Junction Elements Research Articles

Superficial Wnt-Activated Melanocytic Nevi/Melanocytomas With a Junctional Component: A Case Series.

The conventional morphological characteristics of Wnt-activated deep penetrating/plexiform melanocytomas/nevi (DPN) are those of large spindled or epithelioid melanocytes with distinctive voluminous amphophilic cytoplasm, fine pigmented granules, and surrounding melanophages. The central molecular hallmark is the activation of the Wnt-pathway predominantly driven by mutations in the beta-catenin ( CTNNB1 ) gene. Although typically lacking a junctional component, a lesser-known superficial variant with a junctional component has been identified, which could potentially lead to diagnostic challenges. This study presents a cohort of 11 such cases displaying a junctional component of DPN from 10 patients (5 women and 5 men; age range: 27-78 years; median age: 51 years). The nevi were distributed as follows: 1 conjunctival, 1 scalp, 2 lower limb, and 6 truncal lesions. Eight cases were combined with a conventional nevus, 2 cases displayed pure DPN cytology exhibiting only a junctional element, and 9 cases exhibited some degree of lentiginous architecture. All cases demonstrated a low mitotic index (<1 mitosis/mm 2 ). Immunohistochemistry revealed positive BRAF V600E staining in 8 cases (8/11), whereas all cases tested (11/11) were PRAME negative. Nuclear beta-catenin and LEF1 staining was consistently strong and diffuse with DPN cytology (11/11), along with robust cyclin D1 staining in all cases tested (11/11). By contrast, all 9 conventional nevi showed an absence of nuclear beta-catenin staining (0/9) and weaker, mosaic-type LEF1 and cyclin D1 staining was observed. This study emphasizes the diagnostic challenge these nevi can pose in the absence of a conventional, deeper DPN component, which can potentially be misdiagnosed as melanoma.

Wattmeter based on tunnel-effect magnetoresistance sensor.

This work shows how the tunnel-effect based magnetoresistance (TMR) technology can be used as a competitive sensing method in electrical current and power processors. The sensor is arranged in a Wheatstone bridge topology, and each magnetoresistance was composed of a series connection of 360 magnetic tunnel junction elements with the following structure (thickness in nm): 100 SiO2/5 Ta/15 Ru/5 Ta/15 Ru/5 Ta/5 Ru/20 IrMn/2 CoFe30/0.85 Ru/2.6 CoFe40B20/1.2 MgO/2 CoFe40B20/0.21 Ta/4 NiFe/0.20 Ru/6 IrMn/2 Ru/5 Ta/10 Ru. First, the electrical and thermal characteristics of the sensor were evaluated by analyzing its response to DC current sweeps at various temperatures, controlled using a climatic chamber. Nominal values of current sensitivity S (0.324 mV/A), bridge output offset voltage Vo,s,o (-37.1 mV), bridge input resistance Rinp,bridge (0.958 kΩ), and their thermal behavior were obtained (0.0036 mV/A°C, 0.079 mV/°C, and -0.31 Ω/°C). Second, an instrumentation system is introduced to characterize the sensor, measuring its sensitivity to AC line currents from the mains up to 10Arms. Finally, an electronic wattmeter was developed showing the relevant quantities of its design. The circuit is able to interface a TMR Wheatstone bridge to an analog processor. Power and current measurements were obtained from a 150Vrms AC mains 1.5 kW load with resistive and capacitive components, achieving less than 1% deviation over the expected values. The circuit shown can be used to interface these signals to more complex smart digital engines with active or reactive energy processing capabilities, while providing inherent high voltage isolation, thanks to its TMR measurement technology.

Probability distribution of write failure in a memory cell array consisting of magnetic tunnel junction elements with distributed write error rates

Write failure (WF) is a major reliability issue for applications of magnetoresistive random access memory (MRAM), and much effort has been devoted to reducing the write error rate (WER), which is the probability of write failures of a memory cell. Recently, it was shown that the WER of MRAM obeys a skewed probability distribution even though the variation in material parameters obeys a normal distribution. However, little is known about the effect of WER distribution on WF in a memory cell array. Here, we study WF in a memory cell array consisting of magnetic tunnel junction elements with distributed WERs based on numerical simulations. We simulated Bernoulli trials of writing, assuming that the WER obeys a beta distribution. The results show that for typical writing patterns, WF in a memory cell array obeys a binomial distribution, with the mean of the WER as the probability of success. The statistical properties of WF in a memory cell array are not affected by the variance and skewness of the WER. The results provide a basic understanding of the statistical properties of WF in a memory cell array and will be useful for the development of computing systems that exploit erroneous memories.

