Terminal Blocks Research Articles

Evaluation of a proposed chair with an arm support for wiring terminal blocks on a vertical plane.

To reduce the muscular exertion of an operator wiring terminal blocks on a vertical plane, a chair with a unique back that can be used as a back support or arm support is proposed in this study. A digital version of the chair was first developed based on anthropometric data and tested with a digital anthropometric subject using the Jack software before the physical chair was developed. To evaluate the effects of the physical chair, an experiment of wiring terminal blocks was conducted with 12 subjects to test whether the use of the arm support can reduce muscular exertion. The results showed that (1) exertion on the anterior deltoid, upper trapezium, and erector spinae muscles decreased with decrease in terminal block height; (2) using the arm support reduced exertion on the anterior deltoid and upper trapezium muscles; and (3) the subjects reported less self-perceived fatigue in the wrist, elbow, and shoulder regions when the arm support was used. These results confirm that the proposed chair can reduce muscular workload in the shoulder muscle over a proper range of working heights. However, using the arm support may restrict certain working postures and lead to force generation in upper extremity muscles.

An improved 1-φ rectifier system using fuzzy logic control with 3-φ variable frequency drive

A 3-Φ VFD steam fed from a 1-Φ AC supply. To stop more stresses in the components within the drive and within the input supply, the drive output power should be restricted. To beat this problem, several VFD makers decided that drive to be de-rated. As often as possible, the drive’s output frequency is limited, supported the dc voltage ripple hence the DC capacitors aren’t overstressed. Through the tradional technique decrement of strain within the DC Capacitors, it doesn’t consider the stresses in other parts of the drive, particularly the diodes at the input and terminal blocks of input. During this paper, brand new fuzzy controller based technique for the protection of the drive the motor current with FLC is projected. The motor current is shown to possess info relating the stresses in numerous elements of the VFD together with the diodes at the input, terminal blocks of the input, and therefore the Dc capacitors. The o/p power is projected to be restricted by decreasing the o/p frequency supported the avg and ripple abundancy of the quadrature axis current rather than the dc voltage ripple. To prove this conception, a comparison is made between fuzzy logic controller based technique employing a less power VFD fed from a 1-Φ ac, and the conventional dc voltage ripple based frequency technique.

Effect of growing glycosylation extents on the self-assembly and active targeting in vitro of branched poly(ethylene oxide)-poly(propylene oxide) block copolymers

In this work, we investigated for the first time the effect of the gradual increase of the glycosylation extent on self-assembly of a highly hydrophilic four-arm poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymer, Tetronic® 1107. After the initial characterization that confirmed the chemical modification, the effect of the glycosylation extent on the critical micellar concentration (CMC) was characterized by dynamic light scattering. Conjugation of a d-gluconic acid (the oxidized form of d-glucose) in each terminal block resulted in a dramatic decrease of the CMC by 8- to 11-fold. In contrast, further glycosylation with lactobionic acid (an oxidized form of lactose) and gluconic acid+lactobionic acid had a detrimental effect due to the increase of the amphiphile hydrophilicity. Then, glycosylated PMs successfully encapsulated the tyrosine kinase inhibitor imatinib, increasing its aqueous solubility by up to 100 times. Glycosylated polymeric micelles showed very good cell compatibility in the Rh30 cell line. These cells are a model of rhabdomyosarcoma, a tumor that overexpresses glucose transporter-1 that is targeted by the sugar residues. Finally, we compared the cytotoxicity of free and nanoencpasulated imatinib to inhibit the proliferation a in which tyrosine kinase signaling promotes growth and glucose transporter-1 (GLUT-1; for which glucose is the main substrate) is overexpressed. Nano-encapsulation reduced the inhibitory concentration 50 (IC50) from 27.80±3.70μM for the free drug to 0.33±0.01μM for the PMs modified with gluconic acid, representing an 84-fold increase in the anti-cancer efficacy in vitro. Overall results highlight the potential of tuned glycosylation to increased the micellization trend of these amphiphiles and, at the same time, increase accumulation in cells that overexpress sugar receptors.

