This is the first combined multiscale approach on nanoparticles of this material. The results indicate the presence of aperiodic disorder on the cation sites that is diminished by annealing. This disorder involves local lattice distortions around the crystallographic sites rather than the presence of interstitial atoms. It is most consistent with the known antisite substitutions that are integral to CZTS (referring to the ordering of the Cu, Zn, and Sn between planes). However, instead of being confined within single unit cells so as to maintain the crystallographic symmetry, periodicity, and homogeneity, the substitutional disorder appears to extend over larger regions consis...

Membranes determine two-dimensional and three-dimensional biochemical reaction spaces in living systems. Defining size and shape of surfaces and volumes encompassed by membrane is of key importance for cellular metabolism and homeostasis, and the maintenance and controlled transformation of membrane shapes are coordinated by a large number of different protein assemblies. The orchestration of spatial elements over distances orders of magnitudes larger than protein molecules, as required for cell division, is a particularly challenging task, requiring large-scale ordered protein filaments and networks. The structure and function of these networks, particularly of cytoskeletal elements, have been characterized extensively in cells and reconstituted systems. However, their co-reconstitution with membranes from the bottom-up under defined conditions, to elucidate their mode of action in detail, is still a relatively new field of research. In this short review, we discuss recent approaches and achievements with regard to the study of cytoskeletal protein assemblies on model membranes, with specific focus on contractile elements as those based on the bacterial division FtsZ protein and eukaryotic actomyosin structures.

The actin cell cortex in eukaryotic cells is a key player in controlling and maintaining the shape of cells, and in driving major shape changes such as in cytokinesis. It is thereby constantly being remodeled. Cell shape changes require forces acting on membranes that are generated by the interplay of membrane coupled actin filaments and assemblies of myosin motors. Little is known about how their interaction regulates actin cell cortex remodeling and cell shape changes. Because of the vital importance of actin, myosin motors and the cell membrane, selective in vivo experiments and manipulations are often difficult to perform or not feasible. Thus, the intelligent design of minimal in vitro systems for actin-myosin-membrane interactions could pave a way for investigating actin cell cortex mechanics in a detailed and quantitative manner. Here, we present and discuss the design of several bottom-up in vitro systems accomplishing the coupling of actin filaments to artificial membranes, where key parameters such as actin densities and membrane properties can be varied in a controlled manner. Insights gained from these in vitro systems may help to uncover fundamental principles of how exactly actin-myosin-membrane interactions govern actin cortex remodeling and membrane properties for cell shape changes. (c) 2013 Wiley Periodicals, Inc.

Diffusion of lipids and proteins within the cell membrane is essential for numerous membrane-dependent processes including signaling and molecular interactions. It is assumed that the membrane-associated cytoskeleton modulates lateral diffusion. Here, we use a minimal actin cortex to directly study proposed effects of an actin meshwork on the diffusion in a well-defined system. The lateral diffusion of a lipid and a protein probe at varying densities of membrane-bound actin was characterized by fluorescence correlation spectroscopy (FCS). A clear correlation of actin density and reduction in mobility was observed for both the lipid and the protein probe. At high actin densities, the effect on the protein probe was ∼3.5-fold stronger compared to the lipid. Moreover, addition of myosin filaments, which contract the actin mesh, allowed switching between fast and slow diffusion in the minimal system. Spot variation FCS was in accordance with a model of fast microscopic diffusion and slower macroscopic diffusion. Complementing Monte Carlo simulations support the analysis of the experimental FCS data. Our results suggest a stronger interaction of the actin mesh with the larger protein probe compared to the lipid. This might point toward a mechanism where cortical actin controls membrane diffusion in a strong size-dependent manner.

A thin layer of actin filaments in many eukaryotic cell types drives pivotal aspects of cell morphogenesis and is generally cited as the actin cortex. Myosin driven contractility and actin cytoskeleton membrane interactions form the basis of fundamental cellular processes such as cytokinesis, cell migration, and cortical flows. How the interplay between the actin cytoskeleton, the membrane, and actin binding proteins drives these processes is far from being understood. The complexity of the actin cortex in living cells and the hardly feasible manipulation of the omnipotent cellular key players, namely actin, myosin, and the membrane, are challenging in order to gain detailed insights about the underlying mechanisms. Recent progress in developing bottom-up in vitro systems where the actin cytoskeleton is combined with reconstituted membranes may provide a complementary route to reveal general principles underlying actin cortex properties. In this chapter the reconstitution of a minimal actin cortex by coupling actin filaments to a supported membrane is described. This minimal system may be very well suited to study for example protein interactions on membrane bound actin filaments in a very controlled and quantitative manner as it may be difficult to perform in living systems.

Use of highly integrated application specific circuits (ASICs) in bioelectric data acquisition systems promise important new insights into the origin of a large variety of health problems by providing light-weight, low-power, low-cost medical measurement devices that allow long-term studies. They also promise significant cost reduction in medical care, as patients in principle become mobile and do not have to be hospitalized for observation. We report on the development and successful implementation of a universal ASIC, designed to meet key characteristics of a broad variety of bioelectric signals in terms of their dynamic range, sampling rate and input referred noise; e.g. electrocardiogram (ECG), electroencephalogram (EEG) and, most constringently, evoked potentials (EPs). Our approach for the first time makes cost-effective use of state-of-the-art microelectronics in medical measurement equipment, thus offering to replace discrete, single application devices used at present.

