Length Modulation Research Articles

Effect of DNA bases on the thermoelectric performance in graphene nanoribbons

The thermoelectric transport properties of four kinds of DNA bases sandwiched between two zigzag-edge graphene nanoribbon electrodes are investigated by first-principles calculation. The modulation of quantum interference, molecular length, and molecular torsion on thermoelectric transport properties are studied. It is found that the thermopower and efficiency can be obviously enhanced in the guanine and electrode coupling geometry that manifests a quantum interference effect. A decrease of thermopower with a number of DNA bases has been found, while the efficiencies have a different trend with the increase of the number of different molecules. In addition, the thermopower and efficiency also can be considerably enhanced by the twisting angle between the molecule and graphene electrodes.

Quadrature-Averaged Homodyne Detection for Estimating Cavity Parameters

Balanced homodyne interferometry is a well-known detection technique that allows for sensitive characterization of light fields. Conventionally a homodyne interferometer is operated by locking the relative phase of a reference beam to the signal beam by means of an active feedback loop. A less often used method is to perform a slow continuous modulation of the reference beam arm length that corresponds to averaging all relative phases during the measurement. Here we show theoretically and experimentally that this quadrature averaging can be advantageous in estimating the parameters of a resonant optical cavity. We demonstrate that the averaging turns the transduction function, from cavity frequency fluctuations into the interferometer signal, into a simple function of the laser detuning that, notably, does not depend on the parameters of possible nonresonant channels present in the system. The method needs no active feedback and gives results that are easy to interpret. Moreover, the phase-averaged measurement allows characterization of the absolute magnitude of a cavity frequency modulation.

Direct parameter extraction method of EEHEMT nonlinear model for InP HEMT

AbstractA direct parameter extraction method of EEHEMT nonlinear empirical model is proposed in this paper. An improved DC model is also presented by considering the channel length modulation parameter () as a function of gate‐to‐source voltage. Model verification is carried out by comparison of measured and simulated current–voltage characteristics and S‐parameters. Good agreement is obtained between the measured and modeled results for 2 × 15 μm gatewidth (number of gate fingers × gatewidth) 70‐nm gatelength InP high electron mobility transistors (HEMT). An increased accuracy in modeling the I–V and RF characteristics is also obtained in the proposed model, compared with the conventional one.

Study on the effect of 65 nm NMOS transistor using SILVACO TCAD

This work aims to study the effect of the short gate length of 65 nm NMOS transistor using SILVACO TCAD. A 65 nm NMOS was designed and virtually fabricated and characterized using the ATHENA and ATLAS process and device simulators, respectively. A shorter gate length is expected to experience short channel effects (SCE) such as channel length modulation and drain induced barrier lowering (DIBL). The SCE was observed from the comparison of the long gate length (0.3 µm) and short gate length (65 nm) NMOS transistors’ performances. The result observed from the ID-VD graph showed that the 65 nm NMOS experienced the channel length modulation where the drain current, ID did not saturate as VD increased with an increment of 1.45 at VD = 3.3 V. Several improvements were done to overcome the SCE which are retrograde well implantation and Halo implantation. A 5 × 1014 cm−3 Boron of 200 keV implant energy and a 5 × 1013 cm−3 Boron of 100 keV implant energy were implanted for the retrograde well implant which was shown to reduce the channel length modulation effect. In addition, from the ID-VG graph, the drain current for the 65 nm NMOS was not zero when VG = 0 V, which indicated the DIBL effect. The phosphorus of 2 × 1012 cm−3 and 1 × 1013 cm−3 concentration was implanted for the Halo implantation. The results showed that the inclusion of Halo implantation has reduced the DIBL effect as the ID-VG plot showed that ID = 0 when VD = 0 with the threshold voltage, VTH = 1.87 V respectively. This shows that the inclusion of retrograde well implant and Halo implantation reduces the channel length modulation as well as DIBL effect of the short gate length NMOS.