Cylindrical Micelles with “Patchy” Coronas from the Crystallization-Driven Self-Assembly of ABC Triblock Terpolymers with a Crystallizable Central Polyferrocenyldimethylsilane Segment

Solution self-assembly of a series of linear ABC triblock terpolymers with a central crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming “B” block and terminal polystyrene (PS) and poly(methyl methacrylate) (PMMA) “A” and “C” blocks has been investigated. Three PS-b-PFS-b-PMMA triblock terpolymers with different block ratios (1, 3.6:1.0:4.7; 2, 7.0:1.0:6.9; and 3, 1.1:1.0:1.4) but with similar degrees of polymerization for the central PFS block were prepared through a combination of living anionic and atom-transfer radical polymerization techniques, together with azide/alkyne “click” chemistry. Cylindrical micelles with a crystalline PFS core were formed in solvents selective for the terminal PS and PMMA blocks. In ethyl acetate, a slightly more selective solvent for the PS block, cylinders with significant microphase separation within the corona in the dry state were observed on the basis of TEM analysis. The use of acetone, which is slightly more selective for the PMMA block than the PS blo...

Supramolecular Multiblock Copolymers Featuring Complex Secondary Structures.

This contribution introduces main-chain supramolecular ABC and ABB'A block copolymers sustained by orthogonal metal coordination and hydrogen bonding between telechelic polymers that feature distinct secondary structure motifs. Controlled polymerization techniques in combination with supramolecular assembly are used to engineer heterotelechelic π-sheets that undergo high-fidelity association with both helical and coil-forming synthetic polymers. Our design features multiple advances to achieve our targeted structures, in particular, those emulating sheet-like structural aspects using poly(p-phenylenevinylene)s (PPVs). To engineer heterotelechelic PPVs in a sheet-like design, we engineer an iterative one-pot cross metathesis-ring-opening metathesis polymerization (CM-ROMP) strategy that affords functionalized Grubbs-II initiators that subsequently polymerize a paracyclophanediene. Supramolecular assembly of two heterotelechelic PPVs is used to realize a parallel π-sheet, wherein further orthogonal assembly with helical motifs is possible. We also construct an antiparallel π-sheet, wherein terminal PPV blocks are adjacent to a flexible coil-like poly(norbornene) (PNB). The PNB is designed, through supramolecular chain collapse, to expose benzene and perfluorobenzene motifs that promote a hairpin turn via charge-transfer-aided folding. We demonstrate that targeted helix-(π-sheet)-helix and helix-(π-sheet)-coil assemblies occur without compromising intrinsic helicity, while both parallel and antiparallel β-sheet-like structures are realized. Our main-chain orthogonal assembly approach allows the engineering of multiblock copolymer scaffolds featuring diverse secondary structures via the directional assembly of telechelic building blocks. The targeted assemblies, a mix of sequence-defined helix-sheet-coil and helix-sheet-helix architectures, are Nature-inspired synthetic mimics that expose α/β and α+β protein classes via de novo design and cooperative assembly strategies.

Supramolecular self-assembly of an ABA-Triblock bottlebrush polymer: Atomic-force microscopy visualization of discrete oligomers

A novel ABA-triblock bottlebrush polymer (PS-PD-PS), whose terminal PS block and central PD block were densely grafted with polystyrene and poly[2-(dimethylamino)ethyl methacrylate], respectively, on polynorbornene backbones was synthesized by three mutually orthogonal types of controlled polymerization. Dynamic light-scattering analysis revealed that in polar solvents such as tetrahydrofuran/water (99:1, v/v), PS-PD-PS self-assembled into oligomeric-to-polymeric aggregates through solvophobic interaction of the PS block. The size of these aggregates depended on the concentration of PS-PD-PS and on the polarity of the solvent. Atomic-force microscopy (AFM), showed that single molecules of PS-PD-PS adopted a dumbbell shape in which the three blocks in PS-PD-PS could be clearly distinguished. In AFM samples prepared under appropriate conditions, PS-PD-PS self-assembled into discrete oligomeric aggregates with well-defined structure, including linear and cyclic dimers, a tadpole-like trimer, and higher oligomers. The arrangement and junctions of the monomeric units could be clearly visualized at a single-molecular level.

