Interconnection Pattern Research Articles

Suffix Graph - An Efficient Approach for Network Motif Mining

Network motif is a pattern of inter-connections occurring in complex network in numbers that are significantly higher than those in similar randomized network. The basic premise of finding network motifs lie in the ability to compute the frequency of the subgraphs. In order to discover network motif, one has to compute a subgraph census on the original network that calculates the frequency of all the subgraphs of certain type. Then there is a need to compute the frequency of a set of subgraphs on the randomized similar network. The bottleneck of the entire motif discovery process is therefore to compute the subgraph frequencies and this is the core computational problem. The proposed work is to present the Suffix-Graph, a data structure that store graphs efficiently and to design an algorithm to retrieve subgraph efficiently that detects network motifs and apply them to transcriptional interactions in Escherichia coli.

Different levels of hyphal self-incompatibility modulate interconnectedness of mycorrhizal networks in three arbuscular mycorrhizal fungi within the Glomeraceae.

Arbuscular mycorrhizal fungi (AMF) live in symbiosis with most plant species and produce underground extraradical hyphal networks functional in the uptake and translocation of mineral nutrients from the soil to host plants. This work investigated whether fungal genotype can affect patterns of interconnections and structural traits of extraradical mycelium (ERM), by comparing three Glomeraceae species growing in symbiosis with five plant hosts. An isolate of Funneliformis coronatus consistently showed low ability to form interconnected ERM and self-incompatibility that represented up to 21% of hyphal contacts. The frequency of post-fusion self-incompatible interactions, never detected before in AMF extraradical networks, was 8.9%. In F. coronatus ERM, the percentage of hyphal contacts leading to perfect hyphal fusions was 1.2-7.7, while it ranged from 25.8-48 to 35.6-53.6 in Rhizophagus intraradices and Funneliformis mosseae, respectively. Low interconnectedness of F. coronatus ERM resulted also from a very high number of non-interacting contacts (83.2%). Such findings show that AMF genotypes in Glomeraceae can differ significantly in anastomosis behaviour and that ERM interconnectedness is modulated by the fungal symbiont, as F. coronatus consistently formed poorly interconnected networks when growing in symbiosis with five different host plants and in the asymbiotic stage. Structural traits, such as extent, density and hyphal self-compatibility/incompatibility, may represent key factors for the differential performance of AMF, by affecting fungal absorbing surface and foraging ability and thus nutrient flow from soil to host roots.

Latitudinal changes in the structure of marine food webs in the Southwestern Atlantic Ocean

Food chain length is known to increase with primary productivity, species richness and environmental stability. Primary productivity and species richness decrease poleward at mid and high latitudes in the Southwestern Atlantic, and hence food chain length of coastal ecosystems is expected to decrease poleward, unless seasonal changes in water temperature destabilise food webs at mid latitude. We used stable isotopes of carbon and nitrogen and SIBER (Stable Isotope Bayesian Ellipses in R) to determine the food chain length and other patterns of interconnections (i.e. topology) of coastal food webs from 3 contrasting regions: the temperate estuarine zone associated with the Rio de la Plata plume, the tidal zone off northern and central Patagonia, and the cold estuarine zone off southern Patagonia. Results indicate that food chain length decreases and trophic redundancy increases as latitude increases in all of the compartments of the food web considered. This is in agreement with results emerging from reconstructions of marine food web length during the late Holocene in the same regions, thus suggesting that they are not artefacts caused by the intense exploitation of top predators in the region since European settlement. Furthermore, differences in primary productivity do not fully explain the observed patterns. Instead, we argue that the latitudinal reduction of species diversity reported for the Southwestern Atlantic may be the primary reason for the observed pattern. The reduction in the diversity of forage fishes and squids at high latitude is proposed to result into a wasp-waist ecosystem, characterised by a high trophic redundancy at high trophic levels.