Actin is a multi-functional protein that is found in almost all eukaryotic cells. When polymerized, it forms robust filaments that participate in a variety of cellular processes. For example, actin filaments are involved in the contraction of muscles, and they are also a major component in the various structures that maintain and control the shape of cells as they move and divide. These structures include the cell cortex, a meshwork of actin filaments that is bound to the inner surface of the plasma membrane by anchor proteins. However, both the cell cortex and the plasma membrane must undergo dramatic changes when a cell divides, and the forces that drive these changes are generated by another protein, myosin II. Myosin II contains three domains: a head domain, also known as the motor domain, that binds to actin; a neck domain; and a tail domain. Like actin, myosin II proteins also form filaments, but these myofilaments have a distinctive structure: the tail domains of two Myosin II proteins join together, with the motor domains being found at both ends of the filament. When activated, the motor domains grab actin filaments and pull against them in a ‘powerstroke’. However, the details of the interactions between the myofilament motor domains and the actin filaments in the cell cortex, which are bound to the plasma membrane, are not fully understood. Studying these processes in living cells is extremely challenging, so Vogel et al. have built an in vitro model of the cell cortex, and then used single-molecule imaging to watch the interactions between the myofilaments and the actin filaments in this model. They show that the myofilaments move along the actin in the cortex, breaking up the filaments and compressing them in the process. They propose that tension builds up between the ends of the myofilaments, leading to compressive stress being exerted on the actin filaments. Computer simulations confirm that the forces generated are high enough to cause the actin filaments to buckle and break. The in vitro model developed by Vogel et al. should allow researchers to clarify the basic biophysical principles that underpin the structure and function of the cell cortex.

In the context of minimal systems design, there are two areas in which the reductionist approach has been particularly successful: studies of molecular motors on cytoskeletal filaments, and of protein–lipid interactions in model membranes. However, a minimal cortex, that is, the interface between membrane and cytoskeleton, has just begun to be functionally reconstituted. A key property of living cells is their ability to change their shape in response to extracellular and intracellular stimuli. Although studied in live cells since decades, the mutual dependence between cytoskeleton and membrane dynamics in these large-scale transformations is still poorly understood. Here we report on inspiring recent in vitro work in this direction, and the promises it holds for a better understanding of key cellular processes.

One of the most fundamental questions in the field of relativistic heavy ion physics is how to reach and explore densities which are needed to cross the chiral and/or the deconfinement phase transition. In this analysis we investigate the information we can gather by analyzing baryonic and mesonic resonances on the hot and dense phase in such nuclear reactions. The decay products of these resonances carry information on the resonances properties at the space time point of their decay. We especially investigate the percentage of reconstructable resonances as a function of density for heavy ion collisions in the energy range between $E_{lab}$ = 30 AGeV and $\sqrt{s}$ = 200 AGeV, the energy domain between the future FAIR facility and the present RHIC collider., Talk given at the International Conference on Strangeness in Quark Matter 2009 (SQM09)

Living cells are highly organized in space and time, which makes spatially and temporally confined manipulations an indispensable tool in cell biology. Laser-based nanosurgery is an elegant method that allows precise ablation of intracellular structures. Here, we show cutting of fluorescently labelled microtubules and mitotic spindles in fission yeast, performed with a picosecond laser coupled to a confocal microscope. Diverse effects from photo- bleaching to partial and complete breakage are obtained by varying the exposure time, while simultaneously imaging the structures of interest. Using this system we developed an efficient technique to generate enucleated cells without perturbing the distribution of other organelles. This enucleation method can be used to study the cytoskeleton in a nucleus- free environment, as well as the role of the nucleus in cell growth and a variety of cellular functions.

The possibility of studying impurity passivation complexes in semiconductors by quadrupole resonance spectroscopy is examined. The problem is illustrated for the case of boron in silicon passivated with hydrogen or, equivalently, with muonium, since the radioactive light isotope in principle offers a greater sensitivity for detection of the spectra. Ab initio calculations on suitable cluster models of the passivation complexes provide estimates of the electric field gradients at the quadrupolar nuclei, and thereby predictions of the quadrupole resonance frequencies. Detection via cross-relaxation techniques is proposed, notably muon level crossing resonance ( mu LCR), and illustrated by calculation of the time dependence of the muon polarization function. Possible reasons for the absence of quadrupolar resonances in mu LCR spectra recorded in exploratory experiments are discussed: these include the existence of a local tunnelling mode for the lighter isotope.

