Active Building Block Research Articles

An active inductor employing a new four terminal floating nullor transconductance amplifier (FTFNTA)

ABSTRACTIn this scientific study, a new analog active building block named as four terminal floating nullor transconductance amplifier (FTFNTA) is implemented. The FTFNTA design offers a combined essence of both traditional four terminal floating nullor (FTFN) and an operational transconductance amplifier (OTA). The FTFNTA design is extended for the design of a lossless floating and grounded inductor simulator with few passive components. In addition, the performance and usefulness of the proposed inductor topology are also expanded for active filter applications: higher-order Butterworth high-pass filter and current mode multifunction filter. The functionality of the CMOS-based FTFNTA is integrated with a 0.18 µm Taiwan Semiconductor Manufacturing Company (TSMC) CMOS technology. Moreover, the FTFNTA is also realised using the current feedback operational amplifier (CFOA/AD844) and OTA (OTA/CA3080) of a commercially available IC to test the viability of the proposed inductor design. Finally, an application based on the inductor topology and its impedance characteristics are well analysed via PSPICE simulation.

2-Phenylbenzothiophene-based liquid crystalline semiconductors

We report herein the design and synthesis of some novel liquid crystalline semiconductors constructed from a biologically and pharmacologically active building block molecule, namely 6-methoxy-2-(4-methoxyphenyl)benzo[b]thiophene, presenting efficient luminescence and medium charge mobility rate. A first series of mesogenic 2-phenylbenzothiophene derivatives (nPBT) was simply and rapidly obtained in good yields by successive demethylation/alkylation reactions of the available methoxy precursor. The further stepwise oxidations moreover resulted in two new sets of the corresponding sulfoxide (nPBTO) and sulfone (nPBTO2) derivatives, respectively, that were also mesomorphic. The liquid crystalline behaviour was comprehensively characterized by DSC, POM and SAXS: all compounds exhibit smectic-like behaviour in agreement with their calamitic shape. More specifically, mesogens nPBT showed a SmA phase, with in addition, a higher ordered smectic phase at lower temperature. As for the oxidized mesogens, they displayed a SmA phase only, and over particularly large temperature ranges for the nPBTO with longer chain lengths (n ≥ 8). The photo-physical properties have also been studied both in solution and thin films, and the molecules were found to display strong absorption in the UV/vis domain and intense luminescence in the range of 400–650 nm (yellowish green light) in high quantum yields (up to 62%). Both absorption and luminescence were also found to be affected by the oxidation of the benzothiophene moiety. Finally, the semi-conducting behaviour of three PBT compounds in the various mesophases was investigated by photocurrent TOF technique. Hole mobility rates of ca. 4 × 10−3 cm2 V−1 s−1 were measured in the lower temperature ordered mesophase for all of them, with the best performances (temperature range and mobility values) however obtained for the shortest homolog (n = 6). With such highly reasonable mesomorphic, light-emitting and semiconducting functional features, as well as being cheap and easy to synthesize and to process, these materials become very attractive and may be incorporated into various kinds of electronic devices (OFET and OLED).

Practical realisation of an active acoustic metamaterial building block

Acoustic metamaterials (AMMs) have been demonstrated as an alternative approach to achieving high levels of noise control using an array of subwavelength unit cells, exhibiting behaviour not seen in conventional materials. Specifically, active AMMs offer the potential for greater levels of broadband wave manipulation, tunability and adaptability. However, determining the optimal control source strengths that achieve broadband negative effective material properties is not straightforward. This study presents a practical method of designing an active system that directly minimises the effective material properties. The optimal control source strengths required for both single monopole and single dipole control sources to minimise the effective bulk modulus and the effective density respectively have been calculated via an optimisation procedure. The ability of the proposed active AMM building blocks to achieve broadband negative effective material properties is tested experientially through offline simulations using measured frequency responses. Interestingly, the optimised single monopole and optimised single dipole control sources achieve broadband negative effective bulk modulus and density respectively. However, when combining the two optimised control sources, the active control system only achieves bands of double negativity and, thus, only exhibits bands of negative refractive index.