Role of Hydrophobic/Aromatic Residues on the Stability of Double-Wall β-Sheet Structures Formed by a Triblock Peptide.

Bioinspired self-assembling peptides serve as powerful building blocks in the manufacturing of nanomaterials with tailored features. Because of their ease of synthesis, biocompatibility, and tunable activity, this emerging branch of biomolecules has become very popular. The triblock peptide architecture designed by the Hartgerink group is a versatile system that allows control over its assembly and has been shown to demonstrate tunable bioactivity. Three main forces, Coulomb repulsion, hydrogen bonding and hydrophobicity act together to guide the triblock peptides' assembly into one-dimensional objects and hydrogels. It was shown previously that both the nanofiber morphology (e.g., intersheet spacing, formation of antiparallel/parallel β-sheets) and hydrogel rheology strictly depend on the choice of the core residue where the triblock peptide fibers with aromatic cores in general form shorter fibers and yield poor hydrogels with respect to the ones with aliphatic cores. However, an elaborate understanding of the molecular reasons behind these changes remained unclear. In this study, by using carefully designed computer based free energy calculations, we analyzed the influence of the core residue on the formation of double-wall fibers and single-wall β-sheets. Our results demonstrate that the aromatic substitution impairs the fiber cores and this impairment is mainly associated with a reduced hydrophobic character of the aromatic side chains. Such weakening is most obvious in tryptophan containing peptides where the fiber core absorbs a significant amount of water. We also show that the ability of tyrosine to form side chain hydrogen bonds plays an indispensable role in the fiber stability. As opposed to the impairment of the fiber cores, single-wall β-sheets with aromatic faces become more stable compared to the ones with aliphatic faces suggesting that the choice of the core residue can also affect the underlying assembly mechanism. We also provide an in-depth comparison of competing structures (zero-dimensional aggregates, short and long fibers) in the triblock peptides' assembly and show that by adjusting the length of the terminal blocks, the fiber growth can be turned on or off while keeping the nanofiber morphology intact.

Photoresponsive polyelectrolyte/mesoporous silica hybrid materials with remote-controllable ionic transportation

We present a comprehensive research on the photo-induced multi-responsibility of azobenzene(azo) diblock copolymer (BPC) grafted from the surface of mesoporous silica as a light-triggered and controllable ions transport system. The surface-initiated RAFT method was used to grow sequentially a first poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block serving as an inner layer for the pH and thermal responsibility and a second terminal azo block functionalizing the trans-cis photoisomerization to control the closure or opening of the brushes in water. We show that the ions conductivity of hybrid system could be controlled by the second block switchable between the coil-recoil brush chain states in response to pH or temperature change or exposure to light. It was confirmed a suitable composition ratio of azo BPC brushes could significantly influence the hydrophilicity and polarity of the out layer with light, resulting the protonation or gelation of PDMAEMA block. For example, the Ru(NH3)63+ cations as probing ions was employed to prototyping the controlled permselectivity triggered by the UV light exposure. This kind of hybrid material is particularly interesting in the versatile utility for drug delivery, separating, biomimic sensor and so on.

Intracellular Delivery of Colloidally Stable Core-Cross-Linked Triblock Copolymer Micelles with Glutathione-Responsive Enhanced Drug Release for Cancer Therapy.

