Inert Targets Research Articles

Deterministic treasure hunt and rendezvous in arbitrary connected graphs

Treasure hunt and rendezvous are fundamental tasks performed by mobile agents in graphs. In treasure hunt, an agent has to find an inert target (called treasure) situated at an unknown node of the graph. In rendezvous, two agents, initially located at distinct nodes of the graph, traverse its edges in synchronous rounds and have to meet at some node. We assume that the graph is connected (otherwise none of these tasks is feasible) and consider deterministic treasure hunt and rendezvous algorithms. The time of a treasure hunt algorithm is the worst-case number of edge traversals performed by the agent until the treasure is found. The time of a rendezvous algorithm is the worst-case number of rounds since the wakeup of the earlier agent until the meeting.To the best of our knowledge, all known treasure hunt and rendezvous algorithms rely on the assumption that degrees of all nodes are finite, even when the graph itself may be infinite. In the present paper we remove this assumption for the first time, and consider both above tasks in arbitrary connected graphs whose nodes can have either finite or countably infinite degrees. Our main result is the first universal treasure hunt algorithm working for arbitrary connected graphs. We prove that the time of this algorithm has optimal order of magnitude among all possible treasure hunt algorithms working for arbitrary connected graphs. As a consequence of this result we obtain the first universal rendezvous algorithm working for arbitrary connected graphs. The time of this algorithm is polynomial in a lower bound holding in many graphs, in particular in the tree all of whose degrees are infinite.

Almost-Optimal Deterministic Treasure Hunt in Unweighted Graphs

A mobile agent navigating along edges of a simple connected unweighted graph, either finite or countably infinite, has to find an inert target (treasure) hidden in one of the nodes. This task is known as treasure hunt. The agent has no a priori knowledge of the graph, of the location of the treasure, or of the initial distance to it. The cost of a treasure hunt algorithm is the worst-case number of edge traversals performed by the agent until finding the treasure. Awerbuch et al. [ 3 ] considered graph exploration and treasure hunt for finite graphs in a restricted model where the agent has a fuel tank that can be replenished only at the starting node s . The size of the tank is B = 2 (1+α) r , for some positive real constant α, where r , called the radius of the graph, is the maximum distance from s to any other node. The tank of size B allows the agent to make at most ⌊ B ⌋ edge traversals between two consecutive visits at node s . Let e(d) be the number of edges whose at least one endpoint is at distance less than d from s . Awerbuch et al. [ 3 ] conjectured that it is impossible to find a treasure hidden in a node at distance at most d at cost nearly linear in e(d) . We first design a deterministic treasure hunt algorithm working in the model without any restrictions on the moves of the agent at cost 𝒪(e(d) log d ) and then show how to modify this algorithm to work in the model from Awerbuch et al. [ 3 ] with the same complexity. Thus, we refute the preceding 20-year-old conjecture. We observe that no treasure hunt algorithm can beat cost Θ ( e(d) ) for all graphs, and thus our algorithms are also almost optimal.

Effect of Surface Diffuseness Parameter on Quasi-elastic Scattering Calculations for 16O+208Pb,63Cu Systems

A systematic study on the surface characteristic of the nucleus-nucleus potential for some heavy-ion. The nuclear potential has been described by using Woods-Saxon (WS), the single-channel (SC) and the coupled-channels (CC) calculations, which were between the relative motion of the colliding nuclei and their intrinsic motions, were conducted to study its influence on calculation, the ratio of the quasi-elastic to the Rutherford cross sections and probe the surface diffuseness method was used to find the best fitted value of the diffuseness parameters in comparison with the experimental data. We find that the best fitted value of the diffuseness parameter which obtained through a coupled-channel calculation with inert target and excited projectile forIn the current work, the single-channel (SC) and the coupled-channels (CC) calculations, which were between the relative motion of the colliding nuclei and their intrinsic motions, were conducted to study its influence on calculation, the ratio of the quasi-elastic to the Rutherford cross sections and probe the surface diffuseness find that the best fitted value of the diffuseness parameter which obtained through a coupled-channel calculation with excited target and projectile excited also inert projectile-excited target for the 16O+208Pb andexcited projectile and inert target for the 16O+63Cu.