Plasmonic Nanoparticle-Interfaced Lipid Bilayer Membranes.

Plasmonic nanoparticles are widely exploited in diverse bioapplications ranging from therapeutics to biosensing and biocomputing because of their strong and tunable light-matter interactions, facile and versatile chemical/biological ligand modifications, and biocompatibility. With the rapid growth of nanobiotechnology, understanding dynamic interactions between nanoparticles and biological systems at the molecular or single-particle level is becoming increasingly important for interrogating biological systems with functional nanostructures and for developing nanoparticle-based biosensors and therapeutic agents. Therefore, significant efforts have been devoted to precisely design and create nano-bio interfaces by manipulating the nanoparticles' size, shape, and surface ligand interactions with complex biological systems to maximize their performance and avoid unwanted responses, such as their agglomeration and cytotoxicity. However, investigating physicochemical interactions at the nano-bio interfaces in a quantitative and controllable manner remains challenging, as the interfaces involve highly complex networks between nanoparticles, biomolecules, and cells across multiple scales, each with a myriad of different chemical and biological interactions. A lipid bilayer is a membrane made of two layers of lipid molecules that forms a barrier around cells and plays structural and functional roles in diverse biological processes because they incorporate and present functional molecules (such as membrane proteins) with lateral fluidity. Plasmonic nanoparticles conjugated on lipid membranes provide reliable analytical labels and functional moieties that allow for studying and manipulating interactions between nanoparticles and molecules with single-particle resolution; they also serve as efficient tools for applying optical, mechanical, and thermal stimuli to biological systems, which stem from plasmonic properties. Recently, new opportunities have emerged by interfacing nanoparticle-modified lipid bilayers (NLBs) with complex systems such as molecular circuits and living systems. In this Account, we briefly review how plasmonic properties can be beneficially harnessed on lipid bilayer membranes to investigate the structures and functions of cellular membranes and to develop new platforms for biomedical applications. In particular, we discuss the versatility of supported lipid bilayers (SLBs), which are planar lipid bilayers on hydrophilic substrates, as dynamic biomaterials that provide lateral fluidity and cell membrane-like environments. We then summarize our efforts to create a quantitative analytical platform utilizing nanoparticles as active building blocks and SLBs as integrative substrates. Through this bottom-up approach, various functionalized nanoparticles have been introduced onto lipid bilayers to render nanoparticle-nanoparticle, nanoparticle-lipid bilayer, and biomolecule-lipid bilayer interfaces programmable. Our system provides a new class of tools for studying thermodynamics and kinetics in complex networks of nanostructures and for realizing unique applications in biosensing and biocomputing.

A New Low-Voltage Low-Power Dual-Mode VCII-Based SIMO Universal Filter

In this paper, a new low-voltage low-power dual-mode universal filter is presented. The proposed circuit is implemented using inverting current buffer (I-CB) and second-generation voltage conveyors (VCIIs) as active building blocks and five resistors and three capacitors as passive elements. The circuit is in single-input multiple-output (SIMO) structure and can produce second-order high-pass (HP), band-pass (BP), low-pass (LP), all-pass (AP), and band-stop (BS) transfer functions. The outputs are available as voltage signals at low impedance Z ports of the VCII. The HP, BP, AP, and BS outputs are also produced in the form of current signals at high impedance X ports of the VCIIs. In addition, the AP and BS outputs are also available in inverting type. The proposed circuit enjoys a dual-mode operation and, based on the application, the input signal can be either current or voltage. It is worth mentioning that the proposed filter does not require any component matching constraint and all sensitivities are low, moreover it can be easily cascadable. The simulation results using 0.18 μm CMOS technology parameters at a supply voltage of ±0.9 V are provided to support the presented theory.

Foundry Photonic Process Extension With Bandgap Tuning Using Selective Area Growth

The extension of a photonic integrated circuit foundry process flow is proposed by integrating selective area growth to enable bandgap tuning for each individual active building block. The process adaptations and the impact on performance are reviewed in terms of morphology requirements and topology reduction. This platform extension enables bandgap tuning for a set of active devices to cover the wavelength range from 1453 to 1651 nm. Integration is demonstrated in combination with active–passive butt-joint technology to create the most comprehensive range of generic building blocks. Performance and limitations of the range of achievable band edges within the same monolithic wafer are studied for amplifiers and extended cavity lasers.