Fabrication and characterisation of field‐effect transistor‐type pressure sensor with metal–oxide–semiconductor/microelectromechanical systems processes

A microfield-effect transistor pressure sensor has been fabricated using conventional complementary metal–oxide–semiconductor process and microelectromechanical systems technology. The sensor platform consisted of a field-effect transistor (FET) device, electrode and Si diaphragm. Six lithography masks were prepared to develop the sensor fabrication process for arsenic ion implantation and diffusion, gate insulation layer (SiO2), gate metal, metal interconnection, passivation layer and bulk micromachining patterns. Pt/Ti thin films as the gate metal, interconnection and electrodes were deposited by DC/radio frequency magnetron sputtering, and patterned and etched using the reactive-ion etching process. The channel length and width between the source and the drain were approximately 10 and 5500 μm (W:L ratio = 550:1), respectively. The pressure sensor produced a change in current when pressure was applied to the sensing element and the electrical circuit was used to convert the current variation of the pressure sensor to a voltage output. The sensor response was measured using a voltage follower circuit to determine the change in drain current. The fabricated FET pressure sensor showed an almost perfect linear response for the applied pressure in the range 0–1200 kPa. The experimental results have shown that the pressure sensor had a sensitivity of 0.0096 μA/kPa.

A Novel FPGA Architecture Based on Ultrafine Grain Reconfigurable Logic Cells

In this paper, we investigate the opportunity brought by controllable-polarity transistors to design efficient reconfigurable circuits. Controllable-polarity transistors are devices whose polarity can be electrostatically programmed to be either n- or p-type. Such devices are used to build ultrafine grain computation cells. These cells are arranged into regular matrices, called MClusters , with a fixed and incomplete interconnection pattern, employed to minimize the reconfigurable interconnection overhead. We subsequently use them into field-programmable gate arrays (FPGAs). To assess this architectural scheme in an efficient and objective manner, we present a complete benchmarking tool flow and focus on the packing algorithm developed to handle the architecture. We finally perform the evaluation with widely used benchmark circuits. Leveraging the ultrafine grain cells compactness from a system-level perspective, we show that FPGAs exploiting MClusters demonstrate average savings of 43% and 23% in area and delay, respectively, as compared with the CMOS lookup table FPGA counterpart at 22-nm technological node.

Development of a Cu and W Compatible PERR Clean in BEOL Advanced Interconnect Patterning

Low-k integration for 22 nm ½ pitch technology requires continuous development of compatible cleaning processes. In this paper the use of acidic (pH:0.5-3) and alkaline (pH:8-13.5) aqueous based chemistries are demonstrated for the removal of post-etch residues after low-k etch and the aim to remove the TiN HM. These chemistries are also compatible with W and Cu, respectively. At the same time, no decrease in CD was observed, which means that the exposed low-k material was not attacked by the cleaning processes used.

Editorial: At the top of the interneuronal pyramid-calretinin expressing cortical interneurons.

Editorial: At the top of the interneuronal pyramid-calretinin expressing cortical interneurons.

A Grounded Theory of Veterans’ Experiences of Addiction-as-Occupation

This study examined how addiction emerges as an occupation in the lives of veterans. Its purpose was to facilitate better knowledge of how addiction is experienced as an occupation by this population, with the goal of destigmatizing addiction and paving the way for innovative ways to help people with addictions to build new occupational lives. Fifty-eight veterans diagnosed with a substance use disorder were recruited from a VA residential treatment center, of which 35 transcripts of the Indiana Psychiatric Illness Interview—a broad interview inquiring about participants’ life experiences—were randomly selected for grounded theory analysis following a 4-step coding procedure as outlined by Charmaz. Data revealed a five step occupational process: Being Initiated; Increasing Engagement; Establishing an Identity; Experiencing Discord and Defeat; and Finding Other Occupations. Addiction is discussed as a behavioral pattern, and the authors discuss how the use of new occupations may provide individuals with new patterns of organization, social interconnection, and identity development needed to sustain a move away from occupations of addiction.

Fault Tolerant Routing in Irregular ModifiedShuffle Network

Interconnection networks (IN) play very important role in various parallel processing applications. The connectivity pattern used in interconnection networks greatly determines the performance of the system. Multistage Interconnection Network is also an IN. The interconnection pattern used also determines the fault tolerance of the network. This paper introduces a new irregular fault tolerant multistage interconnection network named Irregular Modified Shuffle Network (IMSN). IMSN is analyzed in terms of fault tolerance and it has been observed that IMSN provides more alternate paths than existing networks such as Improved Four Tree Network (IFTN), Modified Alpha Network (MALN) and New Irregular Augmented Shuffle Network (NIASN).