Status and future of the soft X-ray free-electron laser beamline at the SHINE

The Shanghai High repetition rate XFEL and Extreme light facility (SHINE) is under construction and aims at generating X-rays between 0.4 and 25 keV with three FEL beamlines at repetition rates of up to 1 MHz. The soft X-ray FEL beamline, FEL-II, will be ready for commissioning in 2025. It is designed to cover the photon energy from 0.4 to 3 keV, in which the baselines of the FEL operation modes are self-amplified spontaneous emission (SASE), self-seeding, echo-enabled harmonic generation (EEHG), and polarization control. Therefore, a high repetition-rate external seed laser, large period length modulator, soft X-ray monochromator, planar undulator, and elliptically polarized undulator have been adopted in the FEL-II beamline. Several potentials such as an ultra-short pulse mode and a multi-color mode are also foreseeable without significant equipment changes in the follow-up operation. A dual-period undulator design is suggested for the echo-enabled harmonic generation (EEHG) commissioning, and it has great potential to break through the unreachable energy of the fully coherent X-ray in the future. The FEL-II beamline will deliver SASE radiation and fully coherent radiation in all the wavelengths of interest.

Effects of His-Tag Length on the Soluble Expression and Selective Immobilization of D-Amino Acid Oxidase from Trigonopsis variabilis: A Preliminary Study

His-tags are widely used for the purification of recombinant proteins. High-cost carriers functionalized with nickel ions are commonly required for the selective immobilization of His-tagged enzymes. In this study, His-tags of varying lengths were fused to the N-terminus of D-amino acid oxidase (DAO) from Trigonopsis variabilis. The attachment of a His6 tag significantly improved the solubility of the recombinant DAO expressed in Escherichia coli. By modulating the tag lengths, a better balance between cell growth and protein solubility was achieved, resulting in a higher volume activity (His3). Furthermore, the fusion of longer tags (His6 and His9) facilitated the rapid immobilization of DAOs onto a commercial epoxy carrier without metal bearing, resulting in more selective immobilization. In conclusion, the modulation of His-tag length was preliminarily demonstrated as a simple and cost-effective approach to achieve efficient expression, as well as fast and selective immobilization of DAO.

Structure–Activity Relationships in Ni- Carboxylate-Type Metal–Organic Frameworks’ Metamorphosis for the Oxygen Evolution Reaction

Metal–organic frameworks (MOFs) have been reported to catalyze the oxygen evolution reaction (OER). Despite the established links between the pristine MOFs and their derived metal hydroxide electrocatalysts, several limitations still preclude understanding of the critical factors determining the OER performance. Of prime importance appears the choice of MOF and how its compositions relate to the catalyst stability and in turn to the reconstruction or metamorphosis mechanisms into the active species under OER conditions. An isoreticular series of Ni-carboxylate-type MOFs [Ni2(OH)2L] was chosen to elucidate the effects of the carboxylate linker length expansion and modulation of the linker–linker π–π interactions (L = 1,4-benzodicarboxylate, 2,6-napthalenedicarboxylate, biphenyl-4,4′-dicarboxylate, and p-terphenyl-4,4″-dicarboxylate). Degradation and reconstruction of MOFs were systematically investigated. The linker controls the transformation of Ni-MOF into distinct nickel hydroxide phases, and the conversion from α-Ni(OH)2 to β-Ni(OH)2, thus correlating the Ni-MOF composition with the OER activity of the Ni-MOF-derived metastable nickel hydroxide phase mixture.

Enhancing Carrier Transport via σ-Linkage Length Modulation in D-σ-A Semiconductors for Photocatalytic Oxidation.

Carrier transport is an equally decisive factor as carrier separation for elevating photocatalytic efficiency. However, limited by indefinite structures and low crystallinities, studies on enhancing carrier transport of organic photocatalysts are still in their infancy. Here, we develop an σ-linkage length modulation strategy to enhance carrier transport in imidazole-alkyl-perylene diimide (IMZ-alkyl-PDI, corresponding to D-σ-A) photocatalysts by controlling π-π stacking distance. Ethyl-linkage can shorten π-π stacking distance (3.19 Å) the most among IMZ-alkyl-PDIs (where alkyl=none, ethyl, and n-propyl) via minimizing steric hindrance between D and A moieties, which leads to the fastest carrier transport rates. Thereby, IMZ-ethyl-PDI exhibits remarkable enhancement in phenol degradation with 32-fold higher rates than IMZ-PDI, as well as the oxygen evolution rate (271-fold increased). In microchannel reactors, IMZ-ethyl-PDI also presents 81.5 % phenol removal with high-flux surface hydraulic loading (44.73 L m-2 h-1 ). Our findings provide a promising molecular design guideline for high-performance photocatalysts and elucidate crucial internal carrier transport mechanisms.