Review and analysis of RC bridge half-joints strengthening techniques

In the past, the extensive use of the Gerber scheme in the construction of existing bridges has been justified by the advantages in terms of reduced stresses of the statically determined scheme and rapid execution. On the other hand, the presence of junction elements at the ends of the beams has over time led to a series of issues, especially related to their durability. In fact, the half-joints’ geometric configuration leads to the accumulation of degradation due to platform water seepage, resulting in the initiation of reinforcement corrosion, especially in the presence of chlorides derived from de-icing salts used in the winter season. Furthermore, these elements have been designed for lower loads than those specified in current regulations, and therefore, they may be in critical conditions where the strength reduction, due to existing degradation, can lead to failure. For these reasons, local repairs and/or strengthening interventions are necessary to ensure adequate levels of safety. Within this study, the topic of reinforcing half-joints is addressed, first by describing the currently available intervention techniques in the literature, and then by deepening an intervention technique based on the use of external post-tensioned bars, applied to a case study bridge through nonlinear numerical simulations. These analyses allow quantifying the performance improvements of this technique under both service conditions and ultimate loads, considering various parameters, including the pre-stress value applied to the external tendons and different scenarios of chloride-induced corrosion.

Modular photoorigami-based 4D manufacturing of vascular junction elements.

Four-dimensional (4D) printing, combining three-dimensional (3D) printing with time-dependent stimuli-responsive shape transformation, eliminates the limitations of the conventional 3D printing technique for the fabrication of complex hollow constructs. However, existing 4D printing techniques have limitations in terms of the shapes that can be created using a single shape-changing object. In this paper, we report an advanced 4D fabrication approach for vascular junctions, particularly T-junctions, using the 4D printing technique based on coordinated sequential folding of two or more specially designed shape-changing elements. In our approach, the T-junction is split into two components, and each component is 4D printed using different synthesized shape memory polyurethanes and their nanohybrids, which have been synthesized with varying hard segment contents and by incorporating different weight percentages of photo-responsive copper sulfide-polyvinyl pyrrolidone nanoparticles. The formation of a T-junction is demonstrated by assigning different shape memory behaviors to each component of the T-junction. A cell culture study with human umbilical vein endothelial cells reveals that the cells proliferate over time, and almost 90% of cells remain viable on day 7. Finally, the formation of the T-junction in the presence of near-infrared light has been demonstrated after seeding the endothelial cells on the programmed flat surface of the two components and fluorescence microscopy at day 3 and 7 reveals that the cells adhered well and continue to proliferate over time. Hence, the proposed alternative approach has huge potential and can be used to fabricate vascular junctions in the future.

Nanojunctions: Specificity of Ca2+ signaling requires nano-scale architecture of intracellular membrane contact sites

Spatio-temporal definition of Ca2+ signals involves the assembly of signaling complexes within the nano-architecture of contact sites between the sarco/endoplasmic reticulum (SR/ER) and the plasma membrane (PM). While the requirement of precise spatial assembly and positioning of the junctional signaling elements is well documented, the role of the nano-scale membrane architecture itself, as an ion-reflecting confinement of the signalling unit, remains as yet elusive. Utilizing the Na+/Ca2+ Exchanger-1 / SR/ER Ca2+ ATPase-2-mediated ER Ca2+ refilling process as a junctional signalling paradigm, we provide here the first evidence for an indispensable cellular function of the junctional membrane architecture. Our stochastic modeling approach demonstrates that junctional ER Ca2+ refilling operates exclusively at nano-scale membrane spacing, with a strong inverse relationship between junctional width and signaling efficiency. Our model predicts a breakdown of junctional Ca2+ signaling with loss of reflecting membrane confinement. In addition we consider interactions between Ca2+ and the phospholipid membrane surface, which may support interfacial Ca2+ transport and promote receptor targeting. Alterations in the molecular and nano-scale membrane organization at organelle-PM contacts are suggested as a new concept in pathophysiology.