Impact of knowledge on the cost of treasure hunt in trees

AbstractTreasure hunt is finding a hidden inert target by a mobile agent. We consider deterministic algorithms for treasure hunt in trees. Our goal is to establish the impact of different kinds of initial knowledge given to the agent on the cost of treasure hunt, defined as the total number of edge traversals until the agent reaches the treasure. The agent can be initially given either a complete map of the tree rooted at its starting node, with all port numbers marked, or a blind map of the tree rooted at its starting node but without port numbers. It may also be given, or not, the distance from the root to the treasure. This yields four different knowledge types that are partially ordered by their precision. The penalty of a less precise knowledge type over a more precise knowledge type measures intuitively the worst‐case ratio of the cost of an algorithm supplied with knowledge of type over the cost of an algorithm supplied with knowledge of type . Our main results establish penalties for comparable knowledge types in this partial order. For knowledge types with known distance, the penalty for having a blind map over a complete map turns out to be very large. By contrast, for unknown distance, the penalty of having a blind map over having a complete map is small. When a map is provided (either complete or blind), the penalty of not knowing the distance over knowing it is medium.

The far right, the mainstream and mainstreaming: towards a heuristic framework

ABSTRACT The study of far-right parties and politics is one of the most high-profile research areas in political science and related disciplines. Far-right parties have been the subject of vast amounts of varied scholarship since their turn-of-the-century resurgence. However, as the far right has become a mainstay, with Brexit and the election of Donald Trump in 2016 blurring the boundaries between mainstream and far-right politics, it has become crucial to pay attention to the process of mainstreaming. Beyond a focus on far-right electoral success, studies of mainstreaming, as well as a critical account of the concept and role of the ‘mainstream’, have proved elusive. This article provides a heuristic framework to understand these concepts and the mainstreaming of the far right. Key to our approach is a more holistic analysis, extending beyond traditional approaches which focus mostly on the electoral outcomes of far-right parties, positioning the mainstream as a relatively inert target or bulwark against them. To achieve this, we seek to reframe the focus towards the centrality of discourse both in the process, and as an outcome, of mainstreaming. Only by doing so can we account for the significant role played by the mainstream in this process.

Advice complexity of treasure hunt in geometric terrains

Treasure hunt is finding an inert target by a mobile agent. We consider treasure hunt in polygonal terrains with polygonal obstacles. The agent finds the treasure when there is a segment of length at most 1 between them, inside the terrain. The cost of treasure hunt is the length of the agent's trajectory. We investigate the amount of information (advice complexity) needed for treasure hunt at cost linear in the length of a shortest path in the terrain from the initial position of the agent to the treasure. A polygon is c-fat if the ratio of the radius of the smallest disc containing it to the radius of the largest disc contained in it is at most c. For regular terrains, defined as convex polygons with convex c-fat obstacles, for some constant c>1, we establish the exact advice complexity of treasure hunt. We then show that advice complexity of treasure hunt for arbitrary terrains is exponentially larger than for regular terrains.

The Active Target Time Projection Chamber at NSCL

Reactions in inverse kinematics close to the Coulomb barrier offer unique opportunities to study exotic nuclei, but they are plagued by the difficulty to efficiently and precisely measure the characteristics of the emerging particles. The Active Target Time Projection Chamber (AT-TPC) offers an elegant solution to this dilemma. In this device, the detector gas of the time projection chamber is at the same time the target in which nuclear reactions take place. The use of this new paradigm offers several advantages over conventional inert target methods, the most significant being the ability to increase the luminosity of experiments without loss of resolution. The AT-TPC and some results obtained on resonant α scattering to explore the clustering properties of neutron-rich nuclei are presented, as well as fusion cross section results using a 10 Be radioactive beam. In addition, the first re-accelerated radioactive beam experiment using the fully commissioned ReA3 linac was conducted recently at the NSCL with the AT-TPC, where proton resonant scattering of a 4.6 MeV/u 46 Ar beam was used to measure the neutron single-particle strength in 47 Ar.

The fungal pathogen Cryptococcus neoformans manipulates macrophage phagosome maturation.