Island intersections: Music and tourism on Fernando de Noronha, Brazil

This article examines the intersections between musical practices and tourism on the island of Fernando de Noronha, Brazil, and draws on field research undertaken by the authors in 2012 and 2014. Tourism currently represents the major source of income for island residents, and musical activity is largely oriented towards the tourism industry. Complex patterns of interconnectivity become apparent when one traces specific links between tourism and musical activity in relation to areas such as ‘covers’ versus original music, musical genre selection, live performance practices and recorded music. The research suggests that while the island’s largely self-contained musical environment fosters and rewards musical versatility, the tourism industry acts as a continuing impediment to the development of original music. This posits a conundrum to the island’s musicians, who need to find their own musical identity within a space that at the same time nurtures and curbs their musical development.

Network motifs emerge from interconnections that favour stability

Small distinctive patterns or ‘motifs’ are more prevalent in real systems than they are in randomly generated networks. It now seems that these motifs emerge naturally according to a principle that favours interconnections biased towards stability. The microscopic principles organizing dynamic units in complex networks—from proteins to power generators—can be understood in terms of network ‘motifs’: small interconnection patterns that appear much more frequently in real networks than expected in random networks1,2. When considered as small subgraphs isolated from a large network, these motifs are more robust to parameter variations, easier to synchronize than other possible subgraphs, and can provide specific functionalities3,4,5,6,7,8,9,10,11,12,13,14,15. But one can isolate these subgraphs only by assuming, for example, a significant separation of timescales, and the origin of network motifs and their functionalities when embedded in larger networks remain unclear. Here we show that most motifs emerge from interconnection patterns that best exploit the intrinsic stability characteristics at different scales of interconnection, from simple nodes to whole modules. This functionality suggests an efficient mechanism to stably build complex systems by recursively interconnecting nodes and modules as motifs. We present direct evidence of this mechanism in several biological networks.

Development of a Cu and W Compatible PERR Clean in BEOL Advanced Interconnect Patterning

In back-end of line (BEOL), the fluorinated polymer deposited on dielectric sidewalls during patterning [1,2] must be removed prior to the subsequent processing steps to achieve good adhesion and coverage of materials (metals) deposited in the etched features. Recent results clearly showed the presence of a highly fluorinated layer deposited on the trench sidewalls during the plasma etch using a fluorocarbon based plasma [3]. The challenges related to the wet cleaning of such structures is the efficient removal of post-etch residues (PERR) by showing high selectivity and compatibility towards a variety of new materials exposed to the wet clean chemistry [4]. This study focuses on the use of acidic (pH:0.5-3) and alkaline (pH:8-13.5) aqueous based chemistries that are compatible with W and Cu, respectively. A schematic overview of a BEOL interconnect structure used for the N10 node (22 nm ½ pitch) is shown in Figure 1. The low-k material and hardmask that are used in this work/stack structure are respectively an OSG type of low-k material with a target value of k=2.4 (~20% open porosity) and TiN. Compatibility tests of different alkaline and acidic chemistries have been performed and proven to be compatible with the OSG 2.4 low-k dielectric material. The alkaline chemistries were compatible with Cu, while the acidic chemistries were compatible with W metal. The etch rate behavior of TiN was also checked. Spectroscopic ellipsometry, capacitance measurements (to measure k-value) and sheet resistance measurements were performed for this study. The test vehicle used to check the cleaning efficiency is a 45 nm ½ pitch BEOL trench short loop structure (Figure 2). A layer of low-k dielectric (80 nm) was first deposited on a 300 mm Si wafer, followed by the deposition of a 30 nm oxide HM and TiN layer (~25 nm), and a BARC/193-nm photoresist layer. The TiN layer was first etched using a HBr/Cl2 plasma, followed by the Oxide HM and OSG etch using a C4F8/CF4-based plasma (TEL Tactras). All dies are fully covered with the same type of 45 nm trench structures. A large choice of techniques was selected to characterize the cleaning efficiency of this test vehicle.One of the techniques used to investigate the cleaning of the CFx residue and TiN removal efficiency, is X-ray photoelectron spectroscopy (XPS). From figure 3, it is clear that the alkaline mixture removes almost completely the TiN within 2 min and at the same time the fluorine-containing residues have almost disappeared. The acidic formulated mixture removed TiFx (684.5 eV) completely while the CFx (688.3 eV) residues were only partially removed. A comparison of these acidic and alkaline formulated mixtures with citric acid and a TMAH:H2O2 mixture respectively, results in various cleaning efficiency but none of the commodity chemistries achieved complete removal of CFx and TiFx. The result obtained on a real device structure of 22.5 nm ½ pitch confirms the good performance obtained on the 45 nm ½ pitch BEOL structure. The SEM images shown in Figure 4 give an evidence that both Cu (M1 level) and the porous dielectrics are fully compatible with the chemistry. Electrical results using this alkaline chemistry, show a very good yield for CD lines, MF structure, and via chains will also be presented and discussed. [1] Y. Furukawa et al., Microelectron. Eng., 70, 267 (2003). [2] Q. T. Le et al., J. Electrochem. Soc. 159, H208 (2012). [3] T. Mukherjee et al., ECS Solid-St. Lett. 2, N11-N14 (2013). [4] E.Kesters et al.,Solid State Phenomena, 219, 201 (2015). Figure 1