The simulation of ice jam profiles in multi-channel systems using a one-dimensional network model

This paper presents a new modelling method for simulating ice jam profiles in channel networks, implemented in the University of Alberta's public-domain hydrodynamic and river ice process model, River1D. The method includes provisions for handling junctions when solving the ice jam stability equation within a channel network. At junction elements, the solution of the ice jam stability equation is calculated as a function of the junction water discharge ratio. The model was first compared to a series of idealized test cases from a previous study that sought to investigation the impact of islands on ice jam profiles. Seventeen tests were performed in rectangular channels with islands of different length. The results from River1D agreed well with the results from the previous study, showing the same stage reduction along the length of the island and minimum depth at the upstream end of the island. The model was then applied to the Hay River Delta in the Northwest Territories of Canada. The model was first validated for open water scenarios (with surveyed data and 2D modelling results) and was then used to simulate a series of ice jam profiles and validated using data collected within the Hay River Delta during the 2009 breakup. Using just a single value of 0.055 for the under ice jam roughness, the modelled ice jam profiles agreed favourably with the surveyed levels. However, the model did have a tendency to under predict levels in the East Channel for the profile that was collected after an upstream ice jam release wave had passed through the delta. When jam consolidation was considered in the simulation, the model was able to more accurately simulate the surveyed levels. The model results suggest that ice jamming conditions during the 2009 breakup reduced the percentage of flow entering the East Channel compared to open water conditions.

Research on high-pressure hose with repairing fitting and influence on energy parameter of the hydraulic drive

Reliability and maintenance analysis of transport machines hydraulic drives, basically focused to power units: pumps, cylinders etc., without taking in to account junction elements. Therefore, this paper proposes a research analysis on high-pressure hoses and junctions during technical maintenance. Comparative analysis of fluid behavior and energy efficiency inside non-repaired and repaired high-pressure hoses is presented in this research. Theoretical and experimental research results for hydraulic processes inside high-pressure hose is based on the numerical simulations using Navier–Stokes equations and experimental measurement of fluid flow pressure inside high-pressure hoses. Research of fluid flow dynamics in the hydraulic system was made with main assumptions: system flow rate in the range from 5 to 100 l/min, diameter of the hoses and repairing fitting are 3/8". The pressure drops, power losses, flow coefficients at non-repaired and after maintenance hose was obtained as a result. Simulation results were verified by running physical experiments to measure the pressure losses.

12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) induces cell growth and improves barrier function through BLT2 interaction in intestinal epithelial Caco-2 cell cultures

12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) is an unusual product of the cyclooxygenase pathway that is an endogenous ligand of the low-affinity receptor for leukotriene 4 (LTB4), BLT2. Recent findings suggested that BLT2 possibly plays an important role in the healing of intestinal lesions and the regulation of barrier function. Here, we studied the role of 12-HHT on intestinal epithelial cell growth and the paracellular permeability of intestinal epithelium using Caco-2 cell cultures as experimental model. Our results demonstrated that 12-HHT stimulates intestinal epithelial Caco-2 cell growth through 12-HHT-BLT2-p38-PKC axis and improves paracellular permeability in differentiated Caco-2 cell cultures through the regulation of tight junction elements such as myosin light chain phosphorylation through 12-HHT-BLT2-p38-PKC-MYPT1 axis. Thus, 12-HHT-BLT2 interaction can be involved in intestinal epithelial cell growth and consequently in the epithelium regeneration/repair processes, together with an interesting improvement on the paracellular permeability. These effects appoint that 12-HHT/BLT2 axis may be a suitable strategy for treating wound healing epithelium and barrier-disrupted intestinal processes.

Magnetoresistive sensor detectivity: A comparative analysis

We report on the noise performance characteristics of magnetic sensors using both magnetic tunnel junction (MTJ) and giant magnetoresistance (GMR) elements. Each sensor studied has a notably different noise and detectivity. Of the sensors we measured, those based on GMR multilayers have the lowest noise and detectivity. However, the GMR sensor also has a significantly smaller linear range. To make a direct comparison between sensors, we scale the linear operating ranges of each sensor to be the same. This is the phenomenological equivalent of modifying the flux concentration. Upon scaling, the low frequency detectivity of the tunneling magnetoresistance (TMR) sensors becomes essentially equal to that of the GMR sensor. Using the scaling approach, we are able to place the detectivity in the context of other key parameters, namely, size and power consumption. Finally, we use this technique to examine the upper limit for magnetoresistive sensor performance based on a notional MTJ sensor using present record setting TMR values.

Carbon Nanotube Film/Silicon Heterojunction Photodetector for New Cutting-Edge Technological Devices

Photodetector (PD) devices based on carbon nanotube/n-silicon heterojunction (NSH) have been realized, with a linear response in a large optical power range, proving competitive performances with respect to a recent nanostructure-based detector and those currently available on the market. The core of these devices is a thin semi-transparent and conductive single-walled carbon nanotubes film with a multitask role: junction element, light absorber and transmitter, photocarrier transporting layer, and charge collector. The PD exhibits rise times of some nanoseconds, detecting light from ultraviolet (240 nm) to infrared (1600 nm), and external quantum efficiency reaching 300% in the VIS spectra region.