Enhancing Carrier Transport via σ‐Linkage Length Modulation in D‐σ‐A Semiconductors for Photocatalytic Oxidation

AbstractCarrier transport is an equally decisive factor as carrier separation for elevating photocatalytic efficiency. However, limited by indefinite structures and low crystallinities, studies on enhancing carrier transport of organic photocatalysts are still in their infancy. Here, we develop an σ‐linkage length modulation strategy to enhance carrier transport in imidazole‐alkyl‐perylene diimide (IMZ‐alkyl‐PDI, corresponding to D‐σ‐A) photocatalysts by controlling π–π stacking distance. Ethyl‐linkage can shorten π–π stacking distance (3.19 Å) the most among IMZ‐alkyl‐PDIs (where alkyl=none, ethyl, and n‐propyl) via minimizing steric hindrance between D and A moieties, which leads to the fastest carrier transport rates. Thereby, IMZ‐ethyl‐PDI exhibits remarkable enhancement in phenol degradation with 32‐fold higher rates than IMZ‐PDI, as well as the oxygen evolution rate (271‐fold increased). In microchannel reactors, IMZ‐ethyl‐PDI also presents 81.5 % phenol removal with high‐flux surface hydraulic loading (44.73 L m−2 h−1). Our findings provide a promising molecular design guideline for high‐performance photocatalysts and elucidate crucial internal carrier transport mechanisms.

A New View on Length Module

This paper consists of several new results about Length property of the module M. F-length of any Module comes from several concepts like Neotherian module and Artinian modules (Neo and Art) with comp- sition series. We proved that any Neo -module has submodule T and Neo -module is F-length. This implies that T also has F-length Property. Finally, some remarks, examples and definitions have been presented in this paper.

Inside Back Cover: A family of oligo(p‐phenylenevinylene) derivative aggregation‐induced emission probes: Ultrasensitive, rapid, and anti‐interfering fluorescent sensing of perchlorate via precise alkyl chain length modulation

In this work (e315), Dou and coauthors demonstrated a molecular regulating strategy to improve the sensitivity of oligo(p-phenylenevinylene) derivative AIE probe towards perchlorate anion by regulating the van der Waals interactions between the probe and perchlorate anion through precise manipulation of the alkyl chain length, consequently achieving superior turn-on fluorescent sensing performances.

A new low voltage low power fully differential CMOS class AB current output stage with unique current drive capability

ABSTRACT This paper presents a novel low-voltage low power fully differential class AB current output stage with high linearity and unique current drive capability. The proposed circuit is based on a simple and efficient structure to obtain high linearity by minimising the channel length modulation effect and also avoids cascade structure to act best in low-voltage applications. Giving the complete analyses and equations of the circuit, its properties are verified by Cadence using TSMC 0.18 µm CMOS parameters. In order to study its performance at the presence of non-idealities, Pre-layout and Post-layout both plus Monte–Carlo simulations are also performed. Under±0.9 V supply and 35 µA output bias current, it can deliver the ever high output current of ±350 mA with THD of −49 dB and output impedance of 2.8 MΩ, which leads to a unique high current drive ratio (Ioutmax/Ibias) of 10,000 and low consumed power of 150 µw in pre-layout simulation. In post-layout plus Monte–Carlo simulation, the results will be as ±320 mA output current, −42 dB THD, 2.2 MΩ output impedance, 40 µA DC current of the output branch, 8000 current drive ratio and 160 µw consumed power. These remarkable results prove the proposed novel COS not only as the unique one in the world but Longley ahead of the yet second rank COS by some unbeatable ratios as 11300×,14×,4× and3× in F T , I outmax , (Ioutmax/power), and current drive, respectively, that promise to keep it as the lead one for many years in low-voltage/power ultra-high current applications.