Phagocytosis by cells of the innate immune system, such as macrophages, and the subsequent successful maturation of the phagosome, is key for the clearance of pathogens. The fungal pathogen Cryptococcus neoformans is known to overcome killing by host phagocytes and both replicate within these cells and also escape via a non-lytic process termed vomocytosis. Here we demonstrate that, during intracellular growth, cryptococci modify phagolysosome maturation. Live cryptococci, but not heat-killed pathogens or inert targets, induce the premature removal of the early phagosome markers Rab5 and Rab11. In addition, significant acidification of the phagosome, calcium flux and protease activity is hindered, thus rendering the phagosome permissive for cryptococcal proliferation. Interestingly, several attenuated cryptococcal mutants retain this ability to subvert phagosomal maturation, suggesting that hitherto unidentified pathogen mechanisms regulate this process.

Effects observed when using metallic flyers and barriers with the embedded particle velocity gauge technique

A number of experiments were carried out using a modified version of the standard particle velocity gauge technique in plate impact experiments with inert targets. Unusually these utilised dynamic metallic elements. Traditional methodology advises against the use of metallic flyers/barriers with this technique as conductive objects moving in the magnetic field produce perturbations in the output gauge voltage leading to inaccuracies in the derived particle velocities. This body of work investigated the causes of the perturbation effect, methods of minimising its magnitude and possible post-processing correction methods. In experiments with Al flyers, perturbations on the order of 10-15% of signal strength were observed. While the magnitude of the voltage traces were distorted, key features such as shock impact could still be observed, and shock tracker gauges were still effective. The case of metallic barriers was also examined and similar effects observed. This study has indicated that while a coarse empirical correction is possible, uncertainty in the validity of the correction would preclude the use of dynamic metallic elements in experiments where high fidelity data is required.

Initiation of a passive explosive charge through a target with gaps

Experimental data on the measurement of time of passive explosive initiation by an active charge through an inert target with air gaps are presented. Two types of gaps are considered: perpendicular to the passive charge (a slit in the inert target) and parallel to the surface of the passive charge (between the inert target and the passive explosive). In the case of gaps parallel to the surface of the passive explosive charge, two-wave loading of the passive explosive charge created by impacts of thin plates, which are located on the surface of the main target on the side facing the passive explosive charge, is studied. Experimental data are analyzed by numerical calculations with the EGAK software on a Eulerian grid, and the instant of initiation is determined by a criterial parameter F, which is proportional to the energy released in shear strains, when a shock wave passes through the passive explosive charge.

Detecting fissionable materials in a variety of shielding matrices via delayed gamma and neutron photofission signatures—Part 2: Experimental results

Abstract Successful detection of fissionable material contained in a variety of matrices was demonstrated by photon active interrogation of fissionable and inert target materials. Samples were irradiated with pulsed 15 MeV photons generated by a LINAC and tungsten electron/photon converter, operating at 15 Hz. Matrix materials included air (no matrix), wood, water, and lead. A unique dual mode gamma/neutron detector was used to acquire data from both fission product gamma and fission product neutron emission. Neutron emission was recorded by detecting the 478 keV capture gamma from the 10 B (n,α) 7 Li reaction, generating a photopeak in the recorded gamma spectrum. Two signatures were found to correctly differentiate between the fissionable target ( 238 U) and inert targets (lead, steel, air, and beryllium), with substantial differences in delayed gamma and neutron signatures for fissionable and inert materials in all cases. The signatures are simple to compute and are not significantly affected by system variations or interferences expected during cargo scanning.

Target-Mediated Protection of Endogenous MicroRNAs in C. elegans

MicroRNAs (miRNAs) are tightly regulated through transcriptional and posttranscriptional mechanisms, including degradation by nucleases. Here, we report that in C. elegans, target mRNAs can protect their cognate miRNAs from degradation invivo. We show that the let-7(n2853) mutation destabilizes the mature let-7 miRNA by impairing this protection. Moreover, presence of a cognate target or depletion of the xrn-1 (XRN1) or xrn-2 (XRN2/Rat1p) exoribonucleases enforces accumulation of certain miRNA passenger (miR(∗)) strands. Thus, following biased miRNA strand loading into Argonaute, elimination of nonfunctional RNAs can further refine miRNA strand selection. Conversely, by aligning the levels of miRNAs with those of their targets, the opposing activities of mature miRNA degradation and target-mediated miRNA protection (TMMP) may enable dynamic expression of either mature strand ofa pre-miRNA, and evolution of miRNAs. Thus, it seems that mRNAs are more than inert targets and function with miRNAs in a network of mutual regulation.