INCREASING RADIATION RESISTANCE OF MEMORY DEVICES BASED ON AMORPHOUS SEMICONDUCTORS

A memory cell structure is proposed that uses a Schottky barrier thin film transistor based on an amorphous semiconductor as a junction element, and a chalcogenide glassy semiconductor film as a switching element. A physical storage cell model has been developed. The dependence of the transistor and memory cell parameters on the dose of neutron flux and γ - quanta was investigated. It is shown that when the dose of neutron irradiation is changed, the steepness of the drain-gate characteristic (DGC) decreases by 10% at a dose of the order of 1015 n/s, at the same time, the transfer coefficient of the bipolar n-p-n transistor decreases by 20% already at doses of 1013 n/s, indicating a significant increase in the radiation resistance of the proposed memory cell. In the case of irradiation with γ - quanta in the range up to 2.6 MRad, the steepness of the DGC of the proposed structure changes by only 10%. When used as an isolation element, a field-effect transistor with an insulated gate, the slope of the DGC is reduced by 50%. It is shown that the current of recording information of the proposed structure when changing the dose of γ - quantum flux to 2.6 MRad changes by about 10%, at the same time, in the case of using a field-effect transistor with an isolated cover, the information recording current changes by 50%. The study of the dependence of the gate current on the dose of γ – quanta is showed. When the radiation dose changes from 0 to 2.6 MRad, the gate current changes only by 10%, which indicates the high resistance of the proposed structure to the action of permeable radiation. Also, studies of the dependence of the conductivity of single-crystal semiconductors on the radiation dose ɣ by quanta and neutron flux show that a significant increase in the specific resistivity of AS occurs at doses 2-3 orders of magnitude larger than in the case of single-crystal n-type conductivity semiconductors.

Indium Tin Oxide optical access for magnetic tunnel junctions in hybrid spintronic–photonic circuits

The all-optical magnetization reversal of magnetic layers, by picosecond optical pulses, is of particular interest as it shows the potential for energy-efficient and fast magnetic tunnel junction (MTJ) elements. This approach requires memory elements that are optically and electronically accessible, for optical writing and electronic read-out. In this paper, we propose the integration of indium tin oxide (ITO) as a transparent conducting electrode for magnetic tunnel junctions in integrated spintronic–photonic circuits. To provide light with sufficient energy to the MTJ free layer and allow electrical read-out of the MTJ state, we successfully integrated indium tin oxide as a top transparent electrode. The study shows that ITO film deposition by physical vapor deposition with conditions such as high source power and low O2 flow achieves smooth and conductive thin films. Increase in grain size was associated with low resistivity. Deposition of 150 nm ITO at 300 W, O2 flow of 1 sccm and 8.10−3 mbar vacuum pressure results in 4.8 × 10−4 Ω.cm resistivity and up to 80% transmittance at 800 nm wavelength. The patterning of ITO using CH4/H2 chemistry in a reactive ion etch process was investigated showing almost vertical sidewalls for diameters down to 50 nm. The ITO based process flow was compared to a standard magnetic tunnel junctions fabrication process flow based on Ta hard mask. Electrical measurements validate that the proposed process based on ITO results in properties equivalent to the standard process. We also show electrical results of magnetic tunnel junctions having all-optical switching top electrode fabricated with ITO for optical access. The developed ITO process flow shows very promising initial results and provides a way to fabricate these new devices to integrate all-optical switching magnetic tunnel junctions with electronic and photonic elements.

Analogue gravity on a superconducting chip.

We describe how analogues of a Hawking evaporating black hole as well as the Unruh effect for an oscillatory, accelerating photodetector in vacuum may be realized using superconducting, microwave circuits that are fashioned out of Josephson tunnel junction and film bulk acoustic resonator elements. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.

Observation of domain wall creation and propagation using the magnetic fixed region with a synthetic antiferromagnetic configuration

Spin-memristors using a magnetic domain wall (DW) have drawn attention as possible candidates for an essential element of the analogue neuromorphic device. In this study, we fabricated a DW type three-terminal magnetic tunneling junction element with a magnetic fixed region having a synthetic antiferromagnetic configuration. The DW creation and subsequent measurement of current-induced domain wall motion were investigated. The magnetic DW was successfully introduced through a simple operation using the magnetic fixed region as a DW injector. This element structure will be one of the key technologies for realizing an array level production of the spin-memristor.

