Selective Gating Research Articles

High-selectivity quantum pulse gating of photonic temporal modes using all-optical Ramsey interferometry

Temporal modes (TMs) are field-orthogonal broadband wave-packet states of light occupying a common frequency band, and they can encode information in a higher-dimensional alphabet compared to, say, photon polarization. The key—yet still missing—ingredient for the full implementation of a system deploying TMs is a highly selective quantum pulse gate—a multiplexing device that can route photonic packets according to their temporal shape with high temporal-mode discrimination and high efficiency, figures of merit that together we call high selectivity. Here, we present the first implementation of a highly selective quantum pulse gate. The method is a generalization of all-optical Ramsey interferometry, so far demonstrated only for continuous-wave light fields [Phys. Rev. Lett.117, 223601 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.223601]. As applied to temporal modes, we refer to the method as temporal-mode interferometry.

Structure and Mechanisms of Selectivity Gating, Inhibition and Activation in an Ion Channel

Structure and Mechanisms of Selectivity Gating, Inhibition and Activation in an Ion Channel

Contribution of intraoperative radiotherapy (IORT) for therapeutic de-escalation in early breast cancer: Report of a single institution's experience.

The spread of systematic screening and the emergence of oncoplastic techniques allow more breast conservative treatment associating lumpectomy and external beam radiation therapy. In order to furthermore facilitate the patient's treatment, intraoperative radiation therapy (IORT) has been developed. The oncological safety of this technique has been studied, and is considered acceptable. Many questions remain unsolved in regard of the toxicity of this procedure as well as the patient's selection criteria. In this study, we present the first results and complications rate of patients treated by IORT in a single French institution. Between 2012 and 2015, all patients with breast cancer treated in a one-step procedure associating lumpectomy and IORT were retrospectively included in a monocentric cohort. Acute and long-term toxicities were evaluated using CTCAE v4.0 classification. 280 breast cancers were treated using IORT procedure. Additional external beam radiation therapy was requested for 45.7% patients. The acute complications rate was 14.6%, with 5 surgical revisions needed (1.78%). With a median follow up of 911 days, the long-term grade-3 toxicity rate was 1.1%. The only risk factor for local fibrosis was external beam radiation therapy (EBRT) (OR = 1.99; IC95 [1.05-3.81], P = 0.036). Three patients (1.07%) were diagnosed with local recurrence. The results from this cohort confirm the low complication and recurrence rate of IORT procedure. A good selection of patients is necessary in order to lower the EBRT rate and allow therapeutic de-escalation. The classification of tumors into IHC subsets seems a good selection gate. Intraoperative radiation therapy appears to have a low toxicity rate with an acceptable local recurrence risk, and should therefore be considered as an option in the treatment of early breast cancer.

Bioinspired Heterogeneous Ion Pump Membranes: Unidirectional Selective Pumping and Controllable Gating Properties Stemming from Asymmetric Ionic Group Distribution.

The creation of an artificial solid-state ion pump that mimics the delicate ion transport behaviors of a biological protein-based ion pump is drawing more and more research attention due to its potential applications in energy conversion, biosensor, and desalination. However, the reported bioinspired double-gated ion pump systems are generally very primary and can only realize nonselective ion pumping functions with no directionality and uncontrollable ion gating functions, which are far from their biological counterparts. To make the bioinspired device "smart" in a real sense, the implementation of high-level selectivity and directionality in the ion pumping process, while achieving great controllability in the ion gating process, is a necessity. Here, we developed a bioinspired heterogeneous ion pump membrane by combining block copolymer membrane sacrificial coating and plasma grafting technique. The system has unidirectional selective ion pumping and controllable ion gating properties. The introduction of asymmetric ionic group distribution is the key reason for its novel transport behaviors. Such a heterogeneous ion pump could not only provide a basic platform that potentially sparks further efforts to simulate the smart ion transport processes in living bodies but also promote the application of artificial nanofluidic devices in energy conversion, water treatment, and biosensing.

Learning and transfer of working memory gating policies

Abstract knowledge about the tasks we encounter enables us to rapidly and flexibly adapt to novel task contexts. Previous research has focused primarily on abstract rules that leverage shared structure in stimulus-response (S-R) mappings as the basis of such task knowledge. Here we provide evidence that working memory (WM) gating policies – a type of control policy required for internal control of WM during a task – constitute a form of abstract task knowledge that can be transferred across contexts. In two experiments, we report specific evidence for the transfer of selective WM gating policies across changes of task context. We show that this transfer is not tied to shared structure in S-R mappings, but instead in the dynamic structure of the task. Collectively, our results highlight the importance of WM gating policies in particular, and control policies in general, as a key component of the task knowledge that supports flexible behavior and task generalization.

