Influence of adsorption on the optical properties of the electrode-solution interface

Electroreflection (ER) of metal electrodes shown to be determined by the modulation of the surface excesses of electrons, ions and other adsorbed particles as well as the modulation of their polarizabilities. One of the form of modulation of polarizability is the modulation of surface relaxation time of metal electrons. Experimental study of silver ER and “electrotransmission” in Na₂SO₄ solution revealed that the contribution of this latter mechanism is the main one in the visible range. Taking into account the electron plasma background in the ER spectra permits a quantitative study of the adsorption equilibrium and kinetics. Adsorption of I^? anions on vacuum evaporated silver films studied by ER measurements was shown to obey Temkin type isotherm.     

Conformational change of a helical polymer molecule induced by periodic modulation of the internal coordinates

Conformational change of a helical polymer molecule induced by periodic modulation of the internal coordinates around constant values of a uniform helix was studied by numerical calculation. We paid attention to the ‘spatial resonance' found by Yamamoto et al., who carried out analytical calculation to a linear approximation (Yamamoto, M., Kasai, K. and Hikichi, K., J. Macromol. Sci. (Phys.), 1967, B1(2), 213). The spatial resonance means that when the wavelength of the modulation is equal to one turn of the helix, a finite amplitude of the modulation of the internal coordinates leads to divergence of the fluctuation in the external coordinates. We found that the molecular conformation in the spatial resonance induced by the modulation of the internal rotational angle or the bond angle is not a straight helix but is deformed into a ring-shaped helix, which we call ‘ringed-coil' conformation. On the other hand, the modulation of the bond length does not give rise to the spatial resonance. When both the internal rotational angle and the bond angle are modulated in a proper way the molecular conformation remains as a straight helix, but the atomic positions are displaced from those of the uniform helix. A few possible applications of the concept of the spatial resonance are proposed.     

Reversible photoluminescence modulation in praseodymium-doped bismuth titanate ceramics for information storage based on photochromic reaction

Photoluminescence materials with reversible luminescence regulation properties have great potential for applications in photoswitches, optical sensing, and high-density optical data storage devices. In this work, a series of Pr³⁺-doped Bi₄Ti₃O₁₂ (BiT) ceramics were synthesized by a high-temperature solid-phase reaction method. It is well known that BiT is the most famous one within the Aurivillius ferroelectric (FE) system. Previous works routinely focused on the FE-related properties of BiT-based compounds, but little attention has been devoted to the luminescence, especially the luminescence modulation performance. Here, a large and reversible photoluminescence modulation by alternating visible light irradiation and thermal stimulus based on photochromic (PC) process was achieved. Meanwhile, the influence of sintering temperature on the luminescence modulation behavior was also illustrated. The luminescence regulation properties of the Pr³⁺-doped BiT ceramics prepared at optimized sintering temperature were investigated in detail. The mechanisms connected to the luminescence, luminescence manipulation, and PC effect were discussed. It is believed that Pr³⁺-doped BiT materials can be utilized as a kind of ideal optical medium for future information storage device.     

Electrodeposition of CuNiW alloys: thin films,nanostructured multilayers and nanowires

Electrodeposition operating conditions were determined for the deposition of copper–nickel–tungsten alloys and compositionally, multilayered deposits. Multilayered alloys with one layer rich in Cu and the other layer rich in NiW were fabricated as both thin films and nanowires. The electrolyte contained 0.6 M Na₃C₆H₅O₇, 0.2 M Na₂WO₄, 0.3 M NiSO₄ and variable CuSO₄ concentration at a pH of 8 adjusted with ammonium hydroxide at 70 ± 2 °C. The deposit composition and current efficiency were characterized using rotating cylinder electrodes with and without a Hull configuration. Addition of Cu(II) to the electrolyte lowered the tungsten partial current density and hence the W wt% in the deposit. Thin film multilayered alloys, with a modulation in composition, were fabricated with pulse current deposition and conditions to selectively etch one layer was determined with a view towards fabricating nanotemplates. Nanowires with modulated composition were also demonstrated, electrodeposited into alumina nanoporous templates. However, the nanowire deposition was confounded by the formation of oxide during the modulation, and results herein recommend that the potential of the more noble step be more negative than −0.9 V versus SCE to avoid this situation, despite metallic alloy formation in unrecessed electrodes.     