(e, 2e) processes on Ne, Ar and Xe targets

Recently, there have been several attempts to explain the features of triple differential cross section (TDCS) for the (e, 2e) processes on inert targets Ne, Ar and Xe but there are still certain discrepancies in theoretical results and measurements, which require more theoretical efforts to understand the collision dynamics of these targets. We present in this paper the results of our modified distorted wave Born approximation (DWBA) calculation of TDCS for the ionization of Ne (2p), Ar (3p) and Xe (5p) targets. We modify the standard DWBA formalism by including the correlation-polarization potential (which is function of electron density) and compare our computed results with the available experimental and theoretical data. We observe that the polarization potential is able to improve the agreement with experimental results.

Apparatus for reactive cluster-surface studies

We present a new instrument that has been specifically designed for systematic studies of reactive cluster-surface collisions under well-defined ultrahigh-vacuum conditions. As a key feature, it incorporates a temperature-controlled, high-pressure cluster source with an unsurpassed pulse-to-pulse stability for the generation of weakly bound molecular aggregates. Impact processes can be investigated in two experimental configurations complementing one another: In the first, the exploration of intracluster reactions of accelerated, size-selected, positively or negatively charged cluster ions (1–100eV∕molecule) is accomplished, employing an inert target surface combined with angular-integrated ion detection. This arrangement uses a compact, homebuilt dual time-of-flight mass spectrometer with excellent mass resolution m∕Δm>2000 and postacceleration capabilities. In the second configuration, the detailed analysis of chemical reactions between neutral clusters and a well-defined single crystal at lower kinetic energies (0.01–1eV∕molecule) is possible. Here, the surface interaction of a seeded supersonic cluster beam is probed with angular-, time-, and velocity-resolved detection of neutral reaction products using a high-performance quadrupole mass spectrometer.

De que modo os textos oficiais prescrevem o trabalho do professor? Análise comparativa de documentos brasileiros e genebrinos

Neste artigo, são apresentados os resultados de análises de dois documentos produzidos por instâncias oficiais para orientar o trabalho dos professores no Brasil e na Suíça. De um lado, buscamos detectar as características da textualização da prescrição do trabalho do professor. Os resultados mostram que, além das propriedades comuns aos textos prescritivos (apagamento do enunciador, contrato de felicidade etc.), esses documentos se caracterizam por apresentar uma estrutura temática mais complexa, articulando um agir prescritivo, um agir-fonte e um agir - prescrito. Além disso, buscamos identificar as formas de construção do objeto da prescrição, o que permitiu verificar que, nos dois contextos, esse objeto se configura como uma proposta pedagógica global e não como trabalho concreto dos professores, não estando eles representados, nesses textos, como atores que têm uma real responsabilidade no desenvolvimento das propostas e, paralelamente, apresentando-se os alunos como alvos inertes. Esse trabalho também nos permitiu levantar algumas diferenças das formas de textualização das prescrições examinadas, diferenças essas que relacionamos ao contexto político-econômico dos dois países. Ao final, chegamos a questionamentos referentes às razões da não-consideração do trabalho efetivo dos professores nesse tipo de documento.

Improving the Effectiveness of Aerial Pesticide Sprays

Abstract Thirty-eight aircraft setups were submitted in order to have droplet size and drift analyses performed. Four of the eleven insecticides predicted Dv0.5s were in the 351–400 µm range. Seven of the herbicide setups had predicted Dv0.5s in the 205–250 µm range, while ten Dv0.5s were > 351 µm. Five of the ten predicted Dv0.5s were between 386 and 413 μm. Twelve different herbicides were reported as having been applied with aircraft setups that had predicted Dv0.5s between 386 and 413 µm. A summary of the prior swath deposit data indicated that the percent recovery generally increased as the Dv0.5 increased. The magnitudes of the deposits on inert targets and cotton leaves appeared to be about equal for a given Dv0.5. The correlation coefficient between the “percent of the spray volume in droplets ≤100 µm and ≤200 µm in diameter” was 0.983. This result is consistent with prior results and indicates that either 100 or 200 µm can be effectively used as the upper limit when studying the “small droplet” component in sprays. We found several similarities or differences in the “small droplet” components based on data from different atomization tests. According to one set of atomization models, agricultural aircraft will be limited to about 225 km/h (i.e., 140 mph) in order to produce a 400 µm Dv0.5 spray when using currently available nozzles and water plus one or more pesticides. The extremes of the predicted drift deposits for 38 agricultural aircraft setups were over 30-fold apart.