Modeling of Flexible Beam Networks and Morphing Structures by Geometrically Exact Discrete Beams

Abstract We demonstrate how a geometrically exact formulation of discrete slender beams can be generalized for the efficient simulation of complex networks of flexible beams by introducing rigid connections through special junction elements. The numerical framework, which is based on discrete differential geometry of framed curves in a time-discrete setting for time- and history-dependent constitutive models, is applicable to elastic and inelastic beams undergoing large rotations with and without natural curvature and actuation. Especially, the latter two aspects make our approach a versatile and efficient alternative to higher-dimensional finite element techniques frequently used, e.g., for the simulation of active, shape-morphing, and reconfigurable structures, as demonstrated by a suite of examples.

Radiation-Resistant Memory Device Based on Chalcogenide Glassy Semiconductor

A memory cell structure is proposed that uses a Schottky barrier thin film transistor based on an amorphous semiconductor as a junction element, and a chalcogenide glassy semiconductor film as a switching element. A physical storage cell model has been developed. The dependence of the transistor and memory cell parameters on the dose of neutron flux and γ - quanta was investigated. It is shown that when the dose of neutron irradiation is changed, the steepness of the drain-gate characteristic (DGC) decreases by 10% at a dose of the order of 1015 n/s, at the same time, the transfer coefficient of the bipolar n-p-n transistor decreases by 20% already at doses of 1013 n/s, indicating a significant increase in the radiation resistance of the proposed memory cell. In the case of irradiation with γ - quanta in the range up to 2.6 Mrad, the steepness of the DGC of the proposed structure changes by only 10%. When used as an isolation element, a field-effect transistor with an insulated gate, the slope of the DGC is reduced by 50%, that it is bad result. It is shown that the current of recording information of the proposed structure when changing the dose of γ - quantum flux to 2.6 Mrad changes by about 10%, at the same time, in the case of using a field-effect transistor with an isolated cover, the information recording current changes by 50%. The study of the dependence of the gate current on the dose of γ – quanta is showed. When the radiation dose changes from 0 to 2.6 Mrad, the gate current changes only by 10%, which indicates the high resistance of the proposed structure to the action of permeable radiation.

Cryogenic Memory Architecture Integrating Spin Hall Effect based Magnetic Memory and Superconductive Cryotron Devices

One of the most challenging obstacles to realizing exascale computing is minimizing the energy consumption of L2 cache, main memory, and interconnects to that memory. For promising cryogenic computing schemes utilizing Josephson junction superconducting logic, this obstacle is exacerbated by the cryogenic system requirements that expose the technology’s lack of high-density, high-speed and power-efficient memory. Here we demonstrate an array of cryogenic memory cells consisting of a non-volatile three-terminal magnetic tunnel junction element driven by the spin Hall effect, combined with a superconducting heater-cryotron bit-select element. The write energy of these memory elements is roughly 8 pJ with a bit-select element, designed to achieve a minimum overhead power consumption of about 30%. Individual magnetic memory cells measured at 4 K show reliable switching with write error rates below 10−6, and a 4 × 4 array can be fully addressed with bit select error rates of 10−6. This demonstration is a first step towards a full cryogenic memory architecture targeting energy and performance specifications appropriate for applications in superconducting high performance and quantum computing control systems, which require significant memory resources operating at 4 K.

Femtosecond light pulse response of photodetectors based on Graphene/n-Si heterojunctions

To take advantage of the graphene appealing electronic properties, in this work we present a photodetector (PD) based on graphene/n-silicon heterojunction (GSH). In this device, graphene acts as light transmitter, counter electrode junction element and photocarrier collector. The photodetector has been provided with metal contacts allowing either photovoltaic or photoconductive operation mode. We investigated the response of GSH PD to a 35-femtosecond laser pulse. In the photovoltaic configuration, the PD exhibits rise times of some tens of nanoseconds, detecting light from ultraviolet (275 nm) to infrared (1150 nm). In photoconductive mode applying a gate voltage VG, the external quantum efficiency hugely increases, from a value of 2% up to 200%. Together with the observation of a rise time, that decreases down to a minimum value of about 1 ns, this makes our device even more competitive and comparable with commercial photodetectors.

High write endurance up to 1012 cycles in a spin current-type magnetic memory array

We demonstrated high write endurance of up to 1012 cycles with a pulse write current of 10 ns in a spin current-type (SC) single magnetic tunnel junction (MTJ) element and 8×8 memory array. Furthermore, we demonstrated an accelerated test of failure elements by increasing the write current density. According to cross-sectional TEM images of the failure MTJ elements, one of the failure models is caused only on the spin orbit torque (SOT) line by electrical-open and electrical-short conditions. We concluded that SC-MTJ will have strong write endurance against a high write current if the SOT-line is improved. SC-MTJ offers an alternative to spin transfer torque (STT)–MTJ as a high write endurance magnetic memory.