Stretchable Silver Nanowire-Elastomer Composite Microelectrodes with Tailored Electrical Properties.

We introduce a photolithography process compatible with soft and rigid substrates, enabling the fabrication of complex 3D interconnected patterns of silver nanowire (AgNW) networks embedded in polydimethylsiloxane (PDMS). Dimensions of the AgNW micropatterns are controlled within the film plane by photolithography, whereas thickness is controlled via a novel and uniform deposition technique using centrifugation. We report the first systematic characterization of the electromechanical properties of such microelectrodes with finest stretchable feature of 15 μm. We observe a geometry-dependent behavior of the gauge factor not only by changing the thickness of the microelectrodes, as it has been commonly reported so far, but also by varying their lateral dimensions. The presented nanocomposites exhibited sheet resistances down to 0.6 Ω/sq, gauge factors ranging from 0.01 to 100, and stretchability above 50% uniaxial strain. This versatile process allows for the production of highly sensitive strain sensors and robust high-density stretchable conductors on a wafer scale with direct implications in mass production of stretchable electronic devices.

A Hybrid Implicit–Explicit and Conformal (HIE/C) FDTD Method for Efficient Electromagnetic Simulation of Nonorthogonally Aligned Thin Structures

In a conventional finite-difference time-domain (FDTD) method, the computational cost increases as a grid spacing decreases because the number of unknowns increases and a time step size decreases to fulfill a numerical stability condition. Especially, it is inherently time-consuming to analyze thin structures such as a printed circuit board (PCB) and nonorthogonally aligned objects such as interconnection patterns on the PCB. In this paper, we propose an efficient electromagnetic simulation technique which is constructed by combining a hybrid implicit–explicit (HIE)-FDTD method and a conformal FDTD (CFDTD) method. The proposed technique can avoid the aforementioned problems by exploiting advantages of the HIE-FDTD and CFDTD methods. An example model of the interconnection pattern on the PCB is analyzed by the proposed and conventional methods, and we compare their accuracy and efficiency.

Dielectric-loaded surface plasmon polariton crossing waveguides using multimode interference.

A low-loss low-crosstalk multimode interference (MMI) crossing design for dielectric-loaded surface plasmon polariton waveguides (DLSPPWs), which are SiO2 stripes on Au films, is demonstrated numerically and experimentally. DLSPPWs are compatible with strong surface plasmon polariton (SPP) field confinement and maintain relatively low propagation losses. Unlike simpler crossings without MMI structures, low insertion loss of 0.65 dB and low crosstalk of -20.27 dB is confirmed numerically at a crossing angle of 10° when using tilted mirror-imaged MMI crossings. Similar insertion losses were also confirmed experimentally. The proposed structure will be beneficial for plasmonic device miniaturization and flexible patterning of optical interconnections.