Design and development of amphiphilic block copolymer-based nanocarriers exhibiting enhanced colloidal stability upon dilution in the blood and cellular glutathione-responsive rapid drug release is highly desired for tumor-targeting chemotherapy. Herein, we report a novel ABA-type triblock copolymer consisting of a hydrophilic central poly(ethylene glycol) block and two terminal hydrophobic blocks of a polymethacrylate having pendant disulfides (PHMssEt), thus PHMssEt-b-PEG-b-PHMssEt (ssTP). Aqueous self-assembly and the following disulfide-exchange reaction of the resulting ssTP allow for formation of core-cross-linked micelles (CCMs) through the formation of new disulfide linkages, retaining enhanced colloidal stability in physiological conditions and in the presence of proteins. Further, they exhibit reduction-responsive enhanced release of encapsulated drugs in response to cellular concentrations of glutathione in cancer cells, confirmed by dynamic light scattering and spectroscopic analysis. Combined with these results, in vitro (cells) and in vivo (mouse model) biological results suggest that ssTP-based CCMs are effective candidates as intracellular nanocarriers targeting tumors for cancer therapy.

Electronically Tunable Quadrature Sinusoidal Oscillator with Equal Output Amplitudes during Frequency Tuning Process

A new configuration of voltage-mode quadrature sinusoidal oscillator is proposed. The proposed oscillator employs two voltage differencing current conveyors (VDCCs), two resistors, and two grounded capacitors. In this design, the use of multiple/dual output terminal active building block is not required. The tuning of frequency of oscillation (FO) can be done electronically by adjusting the bias current of active device without affecting condition of oscillation (CO). The electronic tuning can be done by controlling the bias current using a digital circuit. The amplitude of two sinusoidal outputs is equal when the frequency of oscillation is tuned. This makes the sinusoidal output voltages meet good total harmonic distortions (THD). Moreover, the proposed circuit can provide the sinusoidal output current with high impedance which is connected to external load or to another circuit without the use of buffer device. To confirm that the oscillator can generate the quadrature sinusoidal output signal, the experimental results using VDCC constructed from commercially available ICs are also included. The experimental results agree well with theoretical anticipation.

A new topological structure for the Langevin-type ultrasonic transducer

In this paper, a new topological structure for the Langevin-type ultrasonic transducer is proposed and investigated. The two cylindrical terminal blocks are conically shaped with four supporting plates each, and two cooling fins are disposed at the bottom of terminal blocks, adjacent to the piezoelectric rings. Experimental results show that it has larger vibration velocity, lower temperature rise and higher electroacoustic energy efficiency than the conventional Langevin transducer. The reasons for the phenomena can be well explained by the change of mass, heat dissipation surface and force factor of the transducer. The proposed design may effectively improve the performance of ultrasonic transducers, in terms of the working effect, energy consumption and working life.

Getting the Most from a Variable Frequency Drive: The Optimal Way to Improve Lifetime and Reliability

When using a three-phase variable frequency drive (VFD) powered from a single-phase ac source, the drive's output power has to be limited to prevent higher component stresses in it and in the input power system. To address this issue, many VFD manufacturers derate the drive. Typically, based on the dc-bus-voltage ripple, the output frequency of the drive is limited so that the capacitors are not overstressed. This method does not take into account the stresses in other VFD components, especially the input diodes and terminal blocks. In this article, a new method of protecting the drive using the motor q-axis current is proposed. The motor q-axis current has information that is relevant to the stresses in various parts of the VFD, including the input diodes, input terminal block, and the dc bus capacitors. The output power can be limited by reducing the output frequency based on the average and ripple amplitude of the q-axis current instead of the dc-bus-voltage ripple. The traditional dc-bus-voltage-ripple-based fold-back method is experimentally compared with the proposed method using a VFD fed from a single-phase ac source to prove the concept.