Flat Families of Point Schemes for Connected Graded Algebras

We study truncated point schemes of connected graded algebras as families over the parameter space of varying relations for the algebras, proving that the families are flat over the open dense locus where the point schemes achieve the expected (i.e., minimal) dimension. When the truncated point scheme is zero-dimensional, we obtain its number of points counted with multiplicity via a Chow ring computation. This latter application in particular confirms a conjecture of Brazfield that a generic two-generator two-relation algebra has seventeen truncated point modules of length six.

Modulation of Alkyl Chain Length on the Thiazole Side Group Enables Over 17% Efficiency in All‐Small‐Molecule Organic Solar Cells

AbstractMolecular innovation is highly desirable to achieve efficient all‐small‐molecule organic solar cells (SM‐OSCs). Herein, three small‐molecule donors (SMDs) with alkylated thiazole side groups (namely BO‐1, HD‐1, and OD‐1), which differ only in the alkyl side chain are reported. Although these SMDs possess similar absorption profiles and molecular energy levels, their crystallinity and miscibility with BTP‐eC9 slightly decrease along with the elongation of the alkyl side chain. After blending with BTP‐eC9, different miscibility leads to different degrees of phase separation. Among these SM‐OSCs, the HD‐1‐based device shows a decent bulk‐heterojunction (BHJ) morphology with proper phase separation and more dynamic carrier behavior. Thus, compared to the BO‐1 and OD‐1‐based devices, the HD‐1‐based device achieves a higher short‐circuit current of 26.04 mA cm−2 and a fill factor of 78.46%, leading to an outstanding PCE of 17.19%, which is one of the highest values among SM‐OSCs. This work provides a rational design strategy of SMDs for highly efficient SM‐OSCs.

A W-Band Vector Modulator Using Short-Channel Transistor Current Sources and Impedance Compensation Varactors

A W-band vector modulator based on vector summing with a Gilbert-cell is presented, in which two kinds of error-reducing schemes are applied to the summing circuit. One is to use current sources made of short channel transistors to take advantage of the channel length modulation effect. The other is to introduce impedance correction varactors at the input. It controls both gain and phase by using a digital-to-analog converter (DAC) which is designed to make the output impedance of the summing circuit constant regardless of states. The intrinsic gain and phase errors are also analyzed with the help of a simple current model of a MOS transistor, which explains the error-reducing schemes. It was implemented in 28-nm CMOS technology, which consumes only 7.7mA of DC and occupies an area of 0.11mm2 (excluding pads). The RMS gain error of 0.1dB and the RMS phase error of 1.3° were measured with 4-bit gain and 6-bit phase controls at 94 GHz, where the gain dynamic range was around 15 dB.

Experiment study and analytical modeling of fully solution processed organic thin film transistors with conductive polymer top-gate electrode: Performance optimization

In this paper, various fully solution-processed top-gate bottom contacts organic thin-film transistors based on printed silver nanoparticles electrodes were fabricated, electrically characterized, and analytically modeled. The performance of the designed devices thermally and laser sintered nanoparticles electrodes was investigated. The device based on electrode sintered thermally exhibits improved contacts with an on/off ratio of 1.6 × 103 and a saturation mobility of 1.23 × 10−2 cm2V−1s−1. The current–voltage characteristics of OTFTs in terms of the transfer and output characteristics were also modeled and reproduced using an analytical model. Furthermore, various effects were considered in the used model, including the channel length modulation and contact resistance effects as well as field-effect mobility dependence of the gate voltage. The proposed model results for the devices were found to be in a good agreement with the experimental data in terms of the transfer and output characteristics. It was found that the used analytical model correctly describes the electrical characteristics, and it is proved to be accurate enough to explain the charge transport in these types of OTFTs. The development of such model will certainly help in the design of high-performance nanomaterials based OTFTs and their future advancement as well.

Demonstration and analysis of ambipolar SnO inverter with high gain

Ambipolar materials offer a unique and simple route toward cost-effective complementary thin film circuits. SnO is one of the few metal oxide semiconductors that demonstrates ambipolar behavior. In this work, we demonstrated an ambipolar SnO inverter with record high inverter gain and corroborated our experimental results with a comprehensive analytical model. First, we developed ambipolar SnO thin film transistors (TFTs) with symmetric p-type and n-type conduction. Using these ambipolar SnO TFTs, we fabricated ambipolar SnO inverters. Our ambipolar SnO inverter shows a record gain of 432 (V/V), which is the highest reported among all ambipolar material systems. To understand our high inverter gain, we developed a comprehensive analytical model to analyze the transition region of an ambipolar inverter. Our analytical model showed an excellent match with our experiment results. Furthermore, our analytical model shows that to achieve a high inverter gain and a voltage transition point in the middle of the supply voltage range, we must minimize channel length modulation and match the p- and n-type behaviors of the ambipolar TFTs. By expanding our understanding of ambipolar inverter behavior, this work highlights the possibilities of ambipolar SnO TFTs for future high performance complementary thin film circuits.