Tunable upconversion luminescence in new Ho3+/Yb3+-doped SrBi4Ti4O15 photochromic ceramics for switching application

Upconversion (UC) luminescence modulation is quite important in controlling and processing light for active components of light sources, photoswitches, optical memories, and optical sensing devices. In this work, we reported one kind of novel phosphor, Ho³⁺/Yb³⁺-doped SrBi₄Ti₄O₁₅ ceramics, which displayed both strong UC luminescence and obvious photochromic (PC) reaction. The UC luminescence, PC effect, and the modulation of UC performance based on PC behavior were investigated in detail. By alternating visible light irradiation and thermal stimulus, the UC luminescence could be reversibly regulated. Meanwhile, the modulation was unveiled to tightly rely on the irradiation time and thermal treatment processes. Excellent reproducibility was also achieved. In addition, as an alternative method to thermal treatment, the manipulation of luminescence by electric field was also explored. Finally, the mechanism related to the UC luminescence manipulation was illustrated. The results indicate that these samples could be potentially utilized in optical data storage and anti-counterfeiting security fields.     

离子替代M型Ba铁氧体的最新研究进展

六角晶系M型钡铁氧体(BaO·6Fe2O3)是一种应用范围十分广泛的磁性材料.采用离子替代的方法,可以根据不同的应用需要对其各种性能作调整,如今仍然是磁性材料研究的热门之一.本文综述了近年来国内外一元、二元和三元离子替代M型钡铁氧体所取得的研究成果,并指出了离子替代M型钡铁氧体的下一步研究重点.     

Modulated temperature differential scanning calorimetry for examination of tristearin polymorphism: I. Effect of operational parameters

The transformations of tristearin were examined by modulated temperature differential scanning calorimetry (MTDSC) in order to study the effect of operational parameters on the nature of information obtained from this technique. Tristearin has been used as a model polymorphic system showing metastable phases and complicated transformation routes occurring at relatively slow rates. The parameters examined were underlying heating/cooling rates and the amplitude of modulation. The first conclusion is that MTDSC enables overlapping α-melting and β-crystallization events to be separated, thus increasing the information obtained compared to normal thermal analysis. Other general conclusions are that observation of reversible processes is strongly influenced by the underlying heating rate; low to moderate heating rates are recommended. Amplitude of modulation has a complicated effect on the phenomenon being studied; when studying systems that exhibit metastable or polymorphic transitions, it is recommended that a range of amplitudes be tested to enable confirmation of whether an observed ‘recrystallization’ effect is a new phase or the same phase as the one melting. Cooling with modulation disturbs the crystallization process, possibly leading to smaller or imperfect crystals; however, the phases obtained are not different compared to normal DSC. The usefulness of MTDSC in analyzing these types of complicated systems is primarily qualitative at the moment. Some recommendations have been made as to the combinations of parameters for studying such systems.     

The research of preparation of polyvinyl acetate with lower polydispersity index

In this study, the way of preparing polyvinyl acetate (PVAc) with lower polydispersity index (PDI) was studied. By adding small amount of monomer with polar group, such as acrylic acid (AA), α-methacrylic acid (MAA), or acrylamide (AM), as modulation monomer, the polymerization was carried out at 65°C with a mechanical agitator using AIBN as initiator under N₂ atmosphere. Effects of the mol ratio of modulation monomer/VAc and structure of the modulation monomer on the polymerization conversion, the molecular weight and molecular weight distribution of the obtained polymers were investigated through ¹H NMR, gravity method, and gel permeation chromatography. The results show that by adding modulation monomer into the reactive system the PVAc with lower PDI could be got. With the increase of the modulation monomer amount, the conversion and the molecular weight decrease, and the PDI of the obtained polymer is lower. When the mol ratio of AA/VAc is 3 : 100, the PDI of the obtained polymer is 1.84. When the mol ratio of AM/VAc is 1 : 100, the PDI of the obtained polymer is 1.68, which is narrower than that without AM. All researches we have done laid a foundation for further study. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multistep synthesis of VO2 (M) nanoparticles and their application to thermochromic hybrid films for IR modulation