Realization of Voltage-mode Multifunction Biaquadratic Filter Using Minimum Number of Active Element

The realization of voltage-mode multifunction biquadratic filter has been presented in this research contribution. The proposed circuit contains three input voltage nodes and one output voltage node. The structure of proposed filter is simple consisting of one modified current controlled current conveyor transconductance amplifier (M-CCCCTA) as active building block with one resistor and two capacitors. With electronically controllable property of M-CCCCTA, the parameters, natural frequency (ω0) and quality factor (Q) are electronically controlled by changing the external DC bias currents of the M-CCCCTA. The tuning characteristic of Q is also done without effect the w0. In the same circuit construction, five second order filter responses, all-pass, high-pass (HP), band-reject (BR), low-pass (LP) and band-pass (BP) functions are obtained. The output filter responses are obtained with applying appropriate input voltage to input node without the matching condition of active and passive elements. The performances of the proposed biquadratic filter have been verified through Pspice simulation in TSMC 0.25 μm CMOS technology parameters.

A novel CNFET based tunable memristor emulator

This paper presents a novel carbon nanotube field effect transistor (CNFET) based memristor emulator circuit. The proposed memristor emulator circuit utilizes voltage differencing transconductance amplifier (VDTA) as an active building block. The emulator circuit employs two VDTAs, two grounded resistors, one grounded capacitor and one four-quadrant analog multiplier. The working concept along with the detailed derivation of the mathematical model of the circuit has been discussed analytically and numerically to confirm the operation of the circuit. The operation of the proposed emulator circuit, as governed by the established equations, has been verified by performing simulations using 32-nm Stanford CNFET model. Further, the robustness of the emulator circuit has been investigated by subjecting it to process and temperature variations. Variability analyses reveals significant tolerance towards aforementioned fluctuations in parameters.

Regioselective C3-H Trifluoromethylation of 2 H-Indazole under Transition-Metal-Free Photoredox Catalysis.

Trifluoromethyl-substituted heteroarenes are biologically active compounds and useful building blocks. In this sequence, we have developed a visible-light-promoted regioselective C3-H trifluoromethylation of 2 H-indazole under metal-free conditions, which proceeds via a radical mechanism. The combination of photocatalysis and hypervalent iodine reagent provides a practical approach to a library of trifluoromethylated indazoles in 35-83% yields.

Phosphorylation of the Bruchpilot N-terminus in Drosophila unlocks axonal transport of active zone building blocks.

Protein scaffolds at presynaptic active zone membranes control information transfer at synapses. For scaffold biogenesis and maintenance, scaffold components must be safely transported along axons. A spectrum of kinases has been suggested to control transport of scaffold components, but direct kinase-substrate relationships and operational principles steering phosphorylation-dependent active zone protein transport are presently unknown. Here, we show that extensive phosphorylation of a 150-residue unstructured region at the N-terminus of the highly elongated Bruchpilot (BRP) active zone protein is crucial for ordered active zone precursor transport in Drosophila Point mutations that block SRPK79D kinase-mediated phosphorylation of the BRP N-terminus interfered with axonal transport, leading to BRP-positive axonal aggregates that also contain additional active zone scaffold proteins. Axonal aggregates formed only in the presence of non-phosphorylatable BRP isoforms containing the SRPK79D-targeted N-terminal stretch. We assume that specific active zone proteins are pre-assembled in transport packages and are thus co-transported as functional scaffold building blocks. Our results suggest that transient post-translational modification of a discrete unstructured domain of the master scaffold component BRP blocks oligomerization of these building blocks during their long-range transport.

Ultrasound one pot synthesis of fused quinazolinones and quinazolinediones, screening and molecular docking study as phosphodiesterase 7A inhibitors.