Rare earth tungsten bronzes: a new method of synthesis. Perspectives for their application as inert matrices for transmutation of long-life actinide elements

A new method of synthesis of oxide tungsten bronzes containing lanthanide ( Ln) Nd and Eu, based on thermal degradation of polyoxotungstate compounds, is proposed. The simplicity of the method allows to consider this class of compounds with chemical formula, Ln x WO 3, as potential inert target for incineration or transmutation of minor actinides, Am and Cm, in neutron reactors. Nd and Eu were used as analogues of transplutonium elements. Powder X-ray diffraction patterns of compounds synthesized reveal a cubic perovskite structure. The lanthanide content in bronzes was determined by optical spectroscopy analysis. The experimental density of the pressed bronze samples was estimated at 6.58 g cm −3, i.e., 89% of the crystallographic value. The thermal stability of the bronzes synthesized was checked up to 900°C in an inert atmosphere. Leaching tests were performed for europium bronzes in nitric acid solutions using luminescence technique.

Analytical model for the disruption of a metal jet penetrating detonating high explosive

We investigate the interaction of a constant-velocity, long-rod penetrator with detonating high explosive. An analytical flow-field model extending the Birkhoff model of inert target penetration is developed and compared with numerical simulations. We propose a rod-disruption model, discuss the effect of enhanced “anomalous” rod erosion on penetration history, and estimate the maximum coherent penetration depth. The model is extended to idealized stretching jet penetrators and its predictions are compared with jet-high-explosive (HE) interaction experiments. We predict a strong dependence of the high-explosive penetration on penetrator diameter and a very high “virtual” HE density in agreement with experimental observations.

Modulation of alveolar macrophage phagocytosis by leukotrienes is Fc receptor-mediated and protein kinase C-dependent.

We have previously established an important role for leukotrienes (LTs) in augmenting rat alveolar macrophage (AM) phagocytosis of Klebsiella pneumoniae opsonized with complete immune serum (IS), which contains the two well-known opsonins, immunoglobulin (Ig) G and complement (C). In this report, the specific opsonin requirements for LT modulation of AM phagocytosis and the dependence of this response on protein kinase (PK) C activity were investigated. Phagocytosis of K. pneumoniae opsonized with IS, non-immune serum, or heat-inactivated immune serum and of inert targets (IgG-opsonized fluorescent microspheres or C-opsonized sheep red blood cells) was examined. Inhibition of endogenous LT synthesis or action attenuated, whereas the addition of exogenous LTs augmented, phagocytosis only of targets opsonized with IgG. LTs had no effect on phagocytosis of C-opsonized or unopsonized targets. LTs did not affect adherence of IgG-opsonized targets, implying instead an enhancement of internalization. Macrophage internalization of phagocytic targets has previously been shown to require PKC activity. Pretreatment of AMs with the PKC inhibitors staurosporine or calphostin C, or with phorbol 12-myristate 13-acetate to deplete PKC, completely inhibited the ability of LTB(4) and largely inhibited the ability of LTC(4) to augment phagocytosis of IgG-opsonized microspheres. These results demonstrate that LT enhancement is confined to Fc receptor (FcR)-mediated phagocytosis. Moreover, PKC activation represents an important mechanism by which LTs promote FcR-mediated phagocytosis.

Solar production of carbon nanotubes; structure evolution with experimental conditions

In this work we report the production of carbon nanotubes by direct vapourization of graphite targets containing different couples of catalysts using a 2 kW solar furnace. With this small-scale experimental set-up we observed the evolution of the structure of the produced nanotubes with experimental conditions, pressure and flow rate of the inert gas (argon) and target composition. High pressure favours the production of bundles of single-wall nanotubes (SWNTs) and the purity of the produced material depends on the target temperature and the cooling rate of the vapour. We also discuss the influence of the target composition.