Reflective epoxy resin/chitosan/PAA composite-functionalized fiber-optic interferometric probe sensor for sensitive heavy metal ion detection.

A highly sensitive label-free chemical sensing platform for the detection of various metal ions is demonstrated. The chemical sensor was derived from a single-mode fiber that is inserted into the ceramic tube with epoxy resin (ER) on the end face for reflecting light and forms the Fabry-Perot (F-P) interferometric cavity. Multilayer chitosan (CS)/polyacrylic acid (PAA) were coated on the surface of the epoxy resin and act as the sensitive film. Based on the analysis of the sensing principle and the F-P cavity structure, the parameters were numerically simulated and experimentally evaluated, which enables ease of fabrication and real-time modulation of the cavity length. The sensitivity of sensing Ni2+, Zn2+, and Na+ reached 9.95 × 10-4 nm ppb-1, 2.31 × 10-4 nm ppb-1, and 4 × 10-4 nm ppb-1, respectively, and the sensing results were theoretically analyzed by the Langmuir adsorption model, which corresponds to the surface atom percentage results obtained by SEM and EDS measurements for sensing three types of metal ions. The proposed ER/CS/PAA multilayer film-coated F-P sensor can be employed as a probe, which features label-free, highly sensitivity, real-time monitoring, ease of measurement, stability, and therefore provides a remarkable analytical platform for chemical applications.

One-Time Pad Strategy Combined With Dynamic Key Embedding and Multi-Level Chaotic Encryption for RoF

Chaotic encryption is a potential scheme for the communication security of radio-over-fiber (RoF) system. In this paper, a one-time pad strategy combined with dynamic key embedding and multi-level chaotic encryption is experimentally demonstrated for RoF system. The keys are divided into dynamic and static key. The static key is randomly selected and encrypt dynamic key which is extracted according to the transmission information. The dynamic key is employed in polar coding encryption (bit- level) and static key is employed in dynamic key embedding, constellation masking (symbol-level) and chaotic synchronization. The receiver selects the required static key according to the synchronization information and recovers the dynamic key from the received data, which realizes the one-time pad strategy and greatly enhances the security of the system. Transmission experiments are successfully conducted over 50 km standard single-mode fiber (SSMF) and 5 m wireless channel. Compared with the traditional OFDM, the experimental results show the proposed scheme adopting successive cancellation list 8 (SCL8) decoder can acquire ∼2.1 dB gain at the BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> . In addition, experiments verify the influence of code length, code rate and different modulation formats, which further explains the feasibility of the scheme. Experiments show that the proposed scheme has great practical potential for future optical wireless secure communication.

Bidirectional Bluetooth Backscatter with Edges

Bidirectional links are widely adopted in many active radios to provide efficient data exchanges, e.g., WiFi and Bluetooth. However, they are underexplored for general-purpose backscatter communications. The downlinks of state-of-the-art Bluetooth backscatter systems are based on packet length modulation, which is inefficient and unreliable. In this paper, we propose BiBlue, a bidirectional Bluetooth backscatter system that uses an edge server to enable fast and reliable downlinks. Specifically, our edge server acts like a bridge that can translate commercial Bluetooth signals to Amplitude Shift Keying (ASK) signals. In addition, we design a reliable edge-to-tag link that adaptively decodes ASK signal under variance. Finally, we propose a low-power uplink design that enables connection-based bidirectional communication with commodity devices. We prototype BiBlue using FPGA and Software Defined Radio (SDR). Extensive experimental results demonstrate that BiBlue achieves more than 62x downlink throughput gains over FreeRider and meanwhile supports an 80 cm communication range of edge-to-tag with BER at around 1%.