Phosphodiesterase 7A enzyme is one the most recent targets for designing potent anti-inflammatory agents with minimal side effects. Quinazolinones are unique building blocks of wide biological activities. Different Quinazolinones were reported to act as Phosphodiesterase 7A inhibitors anti-inflammatory particularly against choronic inflammation and autoimmune disease. Ultrasound is a green convenient method for synthesis of different heterocyclic ring system that is advantageous in terms of yield and reaction time. Ultrasound was used for one pot synthesis of 3-substituted 6-aryl-dihydroisoindolo[2,1-a]quinazoline-5,11-diones and 3-Aryl quinazoline-2,4(1H,3H)-diones. Seventeen compounds were synthesized in good yields. The synthesized compounds were inspected for in vitro inhibitory activity against phosphodiesterase7A enzyme. Molecular docking was used to study the mode of interaction of all the synthesized compounds into the enzyme phosphodiesterase 7A binding site. Five compounds showed high inhibitory activity of enzyme Phosphodiesterase 7A at micro-molar level compared to reference drug. The compounds showed good recognition at the enzyme binding site in the molecular docking. There was a good agreement between the molecular docking and the biological screening results.

Generalized two-port network based fractional order filters

This paper proposes a general prototype fractional order filter based on a two-port network concept with four external impedances. Three induced classifications from the general prototype are extracted with one, two and three external impedances, achieving ten possible generalized topologies. The external impedances are fractional-order elements and resistors. There are forty-six filters divided into twenty-two and twenty-four different general fractional filters of order “α” and order “α + β”, respectively. The general transfer functions, the necessary network conditions, and the critical frequencies are presented for each topology in terms of the transmission matrix parameters of a general two-port network and the fractional order parameters. These aspects add extra degrees of freedom, which increase the design flexibility and controllability; it is up to the designer to select any network suitable for his application. Six special cases of two-port networks based on the second generation current conveyor (CCII) active building block are synthesized to realize the proposed topologies. CCII family has four members that yield twenty-four different transmission matrices, resulting 480 filters. Due to the large number of the introduced filters, selected cases are investigated in detail to validate the theoretical findings through numerical simulations, Spice simulations, and experimental results.

Label-Free SERS Detection of Bovine Serum Albumin Protein Based on Au@Ag Core/Shell Nanobricks

In this study, a simple yet effective protein detection method was established by using bimetallic Au@Ag core-shell nanobrick as SERS active building blocks. The Au@Ag core-shell nanobrick is synthesized by well-defined ‘two-step’ growing method, enabling uniform and controllable silver shell growth on the surface of the gold nanorods induced by surfactant replacement. The thickness of the silver shell can be programmably adjusted by controlling the amount of silver nitrate in the system, which in turn realized the controllable adjustment of the optical properties of Au@Ag core-shell nanobrick. We selected bovine serum albumin as a model protein and established a highly-sensitive assay for label-free SERS detection of protein. The detection limit can reach to as low as 0.5 μg/mL, enabling promising avenue for its clinical application in ultrasensitive biomarker detection.

Cyclization of mercaptopyrimidine derivative: a facile synthetic approach for condensed pyrimidines

In the present study, we report the synthesis of different condensed pyrimidine derivatives by the exploitation of addition reactions to π-deficient systems or active methylene building blocks. For instance, the Diels–Alder reaction of pyrimidinethione 1 and benzalacetophenone 2 yielded pyridopyrimidine 5 (Scheme 1). On the other hand, the Michael addition of active methylene containing compounds to 1 produced derivatives 8, 10, 11, 12 and 14 (Scheme 2). The alkylation of 1 by ethylchloroacetate yielded 16. Furthermore, a triazinoquinazoline 19 was obtained through the cyclic condensation reaction of 1 with benzilmonohydrazone (Scheme 3). All reactions proceeded in good to moderate yields and the resulting compounds were characterized by different spectroscopic techniques.

Voltage-mode third-order quadrature sinusoidal oscillator using VDIBAs

A third-order quadrature sinusoidal oscillator (TOQSO) is proposed employing two voltage differencing inverting buffered amplifiers (VDIBAs), three grounded capacitors and a resistor. The proposed TOQSO enjoys electronically tunable, non-interactive condition and frequency control. The TOQSO uses all grounded capacitors, which is suitable for IC implementation. Moreover, the internal CMOS realization of VDIBA is possibly the simplest among all recently introduced new active building blocks. SPICE simulation results have been provided to support the validity of proposed TOQSO using TSMC 0.18 µm technology.