Protonation equilibria and pore-opening structure of the dual-histidine influenza B virus M2 transmembrane proton channel from solid-state NMR

The influenza A and B viruses are the primary cause of seasonal flu epidemics. Common to both viruses is the M2 protein, a homotetrameric transmembrane proton channel that acidifies the virion after endocytosis. Although influenza A M2 (AM2) and B M2 (BM2) are functional analogs, they have little sequence homology, except for a conserved HXXXW motif, which is responsible for proton selectivity and channel gating. Importantly, BM2 contains a second titratable histidine, His-27, in the tetrameric transmembrane domain that forms a reverse WXXXH motif with the gating tryptophan. To understand how His-27 affects the proton conduction property of BM2, we have used solid-state NMR to characterize the pH-dependent structure and dynamics of His-27. In cholesterol-containing lipid membranes mimicking the virus envelope, 15N NMR spectra show that the His-27 tetrad protonates with higher pKa values than His-19, indicating that the solvent-accessible His-27 facilitates proton conduction of the channel by increasing the proton dissociation rates of His-19. AM2 is inhibited by the amantadine class of antiviral drugs, whereas BM2 has no known inhibitors. We measured the N-terminal interhelical separation of the BM2 channel using fluorinated Phe-5. The interhelical 19F-19F distances show a bimodal distribution of a short distance of 7 Å and a long distance of 15-20 Å, indicating that the phenylene rings do not block small-molecule entry into the channel pore. These results give insights into the lack of amantadine inhibition of BM2 and reveal structural diversities in this family of viral proton channels.

The Role of Ion Exchange Membranes in Membrane Capacitive Deionisation.

Ion-exchange membranes (IEMs) are unique in combining the electrochemical properties of ion exchange resins and the permeability of a membrane. They are being used widely to treat industrial effluents, and in seawater and brackish water desalination. Membrane Capacitive Deionisation (MCDI) is an emerging, energy efficient technology for brackish water desalination in which these ion-exchange membranes act as selective gates allowing the transport of counter-ions toward carbon electrodes. This article provides a summary of recent developments in the preparation, characterization, and performance of ion exchange membranes in the MCDI field. In some parts of this review, the most relevant literature in the area of electrodialysis (ED) is also discussed to better elucidate the role of the ion exchange membranes. We conclude that more work is required to better define the desalination performance of the proposed novel materials and cell designs for MCDI in treating a wide range of feed waters. The extent of fouling, the development of cleaning strategies, and further techno-economic studies, will add value to this emerging technique.

New structure with SiO2-gate-dielectric select gates in vertical-channel three-dimensional (3D) NAND flash memory

This paper presents a novel vertical-channel three-dimensional (3-D) NAND flash structure with robust reliability. By employing a more reliable selector, the proposed structure overcomes the key drawback of the conventional 3-D NAND flash which is caused by charge storage in global select gate (GSG) and string select gate (SSG). Based on TCAD simulation, the conventional structure shows a threshold voltage shift of more than 1.5V, while the proposed structure is immune to this issue completely. Key parameters were analyzed to offer guidance on design and fabrication. Thickness of gate dielectric and thickness of SiO2 spacing layer beneath GSG are key parameters for the electrical property of select gate, and thus should be designed accurately.

Nanoscale Ion Pump Derived from a Biological Water Channel.

Biological molecular machines perform the work of supporting life at the smallest of scales, including the work of shuttling ions across cell boundaries and against chemical gradients. Systems of artificial channels at the nanoscale can likewise control ionic concentration by way of ionic current rectification, species selectivity, and voltage gating mechanisms. Here, we theoretically show that a voltage-gated, ion species-selective, and rectifying ion channel can be built using the components of a biological water channel aquaporin. Through all-atom molecular dynamics simulations, we show that the ionic conductance of a truncated aquaporin channel nonlinearly increases with the bias magnitude, depends on the channel's orientation, and is highly cation specific but only for one polarity of the transmembrane bias. Further, we show that such an unusually complex response of the channel to transmembrane bias arises from mechanical motion of a positively charged gate that blocks cation transport. By combining two truncated aquaporins, we demonstrate a molecular system that pumps ions against their chemical gradients when subject to an alternating transmembrane bias. Our work sets the stage for future biomimicry efforts directed toward reproducing the function of biological ion pumps using synthetic components.