A Self-adaptive Access Selection Algorithm for Cognitive Networks Based on Fuzzy Neural Networks

In order to improve the performance of access network and terminal services, an intelligent access selection algorithm based on fuzzy neural networks is presented. By establishing fuzzy neural networks that meets specific needs, network bandwidth, delay, load balancing at network side and moving speed at terminal-side are considered as access factors determined the pros and cons for access network. Then, fuzzification of access factors above by fuzzy logic is done, and fuzzy neural networks are employed to inference. At last, the optimal access network can be selected. To improve the performance of parameters learning, a fuzzy particle swarm optimization algorithm is proposed. Compared to the basic particle swarm optimization algorithm, fuzzy particle swarm optimization can overcome the disadvantages that convergence speed slows down even tends to stagnate in the latter, ensure parameter optimization quality for fuzzy neural networks. Experimental results show the intelligent access selection algorithm can reduce terminal access blocking rate and packet loss rate, as well as increase the average throughput of access network effectively.

3,4-Ethylenedioxythiophene (EDOT) and 3,4-ethylenedithiathiophene (EDTT) as terminal blocks for oligothiophene dyes for DSSCs

Thiophene pentamers with a cyanoacrylic acid anchoring group at one end and 3,4-ethylenedioxythiophene (EDOT) or 3,4-ethylenedithiathiophene (EDTT) units at the other end have been synthesized. Preliminary evaluation in DSSCs with a iodide/triiodide liquid electrolyte shows that in spite of the very close electronic properties of the two dyes, replacing EDOT by EDTT leads to a noticeable improvement of conversion efficiency under simulated solar light.

Controlled spatial dispersion of CdSe tetrapod nanocrystals with amphiphilic block copolymer particles

Abstract We report, for the first time, a nanoscale control of the spatial distribution of semiconducting tetrapod (TP) nanocrystals within block copolymer particles. Polystyrene (PS) block copolymer (BCP)/CdSe TP nanocrystal hybrid particles were prepared by the nanoprecipitation of TP/BCP mixtures into methanol. The BCPs consisted of short, polar terminal block bearing methyl disulfide anchoring moiety which serves both to bind to CdSe TP surfaces as well as to drive self-assembly during nanoprecipitation into polar solvent systems. The resulting BCP/TP hybrid particles showed various spatial distribution and the number density of TPs with respect to individual polymer particles depending on the degree of polymerization of the block copolymer as well as the nature of the solvent in which nanoprecipitation was done.

Thioetherphenolate group 4 metal complexes in the ring opening polymerization of rac‐β‐Butyrolactone

ABSTRACTGroup 4 complexes 1–3 [1 = (t‐BuOS)2Ti(O‐i‐Pr)2; 2 = (t‐BuOS)2Zr(O‐t‐Bu)2; 3 = (t‐BuOS)2Hf(O‐t‐Bu)2] supported by two phenolate bidentate ligands (t‐BuOS‐H = 4,6‐di‐tert‐butyl‐2‐phenylsulfanylphenol) promote the well‐controlled ring opening polymerization of rac‐β‐butyrolactone. In presence of isopropanol, low dispersities and molecular weights proportional to the equivalents of isopropanol are achieved. Moreover, the zirconium complex is effective in the copolymerization of rac‐β‐butyrolactone with rac‐lactide. The C nuclear magnetic resonance analysis revealed that the obtained copolymers have a tapered diblock microstructure consisting of an initial block composed of lactide sequences and a terminal block composed of butyrolactone sequences. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3132–3139

Epoxy formulation including an acrylic triblock copolymer adapted for use in filament winding

Commercial triblock copolymers with a poly(butyl acrylate) (PBuA) central block joined to two poly(methyl methacrylate) (PMMA) end blocks (denoted as MAM) or to two random copolymers end blocks based on MMA and N,N′-dimethylacrylamide (DMA) (denoted as MAM-N), can be employed as toughening agents for thermoset composites. However, their use in epoxy formulations for filament winding, requiring low viscosities during the fiber-impregnation step associated with an adequate glass transition temperature of the cured product is not trivial. In this study, we show that a blend of diglycidylether of bisphenol A (DGEBA), 4,4′-diamino-3,3′-dimethyldicyclohexylmethane (3DCM) and benzylamine (BA), with 20% of amine hydrogens provided by BA, and containing 5 wt% MAM, can be used for these purposes. The addition of MAM increased the critical stress intensity factor from 0.63 MPa.m1/2 to 1.0 MPa.m1/2, the glass transition temperature from 138°C to 145°C, and the glassy modulus at 25°C from 2.95 GPa to 3.15 GPa. MAM was a better choice for the envisaged applications than MAM-N because it led to solutions of lower viscosity. The higher viscosity produced by MAM-N was explained by specific interactions between the epoxy-amine solvent and DMA units present in its terminal blocks. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