Biocatalytic synthesis of lactones and lactams.

Cyclic esters and amides (lactones and lactams) are important active ingredients and polymer building blocks. In recent years, numerous biocatalytic methods for their preparation have been developed including enzymatic and chemoenzymatic Baeyer–Villiger oxidations, oxidative lactonisation of diols, and reductive lactonisation and lactamisation of ketoesters. The current state of the art of these methods is reviewed.

Voltage difference transresistance amplifier and its application: floating FDNR simulator circuit

ABSTRACTIn this article, a new active building component with electronically tunable transresistive block, voltage difference transresistance amplifier, and its floating frequency dependent negative resistor simulator circuit application is presented. The simulator circuit is shown to operate using single active building block with two grounded passive components, to be electronically tunable over its value which is controlled by an independent current source, not to require any conditions of component matching and to have good sensitivity performance with respect to tracking errors. To examine functionality of the design, a CRD band-pass filter example is given.Numerous simulation program with integrated circuit emphasis (SPICE) simulations are performed and depicted through the article to verify validity of the study. Taiwan semiconductor manufacturing company (TSMC) 0.18 µm complementary metal oxide semiconductor technology parameters are used through simulations.

Current and transimpedance mode instrumentation amplifier using a single new active component named CDTRA

In this study, both current and transimpedance mode instrumentation amplification operations are met through a new active building block proposal, namely Current DifferencingTransresistance Amplifier block, CDTRA. In order to regard CDTRA as an instrumentation amplifier (IA), two grounded passive resistors are needed. Passive resistors together with electronically tunable transresistance parameter of active block, rm, set versatility over gain tunability for instrumentation amplifier. Proposed active block is current input, current/voltage output design. It has low impedance input, high impedance for current output, and low impedance for voltage output respectively. Since this particular IA is based on CDTRA, then it inherits these electrical characteristics fully. Numerous SPICE simulations are performed through the paper to verify validity of the study. TSMC 0.18 µm CMOS technology parameters are utilized through simulations. Experimental work is performed for the proposed IA circuit.

Analysis and design of a new COA-based current-mode instrumentation amplifier with robust performance against mismatches

In this paper, analysis and design of a new current-mode instrumentation amplifier (CMIA) circuit is presented. The proposed circuit employs two Current Operational Amplifiers (COA) as active building blocks, one resistor and two transistors operating as variable resistors to electronically control the differential-mode gain. The main feature of the proposed CMIA is that unlike most previously reported CMIAs, its CMRR has negligible sensitivity to mismatches. In addition, in the proposed circuit both active building blocks operate in negative feedback loop which results in an overall enhanced performance. SPICE simulation results using 0.18 μm TSMC CMOS parameters and supply voltage of ±0.9 V show a constant CMRR of about 51 dB regardless of mismatches and wide bandwidth ranging from 14.8 MHz to about 3 MHz for differential-mode gains between 3 and 18 dB, respectively.

Reversibly Bound Kinesin-1 Motor Proteins Propelling Microtubules Demonstrate Dynamic Recruitment of Active Building Blocks.

Biological materials and systems often dynamically self-assemble and disassemble, forming temporary structures as needed and allowing for dynamic responses to stimuli and changing environmental conditions. However, this dynamic interplay of localized component recruitment and release has been difficult to achieve in artificial molecular-scale systems, which are usually designed to have long-lasting, stable bonds. Here, we report the experimental realization of a molecular-scale system that dynamically assembles and disassembles its building blocks while retaining functionality. In our system, filaments (microtubules) recruit biomolecular motors (kinesins) to a surface engineered to allow for the reversible binding of the kinesin-1 motors. These recruited motors work to propel the cytoskeletal filaments along the surface. After the microtubules leave the motors behind, the trail of motors disassembles, releasing the motors back into solution. Engineering such dynamic systems may allow us to create materials that mimic the way in which biological systems achieve self-healing and adaptation.