SummaryIn the fission yeast Schizosaccharomyces pombe, interphase microtubules (MTs) position the nucleus [1, 2], which in turn positions the cell-division plane [1, 3]. It is unclear how the spindle orients, with respect to the predetermined division plane, to ensure that the chromosomes are segregated across this plane. It has been proposed that, during prometaphase, the astral MT interaction with the cell cortex aligns the spindle with the cell axis [4] and also participates in a spindle orientation checkpoint (SOC), which delays entry into anaphase as long as the spindle is misaligned [5–7]. Here, we trace the position of the spindle throughout mitosis in a single-cell assay. We find no evidence for the SOC. We show that the spindle is remarkably well aligned with the cell longitudinal axis at the onset of mitosis, by growing along the axis of the adjacent interphase MT. Misalignment of nascent spindles can give rise to anucleate cells when spindle elongation is impaired. We propose a new role for interphase microtubules: through interaction with the spindle pole body, interphase microtubules determine the initial alignment of the spindle in the subsequent cell division.

The spliceosomal component Prp1 (U5-102 kD) is found in Schizosaccharomyces pombe, a physiological substrate of Prp4 kinase. Here, we identify, spp41-1, a previously isolated extragenic suppressor of Prp4 kinase. The gene encodes an ATP-dependent RNA helicase homologous to the splicing factor Brr2 of Saccharomyces cerevisiae and U5-200 kD of mammalia. The suppressor allele, spp41-1, interacts genetically with alleles of prp1. We show that Prp1 and Brr2 are complexed in vivo with spliceosomal particles containing the five snRNAs U1, U2, U5, and base-paired U4/U6. Prp1 was found exclusively in small ribonucleoprotein particle (snRNP) complexes sedimenting in the range of 30S–60S, whereas Brr2 was also found sedimenting lower than 30S and free of snRNAs. Moreover, we find that the splicing factor Prp31 is complexed with Prp1 in the same spliceosomal particles containing the five snRNAs. These data indicate that in fission yeast spliceosomal particles larger than 30S exist, which can be considered as pre-catalytic spliceosomes. In addition, we show that S. pombe cells lacking Prp1 still contain these large pre-catalytic spliceosomal particles associated with Prp31. These data are consistent with the notion that in fission yeast phosphorylation of Prp1 by Prp4 kinase is involved in the activation of pre-catalytic spliceosomes.

Transverse hadron spectra from proton-proton, proton-nucleus and nucleus-nucleus collisions from 2 AGeV to 21.3 ATeV are investigated within two independent transport approaches (HSD and UrQMD). For central Au+Au (Pb+Pb) collisions at energies above $E_{\rm lab}\sim$ 5 AGeV, the measured $K^{\pm}$ transverse mass spectra have a larger inverse slope parameter than expected from the default calculations. The additional pressure - as suggested by lattice QCD calculations at finite quark chemical potential $��_q$ and temperature $T$ - might be generated by strong interactions in the early pre-hadronic/partonic phase of central Au+Au (Pb+Pb) collisions. This is supported by a non-monotonic energy dependence of $v_2/< p_T>$ in the present transport model., Proceedings of Strange Quark Matter 2004

The electronic structure of interstitial hydrogen in diamond, silicon and germanium is investigated by means of cluster calculations on the level of the unrestricted Hartree-Fock self-consistent field approximation. A stable configuration for H is found at a bond-centred site and its hyperfine properties are compared to experiments on paramagnetic muonium states.

SummaryCytoplasmic dynein is a motor protein that exerts force on microtubules. To generate force for the movement of large organelles, dynein needs to be anchored, with the anchoring sites being typically located at the cell cortex. However, the mechanism by which dyneins target sites where they can generate large collective forces is unknown. Here, we directly observe single dyneins during meiotic nuclear oscillations in fission yeast and identify the steps of the dynein binding process: from the cytoplasm to the microtubule and from the microtubule to cortical anchors. We observed that dyneins on the microtubule move either in a diffusive or directed manner, with the switch from diffusion to directed movement occurring upon binding of dynein to cortical anchors. This dual behavior of dynein on the microtubule, together with the two steps of binding, enables dyneins to self-organize into a spatial pattern needed for them to generate large collective forces.

A key aspect of life is sexual reproduction, which requires concerted movement. For successful mixing of the genetic material, molecular motors move the nucleus back and forth inside the cell. How motors work together to produce these large-scale movements, however, remains a mystery. To answer this question, we studied nuclear movement in fission yeast, which is driven by motor proteins pulling on microtubules. We show that motor proteins dynamically redistribute from one part of the cell to the other, generating asymmetric patterns of motors and, consequently, of forces that generate movement. By combining quantitative live cell imaging and laser ablation with a theoretical model, we find that this dynamic motor redistribution occurs purely as a result of changes in the mechanical strain sensed by the motor proteins. Our work therefore demonstrates that spatio-temporal pattern formation within a cell can occur as a result of mechanical cues (Vogel et al., 2009), which differs from conventional molecular signaling, as well as from self-organization based on a combination of biochemical reactions and diffusion.

La structure a l'equilibre de l'hydrogene interstitiel neutre pres du site a liaison centree, dans le GaAs, est calculee au niveau de Hartree-Fack ab initio dans le cluster HGa 4 As 4 H 18 . On utilise une base de valence decomposee et des pseudo-potentiels ab initio pour les orbitales du cœur