Highly selective tungstate transporter protein TupA from Desulfovibrio alaskensis G20

Molybdenum and tungsten are taken up by bacteria and archaea as their soluble oxyanions through high affinity transport systems belonging to the ATP-binding cassette (ABC) transporters. The component A (ModA/TupA) of these transporters is the first selection gate from which the cell differentiates between MoO42−, WO42− and other similar oxyanions. We report the biochemical characterization and the crystal structure of the apo-TupA from Desulfovibrio desulfuricans G20, at 1.4 Å resolution. Small Angle X-ray Scattering data suggests that the protein adopts a closed and more stable conformation upon ion binding. The role of the arginine 118 in the selectivity of the oxyanion was also investigated and three mutants were constructed: R118K, R118E and R118Q. Isothermal titration calorimetry clearly shows the relevance of this residue for metal discrimination and oxyanion binding. In this sense, the three variants lost the ability to coordinate molybdate and the R118K mutant keeps an extremely high affinity for tungstate. These results contribute to an understanding of the metal-protein interaction, making it a suitable candidate for a recognition element of a biosensor for tungsten detection.

A macro SPICE model for 2-bits/cell split-gate flash memory cell

A SPICE macro-model constructed of 3-series-connected-transistors is proposed to describe the IV behavior of a 2-bits/cell split-gate flash memory cell for the first time. The model features 3 different memory states of the cell, namely ‘11′, ‘10′ and ‘01′ at different temperatures (−40 to 125°C). The cell is constructed of a select-gate transistor in the center with two symmetrical floating gate transistors in two sides. Using the method of capacitive coupling, the model describes the floating gate transistor with BSIM4 (level=54) model with the floating gate voltages changed into a linear combination of the control gate voltage and the select gate voltage. All the BSIM model parameter extraction strategies are applicable for the extraction flow. This novel 2-bits/cell split-gate flash memory cell is fabricated by a 90nm 4-poly 4-metal CMOS process of Shanghai Huahong Grace Semiconductor Manufacturing Corporation.

Sub-half-wavelength atom localization via two standing waves

We present a simple scheme of high-efficiency one-dimensional (1D) atom localization via manipulation of excited state population in a four-level inverted-Y atomic system. Because of the joint quantum interference induced by the two standing-wave fields, the 100% detecting probability of the atom in the subwavelength domain appears when the corresponding conditions are satisfied. The proposed scheme may open a promising way to achieve high-precision and high-efficiency 1D atom localization, which provides some potential applications to spatially selective single-qubit phase gate, entangling gates, and quantum error correction for quantum information processing.

Fish Gill Inspired Crossflow for Efficient and Continuous Collection of Spilled Oil.

Developing an effective system to clean up large-scale oil spills is of great significance due to their contribution to severe environmental pollution and destruction. Superwetting membranes have been widely studied for oil/water separation. The separation, however, adopts a gravity-driven approach that is inefficient and discontinuous due to quick fouling of the membrane by oil. Herein, inspired by the crossflow filtration behavior in fish gills, we propose a crossflow approach via a hydrophilic, tilted gradient membrane for spilled oil collection. In crossflow collection, as the oil/water flows parallel to the hydrophilic membrane surface, water is gradually filtered through the pores, while oil is repelled, transported, and finally collected for storage. Owing to the selective gating behavior of the water-sealed gradient membrane, the large pores at the bottom with high water flux favor fast water filtration, while the small pores at the top with strong oil repellency allow easy oil transportation. In addition, the gradient membrane exhibits excellent antifouling properties due to the protection of the water layer. Therefore, this bioinspired crossflow approach enables highly efficient and continuous spilled oil collection, which is very promising for the cleanup of large-scale oil spills.

Selective gating to vibrational modes through resonant X-ray scattering

The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.

Does the Superior Colliculus Control Perceptual Sensitivity or Choice Bias during Attention? Evidence from a Multialternative Decision Framework.

Attention involves the selection of the most relevant information for differential sensory processing and decision making. While the mechanisms by which attention alters sensory encoding (sensitivity control) are well studied, the mechanisms by which attention alters decisional weighting of sensory evidence (choice-bias control) are poorly understood. Here, we introduce a model of multialternative decision making that distinguishes bias from sensitivity effects in attention tasks. With our model, we simulate experimental data from four seminal studies that microstimulated or inactivated a key attention-related midbrain structure, the superior colliculus (SC). We demonstrate that the experimental effects of SC manipulation are entirely consistent with the SC controlling attention by changing choice bias, thereby shedding new light on how the brain mediates attention.

Modified and Mutant Porins in the Study on Molecular Basis of Non- Specific Diffusion.

Site-directed mutagenesis allows elucidation of the basic principles of the porin-driven membrane permeability and opens the possibility for the modulation of functional states of porin channels. The review is aimed to show the advantages of using mutant and chemically modified porins for obtaining detailed information about molecular mechanisms that underlie the non-specific transmembrane diffusion. We summarized data regarding the effects of the point substitutions and the external loop deletions on electrophysiological properties of general porins. The influence of charges inside the pore eyelet and the roles of external loops in ion conductance, ion selectivity, and voltage gating were described.