Conceptualizing connections

Problems of climate change present new challenges for social theory. In this article we focus on the task of understanding and analyzing car dependence, using this as a case through which to introduce and explore what we take to be central but underdeveloped questions about how infrastructures and complexes of social practice connect across space and time. In taking this approach we work with the proposition that forms of energy consumption, including those associated with automobility, are usefully understood as outcomes of interconnected patterns of social practices, including working, shopping, visiting friends and family, going to school, and so forth. We also acknowledge that social practices are partly constituted by, and always embedded in material arrangements. Linking these two features together, we suggest that forms of car dependence emerge through the intersection of infrastructural arrangements that are integral to the conduct of many practices at once. We consequently explore the significance of professional – and not only ‘ordinary’ – practices, especially those of planners and designers who are involved in reconfiguring infrastructures of different scales, and in the practice dynamics that follow.

Hydrogen Bond Controlled Anti‐Aza‐Michael Addition: Diastereoselective Synthesis of Cyclobutene‐Containing Amino Acid Derivatives

AbstractThe chemical reactivity encoded in a highly substituted cyclobutane platform, which contains the (E,E)‐dimethyl 2,2′‐(cyclobutane‐1,2‐diylidene)diacetate structural motif, has been explored. The cyclobutane platform features a C2 axis of symmetry as well as a dense and interconnected ring functionalization pattern that is defined by two allylic/benzylic stereogenic oxygen‐containing quaternary centers with a 1,2‐trans configuration and two exocyclic acrylate chains. The reactivity profile of the cyclobutane platform is defined by two important kinetic barriers (steric strain and antiaromaticity) and two structure‐biased chemical processes: (1) the thermally‐driven [3,3] sigmatropic rearrangement between one of the two equivalent aryloates and the corresponding allylic acrylate chain and (2) the allylic nucleophilic substitution (SN2′ reaction) that involves a tertiary aryloate and its exocyclic double bond (anti‐Michael addition). The reaction of platform 3a with secondary amines delivered the corresponding cyclobutene amino acid derivatives 15a–15f in excellent yields (up to ≥95 %) and high diastereoselectivities (up to 99:1). Computational studies are described to rationalize the observed diastereoselectivity.

Exactly scale-free scale-free networks

Many complex natural and physical systems exhibit patterns of interconnection that conform, approximately, to a network structure referred to as scale-free. Preferential attachment is one of many algorithms that have been introduced to model the growth and structure of scale-free networks. With so many different models of scale-free networks it is unclear what properties of scale-free networks are typical, and what properties are peculiarities of a particular growth or construction process. We propose a simple maximum entropy process which provides the best representation of what are typical properties of scale-free networks, and provides a standard against which real and algorithmically generated networks can be compared. As an example we consider preferential attachment and find that this particular growth model does not yield typical realizations of scale-free networks. In particular, the widely discussed “fragility” of scale-free networks is actually found to be due to the peculiar “hub-centric” structure of preferential attachment networks. We provide a method to generate or remove this latent hub-centric bias—thereby demonstrating exactly which features of preferential attachment networks are atypical of the broader class of scale-free networks. We are also able to statistically demonstrate whether real networks are typical realizations of scale-free networks, or networks with that particular degree distribution; using a new surrogate generation method for complex networks, exactly analogous the widely used surrogate tests of nonlinear time series analysis.

Central dogma alchemy.

Central dogma alchemy.

Thermal-Aware Non-slicing VLSI Floorplanning Using a Smart Decision-Making PSO-GA Based Hybrid Algorithm

Floorplanning is an important physical design step in the ASIC design flow. It is the process of estimating the area to be occupied by various blocks in a layout together with a precise interconnection pattern. In this work, a smart decision-making hybrid particle swarm optimization-genetic algorithm that aims at reducing the area, wirelength, and hotspot by distributing the temperature evenly across the chip is presented. B*-tree is used to generate the initial floorplan and later a PSO-GA based hybrid algorithm is used to obtain an optimal placement solution. Temperature-driven floorplanning is considered at the perturbation stage to separate the hotspots, thereby reducing the average and maximum temperature. The experimental results of the proposed algorithm are compared with other stochastic algorithms using MCNC and Alpha processor floorplan benchmark circuits. The result shows that the proposed algorithm performs efficient floorplanning, with reduced average and peak temperature.