Vanadium dioxide (VO₂) is widely known as one of the excellent thermochromic materials based on a reversible insulator-to-metal phase transition upon temperature change. In this study, VO₂ (M) powder was initially synthesized through a hydrothermal method and a subsequent post-annealing treatment. Additionally, a particle size of the VO₂ (M) powder was reduced and uniformized by introducing a ball-milling process. The resultant VO₂ (M) nanoparticles (NPs) were dispersed in ethanol with the addition of polyvinylpyrrolidone (PVP). The ethanolic dispersion was then coated on a transparent heater used as a substrate by spin-coating to produce VO₂ (M)/PVP composite films. We have attained an exact temperature control of the films by applying voltages to the heater for the assessment of their thermochromic performance such as the solar and the infrared modulation ability. For example, the film temperature could be raised from room temperature to 85.5°C within 180 s at a low voltage of 11 V, which was enough for inducing the phase transition of the VO₂ (M) NPs showing the infrared modulation ability of 19.3%. The combination of the composite films and the heater was thus proved to be a promising way for realizing transparent thermochromic devices.     

光诱导光子晶格折射率对比度影响因素的探究

由实验测量得到的不同写入角度下的衍射效率,通过衍射效率与折射率对比度的关系,间接得到了折射率对比度与光子晶格周期的关系.关系表明折射率对比度随晶格周期的变化确实有一极值存在.说明写入不同周期的光子晶格会有不同的折射率对比度.用不同掺铁浓度的晶体实验时发现随着掺铁浓度的增大折射率对比度的最大值也增大,并且最大值的位置向晶格周期人小的方向移动,这与理论计算结果相吻合.因此,在实验与理论上证实了折射率对比度确实与写入的光子晶格的周期和掺铁浓度有关.     

Influence of interface intermixing and periodicity on internal electric field and polarization in ferroelectric superlattices

A thermodynamic model is developed to study the effect of interface intermixing and modulation period on the internal electric field of a superlattice comprising alternate layers of ferroelectric and dielectric. The intermixed layer plays an important role in determining both the polarization and internal electric field modulation profiles of the superlattice. The presence of interface intermixed layer gives rise to inhomogeneous internal field and polarization, which enhances the depolarization field of the superlattices. Interface intermixing; however, does not have much influence on the polarization behavior of the superlattice. Ferroelectric volume fraction or thickness ratio of ferroelectric to dielectric is one of the key parameter for controlling the properties of a superlattice consisting alternate layers of ferroelectric and dielectric.     

Thermal Effects and Small Signal Modulation of 1.3-μm InAs/GaAs Self-Assembled Quantum-Dot Lasers

We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.     

Experimental investigation of fast-mode liquid modulation in a trickle-bed reactor

Unsteady-state operation of trickle-bed reactors (TBRs) is a promising technique to improve reactor performances especially when mass transfer phenomena are rate controlling. Among the different techniques, fast-mode modulation of the liquid flow rate seems to be one of the most successful. In fact cycling the liquid flow rate at very low frequencies can induce the reactor to work at the high-interaction regime where mass and heat transfer phenomena are strongly enhanced. Fast-mode periodic operation, then, can be considered an extension of the natural high-interaction regime at a mean range of gas and liquid flow rate normally associated with trickling regime in steady-state conditions.Experimental tests have been performed in a TBR employing α-methyl styrene hydrogenation on Pd/C catalyst in unsteady-state conditions by “on-off” fast-mode liquid modulation. Results have been compared with the steady-state experiments at the corresponding average liquid flow rate, revealing a conversion rate improvement up to 60%. All experiments have been performed in isothermal conditions, so conversion improvement can be ascribed only to mass transfer increase and not to thermal effects. The variation of gas and liquid flow rates and liquid cycle parameters presented several important implications about the optimal working conditions.     