Label-free detection of EcoRI endonuclease activity via fluorescent DNA logic gate

A novel AND logic gate has been constructed for label-free detection of EcoRI endonuclease activity based on configuration conversion of hairpin probe with EcoRI and K+ as two inputs. An ingenious hairpin DNA (hpDNA) contained a G-rich loop as a quadruplex-forming oligomer and a long stem as the substrate of EcoRI. In the presence of EcoRI, the stem of hpDNA will be specifically cleaved by EcoRI. The shortened stem was opened by K+ to make G-rich DNA fold into a quadruplex. And then G-quadruplex interacts with N-methyl mesoporphyrin IX (NMM) which is a specific G-quadruplex binder, leading to a dramatic increase in fluorescence of NMM. Based on this, EcoRI activity can be easily and sensitively detected. The linear range is from 0.0001U/μL to 0.03U/μL, and the detection limit is 6.8×10−5U/μL. The high specificity was ensured due to the target-induced ingenious switch of DNA conformation. Compared with the previous reports, EcoRI activity can be conveniently and specifically detected in homogeneous solution by one step. No sophisticated experimental techniques or chemical modification of DNA is required. Therefore, it offers a cost-effective, highly sensitive and selective fluorescent AND logic gate platform for label-free bioanalysis.

Scalability conditions of the measuring points network in a production system using the RFID selective gate technology

The aim of paper is to present results of the research work in development conducted to define the scalability conditions for the measuring points network at production cells in the resistant to the electromagnetic disturbances system based on the patented selective RFID gate technology. This is a conceptual paper that includes research results of the selective RFID gate and its place in a production system, a communication model between two measuring points in a complex production system that was the input to do further analysis required to define its scalability conditions. The proposed approach provides the following results: order and speed of data reading from measurement points, data transfer between measurement points, access to database, communication between the database and measurement points, data archiving, procedures of changing the measurement point configuration in the system, including error handling and network re-configuration. It is believed that both practitioners and researchers will benefit from it.

Performance of nano-assembly logic gates with a DNA multi-hairpin motif.

DNA nano-assemblies have far-reaching implications for molecular computers. Boolean logic gates made from DNA respond to specific combinations of chemical or molecular inputs. In complex samples an assortment of other chemicals and molecules may interfere with the gate's recognition and response mechanisms. For logic gates to accept an increasing number of inputs, while maintaining selectivity, their design must only respond when specific input combinations are available simultaneously. Here we present proof-of-principle for a fluorescent-based nano-assembly logic gate for three inputs. Central to the gate's design is a multi-hairpin motif that distinguishes it from other works in this area. The multi-hairpin motif facilitates a larger and increasing number of inputs and a place to generate FRET-based signal enhancement. We will show the nano-assembly logic gate worked in aqueous buffer and in crude MCF-7 cell lysate. We will demonstrate the gate's selectivity against off-analyte cocktails. Finally, multi-hairpin motifs with different chemical and physical properties were evaluated to test their logic capabilities. Future work will demonstrate the gate's ability to visually identify specific combinations of oligonucleotides called small non-coding RNAs (ncRNAs) in cells. This nano-assembly logic gate for small ncRNA has far reaching cellular computation and single-cell analysis applicability. The gate can be used for basic cellular analysis, computing and observing the unique molecular expression patterns in tumor microenvironments, and advancing the field of therapeutics.

Controlling Working Memory Operations by Selective Gating: The Roles of Oscillations and Synchrony.

Working memory (WM) is a primary cognitive function that corresponds to the ability to update, stably maintain, and manipulate short-term memory (ST M) rapidly to perform ongoing cognitive tasks. A prevalent neural substrate of WM coding is persistent neural activity, the property of neurons to remain active after having been activated by a transient sensory stimulus. This persistent activity allows for online maintenance of memory as well as its active manipulation necessary for task performance. WM is tightly capacity limited. Therefore, selective gating of sensory and internally generated information is crucial for WM function. While the exact neural substrate of selective gating remains unclear, increasing evidence suggests that it might be controlled by modulating ongoing oscillatory brain activity. Here, we review experiments and models that linked selective gating, persistent activity, and brain oscillations, putting them in the more general mechanistic context of WM. We do so by defining several operations necessary for successful WM function and then discussing how such operations may be carried out by mechanisms suggested by computational models. We specifically show how oscillatory mechanisms may provide a rapid and flexible active gating mechanism for WM operations.