2-Mercaptopyridine as a new leveler for bottom-up filling of micro-vias in copper electroplating

In order to achieve a perfect bottom-up electroplated Cu filling with a minimal surface thickness, 2-mercaptopyridine (2-MP) was investigated as a new leveler for replacing Janus Green B (JGB) for bottom-up copper filling. Electrochemical impedence results indicate that 2-MP has a stronger suppression for Cu deposition than JGB. With the addition of 2-MP, the filling capability of the electroplating solution is improved significantly with the Cu thickness on surface decreasing from ∼16μm to ∼10μm. The interaction mechanisms of 2-MP, bis(3-sulfopropyl) disulfide (SPS), Cl− and tri-block copolymer of PEG and PPG with ethylene oxide terminal blocks (EPE) in the plating solution are studied by galvanostatic measurements (GMs). The acceleration effect of SPS and the inhibition effect of 2-MP on copper deposition occur in the presence of EPE, and the convection-dependent adsorption (CDA) behavior of additives usually occurs with the injection of four additives at optional concentrations. Further, it was found that when 1.0ppm 2-MP, 1.0ppm SPS and 200ppm EPE were injected into the basic electrolyte, the potential difference (Δh) value of the electrolyte became positive, and the bottom-up electroplated copper filling was obtained in the electrolyte in absence of Cl−. The interaction mechanisms of three additives for bottom-up filling have been investigated by GMs.

Synthesis and characterization of well-defined ligand-terminated block copolymer brushes for multifunctional biointerfaces

Abstract Polymer brush-functionalized surfaces promise to provide access to absolute control over the biointerface functionality. To enable in this context systematic studies of cell attachment and proliferation, we investigated the synthesis of well-defined block copolymer brushes of poly(acrylamide) (PAAm), poly(oligo(ethylene glycol)methylether methacrylate) (POEGMA) and poly(acrylic acid) (PAA) by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently the introduction of exposed ligands for cell adhesion. Detailed X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, time of flight secondary ion mass spectrometry (ToF-SIMS) and ellipsometry measurements unraveled the progress and the livingness of the homo- and copolymerization of the three monomers. In particular, the correlation of the temporal evolution of the ellipsometric thickness with the decrease in bromine content pointed to a progressive loss of active chain ends, which limits the attainable maximum brush thickness. Non-fouling brushes of POEGMA and PAAm exhibited long term stability and full functionality in cell medium for more than 1 month. Block copolymer brushes with defined thickness comprising a non-fouling POEGMA or PAAm block and a short terminal PAA block were functionalized with a peptide containing the arginine-glycine-aspartic acid (RGD) sequence. Cell attachment assays with fibroblasts revealed facilitated cell adhesion on RGD modified block copolymer brushes. The specific signaling was further confirmed with inhibited cell adhesion on arginine-alanine-aspartic acid (RAD) functionalized brushes (negative control). Hence on the basis of the unraveled synthesis behavior of block copolymer brushes and side chain modification a versatile strategy to fabricate biologically inert surfaces that facilitate integrin-specific cell adhesion has been developed.

Low concentration thermoresponsive hydrogels from readily accessible triblock copolymers

Dilute (<1 wt%) aqueous solutions of ultrahigh molecular weight triblock copolymers (with Mn up to 500 000 g mol−1) comprising a long central hydrophilic block of polydimethylacrylamide and shorter terminal blocks of poly(N-isopropylacrylamide) form gels on heating.