准连续调制光谱测量信号的软件锁相解调仿真与分析

准连续调制光谱测量技术是准连续调制信号典型应用之一,具有灵敏度高,响应速度快、选择性好的特点,因此在炼焦工业、灾害救援、垃圾处理等领域的气体检测方面有着广泛应用。光谱测量系统中非常重要的一项内容为对输出信号进行锁相解调。传统锁相放大器进行解调难以满足准连续调制光谱高精确度测量结果的要求。因此,利用Matlab设计了软件锁相放大器,并对准连续信号解调进行仿真分析。结果表明,软件锁相放大器能够弥补传统锁相放大器的不足,在准连续调制光谱分析中可以进一步应用。     

Enantioselective Organocatalytic Synthesis of a Secoyohimbane‐Inspired Compound Collection with Neuritogenic Activity

Natural products provide evolutionary validated core structures to inspire the synthesis of new compound collections endowed with neurite growth‐promoting activity. Rhynchophylline is the major component of Uncaria species, and has been used to treat neurological diseases in Chinese traditional medicine. Based on the structure of this spirocyclic secoyohimbane alkaloid, we developed a highly enantioselective and efficient organocatalyzed synthesis method to provide a tetracyclic secoyohimbane scaffold incorporating a quaternary and three tertiary stereogenic centers, in a one‐pot multistep reaction sequence. A compound collection of derived secoyohimbanes was synthesized and expanded by decorating the periphery of the basic scaffold with additional substituents to increase the diversity. Evaluation of the different subcollections of secoyohimbanes for modulation of neurite outgrowth in the SH‐SY5Y human cell line led to the discovery of new compounds that promote neurite outgrowth.     

Isoflurane Potentiation of GABAA Receptors Is Reduced but Not Eliminated by the β3(N265M) Mutation

Background: Mice carrying the GABA_A receptor β3(N265M) point mutation, which renders receptors incorporating β3-subunits insensitive to many general anesthetics, have been used experimentally to link modulation of different receptor subtypes to distinct behavioral endpoints. Remarkably, however, the effect of the mutation on the susceptibility to modulation by isoflurane (a standard reference agent for inhalational vapors) has never been tested directly. Therefore, we compared the modulation by isoflurane of expressed α5β3(N265M)γ2L receptors with their wild type counterparts. Methods: Using whole-cell electrophysiological recording and rapid solution exchange techniques, we tested the effects of isoflurane at concentrations ranging from 80 μM to 320 μM on currents activated by 1 μM GABA. We measured drug modulation of wild-type α5β3γ2L GABA_A receptors and their counterparts harboring the β3(N265M) mutation. Results: Currents elicited by GABA were enhanced two- to four-fold by isoflurane, in a concentration-dependent manner. Under the same conditions, receptors incorporating the β3(N265M) mutation were enhanced by approximately 1.5- to two-fold; i.e., modulation by isoflurane was attenuated by approximately one-half. Direct activation by isoflurane was also present in mutant receptors but also attenuated. Conclusions: In contrast to the complete insensitivity of β3(N265M) mutant receptors to etomidate and propofol, the mutation has only a partial effect on receptor modulation by isoflurane. Therefore, the persistence of isoflurane effects in mutant mice does not exclude a possible contribution of β3-GABA_A receptors.     

Design criterion based on the cohesive energy and defect patterns of VO2 thermally induced phase transition materials

Vanadium dioxide (VO₂) is one of the most widely used thermally induced phase transition materials. However, the phase transition regulation mechanism and specific modulation relationship of VO₂ materials are still not entirely clear. Here, we propose a comprehensive and precise phase transition material design criterion based on the cohesive energy and defect patterns. The results revealed that the associated regulation mechanism, including the size, strain, vacancy as well as crystal plane and shape, of these materials can be determined via design criteria and first principles calculations. Moreover, the specific modulation relationship of the thickness-induced phase transition can also be confirmed by means of experiments. These findings show that our design criterion provides an effective approach for the design of VO₂ thermally induced phase transition materials.     

Improved ground-state modulation characteristics in 1.3 μm InAs/GaAs quantum dot lasers by rapid thermal annealing

We investigated the ground-state (GS) modulation characteristics of 1.3 μm InAs/GaAs quantum dot (QD) lasers that consist of either as-grown or annealed QDs. The choice of annealing conditions was determined from our recently reported results. With reference to the as-grown QD lasers, one obtains approximately 18% improvement in the modulation bandwidth from the annealed QD lasers. In addition, the modulation efficiency of the annealed QD lasers improves by approximately 45% as compared to the as-grown ones. The observed improvements are due to (1) the removal of defects which act as nonradiative recombination centers in the QD structure and (2) the reduction in the Auger-related recombination processes upon annealing.     

Metabolic Factors Affecting Tumor Immunogenicity: What Is Happening at the Cellular Level?

Immunotherapy has changed the treatment paradigm in multiple solid and hematologic malignancies. However, response remains limited in a significant number of cases, with tumors developing innate or acquired resistance to checkpoint inhibition. Certain “hot” or “immune-sensitive” tumors become “cold” or “immune-resistant”, with resultant tumor growth and disease progression. Multiple factors are at play both at the cellular and host levels. The tumor microenvironment (TME) contributes the most to immune-resistance, with nutrient deficiency, hypoxia, acidity and different secreted inflammatory markers, all contributing to modulation of immune-metabolism and reprogramming of immune cells towards pro- or anti-inflammatory phenotypes. Both the tumor and surrounding immune cells require high amounts of glucose, amino acids and fatty acids to fulfill their energy demands. Thus, both compete over one pool of nutrients that falls short on needs, obliging cells to resort to alternative adaptive metabolic mechanisms that take part in shaping their inflammatory phenotypes. Aerobic or anaerobic glycolysis, oxidative phosphorylation, tryptophan catabolism, glutaminolysis, fatty acid synthesis or fatty acid oxidation, etc. are all mechanisms that contribute to immune modulation. Different pathways are triggered leading to genetic and epigenetic modulation with consequent reprogramming of immune cells such as T-cells (effector, memory or regulatory), tumor-associated macrophages (TAMs) (M1 or M2), natural killers (NK) cells (active or senescent), and dendritic cells (DC) (effector or tolerogenic), etc. Even host factors such as inflammatory conditions, obesity, caloric deficit, gender, infections, microbiota and smoking status, may be as well contributory to immune modulation, anti-tumor immunity and response to immune checkpoint inhibition. Given the complex and delicate metabolic networks within the tumor microenvironment controlling immune response, targeting key metabolic modulators may represent a valid therapeutic option to be combined with checkpoint inhibitors in an attempt to regain immune function.     

Evaluation of periodic operation of a trickle-bed reactor based on empirical modeling

In this paper, we propose a new procedure for fast evaluation of the potential of periodic operations in trickle-bed reactors, based on empirical modeling. Step response experiments, with different input amplitudes, were performed on a laboratory trickle-bed reactor, in order to derive a simple nonlinear dynamic model. α-methylstyrene (AMS) hydrogenation was used as a test reaction and the feed AMS concentration was used as the modulated input. An empirical nonlinear model was postulated and used for simulation of periodic operations. The simulation of a periodic operation with sinusoidal modulation of the inlet AMS concentration with 40 % amplitude resulted up to 35% higher time-averaged conversion than the corresponding steady-state one.